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Mechanisms of particle vertical diffusion in sediment-laden flows

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Chinese science Bulletin 2004年第10期49卷 1086-1090页

作者： wang guangqian {2. xudong key lab for water and Sediment sciences of ministry of education, tsinghua university, beijing 100084,{12.Correspondence should be addressed to wang Guanqian key lab for {2. and Sediment sciences of ministry of education Tsinghua University Beijing 100084 China

Diffusion coefficient of natural sediments andeffects of lift force and gradient in particle velocity fluctua-tions were investigated through using a closed kinetic *** against experimental data of Einstein ＆ Chien(1955) validated the model. The diffusion coefficient εyy ofmedium and large sediments distinctly exceeds fluid eddyviscosity V^tf, while εyy of fine sediments approximately equals V^tf. In the measured region of 0.03＜y/H＜0.4, εyy/V^tf increaseswith the distance from the wall decreasing. Combined effectsof lift force and gradient in particle velocity fluctuationschange sediment gravitational settling remarkably below y/H=0.2. and need to be accounted for describing sedimentdiffusion in this region.

关键词：沉积物两相流动力模型扩散效率升力

KINETIC MODELING OF CONSTITUTIVE RELATIONS FOR PARTICLE MOTION IN LOW TO MODERATELY CONCENTRATED FLOWS

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International Journal of Sediment Research 2005年第4期20卷 305-318页

作者： guangqian wang1, {2. fu1 and Xingkui wang11 key lab for water and Sediment sciences of the ministry of education, Department of Hydraulic Engineering, tsinghua university,{12., china key lab for {2. and Sediment sciences of the ministry of education Department of Hydraulic EngineeringTsinghua University Beijing 100084 China

Formulating underlying mechanisms of concentrated solid-liquid flows is essential for simulation of various industrial processes and natural phenomena. A generalized constitutive model for particle motion in flows with low to moderate solids concentrations is developed. This generalized model facilitates characterization of inelastic collisions, particle-fluid interactions, and shearing effects. Moderately concentrated simple shear flows of a sand-water mixture are analyzed, and comparisons of model predictions and experimental data are in good agreement. This model exhibits sound performance in characterizing particle motion for wide ranges of concentration and shear rate, and may supply a reasonable and competent alternative to previous models developed for dilute and rapid-granular flows when applied to moderately concentrated situations. The concentration approaches zero (C → 0) asymptote is observed at a relatively high shear rate in model predictions. Assumption of low collisional dissipation of the particle phase as C → 0 is more reasonable for this observation, compared to that without the interstitial fluid effect. Accurately modeling energy dissipation is important for characterizing the stability of dilute simple shear flows of solid-liquid mixtures. Incorporating friction forces will also facilitate improvement of the applicability of this generalized model to flows at extremely high concentrations.

关键词： Constitutive relations Kinetic model Two-phase flow Turbulent diffusion Collisions Stress Concentration Shear rate

water demand for ecosystem protection in rivers with hyper-concentrated sediment-laden flow

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science china.Technological sciences) 2004年第z1期47卷 186-198页

作者： LUO Huaming, LI Tianhong, NI Jinren & wang Yudong Department of Environmental Engineering, Peking university, {2. 100871, china.The key laboratory of water and Sediment sciences, ministry of education, {2. 100871, china Peking Univ Dept Environm Engn Beijing 100871 Peoples R China key lab {2. & Sediment Sci Minist Educ Beijing 100871 Peoples R China

Sediment transport is one of the main concerns in a river system with hyper-concentrated flows. Therefore, the water use for sediment transport must be considered in study on the water demand for river ecosystem. The conventional methods for calculating the Minimum water Demand for River Ecosystem (MWDRE) are not appropriate for rivers with high sediment concentration. This paper studied the MWDRE in wet season, dry season and the whole year under different water-and-sediment conditions in the Lower Yellow River, which is regarded as a typical river with sediment-laden flows. The characteristics of MWDRE in the river are analyzed. Firstly, the water demand for sediment transport (WDST) is much larger than the demands for other riverine functions, the WDST accounts for the absolute majority of the MWDRE. Secondly, in wet season when the WDST is satisfied, not only most of the annual incoming sediment can be transported downstream, but also the water demands for other river functions can be satisfied automatically, so that the MWDRE in wet season is identical to the WDST. Thirdly, in dry season, when the WDST is satisfied, the water demands for other river functions can also be satisfied, but the low sediment transport efficiency results in significant waste of water resources. According to these characteristics and aiming at decreasing sediment deposition in the riverbed and improving the utilization efficiency of water resources, hydrological engineering works can be used to regulate or control flow and sediment so that the sediment incoming in dry season can be accumulated and be transported downstream intensively and thus efficiently in wet season.

关键词： sediment-laden flow, the Lower Yellow River, water demand for river ecosystem, water demand for sediment transport

Distribution and origin of biologically available phosphorus in the water of the Meiliang Bay in summer

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science china.Earth sciences 2006年第z1期49卷 146-153页

作者： HUANG Qinghui, wang Zijian, wang Donghong, MA Mei & wang Chunxia State key laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental sciences, Chinese Academy of sciences, beijing 100085, china.key laboratory of Yangtze Aquatic Environment (ministry of {12.), College of Environmental science and Engineering, Tongji university, Shanghai 2.0092. china Chinese Acad Sci Ecoenvironm Sci Res Ctr State Key Lab Environm Aquat Chem Beijing 100085 Peoples R China Tongji Univ Coll Environm Sci & Engn Minist Educ Key Lab Yangtze Aquat Environm Shanghai 200092 Peoples R China

The investigation and continuous monitoring with an innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) on the concentrations of biologically available phosphorus (BAP) were conducted in the Meiliang Bay of the Taihu Lake during summer in 2.04. The results showed that the concentrations of dissolved (FeO-DP), particulate (FeO-PP) and total bioavailable phosphorus (FeO-P) had similar horizontal distribution. The BAP concentrations were the highest in those estuaries in the northern bay. With the decrease of the distance to the estuary or long shore,there was little difference between BAP concentrations in an open lake area. During the observation period, algal blooms occurred in most {2.s of the northern bay, which was reflected from the high concentrations of chlorophyll a (Chl-a). While they were not highest in the estuarine {2.s of those major rivers, this is the case for the BAP concentrations. The concentrations of Chl-a had a significantly positive correlation with those of bioavailable phosphorus in the open area of the Meiliang *** the sediment resuspension induced by wind and wave, BAP concentrations increased in a short-term, indicating that the riverine P inputs mainly contribute to the concentrations of BAP in the estuarine {2. while internal P release was the major source of BAP in the open lake area. In the eutrophic shallow lake, the blooms of alga may cause pH increase and further result in internal P release. The above results showed that the new membrane of FeO/CAM can be used to monitor the concentrations of BAP and provide the scientific justifications for the control strategy of the lake eutrophication.

关键词： phosphorus, bioavailability, eutrophication, resuspension, Taihu Lake.

Dynamic recrystallization during hot torsion of Al-4Mg alloy

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Journal of university of science and Technology {2. 2003年第2期10卷 45-48页

作者： Junpin Lin, Yanli wang, Zhi Lin, and Guoliang ChenState key {2.oratory of Advanced Metal Materials, university of science and Technology beijing, beijing 100083, china lab. of Adv. Metal Mat. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched. The study indicates that the dynamicrecrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter(Zener-Hollmon Parameter), i.e. 19.3 2..8. Increasing the strain rate at higher deformationtemperature or reducing the strain rate at lower deformation temperature accelerates the occurrenceof dynamic recrystallization in the alloy.

关键词： Al-4Mg alloy dynamic recrystallization hot torsion

Spatio-Temporal Dynamics of Soil Moisture in Silvopastoral System in the Loess Plateau of West Shanxi Province

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Spatio-Temporal Dynamics of Soil Moisture in Silvopastoral S...

硅藻土原位生长Nb_2._5纳米棒及表面Cr(Ⅵ)吸附转化行为研究

International Conference on Environmental science and Technology（ICEST 2.11）

作者： Lei Yun Lubo Gao Huaxing Bi Qingke Zhu Xiaoyan wang College of Soil and water Conservation {2. Forestry university key lab.Soil and water Conservation and Desertification Combating ministry of education {2. china

The objective of this study was to investigate the spatio-temporal dynamics of soil moisture in silvopastoral system in the Loess Plateau of west Shanxi *** moisture in 0-100 cm layer was measured and analyzed in locust-natural grass *** results showed as following:（1） There were significant differences of soil moisture in 0-100cm layer in different phenological *** moisture contents in different patch types were different in silvopastoral *** soil moisture contents of the grassland were significantly greater than the forestland’s.（2. There were obvious hierarchy characteristics in soil profile in locust-natural grass *** soil moisture contents and coefficient of variation both decreased with increase of soil *** horizontal direction,variations of soil moisture were relatively obvious in grassland,and soil moisture increased with the increase of the distance from forest edge to *** forestland,variations of soil moisture were relatively complicated and soil moisture decreased with the increase of ***-dimension isogram map gave a very strong visual impression,and it obtained good results in expressing the spatial structural characters.

关键词： Silvopastoral system Dynamics of soil moisture Spatial and temporal change Loess Plateau

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无机材料学报 2018年第5期33卷 557-564页

作者：杜玉成王学凯侯瑞琴吴俊书张时豪祁超北京工业大学新型功能材料教育部重点实验室北京100124 北京特种工程设计研究院北京100028

以活化铌酸为铌源,草酸铵为沉积剂,十二烷基苯磺酸钠为模板剂,采用水热法在硅藻土表面原位生长Nb_2._5纳米棒。采用SEM、TEM、XRD、BET、FT-IR和XPS等分析方法对样品进行表征,反应14 h后,Nb_2._5纳米棒长度为500~700 nm,直径为2.~35 nm... 详细信息

以活化铌酸为铌源,草酸铵为沉积剂,十二烷基苯磺酸钠为模板剂,采用水热法在硅藻土表面原位生长Nb_2._5纳米棒。采用SEM、TEM、XRD、BET、FT-IR和XPS等分析方法对样品进行表征,反应14 h后,Nb_2._5纳米棒长度为500~700 nm,直径为2.~35 nm;硅藻土原位生长Nb_2._5纳米棒样品比表面积为157 m^2.g。研究了样品对Cr(Ⅵ)的吸附与光还原行为,可见光条件下对Cr(Ⅵ)吸附量可达2.0 mg/g;紫外光条件下,可将表面吸附的Cr(Ⅵ)转变为Cr(Ⅲ),样品经过5次循环使用后,对Cr(Ⅵ)(100 mg/L)降解率仍能保持在93%左右。样品可对重金属污染废水中Cr(Ⅵ)进行吸附与毒性降解一体化去除。

关键词：硅藻土氧化铌纳米棒 Cr(VI) 吸附毒性降解

重庆缙云山典型林分林地土壤微团聚体特征分析

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土壤通报 2009年第6期40卷 1240-1244页

作者：储小院王玉杰刘楠齐娜杨小梅申彦科北京林业大学水土保持学院水土保持与荒漠化防治教育部重点实验室北京100083

采用吸管法分散分离提取土壤微团聚体和机械组成,通过测定土壤有机质含量和pH值,研究了重庆缙云山典型林分林地土壤微团聚体特征及其与土壤理化性质的关系。结果表明:重庆缙云山典型林分林地土壤均呈酸性,沿土壤自然剖面向下pH值呈逐渐... 详细信息

采用吸管法分散分离提取土壤微团聚体和机械组成,通过测定土壤有机质含量和pH值,研究了重庆缙云山典型林分林地土壤微团聚体特征及其与土壤理化性质的关系。结果表明:重庆缙云山典型林分林地土壤均呈酸性,沿土壤自然剖面向下pH值呈逐渐增大趋势,而有机质含量逐渐降低。各林地的土壤物理性粘粒综合含量依次为农地(对照)(75.31%)>混交林地(69.87%)>灌木林地(68.81%)>阔叶林地(55.19%)>楠竹林地(44.87%)。各林分一定程度上均能改善土壤的颗粒组成状况,调节土壤结构和土壤肥力,楠竹林分相对较弱。各林地土壤沿自然剖面向下,土壤微团聚体水稳定性减弱。林地土壤微团聚体的团聚度大小为灌木林地(36.4%)>农地(对照)(2..96%)>混交林地(2..19%)>阔叶林地(15.13%)>楠竹林地(10.86%),分散系数大小为灌木林地(2..43%)1048x有机质-0.8413与y=0.9097x粘粒+41.61。有机质是典型林分林地土壤微团聚体形成的重要因素,物理性粘粒则对其形成起着重要的胶结作用。灌木林地土壤微结构水稳定性优于其他林地,其改善土壤微结构、调节土壤保水保肥能力最好,而楠竹林地相对最差。

关键词：微团聚体水稳定性土壤理化性质

Modified electronic structure and enhanced hydroxyl adsorption make quaternary Pt-based nanosheets efficient anode electrocatalysts for formic acid-/alcohol-air fuel cells

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Journal of Energy Chemistry 2024年第5期92卷 142-150页

作者： Fengling Zhao Qiang Yuan Siyang Nie Liang Wu Xun wang State-Local Joint laboratory for Comprehensive Utilization of Biomass Center for R&D of Fine ChemicalsCollege of Chemistry and Chemical EngineeringGuizhou UniversityGuiyang 550025GuizhouChina key lab of Organic Optoelectronics&Molecular Engineering Tsinghua UniversityBeijing 100084China School of Chemistry and Chemical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet ***,using visible light,a class of quaternary Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.2.)ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel *** modified electronic structure of Pt,enhanced hydroxyl adsorption,and abundant exterior defects afford Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.2.)/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells,and the corresponding peak power density of Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.2.)/C is respectively 12..7,142.3,105.4,12..3,and 12..0 mW cm^(-2.,considerably outperforming Pt/*** in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.2.)/C occurs via a CO_(2.-free direct *** functional theory calculations show that the presence of Ag,Bi,and Te in Pt_(1)Ag_(0.1)Bi_(0.16)Te_(0.2.)suppresses CO^(*)formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H_(2.O dissociation to improve electrocatalytic *** synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets(from ternary to octonary nanosheets),and efficiently capture precious metals(i.e.,Pd,Pt,Rh,Ru,Au,and Ag)from different water sources.

关键词： Pt-based nanosheets Modifiedelectronic structure Enhanced hydroxyl adsorption Formicacidand alcohol oxidation Direct liquid fuel cells