1. China University of Mining and Technology (Beijing), State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, Beijing, China and China University of Mining and Technology (Beijing), College of Geoscience and Surveying Engineering, Beijing, China.
2. China University of Mining and Technology (Beijing), State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, Beijing, China and China University of Mining and Technology (Beijing), College of Geoscience and Surveying Engineering, Beijing, China. (corresponding author)