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395 个结果
  • 简介:Areviewontheprogressofpowerful2μmsilicafibersourcesinpastdecadesispresented.Wereviewthestate-of-the-artrecordsandrepresentativeachievementsof2μmhigh-average-powercontinuouswave,pulsedfiberlasersandamplifiers,andpowerfulsuperfluorescentsources.Challengeswhichlimitthefurtherpowerscalingof2μmsilicafibersourcesarediscussed,includingpumpingbrightnesslimitation,thermalproblem,andnonlineareffects.Potentialandpromisingroadmapstogobeyondtheselimitations,liketandempumpingandbeamcombining,arediscussed.Prospectsofpowerful2μmsilicafibersourcesarealsopresentedintheendofpaper.

  • 标签: 微米 硅纤维 脉冲光纤激光器 高功率连续波 石英纤维 超荧光光源
  • 简介:Globalpositioningsystem(GPS)forvehicleapplicationsintheurbanareaischallengedbylowsignalintensity.ThecarrierloopbasedonfastFouriertransform(FFT)canobtainahighsignaltonoiseratio(SNR)gainbyincreasingtheobservationtime.However,thisleadstoamajorproblemthattheaccelerationcannotbeignored.TheperformanceoftheFFT-basedloopwilldeclinewiththeaccelerationincreasing.ThispaperdiscussestheeffectofthedynamiconFFTfirst.ThenahighperformancecarriertrackingloopforweakGPSL5signalsisproposed.Itcombinesdiscretechirp-Fouriertransform(DCFT)andthephasefittingmethodtoestimateDopplerfrequencyandDopplerratesimultaneously.First,asequenceofintegrationresultsisusedtoperformDCFTtoestimatecoarseDopplerfrequencyandDopplerrate.Second,thephaseofthesequenceiscalculatedandusedtoperformlinearfitting.Bythephasefittingmethod,thefineDopplerfrequencyandDopplerratecanbeestimated.ThecomputationcostissmallbecausetheintegrationresultsareusedandthephasefittingmethodneedsonlycoarseestimatesofDopplerfrequencyandDopplerrate.ComparedwithFFTandDCFT,theprecisionofthephasefittingmethodisnotlimitedbytheresolution.Thustheproposedloopcangethighprecisionandlowcarriertonoiseratio(C/N0)trackingthreshold.Simulationresultsshowthisloophasagreatimprovementthanconventionalloopsforurbanweak-signalapplications.

  • 标签: SATELLITE NAVIGATION RECEIVER signal processing FREQUENCY
  • 简介:TheopticalabsorbanceinnearUVwavelengthregioninSnO2nanoclustersinanexternalelectricfieldisdeterminedatroomtemperature.Theabsorbancespectraasapplicedfieldandtheabsorbancevariationswiththeappliedfieldareobtained.Therelationbetweenabsorbancechangeandappliedfieldisnon-linear.andissaturatedathighfieldregion.

  • 标签: 吸收率 外部电场 二氧化锡 半导体
  • 简介:用photonic晶体(PC),轻射出的二极管(LEDs)的抽取效率能被photonic乐队差距(PBG)和栅栏衍射的效果极大地提高。二个理论方法也被讨论。同时,我们证明LEDs能由作为衍射栅栏采用photonic水晶完成高抽取效率。有圆柱的单位房间的方形的格子的PC被制作在轧了带的基于陷阱的蓝色的层。我们在场PC-LED的抽取效率的理论讨论,它依靠有效中等理论和传播矩阵方法调查格子常数的效果。当格子常数是270nm时,结果证明高效LEDs的抽取效率能完成61.8%。

  • 标签: 提取效率 光子晶体 LED 蓝色发光二极管 有效介质理论 光栅衍射
  • 简介:VO2thinfilmswithgoodswitchingpropertieswerepreparedbycontrollingtheannealingtimeandtheannealingtemperatureinavacuumsystem.Thestructural,opticalandelectricalpropertiesofthesampleswerecharacterizedbyusingXRD、XPS、UV-VISandelectricalmeasurements.TheswitchingparametersofVO2thinfilmwereinvestigatedtoo.TheresultsindicatethatbeforeandafterphasetransitiontheresistanceofVO2thinfilmschangesaboutthreeordersofmagnitude,thevariationoffilmtransmittanceof40%hasbeencarriedoutwiththeabsorptivityswitchingvelocityofabout0.2607/minat900nm.Thestructuralpropertyofsampleshasbeenimprovedbutthephase-transitionpropertieshavebeendecreasedbyincreasingtheannealingtimeandannealingtemperature.ThevalenceofVionsandthestructureofsampleshavegreateffectonphasetransitionpropertiesofVO2thinfilms.Discussionontheeffectsofannealingtimeandannealingtemperatureonthephase-transitiontemperatureandhysteresiswidthshowsthatthebestreasonableannealingtimeandannealingtemperaturecanbeachieved.

  • 标签: 氧化钒薄膜 相变 薄膜结构
  • 简介:Analternativemethodisproposedinthisletterfordescribingthearbitraryshapeandsizeforgranulesin2Dimage.Afterimagebinarization,theedgepointsoncontouraredetected,bywhichthecentroidoftheshapeinquestionissoughtusingthemomentcalculation.UsingPrincipalComponentAnalysis(PCA),themajorandminordiametersarecomputed.Basedonthesignaturecurve-fitting,thefirst-orderderivativeistakensoastoseekallthecharacteristicvertices.Byconnectingtheverticesfound,thesimplifiedpolygonisformedandutilizedforshapeandsizedescriptivepurposes.Thedevelopedalgorithmisrunontwogivenrealparticleimages,andtheexecutionresultsindicatethatthecomputedparameterscantechnicallywelldescribetheshapeandsizefortheoriginalparticles,beingabletoprovideaready-to-usedatabaseformachinevisionsystemtoperformrelateddataprocessingtasks.

  • 标签: 任意形状 二维图像 颗粒 机器视觉系统 直径计算 粒子图像
  • 简介:SprintNextel与WaltDisney旗下ABC集团在重新部署频谱使用问题上达成统一意见,协议中允许Sprint在超过2千兆赫的波段提供商业移动无线服务。Sprint将支付ABC重新部署网络所需的费用,其中包括了使用在新频率中设备资金。基于FCC美国联邦通信委员会的规定,持有2千兆赫广播辅助服务的许可人,例如ABC,必须在2007年9月前完成频率重新部署的工作。

  • 标签: SPRINT 移动服务 频谱 美国联邦通信委员会 ABC 使用问题
  • 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.

  • 标签: 点对点技术 计算机技术 网络 设计方案
  • 简介:意法半导体推出了采用先进的PowerFLATTM5×6双面散热(DSC)封装的MOSFET晶体管,新产品可提高汽车系统电控单元(ECU)的功率密度,已被为全球所有的汽车厂商提供先进技术的汽车零配件大厂电装株式会社选用。

  • 标签: MOSFET管 微型封装 功率密度 汽车系统 散热 双面
  • 简介:在中国产业发展的历史上,"大步向前"和"产能过剩"始终如影随形,即将在未来10年投入5万亿元倾力发展的新兴能源产业莫不如此。在国家经济转型结构调整、发展低碳环境友好型产业的背景下,新能源产业的前景被一致看好。不过,如何平衡"速度"与"质量"之间的关系,也一直是一道难题。

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  • 简介:摘要芬兰在PISA测评中的成绩令世界称赞。其“先见中体现的“人”的思想向真正的“诗性”发展,那么“从林到树”能否在我国加以实践,成为真正意义上中国化的教育模式呢。

  • 标签: 从林到树 理念推动 诗性教学 人本思想 中国实践
  • 简介:AnewcompactopticalFanofiltersuitableforbiologicalsensingisproposed,whichpatternsphotoncrystalinsinglecrystallinesiliconnanomembranes(SiNMs)andtransferringontotransparentglasssubstrates.Theeffectsofairholesizeandsiliconthicknessonthetransmissioncharacteristicsofnewfilterarenumericallyinvestigatedbyusingthree-dimensionalfinite-differencetime-domain(FDTD)technique,thespectralresponseisalsostudiedbyback-fillingbioliquid.Theresultsshowthatthedipwavelengthwillshifttowardlongerwavelengthbyeitherreducingairholeradiusorfillingbio-liquid.Thenumberofdipswillincreasewiththeincreaseofsiliconthickness.Thesizeofproposedfiltercanbelessthan1mm2.

  • 标签: 二维光子晶体 生物传感 玻璃基板 过滤器 三维有限差分 光学遥感器
  • 简介:1O月19日.第2届亚洲印刷奖颁奖大会在新加坡RitzCarltonHotel举行。作为此次亚洲印刷奖的重要赞助商之一。柯达保丽光印艺集团通过此次大会。又在提升亚洲印刷和包装质量的标准中发挥了重要作用。

  • 标签: 第2届 印刷 亚洲 柯达保丽光印艺集团 包装质量 新加坡
  • 简介:文章主要阐述了I^2C总线控制音响电路的工作原理,探讨I^2C总线控制音响电路的测试方法,介绍了在A370测试系统上使用高速数字模块(M621)对I^2C总线控制的编码方法以及配合M625和M601模拟模块对输出音频信号进行测试的软件开发。

  • 标签: I^2C总线 音响电路 测试系统
  • 简介:Videoobjectextractionisakeytechnologyincontent-basedvideocoding.AnovelvideoobjectextractingalgorithmbytwoDimensional(2-D)mesh-basedmotionanalysisisproposedinthispaper.Firstly,a2-Dmeshfittingtheoriginalframeimageisobtainedviafeaturedetectionalgorithm.Then,higherorderstatisticsmotionanalysisisappliedonthe2-Dmeshrepresentationtogetaninitialmotiondetectionmask.Afterpost-processing,thefinalsegmentingmaskisquicklyobtained.Andhencethevideoobjectiseffectivelyextracted.Experimentalresultsshowthattheproposedalgorithmcombinesthemeritsofmesh-basedsegmentingalgorithmsandpixel-basedsegmentingalgorithms,andherebyachievessatisfactorysubjectiveandobjectiveperformancewhiledramaticallyincreasingthesegmentingspeed.

  • 标签: 视频 对象分析 2-D 网孔 统计学