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| 1 | ANALYSIS ON THE DEBRIS FLOW SURGES显示文摘ANALYSISONTHEDEBRISFLOWSURGES￥WangGuangqian(Professor,Dept.ofHydraulicEngineering,TsinghuaUniversity)Abstract:Basedonthefunda... | Wang Guangqian( Hydraulic Engineering, Tsinghua University) | 1994 | International Journal of Sediment Research1994，9，3： | 1 |
| 2 | Mechanism and control of convective heat transfer——Coordination of velocity and heat flow fields显示文摘A second look has been given at the mechanism of convective heat transfer based on the analogy between convection and conduction with heat sources. The strength of convective heat transfer depends not only on the fluid velocity and fluid properties, but also on the coordination of fluid velocity and heat flow fields. Hence, based on the included angle of velocity and temperature gradient vectors, the presence of fluid motion may enhance or reduce heat transfer. With this concept, the known heat transfer phenomena may be understood in a deeper way. More important is that some novel approaches of heat transfer control can be developed. | QUO ZengyuanDepartment of Engineering Mechanics, Tsinghua University, Beijing 100084, China | 2001 | Chinese Science Bulletin2001，46，7： | 60 |
| 3 | Microstructural variation of hardened cement-fly ash pastes leached by soft water显示文摘The microstructural variations of hardened cement-fly ash pastes leached by soft water were investigated by MIP, XRD, TG and SEM. The results show that the mass of hardened cement-fly ash paste reduces and its microstructure deteriorates partly after leaching of soft water. At the leaching duration of 180 days, the hardened paste containing fly ash deteriorated a little more serious than the plain cement paste, but the incorporation of fly ash in a proper ratio was helpful to defer the trend of deterioration of the hardened paste microstructure. The microstructural stability of hardened cement-fly ash paste wasn’t damaged severely during the 180 days leaching duration. | LI Xiang & YAN PeiYu* Department of Civil Engineering, Tsinghua University, Beijing 100084, China | 2010 | Science China(Technological Sciences)2010，53，11： | 12 |
| 4 | Studies of the unsteady supersonic base flows around three afterbodies显示文摘<正> Unsteady supersonic base flows around threeafterbodies,cylindrical(Cy),boattailed(BT)and three-step(MS),are investigated in this paper.Reynolds-averagedNavier-Stokes(RANS)and two RANS/LES(large-eddysimulation)hybrid methods,detached eddy simulation(DES)and delayed-DES(DDES),are used to predict the base flowcharacteristics around the baseline Cy afterbody.All theRANS and hybrid methods are based on the two-equationSST(shear-stress transport)model with compressible correc-tions(CC).According to the comparison of measurements,both DES and DDES can produce more satisfactory resultsthan RANS.RANS can only present the 'stable' flow pat-terns,while the hybrid methods can demonstrate unsteadyflow structures.DDES and DES results are little differentfrom one another although the latter exhibits better agree-ment with the experiment.DES is taken to investigate the5~ BT and three-step afterbodies.The mean flow data andthe instantaneous turbulent coherent structures are comparedagainst available measurements. | Zhixiang Xiao Song Fu School of Aerospace Engineering,Tsinghua University, 100084 Beijing, China | 2009 | Acta Mechanica Sinica2009，25，4： | 12 |
| 5 | Development of SOM combustion model for Reynolds-averaged and large-eddy simulation of turbulent combustion and its validation by DNS显示文摘The derivation and closure methods of the second-order moment (SOM) combus- tion model are proposed. The application of this model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion combustion, and bluff-body stabilized premixed combustion is sum- marized. It is indicated that the SOM model is much better than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engi- neering. The SOM modeling results are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS) of turbulent reacting channel flows. | ZHOU LiXing Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China | 2008 | Science China(Technological Sciences)2008，51，8： | 9 |
| 6 | FACTORS AFFECTING FORMING PRECISION IN PATTERNLESS CASTING MANUFACTURING显示文摘The patternless casting manufacturing(PCM) technique adopts a new method of double scanning which combines the principle of discreteness and deposition with the resin-bonded sand technique.Two main factors, the liquid penetration regularities in the space between particles and the shape and dimension of the agglomeration unit body, are studied qualitatively and quantitatively.This provides the theoretical basis for selecting the forming technical parameters.The experiments verify the analysis. | Yang WeidongYan YongnianXu DanZhai LeiDepartment of Mechanical Engineering,Tsinghua University,Beijing 100084, China | 2003 | Chinese Journal of Mechanical Engineering2003，16，2： | 9 |
| 7 | Three Dimension Rigid-plastic Finite Element Simulation for Two-Roll Cross-wedge Rolling Process显示文摘Cross-wedge rolling (CWR) is a metal process of ro ta ry forming. To produce a part, one cylindrical billet should be placed between t wo counterrotating and wedge-shape dies, which move tangentially relative each other. The billet suffers plastic deformation (essentially, localized compressio n) during its rotation between the rotating dies. Compared to other numerical si mulation methods, the finite element method (FEM) has advantages in solving gene ral problems with complex shapes of the formed parts. In cross-wedge rolling, t here are four stages in the workpiece deformation process, namely knifing, guidi ng, stretching and sizing stage. It is time-consuming and expensive to design t he CWR process by trial and error method. The application of numerical simul ation for the CWR process will help engineers to efficiently improve the process development. Tselikov, Hayama, Jain and Kobayashi, and Higashimo applied the sl ip-line theory in study of CWR process analysis. Zb.pater studied CWR process i ncluding upsetting by upper-bound method. The above numerical simulation were b ased on the two-dimensional plain-strain assumption ignored the metal flow in workpiece axial direction. Therefore, the complex three-dimensional stress and deformation involved in CWR processes were not presented. Compared to other nume rical simulation methods, the finite element method (FEM) has advantages in solv ing general problems with complex shapes of the formed parts. As yet, a few 3-D finite element simulation studies on CWR process have been reported in literatu res. In this paper, the process of cross wedge rolling (CWR) has been simulated and analyzed by 3D rigid-plastic finite element method. Considering the charact eristic of CWR, the static implicit FEM program is selected. The models proposed in this study uses the commercial code DEFORM 3D to simulate the CWR process. T his is an implicit Lagrangian finite element code, which includes many new enhan cements functions. A new method of utilizing multiple processors using the MPI s tandard has been implemented. Automatic switching between the two different defo rmation solvers (Sparse Solver and Conjugate Gradient Solver) has also been impl emented in order to increase the speed of simulations. In this paper, all stages in CWR process are simulated to be able to closely understand and analyze the a ctual CWR process. For simulating all forming stages in CWR process, the dynam ic adaptive remeshing technology for tetrahedral solid elements was applied. T he stress distributions in cross section of forming workpiece are analyzed to in terpret fracture or rarefaction in the center of workpiece. Authors also analyze d the time-torque curve and the laws of load changing. | FANG Gang, LEI Li-ping, ZENG Pan (Dept. of Mechanical Engineering, Tsinghua University, Beijing 100084, China) | 2002 | 厦门大学学报(自然科学版)2002，41，S1： | 7 |
| 8 | Analysis of finite-element-based methods for reducing the ill-posedness in the reconstruction of fluorescence molecular tomography显示文摘The major issue in reconstruction of optical imaging might be the ill-posedness of the problem. In this paper, four different algorithms, including singular value decomposition (SVD), the truncated SVD, Tikhonov regularization and adaptive regularization, are analyzed and applied for solving the matrix equation generated from diffuse equation based on finite-element method in fluorescence molecular tomography. Results illustrate the need for either imposition of regularization term or elimination of too small singular values in reducing the illposedness. The results also suggest that the adaptive-regularization method offers superior performance in the reconstruction among the four methods in most cases even if the initially selected regularization parameter is not optimal, thus providing the convenience for the reconstruction. | Zhun Xu, Jing Bai Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing 100084, China | 2009 | Progress in Natural Science:Materials International2009，19，4： | 6 |
| 9 | A SINGLE-PERIOD INVENTORY SYSTEM WITH A GENERAL S-SHAPED UTILITY AND EXPONENTIAL DEMAND显示文摘We discuss a single-period inventory system with a general S-shaped utility function and exponential demand.It is shown that there exists a state-dependent order-up-to policy to be optimal.Behaviors of optimal policy are illustrated by a numerical example. | Wei GENG1 Xiaobo ZHAO2 Deng GAO3 Department of Industrial Engineering,Tsinghua University,Beijing 100084,China | 2010 | Journal of Systems Science and Systems Engineering2010，19，2： | 6 |
| 10 | Semi-solid Processing of Al-7Graghite Composite显示文摘Al-7graphite composite was processed using Al-7graphite mushy prepared by electromagnetic-mechanical stirring method, and the influence of solid fraction on the distributing of graphite particles in ingot was studied. The results shows that the relationship between solid fraction and stirring temperature of mushy is:fs=591.5-0.897 t(wherefs is the solid fraction, t is the stirring temperature). For Al-7graphite composite, with the increasing of solid fraction, the aggregation extent of graphite particles reduced gradually, and when solid fraction was larger than 30%, graphite particles could distribute evenly in ingot. | Peng Zhang, Yunhui Du, Daben Zeng Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China | 2001 | Journal of University of Science and Technology Beijing2001，8，3： | 4 |
| 11 | Expression of lignin peroxidase H2 from Phanerochaete chrysosporium by multi-copy recombinant Pichia strain显示文摘The lipH2 gene,encoding the expression of lignin peroxidase,was cloned from Phanerochaete chrysosporium BKM-F-1767 and expressed in Pichia pastoris X-33,a yeast.The cDNA of LiPH2 was generated from total RNA extracted from P.chrysosporium by PCR with primers that do not contain a P.chrysosporium lignin peroxidase secretion signal.The gene was then successfully inserted into the expression vector pPICZα,and resulted in the recombinant vector pPICZα-lipH2.The transformation was conducted in two ways.One was using the wild Pichia pastoris as the recipients,which results in the recombinant P.pastoris with single or low lipH2 gene copy.The second was using P.pastoris and single or low lipH2 gene copy as the recipients,which results in the recombinant P.pastoris with multi-copies of lipH2 genes.This study firstly expressed the gene lipH2 in P.pastoris and achieved the successful expression of the lipH2 depending upon the generation of a recombinant strain that contained multiple copies.The lignin peroxidase activity reached a maximum of 15 U/L after 12 h induction. | WANG Wei,WEN Xianghua Department of Environmental Science and Engineering,Tsinghua University,Beijing 100084,China. | 2009 | Journal of Environmental Sciences2009，21，2： | 3 |
| 12 | A NEW APPROACH TO THE NUMERICAL SIMULATION OF MASS TRANSPORT显示文摘A refined numerical method, based upon time-line interpolation, for the simulation of advection and diffusion has been tentatively explored. A complete set of temporal reachback numerical scheme in applying the method of characteristics has been derived, and the favorable accuracy of the method demonstrated. The use of interpolations in time, rather than the more widely used interpolations in space, demonstrates that it generates a much smaller numerical error. | Mao Ze-yu, Dong Zeng-nanHydraulics Group, Dept. of Hydraulic Engineering, Tsinghua University, Beijing100084, P. R. China | 1997 | Journal of Hydrodynamics1997，9，2： | 3 |
| 13 | NUMERICAL SIMULATION OF DISCONTINUOUS FLOW IN CIRCULAR CONDUITS显示文摘NUMERICAL SIMULATION OF DISCONTINUOUS FLOW IN CIRCULAR CONDUITSNUMERICALSIMULATIONOFDISCONTINUOUSFLOWINCIRCULARCONDUITS￥MaoZe... | Mao Ze-Yu (Hydraulics Group, Department of hydraulic enginering, Tsinghua University, Beijing 100084, P. R. China) | 1996 | Journal of Hydrodynamics1996，8，3： | 3 |
| 14 | Performance of Electric Double Layer Capacitors using Active Carbons Prepared from Petroleum Coke by KOH and Vapor Re-Etching显示文摘The electrochemical storage of energy in a special kind of active carbon materials used as capacitor electrodes isconsidered. Pet roleum coke was used for preparation of carbons with different porosities by KOH and vapor etchingwith catalysis of FeCl3 in turn. Carbon electrodes were fabricated and used as electrodes of double layer capacitors.Nitrogen adsorption was used to characterize the porous structure of the carbons. The electrochemical performanceof the capacitors in 6 mol/L KOH was investigated with constant current charge and discharge experiments. Aspecific capacitance larger than 160 F/g was achieved with an electrode composed of 75% active carbon with aspecific surface area of 1180 m2/g and 20% graphite as conductive agent. Evaluation of capacitor performance wasconducted by different techniques, e.g. voltammetry and impedance spectroscopy. Characteristics of the capacitorwere also discussed. A hybrid power source consisting of nickel- hydrogen and double layer capacitor was demonstratedby powering successfully a simulated power load encountered in communication equipment. | Xiaofeng WANG, Dazhi WANG Ji LIANGDepartment of Mechanical Engineering, Tsinghua University, Beijing 100084, China | 2003 | Journal of Materials Science & Technology2003，19，3： | 3 |
| 15 | A NEW APPROACH TO THE SIMULATION OF UNSTEADY SUBCRITICAL FLOW显示文摘ANEWAPPROACHTOTHESIMULATIONOFUNSTEADYSUBCRITICALFLOW￥MaoZe-yu(DepartmentofHydraulicEngineering,TsinghuaUniversityBeijing10008... | Mao Ze-yu(Department of Hydraulic Engineering, Tsinghua University Beijing 100084, P. R. China) | 1995 | Journal of Hydrodynamics1995，7，3： | 2 |
| 16 | A SOLUTION PROCEDURE FOR LOWER BOUND LIMIT AND SHAKEDOWN ANALYSIS BY SGBEM显示文摘The symmetric Galerkin boundary element method (SGBEM) instead of the finite element method is used to perform lower bound limit and shakedown analysis of structures. The self-equilibrium stress fields are constructed by a linear combination of several basic self-equilibrium stress fields with parameters to be determined. These basic self-equilibrium stress fields are expressed as elastic responses of the body to imposed permanent strains and obtained through elastic-plastic incremental analysis. The complex method is used to solve nonlinear programming and determine the maximal load amplifier. The limit analysis is treated as a special case of shakedown analysis in which only the proportional loading is considered. The numerical results show that SGBEM is effcient and accurate for solving limit and shakedown analysis problems. | Zhang Xiaofeng Liu Yinghua Cen Zhangzhi (Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China) | 2001 | Acta Mechanica Solida Sinica2001，14，2： | 2 |
| 17 | SPACE-TIME ADAPTIVE PROCESSING FOR AIRBORNE RADAR:A CONVENIENT IMPLEMENTATION APPROACH显示文摘A convenient implementation approach to space-time adaptive processing for airborne radar has been proposed, which is added by some auxiliary array elements in the area of main-lobe clutter on the basis of 2-D Capon approach . It is of practical use for its small computational load. This approach possesses the ideal performance in the area of main-lobe clutter . In addition, the approach which is added by some auxiliary beams in the area of main-lobe clutter has also been discussed. | Wang Yongliang Peng Yingning(Dept. of Electronic Engineering, Tsinghua University, Beijing, 100084) | 1996 | Journal of Electronics(China)1996，13，4： | 2 |
| 18 | Numerical Simulation of Microporosity Evolution of Aluminum Alloy Castings显示文摘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. | Shuyong DONG, Shoumei XIONG and Baicheng LIUDepartment of Mechanical Engineering, Tsinghua University, Beijing 100084, China | 2004 | Journal of Materials Science & Technology2004，20，1： | 2 |
| 19 | ELASTO-PLASTICITY ANALYSIS BASED ON COLLOCATION WITH THE MOVING LEAST SQUARE METHOD显示文摘A meshless approach based on the moving least square method is developed for elasto-plasticity analysis, in which the incremental formulation is used. In this approach, the displacement shape functions are constructed by using the moving least square approximation, and the discrete governing equations for elasto-plastic material are constructed with the direct collocation method. The boundary conditions are also imposed by collocation. The method established is a truly meshless one, as it does not need any mesh, either for the purpose of interpolation of the solution variables, or for the purpose of construction of the discrete equations. It is simply formulated and very efficient, and no post-processing procedure is required to compute the derivatives of the unknown variables, since the solution from this method based on the moving least square approximation is already smooth enough. Numerical examples are given to verify the accuracy of the meshless method proposed for elasto-rdasticity analysis. | Song Kangzu Zhang Xiong Lu Mingwan (Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China) | 2003 | Acta Mechanica Solida Sinica2003，16，2： | 2 |
| 20 | EFFECTIVE NUMERICAL METHODS FOR ELASTO-PLASTIC CONTACT PROBLEMS WITH FRICTION显示文摘Several effective numerical methods for solving the elasto-plastic contact problems with friction are pres-ented.First,a direct substitution method is employed to impose the contact constraint conditions on condensed finite ele-ment equations,thus resulting in a reduction by half in the dimension of final governing equations.Second,an algorithmcomposed of contact condition probes and elasto-plastic iterations is utilized to solve the governing equation,whichdistinguishes two kinds of nonlinearities,and makes the solution unique.In addition,Positive-Negative Sequence Modifica-tion Method is used to condense the finite element equations of each substructure and an analytical integration is intro-duced to determine the elasto-plastic status after each time step or each iteration,hence the computational efficiency is en-hanced to a great extent.Finally,several test and practical examples are pressented showing the validity and versatility ofthese methods and algorithms. | Wang Xucheng Chang Liangming Cen Zhangzhi (Department of Engineering Mechanics,Tsinghua University) | 1990 | Acta Mechanica Sinica1990，6，4： | 2 |
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