摘要:

A wide variety of carbide structures is described, as found in the surface layer of carburized thoriated‐tungsten filaments. Their origin is traced back to carburizing conditions and subsequent processing during tube making. A frequently occurring laminated carbide structure is found to contain less carbon than W2C. The thyratron relay method of carburizing control is critically reviewed. Abnormal filament current in manufactured tubes is explained as due to surface conditions which cause changes in thermal emissivity.

ISSN:0021-8979    

DOI:10.1063/1.1697558

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The determination of column deflections and column buckling loads has been considered for many years. The available theories, however, do not provide for materials which creep with time under constant loads. For the design of structural members made of these materials, a consideration of creep may be of practical importance. Plastics, concrete, and some metals creep at normal temperatures while other metals creep only at high temperatures and at stress values beyond the yield point. A consideration of creep in the design of some structures appears appropriate in view of the modern developments in plastics and the presence of high stress values which are sometimes beyond the yield stress. This paper gives a rational theory for predicting creep deflections in columns. A special case using this theory is applied to the interpretation of some preliminary tests of an aluminum alloy.

ISSN:0021-8979    

DOI:10.1063/1.1697543

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The voltage disturbances in hot‐cathode arcs are markedly affected by a magnetic field transverse to the normal flow of current. The normal plasma oscillations can be suppressed and the noise level above 1 Mc/sec. greatly increased. The oscillations appear to be transmitted to the electrodes by electrons whose velocity is modulated by the plasma ion oscillations as they travel directly from cathode to anode. The effect of the magnetic field is to remove these electrons from the current reaching the anode. A critical value of magnetic field will suppress the oscillations and reduce the noise to a minimum. As the magnetic field is further increased the high frequency noise level increases. The high frequency noise level also increases if the pressure decreases, or if a lighter gas is used. The noise level is independent of the plasma volume. The effect of the magnetic field is to build up a region of high ion density in a narrow region near the electron source. Plasma oscillations with continuous spectrum are generated in this region of high density and high density gradient.

ISSN:0021-8979    

DOI:10.1063/1.1697544

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Numerical methods are given for solution of axisymmetrical problems involving the partial differential equation∂2&psgr;∂z2+∂2&psgr;∂&rgr;2+K&rgr;∂&psgr;∂&rgr;=0,where &rgr; is the radial coordinate andzthe coordinate parallel to the axis. The various values ofKwhich occur in physical situations are discussed, and common iteration methods for handling these problems are given. For Laplace's equation,K= 1. For the Stoke's stream function,K= − 1, but it is pointed out that for numerical work a new function, called theflow‐disturbance function, havingK= 3, is more tractable. Similarly a new function withK= 5, thestress‐concentration function, is much easier to compute than the usual stress function (K= − 3) for the case of the torsion of a circular shaft of varying diameter. The methods are illustrated by computation of the equipotentials for an electron lens, and by a complete computation of the stresses and strains in a particular grooved circular shaft under torsion.

ISSN:0021-8979    

DOI:10.1063/1.1697545

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1697546

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1697547

出版商:AIP    

年代:1947

数据来源: AIP