MVC设计模式在水环境模拟中的应用

采用MVC软件设计模式能够有效的提高软件的可扩展性、可维护性和代码复用率。并在此思想基础上探讨了利用该方法实现可灵活配置的水质模型系统,为实现动态的水质预测过程提供了一种新途径。     

通用Web日志挖掘系统(CWLMS)设计实现

本文介绍了通用Web日志挖掘系统(CWLMS)的设计与实现。将网站的结构和日志文件格式定义引入Web日志挖掘预处理过程以提高预处理的通用性和准确性;在模式挖掘方面,集成了目前有效的最大向前路径挖掘算法和频繁遍历路径挖掘算法,并且将孤立点分析方法引入日志挖掘中。     

基于ASP毕业论文选题系统的设计

毕业论文选题系统包括后台数据库的建立以及前端应用程序的开发两个方面.教师可以利用IE浏览器发布自己的课题,学生则可以选择自己喜欢的课题.对于教师发布的选题,还可以通过先来先到原则进行自动筛选,此外学生还可以自主命题.图1,参4.     

Nest-size variation reflecting anti-predator strategies in social spider mites of<Emphasis Type="Italic"> Stigmaeopsis</Emphasis> (Acari: Tetranychidae)

The social spider mites (Acari: Tetranychidae) of Stigmaeopsis weave dense nests on the underside of host leaves. Four species occur on the leaves of bamboo in Japan: Stigmaeopsis longus, S. celarius, S. takahashii and S. saharai. We initially reconfirmed the occurrence of distinct variation in nest size among the species. Based on the hypothesis that this variation plays a role in protecting the spider mites from predators, we looked at the behavior of the natural enemies that occur on the host plants along with members of Stigmaeopsis. We found considerable variation in the ability of nests to protect the spider-mite eggs. The smallest nests protected the eggs against three predators, whereas the largest nests protected the eggs against only one predator species. So, decreases in nest size increased egg defense. Thus we concluded that nest-size variation reflects a strategy for reducing predation.Communicated by D. Gwynne     

Mercury bioaccumulation in aquatic biota along a salinity gradient in the Saint John River estuary

Although estuaries are critical habitats for many aquatic species, the spatial trends of toxic methylmercury(MeHg) in biota from fresh to marine waters are poorly understood. Our objective was to determine if MeHg concentrations in biota changed along a salinity gradient in an estuary. Fourspine Stickleback(Apeltes quadracus), invertebrates(snails,amphipods, and chironomids), sediments, and water were collected from ten sites along the Saint John River estuary, New Brunswick, Canada in 2015 and 2016, with salinities ranging from 0.06 to 6.96. Total mercury(proxy for MeHg) was measured in whole fish and MeHg was measured in a subset of fish, pooled invertebrates, sediments, and water. Stable sulfur(δ~(34)S), carbon(δ~(13) C), and nitrogen(δ~(15)N) isotope values were measured to assess energy sources(S, C) and relative trophic level(N). There were increases in biotic δ~(13)C and δ~(34)S from fresh to more saline sites and these measures were correlated with salinity.Though aqueous MeHg was higher at the freshwater than more saline sites, only chironomid MeHg increased significantly with salinity. In the Saint John River estuary, there was little evidence that MeHg and its associated risks increased along a salinity gradient.     

蓄水对水库下游食物网中汞生物累积影响研究进展

1991年,加拿大学者Verdon首次报道了加拿大拉格朗德二级水库下游鱼体中汞含量显著高于水库库区的现象,发现水库下游是新建水库汞输出的重要场所,因此水库下游鱼类汞升高的风险继水库本身后成为新的关注热点.通过对相关野外研究的回顾,表明蓄水对水库下游食物网的鱼类、浮游生物以及水体中汞的富集产生影响,水生食物网中各组分甲基汞含量和比例随着营养级的升高而增加.蓄水加速了水库的甲基化过程,使水库自身成为巨大的汞源,不仅影响水库自身食物网中汞的分布,而且更加剧烈地影响水库下游食物网中汞的分布.水库既向下游直接输送溶解态和悬浮颗粒态的甲基汞,又向下游输送丰富的、可被杂食性鱼类和动物直接利用和吸食的甲基汞食物源.在下游食物网中,甲基汞有可能通过微型浮游生物网（悬浮颗粒物-浮游植物-浮游动物经典食物链）,或者通过杂食性鱼类主动摄食来自水库直接输送的浮游动物,或者通过杂食性鱼类被动吸食来自水库直接输送的悬浮颗粒物富集途径,向位于更高营养级位置的鱼类进行传递.在我国,水库蓄水对下游汞输送机制以及对下游微型、底层食物网中生物累积和迁移转化的影响需要更加深入的定量研究.      

Web Service技术在安全生产培训考核管理中的研究和应用

随着业务应用的日益复杂，人们逐渐意识到，在各种复杂的应用需求中单纯依靠某种技术多半无法达到快速开发、快速验证和快速部署的最佳境界。而Web Service体系可将不同的服务端、不同的客户端乃至不同的应用类型、不同的计算设备之间以提供服务的方式进行互联。在上海市安全生产培训考核管理系统开发的过程中，由于其业务流程涉及培训机构、考核机构、安全生产监督管理部门等多个部门协同工作的问题，因此采用了基于Web Service的解决方案，并在．NET Framework开发环境下实现了整个安全生产培训考核管理系统的功能。     

Human drivers,biophysical changes,and climatic variation affecting contemporary cropping proportions in the northern prairie of the U.S

Grassland to cropland conversion in the northern prairie of the United States has been a topic of recent land use change studies. Within this region more corn and soybeans are grown now (2017) than in the past, but most studies to date have not examined multi-decadal trends and the synergistic web of socio-ecological driving forces involved, opting instead for short-term analyses and easily targeted agents of change. This paper examines the coalescing of biophysical and socioeconomic driving forces that have brought change to the agricultural landscape of this region between 1980 and 2013. While land conversion has occurred, most of the region’s cropland in 2013 had been previously cropped by the early 1980s. Furthermore, the agricultural conditions in which crops were grown during those three decades have changed considerably because of non-biophysical alterations to production practices and changing agricultural markets. Findings revealed that human drivers played more of a role in crop change than biophysical changes, that blending quantitative and qualitative methods to tell a more complete story of crop change in this region was difficult because of the synergistic characteristics of the drivers involved, and that more research is needed to understand how farmers make crop choice decisions.     

How might we model an ecosystem?

Predicting ecosystem effects is of crucial importance in a world at threat from natural and human-mediated change. Here we propose an ecologically defensible representation of an ecosystem that facilitates predictive modelling. The representation has its roots in the early trophic and energetic theory of ecosystem dynamics and more recent functional ecology and network theory. Using the arable ecosystem of the UK as an example, we show that the representation allows simplification from the many interacting plant and invertebrate species, typically present in arable fields, to a more tractable number of trophic-functional types. Our compound hypothesis is that “trophic-functional types of plants and invertebrates can be used to explain the structure, diversity and dynamics of arable ecosystems”. The trophic-functional types act as containers for individuals, within an individual-based model, sharing similar trophic behaviour and traits of biomass transformation. Biomass, or energy, flows between the types and this allows the key ecological properties of individual abundance and body mass, at each trophic height, to be followed through simulations. Our preliminary simulation results suggest that the model shows great promise. The simulation output for simple ecosystems, populated with realistic parameter values, is consistent with current laboratory observations and provides exciting indications that it could reproduce field scale phenomena. The model also produces output that links the individual, population and community scales, and may be analysed and tested using community, network (food web) and population dynamic theory. We show that we can include management effects, as perturbations to parameter values, for modelling the effects of change and indicating management responses to change. This model will require robust analysis, testing and validation, and we discuss how we will achieve this in the future.     

Evolutionary cause of the vulnerability of insular communities

Communities on oceanic islands are considered to be vulnerable to biological invasion. However, because the detailed structures of such communities have not yet been revealed, the relationship between their vulnerability and structure is not clear. Because such communities evolved without biological invasion, they are expected to have structures different from those of mainland communities, and this difference is expected to affect their vulnerability to invasion. I conducted computer simulations based on a food web model and investigated the difference in structure between mainland and insular model communities, the former of which evolved with frequent invasion and the latter without invasion. In addition, by conducting computer simulations of invasion of these model communities, I investigated the relationship between community structure and vulnerability to biological invasion. The insular model community evolved to have an unstable structure, in that a small number of plant species supported a large number of animal species, and each species in the community had a small biomass. When a plant species invaded and disturbed the base of the insular model community, many animal species relying on the plants easily became extinct. In addition, when a carnivorous species invaded, animal species with small biomass tended to become extinct. Community collapses caused by biological invasion occurred more frequently in the insular model community than in the mainland model community. These results indicated that those communities that evolved without invasion were vulnerable to invasion. The available data on real insular communities suggest that some have reached the endangered state predicted by this model.