A pipelined architecture for distributed text query evaluation

Two principal query-evaluation methodologies have been described for cluster-based implementation of distributed information retrieval systems: document partitioning and term partitioning. In a document-partitioned system, each of the processors hosts a subset of the documents in the collection, and executes every query against its local sub-collection. In a term-partitioned system, each of the processors hosts a subset of the inverted lists that make up the index of the collection, and serves them to a central machine as they are required for query evaluation. In this paper we introduce a pipelined query-evaluation methodology, based on a term-partitioned index, in which partially evaluated queries are passed amongst the set of processors that host the query terms. This arrangement retains the disk read benefits of term partitioning, but more effectively shares the computational load. We compare the three methodologies experimentally, and show that term distribution is inefficient and scales poorly. The new pipelined approach offers efficient memory utilization and efficient use of disk accesses, but suffers from problems with load balancing between nodes. Until these problems are resolved, document partitioning remains the preferred method. Alistair Moffat was supported by the Australian Research Council, the ARC Special Research Center for Perceptive and Intelligent Machines in Complex Environments, and the NICTA Victoria Laboratory. William Webber and Justin Zobel were supported by the Australian Research Council. Ricardo Baeza-Yates was supported by Grant P01-029-F from Millennium Initiative of Mideplan, Chile; and by the University of Melbourne as a visiting scholar at the time this project was undertaken.     

改进的一致性哈希算法及应用

针对分布式入侵检测中的数据分割问题,给出一种改进的一致性哈希算法。该算法针对采集的数据包,通过TCP流重组建立TCP数据链,保证数据流的完整性;再通过结点的分组对一致性哈希算法进行改进,并实现组间和组内的数据分配,减少虚拟结点数量;对结点的负载均衡检测和调整策略,改善了系统的负载均衡性。仿真测试结果表明该算法具有较好的负载均衡性。     

Lyapunov-based design of locally collocated controllers for semi-linear parabolic PDE systems

The design problem of collocated feedback controllers is addressed in this paper for a class of semi-linear distributed parameter systems described by parabolic partial differential equation (PDE), where a finite number of local actuators and sensors are intermittently distributed in space. A Lyapunov direct method for the exponential stability analysis of the resulting closed-loop system is first presented for the system, in which the first mean value theorem for integration and the Wirtinger's inequality are employed. The corresponding stabilization condition is then derived through the analysis result. Finally, the proposed design method is implemented on the feedback control of a fisher equation and its effectiveness is evaluated through simulation results.     

基于XML的分布式信息检索

提出了一种对互联网信息进行分布式信息检索的方法：利用代理程序和XML技术向多个相同类型的网站同时发送检索请求文档并接收它们返回的检索结果文档，经过统一处理后将检索结果显示给读者     

基于多代理机制的分布式入侵检测系统的研究

鉴于当前基于主机入侵检测系统的局限性,使得基于代理的入侵检测技术显得日益重要。讨论从基于主机的入侵检测系统的局限性出发,提出了一种基于多代理机制的分布式入侵检测系统方案,并对入侵检测系统中主机检测器基于多代理的技术进行了详细分析和难点解析。     

SWAT 2000气象模拟器的随机模拟原理、验证及改进

该文详细介绍了SWAT 2000气象模拟器(最高、最低气温、太阳辐射)的随机模拟原理,利用甘肃河西地区酒泉、张掖等7个站的完整气象资料,提出了气候条件相似的区域气象台站月平均气象数据的计算方法,并计算出模拟器需要的输入参数,对气象模拟结果进行了验证.在此基础上利用逐日平均气温修正模拟生成的最高、最低气温并求5日滑动平均,对模拟器进行了改进.通过模拟结果与气象台站实测资料的对比可以看出,改进后最高气温相关系数从0.85提高到0.90,最低气温相关系数从0.89提高到0.94,气温数据模拟精度有一定提高.最后利用改进后的气象模拟器对河西黑河地区祁连、札马什克、莺落峡3个数据短缺站点进行了气温和太阳辐射的模拟,通过SWAT模型的应用证明模拟结果能够满足分布式水文模型的气象输入数据精度要求.     

面向网络科技监测的分布式定向资源精确采集研究和应用

在分析研究现有开源信息采集系统的基础上,综合应用开源框架,以开源爬虫Crawler4j为基础,设计开发基于开源框架的分布式定向资源采集系统,实现对网络信息实时精确的采集,以满足网络监测系统的及时性和准确性的要求。主要介绍系统的结构设计和功能实现,并详细阐述精确采集的方法和技术路线。     

火电公司分散控制系统的评估与选型

讨论了火电公司应用中分散控制系统评估的内容和一般准则,并介绍了一种评估和选型的具体方法和步骤,这对火电公司分散控制系统的工程设计以及提高发电效率具有一定的借鉴意义。     

基于Web services的分布式信息检索机制的研究

为进一步提高系统的信息处理能力,提出一种基于Web services的分布式信息检索机制,通过研究调度、索引、负载、分配服务器、结果集的汇总排序等关键问题,实现分布式信息检索的研究,具有更高的跨平台性和较好的通用性。     

Node.js高效分布式实时应用研究

Node.js应用平台的出现,为大数据实时应用提供了一个很好的可选技术方案。研究了分布式实时应用处理中任务的抢占式处理策略和双路由策略,并探讨了在Node.js平台上利用Redis或ZeroMQ技术实现高效可靠分布式实时应用的方法。