简介:TN1595010522光电器件近年来的发展趋向=Reviewofrecentdevelopmentinoptoelectronicdevices[刊,中]/缪家鼎(浙江大学.浙江,杭州(310027))//半导体光电.—1994,15(1).—1—6文章从光电器件的单元技术、成像器件和垂直腔面发射半导体激光器三方面评述了光电器件的进展,说明它是一个充满活力的研究领域。图12表1参2(任延同)TN1595010523光学器件与光计算机=Opticaldeviceandopticalcomputer[刊,中]/张桂萍(河北大学电子系,
简介:Multimediastreamingservedthroughpeer-to-peer(P2P)networksisboomingnowadays.However,theend-to-endstreamingqualityisgenerallyunstableduetothevariabilityofthestateofserve-peers.Ontheotherhand,proxycachingisabandwidth-efficientschemeforstreamingovertheInternet,whereasitisasubstantiallyexpensivemethodneedingdedicatedpowerfulproxyservers.Inthispaper,wepresentaP2PcooperativestreamingarchitecturecombinedwiththeadvantagesofbothP2Pnetworksandmultimediaproxycachingtechniquestoimprovethestreamingqualityofparticipatingclients.Inthisframe-work,aclientwillsimultaneouslyretrievecontentsfromtheserverandotherpeersthathaveviewedandcachedthesametitlebefore.Inthemeantime,theclientwillalsoselectivelycachetheaggregatedvideocontentsoastoservestillfutureclients.Theassociateprotocoltofacilitatethemulti-pathstreamingandadistributedutility-basedpartialcachingschemearedetailedlydis-cussed.Wedemonstratetheeffectivenessofthisproposedarchitecturethroughextensivesimulationexperimentsonlarge,Inter-net-liketopologies.
简介:P2Psystemsarecategorizedintotree-basedandmesh-basedsystemsaccordingtotheirtopologies.Mesh-basedsystemsareconsideredmoresuitableforlarge-scaleInternetapplications,butrequireoptimizationonlatencyissue.Thispaperproposesacontentsubscribingmechanism(CSM)toeliminateunnecessarytimedelaysduringdatarelaying.Anodecansendcontentdatatoitsneighborsassoonasitreceivesthedatasegment.Noadditionaltimeistakenduringtheinteractivestagespriortodatasegmenttransmissionofstreamingcontent.CSMconsistsofthreesteps.First,everynoderecordsitshistoricalsegmentslatency,andadoptsgammadistribution,whichpossessespowerfulexpressionability,toexpresslatencystatistics.Second,anodepredictssubscribingsuccessratioofeveryneighborbycomparingthegammadistributionparametersofthenodeanditsneighborsbeforeselectinganeighbornodetosubscribeadatasegment.Theabovestepswouldnotincreaselatencyastheyareexecutedbeforethedatasegmentsarereadyattheneighbornodes.Finally,thenode,whichwassubscribedto,sendsthesubscribeddatasegmenttothesubscriberimmediatelywhenithasthedatasegment.ExperimentsshowthatCSMsignificantlyreducesthecontentdatatransmissionlatency.
简介:ThespectrumoftheΣ(1193)excitedstates,Σ,withisospinI=1andstrangenessS=??1isoneofthemostimportantissuesinhadronicphysics.TheΣresonancesaremostlyproducedandstudiedinK-inducedreactions.ManyΣresonancesarenowcatalogedbytheParticleDataGroup[1].However,ourknowledgeoftheseresonancesisstillverypoor.Intheenergyregionbelow2GeV,onlyafewofthemarewellestablished,suchastheΣ(1385)ofspin-parityJP=3=2+,Σ(1670)ofJp=3=2??andΣ(1775)ofJp=5=2??.Theothersarenotwellestablishedandsomeofthemareevenoflargeuncertaintiesontheirexistence.Thus,thestudyoftheΣresonancewiththeavailableexperimentaldataisnecessary.
简介:本文介绍由三片集成块CS8204、WE9140A、TEA1061组成的典型电话机电路,主要分析电话机的电源供给电路、振铃电路、拨号电路和通话电路。
简介:目的:研究P波斜入射下的地基动应力路径,探讨其影响因素和可能变化范围,为进一步研究斜入射地震波作用下场地动力响应奠定理论基础。创新点:1.从数学上证明斜入射P波在任一深度的地基中形成的应力路径在剪应力分量(偏差正应力-水平剪应力)组成的平面中为一个斜椭圆;2.分析了P波入射角、土体泊松比和单位波长深度对斜椭圆应力路径形状与大小的影响。方法:1.基于半无限弹性空间的地震波传播理论,考虑地震波在自由界面的反射,推导土体中任一深度处由P波斜入射产生的动应力,并表示成由剪应力分量组成的平面下的应力路径(公式(9))及该应力路径的特征参数表达式(公式(A12)~(A14));2.通过控制变量法,分析参数敏感性(图7、9、10和12)。结论:1.虽然证实P波斜入射引起的应力路径为斜椭圆形式,但在地基深度、入射波频率和波速的特定组合下,斜椭圆仍可从斜线一直变化到圆形,形式较为多样化;2.P波斜入射角度在30?~60?时引起的动偏应力幅最大,最大可达同等条件下其它入射角产生的动应力幅的2倍以上;3.斜入射角大于45?后,斜椭圆路径形状几乎不随入射角改变,在研究范围内以竖直扁椭圆形为主;4.土体饱和度大于70%时,泊松比的变化对土体斜椭圆路径形状影响不大,但动应力幅随泊松比增大而显著降低。