1, baumol-Wolff model The problem considered in this model: How many goods are transported by each factory to which warehouses? How many goods does each warehouse send to which users? Then, according to the volume of Wiki logistics [/Wiki], determine the capacity of the warehouse. Objective: Under the constraints of supply and demand, to pursue the lowest total cost consisting of transportation expenses (from factory to warehouse), transportation expenses (from warehouse to customer) and variable expenses, so as to choose [wiki] logistics center [/wiki]. Advantages: the variable cost of logistics center operation is expressed as a concave function, that is, considering batch benefits; You can estimate the flow of the selected logistics center. Insufficient: The fixed cost and capacity limitation of logistics center are not considered. 2. elson mixed integer programming model This model has the following assumptions: only consider the alternative locations where the new logistics center is located within a certain range; User needs are aggregated by region; Use service level to represent different means of transportation; Freight is directly proportional to traffic volume; For warehouses that need to be expanded, they should be expanded to the predetermined minimum expansion capacity first, and then allowed to continue to expand between the minimum expansion capacity and the maximum expansion capacity according to the requirements of improving economic efficiency, and the required expansion cost is directly proportional to the expansion capacity; The newly-built warehouse should ensure the capacity at the time of opening and allow it to be expanded to the predetermined maximum possible capacity in the future; For planned investment, whether it is reasonable or not is judged according to the rate of return on investment. 3. Kuehn-Hamburg model considers the influence of many structural factors: the transportation cost from suppliers to logistics facilities, the transportation cost from logistics facilities to users, the fixed cost of logistics facilities and the variable cost of operation and management, and the limitation of the number and capacity of facilities. The model is closer to reality. However, it also has its disadvantages. The model does not consider the fixed cost of fixed assets, such as the construction cost of logistics facilities. In addition, when there are many suppliers, logistics facilities and customers, the amount of calculation is very huge.