T.Т. Nguyen Post-graduate Student, Department of Biotechnical Systems, Saint Petersburg Electrotechnical University «LETI» E-mail: nguyentuyen1988@gmail.com Z.M. Yuldashev Dr.Sc. (Eng.), Professor, Head of Department of Biotechnical Systems, Saint Petersburg Electrotechnical University «LETI» E-mail: yuld@mail.ru