bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering of Plane Waves by Soft Obstacles. II. Scattering by Cylinders, Spheroids, and Disks
Authors: Montroll Elliott W. , Hart Robert W.
Published: April 2005

Approximate closed form analytical expressions are derived for the total and differential scattering cross sections of cylindrical, prolate spheroidal, and disk-shaped scatterers which subject scalar plane waves to only a small phase shift.

When a plane wave excites a sphere or infinite cylinder, the internal field of these objects can be expressed as an infinite series of bessel functions. By making an approximation in coefficient of the nth bessel function which is valid for either 2πa/λ0»n (a = sphere or cylinder radius, λ0 = wavelength of incident plane wave) or |m−1| «1 (m = λ0/λ1, λ1 = wavelength of plane wave in medium composed of material of scatterer), it is possible to obtain a closed form expression for the series. The scattered field is obtained by integrating over these internal fields.

The scattered fields for long but finite cylinders and prolate spheroids are calculated by approximating their internal fields by those of infinite cylinders of the same radius. The scattered fields of thin disks are obtained by assuming the internal fields to be that of an infinite flat plate of the same thickness.
The Susceptance of a Thin Iris in Circular Wave Guide with the TM01 Mode Incident
Authors: Dunning Kenneth L. , Fellers Rufus G.
Published: April 2005

Certain wave-guide boundary value problems can be formulated in terms of lumped-constant circuits and distributed-constant transmission lines. Equivalent circuit voltages and currents can be introduced as measures of the transverse electric and magnetic fields. Making use of these concepts and Schwinger's integral equation method, the susceptance of a thin circular iris in circular cylindrical wave guide with the TM01 mode incident is discussed and calculated. Results are compared with experimental data.
The Transit Time Effect in a Cylindrical Diode
Authors: Woo Way Dong
Published: April 2005

The impedance offered to a small superposed alternating current by a space-charge limited cylindrical diode is expressed in terms of the variational plate conductance, the transit time angle, and a group of constants which are functions of the ratio of the plate to cathode radii. The result covers the range of transit-time angle up to π-radian and of the ratio of the plate to cathode radii from unity up to 100.
The Application of Nutting's Equation to the Viscoelastic Behavior of Certain Polymeric Systems
Authors: Buchdahl Rolf , Nielsen Lawrence E.
Published: April 2005

The Nutting equation ε=ψ×σβ×tn, where ε=strain, σ=stress, t=time, and ψ, β, and n are material constants, is applicable to a large number of polymeric systems, such as plasticized polyvinyl chloride, styrene-butadiene copolymers, polystyrene. It has been shown that the material constant n is closely related to the damping coefficient as obtained from dynamic mechanical measurements The temperature dependence of n and δ (damping coefficient) are about the same; and, in some cases, there exists a simple quantitative relationship between the two constants. A mathematical derivation of the relationship between n and δ is given and a physical interpretation of the dimensional changes in the Nutting equation, in terms of complex moduli, is presented. Furthermore, it is shown that, in the case of styrene-butadiene copolymer, n varies with the differences in gel content and gel structure.
Formation of Annealing Twins During Grain Growth
Authors: Fullman R. L. , Fisher J. C.
Published: April 2005

It is proposed that annealing twins form during grain growth as a result of a decrease in the interfacial free energy of grain boundaries that would not be achieved in the absence of twinning. Experiments designed to permit detection of the changes in grain boundary free energy accompanying the formation of twins give results in agreement with this concept. The abundance of twins found in annealed copper depends on the texture in a manner that is consistent with the theory.
The Crystallographic Aspect of Slip in Body-Centered Cubic Single Crystals. I. Theoretical Considerations
Authors: Opinsky A. J. , Smoluchowski R.
Published: April 2005

The mechanism of slip in body-centered cubic lattices is considered in terms of the relation between the orientation of the tensile axis and the active slip system. A ``projection'' of points in the unit stereographic triangle on its [001]–[011] side permits an analysis of experimental data and leads to an accurate determination of the ratio of the critical shear stresses on various planes.
Studies in Nonlinear Vibration Theory
Authors: Fifer Stanley
Published: April 2005

In his paper, the author determines the stability of periodic solutions of (1) the general forced Duffing equation without damping, x¨+x+εf(x)=εE cosωt, f(x) a polynomial, ε≪1; (2) the forced Duffing equation with damping, x¨+εrẋ+αx+εx3=εE cos(ωt+ψ), ε≪1; and (3) the general forced Van der Pol equation, x¨−εf(ẋ)+x=εE cos(ωt+ψ), f(ẋ) an odd polynomial, ε≪1, by seeking conditions necessary to insure periodic or almost-periodic solutions of the corresponding variational equation. The former are obtained rigorously by means of an existence proof and the latter formally by perturbation series. A vertical tangent theorem is derived which states that the locus of the points of contact of the vertical tangents to the response curves is a stability boundary, since it coincides, in the first approximation, with the locus of periodic solutions of the variational equation. These techniques are illustrated by considering the forced vibrations of a triode oscillator with a fifth-order tube characteristic, this being a particular case of (3), where we set f(ẋ)=ẋ−13ẋ3+λẋ5.
A Critical Study of the Circuit Concept
Authors: Chaney Jesse Gerald
Published: April 2005

From Maxwell's equations, an expression for the complex power associated with a wire circuit is formulated and broken into a complex input power and a complex power into the external fields associated with the circuit, the latter including the radiated power. From these powers, the internal and external impedances of the circuit are obtained such that the current is not required to be everywhere in time phase within the circuit. This concept is extended to coupled circuits, bringing out some of the relations between some conventional methods for obtaining the driving point impedance of antenna arrays. The theory does not require the current distributions to be postulated, but in practical applications such a postulate becomes necessary unless the solution is obtained by a method such as the integral equation method. The resulting circuitry may readily be reduced to that for lumped elements. A more critical study of the impedance formulas is given in the appendix, based upon the reciprocity theorem which is derived therein.
Free Convection Heat Transfer from Electrically Heated Wires
Authors: Farber Erich A.
Published: April 2005

In this paper the author discusses the heat transfer by free convection from electrically heated wires (copper and iron) to distilled water between freezing and boiling, to water boiling at atmospheric conditions and to air at room temperature. The wire surface temperatures needed for the heat transfer determination are calculated from the theoretical temperature distribution in the wire. The experimental results show maximum heat transfer rates of about 2,200,000 Btu/hr, ft2 near freezing and 450,000 Btu/hr, ft2 near boiling. For boiling water, as the temperature difference between the wire surface and water is increased, the heat transfer coefficient first increases reaching a maximum, then decreases reaching a minimum and increases again (because of radiation) until the wire fails by melting. For copper the maximum film coefficient of 9100 Btu/hr, ft2, °F is observed at 49 degrees temperature difference and the minimum of 136 Btu/hr, ft2, °F at a temperature difference of 690 degrees F. Corresponding values for iron are 12,300 Btu/hr, ft2, °F at a 33 degree temperature difference and 142 Btu/hr, ft2, °F at a 620 degree difference. When air at room temperature surrounds the wire the heat transfer coefficient for copper with an oxide film varies from 0 to 30 and for iron from 0 to 26 Btu/hr, ft2, °F as the surface temperature of the wires is raised until failure occurs.
A Finite Difference Treatment of a Helium Cryostat Design Problem
Authors: Henry Warren E.
Published: April 2005

A mathematical expression is derived for computing dimensions of a liquid helium cryostat of specified performance characteristics. Use is made of a finite difference summation scheme applied to a simple thermomechanical model, using T as the independent variable, for a liquid evaporating in a container with good exchange to the walls. The scheme thus takes into account the heat capacity of the gas between the boiling point and the upper cryostat temperature. The results obtained are compatible with the actual performance of cryostats in operation.
General Theory of Electromagnetic Horns
Authors: Stevenson A. F.
Published: April 2005

Exact equations for the propagation of electromagnetic waves in a perfectly conducting horn of arbitrary shape are given. They take the form of an infinite set of simultaneous ordinary linear differential equations, and can be interpreted as the equations of propagation of a system of coupled E- and H-waves. If the coupling is neglected, we need only consider a single differential equation for each E- and H-wave, which can be solved approximately by the W.K.B. method. This approximate solution brings out the distinction between ``transmission regions'' and ``attenuation regions'' of the horn, as found by Barrow and Chu for the sectoral horn.

It is shown that the error due to neglect of coupling is, in general, of the order of the square of the flare angle as far as the variation of the field along the horn is concerned, but is of the first order in the flare angle as regards the variation of the field over the cross section. The coupling cannot, however, be neglected between modes of propagation which have the same cut-off frequency for all cross sections. The propagation characteristics of several special shapes of horn are discussed in detail.
Atomic Size Effect in the X-Ray Scattering by Alloys
Authors: Warren B. E. , Averbach B. L. , Roberts B. W.
Published: April 2005

In a random solid solution, if the two atoms have appreciably different sizes, the nearest-neighbor distances and to a lesser extent the higher neighbor distances will be of three kinds, γAA, γAB, and γBB. The effect produces modulations in the diffuse intensity similar to those produced by short-range order. The size effect is important when the difference in scattering power is large, the difference in size is large, and the short-range order is small. The size effect is illustrated by a single crystal pattern of Cu3Au and a powder pattern of Ni3Au2. An asymmetry in the wings about a fundamental reflection is a result of the size effect.
An Objective for Use in the Electron Microscopy of Ultra-Thin Sections
Authors: Hillier James
Published: April 2005

An objective has been designed which is particularly suitable for the study of tissue sections. It consists of a large opening polepiece system operated at a focal length of 12 mm. It includes a diaphragm which can be centered (not during operation) and translated on the axis. Angular apertures of as low as 2×10−3 radian with large areas of bright field can be achieved. A simple method of aligning the aperture is described.
The Leaky-Condenser Oxide Cathode Interface
Authors: Eisenstein A.
Published: April 2005

The time dependence of current passed by commercial pentodes has been studied under pulsed conditions of operation. A decay of current is observed in the microsecond time range for those tubes operated for long periods under cut-off conditions. This decay has been interpreted in terms of the resistance and capacitance of the interface layer known to exist from x-ray diffraction studies. Techniques are developed and applied to the measurement of this interface resistance and capacitance as a function of temperature. Following the initial current decay, a partial recovery is observed when long pulses are used. This effect results from Joule heating of the interface layer.
Dry Metallic Friction as a Function of Temperature Between 4.2°K and 600°K
Authors: Šimon I. , McMahon H. O. , Bowen R. J.
Published: April 2005

Coefficients of static friction of six metals (Fe, Ni, Cu, Pb, Sn, and Zn) have been measured at temperatures ranging from liquid helium up to room conditions (and in two cases above this). Shear strengths and hardnesses of these metals were measured over the same range of temperatures. It was found that in spite of the generally large variation of both of these latter quantities with temperature, their ratio is in most cases dependent, to only a slight extent, on temperature, following rather closely the change of the static-friction coefficient with temperature. This fact tends to substantiate the adhesion theory of friction proposed by F. P. Bowden.
Deceleration and Ionizing Efficiency of Radar Meteors
Authors: McKinley D. W. R.
Published: April 2005

Improved instrumentation of the radar system has permitted a more accurate analysis of range-time records of meteor echoes and enabled the meteor deceleration to be determined in a few special cases. Three illustrative examples are described in which the measured mean decelerations were −0.48, −1.1, and −1.5 km sec−2. Velocity data from a continuous wave Doppler system were also available for these meteors and are compared with the radar data.

Using existing atmospheric density values and Lovell's scattering formula, it is computed that the ionizing efficiency, or the fraction of the kinetic energy of the meteor converted to ionization, is 10−6 for a 60-km/sec meteor and 10−8 for a 20-km/sec meteor. If lower values of the air density are adopted, the efficiency figures are increased and at the same time the gap is narrowed between the rates of electron production deduced from loss of mass considerations and the rates calculated from the radar data. More statistical data on radar meteors and further information on the ionizing properties of 1000 electron-volt atoms are required before definite conclusions can be drawn.
Electron Optical Exploration of Space Charge in a Cut-Off Magnetron
Authors: Reverdin D. L.
Published: April 2005

The main effort in the work described has been directed towards the measurement of the electric field distribution in a cut-off magnetron, based on the electron optical shadow method. The space charge distribution can be determined qualitatively from the measured electric field distribution. The first objective is the development of a convenient method for such a study. In this work an elementary magnetron was investigated by sending an electron beam axially through the tube.

The conclusions of the study are that the space charge distribution does not conform to Hull's classical theory (which predicts that the space charge density is approximately constant out to a well-defined radius and zero beyond this cloud radius). Three different space charge distributions have been observed. One distribution has a sharp maximum near the cloud radius. Another falls off gradually toward the cathode; a third is time-variant. The shape of the space charge distribution is closely related to the symmetry of the magnetron.
A Theory of the Envelope Type of Thermal Conductivity Tests
Authors: Loeb Arthur L.
Published: April 2005

The well-known problem of the end effects in a cylinder of finite length has been circumvented by the use of spheroidal rather than cylindrical apparatus. After a general theory of heat flow is given, applications demonstrate the mathematical difficulties caused by discontinuities in the curvature of the surface of the heat conductor. The suitability of the spheroidal shape is demonstrated, and corresponding heat flow equations are derived demonstrating the effects of the variable distance between any two isotherms on the amount of heat crossing any unit area of an isotherm. It is proven that the amount of heat flowing through a slice of a spheroidal isotherm made perpendicular to the axis of the spheroid is proportional to the width of the slice, and independent of the position of the slice with respect to the spheroid. This theorem is applied to find the heat distribution necessary to keep the core of the apparatus at uniform temperature. Because all measurements are made at thermal equilibrium, a rough estimate is given for the time necessary to reach equilibrium.
Phase Equilibria in an Ordering Alloy System
Authors: Newkirk J. B. , Smoluchowski R. , Geisler A. H. , Martin D. L.
Published: April 2005

The equilibria between phases in platinum alloys containing 42, 48, and 54 atomic percent cobalt were determined at temperatures below 1000°C. This system of alloys exhibits an order-disorder transition analogous to that for CuAu. A temperature range in which ordered and disordered phases coexist in equilibrium was determined for each alloy. These data were incorporated in the phase diagram. The Co-Pt system is the first ordering alloy system in which it has been shown that this reaction is a true phase transformation contrary to the prevalent concepts of the phenomena.
A Correlating Modulus for Fluid Resistance in Accelerated Motion
Authors: Iversen H. W. , Balent R.
Published: April 2005

The resistance to accelerating movement of objects in a fluid is normally evaluated with a mass term in the equation of motion that is greater than the actual mass of the object by an added mass described as a constant times the displaced mass of fluid. This added mass has been evaluated by numerous investigators for different body shapes from potential flow considerations. Published experimental results, mostly with oscillating systems with small amplitudes of motion, show an added mass constant that is higher than that derived from potential flow with values that are dependent upon the fluid and the object size. A few previous experiments on resistance in unidirectional accelerated motion indicate that the added mass is variable and depends upon the state of motion.

The present investigation includes a development from model law considerations that results in a resistance equation of the form F=C12ρV2S. This is identical with the normal resistance equation for steady state except for the coefficient C which, in addition to being a function of Reynolds' modulus, Froude's modulus, and the geometry, is also a function of a modulus, AL/V2, where A is the acceleration, L is a characteristic length, and V is the velocity.

Experiments with circular disks moving perpendicular to the plane of the disk under the action of approximate constant driving forces show this resistance coefficient to be correlated by the modulus AL/V2.
Cut-Off Frequency in Two-Dielectric Layered Rectangular Wave Guides
Authors: Van Bladel J. , Higgins Thomas J.
Published: April 2005

Equations for the modes and eigenvalues of two-dielectric layered rectangular wave guides with cross sections as in Fig. 1(a), (b), and (c) are derived. From these equations are plotted graphs of cut-off frequency over a range of geometric and dielectric parameters sufficiently wide to cover most requirements of design.
On the Scattering of Plane Waves by Soft Obstacles. I. Spherical Obstacles
Authors: Hart Robert W. , Montroll Elliott W.
Published: April 2005

An approximate theory is developed for the scattering of plane waves by spherical obstacles with the property m = λ0/λ1<1.5, where λ1 and λ0 are, respectively, the wavelengths of a plane wave in the scattering material and in the surrounding medium. In the exact theory the scattered field is found to be an infinite series of legendre polynomials whose coefficients are complicated combinations of Bessel functions. By making an approximation in the nth coefficient that is valid when either |m-1|«1 or 2πa/λ0»n (a = sphere diameter) it is possible to sum the series and obtain analytical closed form expressions for the total scattering cross section of the sphere and the intensity of the scattered wave as a function of angle. These approximate expressions are compared in the optical case with the results obtained numerically by the Bureau of Standards Computing Laboratory. As an example of their accuracy and range, it is found that when m<1.1 the relative error in the approximate total scattering cross section is less than 5 percent for scatterers of any size; when 1.1<m<1.5, the relative error is less than 5 percent if 2πa(m-1)/λ0<6 and less than 25 percent for any size sphere.
Separation of Variables in Electromagnetic Theory
Authors: Spencer Domina Eberle
Published: April 2005

Separability conditions are obtained for the partial differential equations of electromagnetic theory. Wave guide and antenna problems are expressed in terms of the vector Helmholtz equation, and solutions are indicated by use of the simple method of separation of variables without recourse to Green's functions. It is shown that complete separation occurs only in rectangular coordinates, but that separation of the equation for one component of the vector field occurs in two coordinate systems. With cylindrical or rotational symmetry, separation is possible in eight coordinate systems.
Effect of Hydrostatic Pressure in an Electron Beam on the Operation of Traveling-Wave Devices
Authors: Parzen Philip , Goldstein Ladislas
Published: April 2005

Small velocity spreads in an electron beam appear to cause a decrease in gain and noise figure of a traveling-wave tube. The actual decrease depends on a quantity μ, which can be interpreted physically as a measure of the ratio of the coupling of the electrons to each other via the hydrostatic pressure to the coupling of the electrons to the external wave guide circuit. Thus, physically, the effect of the velocity spread is to introduce further interactions among the electrons, in which the external circuit does not take part. This interaction may be thought of as a hydrostatic pressure similar to that in a liquid or gas.
The Effect of a Grounded Slab on the Radiation from a Line Source
Authors: Tai C. T.
Published: April 2005

A theoretical investigation, based upon the method of fourier transforms, is made of the effect of a grounded dielectric slab on the radiation from a line source. It is shown that the principal part of the electric field above the dielectric slab can be found either by evaluating the resultant contour integral, using the saddle-point method of integration, or by evaluating the integral containing the tangential H-field along the interface. The radiation pattern of the principal field is found to be identical with the resultant field of a direct ray and a reflected ray that can be obtained by a simple consideration of geometrical optics. The condition of the existence of propagating modes in the dielectric slab has been discussed in detail. When the slab is thick enough to support a propagating mode, in addition to the space wave, a surface wave will appear in the neighborhood of the interface. The latter attenuates rapidly as the point of observation is moved away from the interface. The deformation of the path of integration corresponding to different angles of observation has been displayed graphically both in the original h-plane and the transformed τ-plane.
Directional Distribution of 1040-Kev Radiation from a High Voltage X-Ray Tube
Authors: Goldstein N. , Fano U. , Wyckoff H. O.
Published: April 2005

The distribution of the 1040-kev x-rays emitted in various directions by a high voltage x-ray tube has been measured by means of an indium resonance detector.
Lattice Distortion Spectrum of Evaporated Gold
Authors: Wilkinson P. G.
Published: April 2005

Gold was deposited in various pressures of nitrogen from 0.001μ to 110μ at low temperatures. The electrical resistance of the gold film was observed to decrease as it warmed, enabling the distribution of lattice distortions to be computed as a function of decay energy. The distortion spectrum from 70·10−14 to 130·10−14 erg was found to consist of three peaks—one at 80·10−14, one at 100·10−14, and one at 120·10−14 erg. The relative number of distortions for a particular decay energy was found to decrease as the nitrogen pressure increased. The final resistivities of the gold films were shown to be dependent on the film thickness over the range 40A to 420A in a manner which agreed with theory and gave a value of 970A for the mean free path of the conduction electrons.
The Oscillations of Magnetic Suspensions
Authors: Millsaps Knox , McPherson J. C.
Published: April 2005

The oscillations of a magnetic suspension between two equal poles are formulated in terms of a nonlinear ordinary differential equation of the second order that may be integrated in terms of elliptic integrals of the second kind. The case of unequal poles is treated by an analogous procedure involving a Legendre reduction. The further refinement of viscous damping is treated by numerical integration, and the relaxation times are found by exponential extrapolation.
Amplification of the Traveling Wave Tube
Authors: Friedman Bernard
Published: April 2005

A method is presented for solving the equation which determines the modes of a helix with an electron beam [Chu and Jackson, Proc. Inst. Radio Engrs. 36, 853 (1948)]. The essential idea is to consider the modes as a perturbation of the modes produced by the cold helix. From the solution of the equation, the dependence of the amplification factor of the tube upon the geometrical parameters and the operating conditions is explicitly determined. The solution shows also that the tube will not amplify for too large values of the dc electron beam current.
Crystallography and Interfacial Free Energy of Noncoherent Twin Boundaries in Copper
Authors: Fullman R. L.
Published: April 2005

The crystallography and interfacial free energy of noncoherent twin boundaries in copper have been investigated. It is found that the noncoherent twin boundary is approximately parallel to a {113} plane of one crystal and to a {335} plane of the other. The ratio of the interfacial free energy of noncoherent twin boundaries to the average grain boundary free energy in copper is found to be 0.80±0.015. Two measurements by a second method confirm the magnitude of this value.
Leak Location by Radioactive Gases in Buried Pipes
Authors: Gemant Andrew , Hines Edward , Alexanderson E. L.
Published: April 2005

This paper describes basic considerations and experiments on leak location by means of radioactive tracer gases in underground pipes. C-14 labelled carbon monoxide and radon were used as tracers. The principles of the method are described. Suitable techniques for preparing and detecting the tracer gas have been worked out. Calculations on the spreading of a column of tracer gas in a pipe follow. Leak location on two small scale installations was carried out experimentally.
Diffraction Pattern of Microwaves Near Rods
Authors: Andrews C. L.
Published: April 2005

The diffraction patterns of electromagnetic waves in the neighborhood of rods a half-wave long have been calculated from rigorous electromagnetic theory and checked with 8-cm microwaves. This was the one case in which the patterns could be calculated at short distances from the diffracting objects without undue difficulty. The agreement of measurements and exact theory was sufficient to suggest that microwave measurements within a few wavelengths of diffracting objects will be a fruitful approach to diffraction problems. Heretofore most calculations of diffraction patterns at large distances have been based on blind assumptions as to the distribution of intensity near the diffracting apertures and objects.
Lubrication at Extreme Pressures with Mineral Oil Films
Authors: Clark O. H. , Woods W. W. , White J. R.
Published: April 2005

Intact mineral oil films at average pressures ranging from 86,000 to 215,000 psi and at high rates of shear have been obtained using a bearing consisting of the contact area between crossed axis steel cylinders. Intact films have also been maintained at low rates of shear and lower pressures using a bearing consisting of a sphere in a spherical shell. The lubricating films possess the shearing properties of plastic solids, a fact which is consistent with solidification observations reported in the literature of high pressure viscometry. In the crossed cylinder bearing the high film pressures required for lubrication are induced by hydrodynamic forces. Such forces can be very large as a result of the rapid increase in viscosity incurred by mineral oils under increasing pressure. The observation of complete mineral oil lubrication at such extreme pressures resulting from known bulk properties, namely, viscosity increase and solidification under pressure, suggests that these properties are sufficient to account for practical mineral oil lubrication.
X-Ray Measurement of Short Range Order in Ag-Au
Authors: Norman N. , Warren B. E.
Published: April 2005

The diffuse intensity from single crystals of AgAu and Ag3Au was measured with crystal monochromated CuKα radiation and a Geiger counter spectrometer. Measurements were made at a series of points in the (h1h20) layer of reciprocal space. The measurements were made at both room temperature and at 160°K to allow a correction for temperature diffuse scattering. For the final annealing temperature of 300°C, the short-range order parameters obtained were α1 = −0.08 for AgAu and α1 = −0.05 for Ag3Au.
Kerr Cell Photography of High Speed Phenomena
Authors: Pugh E. M. , Heine-Geldern R.v. , Foner S. , Mutschler E. C.
Published: April 2005

Visible light photographs have been obtained of metal jets squirted from the lined conical cavities of high explosive charges. Since these jets travel through air at nearly meteoric velocities (7 to 12×105 cm/sec), their front ends are heated to incandescense and vaporized. The remainder of the jet is relatively nonluminous and is photographed by synchronizing a Kerr cell shutter (exposure time <1 μsec) and an exploding wire light source (peak intensity 4×108 candlepower) with the phenomenon. Schlieren type photography cannot be used because of the luminosity accompanying the phenomenon. Detail is obtained in the photographs by using a large lens with a seven-in. focal length. To maintain the effective aperture at f/4 requires a large Kerr cell which in turn requires a 25,000 volt pulse for its operation.

The technique is used in studying the action of these jets on steel, water, glass, and Plexiglas. The technique is also used in studying the propagation of shock waves in solids and liquids when these phenomena are due to the action of the metal jets or to the more direct action of explosives.
Positive Coaxial Cylindrical Corona Discharges in Pure N2, O2, and Mixtures Thereof
Authors: Miller Charles G. , Loeb Leonard B.
Published: April 2005

Dc corona studies were made on coaxial cylinders with inner cylinder at positive potentials in pure N2, pure O2, and mixtures of 1 percent, 10 percent O2 in N2 and on clean air from 27-mm to 760-mm pressure. Observations of current-potential relations from field intensified ionization currents to as near breakdown as possible were made noting thresholds for current transitions, pulsed discharges, and other oscillographic as well as visual appearances. Positive corona in pure N2 does not exist as such. Predischarge Townsend currents by photon action on the cathode condition the outer Ni cathode until it spontaneously develops a glow discharge focusing in a spot on the anode wire. The discharge sets in at high potential and persists with lowering by hundreds of volts. Increase in current gives multiple spots and irregular current fluctuations. At lower pressure potential overshoot gradually disappears and the discharge begins as a regular glow discharge. Positive coronas with 1 percent O2 show burst pulses at threshold, these being longer in duration (1000 μsec) than in air because of spread down the wire. At lower pressure burst pulses lasted still longer. Breakdown streamers were observed at lower pressures where the applied potential was adequate. The Townsend equation for current in coaxial geometry applies above threshold both for N2 and N2+1 percent O2. In air the positive corona sequence showing only burst pulses at threshold and breakdown streamers were observed. Burst pulses lasted two to four times those with 1-mm diameter point to plane corona in air owing to spread along the wire, which was less extensive than in 1 percent O2. In pure O2 the high absorption of photons ionizing the gas led to pre-onset streamers and no burst pulses at thresholds above 200-mm pressure. Below 200 mm streamer pulses and burst pulses were observed and below 50 mm only burst pulses were observed. The streamers above 200-mm spread down the whole length of the tube by transparency of O2 to photons liberating electrons from the Ni cathode cylinder.
Electric and Magnetic Forces between Sphere and Wire
Authors: Smythe W. R.
Published: April 2005

Formulas are derived for the force and scalar potential of a dielectric sphere in the field of a charged wire and for the force and vector potential of a permeable sphere and a circular cylinder carrying current. When the sphere is conducting the electric force is q2a2(πενb)−1(b2−a2)−12 sin−1(a/b) in mks units, where q is the charge per unit length on the wire, a the sphere radius and b the distance from its center to the wire. The same formula, with i for q and μv−1 for εv applies to a sphere of large permeability in the magnetic field of a circular cylinder carrying a current i.
Applications of the Radiation from Fast Electron Beams
Authors: Motz H.
Published: April 2005

The radiation from fast electron beams passing through a succession of electric or magnetic fields of alternating polarity is examined. The radiation of maximum frequency is emitted in the forward direction. If the deflecting fields are not too large, a semiqualitative argument shows that the maximum frequency is the lowest possible harmonic. The frequencies emitted are determined by studying the Doppler effect, and the angular distribution of radiated energy as well as the total radiation are calculated in a simple straight-forward manner with reference to well-known formulas of special relativity. The question of the coherence of the radiation is discussed. The spectral distribution of radiated energy is then calculated more exactly. It is concluded that several applications of the radiation appear possible. A scheme for obtaining millimeter-waves of considerable power is outlined. The upper limit of the power in a band extending down to a wave-length of 1 millimeter is calculated to be of the order of several kilowatts for a beam of one ampere and an energy of 1.5 megavolt. The use of the radiation for speed monitoring of beams with energies up to 1000 megavolt is discussed.
Electrical Breakdown over Insulators in High Vacuum
Authors: Gleichauf Paul H.
Published: April 2005

In the investigated range of 5×10−3 to 10−7 mm Hg, the breakdown voltage over insulators in high vacuum is independent of pressure. Currents of 10−11 to 10−8 ampere were observed in the region below breakdown voltage by detecting x-ray quanta with a Geiger-Mueller counter. Pinhole camera x-ray pictures revealed that practically all radiations originate from an area on the anode a distance from the insulator, with a weaker radiation coming from a ring immediately adjacent to the insulator. Current-voltage relationships as usually observed in these experiments indicate a roughness factor and an emitting area on the cathode similar to previous findings in vacuum gaps. Current bursts were observed which did not develop into complete breakdown. Oscilloscopic observations revealed that sometimes at breakdown over insulators the voltage on the test sample drops to 2.5 kv; in other cases it falls to less than 100 volts. The low voltage arc-like discharge extinguishes at a current of about one ampere for copper electrodes in contact with Pyrex glass. When a resistance in series with the test sample is increased to keep the maximum current below one ampere, no stable discharge is observed. As in a vacuum gap, the breakdown voltage over an insulator is increased by successive breakdowns. Part of this ``conditioning'' is permanent. The nonpermanent part is dependent on the state of the test sample prior to conditioning. The anode does not appear to influence conditioning. When the resistance in series with the test sample allows a discharge current above one ampere to flow, a fast conditioning usually occurs which results in a high permanent breakdown voltage.
The Electric Tunnel Effect across Thin Insulator Films in Contacts
Authors: Holm Ragnar
Published: April 2005

Existing calculations on the tunnel effect through thin films in contacts apply to very weak and very strong electric fields. It is the main purpose of the present paper to complete the picture by the treatment of intermediate cases, which are important for many contact applications.
A Problem in Heat Conduction
Authors: Podolsky Boris
Published: April 2005

A steady-state temperature distribution is found for the case of a periodically varying point source of heat, immersed in a homogeneous isotropic infinitely extended fluid, moving with a constant velocity. The phase velocity of the generated temperature wave is discussed. If the phase velocity in a stationary medium is V0, and the fluid velocity v>V0, the phase velocity in a moving medium is given by V=v[1+½(V0/v)4 −(5/8)(V0/v)8+…]. For practical cases one can usually assume V=v, with an error of less than 0.1 percent, even when V0 is as large as 20 percent of v.
Probe Technique for the Measurement of Electron Temperature
Authors: Easley M. A.
Published: April 2005

Discontinuities in the slopes of Langmuir probe characteristics for discharges in mercury vapor in the presence of argon or krypton gas were eliminated by heating the wire probe by electron bombardment before each reading. The results indicate that in many cases nonlinear probe plots are due to change in the contact potential of the probe and do not mean a non-maxwellian distribution of electron velocities. Typical probe plots are given for discharges with and without striations, and also for a discharge in gas contaminated by a trace of CO or CO2. Electron temperature data are listed for representative pressures of gas and mercury vapor and for various discharge currents.
Electromagnetic Scattering from Spheres with Sizes Comparable to the Wavelength
Authors: Aden A. L.
Published: April 2005

By using suitably defined logarithmic derivative functions and the recurrence formulas due to Infeld, the problem of obtaining numerical answers for the scattering of a plane electromagnetic wave by a sphere can be simplified. This is particularly true if the sphere has a complex index of refraction. The nature of these logarithmic derivative functions is shown for one special case involving water spheres.

Experimental results are given for the back-scattering cross sections of water spheres in the electrical size region 0.74≤2πa/λ≤5.90. These results were obtained at a wavelength of 16.230 cm using the standing-wave method of measurement. It is believed that these were the first laboratory measurements of the back-scattering cross section made on individual water spheres in this critical size region.

Comparison is made between the experimental and theoretical results.
Negative Coaxial Cylindrical Corona Discharges in Pure N2, O2, and Mixtures Thereof
Authors: Miller Charles G. , Loeb Leonard B.
Published: April 2005

Direct-current corona studies were made on coaxial cylinders with inner cylinder at negative potentials in pure N2, pure O2, and mixtures of 1 percent 10 percent O2 in N2, and on clean dry air from 27-mm to 760-mm pressure. Observations of current potential relations from field intensified ionization currents to as near breakdown as possible were made noting thresholds for current transitions, pulsed discharges and other oscillographic as well as visual appearances. Negative wire corona does not exist as such in truly pure N2. Unless a high series resistance was in the line once the critical region of potential was reached, the gap broke down to an arc. With current limiting resistor bombardment of the filament with positive ions from the low order pre-discharge released enough gaseous impurity so that after six minutes the resistor could be removed and the internal resistance of the negative ion space charge near the anode held the current at 2000 μa. The behavior indicated that breakdown was preceded by a low current Townsend discharge that cleaned up or conditioned the filament. In all the negative wire studies the onset thresholds vary with the past history of the wire, and the threshold potential at higher pressures overshoots the minimum operating potential of the discharge once it has set in. Studies with 1 percent O2 indicate that the threshold discharge with clean gas is a continuous current with a diffuse glow which in time contracts to a cathode spot with Trichel pulses. Similar behavior applies to air at lower pressure. The negative wire in O2 shows very heavy predischarge currents with relatively small current jumps when random Trichel pulses appear, and further small current jumps when the fixed spot with regular Trichel pulses appears. There is evidence for a continuous heavy background of Townsend discharge along the whole wire until the visible spot and heavy pulsed discharge appears. The duration of Trichel pulses in pure O2 is two to ten times those in air with point to plane geometry and two to three times those in air with coaxial cylindrical geometry. Lower pressures in pure O2 show many current transitions and transitions between discharge forms.
A New X-Ray Diffraction Method for Studying Imperfections of Crystal Structure in Polycrystalline Specimens
Authors: Reis Alfred J. , Slade Jerome J. , Weissmann Sigmund
Published: April 2005

A new double spectrometer method for the study of polycrystalline materials is developed. From intensity data of the diffracted spots and known angular settings of the specimen, the angular range of reflection of the misaligned scattering regions in a crystallite is determined statistically.

The instrument and the technique of the multiple exposure method is described. The statistical evaluation of the data is discussed and a mathematical treatment introducing correction terms as functions of the azimuth and of the Bragg angle is presented.

A commercial silicon powder specimen was investigated. The average angular range of reflection was found to be nearly the same for all (hkl)-reflections with exception of (111), (333), and (444).

The study of broadening effects with the same instrument has been started.

The new double spectrometer method for polycrystalline specimens described in this paper is based on the examination of numerous microscopic spots reflected by individual crystallites. The small spots on the diagram facilitate the detection and measurement of small broadening effects. Independently, the pattern of angular misalignment of the same reflecting crystallite can be accurately determined. For both broadening and misalignment, the method offers statistical information which is representative of the specimen and which can be compared for different (hkl)-reflections.

The total information on imperfections obtained in this manner may serve to correlate experimental observation with the theory of dislocations and hence, may be useful in the understanding of structure-sensitive properties of solids.
Attenuation of Radio Signals Caused by Scattering
Authors: LaGrone A. H. , Benson W. H. , Straiton A. W.
Published: April 2005

An equation is developed for determining the total power scattered from an incident radio beam during its passage through a unit scattering volume. Curves are plotted from which the attenuation of the incident signal caused by scattering may be obtained.
Stress-Temperature Studies of Transitions in Rubbers
Authors: Witte Robert S. , Anthony Robert L.
Published: April 2005

The stress-temperature method was employed as a means of studying the apparent ``second-order'' transition occurring in rubbers. The rubbers studied were a natural rubber gum, a butyl gum, a loaded GR-S, and a loaded Hycar OS-10. Pronounced stress relaxation was observed for all rubbers at temperatures not too far below the transition region, but not at temperatures a few degrees above the transition. For both the butyl and the Hycar OS-10 rubbers the transition temperature was observed to depend strongly upon extension, the transition temperature decreasing with increasing sample extension. No such dependence upon extension was observed for the natural rubber stock. Comparison data were also obtained from volume dilatometric studies. With the exception of the data for natural rubber, the transition temperatures determined by the volume dilatometric method were somewhat lower than the lowest values obtained in the stress-temperature studies.
Mechanical Properties of Substances of High Molecular Weight. IX. Non-Newtonian Flow and Stress Relaxation in Concentrated Polyisobutylene and Polystyrene Solutions
Authors: Schremp Frederic W. , Ferry John D. , Evans Warren W.
Published: April 2005

A coaxial cylinder apparatus serves to measure the apparent viscosity of a concentrated polymer solution at various shearing stresses and to follow the relaxation of stress after sudden cessation of flow. The dependence of rate of strain (γ̇) on shearing stress (T) can be represented by the equation γ̇=k1 sinhk2T. The constant k2 is almost independent of temperature, and decreases with increasing concentration. The course of the stress relaxation depends on the steady-state value of γ̇ preceding cessation of flow. By assuming a logarithmic distribution function Φ of elastic mechanisms which are relaxed by hyperbolic sine flow mechanisms, it can be shown that Φ≅−(dT/d logt)/2.303k1t2 tanh−1{(γ̇/k1)/(1+[1+(γ̇/k1)2]12)}, where t is the elapsed time. Values of Φ obtained from this equation are essentially independent of the rate of shear. The reduced distribution function, Φr=ΦT0/Tc, plotted against the logarithm of the reduced relaxation time, τr=τcT/T0η, where T is the absolute temperature, T0=298°K, c is the concentration in g/cc, and η the viscosity at zero stress, is independent of temperature and concentration over the ranges studied for each of three polymer samples.
Relation of Tensile Strength to Brittle Temperature in Plasticized Polymers
Authors: Boyer R. F.
Published: April 2005

Since both the second-order transition temperature and the tensile strength of plasticized polymers decrease linearly with plasticizer content, and frequently in inverse proportion to the molecular weight of the plasticizer, it was predicted that a linear relationship should exist between tensile strength and transition temperature for plasticized polymers, independent of the nature of the plasticizer. Tensile strength versus heat distortion for four different plasticizers in polystyrene follows this prediction very well. However, tensile strength versus brittle temperature for plasticized Vinylite VYNW gives a different straight line for each plasticizer. It is suggested that the diffusion rate of a plasticizer molecule is important in the fast brittle point test. The hypothesis is proposed that the brittle temperature of a plasticized polymer represents an isodiffusion constant state. It follows on the basis of some semi-empirical equations that the brittle temperature should decrease linearly with plasticizer content, and inversely as the activation energy for diffusion of the plasticizer molecule in the plasticized polymer. This latter prediction appears in accord with existing data. This diffusion concept allows one to predict that the brittle temperature should increase linearly with logarithm of frequency of the test, but inversely as the activation energy for diffusion.