海南省热带农产品封闭供应链模式设计研究

为提高海南热带农产品流通的现代化水平,确保海南热带农产品的质量安全,在分析海南省热带农产品供应链现有模式及存在问题的基础上,结合封闭供应链的概念及研究现状,设计4种类型核心企业主导的基于质量可跟踪和追溯的海南省热带农产品封闭供应链模式。为海南省热带农产品封闭供应链模式设计、工程应用和系统开发提供参考,对于确保海南省热带农产品质量安全具有重要意义。     

Compartmentalization of the soil animal food web as indicated by dual analysis of stable isotope ratios (N/N and C/C)

The soil animal food web has become a focus of recent ecological research but trophic relationships still remain enigmatic for many taxa. Analysis of stable isotope ratios of N and C provides a powerful tool for disentangling food web structure. In this study, animals, roots, soil and litter material from a temperate deciduous forest were analysed. The combined measurement of δ¹⁵N and δ¹³C provided insights into the compartmentalization of the soil animal food web. Leaf litter feeders were separated from animals relying mainly on recent belowground carbon resources and from animals feeding on older carbon. The trophic pathway of leaf litter-feeding species appears to be a dead end, presumably because leaf litter feeders (mainly diplopods and oribatid mites) are unavailable to predators due to large size and/or strong sclerotization. Endogeic earthworms that rely on older carbon also appear to exist in predator-free space. The data suggest that the largest trophic compartment constitutes of ectomycorrhizal feeders and their predators. Additionally, there is a smaller trophic compartment consisting of predators likely feeding on enchytraeids and potentially nematodes.     

基于灾变链式理论的日光温室黄瓜霜霉病警源追溯模型研究

追溯警源是日光温室蔬菜病害预警中提供排警措施的依据。结合灾变链式理论和植物病害流行学,对日光温室黄瓜病害警源追溯问题及孕源断链减灾模式进行了系统分析。考虑到日光温室作物病害预警对象多警源的特点及其对预警解释推理方式的影响,采用数字化方法,构建了易于系统实现的日光温室黄瓜霜霉病警源追溯模型。对日光温室黄瓜霜霉病实例进行追溯分析,结果表明,外界出现的阴雨雪雾天气是导致该实例中霜霉病发生的警源。并可用方差分析来检测日光温室环境的时空突变,以验证警源信息。该模型能够为日光温室黄瓜霜霉病排警措施提供决策支持。     

Seasonal and interannual ecophysiological responses of beech (Fagus sylvatica) at its south-eastern distribution limit in Europe

Due to its wide European distribution and its drought-susceptibility, beech (Fagus sylvatica L.) received intensive attention recently in the light of global warming. Contrary to central European beech ecosystems, little is known about the ecophysiology of beech at its south-eastern European distribution limit. Here we tested whether climatic fluctuations during a three-year period affected the ecophysiology of a beech site in Greece. Attention was paid at comparing our findings to the intense effects the 2003 extreme drought had on beech forests in central Europe.     

Detecting changes in habitat-scale bee foraging in a tropical fragmented landscape using stable isotopes

As the body of research on the ecosystem service of pollination grows, our ability to tackle a range of agricultural, conservation, and land management issues is limited by our understanding of pollinator foraging patterns and requirements. In particular, better knowledge of which habitats bees utilize for foraging over their lifetime would inform a range of applied and theoretical questions. Traditional methods of studying foraging are either impractical for insects (e.g. radio tracking) or else are limited spatially or temporally (e.g. observations by researchers). Here we describe a method for using stable isotopes of carbon and nitrogen from bee tissues to gain an integrated signal of which habitats a bee has foraged in over its lifetime, using three species of social stingless bee (Apidae: Meliponini) in a fragmented tropical forest landscape in southern Costa Rica as a test case.     

Theory and approach to reactive power flow tracing

Based on an analysis of the characteristics of reactive power supplies and reactive loads, this paper presents a method for forming a lossless reactive network using an equivalent technique of modeling the branch admittance as a reactive power supply and the branch power loss as a virtual load. A downstream distribution matrix for a power system is constructed based on its reactive lossless network, and the analytical model and its algorithm for tracing reactive power flow (TRPF) is proposed. A method dealing with the abnormal downstream distribution matrix of active power flow also is discussed. The main advantage of the proposed method is that the matrix theory is used to analyze the TRPF model directly and no assumption on the flow distribution is needed. Case studies of the IEEE14 Bus and IEEE30 Bus systems demonstrate the accuracy and the validity of the proposed method.     

基于投影寻踪的模糊综合评价模型研究及应用

依据建立的水资源可持续利用的分级标准在各等级取值范围内随机生成数据作为样本,采用投影寻踪的思想优化投影方向,得到客观权重,并与层次分析法得到的主观权重相结合,建立了基于投影寻踪的模糊综合评价模型,并将模型应用于海南省水资源可持续利用综合评价。结果表明,该模型计算简便,评价结果可信度较高。     

园林手工制图转化为电脑制图的探讨

通过对手工制图与电脑制图优缺点进行比较,并且对描图、制图两种基本方法的具体论述,详细阐述了将手工制图转化为电脑制图的途径和基本方法,旨在提高园林制图的准确性与制图速度。     

农产品质量追溯体系建设现状与问题及对策

目前中国农产品质量追溯体系建设的现状与存在的问题,已经成为政府和学术界关心的热门话题。通过对中国现有的农产品质量追溯体系的现状与问题进行分析,总结出中国农产品质量追溯体系建设的成果和不足,通过对发达国家农产品质量追溯体系的研究与分析,指出发挥政府和大型生产的作用,以及追溯体系从畜牧开始是发达国家农产品质量安全追溯体系建设的特点。在研究和分析的基础上,提出了完善中国农产品质量追溯体系的对策。