Uncapacitated singleandmultipleallocation p-hub centerproblems

The hubmedianproblemistolocatehubfacilitiesinanetworkandtoallocatenon-hubnodestohub nodes suchthatthetotaltransportationcostisminimized.Inthehubcenterproblem,themainobjective is oneofminimizingthemaximumdistance/costbetweenorigindestinationpairs.Inthispaper,westudy uncapacitated hubcenterproblemswitheithersingleormultipleallocation.Bothproblemsareproved to beNP-hard.Weevenshowthattheproblemoffindinganoptimalsingleallocationwithrespecttoa given setofhubsisalreadyNP-hard.Wepresentintegerprogrammingformulationsforbothproblems and proposeabranch-and-boundapproachforsolvingthemultipleallocationcase.Numericalresultsare reported whichshowthatthenewformulationsaresuperiortopreviousones.