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A stacked hexagonal prism, Ag@Ni-MOF-1, was developed as an integrated SERS platform not only for in situ catalyzing in situ synthesis of DA-quinone at physiological pH, but for establishing an approach for specific determination of Cys in brain.

The wheel polygonization and rail corrugation are typical wheel–rail periodic wear problems, which seriously affect the safe operation of high-speed railways. In the present paper, the interaction between the wheel polygon and the rail corrugation in the long-slope section of high-speed railways is mainly studied based on theory of friction coupling vibration. Firstly, the simulation model of the wheel–rail contact model is established, as well as the polygonal wear of the wheel and the corrugated wear of the rail. Then, the stability analyses of the wheel–rail system with periodic wear are studied, in which the four working conditions of smooth rail–smooth wheel, polygonal wheel–smooth rail, smooth wheel–corrugated rail and polygonal wheel–corrugated rail are compared. Finally, the competition mechanisms between the wheel polygon and rail corrugation under different parameters are discussed, including the wheel–rail friction coefficient and the depth of periodic wear of the wheel–rail system. The numerical results show that both the periodic wear of the wheel and rail with certain relevance will increase the friction coupling vibration of the wheel–rail system, which may aggravate the subsequent relevant wheel polygonal and rail corrugation wear. With the increase of the friction coefficient between wheel and rail, as well as the depth of the wheel polygon and rail corrugation, the vibration trend of the friction coupling vibration of the wheel–rail system increases gradually. Moreover, the proportion of the wheel polygon’s influence on the friction coupling vibration of the wheel–rail system is greater than that of rail corrugation.

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Focusing on the mechanism of the abnormal phenomenon of rail corrugation on the low rail of small-radius curve section of Guangzhou–Zhuhai intercity railway, the distribution regularities and the track irregularities are studied through the overall and local field surveys. Then, the dynamic model of vehicle-track system on the section is established to explore the wheel-rail dynamic characteristics. Next, the relevant finite element model of the wheel-rail system and the wear model of rail corrugation are established. The friction self-excited vibration analysis and feedback vibration analysis are carried out to investigate the dynamic causes of such abnormal rail corrugation. Field survey proposes that the dominant wavelength of the abnormal rail corrugation is 200–300 mm and the sub-wavelength is 70–100 mm. Analyses show that the friction self-excited vibration of the multi-wheelset-track system caused by the saturated creep force on the guide wheelset in the small-radius section may induce the rail corrugations with these two wavelengths. The possibility of inducing the rail corrugation with 200–300 mm wavelength is greater. On the other hand, the feedback vibration of corrugated wear will aggravate the development of the two corrugated wears. Overall, the generation and development of the abnormal rail corrugations are affected by the self-excited vibration of the wheel-rail system and the feedback vibration of track irregularity.