Research On Empty Container Repositioning Optimization Of China Railway Express

The problem of empty container repositioning caused by the trade imbalance between China and Europe is not only reflected in the maritime transportation,but also in the intercontinental railway transportation,that is,the China Railway Express(CRE).According to the actual operation characteristics of CRE,this thesis puts forward three modes of CRE empty container repositioning,which are independent repositioning,cooperative repositioning between CRE companies,and cooperative repositioning between CRE companies and international liner company,in order to reduce the empty container repositioning cost of the CRE companies.At the same time,three modes of empty container repositioning optimization under demand uncertainty are studied.(1)For the empty container repositioning optimization problem of one CRE company,considering the factors of sea land intermodal transportation and the use of foldable containers,this thesis constructs the optimization model of empty container repositioning of CRE under three situations: "only using standard containers","only using foldable containers","using standard containers and foldable containers at the same time",which is solved by CPLEX.The influence of different parameters on the total cost is analyzed.The results show that the total cost can be greatly reduced by transport some empty containers back by sea land intermodal transport mode.Secondly,the use of foldable containers in a specific situation can greatly reduce the cost of the train company.(2)For the empty container repositioning optimization problem under the cooperation between CRE companies,an empty container repositioning optimization model based on the cooperation of empty container mutual rent and line sharing is constructed.The multi period dynamic optimization problem is transformed into several single period static optimization problems to solve.The genetic algorithm is designed to solve the single period static optimization problem,and the optimal solution of the multi period optimization problem is obtained by greedy strategy.Through the analysis of the examples,we can get the following conclusions: Firstly,the empty container repositioning cost under the cooperation mode is lower than that under the single repositioning mode.Secondly,the total cost of empty container repositioning has been greatly reduced through empty container mutual rent.At the same time,the revenue from empty container mutual rent can also offset part of the empty container repositioning cost.Thirdly,the cooperation between the CRE companies can better cope with the changes of demand,supply and unit transportation cost,making the final optimization result lower than that of the single repositioning.(3)For empty container optimization under the cooperation of CRE companies and international liner liner company,based on the cooperation between CRE companies,this thesis puts forward the cooperation form of empty container mutual rent between CRE companies and international liner liner company in hinterland cities,and the international liner company provides lower booking price for the CRE companies in maritime transportation,and constructs the empty container repositioning optimization model under the cooperation of CRE companies and international liner liner company.The multi period dynamic optimization problem is transformed into several single period static optimization problems to solve.The genetic algorithm is designed to solve the single period static optimization problem,and the optimal solution of the multi period optimization problem is obtained by greedy strategy.The results show that: Firstly,the cooperation with liner company can further reduce the total cost of empty container repositioning.Secondly,in terms of the influence of demand,supply and unit transportation cost changes,the cooperation with liner company will make the final optimization result lower than that of single repositioning mode,and the change of parameters has little influence on the cooperation mode.Thirdly,through mutual rent,participants can greatly save the cost of renting containers,and also reduce part of the transportation cost and storage cost.Lastly,in terms of maritime transportation,CRE companies have saved more transportation costs due to cooperation with international liner liner company.(4)For the empty container repositioning optimization problem of demand uncertainty,considering the randomness of demand,this thesis introduces the distributed robust chance constraint theory,and constructs three modes of empty container repositioning optimization models based on demand uncertainty.By proving that the chance constraint is transformed into an equivalent form which is easy to solve,CPLEX and hybrid genetic algorithm are used to solve the empty container repositioning optimization models under different modes.The effectiveness of the model is verified by examples.It can be found that in the case of demand uncertainty,the optimization results of CRE companies and liner cooperation are still better than the calculation results of CRE companies cooperation and single repositioning.The total cost of the three modes will increase with the increase of uncertain parameters.The research results of this thesis can promote the exploration and promotion of the empty container repositioning mode of CRE,and provide decision support for the corresponding managers in the aspect of operation.