bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reflecting Surface to Simulate an Infinite Conducting Plane
Authors: Raff S. J. 
Published: April 2005

In measuring small microwave reflections back to the transmitting antenna, a finite reflecting surface which simulates the reflection of an infinite plane is desirable for calibration. Treating a flat reflecting surface by the methods of physical optics, the reflection can be represented as the sum of the contributions of Fresnel zones. Owing to the slow rate of decrease of reflections from successive zones, the shape of the surface has considerable effect on the accuracy with which its reflection simulates that of an infinite plane.
By means of the calculus of variations, an optimum shape is designed which, for a given antenna pattern, reflector size, and range of antenna to reflector distances, will give the closest simulation of the reflection of an infinite plane. Such an optimum surface of 23 wavelengths extreme dimensions has been constructed for use at 25 wavelengths from a dipole antenna. The maximum simulation error was calculated to be ±3 percent. The reflection from this surface has been measured and is within ±4 percent of that of an infinite plane over the range of 15 to 35 wavelengths from the antenna.
Recovery of Selenium Rectifiers after a Voltage Pulse in the Blocking Direction
Authors: Lehovec K. 
Published: April 2005

The capacitance of selenium rectifiers which have been subjected to a voltage pulse in the blocking direction is found to be temporarily decreased after the pulse has ceased. The recovery of the changed capacity to its original value is investigated as a function of pulse height, pulse duration, and temperature. The speed of the recovery can be greatly increased by illumination (through a transparent electrode) with light of the same spectral range which is effective in causing the photoeffect in selenium photovoltaic cells. This is an indication that the phenomenon is of electronic and not of ionic nature.
As an explanation it is proposed that an electric pulse in blocking direction removes electrons from elevated energy states in the electrode-selenium boundary. Recovery occurs because electrons are returned to the elevated energy states by thermal agitation and also by photoelectric effect if the selenium is illuminated.
Arcing at Electrical Contacts on Closure. Part I. Dependence upon Surface Conditions and Circuit Parameters
Authors: Germer L. H. 
Published: April 2005

In a low voltage circuit the occurrence of an arc between approaching electrodes is dependent upon the nature of the surfaces and upon the circuit inductance. For carbon surfaces, or noble metal surfaces which have been ``activated'' by operation in various organic vapors resulting in a carbonaceous layer, the limiting circuit inductance is somewhat above 10−3h, which is much higher than the limiting inductance for clean noble metal surfaces. This activation by organic vapors occurs for noble metals only and for certain vapors; for example, benzene derivatives. In the case of silver and benzene vapor, it has been shown that the activation is due to adsorption of benzene onto a greasy surface layer and its decomposition there by the heat of subsequent closures. A metal surface, which has been activated by organic vapor, remains active indefinitely if there is no arcing at the surfaces; but with continued operation and accompanying arcing, the activating material is burned away, and the surface returns to the inactive condition if no activating vapor is supplied.
Arc voltages, which are independent of current and of ambient gas, as far as tested, have been measured for a number of metals and for carbon; the arc voltage for carbon is quite erratic in the range between 20 and 30 volts, but for each of a number of metals the arc voltage is steady.
Arcing at noble metal surfaces, similar to that induced by carbonaceous material from organic vapors, can be produced also by insulating particles or insulating films. The active condition gradually disappears with continued arcing, unless there is a steady supply of insulating material to the surface.
The minimum arc current has been measured to be 0.6 amp for active silver and for carbon, and 0.03 amp for inactive silver. These are the currents at which an established arc is extinguished.
Pulse-Annealing for the Study of Relaxation Processes in Solids
Authors: Parkins W. E. , Dienes G. J. , Brown F. W. 
Published: April 2005

A new experimental technique is presented for studying rate processes in solids. The method, termed ``pulse-annealing,'' involves direct heating of a very small sample to a chosen annealing temperature for a short period, followed by rapid cooling to some fixed temperature for an in-place physical property measurement. The method is a very flexible one, as the above cycle may be repeated to obtain any desired time-temperature history. General experimental techniques are described and specific application to graphite and metals noted.
The annealing process is examined theoretically. A method is described for deriving the activation energy of the fundamental relaxation process from the isothermal annealing curves of a physical property, the physical property being used as an index of the annealing process. It is shown that the activation energy is derivable without knowledge of the relation between the measured physical property and the fundamental kinetic variable. For further kinetic analysis (determination of rate constants and orders of reaction), however, it is necessary to know this relation. The analysis of isothermal and tempering experiments is compared.
Axially Symmetric Systems for Generating and Measuring Magnetic Fields. Part I
Authors: Garrett Milan Wayne 
Published: April 2005

This is Part I of a systematic discussion of axially symmetric magnetic fields, both central and remote from the origin, search coils reporting the field or gradient at a single point, and mutual inductances. Here the central uniformity of symmetrical fields and gradients is analyzed by zonal harmonic expansion. Laplace's equation and symmetry restrict these fields to a few types, regardless of the detailed geometry of the generating system. Universal error-contour maps are derived for the central field or gradient in systems having errors of second, fourth, or sixth order, and for hybrid types combining second and fourth. One hybrid has an oblate error field suitable for cloud-chamber and orbital applications.
Source systems include circular filaments, cylindrical or plane circular current sheets, and thick solenoids of rectangular or notched section. Each type of source may be designed to produce any of the field patterns. To this end, source constants derived for the particular source type are combined into a set of over-all coefficients that express the field constants for a complete system. Rapid methods are given for computing the source constants and from them all the field derivatives, using recurrence relations or tables of Legendre functions. In particular, computing time for thick-solenoid fields or gradients is greatly reduced, using a new series with a recurrence formula. The text includes tabular aids and reference formulas, and discusses the rate of convergence of series for central and remote fields, and for mutual inductances.
Special systems briefly described include several infinite series of systems like that which starts with Ampere's loop, the Helm-holtz pair, and Maxwell's three-loop system. These have integral numbers of circular filaments from two to infinity. More practical are the thin solenoids. Those that produce a fourth-order (Helm-holtz) field by omission of central turns are fully tabulated for all lengths. A short solenoid with double-wound ends and sixth-order error may realize greater uniformity in actual practice than any previously described system. Still greater (theoretical) uniformity is achieved in two eighth-order combinations of a short solenoid with a loop pair; these are described and depicted, with error limits.
The Offset Wave-Guide Junction as a Reactive Element
Authors: Smullin L. D. , Glass W. G. 
Published: April 2005

A new type of wave-guide circuit element has been described that has a number of desirable electrical and mechanical properties. These include ease and accuracy of adjustment, and simple analytical expressions for some of the more important properties.
The capacitive junction allows the practical construction of capacitively coupled resonant cavities. Such cavities have a relatively constant band width over their tuning range, as compared with the more commonly used inductively coupled cavities.
X-Ray Absorption in a Crystal Set at the Bragg Angle
Authors: Campbell H. N. 
Published: April 2005

Whereas extinction effects would be expected to decrease the x-ray transmission through a crystal when it is set at a reflecting angle, it is shown experimentally that in many cases the transmission increases at the Bragg angle.
This is believed to be due to the fact that the decrease in the effective absorption coefficient overshadows the losses due to reflection.
A reconsideration of Darwin's presentation of extinction allowing for variable μ shows that the transmission may increase or decrease depending on the values of μ and p. Thus the earlier observations of Bragg and co-workers are reconciled with the observations reported here.
The importance, to crystal structure workers, of determining how μ varies with direction in periodic media is obvious.
Direct Determination of the Flow Curves of Non-Newtonian Fluids
Authors: Krieger Irvin M. , Maron Samuel H. 
Published: April 2005

A method is proposed for the direct determination of the rate of shear-shearing stress curve of a fluid from data obtained in concentric cylinder viscometers. The method involves the use of a viscometer in which the ratio of outer to inner cylinder radii can be varied. It is further shown that to a close approximation two such radius ratios are sufficient to define the flow curve.
Data for two non-Newtonian systems are presented to show that the proposed method is valid.
The Temperature Dependence of Viscosity for Water and Mercury
Authors: Kampmeyer Preston M. 
Published: April 2005

Smoothed values for the viscosities of water and mercury, as reported in the literature, show surprisingly large percentage deviations from the experimental data. Because water is frequently used as the calibrating fluid in viscometry, it was of interest to apply expressions, suggested by the theory of Eyring, for smoothing experimental data. It was of further interest to apply the Arrhenius expression for the variation of viscosity with temperature to the data for both water and mercury and to compare the closeness of fit with that obtained by the use of the aforementioned expressions. As judged by the Gaussian criterion of fit, an expression suggested by the Eyring theory provides smoothed values for the viscosities of both water and mercury which are believed to be more reliable than those in common use. This is especially true for the viscosity of water, for which relative viscosity data were first smoothed and then pinned to the recent value of 10.019±0.003 millipoises at 20°C as reported by Swindells and Coe.
From other empirical equations relating densities and energies of vaporization to temperature, equations are derived for expressing the activation energies for viscous flow as a function of temperature.
Electrical Conductivity and Thermoelectric Power of (BaSr)O and BaO
Authors: Young J. R. 
Published: April 2005

A study has been made of the thermoelectric power, the electrical conductivity, and the thermionic emission of (BaSr)O and BaO at different states of activation and on different base metals over a temperature range of 1100°K to 300°K. A plot of the logarithm of the conductivity vs reciprocal temperature showed two straight line regions. The temperature dependence of the thermionic emission was found to be the same as the temperature dependence of the conductivity in the temperature range 700°K to 1100°K. The slope of a plot of the thermoelectric power vs reciprocal temperature was also similar to the thermionic work function and the conductivity activation energy in this temperature range.
The thermoelectric power varied with temperature from a value of about 2.0 mv/° at 1100°K, increasing to about 2.5 mv/° at 800°K, reducing to between 1.0 and 0.5 mv/° at about 500°K, and remaining practically constant or increasing slowly at still lower temperatures. In all thermoelectric power measurements the hot junction was positive indicating negative charge carriers.
The simple semiconductor theory does not adequately account for these results which seem to be in good agreement with the pore conduction hypothesis.
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.
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.
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.
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.
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.
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.
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.
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.