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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 ma02.15, usa School of Navigation Wuhan University of Technology Wuhan 430063 P. R. China Wuhan Second Ship Design and Research Institute Wuhan 430064 E 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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Elasticity meets topology

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National Science Review 2024年第6期11卷 84-85页

作者： Guancong ma department of Physics Hong Kong Baptist University

We are surrounded by environments and items that are made from solid materials in our daily life. Any physical contact with any items is a mechanical disturbance that produces mechanical *** underlines the crucial role that such vibrations play in our daily interactions,highlighting the need for a deeper understanding and improved manipulation of these fundamental phenomena.

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Rolling Element Bearing Diagnostics by Combination of Envelope Analysis and Wavelet Transform

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Journal of university of Science and Technology Beijing 2001年第1期8卷 69-74页

作者： Ying Tang, Qiao Sun mechanical engineering School, university of Science and Technology Beijing, Beijing 100083, China department of mechanical engineering, university of Calgary Calgary Alberta T2N 1N4. Canada Univ Sci & Technol Beijing Sch Mech Engn Beijing 100083 Peoples R China Univ Calgary Dept Mech Engn Calgary AB T2N 1N4 Canada

Rolling element-bearing diagnostics has been studied over the last thirty years, and envelope analysis is widely recognized as being the best approach for detection and diagnosis of rolling element bearing incipient failure. But one of the on-going difficulties with envelope technique is to determine the best frequency band to envelop. Here, wavelet transform technique is introduced into envelope analysis to solve the problem by capturing bearing defects-sensory scales (i.e. frequency bands). A modulated Gaussian function is chosen to be the analytical wavelet because it coincides well with bearing defect-induced vibration signal patterns. Vibration signals measured from railway bearing tests were studied by the proposed method. Cases of bearings with single and multiple defects on inner and outer race under different testing conditions are presented. Experimental results showed that the proposed method allowed a more accurate local description and separation of transient signal part, which were caused by impacts between defects and the mating surfaces in the bearing. The combination method provides an effective signal detection technique for rolling element-bearing diagnostics.

关键词： continuous wavelet transform envelope analysis rolling element bearing diagnostics

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STUDY ON THE OPTICAL FLAT PROFILE HIGH PRECISION MEASURING TECHNOLOGY IN THE METHOD OF LASER DATUM

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Chinese Journal of mechanical engineering 1999年第4期12卷 312-316页

作者： Liu Haijiang Wan De’an department of mechanical engineering,Tongji university 同济大学机械工程系上海 200092 同济大学机械工程系上海

The physical datum method that uses the laser beam as the physical datum is proposed.A high accuracy of the straight movement on the line above 0.01 μm/100 mm is achieved through applying the method of the closed loop feedback control that uses the laser beam as the *** measuring accuracy above 0.05 μm is obtained by applying the self making electric eddy displacement sensor to detect the geometric accuracy of the optical *** proves that the laser beam datum method can achieve the high accurcy of the straight movement and has the huge advantage.

关键词： Laser beam datum Optical flat Profile precision measurement

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THE TOLERANCE DESIGN maNUFACTURE AND RELIABILITY

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中国有色金属学会会刊：英文版 1995年第2期5卷 127-130页

作者： Jiang, Jianchun(department of mechanical engineering,Central South university of Technology, Changsha 4.0083) Central South Univ of Technology Changsha China

ＴＨＥＴＯＬＥＲＡＮＣＥＤＥＳＩＧＮＭＡＮＵＦＡＣＴＵＲＥＡＮＤＲＥＬＩＡＢＩＬＩＴＹ￥Ｊｉａｎｇ，Ｊｉａｎｃｈｕｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉ... 详细信息

ＴＨＥＴＯＬＥＲＡＮＣＥＤＥＳＩＧＮＭＡＮＵＦＡＣＴＵＲＥＡＮＤＲＥＬＩＡＢＩＬＩＴＹ￥Ｊｉａｎｇ，Ｊｉａｎｃｈｕｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏ...

关键词： tolerance fit reliability service probability distribution machining precision tribology design CAD

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SiC-Mg INTERFACE OF SiC_p/AZ80 COMPOSITE

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中国有色金属学会会刊：英文版 1996年第4期6卷 114-116页

作者： Cai Ye Su Huaqin(department of mechanical engineering,Southeast university,Nanjing 210096) SOUTHEAST UNIV DEPT MECH ENGNNANJING 210096PEOPLES R CHINA

ＳｉＣ－ＭｇＩＮＴＥＲＦＡＣＥＯＦＳｉＣ_ｐ／ＡＺ８０ＣＯＭＰＯＳＩＴＥ￥ＣａｉＹｅ；ＳｕＨｕａｑｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＳｏｕｔｈｅａｓｔＵｎｉｖｅｒｓｉｔｙ，Ｎａ... 详细信息

ＳｉＣ－ＭｇＩＮＴＥＲＦＡＣＥＯＦＳｉＣ_ｐ／ＡＺ８０ＣＯＭＰＯＳＩＴＥ￥ＣａｉＹｅ；ＳｕＨｕａｑｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｉｎｅｅｒｉｎｇ，ＳｏｕｔｈｅａｓｔＵｎｉｖｅｒｓｉｔｙ，Ｎａｎｊｉｎｇ２１００９６）Ａｂｓｔｒ?..

关键词： magnesium alloy composite interface SiC particles

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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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Tribological applications of biomaterials: an overview

引用

Science China mathematics 2001年第S1期44卷 297-306页

作者： Bing Shi Hong Liang department of mechanical engineering, university of Alaska Fairbanks Fairbanks, AK,{4. Univ Alaska Fairbanks Dept Mech Engn Fairbanks AK 99775 USA

Tribological research is the study of lubrication, friction, and wear. Tribology of biomate-rials is to study how the materials work and fail. This will help us to produce better *** plays a very important role in improving the design and making successful biomaterialsfor medical purposes. Joints of human body, such as hip, knee, jaw, dental parts etc., all need toconsider the wear and lubrication problem. In this paper, we give a general introduction of bioma-terial research in tribological applications. materials, the synthetic characterization, and their failureare introduced.

关键词： Biomaterials Tribological materials

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