1. Institute of Technical Physics Faculty of Natural Sciences and Technology Riga Technical University P. Valdena Street 3/7 Riga LV‐1048 Latvia
2. Institute of Materials and Surface Engineering Faculty of Natural Sciences and Technology Riga Technical University P. Valdena Street 3/7 Riga LV‐1048 Latvia
3. Institute of Mechanics and Mechanical Engineering Faculty of Civil and Mechanical Engineering Riga Technical University Kipsala Street 6b Riga LV‐1048 Latvia