• 천문학회보
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• 제40권2호
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• pp.30.3-31
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• 2015

We present a kinematic analysis of 172 likely member galaxies of the Ursa Major Cluster. In order to understand the dynamical state of the cluster, we investigate the correlation of the cluster morphology with rotation, the velocity dispersion profile, and the rotation amplitude parallel to the global rotation direction. Both the minor axis and the rotation are very well-aligned with the global rotation axis in the outer region at half radius (> 0.5 $R_{max}$), but not in the inner region. The cluster exhibits low velocity dispersion and rotation amplitude profiles in the inner region, but higher in the outer. Both profiles exhibit outwardly increasing trends, suggesting an inside-out transfer of angular momentum of dark matter via violent relaxation, as revealed by a recent off-axis major-merging simulation. From Dressler-Schectman plots in the plane of galactic positions, and velocity versus position angle of galaxy, we are able to divide the Ursa Major Cluster into two substructures: Ursa Major South (UMS) and Ursa Major North (UMN). We derive a mass of $3.2{\times}10^{14}M_{\odot}$ for the cluster through the two-body analysis by the timing argument with the distance information (37 for UMN and 36 for UMS) and the spin parameter of ${\lambda}=0.049$. The two substructures appear to have passed each other 4.4 Gyr ago and are moving away to the maximum separation.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.309-314
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• 2002

The ablation dynamics and cluster formation of $C_n^+$ ions ejected from 355 nm laser ablation of a graphite target in vacuum are investigated using a reflectron time-of-flight (RTOF) mass spectrometer. At low laser fluence, odd-numbered cluster ions with $3{\leq}n{\leq}15$ are predominantly produced. Increasing the laser fluence shifts the maximum size distribution towards small cluster ions, implying the fragmentation of larger clusters within the hot plume. The temporal evolution of $C_n^+$ ions was measured by varying the delay time of the ion extraction pulse with respect to the laser irradiation, providing significant information on the characteristics of the ablated plume. Above a laser fluence of $0.2J/cm^2$ , large cluster ions ($n{\geq}30$) are produced at relatively long delay times, indicating that atoms or small carbon clusters aggregate during plume propagation. The dependence of the intensity of ablated $C_n^+$ ions on delay time after laser irradiation shows that the most probable velocity of each cluster ion decreases with cluster size.

• 농촌계획
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• 제11권4호
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• pp.33-45
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• 2005

This study investigates the core elements of the formation and development of cluster using a multi-disciplinary approach and suggests a promoting strategy by development stage of cluster. As a sub-category of regional innovation system, the cluster has been considered as one of the most noticeable methodological argument to make the regional innovation system come true. In the meantime, this study examines the core elements of cluster shown in the theories and examples through six academic fields such as economics, geography, regional development, business administration, sociology and pedagogy and their educational back-ground. By means of establishing the incubation stage in the development of cluster, core elements are composed in the stages of birth, incubation and evolution in subsequent manner. A promoting strategy will be suggested through the implication of core elements in the reestablished stages.

• 천문학논총
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• 제19권1호
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• pp.77-81
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• 2004

A high performance computing cluster for astronomical computations has been built at Korea Astronomy Observatory. The 64 node cluster interconnected with Gigabit Ethernet is composed of 128 Intel Xeon processors, 160 GB memory, 6 TB global storage space, and an LTO (Linear Tape-Open) tape library. The cluster was installed and has been managed with the Open Source Cluster Application Resource (OSCAR) framework. Its performance for parallel computations was measured with a three-dimensional hydrodynamic code and showed quite a good scalability as the number of computational cells increases. The cluster has already been utilized for several computational research projects, some of which resulted in a few publications, even though its full operation time is less than one year. As a major resource of the $K^*Grid$ testbed, the cluster has been used for Grid computations, too.

• 천문학회지
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• 제40권4호
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• pp.153-155
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• 2007

We have analyzed H and $K_s$-band images of the Arches cluster obtained using the NIRC2 instrument on Keck with the laser guide star adaptive optics (LGS AO) system. With the help of the LGS AO system, we were able to obtain the deepest ever photometry for this cluster and its neighborhood, and derive the background-subtracted present-day mass function (PDMF) down to $1.3M_{\bigodot}$ for the 5"-9" annulus of the cluster. We find that the previously reported turnover at $6M_{\bigodot}$ is simply due to a local bump in the mass function (MF), and that the MF continues to increase down to our 50 % completeness limit ($1.3M_{\bigodot}$) with a power-law exponent of ${\Gamma}$ = -0.91 for the mass range of 1.3 < M/$M_{\bigodot}$ < 50. Our numerical calculations for the evolution of the Arches cluster show that the ${\Gamma}$ values for our annulus increase by 0.1-0.2 during the lifetime of the cluster, and thus suggest that the Arches cluster initially had ${\Gamma}$ of $-1.0{\sim}-1.1$, which is only slightly shallower than the Salpeter value.

• 천문학회보
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• 제35권2호
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• pp.41.2-41.2
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• 2010

We present ultraviolet (UV) properties of dwarf galaxies in the Ursa Major cluster comparing with those in the Virgo cluster. We have constructed SDSS DR7/GALEX GR5 matched optical/UV catalog for dwarf galaxies with various morphologies in these two clusters. Membership of galaxies belonging to the Ursa Major cluster was made by hierarchical grouping method using SDSS spectroscopic data. We classified morphologies of dwarf galaxies using the combination of visual inspection of the images and spectral features returned from SDSS data. In contrast to the case of the Virgo cluster, majority of dwarf galaxies in the Ursa Major cluster lies in the blue cloud of the UV color-magnitude relations (CMRs) implying strong recent or on-going star formation. We discuss the cluster environment on the star formation history and evolution of dwarf galaxies.

• 천문학회보
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• 제37권2호
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• pp.70.1-70.1
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• 2012

We investigate 53 late-type galaxies in Virgo to get better understanding galaxy evolution driven by environmental effects in the cluster. The goal is to study how galaxies are strongly affected gravitationally by their surroundings and/or how interstellar medium (ISM) of galaxies changes through the interaction with intracluster medium (ICM). To quantify these, a variety of diagnostic methods have been introduced. Our diagnostics have two different perspectives. First, we have carefully examined the morphological and kinematical properties of individual galaxies using high resolution HI images and compared with multi-wavelength data. Based on the visual inspection, we have identified signatures of the interactions with other galaxies or the ICM. Second, we have quantified influence of local environments of individual galaxies using X-ray data and optical catalog of the cluster. By combining all the diagnostics, we have identified the environmental effect(s) at work on individual galaxies. We also probe the environmental processes as a function of the cluster centric distance. Various gravitational interactions are found throughout the cluster, while the ICM-ISM interaction is mainly dominant near the cluster center. However, we find some evidence that galaxies start losing their gas already in the low density outskirts of the cluster.

• 한국경제지리학회지
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• 제21권4호
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• pp.303-320
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• 2018

본 연구는 클러스터 적응주기 모델에 기반하여 구미국가산업단지의 진화 과정의 특성과 그 내 외적 동인을 분석하였다. 구미국가산업단지는 공간적 산업적 영역의 확대를 통해 비약적인 발전을 거듭하면서 우리나라 대표적인 IT산업 클러스터로서의 위상을 차지하고 있다. 그러나 1990년대 이후의 성장기, 2000년대 중반 이후의 성숙기 그리고 2010년대 중반부터의 성숙정체기로 진화한 이후 쇠퇴기로 들어서고 있다. 이는 기반구축기에서 성장기를 거쳐 성숙기로 진화하기까지 구미국가산업단지에 크게 영향을 미쳤던 국제적 국가적 수준의 외적 동인이 아닌, 대기업의 역외 유출, 중소기업의 미흡한 연구역량 그리고 획기적인 제도적 기반의 미흡과 같은 내적 동인이 중소기업들의 경영상 어려움을 가중시켰기 때문이다. 따라서 외부 충격에 대한 회복력 강화를 통해 구미국가산업단지가 재활성화기로 진화하도록 하기 위해서는 무엇보다 국가적 차원에서 영세 소기업의 역량강화에 초점을 두고 중앙정부 및 지자체, 그리고 지원기관의 역할을 보다 확대할 필요가 있다. 또한 지역경제를 이끌어 갈 중견기업을 집중적으로 육성시켜 이를 지역에 성공적으로 뿌리내리게 하여 구미국가산업단지가 지속가능한 혁신 생태계로 거듭날 수 있도록 해야 할 것이다.

• 한국경제지리학회지
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• 제10권1호
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• pp.1-18
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• 2007

본 연구에서는 개방경제체제로 전환되는 과정에서 울산이 가질 수 있는 시스템 전환의 가능성에 기초해서 울산 자동차클러스터의 발전방향을 탐색하고 바람직한 전략적 개입의 방향을 제시하고자 했다. 울산의 자동차 클러스터의 조건을 탐색하기 위해 생산 및 연구개발 네트워크의 글로벌 차원, 국가 차원, 지역 차원의 공간적 특성에 대하여 분석하였다. 그리고 현대자동차가 울산공장을 설립하면서 시작된 울산의 자동차 산업의 집적과정의 특징과 그 동안 축적한 역량에 대한 분석에 기초해서 대안적 발전경로를 탐색하고 정책적 시사점을 도출하였다.

• 천문학회보
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• 제40권1호
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• pp.80.3-81
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• 2015

Globular clusters (GCs) are known to have a very small amount of or no dark matter (DM). Several studies propose that GCs may have formed in individual dark halos. Thus, some of the current GCs might have a non-negligible DM content. Using the Fokker-Planck (FP) calculations, we investigate the dynamical evolution of the Galactic GCs residing in mini DM halo. We trace the initial amount of DM of 47 Tuc, NGC 1851, and M15, which is a 'disk/bulge' cluster, an 'old halo' cluster, and a 'young halo' cluster, respectively. We find that the three GCs have initially insignificant amounts of DM, less than 20 percent of the initial stellar mass of the each cluster.