Caching and optimized request routing in cloud-based content delivery systems

Geographically distributed cloud platforms enable an attractive approach to large-scale content delivery. Storage at various sites can be dynamically acquired from (and released back to) the cloud provider so as to support content caching, according to the current demands for the content from the different geographic regions. When storage is sufficiently expensive that not all content should be cached at all sites, two issues must be addressed: how should requests for content be routed to the cloud provider sites, and what policy should be used for caching content using the elastic storage resources obtained from the cloud provider. Existing approaches are typically designed for non-elastic storage and little is known about the optimal policies when minimizing the delivery costs for distributed elastic storage.In this paper, we propose an approach in which elastic storage resources are exploited using a simple dynamic caching policy, while request routing is updated periodically according to the solution of an optimization model. Use of pull-based dynamic caching, rather than push-based placement, provides robustness to unpredicted changes in request rates. We show that this robustness is provided at low cost. Even with fixed request rates, use of the dynamic caching policy typically yields content delivery cost within 10% of that with the optimal static placement. We compare request routing according to our optimization model to simpler baseline routing policies, and find that the baseline policies can yield greatly increased delivery cost relative to optimized routing. Finally, we present a lower-cost approximate solution algorithm for our routing optimization problem that yields content delivery cost within 2.5% of the optimal solution.     

面向大规模定制产品成本估算方法的比较研究

首先分析了大规模定制企业开发成本估算方法对获得客户订单的重要性，接着对适用于大规模定制环境下的成本估算方法进行分类，归纳成几种典型的成本估算方法，并对各个方法的特点进行对比分析，提出了大规模定制环境下成本估算方法的发展趋势，最后针对客户订单的获取和成本估算方法开发提出了自己的看法。     

大型油船结构优化系统分析

将传统的瀑布模型和敏捷模型结合起来，作为指导大型油船结构优化系统（OSOTS）开发的软件方法学。推迟了编码工作，对系统的稳定和变化部分进行了具有高度可靠性和扩展弹性的设计，保证了编码的顺利进行。     

基于Sniffer的动态主机配置协议研究及分析

在一个较大规模的网络架构中,管理员往往会通过DHCP Service来集中分配和管理客户端的IP地址。本文结合了目前最流行的网络数据包嗅探软件Sniffer对这一过程进行了直观的研究与分析。     

基于AJAX技术创建的异步方法应用研究

遵循AJAX技术的基本原理,创建了一个简单的异步引用方法,并给出登录实例来说明如何实现该方法的引用,减少代码冗余。主要阐述了通过创建方法,并引用方法到不同Web应用程序中,实现了代码的优化。     

Servlet技术在提高Web应用客户响应速度中的实现

以J2EE平台下运用Servlet技术提高Web应用客户响应速度为事例，论述了Servlet的技术优势，介绍了主要的Servlet方法，给出了Web应用中如何规划构架EJB-Servlet-JSP组合模型的技术思路和Servlet技术在Web应用中的具体实现。     

An evaluation of extraction techniques for the fractionation of copper and lead in model sediment systems

Model sediments were used to evaluate four extraction methods for fractionation of metals in sediment: 1. dilute HNO₃ (total specifically-adsorbed metal); 2. 1 M NH₄Cl (ion-exchangeable); 3. H₂O₂ (organic); 4. density separation using bromoform. The studies indicated that dilute HNO₃ could not remove all the lead from MnO₂, that intercomponent interferences prevented 100% removal by H₂O₂ and NH₄Cl, and that density separations could not separate oxide coatings from clay minerals.     

一种网格计算中的资源定位策略

简述了网格计算的概念及其背景,然后引出资源定位问题,在资源定位问题上对如Napster采用的对等网格环境下的资源定位策略进行探讨,最后给出了策略的一种实现方法.     

深入浅出ASP．NET页面对象模型

本文主要从IIS与ASP．NET的通信处理模型，IHttpHandler与IHttpModule之间的区别，页面类，事件，页面生命周期等方面深入浅出地论述了ASP．NET页面对象模型。其是开发更深层次的Web组件的基础。     

大型油船结构优化系统分析

将传统的瀑布模型和敏捷模型结合起来,作为指导大型油船结构优化系统(OSOTS)开发的软件方法学。推迟了编码工作,对系统的稳定和变化部分进行了具有高度可靠性和扩展弹性的设计,保证了编码的顺利进行。