Visitors view a model of high-speed cargo train with a top speed exceeding 250 km per hour in Beijing, capital of China, May 21, 2019. The 19th National Science and Technology Week is held from May 19 to 26. In Beijing, the main venue of the event, more than 410 major scientific and technological achievements in aerospace, artificial intelligence, information technology and biotechnology are displayed. (Xinhua/Ren Chao)