摘要:

The oxygen content of pulled silicon crystals, determined by vacuum fusion gas analysis, is correlated with the infrared absorption at 9 &mgr;. In vacuum and in helium or hydrogen of 1 atmos, the oxygen concentration of a liquid zone of silicon (about 20 mm2in cross section) can be rapidly decreased. In an oxygen atmosphere or in contact with quartz, liquid silicon picks up oxygen quite readily. A maximum oxygen content of 2×1018oxygen atoms per cm3was observed. Silicon single crystals pulled from a quartz crucible exhibit fluctuations in oxygen concentration both perpendicular and parallel to the pulling direction. Explanations of these effects are offered and the influence of various pulling parameters is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1722880

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The stable orientation of a 180° ferromagnetic domain wall in a cubic crystal with <100> easy directions is calculated as a function of crystal orientation for a sheet specimen with a <100> direction parallel to the surface. The effect of the second crystal anisotropy constantK2on the domain wall energy is considered and shown to be negligible if |K2| <K1. If the crystal surface is a {110} plane, there are two equivalent stable domain wall positions, with the wall making an angle of ±32° with the normal to the specimen surface. If the crystal surface is a {100} plane, the domain wall lies normal to the surface. These results are changed if a stress is applied to the sample. Experimentally determined domain wall orientations agree with the calculated positions.

ISSN:0021-8979    

DOI:10.1063/1.1722881

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

A new range of muzzle velocities has been achieved by propelling a projectile in a gun barrel by a column of hydrogen or helium instead of the conventional powder gas. The first gun built, the design of which probably was far from optimum, yielded muzzle velocities in excess of 12 000 ft/sec with spherical and cylindrical steel projectiles.

ISSN:0021-8979    

DOI:10.1063/1.1722882

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An attempt has been made to evaluate the activation energy of interstitial diffusion in body‐centered cubic metals on the basis of the distortion energy necessary to open one of the flat interstitial cavities (½ 0 0) adjacent to an occupied one to a size equal to the diameter of the interstitial atom. The frequency on which the diffusion process depends, and hence the frequency value to be used in calculatingD0, is simply the maximum frequency of the lattice along the (100) direction. The results obtained forQandD0agree satisfactorily with the experimental data and thus show clearly the dependence of the activation energiesQon the elastic constants of the metal of the matrix and on the interstitial atom diameter. Moreover the theory confirms the origin of some observed relaxation effects still uncertain and the evaluation of the activation energies of interstitial atoms anchored around lattice defects such as dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1722883

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Values of the limiting specific volumev0calculated by a trial‐and‐error procedure fromn‐alkane viscosity data using the author's free‐space viscosity equation,ln&eegr;=B(v0/vf)+lnA,agree substantially with previously published values obtained by extrapolation of density data. Values ofv0for mercury, sodium, benzene, carbon tetrachloride, dichlorodifluoromethane, and water were calculated by the same trial‐and‐error procedure. In all cases the free‐space equation gave a much better fit than the corresponding Andrade temperature equation,ln&eegr;=B/T+lnA.

ISSN:0021-8979    

DOI:10.1063/1.1722884

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The creep function for the ``National Bureau of Standards'' polyisobutylene at 25°C is calculated from the relaxation function, using the integral equation connecting them. The calculated function is shown to be correct in its initial slope, to satisfy the inequality&fgr;(t)&psgr;(t)⩽1throughout, and to approach satisfactorily the independently determined asymptote.

ISSN:0021-8979    

DOI:10.1063/1.1722885

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Values of the drag coefficient have been obtained for spheres in the region 1.5<M<3.0, 350<Re<3000 in the Pressurized Ballistics Range at the Naval Ordnance Laboratory. This region borders, on the low Reynolds number side, one investigated previously. The low Reynolds numbers were obtained by using air pressures of about 7 mm Hg and spheres as small as132in. in diameter. A contour map ofCDon Mach number and Reynolds number coordinates has been derived from the experimental data.

ISSN:0021-8979    

DOI:10.1063/1.1722886

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The electrical cleanup of helium on molybdenum surfaces has been investigated. In this case, the phenomenon can be described by a trapping of ions upon impact with the surface. Measurements of the trapping efficiency &eegr; (atoms removed/ions collected) have been made over a range of ion energies from 150 to 2600 ev. The re‐emission of trapped helium atoms was investigated in detail. The contribution of re‐emission to the pumping process is described by a phenomenological theory. The results indicate that the trapping efficiency is lowered by a short time re‐emission of trapped atoms. Through the long‐time re‐emission of atoms, the theory accounts quantitatively for the observed saturation of the cleanup process.

ISSN:0021-8979    

DOI:10.1063/1.1722887

出版商:AIP    

年代:1957

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722889

出版商:AIP    

年代:1957

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722891

出版商:AIP    

年代:1957

数据来源: AIP