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Research on dynamic characteristics of multi-sensor system in the case of cross-sensitivity

Science China(Technological Sciences) 2005年第1期48卷 1-22页

作者： tang Xiaojun liu Junhua School of Electrical Engineering Xi'an Jiaotong University Xi'an 710049 China School of Electrical Engineering Xi'an Jiaotong University Xi'an 710049 China

In this study, the dynamic characteristic of a multi-sensor system made up of such sensors as are sensitive to several parameters is discussed, and the effect of cross-sensitivity on the precision of a measurement system is also discussed. A multi-sensor system is looked as a serial of a linear filter and a memoryless nonlinear system, i.e. Wiener system, and the subsequent information fusion system is regarded as a Hammerstein system, i.e. a serial of a memoryless nonlinear system and a linear filter. On the basis of static calibration, it is presented to determine the inverse filter in a Hammerstein system using blind deconvolution. In order to control the uncertainty of amplitude of signals recovered by blind deconvolution well, a regulation approach to regulating the inverse linear filter coefficient matrixes is presented according to the identity between inverse filter coefficient matrixes and static calibrating matrix. So the approximate inverse dynamic model of multi-sensor system is obtained, the degree of distortion of dynamic measurement result is reduced, the measurement precision is improved, and the need of practice can be reached. Simulation example and simulation result show that the recovered error of the inputs of sensor system, the frequency of which is 1/10 of sampling frequency, is 1/20 of the measurement results without dynamic compensation, and is one half of the measurement results with sole dynamic compensation, and the rapidity is improved 2 times. The dynamic compensation results of a metal oxide semiconductor methane sensor show that the dynamic measurement error is less than one half of that without dynamic compensation. So this method expands the bandwidth of multi-sensor system.

关键词： dynamic compensation, multi-sensor system, cross-sensitivity, blind deconvolution.

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Relaxation Dynamics in Condensation on Weighted Scale-Free Networks

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Communications in Theoretical Physics 2008年第1期49卷 252-256页

作者： tang Ming liu Zong-Hua Institute of Theoretical Physics and Department of Physics East China Normal University Shanghai 200062 China

Most of the realistic networks are weighted scale-free networks. How this structure influences the condensation on it is a challenging problem. Recently, we make a first step to discuss its condensation [Phys. Rev. E 74 （2006） 036101] and here we focus on its evolutionary process of phase transition. In order to show how the weighted transport influences the dynamical properties, we study the relaxation dynamics in a zero range process on weighted scale-free networks. We find that there is a hierarchical relaxation dynamics in the evolution and there is a scaling relation between the relaxation time and the jumping exponent. The relaxation dynamics can be illustrated by a mean-field equation. The theoretical predictions are confirmed by our numerical simulations.

关键词： relaxation dynamics condensation scale-free networks

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RICHARDSON EXTRAPOLATION AND DEFECT CORRECTION OF FINITE ELEMENT METHODS FOR OPTIMAL CONTROL PROBLEMS

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Journal of Computational Mathematics 2010年第1期28卷 55-71页

作者： tang liu Ningning Yan Shuhua Zhang Research Center for Mathematics and Economics Tianjin University of Finance and Economics Tianjin 300222 China Institute of System Sciences Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing 100190 China

Asymptotic error expansions in H^1-norm for the bilinear finite element approximation to a class of optimal control problems are derived for rectangular meshes. With the rectan- gular meshes, the Richardson extrapolation of two different schemes and an interpolation defect correction can be applied. The higher order numerical approximations are used to generate a posteriori error estimators for the finite element approximation.

关键词： Optimal control problem Finite element methods Asymptotic error expansions Defect correction A posteriori error estimates.

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Adaptive Control of Accumulative Error for Nonlinear Chaotic Systems

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International Journal of Automation and computing 2014年第5期11卷 527-535页

作者： Fang-Fang Zhang Shu-tang liu Ke-Xin liu School of Electrical Engineering and Automation Qilu University of Technology College of Control Science and Engineering Shandong University

We present an adaptive control scheme of accumulative error to stabilize the unstable fixed point for chaotic systems which only satisfies local Lipschitz condition, and discuss how the convergence factor affects the convergence and the characteristics of the final control strength. We define a minimal local Lipschitz coefficient, which can enlarge the condition of chaos control. Compared with other adaptive methods, this control scheme is simple and easy to implement by integral circuits in practice. It is also robust against the effect of noise. These are illustrated with numerical examples.

关键词： Adaptive control accumulative error chaotic systems fixed point convergence Lipschitz coefficient

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Aerodynamic performance analysis of trains on slope topography under crosswinds

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Journal of Central South University 2016年第9期23卷 2419-2428页

作者： liu tang-hong Key Laboratory of Traffic Safety on Track of Ministry of Education (Central South University) Changsha 410075 China School of Traffic & Transportation Engineering Central South University Changsha 410075 China

This work used the computational fluid dynamics method combined with full-scale train tests to analyze the train aerodynamic performance on special slope topography. Results show that with the increment in the slope gradient, the aerodynamic forces and moment increase sharply. Compared with the flat ground condition, the lateral force, lift force, and overturning moment of the train on the first line increase by 153.2%, 53.4% and 124.7%, respectively, under the slope gradient of 20°. However, with the increment of the windward side's depth, the windbreak effect is improved obviously. When the depth is equal to 10 m, compared with the 0 m, the lateral force, lift force and overturning moment of the train on the first line decrease by 70.9%, 77.0% and 70.6%,respectively. Through analyzing the influence of slope parameters on the aerodynamic performance of the train, the relationships among them are established. All these will provide a basic reference for enhancing train aerodynamic performances under different slope conditions and achieve reasonable train speeds for the operation safety in different wind environments.

关键词： train wind slope topography aerodynamic performance

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Influence of isothermal bainitic processing on the mechanical properties and microstructure characterization of TRIP steel

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Journal of University of Science and Technology Beijing 2008年第5期15卷 574-579页

作者： Haitao Jiang Hubin Wu Di tang Qiang liu National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China

The mechanical properties of transformation induced plasticity （TRIP） steel are strongly affected by the conditions of iso-thermal bainitic processing. The multiphase microstructure of TRIP steel under different conditions of isothermal bainitic processing was investigated using OM,SEM,XRD and TEM. The volume fraction of retained austenite and the carbon content in austenite were determined quantitatively using X-ray diffraction patterns. The relationship between mechanical properties and isothermal bainitic processing parameters was investigated. The stability of retained austenite was analyzed by the volume fraction of retained austenite and the carbon content in retained austenite. The experimental results show that the multiphase microstructure consists of ferrite,bainite and metastable retained *** obtain good mechanical properties,the optimal conditions of isothermal bainitic temperature and holding time are 410-430°C and 180-240 s,respectively. After isothermal bainitic processing under the optimal conditions,the corresponding volume fraction of retained austenite is 5vol%-15vol%,which can provide enough retained austenite and plastic stability for austenite with high carbon content.

关键词： transformation induced plasticity steel isothermal bainitic processing mechanical properties microstructure

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Distinct community assembly processes underlie significant spatiotemporal dynamics of abundant and rare bacterioplankton in the Yangtze River

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Frontiers of Environmental Science & Engineering 2022年第6期16卷 145-158页

作者： Malan Yi Yao Fang Guoping Hu Shufeng liu Jinren Ni tang liu College of Environmental Sciences and Engineering Peking UniversityKey Laboratory of Water and Sediment Sciences(Ministry of Education)Beijing 100871China Fluid Science and Resources Division Department of Chemical EngineeringThe University of Western AustraliaCrawleyWA 6009Australia College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China State Environmental Protection Key Laboratory of All Material Fluxes in River Ecosystems Peking UniversityBeijing 100871China

The rare microbial biosphere provides broad ecological services and resilience to various ***,the biogeographical patterns and assembly processes of rare bacterioplankton communities in large rivers remain *** this study,we investigated the biogeography and community assembly processes of abundant and rare bacterioplankton taxa in the Yangtze River(China)covering a distance of 4300 *** results revealed similar spatiotemporal patterns of abundant taxa(AT)and rare taxa(RT)at both taxonomic and phylogenetic levels,and analysis of similarities revealed that RT was significantly influenced by season and landform than ***,RT correlated with more environmental factors than AT,whereas environmental and spatial factors explained a lower proportion of community shifts in RT than in *** steeper distance–decay slopes in AT indicated higher spatial turnover rates of abundant subcommunities than rare *** null model revealed that both AT and RT were mainly governed by stochastic ***,dispersal limitation primarily governed the AT,whereas the undominated process accounted for a higher fraction of stochastic processes in *** flow and suspended solids mediated the balance between the stochastic and deterministic processes in *** spatiotemporal dynamics and assembly processes of total taxa were more similar as AT than *** study provides new insights into both significant spatiotemporal dynamics and inconsistent assembly processes of AT and RT in large rivers.

关键词： Rare taxa Biogeography Community assembly Bacterioplankton The Yangtze River

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A novel Na_(1−x)K_(x)TaO_(3)perovskite microwave dielectric ceramic with high permittivity and high positive temperature coefficient

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Journal of Advanced Ceramics 2023年第11期12卷 2053-2061页

作者： liu tang Hongcheng Yang Enzhu Li Chaowei Zhong State Key Laboratory of Electronic Thin Films and Integrated Devices School of Electronic Science and EngineeringUniversity of Electronic Science and Technology of ChinaChengdu 610054China National Engineering Research Center of Electromagnetic Radiation Control Materials University of Electronic Science and Technology of ChinaChengdu 611731China School of New Energy and Materials Southwest Petroleum UniversityChengdu 610500China

A novel Na_(1−x)K_(x)TaO_(3)(x=0,0.025,0.05,0.075,0.1,and 0.15)ceramic with high permittivity and high positive temperature coefficient was synthesized via the conventional solid-state *** samples were determined to be pure phase orthorhombic NaTaO3 structure of space group Pmcn,and larger grain and lower porosity were observed after adding an appropriate amount of K+*** Q×f value is majored by the packing fraction and grain size,while the value ofτf is influenced by Ta–O bond *** Na_(0.95)K_(0.05)TaO_(3) ceramic possesses excellent dielectric properties ofεr=164.29,Q×f=9091 GHz(f=3.15 GHz),tanδ=3.46×10^(–4),τf=+809.52 ppm/℃,sintered at 1550℃.Compared with NaTaO_(3) ceramics,the Na_(1−x)K_(x)TaO_(3)ceramics prepared in this study demonstrate higher dielectric constants and higher positive temperature coefficients,which are promising for device miniaturization andτf compensators.

关键词： Na_(1−x)K_(x)TaO_(3)ceramics high permittivity high positive temperature coefficient perovskite

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Annealing Effects on Structural,Optical Properties and Laser-Induced Damage Threshold of MgF2 Thin Films

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Acta Metallurgica Sinica(English Letters) 2017年第1期30卷 73-78页

作者： Ting-Ting Tan Bang-Jie liu Zhi-Hui Wu Zheng-tang liu State Key Lab of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi'an 710072China

The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF2 film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the asdeposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.

关键词： Annealing temperature Chemical structure Optical properties Laser-induced damage threshold (LIDT) MgF2 films

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Multi-resolution image segmentation based on Gaussian mixture model

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Journal of Systems Engineering and Electronics 2006年第4期17卷 870-874页

作者： tang Yinggan liu Dong Guan Xinping Inst. of Electrical Engineering Yanshan Univ. Qinhuangdao 066004 P. R. China

Mixture model based image segmentation method, which assumes that image pixels are independent and do not consider the position relationship between pixels, is not robust to noise and usually leads to misclassification. A new segmentation method, called multi-resolution Ganssian mixture model method, is proposed. First, an image pyramid is constructed and son-father link relationship is built between each level of pyramid. Then the mixture model segmentation method is applied to the top level. The segmentation result on the top level is passed top-down to the bottom level according to the son-father link relationship between levels. The proposed method considers not only local but also global information of image, it overcomes the effect of noise and can obtain better segmentation result. Experimental result demonstrates its effectiveness.

关键词： image segmentation multi-resolution Ganssian mixture model.

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