A visitor (center) asks questions on a "Real-time Navigation System for Large Underground Garage Based on LED Optical Communication" brought by China University of Petroleum at the 15th Challenge Cup Shandong province's University Students Extracurricular Academic Technology Competition in Yantai, East China's Shandong province, on May 21, 2017. The competition attracted 206 teams from 59 universities who brought projects covering 10 areas such as mechanical control, life sciences, energy and chemical industry and social management. [Photo/VCG]