A search space “cartography” for guiding graph coloring heuristics

We present a search space analysis and its application in improving local search algorithms for the graph coloring problem. Using a classical distance measure between colorings, we introduce the following clustering hypothesis: the high quality solutions are not randomly scattered in the search space, but rather grouped in clusters within spheres of specific diameter. We first provide intuitive evidence for this hypothesis by presenting a projection of a large set of local minima in the 3D space. An experimental confirmation is also presented: we introduce two algorithms that exploit the hypothesis by guiding an underlying Tabu Search (TS) process. The first algorithm (TS-Div) uses a learning process to guide the basic TS process toward as-yet-unvisited spheres. The second algorithm (TS-Int) makes deep investigations within a bounded region by organizing it as a tree-like structure of connected spheres. We experimentally demonstrate that if such a region contains a global optimum, TS-Int does not fail in eventually finding it. This pair of algorithms significantly outperforms the underlying basic TS algorithm; it can even improve some of the best-known solutions ever reported in the literature (e.g. for dsjc1000.9).     

Transit network timetabling and vehicle assignment for regulating authorities

In the literature on transit planning, network timetabling and vehicle scheduling are usually treated as separate problems. In this paper, we focus on combining important features of these two steps and propose a simultaneous solution approach to redefine timetables with the objective of bringing improvements to both quality of service and vehicle costs incurred. This includes the objectives of quantity and quality of the transfers proposed, evenness of the line headways, fleet size and length of the deadheads. The model proposed for this simultaneous approach is adapted to the problem faced by regulating authorities, encouraging intermodality and taking into account a variety of practical features. We introduce an optimization procedure based on Iterated Local Search and present computational experiments carried out on data from a large existing transit network, showing substantial improvements in both quality of service and level of resources compared to the current practice.     

Analytical modelling of networks in multicomputer systems under bursty and batch arrival traffic

The hypercube and torus are two important message-passing network architectures of high-performance multicomputers. Analytical models of multicomputer networks under the non-bursty Poisson traffic have been widely reported. Motivated by the convincing evidence of bursty and batch arrival nature of traffic generated by many real-world parallel applications in high-performance computing environments, we develop a new and concise analytical model in this paper for hypercube and torus networks in the presence of batch message arrivals modelled by the compound Poisson process with geometrically distributed batch sizes. The average degree of virtual channel multiplexing is derived by employing a Markov chain which can capture the batch arrival nature. An attractive advantage of the model is its constant computation complexity independent of the network size. The accuracy of the analytical performance results is validated against those obtained from simulation experiments of an actual system.     

基于Edius5的影视制作

Edius5是工作在PC平台上的制作视频内容的非线性编辑软件,它提供了无限的视频、音频、字幕和图文界面,可进行不同格式、不同制式、不同分辨率素材的混合编辑。优秀的编／解码技术和可升级的无限实时能力,延长了该软件的生命周期,可自定义的操作界面和快捷键为视频编辑带来了极大的便利,既使是初学者也可以依靠图标按钮上的功能描述,以简单的方式来轻松地操作这个系统。     

AC48304C－C语音芯片在卫星通信系统中的应用

语音是卫星通信中很重要的一种业务,简要介绍了AC48304C－C语音芯片的基本性能及工作原理,并结合时分多址（TDMA）卫星通信系统的特点,给出了一种基于这种芯片设计的四路语音编解码系统的软硬件设计,以及实现方案,在构建的卫星通信系统平台上进行了大量的软硬件实验和测试,结果表明此方案具有很好的效果,从实际工作经验中总结出该芯片开发的设计要点。     

VPN技术及其应用的研究

随着电子信息的高速发展,政府机关、企业等大型机构对网络的需求越来越高,促进了VPN技术的快速发展。VPN技术应用范围也越来越广,像电力、证券、高校、大型连锁企业以及财政、金融、公安等政府部门都在应用VPN技术。该文主要通过介绍VPN技术概念以及VPN技术在电子政务外网的应用对VPN进行分析。     

光纤线路的常用测试方法

随着光缆线路的大量敷设与使用,网络数据传输对光纤通信系统的依赖程度日益加深。在网络建设、改造和维护中,我们不得不面对伴随而来的各类光纤故障。对光纤线路如何进行测试,是网管员们比较关心的问题。该文介绍了连通性测试、光功率损耗测试、收发功率测试和反射损耗测试等四种光纤检测的常用方法。     

对等网在网络教学资源平台中的应用

利用对等网技术结合C/S模式来构建网络教学资源系统,能解决当前教学资源平台存在的问题,为网络教学的发展提供一种全新的平台,系统可方便的扩展为更高一级的系统。