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Effect of Process Factors on Microstructure of Semisolid Continuous Casting Billets

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 242-245页

作者： Shuming Xing, Qijie Zhai, Hanqi Hu ( Department of Mechanical Engineering, tsinghua univer.ity, Beijing 100084, China School of Material Science and Engineering, Shanghai univer.ity, Shanghai 200072, China Material Science and Engineering School, univer Department of Mechanical Engineering Tsinghua University Beijing 100084 China School of Material Science and Engineering Shanghai University Shanghai 200072 China Material Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

Semisolid continuous casting (SSCC) is a new technology to produce billets for semisolid metal forming (SSMF). The effect of process factors, such as pouring temperature, stirring rate, preheating temperature and thermal conductivity of stirring chamber, on the microstructure of SSCC billets was studied by means of the factorial experimental method. The results show that the microstructure of SSCC billets can be controlled by the above-mentioned four process factors. In order to obtain fine and rounded granular grains in an SSCC billet, the pouring temperature, preheating temperature and stirring rate should be kept in a moderate range, and the thermal conductivity of stirring chamber should be high. The regression equations with the process factors connecting the microstructure was also set up based on experimental data.

关键词： semisolid metal continuous casting process factors microstructure Metallurgy

Product Family Design Methodology Using Object-Oriented Approach

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厦门大学学报（自然科学版） 2002年第S1期41卷 141-142页

作者： WANG Ai-min, MENG Ming-chen, HUANG Jing-yuan (Department. of Precision Instruments and Mechanology, tsinghua univers ity, Beijing 100084, China)

The serious competition environment of global marke t requests the enterprise to change traditional product development strategy and a dopt new theory in order to meet diverse customer needs while maintaining near m ass production efficiency, which is the main philosophy of mass customization. P roduct family design is research focus at present and also is the core technolog y of DFMC (design for mass customization). Firstly, this paper explores the fund amental issues of product family, such as concepts of modularity, commonality/di versity, product platform and product family architecture etc. We compare the te rminology between product family and object-oriented approach in the next step. Thirdly, this paper puts forwards one product family design methodology based o n product platform and under different phase of product life cycle constrains, f or example, functional, assembly and service etc. At the end section of this pap er, we applied, the object-oriented approach in above mentioned product family design methodology to realize the design process. In one word, this paper propos ed one product family design methodology based on object oriented approach and p roduct life cycle consideration, especially the conjointness of characteristic o f OOA and concepts of product family. The main property of OOA are encapsulation , inherence and polymorphism. Encapsulation can represent the module or building blocks of product family. Inherence can be extended to describe the modularity and commonality, and also be used to construct variant space. Alternative specif ic of product family architecture can be embodied with polymorphism. And fin aly, we give the future work contents. In order to derive the product platform a nd achieve modularity and commonality/diversity, interface management between bu ilding block is necessary. The question is how the OOA can be applied in interfa ce management to get our aim OOA is the basis of many information management sy stem, then th

关键词： product family design product platform object- oriented approach (OOA) product life cycle

An introduction to tsinghua Cloud

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Science China(Information Sciences) 2010年第7期53卷 1481-1486页

作者： ZHENG WeiMin1,2 1Department of Computer Science and Technology, tsinghua univer.ity, Beijing 100084, China 2tsinghua National Laboratory for Information Science and Technology, Beijing 100084, China 1. Department of Computer Science and Technology Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

Cloud computing has become a trend that draws attention from both academia and industry all over the world. This paper unveils details of tsinghua Cloud, a comprehensive solution for cloud computing developed by Tsing... 详细信息

关键词： cloud computing distributed file system virtual computing environment data sharing

Experimental realization of quantum cryptography communication in free space

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 237-246页

作者： WANG Chuan1, ZHANG Jingfu1, WANG Pingxiao1, DENG Fuguo1, AI Qing1 & LONG Guilu1,2 1. Department of Physics, Key Laboratory for Quantum Information and Measurements, tsinghua univer- sity, Beijing 100084, China 2. Center for Atomic and Molecular NanoSciences, tsinghua univer.ity, Beijing 100084, China Department of Physics Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing 100084 China Atomic and Molecular NanoSciences Tsinghua University Beijing 100084 China

Utilizing linear optical devices, the principle of B92 quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2 meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.

关键词： quantum key distribution, free space, linear optics, faint pulses.

DIRECT SPECTURM ANALYSIS OF THE STATE SPACE FOR RANDOM VIBRATION OF MDOF LINEAR DAMPED SYSTEM

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Acta Mechanica Sinica 1990年第4期6卷 367-373页

作者： Zheng Zhaochang (tsinghua univer.ity) 1. tsinghua univer.ity Beijing China

This paper proceeds from the general case of the unsymmetric linearized multi-degrees of free- dom(MDOF)*** adopting the general complex modal theory of the state space,the response analysis for a sys- tem subjected to random excitation of the same source is carried out using as a kind of direct spectrum analysis method in frequency *** the input of power spectral density function given,the explicit expression of the power spectral density function matrix of the output response can be *** taking Fourier inverse transform,the integrated expres- sions of the correlation function matrix and of the spectrum moment matrix are *** with the time domain method,this method enjoys the merit of visualization and avoids the procedure of transformation from the obtained re- sponse correlation function to be solved for the output spectrum utilizing Fourier *** paper has extended the application range of the traditional frequency domain analysis *** mean square values and variety of statistical val- ues can be obtained *** method and the time domain method are different in approach but equally satisfac- tory in their results.

关键词： spectrum analysis space state complex modal random vibration

EXTRACTION KINETICS,SYNERGISTIC EFFECTS AND INTERFACIAL CHEMISTRY FOR D_2 EHPA MPA-Fe^(3+) MIXED EXTRACTION SYSTEM

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Acta Metallurgica Sinica(English Letters) 1993年第12期6卷 405-410页

作者： YU Jingfen LIU Difei tsinghua univer.ity,Beijing,China professor,Dept.of Chemical Engineering,tsinghua univer.ity,Beijing 100084,China tsinghua Univ Beijing China

The thermodynamics of micella formation,interfacial characteristics,synergistic effects and interfacial kinetics for synergistic extraction system D_2 EHPA-MPA-Fe^(3+) have been *** was found that D_2EHPA in the mixed system strongly exhibits the effect on the micella formation thermodynamics and interracial characteristics of *** ther- modynamic parameters for constants of micelles formation(K_m).free energies of micelles formation(ΔG_m)and critical micella concentrations(CMC)were *** inter- facial adsorption behaviour of D_2EHPA is opposite to that of *** emulsification for single MPA and the mixed system was *** synergistic effects were found in this mixed extraction *** is proved that the process of the Fe^(3+) extraction for non-mixed extraction system is controlled by chemical reaction and the controlling reaction occurs at the interface.

关键词： interfacial chemistry synergistic effect Fe^(3+) extraction kinetics

TEXTURE DETERMINATION OF THIN FILM ZrO_2 BY ELECTRON DIFFRACTION

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Acta Metallurgica Sinica(English Letters) 1993年第12期6卷 472-473页

作者： WANG Yinghua tsinghua univer.ity,Beijing,China Department of Materials Science and Engineering,tsinghua univer.ity,Beijing 100084,China tsinghua Univ Beijing China

A method for semi-quantitative determination of thin film texture using electron diffrac- tion is *** texture state of a zirconia thin film with a cubic structure has been determined in this way and is presented as an... 详细信息

关键词： texture thin film electron diffraction ZrO_2

On Mao Zedong's Strong Power Dream of Catching up and Overtaking the United States

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学术界 2011年第4期 272-279页

作者： Hu Angang tsinghua univer.ity

Reviewing the past is beneficial not only to the present but also to the *** has the two sides of both repeating itself and constantly renewing itself and so does future *** is like a vast and boundless *** should we ... 详细信息

关键词： On Mao Zedong’s Strong Power Dream of Catching up and Overtaking the United States

HIGH ACCURACY NUMERICAL METHOD OF THIN-FILM PROBLEMS IN MICROMAGNETICS

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Journal of Computational Mathematics 2003年第1期21卷 33-40页

作者： Zhongyi Huang (Deft, of Mathematical Sciences, tsinghua univer.ity, Beijing, 100084, China) Dept. of Mathematical Sciences Tsinghua University 北京 100084

In this paper, a new high accuracy numerical method for the thin-film problems of micron and submicron size ferromagnetic elements is proposed. For the computation of stray field, we use the finite element method(FEM) by introducing a semi-discrete artificial boundary condition [1, 2]. In our numerical experiments about the domain patterns and their movement, we can see that the results are accordant to that of experiments and other numerical methods. Our method are very convenient to deal with arbitrary shape of thin films such as a polygon with high accuracy.

关键词： Thin-film Micromagnetics stray field Semi-discrete artificial boundary condition.