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.
简介:Reversibledatahidingtechniquesarecapableofreconstructingtheoriginalcoverimagefromstego-images.Recently,manyresearchershavefocusedonreversibledatahidingtoprotectintellectualpropertyrights.Inthispaper,wecombinereversibledatahidingwiththechaoticHénonmapasanencryptiontechniquetoachieveanacceptablelevelofconfidentialityincloudcomputingenvironments.And,Haardigitalwavelettransformation(HDWT)isalsoappliedtoconvertanimagefromaspatialdomainintoafrequencydomain.Andthenthedecimalofcoefficientsandintegerofhighfrequencybandaremodifiedforhidingsecretbits.Finally,themodifiedcoefficientsareinverselytransformedtostego-images.
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:Electricallypumpedhighpowerterahertz(THz)emittersthatoperatedaboveroomtemperatureinapulsemodewerefabricatedfromnitrogen-dopedn-type6H-SiC.Theemissionspectrahadpeakscenteredon5THzand12THz(20meVand50meV)thatwereattributedtoradiativetransitionsofexcitonsboundtonitrogendonorimpurities.Duetotherelativelydeepbindingenergiesofthenitrogendonors,above100meV,andthehighthermalconductivityoftheSiCsubstrates,theTHzoutputpowerandoperatingtemperatureweresignificantlyhigherthanpreviousdopantbasedemitters.Withpeakappliedcurrentsofafewamperes,andatopsurfaceareaof1mm2,thedeviceemittedupto0.5mWatliquidnitrogentemperature(77K),andtensofmicrowattsupto333K.ThisresultisthehighesttemperatureofTHzemissionreportedfromimpuritybasedemitters.
简介:Aneworganicsemiconductortartaricaciddopedsaltofemeraldinepolyaniline(PANI-C4H6O6)hasbeenobtainedbythemethodofoxidativepolymerizationofmonomericanilinewithammoniumpersulfateinacidicsolution.ThestructurewascharacterizedbyFourierTransformInfraredtechnique(FTIR)andX-raydiffraction(XRD).Thetemperaturedependencedcconductivityδdc(T)showsasemiconductorbehaviorandfollowsthequasionedimensionalvariablerangehopping(Q1D-VRH)model.Dataonδdc(T)arealsodiscussed.
简介:在数字视频应用产业链的快速发展中,面对视频应用不断向高清晰度、高帧率、高压缩率方向发展的趋势,当前主流的视频压缩标准协议H.264(AVe)的局限性不断凸显。同时,面向更高清晰度、更高帧率、更高压缩率视频应用的HEVC(H.265)协议标准应运而生。本文重点分析了下一代视频压缩协议标准HEVC(H.265)的技术亮点,并对其在未来应用中将给整个产业带来的深刻变化予以展望。
简介:在这篇文章,在包有损耗的网络上开始为一个H.264流录像的计划设计的一个时间空间的processing以后错误隐匿算法被介绍了。它瞄准优化恢复录像和常规客观度量标准的主观质量,山峰signal-to-noise比率(PSNR),也在低延期和计算复杂性的限制下面,它对即时应用程序和便携式的设备批评限制了资源。明确地,它拿进运动的考虑物理性质完成更有意义的感性的录像质量。进一步,一条内容适应的双线性的空间插值途径和隐匿接近的一个时间的错误基于质地和运动活动分析在一个统一边界火柴标准下面被联合。广泛的实验证明了这个建议不仅在更好的重建的结果,客观地并且主观上与在到不同录像的更好的坚韧性的参考软件模型基准,而且结果定序比。
简介:由于数字高清晰度电视(HDTV)技术在全世界范围内的快速发展和普及,SonyHDCAM格式的系列产品和相应的系统以其完美的画质、稳定的表现和方便灵活的操作,很快就得到了众多的电视制作人、电视台以及电影导演的青睐,因此,近来愈来愈多的采用HDCAM格式制作的优秀的高清晰度电视片、商业广告和电影层出不穷。为了减少节目制作中的差错,如何才能进行既方便又快速的节目审看;为了提高节目的制作效率,如何才能在普通的非线性编辑系统中完成EDL清单的制作;为了节约投资成本,是否可以用普通的计算机显示器替代专业的视频监视器。以上这些令所有HDTV节目创作人员十分头疼的难题,都将随着Sony最新的J-H系列HDC
简介:ThispaperfocusesontheH∞controllerdesignforlinearsystemswithtime-varyingdelaysandnormboundedparameterperturbetionsinthesystemstateandcontrol/disturbance.Ontheexistenceofdelayed/undelayedfullstatefeedbackcontrollers,wepresentasufficientconditionandgiveadesignmethodintheformofRiccatiequation.Thecontrollercannotonlystabilizethetime-delaysystem,butalsomaketheH∞normoftheclosed-loopsystembelessthanagivenbound.Thisresultpracticallygeneralizestherelatedresultsincurrentliterature.