bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusional Creep in Polycrystalline Sodium Chloride
Authors: Kingery W. D. , Montrone E. D.
Published: April 2005

Steady-state creep of polycrystalline sodium choride having grain size stabilized by the addition of an aluminum oxide dispersion and containing about 4% porosity was investigated at 740°C over a range of grain sizes from 65–130 μ and at stresses from 2.1–8.4 kg/cm2. Deformation was viscous (strain rate directly proportional to stress) at a rate in good agreement with the Nabarro—Herring equation, assuming the deformation rate to be limited by chlorine ion diffusion. Grain-size dependence and absolute creep rates were satisfactorily predicted with Laurent and Bénard's diffusion data, including the influence of grain size on diffusion coefficients.
Dielectric Constant and Magneto-Optical Kerr Rotation of Ferromagnetic Chromium Tribromide above the Absorption Band Edge
Authors: Jung Wun
Published: April 2005

By extending the optical and magneto-optical measurements of the insulating ferromagnet CrBr3 (hexagonal layer structure, Tc=36°K, and 4πMs=3520 G) beyond the absorption band edge near 22 000 cm−1 with reflection techniques, three absorption bands representing the π and σ processes of electron transfer transitions and an internal transition of Cr3+ have been observed. The room-temperature dielectric constant was measured by means of an ellipsometer. The σ process and the internal transitions give rise to the two absorption bands at 24 310 cm−1 and 29 580 cm−1 with oscillator strengths of 0.30 and 1.61, respectively. They account for most of the dielectric constant. While the π process is too weak to be resolved in the dielectric constant data, it accounts for the main peak of the normal incidence polar Kerr rotation at 1.5°K of 3.5° at 23 500 cm−1. The σ process accounts for the relatively sharp negative peak in the Kerr rotation of −2.5° at 26 700 cm−1. The data further suggest that the π process component of the off-diagonal element of the electric polarizability tensor has opposite sign to the σ process and the internal transitions.
Effect of Stress on the Superconducting Transition Temperature of Thin Films of Tin
Authors: Hall P. M.
Published: April 2005

Factors which affect the superconducting transition temperature (Tc) of thin tin films are of considerable importance in the design of thin film devices. This paper reports an investigation of one such factor, the stress state of the film. Two approaches were used. First, the transition temperature was correlated with the differential thermal contraction between film and substrate. Six different types of glass were used for substrates, and the six films were evaporated simultaneously to ensure similar conditions of evaporation. Secondly, a substrate-bending technique was used to stress the film while holding it near its transition temperature. For both of these methods, shifts of the transition temperature greater than 0.1°K have been observed. However, it was found that agglomeration of the film can greatly reduce the dependence of the transition temperature on stresses transmitted to the film by the substrate.

When agglomeration was negligible, both these approaches yielded a linear increase in Tc with tensile strain. Values for d lnTc/d lnv were obtained, where v is the volume of the tin film. The average values were +8.6 from the differential thermal contraction measurements, and +8.1 from the substrate bending measurements. These results are in reasonable agreement with the properties of bulk tin (d lnTc/d lnv=+7.5). However, the films were able to withstand tensile stresses more than an order of magnitude greater than the elastic limit of bulk tin and still recover their original properties upon relaxation.
Saturation Effects in High-Gain Lasers
Authors: Rigrod W. W.
Published: April 2005

Earlier calculations of the radiation intensity obtainable from lasers with homogeneous line broadening are generalized to include arbitrarily large loss fractions per pass. The conditions for maximum transmitted or internally dissipated power are derived, as well as the axial distribution of radiation within the active medium. The relevance of these calculations to high-gain gas lasers is discussed.
Initial Permeability and Derived Anisotropy of Scandium-Substituted Yttrium Iron Garnets
Authors: Cunningham J. Richard
Published: April 2005

Effects of nonmagnetic scandium octahedral substitution in yttrium iron garnet were studied in a series of polycrystalline garnets having the unit formula Y3ScxFe2−xFe3O12 where x was varied from 0 to 1.7. Measurements of the lattice parameters, spontaneous magnetization, Curie temperature, and the initial permeability as a function of frequency and temperature are reported. The lattice parameter varied linearly from 12.376±0.003 Å for x=0(YIG) to 12.495±0.005 Å for x=1.5 Sc3+. Single-phase garnet was not obtained for x>1.5. The apparent spontaneous magnetization at T=0°K and the Curie temperature dependence on substitution are qualitatively explained using Gilleo's statistical theory of incomplete super-exchange interactions. The initial permeability at room temperature is strongly affected by the addition of scandium, increasing from 120 (YIG) to a maximum value of 1934 (x=0.9 Sc3+) and then to unity for larger x values. The value of 1934 is the largest room-temperature initial permeability reported in garnets to date; the corresponding Curie temperature is 320°K. The frequency spectra of the initial permeability for x≤0.7 Sc3+ display the usual two characteristic loss peaks identified with domain wall motion and domain rotation mechanisms. The high-frequency (domain rotation) peak appears only as a shoulder on the broad wall motion resonance. The wall motion peak does not exhibit electronic diffusion effects. In the absence of experimental anisotropy data on Sc3+ substituted garnets, the temperature dependence of the initial permeability was used to deduce K1(T) by assuming that the rotational permeability contributes ∼20% to the total measured permeability. The rotational resonance frequencies calculated using the deduced anisotropy constants at room temperature agree quite well with experimental data. The derived K1(T) seem to be in good agreement with the available single-crystal experimental data.
Gas-Surface Interactions and Field-Ion Microscopy of Nonrefractory Metals
Authors: Müller E. W. , Nakamura S. , Nishikawa O. , McLane S. B.
Published: April 2005

The performance of the helium field-ion microscope depends critically upon accommodating He atoms of 0.15-eV kinetic energy to the specimen tip. The small accommodation coefficient requires the field-trapped He atom to make several hundred contacts with the cold tip surface. The hopping He atoms diffuse preferentially to tip regions where the high local field permits ionization before full accommodation is reached. Improved accommodation is achieved with the provision of an intermediate collision partner in the form of adsorbed neon or, preferably, hydrogen or deuterium. Now a high-resolution He ion image is obtained at 70% of the field used before. As the addition of hydrogen promotes field evaporation, its partial pressure must be carefully controlled to achieve image stability of the nonrefractory metals. Low-field evaporation by the hydrogen reaction permits easy conditioning of the tip surface of the nonrefractory transition metals so that artifacts caused by yielding to He evaporation field stress are no longer a problem. The field evaporation end form obtained with hydrogen added to He more closely approaches the desirable spherical shape of the emitter than does field evaporation in vacuum or in a single imaging gas. As examples, ion images of niobium, nickel, iron, and high carbon steel are shown.
Growth Pips and Whiskers in Epitaxially Grown Silicon
Authors: Mendelson S.
Published: April 2005

Growth pips on epitaxial {111} silicon films result when growth occurs preferentially around tripyramid hillocks which nucleate on the substrate surface and propogate ahead of the film; whiskers sometimes propagate from these. The tripyramids are often associated with and are the mirror image of stacking-fault triangles. The stacking-fault tetrahedra are not always complete or necessary for tripyramid formation. The studies indicate that both stacking faults and tripyramids propagate from twinned triangular deposits, the mechanism for stacking-fault nucleation being a twinned deposited layer model. This model also accounts for the presence of microtwin lamellae recently reported around tripyramids. The possible whisker growth mechanisms are discussed in relation to the observations. The results indicate that a re-entrant twin mechanism for whisker growth may operate in some cases.
Time-Dependent Computer Analysis of Electron—Wave Interaction in Crossed Fields
Authors: Yu S. P. , Kooyers G. P. , Buneman O.
Published: April 2005

A time-dependent analysis of crossed-field interaction has been formulated for computer calculation. The computer program has achieved, for the first time, accurate and complete simulation of the magnetron oscillator, magnetron amplifier, and smooth-bore magnetron. We believe that crossed-field interaction of the distributed-emission type is finally predictable. The computer results are reliable enough to serve as design information. They also indicate that the nature of the interaction is turbulent in the sense that the operation of these devices borders between order and disorder under certain conditions.

The techniques used in this analysis are applicable to a wide range of problems dealing with other types of electron—wave interaction, and to plasmas.
Octagonal Coil Systems for Canceling the Earth's Magnetic Field
Authors: Bloom A. L. , Innes D. J. , Rempel R. C. , Ruddock K. A.
Published: April 2005

An analysis is made of coil systems employed to cancel the earth's magnetic field. It is shown, in regard to N-coil systems designed for field homogeneity such that the first nonzero derivative is the 2Nth, that the circular coils may be replaced by polygons of not less than 2N sides. Specifically, the four-coil Braunbek configuration cannot be approximated by square coils, but four octagonal coils can produce fields that are indistinguishable from those of circular coils in the region of high homogeneity. A set of field plots is presented for two types of octagonal coil configurations, and tables are given of the field gradients generated by certain deformations of the coil system.
Magnetic and Ionic Structure of An Electromagnetically Produced Shock
Authors: Guthart H. , Morita T.
Published: April 2005

The structure of the gas behind a strong shock generated by an electromagnetic shock tube has been investigated using magnetic pickup loops, an asymmetrical ion probe, an image-converter camera, and a piezoelectric pressure probe. The shock tube consists of a 15-cm-i.d. Pyrex tube of adjustable length connected to a conical discharge section. Four 7.5-μF capacitors were charged to 12 kV and fired into the tube at a pressure of 30 μHg. The azimuthal magnetic field generated by the electrical discharge is ``frozen'' into the gas behind the shock because of the high magnetic Reynolds number (Rm∼2). Its transverse distribution is shown to be consistent with a toroidal current hypothesis. The peak magnetic field strength measured was 5000 G at 10 cm from the discharge section and 20 G at 40 cm. The peak ion concentration was observed to be 8 × 1014 cm−3 at 50 cm and 3×1014 cm−3 at 190 cm from the discharge section. A precursor ion density three orders of magnitude below the shock maximum is also observed 6 cm in front of the shock at a position 70 cm from the discharge section.
Entropy Contributions to the Restoring Force of a Dislocation Kink Chain
Authors: Alefeld Georg
Published: April 2005

The application of a shear stress to a dislocation segment causes not only energy changes of the dislocation but also entropy changes. For a dislocation kink chain, the entropy change leads to a significant increase in the restoring force for dislocations which have small angles against close-packed directions. For a dislocation string, the entropy contribution to the restoring force is negligible.
Field Desorption of Thorium from a Field-Evaporated Tungsten Surface
Authors: Young Russell D.
Published: April 2005

The field-desorption of thorium from a thermally smoothed tungsten substrate has previously been investigated in the temperature range between 300° and 1090°K. The present work extends these measurements to 77°K and includes desorption from a field-evaporated surface as well as a thermally smoothed surface. For both types of surfaces at 77°K the desorption field strength was found to be 263×106 V/cm±10%.
Electron Microscope Study of the Effect of Oxygen Ion Irradiation on Lithium Fluoride
Authors: Carroll Dennis B. , Birnbaum H. K.
Published: April 2005

Large numbers of point defects were produced by the room-temperature bombardment of LiF by 100-kV oxygen ions. Clusters of these defects were studied in the electron microscope by means of their diffraction effects and their appearance in bright-field and dark-field images. Platelets of polycrystalline lithium were observed to form on {100}LiF planes. The mechanism of formation of these precipitates is discussed.
High-Temperature Dislocation Damping in Covalent Crystals
Authors: Southgate P. D. , Mendelson K. S.
Published: April 2005

Dislocation damping in deformed single-crystal silicon has been measured in the frequency range from 400 cps to 70 kc/sec and at temperatures between 500° and 1200°C. At low temperatures the logarithmic decrement shows a thermally activated rise with temperature, of activation energy 1.6 eV, varying approximately inversely with frequency. Deviation from this behavior is seen at the lower frequencies, where a peak appears near 800°C, followed by a second rise with temperature which is significantly faster than the initial rise. The results are interpreted in terms of an extensible string model, in which it is assumed that the dislocation is pinned by point defects which may diffuse with the dislocation. Agreement is obtained between theory and experiment for very reasonable values of mean dislocation length, and values of dislocation damping constant consistent with a geometrical kink diffusion model. The activation energy of motion for the pinning points is about 3.1 eV. Measurements on indium antimonide yield similar results, and it is supposed that a similar interpretation applies, although the data is not complete. The ratio of activation energies in the two materials is approximately the same as that for bond-breaking, which is believed to be the major energy barrier to kink diffusion in covalent materials.
Transient Radiation Environment of Nuclear Weapon Detonations
Authors: Boucher R. J. , Pearson J. B.
Published: April 2005

Mathematical models, including a generalized diffusion equation with time varying coefficients, are developed which approximate the propagation of both the initial neutron and the initial gamma radiation from nuclear weapon detonations. Typical plots of neutron and gamma pulse shapes obtained from these models are compared and show that for many cases the gamma spike, or unscattered components of gamma radiation, is predominant. Therefore, it is concluded that for most cases the simplified gamma spike formula commonly used in calculating the radiation environment is appropriate for use in predicting the effects of nuclear weapon detonations upon electronic equipment.
Relation between Diochotron and Negative Mass Instabilities
Authors: Neil V. Kelvin , Heckrotte Warren
Published: April 2005

A cylinder of electrons infinitely long and infinitesimally thin in the radial direction is used to show the equivalence of the diochotron and negative mass instabilities. The electrons have a unique relativistic velocity in the azimuthal direction. The external magnetic field has a radial gradient, and a criterion for stability is derived that places a lower limit on the field gradient. This criterion shows that the instability can occur at energies below the transition energy of the magnetic field.
Surface-Charge Layers in BaTiO3 Whiskers
Authors: Crawford J. C. , Dragsdorf R. D.
Published: April 2005

The presence of a surface-charge layer has been found in BaTiO3 whiskers. A particular example is discussed where the surface-charge layer completely dominated the properties of the whisker. A transition layer between the surface layer and the interior of the whisker was observed optically and found to be approximately 1 μ thick. The domain structure of the whisker could be changed by applying an external axial electric field. The whisker always returned to its own unique equilibrium configuration when the field was removed. This equilibrium configuration was a direct result of the presence of the surface layer. The spontaneous polarization vector within the surface layer was saturated normal to the surfaces and toward the interior of the whisker. It was demonstrated both experimentally and analytically that this surface layer could cause spontaneous nucleation of spike-shaped domains. These spikes extended through the surface layer and into the interior of the whisker. Nucleation occurred even in the presence of an opposing electric field. The magnitude of the potential drop across the surface layer apparently depends upon imperfections.
Microdynamics of Plastic Flow at Constant Stress
Authors: Gilman John J.
Published: April 2005

Arguments are presented which conclude that the mean density of mobile dislocations in a crystalline solid increases linearly with plastic strain for small strains and decays exponentially for large strains, all at constant stress and low temperatures. The resulting analytic expression combined with the strain-rate equation can be integrated explicitly in terms of tabulated exponential integral functions. This creep equation has a general form that is consistent with many experiments and detailed comparison with a particularly well-documented experimental curve yields quantitative agreement. The large strain limit of the proposed creep equation is the familiar logarithmic creep law. A simple transformation of the creep equation yields the shape of a slowly propagating plastic front, and it is shown that the predicted shape corresponds to experimental observations for mild steel. The lengths of the incubation periods that precede fast flow, as predicted by the equation, have a stress dependence that agrees with experiment. Finally, the present arguments together with previous ones yield a strain-rate equation which generates both stress-strain and strain-time curves that are good reproductions of experimental observations.
Influence of the Internal Field on the Residual Resistance of Very Pure Iron
Authors: Berger L. , De Vroomen A. R.
Published: April 2005

It is shown that the field B = 22 kG which exists in each Weiss domain even in the absence of an applied field should cause certain anomalies in the residual resistance of very pure polycrystalline iron. The residual resistance in zero applied field is no longer proportional to impurity concentration. It may even have a minimum as a function of impurity concentration. The minimum should correspond to a resistivity ratio R273/R4.2 of roughly 300. This explains why the resistivity ratio of samples of zone-refined polycrystalline iron is usually found to be no higher than 200 or 300. The same internal field is also shown to be the cause of the resistance decrease in a small longitudinal field, observed in very pure iron and nickel at low temperature. A decrease is also expected in a small transverse field if the sample is very slightly misoriented.
Dehydration of Phlogopite Micas Studied by High-Temperature Transmission Electron Microscopy
Authors: Cartz L. , Tooper B.
Published: April 2005

Phlogopite micas have been studied at high temperatures in the electron microscope and the observations related to the known behavior of micas to dehydrate, to undergo swelling over a wide temperature range, and to their anomalous thermal expansion. The specimens showed evolution of bubbles at room temperature and also on heating in the electron microscope. The bubbles are lenticular flaws from the separation of (0001) cleavage planes and these lenticular flaws exhibit intricate Bragg extinction contours. Areas of lenticular flaws frequently display complex diffraction patterns. The bubbles occur particularly on dislocation networks, tend to nucleate and grow at nodal points, and whole dislocation networks have been observed to convert at 700°C into large lenticular flaws It is shown that dehydration of mica can refer to two different processes. The first below 500°C is the removal of water molecules from between the silicate layers into lenticular flaws and the second above about 800°C is the escape of water from the mica by splitting of the crystal.
Epitaxial Growth of Evaporated Cobalt Films
Authors: Honma T. , Wayman C. M.
Published: April 2005

The characteristics of cobalt films of initial purity 99.91% and 99.999% prepared by vacuum evaporation on various substrates were studied. Variables were substrate type (KCl, NaCl, and natural graphite), substrate temperature, vacuum during evaporation, and vacuum cleavage vs cleavage in air. Epitaxial fcc cobalt films could be obtained on KCl and NaCl, and ``semiepitaxial'' hcp cobalt films could be obtained on graphite. The change in texture of the films upon annealing and their subsequent transformation behavior is discussed.
Interaction of Elastic Waves with Ferromagnetic Spin Waves in Bloch Walls
Authors: Paul David I.
Published: April 2005

The interaction of an elastic wave with the two-dimensional bound spin waves of a Bloch wall is investigated. Our formulation shows that the 180° Bloch wall couples only with the shear waves while the 90° wall couples with both longitudinal and shear waves. We have computed the spin-wave amplitude, the power absorbed, the change in the modulus, and the Q of the interaction for both these cases. The major effect comes from the coupling of the 90° wall with the longitudinal waves which yields, for iron, a 0.1% to 1.0% change in the elastic constant and a logarithmic decrement of approximately 0.02 for a density of Bloch walls equal to 330/cm.
Interaction of Diffusion and Stacking Faults in Si Epitaxial Material
Authors: Jaccodine R. J.
Published: April 2005

The effect of diffusions and heat treatments on faulted epitaxial materials has been investigated using thinned-film electron microscopy. Samples of epitaxial silicon were grown with a deliberately high concentration of stacking faults for these studies. Heat treatment were performed in N2 and He ambient at 1000°, 1100°, 1200°, and 1300°C. Diffusion consisted of a 1050°C heat treatment for 30 min in P2O5 (platinum box technique) to give a high concentration layer (> 1020/cm3). Heat treatments alone had a minor effect on the faulted material. The diffusion process, on the other hand, caused major alteration in the nature and density of faults. Stacking faults were altered to the extent that the orderly striped contrast disappeared and was replaced by individual or piled-up groups of dislocations. Large clusters of precipitate were observed inside stacking fault regions and on helical dislocations. Dislocation climb was detected as indicated by a large number of helical dislocations.

The presence of a ``necklace of precipitate'' associated with stacking faults and dislocations illustrates the role played by these faults as nucleation sites. Such precipitation occurring in an active device region might well be sufficient to drastically alter or destroy the device.
X-Ray Measurements of Stacking Faults and Internal Strains in α-Cu-Zn and α-Cu-Sn
Authors: Wagner C. N. J. , Hélion J. C.
Published: April 2005

Powder-pattern peaks of cold-worked and annealed fcc Cu-Zn and Cu-Sn filings were measured with a diffractometer using filtered Cu radiation. The plots of the lattice parameter ahkl, calculated from the peak maximum position of the individual (hkl) reflections, as a function of cosθ·cotθ proved to be linear for all annealed powder samples. The large scatter of the individual ahkl values of the cold-worked filings could be related to the deformation stacking-fault probability α=α′-α″ (intrinsic-fault probability α′ and extrinsic-fault probability α″), segregation Δx, and internal stresses σ. The lattice parameters (a0)CW of the cold-worked filings of the Cu-Zn alloys were larger, whereas (a0)CW of the Cu-Sn alloys were smaller than the corresponding (a0)Ann values of the annealed filings. The deformation-fault probability α increases with increasing solute concentration.

The combined twin-fault probabilities β and extrinsic-fault probability α″, i.e., 4.5 α″+β, were determined from the displacements of the center of gravity from the peak maximum positions of the (111) and (200) reflections. Fourier analysis of the line shapes allowed the determination of the fault probabilities [1.5(α′+α″)+β], the average domain size D, and the rms strain components in the [111] direction. Using the quantities α′-α″, 4.5 α″+β, and 1.5(α′+α″)+β and solving for α′, α″, and β, no evidence of the occurrence of extrinsic faults in the cold-worked filings could be found. The values of 1.5 α′+β calculated from line broadening agree rather well with those obtained from lattice-parameter and center-of-gravity changes, indicating that intrinsic deformation and twin stacking faults are the primary causes of the broadening and shifts of the powder-pattern peaks from cold-worked α-Cu-Zn and α-Cu-Sn filings.
Elastic Behavior of Polycrystalline Chromium near the Néel Temperature
Authors: Roberson J. A. , Lipsitt H. A.
Published: April 2005

Young's modulus, the shear modulus, and Poisson's ratio have been determined for pure polycrystalline chromium as a function of temperature and thermal history. Both sonic and mechanical measurements were made, and it was found that all of the above properties show anomalous behavior near 37°C. The nature of the anomalies is such that Young's modulus and Poisson's ratio drop rather sharply over a narrow temperature range while the shear modulus increases slightly. The temperature at which this occurs seems to be fixed for a fixed composition and stress condition, although the extent of the anomalies is strongly influenced by thermal history. It is believed that this behavior is a result of an antiferromagnetic to paramagnetic transition, and that it is influenced by both internal and applied stresses. A model is developed to explain the observed behavior. Since Poisson's ratio is very nearly zero in the temperature range of the magnetic transition, it becomes necessary to consider the volume changes occurring under stress. When this is done, the anomalous behavior in Young's modulus is shown to be a necessary consequence of the anomaly in Poisson's ratio, which is described in terms of magnetostrictive versus elastic strain energy.
Reflectivity of Silver and Gold
Authors: Doremus R. H.
Published: April 2005

Reflectivities of silver and gold as measured by Bennett and Ashley are compared to the equations of Dingle for free electrons, including the anomalous skin effect. At a wavelength of about 5 μ, the measurements are consistent with Dingle's equations with about half of the electrons specularly reflected from the metal surface. At lower wavelengths the measured reflectivities are lower than the theoretical ones; the origin of this deviation is not clear.
Mass Transfer Problems in Ionic Crystals with Charge Neutrality
Authors: Ruoff A. L.
Published: April 2005

Both diffusional creep and sintering involve mass transport of the stoichiometric group of atoms AαBβ. The driving force in each case is external to the lattice, being applied mechanical stress in the case of diffusional creep and surface tension in the case of sintering. It is assumed that point defect mechanisms are involved in the diffusion process. Herring has considered the case of diffusional creep by lattice diffusion where charge effects are absent. The analogous case of creep by grain-boundary diffusion, which becomes the important process at small grain size, has also been treated. [A. L. Ruoff, Materials Science Center Rept. No. 298, Cornell University, Ithaca, New York; and R. L. Coble, J. Appl. Phys. 34, 1679 (1963)]. The diffusional creep of a polycrystalline specimen is here formulated exactly and terms which must be dropped to obtain Herring's expression (for either metallic or ionic crystals) are directly specified. It is then shown that Herring's equations apply to a pure ionic crystal when the conduction is purely ionic and space-charge effects can be ignored if the tracer diffusion coefficient D in Herring's equations is replaced by DM, and the atomic volume Ω in his equations is replaced by the molecular volume VM of the diffusing ``molecule'' of AαBβ. If A atoms have the smallest tracer diffusion coefficient DTa0, then DM=DTa0/faα, where fa is the correlation factor.
The Elastic Constants of Cu—4 Percent Si
Authors: Smith Charles S. , Burns J. W.
Published: April 2005

The elastic constants of a Cu—4 atom percent Si crystal have been determined by the pulsed ultrasonic method to be C11=1.62, C12=1.20, and C44=0.755, all in units of 1012 dyne cm−2. The changes in the fundamental shear constants C44 and ½(C11–C12) owing to alloying have been expressed in terms of a change in electrostatic stiffness and a change in ionic stiffness, both of which are shown to be reasonable. The experimental ionic effect is interpretable in terms of the solute-solvent ion core interaction and the local distortions around a solute atom. The previously known results for Cu—28 Zn also conform to this picture.
Forces Acting on Superconductors in Magnetic Fields
Authors: Šimon I.
Published: April 2005

The forces acting on a superconducting body in a magnetic field may be obtained by analogy with hydro-dynamics, considering the similarity of the force field around a perfect diamagnetic with the flow field of an ideal liquid past an impermeable body of the same shape. The translation is provided by replacing ½ρv2 by (⅛π)μH2. As a practical application of the repulsive forces acting on superconductors in a diverging magnetic field, design of two types of magnetic supports for a sphere is described. In the coil-type support, two coils with opposed currents are necessary to provide stable equilibrium. Similarly, the permanent-magnet-type support requires two transversely magnetized rings with opposed polarity. The dissipation of energy in a rotating sphere by eddy currents and by viscous drag of the surrounding gas was studied. The nonexistence of any torque on a freefloating, superconducting sphere in a rotating, transverse field indicates absence of interaction between the superconducting electrons and the metallic lattice.
Diffraction Patterns in Circular Apertures Less Than One Wavelength in Diameter
Authors: Robinson H. L.
Published: April 2005

Measurements were made of the diffraction patterns of circular apertures from 0.2 to 1.0 wavelength in diameter when a plane polarized electromagnetic wave was incident normally upon them. Microwaves of wavelengths 16 cm and 32 cm were employed. The intensity of radiation relative to that of the unperturbed beam was determined at points along the electric and magnetic diameters of the apertures. The data disagreed with calculations from Young's circuital form in two major ways: (1) A sharp increase in intensity was observed at the ends of the electric diameter, (2) a surprising peak in intensity at the centers of apertures near one-half wavelength in diameter was 50 percent greater than calculations from the integral. A more complete interpretation of Young's theory of diffraction would include multiple reflections from the edges. The high intensity at the center of the aperture a half-wavelength in diameter was qualitatively accounted for by multiple reflections from the edges near the ends of the magnetic diameter.
Free Surface Properties of Explosive-Driven Metal Plates
Authors: Shreffler R. G. , Deal W. E.
Published: April 2005

A photographic technique for study of metal free surfaces under acceleration by high explosives is presented. Methods for reducing the data from the photographic record are described. Specific results using brass plates driven by Composition B explosive are cited.
Thermionic Emission from Oxide-Coated Tungsten Filaments
Authors: Hadley C. P.
Published: April 2005

A study has been made of thermionic emission from tungsten filaments cataphoretically coated with alkaline earth oxides. It was found that the emission from the oxide-coated filament was not influenced by the variation of work-function with crystallographic direction of the base metal. A Richardson plot of emission at zero field yielded an apparent work function of 1.3 volts and an A value of 0.048 amp/cm2-deg2. In retarding potential data, the energy of thermionic electrons showed an apparent deviation from Maxwell-Boltzmann statistics. This deviation was interpreted as due to a potential drop through the coating. Such an interpretation led to a conductivity activation-energy of 1.3 volts. A strip theory of patches was used to explain the accelerating potential data. Satisfactory agreement with experiment was found with a patch amplitude of 0.2 volt and a period of 2×10−6 meter.
X-Ray Study of Cold Work in Thoriated Tungsten
Authors: McKeehan M. , Warren B. E.
Published: April 2005

Spectrometer measurements were made of the x-ray diffraction peaks for cold-worked filings of thoriated tungsten: 99.25 tungsten, 0.75 thoria. A Fourier analysis was made of the peak shapes, and the instrumental broadening corrected by using the peaks of annealed material. When the particle size and the distortion effects were separated, it was found that the particle size broadening corresponded to a size L̄=200A. This value is to be interpreted as the size of the coherently diffracting domains, and is a measure of the distance between layers of slip planes or layers of dislocations. The coherent distortion broadening indicated that strains in this material vary appreciably over distances of 25A or less. Strain distribution curves were obtained from a Fourier transform of the experimental coefficients. There is an indication that strains are smaller in the larger coherent regions. The measured root mean square strain corresponds to an elastic energy of 0.18 cal/g. Within experimental accuracy the integrated intensities are the same for the cold-worked or the annealed samples.
Electric Fields within Cyclotron Dees
Authors: Murray Raymond L. , Ratner Lawrence T.
Published: April 2005

Formulas for the electric field strength parallel to and perpendicular to the magnetic field for an idealized cyclotron dee system are derived by use of the Schwarz-Christoffel transformation. A convenient method for computing numerical values for any geometry characterized by the ratio of dee gap to dee height is presented and applied.
Current Flow in Cylinders
Authors: Smythe W. R.
Published: April 2005

The mixed boundary value problem arising from the flow of current into a right circular cylinder of radius a through a perfectly conducting coaxial disk electrode at one end is solved approximately. The boundary conditions are met rigorously except that the electrode is not quite plane. A solution valid for all values of the disk radius is given for which in the worst case the deviation from flatness is nearly 0.01a. More exact solutions are worked out for disk radii ¼a, ½a, and ¾a and the first forty coefficients in the Bessel function series for the potential in the cylinder are tabulated. A cylinder whose diameter is eight times its length is also treated for disk radii ¼a and ½a and the first forty coefficients in the potential series are tabulated. The probable errors in the resistance formulas derived from these solutions are given.
Temperature Dependence of the Elastic Moduli and Internal Friction of Silica and Glass
Authors: Marx J. W. , Sivertsen J. M.
Published: April 2005

The dynamic Young's moduli and the internal friction of fused quartz, Pyrex glass, and soft glass rods were measured at a frequency of 37 kilocycles, in longitudinal vibration, within the temperature range −170° to 1000°C. The moduli of Pyrex and quartz increased with rising temperature, up to the softening point of the glass, while that of soft glass decreased. All three moduli were approximately linear with respect to the temperature over most of the measurement interval. Internal friction maxima were noted at high temperatures, while at the lowest measurement temperatures a significant increase in background damping occurred. A brief recapitulation of existing theory is given and employed to interpret the internal friction data. It is suggested that, in microscopically inhomogeneous media, the diffusion measurement by internal friction methods is not equivalent to the determination by other techniques.
Enriching Stable Isotopes Electromagnetically
Authors: Keim C. P.
Published: April 2005

The natural stable isotopes of forty-three elements, comprising 177 different nuclides, have been enriched; the goal is to enrich 257 isotopes of fifty-nine elements. The isotopic enrichments, the operation of the production mass spectrographs including a listing of best charge materials, a brief review of the chemical and analytical problems, a tabulation of the best compounds of the separated isotopes for mass spectrometer analyses, and a listing of some of the major uses of separated isotopes have been included in this survey of the electromagnetic isotope separation program.
Trajectories in the Symmetrical Electron Lens
Authors: Jacob L. , Shah J. R.
Published: April 2005

The complete field plot obtained by ``relaxation'' was used to determine electron trajectories for parallel incidence at heights up to one-third the bore diameter, from a numerical integration of the trajectory equation using the method of differences. The accuracy attained in this method yields cardinal points to within one percent. It was found that the focal length fn for a ray of height rn was given by fn=f0−brn2, where b is a constant; also, because of the curvature of the principal planes, the distance dn to the midplane follows a law dn=c−drn2 where c and d are constants. A consequence of this is that for the same variation in focal length, the greater the curvature of the principal plane the larger the spherical aberration of the lens.

The trajectory tracings indicate that spherical aberration is small at heights up to one-twelfth the bore diameter, but increases with height till at a value of one-third the bore, the percentage change in focal length has decreased by some 40 percent. Confirmation of focal properties was obtained using the lens in a single stage electron microscope and examining the pincushion distortion in the image of a gauze object.

Evaluation of the spherical aberration using the weak lens approximation of Scherzer leads to gross errors both in magnitude and variation, e.g., the aberration does not remain constant with voltage ratio. The experimental data with the electron microscope indicate little or no change in aberration with increase in the power of the lens; this does not agree with the results of the mathematical analysis of Ramberg.
Measurement of the Heat of Activation for Sodium Ion Diffusion in Glass
Authors: Kamel R.
Published: April 2005

Internal friction peaks resulting from sodium ion diffusion in three kinds of soda glasses have been observed in the temperature range 100° to 200°C for transverse and torsional frequencies between 20 to 400 cps. The heat of activation for sodium ion diffusion was found to range between 17 000–21 000 cal/mole and might probably be slightly dependent on the sodium content. The results obtained were confirmed by electrical resistivity measurements. For quartz glass and for soda glass having Na2O content less than 4 percent, the internal friction peak of the type discussed here could not be noticed, thus indicating that below a minimum Na2O content of about 4 percent, ionic sodium diffusion does not contribute to the anelastic behavior.
Heat Transfer at High-Power Densities
Authors: Hickey John S.
Published: April 2005

The power densities that liquid metal cooling is capable of are explored. The advantages of liquid metals over conventional water cooling are shown. The presentation is such that one can choose between the available coolants for any particular application with a minimum of background. The work done at the General Electric Research Laboratory in developing a vacuum tube anode capable of handling 5 kw/cm2 is covered.
Preliminary Results on Photoelectric Yields of Pt and Ta and on Photoionization in O2 and N2 in the Vacuum Ultraviolet
Authors: Wainfan N. , Walker W. C. , Weissler G. L.
Published: April 2005

Absolute photoelectric yields of Pt and Ta and photoionization yields in O2 and N2 are reported for the spectral region from 436 to 1004 angstroms. The experimental methods as well as the monochromator, light source and associated apparatus are described. The results for Pt and Ta give photoelectric yields between 10−1 and 10−2 electron per photon for wavelengths shorter than 1000A. These values are 10 to 100 times larger than those obtained for the same metals between 2000A and 3000A. Photoionization results for O2 indicate that below 700A almost all absorbed photons produce ion pairs, while in the region between 700A and the first ionization limit at 1000A the yield varies rapidly. In the case of N2 at wavelengths shorter than 796A, its first ionization limit, the yield rises steeply. Below 725A almost all absorbed photons produce ion pairs. The over-all error is estimated to be within ±20 percent.
Propagation Along a Slotted Cylinder
Authors: Harrington Roger F.
Published: April 2005

A variational method of determining the attenuation and phase constants for the fields along a slotted wave guide is presented. Calculated and experimental values for a slotted circular wave guide excited in the TE11 and TM01 modes are included.
Pressure Thresholds for Biologically Active Cavitation
Authors: Ackerman Eugene
Published: April 2005

Experiments are described which measure the threshold acoustic pressures necessary for cavitation which can destroy certain biological cells. These thresholds are in the neighborhood of 0.3 atmospheres in the frequency range from 0.4 to 500 kc. At lower frequencies much greater pressures appear necessary and the type of biological damage is different. An interpretation of these results is discussed.
Interferometric Studies of Supersonic Flows about Truncated Cones
Authors: Giese J. H. , Bergdolt V. E.
Published: April 2005

Fringe shifts on interferograms of flows at M = 2.45 about variously truncated 15° (half-angle) cone cylinders in free flight in a pressurized range have been examined for similarity of the flow fields, occurrence of scale effects, and convergence to conical flow. It was found that flows over similar objects with equal tip Reynolds numbers were similar and that convergence to conical flow occurred before the disturbance at the tip had been reflected the second time along characteristics to the body. Density distributions have been determined, and a number of comparisons have been made with theoretical predictions.
Preparation of p — n Junctions by Surface Melting
Authors: Lehovec Kurt , Belmont Emanuel
Published: April 2005

A new method is described for preparation of p — n junctions in single-crystal semiconductors: the upper part of a slice cut from a single-crystal semiconductor is melted by radiation. Impurities of the opposite type than those present in the crystal are introduced into the melt. Upon slow solidification of the melt a single crystal is obtained with a p — n junction at the original position of the solid-liquid interface. The method is capable of producing multiple junctions.

The influence of (a) heater temperature, (b) forced cooling, and (c) thickness of the slice on the position of the solid liquid interface is calculated for a one-dimensional model, assuming that the temperature difference between bottom and top of the semiconductor is small compared to the melting temperature of the semiconductor. The time constant characterizing the rate of reaching equilibrium conditions after a sudden small change in heater temperature is estimated.
The Generation of Wind Waves on a Water Surface
Authors: Eckart Carl
Published: April 2005

The statistical methods for treating continuous media developed elsewhere are applied to the generation of surface gravity waves. The wind stress is assumed to be everywhere normal to the disturbed surface of the water and caused by a known ensemble of ``gusts.'' Each gust is considered to be a center of high or low pressure, which moves with the mean wind speed, and has a radius L, and duration T. The rms value of the variable wind pressure is assumed to vary systematically from point to point in a storm. The calculations are made for an idealized, long continuing storm; before applying the statistical equations, the effect of a single gust is calculated.

It is shown that the single gust produces a V-shaped wake, which, after the gust has blown itself out (t>T) can be considered as a packet of free gravity waves, which moves and spreads under the influence of divergence and dispersion.

The results of the statistical calculation are compared with known general facts, and with an actual storm. From the fact that the storm waves have a non-sinusoidal character, and arrive at any one point in groups of 5 to 10 crests, it is deduced that the duration of a gust is from 15 to 30 seconds. From the fact that the majority of the wave energy travels in directions that are within 30° of the wind, and with phase velocities that are nearly equal to the wind speed, the mean radius of the gusts is deduced to be about 40 meters in the case of a wind speed of 20 meters per second.

The crest length of the waves is proportional to the distance r from the storm, and inversely to its diameter, D; when r/D=10, the dominant length of the crests is 2.2 wavelengths.

The rms displacement, H, of the sea-surface from its horizontal mean is a function of the parameters already mentioned and of P, the rms value of the variable component of the wind pressure at the center of the storm; for the idealized storm considered, and for r/D≫1, this is approximated by H2=10P2D2/rL,all quantities being in centimeters, including P, which is measured in centimeters on a water barometer. Comparison with data for an actual storm indicates that this theory requires a value of P that is possibly 10 times greater than its actual value.

While the theory explains many of the phenomena of storm waves, it is therefore incapable of accounting quantitatively for the wave height. The possible reasons for this inadequacy are discussed. The relation of the theory to Jeffreys' sheltering theory is also discussed, and it is shown that both postulate that the variable component of the wind stress is normal to the water surface. The sheltering theory also postulates that the wind pressure lags 90° behind the surface disturbance. A similar phase lag is a consequence of the assumptions of the present theory.
Electron Microscopical Studies of the Latent Image Obtained by Exposures to Alpha Particles, X-Rays, and Light
Authors: Hoerlin H. , Hamm F. A.
Published: April 2005

The latent image of ordinary photographic emulsions has not been resolved. However, the slightly enlarged latent image as obtained by physical gold development can be demonstrated by means of the electron microscope. For the case of a fast negative emulsion it is shown that different types of exposures result in latent image centers of significantly different size distribution characteristics. High-intensity alpha-particle and x-ray exposures produce a very large number of finely dispersed centers; irradiation with light of optimum intensity and 1/100 sec duration forms a small number of centers; only very few specks result from exposures to light of very low intensity. The patterns observed are in line with expectations based on current photographic theory.