排序方式: 共有11条查询结果,搜索用时 15 毫秒
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El Kettani SE Escudié J Couret C Ranaivonjatovo H Lazraq M Soufiaoui M Gornitzka H Nemes GC 《Chemical communications (Cambridge, England)》2003,(14):1662-1663
The first alpha-germyl-substituted alpha-amino ester and alpha-germyl-substituted alpha-aminophosphonic ester have been synthesized by a one-pot reaction between the germene Mes2Ge=CR2 (CR2 = fluorenylidene) and the iminoester or iminophosphonate Ph(H)C=NCH2-Y (Y = COOMe, P(O)(OEt)2). 相似文献
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In this paper, we develop a method for constructing minimum volume ellipsoids containing a wedge-shaped subset of a given
ellipsoid. This construction yields a class of ellipsoid algorithms for convex programming that use rank-two update formulae.
Research supported by the National Science Foundation, Grant No. MC582-01790. 相似文献
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We study the performance of some rank-two ellipsoid algorithms when used to solve nonlinear programming problems. Experiments are reported which show that the rank-two algorithms studied are slightly less efficient than the usual rank-one (center-cut) algorithm. Some results are also presented concerning the growth of ellipsoid asphericity in rank-one and rank-two algorithms. 相似文献
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Mustapha Ech-Cherif El Kettani Hassane Benbouziane 《Rendiconti del Circolo Matematico di Palermo》2014,63(2):311-316
Let \({\mathcal {B}}(X)\) be the algebra of all bounded linear operators on an infinite dimensional complex Banach space \(X\) . We determine the form of surjective additive maps \(\varphi :{\mathcal {B}}(X)\rightarrow {{\mathcal {B}}(X)}\) which preserve operators of inner local spectral radius zero at points of \(X\) . 相似文献
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Nadia Harhad Mounsif Ech-Cherif El-Kettani Hakim Djelouah Jean-Louis Izbicki Mihai Valentin Predoi 《Ultrasonics》2014
Guided waves propagation in immersed plates with irregular surfaces has potential application to detection and assessment of the extent, depth and pattern of the irregularity. The complexity of the problem, due to the large number of involved parameters, has limited the number of existing studies. The simplest case of irregularities of practical interest is the two-dimensional corrosion profile. Even this case is in general so complex, that one can extract several amplitude dominant periodic surfaces only by using a Fourier spectrum of the surface. Guided waves in plates, with one or both free surfaces having periodic perturbations of different shapes, have been presented in specialized literature. 相似文献
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The aim of this work is to give experimental and numerical results on the behaviour of guided waves that propagate downslope in a free elastic plate with slowly linearly varying thickness. We show experimentally the propagation of adiabatic modes, which are guided waves that adapt to the varying thickness of the plate. As the thickness is decreasing, a given guided wave will reach its thickness cut-off. When this happens, we show that two phenomena occur: the reflection of this wave and its propagation backward in the plate, its conversion into a different guided wave which goes on propagating downslope in the plate. The numerical study is done with the software Ansys, based on the finite element method. The results obtained confirm the experimental ones. 相似文献
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Experimental and numerical results are presented on the behavior of guided waves in elastic plates in plane strain that include a Gaussian variation of their section, located between two areas of constant thickness. The area of varying section is wide compared to the used wavelengths, which allows wave propagation inside this area. The experimental results show that an incident Lamb wave is indeed converted into an adiabatic wave inside the varying section domain. A trapped wave in the Gaussian domain is also observed, depending on the incident mode and on the Gaussian maximum height. Outside the varying section domain, conversion into different Lamb waves is observed. This conversion phenomenon is experimentally quantified by the measurement of the Lamb wave normal displacement and of its carried energy. A numerical study, based on the Finite Elements Method is performed, and successfully compared to the experimental results. 相似文献