1. Faculty of Mechanical Engineering, University of Žilina, Univerzitná 1, 01026 Žilina, Slovakia
2. Research Centre, University of Žilina, Univerzitná 1, 01026 Žilina, Slovakia
3. Faculty of Civil Engineering, University of Žilina, Univerzitná 1, 01026 Žilina, Slovakia
4. Institute of Physics, Slovak Academy of Science, Dúbravská Cesta 9, 84511 Bratislava, Slovakia
5. Institute of Experimental Physics, Slovak Academy of Science, Watsonova 47, 04001 Košice, Slovakia