[Yang, Qing] Wuhan Univ, Sch Water Resources & Hydropower Engn, Wuhan 430072, Peoples R China.
[Yang, Qing] South Central Univ Nationalities, Sch Math & Stat, Wuhan 430074, Peoples R China.
[Zhu, Jiayan; Li, Zhengbang] Cent China Normal Univ, Sch Math & Stat, Wuhan 430079, Peoples R China.
[Zhu, Jiayan] Wuhan Coll, Sch Informat & Commun, Wuhan 430079, Peoples R China.
[Li, Zhengbang] Cent China Normal Univ, Hubei Key Lab Math Sci, Wuhan 430079, Peoples R China.