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Second-order consensus in networks of dynamic agents with communication time-delays

Journal of Systems engineering and Electronics 2010年第1期21卷 88-94页

作者： Bo Yang1,2, Huajing Fang3, and Hua Wang4.1. School of Navigation, Wuhan university of Technology, Wuhan 4.0063, P. R. China 2. Wuhan Second Ship Design and Research Institute, Wuhan 4.0064. P. R. China 3. department of Control Science and engineering, Huazhong university of Science and Technology, Wuhan 4.0074. P. R. China {4., boston university, boston ma02215, usa School of Navigation Wuhan University of Technology Wuhan 430063 P. R. China Wuhan Second Ship Design and Research Institute Wuhan 430064 P. R. China department of Control Science and engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China department of aerospace and mechanical engineering Boston University Boston MA02215 USA

This paper proposes second-order consensus protocols with time-delays and gives the measure of the robustness of the protocols to the time-delay existing in the network of agents with second-order dynamics. By employing a frequency domain method, it is proven that the information states and their time derivatives of all the agents in the network achieve consensus asymptotically, respectively, for appropriate communication timedelay if the topology of weighted network is connected. Particularly, a tight upper bound on the communication time-delay that can be tolerated in the dynamic network is found. The consensus protocols are distributed in the sense that each agent only needs information from its neighboring agents, which reduces the complexity of connections between neighboring agents significantly. Numerical simulation results are provided to demonstrate the effectiveness and the sharpness of the theoretical results for second-order consensus in networks in the presence of communication time-delays.

关键词： second-order consensus protocols dynamic networks algebraic graph theory frequency domain analysis com-munication constraints.

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CRITICAL ISSUES OF POWDER METALLURGY TURBINE DISKS

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Acta Metallurgica Sinica(English Letters) 1996年第6期9卷 467-471页

作者： K.M. Chang(department of mechanical and aerospace engineering,West Virginia {4., P.O. Box 6160, Morgantown,WV 26506, usa West Virginia Univ Morgantown United States

P/M superalloy disks obtain their final strength by appropriate heat treatments; the maximum attainable strength depends on the rapid cooling rate from the solution annealing. A rapid quench of a large disk forging can cause two problems, surface cracking and shape *** the past,many attempts employ the finite element code to model and to predict temperature evolution and induced stress distribution in a large turbine disk. The major difficulty was the correct description of alloy behavior; particularly the thermomechanical properties and the failure criteria of material during the cooling. High temperature fatigue resistance is always the key requirement for disk materials. New methodology of residual life management emphasizes the initiation as well as the propagation of the cracks developed under the service conditions. One of major challenges to P/M superalloys is the time-dependent behavior of fatigue cracking, which relates to the well-known SAGBO (stress-assisted grain boundary oxidation) phenomenon.A great effort has been done to understand the micro-mechanism of time-dependent fatigue crack propagation resulted in the second generation of P/M superalloys. Further improvement on temperature capability of disk alloys at rim area may lead to the idea of dual-property *** grain structures at different portions of a large disk are possible,as the property requirements for different locations are different. This goal is achievable if the thermal history at specific disk locations can be controlled to develop desirable microstructures and *** suggestions on the future direction of research efforts will be discused.

关键词： superalloy disk,powder metallurgy (P/M) quench cracking,fatigue crack propagation SAGBO (stress-assisted grain boundary oxidation),dual-property disk grain size

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New Sensor Concepts for Enhancing Heat Treatment Processes and Analysis

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材料热处理学报 2004年第5期25卷 443-446页

作者： Jay I. Frankel mechanical Aerospace and Biomedical Engineering Department University of Tennessee Knoxville Tennessee USA

The need for developing accurate quenching models requires an extensive experimental database that includes surface heat flux characterization. Quantification of the quenching process permits i) the development of high-quality heat treated products, ii) the evaluation of new quenchants and quenchant systems, and iii) the evaluation of quenchant quality over usage time. The surface heat transfer coefficient (or heat flux) is rarely measured, calculated or modeled in sufficient detail for real scientific use. many single-thermocouple based probes are designed for the purpose of measuring the cooling power of a liquid quenchant or for monitoring quenchant quality. Lumped based probes are sufficient for these types of applications. However, the lack of sufficient distributed detail impedes the development of future high-quality heat-treated products. Frankel and his coworkers are developing a new family of transient thermal-rate sensors that will improve both diagnostic and real-time analyzes in heat transfer studies. Analyzes have been performed indicating that there exists a novel, thermal-rate sensor hierarchy that stabilizes predictions when used with analysis. This concept can be used for investigating both (i) direct surface heat transfer effects, and (ii) projective surface analysis based on embedded sensors. This new sensor family includes the ability to measure temperature, T; heat flux, q"; and their temporal derivatives, i.e., dT/dt, d^T/dt2 and dq’Vdt.

关键词：传感器热处理热通量传热系数

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Impulsive Control of Bifurcation in Nonlinear System

Impulsive Control of Bifurcation in Nonlinear System

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第25届中国控制会议

作者： Liu Feng, Guan Zhihong, Wang Hua department of Control Science and engineering ,Huazhong university of science and technology, Wuhan 4.0074.College of mechanical and Electronic engineering ,China university of Geosciences, Wuhan 4.0074.department of aerospace and mechanical engineering, boston university, boston, ma02215,usa

＜正＞In this paper a method of impulsive control bifurcation in a nonlinear system is presented. Some sufficient conditions for the asymptotically stable of a general nonlinear system via impulsive control were deriv... 详细信息

关键词： Bifurcation control Impulsive control Asymptotically Stability

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Impulsive Synchronization for Chaotic System Based on T-S Fuzzy Model

Impulsive Synchronization for Chaotic System Based on T-S Fu...

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第二十二届中国控制会议

作者： Wang Yanwu Guan Zhihong Wang H. O. (department of Control Science and engineering Huazhong university of Science and Technology Wuhan 4.0074. (department of {4. and mechanical engineering boston university boston ma 02215 usa)

＜正＞An impulsive control based on fuzzy model is developed for continuous chaotic system. The upper bound of impulsive interval is estimated. The method is illustrated by application to Lorenz system and the simulat... 详细信息

关键词： Impulsive control T-S fuzzy model Synchronization Lorenz system.

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Hydration lubrication modulated by water structure at TiO2–aqueous interfaces

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Friction 2024年第4期12卷 591-605页

作者： Pingsu ma Yuan LIU Ke HAN Yu TIAN Liran ma State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

The nature of solid-liquid interfaces is of great significance in *** advances have been made in lubrication based on hydration ***,a detailed molecular-level understanding is still ***,we investigated water molecule behaviors at the TiO2-aqueous interfaces by the sum-frequency generation vibrational spectroscopy(SFG-VS)and atomic force microscope(AFM)to elucidate the fundamental role of solid-liquid interfaces in *** contributions of water structures and hydration effects were revealed,where water structures played the dominant role in lubrication for TiO2 surfaces of varying hydrophilicity,while hydration effects dominated with the increasing of ion *** lubrication is observed on the initial TiO2 surfaces with strongly H-bonded water molecules compared to the hydrophilic TiO2 surfaces with more disordered *** stable ordered water arrangement with strong hydrogen bonds and the shear plane occurring between the ordered water layer and subsequent water layer may play a significant role in achieving lower *** adsorbed hydrated molecules with the increasing ionic concentration perturb ordered water but lead to the enhancement of hydration effects,which is the main reason for the improved lubrication for both *** work provides more insights into the detailed molecular-level understanding of the mechanism of hydration lubrication.

关键词： hydration lubrication interfacial water structures hydration effects titanium dioxide(TiO2)

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Nonlinear constitutive law for ferroelectric/ferroelastic material and its finite element realization

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Science China(Physics,Mechanics & Astronomy) 2007年第1期50卷 70-86页

作者： LI YaoChen department of aerospace engineering and Applied Mechanics,Tongji university,Shanghai 200092,China department of aerospace engineering and Applied Mechanics Tongji University Shanghai 200092 China

The hysteresis phenomena of ferroelectric/ferroelastic material in polarization procedure are investigated. Some assumptions are presented based on the published experimental data. The electrical yielding criterion, mechanical yielding criterion and isotropic hardening model are established. The flow theory in incremental forms in polarization procedure is presented. The nonlinear constitutive law for electrical-mechanical coupling is proposed phenomenologically. Finally, the nonlinear constitutive law expressed in a form of matrices and vectors, which is immediately associated with finite element analysis, is formulated. In the example problem of a rectangular specimen subjected to a uniaxial electric field, the procedure from virgin state to fully polarized state is simulated. Afterward, a uniaxial compressive loading is applied to depolarizing the specimen. Results are in agreement with the experimental data.

关键词： ferroelectric/ferroelastic material constitutive law nonlinear finite element method.

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BREAKING WAVE FORCES ON VERTICAL CYLINDERS

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Journal of Hydrodynamics 2002年第4期14卷 110-112页

作者： ma Ru-jian, Li Gui-xi department of mechanical and Electronic engineering, Jinan university, Jinan 250022, China Dept. of Mech. and Electron. Eng. Jinan Univ. Ji'nan 250022 China

The breaking wave forces on vertical cylinders in shallow waters were studied by means of experimental methods. The results indicate that the breaking wave pressure is distributed exponentially with respect to water depth. An experimental formula was given using the test data. Compared with test data, the calculated breaking wave forces are in good agreement with the test data.

关键词： breaking wave forces pressure distribution of breaking waves experimental study

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ZERO TRANSMISSION AND ITS APPLICATION IN HIGH SPEED CNC maCHINE TOOLS

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Chinese Journal of mechanical engineering 2000年第3期13卷 184-189页

作者： Zhang Bolin, ma Ping, Xiao Shuhong ,Li Yiping, Xiao Zhanglin (department of mechanical and Electronical engineering,Guangdong university of Technology) 广东工业大学广东广州

In order to realize high speed machining,the special requirements for the transmission and sturctrue of CNC machine tool have to be satisfied.A high speed spindle unit driven by a built-in motor is *** oil-water heat exchange system is used for cooling the spindle *** spindle is supported by Si_4._3 ceramic ball angular contact bearings. An oil-air lubricator is used to lubricate and cool the spindle *** special structures are taken for balancing the spindle.

关键词： High speed machining machine tool Spindle Ceramic ball bearing\

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Consistent Analytic Embedded Atom Potential for Face-Centered Cubic Metals and Alloys

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Journal of materials Science & Technology 2009年第6期25卷 835-846页

作者： Iyad A. Hijazi Young Ho Park mechanical and aerospace engineering department New Mexico State University Las Cruces

A consistent empirical embedded-atom potential that includes a long range force was developed for fcc （face-centered cubic） metals and alloys. The proposed potential for pure metals does not require modification of the initial function form when being applied to alloy systems. The potential parameters of this model were determined by fitting lattice constant, three elastic constants, cohesive energy, and vacancy formation energies of the pure metals and the heats of solution of the binary alloys via an optimization technique. Parameters for Ag, AI, Au, Cu, Ni, Pd and Pt were obtained. The obtained parameters were used to calculate the bulk modulus, divacancy formation energy, crystal stability, stacking fault energy, vacancy migration energy, and melting point for each pure metal and the heats of formation and lattice constants for binary alloys. The predicted values were in good agreement with experimental results.

关键词： EAM (embedded-atom method) Consistent analytic potential Molecular dynamics Face-centered cubic alloy

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