利用CC-PN建立机组组合问题中时间约束辅助模型

在为机组组合问题编制算法的过程中，因需要满足错综复杂的约束条件，容易使程序结构混乱、逻辑判断出错，最终导致算法求解失败。文中提出一种用于解决水力机组组合中时间约束问题的受控着色Petri网(CC-PN)模型，以指导和辅助机组组合算法程序的编制。该模型能直观地表达水力机组的启／停状况，并输出计算流量费用的开关量，将机组组合算法中面临启／停新机组时的约束判定和流量损失计算单独处理，为解决考虑时间约束的机组组合问题提供了新的辅助方法。     

具特征约束的有限元三角网格自动生成方法

 鉴于地下水数值计算中有限元剖分的特殊需要，提出了一种满足一定约束条件下某一区域内的三角网格自动生成方法，并给出了该方法实现的过程。该网格生成方法综合考虑了两种类型的内部特征约束：固定结点和固定单元边，在此基础上产生满足约束的离散点序列以及已有结点联系表，从而进行三角形网格的自动生成，自动便捷提供数值计算所需的模拟区离散的各种数据信息。另外，还讨论了网格生成后的校验与校正以及向四边形单元的拓展。     

用受控有色Petri网解决水力机组组合中时间约束问题的研究

提出一种应用于解决水力机组组合中时间约束问题的受控有色Petri网模型．该模型能够直观地表达水力机组的启／停状况，并输出计算流量费用的开关量，将机组组合算法中面临开／停新机组时的约束判定和流量损失计算单独处理，为解决考虑时间约束的机组组合问题提供了新的辅助方法。     

冰温度膨胀力的有限元分析

本文在对冰温度膨胀力的作用机理作简要分析的基础上，将有限元方法引入到冰温度膨胀力的计算中，对工程中常见的两类边界条件(即固定约束和摩擦约束)下的冰温度膨胀力进行了计算。通过对计算结果的分析，得到以下结论：从与现场实测数据的比较来看，有限元计算的结果比较合理。可以在设计中应用；冰盖一侧固定约束、另一侧摩擦约束时。冰作用于固定约束边上的膨胀力会产生高度的应力集中；两侧都是摩擦约束的膨胀力远小于其它约束时的冰膨胀力；温升率对直立墙上冰膨胀力沿冰厚分布的影响远大于对斜坡的影响。     

基于机会约束规划的输电系统规划方法

输电系统在电力市场中扮演着十分重要的角色，因为其提供了实现公平竞争的场所。输电系统的状况如容量充裕性对电力市场的竞争性有重要的影响。适当地扩展或加强输电系统对满足发电公司和用户的需要、消除或减缓输电系统阻塞具有重要作用。与传统的输电系统规划问题相比，电力市场环境下的输电系统规划更加复杂，需要处理的不确定性因素更多。机会约束规划是专门用于解决包含不确定性因素的优化问题的一类随机优化方法，适用于市场环境下的输电系统规划问题。文中将机会约束规划引入到市场环境下的输电系统规划研究中，给出了基于蒙特卡罗仿真和遗传算法的求解方法，为解决这一重要而困难的问题做了一些新的尝试，并通过一个算例系统说明了该方法的可行性。     

具有状态约束的动态系统优化调度方法及其应用

给出了一种求解具有状态约束的动态系统优化问题的新方法，该方法充分利用了系统状态空间的结构信息而不必离散化状态变量，能快速递推得到相邻两时段costtogo函数的反向传递关系，进而前向传递求得问题的最优解。还给出了该法在电力系统优化调度中的应用实例，根据仿真试验表明，可成功地解决有爬升约束发电机组的优化调度问题，能得到问题的最优解，算法的效率较高。     

安全约束对区域电力市场的影响

网架结构薄弱与安全约束问题是影响区域市场交易的重要因素。安全约束的存在使电力市场产生了有约束成交与无约束成交的差别，直接影响了市场成交结果；安全约束还改变了电力市场不同地区实际的市场结构和供需平衡，改变了市场参与者的竞标地位和市场力，从而间接影响了市场参与者的竞标策略。文中根据区域电力市场的规则特点和模拟运行实践，研究了评价安全约束对市场影响程度的指标，并提出了“等效区外供应者”的概念，深入分析了安全约束对各地区市场结构和参与者报价策略的影响。     

水火电系统古诺模型的均衡分析

利用古诺（Cournot）模型研究了在联营模式下多时段水火电混合系统的纳什（Nash）均衡策略问题。首先建立了水火电系统的Cournot模型，模型中火电系统考虑了机组的最小开停机时间的限制，水电系统则考虑了用水量、库容限制等约束。同时，利用迭代法并结合动态规划对发电商的Nash均衡策略进行了求解。最后以IEEE 6机系统为例研究了最小开停机时间和用水量限制等约束对均衡结果的影响。仿真结果表明，考虑最小开停机时间约束时，即使某些时段利润为负，但为了避免后续时段的持续停机使利润受到更大的损失，一些机组在这些时段仍需开机；考虑水电厂商用水量约束时，水电厂商有动力在高峰时段持留发电量。     

电力市场中爬坡约束问题的一种实用算法

针对电力市场的要求，分析了3种解决爬（下）坡约束问题的算法，即线性规划法、调整机组有功功率法和修改机组竞价曲线法。在分析比较的基础上，选择调整机组有功功率解决辽宁发电市场爬坡约束问题，并以实际算例说明了其合理性。     

电力系统实时安全约束调度的混合算法 

提出了一种实时安全约束调度的混合算法，该算法结合了基于灵敏度的反向等量配对法和非线性原对偶内点算法的优点，并进一步与自动发电控制(AGC)相结合，构成闭环控制系统，实现稳定断面越限的校正控制。当发现稳定断面越限时，由安全约束调度提供校正控制策略，并在AGC控制下执行，以自动完成解除越限的调整。在江苏省调能量管理系统（EMS）的实际工程应用表明，该方法可以满足实时安全约束调度的要求，有效地将稳定断面有功功率控制在允许范围内，保证电力系统的安全、稳定运行。     

Effects of grade control structures on the macroinvertebrate assemblage of an agriculturally impacted stream

Nearly 400 rock rip‐rap grade control structures (hereafter GCS) were recently placed in streams of western Iowa, USA to reduce streambank erosion and protect bridge infrastructure and farmland. In this region, streams are characterized by channelized reaches, highly incised banks and silt and sand substrates that normally support low macroinvertebrate abundance and diversity. Therefore, GCS composed of rip‐rap provide the majority of coarse substrate habitat for benthic macroinvertebrates in these streams. We sampled 20 sites on Walnut Creek, Montgomery County, Iowa to quantify macroinvertebrate assemblage characteristics (1) on GCS rip‐rap and at sites located (2) 5–50 m upstream of GCS, (3) 5–50 m downstream of GCS and (4) at least 1 km from any GCS (five sites each). Macroinvertebrate biomass, numerical densities and diversity were greatest at sites with coarse substrates, including GCS sites and one natural riffle site and relatively low at remaining sites with soft substrates. Densities of macroinvertebrates in the orders Ephemeroptera, Trichoptera, Diptera, Coleoptera and Acariformes were abundant on GCS rip‐rap. Increases in macroinvertebrate biomass, density and diversity at GCS may improve local efficiency of breakdown of organic matter and nutrient and energy flow, and provide enhanced food resources for aquatic vertebrates. However, lack of positive macroinvertebrate responses immediately upstream and downstream of GCS suggest that positive effects might be restricted to the small areas of streambed covered by GCS. Improved understanding of GCS effects at both local and ecosystem scales is essential for stream management when these structures are present. Copyright © 2007 John Wiley & Sons, Ltd.     

EFFECTS OF GRADE CONTROL STRUCTURES ON FISH PASSAGE,BIOLOGICAL ASSEMBLAGES AND HYDRAULIC ENVIRONMENTS IN WESTERN IOWA STREAMS: A MULTIDISCIPLINARY REVIEW

Land use changes and channelization of streams in the deep loess region of western Iowa have led to stream channel incision, altered flow regimes, increased sediment inputs, decreased habitat diversity and reduced lateral connectivity of streams and floodplains. Grade control structures (GCSs) are built in streams to prevent further erosion, protect infrastructure and reduce sediment loads. However, GCS can have a detrimental impact on fisheries and biological communities. We review three complementary biological and hydraulic studies on the effects of GCS in these streams. GCS with steep (≥1:4 rise : run) downstream slopes severely limited fish passage, but GCS with gentle slopes (≤1:15) allowed greater passage. Fish assemblages were dominated by species tolerant of degradation, and Index of Biotic Integrity (IBI) scores were indicative of fair or poor biotic integrity. More than 50% of fish species had truncated distributions. After modification of GCS to reduce slopes and permit increased passage, IBI scores increased and several species were detected further upstream than before modification. Total macroinvertebrate density, biomass and taxonomic diversity and abundance of ecologically sensitive taxa were greater at GCS than in reaches immediately upstream, downstream or ≥1 km from GCS. A hydraulic study confirmed results from fish passage studies; minimum depths and maximum current velocities at GCS with gentle slopes (≤1:15) were more likely to meet minimum criteria for catfish passage than GCS with steeper slopes. Multidisciplinary approaches such as ours will increase understanding of GCS‐associated factors influencing fish passage, biological assemblage structure and other ecological relationships in streams. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of channel restabilization on habitat diversity,twentymile creek,mississippi

Twentymile Creek, a sand-bed stream draining a 450 km² catchment in northeast Mississippi, was channelized prior to 1910, in 1938, and in 1966. Straightening and enlargement in 1966 was followed by channel instability—rapid bed degradation (2-4 m) and cross-section enlargement by 1.4 to 2.7 times. Grade control structures (GCS) (weirs with stoneprotected stilling basins) and various types of streambank protection were constructed along the channel in the early 1980s to restore stability. Other investigators have suggested that habitat recovery in incised, channelized streams is facilitated by construction of GCS because they create stable scour holes and promote natural formation of a low-flow channel flanked by vegetated berms. Effects of restabilization of Twentymile Creek on aquatic habitats were assessed in four ways. The fraction of the bank line covered by woody vegetation was mapped from aerial photographs taken in 1981 and 1985; physical habitat (depth, velocity, substrate, and cover) and fishes were sampled at base flow; and the existence and size of a low-flow channel was ascertained from cross-section surveys taken in 1980 and 1989. Woody vegetation, physical aquatic habitat, and fishes were also sampled from Mubby-Chiwapa Creek, a similar-sized unstable channel with no GCS. Physical habitat variables and fishes were sampled concurrently at five stations on Twentymile Creek, and four stations on Mubby-Chiwapa. Four of the five Twentymile stations were either above or below a GCS. Bank-line woody vegetation cover increased 8 per cent between 1981 and 1985 along Twentymile Creek but was stable along Mubby-Chiwapa. Reaches above and below GCS were deeper with slower current velocities than elsewhere. Mean Shannon diversity indices based on physical data were similar for both streams, but were 58 per cent higher for stations immediately above and below GCS than for other stations. Since construction of the GCS and bank protection measures, longitudinal berms have formed within the enlarged Twentymile Creek channel, creating a low-flow channel. Low-flow channel capacity was equivalent to a mean daily discharge equalled or exceeded 30 per cent of the time, and was considerably lower than the effective discharge. Differences in aquatic habitat diversity among the stations sampled were primarily due to the scour holes below the GCS and the low-flow channel. Thirty-nine fish species were collected from Twentymile Creek, but only 22 from Mubby-Chiwapa. Fourteen species were collected exclusively at GCS. Principal component analyses of the abundance of the eight numerically dominant fish species indicated similar faunas at most stations, but Twentymile Creek GCS stations were faunistically distinct. Abundance of several of the numerically dominant species was positively influenced by greater depths and lower velocities found near Twentymile GCS. The mean fish diversity index for Twentymile Creek was 29 per cent higher than for Mubby-Chiwapa, and fish diversity was positively correlated with substrate diversity and mean depth.     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

Management Implications to Water Resources Constraint Force on Socio-economic System in Rapid Urbanization: A Case Study of the Hexi Corridor,NW China

As water has become the shortest resources in arid, semi-arid and rapid urbanization areas when the water resources utilization has approached or exceeded its threshold, water resources system slows down the socio-economic growth rate and destroys the projected targets to eradicate poverty and realize sustainable development. We put forward the concept of Water Resources Constraint Force (WRCF) and constructed a conceptual framework on it. Conceptual models on the interactions and feedbacks between water resources and socio-economic systems in water scarce regions or river basins indicate that, if the socio-economic system always aims at sustainable development, WRCF will vary with a normal distribution curve. Rational water resources management plays an important role on this optimistic variation law. Specifically, Water Demand Management (WDM) and Integrated Water Resources Management (IWRM) are considered as an important perspective and approach to alleviate WRCF. A case study in the Hexi Corridor of NW China indicates that, water resources management has great impact on WRCF both in Zhangye and Wuwei Region, and also the river basins where they are located. The drastic transformation of water resources management pattern and the experimental project – Building Water-saving Society in Zhangye Region alleviated the WRCF to some extent. However, from a water resources management view, WRCF in Zhangye Region still belongs to the severe constraint type. It will soon step into the very severe constraint type. In order to shorten the periods from the very severe constraint type finally to the slight constraint type, WDM and IWRM in the Hei River Basin should be improved as soon as possible. However, in the Shiyang River Basin, WRCF belongs to the very severe constraint type at present due to poor water resources management in the past. Though the socio-economic system adapted itself and alleviated the WRCF to some extent, the Shiyang River Basin had to transform the water supply management pattern to WDM, and seek IWRM in recent years. It is concluded that WDM and IWRM is a natural selection to alleviate the WRCF on the socio-economic system and realize sustainable development.     

Development of Cartesian grid method for simulation of violent ship-wave interactions

We present a Cartesian grid method for numerical simulation of strongly nonlinear phenomena of ship-wave interactions. The Constraint Interpolation Profile(CIP) method is applied to the flow solver, which can efficiently increase the discretization accuracy on the moving boundaries for the Cartesian grid method. Tangent of Hyperbola for Interface Capturing(THINC) is implemented as an interface capturing scheme for free surface calculation. An improved immersed boundary method is developed to treat moving bodies with complex-shaped geometries. In this paper, the main features and some recent improvements of the Cartesian grid method are described and several numerical simulation results are presented to discuss its performance.     

水资源约束下城市需水量预测研究

在分析需水量预测和水资源约束的基础上,本文探讨了水资源约束的量化指标。提出城市需水量预测应和水资源约束结合,并将水资源约束系数引入需水量预测中。应用BP网络,建立了水资源约束下的城市需水量预测模型。本文以郑州市为例,应用预测模型进行需水量预测,并对预测结果进行了分析。结果表明:本文建立的模型具有一定的实用价值,为区域的发展规划、供水工程规划以及节水规划提供更科学的依据。     

Operating Rules of an Irrigation Purposes Reservoir Using Multi-Objective Optimization

A multi-objective optimization technique for the operation of an irrigation reservoir is presented in this paper. The study deals with two different objective functions (OF): the minimization of reservoir release deficit from the irrigation demand (OF1) and the maximization of net benefit by the demand sector (OF2). In the first step, monthly optimization of each individual objective was performed with a deterministic non-linear programming (NLP) algorithm, that gave the lower and upper bounds for the multi-objective analysis. In the second step, multi-objective optimization was performed through the Constraint method that operates by optimising the objective function OF1, while the other (OF2) was constrained to satisfy release strategies generated by the optimization. Non-dominated set of release strategies is generated by parametrically varying the bounds of the constraints obtained from the individual optimal solutions. In the third step, the interactive analytical Step method was applied to find the best compromise solution, between the two OFs, by minimizing the distance of each non-dominated solution to an ideal solution that represents the utopian optimum for both OF1 and OF2. Furthermore, the interactive approach allows to improve the performance of the reservoir in terms of compromise irrigation releases, by changing the OF values until the satisfaction of predetermined criteria fixed by the planners and decision makers. The proposed water allocation model was applied to the Pozzillo reservoir operation, that supplies the Catania Plain irrigation area (Eastern Sicily).     

我国工程技术标准化初探

通过对我国部分行业(建设、交通、铁路、水电等)工程技术标准化发展历程的回顾与分析,提出了存在问题及不足之处。并根据我国工程发展的新形势以及WTO/TBT协定要求,对新时期我国工程技术标准化的建设与完善提出了建议与展望。     

有中间支承的轴心压杆长度系数的求解

本文通过引入拉格朗日待定乘子，将有约束条件的驻值问题转化为无条件的另一驻值问题来处理；采用里兹法求解了四种有任意位置中间支承的轴心压杆的长度系数，最后将结果归纳成计算公式，以便应用。