• Journal of Astronomy and Space Sciences
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• 제30권4호
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• pp.327-334
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• 2013

The purpose of this study is to develop an observation program for obtaining effective flat images that are necessary for photometric observation. The development of the program was achieved by improving the existing method for obtaining twilight flat images. The existing method for obtaining twilight flat images acquires flat images by observing the sky light after sunset or light before sunrise. The decision of when to observe flat images at each night is solely dependent on the judgment of an observer, and thus the obtained flat images for particular nights may not be clean. Especially, in the case of the observatories where an automated observation system is in operation, there is a difficulty that an observer should pay attention during sunrise and sunset in order to obtain flat images. In this study, a computer program is developed to improve this inconvenience and to efficiently perform photometric observation in the observatories where an automated observation system is applied. This program can obtain flat images by calculating the time for obtaining flat images automatically and the exposure time using a numerically calculated function. When obtaining twilight flat images at dusk and at dawn, the developed program performs automated observation and provides effective flat images by acquiring appropriate exposure time considering the sunrise and sunset times that vary depending on the day of observation. The code for performing this task was added to Obs Tool II (Yoon et al. 2006), which is the automated observation system of the Chungbuk National University Observatory, and the usefulness of the developed program was examined by performing an actual automated observation. If this program is applied to other observatories where automated observation is in operation, it is expected that stable and high-quality flat images could be obtained, which can be used for the pre-processing of photometric observation data.

• 대한수학회논문집
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• 제12권4호
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• pp.999-1006
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• 1997

We proved that if a fibred Riemannian space $\tilde{M}$ with cosymplectic structure is conformally flat, then $\tilde{M}$ is the locally product manifold of locally Euclidean spaces, that is locally Euclidean. Moreover, we investigated the fibred Riemannian space with cosymplectic structure when the Riemannian metric $\tilde{g}$ on $\tilde{M}$ is Einstein.

• 대한수학회보
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• 제50권6호
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• pp.2089-2101
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• 2013

The aim of this paper is to introduce the notion of Lie recurrent structure Jacobi operator for real hypersurfaces in non-flat complex space forms and to study such real hypersurfaces. More precisely, the non-existence of such real hypersurfaces is proved.

• Journal of applied mathematics & informatics
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• 제7권1호
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• pp.297-303
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• 2000

We investigate the conformally flat warped product manifolds and study the geometric structure of the base space and each fibre. Moreover we find the conditions that the base space and each fibres to be the space of constant curvatures.

• 대한지리학회지
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• 제51권6호
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• pp.799-817
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• 2016

본 논문은 초국적 이주노동자들이 거주국 내에서 수행하는 다층적인 사회적 관계와 공간적 실천을 살펴봄으로써 '차이의 공간'이 생산되는 과정을 고찰하고, 이러한 이질적인 공간을 단순히 외부 세계로부터 분리되고 타자화된 공간이 아니라 이주자들의 일상적 경험이 외부 세계와 상호작용하는 과정에서 새로운 의미와 질서가 재생산되는 헤테로토피아 공간으로 분석한다. 필자는 입주돌봄노동자로서 이스라엘에 체류하는 필리핀 이주자들의 일상 리듬이 주중-작업장, 주말-아파트로 패턴화된다는 사실에 주목하고, 이들이 주말마다 점유하는 텔아비브 네베셰아난의 '아파트'에 분석의 초점을 둔다. 이러한 주말아파트는 비록 주말에만 일시적으로 존재하는 공간이지만 필리핀 이주민사회를 구성하는 최소한의 사회적 단위인 동시에 경제, 사회, 종교적 활동의 핵심 장소로서 기능하며, '위험하고 적대적인 외부 세계'로부터 분리된 '안식처(shelter)'로 기능함으로써 거주국에서 배제되고 주변화된 이주노동자들이 "그들만의 세계"를 구축하는 것을 가능케 한다. 이 논문에서 이주노동자들의 일상적 실천을 통해 유의미한 공간으로 전환되는 '주말아파트'는 이주노동자 삶의 역동성을 이해하고 지배집단의 통제 속에서도 능동적으로 공간을 전유하는 이주자들의 적극적인 행위성을 드러내는 데 유용한 통로로 분석된다. 주말아파트는 이주자들의 필요를 충족시켜주는 다양한 기능을 가진 독특한 공간으로서 다른 공간들과 경계가 뚜렷하고 철저하게 분리된 공간으로 나타나지만, 그것을 둘러싼 외부 공간과의 관계 속에서 형성되는 헤테로토피아 공간으로 해석될 수 있다.

• 대한수학회지
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• 제55권3호
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• pp.735-747
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• 2018

Let M be a real hypersurface of a complex space form with constant curvature c. In this paper, we study the hypersurface M admitting Miao-Tam critical metric, i.e., the induced metric g on M satisfies the equation: $-({\Delta}_g{\lambda})g+{\nabla}^2_g{\lambda}-{\lambda}Ric=g$, where ${\lambda}$ is a smooth function on M. At first, for the case where M is Hopf, c = 0 and $c{\neq}0$ are considered respectively. For the non-Hopf case, we prove that the ruled real hypersurfaces of non-flat complex space forms do not admit Miao-Tam critical metrics. Finally, it is proved that a compact hypersurface of a complex Euclidean space admitting Miao-Tam critical metric with ${\lambda}$ > 0 or ${\lambda}$ < 0 is a sphere and a compact hypersurface of a non-flat complex space form does not exist such a critical metric.

• Journal of applied mathematics & informatics
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• 제24권1_2호
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• pp.541-545
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• 2007

In this paper, we study the infinitesimal transformation on the fibred Riemannian space. The conharmonic curvature tensor is invariant under the conharmonic transformation. We have proved that the conharmonically flat fibred Riemannian space with totally geodesic fibre is locally the Riemannian product of the base space and a fibre.

• 대한수학회논문집
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• 제17권1호
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• pp.57-69
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• 2002

We study a unifying method to obtain nondegenerate isometric immersions of manifolds of constant sectional curvatures c with flat normal bundles into the space forms of curvature c for c= -1,0,1.

• 대한수학회논문집
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• 제11권2호
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• pp.407-413
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• 1996

The $(\alpha, \beta)$-metric is a Finsler metric which is constructed from a Riemannian metric $\alpha$ and a differential 1-form $\Beta$; it has been sometimes treat in theoretical physics. In particular, the projective flatness of Finsler space with a metric $L^2 = 2\alpha\beta$ is considered in detail.

• East Asian mathematical journal
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• 제19권2호
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• pp.261-271
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• 2003

We deal with two metrics of Randers type, which are characterized by the solution of certain differential equations respectively. Furthermore, we will give the condition for a Finsler space with such a metric to be a locally Minkowski space or a conformally flat space, respectively.