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

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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. department of {4. and mechanical Engineering, 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.

SOME RECENT PROGRESS IN STUDIES ON ACTIVE CONTROL OF WALL-JET FLOWS

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Transactions of Nanjing university of Aeronautics and Astronautics 1994年第2期11卷 119-131页

作者： Zhou Mingde.(aerospace and mechanical Engineering,The university of Arizona tucson,Arizona {4.,usa)

Active control of wall his is important in both application and basic researches. In order to establish a solid background for the expected application,it is necessary to perform detailed studies on the base nows,on their stability characteristics and on the identification technique of coherent structures. This paper is a summarizing article rather than a detailed technical report, Its main purpose is just to introduce the recent progress in the related area.

关键词： turbulent flow control wall jets coherent structure flow stability

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 university, P.O. Box 6160, Morgantown,WV 26506, {4. 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

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

A conceptual evolutionary aseismic decision support framework for hospitals

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Earthquake Engineering and Engineering Vibration 2012年第4期11卷 499-512页

作者： Yufeng Hu Gary F. Dargush Xiaoyun Shao department of Civil and Construction Engineering Western Michigan UniversityKalamazoo department of mechanical and aerospace Engineering University at BuffaloState University of New YorkBuffalo

In this paper, aconceptual evolutionary framework for aseismic decision support for hospitalsthat attempts to integrate a range of engineering and sociotechnical models is presented. Genetic algorithms are applied to find the optimal decision sets. A case study is completed to demonstrate how the frameworkmay applytoa specific *** simulations show that the proposed evolutionary decision support framework is able to discover robust policy sets in either uncertain or fixed environments. The framework also qualitatively identifies some of the characteristicbehavior of the critical care organization. Thus, by utilizing the proposedframework, the decision makers are able to make more informed decisions, especially toenhance the seismic safety of the hospitals.

关键词： decision making seismic engineering hospital genetic algorithms

Heat treatment of novel low-carbon multi-alloyed anti-wear marine steel

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Progress in Natural Science:Materials International 2011年第3期21卷 254-261页

作者： Jing-hua JIANG~(1,2),Qiu-yue WANG~1,Ai-bin MA~(1,2),Jun SHI~1,Liu-yan ZHANG~1, Hui-dong YANG~(2,3),Fu-min LU~2,Qi ZHOU~2 1.National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai university,Nanjing 210098,China 2.College of Mechanics and Materials,Hohai university,Nanjing 210098,China 3.department of mechanical and {4. Engineering,North Carolina State university, Raleigh,North Carolina 27695-7919,usa National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Nanjing 210098 China College of Mechanics and Materials Hohai University Nanjing 210098 China department of mechanical and aerospace Engineering North Carolina State University Raleigh North Carolina 27695-7919 USA

A low-carbon anti-wear steel,multi-alloyed with Si-Cr-Mn-Al-Ni-Mo-（Nb,RE）,was designed for vane pumps of ships. The novel cast steel after various heat treatments was characterized by microstructure observations and mechanical properties measurement in order to achieve an optimal process correlated with good abrasive resistance for a long marine *** scanning calorimetry and hardness analyses deduced a complete austenitizing temperature of 1 000℃,based on the alloying element homogenization and defective structure elimination without grain *** optimal austempering process（austenitized at 1 000℃,quick cooled for holding at 350℃for 1.5 h and then air-cooled to room temperature） produced a uniform mixture structure of fine carbide-free aciculate bainites and few lath martensites,resulting in the tensile strength increase of 34.and impact toughness increase of 50%compared with that of the as-cast *** abrasive wheel tests show that the austempered steel has good wear resistance with a mass-loss rate of 170 mg/（km·cm2） under applied load of 70 N in acidic *** new grade steel （containing anti-corrosion elements of Cr and rare earth） can find wide application in marine engineering,with further enhanced comprehensive properties via melting process improvement.

关键词： abrasive resistance carbide-free bainite marine steel mechanical performance heat treatment

Dynamics analysis and experiment on the fishtailing type of valveless piezoelectric pump with rectangular vibrator

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Science China(Technological Sciences) 2010年第12期53卷 3241-3247页

作者： HUANG Yi1, ZHANG JianHui1, HU XiaoQi1, XIA QiXiao2, HUANG WeiQing1 & ZHAO ChunSheng1 1 department of aerospace Engineering, Nanjing university of Aeronautics and Astronautics, Nanjing 210016, China 2 department of {4. and Electrical Engineering, Beijing Union university, Beijing 100020, China department of aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing China department of mechanical and Electrical Engineering Beijing Union University Beijing China

In recent years, the research and development of piezoelectric pumps have become an increasingly popular topic. Minimization, structure simplification and stronger output become the focus of piezoelectric pumps’ research due to its possible application in MEMS technology. The valveless fishtailing piezoelectric pump, neither a volumetric nor a rotating pump, was invented according to the bionics of fish swimming. With assumption that the head of the fish is fixed while its tail is swinging, fluid would flow toward the end of the tail, achieving the function of a valveless pump. This type of pumps creates a new branch for the piezoelectric pump research, which is proposed for the first time in this paper. The relationship between the flow rates and vibrating frequencies was derived from the interaction between the vibrator and fluid. Numerical simulations with FEM software were conducted to study the first and second vibration modes of the piezoelectric vibrator. The results showed that the maximum amplitude of the vibrator was 0.9 mm at the frequency of 76 Hz for the first vibration mode, while the maximum amplitude of the vibrator was 0.22 mm at the frequency of 781 Hz for the second vibration mode. Experiments were conducted with the Doppler laser vibration measurement system, and the results were compared to those of the FEM simulation. It was shown that in the first vibration mode the piezoelectric vibrator reached its maximum amplitude of about 0.9 mm at the driving frequency of 4. Hz, which gives the flow rate of 2.0 mL/min, in the second vibration mode, the maximum amplitude was about 0.25 mm at the frequency of 4.0 Hz with the flow rate being 6.4.mL/min.

关键词： piezoelectric pump valveless fishtailing rectangular vibrator dynamics analysis experiment

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

Exact traveling wave solutions of some nonlinear physical *** fifth order KdV type equations

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Communications in Nonlinear Science and Numerical Simulation 2000年第3期5卷 118-124页

作者： Jianlan HU X. FENG and Zhi LI(department of Applied Mathematics, Beijing Polytechnic university, Beijing 100022, ChinaCenter for Space Plasma and Aeronomic Research / department of mechanical and {4. Engineering, university of Alabama in Huntsville department of Applied Mathematics Beijing Polytechnic University Beijing 100022 China Center for Space Plasma and Aeronomic Research / department of mechanical and aerospace Engineering University of Alabama in Huntsville Huntsville AL 35899 USA department of Mechanics & Engineering Science Peking University Beijing 100871 China

New exact traveling wave solutions are derived for the fifth order KdV type equations by using a delicate way of rank analysis two-step ansatz method. Solitary shallowwater waves described by the above equation are di... 详细信息

关键词： the fifth order KdV type equations exact traveling wave solution solitary waves rank analysis method