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This invention was made with support under contract N00014-90-C-2060 awarded by the Naval Research Laboratory. The United States Government has certain rights in this invention. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved electron gun, and more particularly, to an advanced center post (ACP) gun for producing a hollow electron beam having either a small orbit or a large orbit. 2. Description of Related Art It is well known in the art to utilize a linear beam device within a traveling wave tube (TWT), klystron, magnetron or other microwave device. In a linear beam device, an electron beam originating from an electron gun is caused to propagate through a tunnel or a drift tube generally containing an RF interaction structure. At the end of its travel, the electron beam is deposited within a collector or beam dump which effectively captures the spent electron beam. The beam is generally focused by magnetic or electrostatic fields in the interaction structure of the device in order for it to be effectively transported from the electron gun to the collector without loss to the interaction structure. An RF wave can be made to propagate through cavities within the interaction structure and interact with the electron beam which gives up energy to the propagating wave. Thus, the microwave device may be used an amplifier for increasing the power of a microwave signal. The electron gun which forms the electron beam typically comprises a cathode and an anode. The cathode includes an internal heater which raises the temperature of the cathode surface to a level sufficient for thermionic electron emission to occur. When the potential of the anode is positive with respect to the cathode, electrons are drawn from the cathode surface and moved towards the anode. The geometry of the cathode and anode provide an electrostatic field shape which defines the electron flow pattern. The electronic flow then passes from the electron gun structure to the interaction region of the microwave device. An electron gun of this type is known as a Pierce gun. In one particular type of Pierce gun, a hollow electron beam is formed. By varying the axial magnetic field, the electrons in the hollow beam can be made to orbit some of the magnetic flux lines. As the magnetic field is increased, a significant fraction of the axial energy of the electron beam is converted to motion transverse to the beam axis. This gyrating beam is used in several microwave devices which convert the transverse energy of the beam into RF energy. Examples of these devices are the peniotron, gyrotron, gyroBWO, gyroTWT, etc. A prior art gyrotron is shown in FIG. 1. The cathode of a hollow beam gun is generally annular so that it emits a circular beam of electrons 18, as shown in FIG. 2a. The hollow beam can be characterized as either a large orbit beam in which the electrons 44 spiral about a guiding center of the beam near the axis of the microwave device in a circular path 42, or a small orbit beam in which the electrons orbit around individual flux lines of the guiding magnetic field in the interaction region. The rotation of the electrons in a large orbit beam is induced by a magnetic field reversal at the front end of the interaction region. The large and small orbit beams are shown graphically at FIGS. 2a and 3, respectively. One class of devices utilize large orbit beams for production of a microwave output through a process known as cyclotron resonance maser (CRM) interaction. Maser is an acronym for microwave amplification using stimulated emission of radiation. CRM interaction devices extract rotational energy from the beam in radial cavities disposed within the interaction region. The electrons 44 orbit about the guiding center at a rate known as the cyclotron frequency Ω c . The space charge forces within the gyrating electron beam result in azimuthal bunching 46 of the orbiting electrons, shown graphically in FIG. 2b. If the frequency of the propagating RF wave is slightly greater than the cyclotron frequency, the electron bunches fall back into a decelerating field and transfer their energy to that field. Interaction can also take place at harmonics of the cyclotron frequency. In this case, multiple bunches are formed equally spaced about the cyclotron orbit. Both the efficiency and stability of CRM devices and peniotrons are strongly dependant on the ratio of transverse velocity to axial velocity of the beam, known as α. In these devices, the α value is usually between 1 and 2. Increasing αwill raise the efficiency of these devices until the device becomes unstable. In order to obtain maximum efficiency of energy transfer to the RF wave, uniform transverse and axial velocity of the orbiting electrons is desired. In practice, such velocity uniformity is difficult to achieve. A standard magnetron injection gun (MIG) has a conical cathode which produces a small orbit beam that is constrained to move axially by the applied magnetic field. In the standard MIG gun, magnetic flux threads the cathode in order to control the beam radius and improve beam stability. However, this type of MIG gun is impractical for producing a large orbit beam since the variation in flux across the cathode surface translates to variation in angular velocity after the magnetic field reversal. Other electron gun designs utilize a shielded cathode with a center post to reduce or eliminate the magnetic field at the cathode and decreases the transverse velocity spread. However, the beam radius of these guns is typically limited to the cathode radius, and can not be readily adjusted to accommodate very short wavelength RF signals, such as in the millimeter wavelength range. Thus, these shielded cathode designs have not been successfully applied in forming large orbit axis encircled beams in these applications. SUMMARY OF THE INVENTION Accordingly, a principal object of this invention is to provide an electron gun capable of producing a hollow electron beam which can form either a large electron orbit or a small electron orbit. An additional object of this invention is to provide an advanced center post electron gun which produces an axis encircling electron beam for CRM interaction wherein the beam has reduced axial and transverse velocity variation over that of a conventional axis encircling beam. Yet another object of this invention is to provide an electron gun which produces an axis encircling large orbit beam in which the beam radius α and rotational frequency can be independently varied. In accomplishing these and other objects, there is provided an electron gun having an annular shaped cathode, a control electrode adjacent the cathode, and an annular anode disposed a fixed distance from the cathode and having an opening therethrough. A center post is disposed axially within a center region of the cathode and the control electrode along a center line of the electron gun and interaction region of a microwave device. The anode is shaped in conjunction with the center post to control position of equipotential lines of an electric field provided in an inter-electrode space between the cathode and the anode so that an electron beam emitted by the cathode converges at the opening in the anode. The control electrode provides electrostatic focusing of the beam to further control the beam convergence. In particular, the control electrode further comprises an inner and an outer beam control electrode spaced a fixed distance from the cathode. A bias voltage is provided between the outer and inner beam control electrodes, to deflect the electron beam relative to the center line and to determine the convergence point of the beam. In one embodiment of the invention, a magnetic field reversal is applied after the convergence point of the electron beam. A triple polepiece structure is provided to perform the magnetic field reversal. The polepieces have tapered ends which minimize the axial length in which there is an absence of magnetic field. Once it passes the field reversal point, a portion of the axial velocity of the electron beam is converted to angular velocity, resulting in a rotation of the beam at the cyclotron frequency ω c . The guiding center for this rotation is at or near the beam axis. In an additional embodiment of the invention, the center post has a liquid cooled core. Spiralling coolant channels extend axially through the center post beneath the outer surface of the center post. A coolant exhaust channel extends through the center of the center post. A coolant fluid entering the center post flows through the radial coolant channels, and then is exhausted through the central channel. The coolant maintains the center post at a constant temperature, which prevents deformation of the center post surface. A more complete understanding of the electron gun of the present invention will be afforded to those skilled in the art as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings, which will be first described briefly. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic side view of a prior art hollow beam gyrotron having a cathode assembly, an interaction area, and a collector; FIG. 2a is a sectional view of a gyrating electron beam; FIG. 2b is a view as in FIG. 2a showing azimuthal electron bunching due to a transverse electric field; FIG. 3 shows a normal small orbit gyrotron beam; FIG. 4 is a side sectional view of a gyrotron electron gun of the present invention; FIG. 5 is an enlarged side view of the electron gun showing the equipotential lines between the cathode and anode; FIG. 6a shows a prior art triple polepiece magnetic field reversal configuration; FIG. 6b is a graph showing the reversal of magnetic flux density through the triple polepiece of FIG. 6a; FIG. 6c is a graph showing the behavior of an electron beam passing through the field reversal element of FIG. 6a; FIG. 7 is a detailed side view of a preferred embodiment of the gyrotron electron gun of the present invention; and FIG. 8 is an enlarged side view as in FIG. 7. DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention represents a significant improvement over the prior art gyrotron electron guns, in that it permits a single gun to produce either a small orbit or a large orbit electron beam. Moreover, a large orbit beam produced with this gyrotron gun experiences dramatically reduced axial and transverse velocity spreads over the prior art devices, which significantly increases the efficiency of CRM interaction. Referring first to FIG. 1, a diagram of a prior art gyrotron assembly 10 is shown. An electron gun assembly 12 has a thermionic emitting cathode 14 with an emitting surface 16 that emits a circular electron beam 18. The beam 18 passes from the electron gun assembly 12 into an interaction structure 20 through a centrally disposed interaction region 25 of the structure. A magnetic field reversal occurs at an initial portion 26 of the interaction structure 20, which imparts an angular velocity on the electron beam, resulting in the beam spiraling as shown at 22. An RF signal is introduced into the interaction structure 20 through one or more couplers 24. The RF signal interacts with the spiraling beam and energy from the beam transfers to the moving wave. At the end of the interaction structure 20, the spent electron beam exits the interaction structure through the second aperture 28 and is gathered in the collector 30. Before exiting the interaction structure 20, the spiraling beam 22 passes a second magnetic field reversal, which linearizes the beam. The now linear beam enters the collector 30 and is rapidly decelerated by numerous stages of depression electrodes 32. Each of the stages of depression electrodes 32 have increasingly negative voltages applied to rapidly decelerate the electrons of the linearized beam, so that only a small portion of the electrons reach the back wall 34 of the collector 30. By dispersing the electrons in this manner, the electrons do not focus on any one individual point in the collector, which would generate excess heat that can overstress or cause damage to the collector structure. In the absence of the first field reversal, the individual electrons of the beam 18 would produce the small orbit beam 48 shown in FIG. 3. Rather than gyrating about the centerline of the beam, the individual electrons would gyrate around the magnetic field lines within the interaction region 25. The radius of the orbit path around the magnetic field lines is known as the Larmor radius of the beam. In a small orbit beam, the Larmor radius is relatively small relative to the guiding center of the beam. However, in a large orbit beam the Larmor radius is roughly equivalent to the radius relative to the guiding center of the beam. Referring now to FIGS. 4 and 5 there is shown an electron gun 50 of the present invention. The gun has an outer support structure 51 and a backwall 55. The structure 51 is generally cylindrical in shape, as are a majority of the components of the electron gun. Due to this cylindrical geometry, the side view of FIG. 4 shows the symmetry of the gun. Thus, it should be apparent that like elements from the upper and lower portions of the figure are counterparts of the same component. An internal cylindrical structure 57 supports the gun assembly as will be described below. Insulating support cylinders 52 and 53 are disposed concentric within the outer structure 51 and inner cylinder 57. The support cylinders 52 and 53 electrically insulate the various components of the gun and provide structural support for the cathode components. A cathode support ring 54 is secured to an end of the insulating support cylinder 53. The support ring 54 and support cylinder 53 can be secured together by brazing or other known joining technique. The support ring 54 is annular in shape and extends inwardly relative to the support cylinder 53. A cathode assembly 56 is secured to an inner diameter portion of the cathode support ring 54. The cathode assembly 56 has an inner core 58 with a heater filament 62 disposed below an external emitting surface 64. The emitting surface 64 has a generally concave annular shape. A highly negative voltage of approximately -5 kilovolts is applied to the cathode emitting surface 64. The internal heater filament 62 increases the temperature of the surface to produce thermionic emission of electrons from the surface. At an outside diameter and inside diameter of the emitting surface 64, outer and inner focus electrodes 65 and 66 are disposed, respectively. The focus electrodes 65 and 66 are electrically connected to the emitting surface 64, and contribute to shaping the electric field as will be further described below. In the preferred embodiment, the focus electrodes 65 and 66 form a 62.5° angle with the emitting surface 64. The focus electrodes 65 and 66 ensure that the electron beam remains uniform as it exits the cathode. Adjacent to the cathode emitting surface 64, outer and inner beam control electrodes 67 and 68 are provided. The inner beam control electrode 68 extends from a support cylinder 74 having a lower flange which mounts to an insulator ring 76 secured to a rear portion of the cathode assembly 56. The outer beam control electrode 67 extends from a support cone 72 which attaches to the insulating support cylinders 52 and 53. The support cone 72 has an annular ring portion 73 which is sandwiched between the support cylinders 52 and 53. The ring portion 73 secures to the support cylinders 52 and 53 by known joining technique, such as by brazing. A bias voltage of approximately 100 volts may be applied between the inner and outer beam control electrodes 67 and 68, as will be further described below. An anode 80 is disposed a fixed distance from the cathode and the beam control electrodes 67 and 68. The anode 80 has an external surface 82 having a generally angled portion which contributes to shaping the electric field. The angle formed between the anode surface 82 and the cathode emitting surface 64 is roughly equal to the angle formed between the emitting surface and the center post 84. The anode 80 is maintained at ground potential, and thus is highly positive with respect to the cathode. Typically, the anode 80 is made of copper material. The center post 84 is disposed along a centerline of the electron gun 50, and is concentric with the cathode assembly 56. The center post 84 has a rounded cap 86 which extends into the first aperture 26 leading to the interaction region 100. The center post 84 is rigidly secured to the back wall 55 of the electron gun by a support cone 94. It is critical that the center post 84 be as stiff as possible, since any deformation of the center post would alter the electric and magnetic fields and consequently the electron beam. With the negative voltage applied to the cathode, an electric field is formed between the cathode surface 64, the anode 80, and the center post 84. Since the cathode surface 64 is highly negative with respect to the anode 80 and center post 84, a beam of electrons 18 are drawn from the emitting surface 64. The electron beam 18 and the equipotential lines 124 of the electric field are shown graphically in FIG. 5. The equipotential lines 124 fall along the outer surface of the center post 84. Since the center post 84 carries the magnetic flux enclosed by the beam, no magnetic field variation occurs across the cathode surface. The cathode 56 and control electrodes 67 and 68 are enclosed within the iron cylinder 57 and backwall 55 such that the cathode region is magnetic field free. All the magnetic flux that would normally be present within the cathode diameter is carried by the center post 84. The electron beam 18 follows a path which is generally perpendicular to the equipotential lines. Thus, it should be apparent that the direction of the beam can be controlled by selecting the angle of the anode surface 82 relative to the position of the center post 84 to control the shape of the equipotential lines. A beam control voltage is provided between the cathode surface 64 and the beam control electrodes 67 and 68. This beam control voltage is up to 4,000 volts, and provides electrostatic focusing of the beam 18. The shape of the beam control electrodes 67 and 68 produces a compound electrostatic lens which causes beam divergence 120 at the entrance of the lens and beam convergence at the exit 70. This has the effect of increasing the annular width of the beam and extends the "throw" of the beam. The throw of the beam is the distance from the cathode emitting surface 64 to the plane where the annular width of the beam is at its minimum value. This minimum annular width plane is positioned at the center of the magnetic field reversal described below, in order to achieve minimum velocity spread in the beam. The electrostatic lens effect is shown graphically in FIG. 5. Between the inner and outer beam control electrodes 67 and 68, a small bias voltage is applied to deflect the beam trajectories slightly in order to optimize the entrance angle into the magnetic field reversal. This voltage is nominally less than one percent of the cathode to anode voltage. Thus, varying the shape, control voltage and bias voltage of the beam control electrodes 67 and 68 each contributes to altering the orbit radius of the beam, and its velocity and guiding center spread. Once the circular beam reaches the interaction region 100, it remains focused at the minimum orbit radius by the magnetic field disposed within the interaction region. The individual electrons of the beam would tend to gyrate around the magnetic field lines, producing a small orbit beam. However, if it is desired to produce a large orbit beam, a larger portion of the electron's axial velocity must be converted to a transverse or angular velocity. To accomplish this, a magnetic field reversal is provided. As known in the art, a magnetic field reversal would impart an azimuthal force on the moving electrons. The field reversal can be accomplished by simply reversing the polarity of the magnetic field B o within the interaction region forming a boundary in which the field changes from +B o to -B o . However, it has been found that an abrupt change in field causes ripples or scalloping of the beam downstream from the field reversal point. The scalloping causes inefficient CRM interaction and should be avoided. To minimize this scalloping, a triple polepiece magnetic field reversal element is applied. An example of a triple polepiece element is shown in FIG. 6a. The element comprises outer polepieces 132 and 133, a first inner polepiece 134, a second inner polepiece 136, and a third inner polepiece 138. Outer magnets 142 and 143 are provided between the outer polepiece 132 and first inner polepiece 134, and the outer polepiece 133 and third polepiece 138, respectively. Inner magnets 144 and 145 are disposed between the first and second inner polepieces 134 and 136 and the second and third inner polepieces 136 and 138, respectively. As shown in FIG. 6a, the polarity of the outer magnet 142 and inner magnet 144, are equivalent, as are the outer magnet 143 and inner magnet 145. These magnets can be either permanent magnets or solenoid coils. The arrangement results in the change in magnetic flux density Z shown in FIG. 6b. There is an abrupt change in the magnetic field, from +B o to -B o , during which there is a point of zero magnetic flux Z o . FIG. 6c shows the behavior of the electron beam 18 passing through the reversal point at Z o . At the first portion of the beam, the beam rotation Θ is equal to zero. After the field reversal, the rotation of the beam Θ is equal to the cyclotron frequency ω c . The triple polepiece magnetic field reversal is applied in the present invention to initiate gyration of the hollow electron beam 18. To further minimize the scalloping of the beam, and to produce a more uniform axial and transverse velocity, the polepieces are tapered to minimize the axial length of the zero magnetic field region. Referring to FIG. 4, a first polepiece 102 is disposed at the beginning of the interaction region 100 and has the anode 80 secured thereto. A first magnet 104 is disposed adjacent the first polepiece 102 and adjoins a second polepiece 106. Similarly, a second magnet 112 is disposed alongside the second polepiece 106 and a third polepiece 114. Both the second and third polepieces 106 and 114 have tapered surfaces 108 and 116, respectively. The tapered surfaces 108 and 116 are generally convergent, and result in end points 110 and 118, respectively. It has been found that these tapered polepieces effectively reduce the axial length of the zero magnetic field region, and further minimize deformation of the gyrating beam 18 after the field reversal point. The preferred embodiment of an advanced center post gun 150 of the present invention which takes advantage of the inventive concepts discussed above, is shown in FIGS. 7 and 8. The gun has an outer support structure 151 and a back wall 155. An insulating support cylinder 152 is disposed concentric within the outer structure 151 and provides structural support to the cathode assembly 156. The cathode assembly 156 has a heater filament 162 disposed below the emitting surface 164. The emitting surface 164 has a generally annular conic shape. Outer and inner focus electrodes 165 and 166, respectively, are disposed adjacent the emitting surface 164. Outer and inner beam control electrodes 167 and 168 are provided adjacent the cathode emitting surface 164. The outer and inner beam control electrodes 167 and 168 are physically supported by the insulating support cylinder 152. To provide electrical connection to the cathode emitting surface 164, the heater filament 162, and the inner and outer control electrodes 167 and 168, a plurality of electrical feedthroughs 170 1 and 170 2 are provided. Each feedthrough is formed of an electrically insulative and thermally conductive material, such as ceramic. The feedthroughs 170 have a central conductive core 172 which provides electrical conduction from outside the gun 150 to within the gun. The internal portion of the feedthrough has a plurality of thermally radiating fins 174. An extension rod 176 carrying a wire 178 extends from the core 172 to a depth equivalent with the component to which the electrical connection is desired. In FIG. 7, a first feedthrough 170 1 is shown providing an electrical connection to the cathode heater 162, and a second feedthrough 170 2 is shown providing a connection to the inner control electrode 167. Although not shown in the figure, it should be understood that a third feedthrough provides an electrical connection to the cathode emitting surface 164, and a fourth feedthrough provides an electrical connection to the outer control electrode 168. An anode 180 is shown disposed adjacent to the cathode assembly 156 and control electrodes 167 and 168. As described above, an angle formed by the anode surface 182 is selected so that the electron beam roughly bisects the angle between the anode surface 182 and the center post 184. FIG. 7 shows an estimated convergence point within the interaction region 200 of the gyrotron. The triple polepiece field reversal element is also shown, with a center polepiece 206 having a tapered end 208, and an outer polepiece 214 with a tapered end 216. The tapered ends 208 and 216 converge towards each other. In the preferred embodiment, the field reversal point approximately coincides with that of the beam convergence point. Also included in FIG. 7 is an ion pump 190. As known in the art, the generation of an electron beam often results in the development of undesired ions within the gun structure 151. The ion buildup can be detrimental to the operation of the gun. Accordingly, the pump 190 removes ions from within the gun structure 151 and maintains a near vacuum environment. As described above, it is necessary to maintain the center post 184 at a near uniform temperature so as to avoid deformation of the center post surface. To accomplish this, a coolant fluid radiates from intake 193 into the center post 184 and through spiral channels 192 disposed below the surface of the center post as shown in FIG. 8. The coolant fluid then exhausts through center drain 188 to exhaust line 195. The center post 184 is rigidly secured to the back wall 155 by the use of a support cone 194. Having thus described a preferred embodiment of an advanced center post gun, it should now be apparent to those skilled in the art that the aforestated objects and advantages for the within system have been achieved. Although the present invention has been described in connection with the preferred embodiment, it is evident that numerous alternatives, modifications, variations, and uses will be apparent to those skilled in the art in light of the foregoing description. For example, alternative materials, joining techniques, voltages, and spacing can be selected to vary the operating characteristics of an electron gun as contemplated by the invention.

An advanced center post (ACP) gun is provided which is capable of producing either a large orbit or small orbit electron beam. The gun comprises an annular shaped cathode, a control electrode adjacent the cathode, and an annular anode having an opening therethrough. A center post is disposed axially within the center region of the cathode and the control electrode along a center line of the electron gun and interaction region of a microwave device. The anode is shaped in conjunction with the center post to control position of equipotential lines of an electric field provided in an inter-electrode space between the cathode and the anode so that an electron beam emitted by the cathode converges at the anode opening. The control electrode provides electrostatic focusing of the beam to further control the beam convergence. Multiple polepieces provide accurate control of the magnetic field in the interaction region to shape the beam and control the orbit size and velocity spread.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to drain valves and drain valve systems for use in water supply systems requiring periodic purging of the water supply systems. 2. Description of Prior Art Generally underground watering systems with drain valves that automatically drain the water from underground water supply pipes to prevent freezing and rupture of the water supply pipes are well known in the art. My U.S. Pat. No. 3,779,276 shows one such drain valve. The drain valve includes a resilient valve member which prevents water from escaping from the underground water system under high water pressures but opens as the water pressure decreases to permit the water in the underground water lines to drain into the surrounding soil. My U.S. Pat. No. 4,890,640 shows another type of drain valve having a nonextrudable sealing member. This valve is well-suited in locations where pressure surges occur in the water supply line, since the drain valve contains a valve member that is nonextrudable in relation to the discharge opening. Consequently, the drain valve continues to function normally even though high-pressure surges occur which could normally blow out other valve members. The present invention comprises an improvement over U.S. Pat. No. 3,779,276 by providing a family of drain valves which can be made to operate under different pressures by changing the internal valve member of the drain valve. One feature of the invention is a drainage system that conserves water by retaining a portion of the water in the underground water lines. A further feature of the invention is a field modifiable drain valve which can be set to operate under various field conditions. Still another feature of the invention is a water drainage system having at least two drain valves responsive to different operating pressures to accommodate the different water pressures at different locations in the watering system. BRIEF SUMMARY OF THE INVENTION Briefly, the present invention includes a drain valve modifiable for use under different water pressures by merely changing the material of valve member within the drain valve. The drain valves that respond to local water pressure conditions ensures proper functioning of the drain valve in response to the local water pressure. In addition in one embodiment the drain valves include an extended screened inlet port that project into the water supply line to prevent complete drainage of the irrigation system and thus conserve water from one watering cycle to the next. BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a partial schematic view of a house with an irrigation system located around the house; FIG. 2 is a sectional view of one embodiment of my invention in the drain mode; FIG. 3 shows an sectional view of an alternate embodiment of my invention in the drain mode; FIG. 4 is a top view taken along lines 4--4 of FIG. 3; FIG. 5 is a partial sectional view of an alternate embodiment of my drain valve; FIG. 6 shows an insert from my drain valve to control the outlet drain area; FIG. 7 shows an alternate embodiment of my invention for use in large-volume water systems; FIG. 8 shows a partial cutaway view of a water conservation system; FIG. 9 shows a drain valve with an extended screened inlet port for use in a water conservation irrigation system; and FIG. 10 shows the valve member or resilient plug used in the drain valve. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 reference numeral 10 generally identifies a lawn surrounding a house 11. Connected to the water supply of house 11 is an underground irrigation system 12 having a plurality of sprinkler heads identified by reference numeral 20. The sprinkler heads are known in the art and comprise a general circular member with a plurality of holes to discharge water to the lawn area surrounding the sprinkler head. Irrigation system 12 generally comprises three different pressure regions a high-pressure region, an intermediate-pressure region and a low-pressure region. In general the water pressure in the water lines decreases as the water flows through the water lines and is diverted from the water lines to irrigate the lawn. Typically one may have a water pressure of 120 psi at the inlet to the irrigation system and only 10 to 15 psi at remote portions of the irrigation system. House 11 includes a high pressure water supply 21 which directs high pressure water to a vacuum breaker valve 22. Water from vacuum breaker valve 22 flows into primary high pressure water supply pipes 23 and 24. Water supply pipe 23 directs high pressure water to three remotely controlled electric solenoid valves 31, 32, 33 and 34. Similarly, water pipe 24 directs high pressure water to three remotely controlled electric solenoid valves 34, 35 and 36. Connected to water supply lines 23 and 24 are three high pressure drain valves identified by reference number 30H. High pressure drain valves 30H are located in a portion of the water supply line closest to the source that generally contains the highest water pressure in the irrigation system. Connected to solenoid valve 35 is a secondary water line 40 that contains a number of sprinkler heads 20 and four underground drain valves 30M. The secondary waterline contains intermediate water pressures that are generally less than the water pressure in primary water lines 23 and 24. Reference numerals 38, 39, 40, 41 and 42 identify similar secondary water lines wherein the water pressure is generally less than the water pressure in water lines 23 and 24. Connected to solenoid valve 34 is a tertiary low pressure drip irrigation system having a first pipe line 48 and a second pipe line 49. Typically drip irrigation systems contain restrictions to reduce the water pressure to permit slow irrigation of area such as shrubs or bushes around the house. While a drip irrigation system can be used to irrigate selected areas one can also use sprinkler heads that operate with low water pressures. In general, the water pressure in tertiary lines 48 and 49 is considered low relative to the water pressure in the primary and the secondary water lines. Connected to the low pressure tertiary lines 48 and 49 are three low pressure drain valves 30L that permits one to drain water from the low-pressure underground lines 38 and 49. The irrigation system shown in FIG. 1 comprises three zones of different water pressure: a primary high pressure zone proximate to the water supply, a secondary intermediate-pressure zone extending outward from the primary high pressure zone and a third low-pressure zone. The pressure in each zone is an inherent function of the line loses as water flows through the lines as well as an effect of continually diverting water from the water lines. Also if the irrigation system is located on a hill the variation in the location of the water lines can produce pressure differences in the water lines. One of the difficulties with complicated underground watering systems is that if the variation in water pressure within the water lines is extreme one set of drain valves may not properly work with the underground water system. For example, the water line pressure in the underground water line systems 23 and 24 may be 120 psi, the water line pressure in the secondary lines may be 60 psi, and the water pressure in the tertiary lines may have water pressure of 10 to 15 psi. To have an underground water system that closes the drain valves as the water pressure increases and opens the drain valves as the water pressure decreases one should match the drain valve operating pressures to the local water pressures in the underground water system. The present invention provides drain valves for use in each of the three or more pressure zones of the irrigation system of FIG. 1. FIG. 2 illustrates a preferred embodiment of drain valve 30 that operates under different line pressures. Drain valve 30 includes a housing 61 having a drain pad 62 located beneath housing 61. Drain pad 62 disperses water from the water line to the surrounding subsoil. Located in the upper portion of housing 61 is a resilient plug 64 forming a resilient two-way valve member which has a top conical portion 69 that seals against an annular seat 63a on one end of top member 63. Located on the opposite end of member 64 is a lower sealing surface 64a that seals against a seat 70 having a plurality of discharge openings 65 located therein. Resilient plug 64 is shown in greater detail in FIG. 10. Resilient plug 64 includes resilient nipples 52, neck 60, and retaining end 64b which has an end surface 64a that abuts against support surface 70, resilient plug 64 and the resilient nipples 52 are known in the art and do not constitute a novel part of this invention. Other types of resilient plugs or valve members suitable for use in my invention are shown in U.S. Pat. No. 4,890,640. Extending from surface 70 and into region 66 are a plurality of drain openings 65 which permit water to flow around member 64 when it is in the relaxed condition as shown in FIG. 2. In general, member 64 comprises a resilient material such as rubber, flexible PVC or santoprene or the like. The inherent resiliency of the material forming member 64 permits member 64 to move in response to the water pressure in the drain valve. That is, under high-water pressure at the inlet 63b, member 64 seals the drain openings 65 thereby preventing water from draining into the soil surrounding drain valve 30. When the pressure is removed from the water line, the resiliency of member 64 causes member 64 to move upward to the position shown and allow water to drain around member 64 and into the subsoil surrounding drain pad 62. In the preferred embodiment member 64 is made of a material that is about the same spedific gravity as the fluid being directed through valve 30. If member 64 floats then any fluid attempting to flow back into the water lines will be sealed off from the drain lines by member 64 seating and sealing against upper seat 63a. One feature of the present invention is the creation of a family of drain valves that can open and close under different water pressures to permit the irrigation installer to match the operating pressures of the drain valve to the local pressures in the water lines. For example, adding additional sprinklers in a specific zone can create a different operating pressure in that zone. By matching the operating pressures of the drain valve to the local water pressures the installer insures that the system operates properly. For example, in a typical system that has an extended irrigation system the pressure at the end of the water line may never get above 10 psi. If the water pressure never gets above 10 psi one should have a drain valve that closes at less than 10 psi. Yet the primary pressure zone of the irrigation systems may require a drain valve that closes at 40 psi. Obviously, a drain valve that closes at 40 psi would not be useable in the portion of the system where the pressure does not exceed 10 psi. In order to have the drain valves close as the water begins to flow through the pipes the drain valves in the secondary and tertiary zones should have drain valves that are more sensitive to lower closing pressures. A method for installing drain valves in an irrigation system having zones of high and low pressure includes the step of determining the primary high pressure region and the secondary low pressure region of the irrigation system. A user then attaches a drain valve responsive to high pressure to the high pressure region of the irrigation system. In order to permit the installer to readily identify where the drain valve is to be located a visual indication such as a colored drain valve housing allow an installer to quickly identify that the drain valve should be located in said high pressure region. The user then attaches a different drain valve responsive to low pressure to the low pressure region of the irrigation system. In order to permit the installer to readily identify where the low pressure drain valve is to be located a visual indication such as a different colored drain valve housing allow an installer to quickly identify that the drain valve should be located in the low pressure region. While only two pressure regions are described it is apparent that if desired one can break the irrigation pressure zones into multiple zones of different pressures and use multiple drain valves. For example, four differently colored drain valves each responsive to five different pressures can be used in an irrigation system. One may use an orange drain valve for the main high pressure line, a green drain valve for a lower pressure lateral line, a yellow drain valve for placing next to solenoid valves of the irrigation system, and a blue valve to place under sprinkler heads in the irrigation. With the drains continuing visual indicators such as colored housing it permits the installer to quickly install the drains in their proper location. The present invention provides for modification of known drain valves to create a family of identical appearing drain valves that are only distinguishable by visual indicators incorporated into the drain valve. That is, drain valves 30 substantially identical except for resilient plug or member 64. I have found that I can create a family of drain valves for use through the watering system by only changing the durometer of member 64. By changing the durometer or the hardness of member 64 I have been able to create a family of drain valves to operate under different pressures. The below-listed table indicates the average operating pressures and average durometers of resilient plug 64 for identical drain valve housings. ______________________________________ OPENINGVALVE CLOSING PRESSURES PRESSURESDURO- 70% 90% 100% 10% 100%METER CLOSED CLOSED CLOSED OPEN OPEN______________________________________40 3 psi 5.5 psi 5 psi 3 psi50 6.5 psi 10 psi 11 psi 10 psi 4.75 psi60 8 psi 11 psi 16 psi 14.5 psi 6 psi70 9 psi 20 psi 15 psi 7 psi80 17 psi 40 psi 30 psi 11 psi______________________________________ The table shows that if drain valve 30 is fitted with a sealing member 64 having a durometer of 40 the drain valve is approximately 90 percent closed at about 3 psi and is 100 percent closed at about 5.5 psi. When the same drain valve 30 is fitted with a sealing member having a durometer of approximately 80 the drain valves is approximately 70 percent closed at 17 psi and is 100 percent closed at 40 psi. Consequently, the changing of the durometer of sealing member 64 changes the operable range of closing pressure of the drain valve. In addition to changing the closing pressure, the pressures at which the valve opens to drain water into the surrounding subsoil also changes with a change in the durometer of sealing member 64. Note if drain valve 30 had a two way sealing member 64 with a durometer of 40 the drain valve starts to open when the pressure decreases to approximately 5 psi and is fully open when the pressure is less than approximately 3 psi. Similarly, when drain valve 30 has a sealing member of a durometer of approximately 80, the drain valve begins to open as the pressure decreases to approximately 30 psi and is fully open when the pressure decreases to approximately 11 psi. The above table showing opening and closing pressures are approximate average values of pressures and are provided as guidance to show the relative difference of operating pressures one can produce a family of valves by only changing the durometer of the resilient sealing member 64. Consequently, one can use the identical housing for each drain valve and install the proper sealing member 64 to produce a drain valve that operates properly in the normal pressure ranges. Referring to FIG. 3 reference numeral 70 shows an alternate embodiment of a drain valve that is similar to drain valve 30, except instead of having a drain pad, it includes a lower housing 71 with threads 72 for attachment to a sump line. Since use of drain valve 70 with a sump may now require the drain valve to prevent backflow drain valve 70 contains a one-way valve that does not prevent back flow. FIG. 4 shows a top view of drain valve 70, showing drain opening 65 spaced in top member 78. Illustrated by dotted lines is the normal position of the exterior cylindrical portion of sealing member 64. Reference numeral 79 indicates the cylindrical side wall of the drain valve that confines member 64 from lateral movement. Note, in any lateral position of valve member 64 the exterior cylindrical surface of member 64 are over drain openings 65. That is drain holes 65 are spaced sufficiently inward from the exterior so that a portion of resilient valve member 64 always covers the openings regardless of the lateral position of valve member 64. FIG. 5 shows an alternate embodiment of the invention which includes a valve housing 90 having a resilient sealing member 64 therein. Housing 90 has a member 91 extending across valve housing 90 with an opening 92 having an insert 93 fitted therein. The purpose of insert 93 is to reduce the diameter of the drain passage of an existing drain valve. Insert 93 is shown in greater detail in FIG. 6 and comprises a first cylindrical section 94 and a second cylindrical head section 95. Extending completely through both cylindrical head sections is an opening 92. Insert 93 permits a user to adjust the size of the drain holes in the valve by merely inserting one or more inserts into the drain valve. That is, member 93 may be made from a polymer plastic and can be fastened into an opening 92 in drain valve 90 with a solvent cement or the like. Thus an operator can adjust the size of the drain passage by merely placing an insert into the housing 90. If desired the operator can place the insert 93 in from the top to allow a field user to change the drain passage area. Referring to FIG. 7 reference number 100 generally identifies an alternate embodiment of my drain valves for use in areas where large volumes of water may be drained or discharged from a water line. Drain valve 100 includes a drain pad 101, a housing 102, a lower multiple seat 103, having a plurality of drain passage openings 104, 105, 106 and 107. Located directly above opening 104 is a first resilient valve member 110. Located directly above opening 105 is a second resilient valve member 111, located above opening 106 is a third valve member 112 and located above opening 107 is a fourth valve member 113. Extending across the top of housing 102 is a top seat 120 which has a set of openings 121, 122, 123 and 124. The resilient valve members 110, 111, 112 and 113 are identical in size and shape and operate in the same manner as the resilient valve member of FIG. 2. However, instead of having only one resilient member in the housing, the present invention has multiple resilient valve members. A feature of the embodiment shown in FIG. 7 is that the valve can be made tuned more precisely for high and low pressure openings and closings where large volumes of water are discharged. For example, if one wants a drain valve to begin closing at a low pressure so the water pressure can begin to build up in the system one or more of the resilient valve members can be made of sufficient durometer to open and close with pressures as low as 3 to 5 psi while the remaining resilient valve members can be made of different material that allows the valve 100 close at pressures of 17 to 40 psi. Consequently, by using resilient valve members of different hardness one can produce a sequencing effect where drain passages continue to close as the pressure increases or the drain passages begin to open as the pressure decreases. FIGS. 8 and 9 show an alternate embodiment of my system for conservation of water in the drain lines. One of the problems with irrigation, particularly in climates with limited water supplies, is that the water should not be unnecessarily wasted. Since the underground water lines contain substantial amounts of water, it would be desirable if some of the water could be retained in the water lines, yet one does not want to retain sufficient water in the lines so that if freezing occurs, the underground lines rupture and break. For example a 3/4 inch irrigation system may require any where from 10 to 20 gallons of water to fill the underground water lines. If only half of the water was drained from the underground irrigation lines each time the lawn was irrigated there would be a saving of 5 to 10 gallons of water each time the irrigation system is used. The present invention provides an underground drain valve 130. Drain valve 130 is identical to drain valve 30 except drain valve 130 has an upwardly extending neck 131 with an inlet port having a series of openings 132 to permit water to enter drain valve 130. To illustrate how drain valve 130 operates to conserve water and yet prevent freezing, refer to FIG. 8. A first drain valve 130 and a second drain valve 130 are attached to opposite ends of an underground water line 141 having a spray head 142. Underground water line 141 could be a portion of any the underground lines shown in FIG. 1. The water level in the line 141 is indicated by reference numeral 143. Note that the water drains to the top surface of each drain valve inlet port 132 and remains in the underground line 141 since the water can not flow upward and through the openings 132. Thus by controlling the height H that the extension 131 extends into the underground water system, one can generally control the amount of water left in the water line. Preferably, one would leave about one-half of the water in the line using underground drain valves 130. A further feature of having a screen located over the inlet to the drain valve that is spaced sufficiently far into the water supply pipe so that the water flowing past the screen produces a cleaning action on the screen to remove particles deposited on the screen. While my drain valve is shown in use for underground watering systems my drain valve can also be used as a flush valve at the end of an underground watering system. Other applications of my drain valve are as a boat drain valve, an air compressor drain valve, an overhead fire sprinkler drain, or as a drain valve for a heating and cooling condensers.

A drain valve modifiable for use under different water pressures by merely changing the material of valve member within the drain valve. The drain valves are used in a fluid system to produce a fluid system that respond to local water pressure conditions. In one embodiment the drain valves include an extended inlet port that project into the water supply line to prevent complete drainage of the irrigation system and thus conserve water from one watering cycle to the next. Another embodiment of the drain valve includes multiple resilient members for sequence action in opening and closing of the drain valve. Still another embodiment permits a user to change the size of the drain passage by placing an insert in the drain passage of the drain valve.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not applicable. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not applicable. BACKGROUND [0003] 1. Field of the Disclosure [0004] The present disclosure relates generally to the shale shaker screens used to filter solids out of drilling mud. [0005] 2. Description of Related Art [0006] When drilling a well (e.g., for oil or gas), a drill bit is attached to the end of a drill string and drills a hole through the subsurface to access the oil or gas reservoir. Drilling fluid is used during drilling operations. Drilling fluid comprises, for example, a finely ground clay base material to which various chemicals and water are added to form a viscous fluid designed to meet specific physical properties appropriate for the subsurface conditions anticipated. This drilling fluid is pumped down the hollow drill pipe, through the drill bit and returned to the surface in the annular space between the drill pipe and the well bore. [0007] The drilling fluid serves three main purposes. First, it aids in cooling the drill bit and thereby increasing its useful life. Second, the mud flushes the cuttings or “solids” from the well bore and returns them to the surface for processing by a solid control system. Third, the mud leaves a thin layer of the finely ground clay base material along the well bore walls which helps prevent caving in of the well bore wall. [0008] Although often referred to simply as “mud,” the drilling fluid is a complex composition which must be carefully engineered and tailored to each individual well and drilling operation. The drilling fluid is costly and, thus, is cleaned and reused in a closed loop system in which a solids control system and a shaker play important roles. [0009] A shaker, often referred to as a “shale shaker,” is part of a solids control system used in oil and gas drilling operations to separate the solid material (“solids”), removed from the well bore by the drilling operation, from the drilling mud. For the drilling fluid to be used and reused, it must be processed after returning from the well bore to remove the aforementioned solids and maintain its proper density, often expressed as pounds per gallon or “mud weight”, i.e., 10 lb./gal. mud or “10 lb. mud”. The first step in processing the returned drilling fluid is to pass it through a shaker. The returned drilling fluid from the flow line flows into a possum belly, a container mounted at one end of the shaker, and then flows over one or more screens. A shaker includes a support frame on which the shaker screen is mounted. One or more motors in the shaker causes the screen assemblies to vibrate or oscillate, depending on the type of motors utilized. The vibrating action of the screens over which the mud passes removes larger particle size solids (e.g., in the 200 to 700 micron size range) while allowing the drilling fluid and smaller particle size solids to pass through the screen. Solids, which are discarded from the top of the shaker screen, discharge into a pit or onto a conveyor for further treatment or disposal and the underflow drilling fluid flows into the tank below. [0010] A common means to secure the screen in the shaker is through the use of a wedge block. A wedge block is typically inserted between the screen and a bracket located along the inside walls of the shaker. The wedge block is pushed further back under or into the bracket, in turn pushing the wedge downward onto the screen and onto the shaker. Two wedges are typically used per screen, but other combinations of wedges may be utilized. [0011] A common means to seal the screen in the shaker is through the use of gaskets secured to the shaker at the screen interface. The gasket is typically secured to the shaker with various fasteners that wear out due to contact with the drilling fluid and solids. Thus, maintenance is required to replace worn gaskets and/or fasteners. Replacing the gaskets is time- and labor-intensive—the shaker must be taken offline, the wedge blocks removed, the screens removed, the fasteners ground off, the old gasket material removed, and the new gaskets installed with new fasteners, and then the screens and wedge blocks reinstalled. [0012] Accordingly, there remains a need in the art for a shaker screen and sealing gasket capable of easy and efficient replacement, while retaining the necessary securing and sealing properties within a shaker device. SUMMARY OF THE PRESENT DISCLOSURE [0013] The embodiments described herein are generally directed to a means for securing and sealing a shaker screen in a shaker device. [0014] In an embodiment, an assembly for securing and sealing a shaker screen in a shaker device comprises a shaker screen with tapered side members on which an elastomeric or plyable gasket is adhered. The assembly also comprises a support frame with angular channels that sealingly mate with the gaskets on the side members of the screens. The assembly further comprises a central, angular, bar anchor affixed to the shaker in between each group (upper and lower) of two shaker screens; the central, angular, bar anchor comprises an angular channel on each side, each of which retains a side member of a shaker screen. In addition, the assembly comprises a wedge block retention bracket affixed to the shaker side walls above each shaker screen. Moreover, the wedge block is insertable between the wedge block retention brackets and the shaker screens, providing forces both down onto the screen side member and laterally onto the tapered screen side member, which further presses the screen side member with a gasket into the angular channel of the central, angular, bar anchor, creating a seal. [0015] Thus, embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the embodiments described herein. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0016] For a more detailed understanding of the preferred embodiments, reference is made to the accompanying Figures, wherein: [0017] FIG. 1 is a perspective view of an embodiment of a shaker made in accordance with the principles described herein. [0018] FIG. 2A is a top view of an embodiment of a shaker screen made in accordance with the principles described herein. [0019] FIG. 2B is a side view of the screen shown in FIG. 2A . [0020] FIG. 2C is a perspective view of a portion of the screen shown in FIG. 2B . [0021] FIG. 3A shows a lateral cross-sectional view of the screen shown in FIG. 2A . [0022] FIG. 3B illustrates a perspective view of the screen shown in FIG. 3A . [0023] FIG. 4A is a view of the front face of an embodiment of a wedge block made in accordance with the principles described herein. [0024] FIG. 4B is a side view of the wedge block shown in FIG. 4A . [0025] FIG. 4C is a perspective view of an embodiment of a wedge block installed in a shaker in accordance with the principles described herein. [0026] FIG. 5A is a perspective view of an embodiment of a shaker support frame in accordance with the principles described herein. [0027] FIG. 5B shows a lateral cross-sectional view of a portion of the support frame shown in FIG. 5A . [0028] FIG. 6A is a perspective view of an embodiment of a central, angular, bar anchor in a shaker in accordance with the principles described herein. [0029] FIG. 6B is a partial schematic view showing an embodiment of a screen being installed in a shaker in accordance with the principles described herein. [0030] FIG. 6C is a partial schematic view showing an embodiment of a screen installed in a shaker in accordance with the principles described herein. [0031] FIG. 7 is a perspective view of an embodiment of a shaker made in accordance with the principles described herein. NOTATION AND NOMENCLATURE [0032] Certain terms are used throughout the following description and claim to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function. Moreover, the drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. [0033] In the following discussion and in the claims, the term “comprises” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0034] FIG. 1 depicts a shaker 500 in accordance with various embodiments. In the example of FIG. 1 , a plurality (e.g. 4) of shaker screens 100 is secured to the shaker 500 using both a central, angular, bar anchor 530 (anchor) and a wedge block 200 with a wedge block retention bracket 540 . In other embodiments, only a single screen may be used. Though all four screens 100 and both anchors 530 , 535 are visible, only one of the four wedge block retention brackets 540 and one of the four wedge blocks 200 are visible in the perspective view of FIG. 1 . It should be appreciated that there are four wedge block retention brackets 540 , each with a wedge block 200 , in the illustrative shaker 500 shown in FIG. 1 . The shaker 500 also comprises a gumbo tray 520 and a possum belly 510 . [0035] FIG. 2A illustrates a top view of a shaker screen frame 100 . In a preferred embodiment, the screen frame 100 comprises side members 105 , 110 and a plurality of cross members 115 that extend between and are secured to side members 105 . The screen frame can further comprise a plurality of mesh screens (not shown) disposed on the cross members 115 . The type and size of mesh screen (not shown) installed on the screen frame 100 can vary and does not affect the principles relied on herein; thus, shaker screen frame 100 will hereinafter be referred to simply as shaker screen 100 or screen 100 . The cross members 115 preferably comprise square tubular members typically with smaller dimensions than the side members 105 , 110 . The side members 105 , 110 are comprised of tubular members that are tapered at the sides (as will be discussed below in greater detail). Welds may be used to secure each end of side members 105 to each end of side members 110 ; welds also secure each end of the cross members 115 to the side members 105 . The tapered configuration of the side members 105 , 110 eliminates shearing weld stress on the screen 100 during shaker 500 operation. In other embodiments (not specifically illustrated) the quantity of cross members 115 may be increased or decreased from that shown in FIG. 2A . [0036] Referring now to FIGS. 2B and 2C , FIG. 2B illustrates a side view of the screen 100 shown in FIG. 2A and FIG. 2C depicts a perspective view of a portion of the screen 100 shown in FIG. 2B . In an embodiment, the screen 100 further comprises an elastomeric gasket 120 that surrounds the outermost edge 130 of all exterior sides (indicated by dashed lines in FIG. 2B ) of the screen 100 and a portion of the side members 105 , 110 . The gasket 120 can be of varying thicknesses and widths and can cover equal or non-equal portions above and below the outermost edge 130 of side members 105 , 110 . For example, the seal may be ½″ wide with a total thickness of 1/16″ and cover ¼″ above and below the outermost edge 130 . For ease of illustration of the screen 100 geometry, the gasket 120 is only depicted in FIGS. 2B and 2C ; however, the gasket 120 can be assumed to be present but not shown in the remaining illustrated embodiments of the present disclosure. [0037] As previously discussed, the side members 105 , 110 are comprised of tubular members that are tapered at the sides, rather than square as with conventional screens. Tapered sides provide the screen 100 described herein with various benefits as explained below. The geometry of the tapered side members 105 , 110 can be more easily understood when viewing the side members 105 , 110 in cross section. FIG. 3A illustrates a lateral cross-sectional view along line 125 of FIG. 2A and FIG. 3B depicts a perspective view of same. Each side member 105 further comprises a tubular member having an inner edge 140 and outer edge 130 , a central axis 150 that runs longitudinally through the center of side member 105 and a horizontal plane 155 , which intersects the central axis 150 , the inner edge 140 , and the outer edge 130 of each side member 105 . Thus, in the cross sectional view, the side members 105 appear tapered at the outermost edge 130 and innermost edge 140 . The taper angle 160 is measured from the horizontal plane 155 to an outer planar surface of side member 105 such that the apex is outer edge 130 . It can be appreciated that a similar cross section 126 , depicted in FIG. 2A , of side members 110 would yield a substantially similar cross-sectional view as that of cross section 125 . Though not shown, the elastomeric gasket 120 would surround the outermost edge 130 of all side members 105 , 110 . [0038] As shown in FIGS. 4A and 4B , wedge block 200 comprises a front face 220 , back face 221 , top end 211 , bottom end 213 , first side 230 , second side 231 , and a central axis 250 that runs longitudinally through and halfway between the first side 230 and second side 231 and halfway between the front face 220 and back face 221 . Wedge block 200 also includes a bottom end 213 made up of two planar surfaces 214 , 216 , which are tapered and intersect to form bottom edge 218 —bottom edge 218 is off center from the central axis 250 such that the bottom edge 218 is located closer to the back face 221 than to the front face 220 as can more easily be seen in FIG. 4B . Wedge block 200 is also provided with a top end 211 that is tapered from the first side 230 and second side 231 toward the central axis 250 . [0039] In an embodiment, the wedge block 200 further comprises a plurality of notches or cutouts including a notch 260 in the top end 211 such that the center of the cut out 260 aligns with the central axis 250 and the notch 260 extends from the front face 220 through the back face 221 . In different embodiments (not specifically illustrated), the cut out 260 at the top end 211 may be off center from the central axis 250 . In an embodiment, the wedge block comprises a notch 225 disposed on both the front face 220 and on the top end 211 , extending from the first side 230 through the second side 231 . Notch 225 also follows the same tapered configuration as the top end 211 , which is tapered from the first side 230 and second side 231 toward the central axis 250 . In the embodiment shown, each wedge block 200 is symmetrical along the central axis 250 , thus, allowing one wedge block 200 to be used with any screen 100 , regardless of the screen's location. [0040] Referring to FIG. 5A , an interface between screens 100 and the shaker 500 comprises a support frame 525 . The support frame 525 includes a plurality of angled support members 548 , 549 that sealingly contact the gasket 120 on side members 105 , 110 of the screen 100 . Referring now to FIG. 5B , which illustrates a lateral cross-sectional view of a portion of the support frame 525 along line 534 shown in FIG. 5A ; a partial outline of a side member 105 of screen 100 (without gasket material) is shown in a substantially installed position merely to provide context. In an embodiment, angle 533 is measured from the top surface 538 to the base 539 of support member 548 . The angle 533 of the support frame members 548 , 549 is substantially the same as the taper angle 160 of side members 105 , 110 as shown in FIG. 3A . In some embodiments, the angle 533 of the support frame members 548 , 549 may be 45 degrees, but can be a different angle in other embodiments. For example, the angle 533 of the support frame members 548 , 549 may be less than 45 degrees. In other implementations, the angle 533 of the support frame members 548 , 549 is greater than 45 degrees. [0041] The screen 100 and wedge block 200 interface with various components of the shaker device 500 , which will be discussed herein in more detail. Referring back to FIG. 1 , a shaker interface with screens 100 comprises a plurality of central, angular, bar anchors 530 , 535 (anchor)—a lower anchor 530 and an upper anchor 535 . Anchors 530 , 535 are disposed axial to the central axis 550 and substantially in the center of shaker 500 such that a screen 100 may fit between the anchor and each side wall 545 of the shaker 500 . Referring to FIG. 6A , anchor 530 further comprises angular channels 531 , 532 that are diametrically opposed to one another. In an embodiment, each angular channel 531 , 532 sealingly retains one side member 105 of each screen 100 . Though only the lower anchor 530 is visible in FIG. 6A , it should be appreciated that the upper anchor 535 , shown in FIG. 1 , comprises angular channels 536 , 537 and operates in substantially the same way as lower anchor 530 . [0042] Referring back to FIGS. 1 and 4C , a shaker interface with screens 100 comprises a plurality of wedge block retention brackets 540 , each configured to retain a wedge block 200 against a screen 100 . Each wedge block retention bracket 540 comprises an elongated substantially “L” shaped member disposed radially from the central axis 550 and attachably connected to the shaker side wall 545 above each shaker screen 100 . A wedge block 200 is insertable between the wedge block retention brackets 540 and the shaker screens 100 such that the back face 221 of the wedge block is flush against the shaker wall 545 and the bottom end 213 interfaces with the screen side member 105 . Though only one of the four wedge block retention brackets 540 and one of the four wedge blocks 200 are visible in the perspective view of FIG. 1 , it should be appreciated that there are four wedge block retention brackets 540 , each with a wedge block 200 , disposed radially from the central axis 550 on the shaker side wall 545 above each shaker screen 100 . Conventional shakers typically require the use of two wedge blocks per screen; the present disclosure uses half as many wedge blocks; thus, greatly reducing installation time. [0043] Further, in an embodiment, each wedge block 200 is symmetrical along the central axis 250 (see FIG. 4A ), thus, allowing one wedge block 200 configuration to be used with any screen 100 —the wedge block 200 is simply oriented such that the back face 221 of the wedge block 200 is always flush against the shaker wall 545 while the top end 211 interfaces with the wedge block retention bracket 540 (see FIGS. 4A and 4C ). Thus, in some embodiments, first side 230 will be inserted under a wedge block retention bracket 540 and in other embodiments, second side 231 will be inserted under a wedge block retention bracket 540 . [0044] Referring to FIG. 1 , before a shaker 500 can be used to remove solids from waste drilling fluids, shaker screens 100 must be installed in shaker 500 . Referring now to FIG. 6A , in an embodiment, a screen 100 is installed into the shaker 500 , by first placing a side member 105 into an angular channel 531 , 532 , 536 , 537 of an anchor 530 , 535 . The mesh layers (not shown) should be facing upward when the screen 100 is installed in shaker 500 . Once the side member 105 is placed in angular channel 531 , 532 , 536 , 537 (see FIG. 6B ), the screen is essentially self-seating—the screen 100 pivots along angular channel 531 , 532 , 536 , 537 and can be released to drop in place (the motion of the screen 10 generally follows arrow 600 ) because the angles 533 of the support frame angular members 548 , 549 form an inverted pyramidal shape (i.e. a funnel) configured to align with the taper angle 160 of the screen side members 105 , 110 . Once a screen 100 is seated in the support frame (see FIGS. 6C and 4C ), a wedge block 200 is inserted between the wedge block retention bracket 540 and the shaker screen 100 such that the back face 221 of the wedge block is flush against the shaker wall 545 . A hammer or other suitable tool is then used to pound the wedge block further under the wedge block retention bracket 540 . [0045] As previously described, certain embodiments disclosed herein comprise a gasket 120 fitted on the outer edge 130 of the screen 100 (see FIG. 2B ). The application of a gasket 120 on the screen 100 itself removes the need to install gasket material on the support frame of the shaker 500 with the use of bolts or screws. Further, whenever a screen 100 is replaced due to normal wear and tear of the mesh layers (not shown), a new gasket 120 is automatically installed. Thus, replacing gasket material no longer requires the grinding of bolts and screws, reducing down time of the shaker 500 . [0046] As previously described, in an embodiment, the bottom edge 218 of the wedge block 200 is tapered (see FIG. 4B ), which provides a force both downward onto the screen side member 105 , but also laterally onto the tapered screen side member 105 . This lateral force further presses the side member 105 with an elastomeric gasket 120 into the angular channel 531 , 532 , 536 , 537 of the central, angular, bar anchor 530 , 535 , forming a substantially fluid tight seal. [0047] Referring to FIG. 7 , in an embodiment, the gumbo tray 520 may be rotated up along central axis 555 and into the cavity of the possum belly 510 to allow for easier access to the upper screens 100 for installation or removal.

A shaker screen comprises a frame that has a plurality of opposing sides. The shaker screen also comprises a screen assembly attached to the frame. In addition, each side of the shaker screen comprises a tubular member having an inner edge, an outer edge, and defining a central axis. Further, a horizontal plane intersects the central axis, the outer edge, and the inner edge of each side.

REFERENCE TO RELATED APPLICATION [0001] This application claims priority to U.S. Provisional Application Ser. No. 60/520,213, filed Nov. 14, 2003, the disclosure of which is hereby incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to integrated circuit devices and methods of operating same, and more particularly to integrated circuit devices that utilize scan chains to facilitate device testing. BACKGROUND OF THE INVENTION [0003] Scan design test techniques are frequently used to facilitate testing of complicated integrated circuit devices. A variety of these techniques are disclosed in U.S. Pat. Nos. 6,453,456 and 6,490,702. In particular, FIG. 10 of the '702 patent discloses a scan chain circuit 110 that purports to solve a latch adjacency problem when testing for delay faults within an integrated circuit. This scan chain circuit 110 includes a plurality of shift register latches 30 that operate as stages within the scan chain circuit 110. One shift register latch is illustrated as including a master latch 32 a and a slave latch 34 a . The output of the slave latch 34 a is provided to a first input of a combinational logic device 122. This combinational logic device 122 is illustrated as a two-input AND gate. The output of the slave latch 34 a is also provided to a first input of a multiplexer 112 a , which is responsive to a select signal SEL. A second inverted input 116 of the multiplexer 112 a also receives the output of the slave latch 34 a . The output of the multiplexer 112 a is provided to an input of a next shift register latch within the scan chain circuit 110. This next shift register latch is illustrated as including a master latch 32 b and a slave latch 34 b . The output of the slave latch 34 b is provided to a second input of the combinational logic device 122. This combinational logic device 122 is illustrated as undergoing a conventional delay fault test by having one input of the device 122 switch low-to-high while the other input of the device 122 is held high. The timing of this low-to-high switching of the one input of the device 122 is synchronized with a leading edge of the next clock pulse (not shown). To facilitate this delay fault test, the second inverted input 116 of the multiplexer 112 a is selected (i.e., SEL=0) so that the output of the next shift register latch (i.e., output of the slave latch 34 b ) is held at a logic 1 level when the next clock pulse is received. [0004] Accordingly, based on the illustrated configuration of the shift register latches 30 within the scan chain circuit 110, a value of the select signal SEL can be used to control whether the multiplexers 112 a -112 c operate to pass a true or complementary version of the output of a respective slave latch 34 a -34 c to the next shift register latch within the scan chain circuit 110. Nonetheless, even if the output of the slave latch 34 a can be controlled to switch states (i.e., switch 0→1 or 1→0) in response to the clock pulse (not shown), an output of the next shift register latch within the scan chain circuit 110 (i.e., the output of the slave latch 34 b ) will nonetheless be a function of a value of the output of the preceding slave latch 34 a during the delay fault test operation. This functional dependency between the output of one shift register latch and the output of a preceding shift register latch during the fault test operation can limit the effectiveness of the scan chain circuit 110 when testing for other more complicated types of delay faults within an integrated circuit device. SUMMARY OF THE INVENTION [0005] Embodiments of the present invention include an integrated circuit device that utilizes a scan chain register to support efficient reliability testing of internal circuitry that is not readily accessible from the I/O pins of the device. This reliability testing includes the performance of, among other things, delay fault and stuck-at fault testing of elements within the internal circuitry. According to some of these embodiments, an integrated circuit device is provided with a scan chain register having a plurality of scan chain latch units therein that support a toggle mode of operation. The scan chain register is provided with serial and parallel input ports and serial and parallel output ports. Each of the plurality of scan chain latch units includes a latch element and additional circuit elements that are configured to selectively establish at least one feedback path in the respective latch unit. This feedback path can operate to pass an inversion of a signal at an output of the latch to an input of the latch when the corresponding scan chain latch unit is enabled to support the toggle mode of operation. Accordingly, if the output of the latch is set to a logic 1 level, then a toggle operation will cause the output of the latch to automatically switch to a logic 0 level and vice versa. Because of the presence of a respective feedback path within each scan chain latch unit, the toggle operation at the output of a scan chain latch unit will be independent of the value of any other output of any other scan chain latch unit within the scan chain. [0006] According to additional embodiments of the present invention, a scan chain latch unit includes a latch and a pair of multiplexers that route data through the latch unit. The latch may constitute a flip-flop device that is synchronized to a clock signal, such as a positive edge triggered D-type flip-flop. In particular, a first multiplexer is provided having first and second data inputs and a select terminal that is responsive to a toggle signal. A second multiplexer is provided having a first data input electrically coupled to an output of the first multiplexer, a second data input configured as a parallel input port of the scan chain latch unit, a select terminal responsive to a scan enable signal (SE i ) and an output electrically coupled to an input of the latch. The scan chain latch unit further includes an inverter having an input electrically coupled to a true output of the latch and an output electrically coupled to the second data input of the first multiplexer. Accordingly, through proper control of the select terminals of the first and second multiplexers, a signal generated at an output of the inverter can be passed to the input of the latch and then loaded into the latch upon performance of the toggle operation. In the event the latch includes true and complementary outputs, then the complementary output may be fed back directly to the second data input of the first multiplexer and the inverter may be eliminated. [0007] Further embodiments of the present invention include a sequential scan chain register having a serial input port, a serial output port and a plurality of parallel output ports. The sequential scan chain register is configured to generate at least a first portion of a serially scanned-in test vector at a plurality of immediately adjacent ones of the parallel output ports during a preload time interval that spans multiple consecutive cycles of a clock signal. This register is further configured to respond to a launch edge of the clock signal and an active toggle signal by toggling each and every one of the bits in the first portion of the serially scanned-in vector regardless of a value of the serially scanned-in vector. [0008] According to still further embodiments of the present invention, a scan chain latch unit is configured to support a toggle mode of operation that establishes a next output state (NS) of the scan chain latch unit as an invert of a current output state (CS) of the scan chain latch unit, while blocking data at serial and parallel inputs of the scan chain latch unit from influencing a value of the next output state. The scan chain latch unit is further configured to support a freeze mode of operation that establishes a next output state of the scan chain latch unit as equivalent to a current output state of the scan chain latch unit. This mode of operation also blocks data at the serial and parallel inputs of the scan chain latch unit from influencing a value of the next output state. In these embodiments, the scan chain latch unit may include a four input multiplexer that is responsive to a pair of select signals. The scan chain latch unit may also generate a true output state (Q) that is fed back to a first data input of the four input multiplexer and a complementary output state (QB) that is fed back to a second data input of the four input multiplexer. The four input multiplexer may include first and second totem pole arrangements of PMOS and NMOS transistors having commonly connected outputs. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1A is an electrical schematic of a scan chain latch unit according to an embodiment of the present invention. [0010] FIG. 1B is a timing diagram that illustrates operation of the scan chain latch unit of FIG. 1A . [0011] FIG. 1C is an electrical schematic of a scan enable signal SE i generator according to an embodiment of the present invention. [0012] FIG. 1D is an electrical schematic of a circuit that is configured to generate scan enable and toggle signals, which are received by the scan chain latch unit of FIG. 1A . [0013] FIG. 2A is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0014] FIG. 2B is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0015] FIG. 2C is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0016] FIG. 2D is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0017] FIG. 3A is a block diagram of a scan chain latch unit according to an embodiment of the present invention. [0018] FIG. 3B is an electrical schematic of an embodiment of the scan chain latch unit of FIG. 3A . [0019] FIG. 3C is an electrical schematic of an embodiment of the scan chain latch unit of FIG. 3A . [0020] FIG. 3D is an electrical schematic of an embodiment of the scan chain latch unit of FIG. 3A . [0021] FIG. 3E is an electrical schematic of an alternative embodiment of the scan chain latch unit of FIG. 3C . [0022] FIG. 3F is an electrical schematic of an alternative embodiment of the scan chain latch unit of FIG. 3D . [0023] FIG. 4A is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0024] FIG. 4B is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. [0025] FIG. 4C is an electrical schematic of a portion of a scan chain register according to an embodiment of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS [0026] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. The suffix B or prefix symbol “/” to a signal name may denote a complementary data or information signal or an active low control signal, for example. [0027] Referring now to FIG. 1A , a scan chain latch unit 10 according to an embodiment of the present invention is illustrated as including first and second multiplexers M 1 and M 2 , a latch L 1 and an inverter I 1 . The latch L 1 is shown as a D-type flip-flop having an input D and a “true” output Q that is fed back to an input of the inverter I 1 . The latch L 1 is synchronized to a clock signal CLK. As described more fully hereinbelow with respect to FIG. 2B , the latch L 1 may also be configured as a flip-flop having true and complementary outputs Q and QB and the inverter I 1 may be eliminated. Other types of latches may also be used. The scan chain latch unit 10 has a number of ports. These ports include a serial input port SI, a serial output port SO, a parallel input port DI and a parallel output port DO. The first multiplexer M 1 has a select terminal that is responsive to a toggle signal TOG and the second multiplexer M 2 has a select terminal that is responsive to a scan enable signal SE i . When the toggle signal TOG is set to a logic 0 level (i.e., low state) and the scan enable signal SE i is set to a logic 1 level (i.e., high state), serial input data can be passed from the serial input port SI to the input D of the latch L 1 and then transferred to the output Q of the latch L 1 in-sync with a rising edge of the clock signal CLK. Alternatively, when the scan enable signal SE i is set to a logic 0 level, parallel input data can be passed from the parallel input port DI to the input D of the latch L 1 . Finally, in preparation of a toggle operation, both the toggle signal TOG and the scan enable signal SE i can be set to logic 1 levels to thereby connect an output of the inverter I 1 to the input D of the latch L 1 . In this manner, an inversion of the output Q of the latch L 1 can be passed to the input D of the latch L 1 . Stated alternatively, setting both the toggle signal TOG and the scan enable signal SE i to logic 1 levels will operate to establish an active feedback path that passes an inversion of a signal from the output Q of the latch L 1 to the input D of the latch L 1 . Then, upon receipt of a leading “launch” edge of the clock signal CLK, the output Q of the latch will undergo a toggle operation (i.e., switch high-to-low or low-to-high). [0028] The timing diagram of FIG. 1B also illustrates operation of the scan chain latch unit 10 of FIG. 1A . In FIG. 1B , the clock signal CLK is shown as having an initial leading edge that operates to synchronize the loading of data from the serial input port SI to the serial output port SO. This leading edge is received while the toggle signal TOG is held at a logic 0 level and the scan enable signal SE i is held at a logic 1 level. These settings establish a data path that extends from the serial input port SI to the input D of the latch L 1 , via the first and second multiplexers M 1 and M 2 . After this initial loading operation, the toggle signal TOG is switched low-to-high and the scan enable pad signal SE pad is switched high-to-low in advance of the next leading edge of the clock signal CLK, which is referred to herein as the launch edge of the clock signal CLK. The timing of when the toggle signal TOG switches low-to-high is somewhat flexible because it is only necessary that the low-to-high transition of TOG occur after the serial data has been loaded (i.e., after the initial leading edge of the clock signal CLK has been received) and before the launch edge of the clock signal CLK is received. As illustrated by the scan enable signal generator 12 of FIG. 1C , which includes a latch L 2 , a NOR gate NR 1 and an inverter I 2 , switching the scan enable pad signal SE pad high-to-low in advance of the launch edge of the clock signal CLK will cause the scan enable signal SE i to switch high-to-low in-sync with the launch edge of the clock signal CLK. When this occurs, a data path between the parallel data input DI of the scan chain latch unit 10 and the data input D of the latch L 1 will be enabled. The signal generator 12 of FIG. 1C has the advantage of being responsive to the scan enable pad signal SE pad , which, as illustrated by FIG. 1B , has more relaxed timing requirements and can be more easily distributed within a chip (with the scan enable signal SE i being separated for each block within the chip). [0029] Upon receipt of the launch edge of the clock signal CLK, the true output Q of the latch L 1 will undergo a toggle operation by switching from a previously loaded high state to a low state. The toggle operation is made automatic because both the toggle signal TOG and the scan enable signal SE i are high at the moment the launch edge of the clock signal CLK is received, which means the feedback path between the output of the inverter I 1 and the input D of the latch L 1 is enabled pending receipt of the launch edge. Following this, the scan enable signal SE i switches high-to-low to thereby enable the true output Q of the latch L 1 to switch to the current value of the parallel data input DI upon receipt of the next leading edge of the clock signal CLK that follows the launch edge. After this next leading edge, the scan enable pad signal SE pad switches low-to-high and the scan enable signal SE i follows in-sync with the rising edge of the scan enable pad signal SE pad signal, as illustrated by FIG. 1C . Setting the scan enable signal SE i high while the toggle signal TOG remains low will operate to connect the serial input port SI to the data input D of the latch L 1 . The data at the serial input port SI will then be passed to the true output Q of the latch L 1 in-sync with the next leading edge of the clock signal CLK, which is shown as the final leading edge illustrated by FIG. 1B . [0030] Control of the generation of the toggle signal TOG in FIG. 1B may be independent of the scan enable pad SE pad signal in some embodiments of the present invention. In particular, separate bond pads may be provided on an integrated circuit substrate and these bond pads may be electrically coupled to separate pins of an integrated circuit package that is configured to receive the scan enable pad SE pad signal and the toggle signal TOG, respectively. However, in other embodiments, the toggle signal TOG may be generated by an alternative scan enable signal generator 12 ′, which is illustrated by FIG. 1D . In particular, the toggle signal TOG may be generated at the output of an inverter I 3 , which receives the scan enable pad signal SE pad as an input signal. Thus, in the timing diagram of FIG. 1B , the timing of the toggle signal TOG may be modified so that it is set high when the scan enable pad signal SE pad switches low and set low when the scan enable pad signal SE pad switches high. [0031] FIG. 2A illustrates a scan chain register 20 according to an embodiment of the present invention. This scan chain register 20 is illustrated as including a plurality (i.e., n+1) of the scan chain latch units 10 illustrated by FIG. 1A . These scan chain latch units are shown by the reference numerals 10 a - 10 c . The first scan chain latch unit 10 a includes first and second multiplexers M 1 a , M 2 a , a D-type latch L 1 a and an inverter I 1 a . The second scan chain latch unit 10 b includes first and second multiplexers M 1 b , M 2 b , a D-type latch L 1 b and an inverter I 1 b . The last scan chain latch unit 10 c within the scan chain register 20 includes first and second multiplexers M 1 c , M 2 c , a D-type latch L 1 c and an inverter I 1 c . The scan chain register 20 is provided with a serial input port SI, a serial output port SO, a parallel input port DI 0 -DIn and a parallel output port DO 0 -DOn. By setting the toggle signal TOG high and the scan enable signal SE i high, a toggle operation can be performed in-sync with a launch edge of the clock signal CLK. This toggle operation will cause all of the data signals at the parallel output port DO 0 -DOn to be inverted to thereby facilitate a scan test operation. Moreover, this toggle operation will not be functionally dependent on the values of any of the data signals at the parallel output port DO 0 -DOn. Accordingly, if a scanned-in test vector equivalent to DO 0 -DOn=101100 . . . 1 is loaded into the scan chain register 20 in a serial fashion (i.e., in-sync with a plurality of consecutive leading edges of the clock signal CLK), then the receipt of the launch edge of the clock signal CLK will cause each bit of this test vector to become inverted (i.e., DO 0 -DOn=010011 . . . 0). [0032] Referring now to FIG. 2B , an alternative scan chain register 20 ′ is illustrated. This scan chain register 20 ′ is similar to the scan chain register 20 of FIG. 2A , however, the scan chain latch units 10 a ′- 10 c ′ have been modified to include latches L 3 a , L 3 b and L 3 c , respectively. These latches L 3 a , L 3 b and L 3 c have true and complementary outputs Q and /Q. These complementary outputs /Q are fed back to corresponding inputs of the first multiplexers M 1 a , M 1 b and M 1 c , as illustrated. The use of complementary outputs /Q with each latch L 3 a , L 3 b and L 3 c eliminates the requirement of using inverters within the feedback paths of the scan chain latch units. The scan chain register 20 ″ of FIG. 2C is illustrated as including one (or more) conventional scan chain latch unit 14 b within the chain, which is not configured to perform a toggle operation as described herein. Thus, it is not necessary that every scan chain latch unit within a scan chain register 20 ″ be configured to perform a toggle operation as described above with respect to FIGS. 1A-1B . The scan chain register 20 ′″ of FIG. 2D is illustrated as including three different configurations of scan chain latch units. The use of different scan chain latch units supports reduction in hardware (e.g., transistor count) and optimization for each configuration of combinational logic connected to the parallel data outputs DO 0 -DOn. The scan chain latch units 10 a and 14 b are similar to those illustrated by FIG. 2 C, however, the scan chain latch unit 14 c is illustrated as being responsive to the scan enable pad signal SE pad . Based on the timing diagram of FIG. 1B , upon receipt of the launch edge of the clock signal CLK, the next state (NS) of the output of the scan chain latch unit 14 c will be equivalent to the value of the data at the parallel input port DIn. [0033] As illustrated by FIGS. 3A-3B , alternative embodiments of a scan chain latch unit 30 may be configured to support a toggle mode of operation and a freeze mode of operation. The toggle and freeze modes, which are synchronized with the clock signal CLK, may utilize a pair of feedback paths that are each selectively enabled to pass data to support a respective one of the toggle and freeze modes. Other embodiments of the scan chain latch unit 30 that do not utilize feedback paths to support the toggle and freeze modes may also be implemented. In the toggle mode of operation, the next output state (NS) of the scan chain latch unit 30 equals an opposite of the current output state (CS) of the scan chain latch unit 30 (i.e., NS=/CS, where “/” designates an inversion operation). The scan chain latch unit 30 is similar to the scan chain latch unit 10 of FIG. 1A , however, the two select signals (TOG and SE i ) in FIG. 1A have been replaced by a pair of select signals SA and SB. This pair of select signals SA and SB enables selection between as many as four modes of operation. In addition to the toggle and freeze modes, two additional modes of operation include: (i) a “scan-in” mode whereby the next state of the latch unit 30 is equivalent to the data at the serial input port (SI) of the latch unit 30 when a next leading edge of the clock signal CLK is received and (ii) a “data-in” mode whereby the next state of the latch unit 30 is equivalent to the data at the parallel data input port (DI) of the latch unit 30 when a next leading edge of the clock signal CLK is received. The four possible combinations of the select signals SA and SB are illustrated more fully by TABLE 1. With these select signals, as many as four states may be established at an output of a scan chain latch unit 30 in-sync with the clock signal CLK. TABLE 1 SA SB OUTPUT OF SCAN CHAIN LATCH UNIT 30 0 0 NS = DI; NORMAL LOGIC OPERATION 0 1 NS = Q; FREEZE MODE FOR SPEED TEST 1 0 NS = QB; TOGGLE MODE FOR SPEED TEST 1 1 NS = SI; SCAN-IN MODE FOR SCAN CHAIN SHIFTING [0034] FIG. 3B illustrates a detailed electrical schematic of one embodiment of the scan chain latch unit 30 of FIG. 3A . This electrical schematic includes two totem pole arrangements of PMOS and NMOS transistors having commonly connected outputs, which are provided as an input to a first transmission gate TG 1 . The first totem pole arrangement of transistors includes PMOS transistors P 1 -P 4 and NMOS transistors N 1 -N 4 , connected as illustrated. The second totem pole arrangement of transistors includes PMOS transistors P 5 -P 8 and NMOS transistors N 5 -N 8 . These two totem pole arrangements of transistors operate as a 4-input multiplexer that is responsive to the two select signals SA and SB. The four data inputs of the multiplexer include the serial input port (SI), the data input port (DI), a first feedback path, which electrically connects a complementary output (QB) of a latch unit to gate terminals of PMOS transistor P 3 and NMOS transistor N 3 , and a second feedback path, which electrically connects a true out (Q) of the latch unit to gate terminals of PMOS transistor P 7 and NMOS transistor N 7 . Inverters I 2 and I 3 are also provided for inverting the select signals SA and SB. The latch unit is illustrated as including a first latch, which is synchronized with a clock signal CLK, and a second latch connected to an output of the first latch. This first latch includes a first pair of inverters connected in antiparallel (L 4 ), first and second transmission gates TG 1 and TG 2 , which are synchronized with the clock signal CLK, and an inverter I 5 which generates a complement of the clock signal CLK. The second latch includes a second pair of inverters connected in antiparallel (L 5 ) and an output inverter I 4 . The second latch is configured to generate the true output signal Q and the complementary output signal QB. [0035] Based on the illustrated configuration of the scan chain latch unit 30 of FIG. 3B , setting the select signals SA and SB to a value of “00” will operate to turn on NMOS transistors N 1 and N 4 and PMOS transistors P 1 and P 4 . When this occurs, the value of the data at the data input port DI will operate to pull the output of the first totem pole arrangement high when DI=0 or low when DI=1. In contrast, setting the select signals SA and SB to a value of “11” will operate to turn on NMOS transistors N 5 and N 8 and PMOS transistors P 5 and P 8 . When this occurs, the value of the data at the serial input port SI will operate to pull the output of the first totem pole arrangement high when SI=0 or low when SI=1. Setting the select signals SA and SB to a value of “01” will operate to turn on NMOS transistors N 4 and N 5 and PMOS transistors P 1 and P 8 . When this occurs, the value of the feedback signal line Q will operate to pull the output of the first totem pole arrangement high when Q=0 and PMOS transistor P 7 is “on” or low when Q=1 and NMOS transistor N 7 is “on”. Finally, setting the select signals SA and SB to a value of “10” will operate to turn on NMOS transistors N 1 and N 8 and PMOS transistors P 4 and P 5 . When this occurs, the value of the feedback signal line QB will operate to pull the output of the first totem pole arrangement high when QB=0 and PMOS transistor P 3 is “on” or low when QB=1 and NMOS transistor N 3 is “on”. [0036] When the clock signal CLK is low (CLK=0), the output of the 4-input multiplexer is passed to an input of the first latch while the output of the first latch remains in a high impedance state by virtue of the fact that the second transmission gate TG 2 is “off”. When the clock signal CLK switches high (e.g., when a “launch” edge of the clock signal CLK occurs), the first transmission gate TG 1 is turned off, the second transmission gate TG 2 is turned on and the data at the output of the first pair of inverters L 4 is passed to an input of the second pair of inverters L 5 and the next state values of Q and QB are established. These values Q and QB are fed back to inputs of the 4-input multiplexer. [0037] The scan chain latch unit 30 ′ of FIG. 3C represents an alternative scan chain latch unit embodiment that utilizes a single feedback path from the true output Q and a feed-forward path from the data input port DI. As illustrated by TABLE 2, this scan chain latch unit 30 ′ supports a freeze mode of operation but not a toggle mode of operation. A more preferred embodiment of the scan chain latch unit 30 ′ of FIG. 3C is illustrated by the scan chain latch unit 30 ′″ of FIG. 3E , which has a reduced transistor count. The scan chain latch unit 30 ″ of FIG. 3D represents yet another scan chain latch unit embodiment that utilizes a single feedback path from the complementary output QB and a feed-forward path from the data input port DI. As illustrated by TABLE 2, this scan chain latch unit 30 ″ supports a toggle mode of operation but not a freeze mode of operation. A more preferred embodiment of the scan chain latch unit 30 ″ of FIG. 3D is illustrated by the scan chain latch unit 30 ″″ of FIG. 3F , which has a reduced transistor count. TABLE 2 OUTPUT OF LATCH OUTPUT OF LATCH UNIT 30″ SA SB UNIT 30′ and 30′″ and 30″″ 0 0 NS = DI; NORMAL NS = DI; NORMAL OPERATION OPERATION 0 1 NS = Q; FREEZE MODE NS = QB; TOGGLE MODE 1 0 NS = DI; NORMAL NS = DI; NORMAL OPERATION OPERATION 1 1 NS = SI; SCAN-IN MODE NS = SI; SCAN-IN MODE [0038] As illustrated by FIG. 4A , a scan chain register 40 according to another embodiment of the present invention includes a plurality of scan chain latch units 30 a - 30 n , which are illustrated in greater detail by FIGS. 3A-3B . This scan chain register 40 supports the four modes of operation illustrated by TABLE 1, with the SA and SB select terminals of the illustrated units 30 a - 30 n being connected to select lines SA and SB, respectively. Based on this configuration of the select lines and terminals, each of the scan chain latch units 30 a - 30 n will operate in the same mode of operation at all times. In contrast, the segment of a scan chain register 40 ′ illustrated by FIG. 4B demonstrates how a first select terminal SA of one scan chain latch unit 30 e may be connected to a second select terminal SB of another scan chain latch unit 30 f by a first select line S 1 . Similarly, the first select terminal SB of the scan chain latch unit 30 e may be connected to a second select terminal SA of the scan chain latch unit 30 f by a second select line S 2 . Based on this illustrated configuration, disposing the scan chain latch unit 30 e in a toggle mode of operation by setting S 1 , S 2 equal to 10 will operate to dispose the scan chain latch unit 30 f in a freeze mode of operation. Likewise, disposing the scan chain latch unit 30 e in a freeze mode of operation by setting S 1 , S 2 equal to 01 will operate to dispose the scan chain latch unit 30 f in a toggle mode of operation. [0039] This configuration of the scan chain latch units 30 e and 30 f enables at-speed testing of combinational logic devices. For example, all of the possible speed paths that can be tested in the two-input NAND gate ND 1 illustrated by FIG. 4B may be tested at-speed using the four test sequences illustrated by TABLE 3. The four test sequences also demonstrate the independence of the next states (NS) on the data values established at the serial input ports (SI) and the data input ports (DI) of the illustrated scan chain latch units 30 e and 30 f . TABLE 3 Z falling Z rising CS NS CS CS NS X 1  1  0  1  0 1 (NS = CS) (NS = /CS) (NS = CS) (NS = /CS) Y 1  0  1  0  1 1 (NS = /CS) (NS = CS) (NS = /CS) (NS = CS) S1 S2 01 10 01 10 [0040] In the event the 2-input NAND gate ND 1 of FIG. 4B is replaced by a 2-input XOR gate, then TABLE 4 illustrates the eight test sequences that may be required to test the 2-input XOR gate, with each sequence being independent of the data values established at the serial input ports (SI) and the data input ports (DI) of the illustrated scan chain latch units 30 e and 30 f . TABLE 4 Z rising Z falling CS NS CS NS CS NS CS NS X 0 0 1 1 0 1 0 0 1 1 0 1 Y 0 1 0 1 1 0 1 0 1 0 0 1 S1 S2 01 10 10 01 01 10 10 01 [0041] Increased controllability may also be achieved for more complex applications by inserting one or more dummy flip-flops into a scan chain register. As illustrated by FIG. 4C , a scan chain register 40 ″ may include a plurality of scan chain latch units 30 g - 30 i and at least one dummy flip-flop 32 , which is illustrated as a D-type flip-flop. Each of these latch units 30 g - 30 i may be configured as illustrated by FIGS. 3B-3F , however, other configurations of the latch units (not shown herein) may also be possible. Moreover, the latch units 30 g - 30 i need not be equivalent. The inputs (SA 1 , SB 1 ), (SA 2 , SB 2 ) and (SA 3 , SB 3 ) to each of the scan chain latch units 30 g - 30 i may be connected to respective pairs of terminals or may be connected in different ways to a single pair of input terminals (e.g., S 1 and S 2 ) to achieve desired functions for each of the latch units. The inclusion of this dummy flip-flop 32 (and others at strategic locations within the scan chain register 40 ″) may enable the at-speed testing of complex logic 34 with 100 percent controllability of the third input to the complex logic 34 (i.e., the last input of the complex logic 34 that is connected to output of scan chain latch unit 30 i ), albeit using a somewhat longer scan chain register 40 ″. The inclusion of one or more dummy flip-flops can enable all speed paths within the complex logic 34 to be checked using a smaller number of test vectors. As illustrated, the dummy flip-flop 32 may be programmed to store a desired next state for the following scan chain latch unit 30 i when the corresponding select signals SA 3 and SB 3 are set to a predetermined value. This value may equal a 11 value (i.e., SA 3 =SB 3 =1) in the event the latch unit 30 i is configured to operate in accordance with TABLES 1-2, however, alternative configurations of the latch unit 30 i (not shown herein) may also be utilized to achieve the desired operation. [0042] In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

An integrated circuit device utilizes a serial scan chain register to support efficient reliability testing of internal circuitry that is not readily accessible from the I/O pins of the device. This reliability testing includes the performance of, among other things, delay fault and stuck-at fault testing of elements within the internal circuitry. The scan chain register has scan chain latch units that support a toggle mode of operation. The scan chain register is provided with serial and parallel input ports and serial and parallel output ports. Each of the plurality of scan chain latch units includes a latch element and additional circuit elements that are configured to selectively establish a feedback path in the respective latch unit. This feedback path operates to pass an inversion of a signal at an output of the latch to an input of the latch when the corresponding scan chain latch unit is enabled to support a toggle mode of operation. Thus, if the output of the latch is set to a logic 1 level, then a toggle operation will cause the output of the latch to switch to a logic 0 level and vice versa. Because of the presence of a respective feedback path within each scan chain latch unit, the toggle operation at the output of a scan chain latch unit will be independent of the value of any other output of other scan chain latch units within the scan chain.

FIELD OF THE INVENTION The invention pertains to the field of using computational methods in predictive chemistry. More particularly, the invention utilizes a neural network with associated algorithmic functions, and the quantum mechanical properties of the molecules investigated or portions of those molecules, to optimize the prediction of bioactivity or the mode of chemotherapeutic action for molecules of interest. BACKGROUND OF THE INVENTION The role of medicinal chemist has not been altered in several decades. Their efforts to identify chemotherapeutic compounds, and thereafter devise more potent variations to them for medicinal use has long been one involving the arduous task of testing one compound at a time to determine individual bioactivity. This slow throughput system is made even more costly by the fact that historically over 10,000 compounds must be individually tested and evaluated for every one that actually reaches market as a therapeutic agent, as discussed in SCRIP, World Pharmaceutical News, Jan. 9, 1996, (PJB Publications). These facts have driven many scientists and pharmaceutical houses to shift their research from traditional drug discovery (e.g. individual evaluation) towards the development of high throughput systems (HTP) or computational methods that will bring to bear increasingly powerfull computer technology for the drug discovery process. To date none of these systems have been proven to significantly shorten discovery and optimization time for the development of chemotherapeutic agents. The first attempts to develop computational methods to predict the inhibitory potency of a given molecule prior to synthesis have been broadly termed quantitative structure activity relationship (QSAR) studies. These techniques require the user to define a functional relationship between a specific molecular property and a given molecular action. In the QSAR approach, or any approach where an individual is responsible for adjusting a mathematical model, the investigator must use variations in the structure of a molecule as the motivation for changing the value of coefficients in the computer model. For a chemical reaction as complex as an enzymatically mediated transformation of reactants to product, often an important part of therapeutic or medicinal activity, it is not possible to predict a priori all the effects a change to a substrate molecule will have on enzymatic action. This fact has made the QSAR approach to drug discovery exceptionally impracticable and inefficient. Accordingly, a need exists to optimize the prediction of bioactivity in chemical compounds such that the discovery and development of therapeutically valuable compounds is made more rapid and efficient. SUMMARY OF THE INVENTION Briefly stated, the invention described herein provides a neural network approach to the prediction of chemical activity in at least one molecule of interest. The example provided herein demonstrates how this methodology is useful in the prediction of bioactivity for a molecule capable of acting as an enzymatic inhibitor. This same methodology is also applicable to a variety of compounds of interest using the same training protocols and the same quantum mechanical properties of given molecules, or portions thereof discussed herein. The neural network provided herein is comprised of an input layer having at least one neuron where input data is sent and then given a vector value, a hidden layer having at least one neuron such that when data is received from the input layer that vector data is multiplied by a set weight and thereafter generates a weight matrix having the dimensions n by m where n is the length of an input vector and m is the number of hidden layer neurons available, and an output layer consisting of at least one neuron where the weight matrix data is sent before it is then sent to a transfer function. The transfer function is a non-linear equation that is capable of taking any value generated by the output layer and returning a number between −1 and 1. Feed-forward neural networks with back-propagation of error, of the type disclosed herein (see pages 7-10), are trained to recognize the quantum mechanical electrostatic potential and geometry at the entire van der Waals surface of a group of training molecules and to predict the strength of interactions, or free energy of binding, between an enzyme and novel inhibitors of that enzyme. More generally, the input for the functions of the neural network are the quantum mechanical electrostatic potentials of various molecules of interest. The predictive value of the system is gained through the use of a “training” process for the neural network using the known physicochemical properties of at least one training molecule, such as Inosine-Uridine Preferring Nucleoside Hydrolase (IU-NH). IU-NH is a nucleoside hydrolase from first isolated from the organism Crithidia fasciculata . The neural network is given input generated from the known electrostatic potential surfaces of the known molecules and attempts to predict the free energy of binding for that training set of molecules. When the neural network is able to accurately predict the free energy of binding of the training set of molecules, then the same neural network can be used with high accuracy to determine the free energy of binding, and hence the chemical characteristics, of unknown molecules. Among the novel aspects of the present invention is the utilization in the current invention of the quantum mechanical electrostatic potential of the molecule of interest at the van der Waals surface of that molecule as the physicochemical descriptor. The entire surface for each molecule, represented by a discrete collection of points, serves as the input to the neural network. In this way the invention utilizes quantum mechanical means to describe the molecular activity of a compound of interest. With improved knowledge of molecular activity the method described herein provides for enhancing the predictive value of neural networks with regard to phyisicochemical properties of compounds of interest either with regard to therapeutic compounds or compounds that would have other commercial or scientific value. The neural networks provided herein are useful in modeling chemical interactions that are non-covalent in nature. That is, as long as a reaction is mediated by electrostatic forces, including Van der Waals forces, the neural networks provided herein, and the associated algorithms, are accurate predictors of chemical activity and interaction. In this way they will save time and money in drug discovery and chemical evaluation processes. Specifically, with regard to enzymatic action, the neural networks herein described are able to determine chemical configurations that will optimize known chemotherapeutics and allow the discovery of new compounds that need to have specific binding characteristics or activity. These new compounds can be developed by modeling the quantum characteristics of specific molecular moieties with a trained neural or double neural network. According to an exemplary embodiment of the invention, a computational method has been developed to predict the free energy of binding for inhibitor or untested enzyme molecules. Other features and advantages of this invention will become apparent in the following detailed description of a preferred embodiment of this invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawing(s) will be provided by the Patent and Trademark Office upon request and payment of the necessary fee. FIG. 1 shows a neural network with a back-propagation of error function, with an input layer i through n, a hidden layer j through m, and output layer p. The biases B are added to the hidden and output layers. FIG. 2 shows a double neural network comprised of a coupled inner and outer neural network. FIG. 3 a shows surface point comparisons of the geometry of unaltered input molecules 4 and 2 . FIG. 3 b shows surface point comparisons of the geometry of unaltered input molecule 4 and an idealized molecule 4 . FIG. 3 c shows surface point comparisons of the geometry of unaltered input molecule 2 and idealized molecule 2 . FIG. 4 shows a two dimensional representations of the molecules used in an exemplary study described herein. FIGS. 5 a and 5 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 4 , FIG. 5 a , with the double neural network idealized form of input molecule 4 , FIG. 5 c. FIGS. 5 b and 5 d show a surface point comparison of the geometry of unaltered input molecule number 4 , FIG. 5 b , with double neural network idealized form of input molecule number 4 , FIG. 5 d. FIGS. 6 a and 6 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 9 , FIG. 6 a , with the double neural network idealized form of input molecule number 9 , FIG. 6 c. FIGS. 6 b and 6 d show a surface point comparison of the geometry of the unaltered molecule number 9 , FIG. 6 b , with the double neural network idealized form of input molecule number 9 , FIG. 6 d. FIGS. 7 a and 7 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 14 , FIG. 7 a , with the double neural network idealized form of molecule number 14 , FIG. 7 c. FIGS. 7 b and 7 d show a surface point comparison of the geometry of unaltered input molecule number 14 , FIG. 7 b , with the double neural network idealized form of molecule number 14 , FIG. 7 d. FIGS. 8 a and 8 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 1 , FIG. 8 a , with the double neural network idealized form of molecule number 1 , FIG. 8 c. FIGS. 8 b and 8 d show a surface point comparison of the geometry of unaltered input molecule number 1 , FIG. 8 b , with the double neural network idealized form of molecule number 1 , FIG. 8 d. FIGS. 9 a and 9 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 12 , FIG. 9 a , with the double neural network idealized form of molecule number 12 , FIG. 9 c. FIGS. 9 b and 9 d show a surface point comparison of the geometry of unaltered input molecule number 12 , FIG. 9 b , with the double neural network idealized form of molecule number 12 , FIG. 9 d. FIGS. 10 a and 10 c show a surface point comparison of the electrostatic potential of unaltered input molecule number 15 , FIG. 10 a , with the double neural network idealized form of molecule number 15 , FIG. 10 c. FIGS. 10 b and 10 d show a surface point comparison of the geometry of unaltered input molecule number 15 , FIG. 10 b , with the double neural network idealized form of molecule number 15 , FIG. 10 d. DESCRIPTION OF THE PREFERRED EMBODIMENT The following abbreviations have designated meanings in the specification: Abbreviation Key High Throughput System: (HTP) Inosine-Uridine Preferring Nucleoside Hydrolase: (IU-NH) Quantitative Structure Activity Relationship (QSAR) p-aminophenyliminoribitol (pAPIR) Neural Networks The present invention discloses a neural network for improving the identification of chemically useful compounds without having to test each investigated compound individually. As is known in the art, a computational neural network is a computer algorithm which, during its training process, can learn features of input patterns and associate these with an output. Neural networks learn to approximate the function defined by the input/output pairs. The function is rarely, if ever specified by the user. After the learning phase, a well-trained network should be able to predict an output for a pattern not in the training set. In the context of the present invention, the neural net is trained with a set of molecules which can act as inhibitors for a given enzyme until the neural network can associate with every quantum mechanical description of the molecules in this set, a free energy of binding (which is the output). The network is then used to predict the free energy of binding for unknown molecules. Known computational neural networks are composed of many simple units operating in parallel. These units and the aspects of their interaction are inspired by biological nervous systems. The network's function is largely determined by the interactions between units. An artificial neural network consists of a number of “neurons” or “hidden units” that receive data from the outside, process the data, and output a signal. A “neuron” is essentially a regression equation with a non-linear output. When more than one neuron is used, non-linear models can be fitted. Networks learn by adjusting the values of the connections between elements (Fausett, L. FUNDAMENTALS OF THE NEURAL NETWORKS; Prentice Hall: New Jersey, 1994). The neural network presented by this invention is a feed-forward model with the back-propagation of error. This type of art recognized neural network learns with momentum. A back propagation neural network has three layers: an input layer, a hidden layer, and an output layer. The input layer is where the input data is sent. The link between the layers of the network is one of multiplication by a weight matrix, where every entry in the input vector is multiplied by a weight and sent to every hidden layer neuron, so that the hidden layer weight matrix has the dimensions n by m, where n is the length of the input vector and m is the number of hidden layer neurons. A bias is added to the hidden and output layer neurons. The hidden layer then functions to scale all the arguments before they are input into the transfer function. Each neuron has one bias. The function of the bias is to adjust the influence of neurons with greater and lesser roles in the model that the neural network is learning how to model. Neural Network Formulas Referring to the schematic in FIG. 1, the input layer 110 is represented by the boxes at the top-left of the figure. The weights 120 are represented by the lines connecting the layers: w ij is the weight between the i th neuron of the input layer and j th neuron of the hidden layer 130 and w jk is the weight between the j th neuron of the hidden layer 130 and the k th neuron of the output layer 190 . In FIG. 1 the output layer 190 has, as an exemplary example, only one neuron 191 because the target pattern is a single number, the binding energy (represented as “B p2 ”). The hidden layer 130 input from pattern number 1 for neuron 140 j, is h I j , and is calculated: h j 1  ( 1 ) = b j + ∑ i = 1 n     x i o  ( 1 ) × w ij Formula [1] where x o i is the output from the i th input neuron, w ij is the element of the weight matrix connecting input from neuron i with hidden layer neuron j and b j is the bias 150 on the hidden layer neuron j. This vector h I j is sent through a transfer function, ƒ. This function is non-linear and usually sigmoidal, taking any value and returning a number between −1 and 1, see page 4, (Fausett, L. FUNDAMENTALS OF THE NEURAL NETWORKS; Prentice Hall: New Jersey, 1994). A typical example is: f  ( h j 1 ) = 2 1 + e - h j 1 - 1 ≡ h j o Formula [2] The hidden layer output, h o j is then sent to the output layer 190 . The output layer input o i k is calculated for the k th output neuron o k 1 = b k + ∑ j = 1 m     h j o  w jk Formula [3] where w jk is the weight matrix element connecting hidden layer neuron j with output layer neuron k. The output layer output, o o k , is calculated with a similar transfer function as the one given above: g  ( o k 1 ) = γ 1 + e ( - o k 1 ) - η ≡ o k o Formula [4] where γ i is the range of the binding energies of the molecules used in the study and η i is the minimum number of all the binding energies. The minimum and maximum values are decreased and increased 10% to give the neural network the ability to predict numbers larger and small than those in the training set: min new =min old −abs (min old x .1),  Formula[5] max new =max old +abs (max old x .1)  Formula[6] The calculation of an output concludes the feed forward phase of training. The weights and biases are initialized with random numbers, during the first iterations the output of the network will be random numbers. Back propagation of error is used in conjunction with learning rules to increase the accuracy of predictions. The difference between o o k and the target value for input pattern number 1, t k , determines the sign of the corrections to the weights and biases. The size of the correction is determined by the first derivative of the transfer function. The relative change in weights and biases are proportional to a quantity δ k : δ k =( t k −o O k ) g′ ( o l k )  Formula[7] where g′ is the first derivative of equation 4. The corrections to the weights and biases are calculated: Δ w jk =αδ k h j o   Formula[8] Δ b k =αδ k   Formula[9] The corrections are moderated by α, the learning rate, this number ranges from zero to one exclusive of the end points. α functions to prevent the network from training to be biased to the last pattern of the iteration. The network's error should preferably be minimized with respect to all the patterns in the training set. The same learning rule is applied to the hidden layer weight matrix and biases. In most adaptive systems, learning is facilitated with the introduction of noise. In neural networks this procedure is called learning with momentum. The correction to the weights of the output layer at iteration number τ is a function of the correction of the previous iteration, τ−1, and μ, the momentum constant; Δ w jk ( τ )=αδ k h j o +μΔw jk ( τ −1)  Formula [10] Δ b k ( τ )=αδ k +μΔb k ( τ −1)  Formula [11] The same procedure is applied to the hidden layer weights and biases. The correction terms are added to the weights and biases concluding the back-propagation phase of the iteration. The network can train for hundreds to millions of iterations depending on the complexity of the function defined by the input/output pairs. This type of back-propagation is a generalization of the known Widrow-Hoff learning rule applied to multiple-layer networks and nonlinear differentiable transfer functions (Rumelhart, D. E.; Hinton, G. E.; Williams, R., J. Parallel Distributed Processing , Vol. 1; MIT Press: Massachusetts, 1986). Input vectors and the corresponding output vectors are used to train until the network can approximate a function. The strength of a back-propagation neural network is its ability to form internal representations through the use of a hidden layer of neurons. For example, the “exclusive or” problem demonstrates the ability of neural networks, with hidden layers, to form internal representations and to solve complex problems. Suppose four input patterns [(0,1) (0,0) (1,0) (1,1)] with output targets [1, 0, 1, 0], respectively are used. A perceptron or other single layer system would be unable to simulate the function described by these four input/output pairs. The only way to solve this problem is to learn that the two types of inputs work together to affect the output. In this case the least similar inputs cause the same output, and the more similar inputs have different outputs (Rumelhart, D. E.; Hinton, G. E.; Williams, R., J. Parallel Distributed Processing , Vol. 1; MIT Press: Massachusetts, 1986). The ability required to solve the aforementioned exemplary problem is not unlike that required to find the best inhibitor when it does not share all the same quantum features of the transition state. It is this inherent ability of neural networks to solve complex puzzles that makes them well conditioned for the task of simulating biological molecular recognition for a variety of molecule families including hydrolases, proteases, polymerases, transcriptases, phosphatases, and kinases. Each input neuron is given information (electrostatic potential or geometry) about the nearest point on the surface of the inhibitor. In this design each input neuron may be imagined to be at a fixed point on the sphere around the inhibitors, judging each inhibitor in the same way the enzyme active site would. Training a neural network requires variation of four adjustable parameters; number of hidden layer neurons, the learning rate, momentum constant and number of training iterations. One way to tell that a network is well trained is to minimize the training set prediction error. This can be calculated by taking the difference between the target i value for a molecule (experimentally determined binding energy), and the number the neural network predicted for that pattern i , and summing the absolute value of this number for all the molecules in the training set. As training progresses the training set prediction error will decrease. Minimizing training set error is not without negative consequence; over-training occurs when the network trains for too many iterations, has too many hidden layer neurons, has too large of a learning rate or too small of a momentum constant. One way to tell that a neural network has not been over-trained is to have it make a prediction for a pattern not in the training set. That is, see if the network can generalize from the information contained in the input/output pairs of the training set and apply that information to a molecule it has not trained with. In accommodation of this fact a training set of molecules is used as an “adjuster” molecule. This molecule is left out of the training set during training and used to check if the neural network was over-trained. The procedure is to train the neural network until the prediction set error has decreased until it plateau's. At this point the training procedure is ended and the resulting neural network is tested with the previously unused adjuster molecule or molecules. Preferably, if the neural network predicts the adjuster molecules binding energy within 5%, that neural network's construction is saved, if the prediction is more than 5% off, a new construction is chosen. This procedure is repeated until a construction is found that allows the neural network to predict the adjuster molecule's binding energy within 5%. This is done for all of the molecules in the training set, and the most common neural network construction is chosen as the final construction. The final construction for this system is 5 hidden layer neurons, ten thousand iterations, learning rate equals 0.1 and the momentum term equals 0.9. Quantum chemical data can also be input to train a neural network. As part of an exemplary description of a use of the present invention, quantum descriptions of molecules were created in the following way: First the molecular structures are energy minimized using semi-empirical methods. Molecules with many degrees of freedom, are configured such that they all have their flexible regions in the same relative position. Then the wave function for the molecule is calculated with an available software program Gaussian 94 (Gaussian 94, Revision C.2; Gaussian, Inc., Pittsburgh, Pa., 1995). Preferably, a variety of basis tests are used to insure converged results. From the wave function, the electrostatic potential is calculated at all points around and within the molecule. The electron density, the square of the wave function, is also calculated at all points around and within the molecule. With these two pieces of information the electrostatic potential at the van der Waals surface can be generated. Such information sheds light on the kinds of interactions a given molecule can have with the active site (Horenstein, B. A.; Schramm, V. L. Electronic nature of the transition state for nucleoside hydrolase—A blueprint for inhibitor design, Biochemistry 1993, 32, 7089-7097). Regions with electrostatic potentials close to zero are likely to be capable of van der Waals interactions, regions with a partial positive or negative charge can serve as hydrogen bond donor or acceptor sites, and regions with even greater positive or negative potentials may be involved in coulombic interactions. The electrostatic potential also conveys information concerning the likelihood that a particular region can undergo electrophilic or nucleophilic attack. Since molecules described by quantum mechanics have a finite electron density in all space, a reasonable cutoff is required to define a molecular geometry. One choice is the van der Waals surface, within which 95% of the electron density is found. One can closely approximate the van der Waals surface by finding all points around a molecule where the electron density is close to 0.002 ±δ electrons/bohr (Wagener, M.; Sadowski, J.; Gasteiger, J., Autocorrelation of molecular surface properties for modeling corticasteriod binding globulin and cytosolic Ah receptor activity by neural networks, J. Am. Chem. Soc. 1995, 117, 7769-7775). In this formula δ is the acceptance tolerance, δ is adjusted so that about 15 points per atom are accepted, creating a fairly uniform molecular surface, as shown previously (Bagdassarian, C. K.; Braunheim, B. B.; Schramm, V. L.; Schwartz, S. D., Quantitative measures of molecular similarity: methods to analyze transition-state analogues for enzymatic reactions. Int. J. Quantum Chem., Quant. Biol. Symp. 1996, 23,73-80)(Hammond, D. J.; Gutteridge, W. E.; Purine and Pyrimidine Metabolism in the Trypanosomatide, Molecular and Biochemical Parasitology , 1984, 13, 243-261). The information about a given molecular surface is thus described by a matrix with dimensions of 4×n where n is the number of points for the molecule, and the row vector of length 4 contains the x,y and z-coordinates of a given point and the electrostatic potential at that point. To preserve the geometric and electrostatic integrity of the training molecules, a collapse onto a lower dimensional surface is preferably avoided. The molecules are preferably oriented using common atoms and rotation matrices. Three atomic positions that all the molecules share are chosen and named a,b and c;−a is then translated to the origin, and this translation is performed on b and c and all the surface points. The basis set is rotated such that b is on the positive x axis. Then the basis set is rotated such that c is in the positive x, z plane. Inputs to a neural network must be in the form of a vector not a matrix. In an exemplary utilization of the present invention, the aforementioned transformation, the electrostatic potential of the different molecular surfaces was mapped onto a common surface; a sphere with a larger radius than the largest molecule in the study. The nearest neighbor for each point on the sphere is found on the surface of the molecule. The sphere is larger than the molecules so all mapping is outward. The electrostatic potential of this molecular point is then given the x, y and z coordinates of its nearest neighbor on the sphere. This mapping insures that similar parts of the molecules occupy a similar position in the input vector. The input to the neural network is a vector of these mapped electrostatic potentials and the distance the points were mapped from the molecular surface to the sphere. The information in the second half of the input vector are scalars that relate the distance, in Å (angstroms), between a point on the sphere and the nearest neighbor point on the molecule's surface. This portion of the input is designed to inform the neural network about the relative shapes and sizes of the molecular surfaces. In the limit term of the algorithms, with an infinite number of points, all mappings are normal to the inhibitor's surface, and the mapping distances will be as small as possible. To approach this limit a ten fold excess of points was selected to describe the molecules. The molecule's surfaces are described by 150 points per atom. The reference sphere that the points are mapped onto is described by a smaller number of points, 15 times the average number of atoms in the molecules of the study. As a result of mapping to the reference sphere all molecules are described by the smaller number of points. Double Neural Networks It is known in the art that neural networks can be used to predict how well molecules will function as inhibitors before experimental tests are done (Braunheim, B. B.; Schwartz, S. D. Computational Methods for Transition State and Inhibitor Recognition. Methods in Enzymology (In press); (Braunheim, B. B.; Schwartz, S. D.; Schramm, V. L. The Use of Quantum Neural Networks in a Blind Prediction of Unknown Binding Free Energies of Inhibitors to IU-Nucleoside Hydrolase, J. Am. Chem. Soc ., (Submitted)). The present invention, however, presents methods that can be used to design inhibitors that are more potent than those in the training set. Specifically, a double neural network has been devised whose function is to optimize the characteristics of molecules needed for bioactivity. A standard neural network, shown in FIG. 1, and whose function is determined by equations 1 through 10, is used to learn the rules of binding to the enzyme. Once a neural network has been trained to recognize what features of inhibitors are necessary to bind to the enzyme, this network is preferably integrated into another neural network to form a double neural network. The goal of this construction is to use these learned binding rules to discern how to create a quantum object which binds more strongly than any yet presented to the neural network. The trained and fixed network is called the inner network 210 and the other part is called the outer network 220 , as seen in FIG. 2 . The double network preferably has five layers and it is preferred that only the weights and biases between the first two layers 250 and 260 , respectively, are allowed to vary during training. That is, during the training of the double network, the outer network's weights and biases, 250 and 260 , respectively, are responsible for minimizing prediction set error. The inputs to the double network are preferably the same as the ones used to train the inner network, and input into first input layer 290 . The outer network's output layer 230 is the input layer to the inner network, therefore the output of the outer network is the input to the inner network. The inner network's output values 240 are the same as those used before, the difference being that they have been decreased by least 1ΔG/RT. Preferably, they are decreased 3ΔG/RT. That is, they are the binding energies of slightly better inhibitors. To reduce the error of the inner network the outer network must output altered descriptions of the input molecule, but altered in a way such that it describes an inhibitor with a greater affinity for the enzyme. The outer network becomes an inhibitor “improver” because the inner network's fixed weights and biases contain the rules for binding to the enzyme. In order to compensate for the altered binding energies the outer network must output altered versions of the input molecules that would bind to the enzyme with greater affinity. The inputs to the double neural network contain both electrostatic potential and geometrical information. During the training of the double neural network both of these descriptors are preferably allowed to vary. The range of the output functions of the output layer of the outer network 230 had to be modified in a similar way as that seen in formula 4 above, δ i (x)=(γ i /l+e (−x) )−η i   Formula [12] Where γ i is the range of the numbers at position i in the input patterns and η i is the minimum number at position i in the input patterns. Preferably, the double neural network trains for many iterations in the same fashion as mentioned before, the only difference being that there is no established rule which defines the correct training parameters. When the inner network was trained the optimum number of hidden layer neurons, training iterations, learning rate and momentum term could be found through trial and error by testing if the network could make a prediction for a molecule not in the training set. The competency of the outer network cannot be tested independent of the inner network. This being the case the endpoint for training of the double network is preferably chosen as the minimum number of iterations and hidden layer neurons that were needed to minimize training error such that more iterations and hidden layer neurons did not decrease the error significantly. One skilled in the art will recognize that the preferable parameters discussed herein are matters of design choice, and can be varied based upon the preferences and experience of the user. The preferred construction for the double network was 5 hidden layer neurons (in the outer network) and 1 million training iterations. Preferably, the learning rate and momentum term were the same values used to train the inner network. After the double neural network is trained, improved versions of the molecular descriptions are output. These improved versions of input molecules are then transformed back into three dimensional representations of molecules. With the molecules in this format it is possible to identify the molecular features that the neural network found could be altered to result in improved binding characteristics, or in other desirable characteristics dependent upon the intent of the user. To test the double neural network concept, typically an enzyme with known binding or other characteristics is employed in the neural networks herein disclosed such that the molecule is optimized for improved chemical characteristics. The enzyme chosen was nucleoside hydrolase. Use of Neural Networks in Biology Neural networks have previously been used in the art in the task of simulating biological molecular recognition, Gasteiger et. al. have used Kohonen self-organizing networks to preserve the maximum topological information of a molecule when mapping its three-dimensional surface onto a plane (Gasteiger, J.; Li, X.; Rudolph, C.; Sadowski, J.; Zupan, J., Representation of molecular electrostatic potentials by topological feature maps. J. Am. Chem. Soc . 1994,116, 4608-4620). Wagener et. al. have used auto-correlation vectors to describe different molecules. In that work (Wagener, M.; Sadowski, J.; Gasteiger, J. Autocorrelation of molecular surface properties for modeling corticasteriod binding globulin and cytosolic Ah receptor activity by neural networks. J. Am. Chem. Soc . 1995, 117, 7769-7775), the molecular electrostatic potential at the molecular surface was collapsed onto 12 auto-correlation coefficients. Neural networks were used by Weinstein et. al., to predict the mode of action of different chemical compounds (Weinstein, J. N.; Kohn, K. W.; Grever, M. R.; Viswanadhan, V. N.; Rubinstein, L. V.; Monks, A. P.; Scudiero, D. A.; Welch, L.; Koutsoukos, A. D.; Chiausa, A. J.; Paull, K. D. Neural computing in cancer drug development: predicting mechanism of activity, Science 1992, 258, 447-451 ). The effectiveness of these chemical compounds on different malignant tissues served as one type of descriptor for future neural network methodologies. The predictive target for the neural network employed by Weinstein et al., was the mode of action of the chemical compounds tested (e.g. alkylating agent, topoisomerase I inhibitor, etc.). Tetko et. al., used a similar autocorrelation vectors approach (Tetko, I. V.; Tanchuk, V. Y.; Chentsova, N. P.; Antonenko, S. V.; Poda, G. I; Kukhar, V. P.; Luik, A. I. HIV- 1 reverse transcriptase inhibitor design using artificial neural networks. J. Med. Chem . 1994, 37, 2520-2526). So et al., used neural networks to learn and to predict biological activity from QSAR descriptions of molecular structure (Fausett, L. FUNDAMENTALS OF THE NEURAL NETWORKS; Prentice Hall: New Jersey, 1994). Neural networks were used by Thompson et. al. to predict the amino acid sequence that the HIV-1 protease would bind most tightly, and this information was used to design HIV protease inhibitors (Thompson, T. B.; Chou, K. -C.; Zheng, C. Neural network predictions of the HIV-1 protease cleavage sites. J. Theor Biol ., 1995, 177, 369-379). As is known in the art, Neural networks are multi-dimensional non-linear function approximators. However, neural networks can also be used as a decision making algorithm because they require no assumptions about the function they are learning to approximate. This aspect of neural networks is important because it has been assumed in the prior art that the interactions between a chemical or enzymatic inhibitor and the active site of the molecule inhibited are determined by many aspects of the inhibitor and it would be impossible for an individual to a priori predict them all. In this sense the Schrodinger equation creates a complex, nonlinear relationship between a fixed enzyme active site and variable enzymatic inhibitors. However, as disclosed herein, this non-linear relation is what neural networks can be used to discover and in this way can be manipulated to simulate or predict biological activity. The neural network learns to approximate a function that is defined by the input/output pairs. In the current invention the input is preferably a quantum mechanical description of a molecule and the output is the binding energy of that molecule with the enzyme. After the neural network is “trained” with the quantum features of an appropriate set of molecules, of known bioactivity, this network construct has then “learned” the rules relating quantum descriptions to chemical recognition for that type of compound. The current inventions presents the way in which a neural network and/or a double neural network can be created which uses these rules to generate features that optimize bioactivity. The next section of the specification provides a generalization of the neural network concept to the “double neural network” of the current invention in which one neural network is trained to recognize binding features and a second coupled network optimizes these features. The next section of the specification contains application of the concepts to a specific multi-substrate enzyme IU nucleoside hydrolase. EXAMPLE 1 Nucleoside Hydrolase Protozoan parasites lack de novo purine biosynthetic pathways, and rely on the ability to salvage nucleosides from the blood of their host for RNA and DNA synthesis (Hammond, D. J.; Gutteridge, W. E., Purine and Pyrimidine Metabolism in the trypanosomatide, Molecular and Biochemical Parasitology , 1984, 13, 243-261). The inosine-uridine preferring nucleoside hydrolase (IU-NH) from Crithidia fasciculata is unique and has not been found in mammals (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex, Biochemistry, 1998, May). This enzyme catalyzes the N-ribosyl hydrolysis of all naturally occurring RNA purines and pyrimidines (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex, Biochemistry, 1998, May). The active site of the enzyme has two binding regions, one region binds ribose and the other binds the base. The inosine transition state requires ΔΔG=17.7 kcal/mol activation energy, 13.1 kcals/mol are used in activation of the ribosyl group, and only 4.6 kcals/mol are used for activation of the hypoxanthine leaving group (Parkin, D. W.; Limberg, G.; Tyler, P. C.; Fumeau, R. H.; Chen, X. Y.; Schramm,V. L. Isozyme—specific transition state inhibitors for the trypanosomal nucleoside hydrolase. Biochemistry , 1997, 36(12), 3528-3419). Analogues that resemble the inosine transition state both geometrically and electronically have proven to be powerful competitive inhibitors of this enzyme and could be used as anti-trypanosomal drugs (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). The transition state for these reactions feature an oxocarbenium-ion achieved by the polarization of the C4′ oxygen C1′ carbon bond of ribose. The C4′ oxygen is in proximity to a negatively charged carboxyl group from Glutamate 166 during transition state stabilization (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). This creates a partial double bond between the C4′ oxygen and the C1′ carbon causing the oxygen to have a partial positive charge and the carbon to have a partial negative charge. Nucleoside analogues with iminoribitol groups have a secondary amine in place of the C4′ oxygen of ribose and have proven to be effective inhibitors of IU-NH. IU-NH acts on all naturally occurring nucleosides (with C2′ hydroxyl groups), the lack of specificity for the leaving groups results from the small number of amino acids in this region to form specific interactions; Tyrosine 229, Histidine 82 and Histidine 241 (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). The only crystal structure data available concerning the configuration of bound inhibitors was generated from a study of the enzyme bound to p-aminophenyliminoribitol (pAPIR). As seen in FIGS. 7 a - 7 d , the Tyrosine 229 relocates during binding and moves above the phenyl ring of pAPIR. The side chain hydroxyl group of Tyrosine 229 is directed toward the cavity that would contain the six member ring of a purine, were it bound (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). Histidine 82 is 3.6 Å(angstroms) from the phenyl ring of pAPIR, and in the proper position for positive charge-π interactions to occur (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). Histidine 241 has been shown to be involved in leaving-group activation in the hydrolysis of inosine, presumably as the proton donor in the creation of hypoxanthine (Degano, M.; Almo, S. C.; Sacchettini, J. C.; Schramm V. L. Trypanosomal nucleoside hydrolase, a novel mechanism from the structure of a transition state complex Biochemistry, 1998, May). The molecules used in the study are fixed such that their structures are consistent for all molecules. In the experiments it was assumed that the enzyme will bind all molecules in a similar low energy conformation. In the present invention this approach has been developed through experimentation on flexible linear chain inhibitors such as the arginine analogues for nitric oxide synthase. The double neural network of the current invention need not know the configuration as long as the conformation of all molecules that are presented to the neural network are consistent. The known crystal structure of the inhibitor p-aminophenyliminoribitol bound to IU-nucleoside hydrolase was used as the model chemical conformation. The inosine transition state structure is stabilized by a negatively charged carboxyl group within the active site 3.6 Å from the C4′ oxygen (Horenstein, B. A.; Parkin, D. W.; Estupinan, B.; Schramm, V. L. Transition-state analysis of nucleoside hydrolase from Crithidia fasciculata. Biochemistry , 1991, 30,10788-1079520). In order to simulate this aspect of the active site, a negatively charged fluoride ion (at the same relative position of the nearest oxygen of the carboxyl group) was included in the calculations of the electrostatic potential at the van der Waals surface. To underscore the complexity of an investigation of this enzyme the different nature of transition state structures for the two different kinds of substrates was examined, purines and pyrimidines. Inosine's transition state is the only one for which there is a determined structure. The transition state structure for inosine is created by polarization of the ribosyl group across the C4′ oxygen C1′ bond, and protonation of N7 of the purine group. This protonation would be impossible when dealing with the pyrimidine uridine, as there is no place for this group to receive a proton (the electrons of N3 are involved in the ring conjugation). Therefore it is clear that these two types of substrates have quite different transition state structures, and that the rules of tight binding pyrimidine analogues is quite different from those of binding purines. For pyrimidines analogues, the binding energy tends to decrease with increasingly electron withdrawing substitutions. The opposite trend is seen with purine analogues. Any mathematical model of the binding preferences of this enzyme would have to take into account these contradictory trends with the different kinds of substrates. The prior art has determined that with this enzyme system a neural network could make accurate predictions for both purine and pyrimidine analogues when trained with purine and pyrimidine analogues (Braunheim, B. B.; Schwartz, S. D. Computational Methods for Transition State and Inhibitor Recognition. Methods in Enzymology. In press); (Braunheim, B. B.; Schwartz, S. D.; Schramm, V. L. The Use of Quantum Neural Networks in a Blind Prediction of Unknown Binding Free Energies of Inhibitors to IU-Nucleoside Hydrolase. J. Am. Chem. Soc. Submitted). However, with the double neural network of the current invention, there is an added level of complexity, because the inner neural network must teach the outer network during training. That is, when the outer neural network improves the molecular descriptions, it is necessary for purines to be improved in different way than pyrimidines. However, with the use of the double neural network, predictions concerning bioactivity are significantly more precise and effective than previously seen in the art. Surface Analysis of Tested Molecules Because chemical reactivity is controlled by quantum mechanical properties, it was determined that a method could be developed to train neural networks with ab initio quantum chemical data. This method of the current invention has proven itself to be highly accurate in the prediction of binding strengths of diverse inhibitors to a variety of enzymatic systems. The current invention describes a new methodology which optimizes these quantum features to predict and then produce substances of therapeutic value, or commercial value, either through the development of de novo compounds or by providing a molecular structure useful in the search of existing chemical databases. FIGS. 3 a - 3 c , show coincidentally oriented points on the surfaces of some of the molecules used in the study before and after their geometries were modified by the double neural network of the current invention. In FIG. 3 a a purine and a pyrimidine analogue are shown oriented for maximum geometric coincidence, the input molecules are numbers 2 and 4 in FIG. 4 . As seen in FIGS. 3 b and 3 c , the optimized versions of the input descriptions of molecules, are compared to their unaltered input descriptions. The neural networks developed herein have the capacity to rearrange the geometry of the inhibitors enough so that if a purine was input into the outer network it could output a pyrimidine to the inner network. In FIGS. 3 b and 3 c the outer neural network was not found to average the geometric descriptions for the two kinds of inhibitors. This is an important result because from the trends within the molecules of the study that purines bind more tightly as the electron withdrawing tendencies of substituents are increased and the opposite is true for pyrimidines. That is, the enzyme must deal with the two kinds of substrates and inhibitors in different ways, and it is important that the neural network deal with them in different ways as well. It has been determined that the neural network developed herein can learn the different binding rules for the different kinds of inhibitors. The important finding with the double neural network is that it when it is utilized the inner network is able to teach the outer network about the different binding rules as they apply to structurally different molecules. This evidence comes from the fact that purine and pyrimidine geometric characteristics were not averaged. Idealized Molecules Examination of the idealized molecules, their electrostatic potential and geometry, shows that the double neural network changed purines in different ways than it did for pyrimidines. The purine analogues 4 , 9 , and 14 were improved by the double neural network in similar ways. The lower right hand side of the surface points shown in FIGS. 5 a and 5 c show that the neural network improved molecule 4 by making that region more positive. The molecule's entire surface appears to be more positive (red points have a partial positive charge and blue have a partial negative charge), this is consistent with the other improved purines, see FIGS. 6 and 7. This is not surprising, the transition state for inosine is positively charged, it stands to reason that the neural network improve purines by making them look more like the tightest binding purine. In FIG. 7 molecule 14 is shown before and after its description was idealized. Molecule 14 is larger than the other purine analogues, the double neural network improved its description such that it geometrically more resembles the other purines. In order for the double neural network to do this it must have learned that purines analogues that more closely resemble the typical purine form function better. In addition, the double neural network operated on this purine analogue in a different way than it did for any of the other purine analogues. The double neural network of the current invention developed a set of operations that minimized part of the molecule's surface that were applied exclusively to molecule 14 . FIGS. 8 through 10 show that the double neural network idealized pyrimidines by making the lower part of the base more negative. An aromatic ring can be made to be more electron rich by a variety of substituents (Br, OH, NH 2 ) these groups themselves vary greatly in their electrostatic potential, notice how the neural network consistently made the lower portion of the ring more electron rich while the upper part of the ring (where the substituent groups were) is comprised of both positive and negative points. That is, the neural network learned from the molecules in the training set that the top part of the phenyl ring can vary greatly in electrostatic potential, but the electron richness of the mid and lower part of the phenyl ring determines binding strength. Design of Inhibitors and Chemotherapeutic Compounds With the effectiveness of the double neural network method provided above, the automation of inhibitor design, rapid drug discovery and/or optimization, and the construction of an apparatus to complete this work becomes possible. The final step of this method is going from the electrostatic potential at the van der Waals surface points to a description of the molecule of interest's atomic coordinates and atom type. This problem involves an increase in complexity going from the input to the output, and is solved by improving the ability of the inner and outer neural network to work together. Optimizing the Network Function The inner network was trained within its adjusted co-efficients it contains the rules for binding to the enzyme. Molecular descriptions, in this format can be input to this network and a prediction of binding energy will be output. To show the complexity of the function contained within the trained neural network a random number generator was used to provide output numbers, within the ranges of the molecular descriptions, and see if the function contained within the trained neural network could be optimized randomly. This approach was unsuccessful presumably because there are 400 descriptors in the molecular descriptions used, adjusting them randomly would take an almost infinite amount of time if an exhaustive search is required. Therefore it was determined that a smart search was necessary, that is, the search for every one of the 400 descriptors must be guided toward the optimum value. One problem with this is there is no way to know what the optimum value of the descriptors is until the patterns are presented to the trained neural network and an output is generated and even then, this output will not be able to determine which numbers in the input acted to increase and decrease the output. Typically, the only place in a neural network where the values of an input are judged for the degree to which they optimize any function is inside the network. The error term and corrections of the hidden layer are: δ j = f  ( h j 1 )  ∑ k = l m     δ k  w jk Formula [13]  Δ w ij =αδ j x i   Formula[14] Δ b j =αδ j   Formula[15] Equation 13 shows how the error term for the hidden layer, δ j , is a function of both the input to the hidden layer and the error of the output layer. Equations 14 and 15 show how the error term of the hidden layer is preferably used to calculate the correction terms for the input layer so in the next iteration, the error term will be smaller. This sequence shown in equations 13 through 15 shows how the total error of the network is used to adjust the weights and biases of layers separated from the output layer. The neural network is, in fact, optimizing the input to the hidden layer in spite of the fact that there is no preset optimum of what the hidden layer input should be. This ability of the learning rules to find a multi-dimensional optimum is exactly what is exploited in the double neural network of the current invention. The “teaching” of the outer network by the inner network occurs because the input layer's error term of the inner network is optimizing the weights and biases of the output layer of the outer network. The reason why quantum features optimization occurs is because the weights and biases of the inner network are fixed and because the true binding energies have been increased slightly. With these configurations the training rules for the double neural network of the current invention were forced to find the multi-dimensional optimum for the output of the outer network's output layer, which is based on minimizing the error of the input layer of the inner network. Preferably, the only way to do this is to output a molecular description that has a slightly larger binding energy than the one input to the outer network. In satisfying these requirements the outer network of the current double neural network becomes a molecular features “optimizer” based on the rules contained within the inner network. Methods For Generating Input From Quantum Chemical data A second method can be used to transform the three dimensional surfaces of molecules into a common set of points on a sphere that can then be modeled by the neural networks provided for herein. This transformation works in a similar way as the one layered out above, the first step of this algorithm is to find the angle between the vector defined by line between a point on the sphere and the origin, with the line that connects the origin with every point on the molecular surface. The computer being used is utilized to search through this collection of angles and find five points with the smallest angle. These points are closest to the line that connects the origin and the point of the sphere's surface. From these five points one point that is selected, this point is the one closest to the point of the sphere's surface. Its electrostatic potential is the first number of the input vector. The distance between them is the second number in the input vector. Five points are used in this method, those with the smallest angle, to find the one point closest to the point of the surface of the sphere (e.g. the smallest distance). The reason for this is that sometimes molecular surfaces are bent or sterically hindered and it is difficult to determine the surface facing away from the center of the molecule. With this method it is possible to determine that the part of the molecular surface with which the molecule of interest interacts is the outermost part of the molecular surface. In this way it is possible to insure that the double neural network of the current invention “sees” the most physically relevant part of the molecule as its input. Thus, it can be appreciated that a computational method and an apparatus therefore have been presented which will facilitate the discovery of novel bioactive and/or therapeutic molecules, these methods rely on the use of a neural network to recognize and predict binding affinity Accordingly, it is to be understood that the embodiments of the invention herein providing for a more efficient mode of drug discovery and modification are merely illustrative of the application of the principles of the invention. It will be evident from the foregoing description that changes in the form, methods of use, and applications of the elements of the neural network system and associated algorithms disclosed may be resorted to without departing from the spirit of the invention, or the scope of the appended claims.

A computational method for the discovery and design of therapeutically valuable bioactive compounds is presented. The method employed has successfully analyzed enzymatic inhibitors for their chemical properties through the use of a neural network and associated algorithms. This method is an improvement over the current methods of drug discovery which often employs a random search through a large library of synthesized chemical compounds or biological samples for bioactivity related to a specific therapeutic use. This time-consuming process is the most expensive portion of current drug discovery methods. The development of computational methods for the prediction of specific molecular activity will facilitate the design of novel chemotherapeutics or other chemically useful compounds. The novel neural network provided in the current invention is “trained” with the bioactivity of known compounds and then used to predict the bioactivity of unknown compounds.

FIELD OF THE INVENTION This invention relates to “active implantable medical devices” as defined by the Jun. 20, 1990 directive 90/385/CEE of the Council of the European Communities. BACKGROUND OF THE INVENTION The above-identified definition includes in particular devices that monitor cardiac activity and generate impulses of stimulation, resynchronization, defibrillation, and/or cardioversion in the event the device detects a disorder in heart rate. It also includes, for example, neurological devices, pumps for distribution of medical substances, cochlear implants, and implanted biological sensors, as well as devices for measurement of pH or bio-impedance (such as trans-pulmonary impedance or intracardiac impedance measurements). With such devices, it is possible to operate a data exchange with a “programmer,” which is an external instrument that can be used to check the parameter settings of the devices, to read information recorded by the devices, to register information with the devices, and to update the internal control software of the devices. This data exchange is carried out by telemetry, i.e., by a technique of remote transmission of information, without galvanic contact. Until now, telemetry has primarily been carried out by magnetic coupling between coils in the implanted device and the programmer, which is a technique known as “process by induction.” This technique has certain disadvantages, however, because of the low range of an inductive coupling, which necessitates placing a “telemetry head” containing a coil in the vicinity of the implantation site of the active implantable medical device. Implementation of a different nongalvanic coupling technique has been proposed, using the two components of an electromagnetic wave produced by emitting/receiving circuits operating in the field of radio frequencies (RF), typically at frequencies around a few hundred MHz. This technique, known as RF telemetry, makes it possible to program or interrogate implants at distances greater than 3 meters, and thus carry out information exchanges without having to use a telemetry head, and even without intervention of an external operator. U.S. Patent Application Publication Nos. US2003/0114897 and US2003/0149459 describe implants and programmers equipped with such RF telemetry circuits. These RF circuits require, however, a current supply that is greater than what is necessary for the other circuits of the implant (e.g., the stimulation and detection circuits). For example, the current consumption of an RF circuit can exceed 3 mA during emission phases. In the case of defibrillators, taking into account the significant amount of current required by circuits used to apply shock therapy, the batteries used have low internal resistance and can supply without difficulty currents of about a few mA. On the other hand, pacemakers and similar devices, such as multisite or resynchronization devices, are generally supplied by small-size lithium-iodine batteries (or their equivalent), taking into account the low operating current required by the stimulation and detection circuits. These batteries have an internal resistance of about 100 Ω at the beginning of their life, which can increase to 1 kΩ, 2 kΩ, or more as the battery discharges. This internal resistance is not a problem for circuits with low consumption, but can prevent one from being able to provide RF circuits with the required level of current. A first solution is to use a different type of battery, for example, a reduced size lithium-manganese (LiMnO 2 ) weldable button battery with low impedance. There are such batteries whose characteristics are: diameter 12.2 mm, height 1.4 mm, capacity 27 mA/h, nominal voltage 3 V, self-discharge maximum 1% per annum, and which can provide currents of several mA. The current of RF circuits is exclusively provided by the button battery. When the button battery can no longer provide the current, the lithium battery of the pacemaker can provide a low current of 10 μA, which allows the transmitter-receiver to work in pulsated mode. The peak current is provided by a capacitor belonging to a supply circuit controlling the voltage of the battery. OBJECTS AND SUMMARY OF THE INVENTION The present invention provides a novel solution to the above-identified problem, which does not require recourse to an additional battery, due to a circuit making it possible to provide to an RF telemetry circuit incorporated in an implant the high current necessary for operation. For this purpose, the device of the invention, which includes a principal circuit, an auxiliary RF telemetry circuit, and a supply battery for the principal and auxiliary circuits, comprises, between the supply battery and the auxiliary circuit, a regulating circuit including an accumulator of electric power, coupled with the auxiliary circuit to deliver a current ready to feed this auxiliary circuit, and a load circuit coupled with the supply battery to maintain this accumulator with a predetermined level of load. The accumulator can be a rechargeable battery or a condenser. When the voltage corresponding to the predetermined level of load is higher than the voltage delivered by the supply battery, the load circuit includes a voltage multiplying stage. Advantageously, the load circuit is a circuit with intermittent and cyclic operation. The cyclic report/ratio can be a variable report/ratio function of the internal resistance of the supply battery, with the relative duration of the feeding cycles of the regulating circuit decreasing when the aforementioned resistance or level of load increases. The load circuit can stop the load of the accumulator when the terminal voltage level of the accumulator reaches a predetermined upper limit, when the charging current of the accumulator reaches a predetermined lower limit, or after completion of a given maximum duration. BRIEF DESCRIPTION OF THE DRAWINGS One now will describe an example of implementation of the device of the present invention, by reference to the annexed drawings, wherein the same numerical references indicate identical elements from one figure to another and: FIG. 1 is a simplified circuit diagram of the various elements constituting the feeding circuit of the invention; FIG. 2 shows details of the voltage multiplier of the circuit of FIG. 1 ; and FIGS. 3 and 4 show the charge and discharge configurations of the voltage multiplier of FIG. 2 according to the commutation states of the various switches. DETAILED DESCRIPTION OF THE INVENTION One now will describe an embodiment of the device of the invention, which can in particular be applied to the active implantable medical devices marketed by ELA Medical, Montrouge, France, such as the Symphony and Rhapsody-branded devices. These are devices with a programmable microprocessor comprising circuits to receive, format, and treat electric signals collected by implanted electrodes, and to deliver stimulation impulses to those electrodes. Adaptation of these devices to the implementation of the functions of the present invention is deemed to be within the ability of persons of ordinary skill in the art, and will not be described in detail (with regard to its software aspects, the invention can be implemented by suitable programming of the operating software of the pacemaker). In FIG. 1 , reference 10 indicates generally the RF telemetry circuits, which require a relatively high supply current (several mA), in particular during emission phases of the modulated signal. To deliver such a supply current, the invention proposes supplying these RF circuits starting from an accumulator 12 , itself charged by the supply battery 14 of the implanted device by means of a regulating circuit 16 . The supply battery 14 also supplies other circuits of the device (e.g., the detection and stimulation circuits). Accumulator 12 can be an accumulator of the lithium-ion type, of which there are models of reduced size having characteristics compatible with the supply requirements for RF circuits in implanted devices, typically: capacity 10 mA/h, internal resistance 25 Ω uninterrupted and 8 Ω into alternate, self-discharge maximum of 15% per annum, and rechargeable 250 times with a maximum loss of capacity of 14%. Such accumulators are in particular manufactured by the company Quallion LLC, Sylmar, Calif., USA. Alternatively, the lithium-ion accumulator can be replaced by a condenser of very strong rated capacity, typically about 1 Farad. The lithium-ion accumulators present a nominal voltage of 4 V at full load, which can then decrease to a value of about 3 V. Because the lithium-iodine batteries used in cardiac pacemakers have a nominal voltage of about 2.8 V, this voltage is insufficient to charge the accumulator 12 and it is therefore necessary to use an intermediate stage voltage multiplier 18 , making it possible to deliver to the accumulator a charging voltage of 2.8V×1.5=4.2 V. This voltage multiplier 18 is connected to the supply battery 14 by a switch 20 and to the accumulator 12 by a switch 22 . Its operation, and thus the load of the accumulator 12 , is controlled by a control circuit 24 , which includes a load checking circuit 26 whose entry is connected to a reference voltage standard V ref and to the point between voltage divider resistors 28 , 30 , which gives an indication of the terminal voltage of accumulator 12 and is brought into service by closing switch 32 . The internal structure of the voltage multiplier 18 is illustrated in FIG. 2 . It includes an entry 34 connected via switch 20 to the supply battery 14 , making it possible to charge a first condenser 36 by closing a switch 38 . This same entry also makes it possible to charge two condensers 40 , 42 assembled in series, by closing a switch 44 . In addition, a switch 46 makes it possible to connect the point between condensers 40 , 42 to the point between condenser 36 and switch 38 . Lastly, a switch 48 makes it possible to short-circuit the circuit formed by condensers 40 and 42 . In the initial phase, corresponding to the configuration of FIG. 3 , switches 20 , 38 , and 44 are closed, while switches 22 , 46 , and 48 are open. Condenser 36 is thus charged with the voltage of the battery (2.8 V) and condensers 40 and 42 are each charged with half of this voltage (1.4 V). In the subsequent phase, switches 20 , 38 , and 44 are opened, while switches 22 , 46 , and 48 are closed. Condensers 40 and 42 are then in parallel, and the voltage on their terminals (1.4 V) is added to the boundaries of condenser 36 (2.8 V), thus giving an exit voltage of 2.8+1.4=4.2 V. This voltage of 4.2 V produced by the voltage multiplier 18 is used to charge accumulator 12 , with a charging current which can vary from 2 to 0.1 mA, for example, according to changes in the internal resistance of the battery 14 . Advantageously, this load of the accumulator 12 is operated in an intermittent and cyclic way, for example, with a 25% load during a cycle of 1 second, the remaining 75% being devoted to the supply of the other circuits (e.g. the detection and stimulation circuits) of the device. Advantageously, the cyclic report/ratio (25% in the example above) is a variable report/ratio, a function of the internal resistance of the supply battery 14 (the duration of the phases of load becoming shorter when internal resistance increases) and/or of the load level of accumulator 12 (the duration of the cycles of load decreasing as the accumulator 12 approaches its level of maximum loading). The load of the accumulator 12 continues thus until reaching a predetermined level, for example, when the load checking circuit 26 detects that the terminal voltage of the accumulator has reached 4 V. The load checking circuit 26 then operates to suspend the load until the terminal voltage of the accumulator 12 has fallen below a given threshold due to energy consumption by the RF circuits. The load also can be stopped according to other criteria, for example, when the charging current reaches a low limit because of accumulator 12 , or at the end of a given maximum duration, for example, at the end of 100 hours for 10 mA of charging current. RF circuits 10 , supplied with the energy stored in accumulator 12 , could be fed satisfactorily with a relatively significant output current, for example from 3 to 20 mA. To take into account the difference between the terminal voltage of the accumulator (about 3 to 4 V according to the level of load) and the level of nominal voltage required for the supply of RF components (typically between 1.8 and 3 V), use of an adapted regulator is envisaged, for example, a linear or self-inductive regulator, to generate the supply voltage wanted with a suitable capacity while running. One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments which are presented for purposes of illustration and not of limitation.

An active implantable medical device having an RF telemetry circuit. The device is in particular a stimulation, resynchronization, defibrillation and/or cardioversion device. It includes a principal circuit, an RF telemetry auxiliary circuit and a supply battery for the principal and auxiliary circuits. It is envisaged to have between the supply battery and the auxiliary circuit a regulating circuit including an accumulator of electric power coupled with the auxiliary circuit to deliver a current ready to feed the auxiliary circuit, and a load circuit coupled with the supply battery to maintain the accumulator on a predetermined level of load.

[0001] This non-provisional application claims the benefit of U.S. Provisional Application No. 60/357,850, entitled “Zooming Interfaces For Sensemaking, Visualization, and Navigation” which was filed on Feb. 21, 2002, and is hereby incorporated by reference in its entirety. RELATED APPLICATIONS [0002] The following related U.S. patent applications are hereby incorporated herein by reference in their entirety: [0003] U.S. patent application Ser. No. ______, Docket No. D/A1311, entitled “System and Method for Interaction of Graphical Objects on a Computer Controlled System”; [0004] U.S. patent application Ser. No. ______, Docket No. D/A1311Q, entitled “System and Method for Moving Graphical Objects on a Computer Controlled System”; [0005] U.S. patent application Ser. No. ______, Docket No. D/A1687, Attorney Docket No. 111743, entitled “Method and System for Incrementally Changing Text Representation”; [0006] U.S. patent application Ser. No. ______, Docket No. D/A1687Q, Attorney Docket No. 115122, entitled “Method and System for Incrementally Changing Text Representation”; [0007] U.S. patent application Ser. No. ______, Docket No. D/A1309, Attorney Docket No. 112463, entitled “Methods and Systems for Navigating a Workspace”; and [0008] U.S. patent application Ser. No. ______, Docket No. D/A1310, Attorney Docket No.112467, entitled “Methods and Systems for Indicating Invisible Contents of Workspace”. BACKGROUND OF THE INVENTION [0009] 1. Field of Invention [0010] This invention relates to methods and systems for interactive classification of object. [0011] 2. Description of Related Art [0012] “Sensemaking” is a process of gathering, understanding, and using information for a purpose. Sensemaking tasks often involve searching for relevant documents and then extracting and reformulating information so that the information can be better utilized. A sensemaker gathers information, identifies and extracts portions of the information, organizes such portions for efficient use, and ultimately incorporates the information in a work product with the required logical and rhetorical structure. [0013] A common part of many sensemaking tasks is organizing “factoids” or other units of information, or objects, into related groups. Objects may be any form, such as simple text or a list of items. The difficulty of organizing objects depends on several practical factors, including the number of objects to be organized and the efficiency of the operations for finding, reading and manipulating the objects. [0014] A key factor that influences the efficiency of an organizing task on a display, such as a computer display, is the size of a viewed space in a workspace. For a classification task on a display too small to show all of the objects, some objects are necessarily out of sight, so that a sensemaker must take additional steps and often use more time in locating and manipulating objects. In this case, search operations generally require not only scanning with the eyes, but also navigation with a pointer using panning, scrolling, and zooming. Such operations, which bring objects into the viewed space, significantly add to the time required in comparison with larger displays. The overhead of panning or scrolling can also adversely affect overall performance by distracting the sensemaker with extra steps and by requiring the sensemaker to remember things while navigating between objects. [0015] Estes teaches that there are two primary types of models used to explain human classification behavior: exemplar-based models and rule-based models (Estes, W. K. (1994) Classification and Cognition. New York: Oxford University Press, pp 33-87). These two models of classification also correspond well with how humans organize objects into groups using a workspace such as a computer display. [0016] In organizing objects into groups in a workspace, the rule-based classification tends to be formal. In this instance, a set of categories is determined, and explicit membership criteria are established for each of the categories by rules. To classify an object, a sensemaker checks the rules for each category and adds an object to whichever category the object satisfies the rules. Classifying an object amounts to adding the object to a “bucket” containing the objects that satisfy the membership criteria. [0017] Determining or defining a category requires upfront work. A sensemaker may have to assign or allocate a place for the new category, determine the membership criteria, add the object to the category, and write down the membership criteria in a title or other visible label. Once this is done, however, future assignments of objects to this category go faster because the sensemaker need only check the label and then “drop” appropriate objects into the category. [0018] With respect to computer systems, the membership criteria often take the form of a title or label on a window or folder. For example, e-mail systems, such as Eudora® and Microsoft® Outlook®, provide hierarchies of named mail folders for classifying messages. Storing an email message into an appropriate folder is an example of classifying an object. A key feature of interactive rule-based classification is that the decision about how to classify an object requires reading the membership criteria (in the form of titles or folder names), but generally does not require reading the previously classified objects (such as the email messages already in the folder). [0019] Organizing objects into groups in a workspace using exemplar-based classification, on the other hand, is more tentative and informal. To classify an object, one must compare the object with the examples in an informal category or cluster in order to determine whether the object fits. Classifying an object amounts to placing the object in or near a cluster of similar objects. [0020] Creating a cluster or implicit category requires less upfront work than creating a formal, or explicit category, but has greater overhead for future classifications. To set up a new cluster, a sensemaker simply places a new object in some uncrowded region of the workspace, possibly near other clusters or categories that seem somewhat related. No label or membership criteria are supplied. Future classifications are somewhat more tedious than in the case of explicit categories because the sensemaker needs to examine members of clusters in order to determine where to place new objects. Unless the sensemaker remembers tentative abstractions for a cluster, there is no shortcut for membership determination by checking a label or rule. [0021] In a workspace, exemplar-based classification amounts to visual clustering. There are no explicit titles or rules for membership in a cluster. The boundaries of the clusters can be somewhat more tentative and ambiguous, especially when two clusters are near each other. The decision about how to classify an object requires reading or scanning other objects to detect similarity, and then locating the new object near the other objects that the new object best matches. [0022] In interactive sensemaking workspaces, two types of overviews may be available: structural overviews that show a list of categories to which objects may be classified, and special overviews that show positional relationships of objects in the workspace. [0023] Structural overviews are well suited for rule-based classification where the formal categories correspond to labels in an outline. FIG. 1 is an example of structural overviews. An interface, such as a drag-and-drop interface, makes the process of adding objects to a category convenient. Structural overviews can incorporate nesting, yielding hierarchical trees of categories. [0024] However, structural overviews provide no support for exemplar-based classification because the structural overviews show the labels of formal categories, but nothing about the informal categories. [0025] Spatial overviews provide a rendering of the workspace. Such overviews can be allocated permanently or transiently at a portion of the display space, while most of the sensemaker's work is done in a focus of the workspace. Using such spatial overviews, formal categories and informal categories can be both shown at a reduced scale. [0026] However, because of the reduced scale, the sensemaker may have to zoom in the workspace in order or put a desired section of the workspace in focus, to recognize and understand the contents of objects for classification. [0027] [0027]FIG. 2 shows an example of a workspace, a viewed space, an overview and objects. In FIG. 2, a focus 100 includes objects 110 - 130 . An overview 140 provides a rendering of an entire workspace 150 . A frame 160 indicates a currently viewed space within the workspace 150 . An object may have one or more sub-objects within, which may form a multi-level object. A sensemaker can bring any part of the workspace into the viewed space by clicking or dragging on a region in the overview 140 or scrolling the viewed space. [0028] U.S. Pat. No. 6,243,093 to Czerwinski et al. discloses a system for spatially organizing stored web pages that automatically highlights similar web pages during organization and retrieval tasks. When the user drags or clicks on a web page, similarity metrics between the dragged or clicked web page and other stored web pages in a single-level spatial workspace are computed and web pages with such similarity are highlighted to the sensemaker. This system computes similarity metrics between items in a spatial workspace and displays this similarity to the user. However, this system does not indicate how objects are similar, but rather simply indicates numeric scores for the similarity. Similarly, this system does not use automatic similarity indicators for labeled hierarchical organizations rather than large single level spaces. [0029] Similar techniques have also been applied to information retrieval in large document collections, such as the Web. One such technique described by Hearst (Hearst, 1995, TileBars: Visualization of Term Distribution Information in Full Text Information Access, Proceedings of CHI '95. p. 59-66), called TileBars, creates simple colored rectangles to represent the pages in a set of documents. In this technique, the intensity of the fill color of these rectangles signifies the number of query matches on the specified page. A related technique by Woodruff et al. (Woodruff, Faulring, Rosenholtz, Morrison, & Pirolli, 2001, Using Thumbnails to Search the Web, Conference Proceedings of CHI 2001, Vol. 3, Issue 1, p. 198-205, 552) enhances standard web page thumbnails with enlarged text labels. These enlarged labels indicate the location and frequency of query terms, combining the benefits of traditional thumbnails with the benefits of simple text summaries. Nevertheless, both these techniques have been applied only to static one-dimensional documents. These techniques do not extend them to dynamic documents with multiple dimensions. SUMMARY OF THE INVENTION [0030] The interactive classification technique according to the invention facilitates classification of a new object added to a workspace. In a workspace for sensemaking, objects often include text segments. In addition, objects may be made multi-level, that is, objects may have sub-objects within. Sensemakers tend to use a mixture of rule-based and exemplar-based strategies for classification tasks when working in such a workspace. A mixture of strategies enables sensemakers to create tentative clusters when the sensemakers are not yet sure of the criteria, and to create efficient rule-based categories, as the criteria are determined or established. [0031] To increase the efficiency and ease of locating and understanding objects in a workspace, objects may be interactively classified and put together based on the objects' similarity. [0032] Therefore, an object of the invention is to provide methods and systems for interactive classification of objects. In various exemplary embodiments, the method includes receiving an instruction to place a new object into a workspace, determining a similarity of the new object to an existing object, category, or cluster, and providing a visual indication of the similar words in both the new object and an existing object, cluster, or category. The visual indication may also reflect the degree to which the new object is similar to the existing object, cluster, or category. The method may also provide an indication of a place for manual placement of the new object. The method may also include providing a view of a place with objects having the similarity. [0033] Therefore, the methods and systems according to this invention can facilitate classification of objects in a workspace and thus facilitate the sensemaker's understanding of the objects and the workspace. BRIEF DESCRIPTION OF THE DRAWINGS [0034] Various exemplary embodiments of the systems and methods according to this invention will be described in detail, with reference to the following figures, wherein: [0035] [0035]FIG. 1 is an exemplary structural overview; [0036] [0036]FIG. 2 is an exemplary workspace including a current view of objects and an overview; [0037] [0037]FIG. 3 shows a first exemplary embodiment according to this invention in which objects in a workspace are highlighted based on a similarity metric; [0038] [0038]FIG. 4 shows a second exemplary embodiment according to this invention in which terms are enlarged; [0039] [0039]FIG. 5 is an exemplary block diagram of an interactive classification system according to this invention; and [0040] [0040]FIGS. 6 and 7 show a flowchart illustrating an exemplary embodiment of a method of interactive classification according to this invention. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0041] Interactive classification methods according to this invention can provide a way to automatically classify and/or place a new object, or provide assistance for manual classification and/or placement of objects in a workspace, based on similarity of the objects. In various exemplary embodiments, the methods according to this invention facilitate interactive classification with improved performance, such as speed and/or ease. [0042] Various aspects of this present invention may be incorporated in a system, such as the systems disclosed in a co-pending, co-assigned U.S. patent application Ser. No. ______, Docket No. D/A1311, entitled “System and Method for Interaction of Graphical Objects on A Computer Controlled System,” which is incorporated herein by reference in its entirety. [0043] For interactive classification of an object, a similarity metric may be determined for identifying which objects are more similar, and a key element identifier may be used for determining which of various elements, such as words, in an object contributes most to the judgment of similarity. For example, similarity may be determined as follows. [0044] First, an object may be divided into elements, such as, individual words. Then, the words are reduced to the smallest form, or stems, so that variant forms of each individual word become identical. Stem or term frequencies in the object (“document”) and in the collection of objects (“corpus”) are then computed. A combined weight reflecting the relative frequencies of the terms in the document and corpus is computed using a term frequency inverse document frequency (TFIDF) or similar scheme. [0045] A similarity matcher may be used in conjunction with other parts of a sensemaking tool to give a sensemaker more useful feedback and to facilitate an interactive classification task. For example, related objects and groups in the workspace and overview may be highlighted when a new object is selected for classification. For example, as shown in FIG. 2, in an overview 200 , objects 210 that have a similarity with the new object are highlighted for an indication to the sensemaker. Such highlighting may draw the sensemaker's attention to the most likely classification opportunities, depending on the selectivity of the similarity computation. Alternatively or additionally, the system may automatically pan into a view that includes a best-matching object, cluster, or category for the new object. Further, a shortcut operation, such as a gesture or button on the object, may be provided that instructs the system to classify the object, without the sensemaker needing to perform a drag-and-drop operation. In many cases, combining such feedback with what the sensemaker already knows about the collection may be enough to facilitate complete classification. [0046] In addition to determining a similarity metric for individual objects, a similarity score for a group, such as a cluster or explicit category, may be determined. [0047] One approach is to take all of the objects in a group and treat the objects as if the objects constitute a single document. Assuming that the term frequencies are normalized for the document, this approach may essentially create an average document to which the unclassified object may be compared. [0048] Another approach is to take a score of the best matching object in a group as a representative of the group. This approach may tend to emphasize clusters where at least some of the objects have a very high similarity to the unclassified object. [0049] Another approach is to determine a weighted intermediate score between the average match and the best match for a group. For example, a composite score may be determined from the average similarity and the best similarity for the group. [0050] The methods for computing a similarity score for a group as described above may not take into account any explicit rules for formal categories. In classification tasks, the “rules” may be in the form of labels rather than executable rules. Various methods are contemplated for including the content of the label of a group in a similarity matching process, as further described below. [0051] One approach is to simply match the label, ignoring the content of the objects in the group. Another approach is to append one or more copies of the group label to the individual objects in order to enhance the contribution of the label terms in the computation of a similarity score for each object. This approach can be combined with the methods described above. [0052] In the case of informal categories, two exemplary approaches are computing similarities only for individual objects and computing aggregate similarities. The latter approach may require determining which objects are in a cluster. Two kinds of information may be used to in determining cluster membership: the coordinates of the objects in the workspace and the similarity of the objects. Such information may be combined in various ways. Once a cluster is identified, the aggregate scoring methods described above for groups may be used. [0053] One approach to displaying similarity information, either in an overview or in a detailed workspace, is to use a similarity metric to determine which regions to highlight. This approach may be similar to a technique disclosed in a copending, co-assigned U.S. patent application Ser. No. _______, Docket No. D/A1310, Attorney Docket No. 112467, entitled “Methods and System for Indicating Invisible Contents of Workspace”, incorporated herein by reference in its entirety. Various visual effects may be used to convey information, such as color and intensity. [0054] For example, only matches above a predetermined threshold may be included in the visual transfer functions using, for example, one form of highlighting to indicate matches for which there is a very high degree of similarity and another form of highlighting to indicate matches with a significant, but more moderate degree of similarity. [0055] An issue with just using similarity scores for classification is that the scores may be non-specific. An object about, for example, “driving tips” might match one group of objects on the basis of one criterion (e.g., “weather rules” or rules mentioning “fog”) and another group of objects on the basis of another criterion (e.g., “speed rules” or rules mentioning “speed”). If the similarity scores for the two groups are about equal, then highlighting by itself does not convey information for discriminating between the two groups. [0056] An alternative to simple highlighting based on the similarity score is to augment the display of matching objects with a specific indicator of the reason for the match, such as the particular elements that contribute most to the similarity score. In the above-described examples, the indicator may be, for example, temporarily superimposing the most important matching or similarity term(s) in a different color on each object or group. [0057] This approach of enhancing the display of similar objects and groups compensates to some degree for the inevitable irregularities in similarity matching scores and provides more specific signals to the sensemaker about which groups or objects are similar in ways that matter. As shown in FIG. 4, where more than one category is similar, specific terms 300 like “fog” and “speed” may be enlarged to convey more information to the sensemaker. Other indication of terms is contemplated as well, such as highlighting, flashing, and the like. [0058] When similarity signals are displayed, the indication should be clear as to which objects the similarity signals refer. One approach is to display similarity signals, such as similarity terms, within the bounds of the matched object. Another approach is to provide call-outs or labels on arrows that indicate that a similarity signal refers to a particular object. [0059] As new objects are classified, the similarity signals may need to be refreshed to make use of the information in the objects. That is, signals from a previous match may need to disappear. One approach is to make similarity signals transient so that the signals may stay in view only during a specific matching operation. Another approach is to make the signals slowly fade from the display, or to make the signals disappear in response to a sensemaker's request. It will be appreciated that many other approaches are possible. [0060] The strongest matches may not be close enough to be displayed simultaneously. The system may automatically bring into view the objects or groups with the greatest degree of match. Furthermore, the system may automatically pan, scroll, or zoom based on the similarity scores of the groups and/or objects. [0061] Should the sensemaker desire to return to the workspace in which the sensemaker was working before such panning, scrolling or zooming, controls enabling the sensemaker to go forward or backward, for example, by forward and backward buttons, may be provided to help the sensemaker tour the matching groups and/or objects. An example of a technique used to go forward or backward is described in a co-pending, co-assigned U.S. patent application Ser. No. ______, Docket No. D/A1309, Attorney Docket No. 112463, entitled “Method and System for Navigating A Workspace,” which is incorporated herein by reference in its entirety. [0062] Another approach is to use “pop-up signals” such that the similarity signal appears on the objects when an input is received. For example, as the sensemaker moves a cursor, a mouse pointer or the like over an overview or over the workspace, annotations about similarity may transiently appear. [0063] Moreover, when a new object to be classified has a degree of match with nested groups at several levels of a hierarchy, the signal may need to differentiate among the levels and may indicate the level where the similarity is the greatest. [0064] Similarity may be shown either to individual objects of a group or to a group as a whole. Generally, there may not be enough space to display both. The amount of space available can be used to govern the choice. When there is insufficient space to indicate the similarity to each of the separate objects in a group, the display may be limited to the similarity terms for the group as a whole. In the case of clusters, a determination of the elements that are in the cluster may be required. [0065] Drag-and-drop interfaces to an overview may speed up the classification of a new object. Using the drag-and-drop interfaces, when the user places a new object, the system may automatically indicate one or more positions to which the user may place the new object based on the similarity between the new object and the objects that already exist in the workspace. The description of how the drag-and-drop technique works is omitted here since any existing or hereafter developed drag-and-drop technique may be used. It should be understood that any other known or hereafter developed technique for introducing an object to the workspace may be used. [0066] [0066]FIG. 5 shows a block diagram of an interactive classification system 500 according to the invention. The interactive classification system 500 includes a controller 510 , a memory 520 , an input/output (I/O) interface 530 , a new object detection circuit 540 , a similarity signal determination circuit 550 , a cluster detecting circuit 560 , a representation circuit 570 , a placement assisting circuit 580 , and a visual effect circuit 590 , which are connected to each other via a communication link 600 . To the I/O interface 530 , a data sink 610 , a data source 620 and a user input device 630 are connected via communication links 611 , 621 and 631 , respectively. [0067] The controller 510 controls the general data flow between other components of the interactive classification system 500 . The memory 520 may serve as a buffer for information coming into or going out of the system 500 , may store any necessary programs and/or data for implementing the functions of the interactive classification system 500 , and/or may store data, such as history data of interactions, at various stages of processing. [0068] Alterable portions of the memory 520 may be, in various exemplary embodiments, implemented using static or dynamic RAM. However, the memory 520 can also be implemented using a floppy disk and disk drive, a writable or rewritable optical disk and disk drive, a hard drive, flash memory or the like. [0069] The I/O interface 530 provides a connection between the interactive classification system 500 and the data sink 610 , the data source 620 , and the user input device 630 , via the communication links 611 , 621 , and 631 , respectively. [0070] The new object detection circuit 540 receives an instruction from the user to place a new object. To provide the instruction, the user may use a drag-and-drop technique, for example, to place a new object. [0071] The similarity determination circuit 550 determines the similarity of a new object to the objects in the workspace. Such determination may be done by, for example, determining a similarity metric for identifying which object(s) is most similar and determining which of the elements (e.g., words) in the new object most contributed to the judgment of similarity. Such similarity metric may be calculated by breaking an object into elements, such as words, reducing the elements to stems, and computing term (stem) frequencies in the object and in the collection of objects. [0072] The cluster detecting circuit 560 determines a cluster or a group of objects in the workspace. Determination of a cluster or a group may be done by identifying coordinates of the objects in the workspace and/or the similarity of the cluster or the group. [0073] The similarity representation circuit 570 represents the indication of similarity of the new object to the existing objects by, for example, highlighting the most similar categories or objects. In addition, the similarity representation circuit 570 may transiently pop up a similarity signal based on an input from a user interface, such as moving a cursor onto an interface using a mouse or the like. The representation circuit 570 may also represent elements in objects that are most similar to the new object and refresh the similarity signal for previous matches by using, for example, fading operations. [0074] The placement assisting circuit 580 provides assistance to the sensemaker for placement of the new object, including, for example, highlighting a possible space for placement of the object based on the similarity metric or providing an arrow in the overview. [0075] The visual effect circuit 590 provides visual effects after placement of the new object. Such visual effects may include scrolling, panning, and/or zooming in the workspace. [0076] The data sink 610 can be any known or later-developed device that is capable of outputting or storing the processed media data generated using the systems and methods according to the invention, such as a display device, a printer, a copier or other image forming device, a facsimile device, a memory or the like. In the exemplary embodiments, the data sink 610 is assumed to be a display device, such as a computer monitor or the like, and is connected to the interactive classification system 500 over the communications link 611 . [0077] The data source 620 can be a locally or remotely located computer sharing data, a scanner, or any other known or later-developed device that is capable of generating electronic media, such as a document. The data source 620 may also be a data carrier, such as a magnetic storage disc, CD-ROM or the like. Similarly, the data source 620 can be any suitable device that stores and/or transmits electronic media data, such as a client or a server of a network, or the Internet, and especially the World Wide Web, and news groups. The data source 620 may also be any known or later developed device that broadcasts media data. [0078] The electronic media data of the data source 620 may be text, a scanned image of a physical document, media data created electronically using any software, such as word processing software, or media data created using any known or later developed programming language and/or computer software program, the contents of an application window on a sensemaker's desktop, e.g., the toolbars, windows decorations, a spreadsheet shown in a spreadsheet program, or any other known or later-developed data source. [0079] The user input device 630 may be any known or later-developed device that is capable of imputing data and/or control commands to the interactive classification system 500 via the communication link 631 . The user input device may include one or more of a keyboard, a mouse, a touch pen, a touch pad, a pointing device, or the like. [0080] The communication links 600 , 611 , 621 and 631 can each be any known or later-developed device or system for connecting between the controller 510 , the memory 520 , the I/O interface 530 , the new object detection circuit 540 , the similarity determination circuit 550 , the cluster detecting circuit 560 , and the representation circuit 570 , the placement assisting circuit 580 , and the visual effect circuit 590 , to the data sink 610 , the data source 620 , and the user input device 630 , respectively, to the interactive classification system 500 , including a direct cable connection, a connection over a wide area network or local area network, a connection over an intranet, a connection over the Internet, or a connection over any other distributed processing network system. Further, it should be appreciated that the communication links 600 , 611 , 621 and 631 can be, a wired wireless or optical connection to a network. The network can be a local area network, a wide area network, an intranet, the Internet, or any other known or later-developed other distributed processing and storage network. [0081] [0081]FIGS. 6 and 7 show a flowchart of an exemplary embodiment of a method of indicating objects according to the invention. [0082] The process starts at step S 1000 and continues to step S 1010 . In step S 1010 , a new object is introduced to an overview of a workspace, and the process continues to step S 1020 . In step S 1020 , a determination is made as to whether clusters should be determined. If so, the process continues to step S 1030 ; otherwise the process jumps to step S 1040 . [0083] In step S 1030 , clusters are determined, and the process continues to step S 1040 . In step S 1040 , similarity of the objects already existing in the work space is determined with respect to the new object. Then, the process continues to step S 1050 . [0084] In step S 1050 , a determination is made as to whether a threshold on the similarity should be used. If so, the process continues to step S 1060 ; otherwise, the process jumps to step S 1070 . In step S 1060 , the objects having similarity below the threshold are discarded, and the process continues to step S 1070 . [0085] In step S 1070 , a determination is made as to whether there are any objects with the similarity. If so, the process continues to step S 1080 ; otherwise, the process jumps to step S 1150 , at which the process ends. [0086] In step S 1080 , similarity indicators are displayed. The similarity indicators may include similarity metrics and highlighting terms used for determining the similarity, for example. In step S 1090 , a determination is made as to whether a shortcut should be displayed to assist classification of objects. If so, the process continues to step S 1100 ; otherwise, the process jumps to step S 1110 . [0087] In step S 1100 , the shortcut is displayed, and the process continues to step S 1110 . In step S 1110 , a determination is made as to whether a possible location(s) for placing of the new object should be indicated. If so, the process continues to step S 1120 ; otherwise, the process jumps to step S 1130 . [0088] In step S 1120 , a possible location(s) for placing of the new object is indicated, and the process continues to step S 1130 . In step S 1130 , a determination is made as to whether a viewed space should be moved to the similar object(s). If so, the process continues to step S 1140 ; otherwise the process jumps to step S 1150 . At step S 1140 , a viewed space is moved to the similar object(s). Then, the process continues to step S 1150 . The process ends at step S 1150 . [0089] It is apparent that these steps are described in above order for illustration purpose, and in various exemplary embodiments, the determination of similarity of objects, placement of the new object and the like described above, may be performed in different order and/or with additional or fewer steps. Furthermore, the invention is not limited to the above described methods and system. Those skilled in the art would understand that many different modifications are possible without departing from the scope of the invention. [0090] Additionally, those skilled in the art will recognize many applications for the present invention include, but not limited to, document display devices, such as browser devices, that display applications of a personal computer, handheld devices, and the like. In short, the invention has application to any known or later-developed systems and devices capable of interactively classifying objects in a workspace. [0091] In the exemplary embodiments outlined above, the interactive classification system 500 can be implemented using a programmed general-purpose computer. However, the interactive classification system 500 can also be implemented using a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an ASIC or other integrated circuit, a digital signal processor, a hardware electronic or logic circuit, such as a discrete element circuit, a programmable logic device, such as PLD, PLA, FPGA or PAL, or the like. In general, any device, capable of implementing a finite state machine that is in turn capable of implementing the flowchart shown in FIGS. 8 - 10 can be used to implement the interactive classification system 500 . [0092] Each of the circuits or routines and elements of the various exemplary embodiments of the interactive classification system 500 outlined above can be implemented as portions of a suitable programmed general purpose computer. Alternatively, each of the circuits and elements of the various exemplary embodiments of the interactive classification system 500 outlined above can be implemented as physically distinct hardware circuits within an ASIC, or using FPGA, a PDL, a PLA or a PAL, or using discrete logic elements or discrete circuit elements. The particular form each of the circuits and elements of the various exemplary embodiments of the interactive classification system 500 outlined above will take is a design choice and will be obvious and predicable to those skilled in the art. [0093] Moreover, the exemplary embodiments of the interactive classification system 500 outlined above and/or each of the various circuits and elements discussed above can each be implemented as software routines, managers or objects executing on a programmed general purpose computer, a special purpose computer, a microprocessor or the like. In this case, the various exemplary embodiments of the interactive classification system 500 and/or each or the various circuits and elements discussed above can each be implemented as one or more routines embedded in the communication network, as a resource residing on a server, or the like. The various exemplary embodiments of the interactive classification system 500 and the various circuits and elements discussed above can also be implemented by physically incorporating the interactive classification system 500 into a software and/or hardware system, such as the hardware and software system of a web server or a client device. [0094] While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.

Methods and systems provide a computational assistance for interactive classification that compensates for the small size of computer screens and accelerates classification tasks. Similarity indicators reduce manual search by enabling information objects to “call out” automatically to encourage a sensemaker to place related items nearby. Similarity terms signal which groups or objects match and why they match. Using these techniques, an interactive classification tool can focus a sensemaker's attention, move things into view automatically, and provide shortcuts for automatic classification. These techniques speed up classification for rule-based classification, example-based classification, and mixed strategies and have the potential for application in a wide variety of sensemaking tools.

TECHNICAL FIELD [0001] This disclosure relates generally to signal acquisition systems and, more particularly, to a system, apparatus and method for reducing measurement errors due to, for example, probe tip loading of a device under test. BACKGROUND [0002] Typical probes used for signal acquisition and analysis devices such as oscilloscopes and the like have an impedance associated with them which varies with frequency. As the bandwidth of test and measurement instruments and probe system become wider the effects of probe tip loading of non-flat through responses becomes more significant than in past systems. [0003] U.S. Pat. No. 6,725,170 entitled “Smart probe apparatus and method for automatic self-adjustment of an oscilloscope's bandwidth” to Barton Hickman, owned by Tektronix, Inc. and incorporated herein by reference, discloses storing S-parameters of a probe so that equalization filters can be computed when a probe is connected to different input channels of different types of test and measurement instruments. These equalization filters, however, are designed for device under test (DUT) source impedance of 50 ohms. What is needed is an equalization filter that can be calculated using the nominal source impedance of the DUT. Using the prior methods, if the source impedance of the DUT is not 50 ohms, then the acquired waveform received via a probe loading such a circuit may not accurately represent the voltage of the circuit prior to the introduction of the probe. SUMMARY [0004] Certain embodiments of the disclosed technology include a test and measurement system including a test and measurement instrument, a probe connected to the test and measurement instrument, a device under test connected to the probe, at least one memory configured to store parameters for characterizing the probe, a user interface and a processor. The user interface is configured to receive a nominal source impedance of the device under test. The processor is configured to receive the parameters for characterizing the probe from the memory and the nominal source impedance of the device under test from the user interface and to calculate an equalization filter using the parameters for characterizing the probe and nominal source impedance. The equalization filter is adapted to compensate for loading of the device under test caused by a measurement of the device under test. [0005] Certain other embodiments of the disclosed technology include a method for calculating an equalization filter for use in a test and measurement system. The method includes receiving at a processor parameters for characterizing a probe of a test and measurement system, receiving at the processor via a user interface a nominal source impedance of a device under test, and computing an equalization filter adapted to compensate for loading of a device under test caused by measurement of the device under test based on the parameters for characterizing the probe and the nominal source impedance of the device under test. BRIEF DESCRIPTION OF THE DRAWINGS [0006] FIG. 1 illustrates an ideal input waveform and the output waveform using a DUT with a 50 ohm source impedance loading the tip of the probe. [0007] FIG. 2 illustrates the ideal input waveform of the FIG. 1 and output waveforms with varying DUT source impedance values. [0008] FIG. 3 illustrates a block diagram of a test and measurement system of the disclosed technology. [0009] FIG. 4 illustrates a user interface of the disclosed technology. [0010] FIG. 5 illustrates another user interface of the disclosed technology. [0011] FIG. 6 illustrates a variety of equalization filters calculated using the disclosed technology. [0012] FIG. 7 illustrates an ideal input waveform and various output waveforms using different equalization filters for various DUT source impedance. DETAILED DESCRIPTION [0013] In the drawings, which are not necessarily to scale, like or corresponding elements of the disclosed systems and methods are denoted by the same reference numerals. [0014] Traditional accessories for test and measurement instruments are designed so that an accessory's optimal frequency response occurs when the tip of the accessory is connected to a circuit under test in a DUT with a source impedance of 50 ohms. Accessories tend to load the circuit under test in the DUT, which then distorts the waveform read from the circuit in the DUT. Conventionally, an accessory will incorporate hardware equalization to correct an output wave-shape to look more like it did before the accessory loaded the circuit. An equalization filter is calculated and used to process the acquired samples from the DUT such that signal degradation or artifacts imparted to the waveform read from the circuit under test and in the DUT are compensated for within the system, effectively de-embedding the loading of the DUT by the probe tip. FIG. 1 shows an output 100 response of a test and measurement instrument using the conventional approach given an ideal input pulse 102 . As can be seen in FIG. 1 , the output 100 shows some distortion. [0015] A DUT source impedance, however, tends to fall in the range of 25 ohms to 100 ohms. The DUT source impedance tends to vary over that range even if the DUT is specified to have a source impedance of 50 ohms. FIG. 2 shows in the conventional method how the outputs vary from the ideal input 102 shown in FIG. 1 when the source impedance of the DUT is not 50 ohms. As can be seen in FIG. 2 , the errors in the output waveforms can be quite large. [0016] The errors seen in FIG. 2 can be reduced by allowing a user to specify the nominal source impedance of the DUT to calculate an equalization filter. [0017] As seen in FIG. 3 , the system includes a test and measurement instrument 300 and a probe 302 connected to a DUT 304 . The test and measurement instrument 300 , may be for example, an oscilloscope. The test and measurement instrument may also be any other test and measurement instrument, such as a spectrum analyzer, logic analyzer, etc. [0018] The probe 302 includes a memory 306 for storing the S-parameters of the probe. Alternatively, the T-parameters or some other form of parameters to characterize the probe may be stored in the memory 306 . The parameters are measured at the time of manufacturing the probe 302 and then stored in memory 306 . Alternatively, the parameters may be stored in a memory 308 of the test and measurement instrument 300 , or on an external storage device (not shown), the internet (not shown), etc. The parameters merely must be supplied to the processor 310 to calculate the equalization filter as will be discussed in more detail below. [0019] The test and measurement instrument 300 also includes a memory 308 , as discussed above. Memory 308 stores the S-parameters of the test and measurement instrument 300 that are measured at the time of manufacturing. Alternatively, T-parameters or other forms of parameters to characterize the scope may be used and stored in memory 308 . Along with memory 308 , the test and measurement instrument 300 includes a display 312 and a processor 310 . [0020] During operation, the test and measurement instrument 300 is connected to the DUT 304 through the probe 302 . The display 312 contains a user menu or user interface 400 as shown in FIG. 4 . The user menu 400 allows the user to specify the nominal source impedance of the DUT 402 . The user can specify either the real impedance or the complex impedance of the DUT at the menu 402 . The nominal source impedance is then used as part of the calculation for the equalization filter to obtain an ideal target response for the system. [0021] The user menu 400 also contains an option for the user to turn the probe equalization filter on or off 404 . A user may turn off the equalization filter if the results for a particular DUT are better without the filter. The user menu 400 also allows a user to select whether to use nominal equalization view 406 . The nominal equalization view shows the waveform as if the probe did not load the DUT circuit. The user can also select the option of using a probe load filter 408 in the user menu. The probe load filter shows the voltage at the probe tip with the probe loading the DUT circuit. [0022] The user menu 400 may also include a menu 500 to allow a user to load the S-parameters for the DUT test point, as shown in FIG. 5 . The equalization filter is then computed using both the nominal impedance of the DUT and the S-parameters for the DUT test point. [0023] When the user has entered all the desired information into the user menu 400 on display 312 , the information is sent to processor 312 in the test and measurement instrument 300 . Further, the S-parameters of the probe stored in the probe memory 306 are also sent to the processor 310 in the test and measurement instrument 300 . The processor then uses the S-parameters of the probe, the nominal impedance of the DUT provided by the user to compute an equalization filter to provide a more accurate view of the signal from the DUT. To provide an even more accurate view, the processor may also use the S-parameters of the test and measurement instrument 300 stored in the test and measurement memory 310 and the S-parameters of the DUT if the S-parameters of the DUT are loaded into the test and measurement instrument 300 by the user via menu 500 . [0024] FIG. 6 illustrates the various equalization filters created by the processor 310 for each of the various nominal source impedance values. As can be seen in FIG. 6 , the equalization filters are different for each of the nominal source impedance values, which helps create a more accurate view on the display to the user of the signal from the circuit under test in the DUT. [0025] FIG. 7 illustrates output waveforms with the equalization filter applied using nominal input impedance values inputted by the user. For example, FIG. 6 shows an input waveform 700 and the output waveforms 702 for multiple DUT source impedance values. As can be seen in FIG. 7 , for each of the DUT source impedance values, after applying an equalization filter calculated with the nominal DUT impedance input by the user, the output waveforms are nearly identical to the input waveform, unlike the output waveforms shown in FIG. 2 . [0026] The disclosed technology allows a user to control the equalization filter applied to the tip of a probe. The user can specify a DUT source reference impedance at the probe tip and then an equalization filter is computed by the test and measurement instrument based on the measured S-parameters read from the probe. To create an even more refined equalization filter, the S-parameters of the test and measurement instrument and/or the test point of the DUT may be used. Although S-parameters are described above for calculating the equalization filter, as will be readily understood by one skilled in the art, other parameters may be used that characterize the probe, oscilloscope and/or the DUT test point, such as T-parameters. [0027] Although the embodiments illustrated and described above show the disclosed technology being used in an oscilloscope, it will be appreciated that embodiments of the present invention may also be used advantageously in any kind of test and measurement instrument that displays frequency domain signals, such as a swept spectrum analyzer, a signal analyzer, a vector signal analyzer, a real-time spectrum analyzer, and the like. [0028] In various embodiments, components of the invention may be implemented in hardware, software, or a combination of the two, and may comprise a general purpose microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like. [0029] Having described and illustrated the principles of the disclosed technology in a preferred embodiment thereof, it should be apparent that the disclosed technology can be modified in arrangement and detail without departing from such principles. We claim all modifications and variations coming within the spirit and scope of the following claims.

A test and measurement system including a test and measurement instrument, a probe connected to the test and measurement instrument, a device under test connected to the probe, at least one memory configured to store parameters for characterizing the probe, a user interface and a processor. The user interface is configured to receive a nominal source impedance of the device under test. The processor is configured to receive the parameters for characterizing the probe from the memory and the nominal source impedance of the device under test from the user interface and to calculate an equalization filter using the parameters for characterizing the probe and nominal source impedance from the user interface.

FIELD OF THE INVENTION [0001] The present invention is applied generally to the field of telecommunication networks and more particularly this invention relates to configuration, reconfiguration and monitoring of network nodes in networks providing Internet Protocol (IP) connectivity. [0002] More precisely, the present invention discloses a method for simplifying the task of logical deployment to configure a target IP network topology which is to be physically deployed on a background IP network, as well as the inverse task of logical undeployment is simplified. Furthermore, this method allows real time monitoring on the network elements previously deployed in, the target IP network. STATE OF THE ART [0003] Conventional management systems, such as Simple Network Management Protocol (SNMP) [D. Harrington, R. Presuhn, B. Wijnen, “An Architecture fot Describing Simple Network Management. Protocol (SNMP) Management Frameworks”, IETF Standard 62, RFC 3411, December 2002] or Web Based Enterprise. Management (WBEN) [Distributed Management Task Force, “Specification of CIM Operations over HTTP”, Version 1.1, DMTF Standard DSP0200, January 2003]) are based on two functional entities: agents and managers. Agents run in the devices that are being managed and are aware of the internal information and parameters needed for management. Managers connect to agents in order to perform management operations. [0004] The communication between agents and managers is based in an information model, that is, a structured way of describing the management data (for example, CPU load, IP addresses, etc.) and a communication protocol to exchange that information. For example, in the case of SNMP management framework, with SNMP as the communication protocol, the information model is composed of MIBs (Management Information Base) defined in a standardized text-based information structured language called ASN.1 (Abstract Syntax Notation 1). [0005] However, these management systems have some drawbacks for the deployment of global configurations involving several network elements in IP networks. On the one hand, they are very strict in terms of requirements of communication protocol and information model, which are described as part of the management system. Said communication protocol and information model are often incompatible with the communication interfaces of devices provided by certain vendors. On the other hand, well-known management systems provide very simple management operations (“get” and “set” in most of the cases), which make said systems unsuitable for complex configurations. Moreover, when using these well-known management systems, each network element is managed individually, and therefore the management system does not have a global view of the whole network to be configured. [0006] Solutions to these problems usually, rely on building top-level manager applications, which act as front-ends of the network management system. However, these applications are difficult to design and implement. [0007] In addition, a currently widely used industrial standard for data interchange is the eXtensible Markup Language (XML). XML is a World Wide Web Consortium-recommended general-purpose markup language for creating special-purpose markup languages. It is a simplified subset of the Standard Generalized Markup Language (SGML). The primary purpose of XML is to facilitate the sharing of data across different systems, particularly systems connected via the Internet. Many languages based on XML (for example, Geography Markup Language (GML), RDF/XML, RSS, Atom, MathML, XHTML, SVG, Klip and MusicXML) are defined in a formal way, allowing programs to modify and validate documents in these languages without prior knowledge of their particular form. [0008] Network management systems based on XML are described in US 2004/0117452 A1. In particular, US 2004/0117452 A1 describes a network management system and method which employs tree-shaped configurations for individually managed network elements. [0009] With the aim at simplifying the network management, it would be desirable to provide a straightforward data model that defines the global network configuration and eases its management globally, instead of having managed the individual network elements, without being tied to a particular Configuration of each network element. [0010] The model-focused approach has been already successfully applied to other engineering fields, such as software production in the Model Driven Architecture (MDA) framework, [Object Management Group, “MDA Guide Version 1.0.1”, OMG Document Number omg/2003-06-01, June 2003], based on technology-agnostic models of software applications and processing these models in order to build platform-dependent code implementing the desired applications. [0011] On the other hand, a well known management field is Service oriented Provisioning, which requires the network operator to engineer the way in that services are created and distributed into a network, so that a telecom service provider can define his service offering as a specific set of services. US 2002/0178252 discloses some example of mechanisms for Service Provisioning. However, implementing Service Provisioning is focused on the final user (in one end of the network) and does not consider network topology configuration at all. US 2002/0178252 describes a procedural processing of the service configuration based on workflows and does not consider declarative descriptions of configuration. [0012] In contrast to Service Provisioning, the whole network and not just the user end must be taken into account in network topology configuration (as a matter of fact, in some management contexts, such as experimentation infrastructures or testbeds, there is no a final user). Network topology configuration deals with how to define, and configure arbitrary interconnections among network elements, and so declarative descriptions of the network configuration are required. Declarative descriptions can be used from a high-level user perspective to describe the configuration wanted by the user, without specification of the means needed to get that configuration (this specification of the means used by the management engine is needed for the service provisioning mechanism disclosed in US 2002/0178252 in the form of workflow definitions). SUMMARY OF THE INVENTION [0013] One aspect of the present invention is a method for logical deployment of global target network configurations based on a data model defining the intended global network configuration. In this context, “logical” means that the goal is the deployment of a target network on top of an exiting background network, already physically deployed, taking advantage of IP technology to build overlay networks. Besides, this invention provides complementary methods for logical undeployment and monitoring of the target IP network in a global way. [0014] The logical deployment of global network configurations according to the proposed method is based on a text-based information structured language data model, which describes the intended network configuration globally; distinguishing the present invention from others like the one described in US 2004/0117452 A1. The text-based information structured language may be the standardized XML, so the utilization of this invention by third-party applications can be flattered. Other possible text-based information structured languages to write the data model may be SGML or ASN.1. [0015] Therefore, it is an object of the invention to provide an intuitive and user-friendly mechanism for automatically configuring and reconfiguring multiple IP network topologies, involving configuration issues such as number of nodes and link connectivity, as well as remotely configuring the execution of processes at each node (e.g., routing or signalling processes). [0016] Note that for establishment and reconfiguration of a desired network topology, given the usual large size of networks (composed of several devices with different pieces of hardware, each one with its own configuration requirements), manual topology reconfiguration results in elevated time consuming and error prone complex tasks. Usually, these tasks become more critical if the network administrator has to fulfil them “by hand” using command line interfaces (CLI). [0017] In order to solve and speed up those tedious operations, another object of the invention is to allow network administrators performing a high-level specification of a target network configuration in a flexible manner, avoiding spending administration time in carrying out manual configuration node by node. [0018] The administrator or user may apply user-friendly XML existing tools to get the specification of a target IP network. Though, he/she is not required to produce directly a set of XML files, since the present invention may be integrated in a graphical user interface (GUI) just to draw the IP network scenario and logical deploy/undeploy the target network on a background IP network, including configuration and reconfiguration of the processes to be run at each node of the target IP network. [0019] In addition to the aforementioned tasks, the present invention allows monitoring the status of the already logically deployed and working network, being able to alert the administrator when any element involved in the IP network (a node, process in a node, or an interface between nodes) fails or goes wrong. [0020] More concretely, the first aspect of the invention refers to a method for logical deployment of a target IP network on a background IP network. The target IP network comprises at least one network element (NE N ; N≧1) and is supported on the background IP network formed by the at least one network element (NE N ) and at least one network elements controller (NEC Q ; Q≧1). The background IP network provides IP functional interfaces (C ik ) between the at least one network elements controller (NEC k ; k in the 1 . . . Q range) and each network element (NE i ; i=1 . . . N). This method for logical deployment of a target IP network comprises the steps of: [0000] 1 st step). Retrieving at the at least one network elements controller (NEC k ) at least one process information fragment written in the text-based information structured language (e.g. XML) for at least one of said network elements (NE i ), said at least one process information fragment defining the configuration of a network-related process. 2 nd step) Creating, at said at least one network elements controller (NEC k ), a command script for each network element (NE i ), being the command script a list of operations in terms of the functional interface (C ik ) and the operations which are to be executed in that particular network element using the respective functional interface (C ik ) by the corresponding network elements controller (NEC k ). At this step the content of the command script may be void. 3 rd step) Generating or deriving from said process information fragment at least one configuration template, for the configuration of at least one network-related process and for at least one of the network elements. 4 th step) Adding at least a command to the command script corresponding to said at least one network element, for starting each of said at least one network-related process using said configuration template. 5 th step) Pushing each of the configuration templates from the network elements controller (NEC k ) to the respective network element (NE i ); pushing means sending the configuration templates from the network elements controller (NEC k ) through the corresponding functional interfaces (C ik ) and storing said configuration templates at said corresponding network element NE i ). 6 th step) Executing the command script for said network element (NE i ) in a remote mode through the respective functional interface (C ik ) (i=1, . . . , j, . . . , N), which consists of any IP-based protocol allowing the remote executions of commands, either one-by-one or in a batch mode. [0021] The IP functional interfaces (C ik ) between a network element (NE i ) and the respective network elements controller (NEC k ) may be one of the standard protocols: RLOGIN, TELNET, SSH, TL1, RPC, RMI, XML-RPC, HTTP, SOAP, CORBA, COM+ and SNMP. [0022] Regarding configuration templates, they are defined as pieces of information that need to be pushed (sent and stored) to network elements, so that their network-related processes can work properly when they are started (for example, configuration templates contain parameters to be read by a network-related processes when started). [0023] Optionally, the method for logical deployment of the target IP network may include in the mentioned fourth step of adding commands to command scripts at said at least one network elements controller (NEC k ) further adding a command for setting an IP interface (D ij ; obviously, here i≠j, i=1 . . . N, j=1, . . . N) between two network elements (NE i , NE j ). These commands for setting an IP interface (D ij ) are added to each of the two command scripts corresponding to said two network elements (NE i , NE j ) and before the commands used for starting the network-related processes (as specified in step 4 ). In such a case, at step 6 of this method for logical deployment, it is clear that said commands are executed remotely, as part of the two corresponding scripts, through the respective functional interface (C ik , C jk ) of the network elements controller (NEC k ) with network element (NE i ) at its first end and network element (NE j ) at its second end respectively. [0024] The so-called network-related processes, to be started at the network elements (NE N ) may be selected. from a group of: routing daemons, servers, service platforms, hardware controllers, management agents, reservation protocol daemons and link resource management deamons. Some of these network-related processes needs to use the corresponding IP interface (D ij ) for their operation. There can be also network-related processes started at a network element (NE i ) that operate without involving any previous set of an IP interface (D ij ) with another network element (NE j ). [0025] In this context, a “daemon” is a process continuously running in background performing a particular, task, A “server” is a particular kind of daemon that listens for request from network clients, process them and send a response back to the client, implementing a particular service. [0026] Thus, the described method allows the configuration of all needed IP interfaces (D ij ) between pairs of network elements (NE i , NE j ), and their specification is defined as part of the target IP network. The particular information defining the IP interfaces (D ij ) depends on the particular IP connection type (direct or tunnelled), the IP networking protocol version (IPv6, IPV4), on the layer 2 or link layer aspects (Ethernet switching for Virtual Local Area Networks—VLANs—, virtual circuit technologies, etc.). [0027] Furthermore, after having a target IP network deployed according to the steps for logical deploying as described before or by another conventional method for network configuration, another aspect of the invention refers to providing in a similar intuitive way a method for logical undeployment of a target IP network comprising at least one network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) belonging to the previously deployed target IP network. [0028] This method for logical undeploying comprises the following steps: [0000] 1 st step) Retrieving at the at least one network elements controller (NEC k ) at least one process information fragment written in a text-based information structured language, for at least one of the network elements (NE i ), said at least one process information fragment defining a, network-related process; 2 nd step) Creating a command script for each of said network elements (NE i ) at one (or more if necessary) corresponding network elements controller (NEC k ), 3 th step) Adding at least a command to the command script generated at the corresponding network elements controller (NEC k ), being said commands defined for stopping each of the at least one network-related process started for at least one network element (NE i ); and 4 th step) Remotely executing through the respective functional interface (C ik ) the command script for the at least one network element (NE i ), (i=1, . . . , j, . . . , N). [0029] If an at least one IP interface (D ij ) has been specified between a pair of network elements (NE i , NE j ) in the logical deployment of the target IP network, the step of adding commands to command script at said at least one network elements controller (NEC k ) further comprising: [0030] adding a command for unsetting the IP interface (D ij ) between the network elements (NE i , NE j ) to each of the two respective command scripts and said commands are added to the command script after the ones used for stopping the network-related process (as specified in step 3 ). [0031] Another capability of this invention is a global monitoring of the target IP network. Hence, a method for logical monitoring of a target IP network is proposed here and allows a network administrator checking the status of the network-related processes for the network elements from said target IP network, which has been previously deployed by either the already described method for logical deployment or another conventional method for network configuration. The method for logical monitoring comprises the following steps, after steps of retrieving the needed process information fragments and creating new command scripts at the corresponding network elements controller (NEC k ) for each network element (NE i ) as explained before: [0032] adding at least a command to the command script generated at the corresponding network elements controller (NEC k ) for checking the status (active or inactive, running, killed, . . . ) of each of the at least one network-related process started for at least one network element (NE i ); and [0033] remotely executing through the respective functional interface (C ik ) the command script for the at least one network element (NE i ), (i=1, . . . , j, . . . , N). [0034] Additionally, the method for logical monitoring allows an administrator, if at least one IP interface (D ij ) is previously set and needed, monitoring the IP interface (D ij ) between any two network elements (NE i , NE j ). In order to check this IP interface (D ij ), ping is. performed to test Whether the particular pair of network elements (NE i , NE j ) at each end of said IP interface (D ij ) is reachable across the IP network. Thus, this method comprises the step of: [0035] at said at least one network elements controller (NEC k ), adding at least a ping command for the IP interface (D ij ) to each of the two command scripts corresponding to the two interface ending network elements (NE i , NE j ). [0036] The ping commands are added to each command script preferably before the commands used for checking the status of the network-related processes. The step for pinging further comprises sending Echo messages according to the standardized Internet Control Message Protocol (ICMP), which is one of the core protocols of the Internet protocol suite chiefly used by networked computers' operating systems to send error messages-indicating, for instance, that a requested service is not available or that a network element could not be reached. In particular, the method for monitoring performs the following message exchanges in the pinging step: [0037] sending an ICMP Echo Request message to first end of said interface (D ij ) at one of the network elements (NE i ) and listening for ICMP Echo Response message replied from said network element (NE i ) for a determined or pre-selected time, said ICMP Echo Request sent from the other network element (NE j ); and, [0000] if an ICMP Echo Response message is received from said network element (NE i ) within said determined time: [0038] sending an ICMP Echo Request message to second end of said interface (D ij ) at the other network element (NE j ) and listening for ICMP Echo Response message replied from said network element (NE j ) for a determined time (usually applying the same time constraints for both network elements), said ICMP Echo Request sent from the first end of said interface (D ij ) at corresponding network element (NE i ). [0039] There are other aspects of the present invention which refer to providing respective methods for logical deployment, undeployment and monitoring of a target IP network on a background IP network just to implement the setting, unsetting or monitoring respectively of a IP interfaces (D ij ), (i≠j). Obviously, these IP interfaces (D ij ) can be used by network-related processes that can be either configured at a pair of network elements (NE i , NE j ) of the target IP network according to the method for logical deployment described firstly or by employing another conventional method for network configuration which is suitable for managing network-related processes over the background IP network. [0040] Thus, it is provided a method for logical deployment of a target IP network on a background IP network which comprises the steps of: [0000] 1 st step) Retrieving at the at least one network elements controller (NEC k ) a IP networking information fragment written in a text-based information structured language for at least a pair of network elements (NE i , NE j ), said IP networking information fragment defining a IP networking layer (INL). The IP networking layer, also known as network layer and sometimes called the Internet layer, handles the movement of packets around the network [“TCP/IP Illustrated, Volume 1: The Protocols”, by W. Richard Stevens, Addison-Wesley, Chapter 1.2, page 2, 1994]. This layer and, more particularly, the IP networking information fragment comprises the specification of: interfaces provided by each network element (NE i ) and connection to the other network elements (NE j ) through said interfaces: here called IP interfaces (D ij ), IP address (and mask) for each one of said interfaces (D ij ). 2 nd step) Creating, at said at least one network elements controller (NEC k ), a command script for each of said network elements (NE i , NE j ). 3 th step) Adding at least a command for setting an IP interface (D ij ) between said two network elements (NE i , NE j ) to each of the command scripts corresponding to the pair of network elements (NE i , NE i ), using said IP networking information fragment, at said at least one network elements controller (NEC k ). [0043] Correspondingly, a method for logical undeployment of a target IP network is here described, said target IP network already deployed by the very previous method for logical deployment or another conventional method for IP interfaces configuration, in which at least an IP interface (D ij ) between two network elements (NE i , NE j ) has been set. This method for logical undeployment comprises steps for retrieving the IP networking information fragment at the corresponding network elements controller (NEC k ) and creating, at said at least one network elements controller (NEC k ), new command scripts for each of said network elements (NE i , NE j ), and then perform the step of: adding to each of the command scripts corresponding to the pair of network elements (NE i , NE j ) at least a command for unsetting the IP interface (D ij ). [0045] And the invention also provides with a method for logical monitoring of a target IP network already deployed in which at least an IP interface (D ij ) between two network elements (NE i , NE j ) has been previously set according to the three steps explained before for the previous method for logical monitoring or according to another conventional method for IP interfaces configuration, which allows to know whether the IP interface (D ij ) is enabled or, on the contrary, any failure occurs on reaching any of the two network elements (NE i , NE j ) across said IP interface (D ij ). In order to get such proposal, this method for logical monitoring comprising steps for retrieving the IP networking information fragment at the corresponding network elements controller (NEC k ) and creating, at said at least one network elements controller (NEC k ), new command scripts for each of said network elements (NE i , NE j ), and then perform the step of: adding to each of the command scripts created for the pair of network elements (NE i , NE j ) at least a command for pinging the IP interface (D ij ) between the two network elements (NE i , NE j )—as explained before for the pinging step—. [0047] It is another aspect of the present invention to provide a computer, program comprising computer program code means adapted to perform the steps of (any or even all of) the described methods, when said program is run on a central processing unit or processor of a computer, a general purpose processor, on a digital signal processor, a field-programmable gate array, an application-specific integrated circuit, a micro-processor, a micro-controller, or any other form of programmable hardware. [0048] It is further another aspect of the present invention to provide a network node comprising IP networking means for communication to at least another node and processing means adapted to perform the steps of any of the methods proposed. Such network node, at which any or even all of the described methods for logical deploy/undeploy/monitoring can be implemented, is what is denominated here like network elements controller (NEC), provided with means for communication with another nodes so-called network elements (NE). These network elements and network, elements controllers are nodes from an IP network, here the so-called background IP network. [0049] And it is another aspect of the present invention to provide a telecommunications network comprising at least one of these nodes acting as network elements controllers (NEC). [0050] The main advantages and innovations of the proposed invention become apparent in the description and are summarized as follows: [0051] 1. Multiple (per managed device) remote access interfaces vs. fixed explicit communication protocols: The invention described in this document neither defines a particular communication protocol, nor imposes any restriction in the communication interface of the configured elements, as a conventional management system does (like SNMP or HTTP). Instead, the present invention reuses as communication protocol any existing remote access interface the managed device is providing (like Telnet, SSH or TL1), here called as IP functional interface (C ik ). In fact, multiple remote access types can be used seamlessly, since each network element (NE i ) (managed device) can provide a different IP functional interface (C ik ) with the corresponding network elements controller (NEC k ) in the same background IP network. [0052] 2. There are no explicit agents: As explain for invention background, in the current state of the art, conventional management systems need running a dedicated process in the managed device in order to deal with the communication protocol queries from the manager and providing an interface to the device internal data and parameters. This implies complexity (different agents need to be developed, for different devices) and inefficiency (the agent process consumes resources in the managed device). On the contrary, the present invention does not use explicit agent processes, allowing the manager direct access to data and parameters through the remote access or IP functional interfaces. [0053] 3. High-level actions and module-oriented in the global network vs. low-level actions and object-oriented in individual network elements: Conventional management systems are based on atomic actions (“get”, “set”, etc.) applied to elemental data objects (for example, the IP address of the managed device) in individual network elements. Therefore, a user-oriented manager has to integrate many atomic actions to perform high-level management tasks in order to provide global network configurations and the development of such manager could be complex. The present approach is easier and more intuitive because it is based on high-level actions (deploy, undeploy and monitor) and software modules (i.e., a process) instead of low-level actions and atomic object orientation subjects. BRIEF DESCRIPTION OF THE DRAWINGS [0054] To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate a preferred embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be embodied. The drawings comprise the following figures: [0055] FIG. 1 is a schematic representation of a target IP network comprising a plurality of network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) supported on a background IP network composed of these gathered network elements and at least one network elements controller (NEC 1 ), in accordance with an embodiment of the present invention. [0056] FIG. 2 is a detail of the architecture of one network element (NE i ), showing the interfaces with other network elements (NE j ) and other network elements controller (NEC k ). [0057] FIG. 3 is a schematic representation of a target network configuration structure formed by XML modules from a data model, in accordance with a preferred embodiment of the present invention. [0058] FIG. 4 shows a workflow of the invention, specifying the sequence of actions that need to be performed for deploying, monitoring or un-deploying of a particular global network configuration (for instance, the target IP network from FIG. 1 ). [0059] FIG. 5 a - 5 d , put all together, represent a flowchart of a tool implemented at the network elements Controller (NEC k ) performing, in accordance with the preferred embodiment of the present invention, the steps for logical deployment (partially illustrated in FIG. 5 a ), undeployment (partially illustrated in FIG. 5 b , where the common initial step of retrieving from the data module information fragments for deploy/undeploy or monitoring is drawn), and monitoring (partially illustrated in FIG. 5 c ), being the final common step of remotely execution of commands drawn in FIG. 5 d. DETAILED DESCRIPTION OF THE INVENTION [0060] Here below a practical implementation of the invention is described, which is based on the general network architecture shown in FIG. 1 . This general network architecture gathers: several network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) connected to an IP Network ( 10 ) through a plurality of interfaces (A 1 , . . . , Ai, . . . , A j . . . , A N ), and several Network Elements Controllers (NEC 1 , . . . , NEC k , . . . , NEC Q ) connected to the same IP Network ( 10 ) through another plurality of interfaces (B 1 , . . . , B k , . . . , B Q ). [0063] These interfaces (A 1 , . . . , A N , B 1 , . . . , B Q ) on the IP Network ( 10 ) with the network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) and Network Elements. Controllers (NEC 1 , . . . , NEC k , . . . , NEC Q ) respectively could be all of the same type, for example, Ethernet interfaces. [0064] This IP Network ( 10 ) also provides a plurality of IP functional interfaces (C ik ) from each network element (NE i ) to the at least one network elements controller (NEC k ). The configuration of these functional interfaces is not provided by the invention, they are supposed pre-configured, previously to the application of the method described in this document. [0065] FIG. 1 only shows one Network Elements Controller (NEC 1 ) for the sake of clarity, but in a general, case there would be as many as desired (NEC k ), each one with its own C 1k , . . . , C Nk , interfaces. [0066] The IP Network ( 10 ) constitutes an existing background IP network over which is defined a target IP network by the multiple network elements NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) to be managed. [0067] Each network element (NE i ) has a modular architecture, as depicted in FIG. 2 , that implements an IP networking layer ( 9 ) and runs/executes several (L, with L≧0) network-related processes (P 1 , . . . , P L ). The IP networking layer ( 9 ) can be configured to provide IP interfaces (D ij ) from any of the network element (NE i ) to another one (NE j ), being i and j any non equal integers in the 1, . . . , N range. The configuration of these IP interfaces (D ij ) is provided by the method described in this document. [0068] Note that actual implementations of this invention may not implemental the possible interfaces specified in the general description. For example, in a practical implementation with four network elements maybe only four IP interfaces (for example: D 12 , D 23 , D 34 , and D 14 ) could be considered, instead of all the resting possible ones: D 13 , D 14 , D 21 , D 23 , D 24 and D 34 . [0069] An example of application could be configuration of a dynamically switched optical transport network, where the network elements are: Optical Connection Controllers (OCC) implemented in computers and constituting the control part of physical optical nodes, A Link Emulator device Ethernet Switches A router-broadband-tester with vendor-specific technology [0074] In that example, the IP functional interfaces (C ik ) are based either in SSH—for the OCCs and link emulator—, Telnet—for the switches—or RPC—provided by vendor for the router tester device—. There are three kinds of IP interfaces (D ij ): OCC-OCC directly connected through real optical fibber, OCC-OCC not using network constraints—through a dedicated VLAN—, OCC-OCC using network constraints—through link emulator device—and OCC-broadband tester—through a dedicated VLAN—. Each Optical Connection Controller runs five network-related processes (then, L=5 in this example): Optical Link Resource Manager (OLRM), Link Resource Manager (LRM), the Open Shortest Path First (OSPF) routing protocol, the Resource Reservation (RSVP) signalling protocol and SNMP management protocol. The broadband tester runs a RSVP process. [0075] Using a text-based information structured language such as XML, a global network configuration can be specified, defining a plurality of information Modules (M 0 , M 1 , . . . , M L ) that determines a target network configuration structure ( 7 ), drawn in FIG. 3 . There are process information modules (M 1 , . . . , M L ) describing each one of the L network-related processes (P 1 , . . . , P L ) along as one more information module specifying the IP networking configuration needed in the target network configuration structure ( 7 ) and here called IP networking information module (M 0 ). The present invention provides an user/administrator with means for logical deployment, of this global network configuration into the corresponding network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) using the pre-configured IP functional interfaces (C ik ) with at least one of the network elements controller (NEC 1 , . . . , NEC k , . . . , NEC Q . [0076] Each information module (M 0 , M 1 , . . . , M L ) is composed of N+1 sections: there are N sections (NE 1 sec, . . . NE i sec, . . . , NE N sec), corresponding to each one of the network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) and a global section (Gsec) including configurations elements involving several network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ). Empty sections are allowed, but each module (M 0 , M 1 , . . . , M L ) must include at least one section. [0077] A particular set of IP networking information module (M 0 ) plus process information modules (M 1 , . . . , M L ) realization consists of, for example, a set of L+1 XML files stored in the hard disk of any of the network elements controller (NEC 1 , . . . , NEC k , . . . , NEC Q ). Another implementation alternative is a group of records in a XML-based distributed database. [0078] The possible embodiments of the target network configuration structure ( 7 ) define a XML-based data model. Building, storing and retrieving of target network configurations from the XML-based data model is out of the scope of this patent. Network administrators can use any suitable XML tool or database interface, for example, a graphic user interface program or a database manager program for these purposes. [0079] The retrieved XML-based data model structured in the L+1 information modules (M 0 , M 1 , . . . , M L ) specifies the global network configurations to be deployed. The user/administrator can retrieve the needed process information fragments from the process information modules (M 1 , . . . , M L ) describing each one of the L network-related processes (P 1 , . . . , P L ) for the set of network elements at which these processes (P 1 , . . . , P L ) are required to be configured for the target network configuration. Thus, a process information fragment is a set of sections from a process information module, so also written in XML or the text-based, information language used to specify the global network configuration. Likewise, in order to configure the IP interfaces (D ij ) to be provided by the IP networking layer ( 9 ), the user/administrator can retrieve the needed IP networking fragments consisting of a set of sections from the IP networking information module (M 0 ). [0080] Each information module (M 0 , M 1 , . . . , M L ) of the XML data model conforms to a Document Type Definition or XML Schema. The Document Type Definition (DTD) is a standard language developed primarily for the expression of a schema via a set of declarations that conform to a particular markup syntax. It describes a type of documents written in a text-based information structured language (SGML, XML) in terms of constraints on the structure of those documents. XML Schema is similar to DTD, accomplishing the same purpose. Hence, the DTD/XML Schema is a description of a type of XML documents, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntax constraints imposed by XML itself. The DTD/XML Schema provides a view of the document type at a relatively high level of abstraction and is used for validation purposes during the workflow of the method for logical deployment, undeployment and monitoring described as follows and in accordance to FIG. 4 . [0081] More in detail, these information modules (M 0 , M 1 , . . . , M L ) from the XML data model include: The IP networking information module (M 0 ) with specifications of the IP networking layer ( 9 ) to support the IP interfaces (D ij ) comprises: N sections (NE 1 sec, . . . NE i sec, . . . NE N sec) including: Reference to the network element (NE i ) index (i=1 to N). The IP functional interface (C ik ) that each network elements controller (NEC 1 , . . . , NEC k , . . . , NEC Q ) uses to access the network element (NE i ). However, this is not the unique possibility and other implementations of the invention could not include the IP functional interface (C ik ) related information in the IP network information module (M 0 ). For instance, this information could be used implicitly by the software application implementing the very network elements controller (NEC k ) maybe, implemented in some configuration file or database of said network elements controller (NEC k ), which is out of the scope of this invention. A global section (Gsec) must include: The specification of all IP interfaces (D ij ) defined as part of the target IP network, depending upon the particular IP interface requirements (connection type, etc.). The process information modules (M 1 , . . . , M L ) with specifications of the network-related processes (P 1 , . . . , P L ) comprises: N sections (NE 1 sec, . . . NE i sec, . . . NE N sec) including: Reference to the network element (NE i ) index (i=1 to N). The configuration for the process running in the NE. The particular information depends on the particular process. All the necessary information regarding the process environment in network element (NE i ), for each, one of the network-related processes (P 1 , . . . , P L ); although if a particular process is not to be set in that network element (NE i ), it could be omitted. This information depends on the particular process type and the hardware platform of the network element—computer, host, router, etc.—but could include starting and stopping commands, pathname to the binary file implementing the process, location of configuration files, etc. A global section (Gsec) pet network-related processes including: Configuration elements that could affect as several process instances running in several network elements. It is up to the network administrator to use this section to include common configurations for several instances of the process in all network elements (for example, considering a dynamic routing process and supposing that all the instances uses the same routing algorithm configuration, such configuration could be defined in the global section). [0095] Given a particular XML data model to be applied to a particular IP network architecture, the actions taken for logical deploying, undeploying and monitoring that particular IP network follow the workflow of FIG. 4 : (1) Previous to the application of the corresponding method, a target network configuration must be provided by the user by means of any suitable XML tool or database interface in order to do so and it will depend on how the target network configurations are built, stored and retrieved (out of the scope of this patent). (2) User interacts with network elements controller (lets say NEC k ) in order to perform a particular action. There are three possible actions: DEPLOY, to establish the configuration in the network elements; UN-DEPLOY, to clear the configuration in the network elements, reverting the network to an un-configured state; and MONITOR, to check the status of IP interfaces (D ij ) and network-related processes in each network element (NE 1 , . . . , NE i , . . . , NE N ). In addition, the user specify the subset of the L+1 information modules: to which the action will be applied. The interface between users and network elements controller (NEC k ) is out of the scope of this patent. (3) Upon command, an engine module ( 8 ) at network elements controller (NEC k ) retrieves the required target network configuration from the XML data model. The retrieval of the target network configuration data is out of the scope of this patent. If the engine module ( 8 ) is unable to retrieve all the needed modules of the target network configuration; it reports the error to user and the workflow ends. (4) The engine module ( 8 ) processes the target network configuration, performing several actions in sequence: a. Engine ( 8 ) validates the XML data modules against DTD/XML Schema. If validation is unsuccessful, it reports the error to user and the workflow ends. b. If the validation is successful, the engine ( 8 ) generates command scripts in a per network element basis and configuration templates (in a per network element and network-related process basis). Command scripts are sequences of commands expressed in terms of the IP functional interface (C ik ) that will lead, upon execution in each network element, to the desired action (set up or deploy, set down or un-deploy, and monitor). Configuration templates are pieces of information that need to be pushed to network elements so that their network-related processes can work properly (for example, a configuration template could be a file that the process needs to read when it starts). The target network configuration must contain all the needed information and parameters (maybe implicitly) in order to build the command scripts and configuration templates needed to implement the required action (deploy, un-deploy or monitor). Otherwise, this condition is reported to the user as error and the workflow ends. (5) Configuration templates are pushed to each NE 1 , . . . , NE i , . . . NE N using the IP functional interface (C ik ) with the network elements controller (NEC k ). (6) Command scripts are executed in each NE, in a remote mode using the IP functional interface (C ik ). [0105] Finally, the user is reported on the result of the action. In the case of monitor action, this includes information about the status of the IP interfaces (D ij ) and network-related processes. [0106] The engine ( 8 ) constitute an implementation at one network elements controller (NEC k ) of the three complementing methods for logical deployment, undeployment and monitoring of a target IP network, respectively performing configuration, reconfiguration or monitoring of network-related processes (P 1 , . . . , P L ) and also the IP interfaces (D ij ) that may be used by said network-related processes (P 1 , . . . , P L ). [0107] The steps executed in the engine ( 8 ) at a network elements controller (NEC k ) follow the flowchart split in three branches corresponding to actions of logical deployment, undeployment, and monitoring, depicted in FIGS. 5 a , 5 b and 5 c respectively, altogether with a last branch that joins the previous three branches into the end of the flowchart. [0108] The step of adding commands to the command script for setting an IP interface (D ij ) between two network elements (NE i , NE j ) comprises: [0109] allocating an IP address at first end of said interface, (D ij ) at one of the network elements (NE i ); [0110] allocating an IP address at second end of said interface (D ij ) at the other network element (NE j ). [0111] If said IP interface (D ij ) between the two network elements (NE i , NE j ) is a VLAN switched Ethernet based interface, that step further comprises the operations of: [0112] establishing a VLAN identifier at first end of said interface (D ij ) at one of the network elements (NED; [0113] establishing a VLAN identifier at second end of said interface (D ij ) at the other network element (NE j ). [0114] In case that the IP interface (D ij ) between two network elements (NE i , NE j ) is implemented by means of an IP-based tunnel, such as GRE, IPSec or IP-over-IP, it is established a configuration of the two ends of said IP tunnel, said two ends corresponding to the two network elements (NE i , NE j ). [0115] In another possible case, when the target IP network is based on some virtual circuit techonology, like MPLS (Multiprotocol Label Switching), GMPLS (Generalized Multiprotocol Label Switching), ATM (Asynchronous Transfer Mode) or Frame Relay, there are more additional operations in said step in order to establish the virtual circuit or path (for example, in the case of MPLS, setting valour for label identifying the virtual circuit in the MPLS overlaid network). [0116] If establishment of the IP interface (D ij ) needs configuration in at least some other intermediate network element (NE p ) different from NE i or NE j (lets said NE p with p≠i and p≠j), said configuration is added to the command script of the at least said other intermediate network element (NE p ). This is the case when VLAN switches Ethernet based interfaces needing establish configuration in intermediate Ethernet switches or tunnel interfaces are used and so it is needed to configure all the network elements providing the tunnel. [0117] In the step of adding commands to the command script for starting network-related processes, the command added consist merely in a shell command of the operating system if UNIX or compatible operating system is running in the NE. [0118] Inversely, for logical undeployment, in the step of adding commands to the command script for stopping network-related processes, the command added can be the kill UNIX command, if UNIX or compatible operating system is running in the NE. [0119] For logical undeployment, the step of adding commands to the command script for unsetting the IP interface (D ij ) between two network elements (NE i , NE j ) further comprises: [0120] removing the IP address allocated at first end of said interface (D ij ) at one network element (NE i ); [0121] removing an IP address allocated at second end of said interface (D ij ) at the other network element (NE j ). [0122] And depending on the kind of the IP interface (D ij ), this step for unsetting said IP interface (D ij ) correspondingly includes removing the configuration of the VLAN identifiers, the two ends of the IP-based tunnel or the virtual circuit established before and, in such a case that any other intermediate, network element (NE p ) different from NE i or NE j (lets said NE p with p≠i and p≠j) is involved, removing the configuration of each intermediate network elements (NE p ) previously set to provide said IP interface (D ij ). [0123] With regards to monitoring, the step for pinging the IP interface (D ij ) between two network elements (NE i , NE j ) is based on ICMP echo messages, which are built at networking layer and then encapsulated as datagrams to be retransmitted. Hence, monitoring of IP interface (D ij ) is independent from the subjacent technology, since ping is based on IP address whose allocation is always required for setting the IP interface (D ij ), independently from its implementation—VLAN over Ethernet, GRE, IPSec or IP-over-IP, MPLS, GMPLS, ATM, Frame Relay, . . . —. [0124] Besides, in order to monitor the network-related processes (P 1 , . . . , P L ) deployed at the corresponding network element (NE i ), in the step of adding at least a command to the command script for network element (NE i ), the command added consists merely in the pidof command in case that UNIX or compatible operating system is running in the NE i . The pidof command is a UNIX utility that returns a process identifier (PID) of a running process, that is, monitoring network-related processes (P 1 , . . . , P L ) by regards to checking a particular network-related process belongs to the running process list being executed by the operating system kernel, at the network element (NE i ). [0125] Remote execution of command scripts through the IP functional interface (C ik ) depends on the type of said preconfigured IP functional interface (C ik ). For instance, if the IP functional interface (C ik ) is based on RPC or Telnet, the commands added to the command script generated at the network element controller (NEC k ) are executed one by one in sequence at the corresponding, network element (NE i ). In case of SSH, a mixed mode is applied for remote execution of command scripts, which comprises copying firstly the script file to the network element (NE i ) and, next; a command sent by network element controller (NEC k ) is executed through the SSH interface in order to execute that script file—stored in the hard disk of said network element (NE i ) or any other storing media—. In this case, being IP functional interface (C ik ) implemented as SSH, the command script are just a list of shell commands. [0126] The SSH interface can also be used to push configuration templates to the respective network element (NE i ) by copying firstly a file generated at the network element controller (NEC k ) with the configuration template derived from, the proper process information fragment P 1 , . . . , P L ) to the network element (NE i ), since SSH allows sending files from the network element controller (NEC k ) to said network element (NE i ). [0127] In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc. [0128] The invention is obviously not limited to the specific embodiments described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of components, configuration, etc.), within the general scope of the invention as defined in the appended claims. [0129] Some preferred embodiments of the invention are described in the dependent claims which are included next.

The method is applied to configure, reconfigure and monitor globally a plurality of network elements (NE 1 , . . . , NE i , . . . , NE j , . . . , NE N ) connected to an IP Network ( 10 ) through multiple interfaces (A 1 , . . . , A N ), with several Network Elements Controllers (NEC 1 , . . . , NEC k , . . . , NEC Q ) connected to the same IP Network ( 10 ) through respective interfaces (B 1 , . . . , B Q ). The IP Network ( 10 ) also provides a plurality of preconfigured IP functional interfaces (C ik ) from each network element (NE i ) to the at least one network elements controller (NEC k ). Each network element (NE i ) has an IP networking layer ( 9 ) and runs/executes several net-work-related processes (P 1 , . . . , P L ) managed and monitored by this method. The method also provides configuration and monitoring of IP interfaces (D ij ) among network elements. The existing IP functional interfaces (C ik ) are used to perform such managing and monitoring. To get these aims, the method performs high-level actions instead of atomic “get/set” operations. Neither the method neither requires explicit agents-manager paradigm nor depends on a particular communication protocol for network management.

The U.S. Government has rights in this invention pursuant to a fellowship awarded the National Science Foundation. BACKGROUND OF THE INVENTION This invention relates to an improvement in a solar powered tracking device which is then used to drive a concentrating solar collector for concentrating solar radiation, and more particularly, it relates to such a device wherein the radiation received by sensing devices containing a volatile liquid results in a vapor pressure which powers the movement of the device to respond appropriately when subjected to solar radiation of the sun. The technology of utilizing solar energy is not new. It has been known for many years that solar radiation may be concentrated with mirrors and with lenses to produce temperatures of 1000° F. and higher. Tracking devices in the past have been powered by electric motors, clockwork mechanisms, hydraulic cylinders, and even locomotive engines. Clockwork mechanisms are precise but they frequently are limited as to the maximum size of the control surface that can be turned. Electric motor systems are probably the most common devices in this field but these systems can be costly and complex. The use of hydraulic or pneumatic pistons and cylinders is much less expensive if a self-contained driving system can be developed that does not rely upon electricity, fuel oil, or other purchased energy sources. Among the prior art patents in this field in U.S. Pat. No. 4,027,651 to Robbins in which a V-shaped receiver is fitted with mirrors and shading devices that direct the solar radiation or, conversely, shield the solar radiation from tubing coils containing a heat sensitive fluid which produces a differential pressure on a piston that in turn causes the apparatus to be adjusted so that it points directly at the sun. In U.S. Pat. No. 4,038,972 to Orrison a parabolic mirror concentrates the solar radiation and tracks the sun by an automatic control based on a light sensing apparatus which signals an electric motor to turn the mirror in whatever direction is needed. In U.S. Pat. No. 4,078,549 to McKeen et al., a mirror facing the sun concentrates the solar radiation and is kept in the appropriate position by a light-sensing mechanism which controls an electric motor that moves the mirror by a chain drive. The present invention is an improvement on the device described in an article by Morrison et al., entitled "Solar Powered Tracking Device", Building Systems Design, Dec./Jan. 1976. The device described in this article comprises a mirror which is parabolic in cross section and has any suitable and convenient length along which at the focus of the parabola is a metallic tube receiving the concentration of radiation striking the mirror and through which flows any suitable fluid which can receive the solar energy. The device is powered to track the sun by means of two hydraulic/pneumatic cylinders whose pistons are fixed to each other in an opposing relationship. The piston rods are joined to each other through a gear rack which is mated to a pinion gear affixed to the axis of rotation of the mirror such that any movement of the gear rack and pinion gear will cause the control surface to rotate about its axis. The two cylinders are powered with the vapor pressure from a refrigerant liquid which forms the working portion of two radiation sensing bulbs containing the liquid and attached to each side of the movable control surface. Appropriate shading devices are located to shade or not to shade the sensing devices from solar radiation when the control surface is not pointed directly at the sun. Only one of the two sensing devices is more exposed to the sun in any given position of the control surface except when it is pointed directly at the sun, in which event both of the sensing devices are partially shaded from radiation. When the control surface is not pointed directly at the sun the more exposed sensing device is heated by the solar radiation to cause an increase in vapor pressure of the refrigerant liquid which in turn causes a corresponding movement of the pistons in the cylinders, and through the gearing arrangement a corresponding movement of the control surface. While this device has many admirable features it does not track the sun with sufficient precision to be acceptable as a practical means for concentrating solar energy. SUMMARY OF THE INVENTION This invention priovides improvements in the basic device described in the Farber article mentioned above. The improvement lies in the radiation sensing device which functions to cause the control surface to be repositioned with respect to the sun with considerable precision. The device of this invention is capable of maintaining the controlled surface at a position which is not more than 0.5° away from alignment with the sun under normal clear sky radiation conditions. The improvements involve a radiation sensing element which is a light weight metal tubing in the form of a loop which includes a large volume reservoir. The loop is such that liquids or vapor can flow in a closed circuit through the reservoir and the connected tubing. An outlet from the loop leads to the pneumatic cylinders which provide the power for moving the control surface. The loop of tubing and reservoir is constructed such that it extends substantially the length of the sensor element and is joined in a heat conductive manner to a thin, rectangular fin which serves to enhance the heat conductivity of the tube and also to shade the large reservoir from solar radiation. The entire loop of tubing and reservoir is enclosed, except at its end portions, by a tubular shield which permits radiation from one direction and prohibits it from another direction. The tubular shield is transparent to radiation in its portion which faces away from the control surface and is opaque to radiation in its portions which faces toward the control surface. This shield also provides protection against convection due to wind and breezes which would reduce the precision of the device in tracking the sun. BRIEF SUMMARY OF THE DRAWINGS FIG. 1 is a plan view of the solar tracking device of this invention. FIG. 2 is an end elevation view of the device of FIG. 1. FIG. 3 is the other end elevation view of the device of FIG. 1. FIG. 4 is a side elevation view of the device of FIG. 1. FIG. 5 is an illustrative view of the device of this invention in operation. FIG. 6 is a schematic illustration of the connection between the pneumatic cylinders and the sensing elements of this invention. FIG. 7 (A,B,C) are illustrative drawings showing how the sensing elements are activated to track the sun with precision. FIG. 8 is a schematic end view of the sensing element of this invention and its connection to the tracking device. FIG. 9 is a perspective view of the sensing element. DETAILED DESCRIPTION With specific reference to FIGS. 1,2,3, and 4 a general understanding of the operation of the solar tracking device can be obtained. Control surface (11) is parabolic in cross section as seen in FIGS. 2 and 3 and extends over a convenient and suitable length as shown in FIGS. 1 and 4. The control surface is supported by rectangular housing (12) having collars (13) (14) attached at each end. Metal tube (15) is supported by the collars and positioned to be along the focus of the parabolic section of the control surface and thus receives the solar radiation striking the control surface and subsequently being reflected to the focus of the parabola. Any suitable energy absorbing fluid may be circulated through tubing (15), such as water, oil, molten salt, etc. Control surface (11), housing (12) and collars (13) and (14) are all fixed to each other and are rotated around the axis of tubing (15) although the tubing does not turn with the other parts but merely fits loosely through collars (13) and (14) resting in bearings (16) fixed to a supporting structure of legs (17) at each end of the device. The legs are adjustable in length so that the entire device can be positioned as closely as possible perpendicular to the rays of the sun. This position will vary depending upon the seasons of the year. Attached to each of the long sides of housing (12) are brackets (18) to which are attached sun shades (19). Radiation sensor (20) is supported on each side of housing (12) below sun shade (19) and is supported by an appropriate number of arms (21) attached to housing (12). The relative positioning of sensors (20) and sun shades (19) as well as the sizes of the two elements depends upon the tracking sensitivity which the operator desires for this device and the details of this will be explained later. At the end of the device which operates at the highest elevation, as seen in FIG. 5, hereinafter referred to as the "head" of the device, there is located the mechanism which turns control surface (11) in its movement in tracking the sun. Two pneumatic cylinders (22) are assembled in an opposing relationship by joining the piston connecting rods (23) to each other through a rack gear (24). Rack gear (24) mates with stationary pinion gear (25) which is fixed to bearing (16). As the pistons in cylinders (22) move to the right or left that movement is transmitted to rack gear (24) and pinion gear (25) to cause control surface (11) and the equipment attached thereto to turn. Each of sensors (20) is connected by tubing (26) to its appropriate cylinder (22) so that pneumatic pressure generated by the fluid in one of the sensors (20) will oppose the pressure generated in the other sensor (22). The connection between tubing (26) and cylinders (22) will be discussed in detail in the description of FIG. 6. In FIG. 5 there is illustrated a general view of the assembly, upon which is mounted the device of this invention, resting on the ground or any other support parallel to the ground indicated at (27) and receiving radiation (30) from the sun. Due to the fact that the north-south axis of the earth rotates in a conical fashion as the earth orbits the sun, the angle at which the sun's rays hit the earth surface varies throughout the year from a smaller angle in the winter season to a larger angle in the summer season. In order to utilize the maximum of the sun radiation which strikes control surface (11) the focal axis of the control surface, represented by the axis of tubing (15) should be perpendicular to the rays from the sun. In FIG. 6 there is a schematic illustration of the connections between the sensors (20) and pneumatic cylinders (22). The tubing (26) coming from one of sensors (20) leads into one of the two cylinders (22) and the tubing (26) from the other sensor (20) leads into the other cylinder (22) to produce opposing forces on the pistons (29). The tubing (26L)) from sensor (20L) leads to the left hand portion of cylinder (22L) and tubing (26R) from sensor (20R) leads to the right hand portion of cylinder (22R). In this way pressure from sensor (20R) pushes both of pistons (29) to the left, and pressure from the sensor (20L) pushes both of pistons (29) to the right. Whatever the balance of forces on pistons (29L) and (29R) may be, the resultant force moves piston rods (23) and rack gear (24), which translates itself into a movement of control surface (11) and its attached equipment. In FIGS. 7 A, B, and C there are shown schematic illustrations of how the tracking device of this operation functions to align control surface (11) with the rays from the sun (30). In FIG. 7 A there is shown control surface (11) and housing (12) to which are joined sun shades (19) and sensors (20) on each side of the control surface. When the control surface (11) is positioned as shown in FIG. 7A directly perpendicular to the sun's rays (30) sun shades (19) are able to keep sensors (20) partially and equally shaded as shown in cross hatched areas (31). In this mode the fluid in sensors (20) is at the same temperature, and thereby at the same vapor pressure, which produces a balanced pressure on the two pistons to which the sensors are connected as described previously with respect to FIG. 6, and no movement of surface (11) is produced. In FIG. 7 B the rays of the sun (30) are not perpendicular to control surface (11) as indicated by angle (41). In this mode the sensor (20R) is not shaded from radiation by sun shade (19R) while sensor (20L) is shaded by sun shade (19L). In this situation the fluid in sensor (20R) becomes heated by radiation from the sun while the fluid in left hand sensor (20L) is not subjected to that heating. Accordingly the vapor pressure rises in right hand sensor (20R) and an unbalanced pressure is produced in the pneumatic cylinders connected to both sensors (20) which produces a movement of the rack gear which joins the two pistons in those cylinders and that movement is translated into a rotation of control surface (11) and its associated equipment to where it is then aligned with the solar radiation (30) as shown in FIG. 7 A. In FIG. 7 C there is shown exactly the opposite condition to that just described with respect to FIG. 7 B. The same operations in reverse will function to bring the apparatus back into alignment with the sun's rays. In this instance sensor (20L) is heated producing an excess of pressure over that produced by sensor (20R) and a corresponding movement of the gears returns control surface (11) to the position shown in FIG. 7 A. In FIGS. 8 and 9 there are illustrated the details of radiation sensors (20) from the previous description. A suitable number of supporting arm (21) are attached to housing (12) by any convenient means to support sensor (20) as shown in FIG. 4. Bracket (32) is adjustably attached to arm (21), for example by wing nut clamp (33) in order to permit adjustment up or down arm (21). Bracket (32) serves to support the three components of the sensor; namely, tubing (34), fin (35), and reservoir (36). As seen in FIG. 9 these three components of the sensor form a loop in the tubing (34) including reservoir (36) in that loop. Fin (35) is a heat conductive material, preferably a metal, which serves to enhance the ability of tubing (34) to absorb radiation from the sun and to cool when tubing (34) is in the shade. Reservoir (36) serves the purpose of maintaining a large volume of liquid inside of tubing (34) and is positioned to maintain the entire loop substantially full of liquid. Tubing (26) leads directly to pneumatic cylinders (22) as described previously. Surrounding the entire loop of tubing (34), fin (35), and reservoir (36) is an enclosure which serves as a windshield. In order to maintain the highest precision of the apparatus of this invention the windshield should not be in contact with any of the three components just mentioned and thus should be supported by brackets (32). The windshield is made of two parts, the portion (37) facing away from control surface (11) being completely transparent to solar radiation and the portion (38) facing toward control surface (11) being opaque to solar radiation. There are many suitable plastic and/or glass materials which will serve the purpose of being transparent to radiation and will serve conveniently for portion (37). Portion (38) is made of any convenient, lightweight, material such as aluminum, wood, etc. Inside surface (39) of portion (38) is made to be reflective so that any radiation reaching that surface will be reflected in a normal manner. Outside surface (40) is made to be opaque to solar radiation, and preferably not reflective to any great degree, nor should it absorb any great amount of heat. Tubing (34) and fin (35) are preferably painted with a flat black paint in order to absorb as much heat as possible. Reservoir (36) is made of such a size and placed so that it will be shaded from radiation approaching from above by fin (35) and thereby its large volume of liquid will not undergo the same extremes of temperature that will be experienced in tubing (34). The reason for having portion (38) with two different types of surface is that, in some extreme positions of the apparatus of this invention, it is conceivable that the solar radiation would be almost parallel to fin (35) and the responsiveness of the sensor would be reduced. By making surface (39) reflective and setting it at an angle to fin (35) the radiation will be reflected to the underneath side of fin (35) which will thereby be capable of absorbing sufficient heat to provide the necessary responsiveness for this sensor. Similarly outside surface (40) should be opaque to radiation because, in certain extreme positions of the apparatus of this invention, the radiation might pass underneath control surface (11) and strike the temperature sensitive elements when that is not desirable. The principal purpose of the enclosure comprising portions (37) and (38) is to function as a shield against wind and breezes which might cause cooling by convection of the elements of the sensor and thereby disrupt its proper functioning. Although it is feasible to encapsulate these elements completely with a windshield of large volume, it is preferable to employ a small volume with the two ends (39) open to the atmosphere to facilitate cooling of the sensor elements when they have been moved into position where they are partially shaded. While it us conceivable that wind might be blowing in the direction longitudinal to the windshield and thus blow through the length of the enclosure, this same effect will apply to both sensors and thus will substantially balance each other. Tubing (34), fin (35), reservoir (36), and bracket (32) are shown as being welded or soldered to each other to form the necessary connections. However, any suitable mechanical means of connection may be utilized. It is necessary that tubing (34) and (35) be joined in some manner which will provide maximum heat conduction in order to transmit whatever heating or cooling effects that are received by fin (35) immediately and completely to the fluid in tubing (34). It is also important that reservoir (36) be placed in the tubing loop at the end which will be at the highest elevation, that is near the head of the machine. The reason is that this will insure that substantially all of the tubing loop will be filled with liquid contained in the reservoir. This will maximize the amount of liquid in tubing (34) that is attached to fin (35) and subjected to solar radiation, which in turn provides the best responsiveness of the sensor to the presence or absence of radiation. The device of this invention is capable of maintaining the control surface within 0.5° of alignment with the sun's rays under normal clear sky radiation conditions. Furthermore, it is entirely capable of quickly responding to accomplish adjustment from its most westward position at sundown to the most eastward position at dawn the next day when irradiated by the sun. If the device (for example in FIG. 2) is rotated to the extreme westward position, the morning sun at the next dawn will contact the east sensor (20) but will only contact the opaque surface (40 in FIG. 8) of the west sensor (20). In this situation, which is a more extreme version of that shown in FIG. 7 B, radiation will cause heating of the sensor and the liquid contained in the sensor on the east side of the apparatus, but not the elements and the liquid in the sensor on the west side of the apparatus. This will cause an imbalance in vapor pressures forcing pistons in pneumatic cylinders toward the west, which because of the gearing arrangements tilts the control surface to the east until the east sensor is partially shaded and the control surface is aligned with the solar radiation as shown in FIG. 7 A. Because of the difficulties of maintaining appropriate lubrication, it has been found that the cylinders (22) and pistons (29) of the rolling diaphragm type, rather than those in which piston rings are employed to seal against leakage, perform heat, however any arrangement which incorporates positive vapor seal and low friction characteristics may be employed. In cylinders having the rolling diaphragm arrangement there is no sliding frictional contact during the movement of the piston. The diaphragm in modern devices is entirely capable of functioning, under the pressures normally experienced in this tracking device for long periods of time. Fluids employed in this device for producing the necessary vapor pressure are preferably those which can provide a vapor pressure of at least 5 psig at the minimum design temperature setting and provide increasing pressure up through a maximum design temperature setting, the pressure at the upper temperature limit being not more than about 200 psig. The increase in pressure over this range of temperatures should be reasonably constant so that no particular temperature level provides any peculiarities in pressure changes. The fluid should of course be compatible with the materials employed in the cylinders and in the sensor, and also be nontoxic, nonexplosive, and readily available. In general, there are many refrigerants which satisfy these conditions and they may be chosen from American Society of Heating Refrigerating, and Air Conditioning Engineers Handbook, however, any fluid which possesses the aforementioned characteristics may be utilized. While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

A solar powered tracking device for controlling radiation exposure of surfaces, wherein solar radiation increases the vapor pressure of a liquid in a sensing device and the vapor pressure acts on opposed pneumatic cylinders to produce mechanical movement of the controlled surface to track the sun with a maximum deviation of not more than 0.5° under normal clear sky radiation conditions.

BACKGROUND OF THE INVENTION 1. Field of the Invention A rotary sliding vane compressor having means for urging the vanes outwardly and maintaining the vane tips in engagement with the cylinder wall during start-up and at rotational low speeds. 2. Description of the Prior Art Burnett U.S. Pat. No. 3,376,825 describes a rotary vane compressor having a leaf type spring element between the radially inner portion of the vane and the bottom of the vane slot. The spring is designed so that during high speed operation, when centrifugal forces are sufficient to maintain the vane tips in contact with the cylinder wall, the same centrifugal forces will cause the spring to collapse against radially inner edges of the vane and thus become ineffective as a spring element. English U.S. Pat. No. 1,984,365 describes a rotary sliding vane compressor having a leaf type spring in the bottom of the vane slot and having its convex side in contact with the central region of the vane edge which is essentially linear. Kenney et al. U.S. Pat. No. 2,045,014 also discloses a leaf spring with its ends embedded in the bottom of the vane. Fuehrer U.S. Pat. No. 3,191,503 shows a sliding vane fluid handling apparatus which uses O-rings of elastomeric material underneath the vanes to bias the same outwardly. Gibson et al. U.S. Pat. No. 1,857,276 is representative of a large number of prior art references which utilize fluid pressure underneath the vanes to maintain the vane tips in engagement with the cylinder wall. SUMMARY OF THE INVENTION This invention relates in general to rotary sliding vane compressors and more particularly to an effective means for biasing the vanes radially outwardly to maintain the vane tips in sliding engagement with the cylindrical wall of the rotor chamber which forms the gas working space. Although rotor sliding vane compressors are known in a great many forms, the description herein is directed to a conventional type in which a rotor is provided with a plurality of extensible vanes each received with a generally radially oriented or canted vane slot in the rotor. The rotor is received within a cylindrical chamber or stator and mounted such that its axis is offset with respect to the cylindrical stator axis, thus providing a generally crescent shaped gas working space. The rotor is in sliding contact with a portion of the cylindrical wall, and this contact point divides the low pressure side from the high pressure side. An inlet port communicates with one side of the gas working space and a discharge port communicates with the opposite side. Gas is trapped between adjacent vanes and carried around through the compression zone. The volume of each pocket or compartment, as defined between adjacent vanes and the rotor and stator surfaces, becomes smaller as it approaches the discharge port thus compressing the gas trapped therein. A problem is often encountered in operating compressors of the type described above in that the vanes sometimes will not maintain their tips in engagement with the cylindrical stator wall under all conditions. This is especially true at start-up when the rotor is travelling at low rotational velocities. The centrifugal force which would normally tend to throw the vanes outwardly is not sufficient to overcome the vacuum created when the vanes begin to move their most radially inward portion to the point directly opposite the contact point. The latter may be regarded as a dash-pot effect and is extremely powerful in resisting the outward thrust of the vanes. Several techniques have been used in the prior art to hold the vane tips in engagement with the cylindrical wall. Basically, these may be divided into two categories: mechanical (such as spring) and hydraulic or pneumatic. The mechanical springs used may take many forms, such as the leaf springs described in Burnett, Kenney et al and English, or helical (coil) springs. Just as common are the hydraulic or pneumatic means such as described in Gibson et al. In the present invention, a mechanical element is employed which overcomes many of the disadvantages of the springs heretofore known. It is difficult to obtain any significant service life when using a leaf or coil spring in the typical rotary compressor environment. With each revolution of the rotor the spring is compressed and released. Since the compressors operate at several hundred R.P.M., it is apparent that the springs undergo flexing at unusually high rates and thus are subject to fatigue failure. The objective of the present invention is to minimize the amount of flexure involved, especially the total travel distance for each compression and extension of the spring. The present invention employs a novel, three-layer composite spring having (1) a metal portion in contact with the vane to provide the necessary rigidity, (2) a bonded rubber or elastomeric component to extend the life of the metal element, and (3) a bonded fabric wear surface in contact with the bottom of the vane slot to provide resistance to abrasion from rubbing contact with the vane slot and consequent cutting or nicking of the rubber component. Still another aspect of the invention is the superior load distribution which is accomplished by mating the curved vane bottom with a bridge-like rubber/metal composite spring assembly. Further, the surface provided by the metal spring, in combination with the rubber or elastomeric element, is effective in dampening noise during operation. The fabric wear surface extends the useful life of the composite assembly, thus decreasing the need for expensive maintenance due to failure of the unit. The assembly is compact, inexpensive to install, and requires no special modifications to conventional compressor parts. Other advantages to this system include the fact that since no hydraulic means are provided for maintaining the vanes extended, it is not necessary to provide either a lubricant pump or other means for collecting and distributing oil and/or refrigerant to the undervane spaces. It also provides instant pumping action upon start-up, reduces hammering and consequent vane wear caused by delayed movement of the vane to the extended position, eliminates reverse rotation at rotor shutdown often caused by equalization of pressures between the high and low sides of the compressor rotor, and results in lower discharge gas temperature. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view of a rotary sliding vane compressor constructed in accordance with the principles of the present invention; FIG. 2 is a cross sectional view taken along the plane of line 2--2 of FIG. 1; FIG. 3 is a greatly enlarged sectional view showing the relationship of the resilient element with respect to the vane and the vane slot; FIG. 4 is a partial perspective view of the resilient element; FIG. 5 is a cross sectional view taken along the plane of 5--5 of FIG. 3; and FIG. 6 is a view similar to FIG. 5 showing the resilient element in its fully flexed position. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, particularly to FIGS. 1 and 2, there is shown a typical rotary compressor of generally conventional design including a stator housing 10 comprising a cylinder block 12 having a circular bore extending therethrough to provide a cylinder wall 14, a front end plate 16, and a rear end plate 18. Within housing 10 there is provided a rotor 20 connected to and driven by drive shaft 22. The rotor is eccentrically mounted within the cylinder 14 so that it is in close running contact with the cylinder wall 14 at a contact point 28 and forms a crescent-shaped gas working space or compression cavity 26. The rotor is provided with a plurality of vane slots 30 each having a bottom surface 32 and receiving vanes 34 which are adapted to reciprocate within each vane slot with their upper edges 34a in continuous engagement with cylinder wall 14. It may be seen that the lower sides of each slot, the bottom edge 34b of the vanes 34, and the bottom of the vane slot 32 define what will be referred to as the "undervane space", designated 35. Suction gas is admitted to the compression cavity 26 through connection 36 and passage 38. Gas is discharged through a series of openings 42 (adjacent the contact point) which are covered by reed-type discharge valves 44, limited by valve stops 45. Discharge gas flows into chamber 50 and then through passage 52 in rear plate 18. Located between the lower edge of each vane and the bottom of the vane slot 32 is a resilient element 60, shown in partial perspective view in FIG. 4, which includes a first component in the form of a flat spring 62 formed of spring steel or other suitable alloy having good wear characteristics and adapted to withstand a large number of flexures at high frequency without failure. Bonded to the spring element is an elastomeric damper 64 having enlarged, spherically-shaped terminal portions 65 and a central section 66 having a relatively thin cross-sectional area as compared to the end portions. The spherically-shaped ends 65 of damper 66 are adapted to seat in complementary sockets 67 formed in the ends of vane slot 32. This arrangement provides pivot points at each end to minimize abrasion of the ends of resilient element 60 against the bottom of the slot, and further operates to maintain the resilient element in the proper location within the vane slot during assembly and while the pump is operating. Bonded to the peripheral surface of the elastomeric damper 64 is a wear layer 68, formed of woven nylon fabric, or other suitable fabric having good wear characteristics and adapted to stretch elastically at high frequency without failure. As best shown in FIG. 5, the bottom edge 34b of each vane is curved thus forming a convexly shaped edge engageable with the flat spring component 62 of the resilient element 60. When the vanes are fully extended, as shown in FIG. 5, the resilient element 60 lies flat across the entire vane slot region. At this point the resilient element is completely unflexed; and no portion thereof is under either compression or tension. As best shown in FIG. 6, the resilient element 60, after engagement with convexly shaped edge 34b, is in a condition where the resilient element assumes the same general contour as the bottom edge, and the elastomeric portion is forced downwardly so that the central region 66 is closely spaced from the bottom of the vane slot. The spherically-shaped terminal portions 65 are displaced outwardly in contact with the bottom of the vane slot, providing a rubbing contact between the surface of the vane slot and the terminal portion 65 surfaces. At this point, the spring is in a condition to bias the vane upwardly against the inside cylinder wall or stator, and this will result in immediate pumping action upon start-up prior to the generation of enough centrifugal force to hold the vanes in contact with the cylinder wall. It will be apparent that a long term, high frequency flexing of the resilient element 60 will subject the terminal portions 65 to severe abrasion, particularly in the terminal portion 65 surfaces in rubbing contact with the bottom of the vane slot. The addition of the improved wear layer 68 in the form of a woven fabric protects the terminal portion 65 from abrasion and markedly extends the service life. While a variety of elastomeric compounds may be used in making element 66, they should be resistant to the oil-refrigerant environment in which they must operate in a refrigeration/air conditioning application. Suitable materials would include urethane, nitrile, epichlorohydrin, fluorocarbon and silicone rubbers. A number of woven fabric materials may be used in the forming of the wear layer 68, however, it is necessary that such materials be elastic in order to conform to the surfaces during deformation of the composite spring while in use. The preferred materials will stretch at least 25%, preferably greater than 50%, in at least one direction with a high degree of recovery in order to be suitable for the purposes of this invention. A number of such stretch fabrics are commercially available including nylon, polyester and the like, which have the necessary stretch properties together with high wear character and resistance to attack by oil-refrigerant environments in which those pumps are operated. A suitable fabric for the purposes of this invention is a nylon fabric obtained from Stern and Stern Textile Corporation as pattern A-3274/2 and having a thread count of 104 × 70, weighing 6 to 6.7 oz. per square yard. This fabric is stretchable only in the filler direction of the weave, with a grab tensile of 180 psi. and an elongation of 100%. In the warp direction the fabric has a grab tensile value of 400 psi. The fabric is pre-treated on the surface with a resorcinol-formaldehyde resin to provide improved adhesion between the fabric and the rubber component. It is essential that the fabric when applied to the surfaces of the composite spring be oriented so that the stretch (filler) direction of the fabric coincides with the longitudinal axis of the resilient element. The fabric will then stretch and not be torn loose by shear stresses during repeated flexing of the composite spring structure. The composite spring structure according to this invention was formed by compression molding. First the mold cavity was lined with the fabric, pre-cut and oriented in the mold with the stretch (filler) direction of the weave along the longitudinal axis. A molded preform of the rubber component was then placed in the mold cavity. The leaf spring component, coated with a suitable adhesive such as Ty Ply BN, available from Hughson Chemical Corp., was placed in the mold and the mold was closed, placed under clamping pressure and heated to form the part and cure the rubber and adhesive components. When cooled and removed from the mold the resulting composite spring structure was complete. It will be apparent that the molding operation described is one of many common to the rubber manufacturing art and many variations will thus be possible and even desirable for speed and improved economy of manufacture. While this invention has been described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not by way of limitation; and the scope of the appended claims should be construed as broadly as the prior art will permit.

A rotary sliding vane compressor having means for biasing the vanes outwardly. Such means include a resilient element located in the lower portion of the vane slot and engaging a convexly shaped edge on the vane. An improved wear surface on the resilient element at the area of contact with the vane slot provides enhanced service life. The flexing action of the resilient member ensures that the vanes will be moved outwardly during the expansion phase of rotor travel.

DESCRIPTION OF THE PRIOR ART The generation of images on a data carrier such as a paper sheet or web by means of electrostatic copying is well known. In such apparatus, a photoconductive member is charged to sensitize the surface thereof, and the charged member is exposed to a light image of the document to be reproduced. The resulting exposure of the sensitized surface selectively discharges the charge thereon and records an electro-static latent image on the surface which corresponds to the informational areas contained upon the surface of the original document being reproduced. Development of the electro-static image is achieved by transporting developer materials such as dyed or colored heat settable plastic powders called toner particles into contact with the latent image such that the attractive forces thereof cause the toner particles to transfer from the carrier media onto the sensitized surface. Although numerous techniques are utilized for applying the developer material to the latent image, one of the most popular techniques is to mix the toner particles with carrier beads or granuals which can be magnetically picked up and transported to a position proximate the sensitized surface of the photoconductive member. In passing by such surface, the greater attractive force of the charged surface exceeds the triboelectrical force with which the particles adhere to the beads and most of the toner particles are removed and become electro-statically attached to the sensitized surface. The carrier beads and remaining toner particles are then returned to a reservoir for reuse. However, in many device configurations, as the toner and carrier particles fall into the reservoir, they create a downward movement of air which tends to slightly pressurize the reservoir and cause toner dust to be blown out of the reservoir and through the gap between the developer and the photoconductive surface. This dust may then contaminate the photoconductive surface as well as other portions of the machine causing improper operation and increased maintenance problems. One attempt to deal with a related problem is disclosed by Tsukamoto et al in U.S. Pat. No. 4,155,329. However, the Tsukamoto solution concerns itself more with the air flow problem created by the particle carrier transport mechanism than by the problem created by the carrier particles themselves as they are returned to the reservoir and fails to suggest a solution to the latter mentioned problem. SUMMARY OF THE PRESENT INVENTION It is therefore a primary objective of the present invention to provide an improved means for reducing toner dust contamination in electrophotographic printing apparatus. Still another object of the present invention is to provide a simple and inexpensive mechanism which can be added to existing electro photographic systems to seal the toner reservoir and reduce toner leakage. In accordance with a presently preferred embodiment of the present invention, the developer unit of an electro photographic system is modified by attaching a thin strip of resilient material in cantilever fashion to the lip of the developer housing or the toner carrier return side of the toner reservoir so as to resiliently extend to the developer roller. The strip provides a flexible closure which is pliable enough to be opened slightly by the carrier particles as they are delivered back into the reservoir but which is resilient enough to spring back into a closed position against the roller when no developer mix is being returned to the reservoir. Dust created by carrier/developers particles falling into the reservoir is thus contained within the reservoir and prevented from leaking into other portions of the system. An advantage of the present invention is that it provides an inexpensive solution to the problem of toner contamination. Another advantage of the present invention is that it provides a flexible developer unit seal and which is self-actuating and includes no complicated mechanical components. Still another advantage of the present invention is that it provides a toner reservoir sealing device which can easily be retrofit to existing electrophotographic systems. These and other objects of the present invention will no doubt become apparent to those of skill in the art after having read the following detailed description of the preferred embodiment. IN THE DRAWING FIG. 1 is a partially broken perspective view showing an electro-photographic developer unit including a flexible seal in accordance with the present invention. FIG. 2 is a cross section taken along the lines 2--2 of FIG. 1; FIG. 3 is an exploded view further illustrating the flexible seal shown in FIGS. 1 and 2; and FIG. 4 is a cross section taken through an alternative embodiment including a flexible seal in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2 of the drawing, a developer unit 10 and photosensitive drum 12 forming parts of an electro-photographic system are shown in partially broken form. The drum 12 has a photoconductive surface 14 entrained about and secured to the exterior circumferential surface of a conductive substrate in a manner well known in the art. Mounted beneath drum 12, the developer unit 10 includes an outer housing 16, a developer roller 18, a transport roller 20 (FIG. 2) and a pair of mixer spindles 22 and 24. Affixed to the inner side wall of housing 16 is a doctor blade 26 having an edge 28 which is disposed closely adjacent to developer roller 18 so as to define a gap therebetween that regulates the thickness of developer material allowed to adhere to and be carried by developer roller 18. Also disposed within housing 16 is a guide plate 29 which serves to return carrier and toner particles to the bottom of the container as they are removed from drum 18 by doctor blade 26. The rollers 18 and 20 form magnetic brushes which consist of cylinders 30 and 32 that are rotatably mounted at their ends to housing 16 and are made of a suitable non-magnetic material such as, for example, brass, aluminum, copper or stainless steel. Disposed within the respective cylinders are permanent magnets 34 and 36 which are appropriately arranged and have magnetic strengths so as to create magnetic fields that will attract magnetic carrier beads or similar carrier particles contained within the reservoir formed by the lower portion of housing 16 and hold such beads in contact with the portion of the periphery of the cylinders disposed within the magnetic fields. This of course allows roller 20 to pick up the beads and triboelectrically attach toner powder and transport it upwardly into close proximity to drum 12. As will be noted in FIG. 2 of the drawing, the edges of housing 16 surrounding the communicative opening 38 form lips 40 and 42 which are turned back so as to be generally tangent to and conform as close as possible to the surface of drum 12. The lips are however slightly separated from the drum surface so as not to interfere with the turning of the drum or the developer material carried thereby. One of the problems associated with this type of structure is that as the developer material, i.e., the beads and excess toner powder, are carried past the opening 38 and deposited back into the reservoir 44 as indicated at 46 the falling carrier beads and toner material cause air within the reservoir 44 to be displaced and moved around such that an upward flow of toner dust may be caused to be inadvertantly generated in the passage 46 and perhaps even be discharged from the housing by pushing between lip 42 and roller 12. In order to avoid such discharge, the present invention provides an elongated strip or ribbon 50 of flexible material which is affixed to lip 42 by means of a suitable adhesive or the like and is bowed downwardly along its transverse dimension so that when the system is at rest, the opposite unattached edge resiliently bears against the surface of drum 18. As is perhaps better illustrated in FIG. 3 of the drawing, whereas the edge 52 of strip 50 normally bears against the surface of drum 18 to seal the reservoir 44 closed, as the carrier beads (illustrated at 54) fall away from the surface of drum 18 they contact the upper side of strip 50 and cause it to bow and move edge 52 downwardly forming a return slot 56 through which the material may return to the reservoir. The strip 50 thus forms a floating seal which effectively seals the toner reservoir and prevents blowby of any toner dust generated therein. In the preferred embodiment, the strip 50 is a thin plastic member which is resilient enough to spring into engagement with drum 18 but which may be easily deflected away from the drum surface by the falling carrier beads. The film could be made of any of several types of plastics, or could even be comprised of thin sheet metal material or the like. Although the dust blow out problem is of particular concern in the case where the facing surfaces of drum 12 and roller 18 move in the same direction, there is also a somewhat lesser problem created in the case where the drum and developer roller are rotated such that their surfaces move in opposite directions, as illustrated at 118 and 112 respectively in FIG. 4. In this case, the strip of film 150 is affixed to the lip 140 on the particle return side of the opening in housing 116 and is bowed against the surface of drum 118 in a manner similar to that depicted in FIGS. 2 and 3. As in the previously described embodiment, beads carried by the roller 118 will deflect strip 150 out of their way as they fall from the roller surface and procede back into the reservoir via guide plate 129. It will therefore be appreciated that by placing a flexible and resilient strip on the carrier particle return side of the developer roller, an extremely simple but effective means can be provided for reducing contamination which would otherwise deteriorate the background and image carried upon the surface of the developer drum. Although the present invention has been illustrated in terms of a simple, flexible strip adhesively affixed to the housing of the developer unit, it will be appreciated that similarly configured flexible members could be similarly attached using other means to achieve the same objective. It is therefore intended that the following claims be construed as covering all such alterations and modifications as fall within the true spirit and scope of the invention.

The present invention relates generally to electro-photographic printing apparatus and more particularly, to a flexible seal means for reducing leakage of toner particles from the developer unit.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention is related to Enhancement Mode Field Effect Transistors, EMFETs, and Depletion Mode Field Effect Transistor, DMFETs, such as IGFETs, JFETs, MESFETs, MODFETs, HEMTs and so forth, for synchronous rectifier circuits, especially EMFETs or DMFETs with novel structures replacing conventional Static Shielding Diodes, SSDs. According to this invention, traditional SSDs in EMFETs or DMFETs may be replaced with polarity reversed (comparing with traditional SSD) SSDs, Schottky Diodes, or Zener Diodes, or face-to-face/back-to-back coupled Schottky Diodes, Zener Diodes, Fast Diodes, or Four Layer Devices such as DIAC or TRIAC such that conventional functions are preserved and need only to consider the amplitude of the reverse biased voltage for proper semiconductor operating voltage. As shown in FIG. 2 (E) or (F), the amplitude of the reverse biased operating voltage, i.e. Zener Voltage, may be configured according to the needs. The set Zener voltage would be higher than the DC output voltage in actual applications according to this invention. That is, the voltage of conventional SSD in an EMFET or a DMFET is higher than the AC voltage at input side, but the Zener voltage of the polarity reversed coupling Zener Diode is higher than the DC output voltage. According to such design philosophy of this invention, half-wave synchronous rectification may be achieved with a single EMFET or DMFET in coordination with auxiliary circuits, and full-wave synchronous rectification may be achieved with two EMFETs or DMFETs in coordination with auxiliary circuits. Hence, functions of high efficiency synchronous rectification may be achieved. [0003] 2. Description of the Related Art [0004] FIG. 3 shows a circuit of a conventional single ended forward synchronous rectifier, SR. In this figure, FET V 1 is responsible for rectification while FET V 2 is responsible for freewheeling. In operation, when the secondary voltage Us is at the positive half cycle, FET V 1 closes and FET V 2 opens, and FET V 1 acts as a rectifier; when the secondary voltage Us is at the negative half cycle, FET V 1 opens and FET V 2 closes, and FET V 1 acts as a free-wheel. The conductive power waste of FET V 1 and FET V 2 , and the driving power waste of the gates produce the main power waste in the synchronous rectifier circuit. Such scheme comes with the following drawbacks: 1. As far as the power waste is concerned, the power lost due to the follow current results in lower efficiency of synchronous rectification. 2. As far as the cost of material is concerned, EMFETs required for synchronous rectification raises the cost of manufacture. SUMMARY OF THE INVENTION [0007] In order to provide semiconductor devices, which may elevate the efficiency of rectification, this invention is proposed according to the following objects. [0008] The first object of this invention is to provide semiconductor devices that eliminate the drawback of high power consumption of conventional synchronous rectifiers utilizing diodes, such as Schottky diodes. [0009] The second object of this invention is to decrease the cost of manufacture due to EMFETs or DMFETs used for synchronous rectification. [0010] In order to solve the problem of high power consumption in conventional rectifiers and voltage regulation systems, the present invention possesses the following characteristics: 1. Unlike the manufacture process of conventional EMFETs or DMFETs, the polarity of single parasitic diode, SSD, is reversed, or the conventional SSD is replaced with two of face-to-face/back-to-back coupled diodes, i.e., in the manufacture process of EMFETs or DMFETs, coupling characteristic structures of the Lus Semiconductors between drain node and source node shown in FIG. 2 . 2. If no parasitic diodes exist in conventional EMFETs or DMFETs, the characteristic structures shown in FIG. 2 , their permutations and combinations, and even snubber circuits may also be externally coupled between the drain nodes and source nodes to construct the Lus Semiconductors. 3. The Lus Semiconductors in the present invention may also be applied in conventional PWM and PFM power systems. Rectifier diodes may be replaced with Lus Semiconductors and the efficiency may be improved. [0014] According to the defects of the conventional technology discussed above, a novel solution, the Lus Semiconductor, is proposed in the present invention, which provides higher efficiency in synchronous rectification. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 shows the structures of an N-Channel EMFET or DMFET and a P-Channel EMFET or DMFET of the Lus Semiconductor according to the present invention. [0016] FIG. 2 shows characteristic circuit structures of the Lus Semiconductor coupled between the drain and source of the EMFET or DMFET shown in FIG. 1 . [0017] FIG. 3 shows a circuit of a conventional single ended forward synchronous rectifier. [0018] FIG. 4 shows the symbols for N-Channel and P-channel Lus Semiconductors. [0019] FIG. 5 shows one embodiment of full-wave synchronous rectifier and voltage regulation circuit utilizing EMFETs according to the present invention. [0020] FIG. 6 shows one embodiment of half-wave synchronous rectifier and voltage regulation circuit utilizing an EMFET according to the present invention. [0021] FIG. 7 shows one embodiment of full-wave synchronous rectifier and voltage regulation circuit utilizing DMFETs according to the present invention. [0022] FIG. 8 shows one embodiment of half-wave synchronous rectifier and voltage regulation circuit utilizing a DMFET according to the present invention. DETAILED DESCRIPTION OF THE INVENTION [0023] FIG. 1 shows the structures of an N-Channel EMFET or DMFET 100 and a P-Channel EMFET or DMFET 200 of Lus Semiconductor according to the present invention. FIG. 2 shows several characteristic circuit structures 101 of Lus Semiconductor that may be coupled between the drain nodes and the source nodes of EMFETs or DMFETs shown in FIG. 1 . A pair of face-to-face coupled Schottky diodes and a pair of back-to-back coupled Schottky diodes are shown in FIG. 2 (A) and FIG. 2 (B) respectively, and each of the two may be then coupled to the drain node and the source node of the EMFETs or DMFETs. A pair of face-to-face coupled SSDs and a pair of back-to-back coupled SSDs is shown in FIG. 2 (C) and FIG. 2 (D) respectively, and each of the two may be then coupled to the drain node and source node of the EMFETs or DMFETs. A pair of face-to-face coupled Zener diodes and a pair of back-to-back coupled Zener diodes are shown in FIG. 2 (E) and FIG. 2 (F) respectively, and each of the two may be then coupled to the drain node and source node of the EMFETs or DMFETs. FIG. 2 (G) shows a pair of face-to-face coupled Schottky diode and Zener diode, which may then be coupled to the drain node and the source node of the EMFETs or DMFETs. FIG. 2 (H) shows a pair of face-to-face coupled Schottky diode and SSD, which may then be coupled to the drain node and the source node of the EMFETs or DMFETs. FIG. 2 (I) shows a pair of face-to-face coupled Zener diode and fast diode, which may then be coupled to the drain node and the source node of the EMFETs or DMFETs. FIG. 2 (J) shows a DIAC four layer semiconductor and FIG. 2 (K) shows a TRIAC four layer semiconductor, each of the two may then be coupled to the drain node and the source node of the EMFETs or DMFETs. The characteristic circuit structures 101 shown in FIG. 2 (A)˜(K), their permutations and combinations and snubber circuits may all be coupled to the drain node and the source node of the EMFETs or DMFETs and Lus Semiconductors 100 , 200 are thus constructed. With the characteristic circuit structures 101 shown in FIG. 2 (A)˜(K), their permutations and combinations and snubber circuits, high efficiency rectification and voltage regulation may be achieved, with a single EMFET or DMFET. Comparing with the structures of a conventional N-Channel EMFET or DMFET or a conventional P-Channel EMFET or DMFET, one can tell that they are the totally different from the characteristic circuit structures of the Lus Semiconductors. [0024] FIG. 3 shows a circuit of a conventional single ended forward synchronous rectifier. Its operations were described in the description of the related art and will not be discussed here for conciseness. [0025] FIG. 4 shows the symbols for N-Channel and P-channel Lus Semiconductors wherein FIG. 4 (A) is an N-Channel Lus Semiconductor and FIG. 4 (B) is a P-Channel Lus Semiconductor wherein the P junction is the input pole, the N junction is the output pole and the G (Gate) is the control pole. The GN voltage may control the voltage drop between the P junction and the N junction such that the purpose of gate controlled voltage drop may be achieved. [0026] FIG. 5 shows one embodiment of full-wave synchronous rectifier and voltage regulation circuit utilizing EMFETs according to the present invention. In operation, while the voltage at node 8 of the first secondary winding of the high frequency transformer 300 is at positive half cycle, the voltage at node 11 of the secondary winding is also at positive half cycle. The positive voltage at node 11 flows through diode D 4 and voltage dividing resistors RG and RH. Thus the GN voltage of the Lus Semiconductor 100 a equals to the voltage drop between the two ends of the voltage-dividing resistor RG. Because the RDS of the EMFETs of the Lus Semiconductor 100 a is quite small, for example, RDS=5 mΩ. If the current through RDS is 10 A, then the voltage drop between the two ends of RDS is VDS=0.005(Ω)×10 (A)=0.05V. Let the saturation voltage of the diode of the characteristic circuit 101 be VF=0.7V, comparing VDS with VF, the diode of the characteristic circuit can be found open, thus the voltage drop between the two ends of the voltage dividing resistor RG conducts the drain and source of the Lus Semiconductors 100 a . The positive half cycle AC voltage at node 8 passes through the drain and source of the Lus Semiconductor 100 a and a π-type filter constructed with a filter capacitor C 2 , an inductor L 1 and a filter capacitor C 3 , thus becomes DC output voltage Vo. While the AC voltage at the node 10 of the first secondary winding of the high frequency transformer 300 is at positive half cycle, the voltage at node 13 of the secondary winding is also at positive half cycle. The positive voltage at node 13 flows through diode D 5 and voltage dividing resistors RG and RH. Thus the GN voltage of the Lus Semiconductor 100 b equals to the voltage drop between the two ends of the voltage-dividing resistor RG. Because the RDS of the EMFETs of the Lus Semiconductor 100 b is quite small, the voltage drop between the two ends of the voltage-dividing resistor RG conducts the drain and source of the Lus Semiconductors 100 b . The middle node of the second secondary winding is at node 12 which is also coupling to node N, thus formed a complete gate controlled circuit. The operation is identical to that while the AC voltage at the node 8 of the first secondary winding of the high frequency transformer 300 is at positive half cycle. Because those two half-cycle circuits are commonly connected at node N, full-wave rectification may be achieved. While the output voltage Vo is higher than a pre-defined voltage, an adjustable precision shunt regulator integrated circuit IC 1 may be activated, and meanwhile the collector and the emitter at the output side of a photo coupler Ph 0 may be conducted that decreases the duty cycle of the output wave of the PWM control circuit and lower the output voltage Vo to the predetermined voltage; while the output voltage Vo drops, IC 1 deactivates and increase the duty cycle of the output wave of the PWM control circuit and thus raise the output voltage Vo. According to the operation, the Lus Semiconductors 100 a , 100 b are capable of rectification. While the voltage at node 8 of the high frequency transformer 300 is set to be positive, let the reverse biased break down voltage of the diode of the characteristic circuit structure 101 a of the Lus Semiconductor 100 a is higher than the positive voltage at node 8 , thus the voltage at node 8 may not pass through the reversed diode but through the drain and source of the Lus Semiconductor 100 a . While the output voltage Vo is present, even though the voltage at node 8 is at the negative half cycle of the AC voltage, because the reverse biased break down voltage of the reverse coupled Schotty diode in the characteristic circuit structure 101 a is higher than the output voltage Vo, the possibility that the first secondary winding may be burned out by the reverse current of conventional EMFETs can be eliminated. The operation of the characteristic circuit structure 101 b in the Lus Semiconductor 100 b at node 10 is identical. According to the operation of the characteristic circuit structure 101 in the present invention, the reverse biased break down voltage may be configured according to applications and shall not be limited. The operations of voltage regulation in PWM or PFM power systems are known to person skilled in the art and will not be discussed here for conciseness. [0027] FIG. 6 shows one embodiment of half-wave synchronous rectifier and voltage regulation circuit utilizing an EMFET according to the present invention. As shown in the figure, the Lus Semiconductor 100 b , node 10 of the first secondary winding and node 13 of the second secondary winding shown in FIG. 5 were removed and thus became a half-wave synchronous rectifier and voltage regulation circuit. The operation of the circuit is identical to that of the Lus Semiconductor 100 a shown in FIG. 5 and will not be discussed here for conciseness. [0028] FIG. 7 shows one embodiment of full-wave synchronous rectifier and voltage regulation circuit utilizing DMFETs according to the present invention. The difference between the full-wave synchronous rectifier and voltage regulation circuit utilizing EMFETs shown in FIG. 5 and the full-wave synchronous rectifier and voltage regulation circuit utilizing DMFETs shown in FIG. 7 is that DMFETs need a negative voltage supply circuit for the gates to maintain the source and the drain open, such that no source-drain current is developed. The negative voltage supply circuit is constructed with diodes D 6 , D 7 , D 8 , voltage dividing resistors RJ, RG, and a filter capacitor C 4 . The node 14 and node 15 of the third secondary winding are the power source of the negative voltage supply circuit. Diode D 6 functions as a rectifier. Diode D 7 and D 8 prevent the secondary winding from affecting the negative voltage supply circuit of the asynchronous rectification side while the synchronous rectifier is in operation. In short, the operation and structures of the full-wave synchronous rectifier and voltage regulation circuit utilizing EMFETs shown in FIG. 5 and the full-wave synchronous rectifier and voltage regulation circuit utilizing DMFETs shown in FIG. 7 are identical except for the negative voltage required for the gates of DMFETs in FIG. 7 . [0029] FIG. 8 shows one embodiment of half-wave synchronous rectifier and voltage regulation circuit utilizing a DMFET according to the present invention. As shown in the figure, the Lus Semiconductor 100 b , node 10 of the first secondary winding and node 13 of the second secondary winding shown in FIG. 7 were removed and thus became a half-wave synchronous rectifier and voltage regulation circuit. The operation of the circuit is identical to that of the Lus Semiconductor 100 a shown in FIG. 7 and will not be discussed here for conciseness. [0030] It is further stated that EMFETs and DMFETs, like ordinary transistors, are bidirectional, i.e. the drain nodes and the source nodes of the Lus Semiconductors 100 a , 100 b in FIG. 5 , FIG. 6 , FIG. 7 , or FIG. 8 may be reversed while the characteristic of gate-source operating voltage and the characteristic circuits are still maintained. That is, in application, the gate node may be the control node, the source node may be the AC input node and the drain node may be the DC output node, depending on the specifications of the manufacturer, the drain node and the source node may be alternated and is not limited by the embodiments above.

The Lus, Semiconductor in this invention is characterized by replacing the static shielding diode (SSD) of traditional Enhancement Mode Field Effect Transistors (EMFETs) or Depletion Mode Field Effect Transistor (DMFETs) with polarity reversed (comparing with traditional SSD) SSD, Schottky Diode, or Zener Diode, or face-to-face or back-to-back coupled Schottky Diodes, Zener Diodes, Fast Diodes, or Four Layer Devices such as DIAC and TRIAC. With the proposed Power EMFETs or DMFETs of which the drain to source resistors (Rds) are quite low, high efficiency synchronous rectification may be achieved.

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. provisional patent application 60/754,655 filed 30 Dec. 2005 is the national phase under 35 U.S.C. §371 of PCT/SE2006/001489 filed 22 Dec. 2005. FIELD OF INVENTION The present invention relates generally to high voltage bushings and more particularly to a high voltage bushing partially submerged in an insulating liquid, such as oil. The invention also relates to a high voltage device comprising such bushing. BACKGROUND It is known that electrical equipment and devices, such as high voltage transformers, are usually equipped with bushings, which are suitable to carry current at high potential through a grounded barrier, e.g. a transformer tank or a wall. Conventional high voltage transformer bushings are constituted by an insulator made of ceramic or composite material, which is provided with sheds and is generally hollow, and on the inside is the voltage grading performed with a condenser body comprising paper-oil or resin impregnated epoxy through which the electrical conductor passes, allowing to connect the inside of the device on which the bushing is fitted to the outside. Thus, the condenser core provides a smooth electric potential distribution between the high voltage and the grounded parts. Common to transformer bushings with a condenser body is that the part of the bushing that is submerged in the transformer tank contains oil. SUMMARY OF THE INVENTION An object of the present invention is to provide a high voltage bushing which has good dielectric and thermal properties, which contains few parts and is easily adapted to different applications. The invention is based on the realization that a bushing with a grounded shielding tube instead of a condenser core can be used in applications wherein part of the bushing is submerged in oil. This is the case in for example transformer bushings, which are submerged in transformer oil in a transformer tank. According to a first aspect of the invention a high voltage bushing for a high voltage device containing insulating liquid is provided comprising a hollow insulator housing comprising a first side insulator arranged to be provided outside of the high voltage device and a second side insulator arranged to be submerged in the insulating liquid of the high voltage device, and a high voltage conductor provided in the hollow insulator housing; and being characterized by a voltage grading shield provided between the high voltage conductor and the insulator housing. According to a second aspect of the invention a high voltage device comprising at least one such bushing is also provided. With the inventive bushing, several advantages are obtained. By using a shielding tube, the bushing can be made completely dry, i.e., it contains no oil. Also, it has been shown that the electric field pattern in the bushing is almost identical for both AC and DC applications, making the bushing suitable for both AC and DC. In a preferred embodiment, an insulating gas, such as SF6 or N 2 or mixtures thereof, is used as insulating medium inside the part of the bushing that is connected to the high voltage device. This provides good thermal properties due to the insulating gas and the open design allowing the gas to circulate inside the bushing. BRIEF DESCRIPTION OF DRAWINGS The invention is now described, by way of example, with reference to the accompanying drawing, in which the sole FIG. 1 is a sectional view of a high voltage bushing mounted to a high voltage device. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In the following a detailed description of a preferred embodiment of the present invention will be given. In this description, the term “high voltage” will be used for voltages of 50 kV and higher. Today, the upper limit in commercial high voltage devices is 800 kV but even higher voltages, such as 1000 kV or more, are built or envisaged in the near future. Also, in this description the term “voltage grading shield” should be read to exclude condenser cores conventionally found in bushings arranged to be submerged in insulating liquid. Reference is now being made to the FIGURE. The bushing, generally designated 1 , comprises a high voltage conductor 2 that extends through the center of a hollow gas filled bushing insulator 4 a , 4 b that forms a housing around the high voltage conductor. The bushing has two sides, a first side or air side outside the high voltage device to which the bushing is mounted, and a second side or transformer side submerged in an insulating liquid in the high voltage device to which the bushing is fitted, in the present example a transformer, generally designated 20 . The transformer contains insulating liquid 22 , such as transformer oil, which is enclosed by a tank, designated 24 . The air side of the transformer bushing is similar to a conventional gas insulated gas-to-air bushing, mainly consisting of the high voltage conductor 2 and an air side insulator 4 a separating the gas inside the bushing from the surrounding air. Further, the transformer side of the bushing is separated from the oil 22 in the transformer by a transformer side insulator 4 b. The insulator, which is preferably made of a composite material, such as epoxy, but could also be made of porcelain, thus comprises two portions: an air side insulator 4 a on the air side of the bushing and a transformer side insulator 4 b on the transformer side of the bushing. A flange 6 is provided to electrically connect the housing of the bushing to ground 28 through the tank 24 of the transformer 20 . A so-called throat shield or voltage grading shield in the form of a concentric grounded tube 8 is provided inside the hollow bushing insulator 4 a , 4 b around the portion of the bushing going into the tank 24 . This shield 8 , which is made of a suitable conductive material, such as aluminum, accomplishes grading of the electrical field in the bushing and is used instead of a condenser core. The voltage grading shield 8 is surrounded by the insulating gas, such as SF6 or N 2 or mixtures thereof, which is provided in the space 10 a inside of the air side insulator 4 a and the space 10 b inside of the transformer side insulator 4 b . It is preferred that these two spaces 10 a , 10 b are in communication with each other to provide circulation of the insulating gas, thereby improving cooling of the transformer side of the bushing 1 . In DC applications, the inside of the transformer side insulator 4 b , i.e., the surface of the transformer side insulator facing the insulation gas inside the insulator, may be covered with a dielectric material (not shown) with a relatively low resistivity, such as silicone rubber, composite material or varnish. Since the resistivity of silicone rubber is almost of the same order of magnitude as that of the oil inside the transformer, improved electric field distribution is obtained. This layer minimizes internal radial field stresses in the transformer side insulator 4 b separating the gas in the bushing 1 from the oil 22 in the transformer 20 and provides a smooth grading of the potential along the transformer side insulator 4 b between the high voltage and the grounded flange 6 and increases thereby the dielectric strength of the insulator 4 b. Optimal performance is obtained by a geometrical design of the transformer side insulator 4 b . In the preferred embodiment, the transformer side insulator has an essentially frusto-conical shape. This could be supplemented by the thickness of the coating on the inside of the bushing or the thickness of the insulator 4 b housing. In order to further improve the performance, the thickness of the coating can vary along the transformer side of bushing. A shielding ring 12 provided at the end of the transformer side of the bushing and a corresponding barrier system 26 in the transformer connection can further enhance the performance. In both AC and DC applications, in order to achieve a smooth grading of the potential along the transformer side insulator 4 b between the high voltage and the grounded flange, the geometry of the transformer side insulator 4 b is optimized. Also, in DC applications the geometry of the barrier system 26 in the transformer is taken into account when optimizing the bushing. A preferred embodiment of a high voltage bushing and a high voltage device according to the invention has been described. A person skilled in the art realizes that these could be varied within the scope of the appended claims. Thus, although the high voltage device to which the inventive high voltage bushing is attached has been described as a transformer, it will be appreciated that this could be other devices containing insulating liquid, such as reactors or breakers. The inventive bushing has been described as an air-oil bushing, i.e., wherein the first side of the bushing is surrounded by air outside a transformer, for example. It is realized that this first side can be provided in other environments, such as in oil in an oil-oil bushing or in gas in a gas-oil bushing. The transformer 20 has been described with a barrier 26 . It is realized that this barrier is optional. The bushing has been shown with a second side insulator, which has essentially frusto-conical shape. It will be realized that the shapes of the insulators can deviate from this shape without departing from the inventive concept. Thus, an inventive bushing with an insulator that is at least partly cylindrical will be a possibility.

A high voltage bushing for a high voltage device containing insulating liquid includes a voltage grading shield, improving performance and facilitating manufacturing.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an escalator. Definitions The term escalator should comprise both escalators with steps, as they are used in department stores, for example, and moving sidewalks with pallets, as they are used in airports, for example. FIG. 1 schematically shows a pintle chain G and a chain wheel R partially wrapped round the latter, to initially define a few terms. The pintle chain G comprises chain links K linked to each other via a pivot point P. The chain wheel K shown in an exemplary manner, has eight teeth Z, between which tooth spaces are arranged, into which pivot points P can engage. The angular pitch τ between two teeth or two tooth spaces is 45° in the example shown. Furthermore, an entry angle φ is shown at the bottom side of the chain wheel in FIG. 1 , which can arise, for example, due to a guide for deflecting pintle chain G. The entry angle φ is measured between the actual exit direction of the pintle chain G and the normal S on the line connecting detachment point A of the pintle chain G from the chain wheel R and the axis of rotation D of the chain wheel R. The entry angle φ is about 11° in the example shown. A momentary angle of wrap υ is indicated in FIG. 1 , which corresponds to the circumferential angle between two detachment points A of the pintle chain G from the chain wheel R, and is 180° in the case shown. When a chain link K detaches from the chain wheel R, the momentary angle of wrap D will be abruptly reduced, because with different entry angles φ at the top and bottom, a chain link K detaches at the top, for example, while at the same time the next chain link K has not contacted the bottom yet, however. This is why an average angle of wrap υ will be assumed in the following, which is equal to or greater than the minimum angle of wrap and equal to or smaller than the maximum angle of wrap. Furthermore, at the top of the chain wheel R, an effective lever arm H eff is indicated, which corresponds to the vertical distance between the effective line W of force, in particular tensile force of the pintle chain G and the rotary axis D of the chain wheel R. Like the momentary angle of wrap υ, the effective lever arm H eff also varies during the movement of the pintle chain due to the detachment of the pintle chain one link at a time, in particular due to the polygonal contact of the chain on the chain wheel. At the bottom side of the chain wheel R, the effective lever arm H eff ′ is a bit shorter, while due to the slightly inclined effective line W of force of the pintle chain G, the effective lever arm H eff ′ does no longer extend through the detachment point A. State of the Art In escalators or moving sidewalks, their steps or pallets, are usually driven by drive chains, in particular on both sides, formed as so-called step chains or pallet chains, and are also attached to the latter. Usually the drive chains have 3 or 4 subdivisions, i.e. 3 or 4 links per step. The chain wheels used have about 16 to 25 teeth. This relatively high number is chosen to minimize the so-called polygonal effect. The polygonal effect comes about by the variations in the effective lever arm H eff (see FIG. 1 ). Chain wheels are usually driven with constant angular velocity. Due to the variations in the effective lever arms, the velocity of the step chains also varies, the incessant acceleration and deceleration of the moved masses (chains, axles, steps) results in the generation of mass forces, which are transmitted as disturbing forces or torques into the step or pallet chains or into their drives, and lead to a shortened service life, or are a quantity which must be taken into account when designing the drive components, in particular. Moreover, the moving parts in an escalator combined with the surrounding steel structure, form a spring-mass system capable of vibration. In particular, the chains can be seen as springs, and steps, axles (if any), wheels, the people transported (on the steps or pallets) and again the chains, are to be seen as masses. This spring-mass system can have very unfavorable operating points depending on the parameters, as a function of the number of teeth of the chain wheels, the traversing velocity and the load. In practice, this problem is usually solved by reducing the chain pitch and increasing the number of teeth. As the pitch is reduced and the number of teeth is increased, the polygonal effect is reduced, until a degree is reached, where the polygonal effect is so low in practice, i.e. the movement of the chains/steps/pallets is so uniform, that the polygonal effect causes practically no problem, but is still present. Also, guides have been installed in the area of the chain wheels, which effect tangential entry of the chain onto the chain wheels. The primary aim of this measure is to reduce the entry noise of the chain on the chain wheels. Also, the polygonal effect is reduced hereby, but not compensated. The conventional structure with relatively small chain pitch and a relatively high number of teeth of the chain wheels has substantial drawbacks, however. First of all, the high cost of the chain for the steps or pallets is to be mentioned. The more subdivisions (the smaller the pitch) for the latter, the more links per step or per meter, and the higher its cost. Moreover, there is a higher number of positions per step/pallet, subject to wear. Over the period of operation of the escalator, adherence to the maximum admissible spacing between steps/pallets for as long as possible, is a very important criterion. Due to the high number of teeth, the chain wheels have a relatively great diameter and need a large structural space, in particular for the drive station. This is how valuable space is lost in buildings. Due to great diameters, high driving moments are necessary, which entails higher cost for the drives. An escalator of the initially mentioned type is known from European Patent Application EP 1 344 740 A1. The escalator described there has a chain wheel driven in a manner polygonally compensated by the upper strand, wherein a pintle chain partially wraps around the chain wheel. The chain wheel has an odd number of teeth. Due to the odd number of teeth, the lower strand does not run in a polygonally-compensated manner, but rather irregularly. Since the lower strand has also masses applied to it, such as the masses of chains, wheels, axles and steps or pallets, forces result from this irregularity, which are transmitted to the steps or pallets in the upper strand. Such an escalator may run comparatively smoothly in a heavily loaded state, due to the large quotient between the mass in the upper strand and the mass in the lower strand. In the unloaded state, or loaded with only few people, however, the upper strand will also run in a very uneven manner. The problem on which the present invention is based, is the creation of an apparatus of the initially mentioned type, which runs comparatively smoothly even with a relatively low number of teeth on the at least one chain wheel. BRIEF SUMMARY OF THE INVENTION Summary of the Invention The objects of the invention are achieved by the escalator described herein. The effective lever arm of the chain at the at least one chain wheel in the upper strand is essentially equal to the effective lever arm of the chain at the at least one chain wheel in the lower strand. In the polygonal compensation configured for the upper strand, for example, this results not only in a constant velocity of the running of the upper strand, but also of the lower strand. The solution according to the present invention allows step or pallet chains with substantially increased pitch, such as chain pitch equal to half of the step pitch or a chain pitch equal to the step pitch, to be used and/or to reduce the structural space required. In one example the first chain wheel and the second chain wheel are operated in a manner offset with respect to each other in such a way that, with a minimal effective lever arm at the first chain wheel in the same strand, the effective lever arm on the second chain wheel is not minimal, preferably deviates by ±20% or less of the difference between the maximum and minimum values from the maximum value, and is maximal, in particular. For this purpose, for example, the angular position of the first chain wheel can differ from that of the second chain wheel by at least ±30%, preferably by at least ±40% of the angular pitch, in particular by half of the angular pitch. This opposition in phase of the two chain wheels results in a reciprocating movement of the second chain wheel, configured as an idler wheel, for example, being reduced. In one example the escalator has at least one guide, which can influence the entry angle of the chain on the first and/or the second chain wheel, wherein the at least one guide is arranged in such a way that the entry angle with the minimum effective lever arm is smaller than with the maximum effective lever arm. Such an arrangement of the guide has the result that the oscillating movement of the redirecting station approaches zero when the machine is running, which has a positive effect on running smoothness. Moreover, this arrangement of the at least one guide has the effect that the wheels are only minimally loaded. This means that it is possible to use relatively cheap wheels. Further features and advantages of the present invention will become clear in the following description of preferred exemplary embodiments with reference to the accompanying drawings, wherein: BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING FIG. 1 is a diagram of a chain wheel and a pintle chain to illustrate the terms used; FIG. 2 is a diagrammatic side view of an escalator according to the present invention with an idler chain wheel; FIG. 3 is a diagrammatic side view of an escalator according to the present invention with a redirecting arc instead of an idler chain wheel; and FIG. 4 is a diagrammatic enlarged view of several components essential for the function of the escalator according to FIG. 2 . DESCRIPTION OF THE INVENTION The escalator as shown in FIG. 2 comprises a chain 1 configured as a pintle chain, wrapped around a first, driven chain wheel 2 and a second chain wheel 3 acting as an idler wheel. Each of the chain wheels 2 , 3 has six teeth, only diagrammatically indicated. The steps or pallets (not shown) of the escalator are attached to the chain 1 . A circulating hand rail 4 is only schematically shown in FIGS. 2 and 3 , which can be held by a user during the movement of the escalator. Between the chain wheels 2 , 3 , the chain 1 forms an upper strand 5 , shown at the top in each of FIGS. 2 to 4 , and a lower strand 6 , shown at the bottom in each of FIGS. 2 to 4 . The first chain wheel 2 is driven in a manner free of the polygonal effect, or polygonally compensated, by a drive motor 7 via a drive chain 8 . This can be achieved, for example, in the exemplary embodiment shown, by a non-circular wheel 9 engaging the drive chain 8 . Further possibilities of a polygonally-compensated drive are known from the WO 03/036129 A1, which is explicitly incorporated herein by reference. The polygonally-compensated drive allows the first chain wheel 2 to be driven with a non-constant angular velocity in such a way that the driven chain 1 is running at a constant, or near-constant, velocity. I.1. The link chain drive which forms the basis of a first aspect of the invention comprises a drive chain sprocket for a link chain and comprises a drive system which can drive the drive chain sprocket with a non-uniform rotational speed for the purpose of compensating speed fluctuations of the link chain. Here and below, a “drive system” should be understood in a broad sense to mean any system which can output forces or torques to the drive chain sprocket. This encompasses in particular drive systems in the narrower sense, in which said forces or torques are actively generated, for example by means of an electric motor. Also encompassed, however, are “passive” drive systems in which said forces or torques are extracted from inertial systems such as for example a rotating flywheel mass. In a first embodiment, the link chain drive is characterized in that the drive system comprises the following elements: two wheels which are coupled by means of an endlessly encircling flexible traction mechanism, such that the rotation of one wheel can be transmitted to the other wheel via the traction mechanism; a movable tensioning element such as for example a tensioning roller which, by acting on the load-bearing strand of the traction mechanism, changes the effective length of the load-bearing strand; the load- bearing strand of the traction mechanism is by definition that portion of the flexible traction mechanism via which the force is transmitted from the driving wheel to the driven wheel. The stated change in length is preferably periodic and synchronous with the rotation of the drive chain sprocket from tooth to tooth. I.2. The invention furthermore relates to a second embodiment of a link chain drive comprising a drive chain sprocket for a link chain and comprising a drive system (in the broad sense explained above) which can drive the drive chain sprocket with a non-uniform rotational speed for the purpose of compensating speed fluctuations of the link chain. Here, the drive system comprises two wheels which are coupled by means of an endlessly encircling flexible traction mechanism. According to a first variant, the link chain drive is characterized in that the axle of one of the two wheels is mounted eccentrically. According to a second variant, the link chain drive is characterized in that the axle of one of the two wheels is mounted so as to be movable and is connected to a diverting mechanism. The eccentric mounting of the wheel causes a periodic change in length of the load-bearing strand, and as a result a non-uniform rotational speed of the drive chain sprocket, which reduces the polygon effect if the relationships are configured such that a rotation of the eccentric wheel rotates the drive chain sprocket precisely one tooth further. I.3. According to a third embodiment of the underlying link chain drive having a drive chain sprocket for a link chain and having a drive system of non-uniform rotational speed, the drive system comprises the following elements: a motor, in particular an electric motor (geared motor), the rotor (component which is set in rotation) of which is coupled to the drive chain sprocket and the stator (component which does not rotate) of which is movable; a mechanism for moving the stator synchronously with the rotation of the drive chain sprocket. Here, the stated mechanism preferably comprises a cam element which is coupled to and interacts with the drive chain sprocket and which is followed by a follower element, wherein the relative movement generated between the cam element and the follower element is transmitted to the stator of the motor. II.1. According to a second aspect, the invention relates to a link chain drive which may be in particular an intermediate drive for an extended link chain, comprising a drive wheel with a shaft and with radially projecting teeth which engage in a force-transmitting manner into the link chain, and comprising a drive system which is coupled to the shaft in order to be able to actively set the drive wheel in rotation. The link chain drive is characterized in that the shaft— and therefore also the drive wheel— is mounted such that it can be displaced spatially in parallel. Here, the translation of the shaft preferably takes place only radially (without an axial component) with respect to its original position. III.1. According to a third aspect, the invention relates to a link chain guide comprising a diverting wheel around which a link chain is guided. In the present case, “diverting wheel” is intended to denote both an actively driven wheel (“drive wheel”) and also a non-driven wheel. Furthermore, the link chain guide comprises a support element which makes contact with the chain links of the link chain directly before they arrive at the diverting wheel. The link chain guide is characterized in that the support element is movably mounted in such a way that it can be moved synchronously with the rotation of the diverting wheel, in order to reduce the speed difference between the chain links and the diverting wheel at the time at which the chain links arrive at the diverting wheel. III.2 According to the third aspect, the invention furthermore relates to a link chain guide having a diverting wheel around which a link chain is guided, and having a support element which makes contact with the chain links before they arrive at the diverting wheel, wherein the link chain has a bent profile between its primary running direction and the diverting wheel. The link chain guide is characterized in that the support element is arranged in the region of the bent profile of the link chain and is designed such that the movement of the chain links is adapted, before they arrive at the diverting wheel, to the movement of the associated tooth spaces. IV.1. According to a fourth aspect, the invention relates to a link chain guide having a diverting wheel around which a link chain is guided. The link chain guide is characterized in that the diverting wheel is coupled to inertia compensation means, by which forces synchronous with the rotational movement of the diverting wheel are exerted on the diverting wheel such that speed fluctuations of the link chain owing to inertial influences of the diverting wheel are reduced. The hand rail 4 is driven by the drive motor 7 , wherein the hand rail 4 is driven at a constant angular velocity. The second chain wheel 3 is supported by means of a moveable support 10 in a displaceable manner. In the view according to FIG. 4 , the chain 1 is shown shortened. FIG. 4 shows that the second chain wheel 3 is offset from the first chain wheel 2 with respect to its angular position. For example, a radial line 12 extending through one of the contact points 11 of the chain 1 forms an angle α with the horizontal 13 on the first chain wheel 2 in FIG. 4 , which is about 60°. In contrast, a radial line 15 extending through the corresponding contact point 14 of the chain 1 forms an angle β with the horizontal 13 on the second chain wheel 3 in FIG. 4 , which is about 30°. The angular positions of the chain wheels 2 , 3 therefore differ by 30°, which corresponds to half the angular pitch of the chain wheels 2 , 3 each having six teeth, because the angular pitch is 360° divided by the number of teeth. This difference in the angular positions of chain wheels 2 , 3 has the result that precisely at the point, where the chain 1 applies a minimum effective lever arm 16 , 16 ′ on the first chain wheel 2 , the chain 1 applies a maximum effective lever arm 17 , 17 ′ on the second chain wheel 3 (see FIG. 4 ). In the reverse case, the chain 1 applies a maximum effective lever arm to the first chain wheel 2 whenever the chain 1 applies a minimum effective lever arm on the second chain wheel 3 (not shown). Further, it can be seen from FIG. 4 that the effective lever arm 16 in the upper strand 5 on the first chain wheel 2 is equal to the effective lever arm 16 ′ in the lower strand 6 . Further, it can be seen from FIG. 4 that the effective lever arm 17 in the upper strand 5 is also equal to the effective lever arm 17 ′ in the lower strand 6 on the second chain wheel 3 . Guides 18 , 19 as seen from FIG. 4 can define the entry angles φ 1 , φ 2 of the chain 1 on the chain wheels. Herein, in particular, the guide 18 is arranged toward the bottom in FIG. 4 to such an extent, or the guide 19 is arranged toward the top in FIG. 4 to such an extent that the entry angle φ 1 with minimum effective lever arm 16 , 16 ′ (c.f. first chain wheel 2 in FIG. 4 ) is substantially smaller than the entry angle φ 2 with maximum effective lever arm 17 , 17 ′ (c.f. second chain wheel 3 in FIG. 4 ). In the embodiment according to FIG. 3 , a redirecting arc 20 is provided instead of the second chain wheel 3 . The radius for this redirecting arc 20 is chosen such that the effective lever arm (not shown) in the upper strand 5 is equal to the effective lever arm in the lower strand 6 also on the redirecting arc 20 . Furthermore, in the embodiment according to FIG. 3 , the guides 18 , 19 are also able to guide the chain 1 into the redirecting arc in such a way that the entry angle with minimum effective lever arm is substantially smaller than the entry angle with maximum effective lever arm. Furthermore, the redirecting arc 20 , the first chain wheel 2 and the chain 1 can be configured and arranged in such a way that whenever the chain 1 applies a minimum effective lever arm 16 , 16 ′ to the first chain wheel 2 , the chain 1 applies a maximum effective lever arm to the redirecting arc 20 , and vice-versa. A further partially functional description of the exemplary embodiments can be derived from the following. The chain wheels 2 , 3 used have an even number of teeth. This applies in the case that the angle of wrap of the chain 1 is about 180°, which is the normal case for escalators/moving sidewalks. What is crucial is that the effective lever arm on the side of the upper strand is always essentially identical to the effective lever arm on the side of the lower strand. This has the effect, in a polygonal compensation configured for the upper strand, that not only the upper strand runs at a constant velocity, but also the lower strand (in the case of an odd number of teeth and with a angle of wrap of 180° the lower strand would run with about double the irregularity as a conventional, i.e. not polygonally-compensated drive). The angle of wrap can also deviate from 180° under the condition that the effective lever arms are identical for the upper and lower strands. This means that the number of teeth and the angle of wrap must be adapted for this case. When this condition is fulfilled, uniform chain velocities will result in the upper and the lower strand, which are requisite for smooth running of the escalator/the moving sidewalk. The same rule also applies to the non-driven redirecting or idler station (with escalators it is usually the lower landing station) as to the driven chain wheel 2 . Again, it is crucial to provide for identical effective lever arms. This also applies in the case where a chain wheel 3 is not used for redirecting, but a non-toothed, stationary-mounted or spring-loaded/elastically-mounted redirecting arc 20 is used. This means that the radii or diameters of the redirecting arc must be configured in such a way while also taking the diameter of the chain wheels into account, that the link center points of the chain 1 run on a corresponding pitch circle corresponding to that of a chain wheel having the corresponding number of teeth. Since the chain wheels 2 , 3 do not run at a constant angular velocity and this effect becomes greater the smaller the number of teeth, care must be taken that they are configured to be as light as possible, i.e. having only a small moment of inertia, so that the disturbing forces exerted by them on the chains/steps/pallets, are as small as possible. In particular, weight optimization must be observed for the points further removed from the pivot point, and weight reduction recesses or the like must be provided, if necessary. Due to the polygonal contact of chain 1 , in particular with large links, on the chain wheels 2 , 3 , usually the axle distance between the chain wheels 2 , 3 changes from tooth engagement to tooth engagement. The chain 1 always has a constant length, apart from elastic expansion. The drive chain wheels are usually mounted in a stationary manner, and the idler chain wheels are resilient and linearly moveable on the fixture 10 . The idler chain wheels therefore make a linear movement from pitch to pitch. This is the larger the greater the chain pitch and the smaller the number of teeth on the chain wheel. In conventional escalators having a relatively small chain pitch and a relatively large number of teeth, as the case may be, this problem does not need to be addressed. Since the pitch may be very large in an escalator (or moving sidewalk) according to the present invention, namely 1/1 or 1/2 of the step/pallet pitch, and the number of teeth may be very small, namely up to 6 or 4, the linear movement of the second chain wheel 3 acting as the idler wheel or the redirecting arc 20 can be so large that it will develop into a component disruptive for the smooth running of the escalator/the moving sidewalk. Disturbing mass forces result from this large linear movement of the redirecting station, and disturbing noises may also arise. The constellation is particularly disadvantageous if the drive and idler chain wheels have the same angular position (measured, for example, by angle α or β of a chain wheel corner relative to the horizontal). This is why the relative angular position α, β of the chain wheels 2 , 3 must be observed, i.e., it should be opposed in phase: about half of a pitch angle (±20%) must be between the angular position of the first chain wheel 2 and that of the second chain wheel 3 (pitch angle=360° divided by the number of teeth). This means that the axle distance, the lifting height and the length of the chains must be adapted to each other. Further, the first and second chain wheels 2 , 3 should have the same number of teeth, if possible. Deviations from the same number of teeth within a range of ±30% are tolerable. Furthermore, guiding of the chains is important. The guides 18 , 19 used in an exemplary embodiment of the escalator according to the present invention have the effect that the chain 1 runs onto the chain wheels 2 , 3 a little above the minimum effective lever arm. Furthermore, they are optionally curved at their ends, which has the effect that a velocity component in a radial direction is applied to the chain 1 shortly before contacting the chain wheels 2 , 3 , or after running off the chain wheels 2 , 3 . The impact component of the chain link points into the tooth spaces of the chain wheels, or onto the guides 18 , 19 is therefore substantially reduced, which leads to considerably lower noise and more advantageous running properties. Chain guides which cause the chains to run tangentially onto the chain wheels and therefore reduce entry noise (chain on chain wheel) cannot be used in an escalator according to the present invention, because due to the low number of teeth of the chain wheels and the resulting ratios of angles the stresses for the wheels become too great, or the wheels would have to be dimensioned for these stresses, which would make them very expensive. Moreover, a large oscillating movement of the redirecting station would result from this arrangement of the guides, which would lead to the above mentioned drawbacks. In an escalator according to the present invention, the correct height of the guides 18 , 19 between the minimum and maximum effective lever arm is near the minimum lever arm. If they are set at the correct height, the result is that the oscillating movement of the redirecting station approaches zero when the machine is running, which greatly improves smooth running. Moreover, the wheels are only slightly stressed with this arrangement of the guides. This means that relatively cheap wheels can be used. The optimum height of the chain guides is determined as follows: The chain links are pivoted about a predetermined angle, when they leave the guides 18 , 19 . It is possible to draw or conceive small rectangular triangles there, the hypotenuse of which is the chain link in question, wherein one of the small sides is formed by the horizontal. All quantities may also be calculated with the aid of the angular functions. The sum of the horizontal small sides is now formed and various angular positions of the chain wheels are determined within a pitch angle. It is now imagined that the chains continue running another little bit and the chain wheels rotate further until they have rotated about a pitch angle. A pitch angle of about 60°, for example, is thus subdivided into 20 steps of 3° each, for example. The height of the guides is now changed until the sum of the horizontal small sides results in a value which is as constant as possible over the various angular positions. Where these deviations have reached their minimum, the linear movement of the idler chain wheels/the redirecting station is also at its minimum. In real escalators, polygonal effects would also have to be taken into account, if any, which result in the transitions from horizontal to inclined portions (redirecting radii) when the chains run through the chain guides.

An escalator includes a plurality of steps or panels, a chain for driving the steps or panels, at least one chain wheel around which the chain is deflected and wherein the chain, starting from the chain wheel, forms an upper strand and a lower strand. There is also provided a device for the polygonal compensation of the movement of the at least one chain wheel. The effective lever arm of the chain on the at least one chain wheel in the upper strand is substantially equal to the effective lever arm of the chain on the at least one chain wheel in the lower strand.

RELATED APPLICATIONS This application is a continuation application of application Ser. No. 10/978,101 filed Oct. 29, 2004, pending, which is a continuation application of application Ser. No. 10/346,338, filed on Jan. 16, 2003 now abandoned, which is a continuation of application Ser. No. 09/739,089, filed on Dec. 15, 2000, pending, which in turn claims priority to Greek National Application Serial No. 20000/100102 filed on Mar. 28, 2000. The contents of all of the aforementioned application(s) are hereby incorporated by reference. FIELD OF THE INVENTION The present invention is directed to a method and apparatus for the in vivo, non invasive detection and mapping of the biochemical and/or functional pathologic alterations of human tissues. BACKGROUND OF THE INVENTION Cancer precursors signs are the so called pre-cancerous states, which are curable if they are detected at an early stage. In the opposite case the lesion can progress in depth, resulting in the development of invasive cancer and metastases. At this stage, the possibilities of successful therapy are dramatically diminished. Consequently, the early detection and the objective identification of the severity (stage) of the precancerous lesion are of crucial importance. The conventional clinical process of optical examination have very limited capabilities in detecting cancerous and pre-cancerous tissue lesions. This is due to the fact that the structural and metabolic changes, which take place during the development of the decease, do not significantly and with specificity alter the color characteristics of the pathological tissue. In order to obtain more accurate diagnosis, biopsy samples are obtained from suspicious areas, which are submitted for histological examination. However, biopsy sampling poses several problems, such as: a) risk for sampling errors associated with the visual limitations in detecting and localizing suspicious areas; b) biopsy can alter the natural history of the intraepithelial lesion; c) mapping and monitoring of the lesion require multiple tissue sampling, which is subjected to several risks and limitations; d) the diagnostic procedure performed with biopsy sampling and histologic evaluation is qualitative, subjective, time consuming, costly and labor intensive. In recent years there have been developed and presented quite a few new methods and systems in an effort to overcome the disadvantages of the conventional diagnostic procedures. These methods can be classified in two categories: a) Methods which are based on the spectral analysis of tissues in vivo, in an attempt to improve the diagnostic information b) Methods which are based on the chemical excitation of tissues with the aid of special agents, which have the property to interact with pathologic tissue and to alter its optical characteristics selectively, thus enhancing the contrast between lesion and healthy tissue. In the first case, the experimental use of spectroscopic techniques as a potential solutions to existing diagnostic problems, is motivated by their capability to detect alterations in the biochemical and/or the structural characteristics, which take place in the tissue during the development of the disease. In particular, fluorescence spectroscopy has been extensively used in various tissues, where the later are optically excited with the aid of a light source (usually laser), of short wave length (blue—ultraviolet range) and their response is measured as fluorescence intensity vs. wavelength. Garfield and Glassman in U.S. Pat. No. 5,450,857 and Ramanajum et al in U.S. Pat. No. 5,421,339 have presented a method based on the use of fluorescence spectroscopy for the diagnosis of cancerous and pre-cancerous lesions of cervix. The main disadvantage of fluorescence spectroscopy is that the existing biochemical modifications associated with the progress of the disease are not manifested in a direct way as modifications in the measured fluorescence spectra. The fluorescence spectra contain limited diagnostic information of two basic reasons: a) Tissues contain non-fluorescent chromophores, such as hemoglobin. Absorption by such chromophores of the emitted light from fluorophores can result in artificial dips and peaks in the fluorescence spectra. In other words the spectra carry convoluted information for several components and therefore it is difficult assess alterations in tissue features of diagnostic importance; and b) The spectra are broad due to the fact that a large number of tissue components are optically excited and contribute to the captured optical signal. As a result the spectra do not carry specific information for the pathologic alterations and thus they are of limited diagnostic value. The latter is expressed as low sensitivity and specificity in the detection and classification of tissue lesions. Aiming to enhance the sensitivity and specificity of the captured information, Ramanujan et al in the Patent No. WO 98/24369 have presented a method based on the use of neural networks for the analysis of the spectral data. This method is based on the training of a computing system with a large number of spectral patterns, which have been taken from normal and from pathologic tissues. The spectrum that is captured each time is compared with the stored spectral data, facilitating this way, the identification of the tissue pathology. R. R. Kortun et al, in U.S. Pat. No. 5,697,373, seeking to improve the captured diagnostic information, have presented a method based on the combination of fluorescence spectroscopy and Raman scattering. The last has the capability of providing more analytical information, it requires however complex instrumentation and ideal experimental conditions, which substantially hinder their clinical use. It is generally known that tissues are characterized by the lack of spatial homogeneity and consequently the spectral analysis of distributed spatial points is insufficient for the characterization of their status. Dombrowski in U.S. Pat. No. 5,424,543, describes a multi-wavelength, imaging system, capable of capturing tissue images in several spectral bands. With the aid of such a system it is possible in general to map characteristics of diagnostic importance based on their particular spectral characteristics. However, due to the insignificance of the spectral differences between normal and pathologic tissue, which is in general the case, inspection in narrow spectral bands does not allow the highlighting of these characteristics and even more so, the identification and staging of the pathologic area. D. R. Sandison et al, in U.S. Pat. No. 5,920,399 describe an imaging system, developed for the in vivo investigation of cells, which combines multi-band imaging and light excitation of the tissue. The system also employs a dual fiber optic bundle for the transferring of the emitted from the source light onto the tissue and the remitted light from the tissue to the optical detector. These bundles are placed in contact with the tissue, and various wavelengths of excitation and imaging are combined in attempt to enhance the spectral differentiation between normal and pathologic tissue. In U.S. Pat. No. 5,921,926, J. R. Delfyett et al have presented a method for the diagnosis of diseases of the cervix, which is based on the combination of Spectral Interferometry and Optical Coherence Tomography (OCT). This system combines three-dimensional imaging and spectral analysis of the tissue. Moreover, several improved versions of colposcopes have been presented, (D. R. Craine et al, U.S. Pat. No. 5,791,346 and K. L. Blaiz U.S. Pat. No. 5,989,184) in most of which, electronic imaging systems have been integrated for image capturing, analysis of tissue images, including the quantitative assessment of lesion's size. For the enhancement of the optical differentiation between normal and pathologic tissue, special agents are used in various fields of biomedical diagnostics, which are administered topically or systematically. Such agents are acetic acid solution, toluidine blue, various photosensitizers (porphyrines) (S. Anderson Engels, C. Klinteberg, K. Svanberg, S. Svanberg, In vivo fluorescence imaging for tissue diagnostics, Phys Med. Biol. 42 (1997) 815-24). The provoked selective staining of the pathologic tissue is owed to the property of these agents to interact with the altered metabolic and structural characteristics of the pathologic area. This interaction enhances progressively and reversibly the differences in the spectral characteristics of reflection and/or fluorescence between normal and pathologic tissue. Despite the fact that the provoked selective staining of the pathologic tissue is a dynamic phenomenon, in clinical practice the intensity and the extent of the staining are assessed qualitatively and statically. Furthermore, in several cases of early pathologic conditions, the phenomenon of temporary staining after administering the agent, is short-lasting and thus the examiner is not able to detect the provoked alterations and even more so, to assess their intensity and extent. In other cases, the staining of the tissue progresses very slowly, with the consequence of patient discomfort and creation of problems for the examiner in assessing the intensity and extent of the alterations, since they are continuously changing. The above have as direct consequence, the downgrading of the diagnostic value of these diagnostic procedures and thus its usefulness is limited to facilitate the localization of suspected areas for obtaining biopsy samples. Summarizing the above mentioned, the following conclusions are drawn: a) Various conventional light dispersion spectroscopic techniques (fluorescence, elastic, non elastic scattering, etc) have been proposed and experimentally used for the in vivo detection of alterations in the structural characteristics of pathologic tissue. The main disadvantage of these techniques is that they provide point information, which is inadequate for the analysis of the spatially non-homogenous tissue. Multi-band imaging has the potential to solve this problem, by providing spectral information (of lesser resolution as a rule) but in any spatial point of the area under examination. These techniques (imaging and non-imaging) however, provide information of limited diagnostic value, due to the fact that the structural tissue alterations, which are accompanying the development of the disease, are not manifested as significant and characteristic alterations on the measured spectra. Consequently, the captured spectral information cannot be directly correlated with the tissue pathology, a fact which limits the clinical usefulness of these techniques. b) The conventional (non-spectral) imaging techniques provide the capability of mapping characteristics of diagnostic importance in two or three dimensions. They are basically used for measuring morphological characteristics and as clinical documentation tools. c) The diagnostic methods which are based on the selective staining of pathologic tissue with special agents allows the enhancement of the optical contrast between normal and pathologic tissue. Nevertheless they provide limited information for the in vivo identification and staging of the disease. Given the fact that the selective interaction of pathologic tissue with the agents, which enhance its optical contrast with healthy tissue is a dynamic phenomenon, it is reasonable to suggest that the capture and analysis of the characteristics of this phenomenon's kinetics, could provide important information for the in vivo detection, identification and staging of tissue lesions. In a previous publication by the inventors (C. Balas, A. Dimoka, E. Orfanoudaki, E. koumandakis, “In vivo assessment of acetic acid-cervical tissue interaction using quantitative imaging of back-scattered light: Its potential use for the in vivo cervical cancer detection grading and mapping”, SPIE-Optical Biopsies and Microscopic Techniques, Vol. 3568 pp. 31-37, (1998)), measurements of the alterations in the characteristics of the back-scattered light as a function of wave-length and time are presented. These alterations are provoked in the cervix by the topical administration of acetic acid solution. In this particular case, there was used as an experimental apparatus, a general-purpose multi-spectral imaging system built around a tunable liquid crystal monochromator for measuring the variations in intensity of the back-scattered light as a function of time and wavelength in selected spatial points. It was found that the lineshapes of curves of intensity of back-scattered light versus time, provide advanced information for the direct identification and staging of tissue neoplasias. Unpublished results of the same research team support that similar results can also be obtained with other agents, which have the property of enhancing the optical contrast between normal and pathologic tissue. Nevertheless, the experimental method employed in the published paper is characterized by quite a few disadvantages, such as: The imaging monochromator requires time for changing the imaging wavelength and as a consequence it is inappropriate for multispectral imaging and analysis of dynamic phenomena. It does not constitute a method for the mapping of the grade of the tissue lesions, as the presented curves illustrate the temporal alterations of intensity of the back-scattered light in selected points. The lack of data modeling and parametric analysis of the characteristics of the phenomenon kinetics in any spatial point of the area of interest restrict the usefulness of the method in experimental studies and hinder its clinical implementation. The optics used for the imaging of the area of interest are of general purpose and are not comply with the special technical requirements for the clinical implementation of the method. Clinical implementation of the presented system is also hindered by the fact that it does not integrate appropriate means for ensuring the stability of the relative position between the tissue surface and image capturing module, during the snapshot imaging procedure. This is very important since small movements of the patient (i.e. breathing) are always present during the examination procedure. If micro-movements are taking place during successive capturing of images, after application of the agent, then the spatial features of the captured images are not coincide. This reduces substantially the precision in the calculation of the curves in any spatial point, that express the kinetics of marker-tissue interaction. SUMMARY OF THE INVENTION The present invention provides, at least in part, a method for monitoring the effects of a pathology differentiating agent on a tissue sample by applying a pathology differentiating agent, e.g., acetic acid, on a tissue sample and monitoring the rate of change of light reflection from the tissue sample over time, thereby monitoring the effects of a pathology differentiating agent on a tissue sample. The tissue may be a cervical, ear, oral, skin, esophagus, or stomach tissue. Without intending to be limited by theory, it is believed that the pathology differentiating agent provokes transient alterations in the light scattering properties of the tissue, e.g., the abnormal epithelium. In another aspect, the present invention features a method for the in vivo diagnosis of a tissue abnormality, e.g., a tissue atypia, a tissue dysplasia, a tissue neoplasia (such as a cervical intraepithelial neoplasia, CINI, CINII, CIMIII) or cancer, in a subject. The method includes contacting a tissue in a subject with a pathology differentiating agent, e.g., an acetic acid solution or a combination of solutions selected from a plurality of acidic and basic solutions, exposing the tissue in the subject to optical radiation; and monitoring the intensity of light emitted from the tissue over time, thereby diagnosing a tissue abnormality in a subject. The optical radiation may be broad band optical radiation, preferably polarized optical radiation. The non-invasive methods of the present invention are useful for the in vivo early detection of tissue abnormalities/alterations and mapping of the grade of these tissue abnormalities/alterations, caused in the biochemical and/or in the functional characteristics of epithelial tissues, during the development of tissue atypias, dysplasias, neoplasias and cancers. In one embodiment, the tissue area of interest is illuminated with a broad band optical radiation and contacted with a pathology differentiating agent, e.g., an agent or a combination of agents which interact with pathologic tissue areas characterized by an altered biochemical composition and/or cellular functionality and provoke a transient alteration in the characteristics of the light that is re-emitted from the tissue. The light that is re-emitted from the tissue may be in the form of reflection, diffuse scattering, fluorescence or combinations or subcombinations thereof. The intensity of the light emitted from the tissue may be measured, e.g., simultaneously, in every spatial point of the tissue area of interest, at a given time point or over time (e.g., for the duration of agent-tissue interaction). A diagnosis may be made based on the quantitative assessment of the spatial distribution of alterations in the characteristics of the light re-emitted from the tissue at given time points, before and after the optical and chemical excitation of the tissue and/or based on the quantitative assessment of the spatial distribution of parameters, calculated from the characteristic curves that express the kinetics of the provoked alterations in the characteristics of the light re-emitted from the tissue, which characteristic curves are simultaneously measured in every spatial point of the area under examination during the optical and chemical excitation of the tissue. In one embodiment of the invention, the step of tissue illumination comprises exposing the tissue area under analysis to optical radiation of narrower spectral width than the spectral width of the light emitted by the illumination source. In another embodiment, the step of measuring the intensity of light comprises measuring the intensity of the re-emitted light in a spectral band, the spectral width of which is narrower than the spectral width of the detector's sensitivity. In yet another embodiment, the step of measuring the intensity of light comprises measuring simultaneously the intensity of the re-emitted light in a plurality of spectral bands, the spectral widths of which are narrower than the spectral width of the detector's sensitivity. In yet another aspect, the present invention features an apparatus for the in vivo, non-invasive early detection of tissue abnormalities/alterations and mapping of the grade of these tissue abnormalities/alterations, caused in the biochemical and/or in the functional characteristics of epithelial tissues, during the development of tissue atypias, dysplasias, neoplasias and cancers. The apparatus includes optics for collecting the light re-emitted by the area under analysis, selecting magnification and focusing the image of the area; optical imaging detector(s); means for the modulation, transfer, display and capturing of the image of the tissue area of interest; a computer which includes data storage, processing and analysis means; a monitor for displaying images, curves and numerical data; optics for the optical multiplication of the image of the tissue area of interest; a light source for illuminating the area of interest; optionally, optical filters for selecting the spectral band of imaging and illumination; means for transmitting light and illuminating the area of interest; control electronics; and optionally, software for the analysis and processing of data, which also enables the tissue image capturing and storing in specific time points and for a plurality of time points, before and after administration of the pathology differentiating agent. Using the foregoing apparatus an image or a series of images may be created which express the spatial distribution of the characteristics of the kinetics of the provoked changes in the tissue's optical characteristics, before and after the administration of the agent, with pixel values corresponding with the spatial distribution of the alterations in the intensity of the light emitted from the tissue, in given time instances, before and after the optical and chemical excitation of tissue and/or with the spatial distribution of parameters derived from the function: pixel gray value versus time. The foregoing function may be calculated from the captured and stored images and for each row of pixels with the same spatial coordinates. In one embodiment, the step of optical filtering the imaging detector comprises an optical filter that is placed in the optical path of the rays that form the image of the tissue, for the recording of temporally successive images in a selected spectral band, the spectral width of which is narrower than the spectral width of the detector's sensitivity. In yet another embodiment, the image multiplication optics comprise light beam splitting optics that create two identical images of the area of interest, which are recorded by two imaging detectors, in front of which optical filters are placed, with in general different transmission characteristics and capable of transmitting light of spectral width shorter than the spectral width of the detector's sensitivity, so that two groups of temporally successive images of the same tissue area are recorded simultaneously, each one corresponding to a different spectral band. In another embodiment, the image multiplication optics comprise more than one beam splitter for the creation of multiple identical images of the area of interest, which are recorded by multiple imaging detectors, in front of which optical filters are placed, with, preferably, different transmission characteristics and capable of transmitting light of spectral width shorter than the spectral width of the detector's sensitivity, so that multiple groups of temporally successive images of the same tissue area are recorded simultaneously, each one corresponding to a different spectral band. In a further embodiment, the image multiplication optics comprise one beam splitter for the creation of multiple identical images of the area of interest, which are recorded by multiple imaging detectors, in front of which optical filters are placed with, preferably, different transmission characteristics and capable of transmitting light of spectral width shorter than the spectral width of the detector's sensitivity, so that multiple groups of temporally successive images of the same tissue area are recorded simultaneously, each one corresponding to a different spectral band. In yet a further embodiment, the image multiplication optics comprise one beam splitter for the creation of multiple identical images of the area of interest, which are recorded in different sub-areas of the same detector, and in front these areas optical filters are placed with, preferably, different transmission characteristics and capable of transmitting light of spectral width shorter than the spectral width of the detector's sensitivity, so that multiple groups of temporally successive images of the same tissue area are recorded simultaneously in the different areas of the detector, each one corresponding to a different spectral band. In another embodiment, the step of filtering the light source comprises an optical filter, which is placed in the optical path of an illumination light beam, and transmits light of spectral width shorter than the spectral width of sensitivity of the detector used. In a further embodiment, the step of filtering the light source comprises a plurality of optical filters and a mechanism for selecting the filter that is interposed to the tissue illumination optical path, thus enabling the tuning of the center wavelength and the spectral width of the light illuminating the tissue. In another embodiment, the mapping of the grade of the alterations to the biochemical and/or functional characteristics of the tissue area of interest, is based on the pixel values of one image, from the group of the recorded temporally successive images of the tissue area of interest. In a further embodiment, the mapping of the grade of the alterations to the biochemical and/or functional characteristics of the tissue area of interest, is based on the pixel values belonging to plurality of images, which are members of the group of the recorded temporally successive images of the tissue area of interest. In another embodiment, the mapping of the grade of the alterations to the biochemical and/or functional characteristics of the tissue area of interest, is based on numerical data derived from mathematical operations and calculations between the pixel values belonging a plurality of images, which are members of the group of the recorded temporally successive images of the tissue area of interest. In a further embodiment, a pseudo-color scale, which represents with different colors the different pixel values of the image or of the images used for the mapping of abnormal tissue areas, is used for the visualization of the mapping of the grade of the alterations to the biochemical and/or functional characteristics of the tissue area under examination. In one embodiment, the image or images which are determined for the mapping of the grade of the alterations in biochemical and/or functional characteristics of tissue, are used for the in vivo detection, mapping, as well as for the determination of the borders of epithelial lesions. In another embodiment, the pixel values of the image or of the images which are determined for the mapping of the grade of alterations in biochemical and/or functional characteristics of tissue, are used as diagnostic indices for the in vivo identification and staging of epithelial lesions. In yet another embodiment, the image or the images which are determined for the mapping of the grade of the alterations in biochemical and/or functional characteristics of tissue can be overimposed onto the color or black and white image of the same area of tissue under examination displayed on the monitor, so that abnormal tissue areas are highlighted and their borders are demarcated, facilitating the selection of a representative area for taking a biopsy sample, the selective surgical removal of the abnormal area and the evaluation of the accuracy in selecting and removing the appropriate section of the tissue. In a further embodiment, the image or the images which are determined for the mapping of the grade of alterations in biochemical and/or functional characteristics of tissue are used for the evaluation of the effectiveness of various therapeutic modalities such as radiotherapy, nuclear medicine treatments, pharmacological therapy, and chemotherapy. In another embodiment, the optics for collecting the light re-emitted by the area under analysis, comprises the optomechanical components employed in microscopes used in clinical diagnostic examinations, surgical microscopes, colposcopes and endoscopes. In one embodiment of the invention, for colposcopy applications, the apparatus may comprise a speculum, an articulated arm onto which the optical head is attached, which optical head comprises a refractive objective lens, focusing optics, a mechanism for selecting the magnification, an eyepiece, a mount for attaching a camera, and an illuminator, where the speculum is attached in a fixed location onto the system articulated arm-optical head, in such a way such that the central longitudinal axis of the speculum is perpendicular to the central area of the objective lens, so that when the speculum is inserted into the vagina and fixed in it, the relative position of the image-capturing optics and of the tissue area of interest remains unaltered, regardless of micro-movements of the cervix, which are taking place during the examination of the female subject. In a further embodiment, the apparatus may further comprise an atomizer for delivering the agent, where the atomizer is attached in a fixed point onto the system articulated arm-optical head of the apparatus and in front of the vaginal opening, where the spraying of the tissue may be controlled and synchronized with a temporally successive image capturing procedure, with the aid of electronic control means. In another embodiment of the apparatus of the invention, the image capturing detector means and image display means comprise a camera system with detector spatial resolution greater than 1000×1000 pixels and a monitor of at least 17 inches (diagonal), so that high magnification is ensured together with a large field of view, while the image quality is maintained. In a further embodiment, in the case of microscopes used in clinical diagnostic examinations, surgical microscopes and colposcopes, comprise an articulated arm onto which the optical head is attached, which optical head comprises an objective lens, focusing optics, a mechanism for selecting the magnification, an eyepiece, a mount for attaching a camera, an illuminator and two linear polarizers, where the two linear polarizers are attached, one at a point along the optical path of the illuminating light beam and the other at a point along the optical path of the rays that form the image of the tissue, with the capability of rotating the polarization planes of these light polarizing optical elements, so that when these planes are perpendicular to each other, the contribution of the tissue's surface reflection to the formed image is eliminated. In another embodiment, in the case of endoscopy, the endoscope may comprise optical means for transferring light from the light source onto the tissue surface and for collecting and transferring along almost the same axis and focusing the rays that form the image of the tissue, and two linear polarizers, where the two linear polarizers are attached, one at a point along the optical path of the illuminating light beam and the other at a point along the optical path of the rays that form the image of the tissue, with the capability of rotating the polarization planes of these light polarizing optical elements, so that when these planes are perpendicular to each other, the contribution of the tissue's surface reflection to the formed by the endoscope image is eliminated. In another embodiment, in the case of microscopes used in clinical diagnostic examinations, surgical microscopes and colposcopes, may additionally comprise a reflective objective lens, where the reflective objective replaces the refractive one, which reflective objective is devised so that in the central part of its optical front aperture the second reflection mirror is located, and in the rear part (non-reflective) of this mirror, illumination means are attached from which light is emitted toward the object, so that with or without illumination beam zooming and focusing optics the central ray of the emitted light cone is coaxial, with the central ray of the light beam that enters the imaging lens, and with the aid of zooming and focusing optics of illumination beam that may be adjusted simultaneously and automatically with the mechanism for varying the magnification of the optical imaging system, the illuminated area and the field-of-view of the imaging system, are varying simultaneously and proportionally, so that any decrease in image brightness caused by increasing the magnification, is compensated with the simultaneous zooming and focusing of the illumination beam. Other features and advantages of the invention will be apparent from the following detailed description and claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of the present method's basic principle. FIG. 2 , illustrates an embodiment of the invention comprising a method for capturing in two spectral bands simultaneously and in any spatial point of the area under analysis, the kinetics of the alterations in the characteristics of the remitted from the tissue light, before and the after the administration of the contrast enhancing agent FIG. 3 illustrates another embodiment of the invention comprising a method for capturing in different spectral bands simultaneously and in any spatial point of the area under analysis, the kinetics of the alterations in the characteristics of the remitted from the tissue light, before and the after the administration of the contrast enhancing agent. FIG. 4 illustrates a schematic diagram of a medical microscope comprising a light source (LS), a magnification selection mechanism (MS), an eyepiece (EP) and a mount for attaching the image capturing module (CA), (detector(s), readout electronics etc). FIG. 5 illustrates an endoscope comprising an eyepiece (EP), which can be adapted to an electronic imaging system, optical fibers or crystals for the transmission of both illumination and image rays, optics for the linear polarization of light, one interposed to the optical path of the illumination rays (LE) and one to the path of the ray that form the optical image of the tissue (II). FIG. 6 depicts a colposcopic apparatus comprising an articulated arm (AA), onto which the optical head (OH) is affixed, which includes a light source (LS), an objective lens (OBJ), an eye-piece (EP) and optics for selecting the magnification (MS). FIG. 7 illustrates an optical imaging apparatus which comprises a light source located at the central part of its front-aperture. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method and system for the in-vivo, non-invasive detection and mapping of the biochemical and or functional alterations of tissue, e.g., tissue within a subject. Upon selection of the appropriate agent which enhances the optical contrast between normal and pathologic tissue (depending on the tissue's pathology), this agent is administered, e.g., topically to the tissue. In FIG. 1 , the tissue (T), is sprayed using an atomizer (A), which contains the agent, e.g., acetic acid. At the same time, the tissue is illuminated with a source that emits light at a specific spectral band, depending on the optical characteristics of both the agent and the tissue. Illumination and selection of the spectral characteristics of the incident to the tissue light can be performed with the aid of a light source (LS) and a mechanism for selecting optical filters (OFS). Of course there are several other methods for illuminating the tissue and for selecting the spectral characteristics of the incident light (e.g., Light emission diodes, LASERS and the like). For the imaging of the area of interest, light collection optics (L) are used, which focus the image onto a two-dimensional optical detector (D). The output signal of the latter is amplified, modulated and digitized with the aid of appropriate electronics (EIS) and finally the image is displayed on a monitor (M) and stored in the data-storing means of a personal computer (PC). Between tissue (T) and detector (D), optical filters (OFI) can be interposed. The interposition of the filter can be performed for tissue (T) imaging in selected spectral bands, at which the maximum contrast is obtained between areas that are subjected to different grade of alterations in their optical characteristics, provoked after administering the appropriate agent. Before administration of the latter, images can be captured and used as reference. After the agent has been administered, the detector (D), captures images of the tissue, in successive time instances, which are then stored in the computer's data-storage means. The capturing rate is proportional to the rate at which the tissue's optical characteristics are altered, following the administration of the agent. In FIG. 1 , images of the same tissue area are schematically illustrated, which have been stored successively before and after administering the agent (STI). In these images, the black areas represent tissue areas that do not alter their optical characteristics (NAT), while the gray-white tones represent areas which alter their optical characteristics (AT), following the administration of the agent. The simultaneous capture of the intensity of the light re-emitted from every spatial point of the tissue area under analysis and in predetermined time instances, allows the calculation of the kinetics of the provoked alterations. In FIG. 1 , two curves are illustrated: pixel value in position xy (Pvxy), versus time t. The curve ATC corresponds to an area where agent administration provoked alterations (AT) in the tissue's optical characteristics. The curve (NATC) corresponds to an area where no alteration took place (NAT). The mathematical analysis of these curves leads to the calculation of quantitative parameters for every pixel. One example of a quantitative parameter is the value PV xy (t i ), which corresponds to the pixel value at point (x,y) at any point in time (t i ). Another example of a quantitative parameter is the relaxation time t rel , which corresponds to the time when the pixel value at point (x,y) (i.e., PV xy ) attains the value of A/e, where A is the maximum pixel value of the PV xy versus time (t) curve, and the base of Neper logarithms is represented by e. The calculation of these parameters (P) in every spatial point of the area under analysis, allows the calculation of the image or images of the kinetics of the phenomenon (KI), with pixel values that are correlated with these parameters. These values can be represented with a scale of pseudocolors (Pmin, Pmax), the spatial distribution of which allows for immediate optical evaluation of the intensity and extent of the provoked alterations. Depending on the correlation degree between the intensity and the extent of the provoked alterations with the pathology and the stage of the tissue lesion, the measured quantitative data and the derived parameters would allow the mapping, the characterization and the border-lining of the lesion. The pseudocolor image of the phenomenon's kinetics (KI), which expresses the spatial distribution of one or more parameters, can be overimposed (after being calculated) on the tissue image, which is displayed in real-time on the monitor. The using the overimposed image as a guide, facilitates substantially the determination of the lesion's boundaries, for successful surgical removal of the entire lesion, or for locating suspicious areas in order to obtain a biopsy sample(s). Furthermore, based on the correlation of the phenomenon's kinetics with the pathology of the tissue, the measured quantitative data and the parameters that derive from them, can constitute quantitative clinical indices for the in vivo staging of the lesion or of sub-areas of the latter. In some cases it is necessary to capture the kinetics of the phenomenon in more than one spectral band. This can serve in the in vivo determination of illumination and/or imaging spectral bands at which the maximum diagnostic signal is obtained. Furthermore, the simultaneous imaging in more than one spectral bands can assist in minimizing the contribution of the unwanted endogenous scattering, fluorescence and reflection of the tissue, to the optical signal captured by the detector. The captured optical signal comprise the optical signal generated by the marker-tissue interaction and the light emitted from the endogenous components of the tissue. In many cases the recorded response of the components of the tissue constitute noise, since it occludes the generated optical signal, which caries the diagnostic information. Therefore, separation of these signals, based on their particular spectral characteristics, will result in the maximization of the signal-to-noise ratio and consequently in the improvement of the obtained diagnostic information. FIG. 2 , illustrates a method for capturing in two spectral bands simultaneously and in any spatial point of the area under analysis, the kinetics of the alterations in the characteristics of the remitted from the tissue light, before and the after the administration of the contrast enhancing agent. The remitted from the tissue light, is collected and focused by the optical imaging module (L) and passes through a beam splitting (BSP) optical element. Thus, two identical images of the tissue (T) are generated, which can be captured by two detectors (D 1 , D 2 ). In front of the detector, appropriate optical filters (Ofλ 1 ), (Ofλ 2 ) can be placed, so that images with different spectral characteristics are captured. Besides beam splitters, optical filters, dichroic mirrors etc, can also be used for splitting the image of the object. The detectors (D 1 ), (D 2 ) are synchronized so that they capture simultaneously the corresponding spectral images of the tissue (Tiλ 1 ), (Tiλ 2 ) and in successive time-intervals, which are stored in the computer's data storage means. Generalizing, multiple spectral images can be captured simultaneously by combining multiple splitting elements, filters and sources. FIG. 3 illustrates another method for capturing in different spectral bands simultaneously and in any spatial point of the area under analysis, the kinetics of the alterations in the characteristics of the remitted from the tissue light, before and the after the administration of the contrast enhancing agent. With the aid of a special prism (MIP) and imaging optics, it is possible to form multiple copies of the same image onto the surface of the same detector (D). Various optical filters (OFλ 1 ),(OFλ 2 ),(OFλ 3 ),(OFλ 4 ), can be interposed along the length of the optical path of the rays that form the copies of the object's image, so that the captured multiple images correspond to different spectral areas. For the clinical use of the methods of the invention, the different implementations of image capturing module described above can be integrated to conventional optical imaging diagnostic devises. Such devises are the various medical microscopes, colposcopes and endoscopes, which are routinely used for the in vivo diagnostic inspection of tissues. Imaging of internal tissues of the human body requires in most cases the illumination and imaging rays to travel along the same optical path, through the cavities of the body. Due to this fact, in the common optical diagnostic devises the tissue's surface reflection contributes substantially in the formed image. This limits the imaging information for the subsurface characteristics, which are in general of great diagnostic importance. This problem becomes more serious especially in epithelial tissues such as the cervix, larynx, oral cavity etc, which are covered by fluids such as mucus and saliva. Surface reflection also obstructs the detection and the measurement of the alterations in the tissue's optical properties, provoked after the administration of agents which enhance the optical contrast between normal and pathologic tissue. More specifically, when a special agent alters selectively the scattering characteristics of the pathologic tissue, the strong surface reflection that takes place in both pathologic (agent responsive) and normal (agent non responsive) tissue areas, occludes the diagnostic signal that originates from the interaction of the agent with the subsurface features of the tissue. In other words, surface reflection constitutes optical noise in the diagnostic signal degrading substantially the perceived contrast between agent responsive and agent non responsive tissue areas. Based on the above, the effective integration of the method to imaging diagnostic devises, requires embodiments of appropriate optics that ensure the elimination of the contribution of surface reflection to the captured image. FIG. 4 illustrates a schematic diagram of a medical microscope consisted from a light source (LS), a magnification selection mechanism (MS), an eyepiece (EP) and a mount for attaching the image capturing module (CA), (detector(s), readout electronics etc). For the elimination of the surface reflection a pair of linear polarizers is employed. The incident to the tissue light (LS), is linearly polarized by passing though a linear polarizer (LPO). The surface reflected light (TS), has the same polarization plane with the incident to the tissue light (Fresnel reflection). By interposing the other linear polarizer to the optical path of the rays that are remitted from the tissue and form the optical image of the object, with its polarization plane perpendicular to the polarization level of the incident to the tissue light (IPO), the contribution of the surface reflection to the image of the object is eliminated. The light which is not surface-reflected enters the tissue, where due to multiple scattering, light polarization is randomized. Thus, a portion of the re-emitted light passes through the imaging polarization optics, carrying improved information for the subsurface features. FIG. 5 illustrates an endoscope consisted of an eyepiece (EP), which can be adapted to an electronic imaging system, optical fibers or crystals for the transmission of both illumination and image rays, optics for the linear polarization of light, one interposed to the optical path of the illumination rays (LE) and one to the path of the ray that form the optical image of the tissue (II). The polarization plane of the polarizing optics, which are adapted to the exit of light from the endoscope (LPO), is perpendicular to the polarization plane of the polarizer, which is adapted to the point where the light enters the endoscope (IL). The polarization optics of the incident to the tissue light could also be adapted at the point where the light enters the endoscope (IL) but in this case, the endoscope has to be constructed using polarization preserving crystals or fiber optics for transferring the light. If polarization preserving light transmission media are used, then the polarizing optics of the imaging rays can be interposed in their path and before or after the eyepiece (EP). A problem for the effective clinical implementation of the described method herein is the micro-movements of the patient, which are always present during the snapshot imaging of the same tissue area. Obviously this problem is eliminated in case that the patient is under anesthesia (open surgery). In most cases however the movements of the tissue relative to the image capturing module, occurring during the successive image capturing time-course, have the consequence that the image pixels, with the same image coordinates, do not correspond to exactly the same spatial point x,y of the tissue area under examination. This problem is typically encountered in colposcopy. A method to eliminate the influence to the measured temporal data of the relative movements between tissue and image capturing module is presented below. A colposcopic apparatus is illustrated in FIG. 6 , consisted of an articulated arm (AA), onto which the optical head (OH) is affixed, which includes a light source (LS), an objective lens (OBJ), an eye-piece (EP) and optics for selecting the magnification (MS). The image capturing module is attached to the optical head (OH), through an opto-mechanical adapter. A speculum (KD), which is used to open-up the vaginal canal for the visualization of the cervix, is connected mechanically with the optical head (OH), so that the its longitudinal symmetry axis (LA), to be perpendicular to the central area of the objective lens (OBJ). The speculum enters the vagina and its blades are opened up compressing the side walls of the vagina. The Speculum (KD), been mechanically connected with the optical head (OH), transfer any micromovement of the patient to the optical head (OH), which been mounted on an articulated arm (AA), follows these movements. Thus the relative position between tissue and optical head remains almost constant. An important issue that must also be addressed for the successful clinical implementation of the diagnostic method described herein, is the synchronization of the application of the contrast enhancing agent with the initiation of the snapshot imaging procedure. FIG. 6 , illustrates an atomizer (A) attached to the optical head of the microscope. The unit (MIC) is comprised of electronics for controlling the agent sprayer and it can incorporate also the container for storing the agent. When the unit (MIC) receives the proper command from the computer it sprays a predetermined amount of the agent onto the tissue surface, while the same or another command initiates the snapshot image capturing procedure. The diagnostic examination of non-directly accessible tissues, located in cavities of the human body (ear, cervix, oral cavity, esophagus, colon, stomach), is performed with the aid of common clinical microscopes. In these devises the illumination-imaging rays are near co-axial. More specifically, the line perpendicular to the exit point of light into the air, and the line perpendicular to the objective lens, form an angle of a few degrees. Due to this fact, these microscopes operate at a specific distance from the subject (working distance), in which the illuminated tissue area, coincides with the field-of-view of the imaging system. These microscopes are found to be inappropriate in cases where tissue imaging through human body cavities of small diameter and at short working distances, is required. These technical limitations are also constituting serious restricting factors for the successful clinical implementation of the method described herein. As it has been discussed above, elimination of surface reflection results in a substantial improvement of the diagnostic information, obtained from the quantitative assessment of marker-tissue interaction kinetics. If a common clinical microscope is employed as the optical imaging module, then due the above mentioned Illumination-imaging geometry, multiple reflections are occurring in the walls of the cavity, before the light reaches the tissue under analysis. In the case of colposcopy, multiple reflections are much more intense, since they are mainly taking place onto highly reflective blades of the speculum. Recall that the latter is inserted into the vagina to facilitate the inspection of cervix. If the illuminator of the imaging apparatus emits linearly polarized light, the multiple reflections are randomizing the polarization plane of the incident light. And as it has been discussed above, if the incident to the tissue under analysis light is not linearly polarized, then the elimination of the contribution of the surface reflection to the captured image can not be effective. FIG. 7 illustrates an optical imaging apparatus which comprises a light source located at the central part of its front-aperture. With this arrangement, the central ray of the emitted light cone is coaxial, with the central ray of the light beam that enters the imaging apparatus. This enables illumination rays to reach directly the tissue surface under examination and not after multiple reflections in the wall of the cavity. A reflective-objective lens is used, consisted at least of a first reflection (1RM) and a second reflection (2RM) mirror, where at the rear part of the first reflection mirror (2RM), a light source (LS) is attached together (if required) with optics for light beam manipulation such as zooming and focusing (SO). The reflective objective lens (RO), by replacing the common refractive-objective, which is used in conventional microscopes, provides imaging capability in cavities of small diameter, with freedom in choosing the working distance. The zooming and focusing optics of the light beam can be adjusted simultaneously with the mechanism for varying the magnification of the optical imaging system, so that the illumination area and the field-of-view of the imaging system, are varying simultaneously and proportionally. This has as a result, the preservation of image brightness regardless of the magnification level of the lens. The imaging-illumination geometry embodied in this optical imaging apparatus among with the light beam manipulation options, enable the efficient elimination of the contribution of the surface reflection to the captured image and consequently the efficient clinical implementation of the method described herein. EQUIVALENTS Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

The present invention provides a method and an apparatus for the in vivo, non-invasive, early detection of alterations and mapping of the grade of these alterations, caused in the biochemical and/or in the functional characteristics of epithelial tissues during the development of tissue atypias, dysplasias, neoplasias and cancers. The method is based, at least in part, on the simultaneous measurement of the spatial, temporal and spectral alterations in the characteristics of the light that is re-emitted from the tissue under examination, as a result of a combined tissue excitation with light and special chemical agents. The topical or systematic administration of these agents result in an evanescent contrast enhancement between normal and abnormal areas of tissue. The apparatus enables the capturing of temporally successive imaging in one or more spectral bands simultaneously. Based on the measured data, the characteristic curves that express the agent-tissue interaction kinetics, as well as numerical parameters derived from these data, are determined in any spatial point of the examined area. Mapping and characterization of the lesion, are based on these parameters.

TECHNICAL FIELD [0001] The subject matter described herein relates generally to the test and measurement of wireless data communication systems; and more particularly to systems and methods for analyzing waveforms generated by multiple-input multiple-output data communication systems, including but not limited to multi-user multiple-input multiple-output data communication systems. BACKGROUND [0002] Wireless data communications devices, systems and networks that are in widespread use worldwide have become sophisticated and complex, due to the increasing need for higher data rates and the support of an increased number of users and data traffic. Accomplishing these higher rates and traffic capacities usually requires employing complex signal waveforms and advanced radio frequency capabilities such as multiple-input multiple-output (MIMO) signal coding, transmit and receive signal management methods such as beamforming, and spatial multiplexing techniques. MIMO coding in particular has received significant recent interest, as it employs the statistical properties of RF propagation channels to achieve higher data rates as well as to simultaneously accommodate multiple users (spatial multiplexing). All of these techniques, however, increase the complexity of the wireless devices. Manufacturers, vendors and users therefore have a greater need for better testing of such systems. [0003] Unfortunately, the increasing complexity of wireless data communication devices and systems also makes them harder to test. Testing MIMO wireless systems is particularly problematic due to the difficulty of re-creating the dynamic RF channel environment. Actual open-air RF environments contain high levels of uncontrollable noise and interference, and also present time-varying and unpredictable channel statistics. However, the performance of MIMO systems is very dependent on the channel statistics. The lack of controllability and repeatability also makes it difficult or impossible to automate the testing of such wireless systems. Therefore it is very attractive to manufacturers and users to test these devices in a repeatable fashion by excluding the variability of real MIMO RF channels while still interposing accurately simulated but controllable channels. This also enables the tests to be conducted in an automated fashion. [0004] With reference to FIG. 1 , an exemplary MIMO wireless transmitter 101 and an exemplary MIMO wireless receiver 102 is shown in a simplified RF propagation environment, that may consist of an arbitrary number of RF scatterers 107 . MIMO transmitter 101 has a plurality of antennas 103 . Similarly, MIMO receiver 102 has a plurality of antennas 104 . As depicted in FIG. 1 , the multiplicity of antennas enable the transmission of multiple parallel streams of information 106 , utilizing the available transmission paths (or ‘modes’) in the RF environment, which are created by the presence of scatterers 107 . It is apparent that the performance gains due to MIMO occur as a consequence of these multiple transmission modes; removal of the scatterers causes the multiple transmission modes to collapse into a single mode, and the channel will then become unable to support more than one stream of information. Therefore, any MIMO test system must provide a means of supporting multiple transmission modes in the path between the transmitter and the receiver. [0005] FIG. 2 is illustrative of a simplified MIMO wireless traffic and radio analyzer 111 that may be coupled to a wireless device under test (DUT) 110 containing MIMO radio interface 112 by RF cables 113 . In this case, the multiple transmission modes of the real RF propagation channel may be simulated by the multiple separate cables 113 , which may interconnect RF transmitters and receivers in pairs. The number of independent transmission modes (and therefore the number of parallel data streams) is equal to the number of distinct RF cables and associated transmitter/receiver pairs. All external interference, noise and propagation variations are excluded by virtue of the use of such a fully cabled RF setup. [0006] For representational purposes, FIG. 2 and all succeeding figures herein show three cables, antennas, transmission paths, modes, etc. However, it should be understood that this is done for representational convenience, and the actual number thereof may be any number including 1. It is also not necessary for the numbers of transmitters, receivers, cables, antennas, transmission paths, modes, etc. to be equal to each other. The discussion and teachings herein are equally applicable to a MIMO system comprising any number of transmission paths and antennas and any other number of reception paths and antennas. [0007] The exemplary system depicted in FIG. 2 shows an idealized (nearly lossless, noiseless and distortion-free) MIMO RF channel between analyzer 111 and DUT 110 . In practice, however, RF propagation channels are neither lossless nor distortion-free. Turning now to FIG. 3 , the loss and amplitude/phase distortion presented by actual RF propagation channels may be simulated by channel simulator (fader) 120 , which is interposed between analyzer 111 and DUT 110 . Such a channel simulator 120 is connected to analyzer 111 by RF cables 113 , and to DUT 110 by RF cables 121 , and therefore the system continues to exclude external interference and avoid uncontrollable propagation variations. However, the propagation characteristics of actual RF channels can be simulated in a controlled and repeatable fashion by modifying the configuration of channel simulator 120 . The design of such a channel simulator 120 is well known in the art and will not be repeated here. [0008] FIG. 4 depicts a situation where a single MIMO receiver 130 may receive signals concurrently from a plurality of MIMO transmitters 131 , 132 , 133 . With a sufficiently large number of scatterers 135 in the RF propagation environment, it is possible for completely independent transmission paths (i.e., propagation modes) to be present between each of the MIMO transmitters 131 , 132 , 133 with respect to MIMO receiver 130 . By applying appropriate digital signal processing (DSP) functions, it is possible for MIMO receiver 130 to distinguish and separate the transmitted signals from each other by virtue of these independent propagation modes. It may therefore be possible for multiple users to concurrently transmit RF signals within the same frequency band to the same receiver. This is a form of spatial multiplexing referred to as multi-user MIMO (MU-MIMO). It should be noted that the statistical properties of the RF propagation channels between the transmitters and the receiver are even more important for MU-MIMO, as the parallel streams of information are disambiguated and extracted solely by virtue of their having traversed different RF paths and having been subjected to different amplitude/phase distortions. [0009] It will be appreciated that the situation in FIG. 4 may equally apply to a single MIMO transmitter concurrently transmitting data streams to a plurality of MIMO receivers. In this case, the transmitter may accept parallel streams of information destined for separate receivers, apply different signal processing functions to the data streams, and combine these streams for transmission on a single set of antennas. The signal processing functions are selected in such a way as to employ the statistical properties of the different RF channels existing between the transmitter and the various receivers, and maximize the desired signal at each receiver while minimizing the undesired signals (i.e., those destined for other receivers). [0010] To enable distinct RF propagation channels to concurrently support separate MU-MIMO data streams, it may be essential that the characteristics of each individual RF propagation channel be accurately determined. This is normally performed by a process referred to as sounding the channel. Sounding entails transmitting a known signal with precisely defined properties from each transmitter to each associated receiver, and then measuring the received signal at the receiver. The RF channel between the transmitter and the receiver can then be estimated by comparing the received signal with the predetermined transmitted signal. The receiver may then feed the measured RF channel properties back to the transmitter using a predetermined control protocol. The transmitter uses these channel properties to adapt subsequently transmitted signals to the RF channel between itself and the receiver, thereby ensuring that the reception probability is maximized at the target receiver and minimized everywhere else. [0011] With reference to FIG. 5 , a possible arrangement for testing a MU-MIMO DUT 147 containing MU-MIMO radio interface 148 is depicted. In this case, wireless radio and traffic analyzers 141 , 142 , 143 may simulate a plurality of spatially distributed end-stations, generating independent streams of wireless traffic to DUT 147 . As MU-MIMO relies upon the existence of different RF propagation channels between transmitter/receiver pairs, separate channel simulators 144 , 145 , 146 may be employed, one for each of analyzers 141 , 142 , 143 . Each channel simulator may be configured to simulate a different radio channel. The outputs of channel simulators 144 , 145 , 146 may be combined together via RF power combiners 149 and fed to MIMO radio interface 148 in DUT 147 . [0012] Such an arrangement, unfortunately, suffers from several significant shortcomings. Firstly, the use of separate channel simulators 144 , 145 , 146 causes such a system to become prohibitively expensive. This is particularly true as the number of end stations represented by analyzers 141 , 142 , 143 increases to a large number (e.g., 500). Secondly, coupling together multiple channel simulators 144 , 145 , 146 causes them to interact in unpredictable ways, considerably degrading the effectiveness of the simulated RF channels, and often causing substantial distortion effects. Finally, such a system presents significant issues in terms of signal dynamic range, particularly as the number of channel simulators increases; a high-amplitude signal produced by one channel simulator may overload another channel simulator which may be producing a low amplitude signal. For these reasons, simply attaching together multiple channel simulators 144 , 145 , 146 to create an MU-MIMO test system is not feasible except for certain limited and carefully selected cases. [0013] To comprehend the general functioning of an MU-MIMO system, the operation of a simple MIMO system (i.e., a single MIMO transmitter and a single MIMO receiver) will be considered first. With reference to FIG. 6 , an exemplary MIMO transmitter 150 that may incorporate one method of beamforming is depicted, using one or more antennas 157 to transmit RF signals over some RF propagation medium to one or more antennas 161 of an exemplary MIMO receiver 160 . [0014] MIMO transmitter 150 may include: transmit digital data input 151 , digital modulator 152 that may transform digital data to the modulation domain, for example by employing Orthogonal Frequency Division Multiplexing (OFDM); space-time mapper 153 that may map modulated symbols to one or more output streams of symbols according to some MIMO mapping algorithm; transmit precoder 154 that may perform some transformation upon the symbol streams to adapt them for transmission; digital to analog (D/A) converters 155 that may convert the digital representation of the transformed symbols to analog; and transmit RF processing functions 156 that may convert these analog signals to some desired radio frequency and transmit them using one or more antennas 157 . It is understood that other functions and processing elements may also be included in MIMO transmitter 150 , but are not relevant to this discussion and are therefore omitted. [0015] MIMO receiver 160 may receive transmitted RF signals from one or more antennas 161 , and may include: receive RF processing functions 162 that convert one or more streams of RF signals, after which analog to digital (A/D) conversion by A/D converters 163 may be performed to produce digital symbols; receive decoder 164 that may transform the streams of digital symbols prior to demapping and demodulation; and space-time demapper and digital demodulator 165 that may map and integrate one or more streams of symbols according to a predetermined space-time transformation, and may demodulate these symbols to recover received digital data 166 . Channel estimator 167 may calculate the properties of the RF propagation medium that may exist between transmit antennas 157 and receive antennas 161 , and supply this information to receive decoder 164 and space-time demapper and digital demodulator 165 , to aid in transforming and recovering the digital data 166 . It is likewise understood that other functions and processing elements may be included in MIMO receiver 160 but are omitted as they are not relevant to this discussion. [0016] The properties of the RF propagation medium influence the efficiency with which MIMO signals can be transmitted and received. The RF channel properties may be used to derive the coefficients that may be set into transmit precoder 154 to adapt the symbol streams generated by space-time mapper 153 to the propagation modes of the RF channel, which may maximize the information density of the channel. Such an adaptation may be commonly referred to as beamforming or, more specifically, eigen beamforming. The RF channel properties may further be used to calculate coefficients that may be set into receive decoder 164 to post-process the received symbol streams from the propagation modes of the RF channel, which may thereby enhance the signal-to-noise ratio at MIMO receiver 160 (indirectly further maximizing the information density of the channel). Such an enhancement may be commonly referred to as combining diversity. [0017] It is therefore apparent that an accurate knowledge of the properties of the RF channel, in particular its propagation modes, may be of great importance. It is also apparent that the receiver and transmitter may preferably share the properties of the RF channel, so that the processing performed at the transmitter corresponds to the processing performed at the receiver. Therefore, MIMO receiver 160 may preferably share channel information with MIMO transmitter 150 to achieve this goal, further preferably using a known and well defined protocol. Such a protocol for determining and sharing channel state information is commonly known as a beamforming information exchange process. [0018] Turning now to FIG. 7 , an exemplary procedure is depicted that may be used for determining the properties of the RF channel, for communicating these properties between the two ends of an RF link, and for utilizing these properties in the transmission and reception of data. Vertical lines 170 and 172 represent the operations of a MIMO transmitter and a MIMO receiver respectively. At 172 , the MIMO transmitter may generate some fixed test data having a prearranged bit pattern and predetermined modulation and spatial mapping characteristics, and may transmit this data as a sounding signal, for example within a sounding packet, as represented at 173 . At 174 , the MIMO receiver may receive and analyze the sounding signal, which may be a sounding packet. The original sounding signal waveform being known, at 175 the MIMO receiver may calculate the RF channel properties by their effect upon the sounding signal waveform, and may further compute a precoding matrix (that may, for instance, be used within exemplary MIMO transmitter 150 ) that maximizes the information density for the RF channel existing between the MIMO transmitter and receiver at that point in time and space. At 176 , the coefficients of the precoding matrix may be formatted into suitable packet(s) and transmitted at 177 as a beamforming information frame, completing the beamforming information exchange process. This beamforming information exchange process may sometimes also be referred to as a beamforming training sequence. [0019] At 178 , the MIMO transmitter may extract the coefficients of the precoding matrix that have been provided by the receiver and process them to obtain the actual configuration of the precoder, which may then be applied to the transmit precoder at 179 . Once the transmit precoder has been configured, the transmitter may subsequently send user data frames; these frames may be processed by the transmit precoder to adapt them to the RF channel and transmitted as precoded signals 180 . Such a process may maximize the signal to noise and interference ratio (SINR) at the MIMO receiver and may further enable optimal reception of the user data frames. (It is understood that the MIMO receiver may also utilize the RF channel properties to configure a receive decoder and receive demodulator, as is depicted in FIG. 6 and may yet further improve the SINR.) [0020] FIG. 8 shows a simplified exemplary mathematical model of the process of precoding, transmission through a MIMO RF channel, and decoding. With respect to FIG. 8 , vectors [x] and [y] represent complex-valued transmitted and received information signals respectively; complex vectors [V] and [U] may represent transmit precoding matrix and receive decoder matrix coefficients, respectively; and the RF channel existing between the MIMO transmitter and MIMO receiver is represented by [H]. At 200 , the user data stream is input as a sequence of vectors [x]. In transmit precoder 201 , the vectors are multiplied by the transmit precoding matrix [V], after which they are transmitted upon RF channel 202 . The effect of the RF channel 202 upon the transmitted signal is represented by a multiplication by the channel matrix [H]. These signals are received by receive decoder 203 and multiplied further by receive decoder matrix [U], yielding a sequence of vectors [y] that comprise the received data. Note that this depiction is highly simplified for the purposes of explanation and does not include such elements as modulation, demodulation, spatial mapping, spatial demapping, coding, etc. that are not germane to this discussion. Also note that this is a simplified model and does not take into account operations such as vector transposes that may actually be required for the vectors [U] and [V]. [0021] The beamforming information exchange process may attempt to determine the coefficients of vectors [V] and [U] that will maximize the SINR of the signal transmitted through channel matrix [H]. An optimal beamforming information exchange process may calculate these vectors in such a way that, barring the effects of noise, the signal [y] matches the signal [x]; i.e., the effect of RF channel matrix [H] is nullified. [0022] With regards to FIG. 9 , an exemplary mathematical model of an MU-MIMO process is depicted. Note that the model may be applied to any number of transmitters and any number of receivers. It may be observed that the steps are substantially similar to that of the basic MIMO process shown in FIG. 8 . Input signal vectors 210 , 215 , 220 corresponding to vectors [x 1 ], [x 2 ], [x 3 ] respectively may be precoded by transmit precoders 211 , 216 , 221 with transmit precoding matrices [V 1 ], [V 2 ], [V 3 ], after which they may transmitted over RF channels 212 , 217 , 222 with different channel matrices [H 1 ], [H 2 ], [H 3 ] respectively. A distinguishing feature of MU-MIMO is that all of the signals are transmitted concurrently and share the same spatial environment; therefore, at 225 the transmitted signals are shown as being arithmetically combined, so that the same signals are effectively received at all sets of receive antennas. These signals may then be processed by receive decoders 213 , 218 , 223 with receive decoder matrices [U 1 ], [U 2 ], [U 3 ] respectively, which may yield at 214 , 219 , 224 the output signal vectors [y 1 ], [y 2 ], [y 3 ]. Each transmit precoding matrix and each receive decoder matrix may preferably be adapted to the specific RF channel matrix existing between that transmitter/receiver pair. For instance, transmit precoding matrix [V 1 ] and receive decoder matrix [U 1 ] may be adapted to RF channel matrix [H 1 ], which may ensure optimal decoding of signal [y 1 ], and may further enable the RF signals generated by the other transmitter chains to be rejected. Separate channel estimation and beamforming feedback processes may hence be employed for each transmitter/receiver pair. As depicted in FIG. 10 , channel estimation function 230 may process the signal received as [y 1 ], and beamforming feedback function 234 may then pass the coefficients that may be used by transmit precoder 211 to the corresponding transmitter. Similarly, channel estimation functions 231 , 232 and beamforming feedback functions 235 , 236 may perform similar actions for other signal chains. [0023] It is known that if orthogonal channel matrices [H 1 ], [H 2 ], [H 3 ] exist between different transmitter/receiver pairs [V 1 ]/[U 1 ], [V 2 ]/[U 2 ], [V 3 ]/[U 3 ] respectively, then orthogonal transmission modes exist between each transmitter/receiver pair. The transmit precoding matrices may be adjusted to utilize these orthogonal transmission modes. Further, the receive decoder matrices may be adapted to perform diversity reception within these orthogonal transmission modes. This may have the effect of raising the SINR of the desired signals while reducing the SINR of the undesired signals. It is further known that such an arrangement may enable simultaneous transmission and reception of independent signals [x 1 ], [x 2 ], [x 3 ] over the same RF channel, which is the essence of MU-MIMO. [0024] It is understood that the transmitter chains shown in FIG. 10 may be combined into a single device, while the receiver chains may be present in separate devices. Alternatively, the transmitter chains may be in separate devices, while the receiver chain may be combined into one device. (This latter situation is represented in FIG. 4 .) Normal MU-MIMO usage situations entail one or the other of these cases. It is not of significant interest to consider the case of fully independent transmitter chains and fully independent receiver chains, as these degenerate to the standard MIMO usage situation. [0025] It is apparent that an MU-MIMO system requires an RF channel with a multiplicity of orthogonal transmission modes between the different transmitter/receiver pairs, so that the transmit precoders and receive decoders can be adjusted to enhance the desired signals while suppressing undesired signals and noise. However, this situation is not obtained in a fully cabled environment. With reference to FIG. 11 , a single MIMO transmitter/receiver pair is depicted, which may be equivalent to the MIMO transmitter/receiver pair shown in FIG. 8 with the exception that the antennas and the open-air MIMO RF transmission channel have been replaced by RF cables 241 . As these cables may be nearly lossless and free of reflections, they may represent a channel matrix [H c ] as shown at 240 , which is an identity matrix. This may still be a valid MIMO environment for a single transmitter/receiver pair, and may still enable transmit signal [x] at 200 to be transmitted through the system and received as signal [y] at 204 . Therefore, a MIMO system may still continue to function properly when cable-connected instead of using propagation through an actual RF environment. [0026] Turning now to FIG. 12 , a possible mathematical model of the MU-MIMO situation in a cabled environment is shown. This may comprise one or more transmitted signal streams 210 , 215 , 220 that may be precoded by transmit precoders 252 , 253 , 254 which implement the [V 1 ], [V 2 ], [V 3 ] transmit precoding matrices respectively. The signals may then be passed through unitary RF channels 240 , 241 , 242 , all of which have the identical RF transmission channel matrix [H c ] created by cables 243 . They may then be subsequently combined and distributed to receive decoders 213 , 218 , 223 as before, which may implement the [U 1 ], [U 2 ], [U 3 ] matrices respectively. The output signals [y 1 ], [y 2 ], [y 3 ] ( 214 , 219 , 224 respectively) may contain the decoded received data, which may also be fed to channel estimation functions 230 , 231 , 232 , the outputs of which in turn may be fed to beamforming feedback 234 , 235 , 236 and subsequently used to configure transmit precoders 252 , 253 , 254 . [0027] It will be observed that in a cabled environment RF channel matrices [H c ] between every pair of transmitter/receiver chains are identical, and are equal to the identity matrix. Further, channel estimation functions 230 , 231 , 232 will produce identical channel estimates, and hence the coefficients configured into transmit precoders 211 , 216 , 221 will be the same, as will the coefficients for receive decoders 213 , 218 , 223 . As MU-MIMO relies for its operation on orthogonal RF channels creating orthogonal transmission modes, it is readily apparent that such a system cannot support simultaneous transmission and reception of independent signals. In the cabled situation depicted, therefore, the capacity of the RF transmission channel collapses to that of the simple MIMO case, and testing of MU-MIMO operation is not possible. [0028] The known methods of MU-MIMO wireless testing therefore suffers from serious shortcomings. There is hence a need for improved MU-MIMO wireless data communication test systems and methods. A test system that is capable of performing tests upon MU-MIMO systems in a cabled environment may be desirable. It may be preferable for such a test system to eliminate the need for external channel simulators to enable the testing of multiple simultaneous transmitters or receivers at reduced cost. Further, such a test system may preferably permit different RF channels to be simulated for different transmitters or receivers without interaction between the channels. Finally, it may also be desirable for the test system to facilitate the testing of large-scale MU-MIMO systems with many transmitters and receivers. SUMMARY [0029] Systems and methods are disclosed herein that may provide improved techniques for performing testing of MIMO and MU-MIMO wireless data communication devices, systems and networks. Such techniques may enable the testing of such devices with reduced cost and higher efficiency, and may also decrease the complexity of the test system required to perform MIMO and MU-MIMO beamforming tests. The systems and methods disclosed may further extend the range and nature of the tests that may be performed, and may also allow automated tests to be conducted in a controlled and repeatable manner. [0030] In accordance with an aspect of one embodiment, a network equipment test device, such as a wireless signal analyzer, is disclosed that may be operative to perform tests upon MIMO and MU-MIMO transmitters in a controlled RF environment. The analyzer may contain: radio channel generation functions, which create a statistical model of a simulated RF channel; sounding packet handshake logic to exchange sounding signals with the DUT containing suitable channel coefficients; precoding matrix calculation functions, which convert the simulated RF channel properties into the precoder coefficients of the sounding signal sent to the DUT; and receive decoder matrix functions, which perform a matrix decode upon the signals received from the DUT. The system may be further operative to cause the DUT to transmit signals to be analyzed that are precoded with the desired RF channel properties. A network equipment test device according to embodiments of the subject matter described herein may include one or more processors for executing the functions described herein. [0031] Preferably, the wireless signal analyzer may be operative to represent multiple RF receivers with different simulated RF channels interposed between itself and the DUT, each RF channel corresponding to a different RF receiver. The wireless signal analyzer may further be operative to cause the DUT to transmit signals destined for a multiplicity of RF receivers simultaneously. The signal analyzer may be yet further operative to distinguish and decode these signals separately and perform measurements upon the decoded signals. [0032] In accordance with an aspect of another embodiment, a wireless signal analyzer is disclosed that may be operative to perform tests upon MIMO and MU-MIMO receivers in a controlled RF environment. The analyzer may contain: simulated radio channel generation logic to create a statistical model of a simulated RF channel; a transmit precoding matrix function to condition a transmitted test signal according to the properties of the simulated RF channel; sounding protocol logic to perform a sounding packet exchange between the signal analyzer and the DUT containing suitable channel coefficients; and comparison logic to determine the efficacy of the channel estimation implemented by the DUT. [0033] Such a wireless signal analyzer may be operative to represent multiple test signal transmitters with different RF channels between themselves and the DUT, and may further be operative to represent one or more transmitters communicating with multiple counterpart receivers within the DUT. [0034] Advantageously, the coefficients of the sounding packets sent to the DUT may be adjusted to simulate the effect of one or more RF channels interposed between the DUT and the wireless signal analyzer, in a cabled environment without utilizing a channel simulator. [0035] Advantageously, the coefficients of the sounding packets may be adjusted to cause the DUT to perform beamforming according to any simulated RF channel, which may permit increased flexibility in testing beamforming capabilities of the DUT. [0036] Advantageously, the quality of the transmit precoding and beamforming performed within the DUT may be determined by transmitting sounding packets containing known coefficients representing a desired RF channel, causing the DUT to transmit data, decoding the data according to the coefficients of the RF channel, and verifying the quality of the decoded data. [0037] Advantageously, the quality of the channel estimation performed within the DUT may be assessed by transmitting sounding signals that are predistorted in known ways and examining the coefficients within the sounding packets returned by the DUT. [0038] Advantageously, a figure of merit may be measured for the channel estimation performed by a DUT when presented with a channel model by assessing the coefficients of the sounding packets returned by the DUT. [0039] Advantageously, tests may be performed upon a DUT in an MU-MIMO system without requiring multiple channel simulators. [0040] The subject matter described herein may be implemented in hardware, firmware, or software in combination with hardware or firmware. As such, the terms “function” or “module” as used herein refer to hardware, firmware, or software in combination with hardware or firmware for implementing the feature being described. In one exemplary implementation, the subject matter described herein may be implemented using a non-transitory computer readable medium having stored thereon computer executable instructions that when executed by the processor of a computer control the computer to perform steps. Exemplary computer readable media suitable for implementing the subject matter described herein include non-transitory computer-readable media, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein may be located on a single device or computing platform or may be distributed across multiple devices or computing platforms. BRIEF DESCRIPTION OF THE DRAWINGS [0041] The detailed description herein of the features and embodiments are best understood when taken in conjunction with the accompanying drawings, wherein: [0042] FIG. 1 shows a simplified representation of a MIMO transmitter and MIMO receiver operating in an RF channel environment; [0043] FIG. 2 provides an illustrative view of an exemplary conventional wireless test system for testing a MIMO DUT; [0044] FIG. 3 represents an illustrative view of an exemplary conventional wireless test system used in association with a MIMO channel analyzer to test a MIMO DUT under different RF channel conditions; [0045] FIG. 4 shows a simplified representation of an MU-MIMO RF environment, comprising multiple MU-MIMO RF transmitters concurrently transmitting signals to a MU-MIMO RF receiver; [0046] FIG. 5 provides an exemplary block diagram of a test system for conducting tests on an MU-MIMO DUT, in accordance with conventional systems and methods; [0047] FIG. 6 exemplifies a possible block diagram of an MU-MIMO wireless transmitter and an MU-MIMO wireless receiver; [0048] FIG. 7 represents the steps of an exemplary sounding packet exchange wherein beamforming information is calculated from channel sounding measurements and subsequently used for conditioning transmitted signal data packets; [0049] FIG. 8 is representative of a simplified mathematical model of signal transmission and reception in a MIMO RF channel environment; [0050] FIG. 9 illustrates one possible simplified mathematical model of signal transmission and reception in a MU-MIMO RF channel environment comprising one or more receivers and transmitters; [0051] FIG. 10 shows an example of channel estimation and beamforming feedback in the context of a simplified MU-MIMO RF channel environment, with one or more receivers and transmitters; [0052] FIG. 11 depicts a possible mathematical model of a cabled RF environment applied to a MIMO RF transmitter and receiver; [0053] FIG. 12 exemplifies the extension of the mathematical model for a cabled RF environment extended to include MU-MIMO RF transmitters and receivers; [0054] FIG. 13 depicts an exemplary aspect of a test system that utilizes a simulated channel model and beamforming feedback to perform MU-MIMO tests in a cabled RF environment; [0055] FIG. 14 provides another exemplary aspect of a test system that utilizes a simulated channel model and receive decoder matrix coefficients to perform MU-MIMO tests in a cabled RF environment; [0056] FIG. 15 shows an exemplary aspect of a test system that potentially derives channel estimation error vectors utilizing a simulated channel model together with comparison of beamforming feedback parameters; [0057] FIG. 16 shows an illustrative flow chart of one possible method of obtaining the optimal SNR value for a set of one or more simulated RF channels; and [0058] FIG. 17 depicts an exemplary flow chart for a possible procedure for calculating a Figure of Merit for the channel estimation and beamforming feedback parameters produced by a DUT. [0059] It should be understood that like reference numerals are used to identify like elements illustrated in one or more of the above drawings. DETAILED DESCRIPTION [0060] With reference to FIG. 13 , an aspect of an embodiment of a wireless MU-MIMO test system may comprise MU-MIMO test equipment receiver 251 within a test system that may be connected using RF cables 243 to multiple DUT transmitters 255 , 256 , 257 . If required, RF power combiners may be used to couple together the multiple DUT transmitters without mismatch problems. It should be understood that while FIG. 13 (and subsequent drawings) show transmitters, receivers and cables in sets of three, this is done only for representational convenience, and the principles set forth herein apply to arbitrary numbers of transmitters, receivers and cables. [0061] MU-MIMO receiver 251 may further comprise: receive decoders 213 , 218 , 223 that implement calculated receive decode matrices [U 1 ], [U 2 ], [U 3 ] respectively; channel modeling functions 263 , 264 , 265 ; precode matrix calculation functions 260 , 261 , 262 ; and beamforming feedback functions 234 , 235 , 236 . RF cables 243 may be equivalent to RF channels appearing as three identity matrices [H c ] ( 240 , 241 , 242 ) that may couple the DUT transmitters to the test equipment receiver. Each of DUT transmitters 255 , 256 , 257 may contain separate transmit precoders 252 , 253 , 254 , the coefficients of which may be determined by the beamforming feedback received from beamforming feedback functions 234 , 235 , 236 . [0062] Channel modeling functions 263 , 264 , 265 may generate the parameters of any desired RF channel, and may further generate orthogonal RF channels [H 1 ], [H 2 ], [H 3 ] having orthogonal transmission modes. Normally, precode matrix calculation functions 260 , 261 , 262 may simply calculate actual [V 1 ], [V 2 ], [V 3 ] transmit precoding matrices, as it is assumed that real RF channels corresponding to [H 1 ], [H 2 ], [H 3 ] are interposed between MU-MIMO transmitters and receivers. However, in this aspect, precode matrix calculation functions 260 , 261 , 262 may include the modeled RF channels into the calculation, such that the coefficients transmitted by beamforming feedback functions 234 , 235 , 236 may contain the product of [V 1 ], [V 2 ], [V 3 ] and [H 1 ], [H 2 ], [H 3 ] respectively. When these coefficients are sent to DUT transmitters 255 , 256 , 257 , they may configure transmit precoders 252 , 253 , 254 with the appropriate products as shown. [0063] DUT transmitters 255 , 256 , 257 may drive transmit signals through cables 243 to MU-MIMO receiver 251 . The effect upon each transmitted signal is to multiply it with the identity matrix [H c ], which leaves the transmitted signal unchanged. It will be appreciated upon comparison of FIG. 9 and FIG. 13 that transmit data signals [x 1 ], [x 2 ], [x 3 ] ( 210 , 215 , 220 respectively) after processing in this fashion by transmit precoders 252 , 253 , 254 and transmission to MU-MIMO receiver 251 may now represent the effect of having passed through three orthogonal RF channels [H 1 ], [H 2 ], [H 3 ]. It will be further appreciated that external channel simulators (such as those shown in FIG. 5 ) may not be required between DUT transmitters 255 , 256 , 257 and MU-MIMO receiver 251 to achieve this effect. Instead, transmit precoders 252 , 253 , 254 within DUT transmitters 255 , 256 , 257 have accomplished the same effect, considerably reducing the system cost. It will yet further be appreciated that the adverse effects of coupling multiple channel simulators as depicted in FIG. 5 are not present, in spite of the cabled coupling of all the DUT transmitters 255 , 256 , 257 . [0064] Receive decoders 213 , 218 , and 223 may include signal processing functions responsive to signals transmitted by the DUT and coupled to a respective one of the channel modeling functions 263 , 264 , and 265 . Each signal processing function is operative to simulate the effect of a modeled RF channel on the signals transmitted by said DUT. The signal processing function simulates the effect of the modeled RF channel by applying the [U] decode matrix to the received signal. [0065] Turning now to FIG. 14 , an aspect of another embodiment of a wireless MU-MIMO test system may comprise a DUT 258 and MU-MIMO test system 251 . DUT 258 may contain one or more MU-MIMO transmit chains accepting separate input signals [x 1 ], [x 2 ], [x 3 ] ( 210 , 215 , 220 respectively), that may be processed by transmit precoders 252 , 253 , 254 that are configured with matrices [V 1 ], [V 2 ], [V 3 ] respectively. The outputs of the transmit precoders may be coupled together within DUT 258 to drive a single set of cables 245 , whose RF propagation matrix 244 may be represented by [H e ] (an identity matrix). These cables may in turn be coupled to MU-MIMO test equipment receiver 251 , which may contain receive decoders 213 , 218 , 223 that accept and process the signals from cables 245 to generate independent output signals [y 1 ], [y 2 ], [y 3 ] ( 214 , 219 , 224 respectively). Channel modeling functions 263 , 264 , 265 may be used to set up receive decoders 213 , 218 , 223 , as well as to drive precode matrix calculation functions 260 , 261 , 262 respectively. Beamforming feedback functions 234 , 235 , 236 may pass beamforming feedback generated by precode matrix calculation functions 260 , 261 , 262 to DUT 258 , and this feedback may be used to configure transmit precoders 252 , 253 , 254 . [0066] In this aspect, the beamforming feedback to the DUT transmitters may be used to set up transmit precoders 252 , 253 , 254 with the coefficients of the [V 1 ], [V 2 ], [V 3 ] matrices, as may be performed in a normally operating MU-MIMO transmitter. Therefore, the channel models generated by channel modeling functions 263 , 264 , 265 may be used in the same manner as measured channel estimates 230 , 231 , 232 in FIG. 10 . However, the channel modeling functions 263 , 264 , 265 may further be used to configure receive decoders 213 , 218 , 223 with the product of the simulated RF channel matrices [H 1 ], [H 2 ], [H 3 ] and corresponding receive decode matrices [U 1 ], [U 2 ], [U 3 ]. This may have the effect of configuring orthogonal channels between different transmitter/receiver pairs, and may thereby preserve the ability of the system to support MU-MIMO operation. [0067] The system depicted in FIG. 14 may be used for several purposes. As an example of one such application, test equipment 251 may measure the quality of the transmit precoding performed by DUT 258 , by the steps of: a) generating different RF channel matrices [H 1 ], [H 2 ], [H 3 ] in channel modeling functions 263 , 264 , 265 ; b) performing the precode matrix calculation in 260 , 261 , 262 and returning sounding signals via beamforming feedback functions 234 , 235 , 236 ; b) causing DUT 258 to transmit known data [x 1 ], [x 2 ], [x 3 ]; c) decoding the signals received from DUT 258 with the correct set of RF channel matrices [H 1 ], [H 2 ], [H 3 ] and receive decode matrices [U 1 ], [U 2 ], [U 3 ]; and d) comparing the signals [y 1 ], [y 2 ], [y 3 ] against the known data [x 1 ], [x 2 ], [x 3 ] to obtain an error metric, one example of which may be the bit error ratio (BER); Test equipment 251 may use an arbitrary number of complex channel models to determine the capacity of DUT 258 to handle these types of RF channels accurately. [0073] As an example of another application, it may be desirable to simulate the effect of multiple stations (such as wireless clients) at test equipment 251 when testing DUT devices 258 such as APs. In this case, the system may cause channel modeling functions 263 , 264 , 265 to generate multiple RF channel models. Each modeled channel may represent the RF propagation between DUT 258 and one of the multiple simulated stations. The system may further present the precode matrices resulting from these multiple channels to DUT 258 in succession, possibly using separate beamforming exchanges. After this, the system may cause DUT 258 to transmit test traffic to all of the simulated stations, and verify that DUT 258 uses the correct precode matrix for each of these simulated stations. This may enable the test system to verify the station capacity supported by DUT 258 . An example of one means of determining the station capacity is by increasing the number of simulated stations until DUT 258 fails to use the correct precode matrices when transmitting test traffic. [0074] As an example of yet another application, it may be useful to determine whether DUT 258 is capable of quickly responding to RF channel variations over time. Such variations may correspond to those caused by Doppler shifts due to relative motion. In this example, test equipment 251 may cause channel modeling functions 263 , 264 , 265 to generate time-varying simulated RF channels, which may then be processed by precode matrix calculation functions 260 , 261 , 262 to produce transmit precoder coefficients which may then be sent to DUT 258 by beamforming feedback functions 234 , 235 , 236 . An error metric, which may include the BER, may be used to determine the ability of DUT 258 to respond quickly and accurately to RF channel variations. [0075] FIG. 15 depicts an aspect of another embodiment of an MU-MIMO test transmitter 292 within a wireless MU-MIMO test system, which may be used to quantify the channel estimation error within the receiver 293 of an MU-MIMO DUT. This aspect may include input test signals [x 1 ], [x 2 ], [x 3 ] ( 210 , 215 , 220 respectively); transmit precoders 252 , 253 , 254 ; channel modeling functions 280 , 281 , 282 , each of which may model any desired RF channel and may generate RF channel matrices [H 1 ], [H 2 ], [H 3 ]; and beamforming feedback coefficient comparators 283 , 284 , 285 , which may compare expected coefficients corresponding to the modeled RF channels with actual coefficients returned by DUT 293 , and may further generate error signals 297 , 298 , 299 . It is understood that other functions may also be performed within transmitter 292 , but are not relevant to this discussion and are therefore omitted. [0076] DUT receiver 293 may perform the standard MU-MIMO channel estimation and beamforming feedback processes, and may include receive decoders 213 , 218 , 223 , that may process received signals with receive decoder matrices [U 1 ], [U 2 ], [U 3 ] to produce output signals [y 1 ], [y 2 ], [y 3 ] ( 214 , 219 , 224 respectively). DUT receiver 293 may further include channel estimation functions 289 , 290 , 291 and beamforming feedback functions 294 , 295 , 296 that may serve to return transmit precoder coefficients to MU-MIMO test transmitter 292 . [0077] In operation, channel modeling functions 280 , 281 , 282 may generate any desired set of RF channels [H 1 ], [H 2 ], [H 3 ], which may then be multiplied into a set of optimal transmit precoding matrices [V 1 ], [V 2 ], [V 3 ] and configured into transmit precoders 252 , 253 , 254 . Known test signals [x 1 ], [x 2 ], [x 3 ] ( 210 , 215 , 220 respectively) may then be passed into transmit precoders 252 , 253 , 254 , combined via cables 247 and driven to DUT receiver 293 . The cables 247 may present a single RF channel 246 , which may be an identity matrix [H c ]. These signals may be received by each of the receive chains within DUT 293 . A beamforming information exchange process or beamforming training sequence may then be performed between each transmitter/receiver pair by channel estimation functions 289 , 290 , 291 and beamforming feedback functions 294 , 295 , 296 . As the RF channels [H 1 ], [H 2 ], [H 3 ] may be known in advance by MU-MIMQ transmitter 292 , the coefficients expected to be fed back during the beamforming exchange may likewise be precalculated by channel modeling functions 280 , 281 , 282 . These coefficients may be passed to comparators 283 , 284 , 285 , which may compare them to the coefficients actually fed back by DUT receiver 293 , and may generate error signals 297 , 298 , 299 . An assessment of these error signals may provide an indication of the quality of the channel estimation that may be performed by DUT receiver 293 . Further, such an assessment may be performed for different modeled RF channels [H 1 ], [H 2 ], [H 3 ], which may provide a quantitative assessment of the ability of DUT receiver 293 to cope with a wide variety of RF channel conditions. [0078] An example of another application of the aspect depicted in FIG. 15 may be to determine the ability of DUT receiver 293 to handle channel estimation and beamforming feedback for a large number of transmitters with a correspondingly large number of different RF channels between each transmitter/receiver pair. In this application, channel modeling functions 280 , 281 , 282 may be configured to successively generate different RF channel models, and each channel model may correspond to a different simulated transmitter. Test equipment transmitter 292 may then perform sounding packet exchanges with DUT receiver 293 to cause channel estimation and beamforming information exchange to occur between each of these simulated transmitters and DUT receiver 293 . DUT receiver 293 may then store the required [U] matrix for subsequent use when receiving data from that specific simulated transmitter. MU-MIMO test transmitter 292 may then cycle through the [H] and [V] matrices for each of the simulated transmitters, and may further transmit test signals [x] to determine if DUT receiver 293 can identify and configure the correct [U] matrix into receive decoders 213 , 218 , 223 . Determination of whether DUT receiver 293 has successfully identified the simulated transmitter and use the correct [U] matrix may be performed by analyzing the receive signal [y]. One possible analysis method is to compare the received signal [y] with the transmitted test signal [x]. [0079] In situations where it may become necessary to quantitatively assess the efficacy of the channel estimation and beamforming calculations performed by an MU-MIMO DUT, it may be desirable to develop a Figure Of Merit (FOM) for the combined process. The FOM weighs the SNR achievable using the parameters calculated by the DUT against the SNR achieved for the same test signals using the same RF channel but with a known optimal algorithm. One possible example of such an algorithm is a water-filling algorithm. For example, in the MU-MIMO case, the SNR may be expressed as E b /N o , which is the ratio of the signal energy per bit of transmitted data to the specific noise power, at a specific value of an error metric, which may be the BER. It may be possible to calculate the FOM using the arrangement of FIG. 15 , for some predetermined simulated RF channels described by matrices [H 1 ], [H 2 ], [H 3 ]. [0080] Turning now to FIG. 16 , a flowchart of an exemplary iterative procedure for obtaining the optimal SNR and transmit precoding matrices for a set of simulated RF channels [H 1 ], [H 2 ], [H 3 ] and a set of test signals [x 1 ], [x 2 ], [x 3 ] at a predetermined value of an error metric is depicted. The procedure illustrated in FIG. 16 may be implemented by emulated MU-MIMO transmitter 292 illustrated in FIG. 15 where precoders 252 , 253 , and 254 cycle through [V] matrices until an optimal [V] matrix is found. Alternatively, the procedure illustrated in FIG. 16 may be performed by emulated MU-MIMO receiver 251 illustrated in FIG. 13 in combination with a real or emulated MIMO transmitter. As such, MU-MIMO receiver 251 may include an SNR calculation function that calculates the SNR for each iteration of the test, an SNR of different iterations of the test, and saving the precoding matrix that generates the optimal SNR. Precoding matrix calculation functions 260 , 261 , and 262 may be configured to compute the set of precoding matrices [V 1 ], [V 2 ] and [V 3 ] used in each test iteration. Receive decoders 213 , 218 , and 233 may calculate the receive decoder matrices [U 1 ], [U 2 ], and [U 3 ] based on the modeled channel matrices [H 1 ], [H 2 ], and [H 3 ]. The procedure illustrated in FIG. 16 may follow the steps of: a) At step 300 , beginning the process; b) At step 301 , generating a set of modeled RF channel matrices [H 1 ], [H 2 ], [H 3 ]; c) At step 302 , computing a set of candidate transmit precoding matrices [V 1 ], [V 2 ], [V 3 ] that match the RF channel matrices; d) At step 303 , computing the corresponding set of candidate receive decoding matrices [U 1 ], [U 2 ], [U 3 ] e) At step 304 , using a system model, that may be similar to that depicted in FIG. 9 , to calculate the SNR of a predetermined test signal, which may be the E b /N o value required for a predetermined value of the error metric; f) At step 305 , determining whether the SNR so calculated is improved (i.e., is lower than) all previously calculated SNR values; g) At step 306 , if the SNR is in fact improved, saving the SNR value as the best candidate and also saving the corresponding candidate transmit precoding matrices [V 1 ], [V 2 ], [V 3 ] h) At step 307 , determining if more iterations are required, in which case the procedure may return to step 302 to calculate a new set of candidate precoding matrices [V 1 ], [V 2 ], [V 3 ], and may repeat steps 303 through 306 to determine the corresponding SNR value; i) At step 308 , recording the last saved value from step 306 as the optimal SNR value, and the corresponding transmit precoding matrices as the optimal precoding matrices; and j) At step 309 , terminating the process. [0091] Upon calculating an optimal SNR value and corresponding transmit precoding matrices, FIG. 17 may depict one possible procedure for calculating the combined FOM for the channel estimator and beamforming calculator of a DUT receiver, for example DUT receiver 293 shown in FIG. 15 . The procedure may be performed for the same modeled RF channels [H 1 ], [H 2 ], [H 3 ] and test signals [x 1 ], [x 2 ], [x 3 ] as used in the procedure depicted in FIG. 16 . The procedure may take the steps of: a) At step 320 , beginning the process; b) At step 321 , generating predetermined sounding signals [S 1 ], [S 2 ], [S 3 ] according to some predetermined beamforming information exchange process; c) At step 322 , processing these predetermined sounding signals as if they had been transmitted over the set of simulated RF channels; d) At step 323 , transmitting these processed signals to the DUT (for example, DUT receiver 293 ) as part of a beamforming exchange; e) At step 324 , receiving beamforming feedback from the DUT, containing transmit preceding matrix coefficients; f) At step 325 , using this beamforming feedback to set up transmit preceding matrices [V 1 ], [V 2 ], [V 3 ] and corresponding receive decoding matrices [U 1 ], [U 2 ], [U 3 ], possibly in an MU-MIMO system model, for example that depicted in FIG. 9 ; g) At step 326 , generating test signals [x 1 ], [x 2 ], [x 3 ]; h) At step 327 , injecting test signals [x 1 ], [x 2 ], [x 3 ] into the MU-MIMO system model, and simulating the effect of the matrices [V 1 ], [V 2 ], [V 3 ], [H 1 ], [H 2 ], [U 1 ], [U 2 ], [U 3 ] on the test signals, which may include the step of calculating the SNR (such as the Eb/No for a predetermined value of an error metric such as the BER); i) At step 328 , determining the FOM by comparing the SNR determined at step 327 with the optimal SNR, which may be determined according to step (h) of the procedure depicted in FIG. 16 ; and j) At step 329 , terminating the process. [0102] It will be apparent to those of ordinary skill in the art that, in accordance with embodiments described herein, the generation of beamforming feedback coefficients in a MIMO or MU-MIMO test system from modeled or modified RF channel parameters may facilitate a number of useful test functions. These functions may include the use of arbitrary RF channel models, even in a cabled environment. It will be further apparent that such functions may not require the use of external channel simulators. It will be yet further apparent that arbitrary but well-defined RF channel models may be interposed between transmitter/receiver pairs. Advantageously, this may enable the testing of MIMO or MU-MIMO functionality, including beamforming, in a fully cabled environment with reduced cost and complexity, and may improve the ability to test MIMO and MU-MIMO functions in an automated manner. [0103] It will be appreciated by those of ordinary skill in the art that, in accordance with aspects of embodiments described herein, the simulation of arbitrary RF channels between MIMO or MU-MIMO transmitter/receiver pairs may be performed on either the transmitter side or on the receiver side. Advantageously, this may increase the flexibility of the test setup and enable different types of DUTs to be tested. [0104] It will also be appreciated by those of ordinary skill in the art that, in accordance with embodiments described herein, the efficacy of the channel estimation performed within the DUT may be assessed against an arbitrary set of RF channel models. It will be further appreciated that the efficacy of the transmit precoding calculations performed by the DUT may be quantitatively assessed. It will be yet further appreciated that, in accordance with the embodiments described herein, an FOM may be determined for the absolute quality of the channel estimation and beamforming calculations performed by a MIMO or MU-MIMO DUT. Advantageously, this may enable the testing of essential MIMO or MU-MIMO internal DUT functions. [0105] Accordingly, while the subject matter herein has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other aspects or embodiments of the subject matter described herein, will be apparent to persons of ordinary skill in the art upon reference to this description. These modifications shall not be construed as departing from the scope of the subject matter described herein, which is defined solely by the claims appended hereto.

Systems and methods are disclosed herein to provide communication test systems for the testing of multiple-input multiple-output (MIMO) radio frequency wireless data communication devices, systems and networks, including Multi-User MIMO (MU-MIMO) devices and systems. In accordance with one or more embodiments, a test system containing an integrated MIMO signal analyzer is disclosed that includes a protocol engine operative in conjunction with a waveform generator and waveform analyzer that analyzes the signal waveform of a device under test. Such a test system may offer improved capabilities such as a simpler and more flexible measurement of complex MIMO signal waveforms, more automated measurements of MIMO waveforms including beamforming functions, and more accurate measurement of the efficiency of MIMO related functions such as channel estimation, transmit precoding and beamforming.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a 371 of international patent application number PCT/EP2012/050617 filed Jan. 17, 2012, having the same inventor and the same title, and which is incorporated herein by reference in its entirety, which application claims the benefit of U.S. provisional application No. 61/433,621, filed Jan. 18, 2011, having the same inventor and the same title, and which is incorporated herein by reference in its entirety. FIELD OF THE DISCLOSURE [0002] The present disclosure relates generally to communications platforms, and more particularly to systems and methods for collaboration over open platforms. BACKGROUND OF THE DISCLOSURE [0003] Various commercial endeavors require the collaboration of diverse parties with diverse skill sets to bring the endeavor to fruition. Frequently, it is necessary for these parties to exchange data, to obtain access to data generated as part of the endeavor, or to manipulate the data in order to create useful information. These tasks are frequently complicated by the fact that the parties collaborating on the project may be working from geographically disperse locations, and are often business competitors of each other. [0004] For example, in the operation of an oil rig during oil or natural gas exploration, a variety of data is generated concerning the condition or status of the well, rig, drilling equipment, drilling operations, and various supplies and resources. This data will typically be generated by the party responsible for a particular task. Data will also be created in the form of alerts generated by monitoring equipment, which are issued from time to time to notify interested parties of potential problems with the well, the rig or the drilling equipment. All of this data must be processed into information so that appropriate action may be taken at each point in time by the appropriate parties, and the information so generated must typically be monitored by the exploration company. BRIEF DESCRIPTION OF THE DRAWINGS [0005] FIG. 1 is an illustration of a system architecture over which the systems and methodologies described herein may be implemented. [0006] FIG. 2 is an illustration of a first embodiment of a system in accordance with the teachings herein. [0007] FIG. 3 is an illustration of a second embodiment of a system in accordance with the teachings herein. [0008] FIG. 4 is an illustration of the functionality of one particular, non-limiting embodiment of a system in accordance with the teachings herein. SUMMARY OF THE DISCLOSURE [0009] In one aspect, a platform is provided which facilitates collaboration among a plurality of users on a project (such as the exploration for oil or natural gas on an oil rig), data set and/or data stream. The platform comprises (a) a data hub configured to allow a plurality of users to store data on the data hub and to retrieve data from the data hub; (b) an interface associated with the data hub which is independently configurable by each of said plurality of users, wherein each user has a set of user preferences associated with that user which controls the configuration of the interface when it is accessed by that user; (c) a plurality of data files stored on said hub, wherein each of said data files is associated with one of said plurality of users and is accessible via the interface; and (d) a security system which authenticates a user and which restricts access of the data files to those data files associated with the user. [0010] In another aspect, a method is provided for obtaining services from third parties. The method comprises (a) providing a platform (preferably of the type described above) associated with a company and upon which third party service providers can register to receive notices of service requests; (b) posting service requests to the platform, wherein each service request contains a description of the service required; and (c) receiving bids from the third party service providers in response to the posted service requests. [0011] In a further aspect, a method is provided for facilitating collaboration among parties working on a project, data set, and/or data stream, wherein the collaboration involves the generation or manipulation of data by one or more of the parties. The method comprises (a) providing a platform of the type described above; (b) storing the data on the data hub in a plurality of data files; (c) associating a particular data file with a particular set of users; (d) restricting access to each of the plurality of data files to those users associated with the data file; and (e) allowing a user to manipulate data in the hub, including, but not limited to, by the use of external software loaded onto the hub. [0012] In still another aspect, a method is provided by which an entity can offer goods or services to other parties. The method comprises (a) providing a platform associated with the entity and upon which parties can register to post requests for goods or services from the entity; (b) receiving the requests at the platform, wherein each request contains a description of the goods or services required; and (c) posting bids to the platform from the entity in response to the posted requests. [0013] In yet another aspect, a non-transitory computer readable medium is provided which contains programming instructions, the execution of which, by one or more processors of a computer system, causes the one or more processors to carry out the foregoing methods or to establish the foregoing systems. DETAILED DESCRIPTION [0014] A variety of solutions have emerged in the marketplace to deal with the enormous amount of data and information generated during oil and natural gas exploration and other such collaborative endeavors. However, the real time operations (RTO) solutions which have been developed to date suffer from a number of infirmities which adversely affect the ability of parties to collaborate on the underlying project. [0015] At present, RTO solutions are typically implemented as proprietary systems. Thus, most RTO systems in the oil and gas industry are derived from the down-hole data acquisition systems associated with the service company, where proprietary information of their latest technology is utilized. Each service company has its own implementation methods. Recent advances in hardware and software designs allow independent RTO service providers to build their own systems. However, by design, these systems function as a data aggregation service only, and do not provide software as a service (SaaS). [0016] Conventional RTO solutions are also typically configured to provide only passive participation from data sources. In order to protect the proprietary technology implemented by the solution, conventional RTO systems do not allow other parties to control and configure the system. Hence, these systems expect data sources to stream data using industry standard protocols such as WITS and/or WITSML based on predefined or agreed sequences or lists. If there is a new requirement or a change in data type, both parties to a data exchange must typically repeat the cycle in order to ensure that the data being sent and received matches. The major drawback in this scenario is that the data source cannot directly participate to perform in-system data quality control (QC) or to create event/incident entries. Moreover, at present, event recording is typically part of a 12-hour batch reporting practice, which is already after-the-fact instead of real time. [0017] Conventional RTO solutions also typically require a specialist to run the system. In particular, the system must be operated either by the system vendor, by trained customer IT personnel, or by an engineer associated with a 3rd party reseller. [0018] In addition, conventional RTO solutions suffer from an unstructured or oversimplified data ownership structure. In particular, while current RTO systems have proper system authentication and authorization to own and access the data, the security is provided only at the system level. Hence, there is no data level security protection built in. [0019] Finally, current solutions suffer from manual and rigid data control processing. In particular, data integrity checks must be performed manually by an RTO engineer who is typically the system administrator. This situation arises in part from the lack of a clear data ownership structure implemented in the system. [0020] It has now been found that some or all of the foregoing needs may be addressed by the systems and methodologies disclosed herein. These systems and methodologies may be utilized to create an open platform for mobile collaboration which is preferably powered by open source software, and which is preferably enabled by Web 2.0 solutions. This platform may be used to establish a secure solutions marketplace (SSM) along with a real time virtual work space (RVWS). The SSM is secure in that it preferably follows industry standard best practices in protecting data confidentiality and integrity. Typically, this is accomplished through the proper use of authentication to access the system interface, and by requiring that a party have appropriate authorization to access data and system resources. [0021] The systems and methodologies disclosed herein may cover all products and their associated value-added services which are utilized to transform data into information for decision making purposes. These systems and methodologies may include data visualization, data mining, data processing, data interpretation, and data transformation. In a preferred embodiment, the platforms described herein will be openly configurable and accessible to all parties involved with a collaborative endeavor. Thus, for example, in the case of oil and natural gas exploration, the platform may be openly configurable and accessible to oil and natural gas companies or operators, rig companies or drilling contractors, service companies, independent consultants or subject matter experts, and regulatory bodies (including local governments). [0022] For purposes of illustration, the systems and methodologies described herein will frequently be illustrated and explained with respect to their implementation in the oil and natural gas exploration field, since many embodiments of these systems and methodologies are particularly advantageous in facilitating the collaboration required from diverse parties in this field. It will be appreciated, however, that these systems and methodologies are broadly applicable in a variety of fields, especially in applications requiring extensive collaboration between parties, and hence are not limited to the field of oil and gas exploration. [0023] FIG. 1 depicts first 101 , second 103 and third 105 particular, non-limiting embodiments of system architectures over which the systems and methodologies disclosed herein may be implemented. For purposes of illustration, these embodiments are described specifically with respect to their implementation in oil and natural gas exploration. However, it will be appreciated that each of these embodiments is applicable to any type of collaborative effort utilizing the disclosed communications infrastructures. In each of these architectures, a data hub 119 is maintained at a first location (a rig site 111 ) and is replicated at a second location (a third party site 117 ), but the network 112 over which communications occur is different in each instance. [0024] In the first embodiment 101 , the customer 113 (typically an oil and natural gas exploration company) has its own network, and communications between the customer 113 and the rig site 111 (and its associated data hub 119 ) occur via an enterprise service gateway (ESG) 121 (also known as an intranet bridge). The ESG 121 in this embodiment will typically reside behind a corporate firewall 123 . If a contractor or other third party 117 is required to obtain access to data, they do so through the Internet 115 or (other public communications network) and the company's firewall 123 to connect to the ESG 121 . [0025] In the second embodiment, the customer 113 maintains a site on a public communications network such as the Internet 115 , and communications between the customer 113 and the rig 111 occur via an Internet Service Gateway (ISG) 127 (also known as an Internet Bridge). The ISG 127 in this embodiment will typically be associated with an Internet proxy server 125 , and the customer 113 provides Internet connectivity for third parties 117 to send data to the ISG 127 from the third party's data hub 120 . [0026] In the third embodiment 105 , the customer does not maintain a network independent of the data hub 119 on the rig 111 . In this embodiment, communications occur in a point-to-point manner between the data hub 119 on the rig 111 , a data hub 120 associated with a third party 117 , and the associated users at 129 who may be working from various locations. Hence, in this embodiment, a contractor or other third party 117 may have employees on the rig 111 collecting data, and if they wish to send data from the rig 111 to another site, they will have to use the data hub 119 on the rig 111 and a third party data hub 120 (which may be their own data hub or the data hub of another third party) to establish an ad hoc point-to-point connection. Hence, the data in the data hub 119 at the rig site will be exactly the same as the data in the data hub 120 at the corporate office of the customer. In other words, the data from the data hub 119 at the rig site is simply replicated at the customer's data hub 120 . [0027] FIG. 2 illustrates a particular, non-limiting embodiment of a platform which may be utilized to implement some of the methodologies disclosed herein. In the embodiment of FIG. 2 , the platform 201 comprises a data hub 203 which acts as a data logger, and which is equipped with a data interface 205 . The data interface 205 in this particular embodiment is equipped with a variety of connections, including a TCP/IP connection 207 , an RS232 serial cable 209 , and an RS485 cable 211 (a serial cable with a special connection for connecting the data hub to a control system). All three of these connections implement standard industry protocols, and most modern computer equipment has interfaces for all three. [0028] The data hub 203 is adapted to collect data from service companies at the rig site using common data transfer protocols. Many service companies will use the WITSML (Wellsite Information Transfer Standard Markup Language) protocol or the older WITS (Wellsite Information Transfer Specification) protocol for data exchange. [0029] The data hub 203 also collects data from PLCs (programmable logic controllers, which are digital computers used for automation of electromechanical processes) and smart sensors 213 . A protocol known as ModBus, which is a serial communications protocol for PLCs, may be utilized for this purpose. ModBus allows for communication between many devices connected to the same network. By way of example, ModBus may be utilized by a system that measures temperature and humidity to communicate the results to a computer. The rig site automation control system is typically controlled by a PLC system which communicates with a control center via a MODBUS protocol. [0030] ModBus is also preferably used in the platform 201 as the protocol for communications between supervisory computers and remote terminal units (RTUs) in SCADA (Supervisory Control and Data Acquisition) systems 214 associated with the platform 201 . While protocols such as WITSML are commonly used for the exchange of information between a control center and a rig, SCADA protocols are the current industry standard used in oil and gas rigs for monitoring and control systems. Hence, SCADA systems typically collect data and send it to a remote control center, and receive commands from the control center which allow the control center to control system components such as valves and pumps. Thus, by way of example, SCADA systems allow a control center to monitor how much oil and gas is being produced at a rig, and to increase or decrease production by sending appropriate control signals. In contrast to SCADA, which is utilized in systems having both monitoring and control functionalities, WITSML and WITS are purely information exchange protocols (i.e., they provide only a monitoring functionality). [0031] In a typical implementation, the SCADA system 214 may consist of the following subsystems: (a) A Human-Machine Interface (HMI). This is the apparatus which presents process data to a human operator, and through which the human operator monitors and controls a process. (b) A supervisory (computer) system, which gathers or acquires data on the process and sends commands or controls to the process. (c) Remote Terminal Units (RTUs). These units connect to sensors in the process, convert sensor signals to digital data, and send the digital data to the supervisory system. (d) PLCs. These devices are used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs. (e) Communication infrastructure which connects the supervisory system to the RTUs. [0037] The data being generated at the rig site is received and aggregated by the data hub 203 into a database 215 . Depending on the system architecture (see FIG. 1 ), a TCP/IP connection 217 connects the data hub 203 to either a service gateway ( 121 in FIG. 1 ) or to a second data hub ( 120 in FIG. 1 ) to replicate the data that has been collected by the data hub 203 . The TCP/IP connection 217 preferably utilizes secure tunneling (which may be implemented as secure shell (SSH) tunneling or a virtual private network (VPN)) for file synchronization, database synchronization and real-time (RT) streaming. Such secure tunneling may be implemented with the Hypertext Transfer Protocol (HTTP) or Hypertext Transfer Protocol Secure (HTTPS), the latter of which is a combination of HTTP with the secure sockets layer/transport layer security (SSL/TLS) protocol. [0038] Database synchronization is preferably implemented using JavaScript object notation (JSON), a lightweight text-based open standard designed for human-readable data interchange. RT streaming is preferably implemented using asynchronous JavaScript and XML push (AJAX Push), a web application model in which a long-held HTTP request allows a web server to push data to a browser without the browser explicitly requesting it. [0039] The TCP/IP connection 217 to the data hub 203 is preferably secured with a firewall 233 . The firewall 233 is preferably equipped with security certificate finger printing, which preferably utilizes public-key cryptography standards (PKCS) and personal identification numbers (PINs) or other universally unique identifiers (UUIDs) for zero-configuration transparent connectivity service. [0040] Conventional systems for exchanging data between a rig and a control center have an input and an output, and replicate data from the rig site to the control center. By contrast, in the system depicted in FIG. 2 , the data hub 203 is equipped with a full web interface 219 so that any party will be able to operate the data hub 203 and will be able to control and configure the web interface 219 . This web interface 219 provides for the exchange of files 221 , such as pictures and reports, and further provides for the import or export of data in various file formats, such as ASCII (American Standard Code for Information Interchange), LAS (Log ASCII Standard), LIS (Log Information Standard), DLIS (Digital Log Interchange Standard) and XML (Extensible Markup Language) formats. Voice 223 , video 225 and chat 227 functionalities are also preferably supported. [0041] As a result of the web interface 219 , the data hub 203 operates like an independent, stand-alone server which allows any interested party to connect to and access it with web browser software. Consequently, there is no need to download any software—rather, a party only needs to input the web address to gain access to the data hub 203 . After that, the party can configure the data hub 203 with personalized settings as the party sees fit, and the configuration does not require any kind of specialized knowledge (an analogy may be made here to a user's homepage on the FACEBOOK™ social network, in that the homepage does not require that the user have any kind of specialized knowledge in order to use or configure it). [0042] The advantages of the system of FIG. 2 may be more fully appreciated by considering conventional systems used in the oil and gas industry to collect data at a rig. In such systems, the data hub is typically proprietary, and can only be configured by the service provider that is providing the database. Hence, when service companies are providing services at a rig, an expert is typically required to configure the data hub. By contrast, a system of the type depicted in FIG. 2 reduces operating costs by eliminating the need for such an expert. [0043] Moreover, in a typical exploration operation in the oil and gas industry, the operator has to employ service companies in order to drill a well. In particular, the operator typically does not own the drilling rig, but contracts a drilling company to drill the well. During drilling operations, there may be 10 to 15 different service companies operating on the rig, some of which may be in competition with each other. Typically, all of the service companies are generating data of one type or another, and all of the data needs to be available to the operator for monitoring purposes. [0044] Also, in a conventional operation, the communications platform containing the data hub will be owned and operated by one of the service companies, and hence, that company will have to allow the other service companies—some of whom are their competitors—to have access to the data hub. However, service companies are typically reluctant to allow their competitors (the other service companies) to configure their data hubs. Hence, the service company will typically have an engineer available to maintain the data hub, get the data stream from all of the service companies, and send it to the operator so that the operator can monitor the data. [0045] By contrast, the system depicted in FIG. 2 provides an open web interface 219 so that each service company can configure its own data without the need to involve an expert. In particular, the open web interface 219 allows each service company to configure the web interface 219 . However, the data entered into the data hub 203 will ultimately be input in the same format. Each service provider is thus able to establish its own access to its own data, and is able to configure the web interface 219 as it sees fit. Moreover, access to the data of a service provider may be secured with a user ID and password by way of an authentication and authorization system 231 , which may utilize pluggable authentication modules (PAM). [0046] A further advantage of the system of FIG. 2 over conventional systems in the art relates to data security. Conventional communications platforms utilized in the art are equipped with system-based data security. Hence, once a party has access to the system, that party can see all of the data. In such a system, the service companies do not have access to the data hub, and the data hub is proprietary to a particular company. By contrast, in the system of FIG. 2 , all parties of interest will have access to the data hub 203 . However, in order to prevent these parties from being able to see each other's data, security may be provided at both the system level and the data level. Therefore, while all of the parties of interest will have access to the data hub 203 , they will not be able to see each other's data within the data hub 203 . [0047] A further issue faced with conventional systems in the art relates to the operation of software on the data in the data hub. Typically, the data coming into the data hub is useful only after it is processed into information, and hence, a data hub requires applications to process the data contained in the data hub. For example, graphics software may be utilized to visualize the data, and data mining software may be utilized, for example, to perform statistical analyses on the data. It may also be necessary to perform data processing on the data to remove errors or anomalies from the data, to interpret the data, or to perform other such functions. Since data hubs in conventional systems are typically proprietary, the software which processes the incoming data is also a proprietary. This often limits the customer/operator to using specific service providers. Moreover, the data hub itself is typically capable of running few, if any, applications, due to processing power limitations. [0048] FIG. 3 depicts a second particular, non-limiting embodiment of a platform in accordance with the teachings herein. The platform 301 of FIG. 3 overcomes the foregoing infirmity through the provision of a service gateway 334 which is adapted to run the applications used to process data resident in a data hub 315 . [0049] In the system of FIG. 3 , the data hub 315 collects all of the incoming data. The data hub 315 further provides access to a particular service party to the data input by that service party, thus allowing the service party to configure its data stream. The system 301 provides security at the data level, so that the data corresponding to each service party is not accessible to any other party without permission. Hence, the data hub 315 collects the data and configures it correctly, and the security is built in. [0050] As with the previous embodiment, the embodiment of FIG. 3 is equipped with an open web interface 319 which is configurable by each service company, which allows each service company to configure its own data without the need to involve an expert, which allows each service company to establish its own access to its own data, and which provides voice 323 , video 325 and chat 327 functionalities and for the exchange of files 321 as described with respect to the previous embodiment. Also as with the previous embodiment, the embodiment of FIG. 3 is equipped with an authentication and authorization system 331 which may utilize pluggable authentication modules (PAM) and which allows access to the data of a service provider to be secured with a user ID and password. [0051] The system 301 of FIG. 3 is provided with a TCP/IP connection 317 , and the data hub 315 is accessible either through an ESG (within the corporate security firewall) or an ISG (over the Internet). The data hub 315 collects data and replicates it into the service gateway 334 . [0052] One usage for the data hubs described herein relates to the processing of alerts. Currently, some oil companies utilize a so-called real time center (RTC) to monitor the mud level in several different oil wells. The mud pit level may change for several different reasons. Typically, this will trigger an alert, and the person in the RTC (in town) will call the rig crew to find out why the mud pit level changed. If there is a reason for the mud pit level change, an explanation will be provided by someone at the rig, and the alert will be closed. Alerts are classified is red, yellow and green. If a given alert cannot be explained, it may be escalated to a yellow alert. [0053] Typically, the crew on the rig knows the reason for the alert, because they are generating the data which gives rise to it. However, in conventional systems, the personnel with the expertise on the rig to dispense with an alert typically do not have access to the data hub due to its proprietary nature. On the other hand, the person monitoring the alerts in the RTC typically does not know the underlying facts giving rise to an alert. Hence, it is common in the operation of an oil rig for the people in the RTC to have to make numerous calls to the rig simply to find out what is happening. Since approximately 90% of all alerts generated on a typical rig are false in the sense that they do not pertain to a real underlying problem, most of these communications from the RTC to the rig are ultimately unnecessary. [0054] On the other hand, the person in the RTC must be able to respond appropriately to alerts when they are real, and hence must have a significant amount of training and experience (typically at least 20 years). Due to the high incidence of spurious alerts, this person spends much of his time calling the rigs under his supervision just to find out what is happening. Consequently, the person in the RTC can typically monitor no more than three rigs at a time (this number is based on best practices in several oil companies today). [0055] By contrast, in the systems described herein, the crew on the rig will preferably have direct access to the data hub 315 . Hence, the party responsible for monitoring the mud system will see the alert first and can close it down if it is spurious, because he has access to the system. Hence, the systems described herein may achieve significant reductions in overhead (in terms of manpower), because the frequency at which calls must be placed from the RTC to the rig is significantly reduced. Also, the system may be equipped with an e-mail service 341 and an alarm service 343 which is in communication with a beeper or other means for notifying a party responsible for a system or event with respect to which an alert is being generated so that, when an alert is generated, the person responsible for the area to which it pertains will be notified. The systems described herein allow many problems to be disposed of on the rig, because there are personnel on the rig with expertise to dispose of the problem. [0056] It will be appreciated from the foregoing that the systems disclosed herein allow people associated with a project to collaborate more effectively because they have access to the data hub 315 . These systems thus avoid many communications of the type that are necessitated in conventional systems simply by the fact that information is missing or unavailable. In a system 301 of the type depicted in FIG. 3 , the person in the RTC may now merely police the alert system and efficiently focus his expertise to provide more value and better service to his customer. Hence, he will still be notified of alerts, but is no longer required to respond in every case. [0057] Referring again to the system of FIG. 3 , the service gateway 333 is preferably programmed with open source code, and is adapted to have software installed on it. This feature, denoted as an applications service 345 , allows for greater collaboration by experts around the world, because an expert can load his software into the gateway 333 , use it to manipulate data in the hub 315 , and then share that data and information generated from it with other parties. By contrast, the proprietary systems currently in use do not provide a means by which other parties may readily install their software on a service gateway. Instead, in such systems, it is typically necessary for such parties to have the data transferred to their own computer. Hence, the information these parties produce by processing the data in such systems is an isolated product and isolated work. [0058] By contrast, in the systems described herein, the work product generated by a party may be used by anyone, so long as they have authorization to use the software. Hence, these systems enable “software as a service” (SaaS). For example, these systems allow a software producer to simply charge an end user for using the software, rather than selling the software to the end user outright (that is, the software producer can essentially sell time on the software). [0059] An end user may also be given permission to upload software to the service gateway 333 over the web. By having the SaaS feature, the system 301 allows usable information to be extracted from the data in the data hub 315 without physically moving sensitive data out of the system. This may be particularly useful in applications where movement of data is either not permitted, or is closely regulated. For example, government agencies in countries such as Indonesia do not allow down-hole information to leave the country, making this feature particularly useful in oil and natural gas exploration applications there. [0060] A further advantage of the systems and methodologies disclosed herein relates to their ability to act as an expert geo-location service 351 . Since the platform is preferably open by way of a web service 355 , anyone working in the industry can register themselves to it. Hence, the platform facilitates the creation of a directory 353 of all of the people that are registered in the system (a “directory of experts”). Preferably, this directory 353 is implemented with the lightweight directory access protocol (LDAP), an application protocol for accessing and maintaining distributed directory information services over an Internet protocol (IP) network. [0061] Currently, oil and gas exploration companies spend significant resources trying to find people with the expertise that they require. However, the systems and methodologies disclosed herein allow anyone to register with the platform and note their areas of expertise, and hence, the platform acts as a marketplace for people wishing to sell their expertise, and provides a means by which the customer may identify potential experts for future work. These experts can also use the applications on the service gateway 333 to look at the customer's data for the purpose of bidding on a job, assessing their fit for a job, or as part of providing a combination of software and their expertise as a service. Currently in the industry, this type of platform does not exist, so collaboration is difficult. [0062] Such collaboration may be further facilitated in the systems and methodologies by the provision of suitable support services. As indicated in the embodiment of FIG. 3 , such support services may include voice chat services 361 , video conferencing services 363 , voice over IP (VOIP) services 365 , and the like. A TCP/IP connection 318 and a suitable firewall 334 may be provided to support these services. [0063] FIG. 4 summarizes the components of both the data hub 315 and the service gateway 333 for the system of FIG. 3 . All of these components are preferably web enabled, which means that they can be accessed using a platform independent web browser. [0064] While the systems and methodologies described herein have many advantageous features, two features described herein are especially conducive to the use of some embodiments of the platforms described herein in collaborative efforts. These are (a) a data ownership model in which the user has the capability to control the sharing of data directly or indirectly, and in which a data custodian role is introduced to facilitate this; and (b) a data hierarchy structure that acts as label tag to the user data to help connect a user to the correct target experts, and vice versa. [0065] While the systems and methodologies disclosed herein have been described above primarily in reference to their implementation in oil and natural gas exploration, one skilled in the art will appreciate that these systems and methodologies may be applied in a variety of other fields as well, and are potentially useful in any situation where a real time data stream is available. [0066] For example, these systems and methodologies may be adopted for business or consumer usage in various applications, such as equipment monitoring systems in which the usage of feedstocks (such as, for example, coolant, fluids, fuel or other feedstocks necessary for operation of the equipment) is monitored. In such an application, when supplies of a certain feedstock are running low, the system can make that information available to third parties and can, for example, locate the party willing to supply that feedstock at the lowest price. [0067] As a further example, the systems and methodologies disclosed herein may be adapted to monitor components of an automobile and to notify the owner when maintenance is required. Hence, instead of basing vehicle maintenance on an artificial and inefficient maintenance schedule (such as every 5000 miles), an automobile may be monitored in real time by a control room, and the owner may be notified when service is required. As part of this service, when service is required, an appointment may be set up automatically at a nearby dealership or auto repair shop. Also, the system may make the service information available so that third parties are able to bid on any services that are required. It will be appreciated that this application may find use by individual vehicle users or owners (such as, for example, individual consumers), or by businesses that need to maintain a fleet of vehicles. [0068] Similarly, trucking companies may use the systems and methodologies disclosed herein to monitor the maintenance status and location of their trucks. In these applications, the system may act as a resource and scheduling management system. [0069] The systems and methodologies disclosed herein may also be utilized in retail inventory management, especially for small retailers. This may be achieved, for example, by connecting a black box (data hub) to the cash registers of a retail business. In this way, retail sales transactions may be uploaded on a real time basis to a service gateway on the cloud. This could open up a few possibilities. [0070] For example, retailers may want an inventory control mechanism. A cloud based service gateway of the type described herein may be utilized to manage the inventory for a particular retailer. Such a system may generate an automatic replenishment order to maintain a certain level of inventory based on real time sales information, may adjust prices based on sales trends in real time, and may take other suitable actions to allow the retailers to act on information promptly. Additionally, chain retailers could use the system to make stock information available to consumers in real time, for example, the store location(s) in which a given product is available at that time. [0071] The systems and methodologies described herein may also be utilized to allow retailers to form networks and use their collective bargaining power to get better deals from suppliers. This may allow shops which are individually owned by small shop keepers to combine their purchasing power for the purpose of securing more advantageous terms from suppliers. [0072] The systems and methodologies described herein may also be utilized by merchants to identify suitable experts required to address their business needs. For example, once merchants have their sales and inventory information online, they may be able to seek services from business experts to help them optimize their business models. [0073] Assuming they are willing to share part of their real time sales data, manufacturers and suppliers may leverage the systems and methodologies described herein to obtain sales intelligence in different locations of the world. In particular, manufacturers and suppliers may use such real time sales information for business planning purposes. [0074] The systems and methodologies described herein may also be utilized to perform real time, condition based monitoring in the automotive industry. For example, a user may install data hubs on all vehicles the user wishes to monitor. The data hubs may be used to collect RT data from sensors, and to send this data to a service gateway. On the service gateway, the user may be able to opt to share particular information, or to use an SaaS application to transform the data (for example, such an application may be utilized to transform recorded GPS coordinates to distance traveled and engine hours) and to share this new information with several preferred service providers. Service providers may then monitor the information manually, or may use a SaaS application to generate suitable alarms to provide a quote for services (competitive bidding). The user may then select a service provider based on the quote for services, the proximity of the service provider, and the timing required to procure a maintenance service. [0075] It will be appreciated that the concepts underlying the foregoing example may be readily adapted to other industries as well. These concepts may be applied, for example, to the monitoring used in power plants, mining sites, manufacturing plants and prime movers. Rather than commercial competition, such applications may be directed more toward preventive maintenance and logistics management. [0076] The systems and methodologies described herein may also be applied in the health care industry, and more specifically, in intensive care units (ICUs) in medical centers. In such applications, a black box (data hub) may be utilized to get the real time sensor data from patients in an intensive care unit in a hospital. This data may then be uploaded to a service gateway, where it is accessible by various medical experts. Thus, for example, an expert located on the other side of the world may be able to advise a local medical practitioner based on a real time data feed from the patient. [0077] The systems and methodologies described herein may also be utilized for monitoring the real time production of oil and gas wells. In such an application, a data hub may be installed at the well head of a producing well, and pressure, temperature and flow sensors may be installed on the well head and connected to the data hub. The data hub software may then control the sampling rates of the different well head sensors and accumulate the sensor data in a data base. These sensor data may be uploaded to the data base in the service gateway, where various types of software routines (such as, for example, visualization, production analysis and the like) may be run on the service gateway for optimum production planning and management. Using the same system, sensors may be added to different artificial lift mechanisms, such as rod pumps, gas lifts and electrical submersible pumps. Consequently, condition based maintenance may be carried out for artificial lift equipment in addition to optimizing the performance of the artificial lifts. [0078] The systems and methodologies described herein may also be utilized for coal mine equipment performance management. In such an application, a data hub may be installed on heavy mining mobile equipment, and GPS, fuel level sensors and engine hour sensors may be installed on the equipment and connected to the data hub. The data hub software may then control the sampling rates of the different sensors, and may accumulate the sensor data in a database. This sensor data may then be uploaded to the database in the service gateway, where various software routines (such as equipment location, visualization, scheduling and equipment condition monitoring) may be run on the service gateway for optimum production planning and management. As an added advantage, the monitoring of fuel consumption vs. engine hours may be utilized to prevent fuel pilferage from heavy equipment in remote locations. [0079] The systems and methodologies described herein may also be utilized in procurement operations in the oil and gas industry. In such an application, all operational information available at the service gateway from an oil company's RTO operation may be used to determine the future scope of work for procuring services. Consequently, oil field service providers would be able to participate in the system with real time information concerning service equipment availability and the status of current services. Such an application would thus be able to connect the needs of the oil & natural gas field operators to the availability of a service company's equipment and to the company's service availability. This approach may allow different smaller oil companies with similar needs to be able to pool their needs to leverage the buying power associated with larger volumes. Consequently, service companies may be able to reduce their sales and marketing costs and the costs of missed opportunities by their use of such an application in which oil and natural gas companies will be able to publish their precise service needs. [0080] The systems and methodologies described herein may also be utilized for safety and service quality management in the oil and natural gas industry. In particular, a continuous service quality management system may be established for both the oil and natural gas field operators and the oil field service providers by monitoring drilling rig operations using an RTO system throughout the drilling operation. Such an application could be used to set up an auditable approval system for all mandatory safety and operational tests on a drilling well to ensure compliance with local safety regulations. Once data from real time tests is available on the service gateway, various reports may be generated to aid in managing operational excellence, as well as high safety standards. [0081] The above description of the present invention is illustrative, and is not intended to be limiting. It will thus be appreciated that various additions, substitutions and modifications may be made to the above described embodiments without departing from the scope of the present invention. Accordingly, the scope of the present invention should be construed in reference to the appended claims.

A platform is provided which facilitates collaboration among a plurality of users on a project (such as the exploration for oil or natural gas on an oil rig), data set and/or data stream. The platform ( 301 ) comprises (a) a data hub ( 315 ) configured to allow a plurality of users to store data on the data hub and to retrieve data from the data hub; (b) an interface ( 319 ) associated with the data hub which is independently configurable by each of said plurality of users, wherein each user has a set of user preferences associated with that user which controls the configuration of the interface when it is accessed by that user; (c) a plurality of data files stored on said hub, wherein each of said data files is associated with one of said plurality of users and is accessible via the interface; (d) a security system ( 331 ) which authenticates a user and which restricts access of the data files to those data files associated with the user; and (e) functionality allowing a user to manipulate data in the hub, including by use of external software loaded onto the hub.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to structures, structures to which anodized alumina nano-holes are applied, production methods thereof, electron-emitting devices, and image-forming apparatus. Particularly, the structures of the present invention can be applied to electron-emitting devices, image-forming apparatus, electrochromic devices, imaging tubes, and so on. [0003] 2. Related Background Art [0004] Considerable research is now under way on the electron-emitting devices having the properties of uniformity, fineness, high efficiency, and long life, as typified by flat panel displays. For forming microscopic electron-emitting regions of the devices, a lot of processes are performed by making use of the semiconductor processing techniques including photolithography, electron beam exposure, and so on. [0005] However, application of materials having microscopic structure (nano-structures) can be listed as a simple method of forming the electron-emitting regions uniformly and in a large area. Particularly, attention is being drawn to structures formed in a self-organizing manner. [0006] For the nano-structures, it is preferable to employ a porous film of alumina obtained by anodization of aluminum. First, the anodization of aluminum has such features that, when it is done in an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid, pores (nano-holes) are formed in nano-size so as to be surrounded by a barrier layer (alumina), thereby yielding a porous film; and that, when it is done in an aqueous solution of ammonium borate, ammonium tartrate, or ammonium citrate, the pores are not formed but a uniform alumina film (barrier film) is formed, thereby yielding a barrier film. [0007] [0007]FIGS. 2A, 2B, and 2 C are schematic views of films obtained by the anodization of aluminum, wherein FIG. 2A is a plan view of the porous film, FIG. 2B a cross-sectional view along line 2 B- 2 B of FIG. 2A, and FIG. 2C a cross-sectional view of the barrier film. The porous film of alumina is characterized by having such a specific geometrical structure that extremely fine, cylindrical pores having pore diameters 26 of several nm to several hundred nm are arrayed in parallel at spacing 25 of several ten nm to several hundred nm, as shown in FIGS. 2A and 2B. Then the array spacing of pores can be controlled by adjusting an electric current and a voltage during the anodization. [0008] Concerning this porous film of alumina, there are such attempts that an electron-emitting member is placed inside each of the holes to form an electron-emitting region and one electron-emitting device is constructed of an assembly of plural electron-emitting regions (e.g., Japanese Patent Applications Laid-Open No. 05-211030, Laid-Open No. 10-12124, and so on). This structure is characterized in that the sizes of the holes are very small. This makes use of the advantages that the electron-emitting regions have a small radius of curvature at the tip, so as to facilitate concentration of an electric field, and thus electron emission occurs readily and that the electric current is stable, because one electron-emitting device is constructed of a plurality of electron-emitting regions. [0009] There are, however, demands for decreasing dispersion among the individual electron-emitting regions and distribution of the electric field and for making the production process simpler. SUMMARY OF THE INVENTION [0010] For readily forming the electron-emitting devices having the even electron-emitting regions in a large area, it is useful to use the foregoing porous alumina film. In the conventional devices, however, uniformity of the electron-emitting regions was insufficient and unevenness of the field concentration resulting therefrom could lead to decrease in lifetimes of the electron-emitting regions. [0011] For solving it, it is desirable to improve the uniformity of the electron-emitting regions and improve durability against local field concentration. It is also necessary to simplify the production process. [0012] The present invention has been accomplished in order to solve the problems of the prior arts as described above, and an object of the invention is to provide structures with improved durability during the field concentration and with sufficient resistance to chain discharge breakdown and easy production methods of such structures, and also to provide structures with high uniformity, and electron-emitting devices and image-forming apparatus. [0013] The above object can be achieved by the following configurations and production methods according to the present invention. [0014] An aspect of the present invention is a structure comprising an electroconductive film, a layer placed on the electroconductive film and comprising aluminum oxide as a main component, a pore placed in the layer comprising aluminum oxide as a main component, and an electric conductor placed in the pore and comprising a material of the electroconductive film, wherein the electric conductor is porous and is electrically connected to the electroconductive film. [0015] Another aspect of the present invention is an electron-emitting device comprising an electroconductive film, a layer placed on the electroconductive film and comprising aluminum oxide as a main component, a pore placed in the layer comprising aluminum oxide as a main component, and an electron emitter placed in the pore and comprising a material of the electroconductive film, wherein the electron emitter is porous and is electrically connected to the electroconductive film. [0016] Another aspect of the present invention is a structure in which an enclosed substance is formed from a bottom portion of a pore formed by anodization of a film laid on an underlying electrode and comprising aluminum as a main component, wherein the enclosed substance comprises a constitutive element of the underlying electrode or an oxide thereof as a main component and is porous. [0017] Another aspect of the present invention is a method of producing a structure in which an enclosed substance is formed from a bottom portion of a pore formed by anodization of a film laid on an underlying electrode and comprising aluminum as a main component, the method comprising a step of carrying out anodization by use of a bath for forming a porous film, for the film comprising aluminum as a main component, a step of carrying out anodization by use of a bath for forming a barrier film, and a step of carrying out a thermal treatment. [0018] Another aspect of the present invention is a structure comprising: [0019] an electroconductive film; [0020] a layer placed on the electroconductive film and comprising aluminum oxide as a component; [0021] a pore placed in the layer comprising aluminum oxide as a component; and [0022] a porous electric conductor placed in the pore, electrically connected to the electroconductive film, and comprising a material of the electroconductive film, [0023] wherein the electroconductive film consists of two or more layers of films and at least one element out of elements included in every film is different from at least one element out of elements included in the other films. [0024] Another aspect of the present invention is an electron-emitting device comprising: [0025] an electroconductive film; [0026] a layer placed on the electroconductive film and comprising aluminum oxide as a component; [0027] a pore placed in the layer comprising aluminum oxide as a component; and [0028] a porous electron emitter placed in the pore, electrically connected to the electroconductive film, and comprising a material of the electroconductive film, [0029] wherein the electroconductive film consists of two or more layers of films and at least one element out of elements included in every film is different from at least one element out of elements included in the other films. [0030] Another aspect of the present invention is a structure in which a porous enclosed substance comprising a constitutive element of an underlying electrode or an oxide thereof as a component is formed from a bottom portion of a pore formed by anodization of a film laid on the underlying electrode and comprising aluminum as a component, wherein the underlying electrode consists of two or more layers of films and at least one element out of elements included in every film is different from at least one element out of elements included in the other films. [0031] Another aspect of the present invention is a method of producing a structure in which a porous enclosed substance comprising a constitutive element of an underlying electrode or an oxide thereof as a component is formed from a bottom portion of a pore formed by anodization of a film laid on the underlying electrode and comprising aluminum as a component, wherein the underlying electrode consists of two or more layers of films and at least one element out of elements included in every film is different from at least one element out of elements included in the other films. [0032] According to the structure of the present invention, the enclosed substance is electrically conductive and thus is applicable to the electron-emitting region. When the structure of the present invention is used as an electron-emitting device, even if the electric field is concentrated unevenly on the enclosed substance as an electron-emitting region to cause microdischarge, it will act as a current limiting resistance because of the porous structure, thereby making it feasible to provide the nano-structure resistant to discharge. [0033] When the pores (nano-holes) are regularly arrayed, the uniformity of shapes of the nano-holes is considerably improved and the electric field is also applied evenly as compared with irregular arrays, which makes it feasible to stabilize electric current values based on emission of electrons. Further, sizes of portions without the enclosed substance in the nano-holes are larger than those of portions with the enclosed substance, whereby the electric field becomes easier to concentrate and whereby electrons become easier to emerge from the nano-holes. [0034] According to the above features, the electron-emitting regions are protected from discharge, which can lengthen the lifetimes thereof. [0035] When a deriving electrode is formed at the upper part of the nano-hole in the structure of the present invention, electrons can be emitted efficiently. Here the distance between the deriving electrode and the electron-emitting region can be controlled with high accuracy by an anodization voltage during formation of the electron-emitting region. [0036] Further, the production method of the structure according to the present invention enables the enclosed substances serving as electron-emitting regions of uniform height to be formed readily and in a large area. BRIEF DESCRIPTION OF THE DRAWINGS [0037] [0037]FIGS. 1A and 1B are schematic views showing an embodiment of the structure according to the present invention; [0038] [0038]FIGS. 2A, 2B, and 2 C are schematic views of anodized alumina nano-holes; [0039] [0039]FIGS. 3A and 3B are schematic views showing states at respective fabrication stages of the structure according to the present invention; [0040] [0040]FIGS. 4C, 4D, 4 E, 4 F, and 4 G are schematic views showing states at respective fabrication stages of the structure according to the present invention; [0041] [0041]FIGS. 5A and 5B are views showing states of the enclosed substance in the structure of the present invention; [0042] [0042]FIGS. 6A and 6B are schematic views showing regulated nano-holes according to the present invention; [0043] [0043]FIGS. 7A and 7B are schematic views showing another embodiment of the structure according to the present invention; [0044] [0044]FIG. 8 is a profile of electric current for the first anodization in the sixth example of the structure according to the present invention; [0045] [0045]FIG. 9 is a table showing the results of visual observation after execution of the second anodization in 0.05 mol/l ammonium borate aqueous solution and at the applied voltage of 160 V in the sixth example of the structure according to the present invention; [0046] [0046]FIG. 10 is a table showing the results of observation to observe the heights of enclosed substances after formation of the enclosed substances by execution of the second anodization in 0.05 mol/l ammonium borate aqueous solution and at the applied voltage of 160 V in the seventh example of the structure according to the present invention; [0047] [0047]FIG. 11 is a table showing the results of measurement of electron emission ratio in the seventh example of the structure according to the present invention; [0048] [0048]FIGS. 12A, 12B, 12 C, and 12 D are schematic diagrams concerning the shape of an upper underlying electrode layer after production of the structure in the eighth example of the structure according to the present invention; and [0049] [0049]FIGS. 13A, 13B, and 13 C are schematic views of films obtained by the anodization of aluminum. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0050] The first structure of the present invention will be described below on the basis of the drawings. [0051] [0051]FIGS. 1A and 1B are schematic views showing an embodiment of the first structure of the present invention, wherein FIG. 1A is a plan view and FIG. 1B a cross-sectional view along line 1 B- 1 B of FIG. 1A. In FIGS. 1A and 1B, numeral 11 designates pores of nano-size (nano-holes) and 12 a barrier layer (alumina). Numeral 13 denotes enclosed substances (electron-emitting members) of an electric conductor, which have a porous shape, as shown in the cross-sectional shape of FIG. 5B. Numeral 14 represents a portion without the enclosed substances, 15 a portion with the enclosed substances, 16 an underlying electrode of an electroconductive film, 17 a substrate, 18 a deriving electrode, 19 an upper pore size (of the portion without the enclosed substances), 110 a lower pore size (of the portion with the enclosed substances), and 111 a spacing of the pores (nano-holes). In the present invention the “electric conductor” making the enclosed substances embraces metals and semiconductors. The “electric conductor” making the enclosed substances can also be referred to as a material having the band gap of not more than 4 eV and, preferably, not more than 3.5 eV. [0052] The pores (nano-holes) in the structure of nano-size (also called “nano-structure”) can be formed by use of a bath capable of forming a porous film by anodization of aluminum, e.g., by use of oxalic acid, phosphoric acid, sulfuric acid, or the like. Alumina portions surrounding the pores (nano-holes) at this time are the barrier layer (alumina) 12 . [0053] Then the porous enclosed substances (electron-emitting members) 13 can be made by use of a bath capable of forming a barrier film of uniform alumina film by the anodization of aluminum, e.g., by use of ammonium borate, ammonium tartrate, ammonium citrate, or the like. [0054] The enclosed substances (electron-emitting members) 13 are porous and are made of a material a main component of which is a constitutive element of the underlying electrode 16 of the electroconductive film or a material a main component of which is an oxide of the constitutive element. When the structure of the present invention is used as an electron-emitting device, it is preferable to carry out a reduction process described hereinafter to improve the electric conductivity of the enclosed substances 13 , because the enclosed substances 13 immediately after the formation according to the above method are often of oxide form. [0055] The height of the enclosed substances (electron-emitting members) 13 can be controlled by the applied voltage during the anodization in the bath for forming the barrier film. The voltage can be applied stepwise or directly up to a desired voltage to form the enclosed substances at an equivalent height. [0056] The barrier layer (alumina) 12 in the present invention represents the alumina portions separating the pores from each other in the porous film, and the barrier film does a uniform film of alumina obtained when the conventional anodization of aluminum is carried out in the bath of ammonium borate or the like, and is used in comparison with the porous film. Accordingly, when the anodization is carried out using the bath for forming the porous film in the present invention, a porous film is obtained. However, when the anodization of the porous film is subsequently carried out using the bath for forming the barrier film, the cylindrical enclosed substances are formed in the pores without forming the barrier film, which is the feature. [0057] The spacing 111 of the pores (nano-holes) can be controlled by the applied voltage during the anodization in the bath for formation of the porous film. The spacing Ill of the pores (nano-holes) to be formed can be controlled to a desired value by regularly forming pore-forming start points in a surface of aluminum before the anodization by FIB (Focused Ion Beam), a mold with regular projections, the lithography technology with light or an electron beam, or the like. [0058] The size 110 of the lower nano-holes (the portion with the enclosed substances) can be controlled by a time of a hole width enlarging process after the anodization in the bath for formation of the porous film. [0059] The size 19 of the upper nano-holes (the portion without the enclosed substances) can be controlled by a time of a hole width enlarging process after the anodization in the bath for formation of the barrier film, or after the thermal treatment. [0060] The latter hole width enlarging process can be carried out by dipping in phosphoric acid. The size can be controlled by the time. [0061] The substrate 17 in FIGS. 1A, 1B can be any material on which the underlying electrode 16 and the film the main component of which is aluminum can be formed. For example, the substrate can be either of materials flat and resistant to the temperatures of about 400° C.; for example, glasses, oxides such as SiO 2 , Al 2 O 3 , etc., semiconductors such as Si, GaAs, InP, and so on. The underlying electrode 16 can be either material selected from metals such as W, Nb, Mo, Ta, Ti, Zr, Hf, and so on. [0062] When the deriving electrode 18 in FIGS. 1A, 1B is formed so as to overlap like a cap at the upper end of each nano-hole, electrons can be emitted efficiently. [0063] A further preferred structure of the second form according to the present invention will be illustratively described below in detail with reference to the drawings. The structure of the second form described hereinafter is more suitable for the formation of the foregoing enclosed substances 13 in a good yield than the structure of the first form described above with reference to FIGS. 1A, 1B and others. [0064] It is, however, noted that the dimensions, materials, shapes, relative locations, etc. of the components used in the second form described hereinafter are by no means intended to limit the scope of the invention only to them unless otherwise stated in particular. [0065] Further, in the drawings described hereinafter, the same reference numerals will also denote members similar to those described with the drawings heretofore. [0066] The forms and examples of the second structure described hereinafter will also explain embodiments and examples of the electron-emitting devices, image-forming apparatus, nano-structures, and production methods thereof according to the present invention. [0067] [0067]FIGS. 7A and 7B are schematic views of an embodiment of the structure of the second form according to the present invention, wherein FIG. 7A is a plan view and FIG. 7B a cross-sectional view along line 7 B- 7 B of FIG. 7A. [0068] In FIGS. 7A and 7B, reference numeral 11 designates the nano-holes (pores) and 12 the barrier layer (alumina) as a layer containing aluminum oxide as a component. Numeral 13 denotes the enclosed substances (electron-emitting members) consisting of a porous electric conductor. Numeral 13 a represents upper enclosed substances, 13 b underlying-electrode-occupying enclosed substances, 14 the portion without the upper enclosed substances, 15 the portion with the enclosed substances, 16 the underlying electrode (electrode) consisting of an electroconductive film, 16 a an upper underlying electrode (first electrode), 16 b a lower underlying electrode (second electrode), 17 the substrate, 18 the deriving electrode, 19 the size of the upper nano-holes (the portion without the enclosed substances), 110 the size of the lower nano-holes (the portion with the enclosed substances), and 111 the spacing of the pores (nano-holes). [0069] However, the barrier layer 12 is not limited only to the layer containing aluminum oxide as a component, but it may also be a layer containing aluminum oxide as a main component. [0070] The pores 11 can be formed by use of a bath (oxalic acid, phosphoric acid, sulfuric acid, etc.) commonly known as those for formation of porous film in anodization of aluminum. [0071] The alumina portions surrounding the nano-holes at this time constitute the barrier layer (alumina) 12 . [0072] The porous enclosed substances (electron-emitting regions) 13 a and the underlying-electrode-occupying enclosed substances (electron-emitting regions) 13 b can be formed by use of the bath (ammonium borate, ammonium tartrate, ammonium citrate, etc.) capable of forming the barrier film being a uniform alumina film in the anodization of aluminum, as in the case of the enclosed substances of the first structure described previously. [0073] When the second structure of the present invention is used as an electron-emitting device, it is also preferable to carry out the process of enhancing the electric conductivity of the enclosed substances 13 by the reduction process, because the enclosed substances 13 immediately after the formation according to the above method are often of oxide form. [0074] In the second structure of the present invention, the “electric conductor” making the enclosed substances also embraces metals and semiconductors. The “electric conductor” making the enclosed substances can also be referred to as a material having the band gap of not more than 4 eV and, preferably, not more than 3.5 eV. [0075] During the production of the aforementioned first structure of the present invention, where the structure had the underlying electrode of only the W layer, electric current values during the anodization were observed in the step using the bath (oxalic acid, phosphoric acid, sulfuric acid, etc.) for the formation of the porous film in the anodization, and it was found from the observation that unless the anodization was ended at the current value equal to ⅚ of the constant current value, the yield was poor in the next step of forming the enclosed substances. [0076] However, when the structure is constructed like the second structure of the present invention wherein the upper underlying electrode 16 a is a film containing at least one element out of Nb, Mo, Ta, Ti, Zr, and Hf as a main component and the lower underlying electrode 16 b is a film containing W as a main component, the end condition can be expanded to the range of ⅚ to {fraction (1/12)} of the constant current value. [0077] However, the second structure of the present invention is not limited to the configuration wherein the upper underlying electrode (first electrode) 16 a is the film containing at least one element of Nb, Mo, Ta, Ti, Zr, and Hf as a main component and the lower underlying electrode (second electrode) 16 b is the film containing W as a main component, but it can also be of a configuration wherein the upper underlying electrode (first electrode) 16 a is a film containing at least one element of Nb, Mo, Ta, Ti, Zr, and Hf as a component and the lower underlying electrode (second electrode) 16 b is a film containing W as a component. [0078] In the second structure of the present invention, part of the upper underlying electrode 16 a is occupied by the lower enclosed substances 13 b . The upper underlying electrode 16 a is characterized in that it exists in the portions except for immediately below the pores 11 , or in the portions immediately below the junctions of the barrier layer 12 . [0079] The underlying-electrode-occupying enclosed substances 13 b are produced during the process of forming the second structure of the present invention. [0080] The height of the enclosed substances (electron-emitting members) 13 a is proportional to the voltage applied in the step using the bath (ammonium borate, ammonium tartrate, ammonium citrate, etc.) known as one for the formation of barrier film. The height also varies depending upon the material of the underlying electrode 16 . The height of the enclosed substances can be made equal by applying the voltage stepwise or directly up to a desired voltage. [0081] The spacing 111 of the pores can be controlled by the applied voltage during the anodization in the bath for the formation of the porous film, as described previously. When start points are regularly formed before the anodization by making use of the FIB (Focused Ion Beam), the mold with regular projections, the lithography technology with light or an electron beam, or the like, the spacing 111 of the nano-holes can be made constant regardless of locations. [0082] The size 110 of the lower nano-holes (the portion with the enclosed substances) can be controlled by the time of the hole width enlarging process after the anodization in the bath for the formation of porous film. The size 19 of the upper nano-holes (the portion without the enclosed substances) can be controlled by the time of the hole width enlarging process after the anodization in the bath for the formation of the barrier film, or after the thermal treatment. [0083] The substrate 17 can be any material on which the underlying electrode 16 and the film containing Al as a main component can be formed. [0084] For example, the substrate can be one selected, e.g., from the oxides such as SiO 2 , Al 2 O 3 , etc., and the semiconductors such as Si, GaAs, InP, etc. and being flat and resistant to the temperatures of about 400° C. The underlying electrode can be one selected from the metals such as W, Nb, Mo, Ta, Ti, Zr, Hf, and so on. [0085] The substrate 17 and the underlying electrode 16 can be made in an integral form, and the substrate 17 can be a metal sheet of W, Nb, Mo, Ta, Ti, Zr, Hf, or the like. When the substrate 17 is a metal sheet of W, Nb, Mo, Ta, Ti, Zr, Hf, or the like, the underlying electrode 16 consisting of two or more layers means that the substrate 17 is regarded as a single layer, and it is also feasible to achieve the effects of the present invention under such circumstances When the deriving electrode 18 in FIGS. 7A, 7B is formed so as to overlap like a cap at the upper end of each nano-hole, electrons can be emitted efficiently. [0086] When the enclosed substances 13 of the above structure are used as electron-emitting members, the foregoing structure functions as an electron-emitting device. [0087] When this electron-emitting device is combined with a member equipped with an image-forming member, e.g., like a fluorescent member, to be irradiated with electrons emitted from the electron-emitting device, an image-forming apparatus according to the present invention is constructed. EXAMPLES [0088] The present invention will be described below in further detail with examples thereof. In the following description, the anodization in the bath for the formation of the porous film will be called first anodization, and the anodization in the bath for the formation of the barrier film, second anodization. Example 1 [0089] The present example presents procedures of producing the structure of the present invention. [0090] The structure was produced according to the following procedures shown in FIGS. 3A to 4 G. [0091] 1) Layered films consisting of a film of tungsten 32 (50 nm thick) and a film of aluminum 31 (500 nm thick) were deposited on a glass substrate 33 by RF sputtering. Further, indentations were formed as pore-forming start points in a honeycomb pattern at intervals of 100 nm on the surface of aluminum by FIB (Focused Ion Beam). (cf. FIG. 3A) [0092] 2) The first anodization was carried out by dipping the film of aluminum 31 in 0.3M oxalic acid aqueous solution at 16° C. and applying the voltage of 40 V thereto. (cf. FIG. 3B) [0093] 3) Subsequently, the second anodization was carried out by applying the voltage of 200 V in 0.05M ammonium borate aqueous solution at 10° C. (cf. FIG. 4C) [0094] 4) The hole width enlarging process may be conducted in the above state, or the thermal reduction process may also be carried out first. The thermal reduction process reduces the enclosed substances (tungsten oxide) 35 into porous tungsten 36 . (cf. FIGS. 4D and 4E). [0095] 5) When the hole width enlarging process was carried out in the above step, the thermal reduction process is carried out herein; or, when the thermal reduction treatment was carried out in the above step, the hole width enlarging process is carried out herein. (cf. FIG. 4F) [0096] 6) In the final step, a film of tantalum becoming the deriving electrode 37 is formed by oblique incidence sputtering. (cf. FIG. 4G) [0097] Cross sections of samples produced according to the above two ways of production procedures were observed according to the procedures with FE-SEM. [0098] It was verified from the observation that, in each of the procedures, the structure corresponding to FIG. 3A was formed after the procedure 1 ), the structure corresponding to FIG. 3B after the procedure 2 ), the structure corresponding to FIG. 4C after the procedure 3 ), the structures corresponding to FIG. 4D and FIG. 4E after the respective procedures 4 ), the structure corresponding to FIG. 4F after the procedure 5 ), and the structure corresponding to FIG. 4G after the procedure 6 ). Example 2 [0099] The present example concerns the enclosed substances of the nano-structure. [0100] W, Si, Nb, Pt, Mo, Ta, Ti, Zr, and Hf films were deposited in the thickness of 50 nm on respective substrates by RF sputtering, thereby preparing nine types of substrates. After that, an aluminum film was further deposited in the thickness of 500 nm on each of the substrates. Then each of the substrates was subjected to the first anodization and the second anodization in the same manner as in Example 1. After that, they were observed with FE-SEM. For the sample with the tungsten film, the state of the enclosed substances subjected to the thermal reduction process was also observed with FE-SEM. [0101] It was verified from the observation that among the W, Si, Nb, Pt, Mo, Ta, Ti, Zr, and Hf films, the enclosed substances were formed only in the samples using the W, Nb, Mo, Ta, Ti, Zr, and Hf films, but the enclosed substances were not formed in the other samples of Si and Pt. [0102] Among the samples in which the enclosed substances were formed, the sample using tungsten was observed in detail, and it became clear therefrom that there existed voids of bubbles 42 in the enclosed substances (tungsten oxide) 41 before the thermal reduction process, as shown in FIG. 5A. It was also confirmed that the state after the thermal reduction process was that the enclosed substances were reduced into a binding state of particulate substances (porous tungsten), as shown in FIG. 5B. [0103] The packing factor after the formation of the enclosed substances 41 was approximately 78%, and the pacing factor of the enclosed substances 44 after the thermal reduction process was approximately 67%. Example 3 [0104] The present example concerns the applied voltage during the second anodization in the production of the structure and fluctuations of the height of the enclosed substances depending thereupon. [0105] The first anodization step was carried out under the same conditions as in Example 1. [0106] First prepared were four samples which were through the first anodization step as in Example 1. The second anodization step was also carried out under the conditions of the bath as in Example 1. [0107] In the second anodization step, voltages applied to the respective samples were 100 V, 130 V, 160 V, and 200 V, respectively. [0108] Evaluation [0109] After completion of the anodization, cross sections of the samples were observed with FE-SEM to estimate heights of the enclosed substances and rough fluctuation levels. The results are presented in Table 1 below. TABLE 1 Height of Fluctuation of Applied of enclosed height enclosed Voltage (V) substance substance (nm) 100 115 ±10 nm or less 130 175 ±5 nm or less 160 231 ±10 nm or less 200 300 ±5 nm or less [0110] It was found from Table 1 above that the relation between height of enclosed substances and applied voltage was a proportional relation and was generally given by the following equation. Height of enclosed substances ( nm )=[1.8×applied voltage ( V )]−60 [0111] Fluctuation amounts of the height of the enclosed substances were roughly estimated by observing about hundred enclosed substances and maximum fluctuations were obtained as in the above table, which confirmed that the fluctuations were small. Example 4 [0112] The present example concerns regularization of the nano-holes. [0113] The tungsten film (50 nm thick) and aluminum film (500 nm thick) were deposited on a glass substrate by RF sputtering and indentations were formed in the honeycomb pattern therein by FIB (Focused Ion Beam). The spacing of the indentations was 100 nm. [0114] Then the first anodization was carried out by applying the voltage of 40 V in 0.3M oxalic acid aqueous solution, and the second anodization by applying the voltage of 200 V in 0.05M ammonium borate aqueous solution. [0115] Cross sections of this sample were observed with FE-SEM. For comparison, a sample prepared without FIB was also observed. It was verified from the observation that, with the sample produced through the regularization, the normal nano-holes (enclosed substances) 53 were completely normal to the underlying electrode and all were straight, as shown in FIG. 6A. In contrast with it, with the sample produced without the regularization, the nano-holes were approximately normal to the underlying electrode but there were nano-holes 51 failing to reach the underlying electrode and enclosed substances 52 of small sizes, as shown in FIG. 6B. This affects the surrounding nano-holes, so as to cause dispersion of sizes of nano-holes. As a consequence, the electric field was concentrated more there than at the other enclosed substances, so that electric current values became unstable. [0116] It was, therefore, confirmed that the nano-holes thus regularized had high uniformity and were important to stabilization of electric current values. Example 5 [0117] The present example concerns the durability of the electron-emitting device using the structure. [0118] Samples were prepared as follows. By the method similar to that in Example 1, the tungsten film (50 nm thick) and aluminum film (500 nm thick) were deposited on a glass substrate by RF sputtering, and the first anodization and the second anodization were carried out by the voltage of 40 V and by the voltage of 200 V, respectively. After that, one sample was not subjected to the hole width enlarging process, but another sample was subjected to the hole width enlarging process in phosphoric acid 5 wt % for 50 minutes. In the subsequent step, the thermal treatment was carried out at 400° C. in a hydrogen atmosphere (which can be either a carbon monoxide atmosphere or a vacuum) for two hours. [0119] In the final step the deriving electrode of tantalum was formed by oblique incidence sputtering (cf. FIG. 1B). The distance between the deriving electrode and the electron-emitting regions was approximately 300 nm. The size of the electron-emitting regions at this time was 45 nm. The size of the portion without the electron-emitting regions in the upper part of the pores (nano-holes) was 45 nm or 77 nm, depending upon whether or not the hole width enlarging process was carried out. [0120] On the other hand, a sample for comparison was also prepared by burying nickel in the pores of the structure obtained through the hole width enlarging process in the same manner as the above sample, by electrodeposition to form the electron-emitting regions. [0121] Electrodes were attached to the two samples and the voltage was applied thereto in vacuum. Then emission of electrons was recognized near the applied voltage of 50 V from the two samples respectively having the electron-emitting regions of nickel and the electron-emitting regions of porous tungsten metal. [0122] It was verified that electric current values were stabler in the sample with the electron-emitting members of porous tungsten than in the sample with the electron-emitting members of nickel. Then the structure of the electron-emitting members of nickel and the structure of the electron-emitting members of tungsten were observed with TEM and it was found that the tungsten electron-emitting members were porous as shown in FIG. 5B but the nickel electron-emitting members were denser in structure than the tungsten electron-emitting members. [0123] It was thus verified from the above that the electron-emitting regions of the present invention were rarely affected by microdischarge because of the porous structure and sufficient current amounts were able to be ensured on a stable basis from the numerous electron-emitting regions. [0124] The electric current in the sample produced with the hole width enlarging process was approximately two times that in the sample produced without the hole width enlarging process. The reason is that the electric field was concentrated more. [0125] There will be presented examples of the second structure of the present invention to describe the production method thereof and the structure of the present invention. In the description hereinafter, the anodization in the bath (oxalic acid, phosphoric acid, sulfuric acid, etc.) for the formation of the porous film will be called first anodization, and the anodization in the bath (ammonium borate, ammonium tartrate, ammonium citrate, etc.) for the formation of the barrier film, second anodization. Example 6 [0126] The present example concerns the conditions under which the second structure of the present invention can be formed. [0127] A Ti film and a W film were deposited in the thickness of 5 nm and in the thickness of 50 nm, respectively, on a glass substrate by RF sputtering and thereafter an element of Nb, Mo, Ta, Ti, Zr, or Hf was deposited as an upper underlying electrode in the thickness of 2 nm on each substrate, thus preparing six types of substrates, four per type of substrate ( 24 substrates in total). Further, an Al film was deposited in the thickness of 500 nm on each of the substrates. [0128] [0128]FIG. 8 shows the end conditions a, b, c, and d in the first anodization in 0.3 mol/l aqueous solution of oxalic acid for the above samples (substrates). FIG. 8 is the profile of electric current during the first anodization in the present example. [0129] The conditions a, b, c, and d shown in FIG. 8, correspond to respective cases in which the electric current is reduced to (⅚)I 0 , (½)I 0 , (⅙)I 0 , and ({fraction (1/12)})I 0 , respectively, in order from the constant current value I 0 . [0130] Further, these samples were subjected to the second anodization in 0.05 mol/l aqueous solution of ammonium borate at the applied voltage of 160 V and the results of visual observation thereof are presented in the table shown in FIG. 9. FIG. 9 is the table showing the results of visual observation of the samples after the second anodization was carried out in the 0.05 mol/l aqueous solution of ammonium borate at the applied voltage of 160 V in the present example. The comparative example herein was a sample with only the W layer. [0131] It was verified from the above results that the stability in the anodization was able to be enhanced by provision of the new layer on the W layer. The reason for the destruction during the anodization is conceivably bubbles generated by the high voltage and it is speculated from this point that the new layer is also advantageous for enhancement of adhesion with the anodized alumina nano-holes. Example 7 [0132] The present example concerns the enclosed substances in the second embodiment of the present invention. Five types of substrates were prepared in such a way that a Ti layer and a W layer were deposited in the thickness of 5 nm and in the thickness of 50 nm, respectively, on each glass substrate by RF sputtering and thereafter an Nb layer was deposited as an upper underlying electrode in the thickness of 1 nm, 5 nm, 10 nm, or 20 nm for each of four substrates but was not deposited for the other substrate. After that, an Al film was deposited in the thickness of 500 nm on each of the substrates. [0133] Each of the substrates was subjected to the first anodization in 0.3 mol/l aqueous solution of oxalic acid and the first anodization was terminated when the current value I 0 was reduced to (⅓)I 0 . Then the second anodization was carried out in 0.05 mol/l aqueous solution of ammonium borate at the voltage of 160 V, thereby forming the enclosed substances. The height of the enclosed substances was observed by FE-SEM (Field Emission-Scanning Electron Microscopy) and the results thereof are presented in the table shown in FIG. 10. FIG. 10 is the table showing the observation results of the height of the enclosed substances in the samples in which the enclosed substances were formed by carrying out the second anodization in the 0.05 mol/l aqueous solution of ammonium borate at the voltage of 160 V in the present example. [0134] As apparent from the table shown in FIG. 10, the height of the enclosed substances increases with increase in the thickness of the Nb film. [0135] Then these samples were annealed at 400° C. in a reducing atmosphere for the purpose of enhancing the electric conductivity, and presence/absence of electron emission was checked under provision of the deriving electrode of Ta. The condition was expressed by a ratio of electron emission to that of the sample without the Nb layer. FIG. 11 shows a table of the results. FIG. 11 is the table showing the measurement results of electron emission ratio in the present example. [0136] The reason why the electron emission ratio decreased in the presence of the Nb film, as shown in FIG. 11, is conceivably that the oxide produced by the anodization of Nb was not reduced well by the reduction treatment by the heat at 400° C. [0137] It was found from the above that the structure was able to be constructed stably and the electron emission was good in the range where the thickness of the Nb film was 1 to 5 nm. Example 8 [0138] The present example concerns the underlying electrode in the second structure of the present invention. A Ti layer 5 nm thick and a W layer 50 nm thick were deposited on a glass substrate by RF sputtering and thereafter an Nb layer 2.5 nm thick was deposited as an upper underlying electrode. Then an Al film was deposited in the thickness of 500 nm thereon. [0139] This was subjected to the first anodization in 0.3 mol/l aqueous solution of oxalic acid at the applied voltage of 40 V. In the subsequent step the second anodization was carried out in 0.05 mol/l aqueous solution of ammonium borate. The second anodization was carried out at the applied voltage of 100 V, 150 V, or 200 V, and thereafter the upper underlying electrode was observed by FE-SEM. [0140] It was found from the observation that the upper underlying electrode was formed as shown in FIG. 12A with application of 100 V, as shown in FIG. 12C with application of 150 V, or as shown in FIG. 12D with application of 200 V. FIG. 12B shows a cross-sectional shape along line 12 B- 12 B of FIG. 12A. FIGS. 12A to 12 D are schematic diagrams concerning the shape of the upper underlying electrode layer after the production of the structure in the present example. [0141] It was confirmed from the above that, though varying its shape in the production steps, the upper underlying electrode layer existed finally in the forms as shown in FIGS. 12 A- 12 D and coupled the pores formed by the anodization, to the substrate. [0142] As described above, the present invention provides the following effects. [0143] When the electron-emitting device is constructed using the structure having the porous enclosed substances consisting of the electric conductor the main component of which is W, Nb, Mo, Ta, Ti, Zr, Hf, or an oxide of either element according to the present invention, the electron-emitting device is sufficiently resistant to the microdischarge and ensures stable emission current. [0144] When the pores are regularly arrayed by use of FIB (Focused Ion Beam), the straight enclosed substances are formed normally to the substrate, thus considerably enhancing the uniformity. This makes it feasible to apply the electric field uniformly as compared with the conventional electron-emitting devices and to stabilize the electric current values resulting from the electron emission. [0145] Further, the production method of the structure according to the present invention made it feasible to form the enclosed substances becoming the electron emission regions of uniform height readily and in a large area. [0146] Since the second structure of the present invention is characterized in that the oxide produced in the anodization of the layer in contact with the bottom portion of the pores is insoluble or hard to solve in alkali or acid, it becomes feasible to prevent weakening of adhesion between the underlying electrode and pores due to oxidation and erosion of the underlying electrode by repetition of the anodization steps, thereby preventing occurrence of structural destruction. [0147] It also became feasible to select the sufficiently gentle production conditions for production of samples. [0148] In particular, this effect was most prominent when Nb, Mo, Ta, Ti, Zr, or Hf was contained as a component in the layer in contact with the bottom portion of the anodized alumina nano-holes in the underlying electrode and W was contained as a component in the lower underlying electrode adjacent thereto.

Provided are electron-emitting devices improved in durability during concentration of an electric field and thus rarely suffering chain discharge breakdown. An electron-emitting device has an electroconductive film, a layer placed on the electroconductive film and containing aluminum oxide as a main component, a pore placed in the layer containing aluminum oxide as a main component, and an electron emitter placed in the pore and containing a material of the electroconductive film, and the electron emitter is porous and is electrically connected to the electroconductive film.

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of U.S. patent application Ser. No. 29/196,339, filed on Dec. 24, 2003, the disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION The present invention relates generally to a fluid dispenser, and more particularly to a cost-effective dispenser assembly that is fully compatible with high-speed in-line filling apparatuses, capable of dispensing predetermined amounts of fluid materials, and has few components to assemble. Various types of dispensers for fluids are well known in the art. Dispenser's typically comprise a cartridge for holding the fluid material, as well as a spray, pump, or plunger to dispense the fluid material out of the cartridge. Some dispensers have a spray pump attached to a pump line that runs through a cartridge containing fluid material, such as perfume. When the user depresses the spray pump, fluid material flows through the line to the spray, and then onto the desired medium. Other dispensers, such as those used for caulking, have a cartridge filled with caulk, and a trigger mechanism which causes a plunger in the cartridge to push the caulk out of the cartridge. The shortcomings associated with these prior art dispensers concern their manufacture and assembly. Known dispensers typically require several pieces that must be manufactured and then assembled together. Some of the pieces, such as a separate applicator tip, are relatively small in size and can prove difficult to assemble. Known dispensers often have parts that need to be screwed together, or require additional adhesives or the like to secure the various components of the dispenser together. The configuration of known dispensers therefore requires extraneous parts and steps to complete the dispenser assembly process, which, in turn, drives up the costs for the manufacturer. These drawbacks are further compounded by the problems associated with filling known dispensers with fluid materials. Once a dispenser has been manufactured, dispenser manufacturers typically solicit their dispensers to companies desiring to sell fluid products. For example, a cosmetic company may wish to purchase a dispenser designed to dispense a fluid lipstick, lotion, or the like. After purchasing the empty dispensers from a dispenser manufacturer, the cosmetic company will then proceed to fill the dispensers with its own product using a filling apparatus and process. There are many problems, however, associated with the purchase and subsequent filling of known dispensers by a purchasing company. It is not cost-effective to fill known dispensers with fluid product using standard high-speed filling apparatuses and processes. Such dispensers often vary in shape and size and are not readily adaptable to preexisting high speed filling machines utilized by a particular company. For example, the shape of the dispenser body may not be compatible with the parts of the preexisting filling machine used to hold the dispenser during the filling process, or the opening of the cartridge may not be large enough (or even too small) to receive the nozzle of the filling apparatus that dispenses the fluid material from the filling apparatus to the cartridge. To remedy these problems, the cosmetic company is therefore forced to purchase new filling machines, and/or adapters, such as funnels, or custom made holders for the dispenser, commonly referred to as pucks, to make pre-existing filling machines and dispensers compatible with one another. In some situations, it is too costly to adapt a preexisting filling machine to fit a particular dispenser, which results in the inability to use such a dispenser in a high speed filling process, or similar type of filling process. This often forces the cosmetic company to either select an alternative dispenser, or to use an alternative slower process. Each of these problems is a costly venture for a purchasing company, who then passes the additional cost on to the consumer. There are also additional costs associated with assembling the dispenser once the dispenser has been filled with the desired fluid material. In the filling process, typically a separate cartridge must first be filled by the filling apparatus, and then inserted into the dispensing device. Thereafter, the dispenser must be completely assembled and sealed. This task proves to be especially cumbersome when the dispenser has several components that need to be assembled after the filling process is completed. The added steps and time needed to assemble and fill such dispensers, slows down the filling process and drives up the filling costs. It also compromises the quality and integrity of the fluid material sitting in the dispenser because it leaves the fluid materials subject to contamination by dust, air, etc., until the dispenser is sealed. These problems are evident in U.S. Application No. 2003/0123921 to Abbas (“Abbas”), which is directed toward an instrument preferably for applying a fluid material of low viscosity to a surface. FIG. 19 discloses a fluid dispenser that comprises a cartridge of fluid, a holder, an applicator tip, a pump and pump housing, and a retaining ring for holding the pump housing within the holder. Force applied to the cartridge causes fluid in the cartridge to flow from the pump to the holder, and the applicator tip. FIG. 23 of Abbas discloses a toothbrush dispenser preferably for dispensing a fluid of low viscosity, such as a liquid cleaner, mouthwash or perfume, onto teeth. The toothbrush dispenser comprises a cartridge of liquid cleaner having a pump, an outer holder for the cartridge, an applicator tip or toothbrush head attached to the holder, and a feeder line from the cartridge to the applicator tip. FIG. 27 shows a configuration similar to FIG. 23 , the primary differences being that the applicator tip is a pad, and that instead of a feeder line from the inner cartridge to the applicator tip, there is an inking region that collects fluid material dispensed from the cartridge, and then dispenses the fluid material to the applicator tip. In both FIGS. 23 and 27, force applied to the cartridge causes fluid material from the cartridge to flow into either the feeder line or inking region, and then to the applicator tip. Despite the seemingly relative simplicity of these embodiments, there are still costly drawbacks associated with the manufacture of the Abbas dispensers, and the subsequent filling of the Abbas dispensers with fluid materials. The Abbas dispenser is comprised of several parts that require assembly. The applicator tip must be inserted and secured onto the holder, an inner cartridge containing fluid material is inserted into the holder, a retaining ring must also be inserted into the holder to contain the inner cartridge within the holder (or the inner cartridge must be screwed into the holder), a pump mechanism must be attached to the cartridge, and then the cartridge must be sealed with a cap. Prior to installation of the cartridge, the cartridge must first be filled with fluid material. Abbas is designed so that the cartridge is filled with fluid material and then temporarily sealed. The cartridge is then placed into the holder in its sealed form, and later punctured by the tip of the pump when it is desired to permit the free flow of fluid material into the applicator. This design is believed to prevent the pre-assembly of the cartridge into the holder when the cartridge is provided to a filling manufacturer because pre-assembly might cause premature puncturing of the cartridge. Moreover, the design of the cartridge typically requires additional screwing or the use of adhesives or the like to secure the cartridge within the holder. In this regard, it is believed that the Abbas dispenser cannot be sent to a filling manufacturer in a preassembled form, filled, and then simply sealed. Thus, the Abbas dispenser requires the steps of filling the cartridge, sealing the cartridge, and only then installing and securing the cartridge within the holder. The added step in the Abbas dispenser assembly process exemplifies the problems associated with the Abbas dispenser and prior art dispensers. It is therefore beneficial to provide a dispenser assembly, such as those embodiments disclosed by the present invention, that is cheaper to manufacture, easy to assemble, maintains the integrity of the fluid material in the dispenser, and is compatible with pre-existing high speed filling machines. SUMMARY OF THE INVENTION The present invention is designed to overcome the shortcomings associated with the disclosure of Abbas and other known fluid dispensers by providing a dispenser assembly that is cheaper to manufacture, requires few parts to assemble, and is readily compatible with standard high speed filling machines. As discussed more fully herein, the present invention requires few parts; namely, an end cap, a fluid insert containing fluid materials, and an outer casing. Unlike the prior art disclosures, each of these parts can be assembled together without the use of additional parts, such as adhesives or retaining rings, or steps such as screwing the different components together. The present invention further permits a manufacturer to sell a dispenser assembly to cosmetic companies and the like seeking to dispense their products (such as lotions, gels, etc.) into dispensers using a high speed filling process. The present invention is fully compatible with standard high speed filling apparatuses. The dispenser assembly can be provided to cosmetic companies and the like in an almost completely assembled manner and placed directly onto standard high speed filling apparatuses. The only assembly required after filling is the addition of a seal cap to seal the dispenser once the cartridge of the dispenser has been filled with the desired fluid material. In accordance with another important feature of the present invention, the capping process can also take place as part of the high speed filling process, further cutting down on the assembly time. The steps required to assemble the fluid dispenser greatly differs from known dispensers, which require the separate steps of filling the cartridge, sealing the cartridge, and then assembling the cartridge into the holder. The few steps required to assemble and fill the dispenser assembly according to the present invention increases production, while minimizing overall costs. Accordingly, various dispenser assemblies in accordance with the present invention are disclosed which achieves each of these shortcomings. According to one aspect of the present invention, there is provided an instrument for applying a predetermined amount of fluid material to a surface comprising a fluid insert and an outer casing. The fluid insert has a first end and a second end, and a protruding ridge arranged on an exterior of the fluid insert between the first end and the second end. The outer casing has a hollow interior for receiving the fluid insert therein, a first end and a second end, and a pump actuating surface. The outer casing further includes an applicator tip integrally formed with the outer casing at the first end for dispensing fluid material from the outer casing, and an interior ridge arranged within the hollow interior between the first end and the second end for securing the fluid insert within the outer casing when the protruding ridge of the fluid insert is positioned between the interior ridge of the outer casing and the first end of the outer casing. There is also a pump arranged at the first end of the fluid insert that has a pump body and a pump tip. The fluid insert is constructed and arranged to be movable within the outer casing between a stationary position and an actuated position, wherein the pump is in an extended position when the fluid insert is in the stationary position, and the pump is in a retracted position within the pump body when the pump tip is in engagement with the pump actuating surface of the outer casing when the fluid insert is in the actuated position. The pump is operative to dispense a predetermined amount of fluid material as the fluid insert is moved from the stationary position to the actuated position within the outer casing. According to another aspect of the present invention, there is provided an instrument for applying a predetermined amount of fluid material to a surface comprising a fluid insert for storing fluid material, a pump, and an outer casing. The fluid insert has a first end, a second end, and a notch arranged between the first end and the second end. The pump is arranged at the first end of the fluid insert and has a pump body, and a pump tip. The outer casing has a first end and a second end, a tab arranged between the first end and the second end, and an applicator for applying fluid material dispensed into the outer casing. The outer casing is constructed and arranged to receive the fluid insert so as to permit movement of the fluid insert within the outer casing between a first position and a second position. The tab is constructed and arranged to fit within the notch on the fluid insert so as to guide movement of the fluid insert when the fluid insert moves within the outer casing from the first position to the second position. The fluid insert is in the first position when the pump tip is in a fully extended position, and the fluid insert is in the second position when the pump tip is retracted into the pump body. The pump is operative to dispense fluid material into the outer casing when the fluid insert is moved from the first position to the second position. In accordance with another aspect of the present invention, there is provided an instrument for applying a predetermined amount of fluid material that has a fluid viscosity ranging from 1000 centipoise (cps)-10,000 cps to a surface. The instrument comprises a fluid insert for storing fluid material, and an outer casing. The fluid insert has a first end and a second end, and a notch arranged on the fluid insert displaced from the first end of the fluid insert. It has a pump capable of pumping fluid material that has a fluid viscosity ranging from 1000 centipoise (cps)-10,000 cps. The pump is arranged at the first end of the fluid insert, and has a pump body and a pump tip. The pump is operative to dispense fluid material in response to movement of the pump tip. The outer casing has a first end and a second end, a tab arranged on the interior thereof, and an applicator for dispensing the fluid from the pump of the fluid insert within the outer casing. Tab constructed and arranged to fit within the notch so as to guide movement of the fluid insert within the outer casing. In accordance with still another aspect of the present invention, there is provided a device for dispensing a predetermined amount of fluid material to a surface comprising an outer casing and a fluid insert for housing fluid material. The outer casing has first and second ends, an applicator at the first end, a first ridge arranged on an interior of the outer casing and displaced from the second end, and a second ridge arranged within the interior of the outer casing between the inner ridge and the applicator. The fluid insert has a raised band on the surface thereof, the fluid insert being constructed and arranged to fit within the outer casing so that the raised band is arranged between the first and second ridges of the outer casing. The fluid insert is movable from a first position to a second position within the outer casing to disperse fluid material. The fluid insert is in a first position when the raised band is adjacent to the first ridge of the fluid insert, and the fluid insert is in a second position when the raised band is adjacent to the second ridge of the fluid insert. The fluid insert dispenses a predetermined amount of the fluid material contained in the fluid insert through the applicator of the outer casing when the fluid insert moves from the first position to the second position. In accordance with yet another aspect of the present invention, there is provided an instrument for dispensing a predetermined amount of fluid material comprising an outer casing and a fluid insert. The outer casing has an interior chamber, a first tab and a second tab arranged within the interior chamber, and an applicator integrally formed with the outer casing. The fluid insert is arranged and constructed to fit within the outer casing, and has a first notch and a second notch, a pump with an internal check valve, and a stop having a first side and a second side. The fluid insert is rotatable within the outer casing between a first position and a second position. The fluid insert is in the second position when the second side of the stop is adjacent to the second tab and the second notch is displaced from the second tab. The fluid insert is in the first position when the first tab is aligned with the first notch, and the first side of the stop is adjacent to the first tab. The dispenser assembly is adapted to dispense a predetermined amount of the fluid material from the fluid insert through the applicator when the fluid insert is in the first position. In accordance with another aspect of the present invention, there is provided a dispenser assembly for dispensing a predetermined amount of fluid material comprising a fluid insert and an outer casing. The fluid insert has a body including a first end and a second end, a hollow chamber for storing a fluid material, a seal cap mounted to the first end for sealing the fluid insert, a pump connected to the second end for dispensing a predetermined amount of fluid material, a notch on the body displaced from the second end, and a protruding ridge displaced from the first end. The outer casing has an interior chamber for receiving the fluid insert and a first end and a second end. The applicator is arranged at the first end for applying the fluid material dispensed from the pump of the fluid insert to a surface. There is at least one tab arranged within the interior chamber of the outer casing and it is constructed and arranged to fit within the notch so as to guide movement of the fluid insert within the outer casing. The outer casing also has a ridge arranged within the interior chamber of the outer casing that is operative to restrict removal of the fluid insert when the fluid insert is assembled within the interior chamber. In accordance with a further aspect of the present invention, there is provided a method of filling a dispenser assembly using a high speed filling apparatus. First, a pre-assembled dispenser assembly is provided that has an end cap, an outer casing, and an inner fluid receiving body. The outer casing has a first end and a second end, and an applicator at the first end. The inner fluid receiving body has a first end and a second end, a pump arranged at the first end of the inner fluid receiving body, and an opening arranged at the second end of the inner fluid receiving body. The inner fluid receiving body is pre-assembled in the outer casing so that the inner fluid receiving body closes the second end of the outer casing, and the end cap is arranged over the applicator of the outer casing. Second, the pre-assembled dispenser assembly is placed directly onto a filling apparatus. Third, the inner fluid receiving body is filled with a fluid material through the opening of the inner fluid receiving body. Fourth, the inner fluid receiving body of the partially pre-assembled dispenser assembly is sealed with a seal plug so as to provide a fully assembled and filled dispenser assembly. These and other features and characteristics of the present invention will be apparent from the following detailed description of preferred embodiments, which should be read in light of the accompanying drawings in which corresponding reference numbers refer to corresponding parts throughout the several views. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an unassembled cap, outer casing, and fluid insert according to an embodiment of the present invention. FIG. 2 is a perspective view of an assembled cap, outer casing, and fluid insert of the dispenser assembly shown in FIG. 1 . FIG. 3 is a cross-sectional view of the outer casing shown in FIG. 1 . FIG. 4 is an exploded cross-sectional view of the left end of the outer casing shown in FIG. 3 . FIG. 5 is an exploded cross-sectional view of the right end of the outer casing shown in FIG. 3 . FIG. 6 is a front view of the left end of the outer casing shown in FIG. 3 . FIG. 7 is a rear view of the right end of the outer casing shown in FIG. 3 . FIG. 8 is a perspective view of an unassembled inner casing shown in FIG. 1 . FIG. 9 is a cross-sectional view of the body of the fluid insert shown in FIG. 8 . FIG. 10 is a cross-sectional view of section A-A shown in FIG. 9 . FIG. 11 is an exploded cross-sectional view of the right side of the fluid insert body shown in FIG. 9 . FIG. 12 is a cross-sectional view of the assembled fluid insert body, pump, and seal cap of the fluid insert shown in FIG. 1 . FIG. 13 is a front view of the assembled fluid insert and outer casing shown in FIG. 1 . FIG. 14 is a top view of the seal plug of the fluid insert shown in FIG. 12 . FIG. 15 is a cross-sectional view of the seal plug shown in FIG. 14 . FIG. 16 is an exploded cross-sectional view of the ridges shown on the seal plug shown in FIG. 15 . FIG. 17 is a cross-sectional view of the seal cap according to an alternative embodiment of the present invention. FIG. 18 is a cross-sectional view of a seal cap and diaphragm according to an embodiment of the present invention. FIG. 19 is a top view of the diaphragm shown in FIG. 18 . FIG. 20 is a perspective view of the end cap shown in FIG. 1 . FIG. 21 is a cross-sectional view of the end cap shown in FIG. 20 . FIG. 22 is a cross-sectional view of an end cap according to an alternative embodiment of the present invention. FIG. 23 is an alternative embodiment of the fluid dispenser assembly according to the present invention. DETAILED DESCRIPTION In describing the preferred embodiments of the subject matter illustrated and to be described with respect to the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. The present invention is generally directed to a dispenser assembly 100 shown in FIG. 1 for dispensing predetermined amounts of fluid materials. The material, such as lotion, is stored within a fluid insert 108 and dispensed therefrom in response to pressure applied by a user onto the fluid insert 108 , which, in turn, actuates the pump 117 . The dispenser also contains an outer casing 106 that holds the fluid insert 108 . It is to be understood that the dispenser for fluid materials of the present invention may be utilized to dispense various liquids, pastes, semi-liquids, semi-solids, gels, and the like. Such materials are preferably derived from the cosmetics industry and may include gels, medicated creams and lotions, and the like to be dispensed using the dispenser of the present invention. Also for convenience, all such materials will be generally referred to as fluid materials, although they may have semi-solid, paste-like or other consistencies. Referring to FIG. 1 , the dispenser assembly 100 is preferably comprised of a dispenser cap 102 , an outer casing 106 , and a fluid insert 108 . The dispenser assembly 100 is constructed and arranged so that the fluid insert 108 is disposed and secured within the outer casing 106 , and the dispenser cap 102 fits over the outer casing 106 . The dispenser cap protects the applicator 104 from being contaminated or otherwise damaged. As shown in FIG. 2 , when these components are assembled together, they form an elongated cylindrical dispenser assembly that is preferably in the shape of a tubular pen, although the dispenser may take on a variety of alternate shapes, such as animals, flowers, or any desired shape. Referring to FIGS. 3 and 4 , the outer casing 106 is preferably a hollow tube with an elongated outer body 114 having an applicator 104 , and a connector portion 110 that connects the applicator 104 to the outer body 114 . The outer body 114 preferably has a larger diameter than the applicator 104 and connector 110 . In this regard, the connector portion 110 preferably has a diameter greater in size than the applicator 104 , but smaller than the outer body 114 . The connector 110 and applicator 104 are both preferably integrally formed with the outer body 114 so as to minimize the number of parts needed to manufacture and assemble the outer casing 106 , as well as to decrease the overall costs associated with the manufacture and assembly of the dispenser assembly 100 . It should be appreciated, however, that the outer casing 106 may be formed from separate components that are assembled together, and that the connector portion 110 may be removed. The applicator 104 preferably has rounded ends 103 and an opening 107 (see also FIG. 6 ) through which the fluid material from the fluid insert 108 (see FIG. 1 ) is dispersed. As shown in FIGS. 3 , 4 , and 7 , a raised wall 600 arranged on the interior side 117 of the applicator 104 surrounds the opening 107 . The wall 600 helps guide the tip 120 (see FIG. 1 ) of the fluid insert 108 into the opening 107 when the fluid material is dispensed from the fluid insert 108 . It should be appreciated that the applicator can also take on a variety of alternate constructions such as a spray device, brush, roller, scrubbing pad, and the like. Referring to FIGS. 3 and 5 , an edge 302 and protruding inner casing ridge 304 is arranged towards the open end 116 of the interior 117 of the outer casing 106 . In a preferred embodiment, one inner casing ridge 304 is located along the perimeter of the interior 117 of the outer casing 106 , although it should be appreciated that more than one ridge may be used. The edge 302 and innermost edge 303 of the inner casing ridge 304 define the boundaries of a pumping region 306 which, as best shown in FIG. 5 , has a diameter that is slightly larger than the diameter of the remainder of the interior 117 . In a preferred embodiment, the diameter of the pumping region 306 will differ from that of the remainder of the outer body 114 on the order of 0.012±0.003 inches. A similar outer region 309 preferably having a reduced diameter extends from the outermost edge 307 of the inner casing ridge 304 to the open end 116 of the outer casing 106 . Referring to FIG. 5 , the diameter of the area in which the protruding inner casing ridge 304 is located preferably decreases so as to eventually equal the diameter of the pumping region 306 . In the embodiment shown, there is an angular slope 320 that slopes at an angle of 10° from the highest point 311 of the inner casing ridge 304 to the pumping region 306 . It should be appreciated that the size and slope of the ridge may be increased or decreased. As shown in FIGS. 3 , 4 , and 7 , tabs 300 are arranged on opposed surfaces at the front end of the interior 117 of the outer casing 106 . The tabs 300 are elongated and have a first end 308 located at the beginning of the connector portion 110 and a second end 310 located towards the lower end of the body 114 . As will be discussed fully herein, the tabs are designed to help guide the movement of the fluid insert 108 when the dispenser assembly 100 is actuated so as to dispense fluid material. The size of the tabs may therefore vary based upon the size of the fluid insert 108 and/or the travel length of the fluid insert 108 when it moves from a stationary position to an actuated pumping position. Accordingly, the length of the tabs 300 may be altered to suit the desired movement of the dispenser assembly 100 . Referring to FIG. 8 , the components of the fluid insert 108 according to an embodiment of the present invention are shown. The fluid insert 108 is adapted to contain the fluid material to be dispensed within its interior chamber 126 . The fluid insert 108 is comprised of a pump 117 , a seal plug 132 , a fluid insert body 128 , having a first end 125 , a second end 127 , a transition region 124 , and a fluid insert band 130 arranged near the second end 127 of the fluid insert 108 . As shown in FIG. 9 , the fluid insert body 128 is preferably tapered in shape, the diameter of the fluid insert 108 decreasing in size from its second end 127 to the first end 125 . The fluid insert 108 must have an overall diameter that is small enough to fit within and be capable of axially moving within the outer casing 106 (see FIG. 3 ). Preferably, the fluid insert is at least 0.0035±0.0015 inches smaller than the outer casing. As shown in FIGS. 9 and 10 , a first notch 301 is arranged on the exterior of the fluid insert body 128 and a second notch 301 ′ is arranged on the opposed exterior side of the fluid insert body 128 . The notches 301 , 301 ′ are recessed so that they can receive the tabs 300 of the outer casing 106 (see FIG. 3 ) when the dispenser assembly 100 is fully assembled. The notch edge 305 of the notch 301 also creates a stop when the tab 300 (see FIG. 3 ) of the outer casing 106 is inserted into the notch 301 . As shown in FIGS. 9 and 11 , there are preferably two ridges 133 , 135 arranged near the second end 127 of the fluid insert body 128 . The fluid insert ridges 133 , 135 are arranged along the inner perimeter of the interior 138 of the fluid insert body 128 . In the embodiment shown, there are two ridges shown, however, it should be appreciated that any number of ridges may be utilized, and only one ridge is required. As shown in FIG. 11 , the fluid insert ridges 133 , 135 have diameters greater than the remainder of the interior 138 of the fluid insert 108 . Preferably, the diameters of the fluid insert ridges 133 , 135 are 0.0125±0.0015 inches greater than the diameter of the remainder of the interior 138 , although the fluid insert ridges 133 , 135 may differ based on any desired measurements. As will be discussed more fully herein, the fluid insert ridges 133 , 135 can receive a complementary seal plug ridge 136 (see FIG. 8 ) from the seal plug 132 to secure the seal plug 132 within the fluid insert 108 . Referring to FIGS. 8 , 14 , and 15 the seal plug 132 is circular in shape with rounded edges 134 and an inner wall 137 . The seal plug 132 is used to seal the fluid insert 108 so as to prevent fluid from leaking out of the fluid insert 108 , or contamination of the fluid material stored in the fluid insert 108 . As best shown in FIG. 15 , an inner wall 137 is recessed away from the edge 142 of the seal plug 132 and engages the interior chamber 126 (see FIGS. 8 , 9 ) of the fluid insert 108 . As shown in FIGS. 15-16 , the seal plug 132 has two seal plug ridges 136 that are raised and have a height greater than the remainder of the inner walls 137 . The outer end 140 of the seal plug 132 preferably has an indentation 145 that makes it easier for users to apply force to the fluid insert 108 when it is desired to dispense fluid material form the fluid dispenser assembly 100 . In order to connect the seal plug 132 to the fluid insert body 128 , each of the seal plug ridges 136 engage the fluid insert ridges 133 , 135 arranged on the interior 138 of the fluid insert body 128 . (See FIGS. 9 and 11 .) The resistance created by the fluid insert ridges 133 , 135 and seal plug ridges 136 , permits the seal plug 132 to securely snap into place within the fluid insert body 128 . The seal plug 132 is secured within the fluid insert body 128 once the seal plug ridges 136 are locked into position within the fluid insert ridges 133 , 135 . Additional adhesives or the like may be used to further secure the seal plug 132 in the fluid insert body 128 , although it is not necessary. Referring to FIGS. 17-19 , an alternative embodiment of a seal plug 132 ′ is shown. The seal plug 132 ′ is substantially similar to the seal plug shown in FIGS. 14-16 , however the alternative seal plug 132 ′ has a diaphragm holder 150 that is in the shape of an elongated triangle. The base of the diaphragm holder 150 is attached to the interior 143 of the seal plug 132 ′. Diaphragm 152 is designed to fit within the interior of the seal plug 132 ′. The diaphragm 152 is circular in shape and its center rests upon the center 156 of the diaphragm holder 150 . It is not securely fastened to the diaphragm holder 150 and is held in place by the fluid material contained in the interior chamber 126 of the fluid insert 108 (See FIG. 9 .) The diaphragm 152 also has scrapers 154 which extend from the main body 158 of the diaphragm 152 . When the fluid insert 108 withdraws fluid material from the interior chamber 126 , the weight of the diaphragm 152 aids in pushing the fluid material towards the pump 117 , while also scraping the walls of the interior chamber 126 , as the diaphragm moves closer to the pump 117 . Due to the taper of the fluid insert 108 , the diaphragm 152 is preferably slightly smaller than the seal plug 132 so that it can extend down the length of the fluid insert body. It is also preferably comprised of a Low Density Polyethylene (commonly referred to as LDPE) material, which is very thin and flexible and permits the diaphragm 152 to give and flex as it slides down the fluid insert body 128 . The diaphragm may also be constructed and arranged to match the taper of the fluid insert 108 . It should be appreciated that any type of diaphragm may be used to scrape fluid materials from the sides of the interior of the fluid insert. Referring back to FIG. 8 , the pump 117 is a standard pump with an internal check valve, that is preferably capable of dispensing fluid materials of high viscosity, such as those known in the art. For example, an EMSAR Pump, PAV (A45) series having a 130 mcl micro liter output may be utilized. In a preferred embodiment, the pump is capable of pumping fluids having a fluid viscosity ranging from of at least 1000 cps to 10,000 cps, although a pump capable of pumping fluids having a much lower or much higher viscosity is also contemplated. The body of the pump 117 preferably has three tapered regions, a main pump body 122 , an intermediate pump body 123 , and an intake region 118 , respectively decreasing in size and length. The pump 117 preferably has an internal ball check valve 121 to regulate the amount of air permitted to enter into the interior chamber 126 of the fluid insert 108 . As shown in FIG. 12 , when the pump 117 is assembled into the fluid insert body 128 of the fluid insert body 128 , the pump 117 is only partially arranged within the fluid insert body 128 . The intake region 118 and intermediate body 123 of the pump 117 are located within the fluid insert body 128 . A portion of the main pump body 122 is located within the transition region 124 , while the remaining portion of the main pump body 122 , as well as the tip 120 , protrude from the fluid insert body 128 . The shapes and sizes of the transition region 124 of the fluid insert body 128 and main pump body 122 of the pump 117 are complementary to one another so that the pump 117 can securely fit into the transition region 124 of the fluid insert body 128 . The taper of the main pump body 122 prevents the pump 117 from completely entering the interior of the fluid insert body 128 , while permitting for a secure fit within the fluid insert body 128 . The main pump body 122 also rests against the transition region edge 113 to prevent the pump 117 from further advancing into the fluid insert body 128 . Adhesives or the like may be applied to the pump 117 and transition region 124 so as to provide additional security for the pump 117 to remain within the intermediate body 123 of the fluid insert 108 . However, due to the secure fit of the pump 117 within the fluid insert body 128 , additional adhesives are not necessary. It should be appreciated that the shapes and sizes of the complementary parts provide a cost effective means for securely fastening the parts of the fluid insert 108 together. The dosage of fluid desired to be dispensed from the dispenser assembly 100 will determine the size of the pump incorporated into the dispenser assembly 100 . For example, if it is desired to dispense 100 mcl of a fluid product, a standard pump capable of dispensing 100 mcl of a fluid product can be purchased for use in the dispenser assembly 100 of the present invention. Similarly, if it is desired to dispense 200 mcl of fluid product, a standard pump capable of dispensing 200 mcl of fluid can be utilized in the dispenser assembly 100 . The dimensions of the dispenser assembly 100 may need to be adjusted to fit the differing sizes of pumps desired. In the embodiment shown, a 130 mcl pump is used, and the size of the fluid insert body 128 and transition region 124 are complimentary to the pump configuration. When it is desired to assemble the components of the dispenser assembly 100 , the assembled fluid insert 108 ( FIG. 1 ) is inserted into the outer casing 106 ( FIG. 1 ). The fluid insert 108 is secured in the outer casing 106 when the band 130 (see FIG. 8 ) located on the exterior side of the fluid insert 108 is located in the pumping region 306 of the outer casing 106 . When the fluid insert 108 is inserted into the outer casing 106 , the band 130 must pass through the inner casing ridge 304 of the outer casing 106 and into the pumping region 306 . Referring to FIG. 13 , when the dispenser assembly 100 is in a stationary position, the fluid insert 108 will sit within the outer casing 106 , allowing a portion X and the seal cap 132 of the fluid insert 108 to protrude beyond the open end 116 of the outer casing 106 . The outermost edge 131 of the band 130 (see FIG. 8 ) will rest against the innermost edge 303 of the inner casing ridge 304 (see FIG. 3 ). In this stationary position, there is a distance X from the seal cap 132 to the edge 116 of the outer casing 106 . As shown in FIG. 13 , when it is desired to dispense fluid from the dispenser assembly 100 , a Force F is applied to the end 132 of the fluid insert 108 . Due to the reduced diameter of the pumping region 306 , (see FIGS. 3 and 5 ) the fluid insert 108 is able to move a short distance within the outer casing 106 . The movement of the fluid insert 108 forces retraction of the springs 115 into the pump 117 , so that, the tip 120 of the pump 117 is able to retract into the pump 107 . When the tip is retracted into the pump 107 , fluid material is withdrawn from the fluid material contained in the pump 107 and expelled through the opening 107 of the outer casing 106 . In its retraced position, the seal plug 132 abuts the outer edge 116 of the outer casing 106 , thereby eliminating the distance X present when the fluid dispenser 100 is in a stationary position. When the Force F is released, the fluid insert 108 will return to its fully extended position because the Force F that is transferred to the springs 115 is also released. This simultaneously causes the pump 117 to withdraw fluid material from the interior chamber 126 of the fluid insert body 128 , and store it in the pump 117 until another Force F is applied. It should be noted that although a user may continue to apply a Force F to the fluid insert 108 , no additional fluid material will be dispensed until the Force F is released, and a new Force F is applied. In this way, only predetermined amounts of fluid materials are dispensed at any one given time. When the fluid insert 108 is in its actuated or retracted position, the innermost end 129 (See FIG. 8 ) of the band 130 abuts the edge 302 (See FIG. 3 ) of the outer casing 106 . The notches 301 (See FIG. 9 ) will move along the tabs 300 (See FIG. 3 ) and the tip 120 of the pump 117 will be guided by the walls 600 (See FIG. 7 ) located on the interior 117 of the outer casing 106 . In this position, the tip 120 of the pump 118 is partially arranged within the pump 120 , and the distance X that is visible when the fluid insert sits in its stationary position (see FIG. 13 ) within the outer casing 106 is no longer visible. Referring to FIGS. 20-21 , the end cap 102 is shown. The end cap 102 helps to prevent fluid material contained within the fluid insert 108 from spoiling because it provides an additional outer seal to keep the fluid material fresh. The end cap 102 is circular in shape and designed to fit over the applicator 104 and connector 110 of the outer casing 106 . (See FIG. 1 .) The inner walls 250 of the end cap 102 fit snugly over the connector 110 of the outer casing 106 . Due to the minimal differences between the diameter of the end cap 102 and the diameter of the connector 110 , the end cap 102 can be securely positioned over the outer casing 106 so as to remain in place until it is desired to remove the end cap 102 from the outer casing 106 . As shown in FIG. 22 , an alternative embodiment of the end cap 102 ′ is shown. A declogger 252 is arranged at the center of the interior 250 ′ of the base 254 ′ of the end cap 102 ′. The declogger 252 is preferably in the shape of a cylinder that will fit within the opening 107 ′ of the outer casing 106 ′, but any shape of declogger that will fit within the opening 107 of the outer casing 106 will suffice. Placement of the declogger 252 within the end cap 102 ′ helps to prevent any clogging that may occur from fluid materials that dry and clog the opening 107 of the applicator 104 . An important feature of the present invention concerns the ability of the dispenser assembly 100 to be moved from a locked position to an unlocked position in order to avoid accidental discharge of the fluid material contained in the fluid insert 108 . The lock and unlock feature preferably operates by allowing the fluid insert 108 to rotate between a locked and unlocked position. When the dispenser assembly 100 is in an unlocked position, the dispenser assembly 100 is able to discharge fluids through the opening 107 of the outer casing 106 . This occurs when the tabs 300 located on the outer casing 106 are aligned with the notches 301 of the fluid insert 108 , so that the tabs 300 slide within the notches 301 . The first side 160 (see FIGS. 8-9 ) of the stop 111 will also be adjacent to the tab 300 (see FIG. 7 ). The stop 111 will prevent any additional rotation of the fluid insert 108 in the direction of the first side 160 of the stop 111 , to notify a user that the fluid insert 108 cannot be further rotated in that direction. As shown in FIG. 14 , directional arrows can be placed on the top of the seal plug 32 of the fluid insert to further provide visual instructions for the user to place the seal plug 132 into an open position. When the fluid insert 108 is rotated in the opposite direction, the fluid insert 108 moves from the unlocked position to a locked position. In this position, the tab 300 and notch 301 do not align. The tabs 300 will instead contact the inner casing outer edge 109 (See FIGS. 8-9 ), thereby preventing the fluid insert 108 from moving within the pumping region 306 of the outer casing 106 . The fluid insert 108 can only be rotated until the second side 109 of the stop 111 (see FIGS. 8-9 ) is adjacent the notch 300 ′. Thus, the fluid insert 108 is in a locked position whenever stop 11 of the fluid insert 108 is located between the notch 300 and notch 300 ′. In this locked position, fluid materials are unable to accidentally discharge from the fluid dispenser 100 . Due to the location of the tabs 300 and notches 301 on opposed sides of the outer casing 106 and fluid insert 108 , the fluid insert 108 moves from a closed position to an open position whenever the fluid insert 108 is rotated 180°. It should be appreciated, however, that the number of tabs and corresponding notches will determine the amount of rotation necessary to move the fluid insert 108 from a locked position to an unlocked position. The fluid dispenser assembly 100 according to the embodiments described herein is cost effective for the manufacturer, as well as the company desiring to purchase dispensers that can be used to sell their fluid products, such as a cosmetic company. It is comprised of few parts that can be “snapped” into place due to the various shapes of the components. This eliminates the need for the added costs of adhesives and the like, or the additional step of “screwing parts” together. The manufacturer therefore has few parts to produce and assemble, allowing the manufacturer to significantly cut production and materials costs. Due to the design of the dispenser assembly 100 , the manufacturer can then provide the dispenser assembly 100 almost fully assembled to a purchasing company desiring to solicit their fluid materials in a particular dispenser. The pump 107 and fluid insert body 108 can be preassembled into the outer casing 106 , and the end cap 102 can be placed over the applicator 104 of the outer casing 106 . The only part not assembled at that time is the seal plug 132 , which as discussed herein, is assembled after the filling process. The assembled parts of the dispenser assembly 100 are then placed onto a standard filling apparatus, making them immediately available for filling. The simple cylindrical shape of the applicator and the fact that there are no additional obstructions protruding from the dispenser assembly 100 , make the dispenser assembly 100 fully compatible with standard industrial filling machines. For example, the fluid dispenser 100 is fully compatible with a standard filling apparatus such as the NORDENMATIC 3003/5002 line, that is capable of filling 300-500 tubes per minute. The compatibility between the dispenser assembly 100 and a standard filling machine eliminates the need for purchasing additional parts to make the fluid dispenser compatible with the filing machine. Once the dispenser assemblies are positioned on the filling machine, the filling machine will dispense fluid material from the filling machine into the open end 127 of the fluid insert body 128 . Thereafter, the seal plug 132 can be snapped into the fluid insert by a standard capping machine, thereby fully completing the assembly of the fluid dispenser 100 . The capping process may also take place as part of the high speed filling process. The compatibility of the dispenser assembly 100 with standard filling apparatuses, combined with the relative ease of sealing the dispenser assembly 100 after it has been filled, are just some of the advantages of this embodiment of the present invention over the prior art. FIG. 23 shows an alternative embodiment of a fluid dispenser 200 . The outer casing 201 is curved in shape, so as to provide grips 210 for a user to hold the fluid dispenser 200 . The fluid insert 212 protrudes from the end 214 of the outer casing 200 , and is identical to the fluid insert shown in FIG. 1 . This alternative fluid dispenser 200 operates in substantially the same way as the fluid dispenser 100 previously discussed. A Force F is applied to the end of the fluid insert 212 , which causes actuation of the pump (not shown) contained in the fluid insert 212 . Fluid material is then dispersed from the fluid insert 212 to the opening (not shown) of the outer casing 201 . To seal the fluid dispenser 200 , a dispenser cap 216 fits over the outer casing 201 and prevents the fluid material contained in the fluid insert 212 from spoiling. It should be appreciated that the fluid insert 212 can consistently remain the same shape, while the outer casing 201 may take on any desired shape or form. This is advantageous for cosmetic companies and the like seeking to sell a customized dispenser. Although the invention herein has been described with reference to particular embodiments and preferred dimensions or ranges of measurements, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. Additionally, it is to be appreciated that the present invention may take on various alternative orientations. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

The present invention is directed toward a cost effective instrument for storing a fluid material, and applying a predetermined amount of the fluid material to a surface. The instrument is comprised of few parts including an outer casing and a fluid insert, making the instrument cheaper to manufacture, and easy to assemble. The embodiments disclosed can be provided in a pre-assembled form to cosmetic companies and the like seeking to fill a dispenser with their fluid cosmetic products. The ability to provide dispensers in a pre-assembled form, combined with the compatibility of the fluid dispensers with industrial high speed filling machines, reduces the overall filling costs to the cosmetic company, as well as the cost to the consumer.

PRIORITY CLAIM [0001] This application claims the benefit of the filing date of Canadian Patent Application Serial No. 2,708,657, filed Jun. 28, 2010, for “Off-Road Motor Vehicle Warning System,” the entire disclosure of which is hereby incorporated herein by this reference. TECHNICAL FIELD [0002] This invention relates to vehicle warning systems and, in particular, to a traffic warning system for off-road vehicles, such as snowmobiles and all-terrain vehicles. BACKGROUND [0003] For many years, riding off-road vehicles, such as snowmobiles and all terrain vehicles (ATVs), has become a major organized recreational sport. In the province of Ontario alone, there are approximately 40,000 kilometers of snowmobile trails. Many of these trails are maintained by groomers, which are typically approximately 3 meters (10 feet) wide and thus maintain a trail width of at least 3 meters. The average off-road motor vehicle is approximately 1.3 meters (4 feet) in width. However, due to the nature of an off-road environment, many portions of such trails provide very little room for off-road vehicles to pass one another. [0004] Over the years, a hand signal courtesy protocol has evolved to avoid accidents between off-road vehicles. With a legal maximum posted speed of 50 kilometers per hour (km/hr), or in some areas 70 km/hr, the approaching speed of oncoming vehicles can exceed 100 km/hr on a trail or roadway, with little more than a few feet of clearance, leaving very little room for error. [0005] As an example of a protocol that has developed to avoid accidents, in a group of off-road vehicles such as snowmobiles or ATVs, the leader will provide a warning to oncoming traffic and the drivers in their own group by raising their left hand as a signal. For example, in a typical off-road trail protocol, the lead driver in each approaching group provides a warning of an oncoming vehicle to the others in their group that are following, by raising their left hand. The lead driver will also signal the approaching vehicle by raising a number of fingers to indicate the number of vehicles following the leader in the group. The second driver in the group does the same, and this protocol is repeated until the last driver raises a clenched fist to indicate to the oncoming vehicle that it is the last vehicle in the group. [0006] However, given the speeds of approaching vehicles, the narrow width of such trails, and the unevenness and irregular surface jutting back and forth in tracks formed by previous vehicles, this protocol still presents dangers to approaching vehicles, particularly in times of limited visibility. Furthermore, a danger is presented in this conventional method of warning oncoming vehicles by requiring the driver of each vehicle to remove one hand from the vehicle's steering means. [0007] It would be advantageous to provide a system for warning motor vehicles and others of approaching traffic or hazards, and indicating the number of vehicles approaching. BRIEF DESCRIPTION OF THE DRAWINGS [0008] In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention: [0009] FIG. 1 is a schematic view of a sensor for an off-road motor vehicle warning system embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION [0010] In an embodiment, each vehicle is provided with a warning system module, comprising a transmitter and receiver (or transceiver) and one or more warning lamps, which may be a single color or, preferably, different colors. [0011] FIG. 1 illustrates one embodiment of a transmitter-receiver according to the invention. A 12 V DC power source 10 (for example, the vehicle battery, not shown) is coupled to an indicator lamp that emits light in the visible spectrum, for example, an LED module 12 . The LED module 12 may comprise an amber LED and a green LED, or white LEDs covered by amber and green lenses. Amber would indicate “caution, approaching vehicle,” and green would indicate the last vehicle in the group to signal that the way is clear. The amber and green lamps can be in different locations on the vehicle and, in the preferred embodiment, both may flash for greater visibility. [0012] However, if desired, a single color indicator lamp of LED module 12 may be used, being white or any other selected color. If a single light color is used, it can flash as a caution indicator and remain illuminated to indicate the last vehicle in the group. [0013] The power source 10 is also coupled to a 5 V DC low current power supply 14 for powering the transmitter-receiver circuitry. Microcontroller 16 is coupled to the power supply 14 and comprises a clock circuit, which transmits pulses to power the transmitter 20 . The transmitter 20 comprises at least one infrared (IR) LED, or a plurality of IR LEDs, which may be connected in series as shown to form IR LED module 22 , which emits IR radiation at a selected IR frequency. One side of the IR LED module 22 is coupled to the power supply 14 , and the other is grounded through high-speed transistor Q 2 (which may, for example, be a MOSFET). [0014] Microcontroller 16 thus transmits a series of pulses, preferably continuously. The clock signal generated by microcontroller 16 toggles pin 5 of microcontroller 16 high and low, for example, at 38 kilohertz (KHz) generating a string of ten evenly spaced pulses followed by a short quiescent interval over 25 ms. The resulting pulses are transmitted to the gate of high-speed transistor Q 2 , which, in turn, grounds the IR LED module 22 at the selected pulse rate, causing the LEDs in LED module 22 to continuously emit a series of IR pulses at the selected pulse rate. [0015] Microcontroller 16 is also coupled to IR receiver module 30 . IR Receiver module 30 reacts to IR pulses only at the selected pulse transmit frequency (38 KHz in the example given), and does not respond to any other ambient ElectroMagnetic Radiation (EMR). The IR receiver module 30 shown in FIG. 1 , by way of example, is a Vishay model TSOP34338, which has the advantage that it does not react unless it receives at least six pulses in the selected frequency range, thereby reducing opportunities for false alarms. When the IR receiver module 30 detects at least six pulses from a transmitter 20 , the IR receiver module 30 output goes low, pulling pin 8 of microcontroller 16 low and, in turn, pulling pin 3 of microcontroller 16 high. The output of pin 3 is transmitted to the gate of Q 3 , which, in turn, grounds the visible LED module 12 causing the LEDs in module 12 to illuminate. Preferably, the clock circuitry in microcontroller 16 intervenes to toggle pin 3 between high and low states a few times each second, causing the LEDs in the visible indicator module 12 to blink for greater visibility. [0016] The operation of the invention will now be described in the context of an oncoming vehicle approaching a group of five off-road vehicles, for example, snowmobiles, all of which are equipped with the warning system of the invention. The transmitter 20 of an approaching vehicle constantly emits a series of IR pulses via IR LED module 22 , preferably confined to an arc of approximately 30 to 40 degrees directly in front of the vehicle. When the first vehicle in the group comes into range of the approaching vehicle, the IR signal is received by the IR receiver module 30 of the first vehicle in the group. The first vehicle's IR receiver module 30 detects the IR pulses from the oncoming vehicle at the selected transmit rate, causing microcontroller 16 to emit a signal to Q 3 so that visible indicator lamp of LED module 12 on the first vehicle in the group illuminates (preferably, the signal to Q 3 is pulsed, causing visible indicator lamp 12 to flash). The second, third and fourth vehicles' IR receiver modules 30 each respectively react in the same fashion upon coming into range of the signal transmitted from the approaching vehicle. [0017] The fifth (last) vehicle in the group has preferably set its visible indicator module 12 to “trailing vehicle” mode, which is distinct from the visible indicator module 12 of the first four vehicles in the group. For example, where amber and green indicator lamps are used, both preferably flash for greater visibility, but in the normal (front or intermediate vehicle) warning mode, the amber light is enabled and flashes, whereas in the “trailing vehicle” mode, the green light is enabled and flashes. Where a single color of indicator light is used, the visible indicator module 12 of the vehicle in the “trailing vehicle” mode may provide a continuous signal (rather than a flashing signal, as in the case of the front and intermediate vehicles), to indicate to the approaching vehicle that the fifth vehicle is the final vehicle in the group. A driver of the approaching vehicle, seeing the normal warning light (flashing amber, in the two-color embodiment described above), therefore, knows that there are more vehicles in the group that it is approaching and about to pass, and can react to pass safely on a narrow trail. There is no reduction in control, as is the case when hand signals are used, because in the case of all vehicles, both of the driver's hands can remain on the vehicle steering actuator (such as handle bars, a steering wheel, etc.). [0018] Slow moving vehicles such as groomers on an off-road trail can be provided with a similar warning module, optionally providing a different colored visible indicator light 12 , which would instantly indicate to an approaching vehicle that it is approaching a slow moving, and typically wide, grooming vehicle. The driver of the approaching vehicle can react accordingly. Advantageously, the grooming vehicle may have multiple transmitters, allowing it to transmit its signal over a wider arc. Optionally, the grooming vehicle transmitter circuit 42 transmits at a different frequency or signal pattern from vehicles using the trail to activate the warning indicator lamp 12 of approaching vehicles; a second receiver module (not shown) on the approaching vehicle, responsive to the unique grooming vehicle frequency or signal pattern could activate a different colored light on the approaching vehicle, or an audible indicator such as a buzzer or siren, to indicate to the driver of the approaching vehicle that it is approaching a grooming machine (or some other trail hazard). [0019] The electronics may be powered by the off-road vehicle battery, a separate battery or solar power. [0020] Portable warning modules can be provided with a portable power source, such as a battery or solar power, and placed along the trail to warn of stationary hazards on the trail, such as a washed out portion, open water crossing, ice, logging trucks, disabled equipment, etc. [0021] Other potential uses for the warning system of the invention include: construction, particularly road construction; train movement; fire response team and other such road hazards. It can also be used on multi-user trails for hikers, cross-country skiers, snowshoers and horseback riders, who could carry a transmitter or a transmitter-receiver of the invention to warn vehicles of their presence. The device of the invention can also be installed in vehicles as a safety device to warn of intruders, or to prompt inspection of a vehicle such as a school bus to assure that all children have exited at the end of a trip. [0022] Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention.

A warning system for vehicles that comprises a transmitter and a receiver for respectively transmitting a signal to an approaching vehicle or receiving a signal from an approaching vehicle. A light actuated upon receiving a signal from another vehicle and visible to the other vehicle indicates to the other vehicle that it is approaching a vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority of U.S. Provisional Patent Application Ser. No. 60/787,214, filed Mar. 30, 2006. The disclosure of the prior application is hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a node and more specifically but not exclusively to a node within a mobile communications device. 2. Description of the Related Art User equipment have become application rich personal devices capable of more than voice communication. It is for example difficult to purchase user equipment which does not feature a digital camera connected to internal digital image processing elements, polyphonic audio synthesizing equipment. It is also common for user equipment to be connected or incorporate advanced features such as satellite navigation and audio and video recording and playback. In order that the components of the user equipment can communicate with each other user equipment is equipped with a communications link or network designed in such a way that internal systems can communicate with each other to generate this functionality, and that external systems can also be connected to the user equipment, to enable the user equipment to be upgradeable. A known example of such a communication network is the serial interface known as D-Phy (proposed by the mobile industry processor interface alliance (MIPI)). The D-Phy serial interface supports as many as four lanes operating at rates up to 1 Gbit per second per lane and uses low-voltage, source-synchronous, scalable-signalling technology. Operating on these physical networks are protocol stacks. The protocol stacks define how data is transmitted across the physical network. For example the MIPI unified protocol (UniPRO) defines standards for transmitting data packet over the D-Phy network. The current MIPI UniPRO standards and the protocols used by other proprietary user equipment networks suffer from the problem of data integrity—in other words relying that the data transmitted by the data originator (or first end node) of the network has been received and is being processed by a data final destination (or second end node). In these networks the nodes have a limited capacity for receiving and processing data. Thus when the final destination node reaches the capacity the node can not physically receive or process the any further data transmitted through the network. In these situations the typical network protocol allows implements either a stop or discard process. The stop process instructs the final destination node to stop accepting traffic from the network. This results in “head of line blocking” where the data being transmitted is queued in the network nodes between the two end nodes. This queued data causes the network nodes to effectively block the node from passing any further data until the next node accepts the current data packet. This blocking therefore propagates from the final destination node to the originator node resulting in partial or full blocking of the network. The discard process instructs the final destination node to drop a packet. This allows the network to operate efficiently and without blockage, but results in a loss of end-to-end (E2E) reliability as even if the data is reaches the final destination node the data can not be guaranteed to have received and processed the data. Point-to-point (P2P) data flow control is known. In such systems the data transmitted between two immediate nodes can be acknowledged to confirm its receipt. These P2P systems can be divided into two groups. The first group employs flow control without synchronisation information by using flow control tokens. One example is the Spacewire system. These systems have further problems in that they are required to employ complex mechanisms for recovering loss of the flow control tokens. Furthermore it is difficult to estimate the data overhead of transmitting control tokens which prevent such systems from producing accurate quality of service provisions in bandwidth limited networks. The second group of P2P systems operate flow control with synchronisation information. These typically apply techniques synchronising the flow control information at both ends with every flow control signalling packet and therefore are complex and require a greater signalling overhead than the token based group. An example of this synchronised flow control signalling can be found the P2P flow control mechanism featured within the current MIPI UniPRO specifications. Using the P2P flow control mechanisms for both point-to-point and end-to-end reliability produces additional complexity with regards to signalling overhead and complexity of nodes within the network whilst producing a system which is not optimal for end-to-end flow control. SUMMARY OF THE INVENTION Embodiments of the present invention aim to address or at least partially mitigate the problems disclosed above. According to a first aspect of the invention there is provided a node arranged to communicate with at least one further node; comprising: a buffer arranged to receive data transmitted from the at least one further node; an output arranged to transmit data to the at least one further network element, wherein the data comprises information about the ability for the buffer to receive further data transmitted from the further node. The node may further comprise a detector arranged to indicate capacity within the buffer to receive the data from the at least one further node; The data transmitted to the at least one further node may be a data packet. The information about the ability for the buffer to receive further data transmitted from the further node is preferably an end-to-end flow control signal. The node is preferably arranged to communicate over a network within an user equipment. The node is preferably arranged to communicate over a network at least partially external to an user equipment. The network is preferably a D-Phy network. The data packet may be a UniPRO standard data packet. The information about the ability of the buffer to receive further data transmitted from the further node is preferably located within the ATyp=xx field of the UniPRO standard data packet. The information about the ability of the buffer to receive further data transmitted from the further node is preferably the binary value 01 in the ATyp=xx field. The data may comprise a header and a payload, wherein the information about the ability for the buffer to receive further data transmitted from the further node is located within at least one of: the header and the payload. The detector is preferably arranged to indicate when the capacity of the buffer is greater than or equal to a predetermined capacity value. The predetermined capacity value is preferably transmitted to the node on initialisation of the communication with the at least one further node. The node may further comprise reservation logic for reserving the predetermined capacity value within the buffer. According to a second aspect of the invention there is provided a node arranged to communicate with at least one further node; comprising: an input arranged to receive information about the ability for a buffer of the at least one further node to receive further data transmitted from the node; a detector arranged to detect the information; a counter arranged store a value to indicate the ability of the at least one further node to receive further data packets transmitted from the node; an output arranged to transmit further data to the further node dependent on the counter value indicates that the at least one further node has the ability to receive the further data. The reception of the information about the ability for a buffer of the at least one further node to receive further data is preferably arranged to increment the counter value. The counter is preferably arranged to increase the counter value dependent on the information about the ability for a buffer of the at least one further node. The counter is preferably arranged to decrement the counter value when the output transmits further data to the at least one further node. According to a third aspect of the invention there is provided a network comprising at least one node as claimed latterly and at least one node as also described formerly. According to a fourth aspect of the invention there is provided a network comprising a first node and at least one further node, wherein information is provided within data comprising a payload transmitted at least one of the first node to the at least one further node and from the at least one further node to the first node. According to a fifth aspect of the invention there is provided a method for communicating between a first node and at least one further node in communication over a network, comprising the steps of: transmitting from the first node to the at least one further node data comprising information about the ability of the first node to receive further data transmitted from the further node, and receiving at the at least one further node the data comprising information about the ability of the first node to receive further data transmitted from the further node. The method may implement an end-to-end flow control mechanism The method may further comprise the step of: incrementing a counter value within the at least one further node dependent on the reception of data comprising information about the ability of the first node to receive further data transmitted from the further node. The step of incrementing the counter value may increment the counter value dependent on the value of the information. The method may further comprise the steps of: transmitting further data from the at least one further node to the first node dependent the counter value; and decrementing the counter value. The step of decrementing the counter value may decrement the counter value dependent on the size of the further data transmitted from the at least one further node to the first node. According to a sixth aspect of the present invention there is provided a computer program arranged to operate a computer for communicating between a first node and at least one further node in communication over a network, comprising the steps of: transmitting from the first node to the at least one further node data comprising information about the ability of the first node to receive further data transmitted from the further node, and receiving at the at least one further node the data comprising information about the ability of the first node to receive further data transmitted from the further node. BRIEF DESCRIPTION OF THE DRAWINGS For better understanding of the invention, reference will now be made by way of example to the accompanying drawings in which: FIG. 1 shows a schematic view of a user equipment network over which embodiments of the present invention may be implemented; FIG. 2 shows a schematic view of the data flow as produced by the present invention; and FIG. 3 shows a schematic view of a E2E flow control signal embedded in a data packet as employed by embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention relate particularly but not exclusively to MIPI UniPro architecture on top of D-Phy network as employed in user equipment. Embodiments of the invention may be applicable to other user equipment networks for connecting elements within user equipment. For example other embodiments may be employed for use over the Nokia proprietary discobus architecture. Reference is made to FIG. 1 which shows a user equipment comprising several component subsystems connected together via the D-Phy network 51 . For clarity components of the user equipment not directly concerned with the present invention are not shown. It should be appreciated that while embodiments of the invention have been described in relation to user equipment such as mobile stations, embodiments of the invention are applicable to any other suitable type of user equipment. In this document the term, terminal, where used is intended to cover all the examples of user equipment described. The term user equipment can apply to any appropriate mobile device adapted for communication to a wireless cellular communications network. For example, the mobile user equipment may access the cellular network by means of a Personal computer (PC), Personal Data Assistant (PDA), mobile station (MS) and so on. The network 51 comprises a series of nodes 53 which act as switches or routers for receiving and distributing packets in a known manner. The network 51 is also shown connected to a series of processors or sub-systems for carrying out various processes or applications associated with the user equipment. For example, the network is connected to a communications processor 3 (for communicating with the cellular network), an applications processor 5 (arranged to controlling the operation of applications), a radio/TV processor 7 (arranged to receive either analogue/digital radio/TV signals), a Bluetooth processor 9 (arranged to receive and transmit Bluetooth data over a Bluetooth communications channel), a camera sub-system 11 arranged to receive and transmit digital image data from the camera (the camera in some embodiments be connected to the network and transmit raw data to the camera sub-system 11 ), an audio sub-system 13 (arranged to transmit audio data for example MP3 audio data), and a I/O sub-system 15 connected to the earpiece/speaker 17 and the microphone 19 . These processors/subsystems described are examples only and some embodiments of the present invention may have more or fewer sub-systems connected to the network 51 . Furthermore in some embodiments at least one sub-system is connected to the network 51 via an external connection not shown in FIG. 1 . As has been described previously P2P flow control can be used by the network 51 , so that each sub-system or network node can guarantee that the packet integrity between nodes. With regards to FIGS. 2 and 3 an End-to-End flow control (E2E FC) mechanism, embodying the present embodiments of the invention, is described with respect to a D-Phy network. With regards to FIG. 2 the data flow of an embodiment of the E2E flow control mechanism is shown. FIG. 2 shows two network end nodes, node A 251 and node D 257 , in communication with each other via intermediate nodes, node B 253 and node C 255 . At least one of the end nodes comprising, a output for transmitting data to the network, an input for receiving data from the network, a buffer connected to the input for storing the received data, and a detector (such as a pointer) arranged to indicate the capacity within the buffer to receive further data. Furthermore the other end node comprises a counter indicating the capacity of the end node. The other end node comprises an input arranged to receive data from the network, an output for transmitting data to the network, data processing means, which can be hardware, software or a combination thereof, arranged to detect or evaluate the counter value and allow or stop the other end node from transmitting data containing a payload to the end node. In a network arranged for duplex (two-way) communication system both end nodes comprise both sets of elements described above. The arrangement described hereafter demonstrates an example of the flow control mechanism as implemented within an embodiment of the invention, and it would be understood by the person skilled in the art that the two end nodes could be connected directly together or separated by any number of intermediate nodes in further embodiments. The steps 151 to 161 describe the ‘crediting’ E2E flow control steps, or ‘credit’ cycle. In other words the situation when a first end node indicates to another end node that there is free space on the first end node. The steps 163 to 171 describe the ‘debiting’ E2E flow control steps, or ‘debit’ cycle. The ‘debit’ cycle is the situation when the node uses the ‘credit’ allocated to the node to transmit data packets. In step 151 the network end node A 251 determines that it has capacity to receive at least one portion of data (or has at least one ‘free-space’ for data). This in an embodiment of the invention can be implemented by a pointer or pair of pointers pointing to memory locations in a buffer. The number of memory locations between a read and write pointer in a buffer can indicate the presence and amount of free memory available. In step 153 , in response to this determination, end node A 251 transmits via its output an E2E flow control signal to node B 253 (the E2E flow control signal is addressed to end node D 257 but has to initially be transmitted to intermediate nodes B 253 and C 255 ). The transmission of the E2E flow control signal is represented in FIG. 2 by the solid line with an arrowhead showing the direction of transmission. Node B 253 receives the E2E flow control signal and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to end node A 251 that the E2E flow control signal has been successfully received by node B 253 . The P2P flow control mechanism is represented in FIG. 2 by the dashed line with an arrowhead showing the direction of the acknowledgement message. In step 155 , after transmitting the E2E flow control signal, node A reserves the free space in the receiver or processor buffer so that only packets received originating from end node D 257 can be stored in the reserved free space. This can be implemented within a buffer by a pointer pointing to a memory location within a buffer which points to the next unreserved memory location. In step 157 node B 253 transmits the E2E flow control signal to node C 255 . Node C 255 receives the E2E flow control signal from node B 253 and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to node B 253 that the E2E flow control signal has been successfully received by node C 255 . In step 159 node C 255 transmits the E2E flow control signal to end node D 257 . Node D 257 receives the E2E flow control signal from node C 255 and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to node C 255 that the E2E flow control signal has been successfully received by node D 257 . Providing the P2P flow control mechanism within the network is operational and not producing erroneous results, end node A 253 can assume that the E2E flow control signal has been correctly transmitted to end node D 257 . In a further embodiment of the invention, a further safeguard is implemented. In this embodiment end node D 257 , on receiving the E2E flow control signal, transmits to end node A 251 via the nodes C 255 and B 253 an acknowledgement message confirming the successful receipt of the E2E flow control signal. In step 161 , end node D 257 on receipt of the E2E flow control signal increments an internal counter. The internal counter indicates the ‘credit’ limit of the end node A, in other words the amount of free-space reserved at node A 251 for node D 257 data. In step 163 , end node D 257 determines that is has a data packet to transmit to end node A 251 . End node D 257 then examines the value stored in its internal counter. If the counter is equal to zero, and therefore there is no indicated free space, then the method passes to step 163 a . In step 163 a end node D 257 does not transmit any packets to end node A and will pass back to step 163 to check the internal counter at some time later. In some embodiments of the invention the end node D waits a predetermined or random time period before performing the internal counter check again, in other embodiments of the invention the end node D only checks the internal counter after receiving an E2E flow control signal. If the counter is not equal to zero, then the method passes to step 165 . In step 165 , end node D 257 transmits a data packet to node C 255 (the packet is addressed to end node A 251 but has to initially be transmitted to intermediate nodes B 253 and C 255 ). The transmission of the packet is represented in FIG. 2 by the thick line with an arrowhead showing the direction of transmission. Node C 255 receives the packet and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to end node D 257 that the packet has been successfully received by node C 255 . The P2P flow control mechanism is represented in FIG. 2 by the dashed line with an arrowhead showing the direction of the acknowledgement message. In step 167 node C 255 transmits the data packet to node B 253 . Node B 253 receives the data packet from node B 255 and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to node C 255 that the data packet has been successfully received by node B 253 . In step 169 node B 253 transmits the data packet to end node A 251 . Node A 251 receives the data packet, via the node input, from node B 253 and using a conventional P2P flow control mechanism (such as the transmission of an acknowledgement message to the transmitting node) confirms to node B 253 that the data packet has been successfully received by node A 251 . In step 171 end node D decrements the internal counter value. In a further embodiment of the invention, a further safeguard is implemented. In this embodiment end node A 251 , on receiving the data packet, transmits to end node D 257 via the nodes C 255 and B 253 an acknowledgement message confirming the successful receipt of the data packet. It is then in response to this step that the end node D decrements the internal counter. Thus providing the P2P flow control mechanism within the network is operational and not producing erroneous results, end node D 257 can assume that the data packet has been correctly transmitted to end node A 251 . Furthermore the E2E flow control mechanism as described above also enables the end node D to assume that the data packet is also not simply going to be discarded by end node A even if it has been correctly transmitted to end node A 251 . Each E2E flow control signal received by the end node provides the end node with the permission to sending one portion of data. The size of one portion or the ‘free space’ can be set dependent on each connection—for example to be dependent on the buffer sizes of the end nodes or the intermediate nodes. In some embodiments of the invention this is determined during the initial connection establishment procedure. In other embodiments of the invention the portion size or ‘free-space’ is set using a preconfigured connection setting. Although FIG. 2 shows a ‘debit’ cycle (i.e. a transmission of a data packet) immediately following a ‘credit’ cycle (i.e. the transmission of a E2E flow control signal) it would be understood by the person skilled in the art that at least two ‘debit’ or ‘credit’ cycles can be implemented without intervening ‘debit’ or ‘credit’ cycles respectively. For example end node A 251 after reserving the portion or ‘free-space’ size at the end node A 251 after detecting further sufficient capacity for a further portion could transmit a further E2E flow control signal to the end node D 257 before the end node D transmits a data packet. In some embodiments of the invention where the network is a true duplex network the ‘debit’ cycles and ‘credit’ cycles can be implemented concurrently, for example providing that there is sufficient credit (i.e. the internal counter is not equal to zero) node D 257 transmits a data packet to end node A 251 , whilst on detecting sufficient capacity in end node A 251 transmits an E2E flow control signal to end node D 257 . The above ‘credit’ cycle from node A 251 to end node D 257 describes the situation where a connection has been established. In such a system the end node D 257 does not initially know the end node A 251 capacity and is only informed of it by the transmission of E2E flow control signals. If the capacity of end node A is high for example after resetting the user equipment, the establishment of the connection or after flushing the buffer, the data packet rate from end node D 257 to end node A 251 is lower than the optimal rate as node D 257 awaits E2E flow control signals before sending data packets. In some embodiments of the invention an E2E flow control signal is transmitted with the connection establishment confirmation and at the connection restart after reset. This E2E flow control signal is interpreted by the end node as a full buffer ‘credit’ i.e. permission to use the full buffer capacity of the other end node. In such embodiments the end node determines the other end node's buffer size (for example all end nodes of the network can have a predefined minimum buffer size—which is used as the initial counter value, or the buffer size is transmitted as part of the connection establishment message—which is then used as the initial counter value). FIG. 3 shows one possible implementation of the E2E packet data unit (PDU) 51 . The PDU comprises a header 301 , body 303 and tail portion 305 . The header 301 comprises the fields: ESC_DL which is a special code, which allows to distinguish control symbols from data symbols, SoF which is a code that tells that this control symbol starts a new frame, TC/PLx which defines the traffic class or priority level field which identifies to which priority group the frame belongs (has direct impact on the treatment procedure in both ends of the link), Rsv which is a reserved field, Ext=x which is an extension bit which permits packet header to be extended (this bit is set to 0 for conventional header length, but is set to 1 to indicate an extension of the header into the first symbols of the payload, EoM which indicates that this frame is the last frame of the Transport layer message (which for transmission over the network might be split to a number of Datalink layer frames), CportID which is the unique ID number of a port at the destination device within a stack of ports for Connection Oriented applications, and DeviceID which is the unique address of the destination node. The header also comprises the ATyp=xx field 311 , where xx is a pair of binary values. The body 303 of the datagram is contains the payload field, the payload is typically the data to be transmitted. The tail 305 of the datagram comprises the fields: ESC_DL, EoF odd/even which indicates that this is the last control symbol of the frame, Frame sequence number which is a sequence number of the frame in the Datalink layer transmission, which is used for providing P2P reliability, and CRC16 which is a 16 bit cyclic redundancy check value of the payload data. In embodiments of the invention the E2E flow control signal is stored as a value of the ATyp=xx header field 311 or by not currently used by the data packet for any other use. For example The value in an embodiment to indicate that the data packet contains an E2E flow control signal is where the data packet header field has a value ATyp=01. As can be appreciated the E2E flow control signal embedded within the UniPRO data packet structure has a further advantage in that the E2E flow control signal can be transmitted as part of a data packet from one end node to the other end node. In such an embodiment the ‘credit’ cycle for the link from end node A 251 to end node D 257 can be embedded within the ‘debit’ cycle for the link passing the opposite way—in other words from end node D 257 to end node A 251 . Where data traffic is unequal or one-directional the data packets containing the E2E flow control signal can be transmitted by transmitting an empty packet (i.e. a data packet that contains only a header and tail and with no payload). Thus embodiments of the invention proposes an E2E flow control mechanism which is both efficient (the signalling overhead being contained with data being transmitted by the return path) and is also robust (the embodiments of the invention use the P2P flow control mechanisms implemented with regards to data packet transmission), and with minor modification of the end node logic (the end nodes are required to examine one of the data packet fields and to comprise a counter which is modified on transmission of payload containing packets to the end node and receipt of packets comprising predetermined header values). The embodiments further results in a minimal increase of the signalling overhead and under certain conditions do not even introduce additional overhead at all. Comparing to the embodiments of the present invention against prior art solutions, the embodiments are more efficient in respect of all consumed resources—implementation gate count, power consumption, and signalling overhead. Furthermore the amount of E2E flow control signalling overhead is predictable, which enables the maintenance of Quality of Service guaranties for networks with bandwidth reservation. As will be appreciated by the person skilled in the art, although FIG. 3 shows the E2E flow control signal being embedded within a UniPRO datagram and specifically within the ATyp=xx header field 311 , it would be appreciated that the E2E flow control signal could be embedded within a different part of the datagram. In a further embodiment of the invention the E2E flow control signal could be embedded within the data packet payload. In further embodiments of the invention the UE network is a serial network other than a Phy-D network and the protocol used to transmit packets is other than the UniPRO standard used to transmit UniPRO packets as shown in FIG. 3 . In these embodiments the E2E flow control signal from a first end node to another end node containing permission for the another end node to transmit data from the another end node to the first end node is embedded within a data packet transmitted over the serial network from the first end node to the another end node. In further embodiments of the invention the E2E flow control signal contains an E2E flow control value used by the end node to increment the counter. In one of these embodiments the value is used to set the counter to the value. In further embodiments of the invention the value is used to increment the counter by that value. In some embodiments the flow control signal is capable of being modified. In other embodiments of the invention the flow control signal is modified ‘on the fly’ i.e. during the communication process. The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

A node configured to communicate with at least one further node. The node includes a buffer configured to receive data transmitted from the at least one further node. The node also includes an output configured to transmit data to the at least one further network element. The data includes information about the ability for the buffer to receive further data transmitted from the further node.

PRIORITY The present Application claims benefit of priority to U.S. provisional application 61/523,672 filed on Aug. 15, 2011, the entire contents of which are hereby incorporated by reference. TECHNICAL BACKGROUND A key challenge to high resolution imaging sensors used in observing terrestrial activities over a very wide field-of-view (WFOV) (e.g., 50 km 2 ) is to achieve the resolution needed to observe and make inferences regarding events and objects of interest while maintaining the area coverage, and minimizing the cost, size, weight, and power of the sensor system. One particularly promising approach to the data deluge problem is compressive sensing, which involves collecting a small amount of information-rich measurements rather than the traditional image collection from a traditional pixel-based imager. There is no current solution for compressive sensing architectures, especially in the infrared. An eyelid technology, liquid crystal (LC), and microelectromechanical system (MEMS) digital mirror arrays (DMA) have been postulated as potential solutions in a lab environment, but there is no current hardware available. The closest technology to production scale is a visible/short wave infrared compressive sensing camera that uses the DMA array, but this is a reflective design. A DMA solution is limited in resolution by the number of pixels and also to a ±degree tilt in the reflective element(s). Also, the solution is complex and failure-prone due to the complex optics, and the sampling modulation is limited. SUMMARY Aspects of the techniques and solutions disclosed herein are directed at coded masks that include phase change material (PCM). Such masks may be suitable for use with various types of photo-detectors, such as photo-detectors of the type disclosed in U.S. Pat. No. 7,687,871, issued to Shimon Maimon on Mar. 30, 2010, the entire contents of which are hereby incorporated by reference. Other detector types, such as p-n junction detectors, photodiodes, charge-coupled device (CCD) photodetectors, active-pixel sensors/CMOS sensors, and other detector types. Wavelengths detected by the photodetector and/or filtered or otherwise affected by a coded PCM mask applied to the detector may include long-wave, mid-wave, and/or short-wave infra-red, millimeter-wave, visible spectrum, and/or ultra-violet radiation. Aspects of the techniques and solutions discussed herein may pertain to a pixel-level mask for a photo-detector, the mask comprising: a layer of reconfigurable phase-change material (PCM) configured to vary between a first refractive index and a second refractive index; said PCM layer being divided into individual pixel areas such that each individual pixel area may be set to have the first refractive index or the second refractive index; said PCM layer being disposed on a photo-detector such that incident radiation detected by the photo-detector must pass through the PCM layer in order to be detected; and a PCM controller that controls the refractive index of an individual pixel area. In some variations, each pixel area may have a refractive index within a range of values between the first refractive index and the second refractive index, inclusive. In some variations, the PCM includes Ge2Sb2Te5 (GST); the first refractive index is associated with a crystallized state of GST; and the second refractive index is associated with an amorphous state of GST. In some variations, the PCM controller includes a voltage source; and the PCM controller is operably connected to an individual pixel area such that a first voltage level provided by the controller sets the individual pixel area to have the first refractive index and a second voltage level provided by the controller sets the individual pixel area to have the second refractive index. In some variations, the mask includes a voltage source operably connected to the PCM controller; the PCM controller includes a multiplexer PCM controller; and the PCM controller controls the voltage source such that the voltage source provides a first voltage level that sets an individual pixel area to have the first refractive index and such that the voltage source provides a second voltage level that sets the individual pixel area to have the second refractive index. In some variations, the first voltage level is six volts. In some variations, the individual pixel areas are aggregated into superpixels. In some variations, the superpixels are controlled by the PCM controller such that each superpixel may be set to have a particular imaging mask pattern by changing the refractive indices of the pixel areas within each superpixel. In some variations, each superpixel in the mask is the same size and shape. In some variations, a superpixel corresponds to a pixel of the underlying photo-detector. In some variations, the mask includes a laser source; the PCM controller is operably connected to the laser source; the laser source provides a first laser irradiation to the individual pixel area to set the individual pixel area to the first refractive index and a second laser irradiation to the individual pixel area to set the individual pixel area to the second refractive index. In some variations, the first laser irradiation is continuous wave (CW) irradiation and the second laser irradiation is pulsed irradiation. In some variations, the photo-detector is an infra-red detector; the superpixels the PCM layer correspond to pixel areas of the infra-red detector; the pixel areas having the first refractive index are opaque to infra-red radiation; and the pixel areas having the second refractive index are transparent to infra-red radiation. In some variations, the pixel areas having the first refractive index and the pixel areas having the second refractive index are arranged to form an imaging mask for compressive imaging. In some variations, the mask includes an index variation layer of ZnS—SiO2 disposed beneath the PCM layer; a layer of Aluminum disposed beneath the response variation layer; and a layer of glass disposed beneath the layer of Aluminum; where the photo-detector is disposed beneath the layer of glass such that incoming radiation to be detected by the photo-detector must pass through the PCM layer, the index variation layer, the Aluminum, and the glass before being detected by the photo-detector. In some variations, the mask includes a layer of doped silicon and/or alumina disposed beneath the PCM layer, where switching properties of the mask are determined based on a thickness of the doped silicon and/or alumina layers. In some variations, the PCM controller controls a pattern of the imaging mask by selectively changing refractive indexes of individual pixel areas. In some variations, PCM controller includes a laser source; the laser source providing a first laser irradiation to the individual pixel area to set the individual pixel area to the first refractive index; and the laser source providing a second laser irradiation to the individual pixel area to set the individual pixel area to the second refractive index. Aspects of the techniques and solutions discussed herein may pertain to method of controlling the absoption of individual pixel areas in a reconfigurable phase-change material (PCM) mask for a photo-detector, the method comprising: first illuminating at least one pixel area with a continuous wave (CW) laser illumination to increase the absorption of said at least one pixel area from a first value up to a second value; and second illuminating said at least one pixel area with a pulsed laser illumination to set the absorption of said at least one pixel area to the first value; where said first illuminating and said second illuminating are performed selectively on individual pixel areas in the PCM mask to set a mask pattern. Aspects of the techniques and solutions discussed herein may pertain to a method of controlling the absoption of individual pixel areas in a reconfigurable phase-change material (PCM) mask for a photo-detector, the method comprising: first providing at least one pixel area with a SET voltage level to increase the absorption of said at least one pixel area from a first value up to a second value; and second providing said at least one pixel area with a RESET voltage level to set the absorption of said at least one pixel area to the first value; where said first providing and said second providing are performed selectively on individual pixel areas in the PCM mask to set a mask pattern. Further scope of applicability of the techniques, devices, and solutions described herein will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the techniques, devices, and solutions described herein, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF DRAWINGS The techniques, devices, and solutions described herein will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present disclosure, and wherein FIG. 1 a depicts a variation of a PCM coded mask as described herein; FIG. 1 b depicts a variation of a PCM coded mask as described herein; FIG. 1 c depicts a variation of a PCM coded mask as described herein; FIG. 1 d depicts a variation of a PCM coded mask as described herein; FIG. 2 a depicts a variation of a PCM coded mask as described herein; FIG. 2 b depicts a variation of a PCM coded mask as described herein; FIG. 3 a depicts a variation of refraction index changes in a PCM material; FIG. 3 b depicts variations of reflectivity changes in variations of a PCM material. The drawings will be described in detail in the course of the detailed description. DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the techniques, devices, and solutions described herein. Instead, the scope of the techniques, devices, and solutions described herein is defined by the appended claims and equivalents thereof. In a solution to the above-noted problem, phase change materials (PCM) may be used as the active components to create coded apertures (i.e. sub-pixel/sub-wavelength patterns), which in, combination with image read-out and processing algorithms, optimize the “best” possible compressible image that fits the observed measurements for perfect image reconstruction. In some variations, a PCM coded mask may be disposed onto a focal plane array (FPA) such as an infra-red (IR) detector. Other variations may use different types of detectors, such as detectors that operate in some or all of the visible, millimeter-wave, and infra-red spectra. A variation of a PCM coded mask disposed over a pixel array is shown in FIG. 1 a. In the variation shown, a pixel array 1001 such as an FPA may include several individual pixels 1020 . A PCM coded mask 1010 may be disposed over the FPA 1001 . In some variations, the PCM coded mask may include several mask PCM elements 1030 . In some variations, many mask PCM elements 1030 may cover one FPA pixel 1020 . In other variations, a PCM coded mask may be a continuous surface configured for sub-pixel variations in mask structure. In some variations, a PCM coded mask can be used in the Fourier planes as well as in the image plane. In such variations, the PCM coded mask will result in the detection of the image convolved with the PCM mask. For applications in compressive sensing, this would be particularly useful for image sparse images (i.e. imaging objects of interest against a bland background). In some variations, a PCM coded mask may be used to generate one or more masks for compressive sensing applications. Such a variation of a mask is shown in FIG. 1 b . In the variation shown, a PCM film 1110 may be divided into discrete regions 1100 , 1120 which may correspond to pixels on an underlying photodetector (not shown). The film regions may then each be set or otherwise configured to have particular transmission properties. Some film regions may be set to transmit or pass 1120 a certain wavelength or wavelength range. Other film regions 1100 may be set to suppress that wavelength or wavelength range. In further variations, the suppressive regions 1100 may suppress or otherwise reject all incoming radiation that could/would otherwise be detected by an underlying photodetector. In such variations, the PCM film 1110 may be arranged into a compressive imaging mask such that only the transmissive regions 1120 of the mask allow electro-optical radiation to pass through for detection by an underlying photodetector (such as, for instance, an infra-red detector). In some variations, a PCM film may be used in combination to other non-active materials such as alumina on a film stack, to generate masks for a compressive sensing application. In variations where the PCM coded mask elements correspond to one or more particular pixels on an underlying FPA, each individual element or array of elements in the mask (e.g. row or column) can be individually addressed by an external laser or voltage stimuli allowing the PCM material to change its transmission properties. In some variations, this is accomplished by causing the PCM material to change between crystalline and amorphous states; which in turns produces a change in the optical properties of the material (e.g. refractive index, absorption, etc). In some variations, these changes can occur in the nanosecond response time. A variation of such a PCM mask is shown in FIG. 1 c . In the variation shown, each element 1210 , 1220 or the PCM mask 1230 corresponds to one pixel of an underlying photodetector. In the variation shown, the percentage of light transmitted through each pixel 1210 , 1220 of the PCM mask 1230 can be adjusted by controlling an input voltage directed to that pixel 1210 , 1220 by a multiplexer PCM controller 1200 . In some variations, the application of a bias voltage (SET pulse) to a pixel 1210 crystallizes the material and a different bias (RESET), or further increasing the bias voltage, may cause the material to re-amorphize. In other variations, the PCM material may be placed in a crystalline state by a particular voltage pulse and may be triggered to change to an amorphous state by a different voltage pulse. In some variations, a SET pulse may be ˜6 volts and a RESET voltage may be ˜10 volts. In some variations, the multiplexer PCM controller 1200 may be a specialized or otherwise distinct component of an overall PCM mask device. In some variations, such a multiplexer PCM controller 1200 may include a separate voltage supply source to provide the SET and RESET voltages. In the variation shown, the PCM controller 1200 is disclosed as a multiplexer that addresses the individual PCM mask elements 1210 , 1220 . Other variations may address the mask elements by column, by row, or may address the individual elements in non-multiplexed ways. In one variation, each mask element may have a separate signal pathway between it and a PCM controller. In another variation, shown in FIG. 1 d , the percentage of light transmitted through each pixel 1220 , 1230 of the PCM mask 1200 can be adjusted by controlling 1920 a laser power. In one variation, a CW laser 1900 crystallizes the material while a pulsed laser 1910 re-amorphizes it. In the variation shown, a PCM controller 1920 may be equipped with or connected to two different laser sources 1900 , 1910 . A first laser source may be a continuous wave (CW) laser 1900 whereas a second laser source 1910 may be a pulsed laser. In other variations, the PCM controller 1920 may be equipped with or connected to a single laser such as a femtosecond laser. In some variations, reversible switching in PCM can be accomplished, in some variations, by crystallizing with a laser in CW mode and then re-amorphizing with a 40 ns pulse laser at 16 mW. Other variations may use different types or intensities of lasers to SET and RESET the PCM. In some variations using PCM GST (Ge 2 Sb 2 Te 5 ) films, for example, for optical excitation, the energy density required to SET and RESET are: SET ˜24 mJ/cm2 and RESET ˜50 mJ/cm2. Molecular dynamics indicate quenching GST at dT/dt=−15 K/ps produces crystalline/amorphous phase transitions. In some optically switched variations of a coded PCM mask, the mask may be equipped with multiple waveguides or optical fibers feeding each individual pixel to change their properties at adjustable laser power levels. In some variations, the elements of a PCM coded mask may be smaller than the individual pixels in an FPA (focal plane array) covered by the mask. In some cases, a “superpixel” made up of smaller individual PCM coded mask elements may be coded onto one pixel of an FPA or other photodetector. In some variations, a single “pixel” of a PCM coded mask may be 10 microns or smaller. In some variations, the size of the “superpixel” may not necessarily match the pixel size of an underlying detector pixel. In some variations, the “superpixels” may be 2-dimensional arrays of PCM elements. The sizes of such arrays may match those of underlying detector pixels or may have larger or smaller sizes depending on an intended use or desired effect(s) of the PCM coded mask. Such a variation is shown in FIG. 2 a. In the variation shown, a PCM coded mask may be made up of multiple individually controllable PCM elements 2100 , 220 . Such PCM elements may be aggregated into “superpixels” 2000 . In some variations, such PCM coded mask superpixels 2000 may be equipped with a particular pattern that establishes a transmission pattern within the superpixel 2000 . In some variations, such a pattern may be repeated in some or all of the superpixels 2000 , 2300 . In some variations, different patterns may be applied to different superpixels 2400 in the PCM coded mask. In some variations, a superpixel in such a PCM coded mask may be controlled by a PCM controller (not shown) by setting a particular predetermine or otherwise preconfigured pattern onto the superpixel. In some such variations, the PCM controller and/or the superpixel(s) of the PCM coded mask may be equipped with one or more preconfigured or otherwise predetermined mask patterns that may be triggered by a particular signal or signal set transmitted from the PCM controller to a superpixel. In other variations, the PCM controller may address each PCM pixel element 2100 , 2200 individually. In further variations, the PCM controller may optionally address a PCM superpixel 2000 to establish a particular pattern in the superpixel 2000 or address individual PCM coded mask elements 2100 , 2200 to establish a particular refractive index or transmission state of that element. In one particular variation, a coded PCM mask element may be an individually addressable square element measuring 10 microns on a side. In some variations, such individually addressable elements may be aggregated into 16×16 superpixels that each cover one detector pixel of an FPA. In some variations, the coded PCM mask may include a 512×512 array of such 16×16 superpixels. In further variations, each superpixel in such an array may be equipped or otherwise configured with a particular masking pattern. In some variations, a superpixel 2000 may correspond to less than one pixel of an FPA. In some such variations, a group of superpixels may correspond to one or more pixels of an FPA. In other variations, a superpixel may correspond to more than one pixel of an FPA and/or have a shape or arrangement that does not overlap directly with an FPA pixel. For example, an FPA having a 30-micron pixel pitch may be covered by a coded PCM mask equipped with superpixels measuring 20 microns by 40 microns. In other variations, the superpixels may not all be the same shape. In some variations, the superpixels may not be square or rectangular. In some variations, the superpixels may have irregular shapes, such as L-shapes. Such variations are depicted in FIG. 2 b. In one variation, irregularly-shaped coded PCM mask superpixels 2900 , 2920 may be configured to fit together to form a rectangular shape that may be associated with a size of one or more underlying pixels. In some variations, such superpixels 2900 , 2920 may have different PCM masks. Such different masks may complement each-other or may be individually determined. In other variations, such superpixels 2950 , 2940 may have the same masks. In some variations, the PCM mask superpixels may be asymmetrically shaped 2960 , 2930 and may or may not be configured to form regular shapes such as squares, rectangles, triangles, or other polyhedrons. In such variations, the mask of each superpixel 2960 , 2930 may be individually established or separately controlled. In further variations, the PCM mask superpixels may be irregular shapes such as “cross” type shapes 2970 , 2910 , step-sided pyramids, t-shapes, s-shapes, or other shape variations. In some variations, such superpixels 2910 , 2970 may be shaped differently from each-other. In some variations, such superpixels 2910 , 2970 may have different mask patterns. Although discussed so far with respect to only two states (transmission/absorption, or on/off), some PCM mask variations also allow for graded/scaled masking instead of just switching mask elements/pixels into “on” and “off” states. In some variations large refractive index changes (delta n ˜2.4) can be achieved. In some variations, refractive index can be tailored from n˜3.8 in the amorphous to n˜6.2 in the hexagonal crystalline via meta-stable face centered cubic transition of the material structure. FIG. 3 a depicts such a range of refractive indexes for PCM GST in amorphous and crystalline states. The graph in FIG. 3 a shows the refractive index (n) and extinction coefficient (k) dispersion of Ge 2 Sb 2 Te 5 at the two extremes (amorphous and hexagonal crystalline phases). The extinction coefficient is related to the absorption. The index is shown by the solid line and the extinction coefficient by the dotted lines. As can be seen in the diagram, the refractive index of the PCM may vary based on a desired wavelength or wavelength range. In the variation shown, an index of refraction is depicted for near infra red (NIR) and mid-wave infra red (MWIR) imaging. As is shown in the diagram, for imaging wavelengths from approximately 1 to 5 microns, the amorphous PCM has an extinction coefficient of zero, making it essentially transparent to IR radiation. By contrast, the crystalline PCM has an extinction coefficient greater than zero, making it essentially opaque (or lossy) to IR radiation. Such variations may be realized using materials such as GST (Ge 2 Sb 2 Te 5 ) or other materials on the Ge—Sb—Te system or other PCM compositions Using a PCM coded mask as described herein for compressive sensing enables the optical design to be greatly simplified because there is no mechanical actuation of reflective elements and therefore a much simpler optical design. Furthermore, because the solution discussed herein operates in transmission (as compared to reflective designs using DMA) allowing for a simpler optical configuration; it does not require mechanical actuation (on/off states can be achieved by a phase transition from amorphous to crystalline state and design architecture) and can be adapted to the encoding scheme at the same spatial and/or temporal rate as the desired image/video reconstruction (it can be reconfigured/switched at nanosecond speeds using an external laser or voltage stimuli). This is so because switching times can be controlled by changing/optimizing the film structure in which the PCM layer is deposited. FIG. 3 b shows a chart indicating changes in reflectivity of an example of a PCM film stack using GST based on changes to an underlying layer of ZnS—SiO 2 . As can be seen from the chart, an initially crystallized PCM region 300 may have a reflectivity normalized to 1. When amorphized by either an appropriate voltage or laser stimulus 310 , the reflectivity may drop to approximately 0.8, with thicker layers of ZnS—SiO 2 being associated with a higher reflectivity. Subsequently, when re-crystallized 330 , a PCM layer disposed on a thicker region of ZnS—SiO 2 recovers its reflectivity more quickly. In cases where the ZnS—SiO 2 is less than a certain thickness 320 , a PCM film stack may have some difficulty in recovering an initial reflectivity. In some cases, even after a significant time period (160 nsec or more), reflectivity may not be recovered. As can be understood from the diagram in FIG. 3 b , there is flexibility in the design of a PCM coded mask architecture that can be used to optimize or otherwise configure the device properties. Although the example above depicts a particular film stack configuration using GST over ZnS—SiO 2 , other materials and material combinations may be used. Similarly, although the example shown varies the thickness of the ZnS—SiO 2 to change the film stack properties, the composition of that layer (and/or other layers) and the thicknesses of other layers (such as, for instance, the GST layer) may also be altered to change the properties of the PCM film stack. As can be seen in the diagram of FIG. 3 b , switching time for changing from crystallized to amorphous and back to crystallized states can be realized in as little as ˜15 nanoseconds. In some cases, amorphization may be realized in less than one nanosecond and crystallization may be realized in under 15 nanoseconds. Such fast switching time enables the creation and use of PCM coded masks for that can be reconfigured at fast switching times (few nsec as compared to millisecond for the DMA), providing the ability for better image reconstruction and quality, especially when the target object is moving. In the variation shown, the 15 nm, 25 nm, and 50 nm thicknesses of ZnS—SiO 2 require fluencies of 52 mJ/cm 2 , 47 mJ/cm 2 , and 31 mJ/cm 2 , respectively, to achieve the transition from crystallized to amorphous states. Such fluence levels may be realized with nanosecond or femtosecond lasers. Also, in the variation shown, the third layer of the PCM material stack is Aluminum. In other variations, this layer may be omitted or replaced with materials such as doped silicon or indium tin oxide (ITO). Material composition of the underlying layers of a PCM material stack may be determined based on a desired wavelength or waveband of electro-optical radiation to be detected by an underlying photodetector. Doped silicon and ITO, for example, are transparent to infra-red radiation. Only exemplary embodiments of the present invention are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. Such variations are not to be regarded as departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims:

Variations of the techniques, systems, devices, and methods discussed herein pertain to a pixel-level mask for a photo-detector. Such a mask may have a layer of reconfigurable phase-change material (PCM) configured to vary between a first refractive index and a second refractive index. Such a PCM layer may be divided into individual pixel areas such that each individual pixel area may be set to have the first refractive index or the second refractive index. The PCM layer may be disposed on a photo-detector such that incident radiation detected by the photo-detector must pass through the PCM layer in order to be detected. The mask may also include or otherwise be operably connected to a PCM controller that can control the refractive index of an individual pixel area or a group of pixel areas aggregated into a superpixel.

This invention relates to the joining of dense bodies of refractory metal such as tungsten or molybdenum to carbonaceous bodies, and more particularly to the employment of reaction brazing at high temperature to join dense bodies of tungsten or molybdenum or alloys thereof to carbonaceous supports, such as graphite or carbon-carbon composites. Even more particularly, the invention relates to the reaction brazing of x-ray generating anodes made primarily of either molybdenum or tungsten, to graphite supports or to carbon matrix, carbon fiber-reinforced composite supports to produce assemblies suitable for use at high temperature in a vacuum environment where temperature cycling will be experienced and collectively would tend to result in undesirable chemical reactions, e.g. carbon diffusion from the support and formation of substantial metal carbide. BACKGROUND OF THE INVENTION There are various applications where it is desirable to attach a tungsten or molybdenum refractory body to a carbonaceous substrate in a manner so as to create an effective joinder that will remain satisfactory for extended periods in a high temperature environment, i.e. above 1000° C. and in certain instances above 1500° C. or even above 2000° C. One such use of such structures is in the field of rotating x-ray anodes, and U.S. Pat. No. 3,579,022 shows the creation of a rotary anode for an x-ray tube wherein a tungsten-rhenium alloy is bonded to a graphite base by first depositing a thin stratum of rhenium having a thickness of a few micrometers. In U.S. Pat. No. 3,649,355, a graphite base for a rotary x-ray anode is first plasma-sprayed with tungsten to produce a coating of substantially pure tungsten, or an alloy thereof with rhenium, osmium or the like. Thereafter, an outer layer of tungsten is preferably deposited from a gaseous phase using CVD or the like. In U.S. Pat. No. 3,689,795, a molybdenum or molybdenum alloy base having a thickness of about 6 millimeters is used, and a focal track of pure tungsten or a tungsten-rhenium alloy is applied thereto by chemical vapor deposition (CVD) or a like process. To improve the crack resistance of such a molybdenum base, it is suggested to form the base using powder metallurgical techniques from a mixture of metal powders so the base will contain from 50 to 500 ppm of boron. U.S. Pat. No. 4,132,917 shows a graphite body which has a metal band brazed thereon for a focal track. Illustrated in the patent is the use of a molybdenum or molybdenum alloy layer which is contiguous with the graphite body, and a layer of a tungsten-rhenium alloy that is superimposed thereon. In one embodiment, a thin coating of titanium carbide is applied to the graphite by CVD before brazing a metallic ring of the desired shape using Ti or Zr foil or powder paste, which ring may be formed by a powder metallurgical process. U.S. Pat. No. 4,516,255 discloses the use of a rotating x-ray anode made from a molybdenum alloy containing some carbon, such as TZM, which is provided with a focal path of tungsten or a tungsten alloy. Using plasma spraying or the like, an oxide coating, such as titanium oxide, is formed on the TZM body, preferably after an intermediate layer of molybdenum (Mo) or tungsten (W) having a thickness between 10 and 200 μm has been applied by plasma spraying or the like. U.S. Pat. No. 4,990,402 teaches joining a metal part to a fiber-reinforced pyrolytic graphite structure or the like such as a structure wherein which the fibers are irregularly arrayed. In order to solder a molybdenum alloy component, such as TZM, thereto, a solder is used which is 70% silver, 27% copper and about 3% titanium. Although such methods of joinder have proved reasonably effective for certain applications, the search has continued for improved methods of bonding dense refractory metal bodies, such as those of tungsten, molybdenum and their alloys, to carbonaceous supports by creating bonds that will exhibit excellent high temperature stability over a long term even in the face of a relatively substantial difference in coefficients of thermal expansion that would tend to create stresses at such a joint, while also resisting diffusion of carbon from such support into the dense refractory metal body. In addition, when the joinder is of an x-ray anode to a support, the thermal conductivity through the joint should preferably be adequate so that it does not create a heat flow choke that would deter heat being generated from flowing freely away from the anode, and the heat capacity of the support and its emissivity should be adequate to dissipate heat transferred to it. SUMMARY OF THE INVENTION The invention provides methods for joining bodies of refractory metal in elemental form to carbonaceous supports in a manner that creates a bond which is capable of withstanding temperatures at least as high as 1300° C. and preferably of at least 1500 to 1600° C. for substantial lengths of time, even higher temperatures for short periods, and perhaps more importantly of being able to withstand frequent cycling between far lower temperatures, e.g. close to room temperature, and such high temperatures. Alternative methods to certain preferred methods produce bonds which are capable of operating at a temperature of about 2000° C. or above. In certain of these preferred methods, a Reactive metal, preferably in the form of a foil, and a powder mixture containing a boride of the refractory metal being joined, a carbide of the Reactive metal, and preferably additional elemental metal, e.g. of the foil and/or the metal body, are introduced between complementary surfaces of the bodies being joined. This assembly is then heated to a reaction-brazing temperature (as hereinafter more specifically defined). For joining dense tungsten bodies, e.g. those made of single crystal tungsten or the like, an alcohol slurry of particles of tungsten boride plus a carbide of a Reactive metal, e.g. hafnium (Hf), carbide and/or zirconium (Zr) carbide, may be applied to the carbonaceous support, which slurry may also include some of these metals in elemental form. When a Mo or Mo alloy body is being joined, Mo boride is substituted for W boride. Reactive metal in the form of a paste or preferably a foil is juxtaposed with the W or Mo surface to be joined. The slurry does preferably contain powder of the Reactive metal of the foil (and also the metal of the carbide should it be different), and it also preferably contains W or Mo powder (depending upon the body being joined). The method produces a strong joint of low thickness having good thermal conductivity that is particularly valuable in the construction of an x-ray anode. The carbonaceous substrates may, for example, be dense graphite bodies or carbon-carbon composites wherein either bundles of carbon fibers or carbon filaments from woven cloth are oriented in a direction transverse to the surface of the dense refractory body being joined, which composites may also contain fibers oriented parallel to such surface. In a particular aspect, the invention provides a method of making an x-ray tube target anode, which method comprises providing a dense body of tungsten (W) or molybdenum (Mo) metal suitable for serving as a target anode to create x-rays, providing a carbonaceous support body capable of withstanding high temperatures under vacuum conditions and having a surface complementary to a surface of said dense body, coating said complementary surface of said support body with a layer of a material containing a mixture of particulate Hf carbide or Zr carbide and particulate tungsten boride or molybdenum boride, and joining said dense body to said carbonaceous anode support by introducing a layer of elemental hafnium (Hf) or zirconium (Zr) between said complementary surfaces of said support body and said dense body, juxtaposing said complementary surfaces of said dense body and said support, and heating to a reaction-brazing temperature under vacuum or an inert atmosphere such that said dense body thereafter strongly adheres to said carbonaceous support body. The resultant product allows good heat flow from the anode body into the support at its high temperature of operation. In a more particular aspect, the invention provides a method of joining a dense tungsten(w) or molybdenum(Mo) body to a carbonaceous support, which method comprises providing a dense W or Mo metal body, which body has one surface designated for joinder to another body, providing a carbonaceous support body capable of withstanding high temperatures in the absence of air, which support has a surface complementary to said designated surface of said dense body, coating said complementary surface of said support body with a layer of a material comprising a mixture of particles of a refractory metal boride and of a metal carbide, providing a Reactive metal layer and juxtaposing said two complementary surfaces with said layer therebetween, and joining said dense body to said carbonaceous support body by heating to a reaction-brazing temperature such that said refractory metal body thereafter strongly adheres to said carbonaceous support while an intermediate barrier forms between said two bodies which thereafter diminishes diffusion of carbon from said support body into said refractory metal body. In a still more particular aspect, the invention provides a method of joining a dense tungsten(w) or molybdenum(Mo) refractory metal body to a carbonaceous support, which method comprises the steps of providing a dense W or Mo refractory metal body, which body has one surface designated for joinder to another body, providing a carbonaceous support capable of withstanding high temperatures in the absence of air, which support has a surface complementary to said designated surface of said dense body, coating said complementary surface of said support with a layer of a material comprising a mixture of particles of a boride of the refractory metal of the body and of a Reactive or refractory metal carbide, juxtaposing said two complementary surfaces, and joining said refractory metal body to said carbonaceous support by heating to a reaction-brazing temperature of at least about 2200° C. such that said refractory metal body thereafter strongly adheres to said carbonaceous support and an intermediate barrier forms therebetween which diminishes diffusion of carbon from said support into said refractory metal body both during said joining step and later during use of said body in a high temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS Shown in FIG. 1 is a method of joining a dense refractory metal body to a carbonaceous support embodying various features of the invention. Shown in FIG. 2 is an alternative method of joining a dense refractory metal body to a carbonaceous support embodying various features of the invention. Shown in FIG. 3 is another alternative method of joining a dense refractory metal body to a carbonaceous support embodying various features of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found that the general desire to join a dense refractory metal body of tungsten or molybdenum to a carbonaceous substrate having a relatively low coefficient of thermal expansion (CTE), including carbon-carbon composites, can be very effectively achieved using reaction brazing in the presence of a refractory metal boride and a Reactive metal carbide. By “dense body of tungsten or molybdenum”, for purposes of this application, is meant a body having a density at least 80% of its theoretical maximum density (preferably at least about 90% and more preferably at least about 95%), which body contains elemental tungsten, elemental molybdenum or an alloy of either that respectively comprises at least about 90% tungsten or 90% molybdenum. By Reactive metal is meant a metal having a melting point of about 1600° C. or above which forms a carbide and which forms a eutectic with either Mo or W at a temperature below its melting point and below the respective melting point of Mo or W; elements from Groups IVb and Vb of the Periodic Table are preferred, with elements of Group IVb being more preferred and Hf and Zr being most preferred. One of the difficulties in creating a strong, stable bond between a carbonaceous substrate and a dense body of refractory metal such as tungsten or molybdenum, which bond will remain strong and stable for substantial periods of time at high temperatures, i.e. at least about 1300° C. and preferably at least about 1600° C., and conceivably of about 2000° C. is the accommodation of the stresses that necessarily result from the substantial differences in the linear CTEs. It is important to be able to produce a bond having a structure that will withstand the strains and stresses which necessarily will occur during substantial temperature excursions between ambient and operating temperatures because of the CTE differences. For example, at room temperature, the CTE of tungsten is about 4.5×10 −6 /° C., and the CTE of molybdenum is about 5.43×10 −6 /° C., and when there is a substantial difference between the CTE of the dense refractory metal body and that of a carbonaceous substrate (e.g. a fibrous composite substrate may have a CTE of about 1×10 −6 /° C. in the direction of orientation of the fibers whereas dense graphite substrates can vary from about 3-9×10 −6 /° C.), there is the distinct possibility of developing high strains at and near the interface of the bond during temperature excursions. Of course, such excursions are to be expected because high temperature operation for such structures is generally anticipated, as for example when the structure will serve as a rotating x-ray anode, because present x-ray tube anodes reach such high temperatures that their operation must be frequently interrupted to allow them to cool. Various carbonaceous supports are contemplated including graphite, pyrolytic graphite, fiber-reinforced pyrolytic graphite and carbon-carbon composites. Carbon-carbon composites, wherein carbon fibers are embedded in a carbon matrix, have become widely available in recent years and can be created with very good structural properties; accordingly, they have become one preferred material for use in high temperature structural applications, including use as a support base for a rotating x-ray anode. Such a carbon-carbon composite will generally have a density of at least about 1.7 g/cm 3 and an emissivity in the range of about 0.85 to 0.99 so as to allow for adequate dissipation of heat. Such composites may be fashioned from lay-ups having various orientations of carbon fiber arrays or graphite fiber cloths, and often they are fashioned from woven carbon fiber fabric or from bundles or tows of carbon fiber filaments that are suitably aligned in generally parallel fashion in alternating layers, although carbon-carbon composites having a three-dimensional carbon frameworks may also be used and may be preferred. When such a carbon-carbon composite is used for the base material to support a dense refractory metal body, the orientation is preferably such that the alignment of some of the bundles of fiber or of the woven sheets is transverse to, preferably perpendicular to, the juxtaposed surface of the refractory metal body being joined. The carbon fibers or filaments that are present in such composites have higher tensile strength in the axial direction, and because they are preferably aligned transverse to the surface of joinder, the joint will be stronger. Of course, when there is a three-dimensional carbon fiber framework, there will always be some carbon fibers that will be oriented transverse to any surface. Traditional carbonaceous supports for x-ray tube anodes utilize graphite having a density of at least about 75% of theoretical density. Graphite has a number of different crystalline forms, and the preferred graphite forms for use as a rotating anode support are those having a relatively high CTE approaching that of the metallic body. Although isotrophy is not considered to be a criterion of major importance, preferred graphites are those that would be categorized as being isotropic, as opposed to anisotropic. Such graphites are readily commercially available, as from Toyo Tanso and the Poco Graphite Co. One preferred graphite is Toyo Tanso grade IG-610U. While many early attempts at creating joints, as evidenced by some of the patents mentioned hereinbefore, utilized layers of tungsten or the like that had been deposited from a vaporous atmosphere, as by CVD, to serve as a focal path for a rotating anode for x-ray generation, it is believed that the durability of such an arrangement may be inherently limited as a result of the stresses mentioned hereinbefore, i.e. that would be created as a result of the difference in the CTEs, thus limiting the useful lifetime of such a structure. Another limitation on useful lifetime results from the effect that extremely high temperature at the joint would have on the thin metal and the adjacent carbon body. It has since been found that, by using a pre-prepared dense body of tungsten, e.g single-crystal tungsten, or of molybdenum, to support a tungsten focal track, structures having high temperature stability and durability can be created. Although elemental tungsten or elemental molybdenum may be used, an alloy of either TZM (99% Mo, 0.5% Ti, 0.07% Zr and 0.05% C, by weight) or TZC (having a somewhat greater amount of carbon) is often used, rather than Mo, because such has greater strength and is readily commercially available. Likewise, alloys of W, e.g. with a small amount of Re, might also be used. However, for a rotating x-ray anode, single crystal material, rather than polycrystalline material, may be preferred. In addition to creating a strong bond that will resist the strains expected to be experienced during high temperature excursions, it has also been found worthwhile that the joint should provide a thin but effective barrier to carbon diffusion therethrough from the support to the anode body. It is felt that a joint should preferably be constructed to retard the diffusion or migration of carbon from the support body; otherwise, a carbide zone may be formed not only within the region of the initial joint itself, but throughout an expanded region intruding into the surface regions of the anode. Such diffusion-resistance may be particularly of value in the field of x-ray anodes where longevity and continued high thermal conductivity during operation in a high temperature environment are important, because the thermal conductivity of such a metal carbide is substantially lower than that of the bodies being joined. Moreover, a fairly thick carbide zone is more prone to develop cracks as a result of thermal cycling because of inherent differences in CTEs. It is found that such an effective barrier to the creation of a relatively thick layer of metal carbide can be achieved as a part of a strong joint by coating the surface of the carbonaceous substrate, where joinder will take place, with a mixture that contains a particulate boride of the refractory metal body to be joined and a particulate Reactive metal carbide, preferably Hf carbide or Zr carbide. For example, if the intention is to join a dense body of tungsten to the carbonaceous support, an initial precursor layer in the form of a mixture of particulate tungsten boride and hafnium carbide may be applied to the appropriate surface of the composite. Such application may take place in any suitable fashion, and thereafter reaction brazing results in the creation of a relatively thin, strong joint of good overall thermal conductivity. When a Mo dense body is to be joined to a carbonaceous support, a particulate mixture of either Hf carbide or Zr carbide and Mo boride may be used which preferably comprises a major portion of the metal carbide and a minor portion of the metal boride. If for example instead a dense tungsten body is to be attached to a carbonaceous support, tungsten powder in combination with either hafnium or zirconium powder would preferably be used as a minor part of the particulate mixture being employed in the reaction brazing. The particles in such mixtures may range in size up to about 50 μm; however, preferably particles having an average size in the range of about 5 μm to about 25 μm and more preferably particles with an average size between about 5 μm and about 15 μm are used. Often the metal carbide will be present in an amount at least about 2-3 times the weight of the metal boride and more preferably about 2.5 to 3.5 times the weight of the metal boride. Such mixtures of particulate metal carbide and particulate refractory metal boride can be slurried with an alcohol and with a binder, such as a cellulose derivative, to create an adherent, paste-like material that can be conveniently first brushed as a viscous fluid onto the surface in question. The mixture being coated onto the carbonaceous substrate preferably also includes minor amounts of the elemental metals that are present in the carbide and boride constituents; for example, molybdenum or tungsten powder and hafnium or zirconium powder may be present, e.g. in individual amounts equal to about 10 to 20 weight % of the total particulate mixture. The particle size of the elemental metals can be about the same as set forth above, or they may be slightly smaller. As a general rule, such elemental metal powders are each preferably employed in an amount about equal to or within about 25% of the weight of the boride. Moreover, the amount of Mo or W powder should be approximately equal to the amount of Hf or Zr. Overall, Mo or W powder is preferably not employed at a weight percentage that is more than about 20% greater or less than that for the Hf or Zr, and preferably there is not more than about a 10% difference in the weight percents. They are most preferably employed in about equal amounts. Overall, the particulate mixture preferably consists essentially of between about 14% and about 20% by weight of the refractory metal boride, between about 45% and 56% by weight of the Reactive metal carbide, and between about 13% and about 19% each of Hf and Mo powders. More preferably, the mixture contains between about 15% and about 19% of MoB or WB and between about 46% and about 55% of hafnium or zirconium carbide, with the remainder preferably being essentially equal amounts of elemental hafnium and molybdenum. Once the surface has been coated with such a slurry, it may be heated to a temperature sufficient to sinter the boride and carbide particles, as depicted in FIG. 2, under vacuum conditions or in an inert atmosphere which is essentially devoid of O 2 , N 2 , H 2 , CO, CO 2 and SO x , (except for trace amounts such as might be present in high purity commercial gases), all of which are considered to be potentially deleterious to achieving strong bond having long-term stability. The time and temperature of the reaction-sintering step is adjusted as well known to those having skill in this art, depending upon the particular compounds that are present. For example, if the slurried layer includes molybdenum boride and hafnium carbide, a reaction-sintering step might be carried out at a temperature of about 1850 to about 1950° C. for about 20 to 30 minutes, after raising the coated substrate reasonably slowly to this temperature. As a result, there is an interdiffusion of metals and a reaction between the carbonaceous substrate and one or more of the metals and the boride-containing material in the slurry. Only partial melting occurs, and this phase wets and interacts with the carbon surface and create a very thin, adherent layer of hafnium and molybdenum carbide; this layer effectively diminishes the diffusion of carbon into the remainder of the braze region during the subsequent reaction-brazing step and during subsequent use. Although such pre-sintering is effective, it may be unnecessary as alternatively it has been found that such joinder of a dense refractory metal body to a carbonaceous support may be effectively carried out using a single heating step (FIG. 1) as described hereinafter following a brief description of this two-step process, depicted in FIG. 2 . Although use of a boride of the same refractory metal as the dense body that is to be joined is preferred, there are other options. For example, when a Mo body is being joined, one or more other compatible refractory or Reactive metal borides, such as tungsten boride, vanadium boride and/or zirconium boride, may be used either together with, or to the exclusion of, Mo boride. The tungsten boride may be WB, W 2 B or W 2 B 5 ; however, preferably W 2 B is used, particularly when a W body is being bonded. Similarly, the molybdenum boride may be MoB 2 , MoB, Mo 3 B 4 or Mo 3 B 5 ; preferably, however, MoB is used. A relatively thin, but continuous layer of such particulate material slurry is preferably applied so that the final thickness of the joint is about 0.007 in (0.18 mm) or less, preferably not greater than about 0.005 in (0.13 mm) and more preferably about 0.003 in (0.08 mm) plus or minus 0.001 in (0.03 mm). Although hafnium carbide is the more preferred carbide, instead of using hafnium carbide particles in this sintering mixture, zirconium carbide might be substituted for part or all of the Hf carbide. Alternatively, either might be used together with particles of molybdenum carbide, vanadium carbide, or tungsten carbide in the slurry for coating the carbonaceous surface. The second step of the preferred, somewhat lower temperature joining method introduces a layer of Hf or Zr between the surface of the dense refractory metal body and the reaction-sintered surface of the carbonaceous support; thereafter, reaction-brazing is carried out. The layer can be one of a dense paste of metal particles or metallic foil. Metal foil is preferably used, and it may be in the form of sheet material about 1-3 mils (0.001-0.003 in) in thickness. It is placed adjacent the surface of the dense refractory metal body to be joined and can be a single sheet or multiple sheets, depending in part on what is commercially available. For example, two sheets of 1 mil (0.001 in, 0.0254 mm) thick hafnium foil may be used to provide a layer 2 mils in thickness. When the single-step method (FIG. 1) is used, the foil layer is simply located atop the air-dried slurry-coated carbonaceous substrate. The introduction of a continuous layer of a paste mode of small Reactive metal particles is feasible but much less desirable. Then the dense refractory metal body is juxtaposed, and the reaction-sintering step is carried out. Regardless of whether the one-step or the two-step method is used, the composition of the reaction braze material will be essentially the same. As previously mentioned, the material should include a mixture of a refractory metal boride and a Reactive metal carbide, preferably with additional compatible elementary Reactive and refractory metals, e.g. Hf and Mo powder. As earlier mentioned, the braze material is applied as a mixture of a binder and such particulate materials, preferably as an alcohol slurry of a binder and the particulate/powder mixture, using a suitable alcohol, such as ethyl alcohol. A cellulose derivative or a comparable organic binder, that will be removed by dissociation and volatilization during the subsequent heating to the reaction-sintering temperature, is preferably used to create a fluid mixture having the consistency of a flowable paste that can be uniformly brushed or otherwise suitably applied onto the carbonaceous surface. Once the braze material coating has been applied, it is heated in air to cure the binder. For example, heating to 125° C. for about 12 hours will partially polymerize a cellulose binder and vaporize the alcohol. Clean foil which is free of contaminants is then placed to cover the overall coated surface of the substrate, and the dense refractory metal body is lightly pressed thereatop, sandwiching the foil therebetween to prepare the assembly for the thermal braze cycle. Either gravity or preferably a small weight placed atop the dense refractory body is relied upon during the reaction-brazing cycle to maintain the surfaces in juxtaposition with each other. For example, it may be desirable to have a pressure of about 0.2 to 0.8 psi on the foil. The thermal cycle which is used will generally include staged heating as described hereinafter to a temperature at or near that of the desired reaction-brazing temperature. The staged heating up to the reaction-brazing temperature will usually take place over at least 1 hour and preferably over about 2 hours or more. The reaction-brazing temperature should then be held for a period of at least 10 minutes, more preferably at least about 15 minutes, and most preferably over at least about 20 minutes. This arrangement assures that the surface of the metal body alloys with the thin foil, the alloy (eutectic phase) of which also participates with the boride and carbon that may be present to form additional carbides en route to forming a strong, stable reaction-brazed joint, which includes a thin barrier layer of refractory metal carbide and eutectoid phases which collectively diminish diffusion of carbon from the carbonaceous substrate into the upper region of the joint and the dense refractory metal body during future high temperature operation. Moreover, it is believed that the presence of the elemental Hf and/or Zr and the elemental Mo or W are helpful in creating an eutectoid (i.e. solid state) reaction wherein there will be such a metallic alloy zone on the Mo body (or W body) side of the carbide layer. For example, it may be a solid solution of Hf and HfMo 2 that, at and above the eutectic temperature, forms a liquid solution of about 28 weight % Mo and about 72 weight % Hf which dissolves some MoB and carbon; however, there is a reversal during cooling below 1865° C. where an Hf-rich solid solution and the compound HfMo 2 form from the liquid phase. Then, after cooling to about 1230° C., a eutectoid (i.e., solid state) reaction occurs wherein the Hf-rich solid solution phase decomposes to a Hf phase of low Mo solubility plus additional of the compound HfMo 2 ; i.e. Hf(β)←Hf(α)+HfMo 2 . It is felt important that the resultant joint be able to accommodate such thermal cycling, to which an X-ray target anode and other such devices will be subjected, where the temperature exceeds the eutectoid temperature (1230° C.) so that this repeated eutectoid reaction will be experienced within the joint. One example of the preparation of a carbon-carbon composite suitable for joinder as a support for an x-ray anode employs commercially available carbonaceous material which is at least about ½ inch in thickness and which has Z-axis fiber bundles that are oriented substantially perpendicular to the surface at which bonding is to be achieved. The composite is cleaned in ethanol using ultrasonic cleaning and then baked under vacuum conditions at about 1000° C. for an hour, followed by baking at a temperature of about 2600° C. for about 10 to 15 minutes, to remove any volatiles that might otherwise potentially have an adverse effect upon the integrity of the joint. One preferred alternative material is dense graphite such as that available from the Toyo Tanso Co. of Japan as their grade:IG-610U. Generally, the graphite is preferably isotropic and should have a density of at least about 75% of its theoretical density of 2.26 gm/cm 3 , e.g. about 77 to 80%; it should have a coefficient of thermal expansion of at least about 5×10 −6 /° C., but preferably not greater than about 6×10 −6 /° C. Such graphite should also have a thermal conductivity of at least about 100 W/m° C. As previously indicated, the preferred brazing material is a slurry of a mixture of particulates together with an organic binder in a suitable organic solvent, e.g. ethyl alcohol. The binder may be a cellulose compound, such as hydroxypropylcellulose, or any other commercially available organic binder that will be removed as a result of heating under vacuum conditions or leave no more than a minute carbon residue. The metal carbide particles and the refractory metal boride particles may be of about the same size range. Generally, the particle sizes between about 50 μm and about 5 μm may be used, and particles which pass through a 325 mesh (45 μm) screen may be used, but particles between about 5 μm and about 15 μm are generally preferred. Although elemental Reactive and refractory metals may also be used in the same particle size range, these materials are commercially available in powder form; thus, molybdenum and/or tungsten and hafnium and/or zirconium are conveniently supplied as powders in a size between about 20 μm and about 5 μm. The slurry layer is preferably applied in a thickness so as to result in a joint which is about 2 mils (about 50 μm) thick without the contribution of the foil. The reaction-brazing temperature will vary somewhat depending upon the materials that are being used, but the assembly will generally be held at such temperature for at least about 15 minutes. Very generally, a temperature well below the melting point of the dense refractory metal, i.e. molybdenum or tungsten, is chosen so that melting of such clearly does not occur. However, the temperature should be sufficiently high so that a eutectic is formed between the foil, a minor amount of the metal powder and the Mo or W material at the surface being bonded; this eutectic takes part in creating a strong bond at this surface during the reaction-brazing step. For example, molybdenum is considered to have a melting point of about 2890° K. (2617° C.), and whereas alloys of Mo with hafnium (M.P. of 2503° K., 2230° C.) have a measured eutectic point at about 1930° C., it appears to be depressed to about 1865° C. as a result of the presence of carbon and the boride phase. Thus, it is found that operation can be carried out at a temperature slightly below the measured eutectic point for a system using the two metals, i.e. molybdenum and hafnium, and will produce a very effective braze as part of this overall novel joining method. Accordingly, in such a system, a reaction-brazing temperature between about 1835° C. and 1895° C. is preferred, with a temperature between about 1850° C. and about 1880° C. being more preferred and a brazing temperature of about 1865° C. being most preferred. Alternatively, when zirconium carbide and zirconium powder are included in the slurry instead of hafnium carbide and hafnium powder, the measured eutectic temperature of Zr (M.P. of 2125° K., 1852° C.) and Mo is lower, i.e. about 1520° C.; accordingly, such a reaction-brazing might be carried out at a temperature below 1500° C., e.g. about 1460° C., or at a higher temperature if desired. When tungsten or an alloy thereof is used as the dense refractory material, although it has a much higher melting point, i.e. about 3680° K. (3407° C.), it also forms a eutectic with hafnium at close to the eutectic temperature of Mo and Hf, i.e. about 1930° C. Accordingly, brazing temperature ranges below 1900° C., as generally mentioned above, should also be appropriate for W/Hf. Moreover, pure tungsten and zirconium form a eutectic at a temperature of about 1660° C., so temperatures about 20 to 30° C. below this may be suitable for reaction-brazing using a comparable mixture containing W and Zr. However, somewhat higher brazing temperatures, e.g. up to the measured eutectic temperature of the refractory metal of the body and the Reactive metal in the slurry, may generally be used without detriment. In fact, if even higher operational temperatures should be desired, a higher temperature operational joint may be produced, as described hereinafter, by reaction-brazing W to C using a particulate mixture of WB and HfC or WC that is devoid of significant amounts of elemental metals so that the eutectic does not include contribution from an elemental Reactive metal. The amount of alcohol and/or organic binder in the mixture is not particularly critical so long as potential separation of the various particle fractions is prevented, i.e. to prevent partitioning as a result of different weights or densities. It is generally satisfactory that a sufficient amount of binder is used so as to provide integrity in the coated layer, i.e. so that it will remain in place on the surface and there will be uniformity of particle distribution throughout. The thickness of the coated layer will usually be between about 0.5 mil and about 3 mils (0.076 mm) and preferably between about 1 mil and 2 mils (0.051 mm). Once the surface of the substrate has been coated to provide a layer of the appropriate depth, the binder is cured by heating in air for about 12 hours while the alcohol is volatized. The foil sheet or sheets are then positioned thereatop and sandwiched between this coated surface and the dense refractory metal body being joined. A weight is preferably added to the assembly so that gravity will create a light pressure during the reaction-brazing step. Generally, the amount of weight should be equal to the weight of the dense refractory metal body plus or minus about 50%; in one experiment, weight was added to create a normal pressure stress of 0.4 lb/in 2 (0.00276 MPa) which proved adequate. As previously mentioned, the heating (and preferably the cool-down) preferably take place in stages to bring the assembly from ambient or room temperature up to the reaction-brazing temperature, where it will be held for a period of at least about 15 minutes and then returned it to ambient. Such stages may be varied with some amount of latitude; for example, the temperature may be raised at a substantially linear rate from ambient to about 700° C. over a time of about 60 to 90 minutes, although a shorter period may be used. Thereafter, the temperature is preferably raised to the desired reaction-brazing temperature in two or three increments, with brief soakings preferably being used at such intermediate incremental temperatures to assure that temperature gradients within the assembly are minimized. Likewise, upon the initial stage of cooling, a slower rate is preferred to enable any liquid phase to solidify uniformly in place within the assembly, thereby preventing radial flow and the potential creation of voids in the joint. The following examples describe methods presently preferred for the reaction-brazing of such materials and constitute the best mode known by the inventors for carrying out the invention. However, they should be understood to be merely exemplary and not to constitute limitations upon the scope of the invention which is set forth in the claims that are appended hereto. EXAMPLE I Preparations are made to join a graphite ring machined to have an outer diameter of about 5.35 inches (13.59 cm) and an inner diameter of about 2 inches (5.08 cm) to a disk of TZM (molybdenum alloy) of about the same outer diameter (about 5.25 in) which has a central hole of 0.5 inches (1.3 cm) and a thickness of 0.416 inch (1.06 cm) at its greatest thickness. The TZM disk has a flat lower surface and a beveled top surface so that its thickness is greater in the center at the region of the half-inch hole. The graphite ring is machined from IG610U near-isotropic, medium grain, fine porosity graphite having a CTE of about 6×10 −6 /° C., which is relatively close to the CTE of molybdenum, i.e. 5.43×10 −6 /° C. The graphite ring has a thickness of about 2 inches at its center and a bevel toward its outer circumference. The planar face of the graphite ring was ground using abrasive paper having a silicon carbide grit of Mesh Size No. 240 and then cleaned using ultrasonic cleaning in ethanol. After pumping the cleaned part free of alcohol under vacuum, it was subjected to a high temperature bake-out along with a similarly cleaned ¾ inch diameter graphite sample that was to be used as a process control and microstructure analysis specimen. Heating of the graphite parts was carried out for about 30 minutes at 1920° C. under a vacuum of about 10 −4 Torr. This bake-out releases and disperses any volatiles that might otherwise be released during the subsequent reaction-sintering and potentially form undesirable porosity in the liquid phase of the reaction-braze material. A brazing slurry is then formed from a particulate/powder mixture in alcohol, i.e. ethanol, using a solution of 99 parts ethanol and 1 part hydroxypropylcellulose, which was stirred to obtain a solution of transparent clarity and stored so as to prevent absorption of water from the atmosphere. All of the powders used had greater than 99.5% purity. All were of less than 325 mesh size (about 45 μm), and most of them had an average particle size of about 10 μm, being generally between about 5 μm and about 20 μm. The powder mixture was formulated using four different powders in the following weight percents: Hf—16%, Mo—16%, MoB—17% and HfC—51%. Each powder was individually added to the solution and mixed to achieve 10 parts of this powder mixture in 6 parts by weight of the cellulose alcohol solution; it was then stirred slowly by hand with a Teflon stir rod for about 20 minutes to thoroughly mix it and obtain a uniform gray-colored slurry of viscous but pourable and paintable consistency. The top surfaces of the graphite ring and the ¾ inch diameter graphite cylinder were then coated with the powder slurry. The graphite ring weighed about 886 grams, and about 4 grams of the powder slurry were applied uniformly across the flat face of the graphite ring that had an area of about 19.33 in , i.e. about 1 gram of powder slurry per 5 sq. in. Painting was carried out by hand using an artist-quality bristle paint brush. The slurry was applied in layers and allowed to air dry. The graphite ring and the test cylinder were periodically weighed until the desired amount of the powder mixture had been applied to both. Once these levels were achieved, the graphite parts, with the powder slurry-coated faces positioned upwards and horizontal, were heated in a convection oven at about 125° C. allowing the cellulose binder to cure in air over 9 to 10 hours, during which time ethanol and any water that might be present evaporated. The parts were then removed, allowed to cool and then associated with hafnium foil. Two rings of hafnium foil, each about 0.001 in. (0.025 mm) thick, were used; each had an O.D. just slightly less than the O.D. of the graphite ring and slightly greater than the O.D. of the TZM ring, which is about 5.25 in.(13.34 cm) and an I.D. slightly smaller than the I.D. of the graphite rim. Assemblies are then created with the hafnium foil disposed horizontally upon the slurry-coated flat surfaces of the graphite support and with the TZM ring resting upon the Hf foil. A similar TZM disk having a flat lower surface is used to overlie two circular disks of Hf foil on the test cylinder. Three metal weights of tungsten and tantalum were then positioned atop the TZM disk to bring the total weight bearing upon the hafnium foil disks to about 2836 grams, which corresponds to a downward pressure of about 0.4 psi over the surface area of about 19.33 square inches. The test sample was similarly weighted. The two assemblies were then transferred to a vacuum furnace having tungsten heating elements disposed within a water-cooled exterior boundary, which was then evacuated to about 9×10 −6 Torr. Heating was carried out at a rate of about 600° C. per hour until a temperature of about 700° C. was reached, at which time the temperature was held for about 5-15 minutes (soaking). The rate of heating was then increased to about 1,000° C. per hour, which rate was thereafter used. Once the target temperature of 1200° C. was reached, it was held for 5-10 minutes, and after 1600° C. was reached, it was held for about 10-20 minutes. Heating was then continued to about 1865° C., the desired reaction-brazing temperature, and the assembly was held at this temperature for 20-30 minutes at a furnace pressure of about 1×10 −4 Torr. As the temperature rises, the Hf foil becomes joined to the Mo alloy body by solid-state diffusion reaction and by the eutectic reaction, i.e. solid Hf (alloyed with Mo) phase+HfMo 2 phase forms liquid eutectic phase at eutectic temperatures. Following completion of the reaction-brazing step, the assemblies were slowly cooled at a rate of about 200° C. per hour for the first 100° and held at about 1765° for about 10 minutes. Cooling at the same rate to 1600° was then effected, and this temperature was held for about 1 minute. The rate of cooling was then increased to about 1000° C. per hour until about 600° C., where the rate gradually slowed as radiative cooling efficiency begins to diminish. After ambient temperature was reached, e.g. below about 40° C., the furnace vacuum was ended, and pressure was returned to atmospheric. Visual examination of the parts shows that brazing is uniform about the entire periphery and that the Hf foil has formed a smooth substantially continuous fillet at the outer surface of the juncture. Both assemblies were examined under a stereomicroscope at magnifications between 3× and 10×, and no evidence of any microcracks was detected. Examination was then carried out using x-ray radiography, and the results were negative indicating that there appeared to be no substantial defects present in the joint region of either assembly. The smaller assembly was then mounted in epoxy and cross-sectioned across a diameter of the cylinder. It was then remounted in epoxy which was cured to create a metallographic mount. Using standard metallographic grinding and polishing techniques, the cross-section was prepared and then examined in a scanning electron microscope to observe the microstructure in the joint region and check for any voids or large pores, cracks or other nonuniformities; none were found. Measurements of the joint thickness were made, and the thickness was found to be between about 0.0025 and about 0.003 inch (0.064 and 0.076 mm). Based upon these observations, it is concluded that this reaction-brazing has resulted in the creation of a molybdenum disk supported upon a dense graphite substrate that will be excellently suited for use as a rotating anode in commercial x-ray tubes because a strong, defect-free bond has been achieved as a result of this reaction-brazing process. EXAMPLE II A procedure as generally set forth in Example I is carried out using a 2-inch diameter graphite ring and a TZM disk of comparable size. Following application of the slurry to the flat surfaces of the graphite ring substrate and a test cylinder, they are reaction-sintered in accordance with the-two-step process depicted in FIG. 2 . The coated graphite supports are placed in the vacuum furnace under the same vacuum conditions and heated to a temperature of about 1945° C. over a time period of about 2 hours and 30 minutes using a very similar heating schedule to that previously described. Once this reaction-sintering temperature is reached, the coated supports are held at this temperature for about 30 minutes. Thereafter, heating is discontinued, and the furnace is cooled to ambient temperature using a schedule essentially the same as in Example I. Thereafter, the two rings of hafnium foil are inserted atop the sintered layer, and a TZM disk is placed thereatop and weighted generally as described in Example I. The test cylinder is separately assembled as before. The assemblies are then returned to the vacuum furnace, and reaction-brazing is carried out using the time and temperature schedule set forth in Example I heating to a temperature of about 1865° C. Following cooling down under similar conditions to Example I, the assemblies are removed, and examination and cross-sectioning of the test cylinder show that a strong, uniform joinder of the bodies has been achieved. In order to test the longevity and other characteristics of the reaction brazes that are being obtained, the Example II sample and a comparable 2-inch diameter sample fabricated according to the process of Example I are soaked for about 50 hours at about 1600° C. in the vacuum furnace under a vacuum of about 10 −4 Torr. Following such soaking at 1600° C., the samples are caused to cycle between 1600° C. and 750° C., being repeatedly allowed to drop over about 50 minutes to 750° C. before raising the temperature back to 160° C. over the next 50 minutes. This process is repeated 20 times so that the samples have each been subjected to 21 thermal cycles. Each time, the samples are held at the 1600° C. level for about 10 minutes and are similarly held at the 750° C. level for about 10 minutes; this constitutes a severe test cycle designed to test the suitability of the product to withstand the cycling that a rotating anode would be expected to experience. Following the 1600° soak and the 21 cycles as described, the joined bodies are examined by X-ray radiography and otherwise, and the bonds appear to be continuous and strong. When the samples are cross-sectioned transverse to the joint and subjected to metallographic examination, it is seen that the thickness of the joint has not grown and that there are only minor amounts of molybdenum carbide and molybdenum boride phases in the grain boundaries of the TZM body adjacent to the joint microstructure of the assemblies made using the one-step method of Example I. A very thin continuous layer of hafnium-rich carbide (equal to about 20% of the thickness of the joint) extends throughout the entire circular area and has remained substantially the same thickness as when it was formed by reaction-brazing. This continuous carbide layer and the balance of the joint microstructure of carbide and boride discrete phases, in conjunction with the Hf plus HfMo 2 eutectoid phase form a very effective barrier to carbon migration from the graphite substrate into the dense molybdenum alloy (TZM) body. The foregoing is confirmed by microhardness readings. Examination of the Example II sample shows a quite similar joint microstructure; however, there is included a thin zone of molybdenum carbide/boride phase that is formed generally adjacent the eutectoid rich zone of the joint that appears to have resulted from C and B diffusion during the high temperature test exposure following the initial reaction-sintering step. However, because the joint thickness has remained about the same and prevented growth of a thick carbide zone into the TZM alloy body, the sample retains good thermal conductivity across the bond (as does the sample from the method of Example I) which is an important feature for a rotating x-ray anode. Both methods produce quite acceptable resultant products and are considered to be very well-suited for manufacturing rotating x-ray anodes that can be used for a substantial length of time at temperatures in the range of 1500-1600° C. without suffering deleterious consequences. The somewhat simpler one-step process is considered to be presently preferred because of the economics of its practice; moreover microscopy examination shows that there is a lesser indication of carbon and/or boron diffusion, i.e. there is detection of a lesser, minor presence of carbide-boride phases, which are only in the grain boundaries of the adjoining Mo alloy body, and only a minimal increase in microhardness. EXAMPLE III A procedure as generally set forth in Example I is carried out using a 2-inch diameter carbon-carbon composite ring and a single crystal W disk of comparable size. A brazing slurry is formed from a particulate/powder mixture in alcohol, i.e. ethanol, using a solution of 99 parts ethanol and 1 part hydroxypropylcellulose. The powder mixture is formulated using equal weight percents of tungsten boride and tungsten carbide and is mixed to achieve 10 parts of this powder mixture in 6 parts by weight of the cellulose alcohol solution. The top surfaces of the carbon-carbon ring and the test cylinder are coated with the powder slurry by painting by hand using an artist-quality bristle paint brush. The slurry is applied in layers and allowed to air dry. The ring and the test cylinder are periodically weighed until the desired amount of the powder mixture has been applied to both. Once these levels are achieved, the carbon-carbon parts, with the slurry-coated faces positioned upwards and horizontal, are heated in a convection oven at about 125° C. allowing the cellulose binder to cure in air over 9 to 10 hours, during which time ethanol and any water that might be present evaporate. The parts are then removed, allowed to cool and then reaction-sintered as generally depicted in FIG. 3 . The coated carbon-carbon supports are placed in a high temperature furnace under the same vacuum conditions; the furnace is back-filled with argon and heated to a temperature of about 2350° C. over a time period of about 1 hour using a heating schedule similar but more rapid than that previously described. Once this reaction-sintering temperature is reached, the coated supports are held at this temperature for about 7 minutes. Thereafter, heating is discontinued, and the furnace is cooled to ambient temperature using a schedule essentially the same as in Example I. Thereafter, each sintered layer is coated with a second layer of the same slurry material, which may optionally include up to about 5% of carbon powder, and then similarly air-dried. A single-crystal W disk is placed thereatop and weighted generally as described in Example I. The test cylinder is separately assembled as before with a similar W disk. The assemblies are then returned to the vacuum furnace, and reaction-brazing is carried out in vacuum, or optionally in inert gas, using a time and temperature schedule generally as set forth in Example I but heating to a final temperature of about 2350° C. and holding that temperature for about 10 to 15 minutes. Following cooling down under a similar schedule as that in Example I, the assemblies are removed, and examination and cross-sectioning of the test cylinder show that a strong, uniform joinder of the bodies is achieved and that the single crystal W disc will be excellently suited for use as a rotating anode in commercial x-ray tubes because its character will allow its operation at a temperature as high as about 85% of the reaction-brazing temperature, e.g. about 2000° C. Although the invention has been described with regard to certain preferred embodiments, it should be understood that various modifications and changes as would be obvious to one having the ordinary skill in this art may be made without departing from the invention which is set forth in the claims which are appended hereto. For example, other dense graphite such as dense pyrolytic graphite may be used; by “dense” is generally meant having at least about 75% of theoretical maximum density, with at least about 90% being preferred. Likewise, carbon fiber-carbon matrix composites having a density of at least about 1.7 gm/cm 2 may also be employed. Other solvents and binders as well known in this art may be employed as they do not take part in the final brazing step. The disclosures of all U.S. patents mentioned hereinbefore are expressly incorporated by reference. By major amount is meant at least about 40 weight %, and by minor amount is meant not more than about 25 weight %. By a temperature of about a certain number of degrees is meant plus or minus 20 degrees. Particular features of the invention are emphasized in the claims that follow.

Reaction-brazing of tungsten or molybdenum metal bodies to carbonaceous supports enables an x-ray generating anode to be joined to a preferred lightweight substrate. Complementary surfaces are provided on a dense refractory metal body and a graphite or a carbon-carbon composite support. A particulate braze mixture comprising Hf or Zr carbide, Mo or W boride, Hf or Zr powder and Mo or W powder is coated onto the support surface, and hafnium or zirconium foil may be introduced between the braze mixture and the refractory metal body complementary surface. Reaction-brazing is carried out at or near the eutectic point of the components, which may be influenced to some extent by the presence of carbon and boride. Heating to about 1865° C. for a Mo/Hf combination creates a thin, dense, strong braze that securely joins the two bodies and creates a thin barrier of carbide and boride microphases near and along the interface with the carbon support that diminishes carbon diffusion into the metal body during extended exposures at elevated temperatures (above those presently used in x-ray tubes), even well above the eutectoid temperature.

FIELD OF THE INVENTION [0001] The present invention relates to the use of flavone derivatives as TNFα (tumor necrosis factor-α) antagonists or inhibitors. BACKGROUND OF THE INVENTION [0002] Flavonoids are a group of polyphenolic compounds exhibiting a variety of important bioactivities such as anti-inflammatory, antihepatotoxic and anti-ulcer actions. They also inhibit enzymes such as aldose reductase and xanthine oxidase. They are potent antioxidants and have free radical scavenging abilities. Many have antiallergic, antiviral actions and some of them provide protection against cardiovascular mortality. They have been shown to inhibit the growth of various cancer cell lines in vitro, and reduce tumour development in the experimental animals (Narayana et al., Indian Journal of Pharmacology 2001; 33: 2-16). [0003] Flavonoid compounds disclosed in WO 01/64701, or U.S. Pat. No. 6,706,865, has a chemical structure of formula (II) in which R 8 is a substituted or unsubstituted phenyl group; R 7 is a hydrogen atom or a hydroxyl group; and n is an integer of 1 to 4 and have reductase inhibitory effect, active oxygen extinguishing effect, carcinogenesis promotion inhibitory effect, anti-inflammatory effect, and so on. Astilbin is a flavanone represented by the following formula (III) and is one of digydroflavonol glycoside isolated from root of Astilbe thunbergii Miq. , which is gerbaceous perennial of saxifragaceous, as well as from the plant matter of Asmilaxylabra, Engelhardtia, Lyoniaovalifolia, Engelhardtiachrysolepos, Chloranthus glarber, Astilbe, microphylla, and so on. Astilbin has been reported to exhibit some important bioactivities such as aldose redutase inhibitory effect, active oxygen extinguishing effect, carcinogenesis promotion inhibitory effect, anti-inflammatory effect, and so on (Japanese Patent Publication Nos. 97/30984, 94/247851, and 94/256194), and therefore, astilbin is to be a very useful compound as anti-allergic drug or anticancer drug. However the anti-inflammatory mechanism has not yet been established. Of the several inflammatory mediators known to date, TNFα is one of by far the most potent and characterized cytokines, it is selected to test whether flavone derivatives inhibit the binding of TNFα to TNFα-R1 by L929 cell proliferation/cytotoxicity assay. [0004] TNFα plays an important role in the host defense. It causes resistance to many pathogenic microorganisms and some viruses. Even if TNFα has undoubtedly a beneficial function (mainly on the systematic level), it could lead to pathological consequences. TNFα plays a significant role in the pathogenesis of septic shock, characterized by hypotension and multiple organ failure among others. TNFα is the main mediator of cachexia characterized by abnormal weight-loss of cancer patients. Often TNFα is detected in the synovial fluid of patients suffering from arthritis. There was a broad spectrum of diseases, where TNFα could play an important role. Compounds binding with TNFα may be therefore useful in the treatment of numerous pathologies in which TNFα is involved, such as rheumatoid arthritis, Crohn's disease, plaque sclerosis, septic shock, cancer or cachexia associated with an immunodeficiency. SUMMARY OF THE INVENTION [0005] It has been found by the present inventor that a flavone derivative of formula (I) in which R 1 , R 2 , R 3 , R 4 and R 5 independently represent hydrogen, hydroxy or an ester group; R 6 represents hydrogen, hydroxy, an ester group or an O-glycoside group such as O-rhamnose, O-glucoside, O-retinoside or O-xyloside; and represents a single bond or a double bond; or the pharmaceutically acceptable salt thereof is useful for inhibiting the binding of TNFα to TNF-R1 or the release of TNFα and therefore may be used as TNFα antagonists or inhibitors in the treatment of numerous pathologies in which TNFα is involved, such as rheumatoid arthritis, Crohn's disease, plaque sclerosis, septic shock, cancer or cachexia associated with an immunodeficiency. It is found that Myricitrin, quercitrin and quercetin-3-D-glucoside exhibit an inhibitory activity with IC 50 values of 116.03, 160.77 and 95.74 μM on L929 cell proliferation/cytotoxicity assay without cell cytotoxicity. In addition, in the animal model of collagen-induced arthritis, the flavone derivatives exhibited 50% inhibitory activity. The flavone derivatives are promising sources with high TNFα inhibitor or antogonist activity. [0006] Therefore, the first aspect of the present invention is a pharmaceutical composition for antagonizing or inhibiting TNFα in a mammal, including human, comprising an amount of a compound of formula (I) or the pharmaceutically acceptable salt thereof effective in antagonizing or inhibiting TNFα and a pharmaceutically acceptable carrier. [0007] The second aspect of the present invention is a pharmaceutical composition for treating a disease or condition for which a TNFα antagonist or inhibitor is indicated in a mammal, including human, comprising an amount of a compound of formula (I) or the pharmaceutically acceptable salt thereof effective in antagonizing or inhibiting TNFα and a pharmaceutically acceptable carrier. [0008] The third aspect of the present invention is a method for antagonizing or inhibiting TNFα in a mammal, including human, comprising administering to said mammal an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof effective in antagonizing or inhibiting TNFα. [0009] The fourth aspect of the present invention is a method for treating a disease or condition for which a TNFα antagonist or inhibitor is indicated in a mammal, including human, comprising administering to said mammal an amount of the compound of formula (I) or the pharmaceutically acceptable salt thereof effective in antagonizing or inhibiting TNFα. BRIEF DESCRIPTIONS OF THE DRAWINGS [0010] The accompanied drawings are to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [0011] FIG. 1 is a HPLC chromatogram of Chamaesyce hirta ( L ) Millsp. methanolic extract. [0012] FIG. 2 shows the results of L929 cellular assay of Chamaesyce hirta ( L ) Millsp. methanolic extract. [0013] FIG. 3 illustrates the isolation of quercitrin and myricitrin from Chamaesyce hirta ( L ) Millsp. methanolic extract. [0014] FIG. 4 is a HPLC chromatogram of quercitrin. [0015] FIG. 5 is a HPLC chromatogram of myricitrin. [0016] FIG. 6 shows the results of L929 cellular assay on quercitrin. [0017] FIG. 7 shows the results of L929 cellular assay on myricitrin. [0018] FIG. 8 is a LC/MS chromatogram of quercitrin. [0019] FIG. 9 is a LC/MS chromatogram of myricitrin. [0020] FIG. 10 is the 1 H-NMR spectrum of quercitrin. [0021] FIG. 11 is the 1 H-NMR spectrum of myricitrin. [0022] FIG. 12 shows the results of inhibition assay on myricitrin, quercitrin and quercetin-3-D-glucoside. [0023] FIGS. 13-1 to 13 - 10 show in vivo test results by using rats with collagen-induced arthritis. DETAILED DESCRIPTION OF THE INVENTION [0024] The compound of formula (I) may be administered to mammals via oral, parenteral (such as subcutaneous, intravenous, intramuscular, intrasternal and infusion techniques), rectal, intranasal, topical or transdermal (e.g., through the use of a patch) routes, etc. The compound of formula (I) or the salt thereof may be administered alone or in combination with pharmaceutically acceptable carriers or diluents by any of the routes previously indicated, and such administration may be carried out in single or multiple doses. Suitable pharmaceutical carriers include solid diluents or fillers, sterile aqueous media and various non-toxic organic solvents, etc. [0000] Experiments [0000] 1. Preparation of the Methanolic Extract of Chamaesyce hirta ( L ) Millsp. [0025] Possible TNFα inhibitor candidates were found in herbal ingredients fractionated by HPLC from herbal extract. Fifty grams of Chamaesyce hirta ( L ) Millsp. was washed and dried. Methanol was added to the weighed herb (10/1, v/w) to extract the herbal ingredients at room temperature for 3 days. The extract was filtered and the filtrate was concentrated under rotatory evaporator (Heidolph Laborota 4000) until the volume was reduced to about 50 mL. ( FIG. 3 ) [0000] 2. HPLC Analysis of the Methanolic Extract Obtained From Chamaesyce hirta ( L ) Millsp. [0026] Then a separation procedure was performed. One hundred μl of the concentrated filtrate of the herb extract was applied to a pre-equilibrated HPLC system (Shimadu). A TSK Gel 80™ reverse phase column (TOSOH) was used for separation. The solvent used for separation was double distilled water and absolute ethanol at 0˜100% gradient for 96 minutes at a flow rate of 0.75 mL/min. [0027] One-minute fractions were collected and dried using SpeedVac (Savant). Each fraction was re-dissolved in 100 μl 10% ethanol for screening for TNFα inhibitors. The fractions with TNFα inhibitor activity were then further purified by HPLC until the purity was more than 95%. [0028] A compound having TNFα inhibitor activity was found in the methanolic extract of Chamaesyce hirta ( L ) Millsp. by using the procedures described above. In FIG. 1 , a chromatogram of the crude methanolic extract of Chamaesyce hirta ( L ) Millsp. is shown. The crude methanolic extract of Chamaesyce hirta ( L ) Millsp. was fractionalized on a TSK Gel ODS 80™(TOSOH) reverse phase column. The particle size of the gel in this column was 5 μm, and the column size was 250×4.6 mm. The mobile phase used was a mixture of H 2 O (A buffer) and absolute ethanol (B buffer) at a flow rate of 0.75 mL/min. The column was sequentially eluted as follows: 0% B for the first 5 minutes; a linear gradient of 0˜15% B for 15 minutes; 15˜50% B for 60 minutes; 50˜100% B for 10 minutes and 100% B for 6 minutes. The detection was performed at a wavelength of 280 nm with a detection sensitivity of 0.01 AUFS. [0000] 3. L929 Cellular Assay [0000] Cell Culture [0029] L929 cells were cultured in Eagle's Minimal Essential Medium (MEM) containing 10% equine serum, 1% P/S and 1% non-essential amino acid. Confluent L929 cells were washed with 2 ml PBS (phosphate-buffered saline) solution and then trypsinized with 1 ml 1×trypsin, followed by resuspending in complete medium. Two hundred microliter of cell suspension was aspirated for cell density counting. The remainder was centrifuged at 1500 rpm for 5 min. The supernatant was removed and the complete medium was added to dilute cells at a concentration of 1.5×10 5 cells/ml. Add 100 μl of cell suspension to each well in 96-well flat-bottomed microtitre plates and incubated for 24 hrs in 5% CO 2 atmosphere at 37° C. incubator. [0000] TNFα Activity Assay [0030] Crude herbal extracts were resuspended in 1×PBS and sterilized with 0.22 μm filters. Varying concentrations of herbal extract were incubated for 1 hr with equal volume of commercial TNFα 0.2 ng/ml. Before the end of the 1 hr pre-incubation, removing the medium from the 24 hr incubated 96-well plate, and added a 50 μl fresh medium containing 4 μg/ml of Actinomycin D into the 96-well plate. Transferred the 50 μl of pre-incubated mixture of herbal extraction and TNFα to the 96-well plate with the medium containing Act D to give the final concentration of Act D (2 μg/ml), TNFα(0.1 ng/ml). The mixture of Act D (2 μg/ml) and TNFα (0.1 ng/ml) were added as positive control and Act D 2 μg/ml only was used as negative control. Alter gently shaking for 24 hrs in 5% CO 2 atmosphere at 37° C. incubator. [0000] Cytotoxicity [0031] The same samples as those for TNFα activity assay were added to the 96-well plate with the medium containing Act D to give the final concentration of Act D 2 μg/ml. Mixed well by gently shaking and then incubated for 24 hrs in 5% CO 2 atmosphere at 37° C. incubator. 50 μl XTT mixture (XTT−1: XTT−2=50:1) was added to each well, and incubated in a CO 2 incubator for 4 hrs. Read with ELISA (enzyme-linked immunosorbent assay) reader at O.D (optical density) 490/630 nm. Calculation of the TNFα Activity Inhibition and Cytotoxicity TNF ⁢   ⁢ α ⁢   ⁢ Inhibition ⁢   ⁢ % = O . D ⁢ . dilut + TNF + Act . ⁢ - O . D ⁢ . TNFa + Act O . D ⁢ . Act ⁢   ⁢ only ⁢ - O . D ⁢ . TNFa + Act × 100 ⁢ % Cytotoxicity ⁢   ⁢ % = O . D ⁢ . dilut . + ActD O . D ⁢ . ActD ⁢   ⁢ only × 100 ⁢ % 4. Quercitrin and Myricitrin Identification (1) Thin-Layer Chromatography [0032] For TLC experiment, precoated plates of silica gel 60F 254 (E. Merck) were used and spotting was done with capillary tubes. The plates were scanned on a UV observed box (Gamag). The solvent system was chloroform:methanol:ethyl acetate/MeOH=20/1.5 for pure quercitrin and ethyl acetate/MeOH=6/1 for pure myricitrin. TLC of the isolated quercitrin and myricitrin showed a single spot with its R f value 0.63 and 0.6 in this solvent system. [0000] (2) LC/MS Spectrum [0033] The atmospheric pressure ionization with ESI mass spectrum of molecular ions was obtained on a LC/MS (Varian). The mobile phase was water/EtOH. Quercitrin Mass: 445 (M+H) + ( FIG. 8 ), myricitrin 461 (M+H) + ( FIG. 9 ). [0000] (3) HPLC Spectrum [0034] The HPLC spectra of quercitrin and myricitrin were obtained. The reference standard was obtained by TSK Gel ODS 80™ (5 μm) TOSOH reverse phase column (4.6×250 mm) using a Shimadu HPLC system with a mobile phase containing ethanol and water. The HPLC analysis of the quercitrin gave a single peak with retention time of 46.3 min ( FIG. 4 ), and retention time of myricitrin was 51.8 min ( FIG. 5 ). The following HPLC condition should be used when carrying out this analysis: Gradient Time (min) B buffer (EtOH) % 0˜5  0  5˜20 0˜15 20˜80 15˜50  80˜90 50˜100 90˜96 100 [0035] A buffer: H 2 O [0036] Flow Rate: 0.75 mL/min [0037] Detection Wavelength: 280 nm [0038] Injection volume: 100 μL [0000] (4) 1 H-NMR Spectrum [0039] The 1 H-NMR spectrum of quercitrin is shown in FIG. 10 . 1 H-NMR (600 MHz, Acetone-d 6 ) δ0.91 (3H, d, J=6.0 Hz, Me rhamnose), 3.31-4.20 (4H, m, sugar protons), 5.52 (1H, d, J=1.2 Hz, H-1″), 6.26 (1H, d, J=1.8 Hz, H-6), 6.47 (1H, d, J=1.8 Hz, H-8), 6.99 (1H, d, J=7.8 Hz, H-5′), 7.40 (1H, dd, J=2.4, 7.8 Hz, H-6′), 7.50 (1H, d, J=2.4 Hz, H-2′). [0040] The 1 H-NMR spectrum of myricitrin is shown in FIG. 11 . 1 H NMR (600 MHz, CD 3 OD) δ 0.96 (3H, d, J=6.0 Hz, Me rhamnose), 3.31-4.20 (4H, m, sugar protons), 5.31 (1H, d, J=1.2 Hz, H-1″), 6.26 (1H, d, J=1.8 Hz, H-6), 6.36 (1H, d, J=2.4 Hz, H-8), 6.95 (2H, s, H-2′ and H-6′). [0000] 5. Anti-Inflammatory Effect of Myricitrin and Quercetin-3-D-glucoside on Rats With Collogen-Induced Arthritis [0041] SD rats of SPF grade were supplied from BioLasco. Prior to performing the study, the animals were accommodated for 4 days after being received. Weighing, blood sampling, measuring the paw volumes and other related records for each animal were established. The rats were immunized and boosted with bovine collagen II-EFA (Incomplete Freund's Adjuvant, from Sigma) to induce arthritis (CIA). The CIA rats were grouped into 6 groups and daily injected with the drug candidates (myricitrin and quercetin-3-D-glucoside respectively). Dexamethasone (0.2 mg) was used as a positive control and 5% ethanol as a negative control. Treatment period was 7 days. Body weight and paw volumes were measured and blood sampling were collected at day 0, 3, 6, 10 and 14. [0042] Six days after the final dosing, all the animals were sacrificed. The affected hind limbs were removed for histological assessment. The parameters of body weights and paw volumes were measured and compared for before, during and after treatment with drug candidates. [0043] Collagen-induced arthritis was found on day 9th after boostering, the volumes of hind paw swelled 2-2.5 times that of normal hind paws. (See FIG. 13-1 in which FIG. 13-1 a shows hind paw before CII-IFA injection. FIG. 13-1 b shows hind paw with collagen-induced arthritis. Swelling and erythema appeared.) The group treated with myricitrin showing decreased percentage, 65.98%, of edema volumes for hind paws after continual treatment for 6 days. On the 3 rd day and 7 th day after treatment stopped, the decreased percentage of edema were 55.95% and 50.93% for myricitrin. (See FIG. 13-2 , in which FIG. 13-2 a shows volumes of left hind paw for group myricitrin. The volume of T0 is before injected CII-IFA, T1 is before treatment, T3 is day 6th of treatment, T4 and T5 are day 3rd and day 7th after administered. FIG. 13-2 b shows different time points of edema percentage comparison with non-treatment volume of paw. T3 is 1−(T3−T1/T1−T0)%, T4 is 1−(T1-T4/T1−T0)% and T5 is 1−(T1-T5/T1−T0)%.). In the group treated with quercetin-3-D-glucoside, it appeared slight decrease percentage of edema volume in the treatment period (8.59%) in comparison with non-treatment. After stop administer day 3rd the decrease percentage was down to 24.93% and increase to 80.47% on day 7th. (See FIG. 13-3 , in which FIG. 13-3 a shows volumes of left hind paw for group quercetin-3-D-glucoside. The volume of T0 is before injected CII-IFA, T1 is before treatment, T3 is day 6th of treatment, T4 and T5 are day 3rd and day 7th after administered. FIG. 13-3 b shows different time points of edema percentage compared with non-treatment volume of paw. T3 is 1−(T3−T1/T1−T0)%, T4 is 1−(T1-T4/T1−T0)% and T5 is 1−(T1-T5/T1−T0)%.) While the group treated with dexamethasone was 28.21% on the 3 rd day and 29.97% on the 7 th day in decreased percentage of edema. (See FIG. 13-4 , in which FIG. 13-4 a shows volumes of left hind paw for group dexamethasone. The volume of T0 is before injected CII-IFA, T1 is before treatment, T3 is day 6th of treatment, T4 and T5 are day 3rd and day 7th after administered. FIG. 13-4 b shows different time points of edema percentage compared with non-treatment volume of paw. T3 is 1−(T3−T1/T1−T0)%, T4 is 1−(T1-T4/T1−T0)% and T5 is 1−(T1-T5/T1−T0)%.) Histopathological changes with loose connective tissues, lymphocytes infiltration around joint, periarticular edema and proliferation of synovial ling cells were observed in all arthritis samples ( FIG. 13-6 to FIG. 13-10 ) but not in normal samples ( FIG. 13-5 ). FIG. 13-5 shows a normal histological slice of joint of non-immune with collagen II. FIG. 13-6 shows a histopathological slice of rats with CIA and treated (IP) with myricitrin, in which proliferation of cell and infiltration of lymphocytes could be observed. FIG. 13-7 shows a histopathological slice of rats with CIA and treated (IP) with quercetin-3-D-glucoside, in which proliferation of synovial ling cell and infiltration of lymphocytes was shown. FIG. 13-8 shows a histopathological slice of rats with CIA and treated (IP) with dexamethasone. Proliferation of synovial ling cell and infiltration of erythrocytes and some lymphocytes could be observed. FIG. 13-9 shows a histopathological slice of rats with CIA and treated (IP) with 5% ethanol. Proliferation of synovial ling cell and infiltration of lymphocytes could be observed. FIG. 13-10 shows a histopathological slice of rats with CIA treated with dexamethasone. Periarticular edema and infiltration of lymphocytes were observed.

The use of flavone derivatives of formula (I) in which R 1 , R 2 , R 3 , R 4 and R 5 independently represent hydrogen, hydroxy or an ester group; R 6 represents hydrogen, hydroxy, an ester group or an O-glycoside group such as O-rhamnose, O-glucoside, O-retinoside or O-xyloside; and

FIELD OF INVENTION [0001] The invention relates to an apparatus and method for measuring local brain water content, perfusional pulsatile changes and the real time derivation of brain stiffness by comparison of perfusional and intracranial pressure tracings. BACKGROUND OF INVENTION [0002] Monitoring intracranial pressure (ICP) in real time in intensive care units has become an established standard of care in guiding physicians in the management of severe head injury. Treatment of head trauma increases pressure on the brain requiring monitoring intracranial pressure. This is particularly true in complicated cases of hydrocephalus as a post-craniotomy adjunct to detect brain swelling and in selected instances of brain infection and stroke. As brain swelling worsens due to the disease process, baseline pressure and waveform changes signal the need to aggressively attempt to reverse the course of the swelling with medications and pulmonary ventilation changes. [0003] Intracranial pressure monitoring is normally performed by inserting a shunt through a hole in the cranium. A ventriculostomy catheter connected to an external pressure transducer is then introduced via the shunt into the brain substance. The shunt may also be used to drain excess fluid from the brain substance. An external pressure transducer provides accurate pressure measurements since a reliable baseline may be established. However, an external pressure transducer requires invasive procedures, risking a patient's health. [0004] More recently, a miniaturized fiberoptic or strain gauge pressure transducer is inserted into the brain substance. The miniaturized transducer greatly reduces the invasiveness of the insertion procedure, but no practical method exists to establish a baseline measurement. This creates accuracy problems since many factors over the course of treatment may shift baseline measurements. Additionally, the ICP sensor and data from it alone do not allow a direct measurement of how edematous or congested the specific region of the brain is. Furthermore, swelling provides a widely ranging pressure change related to age and causes of the swelling. Finally, the ICP sensor alone does not provide a measurement of real time brain stiffness or compliance, a helpful indicator of imminent deterioration risk. [0005] Static measurement may be achieved by magnetic resonance imaging (“MRI”), but this does not provide real time data. Real time information would greatly facilitate the detection of true shunt failure in the management of hydrocephalus. However, since real time measurement cannot be done with internal sensors, shunt failure must be inferred from late presenting clinical deterioration and anatomical changes as seen in imaging studies of the MRI. Additionally, the transport of a critically ill patient to an MRI facility is hazardous. [0006] There is therefore a need for an instrument which may be inserted through a single aperture in the skull for simultaneous and continuous monitoring of both intracranial pressure and cerebral water content. There is another need for an instrument which may continuously measure pulsatile changes, altering apparent water content relating to beat-to-beat tissue perfusion due to cardiac output of blood to the brain. There is a further need for an instrument which provides the continuous measurement of tissue congestion related to venous back pressure from mechanical ventilation. There is another need for an instrument which derives the percent water content of the brain for comparison against normal values. There is yet another need for a system to monitor the more gradual baseline changes in wetness or brain edema of intracellular or extracellular origin related to the disease process. There is another need for an instrument which can simultaneously display the intracranial pressure (ICP) waveform and the pulsatile perfusional or momentary congestion changes of the brain. There is still another need for an apparatus and method for comparing the differences in lagtime between the ICP and perfusional waveforms, from which a realtime measurement of brain stiffness or compliance is derived. SUMMARY OF THE INVENTION [0007] These needs may be addressed by the present invention which is embodied in one aspect of the invention which is a probe for measuring tissue water content in a region of interest in the brain. The probe has an implantable tissue water content sensor having two plates with a proximal and distal end. The two plates are separated by a dielectric material and the distal end is implantable in brain tissue. An impedance matching circuit is coupled to the proximal end of one of the plates. A first output terminal is coupled to the matching circuit resistor and a second output terminal is coupled to one of the plates. A remotely positioned frequency spectrum analyzer receives an output signal from the first and second output terminals. A digital computer has a display, the digital computer having an input coupled to the output signal from the water content probe and the spectrum analyzer, the computer programmed to display the resonant frequency of the sensor indicative of water content in the brain tissue. [0008] Another aspect of the present invention is a method of measuring tissue water content in a selected region of interest in the brain. A capacitive sensor having two plates outside the selected region of interest is calibrated and the resonant frequency of the sensor in air is determined. The capacitive sensor is calibrated in a mixture of water and NaCl. The resonant frequency of the sensor in the mixture is determined. A linear baseline frequency in relation to water content based on the resonant frequencies of the sensor in air and the mixture is established. The capacitive probe is implanted through a skull aperture such that the capacitive plates are exposed to the brain cortex and subjacent white matter. Interrogatory frequency scanning by a spectrum analyzer coupled to the sensor is produced to determine the center point of resonance by passage of the signal. True tissue water content is approximated by curve-fitting the frequency of resonance with the baseline frequency. [0009] Another aspect of the present invention is a method of deriving beat-to-beat perfusional and congestion changes in brain tissue. The method includes inserting a water content probe having two conductive plates and a dielectric in the brain tissue. Signals at different frequencies on the water content probe are sent. A standing wave ratio at different frequencies is determined. A water content change tracing which fluctuates with cardiac output pulsatile perfusion of the tissue is then determined. [0010] Another aspect of the present invention is a method of deriving realtime compliance or stiffness of brain tissue. The intracranial pressure of the brain tissue is measured. An intracranial waveform from the measurements of the intracranial pressure is then plotted. The pulsatile congestion changes in water content of the brain tissue is measured. A pulsatile congestion change waveform is plotted from the measurements of the pulsatile congestion change. The waveforms of intracranial pressure and the pulsatile congestion change in water content on a computer are simultaneously plotted. The stiffness of the brain is then determined from the simultaneous plotting. [0011] Another aspect of the present invention is a probe for measuring tissue water content in a region of interest in the brain. The probe has an implantable tissue water content sensor having two plates with a proximal and distal end. The two plates are separated by a dielectric material and the distal end is implantable in brain tissue. A signal transmitting circuit is coupled to the proximal end of one of the plates. A signal receiver is provided. A remotely positioned frequency spectrum analyzer is coupled to the signal receiver. A digital computer is provided having a display and an input which is coupled to the output signal from the water content probe and the spectrum analyzer. The computer is programmed to display the resonant frequency of the sensor indicative of water content in the brain tissue [0012] It is to be understood that both the foregoing general description and the following detailed description are not limiting but are intended to provide further explanation of the invention claimed. The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the method and system of the invention. Together with the description, the drawings serve to explain the principles of the invention. BRIEF DESCRIPTION OF DRAWINGS [0013] This invention is pointed out with particularity in the appended claims. However, other objects and advantages together with the operation of the invention may be better understood by reference to the following illustrations, wherein: [0014] FIG. 1 is a perspective view of a brain stiffness probe according to an embodiment of the present invention. [0015] FIG. 2 is a partial cutaway view depicting the probe in FIG. 1 inserted through an aperture in the skull such that it is exposed to direct contact with brain tissue. [0016] FIG. 3 is a block diagram with the probe components and remotely placed measuring equipment for both the water content sensor component and intracranial pressure component according to one embodiment of the present invention. [0017] FIG. 4A - FIG. 4D are frequency resonance curves and calibration and measurement of tissue water content taken using a system according to the present invention. [0018] FIG. 5 is a waveform diagram showing pulsatile changes in microscopic center frequency shifts in the water content probe according to the present invention due to perfusion of the brain by cardiac pulsatile output. [0019] FIG. 6 is a block diagram of a wireless implementation of a water content probe according to the present invention. [0020] FIG. 7A-7B are waveform diagrams which show the phase or lagtime relationship between the pressure waveform and perfusional waveform derived from the water content component of the combined probe according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT [0021] While the present invention is capable of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. [0022] In accord with one embodiment of the invention, a combined probe 10 for measuring brain wetness and intracranial pressure is shown in FIG. 1 . The probe 10 has a water content sensor 11 which has two conductive plates 12 and 14 on opposite sides of a printed circuit board (PCB) substrate 16 . The conductive plates 12 and 14 are silver in the preferred embodiment but any suitable conductor material may be used. The substrate 16 in the preferred embodiment measures 5 cm in length, 2 mm in width, and 0.5 mm in depth. The probe 10 has a proximal end 18 and a distal end 20 . Multiple holes 22 extend across the PCB substrate 16 . The holes 22 increase sensitivity to real time pulsatile perfusional changes in tissue as they increase the surface area in contact with the brain tissue. The proximal end 18 has a surface mount resistor 24 on one side. A coaxial cable 26 has a core conductor member 28 and a shielding conductor 30 which is circumferentially located around the core member 28 . [0023] The surface mount resistor 24 is coupled between the proximal end 18 and one end of the coaxial cable 26 . The surface mount resistor 24 provides impedance matching between the core 28 of the coaxial cable 26 and the plate 12 . The impedance matching provided by the surface mount resistor 24 and the cable 26 is employed to achieve noise immunity in the cable 26 and allow the analysis electronics to be located at a distance from the water content sensor 11 . Other types of impedance matching circuits such as a balanced antenna approach may be used as well. The plate 14 is connected directly to the shielding conductor 30 of the coaxial cable 26 . The other end of the coaxial cable 26 is connected via an adapter 32 to a controller unit 34 . In this sample, the adapter 32 is a PL250 type which minimizes signal loss to the cable 26 . [0024] The water content sensor 11 is inserted through a plastic bolt 36 via an aperture 38 . The plastic bolt 36 has a pair of hex nuts 40 and 42 which are mounted on a main body section 44 . The main body 44 has an exterior surface with threads. A lug nut 46 is coupled to the main body 44 and has corresponding interior threads. The lug nut 46 may be rotated on the main body 44 and provides a connection for the cable 26 . [0025] The probe 10 is inserted to a depth in brain tissue up to the plastic bolt 36 via the aperture. The hex nuts 40 and 42 and the lug nut 46 are tightened on the main body 44 of the bolt 36 to provide a seal and to allow the plastic bolt 36 to be positioned and held in the aperture 38 . The bolt 36 is designed such that the surface mount resistor 24 lies about 1 mm above the surface of the brain, placing nearly the full length of the plates 12 and 14 in the brain tissue. Since the water of the brain bears a moderate salinity (typically 130-150 mEq Na+ per 1000 ml), an extremely thin-sputtered layer of insulation 50 insulates the electrical plates 12 and 14 from direct tissue contact. The insulation layer 50 is Teflon in the preferred embodiment, but any type of insulation may be used. The insulation layer 50 allows the point of resonance of the water content sensor 11 to be precisely measurable. The configuration of the capacitive plates 12 and 14 may be used in a tubular configuration to allow a silicone external ventricular drain through the lumen. In such a configuration, the electrically conductive plate surfaces are located on the length of the tube on opposite hemispheres to create a similar capacitive effect. [0026] FIG. 2 shows a cutaway view of a head 60 with a brain 62 shown through the frontal lobes as seen by a typical MRI. The brain 62 is encased by a cranium 64 . The containment of the cranium 64 creates pressure on the brain 62 which may be excessive due to fluid buildup. A skull aperture 66 (or burr hole) is created in the cranium 64 after a scalp incision. This routine procedure in the intensive care unit would normally be followed by the introduction of an ICP sensor or ventriculostomy catheter as is presently known. [0027] The plastic ventriculostomy bolt 36 in the preferred embodiment is commercially available through Codman and Shurtleff Incorporated, Raynham, Mass. The plastic bolt 36 is tapped and threaded snugly into the cranium 64 . The water content sensor 11 is passed through the bolt 36 to a depth such that the sensing capacitive plates 12 and 14 are exposed to cortex and white matter of the brain 62 . The plastic bolt 36 provides stable fixation of electrical connections and prevents movement of the sensor 11 in the brain 62 by secure fixation at the skull aperture 66 (burr hole). [0028] An intra cranial pressure (“ICP”) sensor 70 passes through the bolt 36 into the subjacent cortical tissue of the brain 62 . The ICP sensor 70 is an electrical strain gauge type and measures changes in resistance due to pressure. Alternatively, any implantable pressure sensor such as a fiber optic sensor may be used. A fiber optic sensor has lasers coupled to dual fiber optic cables. A diaphragm is coupled to the end of the fiber optic cables and distorts light in reaction to pressure, producing changes in either light amplitude or frequency. In other cases, an external strain gauge which is coupled via tubing to a ventriculostomy catheter or a cranial bolt may be used to measure pressure. [0029] The output voltage of the ICP sensor 70 is carried by a cable 72 . The strain gauge ICP sensor 70 in this example is commercially available from Codman and Shurtleff Incorporated, Raynham, Mass. but any appropriate pressure sensor may be used. The ICP sensor 70 may be inserted separately from the bolt 36 and/or inserted at a separate site on the cranium if desired. This is to be avoided in most cases, but certain circumstances may require the separate insertion of the ICP sensor 70 and the water content sensor 11 . [0030] The respective wiring connections to and from the water content sensor 11 and the ICP sensor 70 are coupled to the controller unit 34 which is at a remote location. Alternatively, the cables may be connected to a signal transmitter if it is desired to eliminate the cables. The technique of positioning the combined sensors is identical to the routine insertion of a ventriculostomy catheter for monitoring and carries with it the same acceptably low risks. [0031] FIG. 3 is a block diagram of the control unit 34 of the combined ICP-water content probe 10 . The ICP sensor 70 is a strain-gauge type which has a wheatstone bridge 74 of standard configuration having a pressure transducer 76 and three resistors 78 , 80 and 82 . The voltage of the bridge 74 changes in accordance to pressure changes on the pressure transducer 76 . The output voltage of the bridge 74 represents the sensed pressure on transducer 76 and is coupled to the input of an analog to digital convertor 84 via the cable 72 . The output of the analog to digital convertor 84 is coupled to a digital computer 86 . [0032] The water content sensor 11 is coupled via the coaxial cable 26 to an input of a spectrum analyzer 88 . The spectrum analyzer 88 in the preferred embodiment is an AEA-Tempo 150-525 Analyst manufactured by Tempo Research of Vista, Calif. The spectrum analyzer 88 sweeps an interrogating frequency from 150 MHZ to 550 MHZ every 2 seconds to the water content sensor 11 in the preferred embodiment. The frequency spectrum for measuring brain water content without interference from other sources is optimally measured between 400 and 600 MHZ. However, other ranges may be useful depending on the probe length. [0033] The direct output from the spectrum analyzer 88 is coupled to the digital computer 86 and a second output is coupled to an analog to digital convertor 90 . This allows display of the resonant frequency of the water content sensor 11 determined from the direct output, as well as heart beat to heart beat changes in frequency and standing wave ratio (SWR) from the digital to analog converter 90 . The outputs from the spectrum analyzer 88 and the digital to analog convertor 90 are plotted on a display 92 . The display 92 is preferably a high resolution monitor but any display device may be used. [0034] The digital computer 86 contains software necessary to simultaneously display the pulsatile waveform outputs from the ICP sensor 70 and the water content probe 11 on the display 92 . As will be explained below, the brain water content and blood congestion alter the resonant frequency of the water content probe 11 and provides an indication of the real time read out of apparent tissue water content and the stiffness of the brain 62 which is independent of baseline water content or pressure. [0035] FIGS. 4A-4D illustrates the process of probe calibration and water content determination of brain tissue which is displayed using the software on the digital computer 86 in conjunction with the display 92 . The water content sensed by the water content sensor 11 of the probe 10 in FIGS. 1 and 2 is indicative of the effect of the surrounding tissue dielectric on the speed of transmission of the interrogating signal through the plates 12 and 14 . Similar in concept to time domain reflectometry and familiar to those skilled in the art, the spectrum analyzer 88 will display a resonant frequency when the water content sensor 11 is placed in tissue. This resonance is a function of plate capacitance of the plates 12 and 14 (most strongly affected by probe length in this configuration) and the adjacent dielectric of the material of the substrate 16 . The PCB dielectric material 16 between the plates 12 and 14 and the extremely thin-sputtered layer 50 have dielectric constants near air (dielectric of 1). In contrast, the brain is normally about 70% water. As the dielectric of H2O is 80, the tissue water content overwhelmingly determines the resonant frequency measured from the water content sensor 11 . [0036] FIG. 4A shows the output plot of the spectrum analyzer 88 displayed by the digital computer 86 when the water content sensor 11 is entirely exposed to air. Since no significant water content related dielectric slows the signal in air, the resonant frequency of the water content sensor 11 is 440 MHZ. FIG. 4B shows the output plot when the water content sensor 11 is inserted in a 100% normal saline and water compound (simulating brain water and salinity). The resonant frequency of the water content sensor 11 has decreased to 167 MHZ as shown in FIG. 4B . This reduction is due to the overwhelming dielectric effect of the surrounding water with its high dielectric constant. [0037] FIG. 4C shows the sharp resonant curve of the output of the water content sensor 11 when placed in the brain tissue 62 as shown in FIG. 2 . The resonant frequency is 307 MHZ in FIG. 4C . The water content of the brain tissue 62 is proportional to the resonant frequency. The different resonant frequencies sensed by the sensor 11 in differing conditions of water content may be plotted. FIG. 4D shows the linearity of a typical output curve from the water content sensor 11 from submersing the sensor 11 in water as in FIG. 4A to full exposure in air as in FIG. 4B . By testing the water content sensor 11 in tissue utilizing dry and wet weight water content determinations, the linear range of clinical significance from 65% (very dehydrated brain) to 80% (very edematous brain) may be tested and provides a measurement standard for water content determination. [0038] The measurable accuracy of the water content sensor 11 is up to 0.1% of water content change. In clinical use, however, the absolute local water content determination is not as useful as the trending of water content of the brain tissue over the course in the intensive care unit against a baseline measurement. The long term trends are more useful data since insertion of the water content sensor 11 , as any probe, into the brain 62 , causes a temporary injury edema which develops about the sensor 11 and artificially increases the baseline water content in the region. Additionally, effects of local minor accumulation of a non-flowing blood clot against the sensor plates 12 and 14 or incomplete passage to full depth of the plates 12 and 14 will offset the true water content baseline. Despite these considerations, the baseline measurement is used as a control against the course of illness and therapeutic intervention with dehydrating drugs such as furosemide and mannitol or ventilator changes provide a real time feedback of impact of the physician's regimen on the patient. [0039] When the baseline water content is plotted over hours of time on a computer such as the computer 86 , gradual shifts in the water content may be analyzed. For example, the initial shift in water content represents the initial placement edema and its resolution. The longer term shift in water content may represent the trend of brain swelling in the region of monitoring, edema due to head injury, or the effects of therapy. Alternatively, the changes in resonant frequency may also be logged using a spectrum/frequency analyzer such as a Model HP8568A manufactured by Hewlett-Packard. However, much smaller changes of significance to the course of the illness may be measured from heart beat to heart beat as will be explained below. Thus, the water content sensor 11 may be used in isolation without the associated intracranial pressure sensor 70 , yielding profitable data for the patient. [0040] FIG. 5 shows a pulsatile baseline 500 obtained from minute apparent water content change. Either one of two techniques may be used to obtain the water content change on a heart beat to heart beat basis. The first technique involves use of the frequencies around the resonant frequency. When the spectrum analyzer 88 is employed to identify the standing wave ratio (“SWR”) at resonance, a properly placed water content sensor 11 will show an SWR of 1.0. The frequency of resonance relates to the water content which is 307 MHZ in FIG. 4D . [0041] However, if the frequency just to the right of the resonant point in FIG. 4D is selected where maximum change in SWR occurs per unit frequency change, typically an SWR of about 1.15, the beat-to-beat change of SWR may be plotted. The beat to beat SWR changes thus correlates to the local increased water content sensed by the water content sensor 11 which is due to transient increased tissue congestion and arteriolar dilation due to blood flow. An undulating waveform 502 as a function of time is shown in FIG. 5 . The undulating waveform 502 is measured from the water content sensor 11 as a function of the change in SWR from heart beat to heart beat. A slower baseline undulation relates to back pressure on the venous side of the brain from positive pressure ventilation of the patient or may be evoked by transient jugular vein compression (termed the Queckenstedt maneuver). [0042] Alternatively, the beat-to-beat effect may be measured by tracking the center frequency of resonance deviation when the water content sensor 11 in FIGS. 1 and 2 is viewed as the variable component of a simple LC resonant circuit 100 as shown in FIG. 6 . The sensor 11 is coupled to an inductor 102 . The sensor 11 and the inductor 102 may thus be integrated in an implanted sensor unit 104 . A second inductor 106 is coupled to the processing circuitry which includes a signal generator and resonant frequency measurement device as explained above. Since the value of the first inductor 102 is fixed, the resonant frequency will shift as a function of water content of the tissue surrounding the sensor unit 104 . The resonant frequency is measured wirelessly by sensing magnetic field energy from the second inductor 106 and the signal generator. [0043] A significant advantage of this approach is that beat-to-beat pulsatile changes and baseline water content may be measured wirelessly using a spectrum analyzer pick-up circuit across the scalp from a wholly implanted resonant circuit. This technique allows long term, wireless monitoring of a region of interest over months to years for determining optimal compliance and control of hydrocephalus in patients treated by a ventriculoperitoneal shunting procedure. [0044] With reference to FIGS. 1 and 2 , when the intracranial pressure (ICP) waveform is plotted simultaneously with the pulsatile water content waveform derived from the two techniques described above, a phase relationship between the waveforms is seen. FIG. 7A shows a simultaneous plot of pressure 600 versus a pulsatile water content plot 602 . The pressure plot 600 precedes pulsatile congestion as sensed by the water content probe plot 602 . This indicates that peak vascular congestion lags peak pressure. FIG. 7A depicts the phase relationship plotted of a healthy, normal brain. In FIG. 7A , brain stiffness is within acceptable levels and thus the phase of beat to beat water content resonant frequency is phase shifted from the pressure changes by 115 degrees. [0045] In contrast, FIG. 7B shows the pressure and water content plots 600 and 602 superimposed on each other in an example of worsening brain compliance or stiffness. The beat to beat water content resonant frequency is phase shifted from the pressure changes by 68 degrees. This relationship is also demonstrated by a combined ICP-blood flow probe such as when monitoring a patient with a thermal probe as described in U.S. Pat. No. 4,739,771 to the same inventors and incorporated by reference herein. In a normal, relaxed brain, the peak flow or vascular congestion may lag substantially, especially in a child with an open antereor fontanel. As the brain becomes progressively swollen with brain edema in head injury the lag narrows until the two waveforms are essentially co-incidental. Similarly, poor compliance in a patient with shunt failure will show the pattern of narrowing of lag time. The relationship can also be measured in real time as a function of phase lag adjusted for frequency (heart beat), akin to phase lag plotting in current phase compared to voltage phase in inductive circuits. Thus, the relationship by lag in seconds or phase angle adjusted for frequency provides a measure of brain stiffness which is independent of transducer amplitude, accuracy or stability, allowing a frequency domain relationship applicable to long term monitoring including implants. [0046] It will be apparent to those skilled in the art that the disclosed measurement method and apparatus described above may be modified in numerous ways and assume many embodiments other than the preferred forms specifically set out and described above. Alternatives to the capacitive water content sensing technology include time domain reflectometry and square-wave frequency based sensors as well as fiberoptic sensors. The time domain reflectometry views the sensing components as a model transmission line. The reflection of a signal is measured as a function of water content. The square wave frequency based sensor uses a broad range of frequencies to determine water content as a function of the frequencies observed. The proper interpretation of the square wave frequency signals requires the appropriate circuitry. The fiberoptic sensor uses a light signal of a certain wavelength which is propagated down an implanted fiber. An optical grating is used to determine reflection of the light signal which is a function of the water content. [0047] The pulsatile flow relationship to the ICP waveform can be derived by use of transducers such as thermistors (as described in the author's cited patent), or other heat clearance transducers as well as by transcranial impedance measurement and local tissue laser Doppler technique. The transcranial impedance measurement is performed by placing an ohmmeter on the head and measuring the signals at high frequency. An alternate impedance measurement may be used using a four probe method. Two impedance probes measure the output while two probes input the signal. The laser Doppler technique uses a laser to send a signal to the tissue of interest. The shift in Doppler frequency is measured to determine the water content. [0048] An antenna sensor may be used for the water content sensor instead of the capacitive approach explained above. The entirety of the circuitry which includes the implanted circuit with an antenna to sense the water content in the tissue and a transmitter can be reduced to an integrated circuit as part of an implant or integrated onto the probe itself, allowing transcranial, wireless interrogation. The present invention is not limited by the foregoing descriptions but is intended to cover all modifications and variations that come within the scope of the spirit of the invention and the claims that follow.

A method and system to determine brain stiffness is disclosed. A probe to measure tissue water content is inserted through an aperture (burr hole) in the cranium into brain tissue. The probe has two electrically separated plate conductors with a dielectric which forms a capacitor plane. One conductor has a surface mount resistor to allow exact impedance matching to the core of a coaxial cable. The other conductor attaches electrically to the shield of the coaxial cable. The probe is stabilized in the brain tissue through a plastic ventriculostomy bolt which has been secured by screw tapping into the cranium. The coaxial cable connects to a spectrum analyzer. Brain water content and blood congestion alter the resonant frequency of the probe, allowing a realtime readout of apparent tissue water content. By monitoring the momentary shift in center resonant frequency or, alternatively, the standing wave ratio slightly off resonant frequency, a beat-to-beat pulsatile waveform is derived relating to the perfusion of the brain. A strain gauge intracranial pressure sensor (ICP) is separately affixed through the bolt and adjacent to the water content probe. By comparing the phase angle or lag time difference between the pressure tracing and the perfusion tracing, a realtime measurement of organ stiffness or compliance is derived.

FIELD OF THE INVENTION [0001] The present invention relates to tubular prostheses such as grafts and endoluminal prostheses including, for example, stent-grafts and aneurysm exclusion devices, and methods for placement of such grafts and endoluminal structures. Further, the present invention relates to a stent graft and deployment method. BACKGROUND OF THE INVENTION [0002] A wide range of medical treatments have been previously developed using “endoluminal prostheses,” which terms are herein intended to mean medical devices which are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring or artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries such as those located within coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes. Various types of endoluminal prostheses have also been developed, each providing a uniquely beneficial structure to modify the mechanics of the targeted luminal wall. [0003] A number of vascular devices have been developed for replacing, supplementing or excluding portions of blood vessels. These vascular grafts may include but are not limited to endoluminal vascular prostheses and stent grafts, for example, aneurysm exclusion devices such as abdominal aortic aneurysm (“AAA”) devices that are used to exclude aneurysms and provide a prosthetic lumen for the flow of blood. [0004] One very significant use for endoluminal or vascular prostheses is in treating aneurysms. Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease or a genetic predisposition, which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aneurysms occurring in the abdominal aorta. Typically an abdominal aneurysm will begin below the renal arteries and may extend into one or both of the iliac arteries. [0005] Aneurysms, especially abdominal aortic aneurysms, have been treated in open surgery procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique in view of the alternative of a fatal ruptured abdominal aortic aneurysm, the open surgical technique suffers from a number of disadvantages. The surgical procedure is complex and requires long hospital stays due to serious complications and long recovery times and has high mortality rates. In order to reduce the mortality rates, complications and duration of hospital stays, less invasive devices and techniques have been developed. The improved devices include tubular prostheses that provide a lumen or lumens for blood flow while excluding blood flow to the aneurysm site. They are introduced into the blood vessel using a catheter in a less or minimally invasive technique. Although frequently referred to as stent-grafts, these devices differ from covered stents in that they are not used to mechanically prop open natural blood vessels. Rather, they are used to secure an artificial lumen in a sealing engagement with the vessel wall without further opening the natural blood vessel that is already abnormally dilated. [0006] Typically these endoluminal prostheses or stent grafts are constructed of graft materials such as woven polymer materials (e.g., Dacron,) or polytetrafluoroethylene (“PTFE”) and a support structure. The stent-grafts typically have graft material secured onto the inner diameter or outer diameter of a support structure that supports the graft material and/or holds it in place against a luminal wall. The prostheses are typically secured to a vessel wall above and below the aneurysm site with at least one attached expandable annular spring member that provides sufficient radial force so that the prosthesis engages the inner lumen wall of the body lumen to seal the prosthetic lumen from the aneurysm [0007] Abdominal Aortic Aneurysms are frequently treated with bifurcated devices that provide an artificial lumen for flow of blood past the aneurysm and into the iliac vessels that branch off from the aorta. One such commonly used device comprises a bifurcated device having one branch portion longer than the other branch portion. This enables deployment of the main body through one of the iliac arteries where the longer branch is deployed. An extension leg is then deployed through the second iliac artery and is connected with the shorter branch portion. [0008] Iliac vessels associated with abdominal aneurysms frequently have tortuous and twisted anatomies and other structural abnormalities that can prevent effect introduction of an extension leg through an iliac vessel. Often it must be decided prior to deployment whether to use a single lumen prosthesis through one iliac vessel and join the vessels with a shunt further down in the anatomy, or to use a bifurcated prosthesis with an extension. Often a surgeon may not be able to determine the appropriate course of action until the prosthesis is in place or after attempts have been made to deploy an extension graft through a tortuous iliac artery. It would be desirable to provide a device that would enable the decision to be made during the deployment procedure. Devices have been proposed in U.S. Pat. No. 6,102,938, incorporated herein by reference, that provide for sealing off a bifurcated portion of a bifurcated AAA device before or after deployment. Such device is designed for situations where a determination is made during a procedure that it would not be possible to introduce an extension leg into the shorter bifurcated portion to provide blood flow through one of the iliac vessels. It would be desirable to provide an improved or alternative device for accomplishing such task. [0009] Frequently, the AAA procedures are performed in emergency situations where the aorta has ruptured or is extremely fragile and about to rupture. In these situations, frequently a single leg device is deployed through the aorta and one of the iliac vessels occluding the second iliac vessel. This may be done because of the importance of reestablishing blood flow through the aorta and iliac vessel and stopping the loss of blood through the ruptured or rupturing vessel. Such situations may not permit deployment of the second (extension) leg. During this crucial time, in using an existing bifurcated device, blood would be able to flow through the shorter bifurcated portion of the prosthesis into the area of the aneurysm. Accordingly it would be desirable to provide an improved or alternative device that allows for deployment of a bifurcated device in emergency situations that would prevent further blood flow into the area of the aneurysm. SUMMARY OF THE INVENTION [0010] Accordingly one embodiment according to the present invention provides a novel device and method that include providing a bifurcated device with one leg initially in an occluded position preventing flow of blood through that portion into the aorta. Once the implant is in place and blood is excluded from the aneurysm site, an extension may be introduced and the occluded side opened to blood flow through the extension. [0011] An embodiment of the endoluminal prosthesis comprises a bifurcated tubular member constructed of a graft material and at least one annular support member. The tubular graft is formed of a woven fiber for conducting fluid. The tubular member includes, a proximal opening and distal openings though the bifurcated portions providing a lumen or lumens through which body fluids may flow. When deployed, annular support members support the tubular graft and/or maintain the lumen in a conformed, sealing arrangement with the inner wall of a body lumen. One of the bifurcated portions is provided with a valve that can open or close to permit or prevent the flow of blood through the bifurcated portion. Various embodiments of the valve includes a member that move a section of graft or other material over or away from the opening into the short iliac leg of the bifurcated prosthesis to close or open the short leg to the flow of blood. [0012] The annular support members of an embodiment of the prosthesis each comprise an annular expandable member formed by a series of connected compressible diamond structures. Alternatively, the expandable member may be formed of an undulating or sinusoidal patterned wire ring or other compressible spring member. Preferably the annular support members are radially compressible springs biased in a radially outward direction, which when released, bias the prosthesis into conforming fixed engagement with an interior surface of the vessel. Annular support members are used to create a seal between the prosthesis and the inner wall of a body lumen as well as to support the tubular graft structure. The annular springs are preferably constructed of Nitinol. Examples of such annular support structures are described, for example, in U.S. Pat. Nos. 5,713,917 and 5,824,041 incorporated herein by reference. When used in an aneurysm exclusion device, the support structures have sufficient radial spring force and flexibility to conformingly engage the prosthesis with the body lumen inner wall, to avoid excessive leakage, and prevent pressurization of the aneurysm, i.e., to provide a leak resistant seal. Although some leakage of blood or other body fluid may occur into the aneurysm isolated by the prosthesis, an optimal seal will reduce the chances of aneurysm pressurization and resulting rupture. [0013] The annular support members are attached or mechanically coupled to the graft material along the tubular graft by various means, such as, for example, by stitching onto either the inside or outside of the tubular graft. [0014] An embodiment according to the present invention provides such a tubular graft for endoluminal placement within a blood vessel for the treatment of abdominal and other aneurysms. In this embodiment, the endoluminal prosthesis is an aneurysm exclusion device forming a lumen for the flow of body fluids excluding the flow at the aneurysm site. The aneurysm exclusion device may be used for example, to exclude an aneurysm in the aorta (Abdominal Aortic Aneurysm (“AAA”) device) in which the prosthesis is bifurcated. [0015] The generally Y-shaped bifurcated tubular prosthesis has a trunk joining at a graft junction with a pair of lateral limbs, namely an ipsilateral limb and a contralateral limb. In a bifurcated prosthesis, the proximal portion of the prosthesis comprises a trunk with a proximal opening and the distal portion is branched into at least two branches with distal openings. Preferably the ipsilateral limb is longer so that when deployed, it extends into the common iliac. The contralateral limb includes a valve located therein that is initially in a closed position in which body fluids flow from the proximal opening through the distal opening of the ipsalateral limb while the flow of body fluid through the contralateral limb is prevented by the valve. A single limb extension member is provided having a mating portion for coupling with a lateral limb of a bifurcated member and an adjustable length portion extending along an axis from a distal end of the mating portion. The insertion of the limb extension into the contralateral portion of the main prosthesis opens the valve which is then in part maintained open by the extension limb, permitting blood flow from the proximal opening in the main prosthesis through the distal opening in the contralateral and extension limbs. [0016] The valve in one embodiment comprises a plurality of support members coupled to a section of graft material. One of the support members is an annular member forming an opening for the flow of body fluids. A proximal support member is a semicircular member which has an closed position in which the section of graft material forms a cover over the opening formed by the annular member, and an open position in which the section of graft material is held is a position against the wall of the prosthesis so that the opening formed by the annular member is in fluid communication with the flow of body fluid through the prosthesis. [0017] In another embodiment the valve comprises a plurality of annular support members coupled to a section of graft material where at least one of the annular support members is configured to be folded to form a semicircular member engaged to an inner circumference of the bifurcated prosthesis. When the valve is in an open position, the support members are in an open configuration whereby the annular members and a section of graft material form a lumen through which blood may flow. When the valve is in a closed position, one of the annular support members is folded to that the graft material attached to the folded annular member is drawn across the opening through the short leg in which the valve is located. [0018] In another embodiment the valve comprises a graft material sewn in part on an inner circumference of the bifurcated prosthesis and forming a pocket when the valve is closed. A portion of an annular member is sewn on to at least a portion of the section of graft material not sewn on to the prosthesis. When the valve is in a closed position, the annular member holds section of the graft material in a position over the opening in the short leg of the prosthesis. The annular member in this position is across from the location where the opposite side of the section of graft material is sewn on to the prosthesis. When the valve is in a closed position, the annular member holds the pocket formed by the section of graft material closed. The annular member in this position is against the location where the section of graft material is sewn on to the prosthesis so that the opening in the short leg provides a lumen through which blood may flow from the proximal end of the prosthesis to the distal end of the short leg. [0019] The compressed profile of the prosthesis, including the valve, is sufficiently low to allow the endoluminal graft to be placed into the vasculature using a low profile delivery catheter. The prosthesis can be placed within a diseased vessel via deployment means at the location of an aneurysm. Various means for deliver of the device through the vasculature to the site for deployment, are well known in the art and may be found for example is U.S. Pat. Nos. 5,713,917 and 5,824,041. In general, the endoluminal prosthesis is radially compressed and loaded in a catheter for delivery to the deployment site. The aneurysm site is located using an imaging technique such as fluoroscopy and is guided through a femoral iliac artery with the use of a guide wire to the aneurysm site. Once appropriately located, a sheath restraining the tubular graft may be retracted to release the annular springs to expand and attach or engage the tubular member to the inner wall of the body lumen. The iliac extension is also loaded into a catheter and is then located into the main body of the stent graft and within the iliac vessel and is placed through an opened valve where it is deployed. According to an embodiment, when deployed, the iliac has proximal annular springs which when located within the inner lumen of the main body hold or maintain the valve open. The distal portion of the extension extends into one of the iliac vessels. BRIEF DESCRIPTION OF THE DRAWINGS [0020] [0020]FIG. 1 is a side elevational view of an endoluminal prosthesis of the prior art. [0021] [0021]FIG. 2A is a side view of a valve in a closed position as positioned in a prosthesis according to an embodiment of the invention. [0022] [0022]FIG. 2B is a top cross sectional of a proximal most support member of the valve of FIG. 2A. [0023] [0023]FIG. 2C is a top cross sectional of a middle support member of the valve of FIG. 2A. [0024] [0024]FIG. 2D is a top cross sectional of a distal most support member of the valve of FIG. 2A. [0025] [0025]FIG. 2E is a front cut away view of the valve of FIG. 2A in a closed position. [0026] [0026]FIG. 2F is a back cut away view of the valve of FIG. 2A in a closed position. [0027] [0027]FIG. 3 is a top view of the prosthesis and valve of FIG. 2A. [0028] [0028]FIG. 4A is a side view of a valve of the prosthesis of FIG. 2A in an open position. [0029] [0029]FIG. 4B is a side view of the valve of FIG. 4A in an open position. [0030] [0030]FIG. 5 is a top view of the prosthesis and valve of FIGS. 4 A- 4 B. [0031] [0031]FIG. 6 is a perspective partial cutaway view of the prosthesis of FIG. 2A. [0032] [0032]FIG. 7 is perspective partial cutaway view of the prosthesis of FIG. 4A with an extension in place and the valve in an open position. [0033] [0033]FIG. 8 is a side view of another embodiment of a valve in a closed position according to the invention. [0034] [0034]FIG. 9A is a top view of the prosthesis and valve of FIG. 8. [0035] [0035]FIG. 9B is a front cut away view of the valve of FIG. 9A in an open position. [0036] [0036]FIG. 9C is a back cut away view of the valve of FIG. 9A in an open position. [0037] [0037]FIG. 10 is a side view of a valve of the prosthesis of FIG. 8 in an open position. [0038] [0038]FIG. 11A is a top view of the prosthesis and valve of FIG. 10. [0039] [0039]FIG. 11B is a side view of the valve of FIG. 11A in an open position. [0040] [0040]FIG. 12 is a side view of another embodiment of a valve in a closed position according to the invention. [0041] [0041]FIG. 13 is a perspective partial cutaway view of the prosthesis of FIG. 12. [0042] [0042]FIG. 14 is a side view of a valve of the prosthesis of FIG. 12 in an open position. [0043] [0043]FIG. 15 is perspective partial cutaway view of the prosthesis of FIG. 14. DETAILED DESCRIPTION [0044] [0044]FIG. 1 illustrates a bifurcated prosthesis of the prior art. The prosthesis 210 is shown in place in an abdominal aorta 20 . The aorta 20 is joined by renal arteries 22 and 24 at the aorto-renal junction 26 . Just below the aorta-renal junction 26 is an aneurysm 28 , a diseased region where the vessel wall is weakened and expanded. Below the aneurysm 28 , the aorta 20 bifurcates into right and left iliac vessels 21 , 23 , respectively. The elongated bifurcated tubular prosthesis 210 is deployed at the region of aneurysm 28 for the purpose of relieving blood pressure against the weakened vessel wall, by acting as a fluid conduit through the region of the aneurysm 28 . In its deployed condition, a main body portion 216 of the prosthesis 210 defines a conduit for blood flow through the aorta 20 and into the iliac vessel 21 . Before deploying an iliac extension (not shown), blood unobstructedly flows through the short iliac portion 219 into the aorta 20 as illustrated. [0045] Annular support members (rings) 212 attached to a tubular graft 25 , are designed to exert a radially outward force, sufficient to bias the tubular graft 215 of the endoluminal prosthesis 210 into conforming fixed engagement with the interior surface of aorta 20 above aneurysm 28 . The tubular graft 215 provides a leak resistant seal between the prosthesis and the inner wall of the aorta 20 . The proximal aortic portion 217 of the prosthesis 210 is located within aorta 20 , and the long ipsalateral iliac portion limb 218 is located within the right iliac vessel 21 . The short iliac portion 219 is located within the aorta 20 . The flow of blood after the main body portion 216 has been deployed is illustrated in FIG. 1. [0046] After deployment of the main body portion 216 , a contralateral iliac extension limb (not shown) may be located within left iliac vessel 23 , and near the graft junction 221 within the short iliac portion 219 . The contralateral iliac extension limb (not shown) may include a proximal support member biasing the extension into conforming fixed engagement with the interior surface of the short iliac portion 219 . [0047] To deploy the prosthesis 210 , the main body portion 216 of the prosthesis is loaded into a catheter (not shown). The main body is placed in a constrained position within a sheath or cover (not shown) of the catheter and maintains main body 216 in a compressed configuration as it is delivered to the aneurysm site. The main body portion 216 is delivered in a compressed state via catheter through a surgically accessed femoral artery, to the desired deployment site. The cover is retracted when the distal end of the catheter (not shown) is located at the deployment site, releasing the annular members 212 from the compressed position to expand into the deployed position illustrated in FIG. 1. [0048] Using a second catheter (not shown), the contralateral iliac extension limb (not shown) may be separately deployed through a surgically accessed femoral artery and into the short iliac portion 219 after placement of the main body portion 216 . [0049] FIGS. 2 A- 15 illustrate embodiments of the endoluminal prosthesis, delivery systems and methods according to the present invention. The arrows in these figures indicate the flow of blood when deployed in the corresponding configuration, within an aorta of a patient. Although an endoluminal prosthesis, delivery system and method according to the invention may be used in any bifurcated or branched body lumen that conducts body fluid, they are described herein with reference to a bifurcated device used in the treatment of an aortic aneurysm, in particular in the abdomen of a patient. [0050] FIGS. 2 A- 7 illustrate an embodiment of the invention in which a bifurcated prosthesis 50 includes a main aortic portion 52 , which splits into a long iliac portion 53 and a short iliac portion 54 . The main aortic portion 52 and the iliac portions 53 , 54 define a conduit splitting into two conduits through which blood may flow to bypass an aortic aneurysm. The prosthesis 50 comprises a tubular graft 55 and a series of radially compressible annular support members (not shown but similar to support members 212 described above with reference to FIG. 1) attached to tubular graft 55 . The annular support members support the graft and/or bias the prosthesis 50 into conforming fixed engagement with an interior surface of an aorta 20 . The annular support members are preferably spring members having predetermined radii and are preferably constructed of a material such as Nitinol in a superelastic, shape set annealed condition. The tubular graft 55 is preferably formed of a biocompatible, low-porosity woven fabric, such as a woven polyester. The graft material is thin-walled so that it may be compressed into a small space, yet capable of acting as a strong, leak-resistant, fluid conduit when in tubular form. In this embodiment, the annular support members are sewn to the outside of the tubular graft 55 material by sutures. Alternative mechanisms of attachment may be used (such as embedding or winding within material, adhesives, staples or other mechanical connectors) and the annular support members may be attached to the inside of the tubular graft 55 . [0051] A valve 60 is located adjacent or within the conduit corresponding to the short iliac portion 54 . The valve 60 has an open position (FIGS. 4 A- 4 B, 5 and 7 ) and a closed position (FIGS. 2A, 2E, 2 F, 3 and 6 ). The valve 60 includes three support members 61 , 62 , 63 generally formed of attached diamond-like structures. The distal most support member 61 (FIG. 2D) comprises an annular member in which the diamond-like structures are attached in a ring. The support members 62 (FIG. 2C) and 63 (FIG. 2B) comprise cylindrical-wall-like partial rings or semicircular members. The valve 60 may be a separate insert that is held in position within the short iliac portion 54 by the radial force of the support member 61 which may be a spring member formed e.g., of Nitinol against the inside of the short iliac portion 54 . Alternatively or in addition, the valve 60 may be attached to the inner wall of the short iliac portion 54 by suturing or other attachment means. [0052] The support members 62 , 63 may be flipped (elastically everted) from a first position forming a semicircle with an inner and outer circumference, to a second position in which the side forming the inner circumference in the first position becomes the outer circumference in the second position and the side forming the outer circumference in the first position becomes the inner circumference in the second position (the ends approximately maintaining their position to the inner wall of the short iliac leg). The support members 62 , 63 are in the first and closed position in FIGS. 2A, 2E, 2 F, 3 and 6 and are in the second and open position in FIGS. 4 A- 4 B, 5 and 7 . [0053] The support members 61 , 62 , 63 are sewn onto a section of graft material 65 . The section of graft material 65 is configured to extend around the inner circumference of the annular support member 61 forming a tube around the annular support member 61 . The section of graft material 65 is shaped or cut so that it is generally semicircular in shape where it is sewn around the support members 62 , 63 to match the shape of those members 62 , 63 . The section of graft material 65 is located on the inner circumference of the support members 62 , 63 when they are in the first, closed position, and, on the outer circumference of the support members 62 , 63 when they are in the second, open position. [0054] When in the first and closed position as illustrated in FIGS. 2A, 2E, 2 F, 3 , and 6 , the support member 61 holds the section of graft material 65 in place around the circumference of the lumen in the short iliac portion 54 of the prosthesis 50 where it forms a lumen 66 . The support members 62 and 63 hold the section of graft material 65 in a position over the lumen 66 forming a cover 67 (FIG. 3) that prevents the flow of blood through the lumen 66 or the short iliac portion 54 . The proximal most support member 63 holds a portion 65 a of a section of the graft material 65 against a first portion 55 a of an inner circumference of the tubular graft 55 . (FIGS. 2E, 2F) The support member 62 located between support members 61 and 63 provides a transition for the section of the graft material 65 across the lumen 66 to provide the cover 67 (FIGS. 2E, 2F). [0055] The support members 62 and 63 are flipped (elastically everted) over into the second, open position as illustrated in FIGS. 4 A- 4 B, 5 and 7 . In this position, the graft material 65 surrounding the support members 62 , 63 that in the first position formed the cover 67 , is held in position against the inner wall (i.e., a second portion 55 b of an inner circumference of the tubular graft 55 opposite from the first portion 55 a of the inner circumference) of the short iliac portion 54 of the prosthesis 50 so that it does not interfere with the flow of blood through the lumen 66 . [0056] In one embodiment the prosthesis 50 is deployed as follows. The valve 60 is initially in a closed position and the prosthesis 50 is loaded into a catheter 80 . The prosthesis 50 along with the valve 60 may be radially compressed within a delivery catheter 80 . The catheter 80 is located in position to deploy the prosthesis in the abdominal aorta of a patient with an aneurysm in the aorta (not shown) below the aortarenal junction (not shown). The prosthesis is deployed by retracting a sheath that is holding the prosthesis 50 in its radially compressed position. [0057] Surgical methods and apparatus for accessing the surgical site are generally known in the art and may be used to place the catheter within the vasculature and deliver the prosthesis to the deployment site. Additionally, various actuation mechanisms for retracting sheaths of catheters are known in the art. The prosthesis 50 may be delivered to the deployment site by one of several ways. A surgical cut down may be made to access a femoral iliac artery. The catheter 80 is then inserted into the artery and guided to the aneurysm site using fluoroscopic imaging where the prosthesis 50 is then deployed. The members 51 supporting the graft 55 , biased in a radially outward direction, are released to expand and engage the prosthesis 50 in the vessel against the vessel wall to provide an artificial lumen for the flow of blood. Another technique includes percutaneously accessing the blood vessel for catheter delivery, i.e., without a surgical cutdown. An example of such a technique is set forth in U.S. Pat. No. 5,713,917, incorporated herein by reference. [0058] When deployed, the prosthesis 50 is in position with the aortic portion 52 engaging the neck region just below the renal arteries 22 , 24 . The long iliac portion 53 is located within the iliac vessel 21 while the short iliac portion 54 is within the aorta 20 just proximal of the iliac vessel 23 as illustrated in FIG. 2A, 3 and 6 . [0059] Referring to FIG. 7, a catheter 80 has been inserted through the iliac vessel 23 in a manner that is typically used to deploy an extension graft, and the extension member 68 has been deployed. In inserting the catheter 80 , the tip 81 of the catheter 80 is first inserted by guiding it between the inner wall of the short iliac portion 54 and the outer circumference of the support members 62 , 63 in their closed position. The tip 81 of the catheter 80 is tapered so that as it is inserted, it flips the support members 62 , 63 into the second position, opening the valve 60 . The support members 62 , 63 demonstrate an over center spring action whereby they are stable in both the closed and open valve positions illustrated in FIGS. 2 A- 7 . Once the support members 62 , 63 are moved over a center, they will move to the opposite position. [0060] Once the support member 62 , 63 are moved from the closed valve position to the open valve position, the extension member 68 that is loaded in the catheter 80 is released from the catheter 80 in a position in which at least a portion of the extension member 68 is located within the lumen 66 in the open valve 60 and maintains the valve 60 in an open position with the radial force exerted by support members 69 on the extension member 68 (as shown in FIG. 7). The extension member 68 extends into the iliac artery and forms a lumen for the flow of blood therethrough. The support members are constructed of a Nitinol that is preset to maintain a closed configuration so in the absence of an opening force, the valve will close [0061] According to this embodiment, the valve 60 is initially in a closed position when the prosthesis 50 is deployed. Thus, flow of blood into the aneurysm through the short iliac portion or leg 54 is prevented until an extension member 68 is placed the second iliac artery 23 and into the short iliac portion 54 . The valve 60 thus will remain closed if the surgeon determines that it is not feasible or desirable to deploy an extension member through the iliac vessel 23 . [0062] FIGS. 8 - 11 B illustrate another embodiment according to the invention in which a bifurcated prosthesis 110 includes a main aortic portion 112 , which splits into a long iliac portion 113 and a short iliac portion 114 . The main aortic portion 112 and the iliac portions 113 , 114 define a conduit splitting into two conduits through which blood may flow to bypass an aortic aneurysm. The prosthesis 110 comprises a tubular graft 115 and a series of radially compressible annular support members (not shown but similar to support members 212 described above with reference to FIG. 1) attached to tubular graft 115 . The annular members support the graft and/or bias the prosthesis 110 into conforming fixed engagement with an interior surface of an aorta (not shown). The annular support members are preferably spring members having predetermined radii and are preferably constructed of a material such as Nitinol in a superelastic, shape set annealed condition. The tubular graft 115 is preferably formed of a biocompatible, low-porosity woven fabric, such as a woven polyester. The graft material is thin-walled so that it may be compressed into a small diameter, yet capable of acting as a strong, leak-resistant, fluid conduit when in tubular form. In this embodiment, the annular support members are sewn on to the outside of the tubular graft 115 material by sutures. Alternative mechanisms of attachment may be used (such as embedding or winding within material, adhesives, staples or other mechanical connectors) and the annular support members may be attached to the inside of the tubular graft 115 . [0063] A valve 120 is located adjacent or within the conduit corresponding to the short iliac portion 114 . The valve 120 has an open position (FIGS. 10, 11A and 11 B) and a closed position (FIGS. 8 and 9A- 9 C). The valve 120 includes three support members 121 , 122 and 123 comprising attached diamond-like structures formed into rings. The valve 120 may be held in position within the short iliac portion 114 by the radial force of the distal most support member 121 which may be a spring member formed e.g., of Nitinol. Alternatively or in addition, the valve 120 may be attached in part to the inner wall of the short iliac portion 114 , for example, by suturing or other mechanical means. [0064] The support members 121 , 122 , 123 are sewn onto section of a graft material 125 . The graft material 125 extends around the inner circumference of the annular support members 121 , 122 , 123 forming at tube around the inner circumference of the annular support members 121 , 122 , 123 . [0065] The support members 122 , 123 may be flipped (elastically everted) from a first position in which the support members are folded into semicircular configurations (wherein each ring forming a support member ( 122 , or 123 ) are folded into two folded halves), to a second position in which the support members 122 , 123 are opened into ring configurations. The support members 122 , 123 are in the first and closed position in FIGS. 8 and 9A- 9 C and are in the second and open position in FIGS. 10, 11A and 11 B. [0066] When in the first and closed position as illustrated in FIGS. 8 , and 9 A- 9 C, the support member 121 holds the section of the graft material 125 in place around the circumference of the lumen in the short iliac portion 114 of the prosthesis 110 where it forms a lumen 126 . The support members 122 and 123 are folded so that the outer side of a portion 125 b of the section of the graft material 125 is held in a position over the lumen 126 , thus forming a cover 127 that prevents the flow of blood through the lumen 126 or the short iliac portion 114 . The proximal most support member 123 holds a portion 125 a of a section of the graft material 125 against an inner circumference of a portion of the valve 120 that is held against a first portion 115 a of the inner circumference of the short iliac portion 114 of the tubular graft 115 (FIGS. 9B, 9C). The support member 122 located between support members 121 and 123 provides a transition for the section of the graft material 125 across the lumen 126 to provide the cover 127 (FIGS. 9B, 9C). [0067] The support members 122 and 123 are flipped over into the second, open position as illustrated in FIGS. 10, 11A and 11 B. In this position, the portion 125 a of the section of the graft material 125 surrounding the support members 122 , 123 that in the first position formed the cover 127 , is in tubular configuration, in which the section of the graft material 125 is held against the inner wall of the short iliac portion 114 of the prosthesis 110 so that it does not interfere with the flow of blood through the lumen 126 . The prosthesis 120 in the open position, as illustrated in FIG. 11B, extends partially proximally of the inner wall of the graft junction 121 within the short iliac portion 119 that divides the short iliac portion 119 from the long iliac portion 118 . [0068] The prosthesis 110 is deployed in a manner similar to the prosthesis 50 described above with reference to FIGS. 2 A- 7 . The valve 120 is initially in a closed position and the prosthesis 110 is loaded into a catheter (not shown). The prosthesis 110 along with the valve 120 may be radially compressed within a delivery catheter and is positioned and deployed in the abdominal aorta of a patient. According to this embodiment, the valve 120 is initially in a closed position when the prosthesis 110 is deployed. Thus, flow of blood into the aneurysm through the short iliac portion or leg 114 is prevented until an extension member (not shown) is placed through the second iliac artery (not shown) and into the short iliac portion 114 . The valve 120 thus will remain closed if the surgeon determines that it is not feasible or desirable to deploy an extension member through the iliac vessel. [0069] An extension graft (not shown) is deployed in a manner similar to the deployment of the extension member 68 described above with reference to FIG. 7. Accordingly, the tip of a catheter into onto which the prosthesis 110 is loaded (not shown) is guided between the folded portions 122 a , 122 b of the support member 122 in its closed configuration, and the folded portions 123 a , 123 b of the support member 123 in its closed configuration. The tip of the catheter is tapered so that as it is inserted, it opens the support members 122 , 123 into the second positions, opening the valve 120 . The extension member that is loaded in the catheter is then released from the catheter in a position in which at least a portion of the extension member is located within the lumen 126 in the open valve 120 and maintains the valve 120 in an open position with the radial force exerted by the extension member. The extension member extends into the iliac artery and forms a lumen for the flow of blood therethrough. The support members 122 , 123 are constructed of a similar material as support members 61 , 62 , and 63 , described above with reference to FIGS. 2 A- 7 . [0070] FIGS. 12 - 15 illustrate an embodiment of the invention in which a bifurcated prosthesis 150 includes a main aortic portion 152 , which splits into a long iliac portion 153 and a short iliac portion 154 . The main aortic portion 152 and the iliac portions 153 , 154 define a conduit splitting into two conduits or lumens through which blood may flow to bypass an aortic aneurysm including lumen 156 through the short iliac portion 154 . The prosthesis 150 comprises a tubular graft 155 and a series of radially compressible annular support members (not shown, but similar to support members 212 described herein with reference to FIG. 1) attached to tubular graft 155 . The annular members 151 support the graft and/or bias the prosthesis 150 into conforming fixed engagement with an interior surface of an aorta. The annular support members are preferably spring members having predetermined radii and are preferably constructed of a material such as Nitinol in a superelastic, shape set annealed condition. The tubular graft 155 is preferably formed of a biocompatible, low-porosity woven fabric, such as a woven polyester. The graft material is thin-walled so that it may be compressed into a small diameter, yet capable of acting as a strong, leak-resistant, fluid conduit when in tubular form. In this embodiment, the annular support members are sewn on to the outside of the tubular graft 155 material by sutures. Alternative mechanisms of attachment may be used (such as embedding or winding within material, adhesives, staples or other mechanical connectors) and the annular support members may be attached to the inside of the tubular graft 155 . [0071] A valve 160 is located adjacent or within the lumen 156 of the short iliac portion 154 . The valve 160 has an open position (FIGS. 14 and 15) and a closed position (FIGS. 12 and 13). The valve 160 comprises a support member 161 sewn onto a section of graft material 165 shaped in the form of a pocket. The support member 161 comprises attached diamond-like structures formed into a semicircular member and is sewn onto the top edge of the pocket-shaped section of graft material 165 . The support member 161 is constructed of a similar material as support members 61 , 62 , and 63 , described above with reference to FIGS. 2 A- 7 . The support member 161 has a first position corresponding to the first and closed position of the valve in which the support member is in sealing engagement with a portion of the inner circumference of the tubular graft 155 of the prosthesis 150 . The support member 161 has a second position corresponding to the second and open position of the valve 160 where the support member 161 is in sealing engagement with a second portion of an inner circumference of the tubular graft 155 , the second portion being on a opposite side of the tubular graft from the first portion. A portion of the section of graft material 165 is secured, e.g., sewn, onto the inner wall of the short iliac portion 154 that forms the lumen 156 , i.e. to the second portion of the inner circumference of the tubular graft 155 , so that the portion of the section of graft material provides a leak resistant seal with the inner wall of the tubular graft 155 . The graft material 165 , when the valve 160 is in the first and closed position as illustrated in FIGS. 12 , and 13 , forms a cover 167 over the lumen 156 in the short iliac portion 154 of the prosthesis 150 that prevents the flow of blood through the lumen 156 . The graft material 165 extends around the inner circumference of the annular support members 161 so that graft material 165 and the support structure 161 when in the closed position, form a leak resistant seal with the inner wall of the short iliac portion 154 . In addition to attaching the graft 165 to the inner wall of the short iliac portion 154 , the valve 160 is held in position within the short iliac portion 154 by the radial force of the support member 161 which may be a spring member formed e.g., of Nitinol. The support member 161 holds the valve 160 in the first and closed position in FIGS. 12 and 13 and in the second and open position in FIGS. 14 and 15. [0072] The support member 161 may be flipped from a first position in which the valve 160 is closed, to a second position in which the valve 160 is open. In the first position, the support member forms a semicircle with an inner and outer circumference. When it is in its second position, the side forming the inner circumference in the first position becomes the outer circumference in the second position and the side forming the outer circumference in the first position becomes the inner circumference in the second position. When the support member 161 is flipped over into the second, open position as illustrated in FIGS. 14 and 15 the graft material 165 surrounding the support member 161 that in the first position formed the cover 167 , and the graft material 165 that is attached to the inner wall of the short iliac portion 154 , is held by the support member 161 against the inner wall of the short iliac portion 154 of the prosthesis 150 so that it does not interfere with the flow of blood through the lumen 156 . The graft material 165 is located on the inner circumference of the support member 161 when it is in the first, closed position, and, on the outer circumference of the support member 161 when it is in the second, open position. [0073] The prosthesis 150 is deployed in a manner similar to the prosthesis 50 described above with reference to FIGS. 2 A- 7 . The valve 160 is initially in a closed position and the prosthesis 150 is loaded into a catheter (not shown). The prosthesis 150 along with the valve 160 may be radially compressed within a delivery catheter and is positioned and deployed in the abdominal aorta of a patient. Thus, flow of blood into the aneurysm through the short iliac portion or leg 154 is prevented until an extension member (not shown) is placed through the second iliac artery (not shown) and into the short iliac portion 154 . The valve 160 thus will remain closed if the surgeon determines that it is not feasible or desirable to deploy an extension member through the iliac artery. [0074] An extension graft (not shown) is deployed in a manner similar to the deployment of the extension member 68 described above with reference to FIG. 7. Accordingly, the tip of a catheter into onto which the prosthesis 150 is loaded (not shown) is guided between the inner wall of the short iliac portion 154 and the outer circumference of the support member 161 in its closed position. The tip of the catheter is tapered so that as it is inserted, it flips the support member 161 into the second position whereby the support member 161 holds the graft material 165 in a position against the inner wall of the short iliac portion so that the valve 160 is open and the graft material 165 does not obstruct the flow of blood through the short iliac portion 154 . The extension member that is loaded in the catheter is then released from the catheter in a position in which at least a portion of the extension member is located adjacent the support member 161 and maintains the valve 160 in an open position with the radial force exerted by the extension member. The extension member extends into the iliac artery and forms a lumen for the flow of blood therethrough. [0075] While the invention has been described with reference to particular embodiments, it will be understood to one skilled in the art that variations and modifications may be made in form and detail without departing from the spirit and scope of the invention.

A bifurcated endoluminal prosthesis is provided that includes a valve or gate in one of the bifurcated branches. The valve or gate prevents flow of blood through the branch when it is closed and permits the flow of blood when it is open. In one variation, the valve comprises a spring member attached to a graft material substantially impermeable to the flow of blood. The spring member holds the graft material over the opening that forms a lumen in the bifurcated portion. The spring member may be flipped from a closed position in which it is initially deployed, to an open position whereby the graft material forms an opening continuous with lumen in the bifurcated portion permitting the flow of blood therethrough. The invention may be used in bifurcated or branched tubular grafts for endoluminal placement within a body lumen, including blood vessels, and for the treatment of abdominal and other aneurysms.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ion implantation, and more especially, to −low temperature ion implantation. 2. Background of the Related Art Low temperature ion implantation is a new application of ion implantation. It has been discovered that a relatively low wafer temperature during ion implantation is advantageous for the formation of shallow junctions, especially ultra-shallow junctions, which are more and more important for continued miniaturization of semiconductor devices. Besides, it also has been proven to be useful for enhancing the yield of the ion implantation. At the start of the current low temperature ion implantation, a wafer is moved from an environment, such as an atmosphere environment, into an implanter. As shown in FIG. 1 a , before the implant process is started, a cooling process (from t c to t i ) cools the wafer temperature from an environment temperature (T R ) of about 15˜25° C. to a prescribed implant temperature (T P ) (or to be essentially equal to the prescribed implant temperature), which usually is lower than the freezing point of water and generally is about −15˜−25° C. As usual, the prescribed implant temperature represents the setting temperature of an E-chuck, which is used to hold the wafer. Herein, the wafer can be cooled at least in a cassette outside the implanter, in a loadlock chamber of the implanter, in a chamber of the implanter, and so on. In general, as shown in FIG. 1 b , a backside gas with a constant pressure (P 0 ) is applied to cool the wafer and it requires several seconds (even minutes) to cool down the wafer from the environment temperature (T R ) to the prescribed implant temperature (T P ). After that, the backside gas with the constant pressure is still applied to cool the wafer during the implant process. Referring still to FIG. 1 a , during the implant process (from t i to t h ) of the wafer, the wafer is heated by the ion beam energy and cooled by a cooling mechanism, such as a backside cooling gas. Usually, to keep the wafer to have appropriate implant quality in the low temperature ion implantation, the pressure of the backside gas is properly adjusted to ensure the wafer temperature is always equal to the prescribed implant temperature (T P ) or at least is not higher an upper-limited temperature (T L ) during the implant process. Herein, the rise curve of the wafer temperature during the implant process (from t i to t h ) may be linear or non-linear, and the rise curve shown in FIG. 1 a is only a sketch. On the other hand, if the upper-limited temperature (T L ) is close to the prescribed implant temperature (T P ), as shown in FIG. 1 a ′, the wafer temperature during the implant process (from t i to t h ) may be thought of as constant. After finishing the implant process, referring still to FIG. 1 a or FIG. 1 a ′, a heating process (from t h to t f ) proceeds to heat the implanted wafer until the wafer has an environment temperature (T R ′). Herein the environment temperature (T R ′) may correspond to the atmosphere environment temperature, so that the difference between the implanted wafer temperature, which will be moved out of the ion implanter immediately, and the environment temperature is decreased. Hence, owing to the decreased temperature difference, the water condensation problem on the wafer surface induced by the temperature difference may be avoided or minimized. In general, after the implant process, the implanted wafer is transferred into a loadlock chamber in a vacuum state to proceed with the heating process. As usual, to avoid any potential contamination, the implanted wafer is not heated by an active heat source but is heated by thermal radiation between the wafer and the load-lock chamber walls. After the temperature of the implanted wafer reaches the environment temperature (T R '), the load-lock chamber is vented and the implanted wafer is moved outside the loadlock chamber immediately. Herein, owing to the low efficiency of the radiation heat transfer mechanism, it requires some seconds (even some minutes) to heat up the implanted wafer from the prescribed implant temperature (T P ) to the environment temperature (T R ′). Therefore, both the cooling process and heating process are time-consuming, so that the wafer throughput of the low temperature ion implantation is limited. SUMMARY OF THE INVENTION In order to solve the foregoing problems, this invention provides a method for low temperature ion implantation with improved wafer throughput. A feature of the invention is that the operation of the cooling mechanism is stronger in the cooling process and weaker in the implant process. Hence, the cooling rate can be enhanced and then the required period of the cooling process can be shortened. Accordingly, a low temperature ion implant may proceed in accordance with the following steps in sequence. Firstly, a cooling process proceeds to cool a wafer, wherein a temperature adjustment device is operated in a first state so that a temperature of the wafer is changed from a first temperature to a second temperature. Then, implant the wafer in an implantation chamber, wherein a temperature adjustment device is operated in a second state so that a temperature of the wafer is essentially between the second temperature and a third temperature higher than the second temperature. Next, transfer the implanted wafer into a load lock chamber. Finally, vent vacuum in the loadlock chamber and then move the wafer outside the loadlock chamber. Herein, as an example, the temperature adjustment device applies a gas to cool the wafer, the first state corresponds to a first pressure of the gas and the second state corresponds to a second pressure of the gas, wherein the first pressure is higher than the second pressure. Another feature of the invention is that the wafer is not immediately moved out the ion implanter after a vacuum venting process is finished. Hence, the wafer temperature may be increased quickly inside the ion implanter before the wafer is moved into the outside environment. Accordingly, a low temperature ion implant may proceed in accordance with the following steps in sequence. Firstly, a cooling process proceeds to cool a wafer from a first temperature to a second temperature. Next, implant the wafer in an implantation chamber as a temperature of the wafer is essentially between the second temperature and a third temperature higher than the second temperature; then, transfer the implanted wafer into a load-lock chamber in a vacuum state, wherein the load-lock chamber has at least an atmosphere door as an interface between the load-lock chamber and an outside environment, wherein the atmosphere door is closed when the load-lock chamber in the vacuum state. And then, proceed with a vacuum venting process in the load-lock chamber and wait an extra time after the vacuum venting process until the wafer has a third temperature. Finally, open the atmosphere door and move the wafer outside the load-lock chamber. Still another feature of the invention is that a temperature measurement device is used to monitor the wafer temperature. Hence, to change the operation of the cooling mechanism and to open the atmosphere door can be more precisely controlled. Of course, to minimize potential contamination, a non-contact type temperature measuring device may be used. Significantly, the invention never limits the practical details about the operation of the cooling apparatus in the cooling process and the operation of the cooling apparatus in the implant process. The only limitation is that the operation of the cooling apparatus is higher (stronger) in the cooling process but is lower (weaker) in the implantation process. Similarly, the invention never limits the practical period of the extra waiting time. The only limitation is that the wafer is not moved out the ion implanter immediately after the vacuum venting process. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 a and FIG. 1 a ′ are two diagrams illustrating conventional relations between the wafer temperature and the time during the low temperature ion implantation step; FIG. 1 b is a diagram illustrating a conventional relation between the gas pressure and the time during the cooling process and the implant process; FIG. 2 a and FIG. 2 b are two diagrams respectively illustrating relations between the gas pressure and the time during the cooling process and the implant process in accordance with two embodiments of the present invention; FIG. 2 c is a diagram illustrating relation between the wafer temperature and the time in accordance with an embodiment of the present invention; FIG. 3 is a diagram illustrating different forces applied to a wafer in accordance with an embodiment of the present invention; and FIG. 4 is a diagram illustrating a relation between the wafer temperature and the time during the low temperature ion implantation step in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION The detailed description of the present invention will be discussed in the following embodiments, which are not intended to limit the scope of the present invention, but can be adapted for other applications. While drawings are illustrated in details, it is appreciated that the quantity of the disclosed components may be greater or less than that disclosed, except expressly restricting the amount of the components. In one embodiment, the temperature adjustment device applies a gas to cool the wafer, wherein the gas is a backside gas to take heat away the wafer from the backside of the wafer. As shown on FIG. 2 a , a first state from time of t c to t i is that the temperature adjustment device applies a gas with a first pressure (P 1 ), and a second state from time of t i to t h is that the temperature adjustment device applies a gas with a second pressure (P 2 ). Herein, the first pressure is higher than the second pressure and the first pressure is a constant. Further, the first pressure may be variable with time, or as shown in FIG. 2 b , the first pressure is temporarily increased to be higher than the second pressure. In other non-illustrated embodiment, the first pressure may be temporarily varied, continually varied or continuously varied during the cooling process, when the first pressure is higher than the second pressure. As shown in FIG. 2 c , in the above embodiments, the required time of the cooling process is reduced because the higher gas pressure during the cooling process may more efficiently take the heat away. Herein, the upper-limited temperature (T L ) is assumed to be slightly higher than the prescribed implant temperature (T P ) and the wafer temperature variation is assumed to be linear, although they are independent on the main characteristics of this embodiment. Clearly, the higher the gas pressure is, the faster the wafer temperature is reduced. Hence, the essential mechanism of these embodiments is that the gas pressure is higher during the cooling process but is lower during the implant process. In other words, how the gas pressure is varied during the cooling pressure is not limited. For example, when the average gas pressure during the cooling process is higher than the fixed gas pressure in the implant process, it is optional that the gas pressure is lower than the fixed gas pressure during some portions of the cooling process. To compare with the conventional prior art, the main difference between the above embodiment(s) and the conventional prior art is the gas pressure in the cooling process. Reasonably, the above embodiment(s) use higher gas pressure in the cooling process, and then the decreased rate of the wafer temperature is higher in the cooling process. Therefore, by comparing FIG. 2 c with FIG. 1 a , the above embodiments can effectively shorten the required period of the cooling process to reduce the wafer temperature from environment temperature to the required implant temperature. It is noted that the higher gas pressure will cause a higher pushing force (F p ), which attempts to push the wafer 12 away, as shown in FIG. 3 . In general, the wafer 12 is held by using an E-chuck 14 , which provides an electrostatic force (F e ) to the wafer. The electrostatic force (F e ) is an attracting force to cause the wafer 12 to be held on the E-chuck 14 stably. Hence, to avoid the unacceptable damage or displacement of the wafer 12 , the gas pressure has to be balanced with the electrostatic force. In other words, the pushing force (F p ) from the gas pressure has to be equal to or less than the attracting force. Further, when the higher gas pressure is needed to speed up the cooling process, the electrostatic force (F e ) should be correspondingly increased to prevent unacceptable movement or damage of the wafer 12 . Of course, depending on the design of the ion implanter, sometimes the gravity force on the wafer also is a portion of the repulsing force or the attracting force. However, the gravity force is a constant and may be viewed as a background only. Further, although back side gas cooling is the commonly used cooling mechanism, the invention is not limited by the practical details of the cooling mechanism. In another embodiment, the temperature adjustment device is a temperature controlled chuck capable of holding the wafer. Hence, the temperature adjustment device operated in the first state means that the temperature controlled chuck is adjusted to have a lower working temperature, and the temperature adjustment device operated in the second state means that the temperature controlled chuck is adjusted to have a higher working temperature. According to the different working temperature of a temperature controlled chuck, a wafer held by the temperature controlled chuck will have a different wafer temperature, especially a different changing rate of wafer temperature, during the cooling process and the implant process. In general, the low temperature ion implantation process is divided into at least an implant process, a cooling process to cool down the wafer before the implant process and a heating process to heat up the wafer after the implant process. In the present invention, because the period of the cooling process is shortened, the throughput of the low temperature ion implantation step is improved. Moreover, as an example, to precisely adjust the pressure of the backside gas as the wafer is cooled to the required temperature for properly implanting the wafer, a temperature measurement device is optionally configured near the wafer to detect the wafer temperature so let the wafer temperature may be dynamically monitored in a real-time manner. The temperature measurement device may be a thermocouple, an infrared thermometer, a non-contact type temperature measurement device or any combination thereof. Moreover, to avoid any potential contamination, such as particle contamination from the interaction between the temperature measurement device and the ion beam, a non-contact type temperature measurement device is an option. On the other hand, another embodiment is a method for low temperature ion implantation, please refer to FIG. 4 . Firstly, a cooling process proceeds to cool a wafer from a first temperature to a second temperature, wherein the first temperature is room temperature (T R ). Then, implant the wafer in an implantation chamber as the wafer temperature is essentially between the second temperature and a third temperature, wherein the third temperature is higher than the second temperature and is an upper-limited temperature (T L ) which is allowable for the low temperature ion implantation step. Depending on the additional details of the implant process, the upper-limited temperature may be equal to, close to or visibly different than the second temperature. And then, transfer the implanted wafer into a load-lock chamber in a vacuum state at time of t h , wherein the load-lock chamber has at least one atmosphere door as an interface between the load-lock chamber and outside environment, wherein the atmosphere door is closed when the load-lock chamber is in the vacuum state. Next, execute a vacuum venting process in the load-lock chamber, wherein the vacuum venting process proceeds at a time t v . Sequentially, wait an extra time after the vacuum venting process until the wafer has a fourth temperature at time t f , wherein the fourth temperature (T 4 ) is higher than the prescribed implant temperature (T P ) and the upper-limited temperature (T L ). And finally, open the atmosphere door and move the wafer outside the load-lock chamber. Herein, the upper-limited temperature (T L ) is assumed to be slightly higher than the prescribed implant temperature (T P ) and the wafer temperature variation is assumed to be linear, although that is immaterial to the main characteristics of this embodiment. In this embodiment, the wafer contacts the air from the outside environment after the atmosphere door is opened. Clearly, the wafer has the fourth temperature being higher than the prescribed implant temperature (T P ) and the upper-limited temperature (T L ) before the atmosphere door is opened, and then the water condensation on the surface of the wafer may be minimized. Moreover, during the vacuum venting process, a gas admitted into the load-lock chamber is a warm dry gas or heated nitrogen gas. Hence, after the vacuum venting process and before the opening of the atmosphere door, the wafer in the load lock chamber is surrounded by this gas so that the wafer temperature may be quickly raised. Note that the energy interchange mechanism between the gas surrounding the wafer and the wafer itself is significantly more efficient than the radiation mechanism between the vacuum environment surrounding the wafer and the wafer itself. Therefore, to induce same temperature increase, the required extra time by using the embodiment is significantly shorter than the required time by using the prior art that the wafer is heated by a radiation mechanism between the wafer and a vacuum environment in the load-lock chamber. Accordingly, the throughput of low temperature ion implantation may be further improved by the embodiments. Moreover, as described in the above embodiments, to properly control the extra time, even the fourth temperature, a temperature measurement device is configured near the wafer to detect the wafer temperature, so that the temperature adjusting process may be stopped immediately when the required third temperature is arrived. The temperature measurement device may be chosen from a thermocouple, an infrared thermometer or a non-contact type temperature measurement device for minimizing any potential condensation. Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variations can be made without departing from the spirit and scope of the invention as hereafter claimed.

Techniques for low temperature ion implantation are provided to improve throughput. Specifically, the pressure of the backside gas may temporarily, continually or continuously increase before the starting of the implant process, such that the wafer may be quickly cooled down from room temperature to be essentially equal to the prescribed implant temperature. Further, after the vacuum venting process, the wafer may wait an extra time in the load lock chamber before the wafer is moved out the ion implanter, in order to allow the wafer temperature to reach a higher temperature quickly for minimizing water condensation on the wafer surface. Furthermore, to accurately monitor the wafer temperature during a period of changing wafer temperature, a non-contact type temperature measuring device may be used to monitor wafer temperature in a real time manner with minimized condensation.

This is a continuation of application Serial No. 840,785, filed March 18, 1986 now U.S. Pat. 4,782,526. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone set of the type including a telephone body and a handset adapted to be placed in position on the former and more particularly to improvement of or relation to a telephone of the abovementioned type which assures that the handset is firmly held on the telephone body in order that it is not easy to fall down from the latter. 2. Description of the Prior Art To facilitate understanding of the present invention it will be helpful that a typical conventional telephone of the above-mentioned type will be briefly described with reference to FIG. 1 which is a schematic side view of a telephone adapted to be mounted on a motorcar (hereinafter referred to simply as telephone). The telephone has a pawl B and a pawl C incorporated in a telephone body A and both the pawl B and C are biased in the opposite direction under the effect of resilient force of springs b and c. As is apparent from the drawing, the foremost ends of the pawls B and C are fitted into recesses E and F which are formed on the handset D whereby the latter is firmly held on the telephone body A. In order to inhibit the handset D held on the telephone body from rattling or falling down from the latter during running of a motorcar under the vibratory condition there is a necessity for allowing the pawls B and C to be thrusted against the recesses E and F on the handset D with a high intensity of resilient force. However, the fact that an intensity of thrusting force of the pawls B and C against the handset D, that is, an intensity of urging force of the pawls B and C is determined to a high level means that a high intensity of manual force is required when the handset D is placed in position on the telephone body A or when the handset D is removed or taken up from the telephone body A. As a result, the telephone is difficult or troublesome to operate. Since an arrangement is made such that the two pawls B and C are urged with a high intensity of resilient force, it is unavoidably necessary that both the springs b and c are designed in larger dimensions. This leads to a necessity for a wide hollow space in the interior of the telephone body A so as to allow the larger springs b and c to be accommodated therein. This means that the whole telephone become larger. SUMMARY OF THE INVENTION Thus, the present invention has been made with the foregoing background in mind and its object resides in providing an improved telephone of the early-mentioned type which assures that a handset properly held on a telephone body is reliably inhibited from falling down from the latter and the handset is placed on and taken up from the telephone body with a lower intensity of manual force. Another object of the present invention is to provide an improved telephone of the early mentioned type which is designed in smaller dimensions. To accomplish the above objects there is proposed according to the present invention a telephone of the type including a handset which is formed with a holding recess in the central area thereof, the holding recess having faces oppositely located to one another each of the faces being formed with an engagement recess, and a telephone body which is integrally formed with a projected portion having the trapezoidal configuration as seen from the side, the projected portion being adapted to be fitted into the holding recess of the handset, both the end faces of the projected portion including first and second engagement blocks adapted to be fitted into the engagement recesses of the handset, the first and second engagement blocks being biased in the opposite direction under the effect of resilient force of spring means, wherein the improvement consists in that at least the first engagement block is disposed so as to move in the direction at a substantially right angle relative to the direction of mounting and dismounting of the handset on and from the telephone body and moreover it is formed with an engagement face on the bottom thereof which extends in the direction of movement of the first engagement block and that the engagement recess is formed with an engagement portion adapted to come in contact with the engagement face of the engagement block, the position of the engagement portion being so determined that it is located in alignment with the engagement face of the first engagement block when the latter is fitted into the engagement recess on the handset. By virtue of the arrangement made in that way it is assured that the handset is reliably held on the telephone body. Since holding of the handset is achieved mainly by cooperation of the engagement face with the engagement portion, there is no necessity for a high intensity of urging force for actuating the first and second engagement blocks. Thus, small-sized urging means such as coil spring or the like can be used for the purpose of actuating the engagement blocks, resulting in the whole telephone being designed and constructed in smaller dimensions. Other objects, features and advantages of the present invention will become readily apparent from reading of the following description which has been prepared in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings will be briefly described below. FIG. 1 is a schematic side view of a conventional telephone of the type including a telephone body and a handset. FIG. 2 is a perspective view of a telephone of the above-mentioned type in accordance with the present invention, particularly showing an appearance of the whole structure of the telephone handset of which is held in position of the telephone body. FIG. 3 is a side view of the telephone in FIG. 2. FIG. 4 is a partially sectioned side view of the telephone in accordance with an embodiment of the invention, particularly illustrating how essential components constituting the telephone are arranged. FIG. 5 is a sectional plan view of the telephone taken in line V-V in FIG. 3. FIG. 6 is a fragmental vertical sectional view of the telephone, particularly illustrating how the handset is firmly held in position on the telephone body in the area including a cradle on the telephone sending side. FIG. 7 is a fragmental vertical sectional view of the telephone taken in line VII-VII in FIG. 3, particularly illustrating how an unlocking button is incorporated in the telephone body. FIG. 8 is a sectional plan view of a telephone in accordance with other embodiment of the present invention, wherein leaf springs are employed as actuating means for engagement blocks. FIG. 9 is a sectional plan view of a telephone in accordance with another embodiment of the present invention, wherein the one engagement block is actuated directly by means of an actuating member. FIG. 10 is a fragmental vertical sectional view of a telephone in accordance with further another embodiment of the present invention, wherein the handset is raised up by means of a button with a compression spring accommodated therein in the area including a cradle on the sending side. FIG. 11 is a fragmental vertical sectional view of a telephone in accordance with still further another embodiment of the present invention similar to FIG. 10, wherein the handset is raised up by means of a block made of elastomeric material in the area including a cradle on the sending side. FIG. 12 is a fragmental vertical sectional view of a telephone in accordance with a modified embodiment of the present invention similar to FIG. 10, wherein a pawl and an engagement recess are designed in a different manner on the sending side. FIG. 13 is a fragmental vertical sectional view of a telephone in accordance with other modified embodiment of the present invention, wherein a pawl and an engagement recess are designed in another different manner on the receiving side. FIG. 14 is a fragmental vertical sectional view of a telephone in accordance with another modified embodiment of the present invention similar to FIG. 13, wherein an engagement block is turnably disposed on the receiving side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the present invention will be described in a greater detail hereunder with reference to the accompanying drawings which illustrate preferred embodiments thereof. First, referring to FIGS. 2 and 4, the telephone of the invention includes a telephone body 1 and a handset 2. The telephone body 1 is integrally formed with a projected portion 1a having the trapezoidal configuration as seen from the side on its upper central part and moreover it includes a telephone receiving side cradle 3 on the right-hand side and a telephone sending side cradle 4 on the left-hand side of the trapezoidal projected portion 1a (as seen in FIGS. 3 and 4). The cradle 4 is provided with a first engagement block 100 on the one end face 1c of the projected portion 1a so as to allow an engagement pawl 101 to be projected therefrom, whereas the cradle 3 is provided with a second engagement block 100' on the other end face 1b of the projected portion 1a so as to allow an engagement pawl 101' to be projected therefrom. On the other hand, the handset 2 includes a telephone receiving section 5, a telephone sending section 6 and a junction section 2a by way of which the receiving section 5 and the sending section 6 are jointed to one another whereby a holding recess 2b is formed by the combination of receiving section 5, sending section 6 and junction section 2a. Further, the handset 2 has oppositely located faces in the holding recess 2b, one of the oppositely located faces being an inside face 5a of the receiving section 5 and the other one being an inside face 6a of the sending section 6. The inside face 5a of the receiving section 5 is formed with an engagement recess 7, whereas the inside face 6a of the sending section 6 is formed with an engagement recess 8. As will be apparent from FIG. 4, the handset 2 is held on the body 1 by fitting the pawls 101 and 101' of the engagement blocks 100 and 100' into the engagement recesses 7 and 8. At this moment the central part of the trapezoidal projected portion 1a is received in the hollow space as defined by the holding recess 2b of the handset 2. The handset 2 has a rear face 2c located opposite to the holding recess 2b and a control portion 2e with a number of control buttons 2d arranged thereon disposed in the area located on the left-hand side as seen in FIG. 2 (on the right-hand side as seen in FIGS. 3 and 4) on the rear face 2c. Further, the handset 2 includes a grasping portion 2f in the area located on the right-hand side as seen in FIG. 2 so as to allow the handset 2 to be easily grasped by an operator. As shown in FIG. 4, a hook button 9 is accommodated in the sending side cradle 4 of the telephone body 1. Further, as shown in FIG. 3, the telephone body 1 is provided with an unlocking button 10 which will be described later in more details on the upper part of the side wall of the telephone body 1. It should be noted that the handset 2 is placed on the telephone body 1 at such a properly determined position that operator's fingers can reach the lower area of the grasping portion 2f, that is, an operator can take up the hand set 2 from the telephone body 1. Incidentally, the pair of engagement blocks 100 and 100' disposed on both the side faces 1b and 1c of the trapezoidal portion 1a of the telephone body 1 are designed in the same structure. Since both the engagement blocks 100 and 100' function in the same manner, the same components constituting the engagement block 100 as those of the engagement block 100' are identified by the same reference numerals with a prime mark attached thereto respectively and their detailed description with respect to function and structure will not be required. As shown in FIGS. 4 to 6, the engagement block 100 includes a block body 102 the fore end of which is designed in the form of a pawl 101. The block body 102 is formed with an elongated hole 103 in the longitudinal direction. As will be best seen in FIG. 5, a cam face 104 is formed at the position located behind the elongated hole 103 in the side wall of the block 100 (rightwards relative to the latter as seen in the drawing). Each of the engagement blocks 100 and 100' is disposed to slidably move in both the leftward and rightward directions as seen in FIG. 4, that is, in the direction at a right angle relative to the direction of mounting and dismounting of the handset 2 to and from the telephone body 1 (in the direction as identified by arrow marks W - W in the drawing) in the space as defined by the combination of a ceiling wall 11, side guide plates 12 depending from the ceiling wall 11 and a cover plate 13 bridged between both the lower ends of the side guide plates 12 of the telephone body 1. As will be best seen in FIG. 6, a tongue 14 is fitted into each of the elongated holes 103 and 103' of the engagement blocks 100 and 100' while extending therethrough. With respect to the engagement block 100 disposed on the sending side in the left-hand area as seen in FIG. 4 to function as first engagement block a compression coil spring 15 is interposed between the tongue 14 and the rear face of the pawl 101 whereby the engagement block 100 is normally biased in the leftward direction as seen in the drawing under the effect of resilient force of the compression coil spring 15. On the other hand, with respect to the engagement block 100' disposed on the receiving side in the righthand area in FIG. 4 to function as second engagement block a compression coil spring 17 is interposed between a central partition plate 16 located behind the engagement block 100' and the rear end face of the latter whereby the engagement block 100' is normally biased in the rightward direction as seen in the drawing under the effect of resilient force of the compression coil spring 17. It should be noted that the engagement block 100' on the receiving side is biased under the effect of a higher intensity of resilient force than that of the engagement block 100 on the sending side. Further, it should be noted that the pawls 101 and 101' of the engagement blocks 100 and 100' on both the sending and receiving sides are inhibited from projecting from the end faces 1b and 1c of the trapezoidal portion 1a in excess of a predetermined distance toward the area located above the cradles 3 and 4 due to the existence of the tongue 14 which is fitted into the elongated holes 103 and 103'. As shown in FIG. 6, the pawl 101 of the engagement block 100 is designed in the tapered structure including a larger inclined face 101a and a smaller inclined face 101b. Further, the engagement block 100 has an engagement face 101c on the bottom of the pawl 101, the engagement face 101c extending from the smaller inclined face 101b in the rearward direction (in the rightward direction as seen in the drawing), that is, in the direction of movement of the engagement block 100. As shown in FIG. 4, the larger inclined face 101a' of the engagement block 100' on the receiving side is oriented rightwards and extends upwardly at a certain inclination angle. Next, description will be made below as to the hook button 9 with reference to FIG. 6. As will be apparent from the drawing, the hook button 9 includes a button body 9a vertically slidably fitted into a chamber 18 which is formed in the cradle 4 on the sending side and it is normally biased upwardly under the effect of resilient force of a compression coil spring 19 which is accommodated in the hollow space of the button body 9a. As shown in FIG. 4, the hook button 9 is provided with an arm 9b which extends downwardly of the button body 9a. A magnet 9c is fixedly attached to the lower end of the arm 9b. Further, the telephone body 1 is equipped with a lead switch 30 in the area located below the hook button 9, the lead switch 30 serving as a hook switch for switching from the operative state to the inoperative state and vice versa. Thus, a hook switch mechanism 40 is constituted by the combination of hook button 9, compression spring 19 and lead switch 30. Next, description will be made below as to the unlocking button 10 with reference to FIGS. 5 and 7. The unlocking button 10 comprises a button portion 20 and a rod 21 extending from the inside wall of the button portion 20 toward the side wall of the engagement block 100 on the sending side and the fore end of the rod 21 comes in contact with cam face 104 of the engagement block 100. The button portion 20 is slidably fitted into an opening 22 which is formed on the side wall of the telephone body 1 at the position in the proximity of the upper edge thereof, the opening 22 extending at a right angle relative to the direction of movement of the engagement block 100. A compression spring 23 is interposed between the button portion 20 and the side guide plate 12 whereby the unlocking button 10 is normally biased outwardly of the body 1 (in the rightward direction as seen in FIG. 7) under the effect of resilient force of the compression spring 23. Incidentally, reference numeral 24 designate a stopper pawl which serves to inhibit the unlocking button 10 from being sprung outwardly of the telephone body 1. As shown in FIG. 4 which illustrates the inoperative state where the handset 2 is placed on the telephone body 1, the pawls 101 and 101' of the engagement blocks 100 and 100' on both the sending and receiving sides are engaged to the engagement recess 7 on the receiving section 5 and the engagement recess 8 on the sending section 6. At this moment the fore end 101d of the pawl 101 of the engagement block 100 on the sending side comes in engagement against the rear face 8a of the engagement recess 8, while the engagement face 101c of the pawl 101 comes in contact with the engagement portion 8b of the engagement recess 8. As is apparent from the drawing, the engagement portion 8b occupies a small area in the engagement recess 8 which is located opposite to the engagement face 101c of the pawl 101. Specifically, the engagement portion 8b is designed in the form of a plane extending in the longitudinal direction of the handset 2 in the same manner as the engagement face 101c of the pawl 101. By virtue of the arrangement made in that way it is assured that the handset 2 is inhibited from being unintentionally disengaged from the telephone body 1, because the engagement portion 8b in the engagement recess 8 is locked by means of the engagement face 101c so as not to cause any upward displacement of the engagement portion 8b when an operator takes up the handset 2 from the telephone body 1. Since the sending section 6 of the handset 2 is normally urged upwardly by means of the hook button 9 as mentioned above, it results that the engagement portion 8b is brought in tight contact with the engagement face 101c of the pawl 101. Thus, there is no fear of causing rattling movement of the handset 2 under any vibratory condition. Further, since the engagement block 100 on the receiving side is biased with an intensity of resilient force higher than that of the engagement block 100' on the sending side as mentioned above, the handset 2 is caused to forcibly move in the rightward direction as seen in FIGS. 3 and 4 until the inside face 6a of the sending section 6 abuts against the left-hand end face 1c of the trapezoidal portion 1a of the telephone body 1. As a result, the handset 2 is inhibited from an occurrence of rattling movement. While the handset 2 is properly placed on the telephone body 1, the button body 9a of the hook button 9 is forcibly depressed in the chamber 18 against resilient force of the compression spring 19 by means of the sending section 6 of the handset 2, as shown in FIG. 4. At this moment the magnet 9c moves to the position located in the vicinity of the lead switch 30. This causes the lead switch 30 to be opened under the influence of magnetic force whereby the telephone becomes inoperative. When an operator wants to take up the handset 2 from the telephone body 1, he is required to depress the unlocking button 10. When the unlocking button 10 is displaced in the direction as identified an arrow mark X in FIG. 5, the fore end of the rod 21 on the unlocking button 10 comes in slidable contact with the cam face 104 of the engagement block 100 on the sending side whereby the engagement block 100 is displaced toward the central part of the telephone body 1 in the direction as identified by an arrow mark Y. This causes the engagement face 101c of the pawl 101 of the engagement block 100 to be disengaged from the engagement portion 8b of the engagement recess 8 on the sending section 6 of the handset 2, resulting in the sending section 6 of the handset 2 being raised up under the effect of upward resilient force of the hook button 9. At this moment disengagement of the sending section 6 of the handset 2 achieved in that way is followed by disengagement of the receiving section 5 of the same. Now, the handset 2 is ready to be removed or taken up from the telephone body 1. Alternatively, removal of the handset 2 from the telephone body 1 may be carried out by displacing the handset 2 against resilient force of the engagement block 100' on the receiving side in the leftward direction as seen in FIGS. 3 and 4. Due to the fact that the pawl 101 of the engagement block 100 on the sending side is inhibited from projection into the area located above the cradle 4 on the sending side in excess of a predetermined distance because of the existence of the tongue 14, the pawl 101 of the engagement block 100 can be disengaged from the engagement recess 8 by displacing the handset 2 in the leftward direction. Thereafter, the sending section 6 of the handset 2 is raised up under the effect of upward resilient force of the hook button 9 and the sending receiving section 5 of the same is then released from the engaged state. Now, the handset 2 is ready to be removed or taken up from the telephone body 1. Further, as another method of removing or taking up the handset 2 from the telephone body 1 removal or taking-up of the handset 2 may be achieved by way of the steps of displacing the receiving section 5 of the handset 2 in the upward direction by operator' s force, allowing the lower edge 7a of the engagement recess 7 as shown in FIG. 4 to come in slidable contact with the larger inclined face 101a' of the engagement block 100' on the receiving side, displacing the engagement block 100' in the leftward direction as seen in the drawing until the engagement block 100' is disengaged from the receiving section 5 and thereafter disengaging the sending section 6 from the engagement block 100. Once the handset 2 is removed from the telephone body 1 in accordance with one of the above-mentioned various methods, the hook button 9 is released from the depressed state which is maintained by the dead weight of the sending section 6 and thereafter it is displaced upwardly under the effect of resilient force of the compression spring 19. Thus, the magnet 9c is parted away from the lead switch 30 and thereby the lead switch 30 is closed. This leads to a result that the telephone becomes operative. On the other hand, when the handset 2 is placed on the telephone body 1, it is forcibly depressed on the latter by operator's hand in such a manner that the receiving section 5 of the handset 2 is located opposite to the cradle 3 on the receiving side while the sending section 6 of the same is located opposite to the cradle 4 on the sending side. Thereafter, the pawl 101' of the engagement block 100' on the receiving side is caused to move forward beyond the inside face 5b of the receiving section 5 until it is fitted into the engagement recess 7 and at the same time the pawl 101 of the engagement block 100 on the sending side is caused to move forward beyond the inside face 6b of the sending section 6 until it is fitted into the engagement recess 8 whereby the handset 2 is firmly held on the body 1. At this moment the button body 9a of the hook button 9 is depressed into the chamber 18 by means of the projected part of the sending section 6 and thereby the telephone becomes inoperative again by turning off the lead switch 30. Next, other embodiment of the present invention will be described below with reference to FIG. 8. In this embodiment the engagement block 200 for the sending side disposed leftsides relative to the side guide plates 212 as seen in the drawing is fixedly provided with a leaf spring 215. Both the ends 215a and 215b of the leaf spring 215 are attached to the ceiling wall 11 whereby the engagement block 200 is normally biased in the leftward direction as seen in the drawing under the effect of restorative resilient force of the leaf spring 215. As is apparent from the drawing, the engagement block 200 is formed with a cam face 204 on the one side wall thereof and an unlocking button 10 is disposed at the position located opposite to the cam face 204. The structure of the unlocking button 10 is entirely the same as that shown in FIGS. 2 to 7 and moreover the manner of actuating the engagement block 200 by operating the unlocking button 10 is entirely the same as that in the foregoing embodiment. On the other hand, the engagement block 200' for the receiving side disposed rightwards relative to the side guide plates 212 as seen in the drawing is fixedly provided with a leaf spring 217 and both the ends 217a and 217b of the leaf spring 217 are attached to the ceiling wall 11 whereby the engagement block 200' is normally biased in the rightward direction as seen in the drawing under the effect of restorative resilient force of the leaf spring 217. The handset 2 is firmly held on the telephone body 1 by cooperative function of the engagement blocks 200 and 200'. Next, another embodiment of the present invention will be described below with reference to FIG. 9. In this embodiment the engagement block 300 on the sending side is provided with an actuating member 320 which extends from the one side wall of the engagement block 300 toward the side wall of the telephone body 1. The one end 320a of the actuating member 320 is projected outwardly of an opening 321 which is formed on the one side wall of the telephone body 1. When the end part 320a of the actuating member 320 is displaced in the direction as identified by an arrow mark Z in the drawing, the engagement block 300 on the sending side is caused to move in the rightward direction as seen in the drawing, that is, in the direction as identified by an arrow mark Z whereby the handset 2 is disengaged from the telephone body 1. It should be noted that the manner of disposing the engagement block 300' on the receiving side as well as the manner of actuating it are entirely same the as those relative to the engagement block 100' in the embodiment as shown in FIGS. 2 to 7. FIGS. 10 and 11 illustrate a modified structure in which the hook button 9 adapted to displace the handset 2 in the vertical direction in accordance with the embodiment as shown in FIGS. 2 to 7 is modified. In the case of the embodiment as shown in FIG. 10 an arrangement is made such that a button 90 is slidably accommodated in the chamber 18 which is formed in the cradle 4 on the sending side and a compression spring 19 is interposed in the hollow space as defined between the button 90 and the bottom wall 18a of the chamber 18 in order to displace the sending section 6 upwardly by means of the button 90 under the effect of resilient force of the compression spring 19. On the other hand, in the case of the embodiment as shown in FIG. 11 a chamber 180 formed in the cradle 4 on the sending side is filled with a block 95 made of elastomeric material. The block 95 is fixedly secured to the bottom of the chamber 180 with the aid of an adhesive or the like means in order to inhibit it from being removed from the chamber 180. As will be apparent from the drawing, the block 95 is held in the compressed state under the influence of dead weight of the sending section 6 and the latter is normally urged in the vertical direction under the effect of restorative resilient force of the block 95. It should of course be understood that a distance of displacement of the button 90 from the loaded state to the unloaded state in the embodiment as shown in FIG. 10 as well as a distance of displacement of the elastic block 95 from the loaded state to the unloaded state in the vertical direction in the embodiment as shown in FIG. 11 are so determined that the lower edge 8c of the engagement recess 8 can be raised up above the foremost end 101d of the pawl 101 of the engagement block 100. Next, description will be made below as to other embodiment of the present invention as shown in FIG. 12. In this modified embodiment the pawl 401 of the engagement block 400 has an inclined face 401a which extends toward the foremost end 401b at a certain downward inclination angle and moreover it has an engagement face 401c which extends from the foremost end 401b of the pawl 401 in the direction of movement of the engagement block 400. On the other hand, the engagement recess 80 has a face which extends from the rear wall 80a thereof in the direction of movement of the engagement block 400 whereby an engagement portion 80b is constituted by the aforesaid face. Further, the engagement recess 80 has an inclined face 80c which extends from the right-hand edge of the engagement portion 80b at a certain downward inclination angle as seen in the drawing. While the handset 2 is held at the illustrated inoperative state, the engagement face 401c of the engagement block 400 is engaged to the engagement portion 80b of the engagement recess 80, resulting in the handset 2 being firmly placed on the telephone body 1. In this embodiment removal of the handset 2 from the telephone body 1 is achieved by way of the steps of displacing the engagement block 400 in the rightward direction by a distance corresponding to the depth of the engagement portion 80b in the engagement recess 80 and causing the foremost end 401b of the pawl 401 to move in the rightward direction in conformance with the inclined face 80c of the engagement recess 80 until it moves beyond the ridge 6b' of the sending section 6 while the handset 2 is raised up under the effect of resilient force of the hook button 9. On the other hand, placing of the handset 2 on the telephone body 1 is achieved by way of the steps of locating the sending section 6 above the cradle 4 on the sending side, depressing the handset 2 on the cradle 4 so as to allow the ridge 6b' of the sending section 6 to come in slidable contact with the tapered face 401a of the engagement block 400, displacing the engagement block 400 in the rightward direction as seen in the drawing until the foremost end 401b of the pawl 401 moves beyond the ridge 6b' and finally causing the pawl 401 to be introduced into the engagement recess 80. In the case of another embodiment of the present invention as shown in FIG. 13 the engagement recess 70 in the receiving section 5 has an inclined face 70a in the lower area which extends toward the opened side (in the leftward direction as seen in the drawing) at a certain downward inclination angle. The engagement block 500 on the receiving side includes a pawl 501 of which foremost end is designed in the flat shape and the lower edge 501a of the foremost end of the pawl 501 is adapted to abut against the inclined face 70a of the engagement recess 70 whereby the handset 2 is held in position on the telephone body 1. As the handset 2 is raised up from the illustrated state, the engagement block 500 is forcibly displaced in the leftward direction as seen in the drawing by means of the inclined face 70a and thereafter the pawl 501 moves beyond the ridge 5b' of the receiving section 5. Now, the handset 2 is ready to be taken up from the telephone body 1. On the other hand, holding of the handset 2 on the telephone body 1 is achieved by way of the steps of depressing the receiving section 5 toward the cradle 3 on the receiving side, causing the ridge 5b' of the receiving section 5 to thrust the engagement block 500 in the leftward direction until the ridge 5b' moves beyond the pawl 501 and finally causing the pawl 501 to be introduced into the engagement recess 70. Finally, description will be made below as to a modified embodiment of the present invention as shown in FIG. 14. In this embodiment an engagement block 600 on the receiving side is supported turnable about a shaft 601 which is horizontally held in the telephone body 1. The engagement block 600 is normally turned in the direction as identified by an arrow mark P under the effect of resilient force of a helical torsion spring 602 which is spanned between the shaft 601 and the engagement block 600 and a pawl 603 of the latter is projected into an engagement recess in the cradle on the receiving side. As is apparent from the drawing, the pawl 603 of the engagement block 600 includes a lower inclined face 603a which extends in the rightward direction at a certain upward inclination angle and an upper inclined face 603b which extends in the rightward direction as seen in the drawing at a certain downward inclination angle. The engagement block 600 is formed with a projection 604 which is adapted to abut against a stopper 11a on the inside surface of the ceiling wall 11 of the telephone body 1. Thus, a distance of projection of the pawl 603 outwardly of the trapezoidal portion 1a is restricted by abutment of the projection 604 against the stopper 11a in that way. To firmly hold the handset 2 on the telephone body 1 the receiving section 5 is first located above the cradle 3 on the receiving side and it is then depressed toward it. Thus, the ridge 5a of the receiving section 5 comes in slidable contact with the upper inclined face 603b of the pawl 603 whereby the engagement block 600 is caused to turn in the anticlockwise direction against resilient force of the helical torsion spring 602. When the ridge 5a moves beyond the foremost end 603c of the pawl 603, the latter is introduced into the engagement recess 7. As a result, the handset 2 is firmly held on the telephone body 1. On the other hand, when the receiving section 5 is raised up, the lower edge 7a of the opened side of the engagement recess 7 comes in slidable contact with the lower inclined face 603a of the pawl 603 whereby the latter is displaced in the leftward direction as seen in the drawing. When the ridge 5a of the receiving section 5 moves beyond the pawl 603, the latter is disengaged from the engagement recess 7. Now, the handset 2 is ready to be removed from the telephone body 1. While the present invention has been described above with respect to typical preferred embodiments thereof, it should of course be understood that it should not be limited only to them but various changes or modifications may be made in any acceptable manner without departure from the spirit and scope of the invention as defined by the appended claims.

An improved telephone set of the type including a telephone body and a handset adapted to be placed on the former wherein the telephone set includes features which prevents displacement of the handset from the telephone body. The telephone body has a pair of engagement blocks incorporated therein of which part is projected outwardly of the telephone body and they are fitted into engagement recesses on the handset whereby the latter is firmly placed on the telephone body. At least the one engagement block has an engagement face which is adapted to come in contact with the engagement portion in the corresponding engagement recess, wherein each engagement block includes a pawl portion. Displacement of the handset occurs by displacing one of the pawl portions out of its respective engagement recess followed by displacement of the handset in a second direction which is different from the first direction which causes the displacement of the other pawl portion out of its respective engagement recess. Thus, the handset is reliably held on the telephone body.

FIELD OF THE INVENTION [0001] The present invention relates to an information processing apparatus, control method therefor, computer program, and storage medium. BACKGROUND OF THE INVENTION [0002] A software failure at a low recall ratio is often dealt with by obtaining a software processing log. The processing log is conventionally obtained by correcting an application software module and adding a processing log obtaining routine. The method which requires correction of application software such as embedding of a log obtaining code complicates correction processing. [0003] Against this background, there is proposed a method capable of obtaining a processing log by providing a log obtaining module without performing any complicated correction of application software itself (see Japanese Patent Application Laid-open No. 2004-38311). In software divided into a plurality of modules; the log obtaining module mediates a call for a function present in a given module from a module corresponding to application software, and obtains a processing log in the given module which responds to the call. [0004] Processes executed in the software include processes which must always call a predetermined end function after a call for a function whose operation is paired with that of the end function, such as memory allocation/memory free or the start of a device/the end of the device. At this time, if processing which has not ended because its end function has not been called remains, the processing influences execution of another processing. Thus, it must be reliably determined whether an end function has been called. SUMMARY OF THE INVENTION [0005] It is an object of the present invention to make it possible to determine whether processing by functions whose operations are paired has normally ended. [0006] According to one aspect of embodiments of the present invention, an information processing apparatus which executes a first module, a second module, and a third module for mediating a call from the first module to a function in the second module and obtaining a log of processing in the second module in response to the call comprises a log obtaining unit which obtains the log from the third module, an extraction unit which extracts, from the obtained log, attribute information of functions and identifiers assigned to the functions, and an end determination unit which determines, on the basis of attribute information of a first function and a second function among the extracted functions, identifiers assigned to the first function and the second function, whether the processing in the second module has normally ended. [0007] Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. BRIEF DESCRIPTION OF THE DRAWINGS [0008] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [0009] FIG. 1 is a block diagram showing an example of the configuration of an information processing apparatus according to an embodiment of the present invention; [0010] FIG. 2 is a view for explaining a case wherein software divided into a plurality of modules is loaded into the memory of the information processing apparatus according to the embodiment of the present invention; [0011] FIG. 3 is a view showing an example of the memory configuration of the information processing apparatus when a function call is mediated using IAT Patch as a log obtaining code according to the embodiment of the present invention; [0012] FIG. 4 is a timing chart showing an example when IAT Patch processing is executed in the information processing apparatus according to the embodiment of the present invention; [0013] FIG. 5 is a view showing an example of operation when an executable file EXE is executed in the information processing apparatus according to the embodiment of the present invention; [0014] FIG. 6 is a view showing an example of a memory configuration when the executable file EXE creates an interface instance exported to a COM server in the information processing apparatus according to the embodiment of the present invention; [0015] FIG. 7 is a view showing the memory configuration of the information processing apparatus according to the embodiment of the present invention; [0016] FIG. 8 is a timing chart showing an example when VTable Patch processing is executed in the information processing apparatus according to the embodiment of the present invention; [0017] FIG. 9 is a view showing an example of operation when the executable file EXE is executed in the information processing apparatus according to the embodiment of the present invention; [0018] FIG. 10 is a view showing an example of processing subjected to a handle check when handle check processing is performed in the information processing apparatus according to the embodiment of the present invention; [0019] FIG. 11 is a view showing an example of a handle attribute definition file according to the embodiment of the present invention; [0020] FIG. 12 is a view showing another example of processing subjected to the handle check when handle check processing is performed in the information processing apparatus according to the embodiment of the present invention; [0021] FIG. 13 is a view showing another example of the handle attribute definition file according to the embodiment of the present invention; [0022] FIG. 14 is a flowchart when a handle check application is executed to perform log analysis processing in the information processing apparatus according to the embodiment of the present invention; and [0023] FIG. 15 is a table showing an example of a processing result display window displayed on a display 8 in step 1421 in the flowchart of FIG. 14 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0024] Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. [0025] FIG. 1 is a block diagram showing an example of the configuration of an information processing apparatus according to an embodiment. For descriptive convenience, the information processing system is constructed in one PC in the embodiment. However, characteristic features of the present invention are effective regardless of whether the information processing system is constructed in one PC or in a plurality of PCs as a network system. [0026] The information processing apparatus comprises a CPU 1 , chipset 2 , RAM 3 , harddisk controller 4 , display controller 5 , harddisk drive 6 , CD-ROM drive 7 , and display 8 . The information processing apparatus incorporates a signal line 11 which connects the CPU 1 and chipset 2 , a signal line 12 which connects the chipset 2 and RAM 3 , a peripheral bus 13 which connects the chipset 2 and various types of peripheral devices 4 and 5 , a signal line 14 which connects the harddisk controller 4 and harddisk drive 6 , a signal line 15 which connects the harddisk controller 4 and CD-ROM drive 7 , and a signal line 16 which connects the display controller 5 and display 8 . [0027] To explain the information processing apparatus according to the embodiment, how to load, into a memory in a normal state, software which is divided into a plurality of modules will be explained with reference to FIG. 2 . FIG. 2 is a view showing an example of the internal configuration of the RAM. [0028] In general, software divided into a plurality of modules exists separately as an executable file EXE ( 23 ) which controls the overall operation, and a dynamic link library DLL ( 27 ) which exists as a module and plays a complementary role of EXE. Both EXE and DLL are loaded into the RAM 3 . EXE is made up of a code segment ( 28 ), data segment ( 29 ), and import function address table ( 22 ). The import function address table is subdivided into DLLs ( 21 and 24 ) to which functions belong. Each DLL holds an address at which each function is loaded ( 30 to 35 ). [0029] The entities of the functions in the DLLs are loaded for the respective DLLs ( 25 and 26 ), and the functions are loaded as parts of corresponding DLLs ( 36 to 41 ). In FIG. 2 , one EXE uses functions in two dynamic link libraries for A.DLL and B.DLL. Functions used actually are six functions: Func AA, Func AB, Func AC, Func BA, Func BB, and Func BC. [0030] When a code in the code segment 28 of EXE calls the function Func AA, a Func AA address ( 30 ) that is written in the import function address table is read. In practice, the address of a Func AA code ( 36 ) which is read as part of A.DLL is written. By calling the address, the EXE code can call Func AA of A.DLL. [0031] An example of the memory configuration of the information processing apparatus when a function call is mediated using IAT Patch (Import Address Table Patch) as a log obtaining code will be explained with reference to FIG. 3 . [0032] After the start of obtaining a log, C.DLL ( 58 ) serving as an IAT Patch DLL is loaded into the memory. C.DLL rewrites the addresses of functions written in an import function address table ( 52 ) into those ( 61 to 66 ) of log obtaining codes Func CAA, Func CAB, Func CAC, Func CBA, Func CBB, and Func CBC in C.DLL. The codes ( 73 to 78 ) of Func CAA, Func CAB, Func CAC, Func CBA, Func CBB, and Func CBC in C.DLL record logs, and call corresponding functions Func AA, Func AB, Func AC, Func BA, Func BB, and Func BC ( 67 to 72 ) which have been loaded in the memory and wait for function calls. [0033] FIG. 4 is a timing chart showing IAT Patch processing in FIG. 3 . For descriptive convenience, FIG. 4 shows an example of how the log obtaining code based on IAT Patch operates when EXE calls Func AA in A.DLL. The same processing is also performed for another function. [0034] When EXE ( 91 ) calls Func AA ( 94 ), a log obtaining code in C.DLL saves a DLL name and function name in the memory, saves the call time in the memory, saves parameters upon the call in the memory, and saves memory contents represented by pointer parameters upon the call in the memory ( 95 ). After that, C.DLL calls Func AA in A.DLL ( 93 ) that is supposed to be called ( 96 ). Func AA processing ( 97 ) in A.DLL ends, and control returns to C.DLL ( 98 ). C.DLL saves the return time in the memory, saves the return value in the memory, and saves memory contents represented by pointer parameters upon return in the memory ( 99 ). C.DLL writes the saved log information in a file ( 100 ), and control returns to EXE as if Func AA of A.DLL normally ended ( 101 ). [0035] FIG. 5 is a view showing an example of operation when the executable file EXE is executed in the information processing apparatus according to the embodiment. In general, an executable EXE ( 113 ) calls functions in DLL- 1 ( 116 ) and DLL- 2 ( 117 ). In FIG. 5 , a log obtaining code called an API tracer is embedded ( 114 ) to generate a processing log ( 115 ). The API tracer operates on the basis of a file ( 111 ) which describes the function definitions of DLL- 1 and DLL- 2 , and a setup scenario ( 112 ) representing a DLL and a function in the DLL for which an import function table is rewritten to obtain a log. [0036] FIG. 6 is a view showing an example of a memory configuration when an executable file EXE ( 118 ) creates an interface instance exported to a COM (Component Object Model) server in the information processing apparatus according to the embodiment. [0037] In general, when an interface instance is created, requested interfaces ( 121 and 122 ) and their methods ( 130 to 135 ) are created in the COM server, and loaded into the memory. Virtual address tables ( 118 and 120 ) are created for created interfaces, and passed to EXE which has requested the creation. The virtual address tables hold addresses ( 124 to 129 ) created for the respective methods. EXE utilizes these pieces of information, and calls the interfaces. In FIG. 6 , one EXE creates two interface instances for Interface A and Interface B, and utilizes methods in the interfaces. Methods used actually are Method AA, Method AB, Method AC, Method BA, Method BB, and Method BC. [0038] When the EXE code calls the function Method AA, a Method AA address ( 124 ) written in the virtual address table is read. The address ( 124 ) describes the address of a Method AA code ( 130 ) which is created as part of Interface A in the COM server. By calling the address, the EXE code can call Method AA of Interface A. [0039] FIG. 7 is a view showing the memory configuration of the information processing apparatus according to the embodiment. This memory configuration is different from that in FIG. 6 in that a method call is mediated using VTable Patch (Virtual address Table Patch) as a log obtaining code. [0040] After the start of obtaining a log, a VTable Patch DLL ( 143 ) is loaded into the memory. The DLL rewrites the addresses of methods written in virtual address tables ( 136 and 138 ) into those ( 145 to 150 ) of log obtaining codes Method A′A, Method A′B, Method A° C., Method B′A, Method B′B, and Method B° C. in the DLL. The codes ( 157 to 162 ) of Method A′A, Method A′B, Method A° C., Method B′A, Method B′B, and Method B° C. in the DLL record logs, and call Method AA, Method AB, Method AC, Method BA, Method BB, and Method BC ( 151 to 156 ) which have been loaded in the memory and wait for method calls. [0041] FIG. 8 is a timing chart showing VTable Patch processing in FIG. 7 . For descriptive convenience, FIG. 8 shows an example of how the log obtaining code based on VTable Patch operates when EXE calls Method AA of Interface A in the COM server. The same processing is also performed for another function. [0042] When EXE ( 163 ) calls Method AA ( 166 ), a log obtaining code in the DLL saves a module name, interface name, and method name in the memory, saves the call time in the memory, saves parameters upon the call in the memory, and saves memory contents represented by pointer parameters upon the call in the memory ( 167 ). Thereafter, the DLL calls Method AA in the COM server ( 165 ) that is supposed to be called ( 168 ). Method AA processing ( 169 ) in the COM server ends, and control returns to DLL ( 170 ). The DLL saves the return time in the memory, saves the return value in the memory, and saves memory contents represented by pointer parameters upon return in the memory ( 171 ). The DLL writes the saved log information in a file ( 172 ), and control returns to EXE as if Method AA in the COM server normally ended ( 173 ). [0043] FIG. 9 is a view showing an example of operation when the executable file EXE is executed in the information processing apparatus according to the embodiment. In general, an executable EXE ( 176 ) calls methods in COM server- 1 ( 179 ) and COM server- 2 ( 180 ). In FIG. 9 , a log obtaining code called an API tracer is embedded ( 177 ) to generate a processing log ( 178 ). The API tracer operates on the basis of a file ( 174 ) which describes the function definitions of COM server- 1 ( 179 ) and COM server- 2 , and a setup scenario ( 175 ) representing a COM server, an interface in the COM server, and a method for the interface for which a virtual address table is rewritten to obtain a log. [0044] FIG. 10 is a view showing an example of processing subjected to a handle check when handle check processing is performed in the information processing apparatus according to the embodiment. In the embodiment, a handle corresponds to an identifier for identifying a function. [0045] In FIG. 10 , an application ( 1001 ) calls a device control module ( 1005 ) via a log obtaining module ( 1011 ) to control a device ( 1010 ). In FIG. 10 , the application ( 1001 ) corresponds to EXE ( 91 ) in FIG. 4 and EXE ( 163 ) in FIG. 8 . The log obtaining module ( 1011 ) corresponds to C.DLL ( 92 ) in FIG. 4 and DLL ( 164 ) in FIG. 8 . The device control module ( 1005 ) corresponds to A.DLL ( 93 ) in FIG. 4 and the COM server ( 165 ) in FIG. 8 . [0046] An OpenDevice function ( 1002 ) powers on a device ( 1007 ), obtains and ensures a control handle for the device ( 1006 ), and returns the handle to a host application ( 1003 ). [0047] A CloseDevice function ( 1004 ) powers off the device ( 1009 ) on the basis of the handle obtained by the OpenDevice function, and releases the control handle. When the OpenDevice function is used, the CloseDevice function ( 1004 ) must always be called, in order to free the handle area and power off a device. If the paired OpenDevice ( 1002 ) and CloseDevice ( 1004 ) are not called, the device is kept ON and the handle allocation area is not freed. This may pose a problem in executing another application. [0048] FIG. 11 is a view showing an example of a handle attribute definition file according to the embodiment. The handle attribute definition file is held by a handle check application in the information processing apparatus, and used to check the functions in FIG. 10 . A handle attribute definition file ( 1101 ) describes a DLL ( 1102 ) subjected to a handle check, and a function definition file ( 1103 ) for the target DLL. The DLL subjected to a handle check corresponds to the device control module ( 1005 ) in FIG. 10 . The function definition file ( 1103 ) describes information including the return value and parameters of functions in the target DLL, and is used to extract information necessary to perform a handle check from log data stored in the log obtaining module ( 1011 ). The function definition file ( 1103 ) corresponds to the function definitions 111 and 174 in FIGS. 5 and 9 . [0049] In the handle attribute definition file ( 1101 ), handle attribute settings are defined by TraceFunc ( 1104 ), GroupID ( 1105 ), FuncProperty ( 1106 ), and ParaError ( 1107 ) for each function. More specifically, TraceFunc ( 1104 ) sets a function name, and GroupID ( 1105 ) sets a function group which defines a handle attribute. FuncProperty ( 1106 ) sets which of Open, Close, and OpenClose is defined as a handle attribute of the function. ParaError ( 1107 ) can set the return value of the function or which of arguments is defined with the Open/Close attribute. Further, ParaError ( 1107 ) can make a setting of excluding the function from targets of handle check processing when the return value or argument has a specific value. [0050] In FIG. 11 according to the embodiment, TraceFunc=OpenDevice ( 1104 ) defines the OpenDevice function. It is defined that the OpenDevice function belongs to group 0x01 by GroupID=0x01( 1105 ), it has the Open attribute by FuncProperty=0x02 ( 1106 ), the DWORD value serving as a return value is the Open value by ParaError=0.DWORD, 0x02,!=0.0 ( 1107 ), and handle check processing is done only when the value is not 0. [0051] TraceFunc=CloseDevice ( 1108 ) defines the CloseDevice function. It is defined that the CloseDevice function belongs to the same group 0x01 as that of OpenDevice by GroupID=0x01( 1109 ), it has the Close attribute by FuncProperty=0x01( 1110 ), the DWORD value serving as the first argument is the Close value by ParaError=1.DWORD, 0x01,!=0.0 ( 1111 ), and handle check processing is done only when the value is not 0. These definitions provide handle attribute settings of performing a handle check using the return value of the OpenDevice function and the first argument of the CloseDevice function. [0052] FIG. 12 is a view showing another example of processing subjected to the handle check when handle check processing is performed in the information processing apparatus according to the embodiment. FIG. 12 shows a function when an application ( 1201 ) calls a memory allocation module ( 1207 ) via a log obtaining module ( 1216 ) to request an OS ( 1213 ) to allocate/free the memory. In FIG. 12 , the application ( 1201 ) corresponds to EXE ( 91 ) in FIG. 4 and EXE ( 163 ) in FIG. 8 . The log obtaining module ( 1216 ) corresponds to C.DLL ( 92 ) in FIG. 4 and DLL ( 164 ) in FIG. 8 . The memory allocation module ( 1207 ) corresponds to A.DLL ( 93 ) in FIG. 4 and the COM server ( 165 ) in FIG. 8 . [0053] A MemoryAlloc function ( 1202 ) issues a memory allocation request to the OS ( 1208 ), obtains the handle of an allocated memory ( 1209 ), and returns the handle to a host application ( 1203 ). A MemoryFree function ( 1206 ) requests the OS to free the memory ( 1212 ) on the basis of the handle obtained by the MemoryAlloc function. When the MemoryAlloc function is used, the MemoryFree function must always be called, in order to free the memory in the OS. If the paired MemoryAlloc and MemoryFree are not called, the memory is kept allocated in the OS and memory leak occurs. [0054] The above processing is almost the same as that in the example of FIG. 10 , and in FIG. 12 , a MemoryRealloc function ( 1204 ) further exists. The MemoryRealloc function re-allocates the memory ( 1210 ) on the basis of the memory area allocated by the MemoryAlloc function. When the MemoryRealloc function is used, a memory re-allocation request ( 1210 ) is issued to the OS on the basis of the handle of the MemoryAlloc function. The OS performs memory re-allocation processing and returns the handle ( 1211 ). At this time, in the OS, the handle may be identical to or different from that for the original memory depending on the memory allocation status. [0055] FIG. 13 is a view showing another example of the handle attribute definition file according to the embodiment. The handle attribute definition file is held by the handle check application in the information processing apparatus, and used to check the functions in FIG. 12 . [0056] A handle attribute definition file ( 1301 ) contains the same handle attribute settings as the contents shown in FIG. 11 , and definitions ( 1312 to 1316 ) for the MemoryRealloc function having the OpenClose handle attribute. Definitions ( 1304 to 1307 ) for the MemoryAlloc function and those ( 1308 to 1311 ) for the MemoryFree function have the same contents as those in FIG. 11 . [0057] In the definitions of the MemoryRealloc function, the OpenClose attribute is set by FuncProperty=0x04 ( 1314 ). For this reason, ParaError has two settings, and ParaError=1.DWORD,0x01,!=0.0 ( 1315 ) defines that the DWORD value serving as the first argument is the Close value and handle check processing is done only when the value is not 0. [0058] ParaError=0.DWORD, 0x02,!=0.0 ( 1316 ) defines that the DWORD value serving as the return value is the Open value and handle check processing is done only when the value is not 0. These definitions provide handle attribute settings of performing a handle check at the return value of the MemoryAlloc function, the first argument of the MemoryFree function, and the return value and first argument of the MemoryRealloc function. [0059] FIG. 14 is a flowchart when the handle check application is executed to perform log analysis processing in the information processing apparatus according to the embodiment. The handle check application is stored in the HDD 6 in FIG. 1 , read out to the RAM 3 , and executed by the CPU 1 . [0060] The handle check application obtains the log of a DLL subjected to a handle check from the log obtaining module on the basis of the handle attribute definition file shown in FIG. 11 or 13 (S 1401 ). The log contains a handle serving as a function identifier, and function attribute information such as the function name, function group, and handle attribute. [0061] Handle check processing proceeds by checking the obtained log sequentially from the start to end (S 1402 to S 1419 ). It is determined whether a function obtained as the log has been set by the handle attribute definition (S 1403 ). If it is determined that the function has not been defined, the function is not processed. If it is determined that the function has been defined, it is determined which of the Open, Close, and OpenClose attributes is set as the FuncProperty setting in the handle attribute definition file for the function (S 1404 ). [0062] If it is determined that the function has the Open attribute, a handle value is obtained in accordance with the ParaError setting to determine whether the value is a valid handle value (S 1405 ). Whether the value is valid is based on the setting contents of ParaError in the handle attribute definition file. In FIGS. 11 and 13 , the handle attribute definition file defines that handle check processing is done only when the value is not 0. Thus, it is determined that the handle value is valid unless it is 0. [0063] If it is determined that the handle value is invalid, the flow returns to S 1403 to process another function without performing any handle check processing. If it is determined that the handle value is valid, a function having the same GroupID as that of the current function and having a handle of the Open attribute is registered by handle check processing in a handle registration table for registering an unmatched function. Then, if the function is registered, it is determined whether the handle value of the registered function is different from that of the current function (S 1408 ). If the handle value of the registered function and that of the current function coincide with each other, it is determined that the result of Open processing is invalid, and an error flag is set for the function subjected to handle check processing (S 1412 ). If no function has been registered, or the function has been registered but the handle values are different from each other, function information and the handle value of the Open attribute are saved in the handle registration table (S 1411 ). [0064] If the function attribute is the Close attribute, a handle value is obtained in accordance with the ParaError setting to determine whether the value is a valid handle value (S 1406 ). The determination criterion of whether the value is valid is the same as that for the Open attribute. If it is determined that the handle value is invalid, the flow returns to S 1403 to process another function without performing any check processing. If it is determined that the handle value is valid, it is determined whether a function having the same GroupID as that of the current function and having a handle of the Open attribute or OpenClose attribute has been registered in the handle registration table, and whether the handle value is equal to the handle value of the current function (S 1409 ). If no function has been registered in the handle registration table, or the function has been registered but the handle values are different from each other, it is determined that the current processing is Close processing called without any Open processing, and the error flag is set for the function subjected to handle check processing (S 1414 ). If the handle values coincide with each other, the Open and Close processes are normally done, and the function information and handle values in the handle registration table are deleted (S 1413 ). [0065] If the function attribute is the OpenClose attribute, the handle value of the Close attribute is obtained in accordance with the ParaError setting to determine whether the value is a valid handle value (S 1407 ). This determination method is also the same as the above-described one. If it is determined that the handle value is invalid, the flow returns to S 1403 to process another function without performing any check processing. If it is determined that the handle value is valid, it is determined whether a function having the same GroupID as that of the current function and having a handle of the Open attribute has been registered in the handle registration table, and whether the handle value is equal to the handle value of the current function (S 1410 ). [0066] If no function has been registered, or the function has been registered but the handle values are different from each other, it is determined that the current processing is Close processing called without any Open processing, and the error flag is set for the function subjected to handle check processing (S 1415 ). If the handle values coincide with each other, the Open and Close processes are normally done, and the function information and handle values in the handle registration table are deleted (S 1415 ). [0067] The handle value of the Open attribute is obtained in accordance with the ParaError setting to determine whether the value is a valid handle value (S 1417 ). If it is determined that the handle value is invalid, processing for the current function ends, and processing for another function continues in S 1403 . If it is determined that the handle value is valid, the same processing (S 1418 ) as those (S 1408 , S 1411 , and S 1412 ) for a function of the Open attribute is executed. [0068] The above processing is repeated. If all functions registered in the log have undergone handle check processing, functions left in the handle registration table at that time correspond to Open processes for which no Close processing has been done, and the error flag is set for these functions (S 1420 ). [0069] As a result, handle check processing ends for all functions in the log, and the processing results are displayed on the display 8 (S 1421 ). All the functions contained in the log are listed in a processing result display window. For a function for which the error flag has been set in handle check processing, it is displayed that a handle check error has occurred. [0070] FIG. 15 is a table showing an example of the processing result display window displayed on the display 8 in S 1421 of FIG. 14 . Error information is displayed as “x” in the handle check error column ( 1501 ) of the log. For a function with “x”, the error flag is set in handle check processing. [0071] In FIG. 15 , a function on the first line ( 1502 ) of the log represents that the module is HandleCheck.dll, the function is OpenDevice, no argument is set, and the return value is DWORD handle whose value of 0x5034206D. In handle check processing, information on this function is added to the unmatched-function table at this stage. [0072] The second line ( 1503 ) represents a CloseDevice function for Close processing that is paired with the function on the first line. The first argument defined by the Close attribute is 0x5034206D which is equal to the value of the handle check definition on the first line. In this processing, OpenDevice on the first line and CloseDevice on the second line are normally processed. Thus, the function on the first line is deleted from the table, and no error information is displayed in the handle check error column. [0073] For a CloseDevice function on the third line ( 1504 ), the argument has the same value as that of the Open function on the first line that has already been closed by the Close function on the second line. OpenDevice having the same return value as this argument value does not exist in the table. Thus, an error is displayed in the handle check error column. On the fourth line ( 1505 ), MemoryAlloc is executed, and its information is added to the table. However, MemoryAlloc results in an error because MemoryFree serving as Close processing is not called even after handle check processing proceeds to the end of the log. [0074] Also, a MemoryFree function on the seventh line ( 1508 ) results in an error because this function has the same handle value as a MemoryAlloc function on the fifth line ( 1506 ) that has already been closed by a MemoryRealloc function on the sixth line ( 1507 ). A MemoryFree function on the eighth line ( 1509 ) is normally processed because it has the same value as a value which has been re-allocated and opened by the MemoryRealloc function on the sixth line ( 1507 ). [0075] As described above, according to the embodiment, handles serving as the identifiers of paired functions are defined. Processing which has not normally ended can be detected on the basis of an obtained log. [0076] More specifically, according to the embodiment, whether Open/Close processing of a function is not omitted can be checked. A failure in normally ending processing (e.g., a power On/Off failure of a device or memory leak) can be easily detected, decreasing the number of debagging steps and that of evaluation steps. [0077] A characteristic feature of the present invention is to check processing associated with a function/method handle without changing any function/method code. Handle check processing itself is not limited to the above-described method. Other Embodiment [0078] Note that the present invention can be applied to an apparatus comprising a single device or to system constituted by a plurality of devices. [0079] Furthermore, the invention can be implemented by supplying a software program, which implements the functions of the foregoing embodiments, directly or indirectly to a system or apparatus, reading the supplied program code with a computer of the system or apparatus, and then executing the program code. In this case, so long as the system or apparatus has the functions of the program, the mode of implementation need not rely upon a program. [0080] Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the claims of the present invention also cover a computer program for the purpose of implementing the functions of the present invention. [0081] In this case, so long as the system or apparatus has the functions of the program, the program may be executed in any form, such as an object code, a program executed by an interpreter, or script data supplied to an operating system. [0082] Examples of storage media that can be used for supplying the program are a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a non-volatile type memory card, a ROM, and a DVD (DVD-ROM, DVD-R or DVD-RW). [0083] As for the method of supplying the program, a client computer can be connected to a website on the Internet using a browser of the client computer, and the computer program of the present invention or an automatically-installable compressed file of the program can be downloaded to a recording medium such as a hard disk. Further, the program of the present invention can be supplied by dividing the program code constituting the program into a plurality of files and downloading the files from different websites. In other words, a WWW (World Wide Web) server that downloads, to multiple users, the program files that implement the functions of the present invention by computer is also covered by the claims of the present invention. [0084] It is also possible to encrypt and store the program of the present invention on a storage medium such as a CD-ROM, distribute the storage medium to users, allow users who meet certain requirements to download decryption key information from a website via the Internet, and allow these users to decrypt the encrypted program by using the key information, whereby the program is installed in the user computer. [0085] Besides the cases where the aforementioned functions according to the embodiments are implemented by executing the read program by computer, an operating system or the like running on the computer may perform all or a part of the actual processing so that the functions of the foregoing embodiments can be implemented by this processing. [0086] Furthermore, after the program read from the storage medium is written to a function expansion board inserted into the computer or to a memory provided in a function expansion unit connected to the computer, a CPU or the like mounted on the function expansion board or function expansion unit performs all or a part of the actual processing so that the functions of the foregoing embodiments can be implemented by this processing. [0087] As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims. CLAIM OF PRIORITY [0088] This application claims priority from Japanese Patent Application No. 2004-364782 filed on Dec. 16, 2004, which is hereby incorporated by reference herein.

An information processing apparatus executes a first module, a second module, and a third module for mediating a call from the first module to a function in the second module and obtaining the log of processing in the second module in response to the call. The apparatus obtains the log from the third module, extracts, from the obtained log, attribute information of functions and identifiers assigned to the functions, and determines, on the basis of attribute information of a first function and a second function among the extracted functions, identifiers assigned to the first function and the second function, whether processing in the second module has normally ended.

The present application claims the benefit of U.S. Provisional Patent Application No. 60/487,580, filed on Jul. 17, 2003; the present application is also a continuation-in-part of U.S. patent application Ser. No. 10/234,859, filed Sep. 5, 2002 (status pending), which is a continuation-in-part of U.S. patent application Ser. No. 10/036,796, filed Jan. 7, 2002 U.S. Pat. No. 6,843,657, which claims the benefit of U.S. Provisional Patent Application No. 60/260,893, filed on Jan. 12, 2001 and U.S. Patent Application No. 60/328,396, filed on Oct. 12, 2001. Each above identified application is incorporated herein by this reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to electrical interconnection systems, and more specifically, to a high speed, high-density interconnection system for differential and single-ended transmission applications. 2. Discussion of the Background Backplane systems are comprised of a complex printed circuit board that is referred to as the backplane or motherboard, and several smaller printed circuit boards that are referred to as daughtercards or daughterboards that plug into the backplane. Each daughtercard may include a chip that is referred to as a driver/receiver. The driver/receiver sends and receives signals from driver/receivers on other daughtercards. A signal path is formed between the driver/receiver on a first daughtercard and a driver/receiver on a second daughtercard. The signal path includes an electrical connector that connects the first daughtercard to the backplane, the backplane, a second electrical connector that connects the second daughtercard to the backplane, and the second daughtercard having the driver/receiver that receives the carried signal. Various driver/receivers being used today can transmit signals at data rates between 5–10 Gb/sec and greater. The limiting factor (data transfer rate) in the signal path is the electrical connectors that connect each daughtercard to the backplane. Further, the receivers are capable of receiving signals having only 5% of the original signal strength sent by the driver. This reduction in signal strength increases the importance of minimizing cross-talk between signal paths to avoid signal degradation or errors being introduced into digital data streams. With high speed, high-density electrical connectors, it is even more important to eliminate or reduce cross-talk. Thus, a need exists in the art for a high-speed electrical connector capable of handling high-speed signals that reduces cross-talk between signal paths. SUMMARY OF THE INVENTION The present invention provides a high-speed electrical interconnection system designed to overcome the drawbacks of conventional interconnection systems. That is, the present invention provides an electrical connector capable of handling high-speed signals effectively. In one aspect the present invention provides an interconnect system having a first circuit board, a second circuit board and a connector for connecting the first circuit board to the second circuit board. The first circuit board includes (a) a first differential interconnect path, (b) a first signal pad on a surface of the first circuit board and (c) a second signal pad also on the surface of the first circuit board, wherein the first differential interconnect path includes a first signal path electrically connected to the first signal pad and a second signal path electrically connected to the second signal pad. The second circuit board includes a second differential interconnect path. The connector electrically connects the first differential interconnect path with the second differential interconnect path. The connector may include the following: an interposer having a first face and a second face opposite the first face, the first face facing the surface of the first circuit board; a first conductor having an end adjacent to the second surface of the interposer; a second conductor parallel with and equal in length to the first conductor, the second conductor also having an end adjacent to the second surface of the interposer; a dielectric material disposed between the first conductor and the second conductor; a first elongated contact member having a conductor contact section, a board contact section and an interim section between the conductor contact section and the board contact section, the conductor contact section being in physical contact with the end of the first conductor, the board contact section being in physical contact with and pressing against a surface of the first signal pad, but not being secured to the first signal pad, and the interim section being disposed in a hole extending from the first face of the interposer to the second face of the interposer, wherein the first signal pad exerts a force on the first contact member and the first contact member is free to move in the direction of the force to a limited extent. In another aspect, the present invention provides a connector for electrically connecting a signal path on a first circuit board with a signal path on a second circuit board. The connector may include: a first, a second and a third spacer; a first circuit board disposed between the first and second spacers; and a second circuit board disposed between the second and third spacers. The first circuit board has a first face abutting a face of the first spacer and a second face abutting a face of the second spacer. The second face has a set of signal conductors disposed thereon. Each of the signal conductors disposed on the second face has a first end adjacent a first edge of the second face, a second end adjacent a second edge of the second face, and an interim section between the first end and the second end. The second circuit board has a first face abutting a face of the second spacer and a second face abutting a face of the third spacer. The first face of the second circuit board having a set of signal conductors disposed thereon. Each of the signal conductors disposed on the first face having a first end adjacent a first edge of the first face, a second end adjacent a second edge of the first face, and an interim section between the first end and the second end. The first edge of the second face of the first circuit board is parallel and spaced apart from the first edge of the first face of the second circuit board. Advantageously, to reduce cross-talk, none of the first ends of the signal conductors on the first circuit board are aligned with any of the first ends of the signal conductors on the second circuit board. In another aspect, the present invention provides a spacer for a connector. The spacer may include a first face having a set of M grooves disposed thereon, each of the M grooves extending from a first edge of the first face to a second edge of the first face; a second face having a set of N grooves disposed thereon, each of the N grooves extending from a first edge of the second face to a second edge of the second face; and an elongate finger projecting outwardly from a side of the spacer for attaching the spacer to a part of the connector. The above and other features, embodiments and advantages of the present invention, as well as the structure and operation of preferred embodiments of the present invention, are described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated herein and form part of the specification, help illustrate various embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. FIG. 1 is an exploded view of a connector in accordance with an example embodiment of the present invention. FIG. 2 is a view of a printed circuit board according to an embodiment of the present invention. FIG. 3 is a front side view of the printed circuit board shown in FIG. 2 . FIG. 4 is a perspective view of a spacer in accordance with an example embodiment of the present invention. FIG. 5 is a top view of a first face of the spacer shown in FIG. 4 . FIG. 6 is a top view of a second face of the spacer shown in FIG. 4 . FIG. 7 is a front side view of the spacer shown in FIG. 4 . FIG. 8 is a top view of a first face of a second spacer. FIG. 9 is a top view of a second face of the second spacer. FIG. 10 is a perspective view of an apparatus consisting of a circuit board sandwiched between two spacers. FIG. 11 is a front side view of the apparatus shown in FIG. 10 . FIG. 12 illustrates an arrangement of multiple circuit boards and multiple spacers according to an example embodiment of the present invention. FIG. 13 is a top view of a first face of a circuit board according to an embodiment of the present invention. FIG. 14 illustrates how the alignment of the conductors on an A type circuit board differs from alignment of the conductors on a B type circuit board. FIG. 15 illustrates a contact member according to one embodiment of the invention. FIGS. 16 and 17 illustrate a cell according to one embodiment of the invention. FIGS. 18 and 19 illustrate that cells may be configured to fit into an aperture of an interposer. FIG. 20 illustrates a finger of a spacer inserted into a corresponding notch of an interposer. FIG. 21 illustrates the arrangement of the interposers 180 in relation to board 120 and in relation to boards 2190 and 2180 , according to one embodiment FIG. 22 is a cross-sectional view of an embodiment of the connector 100 . FIG. 23 illustrates an embodiment of backbone 150 . FIG. 24 illustrates an embodiment of an end cap 199 . FIG. 25 is an exploded view of backbone 150 and an end cap 199 . FIG. 26 is a view of a backbone 150 and an end cap 199 assembled together. FIG. 27 is a view of a spacer connected to backbone 150 . FIG. 28 illustrates an embodiment of mounting clip 190 b. FIG. 29 is an exploded view of clip 190 b and end cap 199 . FIG. 30 is a view of clip 190 b having an end cap 199 attached thereto. FIG. 31 illustrates an embodiment of shield 160 . FIG. 32 is an exploded view of shield 160 and an interposer 180 . FIG. 33 is a view of shield 160 being connected to an interposer 180 . FIG. 34 is a view of an assembled connector with an interposer 180 and clip 190 a omitted. FIGS. 35 and 36 are different views of an almost fully assembled connector 100 according to one embodiment assembled without cells in FIG. 35 and with 2 cells in FIG. 36 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is an exploded view of a connector 100 in accordance with an example preferred embodiment of the present invention. Some elements have been omitted for the sake of clarity. As illustrated in FIG. 1 , connector 100 may include at least one printed circuit board 120 having electrical conductors printed thereon. In the embodiment shown, connector 100 may further include a pair of spacers 110 a and 110 b , a pair of interposers 180 a and 180 b , a pair of end-caps 190 a and 190 b , a backbone 150 , a shield 160 , and a pair of endplates 190 a and 190 b . Although only one circuit board and only two spacers are shown in FIG. 1 , one skilled in the art will appreciate that in typical configurations connector 100 will include a number of circuit boards and spacers, with each circuit board being disposed between two spacers, as will be described herein. FIG. 2 is a view of printed circuit board 120 . In the embodiment shown, circuit board 120 is generally rectangular in shape. As shown, circuit board 120 may have one or more electrical conductors disposed on a face 220 thereof. In the embodiment shown, board 120 has four conductors 201 , 202 , 203 , and 204 disposed on face 220 . Each conductor 201 – 204 has a first end, a second and an interim section between the first and second ends. The first end of each conductor is located at a point on or adjacent a first edge 210 of face 220 and the second end of each conductor is located at a point on or adjacent a second edge 211 of face 220 . In many embodiments, second edge 211 of face 220 is perpendicular to first edge 210 , as shown in the embodiment illustrated in FIG. 2 . Although not shown in FIG. 2 , there are corresponding electrical conductors on the opposite face of circuit board 120 . More specifically, for each conductor 201 – 204 , there is a conductor on the opposite face that is a mirror image of the conductor. This feature is illustrated in FIG. 3 , which is a front side view of board 120 . As shown in FIG. 3 , conductors 301 – 304 are disposed on face 320 of board 120 , which face 320 faces in the opposite direction of face 220 . As further illustrated, conductors 301 – 304 correspond to conductors 201 – 204 , respectively. When the interconnection system 100 of the present invention is used to transmit differential signals, one of the electrical conductors 201 – 204 and its corresponding electrical conductor on the opposite face may be utilized together to form the two wire balanced pair required for transmitting the differential signal. Since the length of the two electrical conductors is identical, there should be no skew between the two electrical conductors (skew being the difference in time that it takes for a signal to propagate the two electrical conductors). In configurations where connector 100 includes multiple circuit boards 120 , the circuit boards are preferably arranged in a row in parallel relationship. Preferably, in such a configuration, each circuit board 120 of connector 100 is positioned between two spacers 110 . FIG. 4 is a perspective side view of spacer 110 a according to one embodiment of the invention. As shown, spacer 110 a may have one or more grooves disposed on a face 420 thereof, which face 420 faces away from board 120 . In the embodiment shown, face 420 of spacer 110 a has three grooves 401 , 402 and 403 disposed thereon. Each groove 401 – 403 extends from a point at or near a first edge 410 of face 420 to a point at or near second edge 411 of face 420 . In many embodiments, second edge 411 of face 420 is perpendicular to first edge 410 , as shown in the embodiment illustrated in FIG. 4 . As further shown, face 420 of spacer 110 a may have one or more recesses disposed at an edge of face 420 . In the embodiment shown, there are two sets of four recesses-disposed at an edge on face 420 . The first set of recesses includes recesses 421 a–d , and the second set of recesses includes recesses 431 a–d . Each recess 421 a–d is positioned directly adjacent to the end of at least one groove and extends from a point on edge 410 of face 420 to a second point spaced inwardly from edge 410 a short distance. Similarly, each recess 431 a–d is positioned directly adjacent to the end of at least one groove and extends from a point on edge 411 of face 420 to a second point spaced inwardly from edge 411 a short distance. Accordingly, in the embodiment shown, there is at least one recess between the ends of all the grooves. Each recess 421 , 431 is designed to receive the end of spring element (see FIG. 16 , elements 1520 ). Although not shown in FIG. 4 , there may be grooves and recesses on the opposite face 491 of spacer 110 a . In a preferred embodiment, the number of grooves on the first face of a spacer 110 is one less (or one more) than the number of grooves on the second face of the spacer 110 , but this is not a requirement. Similarly, in the preferred embodiment, the number of recesses on the first face of a spacer 110 is two less (or two more) than the number of recesses on the second face of the spacer 110 . This feature is illustrated in FIGS. 5–7 , where FIG. 5 is a top view of face 420 , FIG. 6 is a top view of the opposite face (i.e., face 491 ), and FIG. 7 is a front side view of spacer 110 a. As shown in FIG. 5 , grooves 401 – 403 , recesses 421 a–d , and recesses 431 a–d are disposed on face 420 of spacer 110 a . Similarly, as shown in FIG. 6 , grooves 601 – 604 , recesses 621 a–c , and recesses 631 a–c are disposed on face 491 of spacer 110 a , which face 491 faces in the opposite direction of face 420 . Grooves 601 – 604 are similar to grooves 401 – 404 in that each groove 601 – 604 extends from a point on a first edge 610 of face 491 to a point on a second edge 611 of face 491 . Likewise, recesses 621 and 631 are similar to recesses 421 and 431 . Like each recess 421 , each recess 621 extends from a point on edge 610 of face 491 to a second point spaced inwardly from edge 610 a short distance. Similarly, each recess 631 extends from a point on edge 611 of face 491 to a second point spaced inwardly from edge 611 a short distance. Each recess 621 , 631 is designed to receive the end of a spring element (see FIG. 16 , elements 1520 ). The figures illustrate that, in some embodiments, the number of grooves on one face of a spacer 110 is one less (or one more) than the number of grooves on the opposite face of the spacer. And also show that the number of recesses on one face may be two less (or two more) than the number of recesses on the opposite face. In the embodiment shown in FIGS. 4–6 , each recess on one face is positioned so that it is generally directly opposite an end of a groove on the other face. For example, recess 421 a is generally directly opposite an end of groove 604 and recess 621 a is generally directly opposite an end of groove 403 . This feature can be more easily seen by examining FIG. 7 , which is a front side view of the spacer. Referring back to FIG. 4–6 , FIG. 4 shows that spacer 110 a may further include three fingers 435 , 437 , and 440 . It also shows that that spacer 110 a may also include a slot 444 and a first pair of bosses 450 disposed on and projecting outwardly from face 420 and a second pair of bosses 650 disposed on and projecting outwardly from face 491 . Bosses 650 are provided to fit in the apertures 244 of circuit board 120 . This feature enables board 120 to be properly aligned with respect to the adjacent spacers 110 a and 110 b. Finger 435 is located towards the top of the front side of spacer 110 a and finger 437 is located towards the front of the bottom side of spacer 110 a . Finger 435 projects outwardly from the front side of spacer 110 a in a direction that is perpendicular to the front side of the spacer. Similarly, finger 437 projects outwardly from the bottom side of spacer 110 a in a direction that is perpendicular to the bottom side of the spacer. Fingers 435 , 437 function to attach spacer 110 a to interposers 180 b , 180 a , respectively. More specifically, interposer 180 a includes a recess 1810 (see FIG. 18 ) for receiving and retaining finger 437 . Similarly interposer 180 b includes a recess for receiving and retaining finger 435 . Fingers 435 , 437 each include a protrusion 436 and 438 , respectively. The protrusions are sufficiently resilient to allow them to snap into corresponding recesses in the corresponding interposers. Slot 444 is located towards but spaced apart from the backside of spacer 110 a . Slot 444 extends downwardly from the top side of spacer 110 to form finger 440 . Finger 440 and slot 444 function together to attach spacer 110 a to backbone 150 . Referring back to spacer 100 b (see FIG. 1 ), in the embodiment shown, spacer 110 b is similar but not identical to spacer 110 a . Accordingly, in some embodiments connector 100 includes two types of spacers: type A and type B. In other embodiments, more or less than two types of spacers may be used. FIGS. 8 and 9 further illustrate spacer 110 b (the type B spacer) according to one embodiment. FIG. 8 is a top view of a face 820 of spacer 110 b . Face 820 faces circuit board 120 . As shown in FIG. 8 , face 820 is similar to face 491 of spacer 110 a , which also faces board 120 . Like face 491 , face 820 has four grooves 801 – 804 , a first set of three recesses 821 a–c , and a second set of three recesses 831 a–c. Grooves 801 – 804 are similar to grooves 601 – 604 in that each groove 801 – 804 extends from a point on a first edge 810 of face 820 to a point on a second edge 811 of face 820 . Likewise, recesses 821 and 831 are similar to recesses 621 and 631 . Like each recess 621 , each recess 821 extends from a point on edge 810 of face 820 to a second point spaced inwardly from edge 810 a short distance. Similarly, each recess 831 extends from a point on edge 811 of face 820 to a second point spaced inwardly from edge 811 a short distance. FIG. 9 is a top view of a face 920 of spacer 110 b . Face 920 faces away from circuit board 120 in the opposite direction of face 820 . As shown in FIG. 9 , face 920 is similar to face 420 of spacer 110 a , which also faces away from board 120 . Like face 420 , face 920 has three grooves 901 – 903 , a first set of four recesses 921 a–d , and a second set of four recesses 931 a–d. Grooves 901 – 903 are similar to grooves 401 – 403 in that each groove 901 – 903 extends from a point on a first edge 910 of face 920 to a point on a second edge 911 of face 920 . Likewise, recesses 921 and 931 are similar to recesses 421 and 431 . Each recess 421 extends from a point on edge 910 of face 920 to a second point spaced inwardly from edge 910 a short distance, and each recess 931 extends from a point on edge 911 of face 920 to a second point spaced inwardly from edge 911 a short distance. Spacer 110 b also includes three fingers 835 , 837 , and 840 , a slot 844 , and a pair apertures 850 extending through spacer 110 b . Apertures 850 are provided to receive bosses 650 . This feature enables spacer 110 b to be properly aligned with respect to spacers 110 a. Unlike finger 435 , which is located towards the top of the front side of spacer 110 a , finger 835 is located towards the bottom of the front side of spacer 110 b . Similarly, unlike finger 437 , which is located towards the front of the bottom side of spacer 110 a , finger 837 is located towards the back of the bottom side of spacer 110 b . Finger 835 projects outwardly from the front side of spacer 110 a in a direction that is perpendicular to the front side of the spacer, and finger 437 projects outwardly from the bottom side of spacer 110 a in a direction that is perpendicular to the bottom side of the spacer. Like fingers 435 , 437 , fingers 835 , 837 function to attach spacer 110 b to interposers 180 b , 180 a , respectively. As discussed above, board 120 is positioned between spacers 110 a and 110 b . This feature is illustrated in FIG. 10 . Although not shown in FIG. 10 , bosses 650 of spacer 110 a protrude though apertures 244 of board 120 and through apertures 850 of spacer 110 b . This use of bosses 650 facilitates the proper alignment of spacers 110 a,b and board 120 . When board 120 is properly aligned with the spacers, conductors 201 – 204 and 301 – 304 are aligned with grooves 601 – 604 and 801 – 804 , respectively. This feature is illustrated in FIG. 11 . As shown in FIG. 11 , grooves 601 – 604 , which are disposed on the side of spacer 110 a facing board 120 , are positioned on the spacer to mirror electrical conductors 201 – 204 on printed circuit board 120 . Likewise, grooves 801 – 804 , which are disposed on the side of spacer 110 b facing board 120 , are positioned on the spacer to mirror electrical conductors 301 – 304 . Grooves 601 – 604 and 801 – 804 , among other things, prevent electrical conductors 201 – 204 and 301 – 304 from touching spacer 110 a and 110 b , respectively. In this way, the electrical conductors disposed on board 120 are insulated by the air caught between board 120 and the grooves. Spacers 110 may be fabricated either from an electrically conductive material or from a dielectric material and coated with an electrically conductive layer to electromagnetically shield the electrical conductors of the printed circuit board 120 . Furthermore, the complex impedances of the electrical conductors and their associated grooves can be adjusted by varying the dimensions thereof. Still furthermore, the grooves can include a layer of a dielectric material, such as Teflon, to further adjust the complex impedances of the electrical conductors and their associated channels as well as adjusting the breakdown voltage thereof. Referring now to FIG. 12 , FIG. 12 illustrates an example arrangement of spacers 110 and circuit boards 120 when multiple circuit boards are used in connector 100 . As shown, boards 120 and spacers 110 are aligned in a row in parallel relationship and each circuit board 120 is sandwiched between two spacers 110 . In the example shown, there are two types of circuit boards (A) and (B), as well as the two types of spacers (A) and (B) discussed above. The A type circuit boards are identical to each other and the B type circuit boards are identical to each other. Similarly, The A type spacers are identical to each other and the B type spacers are identical to each other. In the embodiment shown, spacers 110 and boards 120 are arranged in an alternating sequence, which means that between any two given A type spacers there is a B type spacer and vice-versa, and between any two given A type boards there is a B type board and vice-versa. Thus, an A type spacer is not adjacent to another A type spacer and an A type board is not adjacent to another A type board. Accordingly, in this example configuration, each board 120 is disposed between an A type spacer and a B type spacer. As can be seen from FIG. 12 , each face of each board 120 b (the B type board) has three conductors thereon. FIG. 13 is a top view of one face 1320 of a B type board (the other face not shown is a mirror image of face 1320 ). As shown in FIG. 13 , there are three conductors 1301 , 1302 , and 1303 disposed on face 1320 . By comparing FIG. 13 to FIG. 2 (which is a top view of a face of an A type board), one can see that the A and B type boards are nearly identical. One difference being the number of conductors on each face and the alignment of the conductors on the face. In the embodiment shown, the B type boards have one less electrical conductor than do the A type boards. Referring to FIG. 14 , FIG. 14 illustrates how the alignment of the conductors 1301 – 1303 on the B type boards differs from alignment of the conductors 201 – 204 on the A type boards. FIG. 14 shows representative boards 120 a and 120 b in a side by side arrangement so that a front edge 1401 on board 120 a is spaced apart from and parallel with a corresponding front edge 1402 on board 120 b . From FIG. 14 , one can clearly see that the ends of the conductors on the B type board located at edge 1402 are not aligned with the ends of the conductors on the A type board located at edge 1401 . For example, in the example shown, the end of any given conductor on the B type board is interstitially aligned with respect to the ends of two adjacent conductors on the A type board. That is, if one were to draw the shortest line from the end of each conductor on the B board to the adjacent face of the A board, each line would terminate at a point that is between the ends of two conductors on the A board. For example, the shortest line from the end of conductor 1301 to the adjacent face of board 120 a ends at a point that is between the ends of conductors 204 and 203 . An advantage of having the conductors be misaligned is that it may reduce cross-talk in the connector. Referring back to FIG. 12 , one can clearly see that each conductor on each board 120 is aligned with a groove on the spacer directly adjacent the conductor. That is, each groove on each spacer 110 is designed to mirror a corresponding conductor on an adjacent board 120 . Because each conductor is aligned with a corresponding groove, there is a space between the conductor and the spacer. When connector 100 is fully assembled, each conductor on a board 120 comes into physical and electrical contact with two contact members (see FIG. 15 for a representative contact member 1530 a ), an end of each of which fits into the space between the adjacent spacer and the conductor. More specifically, the first end of each conductor comes into physical and electrical contact with the contact portion of a first contact member and the second end of each conductor comes into physical and electrical contact with the contact portion second contact member, and the contact portions of the first and second contact members are each disposed in the space between the corresponding end of the conductor and the spacer. Each contact member functions to electrically connect the conductor to which it makes contact to a trace on a circuit board to which the connector 100 is attached. FIG. 15 illustrates a contact member 1530 a , according to one embodiment of the invention, for electrically connecting a conductor 201 on a board 120 to trace on a circuit board (not shown in FIG. 15 ) to which the connector 100 is attached. Only a portion of contact member 1530 a is visible in FIG. 15 because a portion is disposed within a housing 122 . As shown in FIG. 15 , contact member 1530 a contacts an end of conductor 201 (the spacers and interposers are not shown to better illustrate this feature). In some embodiments, the ends of the conductor 201 are wider than the interim portions so as to provide more surface area for receiving the contact portion of the contact members. Partially shown in FIG. 15 is another contact member 1530 b . Contact member 1530 b has a bottom portion that is also housed in housing 122 . Contact member 1530 b contacts an end of conductor 301 , which can't be seen in FIG. 15 . Housing 122 is preferably fabricated of an electrically insulative material, such as a plastic. The electrical contacts 1530 of each housing 122 can either be disposed within the housing during fabrication or subsequently fitted within the housing. Contact members 1530 may be fabricated by commonly available techniques utilizing any material having suitable electrical and mechanical characteristics. They may be fabricated of laminated materials such as gold plated phosphor bronze. While they are illustrated as being of unitary construction, one skilled in the art will appreciate that they may be made from multiple components. As further shown in FIG. 15 , housing 122 may be configured to hold two elongate springs 1520 a and 1520 b . Springs 1520 extend in the same direction as contact members 1530 and 1531 . The distal end of a spring 1520 is designed to be inserted into a corresponding spacer recess. For example, distal end of spring 1520 a is designed to be received in recess 621 c . The combination of the housing 122 , contact members 1530 , and springs 1520 is referred to as a cell 1570 . FIGS. 16 and 17 further illustrate cell 1570 according to one embodiment. FIG. 17 is an exploded view of cell 1570 . As shown, the housing 122 is generally rectangular in shape and includes apertures 1710 for receiving springs 1520 and apertures 1720 for receiving contact members 1530 . Apertures 1720 extend from the top side of housing to bottom side of the housing so that proximal ends 1641 of contact members 1730 can project beyond the bottom side of housing 122 , as shown in FIG. 16 . Apertures 1710 extend from the top surface of housing 122 towards the bottom surface, but do not reach the bottom surface. Accordingly, when a spring 1520 is inserted into an aperture 1710 the proximal end will not project beyond the bottom surface of housing 122 . While open apertures 1710 are illustrated, it is understood that closed apertures can also be used As illustrated in FIG. 17 , each contact member 1530 , according to the embodiment shown, has a proximal end 1641 and a distal end 1749 . Between ends 1641 and 1749 there is a base portion 1743 , a transition portion 1744 and a contact portion 1745 . Base portion 1743 is between proximal end 1641 and transition portion 1744 , transition portion is between base portion 1743 and contact portion 1745 , and contact portion 1745 is between transition portion 1744 and distal end 1749 . In the embodiment shown, base portion 1743 is disposed in aperture 1720 so that generally the entire base portion is within housing 122 , transition portion 1744 is angled inwardly with respect to the base portion, and distal end 1749 is angled outwardly with respect to the transition portion and therefore functions as a lead-in portion. In a preferred embodiment, the contact portion of a contact member is not fixed to the end of the conductor with which it makes physical and electrical contact. For example, the contact portions are not soldered or otherwise fixed to the board 120 conductors, as is typical in the prior art. Instead, in a preferred embodiment, a contact member 1630 is electrically connected to its corresponding conductor with a wiping action similar to that used in card edge connectors. That is, the contact portion of the contact member merely presses against the end of the corresponding conductor. For example, referring back to FIG. 15 , the contact portion of contact member 1530 a merely presses or pushes against the end portion of conductor 201 . Because it is not fixed to the conductor, the contact portion can move along the length of the conductor while still pressing against the conductor, creating a wiping action. This wiping action may ensure a good electrical connection between the contact members and the corresponding electrical conductors of the printed circuit boards 120 . Referring now to FIGS. 18 and 19 , FIGS. 18 and 19 illustrate that each cell 1570 is designed to fit into an aperture 1811 of an interposer 180 . In the embodiment shown, each interposer 180 includes a first set of apertures 1811 a (see FIG. 19 ) arranged in a first set of aligned rows to create a first row and column configuration and a second set of apertures 1811 b arranged in a second set of aligned rows to create second row and column configuration. In the embodiment shown, each row in the second set is disposed between two rows from the first set. For example, row 1931 , which is a row of apertures 1811 b , is disposed between rows 1930 and 1932 , each of which is a row of apertures 1811 a. As shown in the figures, the second row and column configuration is offset from the first row and column configuration so that the apertures of the second set are aligned with each other but not aligned with the apertures of the first set, and vice-versa An interposer 180 may electromagnetically shield the electrical conductors of the printed circuit boards 120 by being fabricated either of a conductive material or of a non-conductive material coated with a conductive material. As also shown in FIGS. 18 and 19 , interposers 180 include notches 1810 along a top and bottom side. Each notch 1810 is designed to receive the end of a finger of a spacer 110 . Preferably, the finger snaps into a corresponding notch to firmly attach the spacer 110 to the interposer 180 . This feature is illustrated in FIG. 20 . When connector 100 is fully constructed, each aperture in the first and second set receives a cell 1570 . The housing 122 of each cell 1570 has a tab 1633 arranged to fit within a slot 1888 disposed within a corresponding aperture of the interposer 180 , which slot 1888 does not extend the entire length of the aperture. The tab 1633 , therefore, prevents the cell 1570 from falling through the aperture. It is to be understood that the specific shape of the cells and corresponding apertures are merely for exemplary purposes. The present invention is not limited to these shapes. Additionally, when connector is fully constructed, the interposers are arranged so that the contact portion 1745 of each contact member 1530 contacts a corresponding conductor. FIG. 21 illustrates this concept. FIG. 21 illustrates the arrangement of the interposers 180 in relation to board 120 and in relation to boards 2190 and 2180 . The spacers 110 are not shown in the figure to illustrate that board 120 and interposers 180 are arranged so that the front side 2102 of board 120 is aligned with the center line of a column of apertures on spacer 180 b and so that the bottom side 2104 of board 120 is aligned with the center line of a column of apertures on spacer 180 a . FIG. 21 also shows two cells 1570 , each disposed in an aperture of an interposer 180 . As shown in FIG. 21 , a contact member 1530 of each cell 1570 makes physical contact with a corresponding conductor. Although not shown in FIG. 21 , when connector 100 is in use, the proximal end 1641 of each contact member 1530 a,b contacts a conducting element on a circuit board connected to connector 100 . For example, end 1641 of contact member 1530 b contacts a conducting element on circuit board 2190 and end 1641 of contact member 1530 a contacts a conducting element on circuit board 2180 . Accordingly, FIG. 21 illustrates that there is at least one electrical signal path from board 2190 to board 2180 through connector 100 . This electrical signal path includes conductor 214 , contact member 1530 b and contact member 1530 a . As is appreciated by one skilled in the art, connector 100 provides multiple electrical signal paths from board 2190 and 2180 , wherein each signal path includes two contact members 1530 and a conductor on a board 120 . According to the embodiment illustrated in FIG. 21 , each interposer is arranged in parallel relationship with one circuit board connected to connector 100 . More specifically, interposer 180 a is in parallel relationship with circuit board 2180 and interposer 180 b is in parallel relationship with circuit board 2190 . Accordingly, one face of interposer 180 a faces board 2180 and one face of interposer 180 b faces board 2190 . Referring now to FIG. 22 , FIG. 22 is a cross-sectional view of the connector 100 and shows that when connector 100 is in use, as described above, each proximal end 1641 of each contact member 1530 contacts a conducting element 2194 on circuit board 2190 . In a preferred embodiment, each conducting element 2194 is a signal pad, and not a via. Accordingly, in a preferred embodiment, connector 100 is a compression mount connector because each proximal end 1641 merely presses against the circuit board and is not inserted into a via in the circuit board. However, in other embodiments, each element 2194 may be a via or other electrically conducting element. in a preferred embodiment, the board 2190 includes a differential signal path that includes a first signal path 2196 a (e.g., a first trace) and a second signal path 2196 b (e.g., a second trace). As shown, the first pad 2194 is connected to the first signal path 2196 a and the second conducting element 2194 b is is connected to the first signal path 2196 b . It should be noted that the second circuit board 2180 may also have a pair of conducting elements, like elements 2194 , electrically connected to a pair of signal paths, like paths 2196 . As shown in FIG. 22 , a cell 1570 is inserted into an aperture of interposer 180 . As further shown, the distal end of each contact member 1530 of cell 1570 extends beyond the upper face 2250 of the interposer and the proximal end 1641 of each contact member 1530 extends beyond the bottom face 2251 of the interposer, which faces board 2190 and is generally parallel thereto. Each proximal end 1641 presses against a conducting element 2194 on board 2190 . Likewise, each contact portion 1745 of contact member 1530 presses against a conductor on board 120 . Thus, a contact member 1530 electrically connects a conductor on board 120 with a conducting element 2194 on board 2190 . As illustrated in FIG. 22 , the ends of the conductors on board 120 are near the upper face 2250 of interposer. When end 1641 of a contact member 1530 presses against a corresponding element 2194 a normal force caused by the element is exerted on the contact member. Because the contact member 1530 is held firmly within housing 1570 , the normal force will cause housing 122 to move in the direction of the normal force (i.e., away from the circuit board 2190 ). However, springs 1520 limit how far housing 122 will move away from board 2190 because when the housing 122 moves away from board 2190 , springs 1520 will compress and exert a force on the housing in a direction that is opposite of the direction of the normal force caused by board 2190 . This is so because the distal ends of the springs abut a surface of a spacer 110 and the spacer is firmly attached to the interposer 180 , which itself does not move relative to the board 2190 . Thus, springs 1502 will compress and exert a force on housing in a direction opposite the normal force. Referring back to FIG. 1 , each spacer 110 may be configured to attach to an elongate backbone 150 . Additionally, connector 100 may include two end caps 100 a and 100 b , each of which is designed to attach to a respective end of backbone 150 . The backbone 150 and end caps 100 are discussed below. Referring to FIG. 23 , FIG. 23 illustrates an embodiment of backbone 150 . Backbone 150 , according to the embodiment shown, includes bosses 2300 arranged to mate with the end caps 100 as well as slots 2320 , each arranged to receive finger 440 of a spacer 110 , as shown in FIG. 27 . Backbone 150 may further include tines 2330 arranged to mate with the spacers 110 . Referring to FIG. 24 , FIG. 24 illustrates an embodiment of an end cap 199 . End cap 199 , according to the embodiment shown, includes apertures 2402 arranged to mate with bosses disposed on adjacent spacers as well as bosses 2300 disposed on the backbone 150 . The end cap 199 further includes both a screw 2420 and a pin 2410 arranged to mechanically interface connector 100 with a circuit board, which may have a large number of layers, for example, more than 30 layers, as well as a tongue 2430 arranged to mate with an end plate 190 b (see FIGS. 1 and 25 ). While the end cap 199 is illustrated as being symmetrical, that is, can be used on either end of connector 100 , separate left and right-handed end caps may also be used. The screw 2420 and pin 2410 of the end cap 199 may be integrally formed with the end cap 199 or may be attached thereto after fabrication of the end cap 199 . It has been found that it is often necessary to utilize a metal rather than a plastic screw 2420 in view of the mechanical stresses involved. It is understood that the present invention is not limited to the use of a screw 2420 and pin 2410 but rather other fastening means may also be used. As noted previously, both the end caps 100 and spacers 110 can be fabricated of an insulative material, such as a plastic, covered with a conductive material to provide electromagnetic shielding or can be fabricated entirely of a conductive material, such as a metal. FIG. 25 is an exploded view of backbone 150 and an end cap 199 and FIG. 26 is a view of a backbone 150 and an end cap 199 assembled together. Referring to FIGS. 25 and 26 , the bosses 2300 of the backbone 150 are disposed within corresponding apertures 2402 in the end caps 100 forming a rigid structure. The use of bosses 2300 and apertures 2402 is for exemplary purposes and the present invention is not limited thereto. That is, other fastening means can be used to mechanically connect the backbone 150 to the end caps 100 . Furthermore, as shown in FIG. 27 , a combination of fingers 440 and mating slots are used to mechanically connect the spacers 110 to the backbone 150 . The illustrated combination is for exemplary purposes and the present invention is not limited thereto. In a similar fashion, as discussed above, the fingers 435 , 437 , 835 , 837 of the spacers 110 are arranged to mate with corresponding slots in the interposer 180 . The illustrated combination of fingers and slots is for exemplary purposes and the present invention is not limited thereto. Referring back to FIG. 1 , FIG. 1 shows that connector 100 may also include a two mounting clips 190 a and 190 b and a shield 160 . Mounting clips 190 and shield 160 are combined with the above described parts of the connector 100 to form a composite arrangement. The mounting clip 190 and shield 160 may be electrically conductive so as to electromagnetically shield the signal carrying elements of connector 100 . The mounting clip 190 and shield 160 will be discussed in detail below. FIG. 28 illustrates an embodiment of mounting clip 190 b . Mounting clip 190 b , according to the embodiment shown, includes: (a) pins 2860 arranged to mate with a hole in a circuit board (e.g., board 2190 or 2180 ) and (b) slots 2870 arranged to receive the tongues and 2430 of the end caps 100 . Pins 2860 function to connect clip 190 b to a circuit board by mating with the circuit board holes mentioned above. Pins 2860 may be electrically conducting and may electrically and physically connect to a ground plane of the circuit board to which it is connected. FIG. 29 is an exploded view of clip 190 b and end cap 199 and FIG. 30 is a view of clip 190 b having an end cap 199 attached thereto. As shown in FIG. 30 , tongue 2430 of end cap 199 is arranged to mate with a corresponding slot 2870 in clip 190 b . As with the other illustrated fastening means, the present invention is not limited to the use of a tongue and corresponding slot. Referring now to FIG. 31 , FIG. 31 illustrates an embodiment of shield 160 . Shield 160 , according to the embodiment shown, includes hooks 3100 arranged to fit in slots in an interposer 180 . FIG. 32 is an exploded view of shield 160 and an interposer 180 . FIG. 33 is a view of shield 160 being connected to an interposer 180 . FIG. 33 illustrates how the hooks 3100 of shield 160 snap into slots in interposer 180 , thereby mechanically connecting the two. FIG. 34 is a view of an assembled connector with an interposer 180 and clip 190 a omitted. FIGS. 35 and 36 are different views of an almost fully assembled connector 100 according to one embodiment. When fully assembled, each aperture in each interposer holds a cell 1570 . Referring to FIG. 35 , FIG. 35 shows end caps 199 a and 199 b , shield 160 , interposer 180 a and clip 190 b. Referring to FIG. 36 , FIG. 36 shows end caps 199 a and 199 b , interposers 180 a and 180 b , and clips 190 a and 190 b . The clip 190 a may be attached to the overall assembly by any usual fastening means and can include pins or other fastening means to attach the assembled connector 100 to a daughtercard, for example. The additional interposer 180 b and additional clip 190 a may be identical to the interposer 180 a and end plate 190 b or can be different (or not present at all), depending upon the application of the interconnection system assembly. While the two interposers 180 have been illustrated as being perpendicular to each other, the present invention is not limited thereto. That is, for some applications, the planes of the two interposers 180 can be at a 45-degree angle or other angle, for example. Thus, connector 100 need not be a “right-angle” connector. As can be seen from FIGS. 34–36 , the entire interconnection system assembly attaches together to form a rigid structure in which the electrical conductors on the printed circuit boards 120 may be entirely electromagnetically shielded. While various embodiments/variations of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

The present invention provides a high-speed electrical interconnection system designed to overcome the drawbacks of conventional interconnection systems. That is, the present invention provides an electrical connector capable of handling high-speed signals effectively.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a divisional of U.S. patent application Ser. No. 09/661,657, filed Sep. 14, 2000, now U.S. Pat. No. 6,498,409, the contents of which are incorporated herein by reference. This application claims the benefit of U.S. Provisional Application 60/154,279 filed Sep. 16, 1999, the contents of which are incorporated herein by reference. TECHNICAL FIELD The invention relates to a tachometer apparatus and methodology for determining the velocity of a motor as applied to a vehicle steering system. BACKGROUND OF THE INVENTION Speed sensors, or detectors of various types are well known in the art. In recent years the application of speed detection to motor control functions has stimulated demands on the sophistication of those sensors. Rotational speed sensors are commonly configured in the same manner as an electric machine, for example, a coil is placed in proximity to rotating magnets whereby the magnetic field induces a voltage on the passing coil in accordance with Faraday's Law. The rotating permanent magnets induce a voltage on the coil and ultimately a voltage whose frequency and magnitude are proportional to the rotational speed of the passing magnets. Many of the tachometers that are currently available in the art exhibit a trade off between capabilities and cost. Those with sufficient resolution and accuracy are often very expensive and perhaps cost prohibitive for mass production applications. Those that are inexpensive enough to be considered for such applications are commonly inaccurate or provide insufficient resolution or bandwidth for the application. Thus, there is a need, in the art for a low cost robust tachometer that provides sufficient accuracy and resolution for motor control applications and yet is inexpensive enough to be cost effective in mass production. SUMMARY OF THE INVENTION The above-identified drawbacks of the prior art are alleviated by the method described in the invention. A method and apparatus for determining the velocity of a rotating device is described herein. The apparatus includes a set of sense magnets affixed to a rotating shaft of a rotating device and a circuit assembly, which interact to form an air core electric machine. The circuit assembly includes a circuit interconnection having a plurality of sense coils and sensors affixed thereto. The circuit assembly is adapted to be in proximity to the set of sense magnets on the rotating part. A controller is coupled to the circuit assembly, where the controller is adapted to execute an adaptive algorithm that determines the velocity of the rotating device. The algorithm is a method of combining a derived velocity with a velocity from the tachometer. The algorithm includes a plurality of functions including: receiving a position signal related to the rotational position of the shaft; determining a derived velocity from the position signal; generating a plurality of tachometer velocity signals; determining a compensated velocity in response to the plurality tachometer velocity signals; and blending the compensated velocity with derived velocity to generate a blended velocity output. BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: FIG. 1 depicts the cross-section of the fixed and rotating parts of a tachometer; FIG. 2 depicts the sense magnet end-view illustrating the low and high-resolution poles; FIG. 3 depicts a partial view of a tachometer coil arrangement in the circuit interconnection; FIG. 4 depict the expected output waveform from the low-resolution tachometer coils; FIG. 5 depicts a partial view of an alternative embodiment of the tachometer coil arrangement in the circuit interconnection board; FIG. 6 depict the expected output waveform from the high-resolution position sensor; FIG. 7 depicts a top-level functional block diagram of a method for determination of the rotational speed; FIG. 8 depicts the Speed Estimation process; FIG. 9 depicts the Offset Compensation process; FIG. 10 depicts the Get Phase process; FIG. 11 depicts the Blend process; FIG. 12 depicts the AlignToPolled process; and FIG. 13 depicts the Gain process. DETAILED DESCRIPTION OF THE INVENTION The present invention may be utilized in various types of motors and other rotational devices such as, for example, motors employed in a vehicle steering system. A preferred embodiment of the invention, by way of illustration is described herein as it may be applied to a motor tachometer in an electronic steering system. While a preferred embodiment is shown and described, it will be appreciated by those skilled in the art that the invention is not limited to the motor speed and rotation but also to any device where rotational motion and velocity are to be detected. A preferred embodiment of the invention provides a structure and method by which the rotational position and velocity of a motor are determined. Referring to FIG. 1, the invention employs a tachometer structure 10 comprised of rotational part 20 and a fixed circuit assembly 30 . Where the rotational part, 20 includes a rotating shaft 22 and sense magnet 24 . The rotating shaft 22 is connected to, or an element of the device, (not shown) whose rotational speed is to be determined. Referring to FIG. 2, an axial (end) view of the sense magnet 24 is depicted. The sense magnet 24 is attached to the rotating shaft 22 and arranged in two concentric, annular configurations, a first of smaller radius surrounded by the second of larger radius. The concentric, annular configurations may be coplanar. The low-resolution magnet 26 comprising the inner annulus of sense magnet 24 is constructed as a six-pole permanent magnet. While the preferred embodiment utilizes the stated configuration, other configurations are reasonable. The magnet structure need only be sufficient to allow adequate detection in light of the sensing elements utilized, processing employed, and operational constraints. The high-resolution magnet 28 comprising the outer annulus of sense magnet 24 is configured as a 72-pole permanent magnet 28 . Again, the magnet structure need only be sufficient to allow adequate detection in light of the sensing elements, processing employed, and operational constraints. Each of the magnets 26 and 28 is comprised of alternating north and south poles equally distributed around each respective annulus. One skilled in the art would appreciate that the magnets when rotated generate an alternating magnetic field which when passed in proximity to a conductor (coil) induce a voltage on the conductor. Further, using well-understood principles the magnitude of the voltage induced is proportional to the velocity of the passing magnetic field, the spacing and orientation of the coil from the magnets. FIGS. 1 and 3 depict the circuit assembly 30 . The circuit assembly 30 includes; a plurality of tachometer coils 40 , low-resolution Hall sensor set 34 , and high-resolution position sensor 36 . The circuit assembly 30 is placed parallel to and in close proximity to the axial end of the rotating sense magnet 24 . A circuit interconnection 38 provides electrical interconnection of the circuit assembly 30 components and may be characterized by various technologies such as hand wiring, a printed card, flexible circuit, lead frame, ceramic substrate, or other circuit connection fabrication or methodology. A preferred embodiment for the circuit assembly 30 comprises the abovementioned elements affixed to a printed circuit board circuit interconnection 38 of multiple layers. Referring to FIGS. 1 and 3, the tachometer coils 40 are located on the circuit assembly 30 in such an orientation as to be concentric with the sense magnet 24 in close proximity to the inner annulus low resolution poles 26 . In a preferred embodiment of the invention, the conductive tachometer coils 40 are an integral part of the circuit interconnection 38 . The tachometer coils 40 include two or more spiraling conductor coils 42 - 48 concentrically wound in a serpentine fashion such that each conductor comprises a twelve turn winding on each of two layers. Coil A is comprised of windings 42 and 48 and coil B is comprised of windings 46 and 44 . Each of the windings is configured such that it spirals inward toward the center on one layer and outward from the center on the second layer. Thereby, the effects of the windings' physical construction variances on the induced voltages are minimized. Further, the tachometers coils 40 are physically arranged such that each has an equivalent effective depth on the circuit assembly 30 . That is, the windings are stacked within the circuit assembly 30 such that the average axial distance from the magnets is maintained constant. For example, the first layer of coil A, winding 42 could be the most distant from the magnets, and the second layer of coil A, winding 48 the closest to the magnets, while the two layers of coil B 46 and 44 could be sandwiched between the two layered windings of coil A. The exact configuration of the coil and winding arrangement stated is illustrative only, many configurations are possible and within the scope of the invention. The key operative function is to minimize the effects of multiple winding effective distances (gaps) on the induced voltages. While two twelve turn windings are described, the coil configuration need only be sufficient to allow adequate detection in light of the magnetic field strength, processing employed, physical and operational constraints. FIG. 3 depicts a partial view of a preferred embodiment. Three turns of the first layer of coil A, winding 42 are shown. Each winding is comprised of six active 50 and six inactive 52 segments per turn. The active segments 50 are oriented approximately on radials from the center of the spiral while the inactive segments 52 are orientated as arcs of constant radius. The active segments 50 are strategically positioned equidistant about the circumference of the spiral and directly cutting the flux lines of the field generated by the low resolution magnet 26 . The inactive segments 52 are positioned at equal radial distances and are strategically placed to be outside the magnetic flux lines from the low resolution magnet 26 . One skilled in the art will appreciate that the winding is uniquely configured as described to provide maximum voltage generation with each passing pole of the low-resolution magnet 26 in the active segments 50 and minimal or no voltage generation with each passing pole of the low resolution magnet 26 in the inactive segments 52 . This results in predictable voltage outputs on the tachometer coils 40 for each rotation of the low-resolution magnet 26 . A preferred embodiment employs two coils, on two layers each with 144 active and 144 inactive segments. However, it will be understood that only the quantity of active segments 50 not the inactive segments 52 is relevant. Any number of inactive segments 52 is feasible, only dictated by the physical constraints of interconnecting the active segments 50 . Additionally, the tachometer coils 40 are comprised of two (or more) complete spiral serpentine windings 42 - 48 , 46 - 44 . The windings 42 - 48 and 46 - 44 may be oriented relative to one another in such a way that the voltages generated by the two coils would possess differing phase relationships. Further, that the orientation may be configured in such a way as to cause the generated voltages to be in quadrature. In a preferred embodiment where the low-resolution poles are comprised of six magnets of sixty degree segments, the two coils are rotated concentrically relative to one another by thirty degrees. This rotation results in a phase difference of 90 degrees between the two generated voltages generated on each coil. In an exemplary embodiment, the two generated voltages are ideally configured such that the voltage amplitude is discernable for all positions and velocities. In an exemplary embodiment, the two generated voltages are trapezoidal. FIGS. 4 and 6 depicts the output voltage generated on the two coils as a function of rotation angle of the rotating shaft 22 for a given speed. In another embodiment of the invention, the windings may be individually serpentine but not necessarily concentric. Again, the coil configuration need only be sufficient to allow adequate detection in light of the magnetic field strength, processing employed, physical and operational constraints. One skilled in the art would recognize that the coil could be comprised of many other configurations of windings. FIG. 5 depicts one such a possible embodiment of the invention. Referring again to FIG. 1, in a preferred embodiment, the Hall sensor set 34 is located on the circuit assembly 30 in an orientation concentric with the tachometer coils 40 and concentric with the rotating part 20 . Additionally, the Hall sensor set is placed at the same radius as the active segments 50 of the tachometer coils 40 to be directly in line axially with the low-resolution poles 26 of the sense magnet 24 . The Hall sensor set 34 is comprised of multiple sensors equidistantly separated along an arc length where two such sensors are spaced equidistant from the sensor between them. In a preferred embodiment, the Hall sensor set 34 is comprised of three Hall effect sensors, 34 a , 34 b , and 34 c , separated by 40 degrees and oriented along the described circumference relative to a predetermined reference position so that absolute rotational position of the rotating part 20 may be determined. Further, the Hall sensor set 34 is positioned to insure that the active segments 50 of the tachometer coils 40 do not interfere with any of the Hall sensors 34 a , 34 b , and 34 c or vice versa. It is also noteworthy to consider that in FIG. 1, the Hall sensor set 34 is depicted on the distant side of the circuit assembly 30 relative to the low-resolution magnet 26 . This configuration addresses the trade between placing the Hall sensor set 34 or the tachometer coils 40 closest to the low-resolution magnet 26 . In a preferred embodiment, such a configuration is selected because the signals from the Hall sensor set 34 are more readily compensated for the additional displacement when compared to the voltages generated on the tachometer coils 40 . It will be appreciated by those skilled in the art that numerous variations on the described arrangement may be contemplated and within the scope of this invention. The Hall sensor set 34 detects the passing of the low-resolution magnet 26 and provides a signal voltage corresponding to the passing of each pole. This position sensing provides a signal accurately defining the absolute position of the rotational part 20 . Again, in the preferred embodiment, the three signals generated by the Hall sensor set 34 with the six-pole low-resolution magnet facilitate processing by ensuring that certain states of the three signals are never possible. One skilled in the art will appreciate that such a configuration facilitates error and failure detection and ensures that the trio of signals always represents a deterministic solution for all possible rotational positions. The position sensor 36 is located on the circuit assembly 30 in such an orientation as to be directly in line, axially with the magnets of the outer annulus of the sense magnet 24 , yet outside the effect of the field of the low-resolution magnet 26 . The position sensor 36 detects the passing of the high-resolution magnet 28 and provides a signal voltage corresponding to the passing of each pole. To facilitate detection at all instances and enhance detectability, the position sensor 36 includes two Hall effect sensors in a single package separated by a distance equivalent to one half the width of the poles on the high-resolution magnet 28 . Thus, with such a configuration the position signals generated by the position sensor 36 are in quadrature. One skilled in the art will appreciate that the quadrature signal facilitates processing by ensuring that one of the two signals is always deterministic for all possible positions. Further, such a signal configuration allows secondary processing to assess signal validity. FIG. 6 depicts the output voltage as a function of rotational angle of the position sensor 36 for a given speed. It is noteworthy to point out that the processing of the high-resolution position allows only a relative determination of rotational position. It is however, acting in conjunction with the information provided by the low-resolution position signals from the Hall sensor set 34 that a determination of the absolute position of the rotating part 20 is achieved. Other applications of the low-resolution position sensor are possible. In another embodiment of the invention, the structure described above is constructed in such a fashion that the active segments of the tachometer coils 40 are at a radial proximity to the sense magnets instead of axial. In such an embodiment, the prior description is applicable except the rotational part 20 would include magnets that are coaxial but not coplanar and are oriented such that their magnetic fields radiate in the radial direction rather than the axial direction. Further, the circuit assembly 30 may be formed cylindrically rather than planar and coaxial with the rotational part 20 . Finally, the tachometer coils 40 , Hall sensor set 34 , and position sensor 36 , would again be oriented such that the active segments 50 would be oriented in the axial direction in order to detect the passing magnetic field of the low-resolution magnet 26 . FIG. 7 depicts the top-level block diagram of the processing functions employed on the various signals sensed to determine the rotational speed of a rotating device. The processing defined would be typical of what may be performed in a controller. Such a controller may include, without limitation, a processor, logic, memory, storage, registers, timing, interrupts, and the input/output signal interfaces as required to perform the processing prescribed by the invention. Referring again to FIG. 7, where the blocks 100 - 1000 depict the adaptive algorithm executed by the abovementioned controller in order to generate the tachometer output. The first four blocks 100 , 200 , 400 , 600 perform the “forward” processing of the tachometer coil signals to arrive at the final blended output. While, the last two 800 , 1000 comprise a “feedback” path thereby constructing the adaptive nature of the algorithm. In FIG. 7, the function labeled Speed Estimation 100 generates a digital, derived velocity signal. The process utilizes Motor_Position_HR the high-resolution position sensed by 36 , and a processor clock signal for timing. The process outputs a signal Motor_Vel_Der_ 144 which is proportional to the velocity of the motor over the sample period of the controller. Continuing to Offset Compensation 200 where processing is performed to generate filtered tachometer signals to remove offsets and bias. The process utilizes the two tachometer coil signals HallTachVoltX 1 , HallTachVoltX 2 , the derived velocity Motor_Vel_Der_ 144 and two phase related feedback signals int_Phase 0 and int_Phase 1 as inputs and generates compensated velocity outputs X 1 _Corr and X 2 _Corr. Continuing to Get Phase 400 where processing is performed to ascertain magnitude and phase relationships of the two compensated velocities. Inputs processed include the compensated velocities X 1 _Corr, X 2 _Corr, and the motor position Motor_Position_SPI as derived from the high-resolution position detected by sensor 36 . The process generates two primary outputs, the selected tachometer magnitude tach 13 vel_mag and the selected tachometer phase tach_vel_sign. Moving to the Blend 600 process where predetermined algorithms determine a blended velocity output. The process utilizes the selected tachometer magnitude tach_vel_mag and the selected tachometer phase tach_vel 13 sign to generate two outputs; the blended velocity Blend_Vel_Signed and the velocity sign OutputSign. Considering now the AlignToPolled 800 process wherein the tachometer magnitude tach_vel_mag is time shifted based upon the magnitude of the derived velocity Motor_Vel_Der_ 144 . The selected signal is filtered and supplied as an output as Filtered_Tach. Finally, looking to Gain 1000 where the process generates an error command resultant from the difference between the derived velocity and filtered tachometer under predetermined conditions. The error signal is integrated and utilized as an error command signal for gain adjustment feedback The process utilizes the derived velocity Motor_Vel_Der_ 144 and the Filtered_Tach signal as inputs to generate two outputs int_Phase 0 and int_Phase 1 . These two signals form the gain adjustment feedback that is then utilized as an input in the abovementioned Offset Compensation 200 . Referring now to FIG. 7 and FIG. 8 for a more detailed description of the functional operation of each of the processes identified above. FIG. 8 depicts the functions that comprise the Speed Estimation 100 process block. This process is a method of extracting a digital, derived velocity based on the per sample period of change of the position signal. The process utilizes as an input Motor_Position_HR the high-resolution position detected by sensor 36 , and outputs a signal Motor_Vel_Der _ 144 , which is proportional to the derived velocity of the motor. The process computes the velocity by employing two main functions. The first is the Deltact calculation process 102 where a position change DELTA_POSITION is computed by subtracting the high-resolution position Motor_Position_HR delayed by one sample from the current high-resolution position Motor_Position_HR. That is, subtracting the last position from the current position. The position difference is then divided by the difference in time between the two samples. An equation illustrating the computation is as follows: Deltact = P 0 - P - 1 T 0 - T - 1 A preferred embodiment of the above equation evaluates a changing measured position over a fixed interval of time to perform the computation. It will be appreciated by those skilled in the art, that the computation may be performed with several variations. An alternative embodiment, evaluates a changing measured time interval for a fixed position change to perform the computation. Further, in yet another embodiment, both the interval of time and interval position could be measured and compared with neither of the parameters occurring at a fixed interval. A filter 104 further processes the calculated Deltact value. Where the filtering characteristics are selected and determined such that the filter yields a response sufficiently representative of the true velocity of the motor without adding excessive delay. One skilled in the art will appreciate and understand that there can be numerous combinations, configurations, and topologies of filters that can satisfy such requirements. A preferred embodiment employed a four-state moving average filter. The signal is labeled Motor_Vel_Der, which is then scaled at gain 106 and output from the process as the value labeled Motor_Vel_Der_ 144 . This parameter is utilized throughout the invention as a highly accurate representation of the velocity. FIG. 9 depicts the functions that comprise the Offset Compensation process 200 . The process extracts the respective offset and bias from each of the two tachometer coil signals HallTachVoltX 1 and HallTachVoltX 2 resulting in compensated velocity outputs X 1 _Corr and X 2 _Corr. The extraction is accomplished by an algorithm that under predetermined conditions subtracts from each of the tachometer signals its low frequency spectral components. The algorithm is characterized by scaling 202 ; a selective, adaptive, filter 204 ; and a gain schedule/modulator Apply Gain 210 . Where, the scaling 202 provides gain and signal level shifting resultant from the embodiment with an analog to digital conversion; the adaptive filter 204 comprises dual selective low pass filters 206 and summers 208 enabled only when the tachometer signals' levels are valid; and gain scheduling, which is responsive to feedback signals int_Phase 0 and int_Phase 1 from the Gain process 1000 . The adaptive filter 204 is characterized by conditionally enabled low pass filters 206 , and summers 208 . The low pass filters 206 under established conditions, are activated and deactivated. When activated, the filter's 206 results are the low frequency spectral content of the tachometer signals to a predetermined bandwidth. When deactivated, the filter 206 yields the last known filter value of the low frequency spectral content of the tachometer signals. It is important to consider that the filter 206 is activated when the tachometer signals are valid and deactivated when they are not. In a preferred embodiment, this occurs when the tachometer signals saturate at a high velocity. Various conditions may dictate the validity of the tachometer signals. In a preferred embodiment, within certain hardware constraints, to satisfy low speed resolution and bandwidth requirements, high speed sensing capability with the tachometer signals is purposefully ignored. This results in the tachometer signals saturating under high speed operating conditions. As such, it is desirable to deactivate the filters 206 under such a condition to avoid filtering erroneous information. A summer 208 subtracts the low pass filter 206 outputs to the original tachometer signals thereby yielding compensated tachometer signals with the steady state components eliminated. The filter 206 characteristics are established to ensure that the filter response when added to the original signals sufficiently attenuates the offsets and biases in the tachometer signals. One skilled in the art will appreciate that there can be numerous combinations, configurations, and topologies of filters that can satisfy such requirements. A preferred embodiment employs an integrating loop low pass filter. The gain scheduling function Apply Gain 210 is responsive to feedback signals int_Phase 0 and int_Phase 1 from the Gain process 1000 (discussed below). The Apply Gain 210 process scales the compensated velocity outputs X 1 _Corr and X 2 _Corr as a function of the feedback signals int_Phase 0 and int_Phase 1 . Thereby providing a feedback controlled correction of the velocity signal for accuracy and speed correction. FIG. 10 depicts the internal process of Get Phase 400 where processing is performed to ascertain magnitude and phase relationships of the two compensated velocities. Inputs processed include the offset compensated velocities X 1 _Corr, X 2 _Corr, the motor position Motor 13 Position_ SPI, and a calibration adjustment signal TachOffset. The motor position signal Motor_Position_SPI derived from the high-resolution position as detected by sensor 36 and indexed to the absolute position as described earlier. The TachOffset input allows for an initial fabrication based adjustment to address differences or variations in the orientation of the tachometer coils 40 (FIGS. 1 and 3) and the low-resolution Hall sensor set 34 (FIG. 1 ). The process generates two primary outputs, the selected tachometer magnitude tach_vel_mag and the selected tachometer phase tach_vel_sign. The process independently determines which tachometer signal magnitude and phase to select by making a comparison with the high-resolution position Motor_Position_SPI. The process determines the magnitude of the two velocities X 1 _Corr and X 2 _Corr at 402 . Then at comparator 404 determines the larger of the two and then generates a discrete, Phase_Sel, indicative of which velocity has the larger magnitude. The larger magnitude velocity is selected because by the nature of the two trapezoidal signals, one is guaranteed to be at its maximum. The discrete Phase_Sel controls a switch 406 , which in turn passes the selected tachometer velocity magnitude termed tach_vel_mag. The discrete Phase_Sel is also utilized in later processes. A second and separate comparison at 408 with the high-resolution position Motor_Position_SPI extracts the respective sign associated with the velocity. Again, it will be understood that those skilled in the art may conceive of variations and modifications to the preferred embodiment shown above. For example, one skilled in the art would recognize that the phase information could have also been acquired merely by utilizing the position information alone. Such an approach however, suffers in that it would be highly sensitive to the precise positioning and timing on the trapezoidal waveforms to insure an accurate measurement. Such a restriction is avoided in the preferred embodiment, thereby simplifying the processing necessary. FIG. 11 depicts the Blend 600 process function where predetermined algorithms determine a blended velocity output. The process utilizes the selected tachometer magnitude tach_vel_mag, the derived velocity Motor_Vel Der_ 144 and the selected tachometer phase tach_vel_sign to generate two outputs; the blended velocity Blend_Vel_Signed and the velocity sign OutputSign. A blended velocity solution is utilized to avoid the potential undesirable effects of transients resultant from rapid transitions between the derived velocity and the tachometer-measured velocity. The process selects based upon the magnitude of the derived velocity Motor_Vel_Der_ 144 a level of scheduling at gain scheduler 602 of the derived velocity with the compensated, measured, and selected velocity, tach_vel_mag. Summer 604 adds the scheduled velocities, which are then multiplied at 606 by the appropriate sign as determined from the tachometer phase tach_vel_sign to generate the blended composite signal. The blended composite signal comprises a combination of the tachometer measured velocity and the derived velocity yet without the negative effects of saturation or excessive time delays. FIG. 12 depicts the AlignToPolled 800 process, which time shifts (delays) the tachometer magnitude tach_vel_mag to facilitate a coherent comparison with the derived velocity Motor_Vel_Der_ 144 . The filtering is only employed when the tachometer magnitude tach_vel_mag is within a valid range as determined in processes 802 and 804 . The valid range is determined based upon the magnitude of the derived velocity Motor_Vel_Der_ 144 . As stated earlier, the validity of the tachometer signals is related to high speed saturation, while for the derived velocity it is a function of filtering latency at very low speed. A selection switch 804 responsive to the magnitude of the derived velocity Motor_Vel_Der_ 144 controls the application of the tach_vel_mag signal to the filter. The multiplication at 808 applies the appropriate sign to the tach_vel_mag signal. A filter 806 is employed to facilitate generation of the time delay. The appropriate time delay is determined based upon the total time delay that the derived velocity signals experience relative to the tachometer signals. The time shift accounts for the various signal and filtering effects on the analog signals and the larger time delay associated with filtering the derived velocity signal. As stated earlier, the derived velocity signal experiences a significant filtering lag, especially at lower speeds. Introducing this shift yields a result that makes the tachometer signals readily comparable to the derived velocity. The selected signal is delivered as an output as Filtered_Tach. In a preferred embodiment, the resultant filter 806 is a four state moving average filter similar to the filter 104 (FIG. 8) implemented in the Speed Estimation process. One skilled in the art will recognize that there can be numerous combinations, configurations, and topologies of filters that can satisfy such requirements. Referring now to FIG. 13, the Gain 1000 process block where an error command is generated and subsequently utilized as a gain correction in the adaptive algorithm of the present invention. In a preferred embodiment, the error command is resultant from a ratiometric comparison 1002 of the magnitudes of the derived velocity to the filtered tachometer velocity. The ratio is then utilized to generate an error signal at summer 1004 . Under predetermined conditions, controlled by state controller 1006 , error modulator 1008 enables or disables the error signal. That is, modulator 1008 acts as a gate whereby the error signal is either passed or not. The state controller 1006 allows the error signal to be passed only when the error signal is valid. For example, when both the filtered tachometer velocity and the derived velocity are within a valid range. In a preferred embodiment, the error signal is passed when the magnitude of the Motor_Vel_Der_ 144 signal is between 16 and 66.4 radians per second. However, the modulator is disabled and the error signal does not pass if the magnitude of the Motor_Vel_Der_ 144 signal exceeds 72 or is less than 10.4 radians per second. Under these later conditions, the ratiometric comparison of the two velocities and the generation of an error signal is not valid. At very small velocities, the signal Motor_Vel_Der_ 144 exhibits excessive delay, while at larger velocities, that is in excess of 72 radians per second, the tachometer signals are saturated. The error signal when enabled is passed to the error integrator 1010 , is integrated, and is utilized as an error command signal for gain adjustment feedback. The error integrators 1010 selectively integrate the error passed by the modulator 1008 . The selection of which integrator to pass the error signal to is controlled by the time shifted Phase_Sel signal at delay 1012 . These two correction signals int_Phase 0 and int_Phase 1 form the gain adjustment feedback that is then utilized as an input in the abovementioned Offset Compensation 200 process. The disclosed invention may be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. The present invention can also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. The present invention can also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits. It will be understood that those skilled in the art may conceive variations and modifications to the preferred embodiment shown herein within the scope and intent of the claims. While the present invention has been described as carried out in a specific embodiment thereof, it is not intended to be limited thereby but is intended to cover the invention broadly within the scope and spirit of the claims.

A method and system for determining the velocity of a rotating device is described herein. The system includes an apparatus with a set of sense magnets affixed to a rotating shaft of the rotating device and a circuit assembly. The circuit assembly includes a circuit interconnection having a plurality of sense coils and sensors affixed thereto. The circuit assembly is adapted be in proximity to the set of sense magnets on the rotating part. A controller is coupled to the circuit assembly, where the controller executes an adaptive algorithm that determines the velocity of the rotating device. The algorithm is a method of combining a derived velocity with a velocity from the tachometer. The algorithm includes a plurality of functions including: receiving a position signal related to the rotational position of the shaft; determining a derived velocity from the position signal; generating a plurality of tachometer velocity signals; determining a compensated velocity in response to the plurality tachometer velocity signals; and blending the compensated velocity with derived velocity to generate a blended velocity output.

TECHNOLOGICAL FIELD [0001] The invention generally provides processes for recovery of acid from acid-rich solutions and mixtures. BACKGROUND [0002] The regeneration of chemical-spent acid from industrial processes is highly desirable for a verity of reasons, ranging from reducing industrial waste and contamination of landfills to reduction of costs associated with the reproduction of acid. [0003] The recovery of acid has been demonstrated in a variety of industrial set-ups. [0004] U.S. Pat. No. 2,631,974 [1] discloses an electrolytic system for the recovery of certain ingredients from the waste liquors discharged from various chemical processes, in particular with the recovery of sulfate ions in acid aqueous solutions containing them by the conversion thereof into aqueous sulfuric acid solutions of sufficient purity to be of commercial value. [0005] U.S. Pat. No. 8,052,953 [2] discloses a method for recovering sulfuric acid from concentrated acid hydrolysate of plant cellulose material. [0006] One of the main barriers in utilizing acid in industrial applications is the relatively high cost which is associated mainly with a high energy requirement needed to recover it. Therefore, there is great need for reducing the production cost and energy requirements involved in such processes. [0007] Sulfuric acid is one of the more common acids in industrial use. The addition of hydrogen peroxide to sulfuric acid results in the formation of a very strong oxidizer, known as Caro's Acid or the Piranha solution, which has the ability to oxidize or hydroxylate most metal surfaces and remove most organic matter. The common application of the Piranha solution is in the microelectronics industry to clean photoresist residues from silicon wafers. It is also used to clean glassware by hydroxylating the surface, thus increasing the number of silanol groups on the surface. [0008] U.S. Pat. No. 3,856,673 [3] discloses a process for purifying a spent acid stream containing organic impurities and at least 60% sulfuric acid. The process disclosed utilizes a stoichiometric amount of an oxidizer such as hydrogen peroxide to achieve oxidation of organic materials such as nitrocresols and nitrophenolic compounds. [0009] Huling et al [4] teach oxidation of organic compounds utilizing hydrogen peroxide. REFERENCES [0000] [1] U.S. Pat. No. 2,631,974 [2] U.S. Pat. No. 8,052,953 [3] U.S. Pat. No. 3,856,673 [4] Huling S. G. and Pivetz B. E. In Situ Chemical Oxidation. Engineering Issue. Ground Water and Ecosystem Restoration Information Center, UAEPA, EPA/600/R-06/072 (2006) SUMMARY OF THE INVENTION [0014] The inventors of the present invention have developed a unique, efficient and cost-effective process for the recovery of acid from acid-rich solutions. The process of the invention utilizes a strong oxidizer, such as Caro's acid, to disintegrate or render insoluble organic or inorganic materials such as carbohydrates and complexes thereof contained in acid-rich solutions, to thereby make efficient and simple the separation and recovery of the acid solution. The acid recovered is thus obtained as an aqueous acid solution, being free of organic matter, and containing nearly all of the acid originally contained in the acid-rich solution. [0015] Thus, the invention described herein affords separating and recovering acids, such as sulfuric acid, from a variety of organic components such as hydrolysates of plant cellulose materials commonly used in the paper industry, such components may or may not be “in solution”, namely some or all of the organic components may be insoluble in the original acid-rich solution to be recovered. [0016] In one of its aspects, the present invention provides a process for acid recovery from an acid-rich aqueous solution, the solution comprising at least one acid to be recovered and at least one organic material (being different from the acid material and typically containing at least one carbohydrate material or a complex thereof), the process comprising: treating said solution with at least one oxidizer or at least one precursor of the oxidizer, wherein the oxidizer is capable of oxidizing the organic material contained in the solution into at least one insoluble or gaseous species; removing or allowing separation of said insoluble or gaseous species from the acid solution; [0019] to yield a substantially enriched acid solution, substantially free of organic matter (being free of said organic impurities, as disclosed herein). [0020] The invention further provides a process for recovery of acid, such as sulfuric acid, from an acid-rich mixture comprising at least one acid, e.g., sulfuric acid, and an amount of organic matter, the process comprising contacting the mixture with an oxidizer or a precursor thereof, thus producing an acid enriched solution, wherein the oxidized organic matter precipitates or evaporates from the acid enriched mixture. [0021] The enriched acid solution being substantially free of organic matter may be further treated to further remove traces of unoxidized organic matter, residues of oxidized organic matter and insoluble species. [0022] In some embodiments, the enriched acid solution being substantially free of organic matter contains up to 1,000 ppm of organic matter. [0023] The acid solution may be any acid-containing aqueous solution which is used or generated in any one of a variety of industries or industrial processes, ranging from stainless steel production to microchip manufacturing. As the acid content may vary based on the industry or the process producing the acid waste, the process of the invention may be suitably configured and adapted to achieve full recovery of the acid. [0024] In accordance with the invention, the oxidizer or a precursor thereof (e.g., hydrogen peroxide) is added to the acid-rich solution at room temperature. The reaction mixture comprising the acid-rich solution and the oxidizer or precursor thereof may be allowed to react over a period of between 1 hours and 7 days at room temperature (25-30° C.), at a temperature above 50° C., or at a temperature above 60° C., or at a temperature above 70° C., or at a temperature above 80° C., or at a temperature above 90° C., or at a temperature above 100° C., or at a temperature above 110° C., or at a temperature above 120° C., or at a temperature above 130° C., or at a temperature above 140° C., or at a temperature above 150° C., or at a temperature between 50° C. and 100°, or at a temperature between 60° C. and 110°, or at a temperature between 70° C. and 120°, or at a temperature between 80° C. and 130°, or at a temperature between 90° C. and 140°, or at a temperature between 100° C. and 150°, or at a temperature between 50° C. and 150°, or at a temperature between 60° C. and 140°, or at a temperature between 70° C. and 130°, or at a temperature between 80° C. and 120°, or at a temperature between 90° C. and 100° C. [0025] In accordance with the invention, the oxidizer or a precursor thereof (e.g., hydrogen peroxide) is added to the acid-rich solution at a temperature below room temperature (being the temperature at which the reaction mixture comprising the acid-rich solution and the oxidizer or precursor thereof may be allowed to react). In some embodiments, the temperature is between −30° C. (minus 30 degrees Centigrade) and 0° C. In some embodiments, the temperature is between −30° C. and −20° C. In some embodiments, the temperature is between −30° C. and −10° C. In some embodiments, the temperature is between −20° C. and −10° C. In some embodiments, the temperature is between −20° C. and 0° C. In some embodiments, the temperature is between −10° C. and 0° C. In some embodiments, the temperature is between −30° C. and 5° C. In some embodiments, the temperature is between −30° C. and 10° C. In some embodiments, the temperature is between −30° C. and 15° C. In some embodiments, the temperature is between −30° C. and 20° C. In some embodiments, the temperature is between −30° C. and 25° C. In some embodiments, the temperature is between −30° C. and 30° C. In some embodiments, the temperature is between 0° C. and 5° C. In some embodiments, the temperature is between 0° C. and 10° C. In some embodiments, the temperature is between 0° C. and 15° C. In some embodiments, the temperature is between 0° C. and 20° C. In some embodiments, the temperature is between 0° C. and 25° C. In some embodiments, the temperature is between 0° C. and 30° C. [0026] In some cases, the oxidizer or a precursor thereof is added to the acid-rich solution at room temperature and the temperature of the reaction mixture is allowed to increase spontaneously (in case of an exothermic reaction). In some embodiments, the temperature increase is controlled such that the temperature does not increase above 50° C., above 60° C., above 70° C., above 80° C., above 90° C., above 100° C., above 110° C., above 120° C., above 130° C., above 140° C., or to above 150° C. [0027] After the oxidizer completely oxidizes the organic material, traces of the organic material and the remaining oxidizing agents may be removed from the acid enriched solution using any method that is common in the field of the art. In some embodiments, the solid oxidized material and solid oxidizer may be removed by filtration. Where the oxidized material is a gaseous species, it may be removed from the acid-enriched solution by evaporation, by heating, under vacuum, by stirring, or by saturating the acid-enriched solution with an inert gas. [0028] In some embodiments, the trace materials and the remaining oxidizing agents may be removed by mechanical or chemical adsorption or by absorption e.g., on activated carbon, by flocculation or precipitation. [0029] The process of the invention may be repeated by employing consecutive cycles and using the herein defined substantially carbon-free acid formulation as a substrate in acid-based processes. [0030] The oxidizer used in accordance with the invention is typically a “strong oxidizer” which is capable of converting an organic material into one or more oxide forms which are less soluble or more easily evaporable as compared to the unoxidized form. The oxidizer is said of being a strong oxidizer as it is capable of oxidizing the majority of the organic material contained in the solution, namely 100 wt % of the organic material, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, between 80% and 100%, between 90% and 100%, between 80% and 95%, or between 80% and 90% of the organic material. Typically, the oxidized form of the organic material is insoluble in the acid solution or is easily removable from the acid solution, e.g., by evaporation, by filtration, by heating, under vacuum, by activated carbon, etc. [0031] In some embodiments, the oxidizer has a Standard Electrode Potentials)(E° greater than +1 Volts. [0032] In some embodiments, the oxidizer is selected to have E° between +1 and +2. The oxidizer is selected to effectively oxidize the organic material without substantially chemically affecting the acid component. Some non-limiting examples of oxidizers include ammonium perchlorate, ammonium permanganate, barium peroxide, bromine, calcium chlorate, calcium hypochlorite, chlorine trifluoride, chromium anhydride, chromic acid, dibenzoyl peroxide, fluorine, hydrogen peroxide, magnesium peroxide, nitrogen trioxide, perchloric acid, potassium bromated, potassium chlorate, potassium peroxide, propyl nitrate, sodium chlorate, sodium chlorite, sodium perchlorate, sulphuric acid and sodium peroxide. [0033] In some embodiments, the oxidizer is hydrogen peroxide (H 2 O 2 ). [0034] In other embodiments, the oxidizer is H 2 SO 5 (Caro's acid). In some embodiments, H 2 SO 5 (Caro's acid) is formed in situ. [0035] In some embodiments, the oxidizer is utilized for forming in situ a stronger oxidizer. [0036] According to embodiments where the oxidizer is formed in situ, an oxidizer (e.g., hydrogen peroxide) or a precursor of the oxidizer which is convertible into the oxidizer in the presence of the acid in the acid-rich solution, is added to the acid-rich solution and transforms an amount of the acid in the solution into the oxidizer. In embodiments where a precursor of the strong oxidizer is hydrogen peroxide and the acid is sulfuric acid, a small amount of “Caro's acid” forms in situ and oxidizes the carbon-based or carbon-containing material, e.g., carbohydrates, to at least one insoluble or gaseous species (e.g., CO 2 and SO 2 ) and water; thus, yielding a substantially carbon-free acid enriched solution (e.g., sulfuric acid). [0037] Thus, the invention also contemplates a process for acid recovery from an acid-rich aqueous solution, the solution comprising at least one organic material (being different from the acid material and selected, e.g., from carbohydrates and complexes thereof), the process comprising: treating said solution with Caro's acid or with at least one precursor thereof for enabling in situ formation of Caro's acid in the solution, wherein the organic material contained in the solution is transformed into at least one insoluble or gaseous species; removing or allowing separation of said insoluble or gaseous species from the acid solution; [0040] to yield a substantially enriched acid solution, substantially free of organic matter. [0041] As noted above, where Caro's acid is used in the process of the invention, the acid-rich solution may be treated with an amount of a pre-prepared Caro's acid or may be treated with an amount of sulfuric acid and hydrogen peroxide, step wise, to form in situ the Caro's acid and permit transformation of the organic material, as detailed herein. [0042] The invention further provides a process for recovery of sulfuric acid from an aqueous solution rich in sulfuric acid, the solution further comprising at least one soluble organic material, as defined herein, the process comprising: treating said solution with Caro's acid or with hydrogen peroxide, to transform the organic material contained in the solution into at least one insoluble or gaseous species; removing or allowing separation of said insoluble or gaseous species from the acid solution; [0045] to yield a substantially enriched acid solution, substantially free of organic matter. [0046] The “acid rich solution” is generally a formulation or a combination of materials or a mixture or a medium comprising between about 5% and between about 98% acid by weight, water and at least one carbon material. The acid in the acid-rich solution may be an organic or mineral acid. In some embodiments, the solution comprises between about 5% and about 90% acid by weight, or between about 30% and about 85% acid by weight, or between about 30% and about 80% acid by weight, or between about 30% and about 75% acid by weight, or between about 30% and about 60% acid by weight. [0047] In some embodiments, the solution comprises between about 35% and about 95% acid by weight, or between about 40% and about 95% acid by weight, or between about 45% and about 95% acid by weight, or between about 50% and about 95% acid by weight, or between about 55% and about 95% acid by weight. [0048] In some embodiments, the solution comprises between about 40% and about 90% acid by weight, or between about 50% and about 85% acid by weight, or between about 60% and about 80% acid by weight, or between about 60% and about 75% acid by weight, or between about 60% and about 65% acid by weight. [0049] In some embodiments, the solution comprises between about 60% and about 90% acid by weight, or between about 60% and about 85% acid by weight, or between about 60% and about 80% acid by weight, or between about 60% and about 75% acid by weight, or between about 60% and about 65% acid by weight, or between about 70% and about 90% acid by weight, or between about 70% and about 85% acid by weight, or between about 70% and about 80% acid by weight, or between about 70% and about 75% acid by weight, or between about 80% and about 95% acid by weight, or between about 80% and about 90% acid by weight, or between about 80% and about 85% acid by weight, or between about 90% and about 95% acid by weight. [0050] In some embodiments, the concentration of the acid in the acid-rich solution is between 1 and 98%, or between 30% and 63%. In other embodiments, the concentration of the acid is between 40% and 63%, between 59% and 63% or is between 60 and 64%. [0051] The acid to be recovered from the acid-rich solution may be a single type of acid or a combination of acids. The acid is usually recovered as an aqueous solution. [0052] As the process of the invention permits conversion of the organic soluble and insoluble materials contained in the acid-rich solution into insoluble organic materials or gaseous species, and permitting their removal, without substantially affecting the acid content, the process of the invention is suited for recovering a plurality of acids and acid combinations. In some embodiments, the acid to be recovered is a mineral acid. Some non-limiting examples of mineral acids include hydrochloric acid (HCl), nitric acid (HNO 3 ), phosphoric acid (H 3 PO 4 ), sulfuric acid (H 2 SO 4 ), boric acid (H 3 BO 3 ), hydrofluoric acid (HF), hydrobromic acid (HBr) and perchloric acid (HClO 4 ). [0053] In some embodiments, the acid is sulfuric acid (H 2 SO 4 ). In some embodiments, the acid-rich solution containing sulfuric acid is treated with a precursor of a strong oxidizer capable of reacting with an amount of the sulfuric acid in the solution to form a strong oxidizer. In some embodiments, the precursor is hydrogen peroxide. [0054] As stated above, the majority of the organic material contained in the acid-rich solution is removed. Thus, the resulting substantially carbon-free acid solution contains an aqueous acid (e.g. sulfuric acid) solution that contains less than 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.3%, 0.1% by weight of a carbon material. [0055] The amount of the organic material remaining after acid recovery, namely the Total Organic Carbon (TOC) may be determined by a variety of methods, for example: (1) TOC Analyzer, and (2) titration with analytical KMnO 4 . [0056] In some embodiments, the TOC may be measured in parts per million (ppm). In such embodiments, the resulting substantially carbon-free acid solution contains between 0.05 and 900 ppm TOC. In some embodiments, the amount of TOC is between 5 and 900 ppm, between 5 and 500 ppm, between 5 and 300 ppm, between 10 and 900 ppm, between 10 and 500 ppm, between 10 and 300 ppm, between 50 and 900 ppm, between 50 and 500 ppm, between 50 and 300 ppm, between 100 and 900 ppm, between 100 and 500 ppm, between 100 and 300 ppm, between 500 and 1,000 ppm, between 600 and 1,000 ppm, between 700 and 1,000 ppm, between 800 and 1,000 ppm or between 900 and 1,000 ppm. [0057] The carbon material may be any carbonaceous material, i.e., any material containing or composing carbon. The carbonaceous material may be of high molecular weight. [0058] The “organic material”, or “organic matter”, or “carbon materials”, all being used herein interchangeably, is “carbonaceous material”, based on carbon and may or may not be soluble in the acid solution. In some embodiments, the organic matter is insoluble in the acid solution. In some embodiments, the organic matter is fully soluble in the acid solution. In some embodiments, the organic matter is a mixture of such materials, some are soluble and the remaining insoluble in the acid solution. In some embodiments, the organic matter comprises at least 50% insoluble material (in the acid solution). In some embodiments, the organic matter comprises a mixture of soluble and insoluble materials, present in a ratio of 0.001:99.999, respectively (out of the total amount, weight, of the organic matter to be oxidized and removed). In some embodiments, the w/w ratio is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 2:3, 2:5, 2:7, 2:9, 2:11, 11:2, 9:2, 7:2, 5:2, 3:2, respectively. [0059] The organic material may be selected from biological materials, organic materials derived from nature, solvents, and/or organic chemicals used in various industries. In some embodiments, the organic material is selected from natural materials such as hydrocarbons, carbohydrates, proteins, amino acids, lignin, lipid and natural resins. In some embodiments, the carbonaceous material is at least one carbohydrate material. [0060] In some embodiments, the organic material to be oxidized and thereby removed is at least one hydrolysate of plant cellulose material, e.g., as commonly used in the paper industry. In some embodiments, the organic material to be oxidized and thereby removed is at least one carbohydrate or a complex thereof. In some embodiments, the organic material to be oxidized and thereby removed is at least one carbohydrate decomposition product, such as furfural, levulinic acid, hydroxymethylfurfural (HMF), acetic acid, formic acid, monosaccharides such as glucose and xylose and others. [0061] For example, sulfuric acid-containing waste solutions are products of a great variety of processes used in the biomass industry where biomass, such as wood or wood products, is treated with acid to separate out various hydrocarbons, particularly carbohydrates. Cellulose which makes up the major part of plant biomass is greatly used in a variety of industries, particularly in the paper industry, e.g., acid-rich solutions of hydrolyzed cellulose products. [0062] Nano Crystalline Cellulose (NCC) also known as Cellulose Whiskers (CW) and crystalline nanocellulose (CNC), are fibers produced from acid hydrolysis of cellulose, typically being high-purity single crystals of cellulose. Thus, in such processes for the production of NCC large amounts of acid, e.g., sulfuric acid, are used, which may be regenerated as disclosed herein. [0063] Thus, the herein defined acid-rich solution may be a byproduct of a process of NCC production or a byproduct of any chemical process which yields the herein defined acid-rich solution. Thus, in some embodiments, the carbon material is a hemicellulose derivative. In some embodiments, the carbon material is selected from galactose, rhamnose, arabinose, xylose, mannose, cellulose, glucose, hydroxymethylfurfural (HMF), galacturonic acid, lignin derivatives, levulinic acid, cellulose ethers and cellulose esters. [0064] In some embodiments, the carbon material is a carbohydrate, a disaccharide, a monosaccharide, an oligosaccharide or a polysaccharide. [0065] In some embodiments, the concentration of the acid (e.g., sulfuric acid) in the NCC acid-rich solution comprising acid and a carbohydrate is between 1 and 98%, or between 30% and 63%. In other embodiments, the concentration of the acid is between 40% and 63%, between 59% and 63% or is between 60 and 64%. [0066] Thus, the process of the invention may be utilized to purify and collect acid-rich solutions used in the paper industries and may comprise at least one carbohydrate as defined herein, or at least one hemicellulose or derivative thereof, or any of the carbonaceous materials disclosed. [0067] The amount of oxidizer precursor (e.g., hydrogen peroxide) to be added, according to some embodiments, to the acid-rich formulation for enabling in situ synthesis of the strong oxidizer (e.g., Caro's acid) depends of various parameters inter alia reaction time, temperature, carbohydrate concentration, acid:solid ratio, as recognized by the person of skill in the art. In some embodiments, the precursor, e.g., hydrogen peroxide, is added to the acid-rich formulation at a concentration of between about 2 and about 10%. In other embodiments, the amount of the precursor material, e.g., hydrogen peroxide is between 2 and 9%, between 2 and 8%, between 2 and 7%, between 2 and 6%, between 2 and 5%, between 2 and 4%, between 2 and 3%, between 3 and 10%, between 3 and 9%, between 3 and 8%, between 3 and 7%, between 3 and 6%, between 3 and 5%, between 3 and 4%, between 4 and 10%, between 4 and 9%, between 4 and 8%, between 4 and 7%, between 4 and 6%, between 4 and 5%, between 5 and 10%, between 5 and 9%, between 5 and 8%, between 5 and 7%, between 5 and 6%, between 6 and 10%, between 6 and 9%, between 6 and 8%, between 6 and 7%, between 7 and 10%, between 8 and 10%, or between 9 and 10%. [0068] In other embodiments, the amount of precursor material, e.g., hydrogen peroxide, is between 10 and 30%, between 12 and 30%, between 14 and 30%, between 16 and 30%, between 18 and 30%, between 20 and 30%, between 22 and 30%, between 24 and 30%, between 26 and 30%, between 28 and 30%, between 10 and 25%, between 12 and 25%, between 14 and 25%, between 16 and 25%, between 18 and 25%, between 20 and 25%, between 10 and 20%, between 12 and 20%, between 14 and 20%, between 16 and 20%, between 18 and 20%, between 25 and 30%, between 3 and 30%, between 5 and 30%, between 7 and 30% or between 9 and 30%. [0069] In some embodiments, the amount of the precursor material e.g., hydrogen peroxide, or the amount of the oxidizer is not stoichiometric. BRIEF DESCRIPTION OF THE DRAWINGS [0070] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [0071] FIGS. 1A-C provide a general depiction of carbohydrate decomposition in the presence of a strong oxidizer. [0072] FIG. 1A depicts the carbohydrates produced following hydrolysis of cellulose. [0073] FIG. 1B shows the general decomposition process of carbohydrates. [0074] FIG. 1C shows a suggested mechanism for the oxidation of carbohydrates by H 2 SO 5 (Caro's acid). [0075] FIG. 2 shows the oxidation reaction progress monitored by colorimetric analysis using 5% H 2 O 2 . [0076] FIGS. 3A-B shows the absorbance vs. oxidation time using 3% H 2 O 2 ( FIG. 3A ) and 7.5% H 2 O 2 ( FIG. 3B ) for 0-19 days. [0077] FIG. 4 depicts an example for adsorption of the remaining organic traces and oxidizing agents in the solution using activated carbon. [0078] FIG. 5 describes adsorption of the remaining organic traces and oxidizing agents in the solution using activated carbon over time. DETAILED DESCRIPTION OF EMBODIMENTS [0079] The invention provides a process for separating or recovering acid from acid-rich solutions comprising soluble and/or insoluble organic matter. The cost-effectiveness of the process of the present invention is improved considerably compared to prior art processes as a result of using an oxidizer which is capable of substantially completely oxidizing the organic material while leaving unaffected the acid material, thus not affecting acid losses. Under such a set up, it is possible to carry out the acid recovery at a relatively low temperature, e.g., below 100° C., and from acid solutions containing no less than between 100 and 400 times as much organic contaminants. [0080] An additional advantage of the invention resides in the fact that no, or only little, undesired by-products, such as soluble oxidized organic materials are formed. These too may be removed by further processing of the acid solution. Example 1: Process of Recovering Acid from Acid-Rich Formulations [0081] 7.54 kg of 30% H 2 O 2 (5% of H 2 O 2 weight per weight final solution) were loaded at R.T to 38 kg ˜60% sulfuric acid suspension containing 2.2% carbohydrates (weight per solution weight). The composition of the suspension was around 2/3 of insoluble complex carbohydrates (e.g. cellulose, hemicellulose) and ⅓ soluble carbohydrates (monomeric+polymeric) and their derivatives. Such an acid formulation contained glucose (9.8 g/L-30 g/L), galactose (<0.2 g/L), arabinose (<0.2 g/L), mannose (<0.2 g/L), xylose (0.6 g/L-1.8 g/L), formic acid (<1 g/L), acetic acid (<1 g/L), levulinic acid (<1 g/L), hydroxymethylfurfural (HMF) (<0.2 g/L) and furfural (<0.2 g/L). [0082] The reaction mixture was stirred at R.T until it exothermed or was refluxed)(110°-130° and monitored by spectrophotometer. After 90 minutes the absorption in the region 400 nm-1100 nm reached a minimum, indicating that the majority of the organic material was oxidized. Thereafter, the reaction was cooled down. After 90 minutes, the solution was completely clear. [0083] The thus-obtained cleared acid formulation was basically free of organic matter, or contained very minute amounts of organic matter. To further purify the acid formulation, the following steps were optionally carried out. [0084] 0.76 kg of activated carbon (2% of Activated carbon weight per weight of initial 60% acid) were loaded at R.T to a “cleared solution” of 44 kg ˜50% sulfuric acid solution containing traces of carbohydrates and ˜5% H 2 O 2 . The solution was mixed and monitored by spectrophotometer and TOC levels measured by titration with KMnO 4 . After 8 h the absorption in the region 400 nm-1100 nm and the titer amount reached minimum and the reaction was cooled down and filtered. The “cleaned solution” was thereafter used in further acid-based reactions. Example 2: General Process of Recovering Acid from Acid-Rich Formulations from NCC Production Processes [0085] The above process was also used for acid recovery of acid formulations used in industrial process for utilizing paper products, paper pulp or generally cellulose materials. [0086] The general sequence of process steps is exemplifies herein by acid recovery from an acid-rich solution which is an end-solution in the production of NCC. The process of the invention may comprise: Step 1. Separation of concentrated sulfuric acid from the hydrolyzed NCC suspension; and Step 2. Decomposition of carbohydrates contained in the sulfuric acid solution by the addition of hydrogen peroxide. The oxidized products may thereafter be removed by a multitude of additional steps or ways. [0089] The process of the present invention may further comprise additional steps as follows: Step 1. Separation of concentrated sulfuric acid from the hydrolyzed NCC suspension; Step 2. Decomposition of carbohydrates contained in the sulfuric acid solution by the addition of hydrogen peroxide; Step 3. Decomposition of the remaining oxidizing agents by different methods such as UV, activated carbon etc.; and Step 4. Optionally, adsorption of the remaining organic traces in the solution using an adsorbent such as activated carbon. [0094] In a process conducted according to the invention, implementing steps 1, 2 and optionally steps 3 and 4, and in order to maximize recovery of the sulfuric acid, a controlled hydrolysis of cellulose fibers was further carried out. [0095] The conditions for the acid hydrolysis used to extract the crystalline particles from a variety of cellulose sources was very narrow (e.g., acid concentration, reaction time, temperature, acid:solid ratio). It is commonly known that during at the end of the hydrolysis, during NCC production, the mixture is typically diluted with water to quench the reaction, and only then the mixture undergoes a series of separation and washing (centrifugation or filtration). The more the acid is diluted, the less cost effective its recovery. Thus, the present invention renders such dilution steps unnecessary, and thus cost-effective. Example 3: Process of Recovering Acid from Acid-Rich Formulations from NCC Production Processes Step 1: Separation of Concentrated Acid [0096] Following separation of concentrated sulfuric acid from the hydrolyzed NCC suspension, the high majority of the reaction mixture weight was obtained in the supernatant in the first separation. This “used solution” contained nearly all of the acid originally used in the reaction for making the NCC, along with soluble carbohydrates. [0097] The NCC was precipitated with some of the acid originally put in. Step 2: Decomposition of Carbohydrates in Sulfuric Acid Solution by Hydrogen Peroxide [0098] The “used solution” contained a variety of carbohydrates. The composition of the “used solution” depended on the cellulosic raw material and on the hydrolysis conditions. FIG. 1A shows the carbohydrates produced from the hydrolysis of cellulose. For a solution that also contained other saccharides such as xylose, mannose and other hemicellulose derivatives, similar products were depicted. FIG. 1B shows the general decomposition process of the carbohydrates. [0099] The addition of hydrogen peroxide to sulfuric acid results in the formation of Caro's Acid or Piranha solution. A suggested mechanism for the oxidation of the carbohydrates by Caro's acid is provided in FIG. 1C which demonstrates how the organic matter is converted to carbon dioxide. [0100] 7.54 kg of 30% H 2 O 2 (5% of H 2 O 2 weight per weight final solution) were loaded at R.T to a “used solution” of 38 kg ˜60% sulfuric acid solution containing 2.6% carbohydrates (weight per solution weight). The oxidation reaction of the sulfuric acid solution was carried out five days after separation of the hydrolysis mixture (step 1). The reaction mixture was then refluxed)(110°-130° and monitored by spectrophotometer. After 90 minutes the absorption in the region 400 nm-1100 nm reached a minimum ( FIG. 2 ), indicating that the majority of the organic material was oxidized. Thereafter, the reaction was cooled down. The color reduction could be seen with time. After 90 minutes, the solution was completely clear. [0101] As FIGS. 3A-B show, for a given carbohydrate concentration, the optimal oxidation time was 90 minutes up to 6 days from the day of hydrolysis and first separation (i.e., step 1). Prolonged periods required longer oxidation times. However, complete oxidation and full recovery of acid was always possible. The optimal minimum percentage of hydrogen peroxide required for oxidizing the organic matter, depended on the carbohydrate concentration in the sulfuric acid solution. FIG. 4 shows that for a 2.6% concentration, 5% H 2 O 2 was optimal for some solutions since it enabled the same performance of 7.5% with less dilution of the acid. Step 3 (and Step 4): Adsorption of the Remaining Organic Traces and Oxidizing Agents in the Solution Using Activated Carbon. [0102] This optional step(s) in the recovery process has two objectives: [0103] A. Removal of organic traces that remained after step 2; [0104] B. Removal of oxidizer. [0105] 0.76 kg of activated carbon (2% of Activated carbon weight per weight of initial 60% acid) were loaded at R.T to a “cleared solution” of 44 kg ˜50% sulfuric acid solution containing traces of carbohydrates and ˜5% H 2 O 2 . The solution was mixed and monitored by spectrophotometer and TOC levels measured by titration with KMnO 4 . After 8 h the absorption in the region 400 nm-1100 nm and the titer amount reached minimum ( FIG. 5 ) and the reaction was cooled down and filtered. The “cleaned solution” was thereafter used in further acid-based reactions.

Provided is an unique, efficient and cost-effective process for the recovery of acid from acid-rich solutions. The process of the subject matter utilizes a strong oxidizer, such as Caro's acid, to disintegrate or render insoluble organic or inorganic materials such as carbohydrates and complexes thereof contained in acid-rich solutions, to make efficient and simple the separation and recovery of the acid solution. The acid recovered thus obtained is free of organic matter, and containing nearly all of the acid originally contained in the acid-rich solution.

FIELD OF THE INVENTION [0001] The field of this invention relates to techniques and equipment to gravel-pack and treat closely spaced zones and more particularly in applications where some degree of isolation is desired between the zones for accommodating different treatment plans. BACKGROUND OF THE INVENTION [0002] In producing hydrocarbons or the like from loose or unconsolidated and/or fractured formations, it is not uncommon to produce large volumes of particulate material along with the formation fluids. As is well known in the art, these particulates routinely cause a variety of problems and must be controlled in order for production to be economical. A popular technique used for controlling the production of particulates (e.g., sand) from a well is one which is commonly known as “gravel-packing.” [0003] In a typical gravel-packed completion, a screen is lowered into the wellbore on a work string and is positioned adjacent to the subterranean formation to be completed, e.g., a production formation. Particulate material, collectively referred to as “gravel,” and a carrier fluid is then pumped as a slurry down the work string where it exits through a “cross-over” into the well annulus formed between the screen and the well casing or open hole, as the case may be. The carrier liquid in the slurry normally flows into the formation through casing perforations, which, in turn, is sized to prevent flow of gravel therethrough. This results in the gravel being deposited or “screened out” in the well annulus where it collects to form a gravel pack around the screen. The gravel, in turn, is sized so that it forms a permeable mass, which allows the flow of the produced fluids therethrough and into the screen while blocking the flow of the particulates produced with the production fluids. [0004] One major problem that occurs in gravel-packing single zones, particularly where they are long or inclined, arises from the difficulty in distributing the gravel over the entire completion interval, i.e., completely packing the entire length of the well annulus around the screen. This poor distribution of gravel (i.e., incomplete packing of the interval) is often caused by the carrier fluid in the gravel slurry being lost into the more permeable portions of the formation, which, in turn, causes the gravel to form “sand bridges” in the annulus before all the gravel has been placed. Such bridges block further flow of slurry through the annulus, which prevents the placement of sufficient gravel (a) below the bridge in top-to-bottom packing operations or (b) above the bridge in bottom-to-top packing operations. [0005] To address this specific problem, “alternate path” well strings have been developed which provide for distribution of gravel throughout the entire completion interval, even if sand bridges form before all the gravel has been placed. Some examples of such screens include U.S. Pat. Nos.: 4,945,991; 5,082,052; 5,113,935; 5,417,284; 5,419,394; 5,476,143; 5,341,880; and 5,515,915. In these well screens, the alternate paths (e.g., perforated shunts or bypass conduits) extend along the length of the screen and are in fluid communication with the gravel slurry as the slurry enters the well annulus around the screen. If a sand bridge forms in the annulus, the slurry is still free to flow through the conduits and out into the annulus through the perforations in the conduits to complete the filling of the annulus above and/or below the sand bridge. [0006] One of the problems with the alternate path design is the relatively small size of the passages through them. These tubes are also subject to being crimped or otherwise damaged during the installation of the screen. Thus, several designs in the past have placed these tubes inside the outer surface of the screen. This type of design substantially increases the cost of the screen over commercially available screens. Yet other designs have recognized that it is more economical to place such tubes on the outsides of the screen and have attempted to put yet another shroud over the alternate paths which are on the outside of the screen to prevent them from being damaged during insertion or removal. Such a design is revealed in U.K application No. GB 2317 630 A. [0007] While such designs can be of some benefit in a bridging situation, they present difficulties in attempting to treat and gravel-pack zones which are fairly close together. Many times zones are so close together that traditional isolation devices between the zones cannot be practically employed because the spacing is too short. For example, situations occur where an upper and lower zone are spaced only 5-20 feet from each other, thus precluding a complete completion assembly in between screens for each of the zones. When these closely spaced zones are encountered, it is desirable to be able to gravel-pack and treat the formations at the same time so as to save rig time by eliminating numerous trips into the well. This method was explained in U.S. Pat. No. 6,230,803. At times these types of completions will also require some degree of isolation between them, while at the same time producing one or the other of the formations. In U.S. Pat. No. 6,230,803 a method was disclosed to facilitate fluid treatments such as fracture stimulation, as well as gravel packing, simultaneously, in two or more adjacent producing zones, while providing limited hydraulic isolation between two or more adjacent zones. That method minimized rig time for the completion by reducing the number of trips required to install the gravel screen assemblies and to treat the formation. The limitation of that method was that the two zones had to be treated simultaneously. This caused problems if the nature of the adjacent formations necessitated a different treatment program. The isolation of the zones after completion was also less than ideal. Accordingly, the present method seeks to allow the treatment of adjacent zones in a single trip one at a time so that different regimens can be used. It provides, in the preferred embodiment, a check valve for retention of fluids in the string against loss into the formation. It provides an option of isolating a zone while treating the other. The method of the present invention can also be used in a single producing zone to minimize bridging problems during gravel distribution by splitting the zone into segments and gravel packing each segment individually. These objectives and how they are accomplished will become clearer to those skilled in the art from a review of the detailed description of the preferred embodiment and the claims, which appear below. SUMMARY OF THE INVENTION [0008] A method is disclosed that allows for sequential treatment of two zones in a single trip while isolating the zones. A fluid loss valve prevents the column of fluid in the tubing from flowing into the lower formation until activated. Zone isolation is accomplished by manipulation of a port on a wash pipe attached to the crossover assembly. BRIEF DESCRIPTION OF THE DRAWINGS [0009] [0009]FIG. 1 is a section view of the equipment in place and the upper zone being treated while the lower zone is isolated; [0010] [0010]FIG. 2 is the view of FIG. 1 with the lower zone being treated; [0011] [0011]FIG. 3 shows both zones treated; [0012] [0012]FIG. 4 is an enlargement of the fluid loss prevention valve in the assembly; [0013] [0013]FIG. 5 is a detailed view of the wash pipe in position to allow treatment of the upper zone; and [0014] [0014]FIG. 6 is the view of FIG. 5 showing the wash pipe positioned for squeezing the lower zone. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0015] [0015]FIG. 1 shows a wellbore 10 and zones 12 and 14 to be treated. The preferred embodiment illustrates the method for two zones but those skilled in the art will appreciate that additional zones can be treated in a single trip with duplication of the equipment shown for doing two zones in one trip, as will be explained below. A tubular string 16 is used to run in a known crossover tool 18 , which is movable with respect to packer 20 after it is set. In FIG. 1, the packer 20 is shown in the set position and the crossover is set up to circulate to deposit gravel outside of screen 22 and adjacent the perforations 24 of zone 12 . Arrows 26 show the gravel and fluid mixture coming from the surface through the string 16 and going through the packer 20 . The gravel and fluid stream indicated by arrows 26 goes through crossover 18 and through ports 28 in the crossover tool 18 . Sliding sleeve valve 30 is left in the open position during run in so that the ports 32 are open for the gravel and fluid stream 26 to pass into annulus 34 . The stream passes through the screen 22 leaving the gravel in annulus 34 and the fluid to pass through the screen 22 into annular space 36 around the wash pipe 38 . Wash pipe 38 has several openings 40 which are shown in FIG. 1 as above seal 42 . Seal 42 keeps clean fluid from going down around the outside of the wash pipe 38 . Any fluid 26 that gets into the wash pipe 38 through openings 40 is stopped from exiting the lower end of the wash pipe 38 by a ball 44 pushed by the flow against a seat 46 . Return flow 26 passes through passage 48 lifting ball 50 off seat 52 . The return flow passes through passage 54 in crossover 18 and up to the surface via annulus 56 above the set packer 20 . A flapper 58 is held open by wash pipe 38 . When the wash pipe 38 is removed, the flapper 58 closes to prevent the column of fluid from the surface inside the string 16 from flowing into the formation and potentially causing damage. [0016] Packer 60 is supported by screen 22 and it in turn supports screen 62 at perforations 64 . Packer 60 is multi-bore. The first bore 66 communicates to inside screen 62 . The second bore 68 communicates with a standpipe 70 that is capped at cap 72 at its upper end. As shown in FIG. 1 gravel is deposited around the outside of standpipe 70 and standpipe 70 extends above perforations 24 . After the zone 12 is fully treated, including gravel packing and other operations that may be needed like acidizing, pressure on cap 72 can be raised to break it to provide access to zone 14 through bore 68 . Cap 72 can be a rupture disc or any other type of barrier that can be removed in any number of ways among them pressure, chemical reaction or some applied force. As shown in FIG. 2, the gravel and fluid stream 74 passes through standpipe 70 and bore 68 in packer 60 to lodge in annulus 76 adjacent perforations 64 . Returns pass through screen 62 and into wash pipe 38 to displace ball 44 off of seat 46 . Ports 40 in wash pipe 38 are now below seal 42 . This position of ports 40 effectively isolates zone 12 from returns. The returns 74 pass through passage 48 and return to the surface through annulus 56 in the manner previously described for zone 12 . Thus, although the gravel packing is done from top to bottom, each zone is independent and bridging in zone 12 has no effect on the deposition of gravel in zone 14 . [0017] [0017]FIG. 3 shows the crossover 18 and wash pipe 38 removed. The flapper 58 has slammed shut to prevent fluid loss to either zone 12 or 14 . Sliding sleeve 30 has been pushed closed by the removal of the wash pipe 38 . [0018] [0018]FIG. 5 shows the isolation of the lower zone 14 when treating the upper zone 12 by virtue of having openings 40 above seal 42 . Seal 42 seals around the outside of wash pipe 38 and ball 44 on seat 46 prevents returns from treating the zone 12 from reaching zone 14 . Additionally, bore 68 is closed at this time by cap 72 on standpipe 70 . FIG. 6 shows how zone 12 is isolated when treating zone 14 . Here the returns lift ball 44 off of seat 46 . Ports 40 are now below seal 42 forcing all returns to bypass zone 12 and rise to the crossover 18 . It should be noted that the cross-over 18 can be configured to close access to surface annulus 56 , in which case the gravel packing or acid treating or any other procedure will be without returns or by bull heading into the formation. [0019] [0019]FIG. 4 simply illustrates the flapper 58 held open by the wash pipe 38 . It slams shut as soon as the wash pipe 38 is removed. [0020] Those skilled in the art will appreciate that the zones can be closely spaced and can be treated separately in a single trip. Two or more zones can be sequentially treated in a single trip. The treatment can be by circulation with returns to the surface or elsewhere or without returns with the fluids driven into the formation being treated. When treating two zones, one is isolated when the other is treated. Finally, a fluid loss prevention feature, which is a flapper 58 in the preferred embodiment retains the liquid column in the tubular 16 and prevents its passage into the formation. The fluid prevention feature can be a flapper or ball device or any other valve that hold up the liquid column when the wash pipe 38 is pulled out. [0021] The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:

A method is disclosed that allows for sequential treatment of two zones in a single trip while isolating the zones. A fluid loss valve prevents the column of fluid in the tubing from flowing into the lower formation until activated. Zone isolation is accomplished by manipulation of a port on a wash pipe attached to the crossover assembly.

RELATED APPLICATIONS [0001] This application claims the benefit under 35 USC §119(e) to U.S. Provisional Application No. 62/006,556, filed on Jun. 2, 2014, the contents of which are hereby incorporated by reference in their entirety. FIELD OF THE INVENTION [0002] This invention relates to a system and method for modeling physical phenomena such as internal conditions and/or boundary conditions, as for example to model or determine fluid flows in, around and/or across objects or structures and, in particular, a system and method which operates to provide a numerical solution of partial differential equations (PDEs). BACKGROUND OF THE INVENTION [0003] Computer methods and algorithms which use partial differential equations to analyze and solve complex systems involving various forms of fluid dynamics having input boundary conditions are known. Computer modeling may allow a user to simulate the flow of air and other gases over an object or model the flow of fluid through a pipe. Computational fluid dynamics (CFD) is often used with high-speed computers to simulate the interaction of one or more fluids over a surface of an object defined by certain boundary conditions. Typical methods involve large systems of equations and complex computer modeling and include traditional finite difference methodology, cell-centered finite volume methodology and vertex-centered finite volume methodology, as for example are described in the inventors commonly owned U.S. patent application Ser. No. 14/207,027, filed Mar. 12, 2014, the disclosure of which is hereby incorporated in its entirety. [0004] Current computer modeling schemes have proven limited in the form of objects they can model and require different models and algorithms for different continuum mechanics applications, such as between compressible and non-compressible fluids and deformable solids. SUMMARY OF THE INVENTION [0005] The present invention provides for method and system for determining and/or modeling physical phenomena with internal conditions and/or boundary conditions, as for example, to determine or compute heat conduction and/or heat convection within fluid dynamics of compressible and/or non-compressible fluids around objects. In one particular embodiment, it is an object of this invention to provide a method and system which for example, includes a processor, a display or monitor and programme instructions operable to compute fluid flow over or through objects. In one possible embodiment, the system may be used to compute fluid flow over aircraft components, such as airflow over aircraft wings, fuselage, landing gear, pylons and the like. [0006] Preferably, the present system is operable to provide and display as a visual output a numerical or calculated solution to a physical phenomenon such as heat conduction or fluid flow in either bounded domains such as piping systems bounded by walls, human or animal arteries and the like; as well as unbounded solution domains, where for example, free air or liquid flows past an object. [0007] In another embodiment, the invention provides a method and system for computing and outputting as data, graphics, or other display and/or monitor, fluid dynamics of non-compressible liquids within a pipe or transport mechanisms, as for example, through static and/or movable valves, or other components which are described with other boundary conditions. [0008] The present invention further may provide a system and method for modeling physical phenomena such as internal fluid flows with boundary conditions of both bounded domains and unbounded domains. More preferably, the system provides for a numerical solution of partial differential equations (PDEs) which comprise a pre-processing component, a processing component and a post-processing component. [0009] The system preferably includes a processor and memory or other suitable input means for receiving a Cartesian mesh model of a bounded or unbounded domain or object, defined as a plurality of active, inactive and boundary nodes encompassing the domain and/or object. The processor may operate in conjunction with programme instructions for implementing the steps of discretizing a partial differential equation based on a stencil associated with each node in the mesh by (i) selecting an active node, (ii) identifying the stencil associated with the selected node, (iii) mapping the stencil from the physical domain to a generic uniform computational stencil, (iv) applying finite difference formulas on the computational stencil to approximate the partial differential equation by a finite difference equation, (v) solving the finite difference equation to obtain an approximate value for the solution at the selected node, (vi) repeating the above steps for all active nodes in the mesh, (vii) checking the iteration process for convergence, (viii) repeating the above steps (i)-(vii) if the solution has not converged, or (ix) terminating the iteration process if the solution has converged, and (x) printing all calculated data to an output file. [0010] More preferably, where the system operates to provide PDE models of a physical phenomenon occurring in a bounded domain, such as an internal fluid flow of liquid or air flow within a target object, such as piping or other passage bounded by walls, air flow in an automobile passenger compartment, flow in a pump, blood flow through arteries, or heat conduction in a solid object. A geometric, and preferably rectangular box (rectangle in 2-dimensional modeling; cube in 3-dimensional modeling) and preferably a Cartesian mesh is object-fitted wherein the mesh is superimposed or placed around the object domain, touching the domain at its extreme endpoints. [0011] Where the system operates to provide PDE models of phenomenon occurring in unbounded solution domains, such as external fluid flow or air flow over a target object, such as an aircraft or aircraft component structures such as wings, fuselage, pylon, landing gear, etc., air flow through wind turbines, and/or river flow around bridge piers, the system operates to generate both an object-fitted internal mesh or box superimposed around the object(s), as well as a larger surrounding outer reference mesh or reference box having its sides spaced away from object-fitted mesh and the object(s) inside. [0012] In yet a further alternate embodiment, the system and method provide for analysis and modeling of combinations of dynamic internal and external flows, such as air flow around moving road vehicles, and air flow around an aircraft during take-off or landing, and wherein the system processor is operable to generate superimposed boxes which provide mesh-structures for the solution domain using Cartesian cut-stencil based methods of finite difference solutions of PDEs. [0013] In one preferred method, a two-dimensional Cartesian mesh for a 2D bounded object or solution domain is generated by the system processor. The computer program stored in computer memory is operated to determine the active and inactive nodes in the mesh, as well as coordinates of the boundary nodes, namely the points where the mesh lines intersect with the boundary of the solution domain. Most preferably, the computer program also includes programme instructions to identify the neighbouring nodes for each node, and to record the neighbouring node coordinates or location, such that each node P has associated with it a “stencil” centered at P, with a node identifier (i.e. such as active, inactive, boundary) and in the case where a two-dimensional mesh is generated, a set of 4 (in 2D) neighbour nodes to the west (w), south (s), east (e) and north (n). [0014] In a three-dimensional mesh, a set of 6 (in 3D) neighbour nodes are generated, including further nodes front (f) and back (b). [0015] If all nodes on the stencil are indicated as active nodes, then the stencil does not touch the boundary of the domain and the stencil is described as “regular” or “uncut”. If the node P is adjacent to the boundary, then at least one of its neighbour nodes is identified or recognized as being a boundary node. Preferably, the program includes instructions to determine if the boundary node lies at the intersection of a mesh horizontal grid line and a vertical grid line and if so the node is identified as a “regular” boundary node, or otherwise the node is indicated as an “irregular” boundary node. [0016] Most preferably, for each boundary node, whether regular or irregular, the computer also includes stored program instructions operational to calculate and record an outward unit normal vector to the boundary. [0017] Accordingly, in one aspect, the present invention resides in a computer-implemented method for approximating partial differential equations for determining fluid flow of compressible and non-compressible liquids. The method comprising of a plurality of nodes; for each node P in the plurality of nodes: (i) locating all neighbouring nodes in the Cartesian mesh that are attached directly to the node P (4 neighbouring nodes in 2D, 6 neighbouring nodes in 3D); (ii) grouping all of the neighbouring nodes to form one stencil having a central vertex at node P; (iii) mapping the said stencil from the physical domain to a generic uniform computational stencil; (iv) approximating the transformed partial differential equation(s) at the vertex of the stencil centered at node P using difference formulas to obtain the finite difference equation(s). [0018] In another aspect, the present invention resides in a system for determining a physical phenomenon in relation to an object, and wherein the physical phenomenon is selected as being modelable by partial differential equations; input means for receiving a model of the object, the model defining the object as being contained within the Cartesian mesh comprising a plurality of active nodes, inactive nodes and boundary nodes; a processor coupled to a memory, the processor configured for implementing the steps of A. initializing an expected solution at each said active node; B. obtaining an approximate solution of a partial differential equation based on a stencil for each said active node by: i) selecting a first said active node, ii) identifying and mapping the stencil associated with the selected node to a generic uniform computational stencil, the computational stencil being characterized by an equal node spacing in each direction, iii) applying a finite difference formula at the selected node on the computational stencil to approximate the partial differential equation at the selected node by a finite difference equation, iv) solving the finite difference equation to obtain an approximate value of a calculated solution at the selected active node, and v) selecting a next active node, and repeating steps B (ii) to (iv) for each remaining said active mesh nodes. C. comparing the calculated solution to the expected solution for each said active node to determine convergence, and where convergence is determined, outputting the solution. [0027] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, wherein the processor further is configured whereby where convergence is not determined, select the calculated solution as a new expected solution for each said active node, and repeating steps B and C until convergence is determined. [0028] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the physical phenomenon comprises a fluid flow within the object; said active nodes comprise coordinates of intersecting mesh lines within the object; said inactive nodes comprise coordinates of intersecting mesh lines outside the object; and said boundary nodes comprise coordinates of intersection of mesh lines and object boundary lines. [0029] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the physical phenomenon comprises a heat transfer within the object; said active nodes comprise coordinates of intersecting mesh lines within the object; said inactive nodes comprise coordinates of intersecting mesh lines outside the object; and said boundary nodes comprise coordinates of intersection of mesh lines and object boundary lines. [0030] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein said physical phenomenon comprises a fluid flow about the object; said active nodes comprise coordinates of intersecting mesh lines outside the object; said inactive nodes comprise coordinates of intersecting mesh lines within the object; and said boundary nodes comprise coordinates of intersection of mesh lines and object boundary lines. [0031] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the input means is for receiving a reference boundary surrounding and spaced a distance from the object, wherein the active nodes comprise intersecting mesh line nodes outside the object and within the reference boundary. [0032] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein said Cartesian mesh comprises a uniform object-fitted Cartesian grid. [0033] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the Cartesian mesh is selected as a non-uniformly spaced object-fitted grid, wherein the mesh spacing is selectively biased by proximity to object boundary lines. [0034] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the step of solving comprises, wherein if each neighboring node is an active node, assigning the solution at each neighboring node as the expected solution. [0035] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the step of solving comprises, wherein if each neighboring node is an active node, assigning the solution at each neighboring node as the expected solution. [0036] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the step of solving further comprises, if a said neighboring node is a boundary node, assigning the solution at the boundary node as a known boundary value. [0037] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the step of approximating the partial differential equation comprises approximating the partial differential equation at the common vertex of the stencil centered at the selected node using finite difference formulas. [0038] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein physical phenomenon is one dimensional, and the step of mapping the stencil comprises: [0039] applying mapping of the selected active node P at coordinate x P and next adjacent neighbour nodes at coordinates x W , x E in accordance with formula (1). [0000] x=a 2 ξ 2 +a 1 ξ+a 0   (1) where a 2 =(x W −2x P +x E )/2=x″/2 a 1 =(x E −x W )/2=x′ a 0 =x P [0044] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the physical phenomenon is two dimensional, and the step of mapping the stencil comprises: [0045] applying mapping of the selected active node P at coordinates (x P , y P ) and next adjacent neighbor nodes at coordinates (x W , y W ), (x E , y E ), (x S , y S ), (x N , y N ) in accordance with formula (2): [0000] x=a 2 ξ 2 +a 1 ξ+a 0 [0000] y=b 2 η 2 +b 1 η+b 0   (2) where a 2 =(x W −2x P +x E )/2=x″/2 b 2 =(y S −2y P +y N )/2=y″/2 a 1 =(x E −x W )/2=x′ b 1 =(y N −y S )2=y′ a 0 =x P b 0 =y P [0050] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the physical phenomenon is three dimensional, and the step of mapping the stencil comprises: [0000] applying mapping of the selected node P at coordinates (x P , y P , z P ) and next adjacent neighbor nodes at coordinates (x W , y W , z W ), (x E , y E , z E ), (x S , y S , z S ), (x N , y N , z N ), (x F , y F , z F ), (x B , y B , z B ) in accordance with formula (3): [0000] x=a 2 ξ 2 =a 1 ξ+a 0 [0000] y=b 2 η 2 =b 1 η+b 0 [0000] z=c 2 ζ 2 +c 1 ζ+c 0   (3) where a 2 =(x W −2x P +x E )/2=x″/2 b 2 =(y S −2y P +y N )/2=y″/2 c 2 =(z F −2z P +z B )/2=z″/2 a 1 =(x E −x W )/2=x′ b 1 =(y N −y S )/2=y′ c 1 =(z B −z F )/2=z′ a 0 =x P b 0 =y P c 0 =z P [0057] In another aspect, the invention resides in a system in accordance with any of the foregoing aspects, further wherein the output solution is provided independently of mesh cell flux, mesh cell area and/or mesh cell boundary calculation. [0058] Further and other features of the invention will be apparent to those skilled in the art from the following detailed description of the embodiments thereof. BRIEF DESCRIPTION OF THE DRAWINGS [0059] Reference may now be had to the following detailed description taken together with the accompanying drawings, in which: [0060] FIG. 1 shows schematically a system for modeling flow dynamics or other physical phenomena using a computer system in accordance with a preferred embodiment of the present invention; [0061] FIG. 2 illustrates graphically, the identification of solution domains using the computer of FIG. 1 in modeling both the internal flow in bounded domains and the external flow in unbounded domains in accordance with a preferred method; [0062] FIG. 3 illustrates graphically the computer generation of a Cartesian mesh in a two-dimension bounded solution domain, and the identification of inactive, active and boundary nodes, generated for predicting internal flow in accordance with a preferred embodiment; [0063] FIG. 4 illustrates schematically the mapping of a general two-dimensional stencil associated with Cartesian mesh nodes shown in FIG. 3 , to a generic uniform computational stencil; [0064] FIGS. 5 and 6 illustrate the cut-stencil mapping for a one-dimensional non-uniform cut stencil with arms of arbitrary length, and for an interval containing many non-uniform one-dimensional stencils; [0065] FIG. 7 illustrates schematically the application of an iterative algorithm for time-dependent ordinary differential equation resulting from the discretization of the partial differential equation(s); [0066] FIGS. 8 to 10 illustrate graphically sample data outputs using the cut-stencil method of the current invention; [0067] FIG. 11 illustrates the formulation of a fourth-order solution scheme using the cut-stencil approach of the present invention; [0068] FIG. 12 shows graphically data output solutions obtained using second-order and fourth-order formulation schemes using the current invention, in comparison to an exact solution; [0069] FIG. 13 illustrates graphically determined local truncation errors using second-order and fourth-order formulation schemes of the current invention; [0070] FIGS. 14 and 15 illustrates graphically the results of an adaptive mesh procedure developed based on local truncation error calculations in accordance with the present invention; and [0071] FIG. 16 gives a 2D illustration of the essential difference between the use of cut stencils, which is the subject of this invention, and cut cells which are used in Finite Volume and Finite Element methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0072] FIG. 1 illustrates schematically a system 10 for determining or the predicted modelling of compressible and non-compressible fluids in accordance with a preferred embodiment of the invention. The system 10 includes a computer which includes main memory 25 , read only memory 26 , and storage memory 27 . A bus 12 provides electronic communication between the main memory 25 ROM, 26 and storage memory 27 , and the computer processor 16 and I/O board 14 . [0073] The I/O board 14 communicates via a suitable data connector 18 with the user operable keyboard 23 , video display 24 and cursor control 22 . In addition secondary communication output 21 may also be provided. The processor 16 stores computer program instructions which in operation of the system 10 are adapted to provide and output to a user a graphic and/or data output on the display 24 , which simulates fluid flow dynamics through and/or around physical boundary defining target object 30 (see for example FIG. 2 ). [0074] As will be described, in use of the system 10 , the user enters into the computer memory 25 object modeling parameters such as computer aided design (CAD) model of the target object 30 , boundary conditions and/or fluid properties or conditions by way of the key board 23 , PDA or other suitable input 18 . Optionally the modeling parameters may be displayed on the video display 24 in the manner shown in FIG. 2 . [0075] Preferred objects 30 to be modeled with the system 10 may include without limitation both two-dimensional or three-dimensional bounded structures such as pipes, arteries, and the like; as well as two-dimensional or three-dimensional unbounded domains such as external structures, river beds and the like. The system 10 may thus be used to model external and internal fluid or air flow around buildings, road vehicles or aircraft components, as well as flow along pipes. In an alternate embodiment, the present system 10 may also be used to predict and/or model heat flow or heat conduction through objects and/or liquids. [0076] The system 10 of the present invention provides for the numerical solution of partial differential equations (PDEs) which comprises pre-processing, processing and post-processing components. [0077] FIG. 2 shows a sample finite rectangular domain 32 used in the PDE modelling of a two-dimensional bounded domain system for the object 30 . In particular, the computer processor 16 operates to generate and superimpose a rectangular box 32 around the selected solution domain or domain of interest for the object 30 . The generated box 32 has a dimension selected to contact or touch the selected domain of interest on multiple sides, and preferably at each of its top, bottom and extreme endpoints. [0078] FIG. 3 shows the construction of a Cartesian mesh 50 for a 2D bounded solution domain. The computer processor 16 includes computer program having stored instructions operational to determine the active and inactive nodes 52 , 54 in the mesh 50 , as well as the coordinates of the boundary nodes 56 , namely, points where the mesh lines intersect with the boundary of the domain of interest. Most preferably, the computer program also identifies the neighbouring nodes for each node and records their coordinates (location). In this way, each node P has associated with it a “stencil” centered at P, with a node ID or identifier (active, inactive, boundary) and a set of 4 (in 2D) neighbour nodes to the west (W), south (S), east (E) and north (N), as for example are shown in FIG. 4 . [0079] If all nodes on the stencil are active nodes, then the stencil does not touch the boundary of the domain and the stencil is described as “regular” or “uncut.” If the node P is adjacent to the boundary, then at least one of its neighbours will be a boundary node. If the boundary node lies at the intersection of a horizontal grid line and a vertical grid line, the node is called a “regular” boundary node, otherwise it is an “irregular” boundary node. [0080] For all boundary nodes, whether regular or irregular, the computer program also calculates and records the outward unit normal vector to the boundary. [0081] In the above described construction of a Cartesian mesh, the mesh intersection with a domain boundary and identification of nodes may further form a basis for the Cartesian “cut-cell” and the “embedded mesh” technologies used with Finite Volume and Finite Element codes. However, unlike conventional methods where the discretization of the PDE is based on the geometry and connectivity of the cells in the mesh, Finite Difference discretization is used in the current invention based on the stencil associated with each node in the mesh. [0082] The inventor has further appreciated that cut-cell and embedded mesh formulations may require the computation and storage of a large amount of additional information, such as the unit normal vectors along all edges (2D) or faces (3D) of all cells (interior and cut), cell connectivity (in 2D each cell has 8 connected cells, 4 of them share an edge with the central cell, 4 share a point with the central cell), area (2D) or volume (3D) of each cell, length of each cell edge (2D) or surface area of each face (3D). In contrast, however, this additional information is not needed for the present cut-stencil method. [0083] FIGS. 4 to 6 illustrate graphically the essence of the cut-stencil method in accordance with a preferred embodiment. The general idea of mapping any stencil (stencil arms may be equal or of different lengths) to a generic uniform unit stencil (arms all have unit length) is shown graphically in FIG. 4 . The unique mapping that accomplishes this goal is given in FIG. 5 for the ID case, and is representative of the mappings used in both 2D and 3D application. FIG. 6 demonstrates a feature of the stencil mapping, and in particular, that each individual triplet of adjacent nodes has its own unique quadratic mapping to the uniform computational stencil. Focusing on the stencil as an entity and mapping it to a uniform computational stencil advantageously allows the treatment of cut stencils in the same way as regular stencils, allowing for a Finite Difference discretization of the PDE on any domain, irrespective of its complexity. [0084] It is noted that coordinate mappings are also sometimes used in numerical solutions of PDEs. Such mappings are, however, defined by mathematical functions that maps all logically connected nodes in the physical domain into a set of evenly distributed nodes in a computational domain. As such, the use of a single mapping function limits the ability to deal with highly complex domains. [0085] The general one-dimensional convection-diffusion equation often used by researchers to test their numerical formulations and solution algorithms is as follows: [0000] ∂ ϕ ∂ t  | P  - Γ  [ 1 x P ′ 2  ∂ 2  ϕ ∂ ξ 2  | P  - x P ″ x P ′ 3  ∂ ϕ ∂ ξ  | P ] + u x P ′  ∂ ϕ ∂ ξ  | P = S p [0086] The equation shown above is the 1D version, but extensions to 2D and 3D are straightforward and understood. Transformation of the convection-diffusion equation to the computational stencil centered at node P is illustrated as follows: [0087] Convection-Diffusion equation at node P transforms to [0000] ∂ ϕ ∂ t - Γ  ∂ 2  ϕ ∂ x 2 + u  ∂ ϕ ∂ x = S [0088] The time-dependent ordinary differential equation resulting from space discretization of the above equation is shown in FIG. 7 , and an iterative algorithm is given for the steady (time-independent) case. [0089] FIGS. 8 to 10 illustrate examples of calculations using the cut-stencil methodology in accordance with the present invention, and demonstrate graphically the strength and capabilities of the current system. [0090] The cut-stencil approach is a convenient framework from which to develop high-order solution schemes. Formulation of the 4 th -order scheme is illustrated graphically in FIG. 11 . A comparison between the 4 th -order, 2 nd -order and exact solutions are shown in FIG. 12 . [0091] Two important features of the cut-stencil method should be noted: 1) from a formulation perspective, one can easily devise 8 th -order, 16 th -order and higher-order schemes. 2) Secondly, there is no loss of accuracy at nodes adjacent to the boundary since they are treated in the same way as interior nodes. This is a significant improvement over all existing methods which use a high-order scheme at interior nodes, but must use a lower-order scheme at the boundary, thereby degrading the overall accuracy of the solution. [0092] Formulae for the local truncation errors (LTE) are easily derived in a Finite Difference approach. For the Finite Volume and Finite Element approaches, researchers have developed error estimates, but these serve only as approximations to the true error. Using the Taylor series expansion at node P in the discretized equation gives the modified differential equation, which provides an expression of the leading terms in the local truncation error (LTE), e.g., for steady convection-diffusion. Local truncation errors for second and fourth order schemes may be estimated as follows: [0000] 2 nd  -  order   scheme L . T . E . = R 2   x P ′   2  ϕ P  ξ 2 - x P ″ 6   x P ′3   3  ϕ P  ξ 3 - R 6  x P ′   3  ϕ P  ξ 3 + 1 12  x P ′2   4  ϕ P  ξ 2 4 th  -  order   scheme L . T . E . = 1 1440  x P ′2   6  ϕ P  ξ 6 - R 768   x P ′   6  ϕ P   ξ 6 +  x P ″ 480   x P ′3   5  ϕ P   ξ 5 - 7  R 960  x P ′   5  ϕ P  ξ 5 - R 32  x P ′   4  ϕ P  ξ 4 + R 12  x P ′   3  ϕ P  ξ 3 [0093] FIG. 13 shows graphically the LTE by means of the aforementioned formula, and illustrates one use of the LTE, to compare the accuracy of schemes of different orders. The table shown in FIG. 13 suggests that a prescribed level of accuracy can be achieved with much fewer nodes in a 4 th -order scheme (i.e. 40 cells) compared to a 2 nd -order scheme (i.e. 400 cells), i.e. a ratio of 1 to 10. Some 2D tests have shown that the ratio may be even more dramatic, at 1 to 100. This is significant since a typical industrial simulation may require 20,000,000 nodes or more for a 2 nd -order scheme (some researchers are using more than 1 billion nodes). Such computations are very expensive, requiring large computing resources, 1000's of CPU hours and long run times. The higher-order schemes based on the cut-stencil approach have the potential to reduce these calculations, thereby reducing demands on computer resources and shortening run times. [0094] The cut-stencil method is ideally suited for mesh adapting. FIGS. 14 and 15 show graphically the results of an adaptive mesh procedure that has been developed based on the LTE. Existing adaptive mesh methods are generally based on error estimates or solution gradients, which are not as predictive of the mesh region requiring adapting as the LTE is. [0095] FIG. 16 shows graphically an application of the cut-stencil method in 2D. The domain shown in FIG. 16 cannot be solved by traditional finite difference, due to the cut stencils around the boundary. As illustrated with reference to FIG. 16 , the domain can be solved using Finite Volume or Finite Element, but the solution procedures are much more complicated than the cut-stencil method. [0096] The solution provided by the present invention shows promising results with reduced relative errors and processing requirements, as for example the solution of the problem shown in FIG. 16 , as reflected in the following Table 1: [0000] TABLE 1 Relative Error (N = 242) %(Rel. %(Rel. Boundary error) Avg. at error) Max. at Equation condition internal nodes internal nodes Diffusion Dirichlet 0.021% 0.040% (all) Diffusion Neumann 0.023% 0.041% (West & South) Diff.- Conv. Dirichlet 0.012% 0.031% (central) (all) Diff.- Conv. Neumann 0.013% 0.030% (central ) (West & South) Diff.- Conv. Dirichlet 0.345% 0.873% (central/upwind) (all) [0097] Although the detailed description describes and illustrates various preferred embodiments and methods, the invention is not strictly limited to the best mode of the invention which is described. Variations and modifications will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.

A system includes a processor with stored instructions for generating a Cartesian mesh model of a bounded or unbounded object domain. The model includes active, inactive and boundary nodes which encompass the domain. The processor effects of discretizing a partial differential equation based on a stencil associated with each active node in the mesh by (i) selecting an active node, (ii) identifying the stencil associated with the selected node, (iii) mapping the stencil from the physical domain to a generic uniform computational stencil, (iv) applying finite difference formulas on the computational stencil to approximate the partial differential equation by a finite difference equation, (v) solving the finite difference equation to obtain an approximate value for the solution, and thereafter (vi) checking the iteration process for convergence. If the solution has not converged, the system repeats the aforementioned steps, or terminates the iteration process if the solution has converged, and outputs to a user the calculated data file.

RELATED APPLICATIONS This application is a continuation of co-pending U.S. patent application Ser. No. 12/622,871, filed on Nov. 20, 2009, which is a continuation of co-pending U.S. patent application Ser. No. 10/813,229, filed Mar. 31, 2004, now U.S. Pat. No. 7,660,822, the disclosures of which are hereby incorporated by reference herein. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to information searching systems and, more particularly, to systems and methods for sorting and displaying searches of aggregated information in multiple dimensions. 2. Description of Related Art Existing information searching systems use search queries to search through aggregated data to retrieve specific information that corresponds to the received search queries. Such information searching systems may search information stored locally, or in distributed locations. The World Wide Web (“web”) is one example of information stored in distributed locations. The web contains a vast amount of information and locating a desired portion of that information, however, can be challenging. This problem is compounded because the amount of information on the web and the number of new users inexperienced at web searching are growing rapidly. Search engines attempt to return hyperlinks to web documents in which a user is interested. Generally, search engines base their determination of the user's interest on search terms (called a search query) entered by the user. The goal of the search engine is to provide links to high quality, relevant results to the user based on the search query. Typically, the search engine accomplishes this by matching the terms in the search query to a corpus of pre-stored web documents. Web documents that contain the user's search terms are “hits” and are returned to the user. The search engine oftentimes ranks the documents using a ranking function based on the documents' perceived relevance to the user's search terms. In addition to determining relevance, existing search paradigms may use other dominant characteristics to sort the results of a search. For example, in shopping or product search (e.g., Froogle), users typically like to sort by price. As another example, when searching news stories or USENET/groups, users typically prefer to sort by date or recency. As a further example, when searching images, users may prefer to sort by image quality or image size. As yet another example, in geographic search, users may prefer to sort by distance. With existing search paradigms, users must choose to sort either by relevance or by the alternative characteristic, and can at best toggle between these modes. This creates a frustrating experience for the user in which important sorting dimensions are ignored (e.g., the user retrieves a lot of very cheap products that aren't what they wanted, or the user gets a lot of very recent articles that are not really about the topic they wanted). Existing search paradigms employed in any type of information searching system, thus, make it very difficult for users to easily find reasonably relevant data while, at the same time, also optimizing at least one other desired characteristic. Accordingly, it would be desirable to implement a search paradigm in an information searching system that permits sorting and display of search results by multiple alternative characteristics. SUMMARY OF THE INVENTION Systems and methods, consistent with the principles of the invention, implement a search paradigm that permits users to search and sort data according to multiple characteristics. Such characteristics may include relevance or another alternative characteristic, such as, for example, price, date, recency, image quality, image size, or geographic distance. Consistent with the principles of the invention, results of a search that sorts by multiple characteristics may be displayed in a document that plots the results of the search in a multi-dimensional graph, with each dimension of the graph corresponding to one of the multiple characteristics. According to one aspect consistent with the principles of the invention, a method of displaying the results of a search is provided. The method includes receiving one or more search queries. The method further includes searching stored data based on the one or more search queries to generate results, where the results are orderable by at least one search characteristic. The method also includes providing a document that includes a multi-dimensional graph of the results of the search, where at least one dimension of the multi-dimensional graph corresponds to the at least one search characteristic. According to another aspect, a method of plotting results of a data search is provided. The method includes executing one or more search queries to search stored data. The method further includes receiving results of the executed one or more search queries, where the results are orderable by at least one search characteristic. The method also includes designating a visual representation for each of the results and plotting each of the visual representations on a multi-dimensional graphical display, where at least one dimension of the multi-dimensional graphical display corresponds to the at least one search characteristic. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, explain the invention. In the drawings, FIG. 1 is a diagram of an overview of an exemplary implementation of the invention; FIG. 2 is a diagram of an exemplary network in which systems and methods consistent with the principles of the invention may be implemented; FIG. 3 is an exemplary diagram of a client and/or server of FIGS. 1 & 2 in an implementation consistent with the principles of the invention; FIGS. 4A and 4B are flowcharts of exemplary processing for providing multi-dimensional display documents according to an implementation consistent with the principles of the invention; FIG. 5 is a diagram of an exemplary news search document according to an implementation consistent with the principles of the invention; FIG. 6 is a diagram of an exemplary product search document according to an implementation consistent with the principles of the invention; FIG. 7 is a diagram of an exemplary two-dimensional display document according to an implementation consistent with the principles of the invention; FIG. 8 is a diagram of an exemplary document with news links according to an implementation consistent with the principles of the invention; and FIG. 9 is a diagram of an exemplary news document according to an implementation consistent with the principles of the invention. DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. Systems and methods consistent with the principles of the invention implement a search paradigm that permits users to search and sort data according to multiple characteristics, such as, for example, relevance, price, date, recency, image quality, image size, or geographic distance. The results of the search may be plotted on a multi-dimensional graph, with each dimension of the graph corresponding to one of the multiple characteristics. A “document,” as the term is used herein is to be broadly interpreted to include any machine-readable and machine-storable work product. A document may include an e-mail, a web site, a file, a combination of files, one or more files with embedded links to other files, a news group posting, a blog, a web advertisement, etc. In the context of the Internet, a common document is a web page. Web pages often include textual information and may include embedded information (such as meta information, images, hyperlinks, etc.) and/or embedded instructions (such as Javascript, etc.). Exemplary System Overview FIG. 1 illustrates a system overview of one exemplary implementation of the invention. As shown in FIG. 1 , a server 120 may receive one or more data search queries 130 from a client 110 via, for example, a network (not shown). The one or more data search queries 130 may be explicitly provided by a user at the client 110 , or may, for example, be inferred from the user's past “web browsing” activity. The one or more search queries may be derived in any manner, such as, for example, user selection from a list of related search queries, user selection from a list of “canned” queries, etc. Server 120 may perform a search of aggregated data using the received one or more data search queries. The aggregated data may include data retrieved and aggregated from one or more data sources, such as, for example, news sources, image sources, product sources, or any other type of data source. Server 120 may sort the results of the search using multiple characteristics derived, at least in part, from the received one or more data search queries. For example, in one implementation, server 120 may sort the results of the search based on relevance and one other characteristic, such as, for example, price, data, recency, image quality, image size, or geographic distance. In other implementations, server 120 may sort the results of the search based on multiple characteristics, such as any combination of three or more of the above noted characteristics. Using the results of the search and sort, server 120 may then provide a multi-dimensional display document 140 to client 110 . Multi-dimensional display document 140 may plot the results of the search with each of the multiple characteristics, used to sort the results of the search, being represented as a dimension on the plot. For example, if document 140 includes a two-dimensional plot, then one dimension may be relevance, and another dimension may be price. Multi-dimensional display document 140 may include any number of dimensions (e.g., 2, 3, 4, etc.). Exemplary Network Configuration FIG. 2 is an exemplary diagram of a network 200 in which systems and methods consistent with the principles of the invention may be implemented. Network 200 may include multiple clients 110 connected to multiple servers 120 and 210 via a network 220 . Network 220 may include a local area network (LAN), a wide area network (WAN), a telephone network, such as the Public Switched Telephone Network (PSTN), an intranet, the Internet, a memory device, another type of network, or a combination of networks. Two clients 110 and two servers 120 and 210 have been illustrated as connected to network 220 for simplicity. In practice, there may be more or fewer clients and servers. Also, in some instances, a client may perform the functions of a server and a server may perform the functions of a client. Clients 110 may include client entities. An entity may be defined as a device, such as a wireless telephone, a personal computer, a personal digital assistant (PDA), a laptop, or another type of computation or communication device, a thread or process running on one of these devices, and/or an object executable by one of these devices. Servers 120 and 210 may include server entities that gather, process, search, and/or maintain documents in a manner consistent with the principles of the invention. Clients 110 and servers 120 and 210 may connect to network 220 via wired, wireless, and/or optical connections. In an implementation consistent with the principles of the invention, server 120 may include a search engine 225 usable by users at clients 110 . Server 120 may implement a data aggregation service by crawling a corpus of documents (e.g., web pages) hosted on data source server(s) 210 and store information associated with these documents in a repository of crawled documents. The data aggregation service may be implemented in other ways, such as by agreement with the operator(s) of data source server(s) 210 to distribute their hosted documents via the data aggregation service. Server 120 may additionally provide multi-dimensional plots of data retrieved based on one or more search queries provided by users at clients 110 . Each dimension of a multi-dimensional plot may correspond to a characteristic of the one or more search queries used to sort the searched data. Server(s) 210 may store or maintain documents that may be crawled by server 120 . Such documents may include data related to published news stories, products, images, user groups, geographic areas, or any other type of data. For example, server(s) 210 may store or maintain news stories from any type of news source, such as, for example, the Washington Post, the New York Times, Time magazine, or Newsweek. As another example, server(s) 210 may store or maintain data related to specific product data, such as product data provided by one or more product manufacturers. While servers 120 and 210 are shown as separate entities, it may be possible for one or more of servers 120 and 210 to perform one or more of the functions of another one or more of servers 120 and 210 . For example, it may be possible that two or more of servers 120 and 210 are implemented as a single server. It may also be possible for a single one of servers 120 or 210 to be implemented as two or more separate (and possibly distributed) devices. Exemplary Client/Server Architecture FIG. 3 is an exemplary diagram of a client or server entity (hereinafter called “client/server entity”), which may correspond to one or more of clients 110 and servers 120 and 210 , according to an implementation consistent with the principles of the invention. The client/server entity may include a bus 310 , a processing unit 320 , an optional main memory 330 , a read only memory (ROM) 340 , a storage device 350 , one or more input devices 360 , one or more output devices 370 , and a communication interface 380 . Bus 310 may include one or more conductors that permit communication among the components of the client/server entity. Processing unit 320 may include any type of software, firmware or hardware implemented processing device, such as, a microprocessor, a field programmable gate array (FPGA), combinational logic, etc. Main memory 330 may include a random access memory (RAM) or another type of dynamic storage device that stores information and instructions for execution by processing unit 320 , if processing unit 320 includes a microprocessor. ROM 340 may include a conventional ROM device or another type of static storage device that stores static information and/or instructions for use by processing unit 320 . Storage device 350 may include a magnetic and/or optical recording medium and its corresponding drive. Input device(s) 360 may include one or more conventional mechanisms that permit an operator to input information to the client/server entity, such as a keyboard, a mouse, a pen, voice recognition and/or biometric mechanisms, etc. Output device(s) 370 may include one or more conventional mechanisms that output information to the operator, including a display, a printer, a speaker, etc. Communication interface 380 may include any transceiver-like mechanism that enables the client/server entity to communicate with other devices and/or systems. For example, communication interface 380 may include mechanisms for communicating with another device or system via a network, such as network 220 . As will be described in detail below, the client/server entity, consistent with the principles of the invention, performs certain searching-related operations. The client/server entity may, in some implementations, perform these operations in response to processing unit 320 executing software instructions contained in a computer-readable medium, such as memory 330 . A computer-readable medium may be defined as one or more physical or logical memory devices and/or carrier waves. The software instructions may be read into memory 330 from another computer-readable medium, such as data storage device 350 , or from another device via communication interface 380 . The software instructions contained in memory 330 may cause processing unit 320 to perform processes that will be described later. Alternatively, hardwired circuitry may be used in place of, or in combination with, software instructions to implement processes consistent with the principles of the invention. Thus, implementations consistent with the principles of the invention are not limited to any specific combination of hardware circuitry and software. Exemplary Processing FIGS. 4A and 4B are flowcharts of exemplary processing for providing multi-dimensional display documents according to an implementation consistent with the principles of the invention. As one skilled in the art will appreciate, the processing exemplified by FIGS. 4A and 4B can be implemented in software and stored on a computer-readable memory, such as main memory 330 , ROM 340 or storage device 350 of server 120 . In other implementations, the processing exemplified by FIGS. 4A and 4B can be implemented in hardwired circuitry, such as combinational logic, within processing unit 320 of server 120 . Processing may begin with server 120 accessing external data sources (e.g., from server(s) 210 ), fetching the data content stored at the data sources and aggregating the fetched data content in a local memory (act 405 ) ( FIG. 4A ). For example, server 120 may use a web crawler (e.g., web robot) that may access documents hosted by data source server(s) 210 . Data source server(s) 130 may host, for example, data content related to news, products, images, user groups, or other types of data content. The fetched data content may then be indexed and grouped, using conventional indexing and grouping algorithms (act 410 ). Server 120 may then receive one or more search queries from a user at client 110 (act 415 ). Server 120 may support various types of search queries, such as, for example, searches by price, date, recency, image quality, image size or distance. In one implementation, server 120 may use one or more search queries derived in any type of manner. For example, any type of “clickable” query may be used by server 120 . Such “clickable” queries may, include, for example, selections from a list of related queries or selections from categories of queries. In another implementation, search queries entered by the user in the past may be ranked based on recency and frequency and made accessible through a menu placed on a search page for selection by the user. Selecting such a search query may reissue the search query. In a further implementation, one or more search queries may be inferred from the user's current or past browsing activity (e.g., a data search query may include an inferred set of keywords, etc.). Additionally, any combination of the above search queries may be supported by server 120 . In one implementation of the invention directed to news searching (e.g., Google News), as shown in FIG. 5 , a user may enter search text in a news search page 500 . News search page 500 may include various search features that permit the user to specify customized search parameters. News search page 500 may support search query forms such as (a) one or more keywords (e.g., ‘with all of the words,’ ‘with the exact phrase,’ ‘with at least one of the words,’ ‘without the words’) (b) topical categories (e.g., ‘topic=sports,’ ‘topic=crime’; (c) geographical categories (e.g., ‘geo=Asia,’ ‘geo=USA’); (d) geographical reporting areas (e.g., U.S. newspapers, European newspapers, etc.); (e) restrictions on the news sources to be considered (e.g., ‘return only articles from the news sources named,’ ‘do not return articles from the new source named’); and/or (g) a time window that defines a start and end of a time interval from which articles may be retrieved. A search query may additionally include any combination of the above forms of search query. In another implementation of the invention directed to product searching, as shown in FIG. 6 , a user may enter search text in a product search page 600 . Product search page 600 may include various search features that permit the user to specify customized search parameters. Product search page 600 may support search query forms such as (a) one or more keywords (e.g., ‘with all of the words,’ ‘with the exact phrase,’ ‘with at least one of the words,’ ‘without the words’); (b) a product price range (e.g., ‘display products whose price is between’); (c) a specification of where the one or more keywords should occur (e.g., ‘in the product name or description,’ ‘in the product description’); (d) a product category (e.g., ‘return products from the category’); (e) a specification of whether to group by store (e.g., ‘group by store,’ ‘show all products’); (f) a view selection (e.g., ‘list view,’ ‘grid view,’ ‘graph view’); and/or (g) a time window that defines a start and end of a time interval from which product data may be retrieved. A search query may additionally include any combination of the above forms of search query. Server 120 may then store the one or more search queries in local memory (e.g., main memory 330 , ROM 340 or storage device 350 ) (act 420 ). Server 120 , using search engine 225 , may execute the one or more search queries (act 425 ). The results of the executed search queries may be sorted using existing sorting techniques. Such sorting techniques may, for example, sort the results of the executed search queries by relevance. The sorting techniques may further sort the results of the executed search queries by one or more additional characteristics, such as, for example, price, date, recency, image quality, image size, geographic distance, etc. The sorted results of the one or more search queries may be provided to the user as a multi-dimensional display document (act 430 ) ( FIG. 4B ). The multi-dimensional display document may include a multi-dimensional graph of the sorted results of the one or more search queries, where each dimension of the graph corresponds to a characteristic of the executed search. For example, each dimension of the multi-dimensional display may correspond to one of relevance, price, date, recency, image quality, image size, geographic distance or any other appropriate search characteristic. Each search query result may be represented by small summaries, such as, for example, a small thumbnail image, an icon, or a fragment of text (e.g., a single word or short phrase). Since any form of summary may take up non-zero area in the plot of the multi-dimensional display, not all search results may be able to be displayed simultaneously on a single display document. In such a case, the plot may span across multiple pages of the document (i.e., a user may “page” from one page of the document to the next to view all of the results). In some implementations of the invention, the size of each of the summaries of the results may vary (e.g., more relevant equals a bigger icon or image). Because results may not be points on the plot, two results may overlap if centered about their true points. Therefore, consistent with the invention, the results may not have to be positioned exactly on the multi-dimensional plot. Results plotted on a dimension corresponding to relevance, in particular, may have their position shifted to a significant extent along the relevance dimension. So long as the relative ordering along the different dimensions is substantially preserved, some liberties may be taken in order to plot more results on the multi-dimensional display document. Optimal packing to preserve certain constraints of minimizing out-of-position-ness may likely be NP-hard. However, several simple greedy solutions may be possible to shift result positions slightly to fit more results in the multi-dimensional display document, and to make sure that whatever results are displayed may not be too far from their correct positions. In some implementations, for example, most relevant to least relevant results may be positioned accurately, but if there is overlap with a prior result, then results may be “shifted” in the less relevant direction until there is no overlap. Or, alternatively, an overlapping ‘more relevant’ result can be shifted up or down on the other axis up X % of the size of the thumbnails if it will prevent an overlap. However, this shift should be performed only if it also preserves the relative ordering along the other dimension with all currently positioned results. In one implementation, a fixed number of results may be positioned per “page” of the multi-dimensional display document. For example, each “page” may include the N most relevant results, or the N most relevant results and the M results that optimize another dimension (e.g., 10 most relevant and 10 cheapest in price). Displaying the N most relevant results, and the M results that optimize another dimension, provides advantage over a simple list because it simultaneously shows the relevance of the results and the ordering of the results in at least one other dimension. In another implementation, the particular overlaps on the plot might determine what results get displayed (e.g., continue including more results until there is room for no more, or until a threshold on number or relevance is passed). In yet another implementation, more relevant results may be permitted to overlap on top of less relevant results, but the amount of overlap may be permitted to increase only as relevance decreases, so that from the more relevant side of the plot to the less relevant side there is a sort of “fanning-out” with more and more results able to “peek out” from under their “neighbors.” Consistent with some implementations of the invention, natural restrictions may be performed on the range of one or more of the dimensions of the multi-dimensional display document (e.g., price restrictions, date restrictions). Restriction on the range of one or more of the dimensions may be achieved by implementing multiple (e.g., 2, 3, or 4) overlapping ranges that have different granularities (e.g., prices in $100 increments and prices in $20 increments). The user may implement a restriction (e.g., by “clicking” on a range if using a mouse interface) that “zooms” the display in, causing the selected range to “zoom” out to fill substantially the entire display of the multi-dimensional document. In a further implementation, the axes of the plot on the multi-dimensional display document may be scaled. The axes, thus, need not be linear, and any monotonic transformation of an axis may be used (e.g., a logarithmic scale for price or recency). In some instances, if a large gap between clusters of results exists, a monotonic “squeezing” of the space between the results could be used to bring them closer together and fit more results into the plot with less blank space (e.g., a simple piecewise linear transformation could be used that simply uses a different linear scaling for the gap between two clusters of results). This might be useful if the set of results plotted includes the top N results that optimize each axis independently. In another implementation, the multi-dimensional display document may plot multiple dimensions, with none of the dimensions being relevance (e.g., price vs. merchant rating, image quality vs. staleness, date vs. poster reputation, etc.). FIG. 7 illustrates an exemplary two-dimensional display document 700 consistent with one implementation of the invention. Two-dimensional display document 700 depicts a “graph view” of the results of a product search related to ‘digital cameras’ where the y-axis corresponds to ‘price’ and the x-axis corresponds to ‘relevance.’ If the user is using a “mouse,” moving the mouse over a target in the multi-dimensional display document (e.g., a thumbnail image, icon, etc.) may trigger the display of additional information. For example, in the product searching context, thumbnails with no text might be used to represent each product result and, upon “mouse-over” of a particular thumbnail, the title, exact price, and merchant for the offer might be displayed. Another possible representation for product searching might be a thumbnail image with a single word or phrase displayed in close association with the image (e.g., inside of, on top of, or in close proximity to). In certain subdomains (e.g., product categories), domain-specific summaries may be used. For example, in electronics domains, for queries that return many different models, the model number/string may be an appropriate one word label. For a digital camera query, thumbnails of digital cameras may appear with labels such as “S400,” “A70,” “G3,” etc. Accessories may be labeled with the word that describes the category of accessory (e.g., ‘battery,’ ‘case,’ ‘book,’ etc.). The accessory offers could be classified as accessories by price clustering or other classification signals and classified into the domain specific accessory types by another simple classifier. Upon “mouse-over” of the word or phrase, additional information may be displayed. Server 120 may determine whether a user selects a result from the multi-dimensional display document (act 435 ). In one implementation, for example, the user may select a result by “clicking” on an associated image, icon, or text, with a mouse. If the user selects a result from the provided multi-dimensional display document, then server 120 may provide a document(s) that corresponds to the selected result (act 440 ). For example, FIG. 9 illustrates an exemplary news document 900 that includes a news story 905 that corresponds to a specific selection by a user. According to another exemplary aspect, server 120 may, upon selection of a result, provide a document with one or more links to documents that correspond to the selected result. For example, FIG. 8 illustrates an exemplary document 800 that includes multiple links 805 corresponding to a news story related to a news search query provided by a user. If the user selects one of the one or more links of the provided document, then server 120 may provide a document(s) that corresponds to the selected link. For example, FIG. 9 illustrates an exemplary news document 900 that includes a news story 905 that corresponds to a specific link selected by a user. Returning to act 435 , if the user does not select a result from the multi-dimensional display document, then server 120 may determine whether the user selects a “next page” or a restricted range of the multi-dimensional display document (act 445 ). More results may exist then can fit on one page of the multi-dimensional display document, therefore, the user may select a subsequent page to view additional results. The user may further select a restricted range (e.g., by “clicking” on a range if using a mouse interface) to “zoom” the display in, causing the selected range to “zoom” out to substantially fill the entire display of the multi-dimensional display document. Server 120 may provide the selected “next page,” or the restricted range, of the multi-dimensional display document to the user (act 450 ). If the user does not select a “next page” or a restricted range, then processing may return to act 415 , with receipt of another search query(ies) from the user. CONCLUSION Systems and methods consistent with the principles of the invention enable the sorting of search results by multiple different characteristics, and display of those search results on a multi-dimensional graph. Each dimension of the multi-dimensional graph may correspond to one of the multiple characteristics. The foregoing description of preferred embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. For example, while a series of acts have been described with regard to FIGS. 4A and 4B , the order of the acts may be modified in other implementations consistent with the principles of the invention. Additionally, while aspects of the invention has been described with respect to searching information stored in the world-wide web (WWW), one skilled in the art will recognize that the sorting and displaying of search results in multiple dimensions, consistent with the principles of the invention, may be employed in any other type of information searching system. Also, non-dependent acts may be performed in parallel. It will also be apparent to one of ordinary skill in the art that aspects of the invention, as described above, may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement aspects consistent with the principles of the invention is not limiting of the present invention. Thus, the operation and behavior of the aspects of the invention were described without reference to the specific software code—it being understood that one of ordinary skill in the art would be able to design software and control hardware to implement the aspects based on the description herein. Further, certain portions of the invention have been described as “logic” that performs one or more functions. This logic may include hardware, such as an application specific integrated circuit or a field programmable gate array, software, or a combination of hardware and software. The scope of the invention is defined by the following claims and their equivalents.

A system plots results of a data search. The system executes one or more search queries to search stored data. The system receives results of the executed one or more search queries, where the results are orderable by at least one search characteristic. The system designates a visual representation for each of the results. The system plots each of the visual representations on a multi-dimensional graphical display, where at least one dimension of the multi-dimensional graphical display corresponds to the at least one search characteristic.

[0001] This invention relates to a process and apparatus for the separation of a gas containing hydrocarbons. The applicants claim the benefits under Title 35, United States Code, Section 119(e) of prior U.S. Provisional Application No. 61/186,361 which was filed on Jun. 11, 2009. The applicants also claim the benefits under Title 35, United States Code, Section 120 as a continuation-in-part of U.S. patent application Ser. No. 12/689,616 which was filed on Jan. 19, 2010, and as a continuation-in-part of U.S. patent application Ser. No. 12/372,604 which was filed on Feb. 17, 2009. Assignees S.M.E. Products LP and Ortloff Engineers, Ltd. were parties to a joint research agreement that was in effect before the invention of this application was made. BACKGROUND OF THE INVENTION [0002] Ethylene, ethane, propylene, propane, and/or heavier hydrocarbons can be recovered from a variety of gases, such as natural gas, refinery gas, and synthetic gas streams obtained from other hydrocarbon materials such as coal, crude oil, naphtha, oil shale, tar sands, and lignite. Natural gas usually has a major proportion of methane and ethane, i.e., methane and ethane together comprise at least 50 mole percent of the gas. The gas also contains relatively lesser amounts of heavier hydrocarbons such as propane, butanes, pentanes, and the like, as well as hydrogen, nitrogen, carbon dioxide, and other gases. [0003] The present invention is generally concerned with the recovery of ethylene, ethane, propylene, propane, and heavier hydrocarbons from such gas streams. A typical analysis of a gas stream to be processed in accordance with this invention would be, in approximate mole percent, 90.3% methane, 4.0% ethane and other C 2 components, 1.7% propane and other C 3 components, 0.3% iso-butane, 0.5% normal butane, and 0.8% pentanes plus, with the balance made up of nitrogen and carbon dioxide. Sulfur containing gases are also sometimes present. [0004] The historically cyclic fluctuations in the prices of both natural gas and its natural gas liquid (NGL) constituents have at times reduced the incremental value of ethane, ethylene, propane, propylene, and heavier components as liquid products. This has resulted in a demand for processes that can provide more efficient recoveries of these products and for processes that can provide efficient recoveries with lower capital investment. Available processes for separating these materials include those based upon cooling and refrigeration of gas, oil absorption, and refrigerated oil absorption. Additionally, cryogenic processes have become popular because of the availability of economical equipment that produces power while simultaneously expanding and extracting heat from the gas being processed. Depending upon the pressure of the gas source, the richness (ethane, ethylene, and heavier hydrocarbons content) of the gas, and the desired end products, each of these processes or a combination thereof may be employed. [0005] The cryogenic expansion process is now generally preferred for natural gas liquids recovery because it provides maximum simplicity with ease of startup, operating flexibility, good efficiency, safety, and good reliability. U.S. Pat. Nos. 3,292,380; 4,061,481; 4,140,504; 4,157,904; 4,171,964; 4,185,978; 4,251,249; 4,278,457; 4,519,824; 4,617,039; 4,687,499; 4,689,063; 4,690,702; 4,854,955; 4,869,740; 4,889,545; 5,275,005; 5,555,748; 5,566,554; 5,568,737; 5,771,712;5,799,507; 5,881,569; 5,890,378; 5,983,664; 6,182,469; 6,578,379; 6,712,880; 6,915,662; 7,191,617; 7,219,513; reissue U.S. Pat. No. 33,408; and co-pending application Ser. Nos. 11/430,412; 11/839,693; 11/971,491; and 12/206,230 describe relevant processes (although the description of the present invention in some cases is based on different processing conditions than those described in the cited U.S. patents). [0006] In a typical cryogenic expansion recovery process, a feed gas stream under pressure is cooled by heat exchange with other streams of the process and/or external sources of refrigeration such as a propane compression-refrigeration system. As the gas is cooled, liquids may be condensed and collected in one or more separators as high-pressure liquids containing some of the desired C 2 + components. Depending on the richness of the gas and the amount of liquids formed, the high-pressure liquids may be expanded to a lower pressure and fractionated. The vaporization occurring during expansion of the liquids results in further cooling of the stream. Under some conditions, pre-cooling the high pressure liquids prior to the expansion may be desirable in order to further lower the temperature resulting from the expansion. The expanded stream, comprising a mixture of liquid and vapor, is fractionated in a distillation (demethanizer or deethanizer) column. In the column, the expansion cooled stream(s) is (are) distilled to separate residual methane, nitrogen, and other volatile gases as overhead vapor from the desired C 2 components, C 3 components, and heavier hydrocarbon components as bottom liquid product, or to separate residual methane, C 2 components, nitrogen, and other volatile gases as overhead vapor from the desired C 3 components and heavier hydrocarbon components as bottom liquid product. [0007] If the feed gas is not totally condensed (typically it is not), the vapor remaining from the partial condensation can be split into two streams. One portion of the vapor is passed through a work expansion machine or engine, or an expansion valve, to a lower pressure at which additional liquids are condensed as a result of further cooling of the stream. The pressure after expansion is essentially the same as the pressure at which the distillation column is operated. The combined vapor-liquid phases resulting from the expansion are supplied as feed to the column. [0008] The remaining portion of the vapor is cooled to substantial condensation by heat exchange with other process streams, e.g., the cold fractionation tower overhead. Some or all of the high-pressure liquid may be combined with this vapor portion prior to cooling. The resulting cooled stream is then expanded through an appropriate expansion device, such as an expansion valve, to the pressure at which the demethanizer is operated. During expansion, a portion of the liquid will vaporize, resulting in cooling of the total stream. The flash expanded stream is then supplied as top feed to the demethanizer. Typically, the vapor portion of the flash expanded stream and the demethanizer overhead vapor combine in an upper separator section in the fractionation tower as residual methane product gas. Alternatively, the cooled and expanded stream may be supplied to a separator to provide vapor and liquid streams. The vapor is combined with the tower overhead and the liquid is supplied to the column as a top column feed. [0009] In the ideal operation of such a separation process, the residue gas leaving the process will contain substantially all of the methane in the feed gas with essentially none of the heavier hydrocarbon components and the bottoms fraction leaving the demethanizer will contain substantially all of the heavier hydrocarbon components with essentially no methane or more volatile components. In practice, however, this ideal situation is not obtained because the conventional demethanizer is operated largely as a stripping column. The methane product of the process, therefore, typically comprises vapors leaving the top fractionation stage of the column, together with vapors not subjected to any rectification step. Considerable losses of C 2 , C 3 , and C 4 + components occur because the top liquid feed contains substantial quantities of these components and heavier hydrocarbon components, resulting in corresponding equilibrium quantities of C 2 components, C 3 components, C 4 components, and heavier hydrocarbon components in the vapors leaving the top fractionation stage of the demethanizer. The loss of these desirable components could be significantly reduced if the rising vapors could be brought into contact with a significant quantity of liquid (reflux) capable of absorbing the C 2 components, C 3 components, C 4 components, and heavier hydrocarbon components from the vapors. [0010] In recent years, the preferred processes for hydrocarbon separation use an upper absorber section to provide additional rectification of the rising vapors. The source of the reflux stream for the upper rectification section is typically a recycled stream of residue gas supplied under pressure. The recycled residue gas stream is usually cooled to substantial condensation by heat exchange with other process streams, e.g., the cold fractionation tower overhead. The resulting substantially condensed stream is then expanded through an appropriate expansion device, such as an expansion valve, to the pressure at which the demethanizer is operated. During expansion, a portion of the liquid will usually vaporize, resulting in cooling of the total stream. The flash expanded stream is then supplied as top feed to the demethanizer. Typically, the vapor portion of the expanded stream and the demethanizer overhead vapor combine in an upper separator section in the fractionation tower as residual methane product gas. Alternatively, the cooled and expanded stream may be supplied to a separator to provide vapor and liquid streams, so that thereafter the vapor is combined with the tower overhead and the liquid is supplied to the column as a top column feed. Typical process schemes of this type are disclosed in U.S. Pat. Nos. 4,889,545; 5,568,737; and 5,881,569, co-pending application Ser. Nos. 11/430,412 and 11/971,491, and in Mowrey, E. Ross, “Efficient, High Recovery of Liquids from Natural Gas Utilizing a High Pressure Absorber”, Proceedings of the Eighty-First Annual Convention of the Gas Processors Association, Dallas, Tex., Mar. 11-13, 2002. [0011] The present invention employs a novel means of performing the various steps described above more efficiently and using fewer pieces of equipment. This is accomplished by combining what heretofore have been individual equipment items into a common housing, thereby reducing the plot space required for the processing plant and reducing the capital cost of the facility. Surprisingly, applicants have found that the more compact arrangement also significantly reduces the power consumption required to achieve a given recovery level, thereby increasing the process efficiency and reducing the operating cost of the facility. In addition, the more compact arrangement also eliminates much of the piping used to interconnect the individual equipment items in traditional plant designs, further reducing capital cost and also eliminating the associated flanged piping connections. Since piping flanges are a potential leak source for hydrocarbons (which are volatile organic compounds, VOCs, that contribute to greenhouse gases and may also be precursors to atmospheric ozone formation), eliminating these flanges reduces the potential for atmospheric emissions that can damage the environment. [0012] In accordance with the present invention, it has been found that C 2 recoveries in excess of 95% can be obtained. Similarly, in those instances where recovery of C 2 components is not desired, C 3 recoveries in excess of 95% can be maintained. In addition, the present invention makes possible essentially 100% separation of methane (or C 2 components) and lighter components from the C 2 components (or C 3 components) and heavier components at lower energy requirements compared to the prior art while maintaining the same recovery level. The present invention, although applicable at lower pressures and warmer temperatures, is particularly advantageous when processing feed gases in the range of 400 to 1500 psia [2,758 to 10,342 kPa(a)] or higher under conditions requiring NGL recovery column overhead temperatures of −50° F. [−46° C.] or colder. [0013] For a better understanding of the present invention, reference is made to the following examples and drawings. Referring to the drawings: [0014] FIG. 1 is a flow diagram of a prior art natural gas processing plant in accordance with U.S. Pat. No. 5,568,737; [0015] FIG. 2 is a flow diagram of a natural gas processing plant in accordance with the present invention; and [0016] FIGS. 3 through 9 are flow diagrams illustrating alternative means of application of the present invention to a natural gas stream. [0017] In the following explanation of the above figures, tables are provided summarizing flow rates calculated for representative process conditions. In the tables appearing herein, the values for flow rates (in moles per hour) have been rounded to the nearest whole number for convenience. The total stream rates shown in the tables include all non-hydrocarbon components and hence are generally larger than the sum of the stream flow rates for the hydrocarbon components. Temperatures indicated are approximate values rounded to the nearest degree. It should also be noted that the process design calculations performed for the purpose of comparing the processes depicted in the figures are based on the assumption of no heat leak from (or to) the surroundings to (or from) the process. The quality of commercially available insulating materials makes this a very reasonable assumption and one that is typically made by those skilled in the art. [0018] For convenience, process parameters are reported in both the traditional British units and in the units of the Systeme International d'Unités (SI). The molar flow rates given in the tables may be interpreted as either pound moles per hour or kilogram moles per hour. The energy consumptions reported as horsepower (HP) and/or thousand British Thermal Units per hour (MBTU/Hr) correspond to the stated molar flow rates in pound moles per hour. The energy consumptions reported as kilowatts (kW) correspond to the stated molar flow rates in kilogram moles per hour. DESCRIPTION OF THE PRIOR ART [0019] FIG. 1 is a process flow diagram showing the design of a processing plant to recover C 2 + components from natural gas using prior art according to U.S. Pat. No. 5,568,737. In this simulation of the process, inlet gas enters the plant at 110° F. [43° C.] and 915 psia [6,307 kPa(a)] as stream 31 . If the inlet gas contains a concentration of sulfur compounds which would prevent the product streams from meeting specifications, the sulfur compounds are removed by appropriate pretreatment of the feed gas (not illustrated). In addition, the feed stream is usually dehydrated to prevent hydrate (ice) formation under cryogenic conditions. Solid desiccant has typically been used for this purpose. [0020] The feed stream 31 is divided into two portions, streams 32 and 33 . Stream 32 is cooled to −26° F. [−32° C.] in heat exchanger 10 by heat exchange with cool distillation vapor stream 41 a, while stream 33 is cooled to −32° F. [−35° C.] in heat exchanger 11 by heat exchange with demethanizer reboiler liquids at 41° F. [5° C.] (stream 43 ) and side reboiler liquids at −49° F. [−45° C.] (stream 42 ). Streams 32 a and 33 a recombine to form stream 31 a , which enters separator 12 at −28° F. [−33° C.] and 893 psia [6,155 kPa(a)] where the vapor (stream 34 ) is separated from the condensed liquid (stream 35 ). [0021] The vapor (stream 34 ) from separator 12 is divided into two streams, 36 and 39 . Stream 36 , containing about 27% of the total vapor, is combined with the separator liquid (stream 35 ), and the combined stream 38 passes through heat exchanger 13 in heat exchange relation with cold distillation vapor stream 41 where it is cooled to substantial condensation. The resulting substantially condensed stream 38 a at −139° F. [−95° C.] is then flash expanded through expansion valve 14 to the operating pressure (approximately 396 psia [2,730 kPa(a)]) of fractionation tower 18 . During expansion a portion of the stream is vaporized, resulting in cooling of the total stream. In the process illustrated in FIG. 1 , the expanded stream 38 b leaving expansion valve 14 reaches a temperature of −140° F. [−95° C.] and is supplied to fractionation tower 18 at a first mid-column feed point. [0022] The remaining 73% of the vapor from separator 12 (stream 39 ) enters a work expansion machine 15 in which mechanical energy is extracted from this portion of the high pressure feed. The machine 15 expands the vapor substantially isentropically to the tower operating pressure, with the work expansion cooling the expanded stream 39 a to a temperature of approximately −95° F. [−71° C.]. The typical commercially available expanders are capable of recovering on the order of 80-85% of the work theoretically available in an ideal isentropic expansion. The work recovered is often used to drive a centrifugal compressor (such as item 16 ) that can be used to re-compress the heated distillation vapor stream (stream 41 b ), for example. The partially condensed expanded stream 39 a is thereafter supplied as feed to fractionation tower 18 at a second mid-column feed point. [0023] The recompressed and cooled distillation vapor stream 41 e is divided into two streams. One portion, stream 46 , is the volatile residue gas product. The other portion, recycle stream 45 , flows to heat exchanger 10 where it is cooled to −26° F. [−32° C.] by heat exchange with cool distillation vapor stream 41 a. The cooled recycle stream 45 a then flows to exchanger 13 where it is cooled to −139° F. [−95° C.] and substantially condensed by heat exchange with cold distillation vapor stream 41 . The substantially condensed stream 45 b is then expanded through an appropriate expansion device, such as expansion valve 22 , to the demethanizer operating pressure, resulting in cooling of the total stream to −147° F. [−99° C.]. The expanded stream 45 c is then supplied to fractionation tower 18 as the top column feed. The vapor portion (if any) of stream 45 c combines with the vapors rising from the top fractionation stage of the column to form distillation vapor stream 41 , which is withdrawn from an upper region of the tower. [0024] The demethanizer in tower 18 is a conventional distillation column containing a plurality of vertically spaced trays, one or more packed beds, or some combination of trays and packing. As is often the case in natural gas processing plants, the fractionation tower may consist of two sections. The upper section 18 a is a separator wherein the partially vaporized top feed is divided into its respective vapor and liquid portions, and wherein the vapor rising from the lower distillation or demethanizing section 18 b is combined with the vapor portion of the top feed to form the cold demethanizer overhead vapor (stream 41 ) which exits the top of the tower at −144° F. [−98° C.]. The lower, demethanizing section 18 b contains the trays and/or packing and provides the necessary contact between the liquids falling downward and the vapors rising upward. The demethanizing section 18 b also includes reboilers (such as the reboiler and the side reboiler described previously) which heat and vaporize a portion of the liquids flowing down the column to provide the stripping vapors which flow up the column to strip the liquid product, stream 44 , of methane and lighter components. [0025] The liquid product stream 44 exits the bottom of the tower at 64 ° F. [18° C.], based on a typical specification of a methane to ethane ratio of 0.010:1 on a mass basis in the bottom product. The demethanizer overhead vapor stream 41 passes countercurrently to the incoming feed gas and recycle stream in heat exchanger 13 where it is heated to −40° F. [−40° C.] (stream 41 a ) and in heat exchanger 10 where it is heated to 104° F. [40° C.] (stream 41 b ). The distillation vapor stream is then re-compressed in two stages. The first stage is compressor 16 driven by expansion machine 15 . The second stage is compressor 20 driven by a supplemental power source which compresses the residue gas (stream 41 d ) to sales line pressure. After cooling to 110° F. [43° C.] in discharge cooler 21 , stream 41 e is split into the residue gas product (stream 46 ) and the recycle stream 45 as described earlier. Residue gas stream 46 flows to the sales gas pipeline at 915 psia [6,307 kPa(a)], sufficient to meet line requirements (usually on the order of the inlet pressure). [0026] A summary of stream flow rates and energy consumption for the process illustrated in FIG. 1 is set forth in the following table: [0000] TABLE I (FIG. 1) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] Stream Methane Ethane Propane Butanes+ Total 31 12,398 546 233 229 13,726 32 8,431 371 159 156 9,334 33 3,967 175 74 73 4,392 34 12,195 501 179 77 13,261 35 203 45 54 152 465 36 3,317 136 49 21 3,607 38 3,520 181 103 173 4,072 39 8,878 365 130 56 9,654 41 13,765 30 0 0 13,992 45 1,377 3 0 0 1,400 46 12,388 27 0 0 12,592 44 10 519 233 229 1,134 Recoveries* [0027] [0000] Ethane 94.99% Propane 99.99% Butanes+ 100.00% Power [0028] [0000] Residue Gas Compression 6,149 HP [10,109 kW] * (Based on un-rounded flow rates) DESCRIPTION OF THE INVENTION [0029] FIG. 2 illustrates a flow diagram of a process in accordance with the present invention. The feed gas composition and conditions considered in the process presented in FIG. 2 are the same as those in FIG. 1 . Accordingly, the FIG. 2 process can be compared with that of the FIG. 1 process to illustrate the advantages of the present invention. [0030] In the simulation of the FIG. 2 process, inlet gas enters the plant as stream 31 and is divided into two portions, streams 32 and 33 . The first portion, stream 32 , enters a heat exchange means in the upper region of feed cooling section 118 a inside processing assembly 118 . This heat exchange means may be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers. The heat exchange means is configured to provide heat exchange between stream 32 flowing through one pass of the heat exchange means and a distillation vapor stream arising from separator section 118 b inside processing assembly 118 that has been heated in a heat exchange means in the lower region of feed cooling section 118 a. Stream 32 is cooled while further heating the distillation vapor stream, with stream 32 a leaving the heat exchange means at −25° F. [−32° C.]. [0031] The second portion, stream 33 , enters a heat and mass transfer means in demethanizing section 118 e inside processing assembly 118 . This heat and mass transfer means may also be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers. The heat and mass transfer means is configured to provide heat exchange between stream 33 flowing through one pass of the heat and mass transfer means and a distillation liquid stream flowing downward from absorbing section 118 d inside processing assembly 118 , so that stream 33 is cooled while heating the distillation liquid stream, cooling stream 33 a to −47° F. [−44° C.] before it leaves the heat and mass transfer means. As the distillation liquid stream is heated, a portion of it is vaporized to form stripping vapors that rise upward as the remaining liquid continues flowing downward through the heat and mass transfer means. The heat and mass transfer means provides continuous contact between the stripping vapors and the distillation liquid stream so that it also functions to provide mass transfer between the vapor and liquid phases, stripping the liquid product stream 44 of methane and lighter components. [0032] Streams 32 a and 33 a recombine to form stream 31 a , which enters separator section 118 f inside processing assembly 118 at −32° F. [−36° C.] and 900 psia [6,203 kPa(a)], whereupon the vapor (stream 34 ) is separated from the condensed liquid (stream 35 ). Separator section 118 f has an internal head or other means to divide it from demethanizing section 118 e, so that the two sections inside processing assembly 118 can operate at different pressures. [0033] The vapor (stream 34 ) from separator section 118 f is divided into two streams, 36 and 39 . Stream 36 , containing about 27% of the total vapor, is combined with the separated liquid (stream 35 , via stream 37 ), and the combined stream 38 enters a heat exchange means in the lower region of feed cooling section 118 a inside processing assembly 118 . This heat exchange means may likewise be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers. The heat exchange means is configured to provide heat exchange between stream 38 flowing through one pass of the heat exchange means and the distillation vapor stream arising from separator section 118 b, so that stream 38 is cooled to substantial condensation while heating the distillation vapor stream. [0034] The resulting substantially condensed stream 38 a at −138° F. [−95° C.] is then flash expanded through expansion valve 14 to the operating pressure (approximately 400 psia [2,758 kPa(a)]) of rectifying section 118 c (an absorbing means) and absorbing section 118 d (another absorbing means) inside processing assembly 118 . During expansion a portion of the stream may be vaporized, resulting in cooling of the total stream. In the process illustrated in FIG. 2 , the expanded stream 38 b leaving expansion valve 14 reaches a temperature of −139° F. [−95° C.] and is supplied to processing assembly 118 between rectifying section 118 c and absorbing section 118 d. The liquids in stream 38 b combine with the liquids falling from rectifying section 118 c and are directed to absorbing section 118 d, while any vapors combine with the vapors rising from absorbing section 118 d and are directed to rectifying section 118 c. [0035] The remaining 73% of the vapor from separator section 118 f (stream 39 ) enters a work expansion machine 15 in which mechanical energy is extracted from this portion of the high pressure feed. The machine 15 expands the vapor substantially isentropically to the operating pressure of absorbing section 118 d, with the work expansion cooling the expanded stream 39 a to a temperature of approximately −99° F. [−73° C.]. The partially condensed expanded stream 39 a is thereafter supplied as feed to the lower region of absorbing section 118 d inside processing assembly 118 . [0036] The recompressed and cooled distillation vapor stream 41 c is divided into two streams. One portion, stream 46 , is the volatile residue gas product. The other portion, recycle stream 45 , enters a heat exchange means in the feed cooling section 118 a inside processing assembly 118 . This heat exchange means may also be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers. The heat exchange means is configured to provide heat exchange between stream 45 flowing through one pass of the heat exchange means and the distillation vapor stream arising from separator section 118 b, so that stream 45 is cooled to substantial condensation while heating the distillation vapor stream. [0037] The substantially condensed recycle stream 45 a leaves the heat exchange means in feed cooling section 118 a at −138° F. [−95° C.] and is flash expanded through expansion valve 22 to the operating pressure of rectifying section 118 c inside processing assembly 118 . During expansion a portion of the stream is vaporized, resulting in cooling of the total stream. In the process illustrated in FIG. 2 , the expanded stream 45 b leaving expansion valve 22 reaches a temperature of −146° F. [−99° C.] and is supplied to separator section 118 b inside processing assembly 118 . The liquids separated therein are directed to rectifying section 118 c, while the remaining vapors combine with the vapors rising from rectifying section 118 c to form the distillation vapor stream that is heated in cooling section 118 a. [0038] Rectifying section 118 c and absorbing section 118 d each contain an absorbing means consisting of a plurality of vertically spaced trays, one or more packed beds, or some combination of trays and packing. The trays and/or packing in rectifying section 118 c and absorbing section 118 d provide the necessary contact between the vapors rising upward and cold liquid falling downward. The liquid portion of the expanded stream 39 a commingles with liquids falling downward from absorbing section 118 d and the combined liquid continues downward into demethanizing section 118 e. The stripping vapors arising from demethanizing section 118 e combine with the vapor portion of the expanded stream 39 a and rise upward through absorbing section 118 d, to be contacted with the cold liquid falling downward to condense and absorb most of the C 2 components, C 3 components, and heavier components from these vapors. The vapors arising from absorbing section 118 d combine with any vapor portion of the expanded stream 38 b and rise upward through rectifying section 118 c, to be contacted with the cold liquid portion of expanded stream 45 b falling downward to condense and absorb most of the C 2 components, C 3 components, and heavier components remaining in these vapors. The liquid portion of the expanded stream 38 b commingles with liquids falling downward from rectifying section 118 c and the combined liquid continues downward into absorbing section 118 d. [0039] The distillation liquid flowing downward from the heat and mass transfer means in demethanizing section 118 e inside processing assembly 118 has been stripped of methane and lighter components. The resulting liquid product (stream 44 ) exits the lower region of demethanizing section 118 e and leaves processing assembly 118 at 65° F. [18° C.]. The distillation vapor stream arising from separator section 118 b is warmed in feed cooling section 118 a as it provides cooling to streams 32 , 38 , and 45 as described previously, and the resulting distillation vapor stream 41 leaves processing assembly 118 at 105° F. [40° C.]. The distillation vapor stream is then re-compressed in two stages, compressor 16 driven by expansion machine 15 and compressor 20 driven by a supplemental power source. After stream 41 b is cooled to 110° F. [43° C.] in discharge cooler 21 to form stream 41 c, recycle stream 45 is withdrawn as described earlier, forming residue gas stream 46 which thereafter flows to the sales gas pipeline at 915 psia [6,307 kPa(a)]. [0040] A summary of stream flow rates and energy consumption for the process illustrated in FIG. 2 is set forth in the following table: [0000] TABLE II (FIG. 2) Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr] Stream Methane Ethane Propane Butanes+ Total 31 12,398 546 233 229 13,726 32 8,679 382 163 160 9,608 33 3,719 164 70 69 4,118 34 12,164 495 174 72 13,213 35 234 51 59 157 513 36 3,248 132 46 19 3,528 37 234 51 59 157 513 38 3,482 183 105 176 4,041 39 8,916 363 128 53 9,685 40 0 0 0 0 0 41 13,863 30 0 0 14,095 45 1,475 3 0 0 1,500 46 12,388 27 0 0 12,595 44 10 519 233 229 1,131 Recoveries* [0041] [0000] Ethane 95.03% Propane 99.99% Butanes+ 100.00% Power [0042] [0000] Residue Gas Compression 5,787 HP [9,514 kW] * (Based on un-rounded flow rates) [0043] A comparison of Tables I and II shows that the present invention maintains essentially the same recoveries as the prior art. However, further comparison of Tables I and II shows that the product yields were achieved using significantly less power than the prior art. In terms of the recovery efficiency (defined by the quantity of ethane recovered per unit of power), the present invention represents more than a 6 % improvement over the prior art of the FIG. 1 process. [0044] The improvement in recovery efficiency provided by the present invention over that of the prior art of the FIG. 1 process is primarily due to two factors. First, the compact arrangement of the heat exchange means in feed cooling section 118 a and the heat and mass transfer means in demethanizing section 118 e in processing assembly 118 eliminates the pressure drop imposed by the interconnecting piping found in conventional processing plants. The result is that the portion of the feed gas flowing to expansion machine 15 is at higher pressure for the present invention compared to the prior art, allowing expansion machine 15 in the present invention to produce as much power with a higher outlet pressure as expansion machine 15 in the prior art can produce at a lower outlet pressure. Thus, rectifying section 118 c and absorbing section 118 d in processing assembly 118 of the present invention can operate at higher pressure than fractionation column 18 of the prior art while maintaining the same recovery level. This higher operating pressure, plus the reduction in pressure drop for the distillation vapor stream due to eliminating the interconnecting piping, results in a significantly higher pressure for the distillation vapor stream entering compressor 20 , thereby reducing the power required by the present invention to restore the residue gas to pipeline pressure. [0045] Second, using the heat and mass transfer means in demethanizing section 118 e to simultaneously heat the distillation liquid leaving absorbing section 118 d while allowing the resulting vapors to contact the liquid and strip its volatile components is more efficient than using a conventional distillation column with external reboilers. The volatile components are stripped out of the liquid continuously, reducing the concentration of the volatile components in the stripping vapors more quickly and thereby improving the stripping efficiency for the present invention. [0046] The present invention offers two other advantages over the prior art in addition to the increase in processing efficiency. First, the compact arrangement of processing assembly 118 of the present invention replaces five separate equipment items in the prior art (heat exchangers 10 , 11 , and 13 ; separator 12 ; and fractionation tower 18 in FIG. 1 ) with a single equipment item (processing assembly 118 in FIG. 2 ). This reduces the plot space requirements and eliminates the interconnecting piping, reducing the capital cost of a process plant utilizing the present invention over that of the prior art. Second, elimination of the interconnecting piping means that a processing plant utilizing the present invention has far fewer flanged connections compared to the prior art, reducing the number of potential leak sources in the plant. [0047] Hydrocarbons are volatile organic compounds (VOCs), some of which are classified as greenhouse gases and some of which may be precursors to atmospheric ozone formation, which means the present invention reduces the potential for atmospheric releases that can damage the environment. Other Embodiments [0048] Some circumstances may favor supplying liquid stream 35 directly to the lower region of absorbing section 118 d via stream 40 as shown in FIGS. 2 , 4 , 6 , and 8 . In such cases, an appropriate expansion device (such as expansion valve 17 ) is used to expand the liquid to the operating pressure of absorbing section 118 d and the resulting expanded liquid stream 40 a is supplied as feed to the lower region of absorbing section 118 d (as shown by the dashed lines). Some circumstances may favor combining a portion of liquid stream 35 (stream 37 ) with the vapor in stream 36 ( FIGS. 2 and 6 ) or with cooled second portion 33 a ( FIGS. 4 and 8 ) to form combined stream 38 and routing the remaining portion of liquid stream 35 to the lower region of absorbing section 118 d via streams 40 / 40 a. Some circumstances may favor combining the expanded liquid stream 40 a with expanded stream 39 a ( FIGS. 2 and 6 ) or expanded stream 34 a ( FIGS. 4 and 8 ) and thereafter supplying the combined stream to the lower region of absorbing section 118 d as a single feed. [0049] If the feed gas is richer, the quantity of liquid separated in stream 35 may be great enough to favor placing an additional mass transfer zone in demethanizing section 118 e between expanded stream 39 a and expanded liquid stream 40 a as shown in FIGS. 3 and 7 , or between expanded stream 34 a and expanded liquid stream 40 a as shown in FIGS. 5 and 9 . In such cases, the heat and mass transfer means in demethanizing section 118 e may be configured in upper and lower parts so that expanded liquid stream 40 a can be introduced between the two parts. As shown by the dashed lines, some circumstances may favor combining a portion of liquid stream 35 (stream 37 ) with the vapor in stream 36 ( FIGS. 3 and 7 ) or with cooled second portion 33 a ( FIGS. 5 and 9 ) to form combined stream 38 , while the remaining portion of liquid stream 35 (stream 40 ) is expanded to lower pressure and supplied between the upper and lower parts of the heat and mass transfer means in demethanizing section 118 e as stream 40 a. [0050] Some circumstances may favor not combining the cooled first and second portions (streams 32 a and 33 a ) as shown in FIGS. 4 , 5 , 8 , and 9 . In such cases, only the cooled first portion 32 a is directed to separator section 118 f inside processing assembly 118 ( FIGS. 4 and 5 ) or separator 12 ( FIGS. 8 and 9 ) where the vapor (stream 34 ) is separated from the condensed liquid (stream 35 ). Vapor stream 34 enters work expansion machine 15 and is expanded substantially isentropically to the operating pressure of absorbing section 118 d , whereupon expanded stream 34 a is supplied as feed to the lower region of absorbing section 118 d inside processing assembly 118 . The cooled second portion 33 a is combined with the separated liquid (stream 35 , via stream 37 ), and the combined stream 38 is directed to the heat exchange means in the lower region of feed cooling section 118 a inside processing assembly 118 and cooled to substantial condensation. The substantially condensed stream 38 a is flash expanded through expansion valve 14 to the operating pressure of rectifying section 118 c and absorbing section 118 d, whereupon expanded stream 38 b is supplied to processing assembly 118 between rectifying section 118 c and absorbing section 118 d. Some circumstances may favor combining only a portion (stream 37 ) of liquid stream 35 with the cooled second portion 33 a , with the remaining portion (stream 40 ) supplied to the lower region of absorbing section 118 d via expansion valve 17 . Other circumstances may favor sending all of liquid stream 35 to the lower region of absorbing section 118 d via expansion valve 17 . [0051] In some circumstances, it may be advantageous to use an external separator vessel to separate cooled feed stream 31 a or cooled first portion 32 a, rather than including separator section 118 f in processing assembly 118 . As shown in FIGS. 6 and 7 , separator 12 can be used to separate cooled feed stream 31 a into vapor stream 34 and liquid stream 35 . Likewise, as shown in FIGS. 8 and 9 , separator 12 can be used to separate cooled first portion 32 a into vapor stream 34 and liquid stream 35 . [0052] Depending on the quantity of heavier hydrocarbons in the feed gas and the feed gas pressure, the cooled feed stream 31 a entering separator section 118 f in FIGS. 2 and 3 or separator 12 in FIGS. 6 and 7 (or the cooled first portion 32 a entering separator section 118 f in FIGS. 4 and 5 or separator 12 in FIGS. 8 and 9 ) may not contain any liquid (because it is above its dewpoint, or because it is above its cricondenbar). In such cases, there is no liquid in streams 35 and 37 (as shown by the dashed lines), so only the vapor from separator section 118 f in stream 36 ( FIGS. 2 and 3 ), the vapor from separator 12 in stream 36 ( FIGS. 6 and 7 ), or the cooled second portion 33 a ( FIGS. 4 , 5 , 8 , and 9 ) flows to stream 38 to become the expanded substantially condensed stream 38 b supplied to processing assembly 118 between rectifying section 118 c and absorbing section 118 d. In such circumstances, separator section 118 f in processing assembly 118 ( FIGS. 2 through 5 ) or separator 12 ( FIGS. 6 through 9 ) may not be required. [0053] Feed gas conditions, plant size, available equipment, or other factors may indicate that elimination of work expansion machine 15 , or replacement with an alternate expansion device (such as an expansion valve), is feasible. Although individual stream expansion is depicted in particular expansion devices, alternative expansion means may be employed where appropriate. For example, conditions may warrant work expansion of the substantially condensed portion of the feed stream (stream 38 a ) or the substantially condensed recycle stream (stream 45 a ). [0054] In accordance with the present invention, the use of external refrigeration to supplement the cooling available to the inlet gas from the distillation vapor and liquid streams may be employed, particularly in the case of a rich inlet gas. In such cases, a heat and mass transfer means may be included in separator section 118 f (or a collecting means in such cases when the cooled feed stream 31 a or the cooled first portion 32 a contains no liquid) as shown by the dashed lines in FIGS. 2 through 5 , or a heat and mass transfer means may be included in separator 12 as shown by the dashed lines in FIGS. 6 though 9 . This heat and mass transfer means may be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers. The heat and mass transfer means is configured to provide heat exchange between a refrigerant stream (e.g., propane) flowing through one pass of the heat and mass transfer means and the vapor portion of stream 31 a ( FIGS. 2 , 3 , 6 , and 7 ) or stream 32 a ( FIGS. 4 , 5 , 8 , and 9 ) flowing upward, so that the refrigerant further cools the vapor and condenses additional liquid, which falls downward to become part of the liquid removed in stream 35 . Alternatively, conventional gas chiller(s) could be used to cool stream 32 a, stream 33 a, and/or stream 31 a with refrigerant before stream 31 a enters separator section 118 f ( FIGS. 2 and 3 ) or separator 12 ( FIGS. 6 and 7 ) or stream 32 a enters separator section 118 f ( FIGS. 4 and 5 ) or separator 12 ( FIGS. 8 and 9 ). [0055] Depending on the temperature and richness of the feed gas and the amount of C 2 components to be recovered in liquid product stream 44 , there may not be sufficient heating available from stream 33 to cause the liquid leaving demethanizing section 118 e to meet the product specifications. In such cases, the heat and mass transfer means in demethanizing section 118 e may include provisions for providing supplemental heating with heating medium as shown by the dashed lines in FIGS. 2 through 9 . Alternatively, another heat and mass transfer means can be included in the lower region of demethanizing section 118 e for providing supplemental heating, or stream 33 can be heated with heating medium before it is supplied to the heat and mass transfer means in demethanizing section 118 e. [0056] Depending on the type of heat transfer devices selected for the heat exchange means in the upper and lower regions of feed cooling section 118 a, it may be possible to combine these heat exchange means in a single multi-pass and/or multi-service heat transfer device. In such cases, the multi-pass and/or multi-service heat transfer device will include appropriate means for distributing, segregating, and collecting stream 32 , stream 38 , stream 45 , and the distillation vapor stream in order to accomplish the desired cooling and heating. [0057] Some circumstances may favor providing additional mass transfer in the upper region of demethanizing section 118 e. In such cases, a mass transfer means can be located below where expanded stream 39 a ( FIGS. 2 , 3 , 6 , and 7 ) or expanded stream 34 a ( FIGS. 4 , 5 , 8 , and 9 ) enters the lower region of absorbing section 118 d and above where cooled second portion 33 a leaves the heat and mass transfer means in demethanizing section 118 e. [0058] A less preferred option for the FIGS. 2 , 3 , 6 , and 7 embodiments of the present invention is providing a separator vessel for cooled first portion 31 a , a separator vessel for cooled second portion 32 a, combining the vapor streams separated therein to form vapor stream 34 , and combining the liquid streams separated therein to form liquid stream 35 . Another less preferred option for the present invention is cooling stream 37 in a separate heat exchange means inside feed cooling section 118 a (rather than combining stream 37 with stream 36 or stream 33 a to form combined stream 38 ), expanding the cooled stream in a separate expansion device, and supplying the expanded stream to an intermediate region in absorbing section 118 d. [0059] It will be recognized that the relative amount of feed found in each branch of the split vapor feed will depend on several factors, including gas pressure, feed gas composition, the amount of heat which can economically be extracted from the feed, and the quantity of horsepower available. More feed above absorbing section 118 d may increase recovery while decreasing power recovered from the expander and thereby increasing the recompression horsepower requirements. Increasing feed below absorbing section 118 d reduces the horsepower consumption but may also reduce product recovery. [0060] The present invention provides improved recovery of C 2 components, C 3 components, and heavier hydrocarbon components or of C 3 components and heavier hydrocarbon components per amount of utility consumption required to operate the process. An improvement in utility consumption required for operating the process may appear in the form of reduced power requirements for compression or re-compression, reduced power requirements for external refrigeration, reduced energy requirements for supplemental heating, or a combination thereof. [0061] While there have been described what are believed to be preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto, e.g. to adapt the invention to various conditions, types of feed, or other requirements without departing from the spirit of the present invention as defined by the following claims.

A process and an apparatus are disclosed for the recovery of ethane, ethylene, propane, propylene, and heavier hydrocarbon components from a hydrocarbon gas stream in a compact processing assembly. The gas stream is cooled and divided into first and second streams. The first stream is further cooled to condense substantially all of it and is thereafter expanded to lower pressure and supplied as a feed between first and second absorbing means inside the processing assembly. The second stream is expanded to lower pressure and supplied as the bottom feed to the second absorbing means. A distillation vapor stream is collected from the upper region of the first absorbing means and directed into one or more heat exchange means inside the processing assembly to heat it while cooling the gas stream and the first stream. The heated distillation vapor stream is compressed to higher pressure and divided into a volatile residue gas fraction and a compressed recycle stream. The compressed recycle stream is cooled to condense substantially all of it by the distillation vapor stream in the one or more heat exchange means inside the processing assembly, and is thereafter expanded to lower pressure and supplied as top feed to the first absorbing means. A distillation liquid stream is collected from the lower region of the second absorbing means and directed into a heat and mass transfer means inside the processing assembly to heat it and strip out its volatile components while cooling the gas stream. The quantities and temperatures of the feeds to the first and second absorbing means are effective to maintain the temperature of the upper region of the first absorbing means at a temperature whereby the major portions of the desired components are recovered in the stripped distillation liquid stream.

CROSS-REFERENCE TO RELATED APPLICATION This application is the U.S. national phase of PCT Appln. No. PCT/EP2007/061825 filed Nov. 2, 2007 which claims priority to German application DE 10 2006 053 157.4 filed Nov. 10, 2006. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a process for evaporating constituents of a liquid by passing alternating current through the liquid. 2. Description of the Related Art In the process technology sector, it has been known for some time that, for an efficient heat transfer via hot surfaces, the temperature difference between heating surface and liquid to be heated must be at a maximum. However, problems arise when pursuing this maximum in the case of heating of liquids comprising gaseous and/or low-boiling components. When the surface temperature exceeds a critical temperature difference from the boiling point of the low-boiling component, a vapor film thus forms at the heating surface, which thermally insulates the liquid from the heating surface and therefore worsens the heat flow. This phenomenon is known as the “Leidenfrost phenomenon”. The necessary introduction of heat into the liquid in such cases can therefore be achieved only by increasing the heat exchange area. On the other hand, however, such an increase in the heating surface area is impossible or very expensive owing to the nature of the apparatus and process prerequisites. Alkylchlorosilanes are prepared by the route of the so-called direct synthesis from Si and MeCl. This affords a complex mixture of different alkylchlorosilanes with different boiling points. The target product is dichlorodimethylsilane with a boiling point of 71° C. (1013 mbar). In the distillative recovery of the pure alkylchlorosilanes from the product mixture obtainable by the direct synthesis, distillation residues with a boiling point of >71° C. are obtained. These are complex substance mixtures which contain compounds with SiSi, SiOSi, SiCSi, SiCCSi and SiCCCSi structures. The composition of these so-called “high boilers” is described in detail, for example, in EP 0 635 510. As a result of the raw material or of the selective addition of catalytically active constituents, not only Si, but also further impurities of Cu, Zn, Sn, Al, Fe, Ca, Mn, Ti, Mg, Ni, Cr, B, P and C are found in the product stream of the direct synthesis. The impurities are present in suspended or dissolved form. The dissolved impurities are usually chlorides. To heat the distillation residues, according to the prior art, for example, circulation evaporators, thin-film evaporators, short-path evaporators or heat exchangers are used. After removal of the lower-boiling components, in which the above problems exist in heat transfer, however, the thermal stability of the liquid constituents still present decreases under the influence of heat, and in the presence of the suspended or dissolved impurities. This results in oligomerization and polymerization reactions. The viscosities of the mixtures increase. This results in deposition of undesired deposits in pipelines, and in particular on the hot surfaces of the evaporators employed. Mass and energy transfer is increasingly hindered. Owing to heat transfer which has been reduced as a result, the surface temperature of the evaporator surfaces has to be increased further, which in turn leads to accelerated coverage thereof. As a result, the apparatus has to be cleaned often, the distillate yield falls, and the plant availability is unsatisfactory. A disadvantage of the above-described prior art processes is the principle of heat introduction. Heat is transferred to the liquid silanes via hot surfaces, for example metals or graphite, which are in turn heated by heat carriers (steam, heat carrier oil) or electrical heating elements. In the case of this type of heat transfer, the surface temperature of the heat-transferring medium must be higher than the liquid to be heated. These higher surface temperatures are the cause of the problems described. SUMMARY OF THE INVENTION The invention provides a process for evaporating constituents of a liquid which comprises constituents A which have high boiling points and do not boil at 1013 mbar, and constituents B which are gaseous at 20° C. and 1013 mbar and boil at least 30 K lower than the high-boiling constituents A, at least one constituent being at least partly dissociated to ions, wherein the liquid is heated by passing alternating current through it. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates one embodiment of an apparatus suitable for carrying out the process of the invention in plan view. FIG. 2 is a process flow diagram for one embodiment of the inventive process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When electrically conductive liquids comprising gaseous and/or low-boiling components are heated by alternating current, virtually all of the energy in the liquid is utilized for heating, because no thermally insulating vapor film hinders heat transfer. The surfaces of the vessels and pipelines remain free of deposits. The heating and evaporation temperature may be regulated very rapidly and within narrow tolerances, since no heat transfer via hot surfaces is present. In the event of interruption of the liquid stream, no overheating of the liquid by hot surfaces is to be expected, and the introduction of heat can be interrupted abruptly by switching off the alternating current supply. The electrical field generated by the alternating current causes charge carriers to vibrate, which heats the liquid. A previously nonconductive liquid can be made electrically conductive by adding suitable salts, such that the desired heating occurs when an alternating voltage is applied. The high-boiling and nonboiling constituents A may be partly or fully dissociated to ions, i.e. may be electrically conductive, or nonconductive. When the high-boiling and non-boiling constituents A are nonconductive, the constituents B must be electrically conductive. Examples of electrically conductive constituents B are gaseous and low-boiling acids, such as formic acid, acetic acid, hydrochloric acid, nitric acid, and gaseous and low-boiling bases, such as trimethylamine, triethylamine and ammonia. The constituents B preferably boil at least 40 K lower than the high boiling constituents A, more preferably 50 K lower than the high-boiling constituents A. The alternating voltage is preferably at least 10 V, more preferably at least 50 V and most preferably at most 1000 V. The frequency of the alternating current is at least 10 Hz, preferably at least 30 Hz, more preferably at most 10,000 Hz, and most preferably at most 10,000 Hz. Alternating current also includes three-phase current. The specific electrical resistivity of liquid is preferably from 10 10 Ωm to 10 6 Ωm, more preferably from 10 9 Ωm to 10 8 Ωm. The process can be performed continuously or batchwise. A preferred apparatus for the process is constructed as follows: the liquid is at rest or circulates within a tubelike heater composed of two or more tubes one inside another, which function as electrodes. The electrical alternating current is applied to the electrodes. The intermediate space of the tubes which are preferably in a rotationally symmetric arrangement is filled by the liquid, which is heated by the alternating current. The two or more internal tubes are separated by an electrical insulation and are connected to one another in an outwardly liquid-tight manner. The materials of the electrodes must be electrically conductive and may, for example, be metals or graphite. In a preferred embodiment, the electrically conductive fractions of an alkyl chlorosilane distillation, such as the above-described distillation residues from the direct synthesis of methylchlorosilanes with a boiling point of >71° C., are heated by passing alternating current through them. Owing to the impurities present, these have a sufficient electrical conductivity. Values of the specific electrical resistivity of from 1.10 9 Ωm to 10.10 7 Ωm are determined. The constituents which have been dissociated to ions remain in the bottoms of the evaporator in the case of a distillation, or are discharged continuously via the bottom effluent, and do not influence the quality of the distillates. In a further preferred embodiment, the electrically conductive reaction mixtures of chlorosilanes and ethanol or methanol are heated and evaporated or outgassed by means of passage of alternating current. In a further preferred embodiment, the electrically conductive reaction mixture is prepared from chlorosilanes, such as tetrachlorosilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane or mixtures thereof, and an aqueous or nonaqueous alcohol, such as ethanol or methanol, by means of passage of alternating current. The conversion of the reaction can be completed only by driving out the HCl gas which forms in the reaction by increasing the temperature. Since this mixture is saturated with HCl, a thermally insulating gas layer is formed at the interface thereof in the case of heating by means of a heat exchanger. Heating by means of alternating current avoids this problem and allows inexpensive heating which is very effective based on the space requirement, since the heat is generated directly in the liquid volume and need not be transported over a large interface of a heat exchanger. In the example which follows, unless stated otherwise, a) all amounts are based on the mass; b) all pressures are 0.10 MPa (abs.); c) all temperatures are 20° C. Example The example is illustrated by FIG. 1 , which shows a heating and evaporating apparatus as a section view. In this apparatus, the liquid ( 5 ) enters the heating and evaporating apparatus from below, and the liquid is heated in the intermediate space ( 4 ) and exits again at the top as heated liquid or as vapor ( 6 ). Between the electrodes ( 1 ) and ( 2 ) which are in a rotationally symmetric arrangement flows an electrical alternating current. The electrodes ( 1 ) and ( 2 ) are separated from one another by an electrical insulation ( 3 ). The electrodes ( 1 ) and ( 2 ) are installed in a vertical glass vessel ( 10 ). The vapor is passed into a column with random packing ( 9 ), while an overflow of liquid is recirculated through conduit 11 to the vessel. The isolating transformer ( 7 ) and the flow regulator unit ( 8 ) feed the electrodes ( 1 ) and ( 2 ) with regulable electrical energy. Technical data of the heating and evaporating apparatus: electrode material: Cr, Ni steel length of the electrode ( 1 ): 200 mm diameter of the electrode ( 1 ): 50 mm diameter of the electrode ( 2 ): 30 mm electrode separation ( 4 ): 10 mm liquid volume: 700 ml Test results: start of the evaporation test: temperature of the liquid in the inlet ( 5 ) 30° C. temperature of the liquid in the vessel ( 4 ) 30° C. voltage: 240 V, frequency: 50 Hz, current: 0.3 A specific electrical resistivity: 4.5×10 9 Ωm temperature (vapor) at the outlet ( 6 ) 30° C. temperature of the electrodes ( 1 ) and ( 2 ): 30° C. during the continuous evaporating operation: temperature of the liquid in the inlet ( 5 ) 30° C. voltage: 240 V, frequency: 50 Hz, current: 0.3 A temperature of the liquid in the vessel ( 4 ) 220° C. specific electrical resistivity: 4.5×10 8 Ωm temperature (vapor) at the outlet ( 6 ): 190° C. temperature of the electrodes ( 1 ) and ( 2 ): 220° C. After operation for 50 h, the surfaces of the electrodes ( 1 ) and ( 2 ) exhibited neither any deposition nor any encrustation, nor was any abrasion of the electrode material evident.

Mixtures containing high boiling and low boiling components, at least one component being dissociatable into ions, are separated effectively by heating by passing an alternating electrical current through the mixture. The process is particularly effective in the workup of crude alkylchlorosilanes from the direct synthesis.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a method and system for creating a personalized display for a user of an electronic network. More specifically, the present invention relates to a method and system for determining a user's interests from the content of electronic documents viewed by the user and providing recommended documents and recommendation packages to a user based upon the determined interests. 2. Description of Related Art The number of Internet users continues to increase at an explosive rate. The World Wide Web (“Web”) has therefore now become a significant source of information, as well as products and services. As the numbers of Web users rise, Internet commerce, also referred to as “e-commerce” companies, and content providers are increasingly searching for strategies to target their information, products and services to those Web users. One technique that is currently being used to provide Web users with more relevant and timely information is “personalization.” Personalization can include sending a user an e-mail message tailored to that user, or providing customized Web pages that display information selected by, or considered of interest to the user. Personal merchandising, in which a unique view of an online store, featuring offerings targeted by customer profile is displayed, is another effective personalization technique. Personalization facilitates the targeting of relevant data to a select audience and can be a critical factor in determining the financial success of a Web site. Internet companies wishing to create highly personalized sites are currently poorly served by both personalization technology vendors and customer relationship marketing product vendors. Each of these vendors offers only part of the overall solution. In addition, a significant investment of time and resources by the client is required to deploy these current solutions. Most prior art personalization and Web user behavior (also known as clickstream) analysis technologies maintain a record of select Web pages that are viewed by users. This record, known as the “Web log” records which users looked at which Web pages in the site. A typical Web log entry includes some form of user identifier, such as an IP address, a cookie ID or a session ID, as well as the Uniform Resource Locator (“URL”) the user requested, e.g. “index.html.” Additional information such as the time the user requested the page or the page from which the user linked to the current Web page can also be stored in the Web log. Traditionally, such data has been collected in the file system of a Web server and analyzed using software, such as that sold by WebTrends and Andromedia. These analyses produce charts displaying information such as the number of page requests per day or the most visited pages. No analysis is performed of the internal Web page structure or content. Rather, this software relies on simple aggregations and summarizations of page requests. The prior art personalization methods also rely on the use of Web logs. One technology used in prior art personalization methods is the trend analysis method known as collaborative filtering. Examples of collaborative filtering systems are those of Net Perceptions (used for Amazon.com's book recommendations), Microsoft's Firefly, Personify, Inc., and HNC Software Inc.'s eHNC. One method of collaborative filtering is trend analysis. In trend analysis collaborative filtering, the pages requested by a user are noted, and other users that have made similar requests are identified. Additional Web pages that these other users have requested are then recommended to the user. For example, if User A bought books 1 and 2 from an on-line bookseller, a collaborative filtering system would find other users who had also bought books 1 and 2 . The collaborative filtering system locates 10 other users who on average also bought books 3 or 4 . Based upon this information, books 3 and 4 would be recommended to User A. Another type of collaborative filtering asks the users to rank their interest in a document or product. The answers to the questions form a user profile. The documents or products viewed by other users with a similar user profile are then recommended to the user. Systems using this technique include Reel.com's recommendation system. However, collaborative filtering is not an effective strategy for personalizing dynamic content. As an example, each auction of a Web-based auction site is new and therefore there is no logged history of previous users to which the collaborative filtering can be applied. In addition, collaborative filtering is not very effective for use with infrequently viewed pages or infrequently purchased products. Another technique used to personalize Internet content is to ask the users to rank their interests in a document. Recommendations are then made by finding documents similar in proximity and in content to those in which the user has indicated interest. These systems may use an artificial intelligence technique called incremental learning to update and improve the recommendations based on further user feedback. Systems using this technique include SiteHelper (Ngu and Wu, 1997), Syskill & Webert (Pazzani et al., 1996) Fab (Balabanovic, 1997), Libra (Mooney, 1998) and Web Watcher (Armstrong et al., 1995). Another technique that has been used to personalize Internet content is link analysis. Link analysis is used by such systems as the search engine Direct Hit and Amazon.com's Alexa®. The prior art link analysis systems are similar to the trend analysis collaborative filtering systems discussed previously. In the link analysis systems, however, the URL of a web page is used as the basis for determining user recommendations. Other prior art personalization methods use content analysis to derive inferences about a user's interests. One such content analysis system is distributed by the Vignette Corporation. In the content analysis method, pages on a client's Web site are tagged with descriptive keywords. These tags permit the content analysis system to track the Web page viewing history of each user of the Web site. A list of keywords associated with the user is then obtained by determining the most frequently occurring keywords from the user's history. The content analysis system searches for pages that have the same keywords for recommendation to the user. This prior art content analysis systems is subject to several disadvantages. First, tagging each page on the client's Web site requires human intervention. This process is time-consuming and subject to human error. The prior art content analysis systems can only offer recommendations from predefined categories. Furthermore, the prior art content analysis systems require a user to visit the client's Web site several times before sufficient data has been obtained to perform an analysis of the user's Web page viewing history. Other prior art content analysis systems automatically parse the current document and represent it as a bag of words. The systems then search for other similar documents and recommend the located documents to the user. Such systems include Letizia (Lieberman, 1995) and Remembrance Agent (Rhodes, 1995). These content analysis systems base their recommendations only on the current document. The content of the documents in the user's viewing history are not used. Many Web sites offer configurable start pages for their users. Examples of configurable start pages include My Yahoo! and My Excite. To personalize a start page using the prior art method, the user fills in a form describing the user's interests. The user also selects areas of interest from predefined categories. The user's personalized start page is then configured to display recommendations such as Web pages and content-based information that match the selected categories. This prior art method, however, is not automated. Rather, the user's active participation is required to generate the personalized Web start page. Furthermore, pages on the client's Web site must be tagged to be available as a recommendation to the user. In addition, recommendations can only be offered from predefined categories. Thus, the prior art personalized start pages may not provide relevant content to users who have eclectic interests or who are not aware of or motivated to actively create a personalized start page. Content Web sites are increasingly generating income by using advertising directed at users of the Web sites. In the prior art, advertising was targeted to users by using title keywords. In this method, keywords in the title of a Web page or otherwise specified by the author of the page are compared with the keywords specified for a particular advertisement. Another technique used is to associate specific ads with categories in a Web site. For example, advertisements for toys might be associated with Web site categories related to parenting. However, these prior art methods require human intervention to select the keywords or to determine the associations of advertisements with particular categories. Furthermore, the prior art methods cannot readily be used to target advertisements to dynamic content. It would therefore be an advantage to provide a method and system for providing Internet end users with relevant and timely information that is rapid to deploy, easy and inexpensive for client Web sites to use. It would be a further advantage if such method and system were available to automatically and dynamically determine the interests of a user and recommend relevant content to the user. It would be yet another advantage if such method and system were available to provide for a user a personalized recommendation package, such as an automatically generated start page for each user who visits a Web site. SUMMARY OF THE INVENTION One embodiment of the present invention provides a computer-implemented method for creating a personalized display of electronic-mail documents. The method includes creating a database entry including a user ID for each user of a client document server, the document server being coupled to an electronic-mail client. Requests for access to an e-mail document at the client document server are then tracked by a tracking module. Information regarding the request document is then stored, the information including information about the document that is obtained through textual analysis of the requested document. The stored information is then analyzed to construct a profile of the user requesting the document; that profile is then associated with the user ID. From the profile, interests of the user are determined utilizing a recommendation application. The user is then provided with electronic-mail notifications concerning recommended viewing of additional documents on the document server, The recommendations are based on the determined interests of a particular user. In another embodiment of the present invention, a method for automated analysis of electronic-mail documents is provided. The method includes a user viewing a document at a client document server, the document server being coupled to an electronic-mail client. Internal content information from the viewed document is transmitted to a recommendation application, which generates recommendation links in response to the transmitted content information. A further embodiment of the present invention provides an electronic-mail document analysis method. Through this method, internal content information of an e- mail document accessed by a user is received. Themes and concepts of the document are then determined. The document is then grouped into a folder on the client document server according to the themes and concepts; the document server being coupled to an electronic-mail client. Keywords are extracted from the documents in the folders to allow for summarization of the folder. A profile is then developed corresponding to a particular user and based on the themes and concepts of the folder. Utilizing this profile, personalized recommendations are generated with respect to viewing additional e-mail documents on the server. In yet another embodiment of the present invention, a method is disclosed for customizing electronic-mail document information provided over an electronic network. In this method, requests by a user of a client document server for e-mail documents are tracked, Filtered content is extracted from the requested e-mail documents and analyzed. A profile is then constructed based on the analyzed content and a profile is developed. Based on the profile, interests of the user are determined and the user is provided with subsequent information as to e-mail documents for review by the user. An embodiment of the present invention also provides a system for creating a personalized display of electronic-mail documents. The system includes means for: tracking requests by a user of a client document server for a document on the client document server; extracting filtered content from the requested document; analyzing the filtered content; constructing a profile of the user from the analyzed content determining the interests of the user; and providing the user with recommended information by email based upon the determined interests of the user. A further embodiment of the present invention provides a system for providing personalized electronic-mail document information including an e-mail client coupled to a computing device. A processor in the system executes software instructions to extract filtered content a viewed document; analyze the filtered content determine a theme or concept of the document cluster the document into a folder according to a theme or concept in the document; construct a profile of the user from the analyzed content; determine the interests of the user based on the user profile; categorize a second document according to the theme or concept of the folder; and recommend that the user access the second categorized document, the recommendation being based on the theme or concept of the second document. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram of the personalization method according to the present invention FIG. 2 is a block diagram of a computer network system according to one embodiment of the present invention. FIG. 3 is a diagram of the system for Internet personalization, according to the preferred embodiment of the invention. FIG. 4 is a flow chart of the method for Internet personalization, according to the preferred embodiment of the invention FIG. 5 is a flow chart illustrating the formation of interest folders, according to the present invention. FIG. 6 is an example of a user profile generated by the recommendation software, according to the preferred embodiment of the present invention. FIG. 7 is an example of a recommendation start page according to the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION The present invention is a computer-implemented method and system for creating a personalized display for a user of an electronic network. The method can be used with any electronic network including the Internet and, more specifically, the World Wide Web. The preferred embodiment of the present invention includes components for analyzing Web user behavior, for remote user tracking, and for interacting with the user. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one skilled in the art that the present invention may be practiced without the specific details. In other instances, well-known structures and devices are shown in block diagram form to facilitate explanation. The description of preferred embodiments is not intended to limit the scope of the claims appended hereto. Features of the Invention: The present invention provides a user personalization service to businesses and organizations that provide document servers. In the preferred embodiment, the invention is directed primarily to e-commerce and Internet businesses. The invention can be used to provide personalization and Web user behavior (referred to herein as “clickstream”) analysis. This service enables e-commerce and Internet sites to deliver highly personalized and relevant information to each of their users. The invention can be used with, but is not limited to, content sites and e-commerce sites. FIG. 1 is a flow diagram of the personalization method according to the present invention. The invention uses the recommendation software to remotely collect and process end user behavior 100 . Each user action is considered and analyzed in terms of the structural content of the document that is actually viewed by the user 105 . The interests of the user are determined 110 and the user can thereby be provided with a list of recommended documents that are selected according to the analysis of the content of the documents viewed by the user 115 . In addition, the invention can also be used to generate a personalized recommendation package, such as, in the preferred embodiment, a personalized start page or a personalized product catalogue for each user. The present invention is advantageous because, by having more relevant information delivered to each end user, the client can draw users back to the client document server and can create a barrier to their switching to a competing document server. This can result in increased advertising revenue accruing to the client, and e-commerce clients can receive more revenue from sales because each user will receive more relevant suggestions of products to buy and will return more regularly. The invention offers significant advantages to clients over the prior art personalization methods. For example, using the invention, a personalized recommendation package can be rapidly deployed, with minimal effect on the original client document server during deployment. The present invention avoids the requirement for clients to develop and invest in complex techniques for their own tracking and personalization and is therefore more economical than prior art personalization schemes. In addition, the present invention will enable clients to retain customers through improved one-to-one interaction as well as drive revenue from increased sales through cross-selling and up-selling of their products. Definitions: For purposes of this application, the present invention will be referred to as the “recommendation system”. The use of the term recommendation system is in no way intended to limit the scope of the present invention as claimed herein. As described in further detail herein, the recommendation system can include any suitable and well-known hardware and software components, and in any well-known configuration to enable the implementation of the present invention. The present invention is also implemented using one or more software applications that are accessible to the recommendation system. For purposes of this application, these software applications will be called the “recommendation software.” The use of the term recommendation software is in no way intended to limit the scope of the present invention as claimed herein. The personalization service according to the present invention is preferably provided by an entity, referred to for purposes of this application as the market analyst. The term “client,” as used herein, refers to the operator of a document server. In the preferred embodiment of the present invention, the client is the operator/owner of a Web site. The term “user” refers herein to an individual or individuals who view a document served by the client's document server. The recommendation system can include the market analyst's computers and network system, as well as any software applications resident thereon or accessible thereto. For purposes of this application, these components will be collectively referred to as the “marketing system.” The use of the term marketing system is in no way intended to limit the scope of the present invention as claimed herein. As described herein, the marketing system can include any suitable and well-known hardware and software components, and in any well-known configuration to enable the implementation of the present invention. In the presently preferred embodiment, the marketing system is maintained separately from the client document server. However, in alternative embodiments, the hardware and software components necessary to provide the personalization service can be a part of the client document server. In these alternative embodiments, the hardware and software components can be operated by, for example, a client e-commerce or Internet business itself. The client's computers and network system, as well as any software applications resident thereon or accessible thereto will be collectively referred to, for purposes of this application, as the “document server.” The term “document” is used to represent the display viewed by a user. In a Web-based embodiment, the document is a Web page. In an e-mail embodiment, the document can be an e-mail message or listing of messages, such as an in-box. As used herein, the term “database” refers to a collection of information stored on one or more storage devices accessible to the recommendation system and recommendation software, as described previously. The use of the term database is in no way intended to limit the scope of the present invention as claimed herein. The database according to the present invention can include one or more separate, interrelated, distributed, networked, hierarchical, and relational databases. For example, in the presently preferred embodiment of the invention, the database comprises a document database and a user database. The database can be created and addressed using any well-known software applications such as the Oracle 8™ database. The database according to the present invention can be stored on any appropriate storage device, including but not limited to a hard drive, CD-ROM, DVD, magnetic tape, optical drive, programmable memory device, and Flash RAM. The term “content sites” refers to Internet sites that are primarily providers of content based information such as news articles. Examples of content Web sites include CNET, MSN Sidewalk, and Red Herring. These sites can generate income from advertising, as well as syndication or referral fees for content. A content site's income can therefore be greatly dependent upon the Web site's ability to retain users. E-commerce sites are Internet sites whose primary business is the sale of goods or services. E-commerce businesses derive revenue from the sale of goods on their Web sites. A significant factor in the success of an e-commerce Web site is the site's ability to attract and retain customers. Syndicated content, as used herein, refers to other publisher's content that can be integrated into a client's document server. Hardware Implementation: Any or all of the hardware configurations of the present invention can be implemented by one skilled in the art using well known hardware components. In the presently preferred embodiment, the present invention is implemented using a computer. Such computer can include but is not limited to a personal computer, network computer, network server computer, dumb terminal, local area network, wide area network, personal digital assistant, work station, minicomputer, and mainframe computer. The identification, search and/or comparison features of the present invention can be implemented as one or more software applications, software modules, firmware such as a programmable ROM or EEPROM, hardware such as an application-specific integrated circuit (“ASIC”), or any combination of the above. FIG. 2 is a block diagram of a computer network system 200 according to one embodiment of the present invention. Any or all components of the recommendation system, the marketing system, the client document server, and the user's computer can be implemented using such a network system. In computer network system 200 , at least one client document server computer 204 is connected to at least one user computer 202 and to at least one marketing system computer 212 through a network 210 . The network interface between computers 202 , 204 , 212 can also include one or more routers, such as routers 206 , 208 , 214 that serve to buffer and route the data transmitted between the computers. Network 210 may be the Internet, a Wide Area Network (WAN), a Local Area Network (LAN), or any combination thereof. In one embodiment of the present invention, the client document server computer 204 is a World-Wide Web (“Web”) server that stores data in the form of ‘Web pages’ and transmits these pages as Hypertext Markup Language (HTML) files over the Internet network 210 to user computer 202 . Similarly, the marketing system computer can also be a WWW server. Communication among computers 202 , 204 , 212 can be implemented through Web-based communication. In some embodiments of the present invention, computers 202 , 204 , and 212 can also communicate by other means, including but not limited to e-mail. It should be noted that a network that implements embodiments of the present invention may include any number of computers and networks. Software Implementation: Any or all of the software applications of the present invention can be implemented by one skilled in the art using well known programming techniques and commercially available or proprietary software applications. The preferred embodiment of the present invention is implemented using an Apache Web server and Web-based communication. However, one skilled in the art will recognize that many of the steps of the invention can be accomplished by alternative methods, such as by e-mail. In the preferred embodiment of the invention, the operating system for the marketing system is Red Hat™ Linux™. However, any other suitable operating system can be used, including but not limited to Linux™, Microsoft Windows 98/95/NT, and Apple OS. The recommendation software can include but is not limited to a Web server application for designing and maintaining the market analyst's Web site, a database application for creating and addressing the database, software filters for screening the content of documents served by the client's document server, a text clustering application, a text categorization program, a presentation module, a spider and/or search engine for seeking relevant documents, an e-mail application for communication with users, a spread sheet application, and a business application for verifying orders, credit card numbers, and eligibility of customers. The recommendation software can include any combination of interrelated applications, separate applications, software modules, plug-in components, intelligent agents, cookies, JavaBeans™, and Java™ applets. (Java and all Java-based marks are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and other countries.) The software applications that comprise the recommendation software can be stored on any storage device accessible to the marketing system, including but not limited to a hard drive, CD-ROM, DVD, magnetic tape, optical drive, programmable memory device, and Flash RAM. It will be readily apparent to one of skill in the art that the software applications can be stored on the same or different storage devices. In the preferred embodiment of the invention, the clustering application is implemented using the C programming language. However, in alternative embodiments, the clustering application can be implemented using other well-known programming languages, including but not limited to C++, Pascal, Java, and Fortran. The clustering application is preferably stored on the marketing system, but can alternatively be stored on any component accessible to the marketing system. In the preferred embodiment of the invention, the presentation module is implemented using Perl scripts and SQL. However, in alternative embodiments, the presentation module can be implemented in any other suitable programming language. The presentation module is preferably stored on the marketing system, but can alternatively be stored on any component accessible to the marketing system. In the preferred embodiment of the invention, the tracking module that is associated with the client's document server is implemented using Perl scripts. However, in alternative embodiments, the tracking module can be implemented using other well-known programming languages and software applications including but not limited to TCL, Java™ servlet, and Microsoft Active Server Page (“ASP”) applications. The tracking module is preferably stored on the client's document server, but can alternatively be stored on any component accessible to the document server. In the preferred embodiment of the present invention, content analysis and the generation of the user profiles, recommendations, and recommendation packages are all performed by the marketing system and recommendation software. However, in alternative embodiments of the present invention, any or all of these functions can also be performed by the client document server. The client document server performs the functions of data collection, data transfer to the marketing system and presentation of the recommendations and recommendation packages to the user. In the preferred embodiment of the invention, the database is implemented using Data Konsult AB's MySQL. However, in alternative embodiments, the tracking module can be implemented using other software applications including but not limited to Postgres, and Oracle® and Informix® database applications. The database is preferably stored on the marketing system server, but can alternatively be stored on any component accessible to the marketing system. The recommendation software is preferably a separate application from the marketing system operating system. However, one skilled in the art will readily recognize that the present invention can also be fully integrated into the marketing system operating system. DESCRIPTION OF THE EMBODIMENTS FIG. 3 is a diagram of the system 300 for Internet personalization, according to the preferred embodiment of the invention. A tracking module 306 is installed at the client document server 304 . In the presently preferred embodiment, a Web site manager embeds Hypertext Markup Language (“HTML”) links to the marketing system in the client document server and, specifically, on the client document server's start page. While the tracking module is implemented as a Perl module embedded in Apache in the preferred embodiment, the tracking can alternatively be implemented in other ways, for example using hypertext links. At the client document server 304 , the tracking module logs every request made by every user for documents and sends this information to the database 310 associated with the marketing system 308 . In the preferred embodiment of the present invention, the database 310 includes a document database module 312 for storing information relating to the document and contents of the document, and a user database module 314 for storing information relating to the user's document viewing behavior. In the preferred embodiment, each user is sent a user-identifier (“user ID”) 316 that is stored on the user's computer 302 . The tracking module sends the user ID and a document identifier (“document ID”) 318 to the marketing system 308 in response to each user's request to view a document on the client document server 304 . The recommendation software 320 is then used to process this information to construct a profile for the user and to make recommendations based thereupon. In the preferred embodiment, the presentation module 322 is operable to configure a recommendation package for the user into any desired format or appearance. FIG. 4 is a flow chart of the method for Internet personalization, according to the preferred embodiment of the invention. A tracking module is installed at a client document server. In the preferred embodiment of the present invention, the client document server is a Web site. However, in alternative embodiments, the present invention is implemented with a client e-mail or File Transfer Protocol (“ftp”) system. In this preferred embodiment, when a user requests a document on the client document server 400 , the tracking module searches for a user ID on the user's computer 405 . If a user ID is not located, the tracking module creates a new entry in the database and sends a user ID to the user's computer 410 . In the preferred embodiment, this involves sending a cookie to the user's Web browser. However, any other appropriate identifier can alternatively be used, such as an IP number. The tracking module installed at the client document server logs every request made by every user for documents and sends this information to the marketing system. Thus, when the user requests a different document in the client's document server, the tracking module logs this action by sending the user ID and a document identifier (“document ID”) to the database 415 . In the presently preferred embodiment, the document ID is the URL of the particular Web page. However, other document IDs such as a product number can also be used. In alternative embodiments of the present invention, the tracking module can send additional information, such as the time spent viewing a document and the price of items displayed on the document to the marketing system database. The subsequent actions on the client document server of any user who is entered in the marketing system database are similarly recorded in the marketing system database. In yet another embodiment of the present invention, the marketing system can act as a proxy server. In this embodiment, the tracking module could be installed at either the marketing system or the client document server, or at both. In this embodiment, the user requests documents from the marketing system. In response to such request, the marketing system requests the appropriate documents from the client document server and provides them to the user. In the preferred embodiment, documents and meta-data about the documents are stored in the document database module of the database. The document database can include other information obtained from the client, such as the price or size of an item. The user database module can include information obtained from the user, for example, whether the user placed a bid on an item, the user's name and address, which documents were viewed by the user, whether the user purchased an item, user profile or the time the user spent viewing a particular document. Information obtained from text analysis, document clustering, or document categorization can also be stored in the user database module. As the user browses through the client's document server, the marketing system uses the recommendation software to process the user's behavior, analyze the content of the user's document views and construct a profile for the user 420 . The recommendation software uses the information in the user database to make a determination of what interests the particular user. For example a user who browsed an auction Web site for antique Roman coins and baseball cards would be determined to have two interests. These interests are determined by an analysis of the actual content of each browsed document. The recommendation software uses any or all of the gathered information about the user to search through the content on the client's document server to find the local content considered most relevant to that particular user 425 . In the preferred embodiment of the invention, the marketing system regularly retrieves the content for each document and/or product on the client document server, for example, once per hour. The recommendation software analyzes each document a user views in terms of the (a) content and (b) ancillary information related to a user's viewing a document. The present invention uses this analysis of document content to provide a model for automatically deriving reasonable inferences regarding a user's interests and intentions in viewing particular documents. This model can then be used to generate a list of additional documents on the client document server, or elsewhere such as on another document server, that might be of interest to the user. These “recommendation documents” and “recommendation packages” provide a suggested product and/or document that is tailored to a user's interests and to the product and/or document that a user is currently viewing. The marketing system sends the recommended document(s), or a link to the recommended document(s) back to the client's document server 430 . The recommendations can include but are not limited to URLs, product numbers, advertisements, products, animations, graphic displays, sound files, and applets that are selected, based on the user profile, to be interesting and relevant to the user. For example, the most relevant ad for any page can be rapidly determined by comparing the current user profile with the description of the available advertisements. The user recommendations can be provided as a part of a personalized recommendation package. In the preferred embodiment of the invention, the recommendation package is a personalized Web start page for the user. For an e-mail server-based embodiment, the recommendation package can be personalized e-mail. The recommendation package gives each end user a unique view of the client document server by showing information that is relevant to that user. In the preferred embodiment, the document displayed to the user by the client document server includes a hypertext link that is used to access the personalized Web start page. When the user clicks on the hypertext link, the personalized start page is dynamically generated by the recommendation software at the marketing system. Each user will see a different view of the Web site based on the user's personal likes or dislikes, as determined automatically by the user's previous browsing behavior. Such automatic personalization minimizes the need for the client to specifically control document server content and permits the client to transparently provide information regarding the user's interests. When the user clicks on a link to this personalized Web page on the client's document server, the personalized page is served to the user from the marketing system. Although the page is served from the marketing system, the presentation module is operable to configure the personalized page to conform to the client's own branding and image, thereby maintaining the look and feel of the client's site. In addition, the Uniform Resource Locator (“URL”) link, which is the “Web address” of the personalized page is configured to appear to be a link to the client document server. In alternative embodiments of the present invention, the personalized Web page does not have to maintain the look and feel of the client's document server, but can have any desired appearance. In such embodiments, the presentation module is operable to configure the recommendation package into any desired format or appearance. Furthermore, there is no requirement that URL link provided to the user appear to link the Web page to any particular Web site. In one embodiment of the present invention, the user can switch back at any time to the from the personalized recommendation package, such as the personalized Web start page, to a non-personalized document, such as the generic start page of displayed by the client document server. In another embodiment of the invention, portions of the client's document server can be mirrored on the marketing system. The recommendation software can then search through the mirrored client document server for content relevant to the particular user. The recommendation software can also optionally include syndicated content from the marketing system or from the client's syndication providers in the personalized page. New standards based on XML such as Information Content Exchange (“ICE”) will facilitate the incorporation of syndication into Web sites. The recommendation software according to the present invention uses information regarding the client's document server structure in the personalization analysis. For example, if a user typically looks at books in a particular category of a bookseller's Web site, this information will be used by the recommendation software, in addition to any content information, to create a personalized view of the site for the user. FIG. 5 is a flow chart illustrating the formation of interest folders, according to the present invention. The recommendation software thereby extracts and organizes the interests and document viewing habits of the user. In the preferred embodiment of the invention, the recommendation software uses a statistical process referred to herein as document clustering to group together those documents of the client document server that have been viewed by the user according to their common themes and concepts. For each individual user, the recommendation software clusters those documents that have the most themes and concepts in common with one another into interest folders 505 . In the preferred embodiment, the recommendation software continually monitors each user and continually updates the user's interest folders and profile. The set of interest folders for each user can also be used to target advertisements to each user rather than, or in addition to content. In the presently preferred embodiment, each advertisement has an associated simple description. This description is specified by the creator of the ad. The description can be associated with the advertisement by methods including embedding in meta-language tags or in XML. Document clustering according to the present invention includes the automatic organization of documents into the most intrinsically similar groups or segments. As an example of the application of using document clustering, a user who enters the search term “Venus” into a search engine will likely receive documents about (a) Venus the planet; and (b) Venus the goddess. In the preferred embodiment of the present invention, the search results would therefore be clustered accordingly into two separate interest folders. None of the concepts in groups (a) and (b) are predefined but are formed as a result of the intrinsic similarity of the documents in each cluster. As a result, the clustering framework is very flexible for automatic organization of documents into groups. In the preferred embodiment of the present invention, the recommendation software uses a proprietary clustering algorithm to form the user interest folders. The clustering algorithm uses the textual content of the documents viewed by a user, in combination with structural information about the document server, and ancillary information about the user to determine the interest folders for a user. In an alternative embodiment, a clustering algorithm is also used to segment large numbers of users into different user folders. However, one skilled in the art would readily recognize that any other suitable clustering algorithm could also be used in alternative embodiments of the invention. One significant feature of the clustering algorithm used by the invention is that the output of the algorithm can be readily viewed and understood. Each document cluster (interest folder) is described by the most relevant keywords of the documents within the document cluster 510 . This feature enables both users and marketers to understand and control the degree of personalization and targeting that is made. The recommendation software can also be used to categorize documents 515 . Document categorization is the automatic placement of new documents into existing predefined categories. Document categorization is used in the preferred embodiment of the present invention to select, from a database, documents that match a user's interest folders. A document categorizer can learn how to place new documents into the correct categories so that, for example, a new Web page or product can be automatically placed into the correct user interest folder. As an example, given a user interest folder containing documents about Roman coins, a document categorizer could select the most relevant products for that user from a particular Web site. Because Web pages are diverse in structure and form, the recommendation software uses customizable filters that extract only the content deemed to be relevant to users. In addition to extracting the content of each page, the recommendation software uses filters to extract structure within this content. The present invention can also use adaptive filtering algorithms that analyze a Web site and review different filter known structures to automatically find an appropriate filter for a particular Web site. For example, an on-line bookseller's Web page can display information regarding a book that is available for purchase. The Web page can include such structure as: book price, author, description, and reviews. The fields of the document database are preferably customized to the bookseller's Web page such that the names of each of these fields can automatically be stored therein. The fields of the user database are similarly configured for automatic storage of information obtained from the user. This information is then included in the recommendation software's analysis. In the preferred embodiment of the invention, the recommendation software uses proprietary filters that are specific for each Web site. For example, each of two music distribution Web sites would have its own specific customized filter. Alternatively, the recommendation software can use filters that are specific for different types of Web sites. As an example, the recommendation software can have separate specific filters for such sites as auction Web sites, bookseller Web sites, and music Web sites. One skilled in the art would recognize that the recommendation software can also use any suitable commercially available filters. In the preferred embodiment, each interest folder is automatically summarized in terms of the most relevant keywords from the associated collection of pages in the folder. Keywords can be determined, for example, by using an information theoretic measure such as “Minimum Message Length” (“MML”) to determine the most relevant words to define a user's interest folder. Filters, such as the removal of “stopwords,” can be used to screen out common prepositions, articles, possessives, and irrelevant nouns, adjectives, etc. The keywords for a user's interest folders can be determined in any appropriate manner. In one embodiment of the invention, the message length of sending each word using the population frequency of the word is determined. This message length is referred to herein as the population message length of the word. The message length of sending each word using the interest folder's frequency of the word is then determined. This message length is termed herein the interest folder message length of the word. For each keyword, the interest folder message length of that keyword is then subtracted from the population message length of the word. The keywords for the user's interest folders are defined to be the words in which this distance is the greatest. FIG. 6 is an example of a user profile 600 generated by the recommendation software, according to the preferred embodiment of the present invention. The profile shown in the personalized Web page of FIG. 6 comprises two different interest folders 602 , 604 for a user of an on-line auction Web site. Each interest folder contains pages which are intrinsically similar to one another and dissimilar to pages in other interest folders. A specific interest folder contains a set of links 610 to auctions the user has viewed that are related to the theme of the interest folder. An interest folder can also include additional information including but not limited to information regarding the history of the user's Internet viewing, recommendations for the user, a summary of the user's purchases. In the example illustrated in FIG. 6 , each interest folder also has an associated set of keywords 612 that summarize the most important concepts of the particular interest folder, as determined by the recommendation software. In the preferred embodiment of the present invention, the user can display and edit the user profile of FIG. 6 . For example, if the user is no longer interested in Roman antiquities, this interest folder 612 can be deleted from the user profile. It is common for a user to regularly return to particular Web sites to look for specific information having a similar theme. For example, a user of an on-line auction Web site who collects Roman coins might frequently return to the antiquities section of the auction Web site. The present invention uses the profile of each user to automatically find other relevant pages in the Web site to recommend to the user. In the previous example, the recommendation software would search through all of the auctions currently running on the on-line auction Web site to search for those that match most closely with each of the user's interest folders. The present invention uses a sophisticated search engine that can incorporate any or all of the content and ancillary information in the user profile. FIG. 7 is an example of a recommendation start page 700 according to the preferred embodiment of the present invention. The user's interest folders 602 , 604 are displayed on the recommendation document. Each interest folder includes links to documents 610 that the recommendation software has selected based upon the user's profile. In the previous example of the Roman coin collector, the folder relating to this interest 604 includes links to auctions for Roman and other ancient coins. In the preferred embodiment of the present invention, a user can view and manage the user's profile. Thus, in the previous example, the user may wish to remove certain sections of the profile in order to stop receiving recommendations about Roman coin auctions. The recommendation software user interface allows users to delete interest folders, add extra keywords to an interest folder, or create their own interest folder from pages on a client document server. Because the user profiles are based primarily on keywords, the present invention can be used to not only target a user with content from the same Web site that the user is currently browsing, but also with content from other Web sites. For example, a user with an interest in collecting Roman coins could be automatically targeted with content from on-line publications related to antiquities. While the present invention is designed to automatically match users with relevant content, it is recognized that a client might wish to customize the manner in which users receive special promotions, event announcements and special news items. In the example of the Roman coin collector, a marketer of cruises might wish to target the collector with a promotion for a cruise of the Mediterranean. To enable marketers to interact easily with their users, the present invention provides the functionality to allow a marketer to search through the users' profiles using keywords in a standard search paradigm. Groups of users can be selected and then matched with relevant content either by hand or automatically using the present invention's content matching technology. While the invention is described in conjunction with the preferred embodiments, this description is not intended in any way as a limitation to the scope of the invention. Modifications, changes, and variations which are apparent to those skilled in the art can be made in the arrangement, operation and details of construction of the invention disclosed herein without departing from the spirit and scope of the invention. One skilled in the art will readily recognize that, in an embodiment that features Web-based interaction between the user, the market analyst, and the marketer, there are many different ways in which communication can be implemented through the Web page graphical user interface. For example, this communication can be implemented using elements including but not limited to a dialog box, check box, combo box, command button, list box, group box, slider bar, text box. In the preferred embodiment of the present invention, all client's and users use computer-implemented methods to interact with the market analyst, for example, using a Web page or e-mail. However, in alternative embodiments, one or more such customers can communicate with the market analyst using other methods of communication, including but not limited to telephone, fax, and mail. For example, in one embodiment, a user can request modifications to the user's profile by making a telephone call to a client or to the market analyst.

Systems and methods for providing a user with personalized recommendations of accessing electronic-mail at an electronic-mail document server are provided. Recommendations may be based on determined interests of the user based on the theme or concept of a previously categorized document, the previously categorized document having been previously accessed by the user.

FIELD OF THE INVENTION The present invention relates to a thin film transistor, and more particularly to a low-temperature polysilicon thin film transistor having a lightly doped drain (LDD) structure. The present invention also relates to a process for producing a thin film transistor. BACKGROUND OF THE INVENTION TFTs (Thin Film Transistors) are widely used as basic electronic devices for controlling pixels of a TFT liquid crystal display (TFTLCD). FIG. 1( a ) is a block diagram schematically illustrating a conventional TFTLCD. Such TFTLCD comprises an active matrix 10 and driving circuits 11 . The active matrix 10 is formed on a glass substrate 1 , whereas the driving circuits 11 are electrically connected to the active matrix 10 via external lines 12 . Nowadays, a so-called low-temperature polysilicon thin film transistor (LTPS-TFT) technology was developed due to improved electrical properties of TFT transistors and other benefits. Please refer to FIG. 1( b ). The active matrix 10 and the driving circuits 11 can be directly formed on the glass substrate 1 so as to reduce fabricating cost. A process for producing such LTPS-TFT is illustrated with reference to FIGS. 2( a ) to 2 ( f ). In FIG. 2( a ), a polysilicon layer 21 is formed on a glass substrate 2 by laser annealing an amorphous silicon layer applied to the glass substrate 2 at a low temperature, and patterning and etching the annealed silicon layer. Then, as shown in FIG. 2( b ), a photoresist 22 is formed on a selected region of the polysilicon layer 21 , and an ion-implantation procedure is performed on the resulting polysilicon layer 21 with the photoresist 22 serving as a mask. By the ion-implantation procedure, B + ions are implanted to form N-channel TFT zones. Then, a photoresist 23 is partially formed on the N-channel TFT zones, and PHx + ions are implanted into the N-channel TFT zones with the photoresist 23 serving as a mask, thereby forming source/drain regions 24 , as can be seen in FIG. 2( c ). After the photoresists 22 and 23 are removed, a gate insulator 25 is formed on the resulting structure. Then, gate metal 26 (for example made of molybdenum) is formed on the gate insulator 25 , as shown in FIG. 2( d ). The gate metal 26 for each N-channel TFT zone has cross-sectional area less than that of the corresponding photoresist 23 for that N-channel TFT zone formed in the previous step shown in FIG. 2( c ). Then, for N-channel TFT zones, lightly doped drain (LDD) regions 241 are formed by implanting P + ions with the gate metal 26 as a mask. The N-channel TFT zones are covered with a photoresist 27 , and then another ion implantation procedure is performed on the resulting structure with the photoresist 27 serving as a mask to form a P-channel TFT zone, as shown in FIG. 2( e ). The dopants are B 2 Hx + ions, and source/drain regions 242 are formed. Afterwards, an interlayer dielectric layer 28 and source/drain conductive lines 29 are formed in sequence, as shown in FIG. 2( f ), to obtain the desired LTPS-TFT structure. With the increasing development of integrated circuits, electronic devices have a tendency toward miniaturization. As a result of miniaturization, the channel between the source and drain regions in each TFT will become narrower and narrower. A so-called “hot electron effect” is rendered, which impairs stability of the LTPS-TFT and results in current leakage. The LDD regions are useful to reduce the hot electron effect. Conventionally, a process involving many masks and steps are involved in order to form the LDD regions. Another conventional process of forming LDD regions by a self-aligned procedure would involve reduced masking steps. For the self-aligned procedure, the LDD regions do not overlap with the gate metal 26 thereabove. It is found, however, improved device stability will be obtained when the gate metal 26 extends over the LDD region 241 to a certain extent. Unfortunately, there is likely to be parasitic capacitance occurring in the overlapped region between the gate metal 26 and the LDD region 241 , which adversely causes a voltage drift of the storage capacitor and liquid crystal capacitor in a pixel cell when the pixel is turned off. SUMMARY OF THE INVENTION It is an object of the present invention to provide a TFTLCD having an LDD region with satisfying stability and minimized voltage drift. According to a first aspect of the present invention, a thin film transistor display comprises a driving circuit comprising a first thin film transistor structure. The first thin film transistor structure comprises a first gate, source and drain regions, a first LDD region, a second LDD region and a first channel region between the first and the second LDD regions. The first gate region is disposed over the first channel region and overlaps with the first and the second LDD regions. An active matrix is controlled by the driving circuit and comprises a second thin film transistor structure. The second thin film transistor structure comprises a second gate, source and drain regions, a third LDD region, a fourth LDD region and a second channel region between the third and the fourth LDD regions. The second gate region is disposed over the second channel region and overlaps with neither of the first and the second LDD regions. Preferably, the length of the first gate region is greater than the length of the first channel region. Preferably, the length of the second gate region is no greater than the length of the second channel region. More preferably, the length of the second gate region is identical to the length of the second channel region. Preferably, the active matrix and the driving circuit are formed on the same substrate, e.g. a glass substrate. Preferably, the display is a liquid crystal display. Preferably, the thin film transistor display further comprises a passivation layer overlying the first and the second thin film transistor structures; and a plurality of contact plugs extending from the source/drain regions, respectively. According to a second aspect of the present invention relates to a process for producing a thin film transistor display. The process includes steps of providing a substrate; forming a polysilicon layer on the substrate; patterning the polysilicon layer to define a first and a second TFT regions; providing a first and a second doping masks on the polysilicon layer in the first and the second TFT regions to result in a first exposed portion in the first TFT region and a second exposed portion in the second TFT region; implanting a first doping material into the first and the second exposed portions, thereby defining a first doped region and a first channel region adjacent to the first doped region in the first TFT region, and a second doped region and a second channel region adjacent to the second doped region in the second TFT region; removing the first doping mask; providing a third doping mask on the first channel region, which partially overlies the first doped region, so as to result in a third exposed portion in the first TFT region smaller than the first exposed portion; implanting a second doping material into the third exposed portions to form first source/drain regions and simultaneously define a first LDD region; removing the second and the third doping masks; forming an insulator layer and a gate metal layer on the resulting structure; and patterning the gate metal layer to form a first and a second gate structures over the first and the second channel regions, respectively. The first gate structure is longer than the first channel, and the second gate structure has length smaller than or substantially equal to the second channel region. In one embodiment, the process further comprises a step of implanting a third doping material into the second TFT region with the second gate structure serving as a doping mask to form second source/drain regions and a second LDD region. In one embodiment, the process further comprises a step of covering a portion of the patterned polysilicon layer with a fourth doping mask before doping the patterned polysilicon layer for further defining a third TFT region. In one embodiment, the first TFT region is an N-channel TFT region of a driving circuit, the second TFT region is an N-channel TFT region of an active matrix, and the third TFT region is a P-channel TFT region. Preferably, the fourth doping mask is removed along with the second and the third doping masks. In one embodiment, the process further comprises steps of: forming a third gate structure over the third TFT region at the same time when the first and the second gate structures are formed; and implanting a third doping material into the third TFT region with the third gate region serving as a mask to form source/drain regions of the third TFT region. The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1( a ) is a block diagram schematically illustrating a conventional TFTLCD; FIG. 1( b ) is a block diagram schematically illustrating a conventional LTPS-TFTLCD; FIGS. 2( a ) to 2 ( f ) are schematic cross-sectional views illustrating a conventional process for producing an LTPS-TFTLCD having LDD regions; FIG. 3 is a schematic cross-sectional view illustrating the structure of an LTPS-TFTLCD according to a preferred embodiment of the present invention; FIGS. 4( a ) to 4 ( g ) are schematic cross-sectional views illustrating a process for producing an LTPS-TFTLCD having LDD regions according to a preferred embodiment of the present invention; and FIGS. 5( a ) to 5 ( f ) are schematic cross-sectional views illustrating a process for producing a CMOS thin film transistor according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As previously described, the fabricating cost of a low-temperature polysilicon thin film transistor liquid crystal display (LTPS-TFTLCD) is relatively low because the active matrix and the driving circuit are formed on the same glass substrate. In addition, the LTPS-TFTLCD has reduced hot electron effect due to the presence of an LDD region. When the LDD region and the gate metal of the LTPS-TFTLCD overlap with each other, i.e. the gate metal of the LTPS-TFTLCD, an improved device stability is obtained while accompanied by some adverse effects such as current leakage and parasitic capacitance. Therefore, voltage drift of the storage capacitor and liquid crystal capacitor in a pixel cell is caused. As is known, the thin film transistors in the active matrix and the driving circuit perform different functions and thus have different requirements. For example, the thin film transistor in the active matrix requires accurate voltage levels. On the contrary, good device stability is prerequisite for the thin film transistor in the driving circuit. Based on the above concept, a specified LTPS-TFTLCD is developed according to the present invention, as can be seen in FIG. 3 . The LTPS-TFTLCD comprises a driving circuit portion and an active matrix portion, which are formed on the same substrate 3 . In the driving circuit portion, an N-channel TFT M 1 and a P-channel TFT M 2 are included. In the active matrix portion, N-channel TFTs M 3 are included. The N-channel TFT M 1 comprises a gate structure 31 , source/drain regions 32 , LDD regions 33 and a channel region 34 . According to the present invention, the gate region 31 disposed over the channel region 34 overlaps with the LDD regions 33 in order to assure of good device stability. On the other hand, the thin film transistor structure M 3 , which comprises a gate structure 35 , source/drain regions 36 , LDD regions 37 and a channel region 38 , has the gate structure 35 thereof substantially staggered with the LDD regions 37 . In other words, the gate structure 35 does not overlap with the LDD regions 37 so as to reduce current leakage and parasitic capacitance. A process for producing an LTPS-TFT similar to that of FIG. 3 according a preferred embodiment of the present invention is illustrated with reference to FIGS. 4( a ) to 4 ( g ). In FIG. 4( a ), a polysilicon layer 41 is formed on a glass substrate 4 by laser annealing an amorphous silicon layer applied to the glass substrate 4 at low temperature, and patterning and etching the annealed silicon layer. Then, as shown in FIG. 4( b ), a photoresist 42 is formed on a selected region R 2 of the polysilicon layer 41 , which is defined as a P-channel TFT zone, and an ion-implantation procedure is performed on the resulting polysilicon layer 41 with the photoresist 42 serving as a mask. By the ion-implantation procedure, B + ions are implanted to form N-channel TFT zones in regions R 1 and R 3 . Then, photoresists 431 and 432 are formed on the N-channel TFT zones in the active matrix portion and the driving circuit portion, respectively, and PHx + ions are implanted into the exposed parts of the N-channel TFT zones with the photoresist 431 and 432 serving as masks, thereby defining source/drain regions 44 , as can be seen in FIG. 4( c ). Meanwhile, the channel region 442 of the N-channel TFT zone in the region R 1 , is defined. Afterwards, the photoresist 431 is removed and replaced by a photoresist 433 having greater as-shown cross-sectional length than the photoresist 431 . As shown in FIG. 4( d ), PHx + ions are continuously implanted into the N-channel TFT zones in the regions R 1 and R 3 with the photoresist 433 and 432 serving as masks, thereby forming heavily doped source/drain regions 440 and 442 for all the N-channel TFT zones in the regions R 1 and R 3 and LDD regions 441 for the N-channel TFT zone in the region R 1 . After the photoresists 42 , 432 and 433 are removed, a gate insulator layer 45 is formed on the resulting structure. Then, a gate metal layer (for example made of molybdenum) is formed on the gate insulator 45 , and the gate metal layer is patterned to form gate structures 461 , 462 and 463 . As shown in FIG. 4( e ), the gate structure 461 has cross-sectional length substantially the same as that of the photoresist 433 having been removed previously, and thus the gate structure 461 has length greater than the channel region 442 . On the other hand, the gate structure 463 has cross-sectional length less than that of the corresponding photoresist 432 having been removed in the previous step shown in FIG. 4( d ). Then, PHx + ions are continuously implanted with the gate metal structures 461 , 462 and 463 serving as masks in the regions R 1 , R 2 and R 3 , respectively, thereby defining source/drain regions 444 in the region R 2 , and forming LDD regions 445 for the N-channel TFT zones in the region R 3 of active matrix portion, as can be seen in FIG. 4( e ). Meanwhile, the channel region 446 of the N-channel TFT zone in the region R 3 is defined. In this embodiment, the gate structure 463 has length substantially identical to that of the channel region 446 . Depending on various processes, however, the present structure still works if the gate structure 463 is shorter than the channel region 446 . The N-channel TFT zones in the regions R 1 and R 3 are then covered with a photoresist 47 , and then another ion implantation procedure is performed on the resulting structure with the photoresist 47 serving as a mask so as to form a P-channel TFT zone in the region R 2 , as shown in FIG. 4( f ). The dopants are B 2 Hx + ions, and source/drain regions 446 are formed. Afterwards, an interlayer dielectric layer 48 and source/drain conductive lines 49 are formed, as shown in FIG. 4( g ), according to any proper technique, so as to obtain the desired LTPS-TFT structure. That is, the gate electrode 461 of the N-channel TFT in the driving circuit portion overlies the LDD regions 441 to exhibit good device stability, and the effect of the possible parasitic capacitance on a driving circuit is insignificant. On the other hand, the gate electrode 463 and the LDD regions 445 of the N-channel TFT in the active matrix portion stagger from each other to prevent from the voltage level drift resulting from current leakage and parasitic capacitance. The concept of the present invention can also be applied to produce a complimentary metal oxide semiconductor (CMOS) thin film transistor. The process will be illustrated with reference to FIGS. 5( a ) to 5 ( f ). In FIG. 5( a ), a polysilicon layer 51 is formed on a glass substrate 5 by laser annealing an amorphous silicon layer applied to the glass substrate 4 at low temperature, and patterning and etching the annealed silicon layer, thereby defining a first and a second TFT regions R 1 and R 2 to serve as an N-channel TFT zone and a P-channel TFT zone, respectively. Then, as shown in FIG. 5( b ), a photoresist 52 is formed on the polysilicon layer 51 in the N-channel TFT zone R 1 , and an ion-implantation procedure is performed on the resulting polysilicon layer 51 with the photoresist 52 serving as a mask. By the ion-implantation procedure, B + ions are implanted into the polysilicon layer 51 in the N-channel TFT zone R 1 . Then, as shown in FIG. 5( c ), a photoresist 53 is partially formed on the polysilicon layer 51 in the N-channel TFT zone R 1 , and PHx + ions are implanted into the polysilicon layer 51 in the N-channel TFT zone R 1 with the photoresist 53 serving as a mask. After the photoresists 52 and 53 are removed, a gate insulator 55 is formed on the resulting structure. Then, a gate metal layer (for example made of molybdenum) is formed on the gate insulator 55 , and the gate metal layer is patterned to form gate structures 561 and 562 , as shown in FIG. 5( d ). The gate structure 561 has cross-sectional length substantially the same as that of the polysilicon layer 51 in the N-channel TFT zone R 1 . Another ion implantation procedure is performed on the resulting structure with the gate structure 562 serving as a mask in the P-channel TFT zone R 2 . The dopants are B 2 Hx + ions, and source/drain regions 54 are formed. Then, the gate structure 561 is removed and replaced by another gate region 563 having cross-sectional length smaller than the gate structure 561 but greater than the channel region 510 of the polysilicon layer 51 . Preferably but not necessarily, the length of the gate structure 563 is equal to the total length of the channel region 510 plus the LDD regions 591 , as shown in FIG. 5( e ). Then, a photoresist 57 is formed on the gate region 563 , and the P-channel TFT zone is covered with a photoresist 58 . Then, PHx + ions are implanted into the N-channel TFT zone with the photoresist 57 serving as a mask, thereby forming source/drain regions 59 and LDD regions 591 in the N-channel TFT zone R 1 . Afterwards, an interlayer dielectric layer 60 and source/drain conductive lines 61 are formed, as shown in FIG. 5( f ), to obtain the desired CMOS structure. From the above description, it is known that the process for fabricating the TFTLCD having an LDD region is performed without increasing masking steps when compared with the conventional self-aligned procedure. Advantageously, the TFTLCD fabricated according to the present invention has an LDD region and a gate metal overlapped with each other so as to achieve good device stability. While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.

A thin film transistor display includes a driving circuit and an active matrix. The driving circuit comprises a first thin film transistor structure. The first thin film transistor structure includes a first gate, source and drain regions, a first LDD region, a second LDD region and a first channel region between the first and the second LDD regions. The first gate region is disposed over the first channel region, and partially or completely overlies the first and the second LDD regions. The active matrix is controlled by the driving circuit and comprises a second thin film transistor structure. The second thin film transistor structure includes a second gate, source and drain regions, a third LDD region, a fourth LDD region and a second channel region between the third and the fourth LDD regions. The second gate region is disposed over the second channel region and substantially overlaps with neither of the first and the second LDD regions.

BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to a laser-scanning microscope with sample illumination and detector means, which for the purpose of image acquisition illuminates and detects a sample in a raster scanning manner, with a real-time control device. The control device controls the illumination and detector means for illumination and detection and reads out detection signals, whereby the control device performs control and readout synchronously with a pixel cycle that determines the raster scanning. A data port is connected between the control device and the illumination and detector means and communicates with the control device via a parallel, bidirectional data stream and with the illumination and detector means via a serial, bidirectional high-speed data stream and for this reason performs a conversion of data from parallel into serial or vice versa. The invention further relates to a laser scanning microscope with sample illumination and detector means, which for purposes of image acquisition illuminate and detect a sample by raster scanning, with a real-time control device, which controls the illumination and detector means for illumination and detection and reads out detection signals. A control device controls the illumination and detection and reads out the detection signals synchronously with a pixel cycle that determines the raster scanning, a data port, connected between the control device and the illumination and detector means, communicates with the control device via a parallel, bidirectional data stream and with the illumination and detector means via a serial, bidirectional high-speed data stream and for this purpose performs a conversion of data from parallel into serial or vice versa. In a laser scanning microscope of this type, as is offered, for example, by Carl Zeiss AG under the designation LSM 510, image acquisition is carried out by exciting and scanning a sample pixel-by-pixel with excitation or illumination radiation. The image comes about by the intensity of radiation being allocated to the appropriate pixel coordinates and in this way coalescing into an image. Consequently, a pixel-synchronous matching of illumination and detector means, particularly of a scanner, i.e., of a deflecting device is required for illumination and detection in order to gather the information for the image. This implies that the highest data transmission rate possible should be used in the control as well as the readout of it since the speed and volume of the data transmission automatically impacts the length of time that is needed for imaging. Especially with biological samples, it would be desirable, though, to obtain an image as fast as possible, for example, to be able to analyze biological processes. At the same time, this is not only dependent on the data rate, i.e., the product of the data packet size and transmission frequency, but also on the reaction speed at which communication proceeds between the real-time control device and the illumination and detector means. The transmission frequency is a determining factor for this. Here it must also be borne in mind that not only the control of the deflecting device or the illumination units, e.g., lasers, etc., has to be carried out in a pixel-synchronous way, but rather that today's highly sensitive detector means require equally to a certain extent complex control for readout of the intensity of radiation to be allocated to the pixels. Photomultiplier tubes (PMTs) requiring among other things control of the radiation integration procedures and readout processes are cited as an example. For each pixel, data has to be transmitted to the PMT and data also has to be read out by the PMT. In the final analysis, therefore, an effort is being made to design the data communication so fast that it is not the time determinant in the operation chain. This implies that the data communication should be fast enough in order to process the data traffic needed for this within the minimum time that is needed for detection of a pixel's radiation by the detector (which is called the pixel time). For high-speed data communication different approaches, which however either need substantial device-related time and effort or have insufficient speed attainment, are familiar in data processing technology. (2) Summary of the Invention Therefore, the present invention's basic function is to refine a microscope or technique of the type designated at the beginning in such a way that control of the illumination and detector means is achieved with little time and effort. At the same time, the data rate attained allows for transmitting the data required for each pixel within the pixel time specified on the detector side. According to the invention this function is performed with a laser-scanning microscope of the designated type, in which the high-speed data stream from the illumination and detector means to the data port is made up of data packets with data bits and type bits and with no additional header or protocol bits. The data bits contain the data on the illumination and detector means and the type bits code the type of data. In the illumination and detector means, if need be, also in the control device, type information is stored that defines processing functions for data types coded by means of the type bits, and when sending, the illumination and detector means set the type bits for the data types in a type assessment. The function is performed further with a technique of the designated type, in which the high-speed data stream between the illumination and detector means and the data port is made up of data packets with data bits and type bits and with no additional header or protocol bits. The data bits contain data from the illumination and detector means and the type bits code the type of data. In the illumination and detector means and the control device, type information is stored that relates to processing functions for data types coded by means of the data bits, and, when sending the illumination and detector means and/or the control device, set the type bits for the data type in a type specification and the control device and/or the illumination and detector means defines the data types using the type bits in a type assessment and process the data coded in the data bits accordingly. According to the invention header or protocol data, as they are used in usual high-speed data systems (e.g. FireWire or USB) with serial communication and as they usually occur in a normal parallel-to-serial conversion, are dispensed with for the transmission of illumination and detector means. Therefore, a header no longer exists in the data packet as to, e.g., who is sending the data to which address in the bus they are directed, what can be done in case of error handling, etc. From the illumination and detector means to the control device, the data stream is made up exclusively of data bits and type bits, whereas the latter code information on the type of data stored in the data bits. Each module attached to the link carrying the data stream thus makes a type bit specification when delivering the data. The type bits are distinguishable from header bits of normal communications data streams by the fact that they contain no general information, but rather merely provide information on the processing of the data in the data bits which are to be subjected to in combination with type indications, which are authorized at the sending and receiving end, and the type assessment based on this at the receiving end. The high-speed data stream consequently is adjusted in a microscope-specific way and as a rule requires stored type information both on the receiving and sending end as to how the data are to be arranged or processed. This type of data communication, on the one hand, manages to eliminate any redundant information and thereby increases the effective useful rate for the data to be transmitted. On the other hand, it simplifies the data-related time and effort on the sending and receiving end, since the type specification can be designed very simply with the senders or recipients using type bits. This immediately gives the recipients the necessary information as to whether and, if need be, how they have to process data bits, or whether not at all. At the same time the senders do not have to administer and communicate address data. The invention-related conversion of the parallel, bidirectional data stream into a serial, bidirectional high-speed data stream, which is adapted to the requirements in the laser scanning microscope, further simplifies cabling in the microscope, since serial data cables need less space. In addition, a standard computer can be used for the real-time control device, and complex or costly special interfaces on the part of the real-time control device are left out. The conversion into/from the microscope-specific high-speed data stream first takes place at the data port that acts as the microscope's port. The invention-related concept for communication from the illumination and detector means to the control device is indeed particularly advantageous; however, a use in the reverse channel, which is located away from the control device, is equally possible. The utilization of high-speed data transmission with type bits has the added advantage that every data packet made up of data bits and type bits can now simultaneously be sent out or also received by multiple illumination and detector means' positions if for example the type assessment for a type of data reveals that it is relevant at different locations, e.g., by different illumination and detector means' units. With traditional address-based data communications, a simultaneous broadcasting of a data packet from and/or to different units would be impossible and instead of that multiple data packets would have to be furnished with different addresses and transmission delayed via the high-speed data stream. It is easily understandable that the useful data transmission rate achieved then would be reduced a number of times. Usually laser-scanning microscopes are broken down into individual modules, which act together in the illumination and scanning. Various illumination modules, which can be integrated into a microscope and provide radiation of various wavelengths, are an example of this. It is also a familiar practice to equip laser-scanning microscopes with different detector modules, which have, e.g., different spectral analysis capabilities. For such a modular design, it is desirable to provide a data manager to communicate with the individual modules and to connect to the individual modules according to the serial high-speed data stream, since the individual modules must be operated in coordination with each other, however, for the most part individually do not need the full data rate for communication; this data rate is only necessary in the interaction of all the modules on the part of a real-time control device. It is naturally advantageous for this design to make up the individual serial streams (which, e.g., can be designed pursuant to familiar LVDS data transmission) of data bits and types bits as well and dispensing with additional header bits between the individual modules and the data manager, since otherwise address and header information would have to be created and also transmitted by the individual modules. It will be more practical for the data manager to have the appropriate connectors for the individual modules. The data manager continues to work better with a fixed allocation scheme, by which it feeds the individual modules' data packets into the high-speed data stream. A time-consuming analysis of the individual data streams in the data manager or one requiring a processing unit is not necessary then, yet the real-time control device or the data port has to take into consideration the consolidation of the high-speed data stream from the individual data streams that is permanently set in the data manager, i.e., the individual data streams' data packets will be arranged by the data port or the real-time control device accordingly in the high-speed data stream in such a way that the allocation in the data manager is reflected in the structure of the high-speed data stream. Since a modularly designed laser scanning microscope is only seldom changed or in the case of redesign fixed connection regulations can be preset, this limitation does not constitute a hindrance. In addition, if need be, or as an alternative at the data port and/or in the real-time control device, a setting mechanism (e.g., as software or hardware device) can be provided, through which it and/or they are communicated to the individual modules that are bound to the individual data stream connectors so that the data port or the control device knows how the data packets in the high-speed data stream are composed of the individual data streams. For this reason, for a modular microscope it is advantageously provided that the illumination and detector means have multiple individual modules, which interact during the illumination and scanning, a data manager communicating with the individual modules and merging the high-speed data stream from individual serial streams of the individual modules and leading it out of the data port is connected between the data port and the individual modules of the illumination and detector means. The individual serial data streams between the data manager and individual modules are also made up of data bits and type bits and dispensing with additional header bits, the type information is stored in the individual modules and the individual modules perform the type assessment and the processing of the data coded in the data bits. Of course, this concept can also be used in direction of communication from the real-time control to the individual modules. The data manager's work is especially simple if the individual data streams are carrying data packets that are a fraction as long as the high-speed data stream's data packets. Preferably, the individual data streams' data packets are half as long as those of the high-speed data stream. Then the data manager simply composes each high-speed data stream data packet from two halves that are derived from two individual data streams. The data packet frequency of each individual data stream is then equal in size to that of the high-speed data stream, however with half the packet length. Half the frequency of the high-speed data stream is sufficient for an individual module, the data manager can make up each packet of the high-speed data stream alternatively separately from two individual data streams so that overall four individual data streams are used, which in each case have half the frequency of the high-speed data stream and half the packet length. The one high-speed data stream is then simply composed of four individual data streams. This is naturally also possible with simultaneous sending out (broadcast) of the individual data packets. In the same way, naturally, scaling is possible, i.e., two different data ports or a double data port can be provided which convert(s) the parallel data stream from the real-time data control device into two high-speed data streams. This can be practical in very complex laser-scanning microscopes. If it would be desirable to address numerous individual modules, it can be even more advantageous that multiple individual modules are connected to a single common data link and utilize this data link as a type of a data bus, whereas the type assessment in turn implicitly defines which individual module or which individual modules process or in the case of transmission send out a data packet's data that are coded in the data bits. In laser-scanning microscopes, the illumination and detector means also have actuators, which for the most part have a call back function to the control unit and which can be suited or set for operation without any impact occurring in the pixel cycle or shift being necessary, aside from elements to be controlled in a pixel-synchronous way. The pinhole shift mechanical data before the detectors are examples of such actuators. Other examples are the setting of drivers for acoustic-optical filters in illumination units, the drives for color distribution switchers or shutters, and safety screens or the like. All such components do have to have a certain setting during operation of the laser-scanning microscope, yet an activation and/or call back report occurring in the pixel cycle is unnecessary. Usually, such actuators have so far been controlled with slow working data busses, e.g., what is called a CAN bus, which implies that in traditional microscopes a (non-pixel-synchronous) slower (CAN) bus has to still be carried through the entire device along with the high-speed data communication. In the invention-related laser-scanning microscope, it is now possible to make separate settings data bus networking of the entire microscope unnecessary by embedding into the high-speed data stream with a certain type coding the settings data or callback data, which for example are added to the units according to the CAN bus protocol just mentioned, and by having the illumination and detector means extract from the high-speed data stream the settings data or the data port, the data manager or the control unit the reverse data using the type coding carried out by the respective transmitter and leading them to the actuators or processing them. The slow and not necessarily pixel-synchronous settings data, therefore, are fed into the high-speed data stream from the real-time control device or the data port and extracted on the receiving end, i.e. in the illumination and detector means. The opposite applies to reverse data. For this reason, it is provided in a preferable refinement of the microscope that the illumination and detector means have settings elements, which can be controlled when the microscope is in operation asynchronously to the pixel cycle, whereas the control device makes the suitable settings data for the settings elements, the settings elements are embedded, e.g., with a certain type coding or address into the high-speed data stream and the illumination and detector means extract the settings data and lead them to the settings elements. Alternatively or in addition this is carried out in the reverse channel. The CAN bus that was already mentioned is an efficient implementation for the forwarding of settings data to the settings elements. For this reason, it is provided for in a refinement that at least one individual module will make available a CAN bus for at least one settings element allocated to the individual module or provided for in it and will convert the settings data and/or reverse data into and/or from the CAN bus data by means of a converting element. In order to test the settings elements, which are controlled, e.g., via the CAN bus, usually full operation of the microscope is necessary, since all actuators are connected to a common CAN bus system. The invention-related design, in which the settings data are converted from and/or into the high-speed data stream from the illumination and detector means, i.e. usually from the individual modules, now allows for a design, in which the individual modules or individual components of the illumination-detector means can be tested individually. For this a diagnostic connector to the CAN bus is provided for in the individual module through which a direct CAN bus control of the settings element is possible for diagnostic and checking purposes. The diagnostic connector is therefore located between the converting element that converts the settings data from and/or into the high-speed data stream and the settings element. In that way it is possible to check the functionality of a settings element individually without having the rest of the microscope in operation. A more extensive check is possible if the converting element, which makes available, e.g., the CAN bus data, also performs a reverse conversion of the settings data into the serial data stream. Then the interaction between the control device and the individual module or its settings element can also be checked, since the control device obtains values fed in or presetting done by means of a reverse conversion at the diagnostic connector. The forward and reverse conversion in each case can be provided for, not only, individually, but also in combination. The use of individual data streams, as already mentioned, allows for a simple linking of different modules, whereas at the same time an unnecessarily high data rate is avoided on individual modules and the overall transmission rate of the high-speed data stream is distributed accordingly over the individual modules. Now the data manager can be designed in such a way that it will make an individual data stream available for each individual module. Alternatively, a option is presented whereby at least one of the individual modules has an outlet, to which it transfers the individual data stream introduced and assessed by it and through which an additional individual module is supplied. This individual data stream, therefore, is used as a data bus, whereas the length of the chain essentially is only limited by the transit time of the signals up to the last individual module and the data rate made available by the individual data stream. Such an individual data stream bus can be utilized particularly well if individual data modules are combined in it, which modules require varying data rates in both communication directions. Therefore, individual modules with a high upload rate will be more beneficially combined with individual modules that need a high download rate. In turn, naturally settings can be made at the control device or at the data port and consideration can be given to how the individual modules are linked to the individual data streams. In this way, the data manager simply can execute a segmentation and/or combination of the high-speed data stream into and/or out of the individual data stream(s). In other words, the high-speed data stream in its composition reflects the segmentation and/or combination of the individual data streams' data packets that is carried out in the data manager and how the individual modules are linked onto the individual data streams, i.e., which one of the individual data streams a certain individual module will receive. As far as the invention here is described with reference to a mechanism or a technique, this applies accordingly to the invention-related technique or mechanism, even if this matching of mechanism and technique characteristics should not be expressly mentioned. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be depicted more closely below with reference to drawings. The drawings show in: FIG. 1 is a schematic representation of a laser-scanning microscope in relation to control and data communication. FIG. 2 is a schematic representation of the laser-scanning microscope of FIG. 1 in relation to deflecting radiation in the microscope. FIG. 3 is a schematic representation similar to that of FIG. 1 with a more detailed reproduction of the configuration of the components of the microscope. FIG. 4 a is a more detailed schematic representation of a data manager in the microscope of FIGS. 1 and 3 . FIGS. 4 b , 4 c and 5 illustrate the apportionment of data packets by the data manager of FIG. 4 a. FIG. 6 is a schematic diagram of an individual module of the microscope in FIGS. 1 and 3 in relation to the control of a settings element. FIG. 7 is a schematic representation similar to FIG. 6 of a further configuration of an individual module. FIG. 8 is a schematic diagram of several individual modules, which are connected in a bus-like way to the data manager in FIG. 1 or 3 in the microscope. Furthermore, the attached Table 1 shows an example of data conversion of the microscope in FIG. 1 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. The schematic drawing in FIG. 1 shows a laser-scanning microscope system 1 that essentially is made up of a modular microscope 2 and a control device 3 . This microscope 2 represents a laser-scanning microscope known based on its principle of microscopy, with which a sample is scanned by means of raster scanning illumination as well as raster scanning detection. The microscope 2 for this reason is provided with appropriate modules 4 . 1 , 4 . 2 and 4 . 3 (they are taken together also provided with the reference number 4 ), which can be configured, for example, as a scanner module 4 . 1 , as a detector module 4 . 2 and as a laser module 4 . 3 . The modules (the number depicted in FIG. 1 is merely to be taken as an example) can be controlled by the control device 3 , whereby for the imaging a certain control situation has to exist for each pixel of an image in order that the necessary, coordinated operation of the modules is achieved. The control device 3 for this reason passes the appropriate control signals via a parallel data link 5 , which can be configured for example as a familiar PCI bus, on to the microscope 2 and receives the appropriate data from the microscope 2 . The parallel data link 5 on the microscope side is connected to a port 6 , which converts the parallel data stream into a serial data stream and passes it on via a serial high-speed data link 7 . This data link carries a serial high-speed data stream, in which the data delivered via the parallel data link 5 are carried by data packets as a serial sequence. The structure of these data packets and the mode of operation of this port 6 will be explained hereinafter. The functionality described below as well as the corresponding configuration is not limited to one direction of communication. Either of the two can only be implemented in the direction toward the modules, in the direction away from the modules or in both directions. A variation described below possibly only in one direction consequently can also be implemented in the opposite direction or in both directions. The serial data packets that are carried via the data link 7 are forwarded from a data manager 8 to three serial module data links 9 in the embodiment. The data manager 8 segments the high-speed data stream into individual data streams, which are then fed into the serial module data links 9 The control by the control device 3 has to coordinate the modules' work in virtually real time. This may be exemplified by means of the schematic drawing in FIG. 2 . It can be seen in FIG. 2 that that illumination radiation 12 provided by the laser module 4 . 3 , which excites florescence, e.g., in the sample, is directed to a sample field 10 through the scanner module 4 . 1 , whereby the sample field 10 is scanned by raster scanning of different pixels 11 . The radiation (e.g. fluorescence radiation) 13 that is caused and to be detected at an appointed position of the scanner module 4 . 1 by the illumination with an irradiation from the laser module 4 . 3 of one of the pixels 11 of the sample field 10 is in turn imaged by the scanner module 4 . 1 and then divided on a splitter 14 to the detector module 4 . 2 that verifies the radiation accordingly. An illumination beam path therefore exists between the laser module 4 . 3 upstream of the splitter 14 and the scanner module 4 . 1 , and the radiation to be detected is directed through a detection beam path from the pixel 11 , through the scanner module 4 . 1 and the splitter 14 to the detector module 4 . 2 in a detection beam path and verified at the detector. It is self-explanatory that operation and also readout of data from module 4 must be carried out in an inter-coordinated way for each of the pixels 11 . This control device 3 makes sure of this accordingly. For example, first the scanner module 4 . 1 is set to the coordinates of the pixel 11 . Then the laser module 4 . 3 is activated accordingly so that an illumination of the pixel takes place. At the same time or after a lag in time, a read out of the detected radiation is performed at the detector module 4 . 2 . The radiation intensity detected at that time is assigned to the pixel coordinates, stored accordingly and integrated into an image after completely raster scanning all pixels 11 in the sample field 10 . Of course this description as well as the representation in FIG. 2 is extremely simplified; still other controls are necessary, for instance focus adjustments, settings on a sample table, etc. But it is obvious from the description that the illumination and detector means, as they for example can be implemented by means of the individual modules 4 , have to be operated inter-coordinated in a pixel-synchronous manner that includes both the control of the modules as well as possibly the reading out of data from the modules (forward channel). What is essential here, as was mentioned, is that several modules 4 have been provided in the microscope and they, as the modules 4 . 1 - 4 . 3 , have to be operated in a pixel-synchronous manner in relation to each other, so that a certain adjustment of the modules (reverse channel) or read out of the modules is carried out with every pixel for the creation and detection of radiation intensity. The reading out or control here can change from pixel to pixel so that upon transition from one pixel to the next, as for example was already represented in FIG. 2 by means of the solid or the dotted line onto the sample field 10 , a further input of control values or read out of values is necessary at the modules by the control device 3 . The conversion of the data carried out in the microscope system 1 by means of the port 6 has various advantages. On the one hand, the control device 3 can now transmit the data over a traditional parallel data link 5 . Consequently, economical components can be utilized for the control device 3 , possibly even a store bought PC or notebook could be considered. The conversion of these data delivered in a parallel fashion into a serial high-speed data link 7 has the advantage that a simple cabling is possible in the microscope. Furthermore, a serial data stream lends itself far more easily to segmentation into the individual data streams through the serial module data links 9 or combined therefrom, as will be further described below. What is essential in the data that are carried over the serial high-speed data link 7 and then over the serial module data links 9 is that data packets are used in at least in one direction and transmit no protocol. Therefore, no header exists which receives for instance information on the sender, the receiver, address data, error handling specifications, time indications, etc. Instead, the data packets then contain exclusively data bits and type bits, whereby the data bits reproduce control data in the reverse channel, measurement data, or location report data in the forward channel and the type bits provide an indication of the type of data bits. In this way the serial high-speed data stream that runs over the data link 7 contains data packets, which combine two 16-bit packets each into a 32-bit packet, whereby the four more bits for the type coding (in bits 32 through 35 ) are transmitted in addition to the 2 times 16-bit raw data. Since the data communication from modules 4 to the control mechanism 3 contains no address information, the combination of the high-speed data stream has to take into consideration the segmentation into the serial individual data streams on the serial module data links 9 , particularly which individual modules 4 are connected to the respective serial module data links. For this reason, the data port 6 can accomplish the conversion. Alternatively, the data manager 8 can feed the initiating packets of the serial module data links 9 into or in the high-speed data stream according to a fixed plan. For instance every data packet from the link to the module 4 . 1 can become a first element of the high-speed data stream, every data packet from the link to the module 4 . 2 a second and every data packet from the link to the module 4 . 3 a third one. This similarly applies to the reverse channel. It can be provided for this variant which individual module 4 can be connected to which connector on the data manager 8 , or it will be stored in the control device 3 which module 4 is attached onto which connector of the data manager. On the other hand, it is possible that the data manager takes into consideration the structure of the high-speed data stream when it is forwarding to the individual module 4 and performs a variable conversion of the data packets. The use of the data packets of individual modules 4 over the serial module data links 9 is carried out with the configuration shown in FIG. 3 for the individual modules 4 in the following way (the explanation is carried out here, without any restriction, for the reverse channel): in the design, as it is shown in FIG. 3 , every individual module 4 is essentially subdivided into two units. The data packets of modules 4 . 1 - 4 . 3 are respectively gathered by a module operation switch 15 . 1 - 15 . 3 (when all taken together they are referenced under the reference number 15 ) and accordingly converted into control signals for the module. The module operation switches 15 , which for instance can each have an appropriate CPU, a ROM, a RAM as well as an ASIC, therefore, perform the type assessment and convert the data contained in the data packets' data bits, depending on the specification in the type bits, possibly into the corresponding control processes. The control will be carried out then over an operation link 16 . 1 , 16 . 2 , 16 . 3 (taken together under the reference number 16 ). Each operation link 16 leads to the corresponding module element 17 . 1 , 17 . 2 , 17 . 3 , (taken together accessed as module elements 17 ), which carry out the appropriate function in the laser-scanning microscope 2 . In the embodiment in FIG. 3 the module element 17 . 1 includes two galvanometer mirrors positioned at right angles to each other, the module element 17 . 2 a PMT and the module element 17 . 3 an illumination laser. In the forward channel the type assessment is replaced by the type big specification. The corresponding module operation switches 15 provide the respective module elements 17 via the operation links 16 with the appropriate supply voltages, control signals or read out the appropriate location report and measurement value signals. Every module operation switch 15 for this reason with the type assessment in the reverse channel checks whether the type bits indicate that the following data packets' data bits have to be converted from the module operation switch 15 into a corresponding control. At the same time, depending on the module in the reverse channel, the module operation switch 15 can create a corresponding data packet, e.g. with measurement values, by combining a corresponding coding (type bits) with appropriate values (data bits) in a data packet and leading it back over the serial module data link 9 to the data manager 8 and from there over the serial high-speed data link 7 and the port 6 on the parallel data link to the control device 3 . This functionality will now be described for the reverse and the forward channel for the example of the scanner module. For the complete raster scanning of a pixel 11 the control device 3 specifies via the parallel data line 5 that the scanner mirror should assume a certain position. This position specification is converted from the port 6 data packet of the serial high-speed data stream via the serial high-speed data link 7 . Thus at least one data packet runs over the serial high-speed data link 7 , which packet contains type bits (e.g. four type bits) that indicate that the following data bits that reproduce the position (coordinates) to be assumed by the galvanometer mirror. Upon segmentation of the high-speed data stream in the data manager 9 this data packet runs in the reverse channel over the serial module data link 9 to the module operation switch 15 . 1 . The module operation position 15 . 1 initiates a type assessment of all data packets, which are supplied to it over its serial module data link 9 . In this assessment it recognizes in the type bits of the said data packet that new coordinates are specified for the galvanometer mirror. The module operation switch 15 . 1 then provides appropriate voltage signals over the operation data link 16 . 1 to the module element 17 . 1 , i.e. the galvanometer mirror. The galvanometer mirrors thereupon assume the desired position. Since in the embodiment the galvanometer mirrors have a position report, the module operation switch 15 . 1 recognizes through the operation link 16 . 1 that the galvanometer mirror is in the desired position and thereupon creates a data packet for the forward channel, the data bits of which code the position the galvanometer mirror achieved and provides these data bits with the appropriate type bits, which are provided for in system 1 for this type of information and provides these data bits with the appropriate type bits, which are provided for in system 1 for this type of information. This report goes over the serial module data link 9 , the data manager 8 , the high-speed data link 7 , the port 6 as well as the parallel data link 5 and makes its way to the control device 3 , which thereby knows that the galvanometer mirrors, i.e. the scanner module 4 . 1 are adjusted to the coordinates of the desired pixel 11 . In the next step the control device 3 then effects delivery of illumination laser radiation, in turn by carrying out a corresponding reverse channel control via the parallel data link 5 so that in the end the module operation switch 15 . 3 contains a data packet, whose data bits code the details of the illumination radiation to be delivered, for instance the frequency, pulse start and pulse duration of a laser radiation pulse, which is recognized by the module operation switch 15 . 3 in the type bits of the data packet. A status report on delivery of the desired laser pulse is carried out possibly similarly as with the scanner module described in the forward channel. In a similar manner the control device 3 causes the detector module to operate, during which in the forward channel the PMT in the module element 17 . 2 accordingly is also controlled via the operation link 16 . 2 and measurement values are delivered back and in the reverse channel corresponding data packets arrive at the module operation switch 15 . 2 . In the embodiment in FIGS. 1 and 3 , the data manager 8 , as mentioned, performs a fixed combination and/or segmentation of the data stream carried over the serial high-speed data link 7 . For instance, as is shown in FIG. 4 a , the data manager accomplishes a feed from two serial module data links 9 A and 9 B, according to the plan as it is shown in the FIGS. 4 b and 4 c . Naturally, a combination or segmentation can also be carried out from and into more than two module data links. In FIG. 4 a for this reason two additional module data links 9 C and 9 D are shown. FIG. 4 b shows a high-speed data packet (hereinafter HS data packet for short) of the high-speed data stream that is designed as a 32-bit word. The data manager 8 segments this 32-bit word into two 16-bit words, which thereby constitute two data packets 20 and 21 . These data packets are transmitted for instance with signals in accordance with the LVDS standard, as it is described, e.g., in the LVDS Owner's Manual, 3 rd edition, 2004, National Semiconductor, USA. The first data packet 20 is allocated to the first serial module data links 9 A, the second data packet 21 to the second module data link 9 B. Either by means of the control device 3 or by means of the port 6 it is seen to that the configuration of the 32-bit HS data packet 18 takes into consideration this permanently set segmentation in the data manager 8 . An equally possible structure, in which type bits are only used in the forward channel, is shown in the enclosed Table 1. Each data packet 20 , 21 has type bits T and data bits D. The 32-bit HS data packet 18 contains, e.g., starting from the bit no. 0 as well as from the bit no. 16 the type bits T, to which data bits D connect, which run up to bit no. 15 or bit no. 31 respectively. In the variant shown in FIG. 4 b four respective type bits T are provided, which are drawn in the figure hatched. By means of the segmentation into two data packets 20 and 21 , then in the data manager 8 each of the 16-bit words at the beginning has (e.g. four) type bits T, to which the (e.g. 12) data bits D connect. FIG. 5 shows an exemplary case in which the data manager 8 also includes the module data links 9 C and 9 D. Here two subsequent 32-bit long HS data packets 18 and 19 of the high-speed data stream are divided into a total of four 16-bit data packets 20 , 21 , 22 and 23 , which are allocated to the module data links 9 A, 9 B, 9 C and 9 D. That principle corresponds to the one described using FIGS. 4 b and 4 c , with the difference being that two subsequent HS data packets 18 and 19 and brought in. Therefore, the first half of a first HS data packet 18 is allocated to the serial module data link 9 A, the second half of the first HS data packet 18 is allocated to the serial module data link 9 B, the first half of the second HS data packet 19 to the module data link 9 C and the second half of the second HS data packet 19 to the serial module data link 9 D. FIG. 6 schematically shows in detail an exemplary configuration of an individual module, here of a detector. The module operation switch 15 . 2 of the detector as well as the module element 17 . 2 is depicted. As can be seen, the module element 17 . 2 has a schematically drawn in PMT 24 as well as pinhole shift mechanical data 25 , which a pinhole upstream to the PMT 24 shifts in relation to situation and size. This pinhole is of essential significance for the confocal illustration of the laser-scanning microscope 2 . The position and size of the pinhole 25 have to have certain values during the operation of the microscope 2 . A shift during the complete raster scanning of the sample field 2 , i.e., a pixel-specific adjustment is on the other hand as a rule not necessary. Accordingly, the module operation switch 15 . 2 is also equipped with two sub-modules, a PMT operation module 29 as well as a CAN bus module 30 . The PMT operation module performs the control and reading out of the PMT 24 that was already mentioned and for this reason is linked to the PMT 24 via an HS link 31 . The CAN bus module 30 is connected via a CAN bus 32 to the pinhole shift mechanical data 25 and directs this with CAN data pursuant the familiar CAN bus. The module operation switch 15 . 2 therefore has an operation module, which has to work in a pixel-synchronous manner and as a rule in the high frequency range, that is to say the PMT operation module 29 , as well as a slowly working bus module, which controls the pinhole adjustment with non-pixel-synchronous settings data; in the embodiment this is carried out via a CAN bus. Both the pixel-asynchronous data as well as the pixel-synchronous high frequency data are communicated with the module operation switch 15 . 2 via the serial module data link 9 . Not only are pixel-synchronous (high frequency) data included in the data packets, which flow above the data stream of the serial module data link 9 and which also are carried in the serial high-speed data stream of the serial high-speed data link 7 , but rather also pixel-asynchronous settings data are embedded; the latter are used at least in one direction with a certain type recognition also a traditional address indication. In the opposite direction instead of type recognition the corresponding segmentation or combination of these different data types in the individual module is produced by a splitter 28 , which on the one hand is linked to the serial module data link 9 and on the other hand forwards which the high frequency or settings data forward to the PMT operation module 29 or the CAN bus module 30 . For this it performs a type evaluation or assessment. Naturally, this configuration described using the detector module is in principle possible in an embodiment of the invention for additional or all detection and illumination means. This embodiment has the advantage that the control device 3 can control not only those parts of the illumination and detector means in real time, which need pixel-synchronous control or reading out, but rather also part of the microscope 2 , which can only be in a certain position when in operation, yet do not have to be adjusted in the pixel cycle. At the same time, the control of these settings elements with traditional (slow) bus systems, as result from the CAN bus, without a separate cabling of the microscope 2 having to be provided for according to this bus. Thus such a bus interface can itself be dispensed with in the control device 3 and also in the microscope 2 . FIG. 7 shows a further configuration of an individual module controlled via a serial module data link 9 pursuant to FIG. 6 . The configuration essentially corresponds to that in FIG. 6 , so that elements described there do not have to be explained once again. The refinement consists in the fact that in the module operation switch 15 . 2 on the CAN bus 32 a CAN bus branch connection 33 is provided, which empties into a externally accessible CAN bus connector 34 . This connector 34 can either be provided directly on the module operation switch 15 . 2 , or also on a suitable other place on the microscope 2 , particularly an arrangement is possible on a diagnostic adapter board. The proper functioning of the pinhole adjustment mechanical data will now be checked in this simple way by feeding in the appropriate CAN bus signals from a diagnostics device on the connector 34 . The mode of operation of the corresponding module can also be checked by reading along of the signals coming in at the CAN bus connector 34 , which the CAN bus module 30 provides via the CAN bus 32 for the pinhole adjustment mechanical data 25 . Finally, it can also be provided for in a repeated refinement that the CAN bus module 30 on the connector 34 reconverts CAN data fed in and feeds in via the splitter 28 into the module data stream of the serial module data link 9 . Thus a reverse diagnostics is also possible. In the embodiments described, the data manager 8 carries out a combination or segmentation of the high-speed data stream of the high-speed data link 7 out from and into individual data streams, which are linked to serial individual module links 9 , for instance the links 9 A, 9 B and possible 9 C and 9 D. At the same time, case constellations were explained, in which each individual module has an independent serial module data link. This, however, is not absolutely necessary. The data manager 8 for instance can also use the module data link 9 as a bus. For this reason on the corresponding individual modules, which are shown by way of example as individual modules 35 and 40 in FIG. 8 , on the entrance side a branching node 37 is provided that directs all data packets supplied through the module data link 9 to a forwarding branch 38 or funnels incoming data packets to the serial module data link 9 . The forwarding branch 38 ends in a bus connector 39 to which an additional individual module 40 , which essentially corresponds to the individual module 35 , is connected by means of a bus link 40 . Consequently, several individual modes are divided into a serial module data link in the manner of a bus, whereby in turn the type specification or type assessment, which is performed within the module 35 or 40 by an assessment unit 36 , defines which data the data bits contain from which it follows (implicitly) whether the respective module processes a data packet. Such an assessment unit 36 is in principle provided for in each individual module either as an independent element or its function is performed by another component. Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. TABLE 1

Specimen laser-scanning microscope with raster scanning illumination and detector modules, which illuminates and detects a specimen by raster scanning. A real-time control device (device) performs synchronous reading-out with the raster scanning pixel cycle. A data port serially communicates with the device using a bidirectional high-speed data stream and with the resources via a serial, bidirectional high-speed data stream with a data conversion to/from parallel to serial. The high-speed data stream is made up of data packets with data bits and type bits and no additional header or protocol bits. The data bits contain data from/on the resources and the type bits code the type of data. Type information is stored in the resources as well as the device. The type information defines processing functions for data types coded by the type bits, and the resources and/or the device determine the data type using type bits and process data coded in the data bits.

CROSS REFERENCE TO RELATED APPLICATION This application is a divisional of U.S. patent application Ser. No. 09/736,068, filed Dec. 13, 2000 now U.S. Pat. No. 6,516,291 which is hereby incorporated by reference herein in its entirety. BACKGROUND OF THE INVENTION The present invention relates to apparatus and methods for providing an output signal proportional to the root-mean-square (RMS) value of an input signal. More particularly, the present invention relates to apparatus and methods for detecting an output fault condition and for recovering from such a condition so that an output signal is provided. The output signal may be a direct current (DC) signal proportional to the RMS value of an input signal (commonly called RMS-to-DC conversion). The RMS value of a waveform is a measure of the heating potential of that waveform. RMS measurements allow the magnitudes of all types of voltage (or current) waveforms to be compared to one another. Thus, for example, applying an alternating current (AC) waveform having a value of 1 volt RMS gain stage 36 . Gain stage 36 has an output V OUT , and provides a broadband gain A. To simplify the description of pulse modulator 32 and demodulator 34 , the following discussion first assumes that A=B=1 (although in practice it is common for A=B>1). As described below, this assumption only affects a scale factor in the resulting analysis. Pulse modulator 32 may be any commonly known pulse modulator, such as a pulse code modulator, pulse width modulator, or other similar modulator. As shown in FIG. 1, pulse modulator 32 is implemented as a single-bit oversampling ΔΣ pulse code modulator, and includes integrator 40 , comparator 41 , switch 42 , non-inverting buffer 44 , and inverting buffer 46 . As described in more detail below, switch 42 and buffers 44 and 46 form a single-bit multiplying digital-to-analog converter (MDAC) 47 . Integrator 40 has a first input coupled to input V IN , a second input coupled to the pole of switch 42 , and an output coupled to an input of comparator 41 . Comparator 41 has a clock input coupled to clock signal CLK, and an output V 1 coupled to control terminals of switches 42 and 52 . Clock CLK is a fixed period clock that has a frequency that is much higher than the frequency of input V IN (e.g., 100 times greater). Comparator 41 compares the signal at the output of integrator 40 to a reference level (e.g., GROUND), and latches the comparison result as output signal V 1 on an edge of clock CLK. Non-inverting buffer 44 provides unity gain (i.e., +1.0) and has an input coupled to the output of gain stage 38 , and an output coupled to the first terminal of switch 42 . Inverting buffer 46 provides across a resistor produces the same amount of heat as applying 1 volt DC voltage across the resistor. Mathematically, the RMS value of a signal V is defined as: V rms = V 2 _ ( 1 ) which involves squaring the signal V, computing the average value (represented by the overbar in equation (1)), and then determining the square root of the result. Various previously known conversion techniques have been used to measure RMS values. One previously known conversion system uses oversampling analog-to-digital converters to generate precise digital representations of an applied signal. The digital representations are demodulated and filtered to produce a DC output signal that has the same heat potential as the applied signal. This type of system is attractive to circuit designers because it produces highly accurate results and can be efficiently implemented on an integrated circuit. FIG. 1 is a generalized schematic representation of a portion of an RMS-to-DC converter circuit. As shown in FIG. 1, RMS-to-DC converter circuit 30 includes pulse modulator 32 , demodulator 34 , gain stage 36 , gain stage 38 , and lowpass filter 54 . Pulse modulator 32 has a first input coupled to V IN , a second input coupled to the output of gain stage 38 and an output V 1 . Demodulator 34 has an input coupled to V IN , a control input coupled to V 1 , and an output V 2 . Gain stage 38 has an input coupled to V OUT , and provides a broadband gain B. Lowpass filter 54 has an input coupled to V 2 and an output V 3 coupled to the input of inverting gain (i.e., −1.0) and has an input coupled to the output of gain stage 38 , and an output coupled to the second terminal of switch 42 . V 1 is a signal having a binary output level (e.g., −1 or +1). If V 1 =+1, the pole of switch 42 is coupled to the output of non-inverting buffer 44 . That is, (assuming gain B=1)+V OUT is coupled to the second input of integrator 40 . Alternatively, if V 1 =−1, the pole of switch 42 is coupled to the output of inverting buffer 46 . That is, (assuming gain B=1)−V OUT is coupled to the second input of integrator 40 . This switching configuration provides negative feedback in pulse modulator 32 . The first and second inputs of integrator 40 therefore can have values equal to: − V OUT ≦V IN ≦+V OUT   (2) and V IN thus has a bipolar input signal range. From equation (2), if V 1 has a duty ratio D between 0-100%, D can be expressed as: D = 1 2 × ( V IN V OUT + 1 ) , 0 ≤ D ≤ 1 ( 3 ) That is, if V IN −V OUT , D=0, and if V IN =+V OUT , D=1. Demodulator 34 includes non-inverting buffer 48 , inverting buffer 50 and switch 52 , which form a single-bit MDAC. Non-inverting buffer 48 has an input coupled to V IN , and an output coupled to a first terminal of switch 52 . Inverting buffer 50 has an input coupled to V IN , and an output coupled to a second terminal of switch 52 . Switch 52 has a control terminal coupled to V 1 and a pole coupled to the input of lowpass filter 54 . If V 1 =+1, the pole of switch 52 is coupled to the output of non-inverting buffer 48 . That is, +V IN is coupled to the input of lowpass filter 54 . Alternatively, if V 1 =−1, the pole of switch 52 is coupled to the output of inverting buffer 50 . That is, −V IN is coupled to the input of lowpass filter 54 . Demodulator 34 provides an output signal V 2 at the pole of switch 52 that may be expressed as: V 2 =    + V IN × D - ( - V IN ) × ( D - 1 )    ( 4  a ) =    V IN × ( 2 × D - 1 )    ( 4  b ) Substituting equation (3) into equation (4b), V 2 is given by: V 2 = V IN 2 V OUT ( 5 ) Lowpass filter 54 may be a continuous-time or a discrete-time filter, and provides an output V 3 equal to the time average of input V 2 . Accordingly, V 3 equals: V 3 = V IN 2 _ V OUT ( 6 ) Gain stage 36 provides an output V OUT equal to (assuming gain A=1) V 3 : V OUT =    V IN 2 _ V OUT    ( 7  a ) =    V IN 2 _ = V RMS    ( 7  b ) Thus, circuit 30 has a bipolar input range and provides an output V OUT equal to the RMS value of input V IN . Demodulator 34 and stage 47 each are single-bit MDACs and comparator 41 is a single-bit analog-to-digital converter (ADC) that provides a single-bit output V 1 . The difference between the output of integrator 40 and MDAC 47 equals the quantization error e[i] of pulse modulator 32 . Because the output of comparator 41 controls the polarity of the feedback signal from V OUT to the input integrator 40 , converter 30 will remain stable for only one polarity of V OUT . If V OUT has a polarity opposite of that assumed for the connection of switch 42 (e.g., during power up, a brown out, or a load fault), modulator 32 will become unstable, and the output of integrator 40 will quickly approach a rail voltage. With a DC input, this may not be problematic, because the state of V 1 might be such that V IN propagates through MDAC 34 and results in the V 2 polarity desired for V OUT . In this case, once any external influences on V OUT are removed, V 2 (and therefore V OUT ), will return to the proper polarity once it propagates through low pass filter 54 . This sequence, however, has a probability of occurring only about 50% of the time, meaning that converter 30 is unlikely to recover in almost half of the possible DC operating cases. Moreover, RMS-to-DC converters are most often used with AC signals, and in those instances output recovery is even less likely to occur. Thus, in view of the foregoing, it would be desirable to provide methods and apparatus for performing RMS-to-DC conversions that have improved recovery characteristics. SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide methods and apparatus for performing RMS-to-DC conversions that have fault detection and recovery capabilities. In accordance with this and other objects of the present invention, circuitry and methods that supply the root-mean-square (RMS) value of an input signal and that detect and independently recover from output fault conditions are provided. The circuit of the present invention includes reconfigurable circuitry that changes from normal operating mode to fault recovery mode when an output fault is detected. During fault recovery mode, the circuit of the present invention generates a modified output signal that allows independent recovery from an output fault condition. Once recovery is complete, the circuit returns to the RMS mode of operation. BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned objects and features of the present invention can be more clearly understood from the following detailed description considered in conjunction with the following drawings, in which the same reference numerals denote the same structural elements throughout, and in which: FIG. 1 is a schematic diagram of a previously known RMS-to-DC converter circuit; FIG. 2A is a schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 2B is another schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 3A is another schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 3B is another schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 4A is another schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 4B is another schematic diagram of an RMS-to-DC converter circuit of the present invention; FIG. 5 is a schematic diagram of the reconfigurable ΔΣ modulator of FIGS. 2 - 4 . DETAILED DESCRIPTION OF THE INVENTION FIG. 2A illustrates an embodiment of RMS-to-DC converter constructed in accordance with the principles of the present invention. Circuit 130 includes pulse modulator 132 , demodulator 134 , gain stages 36 and 38 , lowpass filter 54 , and optional delay-matching stage 82 . To simplify the description of modulator 132 and demodulator 134 , the following discussion assumes that A=B=1 (although in practice it is common for A=B>1). This assumption only affects a scale factor in the resulting analysis. Pulse modulator 132 includes cascaded AZ pulse code modulators. In particular, pulse modulator 132 includes reconfigurable ΔΣ stage 72 , ΔΣ stage 76 , monitor circuit 73 , delay stage 78 , and subtractor 80 . As described in more detail below, ΔΣ stage 76 , delay stage 78 , and subtractor 80 provide an estimate of the spectrally-shaped quantization error of reconfigurable ΔΣ stage 72 . Reconfigurable ΔΣ stage 72 has a first input coupled to V IN , a second input coupled to the output of gain stage 38 (through switch 75 ), a first output coupled to the input of monitor circuit 73 , and a second output V 4 coupled to a first input of ΔΣ stage 76 . ΔΣ stage 76 has a second input coupled to the output of gain stage 38 , and an output V 5 coupled to a non-inverting input of subtractor 80 and to an input of delay stage 78 . Subtractor 80 has an inverting input coupled to an output of delay stage 78 , and an output V 1b coupled to a control terminal of switch 96 . Monitor circuit 73 may include a delay stage (not shown) to match the delay through ΔΣ stage 76 , and has an output V 1a coupled to a control terminal of switch 88 . ΔΣ stages 72 and 76 may be, for example, single-bit modulators that can be of any order. Preferably, reconfigurable ΔΣ stage 72 is a first-order stage. Reconfigurable first-order ΔΣ stage 72 and monitor circuit 73 provide output V 1a equal to (assuming gain B=1): V 1  a  [ i + 1 ] = ( V IN  [ i - 1 ] ) V OUT + ( e  [ i ] - e  [ i - 1 ] ) V OUT ( 8 ) where index i denotes the sample index and e[i] is the quantization error of reconfigurable ΔΣ stage 72 . V 1a thus equals the desired ratio of the input divided by V OUT , plus the spectrally-shaped quantization error of reconfigurable ΔΣ stage 72 divided by V OUT . ΔΣ stage 76 , delay stage 78 and subtractor 80 provide an output V 1b equal to an estimate of the spectrally-shaped quantization error of reconfigurable ΔΣ stage 72 divided by V OUT . In particular, V 4 is the quantization error e[i] of reconfigurable ΔΣ stage 72 , which is a function of the input signal V IN , the state of the integrator, and the local feedback within the MDAC of reconfigurable ΔΣ stage 72 . ΔΣ stage 76 provides an output V 5 equal to (assuming gain B=1): V 5  [ i + 1 ] = ( 1 V OUT ) × [ e  [ i ] + ( e ′  [ i + 1 ] - e ′  [ i ] ) ] ( 9 ) where e′[i] is the quantization error of ΔΣ stage 76 . Delay stage 78 and subtractor 80 form a digital differentiator that provide an output V 1b equal to (assuming gain B=1): V 1  b  [ i + 1 ] = ( 1 V OUT ) × [ e 1 + e 2 ] ( 10 ) where e 1 =e[i]−e[i −1]  (11a) e 2 =e′[i +1]−2e′[i]+ e′[i −1]  (11b) Delay stage 82 matches the combined delay through pulse code modulator 132 . Demodulator 134 provides an output proportional to input V IN times the ratio of V IN to V OUT . In particular, demodulator 134 includes non-inverting buffer 84 , inverting buffer 86 , switch 88 , subtractor 90 , non-inverting buffer 92 , inverting buffer 94 , three-position switch 96 and multiply-by-two stage 97 . Non-inverting buffer 84 provides unity gain (i.e., +1.0) and has an input coupled through delay stage 82 to input V IN , and an output coupled to the first terminal of switch 88 . Inverting buffer 86 provides inverting gain (i.e., −1.0) and has an input coupled through delay stage 82 to input V IN , and an output coupled to the second terminal of switch 88 . Non-inverting buffer 84 , inverting buffer 86 and switch 88 form a single-bit MDAC. V 1a is a binary signal having a binary output level (e.g., −1 or +1). If V 1a =+1, the pole of switch 88 is coupled to the output of non-inverting buffer 84 . That is, +V IN is coupled to first input V 6 of subtractor 90 . Alternatively, if V 1a =−1, the pole of switch 88 is coupled to the output of inverting buffer 86 . That is, V IN is coupled to first input V 6 of subtractor 90 . V 6 equals (assuming gain B=1): V 6  [ i + 1 ] =    V IN  [ i - 1 ] V OUT × V 1  a  [ i + 1 ]    ( 12  a ) =    V IN  [ i - 1 ] V OUT × ( V IN  [ i - 1 ] + e 1 )    ( 12  b ) Non-inverting buffer 92 provides unity gain (i.e., +1.0) and has an input coupled through delay stage 82 to input V IN , and an output coupled to the first terminal of three-position switch 96 . Inverting buffer 86 provides inverting gain (i.e., −1.0) and has an input coupled through delay stage 82 to input V IN , and an output coupled to the third terminal of three-position switch 96 . The second terminal of three-position switch 96 is coupled to GROUND. Non-inverting buffer 92 , inverting buffer 94 and three-position switch 96 form a 1.5-bit MDAC. Multiply-by-two stage 97 provides a gain of +2.0. V 1b is a tri-level signal having output values of −2, 0 or +2. If V 1b =+2, the pole of three-position switch 96 is coupled to the output of non-inverting buffer 92 . That is, +2V IN is coupled to second input V 7 of subtractor 90 . If V 1b =0, the pole of switch 96 is coupled to GROUND, and therefore 0 is coupled to second input V 7 of subtractor 90 . If, however, V 1b =−2, the pole of switch 96 is coupled to the output of inverting buffer 94 . That is, −2V IN is coupled to second input V 7 of subtractor 90 . V 7 equals (assuming gain B=1): V 7  [ i + 1 ] = V IN  [ i - 1 ] V OUT × ( e 1 + e 2 ) ( 13 ) Subtractor 90 provides an output V 8 that equals the difference between V 6 and V 7 : V 8  [ i + 1 ] =    V 6  [ i + 1 ] - V 7  [ i + 1 ]    ( 14  a ) =    V IN  [ i - 1 ] 2 V OUT - V IN  [ i - 1 ] 2 V OUT × e 2    ( 14  b ) Thus, V 8 is proportional to V IN squared divided by V OUT , substantially without the quantization noise of reconfigurable ΔΣ stage 72 . The quantization noise e 2 of ΔΣ stage 76 remains, but the low frequency portion of that noise is further reduced by the spectral shaping provided by delay 78 and subtractor 80 . Further, because e 2 is uncorrelated with V IN , the DC average of the product of e 2 and V IN equals zero. As a result, output V 9 of lowpass filter 54 approximately equals: V 9 ≈ V IN 2 _ ( 15 ) Output V OUT of gain stage 36 approximately equals (assuming gain A=1): V OUT ≈ V IN 2 _ ( 16 ) The circuit of FIG. 2A may be implemented using single-ended or differential circuitry. During operation, output signals from reconfigurable ΔΣ stage 72 may pass through monitor circuit 73 to the pole of switch 88 . As mentioned above, when V OUT changes polarity, ΔΣ stages 72 and 76 become unstable, producing a string of output bits with the same logic level. Monitor circuit 73 , which may include counter circuits and/or latch circuitry (not shown), detects this string and interprets it as a “fault condition.” In response to the detected fault condition, monitor circuit 73 generates a control signal that causes circuit 130 to switch from RMS-to-DC conversion mode to fault recovery mode. The number of consecutive same logic level bits that constitute a fault condition may be varied if desired. For example, with certain modulator topologies, the number of bits may be set to be relatively long (e.g., about 50) to ensure circuit 130 does not enter recovery mode inadvertently. In other applications, however, the number of bits may be somewhat less (e.g., about 15) to reduce recovery time. In fault recovery mode, switch 75 is opened, breaking the feedback path from output V OUT to ΔΣ stage 72 . In addition, some components within ΔΣ stage 72 are reconfigured so that ΔΣ stage 72 functions as a comparator circuit rather than as a modulator circuit (shown as comparator circuit 77 in FIG. 2 B). With this arrangement, shown in FIG. 2B, circuit 130 operates as a mean-absolute-detect circuit instead of an RMS-to-DC converter. Circuit 130 thus determines the average of the absolute value of input signal V IN . Although this measurement is less meaningful than the RMS value of the input signal, it ensures circuit 130 will produce an output signal V OUT that has the proper polarity. Once V OUT returns to the correct polarity, the bit stream produced by ΔΣ stage 76 toggles, indicating that the fault condition has cleared. Monitor circuit 73 detects this change of logic level and returns circuit 130 to RMS-to-DC conversion mode (i.e., closes switch 75 and reconfigures comparator 77 to operate as ΔΣ stage 72 ). In this way, circuit 130 may detect and recover from fault conditions irrespective of the type and amplitude of input signal V IN . As shown in FIG. 2B, to operate as a mean-absolute-detect circuit, the feedback from V OUT to comparator 77 is disconnected. The output signal produced by comparator 77 is a bit stream that represents the polarity of input signal V IN . Comparator 77 may be configured as a polarity detector using any suitable arrangement known in the art (e.g., by connecting a threshold terminal to ground and a sensing terminal (both not shown) to input signal V IN ). When the output of comparator 77 is provided to demodulator 134 (i.e., the pole of switch 88 ), the input signal V IN is multiplied by its own polarity, thus performing an absolute value operation. The resulting signal is then fed through lowpass filter 54 which provides an output signal V OUT of the desired polarity (assuming any external stimuli has been removed from the output node). As long as output signal V OUT is the incorrect polarity, ΔΣ stage 76 will be unstable, and its output will remain at either a logic low or a logic high (depending on its state when the output fault occurred). When this occurs, subtractor 80 has a substantially zero output and will not affect the value of V OUT . When circuit 130 is operating in mean-absolute-detect mode, error signal V 4 produced by comparator 77 is the input signal V IN (or a scaled version thereof). Thus, the output of ΔΣ stage 76 can be monitored (by monitor circuit 73 ) to determine when recovery from an output fault has occurred. For example, when the bit stream produced by ΔΣ stage 76 toggles from one logic state to another, circuit 130 has recovered from the fault condition and may be reconfigured back to the RMS-to-DC converter shown in FIG. 2 A. The overall gain of circuit 130 during fault recovery (i.e., mean-absolute-detect mode) does not need to be similar to that of the RMS-to-DC mode (i.e., normal operation). However, increased gain during fault recovery does tend to reduce recovery time. Moreover, it will be understood that with certain input waveforms and filter time constants, circuit 130 may go into fault recovery, back to normal operation, and return to fault recovery several times in succession. As long as the output is free of external influences however, circuit 130 will recover. The successive fault mode periods will become shorter in duration until circuit 130 has fully recovered. FIG. 3A shows another illustrative embodiment of RMS-to-DC converter constructed in accordance with the present invention. Converter 230 includes single-sample delay stages 82 and 104 , modulator 232 and demodulator 234 . Modulator 232 includes single-bit reconfigurable ΔΣ stage 72 , ΔΣ stage 76 , and monitor circuit 73 , and demodulator 234 includes single-bit MDAC stages 98 , 100 and 102 , and adder/subtractor 106 . MDACS 98 , 100 , and 102 may be implemented as in demodulator 34 of FIG. 1 . Alternatively, some of MDACS 98 , 100 and 102 may be implemented as a single time-multiplexed MDAC. Reconfigurable ΔΣ stage 72 provides a quantized output V 1c equal to (assuming gain B=1): V 1  c  [ i ] = V IN  [ i - 1 ] + e  [ i ] - e  [ i - 1 ] V OUT ( 17 ) In addition, V 4 equals the quantization error e[i] of reconfigurable ΔΣ stage 72 . ΔΣ stage 76 provides a quantized output V 1d equal to (assuming gain B=1): V 1  d  [ i ] = e  [ i - 1 ] + e ′  [ i ] - e ′  [ i - 1 ] V OUT ( 18 ) Single-bit DACs 98 , 100 and 102 provide outputs V 10 , V 11 and V 12 , respectively, equal to (assuming gain B=1): V 10 [i]=V IN [i −1 ]×V 1c [i]   (19)   V 11 [i]=V IN [i −1 ]×V 1d [i]   (20) V 12 [i]=V IN [i −2 ]×V 1d [i]   (21) Adder/subtractor 106 provides an output V 13 equal to: V 13 [i]=V 10 [i]+V 11 [i]−V 12 [i]   (22) which equals (assuming gain B=1): V 13  [ i ] = V IN  [ i - 1 ] V OUT × ( V IN  [ i - 1 ] + e  [ i ] + e ′  [ i ] - e ′  [ i - 1 ] ) - V IN  [ i - 2 ] V OUT × ( e  [ i - 1 ] + e ′  [ i ] - e ′  [ i - 1 ] ) ( 23 ) Note that: V 13  [ i + 1 ] = V IN  [ i ] V OUT × ( V IN  [ i ] + e  [ i + 1 ] + e ′  [ i + 1 ] - e ′  [ i ] ) - V IN  [ i - 1 ] V OUT × ( e  [ i ] + e ′  [ i + 1 ] - e ′  [ i ] ) ( 24 ) If the time constant of lowpass filter 54 is much greater than the sample period of V 13 [i] (e.g., 10,000 times), lowpass filter 54 provides output V 14 that is the average of sequence V 13 . V 13 as a function of V IN [i−1] approximately equals: V 13 ∣ V IN  [ i - 1 ] ≈ V IN  [ i - 1 ] V OUT × ( V IN  [ i - 1 ] + e  [ i ] + e ′  [ i ] - e ′  [ i - 1 ] ) - V IN  [ i - 1 ] V OUT × ( e  [ i ] + e ′  [ i + 1 ] - e ′  [ i ] ) ( 25 ) which may be written as: V 13 ∣ V IN  [ i - 1 ] = ( V IN  [ i - 1 ] V OUT ) 2 - V IN  [ i - 1 ] × ( e ′  [ i + 1 ] - 2  e ′  [ i ] + e ′  [ i - 1 ] ) V OUT ( 26 ) The first term on the right side of equation (26) is the desired output, and the second term equals the second-order spectrally-shaped quantization noise of ΔΣ stage 76 , which is substantially reduced by lowpass filter 54 . Further, because e′ is uncorrelated with V IN , the DC average of the product of e′ and V IN equals zero. As a result, V 14 approximately equals: V 14 = V 13 _ ≈ V IN 2 _ V OUT ( 27 ) Output V OUT of gain stage 36 approximately equals (assuming gain A=1): V OUT ≈ V IN 2 _ ( 28 ) The circuit of FIG. 3A may be implemented using single-ended or differential circuitry. During operation, output signals from reconfigurable ΔΣ stage 72 may pass through monitor circuit 73 to MDAC 98 . As mentioned above, when V OUT changes polarity, ΔΣ stages 72 and 76 become unstable, producing a string of output signals with a constant logic level. Monitor circuit 73 detects this output string, which it interprets as a “fault condition” and generates a control signal that causes circuit 230 to switch from RMS-to-DC conversion mode to fault recovery mode. In fault recovery mode, switch 75 is opened, breaking the feedback path from output V OUT to ΔΣ stage 72 . Additionally, some components within ΔΣ stage 72 are reconfigured so that ΔΣ stage 72 functions as a comparator circuit rather than as a modulator circuit (shown as comparator circuit 77 in FIG. 3 B). In this arrangement, shown in FIG. 3B, circuit 230 operates as a mean-absolute-detect circuit instead of an RMS-to-DC converter. Circuit 230 thus determines the average of the absolute value of the input signal. Although this measurement is less meaningful than the RMS value of the input signal, it ensures circuit 230 will produce an output signal V OUT that has the proper polarity. Once V OUT returns to the proper polarity, the bit stream produced by comparator 77 toggles, indicating that the fault condition has cleared. Monitor circuit 73 detects this change of logic level and returns circuit 230 back to RMS-to-DC conversion mode (i.e., closes switch 75 and reconfigures comparator 77 to operate as ΔΣ stage 72 ). In this way, circuit 230 may detect and recover from fault conditions irrespective of the type and amplitude of input signal V IN . As shown in FIG. 3B, to operate as a mean-absolute-detect circuit, the feedback from V OUT to comparator 77 is disconnected. The output signal produced by comparator 77 is a bit stream that represents the polarity of input signal V IN . Comparator 77 may be configured as a polarity detector using any suitable method known in the art (e.g., by connecting a threshold terminal to ground and a sensing terminal (both not shown) to input signal V IN ). When the output of comparator 77 is provided to demodulator 234 (i.e., MDAC 98 ), input signal V IN is multiplied by its own polarity, thus performing an absolute value operation. The resulting signal is fed through lowpass filter 54 which generates an output signal (V OUT ) of the desired polarity (assuming any external stimuli has been removed from the output node). As long as output signal V OUT is the incorrect polarity, ΔΣ stage 76 will remain unstable. Its output will therefore remain at either a logic low or a logic high (depending on its state when the output fault occurred). When this occurs, V 11 and V 12 substantially cancel each other out (at summing node 106 ), and thus output V 13 is substantially equal to the value of V 10 . Alternatively, V 11 and V 12 may be disconnected from summer 106 during fault recovery. When circuit 230 is operating as a mean-absolute-detector, error signal V 4 produced by comparator 77 is the input signal V IN (or a scaled version thereof). Thus, the output of ΔΣ stage 76 can be monitored (by monitor circuit 73 ) to determine when recovery from an output fault has occurred. For example, when the bit stream produced by ΔΣ stage 76 toggles from one logic state to another, indicating a change in output polarity, circuit 230 has recovered from the fault condition and may be reconfigured back to the RMS-to-DC converter shown in FIG. 3 A. The overall gain of circuit 230 during fault recovery (i.e., mean-absolute-detect mode) does not need to be similar to that of the RMS-to-DC mode (normal operation). However, increased gain during fault recovery does tend to reduce recovery time. Moreover, it will be understood that with certain input waveforms and filter time constants, circuit 230 may go into fault recovery, back to normal operation, and back to fault recovery several times in succession. As long as the output is free of external influences however, circuit 230 will recover. The successive fault mode periods will become shorter in duration until circuit 230 has fully recovered. FIG. 4A illustrates another embodiment of RMS-to-DC converters constructed in accordance with the principles of the present invention. Circuit 330 includes delay stages 82 and 104 and pulse modulator 332 and demodulator 334 . Circuit 330 includes features of circuits 130 and 230 , but substantially eliminates the effect of any DC offset that may occur in ΔΣ stage 76 and delay stage 104 . Modulator 332 includes single-bit reconfigurable ΔΣ stage 72 and ΔΣ stage 76 , delay stage 78 , and subtractor 80 . Demodulator 334 includes 1-bit DAC 87 , 1.5-bit DAC 89 (which may be constructed similar to the DAC formed by buffers 92 and 94 and switch 96 ), subtractor 90 , and multiply-by-two stage 97 . Delay stage 82 matches the delay through reconfigurable ΔΣ modulator 72 and delay stage 104 matches the delay through ΔΣ modulator 76 . Reconfigurable ΔΣ stage 72 provides a quantized output V 1e equal to (assuming gain B=1): V 1  e  [ i ] = V IN  [ i - 1 ] + e  [ i ] - e  [ i - 1 ] V OUT ( 29 ) ΔΣ stage 76 , delay stage 78 and subtractor 80 provide an output V 1f equal to an estimate of the spectrally-shaped quantization error V 4 of reconfigurable ΔΣ stage 72 divided by V OUT . ΔΣ stage 76 provides an output V 15 equal to (assuming gain B=1): V 15  [ i + 1 ] = ( 1 V OUT ) × [ e  [ i ] + ( e ′  [ i + 1 ] - e ′  [ i ] ) ] ( 30 ) where e′[i] is the quantization error of ΔΣ stage 76 . Delay stage 78 and subtractor 80 form a digital differentiator that provide an output V 1f equal to (assuming gain B=1): V 1  f  [ i + 1 ] = ( 1 V OUT ) × [ e 1 + e 2 ] ( 31 ) where e 1 =e[i]−e[i −1]  (32a) e 2 =e′[i +1]−2 e′[i]+e′[i −1]  (32b) V 16 equals (assuming gain B=1): V 16  [ i ] =    V IN  [ i - 1 ] V OUT × V 1  e  [ i ]    ( 33  a ) =    V IN  [ i - 1 ] V OUT × ( V IN  [ i - 1 ] + e 1 )    ( 33  b ) V 17 equals (assuming gain B=1): V 17  [ i + 1 ] = V IN  [ i - 1 ] V OUT × ( e 1 + e 2 ) ( 34 ) The digital differentiator formed by delay stage 78 and subtractor 80 has a zero at DC, and therefore sequence V 1f substantially has no DC component. As a result, sequence V 17 is substantially free of any DC offset introduced by delay stages 82 and 104 , and ΔΣ stage 76 . Subtractor 90 provides an output V 18 that equals the difference between V 16 and V 17 : V 18  [ i + 1 ] =    V 16  [ i ] - V 17  [ i + 1 ]    ( 35  a ) =    V IN  [ i - 1 ] 2 V OUT - V IN V OUT × e 2    ( 35  b ) Thus, V 18 is proportional to V IN squared divided by V OUT , substantially without the quantization noise of Δ−Σ stage 72 . Output V 19 of lowpass filter 54 approximately equals: V 19 ≈ V IN 2 _ ( 36 ) and output V OUT of gain stage 36 approximately equals (assuming gain A=1): V OUT ≈ V IN 2 _ ( 37 ) The circuit of FIG. 4A may be implemented using single-ended or differential circuitry. During operation, output signals from reconfigurable ΔΣ stage 72 may pass through monitor circuit 73 to MDAC 87 . As mentioned above, when V OUT changes polarity, ΔΣ stages 72 and 76 become unstable, producing a string of output signals with a constant logic level. Monitor circuit 73 detects this output string, which it interprets as a “fault condition” and generates a control signal that causes circuit 330 to switch from RMS-to-DC conversion mode to fault recovery mode. In fault recovery mode, switch 75 is opened, breaking the feedback path from output V OUT to ΔΣ stage 72 . Additionally, some components within ΔΣ stage 72 are reconfigured so that ΔΣ stage 72 functions as a comparator circuit rather than as a modulator circuit (shown as comparator circuit 77 in FIG. 4 B). In this arrangement, shown in FIG. 4B, circuit 330 operates as a mean-absolute-detect circuit instead of an RMS-to-DC converter. Circuit 330 thus determines the average of the absolute value of the input signal. Although this measurement is less meaningful than the RMS value of the input signal, it ensures circuit 330 will produce an output signal V OUT that has the proper polarity. Once V OUT returns to the proper polarity, the bit stream produced by comparator 77 toggles, indicating that the fault condition has cleared. Monitor circuit 73 detects this change of logic level and returns circuit 330 back to RMS-to-DC conversion mode (i.e., closes switch 75 and reconfigures comparator 77 to operate as ΔΣ stage 72 ). In this way, circuit 330 may detect and recover from fault conditions irrespective of the type and amplitude of input signal V IN . As shown in FIG. 4B, to operate as a mean-absolute-detect circuit, the feedback from V OUT to comparator 77 is disconnected. The output signal produced by comparator 77 is a bit stream that represents the polarity of input signal V IN . Comparator 77 may be configured as a polarity detector using any suitable method known in the art (e.g., by connecting a threshold terminal to ground and a sensing terminal (both not shown) to input signal V IN ). When the output of comparator 77 is provided to demodulator 334 (i.e., MDAC 87 ), input signal V IN is multiplied by its own polarity, thus performing an absolute value operation. The resulting signal is fed through lowpass filter 54 which generates an output signal (V OUT ) of the desired polarity (assuming any external stimuli has been removed from the output node). As long as output signal V OUT is the incorrect polarity, ΔΣ stage 76 will remain unstable. Its output will therefore remain at either a logic low or a logic high (depending on its state when the output fault occurred). In this case, subtractor 80 will have a substantially zero output and will not affect the value of V OUT . When circuit 330 is operating as a mean-absolute-detect circuit, error signal V 4 produced by comparator 77 is the input signal V IN (or a scaled version thereof). Thus, the output of ΔΣ stage 76 can be monitored (by monitor circuit 73 ) to determine when recovery from an output fault has occurred. For example, when the bit stream produced by ΔΣ stage 76 toggles from one logic state to another, indicating the output has changed polarity, circuit 330 has recovered from the fault condition and may be reconfigured back to the RMS-to-DC converter shown in FIG. 4 A. The overall gain of circuit 330 during fault recovery (i.e., mean-absolute-detect mode) does not need to be similar to that of the RMS-to-DC mode (normal operation). However, increased gain during fault recovery does tend to reduce recovery time. Moreover, it will be understood that with certain input waveforms and filter time constants, circuit 330 may go into fault recovery, back to normal operation, and back to fault recovery several times in succession. As long as the output is free of external influences however, circuit 330 will recover. The successive fault mode periods will become shorter in duration until circuit 330 has fully recovered. As mentioned above, monitoring circuit 73 may detect an output fault by detecting a string of same logic level output bits from reconfigurable ΔΣ stage 72 . This will occur anytime reconfigurable ΔΣ stage 72 is overloaded, either because it is unstable or because the input signal V IN is excessively large. Thus, under certain circumstances a fault condition may be detected even when the output signal V OUT is the “correct” polarity. One such case is when the amplitude of the input signal (V IN ) increases suddenly. For example, a step change of about a factor of ten may cause reconfigurable ΔΣ stage 72 to overload and produce an output duty cycle of either 0% or 100% at the peaks of the input waveform. This result is acceptable and even desirable because it tends to decrease the output response time. Another case during which a fault condition may be detected is when input signal V IN has a large peak value with respect to the DC level of the output signal V OUT (e.g., this may occur with input signals V IN having a high crest factor). Such an input signal may, during its peak, cause reconfigurable ΔΣ stage 72 to produce an output having a duty cycle of either 0% or 100%. Depending on the duration of the peak and the length of the output string detected by monitor circuit 73 , this may initiate entry into the fault recovery mode of operation. This will increase the magnitude of the output signal V OUT during a time when it otherwise would be underestimated. FIG. 5 is a schematic diagram of one possible embodiment of reconfigurable ΔΣ stage 72 . In FIG. 5, reconfigurable ΔΣ stage 72 , shown as system 500 , includes switches 501 - 508 , capacitors 510 - 517 , amplifier 518 , and comparator 519 . As mentioned above, system 500 may be configured to operate as either ΔΣ modulator 72 or as comparator 77 , depending on the state (i.e., open or closed) of switches 501 - 508 . When configured as ΔΣ stage 72 , system 500 progresses through essentially two phases of operation, an auto-zero phase and integration phase. In auto-zero phase, switches 501 , 506 , and 508 are closed. In addition, either switches 503 or 504 are closed depending on the output of comparator 519 . For example, if the output of comparator 519 is a logic high, switches 504 may be closed and switches 503 may be open. Alternatively, if the output of comparator 519 is a logic low, switches 504 may be open and switches 503 may be closed. Input voltage V IN is applied to node 520 and node 522 is connected to ground (if desired, node 522 may be used as a differential input). In the arrangement shown, capacitor 510 is charged to the value of input voltage V IN , and capacitor 511 is set to ground. Assuming for the sake of illustration, that switches 503 are closed and switches 504 are open, capacitor 512 is charged to the value of V OUT and capacitor 513 is set to ground. Closing switches 506 provides a feedback path from outputs 532 and 536 of amplifier 518 to inputs 530 and 534 , respectively. This sets the gain of amplifier 518 , which is preferably a differential transconductance amplifier, to unity. At this point, system 500 has acquired the values of both the input and output voltages and is ready to proceed to the integration phase of operation. In the integration phase, switches 501 and 506 are opened and switches 502 and 505 are closed, configuring amplifier 518 as an integrator. Furthermore, the state of switches 503 or 504 are interchanged. That is, if switches 503 were closed and switches 504 were open during auto-zero, switches 503 open and switches 504 close during integration (and vice versa). This transfers the charge from capacitors 510 - 513 to capacitors 515 and 516 , respectively. Thus, the resulting charge on capacitors 515 and 516 is now equal to the transferred charge plus any charge from the previous integration phase. Amplifier 518 generates a differential output at terminals 532 and 536 which is a function of the result of the previous integration phase, the value of V IN and V OUT , and the output state of comparator 519 . Comparator 519 , which is preferably a latching comparator, compares these values and generates an output signal based on the comparison. When configured as comparator stage 77 , system 500 also operates in essentially two phases of operation, an auto-zero phase and a sample and hold phase. In auto-zero phase, switches 501 , 506 , and 508 are closed. In addition, either switches 503 or 504 are closed. Input voltage V IN is applied to node 520 and node 522 is connected to ground. In this arrangement, capacitor 510 is charged to the value of input voltage V IN , and capacitor 511 is set to ground. Closing switches 506 provides a feedback path from outputs 532 and 536 of amplifier 518 to inputs 530 and 534 , respectively. This sets the gain of amplifier 518 to unity. At this point, system 500 has acquired the values of both the input and output voltages and is ready to proceed to the sample and hold phase of operation. In the sample and hold phase, switches 501 and 506 are opened and switches 502 and 507 are closed, configuring amplifier 518 as a buffer. In this mode the state of switches 503 or 504 are preferably not interchanged. The charge from capacitors 510 and 511 (but not 512 and 513 ) is transferred to capacitors 514 and 517 , respectively. Thus, the resulting charge on capacitors 514 and 517 is now substantially equal to the input voltage V IN . Amplifier 518 generates a differential output at terminals 532 and 536 based on V IN , which is provided to input terminals 540 and 542 of comparator 519 . Comparator 519 compares these values and generates an output signal based on the comparison. Persons skilled in the art will recognize that the apparatus of the present invention may be implemented using circuit configurations other than those shown and discussed above. All such modifications are within the scope of the present invention, which is limited only by the claims that follow.

A circuit that provides the root-mean-square (RMS) value of an input signal and that detects and independently recovers from an output fault condition is provided. The circuit includes reconfigurable circuitry that changes from normal operating mode to fault recovery mode when an output fault is detected. During fault recovery mode, the circuit provides a modified output signal that allows independent recovery from an output fault condition. Once recovery is complete, the circuit returns to normal operating mode and provides a DC output signal proportional to the RMS value of an AC input signal.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to customer response networks and in particular to internet based response networks. 2. Description of the Related Art Many companies establish and maintain home pages on the Internet's World Wide Web. These home pages may provide an electronic market place to users with a computer, appropriate software and internet access. Companies may set up layered directories that provide information in the form of electronic catalogs or brochures. Often a point of contact such as a telephone number or electronic mail address is provided as a link in the event a user requires more information or has a question for the company. Current data services on the Web are interactive in the sense that information content is provided to a user based on keyboard or mouse input from that user. However, this response is limited to pre-programmed or “canned” text, video and/or audio. Typically, web pages contain an e-mail address where a potential customer may send a question or ask for more information on a particular subject of interest. A response to such an inquiry may take anywhere from minutes to days. Even then, there is no assurance that the e-mailed inquiry will reach the appropriate person within the company. In another scenario, a potential customer may obtain the company's telephone number from the web page or from directory assistance. The potential customer then places a telephone call to the company and may spend an interminable length of time on hold waiting for a customer service representative to become available. If the company number is a WATS line (usually referred to as 800 service), the company incurs a significant cost per minute for the amount of time the customer is in the call waiting queue. On the other hand, if the call is a standard toll call, the customer may incur a significant charge while waiting for his/her call to be routed to an available customer service representative. There is accordingly a need for a new method and apparatus to provide queuing capability between a user and a company's representative in order to facilitate the transfer of information in an effective real-time manner. As services migrate to higher bandwidth requirements and capabilities there is an increasing demand for interactive audio sessions over the internet itself. There is accordingly an additional need for a new method and apparatus to provide an interactive live video session capability between a user and a company's representative in order to facilitate the transfer of information in an effective real-time manner. SUMMARY OF THE INVENTION The method and apparatus of the present invention is accomplished by having a customer or user situated at one of many user computer terminals connected to the Internet. The user accesses a company's World Wide Web Internet home page in an Internet session and decides that more information is needed and would appreciate receiving a telephone call from a live customer service representative. The user presses an appropriate keyboard or mouse clicks on an appropriately labeled button on the Web page. An automatic call distribution device submits the user's IP address and pertinent information from the session to a customer service queue for routing to the next available customer service representative. A voice call over the Internet is then established. When the call request by the user to the customer service representative is submitted, session control passes back to the web page server and a normal interactive session is resumed. The customer then continues his previous activities while awaiting a voice call from the next available customer service representative over the internet. One advantage of the present invention allows the user and customer service representative to conduct an interactive audio session. Another advantage of the present invention allows the user and customer service representative to conduct an interactive audio session while not tying up scarce resources waiting for a customer service representative to become available. Still another advantage of the present invention is the elimination of the toll charges associated with a separate telephone call over the public switched telephone network (PSTN). Further features of the above-described invention will become apparent from the detailed description hereinafter. The foregoing features together with certain other features described hereinafter enable the overall system to have properties differing not just by a matter of degree from any related art, but offering an order of magnitude more efficient use of processing time and resources. Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the apparatus and method according to the invention and, together with the description, serve to explain the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a block diagram of the data network of the present invention. FIG. 2 illustrates a block diagram of the multimedia response server of the present invention. FIG. 3 illustrates a flowchart depiction of the methodology of the present invention. DETAILED DESCRIPTION Referring now to FIG. 1, the data network 100 of the present invention will now be discussed. A customer or user is situated at one of many user terminals 102 , 106 , 110 , 136 , 138 which may be a personal computer, graphic enhanced mobile device such as a laptop PC, Java phone or a personal digital assistant (PDA). The customer may be connected via an analog or digital (Integrated Services Digital Network (ISDN) or XDSL) connection to a Class 5 (local telephone switching) office 108 , which in turn is connected to a tandem switch 114 . Tandem switch 114 is capable of making both local and toll (long distance) telephone connections and is connected through modem 120 , direct connection or ISDN 118 connection to Asynchronous Transfer Mode (ATM) interface 128 . ATM interface 128 is connected to ATM backbone 130 . ATM backbone 130 supplies the interconnections and transport mechanisms of the data communications network, or Internet of the preferred embodiment. These transport mechanisms are well known and thus need not be further explained here. Customers are also connected through terminals 136 , 138 to the Internet embodied by ATM backbone 130 through Local Area Network (LAN) 134 . LAN direct connectivity is an alternative to dial-up connections. A live person acting as a Company's agent or customer service representative is stationed at agent terminal 124 . Terminal 124 contains an autodialer which automatically dials a preprogrammed or an entered telephone number from telephone 122 . This telephone number is the telephone number of the customer who has entered his/her own telephone number sometime during a Web page access session. The telephone call placed by the Customer service agent located at terminal 124 through telephone 122 is switched through tandem switch 116 to class 5 central office 108 to the customer. In an alternative embodiment, a customer may be connected through a mobile terminal via a wireless data link provided by a cellular, PCS or other wireless service provider. Corporate Web Server 132 is connected to ATM backbone 130 through a direct connection. In an alternate embodiment, the corporate Web Server, stationary or mobile, may also be connected via a similar wireless data link interfaced to the Internet. Referring now to FIG. 2, Corporate Web Server 200 will now be discussed in further detail. Multimedia response server 210 is connected to the Internet 230 via ATM link 228 . ATM link 228 is typically either across a T-3 carrier operating at approximately 44 MHz or is an OC-48 (or higher) Synchronous Optical Network (SONET) connection. The details of such connections are well known and need not be discussed further. The T-3 interconnection 228 interconnects with Multimedia Response Server 210 at the communication channel switch 214 . Communication channel switch 214 is controlled by Web page server 222 . Also connected to communication channel switch 214 are the Automatic Call Distribution (ACD) unit 212 , video server 216 and multiple multimedia operator consoles 202 , 204 , 206 . Communication channel switch 214 is a Northern Telecom Magellan, Vector or other suitable switch. Web page server 222 operates to supply content to customers who access the Web page, controls connections to and from communication channel switch 214 . Video server 216 supplies high bandwidth video to customers accessing the Web page through communication channel switch 214 . Automatic Call Distribution (ACD) 212 unit operates by transferring customer information such as telephone number or Internet Protocol (IP) address and subject of the further information requested into a queue for service by the next available operator stationed at one of the multimedia operator consoles 202 , 204 , 206 . A customer who is accessing the Web page on the Web server typically mouse clicks on a hot button or link found on the Web page. This link is identified as a channel for selecting a live interactive call-back session with a human operator. Upon availability of the human operator at one of the multiple multimedia operator consoles 202 , 204 , 206 the interactive call-back session is initiated over the internet to the IP address previously placed in the queue. Upon the successful connection of the call between the customer service representative and the customer, an interactive audio session over the network is conducted. Upon termination of the interactive audio session, the connection is taken down and the next queued interactive audio session is initiated. Multimedia operator consoles 202 , 204 , 206 and customer terminals 102 , 106 , 110 , 136 , 136 are equipped with appropriate multimedia equipment and software. Typical equipment includes commercial off the shelf microphones/headsets with speakers, digital signal processor based peripheral sound cards, and a video camera with its video interface to the terminals and consoles. When the customer initiates the interactive multimedia session the content of the customer's screen is accessible by the agent on the multimedia operator console. The session participants in one embodiment are also able to view each other through the video camera output portion of the link and are able to converse audibly to conduct business. The customer agent is able to see exactly what the customer is trying to describe and is therefore capable of answering questions and solving problems in a much more time efficient manner without tying up more resources. The customer agent is able to diagnose conditions and problems on a customer's computer in real-time or near real-time and can download software to determine configurations, correct errors, modify settings and add or delete software modules as desired. Of course, the multimedia response server automates many of these functions and does not require a human customer agent in many of these situations. Referring now to FIG. 3, the methodology 300 of the present invention will now be discussed. The process begins in step 302 with the program Start function. In step 304 , the Web server makes the Web page available to customers over the Internet or any other suitable public or private data network. A Customer accesses the Web page from his/her computer terminal using the appropriate physical connection and software. As an example, if the Web page is for a travel agent, the customer could search for airline flights to a desired destination at a particular time and for a particular price. If the specific parameters defined do not result in a satisfactory result for the customer, or if at any time during a session live human interaction is desired or required, then the customer clicks on the graphical hot button or link (step 306 ) and optionally is prompted to enter his name, phone number and a description of the subject in question, if this information is not already available. The IP address is transferred in step 308 by an automatic distribution mechanism into a call-back queue via the above described invention and a live call-back session in step 310 is conducted in an effort to satisfy the customer's request. Upon completion of the session, control passes to step 312 , Stop. Other such embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is readily apparent that the above described invention may be implemented in other types of data networks, public and private, including an intranet or an internet, whereby these terms denote an either an internal network of computers or any internetworking of communication devices. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

An interactive data communication user is connected through a network to a multimedia response server. The user presses an appropriate keyboard or mouse clicks on an appropriately labeled button on a data page. An automatic call distribution device switches the session to a customer service queue for routing to the next available customer service representative. The customer service representative automatically places a internet based telephone call to the user. When the interactive session between the user and the customer service representative is completed, session control passes back to the data page server and a normal interactive session is resumed.

CROSS-REFERENCE TO RELATED APPICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 60/604,560 entitled “LAMINATED WEAR-RESISTANT ASSEMBLIES,” filed on Aug. 26, 2004 on behalf of Edward Williams, which is hereby incorporated by reference for all purposes. TECHNICAL FIELD [0002] The invention relates generally to wear-resistant and abrasion-resistant assemblies that can be affixed to a surface to extend the life of the equipment and increase the effectiveness of the equipment. BACKGROUND [0003] The use of wear-resistant material affixed to the working surfaces of equipment that is subject to high wear or abrasion from materials being processed is well known. Various ceramics, tungsten, or tungsten-carbide are some of the more commonly used materials. While wear-resistant materials are very hard, they tend to be expensive, brittle, and difficult to work with. For these reasons, equipment is rarely made from these materials. Depending on the arrangement and material used, such materials can be sprayed on in a thin coating, or sheets or tiles of such wear-resistant material can be affixed to working surfaces of equipment made from materials such as steel, aluminum or other metallic or non-metallic substances. Such wear-resistant materials have been used to prolong the life of a variety of equipment, such as drill bits, rotating fans, centrifuge conveyors, to name a few. [0004] For example, U.S. Pat. No. 4,003,115 to Fisher discloses a system whereby wear resistant-material is sprayed into a cavity created along the leading edge of a conveyor screw. However, in use, the amount of hardened material that can be secured to the surface of such equipment by spraying yields a thin coating of harder material on working surfaces. While this is satisfactory for some uses, many other uses require a thicker layer of wear-resistant material. For example, U.S. Pat. No. 6,648,601 also owned by the same assignee as the present invention, discloses affixing patterns of tiles of a wear-resistant material to rotating fan assemblies used for processing coal dust, which is highly abrasive, and would wear off a thin coating of hardened material in a very short time. Similarly, U.S. Pat. No. 5,380,434 to Paschedag discloses a system for affixing flat, wear-resistant tiles to the leading edge of a centrifuge conveyor screw, and U.S. Pat. No. 6,739,411, owned by the same assignee as the present application discloses affixing tiles of a wear-resistant material to the areas of drill bits that are subject to high wear. [0005] Because such wear-resistant materials tend to be very brittle, they are prone to fractures or cracking. Thus they can be difficult to work with. Additionally, depending on the equipment on which the wear-resistant materials are being used, and the product being processed in the equipment, cracked or chipped materials could contaminate the product, or cause damage in the equipment. [0006] One solution has been to affix them to a carrier, or backing, made of a material that is easier to work with, such as steel. However, there can be difficulties with securing the wear-resistant materials to the carrier, just as there are difficulties in securing the wear-resistant materials directly to the equipment. Because the wear-resistant materials are prone to fracturing or breaking, drilling holes through the materials to secure them to a carrier or other surface with fastening devices can be difficult, and result in a high incident of fracturing, cracking or chipping. One solution has been to solder, or braze the wear-resistant materials to the carrier. However, depending on the material characteristics of the carrier and the wear-resistant materials, it is necessary to heat the materials to a high temperature to perform the soldering or brazing. Because the materials expand and contract at different rates, after being secured, they contract at different rates. If the differences are great enough, the carrier will torque or shear as it cools, and the attached wear-resistant material can also bend, or will crack or fracture, or in some situations, the secure itself will fail and the two materials will detach from each other. [0007] Therefore, what is needed is a system and method for affixing wear-resistant members to equipment that is simple, cost-effective and easy to use. Such systems should provide for a method of securely fastening wear-resistant members to equipment, as wear-resistant materials are typically hard and can be brittle and break easily under certain circumstances. Such systems and methods should, among other things, reduce or eliminate instances of fracturing or cracking of the wear-resistant materials. Such systems should also reduce the possibility of the attached wear-resistant members becoming detached and contaminating product or damaging equipment. SUMMARY [0008] The present invention, accordingly, provides a multi-layer laminated wear-resistant assembly. The assembly comprises a bracket, typically made of steel or some similar material, which can be welded, soldered or glued and can be machined or manipulated. The bracket is layered between a plate wear-resistant material, such as tungsten-carbide on the front, and a third layer at the rear of the bracket, which can be made of the same material as the front layer, or of a different material having similar characteristics of expansion and contraction as the plate of wear-resistant material. The layers of the assembly are secured together by soldering, brazing or some other method. [0009] Because the bracket material is trapped between two layers of harder materials with similar characteristics, it does not warp or shear when the materials begin to cool after brazing, but stays “stretched” between the two layers of harder materials. This “stretched” state is due to the shrinkage differentials of the materials used in the layers of the assembly that occur after brazing when the assembly is cooling. When the entire laminated assembly has cooled, a stronger mechanism is achieved that is more resistant to cracking or fracturing because of the more flexible material that comprises the middle layer of the assembly providing a support structure. [0010] By creating a laminate of a bracket made of a more flexible material, such as steel or other material, with wear-resistant material as the top layer of the laminate, and a third layer of material on the rear side of the steel, a much stronger, more useful product is achieved than would be if only one of the materials was used alone. The face of hardened material prolongs the life of the equipment and increases the effective time of operation before repair or replacement is necessary. Additionally, the individual assemblies can be easily removed and replaced as assemblies wear over time, further increasing the life of the mechanism. [0011] In one preferred embodiment of the present invention, a laminated wear assembly is provided. A core member having a first and an opposite second face and having an attaching member extending substantially perpendicular from the second face to substantially form an “L” shape is included in the laminated wear assembly. Moreover, the core member further comprises a first coefficient of thermal expansion. Additionally, a first wear member is also included having a second coefficient of thermal expansion secured to a substantial portion of the first face, wherein the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion. In addition to having a first wear member, there is also a second wear member having a third coefficient of thermal expansion secured to a substantial portion of the second face, wherein the second coefficient of thermal expansion is approximately equal the third coefficient of thermal expansion. The laminated wear assembly, too, is formed such that the core member remains substantially stretched at approximately room temperature. [0012] In another preferred embodiment of the present invention, the core member comprises a material selected from the group consisting of stainless steel, carbon steel, aluminum, and NiCroMoly. [0013] In yet another preferred embodiment of the present invention, the first wear member and/or the second wear member are made from a composition comprising at least tungsten-carbide. [0014] In another preferred embodiment of the present invention, the core member, the first wear member, and the second wear member are secured to one another by brazing, soldering, welding, or gluing. [0015] In an alternative embodiment of the present invention, a method of forming a laminated wear assembly is provided. A core member is formed having a first and a second opposing face with an attaching member extending substantially perpendicular from the second face to form an “L” shape, and having a first coefficient of thermal expansion. A first wear member is also formed having a second coefficient of thermal expansion, wherein the second coefficient of thermal expansion is less than the first coefficient of thermal expansion. Additionally, a second wear member is formed having a third coefficient of thermal expansion, wherein the second coefficient of thermal expansion is approximately equal to the third coefficient of thermal expansion. Onced formed, the core member, the first wear member, and the second wear member are heated to a sufficient temperature that causes the core member, the first wear member, and the second wear member to secure with one another and to form the laminated wear assembly. After heating, the laminated wear assembly is cooled to approximately room temperature so that the core member remains in tension in a tensile state of stress at approximately room temperature. [0016] Another alternative embodiment of the present invention provides a method of forming a laminated assembly. With this alternative embodiment, a core member, having a first and a second opposing face, a first wear member, and a second wear member are formed. Once formed, each of the core member, the first wear member, and the second wear member are elongated. Once elongated, the first wear member is secured to the first face, and the second wear member is secured to the second opposing face. The first wear member and the second wear member are then reduced, while the elongation of the core member is maintained. [0017] The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0018] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [0019] FIG. 1 is an exploded side view of an assembly embodying features of the present invention; [0020] FIG. 2 is a rear perspective view of an assembly of the present invention; [0021] FIG. 3 is a rear exploded view of an assembly embodying the features of the present invention; [0022] FIG. 4 is a front view showing several assemblies secured to the leading edge of a piece of equipment; and [0023] FIG. 5 is a side view of a secured assembly of FIG. 4 . DETAILED DESCRIPTION [0024] In the discussion of the FIGURES, the same reference numerals will be used throughout to refer to the same or similar components. In the following discussion, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without such specific details. [0025] Referring to FIGS. 1-3 of the drawings, the reference numeral 10 generally designates a laminated assembly of the present invention. The assembly 10 comprises a first wear member 30 , a core member 20 , and a second wear member or backing element 40 . [0026] The assembly 10 is essentially a bracket that can be affixed to machinery to protect wear surfaces. For example, assembly 10 can be affixed to driving faces of an extrusion screw, as shown in FIG. 4 . The assembly 10 is formed by sandwiching the core member 20 made of a workable material, such as steel, between the first wear member 30 and the second wear member 40 , where the core member 20 , the first wear member 30 and the second wear member 40 are secured to one another, such as by brazing, gluing, soldering, or welding. Typically, the first wear member 30 and the second wear member 40 are comprised of a hard material, such as tungsten-carbide. [0027] Specifically, each of the core member 20 and the first wear member 30 have first faces 20 b and 30 b and second faces 20 a and 30 a, respectively. In forming the assembly 10 , the second face 30 a of the first wear member 30 is secured to the first face 20 b of the core member 20 , and the second wear member 40 is secured to the second face 20 a of the core member 20 in slot 24 . However, as it can be seen in FIGS. 1-3 , second wear member 40 does not completely cover the second face 20 a of the core member 20 . There is an attaching member 22 extending substantially perpendicular from the second face 20 b of the core member 20 such that the core member 20 forms an “L” shape. The attaching member 26 would thus allow for a portion of the workable material, such as steel, to be exposed so as to attach to machinery, as shown in FIG. 4 , while the first face 30 b of the first wear member 30 faces outward and comes in contact with the admixture being processed. [0028] In the process of securing the layers of the assembly together, heating is commonly employed; moreover, it is not uncommon to utilize assembly 10 in heated environments. One of the reasons for employing the multiple layers of wear members is due to differing coefficients of thermal expansion of the dissimilar metals. Typically, the hard protective metals, such as tungsten-carbide, have a lower coefficient of thermal expansion than the more workable core materials, such as steel. The relative differential expansions/contractions usually cause bending or bowing, resulting in torsion, compression, and tension that can cause failure. Thus, as stated above, the second wear member 40 does not cover the entire second face 20 a of the core member 20 ; it covers enough area of the second face 20 a of the core member 20 to prevent the core member 20 from bending or bowing as the assembly 10 is heated or cools. Reduction in the relative size of the second wear member 40 can reduce costs because less material can be used to cover the rear side of the assembly 10 . [0029] Additionally, if the assembly 10 is to be secured to the underlying equipment by means of soldering or welding, in many cases, it is easier to weld the exposed material of the core member 20 on the rear side of the assembly 10 to the underlying equipment or machinery than having to weld the types of harder materials that typically comprise the second wear member 40 to standard equipment or machinery. In some cases, depending on the harder materials used, welding of those materials may not even be possible. [0030] Furthermore, as stated above, the layers of the assembly 10 are typically laminated together by soldering, brazing or other means that utilize heat. After they have been heated during one of these processes (or heated independently of the joining process), the dissimilar metals are secured together. As the assembly cools, the core layer 30 remains in an expanded or “stretched” state between the two outer layers 30 and 40 . In other words, once at room temperature, the core member 20 is in tension or in a tensile stress state in its major direction. Thus, additional, intentional residual stresses are added to any inherent residual stresses present in the assembly 10 . As an example, consider that core member 20 and second face 30 a are 1.5 inches in the major (longest) direction before heating, while second wear member 40 is 0.925 inches before heating. After lamination and cooling to ambient temperature, second face 30 a and the second wear member 40 return to 1.5 inches and 0.925 inches, respectively, but the core member 30 remains partially extended. Therefore, the assembly 10 has a dominant or major tensile stress, resulting from differential expansion (contraction) along the major dimension of the assembly 10 . [0031] Moreover, it is also possible to form each of the first wear member 30 and the second wear member 40 of multiple pieces. Depending on the conditions and circumstances of the particular application for the assembly 10 , flexibility may be desirable, which would be provided by replacing a single piece of hard material with multiple pieces of material. Specifically, as can be seen in FIG. 3 , the second wear member 40 is formed of two pieces. However, any number of pieces can be utilized. [0032] Additionally, the core member 20 may also have a variety of configurations. As shown in FIGS. 1-3 , a portion of the second face 20 a of the core member 20 is exposed. This type of configuration allows for additional welds to underlying machinery. However, it is also possible to completely cover both the first face 20 b and the second face 20 a of the core member 20 . [0033] As seen in FIGS. 4 and 5 , in operation, the core member 20 hangs over and is secured to the outer edge 102 of the equipment 100 , such as an extrusion screw, by means of spot welding of the attachment member 26 of the core member 20 to the outer edge 102 of the equipment 100 . Additionally, the bottom of the assembly 10 is spot-welded to the leading edge 104 of the equipment 100 . With this configuration, the core member 20 , is made of a material such as steel, which can be welded to the extrusion screw 100 . However, it can be appreciated that the assembly 10 can be secured to the equipment 100 by a variety of methods, including gluing, brazing, soldering or other securing methods. Another benefit of the present invention is that when an assembly 10 does wear and need replacing, this can be done easily in the field by soldering, welding or gluing a new assembly 10 to the equipment 100 . Because wear-resistant materials such as tungsten-carbide can be brazed, but cannot be welded, replacing surfacing material made only of tungsten-carbide in situ would be difficult, as brazing in typical ambient environments is difficult and does not always produce a strong bond. [0034] The front face 30 b of the first wear member 30 faces outward from the equipment 100 and comes in contact with the material being processed in the equipment 100 . As can be seen, a series of assemblies 10 are placed adjacent to each other and to provide a smooth continuous covering along the leading edge 104 of the extrusion screw 100 . As can be understood, the size and shape of assemblies used can vary in accordance with the size and shape of the equipment 100 . [0035] Thus, the arrangement of the present invention yields an assembly 10 of greater strength and resistance to cracking than use of a single layer of tungsten-carbide, and achieves rigidity from having a layer of more flexible material between two layers of harder material. [0036] It is understood that the present invention can take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Wear-resistant and abrasion-resistant assemblies can be affixed to surfaces of various pieces of equipment to extend the life of the equipment and increase its effectiveness. The assembly is a multi-layer composition of two harder materials that provide wear-resistance surrounding a material that provides strength and flexibility, as well as providing a means of attaching the assembly to the piece of equipment. When one or more assemblies does incur wear, assemblies can be replaced easily to further extend the life of the equipment.

BACKGROUND OF THE INVENTION This invention relates to the electrolytic recovery of metals and, more particularly, is directed to the stripping of electrolytic metal deposits as sheets from cathode plate base plates. In the electrolytic recovery of metals, such as zinc and copper, high quality metal is deposited on electrode plates such as mother plates, starting sheets or base plates, referred to hereinafter as cathode plates, which are made of suitable materials such as aluminum, stainless steel, or titanium. After a period of electro-deposition of metal on the cathode plates, the cathode plates are removed from the electrolytic cells and subjected to a mechanical stripping or peeling operation to remove sheets of refined metal from the cathode plates which are then returned to the cells. PRIOR ART The various mechanized methods and apparatus to facilitate the removal of metal deposits from cathode plates include alone or in combination, the use of impacting, pneumatic or hydraulic spray devices, suction cups, rolling, mangling or bending of the cathode plates and separating knives or wedges. One of the more prevalent methods and apparatus includes the use of knives or wedges. The use of knives or wedges in combination with one or more of the other methods noted above is disclosed, for example, in U.S. Pat. Nos. 3,332,128; 3,935,091; 3,950,232; 3,953,312; and Canadian Pat. No. 1,016,497. Some methods and apparatus are based on the sole use of one or more knives alone or in one or more pairs to separate the metal deposit from the cathode plate, such as disclosed in U.S. Pat. Nos. 1,525,075; 1,553,080; 3,625,806; 3,689,396; 3,847,779; 3,980,548; and 4,137,130. More specifically, U.S. Pat. No. 3,689,396 discloses an apparatus for vertically advancing cathode plates having a movable guard piece at one lateral edge of the cathode plate, means for moving the guard piece, a wedge shiftable relative to the zone at the guard piece to peel the upper edge of the deposit and a vertically moving blade to deflect the deposit from the cathode plate. According to U.S. Pat. Nos. 3,847,779 and 3,980,548 there are disclosed a method and an apparatus including a multiple station stripping unit having means to pivot a cathode plate holder (guard piece) having tapered surfaces for providing an upturned edge of deposited metal and including an enlarged portion adapted to be engaged for pivoting; means for inserting horizontal stripping knives which clamp onto the exposed plate and partially separate the deposit; and means for inserting main stripping blades and moving the inserted blades downwardly to complete the separation, the cathode plates being secured in each station. In connection with these patents, German Pat. No. 512,913 must be noted. This patent shows a removable edge stick with tapered faces which, upon removal of the edge stick from the electrode, leaves V-shaped grooves between deposits and base plate suited for inserting a stripping tool. According to U.S. Pat. No. 4,137,130, a single movement of a unitary stripping means causes a wedge to be inserted in a V-shaped groove between the cathode plate and the deposit and a blade propagates the separation. In the operation of conventional stripping machines, each cathode plate is clamped in a stationary position and the cathode plate edge is approached by a pair of knives which are open to ensure that the knives locate on each side of the cathode plate. The knives are stopped or slowed down, closed onto the cathode plate and then advanced for entering between the deposits and the cathode plate to commence stripping. This procedure is time consuming. In order for the knives to be able to close onto the cathode plate, the removed guard piece must expose an area of the cathode plate surface wider than that normally provided by the standard edge stick. This requires that the guard piece is wider than the edge stick and causes an increased invasion of the guard piece into the anode-cathode plate electric field which results in plating of metal onto the bevelled or tapered edges of the guard piece, often continuing onto the main body of the guard piece. This extended deposition causes undesirable encrustations which can cause electrical shorting, breaking of the guard piece when it is pivoted out of the way, as well as interference with the movement of the knives. The knives not only can be prevented from landing on the cathode plate but can also miss one side of the cathode plate altogether. The clamping or closing of the knives onto the cathode plate causes gouging on the cathode plate surfaces which leads to increased corrosion resulting in further damage to the surfaces, difficulties in stripping and shortened cathode plate life. Most stripping machines use either a chain conveyor or a walking beam in order to transfer the cathode plates through the stripping machine. These structures have serious drawbacks; a chain drive has a return section which interferes with the stripping knives and a walking beam is undesirably slow. STATEMENT OF INVENTION It has been found that the disadvantages of prior art apparatus can be substantially alleviated and the stripping of metal sheet deposits from cathode plates can be accomplished in a fast, simple and efficient manner by using a closed entry horizontal knife to effect initial parting of each deposit while partly outwardly bending the top portion of the deposit and then removing the deposits from the two sides of the cathode plate with vertical stripping knives without clamping of the cathode plate while controlling cathode plate sway. By providing a guard piece on the cathode plate edge with the same profile and width of and interlocked with the permanent edge stick, interference in the cathode plate-anode electric field and undesirable metal growths are eliminated. By using a closed entry knife to effect the initial parting of the deposit from the cathode plate and by the elimination of clamping of the cathode plates at the knives while controlling cathode plate sway, the time required to effect stripping can be shortened. By providing means to bend the deposits by the horizontally moving entry knives when the entry knives enter between the deposits and the cathode plate, the vertically moving main stripping knives can quickly and reliably remove the deposits from the cathode plate without stopping, thereby further reducing the stripping time. A simple transfer mechanism for advancing cathode plates through the stripping machine still further reduces stripping time. Accordingly, there is provided a method for stripping electro-deposited sheets of metal from cathode plates used in tne electrolytic recovery of metals, each cathode plate having a head bar at one end for vertical support of the cathode plate, opposite side faces with metal deposits thereon, and vertical side edges having edge sticks mounted thereon and a pivotal guard piece forming a separate upper portion of one of said edge sticks, said method comprising: advancing said cathode plates crosswise to the direction of travel sequentially through a plurality of equispaced stations in succession by means of a reciprocating transfer carriage, said plurality of stations consisting of a feed station, an initial horizontal parting station, a main vertical stripping station, and a discharge station; said transfer carriage mounted for horizontal reciprocal travel above a pair of parallel, spaced-apart slide bars over a distance equal to the distance between a pair of adjacent stations, said transfer carriage having means formed thereon for engaging a cathode plate head bar at each station for advance of the cathode plates on the slide bars to a successive station; actuating detent means operable into and out of engagement with the opposite side edges of the cathode plates at the initial horizontal parting station and vertical stripping station for positioning the cathode plates and preventing sway of said cathode plates at each of the said stations; pivoting said guard piece upwardly away from the side edge of the cathode plate; initially parting the top edge of the metal deposit on each side face of the cathode plate from the cathode plate and bending the said top edges outwardly away from the cathode plate to form a gap between the top edges and the face of the cathode plate at the initial horizontal parting station; vertically reciprocating main stripping knives to engage the deposited metal at the gap on each side face of the cathode plate and strip metal deposits downwardly from each side face of the cathode plate for removal of the said metal deposits therefrom at the vertical stripping station; and removing stripped cathode plates at the discharge station. The method may include the additional step of positioning the cathode plate and preventing sway thereof while pivoting the guard piece onto the vertical side edge to form the separate upper position of the one edge stick at a replacement station after stripping of the cathode plate. The apparatus of the invention for stripping electro-deposited sheets of metal from cathode plates comprises in combination: a frame having a plurality of equispaced stations therein; means for advancing said cathode plates crosswise to the direction of travel sequentially through the plurality of equispaced stations in succession, said plurality of stations consisting of a feed station, an initial horizontal parting station, a main vertical stripping station, and a discharge station, said advancing means comprising a pair of parallel spaced-apart slide bars for supporting the head bars of cathode plates; a transfer carriage mounted above said slide bars for horizontal reciprocal travel over a distance equal to the distance between a pair of adjacent stations, said transfer carriage having means formed thereon for engaging a cathode plate head bar at each station for advance of the cathode plates on the slide bars to a successive station, said advance extending substantially the distance between two adjacent stations during reciprocal travel of said carriage; detent means operable into and out of engagement with the opposite side edges of the cathode plates at each of said vertical stripping and horizontal parting stations, for positioning the cathode plates and preventing sway of said cathode plates at each of the said stations; means for pivoting said guard piece upwardly away from the side edge of the cathode plate; means horizontally reciprocal adapted to extend across said cathode plate for initially parting the top edge of the metal deposit on each side face of the cathode plate from the cathode plate and for bending the top edges outwardly away from the cathode plate to form a gap between the top edges and the faces of the cathode plate; means at the main vertical stripping station vertically reciprocal for engaging the deposited metal at the gap on each side face of the cathode plate and for stripping metal deposits downwardly from each side face of the cathode plate for removal therefrom; and conveyor means for removing cathode plates and deposits at the discharge station. Preferably means are provided at a replacement station for pivoting said guard piece onto the vertical side edge to form the separate upper portion of the one edge stick while positioning the cathode plate and preventing sway thereof prior to transfer onto the conveyor means for removal of stripped cathode plates at the discharge station. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in detail with reference to the accompanying drawings wherein: FIG. 1 is a perspective view of the stripping apparatus of the present invention showing the components in their retracted positions; FIG. 2 schematically shows the operative stations and the position of the transfer carriage within the stripping apparatus immediately prior to a transfer of cathode plates from one station to the next station; FIG. 3 schematically shows the position of the transfer carriage and placement of cathode plates immediately after a transfer of cathode plates as the transfer carriage begins the return cycle; FIG. 4 is a side elevation of the stripping apparatus; FIG. 5 is an end elevation of the stripping apparatus; FIG. 6 is a perspective view of an upper portion of a cathode plate; FIG. 7 is a persective view of the operative components at the initial parting stage; FIG. 8 illustrates the bending of initially parted deposit shown in FIG. 7; FIG. 9 shows an enlarged detail of the closed entry, initial parting knife illustrated in FIG. 7; FIG. 10 is a perspective view of the main stripping knives; FIG. 11 is a perspective view of the bottom discharge assembly of the main stripping station; and FIG. 12 is a vertical section taken along the line 12--12 of FIG. 11. FIG. 13 is a perspective view of a portion of an embodiment of the stripping apparatus illustrating the upper portion of a bottom discharge chute at the main stripping station; FIG. 14 is a side elevation of the bottom discharge chute; FIG. 15 is a perspective view of the lower portion of the bottom discharge chute; FIG. 16 is a side elevation of the apparatus shown in FIG. 15 illustrating the operation of the discharge mechanism; FIGS. 17-20 are detailed side elevations of the trap mechanism at the base of the vertical portion of the discharge chute illustrating the operation of the said trap mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawings and particularly FIGS. 1-5, the apparatus for stripping metal deposits from cathode plates generally comprises the machine depicted by numeral 10 which is in-line with a conveyor 12 for feeding cathode plates 14 sequentially thereto and a conveyor 16 for conveying stripped cathode plates from the said machine. Cathode plates 14 having head bars 18 and metal deposits on side faces 20, 22 are transferred from feed conveyor 12 by a transfer mechanism 24, comprising reciprocating transfer carriage 26, onto a pair of spaced-apart parallel, fixed slide bars 28. Transfer carriage 26 has rollers 23 provided thereon adapted to co-act with carriage rail 25 secured to frame 36. Piston-cylinder means 70 (FIGS. 2 and 3) are provided between carriage 26 and frame 36 for advancing and retracting the carriage in guided, horizontal travel. The feed conveyor 12 comprises a pair of continuously moving conventional endless chain conveyors 30 passing over sprocket wheels 32 in proximity to each of slide bars 28, one of which is shown in FIG. 1. By keeping the chain conveyor 30 moving continuously at a slow speed, the risk of initiating swing in the cathode plates is reduced. The speed of the conveyor is adjusted to suit the duration of the stripping cycle, to be described. The cathode plates are intermittently advanced by the reciprocating carriage 26 over the slide bars 28 from a feed station A through an initial parting station B, which comprises means to remove a cathode plate guard piece, and a horizontal, initial parting, closed entry knife 94; a main stripping station C, which comprises vertical main stripping knives 29 which complete the stripping of the deposits; and a cathode plate guard replacement station D. The stripped cathode plates are then moved by the carriage 26 from the slide bars 28 onto a transverse conveyor 16 at a pick-up station E for passing the cathode plates to a subsequent operation or returning the cathode plates to the electrolytic process. The success of the stripping machine of the present invention is achieved in part by the simple, quick and accurate method in which the cathode plates are moved from one station to another by the transfer mechanism and by the rapid separation and removal of metal deposits from the cathode plates. CATHODE TRANSFER MECHANISM With particular reference now to FIGS. 1, 4 and 5, the pair of spaced-apart, parallel, fixed slide bars 28 are secured, one on each side, to the interior of frame 36 of the stripping machine and extend horizontally from sprocket wheel 32 at one end 38 of frame 36 in alignment with chain conveyor 30 to project beyond the opposite end 40 of frame 36. The thin slide bars 28 occupy little space and present no interference in either the initial parting station B or the main stripping station C to the stripping of the cathode plates. Four partly rotatable, equispaced pawls or dogs 42, which are pivotally mounted on each side of the interior of the stripping machine on reciprocatable transfer carriage 26, depend downwardly from horizontal side members 27 towards each cathode plate head bar. The rotation of dogs 42 is limited by stops 43 on the frame of carriage 26 such that the dogs can advance cathode plates to the next station when carriage 26 advances and the dogs can pivot and move over the top of cathode plate head bars when carriage 26 is retracted to its starting position. A spring 44 on each of the dogs 42 pushes the dogs against stops 43 preventing the dogs from remaining in an elevated position. Each dog engages and pushes the head bar 18 of a cathode plate 14, shown by ghost lines in FIGS. 4 and 5, on the fixed slide bars 28 from one station to the next station. The transfer carriage 26 moves a set of four cathode plates with each reciprocation; a set of cathode plates comprising one cathode plate 14a moved from conveyor 12 onto slide bars 28 at the feed station A, a cathode plate 14b at the intiial parting station B, a cathode plate 14c at the main stripping station C and a cathode plate 14d at the replacement station D (FIG. 2). When reciprocating, the transfer carriage 26 advances by means of the dogs 42 a set of cathode plates forward to the next successive station, moving the first cathode plate 14a from station A to station B and the last cathode plate 14d at station D from the slide bars 28 onto conveyor 16 (FIG. 3). The cathode plates are laterally guided by fixed guides 31a and 31b secured to the interior of frame 36, one on each side. Both guides extend horizontally from sprocket wheel 32 at end 38 of frame 36, guide 31a to just past main stripping station C (FIG. 1) and guide 31b (FIG. 5) to end 40 of frame 36. Both guides are positioned inside and below the slide bars 28 such that the guides are close to the vertical cathode plate edges. Guides 31a and 31b provide lateral guidance and centering of the cathode plates when they are moved over the slide bars 28. Guide 31b also provides a counterface when horizontal knives 94 move onto the cathode plate surfaces. An upper shaft 46, one on each side of frame 36, with three equispaced detents 48a, 48b and 48c projecting laterally therefrom, is mounted for rotation in journals 50, 52 above each slide rail 28. A corresponding shaft 60 with three equispaced, laterally projecting detents 62a, 62b and 62c is mounted for rotation in journals 56, 58 just above the plane of the bottom edge 64 of cathode plates 14 (FIG. 4) at each side of frame 36 below upper shafts 46. Lower detents 62a, 62b and 62c corresponding to upper detents 48a, 48b and 48c are spaced along tne shafts from each other the same distance as the distance between the initial parting station B and the main stripping station C. The detents are lined up so that, when the shafts 46 and 60 are rotated by piston-cylinder assemblies 66, 68, the detents locate and engage the cathode plate head bars and bottom edges at the initial parting station B, the main stripping station C and the replacement station D. Upper detents 48a , 48b and 48c are aligned to position a cathode plate accurately at each of these stations. Because the transfer carriage 26 with dogs 42 only pushes the tops of the cathode plates 14, the bottom edges of the cathode plates are delayed in forward travel by detents 62a , 62b and 62c. If the bottom edges were not restrained, the lower portions of the cathode plates would continue travelling after the tops have been stopped. This would cause considerable cathode plate sway which cannot be prevented by holding the cathode plate head bars against the upper detents 48a, 48b and 48c with dogs 42. To prevent cathode plate sway, lower detents 62a, 62b and 62c are introduced into each cathode plate path closer to the oncoming cathode plate than the corresponding upper detents so that the bottom edges of the cathode plates will rest against the detents by gravity rather than bounce back and forth against the detents. For very fast transfer of the cathodes plates, the lower detents 62 preferably have a damping device (not shown) such as, for example, a spring or a rubber buffer on the face of each lower detent which will contact the cathode plate to prevent the plate from bouncing. As described above, lateral cathode plate movement is limited by guides 31a and 31b. Thus, when a cathode plate 14 is delivered to the starting point on the fixed slide bars 28 in feed station A by chain conveyor 30, the dogs 42 of carriage 26 pass over head bar 18 to engage the rear side of the head bar. While this occurs, the detents on shafts 46 and 60 remain swung out of the path of the cathode plates. As soon as the transfer carriage 26 from which the dogs depend is pushed forward by the actuation of piston-cylinder assembly 70 (FIG. 2) secured thereto, shafts 46, 60 rotate to swing the detents depending therefrom into the path of the cathode plates. Just before the cathode plates reach the upper detents a shock absorber 72 mounted on carriage 26 abuts a stop 74 on the main frame 36 of the stripping machine (FIG. 1). The shock absorber decelerates the cathode plates and cushions the impact while permitting maintenance of pressure on the head bars 18 so that they are held in place and are prevented from bouncing or swinging when they are subsequently contacted by the parting knives and the main stripping knives, to be described. The detents are installed on the machine such that the cathode plate head bar 18 in main stripping station C in particular is aligned perfectly with the main stripping knives. The vertical, main stripping knives depicted by numeral 29 are sensitive to the position of the cathode plate and also to the amount or degree of sway. If the cathode plate is not accurately positioned at the station or if it is swinging at the time of actuation of the knives, one knife may land on top of the head bar and stripping will not occur on one side of the cathode plate. This leads to cathode plate bending by the knife on the side being stripped. It is, therefore important that dogs 42 of the transfer carriage 26 and the top detents 48b are aligned accurately with the vertical main stripping knives 29. A small tolerance in alignment can be accepted for the cathode plate at the initial parting station B because the initial parting knife 94 will be guided in its travel and is flexible enough to absorb some misalignment and even a minor amount of sway. The detents 48b and the corresponding dogs 42 remain in position to hold cathode plate 14 therebetween until the main stripping knives, to be described, in the main stripping station C have completed their downward stroke. As soon as the stroke is completed, the transfer carriage 26 with dogs 42 is retracted to its starting position, (FIG. 2), the dogs 42 pivoting and lifting over the cathode plate head bars 18 on the return travel while the upper and lower detents are moved out of the path of travel of the cathode plates by rotation of shafts 46, 60. The movement of the transfer carriage 26 from its starting position as shown in FIG. 2 to its forward position as shown in FIG. 3, moving a set of cathode plates from one station to the next, takes about 11/2 seconds. At about one-half second after the transfer carriage initiates forward movement, the three upper detents 48a, 48b and 48c, and the three lower detents 62a, 62b and 62c, move into the path of the cathodes plates. THE INITIAL PARTING STATION B With reference now to FIGS. 6-9, two main functions occur at the initial parting station B: 1. The guard piece 90 on one of the vertical edges 92 of a cathode plate is rotated to a horizontal position; the completion of rotation being checked by a sensor 100 (FIG. 1); and 2. The closed entry, initial parting knives 94 enter horizontally onto the cathode plate 14 to effect the initial parting of the metal sheet deposits 96, one of which is shown, and to bend the deposits outwardly at the top portion 98 to permit easy access for the vertical main stripping knives 29. In more detail, as soon as the cathode plate 14 arrives at the initial parting station B, the guard piece removal mechanism 102 having forked extension 104 adapted to span the thickness of cathode plate 14 is extended by hydraulic piston-cylinder assembly 106 to abut the top portion 108 of pivotally mounted guard piece 90 to rotate and raise body 110 of the guard piece 90 from the cathode plate edge 92 into a substantially horizontal position so that the initial parting knives 94 can engage the cathode plate. A sensor 100 checks that the pivoting of the guard piece into a substantially horizontal position has been completed. If the pivoting has not been completed, the horizontal parting knives 94 are prevented from extending. The guard piece 90 is designed with the same profile as the edge stick 114, thus avoiding any wings and peanut-like encrustations on the metal sheet deposits 96 formed during electrolysis. In addition, the bottom of body 110 of the guard piece 90 interlocks with the top 115 of the fixed edge stick 114 by means of a slight interference fit. This prevents the guard piece 90 from floating away from the cathode plate 14 when it is submerged in the electrolyte. After the guard piece 90 is raised, the closed entry, horizontally moving, initial parting knives 94 are extended by a piston-cylinder assembly, not shown, and are moved onto the cathode plate to part the deposits 96 from the cathode plate faces across the upper portion of the cathode plate at the tops 98 of the deposits. The initial parting knives 94 are horizontally moving, closed entry knives which comprise two interdependent components each composed of a leaf spring 120 attached to a common cross-head support (not shown) and individual nosepieces 122, rollers 124 and guide horns 126, shown most clearly in FIG. 9. The nosepieces 122 have a sharp leading edge 128 with which to penetrate between the deposit 96 and adjacent cathode plate face. Two rollers 124 are journalled into laterally-spaced recesses 130 in each nosepiece 122 at upper and lower faces 132, 134 of the nosepiece 122 such that the rollers 124 slightly protrude above the inner sliding faces 136 of the nosepieces. The rollers 124 prevent the steel nosepieces 122 from galling or scratching the cathode plate surfaces 20,22. The guide horns 126 are mounted onto the top face 132 of each nosepiece 122, their inner surfaces 140 being flush with the inner surfaces 136, i.e. facing surfaces, of the nosepieces 122. The guide horns 126 have a leading edge 142 and a bevelled edge 144 such that a V-shaped opening 146 is defined between the guide horns 126, FIG. 7. The guide horns 126 ride on the cathode plate faces 20,22 above the tops of the deposits 96. Their purpose is to align the nosepiece 122 with the cathode plate 14 so that the leading edge 128 of each nosepiece 122 misses the cathode edge 92 and enters between the deposit 96 and the adjacent cathode plate face 22. The leaf springs 120 of the closed entry knives bias and maintain the two nosepieces 122 against the faces 20,22 of the cathode plate as the knives engage the cathode plate, enabling the nosepieces 122 to straddle the cathode plate and enter behind the deposits 96. In addition, the springs 120 provide sufficient flexibility to allow each nosepiece 122 to ride on the cathode plate 14 if the nosepiece should fail to penetrate and enter under the deposit 96 and thus be deflected to the outside of the deposit. The closed entry, initial parting knives 94 are assembled such that the leaf springs 120 keep the rollers 124 in the nosepieces 122 in contact with each other. Upon moving forward, the guide horns 126 separate the nosepieces 122 when the bottom of the V-shaped opening 146 between bevelled edges 144 reaches the edge 92 of the cathode plate 14, so that the leading edges 128 miss the cathode plate 14 and the nosepieces 122 can enter between the deposits 96 and the cathode plate 14. As soon as entry is made, the rollers 124 approach and reach the cathode plate edge 92 and roll onto the cathode plate surfaces 20,22. The leading edges 128 of the nosepieces 122 are consequently lifted slightly off the cathode plate surfaces 20,22 preventing scratching or galling of the surface metal. The design of the initial parting knives has a number of advantages. The guides horns 126, in addition to opening the nosepieces 122 to miss the cathode plate, also centre the cathode plate between the knives in case it is misaligned. The closed entry knives need no surface to land on because of the effective guidance provided by the guide horns 126, and if wings should be present on the deposits, the wings tend to assist in the entry of the knives into the cathode plate-deposit interface. The speed at which the initial parting knives can approach the cathode plate can be high, thus giving a short cycle time. This is much shorter than the time required for the subsequent stripping at the main stripping station C. The initial parting station B can, therefore, also incorporate the guard piece removal mechanism 102 without incurring any loss in cycle time. The initial parting knives 94 bend the top portions 98 of deposits 96 away from the cathode plate 14 (FIG. 8). This speeds up the subsequent operation of the stripping with the vertical main stripping knives at the main stripping station C. If this were not done, considerable time would be wasted in positioning the main stripping knives behind the deposits. In some operations, the deposits tend to spring back onto the cathode plate faces and it is advantageous in such cases to bend the deposits more positively to ensure a gap between the top portions 98 of deposits 96 and the cathode plate faces 20 and 22. This can be achieved by providing the optional yokes 112 which extend from both sides of frame 36 to engage and envelop a short length of the vertical edge sticks 114 and underlying cathode plate edges. The yokes 112 are each carried by piston 116 (both shown in ghost lines) and operated hydraulically by a cylinder (not shown). Yokes 112 are positioned at the top portion of the cathode plate 14 below the initial parting knives 94 when the knives have moved onto the cathode plate 14. The yokes 112 serve as stops or fulcrums over which the deposits 96 are bent. The width or spacing of the yoke extensions 113 is selected so that the initial parting knives 94 bend the deposits 96 slightly over the extensions 113, as shown in FIG. 8. This ensures there is a gap between the top portion 98 of the deposits 96 and the cathode plate faces after the initial parting knives 94 and the yokes 112 have been withdrawn. THE MAIN STRIPPING STATION C With reference now to FIGS. 4, 5 and 10-12, after the closed entry knives have initially parted the deposits 96 and outwardly bent the top portion 98 of the deposits 96, the cathode plate is moved to the main stripping station C where the vertical main stripping knives 29 are lowered to enter in between the bent deposits 96 and the cathode plate faces 20,22 to complete the separation and removal of the deposits. In order to achieve complete stripping, the knives 29 must travel vertically down the full length of the cathode plate 14 and return upwards before the next cathode plate can be brought into the main stripping station C. On large cathode plates, the distance travelled by the knives 29 can be in the order of five meters which requires a travel time in the order of six seconds. This exceeds the times required in any of the other stations so that any delays which prevent the vertical knives from descending or retracting will add to the cycle time and decrease productivity. As soon as the cathode plate has been transferred from the initial parting station B to the main stripping station C, the vertical knives 29 immediately descend to complete stripping of the deposits and then retract. The knives are accelerated as fast as possible to full speed, then retracted as fast as possible as soon as the stripping stroke is completed. In order to accomplish this consistently, the cathode plate must be accurately positioned, no swinging of the cathode plate must occur when the vertical knives come down over the head bar of the cathode plate, the edge sticks must be retained on the cathode plate, and the released deposits must not interfere with the stripping operation. Accurately positioning of the cathode plate is effected by the transfer mechanism, as has been described above and, in order to prevent swaying of the cathode plate. Tne bottom detents 62b as shown in FIG. 1 are introduced at each side of the bottom of the cathode plate to maintain the cathode plate out of vertical plumb, as described above. The bottom detents 62b thus in cooperation with the top detents 48b hold the cathode plate 14 slightly off the vertical with the bottom of the cathode plate 14 slightly closer to the initial parting station B than the cathode plate head bar. With the cathode plate accurately positioned and stationary, the vertical, main stripping knives 29 are brought down. The knives 29 are hingeably connected via knuckle joints 206 for vertical movement by rods 161 to cylinders 162, FIGS. 4 and 10. Knives 29 are biased together under constant spring pressure by torque springs 164 for closing on cam 166 which is located just above the head bar 18. The springs 164 and cam 166 are of known design. Cam 166 is fixed to the frame 36 of the stripping machine by support bar 167 and does not interfere in any way with the transfer of cathode plates. The cam 166 keeps the knives 29 open and separated until the leading edges 168 of the knives 29 pass below the top 170 of the head bar 18. The knives 29 then immediately close in on the opposite cathode plate faces 20, 22. Because there is a bare and unobstructed portion of the cathode plate between the bottom of the head bar and the top portion 98 of the bent-away deposits 96 as a result of the initial parting and bending, the vertical knives 29 are assured entry between the deposits 96 and the cathode plate faces 20,22 without in any way having to stop or slow down, or require the use of auxiliary equipment. While the deposits 96 are being parted from the cathode plate faces 20,22, they are supported by a support plate 172 (FIG. 1). Support plate 172 is pivotally and fixedly positioned on shaft 174 mounted in journals 175, one on each side of frame 36, from a normal at-rest position as shown in FIG. 11, to an upper position as shown in FIGS. 1 and 12. Support plate 172 consists of a flat-plate section 176 having a transverse ridge 177 and a contiguous, slightly curved extension 178 having two spaced-apart, up-curved extensions 179 each with an upstanding terminal edge 180. The up-curved extensions 179 are spaced apart so as to clear the brackets (to be described) on a lowering conveyor 186 when plate 172 is pivoted to its lower position. Because support of the deposits is not necessary until the end of the stripping stroke by the main knives 29, the support plate 172 swings up under actuation of a piston-cylinder assembly 173 for ridge 177 and upstanding edges 180 to straddle a cathode plate after knives 29 have commenced their downward travel, thereby avoiding delays. The deposits are retained on the plate between ridge 177 and upstanding edges 180 which prevent the separated deposits from moving back and forth on the support plate 172. As the vertical knives 29 push downwardly between the deposits 96 and the cathode plate 14, the deposits 96 are forced outwardly from the cathode plate. To avoid interference with adjacent parts of the stripping machine, guide forks 181, which are situated about midway of the cathode plate and pivotally mounted, one on each side of frame 36, for actuation by piston-cylinder assembly 182, swing in on each side of the cathode plate as soon as the vertical knives start descending to laterally support the deposits 96. A cross bar 183 between the prongs of forks 181, together with the positive placement of the deposits on support plate 172, prevents any sideways movement of the deposits which may have been caused by uneven loosening of the deposits from the cathode plate due to the occasional tendency for deposits to adhere more in certain areas of the cathode plate than in others. The guide forks 181 also prevent overstressing the knife blades 29, torque springs 164 and driving cylinders 161, 162. The deposits on each side of the cathode plate are in fact one deposit plate joined at the bottom. Without the guide forks, the deposits would bow outwards as knives 29 approach the bottom of the cathode plate. The knife blades would then slow down and the knuckle joints 206 bow outwards with the deposits. This puts severe stress on the knife blades, torque springs and driving cylinders. With the guide forks in position, the knuckle joints are prevented from swinging outwards and the knives push down to complete the stripping and sometimes even cut through the bottom joint between the two deposits. The guide forks 181 remains in the upward, supporting position until the deposits are being lowered by lowering conveyor 186. An optical sensor, not shown, senses when knives 29 have completed their downward travel and signals cylinders 162 to retract knives 29 to their upper position. Lowering conveyor 186 comprises a number of transverse plates 187 mounted in parallel, closely spaced-apart relationship on a pair of spaced-apart conveyor chains 188. A plurality of plates 187 has three up-turned angle brackets 189 mounted thereon in spaced-apart relationship such that the curved extensions 179 of curved section 178 of support plate 172 can pass between them. Tne plates 187 which have brackets 189 mounted thereon are distanced apart slightly more than the height of a cathode deposit. Angle brackets 189 are adapted to receive the lower edges of the stripped metal deposits 96 and to lower the deposits from the stripping machine. To ensure that the deposits are received in angle brackets 189, two curved guides 190 are mounted on cross support bar 191 of frame 36, one on each side of support plate 172 (FIGS. 11 and 12), and two inverted hook-shaped guides 192 are mounted on cross support bar 193 of frame 36 in alignment with curved guides 190 and are curved over lowering conveyor 186. Curved guides 190 and hook-shaped guides 192 are curved down toward each other defining a funnel-shaped gap 194 to guide the deposits onto the brackets 189 of the conveyor. Further guidance is provided by cables 195, one attached to the end of each of hook-shaped guides 192 and extending downwardly over plates 187 between angle brackets 189. After deposits 96 have been separated from cathode plate 14, support plate 172 pivots downwardly, activated by assembly 173. The curved extensions 179 of plate 172 moved between brackets 189 and the deposits are guided by the pivoting of plate 172 and by guides 190 and 192 into brackets 189. As soon as deposits 96 are placed in brackets 189, the conveyor lowers the deposits from the stripping machine. Plate 172 is pivoted down sufficiently to clear the conveyor 186 and the deposits 96 on the conveyor. While the deposits are being lowered, assembly 182 is activated to lower the guide forks 181 into their down position. When the deposits have been lowered sufficiently, the transfer carriage 26 is activated to return to its starting position and the shafts 46 and 60 are rotated to move the detents 48 and 62 out of the path of the cathode plates. Carriage 26 is then activated to advance a set of cathode plates through the stripping machine, the cathode plate from which the deposits have just been removed being advanced forward to replacement station D. REPLACEMENT STATION D To replace the guard piece 90 onto the cathode plate 14, the guard piece 90 is first rotated from the horizontal position shown in FIG. 7 downwards through about 60 degrees. The rotation is effected by a stationary cam 200 secured to slide bar 28, which engages the upper surface of the guard piece while the cathode plate is moving from the main stripping station C to the replacement station D, to depress the guard piece. A hydraulically-actuated hammer 202 pivotally mounted on the frame 36 at station D then lightly pushes or taps the guard piece at a right angle to the cathode plate edge onto the cathode plate edge and in interlocking engagement with the cathode plate edge stick 114. PICK-UP STATION E The stripped cathode plate is pushed from slide bars 28 by the last pair of dogs 42 on transfer carriage 26 onto conveyor 16 for transporting the stripped cathode plate 14 from the stripping machine to a subsequent operation or to the electrolytic cells. The pick-up conveyor 16 may be a monorail conveyor, as shown in FIGS. 2-4, or a chain conveyor similar to feed chain conveyor 30. A detent or stop 204, FIG. 4, mounted on frame 36 steadies cathode plates 14 as they are conveyed from the stripping apparatus. All the foregoing description is with reference to a preferred embodiment of the invention, but it is to be understood that changes and variants may be introduced which are equivalent from the point of view of the function and structure, without falling thereby outside the scope of the invention. For example, the guard piece could be moved from and replaced on the cathode plate edge by means outside the stripping machine in which case the replacement station would not be necessary within the confines of the stripping machine. DISCHARGE CHUTE Removal of deposits 96 from a cathode plate 14 may be effected at the main stripping station C by the embodiment of the invention to be described with reference to FIGS. 13-20. Generally, stripped metal deposits are removed by a discharge chute disposed below the vertical stripping station. The discharge chute comprises a plurality of slide rails, each having an upper, an intermediate and a lower section. Trap means are disposed at the upper section for interrupting the fall of the discharging deposits. Speed regulating means are provided at the lower section for controlling the discharge speed of the deposits from the chute. With reference now to FIG. 13, arrow 300 indicates the movement of cathode plates bearing deposits towards the stripping station and arrow 302 indicates the vertically downward movement of stripped deposits into the upper portion of discharge chute 304. Stripped deposits are guided in their downward travel by a pair of opposed elongated U-shaped guides or forks 306, one of which is shown, adapted to be extended as shown during the stripping operation by downward pivotal movement of pivotally-mounted support arms 308 by rotation of shaft 312 by means of piston-cylinder assembly 310. Chute 304 comprises a plurality of equispaced slide rails 312, preferably three slide rails, having their base flanges 318 secured to a transverse support plate 320. The upper portions of rails 312 are substantially vertically aligned in a common plane extending across the chute opening 322 with the exposed surfaces 324 of the rails disposed to one side of a cathode plate located in the stripping station such that stripped deposits, indicated by numeral 326 in FIG. 14, will fall between rail surfaces 324 and a pair of opposed stationary trap arms 328 affixed to frame member 191. Trap arms 328 are inclined at a small angle of about 5° from the vertical towards rails 312 to guide stripped deposits 326 onto opposed pivotal trap arms 330 which are inclined at a small angle of about 5° away from vertical rails 312. Pivotal trap arms 330 are pivoted at their upper ends at 332 and define with stationary trap arms 328 a wedge-shaped trap depicted by numeral 334 for temporarily capturing deposits 326 at trap mechanism 336 located at the bottom of vertical rail section 338. Trap mechanism 336, shown most clearly in FIGS. 14 and 17-20, includes in addition to stationary trap arms 328 and pivotal trap arms 330 a transverse trap or detent plate 339 pivoted at 340 at the base of stationary trap arms 328 to extend across the width of the chute. The free end 342 of plate 339 is adapted to seat in notches 344 formed in the lower ends of pivotal trap arms 330 whereby deposits descending into the trap are stopped at plate 339, as shown in FIG. 18, to break their fall. Double-acting hydraulic piston-cylinder assembly 350, shown most clearly in FIGS. 13 and 14, is pivotally mounted at one end on frame 352 and at the other end on bracket 354 extending from transverse arm 356 secured to pivotal trap arms 330 by connectors 358, to move the trap arms 330 away from stationary trap arms 328 releasing detent plate 339 from notches 344 and permitting said plate to pivot downwardly, FIG. 19, to release deposits supported thereby. Deposits 326 continue their descent down the intermediate curved section 360 of the rails through about 90° to the horizontal discharge rail section 362 with speed regulating means, to be described. Push rod 364, pivotally mounted at one end on bracket 354 and extending through guide sleeves 366, 368 on stationary support 369, is adapted to actuate limit switches 370, 372 operatively connected to piston-cylinder assembly 350 to stop the outward travel of pivotal trap arms 330 and to reverse assembly 350 for return of said pivotal trap arms to the position shown in FIG. 20. Concurrent with retraction of assembly 350, double-acting piston-cylinder assembly 374 is activated by push rod 375 to extend piston 376 and move C-shaped actuator 378 pivotally mounted on at the base of arms 328 in a clockwise direction as viewed in FIG. 20 to reposition detent plate 339 to its normal at-rest horizontal position in notches 344. Push rod 375, slidably mounted for linear reciprocal travel in guide sleeves 377, 379, interacts with limit switches 381, 383 to stop the extension of piston rod 376 and to reverse assembly 374 for return of actuator 378 to its normally at-rest position shown in FIGS. 17, 18. A plurality of equispaced lower wheels 380 journalled on a common axle 385, preferably a wheel 380 adjacent each rail 312, FIGS. 14-16, extend slightly above the bearing surfaces 324 of rails 312 to frictionally engage the underside of deposits 326 as they pass between lower wheels 380 and pivotally-mounted plurality of opposed upper wheels 382 journalled on common axle 384 carried by spaced-apart pivot arms 387, one of which is keyed on shaft 392. Upper wheels 382 pivot substantially vertically upwardly, FIG. 16, sufficiently to allow deposits 326 to pass through to a stacker, not shown, under the downward bias of hydraulic spring 386. Hydraulic spring 386 has piston rod 388 connected to crank 390 which in turn is keyed to shaft 392 for maintaining a downward, or clockwise bias as viewed in FIGS. 15 or 16, on axle 384 and wheels 382. Either one or both axles 384 and 385 has a hydraulic or electric drive motor 396 operatively connected thereto to accelerate or decelerate, as necessary, the discharge speed of the deposits between the opposed sets of wheels to the peripheral velocity of the wheels for a desired exit velocity. A pusher mechanism, shown most clearly in FIGS. 14 and 15, comprises an upstanding pusher plate 398 adapted for horizontal sliding travel in each of spaced-apart guide tracks 400 from the retracted position illustrated to an extended position, not shown, by means of double-acting hydraulic piston-cylinder assembly 402, FIG. 15, having piston rod 404, to engage the deposits and to positively assist the travel and discharge of deposits 326 between the opposed sets of wheels 380, 382. It will be understood that modifications can be made in the embodiment of the invention illustrated and described herein without departing from the scope and purview of the invention as defined by the appended claims.

A method and apparatus for conveying and stripping electro-deposited metal sheets from cathode plates. A plurality of stations including a feed station, initial horizontal parting station, main vertical stripping station, replacement station, and discharge station are sequentially arranged within the stripping apparatus and cathode plates having metal sheet deposits thereon are conveyed through the apparatus by means of a reciprocating transfer carriage in combination with supporting slide bars and indexing means. Metal sheet deposits are stripped in a fast, simple and efficient manner by using closed entry horizontal knives to effect initial parting of each deposit and vertical stripping knives to remove the deposits from the two sides of the cathode plate without clamping of the cathode plate while controlling cathode plate sway. Liberated metal sheets are quickly removed from the apparatus and stripped cathode plates are conveyed from the apparatus at a discharge station.

BACKGROUND OF THE INVENTION The present invention relates to a vocal game apparatus for playing a game using recorded voices, and more particularly, to a game in which the players record the voices to be used. Apparatuses are known for playing a game, etc. using recorded voices. That is, a player listens to a voice reproduced from a recording medium and performs a predetermined operation in accordance with an instruction related to the sounded voice. However, in such conventional vocal game apparatuses, since the voices are fixedly prerecorded and messages reproduced during the game remain unchanged, there is a problem in that they cannot create in the player who is familiar with such a game a continuous interest in that game. SUMMARY OF THE INVENTION With the above-described problem in mind, it is an object of the present invention to provide a vocal game apparatus which gives players the opportunity to record arbitrarily their own messages, also which reproduces the plurality of voiced messages or words in accordance with predetermined game contents, and in which a player competes (with other players or himself) for scores using the recorded messages or words and indications of lights. To achieve the foregoing and other objects of the present invention and in accordance with the purpose of the invention, there is provided a vocal game apparatus, including: a plurality of input switches operated by one or a plurality of players; recording and reproducing means for recording voiced messages or words onto a recording medium at locations corresponding to respective input switches and reproducing the contents of the recording medium in response to a reproduce command; a plurality of lighting indication means, one corresponding to each input switch; and control means for receiving signals derived from said input switches and outputting signals to control operations of said recording and reproducing means and said lighting indication means, said control means in a first game operation lighting said lighting indication means at the same time when the words or messages from said recording and reproducing means are reproduced, and when the player operates one of the input switches (or the switch corresponding to himself in a multi-player game) when the reproduced message corresponds to and is coincident with the lighting of that lighting indication means, recording a score for the player. In a second game operation said control means controls the reproducing means to reproduce a sequence of the words or messages, and immediately following when the player operates the input switches in an order corresponding to the order of the produced sequence, the player scores a point and the process repeats with one additional word or message added to the sequence, until the player fails to correctly operate the input switches. These together with other objects and advantages of the invention will become more apparent from the following description, reference being had to the accompanying drawings wherein like reference numerals designate the same or similar parts throughout. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the game apparatus of the preferred embodiment according to the present invention; FIG. 2 shows the mounting portion of input switch keys used in the present invention shown in FIG. 1; FIG. 3 is a side, cross-sectional view of one of the input switch keys shown in FIG. 1; FIG. 4 is a circuit diagram showing an embodiment of circuitry of the game apparatus shown in FIG. 1; and FIGS. 5, 5A, 6, 7, 7A, 8, 8A, 9, 10, 10A, 11, 12, and 12A are flowcharts indicating processing procedures for the game apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, preferred embodiments will be described with reference to the attached drawings. FIG. 1 illustrates one preferred embodiment according to the present invention. The vocal game apparatus is provided with a disk-shaped casing 1 from which four cylindrical convex portions 6 spaced 90° apart are projected in its radial direction. On the upper surface of the casing 1 are arranged an on/off switch 2, a reset switch 3, a recording microphone 4, and an output surface 5 of a speaker (FIG. 4) housed within the casing 1. In addition, a circular opening 6A is provided on the upper surface of each cylindrical convex portion 6. A cylindrical input switch key 7 is disposed, enabled to move up-and-down, within each opening 6A and projecting above each opening 6A. At least the upper parts of the four input switch keys 7 are made of transparent materials, and each switch key 7 is a different color. For clarity of description, starting from the upper left side of the apparatus in FIG. 1, the switch keys 7 are red, blue, yellow and green sequentially in clockwise direction as viewed from FIG. 1. Hence, when the four colored switch keys 7 are identified in the later description, they are referred to as color keys 7R (red), 7B (blue), 7Y (yellow) and 7G (green). As shown in FIG. 2 and FIG. 3, each input key 7 is provided with an extended portion 8 extending from the lower part of the side surface of each key 7 toward the main body of the apparatus. A tip end of the extended portion 8 is integrally provided perpendicularly with a cylindrical shaft 9. Each switch key 7 is mounted within the casing 1 in each opening 6A so as to enable a pivotal movement in the up-and-down direction, with a shaft 9 pivotally grasped between two sets of up and down journal plates 10a, 10b installed on an upper plate 1a and a bottom plate 1b of the casing 1. Each switch key 7 is held in the position shown in the drawing by means of a switch piece 11 comprising a flexible metal plate bent so as to contact with a lower surface of the extended part 8, rising from the bottom plate 1b of the casing 1. A tip portion 11a of the switch piece 11 is bent downward and another switch piece 12 is fixed so as to face the tip portion 11a. The two switch pieces 11 and 12 are normally in a non-contact "off" position, held apart by means of an elastic force of the upper switch piece 11. However, if a player pushes down on an upper surface of any switch key 7, the tip 11a of the switch piece 11 contacts the switch piece 12, signalling an input. Each input switch is constructed in this way. An electric lamp 13 is arranged as lighting indication means inside each input switch key 7. A circuit 30 shown in FIG. 4 is housed within the casing 1. FIG. 4 schematically shows the reset switch 3 of FIG. 1, input switches 14R, 14B, 14Y and 14G (comprising switch pieces 11 and 12 corresponding to the four color keys 7R, 7B, 7Y and 7G as described above), the electric lamps 13 housed within respective color keys 7R, 7B, 7Y and 7G, a recording and reproducing large scale integration (LSI) chip 16 (which is readily available, manufactured by the Toshiba Corporation, Product No. T6668-BS) and semiconductor memory (RAM) 17 which records voiced messages or words corresponding to the respective input switches 14R, 14B, 14Y and 14G and reproduces the messages or words in response to a reproduce command. These elements are connected to a one-chip microcomputer (CPU) 15 (also readily available, Matsushita Electronic Corp. Product No. MN15543NTV) which serves as control means for the vocal game apparatus. The recording and reproducing LSI 16 is connected to the recording microphone 4 and to the speaker 19 via an amplifier 18. It is noted that this circuit uses four batteries 20 as a power supply and its voltage (6V) is supplied to the circuit via the on/off switch 2. The recording and reproducing LSI 16 stores in the RAM 17 the voiced messages or words inputted into the microphone 4 corresponding to the input switches 14R, 14B, 14Y and 14G during a recording process. Vocal data is fetched from the RAM 17 at random, outputted as a vocal signal, and sent to the speaker 19 via the amplifier 18 in order to reproduce it. Next, a game action according to the preferred embodiment will be described. First, this embodiment is such that the players record a message or sound corresponding to each one of the four color keys 7R, 7B, 7Y or 7G and each of the one to four players selects one of the color keys 7R, 7B, 7Y or 7G as his or her home position. During a game selection stage, a match game selected by pushing the red color key 7R and the memory game is selected by pushing the blue color key 7B. In the match game, each of the one to four players selects one of the color keys 7R, 7B, 7Y or 7G as described above as his home position. In the one player only memory game, the apparatus automatically designates the red color key 7R as the player's home position. After the game is finished, scores can be confirmed by voice and light indications. In the game referred to as the match game, voiced messages or words prerecorded by the players corresponding to the four color keys 7R, 7B, 7Y and 7G are reproduced at random by the game apparatus, and simultaneously the electric lamp 13 of one color key is turned on at random. When the reproduced voice corresponds to the lighted color key and a player pushes that color key, the apparatus adds a point to the score for that player. The score calculation is such that one point is added to the player's score whenever one correct key is operated and one point is subtracted when the player incorrectly pushes a color key 7 or fails to push the correct corresponding key within a predetermined period of time. On the other hand, in the memory game the apparatus sequentially specifies at first three color keys from among the four color keys 7R, 7B, 7Y and 7G through their corresponding prerecorded voiced messages or words. A score is obtained when the player enters the specified color key sequence in the same order as specified by the reproduced voices. This is referred to as a player repeat. After each score, the length of the specified color keys sequence is increased by one. The game is over when the player fails to enter the sequence in the proper order, the sequence is not entered within a certain period of time (for example, 10 seconds), or the length of the specified color key sequence has reached an upper limit (for example, 32). Hereinafter, an operation and game procedure required for carrying out the above-described games will be described with reference to the flowchart shown in FIG. 5-FIG. 12. First, as shown in FIG. 5, when the on/off switch 2 is turned on, the game apparatus enters a record enable state. In this embodiment, to make a 8-word record for the voice, the CPU 15 first clears a word number counter as shown in FIG. 6, next illuminates in a loop form mode the four color keys 7R, 7B, 7Y and 7G in this order to command the player to record and produces a repeating sound such as "PI", "PI". At this time, the CPU starts a timer defining an illumination time of each color key. Then, the CPU 15 sends a record command to the recording and reproducing LSI 16 to wait for the voice input. When a color key is illuminated and the player voices a word, a recording corresponding to that color key is carried out. That is to say, the voice of the player is inputted from the microphone 4 and is stored in a predetermined memory location of the RAM 17 as the vocal data by means of the recording and reproducing LSI 16. It should be noted that since the voice stored in the RAM 17 is within one second per word, the CPU checks to see whether one second has elapsed whenever the voice is inputted and thereafter counts the word number. In addition, since the voice to be recorded is used in the above-described two kinds of games, the first four words of the eight words specifies a name of each color key 7R, 7B, 7Y and 7G (for example, name of each player) and the subsequent four words specifies a color designation or other type of player specified word code for each color key 7R, 7B, 7Y and 7G (for example, red, blue, yellow, green). When the above-described recording is completed, the game apparatus enters a game selection mode and the CPU 15 lights the four color keys 7R, 7B, 7Y and 7G sequentially a predetermined number of times in this order in a loop lighting form. At this time, when a player depresses the red color key 7R or blue color key 7B, the above-described match game or memory game is selected. In addition, when the yellow color key 7Y is depressed, the apparatus returns to the record enable state and can record messages corresponding to each color key again. In this way, the yellow color key 7Y has a function as a reset key. When the red color key 7R is depressed during the above-described loop lighting mode, the match game is selected, and a player registration procedure follows. This procedure starts with a generation of such a repetition sound as "PI", "PI" as shown in FIG. 7. If the player sequentially depresses each color key 7R, 7B, 7Y and 7G within a predetermined period of time (for example, four seconds after either of the color keys is depressed), the corresponding light is turned on and the number of players and positions are registered. For example, if the number of players is three (suppose that the three players are A, B, and C) and A depresses the red key 7R, B depresses the blue key 7B and C depressed the yellow key 7Y, these color keys function as operation keys and home position for the respective players. Then, after a start melody, the match game begins. On the other hand, when the blue key 7B is depressed during the above described loop lighting mode, the memory game is selected, and the above-described player registration is omitted. With the red color key 7R being automatically selected as a home position, the game is continued in accordance with procedures shown in the flowcharts of FIG. 10 and FIG. 11. Upon completion of the match game or the memory game, if the red or blue color key 7R or 7B is depressed, the apparatus returns to a start state of the corresponding game. When the yellow color key 7Y is depressed, the apparatus again lights on each color key in the loop lighting mode for recording messages for each switch key 7. In addition, when the green color key 7G is depressed, the score of the last game is reconfirmed in accordance with procedures shown in the flowchart of FIG. 7 to be described later. Next, a further detailed description of the match game will be described with reference to FIG. 8. As described above, when the match game is selected and player registration is completed, the beginning of the game is signaled by the playing of a start melody. The CPU 15 selects one of the following two procedures according to the number of players based on the number of players registering, i.e., depending on whether the number of players is one or two to four. The Match Game for One Player First, the sole player is preset to have ten scores. This is because the score is decremented by one whenever the player makes a mistake (fails to press the appropriate color key at the proper time or presses the wrong key at any time), and the game is over when he makes ten such errors. During the game, processing is carried out as to slowly change the time interval between each set of lighting and issuing sound, i.e., the time interval from the lighting of the subsequent color key and the producing of the subsequent voice in order to make the game gradually more difficult by shortening the length of time between the lighting and sound sets by a predetermined time (for example, 10 msec.) whenever the voice is once produced regardless of the score. The four different voiced messages which have been recorded (for example, names of the respective color keys) are produced at random at the time intervals set in the above-described processing and the lights of the respective color keys are turned on at the same timings at random until the game is over. These lighting and sound producing operations are executed on the basis of random numbers ranging from zero to n generated in the CPU 15. The lighting and sound producing operations shown in FIG. 9 will be described hereinbelow. Although the numbers from zero to n (n denotes a natural number) are produced at random, n is different depending on whether the number of players is one or two to four. For example, when the number of players is one n=15, and when the number of players are two to four n=8. Depending on the number generated during the random processing, whether or not to match the recorded message to the color key being lit is determined. In detail, if the random number is greater than five, the color key being lit is not matched with its corresponding message and one of the messages which does not correspond to the color key being lit is outputted. If the random number is equal to or less than five, a coincidence flag of the CPU 15 is set to 1. If the random number is equal to or less than three, the color key which has been lighted the least number of times is lighted and the voice corresponding to the lighted color is produced, and a percentage of selection for the lighted color keys is adjusted. That is, the overall percentage that this particular color key has been lighted is adjusted upward, and the percentage of lightings for the other keys is adjusted downward. Furthermore, if the random number is neither equal to nor less than three (the random number is four or five), the message corresponding to the randomly lighted color key is produced. In this way, a probability of matching the lighting of the color keys with its respective word is 6/n in the lighting and sound producing operations. As described above, n is different depending on whether the number of players is one or two to four. This is because in the case where the number of players is two to four, each player may perform a key operation only if the lighting of the color keys at his own home position is matched with the message. A probability that the lighting of the color key is matched with the message for each player becomes less than 6/n. Hence, the above-described n in the case of one player is set larger than that in the case of two to four players to adjust the percentage of selection, thus guaranteeing approximately the same degree of player participation in both the 1 and 2-4 player games. When the one player depresses a color key which is lighted and the reproduced voice corresponds to that color key, the player scores a point. For example, when the blue color key 7B is lighted and the word corresponding to the blue color key 7B is reproduced, the player gets one point if he depresses blue color key 7B. On the other hand, if he depresses a color key different than the lighted color key when a lighted key/reproduced voice match occurs, or depresses any color key when no lighted key/reproduced voice match occurs, or does not depress the lighted color key when a lighted color key/reproduced voice match occurs, one point is decreased from the total running score. At the same time, one point is decremented from the permissible failure score (which was originally preset at ten). When one player is playing and the number of times the player fails reaches ten, the game ends. The final score is then indicated after a predetermined melody is sounded. The game will also end when the number of times the above-described voice producing and lighting operations has reached a predetermined number (e.g., 400 times) even if the number of times the player has failed has not reached ten. The total score indication is carried out in accordance with the flowchart shown in FIG. 12. First, a score melody is produced and the CPU determines whether the number of players is one. Then, for one player, the score is calculated and the score indication is carried out in such a way that the tens digit of the score is indicated by the number of times the color key chosen by the player for his home position is turned on for one second, and the units digit of the score is indicated by the number of times the same color key is turned on for 0.3 seconds. For example, when the color key specified by the player is the red color key 7R and his score is 25, the lighting of the light of the red color key 7R is repeated two times for one second and is repeated five times for 0.3 seconds. In addition, the repeating sounds such as "PI", "PI" are produced at the same time as the above-described lighting repetitions. Thereafter, although a predetermined fanfare sound is produced at the end of first game even when the preset score is further subtracted and the total score becomes a negative number, at the end of second and subsequent games the score of that game is compared with the highest score of previous like games during the same session (since the apparatus was turned on). If the present score is greater than the previous high score, a fanfare sound is produced. If the present score is less, such a sound as "bu" is produced. After the score is indicated, if the same game is to be played again, the player depresses the red or blue color key 7R or 7B. In a case when the different game (in this case, the memory game) or when the match game is to be played with the different number of players, the yellow color key 7Y is depressed. At this time, the routine returns to (2) in FIG. 5, the lights are in the loop lighting mode, and the new game can be selected. At this time, if the red or blue color key is depressed, the corresponding game is selected. In addition, if the score in the previous game is to be reconfirmed, the green color key 7G is depressed. The Match Game for Two to Four Players As shown in FIG. 8, the players' scores are not preset at 10, and the processing that determines the time interval of the lighting and sound producing procedure is changed to vary the difficulty of the game. Then, the four voiced words (for example, names of the respective players) which have been recorded are produced at time intervals defined at the above-described processing and simultaneously the light of a color key is turned on. This lighting and sound producing operations are the same as those in the case when the number of players is one, except the value of the random number for determining whether to output a match is different (n=8). However, in the case of two to four players, a four-person check is carried out whenever one lighting and sound producing operation is carried out. This is a check to see sequentially whether a key operation is correct for a color key to which the above-described player registation is performed. At this time, each player gets one score by depressing his color key at a time interval in which his color key lights and the sound produced corresponds to his color key (which he chose when the player registration was carried out). On the other hand, if the player fails to depress his color key when it is lighted and the corresponding voice is reproduced or if the player depresses his color key when there is no match, the player's score is decreased by one. When the game starts the time interval between consecutive lighting and sound producing operations is set to one second. The time interval decreases by a predetermined period of time (for example, 8 milliseconds) whenever a lighting and sound producing operation is carried out. When the time interval reaches below a predetermined period of time (for example, 0.5 seconds), the subtraction value is reduced (for example, to 2 msec.). Thereafter, when the time interval has reached a predetermined lower limit time (for example, 0.3 seconds), the lighting and sound producing operations are subsequently repeated at the lower limit time interval. Although the game for the two to four players is played in this way, the game is over when the time interval between consecutive lighting and sound producing operations has reached a predetermined value (for example, 0.4 seconds) and thereafter all players make an error. After a predetermined melody is produced, the scores are displayed. The score display procedure is such that a score melody is first produced as shown in the flowchart of FIG. 12. Next, the score of each player is indicated. The electric lamp 13 of the color key of each player is turned on repeatedly for 0.3 seconds and a simultaneous "PI" is sounded. Each coinciding flash and "PI" sound represents a point scored by the players, and simultaneously with each flash and "PI" sound one point is decremented from each players' score. When the score of the player who had accumulated the least number of points reaches zero, the flashing and sounding cease, a "bu" sound is produced and the apparatus indicates the identity of the last placed player by producing the word or message corresponding to his home position. This process is repeated for the remaining players, until only the player who accumulated the most points remains. When his score is finally decremented to zero, a fanfare is sounded and that player is identified as described above. The operation following the end of the game for two to four players is the same as that in the one player game. The Memory Game Next, the memory game will be described with reference to FIG. 10 and FIG. 11. When the memory game is selected by depressing the blue key 7B during the above-described loop lighting mode, a one player game automatically begins with the red color key 7R as the player's home position. First, a start melody is rung and three color keys are sequentially designated (the same key may be specified twice). Then, the CPU 15 adds one to a value of a specified number counter CNT1, which is set at an initialization state to two (2), resulting in three (3) being stored in CNT1. Thereafter, the counter is incremented by one after each successful player response, which is described below. When the value reaches an upper limit (e.g., 32), the game ends. In addition, in this game, this counting corresponds to the increasing length of the color key sequence, in which a newly selected color is added after the last specified color of the preceding sequence. Therefore, initially, with the last color selected sequentially, one is added to a value of a color specification counter CNT2, set to (-1) at the initialization state, to give zero. Thereafter, one is added thereto whenever a color is specified and output by the reproducing means. When the value of the counter CNT2 is matched with the value of the specified number counter CNT1, a "player repeat" is carried out. Since at first three prerecorded words corresponding to the color keys, such as red, blue and green, are sequentially sounded, the player depresses those color keys in that order. When this "player repeat" is correctly carried out within a predetermined time, a repeating sound such as "PI", "PI" is produced and one point is awarded to the player. Next, the game apparatus reproduces the above word sequence again and adds a new word following the above-described sequence, so as to now specify four colors, and waits for the "player repeat". Upon a successful player repeat, again the repeating "PI" sound is produced and the player is awarded another point. A new color is added to the end of the specified color sequence just repeated by the player. In this way the sequence length grows until one of two events occurs. If the player fails to repeat the sequence properly or the sequence reaches a predetermined maximum length (for example, 32), then the game ends. In the first case, the game apparatus produces a "bu" sound, the score melody is sounded, and the score is displayed. In the second case, when the player correctly repeats the sequences until the predetermined maximum sequence length is reached, the score melody is sounded and the score display procedure operates in the same way as in the match game. Alternate Embodiment In an alternate embodiment for the present invention, the procedures for playing the match game and the memory game are slightly different. The differences between this alternate embodiment and the above-described embodiment are found in the flowcharts 5A, 7A, 8A, 10A and 12A, which take the place of flowcharts 5, 7, 8, 10 and 12 of the above-described embodiment respectively in the case of this alternate embodiment. As per FIG. 5A, the first step of the second embodiment is the recording of the voices. In this embodiment, only four words or voiced messages are recorded, one corresponding to each of the color keys 7R, 7B, 7Y and 7G. After the recording is completed, the red and blue color keys 7R and 7B alternately turn on. If the red input key 7R is pressed, the match game has been chosen and a player registration as per the flowchart of FIG. 7A is begun. The only difference between this player registration and the player registration of first embodiment is that the lights alternately turn on around the loop upon the choosing of the red color key 7R, representing that the player registration stage has been entered. The differences between playing the match game of the second embodiment as opposed to that of the first embodiment are found in the flowchart of FIG. 8A. In the alternate embodiment, the game ends when the score of any one of the players reaches 100. Differences also exist between the memory game of the alternate embodiment and the memory game of the first embodiment. In the alternate embodiment, the sequence length limit is 100 rather than the 32 of the first embodiment. That is, upon a successful player repeat of a 100 word sequence, the highest score possible has been achieved and the game ends. Also, as seen from the flowchart in FIG. 10A, a score display step has become part of the memory game procedure. A special memory game display score step has been added, as shown in FIG. 12A. When the one player memory game has been completed, the longest sequence successfully completed by the player is reproduced by the game apparatus. During this playback, both the color key is lit and the corresponding voice reproduced for each step of the sequence. If the sequence that has been successfully reproduced is the longest reproduced so far during a given playing session, a fanfare is sounded upon completion of the repeat by the apparatus. If it is not the best score during a given session so far, a "bu" sound is reproduced. Upon completion of either the memory game or the match game, the game selection mode begins again. Once again, the red and blue color keys 7R, 7B are lighted alternately. At this point, if the red color key is pressed, the match game procedure begins again; if the blue color key 7B is pressed, the memory game procedure begins again. As per the flowchart of FIG. 5A, another difference over the first embodiment is illustrated. If the yellow key is pressed at this point, each color key is lighted once going around the loop, and at the same time as the lighting, the recorded word corresponding to that color key is reproduced, thus confirming the recorded voices. If the green color key 7G is pressed, the score for the last game played is once again displayed. After either the step of confirming the recorded voices or displaying the score of the last game, the procedure returns to the step of alternately lighting color keys 7R and 7B. Although the preferred embodiments have been described hereinabove, the present invention is not limited to these embodiments. For example, although the input switch keys are identified by colors, they may be identified by their profiles and so one. In addition, the game which carries out the plural kinds of voices which have been recorded and lights are not limited to the kinds of games in the preferred embodiments and many kinds of games can be conceived. As described hereinabove, since according to the present invention the game can be played in such a way that the players arbitrarily record their own messages, play back the several kinds of voices which have been recorded in accordance with the predetermined procedures, and compete with each other to make scores, the vocal game apparatus can be devised such that even a skilled player does not easily tire of playing.

A vocal game apparatus records arbitrary sounds and messages from game players. These recorded sounds correspond to input switches, which are different colors and contain a lamp for lighting. Players respond to the reproduced player recorded messages and the lighting of the lamps of the input switches in playing any of a plurality of games, all of which use the messages and light in some form, stored in memory of the vocal game apparatus. In a match game, the players must hit an input key in response to a match of a reproduced player message and lighting of a lamp of an input key. In a memory game, a player must correctly repeat a sequence of the colored input keys voiced by the vocal game apparatus by hitting the corresponding input keys in the proper order. The recorded messages may be changed as often as the players desire, thus giving the players a continuous interest in the vocal game apparatus.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates generally to the field of error correction in bandwidth limited communications systems. More particularly, the invention provides a Frequency Mapping Coding (FMC) scheme for varying the application of error correction redundancy to the transmitted data based on the channel transmission characteristics. [0003] 2. Description of Related Art [0004] For bandwidth limited communications environments, such as digital subscriber lines (DSL), characteristics such as the signal to noise ratio (SNR) are not uniform over the useable bandwidth for communication and are typically not even symmetrical. The SNR in the low frequency range, about 1 MHz or below, is much better than in the higher frequency range from 1 MHz to 10 MHz. Traditional quadrature amplitude modulation (QAM) communication systems are designed to work at a symmetric and relatively flat SNR characteristics and, therefore, cannot fully make use of the SNR characteristics over the entire bandwidth. Selection of a QAM scheme is therefore typically limited by the minimum SNR in the available spectrum and those portions of the spectrum having worse SNR characteristics cannot be fully used. [0005] A common alternative solution to overcome the varying SNR over the spectrum is the use of digital multi tone modulation (DMT). In this solution, the modulated signal is divided into different tones spread over the spectrum and a different number of bits is assigned to each tone. The SNR characteristics in the different portions of the spectrum are better utilized. However, the complexity and cost associated with DMT schemes, both to implement and manage, can be significantly higher than QAM approaches. A DSL communication system employing DMT has much higher implementation complexity than a DSL with QAM. Additionally, the spectrum is not really fully used in DMT schemes, since some guard band is needed to separate the adjacent tones. [0006] It is therefore desirable to employ QAM to avoid the complexity associated with DMT, however, correct for the channel characteristics where SNR may impact signal fidelity. SUMMARY OF THE INVENTION [0007] A Frequency Mapped Coding (FMC) scheme is employed to vary the error correction redundancy provided in the communications signal based on the channel characteristics for IQ based modulation. Additional redundancy is added to the coding of the signal in portions of the spectrum where SNR is low and reduced redundancy in the high SNR portions of the spectrum. The matching of the channel spectral characteristics by the FMC combined with the “analog” nature of an exemplary QAM modulation, more smoothly fits the available spectrum for better use of the channel capacity. The increased redundancy coding reduces the theoretical bit rate of the QAM channel however the constant bit error rate (BER) is maintained. [0008] Trajectories or differential positions rather than the positions of the signal in the constellation are used to measure the degree of vulnerability and add redundancy. The more vulnerable the trajectory is, the more redundancy is added, i.e. less information is transmitted. BRIEF DESCRIPTION OF THE DRAWINGS [0009] These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: [0010] [0010]FIG. 1 is a Power Spectral Density (PSD) plot for the transmission QAM signal with the channel characteristics overlaid on the signal; [0011] [0011]FIG. 2 is a PSD of the Receiving QAM signal; [0012] [0012]FIG. 3 is a plot of the PSD of FIG. 2 with the degree of damage to the QAM signal overlaid; [0013] [0013]FIG. 4 is a constellation diagram for a simplified embodiment of the invention for use with Differential Quaternary Pulse Shift Keying (DQPSK) demonstrating the modulation transition trajectories in the constellation of the DQPSK modulation; [0014] [0014]FIG. 5 shows the frequency spectrum for the trajectories shown in FIG. 5; [0015] [0015]FIG. 6 is an exemplary vulnerability table for the DQPSK modulation trajectories of FIG. 5; [0016] [0016]FIG. 7 is an exemplary bit stream for the DQPSK modulation with redundancy addition through a delay mechanism; [0017] [0017]FIG. 8 is a table of the input words, mapping bits and resulting decoding for the example of FIG. 8; [0018] [0018]FIG. 9 is a block diagram of the elements of the system employing the present invention for transmitting and receiving data; [0019] [0019]FIG. 10 is a schematic block diagram of the FMC elements for the DQPSK exemplary embodiment of FIGS. 4 - 9 ; [0020] [0020]FIG. 11 a schematic block diagram of the FMC decoder elements for the DQPSK receiver corresponding to the transmitter FMC elements disclosed in FIG. 10; [0021] [0021]FIG. 12 is a flow chart of an exemplary initialization and training sequence for a system employing the FMC architecture; [0022] [0022]FIG. 13 is a schematic block diagram of the system elements for performing the exemplary sequence of FIG. 11; and, [0023] [0023]FIG. 14 is a graphical estimation of the BER based on SNR with exemplary Reed Solomon coding only, Trellis Coding and RS coding using the FMC of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0024] For the purposes of description of an embodiment of the invention, a QAM system is employed, however, the invention is applicable to other orthogonal component based modulation in general. Referring to the drawings, FIGS. 1 and 2 demonstrate the distortion of the QAM PSD from the transmitted signal PSD 2 to the received signal PSD 4 based on the channel characteristics 6 . FIG. 3 demonstrates graphically the relative degree of damage 8 to the QAM signal that is caused by the characteristic of the channel. This graphical depiction indicates where and to what degree redundancy should be added for error correction of the signal. FIG. 4 shows the trajectory of the signal in the constellation while FIG. 5 shows the related spectral components resulting from those trajectories. Trajectories 10 in the lower right quadrant of FIG. 4 result in a first frequency “FREQ 0 ”. A counter-clockwise trajectory 12 results in a second frequency “FREQ 1 ” while a clockwise trajectory 14 results in a third frequency “FREQ 2 ”. As seen in FIG. 5, the response 16 at FREQ 0 falls within a portion of the PSD where only moderate damage to the signal would be anticipated. Similarly, the response 18 at FREQ 1 falls in the spectrum with little likely damage due to the channel characteristic. However, the response 19 at FREQ 2 falls in a portion of the spectrum where high damage vulnerability is present. It can be seen that different signals will generate different spectral components and therefore different degrees of damage can be caused. [0025] Continuing the DQPSK modulation example, FIG. 6 is an exemplary table demonstrating a portion of the vulnerabilities for possible trajectories. This table corresponds to the graphical depiction of FIGS. 4 and 5. For a sequence where the last sample offset was 0, the current offset is 0 and the next sample offset is 0, the relative damage or vulnerability has been defined as a “3” on a scale of 0 to 7 based on the anticipated frequency response of FREQ 0 . Similarly for a last sample offset of π/2, a current sample offset of π/2 and a next sample offset of π/2 a relative damage of 7 is established corresponding to the anticipated frequency response of FREQ 2 . A last sample offset of −π/2, a current sample offset of π/2 and a next sample offset of −π/2 shows a relative damage vulnerability of 0 based on the anticipated frequency response of FREQ 1 . Finally, a last sample offset of π, a current sample offset of π, and a next sample offset of π results in a relative damage assessment of 4. [0026] A bit stream for the DQPSK modulation example is shown in FIG. 7. As an example of FMC implementation for this model, to establish redundancy based on the trajectory of the bit transmission sequence, a two bit word or sample is assumed. As shown in the table of FIG. 8, input bits of the two bit words are mapped to define decoding for the bits. If a 1 is present in the first bit, only the first bit is decoded, as will be described in further detail subsequently. The FMC redundancy is added by creating a delay and outputting the second bit of the word a second time as the first bit of the next word. Using the examples of FIG. 7, the first two bits in the sequence are [0, 1] therefore, the first word for output is [0, 1]. The next bit in the sequence is a 1. The second word output is [1, 1]; however, since the first bit of the word is a 1, the second bit is repeated in the third word which is then [1, 0]. The third word, however, now has a 1 in the first bit, consequently, the second bit is again output as the first bit of the next word, resulting the in fourth word being [0, 0]. The convolutional encoder then encodes the sample for transmission in the standard fashion. [0027] The FMC scheme of the present invention can be characterized as a base-band error correction coding algorithm. Signal codes corresponding to higher frequencies in the spectrum have redundancy added for recovery of errors if loss occurs. The FMC scheme is also a bit allocation and management tool which is flexible if the channel characteristic changes. The FMC can adapt to achieve maximum throughput fully using the channel capacity. While similar to Multi-Dimension Trellis coding (MDTC) in the use of convolution coding and redundancy, the FMC scheme does not add the extra bits evenly or in a “color-blind” fashion. MDTC schemes are applied where frequency characteristics are always symmetrical. In the present FMC scheme, however, the unbalanced and unsymmetrical spectrum information of the channel characteristic provides the guide for selection and application of the redundancy coding. [0028] [0028]FIG. 9 shows the system implementation of the present invention in what effectively constitutes a concatenated code arrangement. In the transmitter 20 , the signal receives an outer encoding using Reed Solomon (RS) coding in the RS Coding block 22 followed by application of additional redundancy dependant on the signal frequency and channel characteristic, as described above, in the FMC block 24 . RS encoding and decoding are disclosed in the embodiments herein, however other Forward Error codes are equally applicable within the scheme. The inner coding scheme makes use of the convolution type coding to counteract the vulnerability due to the spectral deficiency. The transitional trajectories or the differential positions of the modulation dictates the spectrum that is used. As previously discussed with respect to FIGS. 7 and 8 for the simplified example, 2 bits or 1 bit can be mapped to each sample depending on whether the first bit is 0 or not. On the average the bit rate will be 1.5 bits/sample. [0029] [0029]FIG. 10 shows the FMC components for the exemplary DQPSK redundancy. The RS coded input signal 36 is provided to an input control circuit 38 as a bit stream for formation of 2 bit words or samples. If the first bit of the word created is a “1”, a halt signal 40 is generated by the input control circuit delaying input of the next bit for one clock cycle generated by the sample clock 42 . The second bit present in the input control circuit is provided to a delay buffer 44 and a normal output node 46 . The output control circuit 48 outputs the two bit word for encoding in the encoder 50 . If a halt single has been generated, the output control circuit will switch on the next clock cycle to the delay buffer node 52 to retrieve the bit stored in the delay buffer and output that bit a second time for modulation retrieving the next bit from the input control as the second bit of the word for modulation. [0030] Returning to FIG. 9, the signal is then modulated using QAM in the QAM block 26 . In the receiver 28 , the incoming signal is demodulated in the QAM block 30 followed by error checking with redundancy as defined by the FMC block 32 which accomplishes the decoding from the redundancy and encoding applied in FIG. 10 as shown in FIG. 11. The signal is then processed through normal RS decoding in RS coding block 34 . The FMC is used jointly with the Reed Solomon coding to reduce the error rate to a level where the RS coding can effectively be applied. Referring to FIG. 11, the FMC decoding for the exemplary embodiment shown employs a modified Viterbi decoder. The basic decoding of the incoming code is accomplished in decoder 54 , which for the exemplary 2 bit sample example results in a corresponding input bit length as in a normal Viterbi decoder. For decoding, the encoder memory also incorporates the vulnerability data present for the FMC application. As shown in FIG. 11, the incoming QAM modulated signal from the channel will be first delayed by the delay element or buffer 62 . The transitional trajectory or the differential positions will be detected by comparing the signals before and after the delayed elements. Such information is compared with the mapping tabled as defined in the vulnerability table. As the example shown in the exemplary DQPSK in FIGS. 7, 8 and 10 , when the clockwise trajectory is detected, it means one bit “1” is received. Otherwise two bits, starting with “0”, are received. The decoded data is subjected to rotation direction (trajectory) detection circuit 56 and output bit length control 58 to compensate for the redundancy added during the FMC encoding process. The trajectory detection circuit includes transitional trajectory decision and coding mapping information for feedback from the trajectory detection circuit to the decoder for decoding path development. [0031] Redundant data is placed in a first buffer 60 and second buffer 62 for comparison of last sample and next sample data for trajectory determination and matching of redundancy sets for reprocessing if required. The data is then provided on output 64 for Reed Solomon decoding as shown in FIG. 9. [0032] For a generalized case, the FMC redundancy approach is defined as described in the flow chart of FIG. 12. The transmitter and receiver of both the local and remote communications systems are initialized 100 . An initial narrow band communication is established with a bit rate much lower than the channel capability 102 to allow reduced error communication. The channel characteristic is analyzed over the whole spectrum and a vulnerability table is generated with a training sequence 104 . The vulnerability table is then exchanged between the local and remote systems 106 . Communications making use of the FMC is established at the operational channel bandwidth 108 . The variable length (added redundancy) convolutional coding created by the FMC is applied to transmitted and received signals by the local and remote system to fully employ the whole channel characteristic. [0033] [0033]FIG. 13 demonstrates an embodiment of the FMC coding block for a time domain implementation to generate the vulnerability table during the training sequence. A random signal is received in the buffer 110 and processed in the normal manner. A filter 112 with the channel characteristic, which may comprise transmission of the data over the channel itself, receives the data stream and provides the filtered data to one input of an exclusive-or (XOR) comparator 114 receiving the raw data stream from the encoder on the other input. The comparator output provides the control signal to the vulnerability table generator 116 also receiving the raw data stream at its input. If a segment of the data stream has a characteristic matching the channel filter, it will be filtered and no error output will be provided to the comparator. The data stream present on the other input to the comparator will pass the XOR function resulting in a control signal requiring no redundancy addition. If a segment of the data stream is not matched, the XOR function will not be satisfied and a vulnerability level will be added to the data. The redundancy logic of the FMC will add redundancy to the data stream based on the input data and vulnerability table created with a mapping code and resynchronize the data stream for output to the modulator as previously described with respect to FIGS. 4 - 10 . The time domain pattern in each data segment is retained and each pattern is transmitted to the receiver. Such patterns in the time domain are related to the frequency response of the channel. Each segment pattern can be used by the receiver to produce an original signal with different length, and therefore to achieve better error correction results. [0034] In the generalized case, the FMC receives a sample into a buffer corresponding to the input control circuit of FIG. 10. A comparison of the sample to the vulnerability table determines the redundancy to be added comparable to the one bit delay buffer of FIG. 10. [0035] For the FMC operation in the receiver, it is important to make use of the information in the information exchange stage as shown in FIG. 12. The FMC decoder obtains redundancy mapping code information and then applies error correction with different redundancy. As the result, different error correction capabilities are applied to different segments. [0036] The FIG. 14 depicts the simulated results with the FMC scheme of the present invention in conjunction with Reed-Solomon encoding in comparison with standard trellis coding and with RS encoding/decoding alone. The analytical result indicates about 2 dB improvement can be obtained. [0037] Having now described the invention in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present invention as defined in the following summary.

A Frequency Mapping Coding (FMC) scheme varies the application of error correction redundancy to transmitted data based on the channel transmission characteristics and the likelihood of error resulting from characteristics of the data stream being transmitted over the channel. The FMC is an error correction coding scheme making use of the non-linear feed-back mechanism and variable bit input step size to control redundancy applied. The FMC scheme accommodates the non-symmetrical nature of the SNR in bandwidth limited communications environments such as DSL to allow application of IQ based modulation, such as QAM, to these channels and is flexible for varying channel characteristics.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims benefit of U.S. Provisional Application Serial No. 60/313,762, filed Aug. 20, 2001, entitled “Phasers-Compiler Related Inventions,” in the names of Liang T. Chen, Jeffrey Broughton, Derek Pappas, William Lam, Thomas M. McWilliams, Ihao Chen, Ankur Narang, Jeffrey Rubin, Earl T. Cohen, Michael Parkin, Ashley Saulsbury, and David R. Emberson. BACKGROUND OF INVENTION [0002] An error or “bug” in a computer program (i.e., executable source program) is one that causes the computer program to malfunction in some way. Debugging refers to the process in which the errors in the computer program are found and removed. Finding an error in a computer program running in a massively parallel processing (MPP) environment can be extremely difficult and time intensive. Before further discussing this problem, an overview of an MPP environment is provided using FIG. 1. [0003] MPP environments are computer environments that operate using a massive number of processors. It is typical for an MPP environment to use tens of thousands of processors. Each processor in such an environment is able to execute computer instructions at the same time, which results in a very powerful system because many calculations take place simultaneously. Such an environment is useful for a wide variety of purposes. One such purpose is for the software simulation of a hardware logic design. [0004] Large logic simulations are frequently executed on parallel or massively parallel computing systems. For example, parallel computing systems may be specifically designed parallel processing systems or a collection, referred to as a “farm,” of connected general purpose processing systems. FIG. 1 shows a block diagram of a typical parallel computing system ( 100 ) used to simulate an HDL logic design. Multiple processor arrays ( 112 a , 112 b , 112 n ) are available to simulate the HDL logic design. A host computer ( 116 ), with associated data store ( 117 ), controls a simulation of the logic design that executes on one or more of the processor arrays ( 112 a , 112 b , 112 n ) through an interconnect switch ( 118 ). The processor arrays ( 112 a , 112 b , 112 n ) may be a collection of processing elements or multiple general purpose processors. The interconnect switch ( 118 ) may be a specifically designed interconnect or a general purpose communication system, for example, an Ethernet network. [0005] A general purpose computer ( 120 ) with a human interface ( 122 ), such as a graphical user interface (GUI) or a command line interface, together with the host computer ( 116 ) support common functions of a simulation environment. These functions typically include an interactive display, modification of the simulation state, setting of execution breakpoints based on simulation times and states, use of test vectors files and trace files, use of HDL modules that execute on the host computer and are called from the processor arrays, check pointing and restoration of running simulations, the generation of value change dump files compatible with waveform analysis tools, and single execution of a clock cycle. [0006] The software simulation of a hardware logic design involves using a computer program to cause a computer system to behave in a manner that is analogous to the behavior of a physical hardware device. Software simulation of a hardware logic design is particularly beneficial because the actual manufacturing of a hardware device can be expensive. Software simulation allows the user to determine the efficacy of a hardware design. Software simulation of a hardware logic design is well-suited for use in an MPP environment because hardware normally performs many activities simultaneously. [0007] When simulating a hardware logic design in an MPP environment, or executing any other type of computer program in such an environment, debugging the program may become necessary. Properly performed debugging of the computer program reduces the probability of errors that could result in a malfunction. In the case of hardware logic design simulation, such an error might result in the eventual fabrication of computer hardware that does not work as expected. Such a malfunction is expensive and wasteful, so debugging plays an important role. [0008] One common method for debugging is to single-step the execution of the computer program. Each step represents an instruction executed on a processor of the computer. At each step, the state of the simulation system, including the variables and registers, is examined. By examining the state of the simulation system at each progressive step, the person debugging the program is able to inspect the program and determine precisely where the problem begins to manifest itself. Once this is known, the person is better able to correct the program and remove the bug. [0009] Another common method for debugging is to insert a breakpoint into the program so execution of the program stops at the inserted breakpoint. This is similar to single-stepping, but the breakpoint is used to specify a specific place to stop execution and examine the state of the simulation system. Breakpoints may normally be inserted at any instruction in a sequence of instructions. At the breakpoint, a determination may be made if there is a problem with the program at that point. By changing the breakpoint, the manifestation of the problem may be precisely found and can then be corrected. [0010] Single-stepping a program or performing a breakpoint in an environment where there are tens of thousands of parallel processors can be extremely difficult. In particular, MPP environments include a massive number of parallel processors, each executing instructions simultaneously. There is no effective way to synchronously halt a massive number of processors executing simultaneously. In particular, to halt all of the processors requires a global signal to be sent to all of the processors. The time the global signal takes to propagate through the system to reach each of the processors differs depending on the distance the signal has to travel. Thus, some of the processors in the system surpass the intended stopping point where the global signal attempted to stop the processors, which makes debugging impossible. Thus, clock skew and speed of light considerations prevent gated clocks and global control systems from being used. SUMMARY OF INVENTION [0011] In general, in one aspect, the invention relates to a method for performing debugging of an executable source program in a massively parallel processing environment. The method comprises associating a major cycle counter and a minor cycle counter with each of a plurality of execution processors in the massively parallel processing environment, obtaining a first stopping point value associated with the major cycle counter and a second stopping point value associated with the minor cycle counter, executing instructions of the executable source program on each of the plurality of execution processors, modifying the major cycle counter and the minor cycle counter, and halting each of the plurality of execution processors and returning control to the user if the major cycle counter reaches the first stopping point value and the minor cycle counter reaches the second stopping point value. [0012] In general, in one aspect, the invention relates to a method for performing debugging of an executable source program in a massively parallel processing environment. The method comprises associating a major cycle counter and a minor cycle counter with each of a plurality of execution processors in the massively parallel processing environment, obtaining a first stopping point value associated with the major cycle counter and a second stopping point value associated with the minor cycle counter, executing instructions of the executable source program on each of the plurality of execution processors, modifying the major cycle counter and the minor cycle counter, halting each of the plurality of execution processors and returning control to the user if the major cycle counter reaches the first stopping point value and the minor cycle counter reaches the second stopping point value, inspecting and modifying the executable source program, storing the first stopping point value in a memory register, storing the second stopping point value in a memory register, storing the major cycle counter in a memory register, and storing the minor cycle counter in a memory register. [0013] In general, in one aspect, the invention relates to an execution control system configured for a massively parallel processing environment. The execution control system comprises a major cycle counter and a minor cycle counter configured to be associated with each of a plurality of execution processors in the massively parallel processing environment, a memory register to store a first stopping point value associated with the major cycle counter, a memory register to store a second stopping point value associated with the minor cycle counter, and an executable source program. Each of the plurality of execution processors is halted and control is returned to the user to inspect and modify the executable source program if the first stopping point value is equal to the major cycle counter and second stopping point value is equal to the minor cycle counter. [0014] In general, in one aspect, the invention relates to an execution control system configured for a massively parallel processing environment. The execution control system comprises a major cycle counter and a minor cycle counter configured to be associated with each of a plurality of execution processors in the massively parallel processing environment, a memory register to store a first stopping point value associated with the major cycle counter, a memory register to store a second stopping point value associated with the minor cycle counter, an executable source program, a memory register to store the major cycle counter, and a memory register to store the minor cycle counter. Each of the plurality of execution processors is halted and control is returned to the user to inspect and modify the executable source program if the first stopping point value is equal to the major cycle counter and second stopping point value is equal to the minor cycle counter. [0015] In general, in one aspect, the invention relates to a computer system to perform debugging of an executable source program in a massively parallel processing environment. The computer system comprises a processor, a memory, and software instructions stored in the memory for enabling the computer system under control of the processor, to perform associating a major cycle counter and a minor cycle counter with each of a plurality of execution processors in the massively parallel processing environment, obtaining a first stopping point value associated with the major cycle counter and a second stopping point value associated with the minor cycle counter, executing instructions of the executable source program on each of the plurality of execution processors, modifying the major cycle counter and the minor cycle counter, and halting each of the plurality of execution processors and returning control to the user if the major cycle counter reaches the first stopping point value and the minor cycle counter reaches the second stopping point value. [0016] In general, in one aspect, the invention relates to an apparatus for performing debugging of an executable source program in a massively parallel processing environment. The apparatus comprises means for associating a major cycle counter and a minor cycle counter with each of a plurality of execution processors in the massively parallel processing environment, means for obtaining a first stopping point value associated with the major cycle counter and a second stopping point value associated with the minor cycle counter, means for executing instructions of the executable source program on each of the plurality of execution processors, means for modifying the major cycle counter and the minor cycle counter, and means for halting each of the plurality of execution processors and returning control to the user if the major cycle counter reaches the first stopping point value and the minor cycle counter reaches the second stopping point value. [0017] Other aspects and advantages of the invention will be apparent from the following description and the appended claims. BRIEF DESCRIPTION OF DRAWINGS [0018] [0018]FIG. 1 shows a typical parallel computer system. [0019] [0019]FIG. 2 shows a parallel computer system in accordance with one embodiment of the present invention. [0020] [0020]FIG. 3 shows a general purpose computer system. [0021] [0021]FIG. 4 shows a program memory of a processor that functions using major and minor cycles in accordance with one embodiment of the present invention. [0022] [0022]FIG. 5 shows debugging in an MPP environment in accordance with one embodiment of the present invention. [0023] [0023]FIG. 6 shows debugging in an MPP environment according to an embodiment of the present invention. [0024] [0024]FIG. 7 shows debugging in an MPP environment according to an embodiment of the present invention. [0025] [0025]FIG. 8 shows debugging in an MPP environment using breakpointing in accordance with one embodiment of the present invention. [0026] [0026]FIG. 9 shows debugging in an MPP environment using single-stepping in accordance with one embodiment of the present invention. DETAILED DESCRIPTION [0027] Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. [0028] The present invention involves a method and apparatus for debugging in a massively parallel processing environment. In the following detailed description of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. [0029] A computer execution environment and a class of simulation systems, e.g., multiple instruction, multiple data (MIMD), used with one or more embodiments of the invention is described in FIGS. 2 - 3 . In an embodiment of the present invention, the computer execution environment may use execution processors to execute execution processor code on a general purpose computer, such as a SPARC™ workstation produced by Sun Microsystems, Inc., or specialized hardware for performing cycle-based computations, e.g., a Phaser system. [0030] The system on which a compiled hardware design logic may be executed in one or embodiments of the invention is a massively parallel, cycle-based computing system. The system uses an array of execution processors arranged to perform cycle-based computations. One example of cycle-based computation is simulation of a cycle-based design written in a computer readable language, such as HDL (e.g., Verilog, etc.), or a high-level language (e.g., Occam, Modula, C, etc.). [0031] [0031]FIG. 2 shows exemplary elements of a massively parallel, cycle-based computing system ( 200 ), in accordance with one or more embodiments of the present invention. Cycle-based computation, such as a logic simulation on the system ( 200 ), involves one or more host computers ( 202 , 204 ) managing the logic simulation(s) executing on one or more system boards ( 220 a , 220 b , 220 n ). Each system board contains one or more Application Specific Integrated Circuits (ASIC). Each ASIC contains multiple execution processors. The host computers ( 202 , 204 ) may communicate with the system boards ( 220 a , 220 b , 220 n ) using one of several pathways. The host computers ( 202 , 204 ) include interface hardware and software as needed to manage a logic simulation. [0032] A high speed switch ( 210 ) connects the host computers ( 202 , 204 ) to the system boards ( 220 a , 220 b , 220 n ). The high speed switch ( 210 ) is used for loading and retrieval of state information from the execution processors located on ASICs on each of the system boards ( 220 a , 220 b , 220 n ). The connection between the host computers ( 202 , 204 ) and system boards ( 220 a , 220 b , 220 n ) also includes an Ethernet connection ( 203 ). The Ethernet connection ( 203 ) is used for service functions, such as loading a program and debugging. The system also includes a backplane ( 207 ). The backplane ( 207 ) allows the ASICs on one system board to communicate with the ASICs of another system board ( 220 a , 220 b , 220 n ) without having to communicate with an embedded controller located on each system board. Additional system boards may be added to the system by connecting more system boards to the backplane ( 207 ). [0033] In one or more embodiments of the present invention, the computer execution environment to perform evaluation of design nodes in a cycle-based, logic simulation system may be a general purpose computer, such as a SPARC™ workstation produced by Sun Microsystems, Inc. For example, as shown in FIG. 3, a typical general purpose computer ( 300 ) has a processor ( 302 ), associated memory ( 304 ), a storage device ( 306 ), and numerous other elements and functionalities typical to today's computers (not shown). The computer ( 300 ) has associated therewith input means such as a keyboard ( 308 ) and a mouse ( 310 ), although in an accessible environment these input means may take other forms. The computer ( 300 ) is also associated with an output device such as a display device ( 312 ), which may also take a different form in an accessible environment. The computer ( 300 ) is connected via a connection means ( 314 ) to a Wide Area Network (WAN) ( 316 ). The computer ( 300 ) may be interface with a massively parallel, cycle-based computing system described above and as shown in FIG. 2. [0034] The computer systems described above are for purposes of example only. An embodiment of the invention may be implemented in any type of computer system or programming or processing environment. [0035] The timing of an executing computer program is defined, in one or more embodiments of the present invention, in terms of major and minor cycles. A major cycle refers to a sequence of instructions that an execution processor is scheduled to execute. A minor cycle refers to each instruction that each execution processor executes at each clock cycle. The program memory of an execution processor that functions using major and minor cycles is shown in accordance with one embodiment of the present invention in FIG. 4. While executing, the execution processor executes instructions loaded into a program memory ( 400 ) until a last instruction ( 410 ) in the program memory is reached. Reaching the last instruction ( 410 ) causes the execution processor to return to an initial memory location ( 420 ). [0036] The transition from a current instruction ( 430 ) to a next instruction ( 440 ) is termed a minor cycle, and constitutes a single global execution clock cycle. Each execution processor in a MPP system typically has a similar memory and simultaneously executes one instruction in the program memory in each of the global execution clock cycles. The execution of the sequence of instructions from the initial instruction ( 420 ), through the remaining sequence of instructions, to the last instruction ( 410 ), and back to the initial position ( 420 ) is termed a major cycle ( 450 ). One skilled in the art will appreciate that an identical number of instructions are not required to be loaded into each execution processor's memory although the number of instructions is a pre-determined number. A final instruction may be inserted into shorter sequences to cause a particular execution processor to wait a specified number of clock cycles before returning to the initial position ( 420 ) and starting a new major cycle. [0037] In one embodiment, two counters are placed in each processor of the MPP system. The counters are termed a “major cycle” counter and a “minor cycle” counter. The major cycle counter changes value (increments or decrements) each time a major cycle is completed. The minor cycle counter changes value (increments or decrements) at each global execution clock cycle. A stopping point is defined by a major and minor cycle count. [0038] Embodiments of the present invention use a stopping point to debug the program that is executing in the MPP system. One embodiment is shown in FIG. 5. A stopping point value is specified in terms of major and minor cycles by a user (Step 500 ). The program begins executing, for instance, by each execution processor executing an instruction in the program memory (Step 510 ). The major and minor cycle counters are modified (Step 520 ). A determination is made whether the major and minor cycle counters are at the stopping point (Step 530 ). If not, the next instruction is executed (Step 540 ) and Step 520 repeats. If, however, the stopping point is reached (Step 530 ), then control is returned to the user and debugging is performed (Step 550 ). [0039] Another embodiment of the present invention is carried out using an architecture in each execution processor as shown in FIG. 6. An execution processor ( 600 ) includes a program memory ( 610 ) for storing instructions. A global execution clock ( 620 ) controls the timing that the execution processor ( 600 ) executes the instructions. At each oscillation of the clock ( 620 ), a next instruction in the program memory ( 610 ) is executed, creating a minor cycle ( 630 ). A major cycle ( 640 ) is reached when the system transitions between a final instruction 650 and a first instruction ( 660 ). [0040] A major cycle counter ( 670 ) and a minor cycle counter ( 680 ) are associated with the execution processor ( 600 ). On each minor cycle, the minor cycle counter ( 670 ) is adjusted. On each major cycle, the major cycle counter ( 680 ) is adjusted. The adjustment may include, incrementing or decrementing the counter. A register ( 690 ) is associated with the major cycle counter ( 670 ). A register ( 695 ) is associated with the minor cycle counter ( 680 ). The registers ( 690 , 695 ) may optionally be used to hold values associated with the major and minor cycle counters ( 670 , 680 ). For instance, at each adjustment of the major and minor cycle counters ( 670 , 680 ), the registers ( 690 , 695 ) may be set to decrement such that a defined stopping point occurs when the registers ( 690 , 695 ) have a value of zero. By examining the registers ( 690 , 695 ) periodically, a precise stopping point may be measured. [0041] An embodiment of the present invention that uses the above architecture is shown in FIG. 7. At Step 700 , the major and minor cycle counter registers in the execution processor are loaded with values corresponding to the stopping point. A determination is made whether the major and minor cycle counter registers are zero (Step 710 ). If so, the processor halts (Step 720 ) and debugging is performed (Step 730 ). [0042] Otherwise, a determination is made whether a new major cycle has initiated (Step 740 ). If so, the major cycle counter and major cycle counter register are adjusted (Step 750 ) and the next instruction is executed (Step 760 ). If, on the other hand, a new major cycle has not initiated (Step 740 ), a determination is made whether a new minor cycle has initiated (Step 770 ). If not, the system waits until a new minor cycle has initiated (Step 770 ). When Step 770 is true, the minor cycle counter along with associated register is adjusted (Step 780 ) and the process repeats until both registers reach zero (Step 710 ). At this point, the execution processor reaches the stopping point and halts synchronously with the other execution processors. [0043] A breakpoint process may be performed by defining a stopping point at a specific time value defined by major and minor cycles. Breakpointing, according to one embodiment of the present invention, is shown in FIG. 8. A stopping point is obtained from a user in terms of a value of major cycle and minor cycles (Step 800 ). The program begins executing, for instance, by each execution processor executing an instruction in the program memory (Step 810 ). The major and minor cycle counters are adjusted (Step 820 ). A determination is made whether the breakpoint is reached by examining the values in the major and minor cycle counters and comparing the value to the stopping point (Step 830 ). If the breakpoint has not been reached, the next instruction is executed (Step 840 ) and Step 820 repeats. If, however, the breakpoint is reached (Step 830 ), the execution processors halt synchronously with the other execution processors and debugging is performed (Step 850 ). [0044] A single-stepping of the program's execution may be performed by defining a stopping point every time the minor cycle counter changes value. To implement a single-step scheme, a machine state is checkpointed at a given major cycle. The major cycle counter and the minor cycle counter are loaded with the appropriate values for the stopping point. Single-stepping is implemented by returning to the checkpoint state and incrementing the value loaded into the major cycle and the minor cycle counters so that the machine state is one minor cycle beyond the previous stopping point. [0045] [0045]FIG. 9 is a flowchart showing virtual single-stepping in accordance with one embodiment of the invention. The major and minor cycle counters are loaded with the appropriate values for a checkpoint (Step 900 ). The machine state is checkpointed at a given major cycle. The system begins executing instructions and the cycle counters are adjusted (Step 910 ). A determination is made whether this is the time for the checkpoint (Step 920 ), if not, Step 910 repeats. When Step 920 is true, single-stepping is implemented by returning to the checkpoint state and incrementing the value loaded into the counters (Step 930 ) so that the machine state is one minor cycle beyond the previous stopping point. In this way, a “virtual” single-stepping is implemented without gated clocks. [0046] Advantages of the present invention include one or more of the following. The invention provides the advantage of placing two counters in each execution processor to define a stopping point to effectively and efficiently debug a hardware logic design program in a MPP environment. The invention provides the advantage of using a defined stopping point to debug allows gated clocks and global control systems to be used in the logic design and simulation system. Those skilled in the art appreciate that the present invention may include other advantages and features. [0047] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

A method for performing debugging of an executable source program in a massively parallel processing environment involves associating a major cycle counter and a minor cycle counter with each of a plurality of execution processors in the massively parallel processing environment, obtaining a first stopping point value associated with the major cycle counter and a second stopping point value associated with the minor cycle counter, executing instructions of the executable source program on each of the plurality of execution processors, modifying the major cycle counter and the minor cycle counter, and halting each of the plurality of execution processors and returning control to the user if the major cycle counter reaches the first stopping point value and the minor cycle counter reaches the second stopping point value.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This patent application claims priority to U.S. Provisional Patent Application Ser. No. 62/081,214, filed Nov. 18, 2014, which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] The present invention relates generally to permanent magnet motors that include interior permanent magnets in a rotor. [0003] Permanent magnet brushless (PMBLDC or PMSM) motors may exhibit relatively high torque densities and are therefore useful in industrial drives for high performance applications. Permanent magnet (PM) motors with buried magnets are used in variable speed drives. [0004] The placement of magnets inside the magnet pockets of interior permanent magnet (IPM) motors with rectangular bar magnets is an issue due to the manufacturing tolerances of both magnet bars and magnet pockets. This magnet placement creates ripple torque depending on the slot/pole combination of the motor. For high performance applications, torque ripple is an important challenge for PM motors as it creates vibration and speed pulsation. Moreover, cogging torque minimization in IPM motors is more challenging compared to surface permanent magnet (SPM) motors. IPM motors allow for smaller air gaps and linear skewing. Shaping of the magnet presents design difficulties due to the rectangular shape of the permanent magnets. [0005] Various techniques have been attempted to minimize the cogging torque. Conventional techniques tend to add to the complexity and can negatively impact output torque. In addition, in motors employing sintered magnets, the increased complexity can contribute significantly to cost. [0006] Magnet pole shaping, skewing of rotor magnets or stator structures, step-skewing of rotor magnets, combining slots and poles, magnet shaping, and incorporation of notches in the stator teeth have been employed to minimize cogging torque in PM motors. Unfortunately, however, these conventional techniques cause additional design challenges. For example, the use of segmented stators, while bringing about improvements in slot fill and manufacturing time of the motor, have also given rise to certain undesirable harmonics, such as a large ninth order harmonic attributed to the gaps disposed between stator segments. [0007] Accordingly, it is desirable to have an improved rotor design and techniques for imbedding magnets in rotors of IBPM. SUMMARY OF THE INVENTION [0008] In one aspect of the invention, an interior permanent magnet motor comprises a housing, a ring-shaped stator fixed in the housing and having a coil which generates a magnetic field when a voltage is applied, a rotor being disposed for rotation within, and relative to the ring-shaped stator, the rotor comprises a shaft rotatably supported by the housing a magnetic plate pair disposed about an outer circumference of the rotor, wherein each magnetic plate of the magnetic plate pair has opposing sides that extend from the outer circumference toward the shaft, the opposing sides are bounded by an inner end of each magnetic plate, and a triangular member disposed between the magnetic plate pair and the shaft, the triangular member having a flat surface mated to each inner end of each magnetic plate of the magnetic plate pair, the triangular member directs flux produced by rotation of the rotor toward the stator. [0009] In another aspect of the invention, an interior permanent magnet rotor comprises a rotor being disposed for rotation within, and relative to the ring-shaped stator, the rotor comprises a shaft rotatably supported by the housing; a magnetic plate pair disposed about an outer circumference of the rotor, wherein each magnetic plate of the magnetic plate pair has opposing sides that extend from the outer circumference toward the shaft, the opposing sides are bounded by an inner end of each magnetic plate; a triangular member disposed between the magnetic plate pair and the shaft, the triangular member having a flat surface mated to each inner end of each magnetic plate of the magnetic plate pair, the triangular member directs flux produced by rotation of the rotor toward the stator. [0010] These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: [0012] FIG. 1 shows a motor in accordance with the invention; [0013] FIG. 2 shows a rotor in accordance with the invention; [0014] FIG. 3 illustrates a magnetic plate pair of the rotor in accordance with the invention; [0015] FIG. 4 illustrates specific geometries of the rotor in accordance with the invention; [0016] FIG. 5 shows a relationship for torque constant (K t ) saturation by comparing results with conventional sintered magnets versus exemplary designs in accordance with the invention; and [0017] FIG. 6 shows an exemplary relationship for average torque by comparing results with conventional sintered magnets versus exemplary designs in accordance with the invention. DETAILED DESCRIPTION [0018] Referring now to the Figures, where the invention will be described with reference to specific embodiments without limiting the same, FIG. 1 illustrates a cross-sectional view of an IPM motor 100 . As shown in FIG. 1 , the IPM motor 100 comprises a housing 102 , a ring-shaped stator 104 fixed in the housing 102 and a rotor 106 . The ring-shaped stator 104 may have a coil suitable for conducting an electrical current. In this embodiment, the coil of the stator 104 is formed by plurality of cores 108 . The rotor 106 includes a shaft 110 rotatably attached to the housing 102 . The electrical current in the coil of the ring-shaped stator 104 may cause rotation of the shaft 110 relative to the ring-shaped stator 104 . The IPM motor 100 , including the ring-shaped stator 104 and the rotor 106 , may be cylindrically shaped or disk shaped, in some embodiments. [0019] FIG. 2 illustrates the rotor 106 in accordance with some embodiments of the invention. In addition to the shaft 110 , the rotor 106 comprises at least one magnetic plate pair 202 . The magnetic plate pair 202 may be disposed about an outer circumference 203 of the rotor 102 . In this embodiment, the outer circumference 203 is spaced inward toward the shaft 110 , leaving a space between the outer surface of the rotor 106 and an outer end of a magnetic plate of the magnetic plate pair 202 . [0020] In the embodiment shown in FIG. 2 , a plurality of magnetic plate pairs 204 are circumferentially spaced about the rotor. Although six magnetic plate pairs are illustrated as the plurality of magnetic plate pairs 204 for purposes of description, any number of magnetic plate pairs may exist in the rotor 106 , such as three, four, ten, etc. [0021] Adjacent magnetic plate pairs may alternate in magnetic polarity. For example, a first magnetic plate pair may have a north magnetic polarity, where second magnetic plate pair may have a south magnetic polarity. The alternation of magnetic polarity of the plurality of magnetic plate pairs may continue throughout the rotor. Furthermore, adjacent magnetic plate pairs may be spaced by a pitch defined by a distance P. As shown in FIG. 2 , the plurality of magnetic plate pairs 204 are approximately equidistantly spaced about the rotor 106 , so the pitch P is approximately equal between magnetic pairs. [0022] In some embodiments, the plurality of magnetic plate pairs 204 are anisotropic injected molded magnets. The rotor 106 can be manufactured by using powder metal, a casting process, or any other suitable metal. [0023] FIG. 3 illustrates the magnetic plate pair 202 of the rotor 106 in more detail. The magnetic plate pair 202 has magnetic plates 304 , 305 . In this embodiment, magnetic plates 304 , 305 each have opposing convex sides 306 , 308 that extend from the outer circumference toward the shaft 110 . The opposing convex sides 306 , 308 of magnetic plates 304 , 305 are bounded by the outer ends 310 , 311 and an inner ends 312 , 313 of the respective magnetic plates 304 , 305 . [0024] In some embodiments, the magnetic plates 304 , 305 may be injection-molded, or filled by using an injection molding process. The invention is not limited to an injection molding process. In addition, in some embodiments, the magnetic plates 304 , 305 may be compressed magnets. The magnetic plates 304 , 305 may represent any magnetic plates of the plurality of magnetic pairs. [0025] In this embodiment, the magnetic plates 304 , 305 are oriented to form an angle α between magnetic plates of the magnetic plate pair. The angle α may increase as a radial distance from the shaft 110 increases (e.g. distance from the inner end toward the outer end of the magnetic plate pair). [0026] As shown in FIG. 3 , the rotor 106 may further comprise a plurality of triangular members. In this embodiment, a triangular member 314 of the plurality of triangular members is disposed between the magnetic plate pair 202 and the shaft. The triangular member 314 has a flat surface mated to inner ends 312 , 313 of the magnetic plates 304 , 305 of the magnetic plate pair 202 . Accordingly, the flat surface of the triangular member 314 may physically contact each the magnetic plates 304 , 305 of the magnetic plate pair 202 . [0027] The flat surface of the triangular member 314 may be bounded by a second side and third side of the triangular member. The second side and third side of the triangular member may be adjacent to one another, and extend from the flat surface toward the shaft 110 , forming an apex of the triangular member 314 . The apex of the triangular member may extend to the shaft, or as shown in FIG. 2 , the apex may be spaced from the shaft. The spacing of the apex from the shaft leaves a space formed by inner circumference to the shaft. [0028] The plurality of triangular members may be made of any non-magnetic material including but not limited to plastic, aluminum, and/or glue. Alternatively, the plurality of triangular members may be an air gap formed by the rotor 106 and the inner ends 312 , 313 of the magnetic plate pair 202 . The composition of triangular members with the rotor 106 may vary within the rotor 106 , or be consistent within the rotor 106 . [0029] The plurality of triangular members are configured to decrease flux leakage by directing flux away from the shaft 110 . Thus, the flux is concentrated radially outward, while softening torque pulsations of the motor. [0030] FIG. 4 illustrates specific geometries of the rotor 106 . A magnet inner arc diameter (IAD), magnet outer arc diameter (OAD) are defined. A minimum distance between the magnet and the outer rotor radius is defined by WEB. An outer magnet thickness (OMT), inner rib thickness (IRT), and an angular distance in between two plates of a single magnetic pole is defined by α. These parameters shape the non-magnetic material, reducing cogging and ripple torque, those parameters are also shown below. An outer non-magnetic thickness (ONMT), an inner non-magnetic thickness (INMT) and non-magnetic width (NMW) may define a triangular member that decreases flux leakage, concentrating the flux radially outward while softening torque pulsations of a motor. [0031] FIG. 5 shows relationships for torque constant (K t ) saturation by comparing results with conventional sintered interior permanent magnets versus exemplary designs in accordance with the invention. In an exemplary embodiment, the injection molded IBPM shows greater K t relative to sintered interior permanent magnet motors. [0032] FIG. 6 shows relationships for average torque (T avg ) by comparing results with conventional sintered interior permanent magnets versus exemplary designs in accordance with some embodiments of the invention. In an exemplary embodiment, the injection molded IBPM shows greater average torque relative to sintered interior permanent magnet motors. [0033] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description.

An interior permanent magnet motor includes a housing, a ring-shaped stator fixed in the housing and having a coil which generates a magnetic field when a voltage is applied, a rotor being disposed for rotation within, and relative to the ring-shaped stator. The rotor includes a shaft rotatably supported by the housing, a magnetic plate pair disposed about an outer circumference of the rotor. A triangular member is disposed between the magnetic plate pair and the shaft. The triangular member having a flat surface mated to each inner end of each magnetic plate of the magnetic plate pair. The triangular member directs flux produced by rotation of the rotor toward the stator.

FIELD OF THE INVENTION This invention relates to internal combustion engines, including but not limited to recirculation of crankcase gases into the intake system of an engine. BACKGROUND The present invention relates to a breather system for a crankcase of an internal combustion engine of the type which separates oil drops or mist from blow-by gases. The blow-by gases are routed to the intake air line of an engine to eliminate the discharge of combustion gases into the environment. Separated oil is routed back to the oil pan. Ideally, the pressure within an internal combustion engine crankcase should be maintained at a level equal to or slightly less than atmospheric pressure to prevent external oil leakage through the various gasketed joints, such as that between the valve cover and the cylinder head. Combustion gases are generated during the operation of an internal combustion engine. A small amount of these gases leaks past the piston seals, valve stems seals, and turbochargers of the internal combustion engine. Because of the “blow-by” gases, the crankcase pressure will inherently rise, promoting leakage of oil from the crankcase. These gases, commonly referred to in the art as “blow-by” gases, need to be released. Environmental considerations suggest that the blow-by gases in the crankcase be vented back to the combustion chamber rather than being released to the atmosphere. Accordingly, it is known to scavenge the crankcase of blow-by gases by connecting the crankcase to the engine air intake. Blow-by gases that are released from the crankcase carry combustion by-products and oil mist caused by splashing of the engine's moving components within the crankcase and the oil pan. It is known to substantially remove the oil mist from the blow-by gas prior to introduction into the intake air system. An apparatus that removes oil mist from blow-by gases is commonly referred to as a “breather.” Known breathers include breathers that include a stack of conical disks that spin at a high speed to fling heavier oil against a wall of the breather and allow gas to pass though the breather. Centrifuge type separators are disclosed for example in U.S. Pat. Nos. 7,235,177 and 6,139,595. Other types of breathers include filters such as described in U.S. Pat. Nos. 6,478,019, 6,354,283; 6,530,969; 5,113,836; swirl chambers or cyclone separators, such as described in U.S. Pat. Nos. 6,860,915; 5,239,972; or impactors, such as described in U.S. Pat. Nos. 7,258,111; 7,238,216 5,024,203. Each type of breather has advantages and limitations. The present inventor has recognized that it would be desirable to provide a breather system that is more economical to produce and more effective in operation than existing breather systems. SUMMARY An exemplary embodiment of the invention provides a breather system for a crankcase of an internal combustion engine. The breather system includes a gas compressor having a compressor inlet and a compressor outlet. The gas compressor is configured to elevate the pressure of blow-by gas received into the inlet and to discharge elevated pressure gas from the compressor outlet. An inlet conduit is arranged to connect the crankcase to the compressor inlet. At least one gas-oil separator includes a gas inlet for receiving the elevated pressure gas from the compressor, an oil outlet for discharging oil separated from the elevated pressure gas, and a gas outlet for discharging a gas having a reduced oil content. The at least one outlet conduit connects the compressor outlet to the gas inlet. The at least one gas-oil separator can comprise a swirl chamber separator in series with an impact separator. The swirl chamber separator and the impact separator can be cast as a unitary housing. The oil outlet can be flow-connected to return the separated oil to the crankcase. According to an exemplary embodiment, the gas outlet is flow connected to an air intake for the engine to re-circulate the gas discharged from the at least one gas-oil separator. According to another aspect of the disclosed embodiment, the at least one gas-oil separator includes a gas outlet and a bypass conduit flow connected between the gas outlet and the compressor inlet. The compressor can be a piston pump type of compressor or other known type of compressor. The disclosed embodiment provides a method for separating oil from crankcase gas from an internal combustion engine, including the steps of: receiving crankcase gas outside of the crankcase and into a compressor; pressurizing the crankcase gas using the compressor; channeling the pressurized crankcase gas into a gas-oil separator; separating oil from the crankcase gas in the gas-oil separator; and returning the separated oil from the gas-oil separator to the crankcase. The method can also include the step of directing crankcase gas from the gas-oil separator to a combustion air intake of the engine. The method can also include the step of: if the capacity of the compressor exceeds the crankcase gas production, directing gas flow from the gas-oil separator to the compressor. Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, and from the accompanying drawing. BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematic diagram of a breather system of the present invention. DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. The FIGURE is a schematic diagram that illustrates an embodiment of an engine breather system 10 according to the present invention. The system 10 is associated with an engine 20 which could be a diesel engine, such as a diesel engine for a long haul truck. The diesel engine can be normally aspirated or turbocharged. The engine 20 includes a crankcase 22 having an upper engine internal volume 23 partly defined by a valve cover 24 . The upper engine internal volume is generally in fluid communication with all the blow-by gases within the crankcase. The system 10 includes a gas compressor or pump 26 that includes a piston or a rotary impeller (not shown) or other fluid actuating device that can be belt driven, gear driven or otherwise driven by the engine 20 . Alternately the compressor could be driven by another power source. A number of compressor or pump types can be used, in addition to the standard piston pump, such as a gear pump, a gear-rotor pump, a vane pump, a rotary screw pump, or a diaphragm pump. According to one embodiment, the compressor would be rated at less than 50 PSI and to maintain a relatively small size, would be capable of being driven at speeds up to 10,000 RPM. A typical maximum bow-by gas flow rate for the compressor is 700 CFH (ft 3 /hour). The gas compressor 26 includes an inlet 26 a that is in fluid communication via a conduit 28 with the internal volume 23 by a connection to the valve cover 24 . An outlet 26 b of the compressor is in fluid communication with an inlet 50 a of a swirl chamber separator or cyclone separator 50 . Such a cyclone separator is described for example in U.S. Pat. Nos. 6,860,915 and 5,239,972, herein incorporated by reference. An outlet 50 b of the swirl chamber is in fluid communication with in inlet 60 a of an impactor or impact separator 60 . such an impact separator is described for example in U.S. Pat. Nos. 7,258,111; 7,238,216 and 5,024,203. An outlet 60 b of the impactor 60 is in fluid communication with a pressure regulator 70 . The pressure regulator maintains a desired gas pressure within the impact separator and swirl chamber separator by varying the gas flow restriction through the regulator. Oil that is separated from the gas in the swirl chamber 50 drains through an oil outlet 50 c at a bottom of the swirl chamber 50 . Oil that is separated from the gas in the impactor 60 drains through an oil outlet 60 c at a bottom of the impactor 60 . The outlets 50 c , 60 c can be small drain orifices. The combined oil from the outlets 50 c , 60 c is collected in a conduit or conduits 80 and returned to the crankcase 22 . The compressor 26 sucks blow-by gases from the crankcase 22 and compresses the blow-by gases to a pre-selected pressure, which may be below 50 PSIG. The blow-by gases are delivered into the swirl chamber 50 and then into the impactor 60 at elevated pressure. Each of the swirl chamber 50 and then into the impactor 60 separate some oil from the oil entrained blow-by gases. The pressure regulator 70 can be set to a desired working pressure to maintain elevated pressures within the components 50 , 60 and allow cleaned gas to pass into a discharge conduit 90 that can either be directed to atmosphere or can be redirected to the engine intake manifold for a normally aspirated engine or to the turbocharger compressor for a turbocharged engine. Alternately, with a sufficient arrangement of valves, the discharge conduit could be directed into the exhaust system. Pressure pulses from the compressor, in the form of a piston pump compressor, aid in the separation of oil and gas from the blow-by gases, because of the instantaneous high velocity of blow-by gases that enter the impactor. According to one embodiment of the invention, the size of the compressor should be large enough to outpace the amount of blow-by gases that are drawn into the compressor, which may be as high as 700 CFH (ft 3 /hour). If the compressor is of the piston type with one-way valve or valves, the piston should be orientated in a manner where the outlet valve is at the lowest point, below the piston so that any condensed oil can drain through the drain orifice and back into the engine to prevent oil from pooling and overwhelming the system when it leaves the compressor. The swirl chamber 50 and impactor 60 typically have no moving components and the swirl chamber 50 and impactor 60 can be cast as part of a common or unitary housing. Additionally, impactors of current design typically require high gas velocity to function. Therefore, small orifices are typically required but are restrictive such as to require a significant pressure drop. However, according to the disclosed embodiment, the compressor elevates the pressure of the blow-by gases to push the air through smaller orifices at higher velocity, i.e., more pressure drop is available. Furthermore, the high velocity of the cleaned blow-by gases from the impactor may reduce condensation and possible ice buildup in the discharge conduit 90 . A screen (not shown) can be used at each of the oil outlets 50 c , 60 c to protect the outlets from clogging with debris. The oil drain diameters for the outlets 50 c, 60 c can be sized in a manner that allows the system 10 to keep up with the amount of oil that is being separated from gas but not allow excessive loss of pressure by venting gas. During high engine speed and low power operation, the outlets 50 c , 60 c will normally be clear of oil and gas pressure may vent through the outlets 50 c , 60 c to the crankcase, which will then vent back to the compressor. This is not detrimental to the system 10 or to engine operation during these engine operating conditions. A bypass conduit 110 can be provided to direct gas from the low pressure output of the regulator 70 at the discharge conduit 90 to a low pressure compressor intake at the conduit 28 . When engine speed is high and the load is low, the compressor will be oversized for the amount of blow-by gas generated, which would result in formation of a vacuum within the engine. To avoid this condition, the bypass conduit 110 can be used to re-circulate cleaned blow-by gas from the discharge conduit 90 back into the compressor 26 where it is re-introduced to the separators 50 , 60 , re-cleaned and proper crankcase pressure can be maintained. If under unusual circumstances blow-by volume from the engine exceeds compressor capacity, the excess blow-by gas will bypass the compressor through the bypass conduit 110 and discharge through the discharge conduit 90 . Parts List 10 engine breather system 20 engine 22 crankcase 23 upper engine internal volume 24 valve cover 26 pump or compressor 28 conduit 50 swirl chamber or cyclone separator 50 a swirl chamber gas inlet 50 b swirl chamber gas outlet 50 c swirl chamber oil outlet 60 impact separator or impactor 60 a impactor gas inlet 60 b impactor gas outlet 60 c impactor oil outlet 70 pressure regulator 80 conduits 90 discharge conduit 110 bypass conduit From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

A breather system for a crankcase of an internal combustion engine includes a gas compressor configured to elevate the pressure of crankcase blow-by gas. At least one gas-oil separator receives gas with entrained oil from the compressor, separates oil from the gas and discharges cleaned gas. The oil is re-circulated back to the crankcase. The cleaned gas is either discharged through the engine exhaust system or re-circulated back into the engine combustion air intake. A bypass conduit allows cleaned gas to be re-circulated from the gas-oil separator outlet to the compressor inlet to balance the blow-by production with the capacity of the compressor.

This is a continuation of application Ser. No. 059,735, filed June 8, 1987 now abandoned. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a slit lamp microscope and more particularly to a slit lamp microscope adapted for use in examination and diagnosis with respect to such tissues of the eye as the cornea and crystalline lens. 2. Description of the Prior Art In the conventional slit lamp microscope, the white light from a light source such as a halogen lamp is passed through a slit formed between the opposing edges of two shield plates, the beam obtained in this way is directed onto an eye to be examined and the state of the cornea, crystal line lens etc. of the eye are observed using the light scattered by these eye tissues. Because of its use of a halogen lamp or the like, however, the conventional slit lamp microscope has low illuminating light intensity and, as a result, it has not been possible with the microscope to observe slight cloudiness, turbidity and the like. Moreover, since the width of the slit is varied by adjusting the gap between the two shield plates, the quantity of light illuminating the eye under examination grows smaller as the width of the gap is narrowed. It has thus been impossible to reduce the size of the observation region beyond a certain limit. SUMMARY OF THE INVENTION One object of the invention is to provide a slit lamp microscope in which the intensity of the illuminating light is high and the ratio between the length and width of the illuminating light cross-section can be accurately adjusted over a wide range. Another object of the invention is to provide a slit lamp microscope in which the quantity of illuminating light is not changed when the width of the light from the slit is narrowed. The slit lamp microscope according to the present invention is used to observe the cornea, crystalline lens and other tissues of the eye. It comprises a laser source for producing a laser beam; a projector for projecting the laser beam onto the eye to be examined; scanning means for scanning the laser beam vertically and horizontally within a selected area of the eye to be examined to form thereon a slit image which illuminates the selected area; optical means for receiving light scattered by the selected area of the eye to be examined and/or photographing an image of the eye; and light regulating means for regulating the intensity of the laser beam to a predetermined level depending upon the quantity of light received by the optical means. In the preferred embodiment of the invention, the scanning area defined by the scanning means is made variable to provide a slit image or pattern which is variable in size. The light regulating means includes a pair of linear polarizers through which the laser beam passes. One of the linear polarizers is caused to be rotated relative to the other to regulate the intensity of the laser beam depending upon the quantity of light received by the optical means. With the aforesaid arrangement according to the present invention, by scanning a laser beam of high light intensity in the vertical and horizontal directions, it becomes possible to freely adjust the ratio between the length and width of the illuminating light cross-section. In particular, if the horizontal scanning width is reduced to the width of a single laser beam, it become possible to observe a cross-section of the cornea, crystalline lens or the like using an extremely narrow slit beam. Moreover, the invention makes it possible to maintain the quantity of received light at a constant value regardless of changes in the dimensions of the slit beam. Further, since the intensity of the laser light is high, it becomes possible to reliably conduct examination and diagnosis even with respect to slight disorders of the cornea, crystalline lens and the like, which facilitates early detection of diseases of the eye. BRIEF DESCRIPTION OF THE DRAWINGS The objects and features of the present invention will become more apparent from a consideration of the following description taken in conjunction with the accompanying drawings in which: FIG. 1 is a schematic diagram of the slit lamp microscope according to the present invention; FIGS. 2A and 2B are explanatory views indicating the manner in which scanning of the laser beam in the vertical direction is conducted; FIGS. 3A and 3B are explanatory views indicating the manner in which scanning of the laser beam in the horizontal direction is conducted; and FIG. 4 is an explanatory view of the light quantity adjustment system. DETAILED DESCRIPTION OF THE INVENTION The invention will now be described with reference to the attached drawings. Referring to FIG. 1, for illuminating an eye 1 to be examined, the slit lamp microscope has an illuminating optical system consisting of a laser source 4, linear polarizers 6 and 7, a reflecting mirror 8, a beam expander 9, a reflecting mirror 10 for vertical scanning, a reflecting mirror 11 for horizontal scanning, a projection lens 12 and a reflecting mirror 13. The slit lamp microscope further has an optical system for visual and photographic observation of a cross-sectional image produced from the light scattered by the eye 1. More specifically, light scattered from the eye 1 and traveling along a different optical path from that of the illuminating light enters an objective lens 14, passes through a variable power optical system 15 and impinges on a swingable reflecting mirror 16. In the case of visual observation, the swingable mirror 16 reflects the light beam onto a beam splitter 17, from which a part of the beam is reflected into an eyepiece 19 for observation by the operator. The remainder of the beam is transmitted through the beam splitter 17 to a light quantity sensor 18 which detects the quantity of light and sends a corresponding signal to a light regulating controller 3 to be described later. In the case of photographic observation, the swingable mirror 16 swings upward, allowing the light beam from the variable power optical system 15 to be reflected by a reflecting mirror 20, to pass through photographic lens 21, 22 and a stop 22, and thereby to be projected onto the surface of a photographic film 23. For producing the slit beam, the slit lamp microscope is provided with a scanning means for scanning the laser beam in the horizontal and vertical directions along a locus. This means is constituted by the reflecting mirror 10 for the vertical scanning, the reflecting mirror 11 for the horizontal scanning and a scanning controller 2. The scanning controller 2 is equipped with a drive mechanism for synchronously driving the reflecting mirror 10 to oscillate about a shaft 10a (extending perpendicularly to the drawing sheet) and synchronously driving the reflecting mirror 11 to oscillate about a shaft 11a. As shown in FIGS. 2A and 2B, the amount of oscillation of the reflecting mirror 10 can be controlled to vary the scanning range V in the vertical direction, while, as shown in FIGS. 3A and 3B, the amount of oscillation of the reflecting mirror 11 can be controlled to vary the scanning range H in the horizontal direction. The reflecting mirrors 10 and 11 are independently controlled by the scanning controller 2 with respect to scanning velocity and scanning range. The maximum quantity of the laser beam light is restricted so as not to exceed the safety standards and the adjustment is carried out to attenuate the light quantity from this maximum quantity by means of the light regulating controller 3, the pair of linear polarizers 6 and 7 and the light quantity sensor 18. As shown in FIG. 4, the light quantity sensor 18 detects the light quantity and sends an electrical signal representing the detected light quantity to the light regulating controller 3. A motor 5 is driven by the light regulating controller 3 to rotate the linear polarizer 6 in such manner than when the light quantity is too large, the linear polarizer 6 is rotated with respect to the linear polarizer 7 so as to bring the angle of intersection between the polarization directions of the linear polarizers 6 and 7 (see arrows) closer to 90 degrees, in this way increasing the amount of attenuation and reducing the light quantity. On the contrary, when the quantity of light is insufficient, the linear polarizer is rotated to bring the polarization directions of the linear polarizers 6 and 7 closer to the alignment, in this way decreasing the amount of attenuation and increasing the light quantity. While the adjustment of the light quantity has been described here as being carried out automatically, it is alternatively possible to carry out the adjustment by manually rotating the linear polarizer 6. Further, the linear polarizers 6 and 7 can be replaced by a continuously variable ND filter of rotationally adjustable type. The operation of the slit lamp microscope of the aforesaid arrangement will now be explained. The laser beam produced by the laser 4 has its light quantity adjusted by the linear polarizers 6 and 7 and then is passed through the beam expander 9 to have its beam diameter enlarged. The loser bam is then scanningly deflected by the reflecting mirrors 10 and 11 so as to produce an appropriate slit beam, and the scanningly deflected beam (slit beam) then proceeds through the projection lens 12 to the reflecting mirror 13 from which it is reflected to illuminate the eye 1. Light scattered from within the eye 1 enters the optical system for visual and photographic observation. The incoming scattered light is first converged by the objective lens 14 and then enters the variable power optical system 15 where the observation magnfication is determined. Next, in the case of visual observation, the scattered light is reflected in the direction of the visual observation optical system (in the direction of beam splitter 17) by the swingable mirror 16, and in the case of photographic observation, the scattered light is passed in the direction of the photographic optical system (in the direction of reflecting mirror 20). During visual observation, the scattered light reflected by the swingable mirror 16 is divided into two beams by the beam splitter 17, one of which advances to the eyepiece 19 and the other of which advances to the light quantity sensor 18. As was mentioned earlier, the light quantity sensor 18 sends a signal representing the light quantity to the light regulating controller 3 which then adjusts the quantity of light based on the signal. Alternatively, however, it is possible for the operator examining the cornea, crystalline lens or the like through the eyepiece 19 to control the quantity of light by manually adjusting the linear polarizer 6. During photographic observation, the scattered light passed to the photographic optical system is reflected toward the photographic lenses 21 by the reflecting mirror 20, whereby the film 23 is exposed to a projected cross-sectional image of the cornea, crystalline lens or the like. In the illumination of the eye with the slit beam, the vertical scanning range V and the horizontal scanning range H can be appropriately varied as desribed earlier by the manner in which the scanning controller 2 drives the reflecting mirrors 10 and 11 to designate an area to be observed. The area of the slit can thus be varied by adjusting the scanning ranges, and if the light quantity of the slit beam should be changed, it is automatically readjusted by the light regulating controller 3 to maintain the light quantity constant. While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention should not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.

A slit lamp microscope for use in observing the cornea, crystalline lens and other tissues of an eye includes a scanning device for scanning the laser beam vertically and horizontally within a selected area of the eye to be examined to form thereon a slit image which illuminates the selected area. A regulating device is provided for regulating the intensity of the laser beam to a predetermined level depending upon the amount of light reflected from the eye. The scanning device is controlled to change its scanning area to make the selected area variable to thereby provide a slit image which is changeable in size.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method for sealing a heat transfer unit and in particular to a method for sealing a heat transfer unit, which significantly reduces the length of the dead zone and improves heat conduction efficiency. [0003] 2. Description of Prior Art [0004] With the rapid development of electronic information industry, the processing capability of the electronic device such as a CPU increasingly grows with the increasing generated heat. The heat-dissipation module combining a heat-dissipation fin and a fan has not been able to meet the requirement of heat dissipation, especially for a notebook computer. The heat pipe is a currently and commonly used device for heat transfer. The heat pipe can be considered a passive heat transfer device with high heat conductivity. Using the mechanism of two-phase heat transfer, the heat transfer capability of the heat pipe is hundreds times as large as copper having the same size. The heat pipe used as a medium of heat transfer has the advantages of fast response and small heat resistance. Therefore, the highly efficient heat-dissipation module developed from the heat pipe or its derived product is suitable to solve the heat-dissipation problems caused by high performance electronic products. [0005] As for the traditional method for sealing a heat pipe, the heat pipe is firstly vacuumed through a pipe opening and a working liquid is filled in the heat pipe. Then, the pipe opening is stretched and shrinks to form a necking end. Next, welding (e.g., argon welding) is performed at the necking end. In this way, the necking end is sealed. However, the necking section of the traditional heat pipe cannot conduct heat, which results in a dead zone of heat transfer. The dead zone will lower heat conduction efficiency of the heat pipe (that is, poor heat conduction of the heat pipe). Also, the necking section of the heat pipe is longer, which shortens the effective heat transfer length of the heat pipe such that when the heat pipe is installed in a smart mobile device such as a smart watch, a smart phone, or a wearable device, the occupied space of the heat pipe will make the assembly of the smart mobile device difficult, which is unfavorable to the shrinking of the smart mobile device. [0006] Therefore, how to overcome the above problems and disadvantages is the focus which the inventor and the related manufacturers in this industry have been devoting themselves to. SUMMARY OF THE INVENTION [0007] Thus, to effectively overcome the above problems, the primary objective of the present invention is to provide a method for sealing a heat transfer unit, which can effectively reduce the length of the dead zone and improves heat conduction efficiency [0008] Another objective of the present invention is to provide a method for sealing a heat transfer unit, which can effectively reduce the arrangement space when the sealed heat pipe is used. [0009] Yet another objective of the present invention is to provide a method for sealing a heat transfer unit, which can reduce the shrinking steps of the heat pipe. [0010] To achieve the above objectives, the present invention provides a method for sealing a heat transfer unit, which includes the steps of (a) to (c). Step (a) provides a heat transfer unit having a chamber and forming at least one opening, wherein an inner wall of the chamber forms at least one wick structure, wherein a working fluid is filled in the chamber; Step (b) welds the opening to form a welding section and close the opening; and Step (c) pinches off the welding section and cuts part of the welding section to form a cutting end and complete sealing the opening of the heat transfer unit. By means of the method of the present invention, an extremely short dead zone can be obtained and high heat conduction efficiency is enhanced, further having the effects of reducing the arrangement space and shrinking steps of the heat pipe. BRIEF DESCRIPTION OF DRAWING [0011] FIG. 1 is a flow chart of the method for sealing a heat transfer unit according to the first embodiment of the present invention; [0012] FIG. 2A is a schematic view of a method for sealing a heat transfer unit according to the first preferred embodiment of the present invention in the first state; [0013] FIG. 2B is a schematic view of a method for sealing a heat transfer unit according to the first preferred embodiment of the present invention in the second state; [0014] FIG. 2C is a schematic view of a method for sealing a heat transfer unit according to the first preferred embodiment of the present invention in the third state; [0015] FIG. 2D is a schematic view of a method for sealing a heat transfer unit according to the first preferred embodiment of the present invention in the fourth state; [0016] FIG. 3 is a view of the finished product made by the method for sealing a heat transfer unit according to the first preferred embodiment of the present invention; [0017] FIG. 4A is a schematic view of a method for sealing a heat transfer unit according to the second preferred embodiment of the present invention in the first state; [0018] FIG. 4B is a schematic view of a method for sealing a heat transfer unit according to the second preferred embodiment of the present invention in the second state; [0019] FIG. 4C is a schematic view of a method for sealing a heat transfer unit according to the second preferred embodiment of the present invention in the third state; [0020] FIG. 4D is a schematic view of a method for sealing a heat transfer unit according to the second preferred embodiment of the present invention in the fourth state; [0021] FIG. 5 is a view of the finished product made by the method for sealing a heat transfer unit according to the second preferred embodiment of the present invention; [0022] FIG. 6A is a schematic view of a method for sealing a heat transfer unit according to the third preferred embodiment of the present invention in the first state; [0023] FIG. 6B is a schematic view of a method for sealing a heat transfer unit according to the third preferred embodiment of the present invention in the second state; [0024] FIG. 6C is a schematic view of a method for sealing a heat transfer unit according to the third preferred embodiment of the present invention in the third state; [0025] FIG. 6D is a schematic view of a method for sealing a heat transfer unit according to the third preferred embodiment of the present invention in the fourth state; and [0026] FIG. 7 is a view of the finished product made by the method for sealing a heat transfer unit according to the third preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0027] The present invention is to provides a method of removing the dead zone of a flat heat pipe. [0028] Please refer to FIG. 1 , which is a flow chart of the method for sealing a heat transfer unit according to the first embodiment of the present invention. Please also refer to FIGS. 2A, 2B, 2C, 2D, and 3 . In the current embodiment, a cylindrical heat pipe is used as an example of the heat transfer unit 1 for explanation. The method for sealing a heat transfer unit includes the following steps. [0029] Step ( 100 ): providing a heat transfer unit having a chamber and forming at least one opening, wherein an inner wall of the chamber forms at least one wick structure, wherein a working fluid is filled in the chamber. [0030] The heat transfer unit 1 which is a cylindrical heat pipe is provided. The heat transfer unit 1 has a chamber 11 therein; each of two ends of the heat transfer unit 1 has an opening 12 communicating with the chamber 11 . An inner wall of the chamber 11 forms at least one wick structure 13 . In the current embodiment, sintered powder is used as an example of the wick structure 13 for explanation, but not limited to this. In practice, the wick structure 13 may be grooves, a metal net, or a fiber net. A working fluid 14 (e.g., pure water, inorganic compound, alcohols, ketones, liquid metal, coolant, or organic compound) is filled in the chamber 11 . Two dead zones 15 are individually defined between the wick structure 13 and each of the two opposite openings 12 at two ends of the heat transfer unit 1 . The wick structure 13 is not formed in the dead zones 15 , which helps the working fluid 14 be filled into the chamber 11 . Therefore, the dead zones 15 of the heat transfer unit 1 cannot be used for heat transfer. [0031] Step ( 101 ): welding the opening to form a welding section and close the opening. [0032] Two openings 12 at two ends of the heat transfer unit 1 have the dead zones 15 . In the current embodiment, the dead zones 15 are the portions which cannot carry out heat transfer on the heat transfer unit 1 and in which the wick structure 13 is not formed. Ultrasonic welding is performed on the dead zones 15 via ultrasonic welding equipment 5 . The inner wall in the portion of welding is welded and closed. Also, a certain range of the inner wall is required to be closed during the ultrasonic welding. Thus, after the ultrasonic welding is performed on two openings 12 of the heat transfer unit 1 , two welding sections 2 will be produced individually to close the individual openings 12 . Besides, the chamber 11 is vacuumed during the closing process to become a vacuumed chamber 11 . [0033] Step ( 102 ): pinching off the welding section and cutting off part of the welding section to form a cutting end and complete sealing the opening of the heat transfer unit. [0034] After the ultrasonic welding is performed, two ends of the heat transfer unit 1 individually form the welding section 2 . Besides, a certain range of the welding section 2 is required to be closed during the welding. Therefore, the pinch-off equipment 6 is used to pinch off the welding section 2 and cut off part of the welding section 2 . At the pinch-off location of the welding section 2 , the pinch-off equipment 6 closes the welding section 2 again to form a cutting end 3 such that the welding section 2 and the cutting end 3 can be closed effectively and thus the heat transfer unit 1 is sealed. [0035] Therefore, the design of the present invention can be directly applied in a common finished heat transfer unit 1 , such as the above-mentioned cylindrical heat pipe, the flat heat pipe, the heat conducting plate or vapor chamber formed by an upper plate and an lower plate stacked to each other, to reduce the length of the dead zone 15 and minimize the area disposed by the dead zone 15 . As a result, the heat conduction efficiency of the heat transfer unit 1 can be relatively improved. (That is, the heat transfer unit 1 is almost the effective area.). In addition, after the dead zone 15 is effectively reduced by means of the design of the present invention, the whole length of the heat transfer unit 1 can be effectively reduced, resulting in a heat transfer unit 1 with a short and small size. In this way, when the heat transfer unit 1 of the present invention is applied in a smart mobile device such as a smart watch, smart phone, or wearable device, it occupies little space and has a space saving effect, facilitating size reduction of smart mobile devices. [0036] Please also refer to FIGS. 1, 4A, 4B, 4C, 4D, and 5 , which are flow charts of a method for sealing a heat transfer unit according to the second preferred embodiment of the present invention. The current embodiment uses a flat heat pipe for explanation, instead of a cylindrical heat pipe as the heat transfer unit 1 of the first embodiment. In the current embodiment, the method for sealing a heat transfer unit mainly includes the following steps. First, a heat transfer unit 1 is provided, which is a finished product of the flat-pressed heat pipe. The heat transfer unit 1 has a chamber 11 therein; each of two ends of the heat transfer unit 1 has an opening 12 . The inner wall of the chamber 11 forms the wick structure 13 ; the working fluid 14 is filled in the chamber 11 . Two dead zones 15 are individually defined between the wick structure 13 of an inner wall of the heat transfer unit 1 and each of the two opposite openings 12 at two ends of the heat transfer unit 1 . Then, the two ends of the heat transfer unit 1 form the welding sections 2 after the ultrasonic welding is performed. Next, the welding sections 2 are pinched off using the pinch-off equipment 6 and part of the welding sections 2 are cut off. At the pinch-off location of the welding section 2 , the pinch-off equipment 6 closes the welding section 2 again to form a cutting end 3 such that the welding section 2 and the cutting end 3 can be closed effectively and thus the heat transfer unit 1 is sealed. In the way, after the dead zone 15 is effectively reduced by means of the design of the present invention, the whole length of the heat transfer unit 1 can be effectively reduced, resulting in a heat transfer unit 1 with a short and small size. Therefore, when the heat transfer unit 1 of the present invention is applied in a smart mobile device such as a smart watch, smart phone, or wearable device, it occupies little space and has a space saving effect, facilitating size reduction of smart mobile devices. [0037] Please refer to FIGS. 1, 6A, 6B, 6C, 6D, and 7 , which are flow charts of a method for sealing a heat transfer unit according to the third preferred embodiment of the present invention. The current embodiment uses a flat vapor chamber formed by an upper plate and a lower plate stacked to each other as an example of the heat transfer unit 1 for explanation, instead of the heat transfer unit 1 of the first embodiment. In the current embodiment, the method for sealing a heat transfer unit mainly includes the following steps. First, a heat transfer unit 1 is provided, which is a flat vapor chamber. The heat transfer unit 1 has a chamber 11 therein and a filling section 4 at one end thereof. An opening 12 is formed in the filling section 4 . The inner wall of the chamber 11 is provided with the wick structure 13 ; the working fluid 14 is filled in the chamber 11 . The wick structure 13 is not disposed in the filling section 4 and thus the filling section 4 is a dead zone 15 in the current embodiment. Next, the filling section 4 of the heat transfer unit 1 is welded by the ultrasonic welding to form a welding section 2 . The welding sections 2 are pinched off using the pinch-off equipment 6 and part of the welding sections 2 are cut off. At the pinch-off location of the welding section 2 , the pinch-off equipment 6 closes the welding section 2 again to form a cutting end 3 such that the welding section 2 and the cutting end 3 can be closed effectively and thus the heat transfer unit 1 is sealed. In the way, after the dead zone 15 is effectively reduced by means of the design of the present invention, the whole length of the heat transfer unit 1 can be effectively reduced, resulting in a heat transfer unit 1 with a short and small size. Thus, when the heat transfer unit 1 of the present invention is applied in a smart mobile device such as a smart watch, smart phone, wearable device, or tablet computer, it occupies little space and has a space saving effect, facilitating size reduction of smart mobile devices. [0038] In summary, compared with the traditional method, the present invention has the following advantages. [0039] 1. The length of the dead zone can be reduced. [0040] 2. The heat conduction efficiency of the heat transfer unit can be improved. [0041] 3. The space is saved. [0042] The above-mentioned embodiments are only the preferred ones of the present invention. All variations regarding the above method, shape, structure, and device according to the claimed scope of the present invention should be embraced by the scope of the appended claims of the present invention

The present invention relates to a method for sealing a heat transfer unit, which includes the steps of providing a heat transfer unit having at least one opening, welding the opening to form a welding section and close the opening, and pinching off the welding section and cutting part of the welding section to form a cutting end and complete sealing the opening of the heat transfer unit. By means of the method of the present invention, an extremely short dead zone can be obtained and high heat conduction efficiency is enhanced, further having the effects of reducing the arrangement space and shrinking steps of the heat pipe.

BACKGROUND OF THE INVENTION [0001] This invention relates generally to a stable aqueous aldehyde solution or mixtures of aldehyde solutions. [0002] Aldehydes are widely used in many industrial processes. Importantly, due to the ability of an aldehyde functional group of an aldehyde molecule to react with free amine groups of, for example, a cell membrane of a microorganism, the aldehyde demonstrates a biocidal effect by disrupting and ultimately killing the microorganism. [0003] Aldehydes are commonly used as preservatives, sanitizers, disinfectants and sporocidal agents. [0004] However aldehydes (with the exception of formaldehyde and aldehydes with carbon chain lengths of 2 to 4 carbon atoms) have a tendency, especially at low concentrations, to adopt a cyclic molecular configuration which results in the aldehyde molecule losing its biocidal efficacy. Furthermore, aldehydes (including formaldehyde and aldehydes with carbon chain lengths of 2 to 4 carbon atoms) when in a monomeric form, which is prevalent at low concentrations, have a tendency to diffuse into the atmosphere causing a health hazard as potent dermal and respiratory irritants. [0005] Aldehydes at relatively higher concentrations, left over a period of time, will polymerize with other aldehyde molecules, a process which accelerates at temperatures greater than 50° C. (and at less than 4° C. for aldehydes that have chain lengths of less than 5 carbon atoms). Once again this will result in a loss of the biocidal effect. [0006] It is known in the art to take a product containing an aldehyde solution and, before use, to dilute it. In doing so the tendency of the aldehyde molecule to polymerize is reduced. Raising the pH subsequently activates the aldehyde solution. The activation increases the reactivity of the aldehyde functional groups with the amine groups and the associated biocidal effect upon cell membranes. However the stability of the aldehyde solution is compromised in so doing to the extent that the solution is only stable for several days. [0007] There are a number of problems associated with the use of an aldehyde solution as a biocidal product. Not only does a user have to dilute the product prior to use but also activate it. The resultant diluted and activated product is corrosive, due to the high pH, and unstable beyond a month. [0008] The invention at least partially addresses the aforementioned problems. SUMMARY OF INVENTION [0009] The invention provides a stable aqueous aldehyde solution that includes: (a) an aldehyde comprising at least one of the following: a monoaldehyde (Diagram 1), a cyclic aldehyde (Diagram 2) and a dialdehyde (Diagram2) and a monoaldehyde or a cyclic aldehyde in a 0.001% to 25% m/v concentration: [0000] R—CHO  Diagram 1 [0000] OHC—R 1 —CHO  Diagram 2 [0000] R 3 —CHO  Diagram 3 and wherein: R=hydrogen, a straight hydrocarbon chain between 1 and 12 carbon atoms in length, or a branded hydrocarbon chain between 2 and 12 carbon atoms in length; —R 1 =a hydrocarbon chain between 2 and 12 carbon atoms in length; and —R 3 =a cyclic hydrocarbon having 5 or 6 carbon atoms. (b) a surfactant or detergent chosen from any one of the following: an alcohol ethoxylate surfactant, a nonylphenol surfactant, sulphonic acid, sodium lauryl ethyl sulphate, sodium lauryl sulphate, a twin chain quaternary ammonium compound and cocopropyldiamide (CPAD); (c) a sufficient amount of a pH modifier to bring the pH of the solution to within a 6.0 to 8.5 range; and (d) a buffer comprising at least one of the following: calcium acetate, magnesium acetate, sodium acetate, sodium acetate tri-hydrate, potassium acetate, lithium acetate, propylene glycol, hexalene glycol, sodium phosphate, sodium tri-phosphate, potassium phosphate, lithium phosphate, zinc perchlorate, zinc sulphate, cupric chlorate and cupric sulphate. [0018] “Stable”, in the context of the invention, refers to an aqueous aldehyde solution capable of being stored for a period of at least six months without the aldehyde molecules polymerizing or the pH dropping below 5. [0019] The stable aqueous aldehyde solution may include any of the following aldehydes: formaldehyde, acetaldehyde, proprionaldehyde, butraldehyde, pentanaldehyde, hexanaldehyde, heptanaldehyde, octanaldehyde, nonanaldehyde, glutaraldehyde, succinaldehyde, Glyoxal™, 2-ethyl hexanal, iso-valeraldehyde, chloraldehyde hydrate, furfuraldehyde, paraformaldehyde. [0020] Preferably, the stable aqueous aldehyde solution includes any of the following aldehyde mixtures: glutaraldehyde and Glyoxal™ (ethane dialdehyde); Glyoxal™ chloraldehyde trihydrate; acetaldehyde and Glyoxal™; paraformaldehyde and glutaraldehyde, glutaraldehyde and succinaldehyde and Glyoxal™ and succinaldehyde. [0021] The stable aqueous aldehyde solution preferably includes the surfactant or detergent in a 0.1% to 25% m/v concentration. [0022] The surfactant is preferably a non-ionic surfactant such as an alcohol ethoxylate surfactant. [0023] The alcohol ethoxylate surfactant may include 3 to 9 ethoxylate groups depending on the composition of the stable aqueous aldehyde solution and the foaming properties required for a specific application of the stable aqueous aldehyde solution. [0024] The buffer is preferably a mixture of sodium acetate trihydrate and potassium acetate. [0025] To maintain the pH of the stable aqueous aldehyde solution at least at 5 or above for at least 6 months, the buffer is preferably included in the solution in a concentration of at least 0.05% m/v. [0026] The pH modifier may be any one or more of the following compounds: potassium hydroxide, sodium hydroxide, sodium phosphate and sodium bicarbonate. [0027] The pH modifier is preferably potassium hydroxide in a one molar solution. [0028] The pH of the stable aqueous aldehyde solution may be maintained, at the time of manufacture, within a 7.0 to 8.5 range. [0029] A twin chain quaternary ammonium compound with sterically hindered ammonium groups may be added to the stable aqueous aldehyde solution for its fungicidal and foaming properties. [0030] To enhance the biocidal efficacy of the stable aqueous aldehyde solution one or more of the following trace elements may be added to the solution: calcium, magnesium, zinc, copper, titanium, iron, silver, sodium and gold. [0031] Sodium nitrite may be added to the stable aqueous aldehyde solution in a concentration exceeding 0.005% m/v for its anti-corrosive properties. [0032] Copper may be added to the stable aqueous aldehyde solution e.g. as cupric chlorate or cupric sulphate. [0033] Zinc may be added to the stable aqueous aldehyde solution e.g. as zinc perchlorate, zinc chloride or zinc sulphate. [0034] The stable aqueous aldehyde solution may be diluted either with distilled or potable water, an alcohol or a solvent to produce a biocidal dispersant with a greater biocidal efficacy at lower temperatures than the stable aqueous aldehyde solution in an undiluted state. [0035] The invention also provides a method of manufacturing a stable aldehyde-surfactant complex solution wherein at least one aldehyde is added to a surfactant in a first aliquot of water, at a temperature of between 40° C. to 50° C., the aldehyde is allowed to interact with the surfactant or detergent, in a complexing reaction, for at least 15 minutes whilst maintaining the temperature between 40° C. to 50° C. to produce an aldehyde surfactant complex solution, and a second aliquot of water is added after at least 15 minutes to cool the aldehyde-surfactant complex solution to below 40° C. to stop the complexing reaction. [0036] The aldehyde may be a monoaldehyde (Diagram 1), dialdehyde (Diagram 2) or a cyclic aldehyde (Diagram 3) in a 0.001% to 25% m/v concentration: [0000] R—CHO  Diagram 1 [0000] OHC—R 1 —CHO  Diagram 2 [0000] R 3 —CHO  Diagram 3 and wherein: R=hydrogen or a straight hydrocarbon chain between 1 and 10 carbon atoms in length or a branded hydrocarbon chain between 2 and 12 carbon atoms in length; —R 1 =a hydrocarbon chain between 2 and 10 carbon atoms in length; and —R 3 =a cyclic hydrocarbon having 5 or 6 carbon atoms. [0041] The surfactant may be at least one of the following; an alcohol ethoxylate surfactant, a nonylphenol surfactant, sulphonic acid, sodium lauryl ethyl sulphate, sodium lauryl sulphate, a twin chain quaternary ammonium compound and cocopropyldiamide (CPAD). BRIEF DESCRIPTION OF THE DRAWINGS [0042] The invention is further described by way of example with reference to the accompanying drawings in which: [0043] FIG. 1 illustrates a commercially available mass spectroscopy scan of acetaldehyde; [0044] FIG. 2A illustrates a mass spectroscopy scan of acetaldehyde treated in accordance with the invention; [0045] FIG. 2B illustrates an expanded portion of the mass spectroscopy scan of FIG. 2A ; [0046] FIG. 3A illustrates a mass spectroscopy scan of untreated acetaldehyde and a surfactant; and [0047] FIG. 3B illustrates an expanded portion of the mass spectroscopy scan of FIG. 3A . DESCRIPTION OF PREFERRED EMBODIMENT [0048] A stable aqueous aldehyde solution, according to the invention, is manufactured, in a concentrate solution (i.e. comprising aldehyde compounds in the range 2 to 10% m/v), by first adding a non-ionic surfactant i.e. alcohol ethoxylate (with 3, 7 or 9 ethoxylate groups), to water heated to a temperature between 40° and 50° C. followed by an aldehyde or an aldehyde mixture chosen from Table 1 (hereinafter referred to as “the aldehyde”). [0000] TABLE 1 aldehyde aldehyde mixture Preferred surfactant 1. Glyoxal ™/glutaraldehyde alcohol ethoxylate 7 2. Glyoxal ™ alcohol ethoxylate 9 3. Glyoxal ™/chloraldehyde alcohol ethoxylate 9 trihydrate 4. succinaldehyde alcohol ethoxylate 7 5. Glutaraldehyde/succinaldehyde alcohol ethoxylate 7 6. Glyoxal ™/succinaldehyde alcohol ethoxylate 9 7. acetaldehyde alcohol ethoxylate 9 8. acetaldehyde/Glyoxal ™ alcohol ethoxylate 9 9. glutaraldehyde/ alcohol ethoxylate 9 paraformaldehyde [0049] The aldehyde is allowed to complex with the preferred alcohol ethoxylate (as indicated in Table 1 alongside the relevant aldehyde) for a period of between 15 and 30 minutes. This produces an aldehyde-surfactant solution, whilst maintaining the temperature of the body of water between 30° C. and 70° C. During this period of heating the aldehyde complexes with the alcohol ethoxylate substantially to completion (see FIGS. 2 and 3 ). [0050] Following this period, a further amount of water, at a temperature of less than 25° C., is added to the aldehyde-surfactant complex solution to reduce the temperature of the solution to below 30° C. thereby to stop the complexing reaction of the alcohol ethoxylate with the aldehyde. [0051] A pH modifier, such as potassium hydroxide, is then added in a sufficient quantity to adjust the pH of the succinaldehyde-surfactant complex solution to within 7.0 to 85 Potassium hydroxide is used in a one molar solution. [0052] Finally a buffer mixture comprising sodium acetate trihydrate and potassium acetate is added to the aldehyde-surfactant complex solution to produce a stable aqueous aldehyde solution in the concentrate solution. [0053] Sodium acetate trihydrate and potassium acetate each have a concentration in the buffer mixture of between 0.250 to 0.500 grams/liter. This concentrated solution is diluted when added to the aldehyde-surfactant complex solution to within the range 0.005% to 0.1% m/v. [0054] The buffer mixture maintains the pH of the concentrate during the shelf life of the stable aqueous aldehyde solution, i.e. at least 6 months from manufacture, at least above pH 5. [0055] The concentrate solution of the stable aqueous aldehyde solution includes the following contents in the following concentrations: [0000] (a) aldehyde  0.01% to 25% m/v; (b) alcohol ethoxylate   0.1% to 25% m/v; and (c) the buffer mixture 0.05% to 0.1% m/v. [0056] To enhance the biocidal efficacy of the stable aqueous aldehyde solution, one or more of the following trace elements are added, in a concentration not exceeding 5 ppm, to the solution: calcium, magnesium, zinc, copper, titanium, iron, silver and gold. [0057] To produce a biocidal product capable of application, by a variety of means, to a variety of surfaces, the concentrate solution of the stable aqueous aldehyde solution is diluted with potable water to produce a dispersant with aldehyde in a 0.001% to 8% m/v concentration. [0058] The dispersant finds application as an additive to degreasing agents, detergents, thickeners, fragrances, colorants, skin conditioners and a variety of anti-microbial products. This list is exemplary and is by no means exhaustive. [0059] On the other hand, the concentrate solution with aldehyde in a concentration in excess of 10% m/v is a favoured composition in which to transport the stable aqueous aldehyde solution. [0060] An end user, on receipt of the concentrate solution, merely has to dilute the concentrate solution by a required dilution ratio for ready incorporation with other appropriate additives, to produce products such as anti-microbial hand soap, hand sanitizers, medical equipment disinfectants, dishwashing liquids, and laundry detergents. Once again, this list is exemplary and is by no means exhaustive. [0061] The concentrate solution finds further application, incorporated with other mediums such as paints, resins etc, to provide a sustained release of the biocidal efficacy. [0062] It is believed that the dispersant and the concentrate solution, in the variety of applications exemplified above, have lower volatility, lower toxicity and corrosive properties, greater stability and biocidal efficacy at room temperatures relatively to an aldehyde (e.g. acetaldehyde and/or Glyoxal™) that has not been subjected to the method of the invention (i.e. at least not bound to a surfactant in a complex configuration), and which is used in comparative applications (see Table 2, Table 3 and Table 4). [0063] The stable aqueous aldehyde solution, like an uncomplexed aldehyde, is incompatible with certain unhindered nitrogen containing chemicals such as triethalamines and cocoamides. This incompatability needs to be kept in consideration when formulating with any aldehyde biocide. Example 1 Proof of Complexing [0064] To demonstrate complexing of the aldehyde with the surfactant a comparison is made between FIG. 1 and FIG. 2 . [0065] From FIG. 2 it is evident that there are no free acetaldehyde spectra between 0 to 100 mass to charge (m/z) where acetaldehyde indicative peaks would appear (see FIG. 1 ) if “free” aldehyde was present. [0066] FIG. 3 exhibits the separate mass spectra of the surfactant and the aldehyde used in FIG. 2 , but uncomplexed with each other. By comparing FIG. 2 with FIG. 3 it can be seen that the spectra of FIG. 2 have shifted to the right with respect to the spectra of FIG. 3 , indicating the complexing of the aldehyde with the surfactant. [0067] The sample of FIG. 2 was produced by adding 50 ml acetaldehyde (10% m/v) to 450 ml of a “premix” solution (2.51 bacterial filtered water, 0.9% m/v alcohol ethoxylate 7, 13.7 g potassium acetate, 13.7 g sodium acetate trihydrate) and heated to 30° C. for 15 minutes. [0068] The sample of FIG. 3 was a sample of acetaldehyde (99% m/v), mixed with an alcohol ethoxylate 7 surfactant without being subjected to the method of the invention. [0069] The method, materials and equipment used in this example are as follows: Agilent 1299LC; Agilent 6210 Agilent 6210 time-of-flight (TOF) mass spectroscopy; LC: mobile phase: 50:50 H20:MeCN+0.1% formic acid; flow: 0.2 ml/min; injection volume: 10 micro-liter; samples were directly infused into the TOF; TOE: positive ionization; gas Temp 300° C.; drying gas 8 L/min; nebulizer 35 psig; Vcap 3500V; fragmenter 140V; skimmer 60V; ref masses: 118.086255 and 922.009798. [0070] The TOF system is used in combination with a dual-nebulizer ESI source and an automated calibrant delivery system to continuously introduce low-level reference masses to achieve accurate mass assignment. For the analysis, the drying gas flow was set at 8 L/min, with gas temperature at 300° C. The nebulizer was set to 35 psig and capillary voltage was 3500V. A Fragmenter setting of 140V was used with skimmer 60V. The mass range was set to 100-3500 m/z with transients/scan equal to 10000. Internal reference mass correction was used. [0071] Stability tests, as above, were repeated on samples of the aldehydes (1 to 21) indicated in the table below. The results showed the same complexing phenomena. Example 2 Biocidal Efficacy Tests [0072] Tests were conducted using a South African Bureau of Standards (SABS) method (i.e. SABS1593), a Kelsey Sykes modified suspension test. The microorganism used in the test was Bacillus subtilis var globi . The results of the tests are tabulated below: [0000] TABLE 2 Aldehyde 2 Suspension Aldehyde 1 (% m/v) Surfactant Contact time Result 1 glutaraldehyde Glyoxal ™ 8% alcohol ethoxylate 7 2 hrs PASS 1.5% 4 hrs PASS 8 hrs PASS 2 Glyoxal ™ 16% alcohol ethoxylate 9 2 hrs PASS 4 hrs PASS 8 hrs PASS 3 Glyoxal ™ 8% chloraldehyde alcohol ethoxylate 9 2 hrs PASS trihydrate 10% 4 hrs PASS 8 hrs PASS 4 succinaldehyde 3% alcohol ethoxylate 7 2 hrs FAIL 4 hrs PASS 8 hrs PASS 5 glutaraldehyde 1% succinaldehyde 2% alcohol ethoxylate 7 2 hrs PASS 4 hrs PASS 8 hrs PASS 6 Glyoxol ™ 8% Succinaldehyde 1% alcohol ethoxylate 9 2 hrs PASS 4 hrs PASS 8 hrs PASS 7 acetaldehyde 3% alcohol ethoxylate 9 2 hrs PASS 4 hrs PASS 8 hrs PASS 8 acetaldehyde 2% Glyoxal ™ 8% alcohol ethoxylate 9 2 hrs BORDER PASS 4 hrs PASS 8 hrs PASS 9 acetaldehyde 1% paraformaldehyde alcohol ethoxylate 9 2 hrs BORDER 1% PASS 4 hrs PASS 8 hrs PASS 10 Glyoxal ™ 10% alcohol ethoxylate 3 2 hrs PASS 4 hrs PASS 8 hrs PASS 11 furfuraldehyde 5% alcohol ethoxylate 3 2 hrs BORDER PASS 4 hrs PASS 8 hrs PASS 12 furfuraldehyde 5% alcohol ethoxylate 9 2 hrs PASS 4 hrs PASS 8 hrs PASS 13 glutaraldehyde 3% alcohol ethoxylate 3 2 hrs FAIL 4 hrs PASS 8 hrs PASS 14 2-ethyl alcohol ethoxylate 3 2 hrs FAIL hexanaldehyde 10% 4 hrs FAIL 8 hrs PASS 15 2-ethyl alcohol ethoxylate 9 2 hrs FAIL hexanaldehyde 10% 4 hrs PASS 8 hrs PASS 16 nonanaldehyde alcohol ethoxylate 3 2 hrs FAIL 15% 4 hrs PASS 8 hrs PASS 17 nonanaldehyde alcohol ethoxylate 9 2 hrs FAIL 15% 4 hrs PASS 8 hrs PASS 18 chloraldehyde alcohol ethoxylate 3 2 hrs FAIL hydrate 20% 4 hrs PASS 8 hrs PASS 19 chloraldehyde alcohol ethoxylate 9 2 hrs FAIL hydrate 20% 4 hrs PASS 8 hrs PASS 20 paraformaldehyde alcohol ethoxylate 9 2 hrs FAIL 3% 4 hrs PASS 8 hrs PASS 21 formaldehyde alcohol ethoxylate 9 2 hrs FAIL 10% 4 hrs PASS 8 hrs PASS [0073] The same aldehydes as used above (i.e. 1 to 21) were re-subjected to the test, with the relevant surfactant added, but without pH adjustment and without the addition of a pH modifier and a buffer. All the aldehydes failed the 8 hour contact time with the exception of glutaraldehyde (sample 13) with a “borderline” pass. [0074] As evident from the above the invention appears effective at improving the biocidal efficacy of aldehydes. Example 3 Stability Tests [0075] [0000] TABLE 3 Sample Description of sample (% number m/v) Start 1 wk 2 wk 1 mth 2 mth 3 mth 25° C. Temp 25° C. 25° C. 25° C. 25° C. 25° C. 25° C. pH pH pH pH pH pH % aldehyde m/v % al % al % al % al % al (% al) 40° C. 40° C. 40° C. (accelerated stability test) pH pH pH % al % al % al 1 Glyoxal 10% 5.38 5.37 5.36 5.37 5.33 Slightly cloudy 10.58 10.62 10.61 10.65 5.25 5.15 2 2-ethly hexanal 10% 5.76 5.73 5.75 5.76 5.70 Milky top clear 10.35 10.35 10.4 bottom mixed all 5.53 5.47 milk 10.4 3 furfuraldehyde 10% 6.91 6.85 6.89 6.93 6.80 Clear yellow top 9.85 9.81 9.75 dark brown 6.57 6.35 bottom Mixed all creamy brown 9.87 4 glutaraldehyde 10% 5.3 5.45 5.32 5.43 5.33 Clear 10.97 10.89 10.95 (Terg 3) 5.11 5.09 11.02 5 acetaldehyde 10% 6.47 6.45 6.51 6.531 6.4 Clear 10.32 10.28 10.33 10.36 6.12 6.06 6 formaldehyde 10% 7.09 7.12 7.17 7.20 6.90 Clear 9.97 9.84 9.99 9.98 6.85 6.73 7 butyraldehyde 10% 5.22 5.3 5.28 5.36 5.20 Smells slight 10.1 10.02 10.00 cloudy top 5.04 5.02 bottom clear mixed all cloudy 10.05 8 nonanal 10% 6.38 6.44 6.43 6.53 6.35 White top cloudy 10.63 10.7 10.45 bottom mix milky 6.16 5.98 10.65 9 chloral hydrate 2% 6.32 6.35 6.3 6.41 6.29 Slight cloudy 2.18 2.19 2.18 2.18 6.00 5.87 10 paraformaldehyde 10% 7.43 7.36 7.42 7.56 7.30 Cloudy ppt 10.19 10.15 10.17 10.16 7.14 6.98 11 3% Glyoxal + tergitol 6.26 6.28 6.3 6.32 6.15 (Terg) 3 Clear oily ppt on 2.97 3.01 2.99 top 6.00 5.86 2.98 12 3% Glyoxal + Terg 9 6.33 6.32 6.33 6.34 6.19 Clear 2.97 2.98 3.00 3.02 5.99 5.74 13 3% furfuraldehyde + Terg 3 7.32 7.27 7.29 7.25 7.18 Oily brown ppt 2.84 2.86 2.84 top bottom 7.01 6.91 cloudy 2.89 14 3% furfuraldehyde + Terg 9 7.59 7.55 7.56 7.51 7.41 Clear yollow 2.81 2.80 2.78 2.79 7.27 7.02 15 3% glutaraldehyde + Terg 3 6.47 6.45 6.38 6.34 6.31 Clear oily ppt on 2.98 2.97 2.86 top 6.24 6.05 3.00 16 3% 2-ethyl hexanal + Terg 3 6.20 6.15 6.10 6.08 6.11 Clear 2.86 2.76 2.89 2.99 6.01 5.91 17 3% 2-ethyl hexanal + Terg 9 5.65 5.4 5.43 5.45 5.50 Cloudy 2.97 2.90 2.95 2.99 5.69 5.56 18 3% nonanal + Terg 3 clear 6.50 6.49 6.46 6.45 6.31 Clear oily top 2.95 2.96 2.87 bottom clear mix 6.19 6.00 cloudy 2.89 19 3% nonanal + Terg 9 clear 6.41 6.4 6.38 6.42 6.32 Milk top cloudy 2.86 2.83 2.87 bottom mix milk 6.06 5.86 2.85 20 3% of 2% chloral hydrate + 6.64 6.65 6.55 6.7 6.35 Terg 3 Clear oily top 0.12 0.11 0.12 bottom clear 6.17 5.99 0.1 21 3% of 2% chloral hydrate + 6.61 6.58 6.53 6.62 6.30 Terg 9 Clear 0.12 0.10 0.11 0.13 6.17 6.00 22 3% sodium perborate tetra 11.01 10.98 10.85 10.9 10.81 hydrate + Terg 9 Clear 10.06 10.54 (gas) 23 3% paraformaldehyde + 8.04 7.89 7.78 7.65 7.85 Terg 9 Clear slight smell 2.99 2.97 2.95 3.01 7.89 7.72 24 3% acetaldehyde + Terg 9 8.09 7.97 7.86 7.78 7.90 Clear slight smell 2.99 2.98 3.00 3.01 7.82 7.73 25 3% formaldehyde + Terg 9 7.82 7.79 7.63 7.55 7.60 Clear smell 3.06 2.99 3.00 3.1 7.46 7.36 [0076] The tests conducted at 40° C. are accelerated stability tests i.e. a 2 week period at the elected temperature (40° C.) is equivalent to a 6 month “shelf-life” period at 25° C. [0077] The aldehyde samples chosen for this test are merely exemplary of the vast number of possible aldehyde and mixed aldehyde permutations of the invention. [0078] The three month results were not available at the time of filing. Example 4 Virucidal Efficacy Tests [0079] The same aldehyde samples as used in Example 3 (i.e. 1 to 25) were tested for virucidal efficacy using a standard SABS method (SANS1288) which uses a bacteriophage with virus standard to represent enveloped and non-enveloped viruses Each of the samples passed the test.

A method of manufacturing a stable aldehyde-surfactant complex solution wherein at least one aldehyde is added to a surfactant in a first aliquot of water, at a temperature of between 40° C. to 50° C., the aldehyde is allowed to interact with the surfactant or detergent, in a complexing reaction, for at least 15 minutes whilst maintaining the temperature between 40° C. to 50° C. to produce an aldehyde-surfactant complex solution, and a second aliquot of water is added after at least 15 minutes to cool the aldehyde-surfactant complex solution to below 40° C. to stop the complexing reaction.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This Application claims the benefit of U.S. Provisional Application 61/329,960 filed on Apr. 30, 2010. BACKGROUND OF INVENTION [0002] A variety of subsea control systems are employed for use in controlling subsea wells during, for example, emergency shutdowns. In many applications, the subsea systems may comprise a number of electrical lines that may be used to control a number of valves. During a specific valve operation, an operations engineer may issue a command via a human machine interface from a topside master controller station. The umbilical may be operationally connected to surface sources of power (e.g., electrical and hydraulic) in addition to electronics, communications, and power that may be provided via the topside master control station. For example, control signals may be sent down the umbilical to operate a number of solenoid valves and a subsea control module to actuate a number of directional control valves. [0003] The umbilical spans the distance necessary to reach the various components of the subsea control systems, which may be located thousands of meters below the sea surface. Thus, the subsea electrical lines and components are difficult to reach while deployed subsea. Accordingly, there remains a need to easily diagnose the integrity of the subsea portions of the umbilical and other electrical lines used to control the various subsea components from the topside master controlled station to ensure the proper operation of, for example, the safety control features of the subsea control system. SUMMARY OF INVENTION [0004] In general, in one aspect, the invention relates to a ground fault detection circuit for detecting ground faults in electrical subsea conductor lines, including a first electrical conductor line, a second electrical conductor line, a first ground fault detection line, a second ground fault detection line, a voltage source, a first resistor operatively connected to the voltage source and the first ground fault detection line, a second resistor operatively connected to the voltage source and the second ground fault detection line, and a voltage detection device configured to detect the voltage at an output end of the first resistor to determine the presence of a ground fault in at least one of the first and second conductor lines. [0005] In general, in one aspect, the invention relates to a ground fault detection system for detecting ground faults in electrical subsea conductor lines including a power supply unit, a ground fault detection circuit, a line enable switching module, and a voltage detection device. One or more embodiments of the ground fault detection system may include a power supply unit that is configured to supply power to the ground fault detection circuit and a subsea load. [0006] In general, in one aspect, the invention relates to a method for detecting ground faults in electrical subsea conductor lines using a ground fault detection system, the method including operatively connecting a first resistor between a voltage source and a first ground fault detection line in a ground fault detection circuit, operatively connecting a second resistor between the voltage source and a second ground fault detection line the ground fault detection circuit, and detecting a voltage at an output end of the first resistor to determine the presence of a ground fault in at least one of the first and second conductor lines. [0007] Other aspects and advantages of the invention will be apparent from the following description and the appended claims. BRIEF DESCRIPTION OF DRAWINGS [0008] FIG. 1 illustrates a subsea production well testing system in accordance with one or more embodiments of the invention. [0009] FIG. 2A is a block diagram of a ground fault detection system in accordance with one or more embodiments of the invention. [0010] FIGS. 2B-2C are block diagrams of ground fault detection circuits in accordance with one or more embodiments of the invention. [0011] FIGS. 3A-3B are schematic diagrams of ground fault detection circuits in accordance with one or more embodiments of the invention. DETAILED DESCRIPTION [0012] Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. [0013] In the following detailed description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. [0014] In general, embodiments of the invention relate to an apparatus and method for detecting ground faults in a subsea control system. More specifically, embodiments of the invention provide an apparatus and method for detecting electrical line shorts to earth ground for electrical lines used to power various subsea well components, for example, test trees and their control systems, tubing hanger running tools, and subsea valves. In accordance with one or more embodiments of the invention, a ground fault detection apparatus may continuously monitor electrical subsea conductor lines for leakage to earth ground so as to provide an indication of a shorted electrical line. Under a ground fault condition, the attempted operation of a shorted electrical line may lead to tool failure and/or damage to sensitive electronics, e.g., the power supply units. [0015] FIG. 1 illustrates a subsea production well testing system 100 which may be employed to test production characteristics of a well, in accordance with one or more embodiments of the invention. Subsea production well testing system 100 includes a vessel 102 which is positioned on a water surface 104 and a riser 106 which connects vessel 102 to a blowout preventer (“BOP”) stack 108 on seafloor 110 . A well 112 is drilled into seafloor 110 , and a tubing string 114 extends from vessel 102 through BOP stack 108 into well 112 . Tubing string 114 is provided with a bore 116 through which hydrocarbons or other formation fluids can be conducted from well 112 to the surface during production testing of the well. [0016] Well testing system 100 includes a safety shut-in system 118 which provides automatic shut-in of well 112 when conditions on vessel 102 or in well 112 deviate from preset limits. Safety shut-in system 118 includes a subsea tree 120 (e.g., subsea test tree, “SSTT”), a subsea tree control system 10 , a topside master control station 5 and various subsea safety valves (“SV”) such as valve assembly 124 , and one or more blowout preventer stack rams. [0017] Umbilical 136 includes conductor lines connecting a topside master control station 5 to subsea tree control system 10 . Furthermore, umbilical 136 is often required to extend to great length, for example 12,500 feet (3,810 m) or more. Umbilical 136 includes one or more conductor lines for transmitting signals from the surface to the subsea control system. [0018] In the illustrated embodiment, subsea tree control system 10 is a modular unit that includes a subsea electronics module (“SEM”) 12 and a hydraulic valve and manifold pod 14 . Subsea tree control system 10 may include other elements such as hydraulic accumulators, electric power sources and the like. Subsea control system 10 is positioned below water surface 104 and proximate to tree 120 in this embodiment. Umbilical 136 may be operationally connected to surface sources of power (e.g., electrical, hydraulic) in addition to electronics, communications, and power that may be provided via topside master control station 5 . Subsea tree control safety system 10 may be positioned in various positions within riser 106 . [0019] Ground faults may occur in subsea systems when, for example, any part of an electrical power line operatively connected to a subsea component makes electrical contact (or “shorts”) to any conductive part of the subsea production well testing system, for example, a subsea test tree. As described herein, a “ground fault” is a low impedance electrical path, or connection, to earth ground in one or more places along the electrical power line. [0020] FIG. 2A is a block diagram of a ground fault detection system in accordance with one or more embodiments of the invention. According to this embodiment, the ground fault detection system 200 includes power supply unit 201 , ground fault detection circuit 203 , line enable relay module 205 , and load 207 . One of ordinary skill will appreciate that many different types of loads may be driven with the ground fault detection system 200 . For illustrative purposes only, load 207 is shown as a solenoid valve in FIG. 2A . In accordance with one or more embodiments, power supply unit 201 may be provided, for example, within a vessel as part of topside master control station as shown in FIG. 1 . Furthermore, fault detection circuit 203 and line enable relay module 205 , may both be provided as part of a subsea tree control safety system, or the like. The particular configuration of the individual components comprising the ground fault detection system 200 are shown as illustrative examples, only. Accordingly, one of ordinary skill will appreciate that any or all of the power supply units 209 and 201 , the fault detection circuit 203 , or the line enable relay module 205 may alternatively be located at any convenient subsea (e.g., at any location within the riser) or topside location without departing from the scope of the present invention. [0021] Power supply unit 201 may include fault detection circuit power supply 209 and load power supply unit 211 . In accordance with one or more embodiments, load power supply unit 211 may be configured as a current source. Accordingly, load power supply unit 211 includes current source line 221 and current return line 223 . Furthermore, in accordance with one or more embodiments of the invention, fault detection circuit power supply 209 may be configured as a regulated DC power supply that includes ground fault detector lines 225 and 227 . In accordance with one or more embodiments, lines 221 , 223 , 225 , and 227 may be incorporated along with all the other necessary control, power, hydraulic, etc., lines into the umbilical 136 . One of ordinary skill will appreciate that the block diagram of power supply unit 201 , shown in FIG. 2A , is greatly simplified. Accordingly, many other known elements may be included within power supply unit 201 , depending on, for example, the particular type and number of subsea loads being driven, e.g., flapper valves, ball valves, solenoid valves, retainer valves, pipe ram seals, shear ram seals, etc. For example, in certain embodiments, dual polarity power may be required to operate the load, in which case, a polarity relay module may be included. Furthermore, various additional control electronics, such as multiplexors and demultiplexors may be implemented to allow for multiple load control and multiple line ground fault detection. [0022] Line enable relay module 205 is configured to allow for switching between two configurations, a fault detect configuration and normal configuration (not shown). Under fault detect configuration, electrical subsea conductor lines 237 and 239 may be connected to ground fault detection lines 225 and 227 , respectively. Alternatively, under normal configuration, electrical subsea conductor lines 237 and 239 may be connected to current source line 221 and current return line 223 , respectively. In accordance with one or more embodiments of the invention, the line enable relay module 205 may be configured to default to the fault detect configuration, i.e., fault detect power lines 225 and 227 are wired to the normally closed terminals of their respective relays on the line enable relay module 205 . In accordance with one or more embodiments, the ground fault detection system may be configured to detect ground faults when in an idle state (i.e., when no subsea loads are being powered). One of ordinary skill will appreciate that the electrical subsea conductor lines 237 and 239 may be switched in a variety of ways using any switching device known in the art, e.g., by using solid state switches, mechanical relays, multiplex/demultiplexors, etc. [0023] While FIG. 2A shows the ground fault detection system in the context of control lines for a solenoid valve, one of ordinary skill will appreciate that without departing from the scope of the present disclosure, the ground fault detection system may be used to detect ground faults in any electrical line, regardless of the specific type of equipment being employed. [0024] FIG. 2B is a block diagram of a ground fault detection circuit in accordance with one or more embodiments of the invention. Ground fault detection circuit 203 includes resistors 229 and 231 , blocking diodes 233 and 235 , and fault detection nodes 217 and 219 . The values of resistors 229 and 231 are not critical to the operation of fault detection circuit 203 . In accordance with one or more embodiments, resistors 229 and 231 may be within a range of 1-10 kΩ or, alternatively, within a range of 1-20 MΩ. The voltage at fault detection nodes 217 and 219 may be independently monitored with any voltage monitor known in the art. For example, FIG. 2A-2C show the nodes being monitored via a programmable logic controller (“PLC”) digital input card. Preferably, the fault detection circuit 203 is deployed subsea along with the subsea electronics module. Thus, the PLC may also be deployed either subsea or topside. Furthermore, the fault detection circuit 203 may alternatively be deployed topside, in which case the PLC may also be deployed topside. Blocking diodes 233 and 235 are optional and serve to protect fault detection circuit power supply 209 and the voltage monitor. [0025] During activation (configuration not shown) of the load 207 , load power supply unit 211 is operatively connected to load 207 , through relays 213 and 215 . Thus, under operational configuration, load power supply unit 211 may provide power to load 207 . In accordance with one or more embodiments of the invention, load power supply unit 211 may be configured as a current source that provides a constant current to solenoid valve 207 . [0026] Under fault detect configuration, as shown in FIG. 2A , fault detection circuit power supply 209 may be electrically connected through relays 213 and 215 to load 207 . If a ground fault is not present anywhere in the circuit beginning at the fault detection circuit power supply 209 and terminating at the load 207 , all points in the circuit will be at the fault detection circuit power supply 209 voltage, or 24V in this example. Thus, any voltage detection devices placed at nodes 217 and 219 may read a voltage equivalent to the fault detection circuit power supply 209 voltage. [0027] Under the conditions where a ground fault has occurred in one or both of lines 237 and 239 , the voltage at one of, or both, of the nodes 217 and 219 drops to a low value, nearly zero, in this example. The low voltage present at nodes 217 and 219 induced by the ground fault may be detected by any known voltage detection device and the output of the detection device may be used to, for example, inform an operator of the ground fault. Furthermore, the detection of a ground fault may trigger an automated response that initiates an appropriate safety protocol, for example, by diverting control to one or more backup valves and, in addition, by disabling any valves that may be electrically connected to the shorted control line or lines. [0028] FIG. 2C shows a block diagram of a fault detection circuit in accordance with one or more embodiments of the invention. In FIG. 2C , FETs 241 and 243 are included to increase the reliability of the voltage detection made at the nodes 217 and 219 . The FETs 241 and 243 are configured in such a way as to have their respective gate terminals connected to nodes 217 and 219 , thereby isolating any voltage detection devices from the rest of the fault detection circuit through the high impedance gate-to-source path. In accordance with one or more embodiments, FETs 241 and 243 are P-channel MOSFETs, but other types of transistors may be used, for example, N-channel MOSFETs or bipolar junction transistors. Accordingly, under normal operating conditions (i.e., no ground fault present, 24V at nodes 217 and 219 ), the voltage measured by a voltage detection device (e.g., a PLC digital input card) at the FET drain terminals is in a low state. In the event of a ground fault, the voltage measured at the FET drain terminals will be in a high state. [0029] While FIGS. 2B-2C show block diagrams of ground fault detection circuits that monitor only one set of electrical subsea conductor lines, the ground fault detection system disclosed herein need not be so limited. For example, using the same operational principles outlined about, the ground fault detection system may be extended to multi-component/multi-control line systems. FIGS. 3A and 3B show examples of a multi-line fault detection circuits, corresponding to FIGS. 2B and 2C , respectively, in accordance with one or more embodiments of the invention. FIGS. 3A-3B show examples of ground fault detection circuits with seven sub-units configured in a parallel configuration. Each sub-unit of the multi-component fault detection circuits shown in FIGS. 3A-3B operates in a substantially similar way to that described above for the single component examples. [0030] FIG. 3A shows a multiple sub-unit parallel combination ground fault detection circuit with a sub-unit design that corresponds to that shown in FIG. 2B . Specifically, fault detection circuit power supply 309 corresponds to fault detection circuit power supply 209 and provides power to ground fault detection lines 325 a - 325 g . Likewise, outputs 337 a - 337 g may be connected to a number of corresponding electrical subsea conductor lines via, for example, a multichannel line enable relay module (not shown). In accordance with one or more embodiments, outputs 339 a - 339 g may be connected to the input channels of a multichannel voltage detection device, as described with reference to FIGS. 2A-2C (e.g., a PLC digital input card). [0031] FIG. 3B shows a multiple sub-unit parallel combination ground fault detection circuit with a sub-unit design that corresponds to that shown in FIG. 2C . Specifically, fault detection circuit power supply 309 corresponds to fault detection circuit power supply 209 and provides power to ground fault detection lines 325 a - 325 g . Likewise, outputs 337 a - 337 g may be connected to a number of corresponding electrical subsea conductor lines via, for example, a multichannel line enable relay module (not shown). In accordance with one or more embodiments, outputs 339 a - 339 g may be connected to the input channels of a multichannel voltage detection device, as described with reference to FIGS. 2A-2C (e.g., a PLC digital input card). P-channel MOSFETS 341 a - 341 g may be used to increase the input impedance to the voltage detection device, as described above with reference to FIG. 2C . In addition, by incorporating two resistors into ground fault detection lines 325 a - 325 g , as shown, the gate voltage to the P-channel MOSFET may be set appropriately. Optionally, for increased reliability, Zener diodes may be wired from gate to source to protect P-channel MOSFETS 341 a - 341 g from high transient voltage spikes (e.g., from electrostatic discharge, or inductive kick back from a switching solenoid valve). One of ordinary skill will appreciate that many different types of transistors and resistors may be used without departing from the scope of the present disclosure. In addition, the appropriate choice of resistance values for the resistors depends on many factors, including but not limited to, the type of transistor used and value of DC voltage provided by the fault detection circuit power supply 309 . [0032] Additional circuitry may be implemented in conjunction with the circuits shown in FIGS. 3A-3B . For example, corresponding multiplexing circuitry and/or multi-channel line enable relay modules may allow for the system to monitor several different sets of subsea conductor lines for driving a number of loads. One of ordinary skill will appreciate that, with the appropriate choice of power supply unit, and monitoring equipment, any number of lines may be monitored without departing from the scope of the present disclosure. Furthermore, as with FIGS. 2B-2C , blocking diodes in line with ground fault detection lines 325 a - 325 g are optional and serve to protect the ground fault detection circuit power supply and PLC digital input card. [0033] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims

A ground fault detection circuit for detecting ground faults in electrical subsea conductor lines including a first electrical conductor line, a second electrical conductor line, a first ground fault detection line, and a second ground fault detection line. The ground fault detection circuit further includes a first resistor operatively connected to a voltage source and the first ground fault detection line, a second resistor operatively connected to the voltage source and the second ground fault detection line, and a voltage detection device configured to detect the voltage at an output end of the first resistor to determine the presence of a ground fault in at least one of the first and second conductor lines.

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] None FEDERALLY SPONSORED RESEARCH [0002] None. SEQUENCE LISTING [0003] None. BACKGROUND Prior Art [0004] The following is a tabulation of some prior art that presently appears relevant: U.S. Patents [0005] [0000] Patent Number Kind Code Issue Date Patentee 5,465,115 B1 Nov. 7, 1995 Conrad, et al. 5,764,283 B1 Jun. 9, 1998 Pingali, et al. 5,973,732 B1 Oct. 26, 1999 Guthrie 6,712,269 B1 Mar. 30, 2004 Watkins 7,612,796 B1 Nov. 3, 2009 Lev-Ran, et al. 7,692,684 B1 Apr. 6, 2010 Ku, et al. 7,903,141 B1 Mar. 8, 2011 Mariano, et al. 8,224,026 B1 Jul. 17, 2012 Golan, et al. 8,229,781 B1 Jul. 24, 2012 Zenor, et al. U.S. Patent Application Publications [0006] [0000] Publication Nr. Kind Code Publ. Date Applicant 20100021009 A1 Jan. 28, 2010 Yao 20120128212 A1 May 24, 2012 Almbladh 20120188370 A1 Jul. 26, 2012 Bordonaro 20120274755 A1 Nov. 1, 2012 Sinha; Aniruddha; et al. [0007] There are many reasons for obtaining information of traffic into consumer locations including recognizing customer counts, determining sales efficiency, estimating customer demographics, and organizing and scheduling the availability of sales people. There are numerous commercial means for obtaining this information, including human observation, both direct and through a surveillance system, tracking by infrared beams, tracking by infrared cameras and evaluation of sales records. These methods suffer from issues with heavy traffic periods, multiple entrance events, consistency and reliability. What is often desired is a system that allows rapid review of the incoming traffic stream to allow management to audit the accuracy of counts and observe the traffic demographics so that assessment can be made of the advertisement targets. It is additionally advantageous if the monitoring system is inexpensive, reviewable both locally and by remote management, is easily installed and maintained and inconspicuous. [0008] It is a tribute to the economic need for traffic information that there have been a number of patents issued in this area. The following discusses some of the prior art. [0009] Conrad, et al. recognized the need for reducing the computations by focusing on a reduced area within a video frame, but required “a linear array of gates consecutively positioned” and looking for “traversing said zone by examining consecutive segments”, “movement transverse to said linear array of gates”, “transverse to said linear array of gates”, “traversing said window by examining consecutive gates”, “traversing said window by examining consecutive gates which are occupied”, or “distinguishing objects of measurement traversing said window by examining consecutive gates”. Gates are defined as: “The window is divided into a number of narrow sectors called gates. These gates are narrow enough so that a person would normally occupy several gates at any one time.” The current invention does not contemplate the reduction into gates and the area 1 and the area 2 need not be confined to contiguous areas and area 2 is independently evaluated and usually separated from area 1. The intention of the windows in Conrad's patent is specified as “the foregoing objectives are realized by using a video imager located above a busy traffic zone”. The present invention works with any camera location, [0010] Guthrie in his patent has a camera recording a “controlled space” and tracks movement within the controlled space without extracting from the controlled space the region of interest in order to reduce computation. Additionally, counts are made “once the object has moved a predetermined distance”, as opposed to the boundary tests used in this invention. Similarly, Pingali in his patent treats the “video frame” without extracting from the video frame the region of interest in order to reduce computation. [0011] Watkins discusses the general abstract evaluation of motion but does not discuss the combination which involves the subtraction from the image of the much lesser area of interest in order to reduce the computational capability of the system. He also specifies using only the grayness level rather than the total available information in a YUYV or RGB representation. [0012] Lev-Ran, et al. in patent U.S. Pat. No. 7,612,796 refers to a directional determination accomplished in FIG. 8 , which contains only the steps of initialization, detection, matching and counting, with no discussion of the functions contained in each block. The specification appears to indicate that a body leaving an area labeled “exit” is leaving the area of interest and one leaving an area labeled “entrance” is entering. This is not the directional definition used in the invention presented here. [0013] Mariano et al. evaluates pixel regions in a traffic system, but relates regions with “scene events”, defined as “a sequence of scene descriptions, where a scene description is the plurality of regions of interest, each with its state of occlusion”. “Each scene event is manually defined when the system is initialized.” Such scene events are not required in the present invention. [0014] Golan, in his patent, requires the background surface “includes a plurality of detectable features on the surface”, a requirement not present in the current patent. [0015] Zenor, in his patent, discusses the advantage of linking consumer traffic data with in-person data which this invention enables by supplying an image linked to the traffic count. Ku attempts to evaluate accuracy by requiring both an entry and an exit count, while this invention requires only an entry or exit determination and allows an accuracy review by the rapid image scan of an associated image. [0016] The application of Yao (20100021009) uses a comparison of a current region “with the target region of the previous frame based on an online feature selection to establish a match tracking link”. The current invention uses neither an online feature selection or a tracking link. [0017] The application of Almbladh (20120128212) requires the calculation of a speed parameter used in the calculations, a step necessary in the offered invention. [0018] The application of Sinha (20120274755) uses descriptors of image comprising background modeling, Histogram of Oriented Gradients (HOG) and Haar like wavelet; all of which are not utilized in the invention presented here. [0019] Bordonaro (app. 20120188370) provides no guidance on monitoring technology, specifying, for example, element 102 in FIG. 1 (the first flowchart block) requires “Providing computer and software program for monitoring, recognizing, tracking entities within boundaries”. The invention presented provides a means for this. [0020] There are a number of additional previous patents and applications that specify the analysis of a full frame without the additional step of extracting from the full frame a smaller region. These often include the tracking of a body across the entire frame and from the computational requirements do not fall within the application of this invention. SUMMARY [0021] A system is described for a providing a microprocessor-controlled camera system for monitoring of consumer traffic to provide detection of incoming traffic, separation outgoing traffic and providing a count, time stamping and image record of each incoming body (person, car, etc.). The image provides a means of verifying the accuracy of the count by allowing the deletion of non-customer traffic such as sales people, mailmen, delivery people, etc. and allows correction of such issues as lumped bodies. The image further allows management to obtain demographics, such as customer age and sex, to allow targeted advertisement. The described system reduces the analysis by extracting from the image one or more areas through which the traffic passes and applies to the areas described algorithms to locate and track moving bodies. When the body is identified to be in a desired class (incoming, exiting or both) the image from which the determination was made is saved in a traffic record together with such pertinent data as time and location. The records are presented in a form allowing review of each image and review of statistical data from all records. ADVANTAGES [0022] The described system has the advantage of the ability to extract from a camera image a restricted area in which bodies are counted and presents several methods whereby the count qualification can be accomplished with minimum calculation. A method of triggering the tracking only on the detection of activity in another area, e.g. a door opening, allows counting in a high background area. [0023] Most inexpensive video cameras deliver a pixel-based image, e.g. the YUYV format. With VGA resolution (307200 pixels or 714400 bytes in YUYV) and if a rate of 10 frames per second is required for sufficiently small incremental movement, more than 7 MBytes of data must be analyzed each second in addition to overhead, operating system, data management and usually an Ethernet connection. Data compression can reduce the data management but the computation involved in the compression makes this unattractive for limited systems. This is not a problem for PC-sized systems but makes full-screen computation beyond the capability of less expensive processing systems. For example OpenCV has many full-screen functions for tracking (e.g. http://www.neuroforge.co.uk/index.php/tracking-methods-in-opencv) illustrating full-screen, high-capacity computer solutions but these techniques are not applicable to small, inexpensive processors. [0024] In many traffic monitoring systems there is background traffic that is not to be counted, with the focus of interest only in a small entrance region. This invention describes a means for traffic monitoring using inexpensive hardware with limited computational power. FIGURES [0025] FIG. 1 shows one method of extracting bodies by comparing a line of pixels or pixel groupings to the values from the immediate preceding image, [0026] FIG. 2 shows how to correlate the overlap of bodies on two lines and identify related bodies. [0027] FIG. 3 shows the calculation of the center of the disturbances as a quick method of checking body travel direction. DETAILED DESCRIPTION [0028] The invention consists of a image acquisition device, such as a camera or holographic imager, which conveys a stream of images to a controller device such as a microcontroller, PGA or microprocessor system, which performs the functions of: [0029] 1) The monitoring of one or more first regions of consecutive images from the stream of images from the image acquisition device looking for activity. [0030] 2) If activity is detected in the first region either, (a) subsequently track the activity within the first region, or (b) generate a second region based on the location of the activity detected within the first region and subsequently track activity within the second region, or (c) subsequent to the detection of the activity within the first region examine a defined second region for activity. [0034] 3) If, with subsequent tracking of activity, it is determined that the activity represent movement of a body in the desired direction, then a record of that body transition is made which contains a copy of the image at the time of qualification, together with any other pertinent information, such as the location and the time. [0035] 4) A means for the storing, retrieval, display and evaluation of the record in isolation and in conjunction with other records is described. [0036] In order to reduce the processing power required to perform the required calculation, and thereby the expense of the processing system, the processor can extracting from the image a small region of interest and evaluate only those pixels in the region of interest. The importance of the processing power limitation can be seen where demonstration systems operating at 600 MHz could successfully calculate in real time at a rate of 10 frames/sec only a line of pixels 600 pixels long while a full VGA representation has over 300,000 pixels . In this discussion when there is reference to pixels it is assumed that this can also refer to groupings of pixels obtained by data compression. For example if the image is rendered in JPEG, rather than rendering the individual pixels from the JPEG representation, the native JPEG average over an 8×8 pixel block can be used. A preferred method for the region selection is the use of one or more lines of pixels or pixel groupings. The lines are easily configured and understood by the user. In the following discussion reference to operation on the preferred regions comprising lines is also to be understood to apply to other regions such as arrays of lines, or of a predefined region that is not comprised of lines. In a region of interest, activity (i.e. motion) can be detected in several ways. The first step is the identification of which pixels are changing. One technique for change detection is to look for the difference of one image compared to a background calculated in a predetermined manned from prior images, with the difference exceeding some predetermined level. A preferred method is to simply use the weighted region Y, U and V differences between one image and the immediately preceding image, and declaring a disturbance if this difference exceeds a predetermined value (which may depend on the remaining values or average values). This avoids propagating disturbances such as sudden lighting changes. A typical webcam-type camera with VGA resolution can easily take 5 or 10 frames per second with sufficient resolution allowing evaluation of the changes in a 100 to 200 millisecond period. While this has been found to be a preferred method of activity detection, the system has also been operated by comparing the current image region to a more persistent background average from previous snaps. This technique of comparing a pixel to a background that is allowed to only change slowly (e.g. by allowing only a fractional change on each snap) is particularly useful when detecting occasional changes such as the opening of a door. In comparing one image's region to the same region in a previous image, differences show the motion of a body, i.e. activity, within the region of interest. The system is compatible with other methods of motion filtering such as edge detection, correlation calculation between images on the lines or second derivative calculation. A combination of motion detection methods can also be used. [0037] The second step is the allocation of the changed pixels into bodies of associated disturbances within the region of interest. The recognition of activity in an region is the recognition of disturbed (i.e. changed) pixels within the region which can be grouped into a body which has movement in a desired direction. We will locate the bodies in an region (demonstrated as a line) in FIG. 1 . We will then show that on two such lines the bodies can be correlated in FIG. 2 . The two lines in FIG. 2 could represent two images of the same region at different times or two spatially related lines. The differences between the correlated bodies then show movement in time between two locations, giving a position and direction of travel, or the distance in space at a given time, giving the position and direction of travel, [0038] FIG. 1 illustrates one method of determining the presence of a body on a line. Here a disturbance at a pixel is found if the absolute value of the Y change plus the UV change between the current image and the previous image exceeds a predetermined value. If a difference is encountered it is taken as the start of a body, and the body is extended over adjacent disturbed pixels. If a region is encountered where there is no disturbance, further checking is continued while incrementing the variable GAPW. If there is a disturbance before GAPW reaches a predetermined limit, the gap is considered to be a slight aberration and the body length is continued. Otherwise the body is considered to have ended and the location along the region is found by subtracting GAPW from the current pixel location. After finishing this examination in FIG. 1 we have a list of the start and end of each body on the line. [0039] If the first regions consist of a single line (function 2a above) then the location along the line of subsequent activity can be tracked. If the image prior to the case where no activity is found on the line shows the activity near one end of the line, it can be assumed that that is the line end from which the body exited. FIG. 2 illustrates how the bodies determined on one line can be tracked against the equivalent bodies on a second line. If the second line (BODYLIST2) is the table of bodies on the previous image of the same region then FIG. 2 would be a means of tracking the body movement within the same region. All bodies in the two lines are compared for overlap with a predetermined allowed separation distance. If the first regions consist of two approximately parallel lines then the analysis in FIG. 1 can associate the bodies on the two lines that are approximately the same distance down the two lines. When such associated bodies had first appeared on one of the lines or appeared last on one line, movement of the body from the body where the line first appeared to the line where the body last appeared can be assumed. This is useful when the camera has an overhead placement and there are multiple bodies crossing the lines. [0040] Often the counting region has background traffic, for example store traffic just behind an entrance. In such cases it is useful to have one line (referred to as a trigger region) which is monitored for the start or finish of activity detected on the region at which time consideration is moved to analyzing activity along a second line. One use of this is to put the trigger line vertically on the door frame where it will see no background traffic, and look for activity on the trigger line. Once the trigger line activity has stopped (with possible delay to allow for the body pausing or momentarily signaling no contrast) then an region inside the door is monitored, possibly looking for no activity indicating the body on the trigger line has left and should not be counted. Another use of the trigger line would be monitoring traffic in a small room with people mulling. Here the trigger line could be placed where the opening of a door would trigger this line and the second line would monitor activity just inside the door. Without the trigger line activity would be frequently detected just inside the door. [0041] Another application of the trigger line is where activity is monitored along the trigger line as described in FIG. 1 and FIG. 2 (where BODYLIST 2 represents the bodies detected in one or more previous images) to detect when and where a body leaves the trigger line. Line 2 can then be dynamically generated from the point where the trigger line was left and further analyzed. In one such example of a second line dynamically generated from the trigger line would be a trigger line across a wide entrance. Bodies can be tracked on this trigger line as described above, and note taken where a body has disappeared from this trigger line. This body is traveling across the trigger line either in a countable direction or in the opposite direction where no count is to be made. To determine this a line or lines can be generated from near the point on the trigger line where the body left the trigger line extending in the countable direction. In practice this has been a “trailer” line scaled to the camera distance with a crossing bar at the end of the trailer bar to catch body travel that was not purely perpendicular to the trailer line. The detection of a disturbance on this dynamically generated second line or lines is then indicative of the body traveling in the countable direction. [0042] Often on line 2 the only information required is the presence or absence of activity showing that the person is present on line 2 (and should be counted) or is not present, and hence was traveling in the direction that is not counted. There have been problems encountered when a body leaves and is immediately followed by another outgoing body which is then present on line 2 so that a simple directional detection on line 2 as will be described next avoids this false count. [0043] If not too many bodies are expected or equivalently line 2 is short, the body centroid of the disturbance can be calculated as shown in FIG. 3 to show the center of disturbances to indicate which end of the line has been exited. Note that in FIG. 3 the DIFFS are accumulated into averaged buckets, or alternatively they could be decimated. This is an optional step that also could have been applied in FIG. 1 to reduce significantly computational time. There are a number of simple calculations, such as shown in FIG. 1 and FIG. 2 , or the calculation of peaks of the correlation coefficient of successive images that also indicate the direction of motion along line 2. An alternative but somewhat equivalent approach is to measure the undisturbed pixels closest to the trigger line and determine if the undisturbed space is increasing (a body tripped the trigger line and is moving away in a countable direction) or is decreasing (indicating a body following the body that tripped the trigger line and should not be counted). [0044] Often there are multiple entrances that are observable from one camera location. In such cases one system can iteratively perform the above evaluations on regions specific to each entrance, and the entrance counts from each evaluation can either be merged or reported as different locations. The use of iteration to investigate movement multiple lines can also be used to investigate the divergence of people within a store or traffic within different regions. [0045] When a body is found to be moving along a direction that is to be counted this is referred to as a countable event. A record of this event is created which includes the image from which the countable event was determined together with all pertinent information, such as the date and time and the location. This record can be as a stand-alone event record or as an entry into a database. The countable event records are made available to users, possibly through a processor-based web server, software and hardware in the computing element having the capability to download to a central server, or commitment to a removable media. If downloaded to a computationally enhanced server, the system described above can be a screener for the server, allowing such filtering as facial recognition or the search for demographic information to be applied to the images in the countable event records to obtain further information to be added to the record. Because of the variables in user firewalls it is advantageous if downloads to remote servers be via tunneling. [0046] While the previous discussion may refer to generalized traffic, or refer to entrances and exits, it should be recognized that the principles of this invention can refer to many types of bodies, e.g. people, cars, or product, and to many types of movement monitoring, e.g. traffic within regions of a store or building, entry to operating rooms, monitoring of entry to restricted regions, etc.

A method and apparatus to monitor and document movement of bodies along or through selected regions is described for the directional counting of such bodies. The reduction of the consideration to selected regions avoids excessive calculation and allows the use of an inexpensive image acquisition and processor. Methods for the determining the direction of movement are described. A record is created for counting events for recording or downloading to a server for further manipulation.

FIELD OF THE INVENTION The invention generally relates to fluid containers, particularly those suited for the storage and dispensing of parenteral solutions and the like. The invention also relates to the attachment of these containers to associated fluid conduits. The invention also generally relates to fluid containers fabricated from materials having low water vapor loss characteristics, as well as the attachment of these containers to conduits fabricated from dissimilar materials. DESCRIPTION OF THE PRIOR ART It is desirable to connect a fluid container to a fluid circuit in a secure and durable manner. This type of connection is particularly desirable when sterile parenteral fluids are involved. It is also desirable to protect solutions stored in containers from the diffusion of water vapor through the container walls, because this can in time lead to a change in the concentration of the stored solution. Protection against water vapor loss is particularly desirable when the stored fluid is a sterile parenteral solution. Formulations of polyvinyl chloride plastic are widely used for parenteral solution containers and the like. However, because polyvinyl chloride plastic has a relatively high water vapor loss characteristic, various substitute plastic formulations have been proposed. In this regard, attention is directed to the following U.S. Patents: Sako et al.--U.S. Pat. No. 3,940,802--Mar. 2, 1976 Grode et al.--U.S. Pat. No. 4,112,989--Sept. 12, 1978 Waage--U.S. Pat. No. 3,942,529--Mar. 9, 1976 Rinfret--U.S. Pat. No. 4,131,200--Dec. 26, 1978 Watt--U.S. Pat. No. 4,183,434--Jan. 15, 1980 Gajewski et al.--U.S. Pat. No. 4,210,686--July 1, 1980 Smith--U.S. Pat. No. 4,222,379--Sept. 16, 1980 Many of the proposed substitutes for polyvinyl chloride plastic, while having lower water vapor loss characteristics, are chemically dissimilar to polyvinyl chloride plastic and, as a result, do not readily and securely bond to polyvinyl chloride plastic tubing by conventional thermal or chemical means. The following pending U.S. Applications, which are assigned to the assignee of the present invention, generally address the problem of interconnecting polyvinyl chloride plastic tubing with fluid containers of dissimilar materials: U.S. application Ser. No. 041,838, filed May 23, 1979, and entitled "TUBING CONNECTION FOR CONCONTAINERS GENERALLY UTILIZING DISSIMILAR MATERIAL". U.S. application Ser. No. 067,068, filed Aug. 15, 1979, and entitled "CONNECTOR MEMBER FOR DISSIMILAR MATERIALS". With the above considerations in mind, it is one of the principal objects of this invention to provide an assembly which serves to interconnect a fluid container with a fluid conduit in a secure and durable manner, and which facilitates the permanent, integral connection of the container with a prearranged fluid circuit, such as that disclosed in pending U.S. application Ser. No. 100,975, filed Dec. 6, 1979 and entitled "MONITOR AND FLUID CIRCUIT ASSEMBLY" (assigned to the assignee of the present invention). It is another principal object of this invention to provide an assembly which facilitates the secure and durable interconnection of a container with a conduit, even though dissimilar materials are utilized. It is still another principal object of this invention to provide an assembly which facilitates the construction of a container having a low water vapor loss characteristic, as well as the interconnection of this container with a fluid conduit fabricated of a polyvinyl chloride plastic material. SUMMARY OF THE INVENTION To achieve these and other objects, the invention provides a port block assembly for interconnecting a fluid container with a fluid circuit. The assembly includes a body portion which has a port and which is operative for attachment to the container with the port in flow communication with the interior of the container. The assembly also includes an insert portion which is engagable within the port of the body portion and which is attachable to a fluid conduit. A secure and durable connection between the container and conduit results. In one embodiment, the insert portion includes, as an attachment thereto, a valve mechanism which normally blocks flow communication through the insert portion. The valve mechanism is manually operative for selectively opening the flow communication. In one embodiment, the fluid container is fabricated of a material which has a relatively low water vapor transmission characteristic and which is not bondable to the polyvinyl chloride plastic material from which the fluid conduit is formed. In this embodiment, the body portion of the port block assembly is fabricated from the same material as the container and is thus directly bondable thereto. On the other hand, the insert portion is fabricated from polyvinyl chloride plastic for direct attachment to the fluid conduit and is adapted for interference fit engagement within the body portion port. The difficulty of effecting a thermal or chemical bond between the two dissimilar materials of the body and insert portions is thus overcome, and a secure, durable interconnection between the dissimilar container and conduit is achieved. The invention also provides a solution container which utilizes the port block assembly as generally described above. In the preferred embodiment, the container includes first wall means, which peripherally encloses a fluid chamber, and second wall means, which is disposed outwardly of the first wall means and peripherally defines an interior area which envelops the fluid chamber. The second wall means includes an opening providing access into this interior area. In this embodiment, the body portion of the port block assembly is engaged in the access opening of the second wall means, and the insert portion is located within the body portion port in flow communication with the enveloped fluid chamber of the first wall means. In this embodiment, the first wall means of the container and the insert portion of the port block assembly are both preferably fabricated from a polyvinyl chloride plastic material, as is the intended fluid conduit. The second wall means of the container is preferably fabricated from a material having a low permeability to water vapor and prevents the loss of water vapor from the interior fluid chamber into the atmosphere. In accordance with the invention, the body portion of the assembly is fabricated from the same material as the second wall means, and the polyvinyl chloride plastic insert portion is engaged in an interference fit within the body portion port to afford the desired interconnection between the container and the polyvinyl chloride plastic conduit. The invention also provides a fluid circuit which includes conduit means defining a predetermined fluid flow path. The circuit also includes a container having an interior fluid chamber and an access opening thereto. The circuit utilizes the port block assembly as heretofore described to permanently and integrally interconnect the container with the conduit means to afford communication between the fluid chamber and the fluid flow path. The conduit means and the preattached containers form a fluid circuit which is substantially closed to the atmosphere. Other features and advantages of the embodiments of the invention will become apparent upon reviewing the following more detailed description, the drawings, and the appended claims. DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, with parts broken away, of a portion of a fluid circuit which includes a pair of "double wrapped" fluid-filled containers, each of which is integrally connected to the circuit by the use of a port block assembly embodying various of the features of the invention; FIG. 2 is an enlarged and exploded view, with parts broken away, of one of the "double wrapped" containers and associated port block assembly shown in FIG. 1; FIG. 3 is an assembled view, with parts broken away, the "double wrapped" container shown in FIG. 2; FIG. 4 is a top view of the port block assembly which embodies various of the features of the invention; and FIG. 5 is a side view of "single wall" container which includes the port block assembly generally shown in FIGS. 2 and 4 and which, like the "double wrapped" container shown in FIGS. 2 and 3, can be integrally attached to the fluid circuit shown in FIG. 1. Before explaining the embodiments of the invention in detail, it is to be understood that the invention is not limited to its application to the details of construction and the arrangement of components as set forth in the following description or as illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Furthermore, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. DESCRIPTION OF THE PREFERRED EMBODIMENT A fluid circuit 10 is shown in FIG. 1. The circuit 10 includes conduit means 12 which defines a prearranged array of fluid flow paths. Such a circuit 10 is particularly well suited for use in environments in which relatively complex or convoluted fluid circuits are involved, and/or in which it is necessary or desirable to protect the interiors of the fluid flow paths from exposure to the atmosphere. For example, the circuit 10 is ideally suited for use in the collection and processing of human blood. The discussion to follow specifically contemplates such use, but the adaptability of the circuit 10 for use in other environments should be appreciated. In the context of human blood collection and processing, the fluid circuit 10 includes a compact, portable module 18, or housing, in which one or more flexible tubes 20 extends. The tubes 20 define an array of paths through which the blood and blood components flow during the processing operation. In the particular embodiment illustrated in FIG. 1, the module 18 is configured to facilitate its mounting on a blood centrifugation device (not shown). Furthermore, portions 22 of the tubes are looped outwardly of the module 12 for operative engagement with peristaltic pump rotors (not shown) carried on the centrifugation device to pump blood and blood components through the tubes 20. A more detailed description of the module 12, its mounting, and the flow of fluids therethrough can be found in now pending U.S. application Ser. No. 100,975, heretofore cited. A pair of fluid-filled containers, designated 14a and b in FIG. 1, are each individually attached to the conduit means 12 by use of a port block assembly 16 which embodies various of the features of the invention. The fluid-filled containers 14a and b thereby form an integral, or preattached, part of the fluid circuit 10. In the environment of human blood collection and processing, one of the integrally attached containers (designated in FIG. 1 as 14a) preferably holds a sterile saline solution. The other one of the integrally attached containers (designated in FIG. 1 as 14b) preferably holds a sterile anticoagulant solution. These sterile solutions are introduced into the fluid paths during the blood processing procedure. As before mentioned, the port block assembly 16 interconnects each container 14a and b with the fluid circuit 10. As can be best seen in FIGS. 2 through 4, the port block assembly 16 generally includes a body portion 24 in which one or more ports 26 are formed. The assembly 16 also includes a separate, generally rigid insert portion 28 for each port 26. Each insert portion 28 includes a bore 30 and is fitted within its associated port 26. The bore 30 thus forms a fluid flow path. Each bore 30 includes an end 32 and an end 34 which extends outwardly beyond the body portion 24 for connection with an end of tubing 20. The number of ports 26 and associated inserts 28 can be preselected according to the number of fluid connections required. Furthermore, as is shown in FIG. 2, the assembly 16 includes valve means 38 which may be attached to the end 32 of a selected insert portion or portions 28, as desired. The valve means 28 normally blocks flow communication through the bore 30 of the selected insert portion 28 and is operative in response to manual manipulation for opening the flow communication through the selected insert portion 28. The valve means 38 itself may be variously constructed. However, in the illustrated embodiment (see FIG. 2), the valve means 38 includes a generally rigid tubular member or cannula 40 which is attached, such as by solvent bonding, to the inner end 32 of the selected insert portion 28. The cannula 40 includes a frangible end wall 42 disposed therein, which normally blocks flow communication through the cannula 40 and, thus, through the selected insert portion 28 itself. In this arrangement, the valve means 38 includes means in the form of a rigid member 44 which extends outwardly from the frangible wall 42. Manual manipulation (generally shown by an arrow in FIG. 2) serves to break the rigid member 44 away and fracture the frangible wall 42 (as shown in phantom lines in FIG. 2). This operation opens flow communication through the cannula 40 and attached insert portion 28. The port block assembly 16 lends itself to use with various types of fluid containers. Two embodiments are shown in the drawings, both of which are equally well suited for interconnection with the circuit 10. Containers 14a and b shown in FIGS. 1 through 3 each incorporates one such embodiment, and the container 46 shown in FIG. 5 incorporates the other. Reference is first made to the container embodiment shown in FIG. 5. Here, the container 46 includes wall means 48 which peripherally encloses an interior fluid chamber 50 having an access opening 52 thereto. The wall means 48 takes the form of two overlapping sheets 54 of plastic material, the peripheral edges of which are joined, such as by solvent, heat, or RF sealing, to form a flexible bag in which a fluid solution can be stored. In this arrangement, the body portion 24 of the port block assembly 16 is fabricated of a plastic material which is similar to the sheet material and which is thus directly bondable to the peripheral edges of the access opening 52 by conventional methods, such as solvent, R.F., or heat bonding. Each insert portion 28 is fabricated of a plastic material which is directly bondable, such as by solvent bonding, to the material of which the associated fluid tubing 20 is made. The plastic materials utilized for the container 46, the port block assembly 16, and tubing 20 can vary according to the intended use of the circuit 10. In the context of the intended use of the fluid circuit 10 in FIG. 1, medical grade polyvinyl chloride plastic formulations (hereafter identified simply as PVC) can be utilized both for the sheet material of the container 46 as well as tubes 20 of the associated circuit 10, because PVC exhibits many characteristics well suited for the storage of parenteral solutions, as well as contact with human blood. In this arrangement, both the body portion 24 and the insert portions 28 of the port block assembly 16 are likewise preferably formed of PVC, and each insert portion 28 may be attached by heat or solvent bonding within the associated port 26. However, since it is recognized that PVC exhibits a high tendency to permit the diffusion of water vapor, which can in time lead to a change in the concentration of the stored solution, the wall means 48 of the container 46 can be constructed of overlapping sheets of a non-PVC material having a lower permeability to water vapor; for example, a polyolefin material, such as polyethylene or polypropylene, or copolymers thereof. In this arrangement, the body portion 24 of the port block assembly 16 is preferably fabricated from the same or similar polyolefin material and can be bonded directly to the wall means 48 by conventional methods, such as solvent or heat sealing. However, since PVC tubing still finds widespread use, the insert portions 28 are preferably fabricated from rigid, nonplasticized PVC, although acrylic or polycarbonate materials could also be used. Recognizing that PVC is dissimilar to and thus does not directly bond to propylene materials, the rigid insert portions 28 are constructed for a friction or interference fit within the ports 26 of the body portion 24, thereby eliminating the need for a thermal or chemical bond. In the container 46 shown in FIG. 5, the tubing 20 associated with the fluid circuit 10 (which tubing is shown in phantom lines in FIG. 5) is secured to one of the insert portions 28 (shown as the left-hand side insert portion in FIG. 5). A cannula 40 and breakaway member 44 are attached to the same insert portion 28, so that fluids stored in the chamber 50 of the container 46 can be selectively dispensed, via the tubing 20, into the fluid circuit 10. As can be seen in FIG. 5, the breakaway member 44 extends partially into the fluid chamber 58 to facilitate manual manipulation to fracture the wall 42, after which the separated member 44 is freed into the chamber 50. In this construction, the cannula 40 and breakaway member 44 are preferably made of PVC to permit a direct solvent or heat bond to the inner end 32 of the PVC insert portion 28. In FIG. 5, another insert portion 20 (shown as the right-hand side insert portion in FIG. 5) includes a section 78 of flexible PVC tubing solvent bonded within the bore 30. The tubing section 78 terminates outwardly of the outer end 34 of the insert portion 28 and can be coupled to a source of sterilizing gas, such as ethylene oxide, to sterilize the interior fluid chamber 50. Radiation sterilization or autoclaving can also be used, depending upon the particular material from which the container 56 is fabricated. After sterilization, the same tubing section 78 can be coupled, utilizing known sterile transfer techniques, to a source of sterile fluid to conduct the sterile fluid into the now sterilized container chamber 50. The tubing section 78 is thereafter crimped or heat sealed closed. When it is subsequently necessary to introduce the sterile fluid into the fluid circuit 10, the breakaway member 44 associated with the other insert portion 28 can be manipulated to open a fluid path leading from the chamber 50. Reference is now made to the container embodiment shown in FIGS. 1 through 3, in which container 14b is specifically shown. Unlike the single wall construction of container 46, the container 14b utilizes a double wall, or "double wrapped", construction to minimize water vapor loss from the stored solution. It should be appreciated that container 14a shares generally the same identical "double wrapped" construction of container 14b. In this embodiment, the container 14b includes the first wall means 56 which peripherally encloses a fluid chamber 58 in which the solution is stored. As illustrated, the first wall means 56 takes the form of overlapping sheets 57 and 59 of material, preferably PVC, the peripheral edges of which are sealed to form a flexible bag 72 in which the fluid chamber 58 is located. Ports 60 are integrally formed in the bag 72 to provide communication with the fluid chamber 58. The container 14b also includes second wall means 62 which is disposed outwardly of the first wall means 56 and which peripherally defines an interior area 64 enveloping the bag 72 and, hence, the fluid chamber 58 itself. An opening 66 is provided for access into the interior area 64. The second wall means 62 preferably takes the form of overlapping sheets 63 and 65 of material having a low vapor transmission characteristic, preferably polyethylene, to define an overwrap pouch 74 which serves as a vapor barrier surrounding the inner PVC bag 72. In this arrangement, the body portion 24 of the port block assembly 16 is preferably fabricated of a polyethylene type material, or a chemically similar material, which is bondable directly to the periphery of the access opening 66 of the overwrap pouch 74 (see FIG. 3), such as by solvent or heat sealing methods. On the other hand, the insert portion 28 of the port block assembly 16 is preferably formulated of rigid, nonplasticized PVC for direct solvent bonding to PVC tubing, although acrylic or polycarbonate materials could also be used. Because of the dissimilar plastics utilized, the rigid PVC insert portion 28 is sized so as to be engagable in an interference or friction fit within the port 26 of the polyethylene body portion 24. In this embodiment, and as best seen in FIG. 2, to effect communication between the insert portion 28 and the fluid chamber 58 of the PVC bag 72, the insert portion 28 includes conduit means 76 which extends within the interior area 64 of the overwrap pouch 74 between the inner end 32 of the associated insert portion 28 and a selected port 60 of the inner bag 72. The conduit means 76 may be variously constructed according to the particular use contemplated. In one embodiment, the conduit means 76 can take the form of the PVC cannula 40, heretofore generally described, which is solvent bonded to the end 32 of a selected insert portion 28 (the left hand insert portion 28 in FIGS. 2 and 3), as well as to an adjacent one of the bag ports 60. If a selectively operable valve mechanism is also desirable (which is usually the case), the cannula 40 can be provided with the heretofore described frangible wall 42 and breakaway member 44. As can be seen in FIG. 3, and like the FIG. 5 embodiment, the breakaway member 44 extends partially into the fluid chamber 58 to facilitate manual manipulation to fracture the wall 42, after which the separated member 44 is freed into the chamber 58. Also like the FIG. 5 embodiment, the insert portion 28 to which the breakaway member 44 is attached is connected to the tubing 20 (shown in phantom lines in FIG. 3) associated with the fluid circuit 10. In this regard, it should be noted that additional insert portions 28 with associated breakaway members 44 can be utilized, if desired, such as the pair associated with container 14a (see FIG. 1), depending upon the number of tubing connections desired. Also as shown in FIG. 1, drip chambers 86 and roller clamps 88 can be employed downstream of the containers 14a and b to further control the fluid flow from the containers 14a and b into and through the circuit 10. In another embodiment, the conduit means 76 can take the form of the section 78 of flexible PVC tubing solvent bonded to a selected one of the bag ports, (see FIG. 2), extending therefrom through the interior area 64 of the pouch 74, and bonded within the bore 30 of another insert portion 28 (shown as the right hand insert portion in FIG. 3). As in the FIG. 5 embodiment, the tubing section 78 terminates outwardly of the outer end 34 of the insert portion 28 and can be utilized, using known sterile transfer techniques, to conduct a sterilizing gas and thence a sterile solution into the inner bag 72, after which the tubing section 78 can be crimped or heat sealed closed. Thus, just as in the FIG. 5 embodiment, when it is subsequently necessary to utilize the sterile solution in the chamber 58, the breakaway member 44 associated with another insert portion 28 can be manipulated to open a fluid path leading from the chamber 58. Furthermore, in the embodiment shown in FIG. 2, the port block assembly 16 includes an additional port 26 and associated insert portion 28 (shown as the left hand insert portion in FIGS. 2 and 3). A section 82 of flexible tubing is bonded to the bore of this insert portion 28 and communicates only with the interior area 64 of the overwrap pouch 74. The tubing section 82 can be utilized to transfer a sterilizing gas into the interior area 74. Preferably, sterile cotton or the like is inserted into the tubing section 82 prior to sterilization to act as a sterile barrier to maintain the interior sterility of the interior area 74 surrounding the solution bag 72. The arrangement just described permits the entire fluid circuit 10, including the integrally attached containers 14a and b, to be preassembled, presterilized, and prefilled with sterile solutions. Preferably, as is best shown in FIG. 4, in each of the above described embodiments, the body portion 24 of the port block assembly 16 has a generally eliptical shape and includes gradually tapering end portions 84. This contoured shape facilitates a smooth and continuous bond between the periphery of the body portion 24 and the periphery of the access opening 52 of the container 46 (in the FIG. 5 embodiment), and between the periphery of the body portion 24 and the periphery of the access opening 66 of the overwrap pouch 74 (in the FIGS. 2 and 3 embodiment). It should be appreciated that the port block assembly 16 heretofore described provides a secure and durable connection between a container and a fluid conduit, a connection which is capable of withstanding rough handling during shipment, storage, and use. The connection thus minimizes the chance of leaks or accidental ruptures. This durability is particularly important when sterile fluids are involved. It should also be appreciated that the port block assembly 16 permits the construction and preattachment of prefilled, sterile solution containers to fluid circuits in a permanent manner. The assembly 16 thus significantly facilitates the creation of essentially "closed" fluid systems. It also significantly facilitates the construction of a container having a low water vapor loss characteristic and the interconnection of this container with a fluid conduit fabricated of a dissimilar material. Finally it should be appreciated that various changes and modifications can be made without departing from the spirit of the invention or from the scope of the appended claims.

A port block assembly for interconnecting a fluid container with a fluid conduit includes a body which has a port and which is attachable to the container with the port in flow communication with the container interior. The assembly also includes a rigid, tubular insert which is engageable within the body port and to which the fluid conduit can be attached. A secure and rugged interconnection between the container and the conduit results. When the container and conduit are fabricated from dissimilar materials, the body of the assembly is fabricated from the same materal as the container, and the associated insert is fabricated from the same material as the conduit and adapted for an interference or friction fit within the body port. The same secure and rugged interconnection between the container and conduit is achieved, despite the presence of dissimilar materials.

FIELD OF THE INVENTION [0001] The invention relates to vancomycin derivatives and preparation processes thereof. BACKGROUND OF THE INVENTION [0002] After penicillin was used clinically in 1940, thousands of antibiotics have been developed, and also hundreds are commonly used in clinical practice. In 2006, among the 500 best-selling drugs in the world, there were 77 anti-infective drugs, which were the first of 19 categories of drugs. Due to wide use of antibiotics in clinical practice, drug resistance has been gradually evolved in bacteria, causing that more and more antibiotics lose their effectiveness gradually. [0003] Vancomycin is a glycopeptide antibiotic produced by the Streptomyces orientalis strain. It was approved by US FDA for clinical use in 1958, effective mainly against Gram-positive bacteria with strong antibacterial activity, and was ever deemed as the last line of defense for human being against bacterial infections. Until 1990s, i.e. after vancomycin had been used for nearly 40 years, bacteria resistant to vancomycin were found and caused panic in the medical field. Therefore, there is an urgent need for discovery and modification of antibiotics. [0004] During modification of vancomycin in a lone time period, scientists from Eli Lilly found in WO9630401A1 that introduction of an aliphatic or aromatic chain into the polysaccharide moiety of such compounds can improve their activities greatly and even show a very good inhibitory effect against drug-resistant bacteria, e.g. Oritavancin as shown by the following formula: [0000] [0005] “Synthesis of Vancomycin from the Aglycon.” J. Am. Chem. Soc. 1999, 121, 1237-1244 demonstrated that vancomycin derivatives modified by a long chain show dual mechanisms of action in the bacteria-killing process: in addition to the original binding mechanism of the polypeptide moiety, the polysaccharide moiety is able to inhibit the glycosyl transferase involved in the process of synthesizing cell wall. These two mechanisms are complementary each other so as to reach the objective of enhancing the activity significantly. [0006] However, with introduction of the aliphatic and aromatic chains, the liposolubility (Log P) of such novel compounds increases greatly, and thus binding to ion channels as well as toxic and side effects on the cardiovascular system also increase, which may be adverse to the cardiovascular system. SUMMARY OF THE INVENTION [0007] The present invention provides vancomycin derivatives and preparation processes thereof, which derivatives have effectively increased water-solubility and reduced liposolubility, thereby solving the problem resulted from high liposolubility. [0008] Specifically, provided is compounds having the following formula: [0000] [0009] wherein: [0010] R 1 is —NHCH 3 or —NH 2 ; [0011] R 2 is H or 4-epi-vancosaminyl; [0012] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a , and R a is H, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl or C2-C12 alkynyl; [0013] R 4 is hydrogen, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl, C2-C12 alkynyl, (C1-C20 alkyl)-R 5 or (C1-C20 alkyl)-O—R 5 , and R 5 has the structure as listed below: [0014] (a) unsubstituted C5-C 12 aryl or mono-substituted C5-C12 aryl or poly-substituted C5-C12 aryl, wherein the substituent independently is: [0015] (I) hydroxyl [0016] (II) halogen [0017] (III) nitro [0018] (IV) amino [0019] (V) C1-C20 alkyl [0020] (b) the following structure: [0000] [0021] A 1 is —OC(A 2 )2—C(A 2 )2-O— or —O—C(A 2 )2-O— or —C(A 2 )2-O— or —C(A 2 )2-N— or —C(A 2 )2—C(A 2 )2—C(A 2 )2—C(A 2 )2-, wherein A 2 independently is hydrogen or C1-C20 alkyl [0022] (c) the following structure: [0000] [0023] p is 1-5, wherein R 7 independently is the following group: [0024] (I) hydrogen [0025] (II) hydroxyl [0026] (III) halogen [0027] (IV) nitro [0028] (V) amino [0029] (VI) C1-C20 alkyl [0030] (d) the following structure: [0000] [0031] q is 0-4, wherein R 7 independently is the following group: [0032] (I) hydrogen [0033] (II) hydroxyl [0034] (III) halogen [0035] (IV) nitro [0036] (V) amino [0037] (VI) C1-C20 alkyl [0038] r is 1-5, but q+r is no more than 5 [0039] Z is the following case: [0040] (I) a single bond [0041] (II) —(C1-C12)alkyl- [0042] R 8 independently is: [0043] (I) C5-C12 aryl [0044] (II) C5-C12 heteroaryl [0045] (III) phenyl unsubstituted or substituted with 1 to 5 substituents independently selected from: [0046] (a) hydrogen [0047] (b) hydroxyl [0048] (c) halogen [0049] (d) nitro [0050] (e) amino [0051] (f) C1-C20 alkyl. [0052] Provided is a vancomycin derivative as shown in formula (I): [0000] [0053] wherein: [0054] R 1 is —NHCH 3 or —NH 2 ; [0055] R 2 is H or 4-epi-vancosaminyl; [0056] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a ; wherein R a is H, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl or C2-C12 alkynyl; [0057] R 4 is C1-C20 alkyl. [0058] Provided is a vancomycin derivative as shown in formula (I): [0000] [0059] wherein: [0060] R 1 is —NHCH 3 or —NH 2 ; [0061] R 2 is H or 4-epi-vancosaminyl; [0062] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a ; wherein R a is H, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl or C2-C12 alkynyl; [0063] R 4 is (C1-C20 alkyl)-R 5 , wherein R 5 has the following structure: [0000] [0064] p is 1-5, wherein R 7 independently is the following group: [0065] (I) hydrogen [0066] (II) hydroxyl [0067] (III) halogen [0068] (IV) nitro [0069] (V) amino [0070] (VI) C1-C20 alkyl. [0071] Provided is a vancomycin derivative as shown in formula (I): [0000] [0072] wherein: [0073] R 1 is —NHCH 3 or —NH 2 ; [0074] R 2 is H or 4-epi-vancosaminyl; [0075] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a ; wherein R a is H, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl or C2-C12 alkynyl; [0076] R 4 is (C1-C20 alkyl)-R 5 , wherein R 5 has the following structure: [0000] [0077] q is 0-4, wherein R 7 independently is the following group: [0078] (I) hydrogen [0079] (II) hydroxyl [0080] (III) halogen [0081] (IV) nitro [0082] (V) amino [0083] (VI) C1-C20 alkyl [0084] r is 1-5, but q+r is no more than 5 [0085] Z is the following case: [0086] (I) a single bond [0087] (II) —(C1-C12)alkyl- [0088] R 8 independently is: [0089] (I) C5-C12 aryl [0090] (II) C5-C12 heteroaryl [0091] (III) phenyl unsubstituted or substituted with 1 to 5 substituents independently selected from: [0092] (a) hydrogen [0093] (b) hydroxyl [0094] (c) halogen [0095] (d) nitro [0096] (e) amino [0097] (f) C1-C20 alkyl. [0098] Provided is a vancomycin derivative as shown in formula (I): [0000] [0099] wherein: [0100] R 1 is —NHCH 3 or —NH 2 ; [0101] R 2 is H or 4-epi-vancosaminyl; [0102] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a ; wherein R a is H; [0103] R 4 is (C1-C20 alkyl)-R 5 , wherein R 5 has the following structure: [0000] [0104] q is 0-4, wherein R 7 independently is the following group: [0105] (I) hydrogen [0106] (II) hydroxyl [0107] (III) halogen [0108] (IV) nitro [0109] (V) amino [0110] (VI) C1-C20 alkyl [0111] r is 1-5, but q+r is no more than 5 [0112] Z is the following case: [0113] (I) a single bond [0114] (II) —(C1-C12)alkyl- [0115] R 8 independently is: [0116] (I) C5-C12 aryl [0117] (II) C5-C12 heteroaryl [0118] (III) phenyl unsubstituted or substituted with 1 to 5 substituents independently selected from: [0119] (a) hydrogen [0120] (b) hydroxyl [0121] (c) halogen [0122] (d) nitro [0123] (e) amino [0124] (f) C1-C20 alkyl. [0125] Provided is a medicament, which comprises the compound of formula (I) or a clinically acceptable salt thereof and is useful for treatment of infection caused by gram-positive bacteria or vancomycin-resistant bacteria. [0126] Provided is a process for preparing vancomycin derivatives, in which [0127] the product is obtained from reductive reaction of vancomycin or an analogue thereof and a compound of formula [0000] [0000] with a reductive agent in a polar solvent followed by hydrolysis, and if R a is H in the formula, the product is directly obtained after reduction without further hydrolysis; [0128] the vancomycin and the analogue thereof are vancomycin of formula (II), norvancomycin of formula (III), 4-epi-vancosaminyl vancomycin of formula (IV) or 4-epi-vancosaminyl norvancomycin of formula (V): [0000] [0129] M is alkali metal or alkaline earth metal; [0130] R 3 is —(R)COOR a or —(S)COOR a or —(R/S)COOR a , and R a is H, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl, or C2-C12 alkynyl; [0131] R 4 is hydrogen, C1-C20 alkyl, C5-C12 aryl, C2-C12 alkenyl, C2-C12 alkynyl, (C1-C20 alkyl)-R 5 or (C1-C20 alkyl)-O—R 5 , and R 5 has the structure as listed below: [0132] (a) unsubstituted C5-C12 aryl or mono-substituted C5-C12 aryl or poly-substituted C5-C12 aryl, wherein the substituent independently is: [0133] (I) hydroxyl [0134] (II) halogen [0135] (III) nitro [0136] (IV) amino [0137] (V) C1-C20 alkyl [0138] (b) the following structure: [0000] [0139] A 1 is —OC(A 2 )2—C(A 2 )2-O— or —O—C(A 2 )2-O— or —C(A 2 )2-O— or —C(A 2 )2-N— or —C(A 2 )2—C(A 2 )2—C(A 2 )2—C(A 2 )2-, wherein A 2 independently is hydrogen or C1-C20 alkyl [0140] (c) the following structure: [0000] [0141] p is 1-5, wherein R 7 independently is the following group: [0142] (I) hydrogen [0143] (II) hydroxyl [0144] (III) halogen [0145] (IV) nitro [0146] (V) amino [0147] (VI) C1-C20 alkyl [0148] (d) the following structure: [0000] [0149] q is 0-4, wherein R 7 independently is the following group: [0150] (I) hydrogen [0151] (II) hydroxyl [0152] (III) halogen [0153] (IV) nitro [0154] (V) amino [0155] (VI) C1-C20 alkyl [0156] r is 1-5, but q+r is no more than 5 [0157] Z is the following case: [0158] (I) a single bond [0159] (II) —(C1-C12)alkyl- [0160] R 8 independently is: [0161] (I) C5-C12 aryl [0162] (II) C5-C12 heteroaryl [0163] (III) phenyl unsubstituted or substituted with 1 to 5 substituents independently selected from: [0164] (a) hydrogen [0165] (b) hydroxyl [0166] (c) halogen [0167] (d) nitro [0168] (e) amino [0169] (f) C1-C20 alkyl. [0170] The polar solvent is methanol, ethanol, iso-propanol, tert-butanol, N,N-dimethylformamide, N,N-dimethylacetamide; the temperature is between 0 and 80° C.; the reductive agent is sodium borohydride, potassium borohydride, borane or a complex containing borane, sodium cyano borohydride, potassium cyano borohydride, sodium triacetoxy borohydride, potassium triacetoxy borohydride; the equivalent ratio of vancomycin to the reductive agent is 1:0.8-5.0. [0171] The present invention is described in detail as follows: [0172] Unless otherwise stated, as used herein, halogen refers to fluorine, chlorine, bromine, iodine, represented by X. [0173] Unless otherwise stated, as used herein, C1-C20 alkyl refers to C1-C20 hydrocarbon radical which is normal, secondary, tertiary or cyclic and contains 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms, and the examples of which include, but are not limited to, the following structures: [0174] —CH 3 , —CH 2 CH 3 , —CH 2 CH 2 CH 3 , —CH(CH 3 ) 2 , —CH 2 CH 2 CH 2 CH 3 , —CH 2 CH(CH 3 ) 2 , —CH(CH 3 )CH 2 CH 3 , —C(CH 3 ) 3 , —CH 2 CH 2 CH 2 CH 2 CH 3 , —CH(CH 3 )CH 2 CH 2 CH 3 , —CH(CH 2 CH 3 ) 2 , —C(CH 3 ) 2 CH 2 CH 3 , —CH(CH 3 )CH(CH 3 ) 2 , —CH 2 CH 2 CH(CH 3 ) 2 , —CH 2 CH(CH 3 )CH 2 CH 3 , —CH 2 C(CH 3 ) 3 , —CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 , —CH(CH 3 )CH 2 CH 2 CH 2 CH 3 , —CH(CH 2 CH 3 )(CH 2 CH 2 CH 3 ), —C(CH 3 ) 2 CH 2 CH 2 CH 3 , —CH(CH 3 )CH(CH 3 )CH 2 CH 3 , —CH(CH 3 )CH 2 CH(CH 3 ) 2 , —C(CH 3 )(CH 2 CH 3 ) 2 , —CH(CH 2 CH 3 )CH(CH 3 ) 2 , —C(CH 3 ) 2 CH(CH 3 ) 2 , —CH(CH 3 ) 2 C(CH 3 ) 3 , cyclopropyl, cyclobutyl, cyclopropylmethyl, cyclopentyl, cyclobutylmethyl, 1-cyclopropyl-1-ethyl, 2-cyclopropyl-1-yl, cyclohexyl, cyclopentylmethyl, 1-cyclobutyl-1-ethyl, 2-cyclobutyl-1-ethyl, 1-cyclopropyl-1-propyl, 2-cyclopropyl-1-propyl, 3-cyclopropyl-1-propyl, 2-cyclopropyl-2-propyl and 1-cyclopropyl-2-propyl. [0175] Unless otherwise stated, as used herein, C2-C12 alkenyl refers to C2-C12 alkene radical which is normal, secondary, tertiary or cyclic and contains 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms, and the examples of which include, but are not limited to, —CH═CH 2 , —CH═CHCH 3 , —CH 2 CH═CH 2 , —C(═CH 2 )(CH 3 ), —CH═CHCH 2 CH 3 , —CH 2 CH═CHCH 3 , —CH 2 CH 2 CH═CH 2 , —CH═C(CH 3 ) 2 , —CH 2 C(═CH 2 )(CH 3 ), —C(═CH 2 )CH 2 CH 3 , —C(CH 3 )═CHCH 3 , —C(CH 3 )CH═CH 2 , —CH═CHCH 2 CH 2 CH 3 , —CH 2 CH═CHCH 2 CH 3 , —CH 2 CH 2 CH═CHCH 3 , —CH 2 CH 2 CH 2 CH═CH 2 , —C(═CH 2 )CH 2 CH 2 CH 3 , —C(CH 3 )═CHCH 2 CH 3 , —CH(CH 3 )CH═CHCH 3 , —CH(CH 3 )CH 2 CH═CH 2 , —CH 2 CH═C(CH 3 ) 2 , 1-cyclopent-1-enyl, 1-cyclopent-2-enyl, 1-cyclopent-3-enyl, 1-cyclohex-1-enyl, 1-cyclohex-2-enyl and 1-cyclohexyl-3-enyl. [0176] Unless otherwise stated, as used herein, C2-C12 alkynyl refers to C2-C12 alkyne radical which is normal, secondary, tertiary or cyclic and contains 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms, and the examples of which include —CCH, —CCCH 3 , —CH 2 CCH, —CCCH 2 CH 3 , —CH 2 CCCH 3 , —CH 2 CH 2 CCH, —CH(CH 3 )CCH, —CCCH 2 CH 2 CH 3 , —CH 2 CCCH 2 CH 3 , —CH 2 CH 2 CCCH 3 and —CH 2 CH 2 CH 2 CCH. [0177] Unless otherwise stated, as used herein, C5-C 12 aryl includes, but is not limited to, an aromatic ring containing 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms or an aromatic ring containing heteroatoms such as O, N, S and the like. The examples are: [0000] [0178] Salts include those formed with suitable anions such as the anions derived from inorganic or organic acids. Suitable acids include those which are sufficient acidic to form stable salts, preferably the acids with low toxicity. For example, the salts of the present invention can be formed by acid addition with certain inorganic or organic acids (such as HF, HCl, HBr, HI, H 2 SO 4 , H 3 PO 4 ) or by addition of organic sulfonic acids or organic carboxylic acids with basic centers (typically, an amine). Organic sulfonic acids include C6-C16 aryl sulfonic acid, C6-C16 heteroaryl sulfonic acid and C1-C16 alkyl sulfonic acid such as phenyl sulfonic acid, methanesulfonic acid, ethanesulfonic acid, n-propyl sulfonic acid, isopropyl sulfonic acid, n-butyl sulfonic acid, sec-isobutyl sulfonic acid, tert-butyl sulfonic acid, pentyl sulfonic acid and hexyl sulfonic acid. Examples of organic carboxylic acids include C6-C16 aryl carboxylic acid, C4-C16 heteroaryl carboxylic acid and C1-C16 alkyl carboxylic acid such as acetic acid, glycolic acid, lactic acid, pyruvic acid, malonic acid, glutaric acid, tartaric acid, citric acid, fumaric acid, succinic acid, malic acid, maleic acid, hydroxyl maleic acid, benzoic acid, hydroxyl benzoic acid, phenylacetic acid, cinnamic acid, salicylic acid and 2-phenoxy benzoic acid. Salts also include addition salts of the compounds of the present invention with one or more amino acids. Many amino acids are suitable, especially those naturally occurring as components of proteins and however, typically those containing a basic or acidic group on the side chain (e.g. lysine, arginine or glutamic acid) or those containing a neutral group (e.g. glycine, serine, threonine, alanine, isoleucine or leucine). These salts are generally biologically compatible or pharmaceutically acceptable or non-toxic, particularly for mammals. Salts of the compounds of the present invention can be in a crystalline or amorphous form. [0179] Unless otherwise stated, as used herein, [0000] [0000] includes, but is not limited to, the following groups: [0000] [0180] Unless otherwise stated, as used herein, [0000] [0000] includes, but is not limited to, the following groups: [0000] [0181] R 7 is C 1-12 alkyl or C 1-12 alkoxyl [0182] Unless otherwise stated, as used herein, [0000] [0000] includes, but is not limited to, the following groups: [0000] [0183] wherein R 8 independently is: [0184] (I) C5-C12 aryl [0185] (II) C5-C12 heteroaryl [0186] (III) phenyl unsubstituted or substituted with 1 to 5 substituents independently selected from: [0187] (a) hydrogen [0188] (b) hydroxyl [0189] (c) halogen [0190] (d) nitro [0191] (e) amino [0192] (f) C1-C20 alkyl. [0193] Beneficial Effects: [0194] (1) The present invention provides a group of compounds, wherein a glycerate moiety is introduced between the vancomycin derivative and the liposoluble modifying group, thereby providing the compounds with a property of high solubility in water similar to amino acids and thus effectively increasing water-solubility and reducing liposolubility of the compounds, so as to solve the problem resulted from high liposolubility and reduce the side effects on the cardiovascular system after being prepared into a medicament. [0195] (2) The present invention provides a group of compounds, most of which exhibit varying degrees of inhibitory activity against vancomycin-sensitive bacteria, wherein aliphatic long chain and substituted biphenyl derivatives have the inhibitory activity superior to that of vancomycin, which is positive for treatment of vancomycin-resistant bacteria infection. DETAILED DESCRIPTION OF THE INVENTION [0196] In vitro Activity Assay [0197] The compound of formula 1 of the present invention or a clinically acceptable salt thereof is intended to be used for treatment of gram-positive bacteria or vancomycin-resistant bacteria infection cases. [0198] To verify the activity, a group of the compounds of the present invention were preferably subjected to in vitro activity assay (Table 1). [0000] TABLE 1 The compounds of formula (I) No. Structure V9 V11 V51 V61 V62 V63 V20 V21 V52 V22 V23 V25 V24 V53 V54 V13 V15 V55 V64 V65 V66 V26 V27 V33 V30 V57 V31 V16 V19 V58 V32 V59 V60 V67 V68 V69 [0199] In vitro activity assay was performed according to Microbiological Identification of Antibiotics, Appendix XIA, Volume II, Chinese Pharmacopoeia 2010. Vancomycin-sensitive Staphylococcus aureus strains (Newman and Mu 50) were selected as the test strains, and trypticase soy broth was selected as the culture medium. The assay for minimum inhibitory concentration (MIC) was performed as follows: the compound to be tested was dissolved in N,N-dimethylformamide to prepare a stock solution at 1.28 mg/ml, the stock solution was diluted with the culture medium to a initial concentration of 1.28 μg/ml, which was subsequently half diluted to prepare test solutions at 64 μg/ml-0.125 μg/ml, and the assay was performed according to Cup-Plate Method, Microbiological Identification of Antibiotics, Appendix XIA, Volume II, Chinese Pharmacopoeia 2010, wherein vancomycin and blank were used as controls. The results of in vitro activity assay of the compounds of formula (I) are listed in Table 2. [0000] TABLE 2 MIC values (μg/ml) Test strains Staphylococcus Compounds Staphylococcus aureus Newman aureus Mu50 V9 8 32 V11 8 32 V13 <0.125 2 V15 <0.125 2 V16 16 64 V19 64 >128 V20 <0.125 2 V21 <0.125 2 V22 2 8 V23 2 8 V24 4 8 V25 4 8 V26 16 64 V27 16 64 V30 4 16 V31 2 8 V32 2 8 V33 16 64 V51 8 32 V52 <0.125 2 V53 <0.125 2 V54 <0.125 2 V55 <0.125 2 V57 4 16 V58 64 >128 V59 2 8 V60 2 8 V61 4 8 V62 4 8 V63 <0.125 2 V64 <0.125 2 V65 <0.125 2 V66 <0.125 2 V67 2 4 V68 4 8 V69 2 8 DMSO >128 >128 Vancomycin 2 8 [0200] It is seen from the results that each group of the compounds exhibited varying degrees of antibacterial activity against vancomycin-sensitive Staphylococcus aureus strains. With increase in liposolubility of the group R 5 , there is a trend in which the inhibitory activity of the compounds against the bacteria is enhanced. [0201] Solubility Test of Compounds [0202] Solubility test of each compound was performed according to the guidelines of General Notices, Volume II, Chinese Pharmacopoeia 2005: weigh out finely powdered compound, place the compound in different volumes of water, strongly shake for 30 seconds at an interval of 5 minutes; observe the solubility behavior within 30 minutes, and obtain the solubility range of the compound, wherein all the solubility data range are measured at a temperature of 25° C. Solubility of vancomycin and the analogues thereof are listed in Table 3. [0000] TABLE 3 Solubility of the compounds in water Solubility in water Compounds (mg/ml) Vancomycin ≧100 Oritavancin <0.1 (data from US2010/045201) V9 <0.1 V11 50-60  V13 50-60  V15 ≧60 V16 ≧60 V19 50-60  V20 <5 V21 >8 V22 <5 V23 >8 V24 >10 V25 <5 V26 4.5 V27 20 V30 4 V31 <1 V32 50-60  V33 5 V51 20 V52 20 V53 20 V54 15-20  V55 3 V57 >60 V58 50-60  V59 <10 V60 >20 V61 20 V62 5-20 V63 5-20 V64 5-20 V65 5-20 V66 5-20 V67 5-10 V68 5-10 V69 5-10 [0203] It is seen from the solubility data that after introducing a glycerate moiety into the structure, the solubility of the compound in water increases by 1-2 orders of magnitude as compared to Oritavancin. This result demonstrates that the glycerate moiety plays a critical role in increasing the solubility in water. [0204] Preparation Process [0205] Provided is a preparation process, which is a process for preparing the vancomycin derivative according to any one of claims 1 - 5 : [0000] [0206] and in which the product is obtained from reductive reaction of vancomycin or an analogue thereof and a compound of formula [0000] [0000] with a reductive agent in a polar solvent followed by hydrolysis, and if R a is H in the formula, the product is directly obtained after reduction without further hydrolysis; [0207] specifically, the reaction is performed as follows: [0000] [0208] The present invention is further illustrated by the following examples, which should not be construed as limiting the present invention. EXAMPLE 1 [0209] [0210] Synthetic Procedure: [0211] Step 1: [0000] [0212] A 500 ml single necked flask was charged with 2.19 g of sodium hydride, suspended with 100 ml of N,N-dimethylformamide, cooled to 0-5° C. under nitrogen atmosphere, 10.0 g of 4-chlorophenyl benzyl alcohol was dissolved in 100 ml of N,N-dimethylformamide and was added to the reaction solution dropwise slowly, and after addition, the reaction was stirred for 0.5 hour followed by addition of 7.6 g of ethyl bromoacetate, and after addition, the temperature was raised to 35-40° C. overnight, and after the reaction completed as shown by TLC, the reaction was poured into 1 L of ice-water and was added with 500 ml of ethyl acetate for extraction, the organic phase was washed with saturated sodium chloride, dried over anhydrous sodium sulfate and then concentrated to dryness by a rotary evaporator to obtain a crude product, which was purified by column eluted with 10% ethyl acetate/petroleum ether to obtain 11.0 g of an oily liquid with a yield of 83.0%. [0213] Step 2: [0000] [0214] A 100 ml single necked flask was charged with 2.5 g of potassium tert-butoxide, dispersed with 15 ml of diethyl ether, a solution of 5.9 g of the product obtained from the previous step in 2.2 ml of methyl formate was added slowly under nitrogen atmosphere, the reaction solution was reacted at room temperature overnight, and after the reaction completed as shown by TLC, 50 ml of diethyl ether was added and stirred for 0.5 hour followed by suction filtration, the filter cake was dried under reduced pressure to obtain 5.6 g of a white solid. [0215] Step 3: [0000] [0216] A 100 ml single necked flask was charged with 743 mg of vancomycin, which was dissolved in 40 ml of N,N-dimethylformamide at 80° C., 214 mg of the product obtained from the previous step was added, followed by addition of 63 mg of sodium cyano borohydride in batch, and after addition, the reaction was performed for 2 hours, 1 ml of acetic acid was added and stirred for 0.5 hour, the reaction solution was poured into 50 ml of diethyl ether whereupon a solid precipitated, suction filtration was performed, the filter cake was stirred/washed with 40 ml of a solvent mixture of methanol and diethyl ether (1:3) followed by suction filtration, the crude product thus obtained was isolated by preparative HPLC to obtain 100 mg of the product. MS m/e 1750.4, 1751.4, 1752.4 (M+1) [0217] Step 4: [0000] [0218] 30 mg of the product obtained from the previous step was dissolved in a solvent mixture of 3 ml of tetrahydrofurane and 3 ml of water, 4.6 mg of lithium hydroxide was added with stirring, the reaction solution was stirred for 4 hours, 18 mg of acetic acid was added to quench the reaction, the organic solvent was removed by a rotary evaporator, purification by preparative HPLC obtained 9.7 mg of the product, MS m/e 1736.5, 1738.5, 1739.5 (M+1) EXAMPLE 2 [0219] Compounds V9, V11, V13, V15, V20, V21, V22, V23, V24, V25, V55, V61 and the like were prepared according to the process as described in Example 1. EXAMPLE 3 [0220] [0221] Synthetic Procedure: [0222] Step 1: [0000] [0223] A 100 ml single necked flask was charged with 20 ml of n-butanol, 1.80 g of pieces of sodium was added in an ice-water bath, and after addition, the mixture was heated at reflux until the solid dissolved, cooled to room temperature, 10.0 g of ethyl bromoacetate was added, after which the temperature was raised to 40-50° C., stirred overnight, and after the reaction completed as shown by TLC, 100 ml of diethyl ether was added, the mixture was washed with 50 ml of water three times, the organic phase was dried by a rotary evaporator under reduced pressure to obtain 9.1 g of an oily liquid, which was directly used in the next step. [0224] Step 2: [0000] [0225] A 100 ml single necked flask was charged with 2.5 g of potassium tert-butoxide, dispersed with 15 ml of diethyl ether, a solution of 3.0 g of the product obtained from the previous step in 2.2 ml of methyl formate was added slowly under nitrogen atmosphere, the reaction solution was reacted at room temperature overnight, and after the reaction completed as shown by TLC, 50 ml of diethyl ether was added and stirred for 0.5 hour followed by suction filtration, the filter cake was dried under reduced pressure to obtain 2.9 g of a white solid. [0226] Step 3: [0000] [0227] A 250 ml single necked flask was charged with 1.48 g of vancomycin, which was dissolved in 80 ml of N,N-dimethylformamide at 80° C., 276 mg of the product obtained from the previous step was added, followed by addition of 126 mg of sodium cyano borohydride in batch, and after addition, the reaction was performed for 2 hours, 5 ml of acetic acid was added and stirred for 0.5 hour, the reaction solution was poured into 100 ml of diethyl ether whereupon a solid precipitated, suction filtration was performed, the filter cake was stirred/washed with 40 ml of a solvent mixture of methanol and diethyl ether (1:3) followed by suction filtration, the crude product thus obtained was isolated by preparative HPLC to obtain 56 mg of the product. MS m/e 1606.5, 1607.5, 1608.5 (M+1) [0228] Step 4: [0000] [0229] 30 mg of the product obtained from the previous step was dissolved in a solvent mixture of 3 ml of tetrahydrofurane and 3 ml of water, 7.8 mg of lithium hydroxide was added with stirring, the reaction solution was stirred for 4 hours, 18 mg of acetic acid was added to quench the reaction, the organic solvent was removed by a rotary evaporator, purification by preparative HPLC obtained 5.0 mg of the product, MS m/e 1592.2, 1593.2 (M+1) EXAMPLE 4 [0230] Compounds V16, V19, V26, V27, V30, V31, V32, V33, V67, V68 and the like were prepared according to the process as described in Example 1. EXAMPLE 5 [0231] [0232] Synthetic Procedure: [0233] Step 1: [0000] [0234] A 250 ml single necked flask was charged with 1.5 g of norvancomycin, which was dissolved in 80 ml of N,N-dimethylformamide at 80° C., 250 mg of the product obtained from Step 2 of Example 1 was added, followed by addition of 130 mg of sodium cyano borohydride in batch, and after addition, the reaction was performed for 2 hours, 5 ml of acetic acid was added and stirred for 0.5 hour, the reaction solution was poured into 100 ml of diethyl ether whereupon a solid precipitated, suction filtration was performed, the filter cake was stirred/washed with 40 ml of a solvent mixture of methanol and diethyl ether (1:3) followed by suction filtration, the crude product thus obtained was isolated by preparative HPLC to obtain 15 mg of the product. MS m/e 1736.5, 1737.5, 1738.5 (M+1) [0235] Step 2: [0000] [0236] 5 mg of the product obtained from the previous step was dissolved in a solvent mixture of 1 ml of tetrahydrofuran and 1 ml of water, 2.0 mg of lithium hydroxide was added with stirring, the reaction solution was stirred for 1 hour, 10 mg of acetic acid was added to quench the reaction, the organic solvent was removed by a rotary evaporator, purification by preparative HPLC obtained 3.5 mg of the product, MS m/e 1722.5, 1723.5, 1724.5 (M+1) EXAMPLE 6 [0237] Compounds V51, V52, V53, V54, V55, V57, V58, V59, V60, V68 and the like were prepared according to the process as described in Example 1. EXAMPLE 7 [0238] [0239] Synthetic Procedure: [0240] Step 1: [0000] [0241] A 500 ml single necked flask was charged with 3.1 g of 4-epi-vancosaminyl vancomycin, which was dissolved in 150 ml of N,N-dimethylformamide at 80° C., 500 mg of the product obtained from Step 2 of Example 1 was added, followed by addition of 250 mg of sodium cyano borohydride in batch, and after addition, the reaction was performed for 2 hours, 7 ml of acetic acid was added and stirred for 0.5 hour, the reaction solution was poured into 150 ml of diethyl ether whereupon a solid precipitated, suction filtration was performed, the filter cake was stirred/washed with 40 ml of a solvent mixture of methanol and diethyl ether (1:3) followed by suction filtration, the crude product thus obtained was isolated by preparative HPLC to obtain 7.8 mg of the product. MS m/e 1896.5, 1893.5, 1894.5 (M+1) [0242] Step 2: [0000] [0243] 5 mg of the product obtained from the previous step was dissolved in a solvent mixture of 1 ml of tetrahydrofurane and 1 ml of water, 2.0 mg of lithium hydroxide was added with stirring, the reaction solution was stirred for 1 hour, 10 mg of acetic acid was added to quench the reaction, the organic solvent was removed by a rotary evaporator, purification by preparative HPLC obtained 1.8 mg of the product, MS m/e 1881.5, 1880.5, 1879.5 (M+1) EXAMPLE 8 [0244] Compounds V61, V62, V63, V64, V65, V66, V69 and the like were prepared according to the process as described in Example 7.

The present invention provides a vancomycin derivative, and a preparation method and an application thereof. The vancomycin derivative of the present invention is obtained by introducing a glycerate moiety between a vancomycin derivative and a liposoluble modification group and has reduced liposolubility and improved water solubility, thereby reducing a side effect in the cardiovascular aspect.

FIELD OF THE INVENTION [0001] The present invention relates to a trash storage device, and more particularly to a trash cart that stores daily trash and makes the transportation of the trash to the curb on pick-up day easier with a wheeled system. The trash cart is designed to protect the trash from animals, allow for ventilation, and to be decorative so as not to be an eyesore next the building in which it is stored. The trash cart can also be customized with decorative panels so as to match or complement the building next to which it is installed. BACKGROUND OF THE INVENTION [0002] Everyday life includes many chores that need to be done on a recurring basis. Home and business owner's daily storage and the task of taking out the garbage can be particularly challenging. In most areas, homeowners need to take the trashcans to the curb for pickup by the municipal or private garbage collectors at least once and most often several times a week. This can mean carrying, or rolling several individual trash cans to the front curb, which can be anywhere from ten feet away from the house to several hundred feet away from the house. [0003] For many homeowners this task is done early in the morning, rather than the night before pickup because animals, such as raccoons, fox, deer and the like often get into the trash cans and throw trash all over the lawn while looking for food. Currently, one of the only alternatives currently available to prevent waking up to a lawn full of trash is to take the trashcans to the curb the morning of pickup. Often, taking the trashcans to the curb the morning of pickup usually means it is done when the homeowner is dressed and rushing to work. [0004] Individual trashcans with wheels are easier to get to the curb than non-wheeled trashcans since they do not have to be carried. However, the wheeled trash cans do very little to protect the cans from being toppled and opened by animals if left outside overnight. Some trash cans use the handles from which they are pulled to lock the cover of the trashcan closed. Although a good concept, the handles are usually easily opened by determined rodents looking for their next meal and therefore are of little help. [0005] Another problem associated with using individual trash cans is the fact that the homeowner can transport only one wheeled trash can at a time to the curb. Therefore, it is often necessary for the homeowner to make several trips to complete the task. Making several trips can be time consuming and depending on the distance and incline from the house to the curb can be exhausting. This fact alone makes the option of using individual trashcans less attractive than the trash cart of the present invention. [0006] Between the assigned days for garbage pick up is the ongoing problem of daily garbage storage. Many people store garbage in their garage until pick up day. This often causes a space issue with cars and/or other items being stored as well as odors permeating the structure. Others opt to keep their garage outside using a multiple of solutions in order to ward off animals. This includes ropes and bungee cords attempting to secure the garbage and/or adding weighted objects to the top of the trash cans. Each time a homeowner adds trash, they must re-secure the trash can covers. [0007] There are devices available today that are used to transport trash cans to the curb for pick up but these devices are not enclosed, leaving the trash cans/garbage exposed to animals. Since the trash cans are not protected against animals, these devices must be stored inside and therefore are only marginally better than individual wheeled trash cans and do not solve the problem of garage space. [0008] Another problem faced by homeowners with trashcan transportation devices and trashcans available on the market today is that they are often unattractive. In stark contrast, the trash cart of the present invention has decorative panels that can be used to either match or complement the building next to which it is stored. [0009] Finally many of the transportation carts available on the market today are made of flimsy tube piping making the overall structure un-sturdy. [0010] Therefore in view of the foregoing shortcomings, what is needed is a trash cart that is sturdy enough to allow a homeowner to store their daily garbage, move the garbage to the curb easily and allow the homeowner to bring the cart to the curb the night before without worrying about the animals getting into the trash. Additionally, the cart is decorative so as to complement a building when stored on the side of the house or left at the curb for pickup. The present invention contains all of these attributes and more and solves the problems and shortcomings described above. SUMMARY OF THE INVENTION [0011] The present invention is directed to a trash cart comprising a front panel, a back panel, a right side panel, a left side panel, a top panel, and a bottom panel all of which are configured so that when they are attached they form an enclosure. The top panel of the trash cart may be configured to have at least one hinge means designed to attach one edge of the top panel of the trash cart to a second edge of the back panel. The result of this configuration is an enclosure having a hinged top panel that can be opened to expose the interior of the enclosure. [0012] The structure may also have a front panel having at least one hinge means that is configured so as to be in direct communication with at least one door, the door being contiguous with the front panel of the trash cart when closed and exposes an interior portion of the trash cart when opened. In an alternative embodiment of the trash cart, the trash cart is configured to have two doors on a hinge means that open in opposite directions to expose the interior of the trash cart. [0013] In still another embodiment the trash cart the trash cart is configured to have at least one wheeled axle located at the back portion of the bottom panel of the trash cart and at least one leg of the same height as the wheel is attached to the front portion of the bottom panel of the trash cart so that the trash cart is leveled. The wheeled axle makes transporting of trash cans in the trash cart easier for the user. In an alternative embodiment of the invention, a second wheeled axle is attached to the front bottom panel of the trash cart replacing the leg previously mentioned. The four-wheeled trash cart is designed to handle more weight than the single axel version. [0014] Both the single and multiple axel version of the present invention may be equipped with a steering mechanism that will allow the user to maneuver the trash cart to the curb on pick-up day and back to the storage place once the trash is collected. [0015] Another embodiment of the invention is directed to a trash cart kit. The trash cart kit comprises a front panel, a back panel, a left side panel, a right side panel, a top panel, and a bottom panel. Each panel having the proper holes, fasteners and bolts that can be used to assemble the individual panels together to form an enclosure. On the outside portion of the front panel, the back panel, the left side panel, the right side panel, and the top panel is an attaching means for attaching decorative panels. The kit can have several different decorative panels that can make the enclosure complement the building in which it belongs or an ornate structure such as plastic overlay design (such as basket weave) wrought iron design, stucco, wood frame, vinyl shingles, aluminum siding or the like to give it a unique look. [0016] The top panel can be hinged to the back panel so that it can open to reveal the trashcans stored inside. In one embodiment of the trash cart the top panel of the trash cart can be split in more than one portion, preferable two portions. Each of the aforementioned portions is configured so that they can be hinged to the back panel so as to open together or independently. The front panel can be designed so as to have a single or double doors hinged so that the door(s) can be opened to reveal the trash cans stored within the enclosure. [0017] As with the other embodiments described above, the trash cart kit may include one or two axles that can be attached to the bottom portion of the trash cart. Each axle may have at least one wheel, preferably two wheels, so as to support the trash cart and make it easy to move from one place to another. The kit may also contain illustrative instructions that describe how the described components fit together. BRIEF DESCRIPTION OF THE FIGURES [0018] FIG. 1 : ( 05 ) a full view of the trash cart with doors and top lids closed. ( 10 ) top panel ( 15 ) top hinges ( 20 ) top handle ( 25 ) right side panel ( 30 ) steering means ( 35 ) front axle ( 40 ) front wheel ( 45 ) rear axle ( 50 ) rear wheel ( 55 ) front door hinges ( 60 ) left front door ( 65 ) front lip ( 70 ) right front door ( 75 ) trash can ( 80 ) front door handle ( 85 ) structural front portion ( 90 ) separator panel [0037] FIG. 2 : ( 100 ) a full view of the trash cart with doors opened. ( 105 ) top hinges ( 110 ) top panel ( 115 ) separator panel ( 120 ) back panel ( 125 ) right side panel ( 130 ) steering means ( 135 ) right front door ( 140 ) front axle ( 145 ) front wheel ( 150 ) hooks for carrying bulky material ( 155 ) front lip ( 160 ) bottom panel ( 165 ) rear axle ( 170 ) rear wheel ( 175 ) left side panel ( 180 ) left front door ( 185 ) front support members ( 190 ) top handles [0057] FIG. 3 : ( 200 ) is a full view of the trash cart with doors open and on and top lid open. ( 205 ) open left top panel portion ( 210 ) left top handle ( 215 ) top panel hinges ( 220 ) closed right top panel portion ( 225 ) right side panel ( 230 ) steering means ( 235 ) open right front door ( 240 ) front axle ( 245 ) front wheel ( 250 ) back panel ( 255 ) separator ( 260 ) front lip ( 265 ) rear axle ( 270 ) wheel lock ( 275 ) rear wheel ( 280 ) left side panel ( 285 ) opened left front door ( 290 ) interior portion of trash cart ( 295 ) structural front member ( 300 ) interior space [0079] FIG. 4 : ( 400 ) a schematic of the kit assembly. ( 405 ) top panel ( 410 ) top panel hinges ( 415 ) separator panel ( 420 ) front panel handle ( 425 ) back panel ( 430 ) right side panel ( 435 ) left side panel ( 440 ) bottom panel ( 445 ) separator panel ( 450 ) wheel ( 455 ) axle ( 460 ) steering means ( 465 ) structural supports ( 470 ) left front door ( 475 ) right front door ( 480 ) steering connection ( 485 ) instructions ( 490 ) fasteners and bolts [0099] FIG. 5 : ( 500 ) is a top view of a panel with attaching hooks and decorative panels. ( 505 ) fastener for decorative panels ( 510 ) wrought iron decorative panel ( 515 ) decorative brick panel ( 520 ) decorative vinyl siding panel DETAILED DESCRIPTION OF THE INVENTION [0105] The present invention is directed to a decorative trash cart that is designed to provide outside storage of trashcans while preventing egress into the trashcans by animals. The trash cart of the present invention is also designed to be mobile so as to make moving the trashcans in the trash cart to the curb faster and easier than without a trash cart. These and other features are shown in FIGS. 1-5 of the present document and are further described below. [0106] One embodiment of the trash cart of the present invention shown in FIG. 1 comprises, a top panel ( 05 ), a bottom panel (shown in FIG. 2 ), a right side panel ( 25 ), a left side panel (shown in FIG. 2 ), a front panel and a back panel (shown in FIG. 2 ). The panels are arranged and fastened to each other so as to create an enclosure having a top, bottom, front, back and two walls. [0107] The top panel ( 10 ) of the trash cart ( 05 ) may be split into two portions by a separator panel ( 90 ) so that each of the two portions of the top panel ( 10 ) can be lifted independently by handles ( 20 ) revealing the top of the trash cans ( 75 ) within. The top panel ( 10 ) is connected to the back panel by multiple hinges ( 15 ) making it easy to lift the top panel portions so as to gain access to the trashcans ( 75 ). This feature can be used when trash is being placed into one of the trashcans ( 75 ) within the cart and there is no need to expose the other trashcans ( 75 ). Having the split top panel on hinges makes it easier for the user to gain access to the trashcans ( 75 ) within the cart. [0108] When the trashcans are filled and they need to be taken out, the top panel ( 10 ) can be opened and the trashcan lifted over the front panel out of the trash cart ( 05 ). This may be done when the trashcans are light, but if this is done when the trashcans are heavy it can cause a strain on the lifters back. It can also be messy if the trashcans are over filled. For this reason and others, the front panel of the trash cart can have at least one door that when closed is flush with the rest of the front panel. In one embodiment of the invention, the front panel comprises a left front door ( 60 ) and a right front door ( 70 ) that is contiguous with the structural front portion ( 85 ) of the trash cart. The left front door ( 60 ) and the right front door ( 70 ) are connected to the structural front portion ( 85 ) by front door hinges ( 55 ) and each door can be equipped with front door handles ( 80 ) so as to make it easy for the user to open the front doors. The front doors may be locked using a latch or a keyed system. [0109] The front panel may also have a front lip ( 65 ) that is in communication with the lower portion of the front panel. The front lip is designed to stop the trashcans ( 75 ) from falling out of the trash cart once the front doors are opened after the cart has been moved. Since the trashcans ( 75 ) may shift during movement of the trash cart, the front lip ( 65 ) is designed to prevent the trashcans ( 75 ) from accidentally falling out when opened. [0110] In another embodiment of the invention, the trash cart ( 05 ) can be equipped with either just a rear axel ( 45 ) having at least one rear wheel ( 50 ) or a front axle ( 35 ) and a rear axle ( 45 ). The front axle ( 35 ) having at least one wheel ( 40 ) and the rear axle ( 45 ) having at least one wheel ( 50 ). In a preferred embodiment of the invention, the front axle ( 35 ) and the rear axle ( 45 ) each have two wheels. One of the two wheels is attached to each end of the axles so as to distribute the load in the trash cart. The rear axle ( 50 ) can be attached to the bottom portion of the bottom panel of the trash cart so as to be stationary. The front axle ( 40 ) on the other hand can be pivotally attached so as to provide the trash cart with some maneuverability. [0111] In addition, the front axle ( 35 ) can be attached to a steering means ( 30 ) that when maneuvered can cause the front axle to turn in the direction that the user wants the trash cart ( 05 ) to move towards. The steering means ( 30 ) can also be used to pull the trash cart to the intended site whether it is to the curb for trash pick-up or back to the storage spot on the side of the building. [0112] As mentioned above, the trash cart ( 05 ) can be equipped with a separator ( 90 ) and a front lip ( 65 ). These structures are designed to aid in keeping the trashcans ( 75 ) in place while the trash cart ( 05 ) is moved from one place to another. The trash cart ( 05 ) can also be equipped with locking trim that can be attached to the interior portion of the bottom panel of the enclosure that will prevent the trashcans ( 75 ) from moving during movement of the trash cart ( 05 ). [0113] The overall construction of the panels can be made out of wood, wrought iron, aluminum, stainless steel, powder coated aluminum, plastic, polyvinyl chloride, powder coated steel, plastic coated metal, man-made materials, new-age materials, or any other material that is washable, and strong and durable enough for the intended use of the trash cart. The trash cart should be designed so as to have enough holes in the structure so as to allow amble ventilation so as to prevent spontaneous combustion of the trash. The holes are also needed to allow rain water and water used to clean the trash cart to run out of the structure so as to prevent pooling of excess water. [0114] FIG. 2 shows the trash cart of the present invention with the front doors in the open position. The trash cart ( 100 ) comprises a top panel ( 110 ), a bottom panel ( 160 ), a right side panel ( 125 ), a left side panel ( 175 ), and a back panel ( 120 ). As in FIG. 1 , the above panels are arranged and fastened to each other so as to create an enclosure having a top, bottom, front, back and two walls. A separator ( 115 ) divides the interior space into two separate portions so as to keep the two trashcans separate. Although FIGS. 1 and 2 are shown having two doors, two top panels, one separator creating two compartments, it is well within the scope of the invention to have additional doors and compartments. [0115] The right front door ( 135 ) and left front door ( 180 ) can be opened so as to be flat against the structural front portion ( 185 ) of the front panel. Using special hinges, the front doors can be made to wrap around the structural front portion ( 185 ) of the front panel so as to remain flat against the left side panel ( 175 ) and the right side panel ( 125 ) when in the opened position. Once in this position, the doors can be latched back so as to not swing close unexpectedly. This feature is extremely helpful when the user is power washing the interior of the trash cart or when the trashcans are being removed from the trash cart and the cart is on unleveled ground. [0116] As in FIG. 1 , the top panel ( 110 ) of the trash cart ( 100 ) may be split into two portions by a separator panel ( 115 ) so that each of the two portions of the top panel ( 110 ) can be lifted independently by handles ( 190 ) revealing the interior portion of the trash cart ( 100 ). The top panel ( 110 ) is connected to the back panel by multiple hinges ( 105 ). [0117] As shown in FIG. 2 , the trash cart ( 100 ) is equipped with a rear axel ( 165 ) having wheels ( 170 ) attached to each end of the rear axle ( 165 ) and a front axle ( 140 ) having wheels ( 145 ) attached to each end of the front axle ( 140 ). The rear axle ( 165 ) is fixed to the bottom portion of the bottom panel ( 160 ) and the front axle ( 140 ) is pivotally attached to a different portion of bottom panel so that the axle can shift from side to side so as to steer the trash cart. [0118] The front axle ( 140 ) is attached to steering means ( 130 ) that when maneuvered causes the front axle and it's attached wheels to turn in the direction that the user wants the trash cart ( 100 ) to move towards. As stated above in FIG. 1 , the steering means ( 130 ) can also be used to pull the trash cart to the intended site. The wheels of the front and/or back wheels can be equipped with a locking mechanism to prevent the trash cart from rolling if left on un even ground. The trash cart can also be equipped with a hook system ( 150 ) (not shown) that can be attached to the side and or back of the trash cart that can be used to carry bulky items such as an old latter, old doors, and the like to the curb on pick-up day. [0119] FIG. 3 shows another view of the present invention wherein the front doors are in the open position and one of the top panel portions is in the lifted position. All of the components of the trash cart of FIG. 2 are also in the embodiment shown in FIG. 3 . The embodiment shown in FIG. 3 shows a locking mechanism ( 270 ) on the rear axle that is designed to lock the wheels in placed so as to prevent the trash cart from rolling if left on un-even ground. This same mechanism can be attached to the front axle instead of the rear axle or on both the front and rear axle of the trash cart. It is within the scope of the invention to use the locking wheel mechanism in all of the embodiments described herein. [0120] Still another embodiment of the invention is directed to a trash cart kit comprising a top panel ( 405 ), top panel hinges ( 410 ), separator panel ( 415 ), front panel handle ( 420 ), back panel ( 425 ), right side panel ( 430 ), left side panel ( 435 ), bottom panel ( 440 ), separator panel ( 445 ), wheels ( 450 ), axles ( 455 ), steering means ( 460 ), structural supports ( 465 ), left front door panel ( 470 ) right front door panel ( 485 ), steering connection ( 480 ), instructions to assemble the trash cart ( 485 ), and various fasteners, bolts and pins necessary to connect all of the parts together. The trash cart kit is shown in FIG. 4 and is designed to be easily assembled. The trash cart kit is easier to ship, store, and package, all of which results in savings that can be passed on to the consumer. In addition, compact packaging also allows the consumer to transport the trash cart from the store to home without a truck. [0121] The trash cart, once assembled, has all of the features, attributes and benefits of the fully assembled versions shown in FIGS. 1-3 . The trash cart kit can also includes special fasteners that allow the owner to decorate the trash cart so as to be pleasing to the eye, match the structure in which is stored next to or to just to personalize the cart. For example, the kit can include special fasteners and a printable plate that can be engraved and/or printed with the name and/or address of the owner. [0122] In still another embodiment of the invention, the panels can be almost completely solid having only a few holes for water drainage and/or ventilation. The fasteners can be attached to the top panels ( 405 ), back panel ( 425 ), right side panel ( 430 ), left side panel ( 435 ), bottom panel, left front door panel ( 470 ) and right front door panel allowing for decorative panels to be attached. The decorative panels can be made out of material selected from the group consisting essentially of wood, wrought iron, aluminum, stainless steel, powder coated aluminum, plastic, polyvinyl chloride, powder coated steel, plastic coated metal, man-made materials, new-age materials, or any other material that is washable, strong enough and durable enough for trash cart wear. Custom panels can be made so as to match any structure or to make any trash cart unique. [0123] Another feature that can be added to the trash cart is an internal light that turns on automatically using a light sensor when either the top panel or front doors are opened. This light can be powered by solar or energy from a battery. The same solar charge/battery pack can be used to power an odor control unit that emits a scent to mask the smell of the trash either on a timer or using a malodorous detector that activates the fragrance emitter when odors reach a certain detectable level. All of these features are known in the art but are unique when incorporated into the present invention. [0124] FIG. 5 gives several examples of decorative panels. These are only examples and many other designs can be used and are anticipated to fall with the scope of the invention. These panels should be weather resistant; however, making the trash cart from a virtually indestructible material will allow the cart to last while changing the decorative panels on the outside would allow the trash cart to look new even though the internal structure is old. This is a direct savings to the consumer and opens up an additional market for decorative panels. [0125] The above embodiments of the present invention can be manufactured using well-established manufacturing techniques used in similar industries today. The technique used to make the present invention is directly related to the material used to make the trash cart. For example, if plastic is used to make the trash cart then the well-established technique of cast molding maybe used. If metals are used to make the trash cart, then welding and/or drop forging of metals maybe used to make the trash cart. And finally, if wood is used to make the present invention then standard wood milling and carpentry techniques can be used. The aforementioned list is not meant to be an exhaustive list designed to cover all of the possible techniques that can be used to make the invention but are only offered as examples. One skilled in the art would manufacture the trash cart using techniques available at the time the trash cart is manufactured. [0126] The materials used to make the present invention should be durable enough to withstand the abuse often associated with trash cans but must be light enough so that the trash cart can be moved easily and without undue effort just to carry the weight of the trash cart. [0127] In another embodiment of the invention, the trash cart is equipped with a motor that is in direct communication with at least one wheel and/or axle of the trash cart that when powered would rotate the wheel and/or axle so as to move the trash cart in the forward or reverse direction. The motor can be powered by gas, electric or some combination of each and can be controlled by either a remote control device or a direct control device. [0128] So as not to allow egress of small animals into the main compartment of the trash cart, the panels should have predominately solid construction having only strategic holes for ventilation and water drainage. The enclosure should also be designed to keep most of the rainwater from getting into the structure. To achieve this task the structure is designed to have a slanted roof so as allow rain to run off of the top panel and avoid pooling of excess water. Although the main compartment of the trash cart is predominately solid construction the homeowner is able to achieve a more airy look using the decorative overlay panels. In other words, the overlay panels, once attached, would allow the home owner to achieve the wrought iron look that by definition has large spaces between each segment—spaces too large to be able to keep animals from getting into the trash cart—while still protecting the trash from animals. [0129] As with most things in life, the trash cart of the present invention would be able to marketed as a standard model containing the basic structure to the deluxe model comprising the basic model plus the add-on features such as decorative overlay panels, outside lighting, odor diffuser, motor with remote control as well as other added features that complement the basic features of the invention. The trash cart can be designed to fit one or more trash cans, preferably two trash cans. [0130] In summary, the present invention is directed to a trash cart that is mobile, easy to get trash cans in and out of, protects the trash cans from animal destruction, is durable, decorative and allows the user to store and transport the trash cans to the curb for collection quickly and without getting soiled. [0131] While the invention has been illustrated and described with respect to specific illustrative embodiments and modes of practice, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited by the illustrative embodiment and modes of practice.

The present invention is directed to a trash cart, namely an enclosed trash cart having a top and front doors that swing open on a hinged system. The enclosed trash cart is connected to at least one wheel axle having wheels that allow the cart to be transported from a storage area to the curb for garbage pickup. The trash cart can also have an attachment system that gives the owner the option of overlaying a number of different external decorative panels to the trash cart making the cart both functional and decorative. The trash cart of the present invention enables a homeowner to store daily garbage outside the home or garage in a decorative enclosure that keeps the garbage protected from animals and makes it easy to transport garbage to the curb on pick-up day.

BACKGROUND OF THE INVENTION [0001] The present invention relates to a method and apparatus for the simultaneous centralized control of capsule-like yarn brakes of several twist spindles of a two-for-one twisting machine. [0002] DE 44 08 262 C2 discloses an apparatus for the central control of a capsule-like yarn brake of a twisting machine, especially a two-for-one twisting machine. This conventional apparatus includes a control device and a common compressed air unit which is communicated with the twist spindles via connecting units each associated with a respective twist spindle and operable to deliver air pulses to a pressurized air cylinder coupled to a brake ring of the respective twist spindle, the control device controlling the common compressed air unit to deliver pressurized air pulses to the pressurized air cylinders, whereby the pressurized air cylinders, upon receipt of the air pulses, effect an axial displacement of the rotatable brake rings of all of the capsule-like yarn brakes over a predetermined extent. [0003] DE PS 32 43 157 discloses a twist spindle having a capsule-like yarn brake, which is supported between upper and lower brake rings. The upper brake ring is mounted to a support body at the lower end of a yarn intake conduit of a twist spindle and is resiliently biased by a spring in the direction of the lower, second brake ring. The support body is provided with a plurality of support shoulders distributed around its circumference at different axial positions so that a respective one of the support shoulders is supported on a stationary detent. An adjustment of the braking force of the capsule-like yarn brake is effected in a manner such that the yarn intake conduit is raised against the force of the spring which biases the support body and, thereafter, the yarn intake conduit is rotated through a pre-determined angular range of traverse such that another support shoulder of the support body comes to rest against the detent. This conventional device is thus directed to an individual adjustment and, especially, a manual individual adjustment, of each individual capsule-like yarn brake. SUMMARY OF THE INVENTION [0004] The present invention offers a solution to the challenge of providing a method and an apparatus for the simultaneous centralized controlled adjustment of the capsule-like yarn brakes of a plurality of twist spindles of a two-for-one twisting machine such that the need for a dedicated pressurized air system can be avoided. [0005] Summarizing the prevalent characteristics of the present invention, the present invention is particularly characterized in that it exerts, in a purely mechanical operation implemented via a plurality of yarn balloon guides commonly supported on a support frame, a sufficiently high pressure on the yarn intake conduits of a plurality of twist spindles such that the yarn intake conduits, which each support one of the two respective brake rings of the respective twist spindle, are axially displaced against the bias of a spring force to an extent such that a brake ring rotation advances the brake ring to a different axial position relative to the other, second respective brake ring following each release of the yarn intake conduit from the axial pressure thereon. [0006] An embodiment of the present invention is described in the following description taken in connection with the figures of the drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0007] [0007]FIG. 1 is a sectional view of a two-for-one twisting machine having a plurality of yarn balloon guides commonly mounted on a yarn guide frame, which is movable upwardly and downwardly; [0008] [0008]FIG. 2 is an enlarged sectional view of a twist spindle having a hollow shaft in which a capsule-like yarn brake is disposed; [0009] [0009]FIGS. 3 a - 3 c are each an enlarged perspective view of a portion of the adjustment unit at a respective different position thereof during movement of the adjustment unit to adjust the braking force of the twist spindle relative to a stationary detent; [0010] [0010]FIG. 4 is an enlarged perspective view of a variation of the one embodiment of the adjustment unit; and [0011] [0011]FIG. 5 is an enlarged perspective view of a twist spindle having a variation of the embodiment of a yarn balloon guide. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0012] [0012]FIG. 1 shows a sectional view of a two-for-one twisting machine which supports the yarn balloon guides 9 of a plurality of twist spindles S arranged in neighboring relation to one another, the yarn balloon guides 9 being commonly mounted to a common yarn guide frame 11 which is movable—in a not illustrated guide—upwardly and downwardly parallel to the axes of the twist spindles S in the direction of the double arrow F 1 . [0013] The yarn guide frame 11 is suspended by means of suspension hangers 12 on a shaft 13 , which is rotatably driven by a rotation drive 14 operatively coupled to a motor 15 . The downward movement of the yarn guide frame 11 is effected under the influence of gravity by corresponding controlled actuation of the motor 15 . The possibility thus exists to position the yarn balloon guides 9 at differing heights over the yarn intake conduits 3 , whereby, to exert an influence on the yarn twisting process, the formation of yarn balloons can be controlled. In accordance with the present invention, the yarn balloon guides 9 can be displaced downwardly through corresponding adjustment of the yarn guide frame 11 to such an extent that the yarn balloon guides 9 exert a downward pressure on the yarn intake conduits 3 of a plurality of the twist spindles S, whereby the yarn intake conduits 3 are pressed downwardly. In this manner, as will be hereinafter described, the possibility exists to provide a centrally controlled adjustment of the yarn brakes of a plurality of spindles S arranged in neighboring relationship to one another. [0014] [0014]FIG. 2 shows a portion of the hollow shaft 2 of a rotationally symmetric housing 16 in which is disposed a capsule-like yarn brake 11 and an adjustment unit 18 which is responsive to downward pressure on the yarn intake conduit 3 , the adjustment unit 18 being operable to effect a variation of the braking force of the capsule-like yarn brake 11 . The adjustment unit 18 is secured to the bottom end of the yarn intake conduit 3 and comprises a cylindrical housing 27 open towards its bottom for receipt therein of a helical spring 28 which biases the adjustment unit 18 upwardly. [0015] The housing 16 is closed on its topside by a threaded cover 19 through which the yarn intake conduit 3 is guided outwardly of the housing 16 . The capsule-like yarn brake 11 includes a bullet-like brake which, in conventional manner, is comprised of two displaceable tube portions 11 . 1 and 11 . 2 biased by a spring to move axially away from one another and each of which includes a cup or cap-shaped end portion. The lower tube portion 11 . 2 is supported against a brake ring 20 , which is disposed in a brake ring carrier 21 disposed in an axial guide or groove 21 . 1 . The brake ring carrier 21 , which is supported against a helical spring 22 , is sealingly guided in a housing bore 16 . 2 formed in the housing 16 such that, for purposes of effecting a pneumatic yarn threading or intake of yarn, an under-pressure is created below the yarn ring carrier 21 so as to effect downward movement of the yarn ring carrier. The lowered yarn ring 20 thus releases the bullet-like yarn brake 11 to fall whereupon it is then caught by a support ring 16 . 3 stationarily mounted in the housing; the support ring 16 . 3 has a partial opening 16 . 31 such that a yarn introduced through the yarn intake conduit 3 can be suctioned in through the yarn intake 8 into the bore 21 . 1 and guided past the released bullet-like brake 11 . A yarn threading system of this type is described in DE 44 08 262 C2 and is, in any event, the basic configuration of the yarn intake assembly as described in the hereinafter-described adjustment unit 18 . [0016] A first annular upper toothed rim 40 is disposed on the adjustment unit 18 above the housing 27 and a second annular lower tooth rim 41 is disposed above the housing 27 as well. The upwardly directed teeth of the lower toothed rim 41 form therebetween axial spaces in the form of openings/slots whose bases or bottoms form notches or, respectively, support shoulders which are distributed about the circumference of the toothed rim at differing axial heights therearound and each notch or support shoulder is engaged upon its turn by a radially inwardly projecting detent 29 as a function of the rotational position of the adjustment unit 18 . [0017] The downwardly directed teeth of the upper-toothed rim 40 form therebetween axially extending slots opening downwardly or, respectively, form downwardly opening notches. [0018] Reference is now had to FIGS. 3 a - 3 c for a description of the configuration of the teeth of the two toothed rims 40 and 41 ; the arrow F 2 indicates the rotational direction of the adjustment unit 18 . [0019] The flanks 40 . 1 and 41 . 1 of the teeth of the upper and lower toothed rims 40 and 41 which extend in the rotational direction F 2 have substantially axial extents. The down sloping flanks 40 . 2 or, respectively, 41 . 2 of the upper and lower toothed rims 40 and 41 are configured as respective rising or falling angled surfaces which form an angle of approximately 45° relative to the rotational direction. The tips or peaks of the teeth of the upper-toothed rim 40 are offset from the tips or peaks of the teeth of the lower toothed rim 41 in the rotational direction by an amount which is slightly greater than the diameter of the detent 29 . [0020] [0020]FIG. 3 a shows an operational condition in which the lower toothed rim 41 is engaged by the detent 29 such that the detent is seated in a notch I between two neighboring teeth of the lower toothed rim with the portion of the adjustment unit 18 comprised of the lower toothed rim 41 being upwardly biased by the spring 28 . If the adjustment unit 18 is displaced downwardly in the direction of the arrow F 3 via a downward pressure on the yarn intake conduit 3 , the detent initially assumes the position shown by the broken lines 29 ′ seen in FIG. 3 b. Upon further downward pressure on the yarn intake conduit 3 , the detent traverses along the toothed flank 40 . 2 extending away from the rotational direction f 2 to thereafter achieve the intermediate position 29 ″ shown in FIG. 3 c in correspondence with the partial rotation of the adjustment unit 18 in the direction of the rotation direction F 2 . The movement of the detent 29 relative to the adjustment unit 18 follows thus along the path of the bent arrow F 5 shown in FIG. 3 a. It is to be understood that the stationary detent 29 does not axially change its position but, rather, the adjustment unit 18 undergoes a partial rotation during this process. [0021] If, thereafter, the yarn intake conduit 3 is again released, the adjustment unit 18 is again biased upwardly, as seen in FIG. 3 c, in the direction of the arrow F 4 due to the biasing action of the spring 28 so that the detent 29 —following the path shown by the bent arrow F 6 —seats into the next following notch 11 , whereby there follows a sliding movement of the detent 29 along the flank 41 . 2 in the direction of the rotation direction F 2 upon a further partial rotation of the adjustment unit 18 . [0022] By virtue of the lowering and subsequent release of the yarn intake conduit 3 and, thus, of the adjustment unit 18 , there follows a sectional rotation of the adjustment unit 18 in the rotational direction F 2 . Since each notch is lower than the immediately preceding notch, it follows, as the detent 29 seats into the respective next following notch, that the brake ring 23 is disposed in progressively lower positions following each operation to lower and release the yarn conduit 3 , thus leading to an increase in the braking force. [0023] The braking force can thus be adjusted in a step-wise manner through individual downward pressure and release sequences of the yarn intake conduit 3 until the braking force has been increased to a maximum value, which value is predetermined by the depth of the deepest notch in the lower toothed rim 41 . [0024] Through multiple sequential actuation—that is, multiple actuation involving downward pressure and release of the yarn intake conduit 3 —the yarn braking force can be increased until the detent 29 is eventually seated in the deepest notch of the lower toothed rim 41 . [0025] By sequential or subsequent activation of the yarn intake conduit 3 , the detent 29 is moved into the next following—that is—the highest disposed notch—of the lower toothed rim 41 , which corresponds to the braking force adjustment position of the lowest value. [0026] The toothed rims 40 ′, 41 ′, as seen in FIG. 4, can be configured as lower components freely rotatable relative to the remainder of the adjustment unit 18 but not, however, adjustable relative thereto in the axial direction, with the toothed rims 40 ′, 41 ′ being supported by, from below, a collar of the housing 27 and, from above, a detent body 60 which is securely mounted via, for example, a threaded screw 61 , on the yarn intake conduit 3 . [0027] The yarn balloon guides can alternatively be configured to be self-centering with respect to the associated yarn intake conduits 3 —e.g., as truncated ball-shaped yarn balloon guides 9 ′, as seen in FIG. 5. [0028] The specification incorporates by reference the disclosure of German priority document DE 100 45 909.9. [0029] The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.

A method and apparatus for the simultaneous centralized controlled adjustment of the braking force of yarn brakes of a plurality of twist spindles of a two-for-one twisting machine are provided, whereby each twist spindle is of the type having, in its hollow shaft, a yarn brake supported between two brake rings with one of the brake rings being rotatable in response to a downward axial pressure thereon in a manner such that the brake ring undergoes a discrete axial displacement to a new axial position. A support frame to which yarn balloon guides are mounted exerts a downward axial force such that the yarn balloon guides simultaneously exert downward axial pressure on the yarn intake conduits of the twist spindles which, in turn, effects axial displacement of the rotatable and axially adjustable brake ring on the yarn intake conduit of each twist spindle into new axial positions.

Detailed Description of the Invention CROSS-REFERENCE TO OTHER APPLICATION [0001] This application claims priority from U.S. Provisional Application 60/408,096 filed Sep. 3, 2002, which is hereby incorporated by reference. BACKGROUND AND SUMMARY OF THE INVENTION [0002] The present application relates to computer architecture, and particularly to techniques for interfacing added modules into existing e-mail programs. [0003] Background: Computer Communications [0004] "Computer communications" was regarded as a specialized area in the 1960s or so, but now most communication is converging to a paradigm of data communication. The endpoints of data communication are not necessarily computers, but can be audio, video, or image interfaces, sensors, switches, control units, or many kinds of "smart" devices. Thus the established engineering principles of computer networks are becoming applicable to a wide range of applications. [0005] Background: Networks, Packets, and Protocols [0006] Computer network structure and operation is one of the basic areas of computer science, and a vast amount of literature has been published. One of the basic ways to structure communications over a network is to use packets of data, as in the pioneering "packet-switched" ARPANET which evolved into the Internet. [0007] Background: Hashing [0008] One of the simplest types of data translation is "hashing," where data is reversibly transformed in a way which randomizes the statistical distribution of bytes. Hashing can be a useful way to disarm viruses and/or provide a more nearly stochastic distribution of data. (Equalizing symbol distribution can help in increasing S/N ratio of data transmission.) [0009] Background: Filtering [0010] A special kind of data translation is filtering, where data is transformed conditionally depending on a certain test. "Packet filtering" is a more specific term for content-dependent routing. Any router performs address-dependent routing, but filtering implies that the data in the packet is analyzed in some fashion to affect routing. (For example, packets in which a virus signature is found may be discarded.) [0011] Background: Digital Signature and Identification [0012] Public-key algorithms (RSA etc.) can be useful for authenticating digital documents. An extension of this is for identification of the specific human who has chosen to authenticate the document. There are many circumstances where it would be useful for persons communicating over the Internet (or over a network) to be able to identify themselves reliably. For example, in arm's-length Internet sales, it can be useful to definitely identify the other party. For another example, electronic publishing over the internet becomes much more practical if working access can be limited to only those users who have paid for it. For another example, some users would like to filter incoming email to exclude mailings (such as spam) which are not tagged with a reliable certificate of origin. [0013] Keys used for digital signatures are a very long series of bits, which can be represented as long series of alphanumeric characters. Unlike Personal Identification Numbers (PINs), it is simply not feasible for individuals to remember them. For access control, such key data is typically stored in a chip (or other electronic memory), which can be embedded in a plastic card, or in another physical object such as a ring. [0014] Background: Interfacing to Programs [0015] In the past decade it has become increasingly difficult to introduce innovative business software products for the personal computer market. Such products must be able to interface to the widely used software application packages, and this is not always easy. In particular, it is important for communications-related software to be able to interface to Outlook, Notes, and GroupWise, and none of these are easy to program for. (The documentation provided to third-party developers is unclear and difficult to use.) [0016] Computer communications are a somewhat unusual area of software development, in that many functions may need to be combined. A user's full-range email program should be able to handle (using calls to other programs as needed) various compression or authentication formats, various image formats, various audio formats, various HTML or XTML extensions, various drawing formats, various special fonts, virus-checking, and other new functions as they come up. (For example, the secure communications capabilities of PGP were integrated into some email programs, such as Eudora, long before PGP was available in other email programs.) As this list indicates, the boundary between browser functions and email functions has blurred somewhat in the last decade, and this trend may continue. Thus, since email handling necessarily involves so many different data types and data operations, smooth integration is particularly important. [0017] Background: Dongles [0018] A recurrent theme in the software industry has been the desire to find some way to make copied software unusable. One of the earliest ways to do this was the "dongle," in which a physical package containing an electronic key was attached to a port of the computer. [0019] Data Translation Architecture [0020] The present application describes a new system architecture for adding in functionality, and particularly for adding data translation functions between a communications program and its target (e.g. the outside world). The preferred embodiment achieves this without any need to intrude on management of the TCP/IP stack; instead, data for communication is simply addressed to a reserved (preferably loopback) address, and is snooped by a "translation agent" (software routine or hardware) either when it is being sent to the network interface unit or when it is echoed back. The translation agent can provide authentication, privacy, data reformatting, or other such functions. In alternative embodiments these ideas can be used in digital systems which are not computers, or can be used as part of a firewall or gateway, or to interface between networks using different protocols, or used in other analogous ways. [0021] The disclosed innovations, in various embodiments, provide one or more of at least the following advantages: [0022] simple interface into existing software; [0023] added IP address uses without added stack handling; [0024] good invisibility to viruses; [0025] easy integration, even with undocumented e-mail programs; [0026] can secure all non-protocol-level data on any TCP/IP port; [0027] transparent to applications which use TCP/IP; [0028] device, platform and operating system independent; [0029] independent of any specific methodology for securing data; [0030] recipient-dependent email modifications are easy. BRIEF DESCRIPTION OF THE DRAWING [0031] The disclosed inventions will be described with reference to the accompanying drawings, which show important sample embodiments of the invention and which are incorporated in the specification hereof by reference, wherein: [0032] [0032]FIG. 1 shows a generic overview of the translation-assistant. [0033] [0033]FIG. 2 shows an example of implementation of the Translation Agent into an existing application environment. [0034] [0034]FIG. 3 shows a generic TCP/IP session. [0035] [0035]FIG. 4 shows a client server environment using some of the disclosed inventions. [0036] [0036]FIG. 5 shows an environment whereby TA secures the transmission between two TA client applications without Server interdiction. [0037] [0037]FIG. 6 shows secure data transmission in a peer-to-peer environment. [0038] [0038]FIG. 7 shows the client to server secure relationship, and [0039] [0039]FIG. 8 shows the server to client relationship. [0040] [0040]FIG. 9 is a flowchart for the TA examining and processing for transmitting data. [0041] [0041]FIG. 10 is a flowchart for the TA examining and processing of received data. [0042] [0042]FIG. 11 is a sample of the devices that can be secured with TA. [0043] [0043]FIG. 12 illustrates the interface between Translation Agent and application software in a device. [0044] [0044]FIG. 13 gives an overview of the installation process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0045] The numerous innovative teachings of the present application will be described with particular reference to the presently preferred embodiment (by way of example, and not of limitation). [0046] Translation Agent (TA) is an architecture for modifying (e.g. securing data in the Telecommunications Control Protocol and Internet Protocol (TCP/IP) data stream. TA is platform, operating system and device independent. TA is independent of any specific technology for securing or otherwise modifying the data. [0047] TA utilizes the TCP/IP "loopback" address 127.0.0.2 and/or other class A addresses in that range to implement a procedure whereby TA can become a pseudo-server on and within the physical device. [0048] TA is then able to monitor all or specific ports on the device and secure the data as it is transmitted or unsecure the data as received. [0049] TA is independent of specific protocols such as SMTP ("Simple Mail Transport Protocol"), POP3 ("Post Office Protocol 3"), FTP, HTTP etc. TA examines the data, passing protocol level information without modification and secures the data portion of the transmission. [0050] TA processes and secures the data based on the requirements and capabilities of the specific method used for securing the data. [0051] TA is designed to be transparent to other applications and virus checking applications. [0052] The TA architecture provides an open framework into which many different algorithm implementations can be inserted as modules. For example, for converting unsecured data to secure data and vice versa, the TA architecture can support insertion of e.g. LZW, DES, DES-3, Rijndael, Blowfish, TwoFish, PGP, RSA, etc. Algorithms used can be, for example, streaming or block-oriented, symmetric or asymmetric. [0053] The Translation Agent architecture is modular to the extent that a wide variety of existing encryption (or other) algorithms can be "plugged in" to the Translation Agent. This means that any existing or later-developed algorithm or system can be used if any sizeable group of users demands it. The amount of administrative overhead created by these systems is reduced, since the activities performed within the Translation Agent module are unseen by the user. This is particularly beneficial in corporate IT departments, where a considerable amount of support is usually necessary to make this systems function properly. [0054] [0054]FIG. 1 shows a generic overview of the TA's function in a device 101 using TCP/IP. (The device 101 can be, for example, a personal computer, or alternatively can be a variety of other device types as discussed below.) The configuration of a software application 100 is modified to send and/or receive TCP/IP packets using a reserved (e.g. "loopback") TCP/IP address 102 in place of its original TCP/IP settings. TA module 103 is configured to listen on the reserved address 102 specified for this application. (Note that multiple reserved addresses can be specified for multiple applications.) TA module 103 then initiates sessions, using the application's data, on another TCP/IP connection 106. (The TA module 103 retains the application's original TCP/IP address and Port configuration data, in order to transmit and receive the data.) For widely used applications, configuring the application settings would be an automated installation process. In most cases, modifications or enhancements by the application vendors should not be required. [0055] As denoted in FIG. 1, the configuration for the application 100 is changed to use the "loopback" address 102, and TA will then communicate with the application 100 as though TA were the intended destination. TA 103 will examine and modify the data as necessary, and will forward the modified (e.g. secured) data to the intended destination through connection 106. In the other direction, TA 103 will receive data for the application 100 from connection 106, examine the data and unsecure it when necessary, and forward it to the application 100 through connection 102. Thus TA 103 allows the application 100 to be secure in transmitting and receiving its data without modification to the application's software. [0056] Sample Implementation: SMTP/POP3 E-Mail Client Interface [0057] [0057]FIG. 2 is a more specific example of implementing TA into an existing application environment. Again, the example shown is based on a device 101, e.g. a personal computer or PDA, with TCP/IP connectivity. The E-Mail client 100' in this example is reconfigured so that its SMTP/POP3 interfaces send and receive on the "loopback" TCP/IP address 127.0.0.2. Specifically, the SMTP target address saved (with many other parameters) in system configuration data file 108 (e.g. a Windows registry file) has been changed to 127.0.0.2, and the POP3 address has also been changed to 127.0.0.2. [0058] In this example the TA module 103' listens on 127.0.0.2 on the "Well known" port 25. When the SMTP interface 100A sends an E-Mail message and/or attachments, TA 103' intercepts the messages. [0059] The protocol level data is preferably be passed through intact, but the message content (indicated by the appropriate SMTP body tags etc.) can be transformed by the TA module 103'. That is, the TA module 103' preferably "parses" the SMTP transmission, to the limited extent needed to identify the message body and/or attachments, and then (depending on is programming) performs a data translation operation on these portions. The possibly-transformed body and attachment data, combined with the untransformed protocol data, is then sent along, through connection 106, to the SMTP server that was originally specified by the application. [0060] Correspondingly, the TA module 103' will listen on the reserved address (in this example 127.0.0.2 on Port 110) for the application to initiate a POP3 session. Thereafter TA 222 will monitor the session, and if secured data is encountered for this application/user, then the TA module 222 will unsecure the data. Otherwise the TA module 103' can simply pass the clear data through to the POP3 interface 100B. [0061] Both the SMTP and POP3 data securing and unsecuring processing are transparent to the application and virus scans implemented at the device. [0062] Installation of TA [0063] [0063]FIG. 13 gives an overview of the installation process (which, as noted, is preferably automatic.) In the presently preferred embodiment, TA (or its installation program) initially examines the windows registry 108 for e-mail client configurations. (The actual entry locations and data will vary depending on the versions of the E-Mail client and possibly the Windows operating system.) TA extracts the client configuration (steps 1310 and 1330) and saves the information in its own configuration file. [0064] TA (or the installation program) then updates the windows registry 108 with POP3 (step 1340) and SMTP (step 1320) configurations set to a reserved address, e.g. a loopback address 127.0.0.x. [0065] The TA module is then configured (step 1360) with logical relations which will cause it to load whatever translation algorithms are desired. (For example, hashing might be used for outbound messages to some addresses, or encryption for others. [0066] Once the TA module itself has been set up to launch automatically, the unit can be restarted (step 1390). [0067] TA then starts a listening function for POP3 and SMTP on the loopback address at the well known ports for POP3 and SMTP. [0068] When the e-mail client starts, it obtains the e-mail server configuration from the windows registry, and is not aware of the changes made by TA. [0069] When the e-mail client initiates a POP3 or SMTP request, it actually connects with TA on the same device. [0070] TA then initiates the same type connection with the actual POP3 or SMTP server. [0071] TA then monitors the information, receiving from the e-mail client and forwarding to the server and visa versa. [0072] If e-mail is being sent (SMTP), then TA looks for the recipient information, both primary and carbon copies. If any recipients are in the list of registered secured recipients for the encryption technology implemented then TA will wait for the actual text and attachments and secure the information. If there are no secure recipients then TA simply continues to pass the information. [0073] If a POP3 session is initiated then TA simply checks the information to determine if it is in a secure format, and unsecures the information if necessary, before passing it to the e-mail client. If TA is not able to decrypt the information, e.g. because the recipient is not the authorized recipient, then the information is passed to the email client in its as-received format. [0074] When TA is uninstalled, the uninstallation program preferably resets the registry entries back to their original configuration. [0075] Preferably, TA performs a test for integrity at startup. (For example, a checksum derived from the updated registry entries can be stored where TA can read it and check it.) [0076] The same general interface should function for Lotus Notes and IMAP with minor changes for these protocols. [0077] The example refers to the windows registry, but the specific client application may use some other form for saving its configuration information, such as an ".ini" file, and in this case the minimal access to registry described above is merely performed on the appropriate .ini file or other location. [0078] Non-E-Mail Applications [0079] [0079]FIG. 3 shows a generic TCP/IP session with a non-email application 100", which can include but is not limited to FTP, VPN, HTTP, video conferencing and peer-to-peer applications. By configuring the application 100" to send and receive using the "loopback" addressing scheme, TA is able to secure an application's data without modification to the application's software. TA can secure all data or selected data based on configuration parameters. TA can be configured using its secured configuration manager to use a different TCP/IP port on the device or for the destination. [0080] TA's mechanics of operation in this configuration are similar to those of the e-mail configuration of FIG. 2. The application's configuration data is preferably altered so that its send routines 100A' use a non-routable address 102A (preferably a loopback address), and its receive routines 100B' use a non-routable address 102B (also preferably a loopback address). The translation agent 103" is set up to capture accesses to these reserved addresses, and to perform data translation operations on the content of the transmissions as described above. Note however that the retransmission functions performed by translation agent 103" can be slightly more complicated than those performed by email translation agent 103', since the ultimate target address is not necessarily static. Where the target address is unpredictable (as in http: or ftp: accesses), the TA 103" is preferably configured either to snoop and divert all communications, or else to access dynamic routing data from inside the application 100". [0081] Secure Communication to Interdicting Server [0082] [0082]FIG. 4 shows a sample implementation in a client-server environment whereby the Server requires the data to be unsecured upon arrival. In this example an application 410, running on a physical device 101A (e.g. a workstation), is backed up by a local TA 420A which secures some or all of the communications over connection 106 (e.g. a LAN or WAN routing). A corresponding server-side TA 420S provides a complementary data translation interface between channel 106S and a server 430. An example of this environment could be organization with a central E-Mail server where the client 410 secures all data to the server (in this case E-Mail messages and attachments), and the E-Mail server 430 unsecures the data to perform a Server level virus scan. [0083] The reverse process can also be employed, where the client 410 only receives data that has been secured by the Server even when the originator did not have the capability. An example of this is shown in FIG. 7, where an application 710 on a remote device 101C can communicate with the application 410, but all communication must be routed through client-server channel 106S which is protected by TA modules 420A and 420S. Thus in this example the server 430 can be programmed (for example) to perform firewall and gateway functions needed for interface to the outside world. [0084] [0084]FIG. 8 shows a different implementation, where client-server communications over local channel 106L are not necessarily mediated by TA modules, but communications which must pass over a more exposed channel 106W are secured by TA modules 420A and 420S. Note that this diagram is very similar to FIG. 4, except that the channel assignments are different; in the embodiment of FIG. 8 the local network is assumed to be protected by (e.g.) physical security precautions, and the problem addressed is that of providing secure communications with remote workstations. [0085] Peer-to-Peer Implementations [0086] [0086]FIG. 6 shows an example where data transmission can also be secured in a peer-to-peer environment. In this example processes 610A and 610B, running on two different physical devices 10A and 101B, have their communications mediated by the complementary operations of respective translation agents 103. Note again that the physical devices 101 do not have to be computers, but can be, for example, components of a computing system. Thus, for example, in a large computing system which uses an array of asynchronous processors to form a "compute farm," or an array of storage devices to form a "server farm," the TA modules can be added in to modify peer-to-peer communications. Note, however, that this modification is not as attractive for applications where latency in communications is a action. [0087] If TA is used to secure information within a device then the same loop interface exists, but TA loops the transmission back to the application after having taken the appropriate action (encrypt or decrypt). [0088] The arrows on the document are meant to show flow of the information. In actuality the information is normally a two way exchange over the one connection between the software. In other words the application probably sends and receives over one TCP/IP connection for one function and likewise TA sends and receives over the one connection. [0089] Adaptation to Mobile Systems [0090] [0090]FIG. 11 is a sample of the devices that can achieve secure communication, using the TA, through the Internet (or other large network). This diagram is not an exhaustive list at all, but does give some idea of the range of applications of TA technology. The illustrated devices, which can be connected through the Internet or some other TCP/IP or analogous network, include without limitation: Windows.TM. computers; Unix/Linux computers; MacIntosh.TM. computers; PDA devices; digital cell phones; other digital devices; mainframe computers; servers; videoconferencing stations; Windows-CE.TM. devices; minicomputers; IP telephones; Bluetooth devices; satellites; digital cameras; and laptop or notebook computers. [0091] A particularly attractive contemplated use of the disclosed inventions is in handheld mobile internet devices. Such devices (such as the Blackberry, or other SIM-enabled PDAs) are increasingly coming to include substantial memory and processing power, and are often designed for easy installation of software applications and accessories. It is contemplated that the modular add-on capability of a "translation agent" as described above can be particularly advantageous for updating such systems to include user-selected translation operations as described above. [0092] The Blackberry, for example, uses a Java.TM. operating system, and therefore the above functionality implies a slight modification to the "JVM" (the "Java Virtual Machine," which any Java-capable computer must be able to emulate). That is, Java instructions are assumed to be executed by the Java virtual machine, and any particular computer must be equipped with software drivers to implement the JVM. Typically Java midlets sit on the Blackberry to perform encryption and related functions. [0093] XDA is a competitor to Blackberry, which uses Windows CE, and the disclosed inventions can be similarly adapted to the XDA. [0094] Other implementations (in Java, embedded Linux, PalmOS, or other system software) can similarly be ported to Epoc or other machines, including but not limited to any "3G" or "2.5G" phone. [0095] In the special case of routing e-mail into PDAs (or telephones or other mobile information appliances), the TA can also be set up for formatting functions, e.g. for selective stripping of attachments and/or images. This function is a normal part of low-bandwidth wide-area wireless network communication, but the ability to include it in the TA, where it is performed transparently to the devices and applications involved, provides a new capability. [0096] Two-Translation-Agent Methods [0097] In one class of embodiments, communications between two Translation Agents (or more precisely, between two TA-mediated devices) can be structured to introduce modifications (e.g. for security) even when using protocols (such as FTP) which are inherently unsecure. Thus TA's capabilities are not limited to securing data in transit. TA's in combination can also implement or enhance security and authentication functions, within the communication architecture, which are virtually impossible to achieve without changes in basic internet standards and/or massive changes in software and servers. [0098] In such embodiments, the TA's which jointly control a communication channel can be programmed to jointly introduce non-standard enhancements to standard protocols. [0099] According to various disclosed embodiments of the present invention, there is provided: A system, comprising: a communications interface module which transmits data over a communication channel according to an addressing protocol which includes one or more reserved addresses which are not freely available for external communication, and also includes non-reserved addresses; at least one active program which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications to said interface module using ones of said reserved addresses; and an additional module which a) detects ones of said second communications, b) modifies data in ones of said second communications, and c) transmits results of said operation b). [0100] According to various disclosed embodiments of the present invention, there is provided: A system, comprising: a communications interface module which transmits data over a communication channel according to an addressing protocol which includes non-reserved addresses and also one or more reserved loopback addresses which are not freely available for external communication, and which echoes back data addressed to one of said reserved addresses; at least one active program which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved loopback addresses; and an additional module which a) detects ones of said second communications, b) modifies data in ones of said second communications, and c) transmits results of said operation b). [0101] According to various disclosed embodiments of the present invention, there A system, comprising: a communications interface module which transmits data over a communication channel according to an addressing protocol which includes one or more reserved addresses which are not freely available for external communication, and also includes non-reserved addresses; at least one active program which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved addresses; and an additional module which a) detects ones of said second communications, b) modifies data content portions thereof but not protocol-related header portions thereof, and c) transmits results of said operation b). [0102] According to various disclosed embodiments of the present invention, there is provided: A system, comprising: a communications interface module which transmits data over a communication channel according to an addressing protocol which includes one or more reserved addresses which are not freely available for external communication, and also includes non-reserved addresses; at least one active program which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved addresses; and an additional module which a) detects ones of said second communications, b) modifies data in ones of said second communications, and c) transmits results of said operation b); and which also d) intercepts and modifies at least some incoming transmissions directed to said active program. [0103] According to various disclosed embodiments of the present invention, there is provided: A system, comprising: a communications interface module which transmits data over a communication channel according to an addressing protocol which includes one or more reserved addresses which are not freely available for external communication, and also includes non-reserved addresses; at least one active program which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved addresses; and an additional module which a) detects ones of said second communications, b) selectively modifies data in only some ones of said second communications, and c) transmits results of said operation b). [0104] According to various disclosed embodiments of the present invention, there is provided: A system, comprising: a communications interface module which transmits data over a communication channel; at least one active program which sends communications into said channel through said interface module; and an additional software module which a) monitors at least some ones of said communications, b) selectively modifies data in only some ones of said second communications, and c) transmits results of said operation b) through said interface module. [0105] According to various disclosed embodiments of the present invention, there is provided: A computer, comprising: a network interface module which transmits and receives data over a communication channel according to an addressing protocol which includes non-reserved addresses and also one or more reserved addresses which are not freely available for external communication; at least one active program, running on a CPU of said computer, which sends first communications into said channel through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved addresses; and an additional module, running on a CPU of said computer, which a) detects ones of said second communications, b) modifies data in ones of said second communications, and c) transmits results of said operation b). [0106] According to various disclosed embodiments of the present invention, there is provided: A macro-system, comprising: multiple complex systems following respective instruction streams; and at least one network linking said multiple complex systems; wherein multiple ones of said complex systems each comprise: a communications interface module which transmits data over said network according to an addressing protocol which includes non-reserved addresses and also one or more reserved addresses which are not freely available for external communication; at least one active program which sends first communications into said network through said interface module, using non-reserved addresses, and which also sends second communications through said interface module using ones of said reserved addresses; and an additional module which a) detects ones of said second communications, b) processes data in ones of said second communications, and c) transmits results of said operation b). [0107] According to various disclosed embodiments of the present invention, there is provided: A modular expandable software architecture, comprising: an application program which performs at least one class of interface operations by looking up, in a configuration file, a network address which is used for said interface operations; said configuration file containing a reserved address, which does not correspond to any externally routable address, in place of the network address expected by said application program; and a functional module which, when said application program attempts to send data to said reserved address, performs data translation on said data, and retransmits said data, as modified by said data translation, to an externally routable network address. [0108] According to various disclosed embodiments of the present invention, there is provided: A method, comprising the steps of: (a.) from an application program, sending out a packet, which is intended for a real destination, to a first reserved address which cannot correspond to any real destination; and (b. ) in a translation program, looking up a second address, corresponding to said real destination in a table in memory, and transforming the data of said packet, and rerouting said packet thereafter to said second address. [0109] According to various disclosed embodiments of the present invention, there is provided: A software structure in a storage medium, comprising instructions which, when activated by at least one processor, will direct the processor to perform operations to implement the method of claim 42. [0110] According to various disclosed embodiments of the present invention, there is provided: A method for adding a data conversion function to a third-party software program, comprising the steps of: in a configuration file, replacing at least one target address with a respective non-routable address; and adding a functional module which, when the third-party program attempts to send a packet to said reserved address, performs data translation on the content of the packet according to stored algorithms, and retransmits the content, as modified by said data translation, to an externally routable address. [0111] According to various disclosed embodiments of the present invention, there is provided: A method for adding data translation functions to a third-party e-mail program, comprising the steps of: in a configuration file, substituting a reserved address, which does not correspond to any externally routable address, for the correct e-mail upload address; and adding an functional module which, when the e-mail program attempts to send a packet to said reserved address, performs data translation on the content of the packet according to stored algorithms, and retransmits the content to the correct e-mail upload address. [0112] Definitions: [0113] Following are short definitions of the usual meanings of some of the technical terms which are used in the present application. (However, those of ordinary skill will recognize whether the context requires a different meaning.) Additional definitions can be found in the standard technical dictionaries and journals. [0114] The term "network" is used very generally in the present application, to include wireless as well as wired, optical as well as electrical, local area networks (LANs) and wide area networks (WANs), the Internet, and closed networks (such as that used by the banking system). [0115] "TCP/IP" is a network addressing protocol dating back to ARPANET, and now in very wide use. The "IP" addresses used by TCP/IP have the format of four numbers, each less than 2{circumflex over ( )}8, separated by periods. (Each of these numbers corresponds to two bytes of data, i.e. 8 bits.) [0116] A "packet" is a block of data, in a defined format, which can be routed independently of other packets; standard rules permit a stream of data to be converted to or from packets. [0117] A "port" is a local destination designator: TCP/IP packets include a two-byte port designation in addition to the eight bytes of IP address. Of the 64K possible port designations, a few (mostly within the first 1K) have standard assignments see http://www.faqs.org/ftp/rfc/rfc1340.txt, which is hereby incorporated by reference. For example, port 110 is normally reserved for POP3, 25 for SMTP, 80 for HTTP, and 23 for telnet. (One of these standard assignments is specifically referred to, confusingly, as the "well-known" port.) [0118] A "reserved address" is an address which cannot be routed over the Internet. In TCP/IP these include the loopback addresses discussed above, and a few other blocks of "non-routable" or "unresolvable" addresses (all 10.x.x.x addresses; all 90.x.x.x addresses; 172.16.x.x through 172.31.x.x; and 192.168.x.x). [0119] "Virtual private networks" (VPNs) are network-type communication schemes which embed limited-access constraints within communications over the Internet (or other open or less-secure network). Some common examples of these are referred to as extranets. [0120] A "hub" is a hardware device which echoes packets from one physical network connection into others. [0121] A "router" is a programmable hub which is normally used to echo packets from a local network into the Internet, and vice versa. A router can be programmed, for example, for address-dependent transmission, address translation, port-mapping, and "firewall" and other such higher-level functions. [0122] A "firewall" is a special network interface function which performs authorization checking, refuses unauthorized connections, and may also do address translation, port-mapping packet filtering, and other high-level functions. Firewall functions are commonly integrated with router hardware, but can be implemented separately. [0123] "Packet filtering" is content-dependent routing. Any router performs address-dependent routing, but filtering implies that the data in the packet is analyzed in some fashion to affect routing. (For example, packets in which a virus signature is found may be discarded.) [0124] "Packet sniffing" is an operation which extracts the contents of packets and (possibly depending on contents, addresses or both) saves them elsewhere. [0125] SMTP (Simple Mail Transport Protocol) and POP3 (Post Office Protocol 3) are commonly-used e-mail protocols (one for outgoing, one for incoming). SMTP implementations in which extra functions have been added are sometimes referred to as "ESMTP." [0126] GSM is a cell phone standard--see e. g. http://www.iec.org/online/t- utorials/gsm/ and links therein, all of which are hereby incorporated by reference. "SMS" (standard Short Message Protocol) and "GPRS" (Global Packetized Radio Service) are also defined by the GSM standard. [0127] "JVM" is the "Java Virtual Machine" which any Java-capable computer must be able to emulated. That is, Java instructions are assumed to be executed by the Java virtual machine, and any particular computer must be equipped with software drivers to implement the JVM. [0128] Modifications and Variations [0129] As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a tremendous range of applications, and accordingly the scope of patented subject matter is not limited by any of the specific exemplary teachings given. [0130] Translation Agent modules are capable of being daisy chained for special functions. In a circumstance such as an environment with multiple encryption technologies, a primary TA would receive and interrogate the data. If it found data it could recognize as another encryption technology or a recipient who is configured for receiving in another supported encryption technology, then TA could open a connection using a loopback address and predetermined port and pass then information to that TA processor. The secondary TA would not necessarily know that the information was routed from a primary TA rather than any other TCP/IP stream. [0131] While the invention is particularly advantageous with TCP/IP address protocols, it can also be used with IPX, NetBEUI, NetBIOS, SMB (used for file and print sharing in MS Network) or other protocols, as long as there is a reserved address which can be used for internal communications (intra-chassis or intra-system). [0132] As noted, the disclosed inventions are particularly useful for adding capability to third-party application programs. Some of the programs which are expected to benefit particularly from this are Notes, Eudora, Outlook, Outlook Express, Groupwise, but of course other commercial software packages can also benefit. [0133] An important security benefit is that, in many embodiments, the data translation into a secure format occurs totally inside the system box. This provides an interesting synergy with computers (or other devices) where the CPU itself controls opening of the box, by a "hoodlock" mechanism. (See e.g. U.S. Pat. No. 6,307,738, which is hereby incorporated by reference.) In such cases the TA's resistance to hacking combines advantageously with the hoodlock's protection against physical intrusion. [0134] In an alternative and less preferred class of embodiments, reserved addresses which are not loopback addresses can be used instead. In this case the TA can merely snoop communications, and grab packets which are directed to the particular reserved address(es) it recognizes. [0135] In another alternative and less preferred class of embodiments, addresses can used for TA interception which are not defined as "reserved" within the protocol. In this case the addresses assigned for TA interception must be ones which will not be the target of any legitimate address generated by application software. For example, when Network Address Translation is being used, it is possible to define the rules so that some otherwise-permissible IP addresses should not appear at some points within the network topology. In this case such addresses can be used to define a "hidden call" to a TA routine at a gateway or router. Here too the TA can merely snoop communications, and grab packets which are directed to the particular reserved address(es) it recognizes. [0136] In another alternative and less preferable class of embodiments, the TA can be used in high-speed networks, such as are used in computation clusters or server farms. Here too the disclosed architecture provides a simple way of adding an overlaid structure into an existing network interface architecture. However, in this environment the TA module should of course have a throughput which is high enough not to impose a bottleneck into the communications channel. [0137] Note that multiple different functions can optionally be assigned to different reserved (loopback) addresses: e.g. FTP, locking functions (dongles), secure email, https:, VPN (of whatever configuration) and others can each be assigned to its own loopback address. This allows multiple different routines to be called merely by specifying an appropriate TCP/IP reserved address, or alternatively different routines can each snoop data content of messages sent to some (but not all) of the reserved addresses. [0138] In one alternative class of embodiments, the TA module can include biometric identification functions. In such embodiments the processing performed by the TA module can be made dependent on various authentication components, such as voice recognition, face recognition, input from a portable electronic key, manual entry of a password or PIN, etc. The sensors and interfaces needed for fingerprint or retinal identification are not currently part of a normal personal computer, and the input for facial recognition is not on all computers, so a hardware security module which implements securitization with the TA interface can include dedicated sensor input connections, or even dedicated sensors. For added security these authentications can be combined with required GPS or time relations. [0139] The present application refers to the "TA module" where it is not necessary to specify whether the described functions are implemented in hardware or in software (or both). There are advantages to be gained in either case; an implementation with separate hardware has the potential to be more secure, but is more cumbersome to install. [0140] The disclosed inventions are believed to be particularly advantageous for wireless networks, which are inherently insecure. (Where the intended RF or IR interfaces have omnidirectional antennas, an eavesdropper's the antenna gain is a potential extra margin which can make the insecure area much larger than the useful area.) For similar reasons, the disclosed inventions can be particularly useful for WANs, where extensive signal routing outside the premises may be necessary. [0141] Typically the data sent out onto a network will have originated in a CPU, but in the present application this term is to be construed broadly to cover anything with computing capacity--e.g. a gate array, microcontroller, mainframe, etc. [0142] In one alternative embodiment the TA module can include dedicated routines and/or hardware for video and graphics decompression and buffering, to facilitate handling of streaming video. [0143] Where the disclosed TA is used with a multiprocessor computer, the CPU which is sending communications requests may not be the same one executing translation routines. [0144] References to digital data do not preclude later adaptation of the disclosed innovative teachings to analog or multi-bit data. [0145] One contemplated class of alternatives requires the router/firewall to have packet filtering capability. In this case the router can be programmed so that NO packets go out unless they include (or are preceded by) a signature from the TA. Where this degree of firewall blockade is available, it is not necessary to divert packet addresses coming out of the application; instead the TA can merely snoop outgoing traffic, and retransmit with authentication only packets of translated data, and packets which do not need to be translated. [0146] Additional general background, which helps to show the knowledge of those skilled in the art regarding the system context, and of variations and options for implementations, may be found in the following publications, all of which are hereby incorporated by reference: Mark Nelson, "The Data Compression Book" (2.ed.) (ISBN 1558514341); Gilbert Held, "Personal Computer File Compression" (ISBN 0442017731); Arturo Trujillo, "Translation Machines: Techniques for Machine (ISBN 1852330570); Tim Kientzle, "Internet File Formats" (ISBN 188357756X); Gunter Born, "The File Formats Handbook" (ISBN 1850321175); Bob Quinn and Dave Shute, "Windows Sockets Network Programming" (ISBN 0201633728); Peter Loshin, "Big Book of World Wide Web RFCs" (ISBN 0124558410); Ralph Droms, "DHCP (Dynamic Host Configuration Protocol)" (ISBN 1578701376); and Eric Hall, "Internet Core Protocols--The Definitive Guide" (ISBN 1565925726). [0147] None of the description in the present application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope: THE SCOPE OF PATENTED SUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED CLAIMS. Moreover, none of these claims are intended to invoke paragraph six of 35 USC section 112 unless the exact words "means for" are followed by a participle. Moreover, the claims filed with this application are intended to be as comprehensive as possible: EVERY novel and nonobvious disclosed invention is intended to be covered, and NO subject matter is being intentionally abandoned, disclaimed, or dedicated.

Abstract of the Disclosure An architecture in which data outputs from an application program into a communication interface are diverted, by changing their address to a reserved address, and then are processed further by an added program which is invisible to the application program.

FIELD OF THE INVENTION [0001] The present invention relates to a liposome having a sugar chain bonded to its membrane surface, preferably through a linker protein, and having excellent qualities in intestinal absorption, and to a liposome product comprising a drug or a gene encapsulated in the sugar-modified liposome. The liposome product may be used in preparations comprising medicinal drugs, cosmetics and other various products in the medical/pharmaceutical fields, and it is particularly useful in a therapeutic drug delivery system that specifically targets selected cells or tissues, such as cancer cells, and in the delivery of drugs or genes locally to a selected region, and in a diagnostic cell/tissue sensing probe. BACKGROUND OF THE INVENTION [0002] The realization of a “drug delivery system (DDS) for delivering drugs or genes intentionally and intensively to cancer cells or target tissues” has been set as one of the specific goals of the U.S. National Nanotechnology Initiative (NNI). The Nanotechnology/Materials Strategy of the Council for Science and Technology Policy in Japan also focuses research on “Medical micro systems/materials, Nanobiology for utilizing and controlling biological mechanisms,” and one of the five year R & D targets is “Establishment of basic seeds in health/life-lengthening technologies such as biodynamic materials and pinpoint treatments.” However, even in view of these goals the incidence and morbidity of cancers become higher year after year, along with a progressive aging of the population, and a serious need for the development of a targeting DDS material which is a novel treatment material exists. [0003] Targeting DDS nano-structured materials for other diseases also come under the spotlight because they have no side effects, and their market size of over 10 trillion yen is anticipated in the near future. Further, it is expected that these materials will be utilized in medical diagnosis as well as medical treatments. [0004] The therapeutic effect of a drug will be achieved only if the drug reaches a specific target region and acts thereupon. If the drug reaches a non-target region, undesirable side effects may result. Thus, the development of a drug delivery system that allows drugs to be used effectively and safely is also desired. In a drug delivery system, the targeting DDS can be defined as a concept of delivering a drug to a “necessary region in a body,” in a “necessary amount” and for a “necessary time-period.” A liposome is a noteworthy particulate carrier regarded as a representative material for a targeting DDS. While a passive targeting method based on modification of lipid type, composition ratio, size, or surface charge of liposomes has been developed to impart a targeting function to this particle, this method is still insufficient and required to be improved in many respects. [0005] An active targeting method has also been researched in an attempt to achieve a sophisticated targeting function. While the active targeting method referred to as a “missile drug” is conceptually ideal, it has not been accomplished in Japan and abroad, and future developments are expected. This method is designed to provide ligands bonded to the membrane surface of a liposome that will be specifically recognized and bound by a receptor residing on the cell-membrane surface of a target tissue, thereby achieving active targeting. The cell-membrane surface receptor ligands include antigens, antibodies, peptides, glycolipids, and glycoproteins. [0006] It is revealing that the sugar chain of glycolipids and glycoproteins bears an important role as an information molecules in various communications between cells, such as in the creation or morphogenesis of tissues, in the proliferation or differentiation of cells, in the biophylaxis or fecundation mechanism, and in the creation and metastasis of cancers. [0007] Further, research on various types of lectins (sugar-recognizing protein) such as selectin, siglec and galectin, which serve as receptors on cell-membrane surfaces of target tissues, has been proposed to serve as receptors for sugar chains having different molecular structures that may be used as noteworthy new DDS ligands (Yamazaki, N., Kojima, S., Bovin, N. V., Andre, S., Gabius, S. and H. -J. Gabius. Adv. Drug Delivery Rev. 43:225-244 (2000); Yamazaki, N., Jigami, Y., Gabius, H. -J., and S. Kojima. Trends in Glycoscience and Glycotechnology 13:319-329 (2001)). [0008] Liposomes having ligands bonded to their external membrane surface have been actively researched in order to provide a DDS material for delivering drugs or genes selectively to a target region, such as cancer. While these liposomes bind to target cells in vitro, most of them do not exhibit adequate targeting to intended target cells or tissues in vivo (Forssen, E. and M. Willis. Adv. Drug Delivery Rev. 29:249-271 (1998); Takahashi, T. and M. Hashida. Today's DDS/Drug Delivery System, Iyaku Journal Co., Ltd. (Osaka, Japan), 159-167 (1999)). While some research has been conducted on liposomes incorporating glycolipids having sugar chains, for use as a DDS material, these liposomes were evaluated only in vitro, and little progress has been reported for similar research on liposomes incorporating glycoproteins having sugar chains (DeFrees, S. A., Phillips, L., Guo, L. and S. Zalipsky. J. Am. Chem. Soc. 118:6101-6104 (1996); Spevak, W., Foxall, C., Charych, D. H., Dasqupta, F. and J. O. Nagy. J. Med. Chem. 39:1918-1020 (1996); Stahn, R., Schafer, H., Kernchen, F. and J. Schreiber. Glycobiology 8:311-319 (1998); Yamazaki, N., Jigami, Y., Gabius, H. -J., and S. Kojima. Trends in Glycoscience and Glycotechnology 13:319-329 (2001)). As above, systematic research into liposomes having a wide variety of sugar chains, on the glycolipids or glycoproteins bonded to the liposomes, including preparative methods and in vivo analyses thereof, is pending and represents an important challenge to be progressed in future. [0009] Further, in research on new types of DDS materials, it is an important challenge to develop a DDS material capable of being orally administered in the easiest and cheapest way. For example, when a peptide medicine is orally administered, it is subject to enzymolysis and may be only partially absorbed in the intestine due to its water solubility, high molecular weight, and low permeability in the mucosa of small intestine. As an alternative, a ligand-bonded liposome is getting attention as a potential DDS material for delivering high molecular-weight medicines or genes into the blood stream through the intestine (Lehr, C.-M. J. Controlled Release 65:19-29 (2000)). However, results from research into an intestinal absorption-controlled liposome, using a sugar chain as the ligand, have not been reported. SUMMARY OF THE INVENTION [0010] It is therefore an object of the present invention to provide a sugar-modified liposome that is specifically recognized and bound by selected lectins (sugar-recognizing proteins) residing on the surface of target cells and tissues, and having excellent qualities of absorption, particularly in the intestine. It is a further object of the present invention to provide a liposome product comprising a drug or gene encapsulated by a sugar-modified liposome that is recognized by cells or tissues in vivo, and that can specifically deliver drugs or genes to target cells or tissues. [0011] In order to meet the challenges mentioned above, various experimental tests and studies have been conducted on the properties of liposome surfaces, and on the sugar chains and linker proteins used to bond the sugar chains to the surface of liposomes. Through this research, it has been shown that the targeting performance of sugar-modified liposomes to particular target tissues can be controlled by the sugar chain structure. It has also been shown that the amount of liposome transferred to each target tissue can be increased by hydrating the liposome surface and/or the linker protein, resulting in more effective delivery of drugs or genes to each of the target cells or tissues. [0012] According to a first aspect of the present invention, there is provided a liposome having a sugar chain bonded to the liposome membrane surface. [0013] According to a second aspect of the present invention, there is provided a liposome having a sugar chain bonded to the liposome membrane surface, and further comprising tris (hydroxymethyl) aminomethane bonded to the liposome membrane surface. [0014] According to a third aspect of the present invention, there is provided a liposome having a sugar chain bonded to the liposome membrane surface through a linker protein. [0015] According to a fourth aspect of the present invention, there is provided a liposome having a sugar chain bonded to the liposome membrane surface through a linker protein, wherein both the liposome membrane surface and the linker protein are hydrophilized. [0016] According to a fifth aspect of the present invention, there is provided a liposome product comprising the sugar-modified liposome according to any one of the first to fourth aspects of the present invention, and a drug or gene encapsulated in the sugar-modified liposome. [0017] In each aspect of the present invention, the sugar chain is preferably selected from the group consisting of lactose disaccharide, 2′-fucosyllactose trisaccharide, difucosyllactose tetrasaccharide, 3-fucosyllactose trisaccharide, Lewis X trisaccharide, sialyl Lewis X tetrasaccharide, 3′-sialyllactosamine trisaccharide, and 6′-sialyllactosamine trisaccharide. [0018] In each aspect of the present invention, preferably an adjusted amount of the sugar chain is bonded to the membrane surface of the liposome. [0019] In each relevant aspect of the present invention, preferably the surface of the liposome and/or the linker protein is hydrophilized. Preferably, the hydrophilization is performed by using tris (hydroxymethyl) aminomethane. [0020] In each relevant aspect of the present invention, the linker protein is preferably human serum albumin or bovine serum albumin. BRIEF DESCRIPTION OF THE DRAWINGS [0021] [0021]FIG. 1 is a schematic diagram of a liposome modified by lactose disaccharide. [0022] [0022]FIG. 2 is a schematic diagram of a liposome modified by 2′-fucosyllactose trisaccharide. [0023] [0023]FIG. 3 is a schematic diagram of a liposome modified by difucosyllactose tetrasaccharide. [0024] [0024]FIG. 4 is a schematic diagram of a liposome modified by 3-fucosyllactose trisaccharide. [0025] [0025]FIG. 5 is a schematic diagram of a liposome modified by Lewis X trisaccharide. [0026] [0026]FIG. 6 is a schematic diagram of a liposome modified by sialyl Lewis X tetrasaccharide. [0027] [0027]FIG. 7 is a schematic diagram of a liposome modified by 3′-sialyllactosamine trisaccharide. [0028] [0028]FIG. 8 is a schematic diagram of a liposome modified by 6′-sialyllactosamine trisaccharide. [0029] [0029]FIG. 9 is a schematic diagram of a liposome modified by tris (hydroxymethyl) aminomethane, as a comparative sample. [0030] [0030]FIG. 10 is a diagram showing respective distribution rates in blood of 4 types of liposome complexes (including a TRIS comparative example), differing in the amount of lactose disaccharide bonded thereto, after 10 minutes from their intestinal administration. [0031] [0031]FIG. 11 is a diagram showing respective distribution rates in blood of 4 types of liposome complexes (including a TRIS comparative example), differing in the amount of 2′-fucosyllactose trisaccharide bonded thereto, after 10 minutes from their intestinal administration. [0032] [0032]FIG. 12 is a diagram showing respective distribution rates in blood of 4 types of liposome complexes (including a TRIS comparative example), differing in the amount of difucosyllactose tetrasaccharide bonded thereto, after 10 minutes from their intestinal administration. [0033] [0033]FIG. 13 is a diagram showing respective distribution rates in blood of 4 types of liposome complexes (including a TRIS comparative example), differing in the amount of 3-fucosyllactose trisaccharide bonded thereto, after 10 minutes from their intestinal administration. [0034] [0034]FIG. 14 is a diagram showing respective distribution rates in blood of 5 types of liposome (including a TRIS comparative example) complexes after 60 minutes from their intravenous administration. [0035] [0035]FIG. 15 is a diagram showing respective distribution rates in liver of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. [0036] [0036]FIG. 16 is a diagram showing respective distribution rates in spleen of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. [0037] [0037]FIG. 17 is a diagram showing respective distribution rates in lung of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. [0038] [0038]FIG. 18 is a diagram showing respective distribution rates in brain of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. [0039] [0039]FIG. 19 is a diagram showing respective distribution rates in cancer tissues of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. [0040] [0040]FIG. 20 is a diagram showing respective distribution rates in inflammatory tissues of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administrations. [0041] [0041]FIG. 21 is a diagram showing respective distribution rates in lymph node of 5 types of liposome complexes (including a TRIS comparative example) after 60 minutes from their intravenous administration. DETAILED DESCRIPTION OF THE INVENTION [0042] The present invention will now be described in detail. [0043] A liposome generally means a closed vesicle consisting of a lipid layer formed as a membrane-like aggregation, and an inner water layer. [0044] As shown in FIGS. 1 to 8 , a liposome of the present invention includes a liposome with a sugar chain covalently bonded to its membrane surface or its lipid layer through a linker protein such as human serum albumin. While only a single sugar chain-linker protein set, bonded to the liposome, is illustrated in FIGS. 1 to 8 , these figures (including FIG. 9) are schematic diagrams, and a number of sugar chain-linker protein sets are actually bonded to the liposome surface. [0045] The liposomes of the present invention are modified by a sugar chain. Preferred examples of the sugar chains include lactose disaccharide (Gal. beta. 1-4 Glc) shown in FIG. 1, 2′-fucosyllactose trisaccharide (Fuc. alpha.1-2 Gal. beta. 1-4 Glc) shown in FIG. 2, difucosyllactose tetrasaccharide (Fuc. alpha. 1-2 Gal. beta. 1-4 (Fuc. alpha. 1-3) Glc) shown in FIG. 3, 3-fucosyllactose trisaccharide (Gal. beta. 1-4(Fuc. alpha. 1-3) Glc) shown in FIG. 4, Lewis X trisaccharide (Gal. beta. 1-4 (Fuc. alpha. 1-3) GlcNAc) shown in FIG. 5, sialyl Lewis X tetrasaccharide (Neu5Ac. alpha. 2-3 Gal. beta. 1-4 (Fuc. alpha. 1-3) GlcNAc) shown in FIG. 6, 3′-sialyllactosamine trisaccharide (Neu5Ac. alpha. 2-3 Gal. beta. 1-4GlcNAc) shown in FIG. 7, and 6′-sialyllactosamine trisaccharide (Neu5Ac. alpha. 2-6 Gal. beta. 1-4 GlcNAc) shown in FIG. 8. [0046] In the present invention, it is preferred to bond the sugar chain to the membrane surface of the liposome through a linker protein. Such liposome structures are shown in FIGS. 1 to 8 , together with the chemical structures of the sugar chain. [0047] The linker protein may be an animal serum albumin, such as human serum albumin (HSA) or bovine serum albumin (BSA). In particular, it has been verified through experimental tests using mice that a liposome complex using human serum albumin is taken into target tissues in a greater amount than a liposome complex using a different linker protein. [0048] The lipid constituting the liposomes of the present invention includes phosphatidylcholines, phosphatidylethanolamines, phosphatidic acids, gangliosides, glycolipids, phosphatidylglycerols, and cholesterol. The phosphatidylcholines preferably include dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine. The phosphatidylethanolamines preferably include dimyristoylphosphatidylethanolamine, dipalmitoylphosphatidylethanolamine, and distearoylphosphatidylethanolamine. The phosphatidic acids preferably include dimyristoylphosphatidic acid, dipalmitoylphosphatidic acid, distearoylphosphatidic acid, and dicetylphosphoric acid. The gangliosides preferably include ganglioside GM1, ganglioside GD1a, and ganglioside GT1b. The glycolipids preferably include galactosylceramide, glucosylceramide, lactosylceramide, phosphatide, and globoside. The phosphatidylglycerols preferably include dimyristoylphosphatidylglycerol, dipalmitoylphosphatidylglycerol, and distearoylphosphatidylglycerol. [0049] While a regular liposome may be used in the invention, it is preferable to hydrophilize the surface of the liposome. [0050] The liposome itself can be produced through any conventional method including a thin film method, a reverse phase evaporation method, an ethanol injection method, and a dehydration-rehydration method. [0051] The particle size of the liposome can be controlled through an ultrasonic radiation method, an extrusion method, a French press method, a homogenization method or any other suitable conventional method. [0052] A specific method of producing the liposome itself of the present invention will be described below. For example, a mixed micelle is first prepared by mixing a compounded lipid consisting of phosphatidylcholines, cholesterol, phosphatidylethanolamines, phosphatidic acids, and gangliosides or glycolipids or phosphatidylglycerols, with sodium cholic acid serving as a surfactant. Particularly, the phosphatidylethanolamines are essentially compounded to provide a hydrophilic reaction site, and the composition of gangliosides or glycolipids or phosphatidylglycerols are essentially compounded to provide a bonding site for the linker protein. [0053] The obtained mixed micelle is subjected to ultrafiltration to prepare a liposome. Then, the membrane surface of the liposome is hydrophilized by applying a bivalent crosslinking reagent and tris (hydroxymethyl) aminomethane onto the lipid phosphatidylethanolamine of the membrane of the liposome. [0054] The liposome can be hydrophilized through a conventional method such as a method of producing a liposome by using phospholipids covalently bonded with polyethylene glycol, polyvinyl alcohol, maleic anhydride copolymer or the like (Japanese Patent Laid-Open Publication No. 2001-302686). However, in the present invention, it is particularly preferable to hydrophilize the liposome membrane surface by using tris (hydroxymethyl) aminomethane. [0055] The technique using tris (hydroxymethyl) aminomethane has some advantages superior to the conventional method of using polyethylene glycol or the like. For example, when a sugar chain is bonded onto a liposome and the molecular recognition function of the sugar chain is utilized for bringing about the targeting performance as in the present invention, the tris (hydroxymethyl) aminomethane is particularly preferable because it is a substance having a low molecular weight. More specifically, as compared to the conventional method using a substance having a high molecular weight such as polyethylene glycol, the tris (hydroxymethyl) aminomethane is less apt to become a three-dimensional obstacle to the sugar chain and to prevent the lectin (sugar-recognizing protein) on the membrane surface of target cells from recognizing the sugar-chain molecule. [0056] In addition, the liposome according to the present invention is excellent in terms of particle-size distribution, composition, and dispersing characteristics, as well as in long-term storage stability and in vivo stability, even after the above hydrophilization, and thereby is suitable for forming into and using as a liposome product. [0057] As an example of the process for forming of a liposome hydrophilized through the use of tris (hydroxymethyl) aminomethane, a bivalent reagent is added to a liposome solution. Exemplary bivalent reagents include bissulfosuccinimidylsuberate, disuccinimidylglutarate, dithiobissuccinimidylpropionate, disuccinimidylsuberate, 3,3′-dithiobissulfosuccinimidylpropionate, ethylene glycol bissuccinimidylsuccinate, or ethylene glycol bissulfosuccinimidylsuccinate. Exemplary lipids include dimyristoylphosphatidylethanolamine, dipalmitoylphosphatidylethanolamine, and distearoylphosphatidylethanolamine. Upon combination, a reaction between the bivalent reagent and the lipid occurs so as to bond the bivalent reagent to the lipid on the membrane of the liposome. Then, the tris (hydroxymethyl) aminomethane is reacted with the bivalent reagent to bond the tris (hydroxymethyl) aminomethane to the liposome surface. [0058] In the present invention, the sugar chain may be bonded to the liposome through a linker protein. The linker protein is first bonded to the liposome by first treating the liposome with an oxidant such as NaIO 4 , Pb(O 2 CCH 3 ) 4 , or NaBiO 3 to oxidize the gangliosides residing on the membrane surface of the liposome. The linker protein is then bonded to the gangliosides on the liposome membrane surface by a reductive amination reaction using a reagent such as NaBH 3 CN or NaBH 4 . [0059] Preferably, the linker protein is also hydrophilized by bonding a moiety having a hydroxy group to the linker protein. For example, tris (hydroxymethyl) aminomethane may be bonded to the linker protein on the liposome by using a bivalent reagent such as bissulfosuccinimidylsuberate, disuccinimidylglutarate, dithiobissuccinimidylpropionate, disuccinimidylsuberate, 3,3′-dithiobissulfosuccinimidylpropionate, ethylene glycol bissuccinimidylsuccinate, or ethylene glycol bissulfosuccinimidylsuccinate, as discussed above. [0060] One of the ends of a bivalent crosslinking reagent is bonded to the amino groups of the linker protein. Then, the reduction terminals of desired types of sugar chains are glycosylaminated to prepare a sugar-chain glycosylamine compound, and the amino groups of the obtained sugar chains are bonded to a part of the other unreacted ends of the bivalent crosslinking reagent bonded to the linker protein on the liposome. [0061] Then, the surface of the resulting linker protein which resides on the membrane surface of the liposome has the sugar chain bonded thereto and is hydrophilized by using the mostly remaining unreacted ends of the bivalent reagent to which no sugar chain is bonded. That is, a bonding reaction is caused between the unreacted ends of the bivalent reagent bonded to the linker protein on the liposome and tris (hydroxymethyl) aminomethane, so as to hydrophilize the liposome surface to obtain the liposome according to the present invention. [0062] The hydrophilization of the liposome surface and the linker protein provides enhanced mobility toward various tissues and enhanced sustainability in various tissues. This advantage is realized because the hydrophilized liposome surface and linker protein become hydrated by water molecules in vivo or in a blood vessel, which allows a portion of the liposome complex, other than the sugar chain, to function as if it is a layer of water which is not recognized by the various tissues. The liposome complex is thus not recognized by any tissues other than target tissues and only through the sugar chain is recognized by the lectin (sugar-recognizing protein) of the target tissues. [0063] As a next general step in the production of the sugar-modified liposomes of the present invention, the sugar chain is bonded to the linker protein on the liposome. For this purpose, the reduction terminal of the sugars constituting the sugar chain is, for example, glycosylaminated by using ammonium salts such as NH 4 HCO 3 or NH 2 COONH 4 , and then the linker protein bonded onto the liposome membrane surface is bonded to the above glycosylaminated sugars using a bivalent reagent such as bissulfosuccinimidylsuberate, disuccinimidylglutarate, dithiobissuccinimidylpropionate, disuccinimidylsuberate, 3,3′-dithiobissulfosuccinimidylpropionate, ethylene glycol bissuccinimidylsuccinate, or ethylene glycol bissulfosuccinimidylsuccinate to obtain the liposomes shown in FIGS. 1 - 8 . [0064] The sugar-modified liposomes of the present invention generally exhibit significantly high intestinal absorption. In addition, the intestinal absorption of the liposomes can be controlled by adjusting the density of the sugar chains bonded to the liposome, so that the liposome can more efficiently deliver drugs to target regions with reduced side effects. For example, FIGS. 10 to 13 show the results of studies performed to determine the rates of distribution (or intestinal absorption) of four different sugar-modified liposomes from intestine to blood, where the amount of sugar chain bonded to the respective liposomes is changed in three levels. [0065] In these experiments, the amount of sugar chain bonded to the respective liposomes is changed by bonding the sugar chain to the linker protein-bonded liposome at three density levels: (1) 50 μg, (2) 200 μg, and (3) 1 mg. As shown in the Figures, when lactose disaccharide is used as the sugar chain, the intestinal absorption is gradually lowered as the density of the sugar chain is increased. By contrast, when 2′-fucosyllactose trisaccharide or difucosyllactose tetrasaccharide is used as the sugar chain, the intestinal absorption is increased as the density of the sugar chain is increased. When 3-fucosyllactose trisaccharide is used as the sugar chain, the intestinal absorption is lowered and then increased as the density of the sugar chain is increased. [0066] These characteristics show that intestinal absorption is altered by the amount of sugar chain bonded to the liposome for each type of sugar chain. Thus, intestinal absorption can be controlled by appropriately selecting the amount and type of sugar chain bonded to the liposome. [0067] The results from additional experiments demonstrate that the type and amount of sugar chain bonded to the surface of the sugar-modified liposomes of the present invention can directly effect the targeting performance of the liposomes to particular target cells or tissues. The results of these experiments are shown in FIGS. 14 to 21 . [0068] For example, it is evident from the results that liposomes (LX, SLX, 3SLN, 6SLN) modified by four types of sugar chains: Lewis X trisaccharide, sialyl Lewis X tetrasaccaride, 3′-sialyllactosamine trisaccharide, and 6′-sialyllactosamine trisaccharide, generally have a high targeting performance to cancer tissues and inflammatory tissues (FIGS. 19 and 20). In particular, sialyl Lewis X tetrasaccaride modified liposomes (SLX) have a high targeting performance to liver, spleen, brain and lymph node (FIGS. 15, 16, 18 and 21 ), 3′-sialyllactosamine trisaccharide modified liposomes (3SLN) have a high targeting performance to blood, brain and cancer tissues (FIGS. 14, 18, and 19 ), and 6′-sialyllactosamine trisaccharide modified liposomes (6SLN) have a high targeting performance to blood and lung (FIG. 14 and 17 ). [0069] The liposome product obtained by encapsulating drugs or genes for therapeutic or diagnostic purposes, using the sugar-modified liposomes of the present invention, would also have a targeting performance selectively controlled by the amount and identity of the sugar chains bonded to the liposome. Thus, the liposome product of the present invention can be used to provide enhanced delivery of therapeutic drugs or diagnostic agents to target cells and tissues, as well as to suppress side effects by reducing the ability of drugs to be taken into non-target cells and tissues. [0070] Drugs, such as cancer drugs, or genes, such as those used in gene therapy, may be encapsulated in the sugar-modified liposomes of the present invention through any suitable conventional method including a method of forming the liposome by using a solution including the drugs or genes, and a lipid such as a phosphatidylcholines or phosphatidylethanolamines. [0071] Various examples of the present invention will be described below, but the invention is not limited thereto. EXAMPLE 1 Preparation of Liposomes [0072] Liposomes were prepared through an improved type of cholate dialysis based on a previously reported method (Yamazaki, N., Kodama, M. and H.-J. Gabius. Methods Enzymol. 242:56-65 (1994)). More specifically, 46.9 mg of sodium cholate was added to 45.6 mg of lipid mixture consisting of dipalmitoylphosphatidylcholine, cholesterol, dicetylphosphate, ganglioside and dipalmitoylphosphatidylethanolamine at a mole ratio of 35:40:5:15:5, respectively, and the lipid mixture was dissolved in 3 ml of chloroform/methanol solution. The solution was then evaporated, and the resulting deposit was dried in vacuo to obtain a lipid membrane. The obtained lipid membrane was suspended in 3 ml of a TAPS buffer solution (pH 8.4), and was subjected to a supersonic treatment to obtain a clear micelle suspension. Then, this micelle suspension was subjected to ultrafiltration by using a PM 10 membrane (Amicon Co., USA) and a PBS buffer solution (pH 7.2) to prepare 10 ml of a uniform liposome (average size of 100 nm). EXAMPLE 2 Hydrophilization of Lipid Membrane Surface of Liposomes [0073] 10 ml of the liposome solution prepared in Example 1 was subjected to ultrafiltration by using an XM 300 membrane (Amicon Co., USA) and a CBS buffer solution (pH 8.5) to adjust the pH of the solution to 8.5. Then, 10 mg of bis (sulfosuccinimidyl) suberate (BS3; Pierce Co., USA) crosslinking reagent was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night to complete the reaction between the BS3 and the dipalmitoylphosphatidyletanolamine of the lipid on the liposome membrane. This liposome solution was then subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5). Then, 40 mg of tris (hydroxymethyl) aminomethane dissolved in 1 ml of CMS buffer solution (pH 8.5) was added to 10 ml of the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and stirred at 7° C. for one night to complete the reaction between the BS3 bonded to the lipid on the liposome membrane and the tris (hydroxymethyl) aminomethane. In this manner, the hydroxyl groups of the tris (hydroxymethyl) aminomethane were coordinated on the dipalmitoylphosphatidyletanolamine of the lipid on the liposome membrane to achieve the hydrophilization of the lipid membrane surface of the liposome. EXAMPLE 3 Bonding of Human Serum Albumin (HSA) to Membrane Surface of Liposomes [0074] Human serum albumin (HSA) was bonded to the membrane surface of the liposome through a coupling reaction method based on a previously reported method (Yamazaki, N., Kodama, M. and H. -J. Gabius. Methods Enzymol. 242:56-65 (1994)). More specifically, the reaction was carried out through a two-stage reaction method. That is, 43 mg of sodium metaperiodate dissolved in 1 ml of TAPS buffer solution (pH 8.4) was added to 10 ml of the liposome obtained in Example 2, and the obtained solution was stirred at room temperature for 2 hours to periodate-oxidize the ganglioside on the membrane surface of the liposome. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 8.0) to obtain 10 ml of oxidized liposome. 20 mg of human serum albumin (HSA) was then added to the liposome solution, and the obtained solution was stirred at 25° C. for 2 hours. Then, 100 μl of 2M NaBH 3 CN was added to the PBS buffer solution (pH 8.0), and the obtained solution was stirred at 10° C. for one night to bond the HSA to the liposome membrane surface through a coupling reaction between the HSA and the ganglioside on the liposome. Then, 10 ml of HSA-bonded liposome solution was obtained through an ultrafiltration using an XM 300 membrane and a CBS buffer solution (pH 8.5). EXAMPLE 4 Bonding of Lactose Disaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0075] 50 μg, 200 μg, or 1 mg of lactose disaccharide (Wako Pure Chemical Co., Japan) was added to 0.5 ml of water solution having 0.25 g of NH 4 HCO 3 dissolved therein, and the obtained solution was stirred at 37° C. for 3 days. Then, the solution was filtered by using a filter of 0.45 μm to complete an amination reaction at the reduction terminal of the sugar chain and obtain 50 μg of glycosylamine compound of the lactose disaccharide. Then, 1 mg of 3,3′-dithiobis (sulfosuccinimidyl propionate) (DTSSP; Pierce Co., USA) serving as a crosslinking reagent was added to 1 ml of a part of the liposome solution obtained in Example 3. The obtained solution was then stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5) to obtain 1 ml of liposome in which the DTSSP was bonded to the HSA on the liposome. Then, 50 μg of the glycosylamine compound of the lactose disaccharide was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to bond the lactose disaccharide to the DTSSP on the human serum albumin bonded on the liposome membrane surface. In this manner, 3 types of liposomes (2 ml each), differing in the amount of sugar chain bonded thereto (referred to as LAC-1 (50 μg), LAC-2 (200 μg), and LAC-3 (1 mg)), in which lactose disaccharide is bonded to the liposome through human serum albumin (FIG. 1) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), were obtained. EXAMPLE 5 Bonding of 2′-Fucosyllactose Trisaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0076] 50 μg, 200 μg, or 1 mg of 2′-fucosyllactose trisaccharide (Wako Pure Chemical Co., Japan) was added to 0.5 ml of water solution having 0.25 g of NH 4 HCO 3 dissolved therein, and the obtained solution was stirred at 37° C. for 3 days. The solution was then filtered by using a filter of 0.45 μm to complete an amination reaction at the reduction terminal of the sugar chain and obtain 50 μg of glycosylamine compound of the 2′-fucosyllactose trisaccharide. Then, 1 mg of 3,3′-dithiobis(sulfosuccinimidyl propionate) (DTSSP; Pierce Co., USA) serving as a crosslinking reagent was added to 1 ml of a part of the liposome solution obtained in Example 3. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5) to obtain 1 ml of liposome in which the DTSSP was bonded to the HSA on the liposome. Then, 50 μg of the glycosylamine compound of the 2′-fucosyllactose trisaccharide was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to bond the 2′-fucosyllactose trisaccharide to the DTSSP on the human serum albumin bonded on the liposome membrane surface. In this manner, 3 types of liposomes (2 ml each), differing in the amount of sugar chain bonded thereto (referred to as 2FL-1 (50 μg), 2FL-2 (200 μg), and 2FL-3 (1 mg)), in which 2′-fucosyllactose trisaccharide is bonded to the liposome through human serum albumin (FIG. 2) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), were obtained. EXAMPLE 6 Bonding of Difucosyllactose Tetrasaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0077] 50 μg, 200 μg, or 1 mg of difucosyllactose tetrasaccharide (Wako Pure Chemical Co., Japan) was added to 0.5 ml of water solution having 0.25 g of NH 4 HCO 3 dissolved therein, and the obtained solution was stirred at 37° C. for 3 days. The solution was then filtered by using a filter of 0.45 μm to complete an amination reaction at the reduction terminal of the sugar chain to obtain 50 μg of glycosylamine compound of the difucosyllactose tetrasaccharide. Then, 1 mg of 3,3′-dithiobis(sulfosuccinimidyl propionate) (DTSSP; Pierce Co., USA) serving as a crosslinking reagent was added to 1 ml of a part of the liposome solution obtained in Example 3. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5) to obtain 1 ml of liposome in which the DTSSP was bonded to the HSA on the liposome. Then, 50 μg of the glycosylamine compound of the difucosyllactose tetrasaccharide was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to bond the difucosyllactose tetrasaccharide to the DTSSP on the human serum albumin bonded on the liposome membrane surface. In this manner, 3 types of liposomes (2 ml each), differing in the amount of sugar chain bonded thereto (referred to as DFL-1 (50 μg), DFL-2 (200 μg), and DFL-3 (1 mg)), in which difucosyllactose tetrasaccharide is bonded to the liposome through human serum albumin (FIG. 3) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), were obtained. EXAMPLE 7 Bonding of 3-Fucosyllactose Trisaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0078] 50 μg, 200 μg, or 1 mg of 3-fucosyllactose trisaccharide (Wako Pure Chemical Co., Japan) was added to 0.5 ml of water solution having 0.25 g of NH 4 HCO 3 dissolved therein, and the obtained solution was stirred at 37° C. for 3 days. The solution was then filtered by using a filter of 0.45 μm to complete an amination reaction at the reduction terminal of the sugar chain to obtain 50 μg of glycosylamine compound of 3-fucosyllactose' trisaccharide. Then, 1 mg of 3,3′-dithiobis (sulfosuccinimidyl propionate) (DTSSP; Pierce Co., USA) serving as a crosslinking reagent was added to 1 ml of a part of the liposome solution obtained in Example 3. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. The solution was subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5) to obtain 1 ml of liposomes in which the DTSSP was bonded to the HSA on the liposome. Then, 50 μg of the glycosylamine compound of the 3-fucosyllactose trisaccharide was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. The solution was then subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to bond the 3-fucosyllactose trisaccharide to the DTSSP on the human serum albumin bonded on the liposome membrane surface. In this manner, 3 types of liposomes (2 ml each), differing in the amount of sugar chain bonded thereto (referred to as 3FL-1 (50 μg), 3FL-2 (200 μg), and 3FL-3 (1 mg)), in which the 3-fucosyllactose trisaccharide is bonded to the liposome through human serum albumin (FIG. 4) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), were obtained. EXAMPLE 8 Bonding of Lewis X Trisaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0079] Liposomes comprising Lewis X Trisaccharide-bonded HSA on the liposome membrane surface were prepared according to the method of Example 4, with the exception that 50 μg of Lewis X trisaccharide (Calbiochem Co., USA) was used in place of the lactose disaccharide. 2 ml of the liposome (LX), in which Lewis X trisaccharide is bonded to the liposome through human serum albumin (FIG. 5) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), was obtained. EXAMPLE 9 Bonding of Sialyl Lewis X Tetrasaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0080] Liposomes comprising sialyl Lewis X tetrasaccaride-bonded HSA on the liposome membrane surface were prepared according to the method of Example 5, with the exception that 50 μg of sialyl Lewis X tetrasaccaride (Calbiochem Co., USA) was used in place of the 2′-fucosyllactose trisaccharide. 2 ml of the liposome (SLX), in which sialyl Lewis X tetrasaccaride is bonded to the liposome through human serum albumin (FIG. 6) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), was obtained. EXAMPLE 10 Bonding of 3′-Sialyllactosamine Trisaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0081] Liposomes comprising 3′-sialyllactosamine trisaccharide-bonded HSA on the liposome membrane surface were prepared according to the method of Example 6, with the exception that 50 μg of 3′-sialyllactosamine trisaccharide (Seikagakukogyou Co., Japan) was used in place of the difucosyllactose tetrasaccharide. 2 ml of the liposome (3SLN), in which 3′-sialyllactosamine trisaccharide is bonded to the liposome through human serum albumin (FIG. 7) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), was obtained. EXAMPLE 11 Bonding of 6′-Sialyllactosamine Trisaccharide to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0082] Liposomes comprising 6′-sialyllactosamine trisaccharide-bonded HSA on the liposome membrane surface were prepared according to the method of Example 7, with the exception that 50 μg of 6′-sialyllactosamine trisaccharide (Seikagakukogyou Co., Japan) was used in place of the 3-fucosyllactose trisaccharide. 2 ml of the liposome (6SLN), in which 6′-sialyllactosamine trisaccharide is bonded to the liposome through human serum albumin (FIG. 8) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm), was obtained. EXAMPLE 12 Bonding of Tris (Hydroxymethyl) Aminomethane to Human Serum Albumin (HSA) Bonded on Liposome Membrane Surfaces [0083] For preparing a liposome as a comparative sample, 1 mg of 3,3′-dithiobis (sulfosuccinimidyl propionate) (DTSSP; Pierce Co., USA) serving as a crosslinking reagent was added to 1 ml of a part of the liposome solution obtained in Example 3. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. The solution was then subjected to ultrafiltration by using an XM 300 membrane and a CBS buffer solution (pH 8.5) to obtain 1 ml of liposome in which the DTSSP was bonded to the HSA on the liposome. Then, 13 mg of tris (hydroxymethyl) aminomethane (Wako Co., Japan) was added to the liposome solution. The obtained solution was stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. Then, the solution was subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to bond the tris (hydroxymethyl) aminomethane to the DTSSP on the human serum albumin bonded on the liposome membrane surface. In this process, an excess amount of tris (hydroxymethyl) aminomethane, that is 13 mg, already exists. Thus, the hydrophilization of the human serum albumin (HSA) bonded on the liposome membrane surface was simultaneously completed. In this manner, 2 ml of the liposome as the comparative sample (TRIS) in which the tris (hydroxymethyl) aminomethane is bonded to human serum albumin (FIG. 9) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm) was obtained. EXAMPLE 13 Hydrophilization of Human Serum Albumin Bonded on Liposome Membrane Surfaces [0084] For the 16 types of sugar-modified liposomes prepared in Examples 4 to 11, the respective HSA protein surfaces were separately hydrophilized through the following process. 13 mg of tris (hydroxymethyl) aminomethane was added to each of the 16 types of sugar-modified liposomes (2 ml each). The respective obtained solutions were stirred at 25° C. for 2 hours, and subsequently stirred at 7° C. for one night. The solutions were then subjected to ultrafiltration by using an XM 300 membrane and a PBS buffer solution (pH 7.2) to remove unreacted materials. In this manner, 2 ml of final product for each of the 16 types of hydrophilized sugar-modified liposome complexes (LAC-1, LAC-2, LAC-3, 2FL-1, 2FL-2, 2FL-3, DFL-1, DFL-2, DFL-3, 3FL-1, 3FL-2, 3FL-3, LX, SLX, 3SLN and 6SLN) (total lipid mass: 2 mg, total protein mass: 200 μg, average particle size: 100 nm) were obtained. EXAMPLE 14 Measurement of Lectin-Binding Activity Inhibiting Effect in Each Type of Sugar-Modified Liposome Complex [0085] The in vitro lectin-binding activity of each of the 16 types of hydrophilized sugar-modified liposomes prepared in Example 13 was measured through an inhibition test using a lectin-immobilized microplate by methods known in the art (see, e.g., Yamazaki, N., et al., Drug Delivery System, 14:498-505 (1999)). More specifically, a lectin (E-selectin; R&D Systems Co., USA) was immobilized on a 96 well-microplate. Then, 0.1 μg of biotinylated and fucosylated fetuin as a comparative ligand, and various types of sugar-modified liposome complexes having different densities (each including 0.01 μg, 0.04 μg, 0.11 μg, 0.33 μg or 1 μg of protein), were placed on the lectin-immobilized plate, and incubated at 4° C. for 2 hours. After washing with PBS (pH 7.2) three times, horseradish peroxidase (HRPO)-conjugated streptavidin was added to each of the wells. The respective test solutions were incubated at 4° C. for 1 hour, and then washed with PBS (pH 7.2) three times. Then, peroxidase substrates were added to the test solutions, and incubated at room temperature. Then, the absorbance at 405 nm of each of the test solutions was determined by a microplate reader (Molecular Devices Corp., USA). For the biotinylation of the fucosylated fetuin, each of the test solutions was subject to a sulfo-NHS-biotin reagent (Pierce Chemical Co., USA) treatment and refined by using a Centricon-30 (Amicon Co., USA). HRPO-conjugated streptavidin was prepared by oxidizing HRPO and bonding streptavidin to the oxidized HRPO through a reductive amination method using NaBH 3 CN. This measurement result is shown in Table 1. TABLE 1 Test Result showing Lectin-Binding Activity Inhibiting Effect of Each Type of Sugar-Modified Liposome Complex Inhibiting Effect (absorbance) at each density Liposome of liposome complexes (μg protein) Complex 0.01 μg 0.04 μg 0.11 μg 0.33 μg 1 μg LAC-1 0.115 0.114 0.112 0.112 0.105 LAC-2 0.112 0.109 0.104 0.104 0.097 LAC-3 0.119 0.118 0.112 0.109 0.108 2FL-1 0.121 0.115 0.106 0.097 0.067 2FL-2 0.131 0.119 0.116 0.111 0.079 2FL-3 0.149 0.133 0.122 0.104 0.073 DFL-1 0.167 0.158 0.146 0.131 0.108 DFL-2 0.136 0.134 0.133 0.120 0.106 DFL-3 0.163 0.150 0.134 0.118 0.097 3FL-1 0.138 0.131 0.121 0.113 0.085 2FL-2 0.148 0.134 0.128 0.123 0.092 3FL-3 0.149 0.134 0.129 0.128 0.110 LX 0.199 0.195 0.195 0.195 0.129 SLX 0.105 0.100 0.100 0.084 0.073 2SLN 0.175 0.158 0.144 0.131 0.095 3SLN 0.256 0.245 0.233 0.200 0.151 EXAMPLE 15 125 I-Labeling of Each Type of Sugar-Modified Liposome through the Chloramine T Method [0086] A chloramine T (Wako Pure Chemical Co., Japan) solution and a sodium disulfite solution were prepared at 3 mg/ml and 5 mg/ml, respectively. 50 μl of the 16 different types of hydrophilized sugar-modified liposomes prepared in Example 13, and the liposome of Example 12, were put into separate Eppendorf tubes. Then, 15 μl of 125 I-NaI (NEN Life Science Product, Inc. USA) and 10 μl of chloramine T solution were added thereto and reacted therewith. 10 μl of chloramine T solution was added to the respective solutions every 5 minutes. After 15 minutes from the completion of the above procedure repeated twice, 100 μl of sodium disulfite serving as a reducer was added to the solutions to stop the reaction. Then, each of the resulting solutions was placed on a Sephadex G-50 (Phramacia Biotech. Sweden) column chromatography, and eluted by PBS to purify a labeled compound. Finally, a non-labeled liposome complex was added to each of the solutions to adjust a specific activity (4×10 6 Bq/mg protein). In this manner, 16 types of 125 I-labeled liposome solutions were obtained. EXAMPLE 16 Measurement of Transfer Rate of Each Type of Sugar-Modified Liposome Complex to Tissues of Mice with Cancer [0087] Using an oral sonde, 13 of the different types of 125 I-labeled, hydrophilized sugar-modified liposomes of Example 15 (LAC-1, LAC-2, LAC-3, 2FL-1, 2FL-2, 2FL-3, DFL-1, DFL-2, DFL-3, 3FL-1, 3FL-2, 3FL-3 and TRIS) (equivalent to 3 μg of protein per mouse) were administered to male ddY mice (7 weeks of age) which had abstained from food, except for water, for one whole day, in an amount of 0.2 ml which is equivalent to 3 μg of protein per mouse. After 10 minutes, 1 ml of blood was taken from descending aorta under Nembutal anesthesia. Then, 125 I-radioactivity in the blood was measured with a gamma counter (Aloka ARC 300). Further, in order to check the in vivo stability of each type of liposome complex, serum from each mouse's blood was subjected to chromatography using a Sephadex G-50. As a result, most of the radioactivity in each sample of serum was found in void fractions having a high molecular weight, and it was proved that each type of liposome complexes has a high in vivo stability. The radioactivity transfer rate from intestine to blood was represented by the ratio of the radioactivity per ml of blood to the total of given radioactivity (% dose/ml blood). This measurement result is shown in FIGS. 10 to 13 . EXAMPLE 17 Measurement of Distribution Rate of Each Type of Sugar-Modified Liposome Complex to Tissues of Mice with Cancer [0088] Ehrlich ascites tumor (EAT) cells (about 2×10 7 cells) were implanted subcutaneously into the femoral region in male ddY mice (7 weeks of age), and the mice were used in this test after the tumor tissues grew to 0.3 to 0.6 g (after 6 to 8 days). Five of the different types of 125 I-labeled, hydrophilized sugar-modified liposome complexes (LX, SLX, 3SLN, 6SLN and TRIS) of Example 15 were injected into the tail veins of the mice in an amount of 0.2 ml which is equivalent to 3 μg of protein per mouse. After 60 minutes, tissues (blood, liver, spleen, lung, brain, inflammatory tissues around cancer, cancer and lymph node) were extracted, and the radioactivity of each of the extracted tissues was measured with a gamma counter (Aloka ARC 300). The distribution rate of the radioactivity in each of the tissues was represented by a ratio of the radioactivity per gram of each of the tissues to the total of given radioactivity (% dose/g tissue). This measurement result is shown in FIGS. 14 to 21 . [0089] The results from these experiments show that the sugar-modified liposomes of the present invention are innovative in that they are excellent in intestinal absorption and are capable of being administered via the intestine, which has not been found in conventional liposome related products. In addition, the intestinal absorption can be controlled by adjusting the identity and amount of the sugar chain bonded to the liposomes. [0090] Furthermore, the in vivo mobility of sugar-modified liposomes of the present invention, and their ability to target selected tissues in vivo, can be facilitated or suppressed in a living body by utilizing the difference in the molecular structure of the sugar chain, and varying their amounts. [0091] Thus, the sugar-modified liposomes of the present invention can be used to deliver drugs or genes through the intestine efficiently and safely without any side effects. They may also be used as an effective delivery mechanism for selectively delivering drugs or genes to target tissues such as blood, liver, spleen, lung, brain, cancer tissues, inflammatory tissue, or lymph node, and can be used in DDS materials in light of their enhanced mobility. Thus, the liposomes of the present invention are useful particularly in the medical and pharmaceutical fields.

The present invention provides a sugar-modified liposome having a sugar chain bonded to its membrane surface, preferably through a linker protein, and having excellent absorption qualities, particularly in the intestine. The molecular structure and quantity of the sugar chain is selectively varied to allow the liposome to be delivered in a targeted manner to selected cells and tissues. The liposome is applicable to medicinal drugs, cosmetics and other various products in the medical/pharmaceutical fields, and it is especially useful in a therapeutic drug delivery system that recognizes target cells and tissues, such as cancer cells, and in the delivery of drugs or genes locally to a selected region, or in a diagnostic cell/tissue sensing probe.

BACKGROUND AND SUMMARY The present invention relates to the field of computer systems. More particularly, the invention relates to a method and system for database optimization. A “query” is a statement or collection of statements that is used to access a database. Specialized query languages, such as the structured query language (“SQL”) are often used to interrogate and access a database. Many types of queries include at least the following. First, the identity of the database object(s) being accessed to execute the query (e.g., one or more named database tables). If the query accesses two or more database objects, what is the link between the objects (e.g., a join condition or column). The typical query also defines selection criteria, which is often referred to as a matching condition, filter, or predicate. Lastly, a query may define which fields in the database object are to be displayed or printed in the result. Optimization is the process of choosing an efficient way to execute a query statement. Many different ways are often available to execute a query, e.g., by varying the order or procedure in which database objects and indexes are accessed to execute the query. The exact execution plan or access path that is employed to execute the query can greatly affect how quickly or efficiently the query statement executes. Cost-based optimization is an approach in which the execution plan is selected by considering available access paths to determine the lowest cost approach to executing the query. In one approach, cost-based optimization consists of the following steps: (1) generating a set of potential execution plans for the database statement to be executed; (2) estimating the cost for each execution plan; and (3) comparing the costs of the execution plans to identify the execution plan having the lowest cost. Conceptually, the term “cost” relates to the amount of a given resource or set of resources needed to process an execution plan. Examples of such resources include I/O, CPU time, and memory. Various measures may be used to identify the execution plan having the lowest cost. For example, the cost-based approach may be used to identify the execution plan providing either the best throughput or the best response time. Many database optimizers use statistics to calculate the “selectivity” of predicates and to estimate the cost of performing database operations. Statistics quantify characteristics of database and schema objects, such as the data distribution and storage characteristics of tables, columns, indexes, and partitions. Selectivity refers to the proportion or fraction of a database object corresponding to a query predicate. An optimizer uses the selectivity of a predicate to estimate the cost of a particular access method and to determine optimal join order. Statistics should be gathered on a regular basis to provide the optimizer with needed information about schema objects. Significant costs may be incurred to collect and maintain statistics for database objects. To reduce this collection cost and improve performance, many database systems use data sampling to reduce the amount of data that must be collected to provide statistics used by the optimizer. With data sampling, only a portion of the rows within a database table is accessed to generate a set of statistics for the entire table or column. The results of the data sampling is thereafter scaled upward to extrapolate the statistics values for the entire population. However, different data distributions may require different sample sizes in order to obtain accurate statistics. If a too-small sample size is selected, then the statistics may be inaccurate, which could lead to sub-optimal execution plans and poor query performance. If a too-large sample size is selected, then resources are wasted to collect more data than is needed to provide accurate statistics. Consequently, it is desirable to use only the minimal sample size needed for accurate statistics collection. In addition to statistics, optimizers often use data value histograms to select an optimal execution plan. A data value histogram is a structure that provides estimates of the distribution of data values in a database object. A histogram partitions the data object values in a set of individual “buckets”, so that all values corresponding to a given range fall within the same histogram bucket. The histogram provides information that is helpful in determining the selectivity of a predicate that appears in a query. In a height-balanced histogram, each bucket of the histogram corresponds to an equal number of rows in a table. The boundaries of the buckets shrink or grow so that all buckets maintain the same number of entries. The useful information provided by the histogram is the range of values that corresponds to each bucket, e.g., the endpoints for each bucket of the histogram. Consider a column C with values between 1 and 100 in which the column data is uniformly distributed. FIG. 1 a shows a height-balanced histogram plotted for this column having ten buckets. The number of rows in each bucket of the histogram is one-tenth the total number of rows in the table. Since the data values are evenly distributed, the endpoints of the buckets are also evenly spaced. Now consider a second column having 100 rows for which column data values are not evenly spaced, in which ninety rows contain the value “1” and the other ten rows contain a column value between 2 and 100. FIG. 1 b shows this column plotted in a height balanced histogram of ten buckets. Since ninety percent of the rows have the value “1”, nine of the ten buckets in the histogram of FIG. 1 b also correspond to the value “1”. Thus, it can be seen that nine of the ten buckets in the histogram of FIG. 1 b have endpoints that end in the number “1”. The last bucket corresponds to the ten rows in the column having data values between “2” and “100”. In operation, such a histogram provides an optimizer with instant knowledge of the selectivity of particular values of a column. This selectivity information can be used, for example, to determine whether either a full table scan or an index access provides the most efficient path to satisfying a query against the database table corresponding to the histogram. Other types of histograms also exist. For example, another histogram used by optimizers is the width-balanced histogram, in which column data is divided into a number of fixed, equal-width ranges and the histogram is organized to count the number of values falling within each range. A histogram may not always provide an appreciable benefit. For example, a histogram may not be useful for a data set having uniform data distribution, since it can be assumed that all data within that set are equally distributed and therefore the histogram will not provide any additional useful information. If a histogram is desired, a significant amount of resources may be needed to collect, maintain, and use histograms. Therefore, it makes sense to only create, store, and/or use a histogram when such a histogram provides benefits greater than the expense of the histogram. However, conventional database systems typically rely upon the skill and knowledge of individual database administrators to manually decide whether histograms should or should not be collected for columns in the database. While guidelines may be provided to assist this decision-making, this manual process by administrators often leads to inconsistent and erroneous decisions resulting in the collection and storage of unneeded histograms, or the failure to collect histograms that could provide more efficient query processing. The present invention provides a method and system for determining when to collect histograms. In an embodiment, the invention provides a mechanism for automatically deciding when to collect histograms upon request from the user. This decision is based on the columns the user is interested in, the role these columns play in the queries as submitted to the system, and the underlying distribution for these columns, e.g., as seen in a random sample. The user specifies which columns are of interest, and the database is configured to collect column usage information that describes how each column is being used in the workload. This column usage information could be stored in memory and periodically flushed to disk. Given a set of potential columns, the distribution of those columns is viewed in combination with the usage information to determine which columns should have histograms. The invention also provides a system and method for determining an adequate sample size for statistics collection. In one embodiment, the invention provides a mechanism for automatically determining an adequate sample size for both statistics and histograms. This is accomplished via an iterative approach where the process starts with a small sample, and for each attribute which may need more data, the sample size is increased while restricting the information collected to only those attributes that require the larger sample. Further details of aspects, objects, and advantages of the invention are described below in the detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of the invention and, together with the Detailed Description, serve to explain the principles of the invention. FIGS. 1 a and 1 b show example histograms. FIG. 2 shows a flowchart of a process for determining sample size for statistics collection according to an embodiment of the invention. FIG. 3 shows a flowchart of a process for histogram determination according to an embodiment of the invention. FIG. 4 shows a flowchart of an alternate process for histogram determination according to an embodiment of the invention. FIGS. 5 and 6 are diagrams of system architectures with which the present invention may be implemented. DETAILED DESCRIPTION The invention is described with reference to specific embodiments. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The reader is to understand that the specific ordering and combination of process actions shown in the process flow diagrams and system components in component diagrams described herein are merely illustrative, and the invention can be performed using different, additional, or different combinations/ordering of process actions and components. For example, the invention is particularly illustrated herein with reference to specific database objects such as tables, columns, and rows, but it is noted that the inventive principles are equally applicable to other types of database objects. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. FIG. 2 shows a flowchart of a process for determining sample sizes for statistics collection, according to an embodiment of the invention. At step 200 , an initial sample size is selected for statistics collection. In an embodiment, the selected sample size could be expressed as a percentage of the rows in a table. Other measures could be used to express sample size, such as an exact number of rows for the table. At step 202 , rows in the table are identified based upon the initially selected sample size. In an embodiment, this is accomplished by attempting to select the number of rows in the table corresponding to the percentage value used to express the initially selected sample size. For example, consider if the initially selected sample size is 20% and the number of rows in the table is 1000. For this example, the expected number of rows to be identified in step 202 is (1000)*(0.20)=200 rows. One way to achieve this is to provide a function (e.g., a “sample( )” function) that chooses rows from the table based upon the selected percentage value, in which each row is individually faced with a given percentage chance of being selected. If the sampling percentage is 20%, then each row in the column individually faces a 20% chance of being selected. In this manner, over the entire table, it is likely that approximately 20% of the rows in the table will be selected. The exact rows to be selected will be subject to a certain amount of randomization, and it is possible that the exact number of rows actually selected will be greater or smaller than 20%. The statistics gathered based upon this sampling can later be used to extrapolate statistics for the entire table. At step 204 , a determination is made regarding whether the number of sample rows identified in step 202 is adequate. In an embodiment, this step is performed by determining whether statistics for the identified rows using the initial sample size can be adequately scaled upward to extrapolate accurate statistics for the entire table. One approach to accomplishing this is to compare the selected number of rows with a minimum value for the particular statistics for which sampling is performed. For example, consider if the statistic being addressed by the sampling is the “Number of Rows in Table.” A minimum value, such as “2500” can be established for this type of statistic. If the identified number of rows from step 202 is less than 2500 rows, then the sample size or sample percentage is increased ( 208 ), and steps 202 and 204 are repeated until the minimum sample size is achieved. If the number of rows identified in step 202 meets or exceeds the minimum value, then the sample size is adequate ( 206 ). It is noted that different statistics may require differing tests to determine whether rows sampled during step 202 can be adequately scaled upward to provide statistics for the entire table. The following are additional examples of statistics used for database optimizers: 1) average column length; 2) number of distinct values in column; 3) minimum value in column; and 4) maximum value in column. For the average length, minimum, and maximum statistics, the number of rows sampled during step 202 can be compared to another minimum value, e.g., “919”, to determine whether the sample size is adequate. FIG. 4 is a flowchart of a process for determining whether a histogram should be collected or saved according to an embodiment of the invention. At step 402 , column usage is tracked during workloads executed against a table. In an embodiment, this is accomplished by marking individual columns while executing queries against those columns. A recordation is made regarding the type of predicate that is evaluated against a column. For example, this type of recordation tracks whether, and how often, an equality, range or like predicate is evaluated against a column. At step 404 , a determination is made whether data skew exists for the column values. The predicate type for a particular column and the data skew within that column are analyzed to determine whether a histogram should be collected for the column ( 406 ). In an embodiment, if equality and/or equijoin predicates are evaluated against a column and the column data exhibits non-uniform value repetition, then a histogram should be collected and/or saved for the column. If like or range predicates are evaluated against a column and the column data exhibits non-uniformity in range, then a histogram should be collected and/or saved. The meaning of “non-uniform value repetition” and “non-uniformity in range” is defined below according to one embodiment of the invention. Instead of, or in addition to, the process of FIG. 4, the process shown in FIG. 3 can be used to determine whether a histogram should be collected or saved for a table column. If data sampling is being performed, then a determination is made at step 300 whether the sample size is adequate. If not, then the sampling rate is adjusted upward to collect an adequate sample size. In one embodiment, if the number of non-null column values in the sample is less than 2500, then the sample rate is increased to provide more samples. At step 302 , a determination is made regarding the expected number of buckets for the histogram. At step 304 , data uniformity/range skew is evaluated for the data sample values with respect to the expected histogram buckets. In an embodiment, this is accomplished by gathering frequency and histogram information for the column values. For example, a simple query can be executed to collect distinct values and their counts for a column. At step 306 , a determination is made whether the column values are uniform. In an embodiment, this determination checks whether any values repeat more than other values in the column, or whether there are any range skews in the data. If so, then the data is non-uniform. If the data is non-uniform, then a histogram is collected for the column ( 310 ). If the column data is uniform then the values in the column are considered to be equally distributed; therefore, either no histogram is collected or a previously collected histogram is not saved/used ( 308 ). Illustrative Embodiment The present section describes pseudocode to implement an illustrative embodiment of the invention. Initially, the illustrative embodiment begins by building an array of columns needing statistics. Then, the illustrative process primes data structure bits that represent which statistics need to be gathered for which columns. The process may re-invoke this procedure when auto-increasing the sample size to re-set the still necessary bits for statistics requiring an increased sample size. The process creates a list of query statements needed to gather all statistics—this “select” list may be reused across all partitions and subpartitions. These queries are executed to gather statistics for every table/partition object requested. Finally, the illustrative procedure sets the gathered statistics in a data dictionary. The sample size used while gathering statistics is automatically adjusted during the procedure to ensure adequate sample size for the particular statistics being collected. The following comprises high-level pseudocode for the illustrative embodiment: if auto sample size do a quick row count estimate of the object initialize all of the statistics bits for the columns while there are still unresolved statistics generate the from clause for the query execute the basic query work on all of the desired histograms evaluate the basic statistics if some statistics are not ready (need larger sample size) construct a new select list using the current statistics bits The following table defines variables used in the illustrative pseudocode. TABLE 1 Term Definition p Sampling fraction (between 0.0 and 1.0) n Number of rows in the table avg Average column length statistic min/max Minimum/maximum column value statistic nv Number of null column values statistic ndv Number of distinct values statistic s Number of rows seen in the sample snnv Number of non-null column values seen in the sample sndv Number of distinct values seen in the sample mnb Maximum number of buckets allowed in the histogram The following is pseudocode for the top level routine for gathering statistics and for determining whether a histogram should be collected: estimate n—use block sample count(*) on user's table initialize_gather_bits( ) while (some statistics still need to be (re)collected) generate_from_clause( )—includes possible materialization of new table execute_basic( ) execute_hist( ) evaluate_basic( ) This top level pseudocode executes the main functions that comprise the statistics gathering processes according to one embodiment of the invention. The initialize_gather_bits( ) function is a procedure which takes in the array of columns for which statistics need to be collected and sets bits representing which statistics are needed. These bits are later individually cleared after gathering statistics and evaluating their probable accuracy. The function is called initially so that the select list can be generated from it for all objects. It is later called again to reset the bits for each new object (e.g., table/partition/subpartition). The process takes in the list of columns (including statistics bits) and creates a select list to be used to gather basic statistics (not including histograms). In an embodiment, the process ensures that the select list does not contain more functions than the server can handle at once, e.g., only 256 distinct aggregates. If it cannot fit them all in one statement, the caller is informed of which columns are included. The generate_from_clause( ) function has the responsibility of generating the FROM clause for the basic query and all the histogram queries. In one embodiment, each histogram uses a separate query, and therefore employs a separate scan of the data. If many scans are required and involve sampling the underlying table, it may be beneficial to materialize the sample once and then pass over that multiple times. If that is the case, this procedure in one embodiment will generate a temporary table and populate it with a sample. The execute_basic( ) function handles the basic statistics query to parse, execute, and fetch information from the database objects. In an embodiment, the query is generated earlier in the process and the column array provides sufficient information to infer the select list. The evaluate_basic( ) procedure looks at the fetched basic statistics and tries to scale them up. This procedure clears the bits for all statistics that are acceptably scaled, and suggests a larger sampling percentage if some statistics need to be recollected. The execute_hist( ) procedure is the driver for collecting and evaluating the histogram statistics. This function looks over all columns that are marked as possibly needing histograms. It then collects a frequency histogram, a height histogram, or both, depending upon the expected number of distinct values and the requested number of buckets. The following comprises pseudocode for an embodiment of the initialize_gather_bits( ) function, in which the following statistics are collected: nv, ndv, min, max, and avg. for each column the user requested mark a bit to indicate need to collect the following statistics: nv, ndv, min, max, avg if there is a need to collect a histogram (see results of FIG. 4) mark a bit indicating this The following comprises pseudocode for an embodiment of the generate_from_clause( ) function, which establishes the initial sampling fraction p for the statistics gathering process: if first time, set p to 5500/n—try for 5500 rows otherwise, p is passed in to this function if ((p<=0) or (p>=0.15)) set p to 1.0—don't sample if p<1.0 and there are multiple passes (due to histograms) materialize the sample in another table and use that table instead In the illustrative embodiment, the process attempts to collect 5500 rows. To accomplish this, it is useful to know in advance the number of rows in the table. Based upon the number of rows, the sampling fraction p is established as shown in the pseudocode. If the number of rows is not known, then estimate this value. Certain thresholds can be established for the sampling fraction, beyond which the sampling fraction is set to 1. Under certain circumstances, it may make sense to create another table to hold the sampled data from the column. For example, if multiple passes are needed, e.g., because histograms are to be collected, then the samples are materialized into a table to prevent repeated accesses to the larger base table. The execute_basic( ) function builds up one or more queries to retrieve sampled data and calculates the desired statistics (excluding histograms in an embodiment). The one or more queries are then executed to retrieve the results for evaluation, as set forth below. In an embodiment, the one or more queries samples rows from the table based upon the sampling fraction p that was previously established. The evaluate_basic( ) function determines whether the number of rows sampled according to the sampling fraction p can be adequately scaled upward for the entire table. The following comprises pseudocode for an embodiment of the evaluate_basic( ) function: if(p<1.0) if(s<2500)—too small a sample bump up p accordingly n=s/p for each column clear all non-histogram bits that indicate which statistics to collect if nv bit was set nv=n−snnv/p if (avg, min, or max bit was set) and (snnv<919) bump up p accordingly set avg, min, and max bits again for next pass if ndv bit was set try to scale it up * if cannot scale upward  bump up p accordingly  set ndv again for next pass else—this was not an estimate set all requested statistics The pseudocode first checks that at least 2500 rows were sampled based upon the current sampling fraction (p). If not, then the sampling fraction is adjusted upward and the table is re-sampled. If a sufficient number of rows has been collected, then the number of rows (n) is estimated based upon the following: n=s/p, where s represents the number of rows that have been collected. For the average length, minimum, and maximum column value statistics (avg, min, max), the pseudocode checks that at least 919 non-null column values (snnv) are detected in the sample. If so, then these values are considered adequate for the entire table. If not, then the sampling fraction p is increased for the next pass through the table. For the number of distinct values statistic (ndv), the pseudocode attempts to scale this statistic up for the entire table. If the statistic based upon the sampled rows cannot be scaled upward, then the sampling fraction is increased for the next pass through the table. The following comprises pseudocode for scaling ndv and density (defined below) statistics according to an embodiment of the invention: sdiv:=sndv/snnv if ((snnv<100) or ((snnv>=100) and (snnv<500) and (sdiv>0.3299)) or ((snnv>=500) and (snnv<1000) and (sdiv>0.4977)) or ((snnv>=1000) and (snnv<2000) and (sdiv>0.5817)) or ((snnv>=2000) and (snnv<5000) and (sdiv>0.6634)) or ((snnv>=5000) and (snnv<10000) and (sdiv>0.7584)) or ((snnv>=10000) and (snnv<1000000) and (sdiv>0.8169)) or ((snnv>=1000000) and (sdiv>0.9784))) cannot reliable use kkesdv to scale the value else can use kkesdv scaling reliably nnv:=snnv/p if ((sndv=snnv) and ((snnv>=29472) or ((nnv<10000) and (snnv>=708)) or ((nnv<40000) and (snnv>=1813)) or ((nnv<160000) and (snnv>=4596)) or ((nnv<640000) and (snnv>=11664)))) then can use linear scaling reliably—ndv:=sndv*1/p else cannot reliably use linear scaling to scale the value The following comprises pseudocode for an embodiment of the kkesdr scaling function: x 1 :=sndv x 2 :=nnv stay_loop:=true while (stay_loop and (x 1 <=x 2 ) x:=floor((x 2 +x 1 )/2) y 2 :=x*(1−power(1−(1/x), snnv)) if (sndv<y 2 ) x 2 :=x−1 elseif (sndv>y 2 ) x 1 :=x+1 else stay_loop:=false ndv:=x The execute_hist( ) function determines whether a histogram should be collected. The following comprises pseudocode for an embodiment of the execute_hist( ) function: for each column with the histogram bit set if ((p<1.0) and (snnv<2500)) not enough data—bump up p for next pass accordingly else if # buckets specified via an integer or repeat set mnb to that value else set mnb to min(75,(max(200, snnv/26))) estimate the ndv based on prior information if available if (estimated ndv<(mnb*0.75))—probably a frequency histogram execute_frequency( ) if still need to collect histogram execute_height( ) As before, the pseudocode checks whether 2500 rows have been collected during the sampling process. If not, then the sampling fraction (p) is increased for the next pass through the table. The maximum number of buckets (mnb) is set as shown in the pseudocode. The number of distinct values (ndv) is estimated, possibly based upon a previous pass through the table and the prior execution of the evaluate_basic( ) function. If it is desired to collect a histogram and the estimated ndv value is below a given threshold (mnb*0.75), then a frequency histogram is generated in an embodiment. A frequency histogram is often appropriate for a column having a small number of distinct values. In a frequency histogram, the endpoints of multiple buckets have the same endpoint value (because the same value entry is in multiple buckets). For this reason, buckets having the same endpoint values often do not need an explicitly expressed endpoint. This provides one or more “bucket gaps” in the histogram that allows comparatively cheap storage and compressed representation of such frequency histograms. If this type of data distribution is identified, then the process preferably creates a frequency histogram using the execute_frequency( ) function. If it is desired to collect a histogram and the ndv value is greater than an established threshold, then the procedure generates a height-balanced histogram using the execute_height( ) function in an embodiment of the invention. The following comprises pseudocode for an embodiment of the execute_frequency( ) function: build up frequency query and execute it if (ndv<=mnb)—have a good frequency histogram clear histogram collection bit The following pseudocode can be used to build up a frequency query according to an embodiment of the invention: select c, count(*) from t sample (s) where c is not null group by c order by c; This query collects column values from a table and performs a count of the values. The following comprises pseudocode for an embodiment of the execute_height( ) function: build up a height-balanced query and execute it check for non-uniformity if non-uniformity exists try to scale the multiplicative inverse of the density if it can be successfully scaled—histogram is ready clear histogram collection bit else clear histogram collection bit—no histogram needed In this pseudocode, the column values are checked for non-uniformity. If the column values are uniform, then no histogram is collected. Otherwise, the pseudocode attempts to scale the multiplicative inverse of the density using the previously described process for scaling ndv. In prior evaluations, the number of repetitions was considered uniform over the values; but once histograms are introduced, the popular values can be removed to remove influence upon non-popular values in the histogram. According to an embodiment, a popular value is a value that corresponds to more than one endpoint in a height-balanced histogram. All values that are not popular are considered non-popular. Density is the expected number of repeated occurrences of a non-popular value. In one embodiment, density can be calculated as the sum of the square of the repetition counts for non-popular values divided by the product of the number of rows in the table and the number of non-popular values in the table. The following comprises pseudocode for building up a height-balanced query according to one embodiment of the invention: select maxbkt, min(value) minval, max(value) maxval, sum(rep) sumrep, sum(repsq) sumrepsq, max(rep) maxrep, count(*) bktndv from ( select value, max(bkt) maxbkt, count(value) rep, count(value)*count(value) repsq from ( select c as value, ntile(mnb) over (order by c) bkt from t sample(s) where c is not null ) group by value; ) group by maxbkt order by maxbkt; Here, the inner select statement calls an ntile( ) function, which creates a height-balanced histogram and places data sample values into appropriate buckets in the histogram. In an embodiment, such a function creates an uncompressed histogram and returns a number representing the bucket that a value falls into. The repetition counts (and square of repetition counts) are selected in the middle statement. The outer loop performs a count and checks the values and buckets for the result set. The max and min values for the buckets are reviewed to obtain the histogram endpoints. Density, which is related to the selectivity of non-popular values in the data sample, is calculated in this procedure using the function results from the outer loop. This is computed in an embodiment by looking at the number of repetitions of a non-popular value. The result of this query is that one row is obtained per bucket, with missing buckets coming from the more popular values. Each row will have the minimum and maximum value for that bucket, along with the number of rows in that bucket, the sum of the repetition counts and square of the repetition counts for rows in that bucket, and the number of repetitions for the most popular value in that bucket. All missing buckets have been folded into the nearest bucket that is larger. For example, consider if the process ends up with the following: maxbkt minval maxval sumrep sumrepsq maxrep 1 1 2 2 2 1 4 3 4 9 65 8 5 5 5 3 9 3 6 6 8 4 6 2 8 9 10 6 20 4 This would mean that the number 3 is popular because it is the largest value in the missing buckets 2 and 3 . Notice that the number 9 is not a popular value because it is only the largest value of a single bucket, bucket 7 , and thus would only appear once as a histogram endpoint. To calculate density, the influence of the popular value, 3 , would be removed. Since the value 3 appears 8 times, the number 8 is subtracted from the sumrep sum and 64 (square of 8) from the sumrepsq sum. This enables the computation at a density which is based upon the number of rows in the table, the number of non-popular values in the column, and the sum of the square of the repetition counts of non-popular values. The following pseudocode provides an illustrative embodiment of the invention for histogram determination that was generally described with respect to FIG. 4 . for each column, c, for which a histogram is considered if the user has specified size create and save a histogram with number of buckets=requested size else if the user has specified size repeat if c already has a histogram with b buckets create and save a histogram with b buckets else if the user has specified size skewonly create a histogram if the created histogram exhibits equality or range skew save it in the dictionary else if the user has specified size auto check the dictionary for column usage information if c has been in a predicate involving an equality, range, or like create a histogram if c appeared in an equality (including equijoin) predicate if the histogram exhibits non-uniformity in value repetition  save it in the dictionary if c appeared in a like or range predicate (not involving join) if the histogram exhibits non-uniformity in range save it in the dictionary any prior histogram on c will be removed The first portion of the pseudocode relates to specific instructions from a user to create a histogram, which results in the creation of the desired histogram. The specific histogram is created without a determination as to whether it is actually needed. Alternatively, the invention can be adapted to automatically check whether a histogram specifically called for by a user should actually be collected and/or saved. The second portion of the pseudocode relates to automated determination of histogram collection. In this illustrative embodiment, the following items of information are utilized for histogram determination: 1) the subset of columns for which the user wants to gather statistics; 2) the columns which already have histograms created for them; 3) column usage information; and 4) the distribution of data, e.g., as seen in a data sample. Because data distribution information is involved, this process may be advantageously used in conjunction with the process of FIG. 2 for automated sample size determination. In the illustrative embodiment, column usage information is considered in conjunction with data distribution information for that column to determine whether a histogram should be collected and stored. Column usage information includes, for example, the type of predicates that is executed against the column. The data skew of the column is evaluated against the type of predicate for that column to determine whether a histogram is needed. When parsing a cursor for the first time in an embodiment, the cost-based optimizer looks at the statistics on all of the objects (tables, columns, etc.) involved in the statement. For each column in the where clause, it will estimate the selectivity of the predicate involving that column. At this point, the system will make an entry in the data structure for the column indicating what type of predicate it was involved in. In an embodiment, column usage information is collected every time a user hard-parses a statement, in which a bit is marked in memory for the column usage information. Whenever information is flushed to disk, these bits indicate whether to increment the appropriate dictionary columns. For example, if a query containing a column with a range predicate was hard parsed since the last flush, the system will increment the range_predicate counter for that column when the next flush procedure takes place, as well as updating the timestamp. One reason for using counters on disk is to provide a better feel for the importance of the predicate. Counters can also be used in memory, but may result in expensive overhead. In the illustrative pseudocode, a histogram is created if the column is involved in equality, range, or like predicates. In an embodiment, the histogram is created based on a sampled portion of the column, and is preferably created using a small sample of the entire population that is sufficient to both determine the need for histograms and produce histograms which are representative of the entire population. The number of buckets in the histogram could be based on the sample size. The range max and min is selected based upon the data samples. Values in the data samples are placed into the selected buckets. The process then counts the number of equi-height endpoints that fall within the equi-width buckets. The buckets are reviewed to determine if any buckets are overly large or small. If so, then it is likely that the column does not have uniform data distribution, thereby indicating range skew. In addition, the act of creating a histogram also provides an estimate for the number of distinct values, providing an extra benefit even if the histogram is later discarded. If an equality or equijoin predicate is involved, then the histogram is saved only if the histogram exhibits non-uniformity in value repetition. For purposes of this example, a column will be considered to have non-uniform value repetition if any value is popular, e.g., repeats as an endpoint in the histogram. If a like or range predicate is involved, then the histogram is saved only if the histogram exhibits non-uniformity in range. In one embodiment, a column is considered to have non-uniformity in range if it passes the following test: given that the created histogram had b equi-height buckets divide the range (max−min) into b equi-width buckets sum=0 for each equiwidth bucket count the number of equi-height endpoints that fall in the bucket sum+=(count*count) if (sum/b)>1.7 this column is considered to be non-uniform in range For a uniform column, the equi-height endpoints would coincide with the equi-width endpoints, and the sum would simply be b. SYSTEM ARCHITECTURE OVERVIEW Referring to FIG. 5, in an embodiment, a computer system 520 includes a host computer 522 connected to a plurality of individual user stations 524 . In an embodiment, the user stations 524 each comprise suitable data terminals, for example, but not limited to, e.g., personal computers, portable laptop computers, or personal data assistants (“PDAs”), which can store and independently run one or more applications, i.e., programs. For purposes of illustration, some of the user stations 524 are connected to the host computer 522 via a local area network (“LAN”) 526 . Other user stations 524 are remotely connected to the host computer 522 via a public telephone switched network (“PSTN”) 528 and/or a wireless network 530 . In an embodiment, the host computer 522 operates in conjunction with a data storage system 531 , wherein the data storage system 531 contains a database 532 that is readily accessible by the host computer 522 . Note that a multiple tier architecture can be employed to connect user stations 524 to a database 532 , utilizing for example, a middle application tier (not shown). In alternative embodiments, the database 532 may be resident on the host computer, stored, e.g., in the host computer's ROM, PROM, EPROM, or any other memory chip, and/or its hard disk. In yet alternative embodiments, the database 532 may be read by the host computer 522 from one or more floppy disks, flexible disks, magnetic tapes, any other magnetic medium, CD-ROMs, any other optical medium, punchcards, papertape, or any other physical medium with patterns of holes, or any other medium from which a computer can read. In an alternative embodiment, the host computer 522 can access two or more databases 532 , stored in a variety of mediums, as previously discussed. Referring to FIG. 6, in an embodiment, each user station 524 and the host computer 522 , each referred to generally as a processing unit, embodies a general architecture 605 . A processing unit includes a bus 606 or other communication mechanism for communicating instructions, messages and data, collectively, information, and one or more processors 607 coupled with the bus 606 for processing information. A processing unit also includes a main memory 608 , such as a random access memory (RAM) or other dynamic storage device, coupled to the bus 606 for storing dynamic data and instructions to be executed by the processor(s) 607 . The main memory 608 also may be used for storing temporary data, i.e., variables, or other intermediate information during execution of instructions by the processor(s) 607 . A processing unit may further include a read only memory (ROM) 609 or other static storage device coupled to the bus 606 for storing static data and instructions for the processor(s) 607 . A storage device 610 , such as a magnetic disk or optical disk, may also be provided and coupled to the bus 606 for storing data and instructions for the processor(s) 607 . A processing unit may be coupled via the bus 606 to a display device 611 , such as, but not limited to, a cathode ray tube (CRT), for displaying information to a user. An input device 612 , including alphanumeric and other columns, is coupled to the bus 606 for communicating information and command selections to the processor(s) 607 . Another type of user input device may include a cursor control 613 , such as, but not limited to, a mouse, a trackball, a fingerpad, or cursor direction columns, for communicating direction information and command selections to the processor(s) 607 and for controlling cursor movement on the display 611 . According to one embodiment of the invention, the individual processing units perform specific operations by their respective processor(s) 607 executing one or more sequences of one or more instructions contained in the main memory 608 . Such instructions may be read into the main memory 608 from another computer-usable medium, such as the ROM 609 or the storage device 610 . Execution of the sequences of instructions contained in the main memory 608 causes the processor(s) 607 to perform the processes described herein. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the invention. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and/or software. The term “computer-usable medium,” as used herein, refers to any medium that provides information or is usable by the processor(s) 607 . Such a medium may take many forms, including, but not limited to, non-volatile, volatile and transmission media. Non-volatile media, i.e., media that can retain information in the absence of power, includes the ROM 609 . Volatile media, i.e., media that can not retain information in the absence of power, includes the main memory 608 . Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise the bus 606 . Transmission media can also take the form of carrier waves; i.e., electromagnetic waves that can be modulated, as in frequency, amplitude or phase, to transmit information signals. Additionally, transmission media can take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. Common forms of computer-usable media include, for example: a floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, any other optical medium, punchcards, papertape, any other physical medium with patterns of holes, RAM, ROM, PROM (i.e., programmable read only memory), EPROM (i.e., erasable programmable read only memory), including FLASH-EPROM, any other memory chip or cartridge, carrier waves, or any other medium from which a processor 607 can retrieve information. Various forms of computer-usable media may be involved in providing one or more sequences of one or more instructions to the processor(s) 607 for execution. The instructions received by the main memory 608 may optionally be stored on the storage device 610 , either before or after their execution by the processor(s) 607 . Each processing unit may also include a communication interface 614 coupled to the bus 606 . The communication interface 614 provides two-way communication between the respective user stations 624 and the host computer 622 . The communication interface 614 of a respective processing unit transmits and receives electrical, electromagnetic or optical signals that include data streams representing various types of information, including instructions, messages and data. A communication link 615 links a respective user station 624 and a host computer 622 . The communication link 615 may be a LAN 526 , in which case the communication interface 614 may be a LAN card. Alternatively, the communication link 615 may be a PSTN 528 , in which case the communication interface 614 may be an integrated services digital network (ISDN) card or a modem. Also, as a further alternative, the communication link 615 may be a wireless network 530 . A processing unit may transmit and receive messages, data, and instructions, including program, i.e., application, code, through its respective communication link 615 and communication interface 614 . Received program code may be executed by the respective processor(s) 607 as it is received, and/or stored in the storage device 610 , or other associated non-volatile media, for later execution. In this manner, a processing unit may receive messages, data and/or program code in the form of a carrier wave.

A method and system for determining when to collect, save, and/or utilize histograms is disclosed. A mechanism for automatically deciding when to collect histograms upon request from the user is provided. The histogram collection decision is based on the columns the user is interested in, the role these columns play in the queries as submitted to the system, and the underlying distribution for these columns, e.g., as seen in a random sample. The user specifies which columns are of interest, and the database is configured to collect column usage information that describes how each column is being used in the workload. This column usage information could be stored in memory and periodically flushed to disk. Given a set of potential columns, the distribution of those columns is viewed in combination with the usage information to determine which columns should have histograms.

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims priority to currently pending U.S. Provisional Application Ser. No. 61/050,406 that was filed on May 5, 2008 and entitled MATERIAL DISPENSING ASSEMBLY. The present application claims priority the above-identified provisional patent application, which is incorporated in its entirety herein by reference for all purposes. TECHNICAL FIELD [0002] The present disclosure relates to a material dispensing assembly, and more particularly, a material dispensing assembly for sausage or bag-type dispensing tools. BACKGROUND [0003] Dispensing tools have been available for a number of years, assisting in the application of material to a desired surface in residential, commercial, or manufacturing environments, Such materials include, for example, adhesives, lubricants, and sealants such as, silicone, urethanes, and caulk. Conventional dispensing tools frequently visualized are of the type of a handheld caulk gun 10 , as illustrated in FIG. 1 , Cartridges 12 shown in FIG. 2 having any number of different types of materials, including those listed above are inserted into a cartridge support sleeve 14 located on the top side of the dispensing tool 10 . A trigger 16 on the gun 10 when actuated drives a rack 18 having a plunger 20 that engages the material located in the cartridge 12 such that each actuation of the trigger, forces material to be dispensed from a nozzle 22 located at an end 24 of the cartridge. [0004] A more modern dispensing tool for applying various materials, including those materials listed above is a power dispensing gun 30 , having a battery, pneumatic, or other means for powering motor for portable use is illustrated in FIG. 3 . The power dispensing gun 30 is also capable of using the cartridges 12 filled with dispensing material by inserting the cartridges 12 into a support sleeve 32 located on the top of the power dispensing gun 30 . A trigger 34 on the power dispensing gun 30 is actuated, driving a rack 36 having a plunger 38 that engages the material located in the cartridge 12 such that each actuation of the trigger forces material to be dispensed from a nozzle 40 located at the end 42 of the gun. Further details of the operation and configuration of a power dispensing gun is explained in U.S. patent application Ser. No. 11/918,689 entitled POWERED DISPENSING TOOL AND METHOD FOR CONTROLLING SAME that is assigned to the assignee of the present invention and is incorporated herein by reference in its entirety for all purposes. [0005] Cartridges 12 are not the only form of container for holding material used by the dispensing guns 10 , 30 , but another known type of container is a sausage pack or bag-type container 50 shown in FIG. 4 . The sausage pack 50 includes a first and second ends 52 , 54 , respectively extending from a main body 56 having dispensing material therein. The sausage pack 50 is positioned in a housing tube 58 located on the guns 10 , 30 in place of the cartridge support sleeves 14 , 32 , respectively as illustrated in FIGS. 5 and 7 . The sausage pack 50 once inserted into the guns has an opening 60 (shown in phantom is typically formed from removal of a containment ring or by piercing the sausage pack) toward the nozzle 22 , 40 and the plunger 20 , 38 squeezes the material out the nozzle when the trigger 16 , 34 is engaged. [0006] One example of a dispensing tool having interchanging support sleeves includes U.S. patent application Ser. No. 11/973,242 filed on Oct. 5, 2007 entitled DISPENSING TOOL that is assigned to the assignee of the present invention and is incorporated herein by reference in its entirety for all purposes. The '242 application illustrates a system for interchanging support sleeves from a cartridge-type dispenser to a sausage pack dispenser and vice versa as desired by the operator on a single power dispenser. [0007] Sausage packs 50 are typically more economical because of their cheaper fabrication. As a result, the sausage packs 50 are typically used more frequently in high volume commercial and manufacturing operations over conventional cartridges 12 in material dispensing guns. SUMMARY [0008] One example embodiment of the present disclosure includes a material dispensing assembly for converting a portable cartridge dispensing tool to a bag-type dispensing tool. The assembly comprises a single piece piston for advancing material though a material housing. The single piece piston includes a substantially square-shaped receptacle. The assembly further comprises a square shaped drive rack for attaching to the piston at the substantially square-shaped receptacle at a connection end. The drive rack further comprises a plurality of teeth located thereon. The assembly further has a support with a substantially square profile for receiving and supporting the drive rack during operation such that the construct of the drive rack and piston are prevented from rotating during operation. [0009] Another example embodiment of the present disclosure includes a single-piece piston for advancing material in a dispensing gun. The piston comprises first and second ends, the first end having a dome profile with an annular taper extending outwardly toward the second end. The piston further comprises a circular seal lip integral with and extending about the perimeter of the piston, the circular seal lip includes a plurality of substantially equal segments located therebetween. A noncircular attachment aperture is located in the piston for attaching the piston to a dispensing gun. The noncircular attachment aperture in the piston prevents loosening and rotation of the piston during operation. [0010] A further example embodiment of the present disclosure includes a material dispensing gun assembly comprising a single piece piston for advancing material though a material housing. The single piece piston includes a substantially square-shaped receptacle for attaching the single piece piston to a dispensing gun and first and second ends. The first end includes an annular dome profile with first and second annular tapered surfaces extending outwardly toward the second end. The piston further comprises a circular seal lip integral and extending from the second annular tapered surface about the perimeter of the piston, the circular seal lip further comprises a plurality of substantially equal segments. The dispensing gun assembly also comprises a square shaped drive rack for attaching to the single-piece piston at the substantially square-shaped receptacle at a connection end and a plurality of teeth located thereon. The dispensing gun also includes a support having a substantially square profile for receiving and supporting the drive rack during operation such that the construct of the drive rack and piston are prevented from rotating during operation. [0011] A yet further example embodiment of the present disclosure includes a method of dispensing material from a material dispensing gun comprising loading a sausage bag comprising dispensing material into a tube removably attached to a dispensing gun, the tube having an exit end from which the dispensing material is dispensed during operation. The method also comprises locating the sausage bag between the exit end and a single piece piston in the tube and engaging the sausage bag with an annular dome located at a front end of the single piece piston located in the tube. The method further comprises advancing the single piece piston against the sausage bag with a rack fixedly attached to the single piece piston such that material located in the sausage bag engaged by the annular dome is dispensed from the exit end of the tube and unadvanced material not engaged by the annular dome extends over first and second tapered annular surfaces of the dome. The method also includes engaging the unadvanced material in the sausage bag with a circular seal lip integral and extending from the second annular tapered surface about the perimeter of the piston, the circular seal lip comprises a plurality of substantially equal segments located about the perimeter of the circular seal lip and advancing the unadvanced material with the plurality of substantially equal segments of the single piece piston such that the unadvanced material located in the sausage bag engaged by the plurality of segments is dispensed from the exit end of the tube. [0012] Another example embodiment of the present disclosure includes a material dispensing housing for use with bag-type dispensing material. The material dispensing housing comprises a transparent tube for supporting bag-type dispensing material, the tube is formed from high-temperature resistant polymeric material. The transparent tube allows for the visualization of the movement of dispensing material located within the housing during operation. The housing also comprises a base coating selected from one of a silicone coating and polysiloxane coating. The base coating provides superior service life and reduced friction of the bag holding the dispensing material and reduces the friction with a piston that engages the tube and the bag-type dispensing material during operation. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The foregoing and other features and advantages of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein like reference numerals refer to like parts throughout the drawings and in which: [0014] FIG. 1 is a side elevation view of a manual dispensing gun adapted for a cartridge-type material container; [0015] FIG. 2 is a side cross sectional elevation view of a cartridge-type material container for use in a manual or powered dispensing gun; [0016] FIG. 3 is a side elevation view of a power dispensing gun adapted for a cartridge-type material container; [0017] FIG. 4 is a side elevation view of a sausage pack material container for use in a manual or powered dispensing gun; [0018] FIG. 5 is a perspective view of a tube for housing a sausage pack material container of FIG. 4 ; [0019] FIG. 6 is an exploded assembly view of a material dispensing assembly adapted for a power dispensing tool constructed in accordance with one embodiment of the present disclosure; [0020] FIG. 7 is a side view of a power dispensing gun adapted to support the material dispensing assembly of FIG. 6 ; [0021] FIG. 8A is a rear isometric view of a single piece piston constructed in accordance with one embodiment of the present disclosure; [0022] FIG. 8B is a front isometric view of the single piece piston constructed in accordance with the example embodiment of FIG. 8A ; [0023] FIG. 8C is a rear elevation view of the single piece piston constructed in accordance with the example embodiment of FIG. 8A ; [0024] FIG. 8D is a side elevation view of the single piece piston constructed in accordance with the example embodiment of FIG. 8A ; [0025] FIG. 8E is a front elevation view of the single piece piston constructed in accordance with the example embodiment of FIG. 8A ; [0026] FIG. 8F is a cross-section elevation side view of the single piece piston constructed in accordance with the example embodiment of FIG. 8A ; and [0027] FIG. 8G is a magnified view of a portion of the single piece piston cross-section identified in the example embodiment of FIG. 8G . DETAILED DESCRIPTION [0028] The present disclosure relates to a material dispensing assembly 100 , and more particularly, a material dispensing assembly for easily converting portable cartridge dispensing tools to sausage or bag-type dispensing tools. One example embodiment of the material dispensing assembly 100 is illustrated in FIG. 6 . The assembly 100 can be adapted to convert a power dispensing tool from the cartridge-type dispenser illustrated in FIG. 3 to that of a sausage type dispenser as illustrated in the example embodiment of the power dispensing tool 102 in FIG. 7 that can be powered by battery, pneumatic means, and the like. [0029] The power dispensing assembly 100 of FIG. 6 comprises a sausage holding tube 104 having first and second ends 106 , 108 , respectively. A sausage pack 50 of various lengths is installed through the first end 106 and material within the sausage pack is forced out by a piston 110 that is located behind the sausage pack in the second end 108 during operation. The material that is dispensed from the sausage pack 50 could include caulk, adhesives, silicone, urethanes, and the like without departing from the spirit and scope of the claimed invention. The piston 110 is advanced by a square piston rack 112 , which forces the piston against the sausage pack 50 , forcing material to dispense from the first end 106 through a nozzle 114 that is retained to the tube 104 by a cap 116 via a threaded connection 117 . [0030] The amount and speed of the material dispensed from the sausage pack 50 by the piston 110 could be a function of the speed of the motor (internal to the gun), or the extent of travel by the piston in the tube 104 . For example, the piston 110 could “bottom-out” against an empty sausage pack 50 that is compressed against the cap 116 and nozzle 114 . The rack 112 moveably passes through components internal to the gun 102 , including a pinion gear 118 (that engages and drives the rack in both forward and reverse directions) coupled to a gear set 120 driven in both a forward and reverse direction by a motor 122 . The positioning of the gear set 120 and pinion gear 118 in combination with supports 124 internal to the gun 102 , fix the orientation of the rack 112 through its path of travel when advancing and reversing the piston. 110 in the tube 104 . The supports 124 comprise square shaped bushings, guides, or fixtures that maintain the orientation of the rack 112 to prevent rotation of the rack or piston 110 during operation. [0031] The rack 112 includes first 126 and second 128 ends. The first end 126 passes through a barrel screw 127 , spacer 130 , end cap 132 , and washer 134 . The barrel screw 127 couples the dispensing assembly 100 through the spacer 130 and end cap 132 to a mating threaded connection 133 located in a housing porting 135 of the gun 102 for engagement with the barrel screw. Attached to the first end 126 of the rack 112 is a rack handle 136 for assisting in the reloading and unloading of the sausage packs 50 from the tube 104 . The rack handle 136 is secured to a threaded aperture located in the first end 126 of rack by a screw 138 . [0032] The first and second ends 106 , and 108 , respectively have respective threaded sections 106 A and 108 A. The first threaded section 106 A co-acts with internal threads 116 A associated with cap 116 and secures the cap to the first end 106 of the tube 104 , locking the nozzle 114 between the tube and cap at the first end. The second threaded section 108 A co-acts with internal threads 132 A associated with end cap 132 . Once the end cap 132 is secured to the housing 135 of the dispensing gun 102 , as described above, the second threaded second 108 A is screwed into the end cap, thereby supporting the tube 104 to the housing. [0033] Plungers 20 used in conventional dispensing guns (see FIG. 1 ), are commonly threaded on the end of a drive rack 18 . Tightening the plunger 20 to the rack and applying a lock-nut is a typical means of securing the plunger. As some cartridges 12 and their corresponding support sleeves are designed to be rotated, the tendency to have the plunger 20 “unscrew” from the drive rack is appreciable, especially during operations when the user is attempting to turn the cartridge 12 while there is axial pressure being applied to the drive rack. [0034] Such problems are resolved by one embodiment of the present invention. In particular, the rack 112 comprises a square configuration to be received and attached to a corresponding a square receptacle 140 in the piston 110 , as illustrated in FIGS. 8A , 8 C, and 8 F. The rack 112 engages the receptacle until it is in contact with an internal face 141 in the piston 110 and is secured to the piston by a fastener 143 that passes through an opening 165 into a counter-bore 167 , for seating the fastener during attachment. Such design and the corresponding square supports 124 internal to the gun 102 prevent rotation of the rack 112 and preclude any loosening of the piston 110 . [0035] The rack 112 construction in the illustrated embodiment of FIG. 6 provides yet another advantage from the present disclosure. The square piston 110 , corresponding square receptacle 140 , and rack 112 allow the rack to be reversed such that the first end 126 can be flipped with the second end 128 . This reversible rack 112 feature is advantageous when the rack becomes worn by the pinion gear 118 along an advanced direction (see arrow A in FIG. 6 ). At such time that the rack 112 shows signs of wear, the mirror image construction and corresponding attachments allow the rack to be flipped 180 degrees between the first and second ends 126 , 128 while remaining in the same orientation as shown in FIG. 6 . The pinion 118 now drives unworn teeth 142 in the advanced direction “A”. The fasteners 138 , 143 and receiving threaded connections in the rack 112 at first and second ends 126 , 128 are the same, allowing the piston 110 and rack handle 136 to be reversed, extending the life of the rack as discussed above. [0036] The piston 110 provides several advantages illustrated in the exemplary embodiment of FIGS. 6 and 8 . While conventional plungers 20 are typically configured from multiple pieces, the piston 110 is a single uniform piece made from a single molding operation. This eliminates both material and assembly costs experienced in conventional plunger designs. While the piston 110 can be made from any number of suitable polymeric materials, the construct of the piston in the example embodiment is formed from Nylon 66 material. The polymeric material of the piston 110 advantageously weighs less than one ounce, while compared to conventional plungers that weigh much more and up to eight ounces. The reduction in weight in the exemplary embodiment of the single piece piston 110 reduces stress, strain, and other ergonomic issues typically experienced in wrists and arms of operators using conventional dispensing guns. [0037] The piston 110 comprises front 144 and back 146 ends as shown in FIGS. 8B and 8D , an annular dome 148 , and circular lip portion 150 , as shown in FIG. 8C . The construct of the annular dome 148 at the front 144 of the piston 110 is designed to extrude the maximum amount of material from the tube 104 and sausage packet 50 therein. In particular, the dome 148 comprises a first tapered annular surface 151 , raising the unadvanced material in the sausage packet 50 up over the tapered annular face to a plurality of segmented sections 152 integrated into the dome and extending from the single piece piston 110 . In the illustrated embodiment, twelve (12) segmented sections represented by 152 A- 152 L (see FIG. 8E ) in the circular lip portion 150 capture and advance forward the remaining material in the sausage packet 50 as the piston 110 advances through the tube 104 . While twelve segmented sections 152 are shown in the illustrated embodiment of FIG. 8 , more or less segmented sections could be used without departing from the spirit and scope of the claimed invention. [0038] The independent flexibility achieved by the segmented sections 152 A- 152 L provide a heightened ability to facilitate a solid lip seal to a tube 104 or cartridge 12 internal wall under varying roundness tolerances especially experienced in cartridge tubes. Further the specific piston 110 diameter, piston lip geometry, including thickness, taper, and edge angles provide dispensing free of “bag wrap” failures, while enabling a low “pull back” force in sausage-type applications. In addition, the piston 110 design provides a low drag force in the forward direction (see arrow A in FIG. 6 ), enabling greater dispensing forces to be achieved. In the illustrated embodiment of FIGS. 8A-8G , the lip thickness represented by dimension “A” in FIG. 8G is approximately 0.34 inches, having a front taper 162 of approximately 6 degrees represented by dimension “B”, and edge angle off a rear edge 160 of each segmented sections 152 of approximately 15 degrees represented by dimension “C”, and a back angle off a second tapered annular surface 163 on the dome 151 of approximately 92 degrees represented by dimension “D”, as illustrated in FIGS. 8F and 8G . [0039] The twelve segmented sections 152 A- 152 L are capable under the current embodiment of FIG. 8 of independently undulating to maintain substantially constant regulated pressure to the sausage pack 50 , preventing bag wrap failures where the bag of the sausage pack 50 would pinch between the plunger and tube in conventional plunger designs. In the exemplary embodiment of FIGS. 8A-8G , a vent spacing 154 is provided between the 12 segmented sections 152 A- 152 L of approximately 0.030 inches represented by dimension “X” in FIG. 8E . The overall length of the piston is approximately 1 inch represented by dimension “E” in FIG. 8D and the overall diameter of the piston 110 in the illustrated embodiment of FIG. 8 is approximately 2.0 inches as illustrated in FIG. 8E by dimension “F”, and the segmented sections extend from the dome 151 outward at approximately 0.69 inch diameter radius from the center “O” of the piston. It should be appreciated however, that proportionally larger and smaller dimensions would be required for larger and smaller diameter tubes and are intended to be covered by the spirit and scope of the claimed invention. [0040] The vent spacings 154 in addition to providing independent pressure to the inner diameter of the tube 104 and/or sausage pack 50 , allow air to escape from the tube when the sausage pack is being inserted or removed. This allows for easier replacement and removal of sausage packs 50 during operation by the user. The piston 110 also comprises a number of voids on the back end 146 . The voids 155 improve the overall structural strength and facilitate a reduction in the weight of the piston 110 . [0041] The tube 104 in one exemplary embodiment is transparent so that the material dispensed from the sausage pack 50 can be observed and visually measured by the user. In addition, the transparent tube 104 allows the user to visually inspect the tube while performing a cleaning operation. [0042] In another example embodiment, the tube 104 is transparent (i.e. clear and chemical resistant) and made from an a high temperature annealed polycarbonate or polyamide based material 82 and lined with a based coating 84 , allowing superior service life in a demanding environment of repeated stress, thermal, and chemical attack. Examples of suitable base coatings include silicone or polysiloxane. Such construction also reduces friction with the piston 110 and sausage bag 50 and reduces the force necessary for dispensing the material from the dispensing gun 102 . The base coatings 84 can be applied to the tube 104 by direct application, such as spraying or wiping the internal portions of the tube, through a heat treatment application process, or by extruding or impregnating the base material 82 with the base coating material during the forming of the base material. [0043] What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. For example, while the material dispensing assembly was illustrated being adapted to a power dispensing gun, it could equally be adapted to a manual dispensing gun without departing from the spirit or scope of the claimed invention. Accordingly, the present invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

A material dispensing assembly ( 100 ) and method of operation is disclosed for converting a portable cartridge dispensing tool to a bag-type dispensing tool. The assembly comprises a single piece piston ( 110 ) for advancing material though a material housing ( 104 ), the single piece piston ( 110 ) includes a substantially square-shaped receptacle ( 140 ). The assembly further comprises a square shaped drive rack ( 112 ) for attaching to the piston ( 110 ) at the substantially square-shaped receptacle ( 140 ) at a connection end ( 128 ). The drive rack ( 112 ) further comprises a plurality of teeth ( 142 ) located thereon. The assembly ( 100 ) further has a support ( 127 ) with a substantially square profile for receiving and supporting the drive rack ( 112 ) during operation such that the construct of the drive rack and piston ( 110 ) are prevented from rotating during operation.

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to processing an audio signal. Spatial processing, also known as 3D audio processing, applies various processing techniques in order to create a virtual sound source (or sources) that appears to be in a certain position in the space around a listener. Spatial processing can take one or many monophonic sound streams as input and produce a stereophonic (two-channel) output sound stream that can be reproduced using headphones or loudspeakers, for example. Typical spatial processing includes the generation of interaural time and level differences (ITD and ILD) to output signal caused by head geometry. Spectral cues caused by human pinnae are also important because the human auditory system uses this information to determine whether the sound source is in front of or behind the listener. The elevation of the source can also be determined from the spectral cues. Spatial processing has been widely used in e.g. various home entertainment systems, such as game systems and home audio systems. In telecommunication systems, such as mobile telecommunications systems, spatial processing can be used e.g. for virtual mobile teleconferencing applications or for monitoring and controlling purposes. An example of such a system is presented in WO 00/67502. In a typical mobile communications system the audio (e.g. speech) signal is sampled at a relatively low frequency, e.g. 8 kHz, and subsequently coded with a speech codec. As a result, the regenerated audio signal is bandlimited by the sampling rate. If the sampling frequency is e.g. 8 kHz, the resulting signal does not contain information above 4 kHz. The lack of high frequencies in the audio signal, in turn, is a problem if spatial processing is to be applied to the signal. This is due to the fact that a person listening to a sound source needs a signal content of a high frequency (the frequency range above 4 kHz) to be able to distinguish whether the source is in front of or behind him/her. High frequency information is also required to perceive sound source elevation from 0 degree level. Thus, if the audio signal is limited to frequencies below 4 kHz, for example, it is difficult or impossible to produce a spatial effect on the audio signal. One solution to the above problem is to use a higher sampling rate when the audio signal is sampled and thus increase the high frequency content of the signal. Applying higher sampling rates in telecommunications systems is not, however, always feasible because it results in much higher data rates with increased processing and memory load and it may also require designing a new set of speech coders, for example. BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is thus to provide a method and an apparatus for implementing the method so as to overcome the above problem or to at least alleviate the above disadvantages. The object of the invention is achieved by providing a method for processing an audio signal, the method comprising receiving an audio signal having a narrow bandwidth; expanding the bandwidth of the audio signal; and processing the expanded bandwidth audio signal for spatial reproduction. The object of the invention is also achieved by providing an arrangement for processing an audio signal, the arrangement comprising means for expanding the bandwidth of an audio signal having a narrow bandwidth; and means for processing the expanded bandwidth audio signal for spatial reproduction. Furthermore, the object of the invention is achieved by providing an arrangement for processing an audio signal, the arrangement comprising bandwidth expansion means configured to expand the bandwidth of an audio signal having a narrow bandwidth; and spatial processing means configured to process the expanded bandwidth audio signal for spatial reproduction. The invention is based on an idea of enhancing spatial processing of a low-bandwidth audio signal by artificially expanding the bandwidth of the signal, i.e. by creating a signal with higher bandwidth, before the spatial processing. An advantage of the method and arrangement of the invention is that the proposed method and arrangement are readily compatible with existing telecommunications systems, thereby enabling the introduction of high quality spatial processing to current low-bandwidth systems with only relatively minor modifications and, consequently, low cost. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which FIG. 1 is a block diagram of a signal processing arrangement according to an embodiment of the invention; and FIG. 2 is a block diagram of a signal processing arrangement according to an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION In the following the invention is described in connection with a telecommunications system, such as a mobile telecommunications system. The invention is not, however, limited to any particular system but can be used in various telecommunications, entertainment and other systems, whether digital or analogue. A person skilled in the art can apply the instructions to other systems containing corresponding characteristics. FIG. 1 illustrates a block diagram of a signal processing arrangement according to an embodiment of the invention. It should be noted that the figures only show elements that are necessary for the understanding of the invention. The detailed structure and functions of the system elements are not shown in detail, because they are considered obvious to a person skilled in the art. According to the invention, a low-bandwidth (or narrow bandwidth) audio signal, e.g. speech signal, is first processed in order to expand the bandwidth of the audio signal; this takes place in a bandwidth expansion block 20 . The obtained high-bandwidth (or expanded bandwidth) audio signal is then further processed for spatial reproduction; this takes place in a spatial processing block 30 , which preferably produces a stereophonic binaural audio signal. The low-bandwidth audio signal can be obtained e.g. from a transmission path of a telecommunications system via an audio decoder, such as a speech decoder 10 , if the audio signal is transmitted in a coded form. However, the source of the low-bandwidth audio signal received at block 20 is not relevant to the basic idea of the invention. Furthermore, the terms ‘low-bandwidth’ or ‘narrow bandwidth’ and ‘high-bandwidth’ or ‘expanded bandwidth’ should be understood as descriptive and not limited to any exact frequency values. Generally the terms ‘low-bandwidth’ or ‘narrow bandwidth’ refer approximately to frequencies below 4 kHz and the terms ‘high-bandwidth’ or ‘expanded bandwidth’ refer approximately to frequencies over 4 kHz. The invention and the blocks 10 , 20 and 30 can be implemented by a digital signal processing equipment, such as a general purpose digital signal processor (DSP), with suitable software therein, for example. It is also possible to use a specific integrated circuit or circuits, or corresponding devices. The input for the speech decoder 10 is typically a coded speech bitstream. Typical speech coders in telecommunication systems are based on the linear predictive coding (LPC) model. In LPC-based speech coding the voiced speech is modeled by filtering excitation pulses with a linear prediction filter. Noise is used as the excitation for unvoiced speech. Popular CELP (Codebook Excited Linear Prediction) and ACELP (Algebraic Codebook Excited Linear Prediction)-coders are variations of this basic scheme in which the excitation pulse(s) is calculated using a codebook that may have a special structure. Codebook and filter coefficient parameters are transmitted to the decoder in a telecommunication system. The decoder 10 synthesizes the speech signal by filtering the excitation with an LPC filter. Some of the more recent speech coding systems also exploit the fact that one speech frame seldom consists of purely voiced or unvoiced speech but more often of a mixture of both. Thus, it is purposeful to make separate voiced/unvoiced decisions for different frequency bands and that way increase the coding gain. MBE (Multi-Band Excitation) and MELP (Mixed Excitation Linear Prediction) use this approach. On the other hand, codecs using Sinusoidal or WI (Waveform Interpolation) techniques are based on more general views on the information theory and the classic speech coding model with voiced/unvoiced decisions is not necessarily included in those as such. Regardless of the speech coder used, the resulting regenerated speech signal is bandlimited by the original sampling rate (typically 8 kHz) and by the modeling process itself. The lowpass style spectrum of voiced phonemes usually contains a clear set of resonances generated by the all-pole linear prediction filter. The spectrum for unvoiced speech has a high-pass nature and contains typically more energy in the higher frequencies. The purpose of the bandwidth expansion block 20 is to artificially create a frequency content on the frequency band (approximately >4 kHz) that does not contain any information and thus enhance the spatial positioning accuracy. Studies show that higher frequency bands are important in front/back and up/down sound localization. It seems that frequency bands around 6 kHz and 8 kHz are important for up/down localization, while 10 kHz and 12 kHz bands for front/back localization. It must be noted that the results depend on subject, but as a general conclusion it can be said that the frequency range of 4 to 10 kHz is important to the human auditory system when it determines sound location. If the bandwidth expansion block 20 is designed to boost these frequency bands, for example 6 kHz and 8 kHz, it is likely that the up/down accuracy of spatial sound source positioning can be increased for an originally bandlimited signal (for example a coded speech that is bandlimited to below 4 kHz). The bandwidth expansion block 20 can be implemented by using a so-called AWB (Artificial WideBand) technique. The AWB concept is originally developed for enhancing the reproduction of unvoiced sounds after low bit rate speech coding and although there are various methods available the invention is not restricted to any specific one. Many AWB techniques rely on the correlation between low and high frequency bands and use some kind of codebook or other mapping technique to create the upper band with the help of an already existing lower one. It is also possible to combine intelligent aliasing filter solutions with a common upsampling filter. Examples of suitable AWB techniques that can be used in the implementation of the present invention are disclosed in U.S. Pat. Nos. 5,455,888, 5,581,652 and 5,978,759, incorporated herein as a reference. The only possible restriction is that the bandwidth expansion algorithm should preferably be controllable, because it is recommended to process unvoiced and voiced speech differently, therefore some kind of knowledge about the current phoneme class must be available. In the embodiment of the invention shown in FIG. 1 , the control information is provided by the speech decoder 10 . It is also useful for optimal speech quality that the expansion method is tunable to various speech codecs and spatial processing algorithms. However this property is not necessary. Output from the expansion block 20 is preferably an audio signal with artificially generated frequency content in frequencies above half the original sampling rate (Nyquist frequency). It should be noted that if the invention is realized with a digital signal processing apparatus and the signals are digital signals, the output signal has a higher sampling rate than the low-bandwidth input signal. The spatial processing block 30 can apply various processing techniques to create a virtual sound source (or sources) that appears to be in a certain position around a listener. The spatial processing block 30 can take one or several monophonic sound streams as an input and it preferably produces one stereophonic (two-channel) output sound stream that can be reproduced using either headphones or loudspeakers, for example. More than two channels can also be used. When creating virtual sound sources, the spatial processing 30 preferably tries to generate three main cues for the audio signal. These cues are: 1) Interaural time difference (ITD) caused by the different length of the audio path to the listener's left and right ear, 2) Interaural level difference (ILD) caused by the shadowing effect of the head, and 3) signal spectrum reshaping caused by the human head, torso and pinnae. The spectral cues caused by human pinnae are important because the human auditory system uses this information to determine whether the sound source is in front of or behind the listener. The elevation of the source can be also determined from the spectral cues. Especially the frequency range above 4 kHz contains important information to distinguish between the up/down and front/back directions. Generation of all these cues is often combined in one filtering operation and these filters are called HRTF-filters (Head Related Transfer Function). The reproduction of the spatialized audio signal can be done either with headphones, two-loudspeaker system or multichannel loudspeaker system, for example. When headphone reproduction is used, problems often arise when the listener is trying to locate the signal in front/back and up/down positions. The reason for this is that when the sound source is located anywhere in the vertical plane intersecting the midpoint of the listener's head (median plane), the ILD and ITD values are the same and only spectral cues are left to determine the source position. If the signal has only little information on the frequency bands that the human auditory system uses to distinguish between front/back and up/down, then the location of the signal is very difficult. The design and parameter selection of bandwidth expansion can affect the spatial processing block and vice versa, when the system and its properties are being optimized. Generally speaking, the more information there is above the 4 kHz frequency range, the better the spatial effect. On the other hand, overamplified higher frequencies can, for example, degrade the perceived speech quality as far as speech naturalness is concerned, whereas speech intelligibility as such may still improve. The properties of the bandwidth expansion block 20 can be taken into account when designing HRTF filters generally used to implement spectral and ILD cues. Some frequency bands can be amplified and others attenuated. These interrelations are not crucial but can be utilized when optimizing the invention. There is also another interrelation between the bandwidth expansion 20 and the spatial processing 30 . The HRTF filters that are preferably used for the spatial processing typically emphasize certain frequency bands and attenuate others. To enable real-time implementations these filters should preferably not be computationally too complex. This may set limitations on how well a certain filter frequency response is able to approximate peaks and valleys in the targeted HRTF. If it is known that the bandwidth expansion 20 boosts certain frequency bands, the limited amount of available poles and zeros can be used in other frequency bands, which results to a better total approximation, when the combined frequency response of the bandwidth expansion 20 and the spatial processing 30 is considered. Therefore, the bandwidth expansion 20 and the spatial processing 30 may be jointly optimized to reduce and re-distribute the total or partial processing load of the system, relating to e.g. the expansion 20 or the spatial processing 30 . The bandwidth expansion 20 may, for example, shape the spectrum of the bandwidth expanded audio signal in such a way that it further enhances the spatial effect achieved with the HRTF filter of limited complexity. This approach is especially attractive when said spectrum shaping can be done by simple weighting, possibly simply by adjusting the weighting coefficients or other related parameters. If the existing bandwidth expansion process 20 already comprises some kind of frequency weighting, additional modifications necessary for supporting the specific requirements of the spatial processing 30 may be practically non-existent, or at least modest. Additionally, aforementioned techniques can be applied in a multiprocessor system that runs the bandwidth expansion 20 in one processor and the spatial processing 30 in another, for example. The processing load of the spatial audio processor may be reduced by transferring computations to the bandwidth expansion processor and vice versa. Furthermore, it is possible to dynamically distribute and balance the overall load between the two processors for example according to the processing resources available for the bandwidth expansion 20 and/or spatial processing 30 . FIG. 2 illustrates a block diagram of a signal processing arrangement according to another embodiment of the invention. In the illustrated alternative embodiment, no control information is provided from the speech decoder 10 to the artificial bandwidth expansion block 20 . Instead, the control information is provided by an additional voice activity detector (VAD) 40 . It should be noted that the VAD block 40 can be integrated into the bandwidth expansion block 20 although in the figure it has been illustrated as a separate element. The system can also be implemented without any interrelations between the various processing blocks. According to an embodiment of the invention the audio decoder 10 is a general audio decoder. In this embodiment of the invention the implementation of the bandwidth expansion block 20 can be different than what is described above. A possible application for this embodiment of the invention is an arrangement in which the coded audio signal is provided by a low-bandwidth music player, for instance. It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

A processor for processing an audio signal can have a receiving unit configured to receive an audio signal, an expansion unit configured to expand a bandwidth of the audio signal, and a processing unit configured to process the audio signal having an expanded bandwidth for spatial reproduction.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation in part of U.S. patent application Ser. No. 12/586,545 filed on Sep. 23, 2009 and claims the benefit of U.S. provisional patent application filed on Sep. 23, 2008. BACKGROUND OF THE INVENTION [0002] This invention concerns ropes or lines as they are called on a boat, and more particularly securing ropes or lines to hold a load, moor a boat, tighten a guy line for a tent, etc. Traditionally, knots have been tied into the rope or line to form a loop but this is time consuming to tie and untie, and also requires a good knowledge of the proper knot for a given purpose. [0003] While rope or wire clamping devices have been devised, these are not particularly suited to nautical application and are themselves sometimes inconvenient to clamp or release. [0004] An object of the present invention to provide a simple but durable and weatherproof device for quickly securing two rope or segments of a rope together or releasing the same which is suitable for boating applications but also for a wide variety of other purposes. SUMMARY OF THE INVENTION [0005] The above recited object as well as other objects which will be apparent upon a reading of the following specification and claims are achieved by a rope or line clamping device comprised of two generally tubular rotary members snap fit together to be securely held assembled to each other while being relatively rotatable to each other about a common axis. The members are preferably molded from a tough plastic material. Each member is formed with a radially extending internal web or wall which are juxtaposed next to each other. Each web has one or two holes formed therein, the holes each being elongated such as of an oval shape and located at a location radially offset from the rotary axis of the members. [0006] In one rotated position of the two members, the elongated holes are aligned with each other. The rope or line segments are inserted therein with the members then relatively rotated causing the holes to become increasingly offset with respect to each other, to in turn cause the size of a through opening defined by the overlapped areas of the holes to become progressively reduced. [0007] This allows a clamping action to be carried out by edges of the two holes which compress the rope segments passed through both holes. [0008] A ratcheting mechanism securely holds each of the members in relatively rotated position to prevent loosening once the rope segments have been clamped together. [0009] A ratchet pawl on one member is radially deflectable inwardly to overrun in one rotational direction in which clamping is carried only and, by the grip of the user to selectively move teeth on a element out of engagement with ratchet teeth formed extending at least partially around the perimeter of the other member, allowing reverse releasing rotation between the two members as long as the pawl is held in its released position. [0010] The pawl element is preferably integrally formed with the one member when molded and is moved radially by bending of a connecting leg within an opening in the one member. [0011] An additional hole can be provided in each member to provide two smaller holes in each web which are caused to be simultaneously increasingly offset when the members are relatively rotated. The smaller sized holes will clamp to individual smaller rope diameters to allow use with a greater range of rope sizes. DESCRIPTION OF THE DRAWING FIGURES [0012] FIG. 1 is a side view of a clamping device according to the invention showing rope segments clamped together therein. [0013] FIG. 2 is an enlarged pictorial view from the top of an outer member forming a part of the clamping device shown in FIG. 1 , the outer member inverted from its position in FIG. 1 . [0014] FIG. 3 is a pictorial view from the bottom of the inner member forming a part of the rope clamping device shown in FIG. 1 . [0015] FIG. 4 is a top view of the clamping device shown in FIG. 1 in the fully open relative rotated position of the members. [0016] FIG. 5 is a top view of the clamping device shown in FIG. 4 with the inner and outer members relatively rotated 180° to the minimum through opening position. [0017] FIG. 6 is a top view of the clamping device as shown in FIG. 4 but with the outer member shown in phantom lines. [0018] FIG. 7 is a top view of the clamping device as shown in FIG. 6 but rotatably advanced to the minimum through opening clamping position. [0019] FIG. 8 is a top view as shown in FIG. 6 but with rope segments disposed therein and rotated to an intermediate clamping position. [0020] FIG. 9 is a fragmentary top view of the clamping device as shown in FIG. 8 , but with the pawl element depressed to be disengaged from the ratchet teeth on the inner member. [0021] FIG. 10 is an enlarged fragmentary sectional view through a portion of the assembled inner and outer members. [0022] FIG. 11 is a top or end view of a second embodiment of a clamping device according to the invention, having two holes in a web of each member, shown in their aligned position. [0023] FIG. 12 is a top or end view of the clamping device shown in FIG. 11 with the members rotated to offset both holes in each member. DETAILED DESCRIPTION [0024] In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims. [0025] Referring to the drawings and FIGS. 1-3 , the rope or line clamping device 10 receives two segments of a rope 12 passing through the device 10 , the rope doubled over to form a loop and are clamped together by limited relative rotation of two members assembled together, for convenient reference referred to as an outer member 14 and an inner member 16 . [0026] The outer member 14 has a ribbed rim 18 for convenient gripping, while the smaller diameter tubular body 20 of the inner member 16 is longer and ribbed also for a convenient gripping. [0027] The outer member 14 also has a smaller diameter tubular body 22 . [0028] Both bodies 20 and 22 have an internal web or wall 24 , 26 extending across the inside diameter thereof. Each web 24 , 26 has a hole 28 , 30 formed therein which are preferably of an elongated shape such as the oval shape shown. [0029] The holes 28 , 30 are both located offset from the center axis of the bodies by preferably the same distance and preferably are of the same shape so that in one relative position of the members 14 , 16 , the holes 28 , 30 are aligned with each other. [0030] This defines the maximum area through opening defined by the overlapped areas of the two holes 28 , 30 and through which the two rope segments 12 A, 12 B of the rope 12 are inserted. [0031] When the two members are relatively rotated, as while gripping the ribbed rim 18 and body 20 in each hand, the holes 28 , 30 become misaligned to a progressively greater extent, as seen in FIGS. 8 and 9 to reduce the area of overlap and thus to reduce the size of the through opening. This causes the edges of the holes 28 , 30 to compress against the two rope segments 12 A, 12 B clamping them together. The thickness of the webs 24 , 26 is sufficient as to not cut into the rope while creating sufficient pressure to securely engage the same, i.e., about an ⅛ inch thickness has been found to be satisfactory for this purpose. [0032] The two members 14 , 16 are preferably molded using a high strength plastic, such as 67% nylon filled with 33% fiberglass fibers. A UV protection additive is also desirable. [0033] The two members 14 , 16 have an internal ratchet mechanism described below which secures the two members 14 , 16 in each advanced rotative position when rotated in one direction (clockwise in the Figures) from the fully open position shown in FIG. 4 . The ratchet mechanism is able to be released by pushing on a release button 32 projecting beyond the rim 18 of the outer remember 14 . [0034] The body 20 of the inner member 16 has a slightly larger diameter rim 34 which projects above the internal web 26 and is formed for about half its inner surface with a series of internal ratchet teeth 36 which are shaped to mate with several ratchet teeth 38 facing out on a pawl 40 connected to the button 32 . [0035] The pawl 40 is molded integrally with the outer member 14 but fit within a recess 42 formed in the rim 18 , the body 22 and web 24 , cantilevered on the end of a leg 44 projecting axially from the body 22 adjacent the upper side of the recess 42 . The leg 44 is thick enough (about 3/16 inches) and short enough to hold the ratchet teeth 36 , 38 firmly in engagement, but still allow the pawl 40 to be deflected radially inward sufficiently to disengage the teeth 36 , 38 when compressed by the user's grip allowing relative opening rotation of members 14 , 16 , and also to allow the ratchet teeth 36 , 38 to overrun each other when relatively rotating the member 14 , 16 in the clamping direction. [0036] The inside diameter 19 of the rim 18 is formed with a groove 46 at the bottom of the rim 18 . The groove 46 extends around to either side of a clearance space 48 formed between the ratchet button 32 and pawl 40 . [0037] This clearance enables the rim 34 to rotate through while allowing engagement of the ratchet teeth 36 and 38 . [0038] The two members 14 and 16 are snap fit together to partially overlap each other with the rim 34 (which is chamfered to make fitting easier) inserted into the inside diameter 19 . [0039] A series of spaced sloping shallow features 50 interact with the rim chamfer to enable the rim 34 to be compressed slightly and also expand the rim 18 during insertion until passing over the features 50 . Thereafter, the rims 34 , 18 snap back to their unstrained dimensions to be captured above the features 50 , and the members 14 , 16 are held together with assembly but able to relatively rotate to a limited extent as will be described below. In order to facilitate expansion of the rim 18 during assembly, a series of spaced windows 52 are formed therein around the perimeter thereof. [0040] The relative rotation between the members 14 , 16 is limited to about one half turn by an axially projecting tab 54 integral with the rim 34 . The tab 54 rides in the groove 46 where it is deepest. The groove 46 has a segment 46 A beyond the adjacent windows on either side of the pawl 40 which is shallower such that the tab 54 prevents relative rotation in either direction past the deep section of the groove 46 . [0041] This prevents relative rotary movement of the members 14 , 16 past the full open position in a counterclockwise direction (shown in FIG. 6 ) or past the most advanced clamped position in a clockwise direction (shown in FIG. 7 ). [0042] Another tab 56 projects radially from the perimeter of the hole 30 at its midpoint. This tends to engage and move the rope segments 12 A to a long ways juxtaposition within the holes 28 , 30 as seen in FIG. 8 to insure a strong grip is achieved. [0043] In use, the members 14 , 16 are rotated to the fully open position seen in FIGS. 4 and 6 . [0044] After insertion of the rope segments into the through opening defined through the holes 28 , 30 , the members 14 , 16 are relatively rotated in a clockwise direction to reduce the through opening size by progressive misalignment of the holes 28 , 30 until the rope segments are tightly compressed by the hole edges as seen in FIG. 7 or 8 . Different size ropes can be clamped within a predetermined range by greater or lesser rotation of members 14 , 16 . [0045] The ratchet teeth 36 , 38 override when the members 14 , 16 are relatively rotated in that direction but immediately lock together upon release of the members preventing any attempted counter rotation so that the members 14 , 16 are held locked together with the rope segments 12 A tightly clamped. [0046] By compressing the release button 32 as with one finger when gripping the rim, the ratchet teeth 36 , 38 are released as seen in FIG. 9 , allowing counter rotation to the release condition of FIG. 6 . [0047] FIGS. 11 and 12 show a second embodiment of a clamping device 10 A in which a pair of ovate smaller holes 28 A, 28 B are formed in web 24 of body 20 A and a pair of similarly shaped holes 30 A, 30 B in web 26 A of body 22 A, each hole in said 28 A, 28 B and 30 A, 30 B located diametrically opposite each other and offset from the common axis of relatively rotation of members 14 A, 16 A. Thus, a rope segment (not shown) can be inserted through each set of holes 28 A, 30 A, and 28 B, 30 B and simultaneously clamped when the members 14 A, 16 A are relatively rotated as seen in FIG. 5 , reducing the through opening size spaces through which the rope or line segments pass to clamp the same. This arrangement allows accommodation of a greater range of rope diameters. [0048] A diametrical reinforcing rib 58 is molded into the web 28 extending between the two holes 30 A, 30 B. [0049] The clamp device described is simple and rugged but highly reliable in operation, providing great convenience in securing or releasing lines on a boat, guy lines on a tent, tying down a load with a rope, etc.

A rope or line clamping device, including an assembly of two interfit tubular molded plastic members each having an internal web which are juxtaposed with each other and formed with elongated holes offset from the rotary axis of the members so that the holes progressively become more misaligned upon relative rotation of the members in a direction reducing the overlapping of the two holes. A ratchet mechanism holds the members in any relatively rotated position to hold rope or line segments inserted into the holes clamped together until the ratchet mechanism is selectively released allowing reverse relative rotation. In a second embodiment two sets of smaller holes are provided to separately clamp two rope or line segments.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoresistive strain sensing device in which diffused resistors are formed in a semiconductor single-crystal substrate. More particularly, it relates to a piezoresistive strain sensing device which is well suited to sensitively and precisely detect a stress field acting on an IC chip within a semiconductor package. 2. Description of the Prior Art Prior art devices wherein a mechanical stress resulting from the application of a strain, is converted into an electric signal by utilizing the piezoresistance effect of a semiconductor, include, for example, a semiconductor strain sensor as disclosed in the official gazette of Japanese Patent Application Laid-open No. 56-140229. In this device, a bridge circuit is formed by diffused resistors on a diaphragm of silicon, and a strain is measured by detecting the fractional change in resistivity based on the deformation of the diaphragm attendant upon a surface strain. Another prior art device has been attempted in which a diffused resistor is formed on a silicon substrate, and the substrate is buried in a resin which acts as sensing means, thereby to detect a two-dimensional stress field acting within a surface formed with the diffused resistor. In either case, however, only the detection on a specified stress component is achieved, and the use is limited. A three-dimensional stress field exists in a general structure, and mechanical strain-electricity transducers including the prior-art semiconductor strain sensors have had the problem that the three-dimensional stress field cannot be separately detected. SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoresistive strain sensing device which sensitively and precisely detects a stress field acting in a semiconductor device. The semiconductor pressure conversion device according to the present invention is formed on a semiconductor single-crystal substrate and consists of a diffusion resistance gauge composed of a combination of p-type and n-type diffusion resistance layers, and of a temperature detecting unit composed of a combination of p-type and n-type diffusion layers. In general, the piezoresistance effect in a semiconductor such as silicon is expressed as: ##EQU1## using a resistivity ρ and a stress tensor X each of which is denoted by a tensor of the second order, and a tensor π of the fourth order. Since, in general, the tensor of the second order such as ρ or X is given by a six-component vector notation, the tensor π of the fourth order is expressed as a 6×6-element tensor. Here, π ik is called the "components of the piezoresistance tensor" and consists, in general, of 21 independent components. The number of the independent components decreases in a crystal of good symmetry, and it becomes 3 (π 11 , π 12 , π 44 ) in a crystal having the cubic symmetry such as silicon or germanium. Since (100) crystallographic plane substrates are generally used for manufacturing IC's, assume in this type of substrate a three-orthogonal x-y-z axis system in which the (100) crystallographic plane defines the x-y plane, and the [001] crystallographic axis and the x-axis are coincident with each other. Under this condition, the piezoresistive effects observed at diffusion resistors formed in parallel with the (100) crystallographic plane are expressed as follows: ##EQU2## where, δ ρij is a resistance value change rate calculated from a voltage measured in the j-direction when a current is applied in the i-direction of each diffusion resistor; σx, σy, σz are stress components along the three axis, respectively; τxy is a shearing stress component in the x-y plane; and π 11 , π 12 , and π 44 are proportional constants (piezoresistance coefficients). Accordingly, stress components which affect the fractional changes of resistivity of the diffused resistor of the (100) planes are four components (σ x , σ.sub.υ Ψσ z , σ xy ), and the resistivity changes which are independently detectible are of three components (δρ xx , δρ yy , δρ xy )001, so that the stress field acting in the crystal plane cannot be uniquely determined. Since, however, the piezoresistance coefficients (π 11 , π 12 , and π 44 ) differ depending upon the kinds of dopants used for diffused resistors, the resistivity changes can be independently detected in the respective diffused regions of the p-type diffused resistor and the n-type diffused resistor which are arranged in proximity to each other, the resistivity changes of a maximum of six components can be independently measured in both the regions. Accordingly, p-type and n-type diffused resistors are formed in the (100) plane of a semiconductor substrate whereby four resistor gauges capable of independent measurements can be provided, and the four stress components influential on the resistivity changes can be uniquely determined. FIG. 1 is a plan view of a first embodiment of a piezoresistive strain sensing device according to the present invention; FIG. 2 is a sectional view taken along line II--II' in FIG. 1; FIG. 3 is a plan view of a second embodiment of the piezoresistive strain sensing device of the present invention; FIG. 4 is a sectional view of a third embodiment of the piezoresistive strain sensing device of the present invention; FIG. 5 is a plan view of a fourth embodiment of the piezoresistive strain sensing device of the present invention; and FIG. 6 is a sectional view taken along line VI--VI' in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a piezoresistive strain sensing device according to the present invention will be described with reference to FIGS. 1 and 2. In this embodiment, a strain sensor is constructed by making a p-type diffused resistor 3 and an n-type diffused resistor 2 on an n-type silicon (100) substrate 1 by a use of the CMOS process. FIG. 1 shows a plan view, while FIG. 2 shows a sectional view taken along line II--II' in FIG. 1 and illustrates the formed states of the diffused resistors. The p-type diffused resistor 3 and the n-type diffused resistor 2, which are buried in a p-type diffused resistor layer 7, are respectively made in the shape of rectangles in proximity to each other, and electrode terminals 4 are provided on the four sides of each rectangle. The electrode terminals 4 are isolated by an SiO 2 film 5, and the whole surface is covered with a passivation film 6. Regarding the directions of the sides of the rectangles, the direction along the line II--II' is set to be the x-direction, and the direction orthogonal thereto in the same plane is set to be the y-direction. A method of measuring the changes of a resistivity in each diffused resistor will be described. Current is caused to flow across the two electrodes opposing in the x-direction, and the potential difference across both the electrodes is measured, whereby δρ xx in the equation (2) mentioned before is measured. A similar method is performed across the two electrodes opposing in the y-direction, whereby δρ yy in equation (2) is measured. In addition, current is caused to flow across the electrodes opposing in the x-direction, and the potential difference across the electrodes opposing in the y-direction is measured, whereby δρ xy in equation (2) is determined. Thus, the resistivity changes of the three independent components can be measured with the single diffused resistor. When δρ xy is measured with either of the p-type and n-type diffused resistors, and three of δρ nxx , δρ nyy , δρ pxx and δρ pyy are measured, four independent resistivity changes can be measured within the single crystal plane. According to the present embodiment, four independent resistivity changes can be measured within the (100) crystal plane of silicon, and this allows for the stresses σ x and σ y in the directions of two axes, a shear stress τ xy and a stress σ z perpendicular to the plane, which act on the crystal plane, to be uniquely determined. A second embodiment of the piezoresistive strain sensing device of the present invention will be described with reference to FIG. 3. This figure shows a plan view of a thin-film stress/strain sensor to which the present invention is applied. A single-crystal thin film of silicon having the (100) plane is formed on a film substrate (of, for example, PIQ) 8, and p-type diffused resistors 3 and n-type diffused resistors 2 are formed as shown in the figure. One end of each of these diffused resistors 2 and 3 are connected by a common pattern 12, and are held in communication with a common electrode terminal 13. The single-crystal thin film is produced by a thin-film manufacturing process such as vacuum evaporation, CVD (Chemical Vapored Deposition), sputtering evaporation or epitaxial growth. Here, when the p-type diffused resistors 3 are arranged along the conventional crystal axis <011> and the n-type diffused resistors 2 along <001>, the resistivity changes of the respective resistors are expressed as: ##EQU3## In equation (3), π ij denotes a piezoresistance coefficient in the case where the direction of the <001> crystal axis is brought into agreement with the directions of the three right-angled axes. Since the resistivity changes in the p-type diffused resistors 3 and the n-type diffused resistors 2 are independently measured, the four components of stresses (σ x , σ y , σ z , σ xy ) are uniquely determined. From this fact, it is apparent that the thin-film stress/strain sensor for semiconductors can be constructed. A third embodiment of the piezoresistive strain sensing device of the present invention will be described with reference to FIG. 4. This figure is a sectional view of a semiconductor pressure sensor. In the surface layer of an n-type silicon (100) single-crystal substrate 1 in the shape of a disc, a p-type diffused resistor 3 and an n-type diffused resistor 2 are formed to construct a gauge. The single-crystal substrate 1 is bonded to a glass substratum 10 by a low-melting glass 9. Further, an n + -type diffused resistor 11 is formed in a p-type diffused layer 7, to construct a p/n-junction, whereupon the temperature of the gauge is detected. Thus, a temperature compensation circuit is formed, and measurements in a wide temperature range become possible. Moreover, since the silicon substrate may be in the shape of a disc, a high degree of etching accuracy as in the case of making a diaphragm is dispensed with, so that enhanced production percentage is achieved. According to the embodiments thus far described, since four resistivity changes within the (100) crystal plane of a semiconductor can be measured, it is possible to realize a piezoresistive strain sensing device which can uniquely determine the four stress components acting on the (100) crystal plane; stress components in the directions of three right-angled axes, two of them being contained in the plane, and a shear stress acting within the plane. A fourth embodiment of the piezoresistive strain sensing device of the present invention will be described with reference to FIGS. 5 and 6. This embodiment is a stress sensor which is fabricated using an n-type silicon (111) single-crystal disc 21 as a substrate FIG. 5 is a plan view, while FIG. 6 is a schematic sectional view taken along line VI--VI' in FIG. 5. Six diffused resistors 22 and 23 formed on the substrate 21 consist of three p-type diffused layers 22 and three n-type diffused layers 23. One end of each of the respective layers 22 or 23 is connected by a single aluminum pattern 24 or 32. It is assumed that the individual diffused resistors 22 or 23 be formed at angular intervals of 45°. It is also assumed that the direction of the line VI--VI' agrees with the direction of the <112> crystal axis. One end of each of the three p-type diffused resistors 22 is connected to a common electrode terminal 29 through the single common A1 pattern 24, whereas the other ends thereof are connected to separate electrode terminals 31 through separate A1 patterns 30. Likewise, one end of each of the three n-type diffused resistors 23 is connected to a common electrode terminal 33 through the single common A1 pattern 32, whereas the other ends thereof are connected to separate electrode terminals 35 through separate A1 patterns 34. The n-type diffused resistors 23 are formed in a p-type diffused layer 25. In addition, the A1 patterns 24 etc. are isolated by an SiO 2 insulator film 26, and the whole surface is covered with a passivation film 27. The p-type diffused layer 25 is formed with an n-type diffused resistor 28, to simultaneously make a p/n-junction for temperature compensation. Now, the operation of this sensor will be described. The three right-angled axes are given with the x-direction being the direction of the line VI--VI', the y-direction being a direction orthogonal thereto within the plane and the z-direction being a direction perpendicular to the plane, and stresses in the axial directions and shear stresses within respective planes are respectively denoted by σ and τ. In FIG. 5, a resistivity on the line VI--VI' is denoted by ρ 2 , that on the left side thereof is denoted by ρ 1 , and that on the right side thereof is denoted by ρ 3 . Then, the corresponding resistivity changes are expressed as: ##EQU4## For diffused resistors of the p-type diffused layers 22 and those of the n-type diffused layers 23, the values of the piezoresistance coefficients π i (i=α, β, . . . ) are different, so that six sorts of independent resistivity changes can be measured. Since stress components contributing to the respective resistivity changes are of six sorts, the respective components of the stress tensor or the three-dimensional stress field are/is separately detected by solving the matrix of equation (1). The embodiment thus far described shows that a sensor for detecting a three-dimensional stress field can be realized, and that measurements at temperatures in a wide range are permitted by utilizing a p/n-junction for temperature compensation. In the foregoing embodiment, the individual diffused resistors 22 or 23 are formed at the angular intervals of 45°. This means that, on the (111) crystal plane, the lengthwise directions of the resistor layers are brought into agreement with the <112> crystal axis and the <110> crystal axis, while one resistor layer is arranged in the direction of 45° between them. In principle, however, the directions of the arrangement of the resistor layers may be as desired (except a case where two or more resistors become parallel among the same kind of diffused resistor layers). Although three diffused resistors of each type of conductivity are shown in FIG. 5, the number of resistors of each conductivity type may well be four or more. Since the number of stress components acting independently is six, the stress components are uniquely determined when there are at least three diffused resistors of each conductivity type, namely, at least six resistors in total. In the case of forming at least four diffused resistors of the same conductivity type, at least three of them may extend in crystal orientations differing from one another. In an actual measurement, changes in the resistivities of the diffused resistors are respectively detected. In each of the foregoing embodiments, the semiconductor single-crystal substrate may be replaced with a single-crystal thin film produced by a thin-film manufacturing process such as vacuum evaporation, CVD, sputtering or epitaxial growth. According to each embodiment described above, six sorts of independent resistivity changes caused by the piezoresistance effect can be detected on the same semiconductor single-crystal substrate and hence, a stress sensor for determining a three-dimensional stress field can be realized.

A piezoresistive strain sensing device is comprised of a semiconductor single-crystal substrate, having crystal indices in the (100) phase, and having p-type and n-type diffused resistors formed therein. A diffused resistance gauge is formed of the p-type and n-type resistors. Temperature compensation means are formed adjacent the resistance gauge in the substrate.

BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] The invention relates to human/computer interfaces on portable devices such as PDA's and other similar telecommunication systems, to provide portable software systems intended for rehabilitation by means of color therapy. [0003] 2. Prior Art [0004] Prior art is divided into three primary categories, diagnostic tools, rehabilitation treatment methods, and previously designed light therapy treatment methods. [0005] The first area of prior art is the manner of diagnostic tools used in the development of wave-front color therapy in conjunction with therapeutic prescriptions. To date, color therapy in conjunction with therapeutic prescription use has been a manual, often tedious process not capable of pinpointing the precise nanometer of a color's wavelength best suited for the patient's use. [0006] The second area of prior art is the manner of rehabilitation treatment methods for neurological impairments such as stroke, brain injury, CVA, and MS to name several, and learning disabilities such as Attention Deficit Disorder, and ADHD. [0007] There is a host of computer based, non-portable, dumb-terminal rehabilitation systems used within the structure of cognitive, vision and learning disability rehabilitations. They are geared at re-training the impaired or injured neurological processes. [0008] Unfortunately, there are two basic shortcomings to the conventional approach of neurological rehabilitations. These machines are only available to the rehabilitation facility due to cost and size and are therefore not available for private patient consumer use. This limits the amount of time a patient can spend using these rehabilitation tools due to a number of factors, as set forth below. [0009] First, a patient who is a candidate for neurological rehabilitation is often also attending physical and occupational therapies, recovering from surgeries or other treatments and procedures associated with their neurological assault. During the time crucial window of cognitive and visual rehabilitation, a patient's day is consumed with therapies and doctors visits, often leaving the time that can be spent on cognitive rehabilitation shortchanged or even completely neglected. [0010] Second, the neurologically impaired patient's rehabilitation is also subject to the schedules of their caretakers as they are often unable to transport themselves, inclement weather, flare-up of injuries, or office scheduling conflicts. [0011] Despite the enormous amount of time devoted to the rehabilitation process involving doctors and rehabilitation specialists, a patient spends a great deal of time waiting in medical waiting rooms, waiting for transportation between appointments, and at the end of the day, is often too exhausted to attend to cognitive rehabilitation and the associated exercises. This time can be recaptured with a portable rehabilitation device to make best use of spare time to become rehabilitation time. [0012] A patient who does not face the aforementioned problems can also use this device to maximize their rehabilitation, reducing rehabilitation expense while making best use of the window of maximum rehabilitative progress. [0013] Third, a fundamental problem in the conventional approach is that is does not fully take into account the need of the learning impaired student. [0014] A learning impaired student is paired with a learning specialist during school hours, which either robs time from their education or uses their break periods, leaving an already overworked student without a break during the day. The second approach is to team a student with a learning specialist after school, taking time away from homework and putting a student further behind in their work. [0015] Any adaptive technology devices that a mainstreamed student may be offered might not be available in all schools, and a student may often be embarrassed to use them in front of others students who may perceive a learning disability as a lack of intelligence on the part of the disabled student. Fear of such a perception may render a student reluctant or too embarrassed to use the adaptive tech tools designed to help them. [0016] Color Therapy has long been used medically. Color, or Light Therapy is used for a number of purposes, including, Seasonal Affected Disorder (SAD), dermatological purposes, cosmetic enhancement, as well as for Syntonic Optometry. The latter has been used for the past 70 years for treatment of several optometric disorders. Recently, it has been shown to be helpful in the diagnosis and treatment of brain injuries, Cerebro-vascular accidents (CVA), and other neurological disorders. [0017] There are, however, several failings of the treatments and therapies developed to date: 1) White light machines. Many light machines emit full spectrum white light, not specific and finite wavelengths. There are multiple benefits to being able to isolate a finite wavelength, as in the case of this claimed computer program: a. The white light machines available today, by their very nature, emit all wavelengths in the visible spectrum. For as therapeutic as certain wavelengths of color can be to a patient, another wavelength could be harmful or uncomfortable, and there is no way to omit the uncomfortable or harmful wavelengths from a white-light machine and only use the helpful ones for therapy. b. Many patients who suffer neurological problems suffer from photophobia, or sensitivity to light and glare. While some white light machines have a dimmer, this may not reduce brightness and glare enough for the patient and cause discomfort, and would not be therapeutic. c. Since all colors are emitted from a white light machine, it is impossible to determine what wavelengths could be most helpful to the patient. In contrast, this computer program can isolate the exact wavelength of color that is beneficial to the patient. d. White light machines often require extended periods of time per day to receive therapeutic benefit. By this program isolating to the most therapeutic range of wavelengths, the patient will receive the most precise diagnosis and the best therapy for their specific disorder in the shortest amount of time. This is essential as there is a limited window of time after neurological injury or onset of a neurological illness that a patient has to capture the majority of recovery they will make—thus, time is of the essence. 2) Methods of color therapy developed to date that isolate certain color spectrums are generally unable to provide the diagnostic benefits of the computer program claimed herein due to their inability to produce the scope of colors necessary. In addition, they also lack certain elements of the ideal color manipulation therapy. One such example is the use of lasers and radiation of certain colors on the eye, with the obvious side effects associated with lasers and radiation. Other methods of light therapy involve physically dangerous illumination apparatuses such as gas or flame, which are dangerous and prohibit unattended or at home use due to their very nature. None of these factors are an issue with the current claimed invention. SUMMARY OF THE INVENTION [0025] It is therefore an object of the current invention to use current and future computer and telecommunication handheld and mobile devices as a method of transportable rehabilitation, light therapy treatments, and a diagnostic device. The use of a handheld device is especially useful in this regard as these handheld devices have a life use beyond the rehabilitation of the patient, and are often distributed to those with neurological impairments by disability agencies making the procurement of such a device far more cost effective than any other rehabilitation device currently available. [0026] Software that is intended for rehabilitation can be adapted for handheld device use. Such software can be purchased or downloaded to the handheld device via the Internet or from the rehabilitation office. This allows the rehabilitation office to provide consistent rehabilitation when a patient is unable to attend. This would require a software suite available to the office, as well as a website for download of software to the handheld device. [0027] It is still a further object of the present invention that it provides a computer display for visually-impaired users that is convenient, lightweight, low-cost, minimally power hungry, and capable of portable operation without degraded performance. [0028] In addition to the objects above, and in all handheld or otherwise portable devices useful in the present invention, less portable means of display such as laptop computers, desktop computers, televisions, or any other telecommunication or display device are also useful in the present invention. [0029] A color light therapy computer method and apparatus has been produced with the capability to display a full range of wavelengths systematically delineated of the visual spectrum. Using said program claimed herein as a foundation application, with various modifications, the preciseness of the wave length production and display thereof allows for a diagnostic process and a host of rehabilitative and treatment applications to be produced from the same fundamental program. BRIEF DESCRIPTION OF THE DRAWINGS [0030] The above-mentioned features and objects of the present invention will become more apparent with reference to the following description taken in conjunction with the accompanying drawings wherein like reference numerals denote like elements and in which: [0031] FIG. 1 is a table illustrating the visible colors spectrum shifting combinations used in a computer program for a computer capable of at least 256,000,000 colors; [0032] FIG. 2 is a block diagram for an apparatus in accordance with the teachings of the present invention; [0033] FIG. 3 is a flow diagram illustrating the method of present invention; and [0034] FIG. 4 is a flow diagram illustrating the shifting of the combination of the visible color spectrum in a computer program of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0035] Although the visual system has been traditionally looked at as a sensory system to provide information about detail and spatial awareness, research has also documented that the eyes deliver important photopic information to brain centers which affect hormonal imbalance, diurnal cycle for sleep regulation, and metabolic function. John Ott has described in his research that various wavelengths in the photopic spectrum have significant affects on the growth of plants as well as human biological functions. [0036] The human eye responds to a visual spectrum between 400 nanometers and 700 nanometers. The change in wavelength is processed by the brain through the eyes and establishes the perception and interpretation of color. Shorter wavelength is perceived in the blue end of the spectrum while longer wavelength is perceived in the red end of the spectrum. It has also been documented that the retina of the eye is characteristically sensitive to long wavelengths in the central or macular region of the eye, while the peripheral part of the retina is more sensitive to short wavelengths or the blue spectrum. [0037] Two visual processing centers have been found in the brain. The occipital cortex is the primary area of the brain for establishing imagery and detail detection through central macular involvement. This portion of the visual system and brain relays information to higher cognitive and perceptual processes. This has been called the focal vision process. A second visual process relays approximately 20% of all of the sensory nerves from the eyes to a lower portion of the brain known as the midbrain or thalamus. It is here that the peripheral information received from the eyes is relayed and matched with balance and movement centers such as the kinesthetic, proprioceptive, and vestibular processes. This portion of the visual system has been called the ambient vision process. It organizes information related to spatial function for support of balance and anticipation of movement. This is the first part of the visual process that must respond to visual stimuli. Once information is matched between the ambient and sensory motor processes, it is feed-forwarded to the occipital cortex and 99% of the higher cerebral cortex. The purpose of which is to relay information particularly to the occipital cortex in order to pre-program it how to see the world spatially or more as a whole. It is responsible to establish relationships among the details as well as to spatially coordinate binocular integration cells to blend and merge the separate images of each eye into one. This process is called fusion. [0038] It is also determined that the focal and the ambient process not only respond to different wavelengths of the visual spectrum, but that they also organize a temporal component related to spatial function in two different manners. The focal process will tend to isolate and upon doing so, will attempt to slow time or temporal relationships. The ambient process conversely tends to speed up temporal relationships. A simple experiment will demonstrate this. If a drum with vertical stripes is rotated at a constant speed, one will perceive the speed of the stripes differently if they concentrate hard on each stripe and attempt to focalize the visual process compared to if they relax and attempt to stare through the drum not concentrating on each stripe. The focal process when engaged will cause the person to perceive that the rotating stripes will appear to slow down in temporal context whereas when staring through the drum and not concentrating on the stripes, the ambient visual process will tend to cause the subject to perceive that the stripes will speed up temporally. [0039] Understanding that the ambient and focal visual processes are critical for organization of space related to temporal function and that the organization of space and time must be established in order for higher cognitive perceptual processes to function properly, the function of the ambient and focal process in relationship to each other can alter function and performance of the individual and further, any interference neurologically with the relationship established between these two processes will interfere with aspects of spatial orientation, perceptual motor function, cognitive function, and higher perceptual interpretation. [0040] Following a neurological event such as a cerebrovascular accident (CVA), traumatic brain injury (TBI), multiple sclerosis (MS), cerebral palsy (CP), autism, etc., interference can alter the relationship between the ambient and focal process. This can cause a wide range of dysfunctions as well as symptoms. Characteristics of the dysfunction visually are that imbalances will occur in oculomotor function such as strabismus (ocular deviation) or variation in phoria (tendency for the eyes to deviate in alignment). Problems with convergence, accommodation, and sensory motor function for pursuit tracking and saccadic fixations are often evident. Also, following a neurological event that is related to higher brain dysfunction, a visual field loss will often occur affecting the common field projected by each eye such as with a homonymous hemianopsia. In this condition either the complete right or left visual field will be lost. The field loss, in turn, affects concepts of visual midline. When the visual midline shifts, individuals will then attempt to lean to one side and drift during ambulation. [0041] To perform the functions described above, an apparatus shown in block diagram in FIG. 2 is utilized. This apparatus utilizes a color display or array 2 which is fed with the display output of a central processing unit 4 . This central processing unit 4 may be any computer device such as a desktop computer, laptop, etc., which includes at least a microprocessor, random access memory, a keyboard, a semi-permanent storage system and a color display driver. As an input to the CPU 4 is clinician input 6 which may be the keyboard of the CPU 4 or some other device such as a touch screen, mouse, joy stick, etc. The CPU 4 is capable of providing data output directly to a portable device 8 such as a laptop computer, PDA, etc. Another data output of the CPU 4 goes to a conversion means 10 . The conversion means 10 may comprise a program within the CPU 4 for converting data stored in the CPU 4 into a format capable of being handled by other devices such as laptop computer, PDA's etc. belonging to or leased by the patient and then storing it on a floppy disk, CDROM, DVD, tape, etc. In addition, the conversion means 10 may also comprise a means for providing an interface between the CPU 4 and a local area network, intemet, phone line, etc. [0042] It should also be apparent to one of ordinary skill in the art that a new and “intelligent” devices with more computing capability are created such as intelligent VCR's, CDROM players and DVD players that the function of the device described above and the patients device could incorporate or in fact be such “intelligent” devices. [0043] Referring to FIGS. 1-4 , a mode of therapy for persons who have experienced a neurological event or a neurological dysfunction which interferes with the processing of ambient or focal image system, will be described in the numbered paragraphs 1-5 below. [0044] 1. The patient will be seated before a visual display 2 such as a television, CRT or LCD monitor, which will provide specific wavelengths that are perceived by the visual process as variation in color. The patient will be seated between 15-25 inches from the monitor. The display 2 will be adjusted using the clinician input 6 to provide initially a balance between the blue or short wavelength end of the visual spectrum and the red or long wavelength of the visual spectrum. For patients who have experienced a neurological event or cause that interferes with the ambient visual process, treatment will then be shifted to the blue end of the spectrum by the clinician. The patient will be given three five-minute therapy sessions exposed to short nanometer wavelengths of light. [0045] 2. The apparatus will then be adjusted through the clinician input 6 to the CPU 4 to shift from the blue end of the spectrum toward longer wavelengths. The design of the apparatus will enable the clinician to develop gradation shifting across the spectrum in a variety of ways as shown in FIG. 1 such that blue can be shifted in wavelength toward various spectrum portions such as green, yellow, or red in accordance with the flow diagram of FIG. 4 . This will enable the clinician to be very specific in delivering the direction of the therapy toward specific aspects of motor function, cognitive ftmction, or higher perceptual processes. For example, shifting from blue to red will be oriented to bring spatial relationships to development of figure/ground relationships and perceptual constancy. Shifting to the yellow end of the spectrum will have more specific function related to movement, object localization, and perceptual transformations. Shifting from blue toward the green end of the spectrum will be more related to affecting those patients who are experiencing a highly focalized nature to their vision such as in autism where the visual system will fragment the world into detail or parts. While FIG. 1 is described in terms of at least 256,000,000 possible colors, it should be apparent to one of ordinary skill in the art that the present invention would function with less color combinations. [0046] 3. A temporal component will be added to the color relationship by establishing a stroboscopic affect to the color presentation via clinician input 6 . For those patients who are highly focalized, blue light will begin in a very high stroboscopic affect since the ambient visual process has a higher critical fusion frequency that the focal process. The stroboscopic affect will be slowed as the wavelengths of light are shifted in the direction of the target and the spectrum from the short wavelengths. For those patients who are highly distractible, the temporal component will be started very slowly and increased toward the higher critical fusion frequency. This step could also include the use of multiple strobes or can be even be used without a strobe if either of these options is considered beneficial. [0047] 4. For those patients who are experiencing neurological dysfinction as related to attention deficit disorders, the color or wavelength variation will be shifted from red, yellow, or green toward the blue end of the spectrum in a similar manner described in method one (1). The temporal component will also be altered related to the critical fusion frequency of the focal or ambient process. [0048] 5. For those patients who have experienced a neurological event causing a visual field loss such as a homonymous hemianopsia, the clinician will adapt the display 2 so that half the portion of the screen will provide a color function while the other half of the screen will provide color and a stroboscopic affect. The stroboscopic affect will be delivered to the portion of the visual process that is in the homonymous hemianopic field. For patients with a field loss on the left side, a slow to rapid stroboscopic affect will be provided while fixation will be centered on a target in the middle of the screen. This is to establish half of the visual field in continuous wavefront modulation while the other half of the field related to the scotoma or field loss would be provided wavefront modulation in a stroboscopic affect. The stimulation in the stroboscopic affect as well as specific nanometers will be used therapeutically in an attempt to reestablish a temporal and spatial relationship of those cortical brain cells that no longer are matching information between focal and ambient processing. [0049] Frequently, patients who have suffered a CVA or TBI will have a homonymous hemianopsia. Stimulation of that field repeatedly will cause the cortical cells to reestablish the visual process in the affected field. The wavefront modulation system is designed as a therapeutic mechanism to treat these visual problems that up to this time no methodology or instrument invention has been found to improve function. [0050] Referring further to FIG. 3 , in operation the clinician will start the apparatus and provide initial operator input into the apparatus. Based on this initial input by the clinician, the color display 2 will be adjusted to provide the correct colors, shift and stroboscopic affect. After the patient has been exposed to the color display 2 for the required time, typically 5 minute sessions, the effect of the color therapy will be observed by the clinician who will determine whether or not the therapy is now at an optimum level. If no, there will be further adjustments made and if yes, the optimum color therapy program which has been developed during the session or sessions will be stored in the CPU 4 . So that the patient can utilize this optimum color therapy program developed during the session or sessions, the optimum color therapy program for this particular patient which is stored in the CPU 4 will be then either directly transferred to the portable device 8 of the patient or sent to the conversion means 10 for conversion either to a program in the format usable by the portable device of the patient or into a format which can be transferred over the internet, a local area network, telephone line, etc., to be accessed by a patient at a remote location. The control program for the operation shown in FIG. 3 can be easily created by one of ordinary skill in the art based upon the flow diagram of FIG. 3 . [0051] By providing the patient with the means for utilizing the optimum color therapy program developed specifically for the patient on a device in the possession of the patient and at a location and times of the patient's choice, many of the disadvantages of the prior art can be overcome. [0052] Still further, the apparatus and method of the present invention provides one or more of the following: [0053] 1) A method of diagnosis of optimal color wavelengths for devising an exact therapeutic prescription including nanometer specifications and hue-saturation to prescribe for individuals with a wide range of visual problems, including but not limited to learning disabilities and neurological problems. [0054] 2) A computer-implemented method for assisting a user in cognitive and vision rehabilitation, as well as the rehabilitation and assistance of learning disabilities via a handheld device to assist the visually impaired, learning impaired, as well as those in need of cognitive rehabilitation due to brain injury, stroke, CVA or other neurological injury or disease. [0055] 3) Adaptations of current rehabilitation software as outlined in other patents by the same inventors (Dara Medes, Heather Medes, William Padula) to be downloaded onto a handheld device. [0056] 4) A website to make said software suite available for download onto a handheld device. [0057] 5) A CD, DVD and any such other recordable medium devices to hold such software for distribution. [0058] 6) The software processes of converting rehabilitation software from dumb-terminal non-portable systems to software that is portable via any handheld or telecommunication device. [0059] 7) Neurological Treatment methods in or outside of traditional rehabilitation setting by using said software suite to do rehabilitation in a setting and schedule most convenient to the patient. [0060] 8) Treatments traditionally associated with light therapy including but not limited to vision therapy, sleep disturbance, headaches, asthma, depression, weight problems, adrenal and hormonal imbalances, dermatological enhancement, cosmetic enhancement, amongst others, can be available in a portable form not requiring constant office supervision. [0061] 9) Treatment services traditionally restricted to directly out of a doctor's office may now be monitored via wire or wireless telecommunication or processing devices, including any other form of transmission technology, or in a doctor's or therapist's office setting. This allows for treating the house bound or those geographically far away in or out of a traditional office treatment setting. [0062] The above description is for the purpose of teaching the person of ordinary skill how to practice the present invention, and it is not intended to detail all obvious modifications and variations of it, which will become apparent to the skilled worker upon reading the description. It is intended, however, that all such obvious modifications and variations be included within the scope of the present invention, which is defined by the following claims.

A method and apparatus of providing wave-front color therapy using a computer or portable handheld devices such as PDA's and other portable telecommunication devices to deliver a specific different nanometer wavelength of light to affect a wide variety of visual, binocular, function, perceptual, and cognitive-related vision imbalances that interfere with function and performance. The current proposed device would provide specific treatment for these difficulties by delivering different wavelengths of light through a computer monitor. The exact therapeutic prescription including nanometer specifications and hue-saturation will be prescribed for individuals with a wide range of visual problems caused by a traumatic brain injury, cerebrovascular accident, and Multiple Sclerosis, and the like, to name a few examples. This disclosure claims analog and digital relations of light as it relates to both the spatial and temporal relationship of light.

RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. JP2009-072646 filed on Mar. 24, 2009, the entire content of which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an animal blood cell measuring apparatus. [0004] 2. Description of the Related Art [0005] In making diagnoses on animals, counting reticulocytes is useful for diagnosing animals with, for example, anemia. At veterinary hospitals, currently, counting of red blood cells or white blood cells is often automatically performed using analyzers; however, reticulocytes are visually counted in general. [0006] United States Patent Publication No. 2006/0004530 discloses an analyzer for automatically counting animal reticulocytes. The analyzer of United States Patent Publication No. 2006/0004530 receives the selection of an animal species to be analyzed, and counts blood cells based on analysis conditions corresponding to the received selection of the animal species. Here, blood cells to be counted include reticulocytes in addition to red blood cells, white blood cells, and the like. [0007] Reticulocytes of some animal species consist of a single type of reticulocytes. However, for example, reticulocytes in felines consist of a plurality of types of reticulocytes including punctate and aggregate reticulocytes. Counting aggregate reticulocytes is useful when diagnosing animal species with anemia, whose reticulocytes consist of a plurality of types of reticulocytes. For example, in the case of felines, the number of punctate reticulocytes reaches a peak within 10 to 20 days after an episode of acute blood loss. Thereafter, the punctate reticulocytes disappear over approximately four weeks. Whereas, the number of aggregate reticulocytes reaches a peak within 4 to 7 days after the episode of acute blood loss. Accordingly, counting aggregate reticulocytes, the number of which reaches a peak at an earlier stage than the punctate reticulocytes, is useful, for example, for determining the degree of recovery from anemia (i.e., useful for determining the effect of medication). [0008] As mentioned above, there are known analyzers that automatically count reticulocytes. However, United States Patent Publication No. 2006/0004530 does not give a description in relation to counting only aggregate reticulocytes among reticulocytes consisting of a plurality of types of reticulocytes. Therefore, even if the analyzer disclosed in United States Patent Publication No. 2006/0004530 is used, aggregate reticulocytes have to be visually counted, which imposes a substantial burden on veterinarians and laboratory technicians. SUMMARY OF THE INVENTION [0009] A first aspect of the present invention is an animal blood cell measuring apparatus comprising: a specimen preparation section for preparing a measurement specimen from blood of an animal; a characteristic information obtaining section for obtaining characteristic information indicating a characteristic of the measurement specimen, from the measurement specimen prepared by the specimen preparation section; and a controller configured for performing operations comprising: (a) classifying aggregate reticulocytes contained in the blood from other blood cells, based on the characteristic information obtained by the characteristic information obtaining section; and (b) outputting information regarding a number of the classified aggregate reticulocytes. [0010] A second aspect of the present invention is an animal blood cell measuring apparatus comprising: a specimen preparation section for preparing a measurement specimen from blood of an animal; a characteristic information obtaining section for obtaining characteristic information indicating a characteristic of the measurement specimen, from the measurement specimen prepared by the specimen preparation section; an aggregate-type classifying section for classifying aggregate reticulocytes contained in the blood from other blood cells, based on the characteristic information obtained by the characteristic information obtaining section; and an output section for outputting information regarding a number of the aggregate reticulocytes classified by the aggregate-type classifying section. [0011] A third aspect of the present invention is animal blood cell measuring apparatus, comprising: a specimen preparation section for preparing a measurement specimen from blood of an animal; a characteristic information obtaining section for obtaining characteristic information indicating a characteristic of the measurement specimen from the measurement specimen prepared by the specimen preparation section; a selector for selecting an animal species to be measured, from at least a first animal species and a second animal species; and a controller configured for performing operations, comprising: (a) receiving a selection of the animal species selected by the selector; (b) classifying reticulocytes contained in the blood from other blood cells based on the characteristic information obtained by the characteristic information obtaining section, in response to the received selection of the animal species; and (c) outputting information regarding a number of the classified reticulocytes. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a front view showing a schematic structure of a blood cell measuring apparatus according to an embodiment of the present invention; [0013] FIG. 2 is a perspective external view of a measurement unit according to the embodiment; [0014] FIG. 3 is a perspective view showing an internal structure of the measurement unit according to the embodiment; [0015] FIG. 4 is a side view showing the internal structure of the measurement unit according to the embodiment; [0016] FIG. 5 is a block diagram showing a configuration of the measurement unit according to the embodiment; [0017] FIG. 6 is a fluid circuit diagram showing a specimen preparation section of the measurement unit according to the embodiment; [0018] FIG. 7 is a perspective view schematically showing a configuration of a flow cell according to the embodiment; [0019] FIG. 8 schematically shows a configuration of a flow cytometer according to the embodiment; [0020] FIG. 9 is a block diagram showing a configuration of a data processing unit according to the embodiment; [0021] FIG. 10 is a flowchart of processing performed when reticulocytes are measured according to the embodiment; [0022] FIG. 11 is a flowchart showing a sub routine of an analysis process according to the embodiment; [0023] FIGS. 12A and 12B each show a scattergram illustrating the analysis process according to the embodiment; [0024] FIGS. 13A and 13B each show a demarcation process performed on the scattergram according to the embodiment; [0025] FIGS. 14A and 14B each show demarcation on the scattergram according to the embodiment; [0026] FIGS. 15A and 15B each schematically show the manner of setting a threshold value Thr according to the embodiment; [0027] FIGS. 16A and 16B each schematically show a micrograph that shows an image of feline blood; [0028] FIGS. 17A and 17B each show an example of verification of the blood cell measuring apparatus according to the embodiment; and [0029] FIG. 18 is a flowchart showing a variation of an analysis routine according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0030] Hereinafter, an animal blood cell measuring apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the description below, from among features of the animal blood cell measuring apparatus, features relating to counting of reticulocytes are mainly described, and descriptions of features relating to measurement of white blood cells and the like are omitted. [0031] FIG. 1 is a front view showing a schematic configuration of the animal blood cell measuring apparatus according to the present embodiment. As shown in FIG. 1 , main components of a blood cell measuring apparatus 1 according to the present embodiment are a measurement unit 2 and a data processing unit 3 . The measurement unit 2 performs predetermined measurement on blood components contained in a blood sample, and transmits measurement data to the data processing unit 3 . The data processing unit 3 performs an analysis process based on the measurement data, and displays analysis results on a monitor. The blood cell measuring apparatus 1 is installed in a veterinary hospital, for example. [0032] The measurement unit 2 and the data processing unit 3 are connected via a data transmission cable 3 a so that the measurement unit 2 and the data processing unit 3 can perform data communication therebetween. Note that the connection formed between the measurement unit 2 and the data processing unit 3 is not limited to a direct connection formed by the data transmission cable 3 a . For example, the measurement unit 2 and the data processing unit 3 may be connected via a dedicated line using a telephone line, via a LAN, or via a communication network such as the Internet. [0033] FIG. 2 is a perspective external view of the measurement unit 2 . As shown in FIG. 2 , provided at the lower right of the front face of the measurement unit 2 is a blood collection tube setting part 2 a on which a blood collection tube 20 containing a blood specimen can be set. When a user presses a push button switch 2 b provided near the blood collection tube setting part 2 a , the blood collection tube setting part 2 a opens and protrudes forward. This allows the user to set the blood collection tube 20 on the blood collection tube setting part 2 a . When the user presses the button switch 2 b again after the blood collection tube 20 is set, the blood collection tube setting part 2 a recedes and closes. On the front face of the measurement unit 2 , a start button 2 c for starting sample measurement is also provided. [0034] FIG. 3 is a perspective view showing an internal structure of the measurement unit 2 . FIG. 4 is a side view of the internal structure. [0035] The blood collection tube setting part 2 a , on which the blood collection tube 20 is set, is accommodated within the measurement unit 2 in the above-described manner. Accordingly, the blood collection tube 20 is positioned at a predetermined aspirating position. Provided within the measurement unit 2 are: a pipette 21 for aspirating the blood specimen; and a specimen preparation section 4 that has, for example, chambers 22 and 23 for mixing the blood and reagents. [0036] The pipette 21 has a tubular shape extending in the vertical direction, and has a sharp-pointed tip. The pipette 21 is connected to a syringe pump that is not shown. The pipette 21 is capable of aspirating and discharging a predetermined amount of liquid through operation of the syringe pump. The pipette 21 is further connected to a moving mechanism, and accordingly, is movable in the vertical and front-rear directions. [0037] The blood collection tube 20 is sealed with a rubber cap 20 a . The sharp tip of the pipette 21 pierces through the cap, which allows the pipette 21 to aspirate, by a predetermined amount, the blood specimen contained in the blood collection tube 20 . As shown in FIG. 4 , the chambers 22 and 23 are provided behind the blood collection tube setting part 2 a . The pipette 21 having aspirated the blood specimen is moved by the moving mechanism and then discharges the blood specimen into the chambers 22 and 23 . In this manner, the blood specimen is supplied to the chambers 22 and 23 . [0038] FIG. 5 is a block diagram showing a configuration of the measurement unit 2 . FIG. 6 is a fluid circuit diagram showing a configuration of the specimen preparation section 4 . As shown in FIG. 5 , the measurement unit 2 includes the specimen preparation section 4 , an RET detector 5 , an RBC detector 6 , an HGB detector 7 , a controller 8 , and a communication section 9 . [0039] The controller 8 includes a CPU, a ROM, a RAM, and the like, and controls the operation of each component of the measurement unit 2 . The communication section 9 is, for example, an RS-232C interface, a USB interface, or an Ethernet (registered trademark) interface, and transmits/receives data to/from the data processing unit 3 . [0040] As shown in FIG. 6 , the specimen preparation section 4 is a fluid unit that includes the chambers, a plurality of solenoid valves, diaphragm pumps, and the like. The chamber 22 is used for preparing a specimen that is used for measuring red blood cells, platelets, and hemoglobin. The chamber 23 is used for preparing a specimen that is used for measuring reticulocytes. Note that, in order to simplify the description, FIG. 6 only shows a part of the configuration of the fluid circuit, the part being in the vicinity of the chamber 23 . [0041] The chamber 23 is connected to a reagent container RC 1 that contains a diluent containing a hemolytic agent and to a reagent container RC 2 that contains a stain solution, via fluid flow paths P 1 and P 2 that are tubes, for example. Along the fluid flow path P 1 connecting the chamber 23 and the reagent container RC 1 , solenoid valves SV 19 and SV 20 are provided. Also, a diaphragm pump DP 4 is provided between the solenoid valves SV 19 and SV 20 . The diaphragm pump DP 4 is connected to a positive pressure source and a negative pressure source so that the diaphragm pump DP 4 can be driven by positive pressure and negative pressure. Further, along the fluid flow path P 2 connecting the chamber 23 and the reagent container RC 2 , solenoid valves SV 40 and SV 41 are provided. A diaphragm pump DP 5 is provided between the solenoid valves SV 40 and SV 41 . [0042] The controller 8 controls these solenoid valves SV 19 , SV 20 , SV 40 , SV 41 , and the diaphragm pumps DP 4 and DP 5 in a manner described below, thereby supplying the diluent containing the hemolytic agent and the stain solution to the chamber 23 . [0043] First, the solenoid valve SV 19 , which is provided closer to the reagent container RC 1 than the diaphragm pump DP 4 , is opened, and the diaphragm pump DP 4 is driven by negative pressure while the solenoid valve SV 20 , which is provided closer to the chamber 23 than the diaphragm pump DP 4 , is kept closed. As a result, a fixed quantity of the diluent is taken from the reagent container RC 1 . Thereafter, the solenoid valve SV 19 is closed and the solenoid valve SV 20 is opened, and the diaphragm pump DP 4 is driven by positive pressure, whereby the diluent of the fixed quantity is supplied to the chamber 23 . [0044] Similarly, the solenoid valve SV 40 , which is provided closer to the reagent container RC 2 than the diaphragm pump DP 5 , is opened. Then, the diaphragm pump DP 5 is driven by negative pressure while the solenoid valve SV 41 , which is provided closer to the chamber 23 than the diaphragm pump DP 5 , is kept closed. As a result, a fixed quantity of the stain solution is taken from the reagent container RC 2 . Thereafter, the solenoid valve SV 40 is closed and the solenoid valve SV 41 is opened, and the diaphragm pump DP 5 is driven by positive pressure, whereby the stain solution of the fixed quantity is supplied to the chamber 23 . In this manner, the blood specimen and the reagents (the diluent and the stain solution) are mixed and thereby a specimen to be used for measurement of reticulocytes is prepared. [0045] The chamber 23 is connected to the RET detector 5 that is a flow cytometer, via a fluid flow path P 3 that includes a tube and a solenoid valve SV 4 . The fluid flow path P 3 has a branch, and solenoid valves SV 1 and SV 3 are serially connected to the branch path. A syringe pump SP 2 is provided between the solenoid valves SV 1 and SV 3 . A stepping motor M 2 is connected to the syringe pump SP 2 . The syringe pump SP 2 is driven through the operation of the stepping motor M 2 . [0046] The fluid flow path P 3 connecting the chamber 23 and the RET detector 5 has another branch, and a solenoid valve SV 29 and a diaphragm pump DP 6 are connected to this other branch. In the case of measuring reticulocytes by using the RET detector 5 , the diaphragm pump DP 6 is driven by negative pressure while the solenoid valves SV 4 and SV 29 are kept open, and the specimen is aspirated from the chamber 23 . In this manner, the fluid flow path P 3 is charged with the specimen. When the charging of the specimen is completed, the solenoid valves SV 4 and SV 29 are closed. Thereafter, the solenoid valve SV 3 is opened and the syringe pump SP 2 is driven, whereby the charged specimen is supplied to the RET detector 5 . [0047] As shown in FIG. 6 , the specimen preparation section 4 is provided with a sheath liquid chamber 24 . The sheath liquid chamber 24 is connected to the RET detector 5 via a fluid flow path P 4 . The fluid flow path P 4 is provided with a solenoid valve SV 31 . The sheath liquid chamber 24 is provided for storing a sheath liquid to be supplied to the RET detector 5 . The sheath liquid chamber 24 is connected to a sheath liquid container EPK containing the sheath liquid, via a fluid flow path P 5 that includes a tube and a solenoid valve SV 33 . Note that the diluent contained in the reagent container RC 1 may be used as the sheath liquid. [0048] Before the measurement of reticulocytes starts, the solenoid valve SV 33 is opened and the sheath liquid is supplied to the sheath liquid chamber 24 . In this manner, the sheath liquid is stored in the sheath liquid chamber 24 in advance. At the start of the measurement of reticulocytes, a solenoid valve SV 31 is opened in synchronization with the aforementioned supplying of the specimen to the RET detector 5 , and thereby the sheath liquid stored in the sheath liquid chamber 24 is supplied to the RET detector 5 . [0049] The RET detector 5 is an optical flow cytometer that is capable of measuring reticulocytes by flow cytometry using a semiconductor laser. The RET detector 5 includes a flow cell 51 for forming a liquid flow of the specimen. [0050] FIG. 7 is a perspective view schematically showing a configuration of the flow cell 51 . The flow cell 51 is formed from a translucent material such as quartz, glass, synthetic resin or the like, and has a tubular shape. The flow cell 51 has a flow path therein, through which the specimen and the sheath liquid flow. The flow cell 51 is provided with an orifice 51 a , at which the inner space of the flow cell 51 is narrower than the inner space of the other parts of the flow cell 51 . The flow cell 51 has a double-tube structure in the vicinity of the entrance of the orifice 51 a . The inner tube portion thereof serves as a specimen nozzle 51 b . The specimen nozzle 51 b is connected to the fluid flow path P 3 of the specimen preparation section 4 . The specimen is discharged from the specimen nozzle 51 b to the orifice 51 a. [0051] Space outside the specimen nozzle 51 b serves as a flow path 51 c through which the sheath liquid flows. The flow path 51 c is connected to the aforementioned fluid flow path P 4 . The sheath liquid supplied from the sheath liquid chamber 24 flows through the fluid flow path P 4 into the flow path 51 c , and is then led to the orifice 51 a . The sheath liquid supplied to the flow cell 51 in this manner flows so as to surround the specimen discharged from the specimen nozzle 51 b . Then, the orifice 51 a narrows down the stream of the specimen. As a result, particles contained in the specimen, such as reticulocytes and red blood cells, which are surrounded by the sheath liquid, pass through the orifice 51 a one by one. [0052] FIG. 8 shows a schematic configuration of the RET detector 5 . In the RET detector 5 , a semiconductor laser light source 52 is disposed so as to output laser light to the orifice 51 a of the flow cell 51 . An illumination lens system 53 including a plurality of lenses is provided between the semiconductor laser light source 52 and the flow cell 51 . The illumination lens system 53 focuses a parallel beam outputted from the semiconductor laser light source 52 , to form a beam spot. [0053] On an optical axis that linearly extends from the semiconductor laser light source 52 , a beam stopper 54 a is provided in an opposed position to the illumination lens system 53 , with the flow cell 51 provided therebetween. Among laser beams outputted from the semiconductor laser light source 52 , a beam that travels straight within the flow cell 51 without being scattered (hereinafter, referred to as “direct light”) is blocked by the beam stopper 54 a . Further, a photodiode 54 is provided on the optical axis so as to be located to the downstream side of the beam stopper 54 a. [0054] When the specimen flows into the flow cell 51 , scattered light signals and fluorescence signals occur due to the laser light, among which forward light signals (scattered light signals) are emitted toward the photodiode 54 . From among lights traveling along the optical axis that linearly extends from the semiconductor laser light source 52 , the direct light from the semiconductor laser light source 52 is blocked by the beam stopper 54 a . Incident on the photodiode 54 is only the scattered light that travels substantially along the optical axis direction (hereinafter, referred to as forward scattered light). [0055] The forward scattered light emitted from the flow cell 51 is photoelectrically converted by the photodiode 54 . Each electrical signal resulting from the photoelectric conversion (hereinafter, referred to as a forward scattered light signal) is amplified by an amplifier 54 b and then outputted to the controller 8 . The forward scattered light signal indicates a size of a blood cell. The forward scattered light signal is, after being processed by the controller 8 , outputted to the data processing unit 3 via the communication section 9 . [0056] A side condenser lens 55 is provided laterally to the flow cell 51 , so as to be located in a direction that is perpendicular to the optical axis that linearly extends from the semiconductor laser light source 52 to the photodiode 54 . The side condenser lens 55 condenses side light that occurs when the semiconductor laser illuminates blood cells that are passing through the flow cell 51 (i.e., light that is outputted in the direction perpendicular to the optical axis). A dichroic mirror 56 is provided to the downstream side of the side condenser lens 55 . Side light signals transmitted from the side condenser lens 55 are separated by the dichroic mirror 56 into scattered light components and fluorescence components. [0057] A photodiode 57 for receiving side scattered light is provided laterally to the dichroic mirror 56 (i.e., provided in a direction that intersects an optical axis direction connecting the side condenser lens 55 and the dichroic mirror 56 ). Further, an optical filter 58 a and an avalanche photodiode 58 are provided, on the optical axis, to the downstream side of the dichroic mirror 56 . [0058] Side scattered light components reflected by the dichroic mirror 56 are photoelectrically converted by the photodiode 57 . Each electrical signal resulting from the photoelectric conversion (hereinafter, referred to as a side scattered light signal) is amplified by an amplifier 57 a , and then outputted to the controller 8 . The side scattered light signal indicates information about the inside of a blood cell (e.g., the size of the nucleus). The side scattered light signal is outputted to the data processing unit 3 via the communication section 9 after being processed by the controller 8 . [0059] Side fluorescence components transmitted through the dichroic mirror 56 are photoelectrically converted by the avalanche photodiode 58 after being wavelength-selected by the optical filter 58 a . Each electrical signal resulting from the photoelectric conversion (a side fluorescence signal) is amplified by an amplifier 58 b , and then outputted to the controller 8 . The side fluorescence signal indicates information about the degree of staining of a blood cell. The side fluorescence signal is, after being processed by the controller 8 , outputted to the data processing unit 3 via the communication section 9 . [0060] The RBC detector 6 is capable of measuring a red blood cell count and a platelet count by the sheath flow DC detection method. The RBC detector 6 has an electrical resistance detector. The aforementioned specimen is supplied from the chamber 22 to this detector. In the case of performing measurement on red blood cells and platelets, the specimen is prepared in the chamber 22 by mixing the blood with a diluent. The specimen is supplied from the specimen preparation section 4 to the detector, together with the sheath liquid. Within the detector, a liquid flow in which the specimen is surrounded by the sheath liquid is formed in the same manner as described above. [0061] Along a flow path within the detector, an aperture having an electrode is provided. When blood cells contained in the specimen pass through the aperture one by one, a DC resistance at the aperture is detected, and an electrical signal corresponding to the DC resistance is outputted to the controller 8 . The DC resistance increases when a blood cell passes through the aperture. Accordingly, the electrical signal is information indicating the passage of the blood cell through the aperture. The electrical signal is processed by the controller 8 , and then transmitted to the data processing unit 3 via the communication section 9 . The data processing unit 3 analyzes the received data to count red blood cells and platelets. [0062] The HGB detector 7 is capable of measuring hemoglobin content by the SLS-hemoglobin method. The HGB detector 7 is provided with a cell for containing the diluted specimen. The specimen is supplied from the chamber 22 to the cell. In the case of measuring hemoglobin, the specimen is prepared in the chamber 22 by mixing the blood with a diluent and a hemolytic agent. The hemolytic agent has a property of converting hemoglobin in the blood to SLS-hemoglobin. A light-emitting diode and a photodiode are arranged so as to be opposed to each other with the cell located therebetween. Light from the light emitting diode is received by the photodiode. [0063] The light-emitting diode emits light of a wavelength having a high rate of absorption by SLS-hemoglobin. The cell is formed from a plastic material having high translucency. As a result, the light emitted from the light-emitting diode is absorbed almost solely by the diluted specimen, and the transmitted light is received by the photodiode. The photodiode outputs an electrical signal corresponding to the amount of the received light (i.e., corresponding to an absorbance) to the controller 8 . The absorbance and an absorbance obtained in advance by measuring only the diluent are subjected to signal processing by the controller 8 , and then transmitted to the data processing unit 3 via the communication section 9 . The data processing unit 3 compares the absorbances in the above two cases to calculate a hemoglobin value. [0064] FIG. 9 is a block diagram showing a configuration of the data processing unit 3 . The data processing unit 3 is structured as a computer system that includes: a CPU 101 ; a ROM 102 ; a RAM 103 ; a hard disk drive (HD drive) 104 ; a communication interface 105 ; an input interface 106 including a keyboard, a mouse, and the like; and an output interface 107 including a monitor, a speaker, and the like. [0065] For example, the communication interface 105 is an RS-232C interface, a USB interface, or an Ethernet (registered trademark) interface, and is capable of transmitting/receiving data to/from the measurement unit 2 . Installed in a hard disk within the HD drive 104 are an operating system and an application program that is used for performing an analysis process on measurement data received from the measurement unit 2 . [0066] Through execution of the application program by the CPU 101 , the analysis process is performed on the measurement data received from the measurement unit 2 . As a result, a red blood cell count (RBC), hemoglobin content (HGB), hematocrit value (HCT), mean red blood cell volume (MCV), mean red blood cell hemoglobin (MCH), mean red blood cell hemoglobin concentration (MCHC), and a platelet count (PLT) are calculated. Further, a scattergram is created based on the forward scattered light signals and the side fluorescence signals, whereby the number of reticulocytes (RET) is counted. [0067] FIG. 10 shows a flow of processing that is performed by the blood cell measuring apparatus according to the present embodiment when the blood cell measuring apparatus performs reticulocyte measurement. Note that the processing flow at the data processing unit 3 as shown in FIG. 10 is performed through execution, by the CPU 101 of the data processing unit 3 , of the application program stored in the HD drive 104 . [0068] When a reticulocyte measurement mode is started, a reception screen for receiving the selection of an animal species is displayed on the monitor of the data processing unit 3 (S 101 ). The reception screen includes icons indicating animal species options (feline, canine, etc). [0069] When a user selects a desired animal species from among the displayed animal species by using a mouse (S 101 : YES), a signal for activating the start button 2 c is transmitted to the measurement unit 2 (S 102 ). Thereafter, the CPU 101 waits for data transmission from the measurement unit 2 (S 103 ). [0070] When the start button 2 c is pressed (S 201 : YES), the measurement unit 2 determines whether or not the start button 2 c is active (step S 202 ). If the start button 2 c is active (step S 202 : YES), the specimen is prepared in the chamber 23 as described above. The measurement unit 2 performs measurement at the RET detector 5 by using the prepared specimen, thereby obtaining the aforementioned forward scattered light signals and the side fluorescence signals (S 203 ). Data that results from processing the obtained forward scattered light signals and the side fluorescence signals are transmitted to the data processing unit 3 (S 204 ). [0071] Upon receiving these data of the forward scattered light signals and the side fluorescence signals (S 103 : YES), the CPU 101 analyzes the data in a manner corresponding to the animal species selected at step S 101 , thereby obtaining the number of reticulocytes contained in the specimen (S 104 ). Information about the obtained reticulocyte count is displayed on the monitor (S 105 ). After the measurement and display of the reticulocytes have been performed for the animal species desired by the user, the processing returns, if the system is not shut down (S 106 : N 0 , S 205 : NO), to step S 101 and step S 201 at which the next measurement instruction from the user is awaited. [0072] FIG. 11 shows a process routine of the analysis process at step S 104 . FIGS. 12A to 14B show the manner of performing demarcation on a scattergram in the process routine. FIGS. 12A to 14A show an example of a scattergram in the case where feline blood is measured. FIG. 14B shows an example of a scattergram in the case where canine blood is measured. These scattergrams may be either two-dimensional scattergrams or three-dimensional scattergrams. For example, a two-dimensional scattergram is a distribution chart in which plot data, which indicate blood cells based on magnitudes of a parameter that is set as the vertical axis and based on magnitudes of a parameter that is set as the horizontal axis, are assigned to predetermined coordinates. Each set of coordinates is associated with values of plot data assigned thereto. [0073] As described above, the analysis process at step S 104 is performed in a manner corresponding to the animal species selected at step S 101 . When the animal species has been selected at step S 101 , demarcation conditions corresponding to the selected animal species (parameter values used for the demarcation) are set. In accordance with the demarcation conditions, demarcation is performed on a scattergram and reticulocytes are counted. [0074] Upon receiving the data of the forward scattered light signals and the side fluorescence signals from the measurement unit 2 , the CPU 101 first generates, at step S 301 , a scattergram whose vertical axis and horizontal axis represent the intensity of the forward scattered light and the intensity of the side fluorescence, respectively (see FIG. 12A ). Next, at step S 302 , the CPU 101 demarcates a coordinate area of platelets (PLT) on the scattergram (see FIG. 12B ), and also, demarcates a coordinate area of white blood cells (WBC) (see FIG. 13A ). Here, demarcation of the coordinate area of white blood cells (WBC) is performed as described below. [0075] First, an axis O that passes through the centroid of a distribution of red blood cells (RBC) is set on the scattergram (see FIG. 13A ). Here, the centroid of the distribution is set based on plot data present within a fixed area R that is set in advance around a coordinate area of the red blood cells (RBC). To be specific, a histogram in the vertical axis direction is obtained for the plot data present within the fixed area R. Then, the mean position of the histogram in the vertical axis direction is calculated. The mean position is set as the centroid of the distribution of red blood cells (RBC), and the axis O is set so as to extend through the centroid of the distribution and so as to be in parallel with the horizontal axis. A straight line with a slope γ is drawn from a point that is shifted in the positive vertical axis direction by β from an intersection point between the axis O set as above and a boundary indicating the maximum value of the side fluorescence intensity. An area, surrounded with the drawn straight line and a straight line that defines a fixed width W together with the boundary, is set as the coordinate area of white blood cells (WBC). [0076] After the coordinate areas of platelets (PLT) and white blood cells (WBC) have been demarcated, the CPU 101 calculates, at step S 304 , a frequency distribution 150 of plot data with respect to the side fluorescence intensity, based on the scattergram from which these coordinate areas have been removed (see FIG. 13B ). [0077] Note that, in the example shown in FIG. 13B , plot data is projected onto an axis that is a result of rotating the horizontal axis of the scattergram by θ in the clockwise direction. In this manner, the frequency distribution 150 is calculated, with the rotated axis representing the side fluorescence intensity. This is because, as is understood from FIG. 13B , an area where a cluster of plot data of red blood cells (RBC) is present is an ellipsoidal area that is in a slightly rotated orientation in the clockwise direction. The rotation angle of the area where the cluster of plot data is present is variable depending on the reagents to be used in preparing the specimen. Depending on the reagents to be used, the area where the cluster of plot data of red blood cells (RBC) is present is not in such a rotated orientation but in the shape of an ellipse that is elongated in the vertical axis direction. Accordingly, when the frequency distribution is calculated, a rotation angle θ by which the axis representing the side fluorescence intensity is rotated is adjusted in accordance with the reagents to be used. Further, when the area where the cluster of plot data of red blood cells (RBC) is present is not in such a rotated orientation as above, the frequency distribution of plot data is calculated with respect to the horizontal axis of the scattergram. [0078] When the frequency distribution has been calculated in this manner, the CPU 101 obtains at step S 305 , fluorescence intensity X that corresponds to a peak of the frequency distribution, and further calculates a variance σ of the frequency distribution. Then, at step S 306 , the CPU 101 determines whether or not the animal species set by the user at step S 101 of FIG. 10 is a first animal species (e.g., a “feline”). In the case of the first animal species (step S 306 : YES), the CPU 101 performs, at step S 307 , calculation based on the fluorescence intensity X, the variance σ, and a coefficient α corresponding to the first animal species (a “feline” in the example of FIGS. 12A to 14A ), thereby calculating a threshold value Thr that indicates a border of aggregate reticulocytes (RET). The calculation is performed using the equation shown below. [0000] Thr= X+α×σ   (1) [0079] After the threshold value Thr has been calculated in the above manner, the CPU 101 demarcates, at step S 309 , a coordinate area of aggregate reticulocytes (RET) and a coordinate area of red blood cells (RBC) (the red blood cells including punctate reticulocytes (RET)), with a straight line L 1 that is inclined by an angle θ with respect to the vertical axis of the scattergram and that passes through the threshold value Thr, and with a straight line L 2 that extends downward, in parallel with the vertical axis, from an intersection point of the straight line L 1 and the axis O (see FIG. 13B ). In this manner, the coordinate area of aggregate reticulocytes (RET) is specified (see FIG. 14A ). Thereafter, at step S 311 , the CPU 101 counts the number of plot data (the number of blood cells) contained in the coordinate area of aggregate reticulocytes (RET). [0080] On the other hand, when the animal species set by the user at step S 101 is not the first animal species (step S 306 : NO), the CPU 101 calculates, at step S 308 based on the above equation (1), a threshold value Thr by using a coefficient α that corresponds to an animal species different from the first animal species. Then, the CPU 101 demarcates, at step S 310 , a coordinate area of reticulocytes (RET) (including both punctate reticulocytes and aggregate reticulocytes) and a coordinate area of red blood cells (RBC), with a straight line L 1 that is inclined by the angle θ with respect to the vertical axis of the scattergram and that passes through the threshold value Thr, and with a straight line L 2 that extends downward, in parallel with the vertical axis, from an intersection point of the straight line L 1 and an axis O. In this manner, the coordinate area of reticulocytes (RET) is specified (see FIG. 14B ). Subsequently, the CPU 101 counts, at step S 311 , the number of plot data (the number of blood cells) contained in the coordinate area of reticulocytes (RET). [0081] In the case of an animal species different from the first animal species (e.g., a “canine”), the coefficient α in the above equation (1) is set to be ½ of the coefficient α in the case of a feline. The rotation angle θ, shift amount β, slope γ, and the fixed width W are the same for both the case of a feline and the case of a canine. As is understood from the comparison between FIG. 14A and FIG. 14B , the border between the coordinate area of red blood cells (RBC) and the coordinate area of reticulocytes (RET) in the case of a canine is, as compared to the case of a feline, shifted to the left in the scattergram. Based on such a difference between the borders, the coordinate area of aggregate reticulocytes is demarcated in the case of a feline, and the coordinate area containing all the reticulocytes (regardless of the difference between punctate reticulocytes and aggregate reticulocytes) is demarcated in the case of a canine. [0082] As described above, the coefficient α of the above equation (1) used at step S 307 and step S 308 is changed as necessary in accordance with the selected animal species. FIGS. 15A and 15B each schematically show, in the case where the plot data frequency distribution calculated at step S 304 of FIG. 11 with respect to the side fluorescence intensity is divided based on blood cell types, the distribution of each type of blood cells. FIG. 15A is a distribution chart for feline blood, and FIG. 15B is a distribution chart for canine blood. [0083] As shown in FIG. 15A , in the case of feline blood, a distribution of red blood cells (RBC), which is a normal distribution, is followed by a distribution of punctate reticulocytes (RET), which is followed by a distribution of aggregate reticulocytes (RET). Counting aggregate reticulocytes is considered to be useful when diagnosing animal species with anemia or the like, whose reticulocytes consist of a plurality of types of reticulocytes in the above manner. Therefore, in the case of feline blood, it is necessary to demarcate the coordinate area of reticulocytes (RET), with the threshold value Thr being set at the border position between the punctate reticulocytes and the aggregate reticulocytes. [0084] On the other hand, in the case of canine blood, as shown in FIG. 15B , it is not necessary to distinguish between punctate reticulocytes and aggregate reticulocytes contained in the reticulocytes, but necessary to count the total number of reticulocytes (RET) that are distributed following the normally distributed red blood cells (RBC). Accordingly, in the case of canine blood, it is necessary to demarcate the coordinate area of reticulocytes (RET), with the threshold value Thr being set at the border position between the red blood cells (RBC) and the reticulocytes (RET). [0085] As described above, the distribution of reticulocytes to be measured is different between the case of a canine and the case of a feline. For this reason, the coefficient α in the above equation (1) is required to be changed between the case of feline blood and the case of canine blood. It is at least necessary to set the coefficient α in the case of feline blood to be greater by a predetermined magnitude than that in the case of canine blood. To be specific, in the case of feline blood, the coefficient α is adjusted to be approximately the double of that in the case of canine blood. [0086] After the blood cells in the RET coordinate area have been counted, the CPU 101 counts, at step S 312 , the number of plot data contained in the coordinate area of red blood cells (RBC), which has been demarcated at step S 309 or step S 310 . Further, the CPU 101 calculates, at step S 313 , a proportion RET % that indicates a proportion of the number of reticulocytes to the counted number of red blood cells (RBC). [0087] In parallel to the above process, the CPU 101 obtains, from the measurement unit 2 at step S 314 , information about the number of red blood cells (RBC), which has been obtained by the RBC detector 6 for the same blood. Further, at step S 315 , the CPU 101 obtains a count RET# that indicates the number of reticulocytes, by multiplying the obtained number of red blood cells (RBC) by the proportion RET %. [0088] Here, the reticulocyte count RET# is obtained here by multiplying, by the proportion RET %, the number of red blood cells detected by the RBC detector 6 . However, as an alternative, the number of reticulocytes (RET) obtained at step S 311 can be used as the reticulocyte count RET#. [0089] The reticulocyte proportion RET % and the reticulocyte count RET# measured in this manner are displayed on the monitor at step S 105 of FIG. 10 . [0090] Described next are results that were obtained when measurement of aggregate reticulocytes (of a feline) was performed with the blood cell measuring apparatus according to the present embodiment (prototype). [0091] FIGS. 16A and 16B are schematic diagrams each showing a micrograph that shows feline blood. In each diagram, a blood cell that contains therein two or more granules (RNA) is a reticulocyte (RET). Among reticulocytes, those with granules aggregated therein are aggregate reticulocytes, and those with granules scattered therein are punctate reticulocytes. [0092] In this measurement, measurement results of aggregate reticulocytes which were obtained when feline blood was measured by the blood cell measuring apparatus according to the present embodiment (prototype) were compared to measurement results of aggregate reticulocytes which were obtained when blood cells in the feline blood were visually measured with a microscope, whereby measurement accuracy of the blood cell measuring apparatus according to the present embodiment was verified. Each measurement was performed on 47 samples. Mean values of results of measurement performed by multiple persons are shown as the results of the visual measurement. The measurement by the blood cell measuring apparatus (prototype) was performed in accordance with the processing described above with reference to FIGS. 11 to 14B . Parameter values used for demarcation on a scattergram were set to those used for measurement of feline blood. The coefficient α in the above equation (1) was set to α=10 (double the coefficient α in the case of human or canines). [0093] FIGS. 17A and 17B show the measurement results. In FIGS. 17A and 17B , the vertical axis represents values obtained by the prototype apparatus and the horizontal axis represents values obtained by the visual measurement. Each single point plotted on these diagrams represents, for the same sample, both a measurement result obtained by the prototype apparatus and a measurement result obtained by the visual measurement. In each diagram, a straight line that approximates all the plotted points therein is calculated, whereby a correlation between the measurement results of the prototype apparatus and the results of the visual measurement is obtained. [0094] FIG. 17A shows, as measurement results, points each representing a proportion RET % that indicates a proportion of aggregate reticulocytes to the number of red blood cells. FIG. 17B shows, as measurement results, points each representing a count RET# that indicates the number of aggregate reticulocytes. Note that the count RET# was, similarly to the above-described manner, calculated by multiplying the number of red blood cells (a measurement result obtained by the RBC detector 6 of FIG. 5 ), which had been obtained based on a change in the electrical resistance value, by the proportion RET % calculated as shown in FIG. 17A . [0095] A correlation r between the measurement results of the prototype apparatus and the results of the visual measurement, which is shown in FIG. 17A , and a correlation r between the measurement results of the prototype apparatus and the results of the visual measurement, which is shown in FIG. 17B , are r=0.924 and r=0.896, respectively. Thus, there is a substantially high correlation between the measurement results obtained by the prototype apparatus and the results obtained by the visual measurement. From these measurement results, measurement accuracy of the blood cell measuring apparatus according to the present embodiment (prototype) was verified to be sufficiently high when used in measurement of feline blood. [0096] As described above, according to the present embodiment, the number of aggregate reticulocytes can be counted accurately. Since the number of aggregate reticulocytes can be counted without depending on visual measurement, a burden on veterinarians and laboratory technicians can be reduced substantially. [0097] Further, in the present embodiment, an animal species to be measured can be selected as necessary. Therefore, not only the number of aggregate reticulocytes of such animal species as felines, but also the total number of reticulocytes of other animal species such as canines, can be measured. To be specific, when a feline is selected as an animal species to be measured, information about the number of aggregate reticulocytes (RET %, RET#) is outputted, and when a canine is selected as an animal species to be measured, information about the total number of reticulocytes (RET %, RET#) is outputted. Accordingly, veterinarians or laboratory technicians are only required to select an animal species to be measured, in order to obtain information about the number of reticulocytes, which is useful for making a diagnosis on the animal species. This substantially reduces their burden in making the diagnosis. [0098] Although the above embodiment takes felines and canines as animal species to be measured, measurement can be performed on other animal species, of course. In such a case, if there exists, other than felines, animal species whose reticulocytes may contain aggregate reticulocytes, the coefficient α in the equation (1) is adjusted for the animal species, and the aggregate reticulocytes are measured, accordingly. Animal species whose reticulocytes may contain aggregate reticulocytes are, for example, rabbits, ferrets, etc. [0099] In the above embodiment, the number of aggregate reticulocytes is measured and displayed in the case of the first animal species (a feline). Here, the number of punctate reticulocytes may be additionally measured and displayed. Alternatively, the total number of reticulocytes may be measured and displayed. Further, in the case of the first animal species (a feline), the user may select as necessary whether to measure and display only the number of aggregate reticulocytes, or to measure and display the number of punctate reticulocytes in addition to the number of aggregate reticulocytes, or to measure and display the total number of reticulocytes in addition to the number of aggregate reticulocytes. [0100] Still further, the above embodiment measures aggregate reticulocytes when the first animal species is selected, and measures all the reticulocytes when the second animal species is selected. However, the present invention is not limited thereto. For example, when the first animal species is selected, punctate reticulocytes may be measured, and when the second animal species is selected, all the reticulocytes may be measured. Alternatively, when the first animal species is selected, aggregate reticulocytes may be measured, and when the second animal species is selected, punctate reticulocytes may be measured. Further alternatively, when the first animal species is selected, punctate reticulocytes may be measured, and when the second animal species is selected, aggregate reticulocytes may be measured. [0101] FIG. 18 shows a flow of processing that is performed when the number of punctate reticulocytes and the total number of reticulocytes are counted and displayed in addition to the number of aggregate reticulocytes, for the first animal species (e.g. a feline). In this processing flow, similarly to the above embodiment, a scattergram is created (S 401 ), and the coefficient α of the above equation (1) is set to a coefficient α 1 that is used for measuring aggregate reticulocytes (S 402 ). Then, similarly to the above embodiment, a coordinate area of aggregate reticulocytes is demarcated using the coefficient α 1 (S 403 ), and a count N 1 indicating the number of aggregate reticulocytes is measured (S 404 ). [0102] Here, when the user has not selected a multiple-result display (S 405 : NO), the number of reticulocytes to be displayed is, similarly to the above embodiment, regarded as the count N 1 which has been measured at step S 404 (S 412 ). Then, a display output is performed based on the count N 1 (S 413 ). [0103] On the other hand, when the user has selected a multiple-result display (C 405 : YES), the coefficient α of the above equation (1) is set to a coefficient α 2 that is used for counting the total number of reticulocytes (including all the types of reticulocytes (e.g., both punctate and aggregate reticulocytes)) (S 406 ). Then, the coefficient α 2 is used, similarly to the above embodiment, to demarcate a coordinate area of reticulocytes (including all the types of reticulocytes (e.g., both punctate and aggregate reticulocytes)) (S 407 ), and a count N 2 indicating the total number of reticulocytes is measured (S 408 ). Further, calculation N 2 −N 1 is performed, whereby a count N 3 indicating the number of punctate reticulocytes is calculated. [0104] The counts N 1 , N 2 , and N 3 obtained in the above manner are set as an aggregate reticulocyte count, a total reticulocyte count, and a punctate reticulocyte count, respectively (S 410 ). Then, similarly to the above embodiment, a display output (RET %, RET#) based on each blood cell count is performed (S 411 ). Note that when the user has selected only a display of the total number of reticulocytes in addition to a display of measurement results of aggregate reticulocytes, a display is performed for the number of aggregate reticulocytes and the total number of reticulocytes. In this case, step S 409 of FIG. 18 is skipped. Further, when the user has selected only a display of measurement results of aggregate and punctate reticulocytes, a display is performed for the aggregate and punctate reticulocytes. [0105] The embodiment of the present invention has been described as above. However, the present invention is not limited by the above embodiment in any way. Other than the foregoing description, numerous modifications of the embodiment of the present invention may be devised. [0106] For example, the above embodiment generates a scattergram based on the intensity of the forward scattered light and the intensity of the side fluorescence, for the measurement of aggregate reticulocytes. Alternatively, aggregate reticulocytes may be measured based on the intensity of the side scattered light and the intensity of the side fluorescence, for example. Further alternatively, aggregate reticulocytes may be measured based on a plurality of types of fluorescence that are generated through illumination of laser light of a specific wavelength. [0107] Further, FIGS. 12A to 14B referred to in the above embodiment indicate a feline as an example of the first animal species whose reticulocytes contain aggregate reticulocytes, and indicate a canine as an example of the second animal species whose reticulocytes do not contain aggregate reticulocytes. However, the first and second animal species may include different animal species other than felines and canines. The present invention can be applied, as necessary, to a blood cell measuring apparatus that performs measurement on animal species different from felines and canines. [0108] Although the above embodiment displays both RET % and RET#, only either one of these may be displayed, alternatively. Further, other than the above information, different information based on the number of aggregate reticulocytes may be displayed. [0109] Note that, in the measurement example of the above embodiment, the coefficient α of the above equation (1) in the case of measuring feline blood is set to be the double of that in the case of animal species whose reticulocytes do not contain aggregate reticulocytes (human or canines). However, the coefficient α here may not necessarily be the double of that in the case of human or canines, so long as the coefficient α is set to an appropriate value that is close to the double of the coefficient α used in the case of human or canines. The term “double” recited in claim 12 covers a range that is slightly greater and slightly less than the value that is double the coefficient α used in the case of human or canines. [0110] Other than the above-described embodiment, various modifications can be devised as necessary without departing from the scope of the technical idea described in the claims.

An animal blood cell measuring apparatus comprising: a specimen preparation section for preparing a measurement specimen from blood of an animal; a characteristic information obtaining section for obtaining characteristic information indicating a characteristic of the measurement specimen, from the measurement specimen prepared by the specimen preparation section; and a controller configured for performing operations comprising: (a) classifying aggregate reticulocytes contained in the blood from other blood cells, based on the characteristic information obtained by the characteristic information obtaining section; and (b) outputting information regarding a number of the classified aggregate reticulocytes.

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to the field of liquid crystal displaying, and in particular to a gate-driver-on-array (GOA) circuit. [0003] 2. The Related Arts [0004] Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus widely used. The development of the liquid crystal display industry brings in increasingly severer performance requirements, such as performance related to high resolution, high brightness, wide view angle, and low power consumption, and associated techniques have been developed. Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that, with liquid crystal molecules interposed between two parallel glass substrates, application of a drive voltage is selectively carried out by means of a driver circuit to the two glass substrates to control the liquid crystal molecules to change direction in order to refract out light emitting from the backlight module for generating images. [0005] The recent development of the LCDs is toward high integration and low cost of which an important technique is the realization of mass production of gate driver on array (GOA) technique. The GOA technique uses the front-stage array process of TFT-LCD (Thin-Film Transistor Liquid Crystal Display) to make a gate line scan drive signal circuit on an array substrate of a liquid crystal display panel in order to achieve progressive gate scanning. Using the GOA technique to integrate the gate line scan drive signal circuit on the array substrate of the liquid crystal display panel allows for omission of a gate driver integrated circuit so as to reduce the cost of product in both material cost and manufacturing operation. Such a gate line scan drive signal circuit that is integrated on an array substrate by means of the GOA technique is also referred to as a GOA circuit. The GOA circuit comprises a plurality of GOA units and as show in FIG. 1 , a circuit diagram of a GOA unit of a conventional GOA circuit is shown, comprising: a pull-up circuit 100 , a pull-up control circuit 200 , a pull-down circuit 300 , a first pull-down holding circuit 400 , and a second pull-down holding circuit 500 , wherein the pull-up circuit 100 functions to output a clock signal CKn as a gate signal G n . The pull-up control circuit 200 controls the activation time of the pull-up circuit 100 and is generally connected to a transfer signal ST n−1 transmitted from a previous stage GOA unit and the gate signal G n−1 thereof. The first pull-down holding circuit 400 pulls the gate line down to a low voltage at first time, namely shutting off the gate signal. The second pull-down holding circuit 500 functions to maintain the gate signal G n and a control signal Q n of the pull-up circuit 100 at a shut-off condition (namely a negative potential). The GOA circuit is commonly provided with two low level signal lines and the two low level signal lines respectively supply a first low level signal V ss1 and a second low level signal V ss2 , whereby the second low level V ss2 is used to reduce the voltage difference V gs between the gate terminal and the source terminal of the pull-up circuit 100 when the scan circuit is at a closed (holding) time so as to reduce the leakage currents of the pull-up circuit 100 and the second pull-down holding circuit 500 . A capacitor C boost provides secondary boost of the control signal Q n of the pull-up circuit 100 to facilitate the output of the gate signal G n . [0006] However, the conventional GOA circuit suffers the following two shortcomings: [0007] (1) A conductive path exists between two different negative potentials. Referring to FIG. 2 , which is an equivalent circuit diagram of FIG. 1 , L 100 indicates a loop of the leakage current induced by the connection of a thin-film transistor T 110 to the previous stage GOA unit and L 200 indicates a loop of the leakage current induced by the connection of a thin-film transistor T 410 to the instant stage GOA unit. The conventional GOA circuit would cause an effect of a great current between the leakage current loops L 100 and L 200 . The magnitude of the current is directly related to the potentials of pull-down points P n and K n . Further, the current conducted therethrough is proportional to the number of the stages of the GOA circuit. This leads to an increase of the loading of the signal sources of V ss1 and V ss2 and in the worst case, abnormality of image displaying may result. [0008] (2) The diode design of thin-film transistors T 510 and T 610 makes it is not possible for the high voltage of the pull-down points P n and K n to be quickly released and the voltage variations at the points of P n and K n are illustrated in FIG. 3 . This increases the influence of stress on four primary thin-film transistors T 320 , T 420 , T 330 , T 430 of the first and second pull-down holding circuits 400 , 500 , eventually affecting the operation service life of the GOA circuit. SUMMARY OF THE INVENTION [0009] An object of the present invention is to provide a GOA (Gate-Driver-on-Array) circuit, which uses a GOA technique to reduce the cost of a liquid crystal display and to overcome the problems of poor performance of the conventional the GOA circuit caused by introduction of two low level signals into the GOA circuit and short operation service life of the GOA circuit and enhance the quality of displayed images. [0010] To achieve the above object, the present invention provides a GOA circuit, which comprises multiple stages of GOA units connected in cascade, wherein: [0011] for each nth stage GOA unit between the second stage and the last second stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal, wherein the first output terminal of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal, the second (n−1)th stage signal input terminal, and the (n+1)th stage signal input terminal of the nth stage GOA unit are respectively and electrically connected to the first output terminal and the second output terminal of the (n−1)th GOA unit and the first output terminal of the (n+1)th GOA unit, the first output terminal of the nth stage GOA unit being electrically connected to the first (n−1)th stage signal input terminal of the (n+1)th GOA unit and the (n+1)th stage signal input terminal of the (n−1)th GOA unit, the second output terminal of the nth stage GOA unit being electrically connected to the second (n−1)th stage signal input terminal of the (n+1)th GOA unit; [0012] for the nth stage GOA unit at the first stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal, wherein the first output terminal of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal of the nth stage GOA unit both provided for receiving an input of a pulse activation signal and the (n+1)th stage signal input terminal is electrically connected to the first output terminal of the (n+1)th GOA unit, the first output terminal and the second output terminal of the nth stage GOA unit being respectively and electrically connected to the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal of the (n+1)th GOA unit; [0013] for the nth stage GOA unit at the last stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal; the first (n−1)th stage signal input terminal and the second input terminal of the nth stage GOA unit are respectively and electrically connected to the first output terminal and the second output terminal of the (n−1)th GOA unit, the (n+1)th stage signal input terminal of the nth stage GOA unit being provided to receive an input of a pulse activation signal, the first output terminal of the nth stage GOA unit being electrically connected to the (n+1)th stage signal input terminal of the (n−1)th GOA unit and the second output terminal being open; [0014] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises a first clock signal input terminal, a first low level input terminal, and a second low level input terminal, the first low level input terminal being provided for receiving an input of a first low level, the second low level input terminal being provided for receiving an input of a second low level, the second low level being smaller than the first low level; [0015] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises: [0016] a pull-up control unit, which is electrically connected to the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal; [0017] a pull-up unit, which is electrically connected to the pull-up control unit and the first clock signal input terminal, the first output terminal, and the second output terminal; [0018] a first pull-down holding unit, which is electrically connected to the first low level input terminal, the second low level input terminal, the pull-up control unit, and the pull-up unit; [0019] a second pull-down holding unit, which is electrically connected to the first low level input terminal, the second low level input terminal, the first pull-down holding unit, the pull-up control unit, and the pull-up unit; and [0020] a pull-down unit, which is electrically connected to the (n+1)th stage signal input terminal, the first low level input terminal, the pull-up control unit, the pull-up unit, the first pull-down holding unit, the second pull-down holding unit, and the first output terminal. [0021] The first clock signal input terminal has an input signal that is a first clock signal or a second clock signal, the first clock signal being opposite in phase to the second clock signal; when the input signal of the first clock signal input terminal of the nth stage GOA unit of the GOA circuit is the first clock signal, the input signal of the first clock signal input terminal of the (n+1)th stage GOA unit of the GOA circuit is the second clock signal. [0022] The pull-up control unit is a first thin-film transistor and the first thin-film transistor comprises a first gate terminal, a first source terminal, and a first drain terminal, wherein the first gate terminal is electrically connected to the second (n−1)th stage signal input terminal; the first source terminal is electrically connected to the first (n−1)th stage signal input terminal; and the first drain terminal is electrically connected to the first and second pull-down holding units, the pull-down unit, and the pull-up unit. [0023] The pull-up unit comprises a capacitor, a second thin-film transistor, and a third thin-film transistor and the second thin-film transistor comprises a second gate terminal, a second source terminal, and a second drain terminal and the third thin-film transistor comprises a third gate terminal, a third source terminal, and a third drain terminal, wherein the second gate terminal is electrically connected to one end of the capacitor, the first drain terminal, the third gate terminal, the first and second pull-down holding units, and the pull-down unit; the second source terminal is electrically connected to the third source terminal and the first clock signal input terminal; the second drain terminal is electrically connected to the second output terminal; and the third drain terminal is electrically connected to the first output terminal, the first and second pull-down holding units, the pull-down unit, and an opposite end of the capacitor. [0024] The pull-down unit comprises fourth and fifth thin-film transistors and the fourth thin-film transistor comprises a fourth gate terminal, a fourth source terminal, and a fourth drain terminal and the fifth thin-film transistor comprises a fifth gate terminal, a fifth source terminal, and a fifth drain terminal, wherein the fourth gate terminal is electrically connected to the fifth gate terminal and the (n+1)th stage signal input terminal; the fourth source terminal is electrically connected to a first low level input terminal and the fifth source terminal; the fourth drain terminal is electrically connected to the first drain terminal, said one end of the capacitor, the second gate terminal, the third gate terminal, and the first and second pull-down holding units; and the fifth drain terminal is electrically connected to the first output terminal, the third source terminal, said opposite end of the capacitor, and the first and second pull-down holding units. [0025] The first pull-down holding unit comprises sixth to ninth thin-film transistors and the sixth thin-film transistor comprises a sixth gate terminal, a sixth source terminal, and a sixth drain terminal; the seventh thin-film transistor comprises a seventh gate terminal, a seventh source terminal, and a seventh drain terminal; the eighth thin-film transistor comprises an eighth gate terminal, an eighth source terminal, and an eighth drain terminal; and the ninth thin-film transistor comprises a ninth gate terminal, a ninth source terminal, and a ninth drain terminal, wherein the sixth drain terminal is electrically connected to the seventh drain terminal, the eighth gate terminal, and the ninth gate terminal; the seventh gate terminal is electrically connected to the first drain terminal, the ninth drain terminal, said one end of the capacitor, the second gate terminal, the third gate terminal, the fourth drain terminal, and the second pull-down holding unit; the seventh source terminal is electrically connected to a second low level input terminal; the eighth drain terminal is electrically connected to said opposite end of the capacitor, the second pull-down holding unit, and the first output terminal; the eighth source terminal is electrically connected to the first low level input terminal; and the ninth source terminal is electrically connected to the first low level input terminal; and [0026] the second pull-down holding unit comprises tenth to thirteenth thin-film transistors and the tenth thin-film transistor comprises a tenth gate terminal, a tenth source terminal, and a tenth drain terminal; the eleventh thin-film transistor comprises an eleventh gate terminal, an eleventh source terminal, and an eleventh drain terminal; the twelfth thin-film transistor comprises a twelfth gate terminal, a twelfth source terminal, and a twelfth drain terminal; and the thirteenth thin-film transistor comprises a thirteenth gate terminal, a thirteenth source terminal, and a thirteenth drain terminal, wherein the tenth drain terminal is electrically connected to the eleventh drain terminal, the twelfth gate terminal, and the thirteenth gate terminal; the eleventh gate terminal is electrically connected to the first drain terminal, the thirteenth drain terminal, the seventh gate terminal, the ninth drain terminal, and said one end of the capacitor; the eleventh source terminal is electrically connected to the second low level input terminal; the twelfth drain terminal is electrically connected to said opposite end of the capacitor, the eighth drain terminal, and the first output terminal; the twelfth source terminal is electrically connected to the first low level input terminal; and the thirteenth source terminal is electrically connected to the first low level input terminal. [0027] The nth stage GOA unit of the GOA circuit further comprises a second clock signal input terminal and a third clock signal input terminal, the sixth gate terminal and the sixth source terminal being connected to the second clock signal input terminal, the tenth gate terminal and the tenth source terminal being connected to the third clock signal input terminal, the second clock signal input terminal receiving an input of the first clock signal, the third clock signal input terminal receiving an input of the second clock signal. [0028] The first pull-down holding unit further comprises a fourteenth thin-film transistor and the fourteenth thin-film transistor comprises a fourteenth gate terminal, a fourteenth source terminal, and a fourteenth drain terminal, wherein the fourteenth drain terminal is electrically connected to the sixth drain terminal, the seventh drain terminal, the eighth gate terminal, and the ninth gate terminal; and the fourteenth source terminal is electrically connected to the sixth gate terminal, the sixth source terminal, and the second clock signal input terminal; and the second pull-down holding unit further comprises a fifteenth thin-film transistor and the fifteenth thin-film transistor comprises a fifteenth gate terminal, a fifteenth source terminal, and a fifteenth drain terminal, wherein the fifteenth drain terminal is electrically connected to the tenth drain terminal, the eleventh drain terminal, the twelfth gate terminal, and the thirteenth gate terminal and the fifteenth source terminal is electrically connected to the tenth gate terminal and the tenth source terminal. [0029] The nth stage GOA unit of the GOA circuit further comprises a second clock signal input terminal and a third clock signal input terminal; the sixth gate terminal, the sixth source terminal, and the fourteenth source terminal are connected to the second clock signal input terminal; the fourteenth gate terminal is connected to the third clock signal input terminal; the tenth gate terminal, the tenth source terminal, and the fifteenth source terminal are connected to the third clock signal input terminal; the fifteenth gate terminal is connected to the second clock signal input terminal; and the second clock signal input terminal receives an input of the first clock signal and the third clock signal input terminal receives an input of the second clock signal. [0030] The nth stage GOA unit of the GOA circuit further comprises a first low frequency signal input terminal and a second low frequency input terminal, the sixth gate terminal; the sixth source terminal and the fourteenth source terminal are connected to the first low frequency signal input terminal; the fourteenth gate terminal is connected to the second low frequency signal input terminal; the tenth gate terminal, the tenth source terminal, and the fifteenth source terminal are connected to the second low frequency signal input terminal; the fifteenth gate terminal is connected to the first low frequency signal input terminal; and the first low frequency signal input terminal receives an input of a low frequency signal or an ultralow frequency signal and the second low frequency signal input terminal receives an input of a low frequency signal or an ultralow frequency signal. [0031] The present invention further provides a GOA circuit, comprising multiple stages of GOA units connected in cascade, wherein: [0032] for each nth stage GOA unit between the second stage and the last second stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal, wherein the first output terminal of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal, the second (n−1)th stage signal input terminal, and the (n+1)th stage signal input terminal of the nth stage GOA unit are respectively and electrically connected to the first output terminal and the second output terminal of the (n−1)th GOA unit and the first output terminal of the (n+1)th GOA unit, the first output terminal of the nth stage GOA unit being electrically connected to the first (n−1)th stage signal input terminal of the (n+1)th GOA unit and the (n+1)th stage signal input terminal of the (n−1)th GOA unit, the second output terminal of the nth stage GOA unit being electrically connected to the second (n−1)th stage signal input terminal of the (n+1)th GOA unit; [0033] for the nth stage GOA unit at the first stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal, wherein the first output terminal of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal of the nth stage GOA unit both provided for receiving an input of a pulse activation signal and the (n+1)th stage signal input terminal is electrically connected to the first output terminal of the (n+1)th GOA unit, the first output terminal and the second output terminal of the nth stage GOA unit being respectively and electrically connected to the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal of the (n+1)th GOA unit; [0034] for the nth stage GOA unit at the last stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal, a second (n−1)th stage signal input terminal, a (n+1)th stage signal input terminal, a first output terminal, and a second output terminal; the first (n−1)th stage signal input terminal and the second input terminal of the nth stage GOA unit are respectively and electrically connected to the first output terminal and the second output terminal of the (n−1)th GOA unit, the (n+1)th stage signal input terminal of the nth stage GOA unit being provided to receive an input of a pulse activation signal, the first output terminal of the nth stage GOA unit being electrically connected to the (n+1)th stage signal input terminal of the (n−1)th GOA unit and the second output terminal being open; [0035] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises a first clock signal input terminal, a first low level input terminal, and a second low level input terminal, the first low level input terminal being provided for receiving an input of a first low level, the second low level input terminal being provided for receiving an input of a second low level, the second low level being smaller than the first low level; [0036] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises: [0037] a pull-up control unit, which is electrically connected to the first (n−1)th stage signal input terminal and the second (n−1)th stage signal input terminal; [0038] a pull-up unit, which is electrically connected to the pull-up control unit and the first clock signal input terminal, the first output terminal, and the second output terminal; [0039] a first pull-down holding unit, which is electrically connected to the first low level input terminal, the second low level input terminal, the pull-up control unit, and the pull-up unit; [0040] a second pull-down holding unit, which is electrically connected to the first low level input terminal, the second low level input terminal, the first pull-down holding unit, the pull-up control unit, and the pull-up unit; and [0041] a pull-down unit, which is electrically connected to the (n+1)th stage signal input terminal, the first low level input terminal, the pull-up control unit, the pull-up unit, the first pull-down holding unit, the second pull-down holding unit, and the first output terminal; [0042] wherein the first clock signal input terminal has an input signal that is a first clock signal or a second clock signal, the first clock signal being opposite in phase to the second clock signal; when the input signal of the first clock signal input terminal of the nth stage GOA unit of the GOA circuit is the first clock signal, the input signal of the first clock signal input terminal of the (n+1)th stage GOA unit of the GOA circuit is the second clock signal; [0043] wherein the pull-up control unit is a first thin-film transistor and the first thin-film transistor comprises a first gate terminal, a first source terminal, and a first drain terminal, wherein the first gate terminal is electrically connected to the second (n−1)th stage signal input terminal; the first source terminal is electrically connected to the first (n−1)th stage signal input terminal; and the first drain terminal is electrically connected to the first and second pull-down holding units, the pull-down unit, and the pull-up unit; [0044] wherein the pull-up unit comprises a capacitor, a second thin-film transistor, and a third thin-film transistor and the second thin-film transistor comprises a second gate terminal, a second source terminal, and a second drain terminal and the third thin-film transistor comprises a third gate terminal, a third source terminal, and a third drain terminal, wherein the second gate terminal is electrically connected to one end of the capacitor, the first drain terminal, the third gate terminal, the first and second pull-down holding units, and the pull-down unit; the second source terminal is electrically connected to the third source terminal and the first clock signal input terminal; the second drain terminal is electrically connected to the second output terminal; and the third drain terminal is electrically connected to the first output terminal, the first and second pull-down holding units, the pull-down unit, and an opposite end of the capacitor; [0045] wherein the pull-down unit comprises fourth and fifth thin-film transistors and the fourth thin-film transistor comprises a fourth gate terminal, a fourth source terminal, and a fourth drain terminal and the fifth thin-film transistor comprises a fifth gate terminal, a fifth source terminal, and a fifth drain terminal, wherein the fourth gate terminal is electrically connected to the fifth gate terminal and the (n+1)th stage signal input terminal; the fourth source terminal is electrically connected to a first low level input terminal and the fifth source terminal; the fourth drain terminal is electrically connected to the first drain terminal, said one end of the capacitor, the second gate terminal, the third gate terminal, and the first and second pull-down holding units; and the fifth drain terminal is electrically connected to the first output terminal, the third source terminal, said opposite end of the capacitor, and the first and second pull-down holding units; and [0046] wherein the first pull-down holding unit comprises sixth to ninth thin-film transistors and the sixth thin-film transistor comprises a sixth gate terminal, a sixth source terminal, and a sixth drain terminal; the seventh thin-film transistor comprises a seventh gate terminal, a seventh source terminal, and a seventh drain terminal; the eighth thin-film transistor comprises an eighth gate terminal, an eighth source terminal, and an eighth drain terminal; and the ninth thin-film transistor comprises a ninth gate terminal, a ninth source terminal, and a ninth drain terminal, wherein the sixth drain terminal is electrically connected to the seventh drain terminal, the eighth gate terminal, and the ninth gate terminal; the seventh gate terminal is electrically connected to the first drain terminal, the ninth drain terminal, said one end of the capacitor, the second gate terminal, the third gate terminal, the fourth drain terminal, and the second pull-down holding unit; the seventh source terminal is electrically connected to a second low level input terminal; the eighth drain terminal is electrically connected to said opposite end of the capacitor, the second pull-down holding unit, and the first output terminal; the eighth source terminal is electrically connected to the first low level input terminal; and the ninth source terminal is electrically connected to the first low level input terminal; and [0047] the second pull-down holding unit comprises tenth to thirteenth thin-film transistors and the tenth thin-film transistor comprises a tenth gate terminal, a tenth source terminal, and a tenth drain terminal; the eleventh thin-film transistor comprises an eleventh gate terminal, an eleventh source terminal, and an eleventh drain terminal; the twelfth thin-film transistor comprises a twelfth gate terminal, a twelfth source terminal, and a twelfth drain terminal; and the thirteenth thin-film transistor comprises a thirteenth gate terminal, a thirteenth source terminal, and a thirteenth drain terminal, wherein the tenth drain terminal is electrically connected to the eleventh drain terminal, the twelfth gate terminal, and the thirteenth gate terminal; the eleventh gate terminal is electrically connected to the first drain terminal, the thirteenth drain terminal, the seventh gate terminal, the ninth drain terminal, and said one end of the capacitor; the eleventh source terminal is electrically connected to the second low level input terminal; the twelfth drain terminal is electrically connected to said opposite end of the capacitor, the eighth drain terminal, and the first output terminal; the twelfth source terminal is electrically connected to the first low level input terminal; and the thirteenth source terminal is electrically connected to the first low level input terminal. [0048] The nth stage GOA unit of the GOA circuit further comprises a second clock signal input terminal and a third clock signal input terminal, the sixth gate terminal and the sixth source terminal being connected to the second clock signal input terminal, the tenth gate terminal and the tenth source terminal being connected to the third clock signal input terminal, the second clock signal input terminal receiving an input of the first clock signal, the third clock signal input terminal receiving an input of the second clock signal. [0049] The first pull-down holding unit further comprises a fourteenth thin-film transistor and the fourteenth thin-film transistor comprises a fourteenth gate terminal, a fourteenth source terminal, and a fourteenth drain terminal, wherein the fourteenth drain terminal is electrically connected to the sixth drain terminal, the seventh drain terminal, the eighth gate terminal, and the ninth gate terminal; and the fourteenth source terminal is electrically connected to the sixth gate terminal, the sixth source terminal, and the second clock signal input terminal; and the second pull-down holding unit further comprises a fifteenth thin-film transistor and the fifteenth thin-film transistor comprises a fifteenth gate terminal, a fifteenth source terminal, and a fifteenth drain terminal, wherein the fifteenth drain terminal is electrically connected to the tenth drain terminal, the eleventh drain terminal, the twelfth gate terminal, and the thirteenth gate terminal and the fifteenth source terminal is electrically connected to the tenth gate terminal and the tenth source terminal. [0050] The nth stage GOA unit of the GOA circuit further comprises a second clock signal input terminal and a third clock signal input terminal; the sixth gate terminal, the sixth source terminal, and the fourteenth source terminal are connected to the second clock signal input terminal; the fourteenth gate terminal is connected to the third clock signal input terminal; the tenth gate terminal, the tenth source terminal, and the fifteenth source terminal are connected to the third clock signal input terminal; the fifteenth gate terminal is connected to the second clock signal input terminal; and the second clock signal input terminal receives an input of the first clock signal and the third clock signal input terminal receives an input of the second clock signal. [0051] The nth stage GOA unit of the GOA circuit further comprises a first low frequency signal input terminal and a second low frequency input terminal, the sixth gate terminal; the sixth source terminal and the fourteenth source terminal are connected to the first low frequency signal input terminal; the fourteenth gate terminal is connected to the second low frequency signal input terminal; the tenth gate terminal, the tenth source terminal, and the fifteenth source terminal are connected to the second low frequency signal input terminal; the fifteenth gate terminal is connected to the first low frequency signal input terminal; and the first low frequency signal input terminal receives an input of a low frequency signal or an ultralow frequency signal and the second low frequency signal input terminal receives an input of a low frequency signal or an ultralow frequency signal. [0052] The efficacy of the present invention is that the present invention provides a GOA circuit, which uses two low level signals to reduce the leakage currents of the thin-film transistors of a pull-down holding unit, wherein the second low level that has a lower level provides a low voltage to pull-down points P n and K n and the first low level that has a higher level provides a low voltage to the pull-down points Q n and G n , so as to reduce the potentials of the pull-down point P n and K n when the pull-down point Q n and G n are activated to thereby facilitate charging of Q n and G n and also to break the leakage current loop of the circuit between two low level signals to greatly reduce the leakage current between the two low level signal, enhance the performance of the GOA circuit, and improve the quality of displayed images; further, the fourteenth thin-film transistor and the fifteenth thin-film transistor are additionally included in respect of the diode design of the sixth thin-film transistor and the tenth thin-film transistor to perform discharging to the pull-down points P n and K n , thereby achieving the potentials of P n and K n changing up and down with the variation of the first clock signal CK 1 and the second clock signal CK 2 , providing alternating operations so as to reduce the influence of the eighth and ninth thin-film transistor and the twelfth and thirteenth thin-film transistor by stresses, extending the lifespan of the GOA circuit. Further, using low frequency or ultralow frequency signals to control the pull-down holding unit effectively reduces power consumption of the circuit. [0053] For better understanding of the features and technical contents of the present invention, reference will be made to the following detailed description of the present invention and the attached drawings. However, the drawings are provided for the purposes of reference and illustration and are not intended to impose limitations to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS [0054] The technical solution, as well as other beneficial advantages, of the present invention will be apparent from the following detailed description of embodiments of the present invention, with reference to the attached drawing. In the drawing: [0055] FIG. 1 is a circuit diagram of a conventional GOA (Gate Driver on Array) circuit; [0056] FIG. 2 is an equivalent circuit of FIG. 1 ; [0057] FIG. 3 is a drive timing diagram of the GOA circuit shown in FIG. 1 ; [0058] FIG. 4 is a circuit diagram of a GOA circuit according to a preferred embodiment of the present invention; [0059] FIG. 5 is a drive timing diagram of the GOA circuit shown in FIG. 4 ; [0060] FIG. 6 is plot of a characteristic I-V curve of a thin-film transistor; [0061] FIG. 7 is a circuit diagram of a GOA circuit according to another preferred embodiment of the present invention; [0062] FIG. 8 is a drive timing diagram of the GOA circuit shown in FIG. 7 [0063] FIG. 9 is a circuit diagram of a GOA circuit according to a further preferred embodiment of the present invention; and [0064] FIG. 10 is a drive timing diagram of the GOA circuit shown in FIG. 9 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0065] To further expound the technical solution adopted in the present invention and the advantages thereof, a detailed description is given to a preferred embodiment of the present invention and the attached drawings. [0066] Referring to FIGS. 4-6 , the present invention provides a GOA (Gate-Driver-on-Array) circuit, which comprises multiple stages of GOA units connected in cascade, wherein: [0067] for each nth stage GOA unit between the second stage and the last second stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal 21 (G n−1 ), a second (n−1)th stage signal input terminal 22 (ST n−1 ), a (n+1)th stage signal input terminal 23 (G n+1 ), a first output terminal 27 (G n ), and a second output terminal 28 (ST n ), wherein the first output terminal 27 (G n ) of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal 21 (G n−1 ), the second (n−1)th stage signal input terminal 22 (ST n−1 ), and the (n+1)th stage signal input terminal 23 (G n+1 ) of the nth stage GOA unit are respectively and electrically connected to the first output terminal 27 (G n ) and the second output terminal 28 (ST n ) of the (n−1)th GOA unit and the first output terminal 27 (G n ) of the (n+1)th GOA unit, the first output terminal 27 (G n ) of the nth stage GOA unit being electrically connected to the first (n−1)th stage signal input terminal 21 (G n−1 ) of the (n+1)th GOA unit and the (n+1)th stage signal input terminal 23 (G n+1 ) of the (n−1)th GOA unit, the second output terminal 28 (ST n ) of the nth stage GOA unit being electrically connected to the second (n−1)th stage signal input terminal 22 (ST n−1 ) of the (n+1)th GOA unit; [0068] for the nth stage GOA unit at the first stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal 21 (G n−1 ), a second (n−1)th stage signal input terminal 22 (ST n−1 ), a (n+1)th stage signal input terminal 23 (G n+1 ), a first output terminal 27 (G n ), and a second output terminal 28 (ST n ), wherein the first output terminal 27 (G n ) of the nth stage GOA unit is provided for driving an active zone of an array substrate; the first (n−1)th stage signal input terminal 21 (G n−1 ) and the second (n−1)th stage signal input terminal 22 (ST n−1 ) of the nth stage GOA unit both provided for receiving an input of a pulse activation signal and the (n+1)th stage signal input terminal 23 (G n+1 ) is electrically connected to the first output terminal 27 (G n ) of the (n+1)th GOA unit, the first output terminal 27 (G n ) and the second output terminal 28 (ST n ) of the nth stage GOA unit being respectively and electrically connected to the first (n−1)th stage signal input terminal 21 (G n−1 ) and the second (n−1)th stage signal input terminal 22 (ST n−1 ) of the (n+1)th GOA unit; [0069] for the nth stage GOA unit at the last stage of the GOA circuit, the nth stage GOA unit comprises a first (n−1)th stage signal input terminal 21 (G n−1 ), a second (n−1)th stage signal input terminal 22 (ST n−1 ), a (n+1)th stage signal input terminal 23 (G n+1 ), a first output terminal 27 (G n ), and a second output terminal 28 (ST n ); the first (n−1)th stage signal input terminal 21 (G n−1 ) and the second input terminal 22 (ST n−1 ) of the nth stage GOA unit are respectively and electrically connected to the first output terminal 27 (G n ) and the second output terminal 28 (ST n ) of the (n−1)th GOA unit, the (n+1)th stage signal input terminal 23 (G n+1 ) of the nth stage GOA unit being provided to receive an input of a pulse activation signal, the first output terminal 27 (G n ) of the nth stage GOA unit being electrically connected to the (n+1)th stage signal input terminal 23 (G n+1 ) of the (n−1)th GOA unit and the second output terminal 28 (ST n ) being open; [0070] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises a first clock signal input terminal 24 , a first low level input terminal 25 , and a second low level input terminal 26 , the first low level input terminal 25 being provided for receiving an input of a first low level V ss1 , the second low level input terminal 26 being provided for receiving an input of a second low level V ss2 , the second low level V ss2 being smaller than the first low level V ss1 ; [0071] for each nth stage GOA unit between the first stage and the last stage of the GOA circuit, the nth stage GOA unit further comprises: [0072] a pull-up control unit 42 , which is electrically connected to the first (n−1)th stage signal input terminal 21 and the second (n−1)th stage signal input terminal 22 ; [0073] a pull-up unit 44 , which is electrically connected to the pull-up control unit 42 and the first clock signal input terminal 24 , the first output terminal 27 , and the second output terminal 28 ; [0074] a first pull-down holding unit 46 , which is electrically connected to the first low level input terminal 25 , the second low level input terminal 26 , the pull-up control unit 42 , and the pull-up unit 44 ; [0075] a second pull-down holding unit 47 , which is electrically connected to the first low level input terminal 25 , the second low level input terminal 26 , the first pull-down holding unit 46 , the pull-up control unit 42 , and the pull-up unit 44 ; and [0076] a pull-down unit 48 , which is electrically connected to the (n+1)th stage signal input terminal 23 , the first low level input terminal 25 , the pull-up control unit 42 , the pull-up unit 44 , the first pull-down holding unit 46 , the second pull-down holding unit 47 , and the first output terminal 27 . [0077] In the instant embodiment, the nth stage GOA unit of the GOA circuit further comprises a second clock signal input terminal 31 and a third clock signal input terminal 32 . The first clock signal input terminal 24 has an input signal that is a first clock signal CK 1 or a second clock signal CK 2 , the second clock signal input terminal 31 having an input signal that is the first clock signal CK 1 , the third clock signal input terminal 32 having an input signal that is the second clock signal CK 2 , the first clock signal CK 1 being opposite in phase to the second clock signal CK 2 , meaning high and low voltages of the signals CK 1 and CK 2 being opposite to each other at a given time point; when the input signal of the first clock signal input terminal 24 of the nth stage GOA unit of the GOA circuit is the first clock signal CK 1 , the input signal of the first clock signal input terminal 24 of the (n+1)th stage GOA unit of the GOA circuit is the second clock signal CK 2 . [0078] The pull-up control unit 42 is a first thin-film transistor T 1 and the first thin-film transistor T 1 comprises a first gate terminal g 1 , a first source terminal s 1 , and a first drain terminal d 1 , wherein the first gate terminal g 1 is electrically connected to the second (n−1)th stage signal input terminal 22 ; the first source terminal s 1 is electrically connected to the first (n−1)th stage signal input terminal 21 ; and the first drain terminal d 1 is electrically connected to the first and second pull-down holding units 46 , 47 , the pull-down unit 48 , and the pull-up unit 44 . [0079] The pull-up unit 44 comprises a capacitor C b , a second thin-film transistor T 2 , and a third thin-film transistor T 3 and the second thin-film transistor T 2 comprises a second gate terminal g 2 , a second source terminal s 2 , and a second drain terminal d 2 and the third thin-film transistor T 3 comprises a third gate terminal g 3 , a third source terminal s 3 , and a third drain terminal d 3 , wherein the second gate terminal g 2 is electrically connected to one end of the capacitor C b , the first drain terminal d 1 , the third gate terminal g 3 , the first and second pull-down holding units 46 , 47 , and the pull-down unit 48 ; the second source terminal s 2 is electrically connected to the third source terminal s 3 and the first clock signal input terminal 24 ; the second drain terminal d 2 is electrically connected to the second output terminal 28 ; and the third drain terminal d 3 is electrically connected to the first output terminal 27 , the first and second pull-down holding units 46 , 47 , the pull-down unit 48 , and an opposite end of the capacitor C b . [0080] The pull-down unit 48 comprises fourth and fifth thin-film transistors T 4 , T 5 and the fourth thin-film transistor T 4 comprises a fourth gate terminal g 4 , a fourth source terminal s 4 , and a fourth drain terminal d 4 and the fifth thin-film transistor T 5 comprises a fifth gate terminal g 5 , a fifth source terminal s 5 , and a fifth drain terminal d 5 , wherein the fourth gate terminal g 4 is electrically connected to the fifth gate terminal g 5 and the (n+1)th stage signal input terminal 23 ; the fourth source terminal s 4 is electrically connected to a first low level input terminal and the fifth source terminal s 5 ; the fourth drain terminal d 4 is electrically connected to the first drain terminal d 1 , said one end of the capacitor C b , the second gate terminal g 2 , the third gate terminal g 3 , and the first and second pull-down holding units 46 , 47 ; and the fifth drain terminal d 5 is electrically connected to the first output terminal 27 , the third source terminal s 3 , said opposite end of the capacitor C b , and the first and second pull-down holding units 46 , 47 . [0081] The first pull-down holding unit 46 comprises sixth to ninth thin-film transistors T 6 , T 7 , T 8 , T 9 and the sixth thin-film transistor T 6 comprises a sixth gate terminal g 6 , a sixth source terminal s 6 , and a sixth drain terminal d 6 ; the seventh thin-film transistor T 7 comprises a seventh gate terminal g 7 , a seventh source terminal s 7 , and a seventh drain terminal d 7 ; the eighth thin-film transistor comprises an eighth gate terminal g 8 , an eighth source terminal s 8 , and an eighth drain terminal d 8 ; and the ninth thin-film transistor comprises a ninth gate terminal g 9 , a ninth source terminal s 9 , and a ninth drain terminal d 9 , wherein the sixth gate terminal g 6 and the sixth source terminal s 6 are connected to the second clock signal input terminal 31 ; the sixth drain terminal d 6 is electrically connected to a pull-down point P n , the seventh drain terminal d 7 , the eighth gate terminal g 8 , and the ninth gate terminal g 9 ; the seventh gate terminal g 7 is electrically connected to the first drain terminal d 1 , the ninth drain terminal d 9 , said one end of the capacitor C b , the second gate terminal g 2 , the third gate terminal g 3 , the fourth drain terminal d 4 , and the second pull-down holding unit 47 ; the seventh source terminal s 7 is electrically connected to a second low level input terminal 26 ; the eighth drain terminal d 8 is electrically connected to said opposite end of the capacitor C b , the second pull-down holding unit 47 , and the first output terminal 27 (G n ); the eighth source terminal s 8 is electrically connected to the first low level input terminal 25 ; and the ninth source terminal s 9 is electrically connected to the first low level input terminal 25 . [0082] The eighth thin-film transistor T 8 is provided generally for maintaining a low voltage of the first output terminal 27 (G n ); the ninth thin-film transistor T 9 is provided for maintaining a low voltage of the pull-down point Q n ; the seventh thin-film transistor T 7 is provided for setting pull-down points P n and K n at low voltages when Q n is at a high voltage and also for deactivating the first pull-down holding unit 46 to prevent the pull-down point Q n from affecting the first output terminal 27 (G n ). The second low level V ss2 being smaller than the first low level V ss1 helps reduce leakage currents of the eighth and ninth thin-film transistors T 8 , T 9 . [0083] The second pull-down holding unit 47 comprises tenth to thirteenth thin-film transistors T 10 , T 11 , T 12 , T 13 and the tenth thin-film transistor T 10 comprises a tenth gate terminal g 10 , a tenth source terminal s 10 , and a tenth drain terminal d 10 ; the eleventh thin-film transistor T 11 comprises an eleventh gate terminal g 11 , an eleventh source terminal s 11 , and an eleventh drain terminal d 11 ; the twelfth thin-film transistor T 12 comprises a twelfth gate terminal g 12 , a twelfth source terminal s 12 , and a twelfth drain terminal d 12 ; and the thirteenth thin-film transistor T 13 comprises a thirteenth gate terminal g 13 , a thirteenth source terminal s 13 , and a thirteenth drain terminal d 13 , wherein the tenth gate terminal g 10 and the tenth source terminal s 10 are connected to the third clock signal input terminal 32 ; the tenth drain terminal d 10 is electrically connected to a pull-down point K n , the eleventh drain terminal d 11 , the twelfth gate terminal g 12 , and the thirteenth gate terminal g 13 ; the eleventh gate terminal g 11 is electrically connected to the first drain terminal d 1 , the thirteenth drain terminal d 13 , the seventh gate terminal g 7 , the ninth drain terminal d 9 , and said one end of the capacitor C b ; the eleventh source terminal s 11 is electrically connected to the second low level input terminal 26 ; the twelfth drain terminal d 12 is electrically connected to said opposite end of the capacitor C b , the eighth drain terminal d 8 , and the first output terminal 27 (G n ); the twelfth source terminal s 12 is electrically connected to the first low level input terminal 25 ; and the thirteenth source terminal s 13 is electrically connected to the first low level input terminal. [0084] The twelfth thin-film transistor T 12 is provided generally for maintain a low voltage of the first output terminal 27 (G n ); the thirteenth thin-film transistor T 13 is provided for maintain a low voltage of the pull-down point Q n ; the eleventh thin-film transistor T 11 is provided for setting the pull-down points P n and K n at a low voltage when Q n is at a high voltage and for deactivating the second pull-down holding unit 47 to prevent the pull-down point Q n from affecting the first output terminal 27 (G n ). The second low level V ss2 being smaller than the first low level V ss1 helps reduce leakage currents of the twelfth and thirteenth thin-film transistors T 12 , T 13 . [0085] Referring to FIG. 5 , in the drawing, signals CK 1 and CK 2 are two clock signals of which the low voltages are opposite at a give time point; the second low level V ss2 is smaller than the first low level V ss1 ; and G n and G n+1 are the output signals of the second output terminals 27 of two adjacent GOA units. It can be seen that Q n and G n can be pulled down to the low voltage of V ss1 and P n and K n can be pulled to the low voltage of V ss2 when Q n and G n are at the high voltage. In this way, the relative potential V gs between the gate terminal and the source terminal of the eighth and ninth thin-film transistors T 8 , T 9 and between those of the twelfth and thirteenth thin-film transistors T 12 , T 13 is less than 0 (V gs =V ss2 −V ss1 ). Since the minimum leakage current of a thin-film transistor in an OFF state is at a location where the relative potential V gs between the gate terminal and the source terminal is less than 0 (as shown in FIG. 6 ), the GOA circuit of the instant embodiment can effectively reduce the leakage currents of the eighth and ninth thin-film transistors T 8 , T 9 and the twelfth and thirteenth thin-film transistors T 12 , T 13 . [0086] Referring to FIGS. 7-8 , which shows a GOA circuit according to another embodiment of the present invention provides, in the instant embodiment, the first pull-down holding unit 46 further comprises a fourteenth thin-film transistor T 14 and the fourteenth thin-film transistor T 14 comprises a fourteenth gate terminal g 14 , a fourteenth source terminal s 14 , and a fourteenth drain terminal d 14 , wherein the fourteenth gate terminal g 14 is connected to the third clock signal input terminal 32 ; the fourteenth drain terminal d 14 is electrically connected to the sixth drain terminal d 6 , the seventh drain terminal d 7 , the eighth gate terminal g 8 , and the ninth gate terminal g 9 ; and the fourteenth source terminal s 14 is electrically connected to the sixth gate terminal g 6 , the sixth source terminal g 6 , and the second clock signal input terminal 31 . The second pull-down holding unit 47 further comprises a fifteenth thin-film transistor T 15 and the fifteenth thin-film transistor T 15 comprises a fifteenth gate terminal g 15 , a fifteenth source terminal s 15 , and a fifteenth drain terminal d 15 , wherein the fifteenth gate terminal g 15 is connected to the second clock signal input terminal 31 ; the fifteenth source terminal s 15 is electrically connected to the tenth source terminal s 10 , the tenth gate terminal g 10 , and the third clock signal input terminal 32 ; and the fifteenth drain terminal d 15 is electrically connected to the tenth drain terminal d 10 , the eleventh drain terminal d 11 , the twelfth gate terminal g 12 , and the thirteenth gate terminal g 13 . [0087] In the instant embodiment, the first and second pull-down holding units 46 , 47 are improved in respect of the drawback of the diode design of the sixth thin-film transistor T 6 and the tenth thin-film transistor T 10 by additionally including the fourteenth thin-film transistor T 14 and the fifteenth thin-film transistor T 15 to discharge to the pull-down points P n and K n in order to fast pull the potentials of the pull-down points P n and K n down to the low voltage of the first clock signal CK 1 or the second clock signal CK 2 the low voltage. Through the alternative operations of the first and second pull-down holding units 46 , 47 , the potentials of P n and K n following variations of the first clock signal CK 1 and the second clock signal CK 2 to change up and down can be achieved, providing alternating operations thereby reducing the influence of the eighth and ninth thin-film transistors T 8 , T 9 and the twelfth and thirteenth thin-film transistor sT 12 , T 13 by stress. [0088] Referring to FIGS. 9-10 , which show a GOA circuit according to a further embodiment of the present invention, the instant embodiment is generally similar to the embodiment with reference to FIG. 7 and a difference therebetween is that in the instant embodiment, the second and third clock signal input terminals 31 , 32 of the first and second pull-down holding units 46 , 47 are replaced by first and second low frequency signal input terminals 34 , 35 and the first and second low frequency signal input terminals 34 , 35 receive inputs of low frequency or ultralow frequency signals LC 1 and LC 2 . This helps reduce power consumptions of the first and second pull-down holding units 46 , 47 , because the first and second pull-down holding units 46 , 47 are constantly kept in operating conditions and for a large number of stages included in the GOA circuit, high frequency signals would increase the power consumption of the GOA circuit. [0089] In summary, the present invention provides a GOA circuit, which uses two low level signals to reduce the leakage currents of the thin-film transistors of a pull-down holding unit, wherein the second low level that has a lower level provides a low voltage to pull-down points P n and K n and the first low level that has a higher level provides a low voltage to the pull-down points Q n and G n , so as to reduce the potentials of the pull-down point P n and K n when the pull-down point Q n and G n are activated to thereby facilitate charging of Q n and G n and also to break the leakage current loop of the circuit between two low level signals to greatly reduce the leakage current between the two low level signal, enhance the performance of the GOA circuit, and improve the quality of displayed images; further, the fourteenth thin-film transistor and the fifteenth thin-film transistor are additionally included in respect of the diode design of the sixth thin-film transistor and the tenth thin-film transistor to perform discharging to the pull-down points P n and K n , thereby achieving the potentials of P n and K n changing up and down with the variation of the first clock signal CK 1 and the second clock signal CK 2 , providing alternating operations so as to reduce the influence of the eighth and ninth thin-film transistor and the twelfth and thirteenth thin-film transistor by stresses, extending the lifespan of the GOA circuit. Further, using low frequency or ultralow frequency signals to control the pull-down holding unit effectively reduces power consumption of the circuit. [0090] Based on the description given above, those having ordinary skills of the art may easily contemplate various changes and modifications of the technical solution and technical ideas of the present invention and all these changes and modifications are considered within the protection scope of right for the present invention.

The present invention provides a GOA (Gate-Driver-on-Array) circuit, which includes multiple GOA units connected in cascade. An nth stage GOA unit of the GOA circuit includes a first (n−1)th stage signal input terminal ( 21 ), a second (n−1)th stage signal input terminal ( 22 ), a (n+1)th stage signal input terminal ( 23 ), a first clock signal input terminal ( 24 ), a first low level input terminal ( 25 ), a second low level input terminal ( 26 ), a first output terminal ( 27 ), and a second output terminal ( 28 ). The nth stage GOA unit further includes: a pull-up control unit ( 42 ), a pull-up unit ( 44 ), a first pull-down holding unit ( 46 ), a second pull-down holding unit ( 47 ), and a pull-down unit ( 48 ). The GOA circuit of the present invention overcomes the problems of poor performance of the conventional the GOA circuit caused by introduction of two low level signals into the GOA circuit and short operation service life and can enhance the quality of displayed images.

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of U.S. patent application Ser. No. 11/562,467, filed Nov. 22, 2006. TECHNICAL FIELD [0002] This invention generally relates to communications. More particularly, this invention relates to wireless communications. DESCRIPTION OF THE RELATED ART [0003] In a UMTS or CDMA radio access network (RAN) deployment a geographical area is divided into cells. A nodeB (UMTS terminology) or base station (CDMA terminology) serves each cell. To assist with mobile station mobility between cells, the RAN maintains a list of neighboring cells for every cell in the network. The mobile station must learn of the neighboring cells so that it can detect signal strengths for selecting a candidate cell for future communications. [0004] Mobility can be broadly split into two mobile station modes: idle mode mobility and active mode mobility. In idle mode, the mobile station has no active radio links to the RAN, so mobility involves choosing a nodeB or base station with a good enough signal strength upon which to “camp”. When camped, the mobile station can listen to the nodeB or base station broadcast channels. This is important because the broadcast channels are used to signal an incoming phone call. The broadcast channels are also used to inform all mobile stations of neighboring cells to be considered for camping on. In active mode, the mobile station has active radio links to the RAN. As the radio channel conditions change between the mobile station and the nodeB or base station, other nodeBs or base stations must be considered as candidates with which to maintain the communication link. [0005] It is expected that the deployment of macro-cellular networks (e.g., existing cellular networks) will be complemented by the deployment of in building (e.g., home, enterprise, government) communication devices that operate as microcell or picocell nodeBs or base stations. The former can be considered an underlay network and the latter an overlay network because the latter will be, in effect, established on top of or in addition to the macro-cellular network. The in-building overlay network will be intended to complement the macro-cellular, underlay network. [0006] Establishing overlay networks will increase cellular coverage and capacity. However, it heralds a new deployment scenario that current specifications and standards are not designed to provide. There are a number of problems associated with this, including how to provide mobile station mobility between the traditional macro-cellular network deployment and the overlay deployment. [0007] In most cases, the mobile station relies on the RAN to inform of it of the presence of neighboring cells (nodeBs and base stations) and their cell codes (scrambling codes or pseudo noise offsets). Neighboring cells use different cell codes compared to those around them to enable the mobile station to separate the transmissions of interest from those of other cells. The number of neighbors is limited to a set of 32 intra-frequency cells. If an overlay network is deployed, the number of neighbors can become much greater than 32. It is possible to have hundreds of apartments inside one underlay cell, for example, with each apartment containing an overlay cell. There needs to be a mechanism to inform the mobile station of all neighbors so they can be considered as a candidate for camping or handoff. [0008] One suggestion is to modify the RAN infrastructure to inform it of the overlay network's presence. For example, a radio network controller could be informed of every cell in the overlay network that the mobile station is permitted to use. Then, when the mobile station is informed of neighbors through messages transmitted by the RAN the list is augmented with mobile-station-specific nodeBs. Providing mobile-station-specific neighbor lists overcomes the limitation of 32 intra-frequency neighbor cells but it increases the task and complexity of maintaining up-to-date neighbor lists. Overlay network devices may be arbitrarily introduced into or removed from a macro-cell coverage area and the RAN would need to be updated accordingly on an inconveniently frequent basis. Additionally, modifying the RAN in this manner does not solve the idle mode mobility problem. In idle mode, no active radio link exists between the mobile station and the RAN. The mobile station therefore relies on the underlay network broadcast channels to inform it of candidate cells upon which to camp. In idle mode there is no facility to provide a mobile-station-specific neighbor list. [0009] Another suggestion instead of modifying the RAN is to modify the mobile station to store the list of overlay cells it is allowed to access. Then the mobile station adds its stored set of potential candidates to any neighbor list received from the RAN. This requires changing the way current mobile stations operate and hinders simple deployment of an overlay network. Existing mobile stations would have to be reconfigured to have the necessary capacity for this feature. [0010] Both of the above suggestions have the drawback of requiring substantial changes to existing equipment (mobile station or RAN). This is expensive, carries significant risk and is unattractive to the network operator. [0011] There is a need for an efficient and economical way of facilitating a mobile station communicating with an overlay network within the coverage area of a macro-cellular underlay network. This invention addresses that need. SUMMARY [0012] An exemplary method of communication is useful in a system including at least one underlay network device having a first coverage area and at least one overlay network device having a second, smaller coverage area within the first coverage area of the underlay network device. The exemplary method includes using a selected plurality of cell codes for identifying overlay network devices exclusively. Communications are conducted using a selected plurality of cell codes exclusively for identifying overlay network devices. The first downlink channel has one of the selected plurality of cell codes such that a mobile station communicating with an underlay network device can detect the overlay network device as a candidate overlay network device for communications with the mobile station. [0013] An exemplary communication device comprises a transmitter that broadcasts at least two downlink channels. A cell code of a first one of the downlink channels is one of a selected plurality of cell codes used for identifying overlay network devices exclusively. A cell code of a second one of the downlink channels is distinct from the selected plurality of cell codes. [0014] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 schematically shows selected portions of a wireless communication system with which an embodiment of this invention is useful. [0016] FIG. 2 is a flowchart diagram summarizing one example approach. DETAILED DESCRIPTION [0017] The following description demonstrates how example embodiments of this invention allow for a mobile station to communicate with underlay network devices (e.g., macro-cell base stations) and overlay network devices (e.g., pico-cell base stations) within the coverage area of the underlay network. The disclosed examples are useful for a variety of communication scenarios including active call handovers between the underlay and overlay networks and idle mode candidate cell identification of underlay cells, overlay cells or both. The disclosed examples facilitate employment of overlay networks and devices within areas covered by existing underlay network devices in an efficient and economical manner. [0018] FIG. 1 schematically shows an example communication system 20 . An overlay network 22 includes a plurality overlay network communication devices 22 that provide wireless communication coverage in corresponding cells. In a UMTS example, the devices 22 are nodeBs and in a CDMA example, the devices 22 are base station transceivers. Only one such device is shown in FIG. 1 for simplicity. Each of the devices 22 provides a coverage area for a corresponding one of a plurality of cells 26 , 28 , 30 , 32 and 34 . The size of the cells 26 - 34 is such that the cells are considered macrocells. [0019] Other communication devices 40 provide wireless communication coverage areas or cells 42 within the coverage areas of the cells 26 - 34 . Only one such device is shown for simplicity but there would be one associated with each of the cells 42 schematically shown in FIG. 1 . The communication devices are considered part of an overlay network for purposes of discussion because the wireless coverage provided by the devices 40 complements and is placed on top of that provided by the overlay network devices 24 . [0020] Each communication device 40 includes a transceiver such that it operates as a nodeB or base station of the corresponding cell 42 . [0021] Mobile stations can communicate with the communication devices 24 , the communication devices 40 , or both, depending on the situation of the particular mobile station. The illustrated example includes a mobile station 50 within the cell 28 and another mobile station 52 within the cell 34 . The mobile station 50 is not within a coverage area of any of the overlay network cells 42 and can only communicate with the underlay network devices 24 . The mobile station 52 , on the other hand, is within the coverage area of one of the overlay cells 42 and the underlay cell 34 . The illustrated example provides the mobile station 52 an ability to communicate with either network by communicating with either or both of the corresponding communication device 24 and the corresponding communication device 40 . In other words, the mobile station 52 has mobility between the overlay and underlay networks. [0022] One example approach is summarized in a flow chart 60 in FIG. 2 . This example includes the mobile station 52 being powered on at 62 . Initially, the mobile station uses known techniques for camping on a channel of the underlay network. This status is shown at 64 . In a known manner, the mobile station 52 receives a neighbor list of cell codes (e.g., scrambling codes or pseudo noise offsets) from the underlay network 22 as shown at 66 . [0023] One example includes cell codes within the neighbor list provided by the underlay network 22 that notify a mobile station of the communication devices 40 of the overlay network within the region of the current mobile station location. One example includes reserving a relatively small number of cell codes exclusively for identifying the cells 42 of the overlay network. In one UMTS example, eight of the 512 available scrambling codes are used exclusively for identifying the cells 42 . In one CDMA example, a plurality of PN offsets are used exclusively for identifying the overlay cells 42 . [0024] In one example, every overlay communication device 40 broadcasts two downlink channels instead of just one. A first one of the downlink channels has one of the cell codes that is exclusively dedicated to identifying the overlay cells 42 . The second one of the two downlink channels has a cell code that is distinct from those in the reserved set used exclusively for identifying the cells 42 . The first downlink channel can be considered a “transitory” broadcast channel because it provides information that facilitates mobile station mobility between the overlay network and the underlay network 22 . The second downlink channel is a “normal” broadcast channel because it is used for communications within an overlay cell 42 in a manner like the normal broadcast channels are used in the overlay cells 26 - 34 . The cell code of the second downlink channel is chosen so that it does not conflict with any neighbor cell codes in the underlay or overlay network. [0025] The neighbor list of the underlay network, which is provided by the traditional RAN is modified in one example to always include the reserved set of cell codes that exclusively identify the overlay cells. The mobile station receiving the neighbor list performs signal strength measurements at 68 to evaluate potential candidate cells on which the mobile station can camp. Because the neighbor list include those cell codes that exclusively identify overlay cells 42 , the mobile station will be monitoring overlay communication device 40 transitory downlink channel broadcasts. [0026] At this stage, the mobile station is informed of the overlay network's presence. The mobile station will now perform signal strength measurements on the reserved cell codes. The overlay cells will therefore be considered as camping candidates and as active mode handover candidates. [0027] At 70 , the mobile station determines whether to switch from a current cell. If not, the mobile station operation returns to 64 . If a monitored broadcast downlink channel indicates that a switch is desirable, a determination is made at 72 , whether the new cell selected by the mobile station is an overlay cell 42 . If so, the mobile station camps on the transitory downlink channel (e.g., the first of the two downlink channels) of the corresponding overlay cell 42 at 74 . Then the mobile station can identify the second of the downlink channels of the corresponding overlay cell 42 based on communications on the first (e.g., transitory) of the downlink channels on which the mobile station has camped. [0028] Essentially, the two downlink channels radiating from a single overlay communication device 40 result in two different cells being presented to the mobile station. A mobile station informed by the underlay network will only be aware of one of these cells (i.e., the “transitory” cell code). Once the mobile station camps on the transitory cell, however, the transitory broadcast channel (BCH) broadcast messages will then inform the mobile station of the second of the two downlink channels (e.g., the “normal” cell). In one UMTS example, the transitory cell's BCH System Information Block 11 (SIB 11 ) is populated to contain the normal cell's cell code. [0029] To reduce radio interference, the transitory downlink channels are only used for a short time in one example in order to bridge the overlay and underlay networks. At 76 , the mobile station determines signal strengths of the neighbor set provided by the overlay communication device 40 . [0030] One example includes fixing the power of the transitory channels to be a fraction of the normal downlink channels of the overlay cells. The second downlink channel cell code is included in the transitory broadcast channel neighbor list. In the transitory broadcast channels of one example, the signal strength at which the mobile station evaluates other candidates for camping on is set very low. In a UMTS example, this parameter is called S intrasearch , included in SIB 3 / 4 messages, which are known from 3GPP specifications 25.304, for example. The mobile station selects the normal cell code associated with the second of the two downlink channels due to its higher signal strength. The mobile station camps on a normal overlay cell channel at 78 . [0031] Once the mobile station camps on the normal overlay cell 42 , it may be desirable that it remains camped on it, even if another cell becomes a better candidate. For example, a network operator's goal may be to take traffic off their macro-cellular network and direct it onto the overlay cells 42 . This is achieved in one example by setting parameters in the BCH channels appropriately. For example, thresholds for starting the cell-reselection procedure are set very high. [0032] In another example, once handover is complete to the transitory overlay cell, the overlay communication device 40 instructs the mobile station to handover to the normal cell of the overlay device 40 . [0033] The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

A wireless communication technique provides mobility for a mobile station to communicate with an overlay network device, which is within a coverage area of an underlay network device, when the mobile station is within a coverage area of both devices. The overlay network device broadcasts at least two downlink channels. A cell code (e.g., a scrambling code or pseudo noise offset) of a first one of the downlink channels identifies an overlay network device exclusively. The mobile station can detect the first downlink channel responsive to an indication of the exclusive cell code from the underlay network device. A second one of the downlink channels allows for subsequent, ongoing communications between the mobile station and the overlay network device.

TECHNICAL FIELD OF THE INVENTION The present invention provides a sterilizing fog, characterized by droplet size range, vapor density range, sterilant concentration range and sterilant concentration within the droplets. Specifically, the inventive fog is achieved by an apparatus combining pressure, temperature and acoustics to form a super-charged ozoneated water and an apparatus that creates small micro droplets which form a highly concentrated sterilizing fog. Specific sterilants used are ozone, chlorine and chlorous acid generating compositions such as sodium hypochlorite. BACKGROUND OF THE INVENTION Food processing and food safety has increasingly relied upon techniques to remove or eliminate harmful microbial organisms from the surfaces of food products. Harmful bacterial products have been found on meat food products, such as salmonella on poultry and E. Coli H057 on various red meats. Various techniques have been developed to test for the presence of such harmful organisms but such tests, inherently, can only sample random surfaces and rely on probabilities to determine of all of the surface area of food products has either been free of such harmful organisms or effectively decontaminated. There are many broad-spectrum sterilizing agents that are strong oxidants, such as chlorine, hypochlorite (bleach), hydrogen peroxide, and ozone or O 3 . Although chlorine is the most common sterilizing agent in the world, ozone is commonly used to sterilize hot tubs and other public swimming pools. In addition, poultry and other meat-processing that historically has relied solely on chlorine, now frequently baths chickens in water containing ozone. However, in order for the ozone, or chlorine or any other sterilant in water to be effective, the sterilizing agent is present in a sufficient concentration within water and in contact with the organisms (and the chicken) for a sufficient period of time (inversely related to concentration) to allow the oxidizing agent to contact and kill microorganisms. It is difficult to achieve such high concentrations in an aqueous liquid. In a gaseous form most sterilizing agents are rather hazardous and difficult to control exposure time. Ozone decays in a gaseous form far too quickly to be useful for food processing. Thus, water is the preferred media for transporting ozone, chlorine, and hypochlorite to a contaminated site for oxidative anti-microbial activity. Unfortunately, the realities of food processing are such that many food products cannot be immersed in a liquid bath (e.g., most fresh meat products and even some dry products like grains) although some moisture is allowed contact. In those instances where water immersion is not permitted, spray systems have been developed to spray a water-laden with oxidizing agent. However, spray systems do not provide a uniform coverage of the product and can utilize large amounts of water. Accordingly, spray systems employing larger droplets of water containing ozone, chlorine or hypochlorite have not been effective because of a droplet size that is too large to effect food surface penetration of irregularities. Moreover, the lower concentrations of sterilizing agents achievable in such spray systems, coupled with short exposure times, do not provide for effective oxidizing potentials and anti-microbial activity to be sufficiently effective as a decontaminating process. This is especially true of chlorine and hypochlorite that require long exposure times. A further issue is that liquid sterilization systems or spray systems with large droplets are unable to penetrate micro-cavities on irregular surfaces of food products, such as meats (e.g., poultry or bovine). Water surface tension prevents the large drops and liquid baths from penetrating these regions and the bacteria present in micro-cavities remains undisturbed (FIG. 1 left panel). Therefore, there is a need in the art to be able to better utilize the anti-microbial power of ozone, chlorine, hypochlorite, and other sterilizing agents, particularly within the context of food processing of meat products having irregular surfaces to hide bacteria from exposure to oxidizing agents. The present invention was made to solve this need. SUMMARY OF THE INVENTION The present invention provides an sterilizing agent-laden fog useful for disinfecting irregular surfaces wherein the fog comprises water and a sterilizing agent selected from the group consisting of ozone, hypochlorite, chlorine and combinations thereof, wherein the fog is characterized by droplets having an average diameter of from about 0.0005 mm to about 0.05 mm, a weight of fog concentration in a treatment space is of from about 0.08 g/m 3 to about 0.8 g/m 3 . Preferably, the concentration of ozone in water of from about 0.5 ppm to about 30 ppm, the concentration of chlorine in water of from about 10 ppm to about 100 ppm, and the concentration of sodium chlorite of 0.001% to about 0.65% by weight based upon the total weight of said composition of sodium chlorite, whereby the chlorite ion concentration in the form of chlorous acid is not more than about 15% by weight of the total amount of chlorite ion concentration. Preferably, sterilizing agent is an aqueous solution consisting essentially of from about 1% to about 6% by weight of citric acid, and from about 0.001% to about 0.65% by weight based upon the total weight of said composition of sodium chlorite, such that the chlorite ion concentration in the form of chlorous acid is not more than about 15% by weight of the total amount of chlorite ion concentration. The present invention further provides a sterilizing fog generator device for generating a sterilant fog having droplets of an average diameter from about 0.0005 mm to about 0.05 mm, comprising: (a) an ozone gas injector for injecting gas into water and having a venturi nozzle; and (b) a vapor cell communicating with the ozone gas injector nozzle, wherein the vapor cell has a bottom and side walls and comprises an ultrasonic focused transducer located on the bottom of the vapor cell and wired to an electronic amplifier and an orifice direct toward a target for the ozone fog. Preferably, the sterilant fog is an ozone fog wherein ozone concentrations of from about 0.5% to about 20% by weight. Preferably, the ultrasonic transducer is operated at multiple frequencies of from about 0.75 MHz to about 2.0 MHz and at multiple pulse shapes, whereby the frequency and pulsed irregular wave forms control droplet size of the fog produced. Preferably, the orifice has a diameter of from about 0.1 cm to about 8 cm whereby the orifice size determines the density of the ozone fog generated. Preferably, the present invention further comprises a plurality of the vapor cells, connected in series or in parallel, and communicating to the target for the ozone fog through a single orifice. The present invention further provides a food disinfection immersion apparatus comprising (a) a means for forming an ozone gas; (b) a means for injecting the ozone gas into a water stream in an injection chamber, wherein the injection chamber further comprises a temperature controller, a pressure controller and an ultrasonic transducer to achieve the highest saturation level of gas in liquid; and (c) an immersion tank for disinfecting the food comprising an entry port for feeding the highly concentrated ozone water, a means for suspending the food product, and one or a plurality of ultrasonic scrubbers that agitate the food product surface microcavities to allow for deeper penetration of the highly concentrated ozone water. Preferably, the food disinfection immersion apparatus further comprises a means for injecting sodium hypochlorite and chlorine solutions into a water stream. The present invention further provides a method for disinfecting irregular surfaces, comprising contacting a product having an irregular surface for disinfecting with a sterilizing fog, wherein the ozone fog comprises water and a sterilizing agent and wherein the fog is characterized by droplets having an average diameter of from about 0.0005 mm to about 0.05 mm, a weight of fog concentration in a treatment space of from about 0.08 g/m 3 to about 0.8 g/m 3 , and an ozone concentration in water of from about 0.5 ppm to about 30 ppm. Preferably, the product having an irregular surface is a food product. Most preferably, the food product is red meat or poultry. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic of an irregular surface of a food product (such as meat or poultry) having a micro-cavity that is often a site harboring bacterial growth (which forms the micro-cavity). The left panel shows a typical spray droplet in approximate relational scale having too much surface tension in order to penetrate and access the micro-cavity irrespective of the concentration or potency of anti-microbial oxidizing agent. The right panel shows the advantage of the inventive fog having a much smaller droplet size and an ability to access the reaches of a micro-cavity. FIG. 2 shows a schematic drawing of an inventive ozone fog generating apparatus having a contact chamber with the high concentration sterilant fog for disinfecting various meat products in an assembly line fashion. FIG. 3 shows the vapor cell component of the inventive apparatus in more detail. Specifically, acoustic transducers generate a high ozone concentrated fog in multiple vapor cells that is released through a variable orifice. FIG. 4 shows a standard curve of fall velocity of droplet is proportional to the square of the droplet diameter. DETAILED DESCRIPTION OF THE INVENTION The present invention provides a more useful ozone fog that is able to access irregular surfaces of food products, such as meats (muscle tissue), due to its very small droplet size coupled with a high ozone concentration in water. The irregular surfaces of meat products can harbor microbial contamination and provide a difficult surface for penetration or access of a liquid-based anti-microbial agent. For example, rain drops and low-pressure sprayers have or provide droplet sizes ranging from 0.15 mm to 0.5 mm. The smaller droplets of the inventive fog are better able to penetrate surface irregularities with “micro-cavity” regions where contaminating microbial growth is present (FIG. 1 right panel). An additional advantage of the smaller droplet size of the inventive fog is a significantly lower “fall velocity” or how fast the droplet will fall to a ground surface (see FIG. 4 ). The fall velocity of the droplets of the inventive fog is about 1000 times that of rain droplets or nearly 1000 cm/sec for rain compared with less than 1 cm/sec for the inventive fog (Schemenauer and Cereceda, Water Int ., 1994). The slower fall rate allows the inventive fog a longer contact time with the surface as it can “hover” over and adjacent to such a surface. In addition, the inventive ozone fog, having the smaller droplets, is more easily moved by fans and enclosures to fill the micro-cavities of an irregular surface and more uniformly surround surfaces for food treatment and a more even coverage. The inventive sterilizing fog generator preferably utilizes highly ozoneated water that can be created by injecting ozone gas into a water stream, such as with a venturi nozzle 17 . Additionally the ozone concentration can be increased by dissolving more ozone or another sterilant gas in the water through the use of ultrasonic transducers ( 14 ). High frequency high power sound waves cause the undissolved gas bubbles to rupture. Each time a bubble divides more gas is dissolved in the water. The ultrasonic transducer is connected to an electronic amplifier (e.g., acoustic driver 19 ) that is operated at multiple frequencies ranging from about 0.1 MHz to about 1. MHz. The highly ozoneated water is used to either feed an immersion tank for direct contact with food product surfaces, or to create the inventive fog in a vapor cell ( 13 ). In the case of an ozone fog, a vapor cell is filled with ozoneated water to a defined level, wherein the vapor cell further comprises an ultrasonic focused transducer ( 14 ) mounted at the bottom of the vapor cell (that is, completely immersed with ozoneated water). The transducer is connected to an electronic amplifier ( 19 ) that can be operated at multiple frequencies. Frequencies control droplet size and thus the control of the frequency settings control the resulting droplet size. However, a frequency setting between 0.75 MHz and 1.5 MHz will produce the desired droplet size with an average diameter of between 0.0005 mm and 0.05 mm. The vapor cell further comprises an orifice ( 22 ) to allow release of the inventive ozone fog. The density of the fog cloud released is a function of orifice size (diameter) wherein an orifice size of from about 0.1 cm to about 8 cm will produce an ozone fog having a density of between about 0.08 g/m 3 to about 0.8 g/m 3 . The orifice opens up to a contact chamber where the product to be disinfected is located. There may be one or a plurality of ozone fog generating devices to communicate with the contact chamber ( 12 ). In addition, a series of fans ( 24 ) can control the flow of the inventive ozone fog and direct it to a specific target surface or object. Moreover, the contact chamber can contain an exit port to allow for recycling of the ozoneated fog back into the vapor chamber for recharging of ozone concentrations. With regard to FIG. 1, A schematic diagram is provided that shows the importance of smaller droplet size able to penetrate irregular surfaces of food particles. The smaller droplet size is able to access bacterial-laden micro-cavities. With regard to FIG. 2, shows a preferred system for generating inventive ozone fog for contacting food in a food contact chamber ( 12 ). There is a water supply 10 pumped 11 to an ozone generator 16 to a recirculation loop 17 having an ozone injector such as a Venturi nozzle. The ozone is supplied to a plurality of acoustic transducers 14 via a ozone supply line 18 and returning via a return line 15 . The acoustic transducers communicate with multiple vapor cells 13 and are controlled by acoustic drivers 19 that have vapor density control 20 and leveling and other controls 21 . Through an orifice 22 in each vapor cell 12 , the inventive ozone fog is released into contact chamber(s) 12 to sterilize food surfaces. With regard to FIG. 3, two acoustic transducers are shown connected to a supply of fresh ozone-enriched water. The fog is formed in adjoining vapor cells. The transducers are commercial ultrasonic focused transducers, such as from Panasonic or others. Although not shown, there is a water recirculation loop to provide only the freshest ozonated water to the transducers. There is a liquid coupling cell to couple the sound to the surface as there is a distance (focal length) needed where the ultrasonic energy is focused onto the surface of the ozoneated water stream. The disruption on the surface of the water stream is from the focused ultrasonic energy to form small droplet ozone fog in the vapor cell. An air supply fan conveys the fog out of the vapor cell, through a variable orifice into a chamber. Preferably, an ozonated air supply is blown (via a fan) to clear the fog our of the vapor cells and through the variable orifice. Alternatively, a food product may be immersed in an immersion tank (not depicted) containing highly ozoneated water. The immersion tank further comprises an entry port for feeding the highly concentrated ozone water, a means for suspending the food product, and one or a plurality of ultrasonic scrubbers that agitate the food product surface microcavities to allow for deeper penetration of the highly concentrated ozone water. It is the presence of the ultrasonic scrubbers that allow for access of the highly ozoneated water into contact with micro-organisms within the microcavities (due to disruption of the food surface) and that creates a better disinfection of food products using the inventive device. Various food (meat) products were tested for disinfection using either a misting of ozonated water using prior art techniques, an immersion in either highly ozoneated water or standard immersion techniques, or contact with the inventive ozone fog. In each test the sample in contact with the ozone fog measured the lowest bacterial counts. The example below provides results from one of these tests. EXAMPLE 1 This example provides the results of an experiment comparing various means for disinfecting food products using a standard ozone mist technique with large droplet sizes and lower concentrations of ozone and standard dipping techniques to the inventive fog. In this case the sample under test was a rump roast purchased from Safeway (a supermarket chain) and packaged 28 days earlier in Wichita, Kans. Table 1 list results as measured by the Benton-Franklin health district. All analysis were performed using methods outlined in the districts Standard Methods for the Examination of Water and Wastewater , 18 edition. TABLE 1 O 3 /water Bacteria ppm application count comment 1.36 Mist 4.92 × 10 5 Sample with least exposure to air 4.25 Fog  1.3 × 10 5 Least amount of applied water 0.25 Dip 5.15 × 10 5 Lowest conc. but full immersion 5.1 Mist 1.28 × 10 6 Sample on counter the longest before ozoneating (touched with hands none Control 1.13 × 10 6 Control sample no disinfection The ozone concentration in water was measured using an Ozotech calibrated 03 probe. It should be noted that the fog application yielded a bacterial count nearly 5 times lower than any other technique and nearly 10 time lower than the control sample. Table 1 also illustrates the inconsistency of a standard spray application independent of concentration. Finally, in accordance with the methods of analysis cited above the samples are measured at 24 hours from disinfection and again at 48 hours from disinfection. This “incubation period allows” stressed bacteria to fully recover. Standard techniques can at best stress bacteria located in microcavities, which is indicated by a low plate count followed by a much higher plate count after the set recovery time. The ozone fog application kills bacteria located in the micro-cavity that is indicated by a low plate count initially as well as after the recovery time. EXAMPLE 2 This example provides the test results of another experiment of product samples of beef and chicken and determining bacterial counts (Benton County and Franklin County (Wash.) Health Department) taken 24 hours after ozone exposure. The test compared the inventive ozone fog to control (no ozone exposure), a mist spray of ozone with large droplet size and a dip or immersion of ozone. The samples were not covered during the 24 hour waiting period and could have been recontaminated. The actual measurements was taken an additional 48 hours from the time of the swab to allow for proper incubation and this also could have allowed for stressed bacteria to recover. Table 2 provides the results showing a significantly greater effectiveness with the inventive fog despite less use of ozone and exposure. TABLE 2 Application Diluted ozone conc. % Bacteria 24 hrs later None na 100%  fog 0.04 12% Spray/mist 0.5 78% dip 0.25 46% These data further support the surprising results achieved with the inventive fog.

There is disclosed a sterilizing fog, characterized by droplet size range, vapor density range, sterilant concentration range and sterilant concentration within the droplets. Specifically, there is disclosed a fog achieved by an apparatus combining pressure, temperature and acoustics to form a super-charged ozoneated water and an apparatus that creates small micro droplets which form a highly concentrated sterilizing fog. Specific sterilants used are ozone, chlorine and chlorous acid generating compositions such as sodium hypochlorite, or combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 12/371,078, filed on Feb. 13, 2009, which is a continuation of International Application No. PCT/CN2007/070384, filed on Jul. 30, 2007. The International Application claims priority to Chinese Patent Application No. 200610115381.3, filed on Aug. 15, 2006. The afore-mentioned patent applications are hereby incorporated by reference in their entireties. FIELD OF THE INVENTION The present invention relates to the field of telecommunications and in particular to a data processing technique and system. BACKGROUND OF THE INVENTION Existing General Package Radio Service (GPRS)/Universal Mobile Telecommunications System (UMTS) techniques employ network architecture similar to second-generation wireless communication systems, including UMTS Territorial Radio Access Network (UTRAN), GSM/EDGE Radio Access Network (GERAN), Core Network (CN) and Mobile Station (MS), as illustrated in FIG. 1 . The GERAN/UTRAN implements all wireless related functions, and the CN handles all voice calls and data connections in GPRS/UMTS and implements switching and routing functions with external networks. Logically the CN can be divided into a Circuit Switched (CS) domain and a Packet Switched (PS) domain, supporting voice and data services respectively. The CS domain includes nodes such as Mobile Switching Center (MSC) server, Media Gateway (MGW) and Gateway Mobile Switching Centre (GMSC) server. The MSC server transmits control plane data of the CS domain, and implements functions such as mobility management, call control and authentication encryption; the GMSC server handles call control and mobility control in the control plane for a GMSC; the MGW handles transmission of user plane data. The PS domain includes nodes such as Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). The GGSN is an interface to interact with external networks. Also, as a user plane anchor (i.e. user plane anchor network element) between a GERAN and a UTRAN, the GGSN transmits data of the user plane. Having a position similar to the MSC server in the CS domain, the SGSN implements functions such as routing forwarding, mobility management, session management and user information storage. Home Location Registers (HLRs) are used in both the CS domain and the PS domain to store user subscription information. In existing 3GPP protocols, user plane processing of UMTS is based on a two-tunnel mechanism illustrated as in FIG. 2 . In UMTS, the user plane processing is between a Radio Network Controller (RNC, a network element of a UTRAN, used to control wireless resources of the UTRAN) and an SGSN, and between an SGSN and a GGSN, over an Iu interface and a Gn interface respectively. For the two-tunnel mechanism, an SGSN handles both the user plane and the control plane; therefore control plane processing and user plane processing are not separate. With the introduction of High Speed Packet Access (HSPA) and IP Multimedia Subsystem (IMS), there will be a significant data flow growth in future 3GPP network. At present, in order to improve data processing capability of UMTS, a new UMTS user plane processing mechanism, i.e. direct-tunnel mechanism, has been proposed. As illustrated in FIG. 2 , in this mechanism, the user plane processing of UMTS is between an RNC and a GGSN, without an SGSN. For the direct-tunnel mechanism, an SGSN handles functions of the control plane only; therefore control plane processing and user plane processing are separate. Now with reference to FIGS. 3 to 6 , the processes of handover or change between a GERAN and a UTRAN are illustrated hereinafter. At present, the process of handing over from a GERAN to a UTRAN according to the protocol 43.129 is illustrated as in FIG. 3 : step S 301 : a source Base Station Subsystem (BSS) decides to initiate a PS handover; step S 302 : the source BSS sends a PS handover request message to an old SGSN, i.e. 2G SGSN; step S 303 : the 2G SGSN sends a forward relocation request message to a new SGSN, i.e. 3G SGSN; step S 304 : the 3G SGSN builds a relocation request message and sends the message to a target RNC; step S 305 : the target RNC sends a relocation request acknowledge message to the 3G SGSN; step S 306 : the 3G SGSN sends a forward relocation response to the 2G SGSN; step S 307 : the 2G SGSN receives an IP packet from a GGSN and sends the IP packet to an MS via the source BSS; step S 308 : the 2G SGSN forwards the IP packet to the target RNC via the 3G SGSN; step S 309 : the 2G SGSN sends a PS handover request acknowledge message to the source BSS; step S 310 : the MS sends a handover to UTRAN complete message to the target RNC; step S 311 : the target RNC sends a relocation complete message to the 3G SGSN; step S 312 : the 3G SGSN sends an update PDP context request message to the GGSN; step S 313 : the GGSN returns an update PDP context response message to the 3G SGSN; The process of handing over from a UTRAN to a GERAN is illustrated as in FIG. 4 : step S 401 : a source RNC decides to initiate a PS handover; step S 402 : the source RNC sends a relocation request message to an old SGSN, i.e. 3G SGSN; step S 403 : the 3G SGSN sends a forward relocation request message to a new SGSN, i.e. 2G SGSN; step S 404 : the 2G SGSN builds a PS handover request message and sends the message to a target BSS; step S 405 : the target RNC sends a PS handover request acknowledge message to the 2G SGSN; step S 406 : the 2G SGSN sends a forward relocation response message to the 3G SGSN; step S 407 : the 3G SGSN receives an IP packet from a GGSN and sends the IP packet to an MS via the source RNC; step S 408 : the 3G SGSN sends a relocation command message to the source RNC; step S 409 : the source RNC forwards the IP packet to the 3G SGSN, the 3G SGSN forwards the IP packet to the 2G SGSN, and the 2G SGSN forwards the IP packet to the target BSS; step S 410 : the target BSS sends a PS handover complete message to the 2G SGSN; step S 411 : the 2G SGSN sends an update PDP context Request message to the GGSN; step 412 : the GGSN returns an update PDP context response message to the 2G SGSN; At present, the process of changing from a GERAN to a UTRAN according to the protocol 23.060 is illustrated as in FIG. 5 : step S 501 : an MS decides to perform an inter-system change; step S 502 : the MS sends a routing area update request message to a new SGSN, i.e. 3G SGSN; step S 503 : the 3G SGSN sends an SGSN context request message to an old SGSN, i.e. 2G SGSN, to obtain user context; step S 504 : the 2G SGSN returns an SGSN context response message to the 3G SGSN, and carries the user context information in the context response message; step S 505 : the 3G SGSN sends an SGSN context acknowledge message to the 2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive data packets; step S 506 : the 2G SGSN duplicates a buffered data packet and forwards to the 3G SGSN; step S 507 : the 3G SGSN sends an update PDP context request message to a GGSN; step S 508 : the GGSN returns an update PDP context response to the 3G SGSN; step S 509 : the 3G SGSN returns a routing area update accept message to the MS; step S 510 : the MS returns a routing area update complete message to the 3G SGSN; step S 511 : the MS sends a service request message to the 3G SGSN; step S 512 : Radio Access Bearer (RAB) Assignment procedure is performed between the 3G SGSN and an RNC, thereby establishing a RAB; At present, the process of changing from a UTRAN to a GERAN according to the protocol 23.060 is illustrated as in FIG. 6 : step S 601 : an MS decides to perform an inter-system change; step S 602 : the MS sends a routing area update request message to a new SGSN, i.e. 2G SGSN; step S 603 : the 2G SGSN sends an SGSN context request message to an old SGSN, i.e. 3G SGSN, to obtain user context; step S 604 : the 3G SGSN sends an SRNS context request message to a source RNC; step S 605 : the source RNC returns an SRNS context response message to the 3G SGSN, stops sending downlink data to the MS, and buffers the data; step S 606 : the 3G SGSN returns an SGSN context response message to the 2G SGSN, and carries the user context information in the context response message; step S 607 : the 2G SGSN sends an SGSN context acknowledge message to the 3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive data packets; step S 608 : the 3G SGSN sends an SRNS data forward command to the source RNC, the source RNC duplicates a buffered data packet and forwards to the 3G SGSN; step S 609 : the 3G SGSN forwards the data packet to the 2G SGSN step S 610 : the 2G SGSN sends an update PDP context request message to a GGSN; step S 611 : the GGSN returns an update PDP context response to the 2G SGSN; step S 612 : the 2G SGSN returns a routing area update accept message to the MS; step S 613 : the MS returns a routing area update complete message to the 2G SGSN; In the processes as illustrated in FIGS. 3 to 6 , the user plane data processing when a handover or change from a GERAN to a UTRAN takes place is that, a 3G SGSN forwards data that are forwarded to by a 2G 3GSN to a target RNC; and the user plane data processing when a handover or change from a UTRAN to a GERAN takes places is that, a 3G SGSN forwards data that is forwarded to by a source RNC to a 2G SGSN. However, in a direct-tunnel mechanism where a 3G SGSN no longer performs user plane data processing, data forwarding can not be done via a 3G SGSN. Therefore, the existing data processing method when a handover or change between a GERAN and a UTRAN takes place does not fit the direct-tunnel mechanism. SUMMARY OF THE INVENTION A data processing method and system are provided by the present invention, in order to implement data forwarding in a direct-tunnel mechanism when a handover or change between a 2G system and a 3G system takes place. The present invention provides a data processing method. The method includes: receiving, by a user plane anchor network element, data forwarded by a source data forwarding network element; and forwarding, by the user plane anchor network element, the data to a target side processing network element. The present invention further provides a data processing method. The method includes: receiving, by a user plane anchor network element, an instructive message, and sending data to at least one of a source data forwarding network element and a target side processing network element; and updating, by the user plane anchor network element, user plane routing, and sending the data to the target side processing network element as instructed in the message according to the updated user plane routing. The present invention provides a data processing system, including a source data forwarding network element, a user plane anchor network element and a target side processing network element, wherein the user plane anchor network element is provided with a receipt unit adapted to receive data forwarded by the source data forwarding network element, and a sending unit adapted to forward the received data to the target side processing network element. The present invention provides a user plan anchor network element, including a receipt unit and a sending unit, wherein the receipt unit is adapted to receive data forwarded by the source data forwarding network element; and the sending unit is adapted to forward the received data to the target side processing network element. With the data processing methods in the direct-tunnel mechanism when a handover or change between a GERAN and a UTRAN takes place, a GGSN can buffer data forwarded by a source data forwarding network element and then send the data to a target side processing network element; alternatively, the GGSN can send the data forwarded by the source data forwarding network element directly to the target side processing network element. The problem that the data processing method in the conventional art is not applicable in the direct-tunnel mechanism is solved and normal forwarding of service data in the direct-tunnel mechanism when a handover or change between a GERAN and a UTRAN takes place is achieved. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates network architecture of GPRS/UMTS; FIG. 2 illustrates user plane processing in the conventional art; FIG. 3 is a flow chart of a data processing method when a handover from a GERAN to a UTRAN takes place according to the protocol 43.129; FIG. 4 is a flow chart of a data processing method when a handover from a UTRAN to a GERAN takes place according to the protocol 43.129; FIG. 5 is a flow chart of a data processing method when a change from a GERAN to a UTRAN takes place according to the protocol 23.060; FIG. 6 is a flow chart of a data processing method when a change from a UTRAN to a GERAN takes place according to the protocol 23.060; FIG. 7 is a flow chart of a data processing method when a handover from a GERAN to a UTRAN takes place according to a first embodiment of the present invention; FIG. 8 is a flow chart of a data processing method when a handover from a UTRAN to a GERAN takes place according to a first embodiment of the present invention; FIG. 9 is a flow chart of a data processing method when a change from a GERAN to a UTRAN takes place according to a first embodiment of the present invention; FIG. 10 is a flow chart of a data processing method when a change from a UTRAN to a GERAN takes place according to a first embodiment of the present invention; FIG. 11 illustrates network architecture of an evolved packet core network in the conventional art; FIG. 12 is a flow chart of a data processing method when a handover from a GERAN to a UTRAN takes place according to a second embodiment of the present invention; FIG. 13 is a flow chart of a data processing method when a handover from a UTRAN to a GERAN takes place according to a second embodiment of the present invention; FIG. 14 is a flow chart of a data processing method when a change from a GERAN to a UTRAN takes place according to a second embodiment of the present invention; FIG. 15 is a flow chart of a data processing method when a change from a UTRAN to a GERAN takes place according to a second embodiment of the present invention; FIG. 16 is a flow chart of a data processing method when a handover from a GERAN to a UTRAN takes place according to a third embodiment of the present invention; FIG. 17 is a flow chart of a data processing method when a handover from a UTRAN to a GERAN takes place according to a third embodiment of the present invention; FIG. 18 is a flow chart of a data processing method when a change from a GERAN to a UTRAN takes place according to a third embodiment of the present invention; FIG. 19 is a flow chart of a data processing method when a change from a UTRAN to a GERAN takes place according to a third embodiment of the present invention; and FIG. 20 is a structural diagram of a data processing system provided in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS Exemplary embodiments of the present invention will be described in details hereinafter with reference to the drawings. In the specification multiple embodiments of data processing method are provided. A first method is described hereinafter. The method includes: when a change or handover from a GERAN to a UTRAN takes place, a 2G SGSN forwards a data packet to a GGSN, and the GGSN forwards the data packet to a target RNC; when a handover from a UTRAN to a GERAN takes place, a source RNC forwards a data packet to a GGSN, the GGSN forwards the data packet to a 2G SGSN, and the 2G SGSN forwards the data packet to a target BSS. Now refer to FIG. 7 . As illustrated in FIG. 7 , a data processing method when a handover from a GERAN to a UTRAN takes place includes: step S 701 : a source BSS decides to initiate a handover; step S 702 : the source BSS sends a handover request message to an old SGSN, i.e. 2G SGSN; step S 703 : the 2G SGSN sends a forward relocation request message to a new SGSN, i.e. 3G SGSN; step S 704 : the 3G SGSN builds a relocation request message, and sends the message to a target RNC; step S 705 : the target RNC sends a relocation request acknowledged message to the 3G SGSN; step S 706 : the 3G SGSN sends an update PDP context request message to a GGSN, to request to change user plane routing from the GGSN to the 3G SGSN; step S 707 : the GGSN returns an update PDP context response to the 3G SGSN; step S 708 : the 3G SGSN sends a forward data request to the GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding; step S 709 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel and carries the data forwarding tunnel identifier in the response message to the 3G SGSN, the data forwarding tunnel identifier includes IP address and TEID (Tunnel End Point Identifier); step S 710 : the 3G SGSN sends a forward relocation response message to the 2G SGSN, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step S 711 : the 2G SGSN receives a data packet from the GGSN, and sends the data packet to an MS via the source BSS; step S 712 : for data of a lossless service, the 2G SGSN forwards the data packet to the GGSN according to the data forwarding tunnel identifier carried in the forward relocation response message sent by the 3G SGSN, the GGSN buffers the data packet after receiving the data packet forwarded by the 2G SGSN; step S 713 : the 2G SGSN sends a handover request acknowledge message to the source BSS; step S 714 : the MS sends a handover to UTRAN complete message to the target RNC; step S 715 : the target RNC sends a relocation complete message to the 3G SGSN; step S 716 : the 3G SGSN sends an update context request message to the GGSN; step S 717 : the GGSN returns an update context response message to the 3G SGSN; step S 718 : the GGSN forwards the buffered forwarded data packet to the target RNC. Now with reference to FIG. 8 , a data processing method when a handover from a UTRAN to a GERAN takes place includes: step S 801 : a source RNC decides to initiate a handover; step S 802 : the source RNC sends a relocation request message to an old SGSN, i.e. 3G SGSN; step S 803 : the 3G SGSN sends a forward relocation request message to a new SGSN, i.e. 2G SGSN; step S 804 : the 2G SGSN builds a handover request message, and sends the message to a target BSS; step S 805 : the target BSS sends a handover request acknowledged message to the 2G SGSN; step S 806 : the 2G SGSN sends a forward relocation response message to the 3G SGSN; step S 807 : the 3G SGSN sends a forward data request to a GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding; step S 808 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 809 : the 3G SGSN receives a data packet from the GGSN, and sends the data packet to an MS via the source RNC; step S 810 : the 3G SGSN sends a relocation command message to the source RNC, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step S 811 : for data of a lossless service, the source RNC forwards the data packet to the GGSN according to the data forwarding tunnel identifier carried in the relocation command message sent by the 3G SGSN, the GGSN buffers the received data packet; step S 812 : the target BSS sends a handover complete message to the 2G SGSN; step S 813 : the 2G SGSN sends an update context request message to the GGSN; step S 814 : the GGSN returns an update context response message to the 2G SGSN; step S 815 : the GGSN forwards the buffered forwarded data packet to the 2G SGSN. Now with reference to FIG. 9 , a data processing method when a change from a GERAN to a UTRAN takes place includes: step S 901 : an MS decides to initiate an intersystem change; step S 902 : the MS sends a routing area update request message to a new SGSN, i.e. 3G SGSN; step S 903 : the 3G SGSN sends an SGSN context request message to an old SGSN, i.e. 2G SGSN, to obtain user context; step S 904 : the 2G SGSN returns an SGSN context response message to the 3G SGSN, and carries the user context information in the message; step S 905 : the 3G SGSN sends an update PDP context request message to a GGSN, to request to change user plane routing from the GGSN to the 3G SGSN; step S 906 : the GGSN returns an update PDP context response to the 3G SGSN; step S 907 : the 3G SGSN sends a forward data request message to the GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding; step S 908 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel, and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 909 : the 3G SGSN sends an SGSN context acknowledge message to the 2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive data packets, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step S 910 : the 2G SGSN duplicates a buffered data packet and forwards to the GGSN according to the data forwarding tunnel identifier carried in the SGSN context acknowledge message sent by the 3G SGSN, the GGSN buffers the received forwarded data packet; step S 911 : the 3G SGSN returns a routing area update accept message to the MS; step S 912 : the MS returns a routing area update complete message to the 3G SGSN; step S 913 : the MS returns a service request message to the 3G SGSN; step S 914 : RAB assignment procedure is performed between the 3G SGSN and an RNC, thereby establishing RAB; step S 915 : the 3G SGSN sends an update context request message to the GGSN; step S 916 : the GGSN returns an update context response message to the 3G SGSN; step S 917 : the GGSN forwards the buffered forwarded data packet to the target RNC. Now with reference to FIG. 10 , a data processing method when a change from a UTRAN to a GERAN takes place includes: step S 1001 : an MS decides to initiate an intersystem change; step S 1002 : the MS sends a routing area update request message to a new SGSN, i.e. 2G SGSN; step S 1003 : the 2G SGSN sends an SGSN context request message to an old SGSN, i.e. 3G SGSN, to obtain user context; step S 1004 : the 3G SGSN sends an SRNS context request message to a source RNC; step S 1005 : the source RNC returns an SRNS context response message to the 3G SGSN, stops sending downlink data to the MS, and buffers the data; step S 1006 : the 3G SGSN returns an SGSN context response message to the 2G SGSN, and carries the user context information in the message; step S 1007 : the 2G SGSN sends an SGSN context acknowledge message to the 3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive data packets; step S 1008 : the 3G SGSN sends a forward data request to a GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding; step S 1009 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel, and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 1010 : the 3G SGSN sends an SRNS data forward command to the source RNC, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN, the source RNC duplicates a buffered data packet and forwards to the GGSN, the GGSN buffers the forwarded data packet; step S 1011 : the 2G SGSN sends an update PDP context request message to the GGSN; step S 1012 : the GGSN returns an update PDP context response message to the 2G SGSN; step S 1013 : the GGSN forwards the buffered forwarded data packet to the 2G SGSN; step S 1014 : the 2G SGSN returns a routing area update accept message to the MS; step S 1015 : the MS returns a routing area update complete message to the 2G SGSN. In order to enhance its competitive advantages in the future, the 3GPP is studying new evolved network architecture, including System Architecture Evolution (SAE) and Long Term Evolution (LTE) access network. The evolved access network is known as E-UTRAN, network architecture of an evolved packet core network, illustrated as in FIG. 11 , includes a Mobility Management Entity (MME), a User Plane Entity (UPE), and an Inter Access System Anchor (IASA). The MME performs mobility management in the control plane, including user context and mobility status management, user temporary identity identifier assignment and so forth, corresponding to the control plane of an SGSN inside GPRS/UMTS; the UPE is used to initiate paging for downlink data in idle state, manages and stores IP bearer parameters and routing information inside the network and so forth, corresponding to the data plane of an SGSN and a GGSN in GPRS/UMTS; the IASA is an anchor in the user plane between different systems. A Policy and Charging Rule Function (PCRF) entity is used for policy control decision and charging control of data flow. A Home Subscriber Server (HSS) is used to store user subscription information. For the SAE system, if the MME and the UPE are separate, and the UPE and the 3GPP Anchor are in a same entity, the systematic architecture is similar to the architecture in the direct-tunnel mechanism where the MME corresponds to an SGSN, and the UPE/3GPP Anchor (referred to as UPE hereinafter) corresponds to a GGSN. Therefore the data forwarding processing method stated above can be used for data forwarding when a handover or change between a GERAN/UTRAN system and an SAE system takes place. When a handover or change from a GERAN system to an SAE system takes place, the MME and the UPE (user plane anchor of the GERAN/UTRAN and the SAE) exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE, and inform the 2G SGSN of the data forwarding tunnel identifier of the UPE. The 2G SGSN forwards a data packet to the UPE; the UPE buffers the forwarded data packet and forwards the buffered forwarded data packet to the evolved access network on completion of update of user plane routing. When a handover or change from an SAE system to a GERAN system takes place, the MME and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE, and inform the evolved access network of the data forwarding tunnel identifier of the UPE. The evolved access network forwards a data packet to the UPE; the UPE buffers the forwarded data packet and forwards the buffered forwarded data packet to the 2G SGSN on completion of update of user plane routing. When a handover or change from a UTRAN system to an SAE system takes place, the 3G SGSN and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE, and inform the source RNC of the data forwarding tunnel identifier of the UPE. The source RNC forwards a data packet to the UPE; the UPE buffers the forwarded data packet and forwards the buffered forwarded data packet to the evolved access network on completion of update of user plane routing. When a handover or change from an SAE system to a UTRAN system takes place, the MME and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE, and inform the evolved access network of the data forwarding tunnel identifier of the UPE. The evolved access network forwards a data packet to the UPE; the UPE buffers the forwarded data packet and forwards the buffered forwarded data packet to the target RNC on completion of update of user plane routing. Now refer to FIGS. 12 to 15 . Another data processing method embodiment provided by the present invention is described. With reference to FIG. 12 , a data processing method when a handover from a GERAN to a UTRAN takes place includes: step 1201 : a source BSS decides to initiate a handover; step 1202 : the source BSS sends a handover request message to an old SGSN, i.e. 2G SGSN; step 1203 : the 2G SGSN sends a forward relocation request message to a new SGSN, i.e. 3G SGSN; step 1204 : the 3G SGSN builds a relocation request message and sends the message to a target RNC; step 1205 : the target RNC sends relocation request acknowledge message to the 3G SGSN; step 1206 : the 3G SGSN sends a forward data request message to a GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding, an identifier of a GTP tunnel of the target RNC side is carried in the message, subsequently the GGSN will forward data of a lossless service to the GTP tunnel; step 1207 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel, and sends to the 3G SGSN in the response message; step 1208 : the 3G SGSN sends a forward relocation response message to the 2G SGSN, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step 1209 : the 2G SGSN receives a data packet from the GGSN, and sends the data packet to an MS via the source BSS; step 1210 : for data of a lossless service, the 2G SGSN forwards the data packet to the GGSN according to the data forwarding tunnel identifier carried in the forward relocation response message sent by the 3G SGSN, the GGSN forwards the data packet forwarded by the 2G SGSN to the target RNC on receipt of the data packet; step 1211 : the 2G SGSN sends a handover request acknowledge message to the source BSS; step S 1212 : the MS sends a handover to UTRAN complete message to the target RNC; step S 1213 : the target RNC sends a relocation complete message to the 3G SGSN; step S 1214 : the 3G SGSN sends an update context request message to the GGSN; step S 1215 : the GGSN returns an update context response message to the 3G SGSN. With reference to FIG. 13 , a data processing method when a handover from a UTRAN to a GERAN takes place includes: step S 1301 : a source RNC decides to initiate a handover; step S 1302 : the source RNC sends a relocation request message to an old SGSN, i.e. 3G SGSN; step S 1303 : the 3G SGSN sends a forward relocation request message to a new SGSN, i.e. 2G SGSN; step S 1304 : the 2G SGSN builds a handover request message, and sends the message to a target BSS; step S 1305 : the target BSS sends a handover request acknowledged message to the 2G SGSN; step S 1306 : the 2G SGSN sends a forward relocation response message to the 3G SGSN; step S 1307 : the 3G SGSN sends a forward data request to a GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding, an identifier of a data forwarding tunnel of the 2G SGSN is carried in the message, subsequently the GGSN will forward data of a lossless service to the data forwarding tunnel; step S 1308 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 1309 : the 3G SGSN receives a data packet from the GGSN, and sends the data packet to an MS via the source RNC; step S 1310 : the 3G SGSN sends a relocation command message to the source RNC, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step S 1311 : for data of a lossless service, the source RNC forwards the data packet to the GGSN according to the data forwarding tunnel identifier carried in the relocation command message sent by the 3G SGSN, the GGSN forwards the data packet forwarded by the source RNC to the 2G SGSN on receipt of the data packet, the 2G SGSN forwards the data packet to the target BSS; step S 1312 : the target BSS sends a handover complete message to the 2G SGSN; step S 1313 : the 2G SGSN sends an update context request message to the GGSN; step S 1314 : the GGSN returns an update context response message to the 2G SGSN. With reference to FIG. 14 , a data processing method when a change from a GERAN to a UTRAN takes place includes. step S 1401 : an MS decides to initiate an intersystem change; step S 1402 : the MS sends a routing area update request message to a new SGSN, i.e. 3G SGSN; step S 1403 : the 3G SGSN sends an SGSN context request message to an old SGSN, i.e. 2G SGSN, to obtain user context; step S 1404 : the 2G SGSN returns SGSN context response message to the 3G SGSN, and carries the user context information in the message; step 1405 : RAB assignment procedure is performed between the 3G SGSN and an RNC, thereby establishing RAB; step S 1406 : the 3G SGSN sends an update PDP context request message to a GGSN, to request to change user plane routing from the GGSN to the 3G SGSN; step S 1407 : the GGSN returns an update PDP context response to the 3G SGSN; step S 1408 : the 3G SGSN sends a forward data request message to the GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding, an identifier of a GTP tunnel of the target RNC side is carried in the message, subsequently the GGSN will forward data of a lossless service to the GTP tunnel; step S 1409 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel, and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 1410 : the 3G SGSN sends an SGSN context acknowledge message to the 2G SGSN, informing the 2G SGSN that the 3G SGSN is ready to receive data packets, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN; step S 1411 : the 2G SGSN duplicates a buffered data packet and forwards to the GGSN according to the data forwarding tunnel identifier carried in the SGSN context acknowledge message sent by the 3G SGSN, the GGSN forwards the data packet forwarded by the 2G SGSN to the target RNC on receipt of the data packet; step S 1412 : the 3G SGSN returns a routing area update accept message to the MS; step S 1413 : the MS returns a routing area update complete message to the 3G SGSN; step S 1414 : the 3G SGSN sends an update context request message to the GGSN, to change a downlink GTP tunnel identifier of user context in the GGSN to the GTP tunnel identifier of the RNC; step S 1415 : the GGSN returns an update context response message to the 3G SGSN. With reference to FIG. 15 , a data processing method when a change from a UTRAN to a GERAN takes place includes: step S 1501 : an MS decides to initiate an intersystem change; step S 1502 : the MS sends a routing area update request message to a new SGSN, i.e. 2G SGSN; step S 1503 : the 2G SGSN sends an SGSN context request message to an old SGSN, i.e. 3G SGSN, to obtain user context; step S 1504 : the 3G SGSN sends an SRNS context request message to a source RNC; step S 1505 : the source RNC returns an SRNS context response message to the 3G SGSN, stops sending downlink data to the MS, and buffers the data; step S 1506 : the 3G SGSN returns an SGSN context response message to the 2G SGSN, and carries the user context information in the message; step S 1507 : the 2G SGSN sends an SGSN context acknowledge message to the 3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive data packets; step S 1508 : the 3G SGSN sends a forward data request to a GGSN, to request the GGSN to assign a data forwarding tunnel for data forwarding, an identifier of a data forwarding tunnel of the 2G SGSN is carried in the message, subsequently the GGSN will forward data of a lossless service to the data forwarding channel; step S 1509 : the GGSN returns a forward data response message to the 3G SGSN, assigns a data forwarding tunnel identifier to the data forwarding tunnel, and carries the data forwarding tunnel identifier in the response message to the 3G SGSN; step S 1510 : the 3G SGSN sends an SRNS data forward command to the source RNC, a data forwarding tunnel identifier carried in the message is the data forwarding tunnel identifier of the GGSN, the source RNC duplicates a buffered data packet and forwards to the GGSN, the GGSN forwards the data packet forwarded by the source RNC to the 2G SGSN on receipt of the data packet; step S 1511 : the 2G SGSN sends an update PDP context request message to the GGSN; step S 1512 : the GGSN returns an update PDP context response message to the 2G SGSN; step S 1513 : the 2G SGSN returns a routing area update accept message to the MS; step S 1514 : the MS returns a routing area update complete message to the 2G SGSN. The data forwarding processing method stated above can be used for data forwarding when a handover or change between a GERAN/UTRAN system and an SAE system takes place. When a handover or change from a GERAN system to an SAE system takes place, the MME and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE. Meanwhile the MME informs the UPE of a tunnel identifier of the access network side, and informs the 2G SGSN of the data forwarding tunnel identifier of the UPE. The 2G SGSN forwards a data packet to the UPE, and the UPE further forwards the data packet to the evolved access network. When a handover or change from an SAE system to a GERAN system takes place, the MME and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE. Meanwhile, the MME informs the UPE of a tunnel identifier of the 2G SGSN, and then informs the evolved access network of the data forwarding tunnel identifier of the UPE. The evolved access network forwards a data packet to the UPE, and the UPE further forwards the data packet the 2G SGSN. When a handover or change from a UTRAN system to an SAE system takes place, the 3G SGSN and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE Meanwhile, the UPE is informed of a tunnel identifier of the evolved access network side. Then the 3G SGSN informs the source RNC of the data forwarding tunnel identifier of the UPE. The source RNC forwards a data packet to the UPE, and the UPE further forwards the data packet to the evolved access network. When a handover or change from an SAE system to a UTRAN system takes place, the MME and the UPE exchange messages including a forward data request message and a forward data response message, to obtain a data forwarding tunnel identifier of the UPE. Meanwhile the MME informs the UPE of a tunnel identifier of the target RNC and then informs the evolved access network of the data forwarding tunnel identifier of the UPE. The evolved access network forwards a data packet to the UPE, and the UPE further forwards the data packet to the target RNC. Another data processing method when an intersystem handover or change takes place is provided with an embodiment of the present invention, including: A user plane anchor network element sends data to a source data forwarding network element and a target side processing network element on receipt of an instruction. The instruction may be a bicast command instruction instructing the user plane anchor network element to send data to the source data forwarding network element and the target side processing network element. On completion of update of user plane routing, the user plane anchor network element stops bicasting and sends data to the target side processing network element only. With reference to FIG. 16 , a data processing method when a handover from a GERAN to a UTRAN takes place includes: step 1601 : a source BSS decides to initiate a handover; step 1602 : the source BSS sends a handover request message to an old SGSN, i.e. 2G SGSN; step 1603 : the 2G SGSN sends a forward relocation request message to a new SGSN, i.e. 3G SGSN; step 1604 : the 3G SGSN builds a relocation request message and sends the message to a target RNC; step 1605 : the target RNC sends relocation request acknowledge message to the 3G SGSN; step 1606 : the 3G SGSN sends a forward relocation response message to the 2G SGSN, an indication is carried in the message to instruct the 2G SGSN not to perform data forwarding; step 1607 : the 3G SGSN sends a bicast command message to a GGSN, instructing the GGSN to send data to the 2G SGSN and the target RNC, a GTP tunnel identifier of the target RNC is carried in the message; step 1608 : the GGSN sends a downlink data packet to the 2G SGSN and the target RNC; step 1609 : the 2G SGSN sends a handover request acknowledge message to the source BSS; step 1610 : an MS sends a handover to UTRAN complete message to the target RNC; step 1611 : the target RNC sends a relocation complete message to the 3G SGSN; step 1612 : a process of PDP context update is performed between the 3G SGSN and the GGSN, which changes a downlink GTP tunnel identifier of user in the GGSN to the GTP tunnel identifier of the target RNC, the GGSN stops data bicasting in the process; step 1613 : the GGSN sends a downlink data packet to the target RNC. With reference to FIG. 17 , a data processing method when a handover from a UTRAN to a GERAN takes place includes: step S 1701 : a source RNC decides to initiate a handover; step S 1702 : the source RNC sends a relocation request message to an old SGSN, i.e. 3G SGSN; step S 1703 : the 3G SGSN sends a forward relocation request message to a new SGSN, i.e. 2G SGSN; step S 1704 : the 2G SGSN builds a handover request message, and sends the message to a target BSS; step S 1705 : the target BSS sends a handover request acknowledged message to the 2G SGSN; step S 1706 : the 2G SGSN sends a forward relocation response message to the 3G SGSN; step S 1707 : the 3G SGSN sends a bicast command message to a GGSN, instructing the GGSN to send data to the source RNC and the 2G SGSN, a GTP tunnel identifier of the 2G SGSN is carried in the message; step S 1708 : the GGSN sends a downlink data pack to the source RNC and the 2G SGSN; step S 1709 : the 3G SGSN sends a relocation command message to the source RNC, an indication is carried in the message to instruct the source RNC not to perform data forwarding; step S 1710 : the target BSS sends a handover complete message to the 2G SGSN; step S 1711 : a process of PDP context update is performed between the 2G SGSN and the GGSN, which changes a downlink GTP tunnel identifier of user in the GGSN to the GTP tunnel identifier of the 2G SGSN, the GGSN stops data bicasting in the process; step S 1712 : the GGSN sends a downlink data packet to the 2G SGSN, the 2G SGSN sends the downlink data packet to the target BSS. With reference to FIG. 18 , a data processing method when a change from a GERAN to a UTRAN takes place includes. step S 1801 : an MS decides to initiate an intersystem change; step S 1802 : the MS sends a routing area update request message to a new SGSN, i.e. 3G SGSN; step S 1803 : the 3G SGSN sends an SGSN context request message to an old SGSN, i.e. 2G SGSN, to obtain user context; step S 1804 : the 2G SGSN returns an SGSN context response message to the 3G SGSN, and carries the user context information in the message; step 1805 : RAB assignment procedure is performed between the 3G SGSN and an RNC, thereby establishing RAB; step S 1806 : the 3G SGSN sends an SGSN context acknowledge message to the 2G SGSN, an indication is carried in the message to instruct the 2G SGSN not to perform data forwarding; step S 1807 : the 3G SGSN sends a bicast command message to the GGSN, instructing the GGSN to send data to the 2G SGSN and a target RNC, a GTP tunnel identifier of the target RNC is carried in the message; step S 1808 : the GGSN sends a downlink data packet to the 2G SGSN and the target RNC; step S 1809 : the 3G SGSN returns a routing area update accept message to the MS; step S 1810 : the MS returns a routing area update complete message to the 3G SGSN; step S 1811 : a process of PDP context update is performed between the 3G SGSN and the GGSN, which changes a downlink GTP tunnel identifier of user in the GGSN to the GTP tunnel identifier of the target RNC, the GGSN stops data bicasting in the process; step S 1812 : the GGSN sends a downlink data packet to the target RNC. With reference to FIG. 19 , a data processing method when a change from a UTRAN to a GERAN takes place includes: step S 1901 : an MS decides to initiate an intersystem change; step S 1902 : the MS sends a routing area update request message to a new SGSN, i.e. 2G SGSN; step S 1903 : the 2G SGSN sends an SGSN context request message to an old SGSN, i.e. 3G SGSN, to obtain user context; step S 1904 : the 3G SGSN sends an SRNS context request message to a source RNC; step S 1905 : the source RNC returns an SRNS context response message to the 3G SGSN, stops sending downlink data to the MS, and buffers the data; step S 1906 : the 3G SGSN returns an SGSN context response message to the 2G SGSN, and carries the user context information in the message; step S 1907 : the 2G SGSN sends an SGSN context acknowledge message to the 3G SGSN, informing the 3G SGSN that the 2G SGSN is ready to receive data packets; step S 1908 : the 3G SGSN sends a bicast command message to the GGSN, instructing the GGSN to send data to the source RNC and the 2G SGSN, a GTP tunnel identifier of the 2G SGSN is carried in the message; step S 1909 : the GGSN sends a downlink data packet to the source RNC and the 2G SGSN; step S 1910 : a process of PDP context update is performed between the 2G SGSN and the GGSN, which changes a downlink GTP tunnel identifier of user in the GGSN to the GTP tunnel identifier of the 2G SGSN, the GGSN stops data bicasting in the process; step S 1911 : the GGSN sends a downlink data packet to the 2G SGSN, the 2GSN sends the downlink data packet to the MS; step S 1912 : the 2G SGSN returns a routing area update accept message to the MS; step S 1913 : the MS returns a routing area update complete message to the 2G SGSN. The data forwarding processing method stated above can be used for data forwarding when a handover or change between a GERAN/UTRAN system and an SAE system takes place. When a handover or change from a GERAN system to an SAE system takes place, the MME sends a bicast command message to the UPE, instructing the UPE to send data to the 2G SGSN and the LTE. The UPE sends a downlink data packet to the 2G SGSN and the LTE. On completion of update of user plane routing, the UPE stops downlink data packet bicasting, and sends a downlink data packet to the LTE only. When a handover or change from an SAE system to a GERAN system takes place, the MME sends a bicast command message to the UPE, instructing the UPE to send data to the LTE and the 2G SGSN. The UPE sends a downlink data packet to the LTE and the 2G SGSN. On completion of update of user plane routing, the UPE stops downlink data packet bicasting, and sends a downlink data packet to the 2G SGSN only. When a handover or change from a UTRAN system to an SAE system takes place, the MME sends a bicast command message to the UPE, instructing the UPE to send data to the source RNC and the LTE. The UPE sends a downlink data packet to the source RNC and the LTE. On completion of update of user plane routing, the UPE stops downlink data packet bicasting, and sends a downlink data packet to the LTE only. When a handover or change from an SAE system to a UTRAN system takes place, the MME sends a bicast command message to the UPE, instructing the UPE to send data to the LTE and the target RNC. The UPE sends a downlink data packet to the LTE and the target RNC. On completion of update of user plane routing, the UPE stops downlink data packet bicasting, and sends a downlink data packet to the target RNC only. With reference to FIG. 20 , a data processing system is provided in an embodiment of the present invention, including a source data forwarding network element, a target side processing network element and a user plane anchor network element, wherein the user plane anchor network element is provided with a receipt unit adapted to receive data forwarded by the source data forwarding network element, and a sending unit adapted to forward the received data to the target side processing network element. In an embodiment of the present invention, the source data forwarding network element is a 2G Serving GPRS Support Node (SGSN), the user plane anchor network element is a Gateway GPRS Support Node (GGSN), and the target side processing network element is a target Radio Network Controller (RNC). In another embodiment of the present invention, the source data forwarding network element is a source RNC, the user plane anchor network element is a GGSN, and the target side processing network element is a 2G SGSN. The data processing system further includes: a tunnel identifier acquisition unit, arranged in the 3G SGSN and adapted to acquire a data forwarding tunnel identifier of the GGSN; and a tunnel identifier sending unit, adapted to send a GTP tunnel identifier of the target RNC side to the GGSN. The data processing system further includes: a data packet buffer unit, arranged in the GGSN and adapted to receive a data packet forwarded by the 2G SGSN and buffer a data packet forwarded by the target side processing network element; and a data packet sending unit, adapted to send the buffered data packet. In the direct-tunnel mechanism, when a handover or change between a GERAN and a UTRAN takes place, data forwarded by the source data forwarding network element can be buffered in the data packet buffer unit, which forwards the buffered data packet to the target RNC when the GGSN completes update of user plane routing or the GGSN receives an update PDP context request message sent by the 3G SGSN. Also, the data forwarded by the source data forwarding network element can be forwarded directly to the target side processing network element. When an intersystem handover or change takes place, interactions among the source data forwarding network element, target side processing network element and the user plane anchor network element are same or similar to the steps described in the above embodiments. When the user plane anchor network element receive an instructive message and sends data to the source data forwarding network element and/or the target side processing network element, the user plane anchor network element updates user plane routing and only sends the data to the target side processing network element as instructed in the message according to the updated user plane routing. Those skilled in the art should understand that each step in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in computer readable storage medium such as ROM/RAM, magnetic disk and optical discs. Alternatively, the embodiments can be implemented with respective integrated circuit modules, or the steps of which can be made into separate integrated circuit modules. Therefore, the present invention is not limited to any particular hardware or software combination. As can be seen from the above embodiments, with the data processing methods in the direct-tunnel mechanism when a handover or change between a GERAN and a UTRAN takes place, a GGSN can buffer data forwarded by a source data forwarding network element and then send the data to a target side processing network element, alternatively, the GGSN can send the data forwarded by the source data forwarding network element directly to the target side processing network element. The problem that the data processing method in the conventional art is not applicable in the direct-tunnel mechanism is solved. Handover or change between a GERAN and a UTRAN in the direct-tunnel mechanism does not affect forwarding of service data. Exemplary embodiments of the present invention are described. It should be noted that those skilled in the art may make various alternations or modifications without departing from the principle of the present invention. The alternations and modifications should be covered within the scope of the present invention.

A data processing method when the handover or change appears between systems includes: the source data forwarding network element forwards the data to the user plane anchor network element; the user plane anchor network element forwards the data to the target side processing network element. A data processing method when the handover or change appears between systems is also provided by the present invention, which includes: the user plane anchor network element receives the message indication, transmits the data to at least one of the source data forwarding network element and the target side processing network element; the user plane anchor network element updates the route of the user plane, and transmits the data to the target side processing network element according to the updated route of the user plane. A data processing method when handover or change appears between GERAN/UTRAN systems under the Direct Tunnel solution is provided by the present invention, which can be applied to the Direct Tunnel solution.

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 61/770,620, filed on Feb. 28, 2013 which is incorporated herein by reference in its entirety. FIELD OF THE ART [0002] The present disclosure generally relates to gel compositions and wellbore treatment fluids for use in hydraulic fracturing applications. BACKGROUND [0003] In the drilling, completion, and stimulation of oil and gas wells, well treatment fluids are often pumped into well bore holes under high pressure and at high flow rates causing the rock formation surrounding the well bore to fracture. A type of well treatment commonly utilized for stimulating hydrocarbon production from a subterranean zone penetrated by a well bore is hydraulic fracturing. Hydraulic fracturing, also referred to as fracing (or fracking), is used to initiate production in low-permeability reservoirs and re-stimulate production in older producing wells. In hydraulic fracing, a fluid composition is injected into the well at pressures effective to cause fractures in the surrounding rock formation. Fracing is used both to open up fractures already present in the formation and create new fractures. Proppants, such as sand and ceramics, are used to keep induced fractures open both during and after fracturing treatment. To place the proppants inside the fracture, the proppant particles are suspended in a fluid that is pumped into the subterranean formation. Generally, this fluid has a viscosity sufficient to maintain suspension of the particles. [0004] For ideal performance, a hydraulic fracturing fluid should be sufficiently viscous to create a fracture of adequate width and be able to transport large quantities of proppants into the fracture. The viscosity of the fluid can be enhanced or modified by addition of synthetic and/or natural polymers, or other rheology modifiers. Examples of polymer-enhanced fluids used to increase the viscosity of hydraulic fracturing fluids include slickwater systems, linear gel systems, and crosslinked gel systems. Of these, crosslinked gel systems are the most viscous. [0005] In a crosslinked gel system, a linear polymer or gel, for example, a fluid based on guar or modified guar, is crosslinked with added reagents such as borate, zirconate, and titanate in the presence of alkali. The most common version of crosslinked gel is known in the art as guar-borate gel. The crosslinked gel fluid increases the viscosity of the fracturing fluid, such that proppants can be effectively suspended. [0006] Once the hydraulic fracturing fluid has delivered proppant to the fracture or delivered sand in gravel packing or frac packing operations, it is often desirable to lower the viscosity of the fracturing fluid such that the fluid can be recovered from the formation using minimal energy. The removal of the spent fracturing fluids from the subterranean formation is typically required to allow hydrocarbon production. This reduction in viscosity of the fracturing fluid is often achieved using a breaker, i.e., a compound that breaks the cross-linking bonds within the gel. [0007] Synthetic polymers, for example polyacrylamide (PAM) polymers, can form permanent gels under acidic conditions with metal crosslinking agents, such as aluminum-, chromium-, zirconium- and titianium-based complexes. Such gels can be used, for example, to control conformance in enhanced oil recovery (EOR) applications, where subsequent breaking to significantly reduce viscosity is not necessary. However, for fracing fluid applications, the acidity of the formation in hydraulic fracturing is usually not high, and breaking of the crosslinked gel improves fluid recovery. SUMMARY [0008] Disclosed herein are gel compositions comprising an acrylamide polymer or copolymer having a charge between about 5% to about 35%, or more specifically about 15% to about 20%, and dialdehyde. The gel composition is formed by combining the acrylamide polymer or copolymer and dialdehyde in an aqueous solution at a pH in the range of about 7.5 to about 11, wherein the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is in the range of about greater than about 0.2 to about 2.0. [0009] Methods to produce the gel composition, methods of treating a wellbore comprising injecting the gel composition into a wellbore, and well treatment fluids comprising the gel composition are also disclosed herein. [0010] Further, methods of treating a wellbore comprising injecting a composition comprising an acrylamide polymer or copolymer having a charge between 15% to 20% into a wellbore; injecting a composition comprising dialdehyde into the wellbore, and injecting a pH modifying agent into the wellbore in an amount sufficient to produce a downhole solution pH in the range of about 7.5 to about 11, to produce an in-situ gel composition comprising an acrylamide polymer or copolymer crosslinked with dialdehyde. [0011] Wellbore treatment fluids comprising an acrylamide polymer or copolymer and dialdehyde are also disclosed herein. The wellbore treatment fluid may be formed (in whole or in part) prior to injection into the wellbore or in situ, where the acrylamide polymer/copolymer and the crosslinker are added to the wellbore separately. The wellbore treatment fluid may optionally comprise one or more additional components, such as proppants and pH control agents. [0012] The disclosure may be understood more readily by reference to the following detailed description of the various features of the disclosure and the examples included therein. BRIEF DESCRIPTION OF FIGURES [0013] FIG. 1 provides a graph showing the results of the viscosity analyses for exemplary gels according to the embodiments and a guar gel. [0014] FIG. 2 provides a graph showing the relationship between charge and viscosity for anionic copolymers at various charges. DETAILED DESCRIPTION [0015] The present disclosure provides cross-linked gel compositions which comprise an acrylamide polymer or copolymer and dialdehyde. The gel compositions are useful for increasing the viscosity of hydraulic fracturing fluids. In particular, the gel compositions have a charge (mole percent) within a specific range that is especially useful for viscosifying wellbore treatment fluids, enhancing delivery of proppants into fractures. The exemplary gel compositions may break under certain conditions, which can increase fluid recovery in hydraulic fracturing applications. The exemplary gel compositions can be used as a synthetic replacement for crosslinked guar compositions in hydraulic fracturing applications, with comparable performance. Like guar gels, the exemplary gel compositions provide high viscosity with a relatively low amount of active polymer in the composition. Exemplary gel compositions may be easier to manufacture, and of a more reliable quality, than guar gels. [0016] Gel Compositions [0017] In one aspect, the present invention is a gel composition comprising an acrylamide polymer or copolymer crosslinked with dialdehyde. [0018] As used herein, the term “acrylamide polymer” refers to a homopolymer of acrylamide and encompasses acrylamide polymers chemically modified (e.g., hydrolyzed) following polymerization. [0019] As used herein the term “acrylamide copolymer” refers to a polymer comprising an acrylamide monomer and one or more comonomers. The comonomer may be anionic, cationic or non-ionic. In certain embodiments, the comonomer is hydrophobic. The acrylamide copolymer may be unmodified or chemically modified. Representative, non-limiting co-monomers include acrylic acid, vinyl acetate, vinyl alcohol and/or other unsaturated vinyl monomers. [0020] In one embodiment, the acrylamide copolymer comprises an anionic comonomer. In some embodiments, the anionic monomer is selected from the group consisting of (meth)acrylic acid, alkali/alkaline/ammonium salts of (meth)acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, alkali/alkaline/ammonium salts of 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, alkali/alkaline/ammonium salts of maleic acid and the like. [0021] In another embodiment, the acrylamide copolymer comprises a cationic comonomer. In some embodiments, the cationic monomer is selected from the group consisting of (meth)acrylamidoethyltrimethylammonium chloride, (meth) acrylamido propyltrimethylammonium chloride and the like. [0022] In another embodiment, the acrylamide copolymer comprises a non-ionic comonomer. In some embodiments, the non-ionic monomer is selected from the group consisting (meth)acrylamide, maleic anhydride. [0023] In an exemplary embodiment, the acrylamide copolymer comprises an acrylamide monomer and an anionic comonomer, but does not include a cationic comonomer. [0024] In one embodiment, the acrylamide polymer or copolymer is characterized by a charge of about 0% to about 40%, about 5% to about 35%, about 15% to about 30%, about 15% to about 20% or about 20% to about 30%. In one embodiment, the charge is in the range of about 5% to about 35% and provides a particularly high viscosity that provides substantial suspending power. In another embodiment, the charge is in the range of about 15% to about 20% and provides a particularly high viscosity that provides substantial suspending power. [0025] In another embodiment, the acrylamide polymer or copolymer is characterized by a charge of about 10%, about 15%, about 20%, about 25%, about 30%, about 35% or about 40%. [0026] The range of charge for the gel composition disclosed herein is a function of the charge of the polyacrylamide copolymer comprising charged monomers or the chemically modified polyacrylamide polymer or copolymer. [0027] In a particular embodiment, the acrylamide copolymer comprises from about 30 to about 90, about 40 to about 80, about 50 to about 70 or about 60 mole % acrylamide. [0028] In a particular embodiment, the weight ratio of the acrylamide monomer to the one or more comonomers is about 10:90 to 90:10. [0029] In a particular embodiment, the acrylamide polymer or copolymer is characterized by a degree of hydrolysis of about 5 to about 10%, about 10 to about 15%, about 15 to about 20%, about 20 to about 25%, about 25 to about 30% or greater than about 30%. In a more particular embodiment, the acrylamide polymer or copolymer is characterized by a degree of hydrolysis of about 15, about 16, about 17, about 18, about 19 or about 20%. [0030] In one embodiment, acrylamide polymers or copolymers are water dispersible. [0031] In one embodiment, the acrylamide polymer or copolymer has a weight average molecular weight of greater than or equal to about 0.5 million g/mol. In another embodiment, the acrylamide polymer or copolymer has a weight average molecular weight of in the range of about 0.5 million g/mol to about 30 million g/mol. [0032] The liquid used to form the gel composition any suitable aqueous liquid that does not adversely react with the acrylamide polymer or copolymer, such as fresh water, salt water, brine, or any other aqueous liquid. [0033] The dialdehyde used to cross-link the acrylamide polymer or copolymer may be any suitable dialdehyde. Representative, non-limiting examples of dialdehydes include glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde, o-phthaldehyde, m-phthaldehyde, p-phthaldehyde, and combinations and mixtures thereof. [0034] In one embodiment, the dialdehyde is a glyoxal. [0035] In one embodiment, the gel composition comprises an acrylamide polymer, crosslinked with glyoxal. In a particular embodiment, the gel composition comprises an acrylamide polymer crosslinked with glyoxal, wherein the acrylamide polymer is characterized by a charge in range of about 5% to about 40% and provides a particularly high viscosity that provides substantial suspending power. In one embodiment, the charge is in the range of about 15% to about 20% and provides a particularly high viscosity that provides substantial suspending power. In a particular embodiment, the charge is about 10%, about 15%, about 20%, about 25%, about 30%, about 35% or about 40%. [0036] In another embodiment, the gel composition comprises an acrylamide copolymer crosslinked with glyoxal. In a particular embodiment, the gel composition comprises an acrylamide copolymer crosslinked with glyoxal, wherein the acrylamide copolymer is characterized by a charge in range of about 5% to about 40% and provides a particularly high viscosity that provides substantial suspending power. In one embodiment, the charge is in the range of about 15% to about 20% and provides a particularly high viscosity that provides substantial suspending power. In a particular embodiment, the charge is about 10%, about 15%, about 20%, about 25%, about 30%, about 35% or about 40%. [0037] The amount of the acrylamide polymer or copolymer in the gel composition may depend, for example, on the particular polymer/copolymer used, the purity of the polymer/copolymer, and properties desired in the final composition. In one embodiment, the gel composition comprises from about 0.05 to about 5% by weight polymer or copolymer, from about 0.1 to about 1% or from about 0.2 to about 5% by weight polymer or copolymer, based on the total weight of the composition. In another embodiment, the gel composition comprises about 5, about 0.1 to about 3, about 0.2 to about 2, or about 0.3 to about 1% by weight percent polymer or copolymer based on the total weight of the composition. [0038] In exemplary embodiments, the gel composition comprises from about 0.1% to about 25% of acrylamide polymer or copolymer, by weight of the composition. In certain embodiments, the gel composition comprises from about 0.01% to about 25% acrylamide polymer or copolymer, by weight of the composition. [0039] In one embodiment, the gel composition comprises an acrylamide polymer or copolymer crosslinked with glyoxal wherein the polymer or copolymer (i) comprises about 0.05 to about 5% by weight polymer/copolymer and (ii) is characterized by a charge in range of about 5% to about 40%, and more particularly about 15 to about 20%. [0040] In one embodiment, the gel composition has a dialdehyde to monomer ratio of from about 0.2 to about 2.0. In exemplary embodiments, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is greater than about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0. In exemplary embodiments, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is in the range of about greater than about 0.2 to about 2.0, about 0.5 to about 2.0, about 0.7 to about 2.0, about 0.8 to about 2.0, about 1.0 to about 2.0, about 1.1 to about 2.0, or about 1.0 to about 1.5. In a particular embodiment, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is greater than about 1.0. [0041] In one embodiment, the gel composition comprises an acrylamide polymer or copolymer crosslinked with glyoxal wherein (i) the polymer or copolymer comprises about 0.05 to about 5% by weight polymer/copolymer and is characterized by a charge in range of about 5% to about 40%, and more particularly about 15 to about 20% and (ii) the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is about 0.2 to about 2.0. [0042] In exemplary embodiments, the gel compositions according to the embodiments have a viscosity of greater than or equal to about 100 cP at about 100 sec-1. The viscosity of the gel may composition may be controlled by varying the concentrations of the crosslinking agent and polymer. In a particular embodiment, the gel composition has a viscosity greater than about 150, or greater than about 200, or greater than about 250 cP, or greater than about 400 cP at about 100 sec-1. [0043] In one embodiment, the gel composition comprises an acrylamide polymer or copolymer crosslinked with glyoxal, wherein (i) the polymer/copolymer comprises about 0.05 to about 5% by weight polymer/copolymer and is characterized by a charge in range of about 5% to about 40%, and more particularly about 15 to about 20% and (ii) the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is about 0.2 to about 2.0; and (iii) the gel composition has a viscosity of greater than or equal to about 100 cP at about 100 sec-1. Wellbore Fluid Compositions [0044] In a second aspect, the present invention is a wellbore fluid composition comprising an acrylamide polymer or copolymer crosslinked with dialdehyde. [0045] The acrylamide polymer or copolymer may be any suitable acrylamide polymer or copolymer, such as those described above. [0046] The necessary or desired amounts of the acrylamide polymer or copolymer and dialdehyde may be determined based on various factors, including, for example, assumptions about the downhole conditions. The presence of a gel down hole may be determined by other indicators other than rheological measurements. [0047] In exemplary embodiments, a wellbore fluid composition may contain from about 0.05 to about 5%, from about 0.1 to about 1%, or from about 0.2 to about 5% by weight acrylamide polymer or copolymer, based on the total weight of the composition. [0048] In exemplary embodiments, the dialdehyde to monomer ratio is from about 0.2 to about 2.0. In exemplary embodiments, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is greater than about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0. In exemplary embodiments, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is in the range of about greater than about 0.2 to about 2.0, about 0.5 to about 2.0, about 0.7 to about 2.0, about 0.8 to about 2.0, about 1.0 to about 2.0, about 1.1 to about 2.0, or about 1.0 to about 1.5. In a particular embodiment, the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is greater than about 1.0. [0049] In exemplary embodiments, the wellbore fluid composition comprises an acrylamide polymer or copolymer crosslinked by dialdehyde and a pH modifying agent. [0050] In certain embodiment, the wellbore fluid composition is formed (in whole or in part) prior to injection into the wellbore. In other embodiments, the wellbore fluid composition is formed (in whole or in part) in situ (i.e., in the wellbore). Where the wellbore fluid composition is formed in situ, the components of the well fluid composition may be injected into the wellbore simultaneously or sequentially, in any order. [0051] In exemplary embodiments, the wellbore fluid composition is formed in situ by injecting (i) a composition comprising an acrylamide polymer or copolymer and a pH modifying agent and (ii) a composition comprising dialdehyde, where the injection of (i) and (ii) occurs simultaneously or sequentially, in any order. [0052] In exemplary embodiments, the wellbore fluid composition is formed in situ by injecting (i) a composition comprising dialdehyde and a pH modifying agent and (ii) a composition comprising an acrylamide polymer or copolymer, where the injection of (i) and (ii) occurs simultaneously or sequentially, in any order. [0053] In exemplary embodiments, the wellbore fluid composition is formed in situ by injecting (i) a composition comprising an acrylamide polymer or copolymer; (ii) a composition comprising dialdehyde may be combined; and (iii) a composition comprising a pH modifying agents, wherein the injection of (i)-(iii) occurs simultaneously or sequentially, in any order. [0054] In exemplary embodiments, the pH modifying agent is any suitable pH modifying agent and may be in the form of an aqueous solution, for example an aqueous solution comprising a base, an acid, a pH buffer, or any combination thereof. In exemplary embodiments, the pH modifying agent is a potassium carbonate and potassium hydroxide mixture or a sodium bicarbonate and sodium carbonate mixture. In exemplary embodiments, a wellbore treatment fluid comprises a gel composition as described herein. [0055] In exemplary embodiments, the wellbore treatment fluid optionally comprises a proppant, for example natural or synthetic proppants, including but not limited to glass beads, ceramic beads, sand, gravel, and bauxite and combinations thereof. Exemplary proppants may be coated or contain chemicals; more than one can be used sequentially or in mixtures of different sizes or different materials. The proppant may be resin coated (curable), or pre-cured resin coated. The proppant may be any suitable shape, including substantially spherical materials, fibrous materials, polygonal materials (such as cubic materials), and combinations thereof. In one embodiment, the proppant is a reduced density proppant. [0056] In exemplary embodiments, the wellbore treatment fluids comprising the gel compositions, or dialdehyde and acrylamide polymer or copolymer compositions for forming the gel compositions, can be used in any well treatment fluid where viscosification is desired including but not limited to stimulation and completion operations. For example, the wellbore treatment fluid can be used for hydraulic fracturing applications. In these applications, the fracturing fluid, i.e. wellbore treatment fluid, can be configured as a gelled fluid, a foamed gel fluid, acidic fluids, water and potassium chloride treatments, and the like. The fluid is injected at a pressure effective to create one or more fractures in the subterranean formation. Depending on the type of well treatment fluid utilized, various additives may also be added to the wellbore fluid to change the physical properties of the fluid or to serve a certain beneficial function. In one embodiment, a propping agent such as sand or other hard material is added which serves to keep the fractures open after the fracturing operation. Also, fluid loss agents may be added to partially seal off the more porous sections of the formation so that the fracturing occurs in the less porous strata. Other oilfield additives that may also be added to the wellbore treatment fluid include antifoams, scale inhibitors, H 2 S and or O 2 scavengers, biocides, surface tension reducers, breakers, buffers, surfactants and non-emulsifiers, fluorocarbon surfactants, clay stabilizers, fluid loss additives, foamers, friction reducers, temperature stabilizers, diverting agents, shale and clay stabilizers, paraffin/asphaltene inhibitors, corrosion inhibitors. [0057] In exemplary embodiments, the wellbore treatment fluid may optionally further comprise additional additives, including, but not limited to, acids, fluid loss control additives, gas, corrosion inhibitors, scale inhibitors, catalysts, clay control agents, biocides, friction reducers, combinations thereof and the like. For example, in some embodiments, it may be desired to foam the storable composition using a gas, such as air, nitrogen, or carbon dioxide. [0058] Method of Making the Gel Composition [0059] In a third aspect, the present invention is a method of making a gel composition comprising an acrylamide polymer or copolymer crosslinked by dialdehyde. [0060] In one embodiment, a method of making a gel composition comprises combining or contacting an acrylamide polymer or copolymer with a dialdehyde in an aqueous medium, wherein the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is in the range of about greater than about 0.2 to about 2.0, or from about 1 to 1.5, at a temperature and for a period of time sufficient to produce the gel composition. [0061] The pH of the aqueous medium may vary. In one embodiment, the pH of the aqueous solution is greater than about 7.5, about 8.0, about 8.5, about 9.0, about 10.0, about 10.2, about 10.5, about 10.7, or about 11. In exemplary embodiments, the pH is in the range of about 7.5 to about 11, about 8.5 to about 11, about 9.0 to about 11, about 10 to about 11, or about 10.2 to about 10.7. In a particular embodiment, the pH is greater than about 9.0. The pH modifying agents which may be used to modify the pH of the gel or the composition in which the gel is formed are any pH modifying agents suitable, for example basic compounds, which are inert relatively to the polymer and the dialdehyde, for example inorganic compounds, such as alkaline and alkaline-earth hydroxides or salts, including but not limited to alkaline carbonate or phosphate. [0062] In exemplary embodiments, acrylamide polymer or copolymer is provided in the form of a fine aqueous dispersion or emulsion of the acrylamide polymer or copolymer. In exemplary embodiments, the acrylamide polymer or copolymer component is about 0.1 to 1 wt. % of the acrylamide polymer or copolymer in the solution, dispersion or emulsion. [0063] In exemplary embodiments, the dialdehyde is in the form of a dialdehyde in an aqueous solution. In exemplary embodiments, the acrylamide polymer or copolymer component and/or the dialdehyde component are each adjusted to a pH in the range of about 7.5 to about 11 prior the step of combining or contacting the components. In exemplary embodiments, the acrylamide polymer or copolymer component is prepared by shearing, agitating or stirring the acrylamide polymer or copolymer in an aqueous medium until a fine dispersion or emulsion is obtained. In exemplary embodiments, the pH of the fine aqueous dispersion or emulsion of the acrylamide polymer or copolymer is adjusted as desired, for example, adjusted to a pH in the range of about 7.5 to about 11.0. In exemplary embodiments, the step of combining or contacting the acrylamide polymer or copolymer with dialdehyde in an aqueous solution includes shearing, agitating or stirring the components to form a thoroughly blended mixture or a gel composition. In exemplary embodiments, the final pH of the mixture or gel composition is recorded, and then the gel is tested for viscosity in a rheometer (e.g. a Grace Instrument M5600 HPHT Rheometer). [0064] In exemplary embodiments, the aqueous solution may be in the form of an aqueous liquid, an aqueous emulsion, an aqueous dispersion or an aqueous slurry. [0065] The period of time sufficient to produce the gel composition may vary. In exemplary embodiments, the formation of the gel composition or the crosslinking of the acrylamide polymer or copolymer and dialdehyde occurs in less than about 1 hour, about 40 minutes, about 30 minutes, or about 20 minutes or less than about 10 minutes, or less than about 5 minutes. [0066] The temperature to produce the gel composition may vary. In one embodiment, the gel composition is produced at a temperature of greater than or equal to about 20° C., about 30° C., about 40° C., about 50° C., about 60° C., about 70° C., about 80° C., or about 90° C. In exemplary embodiments, the gel composition is produced in a period of time of about 1 minute to about 24 hours, about 5 minutes to about 2 hours, or about 10 minutes to about 1 hour. [0067] In one embodiment, a method to produce a gel composition comprises combining or contacting an acrylamide polymer or copolymer, or a fine aqueous dispersion or emulsion of the acrylamide polymer or copolymer, with dialdehyde in an aqueous solution at a pH in the range of about 7.5 to about 11, wherein the molar ratio of dialdehyde to monomers of the acrylamide polymer or copolymer is in the range of about greater than about 0.2 to about 2.0, at a temperature and for a period of time sufficient to produce the gel composition. [0068] In certain embodiments, the method of producing the gel composition comprises combining or contacting an acrylamide polymer or copolymer with dialdehyde in an aqueous solution at a pH in the range of about 7.5 to about 11, at a temperature and for a period of time sufficient to produce a gel composition, wherein the gel composition is partially cross-linked before it is added to the wellbore and then becomes fully-crosslinked in situ. [0069] Methods of Treating Wellbores [0070] In another aspect, the present invention is a method of treating a wellbore using a gel composition. [0071] In exemplary embodiments, a method of treating a wellbore comprises injecting a gel composition described herein into a wellbore. In exemplary embodiments, the gel composition is at least partially pre-formed and subsequently injected into the wellbore. In another embodiment, the gel composition is formed in situ. [0072] In exemplary embodiments, a method of treating a wellbore comprises injecting a composition comprising an acrylamide polymer or copolymer into a wellbore; injecting a composition comprising dialdehyde into the wellbore, and injecting a pH modifying agent into the wellbore in an amount sufficient (or calculated to be sufficient) to produce a downhole solution pH in the range of about 7.5 to about 11, to produce an in-situ gel composition comprising an acrylamide polymer or copolymer crosslinked with dialdehyde. [0073] In exemplary embodiments, the wellbore treatment fluid or gel composition may be used for carrying out a variety of subterranean treatments, including, but not limited to, drilling operations, fracturing treatments, and completion operations (e.g., gravel packing) In exemplary embodiments, the wellbore treatment fluid or gel composition may be used in treating a portion of a subterranean formation. In exemplary embodiments, the wellbore treatment fluid or gel composition may be introduced into a well bore that penetrates the subterranean formation. In exemplary embodiments, the wellbore treatment fluid or gel composition may be used in fracturing treatments. [0074] The wellbore treatment fluids and gel compositions of the present embodiments may be used in any subterranean treatment as desired. Such subterranean treatments include, but are not limited to, drilling operations, stimulation treatments, and completion operations. Those of ordinary skill in the art, with the benefit of this disclosure, will be able to recognize a suitable subterranean treatment where friction reduction may be desired. [0075] In exemplary embodiments, the wellbore treatment fluid, gel compositions and methods can be used in or injected into fresh water, salt water or brines. [0076] In exemplary embodiments, wellbore treatment fluid, gel compositions and methods can be used within a temperature range of about 20° C. to about 205° C., about 50° C. to about 200° C., or about 70° C. to about 200° C. [0077] In exemplary embodiments, a method of fracturing a subterranean formation comprises: providing a wellbore treatment fluid or gel composition according to the present embodiments; and placing the wellbore treatment fluid or gel composition into a subterranean formation so as to create or enhance a fracture in the subterranean formation. [0078] In exemplary embodiments, a method of fracturing a subterranean formation comprises: providing a wellbore treatment fluid or gel composition according to the present embodiments; and pumping the wellbore treatment fluid or gel composition so as to form or extend a fracture in the subterranean formation and deposit the wellbore treatment fluid or gel composition in the fracture. [0079] In exemplary embodiments, the method further comprises allowing the gel composition in the fracture to break. In exemplary embodiments, the gel composition breaks without the addition of breaking agents or breakers. In exemplary embodiments, the method further comprises the addition of breaking agents or breakers. Representative, non-limiting examples of breakers include persulfates of ammonium, sodium and potassium, sodium perborate, hydrogen peroxide, organic peroxides, percarbonates, perphosphates, organic acids, perphosphate esters, amides, ammonium sulfate, enzymes, copper compounds, ethylene glycol, glycol ethers, and combinations thereof [0080] The following examples are presented for illustrative purposes only, and are not intended to be limiting. EXAMPLES Example 1 Preparation and Viscosity Analysis of Exemplary Glyoxal-Crosslinked-Polymer Gels [0081] Exemplary gels were prepared by the following protocol. About 0.4 wt % of active acrylamide polymer in water was stirred for about 10 minutes to about 20 minutes at room temperature. Once the solution was thoroughly blended, the pH of the solution was measured and adjusted using a pH buffer solution to about 9.8 to about 10.3. 0.33, 0.49 or 0.65 wt. % of glyoxal was added to the solution. The mixture was stirred until the glyoxal was well incorporated. The viscosity of each of the resulting gels was measured on a Grace Instrument M5600 HPHT Rheometer at 180° F. [0082] The Grace Instrument M5600 HPHT Rheometer which is a true Couette, coaxial cylinder, rotational, high pressure and temperature rheometer. The instrument is fully automated and all data acquisition is under computer control. The temperature of the sample is maintained with an oil bath which runs from ambient to 500° F. The gel is also subjected to pressure with nitrogen gas to prevent boiling off the solvent. After 20 minutes of shear conditioning, the gel is subjected to a shear sweep which can be programmed in the software that accompanies the Rheometer. The data acquired from the computer is processed and plotted as desired. [0083] FIG. 1 shows the viscosity analyses of three exemplary gels and, for comparison, a guar gel. Example 2 Charge-Viscosity Analysis of Exemplary Dry and Emulsion Glyoxal-Crosslinked-Polymer Gels [0084] The compositions were prepared by adding 200 mL of 2% KCl to a Waring blender jar. 0.3% of active acrylamide copolymer was added along with the pH buffer and mixed for a few minutes. 0.33% glyoxal was added (to provide a molar ratio of glyoxal to monomer of about 1.35) and blended for a few seconds. The obtained crosslinked gel was evaluated on an Anton Paar Physica Rheometer setup with concentric cylinder geometry. The gel was sheared at a constant shear rate of 100 s −1 and at a temperature of 180° F. The viscosity reported in the table is an average reading measured over 30 minutes. [0085] Analysis of Charge-Viscosity was evaluated for a range of dry PAM (DPAM), partially hydrolyzed PAM (HYPAM) and emulsion PAM (EPAM) polymers. Series were arranged in three groups with increasing charges for each group. [0000] TABLE 2 Viscosity of Exemplary Dry and Emulsion Glyoxal-Crosslinked-Polymer Gels Sample# Product Form Charge (mole %) Viscosity (cP) 1 DPAM 2 5 2 DPAM 13 463 3 DPAM 23 343 4 DPAM 33 33 5 DPAM 53 14 6 HYPAM 3 18 7 HYPAM 10 677 8 HYPAM 15 1326 9 HYPAM 20 463 10 HYPAM 30 118 11 HYPAM 40 57 12 EPAM 5 44 13 EPAM 10 412 14 EPAM 15 818 15 EPAM 20 475 16 EPAM 30 306 17 EPAM 40 32 [0086] Conditions: 0.3% active polymer, crosslinked with 0.33% glyoxal, in 2% KCl solution. [0087] Based on viscosity under the testing conditions (shear rate 100 sec −1 at 180F), there is an influence of charge on gel viscosity and performance. An optimum range of the charge appears to be in the 15-20 mole % range. This charge effect is unexpected because one would expect to have increasingly better performance (viscosity) with decreasing charge (which means more acrylamide units available for the crosslinking reaction with glyoxal). To the contrary, an optimum range of the charge appears to be in the 15-20 mole % range. The results of the charge-viscosity analysis are shown graphically in FIG. 2 . Example 3 Static Proppant Settling of PAM Versus Guar [0088] The Static Proppant Settling Column test was used to evaluate settling time of proppants in PAM. This test used a 250 mL graduated cylinder with a proppant loading of 4 lb/gal with a 20/40 mesh. Proppant was blended with the crosslinked PAM using a blender for 10-30 seconds until well mixed. The downward mobility was measured as a function of time. [0000] Sample Correla- Fluid tion to Initial Final containing Viscosity height height Sand suspended Table in Time of sand of sand height proppant Example 1 Type (hours) (mL) (mL) (%) (%) 2 DPAM 0.5 100 100 0 100 17 100 100 0.00 100.00 3 DPAM 0.5 100 100 0 100 17 100 80 20.00 80.00 14 EPAM 0.5 100 100 0 100 17 100 100 0.00 100.00 15 EPAM 0.5 100 100 0 100 17 100 100 0.00 100.00 8 HYPAM 0.5 100 100 0 100 17 100 100 0.00 100.00 9 HYPAM 0.5 100 100 0 100 17 100 100 0.00 100.00 Guar 0.5 100 100 0 100 17 100 100 67 33 [0089] The results of this analysis demonstrate the ability of proppant to remain suspended in the polymer fluid.

Gel compositions comprising an acrylamide polymer or copolymer crosslinked with dialdehyde, methods to produce the gel compositions, welibore treatment fluids comprising the gel compositions, and methods of treating a well bore comprising injecting the gel compositions, are provided. In the drilling, completion, and stimulation of oil and gas wells, well treatment fluids are often pumped into well bore holes under high pressure and at high flow rates causing the rock formation surrounding the well bore to fracture.

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application Ser. No. 61/170,181, filed on Apr. 17, 2009, which is herein incorporated by reference in its entirety. FIELD OF THE INVENTION The present invention relates generally to battery systems and, more particularly, to an intelligent battery system for powering mobile workstations. BACKGROUND OF THE INVENTION Mobile computer workstations are desirable in numerous settings to make computer use more convenient and to make computers more accessible. For example, mobile workstations in the form of mobile medical carts are used in hospitals so that nurses and technicians may continually update patient information and treatment information from a variety of locations. In the hospital setting, for example, mobile workstations or mobile medical carts allow nurses to input changes in patient treatment or otherwise dispense patient care throughout the hospital environment while they are making their rounds. Powering such mobile workstations, however, has proven troublesome. As will be readily appreciated, it is undesirable to plug such workstations into a standard wall outlet, as power will be interrupted when moving from room to room or patient to patient. Battery powered systems have attempted to solve this problem, however, even known battery powered systems have objectionable shortcomings. For example, known battery-powered workstations provide a fixed battery system, mounted underneath the cart/workstation, having a single cell chemistry battery and charging technology. Such systems use a single battery and a “bucket” concept to swap out the single battery. These known batteries for powering mobile workstations, however, are difficult to replace when spent. Moreover, existing systems make it is necessary to interrupt power to the cart when changing such batteries, therefore interrupting work flow and potentially resulting in the loss of data. In view of the problems associated with known mobile workstations and systems for powering mobile workstations, there is a need for an improved battery system and, more particularly, for an intelligent battery system for powering mobile workstations wherein batteries may be swapped out without interrupting power to the workstation. SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an intelligent battery system. It is another object of the present invention to provide an intelligent battery system for powering mobile workstations. It is another object of the present invention to provide an intelligent battery system for powering mobile workstations wherein spent batteries may be swapped out without interrupting power to the workstation. It is another object of the present invention to provide an intelligent battery system for powering mobile workstations that prevents batteries from being accidentally removed from the workstation. It is another object of the present invention to provide an intelligent battery system that is capable of maintaining power even if the main batteries are spent or accidentally removed from the workstation. It is another object of the present invention to provide an intelligent battery system that is capable of warning a user of the system of impending low battery capacity. It is yet another object of the present invention to provide an intelligent battery system that is capable of running multiple batteries in parallel to simultaneously power the workstation. It is another object of the present invention to provide an intelligent battery system that is capable of determining and displaying percent capacity and/or remaining run time of a battery or batteries. It is another object of the present invention to provide an intelligent battery system that regulates voltage output to the mobile workstation. It is another object of the present invention to provide an intelligent battery system and battery charger that can accommodate batteries with various cell chemistries. It is another object of the present invention to provide an intelligent battery system that has low voltage shutdown capability. It is another object of the present invention to provide an intelligent battery system and hot-swap device that can be retrofit on numerous existing medical cart applications. It is therefore a general object of the present invention to provide an intelligent battery system for powering mobile workstations, wherein batteries may be swapped out without interrupting power to the workstation, comprising two snap-on battery interface brackets for accommodating two hot-swap batteries, a main hot-swap battery and a secondary hot-swap battery, and a third snap-on bracket to hold a spare battery. The battery system further comprises an integrated circuit and microprocessor to regulate voltage output and for providing battery parameter information such as percent capacity and/or remaining run time. The spare battery includes an integrated circuit for detecting the removal of either or both hot-swap batteries, for detecting when either or both hot-swap batteries are low in capacity and for providing backup power. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: FIG. 1 is a perspective view of an intelligent battery system and hot-swap device mounted on a medical workstation in accordance with one embodiment of the present invention; FIG. 2 is an enlarged perspective view of a hot-swap device without the batteries in accordance with one embodiment of the present invention; FIG. 3 is an enlarged perspective view of the hot-swap device of FIG. 2 with the batteries attached thereto in accordance with one embodiment of the present invention; FIG. 4 is an enlarged perspective view of a hot-swap device with alternative batteries attached thereto in accordance with another embodiment of the present invention; FIG. 5 is a perspective view of an intelligent battery system and the hot-swap device of FIG. 4 mounted on a medical workstation in accordance with another embodiment of the present invention; FIG. 6 is a perspective view of a charging station of an intelligent battery system showing the alternative batteries of FIG. 4 in accordance with one embodiment of the present invention; FIGS. 7 and 8 schematically illustrate an exemplary control circuit in accordance with one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to an intelligent battery system 8 for powering mobile workstations. More particularly, and as shown in FIG. 1 , the present invention is a multi-cell battery system that powers an in-hospital mobile medical cart workstation. The wireless workstation is typically utilized by nurses to dispense patient care throughout a hospital environment. Preferably the battery system may be used with NiMH, Li-Ion, NiCad, SLA and Li-Poly batteries, although batteries with any battery chemistry known in the art may be used with the present system. As best shown in FIG. 2 , the intelligent battery system of the present invention includes a “hot-swap” device 10 that is mounted to the side of a medical cart or other mobile workstation 12 . As used herein, “hot-swap” refers to a system/device that allows a user to swap batteries in or out of the device without interrupting power to the workstation. The device 10 includes two snap-on battery interface brackets 14 , 16 for releasably attaching two hot-swap batteries, a main hot-swap battery 18 and a secondary hot-swap battery 20 , and a third snap-on bracket 22 for releasably attaching a spare battery 24 in the event that one or both of the hot-swap batteries 18 , 20 are spent and need replacement. This configuration allows a user to perform a fresh battery change at the earliest convenience without interrupting power to the mobile workstation 12 and without having to immediately return to a designated battery charging station in some remote location. The battery interface brackets 14 , 18 , 22 are preferably of the Anton/Bauer Gold Mount® type, although any type of bracket assembly may be used. The Gold Mount® bracket is substantially rectangular in shape and is formed with a plurality of keyholes cut in a front surface thereof, each keyhole having an elongated ovoid or elliptical opening and a narrow depending slot. The keyholes include two upper slots and a centrally located lower slot disposed in a substantially triangular array for releasably attaching each battery. Formed between the two upper keyholes is a connector block having a pair of banana plug terminals for placing each battery in electrical communication with the system. The connector block and its operation are described in detail in U.S. Pat. Nos. 6,247,962 and 4,822,296, which are hereby incorporated by reference. In the preferred embodiment, the third snap-on spare battery bracket 22 is configured with an integrated circuit that enables the user to replace the spent hot-swap batteries 18 , 20 while the spare battery 24 and circuit automatically backs up the system. The spare battery circuitry is configured to detect the removal of either or both hot-swap batteries 18 , 20 from the snap-on interface brackets 14 and provide backup power during the exchange. The spare battery circuitry is also capable of detecting when either or both hot-swap batteries 18 , 20 are low in capacity and is configured to prompt the spare battery 24 to provide backup power when necessary. The two hot-swap batteries 18 , 20 are also configured with an Analog Fuel Gauge in electrical communication with the spare battery circuitry. The Analog Fuel Gauge reading emanating from the two hot-swap batteries 18 , 20 is utilized by the spare battery circuitry to determine low battery pack capacity and/or when one of the two battery packs 18 , 20 are removed from the system. The spare battery circuitry further has the ability to provide an alert to warn of impending low spare battery capacity. Preferably, the alert will be a visual alert in the form of a LED indicator, although other alerts such as audio alerts may also be incorporated into the hot-swap device 10 . The snap-on battery interface brackets 14 may also include a locking device 26 to prevent accidental removal of both batteries simultaneously, thus interrupting power to the workstation 12 . In yet another embodiment of the present invention, the hot-swap bracket contains an integrated circuit that is capable of combining the outputs of batteries 18 , 20 together, thus allowing both hot-swap batteries 18 , 20 to be used in either parallel or series, to power the workstation simultaneously. Fresh batteries may be swapped in or out without interrupting power to the workstation 12 . Preferably, the device further contains a software adjustable voltage regulator circuit, including either a linear regulator or DC/DC converter, that provides a predetermined optimal voltage output depending upon the specific requirements of a particular workstation and associated equipment. In the preferred embodiment, the voltage regulator circuit provides a maximum required 15.5Vdc. The regulator prevents over-voltage conditions due to hot-off-charge battery packs, i.e., battery packs that have just been charged and are at full charge. Without the regulator, hot-off-charge battery packs can reach upwards of 18Vdc open circuit and create operational problems for certain pieces of workstation or medical cart equipment. In another embodiment, the regulated output voltage can be adjusted to provide the voltage requirements for other workstations, medical carts, or other applications. Additionally, an inverter can be added to the device to provide 120/240VAC for AC operated medical carts or workstations. In the preferred embodiment, the device also contains a microprocessor control circuit that communicates with both hot-swap batteries 18 , 20 according to a particular protocol to monitor battery parameters. This communications protocol provides combined fuel gauging information in the form of percent capacity and/or remaining run time in hours and minutes for one or both batteries 18 , 20 . The device also contains an interface with a remote fuel gauge indicator to display percent capacity and/or remaining run time in hours and minutes to a user of the system. Moreover, the software may be modified to report percent capacity and remaining run time to other remote fuel gauges, and can communicate with existing fuel gauge systems. The battery system also includes a separate multi-station battery charger that can handle NiMH, Li-Ion, NiCad, SLA and Li-Poly, and other cell chemistries known in the art. In operation, a user can simply swap out the spent batteries at a designated charging station with fresh batteries from the multi-station charger. All batteries used with the present battery system contain smart battery fuel gauging circuitry that provides on-board LCD indicators of both percent capacity and remaining run time, i.e., real time information regarding battery capacity. Moreover, all batteries used with the present battery system contain a smart battery Analog Fuel Gauge (AFG) circuit that provides an on-board 0-5Vdc representation of percent capacity. The batteries used with the present intelligent battery system also contain competitor lock-out circuitry to prevent possible unsafe charging conditions resulting from differences in battery chemistries. Moreover, in the preferred embodiment, the batteries also contain over-current and thermal protection against end user abuse or workstation or medical cart equipment malfunction. Preferably, the batteries and integrated circuits of the intelligent battery system provide a low voltage shutdown capability to prevent the over discharge of battery packs, thereby eliminating unrecoverable battery failure due to cell reversal. Indeed, if it is detected that battery capacity has reached a predetermined/set lower limit, the batter may be automatically shut down to avoid battery failure. Turning now to FIGS. 7 and 8 , an exemplary control circuit capable of carrying out the advantages and features of the present invention, as discussed above, is shown. As will be readily appreciated by those of ordinary skill in the art, alterations in the configuration of the circuitry shown in FIGS. 7 and 8 are certainly possible without departing from the broader aspects of the present invention. Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of this disclosure.

An intelligent battery system for powering a mobile workstation includes a mounting block having a first battery interface bracket for the releasable attachment of a first battery, a second battery interface bracket for the releasable attachment of a second battery and a third battery interface bracket for the releasable attachment of a backup battery, and a power control circuit functionally integrated with the mounting block and being capable of detecting a change in status of at least one of the first and second batteries and routing the flow of electrical power from the first, second and backup batteries in dependence thereon.

BACKGROUND OF THE INVENTION The invention relates to a multi-function time delay relay with functions which can be changed from the outside. In a known multi-function time delay relay of the above-mentioned kind, a series of terminals are provided at the housing of the relay which make it possible, by changing jumpers or by rewiring the control lines to other terminals, to change the relay to four different functions: delayed make, delayed break, self-wiping make and cycling. This means that changes must be made at the terminals before the relay is placed into operation (Multi-function Relay TRZEU of the firm Metzenauer & Jung, Catalog Sheet W 2934/79). It is an object of the present invention to improve a multi-function time delay relay of the above-mentioned type in such a manner that it is possible to change the timing function in a simple manner from any point and at any time, i.e., even while the multi-function relay is running. SUMMARY OF THE INVENTION In a multi-function relay of the above-mentioned type this is achieved in a simple manner by implementing the delay function with an electronic timer which can be started, stopped and reset, preceded by a logic network with two inputs which, to obtain different modes of operation of the timer, can be supplied with voltage individually, separately and/or jointly at any desired point in time. It has been found to be advantageous if the timer is a programmable timing oscillator with a start (power-on) input, a output which changes the signal at the end of the cycle, a stop and resetting input as well as with an inverting input for the signal at the output. Such programmable timers are commercially available, for instance, from the firm Motorola under the designation MC 14541B. Their operation is described in the data sheets for the programmable timer MC 14541B, pages 9-538 to 9-543 published by Motorola. A particularly simple type of logic circuit for use with the timer is obtained by using a logic network which includes AND, OR and inverting stages and a flipflop. A simple design of the multi-function time delay relay with respect to circuitry is obtained if the voltage of the one input is applied to a first inverter, to the one input of each of two AND stages and the one input of a first OR stage. The voltage of the other input is fed to a second inverter stage, to the second input of the first AND stage and the first OR stage as well as to a first dynamic input of a flipflop. The output of the second inverter is connected to the second input of the second AND stage, the output of which is connected to the resetting input of the flipflop. The output of the first inverter is coupled to the first input of a third AND stage, the second input of which is connected to the second output of the flipflop. The output of the first AND stage is connected to the set input as well as to the second dynamic input of the flipflop and to the first input of a second OR stage, the output of which forms the control output of the time delay relay. The second input of the second OR stage is connected to the output of the programmable timing oscillator. The output of the third AND stage is connected to the inverting input of the programmable timing oscillator, the output of the first OR stage to the start input, and the first output of the flipflop to the stop and reset input of the programmable timing oscillator. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 7 show different level diagrams corresponding to the expected function of the time delay relay. FIGS. 8 to 10 illustrate specific applications of the time delay relay according to the present invention without auxiliary contacts. FIGS. 11 to 13 illustrate specific applications of the timing relay according to the present invention with auxiliary contacts. FIG. 14 shows a conventional application with auxiliary contacts and self-wiping make function. DETAILED DESCRIPTION The heart of the time delay relay according to the present invention is the timer, in the illustrated embodiment, the programmable timer 1. It has a start-up (power-on) input which is designated as U B and is also called Autoreset (AR). It is coupled to the supply voltage of the module. The running cycle is thereby started at T=0 as soon as a positive signal is supplied to the start-up input U B . The output Q of the oscillator changes its polarity at the end of the running cycle. The stop and reset input (MR), also called Master Reset, stops the cycle if a positive signal is present at this input. In addition, the counter is reset. The input designated Q S is an inverting input. During the running time, the output Q has, for instance, an L signal; after the end of the cycle is reached, the L signal changes to an H signal provided that a negative potential, i.e., L signal is present at the inverting input Q S . The output polarity is inverted whenever an H signal is present at the inverting input Q S . The network for addressing the programmable timing oscillator 1 consists, as shown in FIGS. 1 to 7, of two inverters I 1 and I 2 , three AND stages U 1 to U 3 , two OR stages O 1 and O 2 , and a flipflop FF. The flipflop has a first dynamic input C 1 which reacts to an edge rising toward H; a second input C 2 which reacts to an edge falling toward L; two oppositely polarized outputs Q 1 and Q 2 ; a set input S and a reset input R. The line voltage terminals are designated as A 1 and B 1 . The common other pole for the two voltages is designated as A 2 . The electrical combination of the individual AND, OR and inverter stages, and the flipflop with the programmable timing oscillator with each other can be seen from FIGS. 1 to 7 without further explanation. The level diagrams of FIGS. 1-7 show the signals at individual points depending on the manner of operation. FIG. 1 shows the level plan for pick-up delay. Here, voltage is applied to A 1 during the running time. The output Q of the timer 1 and the control output St are inactive. However, an H signal is present at the start input U B , so that the output signal changes when the end of the cycle is reached; the time delay relay switches with a delayed pickup as can be seen from the level plan of FIG. 2. There, voltage continues to be present at A 1 , and an H signal at the output Q and at the control output St, so that the switching member of the time delay relay itself, not shown here, can be activated thereby. FIGS. 3 to 6 represent the drop back delay. In FIG. 3, voltage is applied to B 1 . The output Q 1 of the flipflop FF is set by C 1 and blocks the timing oscillator via the stop and reset input MR. The control output St as well as the output Q of the timing oscillator 1 carry an L signal. If A 1 is not added on, see FIG. 4, the timing cycle, i.e., the output Q of the timing oscillator, remains blocked; the control output St becomes active via the AND gate U 1 and the OR gate O 2 2 , i.e., the time delay relay is switched. This case would correspond to the so-called immediate switching mode during the function "drop-out delay." If the voltage is now removed again from A 1 and voltage remains at B 1 , the outputs Q 1 and Q 2 of the flipflop FF are inverted by C 2 . The stop and reset input MR releases the timing oscillator 1 and the timing cycle runs. The control output remains active via the AND gate U 3 , the inverting input Q 2 , the output Q of the timing oscillator and the OR stage 2, see FIG. 5. When the return time is reached, the output Q of the timing oscillator 1 goes to an L signal; the control output is thereby made inactive and the time delay relay is switched off. This can be seen from the levels in FIG. 5. Simultaneous inversion of the inputs A 1 and B 1 would be an unintended control process which, however, can occur accidentally. A 1 changes from zero to the nominal voltage and B 1 , from the nominal voltage to zero. This corresponds to the start of the response delay, as can be seen from FIG. 1. If A 1 changes from the line voltage to zero and B 1 from zero to line voltage, the dynamic inputs C 1 and C 2 of the flipflop FF are addressed simultaneously by the proper edges. This case can be seen in FIG. 7. Depending on whether simultaneity is briefly interrupting or briefly overlapping, either the case "auxiliary voltage addition" according to FIG. 3 or the case "start drop-back delay" according to FIG. 5 will occur. In inverting, care must therefore be taken that an unambiguous pause or an unambiguous overlap is provided. The specified pick-up delay or drop-back delay can be realized with a relay circuit as shown in FIGS. 8 and 9. In the case of pick-up delay, only the control contacts of FIG. 8 must be closed, i.e., the auxiliary switch SH can be omitted since voltage must be applied only to A 1 . In the case of a drop-out delay as shown in FIG. 9, voltage is also continuously applied to B 1 , i.e. the auxiliary switch SH is closed and the control contacts S merely connect A 1 to the line. FIG. 10 shows a possible circuit for immediate switching or connecting through. As soon as voltage is applied to A 1 and B 1 , simultaneously or in any sequence shifted in time, the output Q of the flipflop FF is set via the AND gate U 1 , which blocks the timing oscillator. At the same time, the control output becomes active via U 1 and the OR gate O 2 . The relay pulls up or remains pulled up, (see the level plan of FIG. 4). The following cases can be distinguished here: If voltage is applied simultaneously to A 1 and B 1 , i.e., the switch SH of FIG. 10, is closed, and the control contact S is actuated later, the relay switch is switched immediately. If B 1 is switched on to A 1 after the end of the cycle, i.e., if SH is closed after S, the relay remains energized. If B 1 is added to A 1 during the running time, the running cycle is shortened. If on the other hand A 1 is added to B 1 after the return time (which is not possible with the circuit arrangement according to FIG. 10), the relay is switched on. If A 1 is switched on in addition to B 1 during the running time, the return time is broken off. If A 1 and B 1 are without voltage, the relay drops off and the timing oscillator stops. Here also, the following possibilities can be distinguished again: No voltage at B 1 and after the end of the cycle, the voltage is removed from A 1 , i.e., the relay drops off. B 1 again has no voltage and the voltage is removed from A 1 during the running time, i.e., the cycle is broken off. If however, A 1 has no voltage and the voltage is removed from B 1 after the return time, the relay remains dropped off. If A 1 has no voltage and the voltage is removed from B 1 during the return time, the return time is shortened. It can be said in summary that, regardless in what state the relay operates, during the running time or after the end of the cycle, and independently of whether the relay operates with a response delay or with a delayed drop-out: if A 1 and B 1 are energized, the relay is switched on and the running cycle stops and, if A 1 and B 1 are de-energized, the relay is switched off and the running time is reset. As has been demonstrated, the timing function can be changed by appropriate addressing regardless of the function phase then running. Thereby, timing functions such as make or break wiping, blinking and pick-up and drop-out delay can be realized in addition to pick-up delay, drop-out delay and immediate switching. Break wiping is shown by way of example in FIG. 11. The auxiliary switch SH is closed and the control contact S is connected in the circuit B 1 , i.e., A 1 and B 1 carry voltage. The break contact of the relay is open, because the switching state according to FIG. 4 is present. If B 1 is de-energized, this corresponds to the level plan of FIG. 1, i.e., delayed pick-up; the relay drops off and pulls up again after the end of the cycle. The break contact acts like a break wiper. FIG. 12 shows pick-up and drop-back delay. If the make contact of the relay is used to connect the control input B 1 to the control voltage (this also can be accomplished via an auxiliary switch SH), the timing function "pick-up and drop-back delay" is obtained, as can be seen from the FIGS. 1, 4 and 5. The make contact is not without potential, however. By including an auxiliary relay R, the timing function "blinking" can be realized as indicated in FIG. 13. The operation is in principle similar to pick-up and drop-back delay except that the return time follows the running time immediately. The auxiliary contact r of the auxiliary relay R controls the blinking cycle automatically. FIG. 14 merely shows that the function "make wiping" can also be carried out with the relay according to the present invention without difficulties, as with conventional response delay relays. The explanations above show that it is possible with the time delay relay according to the present invention to realize, merely by addressing two control inputs, the most important timing functions described above at any time and in any sequence, i.e., even during a running cycle and with remote control. It is possible with the time delay relay according to the present invention to automatically switch timing functions without causing illogical reactions. The timing functions are switched automatically at installations: normal (without auxiliary voltage)=pick-up delayed and with auxiliary voltage=drop-out delayed. Additional adjusting means such as switches, plugs or terminals are unnecessary. The large number of attainable functions is listed in principle in the following function table. The arrow shown there next to the voltage U is to indicate either the addition or removal of the voltage. The central part of the table under "Comments" indicates which function phase is present, and under "level diagram" a reference is made to the corresponding figure, if shown. ______________________________________ LevelA.sub.1 B.sub.1 Comments Diag.______________________________________Pickup U↑ O Start, pick-up delay (AV) FIG. 1Delay U O during the running time (AV) FIG. 1 U O after end of cycle FIG. 2Drop-out O U↑ Addition of auxiliary voltage FIG. 3Delay U↑ U Excitation of drop-back delay FIG. 4 U↓ U Start drop-back delay FIG. 5 O U during the running time (RV) FIG. 5 O U after the return time FIG. 6Immediate U↑ U↑ Immediate switching FIG. 4Switching U U↑ after the end of cycle FIG. 4 U U↑ during the running time (AV) FIG. 4 U↑ U after the return time (Av) FIG. 4 U↑ U during the running time (RV) FIG. 4Immediate U↓ O after end of cycle,-Drop-out U↓ O during the running time (AV),- O U↓ after the return time,- O U↓ during the running time (RV),-Other U U↓ Start, make wiping FIG. 1 U↑ U↓ Start, pick-up delay FIG. 1 U↓ U↑ indifferent, leads to addition FIG. 7 of auxiliary voltage or start, FIG. 3 drop-back delay. FIG. 5______________________________________

A multi-function time delay relay, with functions which can be changed from the outside, includes a timing oscillator and a logic network consisting of AND and OR stages and inverter stages as well as a flipflop interconnected in such a manner that two voltage inputs applied individually, separately or jointly, can bring about different modes of operation of the timing oscillator making it possible to realize different timing functions at any time and in any sequence, even during a running cycle, without having to intervene at the relay itself.

TECHNICAL FIELD This invention relates to reciprocating piston machines, such as internal combustion engines, and to crankshafts for such machines, engines and the like. In a preferred embodiment, the invention relates to multiple throw crankshafts for engines and in combination therewith. BACKGROUND In U.S. Pat. No. 2,103,185 Rumpler, issued Dec. 21, 1937, it is proposed to form a hollow engine crankshaft with progressively increasing wall thickness toward the output end in order to accommodate the accumulative gas forces transmitted by the journals, crankpins and crankarms as the output end is approached. While such a crankshaft design may be appropriate for some engine configurations, the patent's teachings apparently fail to consider that a crankshaft has finite stiffness and will have resonant frequencies excited by the firing loads and/or the engine speed. The absence of concern for torsional vibration in Rumpler's patent is a reflection of the typically lower maximum speed of engines in 1937. The loads caused by torsional vibration of todays high speed engines, commonly operating in the neighborhood of 7-8,000 RPM, must be accounted for in the design in addition to the gas forces. SUMMARY OF THE INVENTION The present invention provides an improved crankshaft construction which, in combination with its connected components, approaches, more closely than conventional designs, a maximum torsional frequency with minimum vibration amplitudes and torsional stress under its design operating conditions. To provide a finished crankshaft design according to the invention requires analysis of the crankshaft system in accordance with known methods of vibration analysis. This analysis is based on the torsional stiffness and inertia characteristics of the entire crankshaft. This information is used in combination with the operating load data (i.e., engine RPM and cylinder pressure data) to determine the vibratory response of the system. The critical pieces of information determined in this analysis are the resonant frequencies, amplitudes of vibration, and the torsional stresses. The torsional stiffness and mass/inertia of the crankarms are varied above the minimum values required for delivering the maximum driving torques applied to the crankarms during operation. The intent is to provide a maximum stiffness near the nodal point of the first resonant mode of the crankshaft system (the nodal point is the position of zero torsional deflection) and then reduce the stiffness and inertia/mass of the other crankarms in relation to their distance from the nodal point. In this manner, inertia torques are minimized and therefore vibration amplitudes and stresses are minimized while increasing the resonant frequencies as compared to conventional designs in which the crankarms all have equal torsional stiffness and inertia/mass. In a practical application of the invention, it may be desirable, for design and manufacturing simplification, to approximate the ideal design by limiting the differences in the crankarms. Thus, it is possible, for example, to make of equal size and torsional strength, pairs of crankarms on either side of each main journal, or both crankarms of each crankthrow, while varying the torsional strengths of the pairs of crankarms generally in proportion to their distances from the vibration node, or nodal point. These and other features, modifications and advantages of the invention will be more fully understood from the following description of a preferred embodiment, taken together with the accompanying drawings. BRIEF DRAWING DESCRIPTION In the drawings: FIG. 1 is a cross-sectional view of an internal combustion engine having a low resonance crankshaft formed in accordance with the invention; FIG. 2 is a side view of the crankshaft having superimposed thereon a mode shape diagram of the crankshaft torsional vibration amplitudes as connected in the engine assembly and operated at a maximum torsional vibration operating condition; and FIGS. 3-10 are transverse cross-sectional views through the crankshaft at the locations indicated by the lines 3--3 to 10--10 respectively of FIG. 2 and showing the configurations of the various crankarms. DETAILED DESCRIPTION Referring now to the drawings in detail, numeral 10 generally indicates a four-stroke cycle four cylinder automotive-type internal combustion engine intended for use in automobiles or the like. Engine 10 includes the usual engine cylinder block 11 having a plurality of cylinders 12 aligned in a single bank and closed at their ends by a cylinder head 14. The block 11 also defines a crankcase having an open bottom that is conventionally closed by an oil pan 15. Rotatably carried in the crankcase portion of the engine block 11 is a crankshaft 16 formed in accordance with the invention. The crankshaft includes five main journals 18-22 supported in axially spaced and aligned main bearing webs 24 of the engine block. Between the adjacent pairs of journals are radially offset crankpins 25-28, each supported by a pair of crankarms. From front to rear the crankarms are indicated by numerals 31-38. In addition, the crankshaft includes a front end stub 42 and a rear end flange 43. As is conventional, the crankpins 25-28 connect through connecting rods 44 with pistons 46 reciprocably movable in the cylinders 12. In assembly in the engine, a flywheel 47 is attached to the flange 43 at the rear of the crankshaft for connection with a clutch, the torque converter of an automatic transmission or other associated output means. At the front end, an oil pump drive gear 48 and a camshaft and accessory drive 50 are mounted on the stub 42. In order to minimize the torsional vibration stress and deflection that occur in the crankshaft during engine operation, the invention provides for the selective sizing of the individual crankarms to obtain the minimum mass and optimum stiffness needed to withstand the combination of torsional vibration and other forces that occur at their respective locations. The design process first requires selection of the major crankshaft characteristics, including main and crankpin dimensions and spacing and the selection of nominal crankarm dimensions to provide a first approximation of a crankshaft design adequate to withstand the calculated driving torque pulses. There follows a torsional vibration analysis of the crankshaft as assembled with its associated pistons, accessory drive, flywheel and other components that are to be fixedly attached to or driven by the crankshaft. The analysis determines the vibration node or zero point of angular deflection in the system in the torsional vibration mode or modes of interest in the engine operating speed range. The angular deflection is then reduced by substantially stiffening the crankarms near the node while increasing less, or even reducing, the stiffness (and mass) of the other crankarms in approximate proportion to their distances from the node. This requires an iterative process of adjusting the stiffness and inertia/mass of the crankarms and then recalculating the torsional vibration characteristics until an overall maximum torsional natural frequency, giving a minimum angular deflection of the crankshaft, is reached, or is approached to a degree considered satisfactory to the crankshaft designer. This process requires recognition that, as the axial distance from the node increases, the crankarms will generate increasing inertia torques. Therefor, it is desirable to make the crankarms near the node as stiff as possible to minimize the angular deflection which occurs there. On the other hand, substantial reductions in the inertia/mass of the crankarms at the greatest distances from the node, or nodal point, will result in the most significant reductions in the maximum angular deflection. This effect may more than offset the resulting reductions in stiffness of the distal crankarms, although, of necessity, they must remain sufficiently stiff to accept the maximum torque loadings imposed on them by the pistons in the normal operation of the engine. The results of applying the described method to the crankshaft 16 described herein are seen in the side view and mode shape diagram of FIG. 2 and the cross-sectional views of FIGS. 3-10, in which the background throws have been omitted for clarity. In FIG. 2, the mode shape diagram indicates, by the distance from the crankshaft axis 51 of a dashed line 52, the relative angular deflection, in degrees double amplitude (DDA), of the adjacent crankshaft portions (in the same normal plane) at the resonant operating speed. The node 54, or nodal point, is where the line 52 crosses the axis 51, indicating that the angular deflection is zero at that point. In the crankshaft development, design and manufacturing simplicity were served by utilizing identical crankarm configurations for the pairs of crankarms on either side of the interior main journals 19-21. Thus, FIGS. 3 and 4, showing the configurations of crankarms 32 and 33, respectively, on opposite sides of main journal 19, indicate identical crankarm shapes of relatively narrow width (i.e. laterally in a plane normal to the axis 51), giving relatively low inertia/mass (and stiffness in view of their location at a relatively great distance from the node 54. FIG. 5 shows the front crankarm 31, at the furthest distance from the node 54, also has the narrowest width and the lowest inertia/mass and stiffness of all the crankarms. At this location, a crankshaft counterweight 55 is also located, extending oppositely from the crankarm 31. FIGS. 6 and 7 illustrate the crankarms 34, 35 and associated counterweights 56, 57 disposed on opposite sides of the center main journal 20. The crankarms of this pair are of substantially greater width, mass and stiffness in view of their closer location to the node 54 than narrow crankarms 32, 33. FIGS. 8 and 9 illustrate the pair of crankarms 36, 37 disposed on either side of main journal 21. Both of these crankarms are of near maximum stiffness as indicated by their greater width, since their locations are at or near the node 54. However, the shape of crankarm 36 differs further since it also incorporates a reluctor ring 58 for use as a timing wheel during engine operation. In view of the extra mass added to the crankshaft by this ring, it is desirably located at a point as near to the node as practical, hence the incorporation into crankarm 36. It should be apparent that crankarm 37 would be an even better location, if permitted by other features of the engine. FIG. 10 shows the configuration of the rear end crankarm 38 together with the associated rear counterweight 59. By virtue of its position very near to the node 54, crankarm 38 is of a relatively great width, mass and stiffness similar to that of the crankarm 36. In the crankshaft embodiment shown, it is apparent that the masses and stiffnesses of the various crankarms have been varied primarily by varying their lateral widths. However, it should be understood that other forms of construction, such as variations in longitudinal thickness or hollowed portions, could be utilized for varying the masses and stiffnesses of the crankarms without departing from the scope of the invention. Thus, while the invention has been described by reference to one illustrated embodiment, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly it is intended that the invention not be limited to the illustrated embodiment, but that it have the full scope permitted by the language of the following claims.

A low vibration crankshaft has crankarms of decreasing inertia/mass and stiffness as their distance torsional vibration node of the rotating vibration system increases. The mass and stiffness of the crankarms may be varied by changing the lateral width of the arms or by other means. The arrangement provides, in combination with an engine or other reciprocating piston machine, an increased or maximized torsional vibration resonant frequency and resulting lower or minimized angular deflections of the crankshaft in the condition of system resonance.

This is a continuation of application Ser. No. 07/672,020, filed Mar. 19, 1991, now abandoned. FIELD OF THE INVENTION This invention relates to aminoalcohols and their derivatives as penetration-enhancers for pharmaceutical, agricultural and cosmetic agents. BACKGROUND OF THE INVENTION Many physiologically active agents are best applied topically to obtain desirable results. Topical application, in the form of creams, lotions, gels, solutions, etc., largely avoids side effects of the agents and permits high level concentrations of the agents. Some therapeutic drugs may also be administered for systemic use through the skin or other body membranes including intranasal and intravaginal application of humans and other animals, utilizing a transdermal device or formulated in a suppository or aerosol spray. For some years, pharmaceutical researchers have sought an effective means of introducing drugs into the bloodstream by applying them to the unbroken skin. Among other advantages, such administration can provide a comfortable, convenient and safe way of giving many drugs now taken orally or infused into veins or injected intramuscularly. Using skin as the portal for drug entry offers unique potential, because transdermal delivery permits close control over drug absorption. For example, it avoids factors that can cause unpredictable absorption from gastrointestinal tract, including changes in acidity, motility, and food content. It also avoids initial metabolism of the drug by the liver known as the first pass effect. Thus, controlled drug entry through skin can achieve a high degree of control over blood concentrations of drug. Close control over drug concentration in blood can translate readily into safer and more comfortable treatment. When a drug's adverse effects occur at higher concentrations than its beneficial ones, rate control can maintain the concentration that evoke only--or principally the drug's desired actions. This ability to lessen undesired drug actions can greatly reduce the toxicity hazards that now restrict or prevent the use of many valuable agents. Transdermal delivery particularly benefits patients with chronic disease. Many such patients have difficulty following regimens requiring several doses daily of medications that repeatedly cause unpleasant symptoms. They find the same drugs much more acceptable when administered in transdermal system that require application infrequently--in some cases, only once or twice weekly and reduce adverse effects. Transdermal delivery is feasible for drugs effective in amounts that can pass through the skin area and that are substantially free of localized irritating or allergic effects. While these limitations may exclude some agents, many others remain eligible for transdermal delivery. Moreover, their numbers will expand as pharmaceutical agents of greater potency are developed. Particularly suitable for transdermal delivery are potent drugs with only a narrow spread between their toxic and safe blood concentrations, those having gastrointestinal absorption problems, those susceptible to a higher first pass liver metabolism or those requiring frequent dosing in oral or injectable form. Transdermal therapy permits much wider use of natural substances such as hormones. Often the survival times of these substances in the body are so short that they would have to be taken many times daily in ordinary dosage forms. Continuous transdermal delivery provides a practical way of giving them, and one that can mimic the body's own patterns of secretion. At present, controlled transdermal therapy appears feasible for many drugs used for a wide variety of ailments including, but not limited to, circulatory problems, hormone deficiency, respiratory ailments, and pain relief. Percutaneous administration can have the advantage of permitting continuous administration of drug to the circulation over prolonged periods of time to obtain a uniform delivery rate and blood level of drug. Commencement and termination of drug therapy are initiated by the application and removal of the dosing devices from the skin. Uncertainties of administration through the gastrointestinal tract and the inconvenience of administration by injection are eliminated. Since a high concentration of drug never enters the body, problems of pulse entry are overcome and metabolic half-life is not a factor of controlling importance. The greatest problems in applying physiologically active agents topically or transdermally is that the skin is an effective barrier to penetration. The epidermis of the skin has an exterior layer of dead cells called the stratum corneum which is tightly compacted and oily and which provides an effective barrier against gaseous, solid or liquid chemical agents, whether used alone or in water or in oil solutions. If a physiologically active agent penetrates the stratum corneum, it can readily pass through the basal layer of the epidermis and into the dermis. Although the effectiveness of the stratum corneum as a barrier provides great protection, it also frustrates efforts to apply beneficial agents directly to local areas of the body. The inability of physiologically active agents to penetrate the stratum corneum prevents their effective use of treating such conditions as inflammation, acne, psoriasis, herpes labialis, herpes genitalis, eczema, infections caused by fungi, viruses and other microorganisms, or or, her disorders or conditions of the skin or mucous membranes or of conditions beneath the exterior surface of the skin or mucous membranes. The stratum corneum also prevents the skin from absorbing and retaining cosmetic-type materials such as sunscreens, perfumes, mosquito repellents and the like. Physiologically active agents may be applied to the locally affected parts of the body in the form of a solution, cream, lotion or gel utilizing the vehicle system described herein. These agents may also be delivered for systemic use utilizing the vehicle system in a transdermal patch. Vehicles such as USP cold cream, ethanol and various ointments, oils, solvents and emulsions have been used heretofore to apply physiologically active ingredients locally. Most such vehicles are not effective to carry significant amounts of physiologically active agents into and through the skin. One such vehicle is dimethyl sulfoxide, which is described in U.S. Pat. No. 3,551,554. My previous inventions disclosed in U.S. Patent Nos. 3,989,816; 3,991,203; 4,122,170; 4,316,893; 4,405,616; 4,415,563; 4,423,040; 4,424,210; 4,444,762; 4,837,026 and 4,876,249 describe a method for enhancing the topical or transdermal administration of physiologically active agents by combining such an agent with an effective amount of a penetration enhancer and applying the combination to skin or other body membranes of humans or animals, in the form of solution, cream, gel, lotion, or a transdermal device. My related U.S. Patent Nos. 4,461,638 and 4,762,549 describe a method for enhancing delivery of plant nutrients and plant growth regulators, and my U.S. Pat. No. 4,525,199 describes an improved method of pest control by enhancing pesticide permeation. My related U.S. application, Ser. No. 218,316, filed on Jul. 12, 1988, describes a method for enhancing topical and transdermal administration of physiologically active agents with membrane penetration enhancers selected from oxazolidone and related heterocyclic compounds. My related U.S. application Set. No. 07/348,387, filed on May 8, 1989 describes a method for enhancing topical and transdermal administration of physiologically active agents with yet another series of membrane penetration enhancers. My related U.S. applications Ser. No. 07/393,584, filed on Aug. 11, 1989 and Set. No. 07/451,124, filed on Dec. 15, 1989, C.I.P.s of U.S. patent application Ser. No. 002,387, filed on Jan. 12, 1987, now U.S. Pat. No. 4,876,249, describe a method for enhancing topical and transdermal administration of physiologically active agents with membrane penetration enhancers selected from heterocyclic compounds containing two heteroatoms. Penetration enhancers for enhancing systemic administration of therapeutic agents transdermally disclosed in the art include dodecyl pyrrolidone, dimethyl lauramide, dimethyl sulfoxide, decyl methyl sulfoxide, ethanol, 1-dodecylhexahydro-2H-azepin-2-one, 1-dodecanoyl hexamethylenimine, 2-nonyl-1,3-dioxolane, fatty acids and their esters, sucrose esters etc. These agents may be used prior to or concurrently with administration of the active agent, see, e.g., U.S. Pat. Nos. 4,031,894; 3,996,934 and 3,921,636. SUMMARY OF THE INVENTION One of the main function of the epidermis is the production of a cohesive, relatively impermeable outer sheath. It has been known that from the time an epidermal cell leaves the basal layer to the time it is desquamated, the cell lipids change both qualitatively and quantitatively. A phospholipid is the most abundant lipid class in basal cell, whereas half of the lipid in a desquamated cell consists of ceramide. The lipid content of desquamated stratum corneum cell is approximately six time that of basal cell. The change in lipid composition of a cell undergoing cornification results mainly from de nuvo synthesis of cholesterol, fatty acid and ceramide. This invention relates to penetranion enhancers closely related to the constituents of the epidermal outer sheath and therefore interact with it without irreversible disruption of the barrier. Moreover, these enhancers possess an advantage that they are expected to yield nontoxic, pharmacologically inert metabolites after passage through the skin and the systemic circulation. The invention further relates to compositions for carrying physiologically active agents through body membranes such as skin and mucosa for retaining these agents in the body tissues and further relates to a method of administering systemically and locally active agents through the skin or other body membranes of humans and animals, utilizing a transdermal device or formulation, containing an effective, non-toxic amount of a membranae penetration enhancer having the structural formula I: ##STR2## wherein: R is selected from H, and an aliphatic hydrocarbon group with from about i to about 20 carbon atoms, optionally containing a heteroatom in the hydrocarbon chain; R1 is selected from H, OH or O-CO-RS, where R5 is an aliphatic hydrocarbon group with from about 1 to about 18 carbon atoms; R2 is selected from H, a lower aliphatic hydrocarbon group, acyl, hydroxyacyl or alkoyloxyacyl group with up to about 40 carbon atoms; R3 is selected from H, an aliphatic hydrocarbon group, with up to about 16 carbon atoms unsubstituted or substituted with hydroxy, acyloxy or alkylthio or an aryl or aralkyl group; and R4 is H or an acyl group with from about 1 to about 18 carbon atoms; or when R1 is OH 1 R1and R4 are combined to form compounds having a 1,3 -dioxane ring, ##STR3## wherein, R6 and R7 are selected from H, an aliphatic hydrocarbon group unsubstituted or substituted with hydroxy, acyloxy, or carboalkoxy, or an aryl group, or they may combine to form a carbonyl group, or a physiologically acceptable salt thereof. It is understood that the aliphatic hydrocarbon groups in the substituents R-R7 may be straight or branched and saturated or unsaturated, such as straight or branched chained alkyl, alkenyl or alkinyl groups. In the substituents where the hydrocarbon group may contain a heteroatom (R), this heteroatom usually is S or O. It will be readily appreciated by those skilled in the art that certain compounds represented by formula I may exhibit optical and geometric isomerism. However, where no designation of isomers is specified with respect to the compounds of this invention, it is to be understood that all possible stereoisomers and geometric isomers (E and Z), and racemic and optically active compounds are included. It will also be readily appreciated by those skilled in the art that certain of the compounds described in the disclosure may form salts with carboxylic and mineral acids and it is understood that all such salts, in particular the physiologically acceptable salts, are included in the invention. In one preferred embodiment of I, R is an alkyl group with from 1 to 20 carbon atoms, R1 and R3 are H, R2 is an acyl group with from 1 to 30 carbon atoms and R4 is an acyl group with from 1 to 18 carbon atoms. In another preferred embodiment of I, R1 is -O-CO-R5, wherein R5 is an alkyl group with from 1 to 18 carbon atoms and R, R2, R3 and R4 are as defined above. Yet in another preferred embodiment of I, R1 is OH, R2 is H or acyl, R3 and R4 are H and R1 and R4 are combined to form a 1,3-dioxane ring and R, R6 and R7 are as defined above. Yet in another preferred embodiment of I, R1 is OH, R2 is H or acyl, R3 is alkyl, aryl, aralkyl, hydroxyalkyl, acyloxyalkyl or alkylthioalkyl, R and R4 are H and R1 and R4 are combined to form a 1,3-dioxane ring, wherein R6 and R7 are as defined above. It has been found that the physiologically active agents are carried through body membranes by the claimed penetration enhancers and are retained in the body tissue when applied topically in form of a cream, gel, or lotion or absorbed systemically when applied in the form of a transdermal device or formulation, for example, as a transdermal patch, a rectal or vagina suppository, as a nasal spray or when incorporated in a vaginal sponge or tampon. This invention also relates to the problems such as skin irritation and skin sensitization that are commonly associated with conventional penetration enhancers found in the prior art. Since the compounds of this invention are structurally closely related to the ceramides, the lipids primarily present in the top layers of the skin, it is believed that skin irritation and skin sensitization can be avoided significantly with the use of these compounds as enhancers in the therapeutic compositions. The invention further relates the penetration enhancers themselves and their method of making. DETAILED DESCRIPTION OF THE INVENTION Typical examples of compounds included in the foregoing formula I of this invention are the following: 1) 2-Ethanoylaminododecyl ethanoate 2) 2-Octanoylaminododecyl octanoate 3) 2-Octadec-9-enoylaminododecyl octadec-9-enoate 4) 2-Octadec-9-enoylaminododecyl ethanoate 5) 2-Octadecanoylaminooctadec-4-enyl-1,3-diethanoate 6) 2-Ethanoylaminooctadec-4-enyl 1,3-diethanoate 7) 2-Ethanoylaminooctadecyl 1,3-diethanoate 8) 5-Amino-2,2-dimethyl-4-(pentadec-1-enyl)-1,3-dioxane 9) 5-Amino-2,2-dimethyl-4-pentadecyl-1,3-dioxane 10) 5-Amino-4-(pentadec-1-enyl)-1,3-dioxan-2-one 11) 5-amino-4-dodecyl-1,3-dioxan-2-one 12) 4-Dodecyl-5-ethanoylamino-1,3-dioxan-2-one 13) 2-Ethanoylaminododecyl octadec-9-enoate 14) 2-Ethanoylamino-3-octadecyloxypropyl ethanoate 15) 5 -Amino-2,2-dimethyl-4-(2,6,10,14 -tetramethylpentadecyl)-1,3-dioxane 16) 5-Amino-2,2-dimethyl-4-(2,6-dimethyl-5-heptenyl)-1,3-dioxane 17) 5-amino-5-ethyl-2-undecyl-1,3-dioxane 18) 5-amino-2,2-dimethyl-5-undecyl-1,3-dioxane 19) 2,2-Dimethyl-5-dodecanoylamino-5-ethyl-1,3-dioxane 20) 5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 21) 5-Amino-5-hydroxymethyl-2-(3-heptyl)-1,3-dioxane 22) 5-Amino-5-ethyl-2-carbobutoxyethyl-2-methyl-1,3-dioxane 23) 5-Dodecanoylamino-5-methyl-1,3-dioxan-2-one 24) 5-Amino-5-undecyl-1,3-dioxan-2-one. The following compounds, encompassed by general formula I of this invention are known in the literature. The 4E,2S,3R isomer of compound 6 is the triacetyl derivative of naturally occurring D-erythro-Sphingosine and has been synthesized by Findeis and Whitesides, J. Org. Chem. 52, 2838 (1987); Julina et. al. Helv. Chim. Acta 69, 368 (1986) and references cited therein; Schmidt and Zimmermann, Tet. Lett. 27, 481 (1986). The 2-octadecanoylamino 2S,3R 1,3-diol derivative of compound 5, a ceramide, has been synthesized by Julina et. al., loc. cit. Compound 7 is the dihydro derivative of compound 6 and the 2S,3R isomer has been prepared by Roush and Adam, J. Org. Chem. 50, 3752 (1985). The E isomer of the 4R,5S stereoisomers of compounds 8 and its corresponding 1-heptadecenyl analog have been synthesized, Hasegawa and Kiso, JPN. Kokai Tokyo Koho JP 62,207,247 [87,207,247], 11 Sep 1987, C.A., 108:P167212 (1988), Hino et. al. J. Chem. Soc. Perkin Trans. I, 1687 (1986) and both E and Z isomers have been prepared by Kiso et. al., Carbohydr. Res. 158, 101 (1986) and J. Carbohydr. Chem. 5, 335 (1986). 4R,5S isomer of Compound 9 have been prepared by Nakagawa et. al., Tet. Lett. 6281 (1987) during the synthesis of Cerebroside B1 b . and Saitoh et. al. Bull. Chem. Soc. Japan, 54, 488 (1981), who also prepared the 4-[(Z)-3pentadecenyl]analog of Compound 8 during the total synthesis of two prosopis alkaloids. Compounds 15 and 16 have been prepared by Umemura and Mori, Agric. Biol. Chem., 46, 1797 (1982) as intermediates in the synthesis of spinghosine analogs. Compound 17 and related 5-amino-1,3-dioxanes have been prepared by Senkus, J. Amer. Chem. Soc. 63, 2635 (1941), ibid., 65, 1656 (1943) and U.S. Pat. Nos. 2,247,256, 2,260,265, 2,370,586, 2,383,622, 2,399,068 and evaluated as coating compounds, as intermediates for the preparation of insecticides and surface active agents and as insecticides, U.S. Pat. No. 2,485,987 and by CIBA Ltd., Fr. 1,457,767, as intermediates in the preparation of isonitriles useful as insecticides, acaricides, ovicides, herbicides, fungicides, bactericides, and molluscicides. Robinette, U.S. Pat. Nos. 2,317,555, 2,320,707 and 2,346,454, has studied the 5-amino-1,3-dioxanes as wetting, penetrating & cleansing agents for various textile and leather treatments. The 2-unsubstituted analog of Compound 19 has been utilized by Tucker, U.S. Patent No. 2,527,078, as an ingredient in detergent mixture for inhibiting the precipitation of lime soaps. Compound 20, 21 and analogs have been prepared and investigated by Senkus for insecticidal properties. Compound 22 has been prepared by Morey, U.S. Pat. No. 2,415,021. Aliphatic substituted 1,3-dioxacycloalkanes, without the prerequisite amino or substituted amino functionality of this invention, have been disclosed as skin penetration enhancers by Samour and Daskalakis, Eur. Pat. Appl. EP 268,460, 25 May 1988 and particularly, 2-nonyl-1,3-dioxolane, Proceed. Intern. Symp. Control Rel. Bioact. Mater. 17, 415 (1990) and references cited therein. To my knowledge the other compounds are novel. The use of the compounds of the present invention as penetration enhancers in drug delivery is, however, novel and not predictable from the prior art. The aminoalcohol derivatives covered by the general formula I may be prepared by any of the processes known in the literature, and are hereby incorporated by reference. For example, Ohashi et. al., Tet. Lett. 29, 1185 (1988); Findeis and Whitesides, J. Org. Chem. 52, 2838 (1987); Nakagawa et. al., Tet. Lett. 6281 (1987); Hino et. al., J. Chem. Soc. Perkin Trans. I, 1687 (1986); Koike et. al., Carbohydr. res. 158, 113 (1986), Kiso et. al., Carbohydr. Res. 158, 101 (1986) and J. Carbohydr. Chem. 5, 335 (1986); Schmidt and Zimmermann, Tet. Lett. 481 (1986); Julina et. al. Helv. Chim. Acta 69, 368 (1986); Roush and Adam, J. Org. Chem. 50, 3752 (1985); Bernet and Vasella, Tet. Lett. 24, 5491 (1983); Chandrakumar and Hajdu, J. Org. Chem. 48, 1197 (1983); Garigipati and Weinreb, J. Amer. Chem. Soc. 105, 4499 (1983); Schmidt and Klaeger, Angew. Chem. Suppl. 393 (1982) and Angew. Chem. Int. Ed. 21, 982 (1982); Umemura and Mori, Agric. Biol. Chem. 46, 1797 (1982); Saitoh et. al., Bull. Chem. Soc. Japan 54, 488 (1981); Newman, J. Amer. Chem. Soc.95, 4098 (1973) and Shapiro et. al., J. Amer. Chem. Soc. 80, 1194 (1958). In addition, the acetal and ketal derivatives of 5-amino-1,3-dioxane can be prepared from the nitro alcohols according to the methods of Senkus mentioned earlier and the corresponding 2-oxo derivatives by processes known for carbonyl group insertion,such as those outlined in my pending U.S. application Ser. No. 218,316, filed on Jul. 12, 1988, followed by hydrogenation of the nitro group. 5-Acylamino-1,3-dioxanes can be easily prepared by acylation of the 5=amino compounds with an appropriate carboxylic acid derivative according to the well established methods in the literature. 5-Amino-1,3-dioxanes with other substituents in 2-position can be prepared by the treatment of the said nitro alcohols with compounds containing a carbonyl group and the desired functionality, for example, with butyl levulinate as outlined by Morey. Other amino alcohols can be prepared as outlined in my pending U.S. application Ser. No. 218,316, filed on Jul. 12, 1988 and derivatized to compounds of formula I. The compounds of the present invention may be used as penetration enhancers in the same manner as described in my U.S. Pat. Nos. 3,989,816; 3,991,203; 4,415,563; 4,122,170; 4,316,893; 4,405,616; 4,415,563; 4,423,040; 4,424,210; 4,444,762; 4,837,026 4,876,249 and U.S. applications Ser. No. 218,316, filed on Jul. 12, 1988; Ser. No. 07/348,387 filed May 8, 1989; Ser. No. 07/393,584, filed Aug. 11, 1989, and Ser. No. 07/451,124, filed on Dec. 15, 1989, which are hereby incorporated by reference. The compounds of the present invention are useful as penetration enhancers for a wide range of physiologically active agents and the compositions disclosed herein are useful for topical and transdermal therapeutic application of these agents. Typically systemically active agents which may be delivered transdermally are therapeutic agents which are sufficiently potent such that they can be delivered through the skin or other membranes to the bloodstream in sufficient quantities to produce the desired therapeutic effect. In general this includes agents in all of the major therapeutic areas including, but not limited to, anti-infectives, such as antibiotics and antiviral agents, analgesics and analgesics combinations, anorexics, anthelmintics, antiarthritics, antiasthma agents, anticonvul sants, antidepressants, antidiabetic agents, antidiarrheals, antihistamines, anti-inflammatory agents, antimigraine preparations, antimotion sickness, antinauseants, antineoplastics, antiparkinsonism drugs, antipruritics, antipsychotics, antipyretics, antispasmodics, including gastrointestinal and urinary; anticholinergics, sympathomimetics, xanthine derivatives, cardiovascular preparations including calcium channel blockers, beta-blockers, antiarryhthmics, antihypertensives, diuretics, vasodilators including general, coronary, peripheral and cerebral; central nervous system stimulants, cough and cold preparations, decongestants, diagnostics, hormones, hypnotics, immunosuppressives, muscle relaxants, parasympatholytics, parasympathomimetics, sedatives, tranquilizers and antiosteoporos is agents. The subject compositions are also useful for topical application of many physiologically active agents in combination with the compounds of this invention. Fungistatic and fungicidal agents such as, for example, thiabendazole, chloroxine, amphotericin, candicidin, fungimycin, nystatin, chlordantoin, clotrimazole, miconazole and related imidazole antifungal agents, pyrrolnitrin, salicylic acid, fezatione, ticlatone, tolnaftate, triacetin and zinc and sodium pyrithione may be combined with the compounds described herein and topically applied to affected areas of the skin. For example, fungistatic or fungicidal agents so applied are carried through the stratum corneum, and thereby successfully treat fungus-caused skin problems. These agents, thus applied, not only penetrate more quickly, but additionally enter the animal tissue in high concentrations and are retained for substantially longer time periods whereby a far more successful treatment is effected. For example, the subject composition may also be employed in the treatment of fungus infections on the skin caused by candida and dermatophytes which cause athletes foot or ringworm, by incorporating thiabendazole or similar antifungal agents with one of the enhancers and applying it to the affected area. The subject compositions are also useful in treating skin problems, such as for example, those associated with the herpes viruses, which may be treated with a cream of iododeoxyuridine or acyclovir in combination with one of the enhancers, or such problems as warts which may be treated with agents such as podophylline combined with one of the enhancers. Skin problems such as psoriasis may be treated by topical application of a conventional topical steroid formulated with one of the enhancers or by treatment with methotrexate incorporated with one of the enhancers of this invention. Scalp conditions such as alopecia arcata may be treated more effectively by applying agents such as minoxidil in combination with one of the enhancers of this invention directly to the scalp. The subject compositions are also useful for treating mild eczema, for example, by applying a formulation of Fluocinolone acetonide or its derivatives; hydrocortisone or triamcinolone acetonide incorporated with one of the enhancers to the affected area. Examples of other physiologically active steroids which may be used with the enhancers include corticosteroids such as, for example, cortisone, cortodoxone, flucetonide, fludrocortisone, difluorasone diacetate, flurandrenolone acetonide, medrysone, amcinafel, amcinafide, betamethasone and its esters, chloroprednisone, clocorelone, descinolone, desonide, dexamethasone, dichlorisone, difluprednate, flucloronide, flumethasone, flunisolide, fluocinonide, flucortolone, fluoromethalone, fluperolone, fluprednisolone, meprednisone, methylmeprednisolone, paramethasone, prednisolone and prednisone. The subject compositions are also useful in antibacterial chemotherapy, e.g. in the treatment of skin conditions involving pathogenic bacteria. Typical antibacterial agents which may be used in this invention include sul fonamides, penicillins, cephalosporins, erythromycins, lincomycins, vancomycins, tetracyclines, chloramphenicols, streptomycins, etc. Typical examples of the foregoing include erythromycin, erythromycin ethyl carbonate, erythromycin estolate, erythromycin glucepate, erythromycin ethylsuccinate, erythromycin lactobionate, lincomycin, clindamycin, tetracycline, chlortetracycline, demeclocycline, doxycycline, methacycline, oxtcetracycline, minocycline, etc. The subject compositions are also useful in protecting ultra-sensitive skin or even normally sensitive skin from damage or discomfort due to sunburn. Thus, actinic dermatitis may be avoided by application of a sunscreen, such as PABA or its well known derivatives or benzophenones in combination with one of the enhancers, to skin surfaces that are to be exposed to the sun; and the protective agent will be carried into the stratum comeurn more successfully and will therefore be retained even when exposed to water or washing for a substantially longer period of time than when applied to the skin in conventional vehicles. This invention is particularly useful for ordinary suntan lotions used in activities involving swimming because the ultraviolet screening ingredients in the carriers are washed off the skin when it is immersed in water. The subject compositions may also find use in treating scar tissue by applying agents which soften collagen, such as aminopropionitrile or penicillamine combined with one of the enhancers of this invention topically to the scar tissue. Agents normally applied as eye drops, ear drops, or nose drops are more effective when combined with the enhancers of this invention. Agents used in the diagnosis may be used more effectively when applied in combination with one of the enhancers of this invention. Patch tests to diagnose allergies may be effected promptly without scratching the skin or covering the area subjected to an allergen when the allergens are applied with one of the enhancers of this invention. The subject compositions are also useful for topical application of cosmetic or esthetic agents. For example, compounds such as melanin-stimulating hormone (MSH) or dihydroxyacetone and the like are more effectively applied to the skin to simulate a suntan when they are used in combination with one of the enhancers of this invention. Depigmenting agents, such as hydroquinone, which bleach and lighten hyperpigmented skin are more effective when combined with one of the enhancers of this invention. Hair dyes also penetrate more completely and effectively when incorporated with enhancers of this invention. These enhancers are also useful in the compositions containing skin moisturizing agents. The effectiveness of such topically applied materials as insect repellants or fragrances, such as perfumes and colognes, can be prolonged when such agents are applied in combination with the vehicles of this invention. It is to be emphasized that the foregoing are simply examples of physiologically active agents including therapeutic and cosmetic agents having known effects for known conditions, which may be used more effectively for their known properties in accordance with this invention. The term "physiologically active agent" is used herein to refer to a broad class of useful chemical and therapeutic agents including physiologically active steroids, antibiotics, anti-fungal agents, antibacterial agents, antineoplastic agents, allergens, antiinflammatory agents, antiemetics, antipruritic agents, antihistaminic agents, vasodilators, expectorants, analgesics, antiosteoporosis agents, sunscreen compounds, antiacne agents, collagen softening agents and other similar compounds. Cosmetic agents, hair and skin dyes, natural and synthetic hormones, perfumes, insect repellents, diagnostic agents and other such compounds may also be advantageously formulated with these penetration enhancers. In addition, these membrane penetration enhancers may be used in transdermal applications in combination with ultrasound and iontophoresis. Moreover, these penetration enhancers are useful in agriculture in the application of fertilizers, hormones, growth factors including micronutrients, insecticides, molluscicides, arachides, nematocides, rodenticides, herbicides, and other pesticides to plants, animals and pests. These penetration enhancers are also useful for penetration of micronutrients and chemical hybridization agents in seeds for enhanced plant growth. Of course, the appropriate dosage levels of all the physiologically active agents, without conjoint use of the penetration enhancing compounds of formula I, are known to those of ordinary skill in the art. These conventional dosage levels correspond to the upper range of dosage levels for compositions including a physiologically active agent and a compound of formula I as a penetration enhancer. However, because the delivery of the active agent is enhanced by compounds of the present invention, dosage levels significantly lower than conventional dosage levels may be used with success. Systemically active agents are used in amounts calculated to achieve and maintain therapeutic blood levels in a human or other animal over the period of time desired. (The term "Animal" as used here encompasses humans as well as other animals, including particularly pets and other domestic animals.) These amounts vary with the potency of each systemically active substance, the amount required for the desired therapeutic or other effect, the rate of elimination or breakdown of the substance by the body once it has entered the bloodstream and the amount of penetration enhancer in the formulation. In accordance with conventional prudent formulating practices, a dosage near the lower end of the useful range of a particular agent is usually employed initially and the dosage increased or decreased as indicated from the observed response, as in the routine procedure of the physician. The present invention contemplates compositions of compounds of formula I, together with physiologically active agents from 0.05% to 100% of conventional dosage levels. The amount of compound of Formula I which may be used in the present invention is an effective, non-toxic amount for enhancing percutaneous absorption. Generally, for topical use the amount ranges between 0.1 to about 10 and preferably about 0.1 to 5 percent by weight of the composition. For transdermal enhancement of systemic agents, the amount of penetration enhancer which may be used in the invention varies from about 1 to 100 percent although adequate enhancement of penetration is generally found to occur in the range of about 1 to 30 percent by weight of the formulation to be delivered. For transdermal use, the penetration enhancers disclosed herein may be used in combination with the active agent or may be used separately as a pre-treatment of the skin or other body membranes through which the active agent is intended to be delivered. Dosage forms for application to the skin or other membranes of humans and animals include creams, lotions, gels, ointments, suppositories, sprays, aerosols, buccal and sublingual tablets and any one of a variety of transdermal devices for use in the continuous administration of systemically active drugs by absorption through the skin, oral mucosa or other membranes, see for example, one or more of U.S. Pat. Nos. 3,598,122; 3,598,123; 3,731,683; 3,742,951; 3,814,097; 3,921,636; 3,972,995; 3,993,072; 3,993,073; 3,996,934; 4,031,894; 4,060,084; 4,069,307; 4,201,211; 4,230,105; 4,292,299 and 4,292,303. U.S. Pat. No. 4,077,407 and the foregoing patents also disclose a variety of specific systemically active agents which may also be useful as in transdermal delivery, which disclosures are hereby incorporated herein by this reference. The penetration enhancers of this invention may also be used in admixture with other penetration enhancers disclosed earlier and incorporated herein by reference. Typical inert carriers which may be included in the foregoing dosage forms include conventional formulating materials, such as, for example, water, ethanol, 2-propanol, 1,2-propanediol, 1,3-butanediol, 2-octyldodecanol, 1,2,3,-propanetriol, oleyl alcohol, propanone, butanone, carboxylic acids such as lauric, oleic and linoleic acid, carboxylic acid esters such as isopropyl myristate, diisopropyl adipate and glyceryl oleate, acyclic and cyclic amides including N-methyl pyrrolidone, urea, freons, PEG-200, PEG-400, Polyvinyl pyrrolidone, fragrances, gel producing materials such as "Carbopol", stearyl alcohol, stearic acid, spermaceti, sorbitan monooleate, sorbital, "polysorbates", "Tweens", methyl cellulose etc., antimicrobial agent/preservative compositions including parabens, benzyl alcohol, potassium sorbate, sorbic acid, or a mixture thereof and antioxidant such as BHA or BHT. The dosage form may include a corticosteroid, such as hydrocortison, to prevent skin sensitization, a local anaesthetic, such as lidocaine or benzocaine to suppress local irritation. The examples which follow illustrate the penetration enhancers and the compositions of the present invention. However, it is understood that the examples are intended only as illustrative and are not to be construed as in any way limiting to scope of this invention. EXAMPLE 1 Preparation of 2-Ethanoylaminododecyl ethanoate To a solution of 4.1 g of 2-aminododecanol, 5 g of triethylamine in 100 ml of dichloromethane was slowly added 3.2 ml of acetyl chloride. The reaction mixture was stirred for 3 hours and then quenched by pouring into ice. The aqueous solution was extracted with dichloromethane. The organic layer was washed with water, brine and then dried, filtered and concentrated to 5.7 g of a waxy solid. Recrystallization from ether/hexane gave 4.22 g (72.2%) of the desired amidoester as white crystals, m.p. 77°-79° C. EXAMPLE 2 Preparation of 5-Amino-5-ethyl-2-carbobutoxyethyl-2-methyl-1,3-dioxane 7.46 g of 2-nitro-2-ethyl-1,3-propanediol, 8.61 g of butyl levulinate, 50 mg of p-toluenesulfonic acid in 50 ml of toluene was refluxed until no more water separated. The reaction mixture was cooled, washed with 2% sodium bicarbonate and water, dried and concentrated to give 13.65 g of 2-carbobutoxyethyl-2-methyl-5-nitro-5-ethyl-1,3-dioxane as a light yellow oil. This was dissolved in 50 ml of ethanol and hydrogenated over 1 g Raney Nickel catalyst at 60 under pressure. Distillation of the crude material at 160° C./3mm gave 11 g of the product. EXAMPLE 3 Preparation of 5-Amino-5-ethyl-2- (3 -heptyl ) -1,3-dioxane Procedure of Example 2 was repeated with 6.41 g of 2-ethylhexanal in place of butyl levulinate to give 11.6 g of the 5-nitro-1,3-dioxane, which was reduced and distilled at 135°-137° C./10 mm to give 9.23 g of the product. EXAMPLE 4 Preparation of 5-Amino-5-hydroxymethyl-2-(3-heptyl)-1,3-dioxane Procedure of Example 2 was repeated with 6.41 g of 2-ethylhexanal and 7.56 g of 2-(hydroxymethyl)-2-nitro-1,3-propanediol to give 11 g of 5-nitro-5-hydroxymethyl-1,3-dioxane derivative, which was reduced and distilled at 175°-178° C. to give 8.7 g of the product. EXAMPLE 5 Preparation of 5-Amino-5-ethyl-2-undecyl-1,3-dioxane Procedure of Example 2 was repeated with 9.216 g of dodecanal in place of butyl levulinate to give 13.4 g of the 5-nitro-1,3-dioxane derivative. Hydrogenation followed by distillation of the crude liquid at 150° C./1 mm gave 10.9 g of the product. EXAMPLE 6 Preparation of erythro-5-Amino-2,2-dimethyl-4-[(E)-pentadec-1-enyl]-1,3-dioxane 17.6 g of nitroethanol was added to a solution of 22 g of (E)-hexa-dec-2-enal in 160 ml of triethylamine under an inert atmosphere. The mixture was stirred and the reaction was followed by t.l.c. After 4 days the reaction mixture was concentrated and the residue was dissolved in dichloromethane. This was washed with ice-cold 5% HCl, water, dried and concentrated to give an orange oil. This was flash chromatographed (silica gel: hexane/ethyl acetate, 7:3) to give 21.2 g of a mixture of threo- and erythro-nitro diols. 20.9 g of the isomeric mixture, 500 ml of 2,2-dimethoxypropane and 100 mg of camphor-10-sulfonic acid was refluxed overnight under an inert atmosphere. The reaction mixture was cooled, concentrated and the residue was dissolved in dichloromethane. The organic solution was washed with bicarbonate solution, water and brine. It was dried and concentrated to give a mixture of acetonides which were dissolved in benzene and the solution was refluxed for 8 hours in presence of Merck silica gel-60. The mixture was filtered and the silica gel was washed with warm benzene. The filtrate was concentrated and the residue was chromatographed to give 16.7 g of erythro-nitro acetonide. To a suspension of 5 g of lithium aluminum hydride in 200 ml of THF was added dropwise a solution of 16.7 g of the erythro-nitro acetonide in 100 ml of THF at room temperature. The reaction mixture was stirred for 8 hours and then excess LAH was quenched with water. THF was removed under reduced pressure, the residue was diluted with ethyl acetate and the mixture was filtered. The organic layer was separated, washed with water, brine and dried. Concentration of the filtrate under reduced pressure gave 15.1 g of erythro-5-Amino-4-[(E)-pentadec-l-enyl]-1,3-dioxane as an oil. EXAMPLE 7 Preparation of erythro-5-Amino-2,2-dimethyl-4-pentadecyl-1,3-dioxane 3 g of the material obtained under Example 6 was dissolved in 50 ml of methanol and hydrogenated over 100 mg of platinum oxide catalyst. Filtration and concentration gave 2.86 g of an oil. EXAMPLE 8 Preparation of erythro and threo-5-Amino-2,2-dimethyl-4-(2,6-dimethyl-5-heptenyl)-1,3-dioxane To a mixture of 11,565 g of racemic citronellal and 13.65 g of 2-nitroethanol was added 872 mg of KF and 1.21 g of tetra-n-butylammonium bromide in 75 ml of acetonitrile and the mixture was stirred at room temperature under an inert atmosphere. After 24 hours the reaction mixture was poured into ice-cold water and extracted with ether. The ether extract was washed with water and brine, dried and concentrated to give 15.6 g of isomeric mixture of 5,9-dimethyl-2-nitro-S-decene-1,3-diol. A mixture of 14,715 g of the nitrodiol, 18.75 g of 2,2-dimethoxy-propane and 30 mg of p-toluenesulfonic acid in 150 ml of toluene was heated to reflux and water was removed by azeotropic distillation. The reaction mixture was cooled, diluted with ether and this was washed with water, brine, dried and concentrated in vacuo to give a yellow oil. The two isomers were separated by chromatography on Merck silica gel 60 and solution with benzene. 5.9 g of equatorial isomer was obtained first followed by 7.9 g of axial isomer, both as pale yellow oils. To an ice-cold mixture of 4.5 g of the equatorial nitro isomer in 210 ml of ether and 13.5 ml of water was added freshly prepared amalgamated aluminum under stirring. The temperature of the reaction mixture was allowed to come to room temperature and then it was stirred for an additional 24 hours. The reaction mixture was filtered through celite and the filter cake was thoroughly washed with ether. The filtrate was concentrated to give an oil which was passed through neutral alumina to give 3 g of erythro isomer of 5-amino-2,2-dimethyl-4-(2,6-dimethyl-5-heptenyl)-1,3-dioxane as a colorless oil. 7.5 g of the axial nitro isomer was similarly reduced to give 4.99 g of the threo isomer as a colorless oil. EXAMPLE 9 Preparation of 2-Octanoylaminododecyl octanoate To a solution of 2 g of 2-aminododecanol, 3 g of triethylamine in 50 ml of dichloromethane is added 3.5 g of octanoyl chloride. The reaction mixture is stirred overnight and then quenched by pouring into ice. This is extracted with dichloromethane and the organic solution is washed with aqueous bicarbonate solution, water and brine. The organic phase is dried over magnesium sulfate, filtered and concentrated to give 3.8 g of the product. EXAMPLE 10 Preparation of 2-Octadec-9-enoylamincdodecyl octadec-9-enoate Example 9 is repeated under identical conditions with a solution of 2 g of 2-aminododecanol, 3 g of triethylamine in 50 ml of dichloromethane to which is added 6.3 g of oleoyl chloride. The reaction mixture is worked up as under Example 8 to give 5.1 g of product. EXAMPLE 11 Preparation of 2-Ethanoylaminododecyl octadec-9-enoate To a solution of 2.43 g of 2-ethanoylaminododecanol, 3 g of triethylamine in 50 ml of dichloromethane is added 3.2 g of oleoyl chloride. The reaction mixture is worked up as under Example 9 to give 4.2 g of product. EXAMPLE 12 Preparation of 2,2-Dimethyl-5-dodecanoylamino-5-ethyl-1,3-dioxane 2,2-Dimethyl-5-amino-5-ethyl-1,3-dioxane is acylated wih dodecanoic acid in methylene chloride in the presence of DCC and 1-hydroxybenzo-triazole. Filtration and concentration gives the product. EXAMPLE 13 Preparation of 5-Dodecanoylamino-5-methyl-1,3-dioxan-2-one A solution of 2-methyl-2-nitro-1,3-propanediol and ethylene carbonate is heated overnight. The reaction mixture is diluted with ethyl acetate and the solution is washed with water. The organic phase is dried and concentrated to obtain 5-methyl-5-nitro-1,3-dioxan-2-one. This is dissolved in methanol and hydrogenated under pressure to give the 5amino compound which is acylated with dodecanoyl chloride to give the product. EXAMPLE 14 Preparation of 5-Amino-5-undecyl-1,3-dioxan-2-one 2-Nitro-2-undecyl-1,3-propanediol is treated under identical conditions according to the reaction sequence outlined under Example 13 to give the product. EXAMPLE 15 The following analgesic gel is prepared: ______________________________________ %______________________________________Carbopol 941 1.5Diclofenac Na 12-Propanal 35Diisopropanolamine 1.8Diisopropyl adipate 55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 2Water 53.7______________________________________ EXAMPLE 16 The following cream formulation is prepared: ______________________________________ %______________________________________Isosorbide dinitrate 1.0Glycerol monostearate 5.5Polyoxyethylene stearate 4.5C8-C18 fatty acid esters of a 8glycerol ethoxylated with about7 moles of ethylene oxide5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 2Sorbic acid 0.165Ascorbyl palmitate 0.055Citric acid 0.1Na EDTA 0.014Fragrance 0.05Water 78.616______________________________________ This formulation is effective in the treatment of angina. EXAMPLE 17 The following skin moisturizing formulation is prepared: ______________________________________ %______________________________________Pyrrolidonecarboxylic acid Na 1Glycerine 4Citric acid 0.03Sodium citrate 0.05Allantoin 0.1Ethanol, 95% 9Oleth-15 1Linaleic acid 15-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 2Sunscreen agent 0.1Water 81.72______________________________________ EXAMPLE 18 The following formulation for promoting hair growth is described. ______________________________________ %______________________________________Minoxidil 2.0Benzyl nicotinate 0.5Ethanol 40.01,2-Propanediol 20.05-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 5.0Ethyl aleate 5.0Water 27.5______________________________________ EXAMPLE 19 The following solution formulation is prepared. ______________________________________ %______________________________________Griseofulvin 15-Amino-5-ethyl-2-(3-heptyl)1,3-dioxane 1.5C12-C15 benzoate 5Fragrance 0.1Ethanol 92.4______________________________________ This formulation is effective in the treatment of fungus infection. EXAMPLE 20 The following depilatory gel is prepared. ______________________________________ %______________________________________Poloxamer 407 15.0Benzyl alcohol 6.0Urea 6.5alpha-Thioglycerol 6.55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 5.0Water q.s. 100.0Sodium hydroxide g.s. to pH 12.5______________________________________ EXAMPLE 21 The following cream formulation is prepared: ______________________________________ %______________________________________Clindamycin Base 1.0Stearyl alcohol, U.S.P. 12.0Ethoxylated cholesterol 0.4Synthetic spermaceti 7.5Sorbitan monooleate 1.0Polysorbate 80, U.S.P. 3.05-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 1.9Sorbitol solution, U.S.P. 5.5Sodium citrate 0.5Chemoderm #844 0.2Purified water 67.0______________________________________ This formulation is effective in the treatment of ache. EXAMPLE 22 The following solution formulations are prepared: ______________________________________ A (%) B (%)______________________________________Clindamycin base -- 1.0Clindamycin phosphate acid 1.3 --Sodium hydroxide 0.077 --1M Hydrochloric acid -- 2.27Disodium edentate.2H20 0.003 0.003Fragrances 0.5 0.55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 1.0 1.0Purified water 20.0 17.73Isopropanal 77.12 77.497______________________________________ These solutions are effective for the treatment of ache in humans. EXAMPLE 23 The following solution formulation is prepared: ______________________________________ %______________________________________Neomycin sulfate 0.5Lidocaine 0.5Hydrocortisone 0.255-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 1.50Propylene glycol 97.25______________________________________ This solution is effective for the treatment of otitis in domestic animals. EXAMPLE 24 The following sunscreen emulsion is prepared: ______________________________________ %______________________________________PABA 2.0Benzyl alcohol 0.55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 2.0Polyethylene glycol 9.0Isopropyl lanolate 3.0Lantrol 1.0Acetylated lanolin 0.5C12-C15 benzoate 5.0Diisopropyl adipate 2.0Cetyl alcohol 1.0Veegum 1.0Propylene glycol 3.0Purified water 70.0______________________________________ EXAMPLE 25 The following antineoplastic solution is prepared: ______________________________________ %______________________________________5-Fluorouracil 55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 1.5Polyethylene glycol 5Purified water 88.5______________________________________ EXAMPLE 26 The following insect repellant atomizing spray is prepared: ______________________________________ %______________________________________N,N-diethyltoluamide 0.55-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 0.5Ethanol 99______________________________________ EXAMPLE 27 The following cream formulation may be prepared containing about 0,001 to 1 percent, with preferably 0.1% fluocinolone acetonide: ______________________________________ %______________________________________Oil PhaseFluocinolone acetonide 0.15-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane 1.6Cetyl alcohol 9.3Stearyl alcohol 1.3Glyceryl monostearate 3.8Water PhasePropylene glycol 10Sodium dodecyl sulfate 0.1Deionized water q.s. 100______________________________________ The steroid is dissolved in the vehicle and added to a stirred, cooling melt of the other ingredients. The preparation is particularly useful for the treatment of inflamed dermatoses by topical application to the affected skin area. The amount and frequency of application is in accordance with standard practice for topical application of this steroid. Penetration of this steroid in the inflamed tissue is enhanced and a therapeutic level is achieved more rapidly and sustained for longer duration than when the steroid is applied in the conventional formulation. EXAMPLE 28 Transdermal patches containing nicotine with the following composition are prepared. 800 mg of Estane (B.F. Goodrich) is dissolved in 10 ml THF and 99 mg of nicotine, 50 mg of 1,2-propanediol and 50 mg of 5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane is added. The homogenous solution is poured in a petri dish and the solvent is removed. The patches are die cut from the polymer film. EXAMPLE 29 Transdermal patches containing progesterone with the following composition are prepared. 9.2 g of PDMS-382 (Dow Corning) pre-polymer, 300 mg of progesterone and 500 mg of 5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane are mixed. One drop of polymerization initiator is added and the contents are thoroughly mixed. The mixture is degassed and allowed to polymerize in sheet molds for 24 hours at room temperature. After the curing is complete disks with 1 cm diameter are die cut. EXAMPLE 30 Transdermal patches containing estradiol with the following compositions are prepared. 8.5 g of PDMS-382 (Dow Coming) pre-polymer, 1 g of estradiol, 500 mg of 5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane are mixed and the patches are prepared as under Example 29. EXAMPLE 31 EXAMPLES 15-30 are repeated, except the 5-Amino-5-ethyl-2-(3-heptyl)-1,3-dioxane is replaced with an equimolar amount of each of the following listed compounds, and comparable results are obtained. 2-Ethanoylaminododecyl ethanoate 2-Ethanoylaminododecyl octadec-9-enoate 5-Amino-2,2-dimethyl-4-(pentadec-l-enyl)-1,3-dioxane 5-Amino-2,2-dimethyl-4-pentadecyl-1,3-dioxane 5-amino-4-dodecyl-1,3-dioxan-2-one 4-Dodecyl-5-ethanoylamino-1,3-dioxan-2-one 2-Ethanoylamino-3-octadecyloxypropyl ethanoate 5-Amino-2,2-dimethyl-4-(2,6-dimethyl-5-heptenyl)l,3-dioxane 5-Amino-5-ethyl-2-undecyl-1,3-dioxane 2,2-Dimethyl-5-dodecanoylamino-5-ethyl-1,3-dioxane 5-Amino-5-hydroxymethyl-2-(3-heptyl)-1,3-dioxane 5-Amino-5-ethyl-2-carbobutoxyethyl-2-methyl-1,3-dioxane EXAMPLE 32 The compounds of the present invention are tested in vitro as penetration enhancers according to the procedure outlined below. Human stratum corneum is isolated from full thickness human skin as described by Bronaugh et al., J. Pharm. Sci. 75, 1094 (1986). The skin is placed between the donor and the receptor compartments of diffusion cells in such a way that the dermal side of the skin faces the receptor compartment which is filled with normal saline (pH 7.2-7.4). The stratum comeurn is equilibriated at 37° C. overnight prior to the application of a topical formulation or transdermal patch. All formulations are studied in triplicate. About 500 mg of the following three Isosorbide Dinitrate (ISDN) formulations (40% ISDN & 60% Lactose) are applied to cover the stratum comeurn surface within the donor compartment. The entire contents of the receptor compartment are removed at specific time intervals over 51 hours and replenished with fresh saline. The aliquots are analyzed by HPLC and the average cumulative amount of ISDN in micrograms permeating over the study period is calculated. The results show that the formulations containing the penetration enhancers of the present invention show superior permeation as compared to control. While particular embodiments of the invention have been described it will be understood of course that the invention is not limited thereto since many obvious modifications can be made and it is intended to include within this invention any such modifications as will fall within the scope of appended claims.

A method and compositions for enhancing absorption of topically administered physiologically active agents through the skin and mucous membranes of humans and animals in a transdermal device or formulation for local or systemic use, comprising a therapeutically effective amount of a pharmaceutically active agent and a non-toxic, effective amount of penetration enhancing agent of the formula I or a physiologically acceptable salt thereof: ##STR1## wherein: R 1 , R 2 , R 3 and R 4 are as defined herein.

BACKGROUND OF THE INVENTION In a selctive call communication system a particular receiver is rendered operative when the carrier wave signal applied thereto contains a certain tone or set of tones to which the decoder in such receiver is designed to respond. These tones are generated by an encoder, which tones are then modulated onto the carrier wave generated by the transmitter with which that encoder is associated. In systems involving voice communication, the tone or set of tones is transmitted to unsquelch the receiver, whereupon the operator at the transmitter can speak into his microphone and the possessor of the associated receiver will hear his words. Alternatively, the system may involve nonvoice communication, wherein the receiver emits an alerting signal such as a tone when the proper tone or set of tones is applied thereto. Usually in such systems, there is a single base station which has a transmitter, an associated encoder, and other interface equipment to enable persons to gain access to the transmitter. Such equipment may take the form of a telephone system in which a person dials a certain number to connect the telephone to the transmitter, whereupon a selected code may be transmitted. Usually a multiplicity of receivers will be associated with such transmitter. For example, a system used in a hospital would entail each doctor being furnished with a receiver designed to emit an alerting signal in response to a unique code. In this type of system, the transmitter is likely to be very expensive compared to the cost of the individual receivers. Since there is only one transmitter, the cost thereof does not render the cost of the entire system prohibitive. It has been proposed to use selective call capability in an automatic identification system. In such system, each user, such as a vehicle, is furnished with a transmitter and an associated encoder to enable the user, not only to receive a voice message, but also to communicate with the base station and also to identify himself without so stating. When the vehicle driver wishes to communicate with the base station, he operates his push-to-talk switch and speaks into his microphone. With automatic identification capabilities, the encoder generates a signal representing that encoder, which signal is modulated onto the carrier wave. The identification signal, by way of a suitable display or otherwise, apprises the base station operator of the identity of the encoder transmitting. The value of such automatic identification is recognized and need not be delved into here. In prior systems, the information automatically sent to the base station has been limited to the identity of vehicle or driver. Such systems have not supplied additional information, such as where the vehicle is located or what is its status, etc. Furthermore, the encoders previously available have not been sufficiently inexpensive to enable widespread use such as is necessary when many vehicles are provided with an encoder. It is important in selective call communication systems to maximize the number of channels used in a given frequency spectrum. In other words, if the frequency spectrum for tones is, for example 500 Hz. to 3,500 Hz., it is desirable to maximize the number of channels within that range that can be utilized. Of course, the limiting factor is that the channels cannot be so close that operation of a decoder responsive to one channel will also operate a decoder responsive to an adjacent channel. Furthermore, with limiting, the encoders generate not only the specific tone, but also its harmonics, particularly its third harmonic. It is therefore important that the third harmonic of one tone in the frequency spectrum not coincide with other channels in the spectrum and, in fact, be as far removed as possible therefrom. Since each vehicle in such a system is also provided with a receiver and an associated decoder to respond to a particular sequence of tones, it is equally desirable that the cost of the decoder be minimized. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide in a selective call communication system encoders and decoders which are less expensive to make. Another object is to provide an automatic identification system which not only supplies the base station with the identity of the encoder transmitting, but also other selected information, such as its status. Still another object is to maximize the frequency difference between tones used in a selective call communication system and third harmonics of such tones. In one aspect of the present invention, there is provided an encoder for a selective call transmitter comprising oscillator means for producing a sequence of first tones, multiplier means coupled to the oscillator means for multiplying the frequencies of the first tones by a predetermined multiplier to produce a sequence of second tones, an output circuit coupled to the oscillator means and to the multiplier means for receiving the sequence of the first tones and the sequence of the second tones, and control means coupled to the output circuit for rendering the output circuit operative to alternate between supplying the first tones and the second tones. In another aspect of the invention, the encoder also comprises switchable impedance means associated with the oscillator means for controlling the frequency of the tone produced thereby, counter means coupled to the switchable impedance means for sequentially changing the value of impedance furnished thereby to cause the oscillator means to produce a sequence of tones, clock means for producing clock pulses at a predetermined rate, and switching means having a pair of inputs respectively coupled to the oscillator means and to the clock means for producing a sequence of pulses at the predetermined rate each having a leading edge in time coincidence with an instant when the amplitude of the tone produced by the oscillator means is substantially zero, whereby each tone in the sequence of tones has a duration substantially proportional to the predetermined rate and is substantially in phase with the preceding tone in the sequence of tones. In yet another aspect of the invention, the oscillator means generates tones selected from a first group of tones in a first band of frequencies and tones selected from a second group of tones in a second band of frequencies separate and distinct from the first band of frequencies, the tones in the second bank respectively being harmonics of the tones in the first bank, and means for receiving the tones from the oscillator means and for producing a sequence of tones alternately from the first and second groups. In a further aspect of the invention, the sequence of tones produced by the oscillator means includes at least one identification tone representing the identification of the encoder and at least one information tone representing information relative to the encoder, program means for internally fixing the frequencies and the order of the identification tones, and selector means for externally selecting the frequencies of the information tones, whereby energization of the encoder automatically produces identification tones corresponding to the program of the program means and information tones corresponding to the condition of the selector means. In a still further aspect, there is provided a single switch for operating the encoder and the decoder, and lockout circuitry to insure that when the decoder is in use, the associated encoder is not accidentally operated. The invention consists of certain novel features and a combination of elements hereafter fully described, illustrated in the appended claims, it being understood that various changes in the details of the circuitry may be made without departing from the spirit or sacrificing any of the advantages of the invention. BRIEF DESCRIPTION OF THE DRAWINGS For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings preferred embodiments thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation, and many of its advantages can be readily understood and appreciated. FIG. 1 is a diagram partially in block and partially in schematic depicting a selective call communication transmitter having an encoder incorporating the features of the present invention; FIG. 1A is a block diagram of the multiplier circuit and the phase-synchronized circuit of FIG. 1; FIG. 2 is a timing diagram showing wave forms at various points in FIG. 1; FIG. 3 is a diagram partially in block and partially in schematic depicting a receiver having a decoder incorporating therein other features of the present invention; and FIG. 4 is a timing diagram showing wave forms at various points in the diagram of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning first to FIG. 1, there is depicted therein a transmitter 20 adapted to generate an RF carrier wave modulated selectively by audio signals and by tones. The transmitter 20 includes an oscillator 22 which develops on its output a relatively low-frequency oscillatory signal. A modulator 24 receives the oscillatory signal from the oscillator and also receives audio signals supplied by an audio amplifier 26. The audio signals are either tones generated by an encoder to be described presently or electrical signals representative of a voice message applied to a microphone 28 and then amplified in a preamplifier 30. The audio signals from the amplifier 26 are modulated by the modulator 24 onto the oscillatory signal. The frequency of the modulated signal is increased in a frequency multiplier 32 and then its amplitude increased in a power output amplifier 34, thereby to provide a high level, frequency multiplied carrier wave which is emitted from an antenna 36. Although the transmitter 20 is of the FM type, that is merely exemplary. The transmitter 20 also includes a power supply 38 which provides a supply voltage to the other elements in the transmitter, including the power output amplifier 34, the audio amplifier 26, etc. The power supply 38 is selectively rendered operative by a relay 40 having a winding 42 and contacts 44. In a manner to be described presently, when the winding 42 is energized, the contacts 44 close to enable the power supply 38 to supply power to the rest of the transmitter 20. The transmitter 20 also includes an encoder 50 which provides the tones to the audio amplifier 26. The encoder 50 includes a switch 52 having a set of normally open contacts 54 and a set of normally closed contacts 56 (FIG. 3). A single actuator (not shown) is adapted simultaneously to close the contacts 54 and to open the contacts 56. A capacitor 60 is charged rapidly through a resistor 58 when the contacts 54 are closed, and discharged relatively slowly through a resistor 61. There is provided a latching circuit 62 which is in the form of a bistable multivibrator and is composed of two NOR gates 64 and 66 connected as shown. When the switch 52 is actuated, the contacts 54 close and, as shown in FIG. 2A, the capacitor 60 charges rapidly, in about 2 ms., to a level 1, at which the latching circuit 62 switches, and the output thereof becomes "high," as can be seen in FIG. 2B. As is standard in logic nomenclature, this application will refer to "high" and "low" inputs and outputs. The term "low" means that the voltage is at its low value, for example, zero, and the term "high" means that it is at its high value, for example, close to the supply voltage. The output of the latching circuit 62 is connected by way of a resistor 68 to an NPN transistor 70, the emitter of which is grounded and the collector of which is coupled through the relay winding 42 to the B+ supply voltage. Thus, when the latching circuit 62 is energized, and the output thereof becomes high, the transistor 70 is rendered conductive to energize the relay 40, closing the contacts 44 and thereby supplying power to the transmitter 20, enabling it to produce a carrier wave prior to transmitting the tones. The output of the NOR gate 66 is coupled through a resistor 92 to one input of a NOR gate 94, the other input of which is derived from the contacts 54. The output of the NOR gate 94 is coupled by way of a resistor 96 to an NPN transistor 98, having its emitter grounded and its collector coupled to a bulb 414 (FIG. 3). The output of the NOR gate 94 is also coupled to a further NOR gate 100 connected to be an inverter. The output of the NOR gate 100 is coupled to an astable multivibrator 102 comprised of two NOR gates 104 and 106, resistors 108 and 110, and a capacitor 112. When energized, the multivibrator 102, as shown in FIG. 2D, produces a sequence of pulses having a predetermined repetition rate determined by the values of the resistors 108 and 110 and the capacitor 112. The resistor 110 is variable to enable selection of such rate, which controls the duration of each tone in the sequence produced by the encoder 50. When the contacts 54 are closed, the capacitor 60 charges rapidly, as previously mentioned. When the switch 52 is released, the contacts 54 open and the capacitor 60 discharges through the resistor 61, causing the NOR gate 94 to switch when the voltage reaches the level 1 2 (FIG. 2A). The output of the NOR gate 94 thereupon becomes high (FIG. 2C), to render conductive the transistor 98 and to cause illumination of the bulb 414 (FIG. 3). The high output from the NOR gate 94 is inverted by the NOR gate 100 to provide a low input to the NOR gate 104, thereby rendering the multivibrator 102 operative to produce the sequence of pulses. One input to the NOR gate 94 remains low until the next time the switch 52 is actuated, while the other input remains low until the latching circuit 62 is opened, in the manner to be described hereinafter. The output of the NOR gate 100 is also coupled by way of a resistor 114 to the base of a PNP transistor 116 having its emitter coupled to the supply voltage and its collector coupled to the preamplifier 30. When the output of the NOR gate 100 becomes low, the transistor 116 is rendered conductive, which applies a disabling voltage to the preamplifier 30. Thus, while the tones are being generated, no speech applied to the microphone 28 will be transmitted. The output of the latching circuit 62 is inverted by an inverter 118, the output of which is coupled to an oscillator 120. An NPN transistor 122, biasing resistors 124, 126, and 128, frequency determining capacitors 130 and 131, and an inductor 132 comprise the oscillator 120. The oscillator 120 begins to produce a signal (FIG. 2E) at the same time the output of the NOR gate 64 becomes high. The inductor 132 has ten taps 132a to 132j. A terminal block 134 has a plurality of electrical sockets 134a through 134j respectively coupled to the taps 132a to 132j. Also, the block has a set of sockets 136a to 136d respectively coupled to the collectors of four switching transistors 138a to 138d, the emitter of each of which switching transistors is coupled to the B+ supply voltage. Associated with the block 134 is a plug 140, having pins 140a to 140j and 142a to 142d. The plug 140 is adapted to be programmed to set the code produced by the encoder 50 by connecting jumper wires from selected ones of the pins 140a to 140j to the pins 142a to 142d. The particular encoder shown is capable of producing a sequence of as many as four tones which can be internally programmed by connecting all four pins 142a to 142d to selected pins 140a-140 j. As an example only pins 140b and 140e, are respectively connected by way of jumper wires to the pins 142a and 142b, so as internally to program two tones. The particular embodiment described envisions a sequence of two internally programmed tones followed by a third externally selected tone, as will be explained. Initially the transistor 138a is conducting, whereas the transistors 138b to 138d are initially nonconducting, which will be described in greater detail hereinafter. Then, the supply voltage on the emitter of the transistor 138a is coupled through its collector, through the terminal 136a, the pin 142a, the corresponding jumper 144, the pin 140b, the socket 134b, whereby that portion of the inductor 132 between a tap 132b and an end 132k will be in circuit with the oscillator 120. The oscillator 120 will therefore produce a tone when energized, in accordance with the value of such inductance and the value of the capacitor 130. As previously explained, the output (FIG. 2B) of the NOR gate 64 becomes high when the switch 52 is closed, which output is inverted by the inverter 118 to provide a low input to the oscillator 120 for energization thereof. The output from the oscillator 120 is derived from the emitter of the transistor 122, the oscillatory signal produced thereby being amplified and inverted by the amplifier 150 to produce a square wave (FIG. 2F) of a frequency corresponding to the frequency of the oscillatory signal from the oscillator 120. Such square wave is applied to the clock input C of a multiplier circuit 152. The multiplier circuit 152 consists of a "dual `D` type flip-flop" device with set and reset capability, having set (S), reset (R), clock (C), data (D), and supply (V) inputs and "Q" and "Q" outputs. Each such device is schematically illustrated in FIG. 1A. As an example, Solid State Scientific, Inc. makes a product under the designation LCL4013A which contains two such flip-flops on a single monolithic silicon chip. The D and Q inputs are connected together, and the R, V, and S are grounded. With such connections, the signal on the Q output has one half the frequency of the signal on the C input, whereby the predetermined multiplier of the multiplier circuit 152 is one half. Therefore, there will appear on the Q output a square wave, as shown in FIG. 2M, at one half the frequency of the oscillatory signal (FIG. 2E) from the oscillator 120. The second input to the NAND gate 154 is derived across a resistor 156 through a diode 158. The signal applied to such diode, as shown in FIG. 2J, becomes high during the second tone, and is low before and after the second tone. The origin of such signal will be described hereinafter. Accordingly, as can be seen in FIG. 2N, the output of the NAND gate 154 is high during the first tone, and follows the Q output (FIG. 2M) during the second tone, but is inverted. The signal represented by the waveform of FIG. 2J is also coupled to a NAND gate 160 connected as an inverter, whereby the output (FIG. 2P) thereof is low during the second tone, but is high the rest of the time. The output of the NAND gate 160 is connected to one input of a further NAND gate 162, the other input of which is coupled to the output of the amplifier 150. The low input to the NAND gate 162 during the second tone causes the output of the NAND gate 162 to be high for that interval, but, during the rest of the time, there appears on such output an inverted form of the square wave from the amplifier 150. The output of the NAND gates 154 and 162 are respectively coupled as inputs to a NOR gate 164. During the first and third tones, the signal from the NAND gate 162 (FIG. 2Q) is inverted and coupled to the output of the NOR gate 164, while during the second tone the output of the NAND gate 154 (FIG. 2N) is coupled to such output, whereby the output of the OR gate 164, shown in FIG. 2R, includes a first tone having a frequency equal to the frequency of the tone produced by the oscillator 120 during the interval t 2 -t 3 , a second tone having a frequency equal to one half the frequency of the tone produced by the oscillator 120 during the interval t 3 -t 4 , and a third tone having a frequency equal to the frequency of the tone produced by the oscillator 120 during the interval t 4 -t 5 . The output of the NOR gate 164 is coupled to a further NOR gate 166 having a second input on which appears a signal represented by the waveform of FIG. 2H. Such input is high prior to time t 2 when the tones commence, whereby the output of the NOR gate 166, as shown in FIG. 2S, is low during the interval t 1 -t 2 . Starting at t 2 , the output of the NOR gate 166 is the inverse of the output from the NOR gate 164 (FIG. 2R). The output of the NOR gate 166 is coupled by way of a resistor 168 to an emitter follower transistor 170, the collector of which is coupled to the supply voltage, and the emitter of which is coupled through a potentiometer 172 to ground. The movable arm of the potentiometer 172 is coupled by way of a capacitor 174 to the audio amplifier 26. The signal coupled to the amplifier 26 consists of a sequence of three square wave tones, shown in FIG. 2T. The transistors 138a to 138d are sequentially rendered conductive by, and certain of the inputs to the gates 154, 160, and 166 are derived from, a counter 176. The counter 176 has a plurality of outputs and a clock input. A pulse train applied to the clock input will cause each output to become high in succession. An example of a counter that may be used, is one sold by Solid State Scientific, Inc. under the designation SCL4017A, which it calls a "CMOS decade counter/divider." Such device has clock (C), reset (R), clock enable (CE) inputs, and ten outputs "0" to "9". In this particular form, only the outputs "0" to "4" are used, and therefore outputs "5" to "9" are not shown. The CE input is grounded, the R input is coupled to the NAND gate 118, and the C input is coupled to a clock 190 which furnishes a sequence of pulses shown in FIG. 2G. With such connections, the "0" output is high and the other outputs "1" to "4" are low in the quiescent condition of the counter 176. The first positive going transition at the C input causes the "0" output to become low, the "1" output to become high, and the "2" to "4" outputs to remain low. The next positive transition at the C input causes the "2" output to become high and the rest of the outputs to be low, etc. In order for the stepping operation just described to take place, the R input must be low. The "0" and "1" outputs are coupled respectively through diodes 180 and 182 to appear across a resistor 184 as inputs to an NPN transistor 186a, the collector of which transistor is coupled to the base of the transistor 138a. The transistors 186a and 138a define an electronic switch. The "2", "3" and "4" outputs are respectively coupled to NPN transistors 186b, 186c and 186d, the collectors of which transistors are respectively connected to the bases of the transistors 138b to 138d. Associated pairs of the transistors (e.g. 186b and 138b) define electronic switches. Initially, the "0" output of the counter 176 is high (FIG. 2H), thereby actuating the switch consisting of the transistors 138a and 186a, to cause the associated portion of the inductor 132 to be coupled in circuit in the oscillator 120, as previously described. As can be seen in FIG. 2G, the first positive transition of the C input to the counter 176 occurs at time t 2 , causing the counter 176 to step so that the "1" output becomes high (FIG. 2I). The transistors 186a and 138a are maintained conductive so that the oscillator 120 continues to run at the same frequency. The next clock pulse, that is, a positive transition, occurs at time t 3 , which causes the "2" output to become high (see FIG. 2J). The transistors 186b and 138b conduct, thereby coupling in the oscillator 120 another portion of the inductor 132. Similarly, when the "3" output of the counter 176 becomes high (FIG. 2K), in response to a clock pulse at t 4 , yet another portion of the inductor 132 is connected in circuit with the oscillator 120 to change the frequency of oscillation thereof. In order to insure that there are no discontinuities as the oscillator 120 changes its frequency of oscillation, there is provided a phase synchronized clock 190 to supply the pulses to the "C" input of the counter 176, such clock is the second flip-flop device on the silicon chip, previously discussed (the first such flip-flop device is the multiplier circuit 152). The flip-flop device constituting the phase synchronized clock 190 also has data (D), set (S), reset (R), and clock (C) inputs and Q and Q outputs. The S and R inputs are connected to ground, the D input is connected to the output of the NOR gate 106, and the clock input C is connected to the inverting amplifier 150. Considering the logic of the clock 190, its Q output will become high if its D input is low and its C input has a rapidly rising transition; the Q output will become low if the D input is high and the C input receives a rapidly rising transition; and the Q output will not change if the C input is receiving a rapidly falling transition, irrespective of the D input. Referring to FIG. 2D, the D input first becomes low shortly before t 2 . Referring to FIG. 2F, the C input receives a rapidly rising transition at t 2 , at which time, therefore, the Q output rises, as may be seen in FIG. 2G. The Q output remains high until the concurrence of a high D input and a rising transition at the C input. Thus, midway between time t 2 and t 3 , the Q output becomes low. At time t 4 , the D input is already low and the C input receives a rising transition, whereby the Q input becomes high. Following through on this analysis the clock signal appearing on the Q output is that shown in FIG. 2G. It should be noted that the leading edge of each positive pulse in the wave form of FIG. 2G is in time coincidence with a leading edge of a pulse in the pulse train at the output of the amplifier 150 (FIG. 2F), which in turn corresponds to the instant when the signal out of the oscillator 120 is substantially zero (FIG. 2E). It is the leading edge of each of the positive pulses on the Q output which, when applied to the clock input C of the counter 176, causes the counter 176 to step to the next output, as may be seen by FIGS. 2G-2L and the dashed vertical lines therebetween. It is at these times, when the frequency of oscillation of the oscillator 120 shifts and because it is shifting at a time when the amplitude of the oscillatory signal produced thereby is substantially zero, there will be no discontinuity between the two tones as the change takes place. In other words, there will be a minimal loss of energy by the oscillator 120 during the transition, because the phase between two tones in sequence is substantially continuous. This also results in a faster tone signaling. While the first two tones in the sequence are internally programmed by the jumpers 144 and the plug 140, the third tone is externally programmed by a switching apparatus 200 having three double-throw switches 202, 204, and 206 connected in the manner shown. Each of the switches has a first position shown and a second position when each slide contact is moved to continue to engage the center fixed contact, and to engage the lower fixed contact rather than the upper fixed contact. If the switch 202 is actuated, there will be coupled to the collector of the transistor 138c the tap 132g. In that case, the oscillator 120 will produce during the last interval t 4 -t 5 an oscillatory signal corresponding to the value of the inductance between the taps 132g and 132j. If, instead, the switch 204 is actuated, then the oscillatory signal will be representative of the inductance between the taps 132h and 132j, while, if the switch 206 is, instead, actuated, the oscillatory signal will have a frequency dependent upon the value of the inductance between the taps 132 i and 132j. When any one of the three switches 202 to 206 is actuated, there will appear a short across the conductors 208 which, in turn, renders the speaker (FIG. 3) operative to hear whether the channel corresponding to the decoder is being used. If he hears communication, then he knows that the channel is being used and he must wait. As soon as the channel is quiet, he can operate the switch 52 to transmit the sequence of three tones, the first two of which were internally programmed by the connector 140 and represent the identification of the encoder 50, while the third tone in the sequence has been manually selected by the operator of the encoder, by actuating one of the switches 202 to 206. Actuation of the switch 202 might mean, for example, that the vehicle in which the encoder 50 is mounted is available for assignment, while actuating the switch 204 might mean that he has just completed assignment and is going home, etc. Upon completion of the three tones, the "4" output of the counter 176 becomes high (FIG. 2L), which output is coupled through a diode 212 as one input to a NOR gate 214, the output of which NOR gate is inverted by an inverter 216, and then coupled as a second input to the NOR gate 64. The high input to the NOR gate 214 supplies a low input to the NOR gate 64, thereby opening the latch at time t 5 , that is, the output of the NOR gate 64 becomes low. Such low output de-energizes the transistor 70, so that the supply voltage from the power supply 38 to the transmitter 20 is disrupted. Also, the low output from the NOR gate 64 is inverted by the inverter 118 to cause the R input of the counter 176 to become high, thereby resetting the counter. When reset, its "0" output becomes high and the other outputs "1" - "4" are low. The high output from the inverter 118 de-energizes the oscillator 120, causing the oscillatory signal (FIG. 2E) to end. The output of the NOR gate 66 becomes high, thereby providing a high input to the NOR gate 94, causing the output of the NOR gate 94 to become low, thereby extinguishing the bulb 414, so as to apprise the operator that the tone transmission has been completed. Also, operation of the multivibrator 102 is disrupted and the preamplifier 30 enabled. A high input to the NOR gate 214, to accomplish the termination and reset just described, is also furnished by the switch apparatus 200. If none of the switches 202, 204 and 206 is actuated, then, during the third tone when the transistor 138c becomes conductive, the supply voltage will be coupled therethrough, through the switches 202, 204 and 206, to provide the high input to the NOR gate 214. It should be understood that the encoder 50 is more inexpensively constructed because of the use of a single oscillator to provide twenty different tones. Ten tones are provided by virtue of the ten taps on the inductor 132, and ten more tones are provided by halving the signals produced by that oscillator. The absence of the additional oscillator and associated circuitry also reduces the weight and size of the encoder. The encoder 50 has capability of being internally programmed to establish the tones for automatic identification. Also, externally selected tones supply information on the status of the encoder. Although only five outputs of the counter 176 are shown, the particular counter used in the example has ten such outputs, so that it has the capability of supplying several more tones in sequence if desired. Also, the number of tones being internally programmed and the number of tones subject to external selection can be varied in accordance with particular needs. There can be provided various socket and plug arrangement, such as has been shown to select the frequencies of oscillation of the oscillator 120, and to select the number of tones. One such socket-plug arrangement could be used which couples all those outputs of the counter that are needed to interconnect the switching transistors 138a-138d to the associated coil taps. Alternately, a socket-plug arrangement may be employed to select all tones in the sequence by the switching apparatus 200. For example, all ten tones could be available for external selection, rather than just the three corresponding to the taps 132j to 132i. The selection of the tones in the encoder 50 is significant. First, it is clear that the every other tone in the transmitted sequence is selected from one bank of frequencies, while the remaining tones are selected from a second bank. The ten tones in the first bank are respectively harmonics of the ten tones in the second bank; in this example, each tone in the first bank is a second harmonic of a corresponding tone in the second bank. However, other harmonic relationships are certainly contemplated. One difficulty in making the proper selection of available tones is to insure that harmonics of the tones in one bank are not the same as tones in the other bank. This consideration is particularly important in an encoder as above described, since it squares the oscillatory signal. A square wave has virtually no second harmonics of the original sine wave, but is rich in third harmonics. In fact, it is desirable that the third harmonics actually be displaced by as much as possible from the tones in the other bank. It has been found that such optimum placement occurs when each tone is the 11th root of 2 times the next lower tone. The tones in the other bank have a similar relationship, but are obtained by halving the frequencies of the tones in the first bank. The tones in the two banks using such a relationship may be as follows: ______________________________________First Bank Second Bank______________________________________# Freq. # Freq.0 2400 OA 12001 2253.43 1A 1126.722 2115.82 2A 1057.913 1986.61 3A 993.34 1865.29 4A 932.645 1751.38 5A 875.696 1644.42 6A 822.217 1544 7A 7728 1449.71 8A 724.859 1361.18 9A 680.59______________________________________ With such tones, the third harmonic of any tones of one bank that happen to fall within the frequency spectrum of the second bank fall substantially midway between the channels. The feature of operating the switch 52 to start the transmitter 20 and then releasing that switch to start the sequence of tones insures that the carrier wave will be produced before the tones commence, so that no part of the tone sequence is lost. Alternatively, there could be employed a delay after the encoder is operated to allow the carrier wave to be produced, after which delay a quick start oscillator produces the tones. It is contemplated that the encoder 50 will be used to transmit to a base station having a display or other means of enabling the base station operator to evaluate the codes received. For example, a board may display a three-digit number in which the first two digits represent the identification of the encoder transmitting, and the last digit represents his status. If the number "123" appeared on the board, the base station operator would know that vehicle 12 is communicating with him and his status is 3 which may mean that that vehicle is ready for assignment. It is also contemplated that the decoder in such base station would have the frequency division structure described above. It becomes even more important in the decoder because the decoder in the base station would have to have capabilities to respond to a large number of different codes corresponding to the number of encoders in the field. FIG. 3 depicts a receiver 250 in which RF signals are applied to an antenna 252, then amplified by an RF amplifier 254, which is heterodyned in a mixer 256, using a local oscillator 258. The resulting IF signal is amplified in an amplifier 260 and then further amplified to limiting by a limiter 262. A discriminator 264 detects the modulation components in the signal, which modulation components include a sequence of tones followed by electrical signals representative of intelligence. The demodulated signal is coupled by way of a transformer 266 to a speaker 268, wherein the signal is converted into sound waves. In order for such conversion to take place, the contacts 270, which are normally open, must be closed. These contacts are part of a relay having a winding 272. When the winding 272 is energized, in the manner to be described hereinafter, the contacts 270 close, and the speaker 268 can reproduce the electrical signals applied thereto. The demodulated signals on the secondary of the transformer 266 are applied to a decoder 280 which includes a transformer 282. The demodulated signals on the secondary of the transformer 282 are depicted in FIG. 4A, and include noise and other extraneous components during the interval t o -t 1 , a first tone during the interval t 1 -t 5 , a second tone during the interval t 5 -t 8 , followed by a voice message during the interval t 8 -t 9 . The gaps in FIG. 4A indicate that many cycles of the signals may appear during each interval. For example, each of the two tones may have a duration of 100-150 ms. The demodulated signals are limited by the back-to-back diodes 284 and 286, and are impedance matched and filtered by the resistors 288-294 and the capacitor 296. The demodulated signals are amplified in an amplifier 298, to convert them into a square wave of the same frequencies, as shown in FIG. 4B. The square wave is applied to a Schmitt trigger circuit 300 which, in turn, supplies a square wave for the clock input C of a multiplier circuit 320. An example of such multiplier circuit is the flip-flop device illustrated in FIG. 1A, and used as the multiplier circuit 152. The R, S, and V inputs of the multiplier circuit 320 are grounded, while the D input and the Q output are connected together. The multiplier circuit 320 performs in the same manner as the multiplier circuit 152 of FIG. 1, that is, the signal produced at the Q output, as shown in FIG. 4C, has a frequency one half the frequency of the square wave shown in FIG. 4B. The Q output of the multiplier circuit 320 provides one input of a NOR gate 322, the other input of which is derived from a counter 382 in a manner to be presently described, which input is shown in FIG. 4K. Such input to the NOR gate 322 is initially low and therefore its output, as shown in FIG. 4H, will be the inverse of the Q output of the multiplier circuit 320. At time t 5 when the input to the NOR gate 322 derived from the counter becomes high, as shown in FIG. 4K, the output from such NOR gate becomes low, as shown in FIG. 4H. The wave form shown in FIG. 4K also constitutes an input to a NOR gate 324 which is connected as an inverter. The output of the NOR gate 324 is connected as one input to a NOR gate 326, the other input thereof being derived from the Schmitt trigger 300. Initially, when the signal shown in FIG. 4K is low, the corresponding input to the NOR gate 326 is high, whereby the output thereof, as shown in FIG. 4I, is low. On the other hand, when the signal shown in FIG. 4K becomes high at time t 5 , the corresponding input to the NOR gate 326 becomes low, and the output thereof follows the output from the Schmitt trigger 300, but is inverted. The output from the NOR gate 326 is shown in FIG. 4I. The NOR gates 322 and 326 are coupled as inputs to a NOR gate 328 which responds to the signals shown in FIGS. 4I and 4H to furnish the signal shown in FIG. 4G. It will be noted that when the first tone is present during the interval t 1 -t 4 , the output of the NOR gate 328 is a square wave having half the frequency of the signal shown in FIG. 4A, wherein, during the interval t 5 -t 9 the frequency of the square wave at the output of the NOR gate 328 is the same as the frequency of the second tone. The signal at the output of the NOR gate 328 is applied to a reference circuit 330 which is a voltage doubler and acts to rectify the signal from the NOR gate 328 and provide a reference voltage on the conductor 332. The signal from the NOR gate 328 is also applied to a filter 334 comprised of a pair of capacitors 336 and 338 and an inductor 340 having ten taps 340a to 340j. One end 340k of the inductor 340 is connected to the junction of the capacitors 336 and 338. A terminal block 342 has a plurality of electrical sockets 342a-342j respectively coupled to the taps 340a-340j. Also, the block has a set of sockets 344a-344d respectively coupled to the collectors of four PNP switching transistors 346a-346d, the emitter of each of which switching transistors is coupled to the supply voltage. Associated with the block 342 is a plug 348, having pins 348a-348j and 350a-350d. The plug 348 is adapted to be programmed to set the code to which the decoder 280 is to respond, by connecting jumper wires from selective ones of the pins 348a-348j to the pins 350a-350d. As an example, the pins 348i, 348g, 348e, and 348b are respectively connected by way of jumper wires 352 to the pins 350a-350d, so as internally to program the decoder to receive a sequence of four predetermined tones. However, as will be described, the decoder 280 has other elements so connected that it requires a sequence of only two tones to become actuated. Initially, during the interval t o -t 5 the transistor 346a is conducting, whereas the transistors 346b-346d are initially nonconducting, the reasons for which will be described in greater detail hereinafter. Then, the supply voltage on the emitter of the transistor 346a is coupled through its collector, through the socket 344a, the pin 350a, the corresponding jumper 352, the pin 348i, the socket 342i, whereby that portion of the inductor 340 between the tap 340i and the end 340k will be in the filter 334. The resonant frequency of the filter 334 will be determined by the value of such inductance and the value of the capacitors 336 and 338. When there is applied to the filter 334 a signal having such resonant frequency, a substantial output will be generated. In a manner to be described hereinafter, the resonant frequency of the filter 334 charges at time t 5 because a different amount of inductance has been switched into the circuit (the inductance between the tap 340g and the end 340k). If the square wave output of the NOR gate 328 (FIG. 4G) during the interval t 1 -t 5 has a frequency corresponding to the resonant frequency of the filter 334 prior to t 5 , the output of such filter will have the substantial amplitude shown in FIG. 4D during the interval t 1 -t 5 . If the square wave output of the NOR gate 328 during the interval t 5 -t 8 has a frequency corresponding to the resonant frequency of the filter 334 during that interval, then the amplitude of the output during that interval will also be substantial, as shown in FIG. 4D. FIG. 4D depicts the characteristic of the output of the NOR gate 328 that it takes some time to increase to full amplitude when the tone begins (on the order of 5-50 ms. for example) and some time to decrease to zero amplitude after the tone terminates (on the order of 20 ms. for example). The output of the filter 334 is applied to a rectifier 362 which detects the envelope of the filter output (i.e., it rectifies such output), as long as the output exceeds the reference voltage on the conductor 332 produced by rectification of the entire demodulated signal. The rectified signal, as shown in FIG. 2E, is applied to a clipper 364. When the amplitude of the rectified signal increases to level "1" at a time t 2 , shortly after the first tone has commenced, the clipper 364 will operate and its output becomes low, as shown in FIG. 4F. The switching level "1" of the clipper 364 is determined by the bias furnished by the resistors 363a and 363b applied to its other input. When the first tone terminates at t 4 , the rectified signal begins to fall in amplitude in accordance with the decreasing amplitude of the envelope shown in FIG. 4D. When the rectified signal amplitude reaches the switching level at time t 5 , the output of the clipper 364 becomes high again and stays high until t 6 , at which time the rectified signal arising from the second tone has reached the switching level, thereby causing the clipper output to become low. Such output remains low until t 8 . At t 8 , shortly after the second tone terminates, the switching level of the clipper 364 is reached and the output of the clipper 364 becomes high, at which level it remains until an ensuing tone sequence. Coupled to the output of the clipper 364 is a resistor 366 and a capacitor 368 in series to the supply voltage, the juncture of the two being coupled to a NAND gate connected as an inverter 370. A diode 369 is coupled in parallel with the resistor 366. Subsequent to the last tone sequence applied to the decoder 280, the capacitor 368 had been rapidly charged through the diode 369. When the output of the clipper 364 becomes low at t 2 , the capacitor 368 discharges through the resistor 366 at a rate determined by the values of the resistor 366 and the capacitor 368. After the resultant delay, the voltage at the input to the inverter 370 reaches a value to cause same to switch, whereby its output becomes high. The inverter 370 is coupled to a Schmitt trigger 384. Referring to FIG. 2M, the output of the Schmitt trigger 384 is normally low. At time t 3 , after the above-mentioned predetermined delay has passed, the output of the inverter 370 becomes high, which causes the output of the Schmitt trigger 384 to become low. After the first tone terminates, at t 5 , the capacitor 368 is rapidly charged through the diode 369, causing the output of the inverter 370 rapidly to become low, thereby causing the output of the Schmitt trigger 384 to become high at time t 5 . After the predetermined delay has passed, following t 6 , that is, at time t 7 , the output of the Schmitt trigger 384 becomes low and remains low until t 8 which is shortly after termination of the second tone. The capacitor 368 is rapidly charged at t 8 , causing the output of the Schmitt trigger 384 to become high and to remain high until the next tone sequence. The delay between time t 2 , when the leading edge of the negative-going transition at the output of the clipper 364 becomes low, and time t 3 , when the output of the Schmitt trigger 384 becomes low, is determined by the values of the resistor 366 and the capacitor 368, which predetermined delay may be on the order of 30 ms., for example. Such delay insures that noise or other short duration signals will not unintentionally trip the decoder 280. The output of the inverter 370 is also coupled to a timing circuit 372, comprising a resistor 374, a diode 376 coupled in parallel therewith, and a capacitor 378 coupled to ground. The output of the timing circuit 372 is coupled to a NAND gate connected as an inverter 380, which in turn is coupled to the counter 382. When the output of the inverter 370 becomes high at t 3 , the capacitor 378 is rapidly charged through the diode 376, causing the output of the inverter 380 to become low, as shown in FIG. 4P. At t 5 , shortly after the first tone terminates, the output of the NAND gate 370 becomes low and the capacitor 378 begins to discharge through the resistor 374. If no second tone is received, then the capacitor 378 will discharge to the point where the output of the inverter 380 will become high. However, in the example of FIG. 4, a second tone of the proper frequency is received at t 4 . At t 7 , after the delay furnished by the capacitor 368 and the resistor 366, the output of the inverter 370 again becomes high rapidly charging the capacitor 378 back to its maximum value, as shown in FIG. 4N. When the second tone terminates, the capacitor 378 again discharges, but because no subsequent tone is received, it discharges to a level at t 9 when the output of the inverter 380 becomes high (FIG. 4P). Thus, the output of the inverter 380 is low from t 3 to t 9 . The transistors 346a to 346d are sequentially rendered conductive by, and certain of the inputs to the gates 322 and 324 are derived from, a counter 382. The counter 382 has substantially the same construction as the counter 176 used in the encoder of FIG. 1. In this form, the "0" to "3" outputs are used, so those are the only ones shown. The CE input is grounded, the R input is coupled to the inverter 380, and the C input is coupled to the Schmitt trigger 384. The "0" output is coupled as an input to an NPN transistor 386a, the collector of which transistor is coupled to the base of the transistor 346a. The transistors 386a and 346a define an electronic switch. The "1", "2" and "3" outputs are respectively coupled to NPN transistors 386b, 386c and 386d, the collectors of which transistors are respectively connected to the bases of the transistors 346b, 346c, and 346d. Associated pairs of the transistors (e.g., 386b and 346b) define electronic switches. Initially, the "0" output of the counter 382 is high (FIG. 4J), thereby actuating the switch consisting of the transistors 386a and 346a, to cause the associated portion of the inductor 340 to be coupled in circuit in the filter 334, as previously described. At time t 3 , the reset input (FIG. 4P) becomes low, whereupon the counter 382 is in condition to be stepped. As can be seen in FIG. 4M, the first positive transition of the C input to the counter 382 occurs at time t 5 , on termination of the first tone, causing the counter 382 to step so that the "1" output becomes high (FIG. 4K). The transistors 386b and 346b conduct, thereby coupling in the filter circuit 334 another portion of the inductor 340, as previously described. Similarly, when the "2" output of the counter 382 becomes high (FIG. 4L), in response to a clock pulse at t 8 , another portion of the inductor 340 is connected in circuit with the filter circuit 334 to change the resonant frequency thereof. Since the decoder 280 is arranged to respond to only two tones, there will be no further clock pulses to cause the counter 382 to step to cause the "3" output to become high. The connections are there, however, so that the decoder 280 can be modified to accept more than two tones. The jumper connected to terminals 350c and 350d would not ordinarily be used if the decoder responds only to two tones. The "1" and "3" outputs of the counter 382 are coupled by way of diodes 388 and 390, across a resistor 392, to the gates 322 and 324 to provide the inputs thereto described previously. At time t 8 , the R input to the counter 382 becomes high, whereupon the counter 382 is reset to cause the "0" output to become high and the rest of the outputs "1"-"3" to be low. Thus, the counter 382 is reset either when the two-tone sequence is completed or when a second tone is not received. The "2" output of the counter 382 is coupled through a resistor 400 to the base of an emitter follower NPN transistor 402, the collector of which is coupled to the supply voltage and the emitter of which is coupled to a resistor 404 connected to ground. The emitter of the transistor 402 is coupled through filtering elements 406 to the control electrode of an SCR 408, the cathode of which is coupled to ground and the anode of which is coupled through a large resistor of for example, 100K to the supply voltage. The anode of the SCR 408 is also coupled to the supply voltage through a diode 412, the relay winding 272 and the normally closed contacts 56 of the switch 52. A bulb 414 and a diode 416 are coupled in series between the contacts 56 and the anode of the SCR 408. The anode of the SCR 408 is coupled through a resistor 418 and a diode 420 to a NAND gate connected as an inverter 422. A resistor 424 is connected across the resistor 418 and the diode 420. A capacitor 426 is connected from the input of the inverter 422 to the supply voltage. The output of the inverter 422 is coupled to the second input of the NOR gate 214 (FIG. 1). The transistor 402 is rendered conductive by the "2" output of the counter 382 becoming high at time t 8 , after termination of the second tone, thereby causing a positive input to be applied to the control electrode of the SCR 408, rendering it conductive to cause current flow from the supply voltage, through the normally closed contacts 56, the relay winding 272, the diode 412 and the SCR 408. The current flow through the winding 272 closes the contacts 270, thereby enabling the speaker 268 so that it can reproduce the voice message which follows the tones (see FIG. 4A). Also, current flows from the supply voltage through the contacts 56, the bulb 414, the diode 416 and the SCR 408, to illuminate the bulb 414 thereby apprising the possessor of the receiver 250 that he is being paged. The relay winding 272 and the bulb 414 will remain energized until the switch 52 is actuated to open the contacts 56. Such actuation disrupts current flow through the winding 272 to open the contacts 270 and also extinguishes the bulb 414. It will be remembered that another set of contacts 54 of the same switch 52 is used to initiate transmission of a sequence of tones by the encoder. In order to so use a common switch, it is necessary to insure that actuation of the switch 52 to extinguish the bulb 414 and de-energize the relay winding 272 does not also send out a tone sequence. To that end, the circuitry 418-424 is provided. When the SCR 408 is rendered conductive at t 8 , shortly after termination of the second tone, a path is provided for the capacitor 426 to charge rapidly through the diode 420 and the resistor 418, thereby causing the output of the gate 422 to become high, as shown in FIG. 4Q. Such high output furnishes a high input to the NOR gate 214 which disables the encoder 50. When the switch 52 is actuated to open the contacts 56, the capacitor 426 discharges slowly to maintain the high input to the NOR gate 214 high for, say, one second. Thus, if the switch 52 is only momentarily actuated, after the decoder 280 receives a coded signal, the encoder 50 will not produce a tone sequence. However, if the switch 52 is maintained actuated for more than one second, then the encoder will produce a sequence of tones. The decoder 280 responds to a sequence of two tones, by virtue of the input to the transistor 402 being derived from the "2" output of the counter 382. By moving the connection to the "3" output, the decoder 280 would be responsive to a sequence of three tones. What has been described, is a decoder in which the frequency of every other tone applied to the filter is multiplied by a predetermined multiplier, in this instance, that multiplier being one half, and the remaining tones are applied to the filter without any change in frequency. In this way, a single filter 334, having one tapped inductor, is able to respond to twenty tones. These principles can be used in a decoder to respond to any number of tones in sequence. Also, because of the smaller size of the encoder 50 and the decoder 280, they can be readily placed in the same package. It is believed that the invention, its mode of construction and assembly, and many of its advantages should be readily understood from the foregoing without further description, and it should also be manifest that, while preferred embodiments of the invention have been shown and described for illustrative purposes, the structural details are, nevertheless, capable of wide variation within the purview of the invention as defined by the appended claims.

The encoder in such system generates a sequence of tones in which every other tone is selected from a first group of tones in one band of frequencies, and the remaining tones in the sequence are selected from a second group of tones in another band of frequencies. The tones in the second group are respectively harmonically related to the tones in the first group, such as having frequencies double the respective frequencies of the tones in such second group. The tones are generated by an oscillator in the encoder, every other tone being multiplied by 1/2, for example. Circuitry, coupled to the oscillator and to the multiplier, alternately delivers the divided and undivided tones, to create the afore-mentioned sequence of tones. The oscillator has associated therewith a switchable impedance, predetermined amounts of which are sequentially switched into the oscillator to cause it to produce the sequence of tones. To minimize energy loss, circuitry is provided to insure that the phase of the tones is substantially continuous as the different amounts of impedance are switched into the oscillator. A programming device enables internal fixing of the frequencies of certain tones, which tones represent the identification of the encoder. A manual selector enables external selection of the frequencies of other tones which represent other information relative to the encoder.

BACKGROUND This description relates to reverse link power control. ACRONYMS AND ABBREVIATIONS 1x-EVDO Evolution Data only, CDMA2000 family standard for high speed data only wireless internet access AN Access Network API Application Programmable Interface ASIC Application Specific Integrated Circuit AT Access Terminal BIO-SC Basic Input/Output-System Controller CDMA Code-Division Multiple Access CPU Central Processing unit CSM5500 ASIC Qualcomm Inc. modem ASIC CSM5500 Drivers Qualcomm Inc. modem ASIC Driver and API FCS Frame Check Sequence FER Frame Error Rate FLM Forward Link Modem IP Internet Protocol PCT Power Control Threshold PCT RNi Power Control Threshold computed at ith RN PCT RNC Power Control Threshold computed at RNC RAN Radio Access Network RL Reverse Link or uplink-from mobile to base station. RLILPC Reverse Link Inner-Loop Power Control RLM Reverse Link Modem RLOLPC Reverse Link Outer-Loop Power Control RLOLPC-RN Power Control Algorithm running on RN RLOLPC-RNC Power Control Algorithm running on RNC RN Radio Node or Base Station RN-BIO-SC Radio Node BIO-SC Card or module RNC Radio Network Controller RNSM Radio Network Serving Module RPC Reverse Power Control RTCHMO Reverse Traffic Channel MAC Object SDU Selection and Distribution Unit SINR Signal-to-Interference Ratio (E b /I t ) Capacity of a cellular system represents the total number of mobile users (access terminals or ATs) that can be supported by the system. Capacity can be an important factor for cellular service providers, since it directly impacts revenue. CDMA wireless communications systems offer improved capacity and reliable communications for cellular and PCS systems. In a CDMA system, each AT transmit signal utilizes a different pseudo random sequence signal that appears as noise to other ATs. This enables many ATs to transmit on the same frequency. However, each AT's transmitted signal contributes to interference to the transmitted signal of all other users. Thus, the total number of users supported by the system is limited by interference. Therefore, reducing the amount of interference in a CDMA wireless communications system increases capacity. A typical problem in a CDMA cellular environment is the near/far problem. This entails the scenario where the transmit power of an AT near the RN may drown out an AT which is far from the RN. This is effectively mitigated by controlling the transmit power of each AT via power control scheme implemented by the access network (AN). AN continuously commands each AT to increase or decrease its transmit power to keep them all transmitting at the minimal power required to achieved the configured error rate for the operating data rate and maintain the overall balance of the power while reducing the interference in the area of coverage. In a CDMA 1x-EVDO system (see e.g., CDMA2000 High Data Rate Packet Data Air Interface Specification, 3GPP2 C.S0024, Version 4.0, Oct. 25, 2002), the reverse link operates in CDMA and hence reverse link power control is needed. The reverse link power control comprises of an open-loop power control (also called autonomous power control) and closed-loop power control. Open-loop power control is implemented in an AT, based on the received pilot-power of an RN. Closed-loop power control includes inner loop power control and outer loop power control, both of which are performed by the access network. Typical operation of a closed loop power control can be found in textbooks (see e.g., Vijay K. Garg, IS-95 CDMA and CDMA2000 Cellular/PCS Systems Implementation, Chapter 10, Prentice Hall, 1999, R. Steele. Mobile Radio Communications. Pentech Press, London, England, 1992, and Rashid A. Attar and Eduardo Esteves, A Reverse Link Outer-Loop Power Control Algorithm for CDMA2000 1xEV Systems, Proceedings of ICC, April 2002). Also, additional details can be found in e.g., U.S. Pat. No. 6,633,552, titled Method And Apparatus For Determining The Closed Loop Power Control Set Point In A Wireless Packet Data Communication System, and issued on Oct. 14, 2003, U.S. Pat. No. 6,507,744, titled Outer Loop Power Control Method During A Soft Handoff Operation, and issued on Jan. 14, 2003, and U.S. Pat. No. 5,884,187, titled Outer Loop Power Control Method During A Soft Handoff Operation, and issued on Mar. 16, 1999. A typical implementation is now described. FIG. 1 illustrates a system 100 implementing the basic closed loop power control operation. In closed loop power control, power adjustment is done at an AT 105 in accordance with the power control commands received from an RN 110 (also referred to as a base station 110 ). RN 110 sends up/down commands to each active AT (e.g., 105 ) to ensure that the AT transmit signal is received at the RN 110 at the lowest possible power required for the RN 110 to receive the data correctly at the operating rate. In a reverse link inner-loop power control (RLILPC) mechanism 115 , the reverse link signal to the interference-noise ratio (SINR) is continuously and frequently measured at a modem receiver of RN 110 . These frequent measurements track rapid channel variations of the link between the AT 105 and the RN 110 and facilitate accurate power control even when the AT 105 is in a deep fade. This measured of SINR is compared to a threshold value called ‘power control threshold’ (PCT). If the measured value is greater than PCTmax (=PCT+PCTDelta), the RPC bit is cleared. If the measured value is less than PCTmin (=PCT−PCTDelta), RPC bit is set. PCTDelta is a small value that provides an interval around the PCT. If the PCT is within this interval, the RPC bit status is unchanged from the previous value. Setting the RPC bits Cup decisions') commands AT 105 to increase its transmit power by a pre-determined step size, say ‘x’ dB. Clearing RPC bits (‘down decisions’) commands the AT 105 to decrease its transmit power by ‘x’ dB. The step size is negotiated a priori between RN 110 and AT 105 . Frame Error Rate (FER) is defined as a ratio of the bad frames to the total number of frames received by the RN 110 . A frame with correct physical layer frame check sequence (FCS) is defined to be a good frame. In 1x-EVDO, the physical layer cyclic redundancy code (CRC) can be used to determine good or bad frames. In a reverse link closed outer-loop power control (RLOLPC) algorithm 120 , the PCT is adaptively adjusted such that the configured target FER is achieved and maintained for the duration of the connection. (A target reverse link FER of 1% is considered typical for wireless networks). The RLOLPC algorithm 120 is implemented in a RNC 125 . It should be noted that there is another parameter beside FCS that is used in the voice application in CDMA system. This parameter is called the quality metric, which is an indication of how “bad” the bad frame is. For voice, it may be beneficial to play out a bad packet in order to maintain the perception of a good voice quality. Therefore, even the bad packets are still sent to the RNC 125 from the RN 110 with the marking for a correct FCS and a quality metric. It's up to the RNC 125 to determine if the quality metric meets the criteria for the packet to be used even when the FCS is incorrect. Typical operation of the RLOLPC algorithm 120 is described now. Upon reception of a RL frame with bad FCS, PCT is increased by a pre-set large value (e.g., 0.5 dB), which is termed a good frame PCT Delta. Upon reception of a RL frame with good FCS, PCT is decreased by a pre-set small value (e.g., 0.5 dB), which is termed a bad frame PCT Delta. Given the values of RL FER and the good frame PCT Delta, the bad frame PCT Delta value is computed as follows: Bad Frame PCT Delta=Good Frame PCT Delta(1−RL FER)/RL FER (Note that this same equation can be used to compute the good frame PCT Delta given the values of RL FER and the bad frame PCT Delta.) Before a connection establishment, or if there is no data on a RL, the PCT is set to a pre-set high value to facilitate rapid reverse link acquisition. A new value of the PCT is computed upon reception of each good/bad RL frame and an updated PCT is input into the RN modem receiver and to the RLILPC algorithm 115 . FIG. 2 illustrates an example system 200 , in which AT 105 is in a L-way soft hand-off (i.e., AT 105 is communicating with L RNs, e.g., RN 1 110 , RN 2 205 , and RN L 210 , at the same time). The selection and distribution unit (SDU) (not shown) at the RNC 125 determines which received frame from all the different ‘legs’ should be used. In addition it determines if correct or incorrect received frame indication needs to be send to the RLOLPC algorithm 120 on each frame boundary. The RLOLPC algorithm 120 uses this information to compute the overall PCT for the AT 105 . This PCT value is sent to all L RNs involved in the soft hand-off. SUMMARY OF INVENTION In one aspect, there is a method of performing reverse link power control in a mobile network having a plurality of first modem devices that receive and transmit signals to wireless access terminals (ATs) and a second device in communication with the plurality of first devices. The method includes transitioning execution between a first and a second loop to control reverse link power of one of the ATs, the transition being based on a state of a connection. The first control loop executes at one of the first devices and the second loop executes at the second device. Other examples can include one or more of the following features. The transitioning can include synchronizing between the first control loop and the control loop based on a change of the state. The change of the state of the connection can include transitioning from the connection not in handoff to the connection in soft handoff. The method can include transmitting to the second control loop a value for a power control threshold calculated by the first control loop. The transmitting can include transmitting the value for the power control threshold during transmission of handoff-related data. The method can include deriving a power control threshold using the first or second control loop. The method can include generating, by the one of the first devices, an indicator representing quality of a signal received from the one of the ATs, and calculating a power control threshold using the indicator. The method can include preventing transmission of a packet from the one of the first devices to the second device if the packet is associated with a bad indication. The method can include transmitting the bad indication to the second device. The method can include determining good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The state of the connection can include the connection not in handoff, the connection in softer handoff, or the connection in soft handoff. The method can include communicating between the first devices and the second device using Internet Protocol (IP) or asynchronous transfer mode (ATM). In another aspect, there is a method of performing reverse link power control in a mobile network having a plurality of first modem devices that receive and transmit signals to wireless access terminals (ATs) and a second device in communication with the plurality of first devices. The method includes deriving, by one of the first devices, a first power control threshold (PCT) value for reverse link power of one of the access terminals (ATs) and deriving, by the second device, a second power control threshold (PCT) value for reverse link power of the one of the ATs. The method also includes transmitting the second power control threshold (PCT) value using a data traffic path and selecting the first PCT value or the second PCT value. Other examples can include one or more of the following features. The transmitting can include transmitting using User Datagram Protocol or Generic Route Encapsulation protocol. The transmitting can include transmitting the second power control threshold (PCT) value based on a state of a connection. The state of the connection can include the connection in soft handoff. The second PCT value can be selected when the second PCT value is received at the one of the first devices. The first PCT value can be selected when a connection is not in handoff or a connection is in softer handoff. The second PCT value can be selected when a connection is in soft handoff. The method can include generating, by the one of the first devices, an indicator representing quality of a signal received from the one of the ATs, and calculating the first PCT and the second PCT using the indicator. The method can include preventing transmission of a packet from the one of the first devices to the second device if the packet is associated with a bad indication; and transmitting the bad indication to the second device. The method can include determining good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The method can include communicating between the first devices and the second device using Internet Protocol (IP) or asynchronous transfer mode (ATM). In another aspect, there is a system for performing reverse link power control in a radio access network (RAN). The system includes a first modem device and a second device in communication with the first device over a network. The first modem device receives and transmits signals to a wireless access terminal (AT). The first device is configured to execute a first loop to control reverse link power of the AT based on a first state of a connection. The second device is configured to execute a second loop to control reverse link power of the AT based on a second state of the connection and to synchronize the second loop with the first loop during a transition from the first state to the second state. Other examples can include one or more of the following features. The first state of the connection can include the connection not in handoff or the connection in softer handoff. The second state of the connection can include the connection in soft handoff. The second device can be configured to obtain a power control threshold calculated by the first control loop. The second device can be configured to obtain a power control threshold calculated by the first control loop during transmission of handoff-related data. The first device can be configured to derive a power control threshold using the first control loop. The first device can be configured to generate an indicator representing quality of a signal received from the AT and to calculate a power control threshold using the indicator. The first device can be configured to prevent transmission of a packet from the first device to the second device if the packet is associated with a bad indication and to transmit the bad indication to the second device in place of the packet. The first device can be configured to determine good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The first device and the second device can communicate using Internet Protocol (IP) or asynchronous transfer mode (ATM). In another aspect, there is a system for performing reverse link power control. The system includes a first modem device and a second device in communication with the first device over a network. The first modem device receives and transmits signals to a wireless access terminal (AT). The first device is configured to derive a first power control threshold (PCT) value for reverse link power of an AT. The second device is configured to derive a second power control threshold (PCT) value for reverse link power of the AT and to transmit the second power control threshold (PCT) value to the first device using a data traffic path. Other examples can include one or more of the following features. The first device can be configured to transmit the second power control threshold (PCT) value to the first device over the data traffic path using User Datagram Protocol or Generic Route Encapsulation protocol. The first device can be configured to select the first PCT value or the second PCT value. The first device can be configured to select the second PCT value when the second PCT value is received at the first device. The first device can be configured to select the first PCT when the connection is not in handoff or the connection is in softer handoff. The first device can be configured to select the second PCT value when the connection is in soft handoff. The first device can be configured to generate an indicator representing quality of a signal received from the AT and to calculate the first PCT using the indicator. The first device can be configured to prevent transmission of a packet from the one of the first devices to the second device if the packet is associated with a bad indication and to transmit the bad indication to the second device. The first device can be configured to determine good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The first device and the second device can communicate using Internet Protocol (IP) or asynchronous transfer mode (ATM). In another aspect, there is a computer program product, tangibly embodied in an information carrier, for performing reverse link power control in a mobile network having a plurality of first modem devices that receive and transmit signals to wireless access terminals (ATs) and a second device in communication with the plurality of first devices. The computer program product includes instructions being operable to cause data processing apparatus to transition execution between a first and a second loop to control reverse link power of one of the ATs, where the transition is based on a state of a connection, and the first control loop executes at one of the first devices and the second loop executes at the second device. Other examples can include one or more of the following features. The computer program product of can include instructions operable to cause the data processing apparatus to synchronize between the first control loop and the control loop based on a change of the state. The change of state of the connection can include transitioning from the connection not in handoff to the connection in soft handoff. The computer program product can include instructions operable to cause the data processing apparatus to transmit to the second control loop a value for a power control threshold calculated by the first control loop. The computer program product can include instructions operable to cause the data processing apparatus to transmit the value for the power control threshold during transmission of handoff-related data. The computer program product can include instructions operable to cause the data processing apparatus to derive a power control threshold using the first or second control loop. The computer program product can include instructions operable to cause the data processing apparatus to generate, by the one of the first devices, an indicator representing quality of a signal received from the one of the ATs, and calculate a power control threshold using the indicator. The computer program product can include instructions operable to cause the data processing apparatus to prevent transmission of a packet from the one of the first devices to the second device if the packet is associated with a bad indication, and transmit the bad indication to the second device. The computer program product can include instructions operable to cause the data processing apparatus to determine good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The state of the connection can include the connection not in handoff, the connection in softer handoff, or the connection in soft handoff. The computer program product can include instructions operable to cause the data processing apparatus to communicate between the first devices and the second device using Internet Protocol (IP) or asynchronous transfer mode (ATM). In another aspect, there is a computer program product, tangibly embodied in an information carrier, for performing reverse link power control in a mobile network having a plurality of first modem devices that receive and transmit signals to wireless access terminals (ATs) and a second device in communication with the plurality of first devices. The computer program product includes instructions being operable to cause data processing apparatus to derive, by one of the first devices, a first power control threshold (PCT) value for reverse link power of one of the access terminals (ATs), derive, by the second device, a second power control threshold (PCT) value for reverse link power of the one of the ATs, transmit the second power control threshold (PCT) value using a data traffic path, and select the first PCT value or the second PCT value. Other examples can include one or more of the following features. The computer program product can include instructions operable to cause the data processing apparatus to transmit using User Datagram Protocol or Generic Route Encapsulation protocol. The computer program product can include instructions operable to cause the data processing apparatus to select the second PCT value when the second PCT value is received at the one of the first devices. The computer program product can include instructions operable to cause the data processing apparatus to select the first PCT value when a connection is not in handoff or a connection is in softer handoff. The computer program product can include instructions operable to cause the data processing apparatus to select the second PCT value when a connection is in soft handoff. The computer program product can include instructions operable to cause the data processing apparatus to generate, by the one of the first devices, an indicator representing quality of a signal received from the one of the ATs, and calculate the first PCT and the second PCT using the indicator. The computer program product can include instructions operable to cause the data processing apparatus to prevent transmission of a packet from the one of the first devices to the second device if the packet is associated with a bad indication and transmit the bad indication to the second device. The computer program product can include instructions operable to cause the data processing apparatus to determine good or bad indication of a packet using a cyclic redundancy code (CRC) associated with the packet. The computer program product can include instructions operable to cause the data processing apparatus to communicate between the first devices and the second device using Internet Protocol (IP) or asynchronous transfer mode (ATM). Among the advantages of the system are one or more of the following. By reducing RNC-RN signaling (e.g., sending PCT only for connections in handoff), there is a reduced backhaul bandwidth consumption. Similarly, by reducing RN-RNC data traffic (e.g., sending only an indication of bad frames to a RNC, excluding the payload), there is a reduced backhaul bandwidth consumption. Other features and advantages will become apparent from the following description and from the claims. DESCRIPTION FIG. 1 is a block diagram illustrating reverse link power control in an example CDMA System. FIG. 2 is a block diagram illustrating reverse link power control in another example CDMA System. FIG. 3 is a block diagram illustrating a system for distributed reverse link power control. FIG. 4 is a block diagram depicting an example system for reverse link power control on the RN. FIG. 5 is a block diagram depicting an example system for reverse link power control on the RNC. FIG. 6 ( a ) depicts an example data structure of a message from RNC to RN. FIG. 6 ( b ) depicts an example data structure of a message from RN-BIO-SC to RLM. FIG. 3 illustrates a 1xEV-DO Radio Access Network (RAN) 300 . The RAN 300 can be built entirely on IP technology, all the way from an AT 305 to a network connection to the Internet (e.g., via a RNC 310 ), thus taking full advantage of the scalability, redundancy, and low-cost of IP networks. The entire service area of a wireless access provider may comprise one or more IP RANs 300 . Each IP RAN 300 can include many radio nodes (RNs), e.g., RN 315 and RN 320 , and one or more radio network controllers (RNC), e.g., 310 . The RNs 315 and 320 and the RNC 310 are connected over an IP (backhaul) network 330 , which supports many-to-many connectivity between RNs 315 and 320 and RNC 310 , and any other RNs and RNCs that may be part of RAN 300 . In presence of an IP connectivity between RNs 315 and 320 and RNC 310 , transmission of PCT values as IP packets over IP backhaul 330 to connections on all RNs can generate a high amount of signaling message transmission. Each RNC could potentially support 100s of RNs and the signaling message overhead for PCT message transmission could be a significant portion of the overall backhaul traffic. System 300 implements a distributed approach to reduce the signaling messaging over IP backhaul 330 , as described in more detail below, since signaling messaging has priority over data, which can cause significant reduction of data throughput to the end user. In system 300 , the RLOLPC functionality (e.g., updating the PCT) is distributed across RNs 315 and 320 and RNC 310 . This distribution is accomplished by using a RLOLPC-RNC module 335 for RLOLPC functionality in RNC 310 and a RLOLPC-RN module 340 for RLOLPC functionality in RNs 315 and 320 . In a general overview, system 300 uses RLOLPC-RNC module 335 or RLOLPC-RN module 340 based on the handoff state of AT 305 . In general, handoff represents the migration of a connection of AT 305 from one RN to another RN. When AT 305 is in communication with only one RN, for example RN 315 , then AT 305 is not in handoff. When AT 305 migrates, for example, from RN 315 to RN 320 , then AT 305 is in handoff. Soft handoff represents the overlapping coverage area of RNs 315 and 320 , where AT 305 can communicate with both RN 315 and RN 320 at the same time. A soft handoff is sometimes referred to as a make before break connection. Softer handoff represents the overlapping coverage area between different sectors for the same RN. If the AT 305 is not in handoff or is in softer handoff, the RLOLPC-RN module 340 of the serving RN handles the RLOLPC functionality. For example, if AT 305 is in communication only with RN 315 or is in a coverage area of RN 315 where AT 305 can communicate with multiple sectors of RN 315 , then the RLOLPC-RN module 340 of the RN 315 handles the RLOLPC functionality. As described above, the RLOLPC algorithm increases or decreases the PCT value based on whether the reverse link receives good or bad frame input. The RLOLPC-RN module 340 can determine bad or good frame input locally at the RN 315 by using the CRC state. Because system 300 is a 1xEV-DO system, there is no quality metric assigned to each received packet. Since the packet of data is either good or bad, the CRC state indicates the usefulness of the packet. In this scenario, the RLILPC 350 receives the PCT locally (shown by arrow 355 ) and not from the RNC 310 (shown by arrow 360 ). Because no information has to be transferred between RN 315 and RNC 310 , this local PCT calculation advantageously generates bandwidth savings on both reverse and forward links in backhaul 330 . Also, there is a saving of processor bandwidth in RNC 310 , since it does not have to execute an RLOLPC algorithm for this connection. If the AT 305 is in soft handoff, the RLOLPC-RNC module 335 of the serving RNC handles the RLOLPC functionality. For example, if AT 305 is in communication with both RN 315 and RN 320 , then the RLOLPC-RNC module 335 of the RNC 310 handles the RLOLPC functionality. In this scenario, like the scenario above, the RN (e.g., 315 and/or 320 ) receiving the packet determines whether it is a good or bad frame using the CRC state. If the RN (e.g., 315 and/or 320 ) determines the packet is a good frame, the RN forwards the packet to RNC 310 . If the RN (e.g., 315 and/or 320 ) determines the packet is a bad frame, the RN does not forward the packet to RNC 310 . Instead, the packet is dropped at the RN and an indication of a bad frame is sent to RNC 310 . This indication is smaller than sending the entire received packet, hence less traffic is generated on the backhaul 330 . An SDU in RNC 310 determines which leg (e.g., the communication between AT 305 and RN 315 or the communication between AT 305 and RN 320 ) is providing the good frame, if any, and inputs the RLOLPC-RNC module 335 accordingly. The RLOLPC-RNC module 335 generates the PCT and sends it to the applicable RNs using, for example, a packet. The PCT packet may be treated as a signaling packet and sent using a signaling path, (e.g., using Transmission Control Protocol (TCP)). This signaling path can be slower but more reliable than the data traffic path. In another example, the PCT packet can be treated as a data packet and sent using a data traffic path (e.g., using User Datagram Protocol (UDP) or Generic Route Encapsulation (GRE) protocol). This data traffic path can be faster but less reliable than the signaling path. For each RN, the PCT for all connections on each carrier in that RN can be multiplexed into one packet and sent to the respective RN. Also, the PCT values for all of the RNs can be multiplexed into one packet and multicast to all of the RNs. These examples of using a single packet advantageously saves bandwidth on the forward link of the backhaul 330 . Sending only a bad frame indication instead of the entire bad frame with appropriate markings advantageously generates bandwidth savings on the backhaul 330 . Also, there is a saving of processor bandwidth in the RNs since the RLOLPC-RN module 340 is not run for this connection. System 300 coordinates RLOLPC between the RLOLPC-RNC module 335 and the RLOLPC-RN module 340 for PCT input into the RLILPC 350 as the connection (with AT 305 ) enters handoff or exits handoff. System 300 coordinates RLOLPC in a number of ways. One way to coordinate RLOLPC is to transition the RLOLPC from RN to RNC and back to RN as connection (with AT 305 ) enters and exists handoff and to synchronize the RLOLPC to generate the same PCT while RLOLPC is transitioned. To start the description of this process, the AT 305 is not in handoff and is communicating with RNC 310 only through RN 315 . At some point, as AT 305 moves closer to RN 320 , AT 305 enters an area where AT 305 can communicate with RNC 310 through both RN 315 and RN 320 (a soft handoff condition). Once RNC 310 detects this condition, which requires the connection to enter into handoff, the RNC 310 requests the channel-element resources from target RN 320 and has to update the source RN 315 with the number of legs in the handoff (in this case 2). During these transactions, source RN 315 responds with the latest value of PCT to initialize the RLOLPC-RNC module 335 in RNC 335 . During resource allocation on target RN, the RNC 335 uses this PCT value to prime the target RN RLILPC 350 . Once initialized, the RLOLPC-RNC module 335 determines the PCT and transmits the value to the RNs 315 and 320 s described above. This transmission of the PCT from the RLOLPC-RN 340 to the RLOLPC-RNC 335 enables the RLOLPC-RNC 335 to become synchronized with the RLOLPC-RN 340 . The RLOLPC-RNC 335 can then take over the RLOLPC functionality seamlessly from the RLOLPC-RN 340 . Once RNC detects the condition that AT needs to leave the handoff state, it has to update the last remaining leg with the number of handoff legs. The latest value of PCT can be also sent to RN at this time, before the periodic update time. Once the RN receives the above message, the RN switches to run RLOLPC (using the RLOLPC-RN 340 ) and generates the PCT locally (e.g., at the RN) for this connection. Another way to coordinate RLOLPC is to simultaneously run RLOLPC in both RLOLPC-RN 340 and RLOLPC-RNC 335 . Unlike the above examples, in this scenario, the RNs send a bad frame indication to the RNC 310 , even when in a no handoff state, because RLOLPC-RNC 335 continuously calculates PCT, regardless of the handoff state. In this way, both RLOLPC-RN 340 and RLOLPC-RNC 335 are synchronized with each other. When, however, the AT 305 is in a no handoff or softer handoff state, RNC 310 does not transmit its PCT value to the RNs. RNs 315 and 320 are configured such that when they do not receive a PCT value from the RNC 310 they use the PCT value calculated by the RLOLPC-RN module 340 . When the AT 305 moves into a soft handoff state, RNC 310 starts transmitting the PCT value calculated by RLOPC-RNC module 335 . When the RNs 315 and 320 receive a PCT value from the RNC 310 , they use that received PCT value instead of their locally calculated value. In other words, a PCT value received from the RNC 310 overwrites, or has higher priority than, the PCT value calculated by the local RLOLPC-RN module 340 . In some examples, the updated PCT is computed immediately after reception of the FCS information. However, since RLOLPC is a slow control loop, other examples input the PCT value to a RN modem receiver only once every ‘N’ RL frames. N represents a configurable parameter. In one example, N is set to 4 RL frames. Typically, each 1x-EVDO RL frame duration is 26.66 ms (see e.g., CDMA2000 High Data Rate Packet Data Air Interface Specification, 3GPP2 C.S0024, Version 4.0, Oct. 25, 2002) and hence an update period where N is set to 4 is 106.64 ms. This characteristic of the RLOLPC algorithm also facilitates transmission of consolidated PCT messages as opposed to individual PCT messages from RNC 310 (e.g., single PCT packets described above). FIGS. 4 and 5 illustrate the modules of RN 315 and RNC 310 in more detail. The modules that are running on RN 315 are shown in FIG. 4 . The modules that are running on RNC 310 are shown in FIG. 5 . In one example, the power control function at RN 315 is distributed across a BIO-SC 515 and modem line cards. The modem line card contains both a FLM module 440 and a RLM module 435 . In one example, the power control function at the RNC 310 resides on a RNSM card 540 . In the illustrated example, the inner loop power control module (RLILPC) 405 exists in a modem receiver 410 of the RN 315 . In the distributed approach for reverse link power control described above, the RLOLPC functionality is distributed across RNs and RNC based on all different handoff scenarios of the mobile (e.g., AT 305 ). In describing FIGS. 4-6 , the following handoff scenarios will be used, and referred to using its respective preceding letter. (a) Connection (AT) is not in hand-off. (b) Connection (AT) is in softer hand-off but not in soft hand-off. (c) Connection (AT) is in softer and soft hand-off. (d) Connection (AT) is in soft hand-off. Handoff areas are located at the cell site boundaries. As described above, an AT 305 is said to be in ‘soft’ handoff if the AT 305 is able to see pilot signals from multiple RNs (e.g., both RN 315 and RN 320 ). An AT 305 is said to be in ‘softer’ handoff if the AT is able to see pilot signals from multiple sectors of a single RN. The AT 305 reports the pilots seen to the AN (e.g., RAN 300 ) as part of the route update message (see e.g., CDMA2000 High Data Rate Packet Data Air Interface Specification, 3GPP2 C.S0024, Version 4.0, Oct. 25, 2002). At the AN, a determination of whether the AT 305 is in no/soft/softer handoff is made based on the number of pilots and corresponding PN offsets. For example: An AT is said to be in ‘three-way’ soft handoff if the AN resolves PN offsets of the three pilots reported in the route update message that corresponds to the three different RNs. For example, if the system is compliant with CDMA2000 High Data Rate Packet Data Air Interface Specification, 3GPP2 C.S0024, Version 4.0, dated Oct. 25, 2002, the maximum number of pilots allowed in soft/softer handoff is 6. The number of pilots in soft handoff is referred to as the “soft handoff count”. During connection establishment, the RNC call control module 505 passes Soft Handoff count down to its peer, a call control agent (CCA) module 510 on each RN in the handoff. This facilitates connection resource allocation at RNs. As described above, the power control for softer handoff can be identical to the no hand-off since the received signals of a specific AT 305 from different sectors on the specific RN are combined before generating FCS on that specific RN. Hence, there is no RNC involvement for softer handoff. The techniques described herein distinguish the fact that for situations (a) and (b), the updated PCT provided by RLOLPC-RN module 340 is sufficient without any necessity of RNC 310 communicating with a RN (e.g., RN 315 ). For situations (c) and (d), updated PCT from RLOLPC-RNC module 335 is sent to all RNs in the handoff (e.g., RN 315 and RN 320 ) and this overrides the updated PCT from the RLOLPC-RN 340 . Power Control when AT is not in Soft Handoff FIG. 4 illustrates portions of RN 315 , highlighting power control operation for scenarios (a) and (b). A reverse link modem 435 receives signals transmitted by the AT 305 . A received signal from the AT 305 is decoded and MAC packets are generated by the modem receiver. This is represented by a RL Decoder block 415 . A RTCHMO block 420 receives FCS and reverse rate indication of the received RL frame. The FCS information is input to the RLOLPC-RN module 340 and the updated PCT is computed. Updated PCT is input to a Decision Module 425 . Soft Handoff Count is a key parameter that is used by the Decision Module 425 to determine whether the AT 305 is in soft handoff. For no handoff or softer handoff, the value of Soft Handoff Count=1. In one example, this soft handoff count parameter is sent from the CCA 510 to a power control connection object module 430 at the RLM 435 during power control connection resource allocation. A connection list scanner module 435 scans a linked list of all active connections on the RN 315 . Entries to this list are added/deleted when a connection is opened/closed with an AT. The scan list is updated from interaction with the RN call control agent module 510 . Updates from the call control agent 510 are based on messages from its peer RNC call control 505 . In one example, upon reception of a timing callbacks (e.g., 4 RL frames detected by RL frame timing callback module 440 ) the entire active connection list is scanned. For each connection, the decision module 425 chooses appropriate PCT depending on the soft handoff count value. In cases (a) and (b), Soft Handoff Count=1 and hence PCT RN is chosen (e.g., the PCT value calculated by the RLOLPC-RN module 340 ). This value is used as the current input to RLILPC 405 . Using the latest PCT value, the RLILPC algorithm 405 determines RPC bits and transmits them to the mobile 305 on a forward link MAC channel. Since there is no involvement of RNC signaling, delays on the backhaul 330 are minimized and bandwidth conserved, as described above. Minimization of delay from the time the updated PCT is determined to the time it is used by RLILPC advantageously offers better power control on the reverse link. This can also help improve capacity on the forward link for high data rate wireless systems. Power Control when AT is in Soft Handoff FIG. 5 illustrates portions of RNC 310 and RN 315 , highlighting power control operation for scenarios (c) and (d). In these scenarios, the AT is power controlled from the RNC 310 . An SDU algorithm 515 running on the RNC 310 processes FCS information received from all RNs that are involved in the soft hand-off and generates the consolidated FCS. If a good frame is received from at least one RN, then consolidated FCS is considered good. Bad FCS indication is generated if bad frames are received from all RNs. The RLOLPC-RNC module 335 gets FCS information from the SDU 515 and determines adaptive PCT that satisfies the FER criterion (RL FER is a configurable parameter. See the description above about the soft handoff count parameter). This value is stored in the power control connection object 520 for the specific connection. A connection list scanner module 525 scans the linked list of active connections that are in soft handoff. Entries to this list are added/deleted when an AT moves in and out of soft handoff. The scan list is updated from an interaction with the RNC call control module 505 . Updates from the call control 505 are based on soft handoff count information. Upon firing of a power control timer 530 (e.g., period=4 RL frames), the connection list is scanned. The RN-IP address and channel record 2-tuple uniquely identifies each RN. For each soft handoff leg (RN) in that connection, a PCT multiplexer 535 updates a consolidated PCT message with a new PCT. The structure of the consolidated PCT message is given in FIG. 6( a ). Once all connections in the list are scanned, PCT messages are transmitted to all RNs. In one example, for load balancing amongst competing tasks on the RNSM 540 , the connection list scanner 525 scans only a subset of connections in the connection list. This scanning size can be a configurable parameter on the RNC 310 and in one example is set to 960. In one example, the signaling PCT messages are sent to the RN 315 over the IP backhaul 330 using proprietary ABIS signaling protocol. In this example, there is no acknowledgement provided by RN 315 to RNC 310 . PCT values are quasi real-time and hence acknowledgements/retransmissions are redundant if messages are lost or dropped on the backhaul 330 . For a received message at RN-BIO-SC 515 , the PCT message remapper 545 strips out the BSCConnectionId and sends the received message to the appropriate RLM card 435 . Contents of this message are illustrated in FIG. 6( b ). PCT demultiplexer 445 located on the RLM 435 populates the appropriate power control connection object 430 with PCT RNC . For each connection, the decision module 425 chooses an appropriate PCT depending on the soft handoff count value. In scenarios (c) and (d), the soft handoff count>1 and hence PCT RNC is chosen. This value is written into the modem receiver and serves as current input to RLILPC 405 .

The description describes examples for performing reverse link power control in a mobile network having a plurality of first modem devices that receive and transmit signals to wireless access terminals (ATs) and a second device in communication with the plurality of first devices. Execution is transitioned between a first and a second loop to control reverse link power of one of the ATs. The transition is based on a state of a connection. The first control loop executes at one of the first devices and the second loop executes at the second device.

TECHNICAL FIELD This invention relates to ring transmission systems and, more particularly, to bidirectional ring transmission systems. BACKGROUND OF THE INVENTION It has become increasingly important to maintain communications connectivity in the presence of transmission system failures. To this end, path-switched ring type transmission systems and, more recently, bidirectional line-switched ring type transmission systems have been proposed that heal communications circuits in the presence of equipment failures, fiber cuts and node failures. Bidirectional line-switched ring transmission systems have a capacity advantage over path-switched ring transmission systems for all communications traffic patterns except a so-called simple hubbed traffic pattern, where the path-switched and line-switched ring transmission systems have the same capacity. On the other hand, a path-switched ring transmission system provides circuit presence at every ring node on the ring transmission system for each communications circuit being transported on the ring. In a bidirectional line-switched ring transmission system, circuit presence at every ring node for communications circuits propagating on the ring can only be established by employing twice the bandwidth as that used for the same communications circuits in the path-switched ring transmission system. Additionally, in the bidirectional line-switched ring transmission system, all service bandwidth is ring-protection-switched when necessary, and it is not possible to leave any of the bandwidth unprotected by ring switching. SUMMARY OF THE INVENTION The problems related to inefficient universal communications circuit presence and of lack of bandwidth unprotected by ring switching in a bidirectional line-switched transmission system are overcome, in accordance with the principles of the invention, by selectively switching, in accordance with the same rules governing the set-up and take down procedures of full line-switching, only that portion of the bandwidth of the particular line which has been provisioned to be ring-switched. In accordance with the invention, the remaining bandwidth can be left unprotected or path-switched on a communications-circuit-by-communications-circuit basis, thereby, for the first time, line-switched ring functionality is combined with path-switched ring functionality in the same ring transmission system. Furthermore, in accordance with the invention, another degree of switching freedom is achieved in a four-optical-fiber bidirectional line-switched ring transmission system by selectively span-switching, but not ring-switching, specific bandwidth on the line. To this end, communications circuit provisioning information is provided in the ring nodes as to whether a particular communications circuit should be line switched or not and, if not, whether it should be path-switched, span-switched or not switched, i.e., left unprotected. Thus, a determination can be made, in accordance with the principles of the invention, on a communications-circuit-by-communications-circuit basis whether an individual communications circuit on the ring should be protection switched and, if so, the type of switching to be effected. BRIEF DESCRIPTION OF THE DRAWING In the drawing: FIG. 1 shows, in simplified block diagram form, a ring transmission system including the invention; FIG. 2 shows, in simplified block diagram form, details of a ring node including an embodiment of the invention; FIG. 3 shows, in simplified block diagram form, details of a squelcher used in the ring node of FIG. 2; FIG. 4 shows, in simplified block diagram form, details of an AIS insert unit employed in the squelcher of FIG. 3; FIG. 5 is an exemplary ring node ID table included in memory of the controller of FIG. 2; FIG. 6 is an exemplary communications circuit ID table also included in memory of the controller of FIG. 2 for ring node 104; FIG. 7 is another exemplary communications circuit ID table also included in memory of the controller of FIG. 2 for ring node 104; FIG. 8 is a flow chart illustrating the switching and possible squelching operation of the controller of FIG. 2; FIG. 9 illustrates the failure message transmission for a complete fiber failure in the bidirectional line-switched ring transmission system; and FIG. 10 illustrates the failure message transmission for a single ring node failure in the bidirectional line-switched ring transmission system. DETAILED DESCRIPTION FIG. 1 shows, in simplified form, a bidirectional ring transmission system, in this example bidirectional line-switched-ring transmission system 100, which for brevity and clarity of exposition is shown as including only ring nodes 101 through 104, each incorporating an embodiment of the invention. Ring nodes 101 through 104 are interconnected by transmission path 110 in a counter-clockwise direction and by transmission path 120 in a clockwise direction. In this example, transmission paths 110 and 120 are comprised of optical fibers and each could be comprised of a single optical fiber or two (2) optical fibers. That is, bidirectional line-switched ring transmission system 100 could be either a two (2) optical fiber or a four (4) optical fiber system. In a two (2) optical fiber system, each of the fibers in transmission paths 110 and 120 includes service bandwidth and protection bandwidth. In a four (4) optical fiber system, each of transmission paths 110 and 120 includes an optical fiber for service bandwidth and a separate optical fiber for protection bandwidth. Such bidirectional line-switched ring transmission systems are known. In this example, transmission of digital signals in the SONET digital signal format is assumed. However, it will be apparent that the invention is equally applicable to other digital signal formats, for example, the CCITT synchronous digital hierarchy (SDH) digital signal formats. In this example, it is assumed that an optical OC-N SONET digital signal format is being utilized for transmission over transmission paths 110 and 120. The SONET digital signal formats are described in a Technical Advisory entitled "Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria", TA-NWT-000253, Bell Communications Research, Issue 6, September 1990. It is noted that requests and acknowledgments for protection switch action are transmitted in an automatic protection switch (APS) channel in the SONET overhead accompanying the protection bandwidth on each of transmission paths 110 and 120. The APS channel, in the SONET format, comprises the K1 and K2 bytes in the SONET overhead of the protection bandwidth. The K1 byte indicates a request of a communications circuit for switch action. The first four (4) bits of the K1 byte indicate the switch request priority and the last four (4) bits indicate the ring node identification (ID). The K2 byte indicates an acknowledgment of the requested protection switch action. The first four (4) bits of the K2 byte indicate the ring node ID and the last 4 bits indicate the action taken. For purposes of this description, a "communications circuit" is considered to be a SONET STS-3 digital signal having its entry and exit points on the ring. Each of ring nodes 101 through 104 comprises an add-drop multiplexer (ADM). Such add-drop multiplexer arrangements are known. For generic requirements of a SONET based ADM see the Technical Reference entitled "SONET ADD-DROP Multiplex Equipment (SONET ADM) GENERIC CRITERIA", TR-TSY-000496, Issue 2, September 1989, Supplement 1, September 1991, Bell Communications Research. In this example, the ADM operates in a transmission sense to pass signals through the ring node, to add signals at the ring node, to drop signals at the ring node, to bridge signals during a protection switch and to loop-back-switch signals during a protection switch at the ring node. FIG. 2 shows, in simplified block diagram form, details of ring nodes 101 through 104, including an embodiment of the invention. In this example, a west(W)-to-east(E) digital signal transmission direction is assumed in the service bandwidth and the protection bandwidth on transmission path 110. It will be apparent that operation of the ring node and the ADM therein would be similar for an east(E)-to-west(W) digital signal transmission direction in the service bandwidth and the protection bandwidth on transmission path 120. Specifically, shown is transmission path 110 entering the ring node and supplying an OC-N SONET optical signal to receiver 201, where N could be, for example, 12 or 48. Receiver 201 includes an optical/electrical (O/E) interface 202 and a demultiplexer (DEMUX) 203, which yields at least one (1) STS-M SONET digital signal. Such O/E interfaces and demultiplexers are known. In this example, M is assumed to be three (3) and N is greater than M. In order to accomplish line-switching in a two optical fiber bidirectional line-switched ring transmission system, M must be a divisor of N/2. In accordance with the principles of the invention, however, M must be no greater than the tributary level which it is desired to path protection switch. The STS-M signal output from DEMUX 203 is supplied to squelcher (S) 204 which, under control of controller, 205 controllably squelches, i.e., blocks, particular incoming communications circuits by inserting an alarm indication signal (AIS), as described below. Details of squelcher (S) 204 are shown in FIGS. 3 and 4 and its operation is described below. Thereafter, the STS-M signal, squelched or otherwise, is supplied to monitor element 230 and to broadcast element 206. Monitor element 230 checks the passing communication circuit signal for conditions such as loss of signal (LOS) or for parameters such as a bit error rate (BER). Such monitor elements are known in the art. A broadcast element replicates the STS-M signal supplied to it and supplies the replicated signals as a plurality of individual outputs. Such broadcast elements are known. Broadcast element 206 generates three identical STS-M signals and supplies one STS-M signal to an input of 3:1 selector 207, a second STS-M signal to an input of 2:1 selector 208 and a third STS-M signal to an input of 3:1 selector 209. An STS-M signal output from 3:1 selector 207 is supplied to squelcher (S) 210, which is identical to squelcher (S) 204. Squelcher (S) 210 is employed, under control of controller 205, to squelch particular outgoing communications circuits. The STS-M signal output from squelcher (S) 210 is supplied to transmitter 211 and, therein, to multiplexer (MUX) 212. The output of MUX 212 is an electrical OC-N digital signal, which is interfaced to transmission path 110 via electrical/optical (E/O) interface 213. Such multiplexers (MUXs) and electrical/optical (E/O) interfaces are well known. Similarly, in the east(E)-to-west(W) direction an OC-N optical signal is supplied via transmission path 120 to receiver 214 and, therein, to optical/electrical (O/E) interface 215. In turn, demultiplexer (DEMUX) 216 yields a STS-M signal which is supplied via squelcher (S) 217 to monitor element 231 and then to broadcast element 218. Broadcast element 218 replicates the STS-M signal into a plurality of identical STS-M signals, in this example, three (3). One STS-M signal is supplied to an input of 3:1 selector 207, a second STS-M signal is supplied to an input of 2:1 selector 208 and a third STS-M signal is supplied to an input of 3:1 selector 209. An output from 3:1 selector 209 is supplied via squelcher (S) 219 to transmitter 220. In transmitter 220, multiplexer (MUX) 221 multiplexes the STS-M into an electrical OC-N and, then, electrical/optical (E/O) interface 222 supplies the optical OC-N signal to transmission path 120. Controller 205 operates to effect the provisioned line-switching and deterministic squelching of communications circuits, or path-switching, in accordance with the principles of the invention. Additionally, as indicated below, a restriction to span-switching of a particular communications circuit can also be realized in a four fiber bidirectional line-switched ring transmission system, in accordance with another aspect of the invention. Controller 205 communicates with receivers 201 and 214 and transmitters 211 and 220 via bus 223 and with interface 224 via bus 227. Specifically, controller 205 monitors the incoming digital signals to determine loss-of-signal, SONET format K bytes and the like. Additionally, controller 205 causes the insertion of appropriate K byte messages for protection switching purposes, examples of which are described below. To realize the desired deterministic squelching of the communications circuits, controller 205 is advantageously provisioned via bus 228 with the identities (IDs) of all the communications circuits passing through the ring node, as well as those communications circuits being added and/or dropped at the ring node and the identities of all the ring nodes in bidirectional line-switched ring 100. The squelching of communications circuits under control of controller 205 to effect the invention is described below. Controller 205 communicates with monitors 230 and 231 to compare the health of two copies of an incoming path-switched communications circuit, and then instructs selector 208 to pick the better of the two copies. Interface 224 is employed to interface to a particular duplex link 225 and could include any desired arrangement. For example, interface 224 could include a DS3 digital signal interface to a DSX, an STS-1E (electrical) SONET digital signal interfacing to a DSX, an optical extension interface to an OC-N SONET optical signal or the like. Such interface arrangements are known. Specifically, a signal (R) to be dropped at the ring node is supplied to interface 224 via 2:1 selector 208, under control of controller 205, from either broadcast element 206 or broadcast element 218. In turn, interface 224 supplies the appropriate signal to duplex link 225. A signal (T) to be added at the ring node is supplied from duplex link 225 to interface 224 where it is convened to the STS-M digital signal format, if necessary. The STS-M digital signal is then supplied to broadcast element 226 where it is replicated. The replicated STS-M digital signals are supplied by broadcast element 226, to an input of 3:1 selector 207 and an input of 3:1 selector 209. In this example, 3:1 selectors 207 and 209, under control of controller 205, select the signal being added for transmission in the service bandwidth or the protection bandwidth on either transmission path 110 or transmission path 120. It should be noted that, in this example, the normal transmission path for a digital signal being added at the ring node would be in the service bandwidth on transmission path 120, for example, towards the west (W). The following describes the procedure for those communications circuits which are to be line-switched, if there were to be a protection switch. The signal (T) being added from interface 224 would be bridged via broadcast element 226 and chosen by 3:1 selector 207, under control of controller 205, to the protection bandwidth on transmission path 110. Similarly, if there were to be a loop-back protection switch and the ring node was adjacent to the failure, the signal (R) to be dropped at the ring node would be received in the protection bandwidth on transmission path 120 and would be switched from broadcast element 218 via 2:1 selector 208 to interface 224. It is noted that "failure" or "ring node failure" as used herein is intended to include node equipment failure and so-called node isolation failure caused by optical fiber cuts, cable cuts or the like. Otherwise, the signal (R) to be dropped would be switched in a ring node adjacent the failure from the protection bandwidth on transmission path 120 to the service,bandwidth on transmission path 110 and received at the ring node in usual fashion. Then, the signal (R) being dropped from transmission path 110 is supplied via broadcast element 206 and 2:1 selector 208 to interface 224. As indicated above, controller 205 monitors the status of interface 224 and the digital signal supplied thereto via bus 227. Specifically, controller 205 monitors interface 224 for loss-of-signal, coding violations and the like, i.e., a signal failure condition. Under control of controller 205, as previously noted, digital signals may be passed through, added at, dropped at, bridged at or loop-back-switched at the ring node. A loop-back-switch of an STS-M digital signal incoming in the service bandwidth on transmission path 110 is effected by controller 205 causing 3:1 selector 209 to select the STS-M digital signal from broadcast element 206 and supplying it via squelcher (S) 219 to transmitter 220. In turn, transmitter 220 supplies an OC-N optical signal to the protection bandwidth on transmission path 120. It will be apparent that in the loop-back-switch operation, if the signal is incoming in a service bandwidth on transmission path 110, it will be loop-back-switched to the protection bandwidth on transmission path 120 and vice versa. If the signal is incoming in protection bandwidth on transmission path 110, it will be loop-back-switched to the service bandwidth on transmission path 120 and vice versa. A signal to be added at the ring node is supplied from interface 224, replicated via broadcast element 226 and selected either by 3:1 selector 207 or 3:1 selector 209, under control of controller 205, to be added on transmission path 110 or transmission path 120, respectively. A digital signal to be dropped at the ring node is selected by 2:1 selector 208, under control of controller 205, either from broadcast element 206 (transmission path 110) or broadcast element 218 (transmission path 120). The pass-through and loop-back-switch functions for a signal incoming on transmission path 120 is identical to that for an incoming signal on transmission path 110. Possible communications circuit misconnections are avoided in bidirectional line-switched ring 100 by deterministically squelching communications circuits to be line-switched that are terminated in a failed ring node in ring nodes adjacent to the failed ring nodes(s). The adjacent failed ring nodes can include a plurality of nodes including those that appear to be failed because of being isolated by other failed ring nodes or by fiber and/or cable cuts. To this end, each ring node in bidirectional line-switched ring transmission system 100 is typically equipped to effect the desired squelching via squelchers (S) 204, 210, 217 and 219, under control of controller 205. In this example, both incoming and outgoing communications circuits are squelched, however, it may only be necessary to squelch outgoing communications circuits. FIG. 3 shows, in simplified block diagram form, details of an exemplary squelcher (S) unit. Specifically, the STS-M digital signal is supplied to demultiplexer (DEMUX) 301 where it is demultiplexed into its constituent M STS-1 digital signals 302-1 through 302-M. The M STS-1 digital signals are supplied on a one-to-one basis to AIS insert units 303-1 through 303-M. AIS insert units 303-1 through 303-M, under control of controller 205, insert AIS in the STS-1 digital signals included in the communications circuits, i.e., STS-M digital signals, to be squelched. Details of AIS insert units 303 are shown in FIG. 4 and described below. Thereafter, the M STS-1 digital signals are multiplexed in multiplexer (MUX) 304 to yield the desired STS-M digital signal. The details of multiplex schemes for the STS-M digital signal are described in the technical advisory TA-NWT-000253, referenced above. FIG. 4 shows, in simplified block diagram form, details of AIS insert units 303. Specifically, shown is an STS-1 digital signal being supplied to AIS generator 401 and to one input of 2:1 selector 402. AIS generator 401 operates to insert AIS in the STS-1 digital signal. As indicated in the technical advisory TA-NWT-000253, the STS path AIS is an "all ones" (1's) signal in the STS-1 overhead bytes H1, H2 and H3 and in the bytes of the entire STS SPE (synchronous payload envelope). Selector 402 selects as an output, under control of controller 205, either the incoming STS-1 digital signal or the STS-1 digital signal with AIS inserted from AIS generator 401. FIG. 5 is a table including the identification (ID) of ring nodes 101 through 104. The ring node IDs are stored in a look-up table which is provisioned via 228 in memory of controller 205. As indicated above, the ring node IDs are 4 bit words and are included in the second 4 bits of the K1 bytes and the first 4 bits of the K2 bytes in the APS channel. FIG. 6 is illustrative of a table including the identification of all the active communications circuits in a ring node, in this example, ring node 104, for a counter-clockwise communication through nodes 101 through 104 (FIG. 1). The active communications circuits include those being added, being dropped or passing through ring node 104. The table including the IDs of the active communications circuits in the ring node are provisioned via input 228 in a look-up table in memory of controller 205. Shown in the table of FIG. 6 are (a) the STS-M communications circuit numbers (#) b through f; (b) an identification of the ring node which includes the communications circuit entry point, i.e., the A termination for the communications circuit; and (c) an identification of the ring node which includes the communications circuit exit point, i.e., the Z termination for the communications circuit. Thus, the communications circuit ID table of FIG. 6, shows that STS-M(b) enters ring 100 at ring node 104 and exits at ring node 102; STS-M(c) enters ring 100 at ring node 103 and exits at ring node 101; STS-M(d) enters ring 100 at ring node 102 and exits at ring node 101; STS-M(e) enters ring 100 at ring node 103 and exits at ring node 102; and STS-M(f) enters ring 100 at ring node 103 and exits at ring node 104. Although the ring nodes designated as A terminations are considered entry points and the ring nodes designated as Z terminations are considered exit points, it will be apparent that the individual communications circuits may be duplex circuits having both entry and exit points at each such node. It should be noted that heretofore all communications circuits would be line-switched, but now it is possible, in accordance with the principles of the invention, to line-switch a subset of the communications circuits and to path-switch another subset of the communications circuits, as desired. Thus, as shown in FIG. 6, STS-M(b), STS-M(c) and STS-M(d) are provisioned, in accordance with the invention, to be line-switched and STS-M(e) and STS-M(f) are provisioned, in accordance with the invention, to be path-switched. Also encompassed within the principles of the invention is the capability of leaving a subset of the communications circuits unprotected. And in a four optical fiber bidirectional line-switch ring transmission system, it is now also possible to specify whether span-switching of communications circuits will be employed or not. These concepts are illustrated in FIG. 7 which, is illustrative of another exemplary table including the identification of all the active communications circuits in ring node 104, for counter-clockwise communication through ring nodes 101 through 104. Specifically, FIG. 7 illustrates how unprotected or span-switched communications circuits are provisioned via input 228 in a look-up table in memory of controller 205 (FIG. 2) in a four fiber ring transmission system. Communications circuits STS-M(b) through STS-M(f) are provisioned as shown in FIG. 6 and described above. Communications circuit STS-M(g) is span-switched only, and communications circuit STS-M(h) is unprotected. FIG. 8 is a flow chart illustrating the operation of controller 205 in controlling the operation of the ring nodes in order to effect the provisioned switching (and the deterministic squelching, if necessary) of communications circuits in the presence of a failure, in accordance with the invention. Specifically, the process is entered via step 801. Then, operational block 802 causes the K bytes of an incoming OC-N signal to be observed and processes the ring node IDs therein. Then, conditional branch point 803 tests to determine if the processed ring node IDs indicate that one or more ring nodes have failed. Again, a ring node failure is defined as to include node equipment failure and so-called node isolation failure caused by fiber cuts and the like. Specific examples of failure conditions are discussed below. If the processed ring node IDs indicate no ring node failure, the failure is other than a ring node failure and control is passed to operational block 804. Similarly, if step 803 indicates a single ring node failure, the failed ring node ID is already known and control is also passed directly to step 804. If the processed ring node IDs indicate a multiple ring node failure, operational block 805 causes the failed ring node IDs to be obtained from the ring node ID look-up table in memory (FIG. 5). Then, as in the other two instances, control is passed to operational block 804. Operational block 804 causes the identity (ID) of the affected communications circuits to be obtained whether or not any particular such communications circuit is to be line-switched (or possibly squelched), and if not line-switched, whether or not it is to be path-switched, and if not path-switched, whether or not it is to be span-switched from the communications circuit ID look-up table (FIG. 7) in memory of controller 205 (FIG. 2). Once the affected communications circuits are identified, conditional branch points 806, 810 and 812 separate the control process depending upon whether the affected individual communications circuit should be line-switched or not, should be path-switched or not, or should span-switched or not. It should be noted that if the communications circuit is not line-switched, path-switched or span-switched, it is left unprotected, in accordance with an aspect of the invention. It will be apparent to those skilled in the art that the individual affected communications circuits can be arranged into subgroups of communications circuits to be either line-switched, path-switched, span-switched only or not switched, i.e., left unprotected. If the communications circuit is to be line-switched, as determined in step 806, operational block 807 causes, if necessary, the appropriate ones of squelchers (S) 204, 210, 217 and 219 (FIG. 2), in this example, to squelch those identified communications circuits in the ring node. As indicated above, all line-switched communications circuits active in this ring node that are terminated in a failed ring node are squelched. Operational block 808 thereupon causes the line-switched communications circuits not terminated in the failed ring node(s) to be bridged and switched to "heal" the ring. Thereafter, the process is ended in step 809. If a communications circuit is to be path-switched, as determined in steps 806 and 810, operational block 811 compares, via monitors 230 and 231 (FIG. 2), the relative health of the two copies of the particular communications circuit, and engages path-switching in selector 208 (FIG. 2), if appropriate. Thereafter, the process is ended in step 809. If the affected communications circuit is not to be either line-switched or path-switched as determined in steps 806 and 810, conditional branch point 812 tests to determine whether or not the communications circuit is to be span-switched. If the affected communications circuit is to be span-switched, operational block 814 effects the span-switching as appropriate. Thereafter, the process is ended in step 809. Again, if the affected communications circuit is to be left unprotected as determined in steps 806, 810 and 812 the process is ended in step 809. FIG. 9 illustrates the failure message transmission in the automatic protection switch (APS) channel K1 bytes for a transmission path failure in bidirectional line-switched ring 100. In this example, the failure is shown as being in transmission paths 110 and 120 between ring nodes 101 and 102. Ring node 101 detects loss-of-signal from ring node 102 on incoming transmission path 120. Loss-of-signal as used herein is intended to include other indicators such as loss-of-frame, high bit error rate or the like. Then, ring node 101 transmits a line-switch request message identifying the signal from ring node 102 as having failed. Specifically, the line-switch request messages are transmitted in the APS channel K1 byte on transmission path 120 away from the failure toward ring node 104. This line-switch request message is designated SF L /102. Ring node 101 also transmits a span-switch request message in the APS channel K1 byte on transmission path 110 towards the failure. The span-switch request message is designated SF L /102. It should be noted, however, that a span-switch request is only issued and can only be realized in a four (4) fiber bidirectional line-switched ring transmission system 100. Ring node 104 recognizes that the line-switch request message SF L /102 in the incoming APS channel K1 byte does not identify an adjacent ring node and passes the line-switch request message on to ring node 103. Similarly, ring node 103 passes the line-switch request message on to ring node 102. In turn, ring node 102 recognizes its own ID in the SF L /102 line-switch request message, which indicates to ring node 102 that a ring node has not failed. Since there was no ring node failure, there is no need to squelch any of the communication circuits active in ring node 102. Ring node 102 does, however, effect a loop-back-switch of line-switched communications circuits received at the ring node in the service bandwidth on transmission path 120 to the protection bandwidth on transmission path 110 for communications circuits intended for other ring nodes in ring 100. Ring node 102 also effects a ring loop-back-switch of line-switched communications circuits entering the node that were intended to be transmitted in the service bandwidth on transmission path 120 to the protection bandwidth on transmission path 110. Any communication circuits received at ring node 102 that are intended to be dropped from either the service bandwidth or protection bandwidth on transmission path 120, are supplied to interface 224 (FIG. under control of controller 205, as described above. Any communications circuits to be path-switched are path-switched at their termination ring nodes if the current path selections are affected by the failure. Similarly, ring node 102 detects a loss-of-signal from ring node 101 on transmission path 110 because of the failure in transmission paths 110 and 120 between ring nodes 101 and 102. Then, ring node 102 transmits a line-switch request message identifying the signal from ring node 101 as having failed in the APS channel K1 byte on transmission path 110. This line-switch request message is designated SF L /101. Ring node 102 also transmits a span-switch request message in the APS channel K1 byte on transmission path 120 towards the failure. The span-switch request message is designated SF S /101. Again, it should be noted that a span-switch request is only issued and can only be realized in a four (4) fiber bidirectional line-switched ring transmission system 100. Ring node 103 recognizes that the line-switch request SF L /101 in the incoming APS channel K1 byte does not identify an adjacent ring node and passes the line-switch request message on to ring node 104. Similarly, ring node 104 passes the line-switch request message on to ring node 101. In turn, ring node 101 recognizes its own ID in the SF L /101 line-switch request message, which indicates to ring node 101 that a ring node has not failed. Since there was no ring node failure, there is no need to squelch any of the communication circuits active in ring node 101. Ring node 101 does, however, effect a loop-back-switch of line-switched communications circuits received at the ring node in the service bandwidth on transmission path 110 to the protection bandwidth on transmission path 120 for communications circuits intended for other ring nodes in ring 100. Ring node 101 effects a ring loop-back-switch of line-switched communications circuits entering the node that were intended to be transmitted in the service bandwidth on transmission path 110 to the protection bandwidth on transmission path 120. Any communications circuits received at ring node 101 that are intended to be dropped from either the service bandwidth or protection bandwidth on transmission path 110, are supplied as described above, under control of controller 205 to interface 224 (FIG. 2). Any communications circuits to be path-switched are path-switched at their termination ring nodes if the current path selections are affected by the failure. FIG. 10 illustrates the failure message transmission in the automatic protection switch (APS) channel via the K1 byte for a single ring node failure in bidirectional line-switched ring 100. In this example, the failure is shown as being in ring node 101. Ring node 102 detects a loss-of-signal from ring node 101 on transmission path 110 because of the failure of node 101. Then, ring node 102 transmits a line-switch request message identifying the signal from ring node 101 as having failed in the APS channel K1 byte on transmission path 110 away from the failure toward ring node 103. This line-switch request signal is designated SF L /101. Ring node 102 also transmits a span-switch request message from the APS channel K1 byte on transmission paths 120 towards failed node 101. The span-switch request message is designated SF S /101. As indicated above, a span-switch is only issued and can only be realized in a four (4) fiber bidirectional line-switched ring transmission system 100. Ring node 103 recognizes that the line-switch request message SF L /101 in the incoming APS channel K1 byte does not identify an adjacent ring node and, therefore, passes the line-switch request message on to ring node 104. Ring node 104 recognizes that the line-switch request message SF L /101 includes the ID of the adjacent failed ring node 101. A single node failure is indicated because ring node 104 has also detected loss-of-signal from ring node 101 on transmission path 120. Consequently, ring node 104, under control of controller 205 (FIG. 2), causes all active line-switched communications circuits in ring node 104 intended for ring node 101 to be squelched. The squelching is realized as described above in conjunction with FIG. 2 and the process of FIG. 8. Specifically, referring to the communications circuit ID table for ring node 104 in FIG. 6 or FIG. 7, it is seen that communications circuits STS-M (c) and STS-M (d) are to be squelched. Line-switched communications circuit STS-M (b) is identified as not being terminated in ring node 101 and, therefore, no squelching is effected for it. Thus, communications circuit STS-M(b) is ring loop-back-switched in ring node 104 to the protection bandwidth on transmission path 120 and supplied thereon to ring node 102 where it is appropriately dropped, in the manner described above. Path-switched communications circuits STS-M(e) and STS-M(f) are path-switched at their terminations if the current path selections are affected by the failure of ring node 101. The mechanics and process for effecting path-switching are well known to those skilled in the art. Communications circuit STS-M(f) is not affected by the failure of node 101 and communications between ring nodes 103 and 104 are realized in normal fashion. As indicated above, ring node 104 detects a loss-of-signal on transmission path 120 from failed ring node 101. Then, ring node 104 transmits a line-switch request message identifying the signal from ring node 101 as having failed in the APS channel K1 byte on transmission path 120 away from the failure toward ring node 103. Again, this line-switch request message is designated SF L /101. Ring node 104 also transmits a span-switch request message in the APS channel K1 byte on transmission path 110 towards the failed node 101. The span-switch request message is designated SF S /101. As indicated above, a span-switch can only be realized in a four (4) fiber bidirectional line-switched ring transmission system 100. Ring node 103 recognizes that the line-switch request SF L /101 incoming in the APS channel on transmission path 120 does not identify an adjacent failed node and passes the line-switch request message on to ring node 102. Ring node 102 recognizes that the line-switch request message includes the ID of an adjacent failed ring node, namely, ring node 101. A single ring node failure is indicated because ring node 102 has detected loss-of-signal from ring node 101 and has received a line-switch request message identifying node 101 as having failed. Consequently, ring node 102 will squelch all active line-switched communications circuits intended for ring node 101. Line-switched communications circuits terminated in others of the ring nodes in ring 100 are appropriately bridged and loop-back-switched as required to "heal" the ring 100. As indicated above, communications circuits to be path-switched are path-switched at their termination ring nodes if the current path selections are affected by the failure. The above-described arrangements are, of course, merely illustrative of the application of the principles of the invention. Other arrangements may be devised by those skilled in the art without departing from the spirit or scope of the invention. For example, it will be apparent to those skilled in the art that a particular communications circuit, i.e., tributary, on the ring could be segmented into portions which can be line-switched, path-switched, span-switched or not switched, i.e., left unprotected with appropriate priorities assigned to the portions and the type of switching, as desired. It will also be apparent that the bidirectional ring transmission system can support only path-switching of some communications circuits while leaving others unprotected. Additionally, it will be apparent that a four (4) fiber bidirectional ring transmission system can support path-switching of some of the communications circuits and span-switching of others. Finally, the four (4) fiber bidirectional ring transmission system can also support span-switching of some of the communications circuits and leaving others unprotected.

Selective tributary switching is realized in a bidirectional transmission system by selectively switching, in accordance with the same rules governing the set-up and take down procedures of full line-switching, only that portion of the bandwidth of the particular line which has been provisioned to be line-switched. The remaining bandwidth can be left unprotected or, by for the first time combining line-switched ting functionality with path-switched ring functionality in the same ring transmission system, some remaining bandwidth can be path-switched. Furthermore, another degree of switching freedom is achieved in a four optical fiber bidirectional ring transmission system by selectively span-switching, but not ring-switching, specific bandwidth on the line. To this end, communications circuit provisioning information is provided in the ring nodes as to whether a particular communications circuit should be line-switched or not and, if not, whether it should be span-switched, path-switched or left unprotected.

[0001] This application is a continuation of application Ser. No. 11/011,008, filed on Dec. 13, 2004, which claims the benefit of Korean Patent Application No. 10-2003-0091341, filed on Dec. 15, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method of controlling a digital photographing apparatus (e.g., a digital camera), and more particularly, to a method of controlling a digital photographing apparatus that receives an image having a resolution with a first pixel number and displays a display image on a displaying unit having a resolution with a second pixel number. [0004] The method of controlling the digital photographing apparatus of the present invention can be adopted in any digital photographing apparatus that captures and stores images in addition to digital cameras. In the present application, a digital camera is used as a typical example in which the present invention can be adopted. [0005] 2. Description of the Related Art [0006] FIG. 1 is a front perspective view of a conventional digital camera 1 . Referring to FIG. 1 , the digital camera 1 includes on its front surface, a microphone MIC, a self-timer lamp 11 , a flash 12 , a shutter button 13 , a mode dial 14 , a function-select button 15 , a photograph information display unit 16 , a view finder 17 a , a function-block button 18 , a flash-light amount sensor (FS) 19 , a lens unit 20 , and an external interface unit 21 . [0007] When in a self-timer mode, the self-timer lamp 11 operates when the shutter button 13 is pressed until a shutter (not shown) operates. The mode dial 14 is used to select one of various operating modes, for example, a still image photographing mode, a night scene photographing mode, a moving picture photographing mode, a reproducing mode, a computer connecting mode, and a system setting mode. The function-select button 15 is used to select one of the operating modes, for example, a still image photographing mode, a night scene photographing mode, a moving picture photographing mode, or a reproducing mode. The photograph information displaying unit 16 displays various information regarding each function related to photographing. The function-block button 18 is used to select one of the functions displayed on the photograph information display unit 16 . [0008] FIG. 2 is a rear view of the digital camera 1 of FIG. 1 . Referring to FIG. 2 , a speaker SP, a power button 31 , a monitor button 32 , an automatic focus lamp 33 , a view finder 17 b , a flash standby lamp 34 , a color liquid crystal display (LCD) panel 35 , a confirm/delete button 36 , an enter/play button 37 , a menu button 38 , a wide-angle zoom button 39 w , a telephoto zoom button 39 t , an up-movement button 40 up , a right-movement button 40 ri , a down-movement button 40 do , and a left-movement button 40 le are included on the back of the digital camera 1 . [0009] The monitor button 32 is used to control the operation of the color LCD panel 35 . For example, if the user presses the monitor button 32 a first time, an image of a subject and photographing information is displayed on the color LCD panel 35 ; when the monitor button 32 is pressed a second time, only the image of the subject is displayed on the color LCD panel 35 ; and when the monitor button 32 is pressed a third time, power supplied to the color LCD panel 35 is blocked. The automatic focus lamp 33 operates when an automatic focusing operation is completed. The flash standby lamp 34 operates when the flash 12 (see FIG. 1 ) is on standby. The confirm/delete button 36 is used as a confirm or delete button in the process in which a user sets one of the modes. The enter/play button 37 is used to input data or perform various functions such as stop or play in the reproducing mode. The menu button 38 is used to display a menu of a mode selected from the mode dial 14 . The up-movement button 40 up , the right-movement button 40 ri , the down-movement button 40 do , and the left-movement button 40 le are used in the process in which a user selects one of the modes. [0010] FIG. 3 is a view illustrating a structure of a surface of the digital camera 1 of FIG. 1 on which light is incident. FIG. 4 is a block diagram of the digital camera 1 of FIG. 1 . [0011] An optical system OPS including the lens unit 20 and a filter unit 41 optically processes light reflected from a subject. The lens unit 20 of the optical system OPS includes a zoom lens ZL, a focus lens FL, and a compensation lens CL. [0012] If a user presses the wide-angle zoom button 39 w (see FIG. 2 ) or the telephoto zoom button 39 t (see FIG. 2 ) included in a user inputting unit INP, a signal corresponding to the wide-angle zoom button 39 w or the telephoto zoom button 39 t is input to a micro-controller 512 . Accordingly, as the micro-controller 512 controls a lens driving unit 510 , a zoom motor M Z operates, thereby moving the zoom lens ZL. That is, if the wide-angle zoom button 39 w is pressed, the focal length of the zoom lens ZL is shortened, and thus increases a viewing angle. On the other hand, if the telephoto zoom button 39 t is pressed, the focal length of the zoom lens ZL is lengthened, and thus decreases a viewing angle. According to the above-mentioned characteristics, the micro-controller 512 can calculate a viewing angle based on the location of the zoom lens ZL from design data of the optical system OPS. Since the location of the focus lens FL is altered while the location of the zoom lens ZL is fixed, the viewing angle is hardly affected by the location of the focus lens FL. [0013] When the focus on a subject is automatically or manually fixed, the current location of the focus lens FL changes with respect to a distance Dc to a subject. Since the location of the focus lens FL is changed when the location of the zoom lens ZL is fixed, the distance Dc to the subject is affected by the location of the zoom lens ZL. In the automatic focusing mode, the micro-controller 512 controls the lens driving unit 510 , thereby driving a focus motor M F . Accordingly, the focus lens FL moves from the very front to the very back. In this process, a number of steps of the location of the focus lens FL (e.g., a number of location steps of the focus motor M F ) are set at which an amount of high frequency in an image signal is increased the most. [0014] The compensation lens CL is not separately operated since it acts to compensate for the overall refractive index. [0015] A motor M A drives an aperture (not shown). A rotation angle of the aperture driving motor M A depends on whether the digital camera 1 is in a specified area exposure mode or in another mode. In the specified exposure mode, when a part of a subject region desired by a user coincides with a specified detected region displayed on the color LCD panel 35 of the digital camera 1 , a light amount of the digital camera 1 is set to a mean brightness value of the specified detected region. [0016] An optical low pass filter (OLPF) included in the filter unit 41 of the optical system OPS removes optical noise with a high frequency. An infrared cut filter (IRF) included in the filter unit 41 blocks infrared components of incident light. [0017] A photoelectric converter OEC of a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) (not shown) converts light from the optical system OPS into an electrical analog signal. Here, a digital signal processor (DSP) 507 controls a timing circuit 502 and controls the operation of the photoelectric converter OEC and a correlation double sampler and analog-to-digital converter (CDS-ADC) device 501 . The CDS-ADC device 501 , which is an ADC, processes the analog signal output from the photoelectric converter OEC, and converts it into a digital signal after removing high frequency noise from the analog signal and altering the bandwidth of the analog signal. The DSP 507 processes the digital signal from the CDS-ADC device 501 , and generates a digital image signal divided into a chrominance signal and a luminance signal. [0018] A light emitting unit LAMP that is operated by the micro-controller 512 includes the self-timer lamp 11 , the automatic focus lamp 33 (see FIG. 2 ), and the flash standby lamp 34 (see FIG. 2 ). The user inputting unit INP includes the shutter button 13 (see FIG. 1 ), the mode dial 14 (see FIG. 1 ), the function-select button 15 (see FIG. 1 ), the function-block button 18 (see FIG. 1 ), the monitor button 32 (see FIG. 2 ), the confirm/delete button 36 (see FIG. 2 ), the enter/play button 37 (see FIG. 2 ), the menu button 38 (see FIG. 2 ), the wide-angle zoom button 39 w (see FIG. 2 ), the telephoto zoom button 39 t , the up-movement button 40 up (see FIG. 2 ), the right-movement button 40 ri (see FIG. 2 ), the down-movement button 40 do (see FIG. 2 ), and the left-movement button 40 le (see FIG. 2 ). [0019] The digital image signal output from the DSP 507 is temporarily stored in a dynamic random access memory (DRAM) 504 . Algorithms needed for the operation of the DSP 507 and for setting data are stored in an electrically erasable and programmable read-only memory (EEPROM) 505 . A memory card is inserted into a memory card interface (MCI) 506 . [0020] The digital image signal output from the DSP 507 is input to an LCD driving unit 514 . As a result, an image is displayed on the color LCD panel 35 . [0021] The digital image signal output from the DSP 507 can be transmitted in a series communication via a universal serial bus (USB) connector 21 a or an RS232C interface 508 and its connector 21 b , or can be transmitted as a video signal via a video filter 509 and a video outputting unit 21 c. [0022] An audio processor 513 outputs an audio signal from the microphone MIC to the DSP 507 or the speaker SP, and outputs an audio signal from the DSP 507 to the speaker SP. [0023] The micro-controller 512 controls the operation of a flash controller 511 according to a signal output from the FS 19 , and thus operates the flash 12 . [0024] FIG. 5 is a flowchart illustrating a method of controlling photographing of the micro-controller 512 illustrated in FIG. 4 . [0025] Referring to FIGS. 1 through 5 , the shutter button 13 included in the user inputting unit INP has a two-step structure. That is, if a user presses the shutter button 13 to a first step after the user operates the wide-angle zoom button 39 w or the telephoto zoom button 39 t , a first signal S 1 output from the shutter button 13 is activated, and if the shutter release button 13 is pressed to a second step, a second signal S 2 output from the shutter button 13 is activated. Therefore, the algorithm for controlling photographing illustrated in FIG. 5 starts when the shutter release button 13 is pressed up to the first step (Operation 101 ). Here, the current location of the zoom lens ZL is already set. [0026] Remaining storage space of the memory card is detected (Operation 102 ), and it is determined whether the storage space is sufficient to record a digital image (Operation 103 ). If there is not enough storage space, a message indicating a lack of storage space in the memory card is displayed (Operation 104 ). If there is enough storage space, the following operations are performed. [0027] Automatic white balance (AWB) is performed, and parameters related to the AWB process are set (Operation 105 ). Then, automatic exposure (AE) is performed in which a brightness of incident light is calculated, and the aperture driving motor M A is operated according to the calculated brightness amount (Operation 106 ). Then, automatic focusing is performed, and the location of the focus lens FL is set (Operation 107 ). [0028] Then, it is determined whether a first signal S 1 , which is a signal generated when the shutter button 13 is at a first step, is activated (Operation 108 ). If the first signal S 1 is inactivated, the user has no intention of photographing, and thus, a perform-program is terminated. If the first signal S 1 is activated, the following operations are performed. [0029] First, it is determined whether the second signal S 2 is activated (Operation 109 ). If the second signal S 2 is not activated, the user has not pressed the shutter button 13 to the second step for photographing, and thus the method moves to operation 106 . [0030] If the second signal S 2 is activated, a photographing operation is performed since the user has pressed the shutter button 13 to the second step for photographing. That is, the micro-controller 512 operates the DSP 507 , and the timing circuit 502 operates the photoelectric converter OEC and the CDS-ADS 501 . Then, image data is compressed (Operation 111 ), and a compressed image file is generated (Operation 112 ). After the generated image file is stored in the memory card via the MCI 506 from the DSP 507 (Operation 113 ), the method is completed. [0031] For reference, Japanese Patent Publication No. hei 11-196301, titled “Electronic Camera Device,” discloses an electronic camera device in which the state of an image, for example, a focusing or a shaking of the image at the moment of photographing, can be easily checked. [0032] FIGS. 6A , 6 B, 6 B′, and 6 C are views illustrating a conventional method of controlling a digital photographing apparatus to enlarge an image to check a focus of the image. [0033] Referring to FIGS. 6A , 6 B, 6 B′, and 6 C, in the conventional method of controlling the digital photographing apparatus, a predetermined region of an image displayed on an image displaying device 35 is set as a focus zone before photographing the image. After displaying an enlarged focus zone, a user focuses the image or presses a shutter switch to perform photographing. [0034] To do so, first, a focus frame 61 for checking the focus of the image is displayed inside a monitor image 60 of the subject, which is displayed on the image displaying device 35 , in a recording mode ( FIG. 6A ). Then, a portion of the image inside the focus frame 61 is automatically or manually at a command of the user enlarged, and displayed on the entire screen 62 or on a portion 63 of the screen (FIGS. 6 B and 6 B′). Then, the user checks whether the image is in focus by looking at the enlarged image, changes the focus if necessary, and performs photographing, and thus a photographed image 64 is displayed ( FIG. 6C ). [0035] Image sensors used in digital photographing apparatuses have an increasing number of pixels due to advancements in technology, and the size of an LCD display window, which is an image displaying device, is becoming smaller due to the miniaturization of digital photographing apparatuses. Therefore, there is a large difference between the resolutions of the image sensor and the LCD display window, which is the image displaying device. [0036] However, in the conventional method of controlling the digital photographing apparatus, the focus region is simply enlarged and displayed and resolutions of an image sensor and the image displaying device are not considered. Thus, it is difficult to achieve a good effect in the situation in which there is a large difference between the resolutions of the image sensor and the LCD display window as the image displaying device. SUMMARY OF THE INVENTION [0037] The present invention provides a method of controlling a digital photographing apparatus that can check the quality of a photographed image by enlarging a portion of the photographed image and displaying it on an image displaying device after photographing considering the difference between the resolution of an image sensor and the resolution of the image displaying device. [0038] According to an aspect of the present invention, there is provided a method of controlling a digital photographing apparatus in which a portion of an input image is enlarged and displayed as a display image on an image displaying unit so that a user may determine the clarity of the input image, the digital photographing apparatus receiving the input image having a resolution of a first pixel number and displaying the display image on the image displaying unit having a resolution of a second pixel number. The method includes: receiving the input image; setting an enlarged display region that is to be enlarged from the input image, dividing the enlarged display region into at least two display images, and continually displaying the display images on the image display unit. [0039] According to another aspect of the present invention, there is provided a method of controlling a digital photographing apparatus in which a portion of an input image is enlarged and displayed as a display image on an image displaying unit so that a user may determine the clarity of the input image, the digital photographing apparatus receiving the input image having a resolution of a first pixel number and displaying the display image on the image displaying unit having a resolution of a second pixel number. The method includes: receiving the input image; determining whether to enlarge the input image; setting a portion of the input image that is to be enlarged as an enlarged display region having a resolution of a third pixel number; calculating a number of display frames that are to be displayed on the image displaying unit by dividing the third pixel number by the second pixel number and rounding the result to an integer, and dividing the enlarged display region into the display images according to the number of the display frames; and displaying the display images on the image displaying unit. BRIEF DESCRIPTION OF THE DRAWINGS [0040] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: [0041] FIG. 1 is a front perspective view of a conventional digital camera; [0042] FIG. 2 is a rear view of the digital camera of FIG. 1 ; [0043] FIG. 3 is a view illustrating a structure of a surface of the digital camera of FIG. 1 on which light is incident; [0044] FIG. 4 is a block diagram of the digital camera of FIG. 1 ; [0045] FIG. 5 is a flowchart illustrating a method of controlling photographing of a micro-controller illustrated in FIG. 4 ; [0046] FIGS. 6A , 6 B, 6 B′, and 6 C are views illustrating a conventional method of controlling a digital photographing apparatus to enlarge a screen to check a focus of an image; [0047] FIG. 7 is a flowchart illustrating a method of controlling a digital photographing apparatus according to an embodiment of the present invention; [0048] FIG. 8 is a flowchart illustrating a method of displaying an enlarged image in the method of controlling the digital camera illustrated in FIG. 7 ; [0049] FIG. 9 is a view schematically illustrating the displaying of the enlarged image of FIG. 8 ; [0050] FIG. 10 is a view illustrating a setting of an enlarged display region in the displaying of the enlarged image described in FIG. 8 [0051] FIG. 11 is a view illustrating dividing of the enlarged display region into display images in the displaying of the enlarged image described in FIG. 8 ; and [0052] FIGS. 12A through 12D are views illustrating the displaying of the respective divided display images in FIG. 11 in an automatic slide show. DETAILED DESCRIPTION OF THE INVENTION [0053] The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The description of a digital photographing apparatus with reference to FIGS. 1 through 5 also applies to all digital photographing apparatuses in embodiments of the present invention. [0054] FIG. 7 is a flowchart illustrating a method 200 of controlling a digital photographing apparatus according to an embodiment of the present invention. [0055] Referring to FIG. 7 , in the method 200 , the digital photographing apparatus receives an input image having a first resolution and displays a display image on an image displaying unit having a second resolution. A portion of the input image is enlarged and displayed as the display image on the image displaying unit so that a user may determine the clarity of the input image. [0056] To do this, the digital photographing apparatus receives an input image (S 201 ). Then, a portion of the input image that is to be enlarged is set as an enlarged display region, the enlarged display region is divided into at least two display images, and the display images are continually displayed on an image displaying unit (S 203 ). The method may further include an operation of determining whether to enlarge the input image (S 202 ). [0057] In the present embodiment, the input image is input from the outside by photographing in operation S 201 . The input image may be input via an image sensor (a charge-coupled device (CCD)) as in a conventional digital photographing apparatus, and the image sensor has a first resolution. [0058] Although the input image is input from the outside by photographing in operation S 201 in the present embodiment, an input image may be obtained from the outside from an external device, and the obtained image may be input as image data via a data input/output unit in operation S 201 . In this case, in order to apply the method 200 of controlling the digital photographing apparatus according to the present invention, the input image data has the first resolution. [0059] In addition, the image data may be stored in a predetermined storage medium or a pre-photographed image may be stored as image data, and the stored input image may be checked by displaying the input image on the image displaying unit through the manipulation of the user. Operation S 203 may be performed by the manipulation of the user that makes the input image to be displayed on the image displaying unit. [0060] When desiring to display the photographed input image or the input image stored in the storage on the image displaying unit in advance, whether to display the enlarged input image or not may be set as a default. [0061] In operation S 202 , when displaying the input image on the image displaying unit using a setting, whether to enlarge and display the image can be determined. In this case, when not enlarging and displaying the input image according to the determination result of S 202 , the input image having the first resolution is converted into an image having a second resolution and displayed on the image displaying unit in S 204 . [0062] Since an image sensor used in a digital photographing apparatus usually has a higher number of pixels due to the advancement in technology, and the size of a liquid crystal display (LCD) display window, which is an image displaying device, is becoming more limited due to the miniaturizing of the digital photographing apparatus. Therefore, the first pixel number is higher than the second pixel number in many cases, and thus an input image with a high resolution is not properly displayed on the image displaying unit that has a lower resolution than the input image. Therefore, there is a limit in properly recognizing the clarity of the input image only with the image displayed on the image displaying unit. [0063] The image displaying unit maybe a display device such as an LCD or an organic electro luminescent may be used. In the present embodiment, an LCD panel is used. [0064] In operation S 203 , when enlarging and displaying the input image according to the determination result from operation S 202 , a portion of the input image that is to be enlarged is set as the enlarged display region. The enlarged display region is divided into at least two display images, and is continually displayed on the image displaying unit. The displaying of the enlarged input image in operation S 203 will be described in more detail with reference to FIG. 8 . In this case, each of the display images may be automatically displayed continually using an automatic slide show, as illustrated in FIG. 8 . [0065] In operation S 203 , one of the divided display images is displayed on the image displaying unit, and each of the display images selected by an input from the outside, for example, by the user, may be manually displayed. [0066] When enlarging a portion of the input image and displaying it on the image displaying unit in operation S 203 , an entire input image may be reduced and displayed on a portion of the image displaying unit on which the display image is displayed. Here, the input image may be surrounded by, for example, a quadrangular line so that it is distinguishable from the display image. The reducing of the entire input image and displaying it on the portion of the image displaying unit is as illustrated in FIGS. 9 and 12 . [0067] The displaying of the entire input image on the portion of the image displaying unit is used to indicate which portion of the entire input image is currently displayed as the display image on the image displaying unit. [0068] The enlarged display region of the input image is divided into at least two display images and displayed in operation S 203 so that the user may determine the clarity of the input image from the display image displayed on the image displaying unit. Here, the clarity of the image may be affected by how much the focus, a white balance, an amount of exposure, the shaking of the hands etc., were controlled. If the clarity of the image is reduced, the quality of the image becomes poorer. [0069] That is, when reproducing the photographed image on the image displaying unit and checking the photographed image in the present embodiment, the image is enlarged and reproduced in consideration of the resolution of the input image and the resolution of the image displaying unit, and thus making it easier for the user to determine the clarity of the input image. An image photographed when it is difficult to focus the image (e.g., when the hand shakes, the surrounding is dark, a manual focus is set, or a near subject is photographed) may be blurred. Even when the image appears to be well focused on the image displaying unit of the digital photographing apparatus, the clarity of the image may still be poor when displaying the image on an external displaying device having a much higher resolution than the image displaying unit. [0070] In this case, a specific region (i.e., a focus zone) of the input image is enlarged and displayed to easily check the clarity of the input image, or the user may easily check the clarity of the input image using a digital zoom. [0071] In addition, the method 200 of controlling the digital photographing apparatus may further include deleting the input image when the clarity of the display image is not satisfactory according to the determination of the user. That is, first, the specific region of the input image is enlarged and displayed so that the user may check the clarity of the input image. Then, when the input image does not have a satisfactory clarity according to the determination of the user and the user desires to delete the currently checked input image, the input image may be deleted. [0072] Furthermore, after checking the clarity of the input image using the method 200 of controlling the digital photographing apparatus, a process of deleting the input image if the clarity of the display image is lower than a standard clarity may be performed automatically by the digital photographing apparatus. The clarity can be determined based on a focus, a white balance, an amount of exposure etc., and a satisfactory clarity may be pre-set as the standard clarity. [0073] To do so, first, it is determined whether the input image is to be deleted by the selection of the user (S 205 ). In the case it is set for the user to delete the input image, the input image is deleted (S 206 ). The input image that does not have a desired quality is deleted so that a new input image may be obtained. [0074] FIG. 8 is a flowchart illustrating the displaying the enlarged image (S 203 ) in the method 200 of controlling the digital camera of FIG. 7 . FIG. 9 is a view schematically illustrating the displaying of the enlarged image (S 203 ) of FIG. 8 . [0075] Referring to FIGS. 7 through 9 , in the method 200 , the digital photographing apparatus receives the input signal having the first resolution and displays the display image on the image displaying unit having the second resolution. A portion of the input image is enlarged and displayed on the image displaying unit so that the user can determine the clarity of the input image. [0076] The method 200 of controlling the digital photographing apparatus includes receiving the input image (S 201 ), and determining whether to enlarge the input image (S 202 ). The operation S 203 of displaying the enlarged image includes setting a portion of the input image that is to be enlarged as an enlarged display region having a resolution of a third pixel number (S 301 ); dividing the second pixel number by the third pixel number, rounding the result to the nearest integer, calculating the number of display frames that is to be displayed on the displaying unit, and dividing the enlarged display region into display images according to the number of the display frames (S 303 ); and displaying each of the display images on the image display unit (S 304 , S 305 , and S 306 ). [0077] In operation S 301 , the portion of the input image that is to be enlarged is set as the enlarged display region, which has the resolution with the third number pixel. That is, the third pixel number expresses the size of the enlarged display region in pixel numbers. [0078] The enlarged display region may be set in a variety of ways in operation S 301 . When enlarging and displaying the enlarged display region, a region in which the user can readily determine the clarity of the input image can be set as the enlarged display region. Here, the user may personally set the enlarged display region via a user input unit of the digital photographing apparatus. [0079] As an example of the method of setting the enlarged display region of S 301 , an input image can be divided into at least two regions, and a region having the most edges may be set as an enlarged display region. That is, the divided regions are examined and a region with the most edge information is found and set as the enlarged display region. [0080] Also in operation S 301 , when a face of a person is included in an input image, the face region may be set as the enlarged display region. Here, color information of the input image can be extracted and the face can be detected by comparing the color information with a face tone of a general person, and it can be determined whether the face of a person is included in the input image. [0081] According to another embodiment of the present invention, in the method of setting the enlarged display region of S 301 , a focus zone for adjusting a focus when automatically focusing, which is used in a conventional method of controlling a digital photographing apparatus, may be set as an enlarged display region. [0082] FIG. 10 is a view illustrating the setting of the enlarged display region (S 301 ) in the displaying of the enlarged input image described in FIG. 8 . In the present embodiment, the whole input image is displayed on the image displaying unit, and the user may select how far a region to be enlarged and displayed is from the center of the input image. For example, a region corresponding to, for example, 1/9, 1/16, and 1/25 region from the center of the input image may be selected as an enlarged display region. [0083] In operation S 303 , the enlarged display region set in operation S 301 is divided into at least two display images. A number of display frames that are to be formed is calculated from the third pixel number of the enlarged display region and the second pixel number of the image displaying unit, and the enlarged display region is divided into equal number of display images and display frames. Here, the number of display frames can be calculated by dividing the third pixel number by the second pixel number and rounding the result into an integer. The result can be rounded to the nearest whole number, rounded up or rounded down. [0084] Also, the method 200 of controlling the digital photographing may further include setting a displaying ratio of a pixel number of an input image that is to be displayed on the image displaying unit and a pixel number of a display image that is displayed on the image displaying unit (S 302 ). Here, the displaying ratio may be a ratio of a pixel number of an input image that is to be displayed on the image displaying unit and a pixel number of a display image that is displayed on the image displaying unit in which 1:1 displaying ratio is preferable. [0085] Operation S 302 is further included in case the user desires to check a further enlarged image simultaneously, and thus the user may select to perform operation S 302 . For example, the display ratio may be 1:1, 2:1, 3:1, . . . , n:1, or set by the user. [0086] FIG. 11 is a view illustrating the dividing of the enlarged display region into display images in the displaying of the enlarged input image described in FIG. 8 . In this case, when further including operation S 302 , the number of the display frames is calculated by dividing the third pixel number by the second pixel number, multiplying the result by a display ratio n, and then rounding the result into an integer in operation S 303 . [0087] Here, it may be difficult to reproduce the set enlarged display region in the selected display ratio in a single operation. For example, when 2/5 of an input image is selected to be displayed after being enlarged in a 1:1 ratio, when the size of the input image is 1,000,000 pixels and the size of an LCD is 100,000 pixels, 2/5 of the 1,000,000 pixels, that is, 400,000 pixels, is divided into four display frames, each having 100,000 pixels, and the four display frames are reproduced. [0088] The display images are displayed on the image displaying unit in operations S 304 , S 305 , and S 306 . In operation S 304 , a method of displaying the display images is determined, in operation S 305 , the display images are displayed in an automatic slide show, and in operation S 306 , the display images are manually displayed. [0089] In operation S 304 , whether to display the display images in the automatic slide show or manually display the display images is determined from a default setting. When photographing using the digital photographing apparatus and checking the photographed image, a user may select whether to use a function in which an enlarged display region is automatically enlarged according to a photographing condition. [0090] In operation S 305 , the display images are sequentially displayed on the image displaying unit when the automatic slide show is selected in operation S 304 . [0091] The configuration of enlargement reproduction, the enlarged display region, the enlargement ratio, the method of displaying, etc. is set by a user with a menu. If the enlarged display function is to be performed on the enlarged display region of a photographed image, the image is photographed as described in FIG. 8 , immediately an entire image is briefly shown, and the enlarged display region is enlarged and displayed according to the settings. Here, the enlarged display function performed on the enlarged display region is selected when a photographing condition is in a manual focus control mode, when a near subject is being photographed, when photographing using a telephoto zoom, when over 1/30 second of exposure is needed, etc. [0092] In operation S 305 , it is preferable that a display image at the center of the enlarged display region is displayed on the image displaying unit, and the display images in the clockwise direction are sequentially displayed on the image displaying unit in the enlarged display region. In FIG. 9 , which schematically illustrates the displaying of the enlarged image (S 203 ) described in FIG. 8 , an entire input image is divided into regions using vertical and horizontal lines as shown, and regions labeled 1 through 9 sequentially are set as the enlarged display region. [0093] In each of operations S 305 and S 306 , region 1 is first enlarged and displayed on the entire image displaying unit. In operation S 305 , display images of region 1 through 9 are sequentially displayed on the entire image displaying unit, which is in the clockwise direction from the center of the image displaying unit. [0094] FIGS. 12A through 12D are views illustrating the displaying of the respective divided display images in FIG. 11 in the automatic slide show. The region of the entire input image that is divided by dotted lines forming a quadrangle at the center thereof according to a setting is set as the enlarged display region. Then, the enlarged display region is divided into regions by horizontal and vertical lines. [0095] The display images shown in FIGS. 12A through 12D are sequentially displayed on the entire image displaying unit in operation S 305 . In this case, the display images are sequentially displayed in the counterclockwise direction. Also, when displaying the display images on the image displaying unit using the automatic slide show, the slide show may stop if an interruption occurs in the middle of the slide show. [0096] In operation S 306 , when manually displaying the display images according to the determination result in operation S 304 , one of the divided display images is displayed on the image displaying unit, and each of the display images selected by external input is displayed. When manually displaying the display images according to the external input, a region selected by the user may be displayed and not the images in display frame units which are formed in operation S 303 . [0097] That is, when manual display is selected, a center frame is reproduced and an image may be displayed in a pre-set pitch units, and not frame units, by moving the enlarged display region little by little to a desired direction using user operating keys. [0098] As illustrated in FIGS. 9 and 12A through 12 D, when enlarging a portion of the input image and displaying the display images on the image displaying unit in operations S 305 and S 306 , the entire input image can be reduced and displayed on a portion of the image displaying unit on which the display images are displayed. The reduced entire input image can be surrounded by, for example, a quadrangular line so that it is distinguishable from the display image. The reduced entire input image is displayed to indicate which part of the entire input image the display image is taken from and displayed on the image displaying unit. [0099] In addition, the method 200 of controlling the digital photographing apparatus can be adopted in a digital photographing apparatus according to an embodiment the present invention. [0100] As described above, in a method of controlling a digital photographing apparatus according to the present invention, a portion of a photographed image is enlarged and displayed on an image display device in consideration of a difference in a resolution of an image sensor and a resolution of the image displaying device. Thus, a user may check the quality of the photographed image and may conveniently determined whether the photographed image has the quality the user desires. In addition, the user may easily determine, for example, the clarity of the photographed image or whether the photographed image is well focused. [0101] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

A method of controlling a digital photographing apparatus to enlarge and reproduce an image is provided. The method includes determining whether an instruction is given in an image reproduction mode, dividing the input image into a predetermined number of blocks when it is determined that the instruction is given, enlarging the small image corresponding to a specific block from among the predetermined number of blocks, and displaying the enlarged small image on an entire screen.

BACKGROUND OF THE INVENTION This invention relates to the pneumatic conveyance of materials and, in particular, to improved apparatus for introducing fluent bulk materials into a pneumatic conveying line. In the pneumatic conveyance of various bulk materials it is well known to provide a hopper or similar collecting arrangement which supplies the bulk material to a feed tube. The feed tube in turn is provided with a suitable means, such as a feed auger, which advances the bulk material along the feeding tube and into some form of chamber through which a current of air is passed by way of air inlet and air outlet lines connected to that chamber. The bulk material which is deposited within the chamber is intended to be fluidized by the air current and carried by the air current through the air line outlet and along the outlet conveying line to a storage site, such as a silo. In order to prevent air blow-back through the feed tube and alongside the auger, the outlet end of the feed tube is provided with a gate or other suitable one way valve arrangement which is intended to close when the flow of bulk material into the chamber slows down or stops thereby to prevent air blow-back through the feed tube and feed hopper. If blow-back occurs, the bulk material being handled may be sprayed around thus creating a potential hazard and, at least, a substantial cleanup problem. The prior art has provided various devices of the nature indicated above as exemplified generally by the following U.S. Pat. Nos.: ______________________________________ 560,381 - Wainwright et al May 19, 18963,106,428 - Lenhart Oct. 8, 19633,460,869 - Herr Aug. 12, 19693,588,180 - Herr June 28, 1971______________________________________ One notable problem with all or virtually all of the prior art devices is that they were prone to a build-up of the material on or adjacent to the movable gate. After a period of time the gate would not close properly thus creating a substantial blow-back problem. Many of the prior art units were also prone to plugging thus requiring substantial down-time to partially dismantle the device and to remove the plugged up material. Part of the problem with many of the prior art designs is that the internal configuration in the region of the gate is such that inadequate fluidization of many materials does not take place thus resulting in the build-up of deposits which eventually render the apparatus inoperative. In addition, no means were provided whereby the operator could observe the action occurring in the vicinity of the gate and take appropriate remedial action before plugging or blow-back occurred. Another problem inherent in many or all of the prior art devices is that they are not sufficiently versatile. Most of them were designed for either only one or a very small number of very similar products. If an attempt is made to use them with products having substantially different characteristics, problems resulting from gate deposit build-up, plugging, and blow-back back soon arise. Another problem inherent in most, if not all, of the prior art devices of the type under consideration is that they are only intended to be used in one fixed location. This necessitates the use of highly specialized and relatively expensive equipment for transporting dry bulk materials. In the past these dry bulk materials have been transported by pneumatic trailers and a relatively small number of specially designed rail cars. In the case of the so-called pneumatic trailers (which are intended for highway use), the entire vessel or container is pressurized during the unloading operation and this necessitates an extremely expensive structure. This, in turn, tends to increase shipping costs. Because of the specialized nature of the container, the pneumatic trailer is generally only usable one way thus meaning that the return trip is made with no load. This again keeps shipping costs high. Various fluent bulk materials, such as cement, lime, sand, salt and various dry chemicals, are commonly carried in this fashion. SUMMARY OF THE INVENTION It is a general objective of the present invention to alleviate or overcome the various difficulties noted above and to provide apparatus for successfully introducing a wide variety of fluent bulk materials into a pneumatic conveying line and which is substantially free from the plugging and blow-back problems inherent in the prior art devices. A further objective is to provide apparatus of the type under consideration wherein the operator can readily observe the action occurring in the vicinity of the gate and take remedial action so as to increase or decrease the rate of flow of the bulk material thereby to provide optimum performance. A further objective of the invention is to provide apparatus of the type under consideration which is readily portable from one job site to another and which is of a relatively low-profile configuration so that it can be slipped under a conventional hopper bottom trailer so as to receive the bulk material from it thus enabling use of the much less expensive hopper bottom trailers, which trailers can carry a load both ways, thus substantially reducing overall shipping costs. A further object of the invention is to provide apparatus of the type under consideration which is capable of successfully handling a very wide variety of fluent bulk materials, all the way from very light and relatively easily handled materials such as flour right through to the more difficult materials such as cement, lime, salt and the like. Accordingly, the present invention in one aspect relates to apparatus for introducing fluent bulk materials into a pneumatic conveying line, comprising: (a) a fluidizing chamber having an air line inlet and an air line outlet for connection to incoming and outgoing air lines respectively; (b) a feed tube connected to the fluidizing chamber, and having an outlet end disposed within said chamber; (c) an assembly for effecting movement of the bulk material through said feed tube from a source of supply into the interior of the fluidizing chamber so that the material may, during use, be fluidized by an air flow passing through the fluidizing chamber from said air line inlet to and through said air line outlet and carried therewith out through the air line outlet; (d) a gate located at said outlet end of said feed tube within the fluidizing chamber and exposed, in use, to the air flow passing from the air line inlet to and through the air line outlet and responsive to opposing forces exerted, thereon by the bulk material moving through the feed tube and the pressure of the air within the fluidizing chamber for permitting flow of said bulk material into said fluidizing chamber through the feed tube and at the same time preventing blow back of air from the fluidizing chamber through said feed tube. In accordance with an aspect of the invention, the air line inlet and the air line outlet noted above are located in substantial alignment with one another along a first axis. The feed tube defines a further axis which is laterally arranged relative to the first axis and is displaced from it in such a way that, during use, bulk material exiting the outlet end of the feed tube falls downwardly under the influence of gravity and passes into and is fluidized by the air flow passing through the fluidizing chamber along the first axis from the air line inlet to the air line outlet. Preferably and in accordance with another aspect of the invention, the gate is hinged adjacent its upper edge for movement from a closed position in close contacting relation to the outlet end of the feed tube to and through a range of partially open positions. During use, the bulk material applies a force to one face of the gate while the pressure of the air applies a force to the opposing face of the gate. In a preferred form of the invention, the fluidizing chamber includes a gate chamber and an air duct section. The air duct section typically includes a tubular section having the air line inlet and the air line outlet disposed at opposing ends thereof. The gate chamber is secured to the air duct section and has its lower end portion opening into and freely communicating with the interior of the duct section. As a result of this construction, the bulk materials falling downwardly by gravity from the outlet end of the feed tube pass into a central region of maximum air flow velocity within the air duct section to effect substantially complete fluidization of the bulk material. Still further according to a feature of the invention, the above-noted gate is disposed in the fluidizing chamber such that, during use, a substantial lower portion Of the gate is disposed within the region of maximum air flow velocity so that the resulting air currents tend to keep the gate clear of deposits which might otherwise tend to prevent full closure of the gate. In a preferred form of the invention, the above-noted assembly for effecting movement of the bulk material through the feed tube includes a variable speed drive and suitable means to control this drive. The control means preferably includes start, stop and reverse valve means for controlling the movement of material through the feed tube. This facilitates safe operation and allows the safe removal of certain foreign materials that may from time to time become lodged in the feed tube. The fluidizing chamber is typically provided with a viewing port above the gate so that the operator can control the rate of movement of material through the feed tube by way of a speed control valve in accordance with conditions as observed within the fluidizing chamber. All of this permits remedial action to be taken before a plugging situation occurs. As a further desirable feature of the invention, a low profile inlet hopper is connected to an inlet end of the feed tube. This low profile hopper allows the apparatus to be located below and to receive bulk material from the outlet of a hopper bottom trailer or the like. Inlet flow control means are typically provided in the hopper to control the rate of flow of bulk material into the feed tube and the device for effecting movement of the bulk material through the feed tube. The device for effecting such movement is typically a feed screw, otherwise known as a feed auger. The above-noted means (e.g. the feed auger) for effecting movement of the bulk material through the feed tube is located in a lower portion of the hopper. The inlet flow control means is typically disposed just above the previously noted means (e.g. feed auger) and may take the form of an inverted V-shaped baffle having suitable means thereon such as adjustable plates arranged to allow the rate of flow of material from the hopper toward and into the feed tube to be varied as desired. Further features, objects and advantages of the present invention will become apparent to those skilled in the art after reading the following description of a preferred embodiment of the invention taken in conjunction with the appended drawings. BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS FIG. 1 is a perspective view of an apparatus for introducing fluent bulk materials into a pneumatic conveying line; FIG. 2 is a side elevation view of the apparatus, certain portions of the same being out away so as to show the internal feed auger; FIG. 3 is a top plan view of the apparatus, a portion of the feed tube being cut away to show the feed auger and the flow control assembly for the hopper having been removed so as to also show the feed auger; FIG. 4 is a top plan view of the hopper with the flow control assembly in place above the feed auger; FIG. 5 is a partial section view through the fluidizing chamber showing the outlet end of the feed tube as well as open and closed positions of the gate within the fluidizing chamber; FIG. 6 is an end elevation view of the apparatus, a wall of the fluidizing chamber having been cut away so as to show the internal configuration including the outline configuration of the gate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings there is shown a preferred form of the apparatus for introducing the fluent bulk materials into the pneumatic conveying line, such apparatus being generally designated by reference numeral 10. The apparatus includes a low-profile hopper 12 which is mounted adjacent one end of an elongated feed tube 14. Feed tube 14 is connected to and enters into a fluidizing chamber 16. The fluidizing chamber 16 is provided with a flow of pressurized air from a suitable blower, preferably a positive displacement lobe blower (not shown), by way of an inlet air line 18 (shown in dotted lines), and the suspended or fluidized bulk material-air mixture leaves via air outlet line 20 (also shown in dotted lines) and is transported thereby to a suitable storage means such as a silo (not shown). The above-noted infeed hopper 12 is provided with four shallowly sloping walls 22, the lower edges of which are secured, as by welding, to the wall of the feed tube 14. The overall height of the apparatus is preferably kept to about 12 inches so that the hopper end of the apparatus may be slid beneath a hopper bottom trailer and the hopper 12 positioned below an outlet port. In order to control the flow of bulk material from the interior of hopper 12 into a feed auger 24 which extends within the feed tube 14, there is provided an inverted V-shaped baffle 26 which extends between and is welded to the opposing end walls 22 of the hopper. This baffle 26 is provided with an opposed pair of adjustment plates 28 which may each be slid upwardly or downwardly in the direction of arrows A thereby to increase or decrease the size of the gap existing between the lower edge of the respective adjustment plate and the adjacent hopper wall 22. These adjustment plates are secured to baffle 26 via a multiplicity of bolts 30 which extend through suitable slots in the adjustment plates 28 thereby to allow the plates 28 to be firmly secured in the desired adjusted positions. The above-noted feed auger 24 is of a conventional design and extends from one end to the other of the feed tube 14. In order to drive the feed auger 24 in rotation, there is provided, at the hopper end of the feed tube 14, a hydraulic drive motor 32 of any suitable commercially available variety, this hydraulic motor 32 being secured to the end of the feed tube via a mounting bracket 34. The outlet drive shaft of the hydraulic motor is connected to the shaft of the feed auger 24 by way of a suitable flex coupling 36. A short skid 38 is also affixed to the hopper end of the feed tube 14 and extends below the hydraulic motor 32 both to protect the hydraulic motor and to allow the apparatus to be slid into position beneath a hopper bottom trailer or the like. With reference to FIG. 3, the hydraulic motor 32 is controlled by way of a control valve module 39 mounted by a suitable bracket to the fluidizing chamber 16. By means of this control valve 39, (which is of any suitable commercially available variety), the operator can start, stop and reverse the motor. To increase or decrease the rate of rotation of the hydraulic motor a flow control valve 41 is provided. These valves together enable the operator to exert a close degree of control on the rate at which the feed auger 24 conveys bulk material toward the fluidizing chamber 16 and enables the operator to take remedial action when appropriate. As noted previously, the fluidizing chamber is provided with air line inlet 40 and air line outlet 42 which are connected to respective inlet and outlet air lines 18 and 20. The incoming and outgoing air lines are each provided with a semi-smooth bore thereby to reduce air friction and the air line inlet and outlet also are each preferably provided with couplers enabling quick connections to be made to the incoming and outgoing air lines. One suitable type of coupler is known as the "Cam-Lock" coupler which provides for quick attachment and detachment while at the same time providing a smooth internal bore so as to reduce air friction losses as well as providing a tight air seal at the point of connection. With particular reference to FIGS. 5 and 6, it will be seen that the fluidizing chamber 16 comprises a gate chamber 50 attached to and located above an air duct section 52. The air duct section comprises a tubular section having the above-noted air line inlet 40 and the air line outlet 42 disposed at opposing ends of same. The box-like gate chamber 50 is secured, as by welding, to the air duct section 52 and has its lower and portion opening into and freely communicating with the interior of the air duct section 52 as clearly illustrated in FIGS. 5 and 6. It was previously noted that the feed tube 14 has its outlet end disposed within the fluidizing chamber 16. As shown in FIGS. 5 and 6, a gate 54 is located at the outlet end of the feed tube 14 within the fluidizing chamber 16 and is exposed, in use, to the airflow which passes through the fluidizing chamber from the air line inlet 40 to and through the air line outlet 42. This gate 54 is responsive to the opposing forces exerted thereon by the bulk material which is being forced through the feed tube 14 by the feed auger 24, and by the pressurized air within the fluidizing chamber. In operation this gate 54 acts to permit the flow of bulk material into the fluidizing chamber 16 while at the same time interacting with the bulk materials to prevent blow-back of pressurized air from the fluidizing chamber through the feed tube 14 and outwardly of the inlet hopper 12. In operation, the bulk material is compressed somewhat as the feed auger pushes the material against the inside surface of the gate thus forming a "plug" of moving material that interacts with the surrounding structures to prevent blow-back. It will be seen with particular reference to FIGS. 5 and 6 that the air line inlet and the air line outlet 40, 42 are located in substantial alignment with one another along a first axis which extends lengthwise and is centered with the air duct section 52 of the fluidizing chamber. The feed tube 14 defines a further axis (which axis extends lengthwise of the feed tube and is centered with the rotation axis of the feed auger 24), such further axis being transversely arranged relative to the first axis noted above. The further axis defined by feed tube 14 is also displaced upwardly from the first axis in such a way that, during use, the bulk material exiting from the outlet end of the feed tube 14 falls downwardly under the influence of gravity and hence passes into and is fluidized by the air flow passing through the fluidizing chamber 16 along the first axis from the air line inlet 40 to the air line outlet 42. The above-noted gate 54 comprises a flat plate of sufficient size as to butt up firmly against the inner end of the feed tube 14 when gate 54 is in its closed position. The gate is hinged adjacent its upper edge by way of hinge 56 fixed to the outlet end of the feed tube 14. Gate 54 can thus pivot from a closed position in close contacting relation to the outlet end of the feed tube 14 to and through a range of partially open positions. One such partially open position is illustrated in dashed lines in FIG. 5. During use, as noted previously, the incoming bulk material applies a force to one face of the gate 54 while the pressure of the air within the fluidizing chamber 16 applies a force to the opposing face of the gate. By virtue of the structure as described above and illustrated in the drawings especially the relationship between the feed tube outlet and the air duct section of the fluidizing chamber, the bulk materials entering fluidizing chamber 16 fall downwardly by gravity from the outlet end of the feed tube 14 and almost immediately pass into a central region of maximum air flow velocity within the above-described air duct section 52 thus effecting substantially complete fluidization of the bulk material. The bulk material has almost no chance of lodging against and building up on any fixed surface from whence it could create gate closure or plugging problems. In this connection the small downwardly extending baffle portions 57 (see FIG. 6) located in flanking relation to the gate 54 are of assistance in establishing air current patterns which enhance the fluidization process. It will also be noted that the abovedescribed gate 54 is disposed in the fluidizing chamber 16 in a manner such that, during use Of the apparatus, a substantial lower portion of the gate (approximately one-quarter to one-third of it) is disposed within the region of maximum air flow velocity so that the resulting air currents tend to keep the gate surfaces clear of deposits which might otherwise tend to prevent full closure of the gate. The upper or top face of the gate chamber 50 is provided with a viewing port 58, this viewing port typically including a sheet of "Plexiglass" material thus enabling the operator to observe conditions existing within the fluidizing chamber 16, particularly conditions in the immediate region of the gate 54. By manipulating the closely adjacent hydraulic flow control valve 41, the operator can control the rotation of the feed auger 24 in accordance with conditions as observed within the fluidizing chamber 16. This permits remedial action to be taken before a plugging condition actually occurs. For the further guidance of those skilled in this art the following detailed example is set forth, it being realized that the invention is not to be limited to the details given but that reasonable modifications may be made by those skilled in this art. EXAMPLE With reference again to FIG. 5 some details for a typical embodiment are given below: ______________________________________DIMENSIONS:A diameter of air duct section 6.0 ins.B distance between LC of feed 5.3 ins. tube and LC of air duct sectionC total height of fluidizing chamber 13.4 ins.D total height of a gate 9.3 ins.E diameter of feed tube 8.0 ins.AIR LINE:semi-smooth bore 6 in. inside dia.air line length (incoming & outgoing) 50 ft. approx."Cam-Lock" couplers-quick detach-tight seal smooth boreBLOWER:Positive displacementlobe-type (make "Vana"; model RSBS) 1100 cfm @ 6 p.s.i. output (this example)MATERIAL:saltRATE OF CONVEYANCE:rate of flow = 1 ton/minute approx.______________________________________ It will be realized by those skilled in this art in light of the foregoing description that the apparatus described herein is extremely versatile and capable of being utilized in an extremely wide variety of situations. The apparatus is extremely simple and, being portable, can be readily carried from one job site to another in a relatively small vehicle, which vehicle also carries the other related ancillary equipment such as the inlet and outlet air lines, the lobe blower, and the hydraulic pump supply lines and hydraulic reservoir and so on. It should also be realized that several of the devices as described may be used, each receiving bulk material from a different source to enable the blending of several fluent bulk materials to provide a specific blend, the several devices being linked together by a common conveying line and sharing a common blower. Numerous advantages will be readily apparent to those skilled in the art. Preferred embodiments of the invention have been described by way of example. Those skilled in this art will realize that numerous modifications and modifications may be made while remaining within the scope of the invention. Accordingly, the invention is not to be limited to the embodiments described. For definitions of the invention reference is to be had to the appended claims.

A portable pneumatic conveyor for various bulk materials includes a hopper which supplies the bulk material to a feed tube. The feed tube is provided with a feed auger which advances the bulk material along the feed tube and into a chamber through which a current of air is passed by way of air inlet and air outlet lines connected to that chamber. The bulk material which is deposited within the chamber is fluidized by the air current and carried by the air current through the air line outlet and along the outlet conveying line to a storage site, such as a silo. In order to prevent air blow-back through the feed tube and alongside the auger, the outlet end of the feed tube is provided with a gate which is intended to at least partly close when the flow of bulk material into the chamber slows down or stops.

FIELD OF THE INVENTION The present invention relates to a media gateway control (megaco) protocol management method using a network adaptor, and more particularly, to a megaco protocol management method for independently managing the megaco protocols according to changes of low level network protocols by implementing the megaco package in the network adaptor and a computer readable recording medium for executing the same method. DESCRIPTION OF THE PRIOR ART A Voice over Internet Protocol (VoIP) is an application technology of the Internet for transferring voice data that is compressed and packetized by end-to-end channel setting base upon Internet Protocol (IP) address. A gateway is necessary so as to provide VoIP through the Internet and terminates Public Switched Telephone Network (PSTN). The gateway is an apparatus for interconnecting signals and media between two networks. The VoIP is connected to a Signaling Gateway (SG) by a media gateway controller for controlling a call process. The media gateway controller controls the media gateway by translating a call number, allocates available Internet Protocol (IP) address by controlling the media gateway and interconnects voice traffics of each terminal by managing compression methods to generate end-to-end IP packet. By separating the media gateway and the signal gateway, independence of an applied protocol is guaranteed, protocol is scalable and service can be easily changed although a new service is added. A gateway is functionally divided into a signal gateway, a media gateway and a media gateway controller. The media gateway transforms data that are used in circuit switching network into data that are used in packet switching network. The media gateway includes a Residential Gateway (RGW), an Access Gateway (AGW) and a Trunk Gateway (TGW). A media gateway control (megaco) protocol is used for communication between the media gateway and the media gateway controller in VoIP service. The megaco protocol defines a communication method between the media gateway and the media gateway controller and is a protocol in master-slave format that the media gateway controller sends instructions for connecting and managing media gateways. Traffic processing of the media gateway is similar to that of node in typical switch. Also, a megaco protocol engine supports communication between the media gateway and the media gateway controller by using the megaco protocol. The megaco protocol engine is interconnected to many low level network protocols, e.g., a Transmission Control Protocol (TCP), a User Datagram Protocol (UDP), Stream Control Transmission Protocol (SCTP), an Asynchronous Transfer Mode (ATM) and Time Division Multiplexer (TDM). New version of the protocol has been developed day by day. As a result, the number of the protocols for being considered by the megaco protocol engine in order to be matched is incredibly increased. Therefore, a source of the megaco protocol engine must be revised whenever the megaco protocol engine is installed according to changes of network protocols or protocol versions. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a megaco protocol management method for independently managing the megaco protocols according to changes of low level network protocols by implementing the megaco package in the network adaptor and a computer readable recording medium for executing the same method. In accordance with an aspect of the present invention, there is provided a method for managing media gateway control (megaco) protocols by using a network adaptor, including steps of: a) requesting an installation of a megaco protocol package of low level network protocols to a network adaptor; b) determining whether the megaco protocol exists in a network protocol table; c) adding a new protocol in the network protocol table in case that the megaco protocol does not exist in the network protocol table; d) searching a specific megaco protocol package in the megaco protocol package list by using the specific package ID and connecting the specific megaco protocol package in case that the megaco protocol exists in the network protocol table; and e) installing the megaco protocol packages and the specific megaco protocols and managing the megaco protocols. In accordance with another aspect of the present invention, there is provided a computer readable recording medium including a microprocessor in communication systems using a megaco protocol, including the instructions of: a) requesting an installation of a megaco protocol package of low level network protocols to a network adaptor; b) determining whether the megaco protocol exists in a network protocol table; c) adding a new protocol in the network protocol table in case that the megaco protocol does not exist in the network protocol table; d) searching a specific megaco protocol package in the megaco protocol package list by using the specific package ID and connecting the specific megaco protocol package in case that the megaco protocol exists in the network protocol table; and e) installing the megaco protocol packages and the specific megaco protocols and managing the megaco protocols. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: FIG. 1 is an exemplary block diagram showing a Voice over Internet Protocol (VoIP) service system in accordance with the present invention; FIG. 2 is an exemplary block diagram illustrating a media gateway in accordance with the present invention; FIG. 3 is an exemplary block diagram depicting a media gateway control (megaco) protocol engine in accordance with the present invention; FIG. 4 shows a network protocol table and a megaco package list in accordance with an embodiment of the present invention; FIG. 5 is a flowchart for explaining management procedures of the megaco protocol by using a network adaptor in accordance with the embodiment of the present invention; and FIG. 6 is a flowchart for explaining procedures for adding a new protocol in the network protocol table by using a network adaptor in accordance with the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an exemplary block diagram showing a Voice over Internet Protocol (VoIP) service system in accordance with the present invention. A media gateway control (megaco) protocol is the protocol used in the Internet. It is distinguished from a protocol used in a Public Switched Telephone Network (PSTN). A call processing unit and a media processing unit were built on one device for the PSTN and the mobile network. However, the call processing unit and the media processing unit are separately implemented as an independent device for the Internet network by standardization of the megaco protocol. Such a separation of call processing unit and media processing unit makes it possible to expand media transfer device for expanding the network. Referring to FIG. 1 , the terminals include an Internet outgoing terminal 21 , a wireless terminal 20 connected to an access point 19 over the air, a terminal 16 connected to a Residential Gateway (RGW) 6 , a terminal 17 connected to an Access Gate (AGW) 7 and a terminal 18 connected to a Private Branch Exchange (PBX) 8 . The terminal connected to the Internet requests an Internet voice telephone service. The request is transferred to a call server 1 through a media gateway controller 2 . Internet telephone call is connected to the PSTN 10 or the mobile network 11 through a Signal Gateway (SG), a Signaling Transfer Point (STP) and a Service Control Point (SCP). Once the Internet telephone call is connected, the Media Gateway Controller (MGC) 2 controls a Trunk Gateway (TGW) 9 by using the megaco protocol to deliver the call to the terminal of the PSTN or the mobile network through a switch 12 , a Mobile Switching Center (MSC) 13 or a Packet Data Serving Node (PDSN) 14 . FIG. 2 is an exemplary block diagram illustrating a media gateway in accordance with the present invention. Referring to FIG. 2 , a media gateway 9 includes a call processing unit 201 for processing calls from a transmitting channel and a receiving channel, a protocol processing unit 202 for processing protocols, e.g., a megaco protocol, a system controller 206 for controlling a media gateway system, a codec 203 for transforming an analog voice signal to a digital voice signal, a trans-codec for transforming a different format of codec to an adequate format of codec, a dynamic media controller 205 for allocating and controlling voice codec data in Real-time Transport Protocol (RTP) payload and a hardware platform for providing a hardware for operating the media gateway 9 . A media gateway control protocol engine is included in a protocol processing unit 202 of media gateway. The media gateways 6 , 7 and 9 communicate with a media gateway controller 2 by using a media gateway control (megaco) protocol. FIG. 3 is an exemplary block diagram showing a megaco protocol engine in accordance with the present invention. Referring to FIG. 3 , a megaco protocol engine 300 includes a connection management unit 303 for managing a connection between a transmitter and a receiver, an instruction processing unit 304 for processing instructions, a package processing unit 305 for processing a megaco protocol package, a transaction management unit 306 for managing a transaction for call processing, a encoder/decoder for encoding and decoding the megaco protocol, a network adaptor 308 for interconnecting network protocols, an administration interface 302 for providing an interface in order to manage the megaco protocol, an Operating System (OS) 309 and a system adaptor 301 for connecting a Digital Signal Processor (DSP) 310 . Particularly, the network adaptor 308 interconnects various low level network protocols including a Transmission Control Protocol (TCP), a User Datagram Protocol (UDP), Stream Control Transmission Protocol (SCTP), an Asynchronous Transfer Mode (ATM) and Time Division Multiplexer (TDM). FIG. 4 shows a network protocol table and a megaco package list in accordance with an embodiment of the present invention. The network adaptor 308 needs a network protocol table 410 and a megaco package list 420 to install the megaco protocol package to the low level network protocols. The protocol information table (Network_Protocol_table) 410 is used for managing the megaco protocol according to characteristics of low level network protocol such as TCP, UDP or SCTP. Referring to FIG. 4 , the network protocol table 410 includes protocol identification (ID) 411 , protocol version information 412 , company information 413 and specific package ID 414 . The protocol ID 411 is an identification defined for discriminating a target network protocol to be interconnected by the megaco protocol engine. Examples of the protocol IDs are defined as 0001 for UDP, 0002 for TCP, 0003 for SCTP, 0004 for RTP, 0005 for ATM and 0006 for TDM in a preferred embodiment of this present invention. Protocol version information 412 represents a version of the protocol defined by the protocol ID 411 . Examples of the protocol version information 412 are defined as 01 for version 1 , 02 for version 2 and 03 for version 3 in a preferred embodiment of this present invention. Company information 413 is used for requesting specific megaco protocol in case that protocol standard is not defined or a protocol is developed regardless with the protocol standard. Examples of the company information 413 are defined as 0001 for company 1 , 0002 for company 2 , 0003 for company 3 and 0004 for company 4 in a preferred embodiment of this present invention. The specific package ID 414 is an identification of a megaco protocol package in a megaco package list 420 . The specific package ID 414 corresponds to package identification (ID) 421 of the megaco package list 420 . That is, the specific package ID 414 is used as an identification of the megaco protocol package that is installed in the megaco package list 420 . Regardless of adding or updating of a new low level network protocol, the megaco protocol package is independently installed in the megaco protocol engine by using the network protocol table 410 that has the protocol ID 411 , the protocol version information 412 and the company information 413 . The megaco package list 420 includes package ID 421 , package version information 422 , property information 423 , event information 424 , signal parameter 425 , statistic information 426 and specific protocol ID 427 for defining other characteristics of megaco protocol package. The package ID 421 is an identification of the megaco protocol package. The package version information 422 defines changes of the property information 423 , the event information 424 , the signal parameter 425 , the statistic information 426 and the special protocol ID 427 . The property information 423 defines data type. Examples of the property information 423 are string, UTF-8 string, integer, 4 byte signed integer, double, 4 byte signed integer, character, enumeration, sub-list and Boolean. The event information 424 is used for the media gateway controller 2 . The signal parameter 425 is an identification of information between the media gateway controller 2 and the media gateway. The statistic information 426 represents a unit, e.g., a second or a packet. The specific protocol ID 427 is an identification of a specific protocol. Management procedures of the megaco protocol in accordance with the present invention are explained by using the network protocol table and the megaco package list. FIG. 5 is a flowchart showing management procedures of the megaco protocol by using a network adaptor in accordance with the embodiment of the present invention. At step 501 , the media gateway 9 receives a list of requests for installing package from the media gateway controller 2 and requests an installation of the megaco protocol package to the network adaptor 308 . At step 502 , the network adaptor 308 receives the request for installing the megaco protocol package and searches a protocol of the list in the network protocol table 410 that has fields of the protocol ID 411 , the protocol version information 412 and the company information 413 . At step 503 , it is determined whether the protocol exists in the network protocol table 410 . If the protocol does not exist in the network protocol table 410 at step 503 , at step 504 , a new protocol is added in the network protocol table 410 and the management procedure is finished. If the protocol exists in the network protocol table 410 at step 503 , at step 505 , the specific package ID 414 is extracted from the network protocol table 410 and the network adaptor 308 searches the megaco protocol package in the megaco protocol package list 420 by using the specific package ID 414 . At step 506 , it is determined whether the searched megaco protocol package is the specific megaco protocol package by using the specific protocol ID 427 of the megaco protocol package list 420 . If the searched megaco protocol package is not the specific megaco protocol package at step 506 , the process proceeds to step 508 . If the searched megaco protocol package is the specific megaco protocol package at step 506 , at step 507 , the specific megaco protocol package is connected. At step 508 , it is determined whether every protocol of the list is processed completely. If every protocol in the list is not processed yet, a procedure continues to step 502 . At step 509 , megaco protocol packages and specific megaco protocol packages are installed. FIG. 6 is a flowchart showing procedures for adding a new protocol in the network protocol table by using a network adaptor in accordance with the embodiment of the present invention. At step 601 , a request for adding a new protocol in the network protocol table 410 is received. At step 602 , it is determined whether the new protocol exists in the network protocol table 410 . If the new protocol exists in the network protocol table 410 , the process is finished. If the new protocol does not exist in the network protocol table 410 , at step 603 , fields of the protocol ID 411 , the protocol version information 412 and the company information 413 is stored in the network protocol table 410 . At step 604 , it is determined whether the new protocol needs a new megaco protocol package. If the protocol does not need a new megaco protocol package, at step 605 , the specific package ID is stored in the existing field of the specific package ID 414 . If the protocol needs a new megaco protocol package, at step 606 , a new megaco protocol package is generated, a new package ID 421 of the new megaco protocol package is allowed and the new package ID 421 is stored. At step 607 , the new megaco protocol package is added in the megaco package list 420 and each field of the megaco package list 420 is stored. At step 608 , the new package ID 421 is stored in the new specific package ID 414 of the network protocol table 410 . As mentioned above, although the number of network protocols and protocol versions has been increased, the megaco protocol can be operated by independently managing the megaco protocol according to changes of lower layer network protocol by implementing the megaco package in the network adaptor without revising the source of the megaco protocol engine. The method of the present invention can be implemented as a program and stored in a computer readable medium, e.g., a CD-ROM, a RAM, a ROM, a Floppy Disk, a Hard Disk, and an Optical magnetic Disk. While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

The present invention manages media gateway control (megaco) protocols according to changes of lower layer network protocol by implementing the megaco package in the network adaptor. A method for managing the megaco protocols by using a network adaptor includes steps of: a) requesting an installation of a megaco protocol package to a network adaptor; b) determining whether the megaco protocol exists in a network protocol table; c) adding a new protocol in the network protocol table; d) searching a specific megaco protocol package in the megaco protocol package list by using the specific package ID and connecting the specific megaco protocol package; and e) installing the megaco protocol packages and the specific megaco protocols, and managing the megaco protocols.

BACKGROUND [0001] 1. Technical Field [0002] The present disclosure relates to illumination, particularly to an illumination device with decreased thickness, and more particularly to a low-profiled LED (light emitting diode) ceiling lamp. [0003] 2. Description of Related Art [0004] A traditional lamp generally includes a housing and a plurality of light sources mounting on the housing. A lamp cover is fastened to one side of the housing to cover the light sources, and a lamp seat is fastened to the other side of the housing to receive electronic elements therein for providing power for the light sources. In the lamp described above, the lamp seat positioned at one side of the housing will occupy a certain space thereto make the lamp have a relatively large thickness. When such a thick lamp is used as a ceiling lamp for a room with a relatively small height, a feeling of constriction will be exerted to a person in the room. Moreover, such a lamp is high power consuming. [0005] What is needed, therefore, is an illumination device which can overcome the limitations described. BRIEF DESCRIPTION OF THE DRAWINGS [0006] Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. [0007] FIG. 1 is an isometric view of an illumination device according to one embodiment of the present disclosure. [0008] FIG. 2 is an inverted view of FIG. 1 . [0009] FIG. 3 is an exploded view of the illumination device of FIG. 1 . [0010] FIG. 4 is an inverted view of FIG. 3 . DETAILED DESCRIPTION [0011] Referring to FIGS. 1-2 , an illumination device 100 according to an embodiment of present disclosure includes a housing 20 and a lamp seat 10 fastened to one side of the housing 20 . The illumination device 100 is particularly used as a low-profiled ceiling lamp with a light source consisting of light emitting diodes. [0012] Referring also to FIGS. 3-4 , the lamp seat 10 includes an upper cover 12 and a lower cover 14 interconnected together. Electronic elements 16 are received between the upper cover 12 and the lower cover 14 . [0013] The upper cover 12 has a substantially trilobate shape, and includes an upper plate 122 and three lateral plates 124 extending downwardly from the upper plate 122 . A central portion of the upper plate 122 protrudes out away from the housing 20 . Three lateral sides of the upper plate 122 are curved towards the central portion. In this embodiment, the three lateral plates 124 one-to-one correspondingly extend down from the three lateral sides of the upper plate 122 . The lateral plates 124 are also curved towards the central portion of the upper plate 122 . The upper plate 122 and the lateral plates 124 cooperatively form a receiving chamber 126 therebetween. Each corner of the upper plate 122 has a first buckle 128 . The first buckle 128 extends downwardly from the upper plate 122 towards the housing 20 . One end of the first buckle 128 is bent inwardly to form a hook to connect with the lower cover 14 . Each lateral plate 124 has two snaps 129 extending horizontally and inwardly from an inner side thereof. The snaps 129 are configured to further strengthen the connection between the upper cover 12 and the lower cover 14 . [0014] The lower cover 14 has a similar configuration with the upper cover 12 . The lower cover 14 includes a bottom plate 142 and an annular sidewall 144 on a central portion of the bottom plate 142 . The sidewall 144 extends vertically from the bottom plate 142 to the upper cover 12 . The central portion of the bottom plate 142 surrounded by the sidewall 144 protrudes outwardly away from the upper cover 12 and forms a protrusion 146 opposite to the sidewall 144 . The protrusion 146 and the sidewall 144 cooperatively define a space 18 for receiving the electronic elements 16 therein. Each corner of the bottom plate 142 has a second buckle 148 . The second buckle 148 extends from the lower cover 14 towards the upper cover 12 . One end of the second buckle 148 is bent to form a hook to clasp with the first buckle 148 . Each corner of the bottom plate 142 defines two holes 141 therein. Screws or rivets (not labeled) are used to extend through the housing 20 and secure in the holes 141 to fix the lamp seat 10 and the housing 20 together. The holes 141 can be blind holes or through holes. [0015] The bottom plate 142 has a plurality of third buckles 149 one-to-one corresponding to the snaps 129 of the upper cover 12 . The third buckles 149 extend from the bottom plate 142 to the upper cover 12 . One end of each third buckle 149 is bent to form a hook to clasp with a corresponding one of the snaps 129 of the upper cover 12 . Therefore, the connection between the upper cover 12 and the lower cover 14 is strengthened. [0016] In assembly, the first buckles 128 of the upper cover 12 and the second buckles 148 of the lower cover 14 are clasped together. The receiving chamber 126 of the upper cover 12 and the space 18 inside the side wall 144 cooperatively receive the electronic elements 16 therein. In other words, one part of the electronic elements 16 is received in the space 18 , and the other part of the electronic elements 16 is received in the receiving chamber 126 of the upper cover 12 . Besides the trilobate shape, the lamp seat 10 can also substantially be a rectangle shape or a pentagonal shape. [0017] The housing 20 is annular, and defines a hole 21 through a center thereof. Alternatively, the housing 20 can be other configurations with the hole 21 defined therein, and the hole 21 is not limited in the center of the housing 20 . The lamp seat 10 is fastened to one side of the housing 20 . The protrusion 146 is inserted into the hole 21 , therefore, a thickness of the illumination device 100 can be decreased. Thus, the illumination device 100 has a low profile which is suitable to be a ceiling lamp for a room with a low height. In this embodiment, the housing 20 includes a base 22 and a cover 24 . The hole 21 is defined through both the base 22 and the cover 24 . [0018] The base 22 is an annular plate. A plurality of light sources i.e. light emitting diodes 222 are arranged on a bottom surface of the base 22 . The light emitting diodes 222 are arranged in two circles with different radius. In addition, the base 22 further defines a plurality of through holes 221 corresponding to the holes 141 of the bottom plate 142 . [0019] The cover 24 is located on the bottom surface of the base 22 with the light emitting diodes 222 facing toward the cover 24 . The cover 24 is made of transparent or translucency material. In addition, an inner surface of the cover 24 can be formed with microstructures to obtain a uniform light output for the illumination device 100 . The cover 24 includes an annular body 242 , and an outer flange 244 and an inner flange 246 extending from an outer edge and an inner edge of the body 242 , respectively. Three protruding platforms 248 extend upwardly from the body 242 , and are located between the inner flange 246 and the outer flange 244 . Each of the protruding platforms 248 defines two through holes 241 therein, corresponding to the two adjacent holes 141 at a same corner of the bottom plate 142 , for connecting the cover 24 , the base 22 and the lamp seat 10 together. When the cover 24 and the base 22 are assembled together, the inner flange 246 abuts against a bottom of the seat 22 . In this embodiment, the inner edge 244 and the outer edge 246 each define a plurality of recesses (not labeled) therein to facilitate airflow flowing through the cover 24 thereby to obtain a better heat dissipation of the light emitting diodes 222 . [0020] During assembly of the illumination device 100 , the electronic elements 16 are arranged in the space 18 inside the annular sidewall 144 of the lower cover 14 . The upper cover 12 is connected with the lower cover 14 with the receiving chamber 126 aligned and communicating with the space 18 , thereby to secure the electronic elements 16 between the upper cover 12 and the lower cover 14 . In this embodiment, the upper cover 12 and the lower cover 14 are connected together by the first buckles 128 clasping with the second buckles 148 . The cover 24 is attached to the bottom surface of the base 22 which have the light emitting diodes 222 mounted thereon. Rivets or screws are brought to extend through the through holes 241 , 221 and secure in the holes 141 to fix the cover 24 and the base 22 to the lamp seat 10 . [0021] In the present illumination device 100 , the protrusion 146 of the bottom plate 142 is configured to define a space 18 to receive the electronic elements 16 therein, and the protrusion 146 is inserted into the hole 21 of housing 20 . Therefore, the thickness of the illumination device 100 can be effectively decreased. Moreover, the use of LEDs 222 as the light source can effectively lower the consumed power while have the same brightness. [0022] It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

An illumination device includes a housing defining a hole therethrogh; a plurality of light sources each is a light emitting diode is disposed in the housing; a lamp seat is securely positioned at one side of the housing. The lamp seat comprises a protrusion configured to receive electronic elements therein. The protrusion of the lamp seat is inserted into the hole of the housing.

INCORPORATION BY REFERENCE [0001] This application claims priority based on a Japanese patent application, No. 2011-218854 filed on Oct. 3, 2011, the entire contents of which are incorporated herein by reference. BACKGROUND [0002] The disclosed subject relates to an access control method for controlling the permission of information display, an information display device using the method, and an information display system. [0003] Information confidentiality must be maintained when we carry a mobile terminal with confidential information, such as customer information, stored therein. Maintaining confidentiality is to establish the state in which only those authorized to access information are allowed to access the information. This means that, if the mobile terminal is stolen, some means is required to prevent a third party from browsing the confidential information. One of the methods for preventing a third party from browsing confidential information is to authenticate a person who accesses the information for browsing. [0004] One of the authentication methods is to authenticate a person using a pre-defined character string information (password, access code, etc.,). An example of such a method is disclosed in U.S. Pat. No. 7,401,229. According to the method, an encrypted access code is stored in a transportable and nonvolatile memory. When a user actually carries the nonvolatile memory to plug it into a computer remotely accessing, remote access is established between the computer to be remotely accessed and the computer remotely accessing. [0005] Another authentication method is a method that uses position information for authentication. An example is disclosed in paragraph 0007 in JP-A-2011-118635. According to this method, security is provided using position information (e.g., a place fixed for meeting or a place fixed for arrangement), directly related to a person, as a key (authentication condition). SUMMARY [0006] The method disclosed in U.S. Pat. No. 7,401,229, in which an encrypted access code stored in a nonvolatile memory is used for authentication, requires that an external device, a nonvolatile memory in this case, be coupled. The problem with this method is that the coupling of an external device to a mobile terminal leads to an increase in the cost and that the need to couple an external device each time the user browses customer information is cumbersome. [0007] The problem with the authentication method using position information, such as the one disclosed in JP-A-2011-118635, is that the method depends largely on the validity of position information but the position information is easily forged. For example, when the position information (latitude, longitude) is identified using a radio wave from a satellite positioning system such as GPS, the position information may be forged by transmitting a forged radio wave. Another forging method is to replace the software, which calculates position information based on a received radio wave, with counterfeit software, resulting in a situation that the user unknowingly uses forged position information. [0008] In view of the foregoing, there is a need for a secure, easy-to-use authentication method. [0009] For use on an information display device, such as a mobile terminal, that accesses (for example, browses) confidential information (for example, customer information) during movement, this specification discloses an access control method for controlling access permission based on the movement route of the terminal position, an information display device that uses the method, and an information display system. [0010] The disclosed access control method, information display device that uses the method, and information display system are characterized as follows. An encryption key is generated on a management terminal based on a planned route, and information is encrypted using the encryption key. When the user accesses the information via the information display device, a decryption key is generated based on the actual movement route (actual route) that is regularly acquired, and the encrypted information is decrypted using the decryption key. That is, the encrypted information can be decrypted if the planned route and the actual route match. [0011] For example, one specific mode that is disclosed is [0012] an access control method for accessing information at a place, to which a user will move, using a portable information display device, the access control method comprising the steps of: [0013] identifying identifiers of planned waypoints during a move to a destination and an identifier of the destination, the destination being a place where the information will be accessed; [0014] creating a planned route of the information display device, the planned route represented as a sequence of the identifiers of the planned waypoints and the identifier of the destination; [0015] generating an encryption key based on the created planned route; [0016] encrypting the information, which will be accessed, using the generated encryption key; [0017] repeatedly acquiring position information on the information display device during the move; [0018] identifying identifiers of waypoints and an identifier of a current position based on the acquired position information; [0019] identifying an actual route of the information display device, the actual route represented by a sequence of the identifiers of the waypoints and the identifier of the destination; [0020] generating a decryption key based on the identified actual route; and [0021] decrypting the encrypted information using the generated decryption key and, if the decryption is successful, permitting the information display device to access the information. [0022] In another preferable mode that is disclosed, a partial-area-based actual route is used as the actual route. [0023] In still another preferable mode that is disclosed, an actual route using a partial area, corresponding to one or more of a origin, a destination, and intersections on the route from the origin to the destination, is used. [0024] In still another preferable mode that is disclosed, a road-link-based actual route is used as the actual route. [0025] In still another preferable mode that is disclosed, a partial route that loops is deleted from the actual route for correcting the actual route and, after that, the decryption key is generated. [0026] The disclosure allows the user to take out information while maintaining information confidentiality. [0027] These and other benefits are described throughout the present specification. A further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0028] FIG. 1 is a diagram showing an example of the system configuration in this embodiment. [0029] FIG. 2 is a diagram showing an example of the hardware configuration in this embodiment. [0030] FIG. 3 is a diagram showing an example of the table configuration of a route information management unit in this embodiment. [0031] FIG. 4 is a diagram showing an example of the table configuration of a customer information management unit in this embodiment. [0032] FIG. 5 is a diagram showing an example of the table configuration of a position information history management unit in this embodiment. [0033] FIG. 6 is a diagram showing an example of the table configuration of a partial area information management unit in this embodiment. [0034] FIG. 7 is a diagram showing an example of the table configuration of a warning information management unit in this embodiment. [0035] FIG. 8 is a flowchart showing an example of the take-out information creation processing in this embodiment. [0036] FIG. 9 is a flowchart showing an example of the customer information encryption processing in this embodiment. [0037] FIG. 10 is a flowchart showing an example of the information display processing in this embodiment. [0038] FIG. 11 is a flowchart showing an example of the update processing for customer information display permission in this embodiment. [0039] FIG. 12 is a diagram showing an example of the image of a planned route in this embodiment. [0040] FIG. 13 is a diagram showing an example of the image of the notification screen that notifies the customer information display permission in this embodiment. [0041] FIG. 14 is a diagram showing an example of the image of a warning notification in this embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS [0042] An embodiment of the present invention will be described in detail with reference to the drawings. In the description of the embodiment below, customer information is used as an example of confidential information and browsing is assumed as an example of access. [0043] FIG. 1 is a diagram showing the configuration of a system in this embodiment. This system includes a management terminal 101 and an information display device 110 . The management terminal 101 and the information display device 110 are coupled over a network 130 for transmitting and receiving information. The network 130 may be a wired link or a radio link. [0044] The management terminal 101 includes the following functional units: route creation unit 102 , route information (inf) management (mng) unit 103 , partial area information creation unit 104 , take-out information creation unit 105 , encryption unit 106 , customer information management unit 107 , and warning information creation unit 108 . These processing units and the processing described below are implemented by executing the programs on the CPU included in the management terminal 101 . [0045] The route creation unit 102 creates a planned route, along which to travel, based on the interaction processing with the user, and records the created planned route in the route information management unit 103 . In this case, multiple routes from the origin to the destination may be registered. For example, when two routes from the origin to the destination are registered, the customer information may be browsed via any one of the routes. [0046] The route information management unit 103 stores not only a route, along which to travel, that is created by the route creation unit 102 but also a route with a past date. For the information on a past route, the route information management unit 103 collects the movement result from a position information history management unit 111 in the information display device 110 and, if the user traveled along a route different from the planned route, updates the information in the route information management unit 103 with the movement result. [0047] The partial area information creation unit 104 creates partial area information based on a route registered in the route information management unit 103 , and the take-out information creation unit 105 creates a planned route using the registered route and the partial area information. The encryption unit 106 encrypts the customer information using an encryption key created based on the planned route, and the warning information creation unit 108 creates warning information based on the planned route. If multiple routes are registered for the same origin and the destination, a planned route is created for each route. If multiple planned routes are created, the encryption unit 106 encrypts the customer information using different encryption keys, once for each planned route. [0048] The information display device 110 includes the following functional units: position information history management unit 111 , map information management unit 112 , position information management unit 113 , sensor information acquisition unit 114 , information access control unit 115 , decryption unit 116 , encrypted information management unit 117 , movement monitoring unit 118 , partial area information management unit 119 , and warning information management unit 120 . These processing units and the processing described below are implemented by executing the programs on the CPU included in the information display device 110 . [0049] The position information management unit 113 regularly acquires the sensor information from a position information sensor 125 , an acceleration sensor 126 , and a gyro sensor 127 via the sensor information acquisition unit 114 , wherein the position sensor 125 receives a radio wave from a satellite positioning system, such as GPS, for identifying the position. The position information management unit 113 identifies the current position on the map using the map information, managed by the map information management unit 112 , and the acquired sensor information and then registers the current position in the position information history management unit 111 . The position information history management unit 111 stores not only today's position information history but also past position information including yesterday's information. The upper limit of data that can be stored is pre-defined and, when the amount of the position information history reaches a predetermined amount, the position information history management unit 111 deletes the information beginning with the oldest information. The upper limit may be fixed or variable. The upper limit may be set using an absolute value (for example, 100 MB), a relative value for the capacity of the storage device (for example, 30%), or an absolute value for the remaining amount of the storage device (for example, history may be stored until the remaining amount becomes 500 MB). [0050] The movement monitoring unit 118 regularly acquires the current position from the position information management unit 113 and, as the current position moves, determines if the user moves to a different partial area or if a warning is required for the user. The information access control unit 115 manages the movement history as an actual route, and the decryption unit 116 decrypts the customer information based on the actual route. [0051] The user creates a route using the management terminal 101 in the office. Next, the user downloads the partial area information created based on the created route, encrypted customer information, and warning information into the information display device 110 via the network 130 . The downloaded partial area information is saved in the partial area information management unit 119 , the encrypted customer information is saved in the encrypted information management unit 117 , and the warning information is saved in the warning information management unit 120 . After downloading the information, the user rides in a car with the information display device 110 , sets it in the car, and starts traveling. [0052] FIG. 2 is a diagram showing the hardware configuration of the information display device 110 . The information display device 110 includes a CPU (processor) 201 , a RAM 202 , a ROM 203 , an external storage device 204 , a sensor interface 205 , and a device interface 206 . The external storage device 204 may be an HDD (hard disk drive), an SSD (flash memory drive), or an optical disc (DVD) device. The sensor interface 205 is coupled to the position sensor 125 , acceleration sensor 126 , and gyro sensor 127 . The device interface 206 is coupled to a display 128 and a speaker 129 . [0053] The programs of the position information management unit 113 , sensor information acquisition unit 114 , information access control unit 115 , decryption unit 116 , and movement monitoring unit 118 and the data of the position information history management unit 111 , map information management unit 112 , encrypted information management unit 117 , partial area information management unit 119 , and warning information management unit 120 , which are shown in FIG. 1 , are stored in the external storage device 204 . When the information display device 110 is powered on, these programs and data are loaded from the external storage device 204 into the RAM 202 and the programs are executed. In this case, the loader program, which loads the programs and data into the RAM 202 , is stored in the ROM 203 . [0054] FIG. 3 is a diagram showing the table configuration of the route information management unit 103 in the management terminal 101 . This table, provided for managing the routes the user visits, is composed of the following columns: user ID 301 , date 302 , order 303 , origin 304 , destination 305 , and road link 306 . The user ID 301 is information for identifying a user. The date 302 represents the date on which the user will move or moved along the route, indicating that the user moves from the place specified by the origin 304 to the place specified by the destination 305 on the date specified by the date 302 . The road link 306 indicates the route from the origin 304 to the destination 305 using a road link sequence. For example, the road link 306 indicates that the user moves from P 1 to P 2 via the road link L 11 →L 12 →L 13 → . . . . In this table, two types of routes are saved: planned route and actual route. The planned route is a route the user will visit in future, and the actual route is a route the user already visited. The date 302 of the planned route is a future data, and the date 302 of the actual route is a past date. [0055] FIG. 4 is a diagram showing the table configuration of the customer information management unit 107 in the management terminal 101 . This table, provided for managing customer information, is composed of the following columns: destination 401 and customer information file 402 . The destination 401 corresponds to the destination 305 in FIG. 3 . The customer information file 402 represents the location of the customer information file corresponding to the destination 401 . For example, the customer information to be browsed at the destination P 2 is stored in the file “C:/data/info1.data”. [0056] FIG. 5 is a diagram showing the table configuration of the position information history management unit 111 in the information display device 110 . This table is composed of the following columns: date/time 501 , coordinate 502 , road link 503 , and destination arrival flag 504 . The coordinate 502 , which indicates the information that identifies a position, may be the latitude/longitude or the relative coordinates with a particular point as the origin. The road link 503 indicates the ID of the road link along which the user travels at that time. For example, the first entry indicates that the user is traveling along the road link “L 11 ” at 14:26:30 on 2011 Jul. 18 and that the coordinates at that time are “X 1 ,Y 1 ”. The destination arrival flag 504 indicates whether or not the user has arrived at a destination at the time indicated by the date/time 501 . For example, the example in the figure indicates that the user has already arrived at the destination at 14:26:30 on 2011 Jul. 18. It is determined that the user has arrived at the destination and therefore the destination arrival flag is set to “1” either when the user presses the “arrival” button displayed on the display 128 or when the customer information is decrypted successfully and the user browses the content of the customer information. [0057] FIG. 6 is a diagram showing the table configuration of the partial area information management unit 119 in the information display device 110 . This table is composed of the following columns: partial area ID 601 and partial area 602 . The partial area 602 is information for identifying a partial area of an area divided into a grid. The partial area 602 , which is represented by a rectangular area, is specified by the two vertices. For example, “M 1 ” is the partial area ID of a rectangular area whose vertices on the diagonal line are “X 1 ,Y 1 ” and “X 2 ,Y 2 ”. [0058] FIG. 7 is a diagram showing the table configuration of the warning information management unit 120 in the information display device 110 . This table, provided for managing information for notifying a warning to the user, is composed of the following columns: before-movement partial area ID 701 and after-movement partial area ID 702 . An entry in this table indicates a warning that is issued when the user moves from the before-movement partial area ID 701 to the after-movement partial area ID 702 . For example, a warning is issued when the user's position moves from “M 1 ” to “M 2 ”. The before-movement partial area ID 701 and the after-movement partial area ID 702 correspond to the partial area ID 601 in FIG. 6 , and the partial area 602 is defined in FIG. 6 . [0059] FIG. 8 is a flowchart showing the take-out information creation processing performed by the take-out information creation unit 105 in the management terminal 101 . The user specifies the “user ID” and the “target date/time” to create the take-out information. [0060] In step 801 , the take-out information creation unit 105 first searches the route information management unit 103 for route information using the specified user ID and the date/time as the key. The take-out information creation unit 105 searches for multiple pieces of route information, for example, the route from the origin P 1 to the destination P 2 , the route from the origin P 2 to the destination P 3 , and so on. If the route creation unit 102 has registered multiple routes from a origin to a destination, the take-out information creation unit 105 searches for multiple routes from the same origin to the same destination. For example, multiple routes from the origin P 1 to the destination P 2 are searched for. Next, the take-out information creation unit 105 acquires a list of destinations from the multiple acquired routes and determines the partial area size so that the destinations are included in different partial areas, one in each partial area. Note that a partial area is a rectangular area created by dividing an area into a grid. First, a partial area that is used as the base partial area is defined in advance. The take-out information creation unit 105 performs calculation to find a partial area to which each destination belongs and, if two or more destinations belong to the same partial area, divides the partial area into four (into two in vertical direction and into two in horizontal direction) to narrow the range of one partial area. The take-out information creation unit 105 repeatedly divides the partial areas until no multiple destinations belong to the same partial area. The size of the base partial area may be set in advance arbitrarily; instead of this, the primary geographic division (about 80 km squares), secondary geographic division (about 10 km squares), or tertiary geographic division (about 1 km squares), which is defined by Japanese Industrial Standards, may also be used. [0061] Next, to identify the destination of the processing target, the take-out information creation unit 105 selects one route from the multiple routes searched for in step 801 (step 802 ) and acquires the road link 306 of the selected path. Based on the acquired road link 306 and the partial area information calculated in step 801 , the take-out information creation unit 105 identifies a planned route from the origin to the destination (step 803 ). [0062] Note that the planned route may be a partial-area-based planned route, a road-link-based planned route, or a destination-based planned route. The partial-area-based planned route is determined as follows. When the road link sequence of the route is L 1 →L 2 →L 3 →L 4 and when the partial area corresponding to the road link L 1 is M 1 , the partial area corresponding to the road link L 2 is M 2 , the partial area corresponding to the road link L 3 is M 2 , and the partial area corresponding to the road link L 4 is M 3 , then the partial-area-based planned route is M 1 →M 2 →M 3 . [0063] For the road-link-based planned route, the road link 306 acquired in step 801 is used directly as the planned route based on a road link. The destination-based planned route is determined as follows. When there is a route via which the user visits the destinations in the order P 1 →P 2 →P 3 and when the partial area corresponding to P 1 is M 1 , the partial area corresponding to P 2 is M 2 , and the partial area corresponding to P 3 is M 3 , then the destination-based planned route is M 1 →M 2 →M 3 . Note that the visiting route P 1 →P 2 →P 3 is registered in the route information management unit 103 as two routes, P 1 →P 2 and P 2 →P 3 . Although, for a destination-based planned route, an array of the partial areas corresponding to the coordinates of the destination is used using the destination as the base point, an array of partial areas corresponding to the destination and the intersections may also be used using not only the destination but also the intersections on the way as the base point. [0064] As the intersections that is used, all left-turn and right-turn intersections may be selected, a part of left-turn and right-turn intersections may be selected randomly, or predetermined particular intersections may be selected. A partial-area-based planned route, a road-link-based planned route, and a destination-based planned route will be described more in detail also in FIG. 12 using an illustration example. [0065] A planned route, from which a loop portion is deleted, is created. Because whether a loop portion is a correct route or a return route after a mistake cannot be determined, the loop portion is excluded from the target of the planned route. For example, for a planned route in which the user moves partial areas “M 1 →M 2 →M 3 →M 2 →M 4 ”, the planned route is changed to “M 1 →M 2 →M 4 ” by deleting the loop portion “M 2 →M 3 →M 2 ”. Doing so produces two planned routes; one is the original planned route from which the loop portion is not deleted and the other is the planned route from which the loop portion is deleted. The planned route from which the loop portion is not deleted is used for the generation of warning information (step 805 ), and the planned route from which the loop portion is deleted is used for customer information encryption (step 804 ). [0066] Next, the take-out information creation unit 105 encrypts the customer information, which will be browsed at the destination, based on the planned route which was acquired in step 803 and from which the loop portion is delete (step 804 ). The take-out information creation unit 105 identifies the customer information to be encrypted by searching the customer information management unit 107 using the destination, identified in step 802 as the key. The detail of the customer information encryption processing will be described later with reference to FIG. 9 . [0067] For stronger encryption, it is required that the size of the planned route, specified as the input, be equal to or longer than a predetermined size and that the size be pre-defined in advance according to the security requirement. That is, the predetermined number or more partial areas or road links must be specified as the planned route. If the number of partial areas or the number of links of the identified planned route from the origin to the destination is insufficient, one or more preceding planned routes are used to extend the route. If multiple routes are registered when using preceding planned routes, which route to use is determined according to the priority that is set at registration time. [0068] For example, consider the example in which the customer information on P 3 is encrypted. In this example, assume that the planned route P 1 →P 2 from which the loop portion is deleted is “M 1 →M 2 →M 3 ”, that the planned route P 2 →P 3 from which the loop portion is deleted is “M 3 →M 4 →M 5 ”, and that the number of partial areas required for encryption is “4”. In this case, because there are only three partial areas in the planned route “M 3 →M 4 →M 5 ” for P 2 →P 3 , the planned route for P 2 is consolidated to create the planned route “M 1 →M 2 →M 3 →M 4 →M 5 ”. After that, the four partial areas closest to the destination are selected to create the planned route “M 2 →M 3 →M 4 →M 5 ”. [0069] As described above, the information amount of a single planned route, if insufficient, is increased by using a past planned route to extend the planned route. A past planned route of different date may also be used. For example, if the information on the planned route P 1 →P 2 on 2011 Jul. 21 is insufficient and if there is no preceding route before P 1 on 2011 Jul. 22, the planned route is extended to a past planned route and the planned route P 10 →P 1 on preceding date 2011 Jul. 21 is used. [0070] Next, the take-out information creation unit 105 generates warning information based on the planned route which is acquired in step 803 and from which a loop portion is not deleted (step 805 ). The warning information is generated to alert the user to the condition in which the user has departed from the route. The generated warning information is downloaded to the information display device 110 to give a warning to the user when the user has departed from the predetermined route. A warning is issued when the user moves out of the planned route which is acquired in step 803 and from which a loop portion is not deleted. [0071] For a partial-area-based planned route, a warning is issued if a partial area array is acquired in step 803 as the planned route from which a loop portion is not deleted and if a transition occurs to a partial area not defined in this partial area array. For example, if the partial area array is M 1 →M 2 and the partial areas surrounding M 1 (up and down, left and right) are {M 2 , M 3 , M 4 , M 5 }, warning information is generated if a transition other than the transition M 1 →M 2 occurs (that is, transitions M 1 →M 3 , M 1 →M 4 , and M 1 →M 5 ). In the warning information, a before-transition partial area is a partial area on the planned route and an after-transition partial area is a partial area out of the planned route. For a road-link-based planned route, a warning is issued if a road link sequence is acquired in step 803 as the planned route and if a transition occurs between road links not defined in this road link sequence. [0072] For example, if the road link sequence is L 1 →L 2 and if the end point of L 1 is an intersection and a transition to {L 2 , L 3 , L 4 } may occur, warning information is generated if a transition other than the transition L 1 →L 2 occurs (that is, transitions L 1 →L 3 and L 1 →L 4 ). In the warning information, a before-transition road link is a road link on the planned route and an after-transition road link is a road link out of the planned route. For a destination-based planned route, the route to the designation may be determined arbitrarily and therefore no warning information is generated. [0073] If the encryption of customer information on multiple destinations, searched for in step 801 , is completed (Yes in step 806 ), the processing is terminated. If there is customer information not yet encrypted (No in step 806 ), control is passed back to step 802 . [0074] FIG. 9 is a detailed flowchart showing the customer information encryption processing (step 804 in FIG. 8 ) performed by the take-out information creation unit 105 . First, in step 901 , the take-out information creation unit 105 generates a random number used for encryption key generation. For the encryption, the common key encryption algorithm is used in which the same key is used for the encryption key and the decryption key. Therefore, the random number generation method is used that generates the same random number for decryption key generation. [0075] Although a fixed value may be used as the initial value for random number generation, using the same initial value leads to the generation of a fixed random number, meaning that the initial value should be varied for stronger security. To vary the initial value, a specific rule may be used or the initial value may be generated based on the movement date. [0076] Next, the take-out information creation unit 105 generates an encryption key using the planned route, which is acquired in step 803 in FIG. 8 and from which a loop portion is deleted, and the random number generated in step 901 (step 902 ). A known generation algorithm is used for generating the encryption key. [0077] As an example of encryption key generation, the following describes a simple example in which bit shifting is used. The character string “M 1 M 2 M 3 M 4 ”, which is the concatenation of the character strings of partial area IDs, is generated from the partial-area-based planned route (M 1 →M 2 →M 3 →M 4 ). The character string “M 1 M 2 M 3 M 4 ” is converted to a binary number and the bits are shifted to the left by the number of the random number generated in step 901 . If the value of the binary number generated by converting the character string “M 1 M 2 M 3 M 4 ” is “11001010” and the random number is 2, the value is shifted to the left by two bits and the encryption key “00101011” is generated as the encryption key. A method other than the bit-shift method may also be used for encryption key generation. [0078] Next, the take-out information creation unit 105 encrypts the customer information, which will be browsed at the destination M 4 , using the encryption key generated in step 902 , (step 903 ). A known encryption method, such as the XOR encryption, may be used for the encryption. As an example, the following shows a specific example in which the XOR encryption is used. When the value generated by converting the customer information to a binary number is “1010111001010001” and the encryption key generated in step 902 is “00101011”, the two values are XORed. The result of the XOR operation between the high-order 8 bits of the customer information and the encryption key is “10000101”, and the result of the XOR operation between the low-order 8 bits of the customer information and the encryption key is “01111010”. As a result, the encrypted customer information is “1000010101111010”. [0079] FIG. 10 is a flowchart showing the information display processing performed by the information display device 110 . First, the information access control unit 115 acquires the history of the position information from the position information history management unit 111 via the position information management unit 113 (step 1001 ). Step 1001 is triggered when the user presses the button, when the pre-set time is reached, or when the information display device 110 is powered on. [0080] Next, the information access control unit 115 initializes the actual route based on the position information history acquired in step 1001 (step 1002 ). First, the information access control unit 115 calculates the road link sequences on a time-series basis from the position information history acquired in step 1001 . Next, the information access control unit 115 acquires the partial area information from the partial area information management unit 119 via the movement monitoring unit 118 . After that, the information access control unit 115 calculates the partial-area-based actual route from the calculated road link sequence and the partial area information and initializes the calculated actual route. When the road-link-based actual route is used, the information access control unit 115 uses the road link sequence, acquired from the position information history, for the initialization. When the destination-based actual route is used, the information access control unit 115 acquires the data, whose destination arrival flag 504 is “1”, from the position information history management unit 111 as the position information history. Next, from the acquired position information history and the partial area information, the information access control unit 115 calculates the partial area array, corresponding to the destination, as the actual route. [0081] The information access control unit 115 regularly executes steps 1003 to 1010 at intervals of a predetermined time. First, the information access control unit 115 transmits a current position acquisition request to the position information management unit 113 . The position information management unit 113 acquires the sensor information from the position sensor 125 , acceleration sensor 126 , and gyro sensor 127 periodically (for example, every second) via the sensor information acquisition unit 114 . The information access control unit 115 identifies the current position on the map based on the acquired sensor information and the map information managed by the map information management unit 112 . [0082] A known method may be used to identify the current position on the map (called mapping). The position information management unit 113 saves the identified position information and the road links in the position information history management unit 111 . The position information management unit 113 returns the identified current position and the road links in response to the request from the information access control unit 115 . [0083] In step 1004 , the information access control unit 115 transmits an inquiry to the movement monitoring unit 118 to identify the partial area corresponding to the current position of the information display device 110 . When road links are used as the actual route, no processing is performed in step 1004 because the road link is already identified in step 1003 . [0084] In step 1005 , the information access control unit 115 determines if the identified partial area/road link is changed. The movement monitoring unit 118 , which memorizes the previous partial area/road link, compares the previous partial area/road link with the partial area/road link identified from the current position to determine if the partial area/road link is changed. If the partial area/road link is changed (Yes in step 1005 ), control is passed to step 1006 . If the partial area/road link is not changed (No in step 1005 ), control is passed to step 1010 . [0085] If the movement monitoring unit 118 determines that the information display device 110 has moved and the partial area, to which the information display device 110 belongs, is changed, the information access control unit 115 updates the actual route (step 1006 ). For example, if the actual route is “M 1 →M 2 →M 3 ” and the partial area is changed from M 3 to M 4 , the information access control unit 115 updates the actual route to “M 1 →M 2 →M 3 →M 4 ”. Next, the information access control unit 115 updates the customer information display permission (step 1007 ), makes the browsable customer information non-browsable, or makes non-browsable customer information browsable. The update processing of customer information display permission will be described later in detail with reference to FIG. 11 . [0086] Next, if it is determined in step 1005 that the partial area is changed, the information access control unit 115 checks if a warning to the user is necessary (step 1008 ). The movement monitoring unit 118 searches the warning information management unit 120 using the IDs, associated with the partial area change (before-movement partial area ID and the after-movement partial area ID) as the key. If the corresponding record is searched for, the warning is necessary; conversely, if the corresponding record is not searched for, the warning is not necessary. For example, if the partial area is changed from M 1 to M 2 in step 1005 , the movement monitoring unit 118 searches for a record whose before-movement partial area ID 701 is M 1 and the after-movement partial area ID 702 is M 2 . If the warning is necessary, the movement monitoring unit 118 transmits a warning notification request to the information access control unit 115 . [0087] In step 1009 , a route departure warning is notified to the user. If it is determined in step 1008 that the warning is necessary, the information access control unit 115 displays the warning screen on the display 128 and outputs the warning sound or warning voice message from the speaker 129 . The warning may be issued only once, may be continued for a predetermined time, or may be continuously issued until the user returns to the original route. [0088] The warning screen and the warning sound/warning voice message may be notified synchronously, the screen and the sound may be notified for different lengths of time, the screen and the sound may be notified at different times, or one of them may be notified. When the user has mistakenly departed from the route, the warning notifies the user that the user has departed from the route to allow him or her to return to the original route. [0089] The number of warning notifications is stored and, if the number of warning notifications exceeds the predetermined upper limit, all the encrypted customer information is deleted. Doing so protects the customer information even if a third party acquires the information display device 110 fraudulently and moves along the routes on a trial and error basis. [0090] In step 1010 , the information access control unit 115 determines if the processing is to be terminated. If the processing is not yet terminated (No in step 1010 ), control is passed back to step 1003 . The determination to terminate the processing may be triggered when the user presses the button or when the information display device 110 is powered off. [0091] FIG. 11 is a detailed flowchart showing the update processing for customer information display permission (step 1007 in FIG. 10 ) performed by the information access control unit 115 . First, the decryption unit 116 generates a random number, which is used for generating the decryption key, in response to a request from the information access control unit 115 (step 1101 ). The initial value of the random number is the same as the initial value used in step 901 in FIG. 9 . [0092] Next, the decryption unit 116 acquires the actual route, which is used as the input information for decryption key generation, from the information access control unit 115 and deletes a loop portion from the actual route (step 1102 ). Assume that the originally-scheduled planned route is “M 1 →M 2 →M 3 ” but that the user mistakenly departed from the route and the actual route becomes “M 1 →M 2 →M 4 →M 2 →M 3 ”. When the user mistakenly takes a wrong route and then returns to the original route, a part of the actual route becomes a loop. In the example given above, the part “M 2 →M 4 →M 2 ” is a loop. This loop portion, which is not an originally-scheduled planned route, is deleted, and the “M 1 →M 2 →M 4 →M 2 →M 3 ” is corrected to “M 1 →M 2 →M 3 ”. [0093] Because all the actual routes, including those of yesterday and days before, can be acquired in step 1102 , the actual route long enough for decryption key generation is selected from the acquired actual route. For example, when the actual route acquired in step 1102 is “M 1 →M 2 →M 3 →M 4 →M 5 →M 6 →M 7 ” and the length of the actual route required for decryption key generation is 3, the three “M 5 →M 6 →M 7 ” closest to the current position are selected for decryption key generation. [0094] The decryption key is generated using the actual route selected as described above and the random number generated in step 1101 (step 1103 ). The initial value, the random number generation method, and the decryption key generation algorithm, which are used for generating the decryption key, are the same as the initial value (or the generation method), the random number generation method, and the key generation algorithm used for encryption key generation in step 902 in FIG. 9 . [0095] In step 1104 , the customer information is decrypted using the decryption key generated in step 1103 . Because it is not determined to which destination the user is traveling, the decryption processing is performed for all the encrypted customer information managed by the encrypted information management unit 117 . In decrypting the customer information, the algorithm corresponding to the encryption algorithm is used. [0096] In step 1105 , the customer information access permission (display permission in this case) is updated based on whether or not the customer information is decrypted successfully, and the result is notified to the user. The method for notifying the result to the user will be described in detail later with reference to FIG. 13 . [0097] One method for determining if the decryption was successfully done is that the character string, such as “OK”, is written in a predetermined position of the customer information and, after the decryption, a check is made if the character string “OK” can be read from the decrypted information to see if the decryption was successful. Another method is that, instead of directly writing the character string in the customer information, a confirmation file in which only “OK” is written is prepared and the confirmation file is decrypted in the same way as the customer information. The confirmation file is decrypted, and a check is made if the character string “OK” is can be read to see if the decryption was successful. [0098] In this case, a confirmation file is required for each piece of customer information. For example, if there are two pieces of customer information named “info1.data” and “info2.data”, the confirmation files “info1.ok” and “info2.ok” corresponding to the customer information are created. “info1.data” and “info1.ok” are encrypted using encryption key 1 , and “info2.data” and “info2.ok” are encrypted using encryption key 2 . [0099] In step 1106 , the information access control unit 115 determines if decryption is performed for all customer information managed by the encrypted information management unit 117 . If decryption is performed for all customer information (Yes in step 1106 ), the processing is terminated. If there is customer information for which decryption is not yet performed (No in step 1106 ), control is passed back to step 1104 . [0100] FIG. 12 is a diagram showing the image of a planned route. The route from the origin to the destination, written in bold, indicates the route along which the user will travel. The solid line indicates a road, and the dotted line indicates the boundary of a partial area in the grid-like area. In the example in the figure, the area is divided into 36 partial areas arranged vertically and horizontally. The top-left partial area is called “A 1 ”, while the bottom-right partial area is called “F 6 ”. L 1 to L 6 indicate the road link IDs each corresponding to a road link from one intersection to the next. [0101] The route, along which the user will travel, is represented by the partial-area-based planned route as “C 5 →C 4 →D 4 →D 3 →D 2 →E 2 ”. The route is represented by the road-link-based planned route as “L 9 →L 8 →L 6 ”. The route is represented by the destination-based planned route as “C 5 →E 2 ”. [0102] FIG. 13 is a diagram showing the image of the notification screen that notifies the customer information display permission. The route, along which the user will travel, is the route from the origin P 3 to the destination P 4 as in FIG. 12 . The figure shows an example in which a partial-area-based planned route is used for determination. [0103] A screen 1301 shows the screen when the user enters the partial area “E 2 ” corresponding to the destination P 4 . The screen displays the destination as well as the customer information file icons corresponding to the destination. The user can press a customer information file icon to browse the content of the customer information. This example shows that the user can browse the content by pressing a solid-line customer information file icon (active state) but cannot browse the content even if the user presses a dotted-line file icon (inactive state). [0104] Whether or not the user can browse the content may be indicated not only by using the solid line (active) and dotted line (inactive) but also by changing the colors of icons or the sizes of icons. When the partial area of the current position changes from D 2 to E 2 , the customer information files corresponding to P 4 , which have been non-browsable, become browsable. The customer information files corresponding to the destinations other than P 4 become non-browsable. [0105] A screen 1302 shows the screen when the user leaves the origin P 3 and the partial area of the current position changes from C 5 to C 4 . The screen shows that the customer information, which has been browsable at P 3 , becomes non-browsable. There are several methods for notifying the user that the customer information becomes non-browsable: the x symbol is displayed on the customer information file to explicitly notify the user about the state, the customer information file is put in the inactive state (state in which the customer information file cannot be browsed even when the icon is pressed) so that the user cannot browse the customer information, the warning sound is output, the screen is erased, or the screen is flashed. [0106] FIG. 14 is a diagram showing the image of a warning notification that is issued when the user departs from the route. The figure shows an example in which the route, along which the user will travel, is the route from the origin P 3 to the destination P 4 as in FIG. 12 and a partial-area-based planned route is used for determination. This example describes a case in which the user mistakenly turned right at the intersection in the partial area D 4 . Because the user originally intended to travel along the planned route “C 5 →C 4 →D 4 →D 3 →D 2 →E 2 ”, the warning screen or the warning sound/warning voice message is used to notify the user that the user took a wrong route and mistakenly turned right when the partial area changed from D 4 to E 4 . [0107] The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto without departing from the spirit and scope of the invention(s) as set forth in the claims.

When a user carries a mobile terminal with confidential information, such as customer information, stored therein, it is required to maintain information confidentiality and to prevent an unauthorized third party from accessing the confidential information even if the mobile terminal is stolen. According to the disclosed access control method, an encryption key is generated based on a planned route and the information is encrypted. When the user accesses the information, a decryption key is generated based on the actual movement route that is regularly acquired. The encrypted information can be decrypted if the planned route and the movement route match.

CROSS-REFERENCE TO RELATED APPLICATION [0001] Priority is claimed from U.S. provisional application No. 60/198,177, filed Apr. 19, 2000. BACKGROUND OF THE INVENTION [0002] The invention generally relates to a mobile wireless communication system. In particular the invention relates to a satellite-based mobile wireless communication system having a relational database and to a method and apparatus for maintaining the database current in the face of interruptions in communication. [0003] Freight carrying operations, and in particular, trucking operations in today's environment are growing increasingly expensive to use and thus are forcing on the trucking companies increasingly efficient methods of operation. Some trucking companies are now using global positioning systems attached to their trucks including transponders or antennas, which will enable the trucking companyies to determine the location of the trucks. [0004] Other companies have attempted to automate at least part of the paper handling associated with the trucking company, for instance. It is known that company's such as United Parcel Service have large easel-type computer systems for entry of signatures thereon and verification that products have been received. In addition, trucking and freight forwarding companies often rely on the use of bar codes to track shipments through client server networks in order to determine the location of goods and services. [0005] Oftentimes, however, even with these added features, it is difficult to handle the flow of information efficiently for shipping operations. For instance, it may turn out that a truck driver is to pick up twelve pallets of a particular freight shipment from a company. A driver arrives at the company and is told that he is only to pick up ten pallets. He makes a separate notation because the freight bill should not be changed indicating that he has received less than the full load, and that hand written notation must later be reconciled through a number of steps between the trucking company, or shipper and the company whose product is being shipped. This is time consuming and wasteful. [0006] Another problem that trucking companies are currently faced with is the recruiting of drivers when there is a high competition for drivers. It is often almost impossible to recruit drivers reliably as by the time employment application form is filled out, and transmitted through the trucking company's internal business systems, the driver may have been hired by a competing company. [0007] In addition, while some wireless communication systems have been provided to trucks, the communications are geographically spotty and in some cases also run at relatively low data rates limiting the amount of data that can be sent to the truck or received from the truck and the flexibility of the system. In addition, the system often requires that a driver may have to physically plug a link into a wall socket or the like to obtain access to a telephone system or network which would necessitate stopping the truck, parking the truck for a certain limited period of time in order to transfer the data. [0008] Thus, what is needed is a wide area coverage system with rapid information updating and convenient linking to a truck driver so that the information may be transmitted as near as possible as real time fashion from the driver to the trucking company and from the trucking company back to the driver. SUMMARY OF THE INVENTION [0009] A method and apparatus embodying the present invention comprised of a hub server for storing trucking and shipping information such as electronic freight bills, driver employment forms, and the like in electronic format. The hub server stores the information in relational database that is updated periodically via communications through a satellite ground station. The satellite ground station communicates with an earth satellite which communicates with multiple ground stations at various locations connected to truck stop servers which function as proxy servers. Each of the truck stop servers has associated with it a spread spectrum communication system which can communicate via spread spectrum through wireless modems connected to personal digital assistance or laptop computers being used by truck drivers. In addition, the hub server may be connected to customer servers and to third party servers to exchange information regarding shipments with them. [0010] The system embodying the present invention includes system level applications including the ability to detect network access, a PDA-based web browser and an e-mail client which may communicate over the system assets. Routines also execute processes,. for instance, sending and receiving e-mail, executing database modifications and queries, executing queued applications and the like. This provides a drive-by feature which will enable truck drivers and others to communicate with the network without the necessity of stopping at a wireless local area network location. In addition, the system includes a web browser which is compatible with standard personal digital assistants and standard TCP/IP HTTP/HTML browsers. The browser is capable of caching web pages for offline viewing and allows real-time access to online forms. The browser supports cookies and and SSL technologies by using a proxy server that resides on a node server. [0011] A PDA-compatible e-mail client also functions on the network. Specific features of the client will include the ability to download email from truck stop server mail servers allowing POP/SMTP access. The ability to link to address books and an option to download email headers only for compact display. In addition, leave message-on-server activities are supported. [0012] More specifically, trucking companies can send pay settlements and pay stubs to drivers over the network in order to provide timely detailed descriptions of the drivers pay. This will reduce operating costs through the elimination of long distance calls to trucking company payroll departments. The system may be integrated with trucking company application servers, typically IBM AS-400 computers in order to automatically generate formatted email pay settlements. [0013] An authorized fuel network application enables trucking companies to inform drivers in real time over the network of fuel network changes including changes in fuel pricing. Drivers are able to receive directions over the network to fuel stops as well as listing of amenities thereat. This enables trucking companies to save significant amounts of money by utilizing appropriate fuel stops with low prices and receiving the most current and lowest pricing available. The fuel network application is managed and updated through-a web browser interface as necessary by trucking company fuel managers. [0014] Truck maintenance tracking is also available. Maintenance information is entered and transmitted wirelessly to a fleet maintenance department of the trucking company over the network for recording. The driver or company receives notification through a PDA or through a hub server of upcoming scheduled maintenance. The database has regularly performed maintenance and time or mileage intervals available. The database may be customized by individual trucking companies to enter their own maintenance schedules. [0015] Local condition reporting may be performed over email. A driver uses his PDA to send email to a maintenance facility warning that there is a problem that needs attention. This enables a maintenance bay to be reserved before the driver arrives at the facility, thereby saving time. [0016] Part of the database information to be made available from the hub server will be indications of freight which is to be hauled. The users have the ability to enter specific search criteria including starting location, destination, trailer type, availability, time and date. Once entered, the search criteria are compared to third party load databases through the hub returning matching loads, as indicated through the PDA. The driver may then have discretion selecting a load. [0017] Electronic freight bills will be prepared by the system and will enable drivers to electronically exchange freight bills with the trucking company, shippers and consignees. Electronic freight bills complete a logistic chain by providing both in-transent visibility and data integrity throughout a shipping cycle.. [0018] Electronic employment applications are also handled by the network and may be completed by driver applicants on hand-held computers such as PDA's or laptops. The application is in a wizard format and captures the applicant's signature. Once complete, the recruit's application and signature are sent electronically over the network to the trucking company's recruiting office for rapid processing. Individual trucking companies may customize at least a portion of the employment application and input the recipient's email address, track sender information, and integrate it into existing services. [0019] Electronic driver logs are handled by the system, wherein drivers through their PDA's will enter time and activity, including driving, sleeper berth, off duty or on duty, not driving. The software will verify that all hours are legal. After entry of the information in the PDA or laptop, a graphic similar to paper logs will be displayed on the PDA or laptop computer. The log book entry will then be delivered electronically to the trucking company over the network for recording in the trucking company databases. The log entries will include the date, including month, day and year, the vehicle number, driver I.D., the miles driven that day, the name of the carrier or carriers, the main office address, the home terminal address, name of co-driver, if any. Including, in addition, the hourly entries will have descriptions associated with them including city, state, shipping yard activity, loading, unloading, fueling and the like. [0020] In order to carry out all of the above tasks, a database replication system is provided by the apparatus and method embodying the instant invention. For scheduling large bursts of data so that when satellite connections are created an efficient use of network resources can be obtained. Between the bursts of data, all data remains available at all access points on the network. Race conditions are eliminated by conflict resolution logic built into the server and client side applications. [0021] A central controlling server or hub functions as a master synchronizing system for all external access points or truck stop stations (TSS). If a change occurs in the database located in the hub, the change is broadcast to all the TSS. If a change occurs in the database located on one of the truck stop servers, then that change is sent back to the hub and then broadcast to all of the stations. All broadcasts are sequenced in a manner similar to that done for transmission control protocol packets for error correction so that the broadcast provides a reliable transport method for all systems. A satellite network compatible with television signals allows six megabit per second bursts to all stations on the hub. TSS stations communicate back to the hub using a 6K per second data rate. The data moving from a TSS back to the hub is relatively small compared to the outbound data from the hub. By design the network only allows forty connections to be created from TSS stations to the hub. This has the benefit that it will guarantee that the hub will not be overrun by communication requests from the TSS station. [0022] The satellite communication is run over a Cislunar Networks system using compression technology that allows data to be efficiently transmitted at low cost. Each of the wireless local area network (WLAN) sites is comprised of a proxy server or TSS and wireless access points. The server enables local storage and rapid access to very large amounts of data. This combination of truck stop server and wireless access points enables information to be accessible by network subscribers from within their vehicles, local restaurants, and the like without being required to send and receive information over land lying communications. The wireless LAN network implements IEEE 802.11 b wireless technology using spread spectrum technology. [0023] This communicates wirelessly to PDAs which, in the present embodiment, are Palm-OS units or devices which are compatible therewith. In the alternative, a Symbol 1740 wireless Palm OS computer may be used. In order to provide security the software performs 128 bit encryption on data being transferred between servers. Encryption is based on 64 wired equivalence privacy standards and uses a 40 bit secret key plus 24 bit initialization vectors. [0024] It is an aspect of the present invention to provide a complete end-to-end wireless communication system for use in the trucking industry to allow truck drivers to quickly and effortlessly communicate trucking related information as well as personal information via email and web browser with a hub server which may be connected to a variety of trucking company servers and third party servers. [0025] It is another aspect of the present invention to provide communication which is wireless and need not be linked to ground-based systems. [0026] It is a still further aspect of the present invention to provide a wireless trucking information communication system which provides rapid and accurately real-time data updating over satellite communications. [0027] Other aspects of the invention will become obvious to one of ordinary skill in the art upon a perusal of the following specification and claims in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0028] [0028]FIG. 1 is a block of an apparatus embodying the present invention; [0029] [0029]FIG. 2 is a block diagram showing the relationship between the hub server and a customer network and the internet; [0030] [0030]FIG. 3 is a block diagram of a link between a hub server and a satellite system to a truck stop server and network connections to wireless access points; [0031] [0031]FIG. 4 is a block diagram of the connection from a satellite receiver to truck stop servers and personal digital assistants and laptops; [0032] [0032]FIG. 5 is a block diagram of the contents of a synchronization packet; [0033] [0033]FIG. 6 is a flow chart showing details of information provided for electronic driver load indications; [0034] [0034]FIGS. 7A and 7B are a table of the types of descriptions of equipment which is stored in the database and handled by the PDAs; [0035] [0035]FIG. 8 is a flow chart of the manner in which an electronic log is kept; [0036] [0036]FIG. 9 is a flow chart of the handling of an electronic flat belt; [0037] [0037]FIG. 10 is a flow chart showing steps of incoming data management for a hub; [0038] [0038]FIG. 11 is a flow chart showing steps of outgoing data management for a hub; [0039] [0039]FIG. 12 is a flow chart showing steps of incoming data management for a truck stop server; [0040] [0040]FIG. 13 is a flow chart showing steps of outgoing data management for a truck stop server; [0041] [0041]FIG. 14 A and 14 B are renderings of screens for the preparation of electronic freight bills; and [0042] [0042]FIG. 15 is a rendering of the driver application screens presented on a personal digital assistant or laptop computer for transfer of data via truck stop server to a hub. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0043] Referring now to the drawings, and especially to FIG. 1, an apparatus that is generally referred to by reference numeral 10 and embodying the present invention is shown therein. The central hub server 12 which includes a web server having a data synchronization system, a database and an interface 13 is connected to a satellite teleport 14 which is able to communicate with an earth satellite 16 with a type which carries television transmissions. In this case it is a GE 4 satellite. The satellite also sends signals to a satellite teleport 18 which is a ground-based station connected over a link to a local node server or proxy server or truck stop server (TSS) 20 which also includes system synchronization process software as well as a TSS database. Multiple TSSs are connected to the system at various truck stops. The proxy server can communicate a portion of its database information to a wireless access point which is a spread spectrum transceiver system communicating using IEEE802.11 b protocols with a hand held computer 24 which may comprise a palmal S device, a Windows CE device, etc. including a wireless modem therein which is compatible with 802.11. In addition, information from the hub server may be shared with a company network 26 which may communicate via the Internet 28 to company customers through an Internet service provider 30 which is coupled to a customer network 32 . The customer network 32 includes customer data 34 which may be related to trucking company data, advertising data, etc. The customer network has connected to it a customer gateway server and storage for intermediate data for manipulation in other instances. [0044] Referring now to FIG. 9 an incoming data management flow for the hub is shown therein, including a step 100 , which the hub incoming data manager receives updates over the satellite network from a truck stop server. In a step 102 the data is placed in an incoming cubed table. In a step 104 the hub cube manager monitors the queue for arriving updates and checks for sequential updates in a step 106 . In a step 108 the system checks for sequenced group updates in order to ensure the groups contain the correct number of entries which are expected. In a step 110 , the updates are applied to the database assuming that the sequence group updates and the sequential updates were in order. In a step 112 , the update entries are placed in a hub outgoing queue. In the event that the sequential update check is not passed in step 106 , a request is made in a step 114 directly to the TSS for missing data. The hub is-then contacted but responds with no data in a step 116 and generates an administrative message in a step 118 . In a step 120 the missing record or group is ignored and the process continues. In the event that the sequence group update check of step 108 fails, the request is made to the TSS for the missing data, which is similar to the step 114 in a step 122 . The TSS responds with the missing records in a step 124 , and transfers control back to the step 110 . [0045] For outgoing data management, as may best be seen in FIG. 11, in a step 130 , the hub outgoing data manager monitors an outgoing queue. In the step 132 , a log is checked for the last broadcast sequence number. In step 134 , a broadcast sequential update and group entries to all TSS systems via packet broadcast across the satellite network takes place and then in a step 136 , the update entry is moved to a revolving history table. In addition, in the step 138 , the hub listens for direct incoming requests for missing update entries and receives requests from the TSS from the missing entries in a step 140 . A lookup update occurs in a step 142 history table if the entry is not found and no response is sent to the TSS in the step 144 , if the entry is found, a request is sent back to the TSS in a step 146 . [0046] The truck stop server incoming data management is handled, as may best be seen in FIG. 12, in a step 150 , an incoming data manager receives updates from the hub server in a step 152 , the data is placed in an incoming queue table. In a step 154 , the TSS queue manager monitors the queue for arriving updates in a step 156 , sequential updates are checked. If the sequential updates check fails, control is transferred to a step 158 causing a request to be made directly to the hub for the missing data. In a step 160 , the hub is successfully contacted but responds with no data and generates an administrative message in step 162 , causing the missing record or group to be ignored in a step 164 , and control to be transferred back to step 154 . In a step 166 , a check is made for sequence group updates in order to ensure that the groups are complete and contain the correct number of entries. In the event that the check fails, control is transferred to a step 168 which requests data from the hub, and the hub responds in a step 170 , with the missing records transferring control to a step 172 , wherein entry is checked to see if the origin TSS I.D. is the current TSS. The updates are applied to the database in a step 174 , and entries are removed from queue and store in a revolving history table which is not allowed to be older than thirty days in a step 176 . [0047] The TSS outgoing data management is handled as may best be seen in FIG. 13, wherein a step 180 the TSS outgoing data manager monitors an outgoing queue. In a step 182 , the log is checked for the last update entry sequence number. In a step 184 , the outgoing queue is checked for grouped entries. In a step 186 , a sequential update and grouped entries are sent to the hub system by a transmission control protocol across the satellite portion of the apparatus 10 . In a step 188 , the update entry is moved to revolving history table. In addition, the TSS listens for direct incoming requests for hub, for missing update entries in a step 190 . If a request is received in a step 192 , a step 194 is executed causing a lookup update entry in the history table. If the entry is found in a step 196 , the information is sent back to the hub, if the entry is not found, a no response is sent to the hub in a step 198 . [0048] Of the types of information which are sent, the information is packaged as may best be seen in FIG. 6, where the synchronization packet detail is shown with the synchronization packet 200 comprising an SQL payload size field 202 , a packet type field 204 , a sequence number 206 , a group sequence number 208 , an origin TSS identifier 210 , a time stamp 212 , a database name 214 , a database user identification 216 , a database password 218 , and finally the SQL statement itself 220 . Thus, it may be appreciated that both group and sequence information as well as time stamping, database naming and database user information and password is transmitted in the synchronization packets. The synchronization packets may be used to send electronic load information as shown in FIG. 6, wherein a step 250 , an authentication is done, a match is checked for in a step 252 , and a load type is selected in a step 254 . Connection may be made to the driver in a step 256 allowing equipment to be selected from a listing in a step 258 , the origin city is inserted in step 160 , the origin state in a step 262 , the distance radius in a step 264 , the destination city in a step 266 . In addition, the destination state is inserted in a step 268 as well as the radius in a step 270 , and the results are compiled in a step 272 . In addition, links can be made to a fleet in a step 280 , or to a fleet intranet in a step 282 to forward the information, as well as the information being sent over the internet in a step 286 to available websites in a step 288 . Equipment type may also be identified as set forth in the tables in FIGS. 7 A and FIG. 7B identifying containers, types of decks, bulk shipping, types of flatbeds, whether hazardous material handling equipment is needed, refrigerated equipment, tankers, vans, or specialized vans. [0049] Furthermore, an electronic log book function is provided as set forth in FIG. 8, at a log start time at a step 300 , the status, city, states, and notes may be entered in a step 302 for transmission. A test is made for a status change in a step 304 , a test is also made for last status off in a step 306 and whether last status is sleeper berth in a step 308 . In addition, a test is made to determine whether the last status indicates driving in a step 310 , if it is then a step 312 a test is made to determine whether the number of driving hours since 8 hours rest exceeds ten hours. If it is, a warning is issued in a step 314 . If it is not, is the driving hours plus the on hours, since eight hours rest greater than sixteen as tested for in a step 316 , if it is a greater-than fifteen hour warning is issued in a step 318 . Control is then transferred to a step 320 , where a determination is made as to whether a seventy hour warning needs to be issued, and if so a seventy hour warning is issued in a step 322 . Control is then transferred back to a test step 324 to test for sleeper berth and to an end of the day log in a step 326 which may loop back to log start times, back in 300 . [0050] As may best be seen in FIG. 9, the carrier database 400 allows data to be automatically extracted and entered by a gateway end server 402 or allows a fleet manager to enter data via website 404 . In step 406 , data populates the hub database and is then replicated to all of the truck stop stations via the network. In a step 408 , the driver information is synchronized over the wireless local area networks and data is downloaded to the end devices such as the PDAs or the laptop computers. A test is made in the step 410 to determine if the shipper information is complete, if not, control is transferred to a step 412 prompting completion of the driver shipper information. A test is made in a step 414 to determine if the consignee information is complete, if it is not, the driver or shipper completes the information in a step 416 . If it is, control is transferred to a stop offs check 418 to determine whether that information has been entered, if it has, the driver and shipper is prompted to complete it in a step 420 and a ship operation signal is given in a step 422 . [0051] A driver consignee review may be made in a step 424 . OSD information is checked for in a step 426 and if it is not present, the information is entered in a step 428 . The consignee can sign off in a step 430 after which the stop officer identified in a step 432 , and the data is stored until the driver enters the wireless local area network in a step 434 where it can be downloaded. [0052] Among the data which can be sent, it may best be seen in FIG. 14A are electronic freight bills which include the originators name, address, city, phone number and directions, as well as consignee information including the destination name, address, city, telephone number, zip code and directions to the consignee. Carrier information may be provided, such as the trucking company, the tractor number, the trailer number, as well as a bill of lading menu to indicate whether signatures are required, identify the load number. The bill of lading will also identify the quantity, the description of the material and the weight. [0053] In addition, information can be sent over the network related to a driver application, employment application form is shown in FIG. 15, which may be completed over a PDA. As shown, the PDA includes personal information, safety record, current employer, screens drivers license information prompts, types of training prompts and employment detail, even asking for specific information such as histories of accidents, citations received, driving under the influence offenses and license suspensions and revocations. Finally, the PDA provides a place for the applicant signature to be inserted and digitized and forwarded to the hub. [0054] While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

An apparatus and method have a hub server for storing a relational database of information relating to trucking operations. The hub server is connected via a satellite link to an earth satellite which is connected through downlinks and uplinks to localize truck stop servers (TSS). The TSS in turn communicate via spread spectrum radio frequency signals with hand-held computers, such as personal digital assistants. The PDAs are used by truck drivers to send and receive e-mails and other information such as electronic freight bills, fuel information, route information and the like from the trucking company and to transmit information to the trucking company. In addition, a trucking company server may be accessed through the Internet by customer servers or third party servers to identify aspects of the trucking shipment.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to digital watches and in particular to a method for manufacturing and assembling a low-cost electronic watch and the resulting structure. 2. Prior Art One of the problems in the volume manufacture of electronic watches is to obtain as low a manufacturing cost as possible commensurate with quality and aesthetic standards. Various structures and methods have been proposed to do this. For example, in co-pending patent application Ser. No. 788,866 filed Apr. 19, 1977 entitled "LOW COST WATCH CASE", on an invention of Schneider and Wickwar, assigned to the assignee of this application, an integral watch case and band is disclosed which comprises one way of achieving this goal. A switch means is provided as an integral part of the case sidewall for selectively actuating certain functions in the watch. SUMMARY OF THE INVENTION This invention provides another structure for achieving a low-cost electronic watch (either digital or analog) while at the same time meeting the high standards of quality and aesthetic appearance demanded by the consumer. According to this invention, a three-part watch case means comprises a top means containing lens means formed in the center portion thereof and first lock means formed in the peripheral portions thereof; flexible band means containing a centered region with a center hole therein of a size sufficient to allow the insertion and passage of a watch module and battery, and containing in the periphery of said centered region selected holes in alignment with said first lock means in said top portion, and optionally containing as an integral part thereof at least one portion of the periphery of said centered region adapted to function as a push pin, and bottom means containing a recessed portion for receipt of a watch module and battery and containing in the outer periphery second lock means adapted to mate with the first lock means in the top means through the holes in said band means, wherein said structure in combination comprises a watch case means with band means adapted both to function as a gasket between said top means and said bottom means and as the band holding said watch case means on the arm of the user. The structure of this invention is particularly adapted for use as the case of a digital watch but can also be adapted for use with a conventional watch movement if desired. As a feature of this invention, the flexible band means functions both as a water resistant gasket and the watch band. In addition, the band means can contain a push pin formed integrally from a portion of the band material directly adjacent a switch formed in the watch module. A watch module particularly suited for use with the watch case of this invention with the integral push pin is described in co-pending patent application Ser. No. 711,016 filed Aug. 9, 1976 on an invention of Duff et al entitled: "STRUCTURE AND METHOD OF MAKING A LOW COST SHOCK RESISTANT WATCH", and assigned to Fairchild Camera and Instrument Corporation, the assignee of this application. As disclosed in that application, the use of a module function switch of the type there described makes possible the use of electrically nonconductive material for the push button activating the function switch in the module. This commensurately reduces the cost of the material in the button and the cost of fabricating and assembling the button into the finished watch. DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of one possible watch assembled in accordance with the method of this invention to yield the structure of this invention; FIG. 2 shows a cross-sectional exploded view of the structure of FIG. 1; and FIG. 3 shows a perspective exploded view of the structure shown in FIG. 1. DETAILED DESCRIPTION FIG. 1 shows a typical watch 10 possessing the structure of this invention and constructed in accordance with the method of this invention. Watch 10 comprises a top means or bezel 20 of any desired aesthetic appearance in which is inserted a lens 30. When used with a digital watch, typical lens 30 comprises a clear transparent portion 30a through which the digits in the watch module can be read and an opaque portion 30b formed either by joining a metal plate to the back surface of the transparent lens or by silk screening the desired pattern onto the back surface of the lens. Of course any other appropriate method of forming the desired pattern on the lens can be used as desired. When used with an analog watch, lens 30 is usually clear. As a feature of this invention, band 40 is formed as an integral part of the watch case. Peripheral portions 40b and 40c of the center region of the band (the "center region" of the band comprises that portion of the band directly beneath bezel 20) are formed such that their exterior shapes have the same outer dimensions as the directly adjacent outer portions of the bezel 20. The interior of the center region of the band directly beneath at least part of the lens portion of bezel 20 has an opening formed therein sufficient to allow watch module 60 (of any standard construction but particularly of a construction such as disclosed in above-mentioned co-pending application Ser. No. 711,016) to pass through said opening so as to be properly located within the case. Bottom means 70 (also called the "back"), is of a unique construction particularly adapted for use with the structure of this invention. Case back 70 is formed with a recess 70a in the center portion thereof for receipt of battery 80 and watch module 60. Recess 70a could also receive a conventional watch movement. Peripheral portion 70b has formed on the top surface thereof pin 71-1 through 71-N where "N" is an integer representing the number of pins formed on the periphery of the back 70. In one embodiment, four pins are sufficient and N equals four. Any other desired number of pins can, of course, be used. Pins 71-n (where "n" is any integer between 1 and N) are formed integrally with 70. Typically back 70 is formed by injection molding using a moldable metal such as zamic. Any other metal (such as powdered metal) capable of being injection molded and suitable for use as a watch cause can, of course, be used. Similarly, a plastic material capable of being molded can also be used in place of the metal parts of the case. The pins or lugs 71-n protruding from the pheripery of the back are formed with a taper such that when a lug 71-n is inserted into a corresponding hole formed in the periphery of bezel 20, the lug locks firmly in this hole preventing bezel 20 from being removed from back 70 except by use of a special tool. While pins 71 are shown formed as part of back 70 these pins could alternatively be formed as part of bezel 20 and holes 21-n could be formed as part of back 70 instead of in bezel 20, as shown. Band 40 has holes 44-1 through 44-N (corresponding to the lugs 71-1 through 71-N) formed in the portions of the band directly above back 70 and beneath bezel 20. During the assembly of the structure (as shown in exploded view in FIG. 3), holes 44-n are located in alignment with lugs 71-n. Lugs 71-n are then inserted into corresponding holes 21-n formed in the adjacent surface of bezel 20. FIG. 2 shows in cross-section the exploded view of the components shown assembled in FIG. 1 and in perspective exploded view in FIG. 3. As shown in FIG. 2, lugs 71-n insert directly into openings 21-n formed in the bottom surface of bezel 20. Lugs 71-n have a taper such that these lugs lock in holes 21-n. A particular feature of this invention is that the center region (including peripheral regions 40b and 40c) of the band 40 located between back 70 and bezel 20 functions not only as a water resistant gasket but, if desired, as least one portion of this center region can also function as a push pin. This portion (shown in FIG. 3), comprises a protuberance 40a extending beyond the side of bezel 20 and back 70 together with indentations 41a and 41b formed from the interior opening 42 into the side 40c of the band material. These indentations give to that portion of material 43 between the indentations 41a and 41b an improved flexibility for lateral movement. In addition the interior point of material 43 extends into the opening 42 beyond the normal perimeter of this opening to make touch contact with the switch 63 on the side of module 60. Slight pressure on the protuberance 40a by the user is sufficient to laterally move point 43 inward (i.e. toward the module 60) a small distance (such as one one hundredth of an inch) to activate the switch 63 on the side of module 60. Of importance, any flexible plastic or other material can be used for watch band 40. Band 40 (other that that portion which comprises part of the case) is a standard watch band containing openings 41a, 41b and 41c (more openings if desired) which mate with the tongue 42b of buckle 42a. Sleeve 43 then receives the portion of tongue 44 which extends beyond buckle 42a. That portion of band 40 between bezel 20 and bottom 70 also serves as a gasket, making the case of this invention water resistant. The watch module 60 can be either a LED and LCD display or any other kind of display appropriate for use with digital or electronic watches. The lens can be either glass or plastic of any desired color. An electronic module with which this particular case structure is best used is a module having a switch of the type disclosed in application Ser. No. 711,016 wherein the case does not have to serve as an integral part of the electrical circuit connected to the switch. An alternate improvement of this invention eliminates the gasket between bezel 20 and back 70, with the back 70 on the bezel 20 on both containing protrusions suitable for the attachment of a conventional watch band.

A watch case and band in combination comprising a back portion containing on the outer periphery thereof first locking means; a center portion comprising a portion of the band containing therein an opening sufficient in size to allow a watch module to pass therethrough and having in the outer periphery of the band around said opening a plurality of smaller openings in alignment with said first locking means; and a top portion having in the outer periphery thereof second locking means located so as to mate with said first locking means locking through said plurality of smaller openings in said band.

BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to methods and apparatus for data storage and retrieval particularly, but not essentially, in conjunction with optical disc storage devices. 2. Related Art Recent years have seen a great expansion in the complexity of consumer electronics equipment with several different proprietary and technical standards governing interconnectivity and data storage. In connection with the latter feature, the domestic user has had to put up with using different mechanical and functional configurations of storage device for different types of equipment, such as a VHS cassette for video recording, an audio compact cassette for audio recordings from Hi-Fi equipment, and floppy discs for data storage on personal computers. With the advent of recordable optical discs conforming to unified standards as far as data layout, bit rates etc. are concerned, such discs may (if configured to the particular recording system) replace many of the disparate options, and hence the possibility of a single unified standard, both in terms of physical configuration and data management, may be contemplated for all types of domestic audio/video/data-processing systems. Whilst each specific application will have its own particular requirements, the physical record carriers to be used (whether optical discs or some other device) should increasingly be capable of use with more than just a single system or medium. It is therefore an object of the present invention to provide a scheme for data storage on a medium readable by devices of different functionalities, with not only effective partitioning of files between applications, but also inherent inter-connectivity such as to permit, at least in a limited fashion, handling of files from one application by apparatus effecting a different application. SUMMARY OF THE INVENTION In accordance with the present invention there is provided a storage device containing a memory space to be accessed by a first read/write apparatus, the memory space being partitioned into an array of fragments, at least some of which are read/write accessible by the first apparatus, and containing a contents table for the fragments stored at a predetermined location within the memory space, said table being updateable by said first apparatus; characterised in that at least some fragments are read/write accessible by a second apparatus, to the exclusion of the first apparatus, and the contents table is arranged to indicate for each fragment whether it carries data from the first or the second apparatus or whether it is free and available for use by either. By holding indication in the contents table of the using device/apparatus for each fragment, two file systems may peacefully co-exist in a single storage device, such that unused storage space from one application is not wasted, but instead may be made available to another device which, though physically compatible with the storage device, functions in a different manner to that device initially utilising the storage. The storage device may be in the form of an optical disc, and data written to fragments (which fragments are suitably of a common size) by the first apparatus may comprise digitised audio and/or video material with the contents table entries in respect of those fragments comprising playlists for the material. The above-mentioned second apparatus may be a data processing apparatus (such as a personal computer) for which the contents table may comprise a logical volume descriptor for those fragments available to the second apparatus. In use, one of the above-mentioned first and second apparatuses is suitably assigned precedence such that it may overwrite fragments in the storage device already used by the other. The contents table may include identifiers for fragments used by the first apparatus in a format supported by the second apparatus, whereby the second apparatus is enabled to identify fragment usage of the first apparatus. The present invention also provides a method for formatting memory space in a storage medium to be accessed by a first read/write apparatus comprising the steps of: partitioning the medium into an array of fragments at least some of which are read/write accessible by the first apparatus; and generating a contents table for the fragments and storing the same at a predetermined location within the memory space, said table being updateable by said first apparatus; characterised in that at least some fragments are read/write accessible by a second apparatus, to the exclusion of the first apparatus, and the contents table is arranged to indicate for each fragment whether it carries data from the first or the second apparatus or whether it is free and available for use by either. Further in accordance with the present invention there is provided a data processing apparatus operable to implement the foregoing method, said apparatus comprising means arranged to receive and format the memory space in said storage medium to be subsequently accessed by said data processing apparatus, the formatting means being configured to partition the medium into an array of fragments at least some of which are read/write accessible by the first apparatus, and to generate a contents table for the fragments, store the same at a predetermined location within the memory space, and periodically update the same; characterised in that the apparatus is further arranged to assign at least some of the fragments as read/write accessible by a second apparatus, and to place in the contents table an indication for each fragment whether it carries data from the data processing apparatus or the second apparatus or whether it is free and available for use by either. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments will now be described by way of example only, and with reference to the accompanying drawings in which: FIG. 1 symbolically represents the application of a record carrier embodying the present invention to different types of AV and data processing apparatus; FIG. 2 illustrates differing control layers as applicable when the record carrier of FIG. 1 is accessed by different configurations of reading apparatus; and FIG. 3 illustrates variation in the file management and availability in the stored data on the record carrier of FIG. 1 depending on the functionality of the reading device. DETAILED DESCRIPTION OF THE INVENTION As mentioned above, there is approaching convergence in terms of data storage media for different domestic applications. FIG. 1 illustrates schematically the scenario of a user who wishes to use a single record carrier device (in this and the subsequent description a writable and optically-read disc) 10 . As shown, the user may have available to them different systems including a personal computer (PC) 12 , video disc recorder 14 (coupled with television 16 and digital broadcast set-top box or satellite decoder 18 ), and Hi-Fi system 20 (including a record/playback component 22 for digital audio). In order that the user does not have to use separately formatted (although physically matching) discs for each type of apparatus, a common format has often been sought. Due to the differing requirements of each use, commonality is still a problem: what is sought here is compatibility, such that a user may use a single record carrier 10 in more than one application, for example to record a film from the television, as well as data files from the PC, with each application respecting (i.e. not overwriting or corrupting) the information stored by a different device. In the following, a file system for a recordable optical video disc is described, which disc is compatible with both consumer electronics (CE) devices and personal computers (PC) The requirements for such a disc system may be summarised as follows: 1. Support for AV (or real-time) files, which are visible to the user as play lists, including support for multiple logical streams which can reference the same AV data, and trick play. 2. Support for (PC) data files. 3. Compatibility with multiple platforms. In providing the video disc compatible with both CE and PC applications, certain attributes and functionalities are of specific value to systems biased toward use in one host system in preference to the other. For a CE-biased arrangement, the first disc fragment would be used for the file system data, with other fragments used for AV data. Rather than an arbitrary disc layout (as for PC file systems) a fixed part of the disc would hold a skeleton standard file to reference the data part of the disc. Disc updates would be kept as simple as possible, playlists would be supported, and non-AV data may be supported. For the PC-biased solution, compatibility results from using a predetermined or standardised file format, one example of which is the Universal Disk Format (UDF). UDF is a specification developed by the Optical Storage Technology Association for use in optical storage devices: the specification derives from International standard ISO 13346. In the following example, compliance with UDF is assumed, although it will be recognised that the present invention is not restricted to, nor constrained by, conformance with this standard. Using UDF data structures and using a logical linear address space enables PC files to be read and written on any PC supporting UDF. A special directory structure would be defined for the consumer video disc with support for play lists and other special AV data and fast access to real-time files. Fragments would be aligned on boundaries to avoid fragmentation, file system data structures would be cached to avoid extra disc accesses during real-time operation, and means would be provided for recovery of unwritten caches in case of disaster. Each of the two ‘biased’ solutions above has particular benefits for its intended target but these detract from the general interchangeability we seek. When a video disc is put in a PC it is possible to obtain some free space to implement a UDF logical volume for PC data use. This space is marked unusable for the video disc application. For this, two interfaces are provided to the block device: one via calls to a video disc API, which is available on the CE device as well as on the PC, and another via an UDF logical volume, whose contents can only be accessed if a full-fledged UDF file system implementation is present, as schematically illustrated in FIG. 2 . The video disc application, running on the PC or the CE device, would have a view on the data of the disc, as shown by the right-hand half of FIG. 3 . If, for some reason, there is not enough space on the disc, a user may decide to delete fragments that contain data not related to the video disc application. If the user wants to be selective about what to delete, a UDF implementation needs to be present on the device. The PC using its UDF entrance to the data will have the view shown by the left-hand side of FIG. 3, whilst a device supporting both the video disc API and UDF has the possibility to access both types of data (FIG. 3 as a whole). For full compatibility, the stored AV files are preferably readable and writeable on a PC: by implementing simple editing facilities on a CE device and leaving advanced editing to the PC, this may be implemented via the video disc. With AV and PC data files residing on the same disc, there are two possibilities for manipulating (PC) data files on the CE device, the first of which is the all-or-nothing approach, i.e., it should be possible for a user to delete all non-AV files to make room for a recording. The second possibility introduces selectivity where it is possible for a user to delete specific (PC) data files. Considering what happens if a user puts a virgin disc in a CE device and, later on, decides to use it in a PC as well, as well as the other way round; namely the user puts a virgin disc in a PC and subsequently decides to use it in a CE device. In the former case, there are two options: either a first area (‘fragment O’) is deliberately ignored by the CE device to subsequently allow the PC to simply add the UDF file system, or repartition of the disc is implemented and a UDF part is created on it. In the latter case, either it is necessary for the CE device to offer reformatting of the disc to the user, or the PC is enabled to repartition the disc and create a VDR file system on the PC, in other words the PC makes the disc suitable for CE applications. In terms of complexity, there is a trade-off between complexity of the solutions and required compatibility as discussed above. A full-fledged UDF implementation plus a video disc API on top is more complex than implementing a video disc API on a block device, but a consideration of possible objections to UDF shows that, on balance, its selection is generally justified. From reading the present disclosure, other variations will be apparent to persons skilled in the art. Such variations may involve other features which are already known in the methods and apparatuses for data management and storage and component parts thereof and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combination of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either implicitly or explicitlyor any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or any further application derived therefrom.

A file management system is provided which enables the peaceful coexistence of two or more file systems from different applications ( 12,16 ) on the same medium ( 10 ). Available free space can be assigned to each of the file systems. Static partitioning of the medium in fixed sized parts is not necessary, as partition sizes can be dynamically changed.

BACKGROUND OF THE INVENTION The invention relates to a materials carrier in the manner of a support for rods and the like that is self-supporting between its long ends. The long ends are embodied by identical vertical closure walls aligned with one another in the longitudinal direction of the materials carrier; horizontally extending holders protrude from the outside of the closure walls, so that the materials carrier can be set down on spaced horizontal shelf-support arms fastened to vertical posts, and so that the materials can be picked up and transported by a shelf service apparatus. Materials carriers of this type are used for instance in the subject of U.S. Pat. No. 4,778,325, which relates to a storage system for rod-shaped material held in self-supporting carriers for rods and the like, with stacking frames disposed transversely to the direction of the storeroom and aligned with one another in the direction of the storeroom; the stacking frames in the manner of shelf systems are provided with adjacent rows of spaced support arms disposed one above the other, extending in the direction of the storeroom and secured to vertical supports, for the carriers. The storage system also has further shelves, embodied on support arms extending in the direction of the storeroom; rod-like material rests directly on these support arms. This storage apparatus is manipulated by a shelf service apparatus, described in detail in the aforementioned U.S. patent, by means of which both the rod-holding supports and the rod-like material resting loosely in the shelves can be moved to a destination and then either returned to storage, or stored at a new location provided for it. With a view to transporting of the rod-holding supports, the shelf service apparatus has a crane bridge that is movable in and extends crosswise to the storeroom direction and has raisable and lowerable load beams on both ends of the crane outside the shelf systems. Support means, extending crosswise to the storeroom direction and pointing with their free ends toward the stacking frames, are adjustable in the storeroom direction so as to be brought into load-bearing engagement, on both sides of the shelf system gangway, which thus forms the middle position, with the inside of the rod-holding supports, by means of holders protruding from the face ends of the support means. However, for the rod-holding supports, the storeroom apparatus described above enables storage only of one type of material, in relatively large quantities of each material, so that if a great variety of material is to be kept on hand, the storage apparatus occupies considerable space and is suitable only for situations in which large quantities of material are needed. Considering not only this problem, but also the shelves in which the material loosely rests, the vertical spacing between shelves disposed one above the other must inevitably be set for the maximum cross section of material to be stored, so that with material of smaller cross section, the shelves can accordingly not be filled full, so that some of the potential storeroom capacity is wasted. Moreover, with storage systems of the type in question a certain amount of reserve capacity is typically provided for, even though some other location in the factory or the like may suffer a lack of storage capacity for products, such as metal sheets, small iron goods or the like, that are not rod-shaped. OBJECT AND SUMMARY OF THE INVENTION It is therefore an object of the invention to disclose a possibility for increasing the utilization of capacity in a storage apparatus of the above type, both in terms of various cross sections of rod-shaped material to be stored and in terms of the exploitation of reserve space for storing other products that are not in the form of rod-shaped material. With a materials carrier of the above generic type as the point of departure, this object is attained in accordance with the invention in that the closure walls are self-supportingly connected to one another solely by a hollow-profiled girder having parallel vertical walls, and that this girder has carrier elements, oriented toward the space between the closure walls, for detachably fastening supports for the material. By these provisions, a component in the manner of a carrier for rods and the like is created, such that the shelf service apparatus can place the carrier inside the storage system and move it, for instance to a materials retrieval and storage station, in the same manner as a rod-holding carrier of the known type. On the other hand, the materials carrier of the invention makes it possible to attach supports for materials of various kinds to the materials carrier in a detachable and hence adjustable and interchangeable manner, so that with the aid of the materials carrier of the invention, not only small quantities of rod-shaped material, but other materials of various types can be stored. To this end, it may be provided that the closure walls are connected to one another on one of their vertical sides by the girder. In that case, one side of the girder is oriented toward the space between the closure walls, and there has the elements for detachably fastening repositores for the material. In another case, it may be provided that the closure walls are connected to one another in the vicinity of their middle between their vertical sides by the ends of the girder, which is provided on both sides with the elements for detachably fastening supports for the material. It thus, also, becomes possible, for supports that are shorter in the direction of the space between the closure walls, to provide these supports on both sides of the vertical walls of the girder; this simultaneously makes it possible to dispose smaller quantities of material of the same type in the same position on both sides of the vertical wall, so that the shelf service apparatus can approach the carrier from both sides and thus handle the material from both sides. To embody the materials carrier, it is practical for the girder to be embodied as a hollow-profiled metal girder. In this way, the materials carrier can be assembled conventionally and hence easily from conventional basic materials in the form of sheet metal, for instance by welding, so that from the standpoint of its particular form as well, the materials carrier of the invention can be provided in quite various forms; the sole condition to be met is that there be space for accommodating it within the dimensions of the storage sites for the known rod-holding carriers. As for the elements for detachably fastening the material supports, they may be embodied by at least two rows of openings disposed one above the other, with the openings of at least one row, preferably a lower row, having a cross section that tapers toward the bottom. This makes it possible to suspend the material supports from the holes or to fasten them to the vertical wall with screws; in the case of the openings with a cross section that tapers toward the bottom, it is also possible to insert the material supports into the vertical wall in the manner of a bayonet mount, with the aid of bolts having heads. In a further feature of the concept of the invention, it may also be provided that a web closing off the girder at the top is formed on the side of the girder oriented toward the space between the closure walls; it is likewise practical to provide this web with a row of openings. This makes it possible for suitably embodied material supports to be suspended from the top of the web by hooks provided on them; in that case, a further fastening to the girder may also be provided lower down, with the aid of screws. Especially for the primary application, that is, storing rod-like material, it may be provided that the supports on the girder are vertically fastenable posts having support arms extending substantially horizontally into the space between the closure walls. Such supports may each have one or more support arms disposed one above the other, depending on the cross section of the rod-like material to be stored, so that even for storing small quantities of material of different cross sections, still every storage site intended for each rod-holding carrier can be fully utilized. This even makes it possible to provide materials carriers that in the vertical direction span more than one storage site for rod-holding carriers, so that even materials of larger dimensions, such as metal sheets or the like, can be kept on hand. The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of preferred embodiments taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary end view of the shelf systems of a storage apparatus; FIG. 2 is a side view of a shelf system for carriers for holding rods or the like, in the system of FIG. 1; FIG. 3 is a perspective view of the materials carrier according to the invention illustrating a bolt insertion opening in a greater detail; FIG. 4 is a partial detailed plan view of the materials carrier of FIG. 3; FIG. 5 is a sectional view taken along the line V--V of FIG. 3 further illustrating an arm support with spaced support arms attached thereto; FIG. 6 is a partial cross-sectional view illustrating the support arms of FIG. 5 connected to the girder of FIG. 1; and FIGS. 7-11 are simplified illustrations of various kinds of supports for the material. DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an upper portion of a materials storeroom having stacking frames 1, 2, which have vertical posts 3, 4 at each end with support arms 5, 6. Stacking frames or shelf systems are typically disposed in alignment beside one another in arbitrary numbers in the direction of the plane of the drawing in FIG. 1, which corresponds to the direction of the storeroom; they extend vertically to the plane of the drawing in FIG. 1 and so crosswise to the storeroom direction as shown in FIG. 2; their length downward is arbitrary, to suit the space available in a given situation. Via arms 5 engaging the ends of the shelf systems 1, these shelf systems carry self-supporting carriers, in other words carriers that need no further support between their ends, for holding rods and similar material. To this end, the carriers 7, which are also shown in FIG. 2, have U-shaped holders 8 on their face ends with which they are pushed onto the support arms 5. This is shown here by only one example and is equally applicable to other types of carriers for rod-like material. Opposite the carriers, rods 9 of any material are laid onto the shelves formed by the support arms 6; a plurality of support arms 6 in line with one another or spaced variously apart from one another are provided for each shelf or a shelf system or stacking frame, so that different lengths of material 9 can be carried, as for instance happens when leftover pieces are returned to storage after machining. A pair of rails 10 extending in the direction of the storeroom is carried by the top of the shelf systems 1, 2; a shelf service apparatus generally identified at 11 and described in detail in U.S. Pat. No. 4,778,325 runs on these rails 10. Only the shelf service apparatus support means 31a that are visible in FIG. 2 will be mentioned here; with their aid, the carrier 7 can be lifted from the support arms 5 and transported along the adjoining shelf system gangway 12 (FIG. 1) to some desired location. As can be seen from FIGS. 1 and 2, the carrier 7 of FIG. 1 has a certain size and shape in terms of height and width, determined by the size of the shelves embodied by the support arms 5. In accordance with this size and shape of the carriers 7, a certain quantity of rod-like material can be stored with these carriers. Even if only small quantities of some types of rods are needed, then for the sake of automated handling in the materials storeroom, a separate carrier must be used, which accordingly is not filled very full at all, so that the remaining space in it is necessarily wasted. Similar problems arise for the shelves embodied by the support arms 6, on which the rod-like material 9 rests loosely. In this case, although as FIG. 1 shows, when the materials storeroom is set up a certain amount of attention must be devoted to storing various cross sections of material, nevertheless once these provisions have been made they cannot be changed, and they also are restricted to only a few sizes of shelf, so that as a result, once again only some of the space on each shelf is actually usable. To overcome these problems, the invention provides the materials carrier, the principle of which is illustrated by FIG. 3. This materials carrier has vertical end closure walls 13, 14 at each end that are in alignment with one another and also has holders 15, 16, protruding horizontally outward from the closure wall; in the present instance the holders are joined to make the U-shaped profile 8 described in conjunction with FIGS. 1 and 2. The closure walls 13, 14 are self-supportingly connected to one another, on one of their vertical sides, by a girder 17 having vertical walls 40 and 41; the embodiment of this girder and the disposition of the remaining space leaves room available that would otherwise be occupied by the full cross section of the rod-holding carrier 7 of FIGS. 1 and 2. On the vertical wall 40 facing the space between the closure walls 13, 14, the girder 17 has rows of openings 18, with the aid of which support arms are secured for supporting material, which will be described hereinafter, can be fastened detachably to the vertical wall 17. The girder 17 is positioned within the stacking frame such that the holders 15 and 16 are supported by the support arms 5 on the vertical posts 3, 4. With the holders 15 and 16 supported by the support arms 5 the vertical walls 40 and 41 will be in a vertical position so that the posts 21 with support arms 22 can be secured to the girder 17. Each end of the girder 17 will be supported by vertical posts 3 or 4. As can be seen, the materials carrier of FIG. 3 may be inserted instead of one of the rod-holding carriers 7 into a corresponding shelf; in terms of the view of FIG. 1, one of the vertical walls of the girder 17 is positioned immediately adjacent to the shelf posts 3. FIG. 4 is a fragmentary top view of the materials carrier of FIG. 3, with a support 19 fastened to it; the support will be described in detail hereinafter. FIG. 5 is a sectional view of the materials carrier of FIG. 3, taken along the line V--V of FIG. 3. As this sectional view shows, the girder 17 is embodied as a hollow-profiled girder, which may be made from sheet metal, for instance by welding. The cross section is embodied such that on the side facing the space between the closure walls 13, 14, the vertical wall has a web 20 or an end that extends above an upper wall closure 39 that closes the girder off at the top; as FIG. 3 shows, this web 20 may also be provided with openings 18 to which supports may be attached. The vertical wall including the web 20 may be made as one continuous wall such that the upper end extends beyond the upper wall of the girder. FIGS. 5 and 6 also show that the supports 19 comprises a post 21, which can be fastened vertically on a vertical wall of girder 17; from this post 21, at least one support arm 22, on which material 23 can be received, protrudes horizontally into the space between the closure walls 13, 14 and parallel thereto. The fastening of the post 21 to the vertical wall of girder 17 is effected via the flanged strips 24, 25 and by screws 26, 27 passing through the openings 18 of the web 20. Bolts 28 are also secured in captive fashion farther down in the flanged strips 24 and 25; the bolts are inserted into openings 29 and locked in place there with their terminal heads 30; to this end, the openings 29 have an upper cross section that narrows from the upper circular portion to a narrow downward extending opening which has a size of the diameter of the bolt so that the bolt head will lock behind the narrow opening when moved toward the bottom of the narrow opening, so that the bolts 28 can be hooked into them in the manner of a bayonet mount. In this way, the post 21 can easily be mounted on the vertical wall of girder 17 with the aid of the bolt 28 first, and then finally fastened there with the aid of the screws 26 and 27. As many posts 21 and support arms 22 as desired may be secured along the rail 17 to accommodate short or long rods, etc. FIGS. 7-9 show how the supports, described in detail in conjunction with FIGS. 4-6, for material can be variously equipped with one or more support arms 22 or 31 or 32, disposed one above the other, depending on the diameter and length of the rod-like material 23 or 24 or 25 that is to be stored. This makes it clear that identical as well as reusable material carriers of the kind shown in FIG. 3 can be used for various applications, with optimal utilization of storeroom space, by using materials supports that are structurally simple and can therefore be manufactured inexpensively for an intended application. FIG. 10 shows that with the aid of the materials carrier of the invention, materials other than rod-like materials can be stored as well. In the example shown, sheet-metal carriers 33, 34 are suspended from a vertical wall 40 of girder 17, or otherwise (not shown) secured to it, for instance with screws; storage cases 35, 36 intended for storing small iron parts, for example, can then be mounted on the carriers. FIG. 11, finally, shows one example of a support 37, fastened to a vertical wall of girder 17. The height of these supports spans a plurality of shelves, so that by using these supports 37, even correspondingly large-sized parts, such as metal sheets 38 shown, can be kept on hand. The shelves that are spanned are represented as girders, shown in dashed lines, in the manner of the girders 17, although it will be appreciated that such vertical walls will not be present at those particular spanned positions. The above description of the subject of the invention made in conjunction with FIGS. 3-11 relates solely to a girder 17 having parallel vertical walls that is secured at its ends on one of the vertical sides of the closure walls 13, 14. As already emphasized in the background section, the girder 17 may also be disposed in the vicinity of the middle between the vertical sides of the closure walls 13, 14, and in that case may be provided with suitable elements on its vertical wall 41 for detachably securing material holders. Especially for a materials carrier that has been taken out of the shelf, this makes it possible for the shelf service apparatus or other equipment to handle the material held in it from both sides of the carrier. The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.

A self supporting carrier for rods, flat sheets, etc., comprising spaced end holders which are held in paralellism by a girder formed as a hollow with vertical aides. The ends of the girder are secured to a vertical wall of the end holders which are U-shaped with one horizontal side used to support the carrier on horizontal supports in a storage area. At least one vertical wall of the girder is provided with equaly spaced rows of apertures by which material supports are secured to the at least one vertical wall of the girder to extend outwardly therefrom between the end holders. One of the rows of apertures may be slotted vertically such as a bayonet type holder.

[0001] This application claims the benefit of provisional application Ser. No. 60/562,488 filed on Apr. 15, 2004, which is hereby incorporated herein by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention relates to dew resistant coatings and articles having the dew resistant coating adhered thereto. The dew resistant coatings are useful on articles or surfaces used in outdoor applications and are particularly useful on retroreflective articles. BACKGROUND OF THE INVENTION [0003] There exists a need for imparting dew resistance to transparent substrates such as windshields, lenses, goggles, and windows, and reflective substrates such as mirrors and retroreflective traffic signs. While retroreflective traffic signs currently provide optimum levels of headlight reflectivity to motorists, accumulation of dewdrops on the surface of the retroreflective sign can result in potentially catastrophic “blackouts” in which the signs are ineffective in providing vital information to motorists. This problem has been described by John A. Wagner in the Florida Sate Department of Transportation Report “HPR Research Study M29-82”, October 1989. In certain parts of the world, the climate is such that moisture from the atmosphere readily condenses onto surfaces when the temperature of the surface drops below the dew point, the temperature at which the air is fully saturated with water vapor and below which precipitation of water in the form of “dew” occurs. When formed on the surface of mirrors and retroreflective surfaces, these dewdrops scatter the incident light, resulting in the loss of reflectivity or “blackouts”. [0004] One method of preventing condensation and the formation of dewdrops is to heat the surface of the substrate to a temperature above the dew point. U.S. Pat. No. 5,087,508 describes the use of phase change materials in a thermal reservoir located behind the outer layer of a display sign. The phase change material undergoes at least one phase change, e.g., from liquid to solid state or from one crystalline state to another, between about −20° C. and about 40° C. During periods of falling ambient temperature, the thermal reservoir will yield heat, thereby warming the outer layer of the display sign. European Patent Application 155,572 describes a device for preventing the formation of dew and frost on retroreflective road sign carriers in which a thermal radiator is arranged above and in front of the road sign. Neither of these devices provides a complete solution to the problems associated with the formation of dew. The device of U.S. Pat. No. 5,087,508 requires “recharging” of the phase change material at higher temperatures, while the device of EP 155,572 simply minimizes dew formation by minimizing radiative cooling of sign surfaces to the night sky. [0005] Surfactants have been used to obtain anti-fog properties on the surface of polymer films. The surfactants used are generally small molecules or oligomeric in nature, and present in relatively low concentrations. Examples of surfactants used for anti-fog applications in food packaging and greenhouse products include those described in U.S. Pat. Nos. 4,136,072; 4,609,688; 5,451,460; 5,766,772; 5,846,650; and 6,296,694 and EP 1,110,993. In general, the surfactant coatings are susceptible to water washing due to the low concentrations of surface active molecules. In addition, many of the anti-fog films are not dew resistant and exhibit only a modest decrease in surface water contact angles. [0006] Polymeric forms of hydrophilic surface agents have been disclosed as being useful for anti-fog films. U.S. Pat. No. 5,877,254 describes an anti-fog and scratch resistant polyurethane composition that include an isocyanate prepolymer, a hydrophilic polyol and an isocyanate-reactive surfactant. U.S. Pat. No. 4,080,476 describes an anti-fog coating for optical substrates wherein the coating comprises a polymerized monomer of, for example, 2-acrylamido-2-methyl propane sulfonic acid. International Publication WO 99/07789 describes the use of siloxane derivatives of polyetheralcohols as an anti-fog additive to a polyolefin prior to formation of a polyolefin film. Many of the prior art coatings do not provide a consistent long-lasting anti-fog coating. Rather, the anti-fog properties of these coatings fail after repeated washings with water. SUMMARY OF THE INVENTION [0007] A dew-resistant coating having particular utility for retroreflective articles is described. The dew-resistant coating is obtainable from a film-forming inorganic or inorganic/organic hybrid composition comprising silica wherein the silica particles comprise elongate particles having an aspect ratio of greater than 1. In one embodiment, the aspect ratio is greater than 2. [0008] In one embodiment the invention is directed to a dew-resistant coating comprising at least about 75% by weight of elongate silica particles having a width of about 9 to about 15 nanometers and a length of about 40 to about 300 nanometers. The coating may optionally include an organic binder. [0009] The dew resistant coatings of the present invention are useful for applications that include, but are not limited to, retroreflective and graphic signage, automotive interior glass, transportation industry paint, i.e., aviation, train and automobile paint, boat and ship bottoms, lubricous pipe coatings, freezer windows, clear plastic packaging, chromatography support, medical equipment surface treatment, bathroom mirrors, shower enclosures, and eyeglasses. [0010] One embodiment of the invention is directed to a retroreflective article comprising a substrate and a coating provided on at least a portion of a surface of the substrate that is exposed to moist air, the coated portion being retroreflective and the coating comprising elongate silica particles having an aspect ratio of greater than 1. Retroreflective articles to which the coating of the present invention may be applied include raised pavement markers having one or more retroreflective elements on the surface, traffic signs, license plates or self-adhesive stickers bearing visually observable information. In one embodiment, the coating on at least a portion of the retroreflective article comprises at least 75% by weight of elongate silica. [0011] Another embodiment of the invention is directed to a method of imparting dew-resistance to a retroreflective article, the method comprising: providing a retroreflective article having a surface; preparing a coating composition comprising elongate silica particles having a width of about 9 to about 15 nanometers and a length of about 40 to about 300 nanometers; applying the coating composition to at least a portion of the surface of the retroreflective article; and heating the coating composition to form a dew-resistant coating. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a schematic diagram of an apparatus used to measure dew resistance of an article having the dew resistant coating of the invention coated thereon. [0013] FIG. 2 is a gel permeation chromatography trace of various hydrolyzate oligomers of 3-glycidoxy propyltrimethoxy silane useful in the present invention. DETAILED DESCRIPTION OF THE INVENTION [0014] The dew-resistant coating of the present invention comprises elongate silica fine particles. The elongate silica particles are coated or grafted onto the surface of the substrate. The substrate is generally glass or a polymeric film. The dew-resistant coating can be transparent. When the substrate to which the dew-resistant coating is applied is a retroreflective film, a transparent dew-resistant coating is required. [0015] The silica useful in the present invention comprises elongate particle silica having an aspect ratio that is greater than 1.0. In one embodiment, the aspect ratio is greater than 2.0. As used herein, the term “aspect ratio” means the ratio of the length of the particle to the width. In one embodiment, the silica particles have an average width (diameter) of about 9 to about 15 nanometers and an average length of about 40 to about 300 nanometers. The elongate silica particles may be dispersed in an alcohol or in water. Commercially available elongate silica includes those available from Nissan Chemical Industries under the trade designations SNOWTEX UP and SNOWTEX OUP. The silica may also comprise string-of-pearls silica particles, which are chain silica particles available from Nisson Chemical under the trade designation SNOWTEX-PS. The solvent in which the particles are dispersed may be water, methanol, ethanol, isopropropanol, etc. [0016] In one embodiment, the coating composition comprises at least 75% by weight fine elongate silica particles. In other embodiments, the coating composition comprises at least 80%, or at least 90%, or at least 95% by weight fine elongate silica particles. In one embodiment, the coating composition comprises fine elongate silica particles and fine spherical particles having an average diameter of less than about 50 nanometers. The spherical particles may be provided in a colloidal dispersion of silica in a solvent that is compatible with the solvent of the elongate silica particles. For example, the spherical silica particles used may comprise Snowtex IPA-ST-MA from Nissan Chemical Industries, which is a silica sol of spherical silica particle having an average particle diameter of about 17-23 nanometers dispersed in isopropyl alcohol. A useful ratio of elongate silica particles to spherical silica particles is in the range of about 100:0 (i.e. 100% elongate silica) to about 70:30. In one embodiment, the ratio of elongate silica particles to spherical particles is in the range of about 100:0 to about 90:10. [0017] In one embodiment of the present invention, the coating composition comprises fine elongate silica particles and an organic binder. The organic binder may be present in an amount of about 0 by weight to about 10% by weight based on the total solids of the coating composition. In one embodiment, the organic binder may be present in an amount of about 4% to about 8%, or about 15% to about 25% by weight. The organic binder may comprise hydrolysis products and partial condensates of one or more silane compounds. Useful silane compounds include, but are not limited to epoxy-functional silanes. Examples of such epoxy-functional silanes are glycidoxy methyltrimethoxysilane, 3-glycidoxypropyltrihydroxysilane, 3-glycidoxypropyl-dimethylhydroxysilane, 3-glycidoxypropyltrimeth-oxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl-dimethoxymethylsilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyltributoxysilane, 1,3-bis(glycidoxypropyl) tetramethyldisiloxane, 1,3-bis(glycidoxypropyl)tetramethoxydisiloxane, 1,3-bis(glycidoxypropyl)-1,3-dimethyl-1,3-dimethoxydisiloxane, 2,3-epoxypropyl-trimethoxysilane, 3,4-epoxybutyltrimethoxysilane, 6,7-epoxyheptyl-trimethoxysilane, 9,10-epoxydecyltrimethoxysilane, 1,3-bis(2,3-epoxypropyl) tetramethoxydisiloxane, 1,3-bis(6,7-epoxyheptyl)tetramethoxydisiloxane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like. [0018] Other useful silanes include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxy silane, octyltrimethoxysilane, decyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexylmethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, allyltrimethoxysilane, dimethyldimethoxysilane, 2-(3-cyclohexenyl)ethyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 2-chloroethyltrimethoxysilane, phenethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, 3-isocyanopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 4-(2-aminoethylaminomethyl)phenethyltrimethoxysilane, chloromethyltriethoxysilane, 2-chloroethyltriethoxysilane, 3-chloropropyltriethoxysilane, phenyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, butyltriethoxysilane, isobutyltriethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltriethoxysilane, cyclohexyl-triethoxysilane, cyclohexylmethyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, allyltriethoxysilane, [2-(3-cyclohexenyl)ethyltriethoxysilane, 3-cyanopropyltriethoxysilane, 3-methacrylamidopropyltriethoxysilane, 3-methoxypropyltrimethoxysilane, 3-ethoxypropyltrimethoxysilane, 3-propoxypropyltrimethoxysilane, 3-methoxyethyltrimethoxysilane, 3-ethoxyethyltrimethoxysilane, 3 propoxyethyltrimethoxysilane, 2-[methoxy(polyethyleneoxy)propyl]heptamethyl trisiloxane, [methoxy(polyethyleneoxy)propyl]trimethoxysilane, [methoxy(polyethylene-oxy)ethyl]trimethoxysilane, [methoxy(polyethyleneoxy) propyl]triethoxysilane, [methoxy(polyethyleneoxy)ethyl]triethoxysilane, and the like. [0019] The organic binder may comprise a polymer that is hydrophilic. [0020] The dew resistant coating of the present invention may comprise a monolayer or a multilayer coating. In one embodiment, a tie layer is applied to the substrate to improve the adhesion of the outer silica containing coating. [0021] In one embodiment, the dew resistant coating comprises a first layer comprising fine spherical particles and an organic binder and a second, outer layer, comprising fine elongate silica. In another embodiment, the dew resistant coating comprises a first layer comprising fine elongate silica and an organic binder and a second, outer layer comprising a photocatalytic layer. [0022] The photocatalytic layer generally comprises TiO 2 particles. Photocatalytic compositions are disclosed in U.S. Pat. Nos. 6,228,480 and 6,407,033 to Nippon Soda Company, the disclosures of which are incorporated by reference herein. The second photocatalytic layer affords additional self-cleaning properties along with increased hydrophilicity upon UV irradiation. [0023] In one embodiment, photocatalytic nanoparticles are incorporated into a dew resistant coating composition that is applied to the substrate in a monolayer. The coating composition may comprise metal oxide particles in addition to the fine elongate silica particles. Such metal oxide particle may be used to obtain a desired refractive index or to obtain desired photoactivity. The elongate silica particles may be used in combination with other metals or metal oxides such as titania, zirconia, tin oxide, antimony oxide, iron oxide, lead oxide, needle TiO 2 , bayerite (Al(OH) 3 ) and/or bismuth oxide to incorporate other adjunct properties including color, conductivity (thermal and/or electrical), abrasion resistance, etc. [0024] In one embodiment, the coating composition comprises elongate silica particles, an organic binder and at least one surfactant. Useful surfactants include alkoxy siloxane-based surfactants, ethoxylated fatty alcohols such as lauryl alcohol, myristyl alcohol, palmityl alcohol and stearyl alcohol; polyethylene oxides; block copolymers of propylene oxide and ethylene oxide; alkyl polyethoxy ethanols; polyethylene lauryl ether; polyethylene stearate; ethoxylated nonylphenol; sorbitan ester of fatty acid; polyethylene sorbitan monostearate; polyglycerol esters of fatty acids such as lauryl acid, palmetic acid, stearic acid, oleic acid, linoleic acid and linolenic acid; polyoxyethylene distearate; polyoxyethylene sorbitan tristearate; ethylene glycol monostearate; sodium lauryl ether sulfate; ethoxylated amine; ethoxylated acetylenic alcohol; sodium sulfosuccinate; sodium dodecyl benzene sulfonate; fluorosurfactants; acetylenics and combinations of two or more thereof. The surfactant may be present in an amount of 0 to 10% by weight of the coating composition. [0025] When an organic binder is used, the coating composition may be cured via free radical, thermal, infrared, electron beam or ultraviolet radiation polymerization. For UV curable compositions, useful photoinitiators include sulfonium or iodonium salts such as SARCAT CD1010, SARCAT CD1011 and SARCAT CD1012 (available from Sartomer) and CYRACURE UVI 6974 available from Dow Chemical, IRGACURE 651, 184 and 1700 and DAROCURE 1173, available from CIBA-GEIGY; as well as GENOCURE LBP available from Rahn; and ESACURE KIP150 available from Sartomer; [4-[(2-hydroxytetradecyl)oxy]-phenyl]phenyliodonium hexafluoroantimonate, benzophenone, benzyldimethyl ketal, isopropyl-thioxanthone, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl) phosphineoxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, diphenyl(2,4,6-trimethybenzoyl) phosphine oxides, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-(dimethyl-amino)-1-4-(4-morpholinyl)phenyl-1-butanone, alpha,alpha-dimethoxy-alpha-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1-4-(methylthio) phenyl-2-(4-morpholinyl)-1-propanone, 2-hydroxy-1-4-(hydroxyethoxy)phenyl-2-methyl-1-propanone. Photosensitizers may be used in combination with the photoinitiator. Examples of photosensitizers include phthalimide derivatives, isopropylthioxanthone and carbazole compounds. [0026] The coating composition of the present invention can be applied to substrates by conventional methods, including flow coating, spray coating, curtain coating, dip coating, spin coating, roll coating, etc. to form a continuous surface film or as a pattern, as desired. In one embodiment, the coat weight of the applied coating is about 1 gsm or less. [0027] Any substrate compatible with the coating composition can be coated with the dew resistant coating. For example, plastic materials, wood, paper, metal, glass, ceramic, mineral based materials, leather and textiles may be coated with the dew resistant coating. Plastic substrates to which the dew resistant coating of the present invention may be applied include acrylic polymers, poly(ethyleneterephthalate), polycarbonates, polyamides, polyimides, copolymers of acrylonitrile-styrene, styrene-acrylonitrile-butadiene copolymers, polyvinyl chloride, butyrates, polyethylene and the like. Transparent polymeric and glass materials coated with these compositions are useful as flat or curved enclosures, such as windows, liquid crystal display screens, skylights and windshields, especially for transportation equipment. [0028] The dew resistant coating composition is particularly useful when applied to retroreflective sheeting. The transparent dew resistant coating enables the underling retroreflective sheeting to maintain its retroreflectivity and decreases or eliminates the likelihood of a “blackout” condition in moist environments. This may be achieved by using a dew resistant coated glass or a transparent plastic film that is adhered as an overlaminate to a retroreflective sign. Alternatively, this may be directly incorporated onto the top surface of a retroreflective article. Retroreflective substrates include raised pavement markers having one or more retroreflective elements on the surface, traffic signs, license plates or self-adhesive stickers bearing visually observable information. [0029] In one embodiment, the dew resistant coating is applied to at least a portion of the surface of a retroreflective sheet. The surface of the retroreflective sheet may comprise an acrylate polymer. In one embodiment, the surface of the retroreflective sheet to which the dew resistant coating is applied comprises a butyl acrylate/methylmethacrylate copolymer. [0030] In one embodiment, a removable protective layer is applied over the dew resistant coating to prevent damage to the dew resistant coating during storage, transport and application to the underlying substrate. The removable protective layer may comprise a polymeric film. In one embodiment, the protective layer comprises a water soluble or water miscible polymeric coating. Examples of such polymers include polyethylene oxide, polyvinyl alcohol, polyacrylic acid, alkyl metal silicate, polyvinyl pyrrolidone, (poly)hydroxyethyl methacrylate, and combinations thereof. TESTING METHODS [0000] Coat Thickness [0031] The coat thickness for film samples coated onto plastic substrates are determined via the cross-section method wherein a 2 micrometer thick slice is cut in the traverse direction through the dew-resistant coating and the film support using a microtome (RMC Rotary Microtome MT 990) equipped with a diamond knife (Delaware Diamond Knife). The microtome is set to operate at −10° C. and a cutting speed of about 10 mm/sec. An Olympus BX 60 optical microscope is used to observe the cross-section and to measure the coat thickness in micrometers via a digital camera (resolution 800×600) and the software package Image Pro-Plus at total magnification of 1000×. A second method used to determine coat weight is X-ray florescence spectrometry, which measures silicon for a silica-based coating, aluminum for an alumina-based coating, etc. A bench-top Oxford Lab-X 3000 XRF analyzer (Oxford Instruments) is used to measure dry coat weight of silica based coatings. Coated samples are die-cut into 3.5 cm diameter disks to measure the quantity of silicon present. [0000] Contact Angle: [0032] The contact angle between the surface of the coated substrate and a droplet of water is an indicator of the hydrophilicity of the coating. The lower the contact angle, the better the hydrophilic properties of the coating. The hydrophilicity of the film surface is measured using an FTA 200 dynamic contact angle goniometer available from First Ten Angstroms Corp. equipped with a Pelco video camera (PCHM 575-4). Contact angle measurements are taken using a 4 microliter water droplet in ambient air humidity at time intervals of 1 second, 5 seconds, and 10 seconds. [0000] Water Wash Resistance [0033] Coated samples are put in a bottle containing water and placed on a mechanical roller (available from Norton Chemical Process Products Division, Akron, Ohio) for 12 hours. Samples are then removed, re-washed under running water, dried and tested appropriately for anti-fog, dew resistance and/or contact angle (hydrophilicity). [0000] Anti-Fog: [0034] The anti-fog property of the coatings is screened by blowing a breath of air onto the surface of the test sample to determine if any haze develops. The sample may also be evaluated by putting the test surface face down, 1 inch away from the top of a boiling beaker of water. If no haze or dew is observed after 30 seconds, the sample is rated to have anti-fog properties. [0000] Dew Resistance: [0035] An outdoor dew resistance testing apparatus schematically represented in FIG. 1 is used to measure dew resistance outdoors. The dew-resistant coated retroreflective samples are laminated onto a metallic traffic sign. Dew is generated naturally by heat loss to the atmosphere provided by satisfactory meteorological conditions. The digital camera (IQEye3 camera server) is accompanied by an axial illumination system (12V white LED array) and a Rotronic 3 meteorological terminal that is linked to the camera server via a local serial bus. The outdoor dew tester transmits, at specified time intervals, images and meteorological data including dew point, relative humidity and air temperature to a data server via TCP communication protocol and the Internet. Reflectivity data for the dew resistant coated retroreflective samples is integrated from the bitmap histograms and compared to a sample of the uncoated retroreflective sample and plotted versus time. Each reflectivity data set includes measured meteorological parameters such as air temperature, air relative humidity and dew point. [0000] Percent Blackout [0036] For a given dew event, the percent blackout of a dew resistant coated sign is calculated as the number of hours the sign loses its reflective properties (loses more than 50% of its original reflectivity) divided by the number of hours the control (uncoated sign) loses its reflective properties, multiplied by 100. The apparatus used to measure the reflective properties of the sign is described above with reference to Outdoor Dew Resistance testing. [0000] Xenon Weathering: [0037] Xenon weathering testing is carried out with an Atlas Ci5000 Xenon Arc Weather-Ometer (Atlas Electric Devices Company, Chicago, Ill.) according to ASTM G155-1 with two light cycle segments. For both light cycles, irradiance is the same: 0.35 watts/M 2 at 340 nm, with black panel temperature set at 63° C., chamber temperature at 40° C., and relative humidity at 50%. The first light cycle is 102 minutes, with no water spray and the second light cycle is 18 minutes with water spray on the sample surface. [0000] QUV Weathering: [0038] A QUV Accelerated Weathering Tester (Q-Panel Lab Products, Cleveland, Ohio) is used to carry out the testing according to ASTM G-154 procedures. A UVA-340 lamp with typical irradiance of 0.77 watts/m 2 or a UVB-313 lamp with typical irradiance of 0.63 watts/m 2 is applied in the test. The UVA-340 lamp has similar spectral power distribution as sunlight. The typical cycles include an 8 hour UV light cycle at 60° C. black panel temperature and a 4 hour condensation cycle at 50° C. black panel temperature. [0000] Retroreflectivity: [0039] A hand-held RetroSign retroreflectometer type 4500 (Danish Electronics, Light & Acoustics of Denmark) is used to measure retroreflectivity according to ASTM D4956-01 Standard Specification for Retroreflective Sheeting for Traffic Control. The retroreflectometer measures with a fixed entrance angle at −4 and observation angle of 0.2°. [0000] Mandrel Test: [0040] The Mandrel test accelerates cracking of the coating, which contributes to increased haze, and therefore, decreases retroreflectivity. Retroreflective sheeting samples with adhesive backing are cut in 2 cm (cross direction)×4 cm (machine direction) strips and applied to a glass rod having a 1 inch diameter. Hand applied pressure is used to wrap the sample around the rod. Tape may be used to further secure the sample strip ends to the glass rod. The rod is then placed in an apparatus for temperature cycling and examined under optical microscope for extent of cracking. A scale of 1 to 5 is used to rate the extent of cracking observed after thermal cycling. The temperature cycling is as follows: Initial Values of Each Step Graded Target Time Step Tempera- Humidi- Tempera- Humidi- Setting No. ture (° C.) ty (%) ture (° C.) ty (%) (hours) 1 Room Room 20 20 1 2 20 20 2 3 20 20 60 20 1 4 60 20 2 5 60 20 60 80 1 6 60 80 2 7 60 80 −10 0 1 8 −10 0 2 [0041] In order to further illustrate the present invention, the following examples are given. However, it is to be understood that the examples are for illustrative purposes only and are not to be construed as limiting the scope of the present invention. EXAMPLES Examples 1-14 [0042] A solution of colloidal elongate silica in isopropyl alcohol (Snowtex IPA-ST-UP from Nissan Chemical Industries, 15% by wt. SiO 2 in isopropanol) is coated onto retroreflective sheeting (Avery Dennison T-7500 Prismatic Grade Reflective Sheeting) or a polyethylene terephthalate (PET) substrate at various coat weights (wet) and at various percent solids of the elongate silica is isopropyl alcohol. The solution is coated using a Sheen automatic coater with drawbars of 1 and 0.5 gauges. The coated substrates are placed in an air convection oven and heated at 75° C. for 15 minutes. Table 1 below shows the measured contact angle and retroreflectivity of the coated substrates. [0043] Also presented in Table 1 is Comparative Example 14 in which elongate silica in MEK solvent is used to coat a retroreflective sheet. The resulting coating has a high contact angle. While not wishing to be bound by theory, it is believed that the high contact angle is the result of the hydrophobization treatment of the silica particles surface carried out to enhance the solution stability of the MEK solvent suspension. TABLE 1 Initial Contact Reflec- % Coat Angle tivity Exam- Sol- Sub- Thickness (5 (cd/lux/ ple Silica ids strate (wet) mil sec.) m 2 ) 1 IPA-ST-UP 15 T7500 1 10.4 1234 2 IPA-ST-UP 10 T7500 1 8.1 1280 3 IPA-ST-UP 5 T7500 1 10.4 1229 4 IPA-ST-UP 1 T7500 1 30.5 1277 5 IPA-ST-UP 0.1 T7500 1 51.2 1172 6 IPA-ST-UP 15 PET 1 10.4 — 7 IPA-ST-UP 15 PET 0.5 7.7 — 8 IPA-ST-UP 10 PET 1 4.4 — 9 IPA-ST-UP 10 PET 0.5 4.7 — 10 IPA-ST-UP 5 PET 1 10.4 — 11 IPA-ST-UP 5 PET 0.5 5.4 — 12 IPA-ST-UP 1 PET 1 11.0 — 13 IPA-ST-UP 1 PET 0.5 21.1 — Comp. MEK-ST-UP 15 T7500 1.0 39.8 N/A 14 Example 15-18 [0044] Colloidal elongate silica particles in isopropyl alcohol (Snowtex IPA-ST-UP) is mixed with spherical silica particles in isopropyl alcohol (Snowtex IPA-ST-MS) in the weight ratios shown in Table 2. The Snowtex IPA-ST-MS silica sol contains 30% by weight silica having an average particle width of 17-23 nanometers. The coatings are prepared substantially in accordance with the procedure of Ex. 1-14 above. The contact angle (10 sec) measured for each of the coated films is presented in Table 2 below. TABLE 2 Ratio of elongate/spherical Coat Weight Contact Angle Example (wt. % solids) (g/m 2 ) 10 sec (deg.) 15 90/10 3.1 4.9 16 100/0  2.3 9.0 17 70/30 3.5 11 18 50/50 3.9 16 [0045] The results indicate that a minor amount of spherical silica added to the elongate particle silica improves the contact angle of the resulting coating. For comparative purposes, a coating of 100% spherical silica (Snowtex IPA-ST-MS) is prepared and coated onto a retroreflective sheet. However, the coating does not adhere to the retroreflective sheet so that the contact angle cannot be measured. Example 19 [0046] A hydrolyzate oligomer of 3-glycidoxypropyl trimethoxysilane (GPTMS) is prepared by mixing 5 g of GPTMS with 1.14 g of aqueous HCL (0.12M), sirring the solution for 1 hour, 24 hours and 1 week to give hydrolysis and condensation product of GPTMS. The coating composition is prepared by mixing the hydrolyzed GPTMS (0.66 g) with 5 g IPA-ST-UP and 2.09 g of a solution of 3,6-dioxa-1,8-octanedithiol (DOT) in isopropyl alcohol. The coating composition is coated onto a retroreflective sheet (T-7500 from Avery Dennison) using a 0.5 mil gauge draw bar and an automatic coater. The coated film is dried at room temperature, and then cured in a convection oven at 75° C. for 1 hour. Table 3 below shows the contact angle and retroreflectivity of the coated substrates with and without Xenon Weathering (383 hours). [0047] FIG. 2 is a gel permeation chromatography trace that plots intensity as a function of elution time. The numbers noted on the plots reflect the molecular weight at the particular elution time. The intensity indicates the concentration and the time indicates the molecular weight. FIG. 2 illustrates the degree of hydrolysis of the GPTMS at 1 hour, 24 hours and 1 week. TABLE 3 Time for Xenon Avg. Retro- Water Contact Angle Hydrolysis Hours reflectivity 0 sec 5 sec 10 sec 1 hour 0 1329 28 26 25 383 1043 12 7 6 24 hours 0 1371 25 24 22 383 1216 9 6 5 1 week 0 1362 23 21 20 383 838 11 8 6 Examples 20-31 [0048] In Example 20, a hydrolyzate oligomer of 3-glycidoxypropyl trimethoxysilane (GPTMS) is prepared by mixing 5 g of GPTMS with 1.14 g of aqueous HCL (0.12M), stirring the solution for 1 hour to give hydrolysis and condensation product of GPTMS. The coating composition is prepared by mixing the hydrolyzed GPTMS (0.75 g) with 5 g IPA-ST-UP and 0.49 g of a 10% by weight solution of Tinuvin 1130 in isopropyl alcohol. Before coating the retroreflective sheet, 2.09 g of a solution of 3,6-dioxa-1,8-octanedithiol (DOT) in isopropyl alcohol is added drop-wise to the composition mixture. The mixture is stirred and degassed. The coating composition is coated onto a retroreflective sheet (T-7500 from Avery Dennison) using a 0.5 mil gauge draw bar and an automatic coater. The coated film is dried at room temperature, and then cured in a convection oven at 75° C. for 1 hour. [0049] Examples 21-31 are prepared substantially in accordance with the procedure of Example 20, with the exception that the weight ratio of hydrolyzed GPTMS is varied as is the presence of UV absorber. Additionally, spherical silica is used in place of the elongate silica in Examples 26 to 31. Table 4 below shows the contact angle and retroreflectivity in the cross direction and in the machine direction of the coated substrates after Xenon Weathering (935 hours). TABLE 4 UV Reflectivity % SiO 2 :Binder Absorber Contact Angle (cd/lux/m 2 ) Example Silica Solids (w/w solids) (3% solids) (degree/5 sec) (CD/MD) 20 IPA-ST-UP 15 1:1 yes — — 21 IPA-ST-UP 15 3:1 yes 10  832/728 22 IPA-ST-UP 15 9:1 yes 7.9  1238/1047 23 IPA-ST-UP 15 1:1 no 15.5  1368/1112 24 IPA-ST-UP 15 3:1 no 9.7 1218/989 25 IPA-ST-MS 15 9:1 no 8.5 1168/917 26 IPA-ST-MS 15 1:1 yes 17  1500/1237 27 IPA-ST-MS 15 3:1 yes 12 1343/960 28 IPA-ST-MS 15 9:1 yes 6.4 1300/986 29 IPA-ST-MS 15 1:1 no 16.6 1042/927 30 IPA-ST-MS 15 3:1 no 9.2  1362/1167 31 IPA-ST-MS 15 9:1 no 9.1  1521/1216 Examples 32-37 [0050] Examples 32-37 are prepared substantially in accordance with the procedure of Example 20, with the exception that the weight ratio of hydrolyzed GPTMS is varied as is the presence of UV absorber. Examples 36 and 37 use elongate silica in MEK in place of the elongate silica in isopropyl alcohol. Table 5 below shows the contact angle and retroreflectivity of the coated substrates. Examples 38-39 [0051] For Example 38, a hydroxyethyl methacrylate (HEMA)/methyl methacrylate (MMA) copolymer solution is prepared by degassing, followed by heating at 60° C. for 24 hours a mixture of 2.3 g HEMA, 17.70 g MMA (10 mol MMA to 1 mol HEMA) and 0.05 g Vazo 64 in 80.0 g dry MEK. The coating composition is prepared by mixing 2.00 g of the polymer solution and 0.018 g aluminum acetylacetonate (AAA, 3% by weight with respect to solids) and 2.0 g Snowtex MEK-ST-UP. The coating composition is coated on retroreflective sheeting (Avery Dennison T-7500) using a 0.5 mil gauge draw bar and an automatic coater. The coated film is dried at room temperature and then cured in a convection oven at 75° C. for 1 hour. [0052] Example 39 is prepared substantially in accordance with the procedure of Example 38, with the exception that weight ratio of silica to organic binder is varied. [0053] Table 5 below shows the contact angle and retroreflection of the resulting coated substrates. Also shown is the contact angle and retroreflection of the coated substrates of Examples 21-35 after they have been subjected to corona treatment. TABLE 5 Contact Angle Reflectivity UV (degree/5 sec) (cd/lux/m 2 ) % SiO 2 :Binder Absorber Contact Angle Reflectivity with corona with corona Example Silica Solids (w/w) (3% solids) (degree/5 sec) (cd/lux/m 2 ) treatment treatment 32 IPA-ST-UP 10 1:1 yes 14.7 1285/1296 13.9 1260/1247 33 IPA-ST-UP 10 3:1 yes 27.7 1276/1319 9.1 1211/1293 34 IPA-ST-UP 10 9:1 yes 18.8 1397/1364 6.9 1255/1293 35 IPA-ST-UP 10 1:0 yes 14.9 1314/1364 6.2 1273/1307 36 MEK-ST-UP 15 1:1 no 56.6 1129/1227 — — 37 MEK-ST-UP 15 9:1 no 65.9 1122/1200 — — 38 MEK-ST-UP 15 1:1 no 62.7 1194/1090 — — 39 MEK-ST-UP 15 9:1 no 25.4 1168/1124 — — Examples 40-43a [0054] Examples 4043a are directed to dual layer dew resistant coatings. Specifically, a first primer layer is formed on the retroreflective sheet, followed by a second top layer formed over the primer layer. [0055] Preparation of Primer A: [0056] Primer A is prepared by mixing together in a 1:1 ratio by weight 3-glycidoxypropyl trimethoxysilane (GPTMS) and Snowtex IPA-ST-MS spherical particles. [0057] Preparation of Primer B: [0058] Primer B is prepared by mixing together in a 4:1 ratio by weight a methyl methacrylate/methoxypropyltrimethoxysilane copolymer (7.65:1 MMA:MOPTS) with hydrolyzed tetraethoxysilane. [0059] Preparation of Primer C: [0060] Primer C is prepared by mixing together in a 1:1 ratio by weight 3-glycidoxypropyl trimethoxysilane (GPTMS) and Snowtex IPA-ST-UP elongate particles. [0061] Top Layer I: [0062] The composition of Top Layer I is Snowtex IPA-ST-UP elongate particles. [0063] Top Layer II: [0064] The composition of Top Layer II is a photocatalyst solution of TiO 2 with a solids content of 9.4% (Bistrator NRC-300C from Nippon Soda Co., Ltd.). Example 40 Control [0065] Top Layer I is coated onto a retroreflective sheet (Avery T-7500) at a coat thickness of 1 mil (wet) and heated in a convection oven at 70° C. for 30 minutes. The contact angle and retroreflectivity of the coated sheet is shown below in Table 6 below. Example 41 [0066] Primer A is coated onto a retroreflective sheet (Avery T-7500) at a coat thickness of 1 mil (wet) and heated in a convention oven at 55° C. for 15 minutes. Top Layer I is then applied over Primer Layer A at a coat thickness of 1 mil (wet) and heated for at 70° C. for 1 hour. The contact angle and retroreflectivity of the coated sheet is shown below in Table 6 below. Example 42 [0067] Primer B is coated onto a retroreflective sheet (Avery T-7500) at a coat thickness of 1 mil (wet) and heated in a convention oven at 70° C. for 1 hour. Top Layer I is then applied over Primer Layer B at a coat thickness of 1 mil (wet) and heated for at 70° C. for 1 hour. The contact angle and retroreflectivity of the coated sheet is shown below in Table 6 below. Example 43 [0068] Primer C is coated onto a retroreflective sheet (Avery T-7500) at a coat thickness of 1 mil (wet) and heated in a convention oven at 55° C. for 15 minutes. Top Layer II is then applied over Primer Layer C at a coat thickness of 1 mil (wet) and heated for at 70° C. for 1 hour. The contact angle and retroreflectivity of the coated sheet is shown below in Table 6 below. Example 43a [0069] Example 43a is substantially the same as Example 43, with the exception that prior to measuring the contact angle and retroreflectivity, the coated substrate is placed in a Xenon Weatherometer overnight for UV activation of the Top Layer II. Subsequent to UV activation of the photocatalytic layer, the contact angle of the coated substrate decreases relative to that Example 43, the un-activated coated substrate. TABLE 6 Exam- Pri- Top Contact Angle degree (std. dev.) Retro- ple mer Layer 0 sec 5 sec 10 sec reflectivity 40 — I 6.5 (0.6) 5.1 (0.5) 4.1 (0.2) 1347 41 A I 21.5 (1.6) 19.2 (3.1) 18.3 (1.0) 1309 42 B I 12.1 (0.2) 5.2 (0.2) 4.0 (0.3) 1288 43 C II 46.4 (4.3) 45.5 (2.4) 45.4 (2.3) 1069 43a C II 5.6 (0.6) 4.5 (0.8) 3.3 (0.5) 1248 Examples 44-49 [0070] A coating of 100% elongate silica (Snowtex IPA-ST-UP) is applied to retroreflective sheeting at various coat weights. The coated sheeting is subjected to the Mandrel Test described above. Table 7 shows the results of the testing. TABLE 7 Example Coat Weight (gsm) Mandrel Rating* 44 0.57 0 45 0.81 1 46 1.12 3 47 1.13 2 48 1.27 3 49 2.85 5 *A rating of 0 indicates no cracks, 1 indicates some tiny cracks, 2 indicates thin and light cracks, 3 indicates moderate cracks, 4 indicates dense and thin cracks, 5 indicates dense and thick cracks. Example 50 [0071] A hydrolyzate oligomer of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane (CHTMS) is prepared by mixing 3 gms of CHTMS with 3.67 gms of isopropanol and 0.66 gms of aqueous HCl (0.12M), stirring the solution for 1 hour to obtain the hydrolysis and condensation product of CHTMS. The coating composition is prepared by mixing the hydrolyzed CHTMS (0.24 gms) with 6 gms of elongate silica particles in isopropyl alcohol (Snowtex IPA-ST-UP) and 0.03 gms [4-[(2-hydroxytetradecyl)oxy]-phenyl]phenyliodonium hexafluoroantimonate (a cationic UV initiator). The total solids content is decreased to a final 10% by weight by the addition of 3.76 gms of coating solvent isopropanol. [0072] The coating composition is coated onto a retroreflective sheet (T-7500 from Avery Dennison Corporation) using a 0.5 mil gauge draw bar and an automatic coater. The coated film is dried at 70° C. for 2 minutes, and then UV cured using a Fusion UV System with an H-bulb at 35 fpm for 1 pass. The film is then corona treated prior to testing. Examples 51-54 [0073] Dew resistant coatings are prepared substantially in accordance with the procedure of Example 50, with the exception that the amount of hydrolyzed CHTMS used is varied as shown in Table 8. The weight percent CHTMS shown is based on the total solids of the coating composition. The refractive index, obtained by the ellipsometry method for the coatings and the retroreflectivity of retroreflective sheets coated with the dew-resistant coatings as compared to the uncoated retroreflective sheets (two samples of each coating) are shown in Table 8. The retroreflectivity was measured in the machine direction (MD) and the cross direction (CD) for each sample. TABLE 8 % wt. Refractive Uncoated After Coating Example CHTPMS Index MD CD MD CD 50 20 1.29 1177 1152 1218 1210 1137 1153 1208 1216 51 5 1.35 1120 1115 1244 1255 1101 1140 1199 1237 52 7 1.38 1054 1119 1302 1299 1103 1121 1232 1257 53 50 1.49 1134 1159 1207 1254 1139 1156 1299 1285 54 10 — — — Example 55 [0074] A dew resistant coating is prepare substantially in accordance with the procedure of Example 50, with the exception that the hydrolysis and condensation reactions of CHTMS are carried out by reacting the monomer CHTMS in an aqueous solution of elongate silica particles followed by vacuum distillation to remove the water and subsequent dilution with isopropanol. Example 56 [0075] A hydrolyzate oligomer of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane (CHTMS) is prepared by mixing 3 gms of CHTMS with 3.67 gms of isopropanol and 0.66 gms of aqueous HCl (0.12M), stirring the solution for 1 hour to obtain the hydrolysis and condensation product of CHTMS. The coating composition is prepared by mixing the hydrolyzed CHTMS (0.24 gms) with 6 gms of elongate silica particles in isopropyl alcohol (Snowtex IPA-ST-UP) and 0.03 gms 3,6-dioxa-1,8-octanedithiol (DOT). The total solids content is decreased to a final 10% by weight by the addition of 3.76 gms of coating solvent isopropanol. The coating composition is coated onto a retroreflective sheet (T-7500 from Avery Dennison Corporation) using a 0.5 mil gauge draw bar and an automatic coater. The coated film is dried at 70° C. for 2 minutes, and then cured in a convection oven at 75° C. for 1 hour. [0076] Table 9 below shows the percent blackout for examples of the dew resistant coating that were coated onto retroreflective sheeting (Avery Dennison T-7500). TABLE 9 Percent Blackout Days Uncoated Example 1 Example 51 Example 52 0 100% 40% 86% 86% 4 100% 67% — — 6 100% 38% — — 13 100% 45% — — 22 100% 50% — — 25 100% — 46% 54% 27 100% — 33% 33% 29 100% — 52% 52% 34 100% —  9%  9% 36 100% — 15% 15% 48 100% 31% — — 50 100% 27% — — 52 100% 67% — — 57 100% 25% — — 59 100% 27% — — [0077] The dew resistant coatings of Examples 1, 50, 52 and 54 were evaluated for durability. Specifically, the retroreflectivity and contact angle for these coatings on a retroreflective sheet (T-7500 from Avery Dennison Corporation) prior to exposure and after 4502 hours of Xenon weathering are Shown in Table 10 below. TABLE 10 Retroreflectivity Contact Angle Before 4502 hrs Before 4502 hrs Example exposure Xe exposure Xe 1 1310 1237 4.7 6.0 50 1010 1124 2.8 8.8 52 1192 1119 3.5 11.6 54 1112 1160 4.5 10.1 [0078] The durability of dew resistant coatings of Examples 50 and 51 were evaluated on various retroreflective substrates as shown in Table 11 below. Specifically, the contact angle was measured for samples coated on Retroreflective sheeting (T-7500 from Avery Dennison Corporation) before and After 2120 hours of Xenon weathering. TABLE 11 Contact Angle Contact Angle Before Exposure After 2120 hours Example Substrate [deg. (std. dev.)] [deg. (std. dev.)] 50 white 25.3 (1.7) 7.2 (1.0) 50 blue 26.7 (1.2) 7.7 (2.0) 50 green 26.4 (0.5) 5.9 (1.0) 51 white 25.0 (0.8) 9.5 (3.0) 51 blue 25.7 (0.9) 10.7 (1.0) 51 green 25.8 (0.2) 11.9 (1.0) [0079] Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. In particular regard to the various functions performed by the above described elements (components, assemblies, compositions, etc.), the terms used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

The present invention relates to dew resistant coatings and articles having the dew resistant coating adhered thereto. The dew resistant coatings comprise elongate silica particles. These coating are useful on articles or surfaces used in outdoor applications and articles and surfaces used in moist indoor environments.

FIELD OF THE INVENTION The present invention generally relates to a dynamic balancing machine, and, more particularly, to an automatic digital dynamic balancing machine wherein the amount and angular location of unbalance in a rotating part is calculated off line and the part is stopped with the unbalance in a predetermined position without using a reference marking on the rotating part. BACKGROUND OF THE INVENTION In the dynamic balancing of a rotating part such as an electric motor armature, the part is mounted on its axis between bearings, rotated, and the unbalance is sensed by vibration or force sensors at the bearing locations. Several methods and devices have been developed to indicate the location of the unbalance on a rotated part. Two early types of machines widely used in industry use stroboscopic and photocell techniques to locate the unbalance. These both had the disadvantage of requiring physical markings on the part being rotated. These machines also required visual estimates of the unbalance location and were therefore subject to operator error. The most advanced machine of this type is disclosed in U.S. Pat. No. 4,419,894 to Matumoto, wherein an unmarked workpiece is rotated, the unbalance measured and located, and the workpiece stopped with the unbalance position in a predetermined orientation for subsequent marking and material mass addition or removal. This machine utilizes vibration sensors to generate an analog unbalance signal which is sinusoidal. An unbalance phase pulse is then electronically generated once per cycle at the positive going zerocrossing of the unbalance signal. The workpiece is driven by a stepper motor. Each drive pulse supplied to the stepper motor causes the workpiece to rotate an unknown but fixed angle. A counter, preset with a number representing an integral number of stepper motor drive pulses, is counted back upon each stepper motor drive pulse, starting with the receipt of an unbalance phase pulse and the rotated workpiece is stopped when the counter reaches zero. It is a real time system in that pulses coming from the unbalance sensor are used to initiate the countdown. There are several limitations and drawbacks associated with this type of machine. First, considerable time is required to initially set up the machine to maximize plane separation, select optimum counter settings, and set acceleration and deceleration rates to minimize belt slippage. These adjustments must be made for each different workpiece type measured. Settings are determined by trial and error methods which are awkward and time consuming. Second, the Matumoto method does not verify the accuracy of the determination of the rotational speed and therefore introduces error due to inherent drive belt slippage between the stepper motor drive and the driven part. Third, minor differences in armature diameters may introduce errors in unbalance positioning because the Matumoto machine does not measure and utilize the actual rotational frequency of the workpiece. Finally, because the Matumoto method involves time consuming setup steps and inherent errors for each workpiece, it entails significant restrictions in efficiency for production line processing. SUMMARY OF THE INVENTION The present invention provides an automatic balancing machine and method that overcomes the above identified drawbacks and disadvantages. It is an object of this invention to provide a dynamic balancing machine and a digital method for automatically determining the amount and angular location of unbalance in a rotating part and stopping the part with the unbalance accurately positioned in a predetermined orientation for marking and correction. It is a further object of this invention to provide an automatic balancing method wherein the angular velocity of the rotating part is accurately measured and a correction made to the assumed angular velocity to accurately calculate the time to decelerate and position the unbalance in a predetermined orientation. It is a further object of this invention to provide an automatic digital balancing machine that digitally calculates the unbalance phase angle off line by use of a microprocessor and displays the unbalance of each correction plane visually using conventional video technology. Accordingly the present invention provides a machine and method for automatically determining the location and amount of unbalance of a rotated part accurately and efficiently. The invention involves a unique combination of steps to determine the unbalance location and magnitude. The method comprises the following operative steps: (a) rotating a part to be balanced between two axially opposed bearings; (b) generating an electrical signal proportional to the rotary unbalanced at one of the bearings; (c) calculating the actual angular velocity from the unbalanced signal and a predetermined assumed angular velocity; (d) calculating the time at which to begin the acceleration of the part at a predetermined deceleration rate in order to stop the part with the unbalanced location in a predetermined position; and (e) decelerating the part at the predetermined rate at the proper time. An illustrative and specific embodiment of the method invention comprises the following steps: (a) rotating the part between stationary bearings, (b) generating an analog electrical unbalance signal proportional to the forces generated by the rotating part at the bearing locations, (c) generating time interval signals synchronous with the rotation, (d) converting the analog unbalance signal to a digital signal, (e) measuring and storing a first digital signal sample during a first set of predetermined repetitive time intervals, (f) measuring and storing a second digital sample during a second like set of time intervals contiguous with the first, (g) calculating the average demodulated phase angles for the first and second sets of samples according to the following equations: ##EQU1## where A x and A y are the demodulated coordinate components of the average unbalance signal from a set of samples "A" N=number of discrete sample elements per revolution M=number of revolutions per sample set S=sample element of the electrical unbalance signal sample (h) calculating the actual angular velocity R according to the following equation: ##EQU2## where M=the number of revolutions between the center of a first sample set to the center of a second sample set at the assumed angular velocity B=the unbalance angle of the second sample set in radians A=the unbalance angle of the first sample set in radians T=the total length of time between the center of the first sample set to the center of the second sample set (i) calculating the number of time intervals corresponding to the unbalance phase angle at the actual angular velocity, (j) calculating the deceleration time period required to bring the part to rest in a predetermined integral number of revolutions, (k) establishing an initial reference point in time corresponding to some point during the measuring intervals, (l) triggering the deceleration of the rotating part when the elapsed time intervals from the initial reference point equals the sum of the calculated time intervals corresponding to the unbalance phase angle plus a predetermined calculation time interval from the initial point. The preferred embodiment of balancing machine includes a frame, axially opposed bearing for rotatably supporting the part to be balanced, at least one force detector for detecting the forces normal to the axis of part rotation, circuit for producing an electrical unbalance signal, clock for generating an indication of repetitive time intervals, sampling device for measuring sets of discrete sequential sample elements, memory for storing the sample sets, device connected to the drive motor for controlling the drive motor synchronous with the sampling device, a microprocessor device for calculating the demodulated average unbalance components of each of two contiguous sample sets, calculating the difference value between the two sets of average unbalance, calculating the actual angular velocity from the difference value, controlling the deceleration of the drive motor at a constant rate unit the part is stationary, and calculating the time to decelerate the part and stop the part with the unbalance in a predetermined position. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a two plane hard bearing balancer; FIG. 2 is a sectional view of the balancer illustrating the different drive belt arrangements between the stepper motor and the driven part; FIG. 3 is a graph of angular velocity versus time for a rotating workpiece illustrating the major events during a measuring cycle; FIG. 4 is a block diagram of a two plane hard bearing balancer utilizing an encoder to generate timing intervals; and FIG. 5 is a partial front view of the two plane hard bearing balancer shown in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIG. 1 there is shown an elementary block diagram of the automatic digital balancing machine and microprocessor components. The workpiece part 180 to be balanced is mounted between hard bearings 190 and 200. A DC stepper motor 160 is connected to the part via belt 170. There are several belt orientations that may be used. Referring now to FIG. 2, there is shown three alternate belt arrangements. The DC stepper motor sheave 330 is connected around idler pulleys 340 and 350 in two orientations of the driven part 180. The belt 170 routed underneath part 180 and over idler pulleys 340 and 350 is a preferred arrangement for small, light parts where production run speed is more important than minimizing signal noise. Belt 171 routed over part 180 and idlers 340 and 350 is an alternate but not preferred arrangement. The belt 172 routed between the stepper motor and the part directly is used where minimizing noise is critical. FIG. 3 illustrates curve 1 of a typical measurement sequence. Curve 1 shows an increasing part angular velocity until full operating speed is reached at which time the speed becomes and remains constant until deceleration begins. During region 80 the part is accelerated at a constant value from rest at point 10 to the operating speed at point 20. At point 20 the acceleration becomes zero and the part rotates at a constant angular velocity during regions 90, 100, 110, and 120. At point 60 deceleration begins at a constant rate in region 130 until the part is stopped at point 70. Acceleration and deceleration in regions 80 and 130 need not be the same rates. The critical rate is in region 130 where deceleration must be slow enough that no slippage occurs between the drive stepper motor, the part, and the drive belt due to inertial forces and must occur in an integral number of revolutions. A first sample set begins at point 20 and is completed at point 30 which is also the beginning of the second sample set. The second sample set ends at point 40. Each sample set 90 and 100 optimally correspond to 16 revolutions of 32 samples per revolution for a total of 512 samples in each set of data. Points 140 and 150 represent the center of the first and second sampling intervals respectively. Returning now to FIG. 1, the DC stepper motor 160 and bearings 190 and 200 are rigidly mounted to the machine frame 5. Piezoelectric transducers 202 and 203 are utilized to generate electrical signals proportional to the forces applied to them. When the part 180 is rotated, these forces are normal to the axis of rotation and represent the unbalance present in the rotating part. The signal generated by piezoelectric transducers 202 and 203 also contain unwanted signals. The unwanted signals at or above the sampling rate are eliminated by antialiasing filters 210 and 220. These unbalance signals (U L , U R ) are then sent to multiplexer 230 where a choice of either S L or S R is made for further processing. Plane separation is required because the signal from the transducer 202 will have part of its magnitude due to the influence of the forces at transducer 203 and vice versa. During calibration the vector constants (K 1 , K 2 , K 3 , K 4 ) are determined in the following set of equations: U.sub.L =K.sub.1 * S.sub.L +K.sub.2 * S.sub.R U.sub.R =K.sub.3 * S.sub.L +K.sub.4 * S.sub.R where S L is the separate left channel signal, S R is the separate right channel signal, U L is the composite left channel signal, and U R is the composite right channel signal. By utilizing known unbalance masses, positions, and the frequency of rotation, constants K 1 , K 2 , K 3 , and K 4 can be determined and entered into random access memory 300 automatically by the microprocessor 270. Microprocessor 270 is then enabled to perform the required plane separation. Referring now to FIG. 5, which is a partial frontview of the rated part mounting configuration, the following physical parameters are required to be input and stored in the microprocessor 270 RAM 300 via keyboard 370 (FIG. 1) prior to measuring or calibration of any rotated part: (a) Left plane 531 location 530, measured from the bearing 190 along the rotational axis; (b) Left correction radius 560, measured from the rotational axis radially to the surface of the part at the location of the left plane 531; (c) Right plane 532 location 540, measured from the bearing 190 along the rotational axis; and (d) Right correction radius 570, measured from the rotational axis radially to the surface of the part in the location of the right plane 532. Note that FIG. 5 illustrates the length 550 of rotating part 180 from bearing 190 to bearing 200. Referring back to FIG. 1, in order to determine the constants K 1 , K 2 , K 3 , and K 4 for a class of rotated parts, a three spin calibration procedure is followed to generate three sets of known unbalance signals which the microprocessor 270 then uses to mathematically determine the constant values. This procedure requires the use of a photoreflector sensor 310 and a reflective target 320 (see FIG. 1) temporarily affixed to a rotating part 180 which is an example of the desired type of rotating parts. Referring back to FIG. 5, the reflective target is shown behind the rotated part 180. In FIG. 5 is also shown a calibration weight 510 placed at the left plane 531. This is the position of the weight during the first calibration spin. The part is then stopped and the calibration weight moved to the right plane 532 (shown in phantom at 520) for the second spin. The third spin is done with the calibration weight removed. Prior to the first spin, however, the following information must be input to the microprocessor 270 via the keyboard 370: (a) Calibration weight; (b) Radius 560 at left plane 531 measured from the rotational axis to the surface of the rotated part 180; (c) Angle between target 320 and left calibration weight location 510; (d) Radius 570 at right plane 532 measured from the rotational axis to the surface of the rotated part 180; (e) Angle between target 320 and right calibration weight location 520; and (f) Photo pickup (310) angle measured from the back of the base unit (5) counterclockwise when viewed from the right side. The three spins provide known values of unbalance from which the microprocessor circuitry determines the values of K 1 , K 2 , K 3 , and K 4 used to correct the actual unbalance signals at the chosen left and right unbalance planes, U L and U R respectively to give the true unbalance signals S L and S R . Referring again to FIG. 1, during a spin of the part 180, corrected signals S R or S L enter the sample hold circuit 240 from the multiplexer 230. The microprocessor 270 also feeds timing pulses to the sample hold circuit to establish the sample increments. Once the rotating part 180 reaches operating speed the two set sampling begins. Each sample element for each sample increment is then converted to a digital equivalent signal by the analog/digital converter 250. Each digital signal element is then stored by the microprocessor in random access memory 300 to await further processing. Each sample set of 512 elements is stored in random access memory 300 in 512 separate locations corresponding to the signal's time interval. The central processing unit 280 marks the time corresponding to an arbitrary point such as the last sample increment in the sample time sequence as an initial point. The clock 305, through the central processing unit 280, also provides the timing pulses to the DC stepper motor such that the position of the DC stepper 160 motor relative to the initial point is currently known by the central processing unit 280. When two contiguous sets of samples S A and S B have been stored by the microprocessor 270, the phase angle relative to the arbitrary reference can be determined. The central processing unit 270 accesses read only memory 290 wherein a 512 element table of sine and cosine functions are stored. These tables are then employed with the stored sample data to calculate the average demodulated components of the phase angle with respect to a predetermined desired position. The sine and cosine table values are employed with the stored sample elements by microprocessor 270 to generate the demodulated phase angle coordinates A x and A y per the following equations: ##EQU3## where M=number of revolutions per sample set N=number of sample elements per revolution S=signal at time increment iM+j The sine and cosine tables are then employed by microprocessor 270 to the second set of samples to determine the demodulated phase angle coordinates B x and B y per the same equations. A correction is then made for any error in the assumed speed of the rotated part. The assumed speed is manually entered via keyboard 370 prior to balancing and is based on the arrangement and relative diameters of the drive pulley 330, the rotated part diameter and the stepper motor rate. In the embodiment of FIG. 1, microprocessor 270 provides pulses to a stepper motor 160 at a rate which is controlled by clock 305. This stepper rate is set synchronous with the sample hold circuit 240, which is also set by microprocessor 270. Should there be an difference between the calculated average phase angles of sample sets A and B, this indicates that the actual speed is not synchronous with the assumed speed. Microprocessor 270 makes correction by calculating the actual angular velocity R according to the following equation: ##EQU4## where M=the number of revolutions between the center of a first sample set to the center of a second sample set at the assumed angular velocity B=the unbalance angle of the second sample set in radians A=the unbalance angle of the first sample set in radians T=the total length of time between the center of the first sample set to the center of the second sample set Referring now to FIG. 3, points 140 and 150 correspond to the midpoints of sample period 90 corresponding to sample A and sample period 100 corresponding to sample B, respectively. Because the sample periods 90 and 100 are the same length, the time increment between points 140 and 150 is this same length. Therefore the equation above yields the corrected or actual rotational velocity. The inverse of this equation provides the number of time increments per revolution of the part. Period 110 shown between points 40 and 50 is an arbitrary assumed time period to compensate for the off line computational time required by microprocessor 270 to calculate actual frequencies and is on the order of 500 milliseconds. One skilled in the art would appreciate that this time must be set with reference to the speed of operation of microprocessor 270. The period 120 between points 50 and 60 represents the time required to position the rotating part with the unbalance located at the desired final position such that at point 60 the unbalance location will be a predetermined integral number of revolutions from the stop position and the deceleration may begin. Deceleration is preprogrammed into the microprocessor 270 as a constant rate. Microprocessor 270 is programmed to generate pulses for driving stepper motor 160 for deceleration in accordance with this constant deceleration rate. Calculation of the time to point 60 is performed by calculating the total amount of time between the initial point and the point 60. The initial point may be any point in the measuring cycle at to or after point 20. Typically point 40 is used. Therefore the time to reach point 60 may be calculated by adding the predetermined delay period 110 to the calculated phase angle 120. When the elapsed time equals the calculated time to point 60 the deceleration ramp is begun. Microprocessor 270 is further connected to display 360. In conjunction with the calculation of the place of imbalance and controlling the deceleration of stepper motor 160 to stop the unbalance at the predetermined position, microprocessor 260 also generates signals for display via display 360. As is conventional in such microprocessor control systems, display 360 is employed to display user prompts for initial set up, as for example requesting entry of the desired speed of rotation of the rotating part, information on the status of dynamic balancing operation and so forth. In addition microprocessor 270 computes the magnitude of the unbalance in the rotating part. Display 360 is employed to display this quantity together with the calculated actual rotational speed and the location of the imbalance after completion of the dynamic balancing operation. Display 360 could be formed of light emitting diodes, a liquid crystal display, however the preferred embodiment is a video display monitor formed with a cathode ray tube. In the embodiment illustrated in FIG. 1, the stepper motor rate was controlled in relation to an independently set sampling rate. FIG. 4 illustrates an alternative embodiment. Microprocessor 270 controls the speed of operation of stepper motor 160 by generation of pulses with the appropriate timing. This timing of pulses takes place in relation to the signals from clock 305. A shaft encoder 400 is coupled to the rotating part by belt 410. Rotation of the rotating part causes belt 410 to rotate shaft encoder 400. Shaft encoder 400 in turn generated a signal which indicates the rotary position of shaft encoder 400. Microprocessor 270 employs this signal from shaft encoder 400 to generate the sampling rate signal for sample hold circuit 240. The sample rate is thus asynchronous with the stepper motor rate. In other regards, the apparatus illustrated in FIG. 4 operates in the same manner as previously described.

The balancing machine of the present invention automatically determines the position of unbalance in a rotating part and stops the rotating part with the unbalance position in a predetermined location. Sensors on the bearings holding the rotating part generate signals proportional to the instantaneous unbalance. These signals are filtered and digitized at a sampling rate synchronous with the motor driving the rotation. Two contiguous sets of samples, each set spanning several revolutions of the part, are stored. The X and Y components of the unbalance signal are calculated for each sample set and the actual rotation rate of the part is calculated from the assumed rate and any difference in the phase angle of the unbalance location between the first and second sample sets. These calculations are performed during a calculation interval of predetermined length which follows the sampling. Once this calculation interval has passed and the unbalance location has rotated to the predetermined location a predetermined deceleration of the rotating part is begun. The motor is controlled to decelerate at a predetermined rate.

BACKGROUND OF THE INVENTION The present invention relates to a door and, more particularly, to a door for a motor vehicle including an outer skin and an inner skin. Conventional car doors generally include an outer skin made of metal which simultaneously provides a supportive and stabilizing function, with the outer skin being provided with rigidifying or reinforcing means in an interior of the door. The inner skin, which can be made of a synthetic resin, forms merely a paneling mounted to the outer skin but contributing little if anything to the ruggedness or sturdiness of the door. Thus, a disadvantage of the conventional motor vehicle door resides in the fact that the doors are not only heavy in weight but also relatively expensive to manufacture. Synthetic-resin doors have also been proposed; however, these proposed synthetic-resin doors are unable to meet the desired functional requirements for a vehicle door and also unable to meet the legal requirements. Moreover, the further disadvantages in the proposed synthetic-resin doors resides in the fact that the doors do not have dimensional stability, they shrink, and do not satisfy the demands posed by large-scale series manufacturing. The aim underlying the present invention essentially resides in providing a vehicle door of the aforementioned type which, in spite of a very low weight, is dimensionally stable and can be manufactured in a simple and economical manner. In accordance with advantageous features of the present invention, a motor vehicle door is provided wherein an outer skin and an inner skin of the door are fashioned of synthetic resin shells, with the inner skin being formed as an integral component of a door body including a supportive skeleton of rod-shaped bars. By virtue of the features of the present invention, the inner skin of the vehicle door represents the supportive member rather than, as with conventional doors, the outer skin, and the supportive skeleton is integrated into the inner skin. The supportive skeleton includes rigid and dimensionally stable struts coated by, for example, molding, with the synthetic resin of the inner skin and the outer skin, shaped as separately produced shells, being attached to the inner skin. The outer skin has no supportive function so that, in the case of damage to the outer skin, the structure of the door will not be adversely affected. The surfaces of the inner and outer skins are elastic so that they regain their original shape if subjected to an impact or shock that is not excessive. Since the vehicle door of the present invention consists almost exclusively of a synthetic resin, the door offers, in addition to the advantage of a low weight, a positive feature in as much as the door is not subject to change by rust or corrosion. Moreover, the struts of the supportive skeleton, which can be fashioned of metal, are entirely embedded in the material of the inner skin and surrounded by this material so that they are also effectively protected against adverse environmental influences. In accordance with the present invention, hinge members are mounted at one end of the supportive skeleton, and a lock is arranged at the opposite end. With this arrangement or construction, the ridged and dimensionally stable supportive skeleton takes care of retaining the correct spacial correlation between the lock and the hinge members thereby insuring that, in the case of dimensional changes taking place at the synthetic resin parts, the door will always close in the correct manner, and the function of the lock is not impaired by any such dimensional changes. Preferably, in accordance with the present invention, the outer skin terminates at the lower boundary line of a window, and the supportive skeleton, integral with the inner skin, is fashioned so that it extends completely around the window. The supportive skeleton constitutes not only the supportive and stabilizing part of the vehicle door, but also simultaneously a frame imbedded in the inner skin, insuring the door retains its shape. The outer skin is not attached directly to the supportive skeleton, but rather to the parts of the inner skin surrounding the supportive skeleton and, consequently, it is unnecessary to attach synthetic resin to metal which would require special mounting elements such as, for example, screws, clips, fasteners or the like, and it is possible to, for example, glue the outer skin to the inner skin. In accordance with still further features of the present invention, the skeleton includes at least one essentially horizontally extending strut means extending over an entire length of the door, and the inner skin, above and/or below the strut, recedes to form an arm rest, a door pouch, or the like, or respectively, is provided with openings for enabling a formation of mounting boards. In this manner, it is possible to optimally utilize the inner space of the door and to greatly reduce idle volume or wasted space. Moreover, the interior of the motor vehicle is enlarged or increased to a considerable extent based on the external dimensions of the vehicle. Advantageously, mounting faces for engaging the outer skin are provided at beads of the inner skin surrounding the struts of the supportive skeleton, whereby the outer skin forming a protective shell, can be joined in a simple manner with the inner skin and, consequently, with the supportive skeleton. In order to seal a door gap, the inner skin and/or the outer skin maybe provided with sealing lips integrally molded along a circumference of the vehicle door, and, consequently, it is unnecessary to provide separate sealing lips of foreign materials since the sealing action is performed or accomplished by the material of the inner skin fashioned to be correspondingly thin at the sealing lips. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken into connection with the accompanying drawings which show, for the purposes of illustration only, several embodiments in accordance with the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exterior side view of a vehicle door constructed in accordance with the present invention; FIG. 2 is a schematic interior view of the vehicle door of FIG. 1; FIG. 3 is an end view taken in a direction of the arrow III in FIG. 2; FIG. 4 is an end view taken in a direction of the arrow IV in FIG. 2; FIG. 5 is a cross-sectional view taken along a line V--V in FIG. 2; FIG. 6 is a cross-sectional view taken along a line VI--VI in FIG. 2; FIG. 7 is an enlarged view of a detail designated VII in FIG. 6; FIG. 8 is a cross-sectional view taken along a line VIII--VIII of FIG. 2; FIG. 9 is a cross-sectional view taken along a line IX--IX in FIG. 2; FIG. 10 is a cross-sectional view taken along a line X--X in FIG. 2; FIG. 11 is a schematic view of a supportive skeleton of a vehicle door constructed in accordance with the present invention; FIG. 12 is an end view of the supportive skeleton taken in a direction of an arrow XII in FIG. 11; FIG. 13 is an end view of the supportive skeleton taken in a direction of an arrow XIII in FIG. 11; FIG. 14 is a cross-sectional view taken along a line XIV--XIV in FIG. 11, with an additional illustration of an outer skin; FIG. 15 is a cross-sectional view taken along a line XV--XV of FIG. 11, with an additional illustration of the outer skin; FIG. 16 is a side view of the outer skin for a vehicle door constructed in accordance with the present invention; and FIG. 17 is a profile view of the outer skin of FIG. 16. DETAILED DESCRIPTION Referring now to the drawings wherein like reference numerals are used throughout the various views to designate like parts and, more particularly, to FIG. 1, according to this figure, a vehicle door adapted to be mounted on a passenger motor vehicle, includes a supportive door body generally designated by the reference numeral 10 to which an outer skin generally designated by the reference numeral 12 is attached beneath a window opening generally designated by the reference numeral 11. Struts or frame members 13 define the window opening 11 toward the top and laterally are parts of the door body 10. The window opening 11 includes a window pane 14 fixably connected to the door body 10 and occupying or covering a largest part of the window opening 11, and a movable window part or pane 15 adapted to be selectively raised and lowered from and into an interior of the vehicle door in order to open at least a portion of the window opening. A forward corner of the fixed window pane 14, which converges pointedly, includes a mounting plate 16 to which a rear view mirror can be attached, with the mounting plate 16 being firmly joined to the door body 10. A door handle 17 and keyhole 18 of a lock are conventionally mounted at the outer skin 12, which is fashioned as a projecting shell. The outer skin 12 terminates approximately at a bottom edge of the window 14 and includes, in a lower zone or area thereof, a longitudinally extending impact protection molding 19 in the form of a hollow bead. As shown in FIGS. 16 and 17, the outer skin 12 is fashioned as a separately manufactured shell produced from a synthetic resin and subsequently fastened to the door body 10. As shown most clearly in FIG. 2, the door body 10 includes a supporting skeleton 20 which, as shown in FIG. 11, is fashioned of a plurality of rigid struts formed preferably of, for example, metal, with a cross-section of the rigid struts being, for example, tubular. The supportive skeleton 20 includes a closed frame 21, a contour of which corresponds to that of the vehicle door. In the closed frame 21, below the opening 11 for the window, a longitudinal strut 22 extends which runs along an entire length of the closed frame 21, and the ends of which are connected to vertical struts of the closed frame 21. Two additional longitudinal struts 23, 24, extend essentially or substantially horizontally in a region or area between the longitudinal strut 22 and the lower frame strut 25. Each of the longitudinal struts 23, 24, extends from one hinge member 26 or 27 at one end of the closed frame 21 to the lock 28 at the other end of the closed frame 21. The longitudinal struts 23, 24, are connected with each other by transverse struts 29, 30, 31, in order to form within the closed frame 21 a rigid carrier extending from the hinge members 26, 27, to the lock 28. The hinge members 26, 27, are attached to two parallel vertical struts 32, 33, constituting the forward end of the closed frame 21. The strut 32 is located in the major plane of the frame 21, whereas the strut 33 is oriented away therefrom towards the interior of the vehicle. The hinge members 26, 27, each of which exhibits a forwardly projecting hinge arm 34 (FIG. 14) are attached to the struts 32, 33. A mounting bridge 35 extends in the center between the hinge members 26, 27, between the struts 32, 33, with the mounting bridge 35 having a passage opening for a holding tongue 36 projecting into the interior of the vehicle door and defining the open position of the door. Moreover, a bearing 38 is provided for the pivoting window 15 and mounting means 39 for a window operating device or crank mechanism (not shown) are attached to the closed frame 21. The supportive skeleton 20, with the exception of the mounting plate 16, hinge members 26, 27 and lock 28, is entirely coated by molding by the synthetic resin of the inner skin 40 and embedded in the synthetic resin. As shown most clearly in FIGS. 5-10, all of the struts of the supportive skeleton 20 are entirely encompassed by the synthetic resin of inner skin 40. The inner skin 40 furthermore is fashioned as a shell 41 extending essentially over the entire area beneath a bottom edge of the window 14 (FIG. 2). A supporting trough or depression 42 for insertion or accommodation of the elbow rest is integrally molded within the shell 41, and, in a lower zone or area of the door body 10, a storage trough or depression 43 (FIGS. 2, 6) is molded in place. The troughs or depressions 42, 43, arranged above and below the beam formed by the longitudinal struts 23, 24, project from an interior of the vehicle toward the outside, that is, the troughs or depressions 42, 43, bulge or protrude in the direction toward the outer skin 12 and are in overlapping relationship, as seen from a top view, with the longitudinal struts 23, 24. A lateral cheek 44 is disposed in front of the storage trough 43 (FIG. 6), with the lateral cheek 44 projecting into the interior of the vehicle and defining the storage pouch formed in the storage trough 43. Furthermore, mounting bores or apertures 46 (FIG. 2) are provided in the inner skin 40. An operating mechanism 47 for the door lock 28, attached to the supportive skeleton 20, is arranged behind one of the mounting bores or apertures 46, with a linkage 48 extending from the operating mechanism 47 through the interior of the vehicle door 10 to the door lock 28. The inner skin 40 is partially covered with a door paneling 49 (FIG. 10) covering the mounting bores or apertures 46. The attachment of the outer skin 12 to the inner skin 40 is most clearly shown in FIGS. 6, 7. The struts of the supportive skeleton 20 include hollow profile members surrounded by beads 50 of the inner skin 40, and the beads 50 include an outwardly oriented contact face 51 which is brought into flat engagement with the outer skin 12. A shallow indentation for accommodating an adhesive media is provided in each contact face 51. On both sides of the contact face 51, the outer skin 12 is provided with webs 52 serving for positioning the outer skin 12 with respect to the inner skin 40 and for preventing an escape of the adhesive media. As shown in FIG. 6, a sealing strip 54 is attached to a stepping sill 53 of the vehicle, with the sealing strip 54 being contacted by a step shoulder generally designated by the reference numeral 45 of the inner skin 40 when the vehicle door 10 is closed. Similar sealing strips 54 are provided at the remaining edges of the frame of the door 10. The outer skin 21 and/or the inner skin 40 additionally include integrally molded or separately attached sealing lips 55 which contact a boundary of a door opening of the vehicle side. As shown in FIG. 5, the movable or pivoting window part 15 is movable or pivotable about a bearing 38 and is adapted to be lowered through a window gap 56 into an interior of the vehicle door 10. For the sake of clarity, the conventional operating mechanism for moving the movable window part 15 which, for example, may be a mechanical construction or a cerval operated mechanism, are not illustrated in detail for the sake of clarity. The window gap 56 is defined on both sides of the pivotable window part 15 by sealing strips 57, 58, with the sealing strip 57 being mounted to a top edge of the outer skin 12, whereas, the opposite sealing strip 58 is attached to the head 50 of the longitudinal strut 22. FIG. 10 provides an illustrated example of an attachment of the fixed pane 14, a lower edge of which, is secured by an adhesive media such as, for example, glue, to an outside of the upper end of the outer skin 12. The upper end of the upper skin 12, is, in turn, glued the mounting face 51 of the bead 50 of the longitudinal strut 22. On a rearward vertical strut 21, the fixed window pane 14, is, as shown in FIG. 9, additionally secured by, for example, an adhesive such as glue to a mounting face 51 with the interposition of a gasket or the like. As can readily be appreciated, the outer skin need not be necessarily be glued or cemented to the inner skin 40 but rather may be attached by faster means such as, for example, screws, clips, spot welding, or the like. While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is succeptable to numerous changes and modifications, and I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such modifications as are encompassed by the scope of the appended claims.

A motor vehicle door including a supportive and dimensionally stable skeleton which, together with an inner shell, constitutes a one-piece door body, to which an outer shell is attached as a separate element. The inner shell and the outer shell are fashioned from a synthetic resin and the supportive skeleton connects hinge members with the door lock of the door. The inner skin is provided with at least one of troughs or depressions and mounting bores or apertures.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a sense amplifier of a memory device, and more particularly, to a method and circuit for automatically controlling an operation of a sense amplifier in correspondence with variations of operating voltage and frequency of a memory device. 2. Description of the Related Art FIG. 1 is a diagram illustrating a read and write operations in a general memory device. As shown in FIG. 1 , during a write operation, data applied through an input/output data pad is transferred to a bitline sense amplifier through a data input buffer and a data input register. While, during a read operation, cell data amplified by the bitline sense amplifier is transferred to the input/output data pad through a data sense amplifier, a pipe register, and a data output buffer. In FIG. 1 , signal Yi is a pulse signal to connect the bitline sense amplifier with the data sense amplifier so as to control an operation of a data bus. While the signal Yi controlling the data bus is being enabled, the write data is transferred to the bitline sense amplifier from a write driver and the read data is transferred to the data sense amplifier from the bitline sense amplifier. It is advantageous to make a pulse width of the signal Yi wider in transferring valid data in an active operation mode (the read or write operation). It is also efficient to improve the performance of tDPL (a time from when a CAS pulse signal is generated internally by a write command to when a precharge pulse signal is generated internally by a precharge command) because the time parameter tDPL contributes to making restoring facilities of data better. Therefore, it is usual to establish the pulse width of the signal Yi as wider as possible within the permissible range and to use it with shrinking down in accordance with operational conditions. In reference, as an operating frequency of a memory device increases (i.e., a clock cycle period is shorter), a permissible pulse width of the signal Yi becomes narrower. Meanwhile, as the signal Yi is made from responding to a read/write strobe pulse signal rdwtatbzp 13 output from a read/write strobe pulse generator, hereinafter will be explained about the read/write strobe pulse generator. FIG. 2A illustrates an example of a conventional read/write strobe pulse generator and FIG. 2B is a waveform diagram of signals used in the circuit shown in FIG. 2A . In FIG. 2A , signals extyp 8 and icasp 6 are signals to make a data transmission line short or open, so as to read data to a peripheral circuit from a cell array of the memory device or to write data in the cell array of the memory device from a peripheral circuit. For information, it's named a core section for the range including a memory cell and a bitline sense amplifier and the rest a peripheral circuit. In detail, the signal extyp 8 is a pulse signal that is generated in sync with a clock signal when a read or write command (burst command) is applied to the memory device. And, the signal icasp 6 is a signal to be used in operating the memory device by generating a self-burst operation command that is established with a burst length set by an MRS (mode register set) mode from a clock time later by one clock cycle period than a clock time when a read or write command is applied from the external. The signal rdwtstbzp 13 is a signal to be active for the burst length set by the MRS mode, being activated in sync with the signals of the burst operation command (external=exryp 8 & internal=icasp 61 ). In other words, the signal rdwtstbzp 13 is to be used to inform an activation time of the input/output sense amplifier in amplifying and transferring data, which is to be sent to a peripheral circuit from a core circuit region, to the data output buffer, resetting the data transmission line of the peripheral circuit after completing the data amplification and transmission by the sense amplifier. A signal pwrup is a signal to set an initial data value, retaining low level after falling down to low level from high level. Signal term_z is a signal used in a test mode being held on low level during a normal operation. A signal tm_clkpulsez is used in a test mode. Such signals will be described in detail in conjunction with embodiments of the present invention hereinafter. A circuit operation of FIG. 2A is illustrated, as follows, with reference to the waveform diagram of FIG. 2B . As illustrated in FIG. 2B , when the read/write command is applied to the memory device in sync with the clock signal clock, the pulse signal extyp 8 is generated. If the pulse signal extyp 8 is enabled, a plurality of pulse signals icasp 6 is generated in sync with the next clocks in sequence. As shown in FIG. 2B , the read/write strobe pulse signal rdwtstbzp 13 is generated in sync with rising edges of the pulse signals extyp 8 and icasp 6 . Here, in the conventional circuit shown in FIG. 2A , it can be seen that the pulse width of the read/write strobe pulse signal rdwtstbzp 13 generated from a pulse width adjusting circuit 200 is fixed nevertheless of the operating frequency of the memory device. Here, a delay time from a node A from a node D is determined by a delay circuit 20 . As the delay time of the delay circuit 20 in the pulse width adjusting circuit 200 is fixed, the pulse width of the signal outputted from the pulse width adjusting circuit 200 is always constant without regarding to the operating frequency of the memory device. But, it needs to adjust a pulse width of the read/write strobe pulse signal rdwtstbzp 13 when an operating frequency of the memory device varies. In a conventional art, while the delay time of the delay circuit 20 is variable by modifying a metal option during a FIB process when an operating frequency of the memory device varies, it needs much costs and times. In addition, with the conventional art, there is no way to correct a variation of the pulse width of the read/write strobe pulse signal rdwtstbzp 13 when an operation voltage of the memory device varies. SUMMARY OF THE INVENTION Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a method of automatically controlling a pulse width of a signal output from a pulse width adjusting circuit in accordance with variation of an operating frequency of a memory device. Another object of the present invention is to provide a method of controlling a pulse width of a read/write strobe pulse signal rdwtstbzp 13 in correspondence with variation of an external clock signal. In order to achieve the above object, according to one aspect of the present invention, there is provided a read/write strobe pulse generator generally usable even when an operating frequency of a memory device varies. According to another aspect of the present invention, there is also provided a method of delaying a signal outputted from a read/write strobe pulse generator by applying an external address signal and controlling a width of the read/write pulse. According to still another aspect of the present invention, what's provided is a method of controlling a pulse width of a read/write strobe pulse signal rdwtstbzp 13 in accordance with variation of an operation voltage of a memory device. By the features of the present invention, an embodiment of the present invention is a circuit for controlling an enabling period of an internal control signal in accordance with variation of an operating frequency in a memory device, which comprises a pulse width adjusting circuit for changing a pulse width of an input signal in accordance with the operating frequency; a signal transmission circuit for buffing a signal outputted from the pulse width adjusting circuit; and an output circuit for outputting a first signal to control an operation of a data bus of the memory device in response to a signal output from the signal transmission circuit. In this embodiment, the pulse width adjusting circuit comprises a first delay circuit and a NAND gate, in which the NAND gate receives the input signal and an output signal of the first delay circuit, and the first delay circuit receives the input signal and a clock signal of the memory device and adjusts a delay time in accordance with a frequency of the clock signal until the input signal is applied to an input terminal of the NAND gate. In this embodiment, as a cycle period of the clock signal is shorter, a pulse width of the first signal is narrower. Another embodiment of the present invention is a method for controlling an enabling period of an internal control signal in accordance with variation of an operating frequency in a memory device, which comprises the steps of: (a) receiving an input signal; (b) delaying the input signal for a predetermined time; (c) operating the input signal and a signal delayed from the input signal in a NAND logic; and (d) outputting a result of operating the NAND logic. In this embodiment, it further comprises the step of: (b-1) determining the predetermined time of the step (b) in accordance with a frequency of a clock signal of the memory device. In this embodiment, as the frequency of the clock signal increases, a pulse width of a signal outputted from the step (d) is narrower. In this embodiment, it further comprises the step of (b-2) more reducing a pulse width of a signal outputted from the step (d) by using an address signal of the memory device. BRIEF DESCRIPTION OF THE DRAWINGS The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which: FIG. 1 is a diagram illustrating a read and write operation in a general memory device; FIG. 2A illustrates an example of a conventional read/write strobe pulse generator; FIG. 2B is a waveform diagram of signals used in the circuit shown in FIG. 2A ; FIG. 3 illustrates an exemplary embodiment of a read/write strobe pulse generator in accordance with the present invention; FIGS. 4 through 10 illustrate embodiments of a delay circuit 30 in a pulse width adjusting circuit 300 shown in FIG. 3 ; FIG. 11 is an operational timing diagram of the conventional circuit shown in FIG. 2A ; FIG. 12 is a waveform diagram illustrating a pulse width variation of the read/write strobe pulse signal rdwtstbzp 13 output from the conventional circuit of FIG. 2A when an operation voltage vdd of a memory device varies; FIG. 13 is a waveform diagram of signals used in the circuit of the present invention, specifically an exemplary waveform diagram of signals used in the circuit of FIG. 5 ; FIG. 14 is a diagram illustrating a procedure of changing logical levels of flag signals Flag 1 and Flag 2 in accordance with a frequency of a clock signal clk_in; FIG. 15 is a diagram illustrating a waveform of an output signal rdwtstbzp 13 when paths C 1 and C 2 shown in FIG. 10 are used therein; and FIG. 16 is a waveform diagram illustrating a variation of the output signal rdwtstbzp 13 in accordance with a variation of the operation voltage. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. FIG. 3 illustrates an exemplary embodiment of a read/write strobe pulse generator in accordance with the present invention. The circuit of FIG. 3 is different from the circuit of FIG. 2A in that a delay circuit 30 in a pulse width adjusting circuit 300 is controlled by a clock signal clk_in and address signals add_ 0 and add_ 1 . The circuit of FIG. 3 is comprised of an input signal receiver 310 , a pulse width adjusting circuit 300 , a signal transmission circuit 320 , a test mode circuit 330 , and an output circuit 340 . The input signal receiver 310 includes inverters INV 30 and INV 31 , and a NAND gate NAND 30 . An input signal extyp 8 is applied to the inverter INV 30 and an input signal icasp 6 is applied to the inverter INV 31 . Output signals of the inverters INV 30 and INV 31 are applied to the NAND gate NAND 30 . The pulse width adjusting circuit 300 includes the delay circuit 30 and the NAND gate NAND 31 . The delay circuit 30 receives an output signal of the NAND gate NAND 30 , a test mode signal tmz_l, the clock signal clk_in, and the address signals add_ 0 and add_ 1 . The NAND gate NAND 31 receives the output signal of the NAND gate NAND 30 and an output signal of the delay circuit 30 . An output signal of the pulse width adjusting circuit 300 is an output signal of the NAND gate NAND 31 . A delay time from a node A to a node D is determined by the delay circuit 30 . The delay time by the delay circuit 30 is adjustable by means of a frequency of the clock signal clk_in and the address signals add_ 0 and add_ 1 . In reference, the test mode signal tmz_l is a control signal to determine whether or not a current operation is a test mode, retaining low level during the test mode while retaining high level during a normal operation mode. The add_ 0 and add_ 1 are external address signals to be used in the test operation mode. Functions of the signals will be explained relative to the detail circuit hereinafter. The signal transmission circuit 320 includes inverters INV 32 , INV 33 , and INV 34 that, receive and buff the signal outputted from the pulse width adjusting circuit 300 . The test mode circuit 330 includes transistors P 31 , P 32 , and N 31 and a latch circuit 301 . As illustrated in FIG. 3 , the PMOS transistor P 31 and the NMOS transistor N 31 are connected between a power source voltage and a ground in series. The PMOS transistor P 32 is connected between the power source voltage and a node NODE 31 . The latch 301 temporarily stores a signal of the node NODE 31 . Here, termz is a signal used in the test mode and the signal pwrup is that as stated in FIG. 2A . The output circuit 340 includes a NAND gate 302 and inverters INV 35 and INV 36 . The NAND gate 302 receives an output signal of the inverter INV 34 , the signal termz, and an output signal of the latch circuit 301 . The signal termz functions to inhibit the read/write strobe pulse signal rdwtstbzp 13 . An output signal of the NAND gate 302 is applied to the inverters INV 35 and INV 36 serially connected from each other. An output signal of the inverter INV 36 as an output signal of the output circuit 340 becomes the read/write strobe pulse signal rdwtstbzp 13 . In a normal operation, the input signals extyp 8 and icasp 6 are generated into the read/write strobe pulse signal rdwtstbzp 13 after a predetermined time. During this, it is possible for the pulse width adjusting circuit 300 to control a pulse width of the read/write strobe pulse signal rdwtstbzp 13 by modifying a pulse width of the input signals extyp 8 and icasp 6 with using the clock signal clk_in that varies dependent on variation of an operating frequency. FIGS. 4 through 10 illustrate embodiments of the delay circuit 30 in the pulse width adjusting circuit 300 shown in FIG. 3 . As described later, the clock signal clk_in is applied to the delay circuit 30 so as to detect an operating frequency of the memory device. And, at the beginning of the test mode, the test mode signal tmz_l of low level is applied thereto. Also, at the beginning of the test mode, the address signals add_ 0 and add_ 1 are applied to further tune a delay time. In reference, the node A and D shown in FIG. 3 correspond to those node A and D shown in FIG. 4 . Hereinafter, it will be described in more detail about the circuits shown in FIGS. 4 through 10 . FIG. 4 is a block diagram illustrating an internal structure of the delay circuit shown in FIG. 3 in detail. As illustrated in FIG. 4 , the delay circuit 30 in FIG. 3 is comprised of delay units 401 , 402 , and 403 , a frequency detector 404 , a voltage detector 405 , a test mode address signal receiver 406 , and a reference voltage generator 407 . Exemplary circuits of the frequency detector 404 , the voltage detector 405 , and the test mode address signal receiver 406 are shown in FIGS. 4 , 5 , and 6 , respectively. In FIG. 4 , the frequency detector 404 receives the clock signal clk_in and then outputs operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z which control a delay path of the delay unit 401 . Logical levels of the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z vary in accordance with a frequency of the clock signal clk_in. The delay path from the node A to the node D is alterable in accordance with a frequency of the clock signal clk_in. The reference voltage generator 407 is enabled by the power-up signal pwrup, outputting a plurality of reference voltages vref_ 0 and vref_ 1 . The reference voltage generator 407 is a circuit capable of outputting stable reference voltages without affecting from an operation voltage, which is constructed with circuit structures well known by those skilled in this art. The voltage detector 405 detects a variation of the operation voltage vdd by comparing the operation voltage vdd to the reference voltages vref_ 0 and vref_ 1 . The voltage detector 405 outputs a plurality of voltage selection signals vsel_ 0 z , vsel_ 1 z , and vsel_ 2 z to control the delay path of the delay unit 402 . Thus, delay times of delay paths C 1 are determined by logical level of the voltage selection signals vsel_ 0 z , vsel_ 1 z , and vsel_ 2 z. In accordance with a logical level of the test mode signal tmz_ 1 , a signal of the node C 1 can be transferred to the node D directly or through the delay unit 403 . When the test mode signal tmz_ 1 is high level, the signal of the node C 1 is transferred directly to the node D. The test mode address signal receiver 406 receives an address signal and outputs a plurality of selection signals sel_ 0 z , sel_ 1 z , sel_ 2 z , and sel_ 3 z . Responding to the selection signals sel_ 0 z , sel_ 1 z , sel_ 2 z , and sel_ 3 z , a delay time of the delay unit 403 is adjusted. As aforementioned, the delay unit 403 is used as a delay path in the test mode, which means that it is possible to conduct an additional delay tuning operation by using the address signal when the test mode signal tmz_ 1 is being low level. Exemplary features of the components shown in FIG. 4 are illustrated in FIGS. 5 through 10 . FIG. 5 illustrates, as an example of the frequency detector 404 shown in FIG. 4 , a circuit for outputting the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z that determine a range of the operating frequency of the memory device in response to the clock signal clk_in. In FIG. 5 , after detecting an operating frequency of the memory device by generating a plurality of internal signals dlic 4 _ref, dlic 4 , dlic 4 d 1 , dlic 4 d 2 , cmp, flag_ 1 , and flag_ 2 in response to the clock signal clk_in, the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z are finally outputted therefrom to be determined the range of the operating frequency of the memory device. As illustrated in FIG. 5 , the clock signal clk_in is applied to a frequency divider 500 . The divider 500 outputs the frequency dividing signal dlic 4 _ref having a period longer than that of the clock signal clk_in. As shown in the waveform diagram of FIG. 13 , a cycle period of the frequency dividing signal dlic 4 _ref is four times of that of the clock signal clk_in. At this case, a low level term of the frequency dividing signal dlic 4 _ref is identical to the cycle period tCLK of the clock signal clk_in. However, the cycle period of the frequency dividing signal dlic 4 _ref may be alterable by those skilled in this art. The frequency dividing signal dlic 4 _ref is outputted with phase inversion after being delayed by a buffer circuit 501 composed of odd-numbered inverters. The phase-inversed frequency dividing signal is denoted as dlic 4 . Waveforms of those signals dlic 4 _ref and dlic 4 are shown in FIG. 13 . In FIG. 5 , the frequency dividing signal dlic 4 _ref and the phase-inversed frequency dividing signal dlic 4 are applied to a NAND gate NAND 51 . An output signal from the NAND gate NAND 51 is applied to a delay unit 506 and a NOR gate NOR 51 . The NOR gate NOR 51 receives the output signal of the NAND gate NAND 51 and an output signal of the delay unit 506 , and outputs the pulse signal cmp. The output signal cmp of the NOR gate NOR 51 is illustrated in FIG. 13 . The phase-inversed frequency dividing signal dlic 4 is applied to delay units delay_A and delay_B. Here, there is a difference between delay times of the delay units delay_A and delay_B. Output signals of the delay units delay_A and delay_B are represented to as dlic 4 d 1 and dlic 4 d 2 , respectively. The output signal dlic 4 d 1 of the delay unit delay_A and the frequency dividing signal dlic 4 _ref are applied to a flipflop circuit 502 . The flipflop circuit 502 is constructed of two NAND gates input/output terminals of which are cross-coupled each other. Output signals from two output terminals of the flipflop circuit 502 are e and f, respectively. The output signal dlic 4 d 2 of the delay unit delay_B and the frequency dividing signal dlic 4 _ref are applied to a flipflop circuit 503 . The flipflop circuit 503 is constructed of two NAND gates input/output terminals of which are cross-coupled each other. Output signals from two output terminals of the flipflop circuit 503 are g and h, respectively. A NAND gate NAND 52 receives the output signal cmp of the NOR gate NOR 51 and the output signal e of the flip-flop circuit 502 . A NAND gate NAND 53 receives the output signal cmp of the NOR gate NOR 51 and the output signal if of the flipflop circuit 502 . A NAND gate NAND 54 receives the output signal cmp and the output signal g of the flip-flop circuit 503 . A NAND gate NAND 55 receives the output signal cmp of the NOR gate NOR 51 and the output signal h of the flipflop circuit 503 . Output signals of the NAND gates NAND 52 and NAND 53 are applied to the flipflop circuit 504 . The flipflop circuit 504 is constructed of two NAND gates input/output terminals of which are cross-coupled each other. An output signal of the flipflop circuit 504 is represented to as a flag signal flag_ 1 . Output signals of the NAND gates NAND 54 and NAND 55 are applied to the flipflop circuit 505 . The flipflop circuit 505 is constructed of two NAND gates input/output terminals of which are cross-coupled each other. An output signal of the flipflop circuit 505 is represented to as a flag signal flag_ 2 . In reference, when a delay time by delay unit 508 is longer than that by delay unit 507 (i.e., delay_A<delay_B), logical levels of the flag signals are as follows. If tCLK<delay_A, the flag signals flag_ 1 and flag_ 2 are all low levels. Here, tCLK is a cycle period of the clock signal clk_in. If delay_A<tCLK<delay_B, the flag signal flag_ 1 is high level while the flag signal flag_ 2 is low level. If tCLK>delay_B, the flag signal flag_ 1 and flag_ 2 are all high levels. In FIG. 5 , the flag signals flag_ 1 and flag_ 2 are applied each to inverters INV 51 and INV 52 . Output signals of the inverters INV 51 and INV 52 are applied to NAND gate NAND 56 . The NAND gate NAND 56 outputs the operating frequency detection signal dec_ 0 z. Next, the flag signal flag_ 2 is applied to an inverter INV 53 . An output signal of the inverter INV 53 and the flag signal flag_ 1 are applied to a NAND gate NAND 57 . The NAND gate NAND 57 outputs the operating frequency detection signal dec_ 1 z. Finally, the flag signals flag_ 1 and flag_ 2 are applied to a NAND gate NAND 58 . The NAND gate NAND 58 outputs the operating frequency detection signal dec_ 1 z. FIG. 6 is a circuit for outputting voltage selection signals vsel_ 2 z , vsel_ 1 z , and vsel_ 0 z so as to control a delay time of an input signal in accordance with variation of an operation voltage. The voltage selection signals generated in FIG. 6 are used for selecting a delay path of a circuit shown in FIG. 9 . FIG. 6 illustrates two differential amplifying comparators. As shown in FIG. 6 , there are a differential amplifying comparator for comparing the operation voltage vdd to the reference voltage vref_ 0 and another differential amplifying comparator for comparing the operation voltage vdd to the reference voltage vref_ 1 . The reference voltage vref_ 0 is lower than the reference voltage vref_ 1 (vref_ 0 <vref_ 1 ). As noticed from FIG. 6 , if vdd<vref_ 0 , output signals DET_ 0 and DET_ 1 of the differential amplifying comparator are all high levels. If vref_ 0 <vdd<vref_ 1 , the output signal DET_ 0 is high level while the output signal DET_ 1 is low level. If vdd>vref_ 1 , the output signals DET_ 0 and DET_ 1 of the differential amplifying comparator are all low levels. The output signal DET_ 0 of the differential amplifying comparator is applied to an inverter INV 61 and an output signal of the inverter INV 61 is DET_ 0 b . The output signal DET_ 1 of the differential amplifying comparator is applied to an inverter INV 62 and an output signal of the inverter INV 62 is DET_ 1 b. In FIG. 6 , NAND gate NAND 61 receives the signals DET_ 0 b and DET_ 1 b and an output signal of the NAND gate NAND 61 is the voltage selection signal vsel_ 2 z. A NAND gate NAND 62 receives the signals DET_ 0 b and DET_ 1 b and an output signal of the NAND gate NAND 62 is the voltage selection signal vsel_ 1 z. A NAND gate NAND 63 receives the signals DET_ 0 and DET_ 1 and an output signal of the NAND gate NAND 63 is the voltage selection signal vsel_ 0 z. As can be seen by FIG. 6 , the circuits of FIG. 6 are provided to detect a fluctuation of the operation voltage vdd relative to the reference voltages vref_ 0 and vref_ 1 . FIG. 7 illustrates circuit elements for generating the selection signals sel_ 3 z , sel_ 2 z , sel_ 1 z , and sel_ 0 z to designate delay paths in response to the address signals add_ 0 and add_ 1 . As illustrated in FIG. 7 , an inverter INV 71 receiving the address signal add_ 0 outputs a phase-inversed address signal add_ 0 b . An inverter INV 72 receiving the address signal add_ 1 outputs phase-inversed address signal add_ 1 b . Next, the delay path selection signals sel_ 3 z , sel_ 2 z , sel_ 1 z , and sel_ 0 z are generated resulting from logical combinations with the address signals. That is, the NAND gate NAND 71 receives the address signals add_ 0 b and add_ 1 b and then outputs the selection signal sel_ 3 z . The NAND gate NAND 72 receives the address signals add_ 0 b and add_ 1 and then outputs the selection signal sel_ 2 z . The NAND gate NAND 73 receives the address signals add_ 0 and add_ 1 b and then outputs the selection signal sel_ 1 z . The NAND gate NAND 74 receives the address signals add_ 0 and add_ 1 and then outputs the selection signal sel_ 0 z. FIG. 8 , as an exemplary feature of the delay circuit 30 , shows an example of a circuit for selecting a delay path of an input signal with using the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z that are generated in FIG. 5 . The circuit of FIG. 8 comprises a plurality of delay units 801 , 802 , 803 , and 804 , and switching units 811 , 812 , 814 , 815 , and 816 which are controlled by the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z . Each of modulation circuits 817 and 818 is composed of a NAND gate and an inverter which are connected in series. Input terminals of the modulation circuits 817 and 818 receive a signal of the node A. In FIG. 8 , the whole delay time is taken from the node A to the node D. Here, the nodes A and D of FIG. 8 are the same with the nodes A and D of FIG. 3 . A signal input through the node A of FIG. 8 is an output signal from the input signal receiver 310 of FIG. 3 , which is the signal extyp 8 or icasp 6 . In FIG. 8 , the operating frequency detection signals dec_ 1 z and dec_ 2 z control turn-on/off operations of the switching units 811 and 814 . The operating frequency detection signal dec_ 0 z controls a turn-on/off operation of the switching unit 812 . The operating frequency detection signal dec_ 2 z controls a turn-on/off operation of the switching unit 815 . The test mode signal tmz_ 1 controls a turn-on/off operation of the switching unit 816 . In operation, when a NAND gate NAND 81 receiving the operating frequency detection signals dec_ 1 z and dec- 2 z outputs a high-level output signal, the switching units 811 and 814 are turned on. Thus, the input signal received through the node A passes by way of the delay unit 801 , the modulation circuit 817 , the delay unit 802 , the modulation circuit 818 , and the switching unit 814 , in sequence. Here, the switching unit 815 is controlled by the operating frequency detection signal dec_ 2 z . Therefore, while a signal passing through the switching unit 814 is transferred to the node B through the delay unit 804 when the operating frequency detection signal dec_ 2 z is low level, it is transferred directly to the node C when the operating frequency detection signal dec_ 2 z is high level. In operation, when the switching unit 812 is turned on in response to the operating frequency detection signal dec_ 0 z , the input signal received through the node A passes by way of the delay unit 801 , the modulation circuit 817 , and the switching unit 812 , in sequence. Here, the switching unit 815 is controlled by the operating frequency detection signal dec_ 2 z . While a signal passing through the switching unit 812 is transferred to the node B through the delay unit 804 when the operating frequency detection signal dec_ 2 z is low level, it is transferred directly to the node B when the operating frequency detection signal dec_ 2 z is high level. Next, a signal on the node B is transferred to the node C 1 through the switching unit 816 . A signal at the node C 1 may be transferred to the node D through the switching unit 816 directly or transferred to the node D through the delay path of C 1 -C 2 -D. Hereinafter, it will be described in detail about the alternative delaying operations. Referring to FIG. 8 , the switching unit 816 is turned on/off by the test mode signal tmz_ 1 . In a test mode, the test mode signal tmz_ 1 retains low level. In a normal operation mode, the test mode signal retains high level. In the normal operation mode, a signal on the node C 1 is forwarded to a delay path of C 1 -D. In other words, the signal on the node C 1 is transferred to the node D by way of the switching unit 816 , an inverter INV 81 , and a NAND gate NAND 83 . Here, the NAND gate NAND 83 receives signals output from the inverter INV 81 and the node A. In the test mode, the signal on the node C 1 is transferred to the node C 2 through the circuit shown in FIG. 10 . The signal transferred to the node C 2 is transferred to the node D by way of the switching unit 816 , the inverter INV 81 , and the NAND gate NAND 83 . FIG. 9 illustrates a circuit disposed on a delay path of B-C 1 . The delay path circuit of FIG. 9 is selected by the voltage selection signals vsel_ 2 z , vsel_ 1 z , and vsel_ 0 z which are generated in FIG. 6 . As illustrated, the circuit of FIG. 9 is comprised of delay units 901 , 902 , and 903 , switching units 911 , 912 , 913 , and 914 , and NAND gates NAND 91 and NAND 92 . The NAND gates NAND 91 and NAND 92 receive the voltage selection signals vsel_ 1 z and vsel_ 0 z . The switching unit 911 is turned on/off by an output signal of the NAND gate NAND 91 . The switching unit 913 is turned on/off by an output signal of the NAND gate NAND 92 . The switching unit 912 is turned on/off by the voltage selection signal vsel_ 2 z . The switching unit 914 is turned on/off by the voltage selection signal vsel_ 0 z. In operation, if the switching units 911 and 913 are turned on, a signal on the node B passes through the delay unit 901 , the switching unit 911 , the delay unit 911 , and the switching unit 913 , in sequence. A delay path of the signal passing through the switching unit 913 is alterable in accordance with the voltage selection signal vsel_ 0 z . That is, when the voltage selection signal vsel_ 0 z is high level, the signal passing through the switching unit 913 is transferred to the node C 1 by way of the switching unit 914 . Otherwise, when the voltage selection signal vsel_ 0 z is low level, the signal passing through the switching unit 913 is transferred to the node C 1 by way of the delay unit 903 and the switching unit 914 . In operation, if the switching unit 912 is turned on, a signal on the node B passes through the delay unit 901 and the switching unit 912 . A delay path of the signal passing through the switching unit 912 is alterable in accordance with the voltage selection signal vsel_ 0 z . That is, when the voltage selection signal vsel_ 0 z is high level, the signal passing through the switching unit 912 is transferred to the node C 1 by way of the switching unit 914 . Otherwise, when the voltage selection signal vsel_ 0 z is low level, the signal passing through the switching unit 912 is transferred to the node C 1 by way of the delay unit 903 and the switching unit 914 . FIG. 10 , as an exemplary feature of a circuit interposed between the nodes C 1 and C 2 , illustrates a circuit for controlling a delay rate with using address signals in a test mode (when tmz_ 1 of FIG. 8 is low level). The circuit of FIG. 10 is comprised of delay units 1000 , 1001 , 1002 , 1003 , and 1004 , switching units 1011 , 1012 , 1013 , 1014 , and 1015 which are controlled by the selection signals sel_ 3 z , sel_ 2 z , sel_ 1 z , and sel_ 0 z , and conversion circuits 1017 and 1018 . Each of the conversion circuits 1017 and 1018 is a NAND gate and an inverter which are connected in series. A signal of the node C 1 is inputted through input terminals of the conversion circuits 1017 and 1018 . In FIG. 10 , the whole delay time is taken from the node C 1 to the node C 2 . Here, the nodes C 1 and C 2 are identical to the nodes C 1 and C 2 shown in FIG. 8 . And, a signal of the node C 1 is inputted through an input terminal of NAND gate NAND 103 . As stated above in connection with FIG. 7 , the selection signals sel_ 3 z , sel_ 2 z , sel_ 1 z , and sel_ 0 z , which control turn-on/off operations of the switching units, are made from logical combinations with address signals. As can be seen from FIGS. 7 and 10 , when the address signals add_ 0 and add_ 1 are all low levels, the selection signal sel_ 3 z is enabled in low level. When the address signals add_ 0 and add_ 1 are respectively low and high levels, the selection signal sel_ 2 z is enabled in low level. When the address signals add_ 0 and add_ 1 are respectively high and low levels, the selection signal sel_ 1 z is enabled in low level. When the address signals add_ 0 and add_ 1 are all high levels, the selection signal sel_ 0 z is enabled in low level. In FIG. 10 , NAND gates NAND 101 and NAND 102 receive the selection signals sel_ 2 z and sel_ 3 z . The switching unit 1011 is turned on/off by an output signal of the NAND gate NAND 101 . The switching unit 1014 is turned on/off by an output signal of the NAND gate NAND 102 . The switching unit 1012 is turned on/off by the selection signal sel_ 1 z . The switching unit 1013 is turned on/off by the selection signal sel_ 0 z . The switching unit 1015 is turned on/off by the selection signal sel_ 3 z. In operation, when the selection signals sel_ 2 z and sel_ 3 z are all low levels, an output signal of the NAND gate NAND 101 receiving the selection signals sel_ 2 z and sel_ 3 z is high level. Thus, the switching units 1011 and 1014 are turned on. As a result, a signal receiver through the node C 1 passes through the delay units 1000 and 1001 , the conversion circuit 1017 , the delay unit 1001 , the switching unit 1011 , the delay unit 1001 , the conversion circuit 1018 , and the switching unit 1014 , in sequence. Here, if the selection signal sel_ 3 z is low level, the signal passing through the switching unit 1014 is transferred to the node C 2 by way of the NAND gate NAND 103 and inverter INV 101 after passing through the delay unit 1004 and the switching unit 1015 . Otherwise, if the selection signal sel_ 3 z is high level, the signal passing through the switching unit 1014 is transferred to the node C 2 by way of the switching unit 1015 , the NAND gate NAND 103 , and inverter INV 101 . Therefore, when the selection signals sel_ 2 z and sel_ 3 z are all low levels, the signal passing through the switching unit 1014 is transferred to the node C 2 by way of the NAND gate NAND 103 and the inverter INV 101 after passing through the delay unit 1004 . In operation, when the selection signal sel_ 1 z is low level, the switching unit 1012 is turned on. Thus, a signal input through the node C 1 passes through the delay units 1000 and 1001 , the conversion circuit 1017 , the delay unit 1002 , and the switching unit 1012 , in sequence. If the selection signal sel_ 3 z is low level, the signal passing through the switching unit 1012 is transferred to the node C 2 by way of the NAND gate NAND 103 and the inverter INV 101 after passing through the delay unit 1004 and the switching unit 1015 . Otherwise, if the selection signal sel_ 3 z is high level, the signal passing through the switching unit 1012 is transferred to the node C 2 by way of the switching unit 1015 , the NAND gate NAND 103 , and the inverter INV 101 . In operation, when the selection signal sel_ 0 z is low level, the switching unit 1013 is turned on. Thus, a signal input through the node C 1 passes through the delay unit 1000 and the switching unit 1013 , in sequence. If the selection signal sel_ 3 z is low level, the signal passing through the switching unit 1013 is transferred to the node C 2 by way of the NAND gate NAND 103 and inverter INV 101 after passing through the delay unit 1004 and the switching unit 1015 . Otherwise, if the selection signal sel_ 3 z is high level, the signal passing through the switching unit 1013 is transferred to the node C 2 by way of the switching unit 1015 , the NAND gate NAND 103 , and inverter INV 101 . As illustrated in FIG. 10 , in the test mode, it is possible to adjust a delay time taken from the node C 1 to the node C 2 by using the selection signals generated from logical combinations with the external address signals add_ 0 and add_ 1 . For example, when the test mode signal tmz_ 1 is high level, the delay path between the nodes C 1 and C 2 is inhibited. But, if the test mode signal tmz_ 1 is low level, the delay path between the nodes C 1 and C 2 is open and adjustable by means of the selection signals. FIG. 11 is an operational timing diagram of the conventional circuit shown in FIG. 2A . As can be seen from FIG. 11 , the conventional circuit is just capable of adjusting only a pulse width of the output signal rdwtstbzp 13 in accordance with a logical level of a signal tmz_clkpulsez. FIG. 12 is a waveform diagram illustrating a pulse width variation of the read/write strobe pulse signal rdwtstbzp 13 output from the conventional circuit of FIG. 2A when an operation voltage vdd of a memory device varies. As illustrated in FIG. 12 , the conventional circuit has a problem that a pulse width of the read/write strobe pulse signal rdwtstbzp 13 decreases when the operation voltage rises. FIG. 13 is a waveform diagram of signals used in the circuit of the present invention, specifically an exemplary waveform diagram of signals used in the circuit of FIG. 5 . FIG. 13 illustrates waveforms of the clock signal clk_in, the frequency dividing signal dlic 4 _ref, the phase-inversed frequency dividing signal dlic 4 , the delay signals dlic 4 d 1 and dlic 4 d 2 , the pulse signal amp, the flag signals flag_ 1 and flag_ 2 , and the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z. In FIG. 13 , the cycle period of the frequency dividing signal dlic 4 _ref is four times of tCLK. And, the low level term of the frequency dividing signal dlic 4 _ref is identical to that of tCLK. The phase-inversed frequency dividing signal dlic 4 is opposite to the frequency dividing signal dlic 4 _ref in phase and generated with a predetermined delay time. The phase-inversed frequency signal dlic 4 is outputted as the delay signal dlic 4 d 1 after passing through the delay unit having the delay time of delay_A. The phase-inversed frequency dividing signal dlic 4 is also outputted as the delay signal dlic 4 d 2 after passing through the delay unit having the delay time delay_B. At this case, the phase-inversed frequency dividing signal dlic 4 and the delay signals dlic 4 d 1 and dlic 4 d 2 have high level terms as same as that of tCLK. In FIG. 13 , it is established of delay_A<delay_B. Hereinafter, it will be described in detail about the signal waveform diagram of FIG. 8 with reference to the circuit of FIG. 4 . In the condition of that the frequency dividing signal dlic 4 -ref, the delay signal dlic 4 d 1 and the pulse signal cmp are all high levels, initial values of the nodes e, f, g, and h in FIG. 4 are all high levels. In this condition, if the delay signal dlic 4 d 1 changes to high level earlier than the frequency dividing signal dlic 4 _ref, the node e transits to low level. Next, when the pulse signal cmp transits to high level, the node h transits to low level. Thus, the flag signal flag_ 1 becomes high level. On the other hand, if the frequency dividing signal dlic 4 _ref changes to high level earlier than the delay signal dlic 4 d 1 , the node f transits to low level. Next, when the pulse signal cmp transits to high level, the node g transits to low level. Thus, the flag signal flag_ 1 becomes low level. As described above, it is important in FIG. 5 that it determines a logical level of the flag signal flag_ 1 in accordance with which one of the two signals dlic 4 _ref and dlic 4 d 1 to be compared transits to high level earlier before the pulse signal cmp goes to high level. A procedure of generating the flag signal flag_ 2 is substantially identical to that of the flag signal flag_ 1 , so will be omitted about it. On the other side, the delay rates represented by delay_A and delay_B are provided to detect a frequency range of the clock signal clk_in. For instance, in FIG. 13 , the fact that a rising edge of the delay signal dlic 4 d 1 is earlier than that of the frequency dividing signal dlic 4 _ref means that the delay rate of delay_A is smaller than the cycle period of the clock signal clk_in. As such, the fact that a rising edge of the delay signal dlic 4 d 2 is later than that of the frequency dividing signal dlic 4 _ref means that the delay rate of delay_B is larger than the cycle period of the clock signal clk_in. Therefore, such cases form the relation of delay_A<tCK<delay_B. FIG. 13 illustrates waveform features satisfying the conditional relation. FIG. 14 is a diagram illustrating a procedure of changing logical levels of the flag signals flag_ 1 and flag_ 2 in accordance with a frequency of the clock signal clk_in. For sections A, B, and C of FIG. 14 , it can be seen of delay_A<delay_B. When tCK<delay_A as like the section A of FIG. 14 , the flag signals flag_ 1 and flag_ 2 are all low levels. When delay_A<tCK<delay_B as like the section B of FIG. 14 , the flag signal flag_ 1 is high level while flag_ 2 is low level. When tCK>delay_B as like the section C of FIG. 14 , the flag signals flag_ 1 and flag_ 2 are all high levels. As such, it can be understood that the flag signals include the information for the operating frequency of the memory device. With those flag signals, logical levels of the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z are determined to select the delay path in the circuit shown in FIG. 8 . FIG. 15 is a diagram illustrating a waveform of the output signal rdwtstbzp 13 when paths C 1 and C 2 shown in FIG. 10 are used therein. As aforementioned, the circuit of FIG. 10 is to be used in the test mode that begins in response to the test mode signal tmz_ 1 shown in FIG. 8 . In other words, the delay time is further adjustable by applying the address signals during the test mode. The selection signals sel_ 3 z , sel_ 2 z , sel_ 1 z , and sel_ 0 z are generated from logical combinations with the address signals as aforementioned with reference to FIG. 7 . Section A of FIG. 15 illustrates waveforms of the input signal extyp 8 and the output signal rdwtstbzp 13 when the operating frequency detection signals dec_ 2 z and dec_ 1 z are all high levels while the operating frequency detection signal dec_ 0 z is low level. Section B of FIG. 15 illustrates waveforms of the input signal extyp 8 and the output signal rdwtstbzp 13 when the operating frequency detection signals dec_ 0 z and dec_ 2 z are all high levels while the operating frequency detection signal dec_ 1 z is low level. Section C of FIG. 15 illustrates waveforms of the input signal extyp 8 and the output signal rdwtstbzp 13 when the operating frequency detection signals dec_ 0 z and dec_ 1 z are all high levels while the operating frequency detection signal dec_ 2 z is low level. As can be seen from the sections A, B, and C in FIG. 15 , a pulse width of the output signal rdwtstbzp 13 is variable in accordance with logical levels of the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z which contain the information for the operating frequency of the memory device. Further, the pulse width of the output signal rdwtstbzp 13 is also variable in accordance with logical levels of the selection signals sel_ 0 z , sel_ 1 z , sel_ 2 z , and sel_ 3 z when the logical levels of the operating frequency detection signals dec_ 0 z , dec_ 1 z , and dec_ 2 z are equal from each other (e.g, in the section A). FIG. 16 is a waveform diagram illustrating a variation of the output signal rdwtstbzp 13 in accordance with a variation of the operation voltage. As illustrated in FIG. 16 , it can be seen that the pulse width of the output signal rdwtstbzp 13 is variable in accordance with logical levels of the voltage selection signals vsel_ 2 z , vsel_ 1 z , and vsel_ 0 z . In the conventional circuit as shown in FIG. 12 , a pulse width of the output signal rdwtstbzp 13 decreases along an increase of the operation voltage vdd. However, the present invention is configured, as shown in FIG. 16 , with that the pulse width of the output signal rdwtstbzp 13 does not decrease even along an increase of the operation voltage vdd. Such a result of simulation, as illustrated in FIG. 16 , is just provided for notifying an improvement by the present invention over the conventional art. It is also possible to enable the pulse width of the output signal rdwtstbzp 13 to be stable by properly selecting the delay path by means of the voltage selection signals even when the operation voltage varies. As apparent from the above description, the present invention provides a method and circuit for controlling a pulse width of the read/write strobe pulse signal rdwtstbzp 13 to control an operation of an Yi pulse signal by detecting an operating frequency of the memory device. By utilizing the method and circuit according to the present invention, the pulse width of the read/write strobe pulse signal rdwtstbzp 13 is optimally adjusted to control an enabling period of the Yi pulse signal. With the method and circuit of the present invention, as it is possible to automatically adjust a pulse width of the Yi signal, there is no need of an FIB process for tuning delay times whenever an operating frequency varies. Therefore, it downs costs and times relative to the conventional case. Moreover, the present invention offers a reliable operation by reducing a pulse width variation of the read/write strobe pulse signal when an operation voltage varies. In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Provided is a circuit for controlling a data bus connecting a bitline sense amplifier to a data sense amplifier in accordance with a variation of an operating frequency of a memory device, being comprised of a pulse width adjusting circuit for varying a pulse width of an input signal in accordance with the operating frequency of the memory device after receiving the input signal, a signal transmission circuit for buffing a signal outputted from the pulse width adjusting circuit, and an output circuit for outputting a first signal to control the data bus in response to a signal outputted from the signal transmission circuit.

CROSS-REFERENCE TO RELATED APPLICATION(S) [0001] This application claims priority to European Patent Application 13178834.1 which was filed Jul. 31, 2013 and is incorporated herein by reference in its entirety. TECHNICAL FIELD [0002] The present disclosure pertains to the field of orthopaedic surgery and relates in particular to the application of an external fixator to a long bone by means of unicortical pins. [0003] The disclosure also relates to an anchoring group comprising the aforementioned pin-locking device articulated to a locking clamp of an external fixator bar, as well as to an external fixator comprising said anchoring group. BACKGROUND [0004] External fixators are widely used for the treatment of bone fractures or for joining together two or more bone fragments. Known fixators comprise bone screws which are inserted in the bones and use external devices such as fixation clamps, fixation bars, rings, etc., that allow the creation of a rigid structure able to hold together the bone fragments in the desired position until completely healed. [0005] These external fixators have the advantage of ensuring strength and stability owing, among other things, to the use of bone screws which penetrate into the bones at a sufficient depth; in particular, these screws pass through the bone cortex in two points so as to provide a flexurally resistant fastening. [0006] However, the use of bi-cortical screws may be excessively invasive for patients in critical conditions, who for example have multiple fractures along with, in some case, extensive wounds and/or contusions. In particular the time devoted to checking the tip which emerges from the second cortex may be critical. [0007] Also, with particular reference to the reduction of fractures in long bones, the aforementioned bi-cortical screws pass through the medullary cavity, which makes it impossible to simultaneously insert a medullary nail, which is particularly suitable for the treatment of certain types of trauma. [0008] Moreover, the surgical implant of a definitive fixator of the aforementioned type requires time and suitable facilities and is not always compatible with the unforeseen circumstances where rapid intervention is required; for example, it is relatively difficult to perform the implant of such an external fixator in the context of a field hospital or in any case under environmental conditions where sterility is not guaranteed and where the fracture must be treated as a matter of emergency. [0009] In order to meet these specific needs, external fixators of a provisional nature have been developed that, in addition to having a structure which is generally slimmer and lighter, use unicortical screws or unicortical pins for the attachment to the bone, i.e. that have been designed to be screwed in superficially so that they are attached to a single bone cortex only. [0010] The unicortical pin undoubtedly represents a less invasive fixation system than conventional bone screws; moreover, owing to its limited penetration, the pin does not reach the medullary cavity of the bone, thus avoiding the risk of unwanted infections. [0011] On the other hand, however, owing to its limited stability—due mainly to the fact that it passes through one cortex only, which means that flexural strength is limited—this type of screw is not widely used in external fixation applications. [0012] It would instead be desirable to be able to use an external fixator, which has the advantages of stability and strength typical of provisional fixation systems, and to combine it with the advantages of ease of application, lightness and limited invasiveness that are instead typical of systems that use unicortical pins. [0013] The technical problem forming the basis of the present disclosure is therefore to devise a locking device for unicortical pins to be associated with external fixators, which is able to create a structure sufficiently rigid for it to withstand the external loads acting on it, so as to allow the formation of external fixators that are extremely flexible, but that at the same time have that degree of structural rigidity that typically distinguishes external fixation systems. [0014] The device should have an optimum performance, under traction and compression, of the tip in the cortex of the bone and should eliminate, as far as possible, the flexural stresses acting on the shank of the single screw. SUMMARY OF THE DISCLOSURE [0015] In some embodiments of the present disclosure, the aforementioned technical problem may be solved by using a locking device for unicortical pins. [0016] In some embodiments of the present disclosure, application of an external fixator to a patient's long bone by means of the unicortical pins is provided for. [0017] The application method described above may make it possible to create fixation systems with exceptional stability, despite its use of unicortical pins only. [0018] Further features and advantages will become clearer from the detailed description provided below of some preferred, but not exclusive, embodiments of the present disclosure, with reference to the attached figures provided by way of non-limiting example. BRIEF DESCRIPTION OF THE DRAWINGS [0019] FIGS. 1-4 show different perspective views of an external fixator associated with the long bone of a patient using the method according to the present disclosure, where the locking devices of the distal and proximal anchoring groups are mounted in different configurations; [0020] FIG. 5 shows a front view of an anchoring group associated with the bone of a patient; [0021] FIG. 6 shows a perspective view of the anchoring group of FIG. 5 ; [0022] FIG. 7 and FIG. 8 show two perspective views of an anchoring group, in which mounting of the locking devices in two different configurations is shown; [0023] FIG. 9 shows a perspective view of a connecting body of the anchoring group; [0024] FIG. 10 shows a front view of the connecting body of FIG. 9 ; [0025] FIG. 11 shows a further perspective view of the connecting body of FIG. 9 ; [0026] FIG. 12 shows a perspective view of the locking clamp of the anchoring group; [0027] FIG. 13 shows a perspective view of the main body of a locking device; [0028] FIG. 14 shows another perspective view of the main body of FIG. 13 ; [0029] FIG. 15 shows a perspective view of the pressing body of the locking device; [0030] FIG. 16 shows a perspective view of the locking means of the locking device; [0031] FIG. 17 shows a perspective view of a deformable sphere forming part of the locking means shown in FIG. 16 ; [0032] FIG. 18 shows a perspective view of a bar/pin clamp which can be associated with the connection bar of the external fixator. DETAILED DESCRIPTION [0033] With reference to the attached figures, and in particular to FIGS. 1-4 , the reference number 1 denotes overall an external fixator applied according to the method of the present disclosure, to a long bone of a patient using only unicortical pins or screws 100 . [0034] The external fixator may comprise in particular a bar 2 , known per se, which may be fixed to the bone by means of two anchoring groups 20 which may be respectively arranged in a distal position and proximal position. [0035] Each of the anchoring groups 20 may comprise two locking devices 10 , each of which may be designed to be locked into position by two unicortical pins 100 which may be implanted into the bone of a patient. The two locking devices 10 may extend laterally, in the manner of wings, from a central connecting body 11 of the anchoring group which may also support a locking clamp 3 designed to grip the bar of the external fixator 1 . [0036] In some embodiments, the locking devices 10 may be made as modular elements which may be mounted separately on the connecting body 11 ; nevertheless, alternative embodiments may be possible in which the entire anchoring group 20 may be formed as one piece, while retaining the particularly advantageous form and functional characteristics described below. [0037] The single locking device 10 may have a substantially L-shaped main body. More specifically, the single locking device 10 may have a pin-locking arm 101 and a connection base 102 which may together form an elbow. An angle α between the direction of extension of the arm x and the direction of extension of the base y, shown in FIG. 13 , is preferably an angle that is substantially greater than a right angle, namely between 120° and 150°. It may be noted that the pin-locking arm 101 and the connection base 102 may extend along a same plane of orientation P 1 of the locking device 10 . [0038] The pin-locking arm 101 may have at its two opposite ends two seats 101 a , 101 b which may be designed to lock a corresponding number of unicortical pins 100 . This locking action may be performed by the locking means 103 described below. [0039] The locking means 103 may comprise, in particular, two deformable spheres 103 a , 103 b , one of which is shown separately in FIG. 17 , which may be provided with a diametral insertion channel 1031 that defines the actual seat 101 a , 101 b for the unicortical pins 100 . The deformable spheres may have a plurality of incisions that may cross the sphere in a planar manner passing through the insertion channel 1031 ; the incisions may lead alternately into one or the other of two opposite openings of the insertion channel 1031 . Because of the incisions, the sphere may become deformed when it is compressed along the axis of the insertion channel. Thus, the insertion channel 1031 may be constricted locally, by which the unicortical pin 100 housed therein may be locked. [0040] The aforementioned deformable spheres 103 may be housed between an elongated impression 101 c , formed along the upper surface of the pin-locking arm 101 , and a pressure plate 103 a shaped to counter the opposite impression 101 c . In particular, both the pressure plate 103 c and the impression 101 c may have smooth through-holes 1011 at their ends; the two deformable spheres 103 may be locked between two smooth through-holes 1011 situated opposite each other. The insertion channel 1031 of the spheres 103 may be accessible via the smooth through-holes 1011 so as to allow the introduction of the unicortical pin 100 . [0041] A pressure plate 103 c may be connected to the impression via tightening means 103 d which may take the form of a screw. The shank of the screw may be inserted into a central through-hole 1010 a of the pressure plate and then into an opposite central hole 1010 b formed in the bottom of the impression 101 c , on the outside of which it may engage with a nut. Resilient setting means 103 e may also be arranged between the pressure plate 103 c and the impression 101 c , which may be formed in particular by two helical springs that are compressed between the two elements and may be retained inside oppositely arranged depressions 1012 of the impression 101 c and the pressure plate 103 c. [0042] The springs, which may be arranged in intermediate positions between the deformable spheres 103 and the screw, may oppose the tightening action of the latter. Such arrangement may allow the deformable spheres 103 to be deformed and the unicortical pins 100 to be locked inside them. [0043] It should be noted that when the compression plate is not clamped, the deformable spheres 103 may be rotatable inside their seat, such that the surgeon may modify as required the orientation of the inserted unicortical pins 100 . Tightening the head of the screw 103 d eliminates this degree of rotational freedom. [0044] The deformable spheres 103 may have, in one of the openings of the insertion channel 1031 , a raised cylindrical edge 1032 which, once inserted inside the smooth through-hole 1011 , may limit the rotational movement of the element, while may allow access to the insertion channel 1031 . [0045] In some embodiments, the deformable spheres 103 may allow the direction of the unicortical pins 100 to be varied with respect to the axis perpendicular to the plane of orientation P 1 by about 20°. [0046] The connection base 102 has at its free end a fastening point 102 a suitable for connection to the connecting body 11 . [0047] Moreover, the connecting body 11 may have, on both sides, two alternative fastening seats 110 a , 110 b for the connection of the fastening point 102 a. [0048] The fastening point 102 of the locking device 10 may present an enlarged portion through which a fastening hole 102 c may passes and, on the opposite side of the enlarged portion, a projecting tenon 102 b ; on the other hand, the fastening seats 110 a , 110 b may present a depression or mortise 110 c shaped to match the tenon 102 b , and a fastening hole 110 d formed in the bottom of the mortise 110 c. [0049] When the tenon 102 b is correctly inserted into the mortise 110 c of one of the fastening seats 110 a , 110 b , the two fastening holes 102 c , 110 d may be aligned so that a threaded connection element 104 that fixes the locking device 10 to the connecting body 11 may pass through them. [0050] The connecting body 11 may have a structure that is substantially symmetrical with respect to its median plane M. Said connecting body 11 may have a cusp portion 111 at the front with opposite inclined surfaces that are symmetrical with respect to said median plane M, and at the rear a hinge portion 112 , which will be described below. [0051] Both the inclined surfaces of the cusp portion 111 have a top section with an inclination greater than the horizontal and a bottom section with a smaller inclination. The first fastening seat 110 a may be formed on the first section and the second fastening seat 110 b may be formed on the second section. Thus, depending on whether the locking device 10 may be connected to the first fastening seat 110 a or to the second fastening seat 110 b , two different inclinations of the plane of orientation P 1 with respect to the median-plane M may be obtained. Consequently, also the inclination of the preferential plane of orientation P 2 of the unicortical pins 100 may be modified, i.e. the plane on which the pins lie, with due allowance for any adjustments performed by means of the deformable spheres 103 a , 103 b. [0052] The inclination imparted to the fastening seats 110 a , 110 b in the present disclsoure may be such that, by associating both locking devices 10 with the respective first seat 110 a , an angle between the two planes of orientation P 1 may be created that is smaller than a right angle; on the other hand, by associating the locking devices 10 with the second seat 110 b , an angle between the two planes of orientation P 1 may be obtained that is greater than a right angle. The first configuration may be particularly suitable for small-size bones (e.g., tibial mounting), while the second configuration may be suitable for large-size limbs (e.g., femoral mounting). [0053] The hinge portion 112 of the connecting body 11 may allow for articulation, around an axis of rotation r 1 perpendicular to the median plane M, of a locking clamp 3 . [0054] The hinge portion 112 may define in particular a cylindrical seat 1120 intended to define interiorly an articulation hinge 33 of the locking clamp 3 . A threaded element, with a shank which defines the pin 33 a of the hinge 33 and a head which acts as a cover for the cylindrical seat 1120 , is in fact screwed laterally into the cylindrical seat 1120 . A shank 30 of the locking clamp 3 , which may comprise an eyelet end 30 a , which may embrace the aforementioned pin 33 a , may also be inserted, via an upper groove 1121 , inside the cylindrical seat 1120 . [0055] Outside of the cylindrical seat, the shank 30 may pass through, in succession, an intermediate element 34 , slidably movable along an outer cylindrical surface of the hinge portion 112 , and two jaws 32 designed to grip in a known manner the bar 2 of the external fixator. A splined coupling IM may be formed between the bottom jaw 32 and the intermediate element 34 that ensures restriction of rotation when the two parts are clamped against each other. The free end of the shank 30 may be threaded and a lock nut 31 may be screwed onto it. [0056] When the abovementioned group is not clamped, adjustments both around the axis of rotation r 1 of the hinge and around the axis r 2 of the shank 30 may be possible. Tightening the lock nut 31 may cause the entire group to be pressed together and performs the triple function of locking the bar 2 between the jaws of the clamp 3 and blocking the two abovementioned rotational axes. In particular, the axis of rotation r 1 may be blocked by the friction between the intermediate element 34 and the outer cylindrical surface of the hinge portion 112 , and the axis of rotation r 2 may be blocked by the locking action of the splined coupling IM. [0057] Having described individually the single elements which make up the anchoring groups 20 of the external fixator 1 , description is now provided below for the different possibilities of assembling them in order to obtain different configurations of the said fixator. [0058] First of all, the locking devices 10 may be constructed in two configurations which may be a mirror image of each other, namely a configuration oriented to the right of the connection base 102 and a configuration oriented to the left of the connection base 102 . [0059] The external fixator 1 , which by nature is modular, may comprise both right-hand and left-hand locking devices 10 which may be used alternatively by the surgeon in the field depending on the actual operating requirements. [0060] Thus, depending on the locking devices chosen, each anchoring group 20 may be mounted in three different configurations: a U configuration, in which the two locking devices 10 may both be oriented in the same direction, away from the locking clamp 3 of the anchoring group 20 ; an M configuration, in which the two locking devices 10 may both be oriented in the direction of the locking clamp 3 of the anchoring group 20 ; and an S configuration, in which the locking devices 10 are oriented in opposite directions. [0061] With reference to the enclosed figures: FIG. 1 shows an external fixator 1 in which both anchoring groups 20 have a U configuration; in FIG. 2 both anchoring groups 20 have an S configuration; in FIGS. 3 and 4 the proximal mounting group 20 has a U configuration and the distal group has an M configuration, i.e. in a position where the pin-locking arms 101 point in a distal direction and proximal direction, respectively. [0062] The various configurations described above may be used alternatively by the surgeon, depending on the specific operating requirements and the morphology of the fractured bone. In particular, with the S configuration two unicortical pins 100 may be arranged in the vicinity of the fracture site, thereby increasing stability. It is a known fact that the relative spacing of the screws may improve the stability of an external fixator 1 . [0063] In the case where additional stability is required, further unicortical pins 100 may be added, being directly fixed to the bar 2 by means of one or more bar/pin clamps 4 of the type known in the art. [0064] In some embodiments, methods for applying an external fixator 1 are provided. Methods may comprise the following steps: [0000] preparing the first anchoring group 20 , for example the distal anchoring group of the type described above, where necessary mounting it in the configuration most suitable for the intervention according to the modes described above; inserting unicortical pins 100 in at least three of the seats 101 a , 101 b (but preferably all four of them) of the two pin-locking devices 101 of the anchoring group 20 ; fixing the unicortical pins 100 to the long bone of the patient, rotating them by means of a special instrument, using the seats 101 a , 101 b as boring guides; locking said unicortical pins 100 inside the seats 101 a , 101 b using the special locking means 103 described above. [0065] It should be noted that before fixing the unicortical pins 100 to the bone, they may be oriented by rotating the deformable sphere 103 a , 103 b in which they are inserted and then locking them in position by tightening the aforementioned locking means 103 . [0066] It should in particular be noted that the unicortical pins may have a self-tapping tip so that it may be sufficient to rotate them, associating their head with a drilling device in order to create the fixation hole in the patient's bone, whereby said hole may only penetrate the first cortex. [0067] The steps described above may then be repeated in order to fix a second anchoring group 20 , for example the proximal anchoring group; following which, by performing the adjustments along the axes r 1 and r 2 of the locking clamps 3 of the two anchoring groups 20 , they are aligned and connected to the bar 2 . [0068] As previously mentioned, in order to improve the stability of the external fixator, further unicortical pins 100 , preferably two in number, may be used, associating them directly to the bar 2 by means of bar/pin clamps 4 . [0069] It should be noted that, during mounting of the anchoring groups, owing to the L-shaped form of the locking device 10 , X-ray access to the bone site concerned in the intervention is never obstructed by the structure of the anchoring groups, so that the various parts which make up the group need not necessarily be made of radiotransparent material. [0070] It should also be noted that the non-invasive form of the anchoring group 20 , in particular in its U configuration with the opening directed towards the bone end, may allow for easy access of an instrument for reaming the long bone of the patient and subsequently inserting an intramedullary nail, even when the anchoring group is positioned at the point where the nail end is inserted. [0071] One of ordinary skill in the art, in order to satisfy specific requirements which may arise, may make numerous modifications and variations to the devices described above, all of which are however contained within the scope of protection of the disclosure, as defined by the following claims.

The present disclosure relates to an anchoring group for an external fixator, that comprises a connecting body designed to be coupled to a bar of an external fixator. A locking device is connected to the connecting body at a fastening point thereof and comprises a pin locking arm provided with two seats suitable for locking a corresponding number of uni-cortical pins. A connection base is intended to be coupled to a connecting body of the anchoring group. An additional member, also associated with the connecting body, comprises at least one auxiliary seat, not aligned with the seats of the locking device, for locking an additional uni-cortical pin. In an additional embodiment, the connection base of the locking device extends in an angled relationship with respect to the pin locking arm and away from both the seats. The connection base has a point for fastening to the connecting body which is not aligned with said seats.

BACKGROUND OF THE INVENTION Open reel type magnetic tape drive, such as used in computers and data processing equipment, are usually installed in a generally upright position, the reels and the head assembly being exposed for access. The tape supply reel is normally secured on one driven hub and the tape is threaded through the head assembly and attached to the take-up reel. Since the reels and head assembly are exposed, their design is usually made attractive in appearance by means of trim, covers and other cosmetic features, which add to the cost of the apparatus. In many installations the mechanism is protected by doors, which are often transparent, leaving the mechanism exposed and thus subject to esthetic treatment. The upright tape drive units require a considerable amount of space and limit the packaging arrangement in many instances. It would be advantageous to have a tape drive unit which would fit into a minimum of space, be easy to load and unload and be concealed in use so as not to require cosmetic trim. SUMMARY OF THE INVENTION The tape drive unit described herein is constructed horizontally to fit into a drawer, or other low profile enclosure. The only access is through a front slot, in which the edge portions of a supply hub and a take-up reel, which grips the tape by vacuum until the first turn or two are wound up. When the starting sequence is initiated, the take-up reel is swung to the rear of the unit on an arm, which action pulls the tape across a guide and head array, so eliminating the need for threading the tape. At the same time the supply hub is retracted and the supply reel is secured on the hub by cam actuated clamps. The supply hub and take-up reel have individual drive motors, but the arm movement and the supply hub retraction are accomplished by a single actuating motor. All of the actuating mechanism is fully enclosed, but is readily accessible for servicing by opening the drawer. The primary object of this invention, therefore, is to provide a new and improved magnetic tape drive unit. Another object of this invention is to provide a tape drive unit which is installed horizontally in a drawer and is loaded and unloaded through a front slot. Another object of this invention is to provide a tape drive unit which is concealed in use and requires a minimum of access for operation. A further object of this invention is to provide a tape drive unit which is adaptable to standard tape reels, read/write means and control operations. Other objects and advantages will be apparent in the following detailed description, taken in conjunction with the accompanying drawings, in which; FIG. 1 is a pictorial view of a typical desk with the tape drive unit installed in a drawer. FIG. 2 is a front elevation view of the tape drive unit. FIG. 3 is a top plan view of the front portion of the tape drive unit, showing the manual tape loading operation. FIG. 4 is an enlarged sectional view taken along line 4--4 of FIG. 2. FIG. 5 is a sectional view taken along line 5--5 of FIG. 4. FIG. 6 is an enlarged front elevation view of the drive unit with the front cover removed. FIG. 7 is an enlarged sectional view taken along line 7--7 of FIG. 4. FIG. 8 is a sectional view taken along line 8--8 of FIG. 7. FIG. 9 is a sectional view taken along line 9--9 of FIG. 6. FIG. 10 is a view taken along line 10--10 of FIG. 9. FIG. 11 is a sectional view taken along line 11--11 of FIG. 9. FIG. 12 is an enlarged sectional view taken along line 12--12 of FIG. 4. FIG. 13 is a top plane view of the structure of FIG. 12, with portions cut away. FIG. 14 is a sectional view taken along line 14--14 of FIG. 12. FIGS. 15-18 illustrate diagramatically the loading and unloading sequence of the mechanism. DESCRIPTION OF THE PREFERRED EMBODIMENT The tape drive unit 10 is contained in a housing 12 constructed as a drawer, which can be installed in a desk 14 with any conventional arrangement of slides or guides, not shown. The housing has a front panel 16 in which the usual controls 18 are mounted, the upper portion of the front panel having a horizontal access slot 20 through which the tape is loaded and unloaded. Since the front panel is the only portion of the unit normally visible, it alone may be made attractive in appearance as desired. The drawer need not be opened except for servicing the mechanism when needed. The specific structure of the housing is not critical, but in the arrangement illustrated all of the mechanism is mounted on a rigid base plate 22, secured in the housing just below the level of slot 20. Housing 12 may have a removable top cover 24 for access to the reels and head assembly, which are on top of base plate 22, all of the actuating mechanism being below the base plate clear of the tape path. In the front right hand portion of base plate 22 is a rearwardly extending opening 26, along the sides of which are rails 28 fixed below the base plate. A mounting plate 30 is slidably mounted between rails 28 to move from front to rear. Suitable bearings could be used between rails 28 and plate 30 to reduce friction. Secured below mounting plate 30 is a motor 32 having an upwardly extending drive shaft 34, on which is a supply hub 36. The supply hub 36 has a raised central boss 38 to fit the opening 40 of a tape supply reel 42 and supports the reel parallel to and above the base plate 22. To the rear of opening 26 is a post 44 projecting below base plate 22 and pivotally mounted on the post is an arm 46. On the outer end of arm 46 is a take-up motor 48 coupled by a belt drive 50 to a take-up reel 52, which is rotatable on a support shaft 54 mounted in a bracket 56 on the arm. Take-up reel 52 projects above base plate 22 through an arcuate slot 58 having its center of radius at post 44. Slot 58 extends from near the front to the rear portion of the base plate. In the forward position of arm 46, the take-up reel 52 is at the front of the unit alongside supply hub 36 and accessible through slot 20. In the rear position of arm 46, the take-up reel 52 is positioned above a raised circular platform 60 on the rear portion of the base plate, as indicated in broken line in FIG. 4. The arm 46 is operated by an actuating motor 62 mounted under base plate 22 adjacent post 44, the actuating motor having a drive shaft 64 carrying a crank 66. A link 68 couples the crank 66 to a lug 70 on arm 46. As illustrated in FIG. 9, rotation of shaft 64 pulls arm 46 from the forward, full line position to the rear, broken line position. The actuating motor 62, shown in FIGS. 4 and 11, is omitted from FIG. 9 for clarity. The supply hub 36 is retracted or pulled rearwardly as arm 46 moves to the rear position and is moved forward when the arm swings forward. This is accomplished by a tie bar 72 pivotally connected between a lug 74 on arm 46 and a lug 76 on the rear edge of mounting plate 30. The two positions of this linkage are also indicated in FIG. 9. Mounted on top of base plate 22 along the inner edge of slot 58 is a tape utilization head assembly 78, over which the tape passes. The head assembly comprises, from the front, a tachometer 80, which is coupled to a suitable readout to show the amount of tape advanced, a guide roller 82, an optical sensor 84 to detect end of tape markings, a read/write head 86 and a guide roller 88. As described later, the tape 89 is stretched across the head assembly 78 when the arm 46 swings to the rear. To maintain tension in the tape, a tension roller 90 is brought into engagement with the tape after it is extended over the head assembly. Since the tension roller must be clear of the tape path during loading and unloading it is retracted and extended by linkage coupled to arm 46. As illustrated in FIGS. 7 and 8, the tension roller 90 is rotatably mounted on a post 92 at the end of a support arm 94, which is pivoted on a horizontal pin 96 in a bracket 98. The bracket 98 is rotatable on a post 100 projecting vertically downward from base plate 22, so that the bracket and support arm can swing horizontally and the support arm can pivot vertically in the bracket. A lifting spring 102 between bracket 98 and the support arm 94 biases the support arm upwardly. The tension roller 90 and its supporting post 92 project above base plate 22 through an arcuate slot 104, centered on post 100 and can move from a forward retracted position indicated in full line in FIG. 4, to a rearward tension position indicated in broken line. The tension roller is retracted below the tape path in the forward position by a roller cam 106 mounted on base plate 22 to engage and depress support arm 94, as in FIG. 7. Since the tension roller must not be raised until after the tape has passed and must be retracted before the tape is unloaded, a lost motion linkage is used to couple the tension roller to arm 46. A generally triangular link plate 108 is pivotally mounted on post 100 below bracket 98 and has upwardly projecting fingers 110 and 112 at opposite corners. The fingers are spaced apart to allow the link plate to have a limited range of rotation between engagements of the fingers with opposite sides of bracket 98. A connecting rod 114 connects the link plate 108 to arm 46. In the forward position of arm 46, finger 110 holds the bracket 98 in place with support arm 94 depressed under roller cam 106, as in the full line position in FIGS. 7 and 8. When arm 46 swings rearwardly, connecting rod 114 pulls link plate 108 back, but there is no movement of bracket 98. When the arm 46 has travelled far enough to extend the tape beyond the start of the head assembly, finger 112 engages bracket rearwardly, as in the broken line position. Support arm 94 rides off roller cam 106 and spring 102 lifts the support arm and tension roller 90 up into the tape path. Continued motion of arm 46 pulls the tension roller into engagement with the tape 89 and pulls an offset loop 116 into the tape, as in FIG. 4. A torsion spring 118 installed between link plate 108 and bracket 98 provides the tensioning force. Forward movement of arm 46 will, of course, reverse the action by swinging link plate 108 until finger 110 engages bracket 98 and retracts the tension roller. To simplify tape loading the take-up reel 52 is provided with vacuum retaining means to hold the end of the tape in place during the first few turns. As illustrated in FIGS. 4 and 5, the take-up reel 52 has an open top 120 and peripheral perforations 122. A small blower 124, mounted at the side of the take-up reel, is coupled by a hood 126 to the open top 120 to draw air in through perforations 122, as indicated by the arrows in FIG. 5. Hood 126 is supported with minimum clearance above the take-up reel to allow the reel to move out from under the hood. The supply hub 36 incorporates mechanism for automatically clamping the supply reel 42 in place when loaded, so that a positive drive is established for controlling and subsequently rewinding the tape. As illustrated in FIGS. 12 and 13, supply hub 36 is rotatable on the drive shaft 34 and is held in place by a thrust bearing 128 on the upper end of the drive shaft. Below supply hub 36 is a circular cam plate 130 keyed to rotate with drive shaft 34, and on the upper surface of the cam plate are three circumferential ramp cams 132, each having a lower platform 134 and an upper platform 136. The supply hub 36 has three equally spaced radial slots 138 and in each slot is mounted a clamp finger 140. The clamp finger is a generally L-shaped element with one end pivoted on a hinge pin 142 at the outer end of the slot 138, to swing upwardly and radially outwardly and project above boss 38. The other end of the clamp finger 140 has a friction pad 144 to engage and grip the inside wall of the central opening 40 in the supply reel, as in the broken line position in FIG. 12. At the apex of the clamp finger 140 is a roller ball 146 which rolls on one of the ramp cams 132. Each clamp finger 140 is biased downwardly by a spring 148 to keep the roller balls in contact with their respective ramp cams and to keep the clamp fingers normally retracted. In the retracted position the roller balls rest on the lower platforms 134 of the ramp cams. When cam plate 130 rotates relative to the supply hub 36, in the appropriate direction, the roller balls 146 will ride up the ramp cams 132 and raise the clamp fingers 140 to the reel clamping position. Thrust bearing 128 resists the upward load on the supply hub caused by the ramp cam action. When the relative rotation is reversed the clamp fingers will be retracted. Fixed beneath the periphery of supply hub 36 is a bracket 150 carrying a bellcrank 152 which is pivotal on a vertical hinge pin 154. Below the bellcrank and also pivotal on hinge pin 154 is a latch arm 156 having an outwardly projecting latch pin 158. Latch arm 156 is biased outwardly by a spring 160, so that the latch pin 158 projects beyond the edge of the supply hub. Outward movement of both the bellcrank 152 and the latch arm 156 is limited by a stop pin 162 on the supply hub. Latch arm 156 has a coupling pin 164 which projects upwardly through an oversize hole 166 in the bellcrank 152, to couple the two elements together. Fixed on the outer edge of cam plate 130 is an upwardly projecting latch bracket 168, having a socket 170 to receive latch pin 158 and an inclined ramp face 172 to lead the pin into the socket. Bellcrank 152 has an outwardly extending stop arm 174 for engagement with a fixed stop 176 on the side of opening 26. OPERATION In the initial loading position the supply hub 36 and take-up reel 52 are in the forward position, the clamp fingers 140 are retracted and the blower 124 is operating. The blower can, if desired, be running at all times, since the air can be used to cool the interior of the machine. As shown in FIG. 3, a supply reel 42 is inserted into slot 20 and placed over the boss 38 of the supply hub. The free end of tape 89 is pulled out and placed against take-up reel 52, where it will be held by the vacuum. The machine is then started by the appropriate one of controls 18 to carry out the loading operations. The electrical circuitry for operating the machine is not shown since it involves only simple switching and suitable circuits are well known. The unit can also be controlled through a computer terminal 178, or the like, as indicated in FIG. 1. Take-up motor 48 is actuated to wind the tape 89 around take-up reel 52, sufficiently to obtain a driving grip. Motor 32 is also started and carries out the sequence of actions illustrated in FIGS. 15-18. Cam plate 130 is rotated in a clockwise direction and carries supply hub 36 with it, by the frictional coupling of the roller balls 146 on the cam plate. After almost one complete revolution, stop arm 174 strikes the rear of 176 and halts the rotation of supply hub 36. The engagement of the stops also turns bellcrank 152 and extends latch pin 158 outwardly, as in FIG. 16. Cam plate 130 is continuing to turn and latch bracket 168 moves around to engage latch pin 158. The oversize hole 166 allows the latch arm 156 to move back against spring 160, so that the latch pin 158 can ride over ramp face 172 and drop into socket 170, latching the cam plate and supply hub together. Since the stop arm 174 is against stop 176, rotation is impeded. At this point any suitable sensing means can be used, either a position detector at the latch mechanism or a load or resistance detector on motor 32, to initiate the next step. The actuating motor 62 is now started to swing arm 46 to the rear and also pull back the mounting plate 30, which moves the supply hub assembly back away from stop 176, as in FIG. 17, so that rotation can continue. The tape 89 is extended around the head assembly 78, tension roller 90 is raised to engage the tape and the take-up reel 52 stops in the rearmost or operating position, completing the loading operation. The machine is now operable as a conventional tape deck with the appropriate controls. Platform 60 prevents the tape from sagging when wound on the take-up reel 52, but in normal use the tape will be wound tightly enough to stay in flat alignment on the reel. In the unloading sequence the tape is rewound on the supply reel 42, then actuating motor 62 is operated to swing arm 46 forward and to move the supply hub 36 forward on mounting plate 30. Motor 32 is operated to rotate the cam plate 130 counter-clockwise, as in FIG. 18, until stop arm 174 strikes the front of stop 176. This stops rotation of the supply hub 36, so that continued rotation of the cam plate allows the roller balls 146 to ride down the ramp cams 132 and retract the clamp fingers 140. Supply reel 42 can now be removed from the boss 38 and the mechanism is left in the initial loading position for subsequent use. The tape drive unit is thus operable without opening the drawer and with access only through the front slot 20. In operation, the tape and the mechanism are completely enclosed and protected. The actuating mechanism is simple and easy to service and is in a compact configuration which can be installed in a minimum of space.

A magnetic tape drive unit constructed in a horizontal configuration to fit in a drawer or similar low profile installation, the tape being loaded and unloaded through a front slot without the need for access to the mechanism. A supply reel is inserted in the slot and placed on a supply hub, the free end of the tape being applied to a take-up reel which has a vacuum action to retain the tape. The take-up reel is mounted on an arm which swings back in the enclosure and pulls the tape over a guide and head array, the supply reel being simultaneously retracted so that the tape and reels are fully enclosed. After rewinding, the arm swings back and the supply hub is extended to the slot for removal of the tape.

BACKGROUND OF THE INVENTION [0001] Prior art chess sets have had various problems. Among others, chess pieces can easily be lost; the large bulky game board can be difficult to store; and also difficult to transport. Other prior art chess sets have attempted to solve this problem by making smaller, portable game boards and game pieces. However, these sets have had their own problems. It can be difficult to keep playing pieces on the board and once a piece is off the board, it is difficult to store the piece and avoid loss. BRIEF DESCRIPTION OF THE DRAWINGS [0002] FIG. 1 is a perspective view of the partially closed chess set of the subject invention; [0003] FIG. 2 is a perspective view of the board with game pieces placed on hinged shelves; [0004] FIG. 3 is a perspective view of the board at the commencement of the game; [0005] FIG. 4 is a perspective view of the board during game play; [0006] FIG. 5 is a side view of the chess set with one shelf partially open; [0007] FIG. 6 is a schematic view of one embodiment comprising a slanted shelf configuration; [0008] FIG. 7 is a perspective view of the subject invention utilizing a particular shelf configuration with feet; and [0009] FIG. 8 is schematic view of the hinge mechanism for folding the shelves from storage position to play position and vice versa. SUMMARY OF THE INVENTION [0010] In consequence of the background discussed above, and other factors that are known in the field, applicants recognized a need for an improved chess set that would allow players to easily play and maintain their chess board and pieces. Thus, the present invention relates to an improved chess set. More specifically the invention relates to a chess set in which the two halves of the playing board can be folded together to form an interior storage area. Hinged shelves are positioned at the periphery of the chess board. The shelves can swing out and reside on the sides (and/or ends) of the chess board when the board is set for play. When the game is stored, the shelves will swing in so that they can be stored in the interior of the chess board. [0011] In one embodiment, the shelves contain metal that attracts magnets located within the chess pieces. In another aspect of the invention the shelves contain magnets and the pieces have a magnet attracting metal. The board and pieces can be made from wood, metal, plastic, or any other suitable material. There can be a variety of configurations for the shelves and a variable number of shelves. DETAILED DESCRIPTION [0012] Turning now to the drawings and particularly to FIG. 1 , wherein like numerals indicate like parts, there is shown a perspective view of the chess set 100 of the subject invention. The board can be folded in two to form an interior space out of the hollow region. Furthermore, the shelves can be designed so that they fold under the board and the chess pieces on the shelves can be stored in the interior space. Hinge mechanism 102 holds the two sides of the set together and allows for rotation from a closed position to an open position and vice versa. When closed, the chess set provides protection and storage for a plurality of game pieces 108 . Front shelves 112 and side shelves 110 can be rotated on a hinge to move from the closed position shown to a position appropriate for play. The top side of the board 106 (not shown) is the actual game play board. The board, shelves, and game pieces may be constructed of any number of materials including wood, metal, or plastic. Additionally, it is not necessary for all pieces to be constructed of the same material. [0013] Turning to FIG. 2 , the chess set 200 of the subject invention is shown fully open with shelves in the open position. Game pieces 202 rest on the shelves that have been turned on hinges from their closed position, shown in FIG. 1 , to this open position. The shelves may be configured to sit below the level of the playing board or level with the playing board. Game surface 208 contains either a single large magnet or metal element, or a plurality of magnet or metal elements to correspond to either magnet or metal elements in each of the game pieces 202 . If the game board is metal then the game pieces will contain magnet elements. If the game board comprises one or more magnets on its surface then the game pieces will comprise metal elements to allow them to be removably adhered to the board during play. These magnets can be hidden inside the body of the game piece or the board. This connection prevents loss of game pieces and difficulty in playing if game pieces were to shift. Any type of connection mechanism would be useful. Other examples include velcro, buttons, or a host of other male/female type releasable connections. Front shelves 206 and side shelves 204 hold any of the game pieces; although the illustration shows a particular placement of game pieces, any configuration would be possible. The game board, when unfolded, meets at point 210 . There may be some mechanical attachment such as a magnet to hold the two pieces in place. [0014] An alternative magnetized embodiment comprises a board that is magnetized to some degree and attracts a metal element in the game piece. At the center of each square on the game board, there is a hidden magnetized element that is greater in mass than the magnet covering the spaces between the centers of the squares. This feature causes the game pieces to “snap” into position and adds greater security. This may also be accomplished by creating a metal board of a given thickness and having a metal “plug” of a greater thickness under the center of each square. A magnet element in the game pieces will “snap” into position above these metal “plugs.” [0015] FIG. 3 shows a perspective view of the chess set 300 of the subject invention. Side shelves 302 and front shelves 306 have been emptied and the game pieces are on the board in their appropriate places for the start of the game. Connection elements 304 may be a magnet to correspond to metal in the game pieces or metal to correspond to a magnet in the game pieces. The game pieces or shelves may also be constructed entirely of the magnetic or metal material. This connection does not have to be magnetic, alternatively, it may be any removable mechanical connection such as velcro, snap buttons, or a releasable male/female connector. [0016] FIG. 4 is a perspective view of the chess set 400 of the subject invention during game play. As can be seen, the captured pieces can be replaced on side shelves 402 and front shelves 406 during play to allow all players to easily see which pieces are no longer in play. Mechanical connection mechanisms 404 , as described above, may be corresponding metal/magnet pairs, snap buttons, or any other releasable connection. [0017] Turning to FIG. 5 , a side view of the chess set 500 of the subject invention is shown. The front edge of 506 is facing with front shelf 504 turned into place for play. Side shelf 502 is partially rotated between the closed position and the open position. Note that when open or closed, the shelves may be mechanically connected to the board by magnets, snaps, or other connection to hold them in place during play or storage. In this embodiment the shelves' closed position comprises swings down and under the chess board so that pieces can be stored under the board facing horizontally and thus protected from damage by dropping or contact with hard objects. [0018] FIG. 6 shows a cutaway view of an alternative embodiment using a slanted shelf. Shelf 604 is rotated along hinge axis 602 between a closed and open position. [0019] FIG. 7 shows an alternative embodiment of the chess set 700 . This set is constructed entirely of metal and the game pieces would have magnet elements to cause them to adhere to the shelves and game playing surface. The board opens at point 702 using a hinge mechanism. Shelves 704 close to allow game pieces to be stored horizontally inside the chess set and open to allow for game play. This embodiment shows only two front shelves but there may be two front and two side shelves as shown above. The shelves each have optional feet 706 that cause the shelves to remain open when the open chess set is placed on a flat surface. [0020] FIG. 8 shows a side schematic view of the chess set illustrating the movement of a shelf from a closed position, through its rotation, to the open position with a game piece connected. The shelf rotates along hinge axis 802 . This hinge can be any appropriate hinge configuration that allows for free rotation. The game piece is magnetically attached in this embodiment at point 806 . Foot 808 operates as described above to hold the shelf stable when the board is placed on a flat surface. [0021] The preceding description has been presented only to illustrate and describe the invention and some examples of its implementation. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. Many modifications and variations are possible and would be envisioned by one of ordinary skill in the art in light of the above description and drawings. [0022] The various aspects were chosen and described in order to best explain principles of the invention and its practical applications. The preceding description is intended to enable others skilled in the art to best utilize the invention in various embodiments and aspects and with various modifications as are suited to the particular use contemplated.

Chess set comprising a housing that closes and creates a space to store game pieces. Shelves are rotatably attached to the side of the board to move from a close position inside the housing to an open position adjacent to the playing board. Game pieces are adhered to the shelves and to the board via a mechanical connection that is releasable such as a magnet, button, adhesive, or other suitable mechanism.

RELATED APPLICATION INFORMATION [0001] The present application claims priority under 35 U.S.C. section 119(e) to provisional application Ser. No. 60/931,220 filed May 22, 2007, the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention is related to radio frequency (RF) on frequency repeaters (OFR) which are used for re-transmission of RF signals from and to Base Stations (BTS) and User Equipment (UE). More particularly, the present invention is related to radio frequency repeaters used in wireless communication applications such as cellular based networks where signals must be retransmitted in order to enhance quality of service within such network. [0004] 2. Description of the Prior Art and Related Background Information [0005] Most conventional on frequency repeaters are used in modern telecommunication systems in order to provide enhancement in coverage within a cellular network. In such networks, to preserve signal coverage in areas obstructed by terrain or man made obstructions, repeaters are used to re-transmit signals to and from BTS. Hence, the repeater operation and its performance provide for extended signal coverage not otherwise possible. [0006] Even from the early days of Amplitude Modulation (AM) and later Frequency Modulation (FM) repeaters used in VHF business bands and in more recent cellular telephony, the repeaters have been mostly used in conjunction with Base Stations to achieve the extend coverage of BTS over obstructions such as hilly terrain and the like. On frequency repeaters are designed to solve coverage problems due to weak signals in outdoor and in some instances in indoor locations using balanced amplification of uplink and downlink signals. [0007] In an on frequency repeater the repeater does not utilize frequency translation. In other words reception frequency and the transmission frequency, for example in downlink direction, are the same, while similarly, reception frequency and the transmission frequency for uplink direction are the same. For example, a repeater operating in UMTS band would receive downlink signals from the BTS in 2110 to 2170 frequency range, amplify them and retransmit toward UE, for example a mobile telephone. Similarly, in the uplink direction the repeater operating in UMTS band would receive uplink signals from UE in 1920 to 1980 MHz band, amplify them, and retransmit toward BTS. Conventionally the antenna in communication with the BTS is referred to as a donor antenna and the antenna used to re-transmit signals to UE's is referred to as a service antenna. [0008] Since the repeater receives and transmits on the same frequency there is always a possibility that the repeater may oscillate due to a self induced radio signal feedback from transmitting to receiving antenna. Due to the bi-directional nature of an on frequency repeater the radio signal feedback may occur in either the downlink or uplink direction. Various methods have been proposed to attenuate the radio signal feedback and to sufficiently reduce the received portion of the transmission radio wave of repeater. Some of these methods utilize directional antennas, while other methods propose utilization of a plurality of antennas to reduce such feedback path. [0009] One of the primary commissioning issues with on frequency repeaters is to provide sufficient radio frequency attenuation between the two repeaters' antennas so as to prevent a self induced radio signal feedback. Commissioning of the repeater requires careful placement and orientation of antenna's and ability to detect and mitigate feedback oscillation. Additionally, operation of an on frequency repeater in a wireless network must be oscillation free while being capable of detecting feedback oscillation, whilst operating with any combination of wireless signal formats such as but not limited to TDMA, GSM, CDMA, WCDMA and others as well being oscillation free when no signals are present at either antenna. [0010] Full time feedback oscillation detection is mandated due to changing operating circumstances, for example, the growth of trees in the vicinity of the wireless repeater may cause the multi path reflection and scattering of radio waves to vary significantly, therefore changing coupling between donor and service antennas of the repeater and cause it to oscillate. When the repeater oscillates, the output signal of the wireless repeater is conventionally hard limited to a predetermined output power level by an Automatic Gain Circuit (AGC) circuit. [0011] An Automatic Gain Circuit (AGC) circuit is primarily used to limit output signal power of the repeater to predetermined power level. Since it is possible for UE, such as a mobile telephone, to be in near proximity of a repeater, the uplink communication radio wave signals may be of a sufficient level to cause distortion and thus cause harmful interference to adjacent services. Under these operational conditions, the repeater's output signal in the uplink path may increase, but due to action of the AGC will be kept at a safe, predetermined maximum output level. AGC is used to limit the output signal of the uplink, and coincidently downlink path, to a predetermined maximum output level. [0012] The on frequency repeater (OFR) must be equipped with an AGC circuit capable of distinguishing between its feedback oscillation and input signals transmitted by numerous UE's. Many conventional AGC circuits utilize low pass filtered output control voltage which is directly proportionate to the detected signal envelope, whereas when the repeater oscillates the input signal levels increase rapidly until operational limits are reached. Conventional AGC circuits are only marginally able or insufficient to resolve the onset of oscillation and thus additional means must be employed to determine oscillatory condition. [0013] Previous attempts to detect oscillatory condition in on frequency repeater focused primarily on received signal envelope detection and post filtering. This approach has severe limitations as it relies on inherent nature of received signal envelope. In one such example, as described in U.S. Pat. No. 5,815,795, an AGC system is equipped with oscillation detecting circuit comprising a band pass filter (BPF) in addition to an envelope detector and a low pass filter. Due to the burst nature of TDMA telephony signals each frame in TDMA system is divided into a plurality of time slots allocated to mobile stations (UE's). The duration of the TDMA frame is 20 ms and the center frequency of the band pass filter is set to 50 Hz. Output of this band pass filter is applied to alternating current level detector which is used to establish presence of TDMA signal. If the repeater self oscillates, a BPF filter will block all signals since the oscillatory condition envelope is constant. [0014] Accordingly, an improved method for detecting oscillation in an on frequency repeater is needed. SUMMARY OF THE INVENTION [0015] The present invention provides a system and method of automatically detecting if an on frequency wireless repeater is oscillating. Accordingly, the present invention also provides an improved on frequency repeater. [0016] In a first aspect the present invention provides an on frequency repeater for a wireless network, comprising a first antenna that is directed toward a first selected location in the wireless network to receive RF signals from the first selected location, an amplification chain coupled to the received signal and amplifying the level of the received signal to generate an amplified RF signal, and a second antenna spaced apart from the first antenna and receiving and transmitting the amplified RF signal to a second location in the wireless network. The repeater further comprises a feedback oscillation detection circuit coupled to the amplification chain in a gain control loop including a gain adjustment circuit and a gain control circuit, the feedback oscillation detection circuit detecting a saw tooth waveform in the gain control loop to detect onset of feedback oscillation between the first and second antennas. [0017] In a preferred embodiment of the on frequency repeater the gain control loop further comprises a signal level detector coupled to the amplification chain. The signal level detector preferably comprises an envelope detector. The gain control loop preferably also further comprises an RC filter circuit coupled to the output of the signal level detector. The amplification chain preferably includes an intermediate frequency amplification stage and an RF power amplifier and the signal level detector may be coupled to the output of the intermediate frequency amplification stage. Alternatively, the signal level detector may be coupled to the output of the RF power amplifier. The first antenna may be a donor antenna that is directed toward a selected base station and the second antenna a service antenna that is directed toward a selected user coverage area. The on frequency repeater may further comprise an uplink path between the second antenna and the first antenna, the uplink path comprising a second amplification chain receiving and amplifying RF signals from the second antenna and providing them to the first antenna for transmission to the first location. The gain adjustment circuit may comprise a voltage variable attenuator. The feedback oscillation detection circuit may issue a feedback oscillation warning signal upon detecting the saw tooth waveform indicating onset of feedback oscillation. The feedback oscillation detection circuit may also reduce a gain setting of the amplification chain upon detecting the saw tooth waveform indicating onset of feedback oscillation. [0018] In another aspect the present invention provides an on frequency repeater for a wireless network, comprising a first antenna that is directed toward a first selected location in the wireless network to receive RF signals from the first selected location, an amplification chain coupled to the received signal and amplifying the level of the received signal to generate an amplified RF signal, a nonlinear gain expander circuit coupled in the signal path of the amplification chain, and a second antenna spaced apart from the first antenna and receiving and transmitting the amplified RF signal to a second location in the wireless network. The repeater further comprises a feedback oscillation detection circuit coupled to the amplification chain in a gain control loop including a gain adjustment circuit and a gain control circuit, wherein the feedback oscillation detection circuit is coupled to control the gain expander circuit to selectively provide a nonlinear gain response, the feedback oscillation detection circuit detecting a saw tooth waveform in the gain control loop to detect onset of feedback oscillation between the first and second antennas during operation of the gain expander circuit. [0019] In a preferred embodiment of the on frequency repeater the feedback oscillation detection circuit controls operation of the gain expander circuit to provide the nonlinear gain expansion when the repeater is not in user service. The feedback oscillation detection circuit preferably controls operation of the gain expander circuit to provide the nonlinear gain expansion periodically for oscillation monitoring. [0020] In another aspect the present invention provides a method for detecting feedback oscillation in a repeater having first and second antennas and one or more amplification paths. The method comprises detecting a signal level in the amplification path, controlling the gain of the amplification path in response to the detected signal level with a gain control signal, and detecting a periodic nonlinear pattern in the gain control signal corresponding to onset of feedback oscillation between the antennas. [0021] In a preferred embodiment of the method for detecting feedback oscillation in a repeater the periodic nonlinear pattern in the gain control signal comprises a saw tooth pattern. Detecting a signal level in the amplification path preferably comprises detecting a signal envelope. The method for detecting feedback oscillation in a repeater may further comprise filtering the detected signal envelope. The method may further comprise selectively providing an additional nonlinear gain to the amplification path and the detecting of a periodic nonlinear pattern in the gain control signal is performed while providing the additional nonlinear gain. The additional nonlinear gain to the amplification path is provided when the repeater is not in user service. [0022] Further features and advantages of the present invention will be appreciated from the following detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0023] FIG. 1A is a schematic representation of a Cellular Network with an on frequency repeater. [0024] FIG. 1B is a top level schematic of a band select on frequency repeater. [0025] FIG. 2 is a schematic drawing of an uplink path of the on frequency repeater with AGC in accordance with a first (and second) embodiment of the invention. [0026] FIG. 3A is a simplified system stability schematic drawing. [0027] FIG. 3B is a system stability schematic drawing identifying control elements of the on frequency repeater with AGC in accordance with one embodiment of the invention. [0028] FIG. 3C is a system stability schematic drawing identifying control elements of the on frequency repeater with AGC in accordance with a second embodiment of the invention. [0029] FIG. 4 is a graphical representation of the dynamic gain response of the on frequency repeater illustrating AGC behavior in accordance with the first or second embodiment of the invention. [0030] FIG. 5 is a system stability schematic drawing identifying control elements of the on frequency repeater with AGC in accordance with a third embodiment of the invention. [0031] FIG. 6 is a graphical representation of the dynamic gain response of the on frequency repeater illustrating AGC behavior in accordance with the third embodiment of the invention. [0032] FIG. 7 is a graphical representation of the AGC control voltage while the repeater is marginally stable (onset of oscillation is imminent). DETAILED DESCRIPTION OF THE INVENTION [0033] Reference will be made to the accompanying drawings, which assist in illustrating the various pertinent features of the present invention. The present invention will now be described primarily in solving feedback stability detection and mitigation while operable with plurality of signals, it should be expressly understood that the present invention may be applicable in other applications where feedback determination in variable signal level environment is required or desired. In this regard, the following description of on frequency repeater (OFR) that solves radio signal feedback between donor and service antennas is presented for purposes of illustration and description. [0034] The present invention provides an improved On Frequency Repeater (OFR). In a preferred embodiment of the present invention, an on frequency repeater (OFR) is provided for a cellular network system having a plurality of BTS and UE's. The OFR includes a donor antenna that is directed toward a selected base station to receive and transmit RF signals to and from such base station. The OFR includes a first amplification chain receptive to the received signal, the amplifier amplifying the level of the received signal to generate an amplified signal in the downlink direction. The repeater further includes a service antenna located at some distance from the donor antenna. The service antenna is driven by downlink amplified signals, and the service antenna positioned to transmit RF signals within a local area providing communication means to UE's located wherein. The aforementioned description provides a brief description for an OFR operating in the downlink direction between the base station and the subscriber units near the repeater. Similarly, the service antenna provides an uplink coverage area proximate to such repeater. Signals received by the service antenna are applied to a second amplification chain receptive to the received signal, the amplifier amplifying the level of the received signal to generate an amplified signal in the uplink direction. Amplified uplink signals are coupled to the donor antenna. [0035] The RF signals received by the donor antenna and the RF signals transmitted by the service antenna may be at substantially the same frequency in the downlink direction. The RF signals received by the service antenna and the RF signals transmitted by the donor antenna may be at substantially the same frequency in the uplink direction. The amplifier includes AGC and RF circuitry therein to substantially prevent feedback oscillation. The circuitry may advantageously prevent occurrence of feedback oscillation by continuously testing for same. The AGC circuitry may reduce amplifier gain if conditions favoring onset of oscillation exist. [0036] The basic circuit schematic of a preferred embodiment of the OFR of the present invention is shown in FIG. 2 , and is described below. First, however, the basic operational characteristics of a repeater employed in cellular network will be described in relation to FIG. 1A and FIG. 1B . [0037] A repeater system 10 implemented in an illustrative cellular network 1 is shown in FIG. 1A . As can be seen, the repeater system 10 is located on the side of a hill, preferably on the side of the hill facing away from BTS 2 antennas. BTS 2 provides wireless communication services to UE's 5 in the adjacent area. OFR 10 is in communication with BTS 2 and thus extends effective coverage of such BTS 2 to provide service coverage to UE's 6 in extended coverage area 4 . Due to terrain features extended coverage area 4 is blocked from direct coverage by BTS 2 . Both near 3 and extended 4 coverage areas may have one or more UE's 5 & 6 (cellular or other wireless telephones). [0038] The wireless telephone system 1 may include a plurality of base stations (BTS) 2 located in operational vicinity to the OFR 10 . As is well known, each of these additional base stations 2 (not shown) may operate on different transmit and receive frequencies and may utilize CDMA, TDMA, or GSM technologies. The present invention is capable of concurrent operation with the above mentioned systems, accordingly the embodiments described herein all may refer to any one transmission format as well as in combination. [0039] OFR 10 is typically positioned in the area where direct signals from primary BTS 2 are attenuated by local terrain. Generally, donor 26 antenna is a directional antenna advantageously mounted and oriented toward BTS 2 . Any suitable directional antenna, for example Yagi, can be used to establish OFR 10 to BTS 2 radio link. Donor 26 antenna is coupled to respective connection 22 -A port ( FIG. 1B ) of the OFR with a suitable radio guide 24 means, for example coaxial cable. Service area 12 antenna is coupled to respective connection 16 -A port of the OFR 10 . Service area 12 antenna is coupled with a suitable radio guide means 14 to provide broad coverage to UE's 6 in extended 4 coverage area. [0040] With reference to FIG. 1B basic features of the OFR will now be described. OFR 10 comprises two independent amplification chains 18 & 20 . First amplification chain 18 is used to amplify signals in downlink direction, wherein RF signals are received from BTS 2 transmitter to be retransmitted to UE 6 . Similarly, second amplification chain 20 is used to amplify signals in the uplink direction, wherein RF signals are received from UE's 6 and retransmitted toward BTS 2 . Frequency selective duplexers 16 & 22 provide frequency separation between various signal paths so that the same antennas 26 & 12 can be used concurrently for OFR 10 to BTS 2 and OFR 10 to UE's 6 communication paths. [0041] With reference to FIGS. 1B and 2 detailed features of a preferred implementation of the OFR will now be described. In FIG. 2 details for uplink amplification 20 chain are described, whereas downlink amplification 18 chain has been omitted for clarity. The two amplification 18 & 20 chains in practice tend to be very similar and may share similar operational parameters. Alternatively, asymmetric amplification chains may be operatively similar. Suitable implementation details will be appreciated by those skilled in the art from the description of uplink amplification chain 20 . [0042] Uplink signals from UE's 6 are received by service antenna 12 and coupled to antenna port 16 -A of first diplexer 16 . Diplexer can be thought as a dual port band pass filter having one common port. Downlink signals transit with minimum attenuation from port 16 -A toward port 16 -U, while being effectively attenuated from reaching downlink port 16 -D. Output signals from uplink 16 -U port are directed toward input port of the Low Noise Amplifier 101 (LNA). Output of the LNA 101 is coupled to a first RF band-pass filter 103 which provides additional uplink signal filtering and image signal rejection. Output of the first RF band-pass filter 103 is coupled to a second amplifier 105 before being applied to the RF port of down mixer 107 . [0043] Mixers are well known devices and are used for signal frequency conversion. A mixer converts RF power from one frequency into power at another frequency to make signal processing, such as amplification and or filtering easier. Each amplification chain 18 & 20 uses down 107 and up 125 mixers to perform RF to Intermediate Frequency (IF) and IF to RF conversion, respectively. Each amplification chain employs a Local Oscillator (LO) synthesizer 123 to provide Center Frequency selection for the OFR operational band. A detailed description for a channel and band selective repeaters can be found in U.S. Pat. Nos. 5,809,398 and 5,987,304, respectively, which are assigned to current assignee and incorporated herein by reference. [0044] The IF output port of the down 107 mixer is coupled to IF pass band filter 109 . The IF processing strip will now be described. The IF pass band filter 109 provides suitable out of band attenuation so as to select only a narrow selection of frequencies that may contain desired signals for re-transmission toward BTS 2 . Continuing on, the filtered IF passband signal at the output port of the IF bandpass filter 109 is coupled to AGC controlled amplitude means 113 . AGC controlled amplitude controlled means 113 can be implemented with a suitable circuit known in the art such as a voltage variable attenuator suitably adapted to operate at IF frequency band. [0045] Additional IF gain stages 115 and 117 are used to increase amplitude level of the filtered IF passband to suitable levels before being coupled to IF port of the up-conversion mixer 125 . LO signal input to up-conversion mixer 125 is supplied by the LO synthesizer 123 . Since the identical LO frequency is used as in down conversion mixer 107 , no RF frequency shift is incurred. [0046] RF output port of the upconversion mixer 125 is coupled to a second RF bandpass filter 129 . Second RF bandpass filter 129 is used to filter out and essentially attenuate LO and unwanted side band signal resultant from up conversion mixer 125 operation. Output port of the band pass filter 129 is coupled to PA 131 section of the amplification 20 chain. Suitably amplified RF signals are coupled to uplink port of the second diplexer 22 before being applied to donor antenna 26 via suitable radio signal guide means 24 . [0047] Signal level detection 119 can be implemented with a suitable envelope detector, such as RF Detector/Controller AD8314 manufactured by Analog Devices Inc, Norwood, Mass. 02062-9106. This device provides is a complete subsystem for the measurement and control of RF signals in the frequency range of 100 MHz to 2.7 GHz, with a typical dynamic range of 45 dB. However, numerous envelope detector alternatives are readily available. In first preferred embodiment signal detector 119 has its input coupled 127 at the output IF stage 117 with a suitable coupler 121 . IF strip signal level detection can be readily implemented wherein gain variation of subsequent stages is acceptably small or controlled by other means. Conversely, if gain variation of PA stages 131 is unacceptably high signal detector 119 may be coupled 127 to the output of PA with a suitably constructed signal coupler 133 as indicated by the dashed line. Detected signal envelope from detector 119 is coupled to AGC control and feedback oscillation determination module 111 . [0048] Output of the signal level detector 119 is coupled to AGC Control Module 111 for AGC level setting and self feedback oscillation determination. AGC Control Module 111 accepts control signals from Master Control Unit (MCU), not shown as well as reports self feedback oscillation presence when detected. AGC Control Module 111 may include a circuit or circuits used for determining presence of a saw tooth signal detected by RMS detector 119 for determining onset of self feedback oscillation (as shown in FIG. 7 and as discussed below). The saw tooth wave form detection function can be implemented with either analog or preferably with a digital signal processor (DSP). By utilizing DSP hardware and Fourier transforms and other signal processing techniques additional flexibility not afforded by analog circuits is readily attained. [0049] Feedback oscillation in amplification chain 20 can be analyzed using a simplified arrangement illustrated in FIG. 3A . As is well known in the art oscillatory condition occurs when there is sufficient positive gain balance in the feedback oscillator loop. All feedback oscillators require some means which provide gain 36 combined with a feedback 28 arrangement that further send some of the system's output back to be re-amplified after a suitable time delay. For an on frequency repeater, gain is provided by many amplification stages, while signal delay is provided by the numerous filters used in amplification chain 20 construction. [0050] As shown in FIG. 3A , amplification chain and related components are simplified to unitary amplifier 36 element which has a voltage gain A(s) whose output is coupled to input with a feedback path 28 . Feedback path 28 returns a part, FB(s), of the output voltage to the amplifier's 36 input. Henceforth, consider that both amplifier 36 and feedback 28 path have complex amplitude and phase signal response and thus any signal analysis must take complex frequency response of the two into account. [0051] For basic oscillatory OFR analysis FIG. 3A is used, wherein amplifier 36 and feedback path 28 form a positive feedback (closed) loop. Onset of oscillation commences from initial input signal fluctuation: [0000] V in ( t )= V 0 −j2πft [0052] And consequently amplifier 36 will produce the following signal output at the amplifier's 36 output terminal: [0000] V out ( t )= A ( f ) V 0 −j2πft [0053] A portion of the output V out signal is feedback to amplifier input terminal: [0000] V′ in ( t )= A ( f ) FB ( f ) V 0 −j2πft [0054] The new V in ′(t) will be again amplified and feedback back to the input terminal of the amplifier. After n trips around the loop the amplitude value of the feedback signal will be: [0000] | V|=|A ( f ) FB ( f )| n |V 0 | [0055] If the value |A(f)FB(f)|<1 then oscillation will eventually dampen out, however if |A(f)FB(f)|≧1 oscillation will grow in amplitude with every single path through of the feedback loop provided ∠A(f)+∠FB(f)=2 πn where n=1,2,3, . . . Marginal instability or at least constant amplitude oscillation will occur when: |A(f)FB(f)|=1. [0056] Feedback oscillation can be viewed as a summation of previous signal pass through being stacked to the end of the prior signal perturbation with the same sinusoidal phase. Oscillations, for |A(f)FB(f)|≧1, may start with application of initial energy perturbation at the input of the amplifier. [0057] As discussed hereinabove, basic oscillation analysis of FIG. 3A can be further expended to the OFR's specific circuit implementation. With reference to FIGS. 3B and 3C selected OFR circuit elements are combined into functional sub-modules to facilitate oscillation analysis. In order to simplify oscillation analysis several elements of FIG. 2 are combined into equivalent functional modules. In reference to FIG. 3B circuit module S 1 ( 30 ) combines service antenna 12 , service antenna feed line 14 , first duplexer 16 , LNA 101 , Bandpass filter 103 , and second amplifier 105 . Similarly circuit module S 2 ( 32 ) provides equivalent amplitude and phase behavior for the following circuit elements: upconversion mixer 125 , second bandpass filter 129 , PA module 131 , coupler 133 , second duplexer 22 , donor antenna feed line 25 and donor antenna 26 . Similarly, In FIG. 3C circuit module S 3 ( 34 ) provides equivalent amplitude and phase behavior for the following circuit elements: second duplexer 22 , donor antenna feed line 25 and donor antenna 26 . [0058] It is highly desirable for the OFR to provide oscillation free operation and consequently it is equally paramount for repeater control circuits to determine operational conditions favoring or leading toward the onset of feedback path oscillation. OFR implementations have utilized band pass RF amplifiers with Automatic Gain Control system (AGC) that allows for a constant output power, Pout (over input power (Pin), temperature range, etc) operation, together with feedback coupled donor and service antennas as a part of a positive RF feedback 28 path. Under nominal operational conditions when feedback closed loop gain balance is less than <1 feedback 28 loop path may create linear amplitude distortions in the output amplified signal passband. Linear amplitude distortions can be readily observed at the output spectrum of the OFR and appear as gain ripple of the frequency response or as output noise floor ripple. [0059] Through experimental measurements it has been determined that periodicity between these ripples depends on a total group delay in closed RF loop including signal propagation time in the feedback 28 between service 12 and donor 14 antennas. Ripple peak maximums correspond to |A(f)FB(f)|→1 approaching unity, i.e. onset of positive feedback 28 ; meanwhile minimum peak values correspond to negative feedback. Based on spectral measurement performed on OFR it has been estimated that 3 dB (peak to peak) amplitude ripples indicate that feedback 28 loop gain is −15 dB (15 dB margin) less than repeaters' gain in the forward direction. From practical consideration placement of service 12 and donor 24 antenna's typically yields better than 15 dB feedback margin provided that installation site allows for sufficient antenna separation. Under less than adequate installation situation, active stability monitoring is required. [0060] Active stability monitoring is achieved through AGC voltage monitoring. With Reference to FIG. 3B AGC circuit monitoring has been implemented which detects the onset of feedback oscillation. AGC circuit provides gain control over various input signal levels. AGC response time is primarily determined by response time of RMS detector 119 and combination of Rf 135 and Cf 137 . AGC control loop comprises the following circuit elements: AGC control 111 , AGC variable element 113 , First IF Gain stage 115 , Second IF Gain stage 117 , directional coupler 121 , RMS detector 119 , video filter R f 135 & C f 137 . To simplify overall analysis pertaining to AGC circuit behavior noncontributory circuit elements are replaced with equivalent circuit elements. Equivalent circuit elements S 1 30 and S 2 32 are used to combine circuitry outside of AGC control loop. It is assumed (for sake of analysis) that circuit elements S 1 30 and S 2 32 do not contribute significantly to gain variation or their overall parametric changes are insignificant against AGC circuit actions. [0061] Donor 26 to service 14 antenna feedback coupling is substituted by equivalent “FP” 28 block. Assign total Gain of the two amplifier stages 115 and 117 to a transfer function G PA (P OUT ) which is dependent on the output power level. The AGC circuit control element transfer function is G AGC (V C ) and the amount of signal feedback between donor 26 to service 14 antenna as function of distance is G FB (Dist). As it was noted before, oscillation condition appears when total gain in the closed loop is equal to or more than 1 and is shown in eq 1. [0000] G AGC  ( V C ) * G PA  ( P OUT ) * G FB  ( Dist ) ≥ 1 ,  or   G AGC  ( V C ) * G PA  ( P OUT ) ≥ 1 G FB  ( Dist ) ( 1 ) [0062] Isolation as a function of distance function Iso(Dist) can now be written: [0000] or Gain( V C , P OUT )≧Iso(Dist)   (2) [0063] where: [0000] Gain  ( V C , P OUT ) = G AGC  ( V C ) * G PA  ( P OUT ) - total   gain , Iso  ( Dist ) = 1 G FB  ( Dist ) - isolation   between   antennas . [0064] Isolation Function Iso(Dist) vs. Gain(V C , P OUT ) are presented in FIG. 4 ( 400 ). Two different operating scenarios will now be described with reference to FIG. 4 and FIG. 7 . [0065] Under first operating conditions 402 donor 26 and service 14 antennas are separated by a Dist 1 such that feedback coupling Iso(d 1 ) provides for oscillation free operation. Under such conditions total gain Gain(V C , P OUT ) even when set at maximum value is much smaller than Isolation Function Iso(Dist). It should be noted that Isolation Function Iso(Dist) is dependent on other variables other then separation distance, such as antenna directivity, surrounding object reflectivity, multipath propagation and others. These contributory environmental variables tend to be secondary in nature, but nevertheless their contributions should be carefully considered by those skilled in the art during OFR installation planning and implementation. [0066] Under second operating conditions ( 404 & 406 ) donor 26 and service 14 antennas are separated by a distance d 2 . Distance d 2 antenna separation is a critical separation distance that results in feedback coupling Iso(d 2 ) function to provide for onset of feedback oscillation. With such antenna separation distance d 2 OFR amplification chain 36 will experience onset of feedback oscillation described in detail by the following operational sequence. [0067] To simplify operational sequence analysis, it is assumed that the OFR has no input signals present at the service antenna. Under such conditions the AGC control circuit 111 would command AGC control element 113 , which can be a voltage variable attenuator, to a minimum allowable attenuation setting so as to provide a maximum gain 404 for the OFR. Corresponding control signal Vc value for a maximum gain setting is Vc 1 . Through extensive experimentation it was determined that self oscillation onset will commence at very low output power level P( 1 ) which corresponds to feedback input signal M 1 . Typically, M 1 signal is a combination of spurious and noise signals which contribute to the oscillation onset. [0068] Once the oscillation feedback starts the output power levels increases rapidly from very low power until output stage saturation. Curve 404 shows power increase from P( 1 ) to P( 2 ). Oscillation rapid signal growth is detected by AGC detector 119 , but its output is low pass filtered through Rf 135 and Cf 137 . Hence, the AGC 111 control module is slow to respond to such rapid output power increase. Oscillatory signal increase (oscillatory power vs. time) takes place rapidly and is governed by the RF bandwidth of the amplification chain 36 . [0069] Timing measurements indicate P( 1 ) to P( 2 ) transitory rate (time=0 to t 1 ) on the order of 100 nSec whilst AGC circuit time constants are typically much slower. The output power of the amplification chain 36 quickly approaches saturation power levels at which time the overall Gain(V C , P OUT ) begins to decrease (P( 2 ) to P(sat)). [0070] Once the output power of the amplification chain 36 reaches saturated power level it will remain at saturated power level unless output devices fail or AGC limits output power. Once AGC overcomes its response time constant the Gain(V C , P OUT ) will be reduced. With reduction of Gain output power will be first reduced from P(sat) to P( 3 ) due to reduction in gain as controlled by AGC. From P( 3 ) the output power will further be reduced due to AGC control voltage vc 2 and slow time constant which effectively reduces output power level along second 406 curve. Once output power is below P( 3 ) oscillation will rapidly subside as AGC have reduced available gain below oscillation feedback threshold. Oscillation will cease and output power level will drop below P( 1 ) on the second gain curve. [0071] Since there is no longer any measurable output power level (just thermal noise) the AGC will slowly increase available gain until there is enough gain for feedback oscillation to re-start again. Hence, the process is repeatable as long as feedback margin FB is below stability margin. The above mentioned system transitions can be readily monitored and recognized by monitoring AGC control voltages shown in FIG. 7 . The saw tooth waveform has a characteristic period (T) and shape making its detection straightforward. For example, as noted above this saw tooth waveform detection may be implemented by a DSP in AGC control module 111 . When oscillation is detected AGC control module 111 sends an OSC Monitor signal to the MCU which may provide an oscillation warning signal to the operator. Also AGC control module 111 may reset the AGC control voltage to a lower level to eliminate oscillation or reduce an amplification setting of an amplifier stage in the amplification chain. [0072] The saw-toothed AGC oscillation is highly dependent on having gain expansion in the amplification chain. Gain expansion is equivalent to having a non-linear response and is highly undesirable in repeaters operating with multiple simultaneous signals as it may result in higher intermodulation products. One way to avoid introduction of higher intermodulation product levels is to employ linear amplifiers that provide linear phase and amplitude response over dynamic range and introduce gain expanding 139 circuit on as needed basis. In FIG. 5 a gain expanding “rabbit circuit” 139 is used to alter dynamic gain response on as needed basis. Gain expanding 139 circuit (or rabbit) is enabled to alter dynamic gain response on as needed basis via control line 141 . Such dynamic gain expanding circuit can be implemented using either a variable gain amplifier (VGA) or with a fast switching bi-state attenuator. The aforementioned devices and circuits topologies are commercially available and can be implemented by a skilled artisan. The control line 141 provides a suitable control signal to provide the desired nonlinear gain expansion under the control of the AGC control module 111 . This may be provided by a suitably programmed DSP. For example oscillation detection can be periodically scheduled to run or it can be enabled under certain operating conditions. [0073] The above AGC detection method can not be readily adapted to repeaters equipped with linear amplifiers. In wireless telephony linear amplifiers are used to provide linear operation so as to not introduce IMD's when amplifying multiple received carrier signals and different signal modulation schemes, such as WCDMA. Coincidently, a linear amplifier will exhibit a flat amplitude (AM-AM) and phase (AM-PM) dynamic response. An amplifier operating in Class A bias will have such response and therefore no oscillation transitory can be readily identified. [0074] Hereinabove described oscillation detection method can be readily used in narrow passband, channelized repeaters where only one carrier signal is amplified, for example GSM. In such GSM repeaters Class AB biased amplifiers can be readily used. Class AB biased amplifier may provide adequate IMD levels while providing desired AM-AM dynamic amplitude behavior. For multi carrier amplification and/or broad band repeaters a linear operation must be maintained and conventionally designed class AB biased amplifiers may not offer sufficient linearity for a majority of applications. [0075] The AGC oscillation detection method can be adapted to a repeater without degrading linear operation. With reference to FIG. 5 and FIG. 6 oscillation feedback detection will now be described. In FIG. 5 a feedback oscillation 28 path provides signal passage—similar to the earlier description. To reduce non-essential circuit clutter circuit module S 1 ( 30 ) combines service 12 antenna, service antenna feed line 14 , first duplexer 16 , LNA 101 , Bandpass filter 103 , and second amplifier 105 and down conversion 107 mixer. Similarly, circuit module S 3 ( 34 ) provides equivalent amplitude and phase behavior for the following circuit elements: second duplexer 22 , donor antenna feed line 25 and donor antenna 26 . [0076] As described herein a feedback path FP ( 28 ) provides positive feedback path between donor 26 and service 12 antennas. The feedback signal is passed through S 3 ( 34 ) equivalent circuit module and coupled to AGC 113 . Output of AGC 113 is coupled through IF gain amplification stages ( 115 & 117 ) before being coupled to up-mixer 125 . Output of the up-conversion mixer 125 is band pass filtered 129 to remove LO carrier and unwanted sideband before being coupled to a controlled rabbit circuit 139 . Output of the rabbit circuit is coupled to power amplification stage 131 (PA). Output of PA 131 stage is sampled with a directional 133 coupler. Coupler 133 output through port is coupled to equivalent circuit module S 3 34 which provides a source signal to feedback 28 path. [0077] Coupler 133 coupled port is coupled to an envelope signal detector 119 with its output low pass filtered through R f 135 and C f 137 . Low pass filtered envelope signal is coupled to AGC control circuit 111 . AGC control circuit 111 receives MCU control commands under which control, among other things, whether controlled rabbit circuit 139 is enabled or alternatively disabled. An MCU feedback voltage is provided, which is used to establish presence of the FP oscillation. Primarily AGC control circuit 111 controls AGC 113 to provide desired gain control for repeater amplification chain. [0078] Controlled rabbit circuit 139 , when enabled, provides a gain expansion region 606 between output power level Pd( 1 ) and P( 2 ) along Gain vs. Ouput Power level along curve 604 . When rabbit circuit 139 is disabled Gain vs. Output power level is slightly increased and returned to a linear condition as indicated by curve 604 -a (dashed line). Typically the repeater is operated with rabbit circuit 139 disabled. Rabbit circuit 139 is typically enabled under selective operational conditions such installation procedure, during prolonged AGC operation or when excessive signal levels have been detected. [0079] Since rabbit circuit 139 introduces non-linear amplitude response its enablement should be limited to periods when uplink path of OFR is not actively re-transmitting user traffic. Numerous detection schemes can be employed for detecting UE traffic presence (or absence) and can be readily adapted by those skilled in the art. [0080] The above description is not intended to limit the invention to the form disclosed herein. Accordingly, variants and modifications consistent with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain modes known for practicing the invention disclosed herewith and to enable others skilled in the art to utilize the invention in equivalent, or alternative embodiments and with various modifications considered necessary by the particular application(s) or use(s) of the present invention.

An on frequency repeater for wireless networks with feedback oscillation detection is disclosed. The on frequency repeater includes an automatic gain control loop which samples amplified signal envelope. The automatic gain control loop is monitored and a characteristic saw tooth pattern in the gain control loop indicating feedback oscillation is detected. A nonlinear gain expander circuit may be periodically activated to allow feedback oscillation detection in repeater applications employing linearized amplifiers.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an accumulator or receiver dryer and a method of making the same, for use in an automobile air conditioning system. More particularly, the present invention relates to packaging replaceable desiccant in an accumulator or receiver dryer. 2. Description of the Prior Art In air conditioning systems, and particularly those for automotive applications, the accumulator is typically located at the outlet end of the evaporator. Its purpose is to filter out any particulates in the refrigerant fluid and remove any moisture present in the refrigerant vapor. A desiccant material is placed within the accumulator housing specifically for the purpose of removing the unwanted moisture from the refrigerant vapor. During assembly of the accumulator, it is important to avoid saturating the desiccant material. Handling the desiccant material during the assembly process introduces the potential for saturation from exposure to humidity of air in the assembly area. Therefore, handling should be kept to a minimum. A fully sealed unitary housing is a desirable feature of an accumulator. A one-piece construction without joints that may leak is an objective of accumulator assemblies. The simplicity of a unitary housing is also an important feature, which reduces costs and improves reliability. Such a unitary housing can be accomplished by spin welding closed the accumulator housing as taught by U.S. Pat. No. 4,675,971 to Masserang. In known accumulator assemblies and methods of making same, the desiccant material is added to the housing prior to welding and leak testing the accumulator assembly. This known method introduces the risk of saturating the desiccant, and results in a high scrap rate and material cost for damage the desiccant bag incurs during brazing and testing operations. In addition, with known devices and methods of making these devices, field repair and rework are not practical. Repairs consist of removing the defective device and replacing the entire accumulator or receiver unit. There are accumulators for air-conditioning systems which sealingly connect a separate desiccant container in the bottom of the accumulator housing prior to permanently assembling the accumulator. The desiccant remains serviceable through the bottom of the housing. This system is disclosed in U.S. Pat. Nos. 4,276,756 and 4,291,548 to Livesay. The Livesay references disclose an access opening in the bottom of the housing that opens into the interior of a desiccant container. A separate, empty desiccant container is placed inside the accumulator housing. A U-shaped tube is placed inside the housing. The empty desiccant container is received in the bight portion of the U-shaped tube. The desiccant container has an open lower end that communicates with the opening in the bottom of the housing. An annular seal attachment sealingly attaches the lower end of the desiccant container through the open lower end thereof. A detachable closure cooperates with the closure fitting to close the access opening in the housing. The desiccant container is filled after the housing has been permanently assembled by inverting the container and gravity feeding desiccant material. U.S. Pat. No. 4,291,548 discloses a desiccant container that is a foldable bag that can be inserted through the opening in the bottom of the housing. U.S. Pat. No. 4,838,040 to Freeman discloses a receiver dryer in which the housing has a readily openable lid held in place by quick disconnect clamps. The lid can be removed to allow a desiccant canister to be inserted inside the housing. To ensure adequate sealing, the housing has an annular O-ring. The separate lid has an overhang that seals against the O-ring of the housing. Additionally, the lid has an internally depending sleeve segment that is provided with another O-ring. The two O-rings are necessary to completely seal the housing against leakage. The lid is secured in place by a quick disconnect clamping band. Accumulators must maintain high standards during testing. Therefore, a one-piece or unitary design is desired for the housing. The number of access openings and weld joints should be kept to a minimum for the housing to withstand the demanding impact, leak and burst test requirements. A drawback associated with prior art arrangements that provide access to the desiccant material is the need for a separate access opening. Additional openings disrupt the integrity of the accumulator or receiver dryer housing. Any opening in the housing introduces the potential for leaks, so a minimum number of openings is desirable. A leak proof housing can be manufactured by spin welding a unitary housing into a closed configuration. Therefore, the number of components and attachments inside the accumulator housing should be kept to a minimum to reduce the risk of components breaking loose during the spin weld process. The accumulator disclosed in Livesay and the receiver dryer disclosed in Freeman require several additional components to accomplish accessibility to the desiccant material making spin welding impractical. In addition, if the devices disclosed by Livesay or Freeman cannot be closed by spin welding without defeating their innovative design feature of a separate opening to provide access to the desiccant. In Livesay, not only is an additional opening required, but a separate desiccant container to hold the desiccant material is necessary. A sealing attachment between the container and the housing is necessary to maintain the desiccant container's position within the housing, and a closure member is necessary to prevent desiccant material from escaping the container. The receiver dryer disclosed by Freeman also requires significant additional structure. A separate lid, two O-rings, a clamping band and a separate desiccant container are all necessary additional components for access to the desiccant material. Additionally, the sealing attachment between the desiccant container and the casing disclosed by Freeman must be extremely reliable to avoid desiccant material from escaping the desiccant container and contaminating the interior of the casing. The location of the desiccant within the housing is an important aspect of an accumulator design. Ideally, the desiccant is located near the top of the housing. Locating the desiccant near the top of the housing ensures all vapor components of the refrigerant pass through the desiccant thereby improving the accumulator's performance. In operation, the liquid refrigerant settles in the bottom of the accumulator housing. Positioning the desiccant in the bottom of the housing introduces the risk of saturating the desiccant material. In addition, all of the vapor inside the accumulator housing is not forced through the desiccant. The vapor that remains near the top of the housing never reaches the desiccant material and may contain unwanted moisture as a result. The Livesay references disclose locating the desiccant in the bottom of the housing, which is not desirable for optimum accumulator performance. What is needed is an accumulator housing that can be accessed for inserting or removing desiccant material, having a minimum of components and without separate access openings that compromise the integrity of the housing. SUMMARY OF THE INVENTION The present invention embodies a housing that can be brazed and leak tested before the desiccant is added, eliminating the risk of damaging desiccant bags during assembly. A loose desiccant material is added directly to the housing of the present invention through an existing inlet opening in the top of the accumulator housing. The loose desiccant material can be added after the accumulator is completely assembled and tested. The potential for damage to the desiccant and the desiccant container are completely eliminated. The integrity of the housing is not compromised as no additional openings in the housing are required to access the desiccant material. The desiccant material is ideally located in the top portion of the housing. The present invention employs a screen permanently mounted inside the pressure vessel that supports the loose desiccant material. Another screen, removably attached to the inlet opening, provides access to the loose desiccant material housed within the pressure vessel. A method of making the present invention allows the accumulator assembly to be leak tested before the desiccant is added. This reduces scrap and allows repair of accumulator assemblies. The method includes spin welding closed a cylindrical tube; attaching an inlet tube to the closed end of the cylindrical tube; assembling an outlet tube, baffle member, and baffle screen; inserting the outlet tube assembly inside the cylindrical tube; attaching the outlet tube to the closed end of the cylindrical tube; spin closing the remaining open end of the cylindrical tube; adding loose desiccant through the inlet tube; and inserting a removable screen to the inlet opening. In one embodiment, the baffle screen is made of a thermoplastic material. The baffle screen is thermally bonded to the vessel's housing by centrifugal force and heat generated during the spin welding process. The removable inlet screen facilitates field repair and rework of the accumulator assembly. It is not necessary to replace the entire accumulator assembly merely because the desiccant material needs to be replaced. The inlet screen can be removed, the accumulator can be emptied of old desiccant material, new material can be added through the inlet opening, and the screen replaced. It is an object of the present invention to add loose desiccant material to the housing after assembly, brazing, and leak testing of the housing. It is another object of the present invention to provide access to the desiccant material without jeopardizing the integrity of the housing. It is yet another object of the present invention to provide access to the desiccant material without removing the housing from the overall air-conditioning system, enabling field repair. It is a further object of the present invention to position the desiccant material in the top of the housing to ensure adequate drying of refrigerant vapor. These objects, features, and advantages of the present invention will become readily apparent from the following detailed description of the preferred embodiment when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view shown in partial cross section of a prior art accumulator; FIG. 2 is a cross-sectional view taken along line II--II of FIG. 1; FIG. 3 is a side view shown in partial cross section of an accumulator of the present invention; and FIG. 4 is a cross-sectional view taken along line IV--IV of FIG. 3 showing the detail of the baffle screen and inlet screen of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is a schematic of a generally conventional vehicular air-conditioning accumulator 100. The structure of the prior art accumulator 100 includes a cylindrical tubular housing 110 that is closed at both ends. Typically, the housing 110 is closed by a spin welding process being conventional in the art as taught, for example, by U.S. Pat. No. 4,675,971 to Masserang, or mig welding a center joint as known by one skilled in the art. The prior art accumulator 100 includes an inlet opening 120 and an outlet opening 140 in the top of the accumulator housing 110 providing access to the interior of the housing 110. An inlet tube 130 is brazed or welded to the inlet opening 120 of the accumulator housing 110. An outlet tube 150 is included which receives additional structure efore it is permanently affixed to the outlet opening 140 of the accumulator housing 110. Typically, the outlet tube 150 has a U-shaped configuration. A bight portion 155 of the outlet tube 150 is located in the lower region of the accumulator housing 110. A first leg 151 of the outlet tube 150 supports a baffle 160, or deflector plate, which is permanently fixed to the outlet tube 150 by brazing or welding. A second leg 152 of the outlet tube 150 is shorter than its first leg 151, and its end located underneath the baffle 160. The outlet tube assembly is welded or brazed to the accumulator housing 110 at the outlet opening 140 in the top of the accumulator housing 110. A desiccant bag 170, or other container holding a desiccant material 180, is attached to the outlet tube 150 prior to the outlet tube 150 being permanently attached to the top of the accumulator housing 110. Usually the desiccant bag 170 is supported in the bight portion 155 of the outlet tube 150. The baffle 160 is permanently affixed to the interior walls of the accumulator housing 110. Usually, this is done by tack welding the baffle 160 to the interior of the housing 110 at several locations around the perimeter of the baffle 160, or by an interference fit between tabs 161 on the outer periphery of the baffle 160 and the interior walls of the accumulator housing 110. It is critical for proper operation of the accumulator that the desiccant bag 170 or container is not damaged while permanently attaching the baffle 160 to the housing 110, yet it is a common occurrence which cannot be detected until after the impact and burst tests are completed. If a damaged desiccant bag is discovered, the entire accumulator 100 is scrapped, which is costly. The outlet tube 150 is permanently attached to the accumulator housing 110. Typically it is brazed or welded. The brazing process used to attach the baffle 160 and outlet tube 150 introduces significant risks to the desiccant material 180. The desiccant 180 can be damaged by the heat generated by the welding or brazing process. The remaining open end of the accumulator 100 is closed. After the accumulator 100 is fully assembled, the unit is tested. Any failures at this stage usually result in irreparable damage to the desiccant bag 170 and the entire unit 100 must be scrapped because there is no way to access the interior of the accumulator housing 110. Repair and rework are not options using this method of manufacture. The structure of prior art accumulators 100 is not consistent with accessing the desiccant material 180 without destroying the integrity of the accumulator housing 110. FIG. 3 is an accumulator 200 of the present invention that is similar to prior art accumulators except for the elimination of a separate desiccant bag 170 or container and the relocation of the desiccant material within the accumulator. Like components of the prior art accumulator of FIGS. 1 and 2 are labeled with the same reference numerals increased to 200. The present invention allows a method of manufacture that eliminates the need for a separate desiccant bag 170, thereby eliminating the risk of damage thereto and costly scrap of to the complete accumulator assembly. Additionally, the accumulator 200 of the present invention allows access to the desiccant material 280 without affecting the integrity of the accumulator housing 210. The majority of components of the accumulator 200 of the present invention are the same as those of prior art accumulators 100. The housing 210 is spun weld closed as in prior art accumulators 100. The inlet tube 230 configuration is the same as prior art accumulators 100. The shape and positioning of the outlet tube 250 is also the same as prior art accumulators. The baffle 260 shape and position of the baffle 260 are also the same as in prior art accumulators 100. The accumulator 200 of the present invention is modified from prior art accumulators 100 by including a screen 290 positioned between the periphery of the baffle 260 and the interior wall of the housing 210. While the shape, position and attachment of the baffle 260 to the outlet tube 250 is the same as prior art accumulators, the present invention includes the baffle screen 290 that surrounds the periphery of the baffle or deflector plate 260. The baffle screen 290 effectively separates the interior of the housing 210 into an upper chamber 211 and a lower chamber 212. The baffle screen 290 supports loose desiccant material, and therefore must have pores 292 which are small enough to prevent any desiccant material 280 from escaping into the lower chamber 212 of the housing 210. The pores 292 are large enough so as not to interfere with the flow of refrigerant fluid into the lower chamber 212 of the housing 210. The baffle screen 290 can be attached to the outer periphery of the baffle 260 by any means sufficient to permanently affix the baffle screen 290 to the baffle 260. Some of the methods will be discussed in detail below. It is imperative that loose desiccant material 280 not escape into the lower chamber 212 of the housing 210. The baffle screen 290 must be attached to the inner wall of the housing 210. The same method used to attach the baffle screen 290 to the baffle 260 could be employed to attach the baffle screen 2902 to the interior wall of the housing 210. The periphery of the baffle screen 290 must be completely sealed against the interior wall of the housing 210, as it is sealed to the periphery of the baffle 260, to prevent any loose desiccant material 280 from escaping. In one embodiment of the present invention, the baffle screen 290 is initially temporarily fastened to the interior of the housing 210 by an interference fit, or tack welding. The baffle screen 290 is permanently bonded to the interior of the housing by heat generated during the welding process used to close the housing 210. The baffle screen 290 can be made of a thermoplastic or a material containing sintered thermoplastic pellets. Under centrifugal force and heat generated during the welding process, the thermoplastic material of the baffle screen 290 bonds to the interior of the housing 210. The baffle screen 290 and baffle 260 combination divide the interior of the housing 210 into the upper and lower chambers 211 and 212. The baffle screen 290 effectively supports the loose desiccant material 280 and prevents it from escaping into the lower chamber 212 of the housing 210. The baffle screen 290 neither prohibits nor interferes with the flow of refrigerant from the upper chamber 211 into the lower chamber 212 of the housing 210. The inlet tube 230 is permanently affixed to the inlet opening 220 in the top of the accumulator housing 210 just as in prior art accumulators 100. However, the present invention includes an inlet screen 221 that covers the inner diameter of the inlet opening 220. The purpose of the inlet screen 221 is the same as that of the baffle screen 290 surrounding the baffle 260. The inlet screen 221 does not prohibit free flow of refrigerant, yet the loose desiccant material 280 is prevented from escaping the interior of the accumulator housing. The inlet screen 221 covering the inner diameter of the inlet opening 220 need not be permanently affixed, and it is in fact desirable to maintain the removability of this screen 221 by mounting the inlet screen 221 against a shoulder on the inlet tube or in any convenient manner providing the inlet screen 221 is removable after installing same in the inlet tube 230. The inlet screen 221 can be removed for emptying and refilling the upper chamber 211 of the housing, facilitating field repair and rework. Finally, as mentioned above, loose desiccant material 280 is located in the upper chamber 212 of the accumulator housing 210. The loose desiccant material 280 is prevented from entering the lower chamber 212 of the accumulator housing 210 by the baffle 260 and the baffle screen 290. Likewise, the inlet screen 221 prevents the loose desiccant material 280 from escaping through the inlet opening 220. The accumulator 200 of the present invention includes introducing loose desiccant material 280 through the inlet opening 220 of the accumulator 200. Once the desiccant material 280 is added, the inlet screen 221 is placed over the inner diameter of the inlet opening 220. One advantage of the present invention is readily apparent. The desiccant material 280 need not be added to the assembly until after the accumulator 200 is completely assembled and pressure and leak tested. This eliminates unnecessary handling of the desiccant material 280, and eliminates potential harm to the desiccant material 280 during the assembly and testing process. Additionally, the entire accumulator assembly 200, minus the desiccant material 280, can be leak, impulse and proof tested, repaired, reworked, and retested before any desiccant material 280 is added. The ability to repair and rework units saves scrapping a fully assembled unit lowering manufacturing costs. Another advantage is that the desiccant material 280 can be accessed in the field. It is now possible to perform field repairs and maintenance procedures that were not possible before. It is no longer necessary to replace accumulators 200 that could not be repaired simply because of inaccessibility to the desiccant material 280. The following steps are included in the method of making an accumulator 200 of the present invention; closing one end of the housing, such as by welding as taught in U.S. Pat. No. 4,675,971, or another welding process known by one of ordinary skill in the art; drilling inlet and outlet openings in the closed end of the housing to the same size as the outer diameter of the inlet and outlet tubes; inserting the inlet tube into the inlet opening and brazing the tube to the top end wall of the housing; axially inserting the baffle over a leg of the outlet tube and fastening the baffle thereto; temporarily fastening the baffle screen around the outer periphery of the baffle by a mechanical fastener; inserting the outlet tube, baffle, and baffle screen through the open end of the accumulator housing; brazing the outlet tube to the housing; fastening, by brazing or otherwise, the baffle to the interior wall of the housing; temporarily fastening the baffle screen to the interior wall of the housing by means of mechanical fasteners; closing the remaining open end of the accumulator housing, by spin welding to generate enough heat to thermally and centrifugally bond the baffle screen to both the baffle and the interior wall of the housing; introducing loose desiccant material through the inlet tube into the upper chamber of the outlet housing; and removably fastening an inlet screen within the inner diameter of the inlet tube over the inlet opening of the accumulator housing. While the preferred embodiment of the present invention is to thermally bond the baffle screen to the interior of the housing, any alternative method of attachment may also be employed to obtain the same results, such as welding or adhesive bonding. Although a particular embodiment of the present invention has been illustrated in the accompanying drawings and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the embodiments disclosed. For example, the baffle screen could be adhesively bonded to the baffle and interior wall of the accumulator housing and the remaining end of the housing closed by means other than spin welding. Another example involves relying on the permanent bond between the interior wall of the housing, the baffle screen and the baffle to maintain the baffle's position within the accumulator housing and eliminating the step of fastening the baffle to the outlet tube. Numerous rearrangements, modifications and substitutions are possible, without departing from the scope of the claims hereafter.

A pressure vessel housing that can be brazed and leak tested before adding desiccant material, eliminating the risk of damaging desiccant bags during assembly. The desiccant is added to the housing of the pressure vessel through an existing inlet opening in the top of the accumulator housing, thereby eliminating the potential for damage to the desiccant and the desiccant container while maintaining the integrity of the housing because no additional openings in the housing are required to access the desiccant material. A screen permanently mounted inside the pressure vessel supports the loose desiccant material and another screen removably attached to the inlet opening provides access to the loose desiccant material housed within the pressure vessel. A method of making the pressure vessel allows the accumulator assembly to be leak tested before the desiccant is added, reducing scrap and allowing repair of accumulator assemblies.

TECHNICAL FIELD [0001] This disclosure is generally directed to field devices in a plant. More specifically, this disclosure is directed to an apparatus and method to detect smart device configuration changes against a reference in process control systems. BACKGROUND [0002] Industrial control systems (ICS) can adhere to safety guidelines set by the International Electrotechnical Commission (IEC). An IEC Final Draft International Standard (FDIS) 61511-1 guidelines have set that smart device configurations should not be changed post commissioning. IEC 61511 categorizes smart instruments as type B devices and fixed program language (FPL) devices. If an accident occurs and these guidelines are not followed, it will be difficult to justify why a company did not comply with the guidelines. Periodically, a report is generated for safety audit purposes to show that the smart device configuration have not changed since commissioning. Customers are concerned that any change in smart device configuration could severely impact their process (continuous/batch). Producing a report for a single smart device could take around an hour. Factories can have more many smart devices, ultimately consuming more manual effort and increasing costs. Customers might miss producing the periodic reports because of many manual dependencies. A maintenance engineer must be well trained to generate the reports, as it involves selecting a right reference and ignoring non-configuration parameters. As the method is human dependent, there can be human errors. SUMMARY [0003] This disclosure provides an apparatus and method to detect smart device configuration changes against a reference in process control systems. [0004] In a first example, a method is provided for managing a master gold record in an industrial automation system. The method includes receiving a master golden record for a device of a plurality of devices in the industrial automation system. The master golden record includes one or more parameter values for the device for a mode of the industrial automation system. The method also includes identifying an active mode for the industrial automation system. The method also includes responsive to a triggering of a comparison, comparing current parameter values of the device with the one or more parameter values of the master golden record for the active mode. The method also includes generating a report comprising differences between the one or more parameters values of the master golden record and the current parameter values of the device. [0005] In a second example, an apparatus includes a memory configured to store a master golden record. The apparatus also includes a processing device coupled to the memory. The processing device is configured to receive the master golden record for a device of a plurality of devices in a industrial automation system. The master golden record includes one or more parameter values for the device for a mode of the industrial automation system. The processing device is also configured to identify an active mode for the industrial automation system. The processing device is also configured to responsive to a triggering of a comparison, compare current parameter values of the device with the one or more parameter values of the master golden record for the active mode. The processing device is also configured to generate a report comprising differences between the one or more parameters values of the master golden record and the current parameter values of the device. [0006] In a third example, a non-transitory computer readable medium includes a computer program. The computer program comprises computer readable program code for receiving a master golden record for a device of a plurality of devices in a industrial automation system. The master golden record includes one or more parameter values for the device for a mode of the industrial automation system. The computer readable program code is also for identifying an active mode for the industrial automation system. The computer readable program code is also for responsive to a triggering of a comparison, comparing current parameter values of the device with the one or more parameter values of the master golden record for the active mode. The computer readable program code is also for generating a report comprising differences between the one or more parameters values of the master golden record and the current parameter values of the device. BRIEF DESCRIPTION OF THE DRAWINGS [0007] For a more complete understanding of this disclosure and its features, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: [0008] FIG. 1 illustrates an example industrial process control and automation system and related details according to this disclosure; [0009] FIG. 2 illustrates an example device for managing recordation of changes in a smart device according to this disclosure; [0010] FIG. 3 illustrates an example block diagram of a configuration management system according to this disclosure; and [0011] FIG. 4 illustrates an example master golden record management process according to this disclosure. DETAILED DESCRIPTION [0012] FIGS. 1 through 4 , discussed below, and the various examples used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitable manner and in any type of suitably arranged device or system. [0013] FIG. 1 illustrates an example industrial process control and automation system 100 and related details according to this disclosure. As shown in FIG. 1 , the system 100 includes various components that facilitate production or processing of at least one product or other material. For instance, the system 100 is used here to facilitate control over components in one or multiple plants 101 a - 101 n . Each plant 101 a - 101 n represents one or more processing facilities (or one or more portions thereof), such as one or more manufacturing facilities for producing at least one product or other material. In general, each plant 101 a - 101 n may implement one or more processes and can individually or collectively be referred to as a process system. A process system generally represents any system or portion thereof configured to process one or more products or other materials in some manner. [0014] In FIG. 1 , the system 100 is implemented using the Purdue model of process control. In the Purdue model, “Level 0” may include one or more sensors 102 a and one or more actuators 102 b . The sensors 102 a and actuators 102 b represent components in a process system that may perform any of a wide variety of functions. For example, the sensors 102 a could measure a wide variety of characteristics in the process system, such as temperature, pressure, or flow rate. Also, the actuators 102 b could alter a wide variety of characteristics in the process system. The sensors 102 a and actuators 102 b could represent any other or additional components in any suitable process system. Each of the sensors 102 a includes any suitable structure for measuring one or more characteristics in a process system. Each of the actuators 102 b includes any suitable structure for operating on or affecting one or more conditions in a process system. [0015] At least one network 104 is coupled to the sensors 102 a and actuators 102 b . The network 104 facilitates interaction with the sensors 102 a and actuators 102 b . For example, the network 104 could transport measurement data from the sensors 102 a and provide control signals to the actuators 102 b . The network 104 could represent any suitable network or combination of networks. As particular examples, the network 104 could represent an Ethernet network, an electrical signal network (such as a HART or FOUNDATION FIELDBUS network), a pneumatic control signal network, or any other or additional type(s) of network(s). [0016] In the Purdue model, “Level 1” may include one or more controllers 106 , which are coupled to the network 104 . Among other things, each controller 106 may use the measurements from one or more sensors 102 a to control the operation of one or more actuators 102 b . For example, a controller 106 could receive measurement data from one or more sensors 102 a and use the measurement data to generate control signals for one or more actuators 102 b . Each controller 106 includes any suitable structure for interacting with one or more sensors 102 a and controlling one or more actuators 102 b . Each controller 106 could, for example, represent a multivariable controller, such as a Robust Multivariable Predictive Control Technology (RMPCT) controller, or other type of controller implementing model predictive control (MPC) or other advanced predictive control (APC). As a particular example, each controller 106 could represent a computing device running a real-time operating system. [0017] In one or more example embodiments of this disclosure, sensors 102 a and actuators 102 b can be smart devices. These smart devices can include different parameter values 160 . Parameter values 160 can be settings and configurations of a smart device to perform specific functions in an active mode of the system 100 . For example, Lower Range Value (LRV) and Upper Range Value (URV) can be configuration parameters while Primary value (PV) can be a non-configuration parameter. Each smart device can have different values for different modes. The different modes can be set based on product, version of the product being manufactured, or a service being executed. [0018] Two networks 108 are coupled to the controllers 106 . The networks 108 facilitate interaction with the controllers 106 , such as by transporting data to and from the controllers 106 . The networks 108 could represent any suitable networks or combination of networks. As particular examples, the networks 108 could represent a pair of Ethernet networks or a redundant pair of Ethernet networks, such as a FAULT TOLERANT ETHERNET (FTE) network from HONEYWELL INTERNATIONAL INC. [0019] At least one switch/firewall 110 couples the networks 108 to two networks 112 . The switch/firewall 110 may transport traffic from one network to another. The switch/firewall 110 may also block traffic on one network from reaching another network. The switch/firewall 110 includes any suitable structure for providing communication between networks, such as a HONEYWELL CONTROL FIREWALL (CF9) device. The networks 112 could represent any suitable networks, such as a pair of Ethernet networks or an FTE network. [0020] In the Purdue model, “Level 2” may include one or more machine-level controllers 114 coupled to the networks 112 . The machine-level controllers 114 perform various functions to support the operation and control of the controllers 106 , sensors 102 a , and actuators 102 b , which could be associated with a particular piece of industrial equipment (such as a boiler or other machine). For example, the machine-level controllers 114 could log information collected or generated by the controllers 106 , such as measurement data from the sensors 102 a or control signals for the actuators 102 b . The machine-level controllers 114 could also execute applications that control the operation of the controllers 106 , thereby controlling the operation of the actuators 102 b . In addition, the machine-level controllers 114 could provide secure access to the controllers 106 . Each of the machine-level controllers 114 includes any suitable structure for providing access to, control of, or operations related to a machine or other individual piece of equipment. Each of the machine-level controllers 114 could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. Although not shown, different machine-level controllers 114 could be used to control different pieces of equipment in a process system (where each piece of equipment is associated with one or more controllers 106 , sensors 102 a , and actuators 102 b ). [0021] One or more operator stations 116 are coupled to the networks 112 . The operator stations 116 represent computing or communication devices providing user access to the machine-level controllers 114 , which could then provide user access to the controllers 106 (and possibly the sensors 102 a and actuators 102 b ). As particular examples, the operator stations 116 could allow users to review the operational history of the sensors 102 a and actuators 102 b using information collected by the controllers 106 and/or the machine-level controllers 114 . The operator stations 116 could also allow the users to adjust the operation of the sensors 102 a , actuators 102 b , controllers 106 , or machine-level controllers 114 . In addition, the operator stations 116 could receive and display warnings, alerts, or other messages or displays generated by the controllers 106 or the machine-level controllers 114 . Each of the operator stations 116 includes any suitable structure for supporting user access and control of one or more components in the system 100 . Each of the operator stations 116 could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. [0022] At least one router/firewall 118 couples the networks 112 to two networks 120 . The router/firewall 118 includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The networks 120 could represent any suitable networks, such as a pair of Ethernet networks or an FTE network. [0023] In the Purdue model, “Level 3” may include one or more unit-level controllers 122 coupled to the networks 120 . Each unit-level controller 122 is typically associated with a unit in a process system, which represents a collection of different machines operating together to implement at least part of a process. The unit-level controllers 122 perform various functions to support the operation and control of components in the lower levels. For example, the unit-level controllers 122 could log information collected or generated by the components in the lower levels, execute applications that control the components in the lower levels, and provide secure access to the components in the lower levels. Each of the unit-level controllers 122 includes any suitable structure for providing access to, control of, or operations related to one or more machines or other pieces of equipment in a process unit. Each of the unit-level controllers 122 could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. Although not shown, different unit-level controllers 122 could be used to control different units in a process system (where each unit is associated with one or more machine-level controllers 114 , controllers 106 , sensors 102 a , and actuators 102 b ). [0024] Access to the unit-level controllers 122 may be provided by one or more operator stations 124 . Each of the operator stations 124 includes any suitable structure for supporting user access and control of one or more components in the system 100 . Each of the operator stations 124 could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. [0025] At least one router/firewall 126 couples the networks 120 to two networks 128 . The router/firewall 126 includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The networks 128 could represent any suitable networks, such as a pair of Ethernet networks or an FTE network. [0026] In the Purdue model, “Level 4” may include one or more plant-level controllers 130 coupled to the networks 128 . Each plant-level controller 130 is typically associated with one of the plants 101 a - 101 n , which may include one or more process units that implement the same, similar, or different processes. The plant-level controllers 130 perform various functions to support the operation and control of components in the lower levels. As particular examples, the plant-level controller 130 could execute one or more manufacturing execution system (IVIES) applications, scheduling applications, or other or additional plant or process control applications. Each of the plant-level controllers 130 includes any suitable structure for providing access to, control of, or operations related to one or more process units in a process plant. Each of the plant-level controllers 130 could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. [0027] Access to the plant-level controllers 130 may be provided by one or more operator stations 132 . Each of the operator stations 132 includes any suitable structure for supporting user access and control of one or more components in the system 100 . Each of the operator stations 132 could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. [0028] At least one router/firewall 134 couples the networks 128 to one or more networks 136 . The router/firewall 134 includes any suitable structure for providing communication between networks, such as a secure router or combination router/firewall. The network 136 could represent any suitable network, such as an enterprise-wide Ethernet or other network or all or a portion of a larger network (such as the Internet). [0029] In the Purdue model, “Level 5” may include one or more enterprise-level controllers 138 coupled to the network 136 . Each enterprise-level controller 138 is typically able to perform planning operations for multiple plants 101 a - 101 n and to control various aspects of the plants 101 a - 101 n . The enterprise-level controllers 138 can also perform various functions to support the operation and control of components in the plants 101 a - 101 n . As particular examples, the enterprise-level controller 138 could execute one or more order processing applications, enterprise resource planning (ERP) applications, advanced planning and scheduling (APS) applications, or any other or additional enterprise control applications. Each of the enterprise-level controllers 138 includes any suitable structure for providing access to, control of, or operations related to the control of one or more plants. Each of the enterprise-level controllers 138 could, for example, represent a server computing device running a MICROSOFT WINDOWS operating system. In this document, the term “enterprise” refers to an organization having one or more plants or other processing facilities to be managed. Note that if a single plant 101 a is to be managed, the functionality of the enterprise-level controller 138 could be incorporated into the plant-level controller 130 . [0030] Access to the enterprise-level controllers 138 may be provided by one or more operator stations 140 . Each of the operator stations 140 includes any suitable structure for supporting user access and control of one or more components in the system 100 . Each of the operator stations 140 could, for example, represent a computing device running a MICROSOFT WINDOWS operating system. [0031] Various levels of the Purdue model can include other components, such as one or more databases. The database(s) associated with each level could store any suitable information associated with that level or one or more other levels of the system 100 . For example, a historian 141 can be coupled to the network 136 . The historian 141 could represent a component that stores various information about the system 100 . The historian 141 could, for instance, store information used during production scheduling and optimization. The historian 141 represents any suitable structure for storing and facilitating retrieval of information. Although shown as a single centralized component coupled to the network 136 , the historian 141 could be located elsewhere in the system 100 , or multiple historians could be distributed in different locations in the system 100 . [0032] In particular embodiments, the various controllers and operator stations in FIG. 1 may represent computing devices. For example, each of the controllers could include one or more processing devices 142 and one or more memories 144 for storing instructions and data used, generated, or collected by the processing device(s) 142 . Each of the controllers could also include at least one network interface 146 , such as one or more Ethernet interfaces or wireless transceivers. Also, each of the operator stations could include one or more processing devices 148 and one or more memories 150 for storing instructions and data used, generated, or collected by the processing device(s) 148 . Each of the operator stations could also include at least one network interface 152 , such as one or more Ethernet interfaces or wireless transceivers. [0033] Although FIG. 1 illustrates one example of an industrial process control and automation system 100 , various changes may be made to FIG. 1 . For example, a control and automation system could include any number of sensors, actuators, controllers, operator stations, networks, servers, communication devices, and other components. In addition, the makeup and arrangement of the system 100 in FIG. 1 is for illustration only. Components could be added, omitted, combined, further subdivided, or placed in any other suitable configuration according to particular needs. Further, particular functions have been described as being performed by particular components of the system 100 . This is for illustration only. In general, control and automation systems are highly configurable and can be configured in any suitable manner according to particular needs. In addition, FIG. 1 illustrates an example environment in which information related to an industrial process control and automation system can be transmitted to a remote server. This functionality can be used in any other suitable system. [0034] FIG. 2 illustrates an example device 200 for managing recordation of changes in a smart device according to this disclosure. The device 200 could represent, for example, the field device 102 , enterprise controller 138 , operator station 140 , or a local or remote server in the system 100 of FIG. 1 . However, the device 200 could be used in any other suitable system. [0035] As shown in FIG. 2 , the device 200 includes a bus system 202 , which supports communication between at least one processing device 204 , at least one storage device 206 , at least one communications unit 208 , and at least one input/output (I/O) unit 210 . The processing device 204 executes instructions that may be loaded into a memory 212 . The processing device 204 may include any suitable number(s) and type(s) of processors or other devices in any suitable arrangement. Example types of processing devices 204 include microprocessors, microcontrollers, digital signal processors, field programmable gate arrays, application specific integrated circuits, and discrete circuitry. [0036] The memory 212 and a persistent storage 214 are examples of storage devices 206 , which represent any structure(s) capable of storing and facilitating retrieval of information (such as data, program code, and/or other suitable information on a temporary or permanent basis). The memory 212 may represent a random access memory or any other suitable volatile or non-volatile storage device(s). The persistent storage 214 may contain one or more components or devices supporting longer-term storage of data, such as a ready only memory, hard drive, Flash memory, or optical disc. [0037] The communications unit 208 supports communications with other systems or devices. For example, the communications unit 208 could include a network interface that facilitates communications over at least one Ethernet, HART, FOUNDATION FIELDBUS, cellular, Wi-Fi, universal asynchronous receiver/transmitter (UART), serial peripheral interface (SPI) or other network. The communications unit 208 could also include a wireless transceiver facilitating communications over at least one wireless network. The communications unit 208 may support communications through any suitable physical or wireless communication link(s). The communications unit 208 may support communications through multiple different interfaces, or may be representative of multiple communication units with the ability to communication through multiple interfaces. [0038] The I/O unit 210 allows for input and output of data. For example, the I/O unit 210 may provide a connection for user input through a keyboard, mouse, keypad, touchscreen, or other suitable input device. The I/O unit 210 may also send output to a display, printer, or other suitable output device. [0039] The device 200 could execute instructions used to perform any of the functions associated with the components of FIG. 1 . For example, the device 200 could execute instructions that retrieve and upload information to and from a transmitter or field device. The device 200 could also store user databases. [0040] Although FIG. 2 illustrates one example of a device 200 , various changes may be made to FIG. 2 . For example, components could be added, omitted, combined, further subdivided, or placed in any other suitable configuration according to particular needs. Also, computing devices can come in a wide variety of configurations, and FIG. 2 does not limit this disclosure to any particular configuration of computing device. [0041] One or more embodiments of this disclosure recognize and take into account that currently an operator chooses an appropriate master golden record (MGR) based on a current plant mode for a smart device. The operator can compare a current online configuration of the smart device with the above selected MGR either manually or by using any compare configuration tools if any provided by existing asset management systems. The operator is able to use personal best knowledge or consult an appropriate guide to determine if any configuration has changed, generate a report manually, and archive the report. The operator may repeat the process for all other smart devices for which reporting is required. Generating a report for a single smart device can take significant amount of time. For a plant where the number of smart devices can be thousands, the approximate manual effort for generating reports for all smart devices would consume many more thousands of man-hours. [0042] One or more embodiments of this disclosure provides an industrial automation system and an automated procedure to periodically compare the current online configuration parameter values of one or more smart devices with its respective MGR in the current running plant modes. The solution does so in defined schedule, notifies the status of execution to the user and generates report. Report will be archived for future retrieval. The solutions also audit trails all the user actions for future audits. [0043] FIG. 3 illustrates an example block diagram of a configuration management system 300 according to this disclosure. For ease of explanation, the system 300 is described as being supported by the industrial process control and automation system 100 of FIG. 1 . However, the system 300 could be supported by any other suitable system. The system 300 can be implemented in a device, such as device 200 as shown in FIG. 2 . [0044] In FIG. 3 , system 300 includes master golden record (MGR) manager 302 , schedule manager 304 , mode manager 306 , configuration comparer 308 , report archiver 310 , report generator 312 , audit trail 314 , configuration database 316 , and communication sub-system 318 . The system 300 can communicate with different smart devices, such as components on FIG. 1 , through the communication sub-system 318 . One or more of the components 302 - 318 used herein can be implemented as part of processing circuitry, instructions on a non-transitory computer readable medium, as a processor, and the like. [0045] In one or more embodiments herein, a smart device can be a field device used in a process control system supporting protocols such as HART, Wireless HART, Foundation Fieldbus, Modbus, IEC 61850, EthernetIP, ISA100, Profibus DP, PA, Profinet, etc. In different embodiments of this disclosure, the smart devices can represent, or be represented by, any of the components 102 - 134 as shown in FIG. 1 . As discussed herein, one or more of the embodiments of this disclosure can be used in any electrical monitoring and control system as well as any process control system. Additionally, the embodiments herein can be in non-safety as well as safety devices. [0046] In an embodiment of this disclosure, the MGR manager 302 is configured to allow a user 301 to create, retrieve, update, and delete the MGR for one or more smart devices. The MGR can be the project engineering configuration parameter with values of any smart device for a given mode. Other terms used for MGR are reference record, golden record, or golden reference record etc. Any history or offline record can be marked as a MGR. the user 301 may define multiple groups of devices that can be verified against a golden record. For batch comparisons, a specific group of devices can be selected each time. In different embodiments, a golden record can be created from a live device. [0047] In different embodiments, a golden record can be a single, well-defined version of all the data entities in an organizational ecosystem. In this context, a golden record is sometimes called the “single version of the truth,” where “truth” is understood to mean the reference to which data users can turn when they want to ensure that they have the correct version of a piece of information. The golden record encompasses all the data in every system of record (SOR) within a particular organization. A SOR is an information storage and retrieval system (ISRS) that serves as the authoritative source for a particular data element in an industrial automation system containing multiple sources of the same element. To ensure data integrity, a single SOR must always exist for each and every data element. [0048] In one or more embodiments herein, a history record is the snapshot of the parameter values of any smart device taken at a given point of interest. The history record can be the same as taking a backup of the parameter values from an online smart device. For example, the backup can be a snapshot taken after commissioning of the smart device, after factory acceptance test, and the like. Other terms used for history record are device snapshot, and the like. The user can optionally select all configuration parameters or few. In another embodiment, the user or system can mark an existing history record as the MGR. In yet another embodiment, the user or system can mark an existing offline record as the MGR. In one or more embodiments herein, an offline record can be the configuration parameters stored in configuration database 316 that is prepopulated either manually or from a connected smart device. The MGR manager 302 can provide an option to the user to view, update, and delete any MGR. The MGR manager 302 can also map any MGR to a mode. [0049] In one or more embodiments of this disclosure, the MGR is set at a time of commissioning. In different embodiments of this disclosure, the MGR can be set after commissioning. In some example embodiments, after setting, the MGR can be modified, such as by use of a proper management of change procedure. [0050] The schedule manager 304 is configured to provide an option to the user 301 to schedule a one time or periodic (daily, weekly, monthly, etc.) configuration comparison mechanism for one or more smart devices. The schedule manager 304 can also allow the user 301 to retrieve, update and delete schedules 305 . [0051] The MGR can be compared to the live online configuration parameter values of any smart device by executing the comparison now, or by scheduling the comparison. For executing now, the schedule manager 304 provides an option to the user to compare online configuration parameter values of a smart device with a MGR. For scheduling, the schedule manager 304 provides an option to create either a one time or recurring schedule for automatic/semiautomatic comparison of online configuration parameter values of a smart device with the MGR. [0052] For an automatic schedule, the schedule manager 304 compares online configuration parameter values of a smart device with the MGR automatically without any user input and archiving the report. For a semiautomatic schedule, the schedule manager 304 compares an online configuration parameter values of a smart device with a MGR post user confirmation via any detectable means such as user interface prompting the user for confirmation or via voice confirmation or via any electronically detectable means like by sending authorization via SMS to a pre defined number, by sending authorization via email to a pre defined E-Mail ID, or the like. [0053] In one or more embodiments, the schedule manager 304 can provide an option to the user to view, update, and delete any schedule. The schedule manager 304 can also provide the user with an option for configuring a reminder for any schedule. The schedule manager 304 can also provide an option to the user for cancelling the occurrence of a schedule or to “snooze” the occurrence to some future time. [0054] The mode manager 306 is configured to provide an option to set the current active modes 307 of the plant. Active mode 307 can be a current mode being used in the plant for an industrial process control and automation system. The mode manager 306 can synchronize the current active modes from the existing distributed control system (DCS), supervisory control and data acquisition (SCADA) system, or programming logic controller (PLC) system automatically or by providing explicit means to update the systems. The mode manager 306 can also allow the 301 to create, retrieve, update and delete modes. In one or more embodiments herein, a mode refers to different production modes of the plant. Difference production modes can be applied to continuous or batch plants, where a startup or high production mode might require different instrumentation settings. Different instrumentation settings can be used in a batch plant where on a particular production line multiple products can be produced. Depending on the product being produced, different product properties may cause different instrument settings to be used. [0055] In different embodiments, multiple golden records can be provided for each device depending on the operational mode of the plant. This type of system can be useful for batch plants or semi-continuous plants that are frequently reconfigured. For example, if there is a soup production line, each device could have one golden record for each device when producing “chicken soup” and another golden record when producing “vegetable soup.” The golden records can be swapped when switching production line items. [0056] In one or more embodiments, the mode manager 306 provides the user with an option to create, retrieve, update and delete modes. The mode manager 306 can sync the modes from DCS, SCADA, or PLC systems automatically or user triggered. The mode manager 306 can set one or more active modes, i.e. the current operating modes of the plant. Setting the modes can involve syncing active modes from DCS, SCADA, or PLC systems. [0057] The MGR manager 302 , schedule manager 304 , and mode manager 306 can all be accessed by the user 301 to modify an MGR, schedule a comparison 309 , or modify a mode of the plant. All of the actions performed with these managers 302 , 304 , 306 can be recorded by an audit trail subsystem 314 . [0058] The configuration comparer 308 is configured to compare the current smart device configuration with a given MGR. The schedule manager 304 can initiate the configuration comparer 308 to begin a comparison 309 . The comparison 309 can provide an identification of added, deleted, or changed parameters or configurations of the smart device. To perform the comparison 309 , the configuration comparer 308 is configured to access the different smart devices through the communication sub-system 318 and compare the current configurations to the MGRs accessed from the configuration database 316 . [0059] In one or more embodiments, the configuration comparer 308 can compare the current smart device configuration parameter values with that of a mapped MGR in the current active mode. The configuration comparer 308 can also identify configuration parameters and comparing only those parameter values while ignoring all other non-configuration parameters. For example, Lower Range Value (LRV) and Upper Range Value (URV) can be configuration parameters while Primary value (PV) can be a non-configuration parameter. The configuration comparer 308 can notify the user about the progress and status of the current execution. The configuration comparer 308 can also allow the user to cancel the current execution. In different embodiments, the configuration comparer 308 can compare the configuration parameter values for multiple smart devices with their respective MGR either sequentially or in parallel. The configuration comparer 308 can be triggered either manually, automatically by the scheduler, or upon authorization from user. [0060] The report generator 312 is configured to generate reports 313 citing differences as reported by the configuration comparer 308 . The reports can be presented in different formats. The report can include or exclude different parameters of the smart devices. For example, in one report, all parameters can be included. In other reports, a subset of parameters can be included. The report generator 312 can retrieve the comparison result from execution and prepare a report in the user or system-configured format. The report generator 312 can report the following data (but not limited to): a summary of the overall execution such as how many smart device comparison have failed or passed; a number of smart devices for which a comparison couldn't be performed, the devices are cancelled, or the devices encountered some issues during execution; and the exact configuration parameters that have changed from their respective MGR values. The report generator 312 can provide an option to the user to view, delete any report. The report generator 312 can also provide an option to print or export to file system in any human readable format such as (but not limited to) PDF, HTML, CSV, DOC, XLS, XPS and the like. [0061] The report archiver 310 is configured to archive the report generated by the report generator 312 and provides means for future retrieval. The report archiver 310 can be a database, either local or remote. [0062] The audit trail subsystem 314 is configured to log all user actions with appropriate user, action, and timestamp details. The audit trail subsystem 314 also provides a mechanism to view, modify, and delete these audit trails. The audit trail subsystem 314 audits all user actions such as creating, updating, and deleting of MGRs, modes, or schedules. The audit trail subsystem 314 retrieves audit trail details as required, exports audit trail records to a human readable format, and logs user info, actions performed, time stamp, and any comments. The audit trail subsystem 314 can also provide an option to the user to print audit trail records. [0063] The configuration database 316 can be a database containing the MGRs 317 for each smart device per specific mode. Each of the MGRs can include one or more parameters or values for the one or more parameters for different smart devices. In one or more embodiments herein, a database is a repository for storing and retrieving the required data. The configuration database 316 could be a file system based repository, an RDBMS, a cloud based repository, or the like. Each MGR 317 includes different parameter values 319 for the smart devices. The parameter values can be the settings and configurations for the smart device for each mode of the system. [0064] The communication subsystem 318 is configured to provide communication with the smart devices. [0065] One or more embodiments provides for golden record management by the MGR manager 302 . Golden record management involves a creation of a history record from live online smart device configuration parameters (i.e., the parameters of the devices currently in use) and saving those parameters as the MGR. The MGR alternatively can also be created from offline dataset of the smart device. [0066] FIG. 4 illustrates an example master golden record management process 400 according to this disclosure. The golden record management process 400 provides for scheduling of a comparison of a MGR with device parameters. Process 400 can be executed within system 300 of FIG. 3 and/or by device 200 of FIG. 2 . [0067] At operation 405 , a processor receives a user selection of a MGR for each smart device. In different embodiments, the selection can be a batch selection for multiple smart devices. In various embodiments of this disclosure, operation 405 is only performed one time. The same MGR will then be used by the comparer every time a schedule elapses. In further embodiments, the MGR can be chosen on different occasions. [0068] At operation 410 , a processor can receive a user setting of a current active mode of a plant. The mode can be based on a product, or a version of a production under production. [0069] At operation 415 , a processor receives a new schedule from a user that is created for one or more smart devices. The schedule can set when the comparison is performed. At operation 420 , the processor can control a scheduler manager to run a schedule based on the defined schedule. [0070] At operation 425 , the processor can control a scheduler manager to trigger a configuration parameter comparison when the scheduled time elapses. While the schedule is running, different scheduled times may elapse and trigger different comparisons. At operation 430 , the processor can compare current online configuration parameter values with a MGR and generate any differences of parameters. The current configuration parameter values can be current parameter settings and configurations being used during current production. [0071] At operation 435 , the processor can configure a comparer triggers report with differences to use when generating a report. At this operation, the report to be generated can be configured with which differences are to be reported. At operation 440 , the processor controls a report generator to generate reports according to the pre-configured format and also trigger a report archiver. [0072] At operation 445 , the processor controls a report archiver to archive the report for future retrieval. At operation 450 , the processor determines if all of the smart devices are done. In an embodiment, the processor determines if all smart devices that are scheduled have been compared to the MGRs. If all of the smart devices are not done, the processor moves to operation 430 with another smart device. If all of the smart devices are done, then the processor, at operation 455 , controls the scheduler manager to wait for the next schedule. [0073] At operation 460 , the processor determines if there is a next schedule available. If no other schedules are available at that time, then the processor controls the scheduling manager to wait for the next schedule at operation 455 . If there is a next schedule available, then the process moves to operation 430 for the device triggered by the schedule. [0074] As discussed herein, one or more steps can be performed by a processor or different components controlled by the processor. However, the processor can directly perform the steps performed by components controlled by the processor. [0075] Although FIG. 4 illustrates one example of a process 400 scheduling of a comparison of a MGR with device parameters in an industrial process control and automation system, various changes may be made to FIG. 4 . For example, while FIG. 4 shows a series of steps, various steps could overlap, occur in parallel, occur in a different order, or occur any number of times. In addition, the process 400 could include any number of events, event information retrievals, and notifications. [0076] In some embodiments, various functions described above are implemented or supported by a computer program that is formed from computer readable program code and that is embodied in a computer readable medium. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device. [0077] It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer code (including source code, object code, or executable code). The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. [0078] While this disclosure has described certain embodiments and generally associated methods, alterations and permutations of these embodiments and methods will be apparent to those skilled in the art. Accordingly, the above description of example embodiments does not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure, as defined by the following claims.

A method is provided for comparing a master gold record with a live device in an industrial automation system. The method includes receiving a master golden record for a device of a plurality of devices in the industrial automation system. The master golden record includes one or more parameter values for the device for a mode of the industrial automation system. The method also includes identifying an active mode for the industrial automation system. The method also includes responsive to a triggering of a comparison, comparing current parameter values of the device with the one or more parameter values of the master golden record for the active mode. The method also includes generating a report comprising differences between the one or more parameters values of the master golden record and the current parameter values of the device.

FIELD OF THE INVENTION [0001] The present invention relates to a process for manufacturing a gas sensor including a detecting element having an electrode of a precious metal formed on the surface of a solid electrolyte. BACKGROUND OF THE INVENTION [0002] In the conventional art, there has been developed an oxygen sensor, which is provided with a detecting element having a detecting electrode and a reference electrode of platinum acting as an oxidation promoting catalyst formed on the outer wall and inner wall of a solid electrolyte (as will be called the “substrate”) of a cylindrical shape having one end closed, so that it may detect an oxygen concentration on the principle of an oxygen concentration cell. This oxygen sensor is attached to the internal combustion engine of an automobile or the like so that it may be used for grasping the combustion state (or the A/F ratio) of the internal combustion engine. [0003] Here, the detecting electrode of the detecting element in that oxygen sensor is formed through a nucleus depositing step of depositing the nuclei of platinum on the surface of the substrate and an electroless plating step of growing the deposited nuclei by an electrolessly plating method or an electrically plating method (as referred to JP-B-62-56978 (the term “JP-B” as used herein means an “examined Japanese patent publication”), for example). [0004] First of all, at the nucleus depositing step (corresponding to the active point forming electrolessly plating step in JP-B-62-56978), the nuclei of platinum are deposited on the outer wall of the substrate by dipping the substrate in a container containing an aqueous solution of platinic ammine and by adding to this aqueous solution a reducer of sodium boron hydride (SBH) having a high reducing power. At this nucleus depositing step, however, at the time of dipping the substrate in the aqueous solution of platinic ammine, the portion of the outer wall of the substrate other than the desired one is coated with masking rubber so that the nuclei may not be deposited on the undesired portion. [0005] At the end of the nucleus depositing step, moreover, the substrate is taken out from the container, and the masking rubber is removed. The substrate is rinsed to clear the outer wall of the substrate of the platinic ammine and the sodium boron hydride, and the process transfers to the nucleus growing step. [0006] At the nucleus growing step (corresponding to the thin film electrolessly plating step and the thick film electric plating step in JP-B-62-56978 (pp. 3 to 4, FIG. 2)), like the nucleus depositing step, the substrate is dipped in the container containing the aqueous solution of platinic ammine, and a reducer of hydrazine having a weaker reducing power is added to that aqueous solution so that the nuclei deposited on the outer wall of the substrate may be gently grown to form the detecting electrode on the outer wall of the substrate. Here, at the nucleus growing step, the substrate is dipped in the plating liquid without being coated with the masking rubber. SUMMARY OF THE INVENTION [0007] Here, the oxygen sensor manufactured by the aforementioned manufacturing process has a problem that the detecting electrode of the detecting element fails to act sufficiently as the oxidation promoting catalyst thereby to cause a loss in the responding performances. [0008] In the aforementioned detecting electrode, more specifically, the crystals of platinum after the nucleus growing step become coarse due to the large size of the nuclei deposited at the nucleus depositing step. Therefore, the number of intergranules of the platinum crystals is so small that the surface area (i.e., the surface area to act as the oxidation promotion catalyst) to contact with the exhaust gas is accordingly reduced. [0009] As a result, it takes a long time for the oxygen existing in the vicinity of the detecting electrode to combine with the unburned contents (e.g., hydrocarbons or carbon monoxide) in the exhaust gas thereby to equilibrate the exhaust gas. Therefore, a delay occurs in the responsibility. [0010] In the aforementioned manufacturing process, moreover, the sizes of the nuclei to be deposited become heterogeneous. Therefore, the thickness of the detecting electrode does not become uniform to cause a problem that the durable performances of the oxygen sensor are lost. In other words, the thinner portion of the detecting electrode sublimates earlier than the thicker portion. [0011] In the aforementioned manufacturing process, moreover, the plating liquid flows in from the clearance, if formed between the masking rubber and the outer wall of the substrate, so that the nuclei are deposited on the portion other than the desired one. Therefore, a problem is that cares have to be troublesomely taken on the mounting of the masking rubber. [0012] In order to solve the above-specified problems, therefore, the invention has an object to provide a process for manufacturing a gas sensor, which is excellent in responding performances and durable performances and which can form an electrode easily. [0013] In order to achieve the above-specified object, according to the invention, a process for manufacturing a gas sensor including a detecting element having an electrode of a precious metal formed on the surface of a solid electrolyte, comprising: a first step of applying the nuclei of a precious metal having a catalyzing action on a gas to be measured; and a second step of growing said nuclei, wherein said first step uses a physical vapor deposition (PVD) method. [0014] According to this gas sensor manufacturing process, the nuclei having the size of an atomic or molecular level can be applied to the surface of the solid electrolyte so that the crystals of the precious metal making the electrode can be made minute after the second step. In the gas sensor manufactured according to the invention, more specifically, the electrode of the detecting element has a number of intergranules of the crystals of the precious metal so that it has an accordingly larger surface area (i.e., a surface area to act as a catalyst) of the electrode to contact with the gas to be measured. In other words, the catalyzing action of the electrode can be improved by the invention thereby to provide a gas sensor having more excellent responding performances than those of the prior art. [0015] According to the invention, moreover, the sizes of the nuclei are individually homogenized so that the electrode to be formed can have a uniform thickness. Therefore, it is possible to provide a gas sensor, which is more excellent durable performances than those of the prior art. [0016] According to the invention, moreover, when the precious metal is to be deposited on the surface of the solid electrolyte, the evaporation of the precious metal can be prevented merely by arranging at least one of shielding plate and a shielding cover at a portion other than that to form an electrode. Therefore, the gas sensor can be troublelessly manufactured. By arranging at least one of the shielding plate and the shielding cover, moreover, an electrode of a desired shape can be easily formed on the surface of the solid electrolyte. [0017] Here, the physical deposition method is preferably exemplified by the sputtering method. In this case, even if the precious metal has a high melting point, the nuclei of the precious metal having a catalyzing action can be easily deposited on the surface of the solid electrolyte. [0018] Moreover, the sputtering is preferably done under a pressure of 5 to 10 Pa. This range may be defined because the residual gas to be ionized may fail to exist sufficiently for a pressure lower than 5 Pa whereas the glow discharge may not be done for a pressure higher than 10 Pa. But, the pressure range is variable due to a condition of a deposition apparatus, and therefore, the range is not essential for the invention. [0019] And, the second step is preferably exemplified by the electrolessly plating method. [0020] By using the electrolessly plating method, more specifically, the precious metal can be homogeneously deposited on the surface of the solid electrolyte. If the electroless plating is done by using the reducer having such a reducing power that the precious metal is not deposited on the portion other than that, to which the nuclei are applied, the nuclei can be homogeneously grown without depositing the precious metal at the portion other than that having the nuclei applied thereto. In other words, it is possible to form an electrode of a uniform thickness on the surface of the solid electrolyte. [0021] Here, the plating liquid of the process of the prior art can be used if it satisfies the condition that the precious metal is not deposited on the portion other that, to which the nuclei are applied. In other words, it is possible to use such an aqueous solution of complex salt of platinum and a reducer as satisfy the above-specified condition. If an aqueous solution of platonic (IV) ammine or an aqueous solution of platinous (II) ammine is used as said aqueous solution of complex salt of platinum, and wherein hydrazine is used as said reducer, more specifically, the deposition rate can be optimized to satisfy the condition that the precious metal is not deposited on the portion other than that, to which the nuclei are applied. [0022] If the plating is done by leaving the substrate, to which the nuclei of the precious metal were applied, to stand while being rocked in an electrolessly plating liquid, moreover, it is more effective to form the electrode having the uniform thickness. BRIEF DESCRIPTION OF THE DRAWINGS [0023] [0023]FIG. 1 is a sectional view showing the entire construction of an oxygen sensor 1 of a first embodiment; [0024] [0024]FIG. 2 is a lefthand side elevation of a detecting element 2 in FIG. 1; [0025] [0025]FIG. 3 is a righthand side elevation of a detecting element 2 in FIG. 1; [0026] [0026]FIG. 4 is a conceptional diagram schematically showing a nucleus applying step in the manufacture of the detecting element 2 ; [0027] [0027]FIG. 5 is a top plan view showing the exterior of a detecting element 70 to be used in an oxygen sensor of a second embodiment; [0028] [0028]FIG. 6 is a top plan view of the detecting element 70 on the back side of FIG. 5; [0029] [0029]FIG. 7 is a waveform diagram of the output of an oxygen sensor 1 , as recorded just after an electric power was supplied to the heater of the oxygen sensor of Example 1; [0030] [0030]FIG. 8 is a waveform diagram of the output of an oxygen sensor 1 , as recorded just after an electric power was supplied to the heater of the oxygen sensor of Example 2; [0031] [0031]FIG. 9 is a waveform diagram of the output of an oxygen sensor 1 , as recorded just after an electric power was supplied to the heater of the oxygen sensor of Comparison 1 ; [0032] [0032]FIG. 10 is a waveform diagram of the output of the oxygen sensor of Example 1 against the change in an A/F ratio control signal; [0033] [0033]FIG. 11 is a waveform diagram of the output of the oxygen sensor of Example 2 against the change in an A/F ratio control signal; [0034] [0034]FIG. 12 is a waveform diagram of the output of the oxygen sensor of Comparison 1 against the change in an A/F ratio control signal; [0035] [0035]FIG. 13 is a schematic diagram showing a modification of the nucleus applying step in Embodiments 1 and 2; and [0036] [0036]FIG. 14 is a schematic diagram showing a modification of the nucleus applying step in Embodiments 1 and 2. DETAILED DESCRIPTION OF THE INVENTION [0037] Embodiments of the invention will be described in the following with reference to the accompanying drawings. First Embodiment [0038] First of all, FIG. 1 is a sectional diagram showing the entire construction of an oxygen sensor, which is manufactured by applying the invention thereto. [0039] As shown in FIG. 1, an oxygen sensor 1 is constructed to include: a detecting element 2 made of a cylindrical substrate 20 composed mainly of zirconia and having one end closed; a rod-shaped ceramic heater (as will be shortly called the “heater”) 3 arranged in the detecting element 2 ; a casing for housing those detecting element 2 and heater 3 ; and a cylindrical protector 5 mounted on the lower end portion of the casing 4 for covering such a bottom portion (i.e., the closed one end) of the detecting element 2 as is protruded from the lower end portion of the casing 4 . [0040] Here, the casing 4 is constructed to include: a main fixture 40 for fixing the detecting element 2 in the casing 4 with annular ceramic holders 6 and 7 and ceramic powder 8 housed therein, and for fixing the oxygen sensor 1 on the exhaust pipe or the like of an internal combustion engine; and a cylindrical outer tube 41 extending upward of the main fixture 40 for introducing the atmosphere downward into the detecting element 2 . [0041] On the inner wall and outer wall of the upper end portion of the detecting element 2 , respectively, there are mounted terminal fixtures 50 and 51 for extracting an electromotive force from the detecting element 2 . With these terminal fixtures 50 and 51 , respectively, through lead wires 52 and 53 , there are connected connecting terminals 54 and 55 , which are protruded from the upper end portions of the outer tube 41 . With the upper end portion of the heater 3 , moreover, there is connected a connecting terminal 31 , which is protruded from the upper end portion of the outer tube 41 . Here, the heater 3 is fixed by the terminal fixture 51 in the detecting element 2 and is brought, by the leftward pushing force from the terminal fixture 51 , into contact with the inner circumference wall of the portion extending from the axially central portion to the bottom portion of the detecting element 2 . [0042] On the upper end portion of the outer tube 41 , moreover, there is caulked a cylindrical protecting outer tube 46 . This outer tube 46 is provided with: signal wires 42 and 43 for extracting the electromotive force generated by the detecting element 2 ; power lines (although not shown) for supplying the electric force to the heater 3 ; female terminals 44 and 45 for connecting the signal wires 42 and 43 and the connecting terminals 54 and 55 ; and female terminals (although not shown) for connecting the power lines and the connecting terminal 31 . The electromotive force of the detecting element 2 is extracted to the outside, and the electric power is supplied from the outside to the heater 3 . [0043] Here, FIG. 2 is a lefthand side elevation of the detecting element 2 in FIG. 1, and FIG. 3 is a righthand side elevation of a detecting element 2 in FIG. 1. [0044] As shown in FIGS. 2 and 3, the detecting element 2 is formed by covering the outer wall of such a portion L 1 with a detecting electrode 26 of platinum while making one round of the outer circumference of the substrate 20 , as extends from the leading end of the bottom portion and to the vicinity of the axially central portion of the substrate 20 . Here, this detecting electrode 26 is coated on its surface with powder of spinel (MgAl 2 O 4 ) (although not shown), thereby to protect the detecting electrode 26 against the heat of the exhaust gas. [0045] On the outer wall in the vicinity of the upper end portion of the substrate 20 , moreover, there is formed a band-shaped terminal connecting portion 28 , which makes one round of the outer circumference of the substrate 20 , thereby to connect the terminal fixture 50 . [0046] Between the detecting electrode 26 and the terminal connecting portion 28 , on the other hand, there is formed along the axial direction of the substrate 20 one long lead portion 27 , which has a sufficiently narrower width W 1 than that of the detecting electrode 26 and through which the detecting electrode 26 and the terminal connecting portion 28 are electrically connected. [0047] All over the inner wall of the substrate 20 , there is formed a reference electrode (although not shown), which is made of platinum like that of the detecting electrode 26 . [0048] A process for manufacturing the detecting element 2 will be described in detail in the following. [0049] At first, the substrate 20 is prepared by pressing a solid electrolyte composed mainly of zirconia into a cylindrical shape having one end closed, and then by sintering the cylindrical shape by exposing it to the atmosphere of 1,500° C. for 2 hours. At the sintering time, a platinum paste is printed in advance on the portions to form the lead portion 27 and the terminal connecting portion 28 , and these lead portion 27 and terminal connecting portion 28 are formed at the time of sintering the solid electrolyte. [0050] Next, the detecting electrode 26 is formed on the prepared substrate 20 . [0051] In order to form the detecting electrode 26 , a nucleus applying step of depositing the nucleus of platinum on the outer wall of the portion L 1 of the substrate 20 is performed by using Ion Coater of IB-3 manufactured by Eikoh Kabushiki Gaisha. Here, the Ion Coater is an apparatus for ionizing the residual gas (or air) by making a glow discharge in a low vacuum region (at 5 to 10 Pa) and for sputtering the atoms or molecules composing a target (i.e., platinum foil) by causing the ions of the residual gas to collide against the target. [0052] Here, FIG. 4 is a conceptional diagram schematically showing the nucleus applying step. [0053] At the nucleus applying step, as shown in FIG. 4, a support rod 81 is inserted at first into the substrate 20 to support the substrate 20 in parallel with the plane of a positive electrode 82 in an ion coater 80 . Subsequently, a shielding plate 85 is so arranged between the substrate 20 and a platinum foil (i.e., target) 84 disposed on a negative electrode 83 of the ion coater 80 as to cover only that portion (i.e., the portion above the portion L 1 in FIGS. 2 and 3) in the substrate 20 , on which the detecting electrode 26 is not formed. [0054] After the pressure of the residual gas in the ion coater 80 was set at about 8 Pa, a voltage is so applied for 5 minutes between the positive electrode 82 and the negative electrode 83 of the ion coater 80 as to make a current value of about 6 mA, so that ions 86 of the residual gas may collide against the platinum foil 84 to deposit nuclei 87 of the platinum atoms, as hit from the platinum foil 84 , on the substrate 20 . In order to deposit the platinum nuclei on the whole portion L 1 of the substrate 20 , however, the substrate 20 is turned for each deposition by 120 degrees on the support rod 81 , and this turn is repeated totally three times. [0055] When the nucleus applying step is thus ended, the manufacturing process transfers to a nucleus growing step of growing the nuclei, as deposited on the substrate 20 , by an electrolessly plating method. [0056] At this nucleus growing step, the substrate 20 is heated at first while being dipped in an aqueous solution of complex salt of platinum. Next, an aqueous solution of hydrazine (in concentration: 85 wt. %) is added to the aqueous solution of complex salt of platinum dipping the substrate 20 is added, and the substrate 20 is left to stand in the electrolessly plating liquid for 2 hours while being rocked, so that the platinum nuclei deposited on the substrate 20 may grow to form the detecting electrode 26 on the outer wall of the substrate 20 . Here, the concentration of the aqueous solution of complex salt of platinum is so adjusted that the thickness of the electrolessly plated platinum may have a thickness of 1.2 μm. [0057] In order to stabilize the detecting electrode 26 , moreover, a heat treatment is done at 1,200° C. for 1 hour, and spinel powder is applied by a plasma spray coating method to the surface of the detecting electrode 26 thereby to form a protective layer (although not shown). [0058] Subsequently, the reference electrode is formed on the substrate 20 . [0059] In order to form the reference electrode, the substrate 20 is left to stand while hydrofluoric acid (in concentration: 5 wt. %)being injected into the substrate 20 . And, the substrate 20 is rinsed by spraying water thereinto, and is then dried. [0060] Next, an aqueous solution of chloroplatinic acid (a platinum concentration: 0.5 g/m 3 ) is injected into the substrate 20 and is heated. After this, the chloroplatinic acid is discharged to form the coating film of an aqueous solution of chloroplatinic acid on the inner wall of the substrate 20 . Subsequently, an aqueous solution of hydrazine (in a concentration: 5 wt. %) is injected into the substrate 20 , and is heated to 75° C. and left to stand for 30 minutes thereby to deposit the nuclei of platinum on the inner wall of the substrate 20 . [0061] When the deposition of the nuclei is ended, the aqueous solution of chloroplatinic acid is discharged. An electrolessly plating liquid, which has been prepared by mixing an aqueous solution of complex salt of platinum (a platinum concentration: 15 g/m 3 ) and an aqueous solution of hydrazine (in a concentration: 85 wt. %), is injected into the substrate 20 , and is heated and left to stand so that the nuclei grow to form the reference electrode. [0062] And, the substrate 20 having the reference electrode formed therein is rinsed by spraying water into its inside, and is put into a driver so that it is sufficiently dried. [0063] Finally, the substrate 20 is aged in a combustion gas to activate the electrode so that the detecting element 2 is obtained. [0064] In the oxygen sensor 1 having the detecting element 2 thus manufactured, the sputtering method is used at the nucleus applying step when the detecting electrode 26 of the detecting element 2 is formed, so that the detecting electrode 26 formed after the nucleus growing step has a number of intergranules of crystals of platinum. In other words, the surface area (i.e., the surface area to act as a catalyst) of the detecting electrode 26 to contact with oxygen is larger than that of the prior art so that the catalyzing action of the detecting electrode 26 becomes higher than that of the prior art. Therefore, the oxygen sensor 1 can exhibit more excellent responding performances than that of the prior art. [0065] By the manufacturing process thus far described, moreover, the sizes of the nuclei are individually homogenized so that the detecting electrode 26 has a uniform thickness. Therefore, the oxygen sensor 1 exhibits a more excellent durability than that of the prior art. [0066] When the nuclei of platinum are to be deposited on the substrate of the detecting element 2 , moreover, the platinum nuclei can be prevented merely by arranging the shielding plate from being deposited on the substrate other than the portion L 1 , on which the detecting electrode 26 is to be formed. It is, therefore, possible to manufacture the oxygen sensor 1 without any trouble. [0067] In short, according to the manufacturing process of the invention, it is possible to manufacture the gas sensor, which is more excellent in the responding performances and the durable performances than the prior and which can form the electrode easily. [0068] According to the manufacturing process of this embodiment, moreover, the electrolessly plating method is used at the nucleus growing step when the detecting electrode 26 is formed. Therefore, the detecting electrode 26 can be formed more quickly than that, in which the nuclei are grown by continuing the sputtering from the nucleus applying step. Second Embodiment [0069] Here will be described a second embodiment. [0070] In the oxygen sensor of this embodiment, the detecting element 2 of the oxygen sensor 1 of the first embodiment is replaced by a detecting element 70 , as shown in FIGS. 5 and 6. [0071] Therefore, the following description is directed exclusively to the detecting element 70 . Here, FIG. 5 is a top plan view showing the exterior of the detecting element 70 , and FIG. 6 is a top plan view of the detecting element 70 on the back side of FIG. 5. [0072] Like the detecting element 2 , the detecting element 70 is constructed to include the substrate 20 , as shown in FIGS. 5 and 6. On the outer wall of the portion L 1 of the substrate 20 , moreover, there is formed such a long-size detecting electrode 71 upward of the substrate 20 from the upper portion at a distance L 2 from the bottom portion of the substrate 20 , as has a width W 3 smaller than the diameter at the portion L 1 of the substrate 20 and a length L 3 (L 3 <L 1 ). However, the outer wall of the portion L 1 of the substrate 20 is so coated with powder of spinel (although not shown) as to cover the detecting electrode 71 . [0073] In the detecting element 70 , as in the detecting element 2 , there is formed on the outer wall near the upper end portion of the substrate 20 a band-shaped terminal connecting portion 73 , which makes one round of the outer circumference of the substrate 20 thereby to connect the terminal fixture 50 . [0074] Between the detecting electrode 71 and the terminal connecting portion 73 , moreover, there is formed along the axial direction of the substrate 20 one long-size lead portion 72 , which has a width W 2 narrower than the detecting electrode 71 so that the detecting electrode 71 and the terminal connecting portion 73 are electrically connected therethrough. [0075] Here, the reference electrode (although not shown) of the detecting element 70 is formed, as in the detecting element 2 , all over the inner wall of the substrate 20 . [0076] The detecting element 70 thus constructed is so mounted in the oxygen sensor as to bring the heater 3 into contact with the inner circumference wall, as opposed to the detecting electrode 71 , of the substrate 20 . [0077] In order to manufacture the detecting element 70 , there may be a process similar to that for manufacturing the detecting element 2 . At the time of forming the detecting electrode 71 , however, there is arranged between the substrate 20 and the platinum foil disposed on the negative electrode of the ion coater a shielding plate, which has an area for covering the substrate 20 as a whole and which has such a through hole at a portion to form the detecting element 71 as has a planar shape congruent with the detecting electrode 71 . Unlike the first electrode, moreover, the sputtering is done for 5 minutes while leaving the substrate 20 to stand on the support rod. [0078] The oxygen sensor of this embodiment having the detecting element 70 thus constructed can attain effects like those of the oxygen sensor 1 of the first embodiment. In the detecting element 70 , moreover, the detecting electrode 71 is formed exclusively at the portion, in which the solid electrolyte is the most active and with which the heater contacts, of the detecting element 70 . Therefore, the oxygen sensor of this embodiment exhibits better responding performances than those of the oxygen sensor 1 of the first embodiment. EXAMPLES [0079] Here, we have performed experiments so as to demonstrate the effects of the oxygen sensors of the first and second embodiments thus far described. In these demonstration experiments: the responding performances and the performances of durability against the heat were compared by causing the oxygen sensor 1 having the detecting element 2 to belong to Example 1 , the oxygen sensor having the detecting element 70 to Example 2 , and the oxygen sensor having the detecting element (although not shown) of the prior art to Example 1. [0080] Here, the detecting element of the prior art is manufactured by using the process of the prior art but is set to have the shapes and sizes of the substrate and electrode absolutely like those of the detecting element 2 . [0081] In these demonstration experiments, the portion L 1 of the detecting elements 2 and 70 from the axial center to the bottom portion has a length set at 22.0 mm, and the lower portion and the upper portion of L 1 have diameters φ1 and φ2 set at 5.0 mm and 6.0 mm, respectively. Moreover, the lead portions 27 and 72 of the detecting elements 2 and 70 have their widths W 1 and W 2 set to 1.5 mm and have their thickness set to 10 μm. [0082] Moreover, the distance L 2 from the bottom portion of the detecting element 70 to the detecting electrode 71 is set at 2.0 mm, and the detecting electrode 71 has its length L 3 set at 20.0 mm. [0083] In both the detecting elements, on the other hand, the detecting electrodes have a thickness set to 1.2 μm, and the spinel coated on the portion L 1 has a thickness set at 200 μm. [0084] Here will be described the process of the prior art for manufacturing the detecting element. This manufacturing process of the prior art is absolutely similar to those of the first and second embodiments, excepting the nucleus applying step of forming the detecting electrode. [0085] In order to apply the nuclei to the detecting electrode, masking rubber is so mounted at first on the substrate as to cover the substrate excepting the portion to form the detecting electrode. Then, the substrate having the masking rubber mounted thereon is dipped in an aqueous solution of complex salt of platinum (a platinum concentration: 15 g/m 3 ). Subsequently, the aqueous solution of platinum complex salt dipping the substrate is heated to 60° C., and an aqueous solution of sodium borate is added. Moreover, the substrate is left to stand in this mixture liquid while being rocked, to deposit the nuclei of platinum on the outer wall of the substrate. [0086] After this nucleus deposition, moreover, the detecting element of the prior art is obtained through the nucleus growing step like that of the detecting elements 2 and 70 of the first and second embodiments. [0087] The results of our demonstration experiments are presented in FIG. 7 to FIG. 12. [0088] First of all, FIG. 7 to FIG. 9 are waveform diagrams of those outputs of the individual oxygen sensors, which were recorded when the aforementioned three oxygen sensors were sequentially mounted on the common internal combustion engine and when the A/F ratio of the internal combustion engine was alternately switched from lean to rich and from rich to lean for a period of 2 Hz. Here: FIG. 7 is the output waveform diagram of the oxygen sensor of Example 1; FIG. 8 is the output waveform diagram of the oxygen sensor of Example 2; and FIG. 9 is the output waveform diagram of the oxygen sensor of Comparison 1. [0089] Here in FIG. 7 to FIG. 9, reference letter T 1 designates the time period till the output of the oxygen sensor, as recorded just after the electric power was supplied to the heater of the oxygen sensor, acquires an amplitude to exceed a threshold value (e.g., 450 mV) at the boundary between the rich and the lean. And, reference letter T 2 designates the time period till the output of the oxygen sensor exceeds the threshold value at first just after the electric power was supplied to the heater of the oxygen sensor, reaches again the threshold value in accordance with the change in the A/F ratio of the internal combustion engine, and reaches a predetermined value (e.g., 550 mV) set higher than the threshold value. Here, the letter T 1 indicates the time period till the detecting element of the oxygen sensor is activated, and the letter T 2 indicates the time period till a stable output is obtained from the detecting element. [0090] In the oxygen sensors of Examples 1 and 2 according to the invention, as presented in FIG. 7 and FIG. 8, the time period T 1 had values of 7.6 seconds and 7.2 seconds, respectively, and the time period T 2 had values of 8.5 seconds and 8.0 seconds, respectively. In the oxygen sensor of Comparison 1, as presented in FIG. 9, on the contrary, the time periods T 1 and T 2 had values of 8.3 seconds and 9.2 seconds, respectively. [0091] From these results, it can be confirmed that the oxygen sensors of Examples 1 and 2 can be activated for shorter time periods to generate stable outputs quickly than the oxygen sensor of Comparison 1 manufactured by the process of the prior art. [0092] Next, FIG. 10 to FIG. 12 are waveform diagrams, which are recorded of the outputs of the aforementioned individual oxygen sensors against the change in the A/F ratio control signal for controlling the A/F ratio of the internal combustion engine. Here: FIG. 10 is the waveform diagram of the oxygen sensor 1 of Example 1; FIG. 11 is the waveform diagram of the oxygen sensor 1 of Example 2; and FIG. 12 is the waveform diagram of the oxygen sensor 1 of Comparison 1. [0093] Here in FIG. 10 to FIG. 12, reference letters TLS designate a time period till the outputs of the individual oxygen sensors exceed a threshold value after the A/F ratio control signal was switched from the lean to the rich, and reference letters TRS designate a time period till the outputs of the individual oxygen sensors fall below the threshold value after the A/F ratio control signal was switched from the rich to the lean. [0094] In the oxygen sensors of Examples 1 and 2, as presented in FIG. 10 and FIG. 11, the time period TLS had values of 0.323 seconds and 0.319 seconds, respectively, and the time period TRS had values of 0.307 seconds and 0.305 seconds, respectively. In the oxygen sensor of Comparison 1, as presented in FIG. 12, on the contrary, the time periods TLS had a value of 0.343 seconds, and the time period TRS had a value 0.324 seconds. [0095] From these results, it can be confirmed that the oxygen sensors of Examples 1 and 2 have quicker responses to the fluctuation in the oxygen concentration in the exhaust gas than the oxygen sensor of Comparison 1. [0096] From these results, it has been verified that the oxygen sensors of Examples 1 and 2 can exhibit satisfactory responding performances. [0097] Here, the aforementioned individual oxygen sensors were exposed for 2,000 hours to the exhaust gas at 1,000° C., and the changes in the outputs of the individual oxygen sensors were confirmed against the change in the A/F ratio control signal for controlling the A/F ratio of the internal combustion engine. [0098] As a result, the oxygen sensor of Comparison 1 was broken at the detecting electrode so that it did not generate no output. On the contrary, the responding time periods (TRS+TLS) of the oxygen sensors of Examples 1 and 2 were 0.661 seconds and 0.650 seconds, respectively. [0099] From these results, it has been verified that both the oxygen sensors of Examples 1 and 2 are neither broken in the detecting electrodes nor seriously changed in the responding performances even if they are exposed for a long time to the atmosphere at a high temperature, so that they have high durable performances against the heat. [0100] At the time of manufacturing the detecting elements individually, as used in the comparison experiments, the Inventors have measured the sizes of platinum crystals constructing the detecting electrodes. As a result, the platinum crystals constructing the detecting electrode had a size of about 0.2 to 0.3 μm. However, the detecting electrode 26 of the detecting electrode 2 and the detecting electrode 71 of the detecting element 70 had such fine platinum crystals as could not be found, even if observed by setting the magnitude of a scanning type electronic microscope (SEM) at 20,000 times. [0101] In short, according to the manufacturing process of the invention, the platinum crystals constructing the detecting electrode can be made fine. Therefore, the intergranules of the platinum crystals in the detecting electrode become so numerous that the surface area of the detecting electrode to contact with the exhaust gas can be made larger than that of the prior art. [0102] Although the invention has been described hereinbefore in connection the embodiments, it should not be limited thereto in the least but can naturally take a variety of modes so far as it belongs to the present invention. [0103] In the foregoing embodiments, for example, the invention has been applied to the manufacture of the oxygen sensor but may also be applied to the manufacture of another mode such as a nitrogen oxide (NO x ) sensor. [0104] In the foregoing embodiments, moreover, platinum was used to form the detecting electrodes or the reference electrodes but may also be replaced by rhodium, palladium, silver or gold. [0105] Moreover, the foregoing embodiments have used the DC glow discharge sputtering method at the nucleus applying step but may also use another sputtering method such as a magnetron sputtering method or an ion beam sputtering method, or a deposition method such as a vacuum evaporation method, a molecular beam deposition method, an ion plating method or an ion beam deposition method. [0106] In the foregoing embodiments, moreover, at the nucleus applying step for forming the detecting electrode 26 of the detecting element 2 , the substrate 20 is turned for every predetermined time periods. However, the nuclei of platinum may also be deposited by turning the substrate 20 at all times or by methods, as shown in FIG. 13 and FIG. 14. [0107] In the method shown in FIG. 13, more specifically, the nuclei of platinum are deposited by inserting the portion L 1 of the substrate 20 into a shielding plate 90 having a hole for inserting the portion L 1 of the substrate 20 thereinto and by fixing the substrate 20 in the ion coater 80 with its bottom portion being directed toward the negative electrode 83 . According to this method, the platinum nuclei can be deposited all over the portion L 1 of the substrate 20 without turning the substrate 20 . If the bottom portion of the substrate 20 is coated with a shielding cover 91 made of rubber or the like, as shown in FIG. 14, the platinum nuclei can be deposited exclusively on the outer wall of the portion L 1 of the substrate 20 excepting the bottom portion. [0108] This application is based on Japanese Patent application JP 2002-322627, filed Nov. 6, 2002, the entire content of which is hereby incorporated by reference, the same as if set forth at length.

A process for manufacturing a gas sensor including a detecting element having an electrode containing a precious metal formed on a surface of a solid electrolyte, comprising: a first step of applying a nuclei of a precious metal having a catalyzing action on a gas to be measured; and a second step of growing the nuclei, wherein the first step uses a physical vapor deposition method.