动态Ad hoc网络环境下组播源认证研究*

就Ad hoc网络环境下基于消息认证码的源认证技术进行了研究和分析,针对TESLA源认证方案给出了一个新的源认证引导方案,并采用间接引导方式来适应Ad hoc网络。实验数据表明,新的引导方案可以在较大程度上减轻系统的负担,从而提高认证的效率。     

A stability-based distributed routing mechanism to support unicast and multicast routing in ad hoc wireless network

An ad hoc network can be envisioned as a collection of mobile routers, each equipped with a wireless transceiver, which are free to move about arbitrarily. In ad hoc wireless networks, even if two nodes are outside the wireless transmission range of each other, they may still be able to communicate in multiple hops using other intermediate nodes. However, the dynamics of these networks, as a consequence of mobility and disconnection of mobile hosts, pose a number of problems in designing routing schemes for effective communication between any pair of source and destination. In this paper, a stability-based unicast routing mechanism, that considers both link affinity and path stability in order to find out a stable route from source to destination, is proposed. It is then extended to support multicast routing as well where only local state information (at source) is utilized for constructing a multicast tree. The performance of the proposed scheme is evaluated on a simulated environment to show that the stability-based scheme provides a unified framework for both unicast and multicast routing and reduces the probability of route error drastically in both the cases.     

Source Choice Perception and Sustainable Rural Water Supply Development: A Case Study of Ban Thadindam,Lopburi, Thailand

Abstract

This study seeks to examine source choice perception and sustainable rural water supply development in Ban Thadindam, a Thai village situated about 220 km north of Bangkok. It makes use of an elementary schematic matrix that was initially developed for the valuation of water sources as perceived by water users in East Africa. In applying the elementary choice scheme, the author interviewed the village Kamnan (district officer) and a few villagers. The results of this study show that a wide range of water supply sources was perceived by the Kamnan. Out of a practical range of six sources, four were perceived and accepted, roof (rain water), river, spring, and pond; and two were perceived but not accepted: well and canal. The reason why well and canal water sources were rejected was because of their hardness and turbidity. Of the four sources accepted, roof (rain water) was rated very favorably as the preferred choice while river, spring, and pond sources were judged equally favorable. Awareness of source choice and the conditions under which choice is made is crucial for the understanding and development of sustainable rural water supply. By adopting a wide combination of sources and integrating them to provide a rich water supply for treatment, and by taking advantage of filtration technology given by the Asian Institute of Technology, Environmental Engineering Division, the villagers, with the help of the Project Managing Committee, transformed the demonstration filtration facility into a sustainable rural water supply system. The latter succeeded not only in providing adequate filtered water for the majority of the households in Ban Thadindam but also in satisfying the water requirements for the whole village for two decades. The success of the rural water supply system has been attributable to many factors, but most important was the awareness the villagers have in the understanding of the interrelations between landscape, range of choice and the interaction between community participation, technology, and environment.     

东江源区重要江河湖泊水功能区纳污能力及限制排污研究

本文以东江源区主要河流为研究对象,以水功能区划为基础,采用河流一维模型对源区内6个国家重点江河湖泊水功能区纳污能力及限制排污总量进行分析计算,并结合上下游水域功能区水质保护目标、源区内采选矿业及果业开发等排污调查资料,分别提出这6个特别是3个不达标重点江河湖泊水功能区的主要污染物分阶段限排总量控制方案,为源区开展水污染防治与污染减排工作提供依据。     

六盘山盆地烃源岩的地球化学特征及油气勘探潜力

依据六盘山盆地露头和钻测井资料,应用有机地球化学的多种分析方法,对六盘山盆地乃家河—马东山烃源岩进行分析评价,分析表明:乃家河组烃源岩有机含量为0.43％～3.18％,平均值为1.76％,有机质类型以偏腐泥为主,镜质体反射率Ro值为0.52％～0.67％,平均值为0.60％,马东山烃源岩有机质含量为0.73％～3.65％平均值为1.69％,有机质类型以偏腐植型为主,晶质体反射率Ro为0.64％～0.75％,平均值为0.69％.对比可知,马东山组烃源岩的有机质丰富,热演化程度好于乃家河组,但同质类型没有乃家河组好.六盘山具有两套生储组合,白垩系李洼峡组发现不同级别油气显示,有较好的油气成藏条件,油气资源丰富,勘探潜力较好.     

潜江凹陷潜江组物源特征和沉积体系

潜江凹陷潜江组是含盐系地层,其物源特征和沉积体系演化对于该区勘探具有重要指导意义,但针对油层组的研究较薄弱。重矿物、碎屑锆石年代和沉积相进行物源和沉积体系研究认为：物源母岩以变质岩为主,次为岩浆岩,少量来自沉积岩。碎屑锆石年代指示物源来于元古代、早古生代和中生代时期的母岩。ZTR指数从荆门凹陷一永隆河隆起一带向潜江凹陷中部增大;南部存在较为稳定的物源,中部和北部的物源存在迁移的特征。各期均发育三个沉积体系,分别是西部三角洲沉积体系、东部盐湖沉积体系和淡水一半咸水湖沉积体系,其演化主要表现为三角洲体系与盐湖沉积体系的进与退之间的耦合。三角洲体系扩大时为淡化期,水下分支河道前端易受湖浪改造形成席状砂;三角洲体系扩大时萎缩时为成化期,水下分支河道前端易形成河口坝以及远砂坝沉积。     

用C#实现大文件切割与合并

我们经常需要将大文件切割成若干小文件来携带或传输,然后在另一台计算机上再度合并。本文介绍了文件切割与合并的原理,以及自动产生.exe合并程序和自动删除合并程序等技巧,并提供了关键部分的C≠源代码。     

基于Web GIS及开源技术的网络管理系统

根据网络管理工作的常见需求,以Google Maps、PHP及相关开源网管技术整合的方式,设计基于WebGIS的网络管理系统。实现了拓扑发现、基于电子地图的网络晴雨表和服务检测、Atmega128微控制器数据中心机房状态检测、基于R T M P的实时曲线、故障告警、资产查询、用户故障报修、网管日志等功能。介绍了系统的设计思路,主要功能及实现方法。     

飞机系统内的干扰源及干扰防止方法

现代飞机电子设备越来越多,而一个良好的电磁环境对于飞机系统正常工作有着重要的作用.该文通过对飞机上干扰源的认识、分析及干扰的防止方法,对从事飞机电气设计的工程技术人员起到一些借鉴作用.     

浅析降低企业物资采购成本的有效途径

企业物流,已成为企业降低经营成本,提升整体效益,促进生产发展的重要因素。国内外知名企业都十分重视物流管理,把物流作为企业“第三利润源泉”。1998年9月,江西铜业集团公司对“大而全、小而全”的物资供应管理体制进行改革,将下属厂矿的物资供应采购权集中起来,进行统一管理,以发挥整体优势,降低采购成本。材料设备公司成立五年多来,不仅确保了集团公司生产、基建所需物资的供应,而且累计降低采购成本(截止2003年底)1. 68亿元,物流管理基本达到了采购业务程序化、采购行为规范化、仓库管理标准化、物流动态信息化的现代管理模式,实现了集团公司物资供应体制的改革目标,成为集团公司的“第三利润源泉”。