bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Experimental Approach to the Study of Boundary Lubrication
Authors: Dacus E. N. , Coleman F. F. , Roess L. C.
Published: January 2005

A description is given of apparatus for measuring the relative ability of rubbed-down monolayers of polar lubricants to maintain low friction under test conditions which do not permit replacement of the lubricant. This quality of a lubricant is called its ``durability.'' The clean polished rim of a slowly rotating steel wheel rubs on the monolayer deposited on a polished steel flat. An account is given of the preparation of the surfaces and films. It was not found possible to prepare reproducible test surface-monolayer combinations, hence it was necessary to compare each lubricant with a standard deposited on a separate area of the same surface. Significant differences are found in the relative durabilities of a number of polar compounds. For the monocarboxylic acids tested, the values are found to increase with the number of carbon atoms per molecule. An investigation of the stability of rubbed-down monolayers on polished stainless steel shows that aging in a desiccator causes a continuous decrease in durability, and also a decrease in molecular orientation as shown by electron diffraction. Similar reduction of durability and orientation results when the film is flushed with a fine stream of benzene. On chromium also the orientation is destroyed by the solvent, but the durability is not changed.
Theory of the Multivibrator
Authors: Webb Harold W. , Becker Gordon E.
Published: January 2005

The theory of the symmetrical multivibrator has been developed in a form which makes possible the computation of the period and the currents in the tubes in a relatively simple manner. The method is largely graphical. The behavior of the corresponding Eccles-Jordan trigger circuit is first determined and a ``trigger'' characteristic constructed, giving the values of the grid voltages of each tube when triggering takes place and the corresponding values of the currents in the tubes before and after triggering. From this characteristic, with slight changes, the operating conditions and the period of the multivibrator circuit are determined. It is found that the grid currents play an important part in determining these conditions and the period. The method was applied to an actual circuit and the computed values agreed well with the experimental results. The effect on the period and operating conditions of varying the parameters is discussed theoretically and the conclusions are compared with experiment.
On the Solution of Definite Integrals Occurring in Antenna Theory
Authors: Weinbaum Sidney
Published: January 2005

A certain type of definite integrals occurring often in the evaluation of mutual impedance of antennas is solved by the use of differential equations.
The Impedance of Short, Long, and Capacitively Loaded Antennas with a Critical Discussion of the Antenna Problem
Authors: King Ronold , Harrison Charles W.
Published: January 2005

In Part I curves computed from Hallén's formula for the self-impedance of a center-driven antenna of half-length h and radius a are given for Ω=2 ln (2h/a)=7, 10, 20, 30 for values of h from zero to two wave-lengths. A simple formula for the impedance of short antennas is obtained; the reactance is shown to agree with that computed from the static capacitance between the two halves of the antenna. The effect of a capacitive reactance connected across the input terminals of the antenna is investigated. It is shown that the resistance at anti-resonance is reduced, the capacitive lobes of the curve for reactance relatively increased, the inductive lobes relatively very much decreased, and curves for both resistance and reactance shifted to shorter lengths. In Part II the differences between various methods used by different investigators to compute the impedance of an antenna are examined critically. It is concluded that Hallén's formula probably is a better approximation for an antenna consisting of two sufficiently thin ellipsoids each of semi-minor axis a placed end to end than for cylinders, but that cylindrical antennas driven in various ways can be approximated by using an effective value of h/a and a suitably chosen capacitance across the input terminals.
Terminal Functions for Antennas
Authors: King D. D. , King Ronald
Published: January 2005

Recently calculated values of the input impedance of cylindrical antennas are expressed in a form adapted to transmission-line equations. Curves are plotted to show the effect of various antenna and line parameters on a circuit consisting of a line with an antenna as load, and application is made to the transfer of power from the line to the antenna.
Research Activities of the Naval Ordnance Laboratory
Authors: Schindler W. G.
Published: January 2005

Author's Note: This article might better have been written after the war is won. The work being done by the Naval Ordnance Laboratory furnishes some extremely interesting examples of the application of theoretical and experimental physics to the practical business of war. Unfortunately, details of this work cannot yet be revealed. It is possible, however, to give general pictures of some of the problems in which the laboratory is engaged and their relation to naval warfare. That is the intent of this article.
Research and Experimental Activities of the U. S. Naval Proving Ground
Authors: Hedrick David I.
Published: January 2005

The United States Naval Proving Ground, Dahlgren, Virginia, is an activity of the Bureau of Ordnance, Navy Department. Rear Admiral George F. Hussey, Jr., U. S. Navy, is Chief of the Bureau of Ordnance. Captain David I. Hedrick, U. S. Navy, is the Commanding Officer of the Naval Proving Ground. All tests and experimental work are conducted in the Ordnance Division of the Proving Ground under the supervision of Captain Festus F. Foster, U. S. Navy, Ordnance Officer. The work carried on in the Ordnance Division is apportioned among several departments, including an experimental department, each headed by an officer of the United States Navy.
Hysteretic and Elastic Properties of Rubberlike Materials Under Dynamic Shear Stresses
Authors: Dillon J. H. , Prettyman I. B. , Hall G. L.
Published: January 2005

The nature of hysteresis in products such as pneumatic tires, solid tires, and transmission belts is analyzed and the requirements of a laboratory test for evaluating the relative hysteretic characteristics of natural and synthetic rubber stocks are developed. The significance of various definitions of the ``hysteresis defect'' in rubberlike materials is discussed. A forced resonance vibrator in which rubber samples are deformed in shear at frequencies of 20 to 300 cycles/sec., shear strains of 0.05 to 0.35, and temperatures of −20 to +120°C is described. Experimental results obtained with natural rubber and GR-S gum and tread stocks are presented. The hysteresis index ωη is found to be nearly independent of dynamic shear strain while the dynamic modulus G decreases moderately with increasing dynamic strain. Neither ωη nor G depends upon the height to diameter ratio of cylindrical samples. These results are at variance with those obtained by previous investigators who, employing compressive vibrations, have reported marked dependences of both modulus and friction upon dynamic strain and the ``shape factor'' of tread type stocks. In agreement with previously reported work, G is found to be independent of frequency and ωη only slightly dependent upon frequency, for treated type stocks. Results are presented for stocks based on Buna S type copolymers with varying monomer ratio and on N-type Butaprenes, Neoprene, and butyl rubbers.
Drift and Relaxation of Rubber
Authors: Mooney M. , Wolstenholme W. E. , Villars D. S.
Published: January 2005

Drift tests lasting 8 years have been carried out on rubber blocks in compression at 35°C. Rate of drift, initially high, attains a low constant value in 200 days or less. The initial, rapid drift is termed transient drift; and the slower, constant drift is termed steady drift. Drift varies considerably with the type of accelerator in the compound, Ureka giving the lowest drift of the accelerators tested. A new method has been developed for measuring stress relaxation in tension. The stress is measured to 0.1 percent by the resonance frequency of lateral vibrations of the stretched sample. The vibrations are impressed on the sample by a mechanical oscillator in which the source of vibrational energy is a steel wire which is under adjustable tension and is kept in circular vibration by a pair of air jets. Relaxation measurements extending over many months are reported on a soft vulcanized rubber at elongations from 10 to 400 percent at 35° and 70°C. The experimental data can be fitted by a two-term stress equation of the Tobolsky-Eyring form representing two slip mechanisms, or transient and steady relaxation. Steady relaxation follows an exponential decay law; and this means that the residual stress goes to zero at infinite time. Other stress relaxation data are reported for rubber tested at 150 percent elongation, at temperatures from 35° to 113°C, in air and in vacuum. Air, as compared with vacuum, produces little effect at 35°; but at 70° and higher, the rate of steady relaxation is greatly increased. Thus oxidation appears to be the major factor in steady relaxation at elevated temperatures. Total transient relaxation is unaccountably increased by vacuum and by heat. A modification of the Tobolsky-Eyring equation is developed for steady relaxation. For transient relaxation a new theory is developed which leads to the Tobolsky-Eyring equation, but involves different interpretation of the parameters. In this theory, transient relaxation is attributed to rupture of secondary chemical bonds or crystal forces, followed by longitudinal slippage of chain molecules, with partial or local equalization of tension along the chains. The crystallites then reform, and the rupture and slippage process is repeated. The energy dissipation is attributed primarily to release of local elastic stresses following bond rupture. Transient relaxation is complete when the tension is completely equalized over the total length of each chain between cross links. Neither of the new equations can be distinguished from the Tobolsky-Eyring equation on the basis of present data.
Elasto-Viscous and Stress-Optical Properties of Commercial Polymerized Methyl Methacrylate as a Function of Temperature
Authors: Robinson Howard A. , Ruggy Ruth , Slantz Elizabeth
Published: January 2005

The elasto-viscous and stress-optical properties of commercial methyl methacrylate polymer have been measured. Between 66°C and 107°C Young's modulus drops from approximately 400,000 pounds per square inch to roughly 200 pounds per square inch and the material behaves like rubber. At 93°C the viscosity is approximately 10 12 poise. This drops to 109 at 177°C. While the curve is not strictly linear with 1/T, an activation energy of 30,000 cal./mole can be deduced for this change. Below 93°C three rate constants are necessary to describe the delayed elastic process, but two suffice between 93°C and 135°C. At 149°C one such constant is enough and above this an instantaneous elastic and a viscous flow is sufficient. The change in rate constants with temperature gives rise to elastic activation energies of 9000 to 11,000 cal./mole. Methyl methacrylate is optically negative but has a stress optical sensitivity about that of glass. The stress optical coefficient varies markedly with temperature, showing a sharp maximum at 93.3°C. The stress-optical coefficient is directly proportional to the average relaxation constant. X-ray diffraction patterns show four rings corresponding to spacings of 2.19, 3.07, 6.7, and 14.7A. Some slight evidences of crystallinity are shown by diffraction patterns in fibers stretched at 93°C. Fibers stretched at 149°C show a lesser amount of order in agreement with the birefringence studies. The second-order transition point occurs at 71.1°C.
Rheological Properties of Natural and Synthetic Rubbers
Authors: Kelsey R. H. , Dillon J. H.
Published: January 2005

An extrusion plastometer for rubberlike materials which measures the shearing stress at a predetermined constant average rate of shear and a given temperature is described. In one filling of the extrusion chamber, requiring about 10 cm 3 of sample, the average rate of shear is set at 3 or 4 different values in the range of 5–100 sec.−1 and corresponding average shearing stresses are read by means of a pressure gauge. A plot of these data thus gives a complete rheological curve from a single determination. Typical curves are given for Hevea smoked sheets, GR-S, and Butaprene NM and for GR-S masterbatches and normal tread stocks. The effect of capillary geometry is estimated. The effects of milling and of temperature upon the rheological properties of several rubbers are discussed. Typical data for GR-S polymers, masterbatches, and tread stocks, together with corresponding data obtained by means of the Mooney shearing disk viscometer and the Firestone constant pressure extrusion plastometer, are presented and their relative significance discussed.
A New Extrusion Plastometer
Authors: Schultz H. A. , Bryant R. C.
Published: January 2005

An instrument has been designed to determine whether a given batch of synthetic rubber tread stock can be forced through a plate die to form a satisfactory tire tread. The instrument takes the form of an extrusion plastometer which uses special dies. The factory tubing properties of a batch can be predicted from the appearance of the sample extruded through this die and from the extrusion rate.
Observations on the X-Ray Structure of Rubber and the Size and Shape of Rubber Crystallites
Authors: Gehman S. D. , Field J. E.
Published: January 2005

Vulcanized rubber is composed of a cross-linked network of chain molecules, segments of which are sufficiently free and mobile in localized regions to form a crystal lattice upon stretching. The crystallites thus formed represent an automatic molecular mechanism for re-enforcement and are analogous to particles of re-enforcing pigment which increase the modulus, strength, and tear resistance. These effects depend upon the number of particles present and their size and shape. X-ray determinations were made of the crystallite sizes in a series of vulcanized gum stocks using the Scherrer method but calculating the diffraction broadening by the formula proposed by Taylor. Evidence was found that the crystallite size distribution was heterogeneous and included small crystallites which broadened the base of the diffraction peaks. It could be shown that a high degree of crystallinity in a compound was associated with small crystallite size. Both of these factors combine to give high modulus stocks. For different cures with a given rubber compounding formula, there is a definite correlation between the amount of combined sulfur and the crystallite size. This indicates that irregularities in the structure caused by the combined sulfur tend to limit the crystallite growth. This interpretation is preferred although the experimental evidence is not decisive as to whether or not lattice distortion contributes to the width of the diffraction spots. Significant conclusions can be drawn from the work in regard to crystallite formation in stretched rubber and effects of crystallites on the physical properties.
Stress Relaxation of Natural and Synthetic Rubber Stocks
Authors: Tobolsky A. V. , Prettyman I. B. , Dillon J. H.
Published: January 2005

Measurements of stress decay as a function of time made at constant elongation on thin bands of gum and tread type natural rubber (Hevea), Neoprene, Butyl, Buna S, and Butaprene N stocks indicate that both secondary and primary bond relaxation occur. Practically complete relaxation is observed to take place in the experimental time (about 100 hours) at temperatures at and above 100 degrees C. The manner in which the rate of relaxation depends on temperature and the fact that the rate is independent of elongation and of the presence of carbon black in the vulcanizate indicate that stress decay is caused by a definite chemical reaction which deteriorates the rubber structure, and oxidative scission is suggested as the mechanism of deterioration of the primary bonds. The stress relaxation data, obtained over a temperature range from −50°C to +150°C, appear to verify modern concepts of the structure of elastomers. Theoretical equations are derived which give very good agreement with the observed relaxation data at high temperatures. The free energy of activation for the oxidative scission is found to be 30.37 kcal. per mole for the Hevea gum stock, and differs from this value by less than ±2.0 kcal. per mole for all other stocks, indicating the same general reaction for all. However, these small differences in free energy of activation correspond to considerable differences in times of decay, which fact might be significant in evaluating the resistance of rubber stocks to deterioration.
General Vibration of a Hinged Beam
Authors: Brown Herbert Kapfel
Published: January 2005

This paper is a continuation of a paper by the author entitled ``The Resolution of Boundary Value Problems by Means of the Finite Fourier Transformation: General Vibration of a String.'' A general boundary value problem of the transverse vibrations of a hinged beam was resolved into the solution of a pair of boundary value problems with much simpler boundary conditions. The finite sine transformation and its property of convolution were used to accomplish this. The transformed boundary value problem was solved by the introduction of a fundamental set of solutions of the homogeneous transformed problem.
Development of the General Antenna Array Equation
Authors: Thomson William T.
Published: January 2005

Interference patterns resulting from a system of orderly arranged sources, whether they be radio, light, or sound waves, can be conveniently analyzed by the use of the exponential operator ej. This paper illustrates the application of the exponential operator in the development of the equation for the general antenna array.
Electron Microscopic Determination of Surface Elevations and Orientations
Authors: Heidenreich R. D. , Matheson L. A.
Published: January 2005

The methods of determining object thickness in electron microscopy are briefly reviewed. Uncertainties in interpretation of surface replicas from a consideration of intensities alone are discussed and three different replicas of etch figures in pure aluminum are presented. The stereoscopic method is analyzed and an equation is derived relating the parallax of image points in stereo micrographs to the elevations in an object. This equation is the parallax equation of aerial photography but written in the form f=(cscσ/2M)×103 microns/mm,where σ is the stereo angle and M the total magnification. The equation is experimentally verified utilizing the cubic etch figures of aluminum. Elevations in the range 0.1–2μ can be determined to within 10 percent and frequently with greater accuracy. A new cartridge for obtaining stereo micrographs at an angle of 10° is described and thicknesses as small as 150±50A are measured using this cartridge. Examples of the use of stereo micrographs are given illustrating different orientations of pearlite in steel and the scratches on a polished steel surface. Elevation changes of 200A and less can be measured in the silica replica of the polished surface. The theoretical resolution of the stereo method is given by xmin=ω/2 sin σ,where ω is the resolution normal to the optic axis and σ is the stereo angle.
The Formation of Bubbles
Authors: Dean Robert B.
Published: January 2005

Extreme values for the negative pressures and the degrees of superheat which water will withstand without forming bubbles are contrasted with the ease of forming bubbles by vibration or by the turbulent flow of liquids. The subject of bubble nuclei is briefly reviewed, and it is pointed out that such nuclei usually function by virtue of sorbed or trapped air which can be removed, rendering the nuclei ineffective. Technique for avoiding extraneous bubble nuclei is presented with some experiments on the formation of bubbles by mechanical action. It is pointed out that free vortices in liquids produce sufficient tension to rupture the liquid, and it is suggested that mechanical disturbance produces bubbles only in such vortices and not by general pressure lowering in sound waves.
Measurements of the Adhesion Component in Friction by Means of Radioactive Indicators
Authors: Sakmann B. W. , Burwell J. T. , Irvine J. W.
Published: January 2005

In friction experiments material is exchanged between the sliding surfaces. A study of this transfer of material was made possible by the development of a radioactive tracer method by means of which one could detect quantities of metal as small as 10−4 microgram. Spherical or hemispherical specimens were slid over an activated base surface. After the friction experiments, the riders were tested for the presence of radioactive material, and the quantity of metal deposited on the rider was determined as a function of various parameters. A copper-beryllium base surface was used for all measurements reported here. For the materials investigated it was found that the amount of base metal adhering to the rider was proportional to the load and increased with the distance of travel. Under otherwise identical conditions the amount of base metal deposited on the rider depended on surface finish and hardness of the rider. If the rider was harder than the base, the transferred material increased with surface roughness. If, on the other hand, the rider was softer than the base, surface finish was found to be of secondary importance. Measurements made with steel specimens showed that the amount of metal deposited on them was inversely proportional to their Brinell hardness. For riders of different materials, but having the same hardness and surface finish, the amount of transferred metal increased with the solid solubility of the base metal in that of the rider. Lubrication decreased the transfer; the reduction depended on load and, for the same load, on the material of the rider. The influence of lubrication was greater for smaller loads.
An X-Ray Study of the Copper-Manganese Binary Alloy System
Authors: Ellsworth L. D. , Blake F. C.
Published: January 2005

The powder method of x-ray analysis has been applied to a series of slowly cooled copper-manganese alloys to ascertain whether anomalous physical effects of these alloys, detected by the Metallurgical Division of the United States Bureau of Mines, may be ascribed to the presence of superstructures. The x-ray analysis does not indicate superstructures, but it presents results quite different from those one would expect from examination of the accepted equilibrium diagram of the copper-manganese binary alloy system. Slowly cooled and annealed samples both give identical results; namely, that copper enters into a continuous series of solid solutions with manganese, crystallizing in a face-centered cubic lattice with a gradually increasing parameter as the manganese content is increased from zero to sixty percent. Above sixty percent manganese, and up to ninety percent manganese, the lattice is face-centered tetragonal. Between ninety and one hundred percent manganese, two phases are present, one phase being the solid solution phase corresponding to an alloy with ninety percent manganese, the other phase being that of alpha-manganese.
The Directional Characteristic of a Half-Wave Doublet Goniometer
Authors: Dwyer Robert J.
Published: January 2005

The directional characteristic of a goniometer using two half-wave doublet antennas mounted at right angles is derived. It is shown that, unlike the double loop goniometer, the directional characteristic is not identical with that of a single half-wave doublet that can be rotated, although the variation from such a case is very small.
Transmission Line Theory Applied to Wave Guides and Cavity Resonators. I
Authors: Middleton David , King Ronold
Published: January 2005

In Part I circuits consisting of hollow metal wave guides of arbitrary cross section are analyzed in terms of scalar and vector potential and stream functions in a form representing a generalization of the treatment of the conventional lines given by R. King. Completely hyperbolic solutions analogous to those given in the usual theory are obtained for the E and H modes; these yield general relations for the stream and potential distributions. Terminal, input, and characteristic impedances are defined for the wave guide or cavity resonator. The propagation constant is discussed, and it is demonstrated that the attenuation (constant) due to the imperfect metal walls of the pipe and the dielectrics in the guide are additive if the materials have low loss. The characteristic impedances for the two types of mode are considered, and general formulae for the practical conditions of operation are included. The analogy between this theory and that of the conventional line is discussed, and it is pointed out that the physical interpretations of results formally identical in the two cases are equivalent for a given mode and a particular cross section of pipe. The analogy breaks down, however, when one attempts to treat different modes and guides of different transverse dimensions at the same time, for example, in the problem of impedance matching. One advantage of the theory is that experimentally meaningful results may be obtained for general terminations which ordinarily cannot be handled analytically.
Transmission Line Theory Applied to Wave Guides and Cavity Resonators. II
Authors: Middleton David
Published: January 2005

In Part II a number of practical applications of the theory outlined in Part I are considered. Formulae for power transfer, efficiency of transmission, standing wave ratios, and insulating disks are given, and the experimental determination of the line and terminal parameters is treated briefly. A number of examples illustrating the theory are discussed: (1) a rectangular wave guide terminated by a section of pipe containing a horizontal slit at one end and a flat horn of 45° aperture at the other, (2) the same guide terminated by a section of tube with a horizontal slit at one end and opening into space at the other, (3) the rectangular guide with a variable horizontal and vertical slit, in either case followed by a closed quarter-wave section of pipe, (4) a closed cylindrical tube containing several transverse slabs of imperfect dielectric material. In (1)-(3) the terminal functions ρ and φ are determined experimentally, and in (4) analytical expressions for the terminal and input impedance are obtained. Experimental and theoretical curves illustrating the examples are included.
Further Studies of the Infra-Red Absorption of Rubber
Authors: Williams Dudley , Dale Brock
Published: January 2005

The transmission spectrum of natural rubber has been studied in the region between 1μ and 15μ and the effects of linear and radial stretch have been observed. Linear extension greater than 400 percent of the original length produces an increase in the C–C vibrational frequency. Both linear and radial stretch produce an increase in absorption coefficient and a decrease in reflection coefficient. The changes in absorption and reflection coefficients are greatest at short wave-lengths.
A Numerical Method in the Theory of Vibrating Bodies
Authors: Vazsonyi Andrew
Published: January 2005

In this paper a numerical method is presented for the determination of the characteristic numbers and modes of vibrating (conservative) systems. The method for continuous bodies is based on a finite difference approximation and is a ``relaxation method'' in the same sense as the term is used by R. V. Southwell. No claim is made of theoretical advancement in the subject; the paper purports to present a thoroughly practical method of obtaining numerical answers speedily. Detailed computations are carried out for the transverse vibrations of a quadrangular elastic membrane. The nature of the method is such that it can be easily extended to other vibrating systems of finite or infinite number of degrees of freedom. It is to be emphasized that the quadrangular shape is just a simple example; the real strength of the method lies in the fact that numerical results can be obtained for bodies with more complicated and irregular boundaries.
Single- and Double-Stub Impedance Matching
Authors: Wing Alexander H. , Eisenstein Julian
Published: January 2005

Single- and double-stub impedance matching on transmission-line feeders are described. Formulae determining the position and the length of a single matching stub for any load impedance or any observed standing-wave voltage distribution are derived, neglecting losses in the matching sections. Conditions for minimum length of stub and minimum distance between load and stub are specified. For the double-stub arrangement, expressions for the lengths of and distance between stubs are derived for any possible combination of load and distance between stubs. A double-stub tuner with any fixed distance between stubs cannot match all loads to the feeder, and the limits are specified. The optimum location on the feeder of the double-stub tuner is discussed. A graphical method employing a circle diagram for computing the lengths and position of the stubs is explained. The graphical determination of the stub lengths of the double-stub tuner is facilitated by auxiliary circular loci which also indicate the range of admittances over which an impedance match may be effected.
The American Institute of Physics Building. II. An Architectural Study of the Building
Authors: Arnaud Blanchette
Published: January 2005

IN the October, 1943 issue of this Journal, an early history of the new American Institute of Physics building was published which created widespread interest and favorable comment. Further articles were promised so that physicists could become better acquainted with their new headquarters. A second article of this series, one devoted to the architectural features of the house is presented below.-The Editor.
Forced Torsional Oscillations of an Elastic Halfhyphen;Space. II
Authors: Sagoci H. F.
Published: January 2005

In this paper a study is made of the forced torsional oscillations of an elastic half-space, the physical constants of which are assumed to be known, under the action of a rigid circular disk oscillating periodically about an axis through its center. A method is also given for the determination of the shear modulus of the half-space through a study of its torsional oscillations.
Torsional Vibration of Multi-Disk Systems
Authors: Fisher Edward
Published: January 2005

An asymptotic method is given for computing the lowest frequencies of multi-disk systems having a large number of disks. It is based on the assumption that the frequency to be computed can be represented approximately by a descending series in the disk number and that the form of the leading term of this series can be obtained by inspection of the frequency equation. The method is tried out on three examples, all six-cylinder Diesel engines.
Studies with the Electron Microscope Diffraction Adapter
Authors: Picard Robert G.
Published: January 2005

The RCA diffraction adapter for its electron microscopes uses a weak magnetic lens to focus the diffraction patterns. The accuracy of the results obtained in electron diffraction analysis with such a system is discussed, and it is shown that lattice spacings may be determined with an accuracy of one percent if reasonable precautions are observed in calibration and operation of the instrument. A method is also described for measuring the accelerating voltage of the electrons from data obtained from the diffraction pattern. Electron diffraction patterns are shown of a number of thin film materials which are commonly used as specimen supports in electron diffraction analyses and electron microscopy. The effects of aging and beam exposure on the patterns produced by these films are determined.
Theory of Filler Reinforcement
Authors: Guth Eugene
Published: January 2005

For small loadings (up to about 10 percent volume parts) the colloidal carbon black spheres may be considered as suspended in a continuous rubber matrix. In the present paper this model is generalized for ellipsoidal (including plate- and rod-like) filler particles and it is extended to the computation of various properties of the suspension in terms of the properties of the matrix and of the fillers. Viscosity, Young's modulus, stress-strain curve below crystallization, and dielectric constant of the suspension are derived as linear functions of the volume concentration for small, and as quadratic functions for higher loadings. The stress-strain curves for varying amounts of fillers are similar. For small loadings the tensile strength first decreases because of the stress concentrations occurring around the carbon black spheres when the samples are stretched. The increase of the tensile strength observed for greater loadings is caused by the tendency of the carbon black spheres to form chains and finally, a type of network. The stiffness increases with loading, up to the point where the suspension becomes a dilution of carbon black by rubber. There the tensile strength decreases too. Binding of rubber by carbon black is similar to solvation. The theoretical conclusions were checked experimentally, in particular, the dependence of Young's modulus on concentration, the similarity of stress-strain curves, and the decrease of the tensile strength for small loadings. The theory of the elastic properties is very similar to the theory of Einstein on the viscosity of colloidal solutions and to Maxwell's and Rayleigh's theory of dielectric properties.
The Thermodynamics of Rubber at Small Extensions
Authors: Elliott D. R. , Lippmann S. A.
Published: January 2005

On analyzing their own data, Meyer and Ferri have concluded that at small extensions, rubber is an ideal elastomer according to the definition that (∂E/∂L)P,T=0. Further analysis of Meyer and Ferri's data does not sustain their conclusion. If, however, (∂E/∂L)V,T=0 is taken as a new criterion for an ideal elastomer, Meyer and Ferri's data do indicate that rubber is ideal, at least for extensions up to 166 percent. The new criterion implies that the valence angles do not store an appreciable amount of energy when the rubber is stretched. However, both the molecular orientation and the interatomic displacements do influence the energy required for extension.
The Magnetic Permeability of Iron Wires at Radiofrequencies
Authors: Smith Alva W. , Dickey F. P. , Foor S. W.
Published: January 2005

The magnetic permeability of iron wires of selected diameters is measured at fields of low intensity and at frequencies corresponding to wave-lengths from 54 to 1150 meters. The observed permeabilities decrease with increase in frequency and increase of wire size. The results do not confirm the existence of an anomalous dispersion of permeability previously reported by some investigators.
The Basic Principles of Semi-Conductors
Authors: Seitz Frederick
Published: January 2005

A review is given of typical deviations from ordinary valence rules by alloys and inorganic compounds. The effect on the electrical properties of a compound of a deviation from stoichiometric proportions is discussed. The value of the information obtained from electrical measurements is illustrated by a discussion of the properties of several semi-conducting compounds.
The Electrical Properties of Semi-Conductors
Authors: Maurer Robert J.
Published: January 2005

The electrical properties of semi-conductors are briefly reviewed. The information concerning the structure of these materials which is obtained by electrical measurements is discussed. The most important of the physical-chemical methods available for the investigation of deviations from stoichiometric proportions in semi-conducting compounds are illustrated by a discussion of several typical examples.
On the Representation of Rigid Rotations
Authors: Schwerdtfeger H.
Published: January 2005

This expository article gives a straight-forward derivation of the classical representation formulas of the three-dimensional rotation group in explicit (non-symbolical) form starting with the most elementary representation of a rotation by a linear homogeneous transformation with a proper orthogonal matrix. Apart from Euler's formula (3.4) (which is taken as starting point in Benedikt's previous paper on the same subject) other representations often used in mechanics and physics are derived and the various connections existing between these formulas are established hereby going beyond Benedikt's paper by taking into account the simplest spin representations of the rotation group. The spin representation by the special unitary group is derived in two ways; the second method (Section 6) is based on a general fact (in italics) which seems not to be generally known. In the footnotes some references to the literature are given.
A 100-Million Volt Induction Electron Accelerator
Authors: Westendorp W. F. , Charlton E. E.
Published: January 2005

The plan and construction of a device capable of accelerating electrons to energies as high as 100 million electron volts are described together with the special building to house it. A more detailed description of the device and its construction will appear in the General Electric Review. The accelerator has a pole face 76 inches in diameter, weighs 130 tons, and operates on 60-cycle current requiring at full load 200 kilowatts. The machine is air cooled and is capable of continuous operation at full voltage. The toroidal glass vacuum tube of oval section has an external diameter of 74 inches and consists of 16 sectors cemented together. At 100 million volts the x-ray output, measured in a thick-walled (¼ inch lead) ionization chamber, is 2600 Roentgens per minute at one meter target-thimble distance and the half-value width of the x-ray beam is 2.0 degrees. The penetrating power of the x-rays in iron at various voltages has been measured and the radiographic possibilities studied.
Thermal Expansion and Second-Order Transition Effects in High Polymers: PART II. Theory
Authors: Boyer R. F. , Spencer R. S.
Published: January 2005

The nature of the thermal expansion anomaly in high polymers, known as the second-order transition, is examined in some detail. It is suggested that below the transition temperature, Tm, polymer chains can expand sidewards but not parallel to their length. At Tm lengthwise expansion becomes prominent, thus accounting for the sudden increase in thermal expansion. Experimental results are presented showing the anisotropic expansion of oriented polymers below Tm. The transition effect is then treated as a problem in viscous flow, which gives rise to various semi-empirical plots connecting Tm with applied forces, plasticizer content, and time effects. The brittle point, Tb, involves highly elastic deformation, and is shown to be a fundamentally different test, although Tm and Tb are sometimes numerically equal. Various factors influencing the brittle point are reviewed briefly.
A Method of Measuring the Radiofrequency Resistance of Wires
Authors: Stewart Chandler
Published: January 2005

A new and relatively simple method of measuring the resistance of wires at frequencies between about 200 kilocycles and about 40 megacycles is described. By this method, the test specimen is strung down the center of a metal pipe about ten to a hundred feet in length, depending upon the test frequency, to form a transmission line. One end of the line is short circuited and the other connected to a standard commercial Q-meter. Readings are taken from the Q-meter and applied to curves to obtain the desired resistance. This method of measurement appears to be more reliable than the use of coils, and the results agree closely with calculations by skin-effect formulas. For round wires known to consist of homogeneous material, calculated values of radiofrequency resistance appear to be just as reliable and accurate as experimental values, and are much more easily obtained.
Molecular Weight Studies on High Polymers with the Electron Microscope
Authors: Boyer R. F. , Heidenreich R. D.
Published: January 2005

Some preliminary results are reported on measurements of molecular weight distributions for polychlorostyrene. The following technique of isolating single polymer molecules is used: A precipitating agent, such as propanol, is added to a very dilute (1 ppm) solution of the polymer in benzene, presumably causing the molecules to coil up. Drops of this mixture are evaporated on a silica screen and examined in the microscope. Circular particles ranging in diameter from 15A to 500A and believed to represent single polymer molecules have been obtained on various polymers. The relationship between measured particle diameter and molecular weight is reviewed in some detail. The data appear to favor the concept of a random coil to the extent that particle diameter varies as the square root of the molecular weight. The molecular weight distribution curves obtained are of the expected shape and extent, although the average molecular weights computed from the distribution curves are 4–5 times greater than values measured by an independent method. Finally, the role of electrical charges in stabilizing isolated polymer molecules is discussed.
Conversion Diagrams for Triode Tube Mixers
Authors: Stockman Harry
Published: January 2005

The theory of the frequency conversion diagram has previously been presented in this journal. The research work is now extended to include triode tubes, and it is shown in the following that the conversion diagram provides a suitable method of treatment of non-linear mixers with more than two electrodes. Actually, the greater the number of variables, and the greater the difficulties in a mathematical analysis, the more important becomes this method of obtaining frequency conversion data. A brief description of the measurement equipment is given in the text and typical diagrams and derived curves are shown.
Crucible Failure in the Induction Melting Process
Authors: Gemant Andrew , Sticher Joseph
Published: January 2005

Experience shows that in the course of the induction melting process occasional local overheating of the crucible takes place, which in extreme cases leads to perforation of the latter. An explanation of this occurrence is presented on the basis that it is essentially a phenomenon of thermal instability. The theory shows that overheating of the crucible is more probable the steeper the electrical resistivity—temperature characteristic of the crucible material, a condition brought about by impurities present. Numerical computations, showing the transition from stable to unstable operating conditions, are carried out for a small experimental and a large industrial furnace. The equations developed show how the various operating conditions, particularly the frequency of the current in the coil, have to be selected in order to insure operation in the stable region.
Rigorous Treatment of the Electrostatic Immersion Lens Whose Axial Potential Distribution Is Given by: φ(z)=φ0eKarctanz
Authors: Hutter R.G.E.
Published: January 2005

Investigations have shown that the electrostatic immersion lens, given by the axial potential distribution φ(z)=φ0 exp(K arctan z), is the simplest electrostatic lens for which Newton's image equations are satisfied throughout the field. The general solution of the paraxial ray differential equation is derived. Based on this solution and the fact that Newton's image equations are satisfied, exact expressions are derived for all important optical quantities such as the focal lengths, the location of the four cardinal points, magnification, the object-image relation, and the spherical and chromatic aberration for any object position. The optimum positions of an object are determined so that the chromatic and spherical aberrations are reduced to a minimum. All quantities are represented graphically. A plot of the equipotential lines in space is given for a special value of the voltage ratio.
The Methods of Specifying the Properties of Viscoelastic Materials
Authors: Alfrey Turner , Doty Paul
Published: January 2005

Seven methods (Voigt model, Maxwell model, operator equation, mechanical impedance function, creep curve, relaxation curve, and dynamic modulus function) of specifying viscoelastic behavior are discussed. A number of exact relations between these methods of specification are worked out in detail. The majority of these relations are simple enough to be of practical value although a few are too cumbersome. Approximate relationships between the creep curve, the relaxation curve, Maxwell model, and Voigt model are discussed; and numerical examples show the magnitude of errors introduced by the approximation to be small even in quite unfavorable cases. A consideration of the practical utility and physical meaning of the various methods of specification distinguishes between (1) those of general descriptive value and those of direct experimental value; (2) those useful in a phenomenological study of mechanical behavior and those more suited to a formulation of molecular theory. A summary of the present molecular theories is presented together with their interpretation in terms of the Voigt and Maxwell specifications.
A Double-Yoke Plate Permeameter
Authors: Brown William F. , Rubens Sidney M.
Published: January 2005

A double-yoke permeameter, with which both normal and ideal permeabilities of moderately large steel plates can be measured, is described. The technique for making these measurements is also given. The permeameter is suitable for measuring plates several feet long, up to a foot wide, and from ⅛″ to 1½″ thick; two approximately identical test plates are required.
An Electron Diffraction Camera for the Study of High Temperature Surface Reactions
Authors: Gulbransen Earl A.
Published: January 2005

An electron diffraction camera is described for the study of physical and chemical reactions occurring on the surfaces of metals and alloys in situ at elevated temperatures. The specimen is mounted in a metal block and shielded from the surrounding cold surfaces by a series of metal shields. The metal block contains an internal electrical heater which allows the temperature of the specimen to be accurately controlled at temperatures of 800°C. Gas purification chains are included for the preparation of pure oxygen, hydrogen, etc. Several typical electron diffraction reflection studies of the oxidation of iron and stainless steel are included.
Virtual Masses of Rectangular Plates and Parallelepipeds in Water
Authors: Yu Yee-Tak
Published: January 2005

The following is a report on experimental results obtained for the virtual masses of thin rectangular plates and rectangular parallelepipeds moving in water. Experimental data, together with an empirical equation, showing the manner in which the virtual mass of a rectangular plate varies with dimensions and direction of motion are given. Data and an empirical equation giving the virtual mass of a rectangular parallelepiped as a function of dimensions and direction of motion, for the special case in which the motion is parallel to one face, are also listed.
Electron Microscopical Replica Techniques for the Study of Organic Surfaces
Authors: Barnes R. Bowling , Burton Charles J. , Scott Robert G.
Published: January 2005

The problem of examining opaque surfaces in the electron microscope is discussed and it is shown that none of the methods heretofore described is completely satisfactory for the examination of organic surfaces. Two new methods, a low pressure polystyrene-silica technique and a silver-silica double evaporation method, are described and it is demonstrated that they allow observation of organic as well as metallurgical surfaces. Electron micrographs of fiber surfaces, biological material, paint films, ores, and metals are included to illustrate the utility of these techniques.