基于风险的低压切负荷量的确定方法

针对低压减载方案中切负荷量的问题,利用马尔可夫方法,计算出低压减载方案各种动作情况的概率。在此基础上,结合电压崩溃的风险理论,以在预想事故下所切负荷量为变量,构造方案引入所带来的电压崩溃风险的函数,再以该风险量最小为标准,确定切除负荷量的多少。与传统方法不同,该方法综合分析了各种意外事件、考虑了低压减载方案本身的可靠性。计算处理的信息更丰富,结果更准确。IEEE 14节点的算例表明了该方法计算的有效性。该方案为低压减载方案的设计提供了参考。     

考虑暂态电压稳定的低压减载地点选择

提出一种考虑暂态电压稳定的低压减载最佳地点的选择方法。在电力系统微分代数方程模型中，系统轨迹碰到奇异面对应着系统发生暂态电压失稳，可以通过切负荷控制使得奇异面远离系统轨迹，从而避免发生电压崩溃。奇异面移动的距离可以看做评估控制效果的一个指标。用文中提出的灵敏度分析方法计算这一指标对于节点负荷的灵敏度，根据灵敏度大小选择低压减载装置的最佳地点。在IEEE 39节点系统中进行了仿真验证，结果说明所提出的低压减载地点选择方法合理有效。     

南方电网失步解列装置整定方案

用BPA（Bonneville Power Administration）程序对南方电网目前配置的失步解列系统的定值设置及协调配合进行研究，特别是研究了低压减载的影响以及判出失步后解列不同断面的效果。研究将BPA程序计算结果回放进实际失步解列装置以检验动作结果与分析是否相符，并建立了由南方电网交直流混合实时数字仿真（RTDS）模型、失步解列系统、功率放大器、直流控制保护装置组成的实时闭环试验系统，对研究结论进行了验证。一系列研究表明，在考虑系统中低压减载装置实际动作效果的情况下，为保证失步解列装置的正确动作，需对当前该装置的配置和整定值进行调整。     

电力系统低压减载和低频减载协调控制策略

低压减载和低频减载是分别解决电力系统中电压稳定问题和频率稳定问题的最常用手段。实际系统中,电压稳定问题和频率稳定问题往往是互相耦合、共同存在的,单独采用一种策略难以同时解决2个问题。文中提出了一种可以实现低压减载和低频减载协调控制的方法。该方法将切负荷控制中的优化问题转化成一个可满足性校验问题,然后采用“搜索+校验”的思路进行求解。求解过程中先采用有序二元决策图（OBDD）等快速搜索算法缩小决策空间,然后针对其中的策略进行可满足性校验。该方法不用求解复杂的多目标、混合整数优化问题,直接得到可行的切负荷策略。最后给出了基于此方法的仿真算例,并通过时域暂态仿真验证了结果的准确性。     

解列和减载技术在印尼INDORAMA工程的应用

针对印尼INDORAMA电厂、IRS化工厂和印尼国家电网（PLN）构成的局部电力网络采用的解列和减载技术方案的特点、逻辑功能和应用情况进行了介绍。在该方案的制订和实施过程中,不仅考虑了国内电力系统规程（规范）的要求,而且也理解、吸收和融合了国外电力系统专家的经验,以保证企业自备电站在电网波动及电网发生事故时,能坚持孤岛运行为目标的逻辑理念且中西兼顾,是对企业自备电站（小电源并网系统）解列和减载方案设计和逻辑功能的总结,希望能对从事电厂建设的工程技术人员有所帮助。     

龙政直流双极闭锁事故华东电网频率特性分析

通过数字仿真复现了“11·20”龙政直流双极闭锁事故华东电网的频率响应。分析了频率仿真结果与实际系统频率响应差异的原因，并以事故前系统运行方式为基础，校核计算了华东电网低频减载整定配置方案，初步分析了华东电网频率响应特性。     

福建500 kV电网初期安全稳定控制研究

认为福建电力系统在500 kV网架的形成初期，福建电网再次出现更高层次的“大机组小电网 ”的结构，其安全稳定问题仍然是电压和频率两个方面，同时存在功角稳定性隐患，应设置 专门的 安全自动化措施，包括在东南部电网逐步投运低频、低压减载装置，并对区域电网安全稳定 控制系统加以改造、完善和新建等。     

基于惩罚函数法的低频切泵与低频减载协调方案

传统的低频减载一般不考虑抽水蓄能的调节作用,抽水蓄能在抽水工况下相当于负荷。文中提出在电网发生大规模功率缺额导致频率急剧下降的情况下,在特定频率段采用低频切泵配合低频减载的方法来抑制电网频率下降,减小切负荷量;重点研究了低频切泵和低频减载的协调,给出了两者优化目标函数及其约束条件;运用惩罚函数法优化计算结果,得到最佳低频切泵方案。最后,利用仿真软件模拟故障场景进行仿真分析,仿真结果表明,所提出的方法能有效抑制电网频率崩溃。     

高填方涵洞加筋减载的数值模拟

为确定高填方涵洞加筋减载效果的影响因素及影响规律,在介绍加筋桥减载法及其减载机理的基础上,通过对加筋减载的高填方涵洞的数值模拟,研究了不同格栅层数、减载孔不同宽度、高度和侧壁角度以及减载孔不同填料性质时高填方涵洞的土压力变化规律,分析了高填方涵洞加筋减载的效果。结果表明:减载孔高度和减载孔填料模量对减载效果有较大的影响,减载孔高度越高,减载孔填料模量越低,减载效果越显著;减载孔宽度、格栅层数和减载孔填料的内摩擦角对减载效果影响较小,但减载孔宽度的增加使涵洞受力更均匀,有利于减小结构物内力。     

电网行波故障定位装置的优化配置

在研究电网行波故障定位方法的基础上,提出了一种行波故障定位装置的优化配置方法。该方法首先依据配置原则对电网中的变电站配置行波定位装置,然后利用模拟退火算法对初始方案进行优化,将配置过程和优化过程有效结合后提高了初始配置方案的质量,缩小了模拟退火算法的寻优范围,从而提高了求解速度。实际系统的配置分析和仿真结果表明适当的优化配置可以在不影响定位可靠性和准确性的前提下减少定位装置的布点,从而有效节省投资。     

地下厂房施工过程的三维非线性数值模拟分析

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。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

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.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

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.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

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. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

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.