• The Pure and Applied Mathematics
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• v.12 no.3 s.29
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• pp.161-167
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• 2005

In this note we consider the projective property $\sigma(Re(T))\;=\;Re\;(\sigma$(T))$ of p-hyponormal operators and log-hyponormal operators.

• Kyungpook Mathematical Journal
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• v.45 no.3
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• pp.363-394
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• 2005

In this expository paper we survey basic results on isotropic immersions.

• Communications of the Korean Mathematical Society
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• v.36 no.4
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• pp.829-833
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• 2021

We investigate the Möbius transformation action of PSL(2, ℝ) on the set of mutually distinct ordered triple points of ℝ ∪ {∞}.

• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.921-934
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• 2019

The object of the present paper is to study generalized pseudo-projectively symmetric manifolds and Einstein generalized pseudo-projectively symmetric manifolds. Finally, the existence of generalized pseudo-projectively symmetric manifolds have been proved by two non-trivial examples.

• East Asian mathematical journal
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• v.35 no.1
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• pp.51-58
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• 2019

For a nondegenerate irreducible projective variety, it is a classical problem to describe its defining equations. In this paper we precisely determine the defining equations of some rational curves of maximal regularity in ${\mathbb{P}}^4$ according to their rational parameterizations.

• Journal of applied mathematics & informatics
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• v.41 no.3
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• pp.577-589
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• 2023

The aim of the present paper is to study LP-Sasakian manifolds admitting *-Einstein soliton satisfying certain curvature conditions. Finally, we have constructed a 3-dimensional example of an LP-Sasakian manifold admitting *-Einstein soliton.

• Bulletin of the Korean Mathematical Society
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• v.60 no.6
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• pp.1621-1639
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• 2023

In this paper, we give an improvement for the second main theorems of algebraically non-degenerate meromorphic maps from generalized p-parabolic manifolds into projective varieties intersecting hypersurfaces in subgeneral position with some index, which extends the results of Han [6] and Chen-Thin [3].

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.871-877
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• 2006

물체의 반사(specular reflection)는 물체의 재질 및 기하학적 모양을 표현하는데 있어 매우중요한 요소이다. 사진품질의 사실적 렌더링에서는 기존의 국소 반사 모델을 사용하여 좋은 결과를 얻을 수 있지만, 사용자의 주관이 중시되는 비사실적 렌더링(non-photorealistic rendering)에서는 사용자가 원하는 반사 효과를 표현할 수 있어야 한다. 텍스처는 사용자가 직관적으로 원하는 반사 효과를 표현할 수 있는 수단이며, 이를 모델에 투영하면 원하는 반사효과를 얻을 수 있다. 이 때 사용자는 텍스처가 투영될 위치와 크기, 방향을 직접 키프레임으로 정해 줄 수 있다. 그러나 모든 반사 효과를 사용자가 직접 정해준다는 것은 번거로운 일이며, 실시간 응용분야에는 적용할 수 없다. 본 논문에서는 국소반사모델(local reflection model)과 주곡률(principal curvature) 해석을 통해 반사효과의 위치, 방향, 크기를 결정하기 위한 텍스처 투영기의 새로운 설정 방법을 제시한다. 광원과 시점 정보를 사용하여 투영기의 위치를 정하고 물체의 주방향(principal direction)과 곡률반지름(radius of curvature)을 이용하여 투영기의 방향과 투영 피라미드의 크기를 정한다 텍스처 투영기의 단순한 이동, 회전을 통하여 반사 영역의 이동, 회전 및 확대/축소가 가능하다. 본 논문에서 제시한 방법은 DirectX 9.0c와 프로그래이 가능한 셰이더 2.0을 사용하여 GeForce FX 7800 그래픽 카드에 구현되었다. 본 논문의 연구 결과는 게임과 같은 실시간 응용분야에 사용될 수 있으며, 실험 결과에 의하면 수천 개의 다면체 모델에 대한 렌더링을 실시간에 수행할 수 있다.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1090-1093
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• 2004

In this paper, a problem of geometrically distorted images is considered. In particular, the paper discusses the detection of a watermark from a photographed image of the watermarked picture. The image is possibly obtained by using a digital camera. This watermark detection problem is made difficult by various geometric distortions added to the original picture through the printing and photographing processes. In particular, the paper focuses on the geometric distortion due to a projective transformation, as part of a camera 3D-to-2D imaging process. It is well-known that a cross ratio of collinear points is invariant under a perspective projection. By exploiting this fact, a projective-invariant digital watermarking technique is developed. By detecting the picture's corners, and the image center point at the intersection of two main diagonal lines, predefined cross ratios are used to compute the watermark embedded locations. From those identified embedding pixel locations, a watermark can be detected by performing a correlation between a watermark pattern and the image over those pixels. The proposed method does not require an inverse transformation on the distorted image, thus simplifying the detection process. Performance of the proposed method has been analyzed through computer experiments

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.11
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• pp.621-628
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• 2003

This paper addresses a method of enabling objects in an image to have apparent 3D motion. Many researchers have solved this issue by reconstructing 3D model from several images using image-based modeling techniques, or building a cube-modeled scene from camera calibration using vanishing points. This paper, however, presents the possibility of image-based motion without exact 3D information of scene geometry and camera calibration. The proposed system considers the image plane as a projective plane with respect to a view point and models a 2D frame of a projected 3D object using only lines and points. And a modeled frame refers to its vanishing points as local coordinates when it is transformed.