1. Faculty of Electrical Engineering and Computer Science, VSB-Technical University of Ostrava 1 , 708 00 Ostrava, Czech Republic
2. Faculty of Materials Science and Technology, VSB-Technical University of Ostrava 2 , 708 00 Ostrava, Czech Republic
3. Czech Advanced Technology and Research Institute, Palacky University Olomouc 3 , 779 00 Olomouc, Czech Republic
4. Faculty of Mathematics and Physics, Charles University Prague 4 , 180 00 Prague, Czech Republic