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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. department of {4. and mechanical Engineering, 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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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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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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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

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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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Bionic soft robotic gripper with feedback control for adaptive grasping and capturing applications

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Frontiers of mechanical Engineering 2024年第1期19卷 129-148页

作者： Tingke WU Zhuyong LIU Ziqi ma Boyang WANG Daolin ma Hexi YU department of Engineering Mechanics School of Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China MOE Key Laboratory of Hydrodynamics Shanghai Jiao Tong UniversityShanghai 200240China

Robots are playing an increasingly important role in engineering *** robots have promising applications in several fields due to their inherent advantages of compliance,low density,and soft interactions.A soft gripper based on bio-inspiration is proposed in this *** analyze the cushioning and energy absorption mechanism of human fingertips in detail and provide insights for designing a soft gripper with a variable stiffness *** investigate the grasping modes through a large deformation modeling approach,which is verified through *** characteristics of the three grasping modes are quantified through testing and can provide guidance for robotics ***,the adaptability of the soft gripper is verified by grasping multi-scale and extremely soft ***,a cushioning model of the soft gripper is proposed,and the effectiveness of cushioning is verified by grasping extremely sharp objects and living ***,we validate the advantages of the variable stiffness of the soft gripper,and the results show that the soft robot can robustly complete assemblies with a gap of only 0.1 *** to the unstructured nature of the engineering environment,the soft gripper can be applied in complex environments based on the abovementioned experimental ***,we design the soft robotics system with feedback capture based on the inspiration of human catching *** feasibility of engineering applications is initially verified through fast capture experiments on moving *** design concept of this robot can provide new insights for bionic machinery.

关键词： soft bionic gripper variable stiffness structure large deformation modeling feedback control soft robotic system

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Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

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Chinese Journal of Aeronautics 2024年第1期37卷 162-172页

作者： Jinfeng DENG Ning AN Qilong JIA Xiaofei ma School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China State Key Laboratory for Strength and Vibration of mechanical Structures School of AerospaceXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China Xi’an Institute of Space Radio Technology Xi’an 710100China

Composite Thin-walled Lenticular Tube(CTLT)is increasingly utilized in small satellites missions as a lightweight,foldable,and rollable structural material that facilitates the construction of large deployable *** CTLT is initially flattened and coiled around a central hub for storage before launch,during which elastic energy is stored as deformation energy,allowing it to be self-deployed on demand for use in *** work presents a comprehensive investigation into the coiling,storage and deployment behaviors of CTLT that wraps around a central hub.A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigidbodies mechanisms including the central hub and guide rollers,as well as the complex interactions among *** coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the ***,the dynamic deployment behaviors were analyzed in terms of two different deployment methods,namely,controlled deployment and free *** effect of material property change during storage was also discussed through numerical experiments.

关键词： Composite deployable structures Deployment dynamics Finite element method Stress relaxation Thin-walled booms

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Non-Fully Conjugated Photovoltaic materials with Y-Series Acceptor Backbone for High-Performance Organic Solar Cells

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Chinese Journal of Chemistry 2024年第11期42卷 1307-1318页

作者： Hairui Bai Qunping Fan Ruijie ma Xia Guo Wei ma maojie Zhang State Key Laboratory for mechanical Behavior of materials Xi’an Jiaotong UniversityXi’anShaanxi710049 China National Engineering Research Center for Colloidal materials School of Chemistry&Chemical EngineeringShandong UniversityJinanShandong250100 China department of Electronic and Information Engineering Research Institute for Smart Energy(RISE)The Hong Kong Polytechnic UniversityKowloon999077 Hong KongChina

In the last few years,organic solar cells(OSCs)have made significant progress in photovoltaic performance,mainly due to the innovative development of active layer materials,especially Y-series and related derivatives as acceptors which have become the key factor that boosts the power conversion ***,to achieve high-performance OSCs,an emerging molecular design strategy of applying flexible alkyl units as linkers to construct non-fully conjugated acceptors has been developed and addressed great *** review highlights the non-fully conjugated photovoltaic materials with Y-series backbone that enable high-performance *** OSCs have been achieved by some representative non-fully conjugated material *** related molecular design strategies are discussed in ***,a brief summary and future prospect are provided in advancing the non-fully conjugated photovoltaic materials with Y-series backbone towards the brighter future.

关键词： Organic solar cells All-polymer solar cells Non-fully conjugated photovoltaic materials Power conversion efficiency Polymer acceptors Organicel ectronics

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Elastic wave insulation and propagation control based on the programmable curved-beam periodic structure

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Applied mathematics and Mechanics(English Edition) 2024年第10期45卷 1791-1806页

作者： Jiajia maO Hong CHENG Tianxue ma Beijing Key Laboratory of Nonlinear Vibrations and Strength of mechanical Structures Department of MechanicsSchool of MathematicsStatistics and MechanicsBeijing University of TechnologyBeijing 100124China department of Mechanics School of Physical Science and EngineeringBeijing Jiaotong UniversityBeijing 100044China

Curved-beams can be used to design modular multistable metamaterials(MMMs)with reprogrammable material properties,i.e.,programmable curved-beam periodic structure(PCBPS),which is promising for controlling the elastic wave *** PCBPS is theoretically equivalent to a spring-oscillator system to investigate the mechanism of bandgap,analyze the wave propagation mechanisms,and further form its geometrical and physical criteria for tuning the elastic wave *** the equivalent model,we calculate the analytical solutions of the dispersion relations to demonstrate its adjustability,and investigate the wave propagation characteristics through the *** validate the equivalent system,the finite element method(FEM)is *** is revealed that the bandgaps of the PCBPS can be turned on-and-off and shifted by varying its physical and geometrical *** findings are highly promising for advancing the practical application of periodic structures in wave insulation and propagation control.

关键词： curved-beam based periodic structure equivalent stiffness spring-oscillator system dispersion relation wave propagation

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Gyroid Triply Periodic Minimal Surface Lattice Structure Enables Improved Superelasticity of CuAlMn Shape Memory Alloy

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Acta Metallurgica Sinica(English Letters) 2024年第6期37卷 1047-1065页

作者： Mengwei Wu Chunmei ma Ruiping Liu Huadong Fu department of materials Science and Engineering China University of Mining and Technology(Beijing)Beijing100083China Institute for Advanced materials and Technology University of Science and Technology BeijingBeijing100083China

Improving the shape memory effect and superelasticity of Cu-based shape memory alloys(Smas)has always been a research hotspot in many *** work systematically investigates the effects of Gyroid triply periodic minimal surface(TPMS)lattice structures with different unit sizes and volume fractions on the manufacturing viability,compressive mechanical response,superelasticity and heating recovery properties of CuAlMn *** results show that the increased specific surface area of the lattice structure leads to increased powder adhesion,making the manufacturability proportional to the unit size and volume *** compressive response of the CuAlMn Smas Gyroid TPMS lattice structure is negatively correlated with the unit size and positively correlated with the volume *** superelastic recovery of all CuAlMn Smas with Gyroid TPMS lattice structures is within 5%when the cyclic cumulative strain is set to be 10%.The lattice structure shows the maximum superelasticity when the unit size is 3.00 mm and the volume fraction is 12%,and after heating recovery,the total recovery strain increases as the volume fraction *** study introduces a new strategy to enhance the superelastic properties and expand the applications of CuAlMn Smas in soft robotics,medical equipment,aerospace and other fields.

关键词： Shape memory alloys Superelasticity Gyroid triply periodic minimal surface(TPMS)lattice structure Selective laser melting(SLM)

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