• East Asian mathematical journal
• /
• v.31 no.1
• /
• pp.33-40
• /
• 2015

We study the geometry of r-lightlike submanifolds M of a semi-Riemannian manifold $\bar{M}$ with a semi-symmetric non-metric connection subject to the conditions; (a) the screen distribution of M is totally geodesic in M, and (b) at least one among the r-th lightlike second fundamental forms is parallel with respect to the induced connection of M. The main result is a classification theorem for irrotational r-lightlike submanifold of a semi-Riemannian manifold of index r admitting a semi-symmetric non-metric connection.

• Communications of the Korean Mathematical Society
• /
• v.33 no.1
• /
• pp.305-315
• /
• 2018

This note provides a study of lightlike hypersurfaces of a generalized Robertson-Walker(GRW) space-time with a certain screen distribution, which are integrable and have good properties. Focus is to investigate geometric features from the relation of the second fundamental forms between lightlike hypersurfaces and leaves of the integrable screen distribution. Also, we shall apply those results on lightlike hypersurfaces of a GRW space-time to lightlike hypersurfaces of a Robertson-Walker(RW) space-time.

• Communications of the Korean Mathematical Society
• /
• v.34 no.1
• /
• pp.267-277
• /
• 2019

In this study, we define the dual surfaces by z = f(u) + g(v) and also classify these surfaces in ${\mathbb{I}}{\frac{1}{3}}$ satisfying some algebraic equations in terms of the coordinate functions and the Laplace operators according to fundamental forms of the surface.

• Nonlinear Functional Analysis and Applications
• /
• v.26 no.1
• /
• pp.83-92
• /
• 2021

This paper studies approximate solutions for a class of nonlinear diffusion population models. Our methods are to use the fundamental solution of heat equations to construct integral forms of the models and the well-known Banach compression map theorem to prove the existence of positive solutions of integral equations. Non-steady-state local approximate solutions for suitable harvest functions are obtained by utilizing the approximation theorem of multivariate continuous functions.

• Kyungpook Mathematical Journal
• /
• v.62 no.3
• /
• pp.509-531
• /
• 2022

In this paper we define a new family of ruled surfaces using an othonormal Sannia frame defined on a base consisting of the striction curve of the tangent, the principal normal, the binormal and the Darboux ruled surface. We examine characterizations of these surfaces by first and second fundamental forms, and mean and Gaussian curvatures. Based on these characterizations, we provide conditions under which these ruled surfaces are developable and minimal. Finally, we present some examples and pictures of each of the corresponding ruled surfaces.

• 대한예방의학회:학술대회논문집
• /
• 1994.02a
• /
• pp.412-415
• /
• 1994

The fundamental assumption that thresholds exist for noncarcinogenic toxic effects of chemicals is reviewed; this assumption forms the basis for the no-observed-effect level/ safety-factor (NOEL/SF) approach to risk assessment for such effects. The origin and evolution of the NOEL/SF approach are traced, and its limitations are discussed. The recently proposed use of dose-response modeling to estimate a benchmark dose as a replacement for the NOEL is explained. The possibility of expanding dose-response modeling of non carcinogenic effects to include the estimation of assumed thresholds is discussed. A new method for conversion of quantitative toxic responses to a probability scale for risk assessment via dose-response modeling is outlined.

• Communications of the Korean Mathematical Society
• /
• v.38 no.2
• /
• pp.629-641
• /
• 2023

The aim of this paper is two-fold. First, we study the Chinea-Gonzalez class C₁₂ of almost contact metric manifolds and we discuss some fundamental properties. We show there is a one-to-one correspondence between C₁₂ and Kählerian structures. Secondly, we give some basic results for Riemannian curvature tensor of C₁₂-manifolds and then establish equivalent relations among 𝜑-sectional curvature. Concrete examples are given.

• Honam Mathematical Journal
• /
• v.45 no.4
• /
• pp.572-584
• /
• 2023

In this study, we search for Pell and Pell-Lucas numbers, which are concatenations of two repdigits and find these numbers to be only 12, 29, 70 and 14, 34, 82, respectively. We use Baker's Theory and Baker-Davenport basis reduction method while finding the solutions.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.14 no.1
• /
• pp.1-11
• /
• 2012

The Original forms of the ancient clothing have been evolved in various designs and showed each unique formativeness based on the basic principles of origami. The purpose of this study was to analyze the basic clothing formativeness in the original forms of the ancient clothing based on the principles of origami. The methods of this study were to identify significant relevant ancient clothing figures with each unique formativeness based on the principles of origami and analyze the formativeness characters and values through comprehensive literature reviews on topic-related books and theses on a foundation of triangulation of observer. The results were as follows: The significant ancient clothing figures with principles of origami were identified as kalasiris, chiton, chlamys, toga, dalmatica, paludamentium, and lorum. The formative principles applied in the ancient clothing figures were identified as exaggerated measurements, folding and unfolding, bending, and angle. And the formative characters and values were identified as potential drape realization, potential silhouette realization, potential three-dimensional design optimality, and potential three-dimensional formativeness realization. The result of this study may be used for a newer approach for the fundamental digging of clothing formativeness in advance.

• Korean Institute of Interior Design Journal
• /
• v.20 no.6
• /
• pp.116-123
• /
• 2011

How to see nature and how to define the relation between nature and the human certainly influence fundamental attitude toward nature and any results derived from the attitude. Therefore, in order to figure out a way for how the humans and nature should coexist, the thesis has began a philosophical analysis on the origin of the biomimetics. Based on findings from the analysis, the thesis would work on the features of biomimicry space, presenting related possibilities. For the philosophical characteristic of the thesis which was an ecological world view, introduced at the end of mechanical world view era, the ideas of Spinoza, Nietzsche, Bergson and Deleuze about nature were quoted. Based on what the philosophers have said, the thesis looks into successful ideas, designs and ways of living that nature has shown by itself. After all, the purpose of the thesis is to investigate the constantly changing space of the biomimetics by organic forms, autonomous systems and dividing programs. Based on this, nine cases were analyzed to derive the characteristics. As a result, organic forms, autonomous systems and dividing programs characteristics of ecological appear simultaneously in harmony. Biomimicry space can coexist with nature and the human is an effective way.