The work is supported by the Scientific Research Fund of Hunan Provincial Education Department under grant No. 15C0659, 14C0542, and National Key Technology Research Program of China under grant No. 2012BAD35B05, 2012BAD35B07, and Research Program of Hunan Rural Information Service Key Lab under grant No. XAI20150326, and the Scientific Research Fund of Sichuan Provincial Education Department under grant No. 15ZA0308.