摘要:

The hydrostatic and steady laminar hydrodynamic equilibria of spatially varying electromechanical flow structures are investigated. Under certain conditions the relationship between the dielectric height of rise and the applied voltage is found to be double valued. It is found that one of the two equilibrium values is always unstable. This gives rise to the experimentally observed spontaneous rise of the fluid to the top of the structure, once a certain critical voltage is reached. Starting above this critical voltage with the structure completely filled and decreasing the applied voltage toward the critical value results in pinch‐in failure at an intermediate point along the structure and trapping of dielectric fluid at the top. The simple mathematical model developed predicts all these phenomena, without recourse to tedious point‐by‐point surface force equilibrium determination. Experiments are reported which verify the results for the hydrostatic case.

ISSN:0021-8979    

DOI:10.1063/1.1663448

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A theoretical analysis of the diffracting effects produced by ASW on light beams contained on the sagittal plane of the wave is presented. The separate contributions have been explicitly studied, produced by periodical changes of the refractive index and by corrugation of the surface in cases ofx‐ andy‐cut crystalline quartz andy‐cut LiNbO3for both states of polarization of the incident light. In all cases analyzed, measurements of light‐deflection efficiency have been performed as a function of the angle of incidence in light‐transmission experiments.

ISSN:0021-8979    

DOI:10.1063/1.1663449

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Phosphorus is diffused into silicon at 900 °C from a phosphorus‐doped silicon‐dioxide layer. Since a profile of phosphorus concentration is expressed by a function ofx/t, wherexis the distance from a surface andtthe diffusion time, diffusion coefficients are determined by the Boltzmann‐Matano method. They are larger than the intrinsic diffusion coefficient and are dependent not only on the concentration (the concentration effect) but also on some unknown condition at a surface (the surface effect). The surface effect extends more than 20 &mgr; deep into a bulk of silicon, and is stronger than the concentration effect. All of phosphorus atoms are located at substitutional sites. Diffusion‐induced dislocations are not found. A new mechanism for the generation of excess vacancies is suggested. The new mechanism consists of the following: (i) Phosphorus diffuses by a vacancy mechanism. The diffusion of phosphorus occurs only through the diffusion ofEcenters. (ii) When phosphorus atoms enter from a surface into a bulk, they should be in a form ofEcenters. Affected by a surface, a large amount ofEcenters is formed per unit time at a surface. (iii) TheEcenters flow into a bulk. (iv) By their dissociations, excess vacancies are generated. The surface effect and the emitter dip effect are attributed to excess vacancies.

ISSN:0021-8979    

DOI:10.1063/1.1663450

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A technique is presented to calculate grain‐boundary widths and grain‐boundary diffusion coefficients in metals and nonmetals using grain growth, sintering, diffusion and/or creep data. High‐purity metals yield boundary widths of the order of a few atomic diameters, whereas ionic materials yield ``effective boundary widths'' orders‐of‐magnitude wider.

ISSN:0021-8979    

DOI:10.1063/1.1663451

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Values of the total powerPthat a window can transmit under specified conditions are calculated for use as figures of merit for window materials. New features of the figures of merit are consideration of edge as well as face cooling, treatment of surface as well as bulk absorption, use ofPrather than intensity as the figure of merit, effects of improving materials, and calculation for 3.8 and 5.25 &mgr;m. New results include the following: For continuous operation, large‐diameter windows should be face cooled, but small‐diameter window may be edge cooled, andPoftendecreasesas the diameterDincreases. For pulsed operation,Pincreases asDincreases, as was intuitively expected. Values of the diameterDEF, above which face cooling should be used, are surprisingly large, ranging between 7 and 100 cm, typically. For pulsed operation and forD>DEFin cw operation,Pis independent of thermal conductivityKwhile forD<DEFin cw operation,P∝K. The alkaline‐earth fluorides have the greatest figures of merit for large‐diameter windows withP=76 MW, &Dgr;T= 50 K, andl=0.5 cm for a 1‐sec pulse on a 10‐cm‐diam window of BaF2at 3.8 &mgr;m with a bulk absorption coefficient of 10−4cm−1. For small‐diameter windows (1‐cm diameter), Si, BaF2, and GaAs have the greatest values ofP=1.8, 0.94, and 0.76 MW, respectively, for cw or 1‐sec pulse duration.

ISSN:0021-8979    

DOI:10.1063/1.1663452

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The diffraction of a light beam by two orthogonal sound waves is described. The Raman‐Nath equation for the diffracting system is derived and is shown to separate into two Raman‐Nath equations, one for each of the two sound‐wave components. Thus it is shown that diffraction by two orthogonal sound waves present simultaneously in a medium is equivalent to diffraction by the two waves present successively. Analytic solutions of the Raman‐Nath equation are obtained in the Raman‐Nath and Bragg regions of diffraction. Practical applications of the diffraction effect in the Bragg region are outlined.

ISSN:0021-8979    

DOI:10.1063/1.1663453

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The structures of both low‐ and high‐angle grain boundaries are examined from a dislocation approach, and it is shown that coincidence‐site lattice theory can adequately account for the structure of boundaries of any angle. For simplicity, the structures of symmetric tilt and twist boundaries in simple cubic structures are analyzed. The concepts that are developed, however, are quite general and can be applied to more complex crystal structures. In particular, it is shown that any grain boundary can be considered to arise from some suitable combination of crystal lattice dislocations associated with each one of the two grains comprising the boundary. Although the analysis is done with rigid models, the conclusions reached are independent of any atomic relaxations that occur at the boundary. The results developed from the dislocation approach are compared with those of Bollmann's O‐lattice theory, and it is shown that the relatively complex O‐lattice theory may not be necessary for an understanding of the dislocation structure of grain boundaries. Also, concepts such as the Burgers circuit are rationalized, and it is shown that the defect content described by a given circuit depends directly on its reference lattice whereas the strain fields are related to the relaxations that occur around the defect.

ISSN:0021-8979    

DOI:10.1063/1.1663454

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The deformation of grain boundaries by crystal lattice dislocations is discussed in detail for the case of symmetric boundaries in simple cubic structures. In particular, It is shown that the motion of grain boundary dislocations that are generated as a result of various combinations of crystal lattice dislocations gives rise to either grain boundary sliding or grain boundary migration or both. The structure and motion of various types of ledges such as glide ledges, climb ledges, and compensated and uncompensated ledges are considered in this analysis. Although the analysis is done for simple cubic structures, the concepts developed are quite general and can be applied to more complex crystal structures. It is also shown that some of the grain boundary dislocation arrays can be suitably described as disclination dipoles, and such a dualistic representation is used to interpret the shape changes associated with the grain boundary deformation.

ISSN:0021-8979    

DOI:10.1063/1.1663455

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A method for the treatment of x‐ray extinction and absorption is developed for thick flat crystals in symmetrical Bragg geometry and for curved crystals in symmetrical Bragg geometry where the diffraction region may be approximated as a thin crystal in Laue geometry. This method permits the calculation of diffracting power vs wavelength. The crystals may have the full range of properties between the ideally imperfect and perfect cases. The parameters describing the mosaic blocks (mosaic block size and mosaic block misorientation) are related to the dislocation arrangement for crystals of Zachariasen's type I (where extinction is primarily controlled by the mosaic block misorientation). It is indicated that for crystals of type II (where extinction is primarily controlled by the mosaic block size) the mosaic blocks are usually due to defects other than dislocations.

ISSN:0021-8979    

DOI:10.1063/1.1663456

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In part I of this series we presented a method for the calculation of the integral diffracting power applicable to flat and curved crystals in symmetrical Bragg geometry. In the present paper we report a test of the above method. The integral reflection coefficient vs wavelength has been measured and calculated for an unusually perfect crystal of LiF and for a crystal of LiF rendered relatively imperfect by ``flexing''. Agreement was good. The mean mosaic block size and misorientation used in the calculation were deduced by using dislocation etch pitting. It is concluded that LiF is of Zachariasen's type I (i.e., extinction is primarily controlled by the mosaic block misorientation).

ISSN:0021-8979    

DOI:10.1063/1.1663457

出版商:AIP    

年代:1974

数据来源: AIP