1. School of Architecture and Engineering, Yan'an University, Yan'an 716000, PR China
2. Engineering Research Center of Efficient Exploitation of Oil and Gas Resources and Protection Ecological Environment, Universities of Shaanxi Province, Yan'an University, Yan'an 716000, PR China
3. School of Chemistry and Chemical Engineering, Yan'an University, Yan'an 716000, PR China
4. Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, PR China
5. School of Physics and Electronic Information, Yan'an University, Yan'an 716000, PR China