A.M. Bashkirev - Post-graduate Student, Department «Physics», Volgograd State Technical University E-mail: alexandr.bashkirev@gmail.com A.G. Shein - Dr. Sc. (Phys.-Math.), Professor, Department «Physics», Volgograd State Technical University E-mail: professor39@mail.ru D.G. Kovtun - Ph. D. (Phys.-Math.), Associate Professor, Department «Physics», Volgograd State Technical University E-mail: kdmob74@gmail.com