[1] Uludag Univ, Dept Phys, Fac Arts & Sci, TR-16059 Bursa, Turkey
[2] Kastamonu Univ, Fac Educ, TR-37200 Kastamonu, Turkey
[3] Univ Surrey, Dept Phys, Fac Engn & Phys Sci, Guildford GU2 7XH, Surrey, England
[4] Kocaeli Univ, TR-41100 Kocaeli, Turkey