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排序方式: 共有297条查询结果,搜索用时 15 毫秒
51.
L. Marsavina R. Susan-Resiga N. Faur R. Negru 《Theoretical and Applied Fracture Mechanics》2010,53(2):136-144
The performance of engineering components and structures is strongly influenced by the interaction between design, manufacture and materials. A methodology to assess the integrity of a circular collector is presented by investigating the failure of copper lamellas. The investigated circular collector, having 315 copper lamellas, is one of the main parts of an electric motor. The fracture of the copper lamellas was observed in normal operation. This unexpected fracture required an investigation of the fracture origin, in order to improve the initial design. The numerical results of the finite element analysis on the stress field in the copper lamellas for the operating regimes, and the stress concentration effects are shown. Failure assessment diagram, based on notch stress intensity factor, was considered in order to estimate if crack initiation can occur. Finally a study of crack propagation will present comparatively the numerical obtained crack path against the one observed in-service. 相似文献
52.
A new series of 3‐[ω‐[4‐(4‐substituted phenyl)piperazin‐1‐yl]alkyl]‐5H‐pyrimido[5,4‐b]indole‐(1H,3H)‐2,4‐diones ( 3–10 and 12–13 ) were synthesized from the N‐(2‐chloroethyl)‐N'‐[3‐(2‐ethoxycarbonyl)indolyl] urea ( 1 ) or the N‐(3‐chloropropyl)‐N'‐[3‐(2‐ethoxycarbonyl)indolyl] urea ( 2 ) and a number of 1‐(4‐substi‐tuted‐phenyl)piperazines. 3‐[2‐[4‐(4‐Aminophenyl)piperazin‐1‐yl]ethyl]‐5H‐pyrimido[5,4‐b]indole‐(1H,3H)2,4‐dione ( 14 ) was obtained by reduction of the parent nitro compound 8 . The obtained 5H‐pyrimido[5,4‐b]indole‐(1H,3H)2,4‐dione derivatives were tested towards cloned α1A, α1B and α1D adrenergic receptors subtypes in binding assays. Some compounds showed good affinity and selectivity for the α1D‐adrenoceptor subtype. 相似文献
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Ohne Zusammenfassung 相似文献
54.
The parsimony haplotyping problem was shown to be NP-hard when each genotype had k?3ambiguous positions, while the case for k?2 was open. In this paper, we show that the case for k?2 is polynomial, and we give approximation and FPT algorithms for the general case of k?0 ambiguous positions. 相似文献
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Armandodoriano?BiancoEmail author Mario?Brufani Romeo?Ciabatti Cristiana?Melchioni Vinicio?Pasquali 《Molecules Online》1998,2(10):129-136
Influenza types A and B both cause serious disease in man; vaccines are in use but must be reformulated each year in response to antigenic variation and are frequently ineffective against new influenza variants. Influenza viruses are enveloped RNA viruses which contain two major surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA, EC 3.2.1.18). These proteins are essential for infection and offer potential targets for antiviral drug development. Based upon the knowledge of the most important steps of the whole interaction between virus and host cell, the main purpose of our research was to find a sialic acid analogue for increasing the affinity of the sialic acid cell receptor analogue to the principal binding site of HA. A series of sialic acid analogues were prepared and their structures were designed with the goal to have molecules able to saturate the HA receptor and thereby be potentially useful as anti-influenza drugs. 相似文献
58.
Barbara Richichi Stefano CicchiUgo Chiacchio Giovanni Romeo Alberto Brandi 《Tetrahedron》2003,59(28):5231-5240
The synthesis of two new bicyclic nucleoside analogues is reported. These compounds are iso-homonucleoside and are synthesised through a 1,3-dipolar cycloaddition of an enantiopure cyclic nitrone to protected allyl acohol and subsequent introduction of thymine by a Mitsunobu reaction. 相似文献
59.
FTIR analysis and monitoring of synthetic aviation engine oils 总被引:2,自引:0,他引:2
Synthetic turbine oils from military aircraft engines were analysed for antioxidant content and total acid number using infrared (IR) spectroscopy. Two-dimensional IR correlation analysis was employed to investigate and interpret observed trends in the spectra, as acid was formed and antioxidant species were depleted in the oils, as a function of aging and engine wear. Principal components and partial least squares algorithms were used and compared for the development of calibration and prediction models. Transmission IR spectrometry is demonstrated to be effective for the analysis and monitoring of synthetic aviation turbine engine oils and shown to provide rapid and accurate information as compared with traditional analytical techniques and methods. 相似文献
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