V.V. Berezhnoy - Ph.D. (Eng.), Associate Professor, Department of the Applied Mathematics and Mathematical Modeling, Institute of Mathematics and Natural Sciences, North Caucasus Federal University (Stavropol) E-mail: beregnoj@yandex.ru N.N. Nagornov - Post-graduate Student, Institute of Mathematics and Natural Sciences, North Caucasus Federal University (Stavropol) E-mail: sparta1392@mail.ru