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排序方式: 共有217条查询结果,搜索用时 46 毫秒
1.
Positivity - We prove new characterisations of exponential stability for positive linear discrete-time systems in ordered Banach spaces, in terms of small-gain conditions. Such conditions have... 相似文献
2.
Arman Melkumyan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(2):330-349
The problem of electric and acoustic waves diffraction by a half-plane crack in a transversal isotropic piezoelectric medium
is investigated. The crack is assumed to be electric permeable and free of tractions. The so-called “quasi-hyperbolic approximation”
[15] is adopted. Applying Laplace transformations and Wiener–Hopf technique a closed form solution is obtained. By the means
of Cagniard–de Hoop method a detailed dynamic full electroacoustic wavefield’s investigation is conducted. Mode conversion
between electric and acoustic waves, effect of electroacoustic head wave, Bleustein–Gulyaev surface wave and the wavefield
structure depending on the type of the incident wave (acoustic or electric) and its angle of incidence are analyzed in details.
The dynamic field intensity factors at the crack tip depending on the angle of incidence and on time are derived explicitly.
Numerical analysis is presented. 相似文献
3.
4.
Shengfei Jin Hang T. Dang Graham C. Haug Viet D. Nguyen Hadi D. Arman Oleg V. Larionov 《Chemical science》2020,11(34):9101
Construction of C–C bonds at the α-carbon is a challenging but synthetically indispensable approach to α-branched carbonyl motifs that are widely represented among drugs, natural products, and synthetic intermediates. Here, we describe a simple approach to generation of boron enolates in the absence of strong bases that allows for introduction of both α-alkyl and α-aryl groups in a reaction of readily accessible 1,2-dicarbonyls and organoboranes. Obviation of unselective, strongly basic and nucleophilic reagents permits carrying out the reaction in the presence of electrophiles that intercept the intermediate boron enolates, resulting in two new α-C–C bonds in a tricomponent process.α-Branched carboxylic acids and other carbonyls are readily accessed by a metal- and base-free deoxygenative α-alkylation and α-arylation of 1,2-dicarbonyls via boron enolates, resulting in a tricomponent coupling with unconventional electrophiles. 相似文献
5.
6.
Andrii Lozynskyi Borys Zimenkovsky Iryna Ivasechko Julia Senkiv Andrzej Gzella Olexandr Karpenko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1149-1157
AbstractThe synthesis and anticancer activity evaluation of new thiazolo[4,5-b]pyridine-5-carboxylic acid amides is described. The structures of the synthesized compounds were confirmed by spectroscopic data and a single crystal X-ray diffraction analysis for 2.4. The synthesized compounds were screened for their in vitro anticancer activity according to US NCI protocols. The most active 7-(4-fluorophenyl)-2-oxo-2,3-dihydrothiazolo[4,5-b]pyridine-5-carboxylic acid (4-chlorophenyl)amide 2.2 and 7-(4-chlorophenyl)-2-oxo-2,3-dihydrothiazolo[4,5-b]pyridine-5-carboxylic acid (4-chlorophenyl)amide 2.5 were screened for their cytotoxicity effects on C6 Rat glioma cells and U373 Human glioblastoma astrocytoma cells which revealed promising results comparable to temozolamide as reference control according MTT assay data. 相似文献
7.
Shishkina Svitlana V. Ishchenko Alexander A. Kulinich Andrii V. 《Structural chemistry》2021,32(3):1341-1345
Structural Chemistry - Herein we report an X-ray crystallographic characterization of tetramethine merocyanine based on benzimidazole and thiobarbituric acid, which shows negative solvatochromism... 相似文献
8.
An efficient stereoselective three-component reaction for the synthesis of functionalized spiro[4H-pyran-3,3′-oxindole] derivatives was realized through an organocatalyzed domino Knoevenagel/Michael/cyclization reaction using a cinchonidine-derived thiourea as the catalyst. Using water as the additive was found to improve the product ee values significantly. Under the optimized conditions, the reactions between isatins, malononitrile, and 1,3-dicarbonyl compounds yield the desired spirooxindole products in good yields (71–92%) and moderate to high ee values (up to 87% ee). 相似文献
9.
A novel scheme for pressure fluctuations in turbulent flows is developed. The pressure fluctuations are sensitive parameter in some of the fluid phenomena. In the computational methods and modeling turbulence flow, the pressure fluctuations are eliminated after averaging of the Navier-Stokes equations, and only average pressure could be calculated. In this research, the Reynolds-averaged Navier-Stokes equations are computed using SIMPLE method. The Reynolds stress transport model (RSTM) is used to determine the Reynolds stresses and the flow details. The velocity fluctuations are simulated using the Kraichnan model. The Poisson equation for the pressure fluctuations is obtained by taking the divergence of the incompressible momentum equation and algebraic operations, and this equation is numerically solved by finite difference method. The effects of Reynolds number on the pressure fluctuations are studied. 相似文献
10.
Farhad Shirini Masoumeh Abedini Somayeh Akbari-Dadamahaleh Arman Rahmaninia 《Journal of the Iranian Chemical Society》2014,11(3):791-824
Xanthenes and their derivatives as very important classes of organic compounds are key structural elements of many biologically active compounds. These materials are important heterocyclic nucleus of various dyes and drugs. Because of their wide range of pharmacological, industrial and synthetic applications, many methods for the preparation of xanthenes are reported in the literature. In recent years, among the other chemists, introduction of new methods for the preparation of these types of compounds has attracted the attention of Iranian chemists. The result of these efforts is the introduction of appropriate, effective and efficient methods. In this paper, we have a brief review on these methods and their main advantages and important applicabilities. 相似文献