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Physical analysis and numerical simulation for the dynamic behaviour of vehicles in pitching oscillations or rocking motions

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Science china(Technological Sciences) 2007年第4期50卷 385-401页

作者： ZHANG HanXin1,2.3, ZHANG Zhao1,3, YUAN XianXu1,2. LIU Wei1, XIE YuFei1,2.& YE YouDa1,2.1 china Aerodynamics Research and Development center, Mianyang 62.000, china 2.national Laboratory for Computational Fluid Dynamics, beijing University of Aeronautics and Astronautics, beijing 100083, china 3 School of Aerospace, Tsinghua University, beijing 100084, china china Aerodynamics Research and Development center Mianyan China national Laboratory for Computational Fluid Dynamics Beijing University of Aeronautics and Astronautics Beijing China School of Aerospace Tsinghua University Beijing China

Analytical methods of nonlinear dynamics and numerical simulations for the cou-pling equations of Navier-Stokes and flight mechanics are used to study the dynamic behaviour of pitching motions of reentry capsules with the variation of Mach number, and rocking motions of swept wings with the variation of angle of attack. Conditions under which the dynamic instability, Hopf bifurcation and saddle-node bifurcation occur are obtained. The node-saddle-node topological structure in the phase portrait, i.e. the state of bi-attractors (attracting basins) is described. The evolving process of dynamic behaviour and flow fields are given. The theories are compared with some numerical simulations conducted by the authors. Besides, some verifiable experi-mental results are cited. The agreement between them is very well.

关键词： physical analysis numerical simulation pitching oscillation rocking motion bifurcation

Climate effects of nuclear war in china

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Journal of Environmental Sciences 1993年第2期5卷 230-240页

作者： Cao HongxingChinese Academy of meteorological Sciences, beijing 100081,{2.Wang Yongzhong Lin Yunmeibeijing Institute of Meteorology, beijing 100081,{2. Chinese Academy of meteorological Sciences Beijing 100081 China. China

By utilizing simulations of climatic respponse to nuclear smoke, which were made by the Lawrence Livermore national Laboratory, USA, climate change in china induced by a large-scale nuclear war is analysed. Remarkable climate change in china following nuclear smoke injections is found. The surface air temperature decreases dramatically around all china, surface cooling is 13 ℃ averaging over whole china in July and maximum cooling is 2.. 4 ℃ , 3 ℃ cooling in January and maximum 8℃ for the 150 Tg smoke injection (equivalent to the base-line nuclear war). However, the change in temperature is unhomogeneous, implying that the rise in temperature happens over some parts of china. An averaging precipitation decrease in many of months of the experimental year. The precipitation defect is dependent on a scale of nuclear war, the deduction is 1.8mm/day averaging over china in July in the 150 Tg smoke injection, and 0.1 mm/d in January. Nevertheless, the precipitation enhancement in a few months over some regions is found. This dramatic climate change brings catastrophe to agriculture, ecology, as well as socio-economics.

关键词： nuclear winter climate simulation precipitation change.

Approaches to improving critical current density of YBCO superconducting thick films deposited by electrophoresis

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Science china(Physics,Mechanics & Astronomy) 2004年第2期47卷 165-172页

作者： ZHU Yabin1,2. ZHOU Yueliang2. LIU Zhen2. WANG Shufang2. CHEN Zhenghao2. L?Huibin2. YANG Guozhen2. XIAO Ling3, REN Hongtao3, JIAO Yulei3 & ZHENG Minghui3 1. Department of Physics, College of Science, beijing Jiaotong University, beijing 100044,{2. 2. Laboratory of Optical Physics, Institute of Physics and center for Condensed Matter Physics, Chinese Academy of Sciences, beijing 100080,{2. 3. General Research Institute for Nonferrous Metals, beijing 100088,{2. Correspondence should be addressed to Zhu Yabin (email: ybzhu@***) Department of Physics College of Science Beijing Jiaotong University Beijing China Laboratory of Optical Physics Institute of Physics and center for Condensed Matter Physics Chinese Academy of Sciences Beijing China General Research Institute for Nonferrous Metals Beijing China

Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (J c) is far from what the practical application requires. The superconducting thick films are obtained using top-seeded melt growth method with different proportional Y2.aCuO5 (Y2.1) addition. High-pressure oxygen has been used in the annealing process to improve the uniformity of the oxygen content in the superconducting thick films. When 40mol% Y2.1 powder is added to the YBa2.u3O7–5 (Y12.) powder,J c for the superconducting thick film by approaches described above reaches 7.008×103 A/cm2.(77 K, 0 T), which is greater than the value ever reported.

关键词： YBCO thick films, electrophoretic deposition, melt-textured.

Study on NDVI-T_s space by combining LAI and evapotranspiration

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Science china Earth Sciences 2006年第7期49卷 747-754页

作者： HAN Lijuan1,2.3, WANG Pengxin4, YANG Hua1,2.3, LIU Shaomin1,2.3 & WANG Jindi1,2.3 1. Research center for Remote Sensing and GIS, School of Geography, beijing Normal University, beijing 100875, china 2. State Key Laboratory of Remote Sensing Science, beijing 100875, china 3. beijing Key Laboratory for Remote Sensing of Environment and Digital Cities, beijing 100875, china 4. Department of Information Management, College of Information and Electronic Engineering, china Agricultural University, beijing 100083, china Research center for Remote Sensing and GIS School of Geography Beijing Normal University Beijing China State Key Laboratory of Remote Sensing Science Beijing China beijing Key Laboratory for Remote Sensing of Environment and Digital Cities Beijing China Department of Information Management College of Information and Electronic Engineering China Agricultural University Beijing China

This paper focuses on interpreting the different spatial relationships between NDVI and Ts, a triangular or a trapezoid, and on analyzing transformation conditions, the physical and ecological meanings of the vegetation index-surface temperature space as well. Further, we use the Tempera-ture-Vegetation Dryness Index (TVDI) to explain the existent meaning of a triangular space after NDVI reaches its saturated state by employing the relationships between NDVI, LAI and evapotranspiration. The specific relations between NDVI and Ts are useful for describing, validating and updating land surface models.

关键词： NDVI, land surface temperature, evapotranspiration, leave area index.

The age of synthesis:From cognitive science to converging technologies and hereafter

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Chinese Science Bulletin 2011年第6期56卷 465-475页

作者： CAI ShuShan1,2.1 Department of Psychology, Tsinghua University, beijing 10084, china 2.{2. for Psychology and Cognitive Science, Tsinghua University, beijing 10084, china Department of Psychology Tsinghua University Beijing China center for Psychology and Cognitive Science Tsinghua University Beijing China

This paper describes the development of two of the most important scientific disciplines in the last quarter of the 2.th century, cognitive science, which emerged in 1975, and nano-bio-info-cogno (NBIC) converging technologies, which emerged in 2.00. In this century, we will achieve cross-disciplinary integration, innovation in comprehensive knowledge and comprehensive devel opment in human resources. NBIC converging technologies will greatly expand human cognition and communication, improve human health, enhance social outcomes, strengthen national security and unify science and education. Cognitive science and converging technologies will have major effects on the future human development. I argue that the 2.st century represents an age of synthesis, reflected in the continual reintegration between scientific disciplines in recent times. This new age of synthesis will require innovations in thought and methodology that differ from those underlying the age of analysis in the 2.th century. I predict that these developments will allow every individual to realize comprehensive development. Accordingly, the education system will be transformed, and a comprehensive human resources system will be created.

关键词：认知科学融合技术化学合成教育系统人力资源人类健康生物信息综合知识

A new navigation approach of terrain contour matching based on 3-D terrain reconstruction from onboard image sequence

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Science china(Technological Sciences) 2010年第5期53卷 1176-1183页

作者： LI LiChun1,2.YU QiFeng2.SHANG Yang2.YUAN Yun2.LU HongWei3 & LIU XiaoLin4 1 beijing Aerospace Control center,beijing 100094,china 2.College of Aerospace and Material Engineering,national University of Defense Technology,Changsha 410073,china 3 Equipment Research Institute of PLA’s Second Artillery,beijing 100085,china 4 College of Mechatronic Engineering and Automation,national University of Defense Technology,Changsha 410073,china beijing Aerospace Control center Beijing China College of Aerospace and Material Engineering National University of Defense Technology Changsha China Equipment Research Institute of PLA’s Second Artillery Beijing China College of Mechatronic Engineering and Automation National University of Defense Technology Changsha China

This article presents a passive navigation method of terrain contour matching by reconstructing the 3-D terrain from the image sequence(acquired by the onboard camera).To achieve automation and simultaneity of the image sequence processing for navigation,a correspondence registration method based on control points tracking is proposed which tracks the sparse control points through the whole image sequence and uses them as correspondence in the relation geometry ***,a key frame selection method based on the images overlapping ratio and intersecting angles is explored,thereafter the requirement for the camera system configuration is *** proposed method also includes an optimal local homography estimating algorithm according to the control points,which helps correctly predict points to be matched and their speed ***,the real-time 3-D terrain of the trajectory thus reconstructed is matched with the referenced terrain map,and the result of which provides navigating *** digital simulation experiment and the real image based experiment have verified the proposed method.

关键词： terrain contour matching vision-based navigation 3-D reconstruction control points key frame registration optimal local homography

The size effect on transport properties of colossal magnetoresistance materials La_(0.67)Ca_(0.33)MnO_3

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Science china(Physics,Mechanics & Astronomy) 2008年第3期51卷 251-257页

作者： LI PeiGang1,2.LEI Ming1,2.GUO YanFeng2.GUO Xi2.CHEN LeiMing2. TANG WeiHua1,2.SONG PengYun3 & CHEN JinPing3 1 Department of Physics,center for Optoelectronics Materials and Devices,Zhejiang Sci-Tech University,Hangzhou 310018,china {2. Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,beijing 100080,china 3 Department of Physics,Peking University,beijing 100875,china Department of Physics Center for Optoelectronics Materials and Devices Zhejiang Sci-Tech University Hangzhou China national Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing China Department of Physics Peking University Beijing China

High quality La0.67Ca0.33MnO3 (LCMO) film was deposited via a novel pulsed electron deposition technique on SrTiO3(100) single crystal substrate. The micro-bridge with different widths was fabricated by using electron beam lithography (EBL) technique and their transport properties were studied. For the micro-bridges with width of 2.and 1.5 μm,the insulator-to-metal transition temperature (TP) keeps un-changed compared with the film. For the micro-bridges with width of 1 μm,the TP shifts towards the lower temperature by 50 K. When the width decreases down to 500 nm,the insulator-to-metal transition disappears. The magnetoresistance be-havior of these micro-bridges was studied,and the results show that the low field magnetoresistance (LFMR) decreases and the high field magnetoresistances (HFMR) keep almost unchanged as the width of micro-bridge is reduced.

关键词： colossal magnetoresistance pulsed electron deposition electron beam lithography electrical transport properties

A property-based attestation protocol for TCM

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Science china(Information Sciences) 2010年第3期53卷 454-464页

作者： FENG DengGuo1,2.& QIN Yu1,2.1State Key Laboratory of Information Security, Institute of Software, Chinese Academy of Science, beijing 100190, china 2.2. Engineering Research center of Information Security, beijing 100190, china State Key Laboratory of Information Security Institute of Software Chinese Academy of Science Beijing China national Engineering Research center of Information Security Beijing China

This paper presents a property attestation protocol for the security chip TCM (trusted cryptographic module) via analyzing the problems of the current property attestation, which is built on the property attestation model with the online trust third party. In the protocol the prover utilizes the zero-knowledge proof by the attribute certificates, configuration commitment and TCM signature, and attests its configuration and status which are compliant with the declarative security property. The protocol is characterized by shorter signature length and lower computations. The security of the protocol is proved at the random oracle model. The protocol can help extend application and improve standard for security chip TCM, and it also has practical value and immediate significance.

关键词： trust computing trust cryptographic module (TCM) property attestation signature of knowl- edge configuration commitment

Numerical simulations of leading-edge vortex core axial velocity for flow over delta wings

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Science china(Technological Sciences) 2009年第7期52卷 2029-2036页

作者： CHEN Lan1, 2.& WANG JinJun1 1 Institute of Fluid Mechanics, beijing University of Aeronautics and Astronautics, beijing 100191,{2. 2.2. Aerodynamic Research and Development center (CARDC), Mianyang 62.000,{2. Institute of Fluid Mechanics Beijing University of Aeronautics and Astronautics Beijing China china Aerodynamic Research and Development center (CARDC) Mianyang China

Numerical simulations have been performed to investigate the characteristics of leading-edge vortex core axial velocity over two delta wings with leading edge swept angles Λ =50°and 76°, respectively. It is obtained that Reynolds number has the most important effect on the axial velocity of the primary leading-edge vortex core. At Reynolds numbers larger than 105, the jet-like flow of the vortex core is the most common type for both the large and the moderate swept delta wings. While if Reynolds number decreases to 103―104, the core axial velocity distributions for these two delta wings present the wake-like profile for all angles of attack considered in the present investigation.

关键词： delta wing low Reynolds number vortex flows