1. Associate Professor, Univ. Politehnica of Bucharest, 313 Splaiul Independentei, Bucharest 060042, Romania.
2. Lecturer, Univ. Politehnica of Bucharest, 313 Splaiul Independentei, Bucharest 060042, Romania (corresponding author). ORCID: .
3. Professor, Univ. Politehnica of Bucharest, 313 Splaiul Independentei, Bucharest 060042, Romania; Member of the Physics Section, Academy of Romanian Scientists, 54 Splaiul Independentei, Bucharest 050094, Romania.