bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epicentral Displacement Caused by Elastic Waves in an Infinite Slab
Authors: Mencher Alan G. 
Published: April 2005

The displacement is determined at the epicenter of a homogeneous isotropic infinitely long elastic slab containing a point source of pressure waves. The source is centrally located between the slab surfaces and is taken to have a step function time dependence.
The formal solution for the Laplace transform of the displacement is obtained as an infinite integral. The integration and the inversion are simultaneously accomplished by an infinite series expansion of the integrand and transformation of variables for each term of the expansion. The resultant integrated series consists of terms having the mathematical form of reflected waves which diverge individually but combine to give a finite resultant.
In view of the fact that the expansion of the integrand is not valid at the upper limit of integration, a justification of the method and of the results is given.
Space Charge Waves in Inhomogeneous Electron Beams
Authors: Kent Gordon 
Published: April 2005

A magnetically confined sheet electron beam filling the space between two plane parallel electrodes is discussed. It is assumed that the average electron space charge is not neutralized by positive ions so that the potential at the center is depressed, and the beam is inhomogeneous in velocity and charge density. The objective of this theoretical treatment is to determine whether or not exponentially growing space charge waves can be supported by such a beam.
For small inhomogeneity and continuous behavior of all quantities as functions of the inhomogeneity, it is shown that growing waves are not possible. This conclusion is supported by discussion of the analogous adjacent beam problem and the analogous velocity distributed filamentary beam. Although the adjacent beams can support growing waves, it is argued that the analogy is not valid because the adjacent beams cannot be obtained by a continuous perturbation of a single homogeneous beam. The analogy of the velocity distributed beam does not suffer from this deficiency. In this case it is shown that growing space charge waves cannot exist unless the distribution function has more than one relative maximum.
Effect of Uniform Displacement on the Stress Distribution of a Wood Plate
Authors: Walters Kenneth C. , Smith C. Bassel 
Published: April 2005

The principle of virtual work was employed to determine the stress distribution in a wood plate subjected to a load distribution such as to effect a uniform displacement in the y direction.
The displacement u along x=±a developed an unexpected contour. The average value of u appears to occur near the ends. This cautions against the common practice of placing the instruments for measuring Poisson's ratio near the middle. In the case of isotropic material the unexpected contours still prevail but are barely perceptible.
The work was carried out for a fourth approximation (not presented) with sufficient accuracy to assure that the same contour was developing. These unexpected results were first observed in the laboratory of the U. S. Forest Products Laboratory, Madison, Wisconsin—an experience which prompted this theoretical confirmation.
Method for Determining the Viscoelastic Properties of Dilute Polymer Solutions at Audio-Frequencies
Authors: Sittel Karl , Rouse Prince E. , Bailey Emerson D. 
Published: April 2005

A sensitive instrument for the measurement of the viscoelastic properties of dilute polymer solutions is described. It makes use of torsion pendulums with resonant frequencies in the range between 200 cps and 2300 cps. The test liquid is contained in a hollow oscillating disk. The shearing stress which is exerted at the liquid-metal interface alters the frequency and rate of decay of the free oscillations of the pendulum. By means of an optical system, the oscillations of the pendulum are caused to modulate the light striking the cathode of a phototube. The frequency and the rate of decay of the resulting alternating voltage are measured electronically.
The operation of the instrument and the factors affecting the precision of measurement are analyzed.
Kinetics of Piles with Reflectors
Authors: Rumsey V. H. 
Published: April 2005

An integral equation for the time-dependent reaction is derived on the basis of the two-group model of neutron multiplication. When the effective multiplication constant is given, the solution reduces to a determination of the mean time T between consecutive generations, which is largely controlled by the circulation of neutrons in the reflector. If the steady distribution is known, T can be calculated from a simple formula.
To illustrate the orders of magnitude which are involved, T was calculated for a small pile surrounded by an infinite reflector. A value of T=450 microseconds was obtained assuming a mean lifetime in the core of 50 microseconds and a mean lifetime in the reflector of 14 000 microseconds.
RLC Canonic Forms
Authors: Reza F. M. 
Published: April 2005

Foster's reactance theorem synthesizes the class of lossless networks in a so-called canonic form. This idea is here generalized in order to show that there is a distinct class of RLC networks possessing a canonic form. It will be shown that when an RLC driving-point impedance or admittance possesses a canonic form, its poles and zeros must alternate on each and every ``separate part'' of an algebraic curve (c) of a special nature located in the left half of the frequency plane s=σ+jω, belonging to one of the following two families: a0+ ∑ 1nak(σ+αk)(σ+αk)2+ω2=0;  a0   ∑ 1nak(σ2+ω2+αkσ)(σ+αk)2+ω2=0. A corollary of this theorem, in the case (c) is a straight line or circle, symmetrically placed with respect to the real axis, unifies the three known cases of LC networks, RL-RC networks, and networks with slight dissipation.
Analysis and synthesis of RLC networks possessing a canonic form is introduced in the light of a more general approach to the problem based on the class consideration. The problem of the driving-point impedances which contain mutual coupling in their Brune configuration has been clarified by outlining their generating functions and their network structure. (The latter part is omitted here and shall be presented in another article.)
Cathode Effects in the Dielectric Breakdown of Liquids
Authors: Bragg J. K. , Sharbaugh A. H. , Crowe R. W. 
Published: April 2005

The apparent (measured) electric strength of a liquid dielectric depends on the nature of the cathode used. The field emission of electrons from the metallic cathode is assumed to be responsible for this effect; it may provide space charge which distorts the electric field in the dielectric. The nature of the cathode determines the range of electric fields over which the emission becomes appreciable.
In this paper we discuss in detail the emission of charge and the formation of space charge. Because of theoretical and experimental uncertainties connected with supposedly uniform metallic surfaces, an electrode consisting of an electrolyte solution is also considered. Although the experimental results demonstrate that ions are emitted from such cathodes under the influence of strong electric fields, the role in providing space charge is similar to that of metal electrodes which emit electrons.
For the former electrode, the considerations regarding space-charge formation predict a definite dependence of apparent electric strength on electrolyte concentration and provide a way of testing the basis of the theory. Certain experiments reported here confirm the predictions of the theory.
Resistivity Striations in Germanium Crystals
Authors: Camp Paul R. 
Published: April 2005

Germanium metal, both single crystalline and polycrystalline, is frequently found to contain sharp fluctuations in impurity concentration. These are superimposed on the gradual variations expected as the result of ordinary segregation processes.
A rather simple technique for detecting fluctuations of this kind has been developed. It is more sensitive than resistivity scanning and does not involve the use of radioactive tracers. This technique has been applied to a number of samples. The origin, value, and elimination of these fluctuations are discussed briefly.
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.
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.
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.
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.
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.
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.
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.
High Field Electron Emission from Irregular Cathode Surfaces
Authors: Lewis T. J. 
Published: April 2005

Electron emission from a cathode surface produced by an applied field E is enhanced by the presence of projections on the emitter surface which cause a local increase in E. The nature of this enhancement factor μ(z), which is a function of the distance z from the cathode, is discussed more fully than hitherto and its magnitude is calculated for certain ideal but realistic geometries. Although such a factor may be large on the surface (z=0), it decreases rapidly as z increases so that the mean field magnification μ̄(z), which is required in the Schottky thermionic emission theory, is unlikely to be &gt;2 and is probably near to unity even for fields as great as 5×105 v/cm. This fact will mean that the Fowler-Nordheim theory frequently used to explain emission results at these fields is not applicable and that a Schottky theory should be used.
It is also shown that μ̄(z) is itself field dependent and produces departures from the Schottky law in such a way that the slope of the current vs E½ plot increases rapidly for E&lt;103 v/cm, remains approximately constant for 103&lt;E&lt;104 v/cm, and then increases again at higher fields. A similar reasoning shows that deviations from the Fowler-Nordheim law for fields &gt;106 v/cm can also be expected.
Finally, the assumption of a constant emitting area for rough cathodes is also shown to give departures from the emission laws in such a manner that the estimated current density at high fields is appreciably less than the expected values.
These deductions help to explain some of the anomalous results frequently found in many conduction experiments in gases and liquids.
Hexagonal Microstructure of Ice Crystals Grown from the Melt
Authors: Truby Frank K. 
Published: April 2005

Electron microscopy of etched and nascent surfaces of single ice crystals shows a characteristic microstructure of elongated, hexagonal prisms. The small hexagonal units vary greatly in size with an expected width of the order of 3 microns and a length of 6 microns. The coordination among microcrystalline units characterizes a particular single crystal, the size of which may be determined by processes of freezing and subsequent history, but the sizes of the microcrystalline units of which they are composed appear to be independent of the rates of freezing. The etched surfaces show that the center of the hexagonal unit etches to a greater depth than does the outer area, indicating a higher degree of crystal disorder along the axis of symmetry.
Ice surfaces in process of growing from the melt also appear to consist of hexagonal pyramidal pits which are built up by concentric steps around the C-axis. This structure appears to be consistent with that of the etched surfaces. Observations of growing-ice surfaces formed from cesium fluoride solutions reveal that the fluoride impurity tends to reduce the prominence of the pyramidal microstructure in a manner dependent upon concentrations such that the structure disappears for concentrations greater than 10−3 M.
Total Emissivities and Absorptivities of Some Commercial Surfaces at Room and Liquid-Nitrogen Temperatures
Authors: Zimmermann F. J. 
Published: April 2005

The heat transferred by radiation was measured between surfaces at room temperature and liquid-nitrogen temperature. The surfaces used were various combinations of electroplated gold and silver and polished copper sheet. From the test data, the approximate total emissivities of the room-temperature surfaces and the total absorptivities of the liquid-nitrogen surfaces were computed.
The results of these tests indicated that electroplated silver surfaces have lower emissivities and absorptivities than equivalently treated electroplated gold surfaces in this temperature range. The best surface tested was a special, bright, unbuffed silver-plated surface. This surface is known to the trade as ``silver lume.'' The room-temperature emissivity of this surface was approximately 0.017, and the absorptivity at 77.3°K for radiation from a 300°K surface was about 0.0083. These are the lowest values at these temperatures of which we have knowledge.
It was found that the electroplated surfaces were best used without buffing or any mechanical working of the surface. It is believed that cold working of the metal surface increases its emissivity and absorptivity by increasing its electrical resistivity.