Contestants prepare an unmanned aerial vehicle (UAV) during the first International Youth UAV Science Camp & Competition (IYUAVSCC) in Xi'an, northwest China's Shaanxi Province, July 21, 2019. The first IYUAVSCC, launched by Chinese Society of Aeronautics and Astronautics (CSAA) and Northwestern Polytechnical University, kicked off here on Monday, attracting high school students from home and abroad. (Xinhua/Shao Rui)