无线局域网的Web 缓存系统研究

由于无线环境中的网络和手持设备的限制,缓存机制在提高移动系统性能方面发挥着重要作用.本文描述了适用于无线LAN的Web缓存系统EasyCache系统的实现,给出了基于数据挖掘理论的移动主机端缓存数据预取算法SEDP.模拟实验数据表明SEDP算法取得了良好的效果.     

移动环境下支持技术的研究

1 背景今天,我们的日常生活和工作中,各种各样的移动设备正发挥着它们各自的作用。移动电话以前所未有的速度迅速普及;手持PC和个人数字助理PDA在保证通信能力和便携性的基础上,加强了计算能力,使人们可以更加便捷地管理个人数据和进行通信;某些功能如触摸屏、声音识别、定位系统更为移动应用提供了良好的支持。在计算和存储能力方面可以与台式机相     

Barriers common to mobile and disabled web users

World Wide Web accessibility and best practice audits and evaluations are becoming increasingly complicated, time consuming, and costly because of the increasing number of conformance criteria which need to be tested. In the case of web access by disabled users and mobile users, a number of commonalities have been identified in usage, which have been termed situationally-induced impairments; in effect the barriers experienced by mobile web users have been likened to those of visually disabled and motor impaired users. In this case, we became interested in understanding if it was possible to evaluate the problems of mobile web users in terms of the aggregation of barriers-to-access experienced by disabled users; and in this way attempt to reduce the need for the evaluation of the additional conformance criteria associated with mobile web best practice guidelines. We used the Barrier Walkthrough (BW) method as our analytical framework. Capable of being used to evaluate accessibility in both the disabled and mobile contexts, the BW method would also enable testing and aggregation of barriers across our target user groups.We tested 61 barriers across four user groups each over four pages with 19 experts and 57 non-experts focusing on the validity and reliability of our results. We found that 58% of the barrier types that were correctly found were identified as common between mobile and disabled users. Further, if our aggregated barriers alone were used to test for mobile conformance only four barrier types would be missed. Our results also showed that mobile users and low vision users have the most common barrier types, while low vision and motor impaired users experiencing similar rates of severity in the barriers they experienced. We conclude that the aggregated evaluation results for blind, low vision and motor impaired users can be used to approximate the evaluation results for mobile web users.     

三维网格压缩方法综述

针对三维网格大数据量与三维图形引擎处理能力及网络带宽限制之间的矛盾,三维网格压缩编码技术提供了一系列解决方法。本文从静态压缩和递进网格两个角度分类,以拓扑信息驱动和几何信息驱动为两条主线,归纳比较了国内外近十年来三维网格压缩的各种方法,并给出其未采发展趋势。     

基于EMDBS的移动学习系统的研究和设计

通过对嵌入式移动数据库关键技术的分析,结合移动学习的具体情况,提出了一种基于EMDBS的移动学习系统,对该系统的开发架构和每个模块的功能实现进行了描述,并把缓存技术应用到系统的移动终端,从根本上解决了移动学习中移动灵活性不够的问题和网络断接的现象.     

Hybrid and forward error correction transmission techniques for unreliable transport of 3D geometry

The continual improvement in computer performance together with the prevalence of high-speed network connections having high throughput and moderate latencies enables the deployment of multimedia applications, such as collaborative virtual environments, over wide area networks (WANs). These applications can serve as simulated environments in scenarios such as emergency response training to catastrophic disasters, military training, and entertainment. Many of these systems use 3D graphics for display and may be required to distribute geometric models on demand between participants. Progressive meshes provide an attractive mechanism for such distribution. Previous uses of progressive meshes have sent data using reliable protocols (TCP). However, such protocols have disadvantages in on-demand settings, in that they: (1) use flow control, which limits performance in WANs; (2) add additional bandwidth when there is loss; (3) treat all loss as an indication of congestion; and (4) require feature-rich multicast support, which is not always available. In this paper, we modify progressive mesh models to allow reconstruction even in the event of packet loss. We use these modifications in two transmission schemes, a hybrid transmission that uses TCP and UDP to send packets and a forward error correction transmission scheme that uses redundancy to decode the information sent. We assess the performance of these transmission schemes when deployed on network testbeds that simulate wide area and wireless characteristics.Published online: 9 February 2005 Correspondence to : Bobby Bodenheimer     

HTML5混合式移动社交应用中缓存管理机制的研究

随着移动互联网的发展,混合式开发作为一种快速开发的方式已经成为一种趋势,这种方式既可以体现Web应用可以同时适用于IOS平台和Android平台的特点,又能解决Web应用中不能调用操作系统底层资源的问题。当今社交类应用中普遍存在大量的图片,重复图片从服务器多次存取会消耗客户端流量、增加访问延迟,当今混合式开发框架中的缓存机制并不能解决这个问题。因此提出一个可以适用于混合式移动社交应用的图片缓存管理机制,提供缓存图片管理的原生模块供开发者在混合模式下使用,并将其应用于社交应用中。同时提出了一种基于社交关系的图片缓存替换算法,该算法结合了社交应用中用户之间的社交关系亲密值、LRU算法、图片占用空间大小。实际应用表明,该算法可以提高混合式移动社交应用中的缓存命中率。     

大规模地形模型的多分辨率显示技术研究

随着虚拟现实和三维显示技术的发展,人们开始研究高精度的大规模地形模型的显示与传输问题。目前较为流行的是采用LOD(levelsofdetail)技术。尤其在微软的渐进格网(ProgressiveMesh)技术出现后,此类问题的研究成为了热点。但是对大规模地形模型应用渐进格网技术仍存在许多困难,为此该文在国防科工委基础理论研究基金的支持下就此问题展开了研究,提出了一种基于块的大地形模型多分辨率显示技术。     

一种基于BREW的移动中间件解决方案

全面介绍了一种基于BREW的移动中间件解决方案,它针对移动设备的特性,将MICO技术与BREW技术相结合,使移动数据应用之间及它们与Internet、普通桌面系统之间实现互联、互通和互操作。     

任意拓扑三角形网格的全局参数化

提出了一种零亏格的任意拓扑流形三角形网格自动全局参数化方法 .算法首先采用顶点对合并的网格简化方法构造一个网格的累进表示 ,在进行网格简化的同时 ,对被删除的顶点相对于顶点合并操作所得到的新顶点的邻域进行局部参数化 ,由此得到一个带局部参数化信息的累进网格 ;然后将网格简化所得到的基网格进行中心投影到一个单位球面上 ,并采用累进恢复的方法将删除的顶点按与删除时相反的顺序逐次添加回网格上来 ,所添加顶点的坐标不再是其删除前的坐标值 ,而是由局部参数化信息计算得到 ,并且保证是位于单位球面上的 .由此得到原始网格的单位球面参数化网格     

移动自组网上基于动态蜂窝的多播路由协议

移动自组网是一种新型的无基站无线移动网络,多播作为通信网络中的重要功能,在这种网络中具有很高的研究及使用价值.针对移动自组网的特性,提出了基于动态蜂窝的多播路由协议.该协议将移动结点组织成动态蜂窝,然后在此基础上以按需的方式建立网格结构的多播路由发送多播数据.仿真实验结果表明该协议具有延迟小、可靠、高效、扩展性强的特点.     

基于频度中心理论的三维模型简化方法

针对三维模型传输技术中的模型简化问题,以边收缩算法思想为基础,应用网络节点频度中心理论(Degree Centrality),提出并实现了一种保持几何封闭性的模型简化方法.该方法能在保证简化模型逼真度的同时较好地保持模型的几何封闭性,避免孤立面的产生,并且生成了渐进网格文件,为模型提供了连续多分辨率的模型重建.实验证明了该方法的有效性.     

A Modified Paving Approach and Automatic Mesh GradingMethod to Quadrilateral Mesh Generation

A modified paving technique for automatic generation of all-quadrilateral mesh fromarbitrary 2-D geometry is presented. The generated mesh elementS are nearly square andperpendicular to boundaries. Aner the nodes and elementS formation is completed. a fully automaticgrading method is applied to increase the accuracy and reliability of engineering analysis. In thispaper, we mainly describe the theory of mathematical algorithm and present some examples ofautomatically generated mesh.     

基于三角形折叠的视相关多层次细节模型

在实际应用中,需要细节层次模型来表示场景中物体的不同细节层次,并降低数据量和复杂度;同时也希望以较精细的网格来表示离视点较近的物体,而以较粗糙的网格表示离视点较远的物体,即实现视相关。基于体积误差与三角形折叠操作,研究了渐进网格(VDPM)的简化算法,对模型的几何数据进行简化预处理,实现了与视点相关的多层次细节模型。     

A Web-based, Offline-able, and Personalized Runtime Environment for executing applications on mobile devices

An increasing number of people use cell phones daily. Users are not only capable of making phone calls, but can also install applications on their mobile phones. When creating mobile applications, developers usually encounter the cross-platform incompatibility problem (for example, iPhone applications cannot be executed on the Android platform). Moreover, because mobile Web browsers have increasingly supported more and more Web-related standards, Web applications are more possible to be executed on different platforms than mobile applications. However, the problem of Web application is that it cannot be executed in offline mode. This study proposes a Web-based platform for executing applications on mobile devices. This platform provides several services for developers such as offline service, content adaptation service, and synchronization service. With the help of the proposed platform, application developers can develop and publish offline Web applications easily with simplified external Web content and synchronization capability.     

Another short proof of optimality for the MIN cache replacement algorithm

When a new item is written into a cache, an old item must be evicted; the latter can be chosen by the offline MIN algorithm, which was first proven to be optimal by Mattson et al. [R.L. Mattson, J. Gecsei, D.R. Slutz, I.L. Traiger, Evaluation techniques for storage hierarchies, IBM Systems J. 9 (2) (1970) 78-117]. Recently a new, short proof was given by van Roy [B. van Roy, A short proof of optimality for the MIN cache replacement algorithm, Inform. Process. Lett. 102 (2007) 72-73]; here we give another short proof using what we call an amortized simulation.     

Landmark detection from mobile life log using a modular Bayesian network model

Mobile devices can now handle a great deal of information thanks to the convergence of diverse functionalities. Mobile environments have already shown great potential in terms of providing customized services to users because they can record meaningful and private information continually for long periods of time. Until now, most of this information has been generally ignored because of the limitations of mobile devices in terms of power, memory capacity and speed. In this paper, we propose a novel method that efficiently infers landmarks for users to overcome these problems. This method uses an effective probabilistic Bayesian network model for analyzing various kinds of log data in mobile environments, which were modularized in this paper to decrease complexity. We also present a cooperative inference method, and the proposed methods were evaluated with mobile log data generated and collected in the real world.     

基于Android的移动终端应用程序开发与研究

主要介绍了Google新近推出的移动设备软件平台Android以及基于此平台的移动终端应用程序开发。