简介：Thegravityp-medianmodelisanimportantimprovementtothewidely-usedp-medianmodel.However,thereisstilladebateonitsvalidityinempiricalapplications.Previousstudiesevendoubtthesignificanceofthegravityp-medianmodel.UsingacasestudyoftertiaryhospitalsinShenzhen,China,thisstudyre-examinesthedifferencebetweenthegravityp-medianmodelwiththep-medianmodel,bydecomposingthedifferencebetweenthetwomodelsintogravityruleandvariantattraction.Thisstudyalsoproposesamodifiedgravityp-medianmodelbyincorporatingadistancethreshold.Theempiricalresultssupportthevalidityofthegravityp-medianmodel,andalsorevealthatonlywhentheattractionsofcandidatefacilitylocationsarevariablewillthegravityp-medianmodelleadtodifferentresultswiththep-medianmodel.Thedifferencebetweenthemodifiedgravityp-medianmodelandthegravityp-medianmodelisalsoexamined.Moreover,theimpactsofthedistance-decayparameteranddistancethresholdonsolutionsareinvestigated.Resultsindicatethatalargerdistance-decayparametertendstoresultinamoredisperseddistributionofoptimalfacilitiesandasmalleraveragetraveltime,andasmallerdistancethresholdcanbetterpromotethespatialequityoffacilities.Theproposedmethodcanalsobeappliedinstudiesofothertypesoffacilitiesorinotherareas.

简介：Forthethree-dimensionalcompressiblemulticomponentdisplacementproblemweputforwardthemodifiedmethodofcharacteristicswithfiniteelementoperator-splittingproceduresandmakeuseofoperator-splitting,characteristicmethod,calculusofvariations,energymethod,negativenormestimate,twokindsoftestfunctionsandthetheoryofpriorestimatesandtechniques.OptimalorderestimatesinL^2normarederivedfortheerrorintheapproximatesolution.Thesemethodshavebeensuccessfullyusedinoil-gasresourcesestimation,enhancedoilrecoverysimulationandseawaterintrusionnumericalsimulation.