简介:In2010,theBESCollaboration[1]foundaclearenhancementintheK0K0massdistributionintheJ=ψ!ηK0K0decay.SuchanenhancementisusuallyasignatureofanL=0resonancearoundthreshold,whichinthiscasewouldcorrespondstoanh1statewithquantumnumbersIG(JPC)=0??(1+??).Thish1statewaspredictedbytheChiralUnitarytheoryintheKKinteraction.Becauseoftheconversationlaw,thisstatecanonlydecaytoK0K0channel,andcanbestudiedefficientlyintheJ=ψ!ηK0K0decay.
简介:Thebaryonspectrumandthebaryoncouplingsaretwoofthemostimportantissuesinhadronicphysicsandtheyareattractingmuchattention.Bothontheexperimentalandtheoreticalsides,thenucleonexcitedstatesbelow2.0GeVhavebeenextensivelystudied[1].However,thecurrentinformationforthepropertiesofstatesaroundorabove2.0GeVisscarce.Ontheotherhand,inthisenergyregion,manytheoreticalapproacheshavepredictedmissingNstates,whichhavenotbeensofarobserved.Hence,thestudyofthepossibleroleplayedbythe2.0GeVregionnucleonresonancesintheavailableaccuratedataistimelyandcouldshedlightintothecomplicateddynamicsthatgovernsthehighexcitednucleonspectrum.
简介:Thespectrumofisospin3/2Δ++(1232)excitedstatesisoneofthemostimportantissuesinhadronicphysicsandisattractingmuchattentionbecauseitisthemostexperimentallyaccessiblesystemcomposedofthreeidenticalvalencequarks.However,ourknowledgeontheseresonancesmainlycomesfromoldNexperimentsandisstillverypoor[1].Intheenergyregionaroundorabove2.0GeV,therearestillmanytheoreticalpredictionsofmissingΔstateswhichhavesofarnotbeenobserved.Searchingforthesemissingstatesfromotherproductionprocessesisnecessary.ApossiblenewexcellentsourceforstudyingtheseΔresonancecomprisesthe+p!K+Σ+(1385)andpp!nK+Σ+(1385)reactions,whichhaveaspecialadvantage,i:e:,thereisnocontributionsfromisospin1/2nucleonresonancesduetotheisospinandchargeconservations.
简介:Themesonproductioninnucleon-nucleoncollisionsnearthresholdhasthepotentialtogaininformationonhadronpropertiesandalsoplaysanimportantroleinexploringthebaryonspectroscopy[1].Inrecentyears,theexperimentaldatabaseonthereactionofpp!ppK+Knearthresholdhasbeenexpandedsignificantly.Inadditiontothemeasurementsofthetotalanddifferentialcrosssections,belowthethresholdoftheproductionofthe?meson,performedexperimentallywithCOSY-11andANKEdetectorsatthecoolersynchrotronCOSYinGermany,invariantmassdistributionsofvarioussubsystemshavebeenobtainedatlowenergies.Unlikeabovethethresholdoftheproductionofthe?meson,inthelowenergyregion,wedonotneedtoseparatethenon-?fromthe?contribution,andduetothefactthatthedatawerespreadoverawiderangeofK+K??invariantmasses,ithasaspecialadvantagetoinvestigatethescalarmesonsa0(980)$andf0(980)whicharedynamicallygeneratedfromtheinteractionsofK ̄K,ππ,andπηtreatedascoupledchannelsinI=0andI=1,respectively.BothofthemcouplestronglytotheK ̄Kchannel.
简介:Inthisstudy,weattempttheanalysisofthepassageflowinthecentrifugalimpellerusingFEMwith/withouttheturbulencemodel,andcomparethisresultwiththeexperimentalresult.TheturbulencemodelisthelowReynoldsk-εmodelproposedbyChien.WeusetheGSMACmethodfortheReynoldsaveragedNavier-Stokesequations,theEulerexplicitmethodforthetransportequationsoftheturbulentkineticenergyandthedissipationrate.AllequationsarediscretizedbytheGalerkin'smethod.Atthemidpassageofthecentrifugalimpeller,thepassagewisevelocitycomponenttendstoincreaseinthepressure-to-suctiondirection,andtheothercomponenttowardthepressuresurfacetendstobelargeintheregionofthemiddleblade-to-bladetothehubside.Thetipleakagesappeararoundtheregionofthemiddleblade-to-bladenearthecasingtogetherwiththesecondaryflowtowardthesuctionsurface.Thesephenomenacorrespondwiththeexperimentalresult,qualitatively.
简介:Mixedalcoholisofgreatpromiseasoctaneimproverinautomotivefuel,andhopefultoreplacetheMTBEtoreducetheenvironmentalpollution,Inthisfield,alkali-promtedmolybdenum-basedcatalystshavebeengivenspecialinterestbecauseoftheirexcellentsulfur-toleranceforsynthesisofmixedalcoholfromCO+H2,Itwasreportedthatthecoblatisafavorablepromoterforenhancingalcoholproduction,especiallyforimprovingtheselectivityforC2+alcohol[1-3],moreover,stronginteractionbetweenConandMoisinfavorofmixedalcoholsynthesis[4].Recently,weprparedakindofK-Co-Moultrafineparticlesbysol-gelmethodanditshowsmuchsmallerparticlesizebuthigheractivtyandselectivitytowardalcoholformationthantheonepreparedbyconventionalmethod[5],TheaimofthepresentworkistoresearchthemicostructuresoftheMoandCospeciesintheK-Co-Mosamplespreparedbydifferentmethod.
简介:Ingasturbineengines,laminar-turbulenttransitionoccurs.However,generally,theturbulencemodelstodescribesuchtransitionresultsintooearlyandtooshorttransition.Combiningaturbulencemodelwithadescriptionofintermittency,i.e.thefractionoftimetheflowisturbulentduringthetransitionphase,canimproveit.Bylettinggrowtheintermittencyfromzerotounity,startandevolutionoftransitioncanbeimposed.Inthispaper,amethodwhereadynamicequationofintermittencycombiningwithatwo-equationk-ωturbulencemodelisdescribed.Thisintermittencyfactorisapremultiplicatoroftheturbulentviscositycomputedbytheturbulencemodel.FollowingasuggestionbyMenteretal.[1],thestartoftransitioniscomputedbasedonlocalvariables.
简介:对将运行于日-地L1点的太阳观测器进行了热设计,重点论述了日-地L1点的轨道外热流计算和Lymanα日冕仪(LACI)反射镜M2光阱、Lymanα日冕成像仪(LADI)滤光片组件、CCD组件、电箱、观测器主体等部分的热设计方案。通过在探测器对日面设置集热板,将观测器的主动加热功耗降低了73%;选用预埋热管的设计方案解决了对日定向观测导致的框架温差问题。仿真分析结果表明,在对日高温工作、对日低温工作、低温存储、轨道转移等4个极端工况下,观测器各组件温度均满足指标要求。该热设计方案以较低的加热功耗,解决了太阳观测器在轨工作阶段的散热、轨道转移阶段的保温等问题,满足CCD焦面工作温度<-50℃的要求。
简介:Thenextgenerationofadvancedlightsourcesrequiresphotonswithlargeaveragefluxandhighbrightness,whichneedsadvancedelectrongunmatchedwithexcellentphotocathodematerials.K2CsSbphotocathodehastheadvantagesofhighquantumefficiency,longlifetimeandinstantaneousresponse.ThisstudyintroducesthedesignofasetofK2CsSbphotocathodepreparationsystemsanddetailedpreparationprocessofK2CsSbphotocathodes,includingsequentialdepositionprocessandco-depositionprocess,andfinallydevelopsaK2CsSbphotocathode.Theinfluenceoflaserpoweronthequantumefficiencyisalsoinvestigated.
简介:Inordertodeepentheunderstandingoftherelationshipbetweenfundamentalproperties(including:microstructureandcomposition)andphotocatalyticperformance,fourbismuthatecompounds,including:LiBiO3,NaBiO3,KBiO3,andAgBiO3,areregardedasresearchexamplesinthepresentwork,becausetheyhaveparticularcrystalstructuresandsimilarcompositions.Usingdensityfunctionaltheorycalculations,theirstructural,electronic,andopticalpropertiesareinvestigatedandcomparedsystematically.Firstofall,thecalculatedresultsofcrystalstructuresandopticalpropertiesareinagreementwithavailablepublishedexperimentaldata.Basedonthecalculatedresults,itisfoundthatthetunneledorlayeredmicro-structuralpropertiesleadtothestrongerinteractionbetweenbismuthandoxygen,andtheweakerinteractionbetweenalkaline-earthmetaland[BiO6]octahedron,resultinginthefeatureofmulti-bandgapsinthecasesofLiBiO3,NaBiO3,andKBiO3.ThisconclusionissupportedbythecaseofAgBiO3,inwhichthefeatureofmulti-bandgapsdisappears,duetothestrongerinteractionbetweenthenoblemetaland[BiO6]octahedron.Thesepropertieshavesignificantadvantagesinthephotocatalyticperformance:absorbinglowenergyphotons,rapidlytransferringenergycarriers.Furthermore,thefeaturesofelectronicstructuresofbismuthatecompoundsarewellreflectedbytheabsorptionspectra,whichcouldbeconfirmedbyexperimentalmeasurementsinpractice.Combinedwiththecalculatedresults,itcouldbeconsideredthatthecrystalstructuresandcompositionsofthephotocatalystdeterminetheelectronicstructuresandopticalproperties,andsubsequentlydeterminethecorrespondingphotocatalyticperformance.Thus,anovelBi-basedphotocatalystdrivenbyvisible-lightcouldbedesignedbyutilizingspecificcompositionstoformfavorableelectronicstructuresorspecificmicro-structurestoformabeneficialchannelforenergycarriers.
简介:Theground-stateandthermodynamicpropertiesofquantummixed-spinchainsof1/2-1/2-1-1and3/2-3/2-1-1areinvestigatedbyaquantumMonteCarlosimulationwiththeloop-clusteralgorithm.For1/2-1/2-1-1chain,wefindithastwophasesseparatedbyanenergy-gapvanishingpointintheground-state.For3/2-3/2-1-1chain,thenumericalresultsshowtwoenergy-gapvanishingpointsisolatedbydifferentphasesinitsground-state.Ourcalculationsindicatethatallthesegroundstatephasescanbeunderstoodbymeansofvalence-bond-solidpicture,andthethermodynamicbehavioratfinitetemperaturesiscontinuousasafunctionofparameterα=J2/J1.
简介:Thereisagrowingsupportforthelowlyingscalarmesonsf0(500),f0(980),a0(980),and(800)tobegenerateddynamicallyfromtheinteractionofpseudoscalarmesons,whilethecaseofthenextsetofscalarresonancesathigherenergies,f0(1370),f0(1710),K0(1430)ismoreaquestionofdebate.Soisthecaseofthetensorresonancesf2(1270),f′2(1525),K2(1430).AnewperspectiveonthesestateshasbeenofferedinRef.[1]wherethef0(1370)andf2(1270)resonancesareshowntobegeneratedfromtheinteractionprovidedbythelocalhiddengaugeLagrangiansimplementingunitarization.Itisshownthattheideaofthenatureofthesestatesasvectormeson-vectormesoncompositestateshasbeentestedinmanyreactions.Yet,thepermanentdiscussionoftheissuedemandsextrachecksforotherobservablesand,inthissense,theweakdecaysbringanewsourceofvaluableinformationthatshouldservetotestdifferentmodels.