1. Ph.D. Candidate, School of Management, China Univ. of Mining and Technology, Xuzhou 221116, P.R. China; Training Center of Chinese Postal Service Group, Shijiazhuang, Hebei 050021, P.R. China.
2. Professor, School of Management, China Univ. of Mining and Technology, No. 1, Daxue Rd., Xuzhou, Jiangsu 221116, P.R. China (corresponding author).
3. Research Assistant, School of Management, China Univ. of Mining and Technology, No. 1, Daxue Rd., Xuzhou, Jiangsu 221116, P.R. China.