bluuebunny/crossref_metadata_2025 huggingface dataset:
On Stability of Linear Varying-Parameter Systems
Authors: Zadeh Lotfi A.
Published: April 2005

A linear varying-parameter system is defined to be stable if and only if every bounded input produces a bounded output. It is shown that a necessary and sufficient condition for stability is that the impulsive response of the system W(t, τ) should be integrable (considered as a function τ) for all t. From this result and the fact that the system function H(s; t) is the laplace transform of W(t, τ), it is deduced that a necessary condition for stability of a linear varying-parameter system is that the system function H(s; t) should be analytic and bounded in the right half and on the imaginary axis of the s-plane for all t. This result represents a generalization of the familiar frequency domain criterion which is commonly used in connection with fixed systems. The generalized criterion is applied to the investigation of stability of a variable feedback system.
Formulas for the Determination of Residual Stress in Wires by the Layer Removal Method
Authors: Read W. T.
Published: April 2005

The distribution of residual axial stress in a beam or wire of circular cross section is derived as a function of the moment required to straighten the wire after removal of successive layers of material. Application of the formulas involves two graphical differentiations and integrations of experimental curves.
High Temperature Structure and Thermal Expansion of Some Metals as Determined by X-Ray Diffraction Data. I. Platinum, Tantalum, Niobium, and Molybdenum
Authors: Edwards James W. , Speiser Rudolph , Johnston Herrick L.
Published: April 2005

The crystal structure and thermal expansion of platinum, tantalum, niobium, and molybdenum have been determined between 1100° and 2500°K. These metals were found to undergo a uniform thermal expansion over the temperature range of this investigation and to undergo no structural change. The permanent elongation of tantalum wires, produced by annealing at temperatures between 2473° and 2773°K, appears to be caused by reorientation of crystal grains in the specimen and to preferred direction of crystal growth during annealing, rather than to a change in crystal structure.

Quadratic equations have been developed for the thermal expansion of platinum, tantalum, niobium, and molybdenum. These equations are represented, respectively, by Δa0/a0=7.543×10−6(T−291)+2.362×10−9(T−291)2,Δa0/a0=6.080×10−6(T−291)+7.50×10−10(T−291)2,Δa0/a0=7.591×10−6(T−291)+6.96×10−10(T−291)2, and Δa0/a0=0.987×10−3+2.40×10−6(T−273)+2.20×10−9(T−273)2.

Values of the expansion coefficient α were computed for each of the metals by differentiating the above equations. Our values were compared with those obtained from the Grueneisen theory and indicate that the theory provides a reasonably satisfactory means of extrapolating thermal expansion data obtained at low and moderate temperatures.
Analysis of Synchronous Conditions in the Cylindrical Magnetron Space Charge
Authors: Welch H. W. , Dow W. G.
Published: April 2005

In the multianode cylindrical magnetron there exist favored phase velocities of the electromagnetic wave around the interaction space between anode and cathode. These velocities are characteristic of the resonant system attached to the anode segments. In the oscillating magnetron the electronic space charge within the interaction space is presumed to maintain sychronism with one of these velocities. Certain of the conditions of synchronism which can be discussed analytically are treated in this paper. The results, although based on restrictive assumptions, can be used in the interpretation of magnetron operation and in predicting regions of efficient behavior.
The Deformation of Gold Wire at High Temperature
Authors: Alexander B. H. , Dawson M. H. , Kling H. P.
Published: April 2005

Gold wires were subjected to small tensile stresses at high temperatures and the strain-time relationships were determined. These creep curves were similar to those generally obtained for metals at lower temperatures, except that the minimum creep rate was proportional to the applied stress; i.e., the flow was viscous. This coefficient of viscosity was determined as well as its variation with temperature. The surface energy of solid gold was also determined. Theories that have been presented to explain the viscous behavior of metals are briefly discussed.
Interfacial Free Energy of Coherent Twin Boundaries in Copper
Authors: Fullman R. L.
Published: April 2005

The ratio of the interfacial free energy of coherent twin boundaries to the average grain boundary free energy in copper has been measured by means of the dihedral angles formed at the intersections of twin boundaries and grain boundaries with each other and with a copper/lead vapor interface. The mean value found for the ratio is 0.035±0.006.
On the Spectrum of Isotropic Temperature Fluctuations in an Isotropic Turbulence
Authors: Corrsin Stanley
Published: April 2005

The one- and three-dimensional spectral equations for a field of isotropic temperature fluctuations in an isotropic turbulence are derived from the correlation equation. Then, except for the degenerate case of simple conductive decay, stationary fluctuation fields are postulated. Largely by dimensional reasoning and some simple postulates, forms of the temperature fluctuation power spectrum for particular wave number ranges are deduced and are compared with the results of previous analyses giving corresponding segments of the velocity spectrum. Finally, the relative ``effective cut-off'' wave numbers of the two spectra are compared in terms of the fluid Prandtl number.
Surface-Wave Propagation Over a Coated Plane Conductor
Authors: Attwood Stephen S.
Published: April 2005

A TM-type wave is assumed propagated parallel to the surface of a plane conductor coated with a thin layer of dielectric. This wave is similar to the wave propagated over a dielectric-coated wire of circular cross section, discussed by Dr. Goubau in the references. Analysis of the cylindrical type wave requires the use of Hankel functions, while the wave over a plane surface may be described by simpler functions, namely, trigonometric functions in the dielectric layer and real exponential functions in the adjacent air region. The calculations thus are considerably simplified and the wave properties more readily observed.

Basic equations are developed for both dielectric layer and air regions, which indicate a criss-cross or multiply reflected wave in the dielectric and a unidirectional wave in the air. Equations are developed also for the electric flux line shapes, power propagated over the cross section, concentration of power flow in neighborhood of the film, attenuation due to conductor wall loss and dielectric film loss. Numerical calculations are given for five film thicknesses varying from 0.0001 to 0.01 meter and for five frequencies ranging from 3×108 to 3×1010 cycles per second.
The Mathematical Basis of the Interpretation of Tracer Experiments in Closed Steady-State Systems
Authors: Sheppard C. W. , Householder A. S.
Published: April 2005

The basic equation for the mixing of radioactive isotopes is dR/dt = I grad a, where dR/dt is the flux of radioactivity; a, the relative specific activity; and I, the interfusion constant. The equation is applied to systems of compartments and some electrical analogies are presented. As special cases of the unconstrained systems treated in an earlier paper two constrained systems are discussed in which only a single radioactive isotope is required for the study of transport phenomena. One of these (mammillary system) consists of a central compartment communicating with a number of peripheral compartments. In the other (catenary system) the compartments are arranged chainwise. Equations are derived for the n-compartment mammillary system relating the time dependent specific activities of the compartments to the exchange rates between the peripheral and central compartments and to their content of substance being exchanged. In analyzing the effect of lumping of a series of compartments into a single equivalent one the case where the exchange rates cluster about a mean is discussed in some detail. In the catenary system the greater mathematical difficulties are indicated including the fact that the results depend on the order of the compartments. It is pointed out that in mammalian physiological experiments observations confined to only one compartment such as the circulating blood are insufficient for a complete analysis.
An Electrical Method for Investigating the Nature and Behavior of Small, Airborne, Charged Particles
Authors: Daniel J. H. , Brackett F. S.
Published: April 2005

A theoretical and experimental analysis of the current-voltage (dc) characteristic of a parallel-plate condenser through which the small, airborne, charged particles of an aerosol are passed continuously shows that a charge-weighted distribution of radius (or radius squared)-charge ratio may be obtained when certain experimental conditions are satisfied. Examination of such a distribution for an aerosol (particles less than a micron in diameter) before and after passage through a small (20-liter) settling chamber shows that the classes of particles in the distribution that are easiest to collect in the condenser are also the classes that disappear most rapidly in the chamber. It is pointed out that the methods employed would become less tedious and more powerful when used with a dispersion of constant-size particles, and that they are well adapted for certain fundamental investigations of aerosol properties.
Some Quantitative Data Bearing on the Scabbing of Metals under Explosive Attack
Authors: Rinehart John S.
Published: April 2005

Fracturing, or scabbing, of a material near a free surface as the result of a transient compressional stress wave of high intensity impinging on that surface has been observed for many years; however, little quantitative data that relate the fracture to the nature of the stress wave and the physical properties of the material seem to exist. The phenomenon has been investigated for five metals, 1020 steel, 4130 steel, 24S-T4 aluminum alloy, brass, and copper, by using an explosive charge to induce a high intensity stress wave in the metal. The distribution of pressure within the wave was determined by a modified Hopkinson-bar type of experiment.

Scabbing has been found to be governed principally by the spatial distribution of pressure within the wave and a critical normal fracture stress σc that is characteristic of the material and perhaps the state of stress. Numerical values of σc were obtained for each of the five metals.
Permanent Magnet Lenses
Authors: Reisner John H.
Published: April 2005

Permanent magnets have been successfully utilized to energize magnetic lens pole pieces for high resolution electron microscopy at direct magnifications of 7000 times with 30-kilovolt electrons, and 6000 times at 50 kilovolts. Stray magnetic fields, which have previously limited high magnification and high resolution, have been minimized by using two circuit gaps in parallel and by surrounding the assembly with a magnetic shield connected to the external pole pieces of the two gaps. Magnetomotive forces of 1400 gilberts have been obtained. A single magnet, magnets in bucking arrangement, and configurations involving magnets disposed either radially or parallel to the optical axis of the lens, have been successfully utilized. The effects of various magnetic circuit parameters on the design and operation of the lens system have been studied.
On the Diffraction of a Plane Electromagnetic Wave by a Paraboloid of Revolution
Authors: Horton C. W. , Karal F. C.
Published: April 2005

The problem of the diffraction of a plane electromagnetic wave by the convex surface of a paraboloid of revolution is examined. Expressions for the components of the incident wave, the scattered wave, and the refracted wave are obtained and are written in such a form that boundary conditions can be satisfied over a paraboloidal surface ξ=ξ0. The analysis is then restricted to the case of a perfectly conducting paraboloid and a wave whose wave front is perpendicular to the axis of rotation. The amplitude of the scattered wave is plotted as a function of the distance along the axis of rotation for three paraboloids. One of these curves is compared with the scattered field produced by a sphere whose radius is equal to the radius of curvature of the paraboloid at the nose.
Some Mechanical Properties of Graphite at Elevated Temperatures
Authors: Malmstrom C. , Keen R. , Green L.
Published: April 2005

The short-time tensile breaking strength of various grades of graphite was measured as a function of temperature from room temperature to the sublimation point. A characteristic common to all the strength versus temperature curves is that the strength approximately doubles in going from room temperature to about 2500°C and then decreases rapidly to zero near the sublimation point. Graphite can be used as a structural material at temperatures much higher than those permissible with other materials. The density distribution within an original block is given for grade EBP graphite. The creep characteristics of grade ECA graphite under tensile stress at elevated temperatures were investigated. The testing temperature ranged from 2200 to 2900°C while the applied stress varied from 500 to 5500 psi. The range of ``steady'' creep rates measured extended from 3×10−8 to 2×10−4 in. per in. per sec. The activation energy and change in entropy defined by rate theory were calculated for the above conditions. Low frequency dynamic measurements of the Young's modulus of grade ECA graphite made at temperatures from 1000 to 2000°C showed an increase of the modulus with temperature.
The Plastic Deformation of Pure Single Crystals of Lead and Copper
Authors: Neurath Peter W. , Koehler James S.
Published: April 2005

Single crystals of 99.999 percent pure lead and copper were grown by the Bridgman method. A tensile creep apparatus is described. Measurements on copper at 23°C and at −190°C show that for resolved shearing stresses below 0.6 kg per mm2 the steady-state creep rate is negligible (i.e., less than 10−6 per minute). The resolved yield stress for copper is 219±21 g per mm2 at both the temperatures used. In the case of lead, for resolved shearing stresses below 0.13 kg per mm2 the steady-state creep is negligible at −190°C. The yield stress at that temperature is 96±8 g per mm2. Measurements were made on the steady-state creep of lead at 25°C and 110°C. The results produced by annealing were investigated.
Relation between Gas Evolution and Physical Properties of Liquids
Authors: Szebehely V. G.
Published: April 2005

Four heavy lubricating oils, three light lubricating oils, and three aircraft engine fuels were tested for viscosity, surface tension, and density, and a relation was established between the time rate of evolution and solution of air and the viscosity of the liquids. A definite relation was also found between solubility constants and half-lives as well as between half-lives of evolution and solution.
The Electric and Magnetic Constants of Metallic Delay Media Containing Obstacles of Arbitrary Shape and Thickness
Authors: Cohn Seymour B.
Published: April 2005

The dielectric constant and permeability of a metallic-obstacle medium are obtained in this paper by various static methods. The equivalent shunt capacitive susceptance and series inductive reactance of the individual obstacles are also determined. In the first part of the paper, a correspondence is established between an infinitely thin conducting obstacle and an aperture in an infinitely thin conducting wall. With the aid of this correspondence, delay medium formulas are given for several obstacle shapes. Formulas are then derived for the effect on the magnetic field of moderate obstacle thickness. Finally, it is shown how the electric and magnetic constants may be evaluated by electrolytic tank measurements in the case of obstacles having completely arbitrary shape and thickness. This has been done for a typical delay medium, and the effect of obstacle thickness on the index of refraction is shown.
Lattice and Grain Boundary Self-Diffusion in Silver
Authors: Hoffman R. E. , Turnbull D.
Published: April 2005

The lattice and grain boundary self-diffusion coefficients of high purity silver have been measured over extended temperature ranges. It has been found that the lattice diffusion coefficients are described by the equation, DL=0.895 exp(−49500/RT) cm2 sec−1 and are independent of the thermal history of the crystals within wide limits. The absolute grain boundary diffusion coefficients fit the equation, DB=0.03 exp(−20,200/RT) cm2 sec−1 and are independent of the grain size of the specimens.
On Shock-Wave Phenomena: Waterlike Substances
Authors: Seeger R. J. , Polachek H.
Published: April 2005

The properties of shock waves in waterlike substances are investigated in detail. A waterlike substance is defined as one for which the intrinsic energy is separable into a sum of two terms, one of which is a function of density only and the second a function of specific entropy. It is known that many substances, including water, behave in this fashion within a large range of pressure variation.

The paper consists of six sections. Section I contains some introductory material. Section II consists of a derivation of the basic equations that govern the propagation of plane shock waves in a waterlike substance. Section III is an analysis of one-dimensional interaction of shock waves, rarefaction waves, and contact discontinuities in a medium of this type. It is shown that a number of intrinsic differences exist between the behavior of shock waves in waterlike substances and their behavior in ideal gases.

In Section IV, one-dimensional interaction of shock waves in arbitrary fluids is discussed. Section V presents the theory of regular reflection of shock waves in waterlike substances; while Section VI presents the theory of triple-shock intersections. In both instances essential differences between the behavior of shock waves in waterlike substances and ideal gases are noted. The text is supplemented by numerous tables and charts.
Scattering Phenomena in Electron Microscope Image Formation
Authors: Hall C. E.
Published: April 2005

Equations are derived for the relative intensities in electron microscope images formed without a limiting aperture in the objective lens. Three components of intensity at the image plane can be distinguished: IT, a transmitted intensity of very small relative aperture; IK, an intensity scattered within the effective aperture of the objective lens; and IB, a background intensity which does not contribute to the recognizable image. The equations derived involve two scattering cross sections, both of which are readily measurable under normal operating conditions. The form of the equations is verified experimentally; and cross sections are measured for Be, SiO, Cr, Ge, Pd, Pt, and U. The effect of altering the beam potential is discussed in the light of the results and the minimum detectable increment in specimen thickness due to scattering is estimated.
X-Ray Measurement of Long-Range Order in β-AgZn
Authors: Muldawer L.
Published: April 2005

The replacement of small amounts of Ag by Au in AgZn raises the critical temperature for long-range ordering and completely suppresses the zeta-phase. Measurements of Tc were made in a high temperature camera using several percentages of Au. Extrapolation to zero content of Au gives Tc=272°C for pure AgZn. The variation of long-range order with temperature was determined from measurements of the integrated intensity of the (111) superstructure line, using a compact of filings of composition 3.5 Au, 46.5 Ag, and 50.0 Zn. The variation is similar to that found in β-brass, and is in agreement with the predictions of the Cowley theory.
On the Diffraction of Electromagnetic Waves by Two Conducting Parallel Half-Planes
Authors: Cheney M. G. , Watson Robert B.
Published: April 2005

An examination is made of the diffraction of radar waves produced by the edges of two parallel half-planes, disposed one behind the other relative to the signal source. A number of experimental patterns are exhibited. Computed patterns are obtained following a line of analysis formulated by Baker and Copson. Comparison between experiment and theory shows only fair agreement, indicating the need for a better theoretical approach.
Nuclear Magnetic Resonance Study of Transitions in Polymers
Authors: Holroyd L. V. , Codrington R. S. , Mrowca B. A. , Guth E.
Published: April 2005

Nuclear magnetic resonance absorption line widths have been studied for several high polymers. The proton line widths were studied in a field of 7000 gauss and at a frequency of about 30 mc. Line widths obtained for Hevea and GR-S were very narrow, indicating a large degree of ``quasi-free rotation'' in these materials. Vulcanization, carbon loading, co-polymerization, and crystallization produced a broadening of the lines as expected from the hindrance to internal motion introduced by these factors. Line width transitions as a function of temperature were observed for several polymers. Linear thermal expansion coefficients and specific heat vs temperature curves have breaks in the region of line transitions for the polymers studied. Swelling of polymers with benzene produced a narrowing of the absorption line throughout the line transition and lowered the transition temperature. Vulcanization broadened the transition range and shifted it to higher temperatures. Of two closely cut fractions of polystyrene, the larger molecular weight sample exhibited a line transition range at a higher temperature. The styrene monomer as well as the two fractions exhibited the same low temperature line width of about 8 gauss. The line width transitions were also studied for three butadiene styrene co-polymers at temperatures where anomalous behavior was found in dynamic measurements. The theoretical implications of these experimental results, together with a survey of other pertinent work, indicate the possibilities of the nuclear resonance method as applied to the study of high polymers in conjunction with other methods.
Electrical Properties of Some Carbon Black-Oil Suspensions
Authors: Forster Michael J. , Mead Darwin J.
Published: April 2005

The dc conductivity and ac (1000 cps) properties of suspensions of R-40 carbon black in transformer, silicone, and linseed oils, and suspensions of Shawinigan black in linseed oil, were studied as functions of time, carbon black concentrations, and rotational speed of test cell. The dc conductivity was also studied as a function of voltage. Immediately after agitating the suspension, both ac and dc conductivities increase rapidly with time, then level off and approach a saturation value. For the dc conductivity, this value increases with increasing voltage in all suspensions studied except the highest concentrations (10 percent by weight), which obey Ohm's law. The rate of approach to saturation is independent of voltage but depends on carbon black concentration. Increasing the concentration increases the conductivity. Increasing the speed of rotation decreases the conductivity. Form factors for the carbon black particles are calculated from the dynamic values of the dielectric constant by Voet's method. Agglomeration factors are then determined. At low speeds the agglomeration factor decreases rapidly with increasing speed. At higher speeds it approaches unity asymptotically.
Sedimentation Equilibrium in Concentrated Polymer Solutions
Authors: Wales M.
Published: April 2005

It has been shown that sedimentation equilibrium can be obtained in polymer solutions of concentration as high as 20 percent by weight. This equilibrium has been approached from both sides, with identical results. The virial coefficients for the osmotic pressure may be calculated from experiments of this kind. The results are in good agreement with the osmotic pressure data of other investigators for polystyrene in butanone and polyvinyl acetate in butanone.
Starting Potentials of Positive and Negative Coronas with Coaxial Geometry in Pure N2, Pure O2, and Various Mixtures at Pressures from Atmospheric to 27 mm
Authors: Miller Charles G. , Loeb Leonard B.
Published: April 2005

Consequent to an exhaustive study of coronas with coaxial cylindrical geometry in pure N2, pure O2, and mixtures over a considerable pressure range, it has been possible to obtain a consistent set of threshold values as a function of gas type and pressure for the principle current transitions signaling the accepted coronas. Thresholds for the positive wire corona should depend on gas characteristics only, while those of negative wires should reflect the second Townsend coefficients characteristic of the cathode material. Observations indicate that interpretation along this simple line is complicated by two factors. First, some current transitions under different conditions, which were in the past assumed to represent the same corona process, have been found to be different mechanisms. Thus, in pure N2 positive wire corona is not a gas determined process but a cathode dependent mechanism, while in pure O2 the corona is a gas dependent process but of the streamer type and not of the burst pulse type. Secondly, all thresholds of the characteristic negative wire corona transitions do not represent a secondary mechanisms characteristic of the cathode surface. These transitions are all preceded by a low order Townsend discharge whose threshold passes unnoticed but is characteristic of the initial cathode state. The commonly noted threshold is determined by a conditioning process which may depend on current density, duration of bombardment, and the composition of the gas. While the data yielded by the antecedent studies permits of interpretation in the present system of gases, this study also indicates that a correct interpretation of relative starting potentials of positive and negative wire coronas requires an extensive investigation of the basic nature of the coronas before it is attempted.
A Preliminary Study of a Physical Basis of Bird Navigation. Part II
Authors: Yeagley Henry L.
Published: April 2005

The previous paper contained a complete statement of the Magnetic-Vertical-Coriolis theory and the experimentation carried on from November, 1943, through July, 1945 (Experiments I through V). The present report presents the results obtained since this latter date and up to the summer of 1949 (Experiments VI through XI).
Electrical Breakdown Over Insulators in High Vacuum
Authors: Gleichauf Paul H.
Published: April 2005

The breakdown voltage of vacuum gaps depends on the electrode material, but when the gap is bridged by an insulator it is independent of the electrode material and varies with the kind of insulator. Some indication is found that the breakdown voltage increases with increasing surface resistivity of the insulator, but no apparent correlation is found between breakdown voltage and dielectric constant, density, or vapor pressure. It is found that a roughening of the intervening surface of the insulator in a region adjacent to the cathode increases the breakdown voltage. For electrode separations of 1 mm or greater the breakdown voltage does not increase linearly with the length of the insulator. Experiments were made in which one of the electrodes was separated from the insulator. It seems that the critical gradient at breakdown in the vacuum space between the cathode and the insulator, calculated for the case of plane electrodes from the ratio of dielectric constants, is not as large as would be required in gaps without insulators. These gradients are almost the same for copper as for stainless steel electrodes. The breakdown voltage over an insulator is raised when the edge of the insulator close to either electrode is rounded. When a layer of glass, thin compared with the separation of electrodes, is fused to the cathode, breakdowns occur at lower voltages than for an identical vacuum gap.
An Application of the Absolute Reaction Rate Theory to Some Problems in Annealing
Authors: Cagle F. Wm. , Eyring Henry
Published: April 2005

Absolute rate theory is combined with molecular models in the study of the annealing of metals and of glass. It is thus possible to obtain expressions which are in close agreement with experimental data. Both the observed first-order data for metals and the second-order data for glass are predicted in this way. A virtue of the rate theory treatment is that it replaces the earlier macroscopic theories with a treatment in molecular terms.
Effect of Size and Spectral Purity of Source on Fringe Pattern of the Mach-Zehnder Interferometer
Authors: Bennett F. D.
Published: April 2005

In analysis of Mach-Zehnder interferograms taken of the axi-symmetric flows about supersonic projectiles, the question arises whether errors in fringe width occur because of the finite size and non-zero spectral width of the source employed. Under the assumptions that the source is a circular area normal to the axis of the interferometer with spectral intensity function approximated by a gaussian error curve, it is shown that the deviations from ideal fringe width λ0/ε caused by source size and spectral line width are negligibly small for an interferogram with 200 fringes on either side of center. The limiting factor is not deviation in fringe width but the exponential damping of fringe intensity amplitude owing to the spectral band width of the source. This reduces the fringe contrast below experimental detectability long before deviations in fringe width become appreciable.
Behavior of the Resistance Ignitor in Mercury
Authors: Rigrod W. W.
Published: April 2005

An empiric expression has been derived for the probability of arc striking per unit time, per unit length of contact perimeter, for a resistance ignitor in a mercury-pool tube: p′=k(E−E0)3/ρ2, where k and E0 are constants, E is the ``useful'' electric field strength near the mercury surface, and ρ the resistivity of ignitor material at the junction with the mercury.

From the foregoing, a formula has been established for the probability of ignition per unit time, for the entire ignitor, in terms of the applied voltage v and ignitor ``firing resistance'' R. With this formula, whose two arbitrary constants can be determined by two sets of measurements, the firing voltage of any ignitor can be predicted under a wide variety of circuit conditions, provided R remains unchanged under these conditions.

The probability formula was found to be consistent with a modification of a theory advanced by L. Tonks, whereby mercury surface distortion and rupture permit field emission at field strengths less than those effective for smooth surfaces. The modification attributes the reduction in ignitor firing voltage by ignitor current to its extremely localized ohmic heating of the mercury. This heating reduces the surface tension and roughens the mercury surface, thereby accelerating the process of surface rupture by the electric field.
On the Nonspecular Reflection of Electromagnetic Waves
Authors: Twersky Victor
Published: April 2005

The nonspecular reflection of plane electromagnetic waves of arbitrary polarization by certain perfectly conducting surfaces composed of either semicylindrical or hemispherical bosses on an infinite plane is analyzed. Solutions for the problem of the single boss on an infinite plane and a plane wave at an arbitrary angle of incidence are given and extended subject to the single-scattering hypothesis to obtain the far field solutions for certain small finite patterned distributions and both small finite and infinite uniform random distributions of bosses small compared with the wavelength. The results for the various cases are then compared in the plane of incidence and similarities between the analogous expressions for the distributions of semi-cylinders and hemispheres are noted. Expressions are obtained for the ratios of the components of the reflected intensity and radial energy flux polarized parallel and perpendicular to the plane of incidence as well as for the total intensity and radial energy flux for the case where the incident wave is unpolarized. It is found that for certain values of the parameters the reflected radiation may consist only of either the specular or the scattered contributions, while for other values one of the scattered contributions, either the parallel or perpendicular component, may vanish. The results also indicate the occurrence of an extremum in the reflected radiation in the vicinity of the specular angle of reflection, which for certain ranges of the parameters for the small finite distributions may be a minimum rather than a maximum. For these cases there is also some critical angle of incidence (not necessarily π/2 or grazing incidence) for which the reflection at the specular angle is completely specular.

The analogous distributions of cylinders and spheres are also considered.
Measurement of Dynamic Internal Dissipation and Elasticity of Soft Plastics
Authors: Rorden H. C. , Grieco A.
Published: April 2005

In order to measure the mechanical properties of soft plastics over wide frequency and temperature ranges two new techniques have been devised. The first one, which operates in the frequency range of a few cycles, uses a horizontal oscillating pendulum. The shear impedance of the sample is measured by mounting a small pad of the material between the vibrating pendulum and a fixed platform and determining the change in frequency and the change in the decrement caused by the sample. From these measurements the shear mechanical resistance and reactance of the specimen can be determined. The other technique, which is applicable in the frequency range from 100 cycles to 10,000 cycles, makes use of a vibrating tuning fork. Two identical samples are mounted between a stationary weight and the moving tines, and the shear mechanical impedance is determined by determining the change in frequency and change in decrement caused by the specimen. These two techniques have been applied to measuring the shear properties of a number of soft plastics including Pyralin, Koroseal, Keldur, polyvinyl butyral, Thiokol, and gum rubber. All of these show relaxation effects. The polyvinyl butyral appears to be approaching a crystalline elastic stage at the low frequency of 1000 cycles, while gum rubber remains in a quasi-configurational stage from 2 cycles to 1000 cycles.
Some Electrical Properties of Zinc Oxide Semiconductor
Authors: Hahn E. E.
Published: April 2005

Measurements of the dark electrical conductivity σ, and Hall coefficient were made on sintered spectroscopically pure zinc oxide powder samples over a temperature range from 100°K to 625°K and at room temperature on zinc oxide crystals containing lead impurities, using both the usual dc potentiometer-probe method and an ac (4000 cps) set. In this reproducible range, lnσ is not linear with 1/T for the sintered samples but exhibits maxima occurring at higher T and σ values, the higher the sintering temperature; the electronic carrier concentration of the different samples, calculated from the Hall data, indicates thermal ionization of 1.6×1016 to 9.0×1017 donors/cm3 lying 0.017 to 0.045 ev below the conduction band, with increasing ionization energy and increasing donor concentration, in general, occurring for higher sintering temperatures. Conductivity measurements are also made on sintered samples from 300°K to 1040°K using the ac (4000 cps) voltmeter-ammeter method; above about 650°K, lnσ versus 1/T is linear and in agreement with the results of previous workers with ionization energies varying from 1.4 to 2.4 ev. Back reflection x-ray patterns indicate an increase in the lattice spacing after sintering; the change can be correlated with the presence of interstitial zinc atoms. The forbidden gap is taken to be about 3 ev, corresponding to an ultraviolet absorption edge and luminescence peak at 3.2 ev; the yellowing of worked or highly conducting or heated samples is attributed to a shift of this absorption edge into the visible. Room temperature impedance measurements show a frequency dependent reactance and resistance attributable to capacitive shunting of the high resistivity grain boundaries (ν∼107 cps). It is shown that the low frequency conductivity of the sintered samples is determined by the conductivity and relative thickness of the grain boundary material while the Hall coefficient depends mainly on the carrier concentration in the semiconducting grains; uncritical use of low frequency and dc results thus would lead to spuriously low values of the conductivity and mobility in relation to the true properties of the grains.
Approximation of Axisymmetric Body Forms for Specified Pressure Distributions
Authors: McNown John S. , Hsu En-Yun
Published: April 2005

The complex relationship between body profile and pressure distribution is important in the design of high-speed undersea bodies. For slender axisymmetric bodies integration of the equations for irrotational flow has been accomplished, the coordinates of the body profile being related to the pressure distribution through coefficients of Legendre polynomials. The limitations and applications of this approximate analysis have been demonstrated through comparisons with preassigned conditions and with the results of experiments. Computed values closely approach those preassigned or measured throughout the central portion of the body if the maximum diameter does not exceed three-tenths of the length. The analysis is accordingly useful in designing bodies with low coefficients of drag and low incipient cavitation numbers.
The Motion and Precipitation of Suspensoids in Divergent Electric Fields
Authors: Pohl Herbert A.
Published: April 2005

The motion of suspensoid particles relative to that of the solvent resulting from polarization forces produced by an inhomogeneous electric field is defined as ``dielectrophoresis.'' It is analogous to the related phenomenon of electrophoresis, in which motion of suspensoid particles is produced by the action of an electrostatic field on the charged particles.

From a consideration of theoretical calculations and from experimental observations it is concluded that the phenomena of ``dielectrophoresis'' and ``dielectro-precipitation'' can be observed under rather ideal conditions, though it is ordinarily often difficult to do so because of the presence of the more easily produced electrophoresis or ion-type migration of charged particles.

The usefulness of dielectrophoresis (and/or electrophoresis) for removing suspended solid particles from polymer solutions during analysis is described.
The Production and Stability of Converging Shock Waves
Authors: Perry Robert W. , Kantrowitz Arthur
Published: April 2005

Converging shock waves offer interesting possibilities of attaining very high temperatures and pressures. A theoretical treatment by G. Guderley which we have confirmed and extended by the method of characteristics indicated that the strength of a strong converging cylindrical or spherical shock varies inversely with a power (0.396 for γ=1.4) of the surface area of the wave, thus becoming very great close to the center of convergence. The experimental production of high temperatures and pressures by means of these converging shocks depends on their ``stability'' of form. A converging wave is said to be stable if it approaches perfect cylindrical or spherical shape, thus damping out random disturbances as it propagates. The experimental work of L. G. Smith on Mach reflection is applied to show that these converging waves are stable for the shock range (M≤2.4) covered by his experiments. Smith's work and the theoretical work of Lighthill indicate that the stability decreases greatly at high Mach numbers.

The simplest experimental method of achieving a cylindrical converging shock is by the use of a shock tube with a converging channel. This, however, results in the hottest region of the gas being in close thermal contact with the cold walls. An axially symmetric shock tube has been designed and constructed which produces a complete converging cylindrical shock rather than just a sector and in which the region of convergence is comparatively well isolated thermally from the walls. It has been found possible to converge a moderate strength shock wave (M=1.7) sufficiently to produce considerable luminosity at the center of convergence. Schlieren photographs are presented showing various phases of the formation and stability of these converging waves.
Theory of Air-Coupled Flexural Waves
Authors: Press Frank , Ewing Maurice
Published: April 2005

The theory of air-coupled flexural waves in a floating ice sheet is derived for the case of an impulsive point source situated either in the air or in the water. It is found that new branches are introduced to the dispersion curve of flexural waves as a result of coupling to compressional waves in the atmosphere. Experimental data are briefly reviewed.
Relations between Initial and Final Orientations in Rolling and Annealing of Silicon Ferrite
Authors: Decker B. F. , Harker David
Published: April 2005

An investigation of the effects of rolling and annealing on the orientation of individual grains in silicon ferrite strip yielded results which led to the formulation of a theory for the appearance of the ``magnetic'' orientation in the final processed strip. It is proposed that, in a fine-grained strip of silicon ferrite, those grains which are already in the ``magnetic'' orientation before rolling will keep that mean orientation during rolling but become more highly strained than other grains, and therefore, they will become the portions of the cold-rolled strip with highest free energy. In the annealing process these highest energy regions will recrystallize first, becoming lowest energy regions which will be able to consume the now higher energy regions surrounding them. Since these nuclei have the ``magnetic'' orientation, the final product also attains the ``magnetic'' orientation.
Wave Propagation on Helical Wires
Authors: Sollfrey William
Published: April 2005

Previous researches on the helix have made simplifying approximations about the nature of the boundary conditions. In this paper the field equations and boundary conditions are formulated exactly. They are then solved by an expansion in powers of the ratio of the thickness of the wire to the distance between turns.

The method used consists of introducing a new coordinate system, which is such that a helical wire of circular cross section is a surface in which one coordinate is constant. Maxwell's equations and the electromagnetic boundary conditions are expressed in terms of this system. Since nonorthogonal coordinates are involved, the equations cannot be solved exactly; but a perturbation procedure may be applied as indicated above.

The result of the analysis is to show that there is a principal mode, which propagates with the free space velocity of light in the direction of the wire. The characteristics of this mode are studied, and they are compared successfully with experiment.
Electrical Properties of Selenium: I. Single Crystals
Authors: Henkels H. W.
Published: April 2005

Crystals of hexagonal selenium have been grown in a melt. Their microstructures have been compared with those arising in vapor crystals.

The dark resistivity has been studied as a function of axis orientation, temperature, field, and time of application of a field. The thermoelectric power has been measured and attempts made to measure Hall effect. The nature of the acceptor levels has been discussed, the approximate hole densities and mobilities have been determined, and values of the activation energies obtained.

The field effects have been discussed and the phenomenon of an apparent semipermanent polarization occurring at quite low fields has been noted.
Anelastic Effects Arising from Precipitation in Aluminum-Zinc Alloys
Authors: Nowick A. S.
Published: April 2005

Torsion experiments on an aluminum-zinc alloy (21 atomic percent zinc) show that precipitation gives rise to large values of internal friction. After prolonged periods of aging, which are sufficient to produce growth of the precipitate particles, the internal friction begins to decrease. The activation energy for the elementary process producing the anelastic behavior is 23 kcal per mole. It is demonstrated, with the help of static measurements, that the curves of internal friction versus temperature do not show a peak but continue to rise indefinitely with increasing temperature. This behavior cannot readily be interpreted in terms of the usual concept of a relaxation spectrum but requires a new concept of coupled relaxations. Metallographic examination of the specimens reveals that the observations of large internal friction are correlated with the occurrence of discontinuous precipitation. The observed anelasticity is interpreted in terms of the fragmentation of the lattice; i.e., the formation of an irregular network of shear-relaxing interfaces during discontinuous precipitation. It is demonstrated that in such a network the coupling, produced by an overlapping of regions within which shear stress is relaxed, makes possible a very large total relaxation. Additional measurements of elastic aftereffect in the supersaturated solid solution permit the determination of the mean time of stay of atoms in this solid solution, between 52°C and 72°C, by the anelasticity resulting from pair reorientation. The results obtained are in excellent agreement with the conventional high temperature diffusion data and correspond to a heat of activation for diffusion of 25.4 kcal per mole.
Heat Conduction in Simple Metals
Authors: Storm M. L.
Published: April 2005

The partial differential equation of heat conduction is a nonlinear equation when the temperature dependence of the thermal parameters (i.e., the thermal conductivity, K, and S, the product of the density and the specific heat at constant pressure) is taken into account. It is shown that a mathematical condition for the transformation to linear form of the one-dimensional, nonlinear, partial differential equation of heat conduction is the constancy of [1/(KS)½](d/dT)log(S/K)½. This discovery is the motivation for an investigation of the relations between the thermal parameters of simple metals on the bases of the theory of solids and available experimental data. It is found that KS is essentially constant, its variation with temperature being much less than that of either K or S considered separately. It is also shown, as a result, that the condition for the above-mentioned transformation is valid for simple metals. Applications of the transformed equation to the solution of problems in heat conduction are considered.
Forced Vibration of Reed as a Method of Determining Viscoelasticity
Authors: Horio M. , Onogi S.
Published: April 2005

The motion of a clamp-free reed excited by a sinusoidal displacement of the clamped end was analyzed by rigorously solving the fundamental equation for vibration. The real and imaginary parts of the modulus are given in terms of resonant frequency and band width of the frequency curves. The results are compared with those of Nolle which were obtained in an approximate manner by introducing an equivalent electric circuit. As long as the mechanical loss tangent is smaller than 10−1, as is the case in most high polymers, the practical error caused by the approximation is estimated to be insignificant. Nolle's network was interpreted from a purely mechanical standpoint by means of the fundamental equation for vibration.
Conduction of Current in a Metallic Pipe Filled with a Conducting Liquid
Authors: Poritsky H. , Weil H.
Published: April 2005

The electric potential across a metallic pipe is investigated when current enters and leaves through two diametrically opposite points and the pipe is either empty, filled with a conducting fluid, or lined with a thin film of the fluid.