• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.60.2-60.2
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• 2014

Hierarchical structure of star-forming regions is widespread and may be characteristic of all star formation. We studied the hierarchical structure of star-forming regions in the Local Group galaxies (M31, M33, Phoenix, Pegasus, Sextans A, Sextans B, WLM). The star-forming regions were selected from Galaxy Evolution Explorer (GALEX) far-UV imaging in various detection thresholds for investigating hierarchical structure. We examined the spatial distribution of the hot massive stars within star-forming regions from Hubble Space Telescope (HST) multi-band photometry. Small compact groups arranged within large complexes. The cumulative mass distribution follows a power law. The results allow us to understand the hierarchical structure of star formation and recent evolution of the Local Group galaxies.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.66.2-66.2
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• 2014

The size evolution of galaxies is one of the fascinating issues in these days. It is known that the size of a galaxy is closely related to other galactic properties, such as the central surface brightness, stellar mass, and redshift. However, we need to measure the sizes of galaxies precisely to understand those relations. We determine the sizes of early-type galaxies in the nearby clusters (z<0.2) using the GALAPAGOS. The GALAPAGOS is a tool which provides surface photometry for multiple sources, which make it fast and convenient to deal with huge image data. We run the GALAPAGOS individually to the Subaru/Suprime-Cam and the HST/ACS images for the same targets. We present and discuss the result of our size measurements for further applications.

• Journal of Drive and Control
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• v.10 no.1
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• pp.21-28
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• 2013

Wind energy has been more and more important and contributive in the energy utilization of the world. This paper proposed a novel method for Wind Energy Conversion System (WECS), in which a secondary control hydrostatic transmission (SC-HST) with two hydraulic accumulators, were employed for wind energy conversion system. This approach can absorb the excessive power of turbine, keep the generator from over-speed and maintain the speed of generator in low speed of turbine. A PID controller was designed for speed control to track a predefined speed. The simulation results indicated that the speed of the generator was ensured with the relative error less than 2%; and the efficiency of the proposed system was 70.4%.

• Publications of The Korean Astronomical Society
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• v.25 no.3
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• pp.59-64
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• 2010

The core and global properties of the early-type ("red sequence") galaxies in the Virgo and Fornax clusters are examined using high-quality HST/ACS imaging for 143 galaxies. Rather than dividing neatly into disparate populations having distinct formation and/or evolution histories, many of the core and global properties of these galaxies show smooth and systematic variations along the galaxy luminosity function. The few examples of the rare class of compact elliptical galaxies in our sample all show properties that are strongly suggestive of tidal stripping by massive galaxies; if so, then these systems should not be viewed as populating the low-luminosity extension of so-called "normal" elliptical sequences. These results demonstrate that complete and/or unbiased samples are a pre-requisite for identifying the physical mechanisms that gave rise to the early-type galaxies we observe locally, and how these mechanisms varied with mass and environment.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.50.1-50.1
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• 2012

As a tracer of star formation history, metallicity provides crucial information for understanding galaxy evolution. In the case AGN, gas metallicity is often derived from the flux ratio of UV emission lines, i.e., NV1240 and CIV1549. To investigate the dependence of metallicity on AGN luminosity, black hole mass, and accretion rate, we measure NV1240 and CIV1549 line fluxes and derive gas metallicity of a sample of 73 local Seyfert 1 galaxies and QSOs, using archival UV spectra obtained with the HST and IUE. In this work, we will present the metallicity of local AGN and its relation with AGN properties.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.76.2-76.2
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• 2017

We present Subaru Near-Infrared (NIR) photometry for globular clusters (GCs) in the giant elliptical galaxy NGC 4649 (M60) belonging to the Virgo cluster. NIR data are obtained in Ks-band with the Subaru/MOIRCS, and matching HST/ACS optical data available in literature are used to explore the origin of GC color bimodality. A clear bimodal color distribution is observed in the optical color (g-z), in which the ratio between blue and red GCs is 4:6. By contrast, the more metallicity-sensitive optical-NIR colors (g-Ks, z-Ks) show a considerably weakened bimodality in their distributions. The color-color relation of the optical and NIR colors for the GC system shows a nonlinear feature, supporting that the optical color bimodality observed in NGC 4649 GC system is caused by nonlinear color-metallicity relations (CMRs).

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.86.1-86.1
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• 2017

오리온 성운은 지구와 매우 가까이에 있고, 무거운 별이 포함된 성단과 성운이 밀접하게 연관되어 있어, 오리온 성운 성단은 가장 많이 연구된 천체 중 하나이다. 1993년 HST를 이용한 오리온 성운 성단의 관측으로 나이가 어린별을 둘러싼 물질의 실루엣을 처음으로 보았다. 이후 이러한 천체를 원시행성계원반(protoplanetary disk, Proplyd)이라 불렀으며, 그 형태와 구조, 물리적 과정에 대해 꾸준히 연구가 진행되고 있다. 이 연구에서는 지상관측에서 얻은 UBVI 및 Ha 측광 자료와 원시행성계원반을 상호 동정하고, 원시행성계원반의 형태학적 특징과 측광인자의 관련성을 조사하였다. 또한 Spitzer 중적외선 자료와 Natta et al.(2004)의 근적외선 자료를 통합하여, 현재 사용되고 있는 자외선 초과와 근적외선 방출선을 이용한 질량 강착률 등의 해석에서 주의해야 할 천체들이 있다는 것을 발견했다.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.970-978
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• 2010

In this study, interior noise of the high speed EMU was estimated by statistical energy analysis (SEA) method. Based on the data measured at a distance of 25m from a running train, exterior noise of the running train was calculated. And then it was designed as noise sources in VA ONE, a commercial software of SEA. coupling and damping loss factor of high speed EMU studied in previous studies is used. The interior noise of the train was estimated for a open-land section. The analysis of interior noise of HST in the tunnel section will be estimated through same method.

• The Plant Pathology Journal
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• v.19 no.5
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• pp.221-226
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• 2003

Twenty universal rice primers (URPs) were used to detect PCR polymorphisms in 25 isolates of six different Alternaria species producing host specific toxins (HST). Eight URPs could be used to reveal PCR polymorphisms of Alternaria isolates at the intra- and inter-species levels. Specific URP-PCR polymorphic bands that are different from those of the other Alternaria spp. were observed on A. gaisen and A. longipes isolates. Unweighted pair-group method with arithmetic mean (UPGMA) cluster analysis using 94 URP polymorphic bands revealed three clustered groups (A. gaisen group, A. mati complex group, and A. logipes group).

• Journal of The Korean Astronomical Society
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• v.42 no.2
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• pp.17-26
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• 2009

We estimate the enclosed mass profile in the central 10 pc of the Milky Way by analyzing the infrared photometry and the velocity observations of dynamically relaxed stellar population in the Galactic center. HST/NICMOS and Gemini Adaptive Optics images in the archive are used to obtain the number density profile, and proper motion and radial velocity data were compiled from the literature to find the velocity dispersion profile assuming a spherical symmetry and velocity isotropy. From these data, we calculate the the enclosed mass and density profiles in the central 10 pc of the Galaxy using the Jeans equation. Our improved estimates can better describe the exact evolution of the molecular clouds and star clusters falling down to the Galactic center, and constrain the star formation history of the inner part of the Galaxy.