摘要:

A solution is given of the field equations of nonlocal elasticity for a line crack interacting with a screw dislocation in an elastic plane under antiplane shear loading. Displacement and stress fields are determined throughout the core region and beyond. In the case when the dislocation is absent, the circumferential stress is shown to vanish at the crack tip, increasing to a maximum along the crack line afterwards decreasing to its classical value at large distances from the crack tip. This is in contradiction with the classical elasticity solutions which predicts stress singularity at the crack tip and it is in accordance with the physical condition that the crack tip surface must be free of surface tractions. The presence of the dislocation alters the stress distribution considerably when it is close to the crack tip. The stress distributions in the core region are displayed. A fracture criterion based on the maximum stress is established and used to determine the theoretical strengths of pure crystals that contain a line crack. Results are in good agreement with those based on the atomic theories and experiments.

ISSN:0021-8979    

DOI:10.1063/1.332001

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We report the results of a study to determine the vibrational temperatures of N2(B3&pgr;g) and N2(C3&pgr;u) ine‐beam pumped N2rare‐gas mixtures. They are analyzed in terms of the kinetics of thee‐beam pumped gas mixtures, and a number of qualitative conclusions are reached.

ISSN:0021-8979    

DOI:10.1063/1.332002

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An iterative procedure is described by means of which the potential distribution can be found in axially symmetrical periodic configurations of juxtaposed coaxial electrodes. The solution is in the form of Fourier–Bessel series, and the procedure involves the potential calculation in the gap by an overrelaxation process in respect of points located on a mesh covering a small region which includes a cross section of the gap. The gap potential is represented either by a polynomial or by the sum of a linear function and a Fourier series. Using this method, the errors on axial potentials are found to be approximately two orders of magnitude smaller than those on potentials calculated by assuming that the potential in a gap is a linear function. Compared to the relaxation method, the present procedure represents a considerable saving on computing time and memory.

ISSN:0021-8979    

DOI:10.1063/1.332003

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The propagation of Bleustein–Gulyaev waves in the presence of a dc electric field in the vacuum baked piezoelectric semiconducting crystals of class 6 has been studied theoretically. By solving the partial differential equations representing the electron–acoustic wave interaction in the piezoelectric semiconducting region, and the Laplace’s equation in the vacuum region separately and fulfilling the relevant boundary conditions, we obtain an expression for the amplification coefficient. The effects of carrier diffusion, resistivity, and carrier drift velocity on the amplification coefficient have been studied based on numerical calculations for the semiconducting CdS sample. It has been observed that, compared to Rayleigh waves, the Bleustein–Gulyaev waves give a much higher amplification.

ISSN:0021-8979    

DOI:10.1063/1.332004

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A regenerator for use with a liquid in a Stirling cycle heat engine is described. Because of the thermophysical characteristics of liquids, such a regenerator can be nearly ideally effective and has thermal properties that can be calculated directly without resort to empirical information. The regenerator described here is designed to minimize loss arising from three sources: thermal conductivity along the regenerator, viscous heating in the working fluid, and imperfect thermal contact between the working fluid and the second thermodynamic medium in the regenerator. Measurements using liquid propylene as a test fluid in the regenerator confirm the design calculations.

ISSN:0021-8979    

DOI:10.1063/1.332005

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

TheI‐Vcharacteristic of dc and rf magnetron sputtering systems has been shown to fit an expression of the formI=&bgr;(V−V0)2, whereV0is the minimum voltage necessary to maintain a discharge. New experimental data is presented for a dc planar magnetron with Al, Cd2Sn, Cr, and CdSe targets in argon discharges and for a dc Research S‐gun with an Al target in argon and argon/oxygen discharges. Literature data for planar, S‐gun, and cylindrical magnetrons has also been shown to fit the above expression; for rf magnetrons,Iis the rms current andVis the target self‐bias voltage.V0decreases from about 400 V at 0.1 Pa to 250 V at 1 Pa and then decreases at higher pressures. &bgr; increases from about 50 to ≤300 A/kV2as the pressure increases from 0.1 to 10 Pa. The actual values ofV0and &bgr; depend on the system, target, and sputtering gas. It is shown that theI∝V2dependence is due to a space‐charge‐limited electron current in the magnetron geometry which reduces the electron mobility by several orders of magnitude from the zero magnetic field value; the mobility ratio depends on the electron‐atom collision frequency.

ISSN:0021-8979    

DOI:10.1063/1.332006

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Magnetization distributions around a circular nonimplanted disk in an ion‐implanted garnet film are calculated through numerical integration of the Landau–Lifshitz–Gilbert equation. In addition to uniform stress‐induced in‐plane anisotropy in the implanted region, the effect of stress relief near the edge of nonimplanted disk is taken into account. Calculation results show that magnetization distributions are strongly affected by the stress distribution near the edge not only in the region close to the implantation edge where charged walls are formed but also in the region rather far away from the edge. With proper choice of stress distribution, the present calculation can reproduce the ‘‘propeller‐like’’ domain wall pattern which is experimentally observed by the Bitter technique. This suggests that the stress distribution near the implantation edge might be determined by comparing calculation results of magnetization distributions with experimental observations of domain wall pattern.

ISSN:0021-8979    

DOI:10.1063/1.332007

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Magnetic resonance (NMR,EPR) and infrared studies are presented of amorphous hydrogenated silicon (a‐Si:H) films prepared by homogeneous chemical vapor deposition (HOMOCVD) and rf plasma decomposition using silane and disilane. Hydrogen incorporation occurs with a small activation energy (∼0.06 eV) for all films, while the barrier for changes in spin defect density is almost an order of magnitude larger and comparable to that measured in defect annealing studies. Films deposited by rf(Si2H6) plasma exhibit the greatest hydrogen contents, followed by HOMOCVD and rf(SiH4) plasma material. NMR measurements suggest that HOMOCVD films are less disordered than plasma‐depositeda‐Si:H. Previous work and recent kinetic studies of plasma and thermal environments are extensively analyzed, along with thermodynamic and kinetic data, to determine aa‐Si:H growth mechanisms most consistent with the experimental results. The model presented to explain compositional and defect changes with substrate temperature emphasizes plasma deposition by monoradical precursors and HOMOCVD growth by diradicals, resulting initially in a similar surface‐bound intermediate in all cases. Plasma growth from Si2H6involves the surface attachment of longer radical chains, compared to SiH4, while oligomeric diradicals could be present in HOMOCVD. The possibility that reactions at the hot reactor wall, as well as in the gas, create monoradicals in HOMOCVD is also explored in detail. Finally, film dehydrogenation and crosslinking reactions are examined, and experiments proposed to determine the channels most relevant for each deposition environment.

ISSN:0021-8979    

DOI:10.1063/1.332008

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The possibility of increasing the degree of multiplexing of twisted nematic cells has been investigated by taking the following factors into consideration: unequal elastic constants and arbitrary dielectric anisotropy for the liquid crystal medium, and a general anisotropic interfacial potential. It can be shown that the achievable degree of multiplexing of twisted nematic cells under the nonrigid boundary condition can be improved by a factor of 10 to 50 over the case of the rigid boundary condition, in contradiction to a factor of two predicted by Nehring, Kmetz, and Scheffer [J. Appl. Phys.47, 850 (1976)]. The effect on the degree of multiplexing by different forms of the anisotropic interfacial potential is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.331990

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The effect of sulfur implant fluence, ion energy, and annealing temperature on the redistribution accumulation of chromium during annealing of GaAs under SiO2and Si3N4caps and a capless condition is shown. The variation of the thickness of the heavily damaged or ‘‘amorphized’’ layer with implant fluence is shown and discussed. Three peaks are seen in the Cr accumulation profiles. When their integrated densities are plotted versus inverse annealing temperature, two peaks exhibit an activation energy for breakup of the Cr‐defect complexes of 0.56 eV, and the third, of 1.8 eV. The nature or origin of these Cr‐defect complexes is discussed. Sulfur migration or ‘‘diffusion’’ versus sulfur density is illustrated and discussed. The correlations of the two Cr peaks observed in 840 °C annealed depth distributions with capping environment and damage depth are discussed. Finally, these Cr accumulation profiles under sulfur implants are compared with those in self‐amorphized GaAs.

ISSN:0021-8979    

DOI:10.1063/1.331991

出版商:AIP    

年代:1983

数据来源: AIP