1. College of Science; Northwest A&F University; Yangling Shaanxi 712100 China
2. Department of Physics; Pukyong National University; Busan 608-737 Korea
3. Department of Physics; Changwon National University; Changwon 641-773 Korea
4. Department of Electronic Material Engineering; Silla University; Busan 617-736 Korea
5. Department of Ophthalmic Optics; Kaya University; Gimhae 621-748 Korea