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The Degree of Symmetry of Certain Compact Smooth Manifolds II

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Chinese Annals of Mathematics,Series B 2007年第2期28卷 195-204页

作者： Bin XU department of Mathematics, University of Science and Technology of china, Hefei 230026, china Chern institute of Mathematics, Nankai University, tianjin 300071, china department of Mathematics, Johns Hopkins University, Baltimore, MD 21218, USA. department of Mathematics University of Science and Technology of ChinaHefei 230026 China

We give the sharp estimates for the degree of symmetry and the semi-simple degree of symmetry of certain compact fiber bundles with non-trivial four dimensional fibers in the sense of cobordism, by virtue of the rigidity theorem of harmonic maps due to Schoen and Yau (Topology, 18, 1979, 361-380). As a corollary of this estimate, we compute the degree of symmetry and the semi-simple degree of symmetry of CP2×V, where V is a closed smooth manifold admitting a real analytic Riemannian metric of non-positive curvature. In addition, by the Albanese map, we obtain the sharp estimate of the degree of symmetry of a compact smooth manifold with some restrictions on its one dimensional cohomology.

关键词： Degree of symmetry Fiber bundle Cobordism Non-positive Curvature Harmonic map First cohomology

Experimental Research on the Erosion Pattern and Protection Using the Extended Modelling Method

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china Ocean Engineering 1997年第4期12卷 441-448页

作者： Liu Shunkuan Senior Engineer, tianjin Port Engineering institute, tianjin 300222 tianjin Port Engineering institute Tianjin 300222 China

In the paper the extended modelling method with serial sands is used in an experimental research on the erosion patterns at the discharge outlet of a beach Hua-Neng power plant. The theoretical basis for the extended modelling method with serial sands is systematically presented in the paper and the method has been successfully employed in the sediment experiment of coastal works. According to the Froude Law, the model is designed to be a normal one with movable bed, the geometric scale lambda(L) = lambda(H) = 15, and three scales of sediment grain size are chosen, i.e., lambda(d1) = 0.207; lambda(d2) = 0.393; and lambda(d3) = 0.656. The median particle diameter of sea beach prototype sand d(50p) = 0.059 mm and the dis-changed water flow of the power plant is 21.7 m(3) / s. Three types of natural sea sands have been chosen as the serial modelling sands to extend the simulation of the prototype, thus replacing the conventional test in which artificial lightweight sands are used. As a result, this method can not only reduce the cost significantly, but also it is an advanced technique easy to use. Upon a series of tests, satisfactory results have been obtained.

关键词： extended modelling method discharge outlet erosion pattern beach protection

The species diversity of fusulinaceans and high-frequency sea-level changes in the Carboniferous-Permian boundary section at Xikou, Zhen'an County,Shaanxi Province, china

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Science china Earth Sciences 2006年第7期49卷 673-683页

作者： ZHANG Haijun1, WANG Xunlian2, DING Lin1, XIA Guoying3 & WANG Lei2 1. institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, china 2. Faculty of Earth Sciences and Mineral Resources, china University of Geosciences, Beijing 100083, china 3. tianjin institute of Geology and Mineral Resources, tianjin 300170, china 1. institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China 2. Faculty of Earth Sciences and Mineral Resources China University of Geosciences Beijing 100083 China 3. tianjin institute of Geology and Mineral Resources Tianjin 300170 China

The study on the interrelation between sea-level changes and biodiversity with its evolu-tion has great significance for understanding the impact of global changes on organic evolution and exploring the inherent laws of life-environment coevolution in geological history. In this paper, the stratigraphic distribution of fusulinacean fauna in the Carboniferous-Permian boundary section at Xikou, Zhen’an County, Shaanxi Province, is analyzed quantitatively, and the relationship between the species diversity of fusulinaceans and relative sea-level changes is discussed. As a whole, the spe-cies numbers of fusulinacean fauna experience a rapid increase and an obvious decline in Xikou, Zhen’an County, from the Late Carboniferous to the Early Permian. There is a significant increase in species diversity around the Carboniferous-Permian boundary, which is one of the biggest bio-events of the fusulinacean fauna, and represents the radiation of Pseudoschwagerininae subfamily in the studied area. Integrated fusulinacean species diversity into sequence stratigraphic framework, de-tailed study suggests that the species diversity of the fusulinaceans is closely related to its relative stratigraphic location, and is essentially controlled by the sea-level changes, especially by the high-frequency sea-level changes. Generally, the species diversity of fusulinaceans is low, and the number of first and last appearance datum is small in the lower unit of high-frequency depositional cycle formed during the quick rise of the sea level; whereas the species diversity of fusulinaceans is high, and the number of first and last appearance datum is large in the upper unit of high-frequency cycle formed during the slow fall of the sea level. Within the third-order depositional sequence, the species diversity of the fusulinaceans at the first flooding surfaces and the maximum flooding surfaces is low, and it increases upward. The fusulinacean species diversity is low within the transgressive syst

关键词： fusulinaceans, species diversity, high-frequency cyclothem, sequence stratigraphy, sea-level changes, Carboniferous-Permian boundary, Zhen'an, Shaanxi.

Study on Potassium Fluoaluminate Eutectic Flux

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Transactions of tianjin University 2004年第3期10卷 184-186页

作者：张韻慧尹淑梅肖莉李宁张则甡 College of Pharmaceuticals and Biotechnology Tianjin University Tianjin 300072 China School of Materials Science and Engineering Tianjin University Tianjin 300072 China tianjin Welding Research institute Tianjin 300110 China

In this study, Nocolok eutectic flux,used widely in the process of the brazing of aluminum and its alloy, was prepared by the reaction between Al(OH) 3/KOH resolution and HF. A series of KF-AlF 3 eutectic productions at various reaction temperatures were prepared. The melting points of the products were measured by differential thermal analysis (DTA), and the composites were characterized by X-ray diffraction (XRD). The results suggest that the temperature control is important to produce an ideal flux consisting of K 2AlF 5, H 2O and KAlF 4, with a low melting point of 560 ℃,which is suitable for the brazing of aluminum and its alloy as the aluminum fluxes.

关键词： potassium fluoaluminate eutectic flux differential thermal analysis X-ray diffraction

System Analysis Applying to Talent Resource Development Research

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Journal of Systems Science and Systems Engineering 2001年第3期13卷 381-384页

作者： WANG Peng-tao, ZHENG Gang department of Computer Science, tianjin institute of Technology, tianjin 300191, china department of Computer Science Tianjin Institute of Technology Tianjin 300191 China

In the development research of talent resource, the most important of talent resource forecast and optimization is the structure of talent resource, requirement number and talent quality. The article establish factor reconstruction analysis forecast and talent quality model on the method: system reconstruction analysis and ensure most effective factor level in system, which is presented by ***, ***. And performing dynamic analysis of example ration.

关键词： reconstruction analysis requirement number talent quality

Emission Performance of Motorcycles in Real-Road Conditions

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Transactions of tianjin University 2007年第5期13卷 322-327页

作者：杜青刘欣尹君尹涛赵杰郭津 Internal Combustion Engine Research institute Tianjin University

WMTC,which means a worldwide motorcycle testing cycle,is now regarded as the most possible choice for the global motorcycle emission testing cycle,but whether or not it can be used in china is still *** this study,a large number of data on the speed-time trace of motorcycles were sampled from various kinds of roads in 5 cities in *** on a series of criterion numbers defined,the driving character of motorcycles in the real-road conditions of china was *** the aid of a specially designed program,an emission testing cycle that can indicate the driving characteristics of motorcycle in the real-road conditions was synthesized,and the exhaust emission tests of 20 motorcycles under the synchronized cycle and WMTC were carried out based on a CVS system and a motorcycle chassis *** results show that although there do exist differences in some criterion numbers between the real-road condition and WMTC,such as proportion of idling mode,mean speed,mean running speed and the average acceleration and deceleration rates,the driving behaviors are *** results of exhaust emission tests indicate that the emission values of motorcycles under the synchronized cycle and WMTC have a relatively strong *** means that WMTC can be introduced as a standard motorcycle emission test regulation into china.

关键词： driving character of motorcycles synthesized emission testing cycle emission perfor- mance in real-road condition WMTC

Effect of Sn^(4+) B-Site Substitution on the Microstructure and Dielectric Properties of Ba(Mg_(1/3)Ta_(2/3))O_3 Microwave Ceramics

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Journal of Materials Science & Technology 2005年第5期21卷 773-775页

作者： Shunhua WU Guoqing WANG, Shuang WANG and Dandan LIUinstitute of Electronics and Information Engineering, tianjin University, tianjin 300072, china institute of Electronics and Information Engineering Tianjin University Tianjin 300072 China

The effect of Sn^4＋（BaSnO3） B-site substitution on the microstructure and dielectric properties of Ba（Mg1/3Ta2/3）O3 microwave ceramics was investigated. X-ray diffraction shows that a complex perovskite material Ba（Mg1/3Ta2/3）O3 was prepared. As Sn^4＋ content x increases in the （1-x） Ba（Mg1/3Ta2/3）O3-xBaSnO3 （x=0.00～0.20） system, the dielectric constant generally keeps unchanged, while TCF changes from positive to negative. Although the addition of Sn^4＋ reduces the ordering degree, Q f0 is still increased when the ceramics density increases. This trend implies that Q f0 of this system is mostly determined by ceramics density rather than ordering degree. After sintering at 1500℃ for 3 h, the system with x=0.15 was found to have excellent dielectric properties as follows：ε≈25, Q f0≥300,000 GHz at 7 GHz, TCF=-0.6×10^-6/℃.

关键词： Ba(Mg1/3Ta2/3)O3 Complex perovskite Microwave Dielectric properties

Numerical Model of Storm Surge and Inundation in Bohai Bay

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Transactions of tianjin University 2011年第1期17卷 57-61页

作者：李大鸣付庆军解以扬白玲 Key Laboratory of Harbor and Ocean Engineering of Ministry of Education of china School of Civil Engineering Tianjin University department of Civil and Environmental Engineering University of Houston institute of tianjin Meteorological Bureau

A two-dimensional numerical model of extratropical storm surge and inundation in Bohai Bay was built based on the unsteady flow Navier-Stokes equations. The model included two sections, one was for the simulation of storm surge tidal level and the other for the simulation of storm surge inundation in the coastal area. While simulating the storm surge tidal level, the alternating direction implicit (ADI) method was applied to dispersing and solving 2D storm surge equations. In the simulation of storm surge inundation, the 2D unsteady flow equations were dispersed and solved using the structureless grids of finite volume method (FVM). A coupling calculation mode of the process of inundation and storm surge tidal level variation was proposed, therefore the storm surge inundation process and area could be calculated while simulating and forecasting the process of storm surge tidal setup. Furthermore, an extratropical storm surge and inundation in Bohai Bay were simulated using this numerical model. Simulation results are in good agreement with the measured data, which shows that this numerical model provides a new method of simulating and forecasting storm surge and inundation in Bohai Bay.

关键词： extratropical storm surge inundation ADI method structureless grid

Experimental study on high-voltage solar array sustained arc discharge induced by high charging

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Science china(Technological Sciences) 2007年第2期50卷 213-220页

作者： LI Kai1,2, XIE ErQing1, WANG Li2, LIU YanXia1, YANG Yang1, SUN YanZheng3, CUI XinYu3 & MAI ShengLi2 1 School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, china 2 Lanzhou institute of Physics, Lanzhou 730000, china 3 tianjin institute of Power Source, tianjin 300381, china 1. School of Physical Science and Technology Lanzhou University Lanzhou 730000 China 2. Lanzhou institute of Physics Lanzhou 730000 China 3. tianjin institute of Power Source Tianjin 300381 China

It has been reported that sustained arc discharge induced by electrostatic discharge (ESD) could cause permanent damage to high-power and high-voltage solar array of spacecrafts. The paper focuses on ESD simulating experiments on Si and GaAs samples, and induces sustained arc discharge. The physical mechanism of sustained arc discharge is discussed by comparing the charging/discharging phenomena between Si and GaAs samples. The experiments show that sustained arc discharge can produce a permanent short-circuit channel between solar cell strings through which the solar array’s photovoltaic power may flow out sustainedly. The analyses show that sustained arc discharge strongly depends on solar array structure, solar array operating voltage, ESD characteristics and cell materials. Keywords high-voltage solar array - electrostatic discharge - sustained arc discharge - mechanism Supported by the National Laboratory of Vacuum, Cryogenics Technology and Physics (Grant No. 51475030504DZ2801), and the National High Technology Development Program of china (Grant No. 2002AA732158)

关键词： high-voltage solar array electrostatic discharge sustained arc discharge mechanism