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水动力学研究与进展（A辑） 2002年第2期17卷 204-209页

作者：胡欣黄永念北京大学力学与工程科学系湍流研究国家重点实验室北京100871

Navier- Stokes方程的理论求解能够最充分地反映出流动的细微性质 ,因而人们总是想给出某些简化情况下的 Navier- Stokes方程的精确解来 ;而求解得面临复杂的数学运算 ,尤其是 Navier- Stokes方程的三维特性及其非线性项难以处理 ,故要... 详细信息

Navier- Stokes方程的理论求解能够最充分地反映出流动的细微性质 ,因而人们总是想给出某些简化情况下的 Navier- Stokes方程的精确解来 ;而求解得面临复杂的数学运算 ,尤其是 Navier- Stokes方程的三维特性及其非线性项难以处理 ,故要得到精确解是较困难的。从 Stokes-Helmholtz分解出发 ,发现若经过一定的处理 ,可得到一类旋涡精确解的构造方法 ,并通过此方法在不同的坐标系下得到了一些新的精确解 ,并且将很多常见的旋涡流的精确解并入到这一体系中来。这种方法给出了这些精确解的更一般的求解途径 ,可以说是对教科书上的这方面内容的完善和补充。

关键词：旋涡精确解 Stokes-Helmholtz分解涡量方程 Lundgren涡非线性项

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Second-Order Consensus for Nonlinear Multi-Agent systems with Intermittent Measurements

Second-Order Consensus for Nonlinear Multi-Agent Systems wit...

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2011 Chinese Control and Decision Conference（CCDC）

作者： Guanghui Wen,Zhisheng Duan are with the state key Lab for turbulence and complex systems and the department of mechanics and aerospace engineering,College of engineering,peking university,beijing 100871,china Guanrong Chen is with the department of Electronic engineering,City university of Hong Kong,Hong Kong SAR,china Wenwu Yu is with the department of Mathematics,Southeast university,Nanjing 210096,china

In this paper,the consensus problem is investigated for a class of second-order nonlinear multi-agent systems with intermittent measurements and directed topology.A novel protocol designed based only on the intermittent local feedback is introduced to guarantee the states of multiple agents to *** virtue of the Lyapunov control approach,it is theoretically proved that second-order consensus can be achieved exponentially if the general algebraic connectivity and the communication time duration are larger than their corresponding threshold values ***,a simulation example is given to verify the theoretical analysis.

关键词： Multi-agent system Second-order consensus Intermittent measurement Directed topology

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Analysis of Nonlinear systems Near Hopf Bifurcation with Periodic Disturbances

Analysis of Nonlinear Systems Near Hopf Bifurcation with Per...

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第三十届中国控制会议

作者： DONG Wanjing~1,WANG Yong~1,WANG Zheng~2 1.department of mechanics and aerospace engineering,state key laboratory of turbulence and complex systems, peking university,beijing,100871,P.R.china 2.Qingdao Branch of Naval Aeronautical engineering Academy,Qingdao,Shangdong Province,P.R.china

＜正＞In this paper,we study the effects of periodic perturbations on a smooth nonlinear system possessing a subcritical Hopf *** goal is to obtain the analytic relations between the region of attraction of the nominal equilibria near the bifurcation and the amplitude and frequency of the ***,via a smooth coordinate transformation,we transform the nonlinear system into a normal form,in which the dynamics of the center manifold and those of the stable manifold are decoupled in the lower order ***,we study the stability of the dynamics on the normal form by using two methods. First,we obtain the periodic solution by using the harmonic balance,and we analyze the linear stability of the periodic solutions. Then we construct Lyapunov functions to evaluate the domain of attraction of the periodic *** Lyapunov method gives more conservative estimate of the critical bifurcation parameters than linear stability analysis.

关键词： Hopf Bifurcation Harmonic Balance Lyapunov’s Direct Periodic Perturbation

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Distributed Quadratic Stabilization of Uncertain Linear Multi-Agent systems

Distributed Quadratic Stabilization of Uncertain Linear Mult...

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第24届中国控制与决策会议

作者： Zhongkui Li, Zhisheng Duan,Lihua Xie Xiangdong Liu the School of Electrical and Electronic engineering, Nanyang Technological university the state key Lab for turbulence and complex systems,department of mechanics and aerospace engineering, College of engineering, peking university, beijing 100871, china the School of Electrical and Electronic engineering, Nanyang Technological university, 639798, Singapore

This paper considers the distributed quadratic stabilization problems of uncertain continuous-time linear multiagent systems with undirected communication topologies. It is assumed that the agents have identical nominal dynamics while subject to different norm-bounded parameter uncertainties, leading to weakly heterogeneous multi-agent systems. A distributed controller is proposed, based on the relative states of neighboring agents and a subset of absolute states of the agents. It is shown that the distributed quadratic stabilization problem under such a controller is equivalent to the H∞ control problems of a set of decoupled linear systems having the same dimensions as a single agent. A two-step algorithm is presented to construct the distributed robust controller, which does not involve any conservatism and meanwhile decouples the feedback gain design from the communication topology. Furthermore, the distributed quadratic ∞ control problem of uncertain linear multi-agent systems with external disturbances is discussed, which can be reduced to the scaled H∞ control problems of a set of independent systems whose dimensions are equal to that of a single agent.

关键词： Multi-agent system distributed control robustness H∞ control parameter uncertainty

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Distributed Output Regulation for Multi-agent systems with Unknown Communication Delays

Distributed Output Regulation for Multi-agent Systems with U...

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第24届中国控制与决策会议

作者： Lu Yu 1 , Jinzhi Wang 1 *, Zhong-Ping Jiang 2 , 3 , Yiguang Hong 4 1. state key laboratory for turbulence and complex systems, department of mechanics and aerospace engineering, College of engineering, peking university, beijing 100871, PRC2. department of Electrical and Computer engineering, Polytechnic Institute of New York university, Brooklyn, NY 11201, USA4. key laboratory of systems and Control, Academy of Mathematics and systems Science, Chinese Academy of Sciences, beijing 100190, PRC

In this paper, the distributed output regulation problem of multiagent linear systems with communication time delays is studied, by means of both dynamic state and output feedback control laws. Given bounded communication delays, distributed control laws are designed via linear matrix inequalities （LMI）. Both delay-independent and delaydependent conditions are discussed.

关键词： Multi-agent systems Output Regulation Time Delay

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Multiscale coupling:challenges and opportunities

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Progress in Natural Science:Materials International 2004年第6期 1-4页

作者： HE Guowei 1,XIA Mengfen 1 *,KE Fuju 1,2 and BAI Yilong 1 (1. state key laboratory of Nonlinear mechanics,Institute of mechanics,Chinese Academy of Sciences,beijing 100080,china 2. department of Applied Physics,beijing university of Aeronautics and aerospace,beijing 100083,china) state key laboratory of Nonlinear mechanics，Institute of mechanics，Chinese Academy of Sciences，beijing 100080，china state key laboratory of Nonlinear mechanics，Institute of mechanics，Chinese Academy of Sciences，beijing 100080，china department of Applied Physics，beijing university of Aeronautics and aerospace，beijing 100083，china

Multiscale coupling is ubiquitous in nature and attracts broad interests of scientists from mathematicians,physicists,machinists,chemists to biologists. However,much less attention has been paid to its intrinsic implication. In this paper,multiscale coupling is introduced by studying two typical examples in classic mechanics: fluid turbulence and solid failure. The nature of multiscale coupling in the two examples lies in their physical diversities and strong coupling over wide-range scales. The theories of dynamical system and statistical mechanics provide fundamental methods for the multiscale coupling problems. The diverse multiscale couplings call for unified approaches and might expedite new concepts,theories and disciplines.

关键词： multiscale coupling statistical mechanics fluid turbulence solid failure.

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EXERGETIC EVALUATION OF THE RENEWABILITY OF CORN-ETHANOL

EXERGETIC EVALUATION OF THE RENEWABILITY OF CORN-ETHANOL

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第三世界生态高峰会

作者： Yang Q.~a Chen B.~(a,b) ji Xi~a Zhou J.B.~a Chen G.Q.~(a+) a National laboratory for turbulence and complex systems.department of mechanics.peking university.beijing 100871.china b state key Joint Lahoratory of Enviromnental Science and Pollution Control.Faeulty of Environment.beijing Normat Universiory.beijing 100875.china.

An exergy-based indicator is proposed to quantify the renewability of corn-ethanol production that consumed both renewable resources and nonrenewable resources. Capturing the exergy of all natural nonrenewable resources (NRRs) consumed by each process including agricultural crop production,transport of corn,industrial conversion and waste treatment,the cumulative exergy method is employed to identify the renewability of the total corn-ethanol production in china. Furthermore,sensitivity analysis shows how the boundaries of the defined system,energy-utilization structure of the country,and technological constraints and choices influence the *** the conditions prevailing in china,the production and utilization of corn-ethanol is with a renewability indicator (Ir) value of ***, a strategic planning for sustainable corn-ethanol production is illuminated.

关键词： Corn-ethanol Exergetic evaluation Renewability indicator

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Controller Design for Discrete Time Generalized systems Subject to Actuator Saturation and L∞ Disturbances

Controller Design for Discrete Time Generalized Systems Subj...

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第三十届中国控制会议

作者： ZHAO Yangyang~1,YANG Jianying~1,JI Jianchao~(1,2) 1.department of mechanics and aerospace engineering,College of engineering,peking university,beijing 100871,P.R.china 2.department of Mechanical engineering,Army Aviation institute,beijing 101123,P.R.china

This paper deals with the problem of controller design for discrete time generalized systems subject to actuator saturation and L disturbances.A new sufficient condition guaranteeing regularity,causality and bounded state stability for the closed-loop system subject to actuator saturation and L disturbances is formulated in term of linear matrix inequalities(LMIs). The problems of estimating the disturbance tolerance capability measured as a bound of the L norm of the disturbance and the disturbance rejection capability measured as a bound of the L norm of the output under regularity,causality and bounded state stability of the closed-loop system are transformed and solved as the LMI constrained optimization problems.

关键词： Discrete time generalized system L∞disturbances Actuator saturation Bounded state stability

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Size and Layout Optimizations of Stiffened Shells under Axial Compression

Size and Layout Optimizations of Stiffened Shells under Axia...

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The Seventh china-Japan-Korea Joint Symposium on Optimization of Structural and Mechanical systems

作者： Bo Wang1 Peng Hao1 Gang Li1 Zhifeng Zhang2 Bin Wang2 and Chunxiao Zhou2 1Dept.of engineering mechanics state key laboratory of Structural Analysis of Industrial Equipment Dalian university of Technology 116023 Dalian china 2beijing Institute of Astronautical systems engineering 100076 beijing china

The extensive use of stiffened shells in aerospace industries is mainly motivated by the high stiffness-to-weight and strength-to-weight *** these thin-walled structures,buckling is one of the main failure *** methods and programs are available for the analysis of stiffened shells,ranging from simple closed form solutions to complicated discrete ***,many optimizations have been carried out for metallic and composite stiffened shells against *** variables involved in the optimizations are usually stiffener size,stiffener spacing,skin laminate sequence and angle,***,the layout optimizations of stiffened shells are rarely reported,which are capable of increasing the bending stiffness without the increase of structural ***,the buckling of stiffened shells can be categorized as elastic and plastic buckling patterns,and the failures mostly occur at the intermediate section of shell and the sections close to both ends *** is supposed to be efficient to adjust the location of stiffeners for the purpose of improving the local stiffness against buckling,moreover,without the increase of additional weight.

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气动声学和流动噪声发展综述:致初学者

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空气动力学学报 2018年第3期36卷 363-371页

作者：钟思阳黄迅香港科技大学机械及航空航天工程系北京大学工学院航空航天工程系湍流与复杂系统国家重点实验室北京100871

本文面向初学者介绍气动声学和流动噪声研究的过去和现况,以声比拟为主要线索展开讨论,澄清了一些常见概念和误区,并解释了代表性问题的气动发声机制,兼顾评述了计算方法和实验技术,最后展望了未来可能有所发展的研究方向。

关键词：气动声学流动噪声声比拟

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