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作者： Shi, Yusheng Sun, Haixiao Huang, Naiyu Huang, Shuhuai State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology School of Material Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

How to rapidly fabricate metallic parts through rapid prototyping technology is a highly researched technique. However, at the present time, there are many problems during the direct manufacturing of functional metallic parts with rapid prototyping technology, which limits its practical application. Therefore, the indirect manufacturing technology based on rapid prototyping is still a main means of the fabrication of functional metallic parts. A indirect process of the fabrication of metallic parts based on combining selective laser sintering with vacuum pressure difference casting is researched. Some metallic parts are successfully fabricated using the indirect process. The precision control problems during selective laser sintering and investing casting process are researched and analyzed, and some means to solve the precision problems are put forward.

关键词： Investment casting

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An investigation into adopting shs technology in SLS metallic material

An investigation into adopting shs technology in SLS metalli...

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作者： Shi, Yusheng Chen, Senchang Lu, Xilong Huang, Shuhuai State Key Laboratory of Plastic Forming Simulation and Die and Mould Technology School of Material Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

Direct fabrication of metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are investigating. Existent problems during directly fabricating metal part by use of SLS are analyzed. For the sake of solving the problems, a new idea of adding self-propagating high-temperature synthesis (SHS) material into metallic powder material to form new type of SLS metallic powder material is put forward. This powder material can release controllable amount of heat during its interaction with the laser beam energy to reduce the requirement to laser power during directly sintering metallic part, to prolong the time of metallic liquid phase existing, and to improve the intensity and accuracy of SLS part. For this reason, SHS material's interaction with the CO2 laser beam energy is investigated, which proves that CO2 laser beam energy may instantly ignite SHS reaction. On the basis of the above-mentioned investigations, the effect of sintering the metal powder material mixing SHS material with CO 2 laser is also investigated, which shows: there is an optimal blending ratio of various material in the new metallic powder material. Under the optimal blending ratio and SLS process parameters, this new metallic powder material can indeed release amount of heat and SHS reaction may be controlled within the laser sintering. This investigation result makes it possible that the metallic part is directly sintered with small CO2 laser (less than 50W), which may greatly reduce the volume, cost and running expenditure of SLS machine, be propitious to application.

关键词： Sintering

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Lead Removal from Aqueous Solutions Using Novel Gel Adsorbent Synthesized from Natural Condensed Tannin

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Chinese Journal of Chemical engineering 2003年第4期11卷 426-430页

作者：占新民赵璇 AKANE Miyazaki YOSHIO Nakano State Key Joint Laboratory on Environment Simulation and Pollution Control Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Section of Environmental Technology Institute of Nuclear Energy Technology Tsinghua University Beijing 100084China Department of Environmental Chemistry and Engineering Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology Nagatsuta 4259 Midori-ku Yokohama 226-8502 Japan

Lead has caused serious environmental pollution due to its toxicity, accumulation in food chains and persistence in nature. In this paper, removal of lead from aqueous solutions is investigated using a novel gel adsorbent synthesized from natural condensed tannin. The novel adsorbent performs in aqueous solutions as a weak base with valid basic groups of 1.2mmol·g-1 tannin gel particles and therefore results in the elevation of pH value of aqueous solutions. Even when initial pH is 3.6, final pH at equilibrium can climb up to 6.5 that is above the pH value for Pb(OH)2 precipitation formation and then lead can be removed from wastewater by this so-called surface precipitation. The adsorption isotherm can be expressed by the Langmuir equation and the maximum capacity for adsorption of Pb is up to 92 mg·g-1 (based on dry adsorbent) when initial pH value is 3.6. Hence, the adsorbent does offer favorable properties in lead removal with respect to its high adsorption capacity at low initial pH value, which is advantageous to lead removal from acidic wastewater. A model is put forward to describe the individual adsorption phenomenon of the tannin gel adsorbent.

关键词： condensed tannin lead removal surface precipitation tannin gel adsorbent

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Scalability of a low-cost multi-Teraflop Linux cluster for high-end classical atomistic and quantum mechanical simulations

Scalability of a low-cost multi-Teraflop Linux cluster for h...

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International Parallel and Distributed Processing Symposium, IPDPS 2003

作者： Kikuchi, Hideaki Kalia, Rajiv K. Nakano, Aiichiro Vashishta, Priya Shimojo, Fuyuki Saini, Subhash Collaboratory for Multiscale Simulations Department of Computer Science Department of Physics and Astronomy Department of Materials Science Department of Biomedical Engineering University of Southern California Los AngelesCA90089 United States Concurrent Computing Laboratory for Materials Simulations Biological Computation and Visualization Center Department of Computer Science Department of Physics and Astronomy Louisiana State University Baton RougeLA70803 United States Faculty of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima739-8521 Japan IT Modeling and Simulation NASA Ames Research Center Moffett FieldCA94035 United States

ISBN: (纸本)0769519261

Scalability of a low-cost, Intel Xeon-based, multi-Teraflop Linux cluster is tested for two high-end scientific applications: Classical atomistic simulation based on the molecular dynamics method and quantum mechanical calculation based on the density functional theory. These scalable parallel applications use spacetime multiresolution algorithms and feature computational-space decomposition, wavelet-based adaptive load balancing, and spacefilling-curve-based data compression for scalable I/O. Comparative performance tests are performed on a 1024-processor Linux cluster and a conventional higher-end parallel supercomputer, 1184-processor IBM SP4. The results show that the performance of the Linux cluster is comparable to that of the SP4. We also study various effects, such as the sharing of memory and L2 cache among processors, on the performance. © 2003 IEEE.

关键词： Scalability

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Growth feature of biomass of Lemna aequinoctialis and Spirodela polyrrhiza in medium with nutrient character of wastewater

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Surface Mining - Braunkohle and Other Minerals 2003年第1期55卷 59-64页

作者： Chong, Yun-Xiao Hu, Hong-Ying Qian, Yi Environmental Simulation and Pollution Control State Key Join Laboratory Department of Environmental Science and Engineering Tsinghua University 100084 Beijing China

Duckweeds have an important potential in nutrient recovery from wastewater because of their rapid multiplication and high protein content in biomass. The growth rate of duckweed biomass has a direct relationship with nutrient removal and recovery. With laboratory experiments of batch culture and continuous culture, the growth curves of two duckweed species, Lemna aequinoctialis and Spirodela polyrrhiza, cultivated in different media were gotten and fitted by Logistic model. The effect of nitrogen on growth of duckweed was evaluated. Experimental results indicated that the growth curve had characteristic of sigmoidal shape and the growth rate had density-dependent characteristic. Results of statistical analysis demonstrated that Logistic model is suitable to describe the growth of single duckweed specie. The maximal growth rate from regression in medium with ammonia nitrogen was lower than those in medium with nitrate nitrogen. The maximal growth rate of Lemna aequinoctialis was higher than Spirodela polyrrhiza The paper also discussed the application of Logistic model in harvesting of duckweed biomass from wastewater.

关键词： Biomass

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Regular pattern of non-point source pollutants losses in Luxi watershed

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Surface Mining - Braunkohle and Other Minerals 2003年第1期55卷 108-112页

作者： Hu, Yuan-An Cheng, Sheng-Tong Jia, Hai-Feng Environmental Simulation and Pollution Control State Key Point Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China

The losses of non-point pollutant combined with natural rainfall events were monitored at outlets of Luxi watershed and several field plots with different land use. The paper probes characteristics of the sediment and chemical losses during a single rainfall-runoff process. The impact of preceding precipitation is also discussed. The results of field experiments show that the concentration of SS in runoff dropped off obviously with the increase of antecedent rainfall. The observed data were 265.6, 145.8, 124.2mg/L respectively with precipitation of 15, 115, 161 mm in preceding 5 days. Compared to the losses of SS, nutrients and COD were not changed greatly by the preceding rainfalls. The fluctuations of pollutant concentration were less than 15%. The results from plots suggested that land use play an important role in pollutant losses. The following is the list ordered according to concentration of pollutant in runoff, from the highest to the lowest: Dry land, residential area, grassland,woodland and paddy land. Vegetation cover is effective on the reduction of soil erosion and sediment loss. About 80% SS could be cut down when the coverage changed from 50% to 90%. Losses of TN were mainly determined by the TN concentration in *** ratios of TN concentration in runoff to that in soil were 2.75%, 2.79%, 2.42% respectively for the land use of dry land, grassland and woodland. Augment of vegetation overage contributed to increment of N losses, including NO3- -N and NH1 +-N.

关键词： Watersheds

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Scalability of a low-cost multi-Teraflop Linux cluster for high-end classical atomistic and quantum mechanical simulations

Scalability of a low-cost multi-Teraflop Linux cluster for h...

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International Symposium on Parallel and Distributed Processing (IPDPS)

作者： H. Kikuchi R.K. Kalia A. Nakano P. Vashishta F. Shimojo S. Saini Concurrent Computing Laboratory for Materials Simulations Biological Computation and Visualization Center Department of Computer Science Department of Physics & Astronomy Louisiana State University Baton Rouge LA USA Collaboratory for Multiscale Simulations Department of Computer Science Department of Physics & Astronomy Department of Materials Science Department of Biomedical Engineering University of Southern California Los Angeles CA USA Faculty of Integrated Arts and Sciences Hiroshima University Higashi Hiroshima Japan IT Modeling and Simulation NASA Ames Research Center Moffett Field CA USA

关键词： Scalability Linux Quantum mechanics computational modeling Testing Density functional theory Clustering algorithms Concurrent computing High performance computing Load management

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NITROGEN REMOVAL ENHANCED BY INTERMITTENT OPERATION IN SUBSURFACE INFILTRATION SYSTEM

NITROGEN REMOVAL ENHANCED BY INTERMITTENT OPERATION IN SUBSU...

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第二届中日化工学术研讨会

作者：张建黄霞刘超翔施汉昌胡洪营邵长飞刘志强 Environment Simulation and Pollution Control State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Environment Simulation and Pollution Control State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Environment Simulation and Pollution Control State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Environment Simulation and Pollution Control State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Environment Simulation and Pollution Control State Key Joint Laboratory Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China Qingdao Institute of Architecture and Engineering Qingdao 266033 Shandong China Qingdao Institute of Architecture and Engineering Qingdao 266033 Shandong China

A pilot subsurface infiltration system filled with red clay and cinder was constructed in a village located in Dianchi valley to treat rural sewage. At first, the system was continuously fed with rural sewage at a hydraulic loading of 2 cm/d. Average removal rates of COD, T-P, NH4+-N and T-N over the operation period of four months were achieved as 82.7%, 98.0%, 70. 0% and 77. 7% respectively. The low nitrogen removal rates were attributed to insufficient nitrification. Intermittent operation was adopted to improve nitrogen removal. Obvious improvement on T-N removal was found. T-N removal rate, over 80%, could be achieved even the hydraulic loading rose up to 6 cm/d. Soil oxidation-reduction potential (ORP) measurement showed that oxidative environment was enhanced through intermittent operation which encouraged nitrification reaction. Correspondingly, soil nitrification potential could be increased from less than 0. 8 mg/(kg ·h) at continuous feeding mode to about 1. 6 mg/(kg ·h) at intermittent operation mode.

关键词： subsurface infiltration system, intermittent operation, nitrogen removal, nitrification

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A multi-level and multi-scale evolutionary modeling system for scientific data

A multi-level and multi-scale evolutionary modeling system f...

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International Joint Conference on Neural Networks (IJCNN)

作者： Zhou Kang Yan Li H. de Garis L.-S. Kang Computation Center Wuhan University Wuhan China State Key Laboratory of Software Engineering Wuhan University Wuhan China Computer Science Department Utah State University Logan Utah USA

The discovery of scientific laws is always built on the basis of scientific experiments and observed data. Any real world complex system must be controlled by some basic laws, including macroscopic level, submicroscopic level and microscopic level laws. How to discover its necessity-laws from these observed data is the most important task of data mining (DM) and KDD. Based on the evolutionary computation, this paper proposes a multilevel and multi-scale evolutionary modeling system which models the macro-behavior of the system by ordinary differential equations while models the micro-behavior of the system by natural fractals. This system can be used to model and predict the scientific observed time series, such as observed data of sunspot and precipitation of flood season, and always get good results.

关键词： Microscopy Fractals Predictive models Control systems Evolutionary computation Floods Time series analysis Differential equations Discrete wavelet transforms Laboratories

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Application of Microbial BOD Sensors in Marine Monitoring

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Marine science Bulletin 2001年第1期3卷 69-73页

作者：张悦王建龙李花子施汉昌竺建荣 tate Key Joint Laboratory of Environment Simulation and Pollution Control Department of Environmental Science and Engineering Tsinghua University Beijing 100084 tate Key Joint Laboratory of Environment Simulation and Pollution Control Department of Environmental Science and Engineering Tsinghua University Beijing 100084 strain of yeast which can endure high osmotic pressure is employed for the sensitive material of the microbial BOD sensor. Two immobilization methods are used i.e. calcium alginate gel beads and PVA gel beads. The results show that the PVA gel beads is better. The influences of osmosis and heavy metal ions on the yeast entrapped in the PVA gel beads are also studied in the experiment.

A strain of yeast, which can endure high osmotic pressure, is employed for the sensitive material of the microbial BOD sensor. Two immobilization methods are used, I.e. Calcium alginate gel be ads and PV A gel beads. The results show that the PVA gel beads is better. The influences of osmosis and heavy metal ions on the yeast entrapped in the PVA gel beads are also studied in the experiment.

关键词： Biochemical oxygen demand, microbial sensor, yeast, immobilized cells, marine pollution, monitoring

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