bluuebunny/crossref_metadata_2025 huggingface dataset:
The Electronic Properties of Barium Sulfide
Authors: Grattidge Walter , John Harold
Published: April 2005

Barium sulfide has been prepared in a form suitable as a cathode emitter as well as in the form of compressed pills. It has a work function of 2.1 ev with a wide variation possible in activation. The most active materials had an emission at temperatures of 900°K and greater comparable to that from pure BaO. Pure nickel and platinum only were used as base metals. An equimolar mixture of BaS-SrS had a work function of 2.6 ev, and x-ray analysis indicated solid solution formation. The electrical conductivity of BaS was found to vary between wide limits depending on the degree of activation and the denseness of the specimen but was much less than for BaO. At 1000°K the specific conductivity of a compressed pill was 10−5 ohm−1 cm−1. The thermoelectric power was found to be constant with temperature although it decreased with increase in the activity of the specimen. The warmer electrode was always positive. Pure BaS had a thermoelectric power of 2.5 mv per degree between 970° and 1270°K. The effect of added impurities of iron on the electrical characteristics was studied. By mass-spectrometer studies, the evaporation rate of BaS was found to be much less than that of BaO, indicating a vapor pressure of the sulfide about 100 times less than that of the oxide. The heat of sublimation was found to be 104 kcal/mole.
Microchronometric Schlieren Study of Gaseous Expansion from an Electric Spark
Authors: Olsen H. L. , Edmonson R. B. , Gayhart E. L.
Published: April 2005

Gaseous phenomena induced by short-duration sparks at atmospheric pressure have been photographed during the first microseconds of their existence by a flash-schlieren technique. The growth of the heated gas domain (kernel) expanding from the spark discharge has been observed for air and argon. The kernel continues to expand rapidly, but subsonically, after the spark current ceases and after the shock wave separates. It develops further into a torus about the spark electrodes and eventually decays. The development of flame from a heated gas kernel in a flammable mixture is illustrated. Energy relationships for the expanding argon kernel are discussed.
Temperature Rise in a Heat-Producing Solid behind a Surface Defect
Authors: Karush William , Young Gale
Published: April 2005

Simple expressions are obtained, in certain cases, for the temperature increase in a heat-producing body when the normal heat flow from the body is blocked by defective cooling on portions of the surface of the body. Defective areas in the shape of long strips and round spots are considered.
On the Relation between the Conductance and the Noise Power Spectrum of Certain Electronic Streams
Authors: Freeman J. J.
Published: April 2005

The noise power spectrum of a diode with a temperature limited current and also for a diode with a retarding field is shown to be the sum of two parts. One, the ``pure'' shot effect, is the spectrum which would obtain if the electrons were all emitted with zero velocity, that is, if the cathode were at zero temperature (and still maintained the same emitting properties). The second is the thermal contribution, namely, 4kTg, where T is the cathode temperature and g is the conductance of the electron stream.
Thermal Stresses in a Partially Clamped Elastic Half-Plane
Authors: Huth J. H.
Published: April 2005

Numerical methods, such as those of Southwell, have made amenable to approximate analysis a large class of problems in the theory of elasticity. However, certain loadings must occasionally be considered which may give rise to theoretical stress singularities. In such cases an analytical study, at least in the immediate neighborhood of the singularities, would appear to be mandatory.

One such problem is that of determining the thermal stresses in a partially clamped elastic half-plane. The solution given in this paper assumes self-equilibrating tractions over the clamped portion of boundary so that the results apply approximately also to large finite areas.
Development of Porosity during Diffusion in Substitutional Solid Solutions
Authors: Balluffi R. W. , Alexander B. H.
Published: April 2005

A metallographic study was made of the diffusion zones present in copper-α-brass, copper-nickel, and gold-silver diffusion couples. Usual sandwich type couples and also vapor-solid type couples in which the higher vapor pressure component was diffused either into or out of the couple through the vapor phase were investigated. Significant porosity was always generated by diffusion in the sandwich couples and also in the vapor-solid couples when the higher vapor pressure component was diffused out of solid solution. Upon inward diffusion from the vapor porosity formed in the gold-silver couples but not in the copper-α-brass or copper-nickel couples.

It is concluded that porosity may form in any alloy system when the components diffuse at different rates and that it may cause appreciable error in the measurement of diffusion coefficients if ignored.
The Effect of Cyclotron Bombardment on Self-Diffusion in Silver
Authors: Johnson R. D. , Martin A. B.
Published: April 2005

Radioactive tracer techniques have been employed to measure the rate of self-diffusion in silver in polycrystalline and single crystal solvents over a wide range of temperatures, and to investigate the effect of bombardment with 10-Mev protons on this diffusion process. A least squares fit of the data from laboratory control experiments with both single crystal and polycrystalline solvents in the temperature range 903°C to 640°C has yielded the diffusion constants Q=40,800±700 cal/mole and D0=0.11±0.05 cm2/sec for the volume diffusion process. No effect of intense proton bombardment ranging from 0.5 to 5μa/cm2 has been detected on the volume self-diffusion process in silver specimens which were simultaneously irradiated in the cyclotron target box and annealed at temperatures ranging from 852°C to 555°C. These results are, at least semiquantitatively, in accord with both the elastic collision model and the thermal spike model of radiation damage. Cyclotron techniques and apparatus are described in some detail.
Effect of Filament Voltage on the Plate Current of a Diode
Authors: Ivey Henry F.
Published: April 2005

The effect of the potential drop across the filament of a diode with directly heated emitter on the plate current of the diode is considered. Calculations are made for both space-charge-limited and retarding-field conditions. Filament heating by direct current and by alternating current is considered. The results are given in convenient graphical form.
The Electromagnetic Field of a Rotating Uniformly Magnetized Sphere
Authors: Baños Alfredo , Golden Robert K.
Published: April 2005

The problem discussed here is a first step towards a more complete understanding of the modern theories of geomagnetism which are based on the differential rotation of the earth's crust with respect to its inner core and on magneto-hydrodynamical effects in the core. This paper considers first the computation of the electric and magnetic fields that a stationary observer attributes to a uniformly magnetized sphere which, in his frame of reference, rotates at constant angular velocity about an axis parallel to the direction of magnetization. It is found that, neglecting the terms of order v2/c2, the observed magnetic fields are identical to the fields of the stationary sphere, but in addition there is an external electric field identical to that produced by an axial quadrupole located at the origin. The interior electric field is directed towards the axis of rotation and its magnitude is proportional to the distance from the axis. Next, when the rotating magnet is surrounded by a stationary concentric shield, it is found that the electric fields vanish in the interior of the shield and in outer space in contrast to the results that one would find on the assumption that the shield was being ``cut'' by the lines of magnetic induction of the rotating magnet. Finally, the limiting case is considered in which the inner radius of the shield approaches the radius of the sphere, an insulating layer still being maintained between them. Here, again, no electric fields are found outside the rotating magnet.
Vertical Entry of Missiles into Water
Authors: May Albert
Published: April 2005

Investigations, carried out principally on the vertical water entry of steel spheres, are described. Graphs show the effect of several experimental parameters on the time and place of occurrence of various events in the life of the cavity which accompanies the entry. These parameters include the density and pressure of the atmosphere above the water, and the velocity, size, and nose shape of the missile. Froude-scaling is found to be a good first approximation in describing cavity behavior, and some improvement is effected by the pressure-density scaling of the atmosphere above the water. The energy lost by a missile during the open-cavity phase of its water entry is found to be used up principally in the formation of the cavity, and the cavity shape is not dependent on the nose shape of the missile for a given drag force.
Phenomena Associated with the Flight of Ultra-Speed Pellets. Part II. Spectral Character of Luminosity
Authors: White W. C. , Rinehart John S. , Allen William A.
Published: April 2005

The spectroscopic character of the luminous trails generated by ultra-speed pellets has been investigated. A total of seven spectrograms have been measured and reduced. Three of these were of 5.0 km/sec aluminum pellets; two were of 5.9 km/sec magnesium pellets; one was of a 6.0 km/sec magnesium-lithium-aluminum pellet; and one was of a titanium pellet whose velocity was estimated at about 4.5 km/sec.

The pronounced features of the spectrograms are: (1) AlO bands in the aluminum spectra, (2) Mg lines and MgO bands at the magnesium spectra, (3) strong Li lines and a pronounced continuum in the magnesium-lithium-aluminum spectra, and (4) TiO bands in the titanium spectra. Other features of the spectra are: (1) prominent AlI lines at λλ3944 and 3961 and a relatively weak continuum in the aluminum spectra, (2) a stronger continuum in the magnesium spectra, and (3) relatively weak MgO bands in the Mg-Li spectra.

The time resolved spectra show that the AlO persists in the excited state twice as long as the aluminum. The aluminum oxidizes almost completely leaving AlO in an excited state which continues to emit light after the aluminum is burned.
Space Charge and Transit Time Considerations in Planar Diodes for Relativistic Velocities
Authors: Ivey Henry F.
Published: April 2005

The usual Child-Langmuir equation is extended to the case of relativistic velocities for a diode with parallel plane electrodes. The solutions obtained are valid for any value of the accelerating voltage. As the variation of mass with velocity becomes important, the exponent giving the dependence of current density on anode voltage becomes less than three-halves, and for very large values of accelerating potential approaches unity. The variation with anode voltage of the transit time, both for the space-charge-free case and for the space-charge-limited case, has been calculated. The potential distribution across the diode is also discussed.
Generalized Ideal Filters
Authors: Zadeh Lotfi A. , Miller Kenneth S.
Published: April 2005

One of the basic concepts in the theory of electrical filters is that of an ideal filter. As commonly defined, an ideal filter is a network which passes without distortion all frequency components falling within a certain frequency range while rejecting all other frequency components. In the present paper a broader definition is formulated which extends the concept of ideal filter to both linear varying-parameter and nonlinear types of systems. Briefly, a filter N is said to be ideal if it can extract a set of signals M from the sum of M and some other set N. A direct consequence of this definition is that any ideal filter N (linear or nonlinear) is idempotent, that is, is equivalent to a tandem combination of two filters each of which is identical with N. The converse, however, is true only in the case of linear filters.

The basic properties of ideal filters are investigated by the use of function space techniques. It is shown, in particular, that by employing linear ideal filters one can separate two (or more) simultaneously transmitted sets of signals which occupy overlapping frequency bands, provided only the sets in question span disjoint manifolds in the signal space.
Diffraction Measurements at 1.25 Centimeters
Authors: Kodis Ralph D.
Published: April 2005

Measurements have been made, using an image plane technique, of microwave diffraction near obstacles whose characteristic dimension is comparable to a wavelength (1.2668 cm). Detector, obstacle, and source of radiation are mounted on one side of a horizontal 4-ft by 6-ft conducting plane, and the operator and all auxiliary apparatus are located on the other. Measured distributions of both the phase and amplitude of the electric field near long cylinders of brass and polystyrene were obtained, and for the conducting cylinders these are compared directly with the results of a suitably modified theory. The technique has been extended to diffraction by a semi-infinite conducting plane screen, and it was found in this case that considerable error is introduced by the point source. With the substitution of a line source the measurements are again in close agreement with the theory.
The Emission of Radiation from Diatomic Gases. III. Numerical Emissivity Calculations for Carbon Monoxide for Low Optical Densities at 300°K and Atmospheric Pressure
Authors: Penner S. S. , Ostrander M. H. , Tsien H. S.
Published: April 2005

Numerical emissivity calculations at 300°K and atmospheric pressure for nonoverlapping rotational lines have been carried out for CO using a dispersion formula for the line-shape representation. Use of the best available experimental data on integrated absorption and rotational line-width leads to calculated emissivities which are in excellent agreement with extrapolated empirical data published by Hottel and Ullrich. In particular, the theoretical dependence of emissivity on optical density, for small optical densities at 300°K, has been shown to follow experimental observations with satisfactory precision.

For small optical densities the calculated emissivity is found to be proportional to the square root of the assumed rotational line-width, thus emphasizing the need for accurate line-width determinations at elevated temperatures. The limits of validity of the treatment utilizing nonoverlapping rotational lines are defined by examining overlapping between adjacent weak and strong rotational lines.

The calculation of emissivities can be simplified by the use of approximate treatments. Thus absolute values of the emissivity can be predicted within 10 percent by utilizing a treatment for nonoverlapping, equally spaced, and equally intense lines, together with empirically determined values for the equivalent mean integrated absorption of the rotational lines of CO. A better analytic solution, which does not involve the assumptions of equal spacing and equal intensity of the rotational lines, has been obtained by utilizing asymptotic relations for large values of modified Bessel functions.
The Electric Field in Diodes and the Transit Time of Electrons as Functions of Current
Authors: Copeland Paul L. , Eggenberger Delbert N.
Published: April 2005

Equations, applicable to all the most simple symmetries, are developed as approximate solutions of the related problems of potential distribution and transit time in diodes as functions of current. For the case of coaxial cylinders, calculations based on these equations have been made. Although these calculations fail to confirm Ivey's suggestion that the ratio of the field at the cathode with any degree of space-charge to that in the absence of space-charge is a universal function of the ratio of the actual current to the space-charge-limited current, they suggest that the function varies slowly as the geometry is changed. Thus small corrections to the function developed for parallel planes suffice to give a solution of high accuracy for any ratio of anode to cathode radius. Functions, applicable to electrons moving between coaxial cylinders, are tabulated to facilitate calculations of off-cathode field, off-anode field, transit time, and the potential distribution for any fraction of the space-charge-limited current.
Measurement of the DC Resistance of Selenium and Copper Oxide Rectifiers below Room Temperature
Authors: Grimes D. M. , Legvold Sam
Published: April 2005

Values of the steady-state dc resistance of copper oxide and selenium rectifiers as a function of temperature from 79°K to 300°K have been obtained. The maximum potentials used were 2.5 volts in the forward direction and 6.0 volts in the backward direction.

It was found that a plot of the logarithm of the resistance against the reciprocal of the temperature was nearly linear for all except the reverse direction of the selenium rectifier. For the latter case at 6.0 volts the resistance went through a minimum below 200°K.
Analysis of Certain Errors in the X-Ray Reflection Method for the Quantitative Determination of Preferred Orientations
Authors: Chernock Warren P. , Beck Paul A.
Published: April 2005

The reflection method for quantitative determination of pole figures, proposed by Schulz, proved to be limited with respect to the range of tilting angles in which satisfactory results can be obtained. It is shown that the previously unexplained decrease in the diffracted intensity with increasing tilting angle for specimens with random orientation distribution can be accounted for on the basis of an elementary analysis of defocusing effects. Experimental evidence is presented to show that variation of the receiving slit length and of the main slit width has the effect predicted by the analysis. The importance of accurate specimen alignment is discussed, and a satisfactory alignment check procedure is described.
Effect of Thermal-Velocity Spread on the Noise Figure in Traveling-Wave Tubes
Authors: Parzen Philip
Published: April 2005

Effects of thermal-velocity spread on the noise figure of a traveling-wave tube have been computed by extending a method of Hahn. To accomplish this, it has been necessary to work out a new theory for the diode-drift tube and traveling-wave tube that includes the effect of the thermal-velocity spread at very high frequencies. Some computations are given for conditions met in practice.
Multiple Scattering of Radiation by an Arbitrary Planar Configuration of Parallel Cylinders and by Two Parallel Cylinders
Authors: Twersky Victor
Published: April 2005

The formal solution for the scattering of a plane wave by an arbitrary configuration of parallel cylinders previously presented is specialized to consider the case where all the axes lie in the same plane. The scattered wave is expressed as an infinite sum of orders of scattering, the first order being the usual single scattering approximation. It is shown that the far field form of the multiply scattered orders is symmetrical with respect to the plane of the configuration for minimum spacing large compared to wavelength. Hence, for the analogous configuration of bosses on a perfectly conducting plane, departures from the predictions of single scattering theory should occur primarily for the component polarized perpendicular to the elements. The problem of two cylinders is considered in detail, the multiply scattered orders being summed explicitly subject to the above conditions. Approximate solutions for radii very small compared to wavelength are derived, the wavelengths for which the effects of multiple scattering are greatest are investigated, and a criterion for the use of the single scattering hypothesis presented. Solutions for two bosses and a single cylinder parallel to a nonabsorbing plane are also stated. Both the electromagnetic and acoustic cases are treated.
Focusing in a Beta-Ray Spectrometer with Tilted Sources
Authors: Fowler C. M. , Domotor P.
Published: April 2005

Formulas are given which express the theoretical line shape obtained in a semicircular beta-ray spectrometer. The sources are taken to be plane, uniform, and isotropic. Line shapes of a monoenergetic electron group are studied as a function of the angle between source and focal planes. The treatment given applies only to the electrons emerging perpendicular to the magnetic field. However, conditions simulating the requirements for qualitative applicability of the formulas may be obtained practically by slitting out electrons having appreciable momentum components along the field. Two figures are given which illustrate line shapes for various spectrometer geometries.
Metallurgical Applications of X-Ray Fluorescent Analysis
Authors: Koh P. K. , Caugherty Betty
Published: April 2005

Techniques are described for fluorescent analysis using an x-ray Geiger counter goniometer. Consideration is given to the influence of potential variations, specimen preparation, and thickness of the diffracting crystal.

The observed intensity of fluorescent radiation from a number of common commercially pure metallic elements was compared under a constant primary radiation that can be closely maintained in practice.

Intensities of fluorescent spectra were measured on constituents of Fe-Ni, Fe-Cr, and Fe-Ni-Cr alloys. Calibration curves correlating line intensity with weight percentage are included for binary Fe-Ni and Fe-Cr alloys.

The thickness beyond which the fluorescent intensity becomes constant has been determined for pure iron, nickel, and chromium. Up to the above thickness for each element an empirical plot of fluorescent intensity against thickness of layer has been established. These empirical plots can be applied to measure the thickness of very thin coatings.

Illustrations are given indicating the applications of the fluorescent analytical technique to the study of oxidation and diffusion processes in metallic systems.

An aluminum holder is used for analyzing small quantities of powder derived from chemical or electrolytic extraction of certain phases from alloys. Fluorescent analysis on the extracted phase supplements the diffraction data when a wide solid solubility exists.
Structure of Oxide Replicas for Electron Microscopy
Authors: Yamaguchi Shigeto
Published: April 2005

The structure of oxide films, which could be used as replicas for electron microscopy, was investigated here. In order to obtain a replica of the metal surface using the oxide film formed on it and isolated from it, the oxide crystals composing the film must be oriented relative to the orientation of the substrate face. The oxide crystals formed on metal, whose atom distances coincided with those of the substrate crystal, could compose a replicating film of the specimen surface. This oxide film did not curl nor expand upon removal from the substrate.
Temperature Dependence of Young's Modulus and Internal Friction of Single Crystals of Beta-Brass
Authors: Artman Robert A.
Published: April 2005

The temperature variation of Young's modulus of beta-brass single crystals of 55 atomic percent copper has been determined. Comparison is made with previously reported results.

Internal friction has been measured at 21 and 42 kilocycles per second at room temperature and as a function of temperature to slightly above the complete disappearance of order. The room temperature decrement is for all crystals of the order of 10−4 and mainly independent of amplitude of oscillation. The decrement as a function of temperature shows a ``relaxation peak.'' Zener's theory for alpha-brass is found to apply and the source of the relaxation is preferential orientation of pair axes of solute atoms in adjacent cells. The heat of activation is about 20×103 calories per mole. The relaxation peak is shown to be characteristic of the disordered state. There seems to be no relaxation phenomenon present in the ordered state.

The effect of precipitation of the alpha-phase on Young's modulus and the internal friction has been found negligible unless a large amount of precipitation occurs.
Oxygen-Free Single Crystals of Lead Telluride, Selenide, and Sulfide
Authors: Lawson W. D.
Published: April 2005

Anomalies in the type of conductivity of artificially prepared crystals of lead selenide and lead telluride have been found to be the result of the presence of oxygen. A method has been developed for eliminating oxygen from the specimens by melting the elements into the crucible in an atmosphere of hydrogen. It has also been found possible to grow single crystals of lead sulfide when oxygen is eliminated from the specimen in this way.
The Computation of Dielectric Constants
Authors: Redheffer R. M. , Wildman R. C. , O'Gorman V.
Published: April 2005

We consider the shorted-line method as applied to general samples, not restricted to quarter-wave, half-wave, thin, or low loss. The complex dielectric constant can be obtained by combination of two measurements, the sample being followed by short and open circuit, respectively. The equation is simple, nontranscendental, and unambiguous (Eqs. (5), (11), (19), (22)). It lends itself to complete graphical representation (Table I, Fig. 2). When only a single measurement is made, as in conventional practice, a change of variable leads to great simplification of detail ((14), (15), (16), Figs. 2, 3, 4). With due regard to the nature and magnitude of experimental errors, we analyze the conditions for optimum graphical representation, and give a reasoned determination of scale ranges. Large scale curves have been constructed, but only reductions are given here.
The Initiation of Electrical Breakdown in Vacuum
Authors: Cranberg Lawrence
Published: April 2005

The hypothesis is suggested that initiation of high voltage breakdown in vacuum is due to traversal of the high voltage gap by a clump of loosely adhering material. The implication of this hypothesis for uniform-field gaps is that the breakdown voltage is proportional to the square root of the gap length. A summary the literature is presented which supports this conclusion for a range of voltages from 20 kilovolts to 7 megavolts, and for a range of gap distance from 0.2 mm to 6 meters. Additional qualitative evidence is presented which tends to support the proposed hypothesis.
Experimental Verification of the Theory of Jet Formation by Charges with Lined Conical Cavities
Authors: Eichelberger R. J. , Pugh Emerson M.
Published: April 2005

Experimental evidence is presented that verifies the assumptions and conclusions of the article, ``Theory of Jet Formation by Charges with Lined Conical Cavities,'' by Pugh, Eichelberger, and Rostoker. A graphical method of predicting the shape of the jet and slug at every instant is presented.
Arcing at Electrical Contacts on Closure. Part III. Development of an Arc
Authors: Germer L. H. , Smith J. L.
Published: April 2005

A description is given of a system made up of experimental electrodes and an oscilloscope by means of which the potential across the electrodes can be recorded with a time resolution of about 10−9 sec and a potential sensitivity of 1-trace width per volt. The closure of the electrodes to produce a short arc is synchronized with the oscilloscope sweep so that the beginning of the arc is photographed.

As an arc starts the potential across the electrodes decreases more or less gradually from the applied voltage to a steady value characteristic of the metal of the electrodes. The course of this change is extremely variable as is also the time over which the change is spread. The average value of the time appears to vary with circuit inductance and with the nature of the electrode surfaces. For inactive silver surfaces and an inductance of 0.10 μh the average value of the time is about 0.007 μsec, and for active surfaces and the same inductance 0.011 μsec. For active surfaces and an inductance of 5 μh the average value of the time is 0.02 μsec.

The electrode separation at which an arc strikes is determined from the oscilloscope traces and from a correction for the height of the mound of metal thrown up by the arc. For active silver electrodes the average separation (at 40 or 45 volts) corresponds to a gross electric field of 0.8×106 volts/cm, and for inactive silver electrodes to a field of 2.3×106 volts/cm. These are probably better values than earlier measurements of these fields. There has not yet been any success in interpreting these phenomena in terms of fundamental processes.
Instabilities in the Smooth-Anode Cylindrical Magnetron
Authors: Harris Lawrence A.
Published: April 2005

A magnetically focused space-charge cloud of the type found in the smooth-anode magnetron is examined to determine whether a perturbation of the equilibrium condition will grow. A field analysis is carried out in which radial admittances are matched at the edge of the cloud. The solutions for the characteristic frequencies are complex, indicating that the disturbance grows with time. These instabilities occur at multiples of the Larmor frequency.

The solutions indicate that electrons oscillate with increasing swings, a process which absorbs energy. Instability therefore gives rise to some anode current even when the tube is ``cut off'' though rf power is not made available by the process.
Heat Conduction in Alloys at Low Temperatures
Authors: Estermann I. , Zimmerman J. E.
Published: April 2005

With a view to studying the mechanism of heat conduction in low conductivity alloys, a method has been devised by which the thermal conductivity of relatively small samples (⅛- to ¼-inch diameter, 1 to 2 inches long) of various materials can be measured in the temperature regions obtainable with liquid nitrogen, liquid hydrogen, and liquid helium.

Preliminary measurements on several commercial alloys (monel, inconel, and stainless steel) gave Wiedemann-Franz ratios several times greater than the theoretical value of 2.45×10−8 watt-ohm/deg2, the deviation being greater for annealed than for cold-worked specimens. This has been interpreted in terms of appreciable lattice conduction of heat in these alloys.

Following these results, samples of an alloy of 90 percent copper 10 percent nickel were prepared with varying amounts of cold-work and with different grain sizes. Results with these samples were similar to those obtained with monel and inconel and confirm the hypothesis of lattice conduction. They also give a qualitative indication of the effectiveness of cold-work in limiting the lattice conduction of heat.
Drift Velocity of Electrons in Argon and Argon Mixtures
Authors: Kirshner J. M. , Toffolo D. S.
Published: April 2005

Since argon is prepared by fractional distillation from liquid air, the greatest impurity found in it is nitrogen whose boiling point lies close to that of argon. For this reason it is believed that some of the previous measurements on supposedly pure argon were actually made on nitrogen contaminated argon. By adding controlled amounts of nitrogen to pure argon, the drift velocity curves of various authors can be duplicated.
On the Kinetics of Ordering in Ni3Mn
Authors: Aronin Lewis R.
Published: April 2005

Kinetic behavior in specimens initially cooled through the ordering range is studied as a function of subsequent prolonged isothermal heat treatments. Room temperature measurement of electrical resistivity and saturation induction give evidence substantiating existence of ordered domains. Anomalous kinetic behavior at intermediate ordering temperatures is interpreted as due to growth of antiphase nuclei. Equilibrium values attainable at low ordering temperatures and multi-valued correspondence between resistivity and magnetic data exhibit dependence upon extent of domain growth.
Incandescent Lamp Bulbs in Voltage Stabilizers
Authors: Cunningham W. J.
Published: April 2005

High vacuum incandescent lamp bulbs have been used as sensitive elements in stabilizing systems for ac power sources. Such a lamp is a nonlinear element and accordingly introduces distortion components into the stabilizer circuit. An analysis of the operation of the lamp is given, based on rather simple assumptions. This analysis allows the prediction of the distortion for given operating conditions and shows the effects of changes in frequency and current.
Electrical Noise from Instrument Cables Subjected to Shock and Vibration
Authors: Perls Thomas A.
Published: April 2005

Existing information on the reduction of spurious signals from instrument cables is reviewed. A tentative theory is formulated to account for the known data. Subsequent experiments confirm this theory and allow the formulation of a detailed mechanism of noise generation in cables. The noise may be eliminated for practical purposes (reduced by a factor of 500 or more in some cases) by having continuous electrical conduction between both surfaces of the insulating dielectric and the adjacent conductors. A simple procedure is outlined to make short lengths of this cable for laboratory use, and an industrially applicable method is suggested. There appears to be no limit on how small the diameter of such cables could be made.
Methods of Measuring the Properties of Ionized Gases at High Frequencies. I. Measurements of Q
Authors: Brown Sanborn C. , Rose David J.
Published: April 2005

Experimental methods are given for determining the Q of both high and low Q resonant cavities at microwave frequencies. The emphasis is placed on the practical measurements necessary in determining the properties of ionized gases in the 3- and 10-centimeter wavelength range.
The Admittance of a Diode with a Retarding Field
Authors: Freeman J. J.
Published: April 2005

The contribution of space charge to the admittance of a diode with a retarding field is calculated by computing the instantaneous electronic current induced in an external circuit. A discussion of the variation of the susceptance of a typical diode with frequency is given.
Measurements of the Physical Properties of Active Nitrogen
Authors: Benson James M.
Published: April 2005

Measurements were made of the heat released during decay of the afterglow, the viscosity, and the free electron density in active nitrogen. Calorimeter measurements of the heat released during decay of the afterglow amounted to as much as 22.3 calories per gram of the gas, corresponding to an excitation of one part in 350 of the molecules present to an energy of 9.6 electron volts. The viscosity of the active nitrogen was found to be the same as that of the unactivated nitrogen within one-half of one percent. Ionization in a stream of active nitrogen is shown to be incidental rather than essential to the production of the Lewis-Rayleigh afterglow. Microwave measurements of the free electron density in a stream of active nitrogen indicated one free electron for each 2.3×108 molecules in the stream. Contrary to Mitra's theory, probes in the stream were found to respond to carriers of negative sign rather than positive ions. Space discharges in an expanding stream of active nitrogen are attributed to free electrons moving with the stream. In the use of active nitrogen for studies of low density flow, by observation of the afterglow, disturbing effects will occur because of heating and ionization, but the disturbances appear not to be so large as to interfere with its use.
Experimental Verification of Source Size Theory for the Mach-Zehnder Interferometer
Authors: Kahl G. D. , Bennett F. D.
Published: April 2005

The simplified theory of the Mach-Zehnder interferometer developed by the latter author is tested. The reduction in the visibility of fringes formed by the interferometer due to an extended area light source is shown experimentally. This reduction is shown to be caused by the superposition of two separate effects which are characteristic of the two angular coordinates of the unit vector pointing from the center of the collimating lens toward each point in the plane of the area-type source. The relation of each of the effects to that coordinate characterizing it is demonstrated experimentally to agree with the theory. The result of combining these two effects from all of the points of an area-type source is experimentally seen to cause the ``focusing'' of the visible fringes and to limit them to a finite region of the intersecting beams determined by the size and shape of the source.
The Dielectric Properties of Ice and Snow at 3.2 Centimeters
Authors: Cumming W. A.
Published: April 2005

A knowledge of the permittivity and loss tangent of snow and ice is essential in studying both radar echoes from snow-covered terrain and the attenuation of microwave energy through snowstorms. To provide this information, a program was carried out at the National Research Council of Canada to measure the permittivity and loss tangent of ice and snow, and also to determine the reflection coefficients of snow-covered surfaces, at a wavelength of 3.2 centimeters.

As a result of these investigations values have been obtained for the permittivity and loss tangent of snow of varying density, temperature, and water content. Theoretical values of the reflection coefficients of snow-covered surfaces, calculated from these data, are compared with the values obtained from the direct measurement of reflections from natural snow surfaces.
The Electrical Resistance of Binary Metallic Mixtures
Authors: Landauer Rolf
Published: April 2005

The existing theories of the resistivity of mixtures assume regular arrangements of the two components, rather than random mixtures. A theory for a random mixture is given, based on the assumption that each crystal acts as if surrounded by a homogeneous medium whose properties are those of the mixture. Comparisons with experiment are made. The experimental data that have been examined fall roughly into two classes. One class consists of mixtures, where the variation of resistivity with composition disagrees violently with this theory, making it clear that the assumptions made are completely inapplicable. The remaining class consists of mixtures which generally agree well with the theory.
The Use of Radioactive Isotopes in a Study of Evaporation from Thermionic Cathodes
Authors: Leverton W. F. , Shepherd W. G.
Published: April 2005

Radioactive tracers have been used in a study of evaporation of the alkaline earths, barium, strontium, and calcium from oxide coatings on passive nickel bases. Several percent of the total cathode Ba, Sr, and Ca leave a triple oxide cathode during processing and aging. The rates of transfer of these elements from the cathode during life tests of 118 hours at true cathode temperatures from 1175 to 1279°K obey equations of the form, logW=A−(B/T), where W is the rate of transfer in g/cm2/sec, T is the absolute temperature of the cathode, A and B are constants. The transfer of Ba from a BaO cathode obeys a similar law. The mass of Ba transferred in 118 hours of life from a triple oxide cathode at 1123°K true as 2.9×10−6g/cm2, and from a BaO cathode 1.4×10−5g/cm2. The masses of Sr and Ca transferred from a triple oxide cathode at the same temperature were 2.1×10−7 and 1.2×10−8g/cm2, respectively.

Bombardment of the anode by an electron beam during life tests decreased the quantity of Sr observed on the anode. Anode current densities of 5 to 10 ma/cm2 at electron energies of approximately 100 volts produced a fiftyfold reduction in the quantity of Sr on the anode. Experiments indicated that this decrease was not due to heating of the anode. The quantity of Ba deposited on the anode was not decreased by electron bombardment.

The very considerable transfer of Ba from the cathode during processing was greatly reduced by breaking down the carbonates and high temperature flashing the cathodes in the presence of a few mm pressure of argon gas.
The Reliability of Internal Standards for Calibrating Electron Microscopes
Authors: Watson John H. L. , Grube William L.
Published: April 2005

Conclusions important to the practice of electron microscopy are drawn from experiments. Particles of Dow Latex 580G are unstable under electron beams and best micrographed at low intensity. Two different effects of radiation are noted. At low intensity the mean diameter in the present work was 2890A, the standard deviation of the spherical particles was 60A. 580G is improved as an internal standard if recalibrated by some other suitable standard (not the reverse) each time before use. Fresh replicas of diffraction gratings are still the most practical standards, reproducing gratings to two percent. By an independent optical method (spectroscopy) one can measure the grating space of a replica when it is on an eighth-inch, 200-mesh specimen screen under exact calibration conditions for electron microscopes. Specific replicas, and from them specific preparations of 580G are checked easily and accurately by the spectroscopic method. Replica age or other factors which may affect accurate reproduction of an original grating are then no longer important in calibration. A reliable method of calibration using 580G is suggested.
X-Ray Diffraction by Face-Centered Cubic Crystals with Deformation Faults
Authors: Paterson M. S.
Published: April 2005

In view of the recent interest in the introduction of stacking faults in crystals during plastic deformation, the x-ray diffraction effects have been calculated for face-centered cubic crystals with deformation faults (as distinct from growth faults, the expressions for which are given in an appendix for comparison). Explicit expressions are derived for the reciprocal lattice intensity distribution, and it is shown how the intensity of faulting can be determined from measurements on the breadths of the reciprocal lattice streaks or the displacements of their peaks. It is then shown how these effects will be revealed in the x-ray powder pattern and some practical aspects are discussed.
A Mathematical Analysis of a Dielectric Amplifier
Authors: Pipes Louis A.
Published: April 2005

This paper presents a mathematical analysis of the fundamental circuit on which the operation of dielectric amplifiers depends. The analysis is based on the assumption that the effective hysteresis curve of the amplifier's dielectric material may be represented by a hyperbolic sine function. The case of resistive load is analyzed and expressions for the steady-state input and output currents are calculated. From a consideration of the transient response of the amplifier, an estimate of its time constant is obtained.
A Point Focusing X-Ray Monochromator for the Study of Low Angle Diffraction
Authors: Shenfil Leon , Danielson Warren E. , DuMond Jesse W. M.
Published: April 2005

A point focusing x-ray monochromator was designed and constructed for low angle scattering studies. The anastigmatic point focus is achieved by means of two cylindrically bent quartz crystals whose focal circles are mutually perpendicular. The beam, emanating from the copper target of an x-ray tube, is reflected in succession, first from the crystal defining the horizontal focal circle, and second from the crystal defining the vertical focal circle following which it comes to a monochromatic point focus of wavelength 1.537A (CuKα1). The sample to be studied is placed between the second crystal and the point focus, and the scattered beam is detected by means of a photographic film placed at the point focus, at right angles to the undeviated beam, the latter being suppressed by means of an absorber, or allowed to pass through a hole in the film.

Mathematical analysis, in which a ray was traced through the two-crystal system, revealed correctly the shape and size of the point focus, and the possibility of reducing the latter in size by stopping down the beam emerging from the target.
Latex Particle Size Determination Using Diffraction Peaks Obtained with the Point Focusing X-Ray Monochromator
Authors: Danielson Warren E. , Shenfil Leon , DuMond Jesse W. M.
Published: April 2005

We describe the results of experiments we have made, using the point focusing monochromator as the primary tool, to determine the particle size of latex spheres. The suitability of the instrument for this particular study is described and the experimental data obtained are tabulated, these data coming from our experiments with three physically distinct samples of Dow latex. We attempt to make a critical interpretation of the data by considering separately several possible space arrangements which the latex spheres might assume when the water, which is initially the suspending fluid, is evaporated. Corrections for the finite size and shape of the ``point'' focus are described. The absence of a significant difference in the mean particle sizes of the three samples considered is established.

The data from all three samples is combined to yield a mean particle diameter under an external pressure of one atmosphere of 2687.5A with a statistical standard deviation of 1.2A and a fixed (systematic) error estimated to be not more than ±7A.
The Decay and Recovery of the Pulsed Emission of Oxide-Coated Cathodes
Authors: Matheson R. M. , Nergaard L. S.
Published: April 2005

The decay and recovery of the pulsed emission of cathodes consisting of BaO on nickel are studied. The emission of the cathodes is measured in diodes of cylindrical geometry having water-cooled copper anodes spaced 0.019 inch from the cathode.

Most of the diodes show a decay of anode current when first put in pulse operation. Decays of 2–50 percent are observed during 150-μs pulses. The decay tends to disappear when the tubes are aged under pulse conditions. The peak current is a linearly decreasing function of the logarithm of the duty cycle, even when there is no perceptible decay during the pulses. The rate of decrease is independent of the pulse repetition rate and decreases with cathode temperature.

Current-voltage characteristics during the pulse and recovery periods are obtained by short sampling pulses. A comparison of these characteristics with computed ideal characteristics does not discriminate unambiguously between a variation of emission and a variation of internal cathode impedance as a source of current decay. Studies to separate the contributions of these effects are in progress.
Electromagnetic Back-Scattering from Cylindrical Wires
Authors: Tai C. T.
Published: April 2005

The problem of electromagnetic back-scattering or radar response from cylindrical wires has been investigated using a variational method. The relation between this method and the induced emf method is discussed. To demonstrate the flexibility of the variational calculation different trial functions have been used to determine the numerical values of the back-scattering cross section for the case of broadside incidence. The boundary condition regarding the currents at the ends of the wire is also carefully examined.
A Treatment of the Viscosity of Concentrated Suspensions
Authors: Simha Robert
Published: April 2005

In current theories of the concentration dependence the solute molecules are treated as point centers of disturbance. The finite size that produces a shielding of two interacting particles in the presence of intervening ones reduces the interaction calculated in the point approximation and thus reduces the discrepancy between experiment and theory. An approximate treatment for a spherical solute based on the cage model, and hence more adequate at high concentrations, is presented. It operates with a spherical enclosure around a central particle. The position of this shell reflects the relative extent to which particles beyond nearest neighbors can hydrodynamically interact with the central molecule. Thus, a parameter f appears in the theory which increases slowly with concentration and approaches a limit corresponding to the coincidence of the shell with the wall of the nearest neighbor cage at high concentrations. In the framework of the present theory, f must be regarded as a semiempirical quantity. The hydrodynamic problem can be handled rigorously. The relative viscosity calculated is in satisfactory agreement over a range of concentrations with empirical expressions successfully applied to pertinent systems. The initial value of f derived from the observed coefficient of the quadratic term is also reasonable.