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Guided wave propagation in multilayered piezoelectric structures

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 73.070, 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 China Key Laboratory of Soft Soils and Geoenvironmental engineering Ministry of Education and Department of Civil Engineering Zhejiang University Hangzhou China Department of engineering Mechanics Zhejiang University Hangzhou China school of civil engineering Lanzhou Jiaotong University Lanzhou 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

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Differences between laminar convections through parallel plain planes with uniform wall temperature and heat flux in terms of process parameter

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Science china(Technological Sciences) 2010年第3期53卷 789-799页

作者： WANG LiangBi,LIN ZhiMin,WU Xiang&SONG KeWei school of Mechatronic engineering,lanzhou jiaotong university,lanzhou 73.070,china school of Mechatronic engineering Lanzhou Jiaotong University Lanzhou China

Using the process parameter description,we analyzed the difference between the characteristics of laminar convections through parallel plain planes with uniform temperature and heat *** results show the following.(1)On the wall surface of the developing region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process although the velocity is zero;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a difussion process.(2)Inside the flow of the developing region,whether under uniform temperature or heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the contributions of velocity and velocity gradient are dependent on the thermal boundary condition.(3)On the wall surface of the fully developed region,under uniform heat flux boundary condition,the heat flux normal to the wall surface is transported through a convection process;the velocity gradient contributes to this transport,but under uniform temperature boundary condition,the heat flux normal to the wall surface is transported through a diffusion process.(4)Inside the flow of the fully developed region,under uniform temperature boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection process,and the velocity and velocity gradient contribute to these transports;under uniform heat flux boundary condition,the heat flux along the main flow direction and the heat flux normal to the wall surface are transported through a convection ***,the transport of the heat flux along the main flow direction is a no-net convection process;the velocity gradient contributes to the transport of the heat flux only in the normal direction o

关键词： mechanism of convective heat transfer description of process parameter parallel plain planes uniform wall temperature uniform wall heat flux laminar flow

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Preliminary study on interaction between plant frictional root and rock-soil mass

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Science china(Technological Sciences) 2010年第7期53卷 1938-1942页

作者： YAN ZhiXin1’2, SONG Yun3, JIANG Ping1’2 & WANG HouYu4 1 Key Laboratory of Mechanics on Disaster and Environment in Western china (lanzhou university), Ministry of Education, lanzhou 730000, china 2 school of civil engineering and Mechanics, lanzhou university, lanzhou 730000, china 3 College of civil engineering and Mechanics, Central South university of Forestry and Technology, Changsha 410004, china 4 Air Force engineering Design & Research Bureau, Beijing 100077, china Key Laboratory of Mechanics on Disaster and Environment in Western china (lanzhou university) Ministry of Education Lanzhou China school of civil engineering and Mechanics Lanzhou University Lanzhou China College of civil engineering and Mechanics Central South University of Forestry and Technology Changsha China Air Force engineering Design & Research Bureau Beijing China

The interaction between lateral root system of woody plant and soil mass is similar to the one between shrub, herbage and soil mass, and has the effect of frictional reinforcement on slope soil. It plays an important role in reinforcing soil strength in shallow slope. Therefore, slope soil mass can be considered as a composite of soil and plant roots and the soil strength and stability of shallow slope soil mass are improved. However, current researches still remain on the level of qualitatively analyzing the relation between root and soil mass. In this paper, some exploratory researches on quantitative analysis of the interaction mechanism between root and soil mass are conducted. With the study of interaction between herbage root system (lateral root system of woody plants) and soil mass, the mechanical model of interaction between frictional root and soil mass is established. The accuracy of the model is verified by field experiments of Pinus Yunnanensis. The mechanical model provides a crucial theoretical guidance to quantitatively analyzing the interaction between plant root and soil mass; it also has certain values in application.

关键词： plant slope protection vegetation for slope protection mechanical model frictional root

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A computer simulation of nucleation and growth of thin films

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Science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 442-451页

作者： ZHENG Xiaoping1,ZHANG Peifeng2,HE Deyan2,LIU Jun2& MA Jiantai3 1. Key Laboratory of Opto-Electronic Technology and Intelligent Control, Ministry of Education, lanzhou jiaotong university, lanzhou 73.070, china 2. school of Physical Science and Technology, lanzhou university, lanzhou 730000, china 3. school of Chemistry and Chemistry engineering, lanzhou university, lanzhou 730000, china Key Laboratory of Opto-Electronic Technology and Intelligent Control Ministry of Education Lanzhou Jiaotong University Lanzhou China school of Physical Science and Technology Lanzhou University Lanzhou China school of Chemistry and Chemistry engineering Lanzhou University Lanzhou China

A three-dimensional kinetic Monte Carlo technique has been developed for simulating the nucleation and growth of thin films. This model involves incident atom attachment, surface diffusion of the atoms on the growing surface and atom detachment from the growing surface. It takes some new effects into account, such as a significant improvement in calculation of activation energy for the atom diffusion, which renders the model more reasonable. In addition three optimum temperatures and the consistency of their dependence on deposition rate have been found out; the dependence of the surface roughness and relative density on the deposition rate has been discussed; and the approximation of freezing neighbour atoms and periodic boundary conditions has been applied.

关键词： Monte Carlo, thin film, nucleation, surface roughness, relative density.

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Improvements on voltage-resistant performance of bipolar static induction transistor (BSIT) with buried gate structure

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Science china(Information Sciences) 2012年第4期55卷 962-970页

作者： WANG YongShun,FENG JingJing,LIU ChunJuan,WANG ZiTing,WANG ZaiXing & ZHANG CaiZhen school of Electronic and Information engineering,lanzhou jiaotong university,lanzhou 73.070,china school of Electronic and Information engineering Lanzhou Jiaotong University Lanzhou China

The breakdown mechanism of power bipolar static induction transistor (BSIT) with buried gate structure is analyzed in depth.A power BSIT sample with high voltage-resistant capability has been designed and fabricated in this *** technological methods for improving high voltage performances are *** active region of BSIT is surrounded with a deep trench to avoid any probable influences of various defects on device *** field-limiting ring-shape junctions and one channel termination ring-shape junction are arranged around the gate region to reduce the electric field *** gate-source breakdown voltage BV GS of power BSIT has been increased to 110 V from previous value of 50-60 V,and its blocking voltage is increased to 1700 *** optimal geometrical dimensions for achieving the maximum breakdown voltage BV GS and blocking voltage V block are also represented in the paper.

关键词： bipolar static induction transistor voltage-resistant capability punch-through deep trench

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On time-step in structural seismic response analysis under ground displacement/acceleration

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Earthquake engineering and engineering Vibration 2009年第3期8卷 341-347页

作者： TianYuji~+ and Yang Qingshan~(++) school of civil engineering,Beijing jiaotong university,Beijing 100044,china +Associate Professor ++Professor school of civil engineering Beijing Jiaotong University Beijing China

There are two models in use today to analyze structural responses when subjected to earthquake ground motions, the Displacement Input Model （DIM） and the Acceleration Input Model （AIM）. The time steps used in direct integration methods for these models are analyzed to examine the suitability of DIM. Numerical results are presented and show that the time-step for DIM is about the same as for AIM, and achieves the same accuracy. This is contrary to previous research that reported that there are several sources of numerical errors associated with the direct application of earthquake displacement loading, and a very small time step is required to define the displacement record and to integrate the dynamic equilibrium equation. It is shown in this paper that DIM is as accurate and suitable as, if not more than, AIM for analyzing the response of a structure to uniformly distributed and spatially varying ground motions.

关键词： integration time step multi-supported structure displacement input model acceleration input model spatially varying ground motions

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Contact position controlling for two-dimensional motion bodies by the boundary element method

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Journal of university of Science and Technology Beijing 2002年第2期9卷 138-141页

作者： Junping Pu and Yuanfeng Wang school of civil engineering and Architecture, Northern jiaotong university, Beijing 100044, china Sch. of civil Eng. and Arch. Northern Jiaotong Univ. Beijing 100044 China

An algorithm is presented for controlling two-dimensional motion contact bodies with conforming discretization. Since a kind of special boundary element is utilized in the algorithm, the displacement compatibility and traction equilibrium conditions at nodes can be satisfied simultaneously in arbitrary locations of the contact interface. In addition, a method is also proposed in which the contact boundary location can be moved flexibly on the possible contact boundary. This method is effective to deal with moving and rolling contact problems on a possible larger moving or rolling contact region. Numerical examples show effectiveness of the presented scheme.

关键词： boundary element method contact move roll

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A new seismic isolation system and its feasibility study

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Earthquake engineering and engineering Vibration 2010年第1期9卷 75-82页

作者： Jia Gaofeng~+ and Shi Zhifei~(++) school of civil engineering,Beijing jiaotong university,Beijing 100044,china Graduated Student ++ Professor school of civil engineering Beijing Jiaotong University Beijing China

This paper introduces a new seismic isolation system called a periodic foundation （PF）, where inclusions are periodically arranged. The PF is different from traditional base isolation in that it causes a fundamental frequency shift in the structure, thus reducing its response and generating a frequency gap. If the frequency contents of a seismic wave fall into the gap, it can not propagate in the foundation. Thus, it will exert no influence on the structure above. A systematic study of the band of frequency gap for a 2D PF is conducted. The influence of physical and geometrical parameters such as density and elastic modulus as well as filling fraction of the PF and its materials on the band of frequency gap are investigated, and a design with a frequency gap as low as 2.49-3.72 Hz is achieved. This band of frequency gap corresponds well to the design spectra in earthquake engineering. Numerical simulations of a six-story frame structure with different foundations demonstrate that a proposed PF can greatly reduce the seismic response of an isolated structure. This investigation shows that PFs have great potential in future applications of seismic isolation technology.

关键词： seismic isolation periodic foundation band of frequency gap

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Multifield coupling model and its applications for pile foundation in permafrost

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Science china Earth Sciences 2005年第7期48卷 968-977页

作者： WU Yaping1,2, ZHU Yuanlin2, GUO Chunxiang1, SU Qiang1 & MA Wei2 1. school of civil engineering, lanzhou jiaotong university, lanzhou 73.070, china 2. State Key Laboratory of Frozen Soil engineering, Cold and Arid Regions Environmental and engineering Research Institute, Chinese Academy of Sciences, lanzhou 730000, china school of civil engineering Lanzhou Jiaotong University Lanzhou 730070 China State Key Laboratory of Frozen Soil engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

Importing the interface element which links the frozen soil base with concrete piles and considering the couplings of stress field, temperature field and moisture field, this paper es- tablishes the nonlinear visco-elastic plastic finite element model of pile-soil. For a practical bridge structure the stress field and displacement field of single pile in freezing process are calculated. This paper emphatically studies the process of the tangential frost heave stress field, freezing stress field and displacement field varying with time, and ulteriorly studies time variation process of single pile carrying capacity in freezing process.

关键词： permafrost pile foundation freezing process multifield coupling analysis model.

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Improvements on radiation-hardened performance of static induction transistor

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Science china(Information Sciences) 2010年第5期53卷 1089-1096页

作者： WANG YongShun 1 , LUO XianLiang 1 , LI HaiRong 2 , WANG ZiTing 1 , WU Rong 1 , ZHANG CaiZhen 2 & LI SiYuan 2 1 school of Electronic and Information engineering, lanzhou jiaotong university, lanzhou 73.070, china 2 Institute of Microelectronics, school of Physical Science and Technology, lanzhou university, lanzhou 730000, china school of Electronic and Information engineering Lanzhou Jiaotong University Lanzhou China Institute of Microelectronics School of Physical Science and Technology Lanzhou University Lanzhou China

The radiation-hardened performances of static induction transistor (SIT) have been studied in depth in this paper. The effects of radiation of electron beam on the I-V characteristics, carrier distribution and potential distribution in the channel of SIT have been represented. A large number of electron-hole pairs are generated in the depletion region of reversely biased gate-channel PN junction. The radiation-generated electrons drift towards the drain region at high positive potential, while generated holes flow into gate region biased to the lowest potential. With the accumulation of holes in gate region, the gate potential is boosted, resulting in a decrease in the height of potential barrier in channel, and an increase in drain current. I-V characteristics of SIT in the presence of radiation have been theoretically derived, and compared with experimental results. With the increase in thickness of epitaxial layer, the radiation-hardened capability of SIT is continuously improved until the optimum thickness of 26 μm is reached. The optimum matching relationship among geometric, material and technological parameters has been represented to acquire excellent radiation-hardened performances of SIT.

关键词： static induction transistor radiation-resistant potential barrier electron beam radiationgenerated carriers

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