Based on panel data from 30 provinces in China from 2008 to 2017, this paper constructs a quantile regression econometric model to analyze whether China's environmental regulation has an impact on export trade and to verify whether the Porter hypothesis has been valid in China in recent years. The results show that in the short term, environmental regulations have a restraining effect on export trade, while in the long run, due to the existence of innovation efficiency, environmental regulations will change from having a restraining effect to a promoting effect on export trade. Strict environmental regulations will reduce the production cost of Chinese products, further improve the export competitiveness of Chinese enterprises, and promote export trade. The empirical results verify the conclusion that the Porter hypothesis is confirmed in China. The following three suggestions are proposed for China's exports to promote the win-win of China's green development and export trade: promote the realization of international and domestic double circulation, avoid becoming "pollution shelters" and support technological innovation in environmental protection industries.

The quadrupole aerodynamic noise is a difficult problem in numerical simulation of the aerodynamic noise. The Kirchhoff-Ffowcs Williams and Hawkings (K-FWH) equation method and the three-dimensional compressible Large Eddy Simulation (LES) method are adopted in this manuscript for aerodynamic noise accuracy simulation of 600km/h high-speed train. The influence of different distributions of penetrable integral surfaces on the results of far-field aerodynamic noise is discussed. The optimum combination form of penetrable integral surfaces is obtained. The aerodynamic noise of high-speed train considering quadrupole can be calculated efficiently and accurately by using the upstream body surface and wake area penetrable integral surface as sound source surface. The wake area penetrable integral surface should contain the main vorticity structure of the wake as far as possible and the surface vorticity amplitude should be insignificant. The contribution rate of the dipole and quadrupole to the total aerodynamic noise energy of high-speed train is different. The aerodynamic noise energy of the upstream measurement points is mainly dipole aerodynamic noise energy, while that of the downstream measurement points is mainly dipole and quadrupole noise energy. The method proposed in this manuscript is of great significance in the aerodynamic noise numerical simulation of 600km/h high-speed train.INDEX TERMS 600km/h high-speed train, quadrupole noise, large eddy simulation, aerodynamic noise, penetrable integral surface method.

No abstract

No abstract