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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 university, beijing 100084,{2. 2.3. National Laboratory for Information Science and Technology, beijing 100084,{2. Department of Computer Science and Technology Tsinghua University Beijing China tsinghua National Laboratory for Information Science and Technology Beijing 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

Truncation error calculation based on Richardson extrapolation for variable-step collaborative simulation

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Science china(Information Sciences) 2011年第6期54卷 1238-1250页

作者： ZHANG HeMing 1 , LIANG SiLu 2., SONG ShiJi 1 & WANG HongWei 3.1 Department of Automation, TNList, tsinghua university, beijing 100084,{2. 2.Computer and Information Management Center, tsinghua university beijing 100084,{2. 3.Engineering Design Centre, Engineering Department, Cambridge university, Cambridge CB2.1PZ, UK Department of Automation TNList Tsinghua University Beijing China Computer and Information Management Center Tsinghua University Beijing China Engineering Design Centre Engineering Department Cambridge University Cambridge UK

Collaborative simulation is an effective approach to performing simulation analysis for complex systems by integrating models developed for different engineering disciplines. Collaborative simulation issues include the modeling of coupled multidisciplinary systems, and the simulation running time integration of these models that are solved parallelly. Estimation of the local truncation error of coupling models is the key to solve multidisciplinary collaborative simulation problem, which is actually used to restrict the simulation step. This paper presents a variable-step method based on Richardson extrapolation for calculating the local truncation error to solve collaborative simulation problem of multidisciplinary coupling models. Formulas for estimating the local truncation error are derived through theoretical analysis by using integration methods and interpolation technologies, respectively. The simulation experiments are illustrated to validate the accuracy and efficiency of proposed collaborative simulation algorithm in comparison with the usual combinative algorithm.

关键词： multidisciplinary systems collaborative simulation variable-step algorithm error estimation

REDUCTIONS OF ADJOINT REPRESENTATIONS TO LAX REPRESENTATIONS FOR CONSTRAINED FLOWS

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Chinese Annals of Mathematics,Series B 1996年第2期17卷 187-198页

作者： ZENG YUNBO Department of Applied Mathematics, tsinghua university, beijing 100084,{2.. 清华大学应用数学系北京

Within framework of zero-curvature representation theory, the Lax representations for x- andtn-constrained flows of soliton hierarchy are obtained from reductions of adjoint representationsof the auxiliary linear problems. This method is applied to the third order spectral problem bytaking modified Boussinesq hierarchy as an illustrative example.

关键词： Constrained flow Lax representation Adjoint representation Soliton hierarchy

Arbitrarily long distance quantum communication using inspection and power insertion

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Chinese Science Bulletin 2009年第1期54卷 158-162页

作者： WANG WanYing1,2.WANG Chuan1,2.ZHANG GuangYu1,3.& LONG GuiLu1,2.1 Department of Physics,{3. university,{2. 100084,china 2.{3. National Laboratory for Information Science and Technology,{3. university,{2. 100084,china 3.College of Applied Science,Harbin university of Science and Technology,Harbin 150080,china Department of Physics Tsinghua University Beijing China tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing China College of Applied Science Harbin University of Science and Technology Beijing China

The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this paper,a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial function of the dis-tance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret messages are transmitted directly over a quantum channel.

关键词：长距离量子通信量子安全通信量子密匙分布噪声

Multi-swingby optimization of mission to Saturn using global optimization algorithms

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Acta Mechanica Sinica 2009年第6期25卷 839-845页

作者： Kaijian Zhu Junfeng Li Hexi Baoyin School of Aerospace, tsinghua university,100084 {2.,{3. School of Aerospace Tsinghua University Beijing China

Based on the trajectory design of a mission to Saturn, this paper discusses four different trajectories in various swingby cases. We assume a single impulse to be applied in each case when the spacecraft approaches a celestial body. Some optimal trajectories ofEJS, EMS, EVEJS and EVVEJS flying sequences are obtained using five global optimization algorithms： DE, PSO, DP, the hybrid algorithm PSODE and another hybrid algorithm, DPDE. DE is proved to be supe- rior to other non-hybrid algorithms in the trajectory optimi- zation problem. The hybrid algorithm of PSO and DE can improve the optimization performance of DE, which is vali- dated by the mission to Saturn with given swingby sequences. Finally, the optimization results of four different swingby sequences are compared with those of the ACT of ESA.

关键词： Swingby trajectory . Global optimization .Hybrid algorithm . Mission design

Buffer planning for application-specific networks-on-chip design

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Science in china(Series F) 2009年第4期52卷 547-558页

作者： YIN ShouYi1,2.LIU LeiBo1,2.& WEI ShaoJun1,2.1 Institute of Microelectronics,{3. university,{2. 100084,china 2.National Laboratory for Information Science and Technology,{3. university,{2. 100084,china Institute of Microelectronics Tsinghua University Beijing China National Laboratory for Information Science and Technology Tsinghua University Beijing China

Networks-on-chip （NoC） is a promising communication architecture for next generation SoC. The size of buffer used in on-chip routers impacts the silicon area and power consumption of NoC dominantly. It is important to plan the total buffer-size and each router buffer-allocation carefully for an efficient NoC design. In this paper, we propose two buffer planning algorithms for application-specific NoC design. More precisely, given the traffic parameters and performance constraints of target application, the proposed algorithms automatically determine minimal buffer budget and assign the buffer depth for each input channel in different routers. The experimental results show that the proposed algorithms can significantly reduce total buffer usage and guarantee the performance requirements.

关键词： buffer planning networks-on-chip (NoC) design automation optimization

Parameter identification theory of a complex model based on global optimization method

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Science china(Physics,Mechanics & Astronomy) 2008年第11期51卷 1722-1732页

作者： QU Jie1, JIN QuanLin2.& XU BingYe3.1 College of Automotive Engineering, South china university of Technology, Guangzhou 510640, china 2.beijing Research Institute of Mechanical and Electrical Technology, beijing 100083. china 3.Department of Engineering Mechanics, tsinghua university, beijing 100084, china College of Automotive Engineering South China University of Technology Guangzhou China beijing Research Institute of Mechanical and Electrical Technology Beijing China Department of Engineering Mechanics Tsinghua University Beijing China

With the development of computer technology and numerical simulation technology, computer aided engineering (CAE) technology has been widely applied to many fields. One of the main obstacles, which hinder the further application of CAE technology, is how to successfully identify the parameters of the selected model. An elementary framework for parameter identification of a complex model is provided in this paper. The framework includes the construction of objective function, the design of the optimization method and the evaluation of the identified results, etc. The parameter identification process is described in this framework, taking the parameter identification of the superplastic constitutive model considering grain growth for Ti-6Al-4V at 92.°C as an example. The objective function is the weighted quadratic sums of the difference between the experimental and computational data for the stress-strain relationship and the grain growth relationship; the designed optimization method is a hybrid global optimization method, which is based on the feature of the objective function and incorporates the strengths of genetic algorithm (GA), the Levenberg-Marquardt algorithm and the augmented Gauss-Newton algorithm. The reliability evaluation of parameter identification result is made through the comparison between the calculated and experimental results and between the theoretical values of the parameters and the identified ones.

关键词： constitutive model parameter identification theory inverse analysis global optimization

Modeling of Mold Filling and Solidification in Lost Foam Casting

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Journal of Materials Science & Technology 2003年第5期19卷 395-397页

作者： Fengjun LI, Houfa SHEN and Baicheng LIUDepartment of Mechanical Engineering, tsinghua university, beijing 100084,{2. Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

Based on the characteristics of the lost foam casting (LFC) and the artificial neural network technique, a mathematical model for the simulation of the melt-pattern interface movement during the mold filling of LFC has been proposed and experimentally verified. The simulation results are consistent with the experiments in both the shapes of melt front and filling sequences. According to the calculated interface locations, the fluid flow and the temperature distributions during the mold filling and solidification processes were calculated, and the shrinkage defect of a lost foam ductile iron casting was predicted by considering the mold wall movement in LFC. The simulation method was applied to optimize the casting design of lost foam ductile iron castings. It is shown that the model can be used for the defects prediction and for casting design optimization in the practical LFC production.

关键词： Lost foam casting Numerical simulation Artificial neural network

3. Stochastic Modeling of Grain Structure for Aluminum Alloy Casting

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Journal of Materials Science & Technology 2003年第5期19卷 391-394页

作者： Qingyan XU, Weiming FENG and Baicheng LIUDepartment of Mechanical Engineering, tsinghua university, beijing 100084,{2. Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

A 3. stochastic modeling was carried out to simulate the dendritic grains during solidification of aluminum alloys, including time-dependent calculations for temperature field, solute redistribution in liquid, curvature of the dendritic tip, and growth anisotropy. The nucleation process was treated by continuous nucleation. A 3. simplified grain shape model was established to represent the equiaxed dendritic grain. Based on the Cellular Automaton method, a grain growth model was proposed to capture the neighbor cells of the nucleated cell. During growing, each grain continues to capture the nearest neighbor cells to form the final shape. When a neighbor cell was captured by other grains, the grain growth along this direction would be stopped. Three-dimensional calculations were performed to simulate the evolution of dendritic grain. In order to verify the modeling results, the predictions were compared with the observation on samples cast in the sand mold and the metal mold.

关键词： 3. stochastic modeling Nucleation Grain growth