简介:高频信号传输基板中低损耗积层材料的半加成法Semi-additiveprocessforlowlossbuildupmaterialinhigh-frequencysignaltransmissionsubstrates半加成法(SAP)已广泛应用于超细电路制作,需要良好的介质材料,应有良好的加工性、耐化学性、尺寸稳定性和足够的机械强度,以及为高速信号传输必需具有优良的电气性能。文章介绍一种新的SAP系统,成功地应用于环氧树脂、氰酸酯型介质材料,取得了非常低的介质表面粗糙度(Ra=80±18nm)和高粘附力(658±18克力/厘米)水平,达到积层介质层表面光滑同时有高的电镀铜层附着力,促进高频信号完整性。
简介:Anoutsourcedatabaseisadatabaseserviceprovidedbycloudcomputingcompanies.Usingtheoutsourcedatabasecanreducethehardwareandsoftware'scostandalsogetmoreefficientandreliabledataprocessingcapacity.However,theoutsourcedatabasestillhassomechallenges.Iftheserviceproviderdoesnothavesufficientconfidence,thereisthepossibilityofdataleakage.Thedatamayhasuser'sprivacy,sodataleakagemaycausedataprivacyleak.Basedonthisfactor,toprotecttheprivacyofdataintheoutsourcedatabasebecomesveryimportant.Inthepast,scholarshaveproposedk-anonymitytoprotectdataprivacyinthedatabase.Itletsdatabecomeanonymoustoavoiddataprivacyleak.Butk-anonymityhassomeproblems,itisirreversible,andeasiertobeattackedbyhomogeneityattackandbackgroundknowledgeattack.Lateron,scholarshaveproposedsomestudiestosolvehomogeneityattackandbackgroundknowledgeattack.Buttheirstudiesstillcannotrecoverbacktotheoriginaldata.Inthispaper,weproposeadataanonymitymethod.Itcanbereversibleandalsopreventthosetwoattacks.Ourstudyisbasedontheproposedr-transform.Itcanbeusedonthenumerictypeofattributesintheoutsourcedatabase.Intheexperiment,wediscussedthetimerequiredtoanonymizeandrecoverdata.Furthermore,weinvestigatedthedefenseagainsthomogeneousattackandbackgroundknowledgeattack.Attheend,wesummarizedtheproposedmethodandfutureresearches.
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.
简介:A2D-directionofarrivalestimation(DOAE)formultiinputandmulti-output(MIMO)radarusingimprovedmultipletemporal-spatialsubspacesinestimatingsignalparametersviarotationalinvariancetechniquesmethod(TS-ESPRIT)isintroduced.InordertorealizetheimprovedTS-ESPRIT,theproposedalgorithmdividestheplanararrayintomultipleuniformsub-planararrayswithcommonreferencepointtogetaunifiedphaseshiftsmeasurementpointforallsub-arrays.TheTS-ESPRITisappliedtoeachsub-arrayseparately,andinthesametimewiththeotherstorealizetheparallellytemporalandspatialprocessing,sothatitreducesthenon-linearityeffectofmodelanddecreasesthecomputationaltime.Then,thetimedifferenceofarrival(TDOA)techniqueisappliedtocombinethemultiplesub-arraysinordertoformtheimprovedTS-ESPRIT.Itisfoundthattheproposedmethodachieveshighaccuracyatalowsignaltonoiseratio(SNR)withlowcomputationalcomplexity,leadingtoenhancementoftheestimatorsperformance.
简介:UnipolarresistiveswitchingbehaviorsoftheZnOandAl2O3/ZnOfilmsfabricatedonflexiblesubstratesbypulselaserdepositionwerestudiedinthispaper.Thefilmsweredepositedatroomtemperaturewithoutpost-annealingtreatmentduringtheprocess.XraydiffractionresultsindicatedthatZnOfilmhasadominantpeakat(002).ScanningelectronmicroscopyobservationshowedacolumnargrainstructureoftheZnOfilmtothesubstrate.ThebilayerdeviceofAl2O3/ZnOfilmshadstableresistiveswitchingbehaviorswithagoodenduranceperformanceofmorethan200cycles,highresistiveswitchingratioofover103atareadvoltageof0.1V,whichisbetterthanthatofthesingleoxidelayerdeviceofZnOfilm.Apossibleresistiveswitchingfilamentarymodewasdemonstratedinthispaper.TheconductionmechanismsofhighandlowresistancestatescanbeexplainedbyspacechargelimitedconductionandOhmic’sbehaviors.Theenduranceofthebilayer(BL)devicewasnotdegradeduponbendingcycles,whichindicatesthepotentialoftheflexibleresistiveswitchingrandomaccessmemoryapplications.