• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.28.2-28.2
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• 2017

Using numerical hydrodynamics code RAMSES, we perform idealized galaxy merger simulations and study the star formation of merging disk galaxies. In our simulations, we consider the active galactic nucleus (AGN) feedback effect. In order to investigate the star formation influenced by AGN, we run ~60 simulations with various initial conditions. We confirm that star formation is more efficiently suppressed in merging galaxies than in isolated galaxies. In the mergers, AGN effect is more significant when the masses of two galaxies are similar. Furthermore, we find that bulge fraction does not affect the star formation when the AGN effect is considered. We discuss the implications on semi-analytic galaxy formation models and the limitation of the current AGN prescriptions.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.52.3-53
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• 2021

It is yet to be understood what controls the star formation activity in high-redshift galaxy clusters. One recently proposed mechanism is that the star formation activity in galaxy clusters are fed by gas and galaxies in large-scale structures surrounding them, which we call as "web feeding model". Using galaxies in the COSMOS2015 catalog, with mass completeness at log(M/M_⦿)≥9.54 and reliable photometric redshift data (σ_Δz/(1+z) ≲ 0.01), we study the star formation activities of galaxy clusters and their surrounding environment to test the web feeding model. We first identify the overdense regions with number density exceeding the 4σ-level from photometric redshift data as galaxy clusters, and we find that they are well matched with clusters identified in the X-ray extended source catalog. Furthermore, we identify galaxy large scale structures, and will present the correlation or anti-correlation between quiescent galaxy fraction, an indicator of star-forming activity, and the prevalence of galaxy large scale structures.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.60.1-60.1
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• 2015

We present the current operation status of StarDB web services by showing its user access statistics. The StarDB web services started its operation in late November, allowing world-wide users to access results of new variability analysis for Northern Sky Variability Survey light curves. New analysis results of various time-series data have been added to the StarDB services. Importantly, our services have supported a simple cone search, which is an internationally well-defined catalog search interface in the international Virtual Observatory systems. We have collected user access statistics such as how users find our analysis data since its operation in later November. We expect our analysis of the StarDB operation to help Korean community members who plan and operate their own web services preparing for a future era of big survey data.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.1
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• pp.13-27
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• 2014

In this paper, we deal with a Steiner Ring Star (SRS) problem arising from the design of survivable telecommunication networks. We develop two mixed integer programming formulations for the SRS problem by implementing Miller-Tucker-Zemlin (MTZ) and Sarin-Sherali-Bhootra (SSB) subtour elimination constraints, and then apply the reformulation-linearization technique (RLT) to enhance the lower bound obtained by the LP relaxation. By exploiting the ring-star structure of underlying network, we devise some valid inequalities that tighten the LP relaxation. Computational results demonstrate the effectiveness of the proposed solution procedure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.59-62
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• 1993

This Paper studies on thermal oxidation of alumina filled epoxy network polymer used in Extra-High voltage application. The thermal oxidation of surface has investigated by yellow index variation and various electrical properties which are surface resistivity, tracking resistance and AC dielectric strength are estimated by yellow index.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.433-437
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• 1996

We have analyzed the content of the Korean stone star chart. Ch'on-Sang-Yul-Cha-Bun-Ya-Ji-Do(here-after Ch'on-Sang-Do). In the star map we have found 1468 stars, 4 more than the Chinese star catalog Bo-Chun-Ga. The four extra stars form a constellation, Jong Dae Boo. The map projection law used in the star chart is found to be the polar equtorial and equidistance projection. The linear distance of an object on Ch'on-Sang-Do from the center is linearly proportional to the north polar angular distance. We have found from a statistical analysis that most stars with declination lower than 50 are at positions representing the epoch of around the first century. On the other hand, stars near the north pole with declination higher than 50 are at the epoch of about 1300, which is close to the time the chart was engraved. This implies that the original Ko-Gu-Rye Dynasty's star chart has been revised by astronomers of Cho-Sun Dynasty. We have also shown that stars on Ch'on-Sang-Do are engraved in such a way that their area is linearly proportional to the visual magnitude.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.878-883
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• 1990

There have been many approaches to solve the disturbance rejection problem in the control of LTI systems with state independent disturbances or possibly nonlinear state dependent disturbances. From the view point of each actuator, robot manipulators can be modeled as the second class of systems. With this model, M.Nakao et al. [1] introduced a decentralized control scheme based on interference estimation which is simple in its implementation and robust to the coupled dynamics and parameter variations. This paper systematically generalizes the control scheme to arbitrary finite dimensional LTI systems with disturbances. In doing so, we develop a disturbance observer theory for solving the disturbance rejection problem. We also present a discrete version of the theory with discussion of sampling and time-delay effects.

• Journal of the Korean Mathematical Society
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• v.49 no.2
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• pp.405-417
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• 2012

We find the Hilbert function and the minimal free resolution of a star-configuration in $\mathbb{P}^n$. The conditions are provided under which the Hilbert function of a star-configuration in $\mathbb{P}^2$ is generic or non-generic We also prove that if $\mathbb{X}$ and $\mathbb{Y}$ are linear star-configurations in $\mathbb{P}^2$ of types t and s, respectively, with $s{\geq}t{\geq}3$, then the Artinian k-algebra $R/(I_{\mathbb{X}}+I_{\mathbb{Y})$ has the weak Lefschetz property.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.376-379
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• 1993

GoldStar Industrial Systems Co. R & D center successfully developed the inverter for welding under the support of GoldStar Electric Machinery Co. Now, we are currently working on the mechanical part of articulated robot and a high-performance general purpose motion controller. By combining the above three items, we will be able to constitute the complete welding robot system on our own. In this article. the welding robot system currently under developing is introduced. The main focus will be placed on the development of general purpose motion controller with welding control module. Therefore, the architecture of welding robot controller where the general purpose motion controller is combined with the welding controller module will be explained. Here, the software system will be explained with regard to the hardware system.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1236-1238
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• 1993

This paper studies on the behaviors of decomposition products from DCP according to various drying conditions of DCP. The decomposition products formed during crosslinking reaction have an harmful influence on XLPE. Especially explosive gases like methane which is one of decomposition products may cause explosion accident. We used the Gas Chromatography and Gas sensor for decomposition gases analysis, FT-IR for investigating the behaviors of decomposition products remained in XLPE.