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The Coupled-mode Theory of Grating-assisted Parallel Optical Fiber Cores

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Chinese Journal of Lasers 2002年第1期11卷 52-57页

作者： ZHU Songlin ZHANG Xianmin CHEN Kangsheng (department of Information & Electronic engineering, zhejiang university, hangzhou 310027, china) department of Information & Electronic engineering Zhejiaiig University Hangzhou 310027

A new coupled-mode formulation is developed for grating-assisted parallel optical fiber cores. The theory is derived from the scalar wave equation by perturbation method. The diffraction caused by grating and coupler in the grating region are both considered. Based on the theory, various experimental phenomena in grating-assisted parallel optical fiber cores can be simulated accurately.

关键词： fiber grating coupled-mode directional coupler

Wake structures of two spheres in tandem arrangement at various gaps for Re=300

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Progress in Natural Science:Materials International 2005年第2期15卷 37-41页

作者： ZOU Jianfeng*, REN Anlu, DENG Jian and CHEN Wenqu(department of mechanics, zhejiang university, hangzhou 310027, china) Dept. of mechanics Zhejiang Univ. Hangzhou 310027 China

The virtual boundary method is extended to a 3D application and used to simulate the flow field of two spheres in tandem arrangement for a Reynolds number of 300. The wake structures and flow spectra at various gaps are investigated. The numerical results show that for small gaps (≈1.5), due to the mutual suppress between the wakes of the two spheres, the full flow field is stable and axisymmetric. As the gap is increased to 2.0, an asymmetric but stable flow is constructed through a certain bifurcation. The downstream wake structure is characterized by a double-thread vortex structure that comprises two slender parallel vortex tubes. The double-thread structure has a planar symmetry at gap 2.0. The hairpin-shape vortices are periodically shed from the downstream sphere at gap 2.5, but the planar symmetry persists. The vortex structures at gaps ranging from 3.0 to 4.0 are irregular and the flow field is undergoing a kind of 3D transition. It is up to the large gap 5.0 that the hairpin-shape structures are reconstructed behind the upstream and the downstream sphere, and the planar symmetry is resumed. All these numerical computations were performed on an SGI Origin3900 machine at the Center for engineering and Scientific Computation of zhejiang university.

关键词： virtual boundary method flow past two spheres wake structure flow spectra

STOCHASTIC PROPAGATION OF SEMI-ELLIPTICAL SURFACE CRACK

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Acta Mechanica Solida Sinica 1995年第3期8卷 236-244页

作者： Zhu Weiqiu Jiang Mingxiao (department of mechanics,zhejiang university,hangzhou,310027,P.R.china) department of mechanics Zhejiang University Hangzhou 310027 China

The semi-elliptical surface crack growth of structural components with uncertain material resistance under random loading is studied by using the stochastic averaging *** FPK equation governing the transition probability density function of crack lengths is *** analytical solution of the FPK equation for the case of that the equations for the crack growth in the surface and depth directions are uncoupled is *** effects of the parameters of the stress process and of the material property on the behavior of semi-elliptical fatigue crack growth of the components with deterministic resistance to crack growth in the stationary Gaussian stress process are *** comparison of the analytical result with digital simulation shows the effectiveness of the present method.

关键词： fatigue crack growth semi-elliptical surface crack fatigue life reliability stochastic averaging

NUMERICAL SIMULATION OF CAVITATION FLOW UNDER HIGH PRESSURE AND TEMPERATURE

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Journal of Hydrodynamics 2011年第3期23卷 289-294页

作者： ZHAO Wei-guo ZHANG Ling-xin SHAO Xue-ming department of mechanics Zhejiang University Hangzhou 310027 China State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

The numerical simulation of cavitation flow on a 2D NACA0015 hydrofoil under high pressure and temperature is performed. The Singhal＇s cavitation model is adopted combined with an improved RNG k-ε turbulence model to study the cavitation flow. The thermal effect in the cavitation flow is taken into account by introducing the energy equation with a source term based on the latent heat transfer. The code is validated by a case of a hydrofoil under two different temperatures in a comparison between the simulation and the experiment. Computational results show that the latent heat of vaporization has a significant impact on the cavitation process in the high temperature state, and the cavity in the high temperature state is thinner and shorter than that in a normal state with the same cavitation number, due to the fact that the heat absorption in the cavitation area reduces the local temperature and the saturated vapor pressure. This numerical study provides some guidance for the design of machineries in the High Pressure and Temperature （HPT） state.

关键词： cavitation NACA0015 thermodynamic CFD high pressure and temperature

RESEARCH ON ADAPTIVE DATA COMPRESSION METHOD FOR TRIANGULATED SURFACES

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Chinese Journal of Mechanical engineering 2004年第2期17卷 189-192页

作者： Wang Wen Wu Shixiong Chen Zichen department of Mechanical engineering,zhejiang university,hangzhou 310027, china department of Mechanical engineering Zhejiang University Hangzhou 310027

NC code or STL file can be generated directly from measuring data in a fastreverse-engineering mode. Compressing the massive data from laser scanner is the key of the newmode. An adaptive compression method based on triangulated-surfaces model is put ***-vector angles between triangles are computed to find prime vertices for removal. Ring datastructure is adopted to save massive data effectively. It allows the efficient retrieval of allneighboring vertices and triangles of a given vertices. To avoid long and thin triangles, a newre-triangulation approach based on normalized minimum-vertex-distance is proposed, in which thevertex distance and interior angle of triangle are considered. Results indicate that the compressionmethod has high efficiency and can get reliable precision. The method can be applied in fastreverse engineering to acquire an optimal subset of the original massive data.

关键词： Data compression Reverse engineering Triangulated surfaces

HYDROGEN IN Pd-In ALLOYS

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Acta Metallurgica Sinica(English Letters) 1996年第5期9卷 367-372页

作者： Y.L. Chen(department of Materials Science and engineering, zhejiang university, hangzhou 310027, china)

The equilibrium p-c-T data were determined by a microbalance in a vacuum system at hydrogen pressures up to 3.5 MPa on four Pd-In alloys between 3.64 and 14.53 at. % In as well as on Pure Pd. The results are similar to those obtained on the analogous alloys Pd-Ag and Pd-Sn and are interpreted in the same manner. In has two opposing effects upon the solubility of H in the Pd alloys, i.e., increase of the Fermi energy upon the donation of valence electrons and a lattice dilatation. At valence electron concentrations below 0.5, the lattice dilatation predominates and the H solubility is increased with addition of In. At valence electron concentrations above 0.5, the influence of the elevated Fermi energy predominates and the H solubility is lowered by addition of In. The molar enthalpy of Pd hydriding at infinite dilution is strongly increased with increasing In content, but the molar entropy is not nearly as much affected by the Presence of In. The excess chemical potential of hydrogen at small hydrogen concentrations and at a given temperature increases with an increase of In content. The apparent H-H attractive interaction energy, W H-H, is decreased by the presence of In. The trend is also similar to that found for the Pd-Ag-H and Pd-Sn-H system.

关键词： Pd-In alloy valence electron lattice dilatation Fermi energy

A NOVEL RESISTIVE HUMIDITY SENSOR BASED ON SODIUM POLYSTYRENESULFONATE/TiO_2 NANOCOMPOSITES

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Chinese Journal of Polymer Science 2002年第3期20卷 237-241页

作者： Yang Li Mu-jie Yang Yong She department of Polymer Science and engineering zhejiang university, hangzhou 310027 china department of Polymer Science and engineering Zhejiang University Hangzhou 310027

A resistive humidity sensor was prepared based on sodium polystyrenesulfonate (NaPSS)/TiO2 nanocomposites, and its electrical response to humidity was examined. The sensor exhibits better linearity, smaller hysteresis (< 4% RH) and quicker response (absorption: less than 2 s; desorption: less than 20 s) in comparison with sensor composed of NaPSS. The effect of concentration of NaPSS and TiO2 on humidity response of sensors was discussed.

关键词： humidity sensor nanocomposites TiO2 sodium polystyrenesulfonate

Surface effect on Bleustein-Gulyaev wave in a piezoelectric half-space

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Theoretical & Applied mechanics Letters 2011年第4期1卷 11-14页

作者： Weiqiu Chen a) department of engineering mechanics,zhejiang university,Yuquan Campus,hangzhou 310027,china department of engineering mechanics Zhejiang University Yuquan Campus Hangzhou 310027 China

Surface effect,which is attributed to the different environment surrounding the surface or near-surface atoms from that embracing the bulk atoms,may become significant when the surface-to-volume ratio of a body is *** paper considers the effect of a plane boundary of a piezoelectric body modeled as a thin layer with specified material properties,for which a transfer relation between the state vectors at the top and bottom surfaces is derived based on the state-space *** equations of surface piezoelectricity for different orders without any bias field are then presented by making use of the power series expression of the transfer *** surface effect is demonstrated by considering the Bleustein-Gulyaev wave existing in a horizontally polarized piezoceramic half-space.

关键词： surface piezoelectricity plane boundary state-space formalism Bleustein-Gulyaev wave

Stochastic stability of quasi-integrable Hamiltonian systems with time delay by using Lyapunov function method

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Science china(Technological Sciences) 2010年第3期53卷 703-712页

作者： LING Quan 1,JIN XiaoLing 1 &HUANG ZhiLong 2 1 department of mechanics,zhejiang university,hangzhou 310027,china 2 State Key Laboratory of Fluid Power Transmission and Control,zhejiang university,hangzhou 310027,china department of mechanics Zhejiang University Hangzhou China State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou China

The asymptotic Lyapunov stability of one quasi-integrable Hamiltonian system with time-delayed feedback control is studied by using Lyapunov functions and stochastic averaging ***,a quasi-integrable Hamiltonian system with time-delayed feedback control subjected to Gaussian white noise excitation is approximated by a quasi-integrable Hamiltonian system without time ***,stochastic averaging method for quasi-integrable Hamiltonian system is used to reduce the dimension of the original system,and after that the Lyapunov function of the averaged It equation is taken as the optimal linear combination of the corresponding independent first integrals in ***,the stability of the system is determined by using the largest eigenvalue of the linearized *** examples are used to illustrate the proposed procedure and the effects of delayed time on the Lyapunov stability are discussed as well.

关键词： Lyapunov stability Lyapunov function time delay stochastic averaging