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Thermoelastic properties of sandwich materials with pin-reinforced foam cores

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Science China(Technological Sciences) 2008年第12期51卷 2059-2074页

作者： LU TianJian1,LIU Tao2,3 & DENG ZiChen2,4 1 MOE Key Laboratory of Strength and Vibration,School of Aerospace,Xi’an Jiaotong university,Xi’an 710049,China 2 department of engineering Mechanics,Northwestern Polytechnical university,Xi’an 710072,China 3 department of engineering,university of cambridge,cambridge cb2.1pz,uk 4 State Key Laboratory of Structural Analysis of Industrial Equipment,Dalian university of Technology,Dalian 116024,China MOE Key Laboratory of Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an 710049 China department of engineering Mechanics Northwestern Polytechnical University Xi’an 710072 China department of engineering University of Cambridge Cambridge CB2 1PZ UK State Key Laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology Dalian 116024 China

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins(trusses) into a foam matrix to create a truss-like network reinforced foam *** loading,the pins deform predominantly by local stretching whilst the deformation of foam is governed by local *** paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich *** calculate the effective thermoelastic properties of pin-reinforced foam cores,the energy-based homogenization approach is employed to develop a micromechanics-based model,calibrated by the existing experimental *** is found that the stiffness of the sandwich core is mainly governed by pin reinforcements:the foam matrix contributes little to sandwich *** with traditional foam cores without pin reinforcements,the changes in inplane thermal expansion coefficients are not vigorous as a result of pin reinforcements,while the through-thickness thermal expansion coefficient changes *** is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context.

关键词： sandwich panel pin reinforcement analytical solutions homogenization thermoelasticity thermal expansion

A flexible framework for HMM based noise robust speech recognition using generalized parametric space polynomial regression

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Science China(Information Sciences) 2011年第12期54卷 2501-2511页

作者： CHENG Ning 1 , LIU XunYing 1,2 & WANG Lan 1 1 Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences/The Chinese university of Hong Kong, Hong Kong, China 2.1} engineering department, cambridge cb2.1pz, uk 1. Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences/The Chinese University of Hong Kong Hong Kong China2. Cambridge University Engineering Department Cambridge CB2 1PZ UK

Handling variable, non-stationary ambient noise is a challenging task for automatic speech recognition (ASR) systems. To address this issue, multi-style, noise condition independent (CI) model training using speech data collected in diverse noise environments, or uncertainty decoding techniques can be used. An alternative approach is to explicitly approximate the continuous trajectory of Gaussian component mean and variance parameters against the varying noise level, for example, using variable parameter hidden Markov model (VP-HMM). This paper investigates a more generalized form of variable parameter HMMs (GVP-HMM). In addition to Gaussian component means and variances, it can also provide a more compact trajectory modeling for tied linear transformations. An alternative noise condition dependent (CD) training algorithm is also proposed to handle the bias to training noise condition distribution. Consistent error rate gains were obtained over conventional VP-HMM mean and variance only trajectory modeling on a media vocabulary Mandarin Chinese in-car navigation command recognition task.

关键词： non-stationary noise generalized variable parameter HMM noise robust speech recognition

The Lightweight design of Low RCS Pylon Based on Structural Bionics

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Journal of Bionic engineering 2010年第2期7卷 182-190页

作者： Hongjie Jiao,Yidu Zhang,Wuyi Chen Mechanical engineering design centre,Beihang university,Beijing 100191,P.R.China [a] Mechanical engineering design centre Beihang University Beijing 100191 P. R. China

A concept of Specific Structure Efficiency (SSE) was proposed that can be used in the lightweight effect evaluation *** main procedures of bionic structure design were introduced *** parameter relationship betweenhollow stem of plant and the minimum weight was deduced in *** order to improve SSE of pylons, the structural characteristicsof hollow stem were investigated and *** pylon was designed based on analogous biological *** finite element method based simulation, the displacements and stresses in the bionic pylon were comparedwith those of the conventional *** show that the SSE of bionic pylon is improved ***, dynamic andelectromagnetism tests were carried out on conventional and bionic *** weight, stress, displacement and Radar CrossSection (RCS) of both pylons were *** results illustrate that the SSE of bionic pylon is markedly improvedthat specific strength efficiency and specific stiffness efficiency of bionic pylon are increased by 52.9% and 43.6% *** RCS of bionic pylon is reduced significantly.

关键词： lightweight design specific structure efficiency low RCS pylon bionic structure

THEORY OF DIELECTRIC ELASTOMERS

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Acta Mechanica Solida Sinica 2010年第6期23卷 549-578页

作者： Zhigang Suo (School of engineering and Applied Sciences,Kavli Institute for Nanobio Science and Technology,Harvard university,cambridge,MA 02138,USA) [a] School of engineering Applied Sciences Kavli Institute for Nanobio Science Technology Harvard University Cambridge MA 02138 USA

In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material （SAM）. This review focuses on one class of soft active materials： dielectric elastomers. When a membrane of a dielectric elastomer is subject to a voltage through its thickness, the membrane reduces thickness and expands area, possibly straining over 100%. The dielectric elastomers are being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. This paper reviews the theory of dielectric elastomers, developed within continuum mechanics and thermodynamics, and motivated by molecular pictures and empirical observations. The theory couples large deformation and electric potential, and describes nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity. The theory enables the finite element method to simulate transducers of realistic configurations, predicts the efficiency of electromechanical energy conversion, and suggests alternative routes to achieve giant voltage-induced deformation. It is hoped that the theory will aid in the creation of materials and devices.

关键词： soft active material, dielectric elastomer, electromechanical instability, large deformation transducer

Evolution of Manufacturing Strategy and System in Multinational Corporations:Internationalisation and Inter-firm Collaboration Redefine the Boundaries of Manufacturing and Firm

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厦门大学学报（自然科学版） 2002年第S1期41卷 118-119页

作者： Yongjiang Shi (Research Director of the centre for International Manufacturing Instit ute for Manufacturing, The university of cambridge, uk)

In recent decades, the world economy has been stron gl y driven by worldwide foreign direct investment (FDI) of transnational corporati ons (TNCs). And business globalisation is leading to widespread re-structuring of international manufacturing systems in TNCs. However, still very little sys tematic research in manufacturing engineering or production/operations managemen t (P/O M) has focused on these new types of globalised manufacturing systems, an d little communication is organised between different academic disciplines such as manufacturing, management/ business studies, economics, geography, internatio nal development studies and so on. Many critical issues are still poorly unders tood and are not covered by current research agendas, for example: · properties of international manufacturing network systems in terms of structu ral architecture, dynamic mechanisms, strategic capabilities, strategy processes , new technology, and alliance relationships · knowledge management and organisational learning mechanisms in international manufacturing context, especially in globally coordinated networks at both intra - and inter- organisational levels · global economic trends, regional collaboration, national culture/identity, an d their impacts on industrial sector development, and company’s manufacturin g system design/re-structuring In industry, lack of global vision and appropriate strategies during internation alisation have become major barrier to the effective management of international operations. In academia, limited multi-discipline exchanges have inhibited de velopments not only in each area but also knowledge contribution to industry whi ch could arise from discipline integration. This paper, based on recent years case observations and action research work on manufacturing internationalisation, especially globalisation, introduces an evol utionary process of manufacturing systems. It seeks to explore the external and internal driving forces of the transforma

关键词： internationalisation inter-firm collaboration global manufacturing network firm evolution

MXene-based hybrid materials for electrochemical and photoelectrochemical H_(2) generation

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Journal of Energy Chemistry 2024年第6期93卷 111-125,I0004页

作者： Jun Young Kim Seung Hun Roh Chengkai Xia uk Sim Jung Kyu Kim School of Material Science and engineering North University of ChinaTaiyuan 030051China School of Chemical engineering Sungkyunkwan University(SKKU)2066Seobu-roJangan-guSuwon 16419Republic of Korea Hydrogen Energy Technology Laboratory Korea Institute of Energy Technology(KENTECH)NajuJeollanamdo 58330Republic of Korea SKKU Advanced Institute of Nano Technology(SAINT) Sungkyunkwan University(SKKU)2066Seobu-roJangan-guSuwon 16419Republic of Korea

The conversion of solar energy to produce clean hydrogen fuel through water splitting is an emerging strategy for efficiently storing solar energy in the form of solar *** aligns with the increasing global demand for the development of an ideal energy alternative to fossil fuels that does not emit greenhouse ***(EC) and photoelectrochemical(PEC) water splitting technologies have garnered significant attention worldwide for advanced hydrogen solar fuel production in recent *** achieve sustainable green H_(2) production,it is essential to create efficient catalyst materials that are low-cost and can replace expensive noble metal-based *** characteristics make them an ideal catalyst material for the ***-dimensional MXenes with M_(n+1)X_(n) structure have been identified as a promising option for EC and PEC water splitting due to their superior hydrophilicity,metal-like conductivity,large surface area,and adjustable surface ***,we present a summary of recent advancements in the synthesis and performance enhancement methods for MXene hybrid materials in hydrogen production through EC and PEC water ***,we examine the challenges and insights associated with the rational design of MXene-based hybrid materials to facilitate efficient water splitting for sustainable solar fuel production.

关键词： MXene Hybrid materials EC PEC HER OER Water splitting

Guided wave propagation in multilayered piezoelectric structures

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Science China(Physics,Mechanics & Astronomy) 2009年第7期52卷 1094-1104页

作者： GUO YongQiang1, CHEN WeiQiu2,3 & ZHANG YongLiang4 1 Key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education, and School of Civil engineering and Mechanics, Lanzhou university, Lanzhou 730000, China 2 Key Laboratory of Soft Soils and Geoenvironmental engineering, Ministry of Education, and department of Civil engineering, Zhejiang university, Hangzhou 310058, China 3 department of engineering Mechanics, Zhejiang university, Hangzhou 310027, China 4 School of Civil engineering, Lanzhou Jiaotong university, Lanzhou 730070, China Key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education and School of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000 China Key Laboratory of Soft Soils and Geoenvironmental engineering Ministry of Education and Department of Civil Engineering Zhejiang University Hangzhou 310058 China department of engineering Mechanics Zhejiang University Hangzhou 310027 China School of Civil engineering Lanzhou Jiaotong University Lanzhou 730070 China

A general formulation of the method of the reverberation-ray matrix (MRRM) based on the state space formalism and plane wave expansion technique is presented for the analysis of guided waves in multilayered piezoelectric structures. Each layer of the structure is made of an arbitrarily anisotropic piezoelectric material. Since the state equation of each layer is derived from the three-dimensional theory of linear piezoelectricity, all wave modes are included in the formulation. Within the framework of the MRRM, the phase relation is properly established by excluding exponentially growing functions, while the scattering relation is also appropriately set up by avoiding matrix inversion operation. Consequently, the present MRRM is unconditionally numerically stable and free from computational limitations to the total number of layers, the thickness of individual layers, and the frequency range. Numerical examples are given to illustrate the good performance of the proposed formulation for the analysis of the dispersion characteristic of waves in layered piezoelectric structures.

关键词： multilayered piezoelectric structures the method of reverberation-ray matrix guided waves dispersion characteristic

Damage and progressive failure of concrete structures using non-local peridynamic modeling

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Science China(Technological Sciences) 2011年第3期54卷 591-596页

作者： HUANG Dan1,2, ZHANG Qing1,2 & QIAO PiZhong1,3 1 State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering, Hohai university, Nanjing 210098, China 2 department of engineering Mechanics, Hohai university, Nanjing 210098, China 3 department of Civil and Environmental engineering, Washington State university, Pullman, WA 99164-2.10, USA 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. Department of Engineering Mechanics Hohai University Nanjing 210098 China3. Department of Civil and Environmental Engineering Washington State University Pullman WA 99164-2910 USA

Peridynamics (PD), a recently developed theory of solid mechanics, which employs a non-local model of force interaction and makes use of integral formulation rather than the spatial partial differential equations used in the classical continuum mechanics theory, has shown effectiveness and promise in solving discontinuous problems at both macro and micro scales. In this paper, the peridynamics theory is used to analyze damage and progressive failure of concrete structures. A non-local peridynamic model for a rectangular concrete plate is developed, and a central pairwise force function is introduced to describe the interior interactions between particles within some definite distance. Damage initiation, evolution and crack propagation in the concrete model subject to in-plane uni-axial tension, in-plane uni-axial compression and out-of-plane impact load are investigated respectively. The numerical results show that discontinuities appear and grow spontaneously as part of the solution to the peridynamic equations of motion, and no special failure criteria or re-meshing techniques are required, which proves the potential of peridynamic modeling as a promising technique for analyzing the progressive failure of concrete materials and structures.

关键词： concrete damage progressive failure peridynamic model discontinuities

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 410083) Central South Univ of Technology Changsha China

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