An index of human alteration of lake shore morphology

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Assessing electric fishing sampling effort to estimate stream fish assemblage attributes

The EU Water Framework Directive (WFD) obligates authorities to assess the ecological status of rivers. The sampling of the fish assemblage must be based on a reliable and cost‐effective monitoring programme, and it should be optimised to measure the ecological quality cost‐effectively. The efficiency of single‐pass versus three‐pass backpack electric fishing was measured to assess ecological status. The data included 295 electric fishing samplings from 137 rivers in Finland and a 5‐year data series from six small forest streams in mid‐eastern Finland. Compared with three‐pass electric fishing, single‐pass electric fishing in the same area increased the risk of missing rare fish species and species with low catchability. The concordance of the calculated fish metrics (e.g. proportion of tolerant and intolerant species) between one‐ and three‐pass measurements was, however, high, suggesting that single‐pass electric fishing was a suitable sampling procedure to evaluate ecological status. Increasing the area sampled by single‐pass removals stabilised the variances in the fish metrics and similarity indexes. It was concluded that in small streams electric fishing an area 24–27 times the stream width and in general a minimum of 300 m², but preferably more than 450 m², was adequate to estimate fish assemblage attributes reliably in boreal streams.     

我国低碳城市发展框架及路径分析

谯碳化是未来全球城市的发展方向,在低碳视角下研究我国城市的发展框架和路径具有重要意义。探讨低碳经济和低碳城市的内涵、国内外低碳城市研究现状及实践,构建我国低碳城市发展框架,并深入分析我国低碳城市实现路径。     

构建少数民族资源管理系统的策略与框架研究

基于互联网和信息处理的发展,从民族地理、风俗习惯、服饰特点等方面入手,结合开放源代码数字资源管理系统DSpace的功能特点,提出了利用DSpace数字仓储技术构建少数民族数字资源管理系统的构想和方案。     

Functional vs scenic restoration – challenges to improve fish and fisheries in urban waters

Abstract Two rehabilitation projects were compared to determine their feasibility for successfully improving habitat for fish in urban waters. The first re‐meandering project involved channel reconstruction in the Müggelspree upstream of Berlin to create an aesthetically pleasing, stable, meandering channel. The second project addressed a typical habitat bottleneck for fish found in urban waterways; that of nursery habitats lost due to river engineering works. Rehabilitated and control sites were sampled before and after in the Müggelspree and once in the urban Spree River. A total of 30 303 fish belonging to 27 species were collected. The fish assemblage was dominated by generalist species with 81% roach, Rutilus rutilus (L.), and perch, Perca fluviatilis L. Species diversity did not improve in either the rural or urban stretch. In the Müggelspree, the loss of riverine habitats was mirrored by significant declines in the densities of chub, Leuciscus cephalus (L.), ide, Leuciscus idus (L.), gudgeon, Gobio gobio (L.), rheophilic and lithophilic species. By contrast, densities of rheophilic species around the artificial structures created in the urban Spree River, although the main effect was an overwhelming increase in roach and perch. The results suggest that if underlying bottlenecks can be identified, artificial structures can provide functional fish habitat that replaces the natural equivalent in urban river stretches. Consequently, even the most heavily degraded waters provide opportunities to improve fish diversity and fisheries using artificial habitat structures.     

Invasive Asian clam distribution pattern reveals minimal constraints to downstream dispersal and imperceptible ecological impacts

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基于产生式与框架知识表示的造林专家系统研建

本文根据造林专家确定造林地立地条件和造林模式的知识构成,采用了产生式表示法与基于框架表示法相结合来表示.设计了相应的规则库和事实库结构,优化了推理规则的表示方法,将多条规则表示的造林推理知识简化为一条规则,给出了实例,在此基础上详细地给出了具体的推理算法.设计了系统的功能结构,实现了一个造林专家系统,在实际生产中进行了应用.     

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本文通过ASP.NET技术及安全性算法(如SSL、MD5、SHA1等)确保数据处理的安全性,在动态Web页面数据处理方面.基本实现应用程序数据处理的过程;使用ⅡS组件、Framework和动态web框架实现数据的交互性处理;ASP.NET技术、加密算法、ⅡS组件、Framework及Windows操作系统是实现数据安全性及数据处理的重要方法与手段;为今后充分利用功能强大的AJAX、SQL Express等新技术工具,开发出高效处理数据的应用程序平台,提供强大的技术支持.     

基于Web GIS农业土地资源信息系统设计

在网络环境下,应用Visual Studio.NET 2003开发平台和MapXtreme 2004集成开发环境,结合沈阳市东陵区农业土地资源详细数据资料以及土地管理部门的需求,设计了基于Web GIS的农业土地资源管理信息系统。该系统可实现对区域性土地资源信息的科学高效管理,方便快捷地获取土地资源的时空分布特征信息,为相关部门在土地资源管理方面提供科学依据,对实现数字化农业以及农业可持续发展具有重要的现实意义。