• 천문학회보
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• 제46권2호
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• pp.68.1-68.1
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• 2021

We study galaxy evolution with the large-scale environment with confirmed galaxy clusters from multi-object spectroscopy (MOS) observation. The observation was performed with Inamori Magellan Areal Camera and Spectrograph (IMACS) mounted on the 6.5 m Magellan/Baade telescope in Las Campanas Observatory. With the MOS observation, we spectroscopically confirm 34 galaxy clusters, including three galaxy clusters discovered in Kim et al. (2016) and 11 of them have halo mass of > 10^14.5 M_◉. Among the confirmed clusters, 12 galaxy clusters are part of large-scale structure at z ~ 0.9, and their size stretches to 40 Mpc co-moving scale. In this study, we checked the 'web feeding model,' which postulates that more linked (with their environment) galaxy clusters have less quenched populations by investigating the correlation between properties of confirmed galaxy clusters and the large-scale structure environment. Lastly, we found that galaxy clusters that make up the large-scale structure have larger and widely spread values of total star formation density (ΣSFR/M_halo) than typical clusters at similar redshifts.

• 한국경제지리학회지
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• 제23권1호
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• pp.35-55
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• 2020

소공인클러스터의 지원정책은 소공인클러스터의 지역적 특성을 반영해야 하지만, 유관기업의 통상적인 정보 수집을 기반으로 비슷한 정책만 내놓고 있다. 소공인클러스터의 지역적 특성이 파악이 안 되므로 지원정책에 반영이 되지 않고 있는 실정이다. 이에 본 연구는 소공인클러스터의 특성을 클러스터의 특징인 국지화, 네트워킹/착근성, 혁신시너지/집단학습의 형성요소로 분석하였으며, 분석된 형성요소를 기반으로 발달단계를 적용해 보았다. 같은 업종이어도 지역적 특성이 다를 수 있으므로, 서울시 의류봉제업의 대표적인 클러스터인 창신지역과 장위지역의 소공인클러스터를 지역적 특성과 발달단계로 비교 연구하였다. 의류봉제 소공인클러스터의 특성 분석 결과, 국지화에서 동종업체 집적은 창신지역이 장위지역보다 높게 나타났으며, 네트워킹/착근성에서 두 지역 모두 잘 형성되어 있었다. 하지만 혁신시너지/집단학습의 협업에서 창신지역은 디자이너 중심으로 장위지역은 소공인 중심으로 이루어져 있고, 박람회 및 세미나 참여와 샘플 및 제작에 있어 창신지역은 적극적인 반면 장위지역은 소극적으로 나타났다. 두 형성요소로 살펴본 결과, 두 지역의 소공인클러스터의 발달단계는 창신 의류봉제 소공인클러스터의 경우 산업지구를 넘어 혁신지구로 진행되고 있고, 장위 의류봉제 소공인클러스터는 산업지구에 머물러 있는 것으로 분석된다. 창신과 장위 의류봉제 소공인클러스터는 지속적인 성장을 위해서는 두 지역의 특성과 발달단계를 반영한 정부의 지원정책이 필요하다고 제언한다.

• 천문학회지
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• 제50권3호
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• pp.51-59
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• 2017

The presence of blue stragglers pose challenges to standard stellar evolution theory, in the sense that explaining their presence demands a complex interplay between stellar evolution and cluster dynamics. In the meantime, mass transfer in binary systems and stellar collisions are widely studied as a blue straggler formation channel. We explore properties of the Galactic open clusters where blue stragglers are found, in attempting to estimate the relative importance of these two favored processes, by comparing them with those resulting from open clusters in which blue stragglers are absent as of now. Unlike previous studies which require a sophisticated process in understanding the implication of the results, this approach is straightforward and has resulted in a supplementary supporting evidence for the current view on the blue straggler formation mechanism. Our main findings are as follows: (1) Open clusters in which blue stragglers are present have a broader distribution with respect to the Z-axis pointing towards the North Galactic Pole than those in which blue stragglers are absent. The probability that two distributions with respect to the Z-axis are drawn from the same distribution is 0.2%. (2) Average values of $log_10(t)$ of the clusters with blue stragglers and those without blue stragglers are $8.58{\pm}0.232$ and $7.52{\pm}0.285$, respectively. (3) The clusters with blue stragglers tend to be relatively redder than the others, and are distributed broader in colors. (4) The clusters with blue stragglers are likely brighter than those without blue stragglers. (5) Finally, blue stragglers seem to form in condensed clusters rather than simply dense clusters. Hence, we conclude that mass transfer in binaries seems to be a relatively important physical mechanism of the generation of blue stragglers in open clusters, provided they are sufficiently old.

• 말소리와 음성과학
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• 제4권4호
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• pp.3-17
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• 2012

This study examines Korean speakers' production of English consonant clusters, focusing on vowel insertion. An acoustic analysis along with a statistical test was carried out to see what factors are involved in this production. The following factors were considered in the present study: phonetic properties, L1 transfer, and cluster types. Specifically, liquid types were considered to see if they cause any difference depending on C+/l/ or C+/r/ clusters in the onset in terms of vowel insertion patterns. That is, it was examined which Korean speakers produce better, C+/l/ or C+/r/ clusters. Interestingly, the result of the present experiment shows that the correct answer percent was higher in the C+/r/ onset clusters than C+/l/ onset clusters unlike Eckman's (1977) Marked Differential Hypothesis. In other words, the occurrence of the vowel insertion in C+/l/ clusters is higher than C+/r/ onset clusters. This may be attributed to L1 transfer. Furthermore, in the present study, three patterns of vowel insertion in the C+/l/ clusters were identified by implementing an acoustic analysis based on vowel duration and formant: a) vowel insertion with gemination, b) phonological epenthesis, and c) phonetic intrusion. However, phonetic intrusion mainly occurred in the C+/r/ clusters. Data were collected from 54 Korean speakers to see what factors are involved in vowel insertion patterns in the production of English consonant clusters. This study provides evidence for L1 transfer, the duration effect of /l/ in a different context, and three kinds of vowel insertion patterns in conjunction with gestural coordination by age groups.

• 품질경영학회지
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• 제52권2호
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• pp.287-301
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• 2024

Purpose: This paper aims to verify the difference in production resilience between local clusters and regions without clusters before and after a major crisis. Furthermore, this paper aims to identify the clusters' quality factors that impact clusters' shock vulnerability and resilience. Methods: Utilizing open-source data from the US Cluster Mapping platform, this paper compares regions with industrial clusters to those without using the Differences-in-Differences (DID) estimator. It considers the regions with industrial clusters as a treatment group and others as the control group, comparing the period before and after the pandemic. Additionally, the paper examines which cluster factors make a difference in economic resilience during the crisis using Regression Discontinuity Design (RDD). Results: The study finds that regions with industrial clusters show higher production resilience compared to regions without clusters. Moreover, the number of establishments, annual payrolls, and employment can have a positive impact on resilience during the pandemic shock. Conclusion: Though clusters could be vulnerable during the global crisis, industrial clusters can contribute to regional economic development and production resilience in the long-term aspect. Thus, it is required to construct a high-quality local cluster and support it during the economic crisis in the long-term aspect.

• 천문학회지
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• 제43권1호
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• pp.1-8
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• 2010

JHK near-infrared photometry of star clusters in the dwarf irregular/dwarf starburst galaxy NGC 1569 are presented. After adopting several criteria to exclude other sources (foreground stars, background galaxies, etc.), 154 candidates of star clusters are identified in the near-infrared images of NGC 1569, which include very young star clusters. Especially, from analysis based on theoretical background, we found ten very young star clusters near the center of NGC 1569. The total reddening values toward these clusters are estimated to be $A_V$=1-9 mag from comparison with the theoretical estimates given by the Leitherer et al. (1999)'s star cluster model.

• 천문학회지
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• 제37권5호
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• pp.461-463
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• 2004

We investigate the role of secondary electrons in galaxy clusters and in ultra-luminous infrared galaxies (ULIGs). The radio emission in galaxy clusters and ULIGs is believed to be produced by the synchrotron radiation of relativistic electrons. Nonetheless, the sources of these relativistic electrons are still unclear. Relativistic secondary electrons can be produced from the hadronic interactions of cosmic-ray nuclei with the intra-cluster media (ICM) of galaxy clusters and the dense molecular clouds of ULIGs. We estimate the contribution of the secondary electrons in galaxy clusters and ULIGs by comparing observational results with theoretical calculations for the radio emission in these sources. We find that the radio halos of galaxy clusters can not be produced from the secondary electrons; on the other hand, at least for some ULIGs, the radio emission can be dominated by the synchrotron emission of the secondary electrons.

• 천문학회지
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• 제37권5호
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• pp.361-369
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• 2004

Galaxy clusters as the densest and most prominent regions within the large-scale structure can be used as well characterizable laboratories to study astrophysical processes on the largest scales. X-ray observations provide currently the best way to determine the physical properties of galaxy clusters and the environmental parameters that describe them as laboratories. We illustrate this use of galaxy clusters and the precision of our understanding of them as laboratory environments with several examples. Their application to determine the matter composition of the Universe shows good agreement with results from other methods and is therefore a good test of our understanding. We test the reliability of mass measurements and illustrate the use of X-ray diagnostics to study the dynamical state of clusters. We discuss further studies on turbulence in the cluster ICM, the interaction of central AGN with the radiatively cooling plasma in cluster cooling cores and the lessons learned from the ICM enrichment by heavy elements.

• 천문학회보
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• 제40권2호
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• pp.58.3-58.3
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• 2015

Blue Straggler Stars (BSSs), kind of unusual main sequence stars, are the brighter and bluer stars than the main sequence turn off (MSTS) stars in coeval clusters. Since the first detection in globular clusters (GCs), BSSs have been shown to reveal an anti-correlation between the luminosity of their host star cluster and the number of BSSs in the cluster. Further, conclusions based on this result can be expanded to the open clusters. BSSs seem to play an important role in GCs according to the relation between the dynamical time scale of GCs and the number of BSSs along the cluster radius. This relation, however, remains to be verified in open clusters, In this study, we divide open clusters by the existence of BSSs into two groups. Then we compare parameters between these groups to specify the role of BSSs in open clusters.

• Communications for Statistical Applications and Methods
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• 제12권1호
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• pp.207-216
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• 2005

A binary segmentation procedure is a simple recursive approach to detect clusters and provide inferences for the study space when the shape of the clusters and the number of clusters are unknown. The procedure involves a sequence of nested hypothesis tests of a single cluster versus a pair of distinct clusters. The size and the shape of the clusters evolve as the procedure proceeds. The procedure allows for various growth clusters and for arbitrary baseline densities which govern the form of the hypothesis tests. A real tree data is used to highlight the procedure.