Workers work at a construction site of the Beijing-Zhangjiakou high-speed railway in Zhangjiakou, north China's Hebei Province, June 11, 2018. The railway, connecting China's capital Beijing and Zhangjiakou of north China's Hebei Province, is designed at a speed of 350 kilometers per hour and is expected to be put into use at the end of 2019. (Xinhua/Yang Shiyao)