bluuebunny/crossref_metadata_2025 huggingface dataset:
Dislocation Etch Pit Formation in Lithium Fluoride
Authors: Gilman J. J. , Johnston W. G. , Sears G. W.
Published: April 2005

Dislocation etch pits can be formed on LiF by a dilute aqueous solution of FeF3. In this report the etch pit formation is described in detail, and the mechanism for pit formation is discussed. The nature of the etch pits depends on the character of the dislocation, and on the exact composition of the etchant. Edge dislocations and screw dislocations etch slightly differently; the former produce deeper pits. The etching is inhibited by some segregated impurities at dislocations, therefore aged dislocations and fresh dislocations etch much differently. Etch pit formation is probably due to the preferential nucleation of unit pits one molecule deep at a dislocation, and the movement of the monomolecular steps across the surface. The relative rates of these two processes determine the shape of the etch pits. The nucleation rate for unit pits depends upon the dislocation energy, hence upon the character of the dislocation and the impurity content as suggested by Cabrera. The nucleation rate is faster at edge dislocations, because of their higher energy. The nucleate rate is low at dislocations with segregated impurities, because the impurities lower the dislocation energy. The ferric ion is adsorbed on the surface and inhibits the motion of steps, so that steeper, more visible pits are produced as the iron content is increased.
Examination of the Surface and Domain Structure in Ceramic Barium Titanate
Authors: Tennery Victor J. , Anderson Franklin R.
Published: April 2005

Polished and etched, as well as free surfaces, of barium titanate were studied by the direct carbon replica technique. Domain configurations of both the 90° and 180° type were made visible at a higher magnification than has been possible by optical methods. The behavior of 90° domains at a grain boundary was studied and photographed. Hexagonal and square growth patterns of the free surface were observed and photographed.
Characteristics of Junctions in Germanium
Authors: Harrick N. J.
Published: April 2005

Infrared radiation has been used to obtain a direct measure of the added carrier concentrations immediately adjacent to a junction when a current was passing through it. The current versus carrier density characteristics thus determined can provide sensitive tests of junction theory. For junctions between two highly doped germanium regions and low injection levels, the experimental results agree with existing theory. For these junctions and high injection levels, or for junctions between regions where one or both sides may be lightly doped and for arbitrary levels of injection, it is necessary to extend the theory. This is done by extending the boundary conditions for higher levels of injection and using the current equations in the ambipolar form, where the field as well as the diffusion currents are considered. The resulting current versus carrier density relationship involves the total current and takes into account, for both sides of the junction, the change in conductivity with injection level and the change in the drift length with the applied electric field. If, in addition, the change in lifetime with injection level is taken into consideration, good agreement obtains between experiment and theory. Current-voltage relationships are also derived which contain the above mentioned improvements.
Etching Studies on Photographic Grains
Authors: Hamilton J. F. , Brady L. E. , Hamm F. A.
Published: April 2005

The application of preferential etching techniques to the study of crystalline imperfection in photographic emulsion grains is described. Both chemical etching and halogen evolution by print-out exposure in the absence of gelatin form well-defined pits in most cases. The concentration of chemical etch pits is dependent on the solvent used but is not sensitive to concentration or etch time over the range investigated. A general increase in etching on certain faces is found after intentionally straining the grains, but the effect is not sufficiently strong to establish a one-to-one relationship between etch pits and dislocations. In both silver bromide and silver bromoiodide grains, no evidence is found for the existence of any type of polycrystalline substructure. Experiments on pitting by print-out exposure indicate that iodide ions provide internal hole traps or recombination centers.
Bulk Viscosity of Liquids
Authors: Hirai Nishio , Eyring Henry
Published: April 2005

The mechanisms for bulk viscosity are different between associated and nonassociated liquids. Here, a new mechanism for bulk viscosity is proposed from the standpoint of the hole theory of liquids and the rate process theory. This mechanism can explain the temperature and pressure dependencies of acoustic absorption for associated liquids and very viscous nonassociated liquids.
Effect of Origin Flaw Characteristics on Glass Strength
Authors: Levengood W. C.
Published: April 2005

Glass breakage experiments were made which indicate two different mechanisms of fracture. The breaking process is dependent on the widths as well as the depth of the origin flaws. When the fracture is of the large, open type, the reciprocal of the breaking stress is a linear function of the depth of flaw; when the flaw is minute, the reciprocal of the breaking stress is a linear function of the square root of fracture depth.

A pronounced strength increase was observed in cuts formed under various liquids and aged for various lengths of time. This increase took place about one hour after cutting and was interpreted as a rehealing phenomenon. Cuts made in air did not show the rapid strength increase.

Cycle fatigue tests were also made on laths of glass and it was observed that there was an initial decrease in strength followed by an increase. This was interpreted as rehealing effect in the minute type of flaw.
Galvanomagnetic Coefficients for Arbitrary Geometry
Authors: Broudy R. M.
Published: April 2005

An analog technique is described by which it is possible to obtain, without analytical computation, the Hall coefficient and magnetoresistance for any two-dimensional sample with the magnetic field perpendicular to the plane of the sample, without regard for sample shape or electrode size and configuration.
Flow of a Viscous Liquid on a Rotating Disk
Authors: Emslie Alfred G. , Bonner Francis T. , Peck Leslie G.
Published: April 2005

Equations describing the flow of a Newtonian liquid on a rotating disk have been solved so that characteristic curves and surface contours at successive times for any assumed initial fluid distribution may be constructed. It is shown that centrifugation of a fluid layer that is initially uniform does not disturb the uniformity as the height of the layer is reduced. It is also shown that initially irregular fluid distributions tend toward uniformity under centrifugation, and means of computing times required to produce uniform layers of given thickness at given angular velocity and fluid viscosity are demonstrated. Contour surfaces for a number of exemplary initial distributions (Gaussian, slowly falling, Gaussian plus uniform, sinusoidal) have been constructed. Edge effects on rotating planes with rising rims, and fluid flow on rotating nonplanar surfaces, are considered.
Dislocations, Point-Defect Clusters, and Cavities in Neutron Irradiated LiF Crystals
Authors: Gilman J. J. , Johnston W. G.
Published: April 2005

Micrographic techniques have been used to study dislocations, point defect clusters, and cavities in neutron-irradiated LiF crystals.

No evidence of inhomogeneous damage caused by ``thermal or displacement spikes'' was found. However, a uniform etching effect was found for doses greater than ∼1015 nvt. The etching is believed to be caused by clusters of point defects greater than 2 A but less than 50 A in size. This agrees with previous x-ray results. The defect clusters decrease in number and increase in size with increasing annealing temperatures. At temperatures greater than ∼400°C only (110) dislocation loops remain and these disappear above ∼600°C. Electron bombardment causes a similar effect.

The as-grown dislocation structure of LiF is not affected by neutron bombardment. However, it becomes increasingly difficult to move fresh dislocations in crystals given neutron doses greater than ∼1012 nvt. The hardening is independent of dislocation velocity and temperature and hence cannot be caused by Cottrellpinning of dislocations. The color changes that accompany hardening suggest that it is caused by defect clusters rather than single defects.

At annealing temperatures above ∼600°C crystallographic cavities appear in LiF crystals. They are rectangular parallelepipeds with (100) sides. Evidence is presented to show that the cavities are not caused by fission gases but probably by loss of fluorine from the crystals.
Mass Spectrometer Measurements of the Diffusion Coefficient of Hydrogen in Steel in the Temperature Range of 25°–90°C
Authors: Frank Robert C. , Swets Don E. , Fry David L.
Published: April 2005

The diffusion coefficients for hydrogen in mild steel have been measured in the temperature range of 25° to 90°C. A mass spectrometer was used to study the movement of hydrogen through thin steel plates. Two methods of measuring diffusion have been used; the rate of approach to equilibrium when hydrogen is supplied to the plate, and the rate of outgassing when the source of hydrogen is removed. Two decidedly different sets of diffusion coefficients were obtained by the two methods. The first method gave diffusion coefficients which agree very well with values obtained by others at higher temperatures while the outgassing method, which was more reproducible, gave values considerably lower. These results are compared with those of other investigators.
Ratio of the Diffusion Coefficients for the Diffusion of Hydrogen and Deuterium in Steel
Authors: Frank Robert C. , Lee Robert W. , Williams Robert L.
Published: April 2005

The ratio of the diffusion coefficients for hydrogen and deuterium in steel have been measured in the temperature range of 26°C to 86°C. A mixture of the two gases was introduced into the steel by abrasion in a mixture of normal and heavy water. The diffusion coefficients were measured simultaneously for the two using the mass spectrometer to observe the rate of evolution of the gases from the steel. The ratio of the diffusion coefficients was found to be constant within the limits of experimental error over the entire temperature range and had a value of 1.37±0.02. The ratio of the permeation rates was found to vary with the temperature. The results are compared with those of other investigators.
Electrical Contacts to Silicon Carbide
Authors: Hall R. N.
Published: April 2005

Rectifying junctions may be made by heating silicon-aluminum or silicon-boron alloys in contact with n-type silicon carbide. The measured solubility of carbon in liquid silicon is consistent with the view that these junctions are produced by an alloying and regrowth mechanism. Nonrectifying contacts may be made in an analogous manner using silicon-phosphorous alloys. Visible radiation is emitted uniformly over the rectifying junctions when current is passed in the forward direction, with a quantum efficiency of the order of 10−6. Current flow in the reverse direction is associated with the appearance of ``blue spots,'' similar in appearance to the points of light that are often observed when silicon junctions are biased in the avalanche region.
Diffraction Patterns at the Plane of a Slit in a Reflecting Screen
Authors: Hadlock R. K.
Published: April 2005

Measurements were made of the diffraction pattern in slits ranging in width from 0.2 to 2.5 wavelengths. Microwave radiation of 10.4 and 16 cm was used. Ratios of intensity in the slit to the intensity of the unperturbed beam were found for plane polarized radiation incident on the conducting slit screen. Comparison with diffraction patterns in the plane of circular apertures was made. A peak of intensity was found for the slit width of one-half wavelength and a plateau was observed in the plot of intensity vs slit width in the region of width equal to one wavelength. A theory involving multiple reflections from the edges was utilized to explain the variations of intensity in the plane of the slit. The electric field was studied when polarized parallel and also perpendicular to the slit edges. A high intensity was found near the edges when the electric field was polarized perpendicular to them.
Higher Approximation to Relaxation Spectra from Dynamic Measurements
Authors: Fujita Hiroshi
Published: April 2005

General methods of successive approximations to calculate the relaxation spectrum from data of dynamic mechanical measurements are worked out using an inversion theorem of integral equations of the Stieltjes type. The idea underlying the methods is essentially the same as that used by Schwarzl and Staverman in their treatment of stress relaxation data. It is shown that the delta-function method of Schwarzl and Staverman and of Leaderman is not a unique process of successive approximations to obtain relaxation spectra from dynamic data. Conditions to obtain a series of best approximations in terms of the delta-function method are discussed.
Analytical Representation of Angular Distribution Data
Authors: Snowdon S. C. , Eisenbud L. , Marshall J. F.
Published: April 2005

A simple method is presented for obtaining an analytical curve fitted to data points. The requirements in least squares analysis that yield a single best curve are relaxed to the extent that it is only necessary to choose one of many possible good fits. The subsequent analytical determination of this good curve may be obtained with relatively little computational effort. Specifically, the method is applied to an analytical representation of angular distribution data by means of a Legendre polynomial series. A smooth curve which one feels is statistically justified is drawn through the data points. The values of this curve at eleven points are chosen as the coefficients in a Lagrange interpolation function series. The intermediate points give back approximately the drawn curve and are also statistically adequate. Subsequent use of a transformation matrix between the Lagrange interpolation basis and the Legendre polynomial basis yields the desired expansion. The transformation matrix is presented for the case in which an 11-point fit adequately characterizes the data curve. Error estimates also are given.
Stability Studies with Longitudinal Magnetic Field on a Straight Pinched Discharge
Authors: Burkhardt L. C. , Lovberg R. H. , Sawyer G. A. , Stratton T. F.
Published: April 2005

Experiments on the effects of a longitudinal magnetic field on a linear pinched discharge indicate that the characteristic m=0 short wavelength instabilities are suppressed by Bz fields, and that pinch life is lengthened. Measurements with a system of magnetic probes indicate that the remaining instability is a long wavelength m=1 helix. Image converter photographs of the pinch development and the short wavelength instabilities are presented.
Relation Between Crystallite Orientation and Magnetic Properties of Elongated Single-Domain Iron Particles
Authors: Luborsky F. E. , Fullam E. F. , Hallgren D. S.
Published: April 2005

Analysis by selected area electron diffraction of aligned elongated single-domain iron particles, each about 150 A by 500 A, indicates that the long axis of the particle is coincident with the [111] crystallographic direction. Diffuse diffraction rings and elongated spots were attributed to a considerable degree of random crystallite orientation. These results confirm predictions based on particle morphology and on the temperature coefficient of coercive force of iron and iron-cobalt alloy particles. This [111] orientation offers an explanation for the increase in coercive force with increase in temperature observed for single domain iron-cobalt alloy particles and suggests a related explanation for the Alnico type alloys.
Ettingshausen Effect and Thermomagnetic Cooling
Authors: O'Brien B. J. , Wallace C. S.
Published: April 2005

The use of the Ettingshausen effect in refrigeration is considered. The phenomenological similarity of this cooling effect with the cooling by a cascade of Peltier couples is treated. Theoretical expressions are derived for the maximum cooling that is possible with the Ettingshausen effect, and it is shown that the optimum shape of the cooling element is an exponential of a given form. Preliminary experiments with bismuth alloys have given a cooling of about 0.25°C.
Dislocations and Selective Etch Pits in InSb
Authors: Venables J. D. , Broudy R. M.
Published: April 2005

A special type of dislocation etch pit has been observed in InSb, which illustrates the polarity of the zincblende structure and the nature of dislocations therein. The dislocation direction and slip plane were found to be <110> and {111}, respectively. Dislocations introduced by plastic bending at 450°C were observed by selective etch pits on {110} faces. The etch pits are ``arrow'' shaped and all point in the same <100> direction regardless of bending direction. The {110} pits develop for only one of two possible types of 60° dislocation which exist in the zincblende structure. One type terminates in a row of In atoms, the other in a row of Sb atoms.
Coercive Force of Iron Oxide Micropowders at Low Temperatures
Authors: Morrish A. H. , Watt L. A. K.
Published: April 2005

The coercive force of some magnetite and gamma-ferric oxide micropowders has been measured in the temperature range 77°K to 300°K. Some of the powders contained essentially only single-domain acicular particles, others contained only multidomain particles. For the former, the results are consistent with an interpretation based on the usual relationship between coercive force and the anisotropies; for the latter with an interpretation based on the variation of the crystalline anisotropy constant with temperature. In addition, a new memory effect has been observed for the multidomain magnetite powders. If a sample was placed in some state of magnetization below the transition temperature, warmed to room temperature and then recooled, the measured value of the coercive force depended on this original state.
Determination of Higher Order Propagating Modes in Wave-Guide Systems
Authors: Forrer Max P. , Tomiyasu Kiyo
Published: April 2005

A measuring technique is described for the quantitative determination of all propagating modes, both dominant and of higher order, in a straight, lossless, rectangular wave guide. Calibrated probes are used to measure the amplitude and phase of the electric fields at various locations on the wave-guide walls. The number of probe locations must be equal to or greater than the number of propagating modes at the frequency being considered. This measuring technique revealed that 31-kw peak power at the third harmonic (X band) was radiated by a 5-megawatt S-band magnetron.
Use of Capacitor Discharges to Produce High-Velocity Pellets
Authors: Bloxsom D. E.
Published: April 2005

There is a limit to pellet velocities obtainable from guns using chemical processes. In order to remove this limit, high pellet accelerating pressure was obtained by heating helium to high temperatures by means of electrical discharges. Helium has been heated to 53 000 psi and 6350°K. This helium has been used to accelerate nylon pellets of ⅛-in. diameter to 9800 ft per sec. Expected nylon pellet velocity of 23 500 ft per sec, from 36% energy transfer efficiency from condensers to helium, was not obtained due to forced convection heat transfer in the gun barrel.
Anisotropic Effects in Geometrically Isotropic Lattices
Authors: Kaprielian Zohrab A.
Published: April 2005

For spacings and element dimensions small with respect to wavelength the directric constant of a completely general lattice of identical elements may be represented by a tensor (ke). In many applications of artificial dielectrics it is important that the dielectric act as an isotropic medium for microwaves. This requires that (ke) reduce to a scalar. The dielectric constant tensor will reduce to a scalar only if the lattice is cubical and the geometry and the material of the elements is restricted so that the induced fields may be represented by a set of three mutually perpendicular static dipoles at the lattice points. Isotropy further requires that the moment of the resultant dipoles be proportional to the inducing field and that the proportionality factor be a scalar independent of direction. However, at shorter wavelengths, the representation of the lattice elements by static dipoles will not be valid and the medium becomes anisotropic. This paper evaluates the anisotropy produced by an arbitrary ratio of element spacing to wavelength, and demonstrates that there is a basic anisotropy associated with the granularity of an array composed of isotropic elements arranged in structurally isotropic patterns.
Physical Processes in Contact Erosion
Authors: Germer L. H.
Published: April 2005

The various causes of the erosion of noble metal contacts are now isolated and understood. They give adequate interpretation of the sign of erosion under various circuit conditions, and of the space distribution of the eroded metal, as well as quantitative agreement with measurements of erosion in repetitive tests. Electric arcs are the chief cause of erosion, although at breaking contacts glow discharges are important under certain circumstances, and at higher currents bridge erosion is significant also. The arcs are of two types, ``anode arcs'' which erode the anode predominantly, and ``cathode arcs'' which erode the cathode. Anode arcs occur at small contact separations, and cathode arcs at large separations. The metals studied were palladium and silver, which have different characteristics because of their different electrical conductivities and also because of the chemical reactivity of silver. The erosion of these metals in the inactive condition, by weighing the contacts before and after many repetitive operations, is of the order of 4×10−14 cc/erg in anode arcs and less than this by a small factor in cathode arcs, on break as well as on closure. In a glow discharge only the chemically active metal silver is appreciably eroded and its erosion is negligible unless the current density results in a glow of the abnormal type. Activation produced by organic vapors often changes the magnitude of the erosion per unit of arc energy and sometimes its sign, these effects being probably attributable to shielding one of the contacts by carbon lying on it as well as to the greater separations at which arcs occur between active surfaces.
Time Dependence of Mechanical Breakdown in Bundles of Fibers. IV. Infinite Ideal Bundle under Oscillating Loads
Authors: Coleman Bernard D. , Marquardt Donald W.
Published: April 2005

The theory of breaking kinetics is used to calculate the behavior of infinite ideal bundles under loads that are periodic functions of time. It is assumed throughout that the bundles are composed of filaments which have been randomly selected from a first-order ensemble. It is shown that the problem of calculating the lifetime of such a bundle can be reduced to one of finding the singular point in an unstable nonlinear first-order differential equation. Some general mathematical theorems are stated which help to locate the singular point in the differential equation when the ratio of the lifetime of the bundle to the period of the loading history is large. The general theory is applied to calculations of lifetimes of bundles for several specific loading histories. Detailed numerical results are reported for the special case of a sinusoidal loading history. Comparisons are made between the breakdown behavior of separate filaments and infinite bundles of filaments.
Effect of Dislocations on Breakdown in Silicon p-n Junctions
Authors: Chynoweth A. G. , Pearson G. L.
Published: April 2005

The light emission patterns of silicon diffused p-n junctions at breakdown have been compared with the etch-pit patterns that reveal dislocations. It is concluded that avalanche breakdown microplasmas occur preferentially where dislocations pass through the junction. In narrow p-n junctions, large numbers of dislocations result in enhanced internal field emission and, consequently, a soft reverse characteristic. A qualitative correlation is found between the nature of the light emission pattern (spots for avalanche breakdown, glow for field emission) and the quality of the reverse characteristic. Possible reasons why breakdown should occur preferentially at dislocations are discussed though no precise conclusion is reached. Peculiar singularities observed in the light emission patterns of some junctions were found to coincide with crystal abnormalities revealed in the etch patterns.
On the Quality of Gray Tin Crystals and Their Rate of Growth
Authors: Becker J. H.
Published: April 2005

Various methods of preparing samples of gray tin suitable for electrical and optical investigations are described. Attempts to deposit atoms of tin directly into the gray tin lattice by vapor- and electrodeposition and by chemical reactions at low temperatures have all yielded crystals of white tin; however, by transformation of white tin under suitable conditions it is possible to obtain large coherent crystals of gray tin. These include samples several cm long showing single crystal regions up to 2 mm, as well as flat thin films as large as 25×25 mm2.

The temperature at which the transformation takes place, the purity of the initial white tin specimen, its size, and the method of attaching a sample to a substrate are important factors for determining both the quality and the rate of transformation. Investigations were carried out over a wide range of temperatures for several sources of high purity tin, as well as with additions of In, Ga, Al, As, and Sb. Effects of mechanical and thermal treatment are also included. A careful distinction is made between the time for nucleation and the rate of growth after nucleation.

Results are analyzed in the light of absolute rate theory and a reasonable explanation is obtained for many of the observed phenomena. The heat of activation for the white to gray tin reaction is determined as (8.7±1.5)×103 cal/mole at 0°K.
Neutron Generation from Straight Pinches
Authors: Dunway R. E. , Phillips J. A.
Published: April 2005

Experiments on the neutrons produced in deuterium gas during a high-current pulsed discharge are described. With 15 kv applied to a straight discharge tube 30 cm long, neutrons are produced during a 0.1 μsec pulse ∼1.4 μsec after gas breakdown. The yield of 107 to 108 neutrons per discharge depends on gas purity and the discharge tube wall material. The axial asymmetry in neutron energy indicates that the neutrons are produced in reactions whose center of mass moves preferentially towards the cathode.
High-Speed Fracture in Rubber
Authors: Mason Peter
Published: April 2005

Cinematographic observations have been made of crack propagation under well-defined boundary conditions in rubbers at speeds up to 30 m/sec. The fracture-markings showed resemblances to those obtained with metals, plastics, and glass, and could be related directly to the corresponding speed of fracture-propagation. In close analogy with Schardin's observations on glass, a noncrystallizing rubber (GR-S) showed a mode of crack propagation in which the fractured surfaces were visually smooth and the speed was about one quarter of the speed of longitudinal elastic waves. A crystallizing rubber (natural rubber) did not show this mode of propagation under the present test conditions. It is suggested that the modes of solid fracture can be usefully classified in three categories: (i) slow propagation, generally with smooth surfaces, obtained by careful control of the boundary conditions; (ii) propagation at intermediate rates with rough surfaces, involving correspondingly greater energy consumption; and (iii) fast propagation with smooth surfaces, the rate of propagation being limited by the speed of elastic waves in the material in accord with Mott's theory.
Freezing of Liquids in Porous Media with Special Reference to Frost Heave in Soils
Authors: Jackson K. A. , Chalmers Bruce
Published: April 2005

If the surface area of a liquid is large compared to its volume, the normal freezing temperature of the liquid will be altered. In a porous material a liquid can therefore exist in equilibrium, below its normal freezing temperature. However, such a liquid will be unstable with respect to bulk solid. This instability provides the driving force for frost heave in soils.
Some Effects of Nonuniform Fields on Dielectrics
Authors: Pohl Herbert Ackland
Published: April 2005

Some of the more interesting effects of nonuniform electric fields are described in this report. Experimental and theoretical studies show the effects to be rather striking for particles larger than molecular size. The results show that the effect can be used to produce a fairly efficient pumping action of nonconducting liquids, to cause continuous and easily measureable separations in coarse suspensions, to cause selective precipitation, and to produce mixing.

By this means, liquids may be thrown several feet into the air with an electromechanical efficiency of about 25%. A separation factor of at least 2.5 in continuous separatory operation may be produced in a suspension of polyvinyl chloride in carbon tetrachloride-benzene mixture. Suspensions of polar materials in less polar liquids may be either dispersed or precipitated. In one interesting ``demonstration'' type experiment, drops were ``hung'' in mid-air.
Note on Diffusive Separation of Gas Mixtures in Flow Fields
Authors: Liu V. C.
Published: April 2005

This paper discusses the effect of pressure-diffusion flux upon the concentration distribution of gas mixtures in flow fields. The equation of concentration is formulated for a binary gas mixture in which the mass ratio is large and the concentration of the lighter gas is very small. An asymptotic solution to the steady-state equation of concentration is given for an irrotational and incompressible flow.

As an illustration, the diffusive separation (i.e., deviation from the original homogeneous state) of a mixture of helium and nitrogen along streamlines at the entrance to a long straight channel is calculated. It is assumed that the pressure inside the channel is 90% of that in the free stream, and that the diffusion coefficient of the mixture corresponds with the atmospheric conditions at 80-km altitude.
Work Function and Sorption Properties of Silicon Crystals
Authors: Dillon J. A. , Farnsworth H. E.
Published: April 2005

The work functions of silicon single crystals have been obtained by measuring the contact potential differences between the crystals and a gold reference whose work function was measured by the Fowler method. The measurements were carried out in high vacuum (p<10−9 mm Hg). For nonfloating-zone silicon, the work function was higher for samples which were radiation quenched from 990°C than it was for samples which were annealed at 500°C. This effect was not observed for floating-zone material and was presumably a function of occluded oxygen. The work functions for the different faces after ion-bombardment cleaning were in the sequence (100)>(110)>(111). The values after quenching were: (100), 4.92 ev; (110), 4.89 ev; (111), 4.77 ev. The values after annealing were: (100), 4.82 ev; (110), 4.70 ev; (111), 4.67 ev. The work function of the (111) face of a 2000-ohmcm, p-type, floating-zone sample was 4.73 ev after quenching or annealing. Changes in both surface and volume properties were observed when silicon was heated above 1000°C in contact with quartz. Oxygen exposures of 5×10−5 mm Hg min resulted in work function increases which were larger on the annealed surfaces than on the quenched ones. This was observed for both floating-zone and oxygen-doped material and is therefore a property of the silicon itself. Photoelectric evidence indicated a diffusion of oxygen into the silicon (1) when silicon was heated in oxygen, (2) when silicon was heated at 990°C in high vacuum after O2 adsorption, and (3) when silicon with residual surface films from chemical etching was heated at 990°C prior to ion bombardment. Hydrogen exposures of 7.5×10−4 mm Hg min resulted in work-function decreases only in the presence of a heated filament. Nitrogen exposures of 4×10−6 mm Hg min resulted in no work-function changes. Heating silicon in high vacuum at 990°C for about 100 hours developed thermal-etch patterns which were rectangular on the (100) face, hexagonal on the (110) face, and triangular on the (111) face. Heating at 1080°C for 24 hours caused further etching which developed the same triangular patterns on the (111) face but left the (100) and (110) faces with a sandblasted appearance.
General Formulation of Powered Flight Trajectory Optimization Problems
Authors: Fried Burton D.
Published: April 2005

A general formalism, applicable to a wide class of missile trajectory optimization problems, is obtained by straightforward application of standard methods of the calculus of variations. In all cases, a point particle model is used for the missile. It is shown that the steering and burning programs are determined always by the same differential equations, different optimization problems corresponding simply to different boundary conditions. Results found previously by assuming the gravitational force field uniform during powered flight are obtained as special cases and the corrections to these due to variations in the force field are discussed. The extensions to variable mass and thrust programs, variable burning times, etc., are also included.
Investigation of Low-Temperature Internal Friction
Authors: Caswell Hollis L.
Published: April 2005

The internal friction in pure copper, in copper doped with nickel and gold, and in magnesium, subjected to various amounts of cold work was measured at 40 kc from 4°K to 300°K. Cold work produces a Bordoni relaxation peak in copper at approximately 80°K. The peak position is independent of the amplitude of vibration for strain amplitudes less than 3×10−5. Suitable annealing reduces and eliminates the peak, as does the presence of relatively large quantities of impurities. Increased cold work and impurity additions also systematically reduce the strain amplitude of the internal friction. A peak was found in cold-worked magnesium at 20°K and also a small peak in crystalline quartz at 39°K. A comparison of present theories with these results is given.
Noise and Electron Temperatures of Some Cold Cathode Argon Discharges
Authors: Collings E. W.
Published: April 2005

Noise temperatures at 3000 Mc were compared with the corresponding electron temperatures for the positive columns of some cold cathode discharges in argon. The noise temperatures were measured using a superheterodyne receiver of low noise figure, by comparing the noise outputs of the various tubes with that from a commercial fluorescent lamp of measured noise output, a rapid comparison between known and unknown noise powers being effected by means of a hand-operated wave-guide switch. The noise temperature of the fluorescent lamp in its mounting was measured by comparison with an absolute standard consisting of an incandescent tungsten filament lamp fitted in a suitable wave-guide holder. Electron temperatures were measured by the Langmuir single-probe method. It is concluded that for most of the tubes measured, noise temperature, and electron temperature are in close agreement as required by the theories.
Liberation of Electrons by Fast Neutral Helium Atoms from a Tungsten Target
Authors: Berry H. W.
Published: April 2005

The electron emission from tungsten by bombarding helium atoms of energy ranging from 300 to 3500 ev has been measured for a surface with less than a monolayer and with multilayers of adsorbed gas. The yield expressed in electrons per particle rises almost linearly from about zero at 300 ev to 0.42 electrons/particle at 3500 ev for a monolayer of adsorbed gas. Further adsorption of gas gives a much increased yield. These yields are compared with the ion under like conditions. The distributions of the normal velocity and a component of the tangential velocity are compared for the ion and neutral atom on hot and cold targets.
Floating Crucible Technique for Growing Uniformly Doped Crystals
Authors: Leverton W. F.
Published: April 2005

The floating crucible method for growing single crystals is described. This method, a simple modification of the Czochralski technique, permits the growing of large germanium single crystals of uniform resistivity. By growing the crystal from an inner crucible floating in the germanium melt, the condition of constant liquid volume in the inner crucible is achieved and the concentration gradient characteristic of crystals grown by the Czochralski method is elminated. Earlier determinations of the distribution coefficients of some doping impurities in germanium have been verified. The density of liquid germanium at the melting point has been determined to be 5.94±0.06 g/cm3. The use of the floating crucible technique for the growing of uniform silicon crystals is discussed.
Effect of a Transverse Field on Switching Rates of Magnetic Memory Cores
Authors: Rossing Thomas D. , Rubens Sidney M.
Published: April 2005

A ferromagnetic material having a rectangular hysteresis loop can be magnetized much easier if a magnetic field is applied transverse to the direction of remanence at the same time the remagnetizing pulse is applied. This effect, which has been observed in cores of ferrite, rolled Permalloy and vacuum-deposited alloys, is shown to be compatible with the existing theories of domain wall motion. It forms the basis of an improved method of writing into magnetic memory cores in a digital computer.
Observation of Domains in the Ferrimagnetic Garnets by Transmitted Light
Authors: Dillon J. F.
Published: April 2005

It has been found that single crystals of the ferrimagnetic garnets are transparent to visible light. Thin sections (e.g., 0.005 cm thick) transmit sufficient light for microscopic examination. The transmitted light undergoes a nonreciprocal rotation similar to the Faraday effect. By virtue of this rotation many features of the domain structure are readily visible. A magnetic birefringence has also been observed which can be used to differentiate domains whose magnetization lies perpendicular to the line of sight. It is possible to study domain structure at any temperature below the Curie point. The effects of strains set up by the polishing procedure are discussed. Finally, mention is made of possible combined microwave-optical experiments, as well as experiments aimed at understanding the switching process.
Factors Determining the Oxygen Content of Liquid Silicon at Its Melting Point
Authors: Kaiser W. , Breslin J.
Published: April 2005

The oxygen content of liquid silicon increases proportionally to the oxygen content of the ambient helium-oxygen mixture for oxygen partial pressures pO2°<8 mm Hg. This observation is explained by the proportionality between the oxygen partial pressure pO2° in the ambient gas and the SiO partial pressure on the surface of liquid silicon. For pO2°>8 mm Hg the silicon melt is covered by a film of silica and asaturation value of about 2×1018 oxygen atoms per cm3 is observed in the crystallized sample.
Passivity during the Oxidation of Silicon at Elevated Temperatures
Authors: Wagner Carl
Published: April 2005

The dependence of the rate of the oxidation of silicon in oxygen-helium mixtures on gas composition at 1410°C is discussed theoretically. At low oxygen contents of the gas, no layer of solid silica is expected to occur and the rate of attack due to formation of volatile SiO is supposed to be proportional to the oxygen partial pressure in the bulk gas. Above a critical oxygen partial pressure, solid silica may be formed and the rate of attack under steady-state conditions may drop by several powers of ten.
Analyses for Diffusion during Plastic Deformation
Authors: Simmons J. , Dorn J. E.
Published: April 2005

This paper presents the general equation for self-diffusion in deforming media. Methods of analyses for determining the self-diffusivity as a function of time for prescribed strain histories are given for special cases of linear diffusion. No unrealistic assumptions relative to the constancy of the diffusivity with time are made.
Crater Formation in Metallic Targets
Authors: Partridge William S. , Vanfleet Howard B. , Whited C. R.
Published: April 2005

Spheres of copper, lead, tin, iron, aluminum, zinc, silver, and lead-tin alloys were accelerated to velocities of 0.75 to 2.25 km/sec and impacted normally upon targets of the same material as the pellets. Conditions were maintained so that pellets lost no mass before striking the target. The target mass was large compared to the mass of the pellet, so the targets could be considered semi-infinite.

The volume of the crater produced was found to be directly proportional to the kinetic energy of the pellet in the energy range investigated.

The penetration varied linearly with the velocity or momentum of the pellet. The area of the crater as measured in the plane of the original surface of the target was found to be directly proportional to the momentum of the pellet at the time of the impact.

In the case of the lead-tin alloy series, a correlation was observed between the crater parameters, the phase diagram of the alloys, and various functions of the pellet mass and velocity for the following series of alloys: 100% lead; 90% lead, 10% tin;...; 10% lead, 90% tin; 100% tin.
Temperature Dependence of Magnetic Properties of Silicon-Iron
Authors: Chen C. W.
Published: April 2005

Permeability, coercive force, remanence, and hysteresis and core losses of a 3% singly oriented silicon-iron alloy are measured in the temperature range of 30° to 700°C. Their temperature dependence is interpreted in terms of either the intrinsic properties of a ferromagnetic or domain theory. The magnetization curve is analyzed on the basis of the crystallographic characteristics of the texture in the material. Domain distribution is discussed at each stage of magnetization. Application of the analysis leads to the establishment of the relationship between the temperature coefficient of permeability and the magnetization processes.
Parametric Amplification and Frequency Mixing in Propagating Circuits
Authors: Tien P. K.
Published: April 2005

When two circuits such as filters or transmission lines are coupled together by means of distributed reactances which can vary sinusoidally in time and space, energy can be converted between waves of different frequencies in a variety of ways. If the waves on the two transmission lines are characterized by frequencies ω1 and ω2 and phase constants β1 and β2, while the coupling reactances vary as ω=ω1−ω2 and β=β1−β2+Δβ, power P1 at ω1 is converted into power P2 at ω2 and vice versa in a manner reminiscent of waves on coupled passive circuits, except that a relationship (P2/ω2)=(P1/ω1) is obeyed. If the group velocities on both transmission lines are in the same direction, the direction of power transfer reverses periodically with distance. If they are not in the same direction, the power transfer increases monotonically with distance for small Δβ but reverses periodically for Δβ larger than a certain limit.

When the coupling reactance varies as given by ω=ω1+ω2 and β=β1+β2, parametric amplification is possible in the form of exponentially growing waves at frequencies ω1 and ω2 if the group velocities are in the same direction, and in a form reminiscent of the backward wave amplifier when the group velocities are not in the same direction. In both cases the excess energy is supplied by the variable coupling reactance and can be indefinitely large.

Possible applications of new principles of these coupled circuits to broad-band frequency converters, frequency-channel selectors, wide-band amplifiers, tunable narrow-band amplifiers, and oscillators are described. Noise performances of the circuits are also discussed.
Elastic-Plastic Transition in Copper Crystals as Determined by an Etch-Pit Technique
Authors: Young F. W.
Published: April 2005

Copper (99.999%) crystals with a dislocation density of 50/mm2 have been prepared. These crystals were stressed by applying a pure bending moment, and they were etched with a dislocation etch either before and after or while the stress was applied. The motion of dislocations was determined by observing the size and nature of the dislocation etch pits. The resolved stress necessary to move grown-in dislocations was about 4 g/mm2. Examples of dislocation motion under stress, then return motion when the stress was removed, and of multiple motion under stress were observed. Multiplication of dislocations occurred at a resolved stress of about 18 g/mm2. The observed phenomena are discussed in terms of simple dislocation theory.
Application of the Czochralski Method to Divalent Metal Fluorides
Authors: Nassau K.
Published: April 2005

The Czochralski method of pulling from the melt has been applied to the growth of single crystals of divalent fluorides of Ca, Sr, Ba, Co, and Mn, and the compound KMnF3. The trivalent rare earth ions Ce, Nd, Sm, Eu, Gd, Tb, and Yb were introduced into CaF2 and the distribution coefficient was determined to be close to unity in all cases.
Properties of Heavily Doped n-Type Germanium
Authors: Spitzer W. G. , Trumbore F. A. , Logan R. A.
Published: April 2005

The electrical and optical properties of n-type germanium have been studied for doping levels greater than 5×1018 cm−3. Hall coefficient and resistivity measurements show that the electron mobility μ depends upon the specific group V donor used as a dopant and, at a given carrier concentration, increases in the order μAs<μP<μSb. In material doped very heavily with arsenic, a large fraction of the arsenic was found to be electrically inactive. Rapid quenching of this material resulted in larger carrier concentrations and a better correlation with crystal growth parameters. Distribution coefficients were calculated from the electrical measurements on antimony-doped crystals grown by a solvent evaporation technique. No significant ``facet effect'' was observed for these crystals. Reflectivity measurements between 2 and 24 μ were used to deduce the electron effective mass as a function of carrier concentration. In the carrier concentration range studied (up to 8×1019 cm−3), the effective mass increases only slightly and is independent of the specific dopant. The free carrier absorption is dependent on dopant. The absorption and electrical data are correlated by using elementary conduction theory.
Effect of Reactor Fast Neutrons on Electron-Hole Recombination in Germanium
Authors: Czachor A. , Piekoszewski J.
Published: April 2005

The properties of recombination centers introduced by reactor fast neutrons in n-type germanium were investigated. From carrier lifetime temperature measurements, using Shockley-Read statistics, recombination-level position has been calculated and found to be dependent on resistivity of germanium. It has been observed for the first time that in the region of low temperature, lifetime increases with decreasing temperature.
Effect of Torsional Deformation on Self-Diffusion in Silver
Authors: Lee C. H. , Maddin R.
Published: April 2005

Data are presented to show that plastic deformation by torsion occuring at temperatures between 700° and 800°C enhance self-diffusion in silver single crystals. The enhancement varies linearly with surface strain rate, is larger the lower the temperature and is independent of surface strain. The results of experiments at constant stress are discussed in relation to ideas developed by Weertmann. The lifetime of point defects (assumed to be vacancies) at 800°C has been measured as about 100 sec. This permitted the calculation of the concentration of vacancies produced per unit strain.