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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 cambridge university 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

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 99164-2910, 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

Physically-based approach to analyze rainfall-triggered landslide using hydraulic gradient as slide direction

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Journal of Zhejiang university-Science A(Applied Physics & engineering) 2012年第12期13卷 943-957页

作者： Qi-hua RAN1,Dan-yang SU1,Qun QIAN1,Xu-dong FU2,Guang-qian WANG1,2,Zhi-guo HE3 (1department of Hydraulic engineering,Zhejiang university,Hangzhou 310058,China) (2State Key Laboratory of Hydroscience and engineering,Tsinghua university,Beijing 100084,China) (3department of Ocean Science and engineering,Zhejiang university,Hangzhou 310058,China) 1. department of Hydraulic engineering Zhejiang University Hangzhou 310058 China 2. State Key Laboratory of Hydroscience and engineering Tsinghua University Beijing 100084 China 3. department of Ocean Science and engineering Zhejiang University Hangzhou 310058 China

An infinite slope stability numerical model driven by the comprehensive physically-based integrated hydrology model(InHM) is *** this approach,the failure plane is assumed to be parallel to the hydraulic gradient instead of the slope *** method helps with irregularities in complex terrain since depressions and flat areas are allowed in the *** present model has been tested for two synthetic single slopes and a small catchment in the Mettman Ridge study area in Oregon,United States,to estimate the shallow landslide *** results show that the present approach can reduce the simulation error of hydrological factors caused by the rolling topography and depressions,and is capable of estimating spatial-temporal variations for landslide susceptibilities at simple slopes as well as at catchment scale,providing a valuable tool for the prediction of shallow landslides.

关键词： Shallow landslide Infinite slope stability model Hydraulic gradient Physically-based hydrology model Integrated hydrology model(InHM)

A study of mechanical behavior of rock-fill materials with reference to particle crushing

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Science China(Technological Sciences) 2007年第z1期50卷 125-135页

作者： HUANG WenXiong1?, REN QingWen1 & SUN DeAn2 1 department of engineering Mechanics, Hohai university, Nanjing 210098, China 2 department of Civil engineering, Shanghai university, Shanghai 200072, China department of engineering Mechanics Hohai University Nanjing 210098 China department of Civil engineering Shanghai University Shanghai 200072 China

In rock-fill dams of 200 to 300 m high, maximum compressive stress can exceed 6 MPa. At such a high stress level, rock-fill materials may experience particle crushing during shear. The material behavior is highly sophisticated exhibiting pressure and density dependency as well as particle crushing effects. Through scrutinizing the relevant experimental data on rock-fill materials and sands published in the literatures, this paper is focused on understanding basic mechanical characteristics of this sort of materials in the light of constitutive modelling.

关键词： rock-fill materials granular materials compressibility shear dilatancy particle crushing

Theory and methods of global stability analysis for high arch dam

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Science China(Technological Sciences) 2011年第S1期54卷 9-17页

作者： REN QingWen 1,LI Qiang 1,JIANG YaZhou 2 & JIANG XiaoLan 3 1 department of engineering Mechanics,Hohai university,Nanjing 210098,China 2 College of Water Conservation and Hydropower engineering,Hohai university,Nanjing 210098,China 3 Changjiang Academy of Sciences,Wuhan 430010,China 1. department of engineering Mechanics Hohai University Nanjing 210098 China2. College of Water Conservation and Hydropower Engineering Hohai University Nanjing 210098 China3. Changjiang Academy of Sciences Wuhan 430010 China

The global stability of high arch dam is one of the key problems in the safety study of arch dams,but no feasible method with theoretical basis is *** this paper,based on the stability theory of mechanical system,it is demonstrated that the global failure of high arch dams belongs to a physical instability starting from local strength failure,which is the extreme point instability according to the characteristics of load-displacement curve obtained from the failure process of dam-foundation system. So the global failure of dam-foundation system should be studied with the stability theory of mechanical *** is also pointed out that the current stability analysis methods used in engineering are consistent with the stability theory,but not established according to the mechanical system stability theory directly.A perfect method can be obtained through the study of physical disturbance equations.

关键词： high arch dam global stability physical instability extreme point instability

Mesh theory of angle modified dual tori double-enveloping toroidal worm drive

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Science China(Technological Sciences) 2010年第7期53卷 1913-1927页

作者： ZHAO YaPing1, SU DaiZhong2, ZHANG Zhao1, WEI WenJun3 & DONG XueZhu3 1 College of Machinery and Automation, Wuhan university of Science and Technology, Wuhan 430081, China 2 Advanced design and Manufacturing engineering Center, Nottingham Trent university, Nottingham NG1 4BU, uk 3 College of engineering, China Agricultural university, Beijing 100083, China 1. College of Machinery and Automation Wuhan University of Science and Technology Wuhan 430081 China2. Advanced Design and Manufacturing Engineering Center Nottingham Trent University Nottingham NG1 4BU UK3. College of Engineering China Agricultural University Beijing 100083 China

In this paper, the meshing theory of the angle modified hourglass worm drive is enriched and developed. The ordinary condition of the angle modification is derived and the physical significance of the modification is interpreted. A normal section methodology is proposed for meshing analysis, which can be used to compute the normal distance near a singular meshing point of a conjugate surface couple. By means of the method and after analyzing the normal transversals, it is specified that the worm helicoid, the nominal former contact zone and the new contact zone intersect each other along the locus of singular points of the instantaneous contact lines of an angle-modified worm pair. As a result, it is explained clearly that those three osculate each other but the osculations are different in degree. Moreover, the mechanism of removing the twice-contacted zone from the worm gear tooth surface is clarified and the reason of shortening the worm working length is also elucidated. With the help of the theory described in the present paper and the thorough and systematic research on the relevant meshing characteristics, the angle modified dual tori double-enveloping toroidal worm drive has been shown to be an excellent new-fashioned hourglass worm set.

关键词： hourglass worm angle modification double-enveloping osculation normal transversal

Thermodynamic properties of under-cooled silver melts

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Science China(Physics,Mechanics & Astronomy) 2010年第1期53卷 76-80页

作者： ZHU YuYing 1 , LI Qiang 1,2,3, WANG Ge 1 , JING Qin 2 , WANG Xu 1 , GAO Ying 3 & GAO JingNa 3 1 department of Mechanical engineering, Yanshan university, Qinhuangdao 066004, China 2 Key Laboratory of Metastable Materials Science & Technology, Yanshan university, Qinhuangdao 066004, China 3 department of Materials Science & engineering, Hebei university of Science and Technology, Shijiazhuang 050018, China 1. department of Mechanical engineering Yanshan University Qinhuangdao 066004 China2. Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao 066004 China3. Department of Materials Science & Engineering Hebei University of Science and Technology Shijiazhuang 050018 China

Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specific heat of the under-cooled melt showed a linear dependence on the temperature in the range of the obtained under-cooling from 0 to 198 K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the under-cooled melt and the solid phase, were derived from the measured specific heat. The relations between the temperature and the thermal diffusion or the thermal conductivity of the under-cooled melt were analyzed respectively.

关键词： under-cooled silver melts specific heat thermodynamic properties

Rank of loop, constraint degree of path, coupling degree of graph and their application

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Progress in Natural Science:Materials International 2005年第2期15卷 79-85页

作者： YANG Tingli1*, LUO Yufeng2, ZHANG Ce3 and YAO Fanghua1(1. SINOPIC Jinling Petrochemical Corp., Nanjing 210037, China 2. department of Mechanical engineering, Nanchang university, Nanchang 330029, China 3. department of Mechanical engineering, Tianjin university, Tianjin 300072, China) SINOPIC Jinling Petrochemical Corp. Nanjing 210037 China. department of Mechanical engineering Nanchang University Nanchang 330029 China. department of Mechanical engineering Tiánjin University Tianjin 300072 China

Some new concepts (rank of a loop, degree of freedom of a graph, path unit and ordered path arrangement, constraint degree of path, coupling degree of a graph, basic graph, etc.), formulas, and algorithms, are proposed in this paper. Based on these concepts, a new systematic theory and practical method for the design of topological structure, kinematics and dynamics of mechanical systems is established. Some conjectures and problems needed to be researched are also put forward. The concepts, formulae and algorithms presented in this paper will find wide potential applications.

关键词： rank of loop degree of freedom of graph constraint degree of path coupling degree of graph