bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of Wave-Guide-Fed Slots Radiating into Parallel-Plate Regions
Authors: Gruenberg Harry 
Published: April 2005

Slotted wave-guide arrays feeding into parallel-plate regions have been used in some high speed scanners. Parallel-plate regions also have been used for the suppression of second-order beams of high gain arrays.
A theoretical expression is derived for the conductance of a longitudinal shunt-slot in a rectangular guide when the slot is radiating into a parallel-plate region of arbitrary plate spacing. Some peculiarities of the theoretical results are discussed. There is good agreement between theory and experiment.
Axial Motion of an Electron in a Constant Wave Velocity Section of a Linear Accelerator
Authors: Caplan David , Akeley Edward 
Published: April 2005

The relativistic differential equations for the axial motion of an electron in a wave guide, excited by a progressive, sinusoidal, longitudinal, electric wave of constant speed less than that of light in vacuum, have been integrated. The first integral yields the results of J. C. Slater and gives the energy-phase relationship, which is periodic. A second integration yields the phase distance relationship and thus completes the determination of the orbits. All separatrices are exactly integrable in terms of trigonometric and hyperbolic functions, while the general case requires elliptic integrals of the first and third kinds. The former are obtainable from tables, while the latter are evaluated by series expansions, or in the case of particles near the self-crossing point of the separatrices where the convergence of the series expansion is slow, by the use of the addition theorem for elliptic integrals of the third kind.
These results are applied to the case of the proposed new Purdue Linear Accelerator. Energy distribution of the particles coming out of the end of the first two sections of this accelerator is in this way obtained.
The Emission of Radiation from Diatomic Gases. IV. Emissivity Calculations for CO and HCl for Nonoverlapping Rotational Lines as a Function of Temperature and Optical Density
Authors: Penner S. S. 
Published: April 2005

Simplified expressions have been developed for the engineering emissivity of uniformly distributed diatomic gases for nonoverlapping rotational lines with a resonance contour. Unfortunately the rotational half-widths for spectral lines arising from transitions between excited vibrational energy levels are generally not known. For this reason it was necessary to make the assumption that the rotational half-widths for transitions of the form n→n+v, v=1 or 2, are identical. The theoretical analysis is, however, sufficiently general to be useful without modification when accurate data concerning the dependence of line-width on vibrational excitation become available. Explicit expressions have been obtained for the contributions to the total emissivity associated with individual vibration-rotation bands.
Representative emissivity calculations have been carried out for CO and HCl. Comparison of the calculated emissivities of CO with experimental data shows only fair agreement, suggesting either that the assumed description of rotational half-widths is inadequate or else that the empirical emissivity data are not reliable at elevated temperatures.
Time-Temperature Dependence of Linear Viscoelastic Behavior
Authors: Schwarzl F. , Staverman A. J. 
Published: April 2005

The question is treated whether in the study of linear visco-elastic behavior of a material change of temperature is completely equivalent to a shift of the logarithmic time scale or not. If it is, the material is termed ``thermo-rheologically simple'' (class A).
It is shown that, by plotting the results of a similar rheological experiment (for instance, a creep experiment) performed at different temperatures and comparing the curves obtained, one can decide whether the materials considered belongs to class A or not, by seeing whether the curves can be made to fit by shifting them along the axis of logarithmic time. Once the material has been decided to behave thermo-rheologically simple, one can plot the function describing the time-shift as function of the temperature.
Some examples of thermo-rheologically simple materials are quoted from the literature.
The micro-rheological conditions for thermo-rheologically simple behavior are discussed. It turns out that this behavior implies that in similar deformations at different temperatures always the same sequence of molecular events follows, whereas in materials not belonging to class A, not only the speed, but also the sequence of molecular processes changes when the temperature of the experiment changes. This implies, that materials of class A cannot from a heat treatment assume a special structure which could not be obtained by one temperature, whereas for materials of class B a heat treatment can indeed result in a special structure. It is reasonable to expect that thermo-rheologically simple materials will be found only among polymers containing no crystallites and no pronounced polar groups.
Free Molecular Flow in the Sample Inlet to the Mass Spectrometer
Authors: Zemany Paul D. 
Published: April 2005

The aspects of free molecular flow in the sample inlet to the mass spectrometer are pointed out and the conditions under which such flow can occur are described. Methods for calculating the leak diameter and sample pressure for various flow rates are developed. These principles are illustrated by consideration of the flow characteristics in the mass spectrometer leak detector, and by an example from reaction kinetic studies.
The decrease in pressure in the sample reservoir is also described. This is applied to a determination of molecular weights. The effect of the pressure decrease on apparent fragmentation patterns is pointed out and a rational expression for spectrometer sensitivity is suggested which is based on the fraction of molecules which flow through the spectrometer which appear as ions.
The Conductivity Change in Polyethylene During γ-Irradiation
Authors: Mayburg S. , Lawrence W. L. 
Published: April 2005

The effect of Co60 γ-irradiation on the direct current conductivity σ of polyethylene has been determined up to an intensity I of 4000 roentgens per hour at room temperature. The equation σ/σ00=1+(I/I0)34describes the data where σ00 is the conductivity without radiation and is the order of 10−18 (ohm cm)−1 and I0 is 20 roentgen/hr. Measurements at liquid nitrogen temperatures give a factor of 20 decrease in the normal conductivity and a factor of 25 decrease in the radiation induced conductivity below their respective room temperature values.
The temperature data serves to suggest an ionic mechanism for electrical conduction in polyethylene as opposed to an electronic mechanism. In fact, the ion contributing most to the conduction in the polyethylene may well be the proton.
Velocity of Propagation and Nature of Luminosity Fluctuations in a Plasma Jet
Authors: Freeman Mark P. , Li Sik U. , Von Jaskowsky W. 
Published: April 2005

The velocity of propagation of the luminous detail in a plasma jet was determined by the time required for transit between photomultiplier stations at different axial positions of an expanded plasma jet. The measurements were synchronized with power supply ripple to eliminate this as a random perturbation.
It is found that the luminous fluctuations travel at two velocities. The slower fluctuations move with nearly the calculated speed of the jet and may therefore be ascribed to temperature or possibly composition fluctuations while the (much) faster fluctuations travel with jet speed plus local sonic velocity and are evidently pressure waves.
Noise on a Drifting Maxwellian Beam
Authors: Bloom Stanley , Vural Bayram 
Published: April 2005

The problem of noise- (and, as a special case, signal-) wave propagation along a drifting, one-dimensional electron stream with a half-Maxwellian velocity distribution is analyzed. The integral equation resulting from the linearized Boltzmann equation is intractable in its exact form and so, heretofore, has succumbed only to machine computation. In this paper closed-form solutions are obtained through the use of a simplified kernel. This approximation, although it limits the analysis to beams with small relative velocity spreads and small ratios of plasma frequency to operating frequency, is yet innocuous enough not to mask the main effects.
The noise current and voltage are found to consist of three wave terms: a ballistic wave describing the injected noisy ``test particle,'' a slow space-charge wave and an aggregate of fast space-charge ``waves'' which decays, en masse, with distance because of phase mixing. This aggregate is approximately representable by a single fast wave with exponential damping. Far downstream the noise power spectra (ψ,Φ,Π,S) lose their familiar sinusoidal pattern and settle to constant values. Along the entire beam the positive rf noise power, S+Π, is invariant.
A Method for Shadowing Electron-Microscopic Specimens with Tungsten
Authors: Hart Roger G. 
Published: April 2005

A method is described for the controlled sublimation of tungsten wire at a temperature just below the melting point. Emission of electrons from the wire provides a sensitive indicator, which enables the operator to regulate the filament temperature by manual or automatic adjustment of the heating current.
The wire is volatilized primarily by sublimation of metallic tungsten, not by oxidation.
Some advantages of tungsten shadowing are considered.
Solubility of Zinc in Gallium Arsenide
Authors: McCaldin J. O. 
Published: April 2005

The distribution of tracer zinc-65 between the vapor and solid GaAs was studied. For dilute concentrations [Zns] of zinc in the solid, the distribution coefficient K is a constant (Henry's law); at higher zinc concentrations, K falls off inversely with [Zns]. These observations can be interpreted simply in terms of an ionization equilibrium Zns → Zns−+e+. Based on this interpretation, the present measurements indicate an intrinsic carrier concentration ni of about 4×1018 cm−3 for GaAs at 1000°C. This value is roughly six times larger than ni estimated by extrapolation of Hall measurements; the latter, it is suggested, may reflect the presence of only the more mobile carriers.
The solubility of zinc was also studied as the arsenic pressure in the system was changed from the dissociation pressure (estimated 10−3 atm) to one atmosphere. The zinc solubility was observed to increase three-to fourfold with the increase in arsenic pressure. This result is in semiquantitive agreement with calculations for the mass action equilibrium of simple stoichiometric defects in GaAs.
Experiments on Mercury-Silicon Surface Barriers
Authors: Donald D. K. 
Published: April 2005

Barrier heights of Si-Hg surface barriers were examined experimentally as a function of the resistivity of the silicon. The saturation reverse current and the resistance at zero bias for the diodes were measured. The simplest Schottky metal-semiconductor theory reasonably explains the resistivity-dependent behavior of ``n''-type Si. However, for ``p''-type Si a surface inversion layer is predicted if the published work functions are superposed on the simplest model. Here the resistivity dependence for the thicker barriers is less strong and the measurements more variable. The results are summarized in terms of the flat band condition (uB=uS) in units of kT/q from midband: Calculated 3±3.5. The experiments are consistent with 3±5, using no surface states to improve the fit. A Shockley surface-charge distribution ±nss≲1012/cm2 is sufficient to suit the experimental data to uB=3.
Sample treatments were ion bombardment with Hg ions, followed by submersion in Hg. Field enhanced desorption in liquid Hg was also used. Cleaved samples produced what seemed to be patchy surfaces with small regions degenerate ``p'' type.
Hardening of Potassium Chloride by Color Centers
Authors: Nadeau John S. 
Published: April 2005

The flow stress of KCl crystals containing color centers was studied in a systematic way to determine which color centers produced significant hardening. The color centers were introduced both by additive coloring and by gamma irradiation. Annealing and optical bleaching techniques were used to alter the relative concentrations of defects.
For a given concentration of electron excess centers (F, M, R, N, etc.), the irradiated crystals were about ten times harder than the additively colored ones. Possible models for the halogen defect responsible for this high hardness were considered and it was concluded that it must be an interstitial ion or atom.
Annealing of additively colored crystals indicated that the ``colloid band was actually two overlapping bands centered at about 735 and 760 mμ. Prior to formation of these bands the crystals became about 40% harder than in the as-colored state indicating the presence of a coherent cluster of elementary defects. The flow stress decreased sharply upon appearance of the colloid bands. A similarly located though broader band was formed after prolonged optical bleaching.
Physical Properties of Titanium. III. The Specific Heat
Authors: Holland Lawrence Rozier 
Published: April 2005

The specific heat of titanium has been measured over a temperature range from 600° to 1345°K. The specific heat at 600°K is 0.72 J/g°K ±2.5%, and increases to 0.93 J/g°K ±6% just below the transition, which takes place at 1155°K. Above this point the specific heat drops to 0.75 J/g°K ±4%, where it appears to remain fairly constant. The increase of the specific heat to 1.7 times the Dulong and Petit value is interpreted as an effect of anharmonic terms in the potential of the atomic oscillators, as proposed by Born and Brody.
The samples were heated by alternating current, varying in frequency from 8.63 to 14.35 cps, causing a temperature fluctuation at twice the heating current frequency, and a resultant resistance fluctuation. The resistance fluctuation was observed electrically, and from it, through the measured temperature coefficient of resistance, the temperature fluctuations and specific heat were calculated.
Energy Band Parameters of Germanium Indicated by Tunnel Diode Reverse Characteristics
Authors: Carr William N. 
Published: April 2005

A precise method for analyzing the current—voltage characteristic of the reverse biased junction has permitted a direct observation of the voltage levels corresponding to the onset of tunneling into several energy subbands of germanium. The experimental technique involves fitting the experimental data to an equation of the form J = αV exp (−βV) derived from the calculations of Price, Radcliffe, and Kane. The onset of the tunneling interaction with each subband is noted as structure in the plots covering the reverse bias range. The values for EΓ2 − RL1 and EΔ1 − EL1, corresponding to the energy separations of the band minima, are found to be 0.152±0.005 and 0.208±0.008 eV, respectively, for slightly degenerate n-type material at 4.2°K.
The conduction energy bands are each found to move closer to the valence band level for increasing degeneracy by comparing the present data with the optical data of Pankove and Aigrain for the direct band gap. Energy spacing of the various conduction band minima is found to remain constant with increased electron concentration. Evidence for a ``tailing'' of the principal conduction band edge into low mass states is discussed for heavily doped n-type material.
Focused Microwave Technique for Measurement of the Ionization Rate and Collision Frequency
Authors: Scharfman W. , Morita T. 
Published: April 2005

A technique for the measurement of ionization rate and collision frequency in gases uses high-powered focused microwaves. By using short pulses and focusing the energy into a small spot within a large vacuum chamber, diffusion losses are made negligible. Under these conditions the breakdown equation can be simply solved for the ionization rate in terms of easily measured parameters—the pressure, pulse width, and electric field. Experimental results with this technique are compared with published results. The agreement between the two is sufficiently good to confirm the usefulness of this technique.
Due to the focusing of energy into a spot remote from walls, the walls do not enter into the ionization process. In this way a possible source of error in the measurement of ionization rate is avoided.
Since the technique arranges conditions so that diffusion losses are negligible, it is not necessary to know the diffusion coefficient in order to determine the ionization rate.
Decay of Elastic Waves in Solids with Dislocations
Authors: Harris Paul , Greene Richard F. 
Published: April 2005

A nonlinear, time-dependent, integral stress—strain relationship is formulated. Response functions for various powers of the retarded stress have transforms which satisfy dispersion relations. Characteristics and characteristic equations for one-dimensional elastic—plastic wave propagation are developed.
We assume that the mechanism for the decay of elastic waves is the same as the mechanism of ultrasonic internal friction. This permits us to evaluate the linear response function by comparison with frequency-dependent internal friction theory and experiment. The functional form of the nonlinear response function is found.
Dislocation Damping in Dilute Cu-Ge Alloys
Authors: Fiore Nicholas F. , Bauer Charles L. 
Published: April 2005

Internal friction measurements have been performed on copper-germanium single crystals, ranging in composition from 0.005 to 0.5 at.% germanium, in order to test some predictions of dislocation damping theory. The Marx composite piezoelectric oscillator has been used with the specimens driven in their fundamental longitudinal mode of vibration at 80 kc/sec and at temperatures ranging between 200° and 600°C.
Three distinct regions appear when the decrement is plotted vs strain amplitude: an amplitude-independent, an amplitude-dependent, and a plateau region. While the Granato-Lücke theory can adequately account for the results in the amplitude-dependent region, behavior of the decrement in the amplitude-independent and plateau regions is more readily explicable in terms of Rogers' modification of the theory. From the appropriate analysis for each region, values of the average dislocation segment length between nodal pinning points, the average length between impurity pinning points, and the damping constant of a dislocation are obtained. These values are compatible with the physical constraints inherent in dislocation damping theory and are in good agreement with present notions concerning the internal structure of solids. In addition, the decrement exhibits a time dependency which qualitatively can be explained by the fact that the mobility of solute atom pinning points increases with increasing temperature.
Dislocation Multipoles and Their Role in Strain-Hardening
Authors: Chen H. S. , Gilman J. J. , Head A. K. 
Published: April 2005

The stress fields of edge dislocation dipoles are able to trap other edge dislocations that pass nearby. The configurations, energies, and trapping stresses of the resulting tripoles are discussed here in some detail. Dipoles may also interact dynamically with approaching dislocations because they cause fluctuating stresses. The decrease in the average velocity of a moving dislocation is given in terms of the fluctuation amplitude and the dislocation's ``mobility parameter.''
On the basis of these results, linear strain-hardening can be accounted for in terms of edge dislocation dipoles. Since dipoles in real crystals tend to be finite in length and their stress fields attenuate rapidly with distance, they act as particles to impede dislocation motions. Thus hardening is proportional to the dipole concentration which is proportional to the plastic strain, so the hardening will be linear in the strain.
Through interactions with approaching dislocations, dipoles may become tripoles, then quadrupoles, etc., leading to some of the characteristic residual structures in plastically strained crystals, such as slip bands, deformation bands, and bands of secondary slip.
No attempt is made to calculate the strain-hardening coefficients of real crystals because concentrations and distributions of dipoles are not known in sufficient detail.
Finally, it is shown that the asymmetric stress fields of dipoles can account in a natural way for the Bauschinger effect.
Thermodynamic Properties of Drawn Linear Polyethylene
Authors: Peterlin A. , Meinel G. 
Published: April 2005

Measurements of melting curves, density, and long period of undrawn and drawn PE as a function of the draw ratio and the annealing temperature between 118° and 129.8°C for different annealing times were performed. Melting experiments show a linear increase of melting point and a reduction of heat content of the noncrystalline component with increasing draw ratio. As a consequence of plastic deformation during drawing, the tied macromolecules partly incorporated in more than one crystal are under high strain. This reduces not only the entropy but also the intra- (trans instead of gauche conformation) and interchain (aligned extended chains are more closely packed) energy of the amorphous regions. Annealing nearly instantaneously removes the strain on tied chains, restores the enthalpy and entropy to the values in a nearly completely relaxed supercooled melt, and increases crystallinity and long period. Subsequent prolonged annealing produces only slight additional changes.
The variation of enthalpy and entropy rather well explains the observed drastic changes in sorption and diffusion of solvent molecules as a consequence of drawing and annealing.
Crystal Structure and a Unique ``Martensitic'' Transition of TiNi
Authors: Wang Frederick E. , Buehler William J. , Pickart Stanley J. 
Published: April 2005

Through single-crystal x-ray diffraction methods, the crystal structure of TiNi has been determined in the temperature range −70° to 900°C. Contrary to what has been assumed from previous work based on the powder pattern methods, the TiNi crystal structure is not a simple CsCl type. Rather, it has an a0=9Å superlattice and an a0=3Å sublattice with 54 atoms per unit cell complex structure.
The 9Å superlattice undergoes, at about 166°C, a ``martensitic'' pseudo order-disorder transition which is not accompanied by a crystallographic transformation. Through the understanding of this unique transition the apparent contradicting observations made on TiNi by various past investigators can now be reconciled and the unusual physical properties associated with the alloy are explained qualitatively.
Field Dependence of Photoresponse in Germanium Bicrystals
Authors: Mataré H. F. , Cho K. S. 
Published: April 2005

Measurements of the photoresponse of germanium bicrystals are reported here with two specific results in mind:
(1)The detailed response at higher optical frequencies. The measured transition steps at larger than band gap energies can be associated with the specific band structure of the dislocation plane taking the stress field into consideration.
(2) The detailed bias or field dependence yields a linear law for the photovoltage. It is found that the electronic dislocation model, as used earlier, explains the linear field dependence of the photoresponse.
Reflection and Transmission of Electromagnetic Waves by a Moving Dielectric Medium
Authors: Yeh C. 
Published: April 2005

The reflection and transmission of electromagnetic waves by a moving dielectric medium are investigated theoretically, and the reflection and transmission coefficients are determined. Two cases of the movement are considered: (a) The dielectric medium moves parallel to the interface. (b) The dielectric medium moves perpendicular to the interface.
Various interesting features concerning the variation of the reflection and transmission coefficients, angles of reflection and transmission, and the frequencies of the reflected and transmitted wave, as a function of the velocity of the moving medium, are discussed.