bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method of Reducing Deflection Defocusing in Cathode-Ray Tubes
Authors: Hutter R. G. E. , Harrison S. W.
Published: April 2005

A discussion of deflection defocusing is given to point out the two-dimensional character of the focusing action of deflection fields. A photograph of spot distortion actually observed is shown. A brief theory of combined spherical and cylindrical lenses is given, and a method of spot correction based on the principle of ``beam predistortion'' is described. An electron gun used for such correction is shown and experimental results obtained with this gun are exhibited.
D.C. Characteristics of Silicon and Germanium Point Contact Crystal Rectifiers. Part I. Experimental
Authors: Yearian H. J.
Published: April 2005

Typical d.c. current-voltage characteristics obtained for Si and Ge crystal rectifiers are described. A survey of the published theories of the rectifier shows that none of them will account for the principal features of the observed characteristics. The most obvious discrepancy is in the low resistance direction of flow where the logarithm of the current rises with increasing voltage at only a fraction of the rate indicated by the theories. The need for a more flexible theory is pointed out and the conditions which it must meet, both as a function of voltage and temperature are outlined.
Some Non-Linear Systems Permitting Simple Harmonic Motion
Authors: Brock John E.
Published: April 2005

By elementary and obvious methods a differential equation is obtained, which in general is non-linear and usually affords a solution which is a simple sinusoidal function of the independent variable (i.e., simple harmonic motion). Two particular examples are studied briefly although no physical realizations are presented. One is led to speculate that new types of oscillators having a sinusoidal output are described by these equations, and that practical applications, such as to frequency metering, may eventually be evolved. However, the writer's speculations along these lines have as yet borne no fruit and his primary object in publishing this material is to bring to the attention of those interested in non-linear phenomena, about which our understanding is so essentially imperfect, an analysis which, though itself possibly trivial, conceivably may prove of service in setting someone else off on a productive investigation.
An Optical Method for Measuring the Stress in Glass Bulbs
Authors: Read W. T.
Published: April 2005

In the sealing and processing of electron tubes residual stresses are introduced into the glass parts. This paper formulates a practical optical method for locating and measuring the maximum tension in the walls of glass bulbs.

The basic principles of photoelasticity in three dimensions are applied to the case of a cylindrical shell. Theoretical results are verified experimentally for a tube in which the stress distribution is axially symmetrical.

Experimental results on tubes in which the stress distribution was unsymmetrical lead to the conclusion that the maximum tensile stress is proportional to the maximum retardation, the factor of proportionality being simply related to the form of the fringe pattern.

A quick and simple technique is described for making the necessary optical measurements.

The method presented herein has been used and found to be practical for routine laboratory testing of tubes in quantity.
A Lapping Technique: To Improve the Image Quality of Electron Microscope Lenses
Authors: Hamm F. A.
Published: April 2005

One factor inherent in most electron microscopes is the magnetic asymmetry (astigmatism) in the objective lens. This is often due to imperfect machining, localized defects (impurities) in the iron, or grain anisotropies. The lapping technique described herein effectively reduces the effect of imperfect machining (misalignment of components). Critical faces and the bores through the pole piece are lapped with a series of powders (alumina) which increase in fineness until the final process is that of polishing. A set of jigs and laps (brass and hard wood) are described; their specifications and use so as to properly alter the critical pole piece surfaces are also described. Electron micrographs illustrating the value of this lapping procedure in the improvement in objective lens symmetry are included.
Variation of Elastic Moduli and Wave Velocity with Pressure and Temperature in Plastics
Authors: Hughes D. S. , Blankenship E. B. , Mims R. L.
Published: April 2005

The variations in velocity of dilatational waves in the pressure range 0 to 15,000 lb./in.2 and temperature range 30° to 90°C have been measured for samples of polystyrene, Lucite, and polyethylene. The velocity of rotational waves was also measured for polystyrene and Lucite. In polyethylene no trace of a rotational wave could be identified. The elastic moduli and Poisson's ratio are computed over the experimental range.
The Summation of Fourier Series by Operational Methods
Authors: Pipes Louis A.
Published: April 2005

A method for the summation of certain types of Fourier series by the use of Laplace transforms is presented. The procedure enables one to easily obtain graphical representations of functions defined by Fourier series in many cases of practical importance.
A Resonant Bar Method for Determining the Elastic Properties of Thin Lamina
Authors: Nolle A. W. , Westervelt P. J.
Published: April 2005

A resonant bar method for obtaining the dynamic elastic properties of a thin cement layer is discussed. Formulas are deduced for the calculation of Young's modulus from the measured resonant frequency and band width of two similar steel bars, cemented end-to-end. The accuracy of the method is discussed.
Diffraction by a Cylindrical Obstacle
Authors: Papas Charles H.
Published: April 2005

The diffraction of a plane electromagnetic wave by an infinitely long, perfectly conducting cylinder has been treated by a variational method (see the two papers by H. Levine and J. Schwinger). The incident field is assumed to be polarized in the direction of the cylinder axis, and thus the entire field is of two-dimensional nature. This formulation yields an expression for the diffracted cylindrical wave amplitude, at distances from the cylinder large compared to its transverse dimension and the wave-length, which is stationary relative to small independent variations of the surface currents arising from plane-wave excitation along a pair of directions in space; furthermore, the stationary form of the diffracted amplitude is independent of the scale of the surface currents. In accordance with a theorem of Levine and Schwinger, the total plane-wave scattering cross section is simply related to the diffracted cylindrical wave amplitude in the direction of incidence. To examine the high frequency behavior of the cross section, the surface current induced by a plane wave is taken different from zero only on the illuminated part of the cylinder, where its value is derived from the tangential component of the incident magnetic field. The resulting cross section is obtained and is shown to approach 4a when ka approaches infinity (k=2π÷wave-length, a equals the radius of cylinder).
On the Shielding Qualities of Different Concrete Mixtures
Authors: Gugelot P. C. , White M. G.
Published: April 2005

Absorption curves for neutrons and γ-radiation produced by 16-Mev protons on beryllium are measured in absorber blocks of various concrete mixtures to obtain information on their shielding properties. It is shown that a mixture of cement, scrap iron, and limonite ore is as efficient as water in slowing down and capturing neutrons and, in addition, has sufficient density (ρ=3.5 g/cm3) to be an effective absorber for γ-radiation. Compared to ordinary concrete, a three-foot wall of iron and limonite concrete is superior by a factor of 280 for neutrons and by a factor of 20 for γ-radiation. Boron is shown to be of little value in this type of shielding. Mechanical properties of the scrap iron-limonite concrete are satisfactory for structural purposes. From the practical cost standpoint, a concrete made entirely of limonite ore is shown to be a reasonable compromise.
The Effect of Compressive Stresses on the Linear Thermal Expansion of Magnesium and Steel
Authors: Rosenholtz Joseph L. , Smith Dudley T.
Published: April 2005

A series of cylinders of annealed, extruded, pure magnesium and medium soft steel were subjected to a sequence of compressive stresses at room temperature and their respective coefficients of linear thermal expansion in the direction of stress application were determined for the range 20° to 100°C. The cylinders were then heat treated to permit either recovery or recrystallization and the changes in length were measured. Characteristic curves are given for each metal in which the coefficient of linear thermal expansion and length changes are plotted as a function of the true compressive stress. It is shown that these properties may be used to determine the stress history of a test specimen for which characteristic curves are available. It is suggested that this stress analysis technique may find application in the study of rock deformation and in the investigation of metals, both before and after failure.
Thermal Noise at High Frequencies
Authors: Van Der Ziel A.
Published: April 2005

Spenke's discussion of thermal noise from the point of view of the electron theory leads to a result which differs from Nyquist's original formula at frequencies ν such that hν/kT≧1. This discrepancy is due to the assumptions which Spenke made in his analysis.
Internal Friction of Metals at Very High Temperatures
Authors: Kê T'ing-Sui
Published: April 2005

In connection with the study of the internal friction peak (versus temperature) associated with the viscous behavior of grain boundaries in metals, some other effects were observed at higher temperatures causing an additional internal friction in superposition with the high temperature branch of this internal friction peak. This additional internal friction at high temperatures was found to have its origins in some effects of cold-working introduced in the interior of the grains which remains even after the complete recrystallization of the cold-worked specimens. It increases with the amount of cold-work the specimen was subjected to before and after recrystallization; it decreases with annealing at successively higher temperatures until a stable value is reached; and it increases with the precipitated impurity content in the specimen. This high temperature internal friction was found to be very high in an aged specimen of high purity aluminum alloyed with 4 percent of copper. These observations are consistent with the viewpoint that this internal friction is caused by the presence of dislocations in the interior of the specimen although the mechanism of giving rise to the internal friction is unknown. It is pointed out that a study of high temperature creep under very low stress may be conveniently carried out through the internal friction measurements described.
The Orientation Dependence of the Rate of Grain Boundary Migration
Authors: Beck Paul A. , Sperry Philip R. , Hu Hsun
Published: April 2005

Very small recrystallized grains of a large variety of orientations were produced locally in lightly rolled high purity aluminum crystals. The rate of growth of these small grains varied greatly, depending on their relative orientation with respect to the matrix crystal. Grains with an orientation corresponding to a [111] rotation of about 40° showed by far the highest rate of growth. These results indicate that recrystallization textures developing in the spontaneous recrystallization of deformed single crystals can be accounted for by the orientation dependence of the rate of growth.
Measurement of the Thermal Diffusivity of a Soil by the Use of a Heat Pump
Authors: Penrod E. B.
Published: April 2005

An earth heat pump was set in operation to abstract heat from soil assumed to be in thermal equilibrium. Temperature-time graphs of the antifreeze and of the soil at distances of six, twelve, and eighteen inches below the center of the antifreeze line were plotted from experimental data. From these graphs data are obtained from which the thermal diffusivity of the soil is calculated. The soil was analyzed and found to fall in the general Casagrande classification of lean clay (CL) with low plasticity.
Load Induced X-Ray Line Broadening in Nylon Filaments
Authors: Kauffman John , George Waller
Published: April 2005

The load induced microscopic structural changes in highly oriented Nylon filaments were followed by changes in the x-ray fiber diffraction pattern as a function of the resulting strain. Observations made included (1) changes in the dimensions of the fiber spots, and (2) a decrease in ratio of the intensity of amorphous to crystalline x-ray scattering. These new results for Type 200 du Pont Nylon indicate a change in the micro deformation mechanism at a strain corresponding to the inflection of the load-strain diagram (14 percent elongation). The mechanism for smaller plastic strains appears to involve a rotation of the crystallized domains into alignment with the fiber axis, accompanied by a small over-all additional crystallization. For strains larger than the inflectional strain, the mechanism seems to involve a progressive reduction in the domain size, and a reduction in alignment with the fiber axis. Both effects appear to saturate in the vicinity of the rupture strain. These results are discussed in terms of load induced effects found in metal single and polycrystals. It is suggested that the qualitative features observed may be representative of a wide class of load or strain induced micro deformation reactions in the solid state.
Surface Tension Effects in Oriented Thin Silver Films
Authors: Johnson G. W.
Published: April 2005

Structural changes of thin oriented films of silver produced by condensation in a vacuum on cleaved surfaces of single crystals of rocksalt were followed as a function of temperature. Marked agglomeration occurred in films of thicknesses less than 1000A. For thicker films in the 1000–2000A range rectangular holes appeared in the films with their edges aligned with the 110 directions of the rocksalt. The effects are attributed to the readjustment of the oriented surface under the influence of surface tension forces.
Mechanical Properties of Oriented Polystyrene Film
Authors: Nielsen Lawrence E. , Buchdahl Rolf
Published: April 2005

Cast films of polystyrene were oriented by stretching at temperatures above the softening temperature of the material and then cooled. A factorially designed experiment was carried out in which the amount of stretching, temperature of stretching, time held in the stretched state before cooling, and effect of several cycles of stretching before cooling were investigated as they affect the birefringence, the stress-strain properties, dynamic modulus and damping, and the softening temperature of polystyrene.

The values of many of the mechanical properties are more closely related to the birefringence than to the amount of hot stretching. In general, the value of the stress-strain properties in the direction of hot stretch, the dynamic modulus, and the birefringence all increase with an increase in the amount of stretching, a decrease in temperature, an increase in rate of cooling after stretching, and a decrease in the number of times the film was stretched before finally cooling. The softening temperature is decreased in direct proportion to the birefringence. Annealed films give higher softening temperatures than films which have been stretched and then allowed to shrink before cooling.
Application of the Membrane Analogy to the Solution of Heat-Conduction Problems
Authors: Wilson L. H. , Miles A. J.
Published: April 2005

This paper establishes the feasibility of applying the membrane analogy to the solution of two-dimensional steady-state heat-conduction problems. The membrane analogy is established, and the construction and the use of the apparatus for measuring the film are described. Inexpensive apparatus and simplicity of execution are the predominating features of this type solution.
Light Energy and Spectral Distribution for Some Important X-Ray Screens
Authors: Sköldborn Holger
Published: April 2005

The absolute energy of the light (ergs/cm2 per r-unit) and its spectral distribution have been determined for four different types of x-ray fluorescent screens: Patterson E-2, Patterson B-2, Patterson D, and Neossal. The investigation was performed in accordance with an objective spectrophotometric process with the aid of a tungsten ribbon filament lamp as a standard, a light attenuator of reflection type, monochromator, multiplier photo-tube, and galvanometer.

The application of the method employed to the weak light intensities in question is made possible on account of the enormous light sensitivity of the multiplier photo-tube and the possibility of reproducible continuous variation of this sensitivity within very wide limits. The method has proved speedy and accurate and appears to be well suited for investigations of similar character, within the spectral range which may be measured by the commercial types of multiplier photo-tubes.
Relations Concerning Wave Fronts and Reflectors
Authors: Kelleher K. S.
Published: April 2005

By means of a vector notation for surfaces, relations are derived among an incident wave front, reflector and reflected wave front. A method is introduced for evaluating the deviation of a wave front surface from a plane. Problems are included in order to indicate the simplicity and utility of the analysis.
Electrical Breakdown in CSF8
Authors: Geballe Ronald , Linn Fred S.
Published: April 2005

The breakdown potential of a new gas, CSF8, has been measured over the range from pδ=4 to 200 mm×cm under conditions approximating plane-parallel geometry. A comparison of breakdown in air Freon-12 and CSF8 in the same apparatus indicates the ratio of the strengths of these gases to be approximately 1:2:3, respectively. CSF8 decomposes rapidly during breakdown into CF4 and SF4 with a consequent doubling of pressure and appreciable increase in breakdown potential.
The Effect of Cold-Work Distortion on X-Ray Patterns
Authors: Warren B. E. , Averbach B. L.
Published: April 2005

With modern experimental technique, it is possible to measure a peak shape with sufficient accuracy to justify an interpretation based on the precise shape of the reflection. The corrected shape is represented by a cosine Fourier series and a set of An coefficients determined. A plot of the An coefficients vs. n will distinguish between distortion and particle size broadening. From the An coefficients, root mean square values of strain averaged over lengths na3 are obtained. The decrease in these values for increasing length na3 is a direct indication of the non-uniform nature of the strains in cold-worked metal. By measuring several orders of a given plane, it is theoretically possible to obtain a distribution function of the strains directly from a Fourier transform of the An coefficients.
A Quantized Theory of Strain Hardening as Applied to the Cutting of Metals
Authors: Shaw Milton C.
Published: April 2005

A theory of strain hardening is presented which utilizes the fact that metals deform blockwise rather than continuously. A metal is assumed to possess an orderly array of weak spots through which slip planes pass. The slip displacement which occurs upon a single plane is related to the spacing of weak points and the slip plane inclination. Use of a linear relation between shear plane displacement and resisting shear stress, enables the mean shear stress to be computed.

In the two examples considered it is seen that the influence of normal stress on the shear plane is less important in cutting than has been generally believed. Strain hardening and the short range inhomogeneity of metals is seen to account for most of the dynamic increase in shear strength during cutting, including the increase in shear energy per unit volume with decreased depth of cut. This size effect is akin to the increase in tensile strength with decreased specimen diameter, both phenomena involving strain hardening as influenced by inhomogeneity. The quantity Aa2 which represents in a single number the strain hardening and short range inhomogeneity characteristics of a metal should prove particularly valuable in analyzing the cutting characteristics of metals which strain harden extensively.
Modulation Conversion in a Wave Guide
Authors: Rogell Paul S.
Published: April 2005

Theory and design equations are presented for the conversion of a microwave, narrow-band f-m signal into very nearly a pure a-m signal within an ordinary wave guide of specified dimensions. Frequency relationships and guide dimensions are arranged so that the f-m side bands are shifted with respect to the carrier until they become a-m side bands at the guide output. A complex intelligence signal may be transmitted with negligible distortion if it is used to amplitude modulate an intermediate carrier which frequency modulates the microwave carrier.
Measurement of Self-Diffusion of Silver without Radioactive Tracers
Authors: Kuczynski G. C.
Published: April 2005

A new method dispensing with the use of radioactive tracers has been developed for measurement of volume self-diffusion. The method is based upon the relationship of the rate of sintering of metallic wires to the coefficients of self-diffusion. The values of the self-diffusion coefficients for silver as measured by this method are in good agreement with those obtained by the radioactive tracers method.
The Determination of the Impulsive Response of Variable Networks
Authors: Zadeh Lotfi A.
Published: April 2005

Starting with the differential equation relating the output and the input of a linear varying-parameter network, it is shown that the impulsive response of the system is related to a Green's function associated with the system through a linear operator which is the adjoint of the right-hand operator in the given differential equation. A perturbation procedure for the determination of the impulsive response of a slowly varying network is outlined. Use of the method is illustrated by a simple example involving a band width-modulated RC half-section.
Potential Flow into Circumferential Openings in Drain Tubes
Authors: Kirkham Don
Published: April 2005

A theoretical analysis of the effect of the spaces between drain tube units as used in the artificial drainage of soil is given. The problem is one of potential flow; therefore, the results are applicable to heat flow, etc. The basic problem solved is that for axially symmetric flow from an external cylindrical boundary at constant potential to a series of equal, equally spaced openings at a lower potential, all located axially on, and comprising a part of, the otherwise impervious drain tube. The radii of the open sections and impermeable sections of the drain tube are equal. The basic problem is extended to obtain the solution to the practical problem—the seepage of ground water into drain tubes beneath a horizontal water table. The exact solution of the basic problem is not suitable for numerical work. Accordingly, approximate solutions of specified uncertainty are derived and are utilized for tabulation of numerical results. As an example, the analysis shows, in the case of 6 in. diameter drain tubes having 1 ft. long impermeable sections and buried 4 ft. deep in uniformly permeable soil, that increasing the openings from 132 in. width to ¼ in. width will increase the flow 36 percent; while embedding the tubes in gravel, to make the 132 in. openings of effectively infinite width, will increase the flow 180 percent.
Determination of Modified Index-of-Refraction over the Gulf of Mexico from Radio Data
Authors: Straiton A. W. , LaGrone A. H.
Published: April 2005

This paper presents the results of measurements of the signal strength and phase of 3.2-centimeter radio waves for a 26.5-mile path over the Gulf of Mexico under a variety of meteorological conditions. The radio data are used to determine the modified index-of-refraction as a function of height and the associated attenuation factor. The modified index-of-refraction curves are compared to those measured meteorologically.
Stress Analysis for Compressible Viscoelastic Materials
Authors: Read W. T.
Published: April 2005

Mathematical methods of stress analysis are presented for linear, compressible, viscoelastic, or anelastic, materials such as metals at high temperatures or high polymers with small strains. For such materials stress, strain and their time derivatives of all orders are related by linear equations with coefficients which are material constants. Fourier integral methods are used to show that static elasticity solutions can be used to determine the time dependent stresses in viscoelastic bodies with any form of boundary conditions.

If stress and double refraction and their time derivatives are also linearly related, the standard photoelastic techniques can be used to determine the directions and difference in magnitude of the time dependent principal stresses, even though the principal stress axes do not coincide with the polarizing axes and both vary with time. When viscoelastic models are used in photoelastic studies, the time variation of the stress distribution in the model represents a first approximation to the dependence of the stress in the elastic prototype on Poisson's ratio.
The Apparent Size of Objects as Observed in the Electron Microscope
Authors: Kern Stanley F. , Kern Raymond A.
Published: April 2005

The image formed in the electron microscope of shadowed polystyrene latex spheres is larger than the image of unshadowed spheres. This increase in image size and probable causes are discussed. Implications of this phenomena on the study of viruses and other biological specimens are mentioned.
The Specific Heats of MgO, TiO2, and ZrO2 at High Temperatures
Authors: Arthur James S.
Published: April 2005

Mean specific heats were determined from 20°C to 800°C for MgO, TiO2, and ZrO2. True specific heats were then calculated assuming that CT=A+BT+CT2. At 350°C the true specific heats were calculated to be MgO 0.276; TiO2 0.210; ZrO2 0.140.
Negative Wire Corona at High Temperature and Pressure
Authors: Koller L. R. , Fremont H. A.
Published: April 2005

The corona characteristics of air and methyl chloride were studied in a modified type of Cottrell precipitator at temperatures from room temperature to 500°C and pressures from 1 to 5 atmospheres. Within this range the corona current is a power function of voltage with gas density as a parameter. This power is independent of density. Values are given for air and methyl chloride.
The Thermal Conductivity of Soils
Authors: Gemant Andrew
Published: April 2005

The thermal conductivity of soils of varying moisture content is calculated on a physical basis. The results of this computation are, in a range of moisture contents from 5 to 25 percent, in agreement with experimental data in the literature. The influence of soil composition on conductivity is also explained by the theory. The use for practical purposes of an average resistivity value of 60 to 70 thermal ohms appears justified in the light of this analysis.
Theory of Blind Navigation by Dynamical Measurements
Authors: Gilvarry J. J. , Browne S. H. , Williams I. K.
Published: April 2005

The differential equation is considered which determines the position of a vehicle from dynamical measurements of the non-gravitational acceleration b made internally. Three linear approximations to the gravitational field g(r) of the earth, which lead to explicit solutions of this equation, are considered and their limitations are discussed. An interval-wise solution (linear continuation) for trajectories of extended range is described, which is based on such linear approximations and has definite advantages in this application. The theory is applied to the trajectory of the German A10 vehicle.
The Retrograde Motion of the Arc Cathode Spot
Authors: Gallagher C. J.
Published: April 2005

The motion of the cathode spot in a direction opposite to that predicted by Ampère's law depends on the arc current, gas pressure, kind of gas, and magnetic field strength. Studies of the effects of these variables have been made, including measurements of velocity and the critical pressure at which reversal of motion occurs. The phenomena observed have not been clearly explained by any of the pictures presented to date. The existence of the retrograde motion indicates very strongly that the positive-ion space charge outside the cathode is all important in determining the mechanism of current transfer.
Transonic Potential Flow of a Compressible Fluid
Authors: Sears W. R.
Published: April 2005

Even under the assumptions of irrotational, isentropic flow, which have been found generally useful for subsonic and supersonic cases, the equations of gas flow are relatively intractable for mixed, transonic situations. Approximate methods of solution used by a number of investigators are reviewed briefly, as well as the hodograph technique, which yields exact solutions of the equations for plane flow. It is pointed out that all the methods predict smooth, potential mixed flows involving imbedded regions of supersonic speed and both acceleration and deceleration through the speed of sound. There is no experimental verification of the existence of such flows.

Three possible explanations for this sharp discrepancy between experiment and perfect-fluid theory have been advanced; namely, (a) effects of viscosity, (b) non-existence of neighboring solutions, and (c) temporal instability. These are reviewed in turn. None has led to a complete explanation, to date. Kuo's stability calculations are described briefly. His results indicate that stable, smooth, mixed flows may exist if certain conditions are satisfied.
Analysis of Intensities Obtainable Using Pinhole and Slit Collimators in X-Ray Powder Diffraction Techniques
Authors: Alexander Leroy
Published: April 2005

Other factors being equal, the integrated intensity of a powder diffraction reflection is a function of the geometry of the source, collimator, and sample. By means of a geometrical and algebraic analysis one can predict the relative intensities to be expected with pinhole or slit collimators of different dimensions. Important gains in intensity can be obtained by replacing pinholes with slits, and the advantage is about the same if the x-ray focal spot is viewed either longitudinally or laterally through slits of sufficient length. These results confirm experimental results reported by other investigators and also re-emphasize the potential value of the ``side'' windows of x-ray tubes, which are commonly neglected.
Average Electron Density Measurements by Low Angle X-Ray Scattering
Authors: Barton H. M. , Brill R.
Published: April 2005

According to Guinier the low angle x-ray scattering of particles should disappear when they are immersed in a fluid of equal electron density. This furnishes a way of measuring the electron density of powders, providing a suitable impregnating fluid can be found. Experiments of this type have been carried out with carbon black. A method of calculating the low angle scattering coefficient defined by Warren is given for impregnated samples. Measurements of the total low angle scattering intensity were made using a double crystal spectrometer and Geiger counter. No liquid was found that would give complete matching but approximate matching was obtained with phosphoric acid solution. The data extrapolate to show an electron density of 1.1N±0.1N where N=Avogadro's number. This compares with a value of 0.99N as calculated from the helium immersion mass density measurement on the same sample.
Microscopic Observation of the Solidification of Small Metal Droplets
Authors: Turnbull D. , Cech R. E.
Published: April 2005

The solidification behavior of small metal (10 to 100 micron diameter) droplets has been observed on a high temperature microscope stage. An abrupt change in surface appearance and in the case of high melting metals a sudden brightening (``blick'') accompanies solidification. The solidification temperatures observed for a collection of droplets may be widely distributed, but a significant, usually the major, fraction of the droplets supercool some maximum amount (ΔT-)max that is reproducible and characteristic of the metal. For many metals (ΔT-)max≈0.18 times the absolute melting temperature. (ΔT-)max is not much changed by wide variations in the cooling rate and droplet size. The growth rate of metal crystals is very great so that the solidification rate of the droplets is controlled by the nucleation frequency.
The Thickness Measurement of Thin Films by Multiple Beam Interferometry
Authors: Scott G. D. , McLauchlan T. A. , Sennett R. S.
Published: April 2005

A method is described for the measurement of the thickness of thin films using the multiple beam interference techniques. Only simple equipment is required, but reduction of the order of interference to as low as one makes possible the measurement of average thicknesses down to 10A. Applications have been made to evaporated films of six different metals and the method appears to be useful for all stable thin films in thicknesses up to several microns.

Possible errors in the method and the precautions which may be taken to avoid them are discussed.
X-Ray Diffraction by Elastically Deformed Crystals
Authors: White J. E.
Published: April 2005

Published articles establish the fact that vibration or other inhomogeneous strain greatly increases the ability of a crystal to diffract x-rays. The present article gives experimentally determined relations between integrated intensity and strain for the rather simple case of static bending. All measurements were made on quartz plates, but a wide range of geometrical and crystalline parameters was covered nevertheless. In some cases, the integrated intensity for extreme bending was more than 20 times that from the unbent crystal. An approximate theory is developed which agrees well enough with the measurements to serve as a means of computing the effects of other types of strain or of other combinations of crystalline parameters. A qualitative study of vibrating crystalline plates is also described briefly.
Some Effects of Nozzle Design on the Diffraction of Electrons by Gases
Authors: Harvey R. B. , Keidel F. A. , Bauer S. H.
Published: April 2005

An evaluation has been made of some of the errors introduced into the electron diffraction of gases by failure of the sample to be localized, and by secondary and higher order scattering.

The degree to which poor nozzle design may contribute to these factors was investigated experimentally by measurements of the pressure in the camera and absorption measurements of the main electron beam when a small volume of gas was allowed to expand into the camera; and theoretically for the cumulative effects of higher order scattering on the final picture. This evidence was complemented by density measurements on photographic plates taken under similar conditions. The effect of using liquid air cooled surfaces around the nozzle was tested.

Of the nozzles tested, better ``image to background'' ratios were obtained with the ``hydrodynamic'' and ``comparison'' nozzles than with the ``conventional'' nozzle, but the gas must be admitted slowly enough so that less than about 10 percent of the main beam is appreciably scattered. The ``image to background'' ratios were always higher using adequate cooling on the condensing surfaces surrounding the nozzle. In the case of pressure and electron beam absorption measurements short exposures were advantageous, where secondary scattering was not directly considered, and high camera pumping speeds were always advantageous.

On the basis of these results some general design suggestions for electron diffraction cameras, and requirements for good efficiency in nozzles can be made. A nozzle design is proposed which would reduce materially the errors normally encountered in electron diffraction work.
Studies with an Aerodynamically Instrumented Shock Tube
Authors: Hertzberg A. , Kantrowitz A.
Published: April 2005

A shock tube has been set up at Cornell University to begin the study of two-dimensional wave propagation. Pressure waves initiated by the shock itself were used to trigger the spark source for the schlieren flow-observation system, to time the instant of exposure and to measure the strength (speed) of the shock waves. These techniques were employed to study the propagation of a wave in a converging channel. Fair agreement between the one-dimensional method of characteristics and these experiments was obtained.
Improved Ultra-Thin Sectioning of Tissue for Electron Microscopy
Authors: Hillier James , Gettner Mark E.
Published: April 2005

The use of a reservoir of liquid to collect ribbons of thin sections as they are cut enables serial sections to be obtained and provides means for detecting variations in thickness. Reducing the effects of static friction and of external vibrations makes it possible to cut long series of sections 0.2μ thick and uniform to better than five percent. Some observations which may throw some light on the mechanics of the cutting process are reported. Mounting the sections without any treatment is shown to be superior to any technique in which the embedding material is removed or replaced. It is shown that the technique provides sections in which a structural resolution of 200A is possible. The remaining artifacts introduced by the sectioning and mounting are easily recognized deformations which do not influence the interpretation.
A Technique for Taking Motion Pictures of Electron Microscope Images
Authors: Preuss Luther E. , Watson John H. L.
Published: April 2005

Lately, for the first time, a technique for taking motion pictures of electron microscope images has been developed which is proving useful in the study of some of the effects of electrons upon matter and particularly upon colloidal crystals. Resolution of 150 to 300A is achieved and is suitable for a host of practical electron microscopical problems. Pictures are taken from outside the instrument, utilizing the radiation emitted by the fluorescent screen. Some instrument adaptation is required for adequate illumination, and precautions must be exercised against toxic x-ray dosages.
Nuclei of Strain in the Semi-Infinite Solid
Authors: Mindlin Raymond D. , Cheng David H.
Published: April 2005

Stress functions are given for forty nuclei of strain in the semi-infinite elastic solid. The corresponding stresses have the property that the traction vanishes across the plane boundary of the solid. The nuclei are derived, by processes of superposition, differentiation and integration, from the solution of the elasticity equations for the single force in the interior of the semi-infinite solid.
The Generalized Response of Linear Systems for Arbitrary Initial Conditions
Authors: Moore John R.
Published: April 2005

A method is presented for the solution of ordinary linear differential equations with constant coefficients. This method stays wholly in the time domain and obtains a general solution in a compact form including the effects of initial conditions. The differential equation as treated involves a driving function made up of the sum of terms involving the system input and its derivatives. The general solution is also given in terms of weighting functions operating on the input (in the driving function) and including outside the weighted integral, terms involving initial conditions of the input as well as the dependent variable.
Applications of Potential Theory to the Design of Linear Arrays
Authors: Taylor Thomas T. , Whinnery John R.
Published: April 2005

The polynomial formulation of the linear array problem introduced by Schelkunoff is studied from the point of view of potential theory. An electrical analogy results which is not only very helpful in qualitative thinking about the problem, but which also makes possible the construction of an analog computer for the synthesis of arrays to produce a desired radiation pattern, and for the evaluation of existing arrays. Such a computer has been built, and tested on known patterns with remarkable success.

Several theorems concerning the effect of the roots of the polynomial on the magnitude and phase of the space factor of an array are given. Some of the most important consequences of these are the lack of uniqueness in the array synthesis problem, and the evaluation of known methods of synthesis which consider only constant-phase patterns.

A method of analysis is sketched which in principle does the same thing as the computer, and the difficulties in applying this are described. It is concluded that the computer would be preferable for a wide range of practical problems.
A Theory of the Dynamic Plastic Deformation of a Thin Diaphragm
Authors: Hudson G. E.
Published: April 2005

The theory presented in this article was developed in an attempt to describe the observed motion and plastic deformation of clamped metal diaphragms used in certain underwater explosion experiments and in certain mechanical gauges. The theoretical attack on this problem enables one to set up certain equations of motion, which may be solved in finite form under certain conditions. The solutions enable one to specify, for instance, the final deformed diaphragm profile, the distribution of thickness after deformation, the swing-time, which is the total time for deformation to take place, and many other quantities.

The simplest case, termed the ``elementary approximation,'' turns out, except for relatively minor details, to describe adequately for many purposes the motion and final shape of the diaphragm; it is found that the deformed diaphragm shape is conical, the thickness distribution shows a marked dimpling at the center of the diaphragm, and the swing-time ts is, to this order of approximation tS=a/c, where a is the radius of the diaphragm, and c is the square root of the ratio of the ``yield stress'' to the density. These results are all in good agreement with experimental facts.
Theory of the Circular Diffraction Antenna
Authors: Levine Harold , Papas Charles H.
Published: April 2005

The circular diffraction antenna consists of a coaxial wave guide fitted with an infinite-plane conducting baffle, and open to free space. An equivalent circuit description, appropriate to principal-mode propagation in the coaxial region, is investigated theoretically. Variational expressions for the circuit parameters are derived, and used for accurate numerical evaluation.
Certain Refractory Compounds as Thermionic Emitters
Authors: Goldwater D. L. , Haddad R. E.
Published: April 2005

Several refractories of the nitride, boride, and carbide families are investigated as sources of thermionic electrons. An activation pattern qualitatively common to several of the compounds is observed. Emission data for the final state of activation are presented. Data concurrently obtained for thoria are also given for comparison.

True temperature used in the Richardson equation is obtained by correction from brightness temperature. Temperature correction curves have been obtained. These curves can be satisfactorily represented in the region of thermionic emission by one value of spectral emissivity, which values are listed for the materials studied.
Secondary Emission of Nickel-Barium Mixtures and Rhenium When Bombarded by Electrons with Energies from 50 to 8000 Electron-Volts
Authors: Farnsworth H. E. , Lun M. J.
Published: April 2005

The experimental tube contains a contamination-free gun which directs an electron beam at normal incidence onto a small thin sheet target which may be heated by conduction. The target is located at the center of a conducting sphere to permit a measure of the secondary current, and also of the energy distribution of the secondary electrons by means of the retarding potential method.

The maximum value of δ, the secondary emission ratio, for a cast alloy of nickel containing 1.5 percent barium is 2.8 and occurs at 800 to 900 volts after a critical amount of previous heat treatment of target. The value of δmax increases with heat treatment of target, subsequent to baking of tube, to the above value and then decreases with further heating. For the critical condition the value of δ above 4000 volts is sensitive to the amount of previous electron bombardment of the target. A δmax of 1.3 for rhenium after thorough out-gassing was obtained at 900 volts.

The most probable energy of low speed secondary electrons from rhenium is approximately 5 ev.
Associated Legendre Polynomial Approximations
Authors: Landauer R.
Published: April 2005

Approximations for the associated Legendre Polynomials are derived by a phase integral method. The method is an extension of the WBK method, applicable to separable multidimensional wave propagation problems.
Effect of Surface Condition of a Sphere on Its Water-Entry Cavity
Authors: May Albert
Published: April 2005

An investigation of factors which influence the formation of a cavity when a sphere enters water vertically is described. It was found that cavities are formed at much lower entry speeds for contaminated spheres than for clean ones, but that there is little dependence on the type of the contaminant. In regard to the scaling of this effect, the tendency to form a cavity varies little with change of size or specific gravity of the sphere. Water-entry cavities are observed to form at velocities much lower than those required for incipient cavitation in the water tunnel; consequently, a relation between the two effects appears improbable. Some dependence of cavity formation on viscosity might be inferred from the observation that cavities were formed at lower entry speeds by spheres coated with liquids of high viscosity than by spheres without this coating.
Design and Analysis of a Conservative Dynamic Load Simulator
Authors: Gamble E. H. , Hatten B. W.
Published: April 2005

The design for a highly versatile dynamic load simulator is described, in which the correct resultant load is computed electrically and applied through a hydraulic servomechanism. One of the significant features of this machine is that virtually all of the power absorbed from the unit to which the load is applied is conserved in the form of electrical energy and returned to the power lines. A complete analysis of this electrohydraulic system is presented for the case in which coulomb friction is negligible. Two basic applications for this simulator are a servo test stand designed primarily for testing autopilots and an aircraft control load simulator for both design and test of control systems.
The Role of Tetragonal Twins in the Internal Friction of Copper Manganese Alloys
Authors: Siefert Arthur V. , Worrell Francis T.
Published: April 2005

Internal friction studies have been made of an alloy 88 percent Mn-12 percent Cu. This alloy when annealed at 925°C and quenched to room temperature has a tetragonal structure of axial ratio 0.97. Twins are readily formed along the (101) and (011) planes. It has been suggested that relaxation across these twin boundaries would account for certain observed internal friction. Verification of this is shown.
Electrical Properties of Selenium. II. Microcrystalline Selenium
Authors: Henkels H. W.
Published: April 2005

The electrical properties of selenium have been studied in their dependence on history of preparation, i.e., as functions of temperature of initial liquid selenium, quench procedure, nucleation procedure, temperature of crystallization, and time of crystallization.

The electrical properties of melt single crystals and the microcrystalline matrix of these crystals have been compared.

The influence of nonmetals S, O2, I2, in small quantities on the electrical properties has been determined.

Carrier densities and effective mobilities as functions of temperature of measurement have been estimated from data on thermoelectric powers and resistivities. The order of the carrier densities have been checked by measurements of the voltage dependence of capacity of completely vacuum prepared rectifiers.

The frequency dependence of resistivity has been determined to gain insight into the nature of the effective mobilities.