bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of Substances of High Molecular Weight. VIII. Dispersion of Dynamic Rigidity and Viscosity in Concentrated Polyvinyl Acetate Solutions
Authors: Ferry John D. , Sawyer W. M. , Browning George V. , Groth Arthur H.
Published: April 2005

The dynamic rigidities and viscosities of concentrated solutions of polyvinyl acetate in 1,2,3-trichloropropane have been obtained from transducer and wave propagation measurements. Two polymer samples with number-average molecular weights of 140,000 and 840,000 were studied in the lower audiofrequency range at concentrations from 3 to 40 percent and temperatures from −3 to 41°C. For each sample, when the reduced dynamic rigidity G′T0/Tc and the reduced dynamic viscosity η′/η were plotted against the reduced frequency, ωηT0/Tc, all the data superposed to give two composite dispersion functions. The distribution of Maxwellian relaxation times can be derived from the dispersion of either G′ or η′, and the two calculations are in reasonable agreement.
Stress Phenomena from the Respective Viewpoints of Solid-State and High Polymer Physics
Authors: Huggins Maurice L.
Published: April 2005

Flow and elastic properties are considered, in a qualitative manner, for the following types of materials: crystalline solids, simple liquids, glasses, and high polymers.
Behavior of Granulated Polymers under Pressure
Authors: Spencer R. S. , Gilmore G. D. , Wiley R. M.
Published: April 2005

In such fabricating processes as extrusion and injection molding it is frequently necessary to force a granular polymer through a channel. Frictional forces between polymer and channel walls lead to a drop in pressure through the granular material. Simultaneously, the applied pressure causes a compaction of the granules.

Assuming that the granular mass has certain fluid-like properties, a simple theoretical expression for pressure transmission is derived. Comparison with data on saran powders and granular polystyrenes shows good agreement between theory and experiment. The effect of lubrication is shown also.

The compaction of granular polystyrene follows the same pattern as that observed in the earth's crust. The porosity decreases exponentially with increasing pressure. The ``compressibility coefficient'' for the porosity of granular polystyrene is comparable with that given for clays and shales.
Ultra Speed Tensile of Rubber and Synthetic Elastomers
Authors: Villars D. S.
Published: April 2005

A high speed stress-strain machine has been developed which is capable of recording the stress-strain curve of elastomers at elongation rates up to 270 percent/msec. Data are reported on two series of gum and tread stocks of hevea and of the synthetic elastomers, GR-S, Hycar OR, butyl, Perbunan, and Neoprene GN. The second (elastomer) series was also run at 150°C. In general, stress-strain curves fall into two classes. Stocks of elastomers which are known to crystallize on stretching tend to show tensiles which decrease with increasing speed up to about 10 percent/msec., pass through a minimum and rise more or less drastically to values 100 percent (or more) greater than the Scott tensile. Elastomers which do not crystallize on stretching tend to show a steady rise in tensile with increasing speed. Elongation at break curves show a maximum with crystallizing stocks and no maximum with non-crystallizing stocks. The shape of the modulus versus speed curves is accounted for on the hypothesis of different types of slipping bonds with different characteristic relaxation times. The shift of curves for tread stocks with temperature allows the estimation of a heat of activation of slippage. This comes out to be of the order of 3 kg cal.
The Effect of an Obstacle in the Fresnel Field on the Distant Field of a Linear Radiator
Authors: Woonton G. A.
Published: April 2005

At radio wave-lengths the use of mirrors and lenses in the measurement of radiators, by methods which are customary in physical optics, is possible only if errors, due to incidental diffraction from the relatively small apertures of such apparatus, can be corrected by calculation. Theory is developed in this paper from which these calculations can be derived for linear radiators. A new relation which expresses the Fresnel field in terms of the distant field is fundamental to the method. Satisfactory agreement has been obtained between the predicted and measured distant fields of several electromagnetic horns whose near fields were obstructed; the dispersion between measured and predicted values is given as under one-half decibel but the details of the experiment are not reported.
Second-Order Transition Temperatures and Related Properties of Polystyrene. I. Influence of Molecular Weight
Authors: Fox Thomas G. , Flory Paul J.
Published: April 2005

Dilatometric and viscometric data on fractionated polystyrenes containing diethylbenzene end groups are presented over wide temperature ranges. The second-order transition temperature, viscosity-temperature coefficient, and specific volume all change rapidly with increasing molecular weight toward asymptotic limits which are practically reached at M≅30,000. Empirical expressions are presented relating these properties to molecular weight and temperature. In each case the dependence on molecular weight is expressed as a simple function of M̄n−1. These observations are interpreted and correlated on the basis of the hypothesis that the local configurational order in a liquid polymer is disturbed by the introduction of end groups to a degree that is proportional to their number. The second-order transition does not represent an isoviscous state. The internal local configurational structure appears to be equivalent, and independent of temperature, in all polystyrenes below their second-order transition temperatures.
The Effective Permeability of an Array of Thin Conducting Disks
Authors: Estrin Gerald
Published: April 2005

A three-dimensional array of thin conducting disks has found special application as an artificial refracting medium at microwave frequencies. Treatment of these refractive properties at oblique incidence requires specification of the dielectric and permeability coefficients of the medium.

When an alternating magnetic field is parallel to the disk faces, the field is undisturbed and the relative permeability coefficient is unity. When the alternating magnetic field is normal to the disk faces, circulating currents are induced on them. The boundary value problem of determining the current distribution on a single perfectly conducting disk is carried out in detail for the case where the disk diameter is small compared to the wave-length. This current distribution is found to be representable by a magnetic dipole. If the disks in an array are far enough apart to neglect interaction, a simple summation of the dipole moments shows the array to have a diamagnetic susceptibility in the direction normal to the disk faces.

Combining this result with an expression for the dielectric coefficient, which was developed earlier by Kock, the constants of the anisotropic array are completely specified.
Electrolytic-Tank Measurements for Microwave Metallic Delay-Lens Media
Authors: Cohn Seymour B.
Published: April 2005

In this paper it is shown how the low frequency index of refraction of a metallic delay-lens medium may be calculated from electrolytic-tank measurements on individual metallic elements of the medium. The proximity between adjacent elements is taken exactly into account for low frequencies. The test apparatus is described, and measured results are presented for three kinds of delay-lens structures.
The Emission of Radiation from Diatomic Gases. I. Approximate Calculations
Authors: Penner S. S.
Published: April 2005

An approximate method for estimating radiant heat transfer from gaseous emitters is proposed. An average absorption coefficient is used for the effective width of an entire vibration-rotation band. The procedure for determining an average absorption coefficient in terms of the integrated absorption is justified, approximately, for very small optical densities and also for large total pressures where the spectral half-width is no longer small compared with the rotational spacing. Because of these limitations it is to be expected that the procedure proposed here will be particularly useful only in estimating gaseous emissivities for emitters in high-pressure combustion chambers. A preliminary compilation is given of the theoretical results which are necessary for making rapid estimates of the emissivities, over a wide temperature range, for CO, HI, HBr, HCl, and HF.
The Current-Hysteresis of the Electrolytic Aluminum-Oxide Rectifier
Authors: Dekker A. J. , Urquhart Helen M. A.
Published: April 2005

A hysteresis in the rectification of the contact aluminum-aluminum oxide-electrolytic solution was found by Dekker and van Geel. In the present paper, measurements of the current-voltage characteristics between 1 and 2000 cycles are described. A tentative explanation of the hysteresis is given in terms of a pre-breakdown phenomenon.
Interpretation of Fracture Markings
Authors: Kies J. A. , Sullivan A. M. , Irwin G. R.
Published: April 2005

This paper presents a study of the sequence of events by which cracks ``grow.'' A careful investigation was made of the origin, development, and characteristic pattern of level-difference markings left by rapidly moving fractures in a wide variety of materials. Characteristic markings indicating discontinuous propagation are found in fractures of plastics, polycrystalline and single-crystal materials, coal, mica, photographic film from which the emulsion was stripped, etc. Thus, the continued occurrence of essentially discontinuous initiations which comprise fracturing becomes clear. These considerations are sufficient to explain a number of well known fracture markings and to clarify what is mean by brittleness and fracture velocity.
Conductivity of Liquid Selenium-200°–500°C
Authors: Henkels Herbert W.
Published: April 2005

The conductivity of liquid selenium has been measured in the temperature range 200°–500°C. The resistivity was expressed by log10ρ=A+(B/T). Average values for different selenium lots and melts of A and B were −3.81 and 5850. The maximum deviations from the averages were 10 percent and 3.4 percent respectively. The resistivity was a function of temperature alone.

Various non-metal impurities Cl2, I2, P lowered the resistivities and produced different values of B in different temperature ranges. Mercury addition caused no change in either A or B although that metal greatly influences the resistance of solid hexagonal selenium. Melts doped with Cl2 or Br2, along with Hg exhibited behaviors different from those with single additions.

It was concluded that selenium is an ideal semiconductor in the range of measurement.
The Effect of a Video Filter on the Detection of Pulsed Signals in Noise
Authors: Middleton David
Published: April 2005

The effects of inserting a video filter of finite width on the observability of pulsed signals in random noise are examined. It is found that at match (when the pulse and IF filter are each other's conjugate Fourier transforms) no improvement is gained from such a video: the infinitely wide response yields the optimum results. This is strictly true when the second detector is a quadratic rectifier; (a slight improvement on narrowing the video is noted, however, for strong signals when a half-wave linear rectifier is used). Away from match a video filter does give noticeable improvement when the pulses are overlong, i.e., narrower spectrally than the IF (λ>1); more noise than signal is then removed by the narrower video filter. The greatest gain over the infinite video is observed for final filters slightly wider than the original pulse. On the other hand, for pulses that are too short (λ<1) the performance is worsened. The mean maximum signal level is decreased more rapidly than the interfering noise background. In all instances the familiar phenomenon of modulation suppression arises. Two different pulse shapes are considered: (1) Gaussian and (2) rectangular, but for wide videos pulse shape is not a critical factor. Curves showing the output signal-to-noise ratios as a function of the input ratio are included for conditions of match (λ=1) and mismatch (λ≠1).
The Wall-Quenching of Laminar Propane Flames as a Function of Pressure, Temperature, and Air-Fuel Ratio
Authors: Friedman Raymond , Johnston W. C.
Published: April 2005

The quenching distance between plane parallel plates has been measured for propane-air flames at eight pressures ranging from 0.0832 to 2.77 atmos., and air-propane ratios ranging from 11 to 24. Other tests have been made at atmospheric pressure in which (a) the temperature of the quenching plates has been varied from 80° to 715°F, (b) the temperatures both of the inlet gas and the quenching plates have been varied from 80° to 545°F, and (c) a series of six different solid surfaces was tested. The minimum quenching distance is found to occur at an air-propane ratio between 13.5 and 14.0, and is proportional to the minus 0.91 power of pressure. Lean mixtures are found to be slightly less pressure-sensitive. When both the inlet gas and plates are heated, the minimum quenching distance is found to be proportional to the minus 0.5 power of absolute temperature. The quenching effect appears to be independent of the nature of the surface.
Electromagnetic Field of the Conical Horn
Authors: Schorr Marvin G. , Beck Fred J.
Published: April 2005

Maxwell's equations are solved for a perfectly conducting conical wave guide and the propagation coefficients of this guide are discussed. The field at the mouth of a finite conical horn is estimated and the radiation therefrom is calculated in integral form. These integrals are solved in series form for horns of small flare angle and moderate length and the results compared with experiment.
Double Crystal and Slit Methods in Small Angle X-Ray Scattering
Authors: Ritland H. N. , Kaesberg P. , Beeman W. W.
Published: April 2005

An angular resolution of about 10 seconds of arc may be obtained with a double calcite crystal spectrometer for Cu Kα-radiation. However, the shape of the rocking curve at large angles is such as to make the detection of radiation from weakly scattering materials difficult. Of the order of 106 counts per second are detected with a stationary, water-cooled copper target and parallel crystals. Wing intensities, even at large angles, do not fall much below 102 counts per second. Wing heights may be considerably reduced by the addition of a third calcite crystal. With this modification the crystal spectrometer is a useful instrument for most scattering experiments in which extremely high resolution is desired. It is inferior to a slit system and Geiger counter arrangement when poorer resolution may be tolerated but high sensitivity is required. A slit instrument with an angular resolution of 4 or 5 minutes of arc provides an effective incident flux of more than 106 counts per second while wing intensities may be as low as 1 count per second.
Generalized Microscopy and the Two-Wave-Length Microscope
Authors: Buerger M. J.
Published: April 2005

In the ordinary simple microscope, the same light is permitted to flow through the entire system. A more general microscope can be devised in which light of one wave-length is permitted to flow as far as the diffraction image of the object, then light of a second wave-length is substituted at this plane, and continues to flow through the rest of the optical system. It is shown that for such a generalized microscope, the magnification depends not only on the ordinary image-to-object distance ratio, but also on the ratio of wave-lengths used. Utilizing x-rays and visible light, this second factor is about 104 diameters, and the whole magnification is of the order of 3×105. This is enough to permit one to see an atom. Apparatus has been built which realizes this theory. A most important characteristic of any such system is that a loss of phase occurs at the first diffraction image, where the wave-length substitution takes place. This phase must be supplied by the apparatus. It is accomplished with the aid of phase shifters prepared from a large uniform mica cleavage fragment. The apparatus and the results achieved with it are described.
A Model of Hurricane Formation
Authors: Riehl Herbert
Published: April 2005

At first, the description of the energy cycle of the mature tropical storm is amplified on the basis of recent upper air observations. Air particles passing through such a storm at first undergo isothermal expansion as they move toward a center. Then they ascend with release of condensation. At high levels they move outward and mix with the environment giving off heat to the surrounding colder air. Several requisites for maintenance of the observed temperature field are stated.

After a discussion of previous theories of hurricane formation the proposed model is described. The initial intensification of the wind field is brought about by mass divergence at high levels that imposes a pressure reduction on the surface layers. This divergence is the result of interaction between the large-scale disturbances of the upper air inside and outside the tropics. A solenoidal circulation is initiated that acts in the kinetic energy producing sense. But this circulation contains an internal mechanism for its own destruction and is maintained only under certain special conditions which are stated.
Thermoelastic Stress in the Semi-Infinite Solid
Authors: Mindlin Raymond D. , Cheng David H.
Published: April 2005

The solution of the elasticity equations for the center of dilatation in the semi-infinite solid is introduced into Goodier's theory of thermoelastic stress. It is shown that the problem of potential to be solved is identical with that for the solid of indefinite extent. The results are applied to the case of an expanding (or contracting) spherical inclusion embedded in an elastic body near its surface.
Improvements in Visual Depiction of Magnetic Lines of Force by Means of a Gas Discharge
Authors: Blaha F. , Schedling J. A.
Published: April 2005

The article shows how lines of force of various magnetic fields can be visually depicted in three dimensions by means of a gas discharge. The method is illustrated by several photographs proving especially its applicability when investigating fields of small geometrical dimensions.
Digital Information Storage in Three Dimensions Using Magnetic Cores
Authors: Forrester Jay W.
Published: April 2005

Present digital storage devices use two space coordinates or time and one space coordinate for selection switching, resulting in bulky construction or long access time. Three-dimensional arrays with efficient high speed selection appear possible after continued development of rectangular-hysteresis magnetic materials. An operating mode is suggested which depends on ability of the magnetic material to discriminate between two values of magnetizing force which differ by a 2:1 ratio. Only one magnetic core per binary digit is required. Tests show that most existing metallic magnetic materials switch in 20 to 10,000 microseconds and are too slow. Nonmetallic magnetic materials can now approach the required magnetic behavior; they switch in less than a microsecond.
Parametric Excitation
Authors: Minorsky N.
Published: April 2005

This paper outlines a theory of excitation of oscillations under the rather slow variations of a parameter on which a system depends. The basic equation is a Mathieu equation. The basic method consists in reducing the system to polar coordinates and applying perturbations.
Expandability of a Wave-Guide Field in Terms of Normal Modes
Authors: Van Bladel J.
Published: April 2005

This article justifies the fact that the fields in a wave guide can be expanded as a linear combination of normal modes. The proof consists in showing that (a) this expansion is possible for the z components of the fields and modes and (b) that, in three dimensions, the fields as a whole are equal to a linear expansion of modes with precisely the same coefficients as were found in the expansion of the z components.
Deterioration of Oxide-Coated Cathodes under Low Duty-Factor Operation
Authors: Waymouth J. F.
Published: April 2005

The behavior of oxide cathodes coated on a nickel alloy containing about 0.1 percent silicon has been investigated under 100 percent and zero duty-factor operation. The operation of these cathodes at zero duty factor was found to be highly favorable to the development of a high resistance in a layer of Ba2SiO4 located at the interface between the oxide and the core. The layer itself was present not only in cathodes that had aged without electron emission and had developed interface resistance, but also in cathodes that had aged with electron emission and had not developed interface resistance. A model is presented to account for the experimental observations. Evidence is also presented which shows that an ``active'' nickel alloy that does not lead to undue interface resistance formation may exist.
A Pulse Method of Determining the Energy Distribution of Secondary Electrons from Insulators
Authors: McKay Kenneth G.
Published: April 2005

A novel method is described of determining the energy distribution of emitted secondaries from an insulator. This is based on an analysis of the transient resulting from pulse bombardment. The analysis is simplest when leakage through the target is negligible, but the effect of leakage is also treated. Space charge limitation of the emitted current is assumed to be negligible.
Investigation of Field Distribution in Symmetrical Electron Lens
Authors: Shah J. R. , Jacob L.
Published: April 2005

High accuracy of measurement in the electrolytic tank can be achieved by a suitable ratio of impedance as between tank and measuring circuit. With this requirement fulfilled, the axial distribution of the symmetrical lens was explored and found to satisfy a relation Vz=V0+Ae−bz(2), where V0 is the potential of the outers with respect to the middle electrode, `z,' the distance from the center of the lens, while A and b are constants from any one geometry.

The effect of varying the separation between the elements was specially investigated. It was found that the maximum value of the gradient between electrodes increases as the separation between them increases, reaches a flat maximum between 0.8 and 0.4 D (D, bore diameter) and then decreases with further increase in spacing. This means that a decrease in separation produces a weaker field and an increased focal length.

The potential at the saddle point is very sensitive to changes in separation in the region up to about 0.5 D; it was also found to vary linearly with bore up to 3 D.

The relaxation method of field plotting was also applied to map the distribution; the results are compared with those given by the tank.
An Experimental Investigation of the Dielectric Rod Antenna of Circular Cross Section Excited in the Dominant Mode
Authors: Horton C. W. , McKinney C. M.
Published: April 2005

The radiation pattern and the gain were measured for four series of dielectric antennas of circular cross section. These antennas were excited by a TE11 mode in a circular metallic wave guide at a frequency of 9275 mcps. Only one parameter was changed in each series of rods so that the effect of this parameter on the pattern and gain could be studied. Measurements of gain are presented for two further series of rods in which the length is varied. The measurements showed that a polystyrene rod of length 6λ0 and constant cross section has maximum gain and best pattern for a diameter of approximately 2λ0. On the other hand when the taper of a Lucite rod was varied while the length and the maximum diameter were held constant at 6λ0 and 0.87λ0, respectively, the gain and the pattern behavior improved as the minimum diameter was decreased to zero. It is shown that losses in the dielectric produce a significant decrease in the gain.
The Response of an Aerodynamic System under External Harmonic Force
Authors: Serbin H.
Published: April 2005

In Part I, the theory of nonconservative linear systems of a finite number of degrees-of-freedom is presented. An expression is derived for the response of the system to external harmonic forces in Sec. 3. The effect of small variations in parameters is obtained in Sec. 4. Section 5 is a discussion of the influence additional degree-of-freedom. Part II is concerned with numerical procedure for the calculation of characteristic roots and vectors. The results are applied to a numerical example in Part III.
The Influence of Magnetic Fields upon the Propagation of Electromagnetic Waves in Artificial Dielectrics
Authors: Wicher E. R.
Published: April 2005

An effect corresponding to the Faraday effect in natural dielectrics is predicted for a class of artificial dielectrics because of the existence of a Hall effect in the metallic components of the structure. A formula for Verdet's constant as a function of element polarizability and Hall coefficient is obtained. The resonance shift to be expected in a cavity resonator, filled with an artificial dielectric, and subjected to a strong magnetic field, is calculated. Prospects for the application of these effects are briefly considered.
Free Longitudinal Vibrations of Rubber and Tissue Strips
Authors: Lawton Richard W. , King Allen L.
Published: April 2005

Frequencies of free longitudinal vibrations of several different specimens of rubber and aortic strips were measured as a function of applied load and relative length L/L0, where L0 is the initial length. Curves of ω2L0/g versus L/L0 have distinct minima that become sharper and move upward and toward the ω2L0/g axis as the specimens become stiffer. The experimental curves are described rather well by theoretical equations derived from current relations for the extension of an ideal elastomer; they may be used for determining values of the elastomeric parameter β. The method is simple and rapid and is applicable to biological tissues as well as to other rubberlike substances.
Discrete Energy Levels of a Nonlinear Oscillator
Authors: Moran James H.
Published: April 2005

Following a brief survey of the theory, especially Eckweiler's work, of nonlinear oscillators satisfying an equation of the form (d2q)/(dt2) + εF(dq/dt) + q=0 a special case is considered for which the stable limit cycles have a definite relation to one another and to the so called Planck oscillator. A nonlinear ``quantum effect'' is discussed and shown to be similar to the harmonic quantum oscillator in some respects. No physical model is proposed for which the equation considered would be a description but various possibilities in this regard are indicated.
The Nature of the Static and Kinetic Coefficients of Friction
Authors: Rabinowicz Ernest
Published: April 2005

Experiments have been carried out to determine the transition between static and kinetic conditions when stationary metal surfaces are set into motion, a simple method being used which measures the energy that has to be given to one of the bodies to start it moving. The method is confined to cases in which the static coefficient exceeds the kinetic. Using a load of 1 kg and metal surfaces of various kinds, it is found that the static coefficient persists for distances of the order of 10−4 cm, and then gradually falls off to values corresponding to the kinetic coefficient. This behavior is shown to be consistent with a simple model based on the assumption that the friction force is needed to shear metallic junctions formed between the metal surfaces. The action of boundary lubricants is discussed, and it is shown that they can act either by diminishing the metallic interaction directly, or by preventing its increase during the sliding process.
The Propagation in a Compressible Fluid of Finite Oblique Disturbances with Energy Exchange and Change of State
Authors: Ross Frederick W.
Published: April 2005

Theory is presented for oblique shock waves involving (1) heat exchange, k1, (2) transfer of part of the compressible fluid, k2, to an incompressible state, and (3) change in specific heat ratios, k3. By matching mass flow, momentum, and energy relations across an oblique finite disturbance it is shown that these additional conditions introduce new terms in the solution of the form kiu1/(u1−u2). For ki not zero a minimum shock angle is found which always exceeds the Mach angle by a definite increment. For air-flow at u1/a* of 1.5 with dew point −20°F this increment is calculated as 3.1 degrees. For expansion about a corner such flow differs from the Prandl-Meyer type and in supersonic nozzles, for example, oblique shock waves are predicted which can explain anomalous pressure losses, the presence of extraneous waves, and non-isentropic effects. Hodographs of the velocity solution include a triply infinite set of curves, one, the usual set, introduced by Mach number as parameter and the other two by ki. The theory includes physically possible normal and oblique flows involving increase of supersonic velocities and subsonic velocities of which oblique flame fronts are indicated as one form. Applied to air condensations in hypersonic flows isentropic disturbances having appreciable angular flow shift and stagnation pressure losses are predicted.
Studies in Newtonian Flow. II. The Dependence of the Viscosity of Liquids on Free-Space
Authors: Doolittle Arthur K.
Published: April 2005

In this paper it is shown that the viscosity of the liquid normal paraffins can be accurately defined as a simple function of relative free-space except for values in the neighborhood of the freezing points of each compound. A novel method of extrapolating the specific volumes of this family of compounds to absolute zero is described which permits the calculation of reliable values of the relative free-space from density data.

An expression of the same form as the author's function, but in which temperature rather than free-space is the primary variable (the so-called Andrade equation), fails to reproduce the viscosity of n-heptadecane over the same range of temperatures within the limits of the known accuracy of the measurements.
Dosimetry of X-Rays and Gamma-Rays by Radiophotoluminescence
Authors: Schulman James H. , Ginther Robert J. , Klick Clifford C. , Alger Raymond S. , Levy Robert A.
Published: April 2005

The effects of high energy radiation on the luminescence properties of solids are surveyed. Of the four effects considered—radiophotoluminescence, radiophotostimulation, radiothermoluminescence, and the ``killing'' of luminescence by x-rays or gamma-rays—the first effect is shown to have advantages in principle over the others as a basis for dosimetry.

The absorption, excitation, emission, sensitivity, energy dependence, and stability characteristics of a radiophotoluminescent Ag-activated phosphate glass are described. It is shown that dosage measurements can be made with this material, employing a simple fluorophotometer, from 10 roentgens to a few thousand roentgens of gamma-rays. By proper shielding, such a dosimeter element can be made reasonably independent of energy. The dosage indication obtained is quite stable with time and is not seriously affected by exposure of the glass to visible or ultraviolet light or to temperatures in the range of −70° to +100°C. Because of its sensitivity range and its stability over a wide range of ambient conditions, the dosimeter appears to be particularly suited for monitoring personnel that may be exposed to rather high doses of gamma-rays, such as may be encountered in A-bomb explosions.
The Crystallographic Aspect of Slip in Body-Centered Cubic Single Crystals. II. Interpretation of Experiments
Authors: Opinsky A. J. , Smoluchowski R.
Published: April 2005

A new method for determining the ratios of the critical shear stresses has been applied to data taken from the literature and to original results. Measurements of yield strength were found to be not too satisfactory for the investigation of the slip behavior of the body-centered cubic materials. On the other hand, any method which determined the slip plane and the orientation of the tensile axis gave useful results. In all instances where the data were available, the ratio of the critical shear stresses on {123} and {112} was very close to one, and did not change with temperature. The ratio of the critical shear stresses on {123} and {110} changes with temperature and composition, with the value of S123 generally being higher than that for S110.
The Capacitance of a Circular Annulus
Authors: Smythe W. R.
Published: April 2005

Two formulas are derived for the capacitance of a flat circular annulus. The first has an accuracy of 1 part in 1000 or better when the ratio of the external to the internal radius lies between 1.1 and ∞ and is exact at ∞. The second, C=34.96R/ln(32R/c) μμf, has an accuracy of 1 part in 1000 when the ratio lies between 1.000 and 1.1 and is exact at 1.000. In this formula c is the difference of the radii and R their mean value in meters. An approximate expression for the charge density is given in the first case.
Compressible Supersonic Flow in Jets under the Kármán-Tsien Pressure-Volume Relation
Authors: Coburn N.
Published: April 2005

The two-dimensional supersonic irrotational flow of a gas in a jet is studied by use of the Kármán-Tsien pressure-volume law. There are two limitations to such a study: (1) since the fluid flow is not continued from the subsonic range, arbitrary boundary conditions must be prescribed; (2) use of the Kármán-Tsien pressure-volume relation implies a restriction on the permissible range of pressure, density, and velocity. On the other hand, use of the Kármán-Tsien law furnishes several advantages: (1) the velocity potential and stream function satisfy the wave equation in the hodograph plane and hence these functions can be easily determined; (2) the mappings between the physical and hodograph planes may be completely characterized and studied in detail. This gain in information should be valuable in the qualitative understanding of phenomena as well as in obtaining first approximations to quantitative solutions. In the case of jets, with free stream lines as boundaries, it is shown that two functions possessing certain desired properties completely determine the Kármán-Tsien flow. Further, the phenomenon of the periodic recurrence of the free stream jet boundary is explained by a folding property of the map of the flow in the hodograph plane.
A Mechanical Determination of Biaxial Residual Stress in Sheet Materials
Authors: Treuting R. G. , Read W. T.
Published: April 2005

A method is given for determining the residual stress in a sheet material by removing successive uniform layers of material from the surface of a test specimen and measuring the resulting curvature. From the condition of equilibrium of a free specimen, a stress vs curvature relation is derived which holds over the depth to which material has been removed. The method applies when the stress is constant in the plane of the specimen and varies through the thickness. An experimental technique is described which is believed to satisfy the essential requirement that the removal of surface layers should not affect the stress in the remaining material, and a practical example is given.
Some Measurements of Thermal Transpiration
Authors: Liang S. Chu
Published: April 2005

Measurements have been made of the pressure ratio, R, due to thermal transpiration in hydrogen, helium, argon, and nitrogen between a warm temperature of 297°K and cold temperatures of 77.3 or 195°K. It is found that R depends on X, the product of the pressure and tube diameter according to the empirical relation, R=P1/P2=(AX2+BX+Rm)/(AX2+BX+1), where A and B are constants which depend on the gas and on the warm and cold temperatures, and Rm=(T1/T2)½. The R against P2, and threfore X, curves for different gases are found to be related by a ``pressure shifting factor'' f.

The use of these results to correct measurements of adsorption equilibrium and vapor pressures at low pressures and low temperatures is discussed.

Vapor pressures at 77.3°±0.5°K corrected for the thermomolecular pressure effect have been measured for krypton and xenon: Krypton1.754±0.002 mm;Xenon1.93 ±0.01×10−3 mm.
On the Directional Patterns of Polystyrene Rod Antennas
Authors: Watson R. B.
Published: April 2005

Experimental and theoretical directional patterns are compared for three polystyrene rod antennas of length variable from about 4 to 10 wavelengths, retaining relative shape in the length direction. The comparison shows that the apparent index of refraction, n, decreases with increasing length. Accordingly, the directional patterns are less sharp than might be expected from the estimated values of n which are constant for a constant relative shape.
On the X-Ray Absorption Correction for Encased Diffracters in the Debye-Scherrer Technique
Authors: Ritter H. L. , Harris R. L. , Wood R. E.
Published: April 2005

In dealing with numerical values for relative intensities derived from the Debye-Scherrer technique, the alteration of diffracted intensities produced by absorption in the sample cannot be ignored. Claassen has shown how this effect can be allowed for in the case of homogeneous cylindrical samples. This paper deals with a sample consisting of a cylinder surrounded by another annular cylinder both when the core is inert (i.e., absorbing and producing only extraneous scattering) and when the annulus is inert. The method is applied to show how the diffraction pattern for a liquid enclosed in a glass container may be corrected for the diffuse diffraction of the container as well as for absorption in the liquid and in the glass.
Optimum Source Size for the Mach-Zehnder Interferometer
Authors: Bennett F. D.
Published: April 2005

A vector analytic treatment is given of the formation of undisturbed fringes by an ideal Mach-Zehnder interferometer with an extended source. The path difference of two interfering rays at an arbitrary point in the field is found to depend, in a simple way, upon the source point from which the rays originate, the field point examined, and a dyadic which is a function of the unit normals to the last mirror and divider plate of the interferometer. The fringe clarity condition, that all pairs of interfering rays reaching the field point have path differences within a specified range, is developed in the form of an inequality. Analysis of this fundamental inequality shows that all admissible area sources must be areas enclosed between two conics in the source plane. For fringes perpendicular to the plane of centers of the interferometer elements, the optimum source is a circle with radius inversely proportional to the square root of the number of clear fringes desired. This result holds for all interferometers of parallelogram planform. For fringes parallel to the plane of centers, each interferometer orientation presents a special case. The optimum source area is obtained for two of these, viz., the 45° and 30° interferometers.
Periodic Statistical Distortion of Unidirectionally Ordered Diffractors, with Application to Collagen
Authors: Bear Richard S. , Bolduan Orvil E. A.
Published: April 2005

The diffraction expected of distorted, one-dimensionally ordered cylinders (fibrils) is considered quantitatively. The distortion involved is statistically of cylindrical symmetry about any point in the fibril, and periodic along the fibril axis. An important case is that of the ``mixed perfect and imperfect fibril,'' in which, at some axial levels, distortion is absent, and at others it is appreciable. For such systems it is shown that the reciprocal-space disk corresponding to a given diffraction layer line may be regarded as composed of three sub-disks: one of perfection, whose central intensity is maximal and whose diameter is small and independent of layer-line index; another of longitudinal or axial imperfection, whose central intensity is also maximal; and a third, related to radial imperfection, whose intensity is noncentrally maximal. Both types of imperfection sub-disk expand linearly in diameter with increase in index.

It is demonstrated briefly that certain dry collagen specimens exhibit small-angle diffraction in which the characteristics of the three types of sub-disk are apparent.
Crystal Systems with Low Loss
Authors: Fry Ruth Baumann , Fry William J.
Published: April 2005

Approximate formulas are derived for computing the effect of mechanical resistance on the electrical characteristics of a piezoelectric crystal system for the case of a general reactive termination and low loss. A comparison of values computed on the basis of these formulas and exact calculations is presented.
The Design of Molecular Pumps
Authors: Jacobs Robert B.
Published: April 2005

A theoretical treatment is given for the operating characteristics of molecular drag type pumps. The present work is based on kinetic theory and is limited to high vacuum operation. The solutions are simple and may be applied readily to practical pump designs. They lead to performance characteristics which are thought to be accurate to ±10 percent.
Hypersonic Flow at a Mach Number of 10
Authors: Faro I. D. V. , Small T. R. , Hill F. K.
Published: April 2005

Tests designed to produce supersonic streams at ten and sixteen times the local speed of sound are described. In contrast to the usual wind tunnel apparatus, a conical nozzle is used for the expansion section, and the supply pressure is varied throughout a wide range. Some properties of the flow at high Mach numbers are discussed, and, in particular, data are given showing a systematic dependence of Mach number on stagnation pressures, a phenomenon not previously reported.
Reflection and Transmission at the Surface of Metal-Plate Media
Authors: Lengyel Bela A.
Published: April 2005

The theory of Carlson and Heins has been extended; an expression is found for the reflection coefficient applicable in the presence of a diffracted beam. Tables and graphs are included for the coefficients associated with electromagnetic phenomena at the surface of metal-plate media. The magnitude of the reflection coefficient was measured at normal incidence and the phase of the transmission coefficient for angles of incidence from 0 to 25°. A satisfactory agreement with theory is obtained.
On Amplitude Bounds for Certain Relaxation Oscillations
Authors: Wax Nelson
Published: April 2005

Amplitude bounds are obtained for the unique periodic solution of the generalized Lienard equation ẍ+f(x)ẋ+g(x)=0, when the functions f(x) and g(x) are restricted suitably. The restrictions are less severe for the lower than for the upper bounds. A class of equations is exhibited which includes the van der Pol equation and satisfies all the restrictions. Numerical results are given for the van der Pol equation.
Boride Cathodes
Authors: Lafferty J. M.
Published: April 2005

The thermionic emission properties of the borides of the alkaline-earth and rare-earth metals and thorium have been investigated. These compounds all have the same formula MB6 and the same crystal structure consisting of a three-dimensional boron framework in whose interlattice spaces the metal atoms are embedded. The valence electrons of the metal atoms are not accepted by the B6 complex, thus giving rise to the presence of free electrons which impart a metallic character to these compounds. This, together with the strong bonds between the boron atoms in the framework, produces a series of compounds which have high electrical conductivities and high thermal and chemical stabilities—ideal properties for a cathode material. When this structure is heated to a sufficiently high temperature, the metal atoms at the surface evaporate away. They are, however, immediately replaced by diffusion of metal atoms from the underlying cells. The boron frame work does not evaporate but remains intact. This process gives a mechanism for constantly maintaining an active cathode surface. Thermionic emission measurements made on these materials show the rare-earth metal borides to be superior to the others. The highest emission was obtained from lanthanum boride. Its emission constants for the Dushman equation were φ=2.66 volts and A=29 amps/cm2/degK2. This is higher than the emission normally obtained from thoria. Lanthanum boride has a relatively low evaporation rate corresponding to a latent heat of evaporation of 169 kilocalories per mole. If the hexaborides are operated at high temperature in contact with the refractory metals, boron diffuses into their metal lattices forming interstitial boron alloys with them. When this occurs, the boron framework which holds the alkaline-earth or rare-earth metal atoms collapses, permitting the latter to evaporate. However, the hexaboride cathodes may be operated at high temperatures in contact with tantalum carbide or graphite. Lanthanum boride cathodes are especially useful in applications where high current densities are required. They are also suitable for high voltage applications because they stand up well under positive ion bombardment. Since they are atmospherically stable and activate easily, they have found wide use in experimental demountable systems.
Physical Entropy and Information. II
Authors: Brillouin L.
Published: April 2005

The laws of statistical thermodynamics are used for the definition of entropy, and it is shown that the definition of information can be reduced to a problem of Fermi-Dirac statistics or to a generalized Fermi statistics. With these definitions, the entropy of a certain message can be defined, and the information contained in the message can be directly connected with the decrease of entropy in the system.

This definition leads directly to the formulas proposed by C. E. Shannon for the measure of information, and shows that Shannon's ``entropy of information'' corresponds to an equal amount of negative entropy in the physical system. The physical background of the whole method is discussed and found in agreement with previous discussions.
A Metallographic Study of Diffusion Interfaces
Authors: Kuczynski G. C. , Alexander B. H.
Published: April 2005

By sintering wires to flat metallic blocks, diffusion interfaces were obtained between the following pairs of metals: Cu-Ni, Au-Ag, Cu-Ag, Cu-Fe, Fe-Ni, Cu-Zn, Ni-Zn, and 70/30 brass-Cu. The interfaces were subsequently investigated metallographically. Grooves were observed in the lower melting point component in the vicinity of the sintered interfaces. This is attributed to the faster diffusion rate in the lower melting point metal.
Study of Precipitates of C and N in Iron with an Electron Microscope
Authors: Radavich John , Wert Charles
Published: April 2005

By the use of the electron microscope it has been possible to study the precipitates of C and N in α-iron. The physical shapes of the precipitates have been determined in each case as well as the fineness of dispersion The results of the investigation confirm the conclusions drawn from internal friction measurements made on these alloys and reported earlier.
Theory of Do for Atomic Diffusion in Metals
Authors: Zener Clarence
Published: April 2005

The theory of the entropy of activation ΔS previously given for interstitial diffusion in metals is herein extended to self- and to chemical diffusion. It is concluded that this entropy of activation will always be positive; and it is shown that in the case of self-diffusion and of chemical diffusion at very low concentrations, the better the empirical ΔS the better does it correlate with the theoretical positive ΔS. The large negative apparent ΔS frequently found for chemical diffusion at higher concentrations must be attributed either to inaccuracies in experiments or to the presence of short circuiting diffusion paths. It is predicted that the presently reported negative values of ΔS will become positive when very small concentrations are used in large grain size specimens.