bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Permanent Three-Dimensional Views of Magnetic Fields
Authors: Crump Lloyd R.
Published: April 2005

A method has been developed for obtaining a permanent three-dimensional view of the flux pattern of a magnetic field by suspending microscopic magnetically-responsive particles in a transparent plastic solution, applying the magnetic force to form the particles into a definitive pattern of the field, and allowing the plastic to set. After the plastic solidifies, the specimen may be cut and polished for observation and later study or reference. A variation of this technique provides for the preparation of views on transparent plates. The process lends itself readily to the study and resolution of problems in magnetics encountered in research and development. It also has possible applications in the fabrication of magnetic and electronic components.
Graphical Analysis of Diffusionless Phase Changes—the Cubic to Twinned Orthorhombic Transformation
Authors: Lieberman D. S. , Read T. A. , Wechsler M. S.
Published: April 2005

A simplified method of calculating the crystallographic features of a diffusionless (martensitic) phase change is described and applied to the gold-cadmium alloy cubic-orthorhombic transformation. Use of the method requires a knowledge of the initial and final crystal structures and the specification of the crystallographic plane and direction of the inhomogeneous shear. It is based on the requirement that after partial transformation the interface between the two phases be free from stress on a macroscopic scale. The method involves representing on a stereographic net (a) the loci of directions in the original phase unchanged in length by the structure change per se and (b) the loci of directions unchanged in length by the inhomogeneous shear. The intersection of these loci determine possible undistorted interface planes. Excellent agreement with experimental observations is found when the method is applied to the cubic-orthorhombic transformation in gold-cadmium alloys.
X-Ray Properties of Plastically Deformed LiF
Authors: Birks L. S. , Seal R. T.
Published: April 2005

Plastic deformation may be introduced in LiF single crystals by abrading, quenching, or bending. For x-ray wavelengths of about 1.5 AU(CuKα) the diffracting power is increased about 4 times by any of the three methods. For shorter wavelengths of about 0.7 au(MoKα) the increase in diffracting power is about 4, 7, and 10 times for abrading, quenching, and bending, respectively. The bent crystals are more effective at shorter wavelengths because the plastic deformation is more uniform throughout the crystal while in the abraded crystal, all the deformation is concentrated in a layer extending only 0.002 inch below the surface. The extent and concentration of plastic deformation is shown by selective etching of dislocation sites.
Magnetic Domain Patterns on Thin Films
Authors: Williams H. J. , Sherwood R. C.
Published: April 2005

Magnetic domain patterns have been observed on evaporated films of iron, cobalt, nickel, and several different alloys of these elements. The films were deposited in the presence of a magnetic field to establish a uniaxial direction of easy magnetization. It was found that the direction of easy magnetization, in films of all compositions, could be changed by re-heat-treating them in a magnetic field with a new orientation. This is of special interest because bulk specimens of the elements do not respond to heat treatment in a magnetic field. Nucleation and growth of domains were observed for fields applied at various angles to the uniaxial direction of easy magnetization in some of the films. Patterns were obtained on films ranging in thickness from approximately 50 A to 12 000 A. Domain walls in films ranging from 50 A to 500 A in thickness tend to aggregate in pairs.
X-Ray Study of Order in the Alloy CuAu3
Authors: Batterman B. W.
Published: April 2005

Measurements of the integrated intensity of the superstructure reflections 100 and 110 from powders and a single crystal of CuAu3 give a long-range order parameter S=0.87±0.04 for a temperature below Tc not well defined. At the composition CuAu3, Tc=199°C. With decreasing Au content, Tc increases. Compositions richer in Au than CuAu3 could not be ordered. No annealing treatment was found which would sharpen the superstructure reflections. The breadths correspond to antiphase domains about 50 A in size. Measurements of the diffuse intensity from a single crystal of CuAu3 quenched from 285°C, or held at temperatures of 250°C and 320°C, gave short-range order coefficients qualitatively similar to those for Cu3Au. Compared with Cu3Au, CuAu3 shows a weaker first neighbor and a stronger second neighbor ordering.
Flux Plotting Analog for an Axially Symmetric Potential Field
Authors: Beaver William L.
Published: April 2005

Plots of flux tubes in axially symmetric static field problems are ordinarily obtained by rather tedious methods from plots of the equipotentials. The differential equation for the flux function in circular cylindrical coordinates does not have the same form as Laplace's equation. Hence, an ordinary wedge-shaped electrolytic tank cannot be used directly to plot flux tubes in an axially symmetric potential field. A direct method is described making use of a coordinate system in which Laplace's equation has the same form as the flux equation in the cylindrical system. An electrolytic tank can then be set up which makes use of this coordinate system in plotting equipotentials which are the analog of the flux tubes in an axially symmetric problem.
Fast Neutron Effects in Tetragonal Barium Titanate
Authors: Wittels M. C. , Sherrill F. A.
Published: April 2005

Tetragonal BaTiO3 is transformed into cubic BaTiO3 as a result of irradiation with fast neutrons at a temperature of approximately 100°C. Sufficient atomic displacements are produced by bombardment with an integrated fast neutron flux of 1.8×1020 n/cm2 so that tetragonal single crystals (c0=4.0349 A and a0=3.9923 A) expand anisotropically to form perovskite-type cubic single crystals with a0=4.0824 A. The irradiated material remains cubic to the lowest temperature of measurement, 78°K, showing none of the low temperature phase transitions of unirradiated BaTiO3, and after annealing at 1000°C the crystal remains cubic but with a reduced lattice parameter. X-ray, thermal, and optical methods were employed in studying these effects.
End Corrections in the Capillary Flow of Polyethylene
Authors: Bagley E. B.
Published: April 2005

End corrections n for the capillary flow of some polyethylenes have been determined as a function of shear rate Gn. The end correction term increases slowly at first with log Gn, but as the shear rate approaches the critical value at which the extruded filament becomes rough, both n and dn/d log Gn increase very rapidly. At the critical shear rate there is an abrupt decrease in dn/d log Gn, and at higher shear rates n increases very slowly with log Gn, with the slope dn/d log Gn being practically constant. All flow curves for a given polyethylene, obtained using capillaries of length to radius ratio ranging from zero to thirty, could be reduced to one single master curve by calculating effective shear stresses using the appropriate values of the end correction term n, with no apparent decrease in viscosity even for short capillaries in which the transit time of the polymer is very short.
Backscattering from Dielectric-Coated Infinite Cylindrical Obstacles
Authors: Tang Charles C. H.
Published: April 2005

The electromagnetic backscattering properties of an infinite conducting cylinder coated with a lossless dielectric layer of thickness comparable to a wavelength is investigated both theoretically and experimentally. The theoretical problem is first formulated with three regions of arbitrary constants and then reduced to the specific cases. The experimental investigation utilizes the parallel-plate-region technique modified to permit the application of the Doppler shift principle. The scattering obstacle is set in motion in the presence of a plane-wave electromagnetic field in the parallel-plate region, and the detected Doppler signal is directly proportional to the backscattered field of the obstacle in question. The theoretical and experimental results are in excellent agreement.
Nonlaminar Flow in Cylindrical Electron Beams
Authors: Harker Kenneth J.
Published: April 2005

Experimental measurements on the transverse velocity distribution in cylindrically symmetric electron beams emergent from magnetically shielded cathodes are reported. For strong magnetic fields the transverse velocity distribution at the beam center has been found to be composed of discrete classes. These results are explained on the basis of a beam model with nonlaminar flow in which thermal velocities and space charge are neglected. The mechanism depends on the periodic passage of electrons through or very near the beam axis and the fact that the wavelength of this periodicity is a decreasing function of the distance between the point of entry into the magnetic field and the axis.

When the space charge and magnetic forces are comparable, no discrete transverse velocity distribution was observed. It is shown, however, that the beam should still be in the same type of nonlaminar flow as above.
On the Width and Energy of Domain Walls in Small Multi-Domain Particles
Authors: Amar Henri
Published: April 2005

A two-domain ferromagnetic particle is considered. It is shown that the inclusion of the magnetostatic energy in the derivation of the wall characteristics yields values of these characteristics considerably different from those in bulk material.
Thermoelectric Power and Resistivity of Solid and Liquid Germanium in the Vicinity of Its Melting Point
Authors: Domenicali C. A.
Published: April 2005

The thermoelectric power of germanium against platinum has been measured between room temperature and 1030°C (melting point is 937°C). Five specimens were studied in the solid phase (three polycrystalline and two single crystalline specimens), and two in the liquid phase (one n type and one p type at room temperature). It is found that the absolute thermoelectric power Q of high purity (50–70 ohm-cm) germanium is nearly linear in 1/T only for the range 0.83<(1000/T)<1.5, or 400<T<937°C. The value of Q for our crystals at temperatures below 400°C is less negative than would be required by an extrapolation of the straight line Q=+140−280(1000/T) μv/deg which represents fairly well the high temperature data. This discrepancy may be due to the presence of very small amounts of acceptor impurity (perhaps boron) in our crystals. The thermoelectric power between liquid and solid germanium is approximately 70 μv/deg, and the liquid is positive relative to the solid. The absolute thermoelectric power of the liquid is very nearly zero and is nearly independent of temperature. Finally, the resistivity of germanium decreases by a factor of approximately 19 upon melting, and is approximately 63 microhm-cm in the liquid phase.
Low-Energy Elastic Scattering of Electrons by Oxygen and Nitrogen
Authors: Hammerling P. , Shine W. W. , Kivel B.
Published: April 2005

The elastic scattering of slow electrons by O and N is calculated by the method of phase shifts. The Hartree potential gives a cross section (2×10−15 cm2) for O on the order of magnitude needed to agree with the experiments of Lamb and Lin in air. Since the Hartree potential is known to be too weak as it neglects exchange and polarization, this agreement is considered fortuitous. Exchange forces are introduced by a new approximation based on a suggestion of Slater for bound atomic states. The exchange approximation is adjusted to fit the more elaborate calculation of Bates and Massey for zero energy and zero polarization. The addition of a reasonable polarization force results in an acceptable potential and closer agreement with experiment. A similar calculation is made for nitrogen. In this case the Hartree potential alone gives a cross section which is too large. The inclusion of exchange and polarization leads to better agreement with the measurements in air.
Frequency Spectrum of the Barkhausen Noise
Authors: Biorci G. , Pescetti D.
Published: April 2005

The spectral density of the Barkhausen noise has been measured and a theoretical interpretation of the results is given. It is assumed that the single pulse is exponential with a time constant of the order of 10−4 second. Then the computed spectral density is constant up to 1 kcps, and then decreases exponentially. This behavior is only slightly dependent on the shape of the pulse. The theoretical conclusions are in good agreement with experimental data taken on iron, nickel, and ferroxcube specimens.

The usual model introduced to explain the mechanism giving rise to the noise leads to the conclusion that the intensity of the spectrum is proportional to the frequency of the magnetizing current. This conclusion is not experimentally verified because of the extreme simplifications involved in the model itself.
Force on an Anisotropic Paramagnetic Crystal in an Inhomogeneous Magnetic Field
Authors: Wolf W. P.
Published: April 2005

A simple expression is derived for the force exerted on an anisotropic paramagnetic crystal by a magnetic field having gradients in two perpendicular directions. It shows that there is in general no direct relation between the force on an isotropic and an anisotropic sample in the same field, so that care must be exercised in interpreting the results of susceptibility measurements on anisotropic crystals by the Faraday method.
Shock Hugoniot of Air
Authors: Deal W. E.
Published: April 2005

Experiments are described in which an explosive-driven plate sets up a strong shock in air in contact with the plate. Plate velocity and air shock velocity are measured by means of a high-speed framing camera. A pressure-compression relation results from these measurements through use of the conservation equations of hydrodynamics. The experimental results up to pressures of 200 bars are compared to a calculated relation.
Partial Polygonization in Impure Copper Crystals
Authors: Young F. W. , Cabrera N.
Published: April 2005

A method to produce etch pits in OFHC copper by electroetching is presented and used to show that ``partial polygonization'' occurs in OFHC copper at or above 900°C. This does not seem to occur in 99.999% copper, indicating that impurities might facilitate climbing of dislocations at high temperatures.
Effects of Radiation Damping on Spin Dynamics
Authors: Bloom Stanley
Published: April 2005

When a two-state quantum system, capable of making radiative transitions, is driven by a high-frequency field, there occur damping effects due to the reaction of the sample to its own radiated field. This damping, which becomes important for high-Q rf structures and for samples of large dc susceptibilities, is here analyzed classically for a simple prototype system—a magnetic spin system obeying the Bloch equations. These equations are augmented to include the radiation-damping torques and are then solved for the four cases of usual interest. Firstly, for steady-state slow passage, radiation damping broadens and lowers the absorption and dispersion signals. Secondly, for adiabatic fast passage, damping causes the dispersion signal to dip at the line center and causes the otherwise absent absorption signal to become finite. However, if the radiation damping field becomes larger than the rf driving field a complete adiabatic inversion is shown to be no longer possible. Thirdly, the conditions for the occurrence of delayed power peaks of the free-precession signal are discussed. Fourthly, for the case of the driven nonsteady state, the stimulated emission may, for large radiation damping, become quite large if the system is driven from an initially ``negative temperature'' condition.
Acoustic Relaxations in Ferrite Single Crystals
Authors: Gibbons D. F.
Published: April 2005

Acoustical wave attenuation measurements have shown the existence of two types of stress-induced relaxations and a transformation in the ferrites examined. A loss mechanism due to stress-induced electron migration of the type Fe++++e⇄Fe++, with an activation energy of 0.03±0.004 ev per electron jump, appears to be common to all ferrites containing di- and trivalent ferrous ions on the octahedral sites. A stress-induced relaxation has been demonstrated in manganese ferrite, with an activation energy of about 0.3 ev per unit process. This relaxation process is sensitive to composition and homogeneity. Finally, a transformation has been observed in manganese zinc ferrite near 10°K, the temperature depending upon composition. A similar transformation probably occurs in manganese ferrite below 1.25°K. Below the transition temperature the intensity of magnetization is found to decrease with decreasing temperature.
Metal Transfer in Sliding Contacts
Authors: Flom D. G.
Published: April 2005

Transfer of radioactive silver has been studied quantitatively in sliding contacts containing graphite and metal. The rate of transfer from silver-graphite riders to graphite cylinders is initially high but soon approaches a limiting equilibrium state. The amount of silver transfer increases markedly with surface roughness. Further, the transfer is enhanced by the addition of liquid water to the rider track. Back transfer to the rider has been found to consist mostly of loosely clinging dust in the rider face.

Silver transfer to a copper cylinder is much greater than to a graphite cylinder, the difference being roughly twenty-fold. Within the experimental conditions, the transfer/unit time to both graphite and copper cylinders is greater at 1 cm/sec than at 390 cm/sec.
Preparation and Photoconductive Properties of Cadmium Telluride Films
Authors: Kretschmar George G. , Schilberg Lloyd E.
Published: April 2005

Cadmium telluride was made by combining purified cadmium and tellurium in stoichiometric proportions in an evacuated Vycor tube. Thin films of this material were deposited by condensation across the short gaps between Aquadag electrodes in Dewar-type tubes. These films have a high resistance at room temperature and show a large photoconductive effect, with a peak response at about 0.8 micron. When the films are deposited in the presence of indium vapor, the dark resistance can be brought down to a value of approximately one to ten megohms for a film of one-half millimeter in width. The resistance of the films under illumination will then be a few tenths of a megohm. Iodine vapor will also reduce the dark resistance of cadmium telluride films, but in this case, the photoconductive effect almost disappears.
Minority Carrier Lifetime in p-n Junction Devices
Authors: Byczkowski M. , Madigan J. R.
Published: April 2005

A relation between minority carrier lifetime and recovery time has been obtained for p-n junction rectifiers of arbitrary base width. In the limiting cases of base width large or small compared to a diffusion length the recovery time is found to depend on the lifetime or on the transit across the base region, respectively. In intermediate cases, the recovery time is a function of both the lifetime and the transit time. Recovery time measurements on diffused junction silicon rectifiers as a junction of base width were found to be in satisfactory agreement with the theory.
Oxygen Content of Silicon Single Crystals
Authors: Kaiser W. , Keck P. H.
Published: April 2005

The oxygen content of pulled silicon crystals, determined by vacuum fusion gas analysis, is correlated with the infrared absorption at 9 μ. In vacuum and in helium or hydrogen of 1 atmos, the oxygen concentration of a liquid zone of silicon (about 20 mm2 in cross section) can be rapidly decreased. In an oxygen atmosphere or in contact with quartz, liquid silicon picks up oxygen quite readily. A maximum oxygen content of 2×1018 oxygen atoms per cm3 was observed. Silicon single crystals pulled from a quartz crucible exhibit fluctuations in oxygen concentration both perpendicular and parallel to the pulling direction. Explanations of these effects are offered and the influence of various pulling parameters is discussed.
Theory of Diffusion Constants in Interstitial Solid Solutions of b.c.c. Metals
Authors: Ferro A.
Published: April 2005

An attempt has been made to evaluate the activation energy of interstitial diffusion in body-centered cubic metals on the basis of the distortion energy necessary to open one of the flat interstitial cavities (½ 0 0) adjacent to an occupied one to a size equal to the diameter of the interstitial atom. The frequency on which the diffusion process depends, and hence the frequency value to be used in calculating D0, is simply the maximum frequency of the lattice along the (100) direction. The results obtained for Q and D0 agree satisfactorily with the experimental data and thus show clearly the dependence of the activation energies Q on the elastic constants of the metal of the matrix and on the interstitial atom diameter. Moreover the theory confirms the origin of some observed relaxation effects still uncertain and the evaluation of the activation energies of interstitial atoms anchored around lattice defects such as dislocations.
Electric Breakdown and Conduction through Mylar Films
Authors: Inuishi Y. , Powers D. A.
Published: April 2005

Dc breakdown studies on Mylar film show that defects cause a decrease in dielectric strength with decreasing film thickness at room temperature but not at −180°C. The breakdown at defects is associated with moisture content. Using self-healing electrodes to eliminate weak areas, a dc dielectric strength of 6 Mv/cm is found, independent of film thickness. Prebreakdown current measurements indicate ionic currents which are fairly uniform throughout a sample, and field emission currents localized at incipient breakdown points. Breakdown probably occurs as a result of local heating by field emission currents.
Thermionic and Semiconducting Properties of [Ag]–Cs2O, Ag, Cs
Authors: Davey John E.
Published: April 2005

Thermionic emission measurements have been carried out on [Ag]–Cs2O, Ag, Cs layers in a state of near maximum thermionic yield. The data have been plotted according to the Fowler equation to determine thermionic work functions; an average value of 0.83 ev has been obtained. However, cooling the layers, below ambient, to temperatures of −40°C, results in an increase of work function of approximately 0.3 ev. Photoelectric emission measurements on these same layers yield an average photoelectric work function of 1.06 ev.

Conductivity measurements on Cs2O, Ag, Cs layers are linear between 100 and −70°C; an activation energy of ∼0.1 ev has been determined from data in this temperature range. Conductivity measurements on Cs2O layers containing no reduced silver exhibit changes in slope similar to the thermionic data. Activation energies computed from above the break in conductivity data are ∼0.25 ev. Cooling the layers to −70°C and below results in increases of activation energy of ∼0.1 ev.
Design and Evaluation of an S-Band Rebatron
Authors: Kaufman Irving , Coleman Paul D.
Published: April 2005

A practical design of an S-band rebatron for producing a high power, bunched, megavolt electron beam, theoretically possessing harmonic current frequencies in the submillimeter range is presented. An indirect experimental method of evaluating the beam obtained from the rebatron, based on measuring momenta spectra, gives very satisfactory agreement with theory. The validity of this indirect method of beam analysis is strengthened by a measurement of the ratio of the 26th beam harmonic current amplitudes under two different sets of conditions determined experimentally by momenta spectra measurements. No highly critical tolerance conditions are encountered in the investigation.
The Harmodotron—a Megavolt Electronics Millimeter Wave Generator
Authors: Sirkis Murray D. , Coleman Paul D.
Published: April 2005

A new method for the coherent generation of relatively high powers at submillimeter wavelengths through the electronic excitation at a single frequency of a selected higher order TM0mn mode in a cylindrical cavity which is large compared to the wavelength is investigated. The theoretical relationship between the generated power, P, the harmonic current component, Is, and the wavelength, λ, is typically of the order of P(watts)≃3000[Is(amp)]2[λ(mm)]12for a 1-Mev electron beam. Experimental measurements at a wavelength of 8.310 mm which successfully demonstrate the method are described.
Photoelectric Effect from Borosilicate Glass
Authors: Rohatgi Vijay Kumar
Published: April 2005

Values of the photoelectric quantum efficiency of glass for different wavelengths have been determined and data have been obtained on the status of electrons placed on glass surfaces. One of the borosilicate glasses commonly used in discharge tube manufacture and soda glass were studied in vacuum with 2537 A photons from a quartz Heraeus mercury arc and with light from a glow discharge operating in pure A and Ne from 10−1 to 10 mm pressure. Clean borosilicate glass in vacuum at 22°C with fields of some 1000 v/cm across it yields photoelectric current densities of the order of 10−12 amp/cm2 for the full light of a 110 volt arc focussed on 10 cm2 area through quartz optics. This current comes from the 3–4% Na impurity atoms on the surface. Soda glass yields currents in proportion to the density of Na atoms. The normal conductivity of the glass comes from Na+ ions of some 0.5 volt activation energy normally present. It is enhanced 10-fold by Na+ ions liberated at the surface by light. Na+ ions next the cathode cannot leave the glass, but electrons enter the glass from the metal cathode backing of lower work function to neutralize the ion space charge as it builds up near the cathode. Electrons sprayed onto the glass surface have a mobility of ∼5×10−5 cm2/volt sec in the glass in contrast to the value of ∼1×10−7 cm2/volt sec for the Na+ ions reported by Kraus. Photons above 3300 A do not contribute to the conductivity in any fashion. The photoelectric yield for 2537 A was obtained directly in absolute magnitude by use of a vacuum bolometer. For the light from glow discharges ≪1200 A, the efficiency was obtained indirectly by comparison with values for Pt and Au. The values obtained are tabulated below. Wave−Borosili−Sodalength Acate glassglassAuPt    Remarks2537 A10−46×10−410−2…Vacuum≫2300 A10−4……10−3Glow discharge≪1250 A10−3…10−110−10.1 to 10 mm Hg
Rippling of Thin Electron Ribbons
Authors: Waters William E.
Published: April 2005

A paraxial equation for thin electron ribbons, or ``sheet beams,'' subject to purely electrostatic fields, and including a first-approximation term for the lateral space-charge force, is derived. Solutions of the equation for several cases of practical interest are discussed. The effect of the possible curvature of the optical axis is shown to be very important in helping to counteract the divergent space-charge forces.
Quantitative Method for the Determination of Fiber Texture
Authors: Cullity B. D. , Freda August
Published: April 2005

A semidirect diffractometer method, requiring little or no specimen preparation, has been developed for the determination of fiber texture in wire or rod. The method is applied to cold-drawn, high-purity aluminum wire, which is found to have a double fiber texture: 80% of the specimen volume has a [111] texture and 20% a [100] texture.
Production of High-Velocity Shocks
Authors: Josephson Vernal
Published: April 2005

High-velocity axial shocks have been produced in linear gas discharge systems by so shaping the discharge tube (and discharge) that a maximum amount of energy is coupled into the ionized gas before the shock is formed. Two methods of coupling energy into the gas are discussed along with their relative merits and shock velocities achieved by each method.
Field Emission from Silicon
Authors: D'Asaro L. A.
Published: April 2005

Field emission patterns were observed using a point made of a single crystal of p-type silicon. Stable patterns were obtained only after the point was distorted by heating in the presence of an electric field. The symmetry of the patterns agreed with the symmetry expected from the known orientation of the crystal.
Magnetic Susceptibility of Neutron-Irradiated Quartz
Authors: Stevens D. K. , Sturm W. J. , Silsbee R. H.
Published: April 2005

Measurements are reported of the magnetic susceptibility of neutron irradiated quartz as a function of irradiation time. The results are interpreted in terms of the density of centers produced by the irradiation and are compared with optical and x-ray studies of neutron damaged quartz.
Radiation Discrimination with Photoconducting Crystals
Authors: Sihvonen Y. T. , Boyd D. R.
Published: April 2005

A mathematical study has been carried out on the discriminatory properties of an array of photoconducting receivers subjected to an influx of photons. Those photons not absorbed by the first receiver pass on to the second receiver and so on until all the initial photons are absorbed. The capture of a photon is indicated by an increase in receiver conductance. Analysis of the problem reveals that if the receiver thicknesses are permitted to vary in a prescribed way interesting response differences result for photons having different energies. Under certain conditions, these response differences can be used to resolve two classes of photons differing in energy into a spectrum.
Mechanical Behavior of a Polymer at Temperatures through the Glass Transition Temperature
Authors: Stevens J. R. , Ivey D. G.
Published: April 2005

Stress-temperature (constant strain) and length-temperature (constant stress) measurements have been made on Paracril-35 (a butadiene-acrylonitrile copolymer) in the temperature range −80°C to 25°C, which includes the glass-like, transition, and rubber-like states for this material (Tg∼−25°C). Time effects are observed in the transition region, but for temperature gradients used (down to about 1°C in 4 hours) the behavior at low temperatures is unique, indicating the existence of a real transition. This behavior is independent of the strain imposed at room temperature. The shift in transition temperature (in the length-temperature work) with extension is found to give quantitative support to the theory that the transition occurs at a certain minimum volume. In the rubber-like region, behavior is represented by the usual equation of state.
Infrared Spectra of High Polymers. VIII. Polyvinyl Nitrate
Authors: Krimm S. , Liang C. Y.
Published: April 2005

The infrared spectrum of polyvinyl nitrate has been obtained in the extended region of 70 to 3600 cm−1. Polarized infrared measurements were made on oriented specimens in the range of 350 to 3600 cm−1. Since x-ray diffraction patterns indicate no crystallinity, the analysis has been based on an assumed atactic configuration. With the help of previous studies of high-polymer spectra and results obtained on small molecules, it has been possible to make a complete assignment of all of the expected fundamentals. Dichroic measurements have not only permitted a decision on the assignment of the controversial NO2 rocking and bending modes, but suggest certain details concerning the local configuration of the nitrate group. There seems to be evidence that, although the specimen is not crystalline, a significant proportion of the chains have configurations not far from a planar zigzag chain.
Surface Energy of a 90° Domain Wall in Iron
Authors: Graham C. D.
Published: April 2005

The relative surface energy of a 90° domain wall in a cubic material with K1>0 (iron) has been evaluated over the range of possible wall orientations. As the plane of the wall passes through a {110} plane, the minimum-energy configuration changes from a right-hand to a left-hand rotation of the atomic moments; this leads to a sharp upward cusp in the energy vs orientation curve. The calculated orientation dependence of the surface energy can be used to predict a stable wall position in an iron whisker. The prediction is in reasonable agreement with observation.
Viscoelastic Properties of Concentrated Solutions of Polyvinyl Alcohol
Authors: Onogi Shigeharu , Hamana Isao , Hirai Hidefumi
Published: April 2005

The dynamic viscosity and rigidity of concentrated solutions of polyvinyl alcohol samples having different molecular weights have been measured by means of a torsionally oscillating rheometer and an electromagnetic transducer within the ranges of frequencies from 0.08 to 400 cps and the temperature range from 20° to 55°C. The solutions behave almost as Newtonian liquids at lower frequencies; however, at the frequencies around 1 to 10 cps the viscosity of solutions begins to decrease while the rigidity increases rapidly. The frequency at which the rather abrupt change in dynamic viscosity and rigidity takes place is lower the higher the concentration, the higher the molecular weight, and the lower the temperature. The effects of the concentration, temperature, and molecular weight on the zero shear (frequency) viscosity have been examined quantitatively, and some of characteristic features observed on other high polymers have also been found. Comparison of the dynamic voscosity with the steady-flow viscosity shows that the frequency dependence of dynamic viscosity is not quite quantitatively equivalent to the rate of shear dependence of steady-flow viscosity. The dynamic data have also been compared with two molecular theories of viscoelastic behavior of high polymers, and showed rather good agreement. A slight discrepancy observed in this comparison may be attributed to the molecular weight distribution in the sample and intermolecular interlacings in the concentrated solution.
Electrical Properties and Thermal Expansion of the Laves Phases, CaMg2 and MgCu2
Authors: Smith J. F. , Ogren J. R.
Published: April 2005

Electrical resistivities, temperature coefficients of resistivity, and Hall coefficients have been measured on single crystals of hexagonal CaMg2 and on polycrystals of cubic MgCu2. The magnitudes of the measured values fall in the range normally observed in metals. In contrast, measured values for the coefficients of thermal expansion are slightly higher than those observed in metallic elements. Appreciable scatter in measured resistivities on different specimens was observed and is presumably due to variations in the degree of crystalline perfection. For CaMg2 the measured Hall coefficients and the temperature coefficients of resistivity and of thermal expansion show only a small degree of anisotropy. The sign of the Hall coefficients was found to be positive for CaMg2 and negative for MgCu2; this is consistent with previous measurements of magnetic susceptibility made on MgCu2 and its alloys.
Current Distribution in Modulated Magnetically Focused Electron Beams
Authors: Chodorow M. , Shaw H. J. , Winslow D. K.
Published: April 2005

Detailed measurements have been made of the dc and rf current distribution in a modulated, magnetically focused electron beam having normalized parameters in the range of values appropriate for practical medium-power and high-power klystrons. The ratio of the total rf current to the total dc current in the beam as a function of drift distance was determined experimentally under Brillouin-flow conditions for selected values of α (the ratio of the rf voltage at the input gap to the dc beam voltage). These experimental values are compared with the results predicted theoretically. Similar experimental results are presented for higher focusing fields. Detailed radial distributions of the dc and rf current were experimentally determined by using an iris (a plate with a small hole) to allow only a small portion of the beam to be selected at any radial position. These measurements were made at various values of α and drift distance. The results for small values of α show, as predicted by theoretical considerations for a modulated Brillouin-flow beam, that the radial rf current distribution in the beam is the same as that of a beam whose modulation is represented as sinusoidal scallops on a beam of constant (volume) charge density. As either α or the focusing field, or both, are increased, the rf current is no longer confined to the beam periphery but becomes more evenly distributed throughout the beam cross section.
Reverse Breakdown in In-Ge Alloy Junctions
Authors: Muss D. R. , Greene R. F.
Published: April 2005

Experimental information is presented which shows that abrupt p+n junctions break down by the Zener internal field emission effect when the base resistivity is low and by ionization avalanche when the base resistivity is high. In intermediate regions of base resistivity both mechanisms are observed in the same junction. The onset of Zener current is accompanied by a drop, of unexplained origin, in the junction collection efficiency for minority carriers photoinjected into the base. Applicability of the Zener theory to abrupt p+n junctions is discussed.
Resolution of Electron Probe Microanalyzers
Authors: Wittry David B.
Published: April 2005

In microanalysis using x-ray emission excited on the surface of a thick specimen by an electron probe, the minimum volume element which can be analyzed is limited by the size of the electron probe, by fluorescence excitation, and by the penetration and diffusion of the electrons in the specimen. With an electron accelerating voltage of about 30 kv the electrons have an energy of the order of 3 times the critical excitation energy of the K or L x-ray levels of the target and the minimum volume which can be analyzed (in the absence of strong fluorescence effects) is of the order of 8 cubic microns for a copper target, and is considerably larger than this for targets of low atomic number or density. It is shown that the resolution in this method of analysis can be improved without loss of statistical accuracy or increase in the time of measurement by (1) improving the quality of the electron optics and by (2) selecting the accelerating voltage and electron probe size. The minimum volume element for practical quantitative analysis can thereby be made as small as about 0.2 cubic microns in a copper target. This is obtained by using slightly larger electron probes and lower accelerating voltages than those representative of current practice.
Static Fatigue of Glass. II
Authors: Charles R. J.
Published: April 2005

Static fatigue of a simple soda-lime glass has been investigated in relation to the sensitivity of this glass to atmospheric corrosion. An analysis of the failure process has been given which is based on the concept that inherent surface flaws grow by corrosive mechanisms to critical dimensions by virtue of a reaction between water vapor in the atmosphere and components of the glass. The rate of this reaction is determined by the stress conditions around local areas and the temperature, pressure, and composition of the surrounding atmosphere. Since the experimental work shows a close relationship between the temperature dependence of the failure process and that of the self diffusion of sodium ion in bulk glass it is concluded that alkali content is responsible for the very low long time strengths of most inorganic glasses.
Approximate Elastic Spectrum of β-AuZn from Temperature Diffuse Scattering of X-Rays
Authors: Schwartz Milton , Muldawer Leonard
Published: April 2005

The temperature diffuse scattering of x-rays from a single crystal of β-AuZn has been measured at room temperature using a Geiger counter diffractometer and crystal monochromatic CuKα radiation. Acoustical frequency and velocity dispersion curves were obtained for the symmetry axes using the theories of James and Laval. Integrated intensity measurements of Bragg reflections from the alloy gave Debye temperatures of 153°K and 220°K for gold and zinc, respectively. The velocities at infinite wavelength yielded elastic constants of c11 = 5.3 c12 = 3.5, and c44 = 3.0 in units of 1011 dynes per cm. An approximate frequency spectrum was calculated.
Effect of Elongation on the Electrical Resistivity of Metals. Part I. Aluminum. Part II. Molybdenum
Authors: Peiffer H. R.
Published: April 2005

The changes in the electrical resistivity of metals at 78°K with elongation are investigated. Part I is devoted to the changes introduced in the face-centered cubic metal aluminum upon elongation at 78°K. Part II discusses the changes that occur in the body-centered cubic metal molybdenum upon elongation at 298°K. Both sections describe the relationship between the portion of the resistivity generally attributed to point defects and the resistivity that remains after the point defect recovery has been completed; these resistivities are proportional to each other for both metals.

It is noted that for both metals the resistivity caused by point defects and the residual resistivity are directly proportional to the elongation. It is further discovered that the rate of resistivity recovery at 145°C for cold-worked molybdenum is directly proportional to the amount of elongation introduced.
Effect of Proton Irradiation Upon Hydrogen Reduction of NiO
Authors: Simnad M. T. , Smoluchowski R. , Spilners Aija
Published: April 2005

It is shown that the reduction of a metal oxide such as nickel oxide by hydrogen gas is strongly influenced by nuclear irradiation. The initial induction period is shortened and the subsequent reduction accelerated. The effects anneal out at higher temperatures. A probable mechanism of this acceleration is suggested.
Dielectric Relaxation Spectra of Lithium Borosilicate Glasses
Authors: Heroux L.
Published: April 2005

The dielectric relaxation spectra of a system of lithium borosilicate glasses have been investigated over the frequency range 0.01 cps to 500 kc and temperatures between 25°–350°C. The spectra of the samples exhibit well-defined peaks in the dielectric loss factor and dispersion in the dielectric constant. The activation energies associated both with the lithium ion mean relaxation frequency and the lithium ion dc conductivity (zero frequency conductivity) are constant with temperature; their difference for each sample appears to be an indication of the distribution of activation energies of the sample. The experimental data show that an analytical function proposed by K. W. Wagner adequately describes the distribution of relaxation times associated with the lithium ion relaxation process in the glass network. The distribution originates from a spread in activation energies for low lithium concentrations and a spread in the period of vibration of the lithium ions about their equilibrium position for higher concentrations.
Dynamic Fatigue of Glass
Authors: Charles R. J.
Published: April 2005

An analytical model, which is applicable to static fatigue of lime glass, has been extended to account for dynamic fatigue of the same glass. The model successfully predicts the room temperature strain rate sensitivity of the failure process in lime glass and indicates a method by which the stress concentration relationship, applicable to microscopic flaws on glass surfaces, may be obtained by experiment. Resulting experiments showed that the stress concentration relationship proposed by Inglis is valid.
Thermometric Study of the Frozen Products from the Nitrogen Microwave Discharge
Authors: Fontana B. J.
Published: April 2005

Thermometric observations have been made of the phenomena accompanying the stabilization and the recombination of free nitrogen atoms in a solid molecular nitrogen matrix at liquid helium temperatures. Condensation from the gas phase may occur at temperatures considerably above the 4.2°K coolant temperature as the result of the normal change in heat content and the heat of atom recombination. Estimates, made from the latter effects, of the free atom concentration in the gas phase were as high as 4 atom %. Qualitative confirmation of the presence of an energetic species stabilized in the solid phase was made by detection of heat release upon warmup. From the latter effect a minimum nitrogen atom concentration in the solid of 0.03 atom % was estimated. For the conditions used the initiation of atom recombination occurs at a temperature of about 9°K. The upper limit of about 36°K for stabilization coincides with the known thermal transition in solid nitrogen. The data suggest that at least above 9°K diffusion of nitrogen atoms occurs throughout the solid matrix during deposition from the gas phase. If recombination during warmup is diffusion-controlled, unusual dependence upon temperature is indicated.
Analysis of the Emissive Phase of a Pulsed Maser
Authors: Theissing H. H. , Dieter F. A. , Caplan P. J.
Published: April 2005

The operation of a pulsed solid-state Maser consists essentially of alternate periods of spin inversion and stimulated spin emission. Inversion can be accomplished by a short driving pulse or an adiabatic rapid passage. In the emission phase a weak signal field causes the spin system to spiral back coherently and radiate. The emissive phase can be treated by equations which for finite relaxation times can not be solved in closed form, but which are amenable to machine computation. Such numerical solutions giving the transverse moment, output field, output power, and power gain as a function of time were computed for various relaxation times, input fields, and values of the oscillation parameter. The results are interpreted with respect to applications of both regenerative and superregenerative modes of operation.
Production of Dislocations in Germanium by Thermal Shock
Authors: Wagner R. S.
Published: April 2005

Dislocations introduced into single crystals of germanium grown by the Czochralski technique have been studied. It was found that most of the dislocations do not originate during growth, but are produced after growth as a result of thermal shock. Thermal stresses resulting from nonuniform temperature gradients during growth seem to have little or no effect on the dislocation density and distribution.
Comparison between the Linear and Nonlinear Steady-State Behavior of a Heated Tube
Authors: McFarland B. L.
Published: April 2005

The range of applicability for the solution of the linearized diffusion equation is discussed for a particular case—heating of a homogeneous tube by internal energy generation. The range is defined by comparisons of series solutions of the linear and nonlinear diffusion equations (constant material properties vs variable material properties). Two sources of errors in the constant-property solution are evaluated and a criterion for the limits of applicability of the linear solution is derived.
Dislocation Model of Low-Temperature Creep
Authors: Weertman J.
Published: April 2005

A low-temperature dislocation creep model of the exhaustion type is proposed to account for the temperature independent activation energies which are found in recent experiments. Logarithmic creep can be obtained from the model if a Gaussian distribution function of Frank-Read sources is assumed. The theory is applicable under easy glide conditions but should not be used when extensive double glide occurs. The theory can be extended into the liquid helium temperature range with the aid of Glen-Mott quantum-mechanical dislocation tunneling.
Modified Rotational Model of Flux Reversal
Authors: Gyorgy E. M.
Published: April 2005

A nonuniform magnetic configuration for rapid rotational flux reversal in square-loop ferrite cores is analyzed. It is shown that the demagnetizing effects due to the boundary of the toroid are, to a good approximation, negligible for toroids with cross-sectional radii as small as 2.5×10−2 cm. A basic assumption of an earlier rotational model of flux reversal was that these demagnetizing fields could be neglected. The predictions of this modified model at high drives are similar to those of the earlier model. The possibility of correlating Hc (the intercept of the extrapolated linear region of the inverse switching time versus drive field plot) with more basic parameters through a model of this type is indicated.