1. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu, China
2. Key Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of Education, Lanzhou University, Lanzhou, Gansu, China
3. Conservation and Research institute, Dunhuang Academy, Dunhuang, Gansu, China
4. National Research Center for Conservation of Ancient Wall Paintings, Dunhuang Academy, Dunhuang, Gansu, China