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Vol.18 No.4

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Abstract

In this paper, we show that if a transitive set <TEX>${\Lambda}$</TEX> is <TEX>$C^1$</TEX>-stably expansive, then <TEX>${\Lambda}$</TEX> admits a dominated splitting.

Kim, Eun-Mi ; Ahn, Sun-Shin pp.293-304 https://doi.org/10.7468/jksmeb.2011.18.4.293
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Abstract

The notions of an initial section and a special set in BH-algebras are defined and some of their properties are obtained. The notion of a complicated BH-algebra is introduced and some related properties are obtained. Finally, the notion of essences in BH-algebras are defined, and many properties are investigated.

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Abstract

In this paper, we denote that R is a near-ring and G an R-group. We initiate the study of the substructures of R and G. Next, we investigate some properties of R-groups, d.g. near-rings and monogenic (R, S)-groups.

Jin, Sun-Sook ; Lee, Yang-Hi pp.313-328 https://doi.org/10.7468/jksmeb.2011.18.4.313
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Abstract

We investigate the stability of the functional equation f(x+y+z+w)+2f(x)+2f(y)+2f(z)+2f(w)-f(x+y)-f(x+z)-f(x+w)-f(y+z)-f(y+w)-f(z+w)=0 by using a flxed point theorem in the sense of L. C<TEX>$\breve{a}$</TEX>adariu and V. Radu.

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Some new Lyapunov-type inequalities for a class of nonlinear differential systems, which are natural refinements and generalizations of the well-known Lyapunov inequality for linear second order differential equations, are given. The results of this paper cover some previous results on this topic.

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In this paper, we investigate h-stability of the nonlinear perturbed differential systems.

Argyros, Ioannis K. ; Ren, Hongmin pp.345-351 https://doi.org/10.7468/jksmeb.2011.18.4.345
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Taylor's formula is a powerful tool in analysis. In this study, we assume that an operator is m-times Fr<TEX>$\acute{e}$</TEX>chet-differentiable and satisfies a Lipschitz condition. We then obtain some Taylor formulas using only the Lipschitz constants. Applications are also provided.

Lee, Jae-Won ; Jin, Dae-Ho pp.353-359 https://doi.org/10.7468/jksmeb.2011.18.4.353
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In this paper, we characterize a semi-Riemannian manifolds satisfies the axiom of indefinite surfaces. We obtain the following result: If a semi-Riemannian manifold satisfies the axiom of indefinite surfaces, then it is a real space form.

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In this paper, we construct a cover (<TEX>$\mathcal{L}(X)$</TEX>, <TEX>$c_X$</TEX>) of a space X such that for any cloz-cover (Y, f) of X, there is a covering map g : <TEX>$Y{\longrightarrow}\mathcal{L}(X)$</TEX> with <TEX>$c_X{\circ}g=f$</TEX>. Using this, we show that every Tychonoff space X has a minimal cloz-cover (<TEX>$E_{cc}(X)$</TEX>, <TEX>$z_X$</TEX>) and that for a strongly zero-dimensional space X, <TEX>${\beta}E_{cc}(X)=E_{cc}({\beta}X)$</TEX> if and only if <TEX>$E_{cc}(X)$</TEX> is <TEX>$z^{\sharp}$</TEX>-embedded in <TEX>$E_{cc}({\beta}X)$</TEX>.

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In this article, we study generalized slant cylindrical surfaces (GSCS's) with pointwise 1-type Gauss map of the first and second kinds. Our main results state that GSCS's with pointwise 1-type Gauss map of the first kind coincide with surfaces of revolution with constant mean curvature; and the right cones are the only polynomial kind GSCS's with pointwise 1-type Gauss map of the second kind.

Journal of the Korean Society of Mathematical Education Series B: The Pure and Applied Mathematics