Energy flow and community structure in freshwater ecosystems

The goal of this article is twofold: 1) It aims at providing an overview on some major results obtained from energy flow studies in individuals, populations, and communities, and 2) it will also focus on major mechanisms explaining community structures. The basis for any biological community to survive and establish a certain population density is on the one hand energy fixation by primary producers together with adequate nutrient supply and the transfer of energy between trophic levels (bottom-up effect). On the other hand, predator pressures may strongly control prey population densities one or more trophic levels below (top-down effect). Other interpopulation effects include competition, chemical interactions and evolutionary genetic processes, which further interact and result in the specific structuring of any community with respect to species composition and population sizes.     

医院信息管理系统业务量估算与网络流量控制

本文介绍医院信息管理系统组成与设计要求;讨论了信息系统业务量估算,网络流量控制方法,保证信息管理系统数据有效性,快速存储,共享使用与安全可靠性。     

工程问题的哲学意义

工程是一种有一定规模的建造活动，当今人类正生活在一个由各种有形和无形的工程所关联起来的网络中，人类当代文明就是一种工程文明。工程的普遍化使得工程问题上升到了哲学层面，具有了哲学意义。工程个案和一般工程学科解决工程中的具体问题，但惟独不对“工程本身”发问。对工程的哲学研究则专门追究“工程之所以为工程”的问题。工程问题的哲学意义至少有两种：一是按照哲学研究的惯常方式建构一门新的部门哲学，二是通过对工程问题的特殊性呈现给人类思维方式的变革提供一个契机。任何一项工程都牵涉无数复杂因素，它们之间尽管具有这样那样的逻辑性关联，但总有一些因素之间没有逻辑联系，这就使得工程问题归根到底不可能逻辑地、理论地和哲学地解决。理论和工程之间不可能逻辑地统一起来，这就是工程问题通过哲学而给我们的最特殊的启示。     

组合式无级变速装置特性分析（续）

揭示了组合式无级变速装置的调速类型、调速范围、功率流和各传动参数间的关系．     

萃淋树脂－流动注射法分离稀土离子

本文采用Ｃｌ－Ｐ２０４萃淋树脂ｐＨ梯度技术分离，流动注射分析仪进样，偶氮氯磷（Ⅲ）光度法检测，对Ｌａ、Ｃｅ、Ｎｄ、Ｓｍ、Ｅｕ５种稀土离子的不同混合溶液进行了分离研究．用０．３２、０．３７、０．４５、０．７５、０、９０ｍｏｌ／Ｌ的盐酸溶液以０．８～１．０ｍｌ／ｍｉｎ的速度进行梯度淋洗，在泵压８～１０ｋｇｆ／ｃｍ￣２，载流速度ｌｍｌ／ｍｉｎ，进样体积２．８ｍｌ的试验条件下，测出这５种稀土离子混合溶液的淋洗曲线，分离效果令人满意．     

ParalelComputationofViscousFluidFlow

ＰａｒａｌｅｌＣｏｍｐｕｔａｔｉｏｎｏｆＶｉｓｃｏｕｓＦｌｕｉｄＦｌｏｗ＊ＣｈｅｎＪｉｎｇｌｉａｎｇ（陈景良），ＧｕＳｈｅｎｇ（顾圣）ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊｉｎｇ１...     

Switched Capacitor Network Analysis by Means of TCM

The totally coded method (TCM) reveals the same objective law, which governs the gain calculating for signal flow graph as Mason formula does. This algorithm is carried out merely in the domain of code operation. Based on pure code algorithm, it is more efficient because figure searching is no longer necessary. The code-series (CS), which are organized from node association table, have the holoinformation nature, so that both the content and the sign of each gain-term can be determined via the coded method. The principle of this method is obvious and it is suited for computer programming. The capability of the computeraided analysis for Switched Capacitor (SCN) can be enhanced.     

人力资本投资理论与我国农村劳动力转移

目前,劳动力流动对农村人力资本投资具有增长效应,而现行城乡教育资源分配和就业机制对农村人力资本投资则有不利影响,应加大农村人力资本投资,实现农村劳动力合理转移.