1. Polytechnic University of Bucharest , Faculty of Power Engineering, Hydraulics, Hydraulic Machines and Environmental Engineering Department , Spl. Independentei 313, Bucharest 060042 , Romania
2. Candida Oancea Institute , Polytechnic University of Bucharest , Faculty of Mechanical Engineering , Spl. Independentei 313, Bucharest 060042 , Romania