1. College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
2. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
3. Western Scientific Observing and Experimental Station for Development and Utilization of Rural Renewable Energy, Ministry of Agriculture and Rural Affairs,Yangling, Shaanxi 712100, P. R. China
4. Shaanxi Master of Business Admistration Institute, Xi’an, Shaanxi 710005, P. R. China
5. Rural Energy and Environment Agency, Ministry of Agriculture and Rural Affairs, Beijing 100125, P. R. China