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Electroabsorption spectrum of substituted polyphenylacetylenes

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Chinese Science Bulletin 1998年第14期43卷 1215-1219页

作者： CHENG Xiaoman department of Optoelectronic Information engineering, Tianjin institute of technology, Tianjin 300191, china department of Optoelectronic Information engineering Tianjin Institute of Technology Tianjin China

Electroabsorption (EA) measurements on thin films of poly[ o (trimethylsilyl) phenylacetylene] and poly[ o (trimethylsilylmethyl) phenylacetylene] have been performed. The spectral change induced by an exernal electric field (EA spectra) has been observed, which shows the similar shape of the second derivative of the optical absorption spectra. The change in the absorption Δ α is obtained from the EA spectrum, and Δ n is calculated through Kramers_Krong transformation. The optical properties of substituted polyphenylacetylenes (PPAs) were discussed.

关键词： substituted polyphenylacetylenes electroabsorption spectrum optical nonlinearities

Analysis on ignition and extinction of n-heptane in homogeneous systems

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Science china.Technological Sciences) 2005年第5期48卷 556-569页

作者： LIU Yongfeng1 & PEI Pucheng2 1. Mechanical and Electrical engineering department, Beijing institute of civil engineering and Architec-ture, Beijing 100044, china.2. State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, china 1. Mechanical and Electrical engineering department Beijing Institute of Civil Engineering and Architecture 100044 Beijing China 2. State Key Laboratory of Automotive Safety and Energy Tsinghua University 100084 Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

Wave-current forces on bipiles in parallel array

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Acta Oceanologica Sinica 1992年第3期11卷 453-462页

作者： Li Yucheng, Wang Fenglong and Wang Hongrong department of civil engineering, Dalian University of technology, Dalian 116024, china

-The inline and lift forces on bipiles in parallel array induced by both irregular waves and currents were investigated experimentally in this paper. The characteristics in both time and frequency domains of inline, lift and resultant forces as well were analyzed. The grouping effect coefficients of inline and resultant forces on two piles related to KC number and relative spacing parameters are given. A comparison of the magnitude and direction of resultant forces on two piles in parallel array with the corresponding values for single cylinder is also made.

关键词： Wave-current forces on bipiles in parallel array

Irregular　wave－induced　seepage　action　on　cylinders　resting　on　rubble　mound　foundation

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Acta Oceanologica Sinica 1996年第3期15卷 377-396页

作者： Qiu Dahong and Yang Gang (department of civil engineering.Dalian University of technology, Dalian 116023, china. department of civil engineering Dalian University of Technology Dalian 116023 China

In this paper, the irregular wave-induced seepage action on cylinders resting on rubble mound foundatoin (RMF) is studied by means of finite element method (FEM). The hydraulic resistance inside RMF is assumed to satisfy the nonlinear Forchheimer's equation and the seepage in the scabed is also considered. Model tests show good agreementwith the numerical results. The influence of several main parameters is discussed on the basis of vast calculations. In addition, the ratio of seepage forces, induced by regular and irregular waves respectively, is analyzed and thus a computaional method is put forward for practical engineering application to simplify the calculation of irregular wave-induced seepage forces.

关键词： Wave-induced seepage forces irregular wave rubble mound foundation

COMPUTATION OF FREE SURFACE FLOWS WITH HIGH RESOLUTION FINITE ELEMENT SCHEME

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Journal of Hydrodynamics 2003年第3期15卷 22-27页

作者： Jin Sheng, Zhang Ri-xiang, Pu Gao-jun department of civil engineering, State Key Laboratory of Offshore engineering, Dalian University of technology, Dalian 116024, china. departmentofcivilengineering StateKeyLaboratoryofOffshoreEngineeringDalianUniversityofTechnologyDalian116024China

A high-resolution finite element scheme is developed for the computation offree surface problems. The present higher-order accuracy scheme is obtained through the introductionof the difference of almost equal amount of diffusion and antidiffusion, where the antidiffusion isformulated as approximation to diffusion making use of consecutive gradient. The non-oscillatoryproperties are secured by limiters to preserve positivity constraints. The implement of the schemeis based on semi-discrete form and can be considered as reconstruction of the coefficient matrix ofalgebraic system, so, it can he conveniently used by either structured or unstructured meshes. Thepower and flexibility of the present high resolution VOF-FEM approach is validated by examplesincluding convective transport, dam breaking flow, and stilling basin flow in hydraulic engineering.

关键词： free surface flow high resolution finite element scheme

Bitstream decoding and SEU-induced failure analysis in SRAM-based FPGAs

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Science china.Information Sciences) 2012年第4期55卷 971-982页

作者： WANG ZhongMing 1,2,YAO ZhiBin 2,GUO HongXia 2 & LV Min 1 1 department of engineering Physics,Tsinghua University,Beijing 100084,china.2 Northwest institute of Nuclear technology,Xi'an 710024,china 1. department of engineering Physics Tsinghua University Beijing 100084 China2. Northwest Institute of Nuclear Technology Xi’an 710024 China

Reconfigurable SRAM-based FPGAs are highly susceptible to radiation induced single-event upsets (SEUs) in space *** bit flip in FPGAs configuration memory may alter user circuit permanently without proper bitstream reparation,which is a completely different phenomenon from upsets in traditional memory *** is important to find the relationship between a programmable resource and corresponding control bit in order to understand the impact of this *** this paper,a method is proposed to decode the bitstream of FPGAs from Xilinx Corporation,and then an analysis program is developed to parse the netlist of a specific design to get the configuration state of occupied programmable logic and *** that,an SEU propagation rule is established according to the resource type to identify critical logic nodes and paths,which could destroy the circuit topological *** decoded relationship is stored in a *** database is queried to get the sensitive bits of a specific *** result can be used to represent the vulnerability of the system and predict the on orbit system failure *** analysis tool was validated through fault injection and accelerator irradiation experiment.

关键词： radiation effect single-event effect single-event upset SRAM-based FPGA fault injection

A new elliptic-parabolic yield surface model revised by an adaptive criterion for granular soils

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Science china.Technological Sciences) 2010年第8期53卷 2152-2159页

作者： LIU HanLong 1,2 ,XIAO Yang 1,2 ,LIU JinYuan 3 &LI GuoYing 4 1 Key Laboratory of Ministry of Education for Geomechanics and Embankment engineering,Hohai University, Nanjing 210098,china.2 Geotechnical Research institute,Hohai University,Nanjing 210098,china.3department of civil engineering,Ryerson University,Toronto,Canada 4 department of Geotechnical engineering,Nanjing Hydraulic Research institute,Nanjing 210014,china 1. Key Laboratory of Ministry of Education for Geomechanics and Embankment engineering Hohai University Nanjing 210098 China2. Geotechnical Research Institute Hohai University Nanjing 210098 China3. Department of Civil Engineering Ryerson University Toronto Canada4. Department of Geotechnical Engineering Nanjing Hydraulic Research Institute Nanjing 210014 China

An adaptive criterion for shear yielding as well as shear failure of soils is proposed in this paper to address the fact that most criteria,including the Mohr-Coulomb criterion,the Lade criterion and the Matsuoka-Nakai criterion,cannot agree well with the experimental results when the value of the intermediate principal stress parameter is too *** new criterion can adjust an adaptive parameter based on the experimental results in order to make the theoretical calculations fit the test results more *** original elliptic-parabolic yield surface model can capture both soil contraction and dilation ***,it normally over-predicts the soil strength due to its application of the Extended Mises criterion.A new elliptic-parabolic yield surface mode is presented in this paper,which introduces the adaptive criterion in three-dimensional principal stress *** new model can well model the stress-strain behavior of soils under general stress *** to the original model which can only simulate soil behavior under triaxial compression conditions,the new model can simulate soil behaviors under both triaxial compression conditions and general stress conditions.

关键词： principal stress space intermediate principal stress yield surface failure criterion constitutive model

The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

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Science china.Technological Sciences) 2009年第1期52卷 72-78页

作者： WANG Bo1, WANG RongXiu2 & WU Yong1 1 School of Mathematic Science, Chongqing institute of technology, Chongqing 400050, china.2.department of Computer Science and Information engineering, Chongqing technology and Business University, Chongqing 400067, china School of Mathematic Science Chongqing Institute of Technology Chongqing 400050 China department of Computer Science and Information engineering Chongqing Technology and Business University Chongqing 400067 China

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be acceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforcement.

关键词： short-fiber reinforcement Young’s modulus finite element Gaussian distribution

A complex variable meshless method for fracture problems

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Science china.Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1 & LI Jiuhong2 1. Shanghai institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, china.2. department of Building engineering, Xi’an University of technology, Xi’an 710048, china Shanghai institute of Applied Mathematics Mechanics Shanghai University Shanghai 200072 China department of Building engineering Xi’an University of Technology Xi’an 710048 China

Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.