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排序方式: 共有691条查询结果,搜索用时 0 毫秒
61.
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Martina Baeumler Frank Gütle Vladimir Polyakov Markus Cäsar Michael Dammann Helmer Konstanzer Wilfried Pletschen Wolfgang Bronner Rüdiger Quay Patrick Waltereit Michael Mikulla Oliver Ambacher Franck Bourgeois Reza Behtash Klaus J. Riepe Paul J. van der Wel Jos Klappe Thomas Rödle 《Journal of Electronic Materials》2010,39(6):756-760
64.
Mathias Deckers Ernst Wilhelm Pfitzinger Wilfried Ulm 《热力透平》2004,33(4):209-215
This paper presents Siemens' latest improvements in steam turbine blading and blading design tools. The technology offers improved performance and highest efficiencies for a wide range of steam turbine applications. 相似文献
65.
66.
Hoffmann M Küppers H Schneller T Böttger U Schnakenberg U Mokwa W Waser R 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(10):1240-1246
High piezoelectric coupling coefficients of PZT-based material systems can be employed for actuator functions in micro-electro-mechanical systems (MEMS) offering displacements and forces which outperform standard solutions. This paper presents simulation, fabrication, and development results of a stress-compensated, PZT-coated cantilever concept in which a silicon bulk micromachining process is used in combination with a chemical solution deposition (CSD) technique. Due to an analytical approach and a finite element method (FEM) simulation for a tip displacement of 10 /spl mu/m, the actuator was designed with a cantilever length of 300 /spl mu/m to 1000 /spl mu/m. Special attention was given to the Zr/Ti ratio of the PZT thin films to obtain a high piezoelectric coefficient. For first characterizations X-ray diffraction (XRD), scanning electron microscopy (SEM), hysteresis-, current-voltage I(V)and capacitance-voltage C(V)-measurements were carried out. 相似文献
67.
Among the various possible ways of dealing with notch and crack situations, the scaled boundary finite element method [SBFEM,
(Wolf and Song in Finite element modelling of unbounded structures. Wiley, Chichester, 1996; Wolf in The scaled boundary finite element method. Wiley, Chichester, 2003)] has been adopted in this work. This method has been proved to be versatile, much less time consuming than the finite element
method and generates highly accurate numerical predictions in cases of structures with notches and cracks. The SBFEM gives
the advantage of boundary element method by reducing one dimension in modelling the structures but the mathematical formulations
are more related to conventional displacement based finite element method. This method requires a certain scalability of the
given structure with respect to a point called similarity center. Like in the case of the boundary element method, the structure
needs to be discretized only at the surface where standard displacement based isoparametric finite element formulations are
adequate. Unlike in the boundary element method, however, no fundamental solution is required by the scaled boundary finite
element method. The similarity or scalability of the method requires separation of coordinates such that in the radial direction
(i.e. scaling direction) it yields simple differential equations that can be solved analytically. So this approach can be
considered as a semi-analytical method. Several two-dimensional examples have been analysed for crack and notch situations
that are well known cases in fracture mechanics. A number of three-dimensional cases have been considered for different crack
configurations that yield high order of singularity. The results, according to the authors’ knowledge are up to now unpublished
in the open literature. Parametric studies are conducted for structures with bi-material interfaces. 相似文献
68.
Using simple simulation methods, the author verifies that the formulas used to estimate both the expected success ratio of a selection and the expected average criterion score of the selectees overestimate the real gain one may expect to obtain when hiring a preestablished proportion of employees from a finite sample of applicants. To correct for this deficiency, the present article shows how an exact estimate of the expected payoff can be obtained. In addition, it indicates how the new approach can be used to assess the sampling variability of the utility estimates. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
Wilfried Brauer 《Informatik-Spektrum》1999,22(6):405-405
Ohne Zusammenfassung 相似文献
70.
Wilfried Gauthier Frédéric Pailler Jacques Lamon Rene Pailler 《Journal of the American Ceramic Society》2009,92(9):2067-2073
The static fatigue of SiC-based fiber bundles and single fibers has been examined in previous papers, with emphasis placed on the analysis of the stress–rupture time data, and on the modelling of delayed failure from slow crack growth. The present paper investigates the oxidation of the fibers during static fatigue, at temperatures in the intermediate temperature range (500°–800°C). Two oxidation-induced phenomena have been evidenced: the formation of a thin silica film at the surface of fibers and the delayed failure of fiber bundles and single filaments. The stress–rupture time data are interpreted with respect to the chemical and structural characteristics of fibers, and to the oxide film growth rate. The structural analysis of the fibers was carried out using scanning electron microscopy and Auger electron spectroscopy. Delayed failure was found to result from slow crack propagation from surface defects, as a result of the consumption of the free carbon at grain boundaries and the local stresses induced by the SiC→SiO2 transformation at the crack tip. The respective contributions of these phenomena to static fatigue are discussed. 相似文献