bluuebunny/crossref_metadata_2025 huggingface dataset:
Lifetime in Pulled Silicon Crystals
Authors: Bittmann C. A. , Bemski G.
Published: April 2005

Lifetime data of 46 pulled silicon crystals are interpreted in terms of the Shockley-Read recombination theory. The data are consistent with the theory under the assumption of a single recombination level and a constant concentration of recombination centers, independent of the resistivity of the crystals. However, it is not possible to distinguish between two possibilities as to the location of the recombination level in the lower or the upper half of the energy gap by this type of experiment.

The energy levels thus obtained are at 0.17 ev from the valence band or 0.20 ev from the conduction band in p-type silicon and at 0.22 ev from the valence band or 0.25 ev from the conduction band in n-type silicon.
Growth and Defect Structure of Sapphire Microcrystals
Authors: Webb W. W. , Forgeng W. D.
Published: April 2005

Examination of small euhedral crystals of α-Al2O3 (sapphire) that were observed following oxidation of aluminum and an aluminum alloy in wet hydrogen at high temperatures showed that growth probably occurs by decomposition of AlO on an Al2O3 surface. Rapid growth occurs on the tips of needles and the edges of platelets at lattice steps formed by intersection of hollow screw dislocations with these surfaces. Screw dislocations were detected by x-ray measurement of the lattice twist they produce in the needle-like crystals or ``whiskers.'' Needles were bent to elastic strains of over 2% corresponding to a strength of 1011 dyne cm−2.
Theory of Peeling through a Hookean Solid
Authors: Bikerman J. J.
Published: April 2005

When the adhesive is a Hookean solid and the adhesive joint between a rigid plate and a flexible ribbon is peeled, the force required for peeling is 0.3799 wσ(E/E1)14δ34y014, if w denotes the width of the ribbon, σ the tensile strength of the adhesive, E and E1 the moduli of elasticity of the ribbon and the adhesive, respectively, δ the thickness of the ribbon, and y0 the initial thickness of the adhesive film. If δ=y0, the ratio of tensile force to stripping force needed for separation is of the order of l/y0, l being the length of the ribbon.
Analysis of the dc and Pulsed Thermionic Emission from BaO
Authors: Haas George A.
Published: April 2005

The effects of field penetration and donor mobility on the chemical potential of BaO have been computed by using a nondegenerate single donor level semiconductor model. Calculations which neglect the effects of surface states and porosity predict that the pulsed emission starts lower, but increases with field more rapidly than given by simple Schottky theory, actually being capable of exceeding the theoretical Schottky emission. The dc emission level is always lower than the pulsed emission, the difference being more pronounced at higher fields and for less active cathodes.
Studies on the Mechanism of Operation of the L Cathode. I
Authors: Rittner E. S. , Ahlert R. H. , Rutledge W. C.
Published: April 2005

Performance characteristics of the L cathode, including emission, evaporation rate, and evaporant composition, are presented, followed by an investigation of the constitution of the emitting surface. Activation of the external tungsten surface is effected by the migration thereover of strongly adsorbed BaO issuing from the pores. The active surface, which is continuously renewed during life, comprises a nearly complete oxygen monolayer on tungsten covered in turn by a complete barium monolayer. The oxygen in the dipole layer enhances emission and drastically increases the sticking time of barium. The cathode emission is close to the maximum that can be expected from a barium activated tungsten dispenser cathode.
Compressional Creep of Tin Single Crystals
Authors: Weertman J.
Published: April 2005

Compressional creep tests were run on single crystals oriented so that the direction of compression was along the c axis. Two activation energies of creep were found: approximately 24 500 cal/mole above 120°C and 12 000 cal/mole below this temperature.
Maser Oscillators
Authors: Helmer J. C.
Published: April 2005

Two maser oscillators have been constructed and operated. The behavior of one maser has been observed under various operating conditions by comparing it with the second maser which is used as a reference standard. The expeimental setup is shown and experimental results are given. The frequency-pulling effects of the beam and the oscillation amplitude as a function of cavity-tuning are compared with the theoretically expected behavior. It is shown that the simple behavior predicted by theory exists only for oscillation frequencies which are well removed from line center.

The theoretical curves are obtained from a new analysis which includes the velocity distribution in the beam. A comparison is made between the velocity-distributed and uni-velocity theories. It is shown that the introduction of the velocity distribution drops the maximum beam efficiency from 1 to 0.76 and causes a region of stability to appear in the beam frequency-pulling function.
Reflection of Plane-Polarized, Electromagnetic Radiation from an Echelette Diffraction Grating
Authors: Meecham William C. , Peters C. W.
Published: April 2005

A variational method is used to calculate the distribution of energy reflected from an echelette diffraction grating. Experiments performed using a klystron generating 3.2-cm electromagnetic waves which impinge upon a large scale grating agree with the calculations to within a few percent, the error being that expected from the variational formulation.
Electrostatic Considerations in BaTiO3 Domain Formation during Polarization Reversal
Authors: Landauer Rolf
Published: April 2005

Merz's picture of spike-shaped domains of reversed polarization emerging from an electrode is analyzed with particular attention to its electrostatic aspects, taking into account the inhomogeneous piezoelectric distortions which accompany domain formation. The depolarization energy of a domain is evaluated. The interaction energy of the applied field and the depolarization field is shown to be negligible. The charge flowing into the electrodes as a domain expands is shown to be related primarily to the reversal of spontaneous polarization, rather than to the changes of the depolarization field. Our final results are similar in form to the expression originally given by Merz. Although a detailed domain wall theory is not yet available, we have combined an existing domain wall estimate with our electrostatic expressions, and this results in an implausibly large critical nucleus. Some effects of nonlinearities in the dielectric behavior and of internal charge distributions are discussed.
Rectification Properties of Metal-Silicon Contacts
Authors: Wurst E. C. , Borneman E. H.
Published: April 2005

Area contacts of twenty different metals were made on n and p silicon. The contacts were applied by the use of jet plating techniques, with the exception of alkali metal contacts which were pressure contact or mercury amalgam contact. A qualitative correlation is shown to exist between the work function of the metals and the rectification of these metals on n and p silicon. I–V characteristics taken on eleven of these metal-silicon contacts lend further support to this picture. Consideration of a quantitative work function model is made difficult due to the many errors and interpretations involved in using metal work function values.

Transistor structures were made and studied for several of the metal-silicon contacts. From analysis of this transistor data it is found that an excess current three orders of magnitude greater than theory predicts, must be present in the diodes made from these metals. This excess current is not adequately explained by any presently known mechanism.
Resonance Absorption of Neutrons by Uranium Cylinders
Authors: Davis Monte V.
Published: April 2005

The integrated effective resonance neutron absorption cross section of uranium-238 cylinders has been experimentally investigated in the Hanford Test Pile. The results of reactivity measurements were interpreted to yield the effective resonance integral as a function of the surface-to-mass ratio of the uranium cylinders. The experiments were extended to determine the Doppler coefficients resulting from heating the uranium in a constant neutron spectrum in the reactor. The effective resonance integral, ∫ (σa0)effdE′/E′, can be approximated as a function of the surface-to-mass ratio by ∫ (σa0)effdE′E′=6.0{1+15.6SM[1−2.18SM+2.19(SM)2]}. The Doppler coefficient of resonance escape probability for the reactor is 1p∂p∂T=(−2.14±0.16)10−5/∘C,and the value assigned to the coefficient of the volume absorption of the resonance integral is 1A∂A∂T=(1.56±0.12)10−4/∘C.
Carbon Tantalum Internal Friction Peak
Authors: Powers R. W. , Doyle Margaret V.
Published: April 2005

The internal friction peak in tantalum arising from the diffusion of interstitial carbon has been located at 338°C for vibration frequencies of 0.55 cps. The corresponding activation energy is 39.6 kcal. The identification of this peak is made difficult by its proximity to the nitrogen peak. However, the two can be distinguished by the lesser stability of the carbon peak with respect to aging at 400°C and by a different dependence of peak height on solute concentration.
Stereo-Micrographs of Conductivity
Authors: Mayer Ludwig
Published: April 2005

The paper deals with the utilization of electron mirror microscopy for pictorial representation of the distribution of electrical conductivity. Previously described conductivity pictures obtained by this novel kind of electron microscopy have been of the normal two-dimensional type; this paper reports three-dimensional display of conductivity distributions. It discusses the concept of ``stereo-micrographs of conductivity.'' It is shown that a three-dimensional display of the conductivity distribution of thin films is possible by combining two electron mirror micrographs to a stereo-pair. The two micrographs are distinguished solely by the amount of current passing through the specimen. As experimental evidence of the feasibility of three-dimensional ``conductivity pictures'' a stereo-micrograph of a test sample with artificially prepared areas of different conductivities is shown. Limitations and precautions to be observed are briefly discussed.
Neutron Yields from Thick Targets Bombarded by 24-Mev Deuterons and 12-Mev Protons
Authors: Crandall W. E. , Millburn G. P. , Schecter L.
Published: April 2005

The gross yields of neutrons produced by 24-Mev deuterons bombarding Be, Cu, Ta, and U and by 12-Mev protons bombarding Be, Cu, and Ta were measured by detecting the neutrons in a solution of MnSO4 that surrounded the targets. The yields were (in neutrons per μcoulomb): 24-Mev deuterons: Be, 1.85×1011; Cu, 0.55×1011; Ta, 0.52×1011; U, 0.73×1011; 12-Mev protons: Be, 4.1×1010; Cu, 0.61×1010; Ta, 0.15×1010.
Dispersion Relations for Tensor Media and Their Application to Ferrites
Authors: Gourary Barry S.
Published: April 2005

The well-known Kronig-Kramers integral relations between the real and imaginary parts of the susceptibility are generalized to the case where the susceptibility is a tensor. The consequences of the principle of energy conservation are discussed. The case of a ferrite is discussed in some detail.
Solar Radiation and Atmospheric Attenuation at 6-Millimeter Wavelength
Authors: Whitehurst Robert N. , Copeland Jack , Mitchell F. H.
Published: April 2005

A microwave radiometer of the Dicke type for the 6-mm wavelength range has been built and operated to measure radiation from the sun and attenuation in the earth's atmosphere. The total vertical attenuation in the earth's atmosphere on four clear summer days averages 1.2 db. It is presumably due principally to oxygen, since the 6-mm wavelength is well up on one wing of the 5-mm absorption line. The quoted values are in agreement with a line-width constant of 0.02 cm−1. Attenuation in clouds is highly variable. An additional 1 db above the fair-weather value is typical for a thin overcast.

Measurements during the summer of 1956 indicate an effective solar temperature of about 4500°K. This value is appreciably lower than temperatures reported at 7.5 and 8.5 mm, and it favors a model of the lower chromosphere which assumes temperatures well below the optical surface value of 5700°K.
Dynamics of a Spinning Rocket with Varying Inertia and Applied Moment
Authors: Jarmolow Kenneth
Published: April 2005

The dynamic motion of a spinning rocket of varying moments of inertia under the influence of a varying torque is analyzed. The varying moments of inertia result from the rapid expenditure of fuel. The varying torque is produced by a constant rocket thrust asymmetrically applied while the body center of gravity location varies as the fuel burns. Aerodynamic forces are assumed negligible. The analysis is performed through the direct application of Euler's equations, which have a special applicability to this type of problem. The resulting motion is described in terms of Euler angles and resembles the motion of an ordinary top with nonsteady precession. The motion is compared to that of a body of fixed moments of inertia caused by a torque of fixed magnitude. It is shown that the variable aspects of the general problem create important characteristics of the resulting motion.
Electroluminescence Deterioration
Authors: Thornton W. A.
Published: April 2005

Electroluminescence intensity of phosphor layers decreases with running time; this decay can be described by the empirical expression, proposed by Roberts, L=L0/(1+t/t½), where t½ is the time to half-intensity. It is also observed that, during electroluminescence decay at room temperature, (1) photoluminescence remains constant, (2) a component of the dark capacitance decreases in proportion to the light output, (3) photoconductivity and dark conductivity show a similar decrease, and (4) the light output wave form shows marked progressive changes. Also, (5) decay at 80°K proceeds at a much slower rate. An approximate derivation of an expression describing trap or donor depletion by electrolysis serves to correlate the data and the empirical expression in the foregoing.
Magnetic Induction and Coercive Force Data on Members of the Series BaAlxFe12−xO19 and Related Oxides
Authors: Van Uitert L. G.
Published: April 2005

Oxides having the magnetoplumbite structure and a wide range of magnetic properties have been examined. The magnetic saturations of the compositions MIIFe12O19 can be lowered by replacing part of the iron with the ions Al3+, Ga3+, Mn3+, Cr3+, and Ge3+ amongst others. MII in the above formula can be Ba2+, Sr2+, or Pb2+. Calcium can replace these ions in part. Even the samples with magnetic saturations below 200 gauss can be prepared as crystallographically oriented compacts. Contrary to its behavior in ferrites, Ga3+ does not appear to occupy tetrahedral sites in the magnetoplumbite structure.

Evidence is presented for the occurrence of points of magnetic compensation in the BaAlxFe12−xO19 series. As the aluminum contents of the materials increase toward such a point, the ratio 2K/I (where K is the magnetocrystalline anisotropy constant and I is the saturation magnetization) also increases. As a consequence the ferromagnetic resonance frequencies associated with the materials move to higher frequencies, and extremely high coercive forces are realized.
Magnesium-Copper-Manganese-Aluminum Ferrites for Microwave Applications
Authors: Van Uitert L. G.
Published: April 2005

Magnesium-manganese-aluminum ferrites prepared by dry pressing techniques are usually fired in the temperature range between 1350 and 1400°C for extended periods of time to obtain samples having high relative densities. When about ten percent of the magnesium in such a system is replaced by copper, as in the series Mg0.9Cu0.1AlxFe1.75−x Mn0.04O4±, it is possible to obtain samples with high relative densities and dc resistivities by firing in the 1250 to 1300°C range. Such materials are suitable for microwave applications.

The preparation of ferrites of this type is discussed and data presented on the saturation inductions, Curie temperatures, densities, and dc resistivities.
Equipment to Measure the Energy Absorption of Films at High Strain Rates
Authors: Spangler R. D. , Cooper E. B.
Published: April 2005

The design and performance of equipment to measure film toughness under impact loading is described. The measured quantity is the amount of energy absorbed by a film when a ball is projected through it. The velocity of the ball can be varied from about 20 ft/sec to 800 ft/sec. A conditioning chamber permits testing over a temperature range of −40°C to +80°C. Individual tests require a specimen of film of about 1¼×1¼ in. and can be made at the rate of about 2/min. Results are given for films of several commercial materials.
On the Determination of Magnetocrystalline Anisotropy Constants from Torque Measurements
Authors: Kouvel J. S. , Graham C. D.
Published: April 2005

According to simple theory, torque measurements on cubic single-crystal disks should give values for the crystal anisotropy constants, K1 and K2, that are independent of field above some minimum saturating field. Our experiments on {100} and {110} disks of 3¼% silicon-iron, and previous experiments of others, show that this theory is inadequate. In a more refined theory it is assumed that the edges of the disk are not saturated even in high fields. The observed increase in the peak values of the torque with increasing field can be attributed to a very small variation of the net magnetization I as the disk is rotated in the field. This variation must be such that I is largest in the hard directions of magnetization and smallest in the easy directions. Direct observation of the domain patterns on a {100} disk appears to confirm these assumptions. For both {100} and {110} disks, K1′ (the effective value of K1) varies as 1−c/√H over the range 1000 to 20 000 oersteds. The corresponding K2′ values for the {110} disk show a more complicated dependence on H. Values of K1′ found from torque peaks differ somewhat from those obtained from torque slopes; the difference between the smaller K2′ values is much more serious. The discrepancy is attributed to the particular way in which I varies with disk rotation.
Dynamics of a Projectile Penetrating Sand
Authors: Allen William A. , Mayfield Earle B. , Morrison Harvey L.
Published: April 2005

The experiment reported in this paper was designed to obtain data on the dynamics of a nonrotating, conical-nosed projectile penetrating randomly-packed sand. Position versus time measurements for the projectile in sand were obtained by means of a photographic-electronic chronograph developed for the purpose. The striking velocity v0 of all rounds was about 700 m/sec. The negative acceleration of a 5-in. long, 0.50-caliber, 80-gram projectile was found to be roughly expressible by the equation −dv/dt=αv2+βv+γ where the coefficients α, β, and γ are positive constants. This general relation includes as special cases the conventional penetration formulas of Robins-Euler, Poncelet, and Résal. A new theory of penetration is proposed based on the equations: −dv/dt=αv2,v0>v>vc;−dv/dt=βv2+γ,vc>v>0 where the coefficients α, β, γ are positive constants and α<β. An abrupt transition in the drag force that occurs at the critical velocity vc of about 100 m/sec is believed due to transition from inelastic to quasi-elastic impact.
Electrical Resistivity of Cyclohexane as a Function of Temperature and Water Concentration
Authors: Staudhammer Peter , Seyer William F.
Published: April 2005

An equation relating the potential applied to and the current flowing in a liquid dielectric has been derived. The theoretical equation predicts that beyond a certain threshold potential the current is independent of the applied potential and is proportional to the number of ions produced per unit volume per unit time.

Measurements of the number of ions produced in cyclohexane as a function of temperature and water concentration were made. It was found that in the pure state about 200 ions/cm3-sec were produced, while in the water saturated cyclohexane at 50°C about 1.6×105 ions per cm3 per sec were produced. It was concluded that the conductance in the pure state was due to ionization by cosmic radiation.

When the cyclohexane was saturated with water, a large increase in the conductivity was observed as the cyclohexane passed through the freezing point. This behavior corresponds to an increase in the dielectric constant as noted by Seyer and Barrow.
Magnetostriction and Magnetic Anisotropy of MnBi
Authors: Williams H. J. , Sherwood R. C. , Boothby O. L.
Published: April 2005

The magnetostriction of oriented polycrystalline MnBi was found to be higher than any published value for a metal. A value of −250×10−6 was measured parallel to a field of 22 000 oersteds oriented perpendicular to the c axis of the aligned hexagonal crystallites. This field magnetized the specimen to only slightly more than half of saturation. A tentative value of −800×10−6 for the magnetostriction at saturation was obtained by plotting the magnetostriction as a function of (B-H)2 and extrapolating to saturation. Magnetic anisotropy constants of K1=9.1×106 ergs per cm3 and K2=2.6×106 ergs per cm3 were obtained by fitting a calculated curve to the experimental magnetization curve.
Electric Strength and Liquid Structure
Authors: Lewis T. J.
Published: April 2005

Recent work on the electric strength of pure hydrocarbon liquids has shown that the strength is probably determined by the amount of energy lost by conduction electrons exciting molecular vibrations by collisions while moving under the applied field through the liquid. The strength can then be determined in terms of a mean free path for the collisions involved. The present paper attempts to show that the liquid structure, i.e., the molecular arrangements in the liquid phase, is also influencing the strength, and this is illustrated by measurements of the temperature effect on the strength of some n-paraffins, the molecules of which are known to pack with their long axes parallel producing a degree of anisotropy.

Distinct breaks in the electric strength vs temperature characteristics are found, even when density changes are accounted for, and these occur at temperatures which are in very good agreement with similar breaks in the characteristics of other properties such as density, viscosity, and heat capacity. These breaks have already been associated with changes in liquid structure from quasi-crystallinity to molecular libration (245°K) and from molecular libration to free rotation (288–353°K). If molecular orientation takes place in the applied field then the electron energy loss will be different in the three liquid ``phases'' and would account for the observed transitions in the breakdown characteristics.
X-Ray Determination of Conjugate Deformation Twins in Copper
Authors: Sherrill F. A. , Wittels M. C. , Blewitt T. H.
Published: April 2005

Deformation twins related to two separate (111) orientations have been observed in a copper single crystal deformed by tensile extension at 4.2°K. The unambiguous determination of the twin relationships is accomplished by a unique x-ray technique which makes use of a single crystal adapter and Geiger counter methods. The adapter permits the detection and measurement of weakly diffracting reflections and the twin relationships are established by the unique application of geometrical data in a stereographic projection.
Diffraction by an Aperture. II
Authors: Keller Joseph B. , Lewis Robert M. , Seckler Bernard D.
Published: April 2005

The field diffracted by an aperture of any shape is evaluated asymptotically for small wavelengths on the basis of several approximate diffraction theories. These are the Kirchhoff method, its two customary modifications, and W. Braunbek's new modification. In each case, a double integral over the aperture is evaluated asymptotically, and contributions from interior stationary points, edge stationary points, and corners of the edge are obtained. The contributions from points of each type, according to all the theories examined are exactly of the form recently deduced by J. B. Keller using his geometrical theory of diffraction. The edge stationary points and the corners correspond respectively to rays singly diffracted from edges and from corners. For edge-diffracted rays the Braunbek diffraction coefficients alone coincide with those given by the geometrical theory of diffraction, but the Braunbek method does not apply to corner diffraction. None of these methods takes account of multiple diffraction as does the geometrical theory of diffraction.
Hydrodynamic Theory for the Flow of a Viscoelastic Fluid
Authors: Pao Yoh-Han
Published: April 2005

A hydrodynamic theory for the flow of a viscoelastic fluid is formulated and applied. The viscoelasticity is specified in terms of the conventional and well-known relaxation and retardation spectra. Time dependent recoverable strains are defined with respect to convected rotating coordinate axes. The theory is linear to the extent that these strains are small although the over-all displacement gradients of the fluid may be large. The theory is applied to two-dimensional steady-state simple shear flow to predict the variation of the apparent viscosity and the steady-state elastic compliance with shear rate. Pressure flow through a pipe of circular cross section has also been treated.

Previous work of a similar nature is reviewed.
Space Charge Effects in Beam-Type Magnetrons
Authors: Gould Roy W.
Published: April 2005

A theoretical treatment of space charge effects in beam-type magnetron amplifiers and oscillators is given. It is assumed that the beam is relatively thin and that the magnetic field is large. The ``cyclotron waves'' are not treated. A space charge parameter appears in this theory of magnetron-type traveling-wave interaction in a manner which is analogous to the manner in which QC appears in ordinary traveling-wave interaction. A distinctive feature of the space charge waves in the magnetron case is that one increases along the beam and the other decreases along the beam. A simple physical explanation of this effect is given.

This theory is then used to determine the starting conditions of an M-type backward wave oscillator. It is found that when the tube is long in space charge wavelengths there is an appreciable reduction of starting current. When the space charge parameter approaches zero, the solutions found here reduce to the usual two-wave solutions.
Low-Temperature Reactor Irradiation Effects in Metals
Authors: Blewitt T. H. , Coltman R. R. , Klabunde C. E. , Noggle T. S.
Published: April 2005

The effects of structural and chemical defects on the low-temperature (30–50°K) annealing peak in low-temperature reactor-irradiated aluminum and copper were studied. From the fact that the density of reactor-induced defects did not affect the annealing kinetics, it was possible to conclude that the low-temperature annealing process was of the first order without a unique activation energy. The fact fact that both oversized and undersized atoms could suppress this annealing peak led to the conclusion that the radiation-induced defects were more complicated than simple point defects. The suggestion is made that a defect similar to a crowdion must be created by low-temperature neutron irradiation. This data also supports to some degree the viewpoint that a radiation-induced defect, possibly a crowdion, has sufficient knock-on energy to migrate several hundred atomic distances. The experiments also contain evidence which rule out all forms of vacancy-interstitial annihilation.
Low-Temperature Deformation of Copper Single Crystals
Authors: Blewitt T. H. , Coltman R. R. , Redman J. K.
Published: April 2005

Single crystals of copper were deformed at 4.2°K and 77.3°K. At 4.2°K, after a large strain produced by normal slip, jerky flow (discontinuous slip) occurs. From the study of reactor irradiated crystals, it was deduced that a packet of 30 slip lines, each containing 104 dislocations, was released to form each jerk of the discontinuous flow. For samples of certain orientation the region of discontinuous flow was followed by a region of deformation twinning. The fact that deformation twinning was taking place was verified by x-ray methods. The twinning elements were determined to be the (111) plane and the [112] direction. At 77.3°K, discontinuous slip was not observed. In a limited range of orientations, twinning has been observed at 77.3°K. The effects of reactor irradiations on discontinuous slip and on twinning were also studied and it was determined that the occurrence of twinning was unaffected by the irradiations.
Waves on the Surface of a Crystal
Authors: Deresiewicz H. , Mindlin R. D.
Published: April 2005

Surface waves in crystals are investigated for surface orientations and directions of propagation which preclude waves of plane strain. These waves are of importance in the study of very high frequency vibrations of certain crystal plates. It is shown that, in the AT cut of quartz, one and only one surface wave can propagate along the digonal axis. By reduction to the case of orthorhombic symmetry, it is shown that the surface wave is the result of coupling between a surface wave of plane strain and either a face-shear mode or a transverse thickness-shear mode. The former combination is associated with flexural and the latter with extensional vibrations of AT plates. Computation of the wave velocity requires the simultaneous solution of algebraic equations of the third and fifth degrees as opposed to a single cubic equation in the case of waves of plane strain.
Universal Gravity Turn Trajectories
Authors: Culler Glen J. , Fried Burton D.
Published: April 2005

One of the simplest trajectory programs for the powered flight of a missile through the atmosphere is the ``gravity turn,'' which results from simply keeping the propulsive thrust always parallel to the vector velocity. However, even for a ``point mass'' missile, in a uniform gravitational field with constant thrust and no aerodynamic forces, the differential equations for the motion are nonlinear and require numerical integration. To avoid the necessity of doing this computation anew for each missile preliminary design, a method has been found for integrating the equations for the singular case of zero initial velocity. When expressed in terms of appropriate dimensionless variables, the resulting solutions are ``universal'' in the sense that they constitute a good approximation to any gravity turn with a small, nearly vertical, initial velocity. The solutions depend upon two parameters, the initial thrust to weight ratio η and a parameter k which corresponds to the initial ``kick angle'' of nonsingular gravity turns.
Scattering by an Inhomogeneous Solid. II. The Correlation Function and Its Application
Authors: Debye P. , Anderson H. R. , Brumberger H.
Published: April 2005

Experiments on the angular intensity distribution of x-rays scattered by porous materials (hole structures) in the range of small angles are described. It is shown that the scattering can be characterized by an exponential correlation function in the case of a distribution of holes of random shape and size in solid; a theoretical derivation of the exponential function is given for this case. When the correlation function is an exponential, the rule holds that the reciprocal square root of the scattered intensity is a linear function of the square of the scattering angle. The specific surface of the material is determined by the slope of this straight line. Specific surfaces of a number of compositions are calculated from their experimental correlation functions and compared to surfaces based on adsorption measurements.
Relation of Radio Measurements to the Spectrum of Tropospheric Dielectric Fluctuations
Authors: Wheelon Albert D.
Published: April 2005

The size spectrum of isotropic fluctuations in the troposphere's dielectric constant is related to quantities measured by radio means. Two classes of experiments are analyzed: (1) line-of-sight phase and amplitude instability and (2) refractometer measurements of dielectric fluctuations. This analysis is independent of models for the dielectric fluctuations and provides a system from which the spectrum can be estimated from experimental data. The measured quantities are expressed as weighted integrals of the spectrum, many of which may be inverted to give the spectrum directly in terms of the data. Aerial smoothing by the receivers and finite data sample effects are studied, in addition to the basic propagation mechanisms.
Magnetostriction of Aluminum-Iron Single Crystals in the Region of 6 to 30 Atomic Percent Aluminum
Authors: Hall R. C.
Published: April 2005

The spontaneous saturation magnetostriction and the forced magnetostriction were measured on slowly cooled single crystals of the ferromagnetic aluminum-iron alloys in the composition range from 6 to 30 atomic percent aluminum. The value of the first constant of spontaneous saturation magnetostriction at 6 atomic percent aluminum is similar to that at 6 atomic percent silicon in iron. At compositions containing larger amounts of aluminum, the first constant becomes very large; however, near 30% aluminum the constant drops and approaches zero. The second constant of spontaneous saturation magnetrostriction is negative below 17% aluminum, reaches a maximum near Fe3Al, and drops near 30% aluminum.

Values of the isotropic forced-magnetostriction constant below 25 atomic percent aluminum were found to be slightly higher than that for iron but less than that for silicon iron. Above 25% aluminum the isotropic constant became very large. The anisotropic forced-magnetostriction constants were the largest for the single crystal having 29.6% aluminum; a good fit of the experimental data to the calculated curve was found for this alloy.
Resonance Absorption of Neutrons by Thorium Cylinders
Authors: Davis Monte V.
Published: April 2005

The integrated effective resonance neutron absorption cross section of thorium-232 cylinders has been experimentally investigated by danger coefficient measurements in the Hanford Test Pile. The results were interpreted to yield the effective resonance integral as a function of the surface-to-mass ratio of the thorium cylinders. The experiments were extended to determine the Doppler coefficients resulting from heating the thorium in a constant neutron energy spectrum in the reactor.

After correction for 1/v neutron absorption, the effective resonance integral can be approximated as a function of the surface-to-mass ratio by ∫ (σa0)effdE′E′=6.11[1+5.0SM(1−0.87SM)]. The value assigned to the Doppler coefficient of the volume absorption of the effective resonance integral is 1A∂A∂T=(2.3±0.2)10−4/∘C. The results are compared to similar measurements on uranium.
Internal Friction in the Presence of a Static Stress
Authors: Baker George S.
Published: April 2005

The internal friction of pure lead, copper, and aluminum single crystals was measured as a function of an externally applied static biasing stress. The low strain amplitude damping of copper and lead was found to be essentially unaffected by the presence of the static stress. Aluminum differs from lead and copper in that at room temperature, damping is independent of amplitude at low strain amplitudes (ε<10−6). The damping in aluminum becomes strain-amplitude dependent only at higher strain amplitudes. The presence of the static stress causes this amplitude dependence to shift to lower stress amplitudes by an amount comparable to the static stress applied.
Infrared Emission from High-Frequency Discharges in CO2
Authors: Cohen David , Lowe Robert , Hampson John
Published: April 2005

The infrared radiation at about 2.7 μ and 4.3 μ from the E type glow discharge in CO2, powered by external electrodes at 10 Mc/sec, was examined with a lead telluride cell, a lead sulfide cell, and a radiation thermo-couple through appropriate filters. The rf power was pulsed at 5–30 cps. The pressure dependence and power dependence of the emitted intensity, and the efficiency of energy conversion to the two infrared bands were measured. The fast photoconductive detectors indicated a radiation decay time of the order of several milli-seconds after the pulse cutoff, and the decay half-life was measured as a function of various discharge parameters, and also in the presence of Hg vapor and N2O. It is concluded that the vibrational states are excited by a purely thermal process, with no significant enhancement due to collisions with slow electrons.
Electrical Conductivity of Thermally Ionized Air Produced in a Shock Tube
Authors: Lamb Lawrence , Lin Shao-Chi
Published: April 2005

The electrical conductivity of shock-heated air at equilibrium temperature from 3500°K to 6200°K, and at densities of the order of 0.01 NTP, has been measured, using the shock wave-magnetic field interaction technique reported by Lin, Resler, and Kantrowitz. The experimental results indicated that the ionization process builds up quickly behind the shock front, and that the measured conductivity agrees quite well with calculated values based on the equilibrium degree of ionization, the electron diffusion cross sections for the molecular species available in the literature, and on a theoretical estimate of the scattering cross sections for oxygen and nitrogen atoms by Hammerling, Shine, and Kivel based on the Hartree potential with appropriate exchange and polarization terms.
Structure and Characteristics of Silicon Carbide Light-Emitting Junctions
Authors: Patrick Lyle
Published: April 2005

Current-voltage characteristics of SiC p-n junctions have been measured on light-emitting samples prepared in such a way as to minimize leakage at the periphery and through ``blue spots.'' The characteristics of such junctions are found to be very different from those previously reported. We deduce from the characteristics that these junctions have a p-n*-n structure rather than a p-n structure. The high resistivity n* layer is essential for the observed light-emission. This layer, together with the blue spots which short circuit the p-n* junction, determines the form of the reverse characteristic. Two portions of the reverse characteristic take their form from space-charge-limited currents in the n* layer.

A theory is given of the forward characteristic of the p-n*-n structure and compared with the experimental I-V curve. The theory permits one to obtain a value of the thermal energy gap from a forward characteristic at a single temperature. From a fit of our data the energy gap is found to be 2.83±0.1 ev at room temperature.

Results of some experiments on crystal growing are presented and an explanation of the manner of growth of light-emitting junctions is suggested.
Application of Luminescence Changes in Organic Solids to Dosimetry
Authors: Schulman James H. , Etzel Howard W. , Allard James G.
Published: April 2005

The degradation of photoluminescence in anthracene and in naphthalene has been studied under gamma-ray and electron irradiation over the range 3×105 to 2×108 rep. For both materials the variation of brightness with Co60 gamma-ray dose D, in rep, may be represented by (I/I0)=(1+AD)−1, where A=8.5×10−7 for anthracene and A=14×10−7 for naphthalene. Irradiation also produces a radiophotoluminescence in naphthalene, with emission in the visible spectral region. Both the degradation and radiophotoluminescence are stable with time at room temperature. The employment of these effects for dosimetry is discussed.
Hall Effect and Ferromagnetism of Very Thin Nickel Films
Authors: Coren R. , Juretschke H. J.
Published: April 2005

Hall effect measurements have been used to determine the two Hall constants and the magnetic properties of nickel films less than 100 A thick at room temperature. The extraordinary Hall constant R1 is found to be very much larger than in bulk nickel. In the thicker films, R1 shows the resistivity dependence predicted by Karplus and Luttinger. For the thinner films, the deviation of the measured initial Hall slope from the value thus predicted is taken as a measure of the hardness of magnetization in the direction normal to the film plane. The saturation magnetization obtained in this manner, and its variation with film thickness, agree fairly well with values found by other methods. For our thinnest films the direction normal to the film plane is one of very hard magnetization.
Luminescent Gas Flow Visualization for Low Density Wind Tunnels
Authors: Kunkel W. B. , Hurlbut F. C.
Published: April 2005

At static pressures below a few millimeters of mercury the optical thickness of wind tunnel gas streams becomes insufficient for conventional flow visualization techniques in aerodynamic testing. In the University of California low density wind tunnel, where the free stream static pressure is of the order of one-tenth of one millimeter of mercury, use has been made of various gaseous afterglow phenomena in the visualization of low density flows. The present paper describes the successful application of afterglows in flows of nitrogen, air, argon, and helium.

On the basis of recent tests the range of practicability of the enriched air glow technique was found to extend from Mach 2 to Mach 4. The argon and helium glows were found to be useful in the range Mach 1.3 to Mach 2. Discussion of the ranges of applicability and of other aspects of the observed glows is supported by representative glow photographs.
Studies of Molecular Scattering at the Solid Surface
Authors: Hurlbut F. C.
Published: April 2005

Experimental studies of molecular scattering at the gas-surface interface are described in which molecular beams of N2 were scattered at surfaces of steel, aluminum, and glass. Polar surveys of the issuing molecule flux indicate the scattering to be well represented by a cosine distribution in most cases. A moderate deviation from such a distribution was observed in the case of the glass-N2 interaction.

It is shown how measurements of scattering at the surface may be used to derive values of the momentum transfer coefficient, f(s), in a rarefied gas flow where s is defined as the ratio of the mass speed of the flow to the most probable thermal speed of the molecules. In order to complete the calculation where scattering information alone is available from experiment, assumptions must be made relating to the energy exchange at the surface. In the case of the present calculation, where a surface interaction model was formed in part from the glass -N2 scattering data, two extremal assumptions relating to the energy exchange lead to values of f(s) of approximately 0.97 at s=0.1.
Magnetization Reversal in Thin Films at Low Fields
Authors: Conger R. L. , Essig F. C.
Published: April 2005

A statistical theory of magnetization reversal in thin films for reversing fields less than the anisotropy field is presented in which it is assumed that reversal takes place by domain wall motion. The number of moving domain walls is determined by a simple statistical model which allows for the random nucleation of walls as the reversing field increases. Experimental data are presented in support of this theory.

Two equations for the velocity of a domain wall in a thin film are presented; these arise since two alternative forms of the equation of motion of the magnetization vector are considered.
Teapot Effect
Authors: Keller Joseph B.
Published: April 2005

When tea is poured from a teapot it often runs along the under side of the spout rather than falling into the cup. Recent experiments have shown that this ``teapot effect'' is not due to surface tension nor adhesion, as many have supposed. Therefore, a new explanation is presented which is based upon certain exact solutions of the hydrodynamic equations and which seems to account for the effect. In connection with the analysis some new fluid flows with free boundaries are obtained. In addition a method more satisfactory than the usual one is used to study the stability of these flows.
Damage to Silicon Produced by Bombardment with Helium Ions
Authors: Gianola U. F.
Published: April 2005

Some of the effects of bombarding a silicon single crystal surface with 3×104 electron volt helium ions have been examined experimentally. The surface recombination velocity was found to be increased by more than two orders of magnitude, but could be restored to its original value by the removal of approximately 1 μ of surface material. This is believed to correspond to the total depth of material affected by the bombardment, and is in fair agreement with a theoretical estimate of the range of the helium ions. Electron diffraction data shows that the effect of bombardment is to convert the surface layer to a quasi-stable amorphous form, which may be partially restored to the crystalline state upon annealing. The amorphous material is soluble in aqueous hydrofluoric acid, and its thickness has been measured by an interferometric technique. It is found to be approximately one tenth of the total thickness of silicon affected, depending on the bombardment dosage. The effect of annealing upon the diode characteristics of point contact diodes made with bombarded silicon have been studied. The general result is that the characteristics tend to revert to those of an unbombarded diode, as expected from the electron diffraction data. These experiments are discussed in terms of radiation damage theory.
Domain Wall Orientations in Silicon-Iron Crystals
Authors: Graham C. D. , Neurath P. W.
Published: April 2005

The stable orientation of a 180° ferromagnetic domain wall in a cubic crystal with <100> easy directions is calculated as a function of crystal orientation for a sheet specimen with a <100> direction parallel to the surface. The effect of the second crystal anisotropy constant K2 on the domain wall energy is considered and shown to be negligible if |K2| <K1. If the crystal surface is a {110} plane, there are two equivalent stable domain wall positions, with the wall making an angle of ±32° with the normal to the specimen surface. If the crystal surface is a {100} plane, the domain wall lies normal to the surface. These results are changed if a stress is applied to the sample. Experimentally determined domain wall orientations agree with the calculated positions.
High-Velocity, Light-Gas Gun
Authors: Crozier W. D. , Hume William
Published: April 2005

A new range of muzzle velocities has been achieved by propelling a projectile in a gun barrel by a column of hydrogen or helium instead of the conventional powder gas. The first gun built, the design of which probably was far from optimum, yielded muzzle velocities in excess of 12 000 ft/sec with spherical and cylindrical steel projectiles.
On Creep and Relaxation
Authors: Hopkins I. L. , Hamming R. W.
Published: April 2005

The creep function for the ``National Bureau of Standards'' polyisobutylene at 25°C is calculated from the relaxation function, using the integral equation connecting them. The calculated function is shown to be correct in its initial slope, to satisfy the inequality φ(t)ψ(t)⩽1 throughout, and to approach satisfactorily the independently determined asymptote.
Supersonic Drag of Spheres at Low Reynolds Numbers in Free Flight
Authors: May Albert
Published: April 2005

Values of the drag coefficient have been obtained for spheres in the region 1.5<M<3.0, 350<Re<3000 in the Pressurized Ballistics Range at the Naval Ordnance Laboratory. This region borders, on the low Reynolds number side, one investigated previously. The low Reynolds numbers were obtained by using air pressures of about 7 mm Hg and spheres as small as 132 in. in diameter. A contour map of CD on Mach number and Reynolds number coordinates has been derived from the experimental data.
Dielectric Strength of Polyethylene at 3300 Megacycles
Authors: Farber Herman , Griemsmann John W. E.
Published: April 2005

The dielectric strength of polyethylene at 3300 megacycles per second was determined as being 16.8 kv/mil, 13.1 kv/mil, and 6.0 kv/mil at 26°C, 57°C, and 95°C, respectively. These values are the same as those reported for measurements using a dc electric field. The electrode system, a high Q resonator, and the experimental procedures were designed to reduce the effects of secondary factors such as heating and corona.