bluuebunny/crossref_metadata_2025 huggingface dataset:
Visco-Elasticity of Rubber
Authors: Blizard Robert B.
Published: April 2005

A theory has been obtained for the visco-elastic behavior of rubber in the frequency range above that at which creep is important and below that at which it behaves like a hard solid. The rubber chains are treated as springs in a viscous medium, and a general expression is obtained for the contribution to modulus of a single section of chain as a function of its length and terminations. A statistical estimate is made of the number of chain segments having given length and terminations. A modulus function is found for the group of chains with each kind of termination and these are added in the proper amounts to give the form of the modulus vs frequency curve for any amount of cross-linking.

Measurements of shear modulus were made on one apparatus at frequencies between 0.0125 and 750 cps. Agreement is good if a pure viscosity is added to the theory. However, at low frequencies the imaginary part of modulus does not decrease as much as predicted.
Finite Deflections of a Cantilever-Strut
Authors: Beth Richard A. , Wells Charles P.
Published: April 2005

A cantilever-strut is an originally straight uniform thin rod clamped or ``built-in'' at one end and acted on by an arbitrary force at the other end. The arbitrary force and the angle it makes with the tangent to the clamped end of the rod are regarded as independent variables. The problem of finding the deflection coordinates of the loaded end of the rod, the tangent angle of the loaded end, and the strain energy of bending in the rod is solved in terms of a newly defined function that satisfies a nonlinear partial differential equation. Solutions are given in series form. Since the cantilever-strut is a segment of an inflectional elastica, the classical elliptic integral solution is also outlined for comparison with the more direct series solution of the problem.
On the Representation of the Electric and Magnetic Fields Produced by Currents and Discontinuities in Wave Guides. I
Authors: Marcuvitz N. , Schwinger J.
Published: April 2005

Electromagnetic scattering problems in cylindrical wave guides, including free space, involve the calculation of the fields produced in the presence of geometrical discontinuities by arbitrary currents. Such discontinuities may be replaced by equivalent electric and magnetic currents. The over-all calculation then leads to two distinct problems: first, the calculation of the fields produced by the prescribed and induced currents in a discontinuity—free guide; second, the self-consistent determination of the induced currents by the condition that the fields so produced satisfy the boundary conditions at the discontinuity surfaces. The first problem is treated herein by representation of the fields in terms of a complete set of vector modes characteristic of the possible transverse field distributions in the guide cross section. This representation transforms the over-all field problem into one-dimensional modal problems of conventional transmission line form. The eigenvalue problem of finding the characteristic modes is discussed in detail for the case of a uniform guide with perfectly conducting walls. The transformation procedure and the solution of the resulting transmission line problem are treated from an impedance point of view. A typical modal analysis and synthesis is presented for the explicit determination of the fields produced by arbitrary electric and magnetic currents in an infinite and semi-infinite wave guide of arbitrary cross section. The connection with a corresponding dyadic Green's function representation (to be treated in Part II) is pointed out.
The Electronic Torch and Related High Frequency Phenomena
Authors: Cobine J. D. , Wilbur D. A.
Published: April 2005

This paper presents the design of a high frequency electronic torch operating at 1000 mc/sec, and some of the physical characteristics of the gaseous discharge produced. The flame produced by polyatomic gases is capable of melting many refractory materials due to the heat of association of the dissociated molecules. Monatomic gases produce little heat. Probe measurements indicate an electron temperature of the order of 105 deg K. The gas temperature near the outer edge of the flame appears to be of the order of 3000°K.
Three-Dimensional Photoelasticity
Authors: O'Rourke R. C.
Published: April 2005

The classical Sommerfeld-Runge method for deriving the laws of geometric optics in isotropic inhomogeneous media from Maxwell's equations is applied to problems in ``weakly'' anisotropic and inhomogeneous media. This leads to a generalized Hamilton-Jacobi partial differential equation for the phases of the two waves (eikonals) which can propagate with finite velocity in such a medium. If one restricts oneself to a limited class of stress distributions, one derives a very powerful method of solving axially and spherically symmetric problems which would be very difficult to treat by the direct solution of the classical equations of elasticity. The Maxwell-Neumann law is derived in variational form so that, in principle, one can estimate in any given case the error involved in the conventional assumption that the paths are straight lines instead of the actual Fermat paths.

The last section treats the so-called general problem of photoelasticity in which the principal stress directions in the plane of the wave front rotate arbitrarily as the latter propagates through the medium. Again the Sommerfeld-Runge method gives one a solution which claims that if the rate of rotation is small in a wavelength one can ignore the contributions of the rotation to the integrated phase. An experiment is proposed to check this claim.
Current and Charge Distributions on Antennas and Open-Wire Lines
Authors: Angelakos D. J.
Published: April 2005

An experimental investigation has been made of the distributions of current and charge amplitude and phase on cylindrical antennas and on the driving lines. The presence of a stub support modifies the distributions on the antenna only near the junction of the antenna, line, and stub; however, for antenna loads near antiresonance, the distributions on the line as well as the impedances of the structure are altered considerably.

A corrective network is defined for the terminal region of the junction. Impedances of theoretical models of antennas, the network, and conventional transmission line equations may then be used to predict the apparent impedances of the structure.
Iron-Silicon Alloys Heat Treated in a Magnetic Field
Authors: Goertz Matilda
Published: April 2005

Heat treatment in a magnetic field has been found effective for iron-silicon alloys between two percent and ten percent silicon, the highest maximum permeability being obtained at about 6.5 percent silicon. In a single crystal of this composition, magnetized parallel to a [100] direction, the hysteresis loop is squared by the magnetic anneal and the maximum permeability is increased from 50,000 to 3,800,000, the highest value yet reported.
Viscoelastic Properties of Several High Polymers
Authors: Horio M. , Onogi S. , Nakayama C. , Yamamoto K.
Published: April 2005

The viscoelastic properties of viscose monofils differing in the degree of orientation were measured by means of the vibrating reed method within the frequency range from 20 to 100 cps. The frequency dependence as well as the orientation dependence of the modulus and viscosity coefficient were discussed and connected with the relaxation mechanism. It could be expected that the anomalous dispersion should occur at frequencies lower than 1 cps and at high frequencies such as 104∼106 cps, the former being due to the motion of secondary cross bonds permitting the chains to slip, and the latter to the motion of segments. In order to supplement the data which support this discussion, measurements were extended to Cellophane, films of cellulose acetate, and Celluloid, and also to films of synthetic high polymers such as Polycaprolactam and polyvinyl chloride. The latter two substances showed noticeably different dynamic properties from that of cellulose, and this could, assumably, be associated with the fact that they lack in crystallization.
Dynamic Measurements of Physical Properties of Pulp and Paper by Audiofrequency Sound
Authors: Horio M. , Onogi S.
Published: April 2005

The dynamic Young's moduli of various types of paper were measured by the vibrating reed method. The Young's modulus of paper increases statistically at a rate approximately proportional to the square of its density. The modulus and density of paper increase with the degree of beating. The sulfite and sulfate fibers behave differently during beating. The angular dependence of Young's modulus, tensile strength, and elongation at break was analyzed mathematically; and the results were verified by experiments. According to this theory, the mean value of Young's modulus and tensile strength of machine-made paper should be expressed by the geometrical mean of the values of the machine and cross directions, whereas the mean value of elongation can be given by the arithmetical mean. The removal of parenchyma cells is very effective in reducing the Young's modulus of dissolving pulp. The viscoelastic properties of paper were observed within the frequency range from 20 to 180 cps. The dynamic modulus and mechanical loss factor of the sheets employed were found to be smaller than one-tenth of those of cellulose films. The interfiber deformation influences the dynamic properties of paper.
Gas Temperatures and Elastic Losses in Low Pressure Mercury-Argon Discharges
Authors: Kenty C. , Easley M. A. , Barnes B. T.
Published: April 2005

The increase ΔT in average gas temperature for ac and dc has been determined from measurements of the increase in pressure. A small McLeod gauge was used. Wall temperature was regulated. Corrections for end effects were made by comparing results for long and short tubes of 3.6 cm diameter. Assuming the radial variation of heat input to be parabolic, the temperature distribution was calculated using published values of heat conductivity K. From the results the heat input Pm per centimeter length was calculated. This value was compared with the elastic loss Pc computed from electron temperature Te and number of electrons Ne per centimeter column, taking into account the variation of mean free path with electron velocity. Good agreement was obtained for mercury pressures ranging from 1 to 25 microns, with the arc current 0.2–0.6 ampere and the argon filling pressure 3.5 mm (Hg).
On Creep and Relaxation. III
Authors: Gross B. , Pelzer H.
Published: April 2005

The previous theory of linear reversible creep is extended and permanent (plastic) deformations are taken into consideration. General relations are established between the distribution functions of relaxation times of stress, and retardation times of strain. A particular type of distribution function is considered in detail and it is discussed in a qualitative way how the existence of a plastic component in creep affects the distribution function of relaxation times.
An Electrostatically Induced Permanent Memory
Authors: Pulvari Charles F.
Published: April 2005

The possibility of using a ferroelectric substance (barium titanate) as a medium for storing information is described. Preliminary experiments were performed to determine the necessary conditions for inscribing and erasing electrostatic preorientation in barium titanate ceramics at a temperature somewhat below the Curie point. The results suggest the possibility of a memory device that can be operated in the range of audio-frequencies or higher.
Expected Number of Crossings of Axis by Linearly Increasing Function Plus Noise
Authors: Lehan Frank W.
Published: April 2005

The expected number of times the function e(t)=at+eN(t) crosses the t axis in a positive direction prior to any given time is calculated, where eN(t) is a random noise function of arbitrary power spectrum. The solution is given as the product of two functions. Curves are presented for the two functions.
Measurement of Velocity and Pressure of Gases in Rocket Flames by Spectroscopic Methods
Authors: Bundy F. P. , Strong H. M. , Gregg A. B.
Published: April 2005

A method for measuring the gas flow velocity in hot high velocity exhaust flames is described. This method is based on the doppler shift of wavelength of the sodium or lithium spectral radiation from the flame when viewed at different angles relative to the flame axis. The same apparatus may be used to measure the gas pressure from the pressure shift of wavelength of the sodium radiation. A Fabry-Perot interferometer and camera assembly was used to determine the small shift in wavelengths. It was concluded that the absolute accuracy of any one velocity measurement by this method is about ±1.5×104 cm/sec, while that of any one pressure measurement is about ±0.3 atmosphere. The method is therefore applicable to flames of very high velocity and to pressures of at least a few atmospheres.
Information Theory and Most Efficient Codings for Communication or Memory Devices
Authors: Brillouin L.
Published: April 2005

Shannon's theorem about the capacity of a channel is discussed, and it is shown that the most efficient coding is the one yielding the most probable distribution of the code symbols. A specific rule is obtained for this most probable distribution. Most efficient coding is essential for communication channels or memory devices in large scale computers.
Theory of V-Antennas
Authors: King Ronold
Published: April 2005

An integral equation for the current in an apex-driven symmetrical V-antenna is derived and solved by successive approximations. General formulas for the distribution of current and the impedance are obtained. The zeroth-order impedance is evaluated for a leg-length h=λ0/4 as a function of the enclosed angle and used to estimate experimental results.
On the Theory of Random Noise. Phenomenological Models. I
Authors: Middleton David
Published: April 2005

Three phenomenological models are considered from which can be constructed a macroscopic statistical description of varieties of electronic noise, of which shot, thermal, and Barkhausen noise, electron multiplier and precipitation noise, clutter, ignition, and impulsive random noise in general are representative examples. The models examined are (I) non-overlapping, periodic noise waves, common in pulse-time modulation and other communication schemes, where the amplitude, phase, duration, and epoch in a period interval are subject to statistical variations; (II), non-overlapping, nonperiodic disturbances, encountered in servo-mechanism operation and keyed-carrier communication techniques, for instance, which are like (I), but lack the basic periodic structure; and (III), poisson noise, consisting of the superposition of independent, randomly occurring elementary impulses. Much of the electronic noise mentioned above belongs to this more comprehensive type, where overlapping of the basic pulses is the characteristic feature. Because all (second-order) moments are required in general for the analysis of noise in nonlinear systems, the attempt is made here to determine explicitly on the basis of the appropriate model the second-order probability density W2 in the important stationary cases. For noise of types (I) and (II) this appears impractical except in the simplest cases: only the lower order moments prove tractable. However, for poisson noise (III) an explicit treatment is possible for impulsive random noise, nearly normal random noise, and for the limiting, normal random cases (of which shot and thermal noise are examples). In Part I the main features of the models (I–III) are discussed, and the general probability density Wl(X1, t1; …; Xs, ts) in the nonstationary instances is formally constructed. In Part II, the distribution density for nearly normal random noise is given, the first and second (second-order) moments of the various distributions are determined, and from these in turn are found the spectral distribution of the energy in the random waves.
The Allotropic Transformation of Hafnium
Authors: Duwez Pol
Published: April 2005

The existence of an allotropic transformation in hafnium, suggested by Zwikker in 1926, has been confirmed. The transformation temperature is 1310±10°C. The high temperature beta-form is probably body-centered cubic.
A Reinterpretation of Experiments on Intermetallic Diffusion
Authors: Nowick A. S.
Published: April 2005

Reported values for the heat of activation, H, for volume chemical diffusion, as obtained from the slope of the best straight line in a semilogarithmic plot of diffusion data against T−1, may often be greatly in error. These values will be too low whenever diffusion along internal surfaces plays a significant role at the lower temperatures of measurement. A method is presented which attempts to avoid such errors in H by using the calculated values of Zener for the intercept of the straight line. When the data is reconsidered in the light of this method, the widely accepted belief that H for chemical diffusion in dilute solid solutions is generally considerably less than H for self-diffusion of the solvent is brought to question. In fact, it is found that the chemical diffusion activation energy is generally within 15 percent of that for self-diffusion. It is further concluded that the process of diffusion under a chemical gradient may itself produce internal surfaces which act as short-circuiting diffusion paths.
Carbon, Oxygen, and Sulfur Content of Chilean Coppers as Related to Cuprous-Oxide Rectifiers
Authors: Hein C. C. , Hickam W. M.
Published: April 2005

Several Chilean coppers used in cuprous-oxide rectifier work have been analyzed for carbon, oxygen, and sulfur. The carbon determinations were in agreement with published solubility data. Large differences were found in the oxygen and sulfur content which could be correlated with the refining data of the copper and the reverse leakage currents of the rectifiers. The change in sulfur content caused by various heat treatment also was investigated.
Hollow Cathode for Positive Ion Studies in Cathode-Ray Tubes
Authors: Bachman C. H. , Eubank Harold , Hall George
Published: April 2005

Apparatus has been designed and tested which makes possible the identification of the positive ions in the beam of a cathode-ray tube. A hollow cathode construction allows the positive ions to pass through the conventional part of the electron gun and be studied as a positive ion beam by another set of focusing electrodes and deflection magnets. Curves of ion yield and bucking potential measurements indicate that most of the ions are formed in the early stages of electron acceleration.
Instantaneous Power Spectra
Authors: Page Chester H.
Published: April 2005

The intuitive concept of a changing spectrum is discussed. The instantaneous power spectrum is defined mathematically and used to make the intuitive concepts more precise. It depends upon the past history of a signal, but not upon the future.

Integration of the instantaneous power spectrum over time yields the conventional energy spectrum. The instantaneous power spectrum of a random function may be averaged over the ensemble of functions, with a resulting stochastic average instantaneous power spectrum that is equal to the conventional time average power spectrum of a stochastic process.
A Direct-Current Network Analyzer for Solving Wave-Equation Boundary-Value Problems
Authors: Swenson George W. , Higgins Thomas J.
Published: April 2005

The analogy between the difference equations of a wave-equation boundary-value problem and the current-law equations of a direct-current network is developed. This theory permits construction of a dc network analyzer for solution of the wave equation. Some of the network parameters are necessarily negative. These ``negative resistors'' are simulated by active dc circuits. The determination of characteristic frequencies, characteristic functions, and response to simple harmonic forces is illustrated by solution of an irregularly shaped membrane. Methods are discussed for solving problems involving inhomogeneous or anisotropic media or various types of boundary conditions.
The Probability Distribution of the Phase of the Resultant Vector Sum of a Constant Vector Plus a Rayleigh Distributed Vector
Authors: Norton Kenneth A. , Shultz Edna L. , Yarbrough Helen
Published: April 2005

Formulas, tables, and graphs are given of the cumulative probability distribution of a function frequently occurring in the theory and practice of radio wave propagation as well as in the study of the influence of noise in phase modulation systems.
Electron Diffraction Evidence for the Existence of Microstress in Evaporated Metal Films
Authors: Halteman Eber K.
Published: April 2005

The line broadening in electron diffraction powder patterns from evaporated nickel films has been investigated. The pure diffraction broadening was found to vary with the Bragg angle in agreement with a microstress theory of broadening rather than with a particle size mechanism. The Fourier transform of the pure diffraction broadening has been determined and also found to be in agreement with a microstress mechanism.
Electromagnetic Resonant Behavior of a Confocal Spheroidal Cavity System in the Microwave Region
Authors: Simons J. C. , Slater J. C.
Published: April 2005

The resonance of a small spheroidal object in a large spheroidal cavity is investigated. This approximates the case of a thin needle-like antenna in a large cavity. It is shown that this needle, if thin enough, shows marked resonant properties, in that when the cavity is tuned to a resonant frequency defined by the needle, the magnetic field on the surface of the needle is greatly enhanced. This property can be used in a practical way, in measuring surface impedance of the material of which the needle is composed: at resonance most of the loss in the cavity is located at the surface of the needle and depends on the material of which it is composed.
Simulation of Trajectories of Charged Particles in Magnetic Fields
Authors: Vineyard George H.
Published: April 2005

A ball rolling on a rotating surface is shown to simulate the motion of a charged particle in a magnetic field. The theory is given for the case of a warped surface undergoing arbitrary rotation about a fixed axis and translation perpendicular thereto, while the system from which the ball is observed partakes of similar but independent motion. With approximations based on not too large departure of the surface from flatness, the following cases can be simulated: (a) The magnetic field is homogeneous and constant. The electric field is perpendicular to the magnetic field, and irrotational, but otherwise arbitrarily spatially dependent, and arbitrarily time dependent within certain limits. (b) The magnetic field is homogeneous but arbitrarily time dependent. The electric field is perpendicular to the magnetic field and may have a variety of space and time dependences, including a part which encircles the axis and has just the right magnitude to produce acceleration in a circular orbit as in the betatron.

Results of rudimentary experiments are presented which indicate that the method is capable of good accuracy.
Glass Cracking Caused by High Explosives
Authors: Pugh E. M. , Heine-Geldern R. v. , Foner S. , Mutschler E. C.
Published: April 2005

High-speed photographs have been obtained of the fracture of glass produced by the detonation of a high explosive charge. Using photoelastic methods, the shock waves set up in the glass can also be photographed. In addition to providing a high intensity loading method, the explosive also serves as a convenient time base for determination of the rates of propagation of shock waves and cracking.

The results presented in this paper extend those obtained by other investigators who used low energy impacts to produce fracture.
Field Strength Measurements in Resonant Cavities
Authors: Maier L. C. , Slater J. C.
Published: April 2005

It is shown that the frequency of a resonant electromagnetic cavity is perturbed by inserting a metallic sphere, needle, or disk of dimensions small compared to a wavelength by an amount depending upon the local electric and magnetic field at the position of the perturbing object. This perturbation is calculated for ellipsoidal objects of needle-shaped, spherical, and disk-shaped form. The perturbations by the different objects depend upon different components of electric and magnetic fields, and by combining measurements with all three, it is in theory possible to measure all the field components. Experimental checks of the calculations are described, resulting in satisfactory agreement between theory and experiment except with the needles, in which the perturbation is very sensitive to the precise shape of the object, and the needles used were not accurate enough ellipsoids to give satisfactorily quantitative results.
Experimental Study of the Formation of a Vortex Ring at the Open End of a Cylindrical Shock Tube
Authors: Elder F. K. , De Haas N.
Published: April 2005

Schilieren spark snapshots spaced at electronically controlled intervals of several hundredths of a millisecond show the emergence of the shock wave and the formation of the vortex ring at the end of a cylindrical shock tube, open to the atmosphere. The axial positions of the vortex ring and shock front are plotted as a function of time for the first millisecond, in which time the vortex forms and is accelerated to about three-quarters of the theoretical particle velocity of the mass flow following the initial plane shock. The diameter of the vortex ring increases nonlinearly with time and distance.
A Property of Bessel Functions and Its Application to the Theory of Two Rheometers
Authors: Markovitz Hershel
Published: April 2005

A method of expanding expressions of the type J(ξ)Y(σ)−J(σ)Y(ξ) and J′(ξ)Y(σ)−J′(σ)Y(ξ) is given. Here J and Y are Bessel functions of the first and second kind. These forms occur frequently in physical problems with cylindrical symmetry. The type of expansion used here can be used with other functions that are solutions of second-order differential equations. The use of these expansions allows the development of theories for two rheometers used for determining dynamic mechanical properties of liquids. In these mathematical treatments, the inertia of the sample is taken into account.
The Concept and Measurement of Impedance in Periodically Loaded Wave Guides
Authors: Jaynes Edwin T.
Published: April 2005

A generalization of ordinary circuit theory which enables one to define impedances in any periodic structure is developed, based on the concept of expansion of electromagnetic fields in terms of a set of linearly independent basis fields. Techniques for measurement of impedances in a periodic structure are described, involving a determination of the parameters of a coupling system by an extension of the well-known nodal shift method.
The Complete Solution of the One-Velocity Diffusion Problem at Intermediate and Large Distances
Authors: Tonks Lewi
Published: April 2005

An approximate evaluation of the branch-cut integral which occurs in the rigorous solution of the Boltzmann equation for intermediate and large distances is of importance in shielding problems. Such an evaluation leads to Eq. (20) for the point source and Eq. (24) for the plane source. Equation (20) is actually 23 percent high for zero absorption (f=0) and rσ=7, but the error decreases with increasing rσ and f. It is seen that the branch-cut term is not simply the contribution of noncollided neutrons.

Figure 2 is a plot of the region in the f−rσ plane where the two terms are comparable.
Influence of Initial Velocities on Electron Transit Time in Diodes
Authors: Wallmark J. T.
Published: April 2005

The transit time spread due to difference in initial velocity in a planar diode has been calculated for the case of nonhomogeneous velocity distribution. The spread is given as a function of the current for two practical cases, the normal diode and an inverted diode (a beam reflected in a diode space). The spread is also given as a function of anode voltage within certain limits. The method may be used to estimate the influence of transit time spread on transit time devices. A special application is described.
On a Multiple Scattering Theory of the Finite Grating and the Wood Anomalies
Authors: Twersky V.
Published: April 2005

The formal multiple scattering solution obtained previously for the scattering of a plane wave by an arbitrary configuration of parallel cylinders is applied to the finite grating of cylinders and to the reflection grating of semicylindrical bosses on a perfectly conducting infinite plane. A far field solution in closed form for spacing large compared to wavelength and radius is obtained on neglecting the ``end effects.'' It is found that for the transmission grating both polarizations may be markedly affected by multiple scattering; for the reflection grating, however, the effects are much more pronounced for polarization perpendicular to the elements. The case of radii≪λ is investigated in detail; the λ's for which the effects are greatest are determined, and various intensity curves are presented. The bright and dark bands appearing on these curves (overlaying the usual continuous spectra observed with broadband radiation) are similar to the ``grating anomalies'' discovered by Wood in 1902. The present analysis provides a simple physical interpretation of their presence in terms of the magnitudes and phases of the various orders of scattering. Simple relations for their dependence on the parameters are derived which agree in general with experimental results. Both the electromagnetic and acoustic cases are treated.
On the Electrical Properties of Porous Semiconductors
Authors: Hensley Eugene B.
Published: April 2005

It has been proposed that the conductivity of a porous semiconductor, such as oxide-coated cathode, may be influenced by the presence of an electron gas in the pores of the aggregate. In this paper calculations for the magnitude of this component of the conductivity are made on the basis of two simplified models approximating the geometry of a pore. The conditions under which such a component of the conductivity can appreciably modify the total conductivity are analyzed. It is further shown that such a porous semiconductor will possess two sources of thermoelectric emf. A simple theory for the thermoelectric power of the electron gas in a pore is developed, and the manner in which it will combine with the normal thermoelectric power of the crystals is shown.
A Method of Solving the Wave Equation in a Region of Rapidly Varying Complex Refractive Index
Authors: Gibbons J. J. , Schrag R. L.
Published: April 2005

A process is described whereby the complex wave equation is transformed into an integro-differential equation in a single real dependent variable. This makes possible a technique for obtaining wave functions, which is believed to offer definite advantages in some instances where the more standard methods are difficult to handle, e.g., in regions where the complex index is varying rapidly. The index may be entered in a tabulated form, and its exact analytical expression is not required.

The technique is then demonstrated by computing the reflection coefficient associated with an extremely critical region, that which one encounters at the ``fourth reflection condition,'' where the refractive index goes through a sharp peak (see reference 3).
A Note on the Approach of Narrow Band Noise after a Nonlinear Device to a Normal Probability Density
Authors: Arthur George R.
Published: April 2005

The output of a low pass filter preceded by a nonlinear device excited by a noise source is given in terms of an integral equation. The first three central moments of the probability density of the output signal are obtained from the integral equation and the approach of these moments to those of a Gaussian or normal density is demonstrated.
Scattering of Electromagnetic Energy in a Randomly Inhomogeneous Atmosphere
Authors: Staras Harold
Published: April 2005

First-order perturbation theory is used to evaluate the scattered power at a receiver resulting from random inhomogeneities in the propagating medium. The integral expression for this scattered power is equivalent to the expressions as used by Pekeris and Booker and Gordon. However, it is shown that it is not appropriate to use a space correlation function of refractive index as defined by the above authors. Instead, this paper defines a time correlation function of refractive index which permits formal evaluation of the time average scattered power. It is also shown that, whereas a space correlation function of refractive index is not amenable to direct experimental evaluation, the time correlation function as defined in this paper is directly measurable. Finally, it is shown that for so-called small-scale turbulence the average scattered power does not depend appreciably on any particular model of atmospheric turbulence, whereas for large-scale turbulence the frequency and scattering angle dependence of the scattered energy is affected greatly by the particular time correlation function chosen or by the assumption that scattering is the result of randomly located spheres.
The Polarization of Acoustic Waves in Cubic Crystals
Authors: Fein A. E. , Smith Charles S.
Published: April 2005

The directions of particle motion associated with acoustic waves have been computed and are displayed graphically, for each of the three waves, as a function of propagation direction. The numerical example used is cubic nickel and the maximum polarization angle found is 11½ degrees.
The Use of Radioactive Material for the Generation of High Voltage
Authors: Linder E. G. , Christian S. M.
Published: April 2005

An investigation has been made of the use of beta-emissive radioisotopes for generating high voltages. Voltage was obtained by supporting a beta-emitter on an insulated electrode in a low-pressure gas and allowing it to charge itself by virtue of its electron emission. This method represents a direct conversion of nuclear energy into electrical energy. The apparatus is described. Data on insulation breakdown, the effect of gas pressure, and the electrode material are given. The maximum voltage was obtained at a pressure of 10−3 mm of Hg. The electrical characteristics of such a generator are discussed. Using an emitter containing 0.25 curie of strontium 90, a voltage of 365 kilovolts was obtained.
Electric Potential Produced by Two Point Current Sources in a Homogeneous Conducting Sphere
Authors: Frank Ernest
Published: April 2005

The electric potential produced by positive and negative point current sources located in a homogeneous conducting sphere, a problem of interest in the field of electrocardiography, is obtained for arbitrary source locations and separations. Certain special cases of the general solution that are of particular value in both experimental and theoretical electrocardiographic research are also presented.
Scabbing of Metals under Explosive Attack: Multiple Scabbing
Authors: Rinehart John S.
Published: April 2005

Further quantitative data bearing on the scabbing of metals under explosive attack are presented in this paper. In particular, the mechanics of the generation of multiple scabs is established. Experimental data have been obtained that show that multiple scabbing will occur whenever the maximum stress σ0 in the transient wave that impinges on a free surface is more than double the critical normal fracture stress σc of the material. The number of scabs that will be formed will be equal to the first whole number smaller than the quotient σ0/σc. The thickness of each scab is governed by the shape of the stress wave.
Initial Behavior of a Spherical Blast
Authors: McFadden J. A.
Published: April 2005

At time t=0 a unit sphere containing a perfect gas at uniformly high pressure is allowed to expand suddenly into a homogeneous atmosphere. Solutions for short times later are sought by analytic (i.e., not numerical) methods. Viscosity and heat conduction are neglected. The particle velocity, sound speed, and entropy are developed in powers of y, which is proportional to the time (more precisely, the distance moved by the head of the rarefaction wave in time t), with coefficients depending on a slope coordinate q=(1/2N)[(2N−1) +(1−x)/y], where x is the radial coordinate, N=(½)(γ+1)/(γ−1), and γ is the ratio of specific heats. The zero-order coefficients are the plane shock-tube solution. First-order corrections are derived for the various regions. Boundary conditions are approximated for small y at the surfaces of discontinuity, and the method for matching the solutions in the different regions is outlined. This matching process is carried out for the expansion of a diatomic gas into diatomic air.
Radiofrequency Field Quenching of Ultraviolet Excited Phosphors
Authors: Miller Theodore
Published: April 2005

The quenching action of radiofrequency field on ultraviolet excited phosphors has been investigated for a number of sulfide phosphors. The phosphor layer is sandwiched between two parallel plane electrodes. The radiofrequency potential is applied to the electrodes. Data are presented showing the dependence of the quenching action on field strength, field frequency, and ultraviolet excitation. The quenching response to an amplitude modulated rf potential, and the fatigue effects resulting from prolonged exposure to the rf field have also been investigated.
Some Experiments on Centimeter-Wavelength Scattering by Small Obstacles
Authors: Labrum N. R.
Published: April 2005

The scattering of electromagnetic waves by small obstacles has been measured in several cases which are of interest in connection with the interpretation of radar echoes from rain and cloud formations. The measurements were made at a frequency of 3000 Mc/sec by an impedance-bridge technique, the specimens being contained in a wave guide. The results verify the theoretical relationship between the size of the scatterer and the intensity of the backscattered wave. Observations have also been made of the variation in scattering during the melting of an obstacle initially composed of ice. In this case, it was not possible to simulate exactly the conditions of large-scale meteorological phenomena; however, the experiments demonstrate qualitatively that, as had been predicted, the power backscattered from an initially nonspherical ice particle passes through a maximum value during the transition to a water drop.
Excess Thermal Noise Due to Current Flow Through (Ba Sr) Oxide Coating
Authors: Amakasu K.
Published: April 2005

A study has been made to clarify the nature of the thermal noise generated within the layer of the (Ba Sr) oxide coating of the cathode when a current flows through it, and to determine how much this noise affects the flicker noise. The results of this investigation show that (1) the excess noise generated by the flow of current is proportional to the square of the current flowing through the coating layers, (2) the frequency spectrum of the noise is inversely proportional to the frequency, (3) the noise is greatly affected by the activation of cathode, a slight decrease in activation causing a sudden increase of noise (4) the portion of the cathode flicker noise due to this excess noise may be neglected when the activation of the cathode is good, but when the activation is poor, it becomes considerably larger. The characteristic of (3) may be considered to give a clue to a clarification of the electron conductivity mechanism in the oxide cathode.
Complicated Domain Patterns on Iron-Silicon Single Crystals
Authors: Ying C. F. , Levy S. L. , Truell R.
Published: April 2005

Domain patterns on (100) surfaces of iron-silicon single crystals were observed between successive electrolytic or mechanical polishings. By repeatedly interrupting the electropolishings to examine the surfaces, complicated patterns were observed before simple ones were seen at the time when the surfaces were deeply polished. With fine mechanical polishing alone, results similar to those observed with interrupted electropolishing were obtained, including the final appearance of simple patterns. These complicated patterns are interpreted as characteristic of strained surfaces. Complicated patterns appearing on heavily polished surfaces are, therefore, believed to be induced by local strains which are not completely removed, like those along deep scratches formed during the rough mechanical polishing.
Elastic Wave Propagation in Solid Media
Authors: Mapleton Robert A.
Published: April 2005

The reflection of elastic waves at plane solid-vacuum interfaces and the two-dimensional solutions of the vector equation of equilibrium for elastic waves propagating through elastic plates of uniform thickness are investigated. Both the isotropic solid and the cubic system of nonpiezoelectric single crystals are treated. The objective is to compare multiple reflection solid delay lines, isotropic versus single crystal, in terms of the thickness of the plate required for satisfactory propagation and reflection characteristics. The sections on wave propagation are not exhaustive, but consider the particular wave mode that most closely resembles the plane shear wave with diplacement component normal to the faces of the plate. In the sections on single crystals, it is shown that plane shear waves propagate with a speed independent of the direction provided that the displacement is parallel to a crystallographic axis. The reflection laws for these plane shear waves are the same for isotropic solids and single crystals provided that the displacement is contained in a plane that is parallel to the stress-free interface. A calculation compares the wave propagating characteristics of plates of fused quartz and calcium fluoride for operation at 15 mcs. The plate of calcium fluoride should be roughly three times thicker to give the same performance as the plate of fused quartz.
A Mathematical Analysis of an Inductively Loaded Parallel-Connected Magnetic Amplifier
Authors: Pipes Louis A.
Published: April 2005

A mathematical analysis of a parallel-connected magnetic amplifier with an inductive load is presented. The analysis is based on the representation of the normal magnetization curve of the core material by a polynomial of the fifth degree. The load current is expressed in terms of the magnetic intensity of one of the cores. The magnetic intensity is shown to satisfy a nonlinear differential equation and an approximate solution of this equation is obtained by an iterative procedure. An estimate of the response time of the amplifier is determined and the steady-state response of the amplifier is obtained.
The Interaction of Plane Shock Waves and Rough Surfaces
Authors: Duff Russell E.
Published: April 2005

Shock tube experiments have been conducted to determine the effect of surface roughness on shock waves in nitrogen passing over the surface. Shock retardation was measured for a series of two- and three-dimensionally rough surfaces at shock strengths from ξ=0.1 to ξ=0.9. The first-order approximation was made that the volume between the positions of the shock wave, with and without the rough surface present, multiplied by the specific energy behind the undisturbed shock wave represented energy dissipated by the roughness. The space rate of energy dissipation is presented as a function of the average particle size of the rough surface. It is also shown that the curvature of the shock wave in the vicinity of the surface depends on the roughness of the surface, the length of roughness covered, and the strength of the shock wave. In addition, the hundreds of measurements of shock wave contours made in this investigation showed that there is a random fluctuation in the angle of incidence of the primary shock wave of 1/15°. This fluctuation is presumably caused by the details of the diaphragm rupture even though measurements were made 14 ft from the diaphragm in a shock tube with a 2×7 in. cross section.
Neutron Diffraction Studies of Cold-Worked Brass
Authors: Weiss R. J. , Clark J. R. , Corliss L. , Hastings J.
Published: April 2005

Powder diffraction data with neutrons have shown the integrated intensities to be identical in cold-worked (filed) and annealed brass with no trace of extinction effects. Long wavelength transmission studies have also shown that the diffuse scattering is increased by less than 0.4 percent upon severely cold rolling brass. A new technique of examining the Bragg discontinuities supports the hypothesis that the major part of the broadening is due to lattice distortion. Some remarks are presented concerning the analogy between long wavelength neutrons and conduction electrons with respect to scattering by dislocations. The effects of dislocations on coherent scattering are also considered.
The Production of High Temperature Gases in Shock Tubes
Authors: Resler E. L. , Lin Shao-Chi , Kantrowitz Arthur
Published: April 2005

This paper is intended to set forth aerodynamic and thermodynamic calculations which are useful in the production of strong shock waves. The experimental production of strong shock waves is discussed. Comparison of the experimental shock strengths with the theoretical calculations is made, and finally, some preliminary results of shock tube studies in high temperature gases (up to 18,000°K) are briefly surveyed.
Cathodic Sputtering for Micro-Diffusion Studies
Authors: Fisher Thomas F. , Weber C. E.
Published: April 2005

A method which has been developed to allow uniform removal of micro-layers of metal from cylindrical specimens is based on sputtering of the metal from the cathode of a gas glow discharge tube. This technique is directly applicable to diffusion studies and offers many advantages over other more common methods.
Space-Charge-Wave Propagation in a Cylindrical Electron Beam of Finite Lateral Extension
Authors: Parzen Philip
Published: April 2005

A method is outlined for obtaining the effect of geometry on the propagation of space-charge waves in a cylindrical electron beam under arbitrary direct current conditions. In particular, the case of the complete-space-charge diode is discussed in detail. The results of this theory are verified by the experiments of Cutler and Quate.
The Effect of Gas Pressure in the Electric Bulb on the Polarity of the Rectified Current
Authors: Ch'en Shang-yi , Li Wei-cheng
Published: April 2005

In sequel to the experiment by Ch'en and Liu (see reference 2) that a rectified current was derivable from the surface of the bulb when the bulb was coated with Chinese ink and was run by alternating current, the following points were observed with 220-v bulbs: (1) When the nitrogen pressure inside the bulb was more than a hundred mm Hg, the polarity of the rectified current was always negative, and the current amounted to a few milliamperes. The current decreased with the decrease of pressure. At a pressure of a few mm Hg the current was decreased to a very small value, and then turned to positive polarity when the pressure was further decreased. The positive current increased to a weak maximum at a few tenths of a mm Hg and came down again as the pressure was further lowered. (2) The current vs pressure curves for argon, helium, and neon were essentially similar to those for nitrogen. (3) When the inner surface of the bulb was coated with a layer of metallic sodium, the rectified current, which was positive while without the coating, turned out to be negative. (4) When the material used to paint the bulb contained no sodium compounds, a quick fatigue was observed.