Research On Location Routing Problem For O2O Drug Delivery Based On Bi-level Programming

The volume of pharmaceutical e-commerce transactions was 6800 million yuan in 2014, with an increase of 59.6%. In the same year, the policy of drug sale on Internet allowed sales of prescription drugs on line and delivery by the third party pharmaceutical logistics enterprises. In terms of investment and finance, the number of financing cases appeared and showed an increasing trend in the last two years. In summary, under the background of good electronic, policy and investment and finance,medical e-commerce,which meets the demand of customers, will rise in the future.According to the operation mode of medical 020, this paper studies the location routing problems under closed and open distribution mode, and the results provided a reference for medical 020 enterprise. The main work of this research is as listed below:The thesis studies the location routing problem under closed delivery model firstly.In previous studies, there are few researches using the bi-level programming model for 020 drug delivery problem recently. Through the analysis of various construction methods of the bi-level programming models, the paper puts forward bi-level programming model for closed O2O drug distribution. In the model, the lower level model made decisions under the preliminary scheme of the upper level model, where the intermediate variable is a part of the objective function of upper level model. In addition, the paper designs a bi-level genetic and ant colony algorithm for the model improved by Halton sequence and memory bank.In view of the difference between delivery modes among the pharmacy and the customers, the paper studies the open O2O drug delivery location routing problem based on the research above. The difference between open and closed 020 drug distribution modes is that in the open O2O drug delivery process, delivery vehicles can return to other pharmacies instead of returning to initial pharmacy after a delivery in the open O2O drug delivery. Therefore, the number of delivery vehicles, which start from all pharmacies, should be equal to the number of delivery vehicles back to all pharmacies in the lower model, and the upper model remains unchanged. The open vehicle routing problem is more complex than the closed vehicle routing problem;therefore, the lower level genetic algorithm is redesigned using single point crossover,partially matched crossover and the evolution of reverse operation.A numerical example is used to analyze the performance of the bi-level model of closed 020 drug delivery problem, and the results show that: under the background of example: i) the best volume of pharmacies is the minimum number of pharmacies which can meet demands of all customers; ii) the main influence factor of 020 enterprise's total cost is the unit price of drug which is need to be paid for pharmacy; iii) an appropriate fixed budget can reduce the total cost of the 020 enterprise; iv) appropriate increasing the service ability of pharmacies with low unit price of drug can reduce the total cost of 020 enterprise. In addition, the same numerical example is used in the analysis of bi-level model of open location routing, and the result shows that location schemes under the two delivery modes are the same and delivery labor cost under open delivery mode is smaller than that under closed delivery mode through the comparison.