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Chaotic attitude and reorientation maneuver for completely liquid-filled spacecraft with flexible appendage

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Acta Mechanica Sinica 2009年第2期25卷 271-277页

作者： B. Yue Department of Mechanics, school of Science,beijing institute of technology, 100081 beijing, china Department of Mechanics School of Science Beijing Institute of Technology 100081 Beijing China

The present paper investigates the chaotic attitude dynamics and reorientation maneuver for completely viscous liquid-filled spacecraft with flexible appendage. All of the equations of motion are derived by using Lagrangian mechanics and then transformed into a form consisting of an unperturbed part plus perturbed terms so that the system＇s nonlinear characteristics can be exploited in phase space. Emphases are laid on the chaotic attitude dynamics produced from certain sets of physical parameter values of the spacecraft when energy dissipation acts to derive the body from minor to major axis spin. Numerical solutions of these equations show that the attitude dynamics of liquid-filled flexible spacecraft possesses characteristics common to random, non- periodic solutions and chaos, and it is demonstrated that the desired reorientation maneuver is guaranteed by using a pair of thruster impulses. The control strategy for reorientation maneuver is designed and the numerical simulation results are presented for both the uncontrolled and controlled spins transition.

关键词： Nonlinear attitude dynamics Attitude reorientation maneuver Control strategyLiquid-filled spacecraft

The effects of relative density of metal foams on the stresses and deformation of beam under bending

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Acta Mechanica Sinica 2007年第4期23卷 409-414页

作者： Aiyu Zhu Tianyou Fan Department of Mathematics,school of Science,beijing institute of technology,P.O.Box 327,beijing 100081,china Department of Physics,school of Science,beijing institute of technology,P.O.Box 327,beijing 100081,china Department of Mathematics School of Science Beijing Institute of Technology P. O. Box 327 Beijing 100081 China Department of Physics School of Science Beijing Institute of Technology P. O. Box 327 Beijing 100081 China

The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.

关键词： Metal foams - Relative density Compressible plasticity Constitutive law - TG model

On the stability of diffusion processes with state-dependent switching

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Science china Mathematics 2006年第9期49卷 1258-1274页

作者： XI Fubao & ZHAO Liqin Department of Mathematics, beijing institute of technology, beijing 100081, china school of Mathematical Sciences, beijing Normal University, beijing 100875, china Department of Mathematics Beijing Institute of Technology Beijing 100081 China school of Mathematical Sciences Beijing Normal University Beijing 100875 China

In this paper we consider the stability for diffusion processes with state-dependent switching. We first prove their Feller continuity by the coupling methods. Furthermore, we also prove their strong Feller continuity and their exponential ergodicity under some reasonable conditions. Finally, we append a very brief discussion about the regularity of these processes.

关键词： Feller continuity, coupling, strong Feller continuity, exponential ergodicity,state-dependent switching.

Visualization of protein RecR in Escherichia coli by fluorescent labelling

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Progress in Natural Science:Materials International 2009年第11期19卷 1545-1551页

作者： Jiefang Qiu,Xuefeng Pan~* school of Life Science,beijing institute of technology,beijing 100081,china [a]school of Life Science Beijing Institute of Technology Beijing 100081 China

RecR protein,a functional equivalent of Rad52 in eukaryotes,plays a critical role in the RecF pathway of homologous recombination in Escherichia *** constructing and expressing the recR-yfp hybrid gene,the distribution of the RecR-YFP fusion protein was visualized in *** by fluorescent *** results showed that RecR proteins can be localized predominantly in the nucleoid region of *** measuring the UV resistance of a recR mutant carrying the recR-yfp gene in the plasmid,the expressed RecR-YFP was found to be functional in improving the UV resistance of the recR deficiency strain.

关键词： RecR YFP DNA Repair Homologous recombination E.coli

Investigation of Phase Excitation Effect on Mixing Control in Coaxial Jets

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Journal of Thermal Science 2009年第4期18卷 364-369页

作者： Yanming LIU,Baoguo WANG and Shuyan LIUschool of Aerospace Engineering,beijing institute of technology,beijing,100081,china school of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China

Detailed unsteady numerical simulation has been carried out to investigate the mechanism of adjacent syntheticjets and the influence of different phases on the mixing of coaxial jets. The results show the combined jet, formedby coupling the vortex pairs at the orifice of two adjacent actuators, can exhibit better controlling effect. Spanwisepressure difference appears because of the existence of phase difference between the left jet and right jet, whichresults in the variation of the combined jet. When the phase difference is greater than zero, mixing enhancementof coaxial jets can be achieved, but there are maximum phase difference and optimal phase difference. On thecontrary, application of adjacent synthetic jets always leads to the mixing reduction when phase difference is lessthan zero.

关键词： adjacent synthetic jets phase difference mixing controlling ability

The influence of synthetic jet excitation on secondary flow in compressor cascade

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Journal of Thermal Science 2010年第6期19卷 500-504页

作者： Yanming LIU, Tuo SUN, Chaobin GUAN and Baoguo WANG school of Aerospace Engineering, beijing institute of technology, beijing, 100081, china Assistant Professor school of Aerospace Engineering Beijing Institute of Technology Beijing China

The detailed numerical simulation has been carried out to investigate the effect of synthetic jet excitation on the secondary flow at 5° incidence in a compressor cascade, in which the synthetic jet actuation is equipped on the suction surface. The influence of excitation position, one fixed near the trailing edge and the other fixed a little far from the trailing edge, has also been studied. The results show that unsteady disturbance of desirable synthetic jet effectively enhances the mixing of the fluid inside the separation region, which reduces the vortex intensity and the energy loss, improves the flow status in the cascade, and also suppresses velocity fluctuation near the trailing edge. Additionally, the actuation fixed near the separation region proves to be more effective and exit load distribution is more uniform due to the employment of the synthetic jet.

关键词： synthetic jet actuator compressor cascade loss velocity fluctuation

A tracking loop based on tightly coupled range and velocity filter equations

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Science china(Information Sciences) 2012年第4期55卷 898-910页

作者： CUI Wei,TIAN Jing & WU SiLiang school of Information and Electronics,beijing institute of technology,beijing 100081,china 1. school of Information and Electronics Beijing Institute of Technology Beijing 100081 China

A joint range-velocity closed tracking loop,which is based on tightly coupled range and velocity filter is *** the measured velocity value is adopted in the range tracking loop to modify the velocity and acceleration equations from traditional α-β-γ filter,the tracking loop based on tightly coupled range and velocity filter can not only track the range and the velocity simultaneously,but also improve the range tracking *** experimental results show that the tracking errors about range thermal noise in the proposed loop is lower than those in the traditional loop over 2.2 dB,when filter parameters satisfy least mean-square error ***,with the increase of the filter parameter,the tracking performance of our schemes are improved accordingly.

关键词： α-β-γ filter tracking loop thermal noise tracking error tightly coupled range and velocity equations

Design of secure operating systems with high security levels

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Science in china(Series F) 2007年第3期50卷 399-418页

作者： QING SiHan1,2 & SHEN ChangXiang3 1 institute of software, Chinese Academy of Sciences, beijing 100080, china 2 school of software and Microelectronics, Peking University, beijing 102600, china 3 institute of Computing technology, Navy, beijing 100841, china 1. institute of software Chinese Academy of Sciences Beijing 100080 China 2. school of software and Microelectronics Peking University Beijing 102600 China 3. institute of Computing technology Navy Beijing 100841 China

Numerous Internet security incidents have shown that support from secure operating systems is paramount to fighting threats posed by modern computing environments. Based on the requirements of the relevant national and international standards and criteria, in combination with our experience in the design and development of the ANSHENG v4.0 secure operating system with high security level （hereafter simply referred to as ANSHENG OS）, this paper addresses the following key issues in the design of secure operating systems with high security levels： security architecture, security policy models, and covert channel analysis. The design principles of security architecture and three basic security models： confidentiality, integrity, and privilege control models are discussed, respectively. Three novel security models and new security architecture are proposed. The prominent features of these proposals, as well as their applications to the ANSHENG OS, are elaborated. Cover channel analysis （CCA） is a well-known hard problem in the design of secure operating systems with high security levels since to date it lacks a sound theoretical basis and systematic analysis approach. In order to resolve the fundamental difficulties of CCA, we have set up a sound theoretical basis for completeness of covert channel identification and have proposed a unified framework for covert channel identification and an efficient backward tracking search method. The successful application of our new proposals to the ANSHENG OS has shown that it can help ease and speedup the entire CCA process.

关键词： secure operating systems with high security levels architecture security model covert channel analysis

Tuning surface active oxygen of lanthanum oxide via partial dissolution and regrowth of crystallites

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Journal of Natural Gas Chemistry 2011年第5期20卷 483-486页

作者： Zhiming Gao, Huili Li Key Laboratory of Cluster Science, Ministry of Education of china Department of Chemistry, school of Science, beijing institute of technology, beijing 100081, china Key Laboratory of Cluster Science Ministry of Education of China Department of Chemistry School of Science Beijing Institute of Technology Beijing 100081 China

A commercial lanthanum oxide was modified into X%-La2O3 samples via partial dissolution and regrowth of crystallites, wherein the X value denotes the weight percent of the initial metal oxide powder dissolved by nitric acid. BET measurements and TEM observations indicate that the 20%-La2O3 sample has an increased specific surface area, relatively thin and small crystallites in size. TPD/TPR profiles also show that the 20%-La2O3 sample has more surface active oxygen than the 0%-La2O3 sample. Among the four X%-La2O3 samples, the highest activity for methane oxidation was obtained over the 20%-La2O3 sample. Therefore, the present work proves that the method of partial dissolution and regrowth of crystallites are effective to modify surface property of lanthanum oxide.

关键词： solid state reaction surface oxygen crystallite regrowth TPR metal oxide