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简介:随着社会进步和生产力的发展,商务的形式及具体内容应市场的需求在不断地变化。作为对传统商务进行改造、补充和拓展的现代化手段,电子商务应运而生。本文阐述其定义、分类、模型等,特别是B2B电子商务的互联技术以及相关核心系统,并分析目前B2B发展过程中遇到的主要问题。
简介:Recently,alotofdigitalsubscriberloopsystems(DSL)andhighratedigitalsubscriberloopsystems(HDSL)havebeendeployedindigitalsubscriberaccessnetworks.DataechocancellerisextensivelyusedintheDSLandHDSLsystemstorealizefullduplextransmissionontwistedcable.Insuchsystems,2B1Qlinecodeisadopted.Therefore,symbolrateisdecreasedanddigitaltransmissionsystemsgetlongerreach.Inthispaper,aperformanceevaluationmethodoftheechocancellerisproposedbasedonanautocorrelationmatrixof2B1Qlinecode.Usingthismethod,theformulaofratioofdatasignaltoechoresidualsignalisobtained.Accordingtotheformula,theratioofdatasignaltoechonoisedependsonFIRfiltertap,convergencefactor,adaptivealgorithmandthecorrelationmatrixofthelinecode.Computersimulationiscarriedouttoverifytheoreticalanalysis.Thesimulationresultscoincidedwiththetheoreticalformulaintheprocessestimatingtheratioofsignaltonoise.
简介:日前,国家广电总局正式颁布了中国移动多媒体广播,即“手机电视”的行业标准,向“手机电视时代”迈出了关键性的一步。国家广电总局确定的手机标准为有自主知识产权的STiMi标准,并将于今年11月1日起正式实施。STiMi标准的胜出,意味着韩国T—DMB、美国MediaFlo、日本ISDB—T和欧洲DVB-H四大国际标准,将退出国内手机电视市场的竞争。此前,国外标准的支持厂商已经开始在国内“试水”手机电视,如以NOKIA为首的欧洲DVB—H阵营,曾陆续在北京、福建搭建实验网络;而以高通公司为首的FLO论坛,也吸引了包括夏新在内的三家中国合作伙伴。
简介:Inthispaper,buildingtogrid(B2G)andvehicletogrid(V2G)havebeendefinedwithclearandpracticalunderstanding.Bothofthemarenewgenerationtechnologieswhicharetheessentialpartofsmartcitylivingandcrowdenergyclustering.Firstly,anin-detailedoverviewhasbeenprovidedwithanintroductiontoB2GandV2Gfollowedbyahistoricaloverviewandtheoreticalanalysisinrespecttosmartcityplanning.Next,areviewisconductedoncurrentandprevioussmartlivingresearch,whichdealswithB2GandV2G.EfficientB2GandV2Gimplementationsinpracticalcasesthenhavebeendiscussed.Lastly,bothofthesetechnicalprospectshavebeenanalyzedincrowdenergydiagram.
简介:Thisletterintroducesthedesignideas,simulationandtestresultsofanS-bandklystronwithbandwidthof11%,whichwasdevelopedbytheInstituteofElectronics,ChineseAcademyofSciences(IECAS).Onthepeakpowerlevelof800kW,theefficiencyofklystronismorethan30%;thegainismorethan41dB;theequal-drivingrelativeinstantaneousbandwidthisover11%;theaveragepowerislargerthan8kW,andthepowerfluctuationwithinbandwidthislessthan1.5dB.