Private electric power generation as an alternative in Nigeria

About 9% of the energy mix in Nigeria is in the form of electricity. It is a major source of energy for the urban population. In the recent past, there has been consistent failure of electricity supplied by the public organisation. Consumers are now turning to private means to meet their electricity needs. We have assessed the electricity supplies from the national grids and from private electricity generators.     

粉沙质海岸泥沙特性实验研究

本研究根据泥沙性质，提出了滩面泥沙中值粒径介于０．０３ｍｍ￣０．１２ｍｍ的海岩为粉沙质海岸，并对其泥沙特性进行了实验研究。结果表明，粉沙质海岸泥沙特性除了与中值料径有关外，还与级配有关。当泥沙中粘性细颗粒物质含量较高时，其整体体现淤泥质泥沙特性，当泥沙中粘性细颗粒物质含量较低时，整体体现散粒体泥沙特性，其运移形态前者是以悬移质运动为主，后者地既有悬移质运动又有推移质运动。对于推移质输沙，其输沙率不     

基于GIS和3D技术的西江航道信息系统

本系统以西江航道的长洲段为研究对象,以基础地形图和各类航道相关的数据要素为平台,以航道相关地理信息的空间数据和属性数据为核心,利用计算机技术、地理信息系统(GIS)技术、数据库技术、三维虚拟仿真技术,建立起一个能快速提供真实准确的地理信息、便于查询统计及决策分析的信息系统;同时能对CAD数据、GIS数据、遥感影像等数据进行快速的读入,将制作的专题图导出。为航道的数据查询、三维模拟显示、专题分析与制作提供强大的解决方案。     

Application of equivalent resistance to simplification of Sutong Bridge piers in tidal river section modeling

This paper describes some details and procedural steps in the equivalent resistance (E-R) method for simplifying the pier group of the Sutong Bridge, which is located on the tidal reach of the lower Yangtze River, in Jiangsu Province. Using a two-dimensional tidal current numerical model, three different models were established: the non-bridge pier model, original bridge pier model, and simplified bridge pier model. The difference in hydrodynamic parameters, including water level, velocity, and diversion ratio, as well as time efficiency between these three models is discussed in detail. The results show that simplifying the pier group using the E-R method influences the water level and velocity near the piers, but has no influence on the diversion ratio of each cross-section of the Xuliujing reach located in the lower Yangtze River. Furthermore, the simplified bridge pier model takes half the calculation time that the original bridge pier model needs. Thus, it is concluded that the E-R method can be use to simplify bridge piers in tidal river section modeling reasonably and efficiently.     

长江口北支围垦对其水动力影响的数值模拟分析

20世纪50年代以来,上海市和江苏省两地对长江口北支实施了大规模围垦,使北支河宽大幅度缩窄,地形边界显著改变。在利用MIKE21_FM构建长江口—杭州湾二维垂向平均潮流数学模型,并用实测数据对模型进行验证的基础上,对北支大规模围垦前后的潮流场进行了模拟分析。研究结果表明：大规模围垦后,北支全河段平均高潮潮位抬升,平均低潮潮位降低;中上游河段涨、落潮流速增大,下游入海河段涨、落潮流速减小;南北支涨潮流汇流点上提至南北支交汇的崇头,涨潮动力增强。     

THREE-DIMENSIONAL NUMERICAL MODELLING OF THE WAVE-IN- DUCED RIP CURRENTS UNDER IRREGULAR BATHYMETRY

A process-based 3-D hydrodynamic model is established to simulate the rip current structures under irregular bathymetry.The depth-varying wave-induced residual momentum,the surface rollers,the turbulent mixing and the wave-current interactions are considered.Experimental datasets are used to validate the model,and it is shown that the model can effectively describe the 3-D structures of the rip currents in both normal and oblique wave incident cases.The flow patterns of the rip currents see various characteristics for different incident wave directions.In the normal incident case,pairs of counter-rotating primary circulation cells are formed,and an offshore rip flow occurs in the embayment troughs.The peak seaward velocities occur at the top of the bed boundary layer,and the undertow is incorporated in addition to the rip currents.In the oblique incident case,the longshore currents are dominant,which result in a meandering flow along the depth contour,and the undertow is weaker compared to that in the normal incident condition.     

库区交汇河段纵向淤积形态分析

库区交汇河段受坝前水位升降与干支流流量丰枯的影响,其侵蚀基面具有双重变化特性,从而产生特殊淤积形态。基于大量实测资料,对库区交汇河段干流与支流河道纵向淤积形态进行分类,提出支流纵剖面倒坡锥体淤积与锥体—倒坡锥体过渡淤积两种特殊类型。从水库运行方式与干、支流顶托两个关键因素入手,将水动力条件的变化与干、支流淤积形态建立联系,指出双重顶托的存在为库区交汇河段淤积形态差异的内在机理。     

超高韧性水泥基复合材料多缝开裂特性及其自生愈合

应变硬化水泥基复合材料(Strain hardening cement-based composites,SHCC)是超高性能水泥基材料的一种。通过三点弯曲加载试验,分别对普通砂浆和SHCC试件诱导开裂,对两种材料的开裂特性及其裂缝分布规律进行了研究。结果表明,SHCC材料试件与普通水泥砂浆试件相比具有更高的承载力和应变能力,初始开裂荷载约为普通砂浆试件的2.5倍。SHCC材料中的PVA纤维的桥接作用有效延迟了裂缝的产生与扩展,将普通砂浆试件中数量少而大的裂缝转化为多而细的微小裂缝,呈现多缝开裂特性,产生的裂缝宽度符合正态分布规律,且90%的微小裂缝小于30μm。这些微小裂缝在潮湿环境中产生一定程度的自生愈合,在水中的愈合程度和速度均高于在潮湿空气中。     

振弦式位移计校准方法的研究

振弦式位移计在水运工程等领域广泛应用,但是国内一直未发布与其专门相关的检定规程或校准规范,缺乏完整的振弦式位移计溯源方法。该文介绍了振弦式位移计的工作原理,提出了振弦式位移计的具体校准方法,选取样机进行了试验测量,论证了校准方法的可行性,为振弦式位移计的质量控制提供了保障。