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In the large-scale and ultra-dense Internet of Vehicles (IoVs), constructing the simplest backbone network is an urgent problem to be solved. In fact, constructing the simplest backbone network is an NP-hard problem, and at present, there is no effective solution. In this paper, we propose a graph-based clustering algorithm to solve this problem and construct the simplest backbone network in the large-scale and ultra-dense IoV. We establish a backbone network model for the large-scale and ultra-dense IoV and optimize the backbone network by employing a novel local search iterative algorithm. Simulation results show that with the increase in node density, the number of clusters selected by the proposed algorithm tends to be stable, while the number of optimized clusters decreases by 28.87% on an average. Thus, the proposed algorithm can effectively simplify the backbone network.

In the present study, the oxidation resistance of magnesium alloyed with Gd and Ce was investigated. The high-temperature oxidation resistance of Mg-3.5Gd-xCe (x = 0, 0.2, 0.4, 0.7 and 1.0 wt%) alloys was evaluated at temperatures between 550°C and 650°C. Results indicate that adding less than 0.7 wt% Ce resulted in high oxidation resistance, whereas the Ce addition exceeding 0.7 wt% deteriorated the oxidation resistance. The high oxidation resistance phenomenon is attributed to the formation of compact oxide films primarily composed of MgO, Gd 2 O 3 , and a small amount of CeO 2 on the surface of Mg-3.5Gd-0.2Ce and Mg-3.5Gd-0.4Ce alloys. These compact oxide films can prevent the matrix from experiencing further oxidation. The deteriorated oxidation resistances of Mg-3.5Gd-0.7Ce and Mg-3.5Gd-1Ce alloys were found to be due to the severe internal oxidation caused by the distributed Mg 12 Ce phases along the grain boundaries.