基于AJAX与CGI的嵌入式瘦Web服务器研究

针对嵌入式Web服务器中资源和处理能力受限的问题,提出基于AJAX与CGI的嵌入式瘦Web服务器软件结构.应用改进的AJAX技术实现了客户端校验和客户端处理,以及无刷新访问服务器端资源.通过设计CGI程序处理来自客户端的URL请求和XMLHttpRequest组件发出的HTTP请求,实现动态Web功能.实现后的嵌入式瘦Web服务器降低了嵌入式Web服务器端的开销,提高了响应速度,适用于资源受限的嵌入式系统,是一种低成本的网络服务器设计方法.     

基于SmartClient的远程电力监控系统设计

在对现有分布式电力监控web发布系统的研究基础上,利用SmartClient技术对客户端功能进行改进,提出了一种新的分布式环境下Web服务的系统构架,并实现了通过Internet对远程电力设备的集中监测,极大的提高了系统的远程处理能力.     

Ajax和Web服务在空间信息发布中的应用研究

采用传统的WebGIS系统发布空间信息,存在着客户端通用性差、对平台的依赖性强等问题,需要引入新技术进行改进.基于ASP.NET AJAX和Web Service技术,结合SOA架构,提出了一种在线发布空间信息的系统框架,并探讨了该架构下服务器端、客户端的具体设计.最后通过此系统框架,实现了综合风险空间信息的在线发布以及相关功能.系统运行证明,该方法能够显著降低服务器端与客户端的通信开销,并克服空间信息的异构性.     

XML的客户端表示技术在网络课件制作系统中的实践与比较研究

XML的客户端表示技术灵活多样,在网络课件开发系统中可以得到较好的应用.在一个远程教育平台的网络课件制作系统开发中应用XML技术,实现了对同样课程内容在多种不同风格模板下的呈现,并实现了各种模板之间的灵活切换和定制.在实现过程中,采用多种技术手段对XML的客户端表示技术进行了多方面实践和比较.     

基于B/S结构的医学影像阅片系统研究与设计

为了实现医学影像的快速传输与处理并且无需安装客户端和插件,设计了一种基于B/S （Browser/Server）结构的医学影像阅片系统.该系统改进了现有的Web PACS在客户端处理图像的框架,采用基于Web医学影像服务的完成端口模式,实现了影像的高并发快速加载.与传统的Web PACS相比,本系统具有无客户端无插件安装的优点,同时在图像的传输和处理性能上有了很大的提高.     

电子商务网站Web IM系统设计与实现

针对新兴电子商务网站首选开放的XMPP协议作为IM系统的需求,分析XMPP、BOSH协议及技术特点,给出Web IM系统总体架构设计,并选择Strophe.js库对Web IM系统客户端进行详细的设计与实现。     

WebSocket协议在IIoT领域的应用优势

作为网络层协议,WebSocket对比Ajax有诸多优势:支持服务器端向客户端推送功能,接入API更加容易,实时性更好.客户端与服务器建立保持型连接,可以持续传送消息.WebSocket协议数据包的首部信息量和通信量更少,减少硬件资源消耗,减轻网络负担.Web版安东系统采用WebSocket协议,实现客户端与服务器的实...     

基于Web技术的RA系统的体系结构设计

CA技术在解决应用系统安全问题比较流行,但很少有介绍RA系统设计的文章。研究了应用Web技术进行RA系统的体系结构设计。首先解释了RA系统及PKI技术的一些基本概念,然后对一种基于Web技术和PKI技术的RA系统的体系结构设计进行了研究,分别说明了客户端控件、服务器端组件等的结构与设计方法,最后对RA系统客户端的安全性提出了一些建议。     

一种Web服务简化客户端的通信模型

目前的Web服务客户端和服务器端直接通信,客户端的实现变得越来越复杂.针对这种情况,提出一种改进的通信模型,增加一个中间层,中间层完成复杂的设置过程和通信任务,简化了客户端的实现,提高了系统效率.     

基于服务器推送技术和XMPP的WebIM系统实现

为解决现有Web IM系统中大量用到AJAX周期请求而产生的系统消息延迟,以及客户端和服务器端通信量大的问题,提出了以服务器推送技术作为基础的Web IM系统,并选择XMPP作为服务器和客户端的通信协议.在比较AJAX和Comet 技术原理的基础上,给出了Comet技术实现HTTP长连接的策略.通过一个原型WebIM系统,验证了Comet技术在Web IM 系统中使用的确可以有效地解决大量AJAX周期请求的问题.     

LESSON: A system for lecture notes searching and sharing over Internet

In this paper, we present a system LESSON for lecture notes searching and sharing, which is dedicated to both instructors and students for effectively supporting their Web-based teaching and learning activities. The LESSON system employs a metasearch engine for lecture notes searching from Web and a peer-to-peer (P2P) overlay network for lecture notes sharing among the users. A metasearch engine provides an unified access to multiple existing component search engines and has better performance than general-purpose search engines. With the help of a P2P overlay network, all computers used by instructors and students can be connected into a virtual society over the Internet and communicate directly with each other for lecture notes sharing, without any centralized server and manipulation. In order to merge results from multiple component search engines into a single ranked list, we design the RSF strategy that takes rank, similarity and features of lecture notes into account. To implement query routing decision for effectively supporting lecture notes sharing, we propose a novel query routing mechanism. Experimental results indicate that the LESSON system has better performance in lecture notes searching from Web than some popular general-purpose search engines and some existing metasearch schemes; while processing queries within the system, it outperforms some typical routing methods. Concretely, it can achieve relatively high query hit rate with low bandwidth consumption in different types of network topologies.     

Proactive planning of bandwidth resource using simulation-based what-if predictions forWeb services in the cloud

Resource planning is becoming an increasingly important and timely problem for cloud users.As more Web services are moved to the cloud,minimizing network usage is often a key driver of cost control.Most existing approaches focus on resources such as CPU,memory,and disk I/O.In particular,CPU receives the most attention from researchers,but the bandwidth is somehow neglected.It is challenging to predict the network throughput of modem Web services,due to the factors of diverse and complex response,evolving Web services,and complex network transportation.In this paper,we propose a methodology of what-if analysis,named Log2Sim,to plan the bandwidth resource of Web services.Log2Sim uses a lightweight workload model to describe user behavior,an automated mining approach to obtain characteristics of workloads and responses from massive Web logs,and traffic-aware simulations to predict the impact on the bandwidth consumption and the response time in changing contexts.We use a real-life Web system and a classic benchmark to evaluate Log2Sim in multiple scenarios.The evaluation result shows that Log2Sim has good performance in the prediction of bandwidth consumption.The average relative error is 2%for the benchmark and 8% for the real-life system.As for the response time,Log2Sim cannot produce accurate predictions for every single service request,but the simulation results always show similar trends on average response time with the increase of workloads in different changing contexts.It can provide sufficient information for the system administrator in proactive bandwidth planning.     

Templates for Search Queries: A User-Centered Feature for Improving Web Search Tools

A template for search queries was developed based on user-centered design principles and was proposed to assist users in formulating Web search queries. The user-centered design was characterized by predefined search queries organized as a hierarchy. Two experimental search engines and browsers were developed: One was based on currently available search engines and the other was based on the user-centered template design. An experiment was conducted to test the effectiveness of the template design. The dependent variables were (a) the number of relevant Web sites identified during a 1-hr test period, (b) the time to find the first relevant Web site, and (c) satisfaction. The independent variable was type of search engine. The experimental results indicated that the user-centered template design improved users' search performance by 70% and satisfaction of use by 23% as compared to the current search engine.     

基于动态隧道技术的主题爬行策略

互联网网页所形成的主题孤岛严重影响了搜索引擎系统的主题爬虫性能,通过人工增加大量的初始种子链接来发现新主题的方法无法保证主题网页的全面性.在分析传统基于内容分析、基于链接分析和基于语境图的主题爬行策略的基础上,提出了一种基于动态隧道技术的主题爬虫爬行策略.该策略结合页面主题相关度计算和URL链接相关度预测的方法确定主题孤岛之间的网页页面主题相关性,并构建层次化的主题判断模型来解决主题孤岛之间的弱链接问题.同时,该策略能有效防止主题爬虫因采集过多的主题无关页面而导致的主题漂移现象,从而可以实现在保持主题语义信息的爬行方向上的动态隧道控制.实验过程利用主题网页层次结构检测页面主题相关性并抽取“体育”主题关键词,然后以此对采集的主题网页进行索引查询测试.结果表明,基于动态隧道技术的爬行策略能够较好的解决主题孤岛问题,明显提升了“体育”主题搜索引擎的准确率和召回率.     

Increasing multimedia system throughput with consumption-based buffer management

In a multimedia server, multiple media streams are generally serviced in a cyclic fashion. Due to non-uniform playback rates and asynchronous arrivals of queries, there tends to be spare disk bandwidth in each service cycle. In this paper, we study the issue of dynamically using spare disk bandwidth and buffer to maximize the system throughput of a multimedia server. We introduce the concept of minimizing buffer consumption as the criterion to select an appropriate media stream to utilize the spare system resources. Buffer consumption measures not only the amount of buffer but also the amount of time such buffer space is occupied (i.e., the space-time product). Different alternatives to utilizing spare disk bandwidth are examined, including different rate-adjustable retrievals of an already activated stream and prefetching the next waiting stream. For rate-adjustable retrievals, we study buffer consumption-based and remaining-time-based criteria for selecting an active stream to increase retrievals. Simulations are conducted to evaluate and compare different cases. The results show that (1) minimizing buffer consumption is the right criterion for maximizing the system throughput with spare disk bandwidth; (2) in general, prefetching a waiting stream incurs more buffer consumption, and thus is less effective than rate-adjustable retrieval of active streams in maximizing the system throughput; and (3) the advantage of rate-adjustable retrieval over prefetching is especially significant when service cycle time is small.     

A comprehensive reconfigurable computing approach to memory wall problem of large graph computation

Graph computation problems that exhibit irregular memory access patterns are known to show poor performance on multiprocessor architectures. Although recent studies use FPGA technology to tackle the memory wall problem of graph computation by adopting a massively multi-threaded architecture, the performance is still far less than optimal memory performance due to the long memory access latency. In this paper, we propose a comprehensive reconfigurable computing approach to address the memory wall problem. First, we present an extended edge-streaming model with massive partitions to provide better load balance while taking advantage of the streaming bandwidth of external memory in processing large graphs. Second, we propose a two-level shuffle network architecture to significantly reduce the on-chip memory requirement while provide high processing throughput that matches the bandwidth of the external memory. Third, we introduce a compact storage design based on graph compression schemes and propose the corresponding encoding and decoding hardware to reduce the data volume transferred between the processing engines and external memory. We validate the effectiveness of the proposed architecture by implementing three frequently-used graph algorithms on ML605 board, showing an up to 3.85 × improvement in terms of performance to bandwidth ratio over previously published FPGA-based implementations.     

基于元数据与Z39.50的分布协作式Web信息检索

Web上大量的异质、分布、动态的信息造成了“信息过载”.如何有效地为用户提供Web信息检索已经成为一项重要的研究课题.Web搜索引擎部分地解决了信息检索问题,然而其效果却远远不能令人满意.提出了Web信息检索的分布协作策略以取代传统的集中式信息检索方式;给出了一种新的Web信息检索系统模型,该模型支持对Web文档的元数据进行检索,并采用Z39.50协议作为接口标准,以克服不同信息检索系统之间的访问异构性.在此基础上,设计了一个分布协作式Web信息检索框架,用以帮助用户有效地进行Web信息检索.     

Handling the load

The Internet's available bandwidth is sometimes just barely enough to sustain the load we're imposing on it. Who's the culprit? The Web, of course, with all its bandwidth devouring technologies. Solving the Web's load problems is no simple task. However, given the speed at which Web sites are adopting bandwidth hungry technology, we can expect serious trouble on the Internet within a few years. This trouble may disappear temporarily with the start-up of projects like Internet 2, whose aim is to greatly increase the Internet's overall bandwidth. But computer technology fills bandwidth like a gas fills a room, taking up as much space as its given. Making greater bandwidth available will most likely spark the creation of more bandwidth hungry technology until the load is once again unbearable. In the end, one important principle remains: decentralization. The load, whatever it is, must be split intelligently between the clients and servers, utilizing bandwidth in an efficient manner. After all, decentralization is the principle on which the Web was built     

Distributed and cooperative information retrieval on the World Wide Web

A masss of heterogeneous,distributed and dynamic information on the World Wide Web(the Web) has resulted in “information overload“ .It‘s an important and urgent reserach issue to provide users with effective information retrieval service on the Web.Web search enginees attempt to solve this problem,yet their effect is far from satisfying.In this paper,a distributed and cooperative strategy for information retrieval on the Web is proposed to substitute the centralized mode adopted by the current search engines.Then a new information retrieval system model IRSM is presented.which supports the retrieval of metadata about web documents and uses Z39.50 standard protocol to unify the heterogeneous interfaces of uments and uses Z39.50 standard protocol to unify the heterogeneous interfaces of different systems.Based on that,a distributed and cooperative information refieval framework,called DCIRF,is designed to help users in fast and effective information retrieval on the Web.     

基于移动爬虫的专用Web信息收集系统的设计

搜索引擎已经成为网上导航的重要工具。为了能够提供强大的搜索能力,搜索引擎对网上可访问文档维持着详尽的索引。创建和维护索引的任务由网络爬虫完成,网络爬虫代表搜索引擎递归地遍历和下载Web页面。Web页面在下载之后,被搜索引擎分析、建索引,然后提供检索服务。文章介绍了一种更加有效的建立Web索引的方法,该方法是基于移动爬虫(MobileCrawler)的。在此提出的爬虫首先被传送到数据所在的站点,在那里任何不需要的数据在传回搜索引擎之前在当地被过滤。这个方法尤其适用于实施所谓的“智能”爬行算法,这些算法根据已访问过的Web页面的内容来决定一条有效的爬行路径。移动爬虫是移动计算和专业搜索引擎两大技术趋势的结合,能够从技术上很好地解决现在通用搜索引擎所面临的问题。