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排序方式: 共有10000条查询结果,搜索用时 217 毫秒
941.
Ivonin I. V. Krasil'nikova L. M. Lavrent'eva L. G. Porokhovnichenko L. P. 《Russian Physics Journal》2002,45(5):493-497
Experimental proofs of asymmetric trapping of atoms at the growth step in vapor-phase epitaxy of gallium arsenide in the GaAs–AsCl3–H2 system are given. The data obtained confirm the important role of the surface diffusion mass transfer in the growth of epitaxial GaAs layers on vicinals in the neighborhood of (111)A. The effective diffusion length is estimated. 相似文献
942.
The most promising next generation Image Velocimtry (IV) is the high-speed Dynamic PIV. It requires the development of innovative
high-speed video camera sensors. We started by specifying the required performance of these new sensors, for measurements
in air and water flows. These criteria founded on the most recent developments in PIV algorithms and incorporate results from
a large questionnaire survey of users of high-speed video cameras in Japan. The results suggest that the followings are required:
(1) frame rate of 1,000,000 fps, (2) pixel count of 1,000,000 pixels, (3) frame storage capacity of 100–200 frames for tracing
a single event and 10,000 frames for turbulent measurements, (4) gray levels of 4–8 bits for PTV; 12 bits for observation.
Finally, we reviewed the state of the art of high-speed video-image sensors. Currently the standard parallel-readout sensors
can operate at 1 Kfps with a pixel count of approximately 1 Kpixels. The In-situ Storage Image Sensor (ISIS) developed by
the authors has recently achieved frame rates of 1 Mfps. 相似文献
943.
944.
用实验的方法,研究电流并联负反馈对放大器性能的改善,提出电流型、并联型负反馈放大器性能参数的测量方法。 相似文献
945.
946.
S. Moss de Oliveira P. M. C. de Oliveira F. C. de Sá Barreto 《Journal of statistical physics》1995,78(5-6):1619-1627
Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint. 相似文献
947.
Several α-ketoalcohols of synthetic value were resolved using lipase as a catalyst. Lipoprotein lipase (LPL) provided the best rate of hydrolysis and kinetic differentiation. One of these optically pure α-ketoalcohol was converted to (5)-ibuprofen in good optical purity. The stereospecific inversion of (R)-alcohol to (S)-alcohol is described. 相似文献
948.
W. A. Rodrigues Jr. Q. A. G. de Souza J. Vaz Jr. P. Lounesto 《International Journal of Theoretical Physics》1996,35(9):1849-1900
In this paper we study Dirac-Hestenes spinor fields (DHSF) on a four-dimensional Riemann-Cartan spacetime (RCST). We prove that these fields must be defined as certain equivalence classes of even sections of the Clifford bundle (over the RCST), thereby being certain particular sections of a new bundle named the spin-Clifford bundle (SCB). The conditions for the existence of the SCB are studied and are shown to be equivalent to Geroch's theorem concerning the existence of spinor structures in a Lorentzian spacetime. We introduce also the covariant and algebraic Dirac spinor fields and compare these with DHSF, showing that all three kinds of spinor fields contain the same mathematical and physical information. We clarify also the notion of (Crumeyrolle's) amorphous spinors (Dirac-Kähler spinor fields are of this type), showing that they cannot be used to describe fermionic fields. We develop a rigorous theory for the covariant derivatives of Clifford fields (sections of the Clifford bundle, CB) and of Dirac-Hestenes spinor fields. We show how to generalize the original Dirac-Hestenes equation in Minkowski spacetime for the case of RCST. Our results are obtained from a variational principle formulated through the multiform derivative approach to Lagrangian field theory in the Clifford bundle. 相似文献
949.
950.