T.I. Svyatova - Post-graduate Student, Department «Applied Mathematics and Informatics», Ulyanovsk State Tech-nical University. E-mail: tatyana.krasko@rambler.ru V.N. Klyachkin - Dr. Sc. (Eng.), Professor, Department «Applied Mathematics and Informatics», Ulyanovsk State Technical University. E-mail: v_kl@mail.ru