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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

APPLICATION OF THE MULTIGRID METHOD IN NUMERICALSIMULATION OF SEDIMENT TRANSPORT

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International Journal of Sediment research 1999年第2期14卷 133-143页

作者： ZHAO Yongqing and FANG HongWei ( Sediment research Lab, tsinghua university, {2., china)

By combining FAS (Full Approximate Scheme) for nonlinear equations of multigrid method with Finite Volume Method, a plane two-dimensional mathematical model of sediment-transport is presented in this paper The analysis on the efficiency of this model shows that it can reduce the amount of computation greatly. Numerical simulation results of the Yellow River Langdian Water Source Project agree well with the test results of the physical model.

关键词： Multigrid method Mathematical model Sediment transport

Suppression of Phase and Amplitude Damping Decoherence in a Three-Level Atom in A-Configuration Using Bang-Bang Controls

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Communications in Theoretical Physics 2007年第7期48卷 71-74页

作者： WANG Yan-Hui LIU Xiao-Shu LONG Gui-Lu1 Key Laboratory for Atomic and Molecular NanoSciences and Department of Physics,tsinghua university,beijing 100084,{2.2.tsinghua National Laboratory for Information Science and Technology,tsinghua university,beijing 100084,{2. Key Laboratory for Atomic and Molecular NanoSciences and Department of Physics Tsinghua University Beijing 100084 China tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

In this paper,we present decoupling bang-bang operations for the suppression of general decoherence,bothamplitude and phase damping,in a three-level system in *** give a program to design a sequence ofperiodic twinbor... 详细信息

关键词： bang-bang operation general decoherence three-level system

3D 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 3D 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 3D 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： 3D stochastic modeling Nucleation Grain growth

Sediment delivery ratio and its uncertainties on flood event scale:Quantification for the Lower Yellow River

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Science china(Technological Sciences) 2010年第3期53卷 854-862页

作者： FU XuDong 1,JIANG LiWei 1,WU BaoSheng 1,HU ChunHong 2.WANG GuangQian 1 &FEI XiangJun 1 1State Key Laboratory of Hydroscience and Engineering,tsinghua university,beijing 100084,{2. 2.2. Institute of Hydropower and Water Resources research,beijing 100044,{2. 1. State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China2. China Institute of Hydropower and Water Resources Research Beijing 100044 China

Sediment delivery ratio(SDR)for fluvial rivers was formulated with sediment rating *** observed data of SDR on flood event scale of the Lower Yellow River(LYR)were adopted to examine the formulation and to calibrate the model parameters.A regression formula of SDR was then established and its 95%prediction interval was accordingly quantified to represent its overall *** types of factors including diversity of the incoming flow conditions,river self-regulation processes,and human activities were ascribed to the *** following were shown:(1)With the incoming sediment coefficient(ISC)being a variable,it was not necessary to adopt the incoming flow discharge as the second variable in the formulation of SDR;and(2.ISC=0.003 and therefore SDR=2.might be a threshold for distinguishing the characteristics of sediment transport within the *** findings would highlight sediment transport characteristics on the scale of flood event and contribute to uncertainty based analysis of water volume required for sediment transport and channel maintenance of the LYR.

关键词： sediment delivery ratio Lower Yellow River flood event uncertainty prediction interval

A scheme to implement the Deutsch-Josza algorithm on a superconducting charge-qubit quantum computer

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Progress in Natural Science:Materials International 2006年第6期16卷 594-599页

作者： HUO Wenyi and LONG Guilu (Key Laboratory for Quantum Information and Measurements, and Department of Physics, tsinghua university, beijing 100084, {2. Key Laboratory for Atomic and Molecular NanoSciences, tsinghua university, beijing 100084, {2.) [a]Key Laboratory for Quantum Information and Measurements and Department of Physics Tsinghua University Bejjing China [b]Key Laboratory for Atomic and Molecular NanoSciences Tsinghua University Bejing China

We have studied the implementation of the Deutsch-Josza quantum algorithm in a superconducting charge-qubit quantum computer. Different from previous studies, we have used the inductance coupled system of You et al. The detailed pulse sequences have been designed for the four possible functions in a 2.qubit system. The result is generalized to an arbitrary n-qubit system. This scheme will be useful for practical implementation of the algorithm.

关键词： superconducting quantum computer Deutsch-Josza algorithm.

A multiphase mesostructure mechanics approach to the study of the fracture-damage behavior of concrete

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Science china(Technological Sciences) 2008年第S2期51卷 8-24页

作者： TANG XinWei1,ZHANG ChuHan1 & SHI JianJun2.1 State Key Laboratory of Hydroscience and Engineering,tsinghua university,beijing 100084,{2. 2.Department of Urban Construction,Nanhua university,Hengyang 42.001,{2. 1. State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China 2. Department of Urban Construction Nanhua University Hengyang 421001 China

A multiphase mesostructure mechanical model is proposed to study the deformation and failure process of concrete considering its heterogeneity at the meso scopic ***,concrete is taken as a type of three-component composite material composed of mortar matrix,aggregates and interfaces on the ***,an efficient approach to the disposition of aggregates of concrete and a state matrix method to generate mesh coordinates for aggregates are ***,based on the nonlinear continuum damage mechanics,a meso-scale finite element model is presented with damage softening stress-strain relationship for describing the mechanical behavior of different components of *** this method,heterogeneities of each component in the concrete are considered by assuming the material properties of three components conform to the Weibull distribution ***,based on this multiphase meso-mechanics model,a simulation analysis of fracture behavior of a rock-fill concrete(RFC) beam is *** study includes experimental tests for determining basic mechanical parameters of three components of RFC and four-point flexural beam tests for verification of the *** is preliminarily shown that the numerical model is applicable to studying failure mechanisms and process of concrete type material.

关键词： concrete multiphase mesostructure mechanics numerical simulation experimental research

Effect of Limestone Powder on Microstructure of Concrete

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Journal of Wuhan university of Technology(Materials Science) 2010年第2期25卷 328-331页

作者：刘数华 State Key Laboratory of Water Resource and Hydropower Engineering Science Wuhan University

The effect of limestone powder on microstructure of concrete was studied by using mercury intrusion porosimetry （MIP）, backscattering scanning electron（BSE）, scanning electron mi- croscopy （SEM） and X-ray diffraction （XRD） techniques. The experimental results show that the compressive strength of concrete containing 100 kg/m3 limestone powder can meet the strength requirement. Limestone powder has not pozzolanic activity; it is still unhydrated at the age of 2. days. But its filling effect can make the paste matrix and the interfacial transition zone between matrix and aggregate denser, which will improve the performance of concrete.

关键词： concrete limestone powder microstructure filling effect hydration characteristic

Numerical Simulation of Microporosity Evolution of Aluminum Alloy Castings

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Journal of Materials Science & Technology 2004年第1期20卷 23-26页

作者： Shuyong DONG, Shoumei XIONG and Baicheng LIUDepartment of Mechanical Engineering, tsinghua university, beijing 100084, {2. Dept. of Mech. Eng. Tsinghua Univ. Beijing 100084 China

A mathematical model to calculate the size and distribution of microporosities was studied and coupled with a stochastic microstructure evolution model. The model incorporates various solidification phenomena such as grain structure evolution, solidification shrinkage, interdendritic fluid flow and formation and growth of pores during solidification processes. The nucleation and growth of grains were modeled with a cellular automaton method that utilizes the results from a macro scale modeling of the solidification process. Experiments were made to validate the proposed models. The calculated results of aluminum alloy castings agreed with the experimental measurements.

关键词： Numerical simulation Microporosity evolution Aluminum alloy castings