简介：懒懒地脱下外套，我又开始了发呆的一天。

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简介：即时通讯软件以其快速便捷的优点赢得了广大用户的青睐和喜欢，但也引来了大量黑客的注意，特别是QQ2003版本的发布，使很多病毒爱好者都盯上了这一新兴的用户平台。QQ病毒的典型特征就是向在线好友发送隐藏的病毒网页链接，当对方点击后，就会自动连接到一个隐藏有病毒的网页，导致用户莫名其妙地中毒。

简介：Itisanefficientwayforamobilehosttoobtainmulticastserviceviaalocalmulticastrouteronthevisitednetwork.However,thereisapossibilityforatemporarydisruptionofmulticastserviceduetothejoinlatencyandotherissuesinhandoffprocedure.Thispaperproposesaschemetosolvesuchaproblem.Asmoothhandoffmechanismisintroducedtoavoidunnecessarydataloss.Besides,anymobilityagentcapableofmulticastcanbeappointedtoprovideservicetomobilehosts,whichmakesitpossibletodeploytheprotocolwidely.Discrete-eventsimulationswereconductedtosurveytheperformanceoftheproposedscheme.Thesimulationresultsshowthattheschemehasbetterperformancethanthecomparedapproaches.

简介：hosts是一个纯文本文件，其作用是提供IP地址和hostsname（主机名）的映射关系。因此，对于恶意网站，我们可以利用hosts把该网站的域名映射到错误的IP地址，这样使计算机无法访问，就达到了屏蔽的目的。这虽然是一个老技巧，但是却非常管用！

简介：ThreeC2-symmetric(10R,11R)-diethylsubstituteddibenzosuberane(DBS)-basedheliceneswithvaryingstericandconjugationdemandsoftheirbottomfragmentsweresynthesized.Onlythehelicene-7a[withthebottompartderivedfromtetralonewasfoundphoto-switchableinreasonabletimescale.Photoisomerizationofthediastereomericallypure(10R,11R,P)-helicene(7a)at280nmledtovirtuallyexclusiveformationoftheoppositeMform-diastereomer7a′(7a′/7a=99.6/0.4).Thepreferentialreturnof7a′to7acanbeeffecteduponirradiationat254nm(7a′/7a=3G/67)orthermallyat1307a′/7a=0/100).Thephoto-inducedswitchingprocessamountstoa133%differenceind.e.(from99.2%to-34%).TheconcomitantchangeofhelicenechiralitybetweenthesetwodiastereomericphotostationarystatesaugurswellfortheirpotentialapplicationasanopticalswitchinLCmaterials.Toourknowledge,oursystemservesasthebestchirochromicopticalswitchascomparedtotheexamplespossessingsimilarphotochromicproperties.