• 충청수학회지
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• 제23권3호
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• pp.481-486
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• 2010

In this paper, we introduce the concepts of strongly c-convex( strongly c-concave) function, almost c-convex function on preconvex spaces. We investigate the relationships between such concepts and several types of preconvex sets.

• 대한수학회보
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• 제58권4호
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• pp.877-884
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• 2021

We prove that if a compact convex hypersurface of ℝⁿ⁺¹ has almost maximal extinction time when it is evolved by the mean curvature flow, then it must be nearly round in the C⁰-norm.

• 대한수학회지
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• 제41권4호
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• pp.737-746
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• 2004

In this paper, from the KKM theorem, we deduce almost fixed point theorems for convex-valued u.s.c. (or l.s.c.) multimaps satisfying certain conditions originated from Zima [19]. From these results, we obtain various fixed point theorems which extend a number of known results.

• 대한수학회지
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• 제45권1호
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• pp.1-27
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• 2008

We introduce a new concept of convex spaces and a multimap class K having certain KKM property. From a basic KKM type theorem for a K-map defined on an convex space without any topology, we deduce ten equivalent formulations of the theorem. As applications of the equivalents, in the frame of convex topological spaces, we obtain Fan-Browder type fixed point theorems, almost fixed point theorems for multimaps, mutual relations between the map classes K and B, variational inequalities, the von Neumann type minimax theorems, and the Nash equilibrium theorems.

• 대한수학회지
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• 제31권3호
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• pp.417-427
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• 1994

Let C be a nonempty closed bounded convex subset of a real Banach space X.

• 대한수학회논문집
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• 제34권4호
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• pp.1279-1287
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• 2019

The main purpose of the paper is to prove that if a compact Riemannian manifold admits a gradient ${\rho}$-Einstein soliton such that the gradient Einstein potential is a non-trivial conformal vector field, then the manifold is isometric to the Euclidean sphere. We have showed that a Riemannian manifold satisfying gradient ${\rho}$-Einstein soliton with convex Einstein potential possesses non-negative scalar curvature. We have also deduced a sufficient condition for a Riemannian manifold to be compact which satisfies almost ${\eta}$-Ricci soliton.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.259-264
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• 2000

The functions of the plug valve are the control of flow rate as well closing and opening pipe lines. Analyses on the flow characteristics in plug valve port are required to improve the performance and safety at severe operating conditions such as high-pressure and high-temperature. In this study, numerical analyses are carried out with varying the opening rate (fraction of the full open to close) of the valve and the shapes of valve Uk: straight, convex, concave and mixed shapes. The parameters influencing the flow characteristics in the valve are the discharge coefficient( $C_v$) and the resistance coefficient( K). Therefore, the distributions of static pressure, velocity vector and stream lines are investigated, and $C_v$ and K are calculated in each opening rate and shape. In case of full open, the static pressure passed through the valve port has almost been recovered. However, in case of other opening rates, the pressure does not permanently regained due to pressure drop leading to loss. This phenomenon in each shape of the valve shows the different behaviors. Calculation results show that the mixed shape has the best flow attribute.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.373-378
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• 2000

An experimental investigation on the incipience of nucleate boiling in forced flow of water is performed as a verification and extension of previous analysis. The effects of the subcooling, Reynolds number and surface curvature on the onset of nucleate boiling(ONB) in a concentric annulus flow channel with smooth inner heating surface is investigated experimentaly. Through flow visualization, the boiling phenomenon was observed directly and the experimental results were examined to find ONB heat flux. The results show that the variation of heat flux at ONB is increased linearly as the Reynolds number and subcooling are increased. The effect of surface curvature is very great specially for a small radius when radius of the inner heating tube is increased, the heat flux at ONB is almost inversely increased for the range of this investigation. It is found that the effect of convex surface curvature on ONB heat flux is very significant for a small radius.

• 한국통신학회논문지
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• 제34권3C호
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• pp.288-296
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• 2009

POCS (projection onto convex sets)를 이용하는 고해상도 영상 재구성에서는 재구성 연산 사이에 프레임간 움직임을 추정함으로써 양질의 HR (high resolution) 영상을 얻을 수 있으나, 반복적인 움직임 추정으로 인해 연산량은 증가한다. 본 논문에서는 기존의 ARPS (adaptive rood pattern search) 움직임 추정법을 수정하여 연산량을 줄이면서, 움직임 추정과 POCS 복원을 동시에 수행하는 HR 영상의 재구성 알고리즘을 제안한다. ARPS에서 필요한 기준 움직임의 값으로 POCS 복원의 이전 단계에서 추정한 움직임 벡터의 값과 위상 상관도법으로 얻은 값을 이용하여 연산량을 줄였다. 또한, 추정된 움직임을 정규화하여 그 정확도를 더욱 향상시켰다. 실험 결과, 전체탐색 블록 정합법과 POCS를 동시에 수행하여 영상을 재구성한 경우와 비교했을 때 유사한 화질의 HR 영상을 약 30배 빠르게 재구성하였다.

• 한국버섯학회지
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• 제6권3_4호
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• pp.115-120
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• 2008

야생에서 수집한 균주를 이용하여 우량 단핵계통을 선발하고, 선발한 단핵주를 이용하여 교잡을 통하여 새로운 품종 '갈뫼' 를 육성하였다. 갈뫼 품종은 균사배양 최적온도는 $25^{\circ}C$, 자실체발생 적온은 $14^{\circ}C$, 생육온도는 $7{\sim}180^{\circ}C$이었다. 갈뫼 자실체의 갓색깔은 갈색이며, 대기부는 진갈색으로 전형적인 야생팽이의 특성을 가셨고, 갓표면에 다소의 점성이 있었다. 갈뫼는 갈색 다수성 품종으로 발이가 고르고, 대가 곧고 강하며, 갓은 반반구형으로 생산력이 안정적이었다. 또한 갈뫼는 조리시 백색팽이 보다 씹는 저작감이 우수하므로 이를 홍보에 적극 이용할 필요가 있다.