bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Measurements of Stacking Faults and Internal Strains in α-Cu-Zn and α-Cu-Sn
Authors: Wagner C. N. J. , Hélion J. C. 
Published: April 2005

Powder-pattern peaks of cold-worked and annealed fcc Cu-Zn and Cu-Sn filings were measured with a diffractometer using filtered Cu radiation. The plots of the lattice parameter ahkl, calculated from the peak maximum position of the individual (hkl) reflections, as a function of cosθ·cotθ proved to be linear for all annealed powder samples. The large scatter of the individual ahkl values of the cold-worked filings could be related to the deformation stacking-fault probability α=α′-α″ (intrinsic-fault probability α′ and extrinsic-fault probability α″), segregation Δx, and internal stresses σ. The lattice parameters (a0)CW of the cold-worked filings of the Cu-Zn alloys were larger, whereas (a0)CW of the Cu-Sn alloys were smaller than the corresponding (a0)Ann values of the annealed filings. The deformation-fault probability α increases with increasing solute concentration.
The combined twin-fault probabilities β and extrinsic-fault probability α″, i.e., 4.5 α″+β, were determined from the displacements of the center of gravity from the peak maximum positions of the (111) and (200) reflections. Fourier analysis of the line shapes allowed the determination of the fault probabilities [1.5(α′+α″)+β], the average domain size D, and the rms strain components in the [111] direction. Using the quantities α′-α″, 4.5 α″+β, and 1.5(α′+α″)+β and solving for α′, α″, and β, no evidence of the occurrence of extrinsic faults in the cold-worked filings could be found. The values of 1.5 α′+β calculated from line broadening agree rather well with those obtained from lattice-parameter and center-of-gravity changes, indicating that intrinsic deformation and twin stacking faults are the primary causes of the broadening and shifts of the powder-pattern peaks from cold-worked α-Cu-Zn and α-Cu-Sn filings.
Trajectories in the Symmetrical Electron Lens
Authors: Jacob L. , Shah J. R. 
Published: April 2005

The complete field plot obtained by ``relaxation'' was used to determine electron trajectories for parallel incidence at heights up to one-third the bore diameter, from a numerical integration of the trajectory equation using the method of differences. The accuracy attained in this method yields cardinal points to within one percent. It was found that the focal length fn for a ray of height rn was given by fn=f0−brn2, where b is a constant; also, because of the curvature of the principal planes, the distance dn to the midplane follows a law dn=c−drn2 where c and d are constants. A consequence of this is that for the same variation in focal length, the greater the curvature of the principal plane the larger the spherical aberration of the lens.
The trajectory tracings indicate that spherical aberration is small at heights up to one-twelfth the bore diameter, but increases with height till at a value of one-third the bore, the percentage change in focal length has decreased by some 40 percent. Confirmation of focal properties was obtained using the lens in a single stage electron microscope and examining the pincushion distortion in the image of a gauze object.
Evaluation of the spherical aberration using the weak lens approximation of Scherzer leads to gross errors both in magnitude and variation, e.g., the aberration does not remain constant with voltage ratio. The experimental data with the electron microscope indicate little or no change in aberration with increase in the power of the lens; this does not agree with the results of the mathematical analysis of Ramberg.
Preparation of p — n Junctions by Surface Melting
Authors: Lehovec Kurt , Belmont Emanuel 
Published: April 2005

A new method is described for preparation of p — n junctions in single-crystal semiconductors: the upper part of a slice cut from a single-crystal semiconductor is melted by radiation. Impurities of the opposite type than those present in the crystal are introduced into the melt. Upon slow solidification of the melt a single crystal is obtained with a p — n junction at the original position of the solid-liquid interface. The method is capable of producing multiple junctions.
The influence of (a) heater temperature, (b) forced cooling, and (c) thickness of the slice on the position of the solid liquid interface is calculated for a one-dimensional model, assuming that the temperature difference between bottom and top of the semiconductor is small compared to the melting temperature of the semiconductor. The time constant characterizing the rate of reaching equilibrium conditions after a sudden small change in heater temperature is estimated.
The Generation of Wind Waves on a Water Surface
Authors: Eckart Carl 
Published: April 2005

The statistical methods for treating continuous media developed elsewhere are applied to the generation of surface gravity waves. The wind stress is assumed to be everywhere normal to the disturbed surface of the water and caused by a known ensemble of ``gusts.'' Each gust is considered to be a center of high or low pressure, which moves with the mean wind speed, and has a radius L, and duration T. The rms value of the variable wind pressure is assumed to vary systematically from point to point in a storm. The calculations are made for an idealized, long continuing storm; before applying the statistical equations, the effect of a single gust is calculated.
It is shown that the single gust produces a V-shaped wake, which, after the gust has blown itself out (t&gt;T) can be considered as a packet of free gravity waves, which moves and spreads under the influence of divergence and dispersion.
The results of the statistical calculation are compared with known general facts, and with an actual storm. From the fact that the storm waves have a non-sinusoidal character, and arrive at any one point in groups of 5 to 10 crests, it is deduced that the duration of a gust is from 15 to 30 seconds. From the fact that the majority of the wave energy travels in directions that are within 30° of the wind, and with phase velocities that are nearly equal to the wind speed, the mean radius of the gusts is deduced to be about 40 meters in the case of a wind speed of 20 meters per second.
The crest length of the waves is proportional to the distance r from the storm, and inversely to its diameter, D; when r/D=10, the dominant length of the crests is 2.2 wavelengths.
The rms displacement, H, of the sea-surface from its horizontal mean is a function of the parameters already mentioned and of P, the rms value of the variable component of the wind pressure at the center of the storm; for the idealized storm considered, and for r/D≫1, this is approximated by H2=10P2D2/rL,all quantities being in centimeters, including P, which is measured in centimeters on a water barometer. Comparison with data for an actual storm indicates that this theory requires a value of P that is possibly 10 times greater than its actual value.
While the theory explains many of the phenomena of storm waves, it is therefore incapable of accounting quantitatively for the wave height. The possible reasons for this inadequacy are discussed. The relation of the theory to Jeffreys' sheltering theory is also discussed, and it is shown that both postulate that the variable component of the wind stress is normal to the water surface. The sheltering theory also postulates that the wind pressure lags 90° behind the surface disturbance. A similar phase lag is a consequence of the assumptions of the present theory.
The Detection of a Sine Wave in Gaussian Noise
Authors: Reich Edgar , Swerling Peter 
Published: April 2005

This paper deals with the problem of finding the ``optimum'' method of detecting a sine wave of known frequency and amplitude in the presence of noise. The type of noise considered is the so-called Gaussian process, which is obtained when thermal noise is passed through an arbitrary linear passive device.
The analysis takes into account the fact that in practice only a finite sample of observed signal is available.
The optimum detection method is defined as that which maximizes the probability of recognizing the presence of a sine wave if one has actually appeared; while the probability of falsely announcing the presence of a sine wave, if none has actually appeared, does not exceed some prechosen value.
It is shown that when the noise has a flat spectrum, all the relevant information is contained in the amplitude and phase of the Fourier transform of the received sample at the frequency of the sine wave. Almost the same result holds in the case where the noise has an exponentially decaying autocorrelation, except that in this case the values of the observed sample at the end points of the sample also play a role.
The Equivalence of Optimum Transducers and Sufficient and Most Efficient Statistics
Authors: Preston Glenn W. 
Published: April 2005

The problem of the design of transducers for the purpose of restoring the fidelity of a signal (which has been corrupted by noise), while preserving information in the sense of Shannon is shown to be a particular though unusual one of statistical inference and to be amendable to the methods of mathematical statistics.
Adopting the view that the inference of the approximate form of a function s(t) (the signal) from the available mixture of the signal and the noise time series n(t) is the natural limiting case of inference from discrete series of random variables, it is seen that the transducer under discussion is the physical analog of a ``statistic''—in the sense of Fisher—and that the properties of the optimum transducer are equivalent to the statistical properties of sufficiency (preservation of information) and efficiency (maximization of fidelity).
The case of a Gaussian signal to which Gaussian noise has been added is considered in detail. Using the probability density functional of the Gaussian time series, the maximum likelihood estimate (which in this case is efficient, hence sufficient) of the signal is derived, and it's physical analog is identified as the smoothing filter of Wiener with infinite lag.
Electrical Properties of Liquid Selenium I
Authors: Henkels H. W. , Maczuk J. 
Published: April 2005

The thermoelectric power of liquid selenium has been measured in the range 250–500°C. Values of activation energies calculated from the temperature dependences of thermoelectric powers and resistivities agree. This activation energy taken as the intrinsic activation energy (or the energy to break the Se–Se bond) is 2.31 ev calculated from data given by Henkels. The mobility of holes in the intrinsic region exceeds that of electrons and has a value (8.4×106)/T32 cm2/volt sec, assuming electronic mass.
As a further check of the electronic nature of the conduction in the liquid and of theories of conduction in the hexagonal form, preliminary measurements of the thermoelectric power of pure selenium doped with small percentages of As, Sb, and Bi up to 4 percent were made. In the intrinsic region the specimens exhibited p type conduction, but at lower temperatures the sign of the thermoelectric powers reversed and values became quite large but negative. The crossover point depended qualitatively on the amount of impurity in the correct manner. The n type conduction is tentatively attributed to donor levels introduced by the normal trivalence of Group Vb elements. Two p electrons are considered bound in the selenium chain, the third ionized at high temperature.
Crystallographic Variations of Field Emission from Tungsten
Authors: Wilkinson M. K. 
Published: April 2005

A photometric method has been developed and used to measure field-emission electron currents as a function of the crystallographic directions found in a tungsten single crystal emission point. Data obtained indicate that the appearance of bright and dark areas on the pattern of a field-emission projection tube can be explained by the differences in the work functions of the various crystallographic directions. The experiments also suggest that the value of the exponent of the work function needed to relate the field-emission equation to observed data is (32) as predicted by theory. The method of analysis is independent of the need for high accuracy of electric field determination. However, it does depend on a knowledge of the electric field distribution about the surface of the emission point. In these experiments, the field distribution was an assumption based on experimental data.
To insure the constancy of the electron emission required for measurement it was necessary to maintain an excellent vacuum. A method is given for the attainment and maintenance of a pressure in the region of 10−12 mm of Hg.
Laminar Flow in Channels with Porous Walls
Authors: Berman Abraham S. 
Published: April 2005

The Navier-Stokes equations have been solved to obtain a complete description of the fluid flow in a channel having a rectangular cross section and two equally porous walls. The scope has been limited to two-dimensional incompressible steady-state laminar flow.
The solution of the flow equations leads to detailed expressions for the dependence of the velocity components and the pressure on position coordinates, channel dimensions, and fluid properties.
Electrical Properties of Selenium. III. Microcrystalline Selenium Metal Doped
Authors: Henkels H. W. , Maczuk J. 
Published: April 2005

The thermoelectric powers and dc and 200-mc resistivities of pure and metal-doped selenium have been studied as functions of temperature. The properties of materials in the two important microstructures (colony and equiaxed) were distinguished. The influences of the metals Na, Cu, Ag, Mg, Zn, Cd, Hg, Ga, In, Tl, Pb, Sb, Bi, Te, Fe, Ni, Co, and Ce were noted.
A working model of the selenium semiconductor was developed. In this model there is an acceptor level &lt;0.15 ev from the full band caused by nonmetals and possibly lattice defects. In strained crystals or material in the colony structure a second acceptor level 0.27 ev from the full band is postulated from the behavior of dc and ac resistivity curves as a function of temperature. The density of the first level varies in the range 1014/cm3 to 6×1016/cm3 with amount of nonmetal impurity. The density of the second level depends on the crystal structure, decreasing as the colony structure recrystallizes to the equiaxed. In the specimens crystallized at 110°C the density was about 2×1016/cm3. Both metals and non-metals are largely segregated at grain boundaries. Metals produce effective donor levels at these places.
The dc properties reflect the presence of internal barriers produced by the segregation. The donor levels enhance barriers existing in the purest selenium tested increasing resistivities and thermoelectric powers.
With increase in temperature &gt;160°C the density of acceptor levels decreases as defects are removed by structural changes in the lattice.
Effect of Gas Slip on Unsteady Flow of Gas Through Porous Media
Authors: Aronofsky J. S. 
Published: April 2005

A numerical method is presented for describing either the one-dimensional or radial transient flow of gases through a porous medium in which the initial and terminal pressures and/or rates are specified. The purpose of this investigation was to evaluate the effect on transient gas flow of a pressure-sensitive gas permeability resulting from gas-slip effects. The gas-slip permeability or apparent permeability is assumed to vary as a linear function with the reciprocal pressure. The computations were carried out by means of punch card machines.
The results demonstrate that under certain conditions, the transient flow system is greatly influenced by gas-slip permeability. However, the results also indicate that the effect of gas slip on transient flow behavior is negligible for pressure conditions usually associated with gas or petroleum reservoirs, and would be of most importance in the conduct and analysis of gas flow experiments in the laboratory. A specific laboratory application of the calculations is a possible transient method for the determination of porosity and/or gas-slip corrected permeability.
Theory of Orientation and Double Refraction in Polymers
Authors: Gurnee Edward F. 
Published: April 2005

Orientation and birefringence in linearly oriented amorphous polymers are discussed with particular emphasis on polystyrene type chains. A system of completely uncoiled parallel zigzag chains is defined as 100 percent orientation. The variation of birefringence with orientation is assumed to follow the same expression as that for the variation of polarization anisotropy with extension for a single random coil chain. With these assumptions and reasonable models for the completely uncoiled polystyrene chain it is possible to express any given birefringence as a percentage orientation.
Methods are developed for the experimental determination of the birefringence at a particular point in an oriented monofilament instead of the usual determination of an average birefringence through the monofilament. The application of these methods to actual examples leads to reasonable values of the orientation.
PPI Light Spot Brightness Probability Distributions
Authors: Sponsler George C. , Shader Fern L. 
Published: April 2005

A mathematical study utilizing the statistics of noise theory is presented which derives light spot brightness probabilities for PPI target returns of various signal-to-noise ratios. An idealized model is employed which differs from similar previous ones by taking account of the cathode-ray tube's highlight brightness vs intensifier electrode voltage characteristic. For the 10KP7 cathode-ray tube this characteristic obeys an approximate 2.5 power law in typical operation. This law, together with a square law second detector, combine to form an over-all fifth power detector. The light spot brightness of the display is assumed to be formed by linear superposition of individual target returns resulting from the radar antenna scan. In the model, seven identical returns are so integrated.
Various mathematical methods of handling the problem are considered. The Edgeworth series approximation is found to give poor results compared with the Laguerre polynomial approximation. By the latter method the light brightness probabilities are found to be obtainable by interpolation from a table of the incomplete gamma function. Ancillary tables of statistical moments and selected values of the confluent hypergeometric function, 1F1(−5n/2; 1; −x), are included in the text.
Spectral Response of a Quadratic Device to Non-Gaussian Noise
Authors: Magness T. A. 
Published: April 2005

In order to compute the spectral response of a quadratic device to noise, a fourth-order moment P of the input noise is sufficient, P being a function of three independent time delays. The function P1 by which this fourth moment for a non-Gaussian noise differs from the corresponding moment for a Gaussian noise having the same spectrum is examined. The Fourier transform of this function is Q1, a function of three frequencies. Q1 is capable of an interpretation in terms of nonlinear correlations between noise components at different frequencies. A specialization of Q1 leads to E, a function of two frequencies which is a measure of the correlation between the squares of the envelopes associated with those frequencies.
Several networks involving quadratic nonlinear elements are examined to illustrate the theory. It is shown that while the function P makes it possible to compute the complete spectral response of the network, the function E (together with the spectrum of the input) is sufficient in order to find the spectral density at zero frequency. Finally, for three examples of non-Gaussian processes, the corresponding P1, Q1 and E functions are computed.
Radiation Damage Effects on Order-Disorder in Nickel-Manganese Alloys
Authors: Aronin Lewis R. 
Published: April 2005

Effects of fast neutron irradiation in a nuclear reactor on order-disorder in a series of nickel-manganese alloys ranging from 16.5 to 31.9 atomic percent manganese have been studied by resistivity and magnetic induction measurements. Attainment of an ``irradiated state'' differing from either cold work or thermal disordering is suggested by comparison of exposure results on initially cold work disordered and initially thermally disordered Ni3Mn. In a region from 16.5 to approximately 22 percent manganese, thermally disordered alloys are markedly affected by irradiation. These effects also appear to be superposed on the disordering produced by irradiation of initially ordered alloys.
From theoretical exponential dependence on period of irradiation, fast neutron disordering of Ni3Mn is determined by relating the Bragg and Williams order parameter quadratically with resistivity and linearly with magnetic induction. This leads to an estimate of 5000 for the ratio of the number of atomic replacements to primary collisions with neutrons of energy in excess of 0.5 Mev.
Propagation of Longitudinal Deformation Waves in a Prestressed Rod of Material Exhibiting a Strain-Rate Effect
Authors: Rubin Robert J. 
Published: April 2005

We consider the longitudinal propagation of stresses above the yield stress in a material exhibiting a strain-rate effect. The system consists of a semi-infinite rod subjected to end impact. If the rod is prestressed above the yield point and if the impact stress is not too large, the equations of motion are linear. Integral representations of the solutions can be obtained by the method of Laplace transforms. It is shown in general that the strain-rate solutions approach asymptotically the solutions obtained by von Kármán and Taylor in a treatment which neglects the strain-rate effect.
The propagation of the unloading wave is considered for the case in which the initial wave is a shock wave. The condition which defines the regions in the x—t plane, where the loading and unloading equations apply, is given. It is shown that an unloading shock wave will be absorbed except for the case of a material which does not work-harden. In this case the complete solution of the unloading problem is obtained.
On the Band Width of Cavity Antennas
Authors: Cohen Marshall H. 
Published: April 2005

The objective of this work is to determine the orders of magnitude of the band width available from a cavity antenna. Fcr simplicity of calculation a piece of shorted square wave guide of side a, opening into a half-space, is considered, and the resonance frequency and band width (1/Q) are calculated from transmission-line theory. The analysis depends on an equivalent aperture admittance which is defined for the lowest-order wave guide mode.
This type of antenna has a minimum Q which is equal to 0.424(a/λ)−3 when (a/λ)&lt;0.35. The cavity depth required for the minimum Q is of the order of 0.4a. The required dielectric constant increases rapidly as a/λ decreases. The effect of dielectric loss is considered. Some experimental results which agree well with theory are presented.
Solution of the Field Problem of the Germanium Gyrator
Authors: Wick R. F. 
Published: April 2005

A mathematical solution is obtained of a two-dimensional boundary-value problem involving flow of electricity in a solid when Hall effect is present, it being assumed that only one type of carrier is involved and that there is no surface recombination. The solution is used to calculate the efficiency of a Hall-effect ``gyrator,'' a four-terminal circuit element which violates the reciprocity law, as function of relative electrode size, shape of boundary, and magnetic field strength. It is also shown how corrections must be applied in measurements of Hall voltage and magnetoresistance in short samples.
Some of the results have been checked experimentally with fields up to 22 000 gauss. The calculations have been carried out for much higher fields as well and should prove useful in studies of materials such as indium antimonide which have higher mobilities than germanium.