[1] Xi An Jiao Tong Univ, Sch Energy & Power Engn, Xian 710049, Peoples R China
[2] Huzhou Univ, Dept Math, Huzhou 313000, Peoples R China
[3] Northwestern Polytech Univ, Dept Math, Xian, Peoples R China
[4] Sun Yat Sen Univ, Dept Math, Guangzhou, Peoples R China
[5] UAE Univ, Dept Math Sci, Al Ain, U Arab Emirates