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The 16th Annual Conference of Hong Kong Society of Theoretical and Applied mechanics 2012、The 1st Mainland-Hong Kong Youth Forum on mechanics 2012、The 8th Shanghai-Hong Kong Forum on mechanics and Its Application 2012

作者： X.Feng B.W.Lu Y.Wang department of Engineering mechanics Tsinghua University department of Engineering mechanics Zhejiang University

Lead zirconate titanate(e.g.,PZT) is one of the most widely used ferroelectric materials, due to its excellent piezoelectric and ferroelectric *** classes of sensors,actuators and memory elements,for use in diverse sectors of industry,ranging from aerospace,automotive, to medicine and microelectronics,rely on PZT.A key disadvantage of this material is that it,like most other ceramics,is brittle,and usually fractures at strains that are substantially less than 1%. As a result,devices built with PZT,in conventional layouts and processed using established,high temperature techniques,can only be subjected to small strain deformations,and can be integrated only with narrow classes of *** limitations frustrate many potentially interesting applications,particularly those that require integration with the curvilinear,elastic surfaces of the human body for energy harvesting or health *** report a strategy for integrating nanoribbons of PZT,the ferroelectric ceramics,in 'wavy' geometries,on soft,elastomeric supports to achieve reversible,linear elastic responses to large strain deformations(*** properties),without any loss in ferroelectric or piezoelectric *** Force Microscope(PFM) is used to characterize the piezoelectricity and ferroelectricy of stretchable PZT *** and computational analysis of the mechanics accounts for these characteristics and also shows that the amplitudes of the waves can be continuously tuned with an applied electric field,to achieve a vertical(normal) displacement range that is near one thousand times larger than is possible in conventional planar *** results suggest new design and application possibilities in piezo/ferroelectric devices.

关键词： Stretchable and Flexible Ferroelectrics:Fabrication,Characterization and Theory

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Average Synchronization and Temporal Order in a Noisy Neuronal Network with Coupling Delay

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Chinese Physics Letters 2007年第10期24卷 2759-2761页

作者：王青云段志生陆启韶 State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Aerospace Engineering College of Engineering Peking University Beijing 100871 department of Statistics and Mathematics Inner Mongolia Finance and Economics College Huhhot 010051 School of Science Beijing University of Aeronautics and Astronautics Beijing 100083

Average synchronization and temporal order characterized by the rate of firing are studied in a spatially extended network system with the coupling time delay, which is locally modelled by a two-dimensional Rulkov map neuron. It is shown that there exists an optimal noise level, where average synchronization and temporal order are maximum irrespective of the coupling time delay. Furthermore, it is found that temporal order is weakened when the coupling time delay appears. However, the coupling time delay has a twofold effect on average synchronization, one associated with its increase, the other with its decrease. This clearly manifests that random perturbations and time delay play a complementary role in synchronization and temporal order.

关键词： coated conductor buffer layer self-epitaxy CeO2

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Theory and Calculation of the J-Integral for Coupled Chemo-Mechanical Fracture mechanics

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Computer Modeling in Engineering & Sciences 2018年第6期115卷 387-409页

作者： Wei Wei Qingsheng Yang Xia Liu Xiaoqiao He Kim-Meow Liew School of Civil Engineering Hebei University of EngineeringHandan 056038China department of Engineering mechanics Beijing University of TechnologyBeijing 100124China department of Civil and Architectural Engineering City University of Hong KongTat Chee AvenueKowloonHong Kong

In this paper,by introducing a chemical field,the J-integral formulation is presented for the chemo-mechanical coupled medium based on the laws of thermodynamics.A finite element implementation of the J-integral was performed to study the mode I chemo-mechanical coupled fracture *** derivation of the coupled J-integral,the equivalent domain integral(EDI)method was applied to obtain the mode I J-integral,with expression of the area integrals based on constitutive relationships of a linear elastic small deformation for chemo-mechanical coupling,instead of the finite deformation problem.A finite element procedure is developed to compute the mode I J-integral,and numerical simulation of the y-direction stress field is studied by a subroutine UEL(User defined element)developed in ABAQUS *** of the numerical results obtained using the mode I J-integral was verified by comparing them to a well-established model based on linear elastic fracture mechanics(LEFM).Furthermore,a numerical example was presented to illustrate path-independence of the formulated J-integral for a chemo-mechanical coupled specimen under different boundary conditions,showing a high accuracy and reliability of the present *** variation laws of J-integral and the y-direction stress field with external chemical,mechanical loading and time are *** J-integral value increases with larger external concentration loading in the same integral *** extent of diffusion is much greater with larger concentration,which leads to a stronger coupling effect due to the chemical *** work provides new insights into the fracture mechanics for the chemo-mechanical coupled medium.

关键词： Chemo-mechanical coupling fracture J-integral equivalent domain integral(EDI)method finite element method

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Numerical Simulation and Experimental Investigation on Performance of the Wells Turbine in Irregular Oscillating Flow

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China Ocean Engineering 2001年第3期16卷 407-416页

作者：黄忠洲蒋念东余志 department of Thermal Science and Energy Engineering The University of Science and Technology of China Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 510070 China Guangzhou Institute of Energy Conversion Chinese Academy of Sciences department of Applied mechanics and Engineering Zhongshan University

The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions, Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow, Therefore, it is possible to predict accurately the performance of the Wells turbine by computer simulation.

关键词： wave energy renewable energy wells turbine irregular oscillating flow fluid machinery

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Elastoplastic constitutive modeling under the complex loading driven by GRU and small-amount data

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Theoretical & Applied mechanics Letters 2022年第6期12卷 389-394页

作者： Zefeng Yu Chenghang Han Hang Yang Yu Wang Shan Tang Xu Guo The State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsDalian University of TechnologyDalian116023China International Research Center for Computational mechanics Dalian University of TechnologyDalian116023China Ningbo Institute of Dalian University of Technology Ningbo315016China

In this paper,a data-driven method to model the three-dimensional engineering structure under the cyclic load with the one-dimensional stress-strain data is *** this method,one-dimensional stress-strain data obtained under uniaxial load and different loading history is learned offline by gate recurrent unit(GRU)*** learned constitutive model is embedded into the general finite element framework through data expansion from one dimension to three dimensions,which can perform stress updates under the three-dimensional *** proposed method is then adopted to drive numerical solutions of boundary value problems for engineering *** with direct numerical simulations using the J2 plasticity model,the stress-strain response of beam structure with elastoplastic materials under forward loading,reverse loading and cyclic loading were predicted *** path dependent response of structure was captured and the effectiveness of the proposed method is *** shortcomings of the proposed method are also discussed.

关键词： Data driven Recurrent neural network Path dependence Small-amount data

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First integrals and stability of second-order differential equations

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Chinese Physics B 2006年第6期15卷 1134-1136页

作者：许学军梅凤翔 department of Physics Zhejiang Normal University Jinhua 321004 China department of mechanics Beijing Institute of Technology Beijing 100081 China

The stability of second-order differential equations is studied by using their integrals. A system of second-order differential equations can be considered as a mechanical system with holonomic constraints. A conserved quantity of the mechanical system or a part of the system is obtained by using the Noether theory. It is possible that the conserved quantity becomes a Liapunov function and the stability of the system is proved by the Liapunov theorem.

关键词： differential equation stability Liapunov function Noether theorem

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基于结构的细胞模型揭示了剪应力下活细胞的幂律流变学和硬化特性

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Acta Mechanica Sinica 2023年第10期39卷 137-144页

作者：梁栋杭久涛徐光魁 Laboratory for Multiscale mechanics and Medical Science Department of Engineering Mechanics State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace Engineering Xi’an Jiaotong University Xi’an 710049 China

剪应力在许多生理过程中都起着至关重要的作用,例如动脉粥样硬化、血管生成和肿瘤转移等.然而,细胞对静态和动态剪应力的响应仍然知之甚少.考虑细胞膜、细胞质和细胞骨架等结构特征,本文提出了一个基于结构的细胞模型以探究细胞的剪切... 详细信息

剪应力在许多生理过程中都起着至关重要的作用,例如动脉粥样硬化、血管生成和肿瘤转移等.然而,细胞对静态和动态剪应力的响应仍然知之甚少.考虑细胞膜、细胞质和细胞骨架等结构特征,本文提出了一个基于结构的细胞模型以探究细胞的剪切流变学.通过模拟单个细胞在剪应力下的力学响应,我们发现该模型可以再现细胞小变形时的幂律流变学和大变形时的应力硬化特性.此外,细胞在高频下的损耗模量表现出比存储模量更强的频率依赖性.进而,我们提出了两个重要关系:一个是幂律指数和细胞刚度之间的关系;另一个是在细胞刚度和外力之间的关系.我们的预测结果与很多实验结果一致.自相似多级理论为细胞在剪应力下的幂律响应提供了物理解释.此外,我们考虑了单根纤维的几何非线性,以便解释细胞的应力硬化.本模型可用于研究剪切流动对生理环境下活细胞的影响.

关键词：频率依赖性细胞模型动脉粥样硬化肿瘤转移生理环境剪切流动单根纤维剪应力

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Mobile Rayleigh Doppler wind lidar based on double-edge technique

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Chinese Optics Letters 2010年第8期8卷 726-731页

作者：唐磊舒志峰董吉辉王国成汪永涛徐文静胡冬冬陈廷娣窦贤康孙东松 Hyunki Cha Anhui Institute of Optics and Fine mechanics Chinese Academy of Sciences Computer department Anhui Finance and Trade Vocational College School of Earth and Space Sciences University of Science and Technology of China Korea Atomic Energy Research Institute

We describe a mobile molecular Doppler wind lidar （DWL） based on double-edge technique for wind measurement of altitudes ranging from 10 to 40 km. A triple Fabry-Perot etalon is employed as a frequency discriminator to determine the Doppler shift proportional to the wind velocity. The lidar operates at 355 nm with a 45-cm-aperture telescope and a matching azimuth-over-elevation scanner that provides full hemispherical pointing. To guarantee wind accuracy, a single servo loop is used to monitor the outgoing laser frequency to remove inaccuracies due to the frequency drift of the laser or the etalon. The standard deviation of the outgoing laser frequency drift is 6.18 MHz and the corresponding velocity error is 1.11 m/s. The wind profiles measured by the DWL are in good agreement with the results of the wind profile radar （WPR）. Evaluation is achieved by comparing at altitudes from 2 to 8 km. The relative error of horizontal wind speed is from 0.8 to 1.8 m/s in the compared ranges. The wind accuracy is less than 6 m/s at 40 km and 3 m/s at 10 km.

关键词： Boundary layer flow Etalons

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Peristaltic Flow of Couple Stress Fluid in a Non-Uniform Rectangular Duct Having Compliant Walls

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Communications in Theoretical Physics 2016年第1期65卷 66-72页

作者： R.Ellahi M.Mubashir Bhatti C.Fetecau K.Vafai department of Mechanical Engineering University of California Riverside Riverside USA department of Mathematics and Statistics FBAS IIUI Islamabad Pakistan Shanghai Institute of Applied Mathematics and mechanics Shanghai University Shanghai 200444 China department of Mathematics Technical University of Iasi Romania Academy of Romanian Scientists 050094 Bucuresti Romania

The present study investigates the peristaltic flow of couple stress fluid in a non-uniform rectangular duct with compliant *** modeling is based upon the laws of mass and linear *** solutions are carried out by the eigen function expansion method under long-wavelength and low-Reynolds number *** features of the flow characteristics are analyzed by plotting the graphs of various values of physical parameters of *** bolus scheme is also presented through streamlines.

关键词： peristaltic flow couple stress fluid compliant walls eigen function expansion method analyticalsolutions

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ORDER REDUCED METHODS FOR QUAD-CURL EQUATIONS WITH NAVIER TYPE BOUNDARY CONDITIONS

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Journal of Computational Mathematics 2020年第4期38卷 565-579页

作者： Weifeng Zhang Shuo Zhang department of Engineering mechanics and department of Applied Mathematics Kunming University of Science and TechnologyKunming 650500China Shuo Zhang LSEC Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and System SciencesChinese Academy of SciencesBeijing 100190China

Quad-curl equations with Navier type boundary conditions are studied in this *** order reduced formulations equivalent to the model problems are presented,and finite element discretizations are *** convergence rates a... 详细信息

关键词： Quad-curl equation Order reduced scheme Regularity analysis Finite element method

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