• 천문학회보
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• 제43권2호
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• pp.38.2-38.2
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• 2018

To understand the assembly of the galaxy population in clusters today, it is important to first understand preprocessing, the impact of environments prior to cluster infall. We use 15 cluster samples from YZiCS, a hydrodynamic cluster zoom-in simulation to determine the significance of preprocessing, and focus on the tidal mass loss of dark matter halos. We find ~48% of the cluster member halos were once satellites of another host. The preprocessed fraction depends on each cluster's recent mass growth history. Also, we find that the total mass loss is a clear function of the time spent in a host. However, two factors can increase the mass loss rate considerably. First, if the satellite mass is approaching the mass of its host. Second, when the halo suffers tidal mass loss at a higher redshift. Being in hosts before cluster infall enables halos to experience tidal mass loss for an extended period of time.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2774-2780
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• 2014

A dynamics study of relaxation and fragmentation of icosahedral argon cluster with a vibrationally excited $Ar_2^+$ (${\nu}$) is presented. Local translation is shown to be responsible for inducing energy flow from the embedded ion to host atoms and fragmentation of the cluster consisting of various low frequency modes. The total potential energy of $(Ar_2^+)Ar_{12}$ is formulated using a building-up procedure of host-guest and host-host interactions. The time dependence of ion-to-host energy transfer is found to be tri-exponential, with the short-time process of ~100 ps contributing most to the overall relaxation process. Relaxation timescales are weakly dependent on both temperature (50-300 K) and initial vibrational excitation (${\nu}$ = 1-4). Nearly 27% of host atoms in the cluster with $Ar_2^+$ (${\nu}$ = 1) fragment immediately after energy flow, the extent increasing to ~43% for ${\nu}$ = 4. The distribution of fragmentation products of $(Ar_2^+)Ar_{12}{\rightarrow}(Ar_2^+)Ar_n+(12-n)Ar$ are peaked around $(Ar_2^+)Ar_8$. The distribution of dissociation times reveals fragmentation from one hemisphere dominates that from the other. This effect is attributed to the initial fragmentation causing a sequential perturbation of adjacent atoms on the same icosahedral five-atom layer.

• 천문학회보
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• 제43권1호
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• pp.61.3-61.3
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• 2018

To understand the assembly of the galaxy population in clusters today, it is important to first understand the impact of previous environments prior to cluster infall, namely preprocessing. We use 15 cluster samples from hydrodynamic zoom-in simulation YZiCS to determine the significance of preprocessing focusing primarily on the tidal mass loss of dark matter halos. We find ~48% of the cluster member halos were once satellites of another host. The preprocessed fraction is not a clear function of cluster mass. Instead, we find it is related to each individual cluster's recent mass growth history. We find that the total mass loss is a clear function of time spent in a host. However, two factors can considerably increase the mass loss rate. First, if the satellite mass is approaching the mass of its host. Second, when the halo suffers tidal mass loss at a higher redshift. The preprocessing provides an opportunity for halos to experience tidal mass loss for a more extended period of time than would be possible if they simply fell directly into the cluster, and at earlier epochs when hosts were more destructive to their satellites.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.903-906
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• 2003

Doping a small amount of a phosphorescent dye into an organic light-emitting diodes(OLED) can lead to a significant improvement in the device properties. The fluorescent host materials like TAZ, CBP have been used, but have a problem of rapid decay of efficiency at high current densities. To alleviate this problem, phosphorescent host was introduced. The whole configuration of OELD fabricated was ITO/a-NPD(50nm)/Zn $cluster:Ir(ppy)_{3}(30nm)/BCP{(10nm)/Alq_{3}(20nm)$ /Al:Li. The OLED showed high luminance (> 50,000 $cd/m^{2}$ ) and external efficiency(5.7%). At higher current densities, rapid decay of external quantum efficiency or host emission, which was frequently observed in the fluorescent host system, were not observed.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.34.4-34.4
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• 2010

We present the properties of globular cluster systems for 10 early-type galaxies in low density environments obtained using deep images from the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). Using the ACS Virgo Cluster Survey as a counterpart in high-density environments, we investigate the role of environment in determining the properties of their globular cluster systems. We detect a strong colour bimodality of globular cluster systems in half of our galaxy sample. It is found that there is a strong correlation between the colour and richness of globular cluster populations and their host galaxy luminosities: the less bright galaxies possess bluer and fewer globular clusters as also seen in rich cluster environments. However, the mean colour of globular clusters in our field sample are slightly bluer than those in cluster environments at a given galaxy luminosity, and the colour of the red population has a steeper slope with absolute luminosity. By employing the YEPS simple stellar population model, the colour offset corresponds to metallicity difference of $\Delta$[F e/H ] ~ 0.15 - 1.20 or an age difference of $\Delta$age ~ 2 Gyr on average, implying that GCs in field galaxies appear to be either less metal-rich or younger than those in cluster galaxies. Although we have found that galaxy environment has a subtle effect on the formation and metal enrichment of GC systems, host galaxy mass is the primary factor that determines the stellar populations of GCs and the galaxy itself.

• 정보처리학회논문지A
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• 제10A권4호
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• pp.389-396
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• 2003

인피니밴드(InfiniBand) 기술은 클러스터 컴퓨팅용 고성능 시스템 연결망으로의 활용을 목적으로 컴퓨터 업계를 중심으로 활발히 개발되고 있는 차세대 시스템 연결망 기술이다. 본 논문에서는 고성능 클러스터 시스템을 위한 인피니밴드 시스템 연결망의 설계와 구현을 다루며, 특히 이중(dual) ARM9 프로세서를 기반으로 한 인피니밴드 호스트 채널 어댑터(host channel adapter HCA) 개발에 초점을 맞추어 기술한다. KinCA라는 코드명이 부여된 HCA는 클러스터 시스템의 각 호스트 노드(host node)를 하드웨어 및 소프트웨어적으로 인피니밴드 연결망에 연결한다. ARM9 프로세서 코어는 다중 처리기 구성을 위해 필요한 기능을 지원하지 않으므로, 두 개의 프로세서간 통신 및 인터럽트 메커니즘을 설계하여 Kinch 칩에 내장하였다. 일종의 SoC인 KinCA 칩은 0.18$\mu\textrm{m}$ CMOS 기술을 사용하여 564핀 BGA(Ball Grid Array) 소자로 제작되었다. KinCA는 호스트 노드에 장착되어 송신과 수신 각각에 대하여 10Gbps의 고속 대역폭을 제공함으로써 고성능 클러스터 시스템의 구현을 가능하게 해준다.

• 천문학회보
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• 제41권2호
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• pp.59.1-59.1
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• 2016

Blue Straggler Stars(BSS) affect their host star cluster in various parameters like color, dynamics, etc. For this reason, it is important to know how to relate BSS frequency and evolution of their host stellar system. To statistical study about global properties of open clusters as the environments of BSS formation, we use three catalogues - (1) two galactic open clusters catalogues including BSS candidate, (2) Milky Way Star Cluster (MWSC) survey data. Then, we compare with the data of two BSS catalogues for test of the result of Marchi et al. 2006. We also investigate the radial mass distribution in open cluster, because it is possible that changing the gradient of radial mass distribution cause increasing the BSS frequency. When we group the open cluster into having BSS or not and other criteria, the groups show slight discrepancies, but we show some important results.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3477-3485
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• 2012

본 논문은 혁신클러스터 추진의 전략방향 설정을 위해서 클러스터 현황을 클러스터분석을 통하여 살펴보았다. 클러스터 분석은 클러스터 내에서 일어나는 다양한 형태의 협력을 파악하고 정책적인 대안의 도출을 위해 활용되는 실제적인 분석도구이다. 이에 본 논문에서는 광교테크노밸리의 발전단계에 따른 협력현황 분석을 위하여 산학연협력체계 분석과 진단을 위한 클러스터분석(Cluster Analysis)을 실시하였다. 클러스터 분석결과 광교테크노밸리내 입주기업의 산학연 협력경험은 67.3%로 매우 높은 것으로 나타났다. 대학과 기업과는 연구개발, 연구기관과는 장비활용 중심으로 협력하고 있었다. 또한, 산학연 협력의 지원정책수요는 협력기관 현황제공, 기술별 정보취득 지원 등 다양한 부문에서 협력의 수요가 존재하고 있었다. 이러한 분석결과를 토대로 혁신클러스터 구성단계를 넘어서 확장단계로 발전하기 위해서는 첫째, 혁신클러스터 발전을 위한 새로운 비전을 조속히 제시하고 단지인근에서 입주기업의 산학연협력의 활성화를 위한 지원을 추진해야 한다. 둘째, 혁신클러스터 단계별 발전을 위한 통합적인 지원역량 강화가 필요하다. 마지막으로 인근의 타 혁신거점과 정책적 네트워크 구축을 통해서 타 혁신클러스터의 자원과 역량을 활용할 수 있는 지원망 구축이 필요하다.

• 천문학회지
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• 제23권2호
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• pp.116-121
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• 1990

It has been suggested that there could be a large number of primordial black holes which were formed in the early universe. We analyze the growth of such a primordial black hole following two different accretion rates - the Eddington accretion rate and the Bondi accretion rate - at the center of a host star like the sun. We find that a primordial black hole with M < ${\sim}10^{17}\;g$ cannot substantially grow in any case throughout the lifetime of a host star. If M > ${\sim}10^{17}\;g$, the evolution of a host star depends entirely on the mode of accretion, but it ends as a black hole in either case. Since more stars may have primordial black holes at the center of a galaxy this may result in a cluster of such black holes, and the cluster may eventually collapse to produce a single supermassive black hole.

• 천문학회보
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• 제38권2호
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• pp.41.1-41.1
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• 2013

To test whether the close relationships between host and satellite galaxies in isolated groups are also found in the harsh environment of a galaxy cluster, we carry out a case study of WHL 085910.0+294957, a galaxy cluster at z=0.30, using deep images obtained with the 2.1-m Otto Struve telescope and CQUEAN CCD camera. When environmental parameters are controlled, the local weighted mean color of faint galaxies shows a measurable correlation with the color of their bright ($M_i$ < -18) neighbor. The most striking result is that the red (r - i > 0.2) and bright galaxies within 200 kpc distance from the center of the cluster are correlated in color with very faint ($M_i$ > -14) galaxies around them by $(r-i)_{satellites}=(7.276{\pm}1.402){\times}(r-i)_{host}-2.434$ (correlation coefficient = 0.665). We suggest three scenarios to interpret the results: vestiges of infallen groups, dwarf capturing, and tidal tearing of bright galaxies.