简介：针对无人作战飞机效能评估问题,构建了主客观结合的效能量化评估指标体系,提出了基于熵值改进层次分析法（AHP）的评估指标权重确定方法.以某型无人作战飞机为例,给出了效能评估指标值选取和量化计算过程.算例结果表明,该方法有效结合了定性和定量分析,在无人作战飞机效能评估中可行.

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：针对大多数空间谱估计方法在单快拍情况下失效的问题,本文以奇异值分解为基本手段,提出一种直接利用单快拍阵列接收数据构造长方形伪协方差矩阵的方法模型。相比于已有构造Hermitian矩阵的伪协方差矩阵构造方法,本文提出的构造方法一方面等效阵列维度更高,角度估计性能更优;另一方面,其基本构造模型兼容已有构造方法,更具一般性。理论分析和仿真试验验证了本文提出构造方法的正确性和有效性。

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：鉴于降雨引发通信衰减，对工作在C，Ku和Ka等较高频段的卫星通信产生较大影响。首先，通过ITU组织的降雨衰减预测（ITU-R）模型分析了雨衰，并得到固定频点上的雨衰；其次，根据实际应用环境及需求，提出了一种基于抛物插值的计算方法，该方法将雨衰计算推广到任意频率，且计算量小，准确度高；最后，对实例计算结果进行了分析，验证了该方法的有效性。

简介：摘要本文通过对影响城市人才吸引力的指标分析，运用熵值法建立了人才吸引力评价力的模型，为量化评价城市人才吸引力水平提供了标准化、合理化方案。首先将人才吸引力水平分解为发展前景、收入水平、环境水平三个二级指标，从三个二级指标与人才吸引力的关系，对应物理学中合力与分力的关系，于是将城市人才吸引力作为合力，发展前景、收入水平、环境水平作为互相垂直的三个分力，从而建立人才吸引力力的模型。

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：作为全球领先的电子行业精密清洗产品和服务供应商，ZESTRON在今年的上海Nepcon展会上（展台：1号展厅1E01）隆重推出最新一代用于PCBA和功率模块的中性pH值助焊剂清洗剂。

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：以卫星两行轨道根数（TLE）和简化常规j深空扰动的近似解析解（SGP4/SDP4）模型预报卫星的空间位置，并以南京地区某地面站为例，分析了单北斗、单全球定位系统（GPS）和GPS-k北斗3种卫星定位系统下南京地区的精度衰减因子（DOP）在2013-05-16-2013-05-231周时间的变化特点，以指导制定地面全球导航卫星系统（GNSS）观测方案。该分析可增强对GPS和北斗系统定位精度了解。

简介：在空间阵列测向机理和空间采样协方差矩阵分析的基础上，提出了在非最小冗余阵列设置的情况下，利用一些先验信息，采用自适应迭代的测向方法，以提高信号的测量精度。同时。本文通过计算机仿真实验证明该方法的正确性和可行性。

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