Research on Distributionally Robust Optimization Method for Railway Empty Container Repositioning
Based on the container utilization data from the China Railway"Container Transportation Full-Process Track-ing System"with a five-day planning cycle,this study defined the difference between the dispatched and arrived loaded containers at container handling stations as"net empty container demand"or"net empty container surplus",and de-signed the sets of probability distribution for this net empty container demand/surplus.Based on the empty container storage capacity of container handling station,a distributionally robust chance-constrained empty container repositioning model was constructed for the whole railway system.The model intended to minimize the empty container repositioning distance while ensuring that handling stations could meet the demand for dispatching loaded containers and handling ar-rived loaded containers even in the worst-case scenario of net empty container demand and net empty container surplus at a certain service level.After model conversion,Cplex was used to solve the problem.The case results of 35 t open-top empty container repositioning plans across the railway system show that the proposed approach can fulfill the requirements for formulating repositioning plans of the current empty container repositioning mode.Taking into account the fundamental demand of loading containers at each handling station,the model,under certain combinations of service level parameters,can significantly promote the typical"discharging empty container stations"to discharge own empty containers outside the station while ensuring the dispatch of loaded containers.This facilitates the orderly circulation of empty containers under conditions of supply-demand imbalance.
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