• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.185-196
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• 1997

We present a code which identifies individual clouds in crowded region using IMFORT interface within Image Reduction and Analysis Facility (IRAF). We define a cloud as an object composed of all pixels in longitude, latitude, and velocity that are simply connected and that lie above some threshold temperature. The code searches the whole pixels of the data cube in efficient way to isolate individual clouds. Along with identification of clouds it is designed to estimate their mean values of longitudes, latitudes, and velocities. In addition, a function of generating individual images (or cube data) of identified clouds is added up. We also present identified individual clouds using a $^{12}CO$ survey data cube of Galactic Anticenter Region (Lee et al. 1997) as a test example. We used a threshold temperature of $5\sigma$ rms noise level of the data With a higher threshold temperature, we isolated subclouds of a huge cloud identified originally. As the most important parameter to identify clouds is the threshold value, its effect to the size and velocity dispersion is discussed rigorously.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.161-163
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• 1996

We have studied the response of molecular clouds in the Galactic disk to a rotating bar by conducting Smoothed Particle Hydrodynamics (SPH) simulations for the Galaxy in order to understand the dynamical structures of the Galactic Center (GC) molecular clouds, and their implications. In our study it was found that the structures of GC molecular clouds could be induced by the combined effects of rotating bar potential, the hydrodynamic collisions and gravitational miss collisions between the clouds.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.42.2-42.2
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• 2019

Turbulence is one of the natural phenomena in molecular clouds. It affects gas density and velocity fluctuation within the molecular clouds and controls the mode and tempo of star formation. However, despite many years of study, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we have fully mapped two star-forming molecular clouds, the Orion A and the Ophiuchus molecular clouds, in 3 sets of lines ($^{13}CO$ J=1-0, $C^{18}O$ J=1-0, HCN J=1-0, $HCO^+$ J=1-0, CS J=2-1, and $N_2H^+$ J=1-0) using the TRAO 14-m telescope. We apply a statistical analysis, Principal Component Analysis (PCA), which can recover an underlying turbulent-power spectrum from an observed P-P-V spectral map. We compare turbulence properties not only between the two clouds, but also between different parts within each cloud. We present the first result of our observation program.

• Journal of Information Processing Systems
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• v.17 no.2
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• pp.284-296
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• 2021

The cloud has already become the core infrastructure of information systems, and government institutions are rapidly migrating information systems to the cloud. Government institutions in several countries use private clouds in their closed networks. However, because of the advantages of public clouds over private clouds, the demand for public clouds is increasing, and government institutions are expected to gradually switch to public clouds. When all data from government institutions are managed in the public cloud, the biggest concern for government institutions is the leakage of confidential data. The public-private-partnership (PPP) cloud provides a solution to this problem. PPP cloud is a form participation in a public cloud infrastructure and the building of a closed network data center. The PPP cloud prevents confidential data leakage and leverages the benefits of the public cloud to build a cloud quickly and easily maintain the cloud. In this paper, based on the case of the PPP cloud applied to the Korean government, the concept, architecture, operation model, and contract method of the PPP cloud are presented.

• Journal of The Korean Astronomical Society
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• v.33 no.3
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• pp.151-158
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• 2000

We conducted a deep CCD observations in V band to obtain stellar density distribution and to determine the distances toward two molecular clouds with anomalous velocity in the Galactic anti-center region. Star count method based on the linear programming technique was applied to the CCD photometric data. We found two prominent peaks at distances of around 1.4 and 2.7 kpc. It is found that the first peak coincides well with stellar density enhancement of B8-A0 stars and the second one with the outer Perseus arm. The effect of the choice of the luminosity function is discussed. The stellar number density distribution is used to derive the distances to the molecular clouds and the visual extinctions caused by the clouds. We found that two molecular clouds are located almost at the same distance of about 1.1 $\pm$ 0.1 kpc, and the peak extinctions caused by the clouds are about 2.2 $\pm$ 0.3 mag in V band.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.319-325
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• 2014

We map two molecular clouds located in the exact anticenter region emitting in the (J = 1-0) transition of $^{12}CO$ and $^{13}CO$ using the 3-mm SIS mixer receiver on the 14-m radio telescope at Taeduk Radio Astronomy Observatory. The target clouds with anomalous velocities of $V_{LSR}{\sim}-20km\;s^{-1}$ are distinguished from other clouds in this direction. In addition, they are located in the interarm region between the Orion Arm and the Perseus Arm. Sizes of the clouds are estimated to be about 8.6 and 10.8 pc, respectively. The total mass is estimated to be about $4{\times}10^3$ $M_{\odot}$ using CO luminosity of the clouds. Several cores are detected, but no sign of star formation is found according to the IRAS point sources. Their larger linewidths, anomalous velocities, and their location at the interarm region make these clouds more distinguished, though their physical properties are similar to the dark clouds in the solar neighborhood in terms of mass and size.

• Journal of The Korean Astronomical Society
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• v.27 no.1
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• pp.31-44
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• 1994

The 4.8GHz formaldehyde absorption line in the dark clouds in M17 and NGC 2024 regions has been mapped. In both nebulae, we detected two $H_2CO$ line components. In M17, the 24km $S^{-1}$ cloud is closely associated with the HII region located in front of the radio continuum source, and the 19km $S^{-1}$ cloud is associated with the visual dark clouds with a larger extent which are closer to us. The 19km $S^{-1}$ cloud has a mass motion approaching to the HII region. In both clouds, a velocity gradient from the north-east to the south-west directions is observed. The linewidth has no variation indicating no collapsing motion. In NGC 2024, the 9km $S^{-1}$ feature is extended along the dark bar in front of the bright nebula and a weak second component at 13km $S^{-1}$ is confined to the immediate vicinity of the radio source. Indications are that the 9km $S^{-1}$ cloud is physically associated with the dark bar and the 13km $S^{-1}$ cloud is located behind the radio source. The angular extent, the column density, and the total mass of the clouds are derived. The radial velocities of other molecular lines observed in these clouds are compared.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.79.3-80
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• 2017

Molecular clouds are the sites of stellar birth. Turbulence is a natural phenomenon in molecular clouds, which largely determines the density and velocity fields. Additionally turbulent energy dissipation can affect the gas kinetic temperature via shocks. Turbulence thus controls the mode and tempo of star formation. However, despite its important role in star formation, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "Mapping turbulent properties of star-forming molecular clouds down to the sonic scale (PI: Jeong-Eun Lee)", we have been mapping two star-forming clouds, the Orion A and the ${\rho}$ Ophiuchus molecular clouds in 3 sets of lines (13CO 1-0/C18O 1-0, HCN 1-0/HCO+ 1-0, and CS 2-1/N2H+ 1-0) using the TRAO 14-m telescope. We apply a Principal Component Analysis (PCA), which is an useful tool to represent turbulent power spectrum. We will present the preliminary results of our TRAO KSP toward two regions: OMC 1-4 in the Orion A cloud, and L1688 in the ${\rho}$ Ophiuchus cloud.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.66.1-66.1
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• 2018

Turbulence is a phenomenon which largely determines the density and velocity fields in molecular clouds. Turbulence can produce density fluctuation which triggers a gravitational collapse, and it can also produce a non-thermal pressure against gravity. Therefore, turbulence controls the mode and tempo of star formation. However, despite many years of study, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "apping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we have mapped two star-forming clouds, the Orion A and the ${\rho}$ Ophiuchus molecular clouds, in 3 sets of lines (13CO 1-0/C18O 1-0, HCN 1-0/HCO+ 1-0, and CS 2-1/N2H+ 1-0) using the TRAO 14-m telescope. We aim to map entire clouds with a high-velocity resolution (~0.05 km/s) to compare turbulent properties between two different star-forming environments. We will present the preliminary results using a statistical method, Principal Component Analysis (PCA), that is a useful tool to represent turbulent power spectrum.

• Korean Journal of Remote Sensing
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• v.23 no.2
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• pp.71-87
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• 2007

In this study, 14 heavy snow events in Yeongdong area which are local phenomena are analyzed using MODIS cloud products provided from NASA/GSFC. The clouds of Yeongdong area at observed at specific time by MODIS are classified into A, B, C Types, based on the characteristic of cloud properties: cloud top temperature, cloud optical thickness, Effective Particle Radius, and Cloud Particle Phase. The analysis of relations between cloud properties and precipitation amount for each cloud type show that there are statistically significant correlations between Cloud Optical Thickness and precipitation amount for both A and B type and also significant correlation is found between Cloud Top Temperature and precipitation amount for A type. However, for C type there is not any significant correlations between cloud properties and precipitation amount. A-type clouds are mainly lower stratus clouds with small-size droplet, which may be formed under the low level cold advection derived synoptically in the East sea. B-type clouds are developed cumuliform clouds, which are closely related to the low pressure center developing over the East sea. On the other hand, C-type clouds are likely multi-layer clouds, which make satellite observation difficult due to covering of high clouds over low level clouds directly related with Yeongdong heavy snow. It is, therefore, concluded that MODIS cloud products may be useful except the multi-layer clouds for understanding the mechanism of heavy snow and estimating the precipitation amount from satellite data in the case of Yeongdong heavy snow.