简介:Afull-duplexopticalpassiveaccessschemeisproposedandverifiedbysimulation,inwhichhybrid64/16/4-quadratureamplitudemodulation(64/16/4QAM)orthogonalfrequencydivisionmultiplexing(OFDM)opticalsignalisfordownstreamtransmissionandnon-return-to-zero(NRZ)opticalsignalisforupstreamtransmission.Inviewofthetransmittingandreceivingprocessfordownlinkopticalsignal,in-phase/quadrature-phase(I/Q)modulationbasedonMach-Zehndermodulator(MZM)andhomodynecoherentdetectiontechnologyareemployed,respectively.Thesimulationresultsshowthatthebiterrorratio(BER)lessthanhardwaredecisionforwarderrorcorrection(HD-FEC)thresholdissuccessfullyobtainedovertransmissionpathwith20-km-longstandardsinglemodefiber(SSMF)forhybriddownlinkmodulationOFDMopticalsignal.Inaddition,bydividingthesystembandwidthintoseveralsubchannelsconsistingofsomecontinuoussubcarriers,itisconvenientforuserstoselectdifferentchannelsdependingonrequirementsofcommunication.
简介:Poly4-vinylphenol(P4VP)/multi-wallcarbonnanotubes(MWNTs)multi-layersensitivefilmsweredepositedoninterdigitatedelectrodesbyairbrushtechnologytodetecttoluenevaporatroomtemperature.Thesurfaceandsectionmorphologiesofthemulti-layerfilmswereobservedbyascanningelectronmicroscope(SEM).Itisfoundthattheresistanceofthesensorincreaseswhenitisexposedtotoluenevaporandtheresponsehasagoodlinearitywiththeconcentrationoftoluene.TheresultsshowthattheP4VP/MWNTsthree-layerfilmsensorshavebettersensingpropertiescomparedwiththetwo-layerfilmsensors.Therelatedsensingmechanismisstudiedindetail.
简介:TheanalysisofsolarcellperformancehasbeendonebysimulatingtheexternalI-Vcharacteristicsofn^+/p/p^+singlecrystalsiliconsolarcellunderhighlightintensityand1.5airmass(AM).Thismethodallowsthemaximizationofsolarcellefficiency.Tofabricatelow-costn^+/p/p^+singlecrystalsiliconsolarcells,solidsourceofdopedphosphorousandboronwasused.
简介:Theletterproposesathree-layermanageablemediadistributionnetworksystemarchi-tecturecalledMSPnet,whichisbasedonSessionInitiationProtocol[1]andPeertoPeer(SIPP2P)technology.MSPnetperformsapplication-levelstructuredDHTroutingandresourcelocationamongdomainsandunstructuredonesindomain.Exceptformediadistribution,itcanbeusedtosupportavarietyofP2Papplications,includingvideobroadcasting,videoondemand,VoIP,etc.MSPnetiscomposedofthreelayers,namely,thesignalcontrollayer,themanagementlayer,andthemediatransportationlayer.TheMSPnetprototypeconsistsoftheSIPserver,themanagementserver,themediaserver,andthenodeUserAgent(UA).Resultsfromaprototypeexperimentinalarge-scaleInternetenvironmentshowthatMSPnetisfeasible,scalableandmanageable.
简介:地理信息系统(GIS)逐渐地正在管理数据的很大的集合,一个因此集中的数据索引不能总是提供最可伸缩的解决方案。最近,p2p(P2P)网络为以一种完全分散的方式分享信息变得很流行。在这份报纸,新混合P2P空间索引网络(HPSIN)被建议,它把分布式的空铅树与基于的分布式的哈希值桌子(DHT)相结合维持询问效率和系统负担的弦网络平衡。另外,一个简单理论模型基于为HPSIN的打开的排队网络被建立。在模型,作为M/M/1排队处理器假定每个同伴系统的基本特征被捕获,并且平均质问延期的表示在靠近的形式被获得。理论分析和数字计算结果证明那在那里存在在效率和负担平衡之间的折衷的一个最佳点。由将开始索引水平ls的合适的值放为不同网络规模和询问率,HPSIN将完成因此,延期能使适应不同P2P应用程序环境的最小的全面询问。
简介:ThekeyprobleminunstructuredP2Psystemishowtocontrol'Flood'.Somestudiesfocusonconstructingmoreefficienttopologywhileothersfocusonbetterqueryalgorithms.ThispaperpresentsHICUS(HierarchicalInterest-drivenCommunity-basedUnstructuredSystem)motivatedbyabasicthought-whethertheresourcescorrelatewithtopologydistinguishesstructuredandunstruc-turedP2Pessentially.Byintroducinghierarchical'interest',HICUSorganizesaquasi-structuredtopologythroughapuredistributedway,andprovidesanewplatformforqueryalgorithms.Westudytheprocedureandperformanceoftopologyorganization,andthesimulationsshowthatHICUSformsasmall-worldwhichcansignificantlyimprovetheroutingefficiency.
简介:这篇文章集中于识别分享文件对等(P2P)(例如BitTorrent(BT))在一个树桩网络的边阶的交通。由分析应用程序的协议和交通,一个单身的用户的分享文件的P2P交通与极大地不同,这被发现传统并且另外的P2P(例如QQ)申请在深奥远程主机和遥远的端口的分发的交通。因此,一个方法基于远程主机(RHD)的组件和遥远的港口(RPD)的组件被建议识别象BT一样交通。这个方法仅仅在一个树桩网络依靠每台用户主机的流动信息,并且没有包收费载重需要被监视。在间隔,为并发的传播控制协议的立刻的RHD和为每台主机的用户数据包协议流动通过由每流动的远程主机属于的树桩网络组织流动分别地是计算的。在给定的条件上,立刻的RPD通过由遥远的港口组织流动修改立刻的RHD被计算。一位主人是否一直在使用象BT一样应用,能为时间的一个时期从立刻的RHD或平均RHD被推出。基于交通,特征是对比基于内容的方法识别变化多端的分享文件的P2P交通合适的更多的建议方法。试验性的结果证明这个方法与高精确性是有效的。