摘要:

Fast moving plasmas encountering transverse magnetic fields of order 104gauss are decelerated so rapidly as to produce reflected shock waves. Observations in hydrogen at gas pressures of 1 to about 10 mm Hg are analyzed. There are critical conditions of magnetic field for the onset of the reflection. The velocities of the advancing and reflected waves are recorded as a function of pressure and field.

ISSN:0021-8979    

DOI:10.1063/1.1735243

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An experimental study has been carried out for the purpose of verifying theoretical predictions concerning the relations between total absorptivities and total emissivities for transparent gases. The experimental conditions have been designed in such a way as to permit a direct check of theoretical relations derived for (a) nonoverlapping dispersion lines and (b) spectral lines with sufficient pressure broadening to permit neglect of the rotational fine structure. A comparison between the emissivities derived from absorptivity measurements and emissivities calculated from the spectroscopic constants of CO shows a good agreement (within 20% for most of the temperature range).The apparatus for the measurement of total gas absorptivities is described. Results for total absorptivities of carbon monoxide measured at temperatures between 300 and 500°K are given and total emissivities have been calculated in the temperature range of 300 to 1600°K. The range of total gas pressure is 0 to 515 psia.

ISSN:0021-8979    

DOI:10.1063/1.1735244

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Dynamic pyroelectric techniques have been used to study single crystal BaTiO3hysteresis loops which have been reported in several recent investigations to be asymmetric with respect to both the polarization and electric field axes. It is shown that an apparent polarization bias occurs because of electrode‐edge effects and that this bias may be shifted with an appropriate application of a dc field which serves to alter the direction of the polarization in fringe regions which contribute to the observed pyroelectric signal. The pyroelectric hysteresis loops are symmetric with respect to the polarization when electrode‐edge effects are eliminated. These data strongly suggest that asymmetric remanent polarizations reported in several piezoelectric and pyroelectric investigations may have been due to edge effects. The pyroelectric hysteresis loops are found to be biased with respect to the electric field axis in the same manner as that reported in a recent piezoelectric study. Small residual pyroelectric signals observed at temperatures above the Curie point of the bulk material do not result from fringe effects, and the earlier interpretation of the residual signals in terms of a polarized surface layer is consistent with the present results.

ISSN:0021-8979    

DOI:10.1063/1.1735245

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Interdiffusion in a nondegenerate, exhaustion range, binary ionic semiconductor is investigated using the recently improved theory for the concentrations of defects in crystals and Wagner's phenomenological flow equation. The composition dependence of the interdiffusion constant is found to be determined by the ratio of the ion jump frequencies, the Schottky constant, and the intrinsic concentration of conduction band electrons. The removal of the restriction to an exhaustion range semiconductor and the replacement of the basic assumption of local electroneutrality are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735246

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The anisotropy and magnetostriction of single crystals of several ferromagnetic materials have been determined experimentally. The materials include the metals iron and nickel, binary alloys of nickel iron, silicon iron, aluminum iron, cobalt nickel, and cobalt iron, ternary alloys of molybdenum nickel iron, nickel cobalt iron, and molybdenum aluminum iron, and magnetite. The effect of the order‐disorder reaction on these properties was measured for several of the alloys.The present data for the nickel iron and silicon iron systems agree well with recently published values. Ordering generally raises the magnetostriction and lowers the anisotropy of the aluminum iron alloys near the Fe3Al composition. The first anisotropy constant,K1, for the cobalt nickel system as derived from torque curves is similar to old data derived from magnetization curves. However,K1for cobalt iron (30, 35, and 45% cobalt) appears to be considerably larger than previously reported. In general, the addition of cobalt to nickel and to iron changes the magnetostriction constants (&lgr;100and &lgr;111) toward large positive values. Thus, &lgr;100increases to 100×10−6for 50% cobalt nickel and to 130×10−6for 45% cobalt iron; &lgr;111increases to 30×10−6for 45% cobalt iron but remains approximately constant for the cobalt nickel alloys.

ISSN:0021-8979    

DOI:10.1063/1.1735247

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

An ultrasonic interferometer technique for measuring the temperature dependence of the relative change in elastic constants is described in detail. Results are reported for measurements carried out as a function of frequency from 10 mc/sec to 170 mc/sec, for compressional wave propagation along the [100] axis of silicon over a temperature range of −60° to +15°C.The mean value of (1/c11)(dc11/dT) obtained is 55.59±0.81×10−6(°C)−1, and no frequency dependence of (1/c11)(dc11/dT) was found.

ISSN:0021-8979    

DOI:10.1063/1.1735248

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A theory of convergent, high‐efficiency electron guns for the production of dense hollow beams is presented. An approximate solution to Poisson's equation is obtained in a cylindrical coordinate system modified to account for the toroidal geometry. Experimental measurements on a series of toroidal guns tend to confirm the space‐charge theory. They also show that the annular slit in the anode very seriously affects the uniformity of cathode emission and diverges the beam more than can be accounted for by present theories. These effects of the slit appear to confine the usefulness of these guns to high‐power applications.

ISSN:0021-8979    

DOI:10.1063/1.1735249

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The density and distribution of dislocations in tip grown iron whiskers produced by the hydrogen reduction of liquid iron halide salts has been measured by means of x‐ray rocking curves. The data show that the more perfect whiskers have dislocation densities below 106dislocation lines per cm2. Thus, many of these whiskers which are less than 10 &mgr; in diameter would contain, at most, only a small number of dislocations and should behave as perfect crystals. No evidence of a large elastic twist was found in any of the whiskers as would be expected for a whisker grown by a screw dislocation mechanism. This did not completely prove that iron whiskers must grow, therefore, by a mechanism based on coherent two‐dimensional nucleation as there are combinations of specific types of screw dislocations which will not produce elastic twists in the whiskers.

ISSN:0021-8979    

DOI:10.1063/1.1735250

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Experimental investigation of the flow rates of normal paraffins in porous Vycor glass shows that there are deviations from the viscosity dependence required by Poiseuille's law. A discussion of the application of capillary models to describe flow in porous media in terms of the measured porosity and surface‐to‐volume ratio points out that such models are not generally applicable, though they give useful results for some purposes. An estimate of the permeability predicted by Poiseuille's law is made by an empirical method which uses gas flow measurements in the Knudsen flow region. The equations of slip flow as derived for gases do not explain the experimental deviations from Poiseuille flow. The concept of a slipping adsorbed layer of molecular thickness at the wall of a capillary is combined with the usual Poiseuille treatment for the interior to give a result which is compatible with experiment.

ISSN:0021-8979    

DOI:10.1063/1.1735251

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The orientations of individual grains in cold‐rolled and annealed silicon‐iron strip are obtained for a single‐component texture and a multiple‐component texture to determine (1) the preferred orientations in the two textures and (2) some information on the nature of formation of the textures. A set of three axis density figures and a (100) pole density figure are synthesized for the multicomponent texture. It is concluded from the figures that the axis density figures give more information about the components present in the texture than a (100) pole figure does. It is also concluded that oriented nucleation is important in the development of the textures.

ISSN:0021-8979    

DOI:10.1063/1.1735252

出版商:AIP    

年代:1959

数据来源: AIP