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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

Scaling parameters selection principle for the scaled unscented Kalman filter

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Journal of Systems Engineering and Electronics 2018年第3期29卷 601-610页

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

The paper deals with the state estimation of the widely used scaled unscented Kalman filter（UKF）. In particular, the stress is laid on the scaling parameters selection principle for the scaled UKF. Several problems caused by recommended constant scaling parameters are highlighted. On the basis of the analyses, an effective scaled UKF is proposed with self-adaptive scaling parameters,which is easy to understand and implement in engineering. Two typical strong nonlinear examples are given and their simulation results show the effectiveness of the proposed principle and algorithm.

关键词： nonlinear filtering scaled unscented Kalman filter scaling parameter selection principle

CLOSED-FORM SOLUTIONS FOR ELASTOPLASTIC PURE BENDING OF A CURVED BEAM WITH MATERIAL INHOMOGENEITY

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Acta Mechanica Solida Sinica 2014年第1期27卷 54-64页

作者： Guojuan nie Zheng Zhong School of Aerospace Engineering and Applied Mechanics Tongji University

The elastoplastic pure bending problem of a curved beam with material inhomo- geneity is investigated based on Tresca＇s yield criterion and its associated flow rule. Suppose that the material is elastically isotropic, ideally elastic-plastic and its elastic modulus and yield limit vary radially according to exponential functions. Closed-form solutions to the stresses and radial displacement in both purely elastic stress state and partially plastic stress state are presented. Numerical examples reveal the distinct characteristics of elastoplastic bending of a curved beam composed of inhomogeneous materials. Due to the inhomogeneity of materials, the bearing capac- ity of the curved beam can be improved greatly and the initial yield mode can also be dominated. Closed-form solutions presented here can serve as benchmark results for evaluating numerical solutions.

关键词： elastoplastic pure bending curved beam inhomogeneous materials closed-form solutions

Method of reverberation ray matrix for static analysis of planar framed structures composed of anisotropic Timoshenko beam members

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Applied Mathematics and Mechanics(English Edition) 2015年第2期36卷 233-242页

作者： Jiao ZHANG Guohua nie School of Aerospace Engineering and Applied Mechanics Tongji University

Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such *** the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.

关键词： planar framed structure anisotropic Timenshenko(T) beam stiffness matrix method of reverberation ray matrix(MRRM) static analysis