bluuebunny/crossref_metadata_2025 huggingface dataset:
A Model Method of Photographic and Photometric Determination of Heat Radiation Between Surfaces and Through Absorbing Gases
Authors: Jakob Max , Hawkins G. A.
Published: January 2005

Straight analytic determination of the heat exchange by radiation in a device is possible only if the emitting and absorbing surfaces are very simple in shape and configuration. In most practical cases, and particularly if the radiation is partly absorbed on its way by gases, approximative calculations and graphical methods have been used in order to evade the mathematical difficulties. In the present paper an experimental model method with the following characteristic features is described. A model, similar to the device under investigation, is constructed. Light is used instead of the long wave heat radiation, and its absorption by photographic films which cover the surfaces of the model, is measured by the methods of photometry. The case of gases which absorb heat radiation is imitated by using liquids which absorb light rays. The application of the method to radiation through a non-absorbing medium is shown by experiments on a tube bank model. The adaption of the method to heat radiation through absorbing gases is demonstrated by photos of the spectrum of a special combination of light filter, absorbing liquid, and photographic film which are in tune in a narrow wave-length range.
Diffusion of Heat Through a Rectangular Bar and the Cooling and Insulating Effect of Fins. I. The Steady State
Authors: Avrami Melvin , Little J. B.
Published: January 2005

Exact solutions for temperature distribution and heat flow through a rectangular fin are rederived in more general and simple form than previously given. These are studied numerically and graphically and shown to yield new results not contained in the approximate formulas hitherto used. Except for the factor of thermal conductivity of the fin material, the cooling effect is a function only of the height-width ratio β of the fin, and of a dimensionless ``relative boundary resistivity'' μ governing the heat loss to the environment. It is shown that, for any value of this boundary resistivity, there is a fairly sharp optimum value of the height-width ratio beyond which further increase in height will not lead to much improvement in cooling effect. This optimum β decreases with decreasing μ until, at a certain critical value μ* in the neighborhood of 1, it becomes zero. At the critical μ*, the cooling effect is altogether independent of β, and the presence of the fin is a matter of indifference. Below μ*, the cooling effect decreases with increasing β, so that the presence of the fin serves merely to insulate the hot plate. This analysis of a single fin is the basis upon which a study of the conditions for optimal cooling by an array of fins will be carried out in a subsequent publication.
Frictional Phenomena. IX
Authors: Gemant Andrew
Published: January 2005

THIS chapter deals with: (1) mechanical processes involving viscosity, particularly (a) impregnation, (b) breathing, (c) oil migration with respect to high voltage cables; (2) chemical processes involving viscosity, such as (a) Voltol process, (b) wax formation in cables, (c) polymerization of styrene; (3) electrical conductivity. With regard to the latter, the fundamental quantities, besides viscosity, that determine the conductivity are discussed, together with the various experimental methods whose interpretation allows the quantities in question to be computed.
On the State of Stress in Thick Bars
Authors: Frocht M. M. , Leven M. M.
Published: January 2005

The view is now generally held that in bars containing circular holes or other discontinuities the state of stress ceases to be two-dimensional when the ratio of the radius of the hole r to the thickness of the bar t is less than unity. It is further believed that the factor of stress concentration in thick bars is materially smaller than in thin bars. This view also forms the basis for the doubts which have arisen regarding the reliability of certain theoretical work on stress concentrations produced by very small holes. In this paper results are reported from a photoelastic investigation using both elastic and frozen (see reference 4, Chapter 10) stress patterns and showing that the present point of view is erroneous. Experimental results show that no deviation from a state of plane stress can be found in bars with central circular holes when r/t is of the order of magnitude of about ¼ instead of unity. Experiments further show that the factors of stress concentration remain essentially the same in thick as in thin bars. The present work may also be taken as experimental corroboration of the theoretical value for the factor of stress concentration obtained by Neuber for a very small hole in a bar in tension or compression.
Measurement of the Initial Inner Permeability of Iron over a Wide Radiofrequency Range
Authors: Woods Robert W.
Published: January 2005

Previous investigations on the variation with frequency of the initial inner permeability μL of iron reveals great disparity of results. In this experiment certain refinements of technique and of analysis have been introduced which make the accuracy adequate for comparison with theory. The method used was to determine the change in resonant frequency of a coil and condenser combination caused by insertion of a permeable sample in the field of the coil. This change in frequency is interpreted as being caused by change of flux through the coil. The same iron wire had been measured previously over a different frequency range by other men working in this laboratory. The value of μL was found to be ∼60 over the frequency range from 30 kc to 40 mc showing no dispersion region between these limits. Results of this method are compared with those of other methods.
Demagnetizing Factors of Rods
Authors: Bozorth R. M. , Chapin D. M.
Published: January 2005

A chart is constructed for converting the apparent magnetic permeability to the true permeability of cylinders of any given ratio of length to diameter. The curves are based on previous calculations in which account was taken of the variation of the demagnetizing factor N with permeability, but in which the permeability was assumed constant over any one cylinder. The flux distribution has been determined experimentally in several cylinders, and as the field acting on the specimen is increased from zero, the positions of the effective poles have been found to move toward the middle of the rod until (if the permeability is sufficiently high) they are located about 0.7 of the distance from the middle to the ends, and then to move toward and approach the ends as limits as the permeability declines in high fields.
The Electrical Oscillations of a Perfectly Conducting Prolate Spheroid
Authors: Ryder Robert M.
Published: January 2005

The forced oscillations of a perfectly-conducting prolate spheroid of eccentricity nearly unity are shown to be decomposable into ``harmonics'' corresponding to different modes of vibration, each harmonic being quantitatively connected with a certain portion of the impressed electric field which drives the antenna. The harmonics contribute additively to the current and field of the spheroid; each offers a characteristic impedance to the driving field, and the properties of the antenna are a composite depending upon the proportions of the various harmonics present. The behavior of the harmonics with frequency is discussed qualitatatively; analytical expressions obtained are useful chiefly at the resonant frequencies of the antenna, where the most important harmonic becomes sinusoidal in character.
Frictional Phenomena. X
Authors: Gemant Andrew
Published: January 2005

THE application of the viscosity concept to this technically important field is presented. Discussed first is film lubrication which occurs when the film thickness is greater than 10−5 cm. This mechanism is chiefly controlled by the viscosity η of the liquid. The basic mathematical theory is developed, and it is shown how this adequately describes the experimental facts. Next boundary lubrication is discussed, a type occurring with stable layers less than 10−5 cm thick. This mechanism is essentially a plastic flow within the boundary layer. The chief experimental data are described together with their technical implications.
An X-Ray Study of Carbon Black
Authors: Biscoe J. , Warren B. E.
Published: January 2005

X-ray studies have been made of a number of carbon blacks, prepared under different conditions, and subject to various heat treatments. The patterns were made in evacuated cameras, using Cu Kα radiation monochromated by reflection from rocksalt. The patterns consist of crystalline reflections (00l), and two-dimensional lattice reflections (hk). The structure is one of true graphite layers arranged roughly parallel and equidistant, but otherwise completely random. The dimensions within a layer are the same as in graphite; the layer separation is somewhat larger than in graphite. The effect of heat treatment is to increase the size of the parallel layer groups. At graphitization the material changes discontinuously to the crystalline graphite structure. The usual carbon black is not finely divided graphite. Small angle scattering studies indicate the existence of clusters a few hundred angstroms in size. It is these clusters which are measured by microscope counts, by the electron microscope, and by surface areas, rather than the much smaller parallel layer groups.
The Cause of High Voltage Surges in Rectifier Circuits
Authors: Hull Albert W. , Elder Frank R.
Published: January 2005

It is shown that high voltage surges are produced in apparatus associated with gas discharge devices when, and only when, the demand for current exceeds the current-carrying capacity of the gas (or vapor). Cathode spot extinction and sputtering of hot cathodes cause only slight disturbances which do not produce high voltage in practical circuits. Experimental data on surge limits, i.e., the maximum currents that can be carried without surges, are given for four types of mercury vapor tube. These data lead to a single set of values of maximum current density as a function of vapor pressure, which may be used for the safe design of apparatus.
Eddy Current Type Flaw Detectors for Non-Magnetic Metals
Authors: Vigness Irwin , Dinger J. E. , Gunn Ross
Published: January 2005

New developments in an eddy current type flaw detector are discussed. Several types of pick-up units, which contain the exciting coils for inducing eddy currents in the test material and pick-up coils for detecting changes in this eddy current pattern when a flaw is approached, are described. The electric power for the exciting current is supplied by a vacuum tube power oscillator at a frequency of 500 or 1000 cycles/second. The circuit for detecting the changes in the eddy current pattern employs vacuum tube bridge circuits sensitive to both amplitude and phase changes. The use of jigs to guide the pick-up unit, automatic scanning, and automatic recording is discussed.
The Vector Potential and Inductance of a Circuit Comprising Linear Conductors of Different Permeability
Authors: Higgins Thomas James
Published: January 2005

Formulas are derived for the vector potential and inductance of a circuit comprised of a long linear cylinder enveloped by a return conductor of eccentric-annular cross section, the two cylinders and the surrounding medium each being of different permeability. The restriction to very long cylinders rendering the problem two-dimensional, a familiar scheme of analysis can be employed. A plane cross section is mapped conformally on a rectangle of infinite length and of breadth 2π, the perimeters of the conductors going over into line segments parallel to the short sides. In each of the three resulting rectangular regions of different permeability the vector potential A is expressed as a sum of appropriate infinite double series of trigonometric functions with constant coefficients, these latter being determined in accordance with the known boundary conditions—continuity of the normal component of induction and of the tangential component of field intensity on the perimeters of the conductors. The magnetic field energy is obtained by evaluating W=½∫SwAdS; whence the inductance follows from W=½LI2. The resulting expression for the inductance yields known formulas for certain special cases of the general problem, thus verifying the analysis. As the symbol for the vector potential is capable of physical reinterpretation as temperature, the foregoing analysis also furnishes solutions to certain heat problems of technical interest.
An Improved X-Ray Tube for Diffraction Analysis
Authors: Machlett R. R.
Published: January 2005

A new x-ray tube for diffraction analysis has been produced which affords much greater x-ray beam intensity than has been possible with previous designs. In addition the purity of the x-ray spectrum is insured. The new tube employs thin sheets of malleable beryllium, produced by additions of minute amounts of titanium, for windows in the metal tube wall. The low inherent absorption of such windows and their electrical and mechanical sturdiness are factors in the improvement in beam intensity. A shockproof form of the new diffraction analysis tube is also described.
Rubber in Vibration
Authors: Gehman S. D.
Published: January 2005

A machine is described which has been used for determining the vibration properties of various types of rubber mountings used for the isolation of mechanical vibrations. The vibrations are excited by oppositely rotating eccentric weights and are recorded on a tape. It was found that resonance curves for various types of rubber vibrations such as shear, torsion, and compression are, except for some minor deviations, adequately accounted for by the equation which contains a damping term proportional to the velocity and inversely proportional to the frequency. The apparent static modulus of rubber in compression depends upon the shape of the piece, more explicitly, on the ratio of load area to the free area. The same is true for the dynamic modulus. It was found that pieces of similar shape have identical values for the dynamic modulus and also for the internal friction. Some curves are given showing the dependence of dynamic modulus and internal friction on the shape factor. The dynamic stiffness shows the largest deviation from the static values at high shape factors. The internal friction has a linear relationship to the dynamic modulus when the shape factor is varied. This results in damping which is practically independent of the shape. The effect of temperature on the vibration properties of mounting stocks for a range −10°F to 160°F was studied and curves are included showing the temperature dependence in this range.
Surface Replicas for Use in the Electron Microscope
Authors: Schaefer Vincent J. , Harker David
Published: January 2005

A simple method is described for making replicas of surfaces for study in the electron microscope. The surface to be studied is cleaned and then coated with a very thin slightly wedge-shaped film of polyvinyl formal having a range in thickness from about 500 to 750A in 2.5 cm. This film is formed by dipping the prepared surface into a 0.5-percent solution of the resin dissolved in dioxane or ethylene dichloride and permitting the solvent to evaporate while the surface is held in a vertical position. The replica film is removed by placing the coated surface under water and peeling the film from it. A description of this technique is given in detail. A graph is presented which shows the thickness of resin films obtainable from various concentrations of resin in dioxane, and a table gives the interference effects which may be used for determining approximate thicknesses of thin resin films. Several easy procedures are described for checking the thickness of such films. A technique is described for preparing strong films having a thickness of 100A and an area of 3 cm2 when mounted in air. Such films are very useful when working with the electron microscope and several methods are described for mounting specimens on them, including a conditioning treatment—useful in mounting water suspensions—which makes one surface very hydrophilic. Five micrographs show the results obtainable with the techniques described.
The Matrix Theory of Torsional Oscillations
Authors: Pipes Louis A.
Published: January 2005

The general case of vibration of a shaft with several rotating masses is discussed. The analysis is reduced to a simple matrix multiplication of second-order matrices and the natural frequencies of symmetrical systems are discussed. The connection of the matrix method and the well-known Holzer method of computing the natural frequencies of torsional oscillations is considered. The analysis of geared systems and continuous shafts is discussed.
The Mechanism of the Electric Spark
Authors: Zeleny John
Published: January 2005

Meek's criterion for the formation of a spark discharge in a gas is criticized. An error in the derivation of his formula for the radial field about an electron avalanche channel is noted, and the value adopted for this field is shown to be too small to draw the postulated number of electrons into the channel from the space outside. The importance attached to the radial field is found to be misplaced because of the above and because a criterion based solely on the total number of ions produced in an avalanche gives results for sparking potentials for different spark lengths and for a gas at different pressures in agreement with those obtained by Meek's method. Both methods give results which, using the values assigned to the constants, fall more and more below the experimental values of the sparking potentials as the length of the spark gap, δ, is increased until at 20 cm the deviation is over 7 percent. To bring the computed value for δ=20 cm into agreement with the experimental value the constants in the equations would have to be increased by a factor 2×1016 over the values which give agreement between formulas and experiment for δ=1 cm. The dominant exponential term in each formula is based on the incorrect assumption that the field is not affected by the space charges in the avalanche. That a large amount of ionization, postulated by Loeb and Meek, is produced by a high potential wave which travels through the channel as soon as the positive streamer reaches the cathode is questioned because the fields found in such waves are too small to produce ionization by electron collision in air at atmospheric pressure.
The Photographic Action of Electrons in the Range Between 40 and 212 Kilovolts
Authors: Baker R. F. , Ramberg E. G. , Hillier J.
Published: January 2005

The Hurter and Driffield curves and the absolute sensitivities of Eastman medium lantern slide plates are determined for electrons accelerated through differences of potential from 40 to 212 kilovolts. Within experimental error the H and D curves are identical in shape for the different voltages. The sensitivity reaches a peak near 100 kv and then drops off rapidly. This phenomenon may be utilized to increase the effective sensitivity of plates at high voltages by applying a thin, high density intensifying screen to the surface of the emulsion.
The Torsion of a Prism with Cross Section the Inverse of an Ellipse
Authors: Higgins Thomas James
Published: January 2005

Saint-Venant's torsion problem is solved for the linear prism with right cross section bounded by the curve, an inverse of an ellipse with respect to its center. By a method developed recently by R. M. Morris, explicit formulas are obtained for the torsion, conjugate torsion, and complex torsion functions; for the twisting moment; for the stress function and the components of shearing stress. This work is of interest as complementing recent work by A. C. Stevenson and by D. L. Holl and D. H. Rock; further, as an addition to the very few exact solutions that have been effected for cross sections bounded by single, closed, continuous, partially concave curves.
Theory of Vehicle Suspensions
Authors: Mercier Pierre Ernest
Published: January 2005

The present theory of the suspension of vehicles is established on the assumption of perfect symmetry and of a linear dependence between elastic forces and the displacements of the wheels and deflections of the tires. The path of the vehicle rolling on uneven ground is supposed nearly straight, but no other important limitations are made in the fundamental hypothesis, so that the results cover any kind of suspension. The relative magnitude of the seven vibrations corresponding to bobbing, rolling, and pitching motions of the body, and to the four specific vibrations of the wheels, are discussed in view of their combined effects on the displacements of the body of the car. The general conclusion, which attempts to separate as much as possible the respective frequencies to avoid beats and also directly to improve comfort, is in accord with several practical experiments made in the industrial field.
Calculation of Axially Symmetric Fields
Authors: Bertram Sidney
Published: January 2005

A practical method is developed for calculating the distribution of scalar fields in axially symmetric systems. To obtain a complete solution a knowledge of the potential distribution along a cylinder of constant radius is required; in many cases the distribution along the cylinder can be estimated with sufficient accuracy by an inspection of the electrode configuration. The solution is first obtained in the form of an integral. This is evaluated for the class of boundary potential functions of the form Vn(1, z)=zn,z>00,z<0.In this expression, Vn(1, z) is the potential along a cylinder of unit radius, z is measured along the axis of the cylinder, and n is a positive integer (zero included). Numerical values are given in tabular form for the cases n=0, 1, 2 and 3. It is then shown how the solution for the above boundary potential functions can be used to obtain the solution for an arbitrary distribution of potential along a cylinder of constant radius. In particular, the potential distribution of a simple electron lens consisting of two coaxial cylindrical electrodes of equal diameters is expressed in terms of the tabulated functions. The calculated equipotential lines for one such case are compared graphically with a plot made in an electrolytic plotting tank. The comparison between the calculated and experimental results is quite favorable.
The Operational Theory of Longitudinal Impact
Authors: Pipes Louis A.
Published: January 2005

The differential equations governing the longitudinal displacement and velocity of a uniform rod are identical to those governing the propagation of charge and current along a uniform electrical transmission line. By making use of this analogy between the rod and the transmission line, it is possible to translate some well-known results of electrical circuit theory to mechanical terms. In this manner, and by the use of the operational calculus, interesting and useful results in the theory of longitudinal impact are obtained. The treatment is vastly simpler and more general than the classical theory of Saint-Venant and Boussinesq and some of the results are thought to be new.
The Use of Secondary Electron Emission to Obtain Trigger or Relay Action
Authors: Skellett A. M.
Published: January 2005

The use of secondary electrons to obtain trigger action similar to that of a thyratron is described. An experimental tube and the necessary circuits by which this action is achieved are discussed. This combination gives the features of a triode with a relay or on and off feature, resulting in an amplifier, oscillator, modulator, or other vacuum tube device which may be turned on or off abruptly at high or low frequencies. In addition, it can be used to replace thyratrons in many of their circuits where very low impedance is not necessary and is capable of much greater speeds of operation in such applications.
Measurement of Relative Abundance with the Mass Spectrometer
Authors: Jordan E. B. , Coggeshall N. D.
Published: January 2005

This paper covers the general methods employed in mass spectrometry, machine design, and possible sources of error in relative-abundance measurements which are inherently associated with instrument design. Also included are graphs for determining the critical constants of the usual types of instruments.
A Diffraction Adapter for the Electron Microscope
Authors: Hillier J. , Baker R. F. , Zworykin V. K.
Published: January 2005

An adapter has been developed which allows a conventional electron microscope to be used interchangeably as an electron diffraction camera or an electron microscope. The adapter comprises a unit which takes the place of the projection lens unit of the microscope, and includes a newly designed microscope projection lens, a specimen holder, and a focusing lens. To transform the instrument from a microscope to a diffraction camera (or vice versa) it is necessary only to transfer the specimen from the regular object chamber to the adapter. Diffraction patterns may be obtained by either reflection or transmission. As a result of the excellent reproducibility of voltages and currents from the regulated power supplies used in the electron microscope, the diffraction camera holds its calibration to within 0.1 percent over long periods. Using a calibration determined by measurements of gold patterns, lattice spacings of a number of common materials were determined and found to agree with x-ray values to within 0.5 percent.
Variation of the Axial Aberrations of Electron Lenses with Lens Strength
Authors: Ramberg E. G.
Published: January 2005

The variation of refractive power and spherical aberration with electrode voltages and field strengths is studied for two characteristic unipotential lenses, an immersion lens, and a magnetic lens. Conclusions are drawn herefrom regarding the variation, with lens strength and applied voltage, of the resolving power obtainable with the lens as an electron-microscope objective. Scattered measurements by other authors agree satisfactorily with the results. The ``relativistic aberration'' of the electrostatic unipotential lenses, i.e., the effect on the image of fluctuations in the over-all applied voltage, is calculated and shown to be of significance in the electrostatic electron microscope. Furthermore, the axial chromatic aberrations are computed for the four systems and the question of upper limits of the last two aberrations is discussed.
Fine Structure of Metallic Surfaces with the Electron Microscope
Authors: Heidenreich R. D. , Peck V. G.
Published: January 2005

Several techniques for producing surface replicas to be used in the transmission electron microscope are briefly discussed and compared on the basis of experience with them in this laboratory. A new two-step replica process is described which utilizes molded polystyrene as the first replica and evaporated silica as the second, thin film replica. The high mobility of condensing silica vapor on polystyrene is pointed out and it is shown that such evaporated films tend to fill in small surface irregularities and so produce a replica of fine surface structure which appears to be reliable. A table is included which gives an idea of the amounts of silica required for several surfaces of different ``roughness'' to yield films that are of about the same quality for use in the electron microscope. Electron micrographs of replicas so prepared are exhibited illustrating some pearlitic structures in a 0.98 C, hot roll steel, precipitation in a Cu–Be alloy, and a calcite cleavage plane. Excellent resolution can be obtained in such replicas and a resolution of approximately 50A is demonstrated in the calcite cleavage plane.
Note on the Annealing of Glass
Authors: Weyl W. A. , Pincus A. G.
Published: January 2005

The rate of removal of mechanical strain should follow Maxwell's first-order law, but for glasses it has been found that the rate is proportional to the square of the birefringence. The present paper explains this in terms of the structural picture of glass. During annealing the stress optical constant of the glass, as well as its viscosity, undergoes a continuous change. Birefringence, therefore, is not a correct measure of the stress, and the Adams-Williamson findings are only apparently in contradiction to the classical derivation of Maxwell.
A New Analytical Method for Solving van der Pol's and Certain Related Types of Non-Linear Differential Equations, Homogeneous and Non-Homogeneous
Authors: Shohat J.
Published: January 2005

A simple analytical treatment is developed for the differential equation (d2u/dt2)−ε(1−u2)×(du/dt)+u=0 (van der Pol), in order to study the behavior of its solution assumed bounded in (0, ∞). It is shown, without any further assumption, that, if ε≪1, u(t) can be approximated closely, for t≧0, by a simple oscillation with amplitude 2. This is a more precise form of a statement due to van der Pol. It is further shown that u2(t)+u′2(t)∼4, t≧0, 0<ε≪1. The method and results are then extended to the more general equation (d2u/dt2)−εF(u)(du/dt)+u=0, in particular, for F(u)=1−u4, 1−2au−u2, a=constant, also to the non-homogeneous equation (d2u/dt2)−εF(u)(du/dt)+u=given function of t. The analytical results obtained in this paper show a remarkable agreement with those obtained for the same equations by mechanical means (on the differential analyzer).
Electrostatic Electron Microscopy. I
Authors: Bachman C. H. , Ramo Simon
Published: January 2005

This paper, consisting of three parts, describes investigations made with the objective of developing a simplified, practical microscope of the type which yields magnified images of transparent specimens with a resolving power superior to that of the best light microscopes. The first part deals with the general problem of design, including the electron gun and the imaging lenses. A later part will describe a completed instrument embodying many of the results of the investigations.
The American Institute of Physics Building. I. Early History of the Building
Authors: Hutchisson Rose V.
Published: January 2005

A HOME office for the American Institute of Physics, as well as a national headquarters for its member societies and for the physicists of America is no longer a dream but a definite accomplished fact. At a fraction of its former value, the Institute has obtained a building eminently suited to its needs. Because of the durable construction and fire-proof nature of the building, upkeep costs will be reasonably low. This fact together with the tax-free status of the Institute makes ``home-ownership'' decidedly a matter of good business.

The suitability of the building for the purposes of the Institute has been emphasized in the appeal for funds. The dignified entrance hall will make physicists proud of ``their building.'' The large member's room on the second floor will provide a place for physicists visiting New York to read, write, telephone, and meet people. In addition, this room will make an excellent board room and meeting place for small groups. The other rooms on the second, third, and fourth floors will provide adequate space for the Director, Publications Manager, and other officers of the Institute, and for the publications staff. Fortunately there is room for the expansion of the activities of the Institute which is sure to come in the near future.

Many of the interior photographs in this issue of the Journal show the furnishings of the building when used as a residence. Naturally when used as an office some of the elegance will be sacrificed for utility. The Institute will of necessity carry out gradually interior decorations adapted to its new use. Since the building has not been used for several years minor repairs and a thorough cleaning will be in order first of all. Although the present appearance of the building inside and out is not as bright as the pictures used here indicate the architectural details are in sound condition underneath the grime.

Dr. Barton has pointed out that the goal of $75,000 which must be raised if this building is to be owned by the Institute free-of-debt has not yet been reached. Physicists are asked to send in their contributions soon. Every physicist will want to own a small part of this building. It is to be hoped that everyone will make a contribution even if it must be small so that the Institute will know that physicists are unanimously back of its carefully formulated program for the future of organized physics in America. Great credit is due to the Governing Board and the War Policy Committee, but those close to the Institute know that were it not for the hard work and unbounded enthusiasm of the Director and the Publications Manager, a national headquarters for physicists would not have been possible for a long time to come.

So that physicists may become better acquainted with their new headquarters, a series of articles describing the building is planned. The first of these is concerned with its early history and follows below.—The Editor
Frictional Phenomena. XVI
Authors: Gemant Andrew
Published: January 2005

THE following technical applications are dealt with in this chapter: (1) belt drives, (2) clutches, (3) brakes, (4) vibration dampers, such as the Lanchester damper, (5) self-excited vibrations, such as shaft whipping and sound production in a violin, and (6) grinding and crushing. In most cases a brief outline of the mechanism of operation is given, followed—in the first three of the above-mentioned applications—by principles of design, chief types of construction, and necessary numerical data on friction coefficients.
Harmonic Analysis by Photographic Method
Authors: Straiton Archie W. , Terhune George K.
Published: January 2005

This paper describes a method for determining Fourier series coefficients from area measureurements on photographs of the function to be analyzed with the graph sheet formed into a series of semi-cyclinders.
The Radiation Field of Long Wires, with Application to Vee Antennas
Authors: Harrison Charles W.
Published: January 2005

The analysis previously made for the current distribution along a symmetrical center-driven antenna of non-vanishing radius, and radiation field thereof, is extended to include long wire center-driven antennas. The results of this investigation are then applied to obtain an approximate solution for the field of a long wire resonant vee antenna.
Dosimetry and Local Distribution of Energy in the Electric High Frequency Field
Authors: Lion K. S.
Published: January 2005

The principles of a short wave dosimetry method, based upon measuring of the electric field strength distribution, are explained. The applicability of this method for measurements outside and inside of the body to be treated is discussed. Measurements in some typical field arrangements are presented.
Thermionic Emission from an Oxide-Coated Cathode
Authors: Fan H. Y.
Published: January 2005

The properties of thermionic emission from a cathode coated with barium oxide are studied. The cathode is indirectly heated and its temperature is measured by a thermocouple. It is found that the emitted electrons have a Maxwellian distribution corresponding closely to the temperature of the cathode. The emission is studied with accelerating voltages up to 1300 volts. The current rises more steeply than predicted by Schottky's theory but begins to bend at the upper end. The variation of the work function and the factor A with the state of the cathode is studied by glowing the cathode at different temperatures. It is found that both the work function and the factor A vary. No appreciable decay of emission with time is observed. The effect of drawing emission on the work function and the factors A is small.
Transmission-Line Theory and Its Application
Authors: King Ronold
Published: January 2005

In Part I several forms of the solution of the transmission-line equations are discussed including, in particular, a completely hyperbolic one in which the over-all attenuation and phase shift of the terminal impedances are expressed in a form involving terminal functions which simplify the analysis of many complex problems. Formulas for the input resistance, reactance, conductance, and susceptance of a section of line of any length and terminated in an arbitrary impedance are given in completely general terms. Curves computed from these formulas for four typical terminations are shown. A general circle diagram for determining the input impedance and admittance as well as the terminal functions is described. It consists of circles of constant over-all attenuation and circles of constant over-all phase shift. The distribution of current is represented in general terms suitable for a line driven at one end or by a generator coupled loosely at any point along the line. In Part II the general formulas described in Part I are applied to practical problems. A simple and completely general formula is derived for determining the transfer of power and the efficiency of transmission for a line of any length terminated in an arbitrary load. An equally simple and general formula for the standing wave ratio is given. Application of the formulas for input impedance and admittance to the problem of bead spacing on resonant and non-resonant lines and to series and shunt impedance transforming or matching sections is outlined. The experimental determination of attenuation and phase constants and of ``Q'' for the line and for the terminations is discussed. The application of formulas and experimental methods to include hollow pipe transmission lines or wave guides is considered briefly in Part III. A method for defining and measuring terminating impedances for hollow pipes is described.
The Resolution of Boundary Value Problems by Means of the Finite Fourier Transformation: General Vibration of a String
Authors: Brown Herbert Kapfel
Published: January 2005

The finite sine transformation and the finite cosine transformation are defined as the linear functional operations S{G}=∫0πG(x)sinnxdx=gs(n) and C{G}=∫0πG(x)cosnxdx=gc(n), respectively. The inversion of the product of two transforms can be made by means of four Faltung theorems. The finite sine transformation was applied to a boundary value problem of a general vibrating string, in which the partial differential equation has coefficients which may be functions of the time. A resolution was made of the transformed boundary value problem by the introduction of a fundamental set of solutions of the homogeneous transformed problem; an inversion in closed form was accomplished by the use of the Faltung theorems. A formal verification of this solution was made as well as a short survey of the applicability of the finite Fourier transformation to problems in engineering and physics.
Theory of Filler Reinforcement in Natural and Synthetic Rubber. The Stresses in and about the Particles
Authors: Rehner John
Published: January 2005

An attempt is made to develop a general theory of filler reinforcement by determining the stresses occurring in and about a spherical particle imbedded in a rubberlike medium subjected to an applied tension. For a system containing a single particle rigidly attached to the adjacent medium, an application of the theory of elasticity shows that, for infinitesimal deformations, the stress components within the particle are independent of the radial distance from the origin, taken at the center of the particle. The stress components at a given point in the surrounding medium depend on the elastic constants both of the particle and of the medium, on the radius of the sphere, on the distance from the origin, and on the angle between the direction vector and the applied tension. Expressions are given for the average stresses in media containing many (independent) particles. Theoretical values of the bulk moduli of the synthetic rubbers considered in the treatment are derived from sound velocity data. Curves showing the spatial distribution of radial and shear stresses are presented for a range of values of elastic constants to be expected for different kinds of filler particles and rubberlike materials.
A Treatment of Non-Linear Devices Based upon the Theory of Related Linear Functions
Authors: Stockman Harry
Published: January 2005

Because of the mathematical difficulties involved in the treatment of large-signal detectors, experimental methods for obtaining design data were early adopted. The procedure has been to replace the detector by a ``model'' described by a rectification or transrectification diagram. The ``model'' for a large-signal detector is developed from practical measurement results. Formulae and results may be extracted from the ``model'' if the existing analogy with the plate-current vs. plate-voltage diagram for a vacuum tube is made use of. This fundamental procedure may be extended to other non-linear devices, and in particular to frequency converters. It is shown in the following that a general theory can be developed, of which the vacuum-tube amplifier, the large-signal detector, the frequency converter and other devices are applications. A double-inpout superheterodyne mixer with straight input characteristics is discussed, and it is shown how the applied general theory predicts the necessity for non-linearity. The general theory is then used for the development of a substituting ``model,'' from which important information on the behavior of a superheterodyne converter can be secured.
Negative Resistance as a Machine Parameter
Authors: Fett G. H.
Published: January 2005

A series generator in the operating range below maximum voltage possesses both d.c. negative resistance, (−V/I), and incremental negative resistance, (−dV/dI). It is shown that the incremental negative resistance is equal to Kn−R, where n is the speed, K the volts per r.p.m. per unit of field current, and R is the armature circuit resistance. Since the series generator has the incremental resistance property, it will support oscillations if the tuned circuit has the proper constants. It is shown that a generator load consisting of a separately excited motor can be represented by a condenser of sufficient size (in the order of farads), that oscillations at mechanically feasible frequencies of 0.2 to 1.5 cycles per second can be obtained. It is shown analytically that the magnitude of the capacitance varies directly with the moment of inertia of the motor armature and inversely with the square of the induction factor. It is shown experimentally that the frequency of oscillation of the circuit depends upon the motor induction factor and moment of inertia, and slightly upon the circuit resistance. The amplitude of oscillation is controlled by the circuit resistance.
Controlled Crystal Growth in Tantalum Ribbons
Authors: Mrowca B. Adalbert
Published: January 2005

Microscopic examination of surfaces developed in tantalum ribbons on heat treatment in vacuum shows a dependency of surface structure on whether a.c. or d.c. supply is used for the heating current. Further modification of surface structure results due to recrystallization over a temperature range of 1900°K to 2500°K. Grain growth is shown to increase exponentially with the temperature. An optimum amount of cold working of the samples before heat treatment results in exaggerated grain growth yielding large single crystals.
Studies in Lubrication: XII. Friction Behavior During the Slip Portion of the Stick-Slip Process
Authors: Sampson J. B. , Morgan F. , Reed D. W. , Muskat M.
Published: January 2005

The jerky form of motion described as ``stick-slip,'' which is sometimes observed in the sliding of surfaces, has been studied by means of the stick-slip apparatus built in this laboratory. A comparative study of motion during the slip has been made for a number of combinations of unlubricated metals. The variation of friction with velocity has been determined for several typical cases. Most slip traces are symmetrical about their point of inflection indicating that the kinetic friction remains approximately constant. The static friction is greater, and a rapid drop to kinetic friction usually occurs. The kinetic friction is least at the end of slip, so that the friction-velocity relation is not reversible. There is evidence that the friction does not return immediately to its higher static value when the sliding surfaces come to rest. These results are considered in terms of several theories of friction.
The Apparent Second-Order Transition Point of Polystyrene
Authors: Alfrey T. , Goldfinger G. , Mark H.
Published: January 2005

(1) At high temperatures (above 80°C) the specific volume of polystyrene is an explicit function of the temperature. dV/dT=0.00043. (2) At low temperatures (below 40°C) the specific volume of polystyrene depends upon its past thermal history dV/dT=0.00024, although V is not explicitly fixed by the temperature alone. (3) When a sample of polystyrene is cooled at constant rate, it contracts according to the higher expansion coefficient until some critical region of temperature, and then contracts according to the smaller coefficient. (4) The position of the critical temperature region depends upon the rate of cooling. The faster the cooling, the higher the ``transition point.'' (5) In the intermediate temperature range (say 40°C to 80°C), complex time effects can be observed. A sample heated from 20°C to this intermediate range will first expand, according to the small expansion coefficient, and then contract slowly toward a smaller volume. The rate of this contraction is greater at higher temperatures. (6) All the observations are in fair accord with the interpretation of the ``second-order transition point'' of polystyrene as the temperature at which rate of volume change becomes comparable with the experimental time scale.
Electrostatic Electron Microscopy. II
Authors: Bachman C. H. , Ramo Simon
Published: January 2005

This paper is a continuation of the description of problems arising in the development and design of an electrostatic electron microscope. The present article discusses depth of focus, lens and field stops, shielding, manufacturing tolerances, the choice of the number of stages of magnification, and alternative methods of viewing and recording the final image. A following paper will describe a completed instrument.
The Ploughing and Adhesion of Sliding Metals
Authors: Bowden F. P. , Moore A. J. W. , Tabor D.
Published: January 2005

Studies of the surface damage caused by the sliding of clean metals on one another show that penetration and distortion occur to some depth beneath the surface. Micro-examination shows that welding of the metals takes place quite readily even at low speeds of sliding when the surface temperature-rise due to frictional heat cannot be very high. In some cases the welded junctions may pluck out portions of the harder metal. These and other results have led to a more quantitative theory of metallic friction. It is suggested that in general the frictional force between clean metal surfaces is made up of two parts. The first is the force required to shear the metallic junctions formed between the surfaces; the second is the ploughing force required to displace the softer metal from the path of the harder. By using steel sliders of various shapes and sizes on a soft metal like indium, these two factors have been estimated separately, and it is shown that an approximate calculation of the friction between metal surfaces may be made in terms of the known physical properties of the metals. The effect of surface contamination is also discussed.
The Lubrication by Thin Metallic Films and the Action of Bearing Metals
Authors: Bowden F. P. , Tabor D.
Published: January 2005

An investigation has been made of the role of thin metallic films in reducing the friction and wear between metal surfaces. It is shown that with metallic films possessing suitable mechanical and surface properties the coefficient of friction is very low and may be similar to that observed on ice. In many cases the behavior of these thin metallic films resembles that of ordinary lubricants except that Amontons' law is not obeyed. The friction and wear properties of some copper-lead alloys have been studied and the results indicate that the lead in the alloy is extruded during sliding and forms a thin lubricating film on the hard copper matrix. It is suggested that these metallic films play an important part in the action of many bearing alloys.