Research On Topological Resilience Of Fractal Logistics Networks

With the extensive socialization of production mode and the globalization of world economy,modern logistics network has grown into a dynamic,stochastic and strong-coupled logistics system,and its evolutionary process is characterized by growth kinetics.In the process of logistics networks operating,the impact brought about by uncertainties may invalidate logistics nodes or transport lines,to cause damage to the logistics networks in structure and function,and then interrupt the logistics service.To overcome vulnerability of modern logistics networks,fault-tolerance is an important and necessary part to keep the logistics networks connected when disasters or disruptions appear.Besides,recovery of logistics networks from disasters or accidents should be concerned.The logistics networks will still be able to offer necessary logistics services in spite of disruptions and recover its logistics functions rapidly after the disappearance of disruptions.In this thesis,the theoretical system of the topological resilience of logistics networks is summed up based on analyzing the cause of modern logistics network vulnerability.Dynamic variation regularity of the topological resilience based on regular growth and random growth are analyzed respectively.To increase topological resilience of real logistics network,the optimization model based on fractal is introduced.The main content in this thesis are as follows:(1)The concept and perimeter of logistics network's resilience are determined by comparison between resilience,reliability and flexibility of logistics networks according to analysis on the cause of modern logistics network's vulnerability.A two-stage measurement method is designed for topological resilience of logistics networks by analyzing the action process of the topological resilience of logistics networks.(2)By analyzing the formation mechanism of fractal logistics networks and researching the necessary and sufficient conditions for the structure of fractal logistics network,the analytical system of fractal logistics networks is built based on box-courting method and renormalization theory.(3)“Growing rules” is set for the regular growth model of fractal logistics networks with the degree of the existing logistics nodes in logistics networks as a basis for the number of emerging logistics nodes.The structural redundancy of logistics networks is set based on “selection rules of spare logistics nodes”.Fractal logistics network model based on regular growth is designed,which shows self-similar and scale-invariance.Dynamic variation regularity on topological resilience of the fractal logistics networks based on regular grow is studied against random failure and attack disruption to identify the dynamic rules by simulation.It is shown that,with the development of fractal logistics network based on regular grow,resilience of logistics network is increasing against node random failure,and resilience of logistics network is unchanged against area random failure and targeted attack.(4)When a new logistics node appears in logistics networks,“attractor node” of new logistics node is selected in accordance with the degree of the existing logistics nodes in logistics networks,and the structural redundancy of logistics networks is set based on “selection rules of spare logistics nodes”.Fractal logistics networks based on DLA stochastic growth,stationary stochastic growth and non-stationary stochastic growth are established respectively.Dynamic variation regularity on topological resilience of the fractal logistics networks based on stochastic grow is studied against random failure and attack disruption to identify the dynamic rules by simulations.It is shown that,with the development of fractal logistics networks based on DLA and stable growth,resilience of logistics network is decreasing against node random failure,and resilience of logistics network is unchanged against area random failure and targeted attack.With the development of fractal logistics network based on unstable growth,resilience of logistics network is unchanged against node random failure and targeted attack,and resilience of logistics network is increasing against area random failure.(5)The optimization model is designed based on fractal to enhance topological resilience of a real airline logistics network.It is found that fractal could improve fault-tolerant and recovery of real logistics network both against random failures and targeted attacks.In this thesis,based on complex networks theory and fractal method,as well as a research of the formation mechanism of fractal logistics networks,fractal logistics network model based on regular growth and stochastic growth are designed.Topological resilience of fractal logistics networks is researched from static and dynamic angle.The conclusion is significant to study the stability of modern logistics networks and to optimize the structure of modern logistics networks.