基于混合云存储多频道视频直播系统方案设计

针对多频道直播系统中存在的用户启动延迟大、播放滞后、频道切换扰动等问题,以及为了满足大规模用户需求而部署大量视频服务器致使成本昂贵的缺点,本文提出了一种基于混合云存储的多频道视频直播方案.该方案设计了公有云服务器和私有云服务器以及与用户间的应用层网络架构,引入P2P技术提升直播系统的协作功能;并构建了服务器选择和带宽分配模型.实施结果表明,该方案能有效提高系统服务能力,改善直播视频质量.     

OSM——一种基于P2P的覆盖网构造协议

提出了一种新的P2P覆盖网构造协议--OSM.节点使用IP地址匹配算法选择邻居节点,优化了应用层网络拓扑结构,使得最接近底层物理拓扑结构;对于对等网络视频直播系统的健壮性来说,覆盖网构造中管理节点的退出和恢复是至关重要的,提出了节点的异常机制,能够及时有效地发现邻居节点失效,保障快速恢复.实验结果表明,OSM协议提高了与底层网络的匹配度,缩短了反应时间,增强了节点的健壮性.     

采用节点优先级的对等网络流媒体请求量分配算法

在多源协同调度的对等网格(P2P)流媒体系统中,针对现有请求量分配算法不能根据源节点性能动态调整向各节点分配的请求量,导致源节点带宽利用率不高以及服务器负载重的问题,提出一种基于节点优先级的请求量分配算法.该算法根据源节点的历史调度评价和可用数据量计算源节点优先级,调度时根据优先级动态调整分配给各源节点的请求量,优先向历史调度评价好和可用数据量多的源节点分配请求.仿真实验与实际系统测试表明,所提算法可以充分利用源节点带宽资源进行数据传输,较传统算法降低服务器负载17.3%以上,提高了系统可扩展性.     

采用改进粒子群的P2P流媒体数据调度算法

P2P技术解决了传统流媒体应用中的不能支持大用户的问题.而数据调度算法一直是P2P流媒体研究领域中的核心问题.为了减轻服务器的负载, 并且有效利用P2P网络中节点的资源.本文提出一种基于改进粒子群算法的P2P流媒体数据调度方法.该算法使用了粒子群算法进行寻优,并对粒子群算法进行改进,算法中定义了 "加法"运算,替换原来的速度方程,并增加变异算子,防止早熟收敛.最后通过对比实验验证了算法的有效性.     

多跳无线网络中具有时间意识的视频流控制协议

为了在多跳无线网络中对实时视频流提供高效的端到端服务质量支持,提出了一种具有时间意识的视频流控制协议(TACP).首先在网络层增加了独立的TACP子层,采用跨层设计方法将各协议层的参数映射至该子层.在此基础上,源节点通告视频同步信息,使中间节点形成时间意识;中间节点通过分布式时延估计方法限制超时视频数据的转发.随后,为了对高优先级视频数据提供保护,研究了一种基于GOP的路径探测机制,并将其与视频流控制协议协同工作.利用仿真实验,对TACP视频通信性能进行分析和评价.结果表明:TACP能够显著改善实时视频流质量,包括可解码帧率、端到端时延和时延抖动等性能指标;该协议极大地提高了网络带宽利用率,并能够有效适应实时性需求的变化.     

利用P2P技术实现移动终端在WLAN内的漫游认证

针对IEEE 802.11i协议中身份认证和主密钥协商造成认证时延过大的问题,提出了一种利用P2P Chord技术管理无线局域网(WLAN)内认证信息的认证优化机制.站点在首次接入WLAN时将协商生成的认证信息发布至P2P Chord环中.当站点在接入点(AP)间发生切换时,可从P2P Chord环中查找出相应的认证信息以完成后续的协议交互,无需通过认证服务器重新认证,从而显著降低复杂认证引起的时延.理论推导及实验结果表明:该认证信息管理方案能够降低站点在AP间的切换时延,满足实时应用通信质量的需求;同时还可以减轻认证服务器的负担,在一定程度上防止单一故障点的存在.     

一种基于流驱动算法的P2P流媒体直播系统

在Internet视频直播服务中,受带宽限制,服务器难以支持大规模并发客户.本文针对该现状,设计并实现了基于P2P技术的流媒体直播系统,文中提出一种三层软件结构并详细介绍了流驱动算法.该系统已在局域网内运行良好,表现出高扩展性和稳定性,以及高质量的流媒体服务.     

基于P2P的流媒体分发关键技术研究

设计一个基于P2P覆盖网的流媒体分发方案,该方案采用Gossip算法进行节点间信息的传递. 仿真实验结果显示,有效的成员管理、伙伴管理和调度管理实现了流媒体内容实时、持续的分发,在动态变化的用户环境下表现较优.     

多客户VOD视频服务器的研究

描述了基于通用工作站的ＶＯＤ（ＶｉｄｅｏＯｎＤｅｍａｎｄ）视频服务器支持多客户并发访问的原理,提出了一个利用时间片轮询的调度算法来给多客户提供视频服务,并给出了一个基于客户／服务器结构的ＶＯＤ视频服务器的结构及其初步实现．实验结果证明了调度算法的有效性和正确性．     

MP2P网络的移动节点域间预切换方法

移动P2P网络具有高度动态性,但节点的频繁移动影响整个网络的可达性,降低了网络的服务质量.为了维护节点的可达性需要减少节点移动时的切换时延,为此文中提出了基于超级节点的分层预切换方法HPH.该方法在基于超级节点分层模型的基础上引入移动IPv6的快速切换的思想,对节点的域间移动采用预切换机制,解决网络中因节点频繁移动而带来的负面影响.仿真结果分析表明,较之传统KaZaA切换方法,HPH方法的切换时延降低了20.5％,丢包率降低了10.2％.     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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     

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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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has