坝体变位和内水压力对坝后背管结构应力的影响

用三维接触单元模拟背管与坝体接触面，分析坝体变形和内水压力对李家峡坝后背管结构应力的影响。坝体变位对背管结构轴向应力的影响表现为上部为拉应力下部为压应力，并且拉应力由背管的上弯段向下弯段逐渐减小，部分轴向拉应力值大于混凝土设计抗拉强度；背管内水压力对背管结构环向应力的影响表现为环向拉应力，并且管腰外缘和管顶内缘混凝土环向拉应力是混凝土设计抗拉强度的2．4倍。根据应力的大小分布可以确定，坝体变形是背管产生较大轴向拉应力的主要因素，是产生环向拉应力的次要因素；内水压力是使背管产生较大环向拉应力的主要因素，是产生轴向拉应力的次要因素。     

硫铵滚筒干燥器自动测控系统的应用研究

简述了硫铵滚筒干燥器的干燥原理及工艺流程,提出自动测控系统的控制要求及实现方案配置,给出了硫铵含水量控制调节、干燥器出口微负压控制调节、水溶雾沫除尘器等几个关键环节的测控原理及控制过程。     

液膜分离技术及其在生物、食品工业下游处理中的应用

液膜分离技术(liquid membrane technique)是近年来发展起来的分离、纯化和浓缩一步完成的新型分离技术,具有专一、高效、快速,经济简便等特点。文章中介绍了液膜的组成和类型、分离纯化浓缩的机理和其不稳定性等特性,叙述了其在脂肪酸、手性化合物、蛋白质、酒及果蔬汁等下游处理中的应用。此外,展望了其在生物、食品工业中的应用前景和发展方向。     

堰塞坝背水面坡度对溃决过程影响机理大尺度试验

堰塞坝溃决物理概化试验是当前研究堰塞坝溃决机理较为可行的方法,但在现有堰塞坝溃决试验中,由于试验坝体尺寸较小、试验上游库容不足,导致试验的溃决过程与实际堰塞坝溃决存在较大差异。为尽量克服库容的不足所带来的影响,本文采用了最大库容达380m3的大尺度堰塞坝溃决试验系统。本文以无粘性、宽级配砂砾料堰塞坝为对象开展了多组室内大尺度溃决试验来揭示堰塞坝溃决机理,并通过设置不同背水面坝坡来研究其对溃决过程的影响。通过试验发现堰塞坝溃决过程可以分为沿程冲刷、溯源冲刷、快速发展和溃口稳定四个阶段。在溃决过程中发现陡坎侵蚀和溃口两侧土体失稳坍塌是溃口快速发展的主要机理。不同背水面坡度下的沿程冲刷阶段冲蚀特征基本相似,而溯源冲刷阶段及快速发展阶段溃决过程差异显著,较大的背水面坡度使溯源冲刷阶段跌坎水流更容易得到发展,进而影响溃口处的垂向冲深及侧向发展,导致快速发展阶段更易形成垂向落差较大的陡坎洪水冲蚀。从溃决历时来看,坡度的增加使溃口发展更快、峰值流量出现时间更早,进而导致溃决历时缩短。坝顶溃口宽度及峰值流量也会随着坡度的增加而增加。在本试验还较好地重现了天然堰塞坝下游河道两岸的淤积现象,并根据堰塞坝溃决过程中的水流特点、泥沙运动及溃决完成后下游河道的地貌,初步分析了淤积区的形成机理。     

水下不分散柔性混凝土研究

南方某水库自蓄水运行以来,大坝出现漏水现象,且呈逐年增加的趋势.针对这一现象,决定在不放空水库的情况下,采用水下灌注铺盖进行渗漏处理.为此进行了水下灌注材料的试验研究,分速凝和普通两类.提出了新型的水下灌注材料-水下不分散柔性混凝土.该材料具有高流动性、高水下抗分散性和低弹模高塑性的特点.对该材料的性能及其影响因素进行了探讨.     

立堵截流规律再探讨

本文从龙口下游水力条件出发，探讨下游水深、河床糙率以及抛料堆积体对立堵规律的影响。最后又介绍了龙口平均流速的理论计算方法。     

石羊河下游民勤水资源与生态环境治理对策

河西走廊石羊河下游———民勤地处我国干旱内陆区 ,民勤绿洲是我国典型的荒漠绿洲之一。由于石羊河水资源不合理开发利用 ,引起其下游民勤盆地的区域地下水位下降、水质恶化、土地沙漠化、盐渍化面积扩大 ,植被退化等一系列生态环境问题。文中对生态环境恶化产生的原因进行了分析 ,并就其生态环境保护与治理提出了对策。水资源问题是民勤生态环境问题的本质 ,要改善民勤的生态环境条件 ,首先必须解决好当地水资源问题     

Domain-oriented design environments

The field of knowledge-based software engineering has been undergoing a shift in emphasis from automatic programming to human augmentation and empowerment. In our research work, we support this shift with an approach that embedshuman-computer cooperative problem-solving tools intodomain-oriented, knowledge-based design environments. Domain orientation reduces the large conceptual distance between problem-domain semantics and software artifacts. Integrated environments support the coevolution of specification and construction while allowing designers to access relevant knowledge at each stage within the software development process.This paper argues thatdomain-oriented design environments (DODEs) are complementary to the approaches pursued withknowledge-based software assistant systems (KBSAs). The DODE extends the KBSA framework by emphasizing a human-centered and domain-oriented approach facilitating communication about evolving systems among all stakeholders. The paper discusses the major challenges for software systems, develops a conceptual framework to address these problems, illustrates DODE with two examples, and assesses the contributions of the KBSA and DODE approaches toward solving these problems.     

Dam effects on bedload transport on the upper Santa Ana River,California, and implications for native fish habitat

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.