检索结果-南通市图书馆

CML MODELS AND THE NONLINEARITY OF TURBULENCE

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 1998年第9期19卷 881-887页

作者：刘兆存 department of sediment China Institute of Water Resources and Hydropower Research Beijing P.R. China

Some new coupled map lattice (CML) models are developed for simulating both convection, diffusion terms and weakly or strongly coupled terms. The structure and features of model are analysed. Numerical results show that the new models are effective for studying spatiotemporal chaos. Finally, the mechanism of turbulence is analysed via the numerical results.

关键词： CML model spatiotemporal chaos turbulence

Contribution of the Kodama and 4S pathways to the dibenzothiophene biodegradation in different coastal wetlands under different C/N ratios

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2019年第2期31卷 217-226页

作者： Lei Wang Guodong Ji Siqiao Huang Key Laboratory of Water and sediment Sciences Ministry of EducationDepartment of Environmental EngineeringPeking University

Dibenzothiophene(DBT) degradation mechanisms and the transformation of pathways during the incubation of three types of coastal sediments with C/N ratios ranging from 1 to 9 were investigated. The DBT degradation efficiencies were clearly improved with increasing C/N ratio in reed wetland sediments, tidal wetlands sediments and estuary wetland sediments. The quantitative response relationships between DBT degradation rates and related functional genes demonstrate that the Kodama pathway-related gene groups were dominant factors at low C/N ratios, while the 4S-related gene groups mainly determined the degradation rate when the C/N ratio was up to 5. Network analysis also shows that the pathway shifts from the Kodama pathway to the 4S pathway occurred through changes in the connections between functional genomes and rates. Furthermore, there were competition and collaboration between the Kodama and 4S pathways. The 4S pathway-related bacteria were more active in estuary wetland sediments compared with reed wetland sediments and tidal wetland sediments. The higher degradation efficiency in estuary wetland sediments may indicate the greater participation of the 4S pathway in the DBT biodegradation reaction. And the effects of ring cleavage of Kodama pathway caused more complete metabolizing of DBT.

关键词： Dibenzothiophene(DBT) Coastal wetlands Functional genes Degradation mechanism Quantitative response relationship Network analysis

On the formation of couplet-style stratifications

在线全文

学校读者我要写书评

暂无评论

International Journal of sediment research 2008年第1期23卷 85-91页

作者： Yu-Hai WANG1, Yan-Hong WANG2, and Li-Qun TANG31 Ph.D., Engineer, department of sediment research, China Institute of Water Resources and Hydropower research, Chegongzhuangxilu 20, Beijing 100044, China, 2 Ph.D., Engineer, Nanjing Hydraulic research Institute, Hujuguanlu 34, Nanjing 210024, China 3 Ph.D., Prof., department of sediment research, China Institute of Water Resources and Hydropower research, Chegongzhuangxilu 20, Beijing 100044, China Ph.D. Engineer Department of Sediment Research China Institute of Water Resources and Hydropower Research Chegongzhuangxilu 20 Beijing 100044 China Ph.D. Engineer Nanjing Hydraulic Research Institute Hujuguanlu 34 Nanjing 210024 China Ph.D. Prof. Department of Sediment Research China Institute of Water Resources and Hydropower Research Chegongzhuangxilu 20 Beijing 100044 China

Couplet-style stratifications refer to the sedimentary sequences that consist of alternating coarse-grain-dominated bed and fine-grain-dominated bed, with or without a sandwiched middle-sized bed. The formation mechanism is complicated due to the interplays of varying driving force (s), sediment supply & transport and topographic configurations. This paper presents a comprehensive overview of such characteristic bedforms, which emerge during the transport and deposition of non-uniform sediments. The leading formative models include water-stage variation, gravel-overpassing process, superimposition of bedload sheets and avalanching process (inverse grading). Each process might produce similar or distinct sedimentological features with respect to grading, matrix content, grain attitude, bounding faces between beds and internal longitudinal/transverse geometry. The couplet-style stratified strata might play an active role in landscape evolution.

关键词： Couplet-style stratification Formative model sedimentological features Landform

Impact Analysis of Coastal Engineering Projects on Mangrove Wetland Area Change with Remote Sensing

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2008年第2期22卷 347-358页

作者：李天宏韩鹏赵志杰 department of Environmental Engineering Key Laboratory of Water and Sediment Sciences of Ministry of Education Peking University

In the past decades, two large scale coastal engineering projects have been carried out in the Deep Bay surrounded by Shenzhen City and Hong Kong Special Administrative Region. One project is Shenzhen River channel regulation and the other is the sea reclamation along the seashore on the Shenzhen side. The two projects are very close to the two national nature reserves, specifically Futian in Shenzhen and Mai Po in Hong Kong, which are important wetland ecosystems worldwide. This paper aims to identify and monitor the mangrove wetland changes with time series of Landsat Thematic Mapper images pre and post to the two engineering projects being launched. Coupled analysis of the image interpretation results and tidal data acquired at the same time in the context of the two works reveals that the mangrove wetland area has increased from year 1989 to 1994, and has changed little from year 1994 to 2002. Binary coding is applied to reveal the distribution image of mangrove at each phase, and the coding image shows that the construction of the two coastal engineering projects has caused frequent changes in mangrove spatial distribution. The study also shows that the change is not significant regarding to the precision of the method and the natural evolution of mangrove wetland, and the projects do not cause apparently influences upon the two national mangrove conservation zones at least for the research time period.

关键词： mangrove wetland remote sensing sea reclamation river channel regulation the Deep Bay

Paper sludge as a feasible soil amendment for the immobilization of Pb^(2+)

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2010年第3期22卷 413-420页

作者： Xiaojia He, Lei Yao, Zhu Liang, Jinren NiThe Key Laboratory of Water and sediment Sciences, Ministry of Education, department of Environmental Engineering, Peking University, Beijing 100871, China. The Key Laboratory of Water and sediment Sciences Ministry of Education Department of Environmental Engineering Peking University Beijing 100871 China

The possibility of amending Pb 2＋ contaminated soil （S） with paper sludge （P） was investigated through adsorption and desorption experiments. The adsorption process of Pb 2＋ in soil containing paper sludge （SP） could be well described by pseudo second-order kinetic model and the Langmuir isotherm model. After P addition, the equilibrium time decreased greatly （from 28 to 8 hr） and the Pb 2＋ maximum adsorbed amount （Q max ） increased by a factor of more than three to 102.04 mg/g. Q max reached its maximum as S：P was 9：1 （m/m） after 10 days contact between S and P. Moreover, Pb 2＋ adsorbed amount increased with the rise of pH during the adsorption process. Desorption experiments indicated that Pb 2＋ adsorption in SP was irreversible. The metal ion fraction was analyzed with Energy Dispersive Spectrometer and Environmental Scan Electron Microscope. As a result, the addition of P to soil was found to induce a decrease in the mobile forms. The Pb 2＋ complexes formation in the presence of carbonates was the main adsorption mechanism. Overall, the paper sludge could be one of the promising soil amendments for the remediation of soil with Pb 2＋ contamination.

关键词： paper sludge pb^2+ adsorption

Experimental investigation on local shear stress and turbulence intensities over a rough non-uniform bed with and without sediment using 2D particle image velocimetry

在线全文

学校读者我要写书评

暂无评论

International Journal of sediment research 2020年第2期35卷 193-202页

作者： Petr Lichtneger Christine Sindelar Johannes Schobesberger Christoph Hauer Helmut Habersack CD-Laboratory of sediment research and Management Institute of Water ManagementHydrology and Hydraulic EngineeringDepartment Water-Atmosphere-EnvironmentUniversity of Natural Resources and Life Sciences

The current work focuses on locally resolving velocities,turbulence,and shear stresses over a rough bed with locally non-uniform character.A nonporous subsurface layer and fixed interfacial sublayer of gravel and sand were water-worked to a nature-like bed form and additionally sealed in a hydraulic ***-dimensional Particle Image Velocimetry(2 D-PIV) was applied in the vertical plane of the experimental flume *** with clear water and weak sediment transport were done under slightly supercritical flow to ensure sediment transport conditions without formation of considerable sediment deposits or *** study design included analyzing the double-averaged flow parameters of the entire measurement domain and investigating the flow development at 14 consecutive vertical *** geometrical variabilities as well the presence of sediment were mainly reflected in the vertical velocity *** the vertical velocity decreased over the entire depth in presence of sediment transport,the streamwise velocity profile was reduced only within the interfacial *** the region with decelerating flow conditions,however,the streamwise velocity profile systematically increased along the entire depth *** increase in the main velocity(reduction of flow resistance)correlated with a decrease of the turbulent shear and main normal ***,effects of rough bed smoothening and drag force reduction were experimentally documented within the interfacial sublayer due to mobile ***,the current study leads to the conclusion that in nonuniform flows the maximum Reynolds stress values are a better predictor for the bed shear stress than the linearly extrapolated Reynolds stress *** is an important finding because,in natural flows,uniform conditions are rare.

关键词： Turbulence measurement Local bed shear stress sediment transport and flow interaction Hydraulic flume experiment Particle image velocimetry

Assessment of heavy metal pollution in sediments from Xiangjiang River(China) using sequential extraction and lead isotope analysis

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Central South University 2014年第6期21卷 2349-2358页

作者：蒋博峰孙卫玲 Key Laboratory of Water and sediment Sciences of Ministry of Education(Peking University) department of Environmental Engineering Peking University

The heavy metal(such as Cr,Ni,Cu,Cd,Pb,and Zn)concentration,speciation,and pollution source in 43 sediment samples from the Xiangjiang River were investigated using sequential extraction combined with Pb isotope ***,Cd,Pb,and Zn concentrations are higher than their background values,while Cr and Ni concentrations are close to *** extraction demonstrates that heavy metals have different fractions,showing different *** w(206Pb)/w(207Pb)ratio increases with decreasing bioavailability in the order of exchangeable

关键词： sediment heavy metals sequential extraction lead isotope

On the variation of water resource structure in the Lower Yellow River

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2004年第Z1期47卷 127-141页

作者： NI Jinren1, WANG Yudong1, QIAN Zhenghan1, LI Tianhong1 & ZHAO Yean2 1. department of Environmental Engineering, Peking University The Key Laboratory of Water and Sedi- ment Sciences, Ministry of Education, Beijing 100871, China 2. Institute of Hydraulic research, Yellow River Conservancy Commission, Zhengzhou 450003, China department of Environmental Engineering Peking University Beijing China The Key Laboratory of Water and sediment Sciences Ministry of Education Beijing China Institute of Hydraulic research YellowRiver Conservancy Commission Zhengzhou China

In view of river functions and the Minimum Water Demand for River Ecosystem (MWDRE), the water resources in the Lower Yellow River is further divided into three portions, i.e. water available for ecosystem (WE), water exploitable for socioeconomic purposes (WS) and excess flood water (WF). Corresponding conceptions and practical significances are expounded in details. The annual amount of the three portions of water resources from 1950 to 2001 is worked out on the basis of the daily hydrologic data, and the division of different portions is discussed. The results indicate that although the essential water demand for river functions is considered preferentially, the amount of the WE has decreased dramatically while its proportion increased gradually since the 1950s, and the shortage to the MWDRE increased markedly; both the amount and the proportion of the WS decreased notably. Since the 1990s, the actual water consumption for socioeconomic purposes in the lower reaches of the river basin has already exceeded the maximum amount of the WS and has to take over the WE which is already insufficient, hence not only the normal river functions are further disturbed and the river course shrinks greatly, but also the proportion and potential danger of the WF show no decreasing tendency in spite of the sharp decrease of upstream runoff.

关键词： the Yellow River, water resource structure, water available for ecosystem, water exploitable for socioeconomic purposes, excess flood water.

Characteristics of Pb^(2+) biosorption with aerobic granular biomass

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2008年第6期53卷 948-953页

作者： YAO Lei YE ZhengFang WANG ZhongYou NI JinRen Key Laboratory of Water and sediment Sciences Department of Environmental Engineering Peking University Beijing 100871China

Experimental studies were conducted on the feasibility of aerobic granular biomass as a novel type of biosorbent for Pb2+ removal. The results show that the initial pH, Pb2+ concentration (C0) and biomass concentration (X0) affected the biosorption process significantly. Both the Freundlich and Langmuir isotherm models describe the biosorption process accurately, with correlation coefficients of 0.932 and 0.959 respectively. The Pb2+ biosorption kinetics is interpreted as having two stages, with the second stage described reasonably well by a Lagergren pseudo-second order model. Moreover, the surface change of granular biomass after the Pb2+ biosorption process appears to be caused by ion exchange and metal chelation according to the analysis results of Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-ray Spectroscopy (EDX).

关键词：需氧颗粒生物量铅离子生物吸附环境生物学