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Journal of Computational Mathematics 2006年第3期24卷 265-280页

作者： qiang du Liyong Zhu Department of Mathematics Pennsylvania State University University Park PA 16802 USA ICMSEC Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100080 China ICMSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

In this paper, we study numerical approximations of a recently proposed phase field model for the vesicle membrane deformation governed by the variation of the elastic bending energy. To overcome the challenges of high order nonlinear differential systems and the nonlinear constraints associated with the problem, we present the phase field bending elasticity model in a nested saddle point formulation. A mixed finite element method is then employed to compute the equilibrium configuration of a vesicle membrane with prescribed volume and surface area. Coupling the approximation results for a related linearized problem and the general theory of Brezzi-Rappaz-Raviart, optimal order error estimates for the finite element approximations of the phase field model are obtained. Numerical results are provided to substantiate the derived estimates.

关键词： Bio-membrane Elastic bending energy Phase field Finite element Nestedmixed saddle point formulation Optimal error estimates.

Modeling of Fatigue Crack Growth Closure Considering the Integrative Effect of Cyclic Stress Ratio,Specimen Thickness and Poisson's Ratio

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Chinese Journal of Mechanical Engineering 2012年第4期25卷 816-825页

作者： LIU Jiantao du Pingan LIU Xiaobao du qiang College of Mechanical and Electronic Engineering University of Electronic Science and Technology of China Chengdu 611731 China

Key components of large structures in aeronautics industry are required to be made light and have long enough fatigue *** is of vital importance to estimate the fatigue life of these structures *** the FCG process is affected by various factors,no universal model exists due to the complexity of the *** of the existing models are obtained by fitting the experimental data and could hardly describe the integrative effect of most existing factors *** order to account for the integrative effect of specimen parameters,material property and loading conditions on FCG process,a new model named integrative influence factor model（IIF） is proposed based on the plasticity-induced crack closure *** to the predictions of crack opening ratio（γ） and effective stress intensity factor range ratio（U） with different material under various loading conditions,predictions of γ and U by the IIF model are completely identical to the theoretical results from the plane stress state to the plane strain state when Poisson＇s ratio equals 1/*** Poisson＇s ratio equals 0.3,predictions of γ and U by the IIF model are larger than the predictions by the existing model,and more close to the theoretical *** addition,it describes the influence of R ratios on γ and U effectively in the whole region from-1.0 to ***,several sets of test data of FCG rates in 5 kinds of aluminum alloys with various specimen thicknesses under different loading conditions are used to validate the IIF model,most of the test data are situated on the predicted curves or between the two curves that represent the specimen with different thicknesses under the same stress *** of the test data slightly departure from the predictions by the IIF model due to the surface roughness and errors in ***,based on the analysis of the physical rule of crack opening ratios,a relative thickness of specimen is defined to describe the influence of mate

关键词： fatigue crack growth crack opening stress cyclic stress ratio constraint factor Poisson's ratio stress intensity factor

Numerical investigation of disc heat transfer with a novel fin-like structure

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Science China(Technological Sciences) 2012年第4期55卷 1050-1056页

作者： du qiang ZHU Junqiang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China Graduate University of the Chinese Academy of Sciences Beijing 100190China Key Laboratory of Advanced Energy and Power(Institute of Engineering Thermophysics) Chinese Academy of SciencesBeijing 100190China

Rotary disc is a key part in aero engine, HPT rotor disc due to its highest thermal load as well as mechanical load, always suffers from thermal or mechanical failure. In this paper, the authors initiate a new kind of novel fin-like structure which is presented on both surfaces of the rotating disc. The presence of the fin-like structure acts like a turbulence & vortex generator and hence increases the heat transfer effectiveness between the cooler cavity flow and the higher temperature disc surface. This paper deals with a numerical investigation of the new kind of fin-like structure which is tending to be applied on the high pressure turbine rotor's rotating disc. Numerical results revealed that with this novel structure thermal load of the disc reduced noticeably ranging from 10℃ to 20℃. This can be explained by the vortex structure generated by the disturbance of the cavity's cooling flow, thus enhancing the convective heat transfer rates between the disc surface and the cavity flow.

关键词： novel fin-like structure convective heat transfer rates cavity flow

A Nonlocal Stokes Systemwith Volume Constraints

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Numerical Mathematics(Theory,Methods and Applications) 2022年第4期15卷 903-937页

作者： qiang du Zuoqiang Shi Department of Applied Physics and Applied Mathematics and Data Science InstituteColumbia UniversityNew YorkNY 10027USA Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China Yanqi Lake Beijing Institute of Mathematical Sciences and Applications Beijing 101408China

In this paper,we introduce a nonlocal model for linear steady Stokes system with physical no-slip boundary *** use the idea of volume constraint to enforce the no-slip boundary condition and prove that the nonlocal model is *** also show that and the solution of the nonlocal system converges to the solution of the original Stokes system as the nonlocality vanishes.

关键词： Nonlocal Stokes system nonlocal operators smoothed particle hydrodynamics incompressible flows well-posedness local limit

Adaptive waveform design based on Morlet wavelet for ultra-wideband MIMO radar

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Journal of Systems Engineering and Electronics 2016年第2期27卷 362-369页

作者： Chenhe Ji Yaoliang Song qiang du School of Electronic and Optical Engineering Nanjing University of Science and Technology

For the issue of deterioration in detection performance caused by dynamically changing environment in ultra-wideband（UWB） multiple input multiple output（MIMO） radar, this paper proposes a novel adaptive waveform design which is aimed to improve the ability of discriminating target and clutter from the radar scene. Firstly, a sequence of Morlet wavelet pulses with frequency hopping and pulse position modulation by Welch-Costas array is designed. Then a waveform optimization solution is proposed which is achieved by applying the minimization mutual-information（MI） strategy. After that, with subsequent iterations of the algorithm, simulation results demonstrate that the optimal waveform design method brings an improvement in the target detection ability in the presence of noise and clutter.

关键词： ultra-wideband(UWB) radar multiple input multiple output(MIMO) waveform design Morlet wavelet mutual information(MI)

Cross-linking density and aging constitutive model of HTPB coating under prestrain thermal accelerated aging

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Defence Technology（防务技术） 2020年第2期16卷 439-446页

作者： Yong-qiang du Jian Zheng Chao Xiong Shijiazhuang Campus Army Engineering UniversityShijiazhuang 050003China

In order to study the cross-linking density and aging constitutive relationship of HTPB coating during storage,the thermal accelerated aging tests at 0%,3%,6%and 9%prestrains were carried *** crosslinking density of HTPB coating at different aging stages were tested using low-field^1 H NMR and the variation of cross-linking density was *** aging model of cross-linking density considering the chemical aging and the physical stretching factors was *** uniaxial tensile tests were carried out on HTPB coating at different aging stages and the cross-linking density was introduced into Ogden hyperelastic constitutive model as a characterization parameter of correction *** with uniaxial tensile test results,a prestrain aging constitutive model of HTPB coating was *** results show that the cross-linking density of HTPB coating increases rapidly at first and then slowly with the increase of thermal accelerated aging time without *** prestrain conditions,the crosslinking density of HTPB coating decreases at the early stage,and increases rapidly at first and then slowly at the middle and late stages of thermal accelerated *** correlation coefficients of aging model of cross-linking density and aging constitutive model with test results are R>0.9500 and R>0.9900 respectively,which can be used to accurately describe the cross-linking density and aging constitutive relationship of HTPB coating under prestrain accelerated thermal aging conditions.

关键词： Prestrain thermal accelerated aging Low-field^1H NMR Cross-linking density Aging constitutive model

Heat Transfer and Aerodynamics of Complex Shroud Leakage Flows in a Low-Pressure Turbine

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Journal of Thermal Science 2013年第5期22卷 447-458页

作者： Wang Pei du qiang Yang Xiao Jie Zhu Jun qiang Institute of Engineering Thermophysics Chinese Academy of Sciences University of Chinese Academy of Sciences

A numerical investigation on over-shroud & inter-shroud leakage flow has been carried out to explore the underneath flow physics at the stage of shrouded Low Pressure(LP) *** with the No inter-Shroud gap's Leakage flow Model(NSLM) and With inter-Shroud gap's Leakage flow Model(WSLM),the aerodynamic characteristics and the heat transfer performance have been *** the aerodynamic point of view,it is concluded that due to the pressure difference between the rotor's passage and the over-shroud cavity,in the stream-wise direction,flow structure has been modified,and the inter-shroud leakage flow may even cause flow separation in the vicinity of the blade passage's *** the circumferential direction,separation flows appear over the rotor's shroud surface(upper platform of the shroud).Meanwhile,from the point of view of heat transfer,further provision on contour maps of the non-dimensional Nusselt number reveals that the reattachment of leakage flow would enhance the heat transfer rates and endanger the rotor's labyrinth fins over the ***,due to the limited amount of inter-shroud leakage flow(current computational model),temperature distribution variation along the blade surface(near the rotor's tip section) seems to have only minor insignificant *** the end of the paper,the author puts forward some recommendations for the purpose of future successful turbine design.

关键词： over-shroud leakage flow inter-shroud leakage flow shrouded LP turbine

On Ginzburg-Landau Vortices of Superconducting Thin Films

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Acta Mathematica Sinica,English Series 2006年第2期22卷 469-476页

作者： Shi Jin DING qiang du Department of Mathematics South China Normal University Department of Mathematics Penn State University

In this paper, we discuss the vortex structure of the superconducting thin films placed in a magnetic field. We show that the global minimizer of the functional modelling the superconducting thin films has a bounded number of vortices when the applied magnetic field hex 〈 Hc1 ＋ K log ｜ logε｜ where Hc1 is the lower critical field of the film obtained by Ding and du in SIAM J. Math. Anal., 2002. The locations of the vortices are also given.

关键词： Superconducting thin films Global minimizer Vortices Pinning mechanism

Merit functions for nonsmooth complementarity problems and related descent algorithm

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Applied Mathematics(A Journal of Chinese Universities) 2010年第1期25卷 78-84页

作者： du Shou-qiang GAO Yan School of Management University of Shanghai for Science and Technology Shanghai 200093 China College of Mathematics Qingdao University Qingdao 266071 China

Under some assumptions, the solution set of a nonlinear complementarity problem coincides with the set of local minima of the corresponding minimization problem. This paper uses a family of new merit functions to deal with nonlinear complementarity problem where the underlying function is assumed to be a continuous but not necessarily locally Lipschitzian map and gives a descent algorithm for solving the nonsmooth continuous complementarity problems. In addition, the global convergence of the derivative free descent algorithm is also proved.

关键词： Nonsmooth complementarity problem merit function nonsmooth continuous map descent algorithm.

Modeling of Solidification Microstructures Based on Fully Coupling of Macro-transport Phenomena with Cellular Automata

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Journal of Materials Science & Technology 2000年第6期16卷 568-572页

作者： qiang du DianZhong LI Yiyi LI Institute of Metal Research Chinese Academy of SciencesShenyang 110015China

This paper has attempted to simulate the microstructure formation based on fully coupling of temperature field, concentration field and velocity field with micro-kinetics. The authors presented a new way, which is the combination of FDM and cellular automata (CAFD) to visualize the microstructure formation of the thin complex superalloy turbine blades cast by the vacuum investment process. The distribution, orientation and mechanism of the heterogeneous nucleation, the growth kinetics of dendrites and the columnar to equiaxed transition (CET) are considered. Capitalizing on these simulating schemes, the comprehensive influence of key process variables on the scale and uniformity of grains has been investigated quantitatively. The simulated grain size and morphology agree well with the experimental results.

关键词： Microstructure