简介：5月11日消息，美国东部时间5月10日，全球手机业巨头诺基亚在芬兰赫尔辛基向外界公布了自行开发的手机移动电视系统技术细节，从而方便服务提供商为用户提供可在手机上播放的多样电视节目。预计手机电视服务的商业运行将从2006年开始。

简介：H-infinityestimatorisgenerallyimplementedintimevariantstate-spacemodels,butitleadstohighcomplexitywhenthemodelisusedformultipleinputmultipleoutputwithorthogonalfrequencydivisionmultiplexing(MIMO-OFDM)systems.Thus,anH-infinityestimatorovertime-invariantsystemmodelsisproposed,whichmodifiestheKreinspaceaccordingly.InordertoavoidthelargematrixinversionandmultiplicationrequiredineachOFDMsymbolfromdifferenttransmitantennas,expectationmaximization(EM)isdevelopedtoreducethehighcomputationalload.JointestimationovermultipleOFDMsymbolsisusedtoresistthehighpilotoverheadgeneratedbytheincreasingnumberoftransmitantennas.Finally,theperformanceoftheproposedestimatorisenhancedviaanangle-domainprocess.Throughperformanceanalysisandsimulationexperiments,itisindicatedthattheproposedalgorithmhasabettermeansquareerror(MSE)andbiterrorrate(BER)performancethantheoptimalleastsquare(LS)estimator.JointestimationovermultipleOFDMsymbolscannotonlyreducethepilotoverheadbutalsopromotethechannelperformance.Whatismore,anobviousimprovementcanbeobtainedbyusingtheangle-domainfilter.

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简介：Reversibledatahidingtechniquesarecapableofreconstructingtheoriginalcoverimagefromstego-images.Recently,manyresearchershavefocusedonreversibledatahidingtoprotectintellectualpropertyrights.Inthispaper,wecombinereversibledatahidingwiththechaoticHénonmapasanencryptiontechniquetoachieveanacceptablelevelofconfidentialityincloudcomputingenvironments.And,Haardigitalwavelettransformation(HDWT)isalsoappliedtoconvertanimagefromaspatialdomainintoafrequencydomain.Andthenthedecimalofcoefficientsandintegerofhighfrequencybandaremodifiedforhidingsecretbits.Finally,themodifiedcoefficientsareinverselytransformedtostego-images.

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简介：ArobustdecentralizedH∞controlproblemforuncertainmulti-channelsystemsisconsidered.Theuncertaintiesareassumedtobetime-invariant,norm-bounded,andexistinboththesystemandcontrolinputmatrices.Thedynamicoutputfeedbackismainlydealtwith.Anecessaryandsufficientconditionfortheuncertainmulti-channelsystemtobestabilizedrobustlywithaspecifieddisturbanceattenuationlevelisderivedbasedontheboundedreallemma,whichisreducedtoafeasibilityproblemofanonlinearmatrixinequality(NMI).Atwo-stagehomotopymethodisusedtosolvetheNMIiteratively.First,adecentralizedcontrollerforthenominalsystemwithnouncertaintyiscomputedbyimposingstructuralconstraintsonthecoefficientmatricesofthecontrollergradually.Thenthedecentralizedcontrollerismodified,againgradually,tocopewiththeuncertainties.Oneachstage,avariableisfixedalternatelyattheiterationstoreducetheNMItoalinearmatrixinequality(LMI).Agivenexampleshowstheefficiencyofthismethod.

简介：中华文明源远流长，几千年来，创造了光辉灿烂的艺术和文化，可是，经历了太多的自然环境的侵蚀和战争等人为的破坏之后，很多艺术品的原作已被损毁，幸存下来的，也多是颜色陈旧灰暗，早已失去了往昔的风采，因为非常珍贵，这些艺术品往往被珍藏在博物馆，纪念馆或美术馆中，与平民百姓保持着一定的距离，怎样对艺术品原作进行有效的保护，怎样让艺术走近平民大众，成为摆在了现今人们面前的一道难题。

简介：Electricallypumpedhighpowerterahertz(THz)emittersthatoperatedaboveroomtemperatureinapulsemodewerefabricatedfromnitrogen-dopedn-type6H-SiC.Theemissionspectrahadpeakscenteredon5THzand12THz(20meVand50meV)thatwereattributedtoradiativetransitionsofexcitonsboundtonitrogendonorimpurities.Duetotherelativelydeepbindingenergiesofthenitrogendonors,above100meV,andthehighthermalconductivityoftheSiCsubstrates,theTHzoutputpowerandoperatingtemperatureweresignificantlyhigherthanpreviousdopantbasedemitters.Withpeakappliedcurrentsofafewamperes,andatopsurfaceareaof1mm2,thedeviceemittedupto0.5mWatliquidnitrogentemperature(77K),andtensofmicrowattsupto333K.ThisresultisthehighesttemperatureofTHzemissionreportedfromimpuritybasedemitters.

简介：采用物理气相传输（PVT）工艺,成功制备出3英寸高纯半绝缘（HPSI）6H-SiC单晶。依据氮在碳化硅晶格中占碳位的规律,通过生长过程温度和压力等工艺参数的优化,减少生长前沿碳空位的数量,实现了在较高碳硅比气氛下低氮含量碳化硅单晶生长的目标。二次离子质谱（SIMS）测试给出了晶体中氮及其他杂质的控制水平,证明单晶的高纯属性;非接触电阻率Mapping（CORE-MA）和电子顺磁共振（EPR）测试进一步证实其高纯半绝缘特性。

简介：Aneworganicsemiconductortartaricaciddopedsaltofemeraldinepolyaniline(PANI-C4H6O6)hasbeenobtainedbythemethodofoxidativepolymerizationofmonomericanilinewithammoniumpersulfateinacidicsolution.ThestructurewascharacterizedbyFourierTransformInfraredtechnique(FTIR)andX-raydiffraction(XRD).Thetemperaturedependencedcconductivityδdc(T)showsasemiconductorbehaviorandfollowsthequasionedimensionalvariablerangehopping(Q1D-VRH)model.Dataonδdc(T)arealsodiscussed.

简介：ThispaperfocusesontheH∞controllerdesignforlinearsystemswithtime-varyingdelaysandnormboundedparameterperturbetionsinthesystemstateandcontrol/disturbance.Ontheexistenceofdelayed/undelayedfullstatefeedbackcontrollers,wepresentasufficientconditionandgiveadesignmethodintheformofRiccatiequation.Thecontrollercannotonlystabilizethetime-delaysystem,butalsomaketheH∞normoftheclosed-loopsystembelessthanagivenbound.Thisresultpracticallygeneralizestherelatedresultsincurrentliterature.

简介：Themixedl1/H2optimizationproblemforMIMO(multipleinput-multipleoutput)discrete-timesystemsisconsidered.Thisproblemisformulatedasminimizingthel1-normofaclosed-looptransfermatrixwhilemaintainingtheH2-normofanotherclosed-looptransfermatrixatprescribedlevel.ThecontinuitypropertyoftheoptimalvalueinrespecttochangesintheH2-normconstraintisstudied.Theexistenceoftheoptimalsolutionsofmixedll/H2problemisproved.Becausethesolutionofthemixedl1/H2problemisbasedonthescaled-Qmethod,itavoidsthezerointerpolationdifficulties.Theconvergentupperandlowerboundscanbeobtainedbysolvingasequenceoffinitedimensionalnonlinearprogrammingforwhichmanyefficientnumericaloptimizationalgorithmsexist.

简介：Anultrahighvacuumchemicalvapordeposition(UHV/CVD)systemisintroduced.SiGealloysandSiGe/Simultiplequantumwells(MQWs)havebeengrownbycold-wallUHV/CVDusingdisilane(Si2H6)andgermane(GeH4)asthereactantgasesonSi(100)substrates.ThegrowthrateandGecontentsinSiGealloysarestudiedatdifferenttemperatureanddifferentgasflow.ThegrowthrateofSiGealloyisdecreasedwiththeincreaseofGeH4flowathightemperature.X-raydiffractionmeasurementshowsthatSiGe/SiMQWshavegoodcrystallinity,sharpinterfaceanduniformity.Nodislocationisfoundintheobservationoftransmissionelectronmicroscopy(TEM)ofSiGe/SiMQWs.TheaveragedeviationofthethicknessandthefractionofGeinsingleSiGealloysampleare3.31%and2.01%,respectively.

简介：Inthispaper,wedemonstratetheacetylehe(C2H2)sensorwithhighsensitivityusingahollow-corephotonicbandgapfiber(HC-PCF).ExperimentsformeasuringC2H2concentrationsingasmixtureareperformed.Usinga2m-longHC-PCFasgascell,thespectrumofacetyleneatn1+n3bandhasbeenmeasured,andtheP11-branchhasbeenselectedforthepurposeofsensing.Aminimumdetectivityof143partspermillionbyvolume(ppmv)forthesystemconfigurationisestimated.

简介：UsingdoublecrystalX-raysdiffraction(DCXRD)andatomicforcemicroscopy(AFM),theresultsofGexSi1-xgrownUHV/CVDfromSi2H6andSiH4areanalyzedandcompared.Adsorbatescanmigratetotheenergy-favoringpositionduetotheslowgrowthratefromSiH4.Inthiscase,aSibufferthatisolatestheeffectofsubstrateonepilayercouldnotbegrown,whichresultsinapitpenetratingintoepilayerandbuffer.TheFWHMis0.055°inDCXRDfromSiH4.Thepresenceofdiffractionfringesisanindicationofanexcellentcrystallinequality,TheroughnessofthesurfaceisimprovedifgrownbySi2H6:however,thecrystalqualityoftheGex2Si1-xmaterialbecameworsethanthatfromSiH4duetomuchlargergrowthratefromSi2H6.ThecontentofGeisobtainedfromDCXRD,whichindicatesthegrowthratefromSi2H6islargest,thenGeH4andthatfromSiH4isleast.

简介：<正>VishayIntertechnology,Inc.增强其通过MIL-PRF-55342认证的E/H系列精密薄膜表面贴装电阻芯片,为重要的航天应用提供"T"级失效率。这些QPL器件经认定具有TCR特性E、H、K、L和M,有12种外形尺寸。为保证VishayDaleThinFilm电阻具有确定的可靠性,这些器件进行了100%的筛选和广泛的环境测试,包括100%的A组功率调节和B组抽样测试,通过这些测试对器件进行分级,认可达到"T"级失效率。另外,这些薄膜电阻满