bluuebunny/crossref_metadata_2025 huggingface dataset:
Method of Measuring the Magnetoelastic Coupling Constants of Cylindrical Magnetic Films
Authors: Goldberg Norman
Published: April 2005

The magnetoelastic energy of a anisotropic film with an axis of symmetry is Bαα12ε112+ Bβα22ε22+ 2Bγα1α2ε12, where the B's are magnetoelastic coupling constants, the α's are direction cosines of the magnetization direction, and the ε's are strains. For a film with an easy axis in the circumferential direction (labeled 1), the effect of applying a tension in the axial direction (labeled 2) and introducing a strain ε22 is to change the uniaxial anisotropy field Hk. The B's are related to this change by Bβ+σBα = ΔHkM/(2ε22), where M is the magnetization and σρ is Poisson's ratio of the wire substrate. The effect of twisting the wire and introducing a strain ε12 is to rotate the easy direction through an angle φ. For small φ, Bγ is related to this skew angle by Bγ=-MHkφ/(2ε12). For an isotropic film the B's are equal. Measurements have been made on a variety of Permalloy films, some with positive and some with negative magnetostriction, electroplated upon 5-mil wire. If it is assumed that Bβ=Bα, Bβ is generally found to be larger than Bγ, and not unexpectedly the anisotropy of B is larger in films with large Hk.
Magnetic Characteristics of Gadolinium, Praseodymium, and Thulium Nitrides
Authors: Schumacher David P. , Wallace W. E.
Published: April 2005

Bulk magnetic measurements were made on GdN, PrN, and TmN over the range 4.2° to 300°K. GdN is ferromagnetic with Tc = 69°K and a saturation moment of 7.03 μB (gJ = 7.00). Results obtained in the paramagnetic region give: for GdN μeff = 7.86 μB {g[J(J+1)]½ = 7.94}, Θp = 75°K; for PrN 3.57 μB (3.58), −11°K; for TmN 7.32 μB (7.56), −21°K. These nitrides all occur in the NaCl structure. Under the influence of the cubic crystal field the 2J+1-fold degenerate multiplet is decomposed so that Pr and Tm have singlet (nonmagnetic) ground states. Thus if the crystal field splitting exceeds the exchange interaction, no cooperative magnetic phase is expected at low temperatures. The measurements indicate this to be the case for TmN, supporting recent neutron diffraction work, and apparently this is also true for PrN. The possibility cannot be excluded, however, the PrN is a weak ferromagnet. If so, its saturation moment is estimated as 0.27 μB (gJ = 3.2 μB), indicating considerable crystal field quenching of the orbital contribution to the moment.
Magnetic Anisotropy in Antiferromagnetic α-(Cr1−fAlf) 2O3
Authors: Artman J. O. , Murphy J. C. , Foner S.
Published: April 2005

In antiferromagnetic crystals the results of AFMR, when combined with other data, yield the anisotropy K. By subtracting the magnetic dipolar anisotropy KMD from K, the fine structure anisotropy KFS is found. For Cr2O3, the KMD computation of Tachiki and Nagamiya, 0.059 cm−1/ion, had been accepted as a basis for further analyses. However, in the course of computing KMD by modern machine methods for various sesquioxide antiferromagnets, we have found this value to be inappropriate. The Shull magnetic structure (c) to which Cr2O3 belongs is one in which the magnetic geometry effectively is almost cubic! The computed KMD value thus is sensitive to small changes in lattice geometry. Presently accepted room-temperature crystal parameters yield KMD = 0.0088 cm−1/ion, ⅙ the former result; consequently Cr2O3 AFMR data have been reanalyzed. The temperature behavior of KFS and KMD in pure Cr2O3 and in (Cr1−fAlf)2O3 crystals is discussed. Similar KMD calculations have been made for the Ti, V, and Fe sesquioxides. In the case of α-Fe2O3 we have been able to predict, with the use of AFMR data, the spin-flip near 263°K. The experimentally found decrease of this spin-flip temperature with increasing f in the α(Fe1−fAlf)2O3 system is discussed in the light of existing information.
Ionization, Diffusion, and Drift Velocities in a Pulsed Townsend Discharge
Authors: Ward A. L.
Published: April 2005

It is shown that an electron avalanche travels with a velocity v_ that is dependent upon Townsend's ionization coefficient α and the diffusion coefficient for the electrons D_. Specifically, v_=μ_E+αD_, where μ_ is the electron mobility, and the applied field E is assumed constant. Numerical machine calculations have been made to study the effect of diffusion and secondary ionization at the cathode in pulsed Townsend discharges. Illustrative examples show the utility of these calculations in measurements of the Townsend ionization coefficients as well as electron and ion mobilities. It is shown that the diffusion-broadened avalanche for high values of αd (d is the gap distance) requires more than the electron transit time d/v_ to make a gap crossing.
Transient Currents in the Ozonizer
Authors: Katakis D. , Bersis D.
Published: April 2005

An oscillographic study of the ozonizer discharge under normal operating conditions is made and is discussed in the light of known mechanisms active in glass vessels with external electrodes. The investigation is extended to various gases and the features of the breakdown attributable to the glass itself are distinguished from those depending on the nature of the gas.
Effective Fluorescent Lifetimes in Ruby Laser Rods
Authors: Fleck J. A.
Published: April 2005

In the presence of a population inversion, fluorescent lifetimes are reduced as a result of stimulated emission. Effective fluorescent lifetimes have been calculated using a Monte Carlo method for ruby rods with Brewster-angle ends and roughened sides. The calculations take into account the dependence of gain and reflectivity on polarization and the dependence of gain on frequency. The reflection characteristics of the roughened surface are assumed to be those of an ideal diffuse reflector. Results show that effective fluorescent lifetimes are quite insensitive to rod length but strongly dependent on rod diameter. They also indicate the possibility of oscillation in a random mode for rods of sufficiently large diameter.
Polarity Effect in Vacuum Breakdown Electrode Conditioning
Authors: Miller H. Craig , Farrall G. A.
Published: April 2005

We wished to determine if an electrode polarity effect existed in vacuum breakdown conditioning. To investigate this conditioning effect, we used a three-electrode experimental tube constructed in such a manner that one electrode (1) could be made to oppose either of the other two (2 or 3) without destroying the vacuum. High-current arcs were drawn between both possible electrode pairs to bring them to a reproducible state of apparent deconditioning. These pairs (1 vs 2 and 1 vs 3) were then, in turn, conditioned by a series of high-voltage pulses at a gap of 2.3 mm. The following conclusions were drawn: (1) within experimental error, all conditioning took place at the pulse cathode, (2) when the arc and pulse polarities were similar, the subsequent pulse breakdown voltage was lower than when the polarities were opposed, and (3) conditioning was not due to the removal of a gas layer from the electrode, but, rather, to removal of cathode deformations. Predictions concerning the polarity effect in vacuum breakdown conditioning were drawn from the major theories of vacuum breakdown, and compared with our experimental results. We found that our results agreed with the predictions of some vacuum breakdown theories, flatly contradicted the predictions of others, and tended to disagree with the predictions of a third group of theories.
Study of the Anomalous Surface Reflection of X Rays
Authors: Guentert O. J.
Published: April 2005

The anomalous surface reflection of x rays reported recently by Yoneda has been investigated for several materials using MoKα1, CuKα1, and CrKα1 radiation. The experimental evidence speaks strongly in favor of the Warren and Clarke interpretation in terms of totally reflected small-angle scattering. For clean surfaces the scattering appears to be due to surface irregularities of the bulk material itself. Because of its sensitivity to the roughness and chemical contamination of optically or near-optically finished surfaces, the Yoneda effect has considerable promise as a new x-ray tool for studying surfaces and thin films.
Method for Hugoniot Equation-of-State Measurements at Extreme Pressures
Authors: Fowles G. R. , Isbell W. M.
Published: April 2005

A brief study is described of a simple method for producing plane shock waves in solids at pressures higher than those attainable by conventional explosive methods. Mach reflection of a conically convergent shock in the specimen yields a disk-shaped front at a pressure of several megabars, depending on the type of explosive employed and the specimen material; this front is accessible to Hugoniot equation-of-state measurements. Results for copper at a pressure of 1.9 Mbar are in good agreement with published values.
Structure and Energy of One-Dimensional Domain Walls in Ferromagnetic Thin Films
Authors: Brown W. F. , LaBonte A. E.
Published: April 2005

The continuous magnetization of a 180° one-dimensional interdomain wall in a ferromagnetic thin film is replaced by a discrete distribution for which the magnetostatic energy can be calculated rigorously. The general functional form of the direction of magnetization within the wall is not restricted by this replacement, and minimization of the total energy with the aid of a digital computer yields both the equilibrium wall structure and its corresponding energy. It is found that only Bloch and Néel types of one-dimensional walls result. The magnetization distribution of a typical Bloch wall is shown, and the Bloch wall energy and wall thickness are calculated as functions of film thickness and compared with values from the literature. Finally, some detail of the Néel wall structure is presented, and it is shown that the transition from one-dimensional Bloch to Néel walls should occur at much larger film thickness than has been reported previously.
High-Field Magnetoresistance of Semiconductors and Plasmas. IV: Dependence on Inclusion Shape
Authors: Frisch H. L. , Morrison J. A.
Published: April 2005

We have obtained exactly the excess dissipation due to a small spherical inclusion in a semiconductor, using the same model of the semiconductor which was investigated in previous papers of this series, and the ``four moment approximation'' to the electron-distribution function. We have also calculated the high-field limit of the transverse magnetoresistance for a dilute sprinkling of spherical inclusions, which is proportional to the high-field limit of the excess dissipation, and varies as |H| as H→∞, where H is the magnetic field. Previously, Herring obtained approximately the excess dissipation of a cylindrical inclusion with axis parallel to the magnetic field and made plausible a high-field transverse magnetoresistance which varies as |H|/ln|H| as H→∞. In the case of spherical inclusion, we can investigate in detail perturbations produced by the external specimen boundaries, and we suggest that analogous results hold for a cylindrical inclusion.
Theory of the Effect of Strain on GaAs Electroluminescent Diodes
Authors: Emtage P. R.
Published: April 2005

A simplified theory of the effect of strain on the acceptor states in GaAs is used to account for observations made on electroluminescent diodes, the optical transition being between the conduction band and the acceptor states. The acceptor states are described as having a hydrogenic envelope in k space, and as being constituted primarily of states of the heavy mass band. The calculated changes in intensity and the line splitting are in fair agreement with experiment, but no explanation of the observed line shift has yet been found.
Metal-Semiconductor Barrier Height Measurement by the Differential Capacitance Method without an Ohmic Reference Contact—One-Carrier System
Authors: Goodman Alvin M.
Published: April 2005

In previous treatments of metal-semiconductor contact barrier height measurements by the differential capacitance method it has been generally assumed that there exists an Ohmic reference contact to the semiconductor. In this paper, the method is extended to those cases where an Ohmic contact to the semiconductor is not available. It is shown that under certain conditions, barrier heights may be determined using only barrier reference contacts. It is also shown that although only two contacts are necessary, a third contact may be advantageously employed to simplify the measurement technique. If four contacts are available, a further simplification may be achieved.

Experimental results on Au–CdS contacts are used to verify the theory for the case of two symmetrical barrier contacts.
Orientation Overgrowth of Condensed Polycyclic Aromatic Compounds Vacuum-Evaporated onto Cleaved Face of Mica
Authors: Uyeda Natsu , Ashida Michio , Suito Eiji
Published: April 2005

When Pt-, Cu-, and Zn-phthalocyanines are vacuum-evaporated onto cleavage faces of muscovite, single-directional orientation occurs at lower substrate temperature. At higher temperature ranges, Zn-phthalocyanine has a double-directional orientation while Pt- and Cu-phthalocyanines show triple-directional ones. High-resolution electron diffraction patterns, which were well-defined fiber diagrams, revealed that all three compounds showed conspicuous isomorphism with one another, and Zn- and Cu-phthalocyanines occurred in the metastable forms of their dimorphs. General crystal structures of metastable forms are discussed on the basis of the found isomorphism with Pt-derivative.

Evaporated films were composed of lamellar crystal strips, and the fiber diagrams showed that at least two kinds of lattice orientations were assumed by all three compounds, while the longitudinal crystal axis of individual strips always ran parallel to their b axes.

As to relative orientation of the evaporated films to the substrate, the b axis of the former was parallel to either of the two directions which made ±60° with the a axis of muscovite in the case of the single-directional orientation. When the evaporated films had double- or triple-directional orientations, the electron diffraction pattern showed twofold symmetries in spite of the apparent triangular configuration. It turned out that this axis of twofold symmetry also coincides with the same axis of muscovite as above. It is presumed that the unique orientation axis of the evaporated films coincides with the staggering direction of the two oxygen tetrahedron sheets in the top subcell of muscovite. Plausible origin of these orientations are also discussed in terms of lattice vibration near the surface.

Lattice imperfections of the evaporated films were directly observed in the lattice image obtained by the high-resolution electron microscopy. The dislocation density seems rather high when compared with other similar lamellar crystal strips of the same compounds formed by colloid chemical methods. This was ascribed to the crystal formation controlled by the epitaxial effect.
Shear Cracks and Double-Ended Dislocation Arrays
Authors: Liu H. W.
Published: April 2005

The relationship between shear cracks and double-ended dislocation arrays is discussed. The density of a double-ended dislocation array under the uniform applied shear stress was calculated by the shear-crack conversion method. The calculated density agrees with that calculated from the dislocation model. A general method of calculating the dislocation densities near the spearheads of dislocation arrays is given. Examples are illustrated; in general, the density as well as the stress and strain fields near the spearhead of a single-ended linear dislocation array are higher than those of a double-ended array under the same applied stress on the slip plane.
Vacancies and Dislocation Loops in Quenched Crystals of Graphite
Authors: Hennig Gerhart
Published: April 2005

The distribution of vacancies and dislocation loops in quenched graphite has been studied by etching and decorating individual vacancies. Quenching in inert gases from 3100°C introduced less than 10−8 vacancies per atom, and no dislocation loops. After quenching in vacuo from 3100°C, large portions of the crystals contained less than 10−10 vacancies per atom, but most peripheral regions contained an abundance of vacancies and dislocation loops. A probable mechanism for vacancy injection and subsequent coagulation has been deduced. It is concluded that the energy of vacancy formation in graphite is larger than 6.6 eV.
Boundary Value Problems in Composite Media: Quasi-Orthogonal Functions
Authors: Tittle C. W.
Published: April 2005

A new theorem is stated on the construction and use of orthogonal sets for solving boundary value problems in a composite medium where the boundary function traverses more than one region. The concept of quasi-orthogonality is introduced and employed in a rigorous expansion of the boundary function into a series of the nonorthogonal eigenset that arises from separation of variables in such instances. Orthogonal sets are constructed from the nonorthogonal (quasi-orthogonal) eigenset by the use of orthogonality factors for each region derived from the orthogonality condition. Orthogonality factors for representative problems in neutron diffusion, heat conduction, scalar wave propagation, and nonrelativistic quantum mechanics are computed for rectangular, spherical, and cylindrical coordinates. The theorem allows a solution of multi-region problems by a direct expansion without resort to integral transformation or Green's functions. It is an extension of the method of separation of variables and generalized Fourier analysis to cases heretofore beyond its scope.
Problem in Barycentric Coordinates
Authors: Klee Victor
Published: April 2005

When the phase coexistence pattern of a multicomponent system is known, it is theoretically a simple matter to decide which of the phase fields is represented by a given mixture of the p primary components. However, when p>3 the usual determinantal procedure is time consuming in practice and may even lead to an erroneous conclusion because of round-off errors. Here is described a short preliminary test which is free of round-off errors and which eliminates most of the phase fields; the determinantal test is then applied only to those which have not been eliminated by the first test.
Characteristics of Resonance Probes
Authors: Dote Toshihiko , Ichimiya Torao
Published: April 2005

In the last few years there have been several experimental results on resonance probes which were poorly explained by existing theories. They are, briefly: the resonant frequency increases (A) as the bias voltage of the probe is biased strongly negative, and (B) as a probe of smaller area is employed. In this paper, the characteristics of the resonance probe are analyzed on the basis of the resultant series impedance of the plasma and the sheath, the former being expressed by an antiresonant circuit and the latter by a capacitor. According to this mechanism, not only the experimental facts described above, but also all the characteristics of the resonance probe can be interpreted. For example, the dependence of the resonant peak on the bias voltage of the probe and on the input alternating voltage is elucidated. Furthermore, most of these properties are verified by experiments using a mercury plasma.
Magnetic Field Effect on the Current Distribution in p-n Junctions
Authors: Garfinkel M. , Engeler W. E.
Published: April 2005

The effects of magnetic fields upon the current distribution across a p-n junction are discussed. The magnetic field, acting through the Hall fields in both n- and p-type material, contributes to the junction bias, thereby altering the current flow. The effects of series resistance are considered. The theory gives results in good agreement with measurements made upon a GaAs laser diode.
Diffusion of Nonvolatile Metallic Elements in Graphite
Authors: Wolfe James R. , McKenzie Donald R. , Borg Richard J.
Published: April 2005

The diffusion coefficients for Ag, Ni, U, Th, and Ra diffusing in various types of graphite have been determined as a function of temperature. Good precision is obtained in all cases and the corresponding activation energies are reported. These values, when comparison is possible, do not agree with values previously reported. An explanation is given for the lack of agreement based upon the relative insolubility of metals in graphite. Experimental evidence is presented which indicates that substitutional, pore, and interstitial diffusion are inoperative and that all mass transport proceeds solely via grain and subgrain boundaries. The activation energies and frequency factors are explained by a diffusion model involving widely spaced traps which are situated at imperfections.
Complex Potential Analysis of Screw Dislocation Arrays
Authors: Webster L. D. , Johnson H. H.
Published: April 2005

Complex potential theory is utilized to analyze the mechanics of screw dislocations on arbitrary glide planes. An analogy with airfoil theory is shown to be useful. General procedures are given for calculating stress fields and distribution functions with the aid of conformal mapping.

The theory is applied to several specific problems, including dislocations on a circular glide plane, on perpendicular intersecting glide planes, and on a glide plane within a thin film. Applications to dislocation pile-ups on neighboring glide planes are also given.
Domain Structure in BaTiO3 Whiskers
Authors: Dragsdorf R. D. , Crawford J. C.
Published: April 2005

Ferroelectric barium titanate whiskers have been grown in the presence of a melt containing BaCl2, BaCO3, and TiO2 in molar ratios of 2:2:1, respectively. These whiskers have dimensions of the order of 10μ×10μ×1mm. The domain configurations have been analyzed by observing all 4 sides of the whisker with transmitted polarized light. The majority of the domains are bounded by 90° domain walls, but 180° walls have been observed in some instances. The visible domains were often found to contain small subdomains which were detected by etching the whisker in HF. Bending the whiskers produced wedge-shaped domains as a stress-relieving mechanism. Such wedges are divided in the center by 180° domain walls and often contain small spike-shaped subdomains. It was possible to remove some of the domain walls by the application of an external axial electric field.
Theory of Large-Amplitude Oscillations in the One-Dimensional Low-Pressure Cesium Thermionic Converter
Authors: Burger Peter
Published: April 2005

The large-amplitude oscillations in a one-dimensional, low-pressure cesium thermionic converter are analyzed. With the help of results obtained from computer calculations designed to simulate the operation of the converter, the current oscillations are explained in terms of the changing forms of the potential distribution in the system. The variations in the form of the potential function are explained by means of the concept of a ``temporary dc state.'' Such a state differs from the ideal self-consistent state in that the electrons and the potential adopt new distributions while the ion distribution stays the same as in the self-consistent state. In fact, the ions are treated as too heavy to respond to the new potentials while the electrons adjust themselves rapidly to them. The existence of a temporary dc state is decided by solving a static problem only; but if such a state exists, then there is a possibility for relaxation-type oscillations in the system with frequencies characteristic of the ions.
Switching Behavior of Ferroelectric Bi4Ti3O12
Authors: Cummins S. E.
Published: April 2005

The switching behavior of single-crystal ferroelectric Bi4Ti3O12 has been determined at room temperature. The switching time for fields from 4 to 14 kV/cm can be expressed as ts = 1.32×10−3 exp [61.6 (kV/cm)/E] μsec. For fields in the range 3 to 4 kV/cm, partial switching occurs; for fields less than 3 kV/cm, switching does not occur. In the region of exponential dependence, ts was measured as a function of E by the direct observation of switching current pulses. For fields in the region of incomplete switching, the behavior was determined by measuring the fraction of polarization reversal as a function of field for different voltage pulse widths. A family of curves with pulse widths ranging from 100 μsec to 5 h clearly shows a switching threshold at a field of approximately 3 kV/cm. Oscilloscope photographs reveal initial hysteresis loops that possess a field axis bias which rapidly anneals to give a nearly symmetrical loop. The dependence of switching time on the frequency of the applied switching voltage indicates that the bias effect has a relaxation time extending from less than 5 msec to several minutes or longer. The unusual switching properties are explained in terms of the rapidly changing bias. The source of the internal bias is not determined in this investigation.
Energy Exchange from Nd3+ to Yb3+ in Calibo Glass
Authors: Peterson G. E. , Pearson A. David , Bridenbaugh P. M.
Published: April 2005

Studies of energy exchange from Nd to Yb in calibo glass were made using the technique of time-resolved spectroscopy. The rate of energy exchange between the systems was of the order of 3×104/sec, while the quantum efficiency for the process was estimated at 0.6. The mechanism is predominately nonradiative.
Process-Introduced Structural Defects and Junction Characteristics in N P N Silicon Epitaxial Planar Transistors
Authors: Jungbluth E. D. , Wang P.
Published: April 2005

X-ray diffraction miscroscopy has been used as a nondestructive technique in order to observe and monitor the effects of process treatments and the relation of structural defects to the variation of junction characteristics from the performance predicted. X-ray topographs were recorded at the following processing stages of electrochemically and mechanically polished wafers: (1) before epitaxial growth, (2) after epitaxial growth, (3) after thermal passivation, (4) after boron diffusion, and (5) after phosphorus diffusion. Poor reverse junction characteristics have been correlated with the coincidence of dislocations and junction areas. Light surface markings due to polishing procedures may not adversely affect the junction characteristics, while scribe marks invariably cause shorted junctions.
Geiger-Müller Discharge Propagation Velocities in Argon-Ethanol Mixtures
Authors: Davis W. P. , Doyle A. M. , Worthington W. C.
Published: April 2005

A new method is described of measuring discharge propagation velocities in Geiger-Müller tubes utilizing the visible radiation emitted by the discharge. Propagation velocity data for argon are given as a function of pressure, overvoltage, and percentage of ethanol quenching agent. The results are in substantial agreement, not only with the available qualitative theoretical predictions, but also with previous quantitative measurements made by other techniques.
Widths of Transmission Kikuchi Lines in Silicon and Diamond
Authors: Fowler H. A. , Marton L.
Published: April 2005

Detailed transmission Kikuchi patterns for silicon and diamond at 80 keV have been measured with high angular resolution (∼10−4 rad). Linewidths of all simple Bragg reflections are consistent with an elastic-scattering model, which uses scattering amplitudes calculated by Ibers in a first Born approximation. Various interferences between strong Bragg reflections are observed.
Harmonic Generation in HCN by Multiple Quantum Conversion
Authors: Akitt D. P. , Coleman P. D.
Published: April 2005

A nonlinear, quantum-mechanics experiment in third-harmonic generation by a traveling wave, multiple photon interaction in HCN gas is presented. The J = 0, J = 1 rotational levels of HCN are used to multiply from 34.7 to 104 Gc/sec with a peak power output at 104 Gc/sec in excess of 1.5 W. The interaction takes place in a length of RG 96/U waveguide. Harmonic power output is plotted against fundamental power input for interaction lengths varying from 0.5 to 3.0 m in 0.5-m steps and gas pressures from 250 to 450 Torr. These data are compared with a theoretical analysis.
Heat Flow as a Limiting Factor in Thin-Film Devices
Authors: Abraham David , Poehler T. O.
Published: April 2005

The performance of thin-film devices can be limited by thermal failure. A model for thermal power dissipation of a thin-film device on a glass substrate has provided the basis for the solution of the heat flow equation. Solutions for the maximum temperature as a function of power input and rectangular device and substrate dimensions have been obtained by digital computations. These results have been applied to the TFT and to the Mead device, and it is concluded that the Mead device will suffer thermal destruction before it can achieve a figure of merit greater than 10 Mc/sec whereas the TFT is not limited by thermal considerations until a figure of merit of several hundreds of Mc/sec has been achieved.
Melting Point and Growth of Barium Telluride Single Crystals
Authors: Lapeyre Gerald J. , Hensley Eugene B.
Published: April 2005

A method is described for determining the melting point of a material by partially melting a long single crystal in a temperature gradient. The melting point of barium telluride was found to be 2070°±10°C. Single crystals of barium telluride were grown in graphite crucibles using a Bridgeman-Stockbarger technique. A procedure for seeding the melt with a portion of a previously grown crystal is described. The lattice constant for barium telluride was found to vary, depending on the history of the sample, from a value of 7.000 Å for freshly prepared powder to as low as 6.950 Å for samples melted in an open crucible.
Diffusion in a Microwave Plasma in the Presence of Turbulent Flow
Authors: Cottingham W. B. , Buchsbaum S. J.
Published: April 2005

Microwave breakdown and diffusion in a weakly ionized microwave plasma was studied in the presence of turbulent flow of the neutral gas. Breakdown was produced by pulsed microwaves in helium, hydrogen, nitrogen, and argon in a tube placed along the E field of an S-band waveguide. The microwave power at breakdown (or at extinction) is a measure of the diffusion rate of the charged particles to the walls of the tube. This power was measured as a function of flow rate of the neutral gas. The minimum microwave breakdown power exhibits a sharp upward break when turbulent flow sets in.
Shock-Induced Polarization in Plastics. II. Experimental Study of Plexiglas and Polystyrene
Authors: Hauver G. E.
Published: April 2005

The polarization produced by a shock wave has been measured for shock pressures up to 297 kbar in Plexiglas and 207 kbar in polystyrene. The polarization is produced at the shock front and undergoes relaxation after the front has passed. For both materials, Hugoniot data indicate a high-pressure phase transition which is correlated with rapid changes in the dielectric properties of the shocked material. At the phase transition, the polarization produced at the shock front and the dielectric constant of the shocked material increase more rapidly, while the relaxation time suddenly decreases. The changes in dielectric properties at the phase transition suggest that the high-pressure phase is more fluid.
Complex Modulus of a Cohesive Soil from Stress Relaxation Response using the One-Sided Fourier Transform
Authors: Kondner Robert L. , Ho Michael M. K.
Published: April 2005

The storage and dissipation resistance to deformation of a cohesive soil as represented by the complex modulus is obtained from stress relaxation response using the one-sided Fourier transform. The soil response is nonlinear. An approximate method of evaluating the transform with digital computer methods is based on the use of straight line segments to form a piecewise continuous representation of the relaxation response. This allows comparison of static and dynamic response characteristics as functions of applied strain level and moisture content through the transformation from the time domain to the frequency domain. For each strain level, large and small time plateau regions of complex modulus are connected with a transition region showing an increase in modulus with increase in frequency. Complex modulus decreases with increased strain level and increased moisture content.
Magnetic Transitions in Dilute Solutions of Iron in Gold and Copper
Authors: Gonser U. , Grant R. W. , Meechan C. J. , Muir A. H. , Wiedersich H.
Published: April 2005

The existence of magnetic transitions in alloys of Fe in Au and Cu has been shown by using the Mössbauer effect. There is a significant difference in the internal-field distribution (and hence alignment of the atomic spins) between the Cu and the Au alloys. In the former a continuous distribution exists, whereas, in the latter a unique (or very nearly unique) internal field occurs in the dilute alloys. The results for the Cu alloys are consistent with an indirect interaction of the Ruderman-Kittel-Yosida type of spins localized at the iron atoms. The internal-field distribution appears to develop a minimum at zero field and a rather broad maximum which shifts gradually to higher fields with decreasing temperature. The nearly unique internal field in the dilute Au-Fe alloys seems to exclude an explanation on the basis of a Ruderman-Kittel-Yosida exchange interaction. A spiral static spin density wave as the mechanism for antiferromagnetically ordering the localized spins (or ferromagnetic order for the case in which the spin density wave vector is zero) seems possible. More concentrated Au-Fe (>16 at. % Fe) alloys show a much more rapid increase in the magnetic transition temperature than the more dilute alloys. Their behavior is ferromagnetic and can be described quite well with a nearest-neighbor interaction using the average coordination number method suggested by Sato, Arrott, and Kikuchi. The appropriate nearest-neighbor exchange interaction energy is J≃2.9×10−2 eV.
Determination of Superconducting Transition Region by Superfluid Phase Transition
Authors: Garbuny Max , Gottlieb Milton
Published: April 2005

A phenomenon is reported consisting of the appearance of a vapor film in He II over superconducting lead film regions which have been driven normal by a critical current. Potential probe measurements verify that the area under the vapor film coincides with the extent of the normal domain within the superconducting environment. Length of the bubble increases linearly with voltage drop across the sample, while the current changes only a few percent for voltage changes of 10:1 or more. This behavior is interpreted by a critical heat flux density which dominates the electrical properties once the vapor film has been established. Quantitative relationships of this kind are not observed if either He I or normal metals are substituted under otherwise equal conditions.
Resistivities and Transformation Rates of High-Pressure InSb—β Sn Alloys
Authors: Banus M. D. , Farrell Lynne B. , Strauss A. J.
Published: April 2005

At atmospheric pressure, alloys of high-pressure InSbII and β Sn are retained indefinitely as metastable phases at 77°K but are transformed into stable two-phase mixtures of low-pressure InSbI and Sn at sufficiently high temperatures. The resistivity of these alloys at 77°K has been measured as a function of composition, and the temperature and time dependence of resistivity up to 300°K has been determined for samples containing up to 60 at.% Sn. The data show that at any temperature the rate of transformation decreases monotonically with increasing Sn content, and, therefore, that solid solutions of InSbII and Sn are formed up to at least 60 at.% Sn. The data are thus consistent with complete solid solution in the InSbII–Sn system, as previously concluded on the basis of superconductivity data.
Dynamic Elastic Properties of Polycrystalline Tungsten, 24°–1800°C
Authors: Lowrie Robert , Gonas A. M.
Published: April 2005

The velocities of ultrasonic shear and compressional waves in polycrystalline tungsten (99.4% dense) have been measured by a pulse-echo technique from 24° to 1800°C. Adiabatic elastic constants have been calculated from these velocities with accuracies of ±0.25% to ±0.65%, and corrections have been applied to obtain the following equations for the elastic constants of fully dense tungsten vs temperature (°C): G=1.5893×1012−1.4733×108T−2.448×104T2 dyn−cm−2,L=5.2415×1012−3.7399×108T−4.598×104T2 dyn−cm−2,K=3.1224×1012−1.7755×108T−1.333×104T2 dyn−cm−2,E=4.0761×1012−3.5521×108T−5.871×104T2 dyn−cm−2,v=0.28247+6.1902×10−6T+3.162×10−9T2.
Diffusion during Deformation by Surface Intensity Methods
Authors: Ruoff A. L.
Published: April 2005

Equations are derived for the surface activity of a diffusion specimen for two cases: In the thin plate case (plane source at the origin of a semi-infinite slab), an analytical solution is obtained for a statically annealed sample and for a sample annealed during simultaneous deformation (either compression or tension normal to the free surface). In the thick plate case, solutions for similar situations are obtained (under proper experimental conditions) in the form of a definite integral convenient for evaluation on an automatic digital computer. Specific cases are shown (using nickel) to illustrate the range in which the thin- and thick-plate solutions are valid. When surface intensity methods are used with a plate sufficiently thick that considerable absorption takes place before diffusion, it is necessary to know precisely the initial plate thickness. This is true regardless of the diffusion time; this is not necessary when the sectioning method is used (with sufficiently long diffusion times). A discussion of a surface intensity experiment by Wazzan is given to illustrate this point.
Magnetomechanical Damping in Iron—Silicon Alloys
Authors: Frank R. C. , Ferman J. W.
Published: April 2005

Experiments with iron-4% silicon wires containing preferred orientation with the 〈110〉 direction along the axis showed that under these conditions, extremely high magnetomechanical damping can be achieved at low strain levels in a torsion pendulum. The effect of crystallographic orientation on the damping was brought out by experiments on wires of square cross section of grain-oriented commercial iron-3% silicon alloy. Internal stress, produced by occluded hydrogen, markedly reduced the magnetomechanical damping in the iron-4% silicon alloy but recovery began to take place after several days at room temperature. Changes in magnetic induction produced during the torsional oscillations by the inverse Wiedemann effect were measured to obtain an indication of the domain boundary movements. These latter experiments together with the damping experiments support the Summer and Entwistle model for the relationship between the magnetic field at maximum susceptibility, the saturation magnetization, the saturation magnetostriction, and the strain at which maximum damping occurs.
Thickness Vibrations of Saturated Magnetoelastic Plates
Authors: Tiersten H. F.
Published: April 2005

The general, linearized, coupled magnetoelastic equations for arbitrarily anisotropic, magnetically saturated insulators, which were derived in a previous paper, are specialized to the important case of a homogeneous, static biasing state. The equations applicable in the special case of a material in cubic class m3m are determined from the more general ones. Consideration of the material constants known for yttrium iron garnet allows the equations to be simplified considerably because many terms are negligible compared to a few which dominate. These latter equations are applied in the determination of the solution for the thickness vibrations of an infinite cubic plate, which is magnetized to saturation along a cube edge, for two special orientations of the magnetization direction relative to the surface of the plate. In both cases the driving field is normal to the magnetization direction, and it is shown that the fundamental solutions of the differential equations are coupled at the traction-free and exchange-torque-free surfaces of the plate. However, when the fundamental solutions are circularly polarized, only those solutions which have the same sense of circular polarization are coupled. It is further shown, in both instances, that this boundary coupling disappears when the exchange interaction is neglected. In an Appendix, the procedure used to determine the influence of material symmetry on the equations is compared with a more accurate procedure.
Diffusion and Solubility of Ag in CdS
Authors: Woodbury H. H.
Published: April 2005

The solubility of Ag in CdS has been measured under conditions of excess sulfur between 375° and 900°C. Also, the distribution coefficient of Ag between CdS and liquid Cd for dilute Ag concentrations has been measured between 500° and 900°C. In addition, the distribution coefficient has been measured at 800°C as a function of the composition of the Cd-Ag alloy. These solubility measurements are interpreted to indicate at least two and probably three different forms of Ag in CdS. Diffusion profiles have been obtained between 300° and 500°C. The rate of diffusion of Ag shows a strong concentration dependence and is extremely rapid for dilute Ag concentrations. The profiles are discussed in terms of three independent steps in the incorporation of Ag in CdS.
Magnetostriction of Nonferromagnetic Metals
Authors: Anderholm N. C. , Peck E. R.
Published: April 2005

Magnetostriction measurements, made with an interferometric dilatometer at room temperature, are reported for Bi, Sb, W, Nb, Mo, Ta, and V. The measurements were made using magnetic fields to 30 kG on high-purity single crystals. The results for Bi agree qualitatively with those of Kapitza and Shoenberg. Generally, the Sb results were smaller. The values obtained for the transition elements were the smallest of those measured, but quantitative information on their magnetostrictive properties was obtained.
Whisker Crystals of Gallium Arsenide and Gallium Phosphide Grown by the Vapor—Liquid—Solid Mechanism
Authors: Barns R. L. , Ellis W. C.
Published: April 2005

GaAs and GaP whisker crystals have been grown by the vapor—liquid—solid mechanism of crystal growth. Gold, palladium, platinum, and gallium have been used to produce the required liquid layer. The system employing wet hydrogen developed by Frosch and Thurmond was used for most of the crystal growing. p- and n-type crystals were produced. GaAs crystals were found to have three morphologies: a twinned ribbon with a 〈112〉 growth direction and {111}, {110}, and {113} lateral faces; a single-crystal hexagonal needle with a 〈111〉 growth direction and {110} lateral faces; and a newly found habit, a single-crystal blade which grows in an 〈001〉 direction with {110} lateral faces. The largest GaAs blades were about 8×0.3 ×0.010 mm and grew at a rate of about 1 mm/h. The twinned ribbon and the 〈001〉, {110} morphologies were found in GaP.
Positron Focusing in an Accelerating Field
Authors: Hong G. W.
Published: April 2005

The equation of motion of positrons (or electrons) in an accelerating field and a focusing magnetic field is analyzed with relativistic effects included. An iterative procedure is used to solve the resulting nonlinear differential equation. An example is included to illustrate this technique; it is found that the assumptions involved are consistent with the numerical calculations. The feasibility of the proposed focusing scheme can be determined from the results obtained by this method of analysis.
Work Function of Cesium-Covered Nickel—Thermionic and Photoelectric Measuring Techniques
Authors: Rump B. S. , Gehman B. L.
Published: April 2005

The work function of cesium-covered nickel has been measured by the thermionic and photoelectric methods. A modulated light beam technique allowed the measurement of the photoelectric emission currents in the presence of thermionic currents that were 106 times larger. The minimum work function of cesium-covered nickel was determined to be 1.42±0.05 eV by the thermionic method at a nickel temperature of 530°K and a cesium reservoir temperature of 333°K. The results obtained by the photoelectric method were, on the average, 0.05 eV lower than the values determined by the thermionic method. The discrepancy is expected because of the bias introduced to both methods by local variations in work function. The agreement of the data obtained by the two methods indicates that the Richardson constant is close to the assumed value of 120 A/cm2·deg2. The work was undertaken as a first step toward the improvement of cesium-filled thermionic generators by lowering the collector work function.
Thermal Conductivity of Sulfur Accompanying Crystal Transition and Phase Change
Authors: Sugawara Akira
Published: April 2005

The thermal conductivities of both the solid sulfur and the liquid sulfur were continuously measured with an accuracy of ±1.0%. The temperature range in this experiment is from 0° to 160°C. In the temperature range from 0° to 160°C, two transition points exist; one of them is the transition point from rhombic sulfur to monoclinic sulfur at 95.5°C, and the other is the change point from monoclinic sulfur to liquid sulfur at 118.9°C. At each transition point, discontinuous and conspicuous changes in thermal conductivities can be observed by this experiment.

Moreover, a new result was obtained: The thermal conductivity of monoclinic sulfur decreases with increasing temperature, although the conductivity which was obtained by Kaye's experiment increases with temperature increment.
Comparison of Observed and Predicted Stimulated Raman Scattering Conversion Efficiencies
Authors: Weiner D. , Schwarz S. E. , McClung F. J.
Published: April 2005

We have measured the absolute Raman scattering cross section for the 1345-cm−1 shifted Stokes line in nitrobenzene using a ruby laser. We have also measured the efficiency of conversion of radiation from a giant pulse ruby laser into stimulated Raman scattered radiation for this line. We have found that the average intensity needed to produce a given conversion is one or two orders of magnitude less than that predicted by the theory of Hellwarth using our measured cross section. We discuss some possible explanations for this disagreement.
Anisotropic Elasticity Solutions for Dislocation Barriers in Face-Centered Cubic Crystals
Authors: Jo/ssang T. , Hirth J. P. , Hartley C. S.
Published: April 2005

The stability of extended dislocation barriers in face-centered cubic metals is determined using the theory of anisotropic elasticity. It is found that the results typically differ from the isotropic elasticity solution by 25%, but the difference can in special cases amount to as much as a factor of four. The anisotropic results are in qualitative agreement with earlier isotropic results in predicting the relative strength of the barriers to dislocation glide. The results suggest that the measurement of barrier extension should provide the most accurate available means of estimating the stacking-fault energy in fcc metals.
Generation of Acoustic Waves in Cadmium Sulfide
Authors: Dinhofer A. D.
Published: April 2005

The possibility of generating high-frequency acoustic waves by illuminating the negative end of a cadmium sulfide rod with light of periodically varying intensity exists. The strains produced and the acoustic gain present under different conditions of drift current and resistivity are calculated for three decades of frequency.
Radiation from a Fully Ionized Gas at the Plasma Frequency
Authors: Taylor Edward C.
Published: April 2005

Thermal radiation from a fully ionized gas near the plasma frequency is investigated theoretically with consideration given to boundary effects. It is shown that the emission spectrum is a relatively complicated function of frequency, temperature, density, and geometry, but that the absorption spectrum can be approximated by a simple function of the three parameters representing frequency, collisions, and geometry. The sensitivity of the absorption curve to these parameters is investigated, and the results are used to interpret recently measured infrared radiation from a theta pinch.