bluuebunny/crossref_metadata_2025 huggingface dataset:
Nondestructive Memory Employing a Domain Oriented Steel Wire
Authors: Gianola U. F.
Published: April 2005

A magnetic memory can be interrogated nondestructively by applying a perturbing field normal to the direction of remanent magnetization, and, at the same time, observing the sign of the reversible flux change. However, there may be a considerable irreversible flux change during the first few interrogations following magnetization. This irreversible component can be reduced by introducing magnetic anisotropy in a direction parallel to the direction of magnetization which is used to store binary information. The characteristics of the ideal memory is analyzed by means of domain theory. In an experimental memory a steel wire under tension was used for the memory material. A small solenoid was used to magnetize the wire locally and also to observe the flux change which was produced by an interrogative current pulsed through the wire itself. The general predictions of the theory were confirmed by experiment. Interrogation is non-destructive and is completed in less than 1 μsec. The output is proportional to the square of the wire current, and discrimination is a matter of observing its polarity. A single bit can be written into a memory array by a coincidence of a wire current and a solenoid current. The wire current can be the same as that used for interrogation. A number of bits can be carried on one wire and interrogated simultaneously. The factors affecting the design of a memory array are discussed.
Friction Coefficients of Graphite over the Temperature Interval 25°C to 2450°C
Authors: Driesner Allen R. , Wagner Paul
Published: April 2005

Measurements have been made of the coefficients of friction for graphite and some graphite-based materials which are of interest for nuclear reactor application. Static and kinetic friction coefficients have been measured as a function of surface conditioning and temperature up to a maximum temperature of 2450°C. In addition, the effects of force, stress, anisotropy, refractory coating, and uranium loading were studied. The most significant effect was found to be caused by the conditioning of the contact surfaces by polishing action, and this was more pronounced in the static than the kinetic friction coefficient. The friction coefficients increase with temperature. Other effects studied had negligible influence.
Solid-State Dissolution of Germanium by Indium in Semiconductor Devices
Authors: Roschen John , Thornton C. G.
Published: April 2005

The development of small pits or cavities has been observed in germanium semiconductor devices with indium metal to germanium semiconductor contacts at temperatures below the melting point of indium. The mechanism of cavity formation is a slid-state dissolution of germanium by indium with a subsequent more rapid diffusion of germanium in the indium, limited by the solid solubility of the germanium in the indium. A small solid solution region exists at the indium-rich end of the germanium-indium constitutional diagram with a solid solubility limit of germanium in indium between 0.001% and 0.011% germanium by weight. The rate of solution of germanium in indium is anisotropic and dependent on the crystal orientation of the germanium. In surface barrier transistors the movement of the indium germanium interface can be expressed approximately by L=(Dτ)½, where the expression for the average diffusion constant is D(cm2/sec)≈4×10−3, exp(−20 800/RT). Through the addition of germanium to indium or an indium alloy, solution cavity formation can be inhibited or eliminated.
Electron Recombination Coefficient Measurements in Nitrogen at Low Pressures
Authors: Faire A. C. , Fundingsland O. T. , Aden A. L. , Champion K. S. W.
Published: April 2005

Rate coefficients for recombination in nitrogen have been determined experimentally with partial pressures ranging from 0.01 mm to 3.00 mm Hg. At the lower nitrogen pressures, inert gases were added as passive recoil agents to reduce diffusion losses in the afterglow of a pulsed microwave discharge. The apparent value of the recombination coefficient obtained from these measurements is 1.2±0.2×10−6 cm3 sec−1 for an electron temperature of approximately 300°K. The coefficient is constant within the experimental error, except at very low partial pressures of nitrogen where a small linear decrease is observed. The probable causes for this deviation are discussed. The magnitude of the rate coefficient and other evidence suggests that dissociative recombination is the most likely loss mechanism.
Determination of X-Ray Absorption Coefficients of Inhomogeneous Materials
Authors: Ergun Sabri , Tiensuu Victor H.
Published: April 2005

A method has been developed for determining x-ray absorption coefficients of inhomogeneous materials. It involves comparison of the reflected and transmitted intensities from the same specimen at various scattering angles. The difference in the geometry of the reflection and transmission techniques permits calculation of the absorption coefficient from the observed intensities. Evaluation of the absorption coefficient at different angles overcomes the uncertainties of the conventional method caused by small angle scattering, white radiation, crystalline mineral impurities, etc., and eliminates the necessity of measuring the intensity of the primary beam. The method is not limited to x-rays; it is equally applicable to γ rays, neutrons, and visible light.
Interaction of Low-Energy Electrons with Ferroelectric Materials
Authors: Miller Robert C. , Heidenreich Robert D.
Published: April 2005

Some of the effects of low-energy electron bombardment on BaTiO3 and triglycine sulfate have been investigated. It is found that the secondary electron emission characteristics allow one to reverse the spontaneous polarization in these materials when the energy of the bombarding electrons is varied through the first crossover. The switching time is determined by the rate at which charge can be built up on the bombarded surface and is limited by the primary electron beam current density. The two stable surface states characteristic of insulators are clearly seen, and transitions between the two can be made without reversing the polarization. There is no indication that the secondary electron yield in the neighborhood of the first crossover depends on the direction of the spontaneous polarization in the ferroelectric material. The resistivities of triglycine sulfate and BaTiO3 have been estimated from the switching transients. These materials exhibit a deterioration in their ferroelectric properties with time of electron bombardment.
Statistics and Time Dependence of Mechanical Breakdown in Fibers
Authors: Coleman Bernard D.
Published: April 2005

A new phenomenological approach to quantitative discussions of the statistics and time dependence of mechanical breakdown is presented. The theory permits the prediction of relationships between the lifetime distributions to be observed for fibers under different loading histories: dead loads, loads proportional to time, and periodic loads. It also permits the calculation of relationships between the strength of separated individual filaments and the strength of bundles of filaments. The present formulation of the theory is more general than the author's previous work on this subject in that the fibers considered here can ``remember'' their past history as far as breakdown is concerned. It is shown that in the case of periodic loadings, depending on the choice of certain arbitrary functions, the theory can be used to discuss either time-dependent fatigue or cycle-dependent fatigue. The relationships between the present approach and the static models used in classical theories of tensile strength distributions for single filaments and bundles are discussed.

This article consists of a formal, axiomatic development of the theory. Future publications will contain detailed comparisons of the various results with available experimental data.
Gray Tin Single Crystals
Authors: Ewald A. W. , Tufte O. N.
Published: April 2005

A method of growing gray tin single crystals from a liquid amalgam is presented together with a description of the apparatus and specification of the conditions of growth. Photographs of typical crystals ranging in size up to 2 cm and showing well-developed crystallographic planes are included. Residual resistance measurements indicate a total impurity content of the order of 0.001%. The energy gap is the same as for transformed material but the low-temperature mobilities are considerably higher. Evidence that the gray-to-white transformation is of the diffusionless type is presented.
Dislocation Etch Pits in Antimony
Authors: Wernick J. H. , Hobstetter J. N. , Lovell L. C. , Dorsi D.
Published: April 2005

Pits which are probably the sites of dislocations have been produced on the (111) cleavage planes of antimony by use of the CP4 etching reagent. Evidence that the pits probably are at dislocation sites was obtained from density counts on intersecting boundaries and from deformation and annealing studies. The Dash etching reagent chemically polishes antimony without producing pits. The Superoxol etch brings out spiral terraced pits and other fine structure.
Design of Linear Electron Accelerators with Beam Loading
Authors: Neal Richard B.
Published: April 2005

The optimum design of linear electron accelerators depends upon the degree of beam loading, i.e., the fraction of the radio-frequency power which is converted into beam power. With very light loading, the product of the radio-frequency attenuation constant I, and the accelerator length L should be approximately 1.26 for maximum beam energy in a given length. For heavier loading the product IL must be reduced to produce maximum electron energy and maximum conversion efficiency from radio-frequency power to electron beam power. The attenuation constant I can be chosen by the proper selection of the dimensions of the accelerating structure. Expressions and design curves are given for the optimum values of IL to maximize electron beam energy and electron beam power as a function of beam loading.
Space Charge Calculations for Semiconductors
Authors: Seiwatz Ruth , Green Mino
Published: April 2005

The electric field at the surface of a semiconductor is obtained as a function of the semiconductor bulk properties and the potential difference across the space charge region. The treatment is general enough to take into account degenerate free carrier distributions and partial ionization of impurities, either in the neutral bulk or the space charge region, or both. A one-dimensional model with a spacially homogeneous impurity distribution is assumed. The density of states in the conduction and valence bands is assumed to be that appropriate for spherical and ellipsoidal energy surfaces. The common model for simple donor and acceptor states is used in the main body of the paper. Conditions under which the equation for the field can be conveniently simplified are discussed, and a particular case is treated numerically.

The validity of the free carrier distribution functions in the high fields near the semiconductor surface is discussed in Appendix I. The equation for the electric field at the semiconductor surface where the bulk impurities are described by a general model is given in Appendix II.
Experiment on the Electron Phase Microscope
Authors: Kanaya Kōichi , Kawakatsu Hisazo , Itō Kazuo , Yotsumoto Haruo
Published: April 2005

A method of electron phase microscopic observation is described which offers greater image contrasts for specimens possessing small phase differences than is possible with conventional methods of electron microscopic observation.

It is shown that observation by dark contrast image using a phase plate, consisting of many holes in a carbon membrane, is very suitable for microtome section specimens as well as for thin crystal specimens, without a decrease in resolving power.
Electron Excitation of Bilayer Screens
Authors: Koller L. R. , Coghill H. D.
Published: April 2005

The control of the color of the luminescence of thin transparent superimposed phosphor films when excited by electron beams of varying voltage is discussed. The quantitative relations are found to be in agreement with a theory based on the laws of electron penetration and scattering.
Modulus of Rupture of zxt 45 ADP Crystals
Authors: Faraday B. J. , Gregan D. J. G.
Published: April 2005

The modulus of rupture (bending strength) of ammonium dihydrogen phosphate (ADP) of the zxt 45 orientation has been determined by the three-point loading method. These measurements were performed with the aid of a breaking apparatus designed for the application of a constant loading rate commencing with the specimen in a zero-load condition. The measured values of the modulus of rupture of 245–480 kg/cm2 with a mean of 340 kg/cm2 agree closely with figures previously reported for ADP crystals of arbitrary orientation. No significant variation of the modulus was observed for different crystal width to length ratios.
Ohmic Probe Contacts to CdS Crystals
Authors: Sihvonen Y. T. , Boyd D. R.
Published: April 2005

Wire probe contacts are found to be diodic upon first touching CdS, but can be permanently changed from diodic to ohmic by the passage of a moderately intense electric current pulse. This result obtained for ten metals, which work-function-wise bracket CdS, supports the idea that an exhaustion barrier exists on the surface and contradicts proposals that ohmic contact is solely dependent upon the relative metal and CdS work functions. It is postulated that the current pulse punctures the exhaustion barrier, thereby permitting electrons to tunnel more freely and in greater numbers.
Adsorption of Oxygen and Carbon Monoxide on Tungsten
Authors: Schlier R. E.
Published: April 2005

The adsorption of oxygen, carbon monoxide, and nitrogen on a tungsten ribbon filament at 300°K has been measured by means of the flash filament technique. An omegatron rf mass spectrometer has been used to measure pressure. It is shown that oxygen pressures cannot be measured satisfactorily with ionization gauges of the hot-tungsten-filament type. The total amounts of gases adsorbed by tungsten are 5.7×1014 molecules/cm2 for oxygen, 5.8×1014 for carbon monoxide, and 1.8×1014 for nitrogen. The sticking probabilities of these gases on the uncovered surface are 0.65 for oxygen, 0.62 for carbon monoxide, and 0.42 for nitrogen. All of the carbon monoxide and nitrogen desorb from the heated filament as the gases CO and N2; less than 1 percent of the oxygen desorbs as O2. The filament pumps oxygen at a rate of 9 liters/cm2 sec at temperatures above 2000°K.
On Asperity Distributions of Metallic Surfaces
Authors: Ling F. F.
Published: April 2005

A distribution of surface asperities is proposed for the case in which both mating surfaces are rough and asperities are in the form of right circular cones. The assumption of this particular asperity form is suggested by roughness measurements of ground steel, brass, and aluminum which yielded similar results for stylus traversing parallel, 45°, and perpendicular to lay. Considering the mating cones perfectly plastic and distributed in the proposed manner, bulk deformation-load is related to compliance.

The essential finding is that the load-compliance characteristics for mating surfaces having comparable roughness have slopes much steeper than those predictable by previous theories, all of which involve the assumption that one of the surfaces is smooth and rigid. A simple experiment is described in which load and compliance are measured. Results seem to support the plausibility of the proposed theory. Moreover, this plausibility shows promise of the calculation of other bulk-quantities such as frictional resistance.
Gamma-Radiation Absorption Coefficients of Air in the Energy Range 0.01 to 100 Mev
Authors: Allison J. W.
Published: April 2005

Two simple formulas are given which enable the total mass absorption coefficient of air to be readily calculated. These formulas, which are derived from published theoretical values of the total coefficient, are applicable to the energy ranges 0.01 to 100 Mev and 0.05 to 10 Mev, and yield results which agree with the theoretical values to within about 5% and 1%, respectively. Comparison is made with values calculated from existing empirical formulas which cover energies up to about 1 Mev.
Experimental Study of dc Corona at High Temperatures and Pressures
Authors: Thomas John B. , Wong Eugene
Published: April 2005

Positive and negative corona characteristics of air and nitrogen are determined experimentally for coaxial cylindrical electrode geometry with gas temperatures from 300°K to 1100°K and with pressures from 0.1 to 8 atmospheres. Over this range, positive corona characteristics appear to be functions of gas density only. On the other hand, negative corona characteristics depend on gas temperature as well as gas density. At high temperatures both positive and negative coronas show instabilities which are pressure dependent.
Tensile Strength of Plastics: Effects of Flaws and Chain Relaxation
Authors: Bueche F.
Published: April 2005

A theory for the tensile strength of amorphous plastics is presented. It extends a previous theory so as to include the effects of imperfections and chain relaxations. The result obtained shows that the time taken for a plastic to break, tc, under constant stress, F, is given by F=−Bln(tc)+C,where B and C are molecular constants. The experimental values found for these constants are shown to be consistent with their molecular interpretation. This extended theory shows that the effect of chain relaxations is the major time dependent factor as far as strength is concerned.
Graphical Method for Estimation of Contrast in Electron Microscopy
Authors: Sadhukhan P.
Published: April 2005

In the preparation of shadowed specimens for electron microscopic examination, it is often required to estimate the contrast to be expected with different thicknesses of films of various metals, different aperture angles, and beam potentials. This communication describes a graphical method for this purpose.
Ultrasonic Measurement of Polarization Switching Processes in Barium-Titanate Single Crystal
Authors: Husimi K. , Kataoka K.
Published: April 2005

A previously developed nondestructive piezoelectric method for studying the state of polarization of ferroelectric crystals is applied to study polarization switching in barium titanate single crystals.

We propose three polarization processes. The first and second processes were designated nucleation and growth by Merz. The third process cannot be measured by conventional pulse methods, and has a very slow polarizing velocity. This indicates the existence of layers which lie between the surface layer and inner layer.

Switching time results are considered in the light of the above experiments.
Primary Pyroelectricity in Barium Titanate Ceramics
Authors: Perls T. A. , Diesel T. J. , Dobrov W. I.
Published: April 2005

Data have been obtained on the pyroelectric and piezoelectric behavior of samples of a polycrystalline barium titanate ceramic in an effort to determine the possible existence of a primary pyroelectric effect. It is shown that the total pyroelectric effect is in a direction opposite to the piezoelectric contribution resulting from volumetric changes and that, as a consequence, there must exist a primary pyroelectric effect. The time constant of the samples for generation of electrical signals from heat pulses was less than 12 μsec. Practical applications of barium titanate sensors may be found in the measurement of heat radiation beams having large cross sections.
High-Temperature Heat Conductivity of Some Metal Oxides
Authors: Jamieson John C. , Lawson A. W.
Published: April 2005

A reanalysis of data on the thermal conductivity of certain metal oxides has shown that the deviation from a T−1 law may be fitted to a law exponential in T−1. Thus the deviations may be ascribed to the flow of excitions. The contribution to the thermal conductivity from radiative transfer is shown to be too small to fit the observed deviations.
Phenomenological Theory of Polarization Reversal in BaTiO3 Single Crystals
Authors: Pulvari Charles F. , Kuebler Wolf
Published: April 2005

A theory describing polarization reversal in BaTiO3 c-domain crystals based on observed time and field dependence of polarization P=f(E,t) is presented, and the activation field α as well as mobility μ are related to the constants appearing in the basic differential equation. The theory gives time and field dependence of the switching current at constant temperature. Although the theory does not imply restriction on the applied field E(t), results are given only for pulsed and sinusoidal fields. The effect of skin properties on the bulk crystal has been considered. Dependence of coercive field on applied field and frequency are readily obtained. Switching resistance is calculated.
Gain, Band Width, and Noise Characteristics of the Variable-Parameter Amplifier
Authors: Heffner H. , Wade G.
Published: April 2005

The variable parameter (or parametric) principle of amplification is characterized by a typical arrangement in which a variable energy storage element, such as an inductor or a capacitor, is suitably coupled to two resonant circuits. If the value of the energy storage element is made to vary in the proper way, energy is fed from the source which drives the element (that is, the pump) to the fields of both the resonant circuits. This paper describes the behavior relative to gain, band width, and noise of this type of amplifier.

Specifically, it is shown that to increase gain, the Q of one of the resonant circuits, the one commonly called the idling circuit, must be increased or the variation in the variable reactance must be increased. The band width is inversely proportional to this Q and to the voltage gain. Hence, for high gain, the amplifier is normally a narrow band device. One of the most important sources of noise is the thermal noise originating in the idling circuit. However, in principle this source can be reduced indefinitely by making the idling frequency approach the pumping frequency or by artificially cooling the idling circuit. In this fashion very low noise figures should be possible.

The parametric principle can also be applied to producing frequency conversion with large conversion gain. The appendix presents the expressions for gain, band width, and noise figure for this application. The behavior of the converter relative to gain, band width, and noise is quite similar to that of the amplifier.
General Solution of the Luneberg Lens Problem
Authors: Morgan Samuel P.
Published: April 2005

The general solution is obtained for the index of refraction of a variable-index, spherical lens which will form perfect geometrical images of the points of two given concentric spheres on each other. One conjugate sphere is assumed to be outside the lens or at its surface, while the other may be either inside, outside, or at the surface. If one of the spheres is of infinite radius, the lens will focus a parallel beam perfectly at a point on the other sphere.

It is shown that the index of refraction may be specified arbitrarily, subject to two simple conditions, in an outer shell of any desired thickness less than the radius of the lens. The index of the central portion is then expressed in terms of a function which is tabulated, and of an integral involving the index of the outer shell. Some properties of the general solution are discussed, and various special solutions are derived.
Nonlinear Effects of Z-Directed Spin Waves in Thin Films
Authors: Kaplan Jerome I.
Published: April 2005

A calculation is made for the high-power instability of the Z-directed spin waves in a thin insulating ferromagnetic film. For complete pinning, the critical field is found to be (γh)2=Δn3n2π2[93(ωM+13ωexa2kn2)]−1. The calculation is also made for the critical field, assuming a mixed boundary condition.
Growth of ZnSb Single Crystals
Authors: Eisner R. L. , Mazelsky R. , Tiller W. A.
Published: April 2005

A zone technique which should be applicable to many peritectic type compounds has been used to grow good-quality single crystals of ZnSb. It consists here of moving a molten antimony-rich zone along a charge of stoichiometric composition headed by some crystalline ZnSb.
Reflection of an Electron Beam from High-Frequency Fields
Authors: Hall R. B. , Brown Sanborn C.
Published: April 2005

Experimental verification of time-average forces due to an rf field acting on charged particles is obtained by measuring the transmission of an electron beam through the high-frequency fields of a cavity. By adjusting the external dc magnetic field so that cyclotron resonance is approached, it is possible to reflect high-energy beams; that is, 66 w of microwave power completely reflected a 24-v beam. Agreement between experiment and theory was close.
Observations on the Growth of α-Iron Single Crystals by Halogen Reduction
Authors: Wayman C. M.
Published: April 2005

By large scale modification of established whisker growing techniques, it was possible to produce single crystals of alpha iron between 1 and 2 mm in diameter and up to 80 mm in length. These crystals grew along a 〈100〉 axis and had {100} faces. The final size of the crystals appeared to depend upon the quantity of FeCl2 vapor available for reduction. Some growth features are reported.
Experimental Investigation of the Sumoto Effect
Authors: Pickard William F.
Published: April 2005

The rising of a dielectric liquid along high-voltage electrodes that are dipped into it is investigated. Qualitative results are given for a number of different combinations of electrode material and liquid. The effects observed for molybdenum-acetone systems, excited by low-frequency applied voltage are discussed in detail.
Radiation Enhancement of Bulk Diffusion in 10% Zn—90% Cu by 30-kev Ne+ Ion Bombardment
Authors: Arndt R. A. , Hines R. L.
Published: April 2005

Diffusion coefficients for the diffusion of zinc in 10% Zn — 90% Cu single crystals are determined for both irradiated samples and unirradiated samples. This is accomplished by measuring the zinc lost from the samples when they are heated in a vacuum of 3×10−5 mm Hg at temperatures from 207°C to 316°C. The zinc loss is measured by observing the change in optical reflection coefficient at a wavelength of 550 mμ. The diffusion length (Dt)½ is then found using the known optical constants of ZnCu alloys and the expected concentration distribution. The diffusion lengths thus obtained range from 20 to 1000 A. Bombardment by a 30-kev Ne+ ion beam of 2.9 μa/cm2 produces defects at a calculated rate of 4.5×10−2 atomic fractions/sec over the depth of 300 A penetrated by the beam. For well-annealed samples the bombardment enhances the diffusion. The radiation-enhanced diffusion coefficient depends on the square root of the bombarding flux density and has an activation energy of 9300±1700 cal/g mole. The results agree with theoretical predictions for enhanced bulk diffusion for the case of defects annealing by direct recombination plus linear anneal to fixed sinks.
Open Circuit Voltages in the Cesium Diode
Authors: Huffman Fred N.
Published: April 2005

A plasma model and a close-spaced model are used to analyze the detailed variation of the open circuit voltage of the cesium diode. The plasma model open circuit voltage expression is compared to one derived by Lewis and Reitz in which the ion contribution to the net electron current is neglected. For either model the main features of the open circuit voltage at emitter temperatures less than 1800°K arise from the complex ion and electron emission properties as a function of emitter temperature and cesium pressure. Although at higher emitter temperatures the plasma model open circuit voltage becomes independent of the detailed surface characteristics of the emitter, the two models continue to give similar numerical results. Calculations based on these models and incorporating the data of Langmuir agree qualitatively with the sinusoidal and discontinuous open circuit voltage variations observed by Pidd et al., as well as the anomalous load characteristic observed by Wilson.
Alternating Current Magnetohydrodynamic Generator
Authors: Smy P. R.
Published: April 2005

The design criteria of a proposed ac magnetohydrodynamic (mhd) generator are discussed. It is found that electrical losses to the moving fluid are serious unless the duct length-to-width ratio is greater than about 30. Two developments of such a generator are suggested. The first would provide a solution to the problem of power output from a segmented-electrode generator. The second development, that of capacitive power transfer at the electrode-fluid interface, would have many benefits, but its application is found to be severely restricted by the limited dielectric strength of materials.
Partial Rotation in Permalloy Films
Authors: Methfessel S. , Middelhoek S. , Thomas H.
Published: April 2005

Magnetization reversal at an angle to the easy direction has been studied on Permalloy films with different values of coercive force Hc and anisotropy field HK. The hysteresis properties show that ``inverted'' films (Hc>HK) do not represent a special case, but that every film exhibits inversion in a certain sector of field direction. In the inversion sector, two critical field values are observed. The corresponding Bitter patterns make it evident that the lower critical field is due to a partial rotation process which is accompanied by a splitting of the film into many fine domains, whilst the higher one is due to wall motion. The observed processes can be understood qualitatively if the dispersion of the local values of the anisotropy field and anisotropy direction, as well as the internal exchange and stray field coupling are taken into account.
Influence of the Hall Effect upon the Transverse Magnetoresistance in Indium Antimonide
Authors: Simmons Charles A.
Published: April 2005

A detailed experimental investigation of the influence of the specimen geometry on the transverse magnetoresistance has been made. Differentiation between the bulk properties and the geometrical contributions has been accomplished. It was found that the enhancement of the magnetoresistance effect in rectangular elements is due to the Hall effect rather than to its absence and that the bulk property has an H2 relationship while the geometry effect is linear with H and inversely proportional to the length-to-width ratio.
Use of Idealized Relaxation Spectra in the Interpretation of Experimental Results Concerning Polymer Solutions
Authors: Walters K.
Published: April 2005

The usefulness of a new representation of the relaxation spectrum for elasticoviscous liquids is discussed, and an idealized form of this spectrum is used to interpret experimental results concerning polymer solutions.
Experimental Study of the Interrelation between the Theory of Dislocations in Polycrystalline Media and Finite Amplitude Wave Propagation in Solids
Authors: Bell James F.
Published: April 2005

By use of experimental data from a large number of free flight impact tests involving diffraction grating measurement of strain, a detailed and very close experimental verification is given for the G. I. Taylor theory of dislocations in polycrystalline annealed aluminum. Applying the finite amplitude wave theory, with a theoretical parabolic stress-strain curve obtained from dislocation theory, experimental and theoretical correlations within approximately 1% are obtained for the velocities of strain propagation, maximum strain, largest distance of penetration of maximum strain, dynamic stress levels in the first diameter, time of contact, coefficient of restitution, mushrooming in the first diameter, and an energy balance before and after impact. Variations in the plastic wave development and dynamic stress behavior below the Karman critical velocity are considered theoretically and experimentally in terms of a difference in the initial elastic reflection behavior below the critical velocity. Plastic deformation is found to be independent of strain rate, even at experimentally determined values of 2000 in./in./sec. Initial shock fronts exceeding the dilatational velocity are experimentally identified near the impact face. The subsequent development of dispersive plastic wave fronts following the passage of the initial shock, also are found to be in accordance with predictions based upon dislocation theory. The equipartition of energy in the vicinity of the impact face has been found to be related to the reflection behavior of these initial shock fronts at the lateral surface of the rod.
Power Output Characteristics of a Ruby Laser
Authors: Stitch Malcolm L.
Published: April 2005

The theoretical power output of a ruby laser is examined under certain idealized operating conditions, and it is found that there are two principal regions of operation. These are the regions of strong oscillation characterized by the condition pτ2/A»hν13/σ13 and the region of saturation in which pτ3/A»hν13/σ13. Here p/A is the ``pumping'' illumination within the absorption band of ruby, τ2 is a charactersitic relaxation time of fluorescence in ruby, τ3 is a characteristic thermal relaxation time from the excited U band, ν13 is the pumping frequency, and σ13 is the cross section for interaction between pumping radiation and Cr3+ ions in ruby. Efficiency of operation is examined under two limiting conditions.
Birefringence due to Dislocations in Glide Bands of Rocksalt Single Crystals
Authors: Mendelson S.
Published: April 2005

Birefringence techniques which emphasize the difference in stress on each side of a slip plane having edge dislocations of one sign are described. The principal stresses due to edge dislocations in a glide band are found to be parallel and perpendicular to the Burgers vector. The opposite stressed regions on both sides of a slip plane produce opposite retardations in the phase of light passing through the slip plane. When this light is retarded in phase by an amount equal to the advancement from the compressive region (or advanced by an amount equal to the retardation from the tensive region), a birefringence band forms which is, for instance, dark on the compressive side, light on the tensive side in a background having an intensity halfway between these two shades. These asymmetrically shaded birefringence bands are observed when viewed both normal and parallel to the Burgers vector and this is shown to be a direct consequence of the edge dislocations in the slip planes and to be independent of screws. The asymmetry of the band permits a determination of the sign of the dislocations in the slip plane and the apparent position of its source. The magnitude of the principal stress parallel to the Burgers vector was computed from the measured retardations and found to be in good agreement with that computed from the dislocation stress fields.
Characteristic Electron Energy Loss Measurements at Low Temperatures
Authors: Hörl E. M. , Suddeth J. A.
Published: April 2005

A method is described for the investigation of characteristic energy losses of electrons in solids at temperatures in the liquid helium and liquid hydrogen temperature range. This method had been primarily developed for the investigation of thin films of solidified permanent gases, but it is also very suitable for the study at low temperatures of any substance, which is obtainable as a thin film. For the measurement of the energy losses itself, a very versatile electrostatic analyzer lens has been constructed which allows the observation of electron diffraction patterns of the samples before and after energy loss measurements. First results are reported on thin films of solid oxygen and solid xenon.
Defect Mechanisms in a Noncrystalline Solid
Authors: Levengood W. C.
Published: April 2005

It is proposed that spiral defects originate at torque stress fields in glass and represent variations in localized bond energy. By postulating shear stress couples across flaw lines, extension and annihilation of flaws from neighboring spiral sources were tentatively explained. Distortion or movement within a spiral was indicated on samples subjected to localized stress before etching. Experimentally it was shown that substitution of lead and bismuth for silica in a nonspiral glass produced a rigid, brittle network which ultimately disclosed spirals originating at minute nuclei. Details of structure were quantitatively studied by using the dynamic spherical indenter. Flaw loops were also discovered which originated at random etch pit sources and increased in diameter with applied stress. Rows of etch pits were observed on samples stressed in torque. The conjecture was introduced that the torsion stress caused collapse of flaws into point defect rows. The etch pit rows appeared to be more stable than linear flaws. The minimum length of stability of a void derived from dislocation theory was in agreement with experimental measurements from the point defect rows.
Theory of the Potential Well Produced by Multipacting Electrons. I. Very Low-Pressure Regime
Authors: Ingraham R. L.
Published: April 2005

Electrons multipacting in an evacuated discharge tube produce an effective static potential well in which the positive ions can be contained. The theory of the positive ion behavior in this ``electron well'' in the very low pressure regime (𝔓 [less than double similar] 10−5 mm Hg) is developed here. The electron potential well is expressed finally as a double numerical integral of complete elliptic integrals for the general field point; for on-axis points it reduces to a single numerical integral of irrational expressions. With the ``short tube'' and ``constant sheet velocity'' approximations, the well is parabolic; the corresponding ion harmonic vibration frequencies are calculated. For the rigorous well these parabolas are flattened in the central parts and steepened near the electrodes. A self-consistent calculation of the ion density is made using an individual particle description of the ion gas (appropriate to very low densities) which results in an inhomogeneous integral equation. The solutions describe ion distributions peaked in the middle of the tube. For comparison with experiment the deflection of an ion beam fired across the tube is worked out.
High-Field Conductivity in Germanium and Silicon at Microwave Frequencies
Authors: Zucker J. , Fowler V. J. , Conwell E. M.
Published: April 2005

The effect on the conductivity of germanium and silicon samples of 2.85-kMc electric fields up to peak values of 10 000 v/cm was measured. These measurements differ from earlier ones in that: (1) the microwave field was in the form of progressive rather than standing waves, which made possible more accurate determination of the field strength in the sample, and (2) to determine whether any frequency effects occur at 2.85-kMc conductivity was measured at high dc fields on the same samples. From the average conductivity under microwave excitation the instantaneous conductivity was calculated and found to agree, within experimental error, with the dc conductivity, indicating that the conductivity can still follow the 2.85-kMc field at least up to peak fields of 10 000 v/cm.
Magnetically Confined Cold-Cathode Gas Discharges at Low Pressures
Authors: Jepsen R. L.
Published: April 2005

Most previous treatments have been restricted to calculations of striking characteristics of planar and cylindrical magnetrons. In the present paper, a theory is developed which considers some effects of space charge in inverted and normal magnetrons and in Penning structures. Estimates are made of current flow and its dependence on voltage, magnetic field, electrode geometry, and pressure. It is shown that discharges of much greater intensity may be expected in normal magnetrons with filamentary cathodes than in inverted magnetrons with filamentary anodes. It is also shown that comparable maximum discharge intensities should be obtainable in Penning structures and in normal magnetrons. A scaling relation involving magnetic field and radial dimensions of the electrodes is obtained.
Rolling Friction of Polymeric Materials. II. Thermoplastics
Authors: Flom D. G.
Published: April 2005

The results of rolling friction studies of several thermoplastics provide additional evidence for the correlation of such friction with dynamic mechanical losses in polymeric materials. Among the polymers discussed are polymethyl methacrylate, polytetrafluoroethylene, polyethylene, nylon, polyvinyl chloride, polyvinyl acetate, and polystyrene. The effects of spin and other deviations from pure rolling are demonstrated for polymethyl methacrylate, polytetrafluoroethylene, and nylon by varing the experimental parameters. In essentially pure rolling, the dependence of friction on temperature illustrates the importance of the extent of crystallinity in polytetrafluoroethylene, the amount of branching in polyethylene, and the concentration of plasticizer in polyvinyl chloride. In the latter effect, it is found that the temperature at which the rolling friction goes through a maximum varies linearly with plasticizer content.
Friction of Metals in Reciprocating Sliding
Authors: Tamai Yasukatsu
Published: April 2005

A number of experiments were conducted on the metallic friction in reciprocating sliding with a pendulum. It was shown that the reciprocating sliding gives quite different results from those of single-traverse or unidirectional repeated sliding, which were emphasized in both the coefficient of friction and the electric contact resistance, surface damage due to sliding, and the low friction phenomenon.
Grain-Boundary Diffusion
Authors: Austin A. E. , Richard N. A.
Published: April 2005

The diffusion of nickel into grain boundaries of various tilt angles in copper bicrystals was studied. The concentration contours from the grain boundary and the lateral lattice diffusion were measured by means of electron-probe microanalysis. The product of grain-boundary width and diffusion coefficient were calculated, and comparisons were made with theoretical solutions. The grain-boundary coefficient is concentration dependent above 3% nickel in a 45° tilt boundary. With lower tilt angles, the coefficient is concentration dependent above 0.5% nickel.
Scattering of Plane Waves by a Rigid Ribbon in a Solid
Authors: Harumi K.
Published: April 2005

The scattering of plane compressional and shearing waves by an infinitely long rigid ribbon with width a in an elastic medium is computed by the use of the Mathieu functions. The diffraction patterns for ka/2=1,2, and 4 are calculated numerically; the distributions-in-angle of the elastic waves bears no resemblance to that of the sound except for the normally incident compressional wave. The expressions for the scattering field and cross section, in powers of ka=h, are obtained in the Rayleigh case. In this case the scattering cross section is of the order of the wavelength, as it is in the case of the scattering of the sound by an absorbing ribbon. Some new expansions of the Mathieu functions in powers of h are listed in the Appendix.
Temperature-Compensated Debye Temperature of Carbonyl Iron
Authors: Gazzara Charles P. , Middleton Raymond M.
Published: April 2005

The explicit temperature function τ which relates the Debye temperature to a change in temperature has been found to be 4.1 for annealed carbonyl iron from x-ray diffraction integrated intensity measurements. The corresponding Debye temperature, corrected for temperature diffuse scattering, was calculated to be 435°K at temperature 310°K.
Ferromagnetic Nucleation Sources on Iron Whiskers
Authors: De Blois R. W.
Published: April 2005

Previous experimental work has established that the near perfection of some selected iron whiskers brings the axial magnetic field required to nucleate the reversal of magnetization close to the theoretical coercive force limit of 2K/Ms (560 oe at 20°C). [R. W. De Blois and C. P. Bean, J. Appl. Phys. 30, 225S (1959)]. Further experiments now show an approximately constant shift of the nucleation-field contour along an iron whisker with change in temperature, increases in nucleation field of several hundred oersteds along the lengths and at the tips of several iron whiskers following electropolishing, and a correlation between observed microscopic surface imperfections and regions of nucleation-field minima. These results support current ideas that abrupt surface contour variations are primarily responsible for reducing the observed nucleation fields for iron whiskers to below the ideal value.
Increase in Dielectric Constant during Switching in Lithium Selenite and Triglycine Sulfate
Authors: Fatuzzo Ennio
Published: April 2005

The dielectric constant of lithium selenite and triglycine sulfate was measured during switching up to frequencies of 100 Mc. The increase in dielectric constant during switching was found to decrease with frequency v as 1/v at low frequencies and as 1/v2 at high frequencies. A model to explain the experimental results is given and discussed. It is shown that information about the domain wall mass can be obtained from this kind of measurement.
Zero-, First-, and Second-Order Theories of a General Thermocouple
Authors: Boerdijk A. H.
Published: April 2005

The thermocouple to be dealt with has two bars of arbitrary shape. Each of the properties of the materials (the thermal resistivity κ, the electrical resistivity ρ, and the Seebeck coefficient S) is represented by a finite number of terms of a MacLaurin series in T (the temperature) and u (a position coordinate). A method is described to obtain a theory of arbitrary order t. Such a theory is based on a solution T = f(u) which satisfies the basic nonlinear differential equation (obtained by application of thermodynamics of irreversible processes) and the boundary conditions if all terms of order >t are neglected. The order of a term is equal to the sum of the orders of all partial differential quotients of κ, ρ, and S with respect to T and u occurring in that term. The method is applied to obtain the electrical output power and the thermal output powers as functions of the electrical current and the temperatures of the junctions in theories of order zero, one, and two. The zero-order theory is identical with the common theory of thermocouples with constant properties κ, ρ, and S. In the first-order theory an expression is obtained for the efficiency for production of cold. This efficiency can be improved by suitable temperature dependence of S and by suitable place dependence of S. Finally the accuracy of approximation is discussed.
Influence of Deformation and Temperature on the Cobalt Gamma Irradiation of Sodium Chloride. Evidence for Electrical Interaction between Dislocations and Point Defects
Authors: Truell Rohn
Published: April 2005

Ultrasonic attenuation measurements in sodium chloride as a function of cobalt 60 gamma-ray irradiation show no appreciable dependence on temperature in the temperature range from room temperature to liquid nitrogen temperature, hence no appreciable thermal activation energy for the process of immobilizing the dislocations. The influence of plastic deformation on the attenuation-irradiation behavior is large; the greater the deformation the more rapid the attenuation change, at least in the deformation range from zero to one percent deformation. The consequences of these effects are discussed in terms of boundary conditions on possible mechanisms for the observed effects.