• Bulletin of the Korean Mathematical Society
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• v.51 no.4
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• pp.1211-1216
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• 2014

In this paper, we study the structure of m-quasi Einstein manifolds when there exists another distinct solution to the (${\lambda}$, n + m)-Einstein equation. In particular, we derive sufficient conditions for the non-existence of such solutions.

• Bulletin of the Korean Mathematical Society
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• v.34 no.4
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• pp.653-665
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• 1997

We define an almost quaternionic Kaehler product manifold and study its submanifolds. Moreover we construct the curvature tensor of the product manifold of two quaternionic forms.

• Kyungpook Mathematical Journal
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• v.59 no.4
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• pp.783-795
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• 2019

We prove that a Lorentzian concircular structure (LCS)-manifold does not admit any null hypersurface which is tangential or transversal to its characteristic vector field. Due to the above, we focus on its ascreen null hypersurfaces and show that such hypersurfaces admit a symmetric Ricci tensor. Furthermore, we prove that there are no totally geodesic ascreen null hypersurfaces of a conformally flat (LCS)-manifold.

• Bulletin of the Korean Mathematical Society
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• v.32 no.1
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• pp.13-18
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• 1995

In order to investigate the differential structure of a Riemannian manifold (M, g), it seems a powerful tool to study the differential structure of its tangent bundle TM. In this point of view, K. Aso [1] studied, using the Sasaki metric $\tilde{g}$, the relation between the curvature tensor on (M, g) and that on (TM, $\tilde{g}$).

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.757-766
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• 1996

The purpose of this paper is to study a real hypersurface of $M_n(c)$ where structure vector $\zeta$ is principal and satisfying $\bigtriangledown_\zeta S = (\bigtriangledown S)\zeta$ (section 2) and also satisfying $\bigtriangledown_\zeta S = a(S \phi - \phi S)$ (section 3) where a is constant.

• Journal of the Korean Mathematical Society
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• v.41 no.3
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• pp.535-565
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• 2004

In this paper we consider the notion of ξ-invariant or (equation omitted)-invariant real hypersurfaces in a complex two-plane Grassmannian $G_2$( $C^{m+2}$) and prove that there do not exist such kinds of real hypersurfaces in $G_2$( $C^{m+2}$) with parallel second fundamental tensor on a distribution ζ defined by ζ = ξ U(equation omitted), where(equation omitted) = Span ｛ξ$_1$, ξ$_2$, ξ$_3$｝.X>｝.

• Bulletin of the Korean Mathematical Society
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• v.42 no.2
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• pp.279-294
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• 2005

We study a real hypersurface M satisfying $L_{\xi}S=0\;and\;R_{\xi}S=SR_{\xi}$ in a complex hyperbolic space $H_n\mathbb{C}$, where S is the Ricci tensor of type (1,1) on M, $L_{\xi}\;and\;R_{\xi}$ denotes the operator of the Lie derivative and the Jacobi operator with respect to the structure vector field e respectively.

• Kyungpook Mathematical Journal
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• v.63 no.1
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• pp.79-95
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• 2023

In this note, we define a Berger type deformed Sasaki metric as a natural metric on the second tangent bundle of a manifold by means of a biparacomplex structure. First, we obtain the Levi-Civita connection of this metric. Secondly, we get the curvature tensor, sectional curvature, and scalar curvature. Afterwards, we obtain some formulas characterizing the geodesics with respect to the metric on the second tangent bundle. Finally, we present the harmonicity conditions for some maps.

• International Journal of Contents
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• v.7 no.4
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• pp.24-29
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• 2011

In this paper, we propose a method to segment the bottle label in images taken by mobile phones using multi-gradient approaches. In order to segment the label region of interest-object, the saliency map method and Hough Transformation method are first applied to the original images to obtain the candidate region. The saliency map is used to detect the most salient area based on three kinds of features (color, orientation and illumination features). The Hough Transformation is a technique to isolated features of a particular shape within an image. Therefore, we utilize it to find the left and right border of the bottle. Next, we segment the label based on the gradient information obtained from the structure tensor method and edge method. The experimental results have shown that the proposed method is able to accurately segment the labels as the first step of product label recognition system.

• Journal of the Korean Magnetic Resonance Society
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• v.7 no.1
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• pp.16-24
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• 2003

Nuclei with the spin quantum number not smaller than unity have not only the nuclear magnetic moment but also the electric quadrupole moment. The quadrupole moment couples with the electric field gradient (EFG) to produce the nuclear quadrupole interaction. It is well known that two independent parameters, i.e. the quadrupole coupling constant (QCC) and the asymmetry parameter ($\eta$) together with the principal axis directions can fully describe the interaction and are very sensitive to the local symmetry and structure of the solid. In order to obtain quantitative estimates of the EFG tensor for various simple ionic configurations surrounding the nucleus under consideration, we employ the simple point charge approximation and apply the calculated results to some real crystals. General agreement is rather satisfactory.