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Effect of the cooling rate on plastic deformability of a Zr-based bulk metallic glass

Science china(Physics,mechanics & Astronomy) 2010年第3期53卷 415-418页

作者： ZHANG Jing, PANG ShuJie & ZHANG Tao key laboratory of aerospace Materials and Performance (Ministry of Education), department of Materials Science and engineering, beijing university of Aeronautics and Astronautics, beijing 100191, china 1. key laboratory of aerospace Materials and Performance (Ministry of Education) Department of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

The present work found the plastic deformability of Zr65Cu17.5Ni10Al7.5 BMG dependent on the cooling rate during the formation from the molten state alloy. The deformation behavior in the compression test of φ 2 mm Zr65Cu17.5Ni10Al7.5 BMGs as-cast or lathed from different sizes as-cast samples was characterized, and they exhibited different plastic strains. The compressive plastic strain increases with the decreasing diameter of the as-cast specimens, i.e. with increasing the cooling rate. It is suggested that free volume content in the BMGs, which is related to the cooling rate during the rapid solidification, could play an important role in the deformation process of the BMGs.

关键词： cooling rate shear band serration bulk metallic glass

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Chaos Control of a Four Order Chua’s Circuit

Chaos Control of a Four Order Chua’s Circuit

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第25届中国控制会议

作者： Liu Xian, Wang Jinzhi, Huang Lin state key laboratory for turbulence and complex systems and department of mechanics and engineering Science, Pecking university, beijing 100871

＜正＞In this paper, eight groups of chaotic attractors including hyperchaotic attractor of a four-order Chua’s circuit with a piecewise-linear nonlinearity are presented and a simple method to control chaos oscillation for this circuit is proposed by exploiting absolute stability theory in nonlinear systems. A linear feedback controller is derived based on linear matrix inequality （LMI）. Numerical simulations are presented to illustrate the efficiency of the proposed method.

关键词： Four Order Chua’s Circuit Chaos Control Absolute Stability LMI

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The Applications of the Observer-Based Beamforming Algorithm for Aeroacoustics

The Applications of the Observer-Based Beamforming Algorithm...

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2011 Chinese Control and Decision Conference（CCDC）

作者： Long Bai1,Chi Xu2,and Xun Huang3 1.department of mechanics and aerospace engineering,College of engineering,peking university,beijing 1008712.department of mechanics and aerospace engineering,College of engineering,peking university,beijing 1008713.state key laboratory of turbulence and complex systems,department of mechanics and aerospace engineering,College of engineering,peking university,beijing 100871

Beamforming based on microphone arrays is widely used in aerospace industry for localizing the distribution of noise sources of an ***,the conventional beamforming computations can only be conducted off-line after the preparations of all of the sampling data,thus cannot be used as a real-time *** addition,the performance of conventional beamforming deteriorates when there exists coherent background *** alternative algorithm is proposed to solve these *** algorithm has a similar form to a state observer in control theory,while operates in the frequency *** derivations and various validations of this algorithm is included in this *** is shown that this so-called observer algorithm not only holds the real-time capability,but can also resolve the coherent restriction between background noise and the signal of interest during the *** the help of this algorithm,any testing defects can be revealed instantaneously and corrected on site.

关键词： state Observer Aeroacoustics Beamforming

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Disturbance Rejection and H∞ Pinning Control of Networked Multi-Agent systems

Disturbance Rejection and H∞ Pinning Control of Networked M...

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第二十七届中国控制会议

作者： Li Zhongkui,Duan Zhisheng,Huang Lin state key Lab for turbulence and complex systems and department of mechanics and aerospace engineering,College of engineering,peking university,beijing 100871,P.R.china

This paper concerns the disturbance rejection problem arising in the coordination control of a group of autonomous agents subject to external *** agent network is said to possess a desired level of disturbance rejection,if the H∞ norm of its transfer function matrix from the disturbance to the controlled output is satisfactorily *** graph is used to represent the information flow between *** is shown that the disturbance rejection problem of an agent network can be solved by analyzing the H∞control problem of a set of independent systems whose dimensions are equal to that of a single node. An interesting result is that the disturbance rejection ability of the whole agent network coupled via feedback of merely relative measurements between agents will never be better than that of an isolated *** improve this,local feedback injections are applied to a small fraction of the agents in the ***,some criteria for possible performance improvement are derived in terms of linear matrix inequalities.

关键词： Coordination control Graph theory Pinning control H∞control Linear matrix inequality (LMI)

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Global Synchronization of complex Lur’e Networks

Global Synchronization of Complex Lur’e Networks

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第二十六届中国控制会议

This paper concerns the global synchronization problem of a class of complex dynamical networks with each node being a Lur’e system whose nonlinearity satisfying a slope *** synchronization problem is reformulated in the framework of the absolute stability *** is shown that the global synchronization of the network can be reduced to the test of a LMI,which in turn guarantees the absolute stability of the corresponding Lur’e system whose dimension is the same as that of a single node.A circle type criterion in frequency domain is further presented,in virtue of which the synchronization of the network can be checked *** is demonstrated that the synchronizabiliby of the network can be characterized by the second largest eigenvalue of its coupling ***,a network of Chua’s oscillators is provided as a simulation example to illustrate the effectiveness of the theoretical results.

关键词： complex dynamical network Lur’e system Global synchronization Circle type criterion Linear matrix inequality (LMI)

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ATF-Q8 element model in piezoelectric materials

ATF-Q8 element model in piezoelectric materials

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2011年全国压电和声波理论及器件应用研讨会

作者： Ying-tao ZHAO~(1,*) Yi CHEN~1 Min-zhong WANG~2 1 department of Applied mechanics,School of aerospace engineering,beijing Institute of Technology,beijing 100081 2.state key laboratory for turbulence and complex systems and department of mechanics and aerospace engineering, College of engineering,peking university,beijing 100871

＜正＞In this paper,the analytical trial function method for the 8-node hybrid element（ATF-Q8） is generalized to piezoelectric material *** on Stroh’s formalism,18 polynomial stress functions are introduced as the ... 详细信息

关键词： Polynomial stress functions piezoelectricity analytical trial function ATF-Q8

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Stability analysis of a simple rheonomic nonholonomic constrained system

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Chinese Physics B 2016年第12期25卷 314-317页

作者：刘畅刘世兴梅凤翔 College of Physics Liaoning University state key laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsDalian University of Technology School of aerospace engineering Beijing Institute of Technology

It is a difficult problem to study the stability of the rheonomic and nonholonomic mechanical systems. Especially it is difficult to construct the Lyapunov function directly from the differential equation. But the gradient system is exactly suitable to study the stability of a dynamical system with the aid of the Lyapunov function. The stability of the solution for a simple rheonomic nonholonomic constrained system is studied in this paper. Firstly, the differential equations of motion of the system are established. Secondly, a problem in which the generalized forces are exerted on the system such that the solution is stable is proposed. Finally, the stable solutions of the rheonomic nonholonomic system can be constructed by using the gradient systems.

关键词： nonholonomic constrained system stabillity gradient system Lyapunov function

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Parameter-Dependent Lyapunov Function Method Applied to Satellite Formation Keeping Control

Parameter-Dependent Lyapunov Function Method Applied to Sate...

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第二十七届中国控制会议

作者： Yue Xincheng,Yang Ying,Duan Zhisheng,Geng Zhiyong state key laboratory for turbulence and complex System,department of mechanics and aerospace Technology,College of engineering,peking university,beijing 100871,P.R.china

In this paper,a parameter-dependent Lyapunov function method is applied to design robust controller for a satellite formation flying system around the Earth based on an uncertainty model derived from a nonlinear relative position *** this model,nonzero eccentricity and varying semi-major axis are included as parametric *** perturbations including J2 perturbation,atmospheric drag and actuation are bounded by functional *** model can be regarded as a polytopic type uncertain system with 8 vertices,then the parameter-dependent Lyapunov function is proposed to design H2 and H∞controllers respectively to maintain the relative position of the formation flying *** simulation demonstrates that the proposed controller can realize the control the satellites formation-keeping.

关键词： Parameter-dependent Lyapunov Function Satellite Formation Keeping Polytope Linear Matrix Inequality (LMI)

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Hierarchical structures in climate and atmospheric turbulence

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Progress in Natural Science:Materials International 2002年第10期 29-34页

作者： SHE Zhensu, FU Zuntao, CHEN Jiong, LIANG Shuang and LIU Shida(1. state key laboratory for Studies of turbulence and complex systems, department of mechanics and engineering Sciences, peking university, beijing 100871, china 2. School of Physics, peking university, beijing 100871, china 3. LAPC, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 100029, china) state key laboratory for Studies of turbulence and complex systems，department of mechanics and engineering Sciences，peking university，beijing 100871，china LAPC，Institute of Atmospheric Physics，Chinese Academy of Sciences，beijing 100029，china School of Physics，peking university，beijing 100871，china state key laboratory for Studies of turbulence and complex systems，department of mechanics and engineering Sciences，peking university，beijing 100871，china School of Physics，peking university，beijing 100871，china

The climatic time series encompass many time scales, forming multi-scale climatic variations and hierarchies. The periods and magnitudes of cooling or warming, especially for extreme climatic events, vary with the time scales. On the other hand, high-frequency atmospheric turbulent motions, which are certainly related to the climatic changes, are also typical multi-scale phenomena. In this paper, certain properties of the fluctuations are examined that are invariant with the change of the time scales. Specifically, the existence of a statistical similarity law is demonstrated in climatic time series and in atmospheric turbulent motions. This is the hierarchical similarity law. Further analyses show that the hierarchical similarity law is a general property of multi-scale fluctuation systems. Therefore, the study on the hierarchical similarity law is important for understanding the inherent universal physical mechanism of complex systems in the atmospheric motions.

关键词： climate multi-scale hierarchical structure atmospheric turbulence.

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H∞ Consensus Regions of Multi-Agent systems

H∞ Consensus Regions of Multi-Agent Systems

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第二十九届中国控制会议

作者： LI Zhongkui 1,DUAN Zhisheng1,CHEN Guanrong2 1.state key laboratory for turbulence and complex systems and department of mechanics and aerospace engineering,College of engineering,peking university,beijing 100871,P.R.china2.department of Electronic engineering,City university of Hong Kong,Hong Kong,P.R.china

This paper addresses the distributed H∞ consensus problem of linear or linearized multi-agent systems subject to external disturbances.A distributed consensus protocol is proposed,based on the relative states of neighboring *** distributed H∞ consensus problem of such a multi-agent network is cast into the H∞ control problem of a set of independent systems having the same dimension as that of a single *** notion of H∞ consensus region is then introduced and analyzed.A necessary and sufficient condition for the existence of a protocol having an unbounded H∞consensus region is derived.A multi-step procedure is further presented for constructing such a *** is shown that the H∞ performance limit of the consensus of the multi-agent network is equal to the minimal H∞ norm of a single agent achieved by using a state feedback controller.

关键词： Consensus Multi-Agent System H∞ Control Consensus Region Performance Limit

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