School of Management;
Fudan University;
Shanghai 200433;
P. R. China and Department of Mathematics and Computer Science;
Chongqing Normal University;
Chongqing 400047;
P. R. China;
Department of Mathematics and Statistics;
Curtin University of Technology;
Perth;
Australia;
Department of Applied Mathematics;
The Hong Kong Polytechnic University;
Kowloon;
Hong Kong;
P. R. China;