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Effect of streambed sediment on benthic ecology

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International Journal of Sediment Research 2009年第3期24卷 325-338页

作者： Xuehua DUAN1, Zhao-Yin WANG2, Mengzhen XU3, and Kang ZHANG4. Ph.D., Jiangyin Environmental Monitoring Station, Jiangyin 214.31, china, Dept. of Hydraulic Engineering, tsinghua University,2 Prof., State Key laboratory of Hydroscience and Engineering, tsinghua University, beijing 100084, china, 3 Doctoral candidate, State Key laboratory of Hydroscience and Engineering, tsinghua University, beijing 100084, china,4.Doctoral candidate, State Key laboratory of Hydroscience and Engineering, tsinghua University, beijing 100084, china [a] Ph.D. Jiangyin Environmental Monitoring Station Jiangyin 214.31 china Dept. of Hydraulic Engineering tsinghua University [b] Prof. State Key laboratory of Hydroscience and Engineering tsinghua University beijing 100084 china Tel: 86-10-627734.8(O) [c] Doctoral candidate State Key laboratory of Hydroscience and Engineering tsinghua University beijing 100084 china [d] Doctoral candidate State Key laboratory of Hydroscience and Engineering tsinghua University beijing 100084 china

Benthic macroinvertebrates have been commonly used as indicator species for assessment of aquatic ecology. Streambed sediment, or substrate, plays an important role in habitat conditions for macroinvertebrate communities. Field investigations were done to study the benthic diversity and macroinvertebrate compositions in various stream substrata. Sampling sites with different bed sediment, latitude, and climate were selected along the Yangtze River, the Yellow River, the East River, and the Juma River, in china. The results show that benthic community structures found in different substrata clearly differ, while those found in substrata of similar composition and flow conditions but in different macroclimates are similar. The study, thus, demonstrates that the benthic macroinvertebrate community is mainly affected by substrate composition and flow conditions, but is generally unaffected by latitudinal position and macroclimate. Taxa richness of the macroinvertebrate community was found to be the highest on hydrophyte-covered cobbles, high on moss-covered bedrock, and low on clay beds and cobble beds devoid of plant biomass. Sandy beds are compact and unstable, thus, no benthic macroinvertebrates were found colonizing such substrata. Aquatic insects account for most of the macroinvertebrates collected in these rivers. Different insects dominate in different types of substrata: mainly EPT species (Ephemeroptera, Plecoptera, Trichoptera) in cobble, gravel, and moss-covered bedrock; and Chironomidae larvae in clay beds. The relation between the number of species in the samples and the size of the sampling area fits a power function of the species area. One square meter (1m2) is suggested as the minimum sampling area. A substrate suitability index is proposed by integrating the suitability of sediment, periphyton, and benthic organic materials for macroinvertebrates. The biodiversity of macroinvertebrates increases linearly with the substrate suitability index. Benthic ta

关键词： Streambed sediment Macroinvertebrates Benthic ecology Substrate suitability Biodiversity

^(234.Th/^(238)U disequilibrium and particulate organic carbon export in the northwestern South china Sea

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Acta Oceanologica Sinica 2011年第3期30卷 55-62页

作者： MA Hao ZENG Zhi YU Wen HE Jianhua CHEN Liqi CHENG Jianping YIN Mingduan ZENG Shi Department of Engineering Physics Tsinghua University Beijing 100084 China Key laboratory of Global Change and Marine-Atmospheric Chemistry State Oceanic Administration Xiamen 361005 China Key laboratory of Particle ＆ Radiation Imaging （tsinghua University） Ministry of Education Beijing 100084 China Key laboratory of High Energy Radiation Imaging Fundamental science for national Defense Beijing 100084 China

234.h was utilized as a tracer of particulate organic carbon （POC） export in the northwestern South china Sea （SCS） on the basis of the data collected at four stations during a spring cruise. Depth profiles of dissolved and particulate 234.h activities were measured in the upper 60m, showing a significant deficit relative to 23Su over the investigated stations. A stratified structure of 234.h-23su disequilibrium was in general observed in the upper 60 m water column, indicating that the euphotic zone of the northwestern SCS in this reason can be divided into two layers, an upper and lower layer, with different export rates. POC export fluxes were estimated from a one-dimensional steady state model of 234.h fluxes in combination with the measurement of POC/234.h ratios on suspended particles. The POC export in this region ranged from 8.2 to 20.0 mmol/（m2.d）, with an average of 16.0 mmol/（m2-d）, and was slightly higher than those previously reported in the southern SCS.

关键词： 234.h 23su disequilibrium POC export South china Sea

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,tsinghua University,{4.. [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

Analytic calculation of formation enthalpies directly from interatomic potentials for binary and ternary refractory metal systems

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science china(Technological sciences) 2010年第7期53卷 2015-2019页

作者： DAI Ye, LI JiaHao, CHE XingLai & LIU BaiXin Advanced Materials laboratory, Department of Materials science and Engineering, tsinghua University, beijing {4., china. 1. Advanced Materials laboratory Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

An analytic method is proposed to calculate the formation enthalpy directly from empirical n-body potential and applied to the binary and ternary systems consisting of the refractory metals Mo, Nb, Ta and W. It turns out that the calculated enthalpies are in overall agreement with experimental observations and some other theoretical calculations. Interestingly, it shows that the formation enthalpies of the ternary systems are significantly affected by those of the constituent binary systems.

关键词： n-body potential refractory materials ternary systems thermodynamic computations

A new method of fabricating strained Silicon materials

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Rare Metals 2006年第z2期25卷 41-44页

作者： YANG Zongren LIANG Renrong XU Jun Institute of Microelectronics Tsinghua University Beijing 100084 China Institute of Microelectronics Tsinghua University Beijing 100084 China Microelectronics and Nanoelectronics Division of the Tsinghua National Lab for Information Science and Technology Beijing 100084 China Institute of Microelectronics Tsinghua University Beijing 100084 China

Strain-relaxed SiGe virtual substrates are of great importance for fabricating strained Si materials. Instead of using graded buffer method to obtain fully relaxed SiGe film, in this study a new method to obtain relaxed SiGe film and strained Si film with much thinner SiGe film was proposed. Almost fully relaxed thin SiGe buffer layer was obtained by Si/SiGe/Si multi-structure oxidation and the SiO2 layer removing before SiGe regrowth. Raman spectroscopy analysis indicates that the regrown SiGe film has a strain relaxation ratio of about 93% while the Si cap layer has a strain of 0.63%. AFM shows good surface roughness. This new method is proved to be a useful approach to fabricate thin relaxed epilayers and strain Si films.

关键词： strained Si SiGe oxidation strain relaxation

Heuristic for no-wait flow shops with makespan minimization based on total idle-time increments

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science in china(Series F) 2008年第7期51卷 896-909页

作者： LI XiaoPing1,2 & WU Cheng3 1 School of Computer science & Engineering, Southeast University, Nanjing 210096, china 2 Key laboratory of Computer Network and information Integration (Southeast University), Ministry of Education, Nanjing 210096, china 3 Department of Automation, tsinghua University, beijing 100084, china 1. School of Computer science & Engineering Southeast University Nanjing 210096 China 2. Key laboratory of Computer Network and information Integration (Southeast University) Ministry of Education Nanjing 210096 China 3. Department of Automation Tsinghua University Beijing 100084 China

No-wait flow shops with makespan minimization are classified as NP-hard. In this paper, the optimization objective is equivalently transformed to total idle-time minimization. The independence relationship between tasks is analyzed, and objective increment properties are established for the fundamental operators of the heuristics. The quality of the new schedules generated during a heuristic is judged only by objective increments and not by the traditional method, which computes and compares the objective of a whole schedule. Based on objective increments, the time complexity of the heuristic can be decreased by one order. A seed phase is presented to generate an initial solution according to the transformed objective. Construction and improvement phases are introduced by experimental analysis. The FCH （fast composite heuristic） is proposed and compared with the most effective algorithms currently available for the considered problem. Experimental results show that the effectiveness of the FCH is similar to that of the best methods but requires far less computation time. The FCH can also be efficient in real time scheduling and rescheduling for no-wait flow shops.

关键词： no-wait flow shops heuristic makespan Tabu search

The quantification of remote sensing

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science china(Technological sciences) 2005年第S2期48卷 1-11页

作者： GU Xingfa1,2,3,TIAN Guoliang1,2, LI Xiaowen1,2 & GUO Jianning4.1. State Key laboratory of Remote Sensing science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of sciences and beijing Normal University, beijing 100101, china 2. The Center for national Spaceborne Demonstration, beijing 100101, china 3. Institut national de la Recherche Agronomique, Climat Sol Environnement, 84.14.Avignon, France 4. china Center for Resource Satellite Data and Application, beijing 100830, china Chinese Acad Sci Inst Remote Sensing Applicat State Key Lab Remote Sensing Sci Beijing 100101 Peoples R China beijing Normal Univ State Key Lab Remote Sensing Sci Beijing 100101 Peoples R China Ctr Natl Spaceborne Demonstrat Beijing 100101 Peoples R China Inst Natl Rech Agron F-84914 Avignon France china Ctr Resource Satellite Data & Applicat Beijing 100830 Peoples R China

The paper firstly defined the remote sensing information quantification, analyzed the necessity of developing remote sensing quantification, figured out the application guidelines requirement, and pointed out the importance of quantification research. Then taking the remote sensing application research of CBERS-02 data quantification as the example, the paper described the whole quantification system of “remotely sensed digital signal-radiation information-field parameter inversion”. Finally the paper gave the prospect for the development trend of the quantitative remote sensing.

关键词： remote sensing information quantification CBERS-02 radiometric calibration surface parame- ter reversion.

Level Set interface treatment and its application in Euler method

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science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 227-236页

作者： WU KaiTeng1,2,HAO Li3,WANG Cheng4.& ZHANG Li1,2 1 Numerical Simulation Sichuan Higher School Key laboratory,Neijiang Normal University,Neijiang 64.112,china 2 College of Mathematics and information science,Neijiang Normal University,Neijiang 64.112,china 3 College of science,beijing University of Civil Engineering and Architecture,beijing 10004.,china 4.State Key laboratory of Explosion science and Technology,beijing Institute of Technology,beijing 100081,china 1. Numerical Simulation Sichuan Higher School Key laboratory Neijiang Normal University Neijiang 641112 China2. College of Mathematics and Information Science Neijiang Normal University Neijiang 641112 China3. College of Science Beijing University of Civil Engineering and Architecture Beijing 100044 China4. State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China

Level Set interface treatment method is introduced into Euler method,which is employed for interface treatment method for multi-materials. Combined with the ghost fluid method,the moving interface is tracked. Fifth-order WENO spatial discretization and third-order TVD Runge-Kutta time discretization methods are used. Shock-wave action on bubble,implosion and velocity field Shock effect bubbles; implosion and velocity field are simulated by means of LS-MMIC3D programmed by C++. Nu-merical results show that the Level Set interface treatment method is effective and feasible for multi-material interface treatment in comparison with the WENO method.

关键词： Euler method Level Set method shock-wave action on bubble implosion numerical simulation

A survey on routing in wireless sensor networks

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Progress in Natural science:Materials International 2007年第3期17卷 261-269页

作者： XIAO Renyi and WU Guozheng (Department of information sciences, national Natural science Foundation of {4., beijing 100085, {4.) [a]Department of information sciences National Natural Science Foundation of China Beijing China

One of the most important issues in wireless sensor networks is data delivery service between sensors and the data collection unit (called sink). Although sensor networks and mobile ad hoc networks are similar to some extent, they are radically distinct in many aspects. Sensor networks have many unique features, making them more challenging and need further research efforts. The existing routing protocols for sensor networks can be classified as indicator-based and indicator-free. In this survey, we make a comparative study of these protocols. Open issues and research directions are pointed out as guidelines for our future work.

关键词： sensor network distributed system routing ad-hoc network.