bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation Energy for Viscous Flow and Short-Range Order
Authors: Dienes G. J.
Published: April 2005

Viscosity-temperature properties of many systems are characterized by highly temperature dependent activation energies for viscous flow. It is generally recognized that structural changes taking place in the material as a function of temperature are responsible for this phenomenon. In this paper a formulation of viscosity-temperature relations is presented in which the structural changes are explicitly taken into account by means of the formalism of short-range order as a function of temperature. The resulting equation is shown to be a generalization of several semi-empirical equations in current use. The equation has been applied to several glasses, high polymers, and water and has been found to describe the experimental viscosity data with high accuracy over a wide temperature range.
The Electromagnetic Transmission Characteristics of the Two-Dimensional Lattice Medium
Authors: Bennett Herbert S.
Published: April 2005

This paper investigates the behavior of the two-dimensional lattice medium in the presence of electromagnetic energy. The conditions for transmission of energy by the medium are derived and studied. In particular, the effects of the various parameters of the problem (e.g., obstacle size, obstacle shape, obstacle spacing, polarization of the electromagnetic energy) on the average propagation constant and impedance function of the medium are considered. The Wigner-Seitz cellular method is applied to the solution of the boundary value problem involving a lattice of elliptic cylindrical obstacles. Various approximate solutions are studied and appropriate functions formulated. Calculations are shown using some of these functions. Practical applications of the theoretical results are indicated, and suggestions for further research are enumerated.
Experimental Verification of the Metal-Strip Delay-Lens Theory
Authors: Cohn Seymour B.
Published: April 2005

In this paper a comparison is made between the index-of-refraction values measured on five metal-strip test samples and values computed from four solutions that have appeared in the literature. Three of the samples are wave-guide equivalents, and two are free-space arrays. The techniques of measurement for the two types of structures are described briefly. It has been found that all four solutions have certain ranges of validity, but that only one is reliable over the full practical range of the design parameters. This solution, derived previously by the writer, is based on a transmission-line equivalent circuit in which proximity effects are taken into account.
Transmission of Electromagnetic Waves through Pairs of Parallel Wire Grids
Authors: Groves Willice E.
Published: April 2005

The control and direction of electromagnetic waves is accomplished, in general, by the use of boundary materials and structures which produce desired effects on such waves when irradiated by them. An important class of boundary structure for this purpose is a surface having alternate areas of conducting and nonconducting material. Grids formed of a large number of parallel cylindrical conductors of circular cross section, uniformly spaced and lying in a common surface, are among the most generally useful of this class of boundary structure. Single layer parallel wire grids have received considerable study in the past. However, little information is available concerning the characteristics of multiple layers of such grids

An analytical solution is obtained for the power transmission coefficient of a double grid system. Power transmission coefficients for various combinations of system parameters are computed from the analytical solution and tested experimentally. The solution is found to yield excellent correlation with experiment until the interwire spacing approaches the wavelength.
New Developments in the Production and Measurement of Ultra High Vacuum
Authors: Alpert D.
Published: April 2005

A new vacuum technology is described which makes it possible to achieve working pressures as low as 10−10 mm Hg in a routine and straightforward fashion. This is accomplished without the use of chemical getters, special traps, or refrigerants of any kind. Essential to this technology are several new instruments which have been especially developed for the production or measurement of ultra high vacua. These new tools have permitted us to carry out a number of researches concerning the phenomena which occur at very low pressures. The ultra high vacuum technology has also made possible a new experimental approach in the fields of gaseous and physical electronics.
Consolidation Around Pore Pressure Meters
Authors: De Jong G. De Josselin
Published: April 2005

Response of pore pressure meter on variations in loading conditions of surrounding soil is retarded by the necessity that pore water has to enter the instrument. This property is introduced as an instruments coefficient influencing the boundary conditions. With regard to the surface of the instrument, two types are considered: a rigid type and a cavernous type. At t=0 for unit step loading, consolidation has not yet started and the response of the instrument depends on shear modulus of soil only. Calculation of response as a function of time involves three-dimensional consolidation theory and is established with the aid of spherical solutions for simple harmonic and unit step loading conditions.
On the Statistical Theory of Detection of a Randomly Modulated Carrier
Authors: Stone W. M.
Published: April 2005

A method is outlined for estimating the probability of detection for a pulsed radar, assuming a randomly modulated carrier. For a square law detector closed forms for the moments of the distribution of the envelope are presented in terms of three different choices of the distribution of carrier amplitude, thus leading to an Edgeworth series representation of the desired probability. At least one choice of distribution of the carrier amplitude leads to closed forms for the moments for the case of a linear detector. Curves of probability of detection vs signal-to-noise power ratio are constructed and cross checked by a method of numerical integration.
Nonlinear Semiconductor Resistors
Authors: Schwertz F. A. , Mazenko J. J.
Published: April 2005

A phenomenological theory for the nonlinear voltage-current characteristic curve displayed by a granular aggregate of silicon carbide is presented. The theory, which should apply to granular semiconductors other than silicon carbide, is based on a very simple model of the aggregate and on the assumption that the essential resistance is located at the grain-grain contacts, the impedance of the bulk material being considered negligibly small. The current i is related to the voltage V by the equation i=kAPn/mdn−2Vn/tn,where A is the cross-sectional area of the aggregate, t the thickness, P the applied pressure, and d the average particle diameter. The constants k, n, and m are structure-sensitive, that is, they depend on the physical-chemical nature of the particles forming the aggregate. Factors influencing the values of these constants include impurity concentration in the semiconductor, elastic constants, and particle shape. The validity of this equation is supported by careful measurements made on granular aggregates of silicon carbide.
Filters for Detection of Small Radar Signals in Clutter
Authors: Urkowitz Harry
Published: April 2005

Radar clutter is distinguished from thermal noise by being caused by random reflection of transmitted electromagnetic energy. This paper considers what may be done by means of linear filtering to improve the detection of small radar signals in the presence of this clutter. Defining the signal-to-clutter ratio as the ratio of the peak signal to the rms value of the clutter, the optimum linear filter is derived for enhancing this ratio. The optimum filter has a frequency characteristic given by the conjugate of the voltage spectrum of the transmitted pulse divided by the power spectrum of the clutter. The synthesis of the optimum filter and various approximations to it are considered. The influence of these filters upon the signal-to-thermal-noise ratio is also investigated. Finally, the influence of the second detector upon the signal-to-clutter or signal-to-noise ratio is considered.
On the Interference of Pulse Trains
Authors: Miller K. S. , Schwarz R. J.
Published: April 2005

A number of problems arising from the undesired overlapping or time coincidence of pulses from separate periodic pulse trains are considered. The coincidence time fraction is determined for two pulse trains with both a fixed initial phase and a randomly varying initial phase. The coincidence time fraction for these cases is then determined if only pulse coincidences equaling or exceeding a specified interval are considered. Finally, some problems involving more than two pulse trains are briefly discussed.
Contact and Rubbing of Flat Surfaces
Authors: Archard J. F.
Published: April 2005

The interpretation of certain phenomena occuring at nominally flat surfaces in stationary or sliding contact is dependent on the assumed distribution of the real area of contact between the surfaces. Since there is little direct evidence on which to base an estimate of this distribution, the approach used is to set up a simple model and compare the deduced theory (e.g., the deduced dependence of the experimental observables on the load) with the experimental evidence. The main conclusions are as follows. (a) The electrical contact resistance depends on the model used to represent the surfaces; the most realistic model is one in which increasing the load increases both the number and size of the contact areas. (b) In general, mechanical wear should also depend on the model. However, in wear experiments showing the simplest behavior, the wear rate is proportional to the load, and these results can be explained by assuming removal of lumps at contact areas formed by plastic deformation; moreover, this particular deduction is independent of the assumed model. This suggests that a basic assumption of previous theories, that increasing the load increases the number of contacts without affecting their average size, is redundant.
The Utilization of Degenerate Modes in a Spherical Cavity
Authors: Currie Malcolm R.
Published: April 2005

A general expression is given for calculation of the coupling coefficients between an arbitrary number of modes simultaneously excited in a cavity resonator. The mechanism of energy conversion between modes is discussed for several practical coupling devices. The technique is applied to the unlimited numbers of degeneracies available in spherical geometry and is shown to offer many interesting possibilities. An experimental model of a spherical cavity is described and shown to demonstrate the theory.
Wave Propagation in Finite Rods of Viscoelastic Material
Authors: Lee E. H. , Kanter I.
Published: April 2005

The paper is concerned in the main with a Maxwell material, which corresponds to a model having a spring and dashpot in series. The equation for longitudinal wave propagation in rods is shown to be equivalent to the telegraph equation, and solutions of transient wave problems are treated briefly in the Appendix using the Laplace transform technique. Impact on a semi-infinite rod is considered in detail in the report. A method of superposition of images is discussed to use this solution to solve boundary value problems for finite rods. The resulting stress distributions are discussed and contrasted with those for an elastic rod. The natural grouping of problems is discussed according to the relative magnitude of the duration of interest, the relaxation time, and the wave traverse time. The influence of the idealization involved in the Maxwell model is briefly touched upon.
Determination of the Surface Stress by Means of Electroplating
Authors: Ōkubo H.
Published: April 2005

This paper presents a new method for the measurement of surface stress. By the use of test pieces plated with copper, the stress is measured by observing the flecks on the surface produced by cyclic stress. The variation in the appearance of flecks which is due to the change of load is very sensitive at a proper load, so an accurate determination of the surface stress is feasible.

The stress concentration factor in torsion is obtained experimentally by the method described for circular shafts with a circumferential notch in each. The results are compared with theoretical values, calculated from two different formulas previously derived by the author and Sonntag, respectively. It is confirmed that the experimental results obtained here are in good agreement with those calculated by the author's formula.
Solution of Electromagnetic Scattering Problems as Power Series in the Ratio (Dimension of Scatterer)/Wavelength
Authors: Stevenson A. F.
Published: April 2005

It is shown that the scattered field and the field inside the body can be expressed formally as power series in the above ratio, the calculation of successive terms in the series requiring the solution of standard problems in potential theory, together with the evaluation of certain potential integrals, so that the process can be carried as far as desired if Laplace's equation can be solved in the coordinate system appropriate for the body. The convergence of the series for the scattered field becomes progressively worse as we recede from the body, but an alternative expression for the field, also proceeding in powers of the same parameter, gives a representation which is valid everywhere except in the immediate neighborhood of the body (in particular, in the wave zone) and which does not suffer from this defect. The case of a perfect conductor, or diffraction through a hole in a perfectly conducting screen, can be treated as particular cases of the general theory. The paper can be regarded as an extension of Rayleigh's work, which confines itself to the first terms in the series.
Electromagnetic Scattering by an Ellipsoid in the Third Approximation
Authors: Stevenson A. F.
Published: April 2005

The method previously described of solving electromagnetic scattering problems as power series in k is here applied to the ellipsoid, the first three terms in the series being obtained. The second term in the series for the wave zone field (that proportional to k3) vanishes, and the same is true of any body possessing a center of symmetry. Thus the terms in k2, k4 in the wave zone field are here obtained. The direction and polarization of the incident wave, and the electromagnetic constants of the ellipsoid, are arbitrary. The final results are expressed in terms of certain elliptic integrals which are functions of the three principal axes of the ellipsoid. These integrals can all be expressed simply in terms of just two such integrals; they become elementary integrals in the case of a spheroid. Various special cases are considered, including that of a perfectly conducting elliptical disk and the complementary problem of diffraction through an elliptical hole in a perfectly conducting screen.
Sinusoidal and Relaxation Oscillations Sustained by Nonlinear Reactances
Authors: Mackay R. Stuart
Published: April 2005

A duality between the two types of negative resistance is noted. It is demonstrated that with series or parallel ``resonant circuits'' one can form either class by using either a nonlinear choke or nonlinear condenser. This ac characteristic can be converted to a similar dc one by using a bridge rectifier. With such an arrangement one can excite oscillations in a resonant circuit or produce relaxation oscillations. Several quite general oscillatory circuits are described, as are some multistable and counter circuits. The interaction with mechanical systems are considered.
The Energy Stored in Metal Chips during Orthogonal Cutting
Authors: Bever M. B. , Marshall E. R. , Ticknor L. B.
Published: April 2005

Chips of a gold-silver alloy were made by orthogonal cutting with apparatus which permitted the determination of the chip geometry and cutting forces. From these data the stresses and strains and the shear and friction energies were calculated. Three rake angles were used to obtain different shear strains. The energy stored in the chips was determined as the difference in the heat effects associated with the dissolution in liquid tin of samples of cold worked and annealed chips in an isothermal calorimeter of high precision. With increasing strain the stored energy increased, but the ratio of the stored energy to the shear energy decreased.
Free Surface Motion Induced by Shock Waves in Steel
Authors: Allen William A.
Published: April 2005

An optical technique, reported in a previous paper, has been used to measure surface oscillations on a series of thick 5.5-in. diam steel plates of different thicknesses while they deform under explosive attack. Data obtained from the four 1025 steel specimens illustrated in the previous paper, and data obtained from two additional specimens have been analyzed partially. Results are compared with predictions from the theory of elasticity for the case of a diverging pulse. Elementary theory, known to be incorrect in the physical regime studied, is shown to give many satisfactory predictions for large distances from the charge.
Electrostatic Potential Plotting for Use in Electron Optical Systems
Authors: Ho Kuo-Chu , Moon Robert J.
Published: April 2005

A noniterative numerical method has been found for solving a partial differential equation when its boundary conditions are not known on the entirety of a closed boundary. Under such conditions, the iterative numerical methods which are generally used, such as the relaxation technique, are not applicable. As an example, this noniterative numerical method has been used to calculate the shapes of a pair of beam forming electrodes for use in an electron gun in which rectilinear flow is desired. The calculated shapes are in almost complete agreement with Pierce's experimental results. Equipotential surfaces calculated by this method have been checked by means of an electrolytic trough which employs a semiautomatic detecting and plotting system.
Some Dielectric Properties of Barium-Strontium Titanate Ceramics at 3000 Megacycles
Authors: Davis Luther , Rubin Lawrence G.
Published: April 2005

The dielectric constant έ/ε0 and loss tangent tanδ of barium-strontium titanate ceramics were measured as a function of temperature and static electric field at frequencies of 10 kc, 500 kc, and 3000 Mc. No frequency dependence of έ/ε0 was apparent at temperatures above the Curie point. An increase in tanδ was observed in going from the low frequencies to 3000 Mc, but above the Curie point the values were not excessively large. A description of the 3000 Mc bridge construction and operation is given.
A More Exact Treatment of the Equations Describing Dielectric Relaxation and Carrier Motion in Semiconductors
Authors: Keilson Julian
Published: April 2005

Previous treatments of the linearized equations describing hole and electron flow in a homogeneous semiconductor have not been wholly satisfying mathematically. An exact treatment of these equations is undertaken and it is demonstrated that the departure from complete local charge neutrality implicit in the equations corresponds to a polarization attributable to local variations of conductivity. The dielectric relaxation is described and exact expressions for the effective mobility and diffusion coefficients are obtained. The corrections to the older values are of magnitude τr/τ, where τr is the relaxation time and τ the lifetime. For semiconductors, these corrections are negligible.
Static and Sliding Friction in Feedback Systems
Authors: Tou J. , Schultheiss P. M.
Published: April 2005

One of the most common nonlinearities encountered in servomechanisms design is the friction phenomenon in electromechanical systems. Conventional linear theory fails to predict its effect upon system performance. This paper extends familiar techniques to the treatment of friction nonlinearity in servosystems. Frequency-response methods are employed throughout and the theoretical results are verified by means of an analog computer. Sliding friction and static friction are represented by describing functions which form the critical factors in determining system stability. The analysis indicates that certain series equalizers designed from linear theory may fail to achieve effective compensation in the presence of sliding and static friction. On the other hand, a subsidiary loop may avoid the stability problem while still realizing an essentially equivalent loop gain function.
The Vector Wave Function Solution of the Diffraction of Electromagnetic Waves by Circular Disks and Apertures. I. Oblate Spheroidal Vector Wave Functions
Authors: Flammer Carson
Published: April 2005

Rigorous solutions are presented of the problems of diffraction of plane electromagnetic waves by an infinitely thin, perfectly conducting, circular disk and by a circular aperture in a plane conducting screen. The analysis utilizes oblate spheroidal vector wave functions. In Part I these vector functions are defined and the expansions of plane-polarized waves in terms of them are obtained. Part II contains the solutions of the diffraction problems.
The Vector Wave Function Solution of the Diffraction of Electromagnetic Waves by Circular Disks and Apertures. II. The Diffraction Problems
Authors: Flammer Carson
Published: April 2005

Rigorous solutions are presented of the problems of diffraction of plane electromagnetic waves by an infinitely thin, perfectly conducting, circular disk and by a circular aperture in a plane conducting screen. A unique solution is obtained in each case when two separate groups of the appropriate oblate spheroidal vector wave functions discussed in Part I are combined to fulfill the condition that the φ component of the electric field vanish on the rims of the disk and aperture.
Electron Flow Through Small Tubes With Magnetic Focusing
Authors: Stewart John L.
Published: April 2005

When a uniform finite magnetic field passing through the cathode is used for focusing a beam of electrons, random emission at the cathode results in the electrons traveling down the beam in a helical manner. Such a rotational motion severely limits the amount of current that can be made to travel through a small tube or between closely spaced parallel plates. The amount of current transmitted through such structures is calculated in this paper and presented in the form of normalized curves. It is assumed that the current initially fills the tube or the region between the parallel plates.

If an alternating electric field having a frequency comparable to the rotational frequency of the electrons is applied normal to the beam, the average electron radius of motion is increased. Should the electron beam be made to flow through a tube after the application of such an alternating electric field, the current transmission through the tube will be reduced over that when no electric field exists. The first-order correction term for this case is calculated and presented in the form of normalized curves. The fact that the average electron radius is increased when an electric field is present implies added energy and leads to the formulation of a conductance expression relating the power in the rotational motion of the beam to the electric field normal to the beam.

The current interception and the equivalent beam conductance are important in many electronic devices such as traveling-wave tubes. The beam conductance may be quite large in some cases—on the order of that present off the axis of a helix.
Some Magnetostriction Relations in Materials Possessing Preferred Domain Orientations
Authors: Rado George T.
Published: April 2005

Simple relations between certain magnetostrictive strains are derived for polycrystalline ferromagnetic materials possessing a preferred axis in the distribution of domain orientations. Good agreement with experimental results is obtained.
On the Summation of Infinite Series in Closed Form
Authors: Wheelon Albert D.
Published: April 2005

A direct approach to the problem of summing infinite series in closed form is described. This method is based on the parametric representation of the general term of a series, so as to produce either the geometric or exponential series inside one or more integral signs. Each of these may be summed in closed form, thereby permitting one to exhibit a given series as a combination of definite integrals. When the original series is summable, these integrations can be performed analytically and the sum presented in closed form. Such a procedure enjoys the evident advantage of exploiting the relative abundance of integral tables, while circumventing the need for extensive preparation in the field of infinite series. The relations of this development to other methods are indicated and a number of illustrative examples presented.
A Simplified Calculation for Dolph-Tchebycheff Arrays
Authors: Van Der Maas G. J.
Published: April 2005

A series is derived for the currents on the radiators of a Dolph-Tchebycheff array, which is more suitable for numerical calculation than the series given by Barbiere, when the number of radiators becomes large. The series is not alternating in character and is given in terms of a variable α=tanh2[ln(r+(r2−1)12)N−1],where r is the side-lobe ratio and N is the number of radiators. α is constrained to the interval 0≤α≤1. The important practical case, when α≈ln2(r+(r2−1)12)(N−1)2,is approximated by a Bessel function. The calculations show that the currents on the two end elements of the array play a special role and that their adjustment should have due attention, whenever the inequality ln[r+(r2[minus]1)½]< (N[minus]1)½ is satisfied.
Ion Trajectories in the Omegatron
Authors: Berry Clifford E.
Published: April 2005

The equations of motion for ions in an idealized two-dimensional Omegatron are solved for the general case of arbitrary initial velocity and arbitrary starting time. A simple picture of the paths is obtained by use of a rotating coordinate system.
Cylindrical Shock Waves Produced by Instantaneous Energy Release
Authors: Lin Shao-Chi
Published: April 2005

Taylor's analysis of the intense spherical explosion has been extended to the cylindrical case. It is found that the radius R of a strong cylindrical shock wave produced by a sudden release of energy E per unit length grows with time t according to the equation R=S(γ)(E/ρ0)1/4t1/2, where ρ0 is the atmospheric density and S(γ) is a calculated function of the specific heat ratio γ. For γ=1.4, S(γ) is found to be approximately unity. For this case, the pressure p1 behind the shock wave decays with radius R according to the relation p1=0.216E/R2. Applying the results of this analysis to the case of hypersonic flight, it can be shown that the shock envelope behind a meteor or a high-speed missile is approximately a paraboloid given by R=(D/ρ0)1/4(x/V)1/2 where D and V denote the total drag and the velocity of the missile, respectively, and x is the distance behind the missile.
Brightness Waves and Transitory Phenomena in the Quenching of Luminescence by Alternating Electric Fields
Authors: Destriau G.
Published: April 2005

Zinc or cadmium sulfide phosphors, especially phosphors having short persistence, are less sensitive to ultra-violet light or to x-rays when they are submitted to the action of an alternating electric field. With a half-wave x-ray generator and an alternating field of frequency equal to the frequency of the potential applied to the x-ray generator (50 cps), and in phase with it, the brightness waves (a curve giving the variation in the instantaneous brightness as a function of time in the interval of a period) are greatly modified. A sharp secondary maximum appears when the field passes through zero in each cycle; the amplitude of this maximum varies quickly during the cycles which immediately follow the application of the field.

If the light is filtered, the shape of the brightness wave varies according to the spectral region which is observed.
Direct Determination of the Flow Curves of Non-Newtonian Fluids. III. Standardized Treatment of Viscometric Data
Authors: Krieger Irvin M. , Maron Samuel H.
Published: April 2005

A scheme is proposed for systematizing the handling of viscometric data through use of the variables apparent fluidity φa and shearing stress F. The rate of shear g(F) is obtained from the relation: g(F)/F =φa[1+Δ(F)]. Methods are presented for obtaining the correction term Δ(F) from capillary and concentric-cylinder viscometric data. Use of the proposed scheme is illustrated.
On the Detection of Sure Signals in Noise
Authors: Davis R. C.
Published: April 2005

The purpose of this paper is to attempt to present known results on detection in simplified form and to relate these to new results found by the author. For a signal of known form and nonrandom in nature (sure signal) upon which a background noise is linearly superimposed, several criteria for an optimum pre-detection filter are compared. The background noise may be of very general nature and restricted merely to possessing a continuous covariance function and need not, in general, possess even a frequency spectrum. Specifically, it is shown that, when the input noise to a pre-detection filter is Gaussian (with no restrictions concerning its possible spectrum), the filter which maximizes—for a fixed ``false alarm'' probability—the probability of detecting the signal when it is present is identical with the linear filter which maximizes the output signal-to-noise ratio. For a Gaussian noise input an explicit expression is obtained for the probability of detection. The stability of the optimum filter is discussed in some detail and some restrictions on the form of the input signal necessary for stability are given. The techniques used throughout limit one, in general, to the practical case of finite memory filters. Finally it is shown how an optimum signal shape of given energy content and duration can be chosen.
Preparation of Aerosols for Electron Microscopy
Authors: Kalmus Ernest H.
Published: April 2005

A technique is described whereby fall-out particles from dust clouds, commonly called aerosols, may be prepared for observation with the electron microscope. Specimens are collected by means of various types of precipitators on molecular filters which are made from cellulose esters. During the process of dissolving this material in acetone, the particles adhering to the filter are transferred to the Formvar-coated specimen screens of the electron microscope. Losses are negligible, residual filter background is eliminated, and particles are clearly visible for measuring.
Velocity Attenuation of Explosive-Produced Air Shocks
Authors: Savitt Jacob , Stresau R. H. F.
Published: April 2005

A method for measuring the velocities of explosive-produced air shocks using an electrical ionization probing system is described. The results of such measurements indicate that under varying conditions of confinement of explosive and air shock, that the reciprocal of the air-shock velocity varies linearly with the distance to the charge surface.
A Method of Measuring Magnetostriction
Authors: Cochardt A. W.
Published: April 2005

Torsion tests are made on wires of various ferromagnetic materials. It is found that the relationship between shear stress and shear strain is different for magnetized and unmagnetized wires. The difference is explained in terms of wall movement and rotation of ferromagnetic domains, and magnetostriction values are derived from it. This method of determining magnetostriction has several advantages. It is simpler to carry out than most other methods, its accuracy is 4×10−7, and it can be used at elevated temperatures. Its main limitation is that saturation magnetostriction values are not obtainable for alloys which have a large crystal anisotropy energy.
Effect of Crystallinity on the Dynamic Mechanical Properties of Polyethylenes
Authors: Nielsen Lawrence E.
Published: April 2005

Six polyethylenes which differed widely in the degree of crystallinity were studied. The crystallinity was determined from density measurements. Both the density and the dynamic mechanical measurements were made over the temperature range from 25°C to above the melting point of the material.

The dynamic shear modulus drops rapidly as the melting point is approached. The mechanical damping goes through a maximum near 60°C and then through a minimum just below the melting point. It is possible to predict the density of any of the polyethylenes at any temperature below the melting point from the value of the shear modulus at the same temperature. The more crystalline materials have the higher shear moduli and the higher melting points.
The Dynamic Bulk Viscosity of Polyisobutylene
Authors: Marvin Robert S. , Aldrich R. , Sack H. S.
Published: April 2005

The dynamic bulk modulus of a high molecular weight polyisobutylene is calculated from measured longitudinal-wave and shear moduli. A viscous or energy-dissipating process associated with pure volume deformation is found, which appears to be a relaxation process. The peak in absorption of the shear and bulk moduli and the apparent activation energies associated with the two types of deformation are at least approximately the same, suggesting that the fundamental molecular mechanism involved in the two types of deformation may be the same.
Spurious Areas in Pole Figures
Authors: Geisler A. H.
Published: April 2005

Spurious maxima are frequently observed in pole figures determined by x-ray diffraction techniques employing the Geiger-counter spectrogoniometer. Their origin must be fully understood in order to avoid misleading interpretations of the pole-figure data. By making film patterns and by the balanced filter technique—in each case with the specimen oriented for the appearance of one of the spurious peaks—these spurious maxima can be identified as diffraction of a component from the white radiation by a strongly diffracting (hkl) plane, and at a 2θ angle corresponding to Ka diffraction from the (hkl) plane under investigation. Spurious (110) and (112) peaks of this type may be observed in the (200) pole figure of iron and its alloys; spurious (111) and (220) peaks may appear in the (200) pole figure of face-centered-cubic metals such as nickel. These cannot be completely suppressed by filtering the Mo radiation used or by modifying the operating conditions such as tube voltage, spectrometer resolution, or counter type. Spurious (101̄1) peaks may appear in the (0002) pole figure of titanium and zirconium as the result of CuKa diffraction, and they can be avoided by increasing the resolution of the slit system.
Effects of Cathode and Anode Resistance on the Retarding Potential Characteristics of Diodes
Authors: Dalman G. C.
Published: April 2005

As a result of the processes of manufacture of tubes having oxide cathodes, high resistance layers often exist in the cathode and tube elements. This can produce anomalous retarding potential characteristics such as, for example, an apparently high electron temperature in diodes. By accounting for the effect of these resistances the apparent anomalies can be explained. Also given are the conditions required to minimize these errors and a method for evaluating the sum of these resistances.
Focusing of a Long Cylindrical Electron Stream by Means of Periodic Electrostatic Fields
Authors: Tien Ping King
Published: April 2005

This paper presents a theory of focusing long cylindrical electron streams by means of electric fields which vary periodically along the stream. The use of a bifilar helix or a series of annular rings to produce periodic electric fields is considered.

The potential distribution at the position of the electrons is expanded in a power series, and an equation of electron motion is written. The solutions obtained indicate that the flow of electrons is essentially parallel, provided that the electrons enter the focusing structure practically without transverse velocities and are distributed across the stream such that the space charge fields decrease radially toward the axis in a manner similar to that of the periodic electric fields.

The method of periodic electrostatic focusing is of particular interest in connection with traveling wave tubes. The possibility of using a bifilar helix as both the slow wave and the focusing structure is discussed.
Transient Flow of Non-Ideal Gases in Porous Solids—One-Dimensional Case
Authors: Aronofsky J. S. , Ferris O. D.
Published: April 2005

Calculations of pressure and production histories are presented for one-dimensional flow of non-ideal gases through porous media. The non-ideal properties considered in this paper are the gas viscosity and deviation factor (compressibility factor) which are assumed to vary as simple functions of pressure. The effect of each of these parameters is investigated independently as well as in combination. The results demonstrate that pressure declines and production histories in linear gas-flow systems are markedly influenced by variations in these parameters. Numerical solutions of the flow equations were obtained by solving the corresponding difference equations on an electronic digital computer.
Analyses of Basic Dielectric Amplifier Circuits
Authors: Chow Shou-Hsien
Published: April 2005

Dielectric amplifiers with high-input impedance and low-output impedance have high power gain and slow response. Analyses of two basic types of dielectric amplifier circuits, i.e., parallel and series, are given here. Both steady-state and transient responses are studied.
Applications of the Dirac Delta Function to the Evaluation of Certain Integrals
Authors: Spiegel Murray R.
Published: April 2005

The evaluation of certain integrals is attained by use of ordinary linear differential equations having inputs that depend on the Dirac delta function. The method is illustrated by several examples.
Thickness-Shear and Flexural Vibrations of a Circular Disk
Authors: Mindlin R. D. , Deresiewicz H.
Published: April 2005

Equations governing the coupled thickness-shear and flexural vibrations of isotropic, elastic plates are solved for the case of a circular disk with free edges. The results of computations are given for the resonant frequencies analogous to those which would be excited in an AT-cut quartz disk with full electrode coating. A marked difference is observed between the frequency spectrum of the disk and the spectrum of cylindrical vibrations of a rectangular plate. The difference is due to the presence of thickness-twist modes of motion, in the disk, which, along with the thickness-shear modes, are coupled to the flexural modes.
Low-Energy Electron Diffraction Investigation of Chemisorbed Gases on the (100) Faces of Copper and Nickel Single Crystals
Authors: Schlier R. E. , Farnsworth H. E.
Published: April 2005

The use of low-energy (10–250 ev) electron diffraction as a method of studying the chemisorption of gases on metal single crystals is described. The apparatus permits controlling the temperature of the crystal in the range from liquid nitrogen to room temperatures during observation. Outgassing the crystal is effected by strong heating using electron bombardment. The residual gas structures on the (100) faces of copper and nickel single crystals are determined to be: (1) a monolayer with a single-spaced square array, found on both copper and nickel after heating at temperatures slightly below the minimum temperature for observable evaporation; and (2) a double-spaced, face-centered square array, found after heating at or above this temperature. Nitrogen adsorbs on the (100) face of a copper single crystal at 25°C and −78°C into an incomplete single-spaced square array. Most of the adsorption at 25°C occurs in a pressure range of 10−4 to 10−1 mm Hg in a ten-minute interval, with little change occurring between 10−1 and 8 mm Hg. At −78°C, the corresponding pressure range is 10−4 to 10−3 mm Hg with little adsorption occurring between 10−3 and 1 mm. At room temperature, oxygen adsorbs into a complete, single-spaced, square array at a pressure of 2×10−3 mm Hg in a ten-minute interval. At higher pressures, additional oxygen adsorbs into a thicker layer of no regular structure.
On the Flicker Noise Generated in an Interface Layer
Authors: Hannam H. J. , Van Der Ziel A.
Published: April 2005

It is shown that a large amount of flicker noise is generated in tubes that have developed a high-resistance interface layer between the cathode-nickel and the oxide coating. The equivalent noise resistance Rn of this effect can be represented by the equation Rn=KIp2Ri2/fα, where K is a constant, Ip the plate current, Ri the interface resistance, and f the frequency whereas α varies between 1.1 (for low Ri) and 1.5 (for high Ri). All evidence suggests that the noise is generated in the interface layer; this was subsequently proved by a direct experiment. The current dependence suggests that the noise is caused by spontaneous fluctuations in the resistance Ri. Experiments up to 1.5 mc indicate a change in the exponent α from 1.1 to 1.6 at high frequencies, indicating that the interface impedance cannot be represented by a fixed resistance Ri and a fixed capacitance Ci in parallel.
On the Concept of an Instantaneous Power Spectrum, and Its Relationship to the Autocorrelation Function
Authors: Turner C. H. M.
Published: April 2005

A definition sufficient to define a function of frequency ρ(t,f) which could be regarded as the instantaneous power spectrum was given by Page. This function is not unique, since it may have added to it a complementary function of frequency ρc(t,f) satisfying ∫ −∞∞ρc(T,f)df=0without changing the original signal in any way.

It is shown that when a signal is observed by different observers, starting their observations at different times, they will not derive the same ``instantaneous power spectral function,'' and the differences between their results will be complementary functions as defined above.

It is well known that the Fourier transform of the autocorrelation function is equal to the square of the magnitude of the spectral function. Analogously, a ``running autocorrelation function'' is defined and it is shown that the Fourier transform of its partial differential coefficient with respect to time is an instantaneous power spectral function.
Electron Emission from Metals under High-Energy Hydrogen Ion Bombardment
Authors: Aarset B. , Cloud R. W. , Trump J. G.
Published: April 2005

Measurements of the electron emission from Mg, Al, Fe, Ni, Au, and Pb surfaces bombarded by atomic (H1+) and molecular (H2+) hydrogen ions with energies from 0.7 to 2.0 Mev showed a diminishing emission with ion energy and little dependence on either atomic number or on the field intensity at the metal surface. Measurements of this type are of interest in connection with the mechanism of high voltage discharges in vacuum. The expected variation of secondary emission with angle of incidence and with conditioning was found. The emission ratios are compared with measurements by others at lower ion energies.
Theory of Stress-Strain Relations in Anisotropic Viscoelasticity and Relaxation Phenomena
Authors: Biot M. A.
Published: April 2005

A thermodynamic derivation is given for the representation of a system having viscoelastic or relaxation properties by means of a potential and dissipation function familiar in Lagrangian mechanics. This leads to modes of relaxation which are used as normal coordinates to derive general expressions for operational tensors relating stress and strain. A large variety of phenomena involving interaction of diffusion, chemical reaction, heat transfer, mechanical deformation, etc., is included in this theory.
Mechanics of Two Immiscible Fluids in Porous Media
Authors: Meyer H. I. , Garder A. O.
Published: April 2005

Flow of two and three immiscible fluids in porous media is considered in which the various fluids are separated into different saturation zones by gravity. An equation of flow for any one fluid is derived with the condition that the other fluids must be stationary. This equation is then applied to solve the question of the maximum rate of flow of one fluid into a well from a radially symmetrical porous medium without producing the other fluid or fluids present in the formation. Different well geometries and fluid systems are considered. These problems are sometimes called ``coning'' problems.
Rocket Measurements of Upper Atmosphere Ambient Temperature and Pressure in the 30- to 75-Kilometer Region
Authors: Sicinski H. S. , Spencer N. W. , Dow W. G.
Published: April 2005

A method for determining ambient temperature and ambient pressure in the upper atmosphere is described, using the properties of a supersonic flow field surrounding a right circular cone. The underlying fundamentals stem from basic aerodynamic principles as combined with the developments of the aerodynamics of supersonic cones by G. I. Taylor, J. W. Maccoll, and A. H. Stone. The experiment provides the necessary cone pressures, velocities and Eulerian angles, such that a Mach number characterizing the ambient space conditions may be computed. A description is given of the requisite experimental equipment and related techniques. Experimental data from two rocket-borne equipments are presented with the resulting calculated pressures and temperatures as experienced over New Mexico to approximately 70 kilometers.
Coupling of Modes of Propagation
Authors: Pierce J. R.
Published: April 2005

When two lossless modes of propagation are coupled, waves which increase or decrease with distance may arise when the power flow of the two modes is in opposite directions or when power is generated in the coupling device. This behavior is characteristic of wave filters, traveling-wave tubes, double-stream amplifiers, and space-charge-wave amplifiers. Such behavior is analyzed assuming linearity and conservation of energy only.
Turbulent Processes as Observed in Boundary Layer and Pipe
Authors: Schubauer G. B.
Published: April 2005

Certain statistical properties of turbulence observed in a boundary layer and in fully developed pipe flow are compared. Differences and likenesses are shown, and in particular certain common properties are found which appear to be indicative of processes governing the finer structure and controlling the origin, form, and life cycle of turbulent motions. An attempt is made to point out some of these processes. Attention is called to a region of high turbulent activity near the wall.
Ultra-High Vacuum. II. Limiting Factors on the Attainment of Very Low Pressures
Authors: Alpert D. , Buritz R. S.
Published: April 2005

Recently developed ultra-high vacuum techniques, with which it is possible to achieve working pressures of 10−10 mm Hg or less, have made feasible the investigation of a number of physical processes occurring at very low pressures. The Bayard-Alpert ionization gauge has been calibrated over its useful range and some of the important limitations on the production and measurement of ultra-high vacuum have been determined. It has been shown that an ultimate limitation on the achievement of very low pressures in glass systems is caused by the diffusion of atmospheric helium through the walls of the system. A simplified omegatron has been developed for the measurement of the partial pressures of residual gases in a highly evacuated system.
Diffusion of Pulsed Currents in Conductors
Authors: Vallese L. M.
Published: April 2005

The density distribution and the equivalent depth of penetration of pulsed currents produced by a plane wave incident normally upon a plane conductor are investigated. In particular the cases i(t)=I0p(t), [I0/(t)12]p(t), I0e−αtp(t), where p(t)=U(t)[minus]U(t[minus]T0), are considered.