1. National Institute of Materials Physics Atomistilor Street, No. 405A, P.O. Box MG 07 Magurele 077125 Romania
2. University Politehnica of Bucharest BN 002, 313 Splaiul Independentei, Sector 6, 060042 Bucharest Romania
3. Faculty of Horticulture University of Agronomic Sciences and Veterinary Medicine 59 Marasti Blvd. Bucharest 011464 Romania
4. Department of Strength of Materials Faculty of Engineering and Management of Technological Systems University Politehnica of Bucharest 313 Splaiul Independentei Bucharest 060042 Romania