bluuebunny/crossref_metadata_2025 huggingface dataset:
The Conical Dipole of Wide Angle
Authors: Smith P. D. P.
Published: January 2005

The following report deals with a method of calculating the admittance of dipoles that consist of complete cones of wide angle. The theory makes use of the orthogonal properties of Legendre's functions and of their derivatives in order to make the outside field's tangential component vanish over the spherical end surfaces of the dipoles, and to make the inside and outside fields fit at the boundary sphere. This is a surface of the same radius as the dipole, extending from the upper to the lower end surface.

This leads to a set of Eqs. (10) for the infinite set of coefficients bk, and an Eq. (3) that expresses the effective load admittance yt in terms of the coefficients bk. If a sufficient number of these coefficients is considered, there should be no appreciable discontinuities in field at the boundary sphere, and the tangential field should vanish on all the surfaces of the dipole.

On the assumption that only the first two outside waves, and the internal T.E.M. and first higher order inside wave are important for dipoles whose radius is less than a half-wave-length, an approximate formula for yt is found, and the results are shown in Figs. 4 and 6. It is unnecessary to evaluate the solutions of Legendre's equation Ln(θ), because the integrals that involve them are expressed in terms of n(μ1) and dn(μ1)/dμ1, n being the root of Ln(A)=0, and μ1=cosA.

The solutions are transformed to the center of the dipole, and plotted in Fig. 6, while the relative terminating admittances, K·yt, are plotted on an impedance diagram in Fig. 7.
Graphite Lubrication
Authors: Savage Robert H.
Published: January 2005

The slipperiness of graphite is not inherent in the crystal structure alone but depends upon adsorption films, especially water, which cover the carbon atoms and provide surfaces of low cohesion. In vacuum graphite rods or brushes seize upon a moving base (copper or graphite) and wear away as a fine dust. This wear and accompanying high friction are instantly stopped by some condensible vapors at low pressures (H2O, C6H6, NH3, etc.) which apparently effect the coverage of the graphite by a reversible adsorption governed by the pressure and surface temperature. Under conditions of optimum coverage (zero wear) the graphite friction is still appreciable but may be accounted for as the heat of cohesion of water monolayers attached to the carbon atoms and undergoing successive makes-and-breaks. From the measured frictional energy and an assigned heat of cohesion based upon surface energy data, the area of molecular contact is estimated to be 4×10−6 cm2 under a real pressure 2×104 kg/cm2.

The wear dust of unlubricated graphite shows a unique adsorptive power at room temperature, greater for hydrogen than that of activated charcoal by five orders of magnitude. This and other characteristics may throw new light upon the mechanism of friction in general and upon the structure of stroked graphite surfaces in particular.
Theory of Slots in Rectangular Wave-Guides
Authors: Stevenson A. F.
Published: January 2005

A basic theory of slots in rectangular wave-guides is given. The analogy with a transmission line is developed and established, and detailed formulae for the reflection and transmission coefficients and for the ``voltage amplitude'' in the slot generated by a given incident wave are given. While the complete expressions for these quantities are quite complicated and involve the summation of infinite series, certain parts of the expressions are comparatively simple. In particular, the ``resistance'' or ``conductance'' of slots which are equivalent to series or shunt elements in a transmission line are given by fairly simple closed expressions. Guide-to-guide coupling by slots and slot arrays are also considered. A more detailed summary of the main results of the paper is given in Section 1.
Scattering of Electromagnetic Radiation by a Thin Circular Ring in a Circular Wave Guide
Authors: Feuer Paula , Akeley Edward S.
Published: January 2005

The scattering of a TE1, 1 wave by a thin, perfectly conducting circular ring suspended in a circular wave guide with perfectly conducting walls is considered, and approximate expressions are obtained for the scattering cross section, resonance maximum, and half-width as a function of the width of the ring.
Temperature Coefficient of Electrical Resistivity for Crystalline Selenium Containing Various Percentages of Bromine
Authors: Blackburn Wayne E.
Published: January 2005

The temperature coefficient of electrical resistance of brominated selenium over the temperature range −30°C to 100°C was found to be negative and variable. The electrical resistivities of the selenium samples varied by factors of three to twelve for the temperature range mentioned, depending upon the bromine content. A reproducible hysteresis loop was obtained on the plot of resistivity versus temperature. A minimum in the plot of electrical resistivity versus bromine content was found with 0.007 percent bromine in selenium. Activation energies for freeing electrons obtained from the slopes of conductivity versus temperature plots indicate a dependence upon bromine content in the selenium.
The Transient Response of Damped Linear Networks with Particular Regard to Wideband Amplifiers
Authors: Elmore W. C.
Published: January 2005

When the transient response of a linear network to an applied unit step function consists of a monotonic rise to a final constant value, it is found possible to define delay time and rise time in such a way that these quantities can be computed very simply from the Laplace system function of the network. The usefulness of the new definitions is illustrated by applications to low pass, multi-stage wideband amplifiers for which a number of general theorems are proved. In addition, an investigation of a certain class of two-terminal interstage networks is made in an endeavor to find the network giving the highest possible gain—rise time quotient consistent with a monotonic transient response to a step function.
A General Divergence Formula
Authors: Riblet H. J. , Barker C. B.
Published: January 2005

A divergence expression for the ratio of energy per steradian reflected from a smooth curved surface to that incident on the surface is derived. It generalizes previous results in that the source and point of observation may both be at finite distances from the reflecting surface. No restrictions are placed on the angles of incidence and reflection except that they be equal. The only limitation placed on the analytical accuracy of the geometrical result is that the surface be sufficiently smooth so that the principal radii of curvature are defined at the point of reflection. It is required, of course, that the wave-length of the energy shall be small compared to the principal radii of curvature of the surface, in order that the geometrical result may be interpreted as a divergence formula. All of the previous results on this problem known to the authors are derived as special cases. Application of the result in connection with the spreading of radio rays by the curvature of the earth leads to somewhat simpler formulas than now available.
The Theory of the Study of Transfers within a Multi-Compartment System Using Isotopic Tracers
Authors: Sheppard C. W.
Published: January 2005

Expressions are derived for a system of n compartments whereby the amount of a substance S which has moved from any one compartment to any other can be determined in a single experiment from measurements of the amounts of n tagged species in the individual compartments. It is shown that n individual species of S are required which must be uniformly mixed and behave identically but must be distinguishable by the observer. The application of the equations to studies using multiple isotopic tracers is described, and the special case of a two compartment system is analyzed in detail.
On the Stresses in a Plate Containing Two Circular Holes
Authors: Ling Chih-Bing
Published: January 2005

This note gives a theoretical solution to a plate containing two circular holes of equal size. The method of solution is to add to the given stress system a suitable biharmonic function which gives no stress at infinity. The parametric coefficients involved in the solution are adjusted so as to satisfy the boundary conditions at the edges of the holes. Bipolar coordinates are used in the solution, by means of which explicit expressions are obtained for the parametric coefficients. Three fundamental stress systems are discussed in some detail, namely, the all-around tension case, the longitudinal tension case, and the transverse tension case. Formulas of the stress along the edges of holes are derived and, in particular, values of maximum stress are calculated. The limiting case in which the holes are tangential is also discussed.
A Simple Procedure for the Making of Alignment Charts
Authors: Bond W. L.
Published: January 2005

Simplified directions are given for the making of alignment charts from equations in three variables. A fixed determinant is used to put the equation in determinantal form. The determinant is manipulated to put it in standard line form; three standard types of distortion factors are used to produce a chart of convenient shape.
Characteristics of Helical Antennas Radiating in the Axial Mode
Authors: Kraus John D. , Williamson J. Claude
Published: January 2005

A helix is a fundamental form of antenna with many radiation modes. A recently reported mode, called an axial or beam mode, occurs for a relatively wide range of helix dimensions, in the region of 0.2 to 0.5 wave-lengths diameter and as high as 0.5 wave-lengths spacing between turns. The radiation is maximum in the direction of the helix axis and is nearly circularly polarized. This mode may persist with a given helix over a considerable frequency range. In this range the phase velocity of wave propagation along the helical conductor is reduced. An approximate expression for the field pattern of a single turn helix is developed. The pattern of a helix of a number of turns is then calculated as an array of such turns. Measured and calculated patterns show good agreement.
On the Structure of Cellulose Acetate Molecules in Acetone Solution
Authors: Singer Seymour J. , Mark Herman
Published: January 2005

Data obtained from sedimentation velocity and viscosity measurements on a series of cellulose acetate fractions in acetone are interpreted in terms of two models, the impenetrable ellipsoid of rotation and the uniform density random coil. The lack of agreement using the former model is shown to be a real effect, rather than one determined by experimental inaccuracy. As other investigations have revealed, the uniform density random coil is not a satisfactory model for these molecules either. Probably the best hydrodynamical model for these and other extended but not perfectly rigid molecules in solution is a penetrable ellipsoid of rotation.
The Magnetic Properties of Ordered Nickel-Manganese Alloys
Authors: Jaffee Robert I.
Published: January 2005

Nickel-manganese alloys containing 20.1 percent, 21.4 percent, and 25.3 percent Mn in the form of Rowland rings were put into an ordered condition by very slow cooling to 380°C, and long annealing at that temperature. Magnetization curves and hysteresis loops at room temperature showed that the 21.4 percent Mn alloy was very soft magnetically, while the 25.3 percent Mn alloy was relatively hard magnetically. The 20.1 percent Mn alloy was magnetically soft, but not so soft as the 21.4 percent alloy. The magnetic properties of the ordered 21.4 percent Mn alloy changed markedly from room temperature to about 120°C. Induction at 30 oersteds decreases very rapidly, and the maximum permeability goes through a sharp maximum at 91°C. Coercive force and remanence also decrease during the same temperature interval.
Gains and Effective Areas of Horn Antennas
Authors: Watson R. B. , McKinney C. M.
Published: January 2005

Two methods are described for determining the gain and effective area of an electro-magnetic horn antenna. The first of these is an experimental method based on the reciprocal properties of antennas. The second method uses data obtained from measured receiving patterns, and from theoretical patterns, for calculation of values for gain and effective area. Comparable values are found from experiment and calculation for eight different horn antennas. It is concluded that the calculations described give satisfactory values of gain and effective area, taking the reciprocity values as standards.
Theory of Formation of Metal Chips
Authors: Piispanen Väinö
Published: January 2005

In this article values for the angles β and ν have been deduced (compare Fig. 3 and Eqs. (2) and (3)). New values have been deduced for the shear angle φ, Eqs. (16), (20), and (21). The increasing of the internal friction and the strain hardening have been considered.

Equations for the work done in cutting per unit of length (6) and (13) have been deduced. For the cutting force Eqs. (14), (15), and (19) have been deduced. A high cutting speed decreases the friction angle τ between the chip and the face of the tool, by which the forces loading the machine tool steeply may be decreased. These forces are very highly dependent on the friction angle τ, since the rake angle α is negative.

A new theory of the formation of a discontinuous chip is presented.
Alloying of Metal Powders by Diffusion
Authors: Weinbaum Sidney
Published: January 2005

In the preparation of alloys by sintering metal powders, the alloy is formed by the diffusion of metals into each other. The distribution of metallic powder in space is expressed by means of a triple series; this series is used to obtain the solution of the diffusion equation. The resulting formula gives the concentration of metal as a function of space, time, temperature, and particle size. Sample calculations made for one-to-one atomic proportion nickel-copper alloys are in general agreement with experimental results.
Scattering of Ultrasonic Radiation in Polycrystalline Metals
Authors: Roth W.
Published: January 2005

A method for measuring absorption and velocity of ultrasonic radiation in the frequency range from 5 to 100 Mc by use of pulse techniques is described. Results of such measurements performed on polycrystalline magnesium and aluminum as a function of frequency and grain size show that the absorption coefficient varies linearly with frequency and inversely with grain size. The scattering power of a metal, and the fidelity with which an ultrasonic pulse is transmitted is shown to depend on the elastic constants of the single crystals. Criteria are established for evaluating the fidelity of pulse transmission in cubic and hexagonal metals, and figures of merit for many such polycrystalline metals are given.
The Bridge Erosion of Electrical Contacts. Part I.
Authors: Lander J. J. , Germer L. H.
Published: January 2005

Bridge erosion is the transfer of metal from one electrode to the other which occurs when an electric current is broken in a low voltage circuit which is essentially purely resistive. It is associated with the bridge of molten metal formed between the electrodes as they are pulled apart, and more specifically with the ultimate boiling of some of the metal of this bridge before the contact is finally broken. This paper is concerned with fundamental studies of this molten bridge and with empirical measurements of the transfer of metal.

From known physical constants one calculates that, when the melting point is reached at a current I, the diameter of the area of contact of two electrodes is about 1.5×10−5 I cm for silver, copper, or gold, and about 7.5×10−5 I for platinum or palladium. When the maximum temperature of the molten bridge reaches the boiling point the mean bridge diameters are roughly 4×10−5 I and 20×10−5 I respectively. Experimental tests have been made of relations entering into these calculations.

On breaking a contact about 6×10−14 I3 cm3 of metal is transferred from the positive to the negative electrode. This represents about 100 percent of the volume of the molten bridge for silver, copper, or gold, and about 0.5 percent for platinum or palladium. The amount of transfer can be decreased, and even its direction reversed, by heating the negative electrode, and by other means. Calculations have been made of temperature distributions in the neighborhood of a contact and a theory has been developed to account for the reversal of direction of transfer. The theory of the fundamental mechanism has, however, been reserved for later publication.
Twinning in Tetragonal Alloys of Copper and Manganese
Authors: Worrell Francis T.
Published: January 2005

Studies have been made of an alloy 88 percent Mn-12 percent Cu. This alloy when annealed at 925°C and quenched to room temperature has a tetragonal structure of axial ratio 0.97. It has been suggested that such a structure would show twinning along the 101 and 011 planes. Verification of this suggestion is presented.
Energy Losses of Sound Waves in Metals Due to Scattering and Diffusion
Authors: Mason W. P. , McSkimin H. J.
Published: January 2005

When high frequency longitudinal and transverse sound waves are sent through a multicrystalline rod of metal, attenuation losses result because of scattering and diffusion of sound waves by the grains. When the grain size is less than one-third of the wave-length, these losses are due to Rayleigh fourth power law scattering and are proportional to the grain volume. The scattering factor depends on the anisotropy of the elastic constants. Two different factors are obtained, one for shear waves and one for longitudinal waves. These factors have been evaluated for cubic and hexagonal metals. From the measured elastic constants the only metals with a low loss are aluminum, magnesium, and tungsten. The calculations indicate that the losses for aluminum and magnesium are about equal for longitudinal waves, but for shear waves magnesium has a very low shear loss. It has been found experimentally that magnesium has nearly as low a loss as fused quartz.

Experiments with higher frequencies show that when the wave-length is one-third of the grain size or less, the transmission process becomes a diffusion process similar to the propagation of a heat wave. The grain sizes determine the mean free path, and the loss becomes inversely proportional to the grain diameter. An approximate formula for diffusion losses has been obtained which agrees closely with the experimental values.
On the Canonical Form of the Equations of Steady Motion of a Perfect Gas
Authors: Munk Max M. , Prim Robert C.
Published: January 2005

The equations for general steady motion of a perfect gas are expressed in terms of a reduced number of basic dependent variables. Neither constant entropy nor constant flow energy is assumed throughout the flow, but only along individual streamlines. The basic dependent variables used are the ``reduced velocity'' vector w≡v/(2γγ−1pρ+v2)12and the logarithm of the pressure, lnp. The resulting form of the dynamic equation is (w·grad)w+γ−12γ(1−w2) grad lnp=0,and that of the continuity equation is div[(1−w2)1/γ−1w]=0,representing four equations in four unknowns. The fundamental characteristic and shock relations are also expressed in terms of these reduced variables.
An Extension of Lagrange's Equations to Electromagnetic Field Problems
Authors: Crout Prescott D.
Published: January 2005

This paper contains the basic theory of an extension of Lagrange's equations which renders these equations and the procedures associated with them in mechanics applicable to electromagnetic field problems such as are encountered in ultra high frequency work and other branches of engineering. In certain important cases the Lagrangean procedures so obtained give equivalent networks. Successful applications of these procedures to several practical problems are indicated.
An Observation on Heat Sources Placed at Random on a Surface
Authors: Wannier Gregory H.
Published: January 2005

A mean value theorem and a fluctuation theorem are derived for the case where a potential is due to sources of potential placed irregularly on a surface. The purpose of the theorems is to provide a check on theories of solid-solid friction where extremely high ``local temperatures'' are sometimes assumed. The result indicates that a certain caution should be exercised in using such concepts.
Divergent Beam X-Ray Photography with Standard Diffraction Equipment
Authors: Geisler A. H. , Hill J. K. , Newkirk J. B.
Published: January 2005

A new method for preparing divergent beam x-ray photographs of crystals is presented. This employs the usual Laue transmission camera and a collimated primary beam of x-rays. Fluorescent radiation originating either in the crystal sample or at a radiator in front of the crystal is used as the source of divergent x-rays. Some applications of the technique to determinations of orientation, lattice parameters, and crystal perfection are illustrated.
An Ion Microscope with a Transverse Magnetic Field
Authors: Sasaki Nobuji
Published: January 2005

A brief discussion of electron and ion microscopes is presented followed by a description of a low magnification, electrostatic ion microscope. This instrument is of the emission type wherein the source of positive ions is imaged. If more than one species of ion is emitted, the images corresponding to the various atom weights may be separated by means of a transverse magnetic field and the ratio of atomic weights calculated from the displacements. The possible uses of such an instrument are pointed out.
Magnitude and Character of Errors Produced by Shape Factors in Stokes' Law Estimates of Particle Radius
Authors: Kunkel Wulf B.
Published: January 2005

In order to estimate the possible errors introduced by deviations from the spherical particle shape in Stokes' law estimates of dust particle sizes, a model study was made with objects of various shapes falling in oil of high viscosity. It was found that all shapes fall more slowly than the sphere of the same mass and volume. The true size and mass will, therefore, always be larger than the estimates calculated from their rate of fall by means of Stokes' law. For shapes of extreme dimensions (very thin plates and needles) the error thus introduced exceeded 50 percent. For more common configurations of spheres it was of the order of 20 percent or less. No simple relation between particle surface or any other parameter and the rate of fall could be discovered. All plates and needles turned their planes and longer axes into a horizontal direction when falling freely, unless one side was distinctly weighted. A small asymmetry in weight distribution tilts the planes slightly, causing the model to drift sideways in its fall. In a Hopper and Laby method of particle analysis such a drift makes a particle appear charged, although it may be neutral. It is, therefore, not possible to analyze platelike and needlelike powder and dust particles by such a method.
On the Measurement of Cavity Impedance
Authors: Hansen W. W. , Post R. F.
Published: January 2005

A method of measuring cavity impedance is described.
The Fracture of Liquids
Authors: Fisher John C.
Published: January 2005

A liquid subjected to negative pressure is metastable; vapor bubbles form spontaneously and grow until the pressure of the system rises to the equilibrium vapor pressure. The rate of bubble formation is calculated from the theory of nucleation, and the negative pressure pt that gives one bubble (i.e., fracture) in t seconds is determined. pt is very nearly independent of t, and is proportional to σ32 where σ is the surface tension. Subcooled liquids such as glass also are metastable under negative pressure; cracks form spontaneously and grow until the pressure rises to the equilibrium vapor pressure. Nucleation theory leads to an expression for the fracture stress of glass that is proportional to (E2σ3)¼ where E is the elastic modulus. The transition from high temperature cavity-nucleated fracture to low temperature crack-nucleated fracture is examined.

Fracture strengths calculated from nucleation theory agree satisfactorily with the maximum experimental values, and are an order of magnitude smaller than the forces required for simultaneous separation of all atomic bonds cut by a plane surface. The frequent occurrence of premature failure is associated with the presence of pre-existing surface cracks in glass, and of positive contact-angle impurity in contact with liquids.
Geometrical Factors Affecting the Contours of X-Ray Spectrometer Maxima. I. Factors Causing Asymmetry
Authors: Alexander Leroy
Published: January 2005

The observed asymmetry of x-ray spectrometer maxima arises principally from three-dimensional properties of the ideally two-dimensional focusing arrangement employed, vertical divergence of the primary beam being the fundamental cause. A mathematical formula is developed that expresses the degree of asymmetry as a function of the reflection angle and the geometrical properties of the apparatus. The asymmetrical effects predicted in this way are qualitatively confirmed with experimental measurements. Practical suggestions are made for minimizing asymmetry.
Theory of the Positive Column in an Annular Discharge Tube
Authors: Pachner Jaroslav
Published: January 2005

On the ground of Schottky's diffusion theory of the positive column, the distribution of the electron and ion concentration and of the current density in an annular discharge tube are calculated.
Plastic Flow, Creep, and Stress Relaxation. Part IV. Anomalous Flow as an Order-Disorder Transition
Authors: Mack Charles
Published: January 2005

Plastic systems show effects of steric hindrance at rest, which results in a molecule preventing its neighbors from occupying certain positions and introduces a certain degree of orientation. Under stress many more positions, resulting from the rotation, are forbidden to a molecule in motion. In order to make more positions available, the system must increase its volume under stress and changes from a state of greater order to a state of greater disorder. Based on this concept equations are given which present the strain-rate at constant temperatures as functions of stress, change in volume and degree of order and disorder. The changes in entropy and energy of interaction, accompanying the strained state, are expressed by a generalized partition function. This concept of anomalous flow is extended to visco-elastic effects for systems with rubber-like elasticity, and has been exemplified by data on polychloroprene under tension.
Velocity of the Anode Spark in Copper Sulfate Solutions Under Application of Impulsive Potential
Authors: Henry Hugh F.
Published: January 2005

The velocity of the luminous anode spark produced in CuSO4 solutions by application of impulsive potential has been measured as a function of the interelectrode gap, input voltage, and solution normality. Determinations were made for input potentials of 15–30 kv, interelectrode gaps of 15–80 mm, and solution concentrations of 0.0125–0.0625N.

The spark velocity was found to depend upon the input potential and the interelectrode gap by the empirical equation: V=311.1(E0−11.7)/G,where V is the spark velocity in meters/sec., E0 is the input voltage in kv, and G is the interelectrode gap in cm. Qualitatively, it was observed that as the solution normality increased, the maximum breakdown distance decreased and the spark behaved more erratically.

The maximum length which the spark streamers reach may be stated empirically by the equation: Lm=2.33×10−3(E0+2.89)2/(N+0.545)(G−0.43)12,where Lm is the maximum streamer length in cm, E0 is the input potential in kv, G is the interelectrode gap in cm, and N is the normality of the solution.

The computed potential at which the spark cases its progress through the liquid, Em, was found to be proportional to the input potential but independent of the interelectrode gap and the solution concentration. The ratio Em/E0 was 0.646. The time lag in initiation of the spark was also found to depend upon the input voltage but to be independent of the interelectrode gap and the solution concentration.
On the Mixing Properties of Non-Linear Condensers
Authors: Van Der Ziel A.
Published: January 2005

The theory of a mixer circuit, containing a non-linear condenser as a mixing element, is developed. It is shown that such a condenser has an imaginary conversion transconductance and a capacitive input and output impedance. It is found that the circuit has widely different properties, depending upon the choice of the frequency, ωm, of the local oscillator, the i-f frequency, ω0, and the input frequency, ωi. The following three cases are considered: (a) ωm = ωi+ω0, (b) ωm = ωi−ω0, and (c) ωm = ω0−ωi. A non-linear condenser in a mixing circuit acts as a transformer; in the cases (b) and (c) the mixing condenser transforms an i-f impedance into a positive input load; in case (a) an i-f impedance is transformed into a negative input load, so that oscillations may even occur. In case (c) the power gain is larger than unity, the power delivered to the circuit by the antenna is smaller than the power dissipated by the output load, and the difference is due to the power delivered by the local oscillator. In case (b) the power gain is smaller than unity, because in this case power is dissipated by the local oscillator. In case (c) instability may occur; the circuit is then capable of splitting the local-oscillator signal into two signals of frequencies, ωi and ω0, respectively. The band width and the noise factor of the circuit are also discussed; it is shown that the circuit might have a very low noise factor. A few experiments are given which show qualitative agreement with theory.
The Effects of Pile Bombardment on Uncured Elastomers
Authors: Davidson W. L. , Geib I. G.
Published: January 2005

Previous work on the effects of ionizing radiations on hydrocarbons has established that four competitive processes are usually operative: (1) dehydrogenation, (2) condensation or polymerization, (3) hydrogenation (action of nascent hydrogen on any unsaturated matter present), (4) decomposition (C-C cleavage). The chain reacting nuclear pile offers an ideal means for subjecting relatively thick samples of matter (such as rubber) to uniformly high concentrations of radiation. Such studies on natural rubber, butyl rubber, and polyisobutylene allow one to draw the following conclusions. 1. Uncured natural rubber undergoes a slight curing action when exposed to pile radiations. 2. Polyisobutylene samples are appreciably degraded by pile radiations. 3. The same effects as noted in (1) and (2) are greatly enhanced by secondary alpha-particles, produced by an (n,α) reaction on boron10 (milled into the elastomer). However, even a 2-hour bombardment of natural rubber yields a product greatly inferior to sulfur vulcanizates. 4. Pile bombardment does not introduce measurable unsaturation in polyisobutylene and decreases the unsaturation in natural rubber but slightly. 5. A typical butyl rubber stock is permanently degraded by pile irradiation showing upon cure reduced tensile strength compared to that of a control sample. 6. Natural rubber shows a weak but measurable radioactivity days after bombardment, probably because of its mineral content. Polyisobutylene is not appreciably active.
The Thermodynamics of a Strained Elastomer. I. General Analysis
Authors: Mooney M.
Published: January 2005

The thermodynamic functions of principal interest in a strained elastomer are the entropy and energy of deformation. The volume is of secondary importance, and it can be assumed, with sufficient accuracy for most purposes, that the volume is linear in the temperature and the mean pressure. The basic partial differential equations of thermodynamics can then be integrated, yielding expressions for the energy and entropy of deformation in terms of observable quantities.

In the present analysis the volume effects caused by changes in mean pressure and crystallinity are taken into account, and the effects associated with change in shape are sharply separated from those associated with change in volume. It is shown that the superelastic functions of deformation previously published (M. Mooney, J. App. Phys. 11, 582–92 (1940)) have a very general validity.
The Thermodynamics of a Strained Elastomer. II. Compressibility
Authors: Copeland L. E.
Published: January 2005

Adiabatic compressibility coefficients were measured on a series of cured polymers of commercial types under pressures up to 5000 lb./in.2. In most cases, the second order as well as the first order coefficient could be determined from the data. The linear isothermal compressibility also was calculated from the measured linear adiabatic coefficient.

Preliminary measurements of the thermal expansion of a stretched Hevea gum stock show that there is a slight decrease in expansion at the 200 percent elongation, presumably due to partial crystallization.
The Thermodynamics of a Strained Elastomer. III. The Thermal Coefficient of Modulus and the Statistical Theory of Elasticity
Authors: Copeland L. E. , Mooney M.
Published: January 2005

Published thermoelasticity data are critically analyzed by means of thermodynamic equations developed in the first paper of this series. Equations known to be of the proper form are fitted by least squares to the experimental data, which were first corrected to allow for the changes in shape when tested under variable temperature and constant length. If the measurements are accepted as truly reversible, the data show that several different elastomers depart considerably in some respects from the predictions of the statistical theory of elasticity.

Some thermoelasticity measurements in torsion are reported which seem to give the most reliable evidence that stress is proportional to absolute temperature.
Creep, Recovery, and Permanent Set for GR-S and Hevea
Authors: Gehman S. D.
Published: January 2005

A study was made of creep, recovery, and permanent set for Hevea and GR-S over a 1000-hr. period and a range of elongations at 35°C. Creep for GR-S is greater than for Hevea. The stress for GR-S is considered to be supported to a greater extent by a relatively unstable secondary bond structure. This is consistent with the large creep values for GR-S at low elongations and the large ratio of primary or recoverable creep to permanent set. Hevea, in contrast, shows low creep at both high and low elongations and maximum creep at intermediate elongations for which the structure is heterogeneous, consisting of amorphous and crystalline phases.

A procedure was worked out for determining the contribution of permanent set to the observed creep. The creep curves were concave to the strain axis when plotted against logarithmic time. After correction was made for permanent set, they were found to be approximately linear, thus extending the range of application of the Tobolsky-Eyring theory of creep.

At the start of the creep test the flow appears to be due largely to the reversible yielding of relatively weak bonds which can reform under the action of the elastic network when the stress is removed. For longer periods of time, or for higher elongations, the flow involves more deep seated changes in structure. Larger units of structure are displaced or stronger bonds broken with resultant permanent molecular displacements upon removal of the stress. For Hevea at high elongations all of the flow was accounted for by permanent set.
Method for the Absolute Measurement of Dynamic Properties of Linear Structures at Sonic Frequencies
Authors: Lyons W. James , Prettyman Irven B.
Published: January 2005

A full account, including the theoretical basis, is given of a method whereby the dynamic stretch modulus, coefficient of internal friction, and hysteretic energy loss of textile yarns and cords, composed of either continuous filaments or staple fibers, can be accurately determined at longitudinal vibration frequencies above 100 cycles/sec. The method, which employs electromagnetic excitation, is applicable also to glass cords, and metallic wires and cables. Results have been obtained at frequencies extending to above 300 cycles/sec. A concise description is given of the improved stretch vibrometer. Results on a typical cotton cord show that energy absorption by this instrument is negligible, permitting the calculation of an accurate internal friction coefficient, and absolute hysteretic loss. Measurements on eight natural and synthetic textile fibers reveal that the dynamic moduli range from 6.4×1010 dynes/cm2 for Velon monofil to 32×1010 dynes/cm2 for a ramie cord. The dynamic moduli of Fiberglas and steel cords are found to be 54 and 106×1010 dynes/cm2, respectively. The internal friction coefficients are found to vary hyperbolically with frequency: in a 11/4/2 cotton cord, for example, from 16 to 3×106 poises between frequencies of 60 and 320 cycles/sec.
Electric Field Intensity Inside of Natural Clouds
Authors: Gunn Ross
Published: January 2005

Measurements of the electric field on the surface of aircraft flying through all types of weather and clouds are summarized. The measured electric field inside a thunderstorm just prior to a lightning strike at 12,900 feet was 3400 volts/cm. The average maximum field for 9 different thunderclouds was 1300 volts/cm. It is noted that large fields usually occur only inside the cloud and at altitudes somewhat comparable to the freezing level. Frequent reversals of the field are observed in these areas. The electric field measured inside a stable non-precipitating cloud is less than 10 volts/cm.
Apparatus for Weighing in Vacuum
Authors: Monk G. W.
Published: January 2005

An apparatus is described which can be used to measure the weight of a sample in a vacuum (0.01 micron) at temperatures up to about 700°C. Typical preliminary results are given for the outgassing of aluminum, carbon, and ``Teflon.''
Ionosphere Reflections Recorded Mechanically by Means of a Repetition Frequency Converter
Authors: Stoffregen W.
Published: January 2005

A method of converting the high repetition frequency used by echo sounding to a lower value by means of a converter between the receiver and the recorder is described. The method is adapted to recordings of radio-echoes from the ionosphere, in which case the repetition frequency of 50 c/sec. of the pulse transmission after reception is converted into a repetition frequency of ½–⅕ c/sec. before being supplied to the recorder. Ionosphere echoes having a delay of the order of milliseconds and a pulse width of about 20–100 μsec. may thus be recorded mechanically.

The principle of repetition frequency conversion described here may also find applications in recording ultrasonic or radar reflections.
Quantitative X-Ray Investigations on the Crystallinity of Cellulose Fibers. A Background Analysis
Authors: Hermans P. H. , Weidinger A.
Published: January 2005

A quantitative investigation of the intensity of scattered radiation in a series of native and regenerated cellulosic objects, including bacterial cellulose and fibers transformed into cellulose IV, is offered. The technique used involves the use of copper radiation monochromatized by reflection, specimens with randomized orientation of equal size and density, rotation of the plane film, and measurement of primary beam intensity by means of a device introduced by Goppel.

The procedure of evaluation consists of measuring integrated intensities of the crystalline peaks and that of the diffuse background. After correction of the latter for radiation scattered by air and for the background components due to Compton radiation and thermal scattering, as derived from exposures of sugar crystals and diamond, the diffuse background is represented by a curve exhibiting a flat maximum.

The height of this maximum was assumed to be a correct relative measure of the disordered portion and the total intensity of the coherently diffracted radiation of the crystalline peaks as a relative measure of the crystalline portion.

Within the series of native specimens the ordered and disordered fractions are found to be equal in cotton, cotton linters, ramie, and flax fibers. In woodpulp the disordered fraction is slightly higher and in bacterial cellulose considerably higher.

Within a series of rayons, including slightly and highly orientated viscose rayons, Cellophane, Lilienfeld rayon, and cuprammonium rayon, the ordered and disordered fractions were also found to be equal. Slightly less disordered substance is found in Fortisan, in mercerized ramie and in specimens where cellulose II has been transformed in cellulose IV by a heat treatment.

It is shown that the relative proportions of the fractions of disordered substance, for all objects investigated, are in satisfactory quantitative agreement with those deduced from the sorptive capacity for water vapor.

The absolute percentage of the crystalline portion calculated from the experimental data is 70±2 percent for the native fibers and 39±3 percent for the rayons. These figures are in reasonable agreement with those previously estimated from sorption isotherms (68 percent and 35 percent), from density determinations (60 percent and 25 percent), from birefringence and x-ray orientation measurements in regenerated fibers (≤40 percent for rayon), and from recrystallization of amorphous cellulose powder (∼35 percent for rayon).

The observed relative intensities of the principal crystalline interferences give rise to a discussion of the limited scope of the concept ``crystallinity'' in cellulose fibers, and it is argued that the concept ``degree of lateral order'' may be preferable.

Comparison of observed relative line intensities with the theoretically calculated ones, reveals another marked difference between native and regenerated fibers, pointing to the fact that certain states of lateral order prevalent in the latter may be absent in the former.
Qualitative Experimental Verification of the Change of Burning Rate of Rocket Powders with Radiation Path Length
Authors: Penner S. S.
Published: January 2005

Experimental studies on step-machined powder grains indicate a small increase in the average burning rate of solid fuel rocket propellants with an increase in the radiation path length. This result is in agreement with theoretical predictions.
Universal Curves for Dielectric-Filled Wave Guides and Microwave Dielectric Measurement Methods for Liquids
Authors: Surber W. H.
Published: January 2005

The characteristics of wave guides containing a non-ideal dielectric medium are expressed in terms of a dissipation factor, D, the effect of which is analogous to that of the loss tangent of the medium, tanδ, for coaxial or two-conductor transmission lines. A set of universal curves may then be constructed for the variation of the wave-guide parameters as functions of the dielectric loss factor in terms of D. These curves are independent of the dielectric constant, ε′, and of the frequency and mode of operation.

An experimental method is described for the measurement of the dielectric constants of medium and high loss liquids using a variable length of liquid dielectric column contained in a section of wave guide or coaxial line and terminated by a perfectly reflecting plane. Either a unidirectional coupler or slotted line may be used to observe the variation of the magnitude of the reflection coefficient with the dielectric sample length. An exact analytical expression is given for the determination of the constants of the medium using the dielectric constant, ε′, and the dissipation factor, D, as the primary independent parameters instead of ε′ and tanδ. A graphical method of solution is also given.
A Method of Determining the Angle of Arrival
Authors: Straiton A. W. , Gordon W. E. , LaGrone A. H.
Published: January 2005

A method is presented for determining the angle of arrival of the direct and reflected wave for line of sight cases. The method assumes one direct and one reflected wave. The phase difference equipment, as developed by the Electrical Engineering Research Laboratory, measures the difference in phase at 3.2-cm wave-length between two points separated vertically by ten feet [F. E. Brooks, Jr. and C. W. Tolbert, Equipment for Measuring Angle-of-Arrival by the Phase Difference Method, Electrical Engineering Research Laboratory, Report No. 2, May 1946] and the signal strength at each point. The normal procedure involves the raising of either transmitter or receiver while the other is held at a fixed level. The data to which the method is applied were collected at the Navy Electronics Laboratory desert site near Gila Bend, Arizona, during April 1947. The results are compared to calculations based on the meteorologically measured distribution of the refractive index and ray theory.
The Choice of Operating Mode for Standing Wave Type Linear Accelerators for Electrons
Authors: Lawton Elliott J.
Published: January 2005

Experimental studies of the wave-length spacing between modes of the spectrum of arrays of 10 and 16 cavities with different cavity-to-cavity couplings have been made. The results indicate greatest mode separation near the center, π/2 mode of the mode spectrum making this mode best for operation. Use of the end π-mode of the spectrum should lead to a limiting length of approximately 3 to 6 ft., while choice of the center π/2 mode would result in a limiting accelerator length of 10 to 20 ft. at 10.7 cm.
The Theory of Extreme Values and Its Implications in the Study of the Dielectric Strength of Paper Capacitors
Authors: Epstein Benjamin , Brooks Hamilton
Published: January 2005

In this paper it is shown that the statistical theory of the distribution of extreme values is pertinent to the study of the way in which the breakdown strengths of paper capacitors depend on capacitor size. The theory presented in this paper permits a quantitative explanation of this phenomenon and results are given which should be useful to design engineers.
Magnetization in Perpendicularly Superposed Direct and Alternating Fields
Authors: Beck F. J. , Kelly J. M.
Published: January 2005

The magnetic properties of an iron specimen under the influence of perpendicularly superposed direct and alternating fields are investigated. For the low and intermediate values of direct longitudinal magnetic field intensity the steady component of the longitudinal intensity of magnetization first increases, goes through a maximum, and then diminishes as the transverse alternating magnetic field intensity is increased. Static hysteresis loops in the longitudinal direction show a suppression of hysteresis with increasing transverse alternating magnetic field intensity. However, dynamic hysteresis loops in the transverse direction indicate that this suppression is merely apparent. Curves of the dynamic longitudinal magnetic induction vs. transverse magnetic field intensity and transverse magnetic induction are included.
Explosives with Lined Cavities
Authors: Birkhoff Garrett , MacDougall Duncan P. , Pugh Emerson M. , Taylor Sir Geoffrey
Published: January 2005

Explosives detonated in contact with thick steel plates produce much deeper holes in the steel when there is a cavity in the explosive in contact with the plate. While this phenomenon has been known for more than 150 years, the enormous increase in penetrating power that can be produced by lining the explosive cavity with thin metal has been discovered only recently. During the war a number of light, low velocity, antitank weapons (e.g., the rocket-propelled Bazooka) were developed which made use of this phenomenon to perforate thick armor plate.

A fairly complete mathematical theory of this essentially new phenomenon is presented together with some of the experimental data that aided in the formulation and testing of the theory. The process is separated into two phases: first, the formation of part of the metal liner into a long thin jet traveling longitudinally at very high velocities (30,000 ft./sec.) and, second, the forcing aside of the target material by the extremely high pressures (0.3-million atmos.) produced by the impact of the high speed jet.

The theories of both of these phases are based upon the classical hydrodynamics of perfect fluids, which is applicable because the strength of the metals involved can be neglected at the high pressures encountered.