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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, tsinghua university, Beijing {3., 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, tsinghua university, Beijing {3., china. department of Environmental Science and Engineering Tsinghua University Beijing 100084 China.

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, tsinghua university, Beijing {3., china. [a]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 20% to more than 50% in summer and from 10% to 3.% in winter, when the nitrate concentration was 3.-40 rag/L, the retention time was 24 h and 25 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

Viability of all-solid-state lithium metal battery coupled with oxide solid-state electrolyte and high-capacity cathode

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Journal of Energy Chemistry 2024年第4期91卷 122-131页

作者： Xingxing jiao Xieyu Xu Yongjing Wang Xuyang Wang Yaqi Chen Shizhao Xiong Weiqing Yang zhongxiao Song Yangyang Liu Research Institute of Frontier Science Southwest Jiaotong UniversityChengdu 610031SichuanChina State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina department of Physics Chalmers University of TechnologyGöteborgSE 41296Sweden

Owing to the utilization of lithium metal as anode with the ultrahigh theoretical capacity density of 3.60 mA h g^(-1)and oxide-based ceramic solid-state electrolytes(SE),e.g.,garnet-type Li7La_(3.Zr_(2)O_(12)(LLZO),all-state-state lithium metal batteries(ASLMBs)have been widely accepted as the promising alternatives for providing the satisfactory energy density and ***,its applications are still challenged by plenty of technical and scientific *** this contribution,the co-sintering temperature at 500℃is proved as a compromise method to fabricate the composite cathode with structural integrity and declined capacity fading of LiNi_(0.5)Co_(0.2)Mn_(0.3.O_(2)(NCM).On the other hand,it tends to form weaker grain boundary(GB)inside polycrystalline LLZO at inadequate sintering temperature for LLZO,which can induce the intergranular failure of SE during the growth of Li filament inside the unavoidable defect on the interface of ***,increasing the strength of GB,refining the grain to 0.4μm,and precluding the interfacial defect are suggested to postpone the electro-chemo-mechanical failure of SE with weak ***,the advanced sintering techniques to lower the co-sintering temperature for both NCM-LLZO composite cathode and LLZO SE can be posted out to realize the viability of state-of-the-art ASLMBs with higher energy density as well as the guaranteed safety.

关键词： All-solid-state lithium metal battery LiNi_(0.5C)o_(0.2)Mn_(0.3.O_(2)-Li7La_(3.Zr_(2)O_(12)composite cathode Co-sintering Lithium metal anode Electro-chemo-mechanical failure

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 china.{3.,Beijing 100084,china. [a] department of Thermal Engineering Key Laboratory for Thermal Science 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 sciences and Engineering, {3., 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, tsinghua university, Beijing {3., china 1. department of Electronic Engineering Tsinghua University Beijing 100084 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, tsinghua university, Beijing {3., china 1. department of Electronic Engineering Tsinghua University Beijing 100084 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)

Facile synthesis of transition metal complexes with five coplanar metal-carbon σ-bonds

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National Science Review 2024年第4期11卷 11-12页

作者： Guocheng jia department of Chemistry Hong Kong University of Science and Technology

Carbon is one of the most important elements in chemistry, forming a vast number of organic compounds. It can also form a variety of organometallic compounds with a metal–carbon bond. Metal alkyl, carbene and carbyne complexes are classical examples of organometallic compounds. A particularly interesting class of organometallic compounds are all-carbon metallacycles formed by combination of a metal and a hydrocarbon chain serving as a chelating agent with only carbon atoms as the donor atoms. Many interesting monocyclic metallacycles made of a chelating bidentate hydrocarbon chain are known, for example, metallacyclobutadienes, metallacyclopentadienes and metallabenzenes[1].

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