Some unmanned aerial vehicles can vertically take off and land with the ducted fan system, but there is no valid method to analyze the aerodynamic characteristics of a ducted fan system currently.是什么意思_Some unmanned aerial vehicles can vertically take off and land with the ducted fan system, but there is no valid method to analyze the aerodynamic characteristics of a ducted fan system currently.在線翻譯_英語_讀音_用法_例句