1. Faculty of Materials Science, Warsaw University of Technology, Warsaw, 02-507 Poland
2. Institute of Mathematics and Physics UTP University of Science and Technology, Bydgoszcz, 85-789 Poland
3. National Centre for Nuclear Research, 05-400 Otwock-Swierk, Poland
4. Faculty of Mechanical Engineering UTP University of Science and Technology, Bydgoszcz, 85-789 Poland