模糊环境下P枢纽中心问题的研究.pdfVIP

p O-D （ p Æ p p  p p 2-  （1） p （2） 2-   （3）  2-  （4）  2-  I Abstract Abstract The p-hub center problem is to locate p hubs in a network and to allocate the non-hub nodes to hubs such that the maximum travel time between any o-d （origin- destination） pair is minimized. In realistic p-hub center problem, the travel time parameters usually present fuzziness, so we should employ fuzzy theory to deal with fuzziness in p-hub center problem. This thesis frst presents a new class of fuzzy p-hub center problems based on credibility criterion. In the case that the fuzzy travel times are mutivariate normal fuzzy vectors, we suggest an approximation approach （AA） to reformulating the original problem as a mixed-integer problem with logic constraints. We design an improved hybrid particle swarm optimization （PSO） to solve the proposed model. Taking into account of the difcult of determining the possibility distributions in re- alistic p-hub center problem, we further develop a new class of p-hubcenter problems with generalized value-at-risk （VaR） by a robust method. When the fuzzy travel times are independent type-2 fuzzy variables, we derive the parametric possibility distributions of reduced fuzzy variables by applying reduction methods. In this case, we discuss its equivalent parametric mixed-integer programming problems and the efective solution methods. Finally, some numerical experiments are performed to demonstrate the modeling ideas and the efciency of the proposed solution methods. The major new results of this thesis con