1. College of Engineering and Technology, Jilin Agricultural University, Changchun 130118, P. R. China
2. Institute of Agricultural Resources and Environment, Jilin Academy of Agricultural Sciences, Changchun 130033, P. R. China
3. Key Laboratory of Engineering Dielectric and Applications (Ministry of Education), School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, P. R. China
4. College of Animal Medicine, Jilin Agricultural University, Changchun 130118, P. R. China