G.G. Vertogradov - D.Sc. (Phys.-Math.), Professor, Southern Federal University. E-mail: vgg@bmail.ru E.G. Vertogradova - Engineer, Southern Federal University. E-mail: evertogr@yandex.ru V.P. Uryadov - D.Sc. (Phys.-Math.), Head of Department. E-mail: uryadovvp@nirfi.sci-nnov.ru