This paper addresses evolutionary multi-objective portfolio optimization in the practical context by incorporating realistic constraints into the problem model and preference criterion into the optimization search process. The former is essential to enhance the realism of the classical mean-variance model proposed by Harry Markowitz, since portfolio managers often face a number of realistic constraints arising from business and industry regulations, while the latter reflects the fact that portfolio managers are ultimately interested in specific regions or points along the efficient frontier during the actual execution of their investment orders. For the former, this paper proposes an order-based representation that can be easily extended to handle various realistic constraints like floor and ceiling constraints and cardinality constraint. An experimental study, based on benchmark problems obtained from the OR-library, demonstrates its capability to attain a better approximation of the efficient frontier in terms of proximity and diversity with respect to other conventional representations. The experimental results also illustrated its viability and practicality in handling the various realistic constraints. A simple strategy to incorporate preferences into the multi-objective optimization process is highlighted and the experimental study demonstrates its capability in driving the evolutionary search towards specific regions of the efficient frontier.

Abslract-With the increasing demands in the storage capacity and access speed of hard disk drive (HDD), data is recorded in ever-narrow tracks that must be followed with extreme precision. This paper presents an encoding and decoding scheme for more eiticient and accurate position sensing. The multiple frequencies servo pattern encoding allows an overall reduction of servo overhead and together with the high flexibility and sensitivity of the digital position sensing technique; precise track following on very narrow track is possible. This paves the way for ultra high track density magnetic recording. Index Terms-hard disk drive, position error signal (PES), servo pattern, servo demodulation.