Research On Optimization Of Emergency Logistics Network Of Various Transportation Considering Facilities Failure

China is a country with many disasters.Every year,the number of casualties and property losses caused by natural disasters such as earthquakes and typhoons is very alarming.Emergency relief supplies can effectively reduce property losses,ensure life safety,and maintain social stability.The timely supply of materials can effectively increase the survival probability of people in the affected areas and alleviate the anxiety of them.On the contrary,it will aggravate casualties.And in reality,the unstable external environment after disaster will lead to the loss of effectiveness of the original emergency facilities and paths,unable to meet the needs of the affected points,resulting in higher operating costs and lower efficiency of the entire logistics network.Therefore,after the occurrence of disasters,the key to post-disaster relief work is to build an efficient emergency logistics network that can quickly and accurately deliver the necessary emergency relief supplies to the victims.Firstly,based on the existing theories and models of emergency logistics,supply chain interruption risk and logistics network,in this dissertation two influencing factors: the failure of emergency logistics distribution center facilities and the road damage in the disaster area are taken into account.Taking the shortest time of material distribution and the minimum total cost of construction cost,transportation cost and dispatch cost as two objectives,a bilevel programming mathematical model of multi-objective emergency logistics network optimization under facility failure is constructed.The upper model is transported by vehicles under the condition that the facility has not failed.When a certain number of facilities fail,the lower layer model judges whether to open the integrated support center without capacity limitation according to the supply of distribution center,and adds helicopter transportation according to the road condition.Secondly,according to the characteristics of emergency logistics network optimization model of various transportation modes under facility failure,the NSGA-? algorithm and Simulated Annealing algorithm are compared and analyzed from the aspects of basic principle,key technology or related parameters,algorithm steps and so on.A hybrid algorithm which integrates Metropolis criterion of Simulated Annealing algorithm into NSGA-? algorithm is proposed,and MATLAB software is used to program the hybrid algorithm of emergency logistics network optimization model of various transportation modes under facility failure.The coding method,fitness function calculation,crossover mutation operation and failure operation of the algorithm are expounded.Finally,a practical example of emergency logistics network optimization for various transportation modes under facility failure is designed,the relevant parameter values in the model are optimized,and the hybrid algorithm is used to solve the example.The location scheme and material distribution route of emergency logistics distribution center under the optimal scheme are obtained.The superiority of the algorithm is proved by the same example.At the same time,the influence of the number of selected emergency distribution centers,the number of failed distribution centers,the weight of cost time and the failure probability of distribution centers on the total cost and time of the network are discussed.It is found that the change of weight is proportional to the distribution time and inversely proportional to the total cost,but the change of the failure probability of the distribution center is not significantly related to the distribution time and the total cost.