简介:
简介:Let{N(t),t≥0}bethenonhomogeneousPoissonprocesswithcumulativeintensityparameterΛ(t),{δt,t≥0}theageprocess,and{yi,t≥0)theresiduallifetimeprocess.Inthepresentpapertheexpressionsofn-dimensionalsurvivaldistributionfunctionsoftheprocesses{δi}and{yi},andtheirLebesguedecompositionsarederived.
简介:Theexistenceanduniquenessofpositivesteadystatesfortheage-structuredMSEIRepidemicmodelwithage-dependenttransmissioncoefficientisconsidered.Thresholdresultsfortheexistenceofendemicstatesareestablished;undercertainconditions,uniquenessisalsoshown.
简介:ThisarticlefocusesonthestudyofallagestructuredSEIRSepidemicmodelwithavaccinationprogramwhenthetotalpopulationsizeisnotkeptatconstant.WefirstgivetheexplicitexpressionofthereproductionnumberR(ψ,^↑λ)inthepresenceofvaccine(^↑λistheexponentofgrowthoftotalpopulation),andshowthattheinfection-freesteadystateislh~earlystableifR(ψ,^↑λ)<1andunstableifR(ψ,^↑λ)>1,thenweapplythetheoreticalresultstovaccinationpoliciestodeterminetheoptimalageoragesatwhichanindividualshouldbevaccinated.Itisshownthattheoptilnalstrategycanbeeitherone-ortwo-agestrategies.
简介:Fatiguepropertiesofage-hardenedAlalloy2017-T4underultrasonicloadingfrequency(20kHz)wereinvestigatedandcomparedwiththeresultsunderconventionalloadingofrotatingbending(50Hz).Thegrowthofacrackretardedatabout500μminsurfacelengthunderultrasonicloading,whileatabout20μmunderrotatingbending.Althoughstriationsbeingatypicalfracturemechanismwereobservedunderconventionalloading,mostoffracturesurfacewascoveredwithmanyfacetsunderultrasonicloading.Thesefacetswerealsoobservedunderrotatingbendinginnitrogengas.Thedifferenceingrowthmechanismdependingontheloadingfrequencyandtheretardationofacrackgrowthunderultrasonicloadingmaybecausedbytheenvironmentatthecracktipduetohighcrackgrowthrateunderultrasonicloading.