Effects of plant community composition and exposure to wave action on invertebrate habitat use of Lake Huron coastal wetlands

Invertebrate communities from different coastal marsh‐plant communities were compared along wave‐exposure gradients using data from 1994, 1998 and 1999. Data were subjected to correspondence analyses to search for patterns in invertebrate communities in relation to plant‐community structure and wave exposure. In 1994, quantitative plant‐ and sediment‐invertebrate samples were taken from nine habitats: four from inland, subsurface‐connected marshes and five from littoral, emergent marshes. In 1998, sweep‐net samples were taken from 13 plant communities: six on the exposed and seven on the protected side of an island. In 1999, 2–3 plant communities/sites were sampled with sweep nets from four sites around the Bay so that intersite differences between inner, less‐exposed and outer, more‐exposed habitats could be examined. In all three studies, correspondence analyses separated inland, protected or inner sites from littoral, exposed or outer sites, suggesting differences in invertebrate‐community structure. For example, Hydracarina and Asellidae occurred in large numbers in inland sites, but were less common or absent from exposed, littoral sites. Littoral marshes also separated along an exposure gradient with Tanytarsini and Orthocladiinae collectors of organic particles occurring in very high numbers in outer, exposed areas where organic particles from the pelagic zone entered the marsh. Certain plant‐community types clustered together (e.g. wet meadow and Scirpus) while others, such as Typha, stands clustered according to exposure to waves suggesting the importance of both plant‐community structure and wave exposure in determining invertebrate‐community structure. We present a conceptual model that suggests that invertebrates in Great Lakes' marshes are distributed along gradients of decreased mixing of pelagic water and increases in sediment organic matter from outer to inner marsh and between littoral and adjacent inland marshes. Some invertebrates do best on one end of these gradients, while the majority are generalists found across habitat types.     

PM2000水电厂生产运行管理系统

介绍了基于Web技术开发的PM2000水电厂生产运行管理系统的软、硬件结 构，详细阐述了该系统所具备的主要功能及其对提高水电厂生产运行管理水平所发挥的作用。     

二滩水电站地下厂房洞室的施工特点

国际承包商在二滩工程中的许多施工布置和方法，施工技术和工艺、施工设备和措施很具有特色，扩展了我们的视野、丰富的我们的思路。总结其经验，可作为国内类似工程的参考。     

关于上海地区屋顶绿化的思考

在上海市平面绿化工作已初见成效,大型公共绿地越来越多,城市越来越美之时,构建立体绿化 成为当务之急。本文通过对上海地区屋顶绿化的现状及存在的问题的阐述,结合绿化植物的选择和维护的一 些基本理论,展示了屋顶绿化广阔的发展前景。     

Price-maker型水电厂策略性报价

用古诺模型研究了Price-maker型水电厂在电力市场下的策略报价问题.将系统中各厂商的竞争简化为己方和虚拟对手组成的双人博弈,提出一种基于历史数据、分析对手行为的可行方法.该方法通过分析历史可获得数据,求取对手成本函数参数及系统的逆需求函数,由此获得合理的对手策略估计,并求取在此可能对手策略下的己方最优策略,从而达到己方收益最大的目标.     

Baseline assessment of metals and hydrocarbons in the sediments of Lake Mulwala, Australia

An assessment of hydrocarbon and metal/metalloids (arsenic, cadmium, copper, lead, mercury, selenium, zinc) contamination in sediments from Lake Mulwala, Australia, was undertaken. The objectives of the study were: (i) to determine the extent of contamination in the lake sediments, compared to Australian and international sediment quality guidelines, and (ii) to attempt to identify the contaminant sources to the lake. With the exception of a few samples containing elevated levels of arsenic and/or mercury, the levels of all contaminants in the sediment samples taken from the lake were below the ‘lower trigger’ of the Australian Sediment Quality Guidelines that would warrant further investigation. High molecular weight hydrocarbons (up to 700 mg kg⁻¹) were found in most sediment samples. Non‐metric statistical analysis indicated that the contaminant distribution was different in different parts of the lake, with the lowest concentrations generally found at the influent to the lake. No definitive source(s) of contamination could be identified for either metalloids or hydrocarbons.     

Multinational Companies,Technology Spillovers and Plant Survival*

How does the presence of multinational companies affect plant survival in the host country? We postulate that multinational companies can impact positively on plant survival through technology spillovers. We examine the nature of the effect of multinationals using a Cox proportional hazard model, which we estimate using plant‐level data for Irish manufacturing industries. Our results show that the presence of multinationals has a life‐enhancing effect only on indigenous plants in high‐tech industries, suggesting the presence of technology spillovers. In contrast, multinationals compete with each other in low‐tech sectors in the host country.     

我国产权制度的变迁及其趋势

我国私营经济是在传统的公有制经济的土壤中发展起来的,其发展必然与传统体制发生摩擦与冲突。本文总结了我国产权制度变革的路径,分析了影响私营经济可持续发展的产权制度障碍,根据我国产权制度改革的轨迹,预测了产权制度变迁的趋势和特征。     

三峡水电站充水保压蜗壳平面非线性分析

采用自编的三维钢筋混凝土非线性有限元程序，对三峡水电站充水保压蜗壳进行了平面非线性分析，分析了钢蜗壳及外围钢筋混凝土的应力变形特性。非线性计算分析表明，在蜗壳进口断面处，虽然外围混凝土较薄，但在设计内水压力、结构自重和设备重量这些荷载组合作用下，蜗壳进口断面混凝土可能不会开裂，因此钢材应力均比较低，结构具有较高的安全度。说明现有配筋方案钢筋用量可能偏多，没有充分发挥钢材的作用，在进一步设计时可以适当优化。     

三峡工地高压供电线路故障判断方法的探讨

高压供电设备故障特别是输电线路的高压接地故障对工地的影响是相当大的。由于接地故障为隐性故障，没有明显的物理现象，且若是长期接地可能会发展成较为严重的两相或三相短路故障，使系统解列运行直至崩溃；由于工地流动人员较多，还易造成电击事故。利用高压一相接地时在线路中产生零序电压这一特性来迅速判断和切除接地的用电设备，可以保证各项施工的顺利进行。