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Thermoelastic analysis of multiple defects with the extended finite element method

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Acta Mechanica Sinica 2016年第6期32卷 1123-1137页

作者： Honggang Jia Yufeng nie School of Mathematics and Statistics Xuchang University School of Science Northwestern Polytechnical University

In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a single macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or microscopic defects under thermal/mechanical load. The effects of different shapes of multiple inclusions on the material thermomechanical response are investigated, and the level set method is coupled with XFEM to analyze the interaction of multiple defects. Further, the discretized extended finite element approximations in relation to thermoelastic problems of multiple defects under displacement or temperature field are given. Also, the interfaces of cracks or materials are represented by level set functions, which allow the mesh assignment not to conform to crack or material interfaces. Moreover, stress intensity factors of cracks are obtained by the interaction integral method or the M-integral method, and the stress/strain/stiffness fields are simulated in the case of multiple cracks or multiple inclusions. Finally, some numerical examples are provided to demonstrate the accuracy of our proposed method.

关键词： Multiple defects Stress intensity factors extended finite element method (XFEM) Thermoelastic

On the improvement of the mutual coupling compensation in DOA estimation

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Journal of Systems Engineering and Electronics 2008年第1期19卷 1-6页

作者： Wu Yujiang nie Zaiping Univ. of Electronic Science and Technology Chengdu 610054 P. R. China Tongyu Comm. Equipment Co. Ltd. Zhangshan 528437 P.R.China

A new and exact calculation method for the mutual impedance matrix of receiving arrays is proposed. The mutual impedance matrix is derived from electromagnetic boundary conditions and can be used to relate the coupling free open-circuit voltages, instead of the conventional ones, to the measured voltages. A remarkable improvement on compensation for the coupling effects is shown in the direction finding applications, while a simple relationship between measured terminal voltages and the coupling free voltages is remained.

关键词： mutual coupling reaction concept mutual impedance receiving array

On the MIMO channel capacity saturation for spatially constrained receive region

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Journal of Systems Engineering and Electronics 2007年第3期18卷 437-442页

作者： Wu Yujiang nie Zaiping School of Electronic Engineering Univ. of Electronic Science and Technology Chengdu 610054 P. R. China

In MIMO wireless communication systems, when more and more antennas are packed into spatiallylimited receive region, the antenna saturation phenomenon will appear. Moreover, the electromagnetic interactions among antennas will also become stronger and stronger and affect the antenna saturation effect considerably. Despite this, few studies consider these two effects jointly. The effects of antenna saturation are investigated under the consideration of mutual coupling, thus a more practical and physically meaningful result can be obtained.

关键词： MIMO systems capacity saturation mutual coupling spatially constrained array.

Analysis of wire antennas mounted on large perfectly conducting platforms using MLFMA

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Journal of Systems Engineering and Electronics 2007年第4期18卷 679-684页

作者： Que Xiaofeng nie Zaiping School of Electronic Engineering University of Electronic Science and Technology of China Chengdu 610054 P. R. China

The electric field integral equation (EFIE) combined with the multilevel fast multipole algorithm (MLFMA) is applied to analyze the radiation and impedance properties of wire antennas mounted on complex conducting platforms to realize fast, accurate solutions. Wire, surface and junction basis functions are used to model the current distribution on the object. Application of MLFMA reduces memory requirement and computing time compared to conventional methods, such as method of moment (MOM), especially for the antenna on a large-sized platform. Generalized minimal residual (GMRES) solver with incomplete LU factorization preconditioner using a dual dropping strategy (ILUT) is applied to reduce the iterative number. Several typical numerical examples are presented to validate this algorithm and show the accuracy and computational efficiency.

关键词： wire antennas platform MOM MLFMA GMRES ILUT.

A fluctuating lattice-Boltzmann model for direct numerical simulation of particle Brownian motion

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Particuology 2009年第6期7卷 501-506页

作者： Deming nie Jianzhong Lin State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China China Jiiiang University Hangzhou 310018 China

A single-relaxation-time fluctuating lattice-Boltzmann （LB） model for direct numerical simulation （DNS） of particle Brownian motion is established by adding a fluctuating component to the lattice-Boltzmann equations （LBEs）. The fluctuating term is proved to be the random stress tensor in fluctuating hydrodynamics by recovering Navier-Stokes equations from LBEs through a Chapman-Enskog expansion. A three-dimensional implementation of the model is also presented, along with simulations of a single spherical particle and 125 spherical particles at short times. Numerical results including the meansquare displacement, velocity autocorrelation function and self-diffusion coefficient of particles compare favorably with theoretical results and previous numerical results.

关键词： Fluctuating hydrodynamics Lattice-goltzmann method Brownian motion Direct numerical simulation

Improved pruning algorithm for Gaussian mixture probability hypothesis density filter

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Journal of Systems Engineering and Electronics 2018年第2期29卷 229-235页

作者： nie Yongfang ZHANG Tao Department of Automation Tsinghua University Department of Strategic Missile and Underwater Weapon Naval Submarine Academy

With the increment of the number of Gaussian components, the computation cost increases in the Gaussian mixture probability hypothesis density(GM-PHD) filter. Based on the theory of Chen et al, we propose an improved pruning algorithm for the GM-PHD filter, which utilizes not only the Gaussian components’ means and covariance, but their weights as a new criterion to improve the estimate accuracy of the conventional pruning algorithm for tracking very closely proximity targets. Moreover, it solves the end-less while-loop problem without the need of a second merging step. Simulation results show that this improved algorithm is easier to implement and more robust than the formal ones.

关键词： Gaussian mixture probability hypothesis density(GM-PHD) filter pruning algorithm proximity targets clutter rate

Analytical model for ultimate loading capacities of continuous composite slabs with profiled steel sheets

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Science China(Technological Sciences) 2015年第11期58卷 1956-1962页

作者： WANG YuHang nie JianGuo School of Civil Engineering Chongqing University Department of Civil Engineering Tsinghua University

Composite slabs with profiled steel sheet are widely applied in practical structures now. Plenty of literatures can be available about simply supported composite slabs with single span. However, continuous slabs always exist in high-rise building structures. In order to obtain the ultimate loading capacity of continuous composite slabs, the full scale test on slab specimens with high cost need to be carried out. This paper presented an analytical model for calculating the ultimate loading capacity of continuous composite slabs. Only the small-scale slide block test needed to be carried out for determining some mechanical parameters, resulting in less cost, compared with the conventional m-k test method. Various load conditions and parameters were considered in the analytical model. The comparison between test results and predicted results showed that the proposed method had enough precision. Furthermore, the simplified method was also proposed for practical design.

关键词： continuous composite slab profiled steel sheet loading capacity iterative solution

Analysis Approach to Durability Based on Material Initial Fatigue Quality and S-N Curve

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Chinese Journal of Aeronautics 2007年第6期20卷 518-523页

作者： Yang Moucuna nie Hong College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality （MIFQ） is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.

关键词： probabilistic fracture mechanics approach durability S-N curve crack propagation rate initial fatigue quality

Blaschke Isoparametric Hypersurfaces in the Conformal Space Q_1^(n+1),Ⅰ

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Acta Mathematica Sinica,English Series 2015年第11期31卷 1751-1758页

作者： Chang Xiong nie Faculty of Mathematics and Statistics Hubei University

Let x ：M - Qn＋l be a regular hypersurface in the conformal space Qn＋I. We classify all the space-like Blaschke isoparametric hypersurfaces with two distinct Blaschke eigenvalues in the conformal space up to the con... 详细信息

关键词： Regular hypersurfaces conformal invariants Blaschke isoparametric Lorentzian spaceforms