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王欢 《水科学与工程技术》2014,(1):25-27
黑沙村隧洞穿越泥砾层,属浅埋隧洞。该文对隧洞洞线选择,输水方式,洞形及断面尺寸确定,衬砌型式等方面进行了比较和理论分析.为今后类似工程设计积累了一定的工程经验。 相似文献
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为确定桂林毛村地下河的氮磷水平及其来源,在毛村地下河出口设置水质自动监测仪,并根据地下河水系分布在流域内布点同时采样监测。结果表明:采用GB/T14848—93《地下水质量标准》Ⅱ类评价,毛村河地下水出口的NH_4~+-N超标率为63.4%,TP达到GB 3838—2002《地表水环境质量标准》的Ⅱ类,氮磷浓度变化与枯雨季无直接联系。毛村地下河流域TN和NO-3-N的浓度呈现出从上游至下游逐渐升高趋势,经过洼地的大岩前采样点和毛村出口的TN浓度超过地表水水质Ⅴ类标准,其他指标均达Ⅱ类标准。对比不同降雨量条件下毛村地下河出水口NH_4~+-N和TP质量浓度实时动态变化发现,在小雨和中雨期间氮磷浓度变化无明显改变,说明农业施肥和生活污水对地下河水质影响除了集中降雨之外,还存在着通过岩溶地下管道直接流入的途径。在大雨期间,集中降雨对土壤冲刷,TP质量浓度出现了瞬间最高值(23.5μg/L),NH_4~+-N质量浓度则在降雨的携带和稀释下产生剧烈波动。 相似文献
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介绍了尊村引黄泵站工程概况,根据其运行现状,分析了泵站更新改造的必要性,从水力机械部分,电气设备、金属结构、土建部分四方面阐述了泵站改造的主要内容。 相似文献
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为推进新农村电气化建设,提高农村配电网建设水平,以《新农村电气化建设实施纲要》和《新农村电气化标准体系》为依据,在充分调研、多方征求意见的基础上,研制、编写了新农村电气化村典型供电模式。根据经济水平将新农村电气化村划分为A,B,C等3类,电气化村的典型供电模式相应分为A,B,C等3类。另外,根据村的建筑布局,将村分为多层、联排和分散居住3类。在此基础上,有针对性地提出了10种电气化村典型供电模式,其中:A类3种,B类3种,C类4种。研究成果已在新农村电气化村建设中广泛应用,效果明显。 相似文献
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根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。 相似文献
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The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects. 相似文献
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In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment. 相似文献
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V. K. Konovalov O. V. Yashkin V. V. Ermakov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2008,42(2):105-109
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed
in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash
and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers
of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional
components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect
dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system,
configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants
of dry ash utilization and the advantages of producing of size-separated particles are considered.
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Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008). 相似文献
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Peter B. Bayley 《河流研究与利用》1991,6(2):75-86
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed. 相似文献
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简述天湖水电站投运以来各种故障的表现形式,分析其原因,提出了相应的处理方法及措施,并对合理利用国内外设备提出建议。 相似文献