bluuebunny/crossref_metadata_2025 huggingface dataset:
Donor Concentration Changes in Oxide-Coated Cathodes Resulting from Changes in Electric Field
Authors: Krusemeyer H. J. , Pursley M. V.
Published: April 2005

Large reproducible changes in work function of oxide cathodes have been observed following step-like changes in dc current drawn from, as well as to, the coating. One type, with a time constant in the range of 10−2 to 1 second, has been reported by others. It appears to be caused by a redistribution of donors by the field set up in the coating. We studied this phenomenon further as a function of temperature, dc current density, coating composition, and barium deposition.

We also discovered a second type of transient which follows the first. It has a time constant, in the range from 100 to 104 seconds. The amplitude of this change is of the same order as that of the first. The time dependence is in most cases given by a simple exponential. Both amplitude and time constant are a function of the cathode itself as well as its environment. This transient is thought to be caused by a change of the total number of donors. A simple analysis accounting for the exponential form yields values for the donor loss rate.
Motion of the Interface between Two Immiscible Liquids of Unequal Density in a Porous Solid
Authors: Kidder Ray E.
Published: April 2005

A general solution is obtained to a two-dimensional problem of the movement of the interface between two immiscible liquids of unequal density in a porous solid, the interface motion being the result of the force of gravity acting on the two liquids. The solution is obtained by direct potential theory methods and employs a method of approximation similar to that used in the linear theory of water waves.

It is shown that the elevation of the interface above its equilibrium position satisfies a ``nonoscillatory'' wave equation, i.e., the classical wave equation in which the wave velocity is pure imaginary.

The solution of the special case of an initially plane tilted interface is included.
Review of Germanium Surface Phenomena
Authors: Kingston R. H.
Published: April 2005

Germanium surface behavior has become of great interest recently, chiefly for its importance in the understanding of diode and transistor technology. In general, the surface may be treated as an assemblage of allowed electron states occurring in the normally forbidden energy range. A review of the measurements of the electrical properties suggests that there are two distinct types of state. The ``fast'' state has a hole or electron capture time not greater than a microsecond and is chiefly involved in the recombination process. The ``slow'' state has capture times from a millisecond to several minutes and determines the density and type of carrier at the surface. ``Fast'' states are believed to occur at the interface between the germanium and the oxide layer, and their density of about 1011 cm−2 is determined by the initial surface treatment. ``Slow'' states are associated with the structure of the oxide layer and the gaseous ambient, and have a density greater than 1013 cm−2. Since these states determine the conductivity type at the surface, they contribute to surface ``leakage'' in diodes and transistors and, because of their long equilibrium times, to low-frequency noise. The adsorption of gases such as water vapor, not only controls the density and energy of the ``slow'' states but also leads to possible electrolytic conduction along the surface, in addition to the normal electron flow in the bulk semiconductor.
Analysis of the Plasma of Fluorescent Lamps
Authors: Waymouth John F. , Bitter Francis
Published: April 2005

An attempt has been made to explain the properties of the ``plasma'' of fluorescent lamps in considerable detail, using the ambipolar diffusion theory of Schottky, modified to include ionization by multiple electron impacts. Ionization is assumed to occur by electron collisions with excited and metastable atoms. The cross section for this process is one of two inaccurately known parameters, which we treat as adjustable constants, occurring in the calculations. The other is the effective diffusion constant for quanta of the resonance line, in the presence of a high-temperature electron gas.

Qualitative agreement of the foregoing theory with experiment is demonstrated for all the derived quantities as functions of the several parameters of the discharge. The magnitudes of the calculated electron temperature, electric field, total light output, and efficiency are also in sufficiently good agreement with experimental values for the lamps of greatest commercial interest to permit extrapolations to be made with reasonable confidence. Optimum agreement of theory with experiment for T-12 lamps is obtained using a mean life time of ultraviolet photons in the discharge 3.6 times that employed by Kenty for diffusion in un-ionized vapor, and with a value 3.3 for the ratio of cross section for ionization of excited state to that of the ground state.
Preparation and Inspection of High-Purity Copper Single Crystals
Authors: Wernick J. H. , Davis H. M.
Published: April 2005

A simple and inexpensive vacuum procedure has been employed to grow copper single crystals by the Bridgman method. Crystals grown at a lowering rate of 2 inches per hour have a high degree of perfection as indicated by the presence of Kikuchi lines on electron diffraction patterns. The perfection varies along the length of the crystal, that portion freezing last being the most perfect. It is suggested that this variation in perfection along the length will occur to some degree in all unseeded crystals made by the Bridgman method because of the greater supercooling that occurs when the first metal freezes.
Collection Efficiency of Aerosol Particles and Resistance to Flow through Fiber Mats
Authors: Wong J. B. , Ranz W. E. , Johnstone H. F.
Published: April 2005

The collection efficiencies for sulfuric acid aerosols of 0.4- to 1.3-microns particle diameter, and the resistance to flow through glass fiber mats composed of 3.5-, 6.2-, and 9.6-micron fibers, were investigated experimentally. The results agree with the theory that particle collection in this range is a function of the inertia of the particles, the interception by the fibers, and the nature of the flow around the fibers, as characterized by the parameters Ψ, R, and NRe, respectively, and that the pressure drop is a function of the flow characteristics and the fiber interference effect. Theoretical equations for collection efficiency and pressure drop of fiber mats were analyzed in terms of the impaction efficiency and drag coefficient of single fibers. These equations were evaluated by comparing the apparent fiber efficiency and drag with theoretical values.
Thermoelectric Power and Electrical Resistivity of Dilute Alloys of Mn, Pd, and Pt in Cu, Ag, and Au
Authors: Otter F. A.
Published: April 2005

Data are given on the resistivities and thermoelectric powers of the alloys Cu–Pd, Ag–Pd, Au–Pd, Cu–Pt, Ag–Pt, Au–Pt, Cu–Mn, Ag–Mn, and Au–Mn from −195°C to +500°C for the resistivities and to +650°C for the thermoelectric powers. The resistivities of the alloys containing Pd and Pt obey the Matthiessen rule well whereas those with Mn do not. The resistivity of the alloys with more than about 8 atomic % Mn deviate from linearity at the lower temperatures, the temperature of deviation increasing with Mn content. The thermoelectric powers of the Pt and Pd alloys are negative relative to the pure solvents and are reasonably constant relative to the solvents at high temperatures. The thermoelectric powers of the Mn alloys become positive relative to the solvents above certain temperatures (25°C for Cu–Mn, −170°C for Ag–Mn, and 150–250°C for Au–Mn). A brief discussion of the data in relation to theory is given.
Temperature Behavior of Ferrimagnetic Resonance in Ferrites Located in Wave Guide
Authors: Duncan B. J. , Swern L.
Published: April 2005

Ferrimagnetic resonance has been investigated in several polycrystalline ferrites located in wave guide over a temperature range from 25°C to the Curie point of each ferrite. The ferrimagnetic resonance line width and the apparent gyromagnetic ratio of two types of ferrites were found to change with increasing temperature. The theories of Wangsness and Kittel have been utilized in interpreting the observed effects. The foregoing effects were shown to influence the temperature behavior of the microwave properties of ferrites away from resonance.
On the Magnification and Resolution of the Field Emission Electron Microscope
Authors: Rose D. J.
Published: April 2005

The resolution of the field emission electron microscope is expressed as a function of the ratio of its magnification M to the time-of-flight τ of an electron from emission tip to screen. It is shown that small protrusions on the surface of the tip can provide areas for which M is much greater than that computed for a perfectly smooth tip. Resolution of the order of 3 A is possible on these protrusions, so that some of their atomic detail should be observable.
On the Vortices Produced in Shock Diffraction
Authors: Howard L. N. , Matthews D. L.
Published: April 2005

The vortex produced by a weak shock passing over a 5° vertical wedge has been studied experimentally and theoretically. The theory applies to any vortex in isentropic flow which has a certain rotational symmetry, and which expands uniformly in time (pseudo-stationary flow), without consideration of how the vortex was formed. By fitting essentially one parameter of the theory to the interferometrically observed density, good agreement is obtained over the region of the vortex, except at the very center. The rate of growth of the vortex as a function of free-stream Mach number has been found in agreement with that predicted by [N. Rott (private communication)] on the basis of another theory. The photographs show a well-developed spiral slip stream winding off the corner which contains small secondary eddies whose average angular spacing, measured from the vortex center, appears to be roughly independent of shock strength and time.
Thermoelasticity and Irreversible Thermodynamics
Authors: Biot M. A.
Published: April 2005

A unified treatment is presented of thermoelasticity by application and further developments of the methods of irreversible thermodynamics. The concept of generalized free energy introduced in a previous publication plays the role of a ``thermoelastic potential'' and is used along with a new definition of the dissipation function in terms of the time derivative of an entropy displacement. The general laws of thermoelasticity are formulated in a variational form along with a minimum entropy production principle. This leads to equations of the Lagrangian type, and the concept of thermal force is introduced by means of a virtual work definition. Heat conduction problems can then be formulated by the methods of matrix algebra and mechanics. This also leads to the very general property that the entropy density obeys a diffusion-type law. General solutions of the equations of thermoelasticity are also given using the Papkovitch-Boussinesq potentials. Examples are presented and it is shown how the generalized coordinate method may be used to calculate the thermoelastic internal damping of elastic bodies.
Photoconductive and Photoelectromagnetic Effects in InSb
Authors: Kurnick S. W. , Zitter R. N.
Published: April 2005

Photoconductive (PC) and photoelectromagnetic (PEM) effects have been observed in p-type InSb single crystals of high purity at 77°K (extrinsic range) and 301°K (intrinsic range). Because of the large electron mobilities in InSb, and because the variation of the PEM response with magnetic field was found to be strongly dependent on surface treatment, it was necessary to develop a new theoretical model to describe the PEM effect, permitting the evaluation of bulk lifetime and both electron and hole mobilities. In addition, the model affords an interpretation of Hall and magnetoresistance effects in intrinsic InSb. When the PEM effect is analyzed using impurity or thermal scattering, assuming Boltzmann statistics, the result does not fit the data so well as the simple model presented here.
Some Experiments on Thermal Contact at Low Temperatures
Authors: Berman R.
Published: April 2005

An apparatus for studying heat contact at low temperatures is described. Measurements of heat transfer between various surfaces in vacuo have been made. The thermal conductance is independent of the area of the surfaces and is nearly proportional to the force between them, up to forces of about 200 lb. At helium temperatures the conductance between all the types of surfaces examined is proportional to T2, but the temperature dependence is small at nitrogen temperatures. For metal contacts the electrical conductance is extremely sensitive to the previous history of the surfaces, but the heat conductance is little dependent on this. The thermal conductance is always much greater than corresponds to the electrical conductance according to the Wiedemann-Franz-Lorenz law and this fact, together with the differing behavior of the two conductances under changing loads, suggests that nearly all the heat flow takes place through electrically nonconducting parts of the surface. The main results are collected together in a table.
Diffusion Effects in Drift Mobility Measurements in Semiconductors
Authors: McKelvey J. P.
Published: April 2005

Drift mobility measurements in semiconductors using small steady dc fields are described. It is necessary in such cases to take diffusion as well as drift into account in calculating the mobility from the transit time, and a calculation is made which considers both effects. If the diffusion corrections are made, one may eliminate the pulsed sweep fields which are customarily used in these experiments. Measurements of transit time vs sweep field show that the diffusion corrections are in agreement with experiment.
Extension of the ``Thin-Sample Method'' for the Measurement of Initial Complex Permeability and Permittivity
Authors: Conrad Edward E. , Porter C. S. , Doctor N. J. , Franklin P. J.
Published: April 2005

A summary is given of the theory of measurement of complex relative permeability and permittivity of low conductivity materials by the thin-sample method using a slotted transmission line. The equations from which to calculate the electrical properties from the measured parameters are extended to apply to a commercial slotted line and thus to a more complex system than that used by other workers. Some errors of the measurements are discussed and various correctional equations derived by other workers are given.
Variational Method for the Calculation of the Distribution of Energy Reflected from a Periodic Surface. I.
Authors: Meecham W. C.
Published: April 2005

A variational method is presented which is used to calculate the energy appearing in the various diffracted orders set up when a plane wave is incident upon a periodic reflecting surface. Either the first or the second boundary condition can be so treated. A sample problem is worked showing that if the average absolute slope of the reflecting surface is small (segments of surface with large slope may be included) and if the displacement of the surface is not large compared with the wavelength of the incident radiation, the formulation gives results correct to within a few percent. The calculation shows the existence of Wood anomalies; these are discussed in the paper.
Gradient Dependence of the Intrinsic Viscosity of Linear Macromolecules
Authors: Peterlin Anton , Čopič Milan
Published: April 2005

The decrease of intrinsic viscosity with increasing gradient was found with all linear macromolecules investigated at high enough molecular weight irrespective of the solvent. But experiments do not agree on the power of the gradient to which the deviations from the zero value are proportional. Exponents ½, 1, and 2 have been proposed to fit experimental data. The necklace model with hydrodynamic interaction yields suitable gradient dependence of the intrinsic viscosity only if either the molecule has a nonvanishing rigidity or the anisotropy of the hydrodynamic interaction is explicitly considered. Since the first effect decreases with increasing M, very likely most of the observed gradient dependence has to be attributed to the second one which is intrinsically connected with the statistical shape of the molecular coil and the character of the hydrodynamic forces.
Mechanical Behavior of Viscoelastic Fibers
Authors: Akutowicz F.
Published: April 2005

The under-determined equation M(F,D,dF/dt,dD/dt)=0, where F=F(t), D=D(t) are measures of force and deformation and t is time, can be transformed into a first-order partial differential equation in F, D, ∂F/∂D, ∂F/∂t whose characteristics represent the totality of all possible force-elongation trajectories in F, D, t space. Historically, M has seen considerable service either as a complete stress-strain relation or an element in a distribution of such relations. A geometric interpretation of M useful in rheological studies of fibers is given. Necessary conditions are given for M to provide a satisfactory description of a fiber's mechanical behavior. An operational procedure is outlined for constructing M in the laboratory based on direct measurements instead of on a priori assumptions involving springs and dash pots. The discussion is brief and theoretical.
Measurement of Minority Carrier Lifetime in Silicon
Authors: Watters R. L. , Ludwig G. W.
Published: April 2005

This report discusses lifetime in silicon as measured by photoconductive decay and checked by a drift technique. The source of pulsed light, the presentation system, and other instrumentation is described. Limitations on the injection level and field are discussed, as well as the problems presented by trapping, barriers, and making contact to the crystal. Lifetime in excess of 1500 μsec in p-type crystals and 2500 μsec in n-type crystals has been observed at room temperature. The photoconductive decay constant (lifetime) is reported in n-type crystals from 78° to 450°K, and in p-type crystals from 160° to 450°K. Measurements on another p-type crystal permitted calculation of the surface recombination velocity (∼3500 cm/sec at 300°K after grinding or etching with CP4) between 175° and 450°K.
Missile Guidance by Three-Dimensional Proportional Navigation
Authors: Adler Fred P.
Published: April 2005

Following a brief comparison of three collision-seeking types of navigation—pure pursuit, constant-bearing collision, and proportional navigation—the usual definition of planar proportional navigation is extended to three dimensions. Based upon a simple criterion for optimum navigation to the line-of-sight motion, a proper formulation is found in terms of the geodesic and normal curvatures of the missile path on the surface generated by the line of sight. By a suitable choice of a reference coordinate system, the missile-target kinematic relationships are then linearized, assuming relatively small deviations of the missile from a collision course. Upon combining these ``geometry feedback'' equations with the equations of guidance, the missile trajectory is found to be given in terms of two independent linear differential equations of identical form and of one higher order than the missile transfer function. Typical solutions are found for some simple cases. The character of the trajectory is shown to depend on an ``effective navigation constant'' proportional to the missile navigation constant (or gain) and the ratio of missile speed to closing speed; a value of this parameter greater than two is found to be necessary to insure finite terminal missile acceleration. Two example trajectories are calculated from both the exact and the linearized trajectory equations to indicate the accuracy of the linearization.
Improved Method for Plotting Reciprocal Lattice Points
Authors: Martin W. G.
Published: April 2005

A chart is presented which saves computational time in analyzing diffraction photographs of crystals. The new chart, used with a standard Bernal chart, facilitates the plotting of reciprocal lattice points from spots which are observed on a single crystal x-ray pattern made with monochromatic radiation.
Thermoelectric Power of AuCu in Nonequilibrium States
Authors: Cooper H. , Schwed P. , Webeler R. W.
Published: April 2005

Measurements have been made of the resistivity ρ and of the thermoelectric power Q (vs Pt) of samples of AuCu in various nonequilibrium states. One set of samples was disordered by quenching from 750°C; and annealing curves were obtained at 100°, 149°, 198°, and 258°C. A second set was first ordered and then cold worked to essentially complete disorder, and annealing curves taken at 149°C and 258°C. Of the former set, the Q—ρ curves for 100° and 149°C showed a maximum at ρ≈11.5μ ohm cm while none was observed in the curves for any of the other cases. It follows from the detailed results that to specify the state of the alloy it is necessary to give, in addition to ρ and Q, at least one other quantity such as the coefficient of magnetoresistivity.
Broad-Band Nonreciprocal Phase Shifts—Analysis of Two Ferrite Slabs in Rectangular Guide
Authors: Weisbaum S. , Boyet H.
Published: April 2005

A compensation technique for broad-banding differential phase shift produced in ferrite loaded rectangular wave guides is discussed. The method involves the use of two magnetized slabs of ferrite on opposite sides of the wave guide, the slabs being different in thickness and in magnetic properties but magnetized in the same direction. The basis of the compensation technique is demonstrated first by a discussion of the thin slab case in which a numerical example showing broad-band differential phase shift is included. An analysis for ferrite slabs of arbitrary thickness is then given and is followed by an example at 6000 Mc/sec in 1.59-in. wide guide. The results of this example indicate that a π differential phase shift, constant to within ±2.5% in the frequency range 5925–6425 Mc/sec, can be obtained using ferrite slabs 5.4-in. long. A scaling principle is discussed and indicates how the numerical results for differential phase shift obtained at 6000 Mc/sec in 1.59-in. wide guide can be extended to other frequencies and geometries with the same degree of broad-banding.
Effect of Vacuum Heating and Ion Bombardment of Germanium on Point Contact Rectification
Authors: Allen R. B. , Farnsworth H. E.
Published: April 2005

An apparatus is described which allows the cleaning of the contact surfaces by vacuum heating and argon ion bombardment. The diode characteristics of a tungsten and a columbium point against the same germanium crystal are measured while a high vacuum is maintained in the experimental tube. If the germanium is heated to above 800°C and cooled suddenly, the room-temperature rectification is lost. The rectification is restored by vacuum annealing at 500°C for 10 hr. The best rectification characteristic is obtained after the germanium has been subjected to a long anneal, argon ion bombardment, and a short anneal. This sequence of treatments approximates that yielding the low-energy electron diffraction pattern to be expected from a pure germanium surface. The diode activation potential, determined from the temperature dependence of the low-level resistance, is shown to change experimentally with the treatment of the semiconductor and with the contact force. With the techniques used, an experimental dependence of the diode activation potential on the metallic work function is not evident. A theoretical expression for the activation potential is given in the Appendix.
Atmospheric Attenuation of Solar Millimeter Wave Radiation
Authors: Theissing H. H. , Caplan P. J.
Published: April 2005

A lumped attenuation figure for the solar millimeter wave radiation in the water vapor of the atmosphere was measured with a thermal detection apparatus. The corresponding theoretical attenuation figure was computed from the solar millimeter spectrum known from previous measurements of the authors and from the Van Vleck-Weisskopf equation and turned out smaller than the first experimental figure by a factor of about 3 in terms of decibels per kilometer. With the general structure of an absorption spectrum considered well traced by theory this disagreement can only mean a failure of the computation to yield the correct absolute absorption level in the window regions to which the experiment predominantly refers. The fault may lie either in the equation itself or in inadequately known constants required in the computation.

Regardless, however, of the cause and magnitude of this discrepancy, the novel method of this paper lies in a combination of the above-mentioned experimental and computed figures to furnish a well-supported spectral attenuation function in the window region. This function, which constitutes the final result, turns out largely independent of the shortcomings in the computation part, inasmuch as theory was used to furnish merely its structure and experiment to provide its absolute level.
Effect of Fast Neutron Bombardment on Physical Properties of Graphite: A Review of Early Work at the Metallurgical Laboratory
Authors: Burton M. , Neubert T. J.
Published: April 2005

Fast neutron bombardment of artificial graphite increases the longitudinal elastic modulus and electrical resistivity and decreases the thermal conductivity. Annealing at temperatures higher than the bombardment temperature reverses the neutron-induced property changes, but complete recovery does not occur until annealing temperatures approach 2000°C. These effects are considered to be the results of the displacement of carbon atoms from normal positions in graphite crystallites to interstitial positions and the production of lattice vacancies. The displaced atoms are trapped in a variety of metastable interstitial trapping centers and, as a result, increase the internal energy of the graphite. Annealing causes interstitial atoms to move to more stable positions, thus releasing stored energy and causing recovery of other neutron-induced changes. Hall effect studies indicate that the neutron-induced disturbances (interstitial atoms and clusters of atoms, and lattice vacancies) are electron traps. Data are presented and the implications of various observations are discussed.
Theory of Mechanical Damping Due to Dislocations
Authors: Granato A. , Lücke K.
Published: April 2005

A quantitative theory of damping and modulus changes due to dislocations is developed. It is found that the model used by Koehler of a pinned dislocation loop oscillating under the influence of an applied stress leads to two kinds of loss, one frequency dependent and the other not. The frequency dependent loss is found to have a maximum in the high megacycle range. The second type of loss is a hysteresis loss which proves to be independent of frequency over a wide frequency range which includes the kilocycle range. This loss has a strain-amplitude dependence of the type observed in the kilocycle range. The theory provides a quantitative interpretation of this loss.
Ferromagnetic Coupling between Crossed Coils
Authors: Gianola U. F. , James D. B.
Published: April 2005

Two coils wound in orthogonal planes are electrically coupled when linked by a saturated ferromagnetic. The coupling is produced by the rotation of the saturated induction vector. This effect is discussed in relation to applications to magnetic gating, coincidence, and memory.
Some Resistivity Effects of Short-Range Order in α Brass
Authors: Damask A. C.
Published: April 2005

The annealing kinetics of resistance changes produced in 30% Zn α brass by quench, neutron irradiation at 50°C, and cold work have been studied. It is shown that the relaxation times for these changes agree with those obtained from measurements of stress-induced changes in local order. These resistance changes are therefore interpreted in terms of changes in short-range order. Measurements of resistance as a function of temperature show that an increase of short-range order decreases ρ0, the residual resistance, and increases ρT, the thermal part of resistance.
Small-Angle X-Ray Scattering
Authors: Dragsdorf R. Dean
Published: April 2005

Colloidal silica of 30, 20, 10, and 5% concentrations by weight have been used to produce small-angle scattering. The resulting scattering showed plateaus which varied in angular position with concentration in the very small angle portion and then showed an approximation to the single particle scattering in the larger small angle region. This scattering from individual scattering centers followed that predicted by Debye. Average distances of separation of randomly spaced particles as determined from the particle-to-particle scattering plateaus checked those calculated from the concentrations. In addition, scattering from various sized particles ranging from diameters of 100 to 500 000 A were measured. Two theories, a refraction and reflection or ray theory and a diffraction or wave theory, have been applied to the analysis of this scattering. A comparison of the particle sizes as obtained using these two theories with the particle size as obtained by means other than x-ray scattering shows that for the larger particles, geometrical optics can be used satisfactorily; while for the small particles the diffraction theory gives the correct scattering relation. Particle size measurements were made on both wetted (colloidal) and dried samples.
Convergent-Beam X-Ray Analysis of Mosaic Structure in Polycrystals
Authors: Berry Chester R.
Published: April 2005

A simple x-ray diffraction method was used to measure the mosaic misalignment and the number of dislocations in the grains of silver halide precipitates and of nickel foils where the grain sizes were in the range from a few tenths of a micron to a few microns. The experimental arrangement is such that separate diffraction spots are produced by each grain and the width of a spot is determined primarily by the mosaic nature of the grain.

It appears that measurements of angular misalignment can be made down to the limit imposed by the natural width of the x-ray spectrum lines. In general, either cold work or the presence of a substitutional impurity causes broadening of the diffraction spots. However, it is possible to incorporate impurities without producing broadening or dislocations. In spite of a 1% substitution of iodide impurity in silver bromide, grains were produced which appear to have no edge dislocations.
On the Dynamic Temperature Response of a Vacuum Calorimeter
Authors: Kouvel J. S.
Published: April 2005

A simple graphical method is described for computing the heat capacity of a specimen in a vacuum calorimeter system from the temperature response in the after-heating period. The applicability of this method when there are appreciable time lags due to thermal gradients in the specimen or due to the characteristics of a galvanometer, is discussed.
Transformations in Disordered Gold Copper Alloys
Authors: Kuczynski G. C. , Doyama M. , Fine M. E.
Published: April 2005

By measurement of the specific heat, temperature coefficient of expansion, Young's modulus and yield point in Cu3Au alloys, it has been established that this alloy undergoes a phase transition between 550° and 600°C and possibly another one near 850°C. The temperature of the 550–600°C transition decreases sharply as the composition of the alloy deviates from Cu3Au.
Stress Analysis in Viscoelastic Materials
Authors: Lee E. H.
Published: April 2005

The problems of stress analysis for linearly viscoelastic materials are considered. This is the simplest group of materials which exhibit the general stress-strain characteristics found in polymers and plastics. Three basic aspects are considered: measurement of material properties, determination from these of the operator equations between stress and strain or equivalently of the viscoelastic model, and use of this in the theoretical analysis of stress distributions. Quasi-static analysis, in which inertia forces are negligible, is treated quite generally. The wave problems which arise when inertia effects are included are restricted to one-dimensional space variations. A series of typical solutions of these types is discussed.
Stress Relaxation Studies of the Viscoelastic Properties of Polymers
Authors: Tobolsky Arthur V.
Published: April 2005

Extensive studies of the viscoelastic properties of polymers undertaken in the author's laboratory by means of the method of stress relaxation are here reviewed. The discussion is divided into four parts: chemical stress relaxation, stress relaxation in amorphous polymers, stress relaxation in crystalline polymers, and stress relaxation in certain natural polymers and polyelectrolytes. Mathematical description of the phenomena are presented in simple form. The relation between structure and viscoelastic properties of polymers are discussed and a rather complete over-all picture of these phenomena seems to be emerging.
Scattering of High-Energy Gamma Rays
Authors: Green David H. , Gregg E. C.
Published: April 2005

The scattering of 16-Mev bremsstrahlung by 3, 6, and 9 in. of iron was measured for small angles using a thallium-activated sodium-iodide scintillation counter. The experimental results closely fitted a theoretical curve calculated on the basis of single scattering.
Turbulent Mixing Theory Applied to Radio Scattering
Authors: Silverman Richard A.
Published: April 2005

Obukhoff's statistical theory of turbulent mixing is proposed as a replacement for the heuristic theories of Gallet and Villars-Weisskopf, and is applied to the problem of the scattering of radio waves by refractive index fluctuations. In the case of ionospheric scattering, order-of-magnitude agreement with the observed scattered power is obtained if the refractive index fluctuations are attributed to electron density fluctuations produced by turbulent mixing in the lower edge of the E layer. In the case of tropospheric scattering, it appears that order-of-magnitude agreement with the observed scattered power can be obtained, except during the summer months, by attributing the refractive index fluctuations to temperature fluctuations. During the summer months and at low scattering heights, humidity and its fluctuations are expected to play a prominent role. Experimental and theoretical evidence is cited in favor of perennial fractional-degree temperature fluctuations in the troposphere. A comparison of the Obukhoff, Villars-Weisskopf, and Booker-Gordon models is given, and it is found that the Obukhoff model predicts the most scattered power.
Nickel Copper Ferrites for Microwave Applications
Authors: Van Uitert L. G.
Published: April 2005

Ferrites having both high relative density (∼98%) and high dc resistivity (>109 ohm-centimeters) can be prepared by properly sintering nickel copper ferrites which have both an iron deficiency and a small amount of manganese or cobalt present. Magnetic saturation at room temperature shows a linear dependence upon copper content in this system varying from 3150 gauss for NiFe1.9Mn0.02O4± to 2400 gauss for furnace cooled CuFe1.9Mn0.02O4±. Direct current resistivity remains high for mixtures of these two ferrites if 2Cu<Ni. An anomalous break in the curve relating dc resistivity with copper content occurs when the copper to nickel ratio exceeds this 1:2 value.
Polarization Reversal in the Barium Titanate Hysteresis Loop
Authors: Landauer R. , Young D. R. , Drougard M. E.
Published: April 2005

In the presence of an opposing field the polarization of tetragonal BaTiO3 reverses itself. Devonshire's phenomenological treatment shows that in a sufficiently large opposing field the original direction of polarization becomes unstable. The values of commonly observed coercive fields are much smaller than this, and the polarization actually reverses while the initial state is still metastable. The observed coercive field and the shape of the audio-frequency hysteresis loop can, however, be explained in terms of the field dependence of the switching rate that was measured by Merz in pulse experiments. Measurements by Drougard, Funk, and Young, of the small signal conductivity, taken while traversing the hysteresis loop, are also explained in terms of Merz's rate. The absence of an appreciable inductive component in the small signal conductivity measurements indicates that variations in the applied field produce corresponding variations in the switching current with a time lag which is at most a few times 10−8 second and possibly much less. The increases in dielectric constant measured during switching remain unexplained.
Stability of Oscillations of Superposed Fluids
Authors: Tchen Chan-Mou
Published: April 2005

The Stokes-Taylor instability of the interface of two superposed fluids is studied. The two uniform layers of heavy fluids are of different densities and viscosities and are incompressible. Surface tension and gravity are taken into consideration. The main problem considered is the role of viscosity on the modes of decay and growth of waves, and the finding of an analytical solution more generally valid than those in existing approximate theories. The present viscous theory is based on an approximation by interpolation exact in three regions of wave numbers (intermediate and two extreme regions). The extreme regions, being most important from the practical point of view and serving as a foundation of the present theory, are studied somewhat in detail up to the fourth order. Results are illustrated graphically and show good agreement with numerical solutions of the complete equation. For the sake of comparison, curves are also drawn according to existing theories and show discrepancies in the maximum rate of growth and decay from 12% to more than 100%.
Reverse Current and Carrier Lifetime as a Function of Temperature in Silicon Junction Diodes
Authors: Pell E. M. , Roe G. M.
Published: April 2005

Earlier measurements of the reverse current and carrier lifetime in germanium have been extended to a series of silicon grown junction diodes, with measurements as a function of temperature between −190°C and 200°C. The lifetime reaches a plateau at low temperatures and can be explained in terms of the Hall-Shockley-Read recombination theory. The slope of logir vs 1/T, the magnitude of ir, and the slope of ir vs V suggests that charge generation from centers about 0.5 ev deep is responsible for most of the reverse current in these samples up to temperatures well above room temperature.
Potential Distribution between Parallel Planes in Electron Tubes
Authors: Copeland P. L. , Sachs L. M. , Czech E. C.
Published: April 2005

In this paper, problems of space charge between parallel planes subject to conventional simplifying assumptions are solved in a way which makes it possible to calculate the potential distribution directly from information about electrode spacing, electrode potentials, and current density restricted to the range in which a stable space-charge distribution is established by a constant current density. The sources of information are (1) the application of the method of Copeland and Eggenberger to the development of the space-charge cloud as the current between parallel planes is increased from zero and (2) at currents high enough to give a potential minimum, the reduction of the problem to the easily solved case of the equivalent distribution between planes of the same potential.
Cascading of Peltier Couples for Thermoelectric Cooling
Authors: O'Brien B. J. , Wallace C. S. , Landecker K.
Published: April 2005

The cooling of a single thermoelectric junction is limited to a certain temperature difference by the inherent properties of the elements used. Altenkirch gave a theoretical treatment of the single couple and showed a way to overcome the limitation on cooling by using a number of thermocouples in thermal cascade. Such an arrangement was constructed by Turrettini and shown to work. A simplified form of Altenkirch's theory is presented and a form of cascade which is simpler and more efficient than that of Turettini is described and experimental results are given. A two-stage cascade of elements limited to 11°C cooling as a single couple reached 15°C cooling while rather heavily loaded by lack of adequate thermal insulation. A good agreement with theory is obtained for the behavior of this cascade. It is shown that such a cascade is in theory more efficient than a single couple under all circumstances.
Effects of Low-Energy Gas Discharges on Evaporated Metal-Semiconductor Contacts
Authors: Hartig Patricia A. , Noyce Robert N.
Published: April 2005

Exposure of the surface of chemically clean 5 ohm-cm germanium to a low-energy gas discharge prior to evaporating onto it a platinum diode produced results dependent on the gas used. Exposure of n-type material to an oxygen or nitrogen discharge destroyed rectification completely; exposure to a hydrogen or argon discharge not only maintained it but tended to counteract the effect of the former gases. These results indicate that such oxygen and nitrogen bombardment lower the effective barrier, making the surface more n-type, but hydrogen and argon bombardment make it more p-type. This can be explained by the introduction of gas-dependent interface states.
High-Frequency Gas Discharge Breakdown in Neon-Argon Mixtures
Authors: Oskam H. J.
Published: April 2005

Breakdown electric fields in a wave guide at 9500 Mc/sec frequency are presented for a number of neon-argon mixtures at various pressures. The argon percentage is found to have a large influence on the breakdown electric field, just as Penning found for the dc discharge. For each argon concentration, only one minimum is found in the curves giving breakdown field as a function of pressure. This result contrasts with the two minima found in the dc discharge for some neon-argon mixtures. This can be explained by the difference between the efficiency of energy transfer from the electric field to the electrons in the dc case and the high-frequency case. The relation between the concentration of argon and the breakdown fields is discussed. The influence of electric field distortions and the standing-wave ratio in the wave guide are investigated.
Time Changes in Thin Films of BaTiO3
Authors: Feldman Charles
Published: April 2005

The decrease of dielectric constant with time under an applied alternating field, less than the coercive field, has been studied in films of BaTiO3 between 1 and 3 microns thick. The phenomenon may be interpreted as being associated with the process of switching the domains to a position more nearly parallel to the applied field.
On the Transient Behavior of Semiconductor Rectifiers
Authors: Gossick B. R.
Published: April 2005

The time dependent behavior of semiconductor surface barrier and point contact diodes has been calculated for small variations. (It is assumed here that the surface barrier lies on a semiconducting pellet with uniform cross section. If, on the contrary, the contact area is small compared with the semiconducting surface, like the case considered by Borneman, Schwartz, and Stickler [J. Appl. Phys. 26, 1021–1028 (1955)], then the analysis given for a point contact applies.) It is pointed out that these rectifying barriers have an ac admittance of the form Y(jω)=G0(1−Γ)+ΓG0(1+jωτ)12+jωCbin which G0 is the slope of the dc characteristic curve, Cb the barrier capacitance, ω and j the angular frequency and √−1, respectively, and τ the recombination time of minority carriers. The dimensionless constant Γ equals the injection ratio γ with surface barriers, but represents γr0(L+r0)−1 with point contacts where r0 is the effective contact radius, and L the diffusion length of minority carriers. The constant conductance G0(1−Γ) is related only to electrons with surface barriers (it is assumed that the semiconductor is n-type and that the rectifying contact emits holes), but with point contacts it is associated with both electrons and holes. The frequency dependent conductance ΓG0(1+jωτ)12 is due only to holes in either case. Compared with the conductance ΓG0(1+jωτ)12 the barrier capacitance Cb ordinarily plays a more dominant role in the frequency dependence of point contacts than with surface barriers, because the value of Γ is r0(L+r0)−1 times its value with surface barriers, and normally r0≪L.

The barrier voltage response f(t) to an impulse current has been calculated. Although the expression f(t) is complicated, it may be approximated under representative conditions (depending on bias and nature of the contact) by one of the following functions: e−t, et erfct½, or {[1–2C(t)] cost+[1–2S(t)] sint} with time t in appropriate units. The functions C(t) and S(t) are the Fresnel integrals defined by the equation C(t)−jS(t)= ∫ 0te−jxdx(2πx)12.

A special case of large amplitude behavior, the open circuit voltage decay following the interruption of forward current is also treated. It is found that with surface barriers, the open circuit decay time depends on recombination time of minority carriers, their penetration depth beyond the barrier in the semiconductor, and the injection ratio. With point contacts the decay time depends primarily on the product of the injection ratio and contact radius.
Oscillating Glow Discharge Plasma
Authors: Stewart A. B.
Published: April 2005

The plasma potential, electron temperature, and electron concentration have been measured as functions of both time and position in the positive column of an argon glow discharge with moving striations using a plane circular probe 0.25 mm in diameter that could be saturated in the electron collecting region. It is found that (1) the radial distribution of charge is that predicted by the ambipolar diffusion theory, (2) in each cycle, close to the time of the negative striation, the potential at all points in the positive column decreases sharply, (3) no increase in electron concentration occurs at the time of the negative striation. It is concluded that the positive striations move from anode to cathode as a result of ionization in front of the charge maximum combined with diffusion and drift of the charges radially and longitudinally. When the ionization function necessary to produce the observed striation motion is calculated from the observed charge concentrations, it is found to agree closely with the observed light emission of the discharge.
Electrical Cleanup of Gases in an Ionization Gauge
Authors: Young J. R.
Published: April 2005

Observations have been made on the electrical cleanup of different gases in a Bayard-Alpert ionization gauge. It has been found that the ion current striking the wall of such a gauge is 5 to 10 times that reaching the ion collector. It is therefore possible to account for a maximum pumping speed of 0.1 to 0.2 l/sec due to ion pumping at the gauge walls. The maximum pumping speed observed was 0.1 l/sec for nitrogen. It was found that the maximum pumping speed for nitrogen remained the same when the inner wall of the ion gauge was covered with a thin metal deposit or Aquadag. An expression has been derived on the basis of ion pumping which describes the observed cleanup.
Effect of Pressure on Glass Structure
Authors: Anderson O. L.
Published: April 2005

The anelastic response of a glass structure to pressure is examined in terms of the random-network hypothesis. The analysis is based upon the premise that an asymmetrical distribution of bond lengths characterizes the randomness of the network. It is found that the effect of pressure is to change the amount of skewness and therefore the average bond length which determines the density. Two kinds of persisting density changes are found. One is reversible and is called densification, and the other is irreversible and is called compaction. Experimental results for Corning 7052 glass show that both densification and compaction exist for combinations of the p, T, τ conditions, 3800 to 6600 atmos, 100–300°C, 15 min—1 week. These experiments also show that the kinetics of the densification process agree qualitatively with that predicted by the theory.