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Sediment transp.r. capacity of hyp.r.oncentrated flow

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Science China(physics,mechanics & Astronomy) 2008年第8期51卷 961-975页

作者： SHU Anping1,2.& FEI XiangJun2.1 School of Environment & key laboratory of Water and Sediment Sciences,{2. of education,beijing Normal university,beijing 100875,China 2.State key laboratory of Hydroscience and Engineering,Tsinghua university,beijing 100084,China School of Environment & key laboratory of Water and Sediment Sciences Ministry of Education Beijing Normal University Beijing 100875 China State key laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China

As one of the most imp.r.ant components of river mechanics,sediment transp.r. capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transp.r. capacity was achieved. Using 115 runs of flume exp.r.mental data,which were obtained through two kinds of sediment transp.r. exp.r.ments in the state of equilibrium,in combination with the basic rheological and sediment transp.r.ing characteristics of hyp.r.oncentrated flow,the main p.r.meters in the structural expression of sediment transp.r. capacity were calibrated,and a new formula of sediment transp.r. capacity for hyp.r.oncentrated flow was developed. A large amount of field data from the Yellow river,Wuding river,and Yangtze river,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

关键词： hyp.r.oncentrated flow turbulent energy equilibrium efficiency coefficient sediment transp.r. capacity

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Inter-phase selective corrosion of γ-TiAl alloy in molten salt environment at high temp.r.ture

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progress in Natural Science:Materials International 2011年第4期21卷 322-329页

作者： Wen-yue ZHAO,Bo-wen XU,Yue MA,Sheng-kai GONG key laboratory of Aerospace Materials and {2.ormance(ministry of education), School of Materials Science and Engineering,beihang university,beijing 100191,China key laboratory of Aerospace Materials and {2.ormance (ministry of education) School of Materials Science and Engineering Beihang University Beijing 100191 China

Hot corrosion behavior of Ti-48Al-2.r-2.b alloy in molten salt environment of 75%Na2.O4and 2.%NaCl(mass fraction) at 800℃was studied using oxidation kinetics analysis,scanning electron microscopy,X-ray energy disp.r.ive and X-ray diffraction *** inter-phase selective corrosion,which caused the corrosion pits initiated from lamellar interfaces and the preferential corrosion ofα2.hases,was observed during the hot corrosion of the *** common controls of thermodynamic and kinetics in corrosion reactions with fluxing and active oxidation process were considered the essential hot corrosion mechanisms of the ***,lamellar refinement was proved to be an effective way to mitigate the inter-phase selective corrosion of the alloy in molten salts.

关键词： hot corrosion TiAl-based alloy inter-phase selective corrosion molten salts

Displacement residual based DDM matching algorithm

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Science China(Information Sciences) 2012年第9期55卷 2090-2101页

作者： ZHANG Lin 1,2.ZHOU Zhong 1,2.LIU Lin 1,2.& WU Wei 1,2.1 State key laboratory of Virtual reality Technology and Systems,{2.,beijing 100191,China 2.School of Computer Science and Engineering,{2.,beijing 100191,China 1. State key laboratory of Virtual reality Technology and Systems Beihang University Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

High level architecture(HLA) is the prevailing standard for modeling and *** data distribution management(DDM) service of HLA is defined for reducing the delivery of irrelevant *** key in DDM implementation is the region overlap computation,*** matching between update and subscription *** algorithms usually make a compromise between region fidelity and network *** pap.r.takes both the matching algorithm efficiency and bandwidth cost into *** main contributions are:1) illustrating the relationship between region changes and overlap changes,as helps reduce the number of region matching and then improves the total matching efficiency;2. classifying region updates into two types of data expression,snapshot and *** network traffic will be reduced by transmitting only residual data instead of full region representations ***,a region matching algorithm called displacement residual-based DDM matching(DrBM) is proposed in the *** analysis,algorithm implementation and exp.r.ment evaluation are *** results show that DrBM provides better matching p.r.ormance and significant network payload reductions especially when there is a large number of changing regions.

关键词： distributed simulation high level architecture data distribution management region snapshot region residual

Kinematics and dynamics of the Mesozoic orogeny and late-orogenic extensional collapse in the Sino-Mongolian border areas

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Science China Earth Sciences 2005年第7期48卷 849-862页

作者： ZHENG Yadong 1 & WANG Tao2.1. key laboratory of Orogenic Belts and Crustal Evolution (peking {2.), ministry of education, beijing 100871, China 2. Institute of Geology, Chinese Academy of Geological Sciences, beijing 100037, China key laboratory of Orogenic Belts and Crustal Evolution (peking {2.) Ministry of Education Beijing 100871 China Institute of Geology Chinese Academy of Geological Sciences Beijinq 100037 China

The Sino-Mongolian border areas underwent two imp.r.ant tectonic events during Mesozoic time after late paleozoic orogeny: a late Triassic to earlier Jurassic contractional event that resulted in a large-scale south-vergent thrust during the orogeny and a late Jurassic-earlier Cretaceous extensional event in a north-south direction that formed a metamorphic core complex. The kinematic and dynamic analyses show that the thrust sheet moved southwards with a kinematic vorticity number of ca. -0.10 and sub-horizontal maximum compressive stress axis that belongs to a contraction-thickening shear. The upp.r.plate of the late-orogenic detachment relatively moved in a 165°direction. The average kinematic vorticity in its earlier stage was 0.74 that belongs to simple shear dominated shearing and related to the maximum compressive stress axes dipping at ～66°, while the later average kinematic vorticity was ～0.55°that belongs to p.r. shear dominated shearing with sub-vertical maximum compressive stress axes. This suggests that the thrusting led to the crust thickened and the lower plate rocks that were originally located in the upp.r.crust depressed through a brittle-ductile transition zone into the lower crust and became warmer. The heated rocks trended to uplift since their increasing volume and decreasing density while the loading of the upp.r.plate rocks increased due to the structural thickening. Under the combined effect of the loading and the thermal-uplifting, the ductile shear zone in between increased in its component of vertical p.r. shear. Once its p.r.-shear component exceeded its simple-shear one the ductile shear zone became an extension-thinned shear zone. This progressive transitional process reflects internal and essential temp.r.l and spatial relationships: the extensional factor nucleated during the crust thickening by thrusting and increase of the extensional factor finally led to late-orogenic collapse.

关键词： Mesozoic thrusting,late-orogenic collapse,kinematic vorticity number,stress state.

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Node ordinal encoded genetic algorithm for the optimal allocation of water resources

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progress in Natural Science:Materials International 2005年第5期15卷 448-452页

作者： YANG Xiaohua1*, YANG Zhifeng 1,2. SHEN Zhenyao1 and LI Jianqiang3(1. State key laboratory of Water Environment Simulation, School of Environment, {2. Normal university, {2. 100875, China 2. key laboratory for Water and Sediment Sciences ministry of education, School of Environment, {2. Normal university, {2. 100875, China 3. Water resources and Hydropower planning and Design General Institute, MWr, {2. 100011, China) State key laboratory of Water Environment Simulation School of Environment Beijing Normal University Beijing 100875 China key laboratory for Water and Sediment Sciences {2. of education School of Environment Beijing Normal University Beijing 100875 China Water resources and Hydropower planning and Design General Institute MWR Beijing 100011 China

A new method, node ordinal encoded genetic algorithm (NOEGA), is proposed for solving water resources optimal allocation problems, in which the capacity of water resources is split into a number of smaller p.r.s so that successive op.r.tions can be overlapped. Our objective is to maximize the whole benefit function. To overcome the “dimensionality and algorithm complexity curse” while searching for solutions and looking for an optimal solution, the op.r.tions of one-point crossover op.r.tor, gene exchange op.r.tor, gene random op.r.tor, gene shift op.r.tor and node ordinal strings are established. It is proved to be an effective optimal method in searching for global solutions. The NOEGA does not need a diversity of initial population, and it does not have the problem of immature convergence. The results of two cases show that using NOEGA to solve the optimal allocation model is very efficient and robust. In addition, the algorithm complexity of NOEGA is discussed.

关键词： water resources optimal allocation node ordinal code genetic algorithm.

Optimization design study of low-reynolds-number high-lift airfoils for the high-efficiency propeller of low-dynamic vehicles in stratosphere

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Science China(Technological Sciences) 2010年第10期53卷 2792-2807页

作者： MA rong1, ZHONG BoWen2.& LIU peiQing1 1 key laboratory of {2. mechanics, ministry of education, Institute of {2. mechanics, School of Aeronautical Science and Engineering, beijing university of Aeronautics and Astronautics, beijing 100191, China 2.Dep.r.ment of Aerospace Science, School of Engineering, Cranfield university, MK43 0AL, United Kingdom 1. key laboratory of {2. mechanics Ministry of Education Institute of Fluid Mechanics School of Aeronautical Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China2. Department of Aerospace Science School of Engineering Cranfield University MK43 0AL Cranfield UK

Aerodynamic p.r.ormance of low-reynolds-number high-lift airfoil makes a great impact on designing a high-efficiency propeller for low-dynamic vehicles in stratosphere. At high altitude,low-reynolds-number airfoils are supposed to have high lift-drag ratio or high endurance factor at cruising attack angle along with good stall characteristics. To design such a high-p.r.ormance low-reynolds-number high-lift airfoil,the pap.r.established a hierarchical multi-objective optimization platform by combing direct search optimization algorithm EXTrEM and airfoil flow field solver XFOIL to automatically and quickly calculate aerodynamic p.r.ormance function of airfoil by computer. It provides an effective solution to multi-point design problem of low-speed low-reynolds-number airfoil. It can be seen from the results of three typical optimization examples,the new airfoil E387_OpT2.FX63-137_OpT2.and S12.3_OpT2.based on hot low-reynolds-number high-lift airfoils (Eppler 387 airfoil,Wortmann FX63-137 airfoil and S12.3 airfoil) can meet the optimization design requirements and have very good aerodynamic characteristics in both design state and non-design state. Thus,the applicability and effectiveness of hierarchical multi-objective optimization platform are verified.

关键词： multi-objective optimization low reynolds number airfoil EXTrEM hierarchical multi-objective optimization

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Gray physical interference model based link scheduling algorithms

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Science China(Information Sciences) 2012年第6期55卷 1337-1350页

作者： SU JinZhao 1,2.CAO Jing 1,2.& WU Wei 1,2.1 State key laboratory of Virtual reality and Systems,{2.,China 2.School of Computer Science and Engineering,beihang university,{2.,China 1. State key laboratory of Virtual reality and Systems Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

To improve the concurrent data transmission capability of wireless multi-hop networks,this pap.r.proposes adopting a gray physical interference model instead of using the threshold physical interference *** model allows non-ideal links to be involved in scheduling,under the premise of not affecting the quality of existing transmission *** addition,we design two greedy algorithms to schedule more links with SINr values located in the transition *** results show that a gray physical interference model is more accurate than a threshold physical interference one,the concurrent transmission capability of a network based on the gray physical interference model is significantly increased,and network throughput is increased by 2.%.

关键词： gray physical interference model threshold physical interference model link scheduling concurrent transmission TDMA

Edaphic factors determining variation of two ecotypes of Leymus chinensis in North China

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progress in Natural Science:Materials International 2006年第11期16卷 1150-1155页

作者： ZHOU Chan~1 and YANG Yunfei~2.*(1. MOE key laboratory of Environmental Change and Natural Disasters, College of resources Science and Technology, {2. Normal university, {2. 100875, China 2. key laboratory of Vegetation Ecology, ministry of education, Institute of Grassland Science, Northeast Normal university, Changchun 13002., China) [a]MOE key laboratory of Environmental Change and Natural Disasters College of Resources Science and Technology Beijing Normal University Beijing China [b]key laboratory of Vegetation Ecology Ministry of Education Institute of Grassland Science Northeast Normal University Changchun China

To identify ecotypic variation of L. chinensis, the physiological characteristics and environmental factors were measured and assessed for grey-green and yellow-green ecotypes of L. chinensis grown in the salt-alkalized and aeolian sandy soils. Although both ecotypes presented a similar salt-alkaline tolerance under the exp.r.mental conditions, they differed in several aspects. The L. chinensis grown in the aeolian sandy soils had higher water potential and chlorophyll content and lower proline content in their leaves than those grown in the salt-alkalized habitat, and the grey-green ecotype of L. chinensis in both types of soils had higher water potential, chlorophyll and proline contents than the yellow-green ecotype. Besides, grey-green ecotypes had higher salt-alkaline tolerance than the yellow-green ecotype. The stepwise regression analysis showed that soil conductance and pH value were the main ecological factors affecting the physiology of L. chinensis. From the natural distribution of the two ecotypes, we considered that salt-alkaline in the soils is the leading factor in determining ecotypic variation of L. chinensis. The two ecotypes were first named grey-green and yellow-green ecotypes respectively.

关键词： L.chinensis ecotype adaptability variation ecological factor salt-alkaline in soil.

Logical verification of scientific discovery

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Science China(Information Sciences) 2010年第4期53卷 677-684页

作者： LI Wei State key laboratory of Software Development Environment, School of Computer Science and Engineering, {2., beijing 100191, China 1. State key laboratory of Software Development Environment School of Computer Science and Engineering Beihang University Beijing 100191 China

This pap.r.shows that the discovery processes of Einstein’s special theory of relativity and Darwin’s theory of evolution of species can be formally verified by r-calculus which is a logical inference system. The aim of r-calculus is to delete the principles of scientific theories which contradict emp.r.cal evidence. The pap.r.shows that the special theory of relativity is the only and correct choice for physics to meet the exp.r.mental evidence given at the time. As far as the biology of Darwin’s time is concerned, however, the r-calculus has derived three logically correct but different theories, which are all consistent with the emp.r.cal evidence provided by Darwin and his principle of natural selection. Darwin’s theory of evolution matches one of the three theories derived by r-calculus. This theory has a logical consequence that is "each species has been independently created is erroneous". But the other two theories supp.r. the negation of the above statement. The existence of the other two theories may be a reason of the controversies over Darwin’s theory.

关键词： r-calculus theory of relativity theory of evolution