Research On Optimization Method And Survivability Of Complex Express Network

Network optimization problem is a popular issue in many research fields, such as logistics, transportation, computer science, communication,mathematic and operation research. Previous studies mainly deal with it focusing on how to design an more effective algorithm to solve optimization problems with properties of multi-objective, multi-constrained and high computation complexity. The express network system is a super-network system with characteristics of multi-dimention, multi-layer and multi-objective, as one part of super-network system, the physical layer network is composed of delivery centers and routes, goods delivery in physical layer network is scheduled and restricted by the management layer network, which consisted of organization management dimension subnetwork and business management dimension subnetwork, the former take the branch company as its management unit and the latter regard the transshipment center as the collecting and distributing center. As a result, the management dimension subnetwork has an effect on the optimal outcome of physical layer network. In addition, for the interdependence of internal factors in express network system, acts of sabotage committed both against physical layer network and against management dimension subnetwork, may bring about heavy loss to the express company, so, to analyze its survivability at a different layer will help to protect express network system better.It analysizes the super-network structure of express distribution system, discusses the optimization problem of physical layer network which restricted by "time-limited delivery" and matrix management mode which is adopted widely in express industry, it also investigates the vulnerability of express network system when the physical layer network and the management dimension subnetwork is damaged respectively.(1)It designs a super-network model which suitable for describing the characteristics of express distribution network systemIn order to consider cost and efficiency simultaneously, a matrix management mode is adopted by express companies, on one hand, they consider province-level branch company as management unit to supervise the physical-layer network and control its operation cost divisionally, on the other hand, they regard the transshipment center as the collecting and distributing center for goods unified dispatching, as a result, two different dimension subnetworks who schedule goods distribution in physichal layer network jointly, are formed in management layer network. A supernetwork model is designed to describe the complex construction and complicated relation of express network system.(2) It proposes a new optimization method of express networkOn the basis of the cost optimization-based method raised in organization management dimension and the time optimization-based method of physical layer network raised in business management dimension, combines with the "time-limited delivery" in express industry, an optimization method of multicriteria express super-network based on time threshold is proposed, the optimization method can reduces the distribution costs to the utmost on the premise of that the express consignments are delivered in the commitment time, the method is also illustrated by an application case, results show that the delivery routes, delivery time and delivery cost is related to time threshold.(3) It designs an optimization algorithm according to structure characteristics of physical layer networkIt proposes a segmental optimization method with features of parallel operation based on local searching, according to the community structure and sub-cores of physical layer network, the method is also illustrated by an application case, results show that our optimization method can effectively reduce computation complexity while keeping the calculation precision.(4) It studies the vulnerability of express network systemIn the first place, it designs an efficiency index to evaluate the vulnerability of express network system, the index can not only accesses the damage of express network structure reasonably, but also can measures the influence degree of flow on network, as a result, it can evaluates the losses of express company scientifically when the express network damaged. Secondly, node-removal method is used to simulates the damage to physical layer network, its vulnerability is also analysized in consideration of the effect of cascading failures and crowding. It defines the management efficiency index of branch company in the end, the drop course of delivery efficiency in physical layer network results from the reduction of management efficiency is also simulated. Results show that a little decrease of management effeciency may results in a sharp increase of total delivery cost of physical layer network, so, we can conclude that compares with local failure in physical layer network, partial failure in management layer network brings express company a worse influence.