一种P2P VOD系统的缓存部署及调度机制

提出一种新的数据缓存机制,通过利用空闲节点加入缓存、节目点播应用前进行缓存部署和基于视频源服务器的请求连接数进行缓存调度等机制优化系统整体缓存能力和缓存分布.实验仿真数据表明,此数据缓存机制能有效提高系统的缓存能力和整体性能.     

嵌入式VOD系统客户端缓存机制研究与实现

基于S3C2410 ARM硬件平台和嵌入式Linux2.4系统设计了一个嵌入式Linux视频点播系统,同时提出一种基于切片式的数据块队列的视频缓存算法,应用于系统的客户端进行缓存管理。试验表明,此系统能够合理地利用有限的嵌入式硬件资源,减少服务器负载,提高网络资源利用率,满足远程教育中用户的点播需求。     

基于代理的视频点播系统中节目调度方案

为了有效地利用视频服务器I/O及网络带宽资源,针对基于代理缓存的节目调度特征,提出一种客户多播补块的视频点播方案·某些客户在播放节目的同时,又作为服务器按一定策略为后续客户多播一部分节目数据,因此,在不增加客户I/O带宽的前提下,通过利用局域网络丰富的带宽资源,有效地节省了视频服务器及主干网的带宽资源,同时对客户请求提供即时服务·此外,本方案自适应于节目流行度,支持任意的客户点播频度,不因无限用户的点播请求而出现带宽瓶颈·仿真结果表明了其有效、可行·     

一种基于内容分发请求的Web集群服务器研究

针对Web集群服务器请求内容的分布特点,提出了一种基于关联内容的请求分发(ACARD)算法.该算法首先以缓存大小为限制,采用FP tree方法挖掘用户的Web使用模式,并把它们所对应的文档映射到不同的后端服务器,然后由前端服务器根据请求的内容匹配相应的模式并进行转发.这种文档的自适应分布提高了集群系统的磁盘利用率和缓存命中率.实验表明,基于内核态的请求分发算法的性能远优于基于用户态的算法,而且在内核态下,ACARD相对加权最小连接算法的系统平均吞吐量可提高20 4%.     

多版本视频点播流媒体服务器集群资源分配方法

针对大规模移动学习应用背景下流媒体服务器集群资源分配过量或不均的问题,提出了一种面向移动学习系统的多版本视频点播流媒体服务器集群资源分配方法。该方法通过用户历史点播行为日志分析,挖掘在不同终端环境下用户点播行为的特征和规律,在此基础之上,采用排队论理论进行多版本视频点播中流媒体服务器集群资源分配建模,并通过实时预测用户请求到达率的变化情况,动态调整资源的分配,从而实现了集群资源的动态配置。实验结果表明,所提方法的平均服务拒绝率和资源利用率分别在1%和80%左右,既保证了用户体验满意度,又降低了系统服务成本。     

一种视频点播系统的研究与实现

在对传统点播视频系统进行比较分析的基础上，给出了一种支持服务器集群的视频点播系统的设计模型、功能与特点，并重点介绍了该系统实现的关键技术和方法。     

视频点播系统中视频分片协同存储方案研究

为了提高视频点播系统的服务质量,减少等待延迟,改善用户体验,将视频协同存储与网络编码技术相结合,以最大化本地命中为目标,提出了一种视频分片协同存储最大化本地命中算法。利用网络编码技术,预先将视频进行分片编码。在接收到视频请求时,将编码后的视频片发给用户。在客户端接收到足够的视频片后,即可进行解码,从而得到完整的视频。该算法构造了一种资源分配有向图,将原问题转化为该图上的最小费用流问题;通过求解该最小费用流问题,在多项式时间复杂度内得到最优化方案。当视频的总容量与服务器的总容量之比较大时,该算法依然有较好的表现。实验结果表明,该算法的性能优于其他已有的算法,特别是在视频总容量与服务器总容量之比较大的情况下,性能有10%的提高。实验分析了不同切片大小对算法性能的影响,选择了1MB作为默认的切片大小。     

基于P2P流媒体的网络视频系统设计

目的 解决目前网络视频系统带宽要求高、系统伸缩性差、大规模用户同时在线时的服务器瓶颈等问题,提出基于P2P流媒体的网络视频系统设计方案.方法 将对等网络(P2P)理论应用到流媒体系统中,采用混合网络模式,运用应用层组播技术和区域自治思想构建组播树,根据实际情况对组播树进行动态调整,采用适合的缓存机制实现媒体数据的平稳传输.结果 通过对系统设计中的关键技术进行分析,采用P2P流媒体技术的网络视频系统在扩展性、服务器带宽要求、视频播放质量等方面都有了极大的改善.结论 在不改变现有网络带宽下,P2P流媒体技术是实现网络视频系统的最佳选择.     

应用层组播在视频监控系统中的应用

本文分析传统C/S模式的视频监控系统存在的视频服务器瓶颈问题,提出了一种将应用层组播技术应用于视频监控系统的方案,在介绍应用层组播算法的基础上,给出了该方案的设计思路.分析表明,该方案可应用于大规模视频监控系统.     

3Tnet视频点播的动态协作合并流调度

中国高性能宽带信息网—3Tnet是一种能提供大规模视频服务的新型网络.基于3Tnet视频点播网络结构,提出一种称为动态协作合并视频流的新方案.该方案在3Tnet视频补充流组播调度算法的基础上,利用动态协作合并视频流的调度算法,以求进一步降低3Tnet视频点播服务中边缘网的带宽需求.仿真结果显示,当视频节目数达到3 000部时,本方案比对等网络(p2p)链式方案可分别节省28.2%边缘网的传输带宽和47.2％驻地网的传输带宽;与补充流组播方案比较,在略微增加3.8％驻地网上传带宽的条件下,可节省17.6%的边缘网传输带宽.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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