V.V. Zemlyakov - Ph. D. (Phys.-Math.), Associate Professor, Southern Federal University (Rostov-on-Don). E-mail: vvzem@yandex.ru V.L. Zemlyakov - Dr. Sc. (Eng.), Associate Professor, Head of Department, Southern Federal University (Rostov-on-Don). E-mail: vlzeml@mail.ru I.S. Shabarshina - Ph. D. (Phys.-Math.), Associate Professor, Southern Federal University (Rostov-on-Don). E-mail: shabarshina@mail.ru