• 천문학회보
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• 제43권2호
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• pp.31.3-31.3
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• 2018

On August 17th 2017, for the first time in the history, the gravitational wave (GW) detectors recorded signals coming from the merger of two neutron stars. This event was named as GW170817, and more interestingly, gamma-ray emission was detected 2 seconds after the gravitational wave signal, and 11 hours later, telescopes in Chile identified that the GW signal came from the NGC 4993 galaxy at the distance of about 40 Mpc. This is again the first time that electromagnetic (EM) signals are detected for a GW source. The follow-up observations by astronomers all around the world, including our group in Korea, successfully identified the optical emission as the kilonova, the elusive optical/NIR counterpart that has been proposed to originate from a neutron star merger. This whole event started the new era of astronomy, so-called the "multi-messenger astronomy", where the combined information from GW and EM radiation reveals an unprecedented view of the universe. In this talk, I summarize this exciting event, and describe the efforts by Korean astronomers that have led to important discoveries about the kilonova and the host galaxy properties, and finally provide the future prospects.

• 천문학회보
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• 제38권1호
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• pp.32.2-32.2
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• 2013

We examine large-scale environmental effects on the formation and the mass growth of dark matter halos. To facilitate this, we constructed dark matter halo merger trees from a cosmological N-body simulation, which enabled us to trace the merger information and the assembly history of individual halos. In fact, since the massive halos are more likely to be distributed in denser regions than in less dense regions (Mo & White, 1996), the large-scale environment dependence of the properties of halos can be partly originated from the halo mass effect. In order to avoid such contamination, caused by the mass dependence of halo properties, we carefully measured the local overdensity as the indicator of large-scale environment, which was calculated to be as independent of halo mass as possible. Small halos (${\sim}10^{11-12}M_{\odot}$), which usually host isolated single galaxies, show a notable difference on the formation time of galaxies depending on their large-scale environments, which reconfirms halo assembly bias (Gao & White, 2007). Furthermore, we investigate how this environmental effect on small halos is correlated with the mass assembly history of galaxies by using our semi-analytic model. We found that assembly bias in small halos does not have significant effects on the formation time or on the star formation history of galaxies residing in those halos except for the individual stellar mass of galaxies at z = 0. On average, isolated galaxies in high-density regions tend to be slightly more massive than those in low-density regions. Although the observational data from the current galaxy surveys is not yet sufficient for testing this prediction, future galaxy surveys will be able to explore these small galaxies more thoroughly.

• 천문학논총
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• 제30권2호
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• pp.463-464
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• 2015

It has been suggested that only the most luminous AGNs ($L{\gtrsim}10^{45}erg/s$) are triggered by galaxy mergers, while less luminous AGNs ($L{\sim}10^{43}erg/s$) are driven by other internal processes. The lack of merging features in low luminosity AGN host galaxies has been a primary argument against the idea of merger triggering of low luminosity AGNs. But a merger, especially a rather minor one, might still have played an important role in low luminosity AGNs, as minor merging features at low luminosities are more difficult to identify than major merging features. Using SNUCAM on the 1.5 m telescope at Maidanak observatory, we obtained deep optical images of NGC 7743, a barred spiral galaxy classified as a Seyfert 2 AGN with a low bolometric luminosity of $5{\times}10^{42}erg/s$. Surprisingly, we discovered a merging feature around the galaxy, which indicates past merging activity in the galaxy. This example indicates that the merging fraction of low luminosity AGNs may be much higher than previously thought, hinting at the importance of galaxy mergers even in low luminosity AGNs.

• 한국기술혁신학회:학술대회논문집
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• 한국기술혁신학회 2010년도 추계 학술대회 논문집
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• pp.203-212
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• 2010

Examining the relation between market structure and the value of innovation is important for competition and STI policy. If the value is large in a specific industry structure, government may lead the industry to take that form to enhance innovation. Our simple calibration in the case of linear demand and constant MC results in the conclusion that the incentive for R&D in the case of major and minor innovation in Cournot competition is less than that of merger and cooperative R&D. This emphasizes again "necessary evil" as a monopoly for innovation.

• 경영정보학연구
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• 제11권2호
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• pp.45-66
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• 2009

수 많은 기업들이 기업 성장 및 생존 전략의 일환으로 인수 합병 (M&A, merger and acquisition)을 선택하고 있다. 그러나 상당수의 기업들이 본래 의도했던 시너지 효과를 창출하지 못하고 인수 합병 실패로 인해 생산성 저하, 시장 점유율 하락, 수익 감소, 유능한 직원의 이직 등 많은 부작용을 경험하고 있다. 이에 따라 인수 합병 성공 및 실패 원인을 분석하고자 하는 많은 연구가 진행되었고, 정보시스템에 대한 기업들의 의존도 증가와 더불어 인수 합병 이후 정보시스템 통합(post-M&A information systems integration)이 인수 합병 성공에 결정적인 영향을 미치는 것으로 확인되었다. 그러나 인수 합병 이후 정보시스템 통합 성공에 대한 연구가 매우 부족하며, 대부분의 선행연구가 정보시스템 조직 통합 또는 물리적인 정보시스템의 통합 등과 같이 단편적으로 이루어져 왔다. 본 연구에서는 인수 합병 이후 정보시스템 통합 성공에 영향을 미치는 요인들에 대한 포괄적인 연구를 위하여 정보시스템뿐만 아니라 전략 경영, 경제학, 재무학, 인사관리, 조직관리 분야의 선행연구를 조사하였다 이를 기반으로 인수 합병 이후 정보시스템 통합 영향요인에 대한 통합 모델을 제시하였다. 제시된 모형에서는 영향요인들을 인수 합병 관점, 전략 관점, 조직 관점, 인사관리 관점, 정보시스템 관점으로 재 분류하고, 사례연구를 통하여 각 요인들이 정보시스템 통합 성공에 미치는 영향을 실증적으로 검증하였다.

• 벤처창업연구
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• 제12권6호
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• pp.49-63
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• 2017

본 연구는 중소기업이 M&A를 할 때 중소기업의 집단적 특성이 합병의 공시효과와 합병 이후 장기영업성과에 미치는 영향을 분석하고자 2000년부터 2012년까지 우리 나라의 인수합병 사건 중 코스닥시장에서 중소기업법 제2조와 동법 시행령 제3조의 규정을 적용하여 선정한 중소기업의 사례 717개 사건을 표본으로 사건연구 및 영업현금흐름수익률을 영업성과변수로 하는 다중회귀분석을 실시하였다. 그 결과 첫째, 합병공시효과에 미치는 영향에 있어서는 기존의 한국자본시장을 대상으로 한 선행연구와 동일하게 중소기업 인수합병 사건에서도 규모효과가 존재함을 확인하였으나 다각화효과, 상장효과, 국제간인수합병효과는 확인하지 못하였다. 그리고 일반적 기업을 대상으로 한 선행연구 결과와는 다르게, 중소기업은 인수합병의 공시효과에 있어서 과거의 생산효율성이 높아 과거의 영업성과가 높은 기업들이 더 높은 초과수익률을 올리고 있음을 확인하였다. 둘째, 인수합병의 집단적 특성에 따른 영업성과에 미치는 영향은 비관련합병이 장기영업성과에 긍정적인 영향을 미친다는 기존의 선행연구와는 다르게, 평균적인 상장기업에 비해 열위의 시장경쟁력을 가지고 있는 중소기업의 특성상 동종기업과 관련합병을 할 때 생산의 효율성을 극대화하여 장기 영업성과에 긍정적인 영향을 미치고 있음을 확인하였다. 이러한 본 연구는 대기업의 산유물로만 여겨져 왔던 인수합병의 사례를 중소기업에 적용하여 인수합병의 공시효과와 집단적 특성에 따른 장기 영업성과에 미치는 영향을 살펴봄으로써 중소기업 인수합병 사건 연구에 새로운 시각을 제공하였다는 데에 큰 의미를 가지고 있다.

• 벤처혁신연구
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• 제6권4호
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• pp.113-131
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• 2023

인수합병 후 통합(post-merger integration; PMI)이 M&A 성공에 있어 매우 중요한 역할을 담당하고 있다. 따라서 본 연구는 PMI에 대한 선행 연구들을 바탕으로 PMI 과정에서 피인수기업 구성원에 대한 의사소통과 '인식된 불확실성 감소', '조직만족도' 그리고 '조직신뢰' 간의 관계를 살펴보고 인수기업과 피인수기업 간의 '사업영역의 일치도'의 조절 효과를 중심으로 조사하고자 한다. 본 연구는 연구목적을 달성하기 위하여 각 변수 간의 관계에 대한 가설을 설정하고 실증분석을 진행하였다. 자료는 중국 내에 인수 기업에서 근무하는 피인수기업의 구성원을 대상으로 설문조사를 실시하여 최종 317개 설문지를 수집하였고 실증분석을 실시하였다. 연구 결과, 의사소통은 피인수기업 구성원들이 인식한 불확실성 감소, 직무만족도 그리고 조직신뢰에 긍정적인 영향을 미친다는 것과 인수기업과 피인수기업 간의 사업영역의 일치도는 의사소통과 '인식된 불확실성' 간의 관계를 약화시킨다는 것을 확인하였다. 의사소통과 직무만족도 및 조직신뢰 간의 긍정적인 관계에서 조절변수가 강화시키는 효과가 확인되지 않고, 오히려 약화시키는 조절효과를 밝혀냈다. 이러한 연구 결과를 토대로 본 연구는 PMI 과정에서 피인수기업 구성원들과의 의사소통 전략은 통합의 성패에 의미를 가지며, M&A 유형에 따른 차별화된 인적자원관리 방안에 대한 제시와 같은 실무적인 시사점을 제시하였다.

• 천문학회지
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• 제35권4호
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• pp.159-174
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• 2002

Cosmological hydrodynamic simulations of large scale structure in the universe have shown that accretion shocks and merger shocks form due to flow motions associated with the gravitational collapse of nonlinear structures. Estimated speed and curvature radius of these shocks could be as large as a few 1000 km/s and several Mpc, respectively. According to the diffusive shock acceleration theory, populations of cosmic-ray particles can be injected and accelerated to very high energy by astrophysical shocks in tenuous plasmas. In order to explore the cosmic ray acceleration at the cosmic shocks, we have performed nonlinear numerical simulations of cosmic ray (CR) modified shocks with the newly developed CRASH (Cosmic Ray Amr SHock) numerical code. We adopted the Bohm diffusion model for CRs, based on the hypothesis that strong Alfven waves are self-generated by streaming CRs. The shock formation simulation includes a plasma-physics-based 'injection' model that transfers a small proportion of the thermal proton flux through the shock into low energy CRs for acceleration there. We found that, for strong accretion shocks, CRs can absorb most of shock kinetic energy and the accretion shock speed is reduced up to $20\%$, compared to pure gas dynamic shocks. For merger shocks with small Mach numbers, however, the energy transfer to CRs is only about $10-20\%$ with an associated CR particle fraction of $10^{-3}$. Nonlinear feedback due to the CR pressure is insignificant in the latter shocks. Although detailed results depend on models for the particle diffusion and injection, these calculations show that cosmic shocks in large scale structure could provide acceleration sites of extragalactic cosmic rays of the highest energy.

• 천문학회보
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• 제41권1호
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• pp.40.1-40.1
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• 2016

Recent integral-field spectrograph surveys have found that similar-looking early type galaxies have wide range of rotational properties (Emsellem et al. 2007). This finding initiated a new point of view to the galaxies; rotation of galaxy as the first parameter of galaxy classification (Emsellem et al. 2011, Cappellari et al. 2011, for example). Some theoretical studies tried to address the origin of galaxy rotation. Idealized galaxy merger simulations have shown that galaxy-galaxy interactions have significant effects on the rotation of galaxies. Cosmological simulations by Naab et al. 2014 also added some more insights to the rotation of galaxies. However, previous studies either lack cosmological background or have not enough number of samples. Running a set of cosmological hydrodynamic zoom-in simulations using the AMR code RAMSES(Teyssier 2002). we have constructed a sample of thousands of galaxies in 20 clusters. Here we present a kinematic analysis of a large sample of galaxies in the cosmological context. The overall distribution of rotation parameter of simulated galaxies suggests a single peak corresponding to fast rotating galaxies. But when divided by mass, we find a strong mass dependency of galaxy rotation, and massive galaxies are distinctively slow rotating. The cumulated effective of mergers seems to neutralize galaxy rotation as suggested by previous studies (Khochfar et al. 2011, Naab et al. 2014, and Moody et al. 2014). This is consistent with the fact that massive galaxies tend to rotate more slowly after numerous mergers. However, if seen individually, merger can either increase or decrease galaxy rotation depending on mass ratio, orbital parameter, and relative rotation axis of the two galaxies. This explains the existence of some non-slow rotating massive early type galaxies.

• STI Policy Review
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• 제3권2호
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• pp.152-171
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• 2012

In April 2001, many Japanese national institutes were reorganized as Independent Administrative Institutions (IAI) based on the General Act for Independent Administrative Institutions and the act for each institution. Under the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the National Institute for Materials Science (NIMS) was established by the merger of the National Research Institute for Metals (NRIM) and the National Institute for Research in Inorganic Materials (NIRIM). One of the biggest changes was the expansion of autonomous administration. The nanotechnology and material R&D field was prioritized in the 2nd (2001-2005) and the 3rd (2006-2010) Science and Technology Basic Plans; subsequently, NIMS was assigned to take the initiative in nanotechnology as well as materials science. NIMS has proactively expanded research fields through the introduction of researchers from polymers, electronics, and biotechnology as well as member institutes of the World Materials Research Institute Forum (WMRIF). Globalization has been promoted through programs that include the International Center for Young Scientists (ICYS) and the International Center for Materials Nanoarchitectonics (MANA). The 4th Science and Technology Basic Plan (2011-2015) emphasizes outcomes-recovery and rebirth from the disaster, green innovation, and life innovation. The Midterm Plan for NIMS also follows it. R&D collaboration by multi-partners (that include industry, university, and GRI) should be strategically promoted where GRI are especially required to play a hub function for innovative R&D and open innovation. NIMS highlights are Tsukuba Innovation Arena (TIA) and the Nanotechnology Platform Project. On January 20, 2012, a new organization was decided on by the Japanese Government where several IAI from different science and technology areas will be merged to realize more effective R&D as well as administrative cost reductions. NIMS is also supposed to be merged with 4 other R&D IAI under MEXT by the end of 2013.