1. Research Associate, School of Mechanical Engineering, National Technical Univ. of Athens, 15780 Athens, Greece.
2. Professor, School of Mechanical Engineering, National Technical Univ. of Athens, 15780 Athens, Greece (corresponding author).
3. Assistant Professor, School of Mechanical Engineering, National Technical Univ. of Athens, 15780 Athens, Greece.
4. Professor, School of Mechanical Engineering, National Technical Univ. of Athens, 15780 Athens, Greece.