我国中/高密度纤维板发展现状与思考

根据调查和有关文献,对我国中/高密度纤维板的发展状况进行了总结,并提出中/高密度纤维板未来发展的建议和设想.     

Importance of the River Teviot to Atlantic salmon, Salmo salar, rod catches in the River Tweed, Scotland

Abstract  The body mass distributions and variations in abundance of the spring and autumn catches of Atlantic salmon, Salmo salar L., were compared between fisheries above and below the confluence of the rivers Tweed and Teviot, Scotland. Significant differences between the distributions were found over three periods, one in spring and two in autumn, when salmon catches were high. Correlations were found between abundance trends for periods when distributions were similar or dissimilar. Abundance of salmon returning to the River Teviot was proportional to the main river. However, its population structure differed when abundances were high, suggesting different survival strategies. It appears that changes in the numbers returning to the river were resultant of changes in the marine rather than freshwater environment.     

哈达门国家森林公园游客量动态预测

根据哈达门国家森林公园的票房数据，应用灰色系统理论建立旅游量灰色动态模型。基此，对哈园游客量进行了中短期预测，其预测检验精度为９３．７２。旨在对该园建设、管理等项决策提供科学依据。     

南京市能见度变化趋势及其影响因素

利用1980~2013年南京国家基本气象站的地面常规气象要素和能见度观测资料,剔除相对湿度和天气现象对能见度的影响,采用等级分析法、"非常好"能见度出现频率法、累积百分率法、Ridit中值分析等方法,分析了南京地区大气能见度的年际和季节变化趋势;并利用偏相关分析法分析了能见度与气温、气压、平均风速和相对湿度的相关关系。结果表明,能见度有明显日变化和季节变化,一天中,8:00最差,14:00最好;一年之中,能见度夏季最好,冬季最差。1980~1984年南京能见度呈上升趋势,1985~2004年呈波动下降趋势,2005~2013年则呈缓慢上升趋势;"较差"和"一般"能见度出现频率呈现上升趋势,"较好"能见度出现频率则明显下降。能见度水平逐年代下降但降幅减小;能见度等级分布的季节差异逐年代减小。能见度与平均风速呈正相关,与相对湿度呈负相关。由于南京地区气候条件的影响,能见度与气压和气温均存在季节性差异,能见度与气压在冬季呈较好的正相关,与气温夏季呈正相关、冬季呈负相关。     

国内气力式玉米精量排种器研究进展

近年来，我国机械化技术水平不断提高，精量播种正逐步取代传统的粗放式播种，从而降低了种植成本，同时提高了生产效率和利润。目前，我国玉米单产水平存在较大提升空间，提升玉米机械播种水平是提高玉米播种质量和增加产量的有效方式。本文对气力式玉米精量排种器的研究现状进行了综述，包括气吸式、气吹式和气压式3种类型，分别总结了其结构、工作原理和工作参数、性能、优势等，评述了试验效果；针对玉米精量排种器目前存在的问题进行了分析，并提出了未来的发展趋势，以期为促进玉米机械化生产提供参考。     

发动机装配线技术现状及发展趋势

汽车发动机在装配中,因为发动机工艺的复杂性、零部件的多样性,发动机装配线就显得十分重要。文章主要阐述了汽车发动机装配线应具有的要求以及发动机装配线应具备的基本功能,并对发动机装配线技术现状提出发展趋势的预测。     

小型潜水电泵的历史与发展趋势

回顾了国内外小型潜水电泵的发展历史；分析了现状与存在问题；探讨了今后的发展趋势。     

中国土地资源安全评价研究进展及展望

土地资源作为国民经济发展的载体,其安全关乎粮食安全、社会安全、生态安全。对区域土地资源进行安全评价研究,既有利于落实国家土地保护政策,也可为区域生态友好型土地利用模式提供现实参考。近些年来,在土地资源安全理论研究、耕地与粮食安全研究、基于承载力的土地资源安全研究、土地生态安全评价等研究领域均取得显著进展。论文着重分析土地资源安全研究的新进展,对近年来我国土地资源安全研究最新成果及其在国民经济与社会发展中的应用、成效和前景进行评析,对我国土地资源安全研究的发展趋势进行展望,并提出了新时期土地资源安全研究的主要方向和重点领域。     

Selection of taxa as indicators of river and freshwater wetland quality in the UK

• 1. To assess the efficacy of environmental management policies and practices, there is a progressive transition from monitoring of activities towards assessment of their outcomes for the environment.
• 2. Population trends of key taxonomic groups can serve as useful indicators of broader environmental integrity and health. Several necessary and desirable criteria for selecting meaningful and suitable indicators are discussed. The attributes of a range of taxa and survey methods used for their assessment are discussed with reference to these criteria.
• 3. Survey methods, data holdings and analytical methods for populations of wild birds at present provide a good basis for developing indicators of the quality of fresh waters at a landscape scale. Other taxa are not necessarily any less appropriate; however, survey design and data representativeness are often limiting factors to the use of other taxa for assessing geographic and temporal trends.
• 4. Taxonomic science and ecological monitoring are necessary for determining society' progress with sustainable development and for informing appropriate enhancements to policy and management practice, particularly so for fresh waters.

Copyright © 2007 John Wiley & Sons, Ltd.