bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brightness Waves and Transitory Phenomena in the Quenching of Luminescence by Alternating Electric Fields
Authors: Destriau G. 
Published: April 2005

Zinc or cadmium sulfide phosphors, especially phosphors having short persistence, are less sensitive to ultra-violet light or to x-rays when they are submitted to the action of an alternating electric field. With a half-wave x-ray generator and an alternating field of frequency equal to the frequency of the potential applied to the x-ray generator (50 cps), and in phase with it, the brightness waves (a curve giving the variation in the instantaneous brightness as a function of time in the interval of a period) are greatly modified. A sharp secondary maximum appears when the field passes through zero in each cycle; the amplitude of this maximum varies quickly during the cycles which immediately follow the application of the field.
If the light is filtered, the shape of the brightness wave varies according to the spectral region which is observed.
Effect of Crystallinity on the Dynamic Mechanical Properties of Polyethylenes
Authors: Nielsen Lawrence E. 
Published: April 2005

Six polyethylenes which differed widely in the degree of crystallinity were studied. The crystallinity was determined from density measurements. Both the density and the dynamic mechanical measurements were made over the temperature range from 25°C to above the melting point of the material.
The dynamic shear modulus drops rapidly as the melting point is approached. The mechanical damping goes through a maximum near 60°C and then through a minimum just below the melting point. It is possible to predict the density of any of the polyethylenes at any temperature below the melting point from the value of the shear modulus at the same temperature. The more crystalline materials have the higher shear moduli and the higher melting points.
Focusing of a Long Cylindrical Electron Stream by Means of Periodic Electrostatic Fields
Authors: Tien Ping King 
Published: April 2005

This paper presents a theory of focusing long cylindrical electron streams by means of electric fields which vary periodically along the stream. The use of a bifilar helix or a series of annular rings to produce periodic electric fields is considered.
The potential distribution at the position of the electrons is expanded in a power series, and an equation of electron motion is written. The solutions obtained indicate that the flow of electrons is essentially parallel, provided that the electrons enter the focusing structure practically without transverse velocities and are distributed across the stream such that the space charge fields decrease radially toward the axis in a manner similar to that of the periodic electric fields.
The method of periodic electrostatic focusing is of particular interest in connection with traveling wave tubes. The possibility of using a bifilar helix as both the slow wave and the focusing structure is discussed.
On the Concept of an Instantaneous Power Spectrum, and Its Relationship to the Autocorrelation Function
Authors: Turner C. H. M. 
Published: April 2005

A definition sufficient to define a function of frequency ρ(t,f) which could be regarded as the instantaneous power spectrum was given by Page. This function is not unique, since it may have added to it a complementary function of frequency ρc(t,f) satisfying ∫ −∞∞ρc(T,f)df=0without changing the original signal in any way.
It is shown that when a signal is observed by different observers, starting their observations at different times, they will not derive the same ``instantaneous power spectral function,'' and the differences between their results will be complementary functions as defined above.
It is well known that the Fourier transform of the autocorrelation function is equal to the square of the magnitude of the spectral function. Analogously, a ``running autocorrelation function'' is defined and it is shown that the Fourier transform of its partial differential coefficient with respect to time is an instantaneous power spectral function.
16 Percent Aluminum-Iron Alloy Cold Rolled in the Order-Disorder Temperature Range
Authors: Nachman Joseph F. , Buehler William J. 
Published: April 2005

The methods of fabricating 16 percent Al-Fe from cast slab to thin-gauge sheet are described in some detail. The melting, casting, homogenizing, hot rolling, and cold rolling at 575°C and room temperature are described. Particular attention is focused upon the 575°C cold rolling from the standpoint of the possible beneficial effects derived from an ordering reaction which occurs in this alloy. The technique of cold reduction from 0.007 in. to 0.0005 in. at room temperature is discussed.
Magnetic data on a limited number of heat-treated laminated cores are given. Useful physical properties, other than magnetic, of previous limited interest because of the inability to fabricate the alloy into ductile strong thin sheets, are discussed. These properties include excellent oxidation resistance at high temperatures, good wet-corrosion resistance to certain chemical solutions, and high electrical resistivity.
The Secondary Electron Resonance Mechanism of Low-Pressure High-Frequency Gas Breakdown
Authors: Hatch Albert J. , Williams H. Bartel 
Published: April 2005

Breakdown field strengths have been measured in air and hydrogen at pressures of the order of 1 micron Hg and frequencies from 25 to 90 Mc/sec between flat metal electrodes at separations from 1 to 4 cm. By suddenly applying a high voltage and then lowering it slowly an upper breakdown curve has been observed. This new curve can be combined with the lower breakdown curve and cut-off frequency such as reported previously by the Guttons, and by Gill and von Engel to form the boundaries of a breakdown region in the frequency-field strength domain.
The simple secondary electron resonance theories developed by Danielsson and Gill and von Engel have been extended by the semi-empirical determination of minimum and maximum limiting values of the electron-emission phase angle, a minimum limiting value of electron arrival energy, and a ratio between electron arrival and emission velocities.
Studies on the Creep Recovery and Annealing of Zinc Single Crystals
Authors: Tanenbaum M. , Kauzmann W. 
Published: April 2005

Part I is a description of some of the factors involved in the recovery by pure zinc single crystals at 35°C of the ability to creep following plastic deformation. The following observations were made: (1) Complete recovery of the ability to show an initial instantaneous plastic extension occurs much less readily than recovery of the ability to show transient creep. (2) Once the quasi-viscous creep stage is reached no recovery of transient creep occurs when the load is partially or completely removed for two minutes, but removal of only 6 percent of the load for 100 minutes permits partial recovery of transient creep at the full load. A 300 minute ``rest'' at 91.5 percent of the full load resulted in complete recovery of the transient creep at full load, even though creep occurred at the reduced stress. (3) The recovery of quasi-viscous creep at a reduced stress after exposure to a higher stress was also investigated. The recovery was slower, the larger the initial load. (4) The rate of the time-dependent contraction of zinc crystals on removal of the load probably follows a power law in the time. There is also an instantaneous nonelastic contraction which is about ten times larger than the elastic contraction.
These results show that the role of thermal fluctuations in activating the units of flow is very different from the role of the stress. The applications of the Eyring rate equation to quasi-viscous creep which have been made in the past are, therefore, not valid. A variable activation energy must be postulated in order to account for the kinetics of creep and recovery. These results are interpreted in terms of the dislocation theory of plastic flow.
In Part II a phenomenon is described in which pure zinc single crystals are consistently found to become temporarily hardened by annealing in vacuum above 200–260°C. The hardness thus introduced can be removed by straining the crystal and then allowing it to stand at temperatures below 200°C. The crystal is in this way returned to its normal plastic state. The hardening is not removed by electropolishing the crystal, so is not a surface phenomenon. Though similar to Orowan's thermal hardening effect, it differs by requiring a much higher temperature and by not requiring the addition of impurities.
Diffusion in Bimetal Vapor-Solid Couples
Authors: Balluffi R. W. , Seigle L. L. 
Published: April 2005

The intrinsic diffusivities of individual components in several binary systems have been determined with vapor-solid type diffusion couples. In this type of couple a high vapor-pressure component is diffused from the vapor phase into a slab of lower vapor pressure initially containing inert markers on its surface. Diffusivities may then be calculated from marker movement and diffusion-penetration curve data. Equations necessary for analysis of such couples are developed.
The alpha brass, copper-nickel, and silver-gold systems were investigated. Observations of polygonization during diffusion and dimensional changes normal to the diffusion direction were also made. Porosity formation, which occurred only in the vapor-solid silver-gold couples, was investigated in detail and was compared to porosity formation in corresponding sandwich couples. The general use and limitations of such couples in diffusion studies are discussed.
Relativistic Dynamics of a Charged Particle in Crossed Magnetic and Electric Fields with Application to the Planar Magnetron
Authors: Gold Louis 
Published: April 2005

Complete characterization of planar magnetron behavior is achieved for intermediate relativistic energies where radiation loss is of no serious consequence. The cut-off condition in the neighborhood of the rest energy of the particle shows a linear dependency on the product of electrode separation and magnetic field LH rather than the classical (LH)2. The modified period assumes a particularly simple form (2π/ω[1/(1−γ2)3/2], γ being the ratio of electric and magnetic fields which reflects a voltage dependency of the period not encountered in the classical case.
A parametric solution for the periodic orbits is derived on the basis of a transformation related to the delineation of the velocity space and, as such, represents a new variety of transcendental curve which degenerates into the cycloid for the limiting case of γ→0.
The spatial-time dependent mass, momenta, and energy relations take on especially straightforward forms in terms of the trajectory parametric solution.
Molecular Structure and the Crystallinity of Long-Chain Polymers
Authors: Bunn C. W. 
Published: April 2005

The molecular characteristics which determine whether a long-chain polymer will crystallize at all—and if so, how readily—are considered. The criterion for crystallization is geometrical regularity of molecular structure; but absolute regularity is not essential, for certain copolymers, as well as certain homopolymers with geometrically irregular structures, do crystallize; the requirement is that the different units which indiscriminately occupy corresponding positions in the structure must be not too different in size and shape (as in monomeric ``mixed crystals''); an approximation to regularity is sufficient.
It is unlikely that quite regular molecules can be incapable of crystallizing; when such substances are reported as noncrystalline, it is more likely that they crystallize only with difficulty, and the right conditions have not been found. Reluctance to crystallize is associated with a small interval between relaxation transition (``second-order transition'') and melting points; this interval appears to be influenced by the general shape of the molecule (though shape is not the only factor). The temperature range within which crystallization proceeds at an appreciable rate may be still further restricted if the chain repeat distance of the molecules is long; and this same factor may make crystallization at any temperature very slow.
On the Chromatic Field Aberration of the Magnetic Electron Lens in the Electron Microscope
Authors: Morito Nozomu 
Published: April 2005

The chromatic field aberration of the magnetic lens in the electron microscope is theoretically studied.
Good results are obtained for the coefficient of the chromatic difference in magnification of the objective, taking into account the inclination of the principal illuminating rays. The same coefficient of the intermediate lens increases rapidly as the magnification is reduced by the intermediate lens. The calculated results agree well with experimental results.
Calculated results are given for the coefficients of chromatic difference in rotation of all lenses as well as for the coefficient of chromatic difference in magnification of the projection lens.
Statistical Hydrodynamics in Porous Media
Authors: Scheidegger Adrian E. 
Published: April 2005

The statistics of disordered phenomena as exemplified by Einstein's theory of the Brownian motion is applied to the flow of fluids through porous media.
It is shown that such a statistical treatment of the hydrodynamics in porous media automatically explains some well-known phenomena in a more satisfactory manner than do capillaric models. The statistical theory leads to a differential equation of motion of the fluid which is a modification of that of Darcy; notably a new macroscopic quantity is introduced which is termed ``dispersivity.'' This quantity is indicative of the sideways dispersion which a stream of fluid undergoes when it is passing through the porous medium. Under certain statistical assumptions outlined in the paper, the dispersivity becomes a constant of the porous medium.
The new differential equation of motion of the fluid is discussed in detail and some indications about applications are given.
The Rheological Unit in Raw Elastomers
Authors: Mooney M. , Wolstenholme W. E. 
Published: April 2005

Reasons are adduced for suspecting that in a raw elastomer subjected to continuous shear there exist groups of molecules which are held together by entanglement or by thixotropic attachments and move and rotate essentially as elastic solid bodies. Such coherent molecular groups are called rheological units.
If an elastomer in continuous shear consists essentially of closely-packed rheological units, such units, rolling on each other, will transfer a rubber soluble dye across the shear planes as the ink rollers transfer ink in a printing press. This predicted phenomena has been observed with a Mooney viscometer fitted with a smooth rotor, the face of which is covered with a thin film of dried cement containing a dye in high concentration. From the velocity of the color front a rough value can be computed for the mean diameter of the rheological units. The diameters for a series of different elastomers lie in the range from 1 to 35 microns.
The Rheology of Suspensions
Authors: Sweeny Keith H. , Geckler Richard D. 
Published: April 2005

The rheological properties of concentrated suspensions of sized glass spheres in an equal-density medium has been investigated with the rotational viscosimeter. It has been found that the variation of fluidity with rate of shear can be expressed satisfactorily by a form of an expression suggested by Reiner relating the fluidity to the shearing stress, the fluidity at rest, and the fluidity at infinite shearing stress. It is also shown that values of the apparent fluidity are influenced by the time of shearing, the aging of the suspensions, and temperature effect attributed to the work of shearing.
The viscosity of suspensions of sized spheres at concentrations as great as 55 volume percent solids may be satisfactorily represented by either the relation of Mooney or of Maron, Madow, and Krieger; the identity of their relations is also shown. The constants for the equation relating viscosity and concentration are shown to be in satisfactory agreement with those predicted by Mooney. Constants for the viscosity-concentration equation are also given for several examples of experimental work selected from the literature; the form of equation proposed by Mooney relating viscosity and concentration is generally useful though the constants may not agree with the predicted values.
It has been found that the apparent fluidity of the glass bead suspensions decreases with an increase in particle diameter when the suspending fluid is zinc bromide in aqueous glycerol though the viscosity is independent of particle diameter when the suspending fluid is the nonaqueous mixture of ethylene tetrabromide and diethylene glycol.
The viscosity of a bimodal system of glass beads was shown to decrease very significantly as the bulk density was increased by packing progressively smaller spheres into the interstices of the larger spheres of the bimodal system, in qualitative agreement with a relation proposed by Mooney.
Electrical Conductivity of Highly Ionized Argon Produced by Shock Waves
Authors: Lin Shao-Chi , Resler E. L. , Kantrowitz Arthur 
Published: April 2005

Shock tube techniques for the production of shock waves up to Mach number 20 have been developed and reported previously by Resler, Lin, and Kantrowitz, J. Appl. Phys. 23, 1390 (1952). These techniques can produce high temperature gas with accurately known enthalpy (e.g., in argon 25 percent ionization has been produced following an incident shock). Spectroscopic studies of high temperature argon produced this way by Petscheck, Rose, Glick, Kane, and Kantrowitz, ``Spectroscopic studies of highly ionized argon produced by shock waves,'' J. Appl. Phys. 26, 83 (1955), showed that equilibrium ionization can be reached in the time available in these experiments (of the order of 100 microseconds). This paper reports a study of the electrical conductivity of high temperature argon produced by shock waves.
At low degrees of ionization (less than 10−3 for argon), the diffusivity of electrons and thus the gas conductivity is determined by the cross section for electron-atom collisions which has been measured by mobility and by scattering techniques. At high degrees of ionization (larger than 10−3 for argon) the diffusion of electrons is primarily limited by long range Coulomb interaction with positive ions and thus is independent of the chemical nature of the gas. Theoretical treatments of this case have been given by Chapman and Cowling, Cowling, and by Spitzer and Härm. At intermediate degrees of ionization additive effects of both of these resistivity mechanisms would be expected.
Preliminary measurements with electrodes indicated large surface resistances. These effects were avoided by the development of an electrodeless technique in which the moving ionized gas deflected a magnetic field. Resultant voltages induced in a search coil were related to the conductivity distribution in the gas following the shock wave. At temperatures greater than 8000–10 000°K (depending on the gas density) the gas conductivity quickly reached a maximum value (up to 80 mhos/cm). The maximum conductivity obtained at these high temperatures agreed within 10 percent with theoretical expectations. It also agreed well with measurement of electrical resistivity in the cesium discharge by F. L. Mohler, Bur. Standards J. Research 21, 873 (1938). At lower temperatures the oscillograms indicated that the conductivity was still rising at the end of the hot region. Under these conditions maximum conductivities reached were much lower than the theoretical values. The ionization rate obtained varied considerably with the gas density.
At the highest temperatures the conductivity declined quickly from the maximum value and the rate of decline could be correlated with the expected cooling due to recombination radiation. Indications of a high conductivity associated with luminous shock fronts were obtained.
Permanent-Magnet Properties of Elongated Single-Domain Iron Particles
Authors: Mendelsohn L. I. , Luborsky F. E. , Paine T. O. 
Published: April 2005

Previously described fine-particle magnets have been based upon crystal anisotropy; this paper reports permanent-magnet properties derived from the shape anisotropy of substantially elongated single-domain iron particles. The shape anisotropy of these particles overcomes the limitation imposed on the energy of previous fine-particle iron magnets by the low crystal anisotropy of iron.
The predicted and observed properties of crystal anisotropy fine-particle magnets are reviewed and compared with an ideal fine-particle iron magnet based upon the shape-anisotropy model of Stoner and Wohlfarth. Experimental results are reported for magnets made by aligning and compacting single-domain iron particles 150 angstrom units in diameter, with a median length-to-diameter ratio of three to one, and an intrinsic coercive force before packing of 1600 oersteds. The effect of particle alignment and packing fraction on magnetic properties is described, and energy products above three million gauss-oersteds are reported. These results are compared with properties predicted from theoretical considerations, and with existing permanent-magnet materials.
Temperature Dependent Creep in Zinc Crystals
Authors: Thompson Donald O. 
Published: April 2005

Tensile creep measurements beginning in a tensile strain region of about 10−6 have been made upon a set of seven single crystals of zinc of 99.99+ percent purity. Measurements were made both by means of electrical resistance strain gauges and an optical lever system. Some of the measurements made in the latter apparatus lasted 100 hours or more, and in both systems, measurements were made at several temperatures.
The creep results obtained in this work can be best described by the single empirical relation η=btmin which η is the shear strain, t is the time after completion of the application of stress to the crystal, and b and m are constants for a given creep test under given experimental conditions. It is found that b increases with the stress but does not vary greatly with temperature. The values of m are practically independent of stress but vary with temperature, and appear to fit best the equation, m=m0exp(−T0/T)in the temperature interval investigated. For these crystals T0 = 1580°K, m0=120, and the temperature at which m=1 is 58°C. Values of m&gt;1 are interesting in dislocation theory.
Surface Matching of Dielectric Lenses
Authors: Jones E. M. T. , Cohn S. B. 
Published: April 2005

Two methods of cancelling the surface reflections of dielectric lenses are described in this paper. The first utilizes a simulated quarter-wave matching layer, and the second a reactive wall embedded within the dielectric. The reactive wall may take a variety of physical forms, such as arrays of thin conducting disks which have a capacitive reactance, or arrays of thin wires which have an inductive reactance. Surface matching is obtained when the disks are placed approximately ⅜ wavelength inside the lens, or the wires ⅛ wavelength. Curves are presented that show how the reflections at the air and dielectric boundary are reduced for various angles of incidence and polarization when quarter-wave layer and reactive-wall matching are employed.
The reactance of the array of disks for waves incident at various angles and polarizations is computed by means of Bethe's small aperture theory, and Babinet's principle. Measurements in wave guide of the reactance of an array of circular disks for various angles of incidence and for both E- and H-plane polarization show close agreement with the theory.