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efficiency of sediment transport by flood and its control in the Lower Yellow River

Science China(Technological Sciences) 2004年第Z1期47卷 173-185页

作者： NI Jinren1, LIU Xiaoyong2, LI Tianhong1, ZHAO Ye’an3 & JIN Ling1 1. Department of Environmental Engineering, Peking University The Key Laboratory of Water and Sedi- ment Sciences, Ministry of Education, Beijing 100871, China 2. General Institute of Water Resources and Hydropower Planning and Design, Ministry of Water Re- sources, Beijing 100011, China 3. The 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 General Institute of Water Resources and Hydropower Planning and Design Ministry of Water Resources Beijing China The Yellow River Conservancy Commission Zhengzhou China

This paper presents the characteristics of sediment transport by flood in the Lower Yellow River with the reach from Huayuankou to Gaocun, which is regarded as a typical braided pattern. The Artificial Neural Network Model on Water Use for Sediment Transport (WUST) by flood was established based on the measured data from 1980 to 1998. Consequently, simulations of controlling process of sediment transport by flood were made in terms of the control theory under different scenarios. According to the situation of sediment transport by flood in the Lower Yellow River, Open-Loop control system and feedback control system were adopted in system design. In the Open-Loop control system, numerical simulations were made to reveal the relationship between average discharge of flood and the WUST with varying sediment concentrations. The results demonstrate that sediment concentration has significant influence on the controlling process of flood flow to WUST. It is practical and efficient to control WUST if sediment concentration is less than 20 kg/m3. In the feedback control system, controlling processes of sediment concentration and flood discharge for sediment transport were simulated respectively under given conditions, and it was found that sediment transport process could be controlled completely by sediment concentration and discharge at the inlet of the reach from Huayuankou to Gaocun. Using the same method, controlling processes of sediment transport by flood in other reaches in the Lower Yellow River were also simulated. For the case of sediment concentration being 20 kg/m3, the optimized controlling discharge ranges from 2390 to 2900 m3/s in the lower reach of Huayuankou. This study is also of significance to flood control and flushing sediment in the Lower Yellow River with proper operation modes of Xiaolangdi Reservoir.

关键词： the Lower Yellow River, flood, sediment transport, efficiency, simulation, control.

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Cereal area and nitrogen use efficiency are drivers of future nitrogen fertilizer consumption

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Science China(Life Sciences) 2005年第Z2期48卷 745-758页

作者： Achim Dobermann Kenneth G.Cassman Department of Agronomy and Horticulture University of Nebraska-Lincoln P.O.Box 830915LincolnNE 68583-0915USA

At a global scale, cereal yields and fertilizer N consumption have increased in a near-linear fashion during the past 40 years and are highly correlated with one another. However,large differences exist in historical trends of N fertilizer usage and nitrogen use efficiency (NUE)among regions, countries, and crops. The reasons for these differences must be understood to estimate future N fertilizer requirements. Global nitrogen needs will depend on: (i) changes in cropped cereal area and the associated yield increases required to meet increasing cereal demand from population and income growth, and (ii) changes in NUE at the farm level. Our analysis indicates that the anticipated 38% increase in global cereal demand by 2025 can be met by a 30% increase in N use on cereals, provided that the steady decline in cereal harvest area is halted and the yield response to applied N can be increased by 20%. If losses of cereal cropping area continue at the rate of the past 20 years (-0.33% per year) and NUE cannot be increased substantially, a 60% increase in global N use on cereals would be required to meet cereal demand. Interventions to increase NUE and reduce N losses to the environment must be accomplished at the farm- or field-scale through a combination of improved technologies and carefully crafted local policies that contribute to the adoption of improved N management; uniform regional or national directives are unlikey to be effective at both sustaining yield increases and improving NUE. Examples from several countries show that increases in NUE at rates of 1% per year or more can be achieved if adequate investments are made in research and extension. Failure to arrest the decrease in cereal crop area and to improve NUE in the world's most important agricultural systems will likely cause severe damage to environmental services at local, regional, and global scales due to a large increase in reactive N load in the environment.

关键词： nitrogen, cereals, nitrogen use efficiency, fertilizer requirements, global food security.

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efficiency OF INVOLUTE GEAR DRIVES WITH UNDERCUT PINIONS USED IN WRIST WATCHES

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Journal of China Textile University(English Edition) 1994年第2期11卷 61-66页

作者：俞明 Mechanical Engineering Department

In wrist watches gear drives with undercut pinions are used. Those pinions have got a tooth number as few as 5—7. The efficiency of such gear drives is important because of the limited energy supply. The mean efficiency of gear drives can be expressed as Em=1/（φ2-φ1）（integral from φ1 to φ2（E（φ）dφ）） in which 01, sub>2 are the approach angle and the recess angle respectively. In the discussion we assume that the friction coefficient between the two tooth flanks is constant because the sliding speed is relatively low in wrist watches and the main purpose is to find out the relation between gear parameters and its efficiency rather than to calculate the exact value of the efficiency. In normal conditions o1 and o2 can be found from the gear geometry without much difficulty. However when the pinion is an undercut one we have to first find the forming diameter where the involute profile starts. In this paper equations for the computation of the efficiency and the contact ratio of those gear drives are discussed.

关键词： watches, involute gears, efficiency, design contact ratio.

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Water, heat fluxes and water use efficiency measurement and modeling above a farmland in the North China Plain

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Science China Earth Sciences 2005年第Z1期48卷 207-217页

作者： QIN Zhong, YU Qiang, XU Shouhua, HU Bingmin, SUN Xiaomin, LIU Enmin, WANG Jishun, YU Guirui & ZHU Zhilin Ecology academy, College of Life Science, Zhejiang University, Hangzhou 310029,China Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China College of Science, Zhejiang University, Hangzhou 310029, China Ecology academy College of Life Science Zhejiang University Hangzhou 310029China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Ecology academy College of Life Science Zhejiang University Hangzhou 310029China College of Science Zhejiang University Hangzhou 310029 China

Net radiation (Rn), water vapor flux (LE), sensible heat flux (Hs) and soil heat flux (G)were measured above a summer maize field with the eddy-covariance technique, simulation and analysis of water, heat fluxes and crop water use efficiency were made with the RZ-SHAW model at the same time in this study. The results revealed significant diurnal and seasonal variability of water vapor flux for summer maize. Most part of Rn was consumed by the evapotranspiration of the summer maize. The proportion of water vapor flux to net radiation ((LE/Rn) increased with the crop development and peaked around milk-filling stage with a value of 60%, a slightly lower than that obtained by the RZ-SHAW model. Daily evapotranspiration estimated by the model agreed with the results measured with the eddy-covariance technique, indices of agreement (IA) for hourly water vapor fluxes simulated and measured were above 0.75, root mean square errors (RMSE) were no more than 1.0. Diurnal patterns of Hs showed the shape of inverted "U" shifted to the forenoon with a maximum value around 11:30 (Beijing time), while LE exhibited an inverted "V" with a maximum value at around 13:00, about an hour later than Hs. Diurnal change of CO2showed an asymmetrical "V" curve and its maximal rates occurred at about 11:30. Variations of water use efficiency during the phonological stages of the summer maize showed a rapid increase with the photosynthetic photon flux density (PPFD) after sunrise, a state of equilibrium around 10:00 followed a decrease. Maximum values of water use efficiency were 24.3, and its average value ranged from 7.6 to 10.3 g kg-1.

关键词： water vapor flux, CO2 flux, water use efficiency, RZ-SHAW model, maize, North China Plain.

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Placing Energy efficiency at the Forefront of CorporateStrategy

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Journal of Energy and Power Engineering 2016年第12期10卷 746-750页

作者： Lucas NG Hong Kiang Petrochemical Corporation of Singapore (Private) Limited 100 Ayer Merbau Singapore 628277 Singapore

In the last four decades, there were several energy crises caused by various factors including peak oil production in majorindustrial nations where energy price increased due to shortage in supply. Back then, energy efficiency improvement was a big subjectto conserve energy. Today, over 80% of current energy needs are derived from fossil fuels, and with the low crude oil price of USD45per barrel there is no conservation incentive for energy users, However, climate change caused by already accelerated emission ofgreenhouse gases into the Earth＇s atmosphere would be aggravated by a combination of low oil prices and abundance of ***, corporations should start energy efficiency campaigns for the purpose of combating climate change by reducing greenhousegas emissions especially for process plants with large energy consumption. The campaigns should include energy management, use ofhigh energy efficient equipment and systems that monitor and optimize the use of energy. Energy benchmarking exercises would helpto check and monitor energy efficiency performance level for continuous improvement.

关键词： efficiency, emission, greenhouse gas, investment, optimization.

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Simulation on Thermal Integrity of the Fin/Tube Brazed Joint of Heat Exchangers

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Journal of Materials Science & Technology 2003年第Z1期19卷 71-72页

作者： Yiyu QIAN Feng GAO Fengjiang WANG Hui ZHAO State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China State Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China

In the applications of heat exchangers, the fin efficiency of heat transfer is the key issue. Thermal distribution withinthe brazed joints in heat exchanger under loading conditions is investigated in this paper. Simulated results showedthat the thermal distribution at the brazed joint zone is related to not only the geometry of the fin and tube, butalso the brazed joint topology. A poor brazed joint will result in very poor heat transfer. Thermal contact resistanceis adopted to analyze the fin heat efficiency.

关键词： Thermal integrity, Fin efficiency, Thermal contact resistance, FEM

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Effects of Nitrogen Rate and Split Application Ratio on Nitrogen Use and Soil Nitrogen Balance in Cotton Fields

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Pedosphere 2017年第4期27卷 769-777页

作者： LI Pengcheng DONG Helin LIU Aizhong LIU Jingran SUN Miao LI Yabing LIU Shaodong ZHAO Xinhua MAO Shuchun State Key Laboratory of Cotton Biology Institute of Cotton Research of Chinese Academy of Agricultural SciencesAnyang 455000China

The Yellow River valley is one of the three largest cotton production areas in *** experiment was performed in cotton fields of Anyang,China from 2013 to 2014 to investigate the effects of nitrogen(N) application rate and the ratio between basal and topdressing N fertilizer on N balance in a soil-plant system,N use efficiency,and cotton *** N application rates as treatments were applied with the same split application *** of the N(50% basal fertilizer) was applied at pre-planting and the other half(50% topdressing fertilizer) at the initial flowering *** treatments were:zero N(N0,control),90 kg N ha^(-1)(N90(5/5)),180 kg N ha^(-1)(N180(5/5)),270 kg N ha^(-1)(N270(5/5),a reduced N rate),and 360 kg N ha^(-1)(N360(5/5),a conventional N rate).Additional 2 split application ratios as treatments were applied with the same N rate of 270 kg N ha^(-1).The split application ratios between basal N and topdressing N were 30%:70%(N270(3/7)) and 70%:30%(N270(7/3)).Results demonstrated that soil NH_4-N content in the 0–60 cm layer and NO3-N content in the 0–20 cm layer increased with increased N rate at the squaring and boll-opening stages and then decreased to lower levels at the initial flowering and harvest *** NO_3-N content in the 20–60 cm layer after the initial flowering stage increased with the increase of topdressing N *** apparent N surplus varied at different growth stages,while the soil apparent N surplus over the entire growth period exhibited a positive relationship at N rates over 180 kg ha^(-1).Seed cotton yield of N270(3/7) was the highest of all *** N uptake,N agronomic efficiency,and apparent N recovery efficiency of N270(3/7) were significantly higher than those of N270(5/5) and N270(7/3) in both growing *** suggest both economic and ecological benefits in cotton production in the Yellow River valley could be created,by appropriately reducing total N application rate and increasing the ratio of top

关键词： apparent N recovery efficiency, crop yield, N agronomic efficiency, N fertilizer, plant growth, soil apparent N surplus

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Characteristics of elution profile in radial chromatography under linear conditions

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Science China Chemistry 2005年第4期48卷 352-360页

作者： Andreas Seidel-Morgenstern Max-Planck-Institut für Dynamik Komplexer Technischer Systeme 39106MagdeburgGermany

Based on the mass balance equations of solute transfer in the radial chroma-tographic column,the theoretical expression to describe the column efficiency and shape of elu-tion profile is obtained under linear isotherm ***,the tendency for the variation of column efficiency and symmetry of peak profile is systematically *** results showed that in radial chromatography the relationship between the column efficiency and volumetric flow rate is similar with that relationship in axial chromatography;relatively high column efficiency still can be obtained under high flow rate in radial *** the increase of retention factor of solutes and injection time,the column efficiency decreases *** effect of column diameter and column length on the column efficiency interfere with each *** is more advantageous to increase the column efficiency by applying columns with larger column diameter and shorter column *** to the discussion of the effect of diffusion on the column efficiency,radial chromatography is proved to be suitable for the separation of samples with relatively high diffusion coefficient,which predicts its obvious advantage in the preparative separation of samples such as proteins and DNA.

关键词： radial chromatography, column efficiency, elution profile, symmetry.

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Large scale petroleum reservoir simulation and parallel preconditioning algorithms research

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Science China Mathematics 2004年第Z1期47卷 32-40页

作者： SUN Jiachang CAO Jianwen R & D Center for Parallel Software Institute of Software Chinese Academy of Sciences Beijing 100080 China R & D Center for Parallel Software Institute of Software Chinese Academy of Sciences Beijing 100080 China

Solving large scale linear systems efficiently plays an important role in a petroleum reservoir simulator, and the key part is how to choose an effective parallel preconditioner. Properly choosing a good preconditioner has been beyond the pure algebraic field. An integrated preconditioner should include such components as physical background, characteristics of PDE mathematical model, nonlinear solving method, linear solving algorithm, domain decomposition and parallel computation. We first discuss some parallel preconditioning techniques, and then construct an integrated preconditioner, which is based on large scale distributed parallel processing, and reservoir simulation-oriented. The infrastructure of this preconditioner contains such famous preconditioning construction techniques as coarse grid correction, constraint residual correction and subspace projection correction. We essentially use multi-step means to integrate totally eight types of preconditioning components in order to give out the final preconditioner. Million-grid cell scale industrial reservoir data were tested on native high performance computers. Numerical statistics and analyses show that this preconditioner achieves satisfying parallel efficiency and acceleration effect.

关键词： petroleum reservoir simulation, parallel preconditioning, parallel efficiency, high performance computing.

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Trace metals in barnacles:the significance of trophic transfer

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Science China(Life Sciences) 2005年第Z1期48卷 110-117页

作者： Philip S. RAINBOW Department of Zoology the Natural History Museum Cromwell Road London SW7 5BD London UK

Barnacles have very high accumulated trace metal body concentrations that vary with local trace metal bioavailabilities and represent integrated measures of the supply of bioavailable metals. Pioneering work in Chinese waters in Hong Kong highlighted the potential value of barnacles (particularly Balanus amphitrite) as trace metal biomonitors in coastal waters,identifying differences in local trace metal bioavailabilities over space and time. Work in Hong Kong has also shown that although barnacles have very high rates of trace metal uptake from solution, they also have very high trace metal assimilation efficiencies from the diet. High assimilation efficiencies coupled with high ingestion rates ensure that trophic uptake is by far the dominant trace metal uptake route in barnacles, as verified for cadmium and zinc. Kinetic modelling has shown that low efflux rate constants and high uptake rates from the diet combine to bring about accumulated trace metal concentrations in barnacles that are amongst the highest known in marine invertebrates.

关键词： barnacles, trophic transfer, assimilation efficiency, trace metals.

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