# Vulnerability Analysis of a Multilayer Logistics Network against Cascading Failure
## 5 Discussion and Conclusions  
Due to increasing globalization, urban socioeconomic linkages are becoming more complex, bringing unstable operating conditions and more difficult challenges to the global logistics system. Logistics hub city transmission performance is mainly maintained by a small number of key logistics hub cities, which have a greater degree of influence on the overall network operation efficiency. In the context of economic globalization, the tendency of spatial decentralization of logistics hub cities will further aggravate the spread of the impact of local logistics hub city disruptions to the external space. Therefore, a vulnerability simulation analysis of the impact of logistics hub cities on the network operation efficiency under the disruption scenario can help to predict the impact of the damage of logistics hub cities on the overall network efficiency to arrange a response in advance. From the perspective of complex network theory, global shipping, air cargo, logistics enterprise organization, and international trade, four types of networks are built to analyze the single network and multilevel logistics hub city network cascade failure phenomenon. The main conclusions are as follows:  
1. Improving the size of urban capacity can effectively improve the operational efficiency of the urban network of logistics hubs. The capacity parameters are affected by the operational capacity of urban logistics. To strengthen the capacity of network components, it is necessary to increase the quick transfer capacity of logistics. However, from the perspective of the economy, the limitation of resources does not allow the expansion of all node capacity, and the expansion of node capacity will consume many logistics resources. However, if nodes do not bear a high load but use a high-capacity configuration, this will cause waste. Thus, there is a trade-off between function and economy. 2. When high-load logistics hub cities are attacked, their network efficiency decreases faster, indicating that cities with a stronger hub nature have a greater impact on the overall network efficiency. However, in the actual operation process, overloaded logistics hub cities often appear. Due to the lack of sufficient resources and costs to ensure that all cities can maintain normal operations in case of emergencies, a reasonable resource allocation strategy can minimize the transmission scale of network cascade failure. Implementing targeted protection measures for key logistics hubs can avoid damage and waste of resources due to the expansion of all urban capacity. Multiple logistics hub cities should be established within a certain range to reduce the dependence on a single city and ensure the efficient operation of the network. 3. Compared with dense and uniform network structures, sparse and heterogeneous network structures can better improve the stability of overall logistics network efficiency when some cities are damaged. The dense and homogeneous topological structure of the network itself leads to the excessive establishment of association relations between logistics hub cities and other cities, resulting in the high dependence of most cities on a few hub cities. After a few key hub cities are attacked and collapsed, they will have a huge negative impact on the overall logistics network structure. Therefore, for logistics systems with different topological structures, the capacity of nodes can be improved by increasing logistics processing resources to reduce the probability of functional failure of logistics hub cities and make the network more efficient. 4. The vulnerability of a multilayer network lies in its network layer vulnerability. Once a key logistics hub city fails in an emergency or interference event, it will have a more profound impact on the damage resistance of a multitiered logistics hub urban network system.