基于力学测量的架空输电线路覆冰监测系统

对输电线路覆冰载荷进行了力学分析，讨论了覆冰厚度的计算方法。开发了基于架空输电线路轴向张力、二维倾角和风速风向、温湿度等气象信息测量的覆冰监测系统。利用全球移动通信系统（GSM）/通用分组无线电业务（GPRS）网络，线路监测终端与中心监控主站进行数据传输，由主站专家系统软件利用相关覆冰理论模型分析导线覆冰状况，及时给出除冰信息，有效预防冰害事故发生。     

输电线路覆冰浅论

输电线路覆冰引起的故障会严重影响电力系统的正常运行，对电力系统的安全产生严重危害。本文介绍了输电线路覆冰的类型、成因、危害、国内外研究状况、覆冰监测、防冰除冰方法及展望等问题。     

覆冰对输电线路的危害及采取新型防冰涂料的可行性

结合“一一·五”事件，分析了输电线路覆冰的原因及其对源-安（霸）线路及绝缘子的损坏方式，指出目前的PRTV涂料不能有效防冰闪。介绍了国内最新型的防冰涂料，论述了新型防冰涂料应用于电厂现场的可行性。     

广西区域输电线路工程覆冰特点分析

笔者通过调研近年来广西各地输电线路工程覆冰情况,介绍覆冰成因及种类,采取长短径法、冰重法及调查或实测覆冰直径法计算导线、地线、树枝等的标准冰厚,分析微地形、微气象区域覆冰案例,总结受损线路历次抗冰加固经验,提出广西区域输电线路覆冰特点,也为覆冰预报与评估提供依据。     

输电线路覆冰在线监测系统的研究现状

介绍了输电线路覆冰的原因、种类和危害,梳理了输电线路覆冰过程的一些研究模型及国内外覆冰导线状态检测技术的研究现状,根据其应用情况和存在的不足,提出了相应的改进措施。     

基于四阶矩法的输电线路覆冰可靠度分析

架空导线长期处于复杂环境下,经常遭受覆冰影响。为了保证输电线路的安全运行,架空导线 的可靠度分析是十分必要的。以输电线路的导线强度失效为失效边界,选择导线的覆冰厚度和容许应 力为基本随机变量建立功能函数。采用简化的四阶矩法计算架空导线的可靠指标,并与一次二阶矩法 和基于ＭＡＴＬＡＢ的蒙特卡洛模拟法的结果对比。另外引入功能函数的峰度及偏度到可靠度分析中。结 果表明:四阶矩法的功能函数值及可靠指标普遍偏于保守,并且其可靠指标计算的结果相比一次二阶矩 法的结果依然可取。因此可将改进的四阶矩法应用于等高悬点输电线路的可靠度计算中。     

设计规程变更后的广西电网220kV及以上输电线路抗冰加固方案研究

为保障电网安全可靠供电,有必要对广西220kV及以上输电线路抵御覆冰灾害的能力进行研究.通过对新旧设计规程相关设计要求的对比分析,结果表明现行规程对输电线路防冰能力的要求远高于旧版规程,从而说明了部分按照旧版设计规程建成的线路是不能满足目前防覆冰要求的.进一步研究提出了广西220kV及以上输电线路抗冰加固原则和具体的项目建议,为后续工程提供参考.     

输电线路覆冰对电力网的影响及危害分析

输电线覆冰将严重影响电网安全运行,会导致杆塔荷载增大、输电线垂度增大。覆冰严重时还会引起倒塔。行对于此,分析了输电线覆冰对输电线安全的影响,即输电线覆冰对输电线负载的影响、覆冰厚度增加时对输电线强度的影响,为输电线路设计和安全提供了参考。     

2008年桂北架空线路覆冰的初步分析

根据2008年广西桂北电网遭受雨雪冰冻灾害的覆冰特点,对强冷空气入侵的天气变化过程、覆冰形成的条件、线路覆冰厚度的计算、本次覆冰的特点、重现期的评估以及实际冰厚与气象区划的比较等多方面进行分析,提出加强电网抗冰能力的建议.     

直流融冰装置的研制与应用

输电线路的持续覆冰会导致输电线路严重受损,造成电网部分或全网停运。为了防止这种情况的再次出现,进行输电线路的融冰是一种很好的方法,直流融冰技术的研究与应用对于电网抗击冰灾具有重大意义。通过对南方电网各电压等级架空线路直流融冰参数进行仔细分析和计算,提出了适用于南方电网的交流输电线路的直流融冰技术方案,介绍了南方电网直流融冰装置样机的研制及其应用,特别介绍了60 MW, 25 MW和500 kW直流融冰装置的样机设计、工厂测试、现场试验和现场实际融冰效果。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

浅谈优化Vray渲染在制作三维场景的应用研究

用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要.     

固结、渗流和沉积控制方程研究

本文从两相流体动力学的守恒方程出发，考虑固相、液相的相对运动，推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程，并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达，可导出用于大、小变形固结、渗流和沉积的简化方程，显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制，适用范围较广。依据实际问题的要求，作了不同形式的简化。     

四川省及重庆市中型水电站效益分析

该文分析了四川省及重庆市几座中型水电站的调查材料表明：四川省及重庆市中型水电站不仅在川渝主网和地方电网中起着很大的作用，并具有巨大的社会效益，同时还有综合利用效益，说明修建中型水电站的优越性．     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

掺MgO混凝土的宏细观试验研究

利用MgO膨胀剂的延迟微膨胀效应能显著提高大体积混凝土的力学性能,产生的预压应力还能有效提高大体积混凝土抵抗温度开裂的能力,但目前对其微观机理研究不多。采用宏观与微观相结合的方式,研究了不同活性指数、不同掺量的MgO混凝土的力学性能,利用SEM/EDS微观分析手段揭示了MgO对混凝土性能影响的作用机理。试验结果表明：MgO取代部分水泥掺入混凝土中,混凝土的力学性能降低;掺量为4%~5%时,活性指数为100s的MgO混凝土的膨胀率大于活性指数为50 s的MgO混凝土;MgO混凝土的膨胀特性与Ca,Si,Mg,Al等元素的分布情况有关,掺入的MgO将改变界面区Ca,Si,Mg元素的富集特性,Ca元素和Mg元素更易于在界面区富集,导致混凝土宏观力学性能的降低。