摘要:

Calculations show that the effect of increasing the resistivity of the wires is to decrease the amplitude of the reflection coefficient and the phase of the transmission coefficient. The sign of the changes in the amplitude of the transmission coefficient and the phase of the reflection coefficient depends upon the amplitude of the reflection coefficient of a geometrically similar grating having no resistance. A numerical example for a typical grating is worked out and several charts are supplied for convenience in computing.

ISSN:0021-8979    

DOI:10.1063/1.1702264

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Silicon monoxide replicas of the surfaces of air‐dried films are shown which were cast from a Saran latex containing various amounts of plasticizer. It can be observed that the poor films are composed of discrete individual particles while in a continuous transparent film the particles have coalesced into a polymeric mass. Replicas of surfaces of films are shown which were produced from different types of synthetic latices before and after they had been plasticized.

ISSN:0021-8979    

DOI:10.1063/1.1702265

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

For resonant sections of a transmission line consisting of parallel silver rods extending vertically above a metal ground plane, the resonance curves of input admittance as a function of line length have been drawn by a synchronized recording meter apparatus, and the effective total resistance of each resonant line calculated. This has been done for frequencies between 300 Mcps and 1400 Mcps, for resonant line lengths up to several wavelengths, for line sections with both open‐circuit and short‐circuit termination at the top, and in each case with and without a large metal pipe shielding the test line. Radiation resistance is obtained as the difference between the resistance calculations for any one resonant line section unshielded and shielded.With a probable error of about 5 percent the radiation resistance is found to be proportional to the square of the frequency, and to be independent of line length and of whether the top termination is an open circuit or a short circuit. The absolute values agree reasonably well with the theory of Storer and King [Proc. Inst. Radio Engrs.39, 1408 (1951)] and disagree conclusively with some predictions of earlier theories.

ISSN:0021-8979    

DOI:10.1063/1.1702266

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The diffusion equation for thermal neutrons in a pile with finite sides and having a three‐dimensional lattice structure of fissionable material and moderator is solved to the first three orders by an expansion in spherical harmonics. This solution is used to calculate the difference in thermal utilizations of a pile of infinite extent and one with finite sides. From this difference is calculated an accurate expression, Eq. (24), for the diffusion length in a pile having a lattice structure. This expression is compared with the usual simplified equation for the diffusion length. The leakage of neutrons from a pile is also obtained from this calculation.

ISSN:0021-8979    

DOI:10.1063/1.1702267

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

A mathematical analysis of a parallel‐connected magnetic amplifier with a resistive load is presented. The analysis is based on two distinct analytical approximations of the magnetization curve of the core material; a polynomial and a hyperbolic function. The variation of the core flux and the output current of the amplifier as a function of time are determined by the solution of an integral equation. A finite difference method is developed to determine the response of the loaded amplifier that makes direct use of the magnetization curve of the core material.

ISSN:0021-8979    

DOI:10.1063/1.1702268

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

The resoftening kinetics for cold work in copper have been studied using residual resistance as a measure of the degree of recovery. The specimens were quickly heated to the annealing temperature, held at temperature for a measured time, and quenched for measurement. It was assumed that the cold work could be characterized by a number of lattice defectsnand that the residual resistance change produced by these defects obeyed Matthiessen's rule. It was found that the resoftening could be represented by a single process of activation energy 28.3 kilocalories per mole. The complete annealing kinetics are described by a fourth‐order reaction,dn/dt=−vn4e−E/RT.

ISSN:0021-8979    

DOI:10.1063/1.1702269

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

When barium carbonate is heated in vacuum in contact with tungsten, the following reactions may occur in sequence as progressively higher temperatures are reached: (1) WO3+BaCO3&rlarr2;BaWO4+CO2. (2) 3BaCO3+W&rlarr2;Ba3WO6+3CO. (3) BaCO3&rlarr2;BaO+CO2. (4) 6BaO+W&rlarr2;Ba3WO6+3Ba.At a temperature of approximately 600°C, reaction (2) begins to occur with appreciable speed. Reaction (3) proceeds at 800–900°C. Reactions (2) and (3) may be made to proceed simultaneously, the preponderance of one over the other depending upon state of subdivision and intimacy of admixture of the reactants. Under favorable conditions, reaction (2) may be driven to completion with almost total absence of reaction (3). Reaction (4) progresses with appreciable speed at temperatures over approximately 1000°C.Activated cathodes of BaO on W will have an interface of Ba3WO6formed by reactions (2) or (4), or both, unless unusual precautions are taken to avoid this. The end result of heating the cathode is the conversion of the entire thickness of the oxide coating to the basic tungstate. The resulting coating of Ba3WO6on W is unreactive and nonvolatile at temperatures up to 1300°C, and provides no significant thermionic emission.

ISSN:0021-8979    

DOI:10.1063/1.1702270

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

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.

ISSN:0021-8979    

DOI:10.1063/1.1702271

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

An experimental study was made of the properties of the high current dc electric arc in argon, helium, and their mixtures at atmospheric pressure. Tungsten‐rod electrodes were used over a current range from 10 to 100 amperes. Measurements of the voltage‐current and the voltage‐electrode separation characteristics were made along with the plasma voltage gradients in both the pure gases and in the mixtures.It was found that this type of arc was very stable when the system was free from oxide impurities and that the cathodic processes played a major role in the arc mechanism. The results obtained suggest that the value of the anode voltage drop for the inert gas arc over the current range studied is negligibly small. At the higher currents or with smaller diameter cathodes, tungsten was able to evaporate from the cathode in sufficient quantities to influence the character of the discharge. It was observed that the properties of the arc in mixtures of gases were in between the properties observed in the pure gases. The lower ionization potential gas, argon, had more effect on the properties of the arc in mixtures than did helium. As long as there was at least 15 percent argon present in the mixture, the arc properties and appearance were more like those observed in argon than in helium.

ISSN:0021-8979    

DOI:10.1063/1.1702272

出版商:AIP    

年代:1952

数据来源: AIP

摘要:

Equivalent forms may be useful in the analysis of the steady‐state operation of circuits containing a nonlinear resistance element. Provided the amount of nonlinearity is not too large, the nonlinear element can be replaced by a linear resistance and several generators of voltage or current. The amplitude, phase, and frequency of these generators are determined by the nature of the nonlinearity and by the fundamental component of current in the nonlinear element.

ISSN:0021-8979    

DOI:10.1063/1.1702273

出版商:AIP    

年代:1952

数据来源: AIP