三峡库区试验性蓄水期间浮游生物群落特点研究

蓄水改变了三峡水库的水文情势,使得浮游生物密度及群落结构出现明显改变,在不同蓄水阶段呈现不同的特点。根据2009年三峡水库试验性蓄水期间分季节实地监测结果,分析了浮游动植物在不同季节、不同蓄水位以干流与支流河口的分布变化情况。结果表明：就季节变化而言,秋季浮游植物种类最多、夏季次之、冬春较少;浮游生物密度整体不高,且时空分布不均,为春夏秋冬依次递减,支流河口密度高于干流;与蓄水前相比,蓄水后浮游生物密度显著增加,但与135 m及156 m蓄水位相比,试验性蓄水期间有下降趋势。库区营养盐水平较高,对浮游生物的生长不形成限制,浮游生物分布的时空显著差异是由流量、流速及浊度造成的。     

亭子口水库淹没区移民复建项目合同管理探讨

亭子口库区交通复建与农田防护工程属水利移民工程项目。在委托建设管理的合同管理上,由于工程实施的特殊性和合同各方关系的复杂性,需要妥善解决比较突出的工程变更处理和合同风险防控问题,在简要介绍参建各方合同关系、合同管理主要内容的基础上,侧重阐述了合理处置变更问题的原则和方法,以及防控有关工程建设与合同风险的措施,为采取委托建设管理模式的类似工程合同管理提供了实例借鉴与参考。     

某库区料场高边坡全过程稳定性评价

针对某一库区层状料场的岩质高边坡,考虑高边坡的复杂地质条件以及料场的实际开挖过程,基于MIDAS/GTS建立了有限元数值计算模型。在进行三维非线性数值模拟时,计入开挖卸荷、不同蓄水位和降雨以及地震荷载等因素对高边坡的变形、应力和稳定性的影响。计算结果表明,各工况下塑性区均属浅表塑性区,边坡整体稳定性良好,且开挖对边坡的稳定性有较明显的改善。研究结果为全面评价该边坡料场的安全稳定性提供了理论依据。     

抽水蓄能电站沥青混凝土防渗面板裂缝处理及防治措施

施工质量良好、致密的沥青混凝土防渗面板几乎是不漏水的,最易出现面板裂缝和缺陷的时期是蓄水初期,过快的水位上升或下降速率极易引起过大的基础层变形,从而导致面板出现裂缝.地质条件、水库的运行条件、不均匀沉降等均可造成沥青混凝土面板的裂缝,应根据工程的实际条件,并结合裂缝的产状及发展情况,对裂缝的成因进行综合判断,并采取相应的防治措施.沥青混凝土防渗面板的裂缝修补较为复杂,对工程的后期运行影响较大,因此修补措施应根据工程的实际特点及已建工程的裂缝修补经验综合制定.     

基于银行系统应用的ETL技术的探讨

介绍运用数据仓库的几个关键特性和ETL技术，构建银行系统数据仓库的过程。并提出了在构建过程中对处理阶段的划分方法和一些处理方式，以便当数据模型变动时，避免大规模修改仓库的构建。     

巫山青石滑坡复活机制研究与稳定性评价

受三峡库区175 m水位蓄水影响,引起了古滑坡复活,前后缘出现了大规模的变形,坡体的稳定性降低,直接威胁到景区、航道、电站的安全。本文根据滑坡的地形地貌及滑坡变形的监测数据,结合所处的地质环境条件,对滑坡的复活机理进行了系统的分析,在此基础上采用极限平衡法和FLAC数值模拟方法分析了滑坡的稳定性,得到滑坡目前处于基本稳定状态。滑坡属于牵引式滑移,其整体的稳定性取决于滑坡前缘强变形B、C区的稳定,若前缘强变形区再次发生大规模变形破坏,势必影响滑坡的整体稳定性。最后,针对滑坡提出了采用专业监测预警+裂缝封闭+截排水沟+清除前缘垮塌区表面危险岩块的综合防治方案的建议。     

电站锅炉高效超低NOx排放控制技术

对电站锅炉低NOx燃烧技术进行了重新分类,然后分析其应用中存在的问题,再结合国外NOx排放控制技术的最新科研成果,提出了电站锅炉高效超低NOx排放控制的双分级再还原方法.该方法采用空气分级,煤粉、燃气或生物质进行再燃,同时使用选择性非催化还原NOx技术,而且添加碱金属盐以增效.双分级再还原低NOx燃烧用技术使用约10%的再燃燃料可以达到85%以上的脱硝率.     

NOx control by air staging in a small biomass fuelled underfeed stoker

There is a need to develop improved designs of environmentally acceptable thermal plant for use in process industries in developing countries. Such plant may take advantage of the underfeed combustion principle which exhibits a tolerance towards smoke emission in the burning of high volatile matter biomass fuels. This paper describes an experimental investigation into the conversion of a small, 30 kW underfeed stoker from coal to wood chip firing. Two methods of air staging are considered for NO_x abatement, including a novel air deflection technique. Comparisons are made between plant performances using the two methods. The results are also compared against representative values for coal firing. It was concluded that the air deflection technique showed potential as a means of NO_x minimisation in small, underfeed stokers taking into account other requirements of adequate plant thermal efficiency and exhaust gas combustion quality. Copyright © 2000 John Wiley & Sons, Ltd.     

Experimental research on air staged cyclone gasification of rice husk

A novel air cyclone gasifier of rice husk has been used to obtain experimental data for air staged gasification. Three positions and five ratios of secondary air were selected to study effect of the secondary air on the temperature profile in the gasifier and quality of syngas. Temperature profile and the syngas component are found to be strongly influenced by the injection position and ratio of the secondary air. Generally, gas temperature in all conditions increased at the early stage of reaction, and then decreased in the reduction zone where reactions were endothermic. The peak temperature in the gasifier changed with the injection positions and ratios of the secondary air, which could be as high as 1056 °C. The concentration of CO₂, CO, H₂ and CH₄ increased with the secondary air while the O₂ concentration remained constant. The syngas component exhibited different laws when the secondary air ratio was changed. It was also shown that the optimum condition was that the secondary air was injected in the oxidization zone at a secondary air ratio of about 31%. Under that condition, the fuel gas production was 1.30 Nm³/kg, the low heating value of the syngas was 6.7 MJ/Nm³, the carbon conversion rate was 92.2% and the cold gas efficiency of the gasifier was 63.2%. The tar content of the syngas was also studied in this paper. It decreased from 4.4 g/m³ for gasification without the secondary air to 1.6 g/m³ for gasification with the secondary air injected in the oxidization zone.     

三峡初期蓄水对典型鱼类栖息地适宜性的影响

三峡工程是长江中游干流最大的骨干工程，蓄水后下游水文情势发生明显改变。分析水库运行后下游水文情势的改变情况，将为了解大型水利工程对河流健康状况的影响程度和开展生态保护提供有意义的信息和帮助。本文选择宜昌站作为研究对象，并以中华鲟和四大家鱼为典型代表物种，研究三峡工程初期蓄水对下游生态系统的影响。结果表明，三峡工程蓄水运行后，(1) 坝下宜昌站生态水文条件发生明显变化，主要表现为多年平均水温上升，多年平均流量、水位和含沙量下降；(2) 非汛期的水温以及汛期的流量、水位和含沙量月径流过程明显改变；(3) 下游生态水文条件的改变，导致中华鲟鲟卵孵化适宜度和四大家鱼产卵适宜度明显降低；(4) 栖息地内生态水文条件的变化是影响中华鲟鲟卵孵化和四大家鱼产卵行为的关键因素，而不是影响中华鲟产卵和四大家鱼鱼卵孵化的关键因素。