• 천문학회보
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• 제38권2호
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• pp.63.2-63.2
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• 2013

Unlike the conventional wisdom, observations made during the past decade have revealed that many globular clusters possess more than one stellar population. Here, we have discovered evidence for multiple red giant branches (RGBs) in the globular cluster NGC 6388 from the narrow-band Calcium and Str$\ddot{o}$mgren b & y (Caby) photometry. In order to confirm the difference in Calcium abundance, we have acquired the low resolution spectroscopy for these RGB stars. In this paper, we will present results of our photometry and hand in the preliminary results of spectroscopic observations.

• 융합신호처리학회논문지
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• 제3권1호
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• pp.87-92
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• 2002

배치(Placement)는 VLSI 회로의 physical design에서 중요한 단계로서 회로의 성능을 최대로 하기 위하여 회로 모듈의 집합을 배치시키는 문제이며, 배치 문제에서 최적의 해를 얻기 위해 클러스터 성장(cluster growth), 시뮬레이티드 어닐링(simulated annealing; SA), ILP(integer linear programming)등의 방식이 이용된다. 본 논문에서는 배치 문제에 대하여 확률 진화 알고리즘(stochastic evolution algorithm; StocE)을 이용한 해 공간 탐색(solution space search) 방식을 제안하였으며, 제안한 방식을 시뮬레이티드 어닐링 방식과 비교, 분석하였다.

• 대한지리학회지
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• 제47권2호
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• pp.226-244
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• 2012

본 연구는 구미 전자산업클러스터의 진화과정을 분석하고 지역산업변화에 정부의 역할을 이해하는데 그 목적이 있다. 1990년대 초반까지 구미 산업단지는 수도권에 본사를 둔 대기업 분공장의 집적지로 구미지역에서의 산업연계가 미약했다. 그러나 최근 20년 동안 구미는 지역 내 기업 간 연계와 중소기업의 혁신활동이 상당히 이루어져 전자산업중심의 클러스터로 발전하고 있다. 정부의 산업정책은 구미전자산업클러스터의 진화과정을 이해하는데 매우 중요하다. 초기의 국가산업정책은 전략산업의 선정과 개발을 통해 구미 국가산업단지의 성장과 전자산업 중심의 전문화에 영향을 미쳤으며, 최근의 혁신클러스터 정책은 기업, 대학, 연구소간의 연계를 강화하고 지역 내 혁신네트워크 형성을 지원하였다. 경상북도와 구미시는 지역 대학 및 기업과 직접 협력관계를 맺고 지역의 연구개발 역량 향상과 중소기업 지원을 위한 정책을 중심으로 지역 발전에 기여하였다. 중앙정부와 대기업의 역할에 더해 지방정부와 중소기업의 역할 증대가 구미산업클러스터 진화의 기반이 되고 있다.

• 천문학논총
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• 제30권2호
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• pp.491-494
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• 2015

We present 12CO (2-1) data for four spiral galaxies (NGC 4330, NGC 4402, NGC 4522, NGC 4569) in the Virgo cluster that are undergoing different ram pressure stages. The goal is to probe the detailed molecular gas properties under strong intra-cluster medium (ICM) pressure using high-resolution millimeter data taken with the Submillimeter Array (SMA). Combining this with Institut de RadioAstronomie $Millim{\acute{e}}trique$ (IRAM) data, we also study spatially resolved temperature and density distributions of the molecular gas. Comparing with multi-wavelength data (optical, $H\small{I}$, UV, $H{\alpha}$), we discuss how molecular gas properties and star formation activity change when a galaxy experiences $H\small{I}$ stripping. This study suggests that ICM pressure can modify the physical and chemical properties of the molecular gas significantly even if stripping does not take place. We discuss how this affects the star formation rate and galaxy evolution in the cluster environment.

• 천문학회보
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• 제44권2호
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• pp.38.1-38.1
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• 2019

The formation and evolution of galaxies is known to be fundamentally linked to the local environment in which they reside. In the highest-density cluster environments, galaxies tend to be more massive, have lower star formation rates and dust content, and a higher fraction have elliptical morphologies. The stellar populations of these cluster galaxies are older implying that they formed the bulk of their stars much earlier and have since evolved passively. Quantifying the specific environmental factors that contribute to shaping cluster galaxies over the Hubble time and measuring their early evolution can only be accomplished by directly tracing the galaxy growth in young clusters and forming porto-clusters. In this talk, I will present a novel technique designed to map out the total dust obscured star formation relative to where existing stars lie. I will demonstrate that this technique can be used 1) to determine if/where/when the activity is heightened or suppressed in dense cluster environment; 2) to measure the total mass and spatial distribution of stellar populations; and 3) to better inform theoretical models. Our ongoing work to extend this analysis out to protoclusters (z~2-4) will be discussed.

• 천문학논총
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• 제30권2호
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• pp.529-530
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• 2015

We investigated the galaxy morphology of 6 Abell clusters at z = 0.0784 - 0.145 based on deep images obtained using MegaCam on the CFHT. For hundreds of galaxies in our data, we classified their morphology based on criteria related to secular or merger related evolution. We found that the morphological mixture of galaxies varies considerably from cluster to cluster. This article contains a general description of our deep imaging campaign and preliminary results for galaxy morphologies in cluster environments.

• 천문학논총
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• 제15권spc1호
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• pp.15-30
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• 2000

A large scatter of the chemical abundances among globular cluster red giants has been observed. Especially the chemical elements C, N, O, Na, Mg, and Al vary form star to star within globular clusters. Except for $\omega$ Cen and M22, most globular clusters could be considered to be monometallic of their iron peak elements within error ranges. The variations in light elements among globuar cluster giants appear much more pronounced than in field halo giants of comparable Fe-peak metallicity. It has been found that in general the nitrogen abundance is anticorrelated with both carbon and oxygen, while it is correlated with Na and AI. These intracluster abundance inhomogeneities can be interpreted either by mixing of nucleosythesized material from the deep stellar interior during the red giant branch phase of evolution or by inhomogeneities of primordially processed material, from which the stars were formed. The simple way of distingushing between two senarios is to obtain the element abundances of main-sequence stars in globular clusters, which are too faint for high resolution spectroscopic studies until now. Both 'evolutionary' and 'primodial' origins are accepted for explanations of abundance variations among red giants and CN-CH anticorrelations among main-sequence stars in globular clusters. This paper reviews chemical abundances of light elements among globular cluster giants, with brief reviews of cannonical stellar evolution of low mass stars after main-sequence and deep mixing for abundance variations of cluster giants, and a possible connection between deep mixing and second parameter.

• 천문학논총
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• 제25권3호
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• pp.101-105
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• 2010

Taking the great advantage of Subaru's wide field coverage both in the optical and in the near infrared, we have been providing panoramic views of distant clusters and their surrounding environments over the wide redshift range of 0:4 < z < 3. From our unique data sets, a consistent picture has been emerging that the star forming activity is once enhanced and then truncated in galaxy groups in the outskirts of clusters during the course of cluster assembly at z < 1. Such activity is shifted into cluster cores as we go further back in time to z ~ 1.5. At z = 2 - 2.5, we begin to enter the epoch when massive galaxies are actually forming in the cluster core. And by z ~ 3, we eventually go beyond the major epoch of massive galaxy formation. It is likely that the environmental dependence of star forming activity is at least partly due to the external environmental effects such as galaxy-galaxy interaction in medium density regions at z < 1, while the intrinsic effect of galaxy formation bias overtakes the external effect at higher redshifts, resulting in a large star formation activity in the cluster center.

• 천문학회보
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• 제38권1호
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• pp.33.1-33.1
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• 2013

Galaxies undergo various processes in the cluster environment, which could affect their evolution. In particular, ram pressure due to intracluster medium (ICM) can effectively remove HI gas, which is a relatively diffuse form of interstellar medium (ISM). On the other hand, molecular gas is not expected to get easily stripped as atomic gas since it is denser and sitting well within the stellar disk in a deeper potential well. However, cluster galaxies are found to be redder and more passive in star formation activity compared to their field counterpart. This implies that molecular gas may also get affected somehow in dense environments. In this work, we investigate molecular gas properties of a sample of galaxies undergoing HI stripping due to the ICM. We present the 12/13 CO (2-1) data of four spiral galaxies in the Virgo cluster at different ram pressure stripping stages, obtained using the Sub Millimeter Array (SMA). CO morphology of the sample appears to be highly asymmetric and disturbed. Using the ratio of different lines, we probe the molecular gas temperature in different regions. We find higher gas temperature than the range normally found among field galaxies. We discuss how these distinct molecular gas properties may affect star formation and hence the evolution of the cluster galaxy population.

• 한국지역지리학회지
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• 제21권3호
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• pp.489-502
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• 2015

실리콘펜 또는 케임브리지 현상으로도 알려져 있는 케임브리지 클러스터는 생명공학 산업 및 정보통신 산업에 특화되어 있는 혁신 클러스터로 잘 알려져 있다. 본 연구는 케임브리지 클러스터의 진화구조를 트리플힐릭스 관점을 중심으로 고찰한 것이다. 케임브리지 클러스터는 케임브리지대학을 중심축으로 형성된 자연발생적 클러스터로 간주할 수 있으나, 오늘날 케임브리지가 세계적인 첨단산업 클러스터의 기반을 갖추게 된 밑바탕에는 1960년대 후반에 결성된 산-학-관 협력체인 '케임브리지지역발전위원회'의 활동과 그 결과로 만들어진 모트보고서가 중요한 영향을 미쳤다. 그 후 1970년대부터 본격화된 클러스터의 성장과정에는 케임브리지대학의 칼리지들이 조성하기 시작한 사이언스 파크와 케임브리지대학의 스핀오프(스핀아웃) 활동이 활발하게 나타났다. 클러스터 진화의 역동성을 주도하는 지역 내 스핀오프 활성화의 기저에는 케임브리지 지역에 오랜 세월 누적되어 온 기업가주의 문화와 창업 및 기업 활동을 촉진하는 기업가 네트워크와 사회자본의 영향이 중요하게 작용했다. 그러나 2000년대 들어 대학의 재정 지원을 축소하고 기업가적 대학으로의 전환을 유도하는 정부의 정책기조가 심화됨에 따라 케임브리지대학의 스핀오프 활동은 크게 위축되었고, 이것이 케임브리지 클러스터의 역동적 진화를 위협하는 요소로 작용하고 있다.