1. Faculty of Mechanical Engineering , Technical university of Košice , Letná 9,042 00 Košice , Slovakia .
2. Faculty of Mining, Ecology, Process Control and Geotechnology , TU Košice , Park Komenského 19, 040 01 Košice , Slovakia
3. Faculty of Mechanical Engineering , Technical university of Košice , Letná 9,042 00 Košice , Slovakia