bluuebunny/crossref_metadata_2025 huggingface dataset:
Concept of Stability for Nuclear Reactors
Authors: Robinson Lawrence Baylor
Published: April 2005

Equations relating neutron density, temperature, and excess multiplication of a nuclear reactor are transformed so as to be suitable for phase plane representation. The concepts of orbital, secular, and asymptotic stability are examined. The significance of each type of stability for reactor operation is discussed. Orbital stability is relevant for reactors whose stable states involve an oscillation of temperature (and neutron density); the other two types involve reactors whose stable states are constant temperatures and neutron density. The latter two types may also be required (for some special considerations) of a reactor possessing orbital stability.
Generalized Off-Axis Distributions from Disk Sources of Radiation
Authors: Smith Jack H. , Storm Martin L.
Published: April 2005

In the field of shielding it is frequently necessary to calculate biological radiation doses at any point in space due to disk sources of radiation. Such a source is the leakage radiation from an end of a cylindrical reactor. If G(R) is the dose at distance R from a unit point source (e.g., G∼e−σR/R2) then the dose due to a disk source of radius ``a'' with source strength S(ρ) is given by D(z,a,ε)= ∫ 0a ∫ 02πG[(z2+ρ2+ε2−2ερ cosθ)12]S(ρ)ρdρdθ,where (z,ρ,θ) are the usual cylindrical coordinates, z=0 is the source plane, and (z,ε,0) locates the dose point.

This integral is quite general, arising in many physical problems. In counter measurements, use of G=z/(4πR3), S=1 yields the solid angle subtended by the counter. In neutron physics the slowing down density of neturons from a circular source of finite radius can be calculated in the age approximation with G∼exp(−R2/τ).

Since for most G's the integral cannot be evaluated in closed form, there are derived three alternative series for D(z,a,ε) each of which has a direct physical interpretation and a different region of convergence. The results are obtained for a class of analytic functions G(R), the possible singularities of which occur only at R=0 for finite R; and for S(ρ) of the form ΣpSpρ2p. The approach in each case is to expand either the double integral or one of the two repeated integrals in a power series in cosθ, ε, or ρ prior to performing the detailed integrations. Numerical results are given for the case of a typical shielding function.
Measurements of the Gas Temperature of a Low-Pressure RF Discharge
Authors: Reingold Irving , Garoff Kenton
Published: April 2005

An experimental investigation has been made of the manner in which the gas temperature resulting from an rf sheath discharge is affected by the incident line power, gas fill, and Q of the cavity in which it is confined. Data are presented of the measured gas temperature as a function of line power for cavities of different Q. Qualitative results are submitted of the effectiveness of the gas and of the cavity in dissipating the heat resulting from the power absorbed by the cavity. Argon, hydrogen, nitrogen, and argon and water vapor were the gas fills investigated.
Transverse Motion of an Electron in a Constant Wave Speed Section of a Linear Accelerator
Authors: Jacobs Ira , Akeley E. S.
Published: April 2005

The relativistic differential equations of motion of an electron in the field of a linear accelerator are considered. Treating only electrons near the axis, the field components are expanded in powers of distance from the axis r, and terms in r and ṙ of order two higher than the lowest order terms are neglected. The first integral of two of the equations of motion are then obtained, and together with the equation of motion for the r coordinate, give a second-order nonlinear differential equation for r as a function of the phase of the electron with respect to the peak of the accelerating electric field. Utilizing earlier results giving the dependence of phase on distance along the axis of the accelerator, a choice of a particular dc magnetic focusing field allows this differential equation to be integrated twice, from which r as a function of distance along the accelerator is plotted.

The need for a focusing field is indicated, and it is shown that the particular field chosen has the advantage that with it, the electron will oscillate between known fixed limits of r. The necessity of shielding the electron emitter from the focusing field is shown, and an indication of the magnitude of the field and length of the accelerator for which it should be used, is given for the Purdue accelerator.
Negentropy and Information in Telecommunications, Writing, and Reading
Authors: Brillouin L.
Published: April 2005

The negentropy principle of information was discussed in a previous paper and applied to a variety of problems of scientific observation. The present paper considers the technical problems of telecommunication. Using a thermodynamical discussion one obtains the Shannon formula for the capacity of a channel with noise. This example proves again the connection between information and negentropy.

The problem of writing and reading is examined. Here we have a type of ``dead information'' which must be re-energized for reading: The source of light needed for reading provides the negentropy which is changed into information by the reader.

The negentropy connected with ``organization'' is also discussed. All these examples show the connection between information and negentropy. They are of great importance for a theory of information, although the entropy amounts involved may be completely negligible.
Electrolytic Analog Transistor
Authors: Letaw Harry , Bardeen John
Published: April 2005

The electrolytic analog transistor is an operating model of the junction transistor which substitutes the reduced and oxidized forms of ions in solution for electrons and holes in a semiconductor. A base electrode makes a low-resistance contact to the solution and also serves to maintain the ratio of oxidized and reduced ions at an equilibrium value, thus establishing the potential of the solution. In P-N-P operation, a polarizable metal electrode (the emitter) is held at such a potential above the base electrode that the majority ions, the reduced form, are readily oxidized at its surface. An identical electrode, the collector, is placed within a few tenths of a millimeter of the emitter. It is biased in such a way that the minority ions (the oxidized form) which diffuse from the emitter to its surface are reduced. Utilizing several oxidation-reduction couples and different base electrodes, it has been found that values of α = − (∂Ic/∂Ie)vc in the neighborhood of unity can be obtained. Because of the relatively low mobilities of ions in solution, the device operates only at low frequencies. The device may also have some application as a constant current element in transistor bias circuits.
Stored Energy and Power Flow in Electron Beams
Authors: Walker L. R.
Published: April 2005

The problem of finding the density of ac energy and the ac power flow in an electron beam, originally uniform in velocity and charge density, which interacts with a weak electromagnetic traveling wave, is considered. For the problem to be significant, the way in which the traveling wave is built up must be specified and the energy and power flow turn out to depend upon the method of establishment.
Limiting Pressure on Hydrofoils at Small Submergence Depths
Authors: Laitone E. V.
Published: April 2005

It is shown that the magnitude of the local velocity and the surface pressure coefficient can be limited over the entire upper surface of a two-dimensional hydrofoil as it approaches the free water surface. In this limiting condition the flow over the upper surface is governed by the shallow water wave propagation phenomenon, and the limiting pressure or velocity is determined by the maximum depth attainable from the hydraulic jump relations. The experimental data verifies this new theory and proves that the previous two-dimensional hydrofoil theories are valid only for relatively deeply submerged bodies.
Fast Time Analysis of Intermittent Point-to-Plane Corona in Air. III. The Negative Point Trichel Pulse Corona
Authors: Amin M. R.
Published: April 2005

Fast oscilloscopic time analysis of the negative point Trichel pulse corona in room air at various pressures and gap geometries reveals the following data. The very short rise and quenching time of the pulse at atmospheric pressure observed by English is confirmed. Under these conditions the secondary action is a photoelectric liberation from the cathode and discharge extinguishes by dissociative attachment to give O− ions. Decreasing pressures reduces space charge density, prolongs the discharge and brings in a secondary liberation by positive ion bombardment. Increasing potential at constant pressure at first decreases clearing time, leaving pulses unchanged and current increases proportional to repeat rate. At higher potentials, photon action is reduced relative to positive ion impact at the cathode, the discharge extends further into the gap, and quenching is very effective with less total ions reducing pulse size. With increasing repeat rate, current no longer increases proportional to repeat rate in consequence of smaller pulse height. The effects of increased point diameter are increased pulse size. Comparable clearing times for large and small points require higher potentials for the former. Thus, at constant pressure and potential, increase in point radius produces a decrease in frequency and increase in total charge per pulse. Conditioning of the point at high-current densities and repeat rates decreases the number of ions per pulse, which is of the order of 109 under normal circumstances, and shortens the pulse by reducing cathode work function and increasing photoelectric liberation, so that choking occurs with little ion action. Since repeat rate is slightly decreased by the charge liberation, the reduced pulse charge yields a reduced current through a conditioning that decreases work function. Comparison of ion movement across the gap during clearing time, with that for O2+ ions of known mobility in air, indicates that the rapid ion transit in Trichel pulses is caused by a majority of O− ions with a mobility of about 4 cm2/volts second from near the cathode with some formation of O2− ions in transit.
Volume and Surface Recombination Rates for Injected Carriers in Germanium
Authors: McKelvey J. P. , Longini R. L.
Published: April 2005

A study of bulk minority carrier lifetimes and surface recombination rates has been made, using experimental equipment similar to that of Navon, Bray, and Fan, wherein the time-decay of carriers injected electrically by a pulse is observed. The diffusion theory for carriers of bulk lifetime τ has been worked out, considering a definite probability of nonrecombination, or reflection coefficient, to be associated with the surfaces of the sample. A simple relationship between this quantity and the surface recombination velocity has been derived. If the surface recombination velocity is known, the effective trapping area at the surface may be calculated from this relation. Values of bulk lifetime and surface recombination velocity have been found for both n- and p-type germanium samples, and for a wide variety of surface treatments. By suitable modifications in experimental technique, this experiment may be utilized to measure drift mobility of minority carriers.
High-Resolution Replicas and Their Application
Authors: Hibi Tadatosi , Yada Keiji
Published: April 2005

Using methyl methacrylate as an intermediate, an attempt was made to obtain a high-resolution two-step replica, by improving evaporation elements and evaporation method. It was found that, by using Zr, Si, and Fe, with Ge and Cr as evaporation elements, the resolution of two-step replicas was superior to that obtained up to the present. It is also known that the resolution of replicas obtained by performing metallic evaporation after treatment by ion or electron bombardment for a methyl methacrylate intermediate replica is superior to that without bombardment. Two evaporation methods—the usual continuous method and an intermittent one—were compared. A new method for the production of surface replicas of microspecimens is also proposed. The high-resolution replica obtained here is compared with others along with a brief consideration of the results obtained.
An Improved Replica Technique for Electron Microscopy of Paint Films
Authors: Powell Allen S. , LeBras Louis R. , Bobalek Edward G. , Von Fischer William
Published: April 2005

Improved polyvinyl alcohol-silica replica techniques are described which allow for more accurate examination by electron microscopy of pigment derived microstructure in paint films. These methods complement the silver-silica techniques which are preferable only for studying much finer details, such as molecular configurations and small distortions of the resinous binder. Procedures have been developed for stripping unaltered baked enamel films from tin plate. The underside of these free films can be examined with the improved replica techniques and it is possible to study differences in top and bottom structure of paint films. Applications of the refined replica techniques in the study of paint films are presented.
A Transform Method for Linear Time-Varying Systems
Authors: Aseltine J. A.
Published: April 2005

This paper discusses a method for finding an integral transformation applicable to certain time-varying systems. Examples of transformations derived by the method, including Laplace, Mellin, and Meijer, are given. A convolution theorem for the general method is presented, and its use in general representation of time-varying systems is illustrated.
Loss Measurements of Surface Wave Transmission Lines
Authors: Scheibe Elmer H. , King Bernard G. , Van Zeeland Donald L.
Published: April 2005

Loss measurements were made on ten dielectric coated wires used as surface wave transmission lines at a frequency of 9365 mc/sec. The purpose of these measurements was (1) to develop a satisfactory method for making the loss measurements, and (2) to compare the measured loss with the calculated or predicted value obtained from theoretical analysis made by Goubau. A resonance method, in which the Q of a resonator formed by short circuiting both ends of a length of line is determined, was found to be most desirable. The loss in the resonator end plates was taken into account in determining the wire loss.

A description of the apparatus required and the experimental procedures used is given. A brief discussion of alternative methods for making the loss measurements, some of which have been tried, is also given.

The losses of the wires measured ranged from about 3.0 db/100 feet for thin dielectric coatings to about 11.5 db/100 feet for thick dielectric coatings. The agreement between measured and calculated losses of wires for which the constants of the dielectric coating are known is considered good.
Relationship of First- to Second-Order Transition Temperatures for Crystalline High Polymers
Authors: Boyer Raymond F.
Published: April 2005

This paper concerns an empirical linear relationship between the melting temperature T1 and the second-order or glassy transition temperature T2 for partially crystalline polymers. Two lines can be drawn, one for symmetrical polymers, the other for unsymmetrical polymers, the latter being of lower slope. These families are only approximate. It is shown for a limited group of polymers, that T2 is proportional to the cohesive energy density of the polymer. Since T1=ΔH/ΔS, it is suggested that the two families of curves arise because of differences in ΔS which depends on symmetry and chain stiffness. It is shown that T1 and T2 are linearly related with diluent as a common parameter.
An Infrared Study of the Crystallization of Polyethylene
Authors: Reding F. P. , Brown Alexander
Published: April 2005

The melting point, temperature for the onset of crystallization, and the isothermal rate of crystallization of polyethylene all decrease on increasing the extent of branching of the polymer chains. In the molecular weight range studied the melting point is independent of the molecular weight. The temperature for the onset of crystallization at any given rate of cooling appears to increase as the molecular weight is decreased. The isothermal rate of crystallization becomes much greater as the crystallization temperature is lowered, however, at a given temperature the rate is affected only slightly by a change in molecular weight and is primarily a function of the degree of branching.
Crystallization in Butadiene-Styrene Copolymers
Authors: Wood Lawrence A.
Published: April 2005

Butadiene-styrene copolymers contain the following units: trans-1,4-polybutadiene, cis-1,4-polybutadiene, 1,2-polybutadiene, and bound styrene. Of these the first is the only type which has been shown to form crystals. By the use of published data on volume change arising from crystallization (largely due to Meyer) and on structure as a function of polymerization temperature (largely due to Hampton) it is found that crystallization in emulsion polymers has been observed only when the trans-1,4-polybutadiene content has been greater than about 58 percent, becoming more complete the more this value is exceeded. From this observation one can then draw the following conclusions, all of which are in accordance with direct experimentation:

(1) Crystallization is not observed if the polymerization temperature is above 60°C.

(2) For polymerizations at 50°C a small amount (2 to 6 percent) of bound styrene inhibits crystallization completely.

(3) For polymerizations at 5°C the limit is at about 15 to 18 percent bound styrene content.

(4) At −40°C (the lowest polymerization temperature normally utilized) this limit is at about 30 percent bound styrene.
Diffusion Coefficient, Solubility, and Permeability for Helium in Glass
Authors: Rogers W. A. , Buritz R. S. , Alpert D.
Published: April 2005

A method is described for simultaneously measuring the diffusion coefficient, solubility, and permeability for a given gas in a single sample of solid material. The method utilizes solutions of the diffusion equation (for both plane and cylindrical geometry) which make it easily possible to calculate the diffusion parameters from data taken either in the period of steady-state gas flow or in the early part of the transient period. Using ultra-high vacuum techniques, it is possible to make the measurements with extremely small amounts of gas and without errors due to leaks or contamination in the gas handling system.

Values for the diffusion parameters have been determined for helium in Pyrex glass (Corning 7740), and comparisons with previous measurements are made. Directly measured values of the diffusion coefficient are given for the first time. The diffusion coefficient and permeability both exhibit a temperature dependence of the form exp (−E/kT) both having the same activation energy (6.4×103 cal/mole) within the experimental error. The solubility exhibits little or no variation with temperature over the range 25°C to 300°C, and is in good agreement with the only previous measurement, carried out at 515°C.
Asymptotic Evaluation of the Field at a Caustic
Authors: Kay Irvin , Keller Joseph B.
Published: April 2005

The asymptotic expansion of wave fields in powers of 1/k for large k, where k is the wave number, has as its lowest-order term what is commonly known as the geometrical optics field. The caustics of geometrical optics are those point sets on which the zero-order terms become infinite. It is well known that caustics may exist even where the exact wave field is perfectly regular. An investigation of reflection from cylindrical walls of arbitrary cross section shows that the occurrence of caustic points means a change in character of the asymptotic expansion of the true field such that the lowest-order term is no longer independent of k but actually contains a factor k raised to a positive power. There also occurs a jump in phase along a ray passing through a caustic which, as is well known, equals π/2. As an application of the general method, the geometrical optics field is worked out in detail for the case of a plane wave incident on a parabolic cylinder, and the field is obtained in its lowest order at the focus and in the neighborhood of the focus. A similar problem for a reflector consisting of a segment of a circular cylinder is also considered in detail.
Decompositions of Inorganic Specimens During Observation in the Electron Microscope
Authors: Fischer Robert B.
Published: April 2005

Several inorganic substances have been examined by electron microscope and selected area electron diffraction techniques. Large crystals of sodium chloride and potassium chloride break up into many smaller crystals of the same substances. Ammonium chloride evaporates, and nitron nitrate appears merely to melt. Reduction to metal was found for silver chloride, silver nitrate, lead carbonate, and cupric oxide. Only morphological changes were observed on bombardment of silver sulfate, lead oxide, lead chloride, and gold chloride. Hydrous ferric oxide and aluminum oxide were converted to crystalline forms which could not be identified by electron diffraction.
Arcing at Electrical Contacts on Closure. Part V. The Cathode Mechanism of Extremely Short Arcs
Authors: Kisliuk Paul
Published: April 2005

The available experimental data on the short arcs which occur on closure of electrical contacts with potential differences less than the minimum sparking potential are shown to be consistent with the hypothesis that the arcs are initiated and sustained by field emission electrons. Positive ions then carry less than 7 percent of the current at the cathode. The primary function of the ions is to supply sufficient positive space charge to maintain the high cathode field, but the action of the discrete ions near the cathode in creating a temporary pass in the potential barrier may result in the attainment of sufficient electron emission to sustain the arc at values of the cathode field somewhat lower than that required by the Fowler-Nordheim equation for the same current density.

It is shown that the supply of volatile impurities on the electrode surfaces is critical in determining the breakdown field and the minimum arc current.
Flicker Noise in Germanium Rectifiers at Very Low- and Audio-Frequencies
Authors: Baker D. K.
Published: April 2005

An investigation of the frequency dependence of flicker noise in point contact and diffusion-alloy type germanium rectifiers is reported. The frequency range extends from approximately 10−3 to 106 cy per sec and the inverse frequency law is found to hold over this range. The current dependence of the flicker noise at 10 cps is also reported.
Coincidence of Pulse Trains
Authors: Friedman Henry D.
Published: April 2005

New methods for determining the time fraction of coincidence of separate periodic pulse trains are considered. The analysis applies solely to pulse trains whose fundamental periods are commensurable. For two pulse trains, the coincidence fraction is easily determined. For three or more pulse trains, a method for determining the largest possible error resulting from direct use of elementary probability theory is developed. Hence the question: ``When does probability theory provide a close approximation to the coincidence fraction?'' is to some degree answered.
An Electrodynamic Perturbation Theorem, with Application to Nonreciprocal Systems
Authors: Redfield Alfred G.
Published: April 2005

By means of a slight modification of the macroscopic electrodynamic reciprocity theorem it is possible to obtain the perturbation of the admittance matrix of an electrodynamic device due to a suitable perturbation of the dielectric susceptibility, conductivity, and magnetic susceptibility tensors in the device. The theory is applicable to nonreciprocal systems, but in practice can be used to obtain only the first-order perturbation of the admittance matrix. An expression relating the current induced in part of a system due to the motion of current in another part of the system is similarly obtained. Dc and microwave gyrators are treated, and the connection is pointed out between Faraday rotation in a transmission cavity and the magnetic energy splitting of its circularly polarized normal modes.
On the Distributions of Signals and Noise after Rectification and Filtering
Authors: Meyer M. A. , Middleton David
Published: April 2005

The probability distributions for broad- and narrow-band signals and normal random noise, following a square-law rectifier and a video (or audio) filter of arbitrary width, are examined. The present approach is based on a method originally used by Kac and Seigert [J. Appl. Phys. 18, 383 (1949)] for noise alone (after quadratic rectification but no filter) in the case of the nth-order distribution (n≥2). The procedure requires an appropriate transformation to express the output waveform in terms of the input disturbance; the statistics of the output are now determined by a suitable transformation with respect to the original, normal statistics. Explicit solutions are obtained for an integral equation involving the autocorrelation function of the noise, the weighting function of the video (or audio) filter, and an orthonormal set of eigenfunctions. For noise alone only the eigenvalues need be determined, but for a signal and noise it is necessary to know the eigenfunctions as well. Among the new results are (1), the calculation of the general, nth-order characteristic function for the filtered output following quadratic rectification for an input noise and a signal and noise; (2), a discussion of the second-order probability density W2 in this case; (3), some examples of practical interest; and (4), the limiting cases of broad and narrow post-detection filters (vis-à-vis the predetection filter), with particular attention to approximations to W2 for signal and noise for narrow videos and an improved approximation for W1 for noise alone, as well.
The Transfer Function as a Tool in the Analysis of a Resistance-Capacitance Coupled Voltage Amplifier
Authors: Ming D. L. , Thorpe R. W.
Published: April 2005

The frequency response of a typical resistance-capacitance coupled voltage amplifier has been theoretically analyzed and the result compared with that given by Terman. The advantages and disadvantages of the two methods have been illustrated both mathematically and graphically. A solution to the phase-shift problem at any frequency considered has been included.
A Capillary Viscometer with Continuously Varying Pressure Head
Authors: Maron Samuel H. , Krieger Irvin M. , Sisko Arthur W.
Published: April 2005

A new capillary viscometer has been designed to study the flow behavior of non-Newtonian fluids. The instrument is convenient, absolute, and accurate, and covers continuously a wide shearing stress range in a single determination. A falling mercury column forces the sample through the capillary. Measurement of the column height as a function of time gives both pressure drop and flow rate. Provision is also made for the use of driving fluids less dense than mercury for measurements at lower shearing stresses. The density of the sample need not be determined. Methods and illustrations are given of the application of the new instrument to the determination of the absolute viscosities of Newtonian liquids, and the flow curves of non-Newtonian fluids.
Physical Theory of New Circuit Representation for Junction Transistors
Authors: Zawels Jakob
Published: April 2005

A circuit representation for a junction transistor is derived which places the mechanism of transistor action in evidence. The circuit is a direct interpretation of the diffusion equation and the boundary conditions which include the effects of base width modulation. It is found that the active part of the circuit is independent of frequency. A modification of the circuit for common emitter operation is shown and experimental results are given.
Some Rheological Properties of Concentrated Polyisobutylene Solutions
Authors: Padden F. J. , DeWitt T. W.
Published: April 2005

Three types of measurements have been made on concentrated polyisobutylene solutions. Dynamic measurements have been extended to low frequencies and the dynamic viscosities and rigidities determined in the region close to that in which pure viscous flow predominates. A modified Stormer viscometer has been used to determine the apparent (non-Newtonian) viscosities of the same solutions. Pressures developed (normal stress) at the inner cylinder have also been measured in a concentric cylinder apparatus with the inner cylinder rotating. It is noted that superposition procedures currently used for dynamic data are apparently applicable to the viscosity and pressure data with the rate of shear taking the place of frequency. Relations between these phenomena are discussed in the light of a theory proposed by one of the authors.
Elastoviscous Properties of Amorphous Polymers in the Transition Region. II. Stress-Relaxation of Butadiene-Styrene Copolymers
Authors: Catsiff E. , Tobolsky A. V.
Published: April 2005

Experimental data have been obtained on the stress-relaxation modulus Er(t) of several copolymers in their transition regions. The new data are expressed as master curves which can be fitted to the Gauss Error Integral form of reduced equation, as previously proposed. It appears possible to characterize the time and temperature-dependence of Er of amorphous polymers in general by means of the parameters of this equation: E1 (glassy-state modulus), E2 (rubbery-state modulus), Td (distinctive temperature, related to second-order transition temperature), Kd (characteristic relaxation time at Td), and h (parameter related to steepness of master curve). In the butadiene-styrene series, the effect of composition on these parameters has been determined.
Transient Response of a p-n Junction
Authors: Lax Benjamin , Neustadter S. F.
Published: April 2005

The authors investigate the transient response of a p-n junction in a circuit where the applied voltage is suddenly switched from the forward to the reversed direction. The behavior is studied as a function of the circuit resistance. The solution of the appropriate diffusion equation is carried out for a time-dependent boundary condition, resulting in an integrodifferential equation. Analytical and numerical results for the current and the junction voltage as a function of time are then obtained by suitable approximations for the ``recovery'' and reverse periods. The ``recovery'' or reversal time tf is the time required for the junction voltage to become negative and is given by erftfτ=11+(If/Ir),where τ is the lifetime of holes, If is the forward current, and Ir the initial reverse current, which is limited by the external resistance.
Minimum Noise Figure of Traveling-Wave Tubes with Uniform Helices
Authors: Pierce J. R. , Danielson W. E.
Published: April 2005

By using a new theorem concerning noise in electron streams together with work by D. A. Watkins, an expression for the minimum noise figure of a traveling-wave tube with a uniform helix is deduced. For reasonable values of tube parameters this minimum lies around 6 db.
Solute Redistribution by Recrystallization
Authors: Pohl Robert G.
Published: April 2005

The time-dependent diffusion equation is solved using transformation calculus to obtain the solute concentration in a solvent after a segregating liquid-solid interface is passed through the material. The results are presented in graphical and tabular form for typical experimental conditions and compared with previously published findings.
Experimental and Theoretical Aspects of Shock-Wave Attenuation
Authors: Glass Irvine I. , Martin Walter A.
Published: April 2005

Experimental results are presented of shock wave and contact front velocity measurements, in air, obtained in a 3 in.×3 in. wave interaction tube. A diaphragm pressure ratio range up to 10 000 was employed, while the distance was varied simultaneously from the origin to 142 in. beyond.

It is shown that when shock-wave attenuation occurs, it consists of two portions; (a) a decrement due to formation, and (b) a further attenuation due to the distance traversed by the shock wave.

Concurrently with the attenuation phenomenon, the contact region spreads with time and its front boundary accelerates. The increase in velocity consists of two portions; (a) an increment due to formation, and (b) a further rise in velocity with the distance travelled by the contact front.

A satisfactory empirical relation is developed for the total shock-wave attenuation.

A Rayleigh-type incompressible ``pipe''-flow analysis applied to the experimental results overestimates the attenuation for stronger shock waves.
An Observation of Circular Patterns in the Vicinity of Small-Area Alloyed Germanium p-n Junctions
Authors: Holonyak Nick
Published: April 2005

Alloyed germanium p-n junctions of 0.1 to 0.2 mm diameter or less have been alloyed upon crystals of roughly ten times greater linear dimensions such that when these units are suitably electrolytically etched, ring formations (both scattered rings and tracks of overlapping rings) occur on the crystal faces in the neighborhoods of the junctions. Best current evidence indicates that the observed effects are etch produced. An explanation of this is given in terms of the action of bubbles accompanying the etching procedure.
Čerenkov Radiation from Extended Electron Beams
Authors: Danos M.
Published: April 2005

The Čerenkov radiation emitted by a bunched electron beam passing along a dielectric material at a close distance is calculated for a flat beam near a plane surface, a flat beam between two plane surfaces and for a circularly cylindrical beam within a cylindrical hole.
Evaporation of Barium and Strontium from Oxide-Coated Cathodes
Authors: Wooten L. A. , Ruehle A. E. , Moore George E.
Published: April 2005

Rates of evaporation of Ba and Sr from oxide cathodes in a practical tube structure were measured during life tests up to 20 000 hours. The effects on evaporation rates are shown for (a) impurity in the Ni support, (b) cathode temperature, and (c) space current. We conclude:

1. The product evaporating from commercial type cathodes under normal conditions is largely Ba metal; less than 5 percent is Sr; less than 2 percent is BaO; and less than 0.01 percent is SrO.

2. Chemical reducing agents in the support metal‡ are important in determining the rate of Ba evaporating during life.

3. A factor not closely controlled in the present experiments—anode and grid composition—affects the rate markedly. This is especially true for the evolution of Ba during exhaust.

4. Within the precision of these experiments, there is (a) no correlation between the rate of Ba evaporation and thermionic activity of individual cathodes, and (b) no effect of space current on the rate of Ba evaporation.
Elastic Description of a High-Amplitude Spherical Pulse in Steel
Authors: Allen William A. , Goldsmith Werner
Published: April 2005

Extensive calculations have been performed with an electronic calculator to evaluate a problem in elasticity that simulates the effect of a cylindrical charge of high explosive detonated in intimate contact with a steel plate. The general method of calculation has been described in detail. Although elastic theory has been extrapolated into a regime where it is known not to apply, insight of a valuable general nature has been obtained on the nature of the negative component of the pulse.
Relaxation Oscillations and Noise from Low-Current Arc Discharges
Authors: Skolnik M. I. , Puckett H. R.
Published: April 2005

Under certain conditions the usual gas-discharge circuit was found to give rise to relaxation oscillations. The relaxation oscillations produce a series of very narrow pulses with random pulse repetition interval, which appear as noise. The amount of noise was found to depend upon the gas, the cathode electrode material, the power supply voltage, and the external circuit configuration. It seems that this mechanism may be responsible for most of the high level noise usually reported from gas discharges. The pulsed nature of the apparently continuous discharge appears to be a fundamental property of the low-current, cold-cathode arc which has not been considered previously.
Study of the Initial Stages of Sintering Solids by Viscous Flow, Evaporation-Condensation, and Self-Diffusion
Authors: Kingery W. D. , Berg M.
Published: April 2005

The mechanism of material transport in sintering can be elucidated in some cases by direct observation of the rate of interface growth and approach of centers between spherical particles. Measurements with glass, sodium chloride, and copper indicate that with these materials viscous flow, evaporation-condensation, and self-diffusion are the rate-determining mechanisms. Values of viscosity, vapor pressure, and diffusion constants have been determined, but calculations of diffusion constants from these data are subject to uncertainties of interpretation. A model is presented for the behavior of copper during the initial stages of sintering, which is in agreement with available experimental data, and which requires vacancy elimination at dislocations or grain boundaries. Data for refractory oxides indicate the importance of purity and fabrication pressure, but the sintering mechanism for these materials is not determined by the present data.
Shape and Crystal Anisotropy of Alnico 5
Authors: Nesbitt E. A. , Williams H. J.
Published: April 2005

It is concluded from torque measurements on single crystals of Alnico 5 that the high coercive force of these crystals depends upon the shape anisotropy of the fine precipitated plates and that the crystal anisotropy of the plates is negligible. The present physical picture of the alloy is that it consists of plates of precipitate of high magnetic saturation separated by a matrix of comparatively low magnetic saturation. The plates are made up of rods of precipitate (approximately 75 A in diameter ×400 long), but they act magnetically like single domain plates. The magnetization vector turns in the plane of the plates, and it is the length-to-width dimension ratio of the plates which determines the effective shape anisotropy and the resulting coercive force of the alloy.
On Representation of Electromagnetic Fields in Cavities in Terms of Natural Modes of Oscillation
Authors: Schelkunoff S. A.
Published: April 2005

In this paper we illustrate by a simple example that when we wish to express the admittance of a cavity excited through a hole in terms of natural frequencies of oscillations which can exist when the cavity is short-circuited, it is important to remember that the short-circuit must conform to the impressed field. When this is done, one need not fear that the ``obvious'' set of natural modes may be incomplete.
Low Magnetic Saturation Ferrites for Microwave Applications
Authors: Van Uitert L. G.
Published: April 2005

Low magnetic saturation ferrites suitable for microwave applications can be prepared in the magnesium aluminum ferrite system. These ferrites can be prepared to possess also relatively high permeabilities at carrier frequencies. Curie temperatures, coercive forces, magnetic saturations at 25°C, and initial permeabilities at 0.1 megacycle/sec for such materials are given.
Small-Angle X-Ray Scattering from Precipitates in Cold-Worked Al–Ag and Al–Zn
Authors: Jan J.-P.
Published: April 2005

A study of aging in cold-worked Al–Ag and Al–Zn alloys during the first stage of precipitation was made, by means of small-angle x-ray scattering. (a) The rate of growth of the Ag or Zn clusters was very little affected by cold-work. (b) Evidence was found that the amount of clustered solute is not altered by aging. (c) The clusters were deformed by cold-work, giving rise to an anisotropic small-angle scattering. This cannot be explained by large amounts of glide taking place in a limited number of slip planes, but rather speaks in favor of zones of homogeneous deformation. The deformation of precipitated particles by cold-work is a new and powerful means of investigating the mechanism of plastic deformation in the interior of a material.
Electrical Analog of the Eddy-Current-Limited Domain-Boundary Motion in Ferromagnetics
Authors: Brouwer G.
Published: April 2005

The observed losses in a ferromagnetic core are always greater than those calculated on the basis of a homogeneous permeability. In a magnetization process by domain-boundary displacements the permeability is certainly not homogeneous, but attains extreme values in the domain walls. As a result of this concentration of the changes in magnetic flux the dispersion curves of the initial permeability as a function of frequency show a shift of the dispersion region towards lower frequencies with increasing domain size. This is the well-known eddy-current anomaly encountered in laminated cores. An electric-circuit model was utilized to determine the eddy-current distribution and domain-boundary motion in a number of idealized cases.
Deterioration of Luminescent Phosphors under Positive Ion Bombardment
Authors: Young J. R.
Published: April 2005

The reduction of cathodoluminescence efficiency of phosphors has been observed after bombarding with H+, H2+, He+, Ne+, N2, and A+ ions having energies from 1 to 25 kev. Detectable deterioration could be observed after a bombardment of less than 10−9 coul/mm2 of ions (5×1011 ions/cm2). The deterioration could be annealed out at temperatures between 450° and 700°C. Results indicate that light 25-kev ions probably penetrate 0.1μ to 0.2μ into the phosphor.
Spin Echo Serial Storage Memory
Authors: Anderson A. G. , Garwin R. L. , Hahn E. L. , Horton J. W. , Tucker G. L. , Walker R. M.
Published: April 2005

By utilizing the method of pulsed nuclear magnetic resonance, radio-frequency energy in the form of pulses can be stored serially in a sample of nuclear spins and recalled at an arbitrary later time within the memory or relaxation time of the spin sample. Weak pulses of radio-frequency energy condition the nuclear spins to start precessing in phase. After they become completely out of phase, a strong recollection pulse brings about a phase reversal of precession and produces a series of spin echoes in a sequence corresponding to direct or reverse order of input pulses. The echo amplitudes in such a series are given as a function of the number and strength of the input pulses and the conditions for maximum storage capacity in a spin ensemble are determined. The maximum specific storage capacity in liquids is expressed in terms of the thermal noise of the detecting apparatus, the effect of self-diffusion of the molecules, and the relaxation times. The origin of undesired spin echoes arising from the interaction of input pulses is discussed, and means for eliminating these echoes by frequency and magnetic field modulation are discussed and applied. Extensive use is made of a magnetic field modulation technique to destroy undesired echoes, and to permit novel types of recall of serially stored groups of pulses. Whereas Fernbach and Proctor [J. Appl. Phys. 26, 170 (1955)] have demonstrated multiple pulse storage under conditions which reproduce the input pulse shape, the present investigation is concerned with the storage of a maximum number of pulses whose shape is ideally determined by the nuclear spin band width. In practice, the order of 1000 rf pulses can be stored and recalled by this method in a proton sample several cc in volume within a memory time of 10 to 50 milliseconds. Large specific storage capacities expected for existing long relaxation time liquids are not realized because of excessive self-diffusion.
Reflection of a Compression Wave from a Symmetrical Wedge
Authors: Skulski R. W. , Weimer D.
Published: April 2005

Compression waves generated by paper pistons accelerated by shock waves in a shock tube have been reflected from a symmetrical wedge. Studies of the density fields in the interaction region have been made with an interferometer, and the parameters, ``wave age,'' distance up the wedge, and angle of incidence have been investigated over a range of incidence angles from 25° to 80° and ``effective shock strengths'' from ξ=1.1 to ξ=2.0. The limit of regular reflection for this type of wave is shown to exist theoretically, and this limit has been verified experimentally. Beyond this limit a type of Mach reflection occurs.
Some Monte Carlo Calculations of Gamma-Ray Penetrations
Authors: Perkins J. F.
Published: April 2005

The transmission of gamma rays through slabs of various shielding materials has been calculated by a random sampling method in which the path lengths between interactions are deliberately chosen larger than those which occur naturally. Results for the case of normal incidence compare reasonably with values obtained by Goldstein and Wilkins for transmission in infinite media. The present results for the case of obliquely incident photons show the same general behavior as noted experimentally by Kirn, et al. In particular, the transmission plotted against slant path length shows a crossover, in the region of 1 or 2 mean free paths, of the curves corresponding to different incident angles. Angular and spectral distributions were obtained in the form of histograms, and it was found that the photons assume spatial equilibrium after one or two mean free paths, as evidenced by the constancy of the flux-to-current ratio. The relative contribution to the total penetration arising from the first, second, etc. scattering has been found to have the same general trend as noted earlier by Peebles. The biased sampling method which was used enables one to use the same set of photon case histories in treating a number of slab thicknesses.
Hysteresis Loops of Mixtures of Ferromagnetic Micropowders
Authors: Bean C. P.
Published: April 2005

A treatment is given of the hysteresis loops of dilute mixtures of various sizes of ferromagnetic particles. Three ranges of particle size are considered: very small particles called ``super-paramagnetic'' which are single domain and equilibrate resulting from thermal vibrations, single domain particles which are large enough that they do not equilibrate, and particles large enough to contain many domains in equilibrium. The results are compared to experiment.
Dielectric Constant of Quartz as a Function of Frequency and Temperature
Authors: Stuart Malcolm R.
Published: April 2005

Measurements of dielectric constant and power loss were made from 1 to 90 kc/sec and from 20°C to 400°C. The dielectric constant parallel to the optic axis for all frequencies shows a sharp rise, which occurs at successively higher temperatures for higher frequencies. The loss at a given frequency has a temperature maximum which is higher, the higher the frequency. The results are partially explained by assuming that ions are present in ``tunnels'' parallel to the optic axis. The density and mobility of these ions are obtained. The density is temperature dependent in such a way as to lead to an activation energy of 17.7 kcal per mole. Lithium ions were introduced into the crystals, and the effects caused by these ions were at least compatible with the assumption that lithium ions were originally present. Perpendicular to the optic axis none of the above effects exist.