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Formation and migration of space charge packet in low density polyethylene

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Science china(Technological Sciences) 2005年第3期48卷 354-360页

作者： ZHENG Feihu 1 , ZHANG Yewen 1 , GONG Bin 1 , ZHU Jianwei 1 & WU Changshun 2.1. Pohl Institute of Solid State Physics, tongji university,{2. 2. {2. National Center for Quality Supervision and Test of Electric Ware and Cable, shanghai 2.0093, {2. Pohl Institute of Solid State Physics Tongji University Shanghai China china National Center for Quality Supervision and Test of Electric Ware and Cable Shanghai China

Pressure wave propagation (PWP) method was utilized to observe the space charges packet-like behavior in sheet samples of low-density polyethylene (LDPE) under the relative low electric field. The experimental results show that space charge packets are always generated at the anode and move across the sample to the cathode regardless of the polarity of DC voltage. This paper discusses the migration of space charge packets at 30–40°C, the possible charge resource of space charge packets carriers and trap level of the space charge.

关键词： solid dielectric,low-density polyethylene,space charge packet,trap.

Homogenization-based multi-scale damage theory

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 690-698页

作者： LI Jie 1,2.& REN XiaoDan 1 1 School of Civil Engineering, tongji university,{2. 2.State Key Laboratory of Disaster Reduction in Civil Engineering,{2. School of Civil Engineering Tongji University Shanghai China State Key Laboratory of Disaster Reduction in Civil Engineering Shanghai China

The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonlinear structural analysis. Starting from the asymptotic expansion based homogenization theory, the multi-scale energy integration is proposed to bridge the gap between the micro and macro scales. By recalling the Helmholtz free energy based damage definition, the damage variable is represented by the multi-scale energy integration. Hence the damage evolution could be numerically simulated on the basis of the unit cell analysis rather than the experimental data identification. Finally the framework of the multi-scale damage theory is established by transforming the multi-scale damage evolution into the conventional continuum damage mechanics. The agree- ment between the simulated results and the benchmark results indicates the validity and effectiveness of the proposed theory.

关键词： Multi-scale damage representation asymptotic method constitutive model numerical simulation

Flexural and Impact Resistance of FRC/Bamboo Laminate

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Journal of Materials Science & Technology 2002年第4期18卷 369-371页

作者： Wu YAOState Key Laboratory of Concrete Materials Research, tongji university, shanghai 2.0092. china Lab. of Concrete Mat. Res. Tongji Univ. Shanghai 200092 China

The flexural and impact resistance of a newly developed FRC/bamboo laminate have been investigated. The laminate considered in this study was combined with reformed bamboo plate and extruded fiber reinforced cementitious (FRC) sheet. Innovated from the raw bamboo, reformed bamboo showed high tensile strength and high strength to weight ratio. It can not only remarkably strengthen the FRC sheet but also reduce the total weight of the laminate. Flexural and impact load, broken energy, deflection and duration were measured. Test results showed that the flexural strength value for the laminate can be improved to greater than 90 MPa, while the impact resistance is increased more than 10 times for the laminate when compared with the FRC sheet only.

关键词： Flexural strength Impact FRC/bamboo composite

Dependence of binaural loudness summation on interaural level difference and frequency for pure tones

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Science china(Physics,Mechanics & Astronomy) 2010年第5期53卷 834-841页

作者： ZHANG Jie & MAO DongXing Institute of Acoustics,tongji university,{{2. 2.0092.china Institute of Acoustics Tongji University Shanghai China

Most of the existing loudness models are based on the diotic listening hypothesis,though human beings always hear in dichotic listening *** this situation,the arithmetic mean of loudness at both ears is usually taken as the approximate value of overall perceived loudness,unaffected by the interaural level difference(ILD).The present work investigated the overall perceived loudness for pure tones in dichotic listening conditions through a subjective *** experimental procedures and systematic errors were investigated to prove the accuracy of the subjective *** results showed that fluctuation was insignificant in the low frequency range,while apparent fluctuation of overall loudness could be observed at a high *** overall loudness deviated from the arithmetic mean value as the ILD became larger.A revised model for overall loudness in dichotic listening conditions was *** proposed model and experiment are consistent.

关键词： dichotic listening subjective experiment interaural level difference overall perceived loudness loudness model

Schwarz-Pick estimates for positive real part holomorphic functions on unit ball and polydisc

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Science china Mathematics 2010年第4期53卷 1017-1024页

作者： LIU Yang 1,& CHEN ZhiHua 2.1 Department of Mathematics,Zhejiang Normal university,Jinhua 32.004,china 2.Department of Mathematics,{2. university,shanghai 2.0092.china Department of Mathematics Zhejiang Normal University Jinhua China Department of Mathematics Tongji University Shanghai China

We give higher order derivatives Schwarz-Pick estimates for all positive real part holomorphic functions on Bn and D n,and generalize early work on Schwarz-Pick estimate of higher order derivatives for holomorphic fun... 详细信息

关键词： Schwarz-Pick estimate holomorphic function Taylor expansion

p-th moment exponential stability of stochastic differential equations with impulse effect

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Science china(Information Sciences) 2011年第8期54卷 1702-1711页

作者： SHEN LiJuan 1,2.& SUN JiTao 11 Department of Mathematics, tongji university,{2. {2.china 2.Department of Mathematics,Luoyang Normal university, Luoyang 47102.,china Department of Mathematics Tongji University Shanghai China Department of Mathematics Luoyang Normal University Luoyang China

The p-th moment exponential stability of stochastic differential equations with impulse effect is *** employing the method of vector Lyapunov functions,some sufficient conditions for the p-th moment exponential stability are *** addition,the usual restriction of the growth rate of Lyapunov function is replaced by the condition of the drift and diffusion coefficients to study the p-th moment exponential *** examples are also discussed to illustrate the effectiremess of the results obtained.

关键词： stochastic differential equations impulse p-th moment exponential stability vector Lyapunov functions

Fredholm operators in Toeplitz algebras associated with discrete abelian groups

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Chinese Science Bulletin 1998年第14期43卷 1175-1179页

作者： XU Qingxiang 1 and CHEN Xiaoman 2.1. Department of Mathematics, shanghai Normal {2., shanghai 2.02.4, china 2. Laboratory of Mathematics for Nonlinear Sciences and Institute of Mathematics, Fudan {2., shanghai 2.0433, china Department of Mathematics Shanghai Normal University Shanghai China Laboratory of Mathematics for Nonlinear Sciences and Institute of Mathematics Fudan University Shanghai China

The locally finite below sets are introduced and the Fredholm operators in Toeplitz algebras associated with discrete abelian groups are studied.

关键词： discrete abelian group quasi_ordered group Toeplitz operator Fredholm operator.

Study on the bulk wave radiation of finite-length SAW devices using FEM/BEM

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Progress in Natural Science:Materials International 2005年第5期15卷 402-406页

作者： WANG Weibiao1*, ZHANG Xiaodong1, SHUI Yongan1, ZHANG De1 and HAN Tao2.1. State Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing university, Nanjing 2.0093, china 2. {2. Jiaotong university, {2. 2.0030, china) State Key Lab. of Modern Acoustics Inst. of Acoustics Nanjing Univ. Nanjing 210093 China shanghai Jiaotong Univ. Shanghai 200030 China

Based on the distributions of stress and free charge on the interface of the surface acoustic wave (SAW) device calculated with the combination of boundary element method and finite element method(FEM/BEM), the power of each of the three possible bulk waves radiated by the SAW device is calculated, and their contributions to the overall input conductance are separated respectively. Moreover, the formula of angular distributions of their power radiation into the substrate is derived. Consider the effect of mass loading, the resistance density,defined as a scalar, is extended to generalized resistance densities which can be written as three 4×4 tensors and for which the formulas are derived. The bulk wave radiations for a synchronous one-port resonator on 42.Y-rotated LiTaO 3 are simulated. It is found that the radiated energy by slow shear wave contributes a very high proportion to input electrical energy in some frequency range.

关键词： SAW device bulk wave radiation FEM/BEM.

A multi-layer model for early diagenesis

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Chinese Science Bulletin 1997年第16期42卷 1385-1387页

作者： MEI HongmingDepartment of Marine Geology, tongji university, shanghai 2.0092. china Department of Marine Geology Tongji University Shanghai China

EARLY diagenesis is defined here as a series of physical, chemical and biological reactions operating between depositional particles, porewaters and environmental water medium in the processes of deposition and shallow burial. Early diagenesis can produce geochemical succession within deposits, which can be divided from top to bottom into oxidation zone (OX), sulphate reduction zone (SR) and methanogenesis zone (ME). Part of the reaction

关键词： early diagenesis biogeochemical zone multi-layer model.