坡沟系统侵蚀产沙及其耦合关系研究

利用变坡度坡沟系统模型和人工模拟降雨试验,定量研究了不同降雨强度下的坡沟系统产流产沙过程,揭示了坡面沟道侵蚀产沙耦合特征。结果表明:坡沟系统累积径流量和累积产沙量与降雨时间呈显著的幂函数关系,随着降雨时间的增大而增大。梁峁坡面来水径流量与沟坡净侵蚀量之间呈幂函数关系,梁峁坡面来水含沙量与沟坡净侵蚀量之间呈反线性相关。从水力学角度对坡沟系统单位水流功率与单宽输沙率的关系进行了分析,得出试验条件下的临界单位水流功率值为0.0043m/s,输沙率随单位水流功率的增大而增大。     

Application of a Three-dimensional Wind Driven Circulation Model to Assess the Locations of New Drinking Water Intakes in Lake Ontario

A 3D transport model is used to perform a comparative analysis of several potential drinking water intakes located along the northwest shore of Lake Ontario between Toronto and Oshawa. The model is specifically used to assess each intake under both long- and short-term transport of a potential pollutant release from the Pickering Nuclear Generating Station and potential and actual pollutant releases from local land sources respectively. A model based on a 500 m grid resolution is calibrated using data collected in the aftermath of the 1992 tritium spill at the Pickering Nuclear Generation Station and subsequently used to simulate long-term transport. A model based on a 100 m grid resolution is verified using drogue studies and used to simulate short-term transport events. Both models are used to assess pollutant levels at each of nine potential intake locations under different wind scenarios and pollutant releases. Field data for the study included water quality and flow measurements from local sewers and rivers, and estimates of pollutant levels from the local waste water treatment plants. This paper describes the model setup for both the long-term and short-term transport models, calibration using field data, long-term transport modeling, short-term transport modeling, and the comprehensive analysis approach used to evaluate the nine potential intake locations proposed. Results indicated that four intakes in particular outperformed other intake locations by maintaining bottom pollutant levels within governmental standards and warning times that exceeded 20 hours.     

基于WebGIS的粗泥沙集中来源区电子地图系统研究

基于WebGIS的粗泥沙集中来源区电子地图系统建设，以粗泥沙集中来源区作为研究区域，以黄河中游粗泥沙集中来源区水土保持工作流程（包括规划设计、计划管理、综合治理、预防监督和淤地坝管理等）为主线，依托黄河流域水土保持生态与环境监测系统网络、黄河流域水土保持监测系统数据库，建立覆盖黄河流域、黄土高原区、多沙粗沙区、粗泥沙集中来源区，面向不同水土保持管理层的水土保持监测与管理信息系统。     

VERIFICATION AND COMPARISON OF FORMULAS FOR BED LOAD TRANSPORT

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙｓｔｕｄｉｅｄｉｎｔｈｅｐａｓｔｆｅｗｄｅｃａｄｅｓａｎｄｍａｎｙｆｏｒｍｕｌａｓｆｏｒｐｒｅｄｉｃｔｉｎｇｂｅｄｌｏａｄｔｒａｎｓｐｏｒｔｒａｔｅｈａｖｅｂｅｅｎｐｒｅｓｅｎｔｅｄ(Ｅｉｎｓｔｅｉｎ 1950 ;Ｍｅｙｅｒ Ｐｅｔｅｒ 194 8;Ｂａｇｎｏｌｄ 1973;Ｅｎｇｅｌｕｎｄ 1976;Ｙａｌｉｎ 1972 ;Ｓａｍａｇａ 1986;ａｎｄＫａｒｉｍ 1998) .Ｗｈｅｎａｐｐｌｉｅｄｔｏｓｔｒｅａｍｓｗｉｔｈｐａｒｔｉａｌ…     

80年代黄河中游来沙减少的原因分析

80年代黄河中游来沙量减少,主要原因是降雨量减少和降雨强度减小,流域综合治理也起到了减沙作用。据分析,降雨因素减沙约占总减沙量的70％,流域综合治理减沙约占30％。     

发展中枢辐射铁路物流的探讨

传统的铁路物流组织模式有其局限性,已难以满足市场对快速运输的需求,铁路企业的改革势在必行。在阐述中枢辐射铁路物流表现形式的基础上,分析铁路企业发展中枢辐射铁路物流的必要性和可行性及所面临的困难,同时就铁路企业如何发展中枢辐射铁路物流提出了建设性意见。     

新财务清算政策下提高铁路城际列车效益的思考

近年来,铁路短途城际客运得到了很大的发展,开行城际列车已成为铁路运输企业新的经济增长点。新财务清算政策实施后,开行城际列车的效益受到一定程度的影响,针对存在的问题,就如何提高其效益水平进行了讨论。提出了完善开行结构、增加营业收入、减少客运付费、降低成本支出等建议措施。     

Simulation of water and nitrogen dynamics in soils during wastewater applications by using a finite-element model

A mathematical model was developed to simulate water movement, mass transport, and nitrogen transformations in soils during wastewater applications. The model is one-dimensional and based on the Galerkin finite-element method. The submodel of mass transport of nitrogen incorporates the convection-dispersion processes of ammonium and nitrate nitrogen, nitrification, denitrification, ammonium exchange and uptake of ammonium and nitrate ions. The accuracy and validity of the proposed model was examined by comparison with an explicit-implicit finite-difference model results. The model was used for simulation of water and nitrogen dynamics during wastewater application in homogeneous and multi-layered soils under different N concentration, rate, duration and scheduling of application.     

平衡纵剖面数值试验及其对防洪的影响研究

本文采用一维非恒定流非均匀沙的水沙数学模型，以长江中游螺山汉口河段为背景，进行了根化数值模拟试验，分析了该概化河段平衡纵剖面的变化规律及其与上游来水来沙条件的关系，并和相应的理论公式进行了比较。在此基础上，对水沙条件发生较在变化时的平衡纵比降以及带来的对长江中下游防洪的影响进行了分析。     

The European high-speed train network: Predicted effects on accessibility patterns

The principal aim of this paper is to evaluate the impact of the future European high-speed train network on accessibility, by reducing time distance between places and modifying their relative location. We compare the current situation with that foreseen for the year 2010, according to the Outline Plan of the European High-Speed Train Network, in order to analyse which areas will most benefit from construction and improvement of the infrastructure. It is hypothesized that the high-speed train will certainly bring the peripheral regions closer to the central ones, but will also increase imbalances between the main cities and their hinterlands. A weighted average distance indicator is applied for this purpose. This measure identifies the spatial distribution of accessibility in the area of study, emphasizing the infrastructure effects, and locates accessibility changes at the European level. A Geographic Information System (GIS) has been used to carry out this study.