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排序方式: 共有88条查询结果,搜索用时 15 毫秒
1.
V. V. Lozhkarev S. G. Garanin R. R. Gerke V. N. Ginzburg E. V. Katin A. V. Kirsanov G. A. Luchinin A. N. Mal’shakov M. A. Mart’yanov O. V. Palashov A. K. Poteomkin N. N. Rukavishnikov A. M. Sergeev S. A. Sukharev G. I. Freidman E. A. Khazanov A. V. Charukhchev A. A. Shaikin I. V. Yakovlev 《JETP Letters》2005,82(4):178-180
In experiments on the parametrical amplification of femtosecond pulses in wide-aperture DKDP crystals, a power of more than 100 TW has been reached, which is much higher than the record level achieved in such lasers. The energy efficiency obtained for the parametric amplifier is equal to 27%. The energy of a 72-fs pulse is equal to 10 J. 相似文献
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The paper deals with the effect of different stress states on damage and failure behavior of ductile materials. To be able to model these effects a continuum damage model has been proposed taking into account the dependence of the stress intensity, the stress triaxiality and the Lode parameter on the constitutive equations. The model is based on the introduction of damaged and fictitious undamaged configurations. Only experiments are not adequate enough to determine all constitutive parameters. Therefore, additional three-dimensional micro-mechanical simulations of representative volume elements have been performed to get more insight in the complex damage mechanisms. These simulations cover a wide range of different void sizes, void shapes and void distributions. After all, the results from the micro-mechanical simulations are used to propose the damage equations and to identify corresponding parameters. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Johanna Flock Dr. Amra Suljanovic Dr. Ana Torvisco Dr. Wolfgang Schoefberger Birgit Gerke Prof. Dr. Rainer Pöttgen Prof. Dr. Roland C. Fischer Prof. Dr. Michaela Flock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15504-15517
Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition‐metal chemistry. However, the stabilization of main‐group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6‐[ArNH‐CH2]2(NC5H3) (Ar=C6H3‐2,6‐iPr2)) with Sn[N(SiMe3)2]2 produces the DIMPYSn complex (DIMPY=(2,6‐[ArN?CH]2(NC5H3)) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low‐valent SnII complexes, including a [DIMPYSnIICl]+[SnCl3]? ion pair, a bisstannylene DAMPY{SnII[N(SiMe3)2]2}2, and the enamine complex MeDIMPYSnII, were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and 119Sn Mössbauer spectroscopy. 相似文献
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Model based prediction of the trap limited diffusion of hydrogen in post‐hydrogenated amorphous silicon
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Sebastian Gerke Hans‐Werner Becker Detlef Rogalla Reinhart Job Barbara Terheiden 《固体物理学:研究快报》2016,10(11):828-832
The diffusion of hydrogen within an hydrogenated amorphous silicon (a‐Si:H) layer is based on a trap limited process. Therefore, the diffusion becomes a self‐limiting process with a decreasing diffusion velocity for increasing hydrogen content. In consequence, there is a strong demand for accurate experimental determination of the hydrogen distribution. Nuclear resonant reaction analysis (NRRA) offers the possibility of a non‐destructive measurement of the hydrogen distribution in condensed matter like a‐Si:H thin films. However, the availability of a particle accelerator for NRR‐analysis is limited and the related costs are high. In comparison, Fourier transform infrared spectroscopy (FTIR) is also a common method to determine the total hydrogen content of an a‐Si:H layer. FTIR spectrometers are practical table‐top units but lack spatial resolution. In this study, an approach is discussed that greatly reduces the need for complex and expensive NRR‐analysis. A model based prediction of hydrogen depth profiles based on a single NRRA measurement and further FTIR measurements enables to investigate the trap limited hydrogen diffusion within a‐Si:H. The model is validated by hydrogen diffusion experiments during the post‐hydrogenation of hydrogen‐free sputtered a‐Si. The model based prediction of hydrogen depth profiles in a‐Si:H allows more precise design of experiments, prevents misinterpretations, avoids unnecessary NRRA measurements and thus saves time and expense. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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We prove part of a conjecture by Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28.) regarding threshold functions for the existence of an H‐factor in a random graph . We prove that the conjectured threshold function is correct for any graph H which is not covered by its densest subgraphs. We also demonstrate that the main result of Johansson, Kahn, and Vu (Factors in random graphs, Random Struct. Algorithms 33 (2008), 1, 1–28) generalizes to multigraphs, digraphs, and a multipartite model. 相似文献
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G. Alexander L. Criegee H.C. Dehne K. Derikum R. Devenish G. Flügge G. Franke Ch. Gerke E. Hackmack P. Harms G. Horlitz Th. Kahl G. Knies E. Lehmann R. Schmitz U. Timm P. Waloschek K. Wacker 《Physics letters. [Part B]》1978,78(1):162-166
The decay of the heavy lepton τ into πv has been established using the magnetic detector PLUTO. The branching ratio is determined to be BR(τ→πv)=(9.0 ± 2.9)% with an additional systematic uncertainty of 2.5%. This value is in good agreement with the theoretical prediction. 相似文献
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A new approach to helical primary structures of four-membered rings uses a cycloaddition of a trimethylenketeniminium salt to suitable tailored methylenecyclobutanes to assemble the desired carbon framework. The results are short and effective syntheses of (M)-trispiro[3.0.0.3.2.2]tridecane [(M)-5], and (P)- and (M)-tetraspiro[3.0.0.0.3.2.2.2]hexadecane [(P)- and (M)-24]. Unlike helices of three-membered rings, the specific rotation decreases, as the length of the helix increases. 相似文献
10.
The paper deals with the effect of stress state on damage and failure behavior of isotropic ductile metals. In the continuum damage model the damage behavior of ductile metals is adequately described by a generalized damage condition and an anisotropic damage rule. The damage criterion is based on series of uniaxial experiments with differently notched specimens and corresponding numerical simulations as well as on various numerical calculations on the micro-scale. Different branches of the damage criterion depending on stress triaxiality and Lode parameter are considered. To be able to validate the proposed stress-state-dependent functions new experiments with two-dimensionally loaded specimens have been developed. Corresponding numerical simulations show that these shear-tension and shear-compression tests cover a wide range of stress triaxialities and Lode parameters. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献