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Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

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Journal of Materials Science & Technology 2000年第3期16卷 269-272页

作者： Liangrong jia, Shoumei XIONG and Baicheng LIU (department of Mechanical Engineering, {2. University, beijing 100084, china. department of Mechanical Engineering Tsinghua University Beijing 100084 China

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

关键词： Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process Mold Simulation

An ecosystem-based understanding and analysis for SENCE toward sustainable development

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Journal of Environmental sciences 2001年第3期13卷 328-332页

作者： CHENG Sheng\|tong, HOU Ji\|xiong , jia Hai\|feng (department of Environmental Science and Engineering, {2. University, beijing 100084, china. 清华大学北京 100084

There is a need to find a comprehensive approach focusing on the conflicts between economical growth and environmental protection. Chinese scholars advocate a comprehensive ecosystem viewpoint named social-economic-natural complex ecosystem(SENCE). The kernel of the concept lies in the hierarchical structure of SENCE, through which methods from ecological network can be useful to the compound system. The author gives a schema depicting its structure, following a made analysis to help understand the reliance of economy on ecosystem. It is obvious that more actions should be done to strive for sustainable development.

关键词： social-economic-natural complex ecosystem (SENCE) ecosystem model sustainable development

Effect of carbon source on the denitrification in constructed wetlands

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Journal of Environmental sciences 2009年第8期21卷 1036-1043页

作者： LU Songliu, HU Hongying, SUN Yingxue, YANG jia ESPC State Key Joint Laboratory, department of Environmental Science and Engineering, {2. University, beijing 100084, china. ESPC State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China

The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source （glucose） can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 2.% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 2. h and 2. mg/L dissolved organic carbon （DOC） was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2.mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.

关键词： constructed wetland carbon source denitrification nitrate nitrite

Investigation of heavy metal partitioning influenced by flue gas moisture and chlorine content during waste incineration

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Journal of Environmental sciences 2010年第5期22卷 760-768页

作者： Qinghai Li,Aihong Meng,Jinyan jia,Yanguo Zhang department of Thermal Engineering,Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education of {2.tsinghua University,beijing 100084,{2. department of Thermal Engineering Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education of China Tsinghua University Beijing 100084 China

The impact of moisture on the partitioning of the heavy metals including Pb,Zn,Cu and Cd in municipal solid waste （MSW） was studied in a laboratory tubular furnace.A thermodynamic investigation using CHEMKIN software was performed to compare the experimental *** waste,representative of typical MSW with and without chlorine compounds,was burned at the background temperature of 700 and 950°C,*** the absence of chlorine,the moisture content has no evident effect on the volatility of Pb,Zn and Cu at either 700 or 950°C,however,as flue gas moisture increasing the Cd distribution in the bottom ash increased at 700°C and reduced at 950°C,*** the presence of chlorine,the flue gas moisture reduced the volatility of Pb,Zn and Cu due to the transformation of the more volatile metal chlorides into less volatile metal oxides,and the reduction became significant as chlorine content *** Cd,the chlorine promotes its volatility through the formation of more volatile CdCl *** a result,the increased moisture content increases the Pb,Zn,Cu and Cd concentrations in the bottom ash,which limits the utilization of the bottom ash as a construction ***,in order to accumulate heavy metals into the fly ash,MSW should be dried before incineration.

关键词： heavy metals partitioning moisture chlorine municipal solid waste incineration

Development and application of a GIS database for the Miyun Reservoir water quality protection

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Journal of Environmental sciences 1999年第4期11卷 485-491页

作者： jia Hai\|feng, CHENG Sheng\|tong, XIAO Yang (department of Environmental {2. and Engineering, tsinghua University, beijing 100084,china. 清华大学环境科学与工程系北京

A high quality database is the starting point for any GIS application. For the Miyun Reservoir, a large amount of spatial data has been accumulated by numerous studies. This paper introduces a GIS database development in support of these studies. And some applications of the GIS database, include integration with GPS, view and management of data, and integration with WASP5 model, are also introduced.

关键词： GIS database ARC/INFO Arcview Miyun Reservoir water quality

Key parameter estimation for radar rotating object imaging with multi-aspect observations

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Science china.Information sciences) 2010年第8期53卷 1641-1652页

作者： YE ChunMao, XU jia , PENG YingNing & WANG XiuTan department of Electronic Engineering, {2. University, beijing 100084, china department of Electronic Engineering Tsinghua University Beijing China

Rotating object model is commonly used for imaging analysis in high resolution radars such as the inverse synthetic aperture radar (ISAR). For a rotating object, it is known that multi-aspect observations can improve cross-range resolution with the known imaging geometry. For the non-cooperative rotating object with unknown imaging geometry, this paper proposes an integrated scheme to estimate the key parameters, e.g., the rotating velocity and the aspect angle difference between every two observations. Furthermore, convolution back-projection (CBP) method is applied to provide fused imaging result with improved resolution. Also, the accuracy of the ultimate parameter estimation is analyzed, which is strongly related with several important factors like position extraction error of scattering centers and so on. Finally, the results of numerical experiments are provided to demonstrate the effectiveness of the proposed method.

关键词： rotating objects multi-aspect observations fused imaging aspect angle difference

Parameter estimation for SAR moving target in complex image domain

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Science china.Information sciences) 2010年第4期53卷 854-866页

作者： ZUO Yu, XU jia*, PENG YingNing & XIA XiangGen department of Electronic Engineering, {2. University, beijing 100084, china department of Electronic Engineering Tsinghua University Beijing China

Based on the proposed parametric model of SAR ground moving target in the complex image domain, this paper derives the Cramer-Rao bounds (CRB) for the unknown model parameters estimation and obtains the inherent limitations for the moving target motion estimation in the SAR complex image domain. Firstly, the relationships are analyzed among the estimation performance and the target’s scattering intensity, Doppler parameters, motion parameters, as well as the power spectra of the target and the clutter. Furthermore, the parameter estimation performance is compared in the signal domain and the complex image domain (CID) to draw some useful conclusions. Besides, the reduction resolution processing is proposed to improve the parameter estimation, and its performance improvement is also presented with analytic expressions. For the homogeneous background, it is shown that the accurate parameter estimation and azimuth location may be realized for SAR ground moving target in the complex image domain. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed methods.

关键词： synthetic aperture radar (SAR) moving target complex image domain parameter estimation Cramer-Rao bound (CRB) reduce resolution processing (RRP)

MEK inhibitor PD98059 acutely inhibits synchronized spontaneous Ca2.oscillations in cultured hippocampal networks

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Acta Pharmacologica Sinica 2006年第7期27卷 869-876页

作者： Yan-fang RUI~1 Zhao-hui SUN~2.jia-ping GU~1 Zhong-hua SHENG~1 Xiang-ping HE~1 Zuo-ping XIE~(1,3)1 department of Biological Science and Biotechnology,State Key Laboratory of Biomembrane and Membrane Biotechnology,{2. University beijing 100084,china.2.Institute of Neurological Disorders,Life Science and Medical department,{2. University,beijing 100084,china department of Biological Science and Biotechnology State Key Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing China Life Science and Medical department Institute of Neurological Disorders Tsinghua University Beijing China

Aim:To investigate the changes in synchronized spontaneous Ca2.oscillationsinduced by mitogen-activated protein kinase kinase（MEK）inhibitor PD98059 atdifferent concentrations in cultured hippocampal ***:Hippocam-pal neurons in culture for 1-2.weeks were used for this *** activities of these hippocampal neurons were examined by Ca2.imagingusing calcium-sensitive *** inhibitor PD98059（10,30,and 60μmol/L）andSB2.2.74（10 and 60μmol/L）,a negative control for mitogen-activated proteinkinase（MAPK）cascade study,were applied to the cells under the microscopewhile imaging was taking ***:PD98059 at a lower concentration of 10μmol/L had little effect on the Ca2.*** the higher concentration of 30μmol/L,5 min after application of PD98059,the spike frequency was decreased to2..38%±7.40%（mean±SEM,n=16,P2.2.74 atconcentrations of 10 and 60 μmol/L had little inhibition effect on the Ca2.***:These results indicate that PD98059 inhibits synchronized sponta-neous Ca2.oscillation through inhibition of MEK,which hints that the MAPKcascade is required to maintain synchronized spontaneous Ca2.oscillation.

关键词： PD98059 MEK calcium oscillation

Laser Measuring System Used for Large Workpiece Diameter

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Chinese Journal of Lasers 1996年第1期B5卷 94-96页

作者： ZHANG jianmin WANG jia LI Dacheng CAO Mang ZHAO Yang({2. of Precision Instruments,tsinghua University,beijing 100084, china. tsinghua Univ Beijing China

This paper reports a new kind of laser measuring instrument applied to detect large diameters of a workpiece on the production floor. The measuring principle of the instrument is specified in detail.

关键词： diameter measurement laser CCD