bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Field Calculations for Large Cross-Section Cloud-Chamber Coils
Authors: Koch H. W.
Published: April 2005

A method is described and equations are presented which permit the calculation of the magnetic field characteristics of large cross-section air core coils. The method is applied to the determination of the field non-uniformities on the median plane to be expected with annular cloud-chamber coils of rectangular cross section. The field non-uniformity results are provided in graph form to facilitate the design of cloud-chamber coils.
I. Indoor Measurement of Microwave Antenna Radiation Patterns by Means of a Metal Lens
Authors: Woonton G. A. , Borts R. B. , Carruthers J. A.
Published: April 2005

The E-plane radiation patterns of two horn radiators have been measured in the laboratory with a metal lens by the same method that is used in optical diffraction pattern measurements. Comparison of patterns measured outdoors, by standard methods, with the lens measurements shows little deterioration in precision over the angular interval between ±15 degrees, for horns of aperture width 32 cm, measured by a lens of aperture 110 cm, at a wave-length of 3.2 cm. It was found that a stepped lens was unsatisfactory for this purpose, possibly because of diffraction caused by the steps.
Streak Photography
Authors: Vigness Irwin , Nowak R. C.
Published: April 2005

A description is given of some methods of ``streak photography'' used for obtaining displacement records as functions of time. Ordinary streak photography consists of photographing a moving object on a moving film camera with an open shutter. The motion of the object should be in a plane parallel to the film and perpendicular to its motion. Large errors in velocity determinations may occur if the motion of the object has components parallel to the film motion. A modified method of streak photography is described in which these errors are reduced to small values. By this method time-displacement curves have been recorded for displacements of many inches and periods of several seconds with accuracies within a few thousandths of an inch and a few hundred thousandths of a second.
Emulsion Polymerization with Ultrasonic Vibration
Authors: Ostroski A. S. , Stambaugh R. B.
Published: April 2005

Emulsion-type polymerization reactions have been accelerated by irradiation with ultrasonic energy.

A magnetostriction oscillator at 15 kc gave essentially the same results as a piezoelectric oscillator at 500 kc. The rate of formation of polystyrene was doubled and higher final yields obtained using about 0.03 watt of vibrational power per cc of latex. Experiments were made to separate local heating effects from those due to vibrational energy.

A thermostatted stainless steel cell was developed for irradiating butadiene emulsions under pressures up to 60 p.s.i. About ½ watt of vibrational power per cc of latex doubled the rate of reaction for GR-S, Redox, and Redsol formulas.

The ultrasonic intensity apparently must exceed a critical value before any appreciable accelerative effect is observed. Above the critical intensity, the time to reach a given yield of polymer is approximately inversely proportional to the power used.
A Non-Destructive Mechanical Test for Animal Fibers
Authors: Burte Harris M.
Published: April 2005

The slope of the force-extension curve in the Hooke's law region can be measured non-destructively, for animal fibers, at three to fifteen minute intervals. The change of this Hookean slope with time is used to follow the course of the heterogeneous reaction between wool and a reagent.

Data are presented on the interaction between concentrated neutral salt solutions and wool fibers. These results indicate that wo processes occur: (a) Relatively rapid hydration or dehydration of the fiber until equilibrium with the activity of water in the salt solution is attained; (b) Relatively slow absorption of salt ions by the fiber. Very concentrated salt solutions dehydrate the fiber so completely that absorption of salt ions is not possible. Swelling experiments and experiments involving other mechanical properties confirm these hypotheses. The interaction between wool fibers and aqueous solutions of large organic molecules follows a similar pattern.
Equivalent Effects of Time and Temperature in the Shear Creep and Recovery of Elastomers
Authors: Conant F. S. , Hall G. L. , Lyons W. James
Published: April 2005

An explicit relationship is set forth for the time-temperature dependence of the viscoelastic phenomena in the superelastic polymers. An empirical equation that was found to represent adequately the above-mentioned relationship over the entire multiple-temperature curve is of the form: logtc = [Cα/(T−b)]+Cβ. Experimental verification is given for the equivalent influence of time and temperature on the creep and recovery of compounds based on Hevea, GR-S, Neoprene GN, Butaprene, and butyl rubber. A comparison of the empirical equation with that of a theoretical reaction-rate equation of Tobolsky and Eyring indicates a temperature dependence of the energy of activation.
Studies in Plasticization of Polyvinyl Chloride. II. Plasticizer Variations in PVC-Plasticizer Systems
Authors: Dannis M. L.
Published: April 2005

Polyvinyl chloride resin is softened by certain liquids, called plasticizers, through a set of processes with high activation energies, 50–100 kcal. At fixed temperature, ``reaction'' rates are directly proportional to vapor pressure of the liquid. The dielectric change may be treated similarly to a chemical reaction between a solid and a vapor, and free energy of activation, ΔF**, evaluated. ΔF** is constant for various liquids with one resin. ΔE**=ΔH**+L in this system, where ΔE** is Arrhenius activation energy, ΔH** energy barrier, L latent heat of vaporization of the liquid.
Some Theoretical Considerations of Dynamic-Property Data on Textile Specimens
Authors: Lyons W. James
Published: April 2005

1. Early stretch-vibrometer data, of quite extensive character, on the frequency dependence of the internal friction μ of a Nylon monofil, has been found to conform to the relation μ=[μ2/(1+ω2τ22)]+μ3which was deduced independently by Tobolsky and Eyring from considerations of molecular structure. Among other constants evaluated was the relaxation time for the secondary-bond network τ2, which was found to have the value 9.3 sec.

2. By more sensitive graphing methods than had been used heretofore, it was confirmed by the Nylon data that the hyperbolic relationship between resonant frequency ω0 and internal friction μ holds equally as well as the foregoing equation. The two relationships are shown to be nearly equivalent in the present experimental range. On evaluation of graphical parameters, the equation μω0=2.47×109 ergs/cm3 was obtained.

3. Using the same graphical method with a set of data on 11/4/2 cotton cord the relation (μ+0.9)ω0=7.05 ×109 ergs/cm3 was established.
Equation of State for High Polymers
Authors: Spencer R. S. , Gilmore G. D.
Published: April 2005

In a former paper the authors suggested the following equation of state, (P+π)(V−ω)=RT, where π is the internal pressure (or cohesive energy density) and ω is the volume at absolute zero. It was found that this equation was in good agreement with data on the thermal expansivity and isothermal compressibility of polystyrene.

The present paper reports isothermal compression measurements on polymethyl methacrylate, polyethylene, cellulose acetate-butyrate, and ethyl cellulose at temperatures within the fabrication range. The above equation of state is shown to apply equally as well to these thermoplastics as to polystyrene and values are given for the constants. The usefulness of this relationship is illustrated in a brief discussion of some phases of the injection molding process.
Work Functions of the Elements
Authors: Michaelson Herbert B.
Published: April 2005

Like the chemical properties of the elements, the work function φ is a periodic function of atomic number, as shown clearly by a new compilation of published data for 57 elements. The progressive rise and fall of work function values throughout the table of the elements appears to be sufficiently regular to permit approximations to be made of values for the metallic and semimetallic elements on which no data has yet been published. Since the first ionization potential Ei and electrode potential E0 exhibit a similar periodic function of atomic number, a striking resemblance exists among the respective plots of φ, Ei, and E0.
Compilation of Body Wave Velocity Data for Cubic and Hexagonal Metals
Authors: Gold Louis
Published: April 2005

The directional variation of body wave velocities has been computed for cubic and hexagonal metals where stiffness coefficients are known; the essential data is presented in the form of tables and graphs. The results for aluminum, copper, gold, iron(α), lead and silver are tabulated in terms of the directional indices, and a stereographic coordinate system has been devised for presenting these data in the form of iso-velocity contours for the three wave vectors. The compressional and shear velocities for cadmium, magnesium, and zinc are plotted as a function of the angle formed by the direction of wave propagation and the hexagonal (c) axis from which have been derived the theoretical average velocities which may be compared with measured values for polycrystalline specimens.
Unbalanced Terminations on a Shielded-Pair Line
Authors: Tomiyasu K.
Published: April 2005

Theoretical calculations indicate that the unbalanced component of current on a two-wire or shielded-pair transmission line can be determined by comparing the different standing-wave distributions on the line conductors. The measurement of reflected components from an unbalanced radiative termination on a slotted shielded-pair line is described. The existence of a condition of minimum unbalanced reflected component from end-coupled antennas is shown experimentally.
Shear Stress in a Turbulent Boundary Layer
Authors: Ross Donald , Robertson J. M.
Published: April 2005

The method initiated by Fediaevsky for evaluating the shear stress distribution in a turbulent boundary layer under the action of an adverse pressure gradient is improved upon. Use is made of a more suitable polynomial and boundary conditions which include the concept that the turbulence which produces the shear at any point has its origin at the surface upstream from its present location. This ``history'' theory predicts that the transverse shear gradient in the outer portion of the boundary layer remains constant as the boundary layer develops. Comparison with shear distributions measured at the National Bureau of Standards along a simulated airfoil shows good qualitative agreement and appreciable improvement over Fediaevsky's theory.
Propagation of theTM01 Mode in a Metal Tube Containing an Imperfect Dielectric
Authors: Hetrick David L.
Published: April 2005

The TM01 mode in a circular dielectric-filled wave guide, where dielectric losses and metal wall losses are considered simultaneously, is analyzed from the viewpoint of the boundary value problem. General expressions for the attenuation and phase constant are obtained, and the percentage errors introduced by (1) neglect of wall losses and (2) assumption that the total attenuation is the sum of dielectric attenuation and approximate wall loss attenuation are computed for a particular case.
Mechanical and Electrical Properties of Plasticized Vinyl Chloride Compositions
Authors: Nielsen Lawrence E. , Buchdahl Rolf , Levreault Rita
Published: April 2005

The temperature dependence of the dynamic mechanical and a.c. electrical properties of a given polyvinyl chloride plasticizer composition can be characterized by two quantities: (a) the transition temperature which is defined as the temperature of maximum dissipation factor and (b) the half-widths of the loss factor-temperature curve. A simple relationship exists between the transition temperature determined mechanically or electrically and the volume fraction of a compatible plasticizer. The modification of this relationship for non-compatible plasticizer has been indicated. The half-width is a function of the volume fraction of the plasticizer, although this relationship is not as simple as the one obtained for the transition temperature. A simple correlation exists between the electrical and mechanical half-width. The compliance measured in tensile creep has been found to be a function of the applied load and the compliance-load relationship varies depending on the region in which the material finds itself. The shape of the creep curve at different temperatures has been correlated with the dissipation factor-temperature curve. The shape of the stress-strain curve has been related to the modulus-temperature curve and a correlation between the initial Young's modulus and the ultimate elongation and breaking strength has been established. It has been shown that the relaxation theory is not sufficient to explain certain features of the modulus (or dissipation factor) temperature relationship. The limited significance of the μ-value and of the viscosity of plasticizers with respect to plasticizer efficiency has been demonstrated.
A Graphical Analysis of the Interference Patterns of an Elevated Ultra-High Frequency Antenna under Conditions of Atmospheric Stratification
Authors: Abbott F. R. , Fisher C. J.
Published: April 2005

Analytical computation of the detailed lobe structure of an elevated meter or centimeter band antenna for a standard atmosphere is quite tedious. In case there are discontinuities in the gradient of refractive index the analysis becomes hopelessly involved.

This paper presents a straightforward method of graphical analysis for the optical region, equally applicable to a standard or stratified atmosphere.
An Extension of Wiener's Theory of Prediction
Authors: Zadeh Lotfi A. , Ragazzini John R.
Published: April 2005

The theory of prediction described in this paper is essentially an extension of Wiener's theory. It differs from the latter in the following respects.

1. The signal (message) component of the given time series is assumed to consist of two parts, (a) a non-random function of time which is representable as a polynomial of degree not greater than a specified number n and about which no information other than n is available; and (b) a stationary random function of time which is described statistically by a given correlation function. (In Wiener's theory, the signal may not contain a non-random part except when such a part is a known function of time.)

2. The impulsive response of the predictor or, in other words, the weighting function used in the process of prediction is required to vanish outside of a specified time interval 0≤t≤T. (In Wiener's theory T is assumed to be infinite.)

The theory developed in this paper is applicable to a broader and more practical class of problems than that covered in Wiener's theory. As in Wiener's theory, the determination of the optimum predictor reduces to the solution of an integral equation which, however, is a modified form of the Wiener-Hopf equation. A simple method of solution of the equation is developed. This method can also be applied with advantage to the solution of the particular case considered by Wiener. The use of the theory is illustrated by several examples of practical interest.
The Role of Cathode Temperature in the Glow Discharge
Authors: Jacobs Harold , Martin Jack
Published: April 2005

Experiments were conducted to study the role of the temperature of oxide-coated cathodes in the glow discharge of argon, neon, and mixtures of neon and argon, and mercury vapor and argon.

It was found that for tubes without mercury present, in the region of cathode temperature between 300°K and 750°K: (1) The sparking potential falls with increasing cathode temperature. (2) The regulation voltage rises with increasing cathode temperature. For argon and mercury vapor, the regulation voltage falls with increasing cathode temperature. The action here is attributed to metastable states of inert gas. (3) The current density in the glow discharge decreases with increasing cathode temperature. This, too, is attributed to the action of metastable states. (4) The minimum sustaining current in a glow discharge is found to decrease with increasing cathode temperature and rise with increasing pressure. (5) The current density in the glow discharge varies roughly linearly with pressure, or at a slightly higher rate, in contrast with the space-charge derivations which claim a variation with pressure squared. (6) The regulation voltage tends to rise very slightly at lower pressures.
X-Ray Measurement of Long Range Order in β-Brass
Authors: Chipman D. , Warren B. E.
Published: April 2005

The long range order in β-Brass has been determined by measuring the integrated intensity of the (100) superstructure reflection from a single crystal held at various temperatures. With a single crystal, and CuKα-radiation obtained by a balanced Ni-Co filter, there is ample intensity for measurement with a Geiger counter spectrometer. The measured long range order parameter S is in satisfactory agreement with the theoretical predictions.
The Resolving Power of an X-Ray Microscope
Authors: Prince Edward
Published: April 2005

A formula for determining the resolving power of an x-ray microscope built according to the design suggested by Kirkpatrick and Baez is derived, and an estimate of that resolving power given. The optimum resolving power is such as to resolve points separated by a distance of the order of 2000A.
Metallic Evaporation and the Diameter of Tobacco Mosaic Virus with the Electron Microscope
Authors: Kahler H. , Lloyd B. J.
Published: April 2005

Tobacco mosaic virus has been used as a known test object for the intercomparison of several methods of small particle measurements, all involving metallic evaporation. Various characteristics of these methods, which determine their accuracy, were investigated. Measurement of groups and the derivation of a mean size therefrom is primarily limited in accuracy only by the exactness of juxtaposition of the successive particles in the group. The measurement of the images of single particles is subject to the relatively large error associated with the uncertainty in the relationship between the true particle edge and the image of the edge which has received a coating of metal. The measurement of shadow lengths reduces this error by the factor 2 tanα/2. A symmetrical shadow method is described which reduces the error of substrate tilt, and is insensitive to amount of metal deposited. An average over the four best methods gave a value 150.0±3.6A agreeing closely with the x-ray determination.
Scheme for Analyzing Capillary Measurements on Non-Newtonian Liquids
Authors: Clark Orrin H. , Deutsch M. L.
Published: April 2005

A powerful new scheme is presented for analyzing capillary flow measurements on non-Newtonian liquids. The basic disability of the capillary method, namely its inability to assign to a flow measurement any particular shear rate, or even a known range of shear rates, is overcome. This is accomplished by developing simple relations connecting the directly measured quantities, pressure and flow rate, with viscosity and shear rate. Application to Bingham bodies is easy and an illustration is given. Application to measurement at high rates of shear is immediate in principle, but there are certain allied measuring difficulties. These are discussed briefly. Finally, a simple approximate formula applicable to cases of moderate deviation from Newtonian behavior is given.
The Radiation from a Transverse Rectangular Slot in a Circular Cylinder
Authors: Silver Samuel , Saunders William K.
Published: April 2005

General results obtained previously for slots of arbitrary shape are applied to the case of a transverse rectangular slot in a circular cylinder. It is shown that the principal transverse plane pattern of such a slot in which the excitation has only a circumferential tangential electric field component is the same as the pattern generated by an infinite axial slot with the same circumferential excitation. Theoretical and experimental curves are given for the narrow-width half-wave-length slot.
Diffraction Pattern in a Circular Aperture Measured in the Microwave Region
Authors: Andrews C. L.
Published: April 2005

Measurements were made of the diffraction patterns of circular apertures from one to eight wave-lengths in diameter in the planes of the apertures and in the neighborhood of the apertures when a plane polarized electromagnetic wave was incident upon them. From Thomas Young's theory that the diffraction pattern is an interference pattern between the incident plane wave and wavelets from the edge of the aperture, the positions of maximum intensity have been predicted in the neighborhood of the aperture and the values of the intensities over the apertures checked with experiment.
A Removable Intermediate Lens for Extending the Magnification Range of an Electron Microscope
Authors: Hillier J.
Published: April 2005

A removable intermediate lens is described which extends the range of magnification of a conventional instrument to 25:1 without sacrificing the accessibility of the objective and projection lens polepieces. The distortion, sensitivity to changes in accelerating potential and reproducibility of calibration are studied and found to be equal to, or better than in the standard arrangement. The system provides two values of the magnification which are essentially independent of the accelerating potential.
On the Diffraction of a Radar Wave by a Conducting Wedge
Authors: Watson R. B. , Horton C. W.
Published: April 2005

Diffraction patterns of radar waves have been measured about the edge of a perfectly conducting wedge. Theoretical patterns have been calculated using an asymptotic solution suggested by Pauli. Good agreement is observed between experimental and calculated patterns. The thin wedge tested showed much similarity in diffracting properties to a suitable semi-infinite conducting screen. The results may have application to diffraction effects about wedge-shaped wings on high speed aircraft and missiles.
Mass Spectrometric Study of Solids I. Preliminary Study of Sublimation Characteristics of Oxide Cathode Materials
Authors: Plumlee R. H. , Smith L. P.
Published: April 2005

Mass spectrometric techniques have been utilized to study sublimation characteristics of materials used in electron tubes. Exploratory experiments and methods are described. Preliminary results concerning general processes induced by heat and by electron bombardment are discussed. Photographs are shown of mass spectrometer traces which demonstrate the effects described. Phenomena noted include (1) the inefficiency of electron bombardment for producing material transport from solids, (2) the thermal evaporation of alkali metal atoms and ions from bare nickel alloys, but no such evaporation from oxide cathodes formed on the same materials, (3) the complex thermal evaporation of oxide cathode constituents, (4) absence of positive ion evaporation from oxide cathodes, (5) the confirmation of mechanisms for negative ion formation in vacuum systems, and (6) the liberation of molecular oxygen from oxide cathodes which increases with electron emission drawn.
The Static Electrification of Dust Particles on Dispersion into a Cloud
Authors: Kunkel W. B.
Published: April 2005

An extensive study of the charge and size distribution of particles from 0.5 to 30 microns radius in dust clouds of diverse exemplary types dispersed in air under a variety of conditions ranging from blowing with minimum of turbulence to conditions of violent and maximum impact with various types of surfaces was made using adaptations of the Hopper and Laby modification of the oil drop experiment. It was observed that all dusts, including homogeneous dusts with no impacts on solid surfaces, were charged. In homogeneous systems the charges of opposite sign were equal, no net charge resulting, the number of particles of similar size with opposite charges being about the same. The magnitude of charges increased somewhat less rapidly than the surface of the particle. There was no correlation between size and sign of charge. There is strong evidence that charging occurs on separation of the contacts between particles in the dispersion of the cloud. Humidity did not affect the charging. Studies of heterogeneous systems making contact with solid walls of different composition from the powder gave consistent asymmetry of charge of varying degrees depending on the proportion of particles striking the surfaces relative to those just separated.
Charge Distribution in Coarse Aerosols as a Function of Time
Authors: Kunkel W. B.
Published: April 2005

The interaction of small particles suspended in air with the ions normally produced in the air is discussed. The neutralization of highly charged dust particles, if suspended in air, is treated in detail. The result is found to be in qualitative agreement with experiment. The special case of final equilibrium is investigated. It is found that multiply charged particles should be present in appreciable number in coarse aerosols at all times. This is confirmed by experiments both for initially charged quartz dust and for initially neutral ammonium chloride smoke. The general nature of an equilibrium charge distribution is presented. Charges up to ten electron units are found to be not uncommon.
Distribution in Energy of Johnson Noise Pulses
Authors: Gossick Ben R.
Published: April 2005

The distribution in energy of Johnson noise pulses (random thermal voltages in a resistor) is derived and checked against pulse-height measurements made with a linear amplifier and electronic counter. The following parameters are determined from the distribution function: (1) time of flight associated with a Lorentz mean free path, (2) the number of electrons which produce a pulse of a given height, and (3) the potential an electron falls through in a Lorentz mean free path.
Note on the Use of Reiner's Equation for Recognition of Pseudoplastics from Their Flow Curves
Authors: Krakauer Vera Osman
Published: April 2005

A method is described which has been found useful to determine by application of the Reiner equation whether certain flow curves obtained with a concentric cylinder rotational viscometer indicate pseudoplastic or Bingham body types of flow.
An X-Ray Study of Thermally Induced Stresses in Microconstituents of Aluminum-Silicon Alloys
Authors: Nielsen John P. , Hibbard Walter R.
Published: April 2005

The changing width of high angle Debye x-ray diffraction lines from eutectiferous aluminum-silicon alloys during thermal cycling as measured by a recording Geiger counter spectrometer is interpreted in terms of stresses resulting from the differences in thermal expansion of the microconstituents.
The Magnetostriction of Permanent Magnet Alloys
Authors: Nesbitt E. A.
Published: April 2005

In order to obtain a better understanding of the mechanism of coercive force in modern permanent magnets, magnetostriction measurements have been made on various alloys having coercive forces from 50 to 600 oersteds. The results can be summarized by discussing two types of alloys. First are the older carbonhardening permanent magnets, and for these alloys high coercive force and high magnetostriction occur together. Second are the newer carbon-free permanent magnets and for these alloys high coercive force does not occur with high magnetostriction. In fact for the Mishima alloys having compositions near 29 percent nickel, 12.5 percent aluminum, and 58.5 percent iron, cooled at the rate of 3°C per second (coercive force 400 oersteds), the magnetostriction actually passes through zero. This is contrary to the classical strain theory of coercive force which states that the latter is proportional to the product of the magnetostriction and internal stress. To explain the mechanism of coercive force for these alloys it is necessary to resort to more recent theories.
Reflection and Transmission of Electromagnetic Waves by Thin Curved Shells
Authors: Keller Joseph B.
Published: April 2005

The scattering of an arbitrary electromagnetic field by a conducting or non-conducting obstacle is investigated. The differential equations and boundary conditions satisfied by the field are transformed into a pair of inhomogeneous linear integro-differential equations for E and H. For an obstacle which is a thin shell of constant thickness h, a formal procedure for obtaining a solution of these equations as power series in h is given. The lowest order term in this solution is the incident field. An explicit expression for the next term is found in the form of a surface integral. This integral is evaluated approximately by the method of stationary phase. The physical properties of the solution are examined in detail, and satisfactory agreement is found with many results previously obtained by other methods.
Motion Picture Studies of Electron Bombardment of Colloidal Crystals
Authors: Watson John H. L. , Preuss Luther E.
Published: April 2005

Phenomena not seen or recorded by orthodox methods are observed on the large number of micrographs which are taken during a motion picture experiment, and reaction times as short as 0.03 sec. can be calculated. The technique is useful for investigating solid-liquid-solid changes both by direct observation and by recording Bragg reflections. In most cases a preliminary effect of electrons upon crystals is to drive off water. In the case of sodium chloride crystals a residual envelope is left. Inside this, small particles, both solid and liquid, are observed to move rapidly due, it is believed, to a combination of Brownian movement and convection. These gradually evaporate and diffuse through the wall. The possibility is discussed that the residual envelope is formed by contamination. Examples are also taken from bombarded, colloidal crystals of tungsten oxide.
The Emission of Radiation from Nitric Oxide: Approximate Calculations
Authors: Benitez L. E. , Penner S. S.
Published: April 2005

Emissivity calculations have been carried out for nitric oxide at temperatures from 300°K to 3000°K. The results may be used, as a first approximation, at elevated total pressures.
Electric Dipoles in the Presence of Elliptic and Circular Cylinders
Authors: Lucke Winston S.
Published: April 2005

A theoretical examination is made of the problem of the electromagnetic fields of electric dipoles in the presence of an infinitely long, perfectly conducting cylinder. Application of the Green's function method to this problem yields expressions for the fields in terms of an integration in the complex plane. Simplified expressions for far zone fields are obtained through the known result of the complex integration for the far zone conditions. Results are given for both circular and elliptic cylinders. In the latter case, it is possible to treat the problem of dipoles in the presence of a ground plane which is finite in one dimension and infinite in the other, since this is equivalent to an elliptic cylinder with a vanishing minor axis. Polar diagrams of calculated far zone fields are included for a number of cases.
Effective Earth's Radius for Radiowave Propagation Beyond the Horizon
Authors: Miller William
Published: April 2005

The geometrical optical arguments underlying the equivalent earth's radius approximation are extended to non-horizontal rays. The appropriate wave equation for a non-uniform, but spherically symmetric, region is derived in a natural way. The notion of a ``primary field'' with the form eikR/R at the source is dropped in favor of a solution to the wave equation in terms of a Green's Function. The formal solution thus obtained is seen to contain the known solutions for a uniform medium. For the non-uniform case, the solutions to the radial equation are found by a technique due to Langer. These functions account for the index variation near the earth without making unwarranted assumptions about the behavior at greater heights. The formal series obtained is summed by the Watson technique. The first term in this series (lowest mode) alone determines the field at large distances and indicates that one may account for standard atmospheric refraction by using an effective earth's radius.
Experimental Measurement of Incompressible Flow Along a Cylinder with a Conical Nose
Authors: Laitone E. V.
Published: April 2005

The experimental pressure distribution data from low speed wind tunnel tests at zero angle of attack on two different conical noses attached to a cylindrical after-body are compared with theory. The simplified theoretical equation used is a higher order approximation valid up to the order r4 lnr. It is shown that the conical nose with a vertex angle of 20 degrees is in agreement but the larger cone with a vertex angle of 30 degrees shows a discrepancy between the measured pressures and the approximate theory. In both cases, however, the theory is in excellent agreement with the surface pressures on the cylindrical after-body.
Graphical Determination of the Fermi Level in a Simple Impurity Semiconductor
Authors: Lehovec K. , Kedesdy H.
Published: April 2005

A graphical determination of the position of the Fermi level in a simple impurity semiconductor at zero space charge is discussed. Measurements by G. Busch and H. Labhard indicate that the effective masses of electrons and holes in SiC crystals are of the order of mass of a free electron.
Calculation of Diffusion Penetration Curves for Surface and Grain Boundary Diffusion
Authors: Fisher J. C.
Published: April 2005

Diffusion in solids is known to occur along grain boundaries and over free surfaces more rapidly than through the interiors of crystals. In order to facilitate quantitative investigation of grain boundary and surface diffusion, a mathematical analysis of the problem has been completed, assuming that grain boundary diffusion is analogous to the diffusion of heat along a thin copper foil imbedded in cork. The calculated diffusion-penetration relationship for grain boundary diffusion is shown to agree with the experimentally determined grain boundary self-diffusion of silver.
Microwave Measurements of the Dielectric Properties of Gases
Authors: Birnbaum George , Kryder S. J. , Lyons Harold
Published: April 2005

An accurate and sensitive method for measuring the complex dielectric constant (ε′-iε″) of gases in the microwave region is described and critically investigated for sources of error. A resonant-cavity method is used in which the cavity response curve is displayed on a cathode-ray tube. The variation of resonance frequency and Q of the cavity when filled with gas are determined from measurements with two frequency markers. The equipment is operated at 9000 Mc, and cavities with Q's of 1×104 are used. In the determination of ε′-1 (dimensionless) of very low loss gases, an accuracy of 0.4 percent and a sensitivity of 4×10−7 can be obtained. In the determination of the loss factor ε″, an accuracy of 2 percent and a sensitivity of 5×10−7 can be obtained. This method is useful for measuring dispersion and absorption in solids and liquids as well as gases.

Experimental results are given and briefly discussed for ε′-1 of O2, N2, CO2, He, and air, and for ε″ of NH3 as a function of pressure up to 20 cm Hg.
Numerical Computation of Neutron Distribution and Critical Size
Authors: Thompson A. S.
Published: April 2005

A numerical procedure is presented for the calculation, by diffusion theory, of the critical size of a nuclear reactor, and of the time-dependent distribution of neutrons in the reactor as a function of position (one-dimensional space) and neutron energy. The partial differential equations for diffusion theory are approximated by a system of ordinary differential equations, for which a stepwise convergent solution for neutron distribution is obtained. The critical size of the reactor is found from a comparison of the magnitude of the slowing down densities of the thermal and fission energy limits. The procedure is applied, by way of example, to a reflected sphere.

This method for calculating neutron distribution is thought to be new in that an integration technique is developed and used for the solution instead of differentiation. Primarily because of this, the convergence to the correct solution is rapid. In a one-dimensional space all physical quantities can be considered as either continuous or discontinuous functions of both position and energy. Such items as fission and nonproductive capture in the slowing down range can be included as part of a standardized procedure. Certain transient and steady-state perturbation like motion of control rods can be studied.
Scattering of Electromagnetic Waves from Two Concentric Spheres
Authors: Aden Arthur L. , Kerker Milton
Published: April 2005

A solution is given for the problem of the scattering of plane electromagnetic waves from a sphere with a concentric spherical shell. The solution is general, and under appropriate conditions is reduced to the well-known solution for scattering from a single sphere.
Diffusion in Grain Boundaries and Their Structure
Authors: Achter M. R. , Smoluchowski R.
Published: April 2005

In order to gain an insight into the structure and properties of grain boundaries, diffusion along grain boundaries has been studied as a function of relative orientation of the grains and of the boundary. Experiments were made by comparing the depth of penetration of silver along the boundaries of columnar copper in the columnar direction [100]. The results indicate that, for angles of misfit between the grains, greater than 20° and smaller than 70°, diffusion along grain boundaries is greater than volume diffusion (near 700°C) and reaches a maximum around 45°. Outside of that range of relative orientation the rate of grain boundary diffusion is not greater than volume diffusion. These results are correlated with the information available about the energy of grain boundaries, and it is concluded that at small angles the dislocation model of grain boundaries describe satisfactorily the situation, while at larger angles the grain boundaries are better described in terms of areas of fit and misfit.
The Necessary Number of Elements in a Directional Ring Aerial
Authors: Knudsen H. Lottrup
Published: April 2005

An investigation is made concerning the dependence of the array characteristic of a directional ring aerial on its number of elements. It is shown that an odd number of elements is more favorable than an even number in approximating the array characteristic of a similar ring aerial with infinitely many elements. It was previously shown by Page that a similar statement applies to an azimuthly omnidirectional, fading-reducing, concentric ring aerial; this result is contained as a special case in this investigation. The present paper deals especially with the case in which the principal direction of the antenna array is horizontal; the theory for this case is illustrated by a numerical example.
Predominantly Subharmonic Oscillations
Authors: Ludeke Carl A.
Published: April 2005

In this paper an electromechanical analog previously reported, is used to investigate the phenomena of subharmonic oscillations. Special consideration is given to the case in which the subharmonic ``predominates,'' i.e., in which the amplitude of the fourier component having the subharmonic frequency is greater than the amplitude of the fundamental. An investigation is then made of the possible transitions between subharmonics of different orders.
General Theory of Symmetric Biconical Antennas
Authors: Schelkunoff S. A.
Published: April 2005

This paper presents the input admittance of a symmetric biconical antenna of an arbitrary angle as the limit of a certain sequence of functions. The first term of this sequence approaches the exact expressions for the input admittance as the cone angle approaches either zero or 90°. For this reason our conjecture is that this term represents a good first approximation for all angles.
The Concept of Force in Dislocation Theory
Authors: Peach M. O.
Published: April 2005

The concept of ``force acting on a dislocation'' (or other imperfection) is intrinsically different from the concept of force as used in newtonian mechanics, and must be defined. A definition is given which preserves the basic property (1) that the direction of the resultant force gives the direction in which the imperfection will actually move if the atomic constraints do not prevent motion. For imperfections in an infinite crystal, and assuming linear elasticity, two further properties are established: (2) the parallelogram law of adding forces is valid, and (3) Newton's law of equal and opposite action and reaction is valid. A critical review of previous work relating to forces between crystal imperfections is given.
Atomic Clocks and Frequency Stabilization on Microwave Spectral Lines
Authors: Townes C. H.
Published: April 2005

Application of the various types of radiofrequency spectral lines to accurate frequency stabilization and time standards is surveyed. Pertinent characteristics of microwave gas absorption lines and the various types of errors in frequency stabilization due to the nature of these absorption lines or to fundamental thermal noise are discussed in detail. It is shown that time standards synchronized with microwave absorption in ammonia or resonances in molecular or atomic beams have limits of accuracy of the order of 1 part in 1012 for a short time, and still smaller limiting fractional errors over longer periods of time.
Contact Potential Variations on Freshly Condensed Metal Films at Low Pressures
Authors: Antes Leland L. , Hackerman Norman
Published: April 2005

The reason for contact differences of potential is discussed. Since it is purely a surface phenomenon, subject to wide variation as the result of adsorbed and chemically combined surface layers, it is of interest to observe the change of contact potential as a function of time for various freshly evaporated metal films in high vacuums. The results thus obtained indicate characteristically different behavior for each of the six metals studied. Electrical resistance measurements made on similar metal films under similar conditions are correlated with contact potential measurements.
Volta Potentials of the Copper-Nickel Alloys and Several Metals in Air
Authors: Uhlig Herbert H.
Published: April 2005

Volta potentials of various metals approximately parallel the emf series. Metals abraded wet are more noble than when abraded dry, the transition metals changing an average of 0.28 volt compared with 0.07 volt for the nontransition metals. This owes possibly to the greater tendency of the transition metals to chemisorb oxygen, especially in the presence of moisture. All metals change in the noble direction upon aging in air, the average value being 0.3 volt after six days.

Potentials for copper-nickel alloys, plotted with composition, fall on a sigmoid curve, whereas potentials for composite electrodes made up of separate nickel and copper areas are linear with percent area of nickel exposed. Commercial nickel-copper alloys above 50 percent nickel age more rapidly than laboratory alloys. The cause may lie in deoxidizers like magnesium or aluminum, present in commercial alloys, but absent in the laboratory alloys. This suggests a nondestructive method for detecting impurities of this kind in metals.
A Technique for Preparing Beta-Ray Autoradiographs of Metals and Minerals
Authors: Michael A. B. , Leavitt W. Z. , Bever M. B. , Spedden H. R.
Published: April 2005

A technique for preparing autoradiographs of metals and minerals on a microscale is described. Limitations of this technique and possible variations are indicated. Illustrative examples of autoradiographs are presented and interpreted.
Ultrasonic Propagation in Liquids under High Pressures: Velocity Measurements on Water
Authors: Holton Gerald
Published: April 2005

The problem under discussion is the velocity of ultrasonics in liquids, specifically water, at various temperatures and high pressures. This report deals with the apparatus, and with some representative results obtainable with it.

The electrical apparatus makes use of a presentation unit (Dumont 256 or A/R 'scope) which synchronizes the sequence of operations by internally generated trigger signals at low repetition rates. Three- to five-microsecond pulses at controllable amplitude and approximately 15 Mc/sec carrier frequency are imposed on an X-cut quartz crystal which has been placed inside a pressure-supporting vessel containing the test sample. The resulting ultrasonic pulses in the liquid are reflected back and forth over a definite path length between the transducer and a mirror. After amplification in a receiver strip the complete echo-pattern becomes available for visual comparison on the presentation screen. The timed relative delay (and the measurable amplitude differences) between successive pulses furnish data for velocity (and attenuation) measurements when certain corrections are attended to.

Representative data are given for the velocity in water (to 0.1 percent) as a function of pressure to about 6000 atmospheres. From the data on water, information is derived on the temperature coefficient of sound velocity and on the ratio of specific heats at increasing pressures. The latter results are compared with those obtained directly from purely static experiments, and the advantages of the ultrasonic measurement technique for the derivation of some of the thermodynamic coefficients are cited.
Electron Microscopic Replica Studies of Porosity in Fused Iron Catalysts
Authors: McCartney J. T. , Anderson R. B.
Published: April 2005

The preparation of various replicas of a fused iron catalyst is described. Micrographs of these replicas show comparable fine structures that are attributed to the pores developed in the catalyst upon reduction. Dimensions of these fine structures compare reasonably well with pore diameters calculated from pore volume-surface area determinations.
A Method of Growing Single Crystals of Lead Telluride and Lead Selenide
Authors: Lawson W. D.
Published: April 2005

Single crystals of lead telluride measuring up to 1¼-cm diameter and 6 cm long have been grown in sealed silica crucibles by the Bridgman-Stockbarger method of lowering a melt slowly through a freezing level. The crystals have been grown for the purpose of testing the semiconducting and allied properties of lead telluride in that form. Extreme purity of the materials and cleanliness of the crucible have been found essential for successful growth. X-ray tests have shown that the specimens are single crystals. The purest crystal grown so far had a conductivity corresponding to an electron concentration of 5×1014 per cc. Attempts to introduce excess of one of the constituents—lead or tellurium into the crystal lattice during growth have not so far been successful.
Exact and Approximate Equations for Wave Propagation in Acoustic Horns
Authors: Stevenson A. F.
Published: April 2005

Exact equations are given for the propagation of acoustic waves in horns of arbitrary shape. These equations are similar to, though simpler than, the equations previously found for electromagnetic horns, and can be regarded as giving rise to an infinite number of coupled modes of propagation. If the coupling is neglected, the equation for the fundamental mode is the familiar one, but the theory also furnishes equations for the higher modes. The error involved in neglecting coupling is discussed.