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Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

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Science china(Technological Sciences) 2006年第5期49卷 521-536页

作者： CHEN Zhiyong1,2, CAI Hongnian1, ZHANG Xinming2, WANG Fuchi1 & TAN Chengwen1,3.1. school of Material Science and engineering, beijing {3. of Technology, beijing 100081, china 2. school of Material Science and engineering, Central South University, Changsha 410083. china 3. school of Material Science and engineering, beijing University of Aeronautics and Astronautics, beijing 100083. china 1. school of Material Science and engineering Beijing Institute of Technology Beijing 100081 China 2. school of Material Science and engineering Central South University Changsha 410083 China 3. school of Material Science and engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112 and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.

关键词： twinning slip face-centered cubic crystals axisymmetric co-deformation Bishop-Hill maximum work principle yield strength anisotropy

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,{3. institute of Technology,{3.,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

Nonholonomic mapping theory of autoparallel motions in Riemann-Cartan space

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Science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1707-1715页

作者： GUO YongXin1,LIU Chang2,WANG Yong3.LIU ShiXing1 & CHANG Peng2 1 College of Physics,Liaoning University,Shenyang 11003.,china 2 school of aerospace engineering,beijing {3. of Technology,beijing 110081,china 3.school of Basic Medical Science,Guangdong Medical College,Dongguan 523.08,china 1. College of Physics Liaoning University Shenyang 110036 China2. School of Aerospace Engineering Beijing Institute of Technology Beijing 110081 China3. School of Basic Medical Science Guangdong Medical College Dongguan 523808 China

The method of nonholonomic mapping is utilized to construct a Riemann-Cartan space embedded into a known Riemann-Cartan space,which includes two special cases that a Weitzenbck space and a Riemann-Cartan space are respectively embedded into a Euclidean space and a Riemann *** means of this mapping theory,the nonholonomic corresponding relation between the autoparallels of two Riemman-Cartan spaces is *** particular,an autoparallel in a Riemann-Cartan space can be mapped into a geodesic line in a Riemann space and an autoparallel in Weitzenbck space be mapped into a geodesic line in Euclidean *** on the Lagrange-d'Alembert principle,the equations of motion for dynamical systems in Riemman-Cartan space should be autoparallel equations of the *** applications,the problem of autoparallel motion of spinless particles,Chaplygin's nonholonomic systems and a rigid body rotating with a fixed point are investigated in space with torsion.

关键词： nonholonomic mapping Riemann-Cartan space connection torsion autoparallel

Studies of the unsteady supersonic base flows around three afterbodies

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Acta Mechanica Sinica 2009年第4期25卷 471-479页

作者： Zhixiang Xiao Song Fu school of aerospace engineering,Tsinghua University, 100084 {3., china school of aerospace engineering Tsinghua University 100084 Beijing China

Unsteady supersonic base flows around three afterbodies, cylindrical （Cy）, boattailed （BT） and three-step （MS）, are investigated in this paper. Reynolds-averaged Navier-Stokes （RANS） and two RANS/LES （large-eddy simulation） hybrid methods, detached eddy simulation （DES） and delayed-DES （DDES）, are used to predict the base flow characteristics around the baseline Cy afterbody. All the RANS and hybrid methods are based on the two-equation SST （shear-stress transport） model with compressible corrections （CC）. According to the comparison of measurements, both DES and DDES can produce more satisfactory results than RANS. RANS can only present the ＂stable＂ flow pat- terns, while the hybrid methods can demonstrate unsteady flow structures. DDES and DES results are little different from one another although the latter exhibits better agreement with the experiment. DES is taken to investigate the 5° BT and three-step afterbodies. The mean flow data and the instantaneous turbulent coherent structures are compared against available measurements.

关键词： Cylindrical Boattailed and three-stepafterbodies DES and DDES Unsteady flow

Target selection and transfer trajectories design for exploring asteroid mission

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Science china(Technological Sciences) 2010年第4期53卷 1150-1158页

作者： CUI PingYuan1,QIAO Dong1,CUI HuTao2 & LUAN EnJie3.1 school of aerospace engineering,{3. institute of Technology,{3. 100081,china 2 Harbin institute of Technology,Harbin 150001,china 3.National Defense Science and Industry Bureau,{3. 100048,china 1. school of aerospace engineering Beijing Institute of Technology Beijing 100081 China2. Harbin Institute of Technology Harbin 150001 China3. National Defense Science and Industry Bureau Beijing 100048 China

Technique of target selection and profiles of transfer trajectory for Chinese asteroid exploring mission are studied systemically.A complete set of approaches to selecting mission targets and designing the transfer trajectory is ***,when selecting a target for mission,some factors regarded as the scientific motivations are ***,when analyzing the accessibility of targets,instead of the classical strategy,the multiple gravity-assist strategy is *** suitable and possible targets,taking into account scientific value and technically feasible,are obtained via selection and *** designing the transfer trajectory for exploring asteroid mission,an approach to selecting gravity-assist celestial body is ***,according to the mission constraints,the trajectory profile with 2-years △V-EGA for exploring asteroid is *** analyzing the trajectory profile,unexpected result that the trajectory would pass by two main-belts asteroids is ***,the original proposal is extended to the multiple flybys *** adds the scientific return for asteroid mission.

关键词： exploring asteroid target selection multiple flybys transfer trajectory

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, {3. institute of Technology, {3., 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 new DNA algorithm to solve graph coloring problem

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Progress in Natural Science:Materials International 2007年第6期17卷 733-738页

作者： Jiang Xingpeng1, Li Yin2, Meng Ya3.and Meng Dazhi2(1. National Laboratory of Pattern Recognition,institute of Automation, Chinese Academy of Sciences, beijing 100080, china 2. College of Applied Sciences, beijing University of Technology, beijing 100022, china 3. school of Science, beijing institute of Technology, beijing 100081, china) National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Beijing 100080 China College of Applied Sciences Beijing University of Technology Beijing 100022 China school of Science Beijing Institute of Technology Beijing 100081 China

Using a small quantity of DNA molecules and little experimental time to solve complex problems successfully is a goal of DNA computing. Some NP-hard problems have been solved by DNA computing with lower time complexity than conventional computing. However, this advantage often brings higher space complexity and needs a large number of DNA encoding molecules. One example is graph coloring problem. Current DNA algorithms need exponentially increasing DNA encoding strands with the growing of problem size. Here we propose a new DNA algorithm of graph coloring problem based on the proof of four-color theorem. This algorithm has good properties of needing a relatively small number of operations in polynomial time and needing a small number of DNA encoding molecules (we need only 6R DNA encoding molecules if the number of regions in a graph is R).

关键词： DNA computing NP-hard problem graph coloring problem.

The precipitation and effect of nano nitrides in HSLC steel

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Science china(Technological Sciences) 2008年第7期51卷 989-998页

作者： FU Jie1, LIU YangChun1,2 & WU HuaJie1,3.1 school of Metallurgical and Ecological engineering, University of Science and Technology beijing, beijing 100083. china 2 Shougang Technology Research institute, Shougang (Group) Corporation, beijing 100041, china 3.Metallurgical engineering Research institute, University of Science and Technology beijing, beijing 100083. china 1. school of Metallurgical and Ecological engineering University of Science and Technology Beijing Beijing 100083 China 2. Shougang Technology Research institute Shougang (Group) Corporation Beijing 100041 China 3. Metallurgical engineering Research institute University of Science and Technology Beijing Beijing 100083 China

The existing forms of N and Al in HSLC (high strength low carbon) steel produced by TSCR (thin slab casting and rolling process), the precipitation thermodynamics and kinetics of AlN, and its effects on structure and mechanical property are studied. The experimental results show that only a small quantity of nitrogen is com- bined into AlN in HSLC steel produced by TSCR and most of the nitrogen in steel is still free nitrogen. Aluminum-nitride is mainly precipitated during the period of slow air cooling after coiling, but not during rolling and water cooling. The acid-soluble aluminum has no obvious effect on the grain size and mechanical property of HSLC steel produced by TSCR whose acid-soluble aluminum content is 0.005%―0.043.. The precipitation of AlN is not the main cause of grain refinement of HSLC steel produced by TSCR, nor is AlN the dominating precipitate that has precipitation strengthening effect. The nano nitrides are not pure AlN, but have complex compositions.

关键词： thin slab casting and rolling high strength low carbon steel AlN nano nitride precipitation strengthening

An efficient chiral synthesis of (R)-N-[3.acetyl-4-(2-hydroxy-3.isopropylamino-propoxy)phenyl]-butanamide with high enantioselectivity

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Science china Chemistry 2009年第8期52卷 1216-1219页

作者： WANG NaiXing1,2 & TANG XinLiang1,3.1 Technical institute of Physics and Chemistry,Chinese Academy of Sciences,beijing 100080,china 2 College of Chemistry and Chemical {3.,Graduate University of Chinese Academy of Sciences,beijing 100049,china 3.school of Chemical {3. and Environment,beijing institute of Technology,beijing 100081,china 1. Technical institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100080 China 2. College of Chemistry and Chemical engineering Graduate University of Chinese Academy of Sciences Beijing 100049 China 3. school of Chemical engineering and Environment Beijing Institute of Technology Beijing 100081 China

R-Enantiomer of the β-receptor antagonist N-[3.acetyl-4-(2-hydroxy-3.isopropylamino-propoxy)phenyl] butanamide with high enantioselectivity was synthesized from cheap starting materials and enantiopure chiral reagent through an efficient,convenient and practical synthetic *** product was detected by 1H NMR,13. NMR,and MS,and the enatiomeric excess was determined by chiral HPLC analysis using a chiracel AD-H column.

关键词： chiral synthesis enantioselectivity enatiomeric excess chiral HPLC analysis