• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.50.2-50.2
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• 2013

In the process of star formation, the density and temperature of associated material, which are the physical conditions for the molecular chemistry, vary dramatically. As a result, the connection between physical and chemical conditions has been used to trace the evolutionary stages in star formation. One chemical tracer for the physical conditions in star forming material is the [HCN]/[HNC] abundance ratio since the ratio strongly depends on the kinetic temperature in molecular clouds. Here we investigate the [HCN]/[HNC] abundance ratios in objects related to the massive star formation. For the investigation, we carried out $H^{13}CN$ and $HN^{13}C$ line observation toward objects in three different evolutionary stages of massive star formation: Infrared dark clouds (IRDCs), High-mass protostellar object (HMPOs), and Ultra-compact HII regions (UCHIIs). According to our observational results, both $H^{13}CN$ and $HN^{13}C$ lines have been detected toward 19 IRDCs, 25 HMPOs, and 31 UCHIIs. We will discuss about the [HCN]/[HNC] abundance ratios in different evolutionary stages of massive star formation and associate the results with the physical conditions of the targets.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.70.2-70.2
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• 2016

Star formation in galaxies is one of the key factors in galaxy evolution. It is believed that star formation is triggered and enhanced by mergers among galaxies or secular evolution. However, how much these two mechanisms contribute on star formation is not well known yet. Recently, many other studies show observational evidences of faint merger features(tidal tails, stellar streams) around nearby galaxies with deep optical imaging. This study aims to investigate the fraction of star forming galaxies exhibiting faint features to total galaxies. We are analyzing samples of 76 star forming galaxies (NUV < -18) to find merger features from stacked B, R band frames taken at Maidanak 1.5m, McDonald 2.1m telescope and g, r frames from Canada-France-Hawaii Telescope (CFHT) MegaCam archival data. With the fraction, we can expect to know the contribution of mergers on star formation to galaxies.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.85.2-85.2
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• 2014

The origin of the Korean Screen Planisphere with both Traditional and New Star-Charts, made by Korean Astronomers in the Royal Astronomical Bureau of the Joseon Dynasty by adopting the knowledge of the European astronomy, is investigated by analyzing its inscriptions and star charts. The considerations on both the changes in notations or representations of names of asterisms and the naming taboos used in the Old-style planisphere imply that the star-chart is originated from either the Sukjong-Stele-Replica of Cheonsang-Yeolcha-Punyajido(天象列次分野之圖). The New style planisphere is just the reproduction of Huangdao-congxingtu (黃道總星圖), with the exception of the non-Chinese-traditional stars. The Huangdao-congxingtu was made in 1723 CE by Ignatius K$\ddot{o}$gler who was a Jesuit missionary and worked for the Bureau of Astronomy (欽天監) in the Qing Dyansty. I find that the star chart was imported in 1742 CE from the Qing by An Gukrin (安國麟) who was an astronomer in the Royal Astronomical Bureau of Joseon. The chart became model for the screen star-chart made in 1743 CE and now housed in Bopju temple. I found that the inscriptions are extracted from the sentences in both Xinzhi Lingtai Yixiangzhi (新製靈臺儀象志) and Qinding Yixiangkaocheng (欽定儀象考成). Korean historical records in either Daily Records of the Royal Secretariat of the Joseon Dynasty (承政院日記) or Annals of the Joseonn Dynasty (朝鮮王朝實錄) show that Xinzhi Lingtai-Yixiangzhi was imported from the Qing Dynasty in 1708 CE, and the Qinding Yixiangkaocheng was imported in 1766 CE. Thus, the Korean Screen Planisphere with both Old and New Star-charts was certainly made after 1766 CE.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10A
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• pp.847-851
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• 2011

In this paper, we reported on a high performance MMIC star mixer for millimeter-wave applications. The star mixer was fabricated using drain-source-connected pseudomorphic high electron mobility transistor (PHEMT) diodes considering the PHEMT MMIC full process on 2 mil thick GaAs substrate. The average conversion loss of 13 dB was measured in the RF frequency range of 81 GHz to 86 GHz at LO frequency of 75 GHz with LO power of 10 dBm. The RF-LO isolation characteristics are greater than 30 dB and the input 1-dB compression are approximately 4 dBm. The total chip size is 0.8 mm ${\times}$ 0.8 mm.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.4
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• pp.389-405
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• 1999

본 논문에서는 상호 연결망의 노드를 행렬로 표현하고 행렬연산을 이용하여 에지를 정의한 새로운 상호 연결망으로 행렬-스타 그래프를 제안한다. 행렬-스타 그래프는 널리 알려진 스타 그래프를 일반화한 그래프이다. 먼저, 행렬-스타 그래프의 노드를 2 $\times$ n 행렬로 표현한 행렬-스타 그래프 MS2,n 에 대하여 주요 망 척도인 분지수, 연결도, 확장성, 대칭성, 리우팅 ,지름 방송등을 분석한다. 다음으로, 행렬-스타 그래프 MS2,n의 노드를 2차원과 3차원으로 일반화한 행렬-스타 그래크 MSk,n과 MS k,n,p를 정의하고 행렬-스타그래프 MSk,n,p 의 라우팅 알고리즘과 지름을 분석한다. 상호연결망의 중요 망 척도중 하나는 망 비용이고 상호연결망의 망 비용은 그 연결망의 분지수와 지름의 곱으로 정의된다. star 그래프는 다른 상호 연결망보다 작은 망 비용을 갖는다. 최근에 제안된 Macro-Star 그래픈 star 그래프에 비해 상대적으로 망 비용이 작은 값을 갖는 연결망이다. (n2)!개의 노드를 갖는 행렬-스타 그래프 MSk,k,k(k={{{{ `^{ 3} SQRT { n$^2$} }}}} )와 ((n-1)2 + 1)!개의 노드를 갖는 Macro-Star 그래프 MS(n-1, n-1)의 망 비용은 행렬-스타그래프 MSk,k,k(k={{{{ `^{ 3} SQRT { n$^2$} }}}})는 O(n2,7)이고, Macro-Star 그래프 MS(n-1 , n-1)은 O(n3) 이다. 이는 행렬-스타 그래프가 스타 그래프와 Macro-Star 그래프보다 망비용이 우수함을 의미한다.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.1-6
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• 2010

Star-like ZnO nanostructures were grown on SI(100) substrates with carbon(C) catalyst by employing vapor-solid(VS) mechanism. The morphologies and structure of ZnO nanostructures were investigated by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Raman spectrum, Photoluminescence spectrum. The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. Nanostructures grown at 1100 were mainly star-like in structure with diameters of 500 nm. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor.solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow emission band peak around 380 nm and a broad one around 491 nm. Raman spectrum of the ZnO nanostructures showed oxygen defects in ZnO nanostructures due to the existence of Ar gas during the growth process, leading to the dominant green band peak in the PL spectrum.

• Journal of Arbitration Studies
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• v.33 no.1
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• pp.23-49
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• 2023

An ICSID award on Lone Star case has been rendered finally on August 31st, 2022 after almost ten years since the Lone Star Funds submitted the request for arbitration against the Republic of Korea in 2012. The Lone Star case is the first investor-state dispute settlement(ISDS) case brought against Korea, and this case, also known as "eat and run" case, has given rise to heated debates for years. Moreover, as the ICSID tribunal has ordered Korea to pay the Lone Star Funds the sum of USD 216.5 million plus interest in the award, this case has become once again the subject of controversy. Any arguments and evidence submitted by the parties in dispute have not been disclosed until recently, however, as the memorials and the award are now open to the public, it has become possible to realize the assertions of each party and the decisions of the tribunal in detail. Therefore, this paper aims at analyzing the main issues of the Lone Star case with a focus on the ICSID award. By examining the substantive and procedural issues of the case one after the other, it might be able to understand the whole picture of the case and prepare for the remaining procedures of this case and other upcoming cases as well.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.36.1-37
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• 2021

Six images of IRC+10216 taken by the Hubble Space Telescope at three epochs in 2001, 2011, and 2016 are compared in the rest frame of the central carbon star. An accurate astrometry has been achieved with the help of Gaia Data Release 2. The positions of the carbon star in the individual epochs are determined using its known proper motion, defining the rest frame of the star. In 2016, a local brightness peak with compact and red nature is detected at the stellar position. A comparison of the color maps between 2016 and 2011 epochs reveals that the reddest spot moved along with the star, suggesting a possibility of its being the dusty material surrounding the carbon star. Relatively red, ambient region is distributed in an Ω shape and well corresponds to the dusty disk previously suggested based on near-infrared polarization observations. In a larger scale, differential proper motion of multiple ring-like pattern in the rest frame of the star is used to derive the average expansion velocity of transverse wind components, resulting in ~12.5 km s-1 (d/123 pc), where d is the distance to IRC+10216. Three dimensional geometry is implied from its comparison with the line-of-sight wind velocity determined from half-widths of submillimeter emission line profiles of abundant molecules. Uneven temporal variations in brightness for different searchlight beams and anisotropic distribution of extended halo are revisited in the context of the stellar light illumination through a porous envelope with postulated longer-term variations for a period of 10 years.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.37.1-37.1
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• 2021

Observations suggest the star formation in nuclear rings of barred galaxies proceeds episodically in time and sometimes asymmetrically in space. Existing theories and numerical simulations suggest that the episodic star formation is perhaps due to either supernova feedback combined with fluid instabilities or time-varying mass inflow rate. However, it has been challenging to discern what dominates in shaping the star formation history because the effects of the inflow and feedback are blended in global simulations of nuclear rings. To understand their effects separately, we construct semi-global models of nuclear rings, which treat the mass inflow rate as a model parameter. By running simulations with the inflow rates kept constant or oscillating in time, we find that the star formation rate (SFR) of the rings varies coherently with the inflow rate, while the feedback is responsible only for stochastic fluctuations of the SFR within a factor of two. The feedback instead plays an important role in maintaining the vertical dynamical equilibrium and setting the depletion time. While the asymmetry in the inflow does not necessarily lead to the asymmetry in the star formation, we find that the rings undergo a transient period of lopsided star formation when the inflow rate of only one dust lane is suddenly increased.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.70.4-71
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• 2020

One of the distinctive characteristics of the evolution of binary systems would be mass transfer. Close binary systems experience so-called Case A mass transfer during the main-sequence. We have performed calculations of the evolution of massive Case A (with the initial period 1.5 ~ 4.5 days) binary systems with the initial mass of 10 ~ 20 solar masses and mass ratio 0.5 ~ 0.95 using the MESA code. We find that in some systems, after the first mass transfer, the secondary stars evolve faster than the primary stars and undergo so-called 'reverse' mass transfer. Such phenomena tend to occur in relatively low-mass (initial mass < 16 solar masses) and close (initial period < 3 day) systems. Unless a system enters the common-envelope phase, the primary star would become a single helium star after the secondary star ends its life if the system were unbound by the neutron star kick. We find the various evolutionary implications of the remaining primary stars. In addition to the evolution into the compact single helium star progenitor, there is a possibility that the remaining primary star could evolve into a helium giant star, which could be a promising candidate for Type Ibn supernova progenitor, depending on the core mass. Further, we find that some primary stars satisfy the conditions for the formation of electron-capture supernova progenitor.