学科分类
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7 个结果
  • 简介:Let{N(t),t≥0}bethenonhomogeneousPoissonprocesswithcumulativeintensityparameterΛ(t),{δt,t≥0}theageprocess,and{yi,t≥0)theresiduallifetimeprocess.Inthepresentpapertheexpressionsofn-dimensionalsurvivaldistributionfunctionsoftheprocesses{δi}and{yi},andtheirLebesguedecompositionsarederived.

  • 标签: 不均匀布松过程 剩余时间 勒贝格分解 分布函数
  • 简介:Theexistenceanduniquenessofpositivesteadystatesfortheage-structuredMSEIRepidemicmodelwithage-dependenttransmissioncoefficientisconsidered.Thresholdresultsfortheexistenceofendemicstatesareestablished;undercertainconditions,uniquenessisalsoshown.

  • 标签: MSEIR EPIDEMIC model AGE-STRUCTURE Co-semigroup abstract
  • 简介:ThisarticlefocusesonthestudyofallagestructuredSEIRSepidemicmodelwithavaccinationprogramwhenthetotalpopulationsizeisnotkeptatconstant.WefirstgivetheexplicitexpressionofthereproductionnumberR(ψ,^↑λ)inthepresenceofvaccine(^↑λistheexponentofgrowthoftotalpopulation),andshowthattheinfection-freesteadystateislh~earlystableifR(ψ,^↑λ)<1andunstableifR(ψ,^↑λ)>1,thenweapplythetheoreticalresultstovaccinationpoliciestodeterminetheoptimalageoragesatwhichanindividualshouldbevaccinated.Itisshownthattheoptilnalstrategycanbeeitherone-ortwo-agestrategies.

  • 标签: 模型 流行病 人口 预防 接种年龄
  • 简介:Fatiguepropertiesofage-hardenedAlalloy2017-T4underultrasonicloadingfrequency(20kHz)wereinvestigatedandcomparedwiththeresultsunderconventionalloadingofrotatingbending(50Hz).Thegrowthofacrackretardedatabout500μminsurfacelengthunderultrasonicloading,whileatabout20μmunderrotatingbending.Althoughstriationsbeingatypicalfracturemechanismwereobservedunderconventionalloading,mostoffracturesurfacewascoveredwithmanyfacetsunderultrasonicloading.Thesefacetswerealsoobservedunderrotatingbendinginnitrogengas.Thedifferenceingrowthmechanismdependingontheloadingfrequencyandtheretardationofacrackgrowthunderultrasonicloadingmaybecausedbytheenvironmentatthecracktipduetohighcrackgrowthrateunderultrasonicloading.

  • 标签: 疲劳性能 超声波 铝合金 负荷 硬化 年龄