1. Department of Physics, West University of Timisoara, Bulv. V. Parvan 4, 300223 Timisoara, Romania, agneta.balint@e-uvt.ro
2. Department of Computer Science, West University of Timisoara, Bulv. V. Parvan 4, 300223 Timisoara, Romania, stefan.balint@e-uvt.ro
3. Department of Physics, West University of Timisoara, Bulv. V. Parvan 4, 300223 Timisoara, Romania, adrian.neculae@e-uvt.ro