检索结果-南通市图书馆

Adaptive control for autonomous rendezvous of spacecraft on elliptical orbit

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第4期25卷 539-545页

作者： Shan lu Shijie Xu school of {2., {2.,100191 beijing, China school of astronautics Beihang University 100191 Beijing China

A strategy for spacecraft autonomous rendezvous on an elliptical orbit in situation of no orbit information is developed. Lawden equation is used to describe relative motion of two spacecraft. Then an adaptive gain factor is introduced, and an adaptive control law for auton- omous rendezvous on the elliptical orbit is designed using Lyapunov approach. The relative motion is proved to be ultimately bounded under this control law, and the final relative position error can achieve the expected magnitude. Simulation results indicate that the adaptive control law can realize autonomous rendezvous on the elliptical orbit with relative state information only.

关键词： Autonomous rendezvous Elliptical orbit Lyapunov approach Adaptive control Gain factor

The anisotropy of suprathermal electrons in the Martian ionosphere

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2024年第3期8卷 459-471页

作者： YuTian Cao Jun Cui XiaoShu Wu WenJun Liang RuiQi Fu haoyu lu Planetary Environmental and Astrobiological Research Laboratory(PEARL) School of Atmospheric SciencesSun Yat-sen UniversityZhuhai 519082China Key Laboratory of Geospace Environment University of Science&Technology of ChinaChinese Academy of SciencesHefei 230026China Center for Excellence in Comparative Planetology Chinese Academy of SciencesHefei 230026China school of Space and Environment Beihang UniversityBeijing 102206China

Suprathermal electrons are an important population of the Martian ionosphere, either produced by photoionization of atmospheric neutrals or supplied from the Solar Wind (SW). This study is dedicated to an in-depth investigation of the pitch angle distribution of suprathermal electrons at two representative energies, 19−55 eV and 12.−356 eV, using the extensive measurements made by the Solar Wind Electron Analyzer on board the Mars Atmosphere and Volatile Evolution. Throughout the study, we focus on the overall degree of anisotropy, defined as the standard deviation of suprathermal electron intensity among different directions which is normalized by the mean omni-directional intensity. The available data reveal the following characteristics: (1) In general, low energy electrons are more isotropic than high energy electrons, and dayside electrons are more isotropic than nightside electrons;(2. On the dayside, the anisotropy increases with increasing altitude at low energies but remains roughly constant at high energies, whereas on the nightside, the anisotropy decreases with increasing altitude at all energies;(3) Electrons tend to be more isotropic in strongly magnetized regions than in weakly magnetized regions, especially on the nightside. These observations indicate that the anisotropy is a useful diagnostic of suprathermal electron transport, for which the conversion between the parallel and perpendicular momenta as required by the conservation of the first adiabatic invariant, along with the atmospheric absorption at low altitudes, are two crucial factors modulating the observed variation of the anisotropy. Our analysis also highlights the different roles on the observed anisotropy exerted by suprathermal electrons of different origins.

关键词： Mars ionosphere suprathermal electron pitch angle distribution

Boosting rate performance of layered lithium-rich cathode materials by oxygen vacancy induced surface multicomponent integration

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2024年第5期92卷 250-262页

作者： Youyou Fang Yuefeng Su Jinyang Dong Jiayu Zhao haoyu Wang Yun lu Bin Zhang Hua Yan Feng Wu Lai Chen beijing Key Laboratory of Environmental Science and Engineering School of Material Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Chongqing Innovation Center Beijing Institute of TechnologyChongqing 401120China Yibin Libode New Materials Co. Ltd.Yibin 64400SichuanChina school of Metallurgy and Environment Central South UniversityChangsha 410083HunanChina Engineering Research Center of the Ministry of Education for Advanced Battery Materials Central South UniversityChangsha 410083HunanChina

The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries,a domain in which Lithium-rich layered cathode(LLO)materials inherently ***,these materials face practical challenges,such as low initial Coulombic efficiency,inferior cycle/rate performance,and voltage decline during cycling,which limit practical *** study introduces a surface multi-component integration strategy that incorporates oxygen vacancies into the pristine LLO material Li1.2.n_(0.6)Ni_(0.2.O_(2..This process involves a brief citric acid treatment followed by calcination,aiming to explore rate-dependent degradation *** induced surface oxygen vacancies can reduce surface oxygen partial pressure and diminish the generation of O_(2.and other highly reactive oxygen species on the surface,thereby facilitating the activation of Li ions trapped in tetrahedral sites while overcoming transport ***,the formation of a spinel-like phase with 3D Li+diffusion channels significantly improves Li^(+)diffusion kinetics and stabilizes the surface *** optimally modified sample boasts a discharge capacity of 2.9.5 mA h g^(-1)at a 0.1 C and 2.1.6 mA h g^(-1)at a 1 C during the initial activation cycle,with an impressive capacity of 2.2.1 mA h g^(-1)at a 5 *** notably,it retained nearly 70%of its capacity after 300 cycles at this elevated *** straightforward,effective,and highly viable modification strategy provides a crucial reso{2.tion for overcoming challenges associated with LLO materials,making them more suitable for practical application.

关键词： Lithium-ion battery Layered lithium rich cathode Surface multicomponent integration Rate-dependent degradation and Li^(+) diffusion kinetics

Analysis and simulation of high strain compression of anisotropic open-cell elastic foams

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2010年第3期53卷 863-869页

作者： lu ZiXing,HUANG JiXiang&CHEN Xin school of Aeronautic Science and Engineering,{2. {2. of Aeronautics and astronautics,beijing 100191,China 1. school of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

By elongating the regular Kelvin model in one direction and keeping unchanged in the other two directions,the anisotropic model was ***,the simplified periodic structural cell was obtained according to the periodicity and symmetry of the model in the whole *** the half-strut element and elastic deflection theory to analyze the mechanical behavior as were adopted in the previous studies,this paper obtained the theoretical expressions for the compressive stress and strain as well as the corresponding curves in the rise and transverse *** addition,the theoretical results were examined by the finite element *** indicated that the theoretical analysis was very close to the finite element simulation when the strain was not too high,which confirmed the validity of theoretical *** the same time,the anisotropy was shown to have a significant effect on the mechanical properties of open-cell *** the anisotropy ratio increased,the compressive stress was improved in the rise direction but dropped in the transverse direction under the same strain.

关键词： open-cell foams elastic deformation Kelvin model anisotropy finite element

Adaptive RBF neural network control of robot with actuator nonlinearities

在线全文

学校读者我要写书评

暂无评论

控制理论与应用（英文版） 2010年第2期8卷 249-256页

作者： Jinkun LIU, Yu lu (school of Automation Science and Electrical Engineering, {2. {2. of Aeronautics and astronautics, beijing 100191, China) school of Automation Science and Electrical Engineering Beijing University of Aeronautics and Astronautics Beijing China

In this paper, an adaptive neural network control scheme for robot manipulators with actuator nonlinearities is presented. The control scheme consists of an adaptive neural network controller and an actuator nonlinearities compensator. Since the actuator nonlinearities are usually included in the robot driving motor, a compensator using radial basis function (RBF) network is proposed to estimate the actuator nonlinearities and eliminate their effects. Subsequently, an adaptive neural network controller that neither requires the evaluation of inverse dynamical model nor the time-consuming training process is given. In addition, GL matrix and its product operator are introduced to help prove the stability of the closed control system. Considering the adaptive neural network controller and the RBF network compensator as the whole control scheme, the closed-loop system is proved to be uniformly ultimately bounded (UUB). The whole scheme provides a general procedure to control the robot manipulators with actuator nonlinearities. Simulation results verify the effectiveness of the designed scheme and the theoretical discussion.

关键词： Adaptive control RBF neural network Actuator nonlinearity Robot manipulator Deadzone

Bursting of Morris-Lecar neuronal model with current-feedback control

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2009年第3期52卷 771-781页

作者： DUAN LiXia1, lu QiShao2.& CHENG DaiZhan3 1 College of Science, North China university of Technology, {2. 100144, China 2.{2. of Science, {2. university of Aeronautics and astronautics, beijing 100191, China 3 Institute of Systems Science, Chinese Academy of Sciences, {2. 100190, China College of Science North China University of Technology Beijing 100144 China school of Science Beijing University of Aeronautics and Astronautics Beijing 100191 China Institute of Systems Science Chinese Academy of Sciences Beijing 100190 China

The Morris-Lecar (ML) neuronal model with current-feedback control is considered as a typical fast-slow dynamical system to study the combined influences of the reversal potential VCa of Ca2. and the feedback current I on the generation and transition of different bursting oscillations. Two-parameter bifurcation analysis of the fast subsystem is performed in the parameter (I, VCa)-plane at first. Three important codimension-2.bifurcation points and some codimension-1 bifurcation curves are obtained which enable one to determine the parameter regions for different types of bursting. Next, we further divide the control parameter (V0, VCa)-plane into five different bursting regions, namely, the "fold/fold" bursting region R1, the "fold/Hopf" bursting region R2. the "fold/homoclinic" bursting region R3, the "subHopf/homoclinic" bursting region R4 and the "subHopf/subHopf" bursting region R5, as well as a silence region R6. Codimension-1 and -2.bifurcations are responsible for explanation of transition mechanisms between different types of bursting. The results are instructive for further understanding the dynamical behavior and mechanisms of complex firing activities and information processing in biological nervous systems.

关键词： neuron bursting bifurcation fast-slow dynamics analysis codimension

Influence of Hall effects on characteristics of magnetohydrodynamic converging channel

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2010年第14期55卷 1454-1460页

作者： lu haoyu {2. chunhian school of astronautics Beihang University Beijing 100191 China school of Aeronautic Science and Engineering and Technology Beihang University Beijing 100191 China

Influences of Hall effects on the flow characteristics and performance of the magnetohydrodyanmic (MHD) converging channel as an MHD generator are studied numerically in the present study. The numerical algorithm used is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations, in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of the electric field. It is found that Hall effects may lead to distortions in both the flow field and electric field in the MHD converging channel. The electric current lines are distorted and induce eddy currents, which will be mitigated by Hall effects. Comparisons of parameters characterizing the performance of the MHD generator for different geometry also reveal that the Hall effects may deteriorate the performance of MHD generator, especially for converging channel.

关键词：霍尔效应通道磁流体发电机磁特性 Stokes方程性能参数血液透析流动特性

Stability on Finite Time interval andTime-Dependent Bifurcation Analysis ofDuffing's Equations

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第4期4卷 268-271页

作者： Cuncai HUA Qishan lu(school of Science, {2. {2. of Aeronautics and astronautics, {2. 100083,China) school of Science Beijing Univ. Aero. and Astronaut. Beijing 100083 China

IntroductionInPhysics,MechanicsandEngineering,ChemistryandLifeScienceetc.,thereealstbfforcationproblemsm***etimepassingthrought... 详细信息

IntroductionInPhysics,MechanicsandEngineering,ChemistryandLifeScienceetc.,thereealstbfforcationproblemsm***etimepassingthrought...

关键词： stability on finite time interval time-dependent bifurcation Duffing’s equa-tion

Rate Equation of Small Particle-Air Bubble Attachment in Turbulent Flow of Flotation Cells

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1998年第4期12卷 185-191页

作者： Shouci lu Jingyong Guo(Resources Engineering school, {2. of Science and Technology {2., {2. 1 00083, China) Resources Engineering school University of Science and Technology Beijing Beijing 100083 China

A rate equation of small particle-air bubble attachment in the turbulent now of flotation cells has beenderived. The equation, integrating both the collision probability and adhesion probability together, represents theprobability of attachment between particle and bubble in the turbulent flow. 'Capture efficiency' f(a) is introducedinto the rate equation to reflect the influence of energy hairier on the attachment rate. Three typical situations of particle-bubble interaction in flotation process have been discussed. For a completely hydrophobic particle-bubble system,f(a) = 1. This means that all collision leads to attachment. Whereas for hydrophilic particle-bubble systems, .f(a) =0. Thus no adhesion of particle on bubble occurs at all. In real notation circumstances, however, there always existsa certain energy barrier between the particle and the bubble. Therefore, f(a) = 0～1. In such cases, not all collisionsresult in particle-bubble attachment.

关键词： rate equation turbulent flow flotation cell capture efficiency