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The mechanism of breakdown in laminar-turbulent transition of a supersonic boundary layer on a flat plate-temporal mode

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Science china(Physics,Mechanics & Astronomy) 2005年第5期48卷 614-625页

作者： HUANG Zhangfeng 1, CAO Wei 1,2.& ZHOU Heng 1,2.1. Department of Mechanics, Tianjin university, Tianjin 300072. china 2. Liu-Hui {2. of Applied Mathematics, Nankai university and Tianjin university, Tianjin 300072. china 1. Department of Mechanics Tianjin University 300072 Tianjin China 2. Liu-Hui center of Applied Mathematics Nankai University and Tianjin University 300072 Tianjin China

Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in laminar-turbulent transition, the mechanism causing the mean flow profile to evolve swiftly from laminar to turbulent was that the modification of mean flow profile by the disturbances,when they became larger,led to a remarkable change of its stability characteristics. Though the most unstable T-S wave was of second mode for laminar flow, the first mode waves played the key role in the breakdown process in laminar-turbulent transition.

关键词： supersonic boundary layer, transition, breakdown.

Lipschitz continuity of best approximations and Chebyshev centers

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Chinese Science Bulletin 1998年第3期43卷 185-188页

作者： LI Chong 1 and WANG Xinghua 2.1. center for Mathematical Sciences, Zhejiang university, Hangzhou 31002.,{2. 2. Department of Mathematics, Hangzhou university, Hangzhou 31002.,{2. center for Mathematical Sciences Zhejiang University Hangzhou China Department of Mathematics Hangzhou University Hangzhou China

The Lipschitz continuity results are given for best approximations and Chebyshev centers. Consequently, the open problem presented by Septycki and Vleck is solved completely.

关键词： best approximation Chebyshev center uniform convexity.

A new parameterization scheme for sea surface aerodynamic roughness

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Progress in Natural Science:materials International 2008年第11期18卷 1365-1373页

作者： Yuping Pan~(a,b) Wenyu Sha~c Shouxian Zhu~c Sufang Ge~(a,*) a nanjing university of Information Science and Technology,nanjing 2.0044,{2. b Air Force Meteorological center of the nanjing Military Region,nanjing 2.0018,{2. c Meteorology College,The PLA university of Information Science and Technology,nanjing 2.1101,{2. nanjing university of Information Science and Technology Nanjing 210044 China Air Force Meteorological center of the nanjing Military Region Nanjing 210018 China Meteorology College The PLA University of Information Science and Technology Nanjing 211101 China

The dimensionless roughness length derived from dimensional analysis bears a relation to wave age,and the dimensionless form of roughness length can be expressed with the relation with a significant wave *** on six experiments(HEXMAX,RASEX,BIO steady platform,Lake Ontario data analysis FETCH,CBLAST low wind),we verified that the Charnock parameter,Zch,and dimension- less roughness length,z0/Hs,are dependent on wave age,u*/***,we constructed a new scheme for roughness length,and explored its sensitivity to friction velocity and wave *** the newly developed parameterization scheme(PS07)with COARE (Coupled Ocean-Atmosphere Response Experiment V.3.0)algorithm,we calculated the data from the North Sea Platform experiment in December,1985,and made an attempt to validate the suitability of the PS07 compared to the other three schemes of *** found that the calculated results based on the PS07 are close to the *** also conducted an experiment in which the PS07 was combined with the nested model of waves coupling in datasets of 3 typhoons that occurred at the Zhanjiang *** comparison results between the calculated and observed waves around the Naozhou Island indicate that the new parameterization scheme(PS07)has a good applicability.

关键词： Sea surface roughness Parameterization scheme Significant wave height Wave age COARE algorithm

Risk analysis model for landslide mass of high slope in dam area

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Science china(Technological Sciences) 2008年第S2期51卷 25-31页

作者： GU ChongShi1,2.HE XianFeng3,4,WU ZhongRu1,2.& SU HuaiZhi1,2.1 College of Water Conservancy and Hydropower Engineering,Hohai university,nanjing 2.0098,{2. 2.National Engineering Research center of Water Resources Efficient Utilization and Engineering Safety,nanjing 2.0098,{2. 3 Yellow River Institute of Hydraulic Research,Zhengzhou 450003,{2. 4 Embankment Security Defect Prevention and Control Engineering Research center of MWR,Zhengzhou 450003,{2. 1. College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China 2. National Engineering Research center of Water Resources Efficient Utilization and Engineering Safety Nanjing 210098 China 3. Yellow River Institute of Hydraulic Research Zhengzhou 450003 China 4. Embankment Security Defect Prevention and Control Engineering Research center of MWR Zhengzhou 450003 China

In order to identify the threat of reservoir bank landslide to dam safety and reduce the risk of dam failure,impact factors of the landslide are *** concept of landslide risk degree is put forward to measure the threat of landslide to dam *** monotony of the landslide risk assessment function which changes with different affecting factors is analyzed *** on gene automatic programming,a data mining model of the landslide risk assessment function is constructed combined with impact factors of reservoir bank landslide on dam *** the assessment function of landslide risk has been excavated and established according to practical project information,which provides a valuable reference for analyzing the impact of landslide on dam risk.

关键词： landslide dam failure risk landslide risk

Seabed Classification Using BP Neural Network Based on GA

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Acta Oceanologica Sinica 2003年第4期22卷 523-531页

作者： Yang Fanlin1, Liu Jingnan2.1. GPS Engineering Research center, Wuhan university, Wuhan 430079,{2.. 2. Presidential Secretariat, Wuhan university, Wuhan 430079,{2. Wuhan Univ GPS Engn Res Ctr Wuhan 430079 Peoples R China

Side scan sonar imaging is one of the advanced methods for seabed study. In order to be utilized in other projects, such as ocean engineering, the image needs to be classified according to the distributions of different classes of seabed materials. In this paper, seabed image is classified according to BP neural network, and. Genetic Algorithm is adopted in train network in this paper. The feature vectors are average intensity, six statistics of texture and two dimensions of fractal. It considers not only the spatial correlation between different pixels, but also the terrain coarseness. The texture is denoted by the statistics of the co-occurrence matrix. Double Blanket algorithm is used to calculate dimension. Because a uniform fractal may not be sufficient to describe a seafloor, two dimensions are calculated respectively by the upper blanket and the lower blanket. However, in sonar image, fractal has directivity, i. e. there are different dimensions in different direction. Dimensions are different in acrosstrack and alongtrack, so the average of four directions is used to solve this problem. Finally, the real data verify the algorithm. In this paper, one hidden layer including six nodes is adopted. The BP network is rapidly and accurately convergent through GA. Correct classification rate is 92.5 % in the result.

关键词： BP network co-occurrence matrix fractal classification genetic algorithin

Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

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Science china(Technological Sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2.& LUO ChengPing2.1 center for High Resolution Electron Microscopy, College of materials Science and Engineering, Hunan {2., Changsha 410082. china 2.College of Mechanical Engineering, South china {2. of Technology, Guangzhou 510641, china 1. center for High Resolution Electron Microscopy College of Materials Science and Engineering Hunan University Changsha 410082 China 2. College of Mechanical Engineering South China University of Technology Guangzhou 510641 China

The microstructure of composite diffusion layer of the nitrided and chromized 0.2. carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-S relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the γN and the α-matrix deviate from the accurate K-S OR, and the OR between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 2., nitriding, composite chromizing

A method of constructing a database-free optimal dynamical system and a global optimal dynamical system

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Science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 905-915页

作者： WU ChuiJie1? & WANG Liang2.1 State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian university of Technology, Dalian 11602., china 2.Research {2. for Fluid Dynamics, School of Science, PLA university of Science and Technology, nanjing 2.1101, china 1. State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China 2. Research center for Fluid Dynamics School of Science PLA University of Science and Technology Nanjing 211101 China

In this paper, to overcome the drawbacks of POT which minimize the reminder, not only the optimal functional with minimal residual is put forward, but also the method of global optimization is used. Under the condition of large reminder, the optimal bases can also be obtained through the method of POTres without the approaching of initial conditions. In addition, compared with local optimization, the advantage of global optimization is remarkable. On the one hand, we can expect that the dynamical system based on the global optimal bases will include more information than the ones based on the local optimal bases, since the global optimal bases are much more precise than the local optimal bases. On the other hand, from the point of view of error, the global optimal bases are independent of the choice of the object functional and the initial bases.

关键词： dynamical system residual global optimization

Sm-Nd isotopic ages of Tiqiushan eclogites in Xinyi region and its geological significance

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Chinese Science Bulletin 1999年第S2期44卷 144-146页

作者： WANG Yinxi~(1,2., YANG Jiedong~(1,2., TAO Xiancong~(1,2., GE Ningjie~4, CHEN Peirong~3, FAN Chunfang~3 and LI Jianhua~5 1. center of Modern Analysis, nanjing university,{2., china 2. State Key Laboratory for Research of Mineral Deposits, nanjing university,{2., china 3. Department of Earth Science, nanjing university,{2., china 4. Department of Earth and Space Sciences, university of Science and Technology of Chian, Hefei 2.002., china 5. No.5 Geological Party of Jiangsu Province, Xuzhou 2.1005, china center of Modern Analysis Nanjing University Nanjing 210093 China State Key Laboratory for Research of Mineral Deposits Nanjing University Nanjing 210093 China Department of Earth and Space Sciences University of Science and Technology of Chian Hefei 230026 China Department of Earth Science Nanjing University Nanjing 210093 China No. 5 Geological Party of Jiangsu Province Xuzhou 221005 China

GEOLOGICAL scientists have paid much attention to the suture zones formed by collision between the Sino-Korean and Yangtze blocks because of the discovery of the ultrahigh pressue metamorphic (UHPM) rocksfrom northern Jiangsu Province (Su), southern Shandong Province (Lu) and the Dabie *** the age of 2.0-2.0 Ma is probably the best estimation for UHPM metamorphism in the DabieMountains, the primary intrusive and metamorphic ages of the complex from northern Jiangsu Provincehave not been determined before. Using the Sm-Nd isotopic dating method, our study is aimed at datingthe UHPM metanorphic event of northern Jiangsu Province and researching a probable relation between theUHPM rocks from the Dabie Mountains and the UHPM rocks from northern Jiangsu Province.

关键词： northern Jiangsu eclogite rocks Sm-Nd isotopic ages.

The correlation of multi-angle thermal infrared data and the choice of optimal view angles

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Science china Earth Sciences 2004年第6期47卷 570-576页

作者： FAN Wenjie1 & XU Xiru1,2.1.Institute of Remote Sensing and GIS of Peking university,Beijing 100871,china {2. of Remote Sensing and GIS of Beijing Normal university,Beijing 100875,china 1. Institute of Remote Sensing and GIS of Peking university 100871 Beijing China 2. center of Remote Sensing and GIS of Beijing Normal university 100875 Beijing China

Based on the matrix formula of thermal infrared radiant system, the components temperature can be retrieved by the inversive matrix. Around the stability problem of retrieved result, the research work we did was focused on (i) the correlation of (wk,j) which is the key to affect the retrieval accuracy, (ii) a general method which can help us find the number of retrievable parameters and evaluate the retrieval error before its performance, (iii) the choice of “optimal viewing angle group” based on the formula of absolute error propagation. The row winter wheat field was chosen as an example. The results can provide a theoretical basis for multi-angle thermal infrared remote sensing and components temperature retrieval.

关键词： components temperature retrieval, correlation, number of retrievable parameters, optimal viewing angle group.