简介:外P-集合是P-集合的一个部分,它是P-集合的一个概念.利用外P-集合,给出了F-递推数据与F-递推数据内-恢复的基本概念、F-递推数据内-恢复定理和内-恢复的属性定理,利用这些结果应用于计算机中.
简介:Theeffectsofthefinalelectromagneticstirring(EMS)onthesolidificationstructureof60Si2CrVAThighstrengthspring(HSS)steelofcontinuouscasting(CC)billetshasbeenstudied.Theanalysisofthesolidificationstructureisbasedonthecomparisonbetweenthemacrostructure,microstructure,carbonsegregationanddefectsofthe60Si2CrVATbilletwithmold-electromagneticstirring(M-EMS)andthosewiththeM+finalsolidificationzoneelectromagneticstirring(F-EMS).ItisfoundthatthesolidificationstructureofthebilletwiththeF-EMSisimprovedwiththetightnessofthebilletandtheincreaseintheratiooftheequiaxedstructure,theinnerporosityandtheshrinkageareremarkablyreduced,andthattheratioofcentralcarbonsegregationsharplydecreases.Meanwhile,thesecondarydendritearmspacing(SDAS)isimproved,andtheratioofcentralequiaxedgrainconsiderablyincreases,whichresultsinfinergrains.Therefore,thequalityofthebilletisenhancedwiththeF-EMS.
简介:TheeffectsofF^-ionsinagermanium-lead-telluriteglasssystemonthespectralandpotentiallaserpropertiesoftheYb^3+areinvestigated.Theabsorptionspectra,lifetimes,theemissioncross-sectionsandtheminimumpumpintensitiesoftheglasssystemwithandwithoutF^-ionshavebeenmeasuredandcalculated.TheresultsshowthatthefluorescencelifetimeandtheminimumpumpintensityofYb^3+ionsincreaseevidently,whichindicatesthatgermanium-lead-oxyfluoridetelluriteglassisapromisinglaserhostmatrixforhighpowergeneration.FT-IRspectrawereusedtoanalysetheeffectofF^-ionsonOH^-groupsinthisglasssystem.AnalysisdemonstratesthatadditionoffluorideremovestheOH^-groupsandresultsinimprovementoffluorescencelifetimeofYb^3+.