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Journal of Materials Science & Technology 2001年第6期17卷 610-614页

作者： Wenzhen LI and Baicheng LIU Department of Mechanical Engineering, Tsinghua University, beijing 100084, China Jiarong LI beijing Institute of Aeronautical Materials, beijing 100095, China [Manuscri Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroids graphite cast iron castings were discussed. Finally, two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

关键词： Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation Graphite Simulation Cast

Key Parameters and Conceptual Configuration of Unmanned Combat Aerial Vehicle Concept

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Chinese Journal of Aeronautics 2009年第4期22卷 393-400页

作者： Wang Ganglin Faculty 513,School of Aeronautic Science and Engineering,beijing University of Aeronautics and Astronautics,beijing 100191,China Faculty 513 School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

The nature and characteristics of attack unmanned combat aerial vehicle （UCAV） are analyzed. The principles of selecting takeoff thrust-weight ratio and takeoff weight of attack UCAV are presented by analyzing the statistical data of weights for various main combat aircraft. The UCAV airborne weapons are analyzed, followed by the preliminary estimation of the payload weight. Various typical engines are analyzed and one of them is selected. Then the takeoff weight of the UCAV is determined. Based on some basic parameters and assumptions, the qualitative decomposition calculation for takeoff weight is completed. The key factors for obtaining longer endurance of aircraft with small aspect ratio configuration are found to be high lift-drag ratio and internal space. On the basis of the conclusions mentioned above, a highly blended flying-wing plus lifting body concept is proposed. According to this concept, the UCAV configuration is designed and optimized. Finally, the UCAV configuration with small aspect ratio, high lift-drag ratio, and high stealth characteristic is obtained.

关键词： aircraft design unmanned aerial vehicles unmanned combat aerial vehicles conceptual design aerodynamicsstealth

Eigenvalues, inequalities and ergodic theory

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Chinese Science Bulletin 2000年第9期45卷 769-774页

作者： CHEN MufaDepartment of Mathematics, beijing Normal University, beijing 100875, China Department of Mathematics Beijing Normal University Beijing China

This paper surveys the main results obtained during the period 1992-1999 on three aspects mentioned in the title. The first result is a new and general variational formula for the lower bound of spectral gap (i.e. the first non-trivial eigenvalue) of elliptic operators in Euclidean space, Laplacian on Riemannian manifolds or Markov chains (?). Here, a probabilistic method -coupling method is adopted. The new formula is a dual of the classical variational formula. The last formula is actually equivalent to Poincare inequality. To which, there are closely related logarithmic Sobolev inequality, Nash inequality, Liggett inequality and so on. These inequalities are treated in a unified way by using Cheeger’s method which comes from Riemannian geometry. This consists of ?2. The results on these two aspects are mainly completed by the author joint with F. Y. Wang. Furthermore, a diagram of the inequalities and the traditional three types of ergodicity is presented (?3). The diagram extends the ergodic

关键词： eigenvalue inequality ergodic theory Markov process.

NEW APPROACH TO THE LIMITER FUNCTIONS

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Journal of Computational Mathematics 1999年第1期17卷 41-58页

作者： Jin Li Ze-min Chen Zi-qiang Zhu(beijing University of Aeronautics and Astronautics, beijing 100083, China) 北京航空航天大学北京

In this paper we discuss three topics on the designing of the limiter functions. (1) To guarantee the TVD property (2) To maintain enough artificial viscosity. (3) A method to form TVB limiter which can ensure second ... 详细信息

关键词： finite difference methods TVD schemes limiter function

Study on Process Parameters of Vacuum Differential Pressure Casting

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稀有金属材料与工程 2011年第S3期40卷 237-240页

作者： You Long, Wang Zidong University of Science and Technology beijing, beijing 100083, China Univ Sci & Technol beijing Sch Mat & Engineer Beijing 100083 Peoples R China

Vacuum differential pressure casting has advantages of smelting in vacuum, filling steadily, solidifying under high pressure. Process parameters of filling and solidification are important to the final castings’ forming properties, the parameters include vacuum degree, gas flow, filling velocity, filling pressure, rising pressure velocity, holding pressure and keeping pressure time. By casting copper alloy impeller, we calculated and deduced the gas flow, filling velocity, filling pressure, rising pressure velocity, holding pressure, and measured the keeping pressure time during experiment. Ultimately we convinced these parameters through experiment and successfully produced the impeller.

关键词： vacuum differential pressure casting copper alloy process parameters

Cutting Performance and Mechanism of RE Carbide Tools

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Rare Metals 2001年第3期20卷 197-201页

作者： Jianbing Cheng, Yufang Wu, Qixun Yu 1) Department of Mechanical Engineering, beijing Technology and Business University, beijing 100037, China 2) College of Mechanical Engineering and Automation, beijing Institute of Technology beijing 100081, China 北京工商大学北京 100037 北京理工大学北京 100081

The research of rare earth elements (RE), added into cemented carbide tools, is one of the recent developments of new types of tool materials in China. Systematic experiments about RE carbides YG8R. (K30), YT14R (P20) and, YW1R (M10) were made to study on the cutting performance in comparison with non-RE carbides YG8, YT14 and YW1. The cutting experiments were as follows: tool life, cutting force, tool-chip friction coefficient and interrupted machining. The action of RE on the carbide materials and the cutting mechanism of the RE carbide tools in the cutting process were verified with the aid of SEM and energy spectrum analysis. Experimental results show that the RE carbide tools have a good overall performance.

关键词： rare earth elements cemented carbide tool cutting performance cutting mechanism

Relativist ic Corrections to the Thermal Sunyaev-Zel'dovich Power Spectrum

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Chinese Journal of Astronomy and Astrophysics 2003年第5期3卷 410-414页

作者： Hai-Ning LiNational Astronomical Observatories, Chinese Academy of Sciences, beijing 100012 lhnDepartment of Astronomy, beijing Normal University, beijing 100875 National Astronomical Observatories CAS NAOC Beijing 100012 China Department of Astronomy Beijing Normal University Beijing 100875

We present a quantitative estimate of the relativistic corrections to thethermal SZ power spectrum produced by the energetic electrons in massive clusters. The correctionsare well within 10% for current experiments with working frequencies below ν 350 GHz. Moreover, the corrections appear to be slightlysmaller at higher l or smaller angular scales. We conclude that there is no need to include therelativistic corrections in the theoretical study of the SZ power spectrum especially at lowfrequencies unless the SZ power spectrum is used for precision cosmology.

关键词： cosmic microwave background cosmology: theory galaxies: clusters: general

ELECTROPLATING　OF　AMORPHOUS　Al－Mn　ALLOYS　（I） KINETIC　FEATURES　OF　ELECTRODEPOSITION　OF　PURE　Al

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中国有色金属学会会刊：英文版 1996年第4期6卷 35-37页

作者： Zhao Guangwen Zhu Teng Liu Lianyu(Department of Physicochemistry,University of Science and Technology beijing,beijing 100083) Department of Physicochemistry University of Science and Technology Beijing Beijing 100083 China

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ＥＬＥＣＴＲＯＰＬＡＴＩＮＧＯＦＡＭＯＲＰＨＯＵＳＡｌ－ＭｎＡＬＬＯＹＳ（Ｉ）ＫＩＮＥＴＩＣＦＥＡＴＵＲＥＳＯＦＥＬＥＣＴＲＯＤＥＰＯＳＩＴＩＯＮＯＦＰＵＲＥＡｌ￥ＺｈａｏＧｕａｎｇｗｅｎ；ＺｈｕＴｅｎｇ；ＬｉｕＬｉａｎｙｕ（Ｄｅｐａｒｔｍｅｎｔｏｆ...

关键词： electroplating AlCl3-NaCl-KCl melt electrodeposition pure Al

Fabrication of Grain-oriented (Bi,Pb)_2Sr_2Ca_2Cu_3O_x Superconducting Tapes Using Magnetic Field and Vibration Technique

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Journal of Materials Science & Technology 1998年第1期14卷 86-88页

作者： Yanwei MA and Xianjin WANG (Dept. of Metal Forming, University of Science and Technology beijing, beijing 100083, China)Zutang WANG (Tsinghua University, beijing 100084, China) Dept. of Metal Forming University of Science and Technology Beijing Beijing 100083 China Tsinghua University Beijing 100084 China

Highly textured (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes have been fabricated by means of magnetic-field and vibration technique. This method is an effective way of improving the degree of grain alignment and density of oxide core in tapes after heat treatment and pressing *** of above 20% was increased than that without treatment.

关键词： Bi,Pb Pb Sr Fabrication of Grain-oriented x Superconducting Tapes Using Magnetic Field and Vibration Technique Ca Cu

High Temperature Ductility Loss of 16MnCr5 Pinion Steels

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 123-128页

作者： Haiwen Luo Pei Zhao Zijiu Dang(Metallurgy School, University of Science and Technology beijing, beijing 100083, China) Metallurgy School University of Science and Technology Beijing Beijing 100083 China

A wide ductility trough covering from 700 to 1100 is observed in the curve of Reduction of Area (RA) *** for 16MnCr5 pinion steel. At 750℃, corresponding to the minimum of RA, it is grain boundary slidingthat controls its hot ductility rather than usual Deforming Induced Ferrite (DIF), which can only appear just below750℃ and slightly improve hot ductility. The volume fraction of ferrite is dependent on the strain and strain *** a critical strain must be necessary for formation of DIF then with strain rate increasing, the volume fractionof DIF decreases but RA is elevated. In the γ phase region, hot ductility is seriously deteriorated because of grainboundary sliding promoted by oxidcs and sulfides at the grain boundary and recovered because of dynamic recrystal-lization at higher temperature; when strain rate increases, ductility is improved as there is insufficient time for cracksto propagate along the γ grain boundary as well as dynamically precipitating, and ductility trough becomes narrowerbecause the temperature for onset of dynamic recrystallization decreases. In addition, γ→α phase transformationintroduced by temperature drop before the tensile test encourages precipitation of AlN and impairs ductility.

关键词： hot ductility deforming induced ferrite grain boundary sliding precipitates