“…Ever since the development of the Black-Scholes derivative pricing model and the Merton portfolio selection model, a large amount of research interest has been led into this area, and various analytical as well as numerical approaches together with their applications in finance practice have been discussed [16,23,24,27,28,29,30,31,32,34,35,36]. In fact, optimal portfolio selection problem is essentially to achieve a balance between uncertain returns and risks, for which the mean-variance methodology has become one of the most important tools, ever since Markowitz's pioneering work on a static investment model [25].…”