一个农户生态经济系统的分析

对沈阳市桃仙镇荒山子村一个农户生态经济系统进行分析,结果表明：该农户正处于从传统农业向现代农业的过渡阶段,经济效益较好,整体技术水平和生态效益低,后两了该农户的进一步发展,以目前的生产水平,应采取户与户联合,取得规模效益,以当前农业产业化的发展。     

Free and forced convection boundary layer flow through a porous medium with large suction

An analytical study is made of the free and forced convection boundary layer flow past a porous medium bounded by a semi-infinite vertical porous plate. Locally similar solutions are then obtained by a perturbation method for large suction. Solutions for the velocity and temperature distributions are shown graphically for various suction velocities and values of the driving parameter G_r/R, where G_r is the Grashof number and R_e is the Reynolds number. The corresponding values of the skin friction coefficient and the Nusselt number are finally shown in tabular form.     

High-pressure plastic flow in silicon: A first-principles theoretical study

Summary Microindentation experiments have recently shown that silicon can exhibit plastic flow when subjected to high pressure. Assuming that under these conditions the relevant reference structure is the -Sn high-pressure phase of silicon, we apply the magic-strain concept to explore the space of configurations that could describe the observed behavior. We use first-principles total-energy calculations (including full relaxation of the atomic basis for every structure) to evaluate the relevance of strained configurations. Using this approach, we were able to identify a low-energy path that corresponds to planar flow of the atoms. The atomic configurations along this path provide insight into possible microscopic motions under high pressure that may be relevant to plastic flow in silicon.     

熔体流动时间法测定PBT树脂特性粘数的研究

开发了一种新的特性粘数分析方法 ,该方法采用熔体流动时间计算特性粘数 ,与经典特性粘数分析方法有很好的相关性且具有分析时间短、费用低、无污染等优点。     

中型山区河流水电站下游的鱼类生态需水量计算

为更好地对河流水电开发后的鱼类进行保护,探讨中型山区河流水电站下游的鱼类生态需水量计算.参照大型河流鱼类水力生境参数标准,根据中型山区河流的特点,得到中型山区河流鱼类水力生境参数的参考标准.选取有代表性的四川中型山区河流杂谷脑河进行鱼类生境原型观测,原型观测结果证实了该参考标准能够满足杂谷脑河鱼类对生境的实际需求.基于所得到的参考标准,应用生态水力学法对杂谷脑河红叶二级、理县以及甘堡3座电站减水河段的鱼类生态需水量进行计算分析,得到3座电站的生态需水量推荐值.通过分析可知,所得到的生态需水量推荐值占年均天然流量以及设计引用流量的比例都不高,在3座电站的运行实践中,具有可操作性.     

小流域设计洪水计算方法的探讨

利用实例对各常用设计洪水流量计算方法进行比较分析,指出各方法的特点。     

基于龙虎山水电站水轮机选型设计

根据龙虎山水电站的工程概况,对该电站的设计参数进行选择分析,综合考虑各种因素,对比国内能量指标较优的转轮,从各个方面对各型号进行了比较,确定了“4大+1小”为最优方案,选择了最适合于本电站的水轮机的机型.     

基于物联网与3G整合的电子商务应用资金流探析

文章在简要介绍物联网与3G网络的基础上,阐述了物联网与3G整合背景下电子商务资金流所具备的特点,进而论述了此背景下资金流的优化和作用,最后重点分析了整合背景下电子商务资金流的两个应用案例。