TY - JOUR TT - On the Quaternionic Focal Curves AU - (bayrak) Gürses, Nurten AU - Bektaş, Özcan AU - Yüce, Salim PY - 2017 DA - August DO - 10.19113/sdufbed.14005 JF - Süleyman Demirel Üniversitesi Fen Bilimleri Enstitüsü Dergisi JO - J. Nat. Appl. Sci. PB - Süleyman Demirel Üniversitesi WT - DergiPark SN - 1308-6529 SP - 357 EP - 366 VL - 21 IS - 2 KW - Quaternions KW - Quaternionic curves; Osculating hypersphere; Focal curves; Semi-Euclidean space N2 - In this study, a brief summary about quaternions and quaternionic curves are firstly presented. Also, the definition of focal curve is given. The focal curve of a smooth curve consists of the centers of its osculating hypersphere. By using this definition and the quaternionic osculating hyperspheres of these curves, the quaternionic focal curves in the spaces $\Q$ and $\Q_\nu$ with index $\nu=\{1,2\}$ are discussed. Some relations about spatial semi-real quaternionic curves and semi-real quaternionic curves are examined by using focal curvatures and "scalar Frenet equations" between the focal curvatures. Then, the notions: such as vertex, flattenings, a symmetry point are defined for these curves. Moreover, the relation between the Frenet apparatus of a quaternionic curve and the Frenet apparatus of its quaternionic focal curve are presented. CR - [1] Ward, J. P. 1997. Quaternions and Cayley Numbers, Kluwer Academic Publishers, Boston/London. CR - [2] Bharathi, K. and Nagaraj, M. 1987. Quaternion Valued Function of a Real Variable Serret-Frenet Formulae, Indian Journal of Pure and Applied Mathematics. 18 (6), 507–511. CR - [3] Tuna, A. 2002. Serret Frenet formulae for Quaternionic Curves in Semi Euclidean Space. Master Thesis, Süleyman Demirel University, Graduate School of Natural and Applied Science, Isparta, Turkey. CR - [4] Çöken, A. C. and Tuna, A. 2004. 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