bluuebunny/crossref_metadata_2025_split huggingface dataset:
Partition Effects in Transverse Electron Beam Waves
Authors: Hart P. A. H. 
Published: April 2005

Theory is presented concerning the attenuation of the original beam waves, the fast, the slow, and two synchronous waves, and the generation of noise waves if part of the beam is intercepted.To obtain compact equations matrix notation is used throughout. The matrix notation offers the additional advantage that both the behavior of the waves and their mutual correlation can be studied simultaneously. This renders the theory, which accounts both for pure interception and for partial scattering of the beam, much more general in nature. The electron beam diameter is finite.In addition to attenuation of the original and generation of noise waves it is found that two new synchronous waves related to the original fast and slow waves are generated.Experiments at 550 Mc with an Adler-Wade tube containing a movable vane show good agreement with the theory presented, provided the forward scattering is taken into account. The experiment indicates that the theory is probably correct at least insofar as the fast wave, the slow wave, and the correlated components of the synchronous waves are concerned.
Applicability of the Taylor Theory of the Polycrystalline Aggregate to Finite Amplitude Wave Propagation in Annealed Copper
Authors: Bell James F. , Werner W. Meade 
Published: April 2005

This paper provides additional experimental evidence for the Taylor theory of dislocations and the Taylor theory of the polycrystalline aggregate. For annealed copper (as had been found by Bell for annealed aluminum) the governing stress-strain curve for plastic wave propagation is a parabola, as predicted by the Taylor theory of dislocations. Using the Taylor theory of the polycrystalline aggregate, the parabolic stress-strain law for annealed copper, as had been shown earlier for annealed aluminum, is determinable from compression stress-strain curves for single crystals.
These experimental data in annealed copper are obtained from the free-flight constant-velocity impact of identical specimens using the diffraction-grating technique for the measurement of strain and surface angle.
From the results given in this paper, together with those obtained earlier by Bell for annealed aluminum and the recent results of Sperrazza for pure lead, it may be concluded that strain rate does not play a significant role in the dynamic plasticity of these annealed face-centered-cubic metals. As in annealed aluminum and pure lead, plastic strain propagation velocities, maximum strain amplitude, surface angle behavior, time of contact, and the coefficient of restitution for annealed polycrystalline copper are found to be given by the strain-rate independent theory of plastic wave propagation.
Ferrimagnetic Resonance with Orthogonal and Parallel Pumping
Authors: White Robert M. , Schlömann Ernst 
Published: April 2005

An rf magnetic field of sufficient amplitude gives rise to a nonlinear absorption caused by the unstable growth of certain spin waves. We have calculated the threshold for the case in which an rf field of frequency ω0 is applied orthogonally to the dc field and another rf field at frequency 2ω0 is simultaneously applied parallel to the dc field.
We find that under these conditions the wave number of the spin waves with the lowest instability threshold varies discontinuously with the ratio of the two rf magnetic fields. If the orthogonal rf field is relatively small, the unstable spin waves have wavelength comparable with the sample dimensions. In this region the critical parallel field decreases linearly with the square of the orthogonal field.
Effect of the Temperature of Formation on the Crystallinity and Electrical Properties of Germanium Films on Fluorite
Authors: Schalla R. L. , Thaller L. H. , Potter A. E. 
Published: April 2005

Crystalline germanium films were grown epitaxially by vacuum evaporation of germanium onto heated fluorite substrates. In the work reported here, the effect of substrate temperature during film evaporation on the crystallinity and electrical properties of the films has been explored. Thirty Ω-cm p-type germanium was evaporated in a conventional bell jar at pressures between 10−5 and 10−4 mm Hg. The germanium was evaporated from a resistance-heated tantalum boat onto a fluorite plate. Substrate temperatures varied from 470° to 915°C, while the rate and duration of evaporation was held constant at about 1500 Å/minute and two minutes, respectively.
The crystalline nature of the films was studied by electron diffraction. The transition from a nearly amorphous film at 470°C to a nearly single-crystal film at 915°C was observed. Hall coefficients and electrical conductivities were measured for the films, which were p type as was the starting material. These results are presented along with the mobilities and carrier concentrations calculated from them. The mobilities increase rapidly with film evaporation temperature. Carrier lifetimes were found to be less than 1 μsec in the most crystalline film, whereas the original germanium had a carrier lifetime of about 12 μsec.
Response of Photoconducting Imaging Devices with Floating Electrodes
Authors: Sommers H. S. 
Published: April 2005

A simplified charge control type of analysis is made of the response of photoconducting imaging devices with a floating electrode. The change of electrode potential with discharge of the device is found to have an importance not previously recognized. The results are relevant for a variety of electrostatic photographic devices and show the dependence of the performance on certain details of the image development process.
The floating electrode limits the gain during exposure to light to one charge pair per quantum absorbed. For the Vidicon TV camera picture tube, a detailed study of the process of reading the stored information demonstrates that net gain exceeding unity can be achieved. The upper limit to the gain is the ratio of the time for the scanning beam to traverse a picture element to the transit time of a free carrier through the layer. This conclusion holds when the time required to trap a free carrier exceeds its recombination lifetime. None of the gain-bandwidth relations yet deduced for photoconductors is applicable to this case. Earlier studies which led to a maximum gain of approximately unity for the Vidicon assumed fast trapping of free carriers.
For the Vidicon, the conditions for gains greater than unity with full frame storage and small lag are developed, including the characteristics of the scanning beam and of the trapping and recombination centers. Suitable targets with only one free carrier should have a low sensitivity photoconductor with a significant density of slow trapping states. Discussion of the similarity between the performance of a homogeneous target with one free carrier and an npn structure shows that the slow trapping states in the uniform layer play the role of the donors and acceptors in the junction device.
An Investigation of the Constant-Current Characteristics of Materials Having a Positive Temperature Coefficient of Resistance
Authors: Wilson G. W. , Schomberg S. 
Published: April 2005

Ferroelectric ceramic compounds doped to make them electrically conducting show a marked increase in resistance over a limited temperature rise. They also show good current regulation over a wide range of applied voltages.
The current regulation is dependent upon the shape of the resistance/temperature curve and also upon the mode of heat dissipation from the ceramic. In particular, the magnitude of the constant current obtained is governed by the minimum resistance of the material used. Experimental investigation of these characteristics revealed that the resistance of the material was affected by the voltage applied to it, decreasing as this potential was increased. This led to the variation in the resistance of the pellet with temperature (determined from current and applied voltage measurements) becoming linear, and considerably reduced the positive temperature coefficient of resistance from that obtained when a low constant voltage was used.
This voltage dependence of resistance can probably be explained on the basis of traps at the grain boundaries forming potential barriers through which electrons taking part in the conduction processes have to tunnel.
Surface Energy of {100} Potassium Chloride
Authors: Westwood A. R. C. , Hitch T. T. 
Published: April 2005

A modified Obreimov-Gilman cleavage technique utilizing the apparent variation of cleavage surface energy with crack length and specimen dimensions has been used to determine the true surface energy γ0 of the {100} planes of potassium chloride at room temperature. γ0 {100} KCl was found to be 110±5 ergs/cm2, in good agreement with Born and Stern's theoretical estimate of γ0 (108 ergs/cm2) but not with more recent estimates of this quantity (160–185 ergs/cm2). Possible causes for this discrepancy are discussed.
Other experiments revealed that the presence of a solvent environment at the crack tip increased the cleavage fracture energy only some two or three times. This suggests that the Gurney-Pulliam phenomenon of precipitation at a crack tip is not primarily responsible for the increased strength and ductility of ionic crystals tested in solvent environments (Joffe's effect).
Tracks in Fission-Fragment-Bombarded Lead Iodide
Authors: Chadderton L. T. , Montagu-Pollock H. M. , Torrens I. McC. 
Published: April 2005

The nature of fission-fragment tracks in crystals of lead iodide is sensitively dependent on the thickness of the crystal as well as on the energy, mass, and direction of the incident particle. As the thickness of the specimen is increased the white contrast tracks seen in the electron microscope become discontinuous, and with diffraction contrast they change to tracks that are dark on a lighter ground. At even greater thicknesses no tracks are visible, but only a random array of inclined dislocation loops.
Tracks formed from fission fragments arising from thick pieces of uranium foil show branching that is interpreted as due to the registration of knocked-on atoms. Calculations of the rate of energy loss for fragments in lead iodide, made on the basis of a treatment first given by Bohr, are in qualitative agreement with the observations.
Work Hardening and Dislocation Arrangement of fcc Single Crystals. I. Plastic Deformation and Slip Line Studies of Nickel Single Crystals
Authors: Mader Siegfried , Seeger Alfred , Leitz Christoph 
Published: April 2005

The work hardening of nickel single crystals and its temperature dependence are investigated. The results are discussed in terms of the long-range stress theory of work hardening. From an analysis of the temperature dependence of the stress τIII at the onset of stage III, we deduce the stacking fault energy of nickel and the magnitude of the stress concentrations in the deformed crystals.
Particular attention is given to the question: Which of the hardening parameters are structure sensitive and which are insensitive to the differences in the microstructure of the crystals?
Simultaneous determinations of the length and height of individual slip lines are carried out. They check with the information on the stress concentrations and agree well with the predictions of the work-hardening theory.
Stacking Fault Probabilities of Some Alloys of Copper and Silver with Zinc and Cadmium
Authors: Vassamillet L. F. , Massalski T. B. 
Published: April 2005

The deformation stacking fault probability has been measured by means of x-ray diffraction in a series of Ag-Cd alloys and additional measurements were done on some Cu-Zn and Ag-Zn alloys. The results obtained for Ag-Cd alloys are, within the experimental error, the same as those for Ag-Zn alloys.
If the reciprocal of the faulting probability is assumed to be proportional to the stacking fault energy, the obtained curves relating stacking fault energy with composition in the systems Cu-Zn and Ag-Zn are very similar to those derived by Howie and Swann who used electron microscopy. A comparison of the results from the x-ray and electron microscopy experiments suggests that the stacking fault energies of pure copper and silver are 67±17 ergs/cm2 and 14±3.5 ergs/cm2, respectively.
Beam-Plasma Discharge: Buildup of Oscillations
Authors: Getty W. D. , Smullin L. D. 
Published: April 2005

Plasma electron heating was accomplished by exciting plasma oscillations with a pulsed, 10-kV, 1-A electron beam drifting in a longitudinal magnetic field of 100 to 1000 Oe. The oscillatory energy gained by plasma electrons leads to an increase in their density and mean kinetic energy. The resulting plasma, which is called the ``beam-plasma discharge,'' is an rf discharge in which a beam-plasma interaction generates the rf fields.
At the beginning of a beam pulse, beam electrons generate a plasma by ionization of the background gas. Within a few microseconds excited plasma electrons become the dominant ionization source. This paper describes the transient rf oscillations that appear in the first few microseconds of the beam pulse. From a detailed study of this transient it was concluded that a nonconvective instability initiates the oscillations, which first appear at the electron cyclotron frequency, and that a convective instability at the plasma frequency generates the oscillations that sustain the discharge.
Scattering Factors and Other Properties of Low-Energy Electron Diffraction
Authors: Lander J. J. , Morrison J. 
Published: April 2005

Improved low-energy electron diffraction equipment which yields better resolution and a proper background is described. The equipment is sufficiently flexible for measurements of total elastic and inelastic backscattering, and this is illustrated with several examples.
Elastic and inelastic scattering factors are considered and illustrated by experimental data. Since they are complex, complicated, and only semiquantitatively understood, precise surface structure analysis is generally not possible at the current stage of development of this technique, though it now provides a very powerful method for characterizing surface structures. Various approximate methods for interpreting diffraction data are outlined. A preferred approach to a dynamic theory is also discussed.
Other physical properties such as Fresnel zone corrections, Lorentz factors, effects of contact potential, properties of diffraction by two-dimensional gratings, properties of averages, specimen orientation effects, effects of steps, and thermal disorder are considered and illustrated. The analytical results for x-ray and high-energy electron diffraction are sueful but sometimes not directly applicable.
Fluctuation of the Object in Electron Diffraction
Authors: Yamaguchi S. 
Published: April 2005

A mechanical fluctuation like Brownian motion takes place for colloidal particles of MgO and ZnO (particle size: 1000×1000×1000 and 5000×500×500 Å3) in a steady flow of electrons (10−5 A/cm2). This is observable as a broadening of the reflections in the electron diffraction patterns obtained with a satisfactorily short wavelength (0.026–0.028 Å).
The mean free path of MgO particles in recoil arising from collision with electrons was about 0.7 Å.
The observations permit not only the measurement of the mean weight of colloidal particles, but also demonstrate the quantum mechanical uncertainty principle.
Interaction of a Bunched Electron Beam with a Gyrotropic Plasma
Authors: Hakki Basil W. 
Published: April 2005

The interaction of a prebunched beam with an anisotropic medium is considered for the generation of coherent electromagnetic energy in the low and submillimeter region. Generalized expressions are obtained for the fields created by a prebunched beam of general shape in an anistropic medium. The permeability is assumed to be a scalar constant whereas the permittivity is tensorial. Two special cases are considered: one is that of a helical prebunched beam and the other is that of a rectilinear beam, both interacting with gyrotropic gaseous plasmas. Ionization, scattering, and rf field effects on the beam are neglected.
In addition to the solutions of the inhomogeneous vector wave equation, a method is suggested whereby the free mode solutions could be directly deduced.
Etched Hillocks in BaTiO3
Authors: Stadler H. L. 
Published: April 2005

Two kinds of mounds or hillocks have been found on BaTiO3 single crystals after etching. Rounded, flat-topped hillocks were found after etching with 1% HF for 30 sec at room temperature. These hillocks were found where a 180° domain wall had been left for several days and had been removed shortly before etching. Their behavior can be explained by the ad hoc assumption that negative charges are attracted to the 180° domain wall at the crystal surface.
Mounds shaped like Egyptian pyramids were found after etching BaTiO3 single crystals for 30 min in H3PO4 at 155°C. The edges between pyramidal faces always project onto the crystal surface (a 100 plane) in 110 directions.
Angular and Magnitude Dispersion of the Anisotropy in Magnetic Films
Authors: Crowther Thomas S. 
Published: April 2005

A physical model for the angular and magnitude dispersion of the anisotropy of magnetic films has been investigated. It is based on the effect of anisotropic strain on a microscopic scale acting on magnetostrictive material. If the strain-induced anisotropy component Hks is less than the intrinsic unstrained value Hko the following results are obtained: (1) Regions with highest and lowest local Hk values are unskewed. Regions with maximum skew have approximately average Hk. (2) Although local skew α and the resultant anisotropy Hk are not uniquely related since each depends on both direction and magnitude of applied stress, their maximum values for a composite film having isotropic strain on a macroscopic scale are related by; αmax=(1/2) arcsin (Hk max−Hko)/Hko.
The following measurements have been taken which tend to support the theory. (1) The angular distribution function has been found to be Gaussian using a measurement technique for which the angle can be read with ±0.1°. (2) The broadening of the Stoner-Wohlfarth switching threshold depends on both angular and magnitude variations. A machine calculation was performed to give this broadening as a function of ασ and Hkσ, the standard deviation of the angular and magnitude distributions, respectively. Using a measured ασ=1.0° the best fit gave Hkσ=0.1 H̄k, which agrees with theory within a factor of three. The data showed that the Hk distribution is not completely symmetric but has approximately 10% of the film with Hk&gt;2Hko.
Measurements of angular dispersion as a function of applied stress for films of known chemical inhomogeneity yield results an order of magnitude below those calculated, using the model described. This is thought to represent the ``stiffening'' effect of magnetostatic and exchange interactions.
Theory of Nernst Generators and Refrigerators
Authors: Norwood M. H. 
Published: April 2005

Formulas for efficiency and coefficient of performance are derived for devices based on the Nernst and Ettingshausen effects. The equations reduce to those of Harman and Honig in the limits of small figure of merit and refrigerator current, but they do not approach the Carnot limits. To obtain a better device theory, one must solve a two-dimensional partial differential equation in which the current density is allowed to vary with position.
A crude maximization procedure for the figure of merit is shown for a one-band nondegenerate semi-conductor in a weak magnetic field. Experimental data indicate that HgxCd1−x Te alloys are perhaps the best materials for such devices at present.
Direct Observation of the Oxidation of Aluminum Single-Crystal Surfaces
Authors: Doherty P. E. , Davis R. S. 
Published: April 2005

A new technique has been developed by which naturally and anodically formed aluminum oxide produced on single-crystal specimens has been studied in the electron microscope. The low-temperature amorphous oxide grown by the transport of cations was smooth at the metal-oxide interface. However, the oxide-oxygen interface exhibited topography on certain crystal orientations. A high-temperature crystalline oxide was found to grow by the transport of anions. Epitaxial growth was observed on several orientations. The anisotropy of oxide thickness which occurred at elevated temperatures is discussed.
The above results are considered in terms of the structure of the metal-oxide interface.
Paraxial Solutions for Accelerated and Decelerated Axially Symmetric Space-Charge Flow
Authors: Borghi R. P. , Dunn D. A. 
Published: April 2005

Particle trajectories in the presence of space charge are calculated for prescribed axial potential variations, including linear, parabolic, and sinusoidal variations, using the paraxial-ray equation including space charge for axial symmetry. Solutions are also presented for the potential as a function of distance corresponding to prescribed hyperbolic and parabolic trajectories. The off-axis equipotentials are calculated for some representative cases.
These two-dimensional results are interpreted in the light of one-dimensional space-arge theory in which exact solutions can be obtained for the potential as a function of distance. Some of the limitations of the present theory in which either the potential or the trajectory is prescribed are pointed out.
Developments in the Generation of Electricity and the Production of Soft Magnetic Steel Sheets in Britain
Authors: Wells J. E. 
Published: April 2005

The development of the electricity generating industry in Britain, and the production of soft magnetic steel sheets are closely linked. The expansion of both these industries is reviewed, with particular reference to the effect of improvements in generating efficiency and magnetic materials. Some of the difficulties experienced in the manufacture and use of the more advanced magnetic materials are described.
An attempt is made to assess past trends and estimate future requirements for soft magnetic steel sheets and an outline is given of some of the new developments in the generation, conversion, and distribution of electric power. The effect of these developments on the demand for magnetic materials, which is also likely to be affected by the new techniques in steelmaking and processing that are now becoming available, is considered. It is concluded that the total demand for soft magnetic sheets in Britain will have almost doubled by 1972, and that there will be a general reduction in the silicon content of the various magnetic grades at present in use.
Exchange Interactions in Magnetic Compounds
Authors: Smart J. Samuel 
Published: April 2005

The basic feature of the Heisenberg-Dirac-Van Vleck model of cooperative magnetic phenomena is the assumption that the interaction Vij between a pair of atoms i and j in a crystal has the form Vij=−2JijSi·Sj,where Jij is an exchange interaction and Si and Sj are spin operators. Such an assumption seems naturally better suited to insulating compounds than to metals and alloys. In principle, it should be possible to determine the Jij for magnetic compounds by comparing experimental data with theoretical predictions based on Eq. (1). In practice, the matter is complicated by the fact that the H-D-VV model is oversimplified, and that even in its oversimplified form exact solutions cannot be obtained for real three-dimensional crystals.
The general problem of evaluating exchange interactions in magnetic compounds from experimental data is reviewed, and specific results are presented for some antiferromagnetic and ferrimagnetic systems where a reasonably good determination of the exchange interactions can be obtained. Some correlations and regularities in the data are noted and discussed. A long review article on this topic is being published elsewhere.