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Many studies have shown that the rail corrugation on the small radius curve section of subway floating slab track is serious. And it seems to be different from the rail corrugation on the common track. The track structure must play an important role in the generation and development of rail corrugation. This paper measured a subway line in Tianjin, including 2 different track structures, and analyzed the measured data by using the international evaluation and acceptance indexes of rail corrugation. The results show that the inner rail of short sleeper monolithic track (SSMT) has poor smoothness in the wavelength range of 0-300 mm, and the overall smoothness of outer rail is good; the inner rail of steel spring floating slab track (SSFST) has poor smoothness in the wavelength range of 100-300 mm, and the outer rail has poor smoothness in the wavelength range of 300-1000 mm. Then the vehicle-track coupling model and wheel-rail wear calculation model is established. The calculation results show that in the existing rail corrugation, the short-wavelength rail corrugation of 20-25 mm will continue to appear or deteriorate, and the development of rail corrugation of other wavelengths will slow down or stop to varying degrees; with the increase of train passing times, the rail corrugation of SSFST with the wavelength of 315 mm develops the fastest, and the rail corrugation of SSMT with wavelengths of 20 mm and 160 mm develops the fastest.

By analyzing the measured corrugation data, the cause of rail corrugation was discussed theoretically. Then, the vehicle-track coupling model was used to study the stick-slip characteristics of wheel-rail system. Finally, the cause of rail corrugation was explained by combining modal analysis and wheel-rail stick-slip relation. The transverse stick-slip curve on the inner rail-inner wheel of the leading wheelset presents a negative slope characteristic, which makes the inner wheel easy to slide on the inner rail surface and aggravates the wear of inner rail; there are also negative slope sections of the stick-slip curve on the outer rail-outer wheel of the trailing wheelset, but the adhesion coefficient is relatively large, indicating that the outer wheel will not slide obviously and the wear is relatively small. Meantime, with the increase of line curve radius, the negative slope phenomenon of stick-slip curves on the inner and outer rail sides shows a decreasing trend, which illustrates that the sliding wear of wheel is gradually reduced, and thus the occurrence probability of rail corrugation decreases. Combined with modal analysis, it can be seen that the coupling action of wheel discs bending vibration and inner rail bending-torsional vibration is the main cause of rail corrugation under the condition of wheel-rail system with stick-slip negative slope.

The aerodynamic noise behavior of flow passing the simplified leading car and nose car scale models of a high-speed train is investigated through the vortex sound theory and acoustic analogy approach. The unsteady flow developed around the geometries is solved numerically and the data are applied to study the near-field quadrupole sound source and calculate the far-field noise radiated. It is found that the turbulent flow developed around the leading car is characterized by multi-scale vortices separated from the geometries. The intensity of volume dipole source is much larger than that of volume quadrupole source and the volume dipole source becomes the predominate source of the near-field quadrupole noise. The flow is separated noticeably in the regions of the nose, bogies, bogie cavities, and train tail of the leading car where the pressure fluctuations are generated largely upon the solid surfaces and correspondingly a dipole noise of high level is produced. By comparison, the noise contribution from the leading bogie and bogie cavity is larger than that from the other components. Moreover, the numerical and experimental results of train nose car model demonstrate that the flow around the bogie region is the dominant aerodynamic sound source. Therefore, the flow-induced noise generated from the leading cars may be reduced efficiently within a certain frequency range and specific direction by mitigating the flow interactions around the areas of leading bogie and bogie cavity.

A mild crystallization approach to MOF@TiO2 core–shell nanostructures for the efficient adsorption and photodegradation of anionic dyes.

The antenna array arrangement determines the rank of the transformation matrix in 1-D mirrored aperture synthesis (1-D MAS). Only when the transformation matrix is of full rank can cosine visibilities be precisely solved from the transformation equations. However, the existing literature states that full rank cannot be realized with the default perpendicular polarization of antennas. In this letter, the transformation matrices of arrays with various polarizations of antennas are discussed, and a type of full array with a full-rank transformation matrix is found. Based on these results, the existence conditions for an array with a full-rank transformation matrix are obtained. In addition, a search algorithm with a shorter search time than the existing algorithm is designed to find low-redundancy arrays with a full-rank transformation matrix. The simulations verify that cosine visibilities are precisely solved from the transformation equations for the array with a full-rank transformation matrix.