• Honam Mathematical Journal
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• v.45 no.3
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• pp.491-502
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• 2023

As a generalization of Berwald spaces, we have the ideas of Douglas spaces and Landsberg spaces. S. Bacso defined a weakly-Berwald space as another generalization of Berwald spaces. In 1972, Matsumoto proposed the (α, β) metric, which is a Finsler metric derived from a Riemannian metric α and a differential 1-form β. In this paper, we investigated an important class of (α, β)-metrics of the form $F={\mu}_1\alpha+{\mu}_2\beta+{\mu}_3\frac{\beta^2}{\alpha}$, which is recognized as a special form of the first approximate Matsumoto metric on an n-dimensional manifold, and we obtain the criteria for such metrics to be weakly-Berwald metrics. A Finsler space with a special (α, β)-metric is a weakly Berwald space if and only if B^m_m is a 1-form. We have shown that under certain geometric and algebraic circumstances, it transforms into a weakly Berwald space.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.65-75
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• 2009

For the large space buildings since 1960s in Korea spanned more than 30m, the establishment feature and the development process were examined. As the Results, physical facilities with 40-70m span were mainly established in 1980s-1990s, but large scale convention centers have been establishing after 2000s as the used of large space buildings are varied. Also, a space frame has been generally used in 1980s while the unique structural shapes were builded in the early age(1960s), the structural design with concerns a form and using various structural systems have been attempting after 2000s.

• Current Optics and Photonics
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• v.3 no.5
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• pp.466-472
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• 2019

A system for continuous-wave coherent Doppler lidar (CW lidar), made up of all-fiber structures and a coaxial transmission telescope, was set up for wind measurement in Hefei (31.84 N, 117.27 E), Anhui province of China. The lidar uses a fiber laser as a light source at a wavelength of $1.55{\mu}m$, and focuses the laser beam on a location 80 m away from the telescope. Using the CW lidar, radial wind measurement was carried out. Subsequently, the spectra of the atmospheric backscattered signal were analyzed. We tested the noise and obtained the lower limit of wind velocity as 0.721 m/s, through the Rayleigh criterion. According to the number of Doppler peaks in the radial wind spectrum, a classification retrieval algorithm (CRA) combining a Gaussian fitting algorithm and a spectral centroid algorithm is designed to estimate wind velocity. Compared to calibrated pulsed coherent wind lidar, the correlation coefficient for the wind velocity is 0.979, with a standard deviation of 0.103 m/s. The results show that CW lidar offers satisfactory performance and the potential for application in wind measurement.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.25.3-25.3
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• 2009

To search for the quasars at z > 7 in early universe, we are developing a optical camera which has a $1k\times1k$ deep depletion CCD chip, with later planned upgrade to HAWAII-2RG infrared array. We are going to attach the camera to the cassegrain focus of Otto Struve 2.1m telescope at McDonald observatory of University of Texas at Austin, USA. We present the design of a hardware interface to attach the CCD camera to the telescope. It consists of focal reducer, filter wheel, and guiding camera. Focal reducer is needed to reduce the long f-ratio (f/13.7) down to about 4 for wide field of view. The guiding camera design is based on that of DIAFI offset guider which developed for the McDonald 2.7m telescope.

• Korean Institute of Interior Design Journal
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• v.17 no.3
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• pp.68-76
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• 2008

This study investigated composition elements and estimation of image in lobby from user viewpoint that is the central space of local cultural institution, and spectator mainly utilizes. Progress process of study develops investigation device including literature investigation, professional panel and lobby space image measurement tool through on-the-spot probe and, executed supporting research to spectator. As the result of the study, first, lobby space image exerts absolute effect to local cultural institution image-building, and is grasped on constituent that floor, ceiling, entrance and lighting and decoration is important in image-building of lobby space. Second, the image of the important lobby space was grasped in order of convenient image(M = 3.98) bright image(M = 3.87), and cozy image(M = 3.80). Third, the results on investigating semantic structure of the lobby image, emotional factor, styling factor, spatial factor, and peculiar factor are composed of important factors that decides image of lobby space. Fourth, as the result of image analysis for lobby space, the degree of satisfaction for the local cultural institution was entirely low against the importance. In particular, the image for convenience, individuality, locality and dignity was not sufficient in all the three places. Therefore, lobby design of local cultural institution shall also suggest more various lobby space image from culture oriented viewpoint.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.193-195
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• 2017

We demonstrate the luminosity dependence of the covering factor (CF) of active galactic nuclei (AGNs), based on AKARI mid-infrared all-sky survey catalog. Combining the AKARI with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 243 galaxies at $9{\mu}m$ and 255 galaxies at $18{\mu}m$. We then identified 64 AGNs at $9{\mu}m$ and 105 AGNs at $18{\mu}m$ by their optical emission lines. Following that, we estimated the CF as the fraction of type 2 AGN in all AGNs. We found that the CF decreased with increasing $18{\mu}m$ luminosity, regardless of the choice of type 2 AGN classification criteria.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.76.1-76.1
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• 2021

Maemi Dual Field Telescope System (MDFTS) is a dual telescope system located at Kyung Hee University. The system consists of 0.4 m telescope and 0.1 m telescope for wide-field observation. The 0.4 m telescope provides photometric observation which covers a field of view of 21'×16'. It has been used for various purposes with Johnson-Cousins UBVRI broadband filter system, e.g., SomangNet and Intensive Monitoring Survey of Nearby Galaxies. In this poster, we present the standard calibration result for our broadband filter system. Also, we suggest a new usage of the KHAO 0.4m telescope which is narrowband photometry by demonstrating the standard calibration of H-alpha filter. For flux calibration, not only R filter but also V filter is used for compensating the central wavelength discrepancy between R filter and H-alpha filter.

• The Pure and Applied Mathematics
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• v.21 no.1
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• pp.39-50
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• 2014

In this paper, we study screen quasi-conformal irrotational half lightlike submanifolds M of a semi-Riemannian space form $\tilde{M}(c)$ admitting a semi-symmetric non-metric connection, whose structure vector field ${\zeta}$ is tangent to M. The main result is a classification theorem for such Einstein half lightlike submanifolds of a Lorentzian space form admitting a semi-symmetric non-metric connection.

• Journal of the Korean Mathematical Society
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• v.35 no.2
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• pp.371-386
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• 1998

Let G be a compact Lie group and M a semialgebraic G space in some orthogonal representation space of G. We prove that if G is finite then M has an equivariant semialgebraic triangulation. Moreover this triangulation is unique. When G is not finite we show that M has a semialgebraic G CW complex structure, and this structure is unique. As a consequence compact semialgebraic G space has an equivariant simple homotopy type.

• Bulletin of the Korean Mathematical Society
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• v.39 no.2
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• pp.327-332
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• 2002

In this paper we prove that if M is a J-invariant sub-manifold of codimension 2 in a complex projective space $P_{n+1}(C)$, and the second fundamental tensor is cyclic-parallel or M has harmonic curvature, then M is locally complex quadric Q$_n$(C) or P$_n$(C).