bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the Temperature Variation of Noise in Diode and Transistor Structures
Authors: Lee C. A. , Kaminsky G.
Published: April 2005

Measurements of the white noise of transistors (principally, diffused-base structures) and diodes have been made at temperatures ranging from ∼77°K to 300°K for a range of about two decades in injection level, and from 10 kc to 10 Mc. Comparisons of the noise measurements with calculated levels are presented. The germanium transistors show a progressively increasing deviation from the theory as the temperature is decreased, and most of the silicon transistors exhibited excess white noise at room temperature and below.
Theory of Oscillation of a Viscoelastic Medium between Parallel Planes
Authors: Thurston George B.
Published: April 2005

A theoretical description of sinusoidal oscillation of an incompressible viscoelastic medium between fixed infinite parallel planes is presented. The mechanical properties of the viscoelastic medium under sinusoidal shear are expressed by a complex viscosity coefficient. The general equation for oscillatory motion of an incompressible viscoelastic medium is developed. The solution to this equation is obtained for rectilinear motion parallel to a pair of infinite planes. The equation for the velocity distribution between the planes is developed and several typical profiles are presented graphically. The equation for the acoustic impedance per unit area of plane is obtained. Functions from which the acoustic resistance and acoustic reactance may be determined are presented in graphical form for media which range from a perfect viscous fluid to a perfect elastic solid. The applicability of the theoretical results to oscillatory flow in rectangular tubes is discussed.
Studies of Cold Cathode Discharges in Magnetic Fields
Authors: Backus John
Published: April 2005

Some experimental studies of a cold cathode discharge in a strong magnetic field are described. Current densities of the order of half an ampere per square centimeter in various gases were used. For such a discharge, the current to the cathodes is about 75% ionic. Positive ions leaving the discharge by moving across the magnetic field were observed with a mass spectrometer and showed a temperature of about 1 v. Fast electrons from the cathode escape from the discharge across the magnetic field without losing the greater part of their energy. By considering the rate of ion production it is shown that the slow electrons in the discharge have a temperature less than about three volts. Fluctuations in charge densities must play a very important role in the mechanism of the discharge.
Thermoplastic Recording
Authors: Glenn W. E.
Published: April 2005

A new method is described for recording electrical signals. Information is written at extremely high density by means of an electron beam on a film consisting of a low melting thermoplastic material. This can be projected as a full color image, or can be converted to an electrical signal. The tape, which is processed by quick heating, can be readily erased and reused.
Low Friction of Metals in Reciprocating Sliding
Authors: Tamai Yasukatsu
Published: April 2005

A very low friction, about 10−2, has been unexpectedly observed in reciprocating sliding with gold, silver, copper, and platinum. It was found that the characteristics common to those metals were soft metal substrate and no surface oxide or soft oxide. Some discussion is given on this phenomenon.
Propagation Characteristics of Detonation-Generated Plasmas
Authors: Cook Melvin A. , Keyes Robert T. , Udy Lex L.
Published: April 2005

Studies are presented showing the electrical properties of the highly ionized, detonation-generated plasmas ejected into various gaseous media at the bare surfaces of high explosives. These external plasmas are shown to originate from chemionization in the reactions of high explosive at free surfaces and are not produced by thermal ionization in the shock wave propagated in the surrounding gaseous medium. The initial external-plasma length Lp* was found to be directly proportional to the length a0 of the reaction zone of the high explosive-generating source. Conduction measurements in plasmas propagating in chlorine, oxygen, argon, nitrogen, helium, and air showed that the electron affinity of the gaseous medium is important in determining the rate of decay of the plasma and its ultimate disintegration. The lifetime of external plasmas are substantial in media of low electron affinity, exceeding appreciably 250 μsec in such media as argon, helium, and nitrogen. Free electrons contribute practically the entire conductivity of these plasmas. Interesting pulsations occur when the external plasmas are generated by a charge of diameter smaller than the constraining tube and upon passing from a smaller into a larger constraining tube. A striking confirmation of the quasi-lattice or metallic-like model of plasmas is the observation that the plasma finally ``explodes'' into a gas cloud many times larger when its ion density decays to a critical low level.
Electrical Measurements on Photographic Emulsion Grains. II. Photoelectronic Carriers
Authors: Hamilton J. F. , Brady L. E.
Published: April 2005

Pulses of electric field applied to silver bromide grains of a photographic emulsion at short time intervals after the application of short light flashes cause displacement of photoelectrons and holes if their lifetimes are greater than the delay interval. The asymmetry in the location of the photoproducts—microscopically visible silver and bromine or developable latent-image specks—is an indication of the fraction of carriers free at the time the electric field is applied. As the delay interval is varied, the decay of the number of free carriers may be followed. In the emulsion system studied, the number of photoelectrons was found to decay approximately according to a 1/(1+αt) law, falling to half the initial value in 0.25 μsec. The lack of a dependence on intensity or temperature is taken to indicate temporary trapping in a distribution of shallow traps, perhaps at the grain surface. The number of free holes decays by an exponential law, with a mean lifetime of about 15 μsec. Indications are that hole mobility is very low, owing either to temporary trapping or self-trapping. The implications of these results in terms of modern theories of latent-image formation are discussed.
Transmission Electron Microscopy Studies of the Mechanism of Plastic Deformation
Authors: Berghezan Aurel , Fourdeux Angéline
Published: April 2005

Observation of the deformation of thin aluminum specimens inside the transmission electron microscope has revealed the intimate connection between deformation and the nucleation and motion of dislocations. Nucleation, slip propagation, and the progress of deformation to the point of rupture have been observed visually on the fluorescent screen and photographed by both ``still'' and motion pucture techniques. In this way even the detailed predictions of the dislocation theory of deformation have been confirmed, and the new phenomena of grain boundaries acting as ``donors'' or ``acceptors'' of dislocations have been discovered.
Effect of Impurity Scattering on the Figure of Merit of Thermoelectric Materials
Authors: Ure Roland W.
Published: April 2005

The thermoelectric figure of merit z=α2/ρκ is calculated for an extrinsic semiconductor with mixed acoustic-mode lattice scattering and ionized-impurity scattering. The result is compared to the value for pure acoustic-mode scattering. As the amount of ionized-impurity scattering is increased, the figure of merit increases by less than 10% and then falls slowly.
Effect of Internal Heating on the Breakdown Characteristics of Silicon p-n Junctions
Authors: Senitzky B. , Radin P. D.
Published: April 2005

The breakdown characteristics of two types of silicon p-n junctions are studied. In the first type of junction which is commonly encountered, the breakdown occurs in many localized regions, the characteristic being determined by the aggregate effect of the localized regions; in the second type of junction the geometry is such that only one localized breakdown region occurs. Whereas the simple avalanche theory can explain the onset of breakdown for both types of junctions, the shape of the V-I curve in the breakdown region cannot be explained without the inclusion of another variable in the theory. Experimental evidence obtained by the use of pulse techniques indicates that this variable is the temperature rise due to the current flowing through the junction. It is found that this self-heating is the most important single factor in determining the shape of the V-I curve and that almost the entire dynamic resistance in this region is due to this effect. A method is given for determining the temperature rise of the junctions, provided that the V-I characteristic is known.
Some Experiments on the Dynamics of Liquid Films
Authors: Ranz W. E.
Published: April 2005

Experiments and theory are described concerning the rupture of soap films and the continuous formation, by impinging jets, of quasi-stationary liquid sheets.
Effect of Fission Recoil Fragments on the Thermal Conductivity of Graphite
Authors: Hunter L. P.
Published: April 2005

The variation of the thermal conductivity of uranium-impregnated graphite is measured continuously while under neutron irradiation. The temperature is continuously monitored and results are reported which show the effects of the uranium oxide particle size as well as the effect of the neutron bombardment as separated from the fission recoil bombardment.
Heat Treatment Centers and Bulk Currents in Silicon p-n Junctions
Authors: Sandiford D. J.
Published: April 2005

A set of small-area, alloy, p-n junction diodes was made from a slice of heat-treated n-type silicon. The carrier lifetimes of the diodes were found to be in the range of 2.5×10−8 sec to 3.5×10−6 sec. Measurements were made of the lifetime and of the current-voltage characteristics in the forward and reverse directions as a function of temperature from room temperature to 165°C. An analysis of the results and, in particular, the correlation of current flow with lifetime values, showed that for the diodes with the shortest lifetimes, centers situated 0.48 ev at 0°K from either the conduction or valence bands were responsible for large space-charge currents. For the diodes with lifetimes in the microsecond range, surface leakage currents were predominant. Evidence was found of a field-dependent emission probability, β, for these centers. The results showed that β∼E0.35 when E, the electric field, is in the range of 2×104 to 8×104 v/cm.
Studies of Vacancies in Dislocation-Free Ge Crystals
Authors: Tweet A. G.
Published: April 2005

Dislocation-free Ge crystals of 50 g weight have been grown from the melt by the Dash technique. We have diffused Cu into slabs of these crystals for 0.5 to 2 hr at 700–850°C. Acceptors with an ionization energy indistinguishable from that of the lowest substitutional Cu level were observed. Their concentration ranged from ∼0.5×1015/cm3 for samples taken from the tops of crystals to ∼3×1015/cm3 for samples from near the bottom. Insufficient time was available for the dissociative diffusion of substitutional Cu into the interior from the surface to account for the observed acceptor concentrations. The data may, however, be interpreted as indicating that vacancies trapped into the crystal during normal growth combine with rapidly diffusing interstitial Cu atoms to make substitutional Cu atoms. According to this interpretation, the data show that the concentration of vacancies trapped into the bottom of a dislocation-free Ge crystal is larger than at the top, presumably as a consequence of the heat treatment the crystal receives during normal growth. The vacancy concentration at the melting point is 2.9–3.9×1015/cm3, on this model. Methods of altering the vacancy content of the crystals by further heat treatment are discussed. Some experimental details of Cu diffusion into dislocation-free Ge are given in an Appendix.
Dislocation Velocities, Dislocation Densities, and Plastic Flow in Lithium Fluoride Crystals
Authors: Johnston W. G. , Gilman J. J.
Published: April 2005

Velocities of individual dislocations have been measured in LiF, covering a range of twelve orders of magnitude in velocity, from 10−7 cm/sec to 105 cm/sec. The velocity is extremely sensitive to applied stress at low velocities, and for each crystal there exists a minimum stress for dislocation motion, below which dislocations do not move. The edge components of dislocation loops move considerably faster than the screw components. The upper limit for dislocation velocity appears to be the velocity of sound in the crystal. The effects of temperature, impurities, and radiation damage on dislocation velocity are described. These variables affect the dynamic resistance to motion encountered by a moving glide dislocation.

The growth of total dislocation density, the growth of individual glide bands, and the distribution of glide dislocations during plastic deformation are described.

The yield stress of LiF is determined by the resistance to motion encountered by a glide dislocation in moving through an otherwise dislocation-free region of the crystal. The yield stress is independent of the dislocations present in an undeformed crystal, and the state of pinning and geometrical arrangement of such dislocations do not affect the yield stress.

Stress-strain curves have been calculated from the data on dislocation mobility and dislocation density, and the calculated and measured curves are compared. At low strains the flow stress can be predicted from measured dislocation properties.
High-Temperature Properties of Graphite. II. Creep in Tension
Authors: Wagner Paul , Driesner Allen R. , Haskin Larry A.
Published: April 2005

Measurements have been made on the steady-state creep rates of graphite in tension in the temperature range 2270 to 3270°K. Molded, extruded, and uranium ``loaded'' graphites were used in the course of investigation. The general characteristics of creep in graphite at high temperatures have been described in the literature and the results presented here covering the range of steady-state creep 10−7 to 10−4 cm/cm-sec are in accord with published results. In addition, the tensile steady-state creep data are correlated by a classical rate equation of the form, rate=f(U)(σ/σB)n exp(−E/RT), where f(U) is a function of the uranium concentration in the graphite.
High-Voltage Photovoltaic Effect
Authors: Goldstein B. , Pensak L.
Published: April 2005

Vacuum evaporated films of cadium telluride have been prepared that show photovoltages as high as 100 v/cm of film length. An oblique angle of deposition of the vapor onto the substrate is required. The photovoltage saturates at high light intensities and low temperatures. At all other light intensities and temperatures it has the same functional dependence on light intensity as that of ordinary p-n junctions. The short-circuit current varies linearly with light intensity at all temperatures and is only weakly temperature-dependent. Analysis of the data suggests a series of p-n junctions (or other photovoltaic elements) arrayed in an additive manner. Estimates of the linear density of photovoltaic elements based on the measurements described above vary from ∼200/cm at room temperature to ∼7000/cm at −170°C. A possible mechanism to explain the effect is proposed, based on an anisotropic growth of crystallites due to the angle of deposition, and on the presence of residual gases in the vacuum chamber.
Domain Behavior in Some Transparent Magnetic Oxides
Authors: Sherwood R. C. , Remeika J. P. , Williams H. J.
Published: April 2005

Magnetic domains were observed by means of the Faraday effect, and by the Bitter technique in a number of compounds having the spinel, magnetoplumbite, and perovskite-like structures. The latter compounds are orthorhombic and have the general formula MFeO3 where M is Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. Domain boundaries in these compounds move for fields less than one oersted, and after saturation, crystals as large as (∼0.2×0.2×0.1 in.) remain single domains. Fields of 2500 oersteds are required to reverse the magnetization in the single domain crystals. Reversal occurs by nucleation and growth of a reverse domain. This is evident from the unusual torque curves. The fact that domain walls occur and move in such weak fields in these compounds indicate that the slight or parasitic magnetization is a uniform body property of the crystals. The parasitic magnetization of these compounds was determined from torque measurements. These crystals are well suited for light modulators because a uniaxial anisotropy holds the magnetization vectors normal to the large surfaces of thin flat crystals and weak fields produce changes in magnetization. Absorption coefficients were measured for some compounds for radiation having wavelengths from 0.6 μ to 13 μ. Thin sections were found to be transparent to light at the red end of the visible spectrum. The Faraday rotation was measured for Li0.5Fe2.5O4, MgFe2O4, YFeO3, and PbFe11Al1O19.
Investigation of an Alloy Surface with the Field Emission Microscope
Authors: Bradley R. C. , D'Asaro L. A.
Published: April 2005

The field emission microscope has been used to investigate the surface of an alloy of a few percent zirconium in molybdenum. The field emission patterns indicate that a high-temperature flash (2000°K) reduces the surface concentration of zirconium to zero. Subsequent heat treatment at 1000°K brings Zr to the emitting surface where it adsorbs preferentially in small clusters on the lattice steps of the {100} planes. These clusters are easily observed because of their high electron emission. Their emission characteristics reveal them to be smooth layers of low work function (2.94±0.01 ev) rather than protruding crystallites. When the bulk concentration of zirconium in the alloy is increased from 1% to 5% the emission patterns change markedly but there is little effect on the adsorption characteristics of the surface. Surface migration, desorption, and bulk diffusion of zirconium were found to proceed rapidly at temperatures above 1200°K, 1500°K, and 2000°K, respectively. Measurements of activation energies for surface migration and desorption gave 2.7±0.3 ev and 4.15±0.15 ev, respectively.
Impurity Bands and Electroluminescence in SiC p-n Junctions
Authors: Patrick Lyle , Choyke W. J.
Published: April 2005

A study of the electroluminescence of certain SiC p-n junctions, between 77°K and 830°K, and over a range of 104 in current density, has been used to verify and to extend a 3-part model (P−N*−N) of the junctions derived from electrical measurements. The electroluminescence, due to recombination in N*, consists of two parts, which may be called impurity luminescence and intrinsic recombination radiation. At low temperatures (≥200°K) only the former is present. Several effects of impurity banding on the electroluminescence can be predicted, and some of these have now been observed. The most striking of these effects is the ``Fermi-level emission edge'' in the low-temperature spectra, an edge which moves to higher energies with increasing current density because of the impurity band injection of electrons. The predominance of impurity band injection at low temperatures excludes the possibility of intrinsic recombination radiation. At higher temperatures, however, electron injection is by way of the conduction band. The intrinsic recombination radiation observed at higher temperatures has been compared with that calculated from our earlier absorption data, using the theory of van Roosbroeck and Shockley. From the comparison we obtain the density of electrons in the conduction band, and the electron lifetime (10−8 sec) at room temperature. This lifetime is very short compared with the measured hole lifetime, and is possibly a result of the merging of impurity band and conduction band levels. Our junction model is now detailed enough to estimate impurity level densities and the hole and electron densities. From these, we are able to calculate cross sections for the various recombination processes involved. All luminescent processes have been found to have a recombination cross section of approximately 10−23 cm2.
Effect of Space Charge Fields on Polarization Reversal and the Generation of Barkhausen Pulses in Barium Titanate
Authors: Chynoweth A. G.
Published: April 2005

The rate of generation of Barkhausen pulses in barium titanate when the polarization direction is slowly reversed is profoundly influenced by the form of the voltage cycling given to the crystal. It is concluded that the rate of nucleation of new domains is determined by the field near the electrodes which, in turn, is the resultant of the applied field and a relaxing space charge field. This result follows directly if the Barkhausen pulses represent individual nucleations though this assumption is not crucial since the generation rate of the pulses parallels the total current at all stages of the polarization reversal. It is concluded also that the majority of the Barkhausen pulses occur independently of each other and of their surroundings.
Temperature Coefficients of Resistance of Metallic Films in the Temperature Range 25° to 600°C
Authors: Belser Richard B. , Hicklin Walter H.
Published: April 2005

The temperature coefficients of resistance (TCR) of films of sputtered Au, Ir, Mo, Ni, Pd, Pt, Rh, Ta, and W, of evaporated Al, Cr, Ti, and Zr, and of the alloy films Pt–Au, Pt–Ir, and Pt–Ni have been measured in vacuo over the temperature range 25° to 600°C; the film thickness range was 75 to 2000 A. The TCR values of films of the substantially pure metals were in the range ⅓ to ⅔ those of the respective bulk metals whether deposited on glass, Vycor, or Stupalith substrates. The departure of the conditions of growth of the film from those usual for the bulk metal, i.e., rapid cooling effects and impurities present, contributed imperfections which reduced the TCR of the film. The TCR values of alloy films were low, 0.0004 per °C for Au–Pt, and resistivities were 3 to 4 times that of either constituent. The TCR values of sputtered films of Mo, W, and Ta and of evaporated Cr, Zr, and Ti were generally less than 0.0001 per °C. Electron diffraction examination of films of these latter metals revealed oxide inclusions in the films. The presence of the oxide of the metal reduced the TCR and increased the R/sq of the film as compared to those of the pure metal. Only films of gold, platinum, and iridium were corrosion resistant in air near 600°C. Overcoats of evaporated SiO provided partial protection for the others. Powers up to 15 watts were dissipated by refractory metal films only132 by ½ in. and about 750 A thick. These high values contrasted with less than ¼ w for a gold film of similar dimensions.
Density Change in Silicon upon Melting
Authors: Logan R. A. , Bond W. L.
Published: April 2005

The density of both solid and liquid silicon has been measured in the vicinity of its melting point. From the average of several determinations, the increase in density upon melting is 9±1%.
Model Wave Function Study of Negative Ion Photodetachment in Oxygen
Authors: Brehm J. J.
Published: April 2005

The total cross section for O− photodetachment is computed using an analytical model to give agreement with the data obtained by Branscomb, Smith, and Burch. For the calculation of the electric dipole matrix element single-electron wave functions are constructed for the initial and final states which reflect the short range of the interaction between the neutral atom and the extra electron. These are written in terms of two parameters which are determined in order to fit the experimental data. The bound state parameter β gives an indication of the weak binding of the system and also gives a measure of the ``size'' of the ion. The continuum state parameter, the s-wave phase shift δ, gives the total cross section for the low energy elastic scattering of electrons by O atoms.
Pressure Dependence of the Viscoelastic Behavior of Polyisobutylene
Authors: Singh Harkrishan , Nolle A. W.
Published: April 2005

The absorption of 4 mc/sec ultrasonic waves in polyisobutylene is measured as a function of temperature, for various pressures. The extreme limits of these variables are 1 to 1400 atmos and −20°C to 80°C, respectively. Approximate measurements of propagation velocity are also obtained. Pulse reflection apparatus is used. A magnetically actuated holder places the sample in the signal path or removes it. Pressure-volume data are obtained for polyisobutylene at 30°C by means of a capillary dilatometer fitted with electrical contacts, in which the sample is placed with mercury. The expected behavior of viscoelastic relaxation times with temperature and pressure is computed by adapting a theory due to Bueche. With additional assumptions concerning the compressibility, the theory gives a shift of the constant-frequency absorption maximum of 0.025 C°/atmos, in approximate agreement with experiment.
Azimuthal Electron Flow in a Spherical Diode
Authors: Waters William E.
Published: April 2005

Solutions of Poisson's equation for a space-charge-limited spherical diode, in which electron trajectories are great circles rather than radial lines, are developed. It is shown how Poisson's equation may be separated to yield ordinary differential equations. The radial equation is solved analytically, whereas accurate numerical solutions of the azimuthal equation are given. A method of truncating the flow so as to produce a ``bowl-shaped'' electron gun, leading eventually to an annular electron beam, is presented, along with power-series solutions of Laplace's equation both inside and outside the region of the flow. The latter series are useful for calculating the shapes of anodes and focusing electrodes.
Effect of Oxide Impurities on the Thermoelectric Powers and Electrical Resistivities of Bismuth, Antimony, Tellurium, and Bismuth-Tellurium Alloys
Authors: Horne R. A.
Published: April 2005

The thermoelectric powers of bismuth and antimony are only slightly altered by the presence of Bi2O3 and Sb2O3, respectively, and the electrical resistivities are increased. The thermoelectric power of tellurium, however, is extremely sensitive to TeO2 imputities. Bismuth-tellurium alloys show greatest sensitivity to oxide impurities when their composition is in the range corresponding to Bi2Te3. The thermoelectric powers of these materials depend in detail on the manner in which the thermal gradient is applied during measurement.
Thermionic Diode as a Heat-to-Electrical-Power Transducer
Authors: Nottingham W. B.
Published: April 2005

The high-vacuum thermionic diode is shown to be capable of converting heat to electric power. For this purpose, a low work-function collector, a small spacing, and sufficient temperature difference between the emitter and the collector are necessary. A detailed understanding of both thermionic emission and space-charge phenomena are needed for evaluating the effectiveness of this transducer. With VR defined as the critical bias potential that gives zero potential gradient at the collector, the maximum available power is given by the relation 3.7×10−6 VT½(VR2/w2) watts/m2. Here, VT is the voltage equivalent of the temperature T/11 600. In the range of emitter temperature from 1200°K to 1700°K, the most optimistic conversion efficiency lies between 3 and 4% for a diode of 0.001-inch spacing. With a suitable choice of emitter inhomogeneity, the introduction of cesium vapor should improve the efficiency of this device.
Measurement of Dislocation Densities by the Lambot Method
Authors: Vassamillet L. F. , Smoluchowski R.
Published: April 2005

The applicability of the Lambot x-ray technique to dislocation density measurements is considered using several sample models of the dislocation array. The expression relating dislocation density of a random array to the angular misorientation of a particular set of lattice planes is derived. The dependence of broadening on the size of the diffracting area is found to satisfy this expression in the case of plastically deformed KCl. Limitations on the use of the method are discussed.
Small-Angle Scattering of X-Rays and Neutrons from Deformed Metals
Authors: Atkinson H. H.
Published: April 2005

X-rays or thermal neutrons may be scattered at small angles from deformed metals due both to ``true'' small-angle scattering and to double Bragg reflections. These two effects are discussed theoretically and compared to see how one may be distinguished from the other in the results of experimental observations. Experiments are described on the small-angle scattering of x-rays from polycrystalline copper and single grains of aluminum deformed by cold-work or fatigued in pulsating tension. The results show in a direct and conclusive way that almost all of the scattering is due to double Bragg reflections. No surface scattering has been observed. Double Bragg reflections have been eliminated in experiments on the small-angle scattering of cold neutrons from cold-worked and fatigued copper and aluminum. The results, which indicate the magnitude of the ``true'' scattering, are consistent with scattering from dislocations. Hence there is no direct evidence of the existence of cavities in cold-worked or fatigued metals as the result of small-angle scattering experiments with either x-rays or neutrons.
Study of X-Ray Scattering from Fatigued Metals
Authors: Thomas K. , Franks A.
Published: April 2005

Various explanations have been put forward to account for the low angle x-ray scattering from cold worked metals. The experimental results obtained by an examination of individual grains of polycrystalline fatigue specimens indicate that double Bragg reflection plays an important role in this phenomenon. The fatigue process resulted in the formation of subgrains, the misorientations within a grain amounting to 15°.
Experiments on Double Bragg Reflections in Deformed and Undeformed Metal Foils
Authors: Fricke H. , Gerold V.
Published: April 2005

Observations of x-ray scattering from deformed and undeformed metal foils using an evacuated film chamber give evidence of double Bragg reflections. Experiments have been done on single crystals and polycrystalline foils of aluminum and copper and also on an annealed powder sample of copper. The scattering was measured in the angular range from 1° to 50° and agrees very well with theoretical considerations of expected double reflection effects in different states of deformation. Diffraction by lattice defects in the deformed state cannot be observed because its intensity is too small in comparison to that of double reflections.
Small Angle X-Ray Scattering from Copper and Aluminum under Cyclic Stress
Authors: Grosskreutz J. C. , Rollins F. R.
Published: April 2005

Copper and aluminum samples were subjected to cyclic stress and run to fatigue while being held in an x-ray beam. Small angle scattering intensities were recorded at various stages of the fatigue life. These intensities were found to increase with the number of elapsed stress cycles.

The observed angular dependence and intensity of the scattered radiation agrees most nearly with a double Bragg scattering mechanism. The relation of the fatigue mechanism to the formation of small angle subgrain boundaries responsible for the double Bragg scattering is not clear-cut. However, the evidence favors the view that the formation of subgrains, while probably necessary to the propagation of the fatigue crack, is not sufficient either for its formation or propagation. Complete annealing of the scattering was not possible, indicating that recrystallization does not take place following cyclic stress of the order of one-fourth the yield stress. No evidence exists for a widespread formation of voids in the fatigued specimen.
Some Surface Properties of Silicon-Carbide Crystals
Authors: Dillon J. A. , Schlier R. E. , Farnsworth H. E.
Published: April 2005

The work functions of a number of commercial-grade silicon-carbide single crystals have been obtained in high vacuum (p<10−9 mm Hg). Low-energy electron-diffraction studies have also been made for one of these samples. Surfaces cleaned by argon-ion bombardment and annealing appeared to contain an excess of carbon. Heating for long periods of time at 1000°C also appeared to produce surfaces which were nonstoichiometric. Oxygen was adsorbed at room temperature on the ion-bombardment cleaned surfaces with a sticking coefficient of the order of 0.01. Differences in adsorption properties were noted which were probably associated with asymmetry in atomic species on different crystal faces. Work-function values on opposite faces of any crystal were the same. Hydrogen exposure resulted in work-function decreases only in the presence of a heated filament. Under similar conditions of ion bombardment and high-temperature heating, the SiC surfaces appeared to be more stable than those of silicon crystals.
Concerning the Design of an Effective Shaped Charge for Oil Well Perforating
Authors: Rinehart John S. , Cocanower R. D.
Published: April 2005

Current shape charge theory and experiment do not provide the requisite basis for the development of a slug-free charge suitable for oil well perforation. Considerations and experiments are discussed which have led to the design of a new type charge. Basically the charge has a thicker than conventional liner containing a low melting point metal which melts during collapse, forming a liquid slug which is dispersed.
Penetration of Transient Electromagnetic Fields into a Conductor
Authors: Grumet Alex
Published: April 2005

The case of a uniform electric field, infinite in extent, abruptly applied to the plane face of a semi-infinite conductor is considered. The amplitude of the field as a function of distance into the conductor and of time is then determined for different conductivities. The time element and distance for ignoring the displacement current term in Maxwell's equations is determined. Finally the time and space nature of the applied electric field at distances far removed from the semi-infinite conductor is considered.
Form Effect in Linear Magnetostriction
Authors: Stauss H. E.
Published: April 2005

The influence of the shape of the specimen upon the measured value of magnetostriction is a matter of importance. The classical thermodynamical calculation of Becker applies to specimens in like magnetic fields and consequently compares bodies with unlike intensities of magnetization. In the present paper use is made of the principle of virtual work to make a calculation of the form effect as dependent upon the intensity of magnetization. The form effect for an ellipsoid in an extended uniform field is found to be a constrictive strain of the magnitude ΔA11=−(1−2μ)ENI22, where ΔA11 is the form effect in strain, μ is Poisson's ratio, E is Young's modulus, N is the coefficient of self-demagnetization, and I the intensity of magnetization. Above saturation the form effect is ΔA11=−(1−2μ)ENIs22, where Is is the saturation value of I.

The meaning of the term form effect has been expanded to include not only the change in strain in the specimen resulting from the shape of the specimen itself, but also the change resulting from the position of the specimen relative to the magnetizing apparatus. A calculation of the form effect in this extended sense is made for two useful experimental arrangements; one where a specimen is sandwiched between two movable rods and the other where the specimen is situated in the fixed gap of a magnet. For the first case it is found that the form effect depends upon the self-demagnetization of the entire ferromagnetic arrangement and not of the specimen itself. In the second case, the form effect is dependent upon the ratio of gap energy to the volume of the ferromagnetic system and can be small, subject to the qualification that the form effect does not include the effects of any stresses that develop within the gap.
Small-Aperture Diaphragms in Ion-Accelerator Tubes
Authors: Cranberg L. , Henshall J. B.
Published: April 2005

An investigation has been made to determine the conditions under which the voltage sustained by a 2-ft length of ion-accelerator tube may be made proportional to the length of the tube. It has been found that such linearity may be obtained if the tube is segmented at 4½-in. intervals by diaphragms which are so arranged that no straight path is possible from one end of the tube to the other. No significant deterioration in performance of the tube was observed when axial holes were made in each diaphragm up to ¾ in. in diameter. The voltage gradient realized on these tests was 60 kv/cm.
New Hollow Cathode Glow Discharge
Authors: White A. D.
Published: April 2005

An experimental study has been made of the properties and characteristics of a glow discharge to a nearly spherical hollow cathode. Current densities in excess of 0.5 amp/cm2 can be drawn from the cathode with negligible deterioration from sputtering. In neon, the discharge exhibits a stable and reproducible negative volt-ampere characteristic at currents of a few milliamperes. At these currents, probe measurements indicate the plasma in the hollow contains ∼1-v electrons in concentrations greater than 1013/cm3.
Time Dependence of Mechanical Breakdown in Bundles of Fibers. V. Fibers of Class A-2
Authors: Coleman Bernard D.
Published: April 2005

The theory of mechanical breakdown in bundles of Class A-2 fibers, whose strength depends on the speed of measurement, is used to find the conditions under which time-dependence effects can be neglected in calculations of relationships between the strength of bundles and the strength of their constituent filaments. (The classical theories of the strength of bundles do not consider time dependence.) Tables and graphs are presented which give the ratio, εA, of the strength of an infinite ideal bundle to the mean strength of its filaments as a function of the coefficient of variation, σ1/E1{f*}, in the strength of the filaments. It is shown that, under certain limiting conditions, εA for an infinite bundle of Class A-2 fibers is the same as it would be for an infinite bundle of classical fibers with an equal value of σ1/E1{f*}, and a numerical investigation is made of the rapidity with which this limiting behavior is approached.
On the Kinetics of Quenched-in Lattice Vacancies in Platinum
Authors: Bacchella G. L. , Germagnoli E. , Granata S.
Published: April 2005

From quenching experiments the activation energy for vacancy formation in high purity platinum is found to be 1.20±0.04 ev. Annealing behavior after quenching is studied. First-order annealing is found when the concentration of quenched-in defects is low; the migration energy turns out to be 1.48±0.08 ev. The annealing kinetics are not simple if the quenching temperature is high and the concentration of defects at least 10−4.
Initiation of Detonations
Authors: Hubbard Harmon W. , Johnson M. H.
Published: April 2005

In order to study the initiation of detonation waves, the time dependent one-dimensional hydrodynamic equations have been numerically integrated for several initial conditions. In all the cases treated, the hydrodynamic motion and the release of chemical energy are practically independent as a consequence of the extreme temperature sensitivity of the reaction rate. At first the chemical energy is released so slowly that it has no effect on the hydrodynamic motion. Thereafter the reaction proceeds so rapidly that the burning is not influenced by the hydrodynamic motion. A simple criterion is established to determine whether or not detonation will result from given initial conditions of pressure and temperature. This criterion is applied to determine how the detonability depends upon the duration of the initial pressure pulse and upon the initial temperature distribution.
Asymmetric Hysteresis Loops and the Pyroelectric Effect in Barium Titanate
Authors: Miller Robert C. , Savage Albert
Published: April 2005

Dynamic pyroelectric techniques have been used to study single crystal BaTiO3 hysteresis loops which have been reported in several recent investigations to be asymmetric with respect to both the polarization and electric field axes. It is shown that an apparent polarization bias occurs because of electrode-edge effects and that this bias may be shifted with an appropriate application of a dc field which serves to alter the direction of the polarization in fringe regions which contribute to the observed pyroelectric signal. The pyroelectric hysteresis loops are symmetric with respect to the polarization when electrode-edge effects are eliminated. These data strongly suggest that asymmetric remanent polarizations reported in several piezoelectric and pyroelectric investigations may have been due to edge effects. The pyroelectric hysteresis loops are found to be biased with respect to the electric field axis in the same manner as that reported in a recent piezoelectric study. Small residual pyroelectric signals observed at temperatures above the Curie point of the bulk material do not result from fringe effects, and the earlier interpretation of the residual signals in terms of a polarized surface layer is consistent with the present results.
Temperature Dependence of Fractional Velocity Changes in a Silicon Single Crystal
Authors: Stein Frances , Einspruch Norman G. , Truell Rohn
Published: April 2005

An ultrasonic interferometer technique for measuring the temperature dependence of the relative change in elastic constants is described in detail. Results are reported for measurements carried out as a function of frequency from 10 mc/sec to 170 mc/sec, for compressional wave propagation along the [100] axis of silicon over a temperature range of −60° to +15°C.

The mean value of (1/c11)(dc11/dT) obtained is 55.59±0.81×10−6 (°C)−1, and no frequency dependence of (1/c11)(dc11/dT) was found.
Toroidal Electron Guns for Hollow Beams
Authors: Harris L. A.
Published: April 2005

A theory of convergent, high-efficiency electron guns for the production of dense hollow beams is presented. An approximate solution to Poisson's equation is obtained in a cylindrical coordinate system modified to account for the toroidal geometry. Experimental measurements on a series of toroidal guns tend to confirm the space-charge theory. They also show that the annular slit in the anode very seriously affects the uniformity of cathode emission and diverges the beam more than can be accounted for by present theories. These effects of the slit appear to confine the usefulness of these guns to high-power applications.
Flow of Liquid Hydrocarbons in Porous Vycor
Authors: Debye P. , Cleland Robert L.
Published: April 2005

Experimental investigation of the flow rates of normal paraffins in porous Vycor glass shows that there are deviations from the viscosity dependence required by Poiseuille's law. A discussion of the application of capillary models to describe flow in porous media in terms of the measured porosity and surface-to-volume ratio points out that such models are not generally applicable, though they give useful results for some purposes. An estimate of the permeability predicted by Poiseuille's law is made by an empirical method which uses gas flow measurements in the Knudsen flow region. The equations of slip flow as derived for gases do not explain the experimental deviations from Poiseuille flow. The concept of a slipping adsorbed layer of molecular thickness at the wall of a capillary is combined with the usual Poiseuille treatment for the interior to give a result which is compatible with experiment.
On the Determination of Preferred Orientations
Authors: Dunn C. G.
Published: April 2005

The orientations of individual grains in cold-rolled and annealed silicon-iron strip are obtained for a single-component texture and a multiple-component texture to determine (1) the preferred orientations in the two textures and (2) some information on the nature of formation of the textures. A set of three axis density figures and a (100) pole density figure are synthesized for the multicomponent texture. It is concluded from the figures that the axis density figures give more information about the components present in the texture than a (100) pole figure does. It is also concluded that oriented nucleation is important in the development of the textures.
Calculation of the Intensity of Small-Angle X-Ray Scattering at Relatively Large Scattering Angles
Authors: Schmidt Paul W. , Hight Robert
Published: April 2005

Since the small-angle x-ray scattering intensity can be expressed as a Fourier integral, the techniques of asymptotic expansion of Fourier integrals can be used to calculate the small-angle x-ray scattering at relatively large scattering angles. Some asymptotic expansion techniques which are often useful are described. The relation between the scattered intensity at relatively large angles and the characteristic function and its derivatives is discussed. The scattered intensity for both prolate and oblate ellipsoids of revolution is calculated to provide examples of asymptotic expansion methods, and the resulting expressions are evaluated numerically. The behavior of the scattered intensity at relatively large scattering angles for platelet particles of negligible thickness is described.
Measurement of the Angular Distribution of Electrons Ejected from Tungsten by Helium Ions
Authors: Abbott Robert C. , Berry H. W.
Published: April 2005

Rotating collector measurements, made at a pressure of 10−5 mm Hg, yielded cosine distributions for all experimental conditions. Data were obtained for gas-covered and partly gas-covered target surfaces, for several beam incidence angles, and for ion energies of 40, 400, and 825 ev. It is postulated that the identical cosine distributions observed for both kinetic and potential ejection are caused by the existence of isotropic angular distributions for both mechanisms within the metal. A general expression is given for the angular distribution of emission from an arbitrarily shaped surface. This expression is a function of the fundamental angular distribution associated with a single element of area on that surface and the orientation distribution of the elements of area.
Study of Oriented Polycrystalline Ferrites with Cubic Anisotropy
Authors: Kooi C. F. , Moss R. W. , Stinson D. C.
Published: April 2005

A study was made of crystallite orientation in cubic ferrites when pressed in a magnetic field. One easy axis orients in the field direction, the other easy axes lying at random in or near a perpendicular plane. Experimental torque curves have the theoretically predicted shape. The magnetic field required for microwave resonance is lower than in the same nonoriented ferrite if the axis of alignment and the field are parallel. This occurs because the anisotropy field Ha is no longer randomly oriented but helps to supply part of the resonant field requirement. Values of saturation magnetization (Ms), anisotropy energy (K), and resonant field (Hr) at 14 775 mc/sec were measured on a series of oriented polycrystalline nickel cobalt ferrites. Values of the measured resonant field are compared with values obtained from Kittel's resonance relation using the independently measured values of Ms and K.