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The propagation of elastic stress waves in a conical shell subjected to axial impulsive loading is studied in this paper by
means of the finite element calculation and model experiments. It is shown that there are two axisymmetrical elastic stress
waves propagating with different velocities, i.e., the longitudinal wave and the bending wave. The attenuation of these waves
while propagating along the shell surface is discussed. It is found in experiments that the bending wave is also generated
when a longitudinal wave reflects from the fixed end of the shell, and both reflected waves will separate during the propagation
due to their different velocities.
Southwest Institute of Structural Mechanics 相似文献
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Uranium Metalla‐Allenes with Carbene Imido R2C=UIV=NR′ Units (R=Ph2PNSiMe3; R′=CPh3): Alkali‐Metal‐Mediated Push–Pull Effects with an Amido Auxiliary 下载免费PDF全文
Dr. Erli Lu Dr. Floriana Tuna Dr. William Lewis Prof. Dr. Nikolas Kaltsoyannis Prof. Dr. Stephen T. Liddle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11554-11558
We report uranium(IV)‐carbene‐imido‐amide metalla‐allene complexes [U(BIPMTMS)(NCPh3)(NHCPh3)(M)] (BIPMTMS=C(PPh2NSiMe3)2; M=Li or K) that can be described as R2C=U=NR′ push–pull metalla‐allene units, as organometallic counterparts of the well‐known push–pull organic allenes. The solid‐state structures reveal that the R2C=U=NR′ units adopt highly unusual cis‐arrangements, which are also reproduced by gas‐phase theoretical studies conducted without the alkali metals to remove their potential structure‐directing roles. Computational studies confirm the double‐bond nature of the U=NR′ and U=CR2 interactions, the latter increasingly attenuated by potassium then lithium when compared to the hypothetical alkali‐metal‐free anion. Combined experimental and theoretical data show that the push–pull effect induced by the alkali metal cations and amide auxiliary gives a fundamental and tunable structural influence over the C=UIV=N units. 相似文献
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Erli Lu Oliver J. Cooper Jonathan McMaster Floriana Tuna Eric J. L. McInnes William Lewis Alexander J. Blake Stephen T. Liddle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(26):6814-6818
We report the uranium(VI) carbene imido oxo complex [U(BIPMTMS)(NMes)(O)(DMAP)2] ( 5 , BIPMTMS=C(PPh2NSiMe3)2; Mes=2,4,6‐Me3C6H2; DMAP=4‐(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two‐electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T‐shaped motif with respect to the carbene, which is consistent with an inverse trans‐influence. Complex 5 reacts with tert‐butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPMTMS)(O)2(DMAP)2] ( 6 ). 相似文献
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Rueping M Sugiono E Theissmann T Kuenkel A Köckritz A Pews-Davtyan A Nemati N Beller M 《Organic letters》2007,9(6):1065-1068
The enantioselective Br?nsted acid catalyzed addition of methyleneaminopyrrolidine to N-Boc imines has been achieved in the presence of chiral phosphoric acids derived from 3,3'-di(phenanthryl)-H8-BINOL. The corresponding aminohydrazones have been isolated in good yields with enantiomeric excesses up to 90%. [reaction: see text] 相似文献
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A highly enantioselective Friedel-Crafts reaction catalyzed by a chiral phosphoric acid was developed. N-Boc-protected ethyl trifluoropyruvate imine was activated by 6 mol % of catalyst and reacted with a wide variety of indole derivatives to afford quaternary α-amino acids in excellent yields (up to 99%) and high enantioselectivities (up to 98:2 er). 相似文献
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