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排序方式: 共有815条查询结果,搜索用时 15 毫秒
121.
A study is reported of the influence of unsteady flow on the aerodynamics and aeroacoustics of vertical axis wind turbines by numerical simulation. The combination of aerodynamic predictions with a discrete vortex method and aeroacoustic predictions based on Ffowcs Williams-Hawkings equation is used to achieve this goal. The numerical results show that unsteady flow of the turbine has a significant influence on the turbine aerodynamics and can lead to a decrease in generated noise as compared to the conventional horizontal axis wind turbine at the similar aerodynamic performance. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
122.
Viorel Barbu 《偏微分方程通讯》2013,38(7):1318-1338
One proves that the generator of the transition semigroup of a stochastic differential equation with boundary reflection on a convex set K is the realization of a second order elliptic operator on K with zero oblique derivative boundary conditions. Several implications to parabolic problems with oblique derivative are also derived. 相似文献
123.
124.
Sebastian Aniţa Viorel Arnăutu Smaranda Dodea 《Numerical Functional Analysis & Optimization》2013,34(4):351-369
We consider a two-component reaction-diffusion system with a nonlocal reaction term. A necessary condition and a sufficient condition for the internal stabilizability to zero of one of the two components of the solution while preserving the nonnegativity of both components have been established in [6]. In case of stabilizability, a feedback stabilizing control of harvesting type has been indicated. The rate of stabilization (for the indicated feedback control) is given by the principal eigenvalue of a certain non-selfadjoint operator. A large principal eigenvalue leads to a fast stabilization. The first main goal of this article is to approximate this principal eigenvalue. This is done in two steps. First, we investigate the large-time behavior of the solution to a logistic population dynamics with migration, and next we derive as a consequence a method to approximate the principal eigenvalue. The other main goal is to derive a conceptual iterative algorithm to improve the position of the support of the control in order to get a faster stabilization. Our results apply to prey-predator systems. 相似文献
125.
126.
Dr. Radu Custelcean Neil J. Williams Charles A. Seipp 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(36):10671-10675
An effective approach to sulfate separation from aqueous solutions is based on the crystallization of extended [SO4(H2O)52−]n sulfate–water clusters with a bis(guanidinium) ligand. The ligand was generated in situ by hydrazone condensation in water, thereby bypassing the need for elaborate syntheses, tedious purifications, and organic solvents. Crystallization of sulfate–water clusters represents an alternative approach to the now established sulfate separation strategies that involve encapsulation of the “naked” anion. 相似文献
127.
Viorel Vâjâitu 《Results in Mathematics》1998,33(1-2):161-168
We show that if (D, π) is an unramified Riemann domain over a distinguished complex manifold X such that D is cohomologically q-convex, then π is locally q-complete with corners. We call X distinguished if for every point x of X there is a holomorphic line bundle $\cal L$ on X (which may depend on x) so that the global sections $\Gamma (X \cal L)$ of $\cal L$ generate its 1-jets at x. Examples of distinguished complex manifolds include all complex submanifolds of Cm × Pn; in particular all Stein or projectively algebraic manifolds. 相似文献
128.
129.
Radu Miculescu Alexandru Mihail 《Proceedings of the American Mathematical Society》2008,136(2):587-592
It is known that Lipscomb's space can be imbedded in Hilbert's space . Let be the imbedded version of endowed with the -induced topology. We show how to construct as the attractor of an iterated function system containing an infinite number of affine transformations of . In this way we answer an open question of J.C. Perry.
130.
Judit Éva Fleischer Radu Levente Novak John F. Hartmann Neda Beheshti Anna-Lena Kjøniksen Bo Nyström János Borbély 《Colloid and polymer science》2008,286(4):365-376
This work describes the formation of water-soluble hydrophilic nanoparticles from biosynthetic poly-γ-glutamic acid (PGA).
Nanoparticles were formed by cross-linking using 2,2′-(ethylenedioxy) diethylamine in the presence of water-soluble carbodiimide.
The structure was determined by nuclear magnetic resonance spectroscopy and the particle size by transmission electron microscopy
(TEM), size exclusion chromatography (SEC), and dynamic light-scattering (DLS) measurements. The results from TEM, SEC, and
DLS reveal that the particle size depends on the ratio of cross-linking. Particle size values measured by TEM were between
20 and 90 nm. Formation of cross-linked nanoparticles results in a dramatic viscosity drop compared to the viscosity of the
corresponding solution of the parent PGA. The viscosity and DLS experiments disclose an intriguing interplay between intrachain
and interchain cross-linking of the polymer chains, depending on the cross-linker density and polymer concentration. The SEC
measurements show that the retention time of the major portion of particles increase because of the higher cross-linking ratio.
At moderate cross-linker concentration, intramolecular cross-linking is the dominant process, whereas at higher cross-linker
densities, the interpolymer cross-linking plays an important role. As a result, large clusters are also formed. 相似文献