bluuebunny/crossref_metadata_2025 huggingface dataset:
Excitation Processes in Ceramics and Anomalous Increase in Thermal Conductivity at Elevated Temperatures
Authors: Whitmore D. H.
Published: April 2005

The problem of the anomalous increase in the observed thermal conductivity of single-phase ceramics at high temperatures has been considered. At temperatures above the onset of this anomalous rise, account has been taken of the possibility that phonon, electronic, and radiative heat transfer, as well as transport of thermal energy by electron-hole pairs, excitons, and dissociated gas molecules, may operate simultaneously and individually contribute significantly to the total heat flow. On the basis of reliable conductivity data on nonporous monocrystals of single-phase ceramics, estimations have been made of the magnitudes of these high-temperature components which reveal that excited states of low excitation energy may occur in certain ceramics. In these instances, such excited energy-carrying states are able to diffuse down the temperature gradient in the specimen thereby producing a non-negligible contribution to its observed thermal conductivity.
Preparation of Large Area Single-Crystal Cuprous Oxide
Authors: Toth Robert S. , Kilkson Rein , Trivich Dan
Published: April 2005

Large area single crystals of Cu2O were grown by the process of high temperature annealing. Cu2O was prepared in finely polycrystalline form by the complete oxidation of Cu plate in air at temperatures of 1020°C to 1050°C. Subsequent annealing of the polycrystalline plates at higher temperatures allowed secondary recrystallization to occur. Single-crystal grains having surface areas larger than 1 in.2 were grown consistently on Cu2O plates having thicknesses of 0.010 in. to 0.060 in. In some cases, entire polycrystalline plates were transformed into single crystals, and as a result, individual single crystals having surface areas of 3 in.2 and larger were obtained. The annealing temperature and the annealing time were found to depend markedly on the plate thickness. Thick plates required lower temperatures and longer annealing times than the thinner plates. X-ray analysis of the large grains verified that they were single crystals without excess strain, and indicated preferred orientation, with the (211) and (311) planes predominating. Resistance profile measurements at room temperature on quenched samples showed that a variation in resistance exists through the thickness of the plate.
Dislocation Damping Effects in Rock Salt
Authors: Bauer Charles L. , Gordon Robert B.
Published: April 2005

Internal friction measurements made as a function of strain amplitude on deformed sodium chloride single crystals were followed by elastic modulus measurements made during x irradiation of the same crystals. Etch pit densities were also determined. These data were used to evaluate the constants in a theory, proposed by Granato and Lücke in 1956, which permits the calculation of the average length of the dislocation segments, L, which vibrate under an applied alternating stress. An independent determination of the magnitude of L was made from the elastic modulus data using a method developed by Gordon and Nowick.

It is concluded that the theories tested in this paper give a useful representation of dislocation damping phenomena in sodium chloride and permit use of internal friction measurements for the continuous observation of dislocations.
Minority Carrier Recombination in a Cylindrical Transistor Base Region
Authors: Kennedy David P.
Published: April 2005

An analysis is given on the influence of bulk recombination within the base region of a mesa-type drift transistor. The minority carrier transport efficiency is established for a solid cylinder base region and also for a simplified one-dimensional structure. A comparison of the two minority carrier transport equations shows the approximate analysis will result in a negligible error when applied to practical semiconductor devices.
pLayers on Vacuum Heated Silicon
Authors: Allen F. G. , Buck T. M. , Law J. T.
Published: April 2005

It has been established that when silicon is heated above 1300°K in a borosilicate glass vacuum system from 1011 to 1015 acceptors per cm2 are normally added to the silicon surface, even though the glass walls remain at room temperature. The acceptor diffuses into the surface upon heating forming a p layer several microns deep.

There is strong evidence that the acceptor is boron from the borosilicate glass envelope. The transfer to the silicon is believed to occur through volatilization of boron oxides by water vapor.
Paramagnetic Susceptibilities of Fe and Fe-Si Alloys
Authors: Arajs Sigurds , Miller D. S.
Published: April 2005

Paramagnetic susceptibilities of Fe and Fe-Si alloys (5.75, 6.82, 9.45, 12.65, 14.70, 18.11, 20.85, and 24.38 at. % Si) have been measured up to 1200°C. At high temperatures the paramagnetic susceptibilities of bcc Fe-Si alloys obey the Curie-Weiss law, possibly indicating that the contribution due to s-d exchange interactions is small in comparison with the temperature dependent paramagnetism. The effective Bohr-magneton number of Fe from the high-temperature region is independent of Si content up to about 14 at. % Si. At higher Si concentrations, gradual decrease in the effective Bohr-magneton number occurs. According to the paramagnetic susceptibility measurements, the α-γ transition in iron takes place at 910±3°C. Assuming that the critical temperatures for chemical ordering as given by Glaser and Ivanick are correct, our measurements indicate that the paramagnetic susceptibility, within the experimental error, is not influenced by the destruction of the superlattice above 13 at. % of Si.
Production and Properties of Thin Layers of Indium Antimonide
Authors: Bate G. , Taylor K. N. R.
Published: April 2005

A new method of producing thin layers of indium antimonide is described. This consists of suddenly squashing a drop of molten indium antimonide between two optical flats and allowing it to cool.

Large area, self-supporting specimens of 10-μ thickness have been prepared in this way and their properties examined. Although these layers are polycrystalline, their electrical and optical properties are in good agreement with the single-crystal materials from which they were obtained.
Vapor-Deposited Single-Crystal Germanium
Authors: Ruth Ralph P. , Marinace John C. , Dunlap W. C.
Published: April 2005

Germanium layers have been formed on single-crystal Ge substrates by the thermal decomposition of GeI2. The single-crystal nature of the layers has been established by x-ray and electron diffraction examination and by electrical measurements. The deposition process is described briefly. The crystal growth rate varies with crystal direction, and under certain conditions Ge whiskers appear. The layers as deposited are generally n type; ρ ranges from 1 to 5 ohm-cm and μH from 1200 to 2700 cm2/v-sec at room temperature. A donor level is found approximately 0.2 ev below the conduction band, with a concentration of active centers of about 1016/cm3. Heat treatment at 550°C gradually converts the layers to p type, for which ρ is 10 to 40 ohm-cm and μH 1500 to 2400 cm2/v-sec at room temperature; an acceptor level is found at about 0.05 ev above the valence band, with a density of active centers of 1014 to 1015/cm3. The layers can be doped intentionally to produce either conductivity type, permitting fabrication of junction devices. Although iodine and other impurity atoms are considered, it is concluded that interstitial Ge atoms and lattice vacancies, occurring in unequal numbers at the time of deposition, are the most likely source of the donor and acceptor levels, respectively, and of the observed heat treatment properties.
Propagation Mechanism of Germanium Dendrites
Authors: Hamilton D. R. , Seidensticker R. G.
Published: April 2005

The role of the twin planes in the rapid dendritic propagation of germanium crystals is examined on the basis of corner nucleation. A model is proposed, and it is shown that at least two twin planes must be present for continued easy propagation in <211> directions, in good agreement with experimental observations. The absence of the dendrite with only one twin is explained.
Monte Carlo Calculation of Molecular Flow Rates through a Cylindrical Elbow and Pipes of Other Shapes
Authors: Davis D. H.
Published: April 2005

A method is devised for the calculation of molecular flow rates through pipes where the mean free path for intermolecular collisions is large compared to the dimensions of the pipes. Results of the calculation are given for a straight cylindrical pipe, a cylindrical elbow, the annulus between two concentric cylinders, a straight cylindrical pipe with restricted openings, and a straight cylindrical pipe with restricted openings and a plate to block the direct beam between the openings.
Transport Equation for the Spectral Density of a Multiple-Scattered Electromagnetic Field
Authors: Bugnolo Dimitri S.
Published: April 2005

The use of a first Born approximation is open to question when the path length is greater than a mean free path in the scattering region. It is therefore of interest to develop a transport equation capable of predicting the spectral density for such cases. The general theory presented in this paper is applied to the case of multiple scattering by dielectric noise. It is independent of models for the dielectric fluctuations. A method of solution is developed for the case of forward scattering. The particular case of a monochromatic plane wave incident of a half space is discussed in detail. The results are applied to a numerical example in the troposphere.
Small Angle Scattering Investigation of Ludox Mixtures
Authors: Bragg Robert H. , Corvin Irene , Buttrey John W.
Published: April 2005

Small angle scattering measurements have been made on distributions of particles prepared by mixing two silica sols of about 90A and 190A mean particle diameter in varying proportions. The scattering at small angles arises predominantly from the larger particles, whereas the smaller ones control the scattering at large angles, as predicted by theory. Attempts to determine the size distribution by the graphical method of Jellinek et al. were unsuccessful, but Porod's result relating the scattering at large angles to the total surface area was verified. Bounds for the largest and smallest sizes were estimated from the experimental data by means of simple calculations based on the properties of the scattering function.
Charged-Particle Orbits in Varying Magnetic Fields
Authors: Gordon E. I.
Published: April 2005

A solution for the paraxial orbits of charged particles in varying magnetic fields is given. The magnetic field is assumed to be azimuthally symmetric but is allowed to vary arbitrarily with time or axial distance. The instantaneous guiding center and radius vector of the orbit are given in terms of the initial guiding center and radius vector and two parameters which are determined from the solution of a first-order differential equation containing the magnetic-field variation. One exact and two approximate constants of the motion are evaluated and discussed.
Growth of Atomically Flat Surfaces on Germanium Dendrites
Authors: Longini R. L. , Bennett A. I. , Smith W. J.
Published: April 2005

This note presents a theory of the formation of extended flat surfaces on germanium dendrites. It is suggested that part of the liquid-solid interface is a supercooled {111} surface, on which new atomic planes are occasionally nucleated. Thermal limitations on the nucleation and propagation of these monolayers are discussed. When such a growing layer reaches the melt surface it creates a step on the solid. It is proposed that the meniscus momentarily sticks to the corner of this step. Subsequent planes nucleated during this sticking period result in a step several atomic layers high, in accord with experiment. Elementary estimates of corner energy and amount of meniscus sticking yield results consistent with experiment.
Parametric Diode Figure of Merit and Optimization
Authors: Mortenson K. E.
Published: April 2005

The noise figure and gain expressions for the diode parametric amplifier are presented and discussed which include the effects of diode losses. From these relationships, a new diode figure of merit is defined as follows: fD=an/ 4πa02C0RD, where an is the normalized Fourier coefficient of the time dependent (pumped) capacitance; C0, the diode capacitance at the operating bias point; and RD, the equivalent series diode resistance. It is shown that this figure of merit is directly applicable in comparing diodes of various types as well as in optimizing their respective design for low-noise amplifier use. Further, it is indicated how this figure of merit can be directly employed by the circuit designer to predict an amplifiers' noise figure performance including the effects of choice of bias, pump swing, and signal and idle frequency for a given diode.

A complete evaluation of the proposed figure of merit is made for the abrupt junction diode by expressing fD in terms of device design parameters and examining as a function of bias and base doping. It is concluded, if no constraints are considered, that the maximum value of fD is obtained for a bias approximately equal to half the breakdown voltage with full pump swing and that fD(max) increases with decreasing base doping from 1018 to 3·1015 atoms/cc. It is further concluded that the maximum possible value of a1/a02 for the inverse square root of voltage capacitance law is approximately 0.557 such that the greatest value fD(max) can attain is 20% of fc, the diode cutoff frequency. Some possible limitations on this evaluation are discussed including the effects of diode deviation from model, pump power or diode dissipation restrictions, nonsinusoidal pumping waveform, and ambient temperature.
Use of the Omegatron in the Determination of Parameters Affecting Limiting Pressures in Vacuum Devices
Authors: Lichtman David
Published: April 2005

The omegatron mass spectrometer has been used to determine residual gases in vacuum systems, including ion pump systems. The predominant residual gas in ion pumps was found to be methane, while the gases found in oil diffusion pump systems include water vapor and carbon monoxide. Analysis has been performed to determine the residual gases in vacuum tubes which are difficult to outgas, and conditions that lead to considerable hydrogen content are described. Examples of the use of the omegatron mass spectrometer as a tool in aiding solution of outgassing problems are given.
Ultra-High-Speed Photographs Refuting ``Cohesion in Plasma''
Authors: Davis W. C. , Campbell A. W.
Published: April 2005

In a recent issue of this journal [M. A. Cook and W. S. McEwan, J. Appl. Phys. 29, 1612 (1958)] and in a recent book [Melvin A. Cook, The Science of High Explosives (Rheinhold Publishing Corporation, New York, 1958), 1st ed., pp. 158, 420–426], a sequence of framing camera pictures was presented, and the sequence was interpreted as evidence that, as the result of the detonation of a quantity of explosive, a plasma was ejected into the atmosphere, and that the plasma exhibited a strong cohesive force. This paper presents pictures of an essentially identical subject, taken at three exposure times: the same exposure time used for the sequence in the references (4 μsec); 1/20th of that time; and 1/400th of that time. These pictures show that the phenomena are those of a shock wave, and that no new assumption of cohesive force is necessary to interpret the pictures. A simple analysis of the shock wave interpretation using the usual theory is presented to show that the interpretation is consistent with the known properties of air and the explosive used.
Response of a Loaded Idealized Piezoelectric Plate to an Electric Signal
Authors: Levi Leo
Published: April 2005

The response of piezoelectric plates and rods are generally treated in the form of ``equivalent'' electric circuits. When the actual mechanical displacements and strains are of interest, such equivalent circuit treatment may be inconvenient. In the present paper the response of a loaded piezoelectric plate to an arbitrary electric input signal is derived on the basis of certain idealizations which are closely approximated by practical systems.
Impact Crater Formation in Rock
Authors: Maurer William C. , Rinehart John S.
Published: April 2005

Craters were produced by firing spherical steel projectiles of 316- and 932−in. diam into sandstone and granite at velocities ranging from 300 to 6000 ft/sec. Impact angles of 30, 60, and 90 deg were used for the sandstone and 90 deg for the granite. The craters are formed by two mechanisms: (a) crushing of material in front of the projectile and (b) fracturing which takes place as fractures are initiated by a constant impulse in steplike fashion in front of the projectile and propagated along logarithmic spirals of maximum shear to the free surface of the rock. The volume of the material removed by crushing varies as the first power of the impact velocity and the volume removed by fracturing, as the second power of the impact velocity. Penetration varies linearly with the impact velocity and is inversely proportional to the specific acoustic resistance of the target material, the proportionality constant being dependent upon the shape of the projectile.
Equation of State for Nineteen Metallic Elements from Shock-Wave Measurements to Two Megabars
Authors: McQueen R. G. , Marsh S. P.
Published: April 2005

Plane-wave explosive systems were used to accelerate thin metal plates to high velocities. Shock pressures resulting from the collision of these driver plates with a stationary target plate are approximately three times greater than the original shock pressure in the driver plate. The photographic flash-gap technique was used to record velocities associated with the shock waves. The new experimental data extend the Hugoniot loci into the one-to two-megabar region for 19 metallic elements: Ag, Au, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sn, Th, Ti, Tl, V, W, Zn, Bi, Fe, Sb.

The Hugoniot P, V, E data have been extended to a more complete P, V, E, T equation of state by use of the Mie-Grüneisen theory. The thermodynamic variable, γ=V(∂P/∂E)v, necessary for this extension, was obtained by solving the Dugdale-MacDonald relation.
Photographic Verification of Ultrasonic Plane Wave Scattering by Cylinders
Authors: Nine Harmon D. , Schubring Norman W.
Published: April 2005

The ability to photograph the ultrasonic field around a model may obviate the need for extensive mathematical analysis of ultrasonic or analogous field problems. In this paper a method of photographing an instantaneous field invariant in one direction is described. Through use of a parallel-beamed light pulse of very short duration photographs were made of the ultrasonic field of continuous 3-Mc traveling sound waves in water impinging perpendicularly upon the side of a cylindrical tube. Shadowgraphs thus obtained verified the wave shapes predicted by IBM 704 computation of the mathematical analysis.
Gamma Irradiation of Silicon. I. Levels in n-Type Material Containing Oxygen
Authors: Sonder E. , Templeton L. C.
Published: April 2005

The resistivity and Hall coefficient of n-type silicon containing oxygen have been measured as a function of temperature before and after a number of successive irradiations in a Co60 gamma-ray source. A net acceptor level 0.17 ev below the conduction band was observed to result from the irradiation. Its rate of introduction was 7×10−4 traps/cm3 per photon/cm2 in 50- ohm-cm material and was about twice that in more heavily doped material (∼2 ohm-cm). Acceptor levels, lying deep within the forbidden gap, were also observed. Their total introduction rate was smaller than that of the 0.17-ev level by a factor of 50. A lowering of the mobility below ∼100°K was also a result of the irradiations. In heavily irradiated samples this lowering of the mobility was much greater than could be explained on the basis of point-charge scattering.
Transitory Electrical Properties of n-Type Germanium After a Neutron Pulse
Authors: Stein H. J.
Published: April 2005

The stability of neutron bombardment damage in Sb-doped Ge has been investigated by making continuous measurements of the electrical conductivity and Hall mobility following a neutron pulse. Measurements were made in the temperature range from 77° to 308°K with a time resolution of 1 sec. At temperatures near 195°K an initial decrease in conductivity and mobility was followed by an additional decrease which exhibited nearly second-order kinetics. At 273°K and above, an initial decrease in conductivity and mobility was observed, but was followed by a recovery consistent with an activation energy of 0.68 ev. The void region model of Gossick and Crawford has been employed to explain the initial decrease in mobility and a major portion of the initial decrease in conductivity. The transitory changes in mobility and conductivity after the neutron pulse are considered as changes in the void volumes.
Performance of a Thermoelectric Converter under Constant Heat Flux Operation
Authors: Castro P. S. , Happ W. W.
Published: April 2005

The performance characteristics of a conventional thermoelectric generator operating under constant heat flux conditions have been computed. Expressions for power output, optimum efficiency, and optimum ratio of internal-to-load resistance show that optimization requires operating conditions appreciably different from those for the operation of thermoelectric generators having constant hot and cold junction temperatures. Performance curves are presented for the optimum ratio of internal-to-load resistance when either the internal resistance or the load resistance is under the control of the designer.
Some Elastic Properties of a Screw Dislocation Wall
Authors: Li James C. M. , Needham Charles D.
Published: April 2005

The stress fields of an infinite and a finite screw dislocation wall are given and from them the interactions of the screw dislocation walls with parallel and nonparallel dislocations have been studied. The nature of the penetration through a screw dislocation wall of a number of parallel screw dislocations driven by external stress and the possible stress concentration for a pileup against the wall are discussed in detail. The forces exerted by a screw dislocation wall on nonparallel edge and screw dislocations are calculated. The significance of the local torques due to these forces as a possible mechanism for the screw dislocation wall to become a source for generating dislocations is pointed out. The metastability of the screw dislocation walls is demonstrated and their strain energy is estimated and compared with that of the edge dislocation walls. It is concluded that the resistance to penetration of a dislocation wall increases in the following order: infinite edge dislocation wall, finite edge dislocation wall, finite screw dislocation wall, and infinite screw dislocation wall. It is also found that the strength of a dislocation wall increases with its surface strain energy.
X-Ray Reflection Studies of the Anneal and Oxidation of Some Thin Solid Films
Authors: Wainfan N. , Parratt L. G.
Published: April 2005

The technique of the total reflection of x rays has been applied to the study of thin films of Cu, Ni, Ge, and Se vacuum-deposited onto polished glass substrates. Starting with fresh films, ``smooth'' enough to exhibit pronounced x-ray interference fringes in the region just beyond the critical angle, the effects of vacuum anneal and oxidation were studied. Changes in the reflection curves are interpreted in terms of possible structural changes in the films. Reflection from layers of particles of carbon or polystyrene latex deposited onto ``smooth'' substrates was also studied for comparison.
Phase Oscillations in High Current Synchrotrons
Authors: Henry Irvin G.
Published: April 2005

The theory of phase oscillations in the synchrotron, first given by Bohm and Foldy, is extended to cover the case where the amplitude of the accelerating voltage is not constant and where the accelerated bunch is itself sufficiently large to produce an appreciable part of the accelerating voltage. It is found that the phase oscillation is more stable when the driving frequency is less than the natural frequency of the accelerating electrode system, and that the plate characteristic of the driving amplifier has a negligible effect on the phase stability.
Growth from the Melt. I. Influence of Surface Intersections in Pure Metals
Authors: Bolling G. F. , Tiller W. A.
Published: April 2005

The solid-liquid interface shape during growth from the melt has been determined for pure materials in the vicinity of external and internal surfaces; both the cases of isotropy and anisotropy of solid-liquid interfacial energy have been considered. From these considerations it is possible to determine some effects associated with interface and external surface anisotropy. For example, a preferred direction of growth, a surface layer phenomenon and stray-crystal formation during seeding and normal crystal growth may arise as a result of the solid-liquid interface configuration.
Partition Noise in Electron Beams at Microwave Frequencies
Authors: Ashkin A. , White L. D.
Published: April 2005

A study was made at 4080 Mc of the partition noise introduced into a beam by a meshed grid as a function of its position along the beam. Simultaneous information concerning the beam dynamics was obtained by means of a beam analyzer. With cathode magnetic fields somewhat below those corresponding to immersed flow, the partition noise exhibited sharp dips as the grid in moving along the beam passed through the planes which corresponded to image planes of the cathode. These observations confirm the picture of noise smoothing taking place over relatively small areas in the vicinity of the cathode and elucidate the contribution of the random interception of electrons to the partition noise. With small cathode magnetic fields the partition noise varied sinusoidally with the cyclotron periodicity as the grid was moved along the beam. This variation with position is thought to result from the contribution to the partition noise of higher-order mode conversion.
Three-Dimensional Space Charge Flow
Authors: Rosenblatt Jorge
Published: April 2005

The general theory of stationary beams of prescribed shape is developed taking into account the electrostatic interaction between the particles. The Hamilton-Jacobi equation, expressed in a particular system of coordinates, allows the determination of the potential distribution inside the beam. Compatibility conditions for the equations are obtained, as well as a general rule for the determination of the feasibility of arbitrarily chosen trajectories. A theoretical expression results for the proportionality coefficient k in Child's law (J=kV32) which relates current density J with the potential difference V between electrodes. The theory was applied to the particular case of a plane beam with hyperbolic boundaries. The beam was experimentally reproduced, providing values for k in close agreement with the theoretical ones.
Spectral Emissivity, Total Emissivity, and Thermal Conductivity of Molybdenum, Tantalum, and Tungsten above 2300°K
Authors: Allen Robert D. , Glasier Louis F. , Jordan Paul L.
Published: April 2005

The emissivities and thermal conductivities of high purity arc melted molybdenum and tantalum and powder metallurgy tantalum and tungsten were measured between 2300°K and their respective melting points. A method is presented for the determination of spectral and total emissivities from the determination of brightness temperature at the center of an electrically heated rod as a function of heat flow rate. The method does not depend on the experimental achievement of blackbody conditions. Spectral emissivities were also determined by measurement of brightness temperatures at the respective melting points. Thermal conductivities of electrically heated rods were determined by the Jain and Krishnan longitudinal heat flow method. The spectral emissivities of tantalum and tungsten decrease linearly with increase in temperature. The spectral emissivity of molybdenum is constant. The total emissivities of molybdenum, tantalum, and tungsten increase with increasing temperature. For any of the metals the spectral and total emissivities are closest to each other at the melting point. The melting point of tantalum is significantly lowered by small increase in impurity content. The thermal conductivities of molybdenum, tantalum, and tungsten decrease linearly with increasing temperature. The ranges of spectral emissivity, total emissivity, and thermal conductivity above 2300°K are as follows: ελεTK (cal. cm−1sec.−1∘K−1)Molybdenum0.300.271–0.2850.34–0.32Tantalum0.361–0.3500.288–0.3240.15–0.11Tungsten0.37 –0.360.268–0.3520.38–0.30
Exchange Anisotropy Memory Effect
Authors: Jacobs I. S. , Lawrence P. E.
Published: April 2005

A magnetic memory effect is observed in a low Curie point ferrimagnetic spinel (∼NiFe0.15Cr1.85O4) containing a coherent antiferromagnetic impurity (NiO) with a high Néel point. It is explained in terms of the Meiklejohn-Bean exchange anisotropy coupling the two phases. The past magnetic history is remembered in the spontaneous reacquisition of a fraction of the past remanent state despite prolonged storage at temperatures above the ferrimagnetic Curie point. A feature of the explanation is the condition that antiferromagnetic domains in NiO rotate irreversibly in accessible fields.
Temperature Dependence of Young's Modulus of Vitreous Germania and Silica
Authors: Spinner S. , Cleek G. W.
Published: April 2005

The temperature dependence of Young's modulus of vitreous GeO2 has been determined by a dynamic resonance method from −195°C to 540°C. The modulus increases with increasing temperature from about −120°C to 400°C. Below and above this range the modulus decreases with increasing temperature. Young's modulus for vitreous SiO2 also increases from about −190°C to 1175°C and decreases with increasing temperature outside this range.

In view of the similarity in structures and bond energies of these two materials, the similarity in the elastic modulus-temperature relations is believed to be significant; especially when contrasted with the lack of agreement in another commonly measured anharmonic property, thermal expansion.
Dislocations in Metal Crystals Grown from the Melt
Authors: Elbaum C.
Published: April 2005

Dislocation densities and arrangements were studied, as a function of specimen thickness, in metal crystals grown from the melt. Aluminum crystals containing fewer than 104 dislocations per cm2 were produced by this method. The results of this study are consistent with the mechanism of collapsing vacancy disks for generating dislocations in crystals grown from the melt.

It was found, in aluminum, that below a dislocation density of about 106 lines per cm2, dislocations remain in a random network and do not form sub-boundary arrays. The range of effective interaction between dislocations, to form arrays, thus appears to be limited to the average distance between dislocations when the density is about 106 lines per cm2, or about 10 μ.
Characteristic Energy Losses of Electrons in Carbon
Authors: Leder Lewis B. , Suddeth J. A.
Published: April 2005

The values reported for the characteristic energy losses of electrons in carbon vary by as much as 50%. In an attempt to resolve this discrepancy the electron energy losses have been remeasured for evaporated carbon and natural graphite, and it is found that there is a large difference for these two forms of carbon. Electron diffraction patterns of evaporated carbon show it to be highly amorphous. Annealing of the films causes growth of the crystallites, and also an increase of the energy loss toward the loss values for graphite. It is shown by calculation that the difference in the energy losses for the two forms is due to a difference in density, and that annealing increases the density of the evaporated carbon and, therefore, the energy loss value.
Elastic Constants of Single-Crystal Aluminum Antimonide
Authors: Bolef D. I. , Menes M.
Published: April 2005

The ultrasonic cw resonance technique was used to measure the adiabatic elastic constants of single-crystal aluminum antimonide at 27°C. The values for the elastic stiffness constants, in units of 1011 d/cm2, are: c11 = 8.939, c12 = 4.427, and c44 = 4.155. A theoretical density of 4.36 g/cc was used. The values of c11 and c44 for single crystal GaSb obtained by the cw resonance technique are compared with previous values obtained by pulse-echo techniques.
Analog Study of Large-Signal High-Frequency Diodes
Authors: Andrews C. L.
Published: April 2005

A rolling-ball analogue for the motion of electrons in a high-frequency longitudinal field has been developed in which the balls, injected at regular time intervals, plotted photographically a family of graphs of distance against time, indicated the electron bunching, velocity modulation, and density modulation. From these graphs the current densities were found as a function of time for a series of equally spaced positions between cathode and anode, and the plate current induced by the electron stream was computed. Graphs of conductance against transit angle revealed that the conductance was independent of the size of signal for indices of modulation 0.25, 0.50, and 0.75. When the transit angle was 2π the induced plate current was almost pure first harmonic plus dc. When the transit angle was 3π the first harmonic disappeared.
Determination of Surface Structure using Ultra-High Vacuum Replication
Authors: Bachmann L. , Orr W. H. , Rhodin T. N. , Siegel B. M.
Published: April 2005

Electron microscopy has been applied to the problem of characterizing the distribution of preferred sites for nucleation and growth on clean surfaces of evaporated films of magnesium metal. The films were deposited, platinum-shadowed, and carbon-backed in the same system under ultra-high vacuum conditions to minimize surface contamination and to improve the fidelity of surface replication. Upon examination of both clean and oxidized films in the electron microscope, the distribution of the platinum deposit was observed to be markedly influenced by the vacuum conditions used in the replication procedure. In addition, the particle size and separation of the platinum grains and their distribution, with relation to the substrate, indicated an enhanced surface mobility on cleaved mica and an apparent reaction on magnesium. These observations may have bearing on both the surface properties of metal deposits and on the development of high-resolution replication techniques.
Negative Glow Plasma as a Cathode for Electron Tubes
Authors: Anderson J. M. , Harris L. A.
Published: April 2005

The plasmas of the negative glow region of a cold-cathode discharge in helium and neon are examined for their ability to supply free electrons for operation of a ``vacuum'' amplifier tube. The plasma replaces the conventional oxide-coated hot cathode in a tube with closely-spaced fine-mesh grids. At gas pressures ∼1-mm Hg the volt-ampere characteristics of the amplifier portion of the total discharge tube are essentially the same as found in the high-vacuum, hot-cathode counterpart.

The noise content of the plate current of the ``glow-cathode'' tube, defined by equivalent noise-diode current, was examined from 50 kc to 50 Mc. At the lower frequency this equivalent current is ∼10 times the actual plate current flowing. At frequencies approaching 50 Mc the equivalent current drops to a factor ∼0.5 and may be considerably lower for unexamined frequencies above 50 Mc.
Permanent Magnets Obtained by Drawing Compacts of Parallel Iron Wires
Authors: Levi F. P.
Published: April 2005

A method of producing permanent magnets, which is believed to be novel, is briefly described. The method consists of drawing a compact containing parallel iron wires spaced by a copper alloy matrix until the iron wires become extremely small.

Intrinsic coercive forces of 400 oe have been measured in samples drawn from compacts in which the initial spacing between the iron wires corresponded to an iron packing fraction p of about 0.45. Annealing of cold-drawn samples generally increased both the coercive force and the squareness of the demagnetizing curve.
Simple Theory Concerning the Reflection of Electrons from Solids
Authors: Everhart T. E.
Published: April 2005

A simple theory concerning the reflection of electrons from solid targets is derived, based on the following assumptions: (1) the primary cause of electron reflection from a solid material is Rutherford scattering through angles greater than 90°; (2) the energy loss of electrons penetrating a solid target is given by the Thomson-Whiddington law, or a modified version of it; (3) no multiple scattering is allowed. An expression for the reflection coefficient r is derived that agrees surprisingly well with experimental data, in view of the above simplifying assumptions. In particular, the correct variation of r with atomic number Z is obtained, and the observed value of the fractional escape energy is calculated in the limit as Z → 0, where the theory is most accurate. A critical discussion of the simplifying assumptions is given, and the range of validity of the theory is estimated. This theory leads to a better understanding of the related phenomena of secondary emission at primary electron energies between 2 and 50 kev.
Spreading Resistance in Cylindrical Semiconductor Devices
Authors: Kennedy David P.
Published: April 2005

For cylindrical semiconductor components, computation of spreading resistance is considered a boundary value problem of the solid circular cylinder. Solutions of this problem may be used, for example, to characterize the thermal spreading resistance within the package of a semiconductor device, the electrical spreading resistance in a mesa type parametric diode, and the extrinsic collector resistance of a mesa transistor. Equations describing the thermal (or electrical) spreading resistance are presented in graphical form for a range of geometrical parameters applicable to many practical situations. Further, examples are given for the potential distribution within each cylindrical structure considered in this analysis.
The Oscillistor—New Type of Semiconductor Oscillator
Authors: Larrabee R. D. , Steele M. C.
Published: April 2005

A new magneto-oscillatory effect has been observed in the electron-hole plasma within a semiconductor. The plasma can be produced by such agents as contact injection and optical or thermal excitation of minority carriers. When the semiconductor specimen is subjected to an electric field (through suitable contacts) and a magnetic field, current oscillations can be detected across a series load resistance. This device has been termed the oscillistor to suggest a semiconductor oscillator. The experiments suggest that the oscillistor mechanism involves a magnetically induced interaction of the bulk plasma of electrons and holes with the exposed free surface areas of the specimen.
Large Temperature Range Annealing
Authors: Primak William
Published: April 2005

Vand's analysis of distributions in activation energy is reexamined through a new derivation which leads to a better approximation to the activation energy spectrum and which permits a treatment of step annealing data. The cases of distributions in frequency factor and the twofold distributions in activation energy and frequency factor are also treated.
Elastic Constants of Bismuth
Authors: Eckstein Yakov , Lawson A. W. , Reneker Darrell H.
Published: April 2005

The six adiabatic elastic stiffness constants of bismuth have been determined at 301°K by an ultrasonic pulse echo technique. The results are: c11 = 63.5, c33 = 38.1, c44 = 11.30, c66 = 19.4, c14 = +7.23, and c13 = 24.5, all in units of 1010 d/cm2. These values were redundantly determined by the measurement of 14 different velocities in four different single crystals of zone-purified bismuth. The velocities are believed accurate to better than 1%, the principal error arising from the uncertainty of the transducer transit time correction. The moduli are in poor agreement with the previously determined static elastic compliance constants reported by Bridgman. Some data on the velocity of sound in bismuth at 98° and at 4.2°K are also presented.
Dislocations in Indented Magnesium Oxide Crystals
Authors: Keh A. S.
Published: April 2005

Dislocation rosette patterns produced by spherical and pyramidal indentors on the cleaved surfaces of magnesium oxide crystals were studied in detail. The three-dimensional arrangement of dislocation loops as deduced from the two-dimensional etching patterns is discussed. Cracks formed on {110}90 planes around pyramidal indentations are believed to be due to the interaction of dislocations on {110}45 planes. The temperature dependence of hardness was found to be related to the widening of dislocation bands, rather than to the distance of travel of leading dislocations. Some observations were also made on the pinning of dislocations and recovery at elevated temperatures, and on the interaction of dislocations with grown-in subboundaries.
Temperature Dependence of the Velocity of Sidewise 180° Domain-Wall Motion in BaTiO3
Authors: Savage A. , Miller R. C.
Published: April 2005

The velocity of the sidewise 180° domain-wall motion in single-crystal BaTiO3 has been measured over a temperature range from 25° to 100°C as a function of the applied electric field. The velocity, described by v = v∞ exp(−δ/E), where δ is the activation field, E the applied electric field, and v∞ the extrapolated wall velocity for E = ∞, increases by about four orders of magnitude with this increase in temperature. It was found that the temperature dependence of v lies primarily in δ and not in v∞. The magnitude of δ decreases with increasing temperature and is also dependent on the impurity concentration in the crystal as well as the crystal thickness. The effects of impurities are most pronounced at room temperature, where (1/δ) (dδ/dT) is 1% °C−1 for undoped samples and 2% °C−1 for Fe doped samples. Though δ itself is very sensitive to the sample thickness, (1/δ) (dδ/dT) does not appear to depend on the crystal thickness. Additional data are required before a critical comparison can be made between experiment and theory.
Circuit Dynamics of the Pinch
Authors: Killeen J. , Lippmann B. A.
Published: April 2005

Instead of analyzing a portion of an hydromagnetic pinch apparatus in detail, and replacing the remainder by a boundary condition, the entire pinch apparatus is treated here as a single dynamical system. A circuit equation and a mechanical equation, coupled together, result. These equations describe the dynamical development of the pinch and exhibit explicity its dependence on the physical parameters (electrical and mechanical) of the system. As examples, the equations have been used to analyze the snow-plow model and the adiabatic pinch, yielding curves that show the geometrical development of the pinch in time, as well as the distribution of mechanical and magnetic energies at any stage. Analogous analyses may be made for other physical quantities of interest, and can be used to adjust the parameters of the system so as to optimize specific pinch characteristics.
Irradiation Effects and Short-Range Order in Fused Silica and Quartz
Authors: Weeks R. A. , Nelson C. M.
Published: April 2005

The eigenvalues of the g tensor of an irradiation produced defect of the quartz structure have been found to be g1 = 2.0003, g2 = 2.0006, g3 = 2.0018. The data on the center are consistent with the assignment of S = ½. Assuming that the hyperfine interaction with Si29 (I = ½ and 4.7% abundant) is negligible, the envelope of the line is calculated for 4 widths of the line. Good agreement is found between the calculated envelope for a width of 0.2 oe and the envelope observed in γ-ray and in neutron-irradiated (≤1018 fast neutrons/cm2) silica. The observed envelope deviates from the calculated envelope for increasing neutron irradiation. It is suggested that a correlation of the Si-O tetrahedra, similar to α-quartz, exists around any point in the more common forms of silicas and has a diameter of ≥5 A.
Chromium-Doped Titania as a Maser Material
Authors: Gerritsen H. J. , Harrison S. E. , Lewis H. R.
Published: April 2005

A discussion of the paramagnetic properties of Cr3+ in TiO2 is given with particular reference to its use in solid-state masers. Energy level diagrams are included for magnetic fields in the (110), (1l̄0), (001), and (100) planes.
Apparatus for the Measurement of the Thermal Diffusivity of Solids at High Temperatures
Authors: Abeles B. , Cody G. D. , Beers D. S.
Published: April 2005

An apparatus is described for measuring the thermal diffusivity of solids in the temperature range 30°–1000°C. It employs a method in which the dispersion and the attenuation of a thermal wave, propagated through the solid, are measured. The theory underlying this method is presented, and results are given of measurements on Armco iron and germanium.
Scattering of Electromagnetic Waves from an Infinitely Long Magnetized Cylindrical Plasma
Authors: Platzman P. M. , Ozaki H. T.
Published: April 2005

The magnetically contained plasma is characterized, in an average way, in terms of its macroscopic dielectric tensor. The problem of the scattering of plane electromagnetic waves from a uniform cylindrically symmetric plasma configuration is solved analytically. Numerical results for the uniform case are obtained and graphed for interesting ranges of the parameters involved. Possible applications of the results for use in investigating the plasma's properties are discussed.
Effect of Orientation on Strength of a Model Solid
Authors: Robinson A. , Osborn J. E. , Hsiao C. C.
Published: April 2005

A mathematical analysis is given to describe the effect of orientation on the variation of the mechanical strength of a model solid. For the simple state of uniaxial orientation the fracture strength in the direction of orientation is evaluated as a function of the degree of orientation in terms of the orientation strain and the strength of the unoriented solid. Assuming the fracture strain remains constant, the maximum fracture strength obtainable for a perfectly oriented solid is found to be six times that of the solid without preferred orientation.
Magnetostatic Modes in Disks and Rods
Authors: Dillon J. F.
Published: April 2005

Ferrimagnetic-resonance experiments have been performed using disk- and rod-shaped samples cut from single crystals of a manganese ferrite and of yttrium iron garnet. A multiplicity of absorption maxima were observed which can be identified as magnetostatic modes. The excitation of different sets of modes by rf magnetic field configurations of varying symmetries aids in assigning indices to the modes observed. By far the narrowest lines were observed in thin disks with the steady field normal to the plane of the disk.
Dielectric Properties of Lead Titanate Zirconate Ceramics at Very Low Frequencies
Authors: Gerson Robert
Published: April 2005

Dielectric properties of lead titanate zirconate were determined between room temperature and 140°C at frequencies between 0.1 and 10 cps. A measured increase in dielectric constant and dissipation factor at low frequency and high temperature was interpreted as an anomalous conduction phenomenon, rather than as an effect due to ferroelectric polarization. Over the frequency and temperature range studied the relationship between the real and the imaginary components of the dielectric constant was found to be linear. The data for unpoled ceramic and for material which had been poled to a maximum in piezoelectric activity were quite similar.