摘要:

In this paper the variational techniques of Levine and Schwinger are used to obtain an approximate solution for the free‐space scattering by a number of finite, perfectly conducting obstacles in which the mutual interactions or coupling are taken into account. The far‐zone scattered field is found in terms of the obstacle currents. Variational principles for the total and backscattering cross sections are included. The special case of two parallel wires of finite length is worked out, and the results agree well with experiment.

ISSN:0021-8979    

DOI:10.1063/1.1721643

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The penetration of the magnetic field intensity into the interior of an infinite slab of ferromagnetic material having a nonlinearB — Hrelationship is governed by a nonlinear diffusion equation. For finite thickness of the slab, the problem is solved by an approximate method. A rigorous solution of the same problem when the thickness of the slab approaches infinity is given to justify the approximate method used. In the paper, one term only is used to represent an infinite series in order to give a readily calculable result in ``switching time.'' The result is then compared with that of the graphical solution of the same problem.

ISSN:0021-8979    

DOI:10.1063/1.1721644

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

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 thationsare 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.

ISSN:0021-8979    

DOI:10.1063/1.1721645

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Paschen's similarity law, which expresses a certain relationship between the breakdown voltage of a gas, the gas pressure, and the distance between electrodes, is known to fail at high pressures. This is owing, at least in part, to a change in the way in which electrons dissipate energy to the gas molecules. At high enough pressure, the electron transfers energy principally to molecular vibrations. In condensed phases this vibrational barrier is dominant, and one should expect a new kind of similarity law to hold under certain controlled conditions. The liquid aliphatic hydrocarbons provide an illustration of such a law. The electric strengths of nine hydrocarbons of various densities were measured and found to depend linearly upon density. It has also been found that the temperature dependence of the electric strength of a liquid aliphatic hydrocarbon can be accounted for by the change in density of the liquid due to thermal expansion.

ISSN:0021-8979    

DOI:10.1063/1.1721646

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

The problem of the reflection of a shock wave from a moving boundary is examined in an idealized one‐dimensional treatment. We consider in detail the head‐on collision of an incident step shock wave and a piston moving at constant velocity into a gas at rest. The calculation involves the head‐on collision of two shock waves and the subsequent reflection of an altered transmitted wave from the piston. The reflected pressure is calculated for a range of incident shock strengths and piston speeds. For a stationary piston both the absolute and excess reflected pressures are at most eight times the absolute or excess pressure of the incident shock wave (with &ggr;=7/5). With a moving piston, however, this limiting factor is greater than eight, but finite for finite piston speed and infinite incident shock strength, and is infinite for infinite piston speed and finite incident shock strength. This last result holds even in the limit of the incident wave being an acoustic pulse. The method of solution for shock‐wave interaction with a piston receding at constant velocity is also indicated. Although the shock is strengthened on passing through the piston rarefaction wave, the reflected overpressure is less than that resulting from the same initial shock wave reflecting from a stationary piston.

ISSN:0021-8979    

DOI:10.1063/1.1721647

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Experiments to measure the heat‐transfer coefficient at a sodium type‐347 stainless steel interface are described. The temperature range is 100–500°C. It is concluded that wetting does not play a significant role in the heat transfer.

ISSN:0021-8979    

DOI:10.1063/1.1721648

出版商:AIP    

年代:1954

数据来源: AIP

摘要:

Near 35°K the internal friction of vitreous silica reaches a peak value which increases with frequency. The temperature curves of the torsion and Young's moduli are concave upward with minima near 65°K and are independent of frequency. These effects are reversible with temperature. Their cause cannot be the usual type of relaxation process or anything involving diffusion or large amounts of shear.

ISSN:0021-8979    

DOI:10.1063/1.1721649

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721651

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721652

出版商:AIP    

年代:1954

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1721653

出版商:AIP    

年代:1954

数据来源: AIP