bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Systems Involving Difference-Differential Equations
Authors: Burford T. M.
Published: April 2005

It is known that many physical systems, both time and space dependent, are described by difference-differential equations. Although the exact solutions to such equations are known to be unique, their determination usually involves a segmented type of solution that is very laborious to obtain. An approximate method of determining any number of roots is described. This approximate procedure allows forward gain and delay to be freely chosen and gives immediately the maximum stable value of forward gain. In many cases, especially where an optimum value of damping constant or forward gain is to be found, it appears that this approximate procedure is more easily applied than any previously described method.
Lower Modes of a Concentric Line Having a Helical Inner Conductor
Authors: Stark Louis
Published: April 2005

The natural, undamped modes of propagation in a concentric line having a circular outer conductor and a tape-helix inner conductor are investigated. The investigation is primarily concerned with a study of the propagation characteristics of the modes and, by making suitable approximations, closed expressions for the propagation factors of a few of the lower modes are obtained. Numerical results are then presented for a system having typical geometrical parameters, and generalizations of a qualitative nature are indicated. In the course of the work, the natural-mode field expressions are derived.
Dielectric Constant and Loss Measurements on Barium Titanate Single Crystals While Traversing the Hysteresis Loop
Authors: Drougard M. E. , Funk H. L. , Young D. R.
Published: April 2005

A small amplitude high-frequency voltage has been superposed on a large amplitude low-frequency sweeping voltage to study the dielectric behavior of barium titanate single crystals while traversing the hysteresis loop. The output of a capacitance bridge (filtered to pass only the high-frequency component) is displayed on an oscilloscope as a function of either the applied sweeping voltage, the polarization, or the current to the sample. As a result, the bridge can be balanced for any portion of the sweeping voltage cycle desired. The dielectric constant and loss obtained in this manner have been studied as a function of measuring frequency, of sweeping frequency, of sweeping voltage and of rate of switching polarization (current). The measuring frequency and the switching current are shown to be the significant variables. The frequency dependence of the dielectric constant and loss can be described by a relaxation type of spectrum with a relaxation time of 5.5 microseconds.
Matrix Analysis of Linear Time-Varying Circuits
Authors: Pipes Louis A.
Published: April 2005

This paper presents a general mathematical technique for studying the response and stability of linear time-varying circuits that contain parameters whose magnitudes vary in a periodic manner with the time. The method presented reduces the solution of the circuit differential equation to that of computing powers of matrices. For purposes of illustration, the method is used to determine the response of an electric circuit consisting of a constant resistance and inductance in series with a periodically varying capacitance. The cases of square-wave and saw-tooth-wave variations of the variable parameter are considered in detail.
Analysis of the Effect of Various Factors on Metal Transfer and Wear between Specimen Pairs of Same Metal and Same Shape. I. The Basic Scheme of Formulation of Metal Transfer and Wear
Authors: Feng I-Ming
Published: April 2005

The fundamental scheme of formulation of the amount of metal transfer and wear is based upon the theory suggested in the previous paper [J. Appl. Phys. 23, 1011–1019 (1953)]. The basic terms used in formulating metal transfer and wear are (1) the potential amount of metal transfer Mt*; (2) the mechanical factor of the chance of metal transfer φm; (3) the thermal factor of the chance of metal transfer ψθ; and (4) the adhesion factor of the chance of metal transfer Xa. The expression for the amount of metal transfer Mt from one specimen to another is Mt=Mt*φmψθ, when ψθ is bigger than Xa, and is Mt=Mt*φmXa when Xa is bigger than ψθ. The equation for the amount of wear Mw represented by the weight loss of a specimen is Mw=Mt*φm (1-ψθ), when ψθ is bigger than Xa, and is Mw=Mt*φm (1-Xa), when Xa is bigger than ψθ.
Analysis of the Effect of Various Factors on Metal Transfer and Wear between Specimen Pairs of Same Metal and Same Shape. II. Effect of the Surrounding Atmosphere
Authors: Feng I—Ming
Published: April 2005

The discussion in this paper is limited to the case where the surface layer is thinner than the average depth of roughening. The surrounding atmosphere influences the adhesion factor Xa through its effect on adhesion that depends on such factors as the nature and thickness of the surface layer and also the degree of plastic roughening. The influence of the surface layer on the thermal factor ψθ is similar to its influence on Xa. Because of the lack of the quantitative knowledge about its effect on adhesion and diffusion, the effect of surrounding atmosphere on metal transfer and wear is discussed qualitatively. The dependence upon such factors as the temperature, gas pressure, time of exposure, etc., of the effect of physically adsorbed and chemical-compound surface layers on metal transfer and wear is also discussed in this paper.
Cross-Wound Twin Helices for Traveling-Wave Tubes
Authors: Chodorow Marvin , Chu E. L.
Published: April 2005

This paper describes a structure, namely, a cross-wound twin helix which overcomes the disadvantages of a conventional helix for high-voltage traveling-wave tubes. The disadvantages of a single helix suitable for high voltages are: (1) the impedance for electron interaction is reduced because of the energy content of the noninteracting space harmonics, and (2) the high impedance of some of the space harmonics can result in backward-wave oscillation. In a structure consisting of two helices wound in opposite directions, the symmetry of the fields results in most of the electric energy being stored in the fundamental component and most of the magnetic energy in the space harmonics. This results in a higher impedance for the fundamental component and a reduced impedance for the space harmonics. Typical numbers for dimensions suitable for 10-kv operation are an increase of a factor of 2 in the fundamental impedance and a reduction of a factor of about 20 in the −1 space harmonic for the twin helix as compared to the single helix.
Effect of Delayed Fission Neutrons on Reactor Kinetics
Authors: Robinson Lawrence Baylor
Published: April 2005

A detailed treatment of reactor kinetics is given. The kinetic equations are derived from a diffusion-Fermi age model. An iterative technique and a matrix method are discussed as possibilities for obtaining solutions. The relationship between the solutions with and without delayed neutrons is pointed out. The concept of stability is discussed for the system which includes the delayed neutrons. The similarity of the treatment here to that used in other branches of mathematical physics (especially quantum mechanics) is noted.
Closed Expansion of the Convolution Integral (A Generalization of Servomechanism Error Coefficients)
Authors: Arthurs Edward , Martin Louis H.
Published: April 2005

This paper presents a closed expansion of the convolution integral, which is useful in approximating the response of a linear time invariant system to an arbitrary forcing function. In a sense it is a generalization of the well known error coefficient expansion frequently discussed in connection with servomechanisms. This expansion is helpful when the response of the system cannot be evaluated exactly (i.e., the input function is specified graphically or input function cannot be transformed conveniently). This expansion differs from the error coefficient expansion in that it is valid for an arbitrary forcing function and is in a closed form accounting for the entire response of the system, rather than in an open form of Taylor's series that either neglects or simply bounds a portion of the total response.
Electrical Conductivity of Highly Ionized Argon Produced by Shock Waves
Authors: Lin Shao-Chi , Resler E. L. , Kantrowitz Arthur
Published: April 2005

Shock tube techniques for the production of shock waves up to Mach number 20 have been developed and reported previously by Resler, Lin, and Kantrowitz, J. Appl. Phys. 23, 1390 (1952). These techniques can produce high temperature gas with accurately known enthalpy (e.g., in argon 25 percent ionization has been produced following an incident shock). Spectroscopic studies of high temperature argon produced this way by Petscheck, Rose, Glick, Kane, and Kantrowitz, ``Spectroscopic studies of highly ionized argon produced by shock waves,'' J. Appl. Phys. 26, 83 (1955), showed that equilibrium ionization can be reached in the time available in these experiments (of the order of 100 microseconds). This paper reports a study of the electrical conductivity of high temperature argon produced by shock waves.

At low degrees of ionization (less than 10−3 for argon), the diffusivity of electrons and thus the gas conductivity is determined by the cross section for electron-atom collisions which has been measured by mobility and by scattering techniques. At high degrees of ionization (larger than 10−3 for argon) the diffusion of electrons is primarily limited by long range Coulomb interaction with positive ions and thus is independent of the chemical nature of the gas. Theoretical treatments of this case have been given by Chapman and Cowling, Cowling, and by Spitzer and Härm. At intermediate degrees of ionization additive effects of both of these resistivity mechanisms would be expected.

Preliminary measurements with electrodes indicated large surface resistances. These effects were avoided by the development of an electrodeless technique in which the moving ionized gas deflected a magnetic field. Resultant voltages induced in a search coil were related to the conductivity distribution in the gas following the shock wave. At temperatures greater than 8000–10 000°K (depending on the gas density) the gas conductivity quickly reached a maximum value (up to 80 mhos/cm). The maximum conductivity obtained at these high temperatures agreed within 10 percent with theoretical expectations. It also agreed well with measurement of electrical resistivity in the cesium discharge by F. L. Mohler, Bur. Standards J. Research 21, 873 (1938). At lower temperatures the oscillograms indicated that the conductivity was still rising at the end of the hot region. Under these conditions maximum conductivities reached were much lower than the theoretical values. The ionization rate obtained varied considerably with the gas density.

At the highest temperatures the conductivity declined quickly from the maximum value and the rate of decline could be correlated with the expected cooling due to recombination radiation. Indications of a high conductivity associated with luminous shock fronts were obtained.
Streaming Birefringence as a Hydrodynamic Research Tool—Applied to a Rotating Cylinder Apparatus above the Transition Velocity
Authors: Wayland Harold
Published: April 2005

Streaming birefringence was studied in the annular space between a fixed outer and a rotating inner cylinder at velocities on both sides of transition to Taylor vortex flow. With a well-collimated light beam, quantitative measurements were possible as close as 0.1 mm from a wall. For an aqueous colloidal solution of bentonite, shear stress could be evaluated from birefringence measurements only when, for a given birefringence, the angle of extinction was the same in the unknown flow as in a known laminar flow. In turbulent shear flow this is not generally the case. For a pure liquid, ethyl cinnamate, the angle of extinction remained at 45° to the streamlines, within experimental error, under all flow conditions obtainable; thus even in turbulent shear flow the birefringence appears to arise primarily from the principal stresses. Assuming birefringence proportional to mean shear stress permits construction of a velocity profile across the gap, yielding the correct value of velocity of the moving wall within limits of experimental error. Thus in this type of two-dimensional shear flow the mean shear stress can be measured by means of the streaming birefringence of a pure liquid.
Theory of Steady-State Creep Based on Dislocation Climb
Authors: Weertman J.
Published: April 2005

A theory of steady-state creep is developed using Mott's mechanism of dislocation climb. It is assumed in the analysis that the rate-controlling process is the diffusion of vacancies between dislocations which are creating vacancies and those which are destroying them. The concentration of vacancies along a dislocation line is determined by setting the change in the free energy caused by a decrease or increase in the number of vacancies equal to the change in the elastic energy occuring during dislocation climb. The creep equation that results from the analysis is creep rate=const (σα/kT)exp(−Q/kT)where α is a constant (α∼3 to 4), Q is the activation energy of self-diffusion, kT has its usual meaning, and σ is the stress. This equation is valid in the stress range from the critical shear stress to a stress about equal to 108 to 109 dynes/cm2. At larger stresses the creep rate increases much more rapidly with stress.
Precise Investigation of the Theory of Damping by Transverse Thermal Currents
Authors: Berry B. S.
Published: April 2005

The frequency-dependence of internal friction of four α brass (62.5% Cu) reeds was measured at room temperature under conditions where contributions to the internal friction other than that arising from transverse thermal currents were small and assessable. Measurements were made by the free-decay method, at maximum strain amplitudes of 5×10−6. By using specimens of two different thicknesses, frequencies differing from the frequency of peak damping by nearly a factor of 20 were obtained by measurements in the range 7–370 cy/sec. The results, in conjunction with measurements of Young's modulus (1.06×1012 dynes/cm2±0.5%), coefficient of linear expansion (18.7×10−6/°C±0.5%), density (8.42 g/cc±0.2%), specific heat (0.088 cal/g/°C±2%), and thermal diffusivity (0.34 cm2/sec±5%), indicate that Zener's theory of damping by transverse thermal currents is probably valid exactly. From the position of the peak, the thermal diffusivity is found more precisely as 0.346 cm2/sec±1.5%.
Surface Friction in Ballistic Penetration
Authors: Krafft Joseph M.
Published: April 2005

The frictional adhesion between projectile and target during a ballistic penetration has been measured with a torsion-type Hopkinson bar. The apparatus allows measurement of the torsional adhesion of a spinning projectile during target penetration. By assuming the friction resisting rotation to be equal to that resisting axial penetration, the energy loss due to friction was computed. The results show that the torque-time pattern during penetration of a ``mechanically'' clean projectile can be predicted with the assumption of a frictional energy loss just sufficient to keep the sliding surfaces at the melting temperature of the metal. Metallographic analysis of the target metal at the projectile interface gives a further indication of a molten interface. In these tests, sliding friction accounts for about 3% of the striking energy of the projectile; common surface contaminants, not necessarily special lubricants, reduce this loss to less than 1%.
Preferred Orientation of Platelets in X-Ray Diffractometer Powder Samples
Authors: Manson James E.
Published: April 2005

A method is described for elimination of the effects of preferred orientation of platelets in a compressed powder sample having a plane surface exposed to the x-ray beam. The powder is diluted with a low absorption amorphous resin and the results extrapolated to zero concentration. The extrapolation is justified by analysis of an idealized model of the sample. A comparison between the analytical results and the results of an experimental study using silver iodide indicates the validity of the process.
Permanent-Magnet Properties of Elongated Single-Domain Iron Particles
Authors: Mendelsohn L. I. , Luborsky F. E. , Paine T. O.
Published: April 2005

Previously described fine-particle magnets have been based upon crystal anisotropy; this paper reports permanent-magnet properties derived from the shape anisotropy of substantially elongated single-domain iron particles. The shape anisotropy of these particles overcomes the limitation imposed on the energy of previous fine-particle iron magnets by the low crystal anisotropy of iron.

The predicted and observed properties of crystal anisotropy fine-particle magnets are reviewed and compared with an ideal fine-particle iron magnet based upon the shape-anisotropy model of Stoner and Wohlfarth. Experimental results are reported for magnets made by aligning and compacting single-domain iron particles 150 angstrom units in diameter, with a median length-to-diameter ratio of three to one, and an intrinsic coercive force before packing of 1600 oersteds. The effect of particle alignment and packing fraction on magnetic properties is described, and energy products above three million gauss-oersteds are reported. These results are compared with properties predicted from theoretical considerations, and with existing permanent-magnet materials.
Ultrashort Light and Voltage Pulses Applied to Silver Halide Crystals by Turbine-Driven Mirror and Spark-Gap Switch
Authors: Webb J. H.
Published: April 2005

Studies of electron mobility in silver halide crystals have been carried out by Haynes and Shockley by means of ultrashort light and voltage pulses applied simultaneously to large, single crystals of these materials. Their apparatus made use of a radar-type, pulse-forming network discharged through mercury spark-gap tubes. An apparatus for carrying out this same type of experiment has been developed using an air-driven turbine with a mirror and a spark-gap switch. Repetitive light pulses of 3.33-microsecond duration and voltage pulses of 10 kv and about 20-microsecond duration can be applied to a crystal at a rate of 500 per second. The light and voltage pulses can be initiated simultaneously or at controlled time intervals. The simplicity and practicality of this type of apparatus for electron mobility and photolysis studies on the silver halides are illustrated by experimental results. Light pulses from a mercury arc release photoconduction electrons in the surface of a silver chloride crystal. The voltage pulse pulls the liberated electrons in a straight column for varying distances through the crystal, where they become trapped. This is shown by the direct photolysis along the column in the crystal. Also, print-out silver specks produced in large photographic grains are displaced to one side of the grains by the voltage pulses applied during exposure. The displacement is in the direction that electrons are pulled in the applied field. By separation of the light pulse and voltage pulse in time, the mean lifetime of the photoliberated electrons can be studied. The lifetime of the electrons was found to be approximately 10 microseconds, of the same order as that of electrons in large, wellannealed single crystals of silver chloride.
Deformation of an Explosively Loaded Aluminum Single Crystal
Authors: Rinehart John S.
Published: April 2005

A hollow cylindrical single crystal of pure aluminum was deformed by detonating an explosive charge that had been placed axially within the crystal. The approximate strain rate achieved was 105 sec−1. The object of the test was to relate the pattern of deformation to the stresses set up by the explosive and the crystallographic axes of the crystal. The reaction of the cylinder was markedly different from the reaction which would be exhibited by a similarly shaped cylinder of polycrystalline material. The deformation was non-uniform with both the fracturing and the plastic flow exhibiting a twofold symmetry that could be unambiguously related to the orientation of stress with respect to the crystallographic axes and their associated slip systems.
Improved Wave Diagram Procedure for Shock Reflection from an Open End of a Duct
Authors: Rudinger George
Published: April 2005

Recently derived improved boundary conditions for the reflection of weak shock waves from an open end of a duct can be well approximated by a centered expansion wave if the center of the later is located on the leading characteristic of the reflected wave and some distance e outside the duct. A relation is derived between e/D (D is the duct diameter), the shock pressure ratio p1/p0, and γ (the ratio of specific heats). This relationship is represented with sufficient accuracy by the empirical formula eD=(0.90+0.677(p1/p0)−1)(γ+1.08)−3.8. This result makes it possible to apply the improved boundary conditions without losing the convenience of of the customarily used wave diagram procedure.
Theoretical Basis for Measuring the Saturation Emission of Highly Emitting Cathodes under Space-Charge-Limited Conditions
Authors: Crowell C. R.
Published: April 2005

The second derivative of the current-voltage relationship of an ideal plane diode is calculated from the Epstein-Fry-Langmuir analysis. From this analysis it is shown that for the large saturation emission characteristic of oxide-coated cathodes at normal operating temperatures, the current at the inflection point (i.e., the zero of the second derivative) is a sensitive measure of the saturation emission and is unaffected by the existence of a linear interface impedance. It is also shown that the general features of the results apply to cylindrical diodes.
Relative Influence of Majority and Minority Carriers on Excess Noise in Semiconductor Filaments
Authors: Bess Leon
Published: April 2005

An experiment has been devised whereby excess noise is measured along various different directions in a germanium filament after the directions of current flow for the majority and minority carriers had been altered by a magnetic field. From this experiment it is possible to determine that whereas shot noise is caused by both majority and minority carrier fluctuation, 1/f noise is essentially produced only by majority carrier fluctuation.
New Active Circuit Element Using the Magnetoresistive Effect
Authors: Aharoni A. , Frei E. H. , Horowitz G.
Published: April 2005

A new multistable element is described, and the conditions under which it may operate are discussed. It is found that a bistable element (flip-flop) with reasonable resolving time may be achieved, though it might be necessary to operate it at low temperatures. A tristable element is found to be possible, but not practical. A slowly operating model is described.
Application of the Engravement Method to the Study of Particle Velocity Distribution in Explosively Loaded Cylinders
Authors: Pearson John , Rinehart John S.
Published: April 2005

Application of the engravement method to the study of particle velocity distribution in the wall of a thick-walled metal cylinder internally loaded with an explosive charge is described. Tests were conducted with this method on modified cylinders of annealed low-carbon steel and of brass. Even though each of the modified cylinders broke into a number of fragments, the engravements were well enough preserved to furnish considerable data. Many measurements were obtained from each cylinder by using a large number of pellets of several thicknesses. Particle velocity data were obtained to within 716 inch from the metalexplosive interface. Temporal particle velocity distribution curves are presented for each of the cylinders.
Space-Charge Waves in Crossed Electric and Magnetic Fields
Authors: Solomon Salim S.
Published: April 2005

The problem of space-charge waves propagating along a neutralized electron stream moving in a medium pervaded by crossed static electric and magnetic fields is discussed. From energy considerations it is shown that gain can be realized either by conversion of the electron kinetic or potential energy into electromagnetic energy. A small signal analysis shows that for the first case the TE and TM modes are coupled in general. However, when the electron velocity is much smaller than the velocity of light the coupling coefficients are negligible and the gain realized is identical with that of the conventional traveling-wave tube. A similar analysis for the second case, which is that of the traveling-wave magnetron tube, yields the interesting result that the TE and TM modes separate even when the electron velocity is comparable with the velocity of light.
Theory of Scattering by an Inhomogeneous Solid Possessing Fluctuations in Density and Anisotropy
Authors: Goldstein Martin , Michalik E. R.
Published: April 2005

The theory of Debye and Bueche for the scattering of light by an amorphous solid is extended to the case where fluctuations in anisotropy as well as density are considered. A generalized correlation function is defined, which gives the probability of a simultaneous occurrence of fluctuations in polarizability in two volume elements a distance r apart. The fluctuations are specified by the magnitudes of the polarizabilities and the directions of the optic axes. The correlation function is assumed to depend on r, on the angle between the axes of the fluctuations, and on the angle giving the position of the second element with respect to the optic axis of the first. The intensities of the horizontal and vertical components of the scattered light are expressed as integrals over the correlation function of explicit functions of r and the two angles. From the initial slopes and intercepts of the intensities plotted against sin2(θ/2) where θ is the scattering angle, one can obtain average values and average dimensions of the fluctuations, and a measure of the extent to which fluctuations in density and anisotropy are correlated. The theory is applicable to glasses, gels, and liquid crystals.
Low Shear Capillary Viscometer with Continuously Varying Pressure Head
Authors: Maron Samuel H. , Belner Robert J.
Published: April 2005

A capillary viscometer is described for the study of the flow behavior of non-Newtonian fluids at shear stresses of 0.06–20 dynes/cm2. The all-glass instrument consists of two units connected by a ball joint, one unit of which contains the capillary while the second is essentially a manometer. As the test fluid moves through the capillary, the rate of rise of the fluid in the manometer is observed. This measurement of the column height as a function of time allows calculation of both pressure drop and rate of flow. Different combinations of capillary and manometer units can be employed interchangeably to study liquids of widely varying viscosities. Data and methods are presented which show that the instrument can be used to determine the absolute viscosities of Newtonian liquids and the flow curves of non-Newtonian fluids over the indicated shear stress region.
Method for Obtaining Complete Quantitative Pole Figures for Flat Sheets Using One Sample and One Sample Holder
Authors: Schwartz Milton
Published: April 2005

The general expressions for the x-ray absorption corrections in the reflection region for flat sheets in any orientation are derived. These equations contain, as special cases, the correction factors of previously reported pole figure techniques and also correction factors for a new method, permitting a rapid and accurate determination of complete quantitative pole figures of flat sheets using one sample and one sample holder. For the outer regions of the polar net a low-order Bragg reflection is used with the technique of Decker, Asp, and Harker; and for the center region a higher order Bragg reflection from the same set of planes is used with a different set of correction factors. Pole figures, obtained by this method, for cold rolled aluminum and magnesium are presented.
Capacitance Measurements on Alloyed Indium-Germanium Junction Diodes
Authors: Muss D. R.
Published: April 2005

Donor densities in the base material of fused junction diodes, inferred from capacitance data, are used to calculate majority carrier mobilities. The dependence of capacitance on reverse bias at very low biases is found to be given by the sum of two terms, a space charge capacitance and a capacitance due to the flow of holes as given by Shockley's low level p-n junction theory.
Relation of Antimony Transmission and the Photoelectric Yield of Cs–Sb
Authors: Rome Martin
Published: April 2005

The relation of transmission of thin films of antimony as a function of thickness expressed in micrograms per cm2 has been determined for blue, red, and white illumination. An abrupt change in optical properties of the antimony layer has been noted at the phase change. The transition occurs at a transmission of approximately 30 percent. Photosurfaces have been prepared by activating the deposited antimony films with cesium. The photoelectric yield for both regular and reverse illumination has been determined for different antimony thicknesses. For reverse illumination the peak response occurs between 5.5 and 6.0 micrograms per cm2 of antimony. Expressing the photoresponse for reverse illumination of green light with decreasing transmission of the original antimony layer for blue, white, and red light shows peaks at 82, 88, and 92 percent, respectively. The transmission of the photosurface, which is substantially independent of processing or photoelectric efficiency of the surface, is given for blue, green, and white light.
Spin-Echo Memory Device
Authors: Fernbach Sidney , Proctor Warren G.
Published: April 2005

A proton-rich sample placed in a strong inhomogeneous magnetic field of mean strength H0 was subjected to a pattern of relatively weak radio-frequency pulses at the Larmor frequency of the protons in the field H0. The pattern was then recalled by applying a strong rf pulse at a later time as in the spin-echo technique. It is shown both mathematically and experimentally that such a series of pulses, varying in amplitude can be ``memorized'' by the spin system of protons for times as long as one second and then repeated, preserving both shape and relative amplitude.
Theory of Elasticity and Consolidation for a Porous Anisotropic Solid
Authors: Biot M. A.
Published: April 2005

The author's previous theory of elasticity and consolidation for isotropic materials [J. Appl. Phys. 12, 155–164 (1941)] is extended to the general case of anisotropy. The method of derivation is also different and more direct. The particular cases of transverse isotropy and complete isotropy are discussed.
Radiation of Plasma Noise from Arc Discharge
Authors: Takakura T. , Baba K. , Nunogaki K. , Mitani H.
Published: April 2005

The mechanism of radiation of plasma noise inherent to arc discharge is studied experimentally. Intense electromagnetic radiation of random noise character is observed at the frequency of plasma oscillation of the ion sheath formed at the cathode drop. Maximum radiation occurs when the external circuit connected to the cathode is in resonance with the plasma frequency. The oscillating current in the external circuit is concluded to be generated by the periodic electron emission from the cathode caused by small perturbation of potential gradient at the cathode surface as a result of the variation in the ion sheath potential. This conclusion is supported by several experiments under various air pressures, electrode materials, current densities, etc.
On the Diffusion of Decaying Particles
Authors: Gold Louis
Published: April 2005

The probability of neutron absorption on a spherical surface for a radial source in a medium for which the particle has prescribed lifetime and rate of diffusion is calculated. This helps illuminate the more intricate, related problem for a charged particle diffusing in the presence of a radial inverse-square electric field to the extent that an explicit relation for the relative absorption probabilities that accompany changes in the direction of the drift field is secured. An asymptotic solution for the absorption probability is also provided which in first-order approximation may be applied in the range of interest for transistors.
Temperature Dependent Creep in Zinc Crystals
Authors: Thompson Donald O.
Published: April 2005

Tensile creep measurements beginning in a tensile strain region of about 10−6 have been made upon a set of seven single crystals of zinc of 99.99+ percent purity. Measurements were made both by means of electrical resistance strain gauges and an optical lever system. Some of the measurements made in the latter apparatus lasted 100 hours or more, and in both systems, measurements were made at several temperatures.

The creep results obtained in this work can be best described by the single empirical relation η=btmin which η is the shear strain, t is the time after completion of the application of stress to the crystal, and b and m are constants for a given creep test under given experimental conditions. It is found that b increases with the stress but does not vary greatly with temperature. The values of m are practically independent of stress but vary with temperature, and appear to fit best the equation, m=m0exp(−T0/T)in the temperature interval investigated. For these crystals T0 = 1580°K, m0=120, and the temperature at which m=1 is 58°C. Values of m>1 are interesting in dislocation theory.
Bistatic Radar Cross Sections of Surfaces of Revolution
Authors: Siegel K. M. , Alperin H. A. , Bonkowski R. R. , Crispin J. W. , Maffett A. L. , Schensted C. E. , Schensted I. V.
Published: April 2005

The results obtained by applying the current-distribution method to the problem of approximating the scattering cross section, when the transmitter and receiver are separated, are presented for several simple geometric configurations. The method is applied for the case in which the transmitter is located on the axis of revolution and the ratio l/λ is large, where l is a ``characteristic dimension'' of the body and λ is the wavelength. These results indicate that in most of the cases considered the cross section increases as the angle between the receiver and the transmitter increases.
Electromagnetic and Acoustic Scattering by a Semi-Infinite Body of Revolution
Authors: Schensted Craige E.
Published: April 2005

The first two terms of Kline's asymptotic expansion are obtained for the scattering of a plane wave incident along the axis of a perfectly reflecting semi-infinite body of revolution. When this method is applied to the paraboloid the exact electromagnetic solution is obtained in closed form. The accuracy of the method of physical optics is studied by using the asymptotic expansion.
Electromagnetic and Acoustical Scattering from a Semi-Infinite Cone
Authors: Siegel K. M. , Crispin J. W. , Schensted C. E.
Published: April 2005

The value of the nose-on back scattering cross section of a semi-infinite cone is determined by the exact methods of electromagnetic and acoustical theory, and by physical optics. It is shown that, to the degree of approximation used, the electromagnetic value and the physical-optics value are equal. The acoustical value is found to be less than the electromagnetic value by a factor which depends only on the cone angle; both are proportional to the square of the wavelength. It is shown that the electromagnetic and physical-optics answers agree with experimental data to within a factor of two. The electromagnetic theory results obtained hold for the cases in which the half-cone angle is close either to 0 or to π/2.
Techniques for Nuclear Magnetic Resonance Measurements on Granular Hygroscopic Materials
Authors: Shaw T. M. , Elsken R. H.
Published: April 2005

An investigation was made of the effects of nonuniformity in the magnetic fields and in the test specimens employed in the measurement of nuclear magnetic resonance absorption. Particular attention was given to the determination of relative integrated line intensity from derivative maxima independently of the uniformity of concentration of the subject nuclei through the available sample volume. The principal objective was to devise techniques applicable to granular hygroscopic materials. A technique applicable for the low-moisture range was tested for materials containing 7 to 16 percent water and found to be satisfactory.
Replica Studies of Bulk Clays
Authors: Comer J. J. , Turley J. W.
Published: April 2005

The electron microscope examination of the surfaces of bulk clays by replica techniques is difficult because of the porosity of the clays and the necessity of using hydrofluoric acid to dissolve the clay from the replicas. The surfaces of some bulk endellite clays were examined by means of collodion, silica, and preshadowed replicas. Collodion and two-step silica replicas were unreliable and difficult to use because of penetration of the collodion or plastic into the pores of the clay. Collodion strippings were of some value in removing layers of clay particles from the surface for direct examination in the microscope. Best results were obtained with the preshadowing technique which employed a shadowing layer of platinum backed by a layer of evaporated carbon or by Parlodion. Micrographs of replicas prepared by the latter technique show the surface of a highly porous endellite clay to consist of tubes in various orientations.
Extensions of the Rouse Theory of Viscoelastic Properties to Undiluted Linear Polymers
Authors: Ferry John D. , Landel Robert F. , Williams Malcolm L.
Published: April 2005

The Rouse theory for viscoelastic properties of very dilute solutions is modified for application to undiluted linear polymers. With the effective segment mobility expressed in terms of steady-flow viscosity, the theory is applied to polymers of rather low molecular weight essentially without further change. In high molecular weight polymers, it is assumed that for modes of motion with relaxation times above a critical value the effective segment mobility drops abruptly, in accordance with the effect of entanglement coupling on steadyflow viscosity as described by Bueche. Properties in both the transition region between glasslike and rubberlike consistency and the rubberlike or plateau region are predicted semiquantitatively with no arbitrary parameters. In an alternative application to the transition region, the average effective friction coefficient per monomer unit can be calculated for both linear and lightly cross-linked systems.
Azimuthal Surface Waves on Circular Cylinders
Authors: Elliott Robert S.
Published: April 2005

Solutions of Maxwell's equations are presented which satisfy the boundary conditions for corrugated and dielectric-clad circular conducting cylinders. These solutions have the physical interpretation of leaky azimuthal surface waves. Values of the complex propagation constant are given as functions of the geometry. For large cylinders the leakage is small and the transmission properties are approximately those of a trapped wave on a flat surface. A coarse experiment gives reasonable agreement with the theory. Some possible applications to transmission lines and antennas are indicated.
Measurement of the Elastic Constants of Single Crystal Cobalt
Authors: McSkimin H. J.
Published: April 2005

The 5 elastic constants of hexagonal cobalt have been determined using pulse modulated ultrasonic waves which are reflected back and forth within the crystal. Frequencies between 10 and 30 Mc/sec were used. Values of the constants were derived from 11 measurements of wave velocities for longitudinal and shear modes in 3 crystals, using a phase comparison technique. At 25°C the constants (all in 1012 dynes/cm2) are: c11=3.071±0.5 percent, c12=1.650±0.5 percent, c13=1.027±1.5 percent, c33=3.581±0.5 percent, c44=0.755±0.5 percent. These are based on a density of 8.836.
Measurement of the Lifetime of Minority Carriers in Germanium
Authors: Spitzer William G. , Firle Tomas E. , Cutler Melvin , Shulman Robert G. , Becker Milton
Published: April 2005

Two methods are described for the measurement of lifetime of minority carriers. One depends on pulse injection of carriers in a filament and detection, after a known time, at a collector. The second makes use of the decay of the conductivity modulation caused by minority carriers after injection at a single contact. Both measure the lifetime in a small region rather than the average value over a large part of the sample.
Electron Temperature in the Parallel Plane Diode
Authors: Chin T. N.
Published: April 2005

Chandrasekhar's relaxation time is applied to the electron gas in flow. By determining the relaxation time, tR, and the mean transit time, tT, two types of electron flow may be characterized: anisotropic flow if tT«tR, and isotropic flow if tR«tT. It is shown that the electron temperature along the flow decreases as the mean velocity of the electrons increases in a parallel plane diode. In the given examples, the boundary conditions are obtained for a particular model which has been recommended in the study of thermionic emission.
Surface Matching of Dielectric Lenses
Authors: Jones E. M. T. , Cohn S. B.
Published: April 2005

Two methods of cancelling the surface reflections of dielectric lenses are described in this paper. The first utilizes a simulated quarter-wave matching layer, and the second a reactive wall embedded within the dielectric. The reactive wall may take a variety of physical forms, such as arrays of thin conducting disks which have a capacitive reactance, or arrays of thin wires which have an inductive reactance. Surface matching is obtained when the disks are placed approximately ⅜ wavelength inside the lens, or the wires ⅛ wavelength. Curves are presented that show how the reflections at the air and dielectric boundary are reduced for various angles of incidence and polarization when quarter-wave layer and reactive-wall matching are employed.

The reactance of the array of disks for waves incident at various angles and polarizations is computed by means of Bethe's small aperture theory, and Babinet's principle. Measurements in wave guide of the reactance of an array of circular disks for various angles of incidence and for both E- and H-plane polarization show close agreement with the theory.
Field Produced by an Arbitrary Slot on an Elliptic Cylinder
Authors: Wait James R.
Published: April 2005

A derivation is given for the electromagnetic field produced by an arbitrary slot cut in the surface of an elliptic cylinder of perfect conductivity and infinite length. The electric field tangential to the slot is assumed to be a prescribed function. The integrals in the formal solution are evaluated by the saddle point method for the far zone fields which when specialized to thin transverse or axial slots agree with known results. As illustrative examples, patterns of thin axial and transverse slots on a strip are computed.
Cubic to Orthorhombic Diffusionless Phase Change— Experimental and Theoretical Studies of AuCd
Authors: Lieberman D. S. , Wechsler M. S. , Read T. A.
Published: April 2005

A theoretical analysis of the cubic to orthorhombic transformation is presented which predicts for a partly transformed crystal, the interface plane, orientation relationships, and macroscopic distortions from a knowledge only of the lattice parameters of the initial and final phases. Arguments are advanced to show that in order to minimize the strain energy associated with the transformation, the interface plane must be one of zero average distortion. This leads directly to considerations of an inhomogeneous product phase. Experimental studies on an AuCd alloy are described and the observed crystallographic features of the transformation compared with values calculated using the theory. The agreement between calculated and observed results for this alloy system as well as others is strong evidence for the theory of diffusionless phase transformations presented.
On a Nonlinear Transfer System
Authors: Flügge-Lotz I. , Wunch W. S.
Published: April 2005

It is shown that a system with discontinuously varying damping and spring coefficients transfers arbitrary inputs well, if the change of the coefficients from one constant value to another is controlled by the deviation between input and output.
Diffusion, Static Charges, and the Conduction of Electricity in Nonmetallic Solids by a Single Charge Carrier. II. Solution of the Rectifier Equations for Insulating Layers
Authors: Skinner Selby M.
Published: April 2005

The discussion of the thermodynamic equilibrium of an electron atmosphere in a dielectric is extended to the current-carrying steady state. Under the assumption that the experimental behavior at zero current is continuous with that when there are finite electrical currents, it is found that forward and reverse currents show distinct behavior. Expressions are developed for the electrostatic potential, field, charge density, the current-applied voltage relation, and the capacity and rectifying behavior of dielectric layers. The non-ohmic conduction exhibits rectification, and departures from the Wagner relation are predicted, of the type observed experimentally, including turnover voltages. The contact charging of a dielectric is the zero-current limit of the non-ohmic behavior which causes rectification.
Small Particle X-Ray Scattering by Fibers, Size and Shape of Microcrystallites
Authors: Heyn A. N. J.
Published: April 2005

A theoretical and experimental analysis is given of small particle x-ray scattering by fibers.

The scattering by different fibers of high orientation is compared with the theoretical scattering curves derived for independent scattering by an assemblage of parallel cylinders. Under certain conditions of swelling, excellent agreement is obtained between experimental and theoretical curves. From this agreement it is concluded that under these conditions, independent particle scattering is realized and that interparticle interference and multiple scattering do not play a part.

Under all other conditions (dry fiber and other conditions of swelling) interparticle interference plays an important role in the scattering by these ``densely packed'' materials as can be concluded from the different distributions of intensity. The swelling method offers a means for separating independent and nonindependent scattering.

An analysis of the influence of various conditions of swelling is made, and the correct experimental conditions for obtaining independent scattering are derived from the results.

From the scattering under such conditions, the particle size in different fibers is determined on the basis of the theoretical formulas for independent scattering.
Effect of Air Damping on Transverse Vibrations of Stretched Filaments
Authors: Stauff D. W. , Montgomery D. J.
Published: April 2005

The effect of air damping on the resonant frequencies of forced vibration of stretched filaments is studied by observing the shift in frequency when the surrounding medium is changed from air at atmospheric pressure to hydrogen at the same pressure, or to air at reduced pressures. For fibers of linear density less than about 10 micrograms per centimeter, the shift between atmospheric air and vacuum exceeds one cycle per second, becoming greater as the fibers become finer. The frequency shifts observed experimentally are compared with those predicted by certain formulas of Stokes. It is found that the theory works well enough to allow the effect of air damping to be taken into account in measurements of linear density by means of the vibroscope. However, the observed shift seems to be about one or two cycles per second higher than that calculated in the case of small shifts, and about 20 or 30 percent higher in the case of large shifts. A rigorous evaluation of the applicability of Stokes' theory would require further investigation.
Anisotropic Diffusion Lengths in Diffusion Theory
Authors: Spinrad Bernard I.
Published: April 2005

A set of formulas defining diffusion lengths in heterogeneous assemblies is presented. Even in the homogeneous limit, these formulas lead to anisotropic diffusion lengths for systems such as rod or slab assemblies which are microscopically anisotropic.