Kil-Woung Jun
Chungnam National University
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Publication
Featured researches published by Kil-Woung Jun.
Journal of Mathematical Analysis and Applications | 2002
Kil-Woung Jun; Hark-Mahn Kim
Abstract In this paper, we obtain the general solution and the generalized Hyers–Ulam stability for a cubic functional equation f(2x+y)+f(2x−y)=2f(x+y)+2f(x−y)+12f(x) .
Proceedings of the American Mathematical Society | 2000
Yang-Hi Lee; Kil-Woung Jun
In this paper we prove a generalization of the stability of approximately additive mappings in the spirit of Hyers, Ulam and Rassias.
Journal of Difference Equations and Applications | 2007
Kil-Woung Jun; Hark-Mahn Kim; John Michael Rassias
In 1940, Ulam proposed the famous Ulam stability problem. In 1941, Hyers solved the well-known Ulam stability problem for additive mappings subject to the Hyers condition on approximately additive mappings. In 2003–2006, the last author of this paper investigated the Hyers–Ulam stability of additive and Jensen type mappings. In this paper, we improve results obtained in 2003 and 2005 for Jensen type mappings and establish new theorems about the Ulam stability of additive and alternative additive mappings. These stability results can be applied in stochastic analysis, financial and actuarial mathematics, as well as in psychology and sociology.
Bulletin of The Korean Mathematical Society | 2005
Kil-Woung Jun; Hark-Mahn Kim
In this paper, we obtain the general solution of a gen-eralized quadratic and additive type functional equation f(x + ay) + af(x - y) = f(x - ay) + af(x + y) for any integer a with a -1. 0, 1 in the class of functions between real vector spaces and investigate the generalized Hyers- Ulam stability problem for the equation.
Bulletin of The Korean Mathematical Society | 2003
Sang-Han Lee; Kil-Woung Jun
In this paper, we prove the stability of a quadratic type functional equation a 2 f x + y + z a + a 2 f x i y + z a + a 2 f x + y i z a + a 2 f ix + y + z a = 4f(x) + 4f(y) + 4f(z):
Bulletin of The Korean Mathematical Society | 2002
Ick-Song Chang; Kil-Woung Jun; Yong-Soo Jung
Our main goal is to show that if there exist Jordan derivations D and G on a noncommutative (n + 1)!-torsion free prime ring R such that D(x)x n i x n G(x) 2 C(R) for all x 2 R, then we have D = 0 and G = 0. We also prove that if there exists a derivation D on a noncommutative 2-torsion free prime ring R such that the mapping x 7! (aD(x);x) is commuting on R, then we have either a = 0 or D = 0.
Journal of The Korean Mathematical Society | 2004
Kil-Woung Jun; Soon-Mo Jung; Yang-Hi Lee
We prove the Hyers-Ulam-Rassias stability of the Dav- ison functional equation f(xy) + f(x + y) = f(xy + x) + f(y) for a class of functions from a ring into a Banach space and we also investigate the Davison equation of Pexider type.
Archive | 2003
Kil-Woung Jun; Yang-Hi Lee
In this paper we prove a generalization of the stability of the Pexiderized quadratic equations f 1(x + y + z) + f 2(x) + f 3(y) + f 4(z) − f 5(x + y) − f 6(y + z) − f 7(x + z) = 0 and f 1(x + y + z) + f 2(x-y + z) + f 3(x + y − z) + f 4(− x + y + z) − 4f 5(x) − 4f 6(y) − 4f 7(z) = 0 in the spirit of D.H. Hyers, S.M. Ulam, Th.M. Rassias and P. Gǎvruta.
Kyungpook Mathematical Journal | 2008
Kil-Woung Jun; Mi-Hyen Han; Yang-Hi Lee
In this paper, we obtain the Hyers–Ulam–Rassias stability of a bi-Pexider functional equation
Journal of Inequalities and Applications | 2008
Kil-Woung Jun; Yang-Hi Lee; Juri Lee