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Optimal terminal guidance for exoatmospheric interception

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Chinese Journal of Aeronautics 2016年第4期29卷 1052-1064页

作者： Yu Wenbin chen wanchun Yang Liang Liu Xiaoming Zhou Hao School of Astronautics Beihang University

In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be considered or neglected by properly adjusting a parameter in the cost function. To make this problem analytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

关键词： Exoatmospheric interception Explicit guidance Guidance Optimal control Proportional navigation Pulsed guidance

In Situ Observation of KB_(5) Crystal Growth Under Purely Diffusion Gel Systems by Holographic Interferometry

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Chinese Physics Letters 1991年第9期8卷 469-471页

作者： chen wanchun SHEN Yunxue MA Wenyi LI Ming chen Yansong Institute of Physics Academia SinicaBeijing 100080

KB_(5)O_(8).4H_(2)O(KB_(5))crystals have been grown in an agar-agar gel by temperature decrease method for simulating crystal growth in *** and growth have been followed by interferometric holography.A concentration field surrounding the growing crystals was obtained and a Liesegang ring was *** pattern are visualized directly to reveal physical phenomena of purely diffusion crystal growth kinetics.

关键词： Diffusion purely

Study on flow characteristics of solid/liquid system in lysozyme crystal growth

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Chinese Science Bulletin 2007年第9期52卷 1196-1204页

作者： CUI HaiLiang YU Yong chen wanchun KANG Qi National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Institute of Physics Chinese Academy of Sciences Beijing 100080 China

During the process of lysozyme protein crystallization with batch method,the macroscopic flow field of solid/liquid system was observed by particle image velocimetry(PIV). Furthermore,a normal growth rate of(110) face and local flow field around a single protein crystal were obtained by a long work dis-tance microscope. The experimental results showed that the average velocity,the maximal velocity of macroscopic solid/liquid system and the velocity of local flow field around single protein crystal were fluctuant. The effective boundary layer thickness δeff,the concentration at the interface Ci and the characteristic velocity V were calculated using a convection-diffusion model. The results showed that the growth of lysozyme crystal in this experiment was dominated by interfacial kinetics rather than bulk transport,and the function of buoyancy-driven flow in bulk transport was small,however,the effect of bulk transport in crystal growth had a tendency to increase with the increase of lysozyme concentra-tion. The calculated results also showed that the order of magnitude of shear force was about 10-21 N,which was much less than the bond force between the lysozyme molecules. Therefore the shear force induced by buoyancy-driven flows cannot remove the protein molecules from the interface of crystal.

关键词：溶菌酶晶体生长固体液体系统流动特性

Progress in Research on Materials Under Microgravity in China

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空间科学学报 2004年第Z1期24卷 138-149页

作者： chen Nuofu chen wanchun LUO Xinghong YE Yude Key Laboratory of Semiconductor Materials Sciences Institute of Semiconductors The Chinese Academy of Sciences Beijing 100083 China National Laboratory of Microgravity Institute of Mechanics The Chinese Academy of Sciences Beijing 100080 China Institute of Physics The Chinese Academy of Sciences Beijing 100080 China National Laboratory of Microgravity Institute of Mechanics The Chinese Academy of Sciences Beijing 100080 China Institute of Metal Research The Chinese Academy of Sciences Shenyang 110016 China Key Laboratory of Semiconductor Materials Sciences Institute of Semiconductors The Chinese Academy of Sciences Beijing 100083 China

Research on materials under microgravity in China began in the 1980s, sparked by Prof. Lanying Lin (academician of CAS), Prof. Xiji Wang (academician of CAS), Prof. Guirong Min (academician of CAS), and Prof. Huabao Lin (academician of CAS), and others. The first semiconductor crystal, first optical crystal, and first alloys were grown in space on board a recoverable satellite in 1987. Since then, microgravity materials science became a new scientific branch in *** and technical activities on space crystal growth and solidification are carried out through two major programs: ground-based studies and orbital experiments. The main results obtained during 2001-2003 are reported below.

关键词： Microgravity, Semiconductor, Metal, Crystal

Trajectory Optimization of a Cruise Missile using the Gauss Pseudospectral Method

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Trajectory Optimization of a Cruise Missile using the Gauss ...

Progress of Microgravity Material Research During the Period of 2007-2009

第26届中国控制与决策会议

作者： Hu Yi chen wanchun School of Astronautics Beijing University of Aeronautics and Astronautics

ISBN: (纸本)9781479937066

Compared with the conventional optimization approaches, Gauss Pseudospectral Method（GPM） can deal better with optimal problems with complex constraints and is less time consuming. As a numerical technique, GPM transforms the optimal control problem to a nonlinear programming problem（NLP） by using discrete *** paper considers a cruise missile’s mission which is to hit a fixed target while minimizing the exposure to anti-air defenses. The objective function can be set as integrated altitude along the trajectory. The Gpops tool kit is used to demonstrate GPM on this problem. The case study’s results show that the method converges fast and precisely.

关键词： Cruise Missile Optimal Control Trajectory Optimization Gauss Pseudodpectral Method Nonlinear Programming

来源： cnki会议评论

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空间科学学报 2010年第5期30卷 504-515页

作者： chen Nuofu Bai Yiming chen wanchun Zhou Yanfei Luo Xinghong Yu Yude Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 Institute of Physics Chinese Academy of Sciences Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion Shanghai Institute of Ceramics Chinese Academy of Sciences Institute of Metal Research Chinese Academy of Sciences School of Renewable Energy North China Electricity Power University

Orbital experimental researches on crystal growth of Mn-doped GaSb and Bi2Se0.21Te2.79 are briefly *** space experiments were completed in September of 2007 on broad the Foton-M3 satellite of ***-based researches on the solidification behaviors of Al-Al3Ni,AlAl2Cu,Ag-Cu eutectic,Al-Pb monotectic and Cu-Co peritectic alloys in a 50-meter-high drop tube were *** experimental results on the ultrasonic field and the temperature recycling induced to chiral symmetry breaking of NaClO3 crystal also were reported in the present paper.

关键词：微重力材料空间实验晶体生长凝固行为包晶合金对称破缺温度诱导

齐齐哈尔市基本公共卫生服务现状、实施路径及政策措施研究

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中国公共卫生管理 2024年第1期40卷 95-99页

作者：陈万春王荭莉陈鹏汪滢陈秀华李争陈至佳陈菁宇齐齐哈尔市疾病预防控制中心黑龙江齐齐哈尔161005 北京中电利德科技有限公司齐齐哈尔市建华区疾病预防控制中心

剖析齐齐哈尔市基本公共卫生项目落实现状,探讨实施路径,完善政策措施,规范项目运行,为全面提升齐齐哈尔市基本共卫服务水平、促进社会经济发展与增强群众健康获得感奠定坚实基础。齐齐哈尔市基本公共卫生服务项目任务基本落实,服务体... 详细信息

剖析齐齐哈尔市基本公共卫生项目落实现状,探讨实施路径,完善政策措施,规范项目运行,为全面提升齐齐哈尔市基本共卫服务水平、促进社会经济发展与增强群众健康获得感奠定坚实基础。齐齐哈尔市基本公共卫生服务项目任务基本落实,服务体系初步建立;项目管理机制明确,管理责任较清晰;重点项目全面推进,防控能力显著增强。但是,仍存在顶层设计不够、管理体系不健全、服务开展不到位、信息化水平低、资金管理不足等问题。应从强化顶层设计、分析短板弱项、健全服务体系、强化培训考核、加强资金监管、加快公共卫生信息化建设等方面构建基本公共卫生服务体系。建议强化政府与部门政策支持、提升服务能力与增强质效、提升公共卫生服务社会认同与增强健康获得感。

关键词：基本公共卫生服务政策措施齐齐哈尔

Growth of α-LiIO_(3) Single Crystal Grown in Space

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Chinese Physics Letters 1991年第4期8卷 191-194页

作者： MAI Zhenhong chen wanchun CUI Shufan MA Wenyi XIE Anyun XU Lu JIN Zecen chen Gang Institute of Physics Academia SinicaBeijing 100080 Department of Applied Physics Beijing Polytechnic UniversityBeijing 100022

α-LiIO_(3) single crystals were grown by the aqueous solution method in a Chinese scientific *** morphology of the crystals grown in space are similar to that of earth-grown *** is found that the growth rates of the positive and negative sides of the space-grown crystals are almost the *** perfection of both crystals grown in space and on earth was examined.

关键词： earth perfect crystals

Numerical modeling of fracture propagation of supercritical CO_(2)compound fracturing

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2607-2628页

作者： Hao chen Yong Kang wanchun Jin Changhai Li Can Cai School of Mechanical Engineering Southwest Petroleum UniversityChengdu610500China Laboratory of High-pressure Jet Theory and Application Technology Southwest Petroleum UniversityChengdu610500China Hubei Key Laboratory of Waterjet Theory and New Technology Wuhan UniversityWuhan430072China Sinopec International Petroleum Exploration and Production Corporation Beijing 100029China

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse *** this paper,we proposed a heat-fluid-solid coupling damage model of supercritical CO_(2)(SC-CO_(2))compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale *** coupling model is solved by the finite element method,and the results are in good agreement with the analytical solutions and fracturing *** on this model,the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate,in situ stress,bedding angle,and other factors are *** results show that at the SC-CO_(2)fracturing stage,a lower pressurization rate is conducive to formation of the branches around main fractures,while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main *** bedding and in situ stress play a dominant role in the fracture *** the in situ stress ratio(δ_(x)/δ_(y))is 1,the presence of bedding can reduce the initiation pressure and failure ***,it will cause the fracture to propagate along the bedding direction,reducing the fracture *** rocks without bedding,hydraulic fracturing has the lengthening and widening effects for SC-CO_(2)induced *** shale,fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation ***,fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO_(2)at the hydraulic fracturing *** the branches converge with the main fractures,fracture zones are easily formed,and thus the fracture complexity and damage area can be significantly *** results are instructive for the design and application of SC

关键词： Compound fracturing Fracture propagation Finite element method Damage evolution