摘要:

The effect of pressure on the fundamental excitation energy of valence electrons in the ferromagnesium orthosilicate, the mineral olivine, is of interest in the theory of the electrical conductivity of the earth's mantle. The experimental determination of this by observation of the displacement of the ultraviolet absorption threshold of olivine up to pressures of about 30 000 bars is described.

ISSN:0021-8979    

DOI:10.1063/1.1722438

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A negative resistance connected to a ``suitable'' resonant circuit (a current‐controlled negative resistance connected to a series‐tuned circuit, or a voltage‐controlled negative conductance connected to a parallel‐tuned circuit) constitutes an almost‐harmonic oscillator. In this paper the ``unsuitable'' connections (a current‐controlled negative resistance connected to a parallel‐tuned circuit, or a voltage‐controlled negative conductance connected to a series‐tuned circuit) are analyzed qualitatively in terms of variables leading to a single‐valued phase plane. Physical considerations, expressed in a jump condition, serve to connect different regions of analyticity of the differential equations of the circuit in this plane. The ``unsuitable'' connections cannot sustain almost‐harmonic oscillations, and their theoretically possible relaxation oscillations are unstable; they yield bistable circuits.

ISSN:0021-8979    

DOI:10.1063/1.1722439

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Two coils wound in orthogonal planes are electrically coupled when linked by a saturated ferromagnetic. The coupling is produced by the rotation of the saturated induction vector. This effect is discussed in relation to applications to magnetic gating, coincidence, and memory.

ISSN:0021-8979    

DOI:10.1063/1.1722440

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The annealing kinetics of resistance changes produced in 30% Zn &agr; brass by quench, neutron irradiation at 50°C, and cold work have been studied. It is shown that the relaxation times for these changes agree with those obtained from measurements of stress‐induced changes in local order. These resistance changes are therefore interpreted in terms of changes in short‐range order. Measurements of resistance as a function of temperature show that an increase of short‐range order decreases &rgr;0, the residual resistance, and increases &rgr;T, the thermal part of resistance.

ISSN:0021-8979    

DOI:10.1063/1.1722441

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

This paper describes the changes in hardness and microstructure in annealed low carbon steel by jets squirted from high explosives with steel‐lined conical cavities. Hardness measurements and photomicrographs were taken along different radii in a plane normal to the axis of the crater in the steel. Each hardnessversusdistance curve exhibited a series of plateaus along which the hardness remained constant. The plateaus appear to be related to Neumann bands which are present in the steel. It appears that the impact of an element of the jet on the steel initiates a transient compressional stress wave in the body of the steel which results in the hardness plateaus and the increase in the number of twin directions with hardness.

ISSN:0021-8979    

DOI:10.1063/1.1722442

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Colloidal silica of 30, 20, 10, and 5% concentrations by weight have been used to produce small‐angle scattering. The resulting scattering showed plateaus which varied in angular position with concentration in the very small angle portion and then showed an approximation to the single particle scattering in the larger small angle region. This scattering from individual scattering centers followed that predicted by Debye. Average distances of separation of randomly spaced particles as determined from the particle‐to‐particle scattering plateaus checked those calculated from the concentrations. In addition, scattering from various sized particles ranging from diameters of 100 to 500 000 A were measured. Two theories, a refraction and reflection or ray theory and a diffraction or wave theory, have been applied to the analysis of this scattering. A comparison of the particle sizes as obtained using these two theories with the particle size as obtained by means other than x‐ray scattering shows that for the larger particles, geometrical optics can be used satisfactorily; while for the small particles the diffraction theory gives the correct scattering relation. Particle size measurements were made on both wetted (colloidal) and dried samples.

ISSN:0021-8979    

DOI:10.1063/1.1722443

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A discussion is presented of the limitation of current density by random irregularities of the cathode surface in an electron beam which is focused by a static electromagnetic field. The Langmuir‐Pierce law for the maximum attainable current density is profoundly altered by the effects of cathode roughness. It is found that the minimum beam diameter attainable in typical cathode‐ray tubes is unaffected by change of cathode temperature or proportional change in the potentials of all electrodes.

ISSN:0021-8979    

DOI:10.1063/1.1722444

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

An earlier theoretical treatment of the Cˇerenkov radiation excited by the passage of a bunched electron beam moving parallel to a dielectric medium at a small distance is extended to the case of a medium with a complex index of refraction. It is found that under suitable conditions, the use of a ferrite material as a medium can in principle enhance the radiated power. This effect is analyzed in terms of the work done by the beam on the field and the coupling between the beam and the medium.

ISSN:0021-8979    

DOI:10.1063/1.1722445

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A simple x‐ray diffraction method was used to measure the mosaic misalignment and the number of dislocations in the grains of silver halide precipitates and of nickel foils where the grain sizes were in the range from a few tenths of a micron to a few microns. The experimental arrangement is such that separate diffraction spots are produced by each grain and the width of a spot is determined primarily by the mosaic nature of the grain.It appears that measurements of angular misalignment can be made down to the limit imposed by the natural width of the x‐ray spectrum lines. In general, either cold work or the presence of a substitutional impurity causes broadening of the diffraction spots. However, it is possible to incorporate impurities without producing broadening or dislocations. In spite of a 1% substitution of iodide impurity in silver bromide, grains were produced which appear to have no edge dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1722446

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A simple graphical method is described for computing the heat capacity of a specimen in a vacuum calorimeter system from the temperature response in the after‐heating period. The applicability of this method when there are appreciable time lags due to thermal gradients in the specimen or due to the characteristics of a galvanometer, is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722447

出版商:AIP    

年代:1956

数据来源: AIP