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许明宇,女,‎1978‎年‎1‎月‎26‎日出生,副高级。 2000年毕业于山东大学,获学士学位 2005年获山东大学理学博士学位与法国UniversiteduMaine博士学位 2006-2008年,复旦大学博士后研究 2008年,中国科学院数学与系统科学研究院助理研究员 现任中国科学院数学与系统科学研究院副研究员

研究领域

随机分析 倒向随机微分方程

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Superhedgingunderratioconstraint. Weconsidersuperhedgingofcontingentclaimsunderratioconstraint.Ithasbeenwidelyrecognizedthattheminimumcostofsuperhedgingacontingentclaimwithcertainportfolioconstraintsisequaltothepriceofaclaimwithappropriatelymodifiedpayoffbutwithoutconstraints.Intermsofthebackwardstochasticdifferentialequation(BSDE)andthevariationalinequalityequationapproach,werevisitthisresultandprovidetwocounterexamples. Numericalalgorithmsandsimulationsforreflectedbackwardstochasticdifferentialequationswithtwocontinuousbarriers. Inthispaperwestudydifferentalgorithmsforreflectedbackwardstochasticdifferentialequations(BSDEinshort)withtwocontinuousbarriersbasedontheframeworkofusingabinomialtreetosimulate1-dBrownianmotion.Weintroducenumericalalgorithmsbythepenalizationmethodandthereflectedmethod,respectively.Intheendsimulationresultsarealsopresented. Thetimefractionalheatconductionequationinthegeneralorthogonalcurvilinearcoordinateandthecylindricalcoordinatesystems. InthispaperatimefractionalFourierlawisobtainedfromfractionalcalculus.AccordingtothefractionalFourierlaw,afractionalheatconductionequationwithatimefractionalderivativeinthegeneralorthogonalcurvilinearcoordinatesystemisbuilt.Thefractionalheatconductionequationsinotherorthogonalcoordinatesystemsarereadilyobtainableasspecialcases.Inaddition,weobtainthesolutionofthefractionalheatconductionequationinthecylindricalcoordinatesystemintermsofthegeneralizedH-functionusingintegraltransformationmethods.Thefractionalheatconductionequationinthecase0<α≤1interpolatesthestandardheatconductionequation(α=1)andtheLocalizedheatconductionequation(α→0).Finally,numericalresultsarepresentedgraphicallyforvariousvaluesoforderoffractionalderivative. ThefractionaldiffusionmodelwithanabsorptiontermandmodifiedFick'slawfornon-localtransportprocesses. Ageneralizednon-localFick’slawonfractal-dimensionisderived.UsingmodifiedFick’slawatime–spacefractionaldiffusionmodelwithafractionaloscillatortermisbuilt.ThesolutionisobtainedintermsofMittag–LefflerfunctionusingfiniteHankelintegraltransformationandLaplacetransformation.Inaddition,numericalsimulationsarediscussed.Theresultsshowthattheeffectrangeoftime-fractionalderivativeνonprobabilitydensityisgreaterthanthatoffractionaloscillatorparameterβ.Theeffectrangeofνonprobabilitydensityisoppositetothatofβ.Thispaperprovidesanewanalyticaltooltodevelopfluidmechanics,heatconductionandotherengineeringscience. AxialCouetteflowoftwokindsoffractionalviscoelasticfluidsinanannulus. ThispaperdealswiththeunsteadyaxialCouetteflowoffractionalsecondgradefluid(FSGF)andfractionalMaxwellfluid(FMF)betweentwoinfinitelylongconcentriccircularcylinders.Withthehelpofintegraltransforms(LaplacetransformandWebertransform),generalizedMittag–LefflerfunctionandH-Foxfunction,wegettheanalyticalsolutionsofthemodels.Thenwediscusstheexactsolutionsandfindsomeresultswhichhavebeenknownasspecialcasesofoursolutions.Finally,weanalyzetheeffectsofthefractionalderivativeonthemodelsbyusingthenumericalresultsandfindthattheoscillationexistsinthevelocityfieldofFMF. SomeexactsolutionstoStefanproblemswithfractionaldifferentialequations. Someexactsolutionstothefirst,secondandextendedStefanproblemswithfractionaltimederivativedescribedintheCaputosensearegivenbymeansoffractionalGreen'sfunctionandWrightfunctioninthispaper.Bytheaidofsimplecalculations,manyresultsofdifferentialequationsofintegerordercanbeobtainedasspecialcasesoftheresultsgivenbythispaper. ComparisontheoremsforforwardbackwardSDEs. WeprovesomecomparisontheoremsforforwardbackwardSDEsin1-dimensionormulti-dimensionbyprobabilisticmethodanddualitytechnique. Backwardstochasticdifferentialequationswithreflectionandweakassumptionsonthecoefficients. Inthispaper,westudyreflectedBSDE’swithonecontinuousbarrier,undermonotonicityandgeneralincreasingconditionsinyandnon-Lipschitzconditionsinz.Weprovetheexistenceanduniquenessofasolutionbyanapproximationmethod. ConvergenceofsolutionsofdiscretereflectedbackwardSDE'sandsimulations. Theobjectiveofthispaperistointroduceelementarydiscretereflectedbackwardequationsandtogiveasimplemethodtodiscretizeintimea(continuous)reflectedbackwardequation.Apresentationofnumericalsimulationsisalsodescribed. ReflectedBSDEswithtwobarriersundermonotonicityandgeneralincreasinggrowthconditions. Inthispaper,weprovetheexistenceanduniquenessresultofthereflectedBSDEwithtwocontinuousbarriersundermonotonicityandgeneralincreasingconditionony,withLipschitzconditiononz. g-GammaExpectationsandtheRelatedNonlinearDoob-MeyerDecompositionTheorem. Inthispaper,wedefineanonlinearexpectationviatheBSDEwithconstraint(BSDEwithsigularcoefficient),thenweintroducedefinitionsofsuperandsubmartingaleunderthisnonlinearexpectationandprovetheirnonlinearDoob-Meyertypedecomposition. ReflectedBackwardStochasticDifferentialEquationswithtwoRCLLbarriers. InthispaperweconsiderBSDEswithLipschitzcoefficientreflectedontwodiscontinuous(RCLL)barriers.Inthiscase,weprovefirsttheexistenceanduniquenessofthesolution,thenwealsoprovetheconvergenceofthesolutionsofthepenalizedequationstothesolutionoftheRBSDE.Sincethemethodusedinthecaseofcontinuousbarriers(seeCvitanicandKaratzas,Ann.Probab.24(1996)2024–2056andLepeltierandSanMartín,J.Appl.Probab.41(2004)162–175)doesnotwork,wedevelopanewmethod,byconsideringthesolutionsofthepenalizedequationsasthesolutionsofspecialRBSDEsandusingsomeresultsofPengandXuinAnnalesofI.H.P.41(2005)605–630. ReflectedBSDEsundermonotonicityandgeneralincreasinggrowthconditions. Weprovetheexistenceanduniquenessofthesolutiontocertainreflectedbackwardstochasticdifferentialequations(RBSDEs)withonecontinuousbarrieranddeterministicterminaltime,undermonotonicity,andgeneralincreasinggrowthconditionsontheassociatedcoefficient.Asanapplication,weobtain,insomeconstraintcases,thepriceofanAmericancontingentclaimastheuniquesolutionofsuchanRBSDE. Thesmallestg-supermartingaleandreflectedBSDEwithsingleanddoubleL^2obstacles. InthispaperweshowhowasolutionofBSDEcanbereflectedbyaveryirregularL^2-obstacle.Weprovethatthisproblemisequivalenttofindthesmallestg-supermartingaleofBSDEthatdominatesthisobstacle.WethenobtaintheexistenceanduniquenessandcontinuousdependencetheoremforthisreflectedBSDE.WealsoconsidertheproblemofexistenceanduniquenessofreflectedBSDEwithdoubleL^2obstacles,byusingapenalizationmethod.Anewmonotoniclimittheoremisdevelopedtoprovetheconvergenceofthepenalizationsequence,andtoprovetheexistencetheorem.WealsoprovethatthisreflectedBSDEwithdoubleobstaclesisequivalenttoaproblemofthesmallestg-supermartingaleandthelargestg-submartingale.

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