| The hub-and-spoke network has been widely used in express,travel,aviation,medical,electronic networks and other industries due to its low transportation cost,high service efficiency and strong resource integration capabilities.However,the importance of hub node in H-S network makes the practical problems such as vulnerability and congestion become more and more obvious.Congestion of centralized flow will increase the cost of transportation delay and the failure of hub will lead to the overall flaw of the logistics network operation.Although the causes of congestion and failure at hub node are not the same,in the case of logistics companies,the sudden situation of any hub will expose the enterprise to the risk of network congestion and increased costs.Therefore,this paper considers the congestion and failure of hub node,models and analyzes hub-and-spoke logistics network,aiming to provide an effective solution to improve the robustness and optimization of the logistics network.Based on the construction of the single-allocation p-hub location model(SApHLP),the paper introduces hub congestion and failure scenarios into the basic model and corrects the model,focusing on the analysis of the impact of hub congestion and failure on location planning.Hub congestion and failure are considered comprehensively,and a 0-1 mixed integer quadratic programming model is constructed to solve the problem of logistics network location planning problem.Since the models constructed in this paper belong to the NP-Hard problem,the complexity of variables and constraints improves the complexity of the model.Therefore,this paper compares and analyzes the existing algorithms and introduces the mutation particle swarm optimization algorithm to improve the speed of model solving.At the same time increase the robustness of the solution.Firstly,this paper introduces hub congestion problem into the basic model.Hub node is limited by certain capacity.Although hub node can achieve scale effect through the distribution of goods,the high concentration of logistics at hub will increase the possibility of hub congestion.Therefore,when the flow rate of the centralized transfer of hub node exceeds its threshold,a congestion situation will occur.This paper believes that when hub congestion occurs,the network can adopt two solutions: congestion flow continues to wait for transport(SApHLP-CW)or congestion flow for path redistribution transport(SApHLP-CR).Secondly,the failure point of hub is introduced into the model.Considering the importance of the vulnerability of hub node to the logistics network transportation,the article divides the failure of hub into local failure and total failure.Partial failure considers that there is still a transshipment function at the hub node but the service capability is reduced.Through the assumptions and parameter settings of related problems,the local failure problem of hub point is equivalent to the congestion of hub point under certain circumstances.Therefore,the focus on the global failure of hub point is analyzed.The tobal failure considers that the complete failure of hub node causes it to fail to provide the transshipment service.In order to avoid the flow loss caused by the failure,it is necessary to introduce an alternative hub point for transshipment,and accordingly construct a network location model(SApHLP-TF)under the complete failure scenario of the hub.Finally,the paper comprehensively analyzes the failure and congestion of the hub,and constructs a pivotal logistics network planning model(SApHLP-RC)that comprehensively considers the failure and congestion of hub node.The model solution results and research conclusions show that:(1)Considering the congestion problem of the hub can promote the optimal layout of the logistics network system,meet the realistic situation constraints and better realize the transportation cost minimization;(2)The logistics network faces the congestion problem,the optimization measures is a scheme of adopting congested flow queues for transportation,and the path redistribution can also promote the balanced distribution of flows at hub node;(3)the bypass and penalty costs caused by the failure of hub account for a large proportion of the cost of logistics network transportation.Only when the network planning fully considers the hub failure problem and enhances the stability of hub,can the network system be better enhanced;(4)Full consideration of hub failure and congestion problem in the logistics network planning can be more goodly optimize the network layout,enhance the stability of the hub,and provide guarantee for the normal operation of the logistics network.The solution and comparative analysis of the model can provide effective decision-making suggestions for the transportation department and logistics enterprises in China:(1)In the logistics network system,the logistics hub can enhance the centralized transportation of the flow and realize the LTL freight.Therefore,we must pay attention to the construction of hub node and enhance the stability of the logistics hub;(2)The logistics network planning should comprehensively consider the real situation constraints such as congestion and failure that may occur in the hub,so as to effectively carry out the system planning;(3)Between the current logistics enterprises,The homogenization competition has caused waste of logistics transportation costs.National and industry associations should introduce relevant policies and measures to promote cooperation between them,realize the effective integration of resources and promote the sustainable development of the logistics industry. |
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