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Adaptive control for autonomous rendezvous of spacecraft on elliptical orbit

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

作者： Shan lu Shijie Xu school of astronautics, beihang university,1.01.1 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

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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 124−356 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

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

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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, beijing 100144, china 2 school of Science, beijing university of Aeronautics and astronautics, beijing 1.01.1, china 3 Institute of Systems Science, Chinese Academy of Sciences, beijing 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

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

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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, university of Science and Technology beijing, beijing 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

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

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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 Li1.2Mn_(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 299.5 mA h g^(-1)at a 0.1 C and 251.6 mA h g^(-1)at a 1 C during the initial activation cycle,with an impressive capacity of 222.1 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 resolution 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

Photocatalytic degradation of formaldehyde by diffuser of solar light pipe coated with nanometer titanium dioxide thin films

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Science china(Technological Sciences) 2010年第1期53卷 150-154页

作者： WU YanPeng1,ZHANG WenMing1,MA ChongFang2,lu YuanWei2 & LIU Li1 1 school of Civil and Environmental Engineering,university of Science and Technology beijing,beijing 100083,china 2 College of Environmental and Energy Engineering,beijing university of Technology,beijing 100022,china 1. school of Civil and Environmental Engineering University of Science and Technology Beijing Beijing 100083 China2. College of Environmental and Energy Engineering Beijing University of Technology Beijing 100022 China

The even and transparent nanometer TiO2 thin films named DegussaP25 as photocatalysis deposited on the surface of diffusers of solar light pipe were prepared by sol-gel *** rugged side of the diffusers of solar light pipe was coated evenly with DegussaP25 solution for the quality of 1.75 *** experiments had showed that when the coated side was away from the sun the lighting degree may be reduced compared with that facing the *** average reduction was only 3.03%,which would not have a significant impact on *** are important parts of a light pipe which can diffuse light evenly to the place needed to be *** experiments showed that in a sunny summer day under the direct sunlight,the solar light pipe combined with photocatalysis could reduce the formaldehyde volume fraction in a box of 0.1 m3 from 1.0×10-6 to 0.16×*** 1 h of photodegradation the formaldehyde volume changed from 1.0×10-6 down to 0.1×10-6 with faster and more complete degradation of *** rate of degradation under cloudy and partly cloudy conditions was slower than that under sunny *** was slower in winter than in summer under sunny *** experimental results also showed that the performance of photocatalysis combined with diffusers of light pipe had better effect in a small *** performance in large space,such as open space,will be the next work in the future,which will be a great challenge.

关键词： solar light pipes diffusers photocatalysis decomposition formaldehyde titanium dioxide

Reverse reconciliation for continuous variable quantum key distribution

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Science china(Physics,Mechanics & Astronomy) 2010年第1期53卷 100-105页

作者： lu ZhiXin 1,2 , YU Li 1,2 , LI Kang 1,2 , LIU BingCan 1,2,3 , LIN JianGui 1,2 , JIAO RongZhen 1,2 & YANG BoJun 1,21 school of Science, beijing university of Posts and Telecommunications, beijing 100876, china 2 Key Laboratory of Information Photonics and Optical Communication, Ministry of Education, beijing university of Posts and Telecommunications, beijing 100876, china 3 Department of Fundamental Courses, Academy of Armored Force Engineering, beijing 100072, china 1. school of Science Beijing University of Posts and Telecommunications Beijing 100876 China2. Key Laboratory of Information Photonics and Optical Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China3. Department of Fundamental Courses Academy of Armored Force Engineering Beijing 100072 China

An efficient and practical post-processing technique based on reverse reconciliation for continuous variable quantum key distribution is proposed and simulated with low-density parity check (LDPC) codes. MultiLevel Coding/ MultiStage Decoding, which fully utilizes optimization technique such as vector quantization and iterative decoding and the optimal channel coding most close to the Shannon limit, was used to realize efficient reverse reconciliation algorithm. Simulation results showed that the proposed method can improve the secure key distribution rate to 2.2 kb/s and the coding efficiency to 0.89 over 20 km in single-mode optical fiber. Moreover, there still is room for much improvement.

关键词： quantum communication key distribution reverses reconciliation low-density parity check codes

Reduced analysis and confirmatory research on co-adaptability theoretical solution to conflicting events in construction engineering projects

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Science china(Technological Sciences) 2010年第2期53卷 480-485页

作者： HOU XueLiang1 , lu Mei2 & WANG Kai3 1 school of Business Administration, North china Electric Power university, beijing 102206, china 2 Department of Construction Management, Tsinghua university, beijing 100084, china 3 College of Management, beijing Jiaotong university, beijing 100084, china 1. school of Business Administration North China Electric Power University Beijing 102206 China2. Department of Construction Management Tsinghua University Beijing 100084 China3. College of Management Beijing Jiaotong University Beijing 100084 China

The co-adaptability theoretical solution to conflicting events in construction engineering projects has three problems. First, the transformation of constraint conditions of theoretical solution is very difficult in practical engineering applications; second, some coefficients are difficult to be determined; third, there are overfull circular arithmetic operations involved in it. To resolve these problems, a new method to reduce the theoretical solution complications is proposed. By analyzing the operating mechanism of theoretical solution model, redundancies in the theoretical solution can be eliminated, and the ISM mapping with the co-adaptability solution can be set up. Based on this approach, a procedure to solve practical conflicting events in construction projects is established by replacing characteristic variables with mathematic variables. The research results show that the procedure can replace the co-adaptability theoretical solution effectively and solve practical conflicting events in construction projects.

关键词： construction project conflict theoretical solution reduced analysis ISM confirmatory research

Surface Inspection System for Cold Rolled Strips Based on Image ProcessingTechnique

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International Journal of Minerals,Metallurgy and Materials 1999年第4期13卷 296-298页

作者： Ke Xu1 Jinwu Xu2 Shouli lu1(l Material Science and Engineering school, university of Science and Technology beijing, beijing 100083, china2 Mechanical Engineering school, university of Science and Technology Beding, Beliing 100083, china) Material Science and Engineering school University of Science and Technology Beijing Beijing 100083 China Mechanical Engineering school University of Science and Technology Beijing Beijing 100083 China

A new surface inspection system for cold rolled strips based on image processing is introduced. The system is equipped withtwo different illumination structures and CCD matrix cameras. The structure and image processing of the inspection system are described. Some efficient algorithms for image processing and classification are presented. The system is tested with strip samples fromcold rolling plants. The results show that the system can detect and recognize six common defects of cold rolled strips successfully.

关键词： surface inspection system cold rolled strip image processing