Audience members examine an unmanned aerial vehicle (UAV) from a Chengdu-based company, JOUAV, at a UAV expo at the Shenzhen Convention and Exhibition Center yesterday. The 4th Drone World Congress 2020 & 5th Shenzhen International UAV Expo 2020 kicked off yesterday in Hall 3 and 4 at the exhibition center and will last until tomorrow. The UAV expo attracted more than 400 exhibitors from UAV, intelligent transportation and civil aviation security industries from around the world. The hydrogen-powered UAV on display is a vertical takeoff and landing aircraft with fixed wings.  Sun Yuchen