bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies in Newtonian Flow. III. The Dependence of the Viscosity of Liquids on Molecular Weight and Free Space (in Homologous Series)
Authors: Doolittle Arthur K.
Published: April 2005

The free-space concept, previously applied to variation resulting from a change in temperature only, is here adapted to a case where both temperature and molecular weight vary. The molecular weight range of the n-paraffins illustrative of this case is limited to m=100 through m=240. Over this range of molecular weights the family of lines represented by lnη=B(ν0/νf)+lnA intersects the vertical axis at very nearly a common point. By assuming a common intercept and representing the slopes of this family of lines in terms of molecular weight, an expression defining viscosity as a function of molecular weight and free space is deduced. This expression reproduces the ``selected data'' satisfactorily over the molecular weight range mentioned. Its greater significance as a step in the development of a far more useful function will become apparent in the succeeding paper.
The Measurement of Ultrasonic Attenuation in Solids by the Pulse Technique and Some Results in Steel
Authors: Roderick R. L. , Truell Rohn
Published: April 2005

Pulse techniques for the measurement of attenuation in solids have been extended and refined sufficiently to obtain dependable measurements over a frequency range from 5 to 50 megacycles. Understanding of the relative importance of beam spreading, geometrical boundaries, and method of coupling has been improved. Coupling by means of water buffer and direct mounting is discussed in detail.

Attenuation measurements in the frequency range from 5 to 50 megacycles have been made on chrome molybdenum steel specimens, and these measurements have shown large differences in ultrasonic attenuation for samples of the same chemical composition but different heat treatment. The resulting differences are connected with anisotropy which appears in the photomicrographs. The attenuation measurements are quite sensitive to heat treatment and other factors. The application of the methods to metallurgical problems and the physics of solids is suggested.
Statistical Theory of Rubber-Like Elasticity. V. The Stress Birefringence
Authors: Isihara Akira , Hashitsume Natsuki , Tatibana Masao
Published: April 2005

The effects of network formation of non-Gaussian chains on the stress-birefringence are calculated. If the birefringence is plotted against the stress, the effects make the curve deviate from a straight line. When it is plotted against the elongation, the curve will rise above that corresponding to independent Gaussian chains in agreement with the experiments.
Domain Structure of Perminvar Having a Rectangular Hysteresis Loop
Authors: Williams H. J. , Goertz Matilda
Published: April 2005

An investigation has been made of the magnetic domain structure of Perminvar (43 percent Ni, 34 percent Fe, 23 percent Co) ring specimens having rectangular hysteresis loops after heat-treatment in a magnetic field. Domain patterns obtained with colloidal magnetite showed curved domain boundaries extending completely around the rings, forming circles concentric with them. Changes in magnetization occur when an applied field causes the circular boundaries either to expand or contract so that there is a change in the relative values of clockwise and counter-clockwise flux. A nucleus of reversed magnetization was formed by making a small notch in a specimen, and this decreased the coercive force and hysteresis loss by a factor of two. It was found that in a 180° domain boundary it was possible to make the change in spin orientations, which occurs in going from one side of the boundary to the other, have either a right- or left-hand screw relation, by the application of a field of appropriate sign perpendicular to the surface. The effect of super-posing an applied alternating field was also investigated, and an effective permeability of 4,000,000 was obtained.
Lattice Parameters, Coefficients of Thermal Expansion, and Atomic Weights of Purest Silicon and Germanium
Authors: Straumanis M. E. , Aka E. Z.
Published: April 2005

Lattice parameter determinations of 99.97 percent pure silicon (containing 0.03 percent carbon) were carried out using the asymmetric method, a 64-mm precision camera in a thermostat at constant temperatures (10, 20, 30, 40, and 50°C). The powder mounts, about 0.12-mm in diameter, were translated and rotated during the exposure. Only the (444)-CuKα1 line was used for the determinations. The lattice parameter a=5.41991±0.00003kX (5.43086A) at 20°C, corrected for refraction, was obtained; the linear lattice expansion coefficient (between 10 and 50°C) was 4.15×10−6, the density at 20°C was 2.32831±0.00031 g/cm3 (determined by the suspension method), and the atomic weight was 28.083±0.013 (in agreement with the new chemical weight 28.09) showing that the silicon crystals used, under certain limitations, were sound although the possibility of interstitial atoms is not excluded.

The lattice parameter of purest germanium (99.99 and 99.999 percent) was measured by the same method using the (422)-CrKα1 and α2 lines: a20=5.64607±0.00004kX (5.65748A) for both materials. The expansion coefficients were α=6.65×10−6 and 5.92 ×10−6, respectively. The density was 5.3234±0.0025 g/cm3 at 25°C and the calculated atomic weight 72.593±0.037 in agreement with the present chemical weight 72.60. Thus, germanium crystals are sound; however, interstitial atoms are possible.

The precision of lattice parameter determination was about 1:200,000, but in the case of 99.999 percent germanium the precision was considerably better. This shows again that lattice constant determinations can be performed with highest precision and without use of any extrapolation method. The method of lattice parameter determination applied is an absolute one.
Approximate Elastic Spectrum of β-Brass from X-Ray Scattering
Authors: Cole H. , Warren B. E.
Published: April 2005

The temperature diffuse scattering of x-rays from a single crystal of β-brass has been measured at room temperature using a Geiger counter spectrometer and crystal monochromated CuKα radiation. Measurements were made throughout a large region in reciprocal space, with special attention given to the hko plane. The results were in excellent qualitative agreement with the theory developed by Laval and James in which temperature vibrations are expressed in terms of elastic waves. From the measurements, dispersion curves are obtained giving the velocity and frequency of the elastic waves, in the [100], [110], and [111] directions, as a function of their wavelengths. An approximate frequency spectrum is then calculated on the basis of these dispersion curves. The velocities at infinite wavelength are shown to agree with those given by elastic theory using the static elastic constants.
The Allotropic Transformation of Hafnium and a Tentative Equilibrium Diagram of the System Zirconium-Hafnium
Authors: Fast J. D.
Published: April 2005

The temperature of the transformation in hafnium is at least 550°C higher than the value recently reported by Duwez (1310°±10°C). A tentative equilibrium diagram of the system zirconium-hafnium is given.
Physical Structure and Magnetic Anisotropy of Alnico 5. Part I
Authors: Heidenreich R. D. , Nesbitt E. A.
Published: April 2005

It is concluded from electron metallographic results that the high coercive force and anisotropy of Alnico 5 are caused by a very finely divided precipitate produced by the permanent magnet heat treatment. This precipitate is a transition structure rich in cobalt and is face-centered cubic with a0 = 10A and appears as rods growing along the [100] directions of the matrix crystal when no magnetic field is applied during heat treatment. The size of the precipitate rods at optimum properties is approximately 75–100A by 400A long. The spacing between rows of rods is about 200A. The rods are not distinctly resolved in the electron images unless they are grown by aging at 800°C. Their orientation and structure is clearly evident in the electron diffraction patterns at all stages of growth. The precipitate responds to a magnetic field applied during heat-treatment both by suppression of nuclei making an angle greater than about 70° with the field and by the forcing of the rods off the [100] direction into that of the field. The precipitate rods tend to scatter in direction about the field vector when the field is off the [100] but are aligned accurately when the field is along [100].
Statistical Errors in Measurements on Random Time Functions
Authors: Davenport W. B. , Johnson R. A. , Middleton D.
Published: April 2005

The statistical errors in time-average measurements of various properties of (stationary) random time functions are analyzed for their dependence on the averaging interval, the method of averaging, and the statistics of the particular time function under observation. The specific averaging processes considered here are as follows:(1) The continuous time average (1T∫0TZ(t)dt),(2) The summation (by discrete sampling techniques) (1N∑n=1NZ(nT0)), and(3) The smoothing accomplished by various low-pass filters (for example, a dc meter).

Here Z(t) may represent the output of a linear or nonlinear device. As a particular example, the measurement of the power in a random noise voltage of band width ωF is analyzed in detail. The expected root-mean-square error approaches asymptotically the value (K/ωFT)½, where K is some numerical constant, depending on the device in question. For (1) and (2) T is the total observation time while for (3) it is proportional to a relevant time constant of the low-pass filter. A short discussion of the relative merits of correlators and spectrum analyzers is included, together with a brief treatment of the distribution function of the error in the measurement.
Studies in Newtonian Flow. IV. Viscosity vs Molecular Weight in Liquids; Viscosity vs Concentration in Polymer Solutions
Authors: Doolittle Arthur K.
Published: April 2005

This is the final installment in the current series entitled ``Studies in Newtonian Flow.'' In this paper, the molecular weight—free-space function applicable to n-paraffins m=100 through m=240 at various temperatures is further generalized to apply to homologous series of all Newtonian liquids at constant temperature. The resulting molecular weight function thereby loses some fidelity, and the slopes and intercepts no longer have physical significance. The generalized logarithmic decrement equation nevertheless reproduces viscosity data over extended ranges of molecular weight (at constant temperature) far better than expressions previously proposed. The equation is extended to apply to mixtures of liquids and finally to polymer solutions.
Flow over Thick Plate with Circular Hole
Authors: Smythe W. R.
Published: April 2005

Formulas are derived for the scalar potential of a uniform magnetic field parallel to the plane face of an infinite nonpermeable medium in which a circular hole of radius, a, is drilled normally. Outside the hole the formula is an oblate spheroidal harmonic series for which eleven coefficients are given, and inside it is a Bessel function series for which twenty coefficients are given. The case of a flat-bottomed hole whose depth is greater than its diameter is included. All series converge slowly in the plane of the opening but rapidly elsewhere. When a plane electromagnetic wave falls on such a hole, the fraction of the energy scattered is approximately 11.7(2a/λ)4 cosθ if the wavelength λ is much greater than 2a and θ is the angle of incidence. Such a hole in the thick plane wall of a resonant cavity, at a point where H is uniform and E is zero, decreases the resonance frequency ω by 0.2366μa3H2Wm−1ω where Wm is the magnetic energy in the cavity when H is measured. A lug of radius a affixed to the plane face of a cylindrical rod of the same material, length l and cross section A changes the resistance in the ratio [1+0.3154a3/(Al)]−1.
Elastic Constants of Beta-Brass Single Crystals
Authors: Artman Robert A. , Thompson Donald O.
Published: April 2005

Measurements of Young's modulus and the rigidity modulus for a set of beta-brass single crystals of 55 atomic percent copper and for single crystals of beta-brass near the zinc-rich phase boundary reveal a dependence of the elastic constants upon composition. Comparison is made with previous results, whereby it is found that the moduli of beta-brass for different compositions may be obtained by the use of a linear interpolation in terms of the atomic ratio of copper to zinc. Derived quantities are generally related in this manner also. The value of Σ111 (Poisson's ratio) is shown to be a positive quantity, in contrast to that derivable from previous results.

Results of bending-torsion measurements are presented. The agreement between measured values and those calculated from the principal elastic constants provides assurance for the consistency of the measurements.
A Steady-State Heat Flow Problem for a Quarter Infinite Solid
Authors: Karush William
Published: April 2005

The steady-state temperature field T(x, y) in a homogeneous solid x≥0, y≥0, z arbitrary is studied when the flow out the face y=0 is a prescribed function g(x). Along the face x=0 either the condition T=0 or k(∂T/∂x) = hT is assumed. Of especial interest is the temperature at the face y=0 and the flow at the face x=0; particular attention is paid to the case g(x)=0 for x>a>0. The results have application to situations in which heat is being drawn off at the corner of a solid.
The Dielectric Constant of Dry Air
Authors: Hughes J. V. , Armstrong H. L.
Published: April 2005

A sensitive and accurate method for determining the real part of the dielectric constant of gases at microwave frequencies is described. The method eliminates some possible sources of systematic error inherent in earlier methods.

The dielectric constant of dry air at N.T.P. has been determined as 1.000569, at a frequency of 3000 Mc/sec. This is in good agreement with other results, at 24,000 Mc/sec, at 9000 Mc/sec, and at low frequencies, thus verifying that the dielectric constant is independent of frequency up to nearly 30,000 Mc/sec An earlier result suggesting the contrary was found to be in error because of insufficient drying of the air.
Information Theory and Its Application to Taxonomy
Authors: MacDonald D. K. C.
Published: April 2005

A possible source of confusion between the concept of information content and entropy in the theory of information is discussed and resolved. Information theory is then applied to the problem of taxonomy or classification of data and several models are discussed, representative of various possible methods of filing data with the purpose of determining the optimum size of filing-unit in relation to the given data. The possible fields of application envisaged include the classification of faults in a system, the statistical analysis of data or the indexing of books, letters, etc.
Theory of Jet Formation by Charges with Lined Conical Cavities
Authors: Pugh Emerson M. , Eichelberger R. J. , Rostoker Norman
Published: April 2005

An article by Birkhoff, MacDougall, Pugh, and Taylor (see reference 1) presented hydrodynamic theories of jet formation and target penetration by explosives with lined conical cavities. However, it was unable to explain satisfactorily why the jets produced are several times as long and, therefore, several times as effective as the steady-state theory predicts. It is shown here that these difficulties are overcome by assuming a variable instead of a constant collapse velocity for the walls of the conical liner. The variability in the collapse velocity produces a surprisingly large change in the process of jet formation.
Magnetically Induced Ultrasonic Velocity Changes in Polycrystalline Nickel
Authors: Johnson S. J. , Rogers T. F.
Published: April 2005

Measurements of magnetically induced velocity changes in polycrystalline nickel rods are discussed. Shear and compressional ultrasonic propagation modes are used throughout the frequency range of 1–10 megacycles. The polycrystalline measurements are compared to recently published single nickel crystal values. The ΔE effect is found to decrease with increasing frequency throughout the megacycle region, showing general agreement with low frequency measurements.
The Radiation Pattern of an Antenna over a Circular Ground Screen
Authors: Storer James E.
Published: April 2005

In a previous paper [The Input Impedance of an Antenna Over a Finite Ground Screen, Technical Report No. 119 (Cruft Laboratory, Harvard University, November 30, 1950)] the author treated the problem of the input impedance of an antenna erected over a large circular screen. Using the formulation developed therein, an expression is obtained for the entire radiation pattern of an antenna over a large circular screen.

The most important difference between the pattern of an antenna over a large screen and an antenna over an infinite screen is the presence of lobes over the antenna. From the expression for the radiation pattern, simple formulas are obtained for: (a) the number of lobes, (b) the angular position of the lobes, and (c) the angle, βmax, within which the lobes occur. One important result obtained is that θmax∼(1/d12),where d is the diameter of the screen. It is apparent that the effects of a finite screen decrease very slowly as the diameter of the screen is increased.
Electromagnetic Reflection and Transmission by Gratings of Resistive Wires
Authors: Lewis Edward A. , Casey Joseph P.
Published: April 2005

Calculations show that the effect of increasing the resistivity of the wires is to decrease the amplitude of the reflection coefficient and the phase of the transmission coefficient. The sign of the changes in the amplitude of the transmission coefficient and the phase of the reflection coefficient depends upon the amplitude of the reflection coefficient of a geometrically similar grating having no resistance. A numerical example for a typical grating is worked out and several charts are supplied for convenience in computing.
Electron Microscope Study of Plasticized Latices
Authors: Bradford E. B.
Published: April 2005

Silicon monoxide replicas of the surfaces of air-dried films are shown which were cast from a Saran latex containing various amounts of plasticizer. It can be observed that the poor films are composed of discrete individual particles while in a continuous transparent film the particles have coalesced into a polymeric mass. Replicas of surfaces of films are shown which were produced from different types of synthetic latices before and after they had been plasticized.
The Thermal Neutron Diffusion Length in a Heterogeneous Pile
Authors: Plass Gilbert N.
Published: April 2005

The diffusion equation for thermal neutrons in a pile with finite sides and having a three-dimensional lattice structure of fissionable material and moderator is solved to the first three orders by an expansion in spherical harmonics. This solution is used to calculate the difference in thermal utilizations of a pile of infinite extent and one with finite sides. From this difference is calculated an accurate expression, Eq. (24), for the diffusion length in a pile having a lattice structure. This expression is compared with the usual simplified equation for the diffusion length. The leakage of neutrons from a pile is also obtained from this calculation.
A Mathematical Analysis of Parallel-Connected Magnetic Amplifiers with Resistive Loads
Authors: Pipes Louis A.
Published: April 2005

A mathematical analysis of a parallel-connected magnetic amplifier with a resistive load is presented. The analysis is based on two distinct analytical approximations of the magnetization curve of the core material; a polynomial and a hyperbolic function. The variation of the core flux and the output current of the amplifier as a function of time are determined by the solution of an integral equation. A finite difference method is developed to determine the response of the loaded amplifier that makes direct use of the magnetization curve of the core material.
A Study of the Annealing Kinetics in Cold Worked Copper
Authors: Bowen Dwain , Eggleston R. R. , Kropschot R. H.
Published: April 2005

The resoftening kinetics for cold work in copper have been studied using residual resistance as a measure of the degree of recovery. The specimens were quickly heated to the annealing temperature, held at temperature for a measured time, and quenched for measurement. It was assumed that the cold work could be characterized by a number of lattice defects n and that the residual resistance change produced by these defects obeyed Matthiessen's rule. It was found that the resoftening could be represented by a single process of activation energy 28.3 kilocalories per mole. The complete annealing kinetics are described by a fourth-order reaction, dn/dt=−vn4e−E/RT.
Chemical Reactions in Barium Oxide on Tungsten Emitters
Authors: Hughes R. C. , Coppola P. P. , Evans H. T.
Published: April 2005

When barium carbonate is heated in vacuum in contact with tungsten, the following reactions may occur in sequence as progressively higher temperatures are reached: (1) WO3+BaCO3⇄BaWO4+CO2. (2) 3BaCO3+W⇄Ba3WO6+3CO. (3) BaCO3⇄BaO+CO2. (4) 6BaO+W⇄Ba3WO6+3Ba.

At a temperature of approximately 600°C, reaction (2) begins to occur with appreciable speed. Reaction (3) proceeds at 800–900°C. Reactions (2) and (3) may be made to proceed simultaneously, the preponderance of one over the other depending upon state of subdivision and intimacy of admixture of the reactants. Under favorable conditions, reaction (2) may be driven to completion with almost total absence of reaction (3). Reaction (4) progresses with appreciable speed at temperatures over approximately 1000°C.

Activated cathodes of BaO on W will have an interface of Ba3WO6 formed by reactions (2) or (4), or both, unless unusual precautions are taken to avoid this. The end result of heating the cathode is the conversion of the entire thickness of the oxide coating to the basic tungstate. The resulting coating of Ba3WO6 on W is unreactive and nonvolatile at temperatures up to 1300°C, and provides no significant thermionic emission.
Characteristics of the High Current Tungsten Arc in Argon, Helium, and Their Mixtures
Authors: Skolnik Merrill , Jones T. B.
Published: April 2005

An experimental study was made of the properties of the high current dc electric arc in argon, helium, and their mixtures at atmospheric pressure. Tungsten-rod electrodes were used over a current range from 10 to 100 amperes. Measurements of the voltage-current and the voltage-electrode separation characteristics were made along with the plasma voltage gradients in both the pure gases and in the mixtures.

It was found that this type of arc was very stable when the system was free from oxide impurities and that the cathodic processes played a major role in the arc mechanism. The results obtained suggest that the value of the anode voltage drop for the inert gas arc over the current range studied is negligibly small. At the higher currents or with smaller diameter cathodes, tungsten was able to evaporate from the cathode in sufficient quantities to influence the character of the discharge. It was observed that the properties of the arc in mixtures of gases were in between the properties observed in the pure gases. The lower ionization potential gas, argon, had more effect on the properties of the arc in mixtures than did helium. As long as there was at least 15 percent argon present in the mixture, the arc properties and appearance were more like those observed in argon than in helium.
Equivalences for the Analysis of Circuits with Small Nonlinearities
Authors: Cunningham W. J.
Published: April 2005

Equivalent forms may be useful in the analysis of the steady-state operation of circuits containing a nonlinear resistance element. Provided the amount of nonlinearity is not too large, the nonlinear element can be replaced by a linear resistance and several generators of voltage or current. The amplitude, phase, and frequency of these generators are determined by the nature of the nonlinearity and by the fundamental component of current in the nonlinear element.
X-Ray Absorption Corrections for Single Crystals
Authors: Evans Howard T.
Published: April 2005

It is shown in this paper that exact expressions may be derived for the absorption factor for the intensity of Bragg reflection by a small euhedral crystal completely bathed in a parallel x-ray beam. The expression is a sum of terms evaluated for subdivisions of the crystal determined according to discontinuities in boundary conditions imposed by the distribution of edges between the plane faces of the crystal. For a prismatic crystal of constant cross section, general expressions are derived for five general types of subdivisions in terms of the linear absorption coefficient and certain linear dimensions. Other expressions are also given for other types of subdivisions which arise in certain cases. The application of the method, including corrections for secondary extinction, is illustrated by calculations on tetragonal barium titanate.
Conical Surfaces of Fracture Produced by Asymmetrical Impulsive Loading
Authors: Rinehart John S. , Pearson John
Published: April 2005

Conical surfaces of fracture generated in thick-walled cylinders that were asymmetrically and impulsively loaded through the use of internal explosive charges are presented. It is deduced from qualitative considerations that the conical fractures result from the interaction between transient tensile stress waves. The two tensile stress waves that are responsible for the fracture arise from a single compressional stress wave that is reflected from two inclined free surfaces. The angle of fracture associated with these conical surfaces has been used to measure the velocity of propagation of the stress waves in low-carbon steel, brass, copper, lead, and 24ST aluminum alloy.
Methods of Measuring the Properties of Ionized Gases at High Frequencies. II. Measurement of Electric Field
Authors: Rose David J. , Brown Sanborn C.
Published: April 2005

Experimental methods are given for determining the electric field within resonant cavities in the microwave region. Methods are discussed of calculating the electric field in both simple and complex structures used in gas discharge studies.
The Initial Conduction Interval in High Speed Thyratrons
Authors: Woodford James B. , Williams Everard M.
Published: April 2005

The initial conduction interval in thyratrons, or time interval during which the major rise in current occurs, is shown to be dependent on two parameters. The first of these is dependent on tube construction and the second on circuit elements. It is shown that both factors are significant in operation of hydrogen thyratrons in millimicrosecond switching service.
Specimen Charging in the Electron Microscope and Some Observations on the Size of Polystyrene Latex Particles
Authors: Ellis S. G.
Published: April 2005

From observations in the shadow electron microscope and the standard electron microscope it is concluded that specimen charging does not significantly change the magnification of the latter, provided that the specimen is less than a few microns in thickness and the illuminating electron beam simultaneously strikes a nearby grounded conductor such as the supporting mesh.

The difference in size of shadowed and unshadowed Dow Latex 580G, lot 3584 reported by Kern and Kern (J. Appl. Phys. 21, 705 (1950)) is attributed to an added layer of material on the shadowed particles. Evidence in support of this view is presented, and the results of other workers are discussed in the light of it.
The Creep of Zinc Single Crystals
Authors: Slifkin L. , Kauzmann W.
Published: April 2005

The transient creep of single crystals prepared from 99.999 percent zinc was studied at 35°C and at strain rates of the order of 10−5/min. The results are given by the relation: creep rate=at−n, where a and n are constants and t is the time after applying the load. This is of the form expected from Andrade's equation, but the exponent n had only approximately the value ⅔ found by Andrade and varied from experiment to experiment. An additional instantaneous plastic strain occurs on applying the stress at the start of a creep test. It was found to be proportional to the subsequent transient creep rate (as measured by a in the above equation) in a series of tests made on a given crystal. In addition to the process of recovery from strain-hardening whereby a zinc crystal completely resoftens in a few days at 35°C, there appears to be a rapid, but very limited, stage of recovery, the effects of which quickly disappear upon further deformation. Some crystals exhibited a decrease in plasticity when allowed to rest for about two days at 35°C after a creep test. The development of this ``rest-hardening'' is dependent to some extent on the occurrence of creep prior to the rest period. Zinc crystals were observed to contract with time after removing the load in a creep test. The extent of this contraction varied among specimens and among different tests made with the same specimen and was of the order of 10−5 cm/cm or less. This appears to be the first report of such an after effect in single crystals of a pure metal. The results are discussed in relation to the findings of other workers and are interpreted in terms of recent models of the metallic state.
The Theory of an Oscillating Cylinder Viscometer. Part I
Authors: Ibrahim Ali A. K. , Kabiel A. M.
Published: April 2005

The theoretical distribution of velocity across a liquid (Newtonian) between two coaxial cylinders and the velocity gradient at the inner cylinder is calculated in a new way. The equation used for calculating the coefficient of viscosity of the liquid is also given. The theory agrees with experiment for all values of θ0/φ0≤1/2 (where θ0 is the amplitude of deflection of the inner cylinder and φ0 is the amplitude of the oscillations inexorably imposed on the outer cylinder).
Grain Boundary Diffusion of Zinc in Copper
Authors: Flanagan R. , Smoluchowski R.
Published: April 2005

In continuation of a previous study of grain boundary diffusion of silver in copper the grain boundary diffusion of zinc along grain boundaries of columnar copper has been investigated at various temperatures. The results confirm the influence of the angle between the grains on diffusion and indicate an angular dependence of the activation energy. The latter reaches very small or even negative values in a certain range of orientation in agreement with the proposed model.
Some Limitations on the Maximum Frequency of Coherent Oscillations
Authors: Elliott Robert S.
Published: April 2005

Electron beam oscillators are placed in one of two groups depending on whether or not they employ resonant energy-extractors. A natural upper frequency limit exists for the group which does. This limit depends chiefly on the ac beam current density and the noise level in the resonant structure. For practical values of these parameters, the maximum frequency is below the range of visible light.
An Estimate of the Energies of the Positive Ions in a Negative Point-to-Plane Corona
Authors: Weissler G. L. , Schindler Mark
Published: April 2005

An attempt has been made to measure the energies with which positive ions arrive at the cathode of a negative point-to-plane corona in N2. A hairpin thermocouple was used as the point electrode. It was heated by the corona current, and its thermal emf was recorded by a galvanometer. After appropriate calibration, the potential across the Crookes darkspace was determined to be about 300 volts, and the average energy with which ions arrive at the corona point to be about 15 ev.
On the Theory of Antenna Beam Shaping
Authors: Dunbar Allen S.
Published: April 2005

The diffraction pattern of an aperture with amplitude distribution A(x) and phase function ψ(x) is examined for two cases: (1) controlled variation of the amplitude distribution with known uniform phase; (2) controlled variation of phase with known amplitude distribution. For Case 1, it is shown that a symmetrically tapered amplitude distribution produces a diffraction pattern with reduced secondary lobes, while an asymmetric amplitude distribution produces a shaped pattern. Thus, antenna beam shaping may be achieved by controlled variation of amplitude distribution in an aperture in which there is uniform phase. For Case 2, it is shown that a specified beam shape may be approximated by controlled variation of phase in the aperture when the amplitude distribution is known. The method of calculation is an extension of the method originally formulated by Chu for calculating cylindrical reflectors to transform a given primary radiation pattern to a specified shaped pattern. A general formulation of Chu's method for an amplitude distribution on a curved surface is developed. The theoretical results are applied to the design of progressive-phase antennas and experimental results given.
Production of Monochromatic X-Radiation for Microradiography by Excitation of Fluorescent Characteristic Radiation
Authors: Rogers T. H.
Published: April 2005

In several types of applications of microradiography, particularly for histochemical and microchemical analysis by x-ray absorption spectroscopy, it is desirable to use monochromatic radiation of a wavelength selected specifically with reference to an absorption edge of the element of interest. An x-ray tube having as its target a material whose Kα characteristic wavelength is suitable is the most usual source of monochromatic x-radiation. In many cases, however, an otherwise desirable target is physically unsuitable for use as a target inside a vacuum tube. Hence, the possibility of producing fluorescent characteristic radiation with intensities sufficient for microradiography becomes of interest. The very high intensity of the primary x-ray beam made available by the newly developed beryllium-window x-ray tubes suggests new possibilities for the excitation of fluorescent radiation.

This paper reports the results of exploratory work attempting to establish the factors governing the intensity and degree of monochromaticity of fluorescent x-radiation. Several materials, ranging from titanium (atomic number 22) to molybdenum (42) were studied comparatively, with exciting radiations of various characteristics; titanium was studied in greater detail. It is concluded that a considerably higher degree of monochromaticity is obtainable by this method than by direct bombardment and that intensities useful for some aspects by microradiography are obtainable.
Electron Microscopy of Synthetic Latices
Authors: Maron Samuel H. , Moore Carl , Powell Allen S.
Published: April 2005

A study has been made by electron microscopy of the size and size distribution of 22 synthetic latices. Included are GR-S latices Types II, III, and V, polystyrene latices, and several latices of special character.

Details are given on sample preparation, measurement, application of corrections, calculation of number, volume to surface, and molecular weight average diameters, as well as the number and weight average distributions.

The weight average particle size range covered was 730 to 3920A. The smallest sizes were shown by Type II latices, followed in order by Type III, polystyrene, Type V, and some of the special latices. The latices were all nonhomogeneous in size and showed size distributions both on a number and weight basis which in some instances contained single and in some cases double maxima.
Thermal Force on an Aerosol Particle in a Temperature Gradient
Authors: Saxton R. L. , Ranz W. E.
Published: April 2005

Data on the thermal forces acting on aerosol particles in a temperature gradient are relatively few. Measurements are reported here on droplets of paraffin oil and castor oil suspended in air, showing the effect of temperature gradient, particle size, and particle material. The thermal force is directly proportional to the temperature gradient prevailing in the gas and to the particle diameter. It is an inverse function of the thermal conductivity of the aerosol material. The agreement between the experimental data and the theory of P. S. Epstein [Z. Physik 54, 537 (1929)] is satisfactory, a fortunate result in view of the approximations to the actual physical situation made in the derivation of the theoretical equation. The velocity of migration of aerosol particles in a temperature gradient can be estimated from Epstein's formula.
An Integrable Case of Electron Motion in Electric and Magnetic Field
Authors: Poritsky H. , Jerrard R. P.
Published: April 2005

Electron motion is studied in a two-dimensional electric field of potential V=A+B(x2−y2)/2 and a uniform magnetic field H=(0,0, −H) normal to the electric field, where A, B, −H are constants. The equipotential lines of the electric field in any plane z=const. consist of rectangular hyperbolas with a point of zero field strength at x=0, y=0. The differential equations of motion are integrated, and expressions are given for the electron paths. For this type of field, the electron motion consists of superposition of elliptic and hyperbolic motions, that is, of a simple harmonic motion along an ellipse whose center moves along a hyperbola. The latter hyperbolas intersect the equipotential hyperbolas, so that, unlike the uniform crossed field case, the electron may drift into regions of higher or lower potential.
The Effect of Accelerating Voltage and Specimen Morphology on Electron Diffraction Patterns
Authors: Ellis S. G.
Published: April 2005

Using empirical relations established in the study of electron diffraction patterns of uniform thin films of aluminum, the contrast between the most intense ring and the background is calculated for other morphologies as a function of the accelerating voltage on the camera.

In all cases the contrast increases with voltage. The gain is marked if the specimen is nowhere very thick. For specimens that have very thick regions the contrast increases approximately as the square root of the voltage in the range 50 to 150 kv. The situation in reflection-diffraction in general lies between these extremes. Increasing the voltage has a more limited effect on increasing the range of specimen thicknesses that can be examined than had been previously supposed.
Methods of Measuring the Properties of Ionized Gases at High Frequencies. III. Measurement of Discharge Admittance and Electron Density
Authors: Rose David J. , Brown Sanborn C.
Published: April 2005

Experimental methods are given for determining the complex admittance and electron density of gas discharges by the use of microwave techniques. Applications are discussed where the discharge is contained in either high or low Q resonant cavities.
On the Theory of Prediction of Nonstationary Stochastic Processes
Authors: Davis R. C.
Published: April 2005

We consider the following problem of prediction: During a finite time interval T the real valued function S(t)+N(t) is observed, in which S(t) is a signal and N(t) is a linearly superimposed noise disturbance. The problem is to predict the value of a given linear functional of S(t), the predictor formula having certain preassigned ``optimum properties'' among a certain class of predictors. In the case in which the mean value of S(t) is known, the random components of S(t) and N(t) are strictly stationary, and the time interval T is infinite, a complete solution to this problem has been given by N. Wiener. (In the case of discrete time series, the solution was given by A. Kolmogoroff.) This theory has been extended by L. Zadeh and J. Ragazzini [J. Appl. Phys. 21, 645 (1950] to the case in which T is a finite time interval and the mean value of S(t) is unknown but is restricted to be a polynomial in time. We extend the above theories to the case in which the random components of both S(t) and N(t) are nonstationary in time and merely possess finite continuous covariance and cross-covariance functions. The analytical tools of probability theory which we use are those developed independently by M. Loève and K. Karhunen in their studies of a class of stochastic processes usually termed processes of second order. Apparently these techniques are practically unknown outside of certain mathematical circles. In the opinion of the author these techniques are extremely powerful in the analysis of transient random phenomena in linear systems.

Finally we give an exposition of a method of prediction by the theory of conditional probabilities. This method is applicable when the form of the joint probability distribution of signal and noise is known and hence is applicable to many practical problems, since this distribution is often Gaussian. In this particular case the predictor formula given by the theory of conditional probabilities is identical with the usual linear predictor formula given by the theory of least squares. In case the signal is a Markoff process, the method of conditional probabilities yields a much simpler prediction formula than the usual method of least squares.
A Study of the Oxide-Coated Cathodes by X-Ray Diffraction Method (I)
Authors: Yamaka Eiso
Published: April 2005

The relation between the crystal size of barium-strontium oxide and its thermionic emission was studied with the same vacuum tube. The crystal size was measured by an x-ray diffraction method. The measurements were made in vacuum by using thin mica windows as the entrance and exit ports for the x-ray beam. The emission was measured with pulse in order to avoid gas from the anode. Below 1050°C the crystal grows slowly, but above it crystal growth is rapid. It seemed that impurity activation is dominant at low temperatures, but heat activation is dominant at high temperatures.
Turbulent Diffusion and Erosion
Authors: Davies Richard W.
Published: April 2005

A new theory of turbulent diffusion is developed so as to describe the dynamics of particulate matter in fluid suspensions. In order that the statistical description be consistent with force equation dynamics of sedimentation, a new diffusion equation is derived from the postulates of a past-future stochastic process.

A steady-state suspension of particles in a turbulent stream is treated like an atomosphere. Dimensional arguments are used to retain the most relevant physical entities in a linear theory. It is shown that the bed load and mid-stream suspension of a muddy stream cannot be considered separately. Some experiments are discussed in this connection. A qualitative theory of sand rippling is explained in terms of the instability of a flat sandy bottom under certain turbulence conditions. A singular perturbation method is employed to obtain an asymptotic expansion of the solution of the equilibrium equation.

Assumptions are discussed and criticized. The advantage of the theory is that all statistical coefficients are averages of familiar dynamical quantities.
Heat Conduction in an Infinite Cylindrical Medium with Heat Generated by a Chemical Reaction
Authors: Nichols Peter L. , Presson Arthur G.
Published: April 2005

The nonlinear partial differential equation for heat conduction in an infinite cylinder with heat generated by a chemical reaction has been solved by means of an electronic differential analyzer. Solutions of the equations in dimensionless variable form have been obtained for a zero-order heat-release term and a first-order heat-release term. Altogether 162 solutions were obtained covering a range of activation energies from 10 to 20 kcal/mole. Empirical relations have been derived for the maximum temperature at the center of the cylinder as a function of the experimental variables involved. Also relations relating to the approximate completion of reaction in terms of the experimental variables were derived from the tabulated data. Several calculations were made to demonstrate the general nature of the numerical solutions.
Electric Strength and Molecular Structure of Saturated Hydrocarbon Liquids
Authors: Crowe R. W. , Sharbaugh A. H. , Bragg J. K.
Published: April 2005

A number of investigators have reported that the apparent electric strengths of straight-chain hydrocarbon liquids increase in a regular manner with increasing molecular chain length. In a recent publication we have presented evidence that this phenomenon is an illustration of a kind of Paschen's law for liquids. An observed linear dependence of the electric strengths of such hydrocarbons upon density suggested that chain length variation merely provided a means of changing the electron mean free path in the liquid.

In the present paper we describe the development of an improved technique for measuring electric strengths of liquids, and the application of this technique to a series of pure straight-chain and branched-chain liquid alkanes. As had been observed previously, the strengths of the straight-chain members of the series exhibit a linear relationship with density. The introduction of branches into the hydrocarbon chain, however, results in a definite decrease in strength. Extension of the measurements to hydrocarbons of more complicated structure has apparently introduced a kind of fine structure.

Measurement of the time dependence of electrical breakdown in liquid hydrocarbons shows that the formative time lag is relatively insensitive to changes in viscosity or molecular weight. For an electrode separation of 0.002 inch, it is approximately one microsecond.
Water Vapor Condensation Process in Supersonic Nozzles
Authors: Wegener Peter P.
Published: April 2005

The history of experimental and theoretical investigations of water vapor condensation phenomena in supersonic nozzles is reviewed. It is then shown empirically for a given experiment that the shocklike disturbance visible in flow pictures delineates the collapse of the supercooled state of the water vapor present in the air. All flow properties are calculated through this extended condensation zone from pressure distribution measurements, and it is seen that no shock waves are involved in the process. Finally a conversion of these data to an equivalent constant-area flow reveals that the latter would be an example of a weak detonation observed in nature as predicted by Burgers and by Reed.
Equivalent Circuit for a Passive Nonreciprocal Network
Authors: Haus H. A.
Published: April 2005

An equivalent circuit is proposed for a linear, passive, nonreciprocal, four-terminal network. It introduces an ideal amplifier and phase shifter. It is shown that the proposed equivalent circuit has certain advantages over equivalent network representations that use gyrators. In particular, standard measuring techniques used on reciprocal networks lead directly to the determination of six elements of the equivalent circuit. One additional measurement gives the remaining two parameters.
A Definition of Passive Linear Networks in Terms of Time and Energy
Authors: Raisbeck G.
Published: April 2005

A definition of passive linear network is made:

(a) The network is linear.

(b) If currents of any wave form are fed to the terminals of the network, the total energy delivered to the network is not negative.

(c) No voltages appear between any pair of terminals before a current is fed to the network.

When this definition is applied to two terminal networks, i.e., impedances, a necessary and sufficient condition that a two-terminal network be linear passive is that its impedance function be a positive real function.

An analysis of multiterminal networks yields as a necessary and sufficient condition from the foregoing hypotheses that a certain Hermitian quadratic form be positive definite. In the case of three-terminal networks, it reduces to 4R11R22−(R12+R21)2−(X12−X21)2≥0,where Rij+jXij=Zij are the terms of the matrix of impedances of the network. The relation of this formula to similar but not identical formulas of Gewertz and Llewellyn, and other consequences of the condition, are discussed.