简介：Inthispaper,theone-dimensional(1D)particle-in-cell(PIC)simulationisusedtostudythemodulationinstabilityofionacousticwavesinelectron–ionplasmas.TheionacousticwaveisdescribedbyusinganonlinearSchr¨odingerequation(NLSE)derivedfromthereductiveperturbationmethod.Formournumericalsimulations,weareabletodemonstratethat,afterthemodulation,theamplitudeincreasessteadilyovertime.Furthermore,bycomparingthenumericalresultswithtraditionalanalyticalsolutions,weacquiretheapplicationscopeforthereductiveperturbationmethodtoobtaintheNLSE.Wealsofindthismethodcanalsobeextendedtootherfieldssuchasfluiddynamics,nonlinearoptics,solidstatephysics,andtheBose–Einsteincondensatetovalidatetheapplicationscopeoftheresultsfromthetraditionalperturbationmethod.

简介：Low-frequencychorusemissionshaverecentlyattractedmuchattentionduetothesuggestionthattheymayplayimportantrolesinthedynamicsoftheVanAllenBelts.However,themechanism(s)generatingtheselow-frequencychorusemissionshavenotbeenwellunderstood.Inthisletter,wereportaninterestingcaseinwhichbackgroundplasmadensityloweredthelowercutofffrequencyofchorusemissionsfromabove0.1fce(typicalordinarychorus)to0.02fce(extremelylow-frequencychorus).Thoseextremelylow-frequencychoruswaveswereobservedinaratherdenseplasma,wherethenumberdensityNewasfoundtobeseveraltimeslargerthanhasbeenassociatedwithobservationsofordinarychoruswaves.Forsuprathermalelectronswhosefreeenergyissuppliedbyanisotropictemperatures,lineargrowthrates(calculatedusingin-situplasmaparametersmeasuredbytheVanAllenProbes)showthatwhistlermodeinstabilitycanoccuratfrequenciesbelow0.1fcewhenthebackgroundplasmadensityNeincreases.EspeciallywhenNereaches90cm^-3ormore,thelowestunstablefrequencycanextendto0.02fceorevenless,whichisconsistentwithsatelliteobservations.Therefore,ourresultsdemonstratethatadensebackgroundplasmacouldplayanessentialroleintheexcitationofextremelylowfrequencychoruswavesbycontrollingthewavegrowthrates.

简介：汽车门板在制造工艺过程中,门板表面的颗粒污染物会降低产品质量,如果在蒙皮粘合前进行等离子清洗,则可有效去除这些污染物。本文介绍了等离子原理及工作过程,并对清洗前后效果进行了对比。

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：Inthispaper,aone-dimensionparticle-in-cell(PIC)code(EDIPIC)isemployedtosimulatetheparallel-plateionextractionprocessunderanexternallyappliedelectrostaticfield,focusingontheanalysisoftheinflueneeoftheinitialelectrontemperatureontheextractedionfluxestothemetalplatesduringtheionextractionprocess.Comparedwithpreviouslypublishedresults,theplasmaoscillationsonatimescaleoftheelectronplasmaperiod,andtheexcitationoftheionacousticrarefactionwavesresultingfromtheplasmaoscillationsoriginatingfromboththenegativeandpositiveelectrodes,arestudiedforthefirsttime.Themodelingresultsshowthatboththenegativeandpositiveextractorscancollectionsduetotheplasmaoscillationsandthepropagationoftheionacousticrarefactionwaves.Withtheincreaseoftheinitialelectrontemperatureachievedbykeepingotherparametersunchanged,ontheonehand,boththeionspeedandfluxtothenegativeandpositiveplatesincrease,whichleadstoasignificantdecreaseoftheionextractiontime,whileontheotherhand,theionfluxtothepositiveplateaftertheformationofaChild-Langmuirsheathismuchmoresensitivetoanincreaseoftheinitialelectrontemperaturethanthattothenegativeplate.ThePICsimulationresultsprovideadeeperphysicalunderstandingoftheinfluenceoftheinitialelectrontemperatureonthecharacteristicsoftheentireionextractionprocessinadecayingplasma.

简介：Sinteredsiliconcarbide(SiC)wasetchedbyadielectricbarrierdischargesource.Ahighvoltagebipolarpulsewasusedwithheliumgasfortheplasmageneration.OnestablefilamentplasmawasgeneratedandcouldbeusedforSiCetching.Astheprocessinggas(NF3)mixingrateincreased,thewidthanddepthoftheetchingprofilebecamenarroweranddeeper.ThedifferentiatedV-QLissajousmethodwasusedformeasuringthecapacitances(Ceq)oftheelectrodeaftertheplasmaturnedon.ThewidthoftheetchingprofilewasproportionaltoCeq.Asthecurrentpeakvalue/smxofthesubstratecurrentincreased,thevolumeremovalrateofSiCincreased.Theetchdepthwasproportionaltotheratioof/smxtoCeq.Additionally,becauseofthedifferentcharacteristicsoftheplasmadisksonSiCsubstratebythevoltagepolarity,theetchingprofilewasunstable.However,inhighNF3mixingprocess,theetchingprofilebecamestableanddeeper.

简介：Aone-dimensional(1D)fluidsimulationofdualfrequencydischargeinheliumgasatatmosphericpressureiscarriedouttoinvestigatetheroleofthesecondaryelectronemissiononthesurfacesoftheelectrodes.Inthesimulation,electrons,ionsofHe+andHe2+,metastableatomsofHe*andmetastablemoleculesofHe*2areincluded.Itisfoundthatthesecondaryelectronemissioncoefficientsignificantlyinfluencesplasmadensityandelectricfieldaswellaselectronheatingmechanismsandionizationrate.TheparticledensitiesincreasewithincreasingSEEcoefficientfrom0to0.3aswellasthesheath’selectricfieldandelectronsource.Moreover,theSEEcoefficientalsoinfluencestheelectronheatingmechanismandelectronpowerdissipationintheplasmaandbothofthemincreasewithincreasingSEEcoefficientwithintherangefrom0to0.3asaresultofincreasingofelectrondensity.

简介：Itisaverydifficulttasktodevelopamethodofreducingturbulentboundarylayerdrag.However,inrecentyears,plasmaflowcontroltechnologyhasdemonstratedhugepotentialinfrictiondragreduction.Tofurtherinvestigatethisissue,asmoothplatemodelwasdesignedasatestingobjectarrangedwithabidirectionaldielectric-barrier-discharge(DBD)plasmaactuator.Inaddition,measurementofskinfrictiondragwasachievedbyapplyinghotwireanemometrytoobtainthevelocitydistributionoftheturbulentboundarylayer.AmethodofquantifyingthefrictiondrageffectwasadoptedbasedontheSpaldingformulafittedwiththeexperimentdata.Whenplasmaactuationwasconducted,avelocitydefectoccurredatthetwomeasuringpositions,comparedwiththenoplasmacontrolcondition;thismeansthattheDBDplasmaactuationcouldreducethedragsuccessfullyinthedownstreamoftheactuator.Moreover,dragreductioncausedbybackwardactuationwasslightlymoreefficientthanthatcausedbyforwardactuation.Withanincreasingdistancefromplasmaactuation,thedrag-reductioneffectcouldbecomeweaker.Experimentalresultsalsoshowthattheimprovementofdrag-reductionefficiencyusingaDBDplasmaactuatorcanachieveabout8.78%inthelocalregionoftheexperimentalflatmodel.

简介：CO2adsorptiononthesurfaceofhydrotalcite-derivedmixedoxidecatalystswasinvestigatedunderlowpressureglowdischargeplasmainopercindoconditionsviaFT-IRspectroscopy.Nickelcatalystswerepromotedwithvarioustransitionmetalspecies(Ce,Fe,La,Zr)toinfluencetheirphysico-chemicalproperties.FeandZrspeciesweresuccessfullyincorporatedintohydrotalcitebrucitelayers.AftercalcinationformedasinglephasewithNi(Mg,A1)Omixedoxide,whileLaandCespeciesformedseparatephases.ThishadaconsequenceinthedistributionofsurfacebasicsitesaswellasintheaffinitytoCOproduceduponCO2dissociationinplasma.Plasmatreatmentactivatedthesurfaceofpreparedmaterialsandchangedtheirpropertiesviathegenerationofstrongbasicsitesassociatedwithlowcoordinatedsurfaceoxygenanions.Moreover,theCO2adsorptioncapacityofpreparedmaterialsincreasedafterplasmatreatment.

简介：Panaxnotoginsengsaponins(PNS)arethemajorcomponentsofPanaxnotoginseng,withmultiplepharmacologicalactivitiesbutpoororalbioavailability.PNScouldbemetabolizedbygutmicrobiotainvitro,whiletheexactroleofgutmicrobiotaofPNSmetabolisminvivoremainspoorlyunderstood.Inthisstudy,pseudogerm-freeratmodelswereconstructedbyusingbroad-spectrumantibioticstovalidatethegutmicrobiota-mediatedtransformationofPNSinvivo.Moreover,ahighperformanceliquidchromatography-electrosprayionizationtandemmassspectrometry(HPLC-ESI-MS/MS)wasdevelopedforquantitativeanalysisoffourmetabolitesofPNS,includingginsenosideF1(GF1),ginsenosideRh2(GRh2),ginsenosidecompoundK(GCK)andprotopanaxatriol(PPT).Theresultsshowedthatthefourmetabolitescouldbedetectedinthecontrolratplasma,whiletheycouldnotbedeterminedinpseudogerm-freeratplasma.TheresultsimpliedthatPNScouldnotbebiotransformedeffectivelywhengutmicrobiotawasdisrupted.Inconclusion,gutmicrobiotaplaysanimportantroleinbiotransformationofPNSintometabolitesinvivo.

简介：Indouble-pulselaser-inducedbreakdownspectroscopy(DP-LIBS),thecollinearfemtoseconddouble-pulselaserconfigurationisexperimentallyinvestigatedwithdifferentinitialsampletemperaturesusingaTi:sapphirelaser.Theglasssampleisablatedtoproducetheplasmaspectroscopy.Duringtheexperiment,thedetectedspectrallinesincludetwoNa(I)lines(589.0nmand589.6nm)andoneCa(I)lineatthewavelengthof585.7nm.Theemissionlinesaremeasuredatroomtemperature(22°C)andthreehigherinitialsampletemperatures(Ts=100°C,200°C,and250°C).Theinter-pulsedelaytimerangesfrom-250psto250ps.Theinter-pulsedelaytimeandthesampletemperaturestronglyinfluencethespectralintensity,andthespectralintensitycanbesignificantlyenhancedbyincreasingthesampletemperatureandselectingtheoptimizedinter-pulsetime.Forthesameinter-pulsetimeof0ps(single-pulseLIBS),theenhancementratioisapproximately2.5atTs=200°CcomparedwiththatobtainedatTs=22°C.Forthesameinter-pulsetimeof150ps,theenhancementratiocanbeupto4atTs=200°CcomparedwiththatobtainedatTs=22°C.Thecombinedenhancementeffectsofthedifferentinitialsampletemperaturesandthedouble-pulseconfigurationinfemtosecondLIBSaremuchstrongerthanthatofthedifferentinitialsampletemperaturesorthedouble-pulseconfigurationonly.