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991.
992.
Limitations of several anisotropic yield criteria are discussed. Hill's 1948 criterion overestimates the variation of yield strength with direction, while the specializations of Hill's 1979 theory assume planar isotropy. Shear stress terms cannot simply be included in either the author's 1979 criterion or in Hill's 1979 general criteria.It is suggested that the author's criterion be modified so that it is expressed in terms of principal stresses rather than referring stresses to the symmetry axes. 相似文献
993.
This paper describes the work done by the Autonomous Systems Lab of Ecole Polytechnique Federale de Lausanne (EPFL) on the global design of an unmanned solar airplane that can fly continuously over days and night. Part of the Sky-Sailor Project, a first prototype was designed and demonstrated to have very good flight characteristics. The prototype achieved an autonomous flight of five hours with its energy only from the sun. A lightweight control and navigation system was also designed for the aircraft. 相似文献
994.
Mueller C. Sullivan C. Chang W. Hall D. Zino J. Rice R. 《Quantum Electronics, IEEE Journal of》1980,16(3):363-372
Calculated butt coupling efficiency between a GaAlAs double heterostructure laser and a single-mode LiNbO3 Ti-diffused optical waveguide is presented in this paper as a function of the transverse displacement, the angular alignment, the longitudinal separation between the laser and the waveguide end surfaces, the radiation field of the laser diode and its dependence on the laser diode structure, and the mode profile of the waveguide and its dependence on experimental diffusion parameters. The maximum efficiency is less than 40 percent because of the mismatch between the waveguide mode and the laser radiation, caused primarily by the experimental limitations in their structures. The effect of the reflection of the waveguide end surface on the laser oscillation has also been estimated. 相似文献
995.
996.
The chemistry and electrochemistry of electroplating baths based on Pd(NH3)2Br2 and Pd(NH3)2(NO2)2 has been investigated and compared with that previously reported for Pd(NH3)2Cl2. It is shown that electroactive species in all the baths is Pd(NH3)
4
2+
and, hence, the mechanisms and current efficiencies for the cathodic deposition of palladium metal are similar in all three media. On the other hand, only in bromide electrolytes is the palladium found to dissolve anodically. 相似文献
997.
MS Oitzl ER de Kloet M Jo?ls W Schmid TJ Cole 《Canadian Metallurgical Quarterly》1997,9(11):2284-2296
Previous studies in rats using the Morris water maze suggested that the processing of spatial information is modulated by corticosteroid hormones through mineralocorticoid and glucocorticoid receptors in the hippocampus. Mineralocorticoid receptors appear to be involved in the modulation of explorative behaviour, while additional activation of glucocorticoid receptors facilitates the storage of information. In the present study we used the water maze task to examine spatial learning and memory in mice homozygous and heterozygous for a targeted disruption of the glucocorticoid receptor gene. Compared with wild-type controls, homozygous and heterozygous mice were impaired in the processing of spatial but not visual information. Homozygous mutants performed variably during training, without specific platform-directed search strategies. The spatial learning disability was partly compensated for by increased motor activity. The deficits were indicative of a dysfunction of glucocorticoid receptors as well as of mineralocorticoid receptors. Although the heterozygous mice performed similarly to wild-type mice with respect to latency to find the platform, their strategy was more similar to that of the homozygous mice. Glucocorticoid receptor-related long-term spatial memory was impaired. The increased behavioural reactivity of the heterozygous mice in the open field points to a more prominent mineralocorticoid receptor-mediated function. The findings indicate that (i) the glucocorticoid receptor is of critical importance for the control of spatial behavioural functions, and (ii) mineralocorticoid receptor-mediated effects on this behaviour require interaction with functional glucocorticoid receptors. Until the development of site-specific, inducible glucocorticoid receptor mutants, glucocorticoid receptor-knockout mice present the only animal model for the study of corticosteroid-mediated effects in the complete absence of a functional receptor. 相似文献
998.
999.
1000.
Black W.Z. Woodruff G.W. Kovalchik P.G. Duda F.T. 《Power Delivery, IEEE Transactions on》1994,9(3):1209-1216
This paper presents a mathematical model that is capable of calculating the ampacity of a wide variety of power cable designs consisting of an arbitrary number of layers on a cable reel. The model considers round cables with copper conductors. The validity and accuracy of the ampacity model were verified by comparing the predicted temperature distribution within the reel with measured temperatures collected during an extensive testing program conducted at the US Bureau of Mines (USBM). The mathematical model predicted a temperature distribution within the cable layers that was very close to the measured variation in temperature. The value of the program is illustrated by calculating ampacities for several copper conductor sizes 相似文献