Study On Network Layout Of Inland Ports In Two Stages Under Uncertain Demand

Since 2013,China has put forward important cooperation initiatives on the construction of the " The Silk Road Economic Belt " and the "21st-Century Maritime Silk Road " to establish and strengthen connectivity with neighboring countries and regions and build a new pattern of all-round opening-up and cooperation.With the implementation of the "The Belt And Road"initiative,a number of inland regions have successively deployed measures to open up,taking foreign trade as the foundation of opening up,and focusing on railway construction to build inland ports and foster One Belt And One Road hub economy.According to statistics,more than 70 cities in China are planning or have completed the construction of international land ports,hoping to lead the rapid development of regional export-oriented economy through "land port economy" in the new round of opening to the outside world.The inland port is an important infrastructure of the "Belt and Road" initiative and an important bridge connecting China's inland areas with coastal ports and border ports.The key to the success of an inland port as an integration point and logistics hub in a multimodal transport network depends on its geographical advantage.Scientific and reasonable location can help inland ports to attract more freight traffic from the surrounding hinterland and achieve economies of scale through rail transport that seamlessly connects with seaports.On the contrary,if the inland port planning is not reasonable,it will lead to overcapacity,redundant infrastructure,low efficiency,and even affect the return on investment.More importantly,once the inland port is constructed,it is almost impossible to relocate due to the large capital investment involved and the impact of geographical restrictions and sunk costs.Therefore,it is necessary to make reasonable planning for the location and radiation range of inland ports in the early stage of development.The existing inland port sites generally adopt the p-median site selection model in the facility site selection model,and the total cost including construction cost,transportation cost,etc.is minimized as the objective function.Only a few studies take the carbon emission cost into account.In the traditional inland port transportation network model,it is assumed that various parameters are determined and known,but in the actual operation process of inland port,many parameters such as construction cost,transportation cost and demand constantly fluctuate.The location of inland port is a strategic decision,Once determined,it will not be easily changed due to environmental changes,and the route allocation can be adjusted according to environmental changes at any time.Therefore,the uncertainty of external environment must be fully considered in the site selection stage of inland port to make a robust site selection decision.However,if too many uncertainty factors are considered,the complexity and difficulty of solving the model will be greatly increased.Therefore,when establishing the robust site selection model for inland ports,it is assumed that other parameters are determined,and only the uncertainty of market demand is considered.The main research contents of this article are as follows:(1)This article relaxes the "all or nothing" assumption of the traditional maximum coverage location problem.We introduce a gradual coverage model.The gradual coverage function is used to describe the gradual decrease of the service,quality level(attraction rate)of inland ports to demand points with increasing distance.With the objective of maximizing the expectation of service quality level as the objective function,a first-stage model is established,that is,the location model of the inland port under demand is determined.(2)We use scenario sets and box uncertainty sets to describe the change in demand at each demand point.Based on the regret value theory,we establish a robust location model for inland ports with a minimum expected deviation as the objective function,and find a robust location.(3)We introduced a carbon tax price to include carbon emissions as the cost of carbon emissions into the total cost of the system.Then the total cost of the system including transportation costs,conversion costs in inland ports,time costs and carbon emission costs is minimized as an objective function.Based on the results of the inland port location in the first stage and considering the inland port capacity constraints,we perform the path allocation of each demand node in the second stage area.