A.Kh. Gilmutdinov - Dr.Sc. (Eng.), Associate Professor, Kazan National Technical Research University named after A.N. Tupolev. E-mail: agilmutdinov@rambler.ru
M.M. Gil-metdinov - Ph.D. candidate, Kazan National Technical Research University named after A.N. Tupolev. E-mail: marat-kzn@list.ru