简介:Itisfoundthatthereisanupper-limitcriticalpowerforself-guidedpropagationofintenselasersinplasmainadditiontothewell-knownlower-limitcriticalpowersetbytherelativisticeffect.Abovethisupper-limitcriticalpower,thelaserpulseexperiencesdefocusingduetoexpulsionoflocalplasmaelectronsbythetransverseponderomotiveforce.Associatedwiththeupper-limitpower,alower-limitcriticalplasmadensityisalsofoundforagivenlaserspotsize,belowwhichself-focusingdoesnotoccurforanylaserpower.Boththeupper-limitpowerandthelower-limitdensityarederivedtheoreticallyandverifiedbytwo-dimensionalparticle-in-cellsimulations.Thepresentstudyprovidesnewguidanceforexperimentaldesigns,whereself-guidedpropagationoflasersisessential.
简介:WithintheframeworkoftheUsdpf(16)interactingbosonmodel(IBM),theeffectsofstrongcorrelationsofthedipole(p--boson)andtheoctupole(f--boson)degreeoffreedomonthepositive-paritystatesofeven-evennucleiinSU(3)limitarediscussed.Itisshownthatconfigurationsofanevennumberofmanyp-andf-bosonscannotonlybeincorporatedintotheusuallow-lyingcollectiverotationalbands,suchasthegroundstateband,β-andγ-vibrationalbands,butalsonaturallyformtheKπ=1+,3+rotationalbands,etc.TheseresultsaresimilartothatofUsdg(15)-IBMandinagreementwellwiththeexperimentaldataofthe17672Hf104nucleus.Besides,severalintrabandE2transitionprobabilitiesaregiven,whichareconsistentwiththatofUsd(6)-IBM.
简介:Thetargetofthelargenegativeionsourcebasedonneutralbeaminjection(N-NBI)istoproduceneutralbeamcurrentof22Aandbeampowerof10MWat500keVwithdurationtimeof10s.Sinceitwassuccessfullyoperatedin1996,the5.3MWneutralbeampowerat380keVwithdurationtimeof3shasbeenachieved.Inrecentyearsimprovingandenhancingthebeampoweraregoingon.Severalreasonssuchasplasmanon-uniformity,higherbeamdensityattheupperregioninthebeamprofile,
简介:WithvonMisesyieldcriterion,theloadingrangeofNetSectionCollapse(NSC)Criteriaisextendedfromcombinedtensionandbendingloadingstocombinedbending,torsionandinternalpressureloadings.AnewtheoreticalanalyzingmethodofplasticlimitloadforpressurepipewithincompleteweldingdefectsbasedontheextendedNSCCriteriaispresentedandthecorrelativeformulasarededuced,theinfluencesofpipecurvature,circumferentiallengthanddepthofincompleteweldingdefectsontheplasticlimitloadofpressurepipeareconsideredaswellinthismethod.Meanwhile,accordingtotheorthogonalexperimentaldesignmethod,theplasticlimitloadsarecalculatedbythefiniteelementmethodandcomparedwiththetheoreticalvalues.Theresultsshowthattheexpressionsofplasticlimitloadofpressurepipewithincompleteweldingdefectsunderbending,torsionandinternalpressurebasedonextendedNSCcriteriaarereliable.Thestudyprovidesanimportanttheoreticalbasisfortheestablishmentofsafetyassessmentmeasuretowardspressurepipewithincompleteweldingdefects.