简介：Forthepurposeofsolvingoptimalcontrolproblemofawall-crawlingmobilerobotworkingonsphericalcontainers,weproposetheHamel'sformalismforPontryaginMaximumPrinciple,whichgivesageneralframeworkfortheoptimalcontrolofamechanicalsystemwithvelocityconstraints,especiallynonholonomicconstraints.Theeffectivenessoftheproposedframeworkisshownbythesimulationsfortheaboveproblem.

简介：AnartificialdisturbanceisintroducedintotheboundarylayeroveraflatplatetoinvestigatetheeffectonthetransitionprocessintheMach6.5windtunnelatPekingUniversity.Alinearstabilitytheory(LST)isutilizedtopredicttheevolutionoftheeigenmodes,andthefrequencyoftheartificialdisturbanceischosenaccordingtotheLSTresults.Theartificialdisturbanceisgeneratedbyglowingdischargeonthesurfaceoftheplateclosetotheleadingedge.TheRayleigh-scatteringvisualizationandparticleimagevelocimetry(PIV)measurementsareperformed.Bycomparingtheexperimentalresultswithartificialdisturbanceswiththoseunderthenaturalcondition(withoutartificialdisturbances),thepresentpapershowsthatthesecond-modeinstabilitywavesaresignificantlystimulatedbytheartificialdisturbances,andtheboundarylayertransitioniseffectivelytriggered.

简介：Graphene,definedasasingleatomicplaneofgraphite,isasemimetalwithasmalloverlapbetweenthevalenceandconductionbands.Thestackingofgrapheneuptoseveralatomiclayerscanleadtodiversephysicalproperties,dependingonthestackingmethod.Bilayergrapheneisalsoasemimetal,adoptingtheAB-stacked(orBernal-stacked)structureortherareAA-stackedstructure.Trilayerorfew-layergraphene(FLG)canbesemimetalsorsemiconductors,dependingonwhethertheyadoptBernal(ABA)stackingorrhoinbohedral(ABC)stacking.

简介：Inthispaper,aerodynamicactuationcharacteristicsofradio-frequency(RF)dischargeplasmaarestudiedandamethodisproposedforshockwavecontrolbasedonRFdischarge.Underthestaticcondition,aRFdiffuseglowdischargecanbeobserved;underthesupersonicinflow,theplasmaisblowndownstreambutremainscontinuousandstable.Time-resolvedschlierenisusedforflowfieldvisualization.ItisfoundthatRFdischargenotonlyleadstocontinuousenergydepositionontheelectrodesurfacebutalsoinducesacompressionwave.Underthesupersonicinflowcondition,aweakobliqueshockwaveisinducedbydischarge.Experimentalresultsoftheshockwavecontrolindicatethattheappliedactuationcandispersethebottomstructureoftheramp-inducedobliqueshockwave,whichisalsoobservedintheextractedshockwavestructureafterimageprocessing.Moreimportantly,thiscontroleffectcanbemaintainedsteadilyduetothecontinuoushigh-frequency(MHz)discharge.Finally,correlationsforschlierenimagesandnumericalsimulationsareemployedtofurtherexploretheflowcontrolmechanism.Itisobservedthatthevortexintheboundarylayerincreasesaftertheapplicationofactuation,meaningthattheboundarylayerinthedownstreamoftheactuationpositionisthickened.Thisisequivalenttocoveringalayeroflow-densitysmoothwallaroundthecompressioncornerandontherampsurface,therebyweakeningthecompressibilityatthecompressioncorner.OurresultsdemonstratetheabilityofRFplasmaaerodynamicactuationtocontrolthesupersonicairflow.

简介：Tuningthecoloroutputofrare-earthiondopedluminescentnanomaterialshasimportantscientificsignificanceforfurtherextendingapplicationsincolordisplays,lasersources,optoelectronicdevices,andbiolabeling.Inpreviousstudies,pre-designedphasemodulationofthefemtosecondlaserfieldhasbeenproventobeeffectiveintuningtheluminescenceofdopedrare-earthions.Owingtothecomplexlight–matterinteractionintheactualexperiment,thedynamicrangeandoptimalefficiencyforcolortuningcannotbedeterminedwiththepre-designedphasemodulation.Thisarticlesharesthedevelopmentofanadaptivefemtosecondpulseshapingmethodbasedonageneticalgorithm,anditsusetomanipulatethegreenandredluminescencetuninginanEr3+-dopedglassceramicunder800-nmfemtosecondlaserfieldexcitationforthefirsttime.ExperimentalresultsshowthattheintensityratioofthegreenandredUCluminescenceofthedopedEr3+ionscanbeeitherincreasedordecreasedconvenientlybythephase-shapedfemtosecondlaserfieldwithanoptimalfeedbackcontrol.Thephysicalcontrolmechanismsforthecolortuningarealsoexplainedindetail.Thisarticledemonstratesthepotentialapplicationsoftheadaptivefemtosecondpulseshapingtechniqueincontrollingthecoloroutputofdopedrare-earthions.