bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Gases at Very Low Pressures by Using the Omegatron Spectrometer
Authors: Wagener J. S. , Marth P. T.
Published: April 2005

A mass spectrometer of the omegatron type is described by which gases up to mass number 44 can be detected and analyzed at pressures as low as 10−10 mm. Performance characteristics of this spectrometer are given together with a description of auxiliary vacuum equipment with which it was used for studies of high vacuum phenomena. Results are given for analyses of: 1. the gas evolving from a number of materials used in high vacuum work; 2. the residual gas existing above getters of the flash type; and 3. the residual gas in television picture tubes. The gases found in the residual gas mainly are argon, methane, and water vapor.
Radiation Due to Adhesive Breaks between High Polymers and Glass
Authors: Williams R. C.
Published: April 2005

Adhesive breaks (separation at the interface) have been obtained between high polymers and glass that require no external mechanical equipment to induce break. Visible light is emitted during these breaks. The polymers are contained in Pyrex vials that are immersed in a 125°C oil bath. After a nominal polymerization period, the polymers are removed from the bath. The adhesive breaks occur while the polymer-glass system is cooling toward room temperature. The properties of the light due to these breaks have been studied with a photomultiplier, pulse-height discriminator combination. The wavelength of the light was measured spectrographically and the internal temperature of the polymers was monitored during the cooling process.
Time Dependence of Mechanical Breakdown in Bundles of Fibers. I. Constant Total Load
Authors: Coleman Bernard D.
Published: April 2005

A previously published phenomenological theory of the statistics and time dependence of the creep failure of oriented polymeric filaments is here applied to bundles of filaments. The mathematical apparatus of the theory of stochastic processes is used to calculate relationships between the strength of filament bundles and the strength of their component filaments. The present paper is concerned with the case in which the total load on a given bundle is maintained contant in time. Two limiting idealized cases are discussed—bundles with no interfiber friction (called ``ideal bundles'') and bundles with very strong interfiber friction (called ``tight bundles''). Only the first case is discussed rigorously. It is assumed throughout that the bundles are composed of filaments which have been randomly selected from a first-order ensemble. The principle mathematical result is that, subject to certain rather general conditions, in the limit as the numbers of filaments, N, becomes infinite the distribution of lifetimes for an ideal bundle becomes normal with a coefficient of variation that is proportional to N−½. The present theory predicts an appreciable loss in strength upon the arrangement of filaments into bundles.
Theory of the Rebatron—a Relativistic Electron Bunching Accelerator for Use in Megavolt Electronics
Authors: Coleman Paul D.
Published: April 2005

Highly bunched electron beams in the 1 to 3 million electron volt range, having a sharply peaked velocity spectrum, represent a powerful attack on the submillimeter wave (100 to 3000 kmc/sec) generation problem. In this paper the theory of a rebatron for producing a high-energy beam, wherein both the current wave form and the velocity distribution function approach delta functions, is presented. Computations indicate that the emergent 1.5-Mev beam has an appreciable harmonic content up to harmonics as high as the 1000th and has a velocity spread of 0.07% for the electrons of interest. Pulsed beam powers of the order of 100 000 w should be possible using a 3 kmc/sec rebatron.
Retardation Effects Caused by Ferrite Sample Size on the Frequency Shift of a Resonant Cavity
Authors: Tompkins J. E. , Spencer E. G.
Published: April 2005

Using perturbation theory, expressions are derived for the frequency shift of a circularly polarized resonant microwave cavity upon insertion of a ferrite sample small compared with the wavelength. Retardation effects are considered in deriving the rf field h2 internal to the sample. By integrating h1·h2dv (where h1 is the applied rf field) over the sample volume, a closed-form expression is obtained for the cavity frequency shift. The theory is applied to the magnetic resonance in ferrites. The calculated magnetic resonance line shape is found to remain symmetrical as the sample size is increased. Retardation effect, thus, does not explain the asymmetry of the resonance lines which have been observed for polycrystalline ferrite. Results of the theory are also compared with measurements on a single crystal of ferrite having the rather large maximum permeability loss term of 100. Theoretical and measured values are in close agreement.

The theory is also compared with the somewhat different results of other recent theoretical treatments, in which an approximate expression for an effective magnetic dipole moment for the sample was computed, rather than integrating the internal rf fields over the volume of the sample.
Electron Mirror Microscopy of Magnetic Domains
Authors: Mayer Ludwig
Published: April 2005

Electron mirror microscopy is a rather novel research instrument. It has recently been demonstrated that it can provide micrographs not only of the relief structure of a specimen but also of such purely electrical properties as contact potentials, conductivities, surface charges, and even space charges. This paper deals with the feasibility of electron mirror microscopy for pictorial representation of magnetic properties in general, and of magnetic domain patterns in particular. It is shown that electron mirror microscopy is actually a feasible and independent method for electronically depicting magnetic patterns. The section of the paper dealing with experimental work begins with magnetic specimens of artificial nature, e.g., a recorder head, containing one or more linear magnetic dipole stray fields which are controllable. After establishing the basic facts of magnetic contrast formation with this type specimen, the paper reports on experiments conducted with specimens of barium ferrite and nickel ferrite containing actual magnetic domain patterns. Samples of electron mirror micrographs of domain patterns of these materials are shown and compared with domain patterns of the same specimen areas obtained by the conventional powder technique. The identical nature of the configurations on both micrographs provided final proof of the feasibility of electron mirror microscopy in depicting magnetic patterns. Criteria required to distinguish magnetic patterns from those of electrical or relief origin are derived from the experimental findings and are verified by elementary theoretical considerations about magnetic contrast formation in electron mirror microscopy.
Multiple Shock Production
Authors: Drummond W. E.
Published: April 2005

A dynamical theory is developed for the explosive production of multiple shocks in metals which undergo a phase transition. In addition to the formation of two compressive shocks, it is found that a rarefaction shock is also produced which will overtake one of the compressive shocks.
Preparation of Polycrystalline Ferrimagnetic Garnet Materials for Microwave Applications
Authors: Wolf W. P. , Rodrigue G. P.
Published: April 2005

A simple chemical method is described for preparing high density, polycrystalline, magnetic garnets suitable for microwave applications, having the formula 3M2O3·5Fe2O3, where M is a rare earth from Sm to Lu, or yttrium. The effect on the dielectric loss of small deviations from the ideal M:Fe composition was investigated, and it was found that, in contrast to ferrites having the spinel structure a small deficiency of iron gives rise to a considerable increase in the loss. The loss tangents for stoichiometric samples were of the order of 0.002 at 20 mc. The effect of porosity on the ferrimagnetic resonance line width was investigated in several samples of the yttrium garnet and it was found that the observed variation could be accounted for almost entirely by Schlömann's theory of pore broadening, with only a small contribution from anisotropy. The narrowest line observed at room temperature, on a sample having 96% of the theoretical x-ray density, was 50 oersteds. The trend of the results indicated that a 100% dense sample should have a line width of about one-half this value.
Critical Study of the Optical and Mechanical Properties of Glass Fibers
Authors: Bateson Sydney
Published: April 2005

The cooling rate for fine glass fibers in the 6–16 μ diameter range has been calculated by means of a new cooling equation. Typical strength vs diameter data are compared with the ratio of quenching time to the Maxwell relaxation; ts/τ. Strength increases rapidly for ts/τ ≤ 1.0 and τ is most probably of the order 10−4 sec at 1100°C. The refractive index decreases slightly in the critical region but the change does not indicate a significant rise in the fictive with increased quenching. For this reason structural changes are considered of secondary importance as a factor contributing to high strength. New strength measurements of glass fibers fit a distribution law with reasonable accuracy. It is therefore concluded that the flaw theory of high strength is valid. The influence of ``hydrostatic'' cooling upon flaw generation is discussed.
Fracture Phenomena and Molecular Weight in Polymethyl Methacrylate
Authors: Newman Sanford B. , Wolock Irvin
Published: April 2005

Tensile specimens of cast polymethyl methacrylate of five different molecular weights varying from 90 000 to 3 160 000 were broken by static loading and the fracture surfaces compared. The fracture appearance was fairly constant for a given molecular weight but there was a continuous development of certain features and a retrogression of others with changes in molecular weight. The series which was developed by varying the molecular weight was similar in appearance to that developed by Zandman by varying the rate of loading of polymethyl methacrylate. The higher molecular weight specimens corresponded in appearance to those obtained at the lower rates of loading. In the higher molecular weights, failure by ``separation'' was most marked whereas fracture by ``pulling out'' of polymer masses became more important at the lower molecular weights.
Initial Wave Phenomena in a Weak Spherical Blast
Authors: Campbell R. Gordon
Published: April 2005

The initial waves created by the sudden release of a spherical volume of compressed air in a limitless environment of air at constant state are predicted analytically using an iterative method of solution by characteristics for the case of a specific weak blast. Pressure-time records have been obtained within the compressed air and in the immediate environment of the spherical blast during its early stages using a pyramidal shock tube. The experimental results corroborate the existence and position in time and space of the inner and reflected shock waves predicted analytically. The present results for a weak spherical blast are in substantial agreement with the analytical and experimental results obtained previously by other investigators for a considerably more powerful blast. The shock tube, in pyramidal or conical form, appears to offer considerable promise for further research on spherical blast phenomena.
Thermionic Emission from Barium Activated Molybdenum
Authors: Rittner E. S. , Ahlert R. H.
Published: April 2005

Measurements are presented of (a) the emission density from clean and oxygen covered molybdenum surfaces as a function of the arrival rate of Ba or of Ba+BaO and of (b) the migration length of Ba and of Ba+BaO over oxygen covered molybdenum surfaces. The emission density is comparable to that obtained from similarly activated tungsten surfaces, but the minimum arrival rate of total barium required for complete surface coverage is much higher than for the tungsten case. The migration length is also comparable for the two systems.
Laminar Flow in an Annulus with Porous Walls
Authors: Berman Abraham S.
Published: April 2005

When certain restrictions are applied to the radial component of flow it is possible to obtain an exact solution to the Navier-Stokes equations describing the steady-state flow of an incompressible fluid in an annulus having porous walls. The effects of such restricted radial flows on the characteristics of the flow field have been examined.
Use of Complex Conductivity in the Representation of Dielectric Phenomena
Authors: Grant F. A.
Published: April 2005

When the dc conductivity of the material is not negligible, the low-frequency part of the Cole-Cole plot loses its distinctive shape. A complementary representation in terms of complex conductivity is proposed, in which a simple Debye mechanism again results in a semicircle. However, a nonzero value of dc conductivity does not cause this representation to lose its distinctive shape in the low-frequency range. Examples of the utility of this representation are given.
Stress-Strain Equation for Rubber in Tension
Authors: Claxton W. E.
Published: April 2005

A stress-strain equation is derived for a homogeneous, isotropic material with the assumptions that for any given homogeneous simple tensile strain, the components of the stress tensor are to the first approximation linear, homogeneous functions of the components of the strain tensor and that no volume change occurs during the deformation. Utilizing the dependence of Poisson's ratio upon the extension referred to the initial coordinates, one elastic coefficient, C12, is found to be sufficient to roughly characterize the first stretch stress-strain curve. Although experimentally this elastic coefficient is found to be essentially constant for extensions greater than 250% its value increases rapidly as zero extension is approached. This behavior agrees qualitatively with data by Blanchard and Parkinson as to the distribution of secondary bond strengths, wherein they found a large number of relatively low-energy bonds which would be effective only at small extensions in contributing to modulus reinforcement. Various aspects of stress strain and cure behavior are examined with the derived equation as a basis.
Birefringence Changes during Retraction of Oriented Polystyrene Monofilaments. III. Correlation with Internal Stress Changes
Authors: Rudd J. F. , Andrews R. D.
Published: April 2005

The changes in average birefringence and internal stress during retraction at 85°C have been measured for four different oriented polystyrene monofilaments. The data for the different filaments all appear to fall on a single curve when plotted as internal stress vs birefringence. Data on internal stress and birefringence obtained for thirteen different oriented filaments (including the four above) in their initial uncontracted state also fall on the same curve. This is in marked contrast with the lack of correlation obtained in Part I where it was attempted to relate birefringence to elongation parameters. Evidently birefringence is related most directly to internal stress rather than elongation, and in fact provides a direct measure of the internal stress. This simple relation seems to be essentially independent of the stress-time-temperature history of the samples during orientation. Measurements on an additional filament which had a very nonuniform birefringence distribution (studied also in Part II) indicate that internal stress should be correlated with area average rather than diameter average birefringence, in cases where such a distinction is necessary. The internal stress-birefringence curve is not linear, contrary to theoretical predictions based on the simple kinetic theory of rubber elasticity. Non-Gaussian chain statistics may explain this nonlinearity. The present results indicate that birefringence provides a more useful index of molecular orientation than measurements of total amount of retraction.
Apparatus for the Measurement of Shear Modulus and Internal Friction between 4.2 and 100°K
Authors: Sinnott K. M.
Published: April 2005

An apparatus has been constructed to measure the shear modulus and logarithmic decrement of polymers from 4.2 to 100°K. The apparatus consists of a small torsion pendulum suspended on a rigid support at the bottom of a large glass Dewar vessel. After cooling to 4.2°K with liquid helium, the pendulum warms up at an initial rate of 0.1° per minute. Torsional oscillations of the pendulum are excited electrically and recorded photographically. The estimated accuracy of the modulus and logarithmic decrement is ±5.0%.

Measurements of the shear modulus and logarithmic decrement have been made, from 4.2 to 100°K, on a series of tetrafluoroethylene-hexafluoropropylene copolymers.
Dynamic Mechanical Properties of Polyvinyl Stearate at Audio-Frequencies
Authors: Fitzgerald Edwin R.
Published: April 2005

Measurements of the complex shear compliance (J*=J′−iJ″) of polyvinyl stearate at frequencies from 50 to 5000 cps have resulted in the discovery of several sharp resonances in the compliance as previously described. The effects of temperature and static stress normal to the direction of the dynamic shearing stress have now been studied for this material. The two principal resonances observed at 25°C were located at (1) 180 and (2) 500 cps. At successive temperatures of 30, 36, and 42°C the first resonance remained essentially unchanged, but the second resonance shifted to higher frequencies and decreased in magnitude until it virtually disappeared at 42°C. A return to 25°C and a reapplication of a slight static stress resulted in the return of the second resonance (at 525 cps). At successively increasing static stresses corresponding to compressions up to 1.8% the second resonance now decreased in magnitude and shifted to higher frequencies. The first resonance disappeared at a static compression of 0.8%. Similar effects of static stress were observed at room temperature (∼25°C) on a second set of samples of different dimensions. The reversibility of the effects of static compression were demonstrated by the second set of samples where for example, a resonance originally present at 2.8% static compression disappeared at 3.7% and reappeared when the static compression was reduced to 3.1%. The reversible nature of the effects of static stress seems to preclude the possibility of an explanation of the resonances in terms of changes in dislocation density.
Dynamic Stability of a Self-Pinched Discharge
Authors: Wyld H. W.
Published: April 2005

The stability of a rapidly contracting self-pinched discharge (fast pinch effect) is studied using three different models for the plasma dynamics: (a) the free particle model; (b) the snowplow model; (c) the shock wave model. For each model the growth in time of a small perturbation on a time-dependent unperturbed solution of the equations of motion is obtained. It is shown that the free particle model and the shock wave model predict instabilities. The instabilities are rather mild, the instability times being of the order of the pinch time itself. The snowplow model predicts stability for the initial stages of the pinch, although instabilities probably develop later on.
Multiple Stage Thermoelectric Generation of Power
Authors: Harman T. C.
Published: April 2005

The efficiency equation for any number of thermoelectric generators thermally in series is derived. The design relationships for maximum efficiency and for maximum power transfer of a multiple stage thermoelectric generator are also given. Since the efficiencies are approximately additive, an appreciable increase in generator efficiency is anticipated by use of multiple stages.
Adiabatic Elastic Moduli of Single Crystal Alpha-Uranium
Authors: Fisher E. S. , McSkimin H. J.
Published: April 2005

The adiabatic elastic moduli at 25°C for single crystal alpha-uranium are reported here as derived from measurements of high-frequency ultrasonic wave velocities. A detailed description is given of the specimens used, and of the technique employed for obtaining small plates of proper orientation suitable for the problem. Although the specimens were small the technique of measurement produced results of relatively good precision, as evidenced by the numerous cross checks obtained. Best values of the moduli and the estimated probable errors are given.

The elastic stiffness moduli in units of 1012 dynes/cm2 are as follows: c11=2.147 ±0.14%,c12=0.465±0.6%,c13=0.218±1.5%,c22=1.986±0.14%,c23=1.076±0.34%,c33=2.671±0.14%,c44=1.2444±0.10%,c55=0.7342±0.10%,c66=0.7433±0.10%.
Germanium Diffused Minicrystals and their Use in Transistors
Authors: Lesk I. A. , Coffman R. E.
Published: April 2005

The diffused minicrystal process yields a germanium drift p-n-p bar-type transistor structure that has fewer practical limitations on emitter, base, and collector resistivities and on base width, than other processes used to make transistor bars for use in high-frequency transistors. Unneutralized power gains greater than 40 db at ½ mc have been commonly attainable with transistors made using bars having 0.1-mil base widths. Although the p-n-p bars are inherently usable to very high frequencies, base lead overlap capacities have thus far limited the application of early developmental units in this region.
Evidence for Vacancy Clusters in Dislocation-Free Ge
Authors: Tweet A. G.
Published: April 2005

This note reports evidence for the existence of vacancy aggregates in Ge crystals. When dislocations are absent over volumes of the order of cubic centimeters the crystal etches much more rapidly than when dislocations are present. This enhanced etching behavior can be eliminated by appropriate heat treatment at 800°C. Ridges of normal etching rate have been observed traversing the rapidly etched areas in 〈110〉 directions. Etch figures, usually spiral dislocations, are always associated with these ridges. Ridges are not observed in completely dislocation-free crystals.
Ion Induced Reemission of Noble Gases from a Nickel Surface
Authors: Carmichael J. H. , Trendelenburg E. A.
Published: April 2005

Each of the noble gases, He, Ne, A, and Kr, has been ionically pumped with an energy of about 100 ev into a nickel target and has been subsequently released by a similar bombardment using a different noble gas. A mass spectrometer permitted the measurement of both the reemission of the trapped atoms and the trapping of the bombarding particles. The reemission mechanism is described in terms of a simple model which assumes that the trapped atoms are released by the bombarding particles through a mechanism of sputtering of either the target material or the trapped gas or a combination of both. The experimental results are in agreement with the model. A direct replacement of a trapped atom from its trapping site by a bombarding particle is shown to be a relatively unimportant factor in the reemission process. Measurements of the reemission rates of the trapped atoms have yielded information concerning the depth distribution of the trapped atoms in the nickel target. In particular, saturation of the depth distribution has been observed for Ne, A, and Kr at concentrations below one equivalent monolayer while He showed no such effects at the highest concentrations used, which corresponded to approximately 15 equivalent monolayers.
Enhanced Cu Concentration in Ge Containing Ni at 500°C
Authors: Tweet A. G. , Tyler W. W.
Published: April 2005

Penning has shown that at 500°C, Cu penetrates into Ni-doped Ge (containing ∼1016 Ni atoms cm−3) to a concentration more than 10 times its thermal equilibrium value. We have confirmed this observation and extended the experiments with the following results. At 500°C the rate of Cu64 penetration (in Ni saturated samples) indicates an effective diffusion coefficient Deff of ∼2×10−8 cm2/sec and a saturation density, n0, of ∼1016/cm3. No detectable Cu penetration occurs after 10 hrs at 400°C. The Cu penetration at 500°C is independent of dislocation density in the sample and also independent of whether or not the Ni has been previously precipitated. The extra Cu is not electrically active. We have similarly studied the rate of mixing of ordinary Cu and Cu64 by diffusion in Ge samples at 500°C and find that Deff for this process is again ∼10−8 cm2/sec. From these experiments we conclude that Cu penetration in Ge is not responsible for the 0.04-ev energy level which appears during the early stages of Ni precipitation at 400°C, as Penning suggests. The enhanced penetration of Cu64 observed at 500°C may be interpreted as resulting from exchange between interstitially diffusing Cu64 and precipitates of either Ni or Cu.
Heat of Formation of BaC2
Authors: Hoch Michael
Published: April 2005

The heat of formation of BaC2 was determined by measuring the Ba pressure above BaC2+C using the Knudsen effusion method. The heat of formation of BaC2 from the elements is ΔHf°298 = −12.1±4 kcal/M.
Hardness of Neutron-Irradiated Diamonds
Authors: Damask A. C.
Published: April 2005

The amount of wear of neutron-irradiated diamonds relative to unirradiated ones is compared after a standard grinding against silicon carbide. It is found that the amount of wear increases with increasing irradiation, i.e., the diamonds become softer with increasing irradiation. Measurements of density show that it decreases with increasing irradiation. The decrease of cohesive energy of an irradiated diamond is estimated from the number of broken bonds and the strain energy of the density change. The experiments indicate that dislocation motion is not responsible for the wearing of diamonds.
Dynamics of Electron Beams from Magnetically Shielded Guns
Authors: Ashkin A.
Published: April 2005

The dynamics of electron beams from magnetically shielded guns is examined in detail both experimentally and theoretically. The electron orbits and beam shape variations are investigated with an electron beam analyzer which measures current density variations and transverse velocity. The existence of rings of charge that move through the beam and the gradual reduction in beam scalloping with length are demonstrated. It is shown that simple energy considerations plus an account of the role of transverse thermal velocities is sufficient to account for the experimentally observed features of beam behavior in the limit of negligible space charge. In the presence of space charge the beam behavior is qualitatively unchanged except for some defocusing and precession of the electron orbits provided that the magnetic field is at least several times the Brillouin field.
Effect of Torsional Stress on the Electrode Potential of Copper
Authors: Nobe Ken , Seyer William F.
Published: April 2005

The emf of a galvanic cell which consisted of a stressed metal electrode and an unstressed metal electrode was measured. The experimental data showed that for low torsional stresses there was a parabolic relationship between the emf and the torsional stress.

It was observed that the stressed electrode was more anodic with respect to the unstressed reference electrode in agreement with the majority of the previous investigations.

Experimental data of emf and torsional stresses for B & S gauge 12, 14, and 16 hard-drawn copper wires are presented.
Revealing Dislocation Sites in Aluminum by Transmission Electron Microscopy
Authors: Robinson D. L.
Published: April 2005

The occurrence of dislocation sites along grain boundaries is shown by transmission electron microscopy. Small thin sections of aluminum for these studies were obtained by electrolytic oxidation, with subsequent dissolution of the oxide. Dislocation sites along grain fragments in cold worked aluminum have been observed which, by Cottrell's formula, indicate grain orientation differences greater than 2° of arc. This method of examination makes possible the observation and analysis of dislocations in metals where boundaries are at other than extremely low angles of crystal misorientations. Also, it has been found useful for following the movement of dislocations within grains of the material and their migration to grain boundaries.
Parametric Amplification of Space Charge Waves
Authors: Ashkin A.
Published: April 2005

By modulating a beam strongly with a high-level signal, called the ``pump'' signal, a low-level space charge wave of another frequency imposed on the beam can be parametrically amplified. With the pump frequency twice the signal frequency, 13-db gain per plasma wavelength has been observed in a movable cavity experiment. Over a 10-in. length of beam the signal has been observed to increase 41 db. When the imposed signal wave's frequency is not exactly half the pump frequency, the beam generates another wave called the ``idler'' such that ωsignal+ωidler=ωpump with both signal and idler growing exponentially with distance along the beam. In another experiment with the pump frequency lower than the signal frequency, the signal was observed to increase by 30 db over a 9.2 in. length of beam.
Electrophotoluminescent Amplification
Authors: Halsted R. E.
Published: April 2005

Alternating electric fields can modify the time distribution of luminescent recombination in sulfide-type phosphors with the expenditure of less electrical energy than is contained in the fluctuating component of the emitted visible radiation. Within the range of excitation and electrical signal input conditions where this is true, the phosphor sample may be regarded as an amplifier deriving its power from incident radiation, which can convert an applied electrical signal into an output light signal with energy gain and frequency fidelity.
Theoretical Surface Conductivity Changes and Space Charge in Germanium and Silicon
Authors: Mowery V. O.
Published: April 2005

Graphs are presented displaying predicted surface conductivity changes as a function of resistivity for various values of surface potential, and space charge as a function of resistivity for the same range of surface potential, in germanium and silicon. The curves display the trends of the two properties over wide resistivity ranges and are particularly convenient for obtaining theoretical field effect curves. A brief discussion of values for the electrical properties of germanium and silicon is included.
Measurements of Quenching Stresses in a Bearing Ring by Interference Fringes
Authors: Mura Toshio , Yoshimoto Hiroshi
Published: April 2005

Measurements have been made for quench induced residual stresses in a ring of bearing steel. The stress distributions vary along the radial direction r and the axial direction z. The mean values of the axial stresses depend on r only and were obtained previously. The deviations of the residual stresses from the mean as a function of z are found at two radii. An interferometric method is used to detect the deflections of the ring, and the spatial variation is obtained by etching one surface in uniform steps. The stress distributions obtained had typical residual stress shapes, and were compression near the surfaces and tension in the middle. In a ring the mean values do not vanish, but the deviations from the mean are found to be small compared to the mean values. This indicates that the radial temperature gradient dominates in determining the stress distribution, regardless of the size of the axial temperature gradient.
Internal Friction in Aluminum at Low Temperatures
Authors: Filmer A. J. , Hutton G. J. , Hutchison T. S.
Published: April 2005

Preliminary measurements at 40 kc of the internal friction of 99.992% aluminum as a function of temperature yield a number of attenuation maxima at temperatures between 90°K and 300°K. These maxima are unlike the cold-worked induced peaks, first reported by Bordoni. They appear to be of two types, a broad maximum at about 225°K and a series of very sharp peaks at lower temperatures. The latter are tentatively associated with the break away of dislocations from minor pinning points.
Low-Temperature Irradiation of n-Type Germanium
Authors: Cleland J. W. , Crawford J. H.
Published: April 2005

The rate of change of conductivity of n-type single crystal plates of germanium at a temperature of ∼16°K during fast neutron irradiation is enhanced over that previously observed at higher temperatures. Annealing studies subsequent to irradiation reveal no evidence of thermally unstable defect states between ∼10 and ∼95°K. Annealing above ∼95°K indicates the presence of thermally unstable minority carrier traps of the type previously observed following irradiation at 120°K. The enhanced decrease in conductivity at 16°K compared to that observed at higher temperatures is believed to reflect a greater rate of introduction of defects, many of which anneal at temperatures above ∼95°K.
Arrangements of Dislocations in Plastically Bent Silicon Crystals
Authors: Patel J. R.
Published: April 2005

Dislocations introduced into single crystals of silicon by plastic bending at an elevated temperature have been studied quantitatively by the etch-pit technique. The average etch-pit density after deformation is approximately two to three times higher than the calculated dislocation density. Prolonged annealing of the deformed samples at a temperature close to the melting point results in polygonization or the alinement of etch pits perpendicular to the active slip planes. Satisfactory agreement was obtained between the densities of etch pits in the annealed and polygonized specimens and the predicted dislocation densities. Piled-up horizontal arrays of etch pits have been observed in lightly bent samples. The value of yield stress obtained from the geometrical distribution of these arrays is an order of magnitude below the reported experimental values. Dislocation lines in single crystals deformed at 1000°C have been revealed by the technique of copper decoration. Examination of the decorated samples by infrared transmission microscopy revealed that the dislocation lines lie in the [211] direction.
Generation Recombination Noise in Intrinsic and Near-Intrinsic Germanium Crystals
Authors: Hill J. E. , Van Vliet K. M.
Published: April 2005

Measurements are reported on noise in germanium single crystals at temperatures between 300°K and 450°K. In this range the crystals were near-intrinsic or intrinsic. The 1/f noise component was negligible in all cases above 1 kc providing the noise was measured between probes. The noise above thermal noise measured in this way could entirely be attributed to spontaneous fluctuations in generation and recombination of carriers. From the spectra lifetimes varying from 2 μsec for poorly etched crystals up to 100 μsec for the best etched crystals were found. The results are compared with the theory considering generation and recombination by means of direct transitions or via recombination centers located either in the bulk or at the surface. Very reasonable agreement is found in most cases. In some cases the spectrum falls off rather weakly at higher frequencies which indicates that the recombination centers do not lie at a single sharp energy in the forbidden gap but are distributed within a small range.
On the Drag of a Sphere at Extremely High Speeds
Authors: Liu V. C.
Published: April 2005

The formula for the pressure-drag coefficient of a sphere which moves at extremely high speeds is derived. In the derivation it is assumed that the nose of the shock contour follows exactly the frontal half of the spherical surface and the local pressure on the frontal spherical surface corresponds to the pressure behind the shock wave after the statistical equilibrium between the various degrees of freedom of the molecule has been reached. The chemical dissociation of the molecules behind the shock wave is taken into account in the analysis. The theoretical results of the drag coefficient of the spheres agree with the corresponding available measured value within the experimental error for the range of Mach number between 5 and 10.
Surface Tension of Titanium, Zirconium, and Hafnium
Authors: Peterson A. W. , Kedesdy H. , Keck P. H. , Schwarz E.
Published: April 2005

The surface tensions of liquid Ti, Zr, and Hf at their melting points were measured in pure argon atmosphere by the drop-weight method. A uniform longitudinal field induction coil was used to melt the sample rod tip. The average values obtained were 1390±40, 1400±40, and 1460±40 dynes/cm, respectively.
Nature of Electrical Resistivity of the Ferromagnetic Metals at Low Temperatures
Authors: Kondorsky E. , Galkina O. S. , Tchernikova L. A.
Published: April 2005

The study of the resistivity of nickel, iron, and nickel-copper alloys with copper concentration up to 25%, at temperatures from 2°K to 78°K, has been carried out. The empirical formulas for resistivity in this temperature range have been found. It has been shown that the ``phonon'' term in T5 does not play an essential role in the resistance of ferromagnetic metals at temperatures up to 20–30°K, but that it contributes to the resistance above these temperatures. The values of (ρ-ρ0)/n for nickel and iron [where ρ and ρ0 are the resistivity and residual resistivity at 0°K, respectively, n=(T/θ)32 is the ``magnon'' concentration, θ is the exchange parameter in Bloch's 32 law], and the value of Δρ/Δn for nickel (where Δρ is the change of resistivity, Δn=ΔIs/I0 is the decrease of magnon concentration, and ΔIs is the increase of true magnetization in strong magnetic field) have been found and compared with each other. It has been shown that both of these values for nickel are of the same order and also the same order as the value of Δρ0/ν, where Δρ0 is the increase of residual resistivity of nickel copper alloys with the concentration, ν, of copper in these alloys. The coincidence of the above-mentioned values is considered to be an indirect proof for the assumption that the temperature dependent part of the resistance of ferromagnetic metals at low temperatures is related to the scattering of electrons by magnon.
Transverse Flux Change in Soft Ferromagnetics
Authors: Humphrey Floyd B.
Published: April 2005

Results of an investigation of magnetic flux change in the direction perpendicular to the direction of the applied field indicate that the maximum flux in the transverse direction does not occur at the time when the sample is half reversed. From these data, taken on thin evaporated films of iron-nickel, it is concluded that a coherent rotation theory which assumes a single magnetization vector to represent the entire sample is not adequate to explain the results. It is suggested that, when a small transverse field is present, the magnetization starts to reverse by coherent rotation but soon loses phase throughout the sample so that the reversal is completed by noncoherent rotation. With no transverse field, the coherence is never established and the reversal is completely by noncoherent rotation. Added evidence for this suggestion is presented in the form of a comparison of thin films with ferrite and Permalloy tape cores. In both the normal and transverse directions, the observations are similar, supporting the view that the reversal of films and cores is by the same general mechanism.
Reversible Rotation in Magnetic Films
Authors: Sanders Richard M. , Rossing Thomas D.
Published: April 2005

The magnetization of permalloy films of 0.1 to 0.3 μ thickness vacuum-deposited in a magnetic field is reversibly rotated by a pulsed external field applied at right angles to the direction of easy magnetization. The total angle of rotation is deduced from the amplitude of the detected signal or from the strength of the applied drive field. Reversible rotations of 60° or more are repeated for at least 108 cy in some films. An excessive drive field results in a loss of remanent magnetization after a few rotations. High wall-motion coercivity is a necessary but not sufficient condition for large reversible rotation angles. Films giving a large rotation tend to have open hysteresis loops in the difficult direction.
Ferromagnetic Resonance in Ultra-Thin Films
Authors: Seavey M. H. , Tannenwald P. E.
Published: April 2005

A ferromagnetic film may be arbitrarily considered as ``ultra-thin'' when its thickness is less than 100 A. It has been possible to observe microwave resonance absorption in Permalloy films down to approximately 15 A thickness. The magnetization drops sharply near 60 A, and ferromagnetism disappears between 8 A and 12 A. Line shape and width and g factor have also been measured.
Some Results of an Electron Microscopical Study of the Metallographic Structure of Two Alloys for Permanent Magnets (Ticonal G and Ticonal X)
Authors: De Jong J. J. , Smeets J. M. G. , Haanstra H. B.
Published: April 2005

The microstructures of Ticonal G and Ticonal X in the condition of optimum magnetic properties are studied by the electron microscope using the direct carbon replica. It is argued that a very critical and extensive checking of results is essential in order to arrive at reliable conclusions. Work along these lines demonstrates that: (a) The main structural patterns for Ticonal G and X are the same; (b) the details of the structure of Ticonal G and X differ strikingly with respect to texture, width, length-to-width ratio, delineation and intergrowth; and (c) the influence of the magnetic field during cooling on the structure of Ticonal G on a plane ∥Hu can be shown directly.

It cannot yet be decided whether the structure in the optimum condition is a true two-phase structure or a single-phase structure with periodic fluctuations in composition.

It is possible that the dimensions revealed by etching do not represent those of the magnetic areas.
Relation between Colloid Pattern and Permanent Magnet Precipitate during the Magnetization Reversal in Alnico V
Authors: Kronenberg K. J. , Tenzer R. K.
Published: April 2005

Improved electron microscope observation technique has confirmed some of the basic assumptions on the structure of Alnico V and has added knowledge of details. The permanent magnet precipitate was investigated at various states of its growth starting from nucleation. Pictures with details smaller than 20 A reveal the completely developed structure of Alnico V which differs somewhat from former descriptions. It can be recognized clearly that the precipitated particles have grown together to a continuous anisotropic network subdividing the matrix.

Colloid patterns on these surfaces have been observed with electron microscope. During the reversal of magnetization, an anisotropic structure in the colloid-covered areas of the pattern can be distinguished. The colloid particles align themselves, preferring one of the two faces of the precipitated structure. This is most pronounced in the steep part of the demagnetization curve. It can be observed as soon as the colloid starts to form patterns.

The necessary surveying of magnet surfaces was possible by preparing very thin oxide replicas with a simple technique that eliminated the former ``floating'' method. Replicas were stripped from the surface which preserved the orientation without destroying the surface of the magnet.
Physical and Magnetic Properties of Elongated Single-Domain Iron and Iron-Cobalt Permanent Magnets
Authors: Lever R. C. , Yamartino E. J. , Falk R. B.
Published: April 2005

The physical and magnetic properties of permanent magnets compacted from elongated single-domain particles with metal and organic matrices are described. Their unique properties which make possible novel design and application possibilities include: demagnetization curve flexibility; high-energy and energy-to-weight ratio; uniformity of pole face flux; low-temperature coefficient of remanence; precise dimensional tolerances; excellent machinability; solderability; low critical material content; and short radioactive half-life. Compacts have been prepared from iron and iron-cobalt particles with energies of 3.5 million and 5 million gauss-oersteds, respectively. Compacts exposed to 200°C for over one year were observed to change remanence less than 1%.
Loss of Exchange Coupling in the Surface Layers of Ferromagnetic Particles
Authors: Luborsky F. E.
Published: April 2005

Experiments with spherical iron particles 28 A to 265 A in diameter demonstrate that the proposed nonferromagnetic surface layer on an iron particle must be less than 1 A thick, i.e., about one atomic radius. This conclusion is based upon a comparison of the ferromagnetic iron calculated from the magnetic saturation, and the total amount of iron as determined by chemical analysis. The 1/H extrapolation of the magnetic induction appears adequate to obtain the saturation induction at room temperature of particles greater than about 100 A in diameter. For particles less than this size, in the superparamagnetic size range, the Langevin function must be used taking into account the size distribution of the particles in the sample. Thus there will be a negligible decrease in saturation induction due to the loss of exchange coupling at the surface of iron particles in the size range above 100 A of interest for fine-particle permanent magnets.
Magnetic Determination of Shape Distribution of Single Domain Powders
Authors: Johnson Clark E. , Brown William Fuller
Published: April 2005

By demagnetizing a magnetic powder specimen with diminishing alternating fields of various initial amplitudes and by interpreting the results with the Stoner-Wohlfarth model, one can obtain information about the shape distribution of the particles. We have done this with powders of acicular γ-ferric oxide at various temperatures; the temperature variation of the results gives information about the size distribution. The sample is first magnetized to saturation; the diminishing ac field is then applied and the remanence measured.

Since the particles are not aligned along the applied field, it is necessary to get the equivalent magnetization curve for an aligned sample by operating on the data mathematically. The results indicate that only a small volume fraction of the γ-ferric oxide particles are small enough to be a paramagnetic. There is a relatively large volume fraction of particles with nearly zero critical field. We believe this is caused by particles which change their magnetization by a mechanism different from the Stoner-Wohlfarth uniform rotation.

On a volume basis, the shape distribution curves peak at a length-to-diameter ratio of about 1.6:1, which gives a coercive force of 300 oersteds. The coercive force agrees very well with measured values. The length-to-diameter ratio does not agree with electron microscopic observations, which give a mean of about 5:1.
Multiplicities of the Uniform Precessional Mode in Ferrimagnetic Resonance
Authors: Solt I. H. , White R. L. , Mercereau J. E.
Published: April 2005

In order to interpret correctly the experimental results obtained from ferrimagnetic resonance experiments, it is necessary to understand completely the multiplicity of lines that can be observed. Most of these lines have been shown [R. L. White and I. H. Solt, Jr., Phys. Rev. 104, 56 (1956); J. E. Mercereau and R. P. Feynman, Phys. Rev. 104, 63 (1956); L. R. Walker, Phys. Rev. 105, 390 (1957)] to be higher order precessional modes which are quite well understood. There still exists, however, some uncertainty connected with the uniform precessional mode. The uniform mode is of most importance since it is for this mode that values of line widths, g values, and anisotropy constants are usually quoted in the literature. It can be distinguished experimentally from the higher order modes since (a) its intensity of absorption is proportional to the uniform component of the rf magnetic field over the sample and (b) its intensity decreases much less rapidly with diminishing sphere size than for the higher order modes. We have observed, however, that there are several lines possessing these characteristics of the uniform mode. The relative intensities of these lines are strong functions of both temperature and frequency, they have different anisotropy constants, and their separation decreases with sphere radius. Data exhibiting these properties will be presented for experiments on spherical single crystals of MnZn ferrites performed in the microwave frequency range of 8000–12 000 Mc. A discussion of several possible mechanisms that might give rise to this phenomena will be given.