bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple Way to Obtain the Velocity Distribution of the Electrons in Gas Discharge Plasmas from Probe Curves
Authors: Medicus G. 
Published: April 2005

Until now no simple technique of determining the velocity- or energy-distribution function of the electrons in gas discharge plasmas was known. Here a method of quickly finding this function from probe curves (preferably automatically plotted ones) is described.
It is shown that for a given probe current-voltage curve J(U) the energy distribution function g(U) of the electrons is proportional to a simple function which may be graphically determined from J(U). This function is U−½ΔJ0/ΔU, where ΔJ0 is the distance between the intersections of the two tangents to the probe curve J(U) at the ends of the voltage interval ΔU with the current axis, and U is the (retarding) voltage in the middle of ΔU. It can be used for a determination of the energy distribution g(U) in a simple and straightforward one-step procedure which is faster and in practice more accurate than the two-step procedure previously used for finding g(U) by means of ∂2J/∂U2.
A set of probe curves which stem from a Maxwellian distribution is evaluated in both the conventional and the new way. The electron temperatures obtained check excellently. A set of probe curves from strongly non-Maxwellian distributions in a Ne fireball discharge is evaluated. The presence of a fast and a slow group of electrons is revealed. The results are interpreted to some extent. Errors and dependability are discussed.
Electromagnetic Transmission Characteristics of a Lattice of Infinitely Long Conducting Cylinders
Authors: Kaprielian Zohrab A. 
Published: April 2005

This investigation is primarily concerned with the study of electromagnetic transmission characteristics of a lattice of infinitely long conducting cylinders. Four approaches to the general problem have been employed and the advantages, disadvantages, and realms of validity of each have been studied. Several of these methods constitute a substantial improvement over previous analyses and are supported by wave-guide and free-space experimental work.
The four approaches are: (1) A molecular analogy with a consideration of dipole interactions leading to the Clausius-Mosotti relations, (2) A transmission line formulation which considers the thick obstacle for both polarizations, (3) An analysis based on the summation of scattered fields which demonstrates that the Clausius-Mosotti relations are a special case of a more general relation which accounts for the effects of higher order multipoles, and (4) A solution formally valid for all values of spacing and cylinder radius based on integral equation formulation of variational principle.
Reflectionless Transmission through Dielectrics and Scattering Potentials
Authors: Kay I. , Moses H. E. 
Published: April 2005

A complete solution is given for the problem of constructing a plane stratified dielectric medium having that the property that at a fixed frequency and polarization a plane wave at any angle of incidence will be transmitted without reflection by the medium. This problem can also be interpreted quantum-mechanically. The dielectric medium of the first interpretation becomes, in the second interpretation, a potential for the one-dimensional Schrödinger equation such that a particle which is sent in from - ∞ is transmitted with probability one of getting through to + ∞, no matter what the initial kinetic energy of the particle may be.
In addition, the results can be applied to the problem of finding perfectly matched nonuniform transmission lines.
Focusing of Low-Energy Electron Beams
Authors: Clarke W. W. H. , Jacob L. 
Published: April 2005

Conventional electrostatic and magnetic lenses were used to focus electron beams in the range of energies 30–70 v, produced by a specially designed experimental tube. The electron distribution in the focused beam was resolved by a series of concentric end collectors and a convention introduced to assess effective beam widths.
With near-symmetrical lenses of the electrostatic type and for energies above 30 v, the beam, if inside the aberration limits of the lens, appears to be acted on as a whole by the field and a definite focus is obtained; for 30-v beams, on the other hand, there is no unique focus since maximum and minimum values of effective beam width were recorded as the focus voltage was varied. Such a periodic variation might arise from the existence of standing wave patterns in the space charge in front of the cathode.
A characteristic feature of the focusing which is most marked in the magnetic case is the disappearance on focus of the Gaussian core of the incident beam distribution. With magnetic lenses having apertures in the ratio 2/1, it was remarkable to find that the smaller aperture lens was the most efficient in bringing beams to a focus. In general, the power of magnetic lenses had to be greatly increased (in the measurements, by a factor of 30) over any expected thin lens performance to achieve a focus. Space charge forces, nonhomocentricity, and potential depression are held to be responsible for the abnormal conditions of focus.
Physical Theory for Capillary Flow Phenomena
Authors: Miller E. E. , Miller R. D. 
Published: April 2005

From the assumption that the microscopic behavior of the liquid in an unsaturated porous medium is controlled by the physical laws of surface tension and viscous flow, differential equations governing the macroscopic flow in such a medium are deduced. No special pore-shape assumptions are required, but one topological approximation is needed; i.e., that neither isolated drops nor isolated bubbles occur. Several nonessential simplifying assumptions are used; i.e., that the macroscopic properties of the medium, the character of the liquid, and the pressure of the gas are independent of position, time, and direction. The macroscopic equations are obtained in a fully reduced form, permitting comparison between two media— or between two flow systems—that differ only by scaling factors.
A novel feature of this calculation is its prediction that the liquid-transmission and liquid-capacity properties of an unsaturated medium will exhibit hysteresis in their dependences upon the liquid-gas pressure differential, p. The properties of the medium depend upon the pressure history but are invariant to monotonic time-scale distortions of that history. Such time-invariant functionals have been termed by the authors ``hysteresis functions,'' symbolized by the subscript, H, e.g. FH(p). Although methods for measuring and describing the characteristics of specific ``hysteresis functions'' have not yet been developed, the general validity of this analysis can be studied experimentally by testing predictions that are contained in the reduced variables.
Strain-Amplitude Dependent Internal Friction Studies of Dilute Alloys of Copper
Authors: Weinig S. , Machlin E. S. 
Published: April 2005

This paper presents an investigation of the room temperature decrement in dilute polycrystalline alloys of copper as a function of strain amplitude and annealing at a frequency of about 1 cps. The characteristics of the internal friction measured are:
(1) The internal friction and strain amplitude dependence of the internal friction decreases with increasing solute content.
(2) The internal friction is reversibly dependent upon the preanneal temperature.
(3) The internal friction is hysteretic with strain amplitude.
From the effect of the solute concentration and annealing temperature on the decrement, values for the binding energy for Al and Si solute atoms to dislocations in copper were calculated. These values are compared to theoretical values calculated on the basis of strain and electrical interaction energies. The experimental binding energy is in good enough agreement with the theoretical values to conclude that the onset of a strain amplitude dependence of the internal friction is caused by the freeing of sufficient dislocations from their pinning solute atoms.
Adhesion and Contact Error in Length Metrology
Authors: Bruce C. F. , Thornton B. S. 
Published: April 2005

An account is given of experimental studies of the nature of the strong adhesive contact between finely finished steel and glass surfaces when a trace of liquid exists between them. These surfaces are of the kind that are of practical use in length metrology where this adhesive action or ``wringing'' is of considerable importance.
The dimensional effects of the thin film between the surfaces have been measured by multiple-beam interferometry and the nature of the adhesive contact has been further studied by measuring tangential forces and electrical characteristics.
The experimental evidence suggests that there is no liquid film effectively separating the surfaces but that the strong adhesive action induced by the presence of the liquid introduces a dimensional contact error. This error is likely to be positive or negative, depending on the degree of contact between the surfaces. Provided the adhesion is good the contact error is not greater than ±0.01μ. Where such an error is undesirable in high precision length metrology it is better to avoid the use of this adhesive contact.
Controlled Field Emission in Hexane
Authors: Green W. B. 
Published: April 2005

The current-voltage relationship for dielectric liquids consists of two portions, usually in superposition: at lower voltages a current of ions flows; at higher voltages, field emission sets in. The field-emission current depends on the material of the cathode, but not simply on its work function. The current may be altered by changing the thickness of the cathode surface layer or the gas adsorbed upon the surface. When the ion content of the liquid is raised, not only the ionic current, but also the field-emission portion of the current increases.
Controlled field-emission currents have been produced.
Detailed Structure of Copolymers from Dielectric Measurements
Authors: Work Richard N. , Tréhu Yves M. 
Published: April 2005

The effective dipole moment of each polar group in polar-polar or polar-nonpolar copolymers is expressed in terms of the moment of an equivalent isolated polar group and the average of the vector sum of the moments of all of the polar groups surrounding it. If effects of short-range forces leading to angular correlations of dipole pairs are neglected except for interactions between nearest neighbors along the chain, an expression for the average of the effective moments of the two types of polar groups present can be written as a function of the composition of the copolymer in the form 〈μ2〉Av=x1(μ12)eff+(1−x1)(μ22)eff=L+Mx1+Nx1P11(x1). Here, x1 is the mole fraction of one of the monomers in the copolymer, (μ12)eff and (μ22)eff are the squares of the effective moments of the two polar groups. L, M, and N are constants involving the dipole-moments of the equivalent isolated groups and the average cosines of the angles between nearest-neighboring dipole pairs of types 1 − 1, 1 − 2, and 2 − 2. The quantity P11(x1) is the probability of a monomer of type 1 adding to a free radical of its own kind at the end of a growing chain in the polymerization mixture. It can be calculated from r1 and r2, the reactivity ratios of the two monomers, and the composition of the monomer feed mixture. Interactions extending farther along the chain than nearest neighbors introduce terms in higher powers of P11(x1).
Onsager's equation for the dipole moments of molecules in mixtures of polar liquids has been modified to express the average of the effective moments of the polar groups present in terms of the dipolar contribution to the dielectric constant, εs−ε∞. Using this equation, values of 〈μ2〉Av have been calculated from measurements of εs−ε∞ for several copolymers of poly-(p-chlorostyrenestyrene) representing the whole range of copolymer composition. Measurements were made on bulk copolymers at temperatures above the glass-transition temperature. A curve of the form L+Mx1+Nx1P11(x) has been fit within experimental error to the calculated values of 〈μ2〉Av over the whole range of copolymer composition. This indicates that within the limits of error of this work only nearest-neighbors on the polymer chain contribute to the effective moments of the polar groups. The average cosines have been calculated for the angles between each of the three kinds of dipole pairs in the copolymer.
Positronium Formation in Gases
Authors: Hughes Vernon W. 
Published: April 2005

The formation of positronium in gases can be investigated by observing the energy spectrum of the annihilation radiation. The increase in positronium formation due to a static electric field has been measured in various gases. For the rare gases the increase has a sigmoid dependence on the ratio of electric field to pressure. The fraction of the positrons that form positronium increases by a maximum factor of 1.5, 1.4, and 2.1 for He, Ne, and A, respectively. A similar increase was observed for H2, D2, and N2. No effect of the electric field was found in the polyatomic gases CO2, CH4, C2H6, and CCl2F2, but a small anomalous decrease in positronium formation was seen in SF6.
The increase in positronium formation occurs in the presence of an electric field because low energy positrons, which die by direct annihilation with atomic electrons without positronium formation in the absence of an electric field, can gain energy from the electric field to cross the threshold energy for positronium formation in the gas. A theory based on the Boltzmann equation describes the behavior of the positrons under the combined influence of the electric field and molecular collisions, and provides the basis for obtaining from the observed data values of the elastic scattering cross section of positrons by the rare gas atoms. The cross sections are 0.023πa02, 0.12πa02, and 1.5πa02±25% for He, Ne, and A, respectively. Quantitative interpretation for the polyatomic gases is more difficult.
An optical search for the 2430 A Lyman line from positronium is described.
Effect of Structural Defects in Germanium on the Diffusion and Acceptor Behavior of Copper
Authors: Fuller C. S. , Ditzenberger J. A. 
Published: April 2005

The effect of dislocations in Ge upon the diffusion of Cu has been studied using Ge crystals having different etch-pit counts as well as on Ge specimens bent on a (112) axis. The percentage of the total Cu introduced in a given time which attains the acceptor state was measured by comparing conductivity to radioactivity determinations employing Cu64. In addition, the detailed diffusion processes have been studied as a function of time and etch-pit density by means of autoradiographs taken both parallel and perpendicular to the direction of diffusion and also by delineation of p-n boundaries.
The two most important findings are: (1) the slow attainment of acceptor equilibrium especially in Ge having low concentrations of dislocations and (2) the identification of dislocations as the initial loci of acceptor copper in Ge.
The results call for a revision of our ideas on the mechanism of diffusion of Cu. The view is advanced that Cu atoms enter Ge interstitially at a high rate (&gt;10−4 cm2/sec), but that their flow and ultimate concentration is limited by the effective rate of generation and equilibrium concentration of vacancies chiefly at dislocations.
Mechanical Behavior of Plastics
Authors: Gruntfest I. J. , Young E. M. , Kooch Walter 
Published: April 2005

The applicability of Nutting's equation of the mechanical behavior of some soft plasticized polyvinyl chloride preparations noted by Dyson in creep experiments is further demonstrated by force-length measurements at constant rate of strain. This suggests new criteria for the characterization of soft plasticized PVC. For example, in a stretching experiment in which the sample is subjected to a strain (L−1) which increases linearly with time (t) at the rate (R), definition of ``modulus'' as the limit at small strains of the ratio of the force (F) to the strain is clearly inappropriate. That is, when L−1=GFmtn,lim lim L−1→0(FL−1)=(L−1)(1−n−m)/mRn/mG−1/m,which may be zero or infinite and also depends on the strain rate.
Some even more general force-length-time relationships for plastic are discussed which have been found useful for predicting the conditions of tensile failure. More complicated relationships of particular interest provide for the possibility of force-time superposition of creep curves. Published creep data are considered from this point of view.
Equipartition of Energy and Local Isotropy in Turbulent Flows
Authors: Uberoi Mahinder S. 
Published: April 2005

Homogeneous turbulence in which 〈v2〉 = 〈w2〉 ≠ 〈u2〉 was produced experimentally, where 〈u2〉, 〈v2〉, and 〈w2〉 are the mean-square turbulent velocities in x, y, and z direction, respectively. The decay of turbulence and the energy transfer between 〈u2〉 and (〈v2〉+〈w2〉) were measured, and it was found that the larger components (〈v2〉 and 〈w2〉) are losing more energy due to viscosity than by transfer to the smaller component (〈u2〉). However, 〈u2〉 is receiving enough energy by transfer to compensate for its decay and is in fact slowly increasing. The measurement of mean-square vorticity components shows that the turbulence is becoming locally isotropic at a faster rate than the equipartition of energy is taking place.
In another set of experiments it was found that when approximately isotropic turbulence is subjected to deformation, the three components of turbulent energy become widely different in magnitude and that the turbulence is not locally isotropic. This indicates that even at high Reynolds number the deformation in a shear flow may cause anisotropy. The data on the turbulent shear flow near a solid wall confirm this conjecture.
The connection of this investigation to turbulent flows in general is discussed. In particular, it follows that neither the turbulent energy nor the small-scale structure of turbulence rapidly settles down statistically to quasi-equilibrium.
Viscosity of Suspensions of Uniform Spheres
Authors: Happel John 
Published: April 2005

A mathematical development of the viscosity of suspensions is presented based on the steady-state Stokes-Navier equations of motion omitting inertia terms. The disturbance due to each sphere is assumed to be confined to a frictionless envelope surrounding it similar to the stream tube for flow inside ducts.
The relationship obtained between relative viscosity and solids concentration is in good agreement with existing data over a wide concentration range without the necessity of introducing empirical constants. It is thus thought that it may be a suitable model for further theoretical study as well as furnishing a basis for empirical correlation equations of rheological properties. In very dilute systems it does not agree with the well-known Einstein formula, and possible reasons for this variation are advanced.
Structure in Magnetically Confined Electron Beams
Authors: Webster H. F. 
Published: April 2005

A number of observations have been made of structure changes that occur in hollow and solid electron beams which are confined by a magnetic field. These structure changes occur in both the density of the beam and the transverse velocity components of the beam electrons. The velocity components have been measured by use of a pinhole camera.
Some of the results obtained are as follows. The density of electron paths in a beam may become non-uniform if there is a spread in the forward component of velocity of the electrons. This may occur either because of a spread in initial angle of the electrons or because of a potential depression in the beam.
In addition, changes in beam shape and transverse velocity components of the beam electrons can occur as a result of drifting of electrons in crossed electric and magnetic fields, the electric fields in this case being provided by the space charge of the electrons themselves. Thin beams have been found to be unstable and it has been observed that they divide into an array of vortex-like current filaments when the beam current is sufficiently high. A possible connection between this occurrence and phenomena in the aurora is suggested.
Application of the Mass Spectrometer to the Study of the Upper Energy States of Molecules
Authors: Morrison J. D. 
Published: April 2005

It is claimed that the poor agreement often found between the energy quantities measured by mass spectrometry, and those obtained by other methods, is due in large part to the interpretation of the experimental data. The conditions necessary for accurate measurement are summarized.
It is shown that by making certain assumptions about the probability of ionization for different processes, ionization efficiency curves can be interpreted to give the probabilities for electronic transitions from the ground state to the various ionic states of molecules. From these electronic transition probabilities, information can be deduced about the potential energy functions for these upper states.
To exploit the method fully, beams of ionizing particles with low spreads in energy are necessary. Electron and photon impact are compared, and it is shown that the latter possesses many advantages.
Measurements of the Effective Resonance Integral in Uranium Metal and Oxide in Different Geometries
Authors: Hellstrand Eric 
Published: April 2005

A series of measurements of the effective resonance integral in uranium metal and oxide, UO2, has been made. Measurements were performed on simple rods, on a few tubes, empty or filled with a moderator, and on clusters of rods. Formulas for the effective resonance integral as a function of S/M and (S/M)½ are given for metal and UO2.
In addition the variation of the resonance absorption of neutrons as a function of depth in metal rods has been studied. The results are given in the form of curves.
Combustion and Detonation in Gases
Authors: Greifer B. , Cooper J. C. , Gibson F. C. , Mason C. M. 
Published: April 2005

A photographic investigation of combustion in gases was undertaken to observe experimentally the mechanism of initiation and structure of detonation waves. Streak schlieren photographs of hydrogen-oxygen and carbon monoxide-oxygen explosions were made in a rectangular shock tube using precision optics and a rotating mirror camera.
The photographs show that compression waves generated during the early stages of propagation of the explosion soon steepen into a shock wave which travels ahead of the combustion wave (zone of chemical reaction). This combination of shock and combustion wave is characteristic of a nonsteady detonation state in the moments before stable detonation is initiated. The distance between the two waves narrows as the explosion progresses down the tube due to the continued formation of new combustion centers ahead of the combustion wave by means of auto-ignitions. Eventually the combustion wave overtakes the shock wave and supplies it directly with energy from the chemical reaction; at this moment stable detonation is initiated.
The internal structure of steady state detonations is found to be different from nonsteady state detonations; for example, whereas the distance between the shock and the zone of chemical reaction is of the order of several centimeters in the nonsteady state detonation, this distance in the steady state detonation is too small to be resolved by the optical system (i.e., less than 1 mm). Other structural features such as spinning detonation and a high-frequency oscillation of propagation velocity are also illustrated.