This paper measures the strength, direction, scope and pattern of the economic ties of American snow sports through the comprehensive use of gravity model, social network analysis and nuclear density analysis, so as to clarify the spatial characteristics of the economic ties of American snow sports, with a view to summing up its reference significance to China. The results show that the economic connection intensity of snow sports in the United States shows a decreasing pattern from east to west to middle. The economic connection direction of snow sports in the United States has regional proximity, economic development level, snow resource abundance and population size. The economic connection range of snow sports is distributed in four major ranges, and the radiation capacity is gradually decreasing from northeast to central to south to west. The economic connection pattern of snow sports in the United States is distinct, showing four vertical subgroups from east to west. Based on the development experience of snow sports in the United States and the current situation of China, the following suggestions are put forward. Based on resource advantages, fully radiate the vitality of the ski industry; taking economic development as the engine, innovate and tap the potential of skiing industry; guided by resource integration, give play to the regional synergy effect of skiing industry; guided by the leading effect, build four high-quality skating industry development zones in the east, west, north and south.

The delayed detached eddy simulation (DDES) coupled with the acoustic finite element method (FEM) is applied to analyze aerodynamic noise characteristics of a high-speed train with a pantograph. Numerical results are presented in terms of spectrum characteristics and distributions of aerodynamic noise in near and far fields in the case of pantograph with demo in up and down situations. The influence of different modeling methods on the flow field of the pantograph is considered, and the effects of scattering and reflection of sound waves from the body and shroud panels on aerodynamic noise results are also took into account. The following interesting phenomena are drawn. 1) Under the pantograph shape and selected opening direction, the noise induced by downpantograph with dome is higher than that induced by up-pantograph with dome. 2) The noise induced by the dome has a large proportion of noise in the low frequency region below 300 Hz, while the noise induced by the pantograph has a greater influence after 300 Hz. Using the dome as the sound source face, the noise is larger in the case of up-pantograph. 3) About the directivity of the induced noise, in the horizontal plane, the front of the pantograph, the dome contributes more to the noise, and in the rear of the pantograph, the pantograph contributes more. In the upper part of the train, the noise induced by the pantograph itself is greater than the noise induced by the dome, becoming the main source of aerodynamic noise in this case.