Vibration-based bearing fault diagnosis of high-speed trains:A literature review

Due to the advantages of comfort and safety,high-speed trains are gradually becoming the mainstream public transport in China.Since the operating speed and mileage of high-speed trains have achieved rapid growth,it is more and more urgent to ensure their reliability and safety.As an important component in the bogies of highspeed trains,the health state of the bearing directly affects the operational safety of the trains.It is therefore necessary to diagnoze the faults of bearings in the bogies of high-speed trains as early as possible.In this paper,the bearing fault diagnostic methods for high-speed trains have been systematically summarized with their challenges and perspectives.First,it briefly introduces the structure of bearings in the bogies as well as the fault characteristic frequencies.Then,a brief review of the research on vibration-based signal processing methods and machine learning methods has been provided.Finally,the challenges and future developments of vibrationbased bearing fault diagnostic methods for high-speed trains have been analyzed.

Evolution of the Raman spectrum of graphene grown on copper upon oxidation of the substrate

在在一部铜电影上种的单个层的 graphene 的拉曼光谱的重要变化在发生在周围的条件下面的内在的底层的自发的氧化以后被观察。graphene G 和 2D 拉曼模式的频率被发现经历红移动，当二个乐队的紧张由超过一个数量级变化时。为了理解这些的起源，完成，我们进一步由扫描通道描绘了样品显微镜学(STM ) ，扫描通道光谱学(圣) ，和原子力量显微镜学(AFM ) 。没有破坏 graphene overlayer 的水晶的顺序或改变做水平的搬运人，底层的氧化在底层生产了可估计的折皱。我们以 graphene 层的折皱导致的张力的紧张解释拉曼频率的红移动。在有氧化的拉曼紧张的变化从对在散布过程的拉曼结合 graphene 层的光的效率的薄亚铜的氧化物电影的影响产生。