• East Asian mathematical journal
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• v.31 no.3
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• pp.337-344
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• 2015

We study screen quasi-conformal irrotational half lightlike submanifolds M of a semi-Riemannian space form $\bar{M}$ (c) equipped with a semi-symmetric non-metric connection subject such that the structure vector field of $\bar{M}$ (c) belongs to the screen distribution S(TM). The main result is a non-existence theorem for such half lightlike submanifolds.

• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.290-295
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• 2007

The Seoul Metropolitan Subway Corp. have gradually installed screen doors in platforms of 115 subway stations in Seoul on lines 1, 2, 3, and 4. Installation in nine areas among those has been completed and screen doors are being operated as a model operation. Traffic signs should be clear for users. The essential functions of signs should be fully investigated from the aspect of user as well as the visual beauty and recognition. Signs should be able to provide users with information regarding location, position, directions, etc. Particularly, safety and convenient signs should be visually and sensually correlated. However, the entire screen doors in platforms installed in line 2 subway in Seoul are used for commercial advertisement, consequently, the functions and roles as public signs are not fulfilled aggravating inconvenience for users. In this study, cases have been studied to investigate requirements for user-oriented sign system in platform and public sign space to fulfill the functions of sign system in platform. Using an anthropometry approach, the study aimed to obtain the space to install the sign system and to systemize necessary and sufficient conditions for user-oriented system for platform in which screen doors have been installed using. The study suggests fundamental information to obtain the space of public sign system on the entire screen door.

• Honam Mathematical Journal
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• v.31 no.1
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• pp.17-23
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• 2009

We study the geometry of screen conformal half lightlike submanifolds of a semi-Riemannian manifod. The main result is a classification theorem for screen conformal half lightlike submanifolds of a semi-Riemannian space form with a Killing co-screen distribution.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1567-1574
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• 2006

To prevent safety accidents such as injury or death from falling by blocking platforms from trains, the Seoul Metropolitan Subway Corp. have gradually installed screen doors in platforms of 115 subway stations in Seoul on lines 1, 2, 3, and 4. Installation in nine areas among those has been completed and screen doors are being operated as a model operation. Traffic signs should be clear for users. The essential functions of signs should be fully investigated from the aspect of user as well as the visual beauty and recognition. Signs should be able to provide users with information regarding location, position, directions, etc. Particularly, safety and convenient signs should be visually and sensually correlated. However, the entire screen doors in platforms installed in line 2 subway in Seoul are used for commercial advertisement, consequently, the functions and roles as public signs are not fulfilled aggravating inconvenience for users. In this study, cases have been studied to investigate requirements for user-oriented sign system in platform and public sign space to fulfill the functions of sign system in platform. Using an anthropometry approach, the study aimed to obtain the space to install the sign system and to systemize necessary and sufficient conditions for user-oriented system for platform in which screen doors have been installed using. The study suggests fundamental information to obtain the space of public sign system on the entire screen door.

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

• Bulletin of the Korean Mathematical Society
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• v.49 no.6
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• pp.1163-1178
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• 2012

In this paper, we study the geometry of Einstein half lightlike submanifolds M of a semi-Riemannian space form $\bar{M}(c)$ subject to the conditions: (a) M is screen conformal, and (b) the coscreen distribution of M is a conformal Killing one. The main result is a classification theorem for screen conformal Einstein half lightlike submanifolds of a Lorentzian space form with a conformal Killing coscreen distribution.

• Bulletin of the Korean Mathematical Society
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• v.50 no.4
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• pp.1367-1376
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• 2013

We study Einstein lightlike hypersurfaces M of a Lorentzian space form $\tilde{M}(c)$ admitting a semi-symmetric non-metric connection subject to the conditions; (1) M is screen conformal and (2) the structure vector field ${\zeta}$ of $\tilde{M}$ belongs to the screen distribution S(TM). The main result is a characterization theorem for such a lightlike hypersurface.

• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.195-213
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• 2020

We define two types of null hypersurfaces as; isoparametric and quasi isoparametric null hypersurfaces of Lorentzian space forms, based on the two shape operators associated with a null hypersurface. We prove that; on any screen conformal isoparametric null hypersurface, the screen geodesics lie on circles in the ambient space. Furthermore, we prove that the screen distributions of isoparametric (or quasi isoparametric) null hypersurfaces with at most two principal curvatures are generally Riemannian products. Several examples are also given to illustrate the main concepts.

• Communications of the Korean Mathematical Society
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• v.25 no.3
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• pp.443-450
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• 2010

In this paper, we study the geometry of lightlike real hyper-surfaces of an indefinite Kaehler manifold. The main result is a characterization theorem for lightlike real hypersurfaces M of an indefinite complex space form $\bar{M}(c)$ such that the screen distribution is totally umbilic.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.43-54
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• 2019

In this paper, we review the applicability of fog screen to implement 'Spatial Augmented Reality' which displays the image on the whole space of real space or in real space by separating display equipment and user, in contrast to the traditional Augmented Reality. Through three exhibitions and one performance, we confirmed t hat the fog screen, which can be passed through, is a suitable material for implementing the Spatial Augment ed Reality. We found that the hologram production was easier than before because of fog screen. Through the questionnaire survey conducted on performers along with the exhibition, we found that only about half of people know what a fog screen is, and about 10% of the total respondents saw the fog screen. In order to investigate the effect of fog screen on the surrounding space, we conducted an experiment to observe the change of humidity according to the time and distance in the Children's Culture Center of the Asian Culture Center. We found that the humidity within a radius of 5m around the fog screen could increase by 2~3%($6,400m^3$ standard). Thus we provided some safety requirement with fog screen when works made of materials vulnerable to moisture such as paint, paper, and wood are exhibited at the same time with fog screen in the exhibition hall.