摘要:

The equations of the hydrodynamic theory of penetration of targets by shaped charge jets are presented first in general form. These equations are then expressed in the ideal form and examined by experimental observations. Then a nonideal theory is presented that takes into account heat losses by compression, shock heating, and radiated shock waves. The conditions for impact explosions of targets are then discussed and a theory extended to cover the entire velocity range of impact from the plastic deformation thresholdv&sgr;to well above the impact explosion thresholdvc. Some experimental evidence relating to this more general theory is also presented.

ISSN:0021-8979    

DOI:10.1063/1.1735222

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Induced conductivity in CdS crystals produced by electron bombardment (cathodoconductivity) and the associated x‐ray production have been studied employing electrons in the 30‐ to 60‐kev range. The conductivity induced solely by these x‐rays has been studied. Using classical x‐ray theory, the production and absorption of x‐rays in the experimental crystals have been calculated. Some confirmatory data are presented. From calculated excitation rates and observed conductivities the x‐rays produced by impinging electrons are shown to be sufficient to explain the effects observed in cathodoconductivity, and may be significant in cathodoluminescence.

ISSN:0021-8979    

DOI:10.1063/1.1735223

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Surface markings observed in the brittle fracture of certain frozen rubbers display striking wave‐like characteristics. They have been identified as ``Wallner'' lines, caused by the interaction of the fracture front with stress waves emanating from the region of the fracture front itself. These oscillations are possibly caused by the supply of excess energy to the fracture tip.A value of approximately 1:2 is obtained for the ratio of fracture velocity to wave velocity.

ISSN:0021-8979    

DOI:10.1063/1.1735224

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A solution of the continuity equations is obtained for the space charge distribution by assuming (1) that deviations from neutrality are small, and (2) that the space charge fields, which are a consequence of the terms containing ▿·Ein these equations give rise to pure diffusion and pure ``drift‐wave'' terms with time dependent coefficients. It is, for equal numbers of holes and electrons initially injected,e[(p−p0)−(n−n0)]=−&tgr;&rgr;∇E·J[1−exp(−t/&tgr;&rgr;)], where &tgr;&rgr;equalsK/4&pgr;&sgr;, the relaxation time,Jis the total current density including diffusion, as well as drift, and∇Emeans that the divergence does not operate onE(the electric field is held constant). In the differentiation ∂n/∂xand ∂p/∂xare considered to be equal, as are ∂2n/∂x2and ∂2p/∂x2.Working independently, H. Brooks and W. van Roosbroeck arrived at expressions for both the ambipolar diffusion coefficient and the ``group mobility'' of the drift of a pulse of excess carriers. This theory yields the same results, and, in addition, transient expressions are gotten for each.

ISSN:0021-8979    

DOI:10.1063/1.1735225

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

From quenching experiments the activation energy for vacancy formation in high purity platinum is found to be 1.20±0.04 ev. Annealing behavior after quenching is studied. First‐order annealing is found when the concentration of quenched‐in defects is low; the migration energy turns out to be 1.48±0.08 ev. The annealing kinetics are not simple if the quenching temperature is high and the concentration of defects at least 10−4.

ISSN:0021-8979    

DOI:10.1063/1.1735226

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Large reversible variations in carrier concentration, Hall mobility, and carrier lifetime have been produced in indium arsenide by heat treatment. For material cut from the parent ingot, carrier lifetimes measured by the photoelectromagnetic‐photoconductive ratio method increase by a factor of over 20 as a result of slow cooling from 850°C. Heat treatment at temperatures of 450°C and above increases the carrier concentration ofn‐type material and decreases the carrier concentration ofp‐type material. Such variations are reversed by heat treatment at temperatures below 350°C. In this way, changes in the carrier concentration of over 1017cm−3have been produced, and InAs has been converted fromptontype. Various heat treatment mechanisms are examined. It is shown that the experimental results are consistent with the model proposed by Kurtz and Kulin involving the segregation and dispersion of donor impurities to and from dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1735227

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A theory of steady‐state creep at high temperature and stress is based on the climb of dislocations limited by the diffusion of vacancies from them. The creep rate is found to be approximately (MnL3)D0exp[− (W+E+U−&Dgr;W)/kT], whereMis the number of dislocation sources per unit volume,nis the number of dislocations of lengthLper unit area, andD0exp (−W/kT) is the coefficient of self‐diffusion. The number of jogs in the dislocations is determined byU, andEis an activation energy for formation of vacancies, due to relaxation of the lattice. The reduction in vacancy formation energy near a dislocation &Dgr;Wis estimated from the interaction energy of the climbing dislocations. A comparison of experimental data for Zn and AgBr suggests thatEis a significant contribution to the activation energy for ionic crystals but not for metals. The predicted increase in vacancy concentration during creep is too small to give observable effects. It is concluded that any observed enhancement of diffusivity during creep is due to increased mobility of defects.

ISSN:0021-8979    

DOI:10.1063/1.1735228

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

In order to study the initiation of detonation waves, the time dependent one‐dimensional hydrodynamic equations have been numerically integrated for several initial conditions. In all the cases treated, the hydrodynamic motion and the release of chemical energy are practically independent as a consequence of the extreme temperature sensitivity of the reaction rate. At first the chemical energy is released so slowly that it has no effect on the hydrodynamic motion. Thereafter the reaction proceeds so rapidly that the burning is not influenced by the hydrodynamic motion. A simple criterion is established to determine whether or not detonation will result from given initial conditions of pressure and temperature. This criterion is applied to determine how the detonability depends upon the duration of the initial pressure pulse and upon the initial temperature distribution.

ISSN:0021-8979    

DOI:10.1063/1.1735229

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The theory of operation, construction, and performance data of an infrared detector based upon the PEM effect in InSb are presented. Theoretical derivations of the spectral noise equivalent input, noise equivalent power, and responsivity are made which show the dependence of these figures of merit upon the electrical properties of the semiconductor, sample thickness, surface area, front and back surface recombination velocities, and magnetic induction. Performance of the detector operating at room temperature shows a spectral response extending to 7.5 microns and a response time of less than 1 microsecond. The noise equivalent input of a detector having a 0.71‐mm2sensitive area has a minimum value at 6.6 microns of 6.7×10−10w.

ISSN:0021-8979    

DOI:10.1063/1.1735230

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The photoelastic constants and their dispersion for visible light were determined for two samples of vitreous silica, Corning and Herasil No. 1. The results for the mercury green line, 546 m&mgr;, are quoted here. The photoelastic constants were 4.22×10−13(d/cm2)−1(ordinary ray) and 3.56×10−13(d/cm2)−1(extraordinary ray). From the ratio of Poisson's ratio to Young's modulus 0.216×10−12(d/cm2)−1and Young's modulus 0.76×1012(d/cm2), which were also determined, there were calculated the pressure coefficient of refractive index 0.909×10−12(d/cm2)−1and the elasticity volume coefficient of refractive indexV dN/dV=0.34. Comparison of these results with those reported for other glasses indicates that the oxygen ions of vitreous silica are more deformable then the oxygen ions of other siliceous glasses. In vitreous silica about ⅓ of the volume change accompanying an elastic dilatation arises from the dilatation of the oxygen ions. A comparison is also made with the results reported for corresponding thermally induced effects. It indicates that (a) during a thermal dilatation of a siliceous glass, the oxygen ion undergoes a dilatation which in the case of most siliceous glasses causes an equivalent dilatation of the body, but which in the case of vitreous occurs internally instead, and (b) in crystal quartz no appreciable dilatation of the oxygen ion occurs during a thermal dilatation. The thermal dilatation of the oxygen ion in the glasses would thus seem related to its strained bond configuration.

ISSN:0021-8979    

DOI:10.1063/1.1735231

出版商:AIP    

年代:1959

数据来源: AIP