Authors
I. Grinevich
Riga Technical University, Daugavpils Branch, 90 Smilshu Str.,, Daugavpils, Latvia
Vl. Nikishin
Riga Technical University, Daugavpils Branch, 90 Smilshu Str.,, Daugavpils, Latvia
M. Laitans
Riga Technical University, 6 Ezermalas Str.,, Riga, Latvia