Dynamic Layout Optimization Of Multi-objective And Multi-period Inland Port Under Demand Fluctuation

As an important link between inland hinterland and seaport,inland port is conducive to relieving the pressure of seaport throughput,simplifying the cargo transportation process,improving the efficiency of collection and distribution network in inland areas,and providing strong support for the implementation of major national strategies such as "the belt and road initiative".However,the freight demand is dynamic.Only considering the single-period onetime inland port location layout can not take into account the multi-period fluctuating demand,resulting in the uneven distribution of the built inland port layout and the changed inland freight demand.In the Layout and Construction Plan of National Logistics Hub jointly promulgated by the National Development and Reform Commission and the Ministry of Transport,it is clearly stated that in order to build 41 national-level land-port hubs,it is necessary to establish a system of regular evaluation and dynamic adjustment,integrate or build new land-port hubs according to the actual situation,remove the facilities that cannot effectively promote the implementation of the overall layout plan,and ensure the overall quality of national-level logistics hubs.In order to solve the problem of uneven distribution of inland port layout and transportation demand,a multi-objective and multi-period inland port dynamic layout model was established with the objective of optimizing the total system cost,carbon emissions and customer satisfaction,and adding the decision of capacity grade selection.According to the fluctuation of demand,the schemes of new construction,closure,reconstruction and capacity adjustment of inland ports in different periods are determined,and the demand points are allocated by routes.According to the characteristics of the model,the NSGA-Ⅱ algorithm is improved.The chromosome double-layer coding scheme can integrally decide the opening and closing of alternative inland ports and the capacity level in each period,and allocate the transit inland ports at the demand points.Considering the relationship that the capacity of open inland ports must at least meet the demand of the city where they are located,the crossover operator and mutation operator improved by the "nearest neighbor" idea are proposed to simplify the modification operation of illegal genes.In Pareto optimal solution set,fuzzy decision is adopted to select the optimal solution.Taking Northeast China as an example,this thesis optimizes the layout of inland ports,selects the inland port alternatives from the inland demand points,sets different alternative capacities,and sets the construction,closure,reconstruction,capacity adjustment and operating costs of inland ports according to the capacity of inland ports and the city where they are located.The results show that,compared with the single-period layout,the multi-period dynamic layout dynamically adjusts to the fluctuation of demand,which saves the total system cost by 6.762 billion yuan,reduces the carbon emissions by 6.449 billion kg,and improves the customer satisfaction by 18.55%.It proves the validity of the multi-period dynamic layout optimization model and the feasibility of the algorithm,and provides a reference for the multi-objective multi-period dynamic layout optimization of inland ports under the fluctuation of demand.The innovative results of the research are as follows:(1)The decision of capacity level is added,and the construction,closure,reconstruction,capacity adjustment and operation cost of inland ports are set according to the city and capacity level,so that the solution results can better reflect the actual situation.(2)During the long planning and operation period of inland ports,the layout of inland ports will be dynamically adjusted according to the fluctuation of demand in different periods.Taking the total cost of the system,carbon emissions and customer satisfaction as the objectives,a multi-objective and multi-cycle dynamic layout optimization model of inland ports under demand fluctuation is established.In addition to considering the situation of building new inland ports in different periods,innovative decisions such as adjusting the capacity of the original inland ports,closing the inland ports with short supply,and reopening the inland ports with sufficient supply have been made,so that the adjusted layout of inland ports can meet the changing freight demand and reduce the waste of resources.