一种基于复数域网络编码的双层卫星通信系统

针对卫星通信网络吞吐量不足、可靠性不高的问题,提出一种基于复数域网络编码(Complex Field Network Coding,CFNC)的卫星通信方案。该方案在信号发送前对源信息作预编码处理,即在复数域上选取一个大小合适的参数化空时码与源信号相乘,编码后的信号与源信号在复数域上有着一一映射关系。对该方案的吞吐量和成对差错概率(Pairwise Error Probability,PEP)做了详尽的理论分析,结果表明,采用该编码方案的卫星通信系统在终端发射功率不变的情况下,吞吐量比路由模式提高了100%以上,比传统的CFNC方式至少可提高75%。该方案还可以扩展至更多的地面源节点,从而支持多用户网络通信。最后,仿真实验表明,在较高的信噪比下,PEP仿真值逼近于渐近值,验证了理论分析的正确性。     

火焰温度场测试中的传感器动态特性补偿

在进行爆温测试时,爆炸伴随的高温火焰具有变化快、温度高、测试环境恶劣等特点.针对这种特定的测温场合,运用火焰温度源法研究了热电偶传感器在火焰温度场中的动态响应特性.为了减小热电偶的动态测量误差,通过粒子群优化算法(PSO)建立了测试系统的动态补偿滤波器模型.实验表明,这种研究方法有效地改善了热电偶的动态测量误差,对通过爆温测试进行弹丸热毁伤评价有一定的参考价值.     

Firms’ involvement in Open Source projects: A trade-off between software structural quality and popularity

Open Source (OS) was born as a pragmatic alternative to the ideology of Free Software and it is now increasingly seen by companies as a new approach to developing and making business upon software. Whereas the role of firms is clear for commercial OS projects, it still needs investigation for projects based on communities. This paper analyses the impact of firms’ participation on popularity and internal software design quality for 643 SourceForge.net projects. Results show that firms’ involvement improves the ranking of OS projects, but, on the other hand, puts corporate constraints to OS developing practices, thus leading to lower structural software design quality.     

Adoption of Open Source Software: The role of social identification

While the benefits of incorporating Open Source Software (OSS) into personal and organizational systems have been widely touted, OSS must be adopted and used by end users before these benefits can be realized. Drawing on research in information systems and sociology, this study develops and evaluates an integrated model for the acceptance of OSS. In addition to the traditional technology adoption variables the findings stress the importance of social identification as a key driver of OSS adoption. The proposed model provides a useful decision support tool for assessing and proactively designing interventions targeted at successful OSS adoption and diffusion.     

一种面向微博用户的标签推荐方法

首先对国内微博平台的信息进行了综合分析,主要介绍了微博信息的定义,在错综复杂的微博信息中哪些信息比较重要,以及这些微博信息包含哪些详细的内容,是如何组织的。然后选取新浪微博平台作为研究对象,利用新浪微博API设计了爬虫程序,抽取用户信息;以用户的关注人数、粉丝数和发布的微博数为标准对用户信息进行了定量分析。最后根据分析结果,针对不同特征的用户群体提出了相应的标签推荐方法。     

一种面向微博用户的标签推荐方法

首先对国内微博平台的信息进行了综合分析,主要介绍了微博信息的定义,在错综复杂的微博信息中哪些信息比较重要,以及这些微博信息包含哪些详细的内容,是如何组织的。然后选取新浪微博平台作为研究对象,利用新浪微博API设计了爬虫程序,抽取用户信息;以用户的关注人数、粉丝数和发布的微博数为标准对用户信息进行了定量分析。最后根据分析结果,针对不同特征的用户群体提出了相应的标签推荐方法。     

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。