Profibus DP现场总线及其在火电厂的应用

现场总线作为过程控制领域的新技术,应用日益成熟和广泛。文章在论述Profibus DP总线通信协议和网络构成的基础上,分析了现场总线控制系统在火电厂应用的潜在问题和可行性,列举了Profibus DP应用实例。最后探讨了Profibus DP在国内首次应用的范围和深度。     

湿地保护与管理之我见

本文对湿地保护与管理存在的问题进行了阐述 ,提出了科学合理的保护与管理建议 ,对今后湿地规划与开发具有重要意义。     

山西太岳山辽东栎夏季树干液流通量研究

树干液流指蒸腾在植物体内引起的上升液流。土壤液态水进入根系后 ,由茎输导组织向上运送达冠层 ,经由气孔蒸腾 (包括角质层及皮孔蒸腾 )转化为气态水扩散到大气中去。根部吸收的水分有 99 8%以上消耗在蒸腾上 (王沙生等 ,1 991 )。通过精确测算茎流量 ,可以基本确定植株蒸腾失     

毛乌素沙地南缘植被类型及其演替规律初步研究

绿色植被是生态系统的核心,是维持生态平衡的支柱,在生态环境建设中有极其重要的防风固沙功能。为了搞好毛乌素沙地南缘盐池中部沙地的生态建设,加快该区植被重建与恢复的速度,引进更适合当地植被重建的树种,营造合理的林分结构,对该地区的植被型与组成以及演替规律的探讨至关重要。本文通过调查分析,对毛乌素沙地南缘盐池中部沙地的植被类型及植被演替特征做了较详细的论述。1　研究区自然概况试验研究区赵家塘位于宁夏盐池县,地处毛乌素沙地南缘,位于37°05′～38°10′N,106°30′～107°39′E,属典型大陆性气候,风大沙多,气候干旱。年…     

周至县核桃溃疡病发生规律及控制方法

调查分析了周至县核桃溃疡病发生规律,提出了包括农业、物理、化学、管理等措施在内的预防和防治方法.     

我国的胶合板工业如何应对WTO

本文从我国加入WTO入手,集中分析了我国胶合板工业的关税、进出口总量、国内市场对胶合板的消费需求,以及加入WTO以后的机遇与挑战。探讨了应对措施,初步阐述了我国胶合板工业的今后发展趋势。     

浅谈绿色建筑设计的发展趋势与实施策略

绿色设计就是以绿色技术为原则所进行的产品设计,即在产品整个生命周期内,着重考虑产品环境属性,并将其作为设计目标,在满足环境目标要求的同时,保证产品应有的基本功能、使用寿命、质量等。     

Division of ecological species groups and functional groups based on interspecific association — a case study of the tree layer in the tropical lowland rainforest of Jianfenling in Hainan Island, China

Twenty-three sample plots dominated by Vatica mangachapoi at various elevations in the tropical lowland rainforest in the Jianfengling National Nature Reserve of Hainan Island were established. The interspecific association among the 32 dominant species was analyzed and the division of ecological species groups and functional groups are discussed. The results showed that these dominant populations had an overall positive interspecific association. The species pairs with significant, positive association accounted for only about 10% of the total 496 species pairs. Most of the other species pairs showed weak association or non-association, i.e., the dominant populations investigated had relatively independent distributions. The 32 dominant species were divided into four ecological species groups and ten functional groups according to their interspecific association coefficients, based on a cluster analysis of the species. Recognition characteristics of the ten functional groups are proposed. __________ Translated from Scientia Silvae Sinicae, 2007, 43(4): 9–16 [译自: 林业科学]     

Spatial distribution pattern and dynamics of the primary population in a natural Populus euphratica forest in Tarim Basin, Xinjiang, China

One 50 m × 50 m standard plot was sampled in a natural forest of Populus euphratica in Awati County, situated at the edge of the Tarim Basin, Xinjiang Uygur Autonomous Region, China. The field investigation was conducted with a contiguous grid quadrate method. By means of a test of variance/mean value ratio, aggregation intensity index and theoretical distribution models, the spatial distribution pattern and the dynamics of primary populations in P. euphratica forest were studied. The results showed that the spatial distribution pattern of two dominant arbor populations conformed to clumped distribution. The aggregation intensity of the P. euphratica population was higher than that of P. pruinosa population. The spatial distribution pattern of two companion plant populations in the shrub layer also conformed to clump type, though the aggregation intensity of Tamarix chinensis was higher. In the herb layer, the distribution patterns of Glycyrrhiza uralensis and Asparagus persicus conformed respectively to a clumped pattern and a random pattern. The results of a Taylor power method test and Iwao’s regression model also verified that both P. euphratica and P. pruinosa populations belong to a clumped pattern. Although the distribution pattern of P. pruinosa population at different development stages all belonged to a clumped distribution pattern, the aggregation intensity dropped gradually along with age development. The distribution patterns of the P. euphratica population at different development stages changed from random type to clumped type, and further to random type. The differences in spatial distribution patterns of different populations at different development stages were related not only to ecological and biological characteristics of each species in the communities in the light of competitive exclusion principle among the populations, but were also closely related to the habitats in which the species lived in. __________ Translated from Journal of Southwest Forestry College, 2007, 27(2): 1–5 [译自: 西南林学院学报]     

世界各国、地区森林数据

联合国粮农组织(FAO)2001年3月发表了“2000年世界森林资源评价:概要报告书(FRA2000 Summary Report)”。该报告书中的一些数据是上次FRA1990年所没有的。此表介绍了各国和各地区的森林面积、森林覆盖率、1990～2000森林面积的年变化率及森林蓄积。