| With the development of the national economy and the improvement of people's living standard,the demand for dairy products is increasing rapidly.As the dairy products(especially low-temperature pasteurized milk)has the characteristics of high water content,short shelf life and strong freshness.And distribution is a process which has long protection time in non-refrigerated environment during the whole dairy cold chain logistics.Therefore,how to improve the distribution efficiency and reduce the risk of the spoilage have become the key problem of the study of cold chain logistics for the dairy products.In recent years,the domestic cold chain logistics of dairy products has developed rapidly,but there are still many problems,such as the irrational distribution routes,the inefficient distribution,the deterioration of dairy products and the difficulty of satisfying the requirements of time window for different customers,which have hindered the development of dairy industry in some extent.The existing researches on the cold chain logistics distribution system of the dairy products usually only considered the single location problem or the single delivery routing planning problem,which were failed to accord with the characteristics of dairy distribution,consider all the relevant factors synthetically in the distribution process,and regard the dairy products cold chain logistics distribution center location and distribution of path optimization as a combinatorial optimization problem to study.This is not consistent with the actual characteristics of the distribution system of dairy cold chain logistics,nor can it provide strong guidances for the development of dairy cold chain logistics.Therefore,it is of great theoretical and practical significance to study the distribution center location and delivery routing planning of dairy cold chain logistics.Based on the related research literatures,combined with the characteristics of dairy products and the operation mode of urban dairy supply chain,this paper studies the combinatorial optimization of the distribution center location problem and delivery routing planning of dairy cold chain logistics.First of all,according to the characteristics of the dairy and the relevant influencing factors in the process of the cold chain logistics distribution of the dairy products,considering the customer requirement for delivery time at the same time,and regarding dairy products cold chain logistics distribution center location and delivery routing planning problem as a combinatorial optimization problem,this paper has established the bi-level programming model that is based on node fixed cost,refrigerating cost,damage cost,transportation cost and punishment cost,and the relevant cost factors which are taken into all links of distribution in the upper and lower model,so that the model is much closer to the actual problems.Secondly,through the comparative analysis of the related optimization algorithms,and due to the characteristics of the calculation complexity,the genetic algorithm is selected to solve the mathematical model.Finally,combined with the example,MATLAB software are applied to realize the solution of problem.The conclusion shows that the bi-level programming model of the location and delivery routing planning of the dairy products in cold chain logistics is much closer to the actual problems.By comparing the results of using the genetic algorithm to solve the bi-level programming model with the result of using the genetic algorithm to solve the two sub-problems of the location and delivery routing planning problem respectively,the correctness of the model and the effectiveness of the genetic algorithm are further proved. |
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