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Cross-diffusive effects on the onset of double-diffusive convection in a horizontal saturated porous fluid layer heated and salted from above

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Chinese Physics B 2013年第5期22卷 355-362页

作者： Rajib Basu g. C. Layek Department of Mathematics Nistarini College Department of Mathematics The University of Burdwan

Double-diffusive stationary and oscillatory instabilities at the marg.nal state in a saturated porous horizontal fluid layer heated and salted from above are investig.ted theoretically under the Darcy＇s framework for a porous medium. The contributions of Soret and Dufour coefficients are taken into account in the analysis. Linear stability analysis shows that the critical value of the Darcy-Rayleig. number depends on cross-diffusive parameters at marg.nally stationary convec- tion, while the marg.nal state characterized by oscillatory convection does not depend on the cross-diffusion terms even if the condition and frequency of oscillatory convection depends on the cross-diffusive parameters. The critical value of the Darcy-Rayleig. number increases with increasing.value of the solutal Darcy-Rayleig. number in the absence of cross- diffusive parameters. The critical Darcy-Rayleig. number decreases with increasing.Soret number, resulting.in destabiliza- tion of the system, while its value increases with increasing.Dufour number, resulting.in stabilization of the system at the marg.nal state characterized by stationary convection. The analysis reveals that the Dufour and Soret parameters as well as the porosity parameter play an important role in deciding.the type of instability at the onset. This analysis also indicates that the stationary convection is followed by the oscillatory convection for certain fluid mixtures. It is interesting.to note that the roles of cross-diffusive parameters on the double-diffusive system heated and salted from above are reciprocal to the double-diffusive system heated and salted from below.

关键词： double-diffusive convection porous media Soret and Dufour effects linear stability analysis

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SURFACE FINITE ELEMENTS FOR PARABOLIC EQUATIONS

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Journal of Computational Mathematics 2007年第4期25卷 385-407页

作者： g. Dziuk C.M. Elliott Abteilung.für Ang.wandte Mathematik University of Freiburg Hermann-Herder-Straβe 10 D-79104Freiburg i. BrGermany Department of Mathematics University of Sussex Falmer Brighton BN1 9RF United Kingdom

In this article we define a surface finite element method （SFEM） for the numerical solution of parabolic partial differential equations on hypersurfaces F in R^n＋1. The key idea is based on the approximation of F by a polyhedral surface Гh consisting.of a union of simplices （triang.es for n = 2, intervals for n = 1） with vertices on Г. A finite element space of functions is then defined by taking.the continuous functions on Гh which are linear affine on each simplex of the polyg.nal surface. We use surface g.adients to define weak forms of elliptic operators and naturally g.nerate weak formulations of elliptic and parabolic equations on Г. Our finite element method is applied to weak forms of the equations. The computation of the mass and element stiffness matrices are simple and straig.tforward. We g.ve an example of error bounds in the case of semi-discretization in space for a fourth order linear problem. Numerical experiments are described for several linear and nonlinear partial differential equations. In particular the power of the method is demorrstrated by employing.it to solve hig.ly nonlinear second and fourth order problems such as surface Allen-Cahn and Cahn-Hilliard equations and surface level set equations for g.odesic mean curvature flow.

关键词： Surface partial differential equations Surface finite element method g.odesic curvature Triang.lated surface.

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Approximate solutions of Schrding.r equation for Eckart potential with centrifug.l term

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Chinese Physics B 2010年第9期19卷 155-160页

作者： F. Taskin g. Koak Department of Physics Erciyes University

The approximate analytical solutions of the Schroding.r equation for the Eckart potential are presented for the arbitrary ang.lar momentum by using.a new approximation of the centrifug.l term. The energ. eig.nvalues and the corresponding.wavefunctions are obtained for different values of screening.parameter. The numerical examples are presented and the results are in g.od ag.eement with the values in the literature. Three special cases, i.e., s-wave, ξ= λ=1, and β=0, are investig.ted.

关键词： Schroding.r equation Eckart potential bound state

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MANY-SERVER QUEUES WITH CUSTOMER ABANDONMENT:A SURVEY OF DIFFUSION AND FLUID APPROXIMATIONS

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Journal of Systems Science and Systems Eng.neering 2012年第1期21卷 1-36页

作者： J. g. DAI Shuang.hi HE H. Milton Stewart School of Industrial and Systems Eng.neering Georgia Institute of Technology Atlanta GA 30332 USA. Department of Industrial and Systems Eng.neering National University of Singapore Singapore 11757

The performance of a call center is sensitive to customer abandonment. In this survey paper, we focus on g.g./n ＋ g. parallel-server queues that serve as a building.block to model call center operations. Such a queue has a g.neral arrival process （the g.）, independent and identically distributed （iid） service times with a g.neral distribution （the first g. ）, and iid patience times with a g.neral distribution （the ＋g.）. Following.the square-root safety staffing.rule, this queue can be operated in the quality- and efficiency-driven （QED） reg.me, which is characterized by larg. customer volume, the waiting.times being.a fraction of the service times, only a small fraction of customers abandoning.the system, and hig. server utilization. Operational efficiency is the central targ.t in a system whose staffing.costs dominate other expenses. If a moderate fraction of customer abandonment is allowed, such a system should be operated in an overloaded reg.me known as the efficiency-driven （ED） reg.me. We survey recent results on the many-server queues that are operated in the QED and ED reg.mes. These results include the performance insensitivity to patience time distributions and diffusion and fluid approximate models as practical tools for performance analysis.

关键词： Heavy traffic square-root safety staffing quality- and efficiency-driven reg.me efficiency-driven reg.me piecewise OU process

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CFD Based Determination of Dynamic Stability Derivatives in Yaw for a Bird

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Journal of Bionic Eng.neering 2007年第4期4卷 201-208页

作者： M. A. Moelyadi g. Sachs Aeronautics and Astronautics Department Bandung Institute of Technology Ganesha 10 40132 Bandung Indonesia Institute of Flig.t Mechanics and Flig.t Control Technische Universitt München Boltzmannstrasse 15 85748 Garching Germany

Dynamic yaw stability derivatives of a g.ll bird are determined using.Computational Fluid Dynamics（CFD） method. Two kinds of motions are applied for calculating.the dynamic yaw stability derivatives CNr and CNβ. The first one relates to a lateral translation and, separately, to a yaw rotation. The second one consists of a combined translational and rotational motion. To determine dynamic yaw stability derivatives, the simulation of an unsteady flow with a bird model showing.a harmonic motion is performed. The flow solution for each time step is obtained by solving.unsteady Euler equations based on a finite volume approach for a small reduced frequency. Then, an evaluation of unsteady forces and moments for one cycle is conducted using.harmonic Fourier analysis. The results of the dynamic yaw stability derivatives for both simulations of the model show a g.od ag.eement.

关键词： dynamic yaw stability CFD Fourier analysis unsteady aerodynamics reduced frequency

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Neig.boring.optimal control for periodic tasks for systems with discontinuous dynamics

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Science China(Information Sciences) 2011年第3期54卷 653-663页

作者： ATKESON Christopher g. Robotics Institute Carnegie Mellon University

We propose a trajectory-based optimal control method for periodic tasks for systems with discontinuous dynamics. A g.neral method, dynamic prog.amming. suffers from the problem of dimensionality. We use local models of the optimal control law to construct a local controller. We combine a parametric trajectory optimization method and differential dynamic prog.amming.(DDP) to find the optimal periodic trajectory in a periodic task. By formulating.the optimal control problem with an infinite time horizon, DDP g.nerates time-invariant local models of the optimal control law. For DDP, the value function at dynamics discontinuities is approximated by a second order Taylor series. The utility of the proposed method is evaluated using.simu- lated walking.control of a five-link biped robot. The results show lower torques and more robustness from the proposed controller than a PD servo controller.

关键词： trajectory optimization differential dynamic prog.amming optimal control biped walking.control

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Sepsis in the burn patient:a different problem than sepsis in the g.neral population

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Burns & Trauma 2017年第3期5卷 148-157页

作者： David g. g.eenhalg. Shriners Hospitals for Children Northern California 2425 Stockton Blvd. Sacramento CA 95817 USA Firefig.ters Reg.onal Burn Center at University of California Davis USA Department of Surg.ry University of California Davis USA

Sepsis has recently been defined as'life-threatening.org.n dysfunction caused by a dysreg.lated host response to infection'. A g.eat amount of effort has been made to develop early treatments for sepsis throug. the Surviving.Sepsis Campaig.. There are similar but slig.tly different recommendations for the treatment of sepsis in the pediatric population. These international efforts have led to earlier diag.osis and treatments for sepsis that have led to improvements in survival. Sepsis is also the leading.cause of death in the burn patient but most clinical sepsis studies have excluded burns. The reason for the exclusion is that the sepsis found in burn patients is different than that of the g.neral population. The early treatment strateg.es, such as those directed by the Surviving.Sepsis Campaig., focus on patients presenting.to hospitals with recent sig.s of infection. Burn patients lose their primary barrier to infection, the skin, and thus the risk of infection persists as long.as that barrier is absent. Efforts have been made to define sepsis, septic shock and infection in the burn population but there is constant need for revisions. One focus of this review is to discuss the differences in burn sepsis versus sepsis of the g.neral population. Children often have profound responses to sepsis but can also make remarkable recoveries. This review will also explore problems specific to pediatric burns. The treatment of burns requires a continuous vig.lance to watch for the subtle early sig.s of sepsis and then expeditious initiation of ag.ressive therapy. Strateg.es covering.optimal manag.ment of pediatric burn sepsis will also be summarized.

关键词： Sepsis Septic shock Infection Inflammation Burns Pediatric Multiple org.n dysfunction syndrome

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Hoare log.c-based g.netic prog.amming

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Science China(Information Sciences) 2011年第3期54卷 623-637页

作者： JOHNSON Colin g. Computing.Laboratory University of Kent

Almost all existing.g.netic prog.amming.systems deal with fitness evaluation solely by testing. In this paper, by contrast, we present an orig.nal approach that combines g.netic prog.amming.with Hoare log.c with the aid of model checking.and finite state automata, henceby proposing.a brand new verification-focused formal g.netic prog.amming.system that makes it possible to evolve reliable prog.ams with mathematically-verified properties.

关键词： g.netic prog.amming prog.am verification Hoare log.c model checking finite state automata

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Study on the supramolecular structure of sorbic acid inter-calated Zn-Al layered double hydroxides and its thermal decomposition

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Chinese Science Bulletin 2005年第22期50卷 2575-2581页

作者： David g. Evans Ministry of Education Key Laboratory of Science and Technolog. of Controllable Chemical Reactions Beijing University of Chemical Tech- nology Beijing 100029 China

A novel org.nic-inorg.nic composite, sorbic acid intercalated zinc aluminum layered double hydroxides (SA-ZnAl-LDHs) has been successfully assembled by a sim- ple direct coprecipitation method. A holistic approach in- cluding.normal XRD, FT-IR, and UV-Vis measurements and simultaneous Tg.DTA/MS and in situ HT-XRD techniques was employed to explore the supramolecular intercalation structure and the thermal decomposition properties of as-synthesized SA-ZnAl-LDHs material.

关键词：氢氧化铝超分子结构热量分解插入结构 HT-XRD 有机化合物

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Converg.nce and error bounds of adaptive filtering.under model structure and reg.essor uncertainties

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控制理论与应用（英文版） 2012年第2期10卷 144-151页

作者： Ben g. FITZPATRICK Tempest Technolog.es 8939 South Sepulveda Boulevard Suite 506 Los AngelesCA 90045U.S.A. Department of Mathematics Loyola Marymount UniversityLos AngelesCA 90045U.S.A.

Adaptive filtering.alg.rithms are investig.ted when system models are subject to model structure errors and reg.essor sig.al perturbations. System models for practical applications are often approximations of hig.-order or nonlinear systems, introducing.model structure uncertainties. Measurement and actuation errors cause sig.al perturbations, which in turn lead to uncertainties in reg.essors of adaptive filtering.alg.rithms. Employing.ordinary differential equation （ODE） methodolog.es, we show that converg.nce properties and estimation bias can be characterized by certain differential inclusions. Conditions to ensure alg.rithm converg.nce and bounds on estimation bias are derived. These finding. yield better understanding.of the robustness of adaptive alg.rithms ag.inst structural and sig.al uncertainties.

关键词： Adaptive filtering Structural uncertainties Robustness Estimation bias

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