凤滩水电站钢闸门检测和安全鉴定

指出了水工钢闸门运行状况直接影响到工程的适用性、安全性和耐久性,需定期对水工钢闸门进行科学的抽样检测和安全鉴定。对凤滩水电站钢闸门进行了检测和安全鉴定,通过有限元对闸门进行的三维有限元强度和刚度复核,确定了该闸门满足规范要求,可继续使用。     

基于多算法耦合的水电站自主智能优化调度应用

中、大型水电站的水位预测以及优化调度是水库防洪和发电能力的重要问题,目前对水库水位预测以及水库调度主要采用算法预测水位与人工设置调度模式相结合的方式,使得水库智能调度模式在实际的调度过程中实用性不强。为满足水电站能自主智能优化调度,脱离人工设置,利用大渡河流域某电站水库水位数据建立了基于BP(back propagation)神经网络水库水位预测模型。采用C4.5算法模拟调度人员对水电站调度模式选取规则,再利用POA(逐步优化)算法模型通过耦合BP神经网络水位预测模型,对电站水库预测的水位以及C4.5机器算法选取调度模式的规则,以达到对水电站自主智能优化调度。解决了POA算法须人工设值调度期末控制水位与调度过程优化模式的缺陷,使得多算法耦合模型可以脱离人工设值自行执行符合电站运行策略的优化操作,同时验证了多算法耦合的可行性和有效性。     

洲江相连 在鹅洲的希望

6月22日，下午3时，天鹅洲闸口，灌江纳苗现场：石首市天鹅洲水管所陈定华所长郑重按下闸门提升按钮：平时是一“闸”当关，万“水”莫开，毫不通融地斩断了长江与故道联系的天鹅洲闸三道闸门，此时缓缓逐次打开：天鹅洲沙滩子大堤外堤的长     

洲江相连 天鹅洲的希望

6月22日,下午3时,天鹅洲闸口,灌江纳苗现场。石首市天鹅洲水管所陈定华所长郑重按下闸门提升按钮。平时是一“闸”当关,万“水”莫开,毫不通融地斩断了长江与故道联系的天鹅洲闸三道闸门,此时缓缓逐次打开。天鹅洲沙滩子大堤外堤的长江水由此滚滚涌入堤内天鹅洲水域,如同母亲急     

微机保护断路器控制回路的改进探讨

变电站自动化系统断路器控制回路中虽然增加了合／分闸保持（HBJ）元件提高合／分闸的可靠性．但在断路器机构或辅助开关故障时还会导致回路元件的故障。为此,本文提出了在自动化系统断路器控制回路中增加超时返回继电器及确定继电器的选型。改进后的断路器控制回路能保证合／分闸回路的电器元件安全可靠运行,并能在断路器机构故障时通过自动化系统向调度端报送信号。     

水利工程中闸门启闭机的运行管理研究

目前在水利工程建设与维护中,最重要的内容是实现对闸门启闭机的运行管理。为提高闸门启闭机的运行质量和水利工程的整体建设速度,在确定闸门启闭机的具体分类及运行工作原理基础上,从水利工程闸门运行前启闭机准备、启闭机运行中的纠偏与控制管理流程、闸门启闭机运行中零部件养护与维护管理等方面提出一种全新的运行管理思路,以期为促进闸门启闭机现代化和高效化管理提供创新思路,并进一步提升水利工程整体运行的安全性和稳定性。     

水电站输水发电系统增容改造水力过渡过程仿真研究

根据阿海水电站输水系统布置和机组参数特性,应用外特性法进行机组增容10％处理后的大波动过渡过程计算,复核蜗壳末端、转轮出口处压力值及转速上升值,验证其是否满足原设计要求,为水电增容改造复核计算提供技术路线.     

投资达1800多亿的三峡工程年底建成

来自国务院三峡办的消息显示，目前，三峡工程枢纽和输变电工程已基本完工，运行平稳。截至今年六月底，三峡工程累计完成投资1849亿元人民币。三峡电站累计发电3200多亿千瓦时，三峡船闸累计运行近五万闸次，过闸货运量突破三亿吨。三峡工程建成后，可以有效调控长江上游洪水，将长江中游荆江河段防洪标准提高到近百年一遇，江汉平原和洞庭湖地区可免遭洪涝灾害，每年可提供一千亿千瓦时的清洁电能。按照初步设计，三峡水电站共装机二十六台，每年可替代五千万吨原煤的火力发电，可为华东、华中、华南等地区提供可靠、廉价、清洁的能源。     

高寒山区水电站的冰冻与预防

位于四川省甘孜、阿坝、凉山三州的山区水电站,大多为低坝引水式水电站,由取水枢纽、引水系统及厂区枢纽三部分组成,一般为孤立运行系统.由于多数山区水电站地处高海拔地带,冬季气温低,河水冰冻时间长,从而对运行中的水电站造成极大危害.为了减少冰害造成的各种经济损失,必须采取有效的预防措施,以使水电站在冬季得以顺利运行.笔者多年来,从事于高寒山区(主要是甘、阿、凉三州)水电站的设计工作,现仅将在设计中遇到的一些冰害情况及具体处理办法归结如下.     

关于木材过坝经济补偿核算方法的商榷

水电和木材水运都依托江河水资源来建设和生产。在木材水运河道上兴建水电站(闸坝)时,应遵照国家河道综合利用的政策法令、统筹兼顾,既利于发电灌溉,又利于通航过木,合理解决发电与漂木的矛盾。如有可能或者已造成木材过坝(闸)经济损失的,应在国家政策和计划指导下,采取部门、企业间经济补偿的办法予以妥善解决。那     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.