Aerial photo taken on Dec. 25, 2020 shows team members walking on a frozen river with yaks during a border patrol in northwest China's Xinjiang Uygur Autonomous Region. A division of Xinjiang Production and Construction Corps in Yecheng County of Tumxuk is stationed in the hinterland of the Kunlun Mountains at an average altitude of about 4,000 meters. A team in the Corps regularly heads towards the mountain peaks and patrols the border with yaks. (Xinhua/Hu Huhu)