• 천문학회보
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• 제37권1호
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• pp.49.1-49.1
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• 2012

Recently it is found that the globular clusters are not only bound in their host galaxies, but also are wandering between galaxies in Virgo and Coma clusters. The cluster-wide distribution of these intracluster globular clusters (IGCs) suggests that IGCs are an important probe to understand hierarchical structure formation. We present a survey of IGCs in Virgo cluster using HST archive images for four HST/ACS fields located from about 9 arcmin to 40 acrmin from the cluster center. We find ten new IGCs and confirm four previously known IGCs. The number density of IGCs decreases as the distance from the cluster center increases. We derive integrated photometry of IGCs. We also obtain photometry of resolved stars in the outer region of each cluster. These IGCs are fainter than $M_V{\approx}-9.5$ and mostly blue in (V-I) color. showing that they are mostly metal poor. The locations of red giant branch stars of IGCs in color-magnitude diagrams also show that they are meal-poor. We discuss the implications of these results.

• Asian Journal of Business Environment
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• 제7권1호
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• pp.25-29
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• 2017

Purpose - In this paper, we categorize and segment the 28 national universities in South Korea and measure the degree of dissimilarity (or similarity) between pairs of ones by using dissimilarity distance matrix and cluster analysis, respectively, based on the seven quantitative evaluation of educational conditions (percentage of small-scale courses, percentage of lecture by the faculty, collection of books per student, material purchase per student, percentage of building capacity, percentage of real estate capacity and rate of accommodation) in 2015. In addition, multidimensional scaling (MDS) techniques can obtain visual representation for exploring patterns of proximities among 28 national universities based on seven attributes of educational conditions. Research design, data, and methodology - This work is carried out by the 2015 Announcement of University Information, which is provided by Ministry of Education in South Korea and utilized by multivariate analyses with CLUSTER, PROXIMITIES and ALSCAL modules in IBM SPSS 23.0. Results - We make certain that 28 national universities can be categorized into five clusters which have similar traits by applying two-stage cluster analysis. MDS is utilized to perform positioning of grouped places of cluster and 28 national universities joining every cluster. Conclusions - Both types and traits of each national university can be relatively assessed and practically utilized for each university competitiveness based on underlying results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1133-1151
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• 2010

Energy balanced consumption routing is based on assumption that the nodes consume energy both in transmitting and receiving. Lopsided energy consumption is an intrinsic problem in low-cost sensor networks characterized by multihop routing and in many traffic overhead pattern networks, and this irregular energy dissipation can significantly reduce network lifetime. In this paper, we study the problem of maximizing network lifetime through balancing energy consumption for uniformly deployed low-cost sensor networks. We formulate the energy consumption balancing problem as an optimal balancing data transmitting problem by combining the ideas of corona cluster based network division and optimized transmitting state routing strategy together with data transmission. We propose a localized cluster based routing scheme that guarantees balanced energy consumption among clusters within each corona. We develop a new energy cluster based routing protocol called "OECR". We design an offline centralized algorithm with time complexity O (log n) (n is the number of clusters) to solve the transmitting data distribution problem aimed at energy balancing consumption among nodes in different cluster. An approach for computing the optimal number of clusters to maximize the network lifetime is also presented. Based on the mathematical model, an optimized energy cluster routing (OECR) is designed and the solution for extending OEDR to low-cost sensor networks is also presented. Simulation results demonstrate that the proposed routing scheme significantly outperforms conventional energy routing schemes in terms of network lifetime.

• 한국콘텐츠학회논문지
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• 제19권7호
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• pp.360-375
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• 2019

본 연구는 2015년도 5만 여개의 기업거래정보(KED(한국기업정보))를 이용하여, 유통업체와 관련이 있는, 지속적인 거래관계를 가진 기업들의 거래관계 네트워크를 형성하여 유통업체의 생태계를 파악하고자 하였다. 클러스터링의 방법을 사용한 결과, 5개 이상의 기업들로 이루어진 731개의 클러스터로 묶여진다. 이들은 KED 자료에서 파악되는 유통산업 매출의 약 80%룰 차지한다. 클러스터들은 소속된 업체들의 거래가 대부분 내부에서 완결되는 모듈화된 거래 패턴을 가진다. 유통 클러스터들은 그들 매출의 70% 이상을 하나 또는 2, 3개의 업체(주기업)가 차지하고 있다. 이러한 특징은 제조업과 유사하다. 그렇지만 유통 클러스터들은 소속 기업수가 제조업과 비교하여 작은 특징을 지니고 있으며 조립 제조업체들에 비해서는 특정 업체와 클러스터에 매출이 집중된 정도도 약하다. 기업연관분석의 결과를 보면, 30대 유통업체들이 소속된 클러스터내의 중소기업들의 주기업에 대한 매출의존도는 롯데쇼핑, 이마트, 이랜드리테일, 신세계, 현대홈쇼핑 등이 최소 35% 이상의 값을 보인다. 이들 클러스터 내에서의 공정거래정책을 통한 중소기업 육성정책의 여지가 크다는 점을 암시한다. 씨제이홈쇼핑, 현대홈쇼핑, 한무쇼핑 등은 아주 높은 생산유발효과를 가지며, 앞의 두 업체는 동일 클러스터 소속 중소기업들에 특히 높은 생산유발효과를 가지고 있다. 그리고 1-9번 클러스터들은 중소기업의 고용 비중이 높고 중소기업의 고용계수가 매우 높은 10번 기업군과 31번 기업군에서 상품을 조달하는 경우가 많다. 중소기업에 높은 생산 및 고용 유발효과를 가지고 있거나, 10, 31번 기업군에 후방연관효과가 높은 기업들은 중소기업 성장 및 고용 정책에서 중시되어야 할 것이다.

• Journal of the Korean Data and Information Science Society
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• 제19권2호
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• pp.451-461
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• 2008

In this study, factor and cluster analysis have been conducted to group the differences in Korean view on national economic policy in the sample of the 2006 Korean General Social Survey (KGSS). According to the 2006 KGSS, the 6 items with a 5-point Likert scale include the questions about whether or the extent to which each respondent supports the specific types of governmental economic policy. In our study, at first, the factor analysis has converted the original 6 items into the 3 composite variables that account for 81% in the total variability. As the second step of factor analysis, factor scores have been computed. Then, the K-means cluster analysis based on the factor scores has been conducted to group the survey respondents into the 3 clusters. In particular, the cross-tabulation analysis has shown that the distribution of the 3 clusters varies with the respondents' socio-demographic characteristics.

• 산업공학
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• 제25권1호
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• pp.127-133
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• 2012

This paper considers the preventive maintenance scheduling problem of the cluster tool which is one of the most important manufacturing equipments in the next-generation semiconductor production environment. We define a random process that expresses the successive amount of chemicals accumulating inside the tool. Based on the renewal theory, we find the expected value and probability distribution of the time that the amount of accumulated chemicals exceeds a predetermined level. For a given probability that the accumulated chemicals exceeds the predetermined level we present a method to obtain the number of chamber operations to perform the preventive maintenance of that chamber. In addition, a method to get the preventive maintenance schedule for the whole cluster tool is presented. A numerical example is provided to illustrate our method.

• 천문학회보
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• 제40권2호
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• pp.41.2-41.2
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• 2015

We have performed deep wide-field CCD photometry of the young open cluster IC 1805 in the famous star forming region W4, and obtained photometric data for more than 91,000 stars in the field of IC 1805 based on observations with the 3.6m CFHT and the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The photometric data cover an area $43^{\prime}{\times}45^{\prime}$ which is far larger and far deeper than any other optical observations made for the cluster. In order to select the young stellar objects with mid-IR excess emission, we have performed mid-IR photometry of the cluster using the archival images obtained with the Spitzer Space Telescope IRAC and MIPS instruments. From a preliminary analysis of the data, we determined the reddening law ($R_V=3.02{\pm}0.05$), distance modulus ($V_0-M_V=11.9{\pm}0.2$), and the spatial distribution of members.

• 한국음향학회지
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• 제14권1호
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• pp.5-12
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• 1995

Training 벡터 집합이 Cluster를 이루는 경우, 벡터 양자화에서 영상과 음성의 압축에 사용되는 코드북의 코드벡터는 Cluster의 중심벡터로 간주된다. 본 연구에서는 Training 벡터 간의 Euclidean 거리가 최소가 되는 벡터를 찾는 과정에서 얻어지는 Euclidean 거리분포를 관찰하여 적절한 Cluster수와 그 중심벡터를 결정할 수 있는 방법을 제시하고, 제안된 방법이 기존의 LBG 알고리즘이나 Competitive 학습 알고리즘에 의한 영상 압축보다 약 4[dB] 이상 향상된 SNR을 얻을 수 있음을 보인다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.511-518
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• 2015

As the cost-per-byte of SSDs dramatically decreases, the introduction of SSDs to Hadoop becomes an attractive choice for high performance data processing. In this paper the cost-per-performance of SSD-based Hadoop cluster (SSD-Hadoop) and HDD-based Hadoop cluster (HDD-Hadoop) are evaluated. For this, we propose a MapReduce performance model using queuing network to simulate the execution time of MapReduce job with varying cluster size. To achieve an accurate model, the execution time distribution of MapReduce job is carefully profiled. The developed model can precisely predict the execution time of MapReduce jobs with less than 7% difference for most cases. It is also found that SSD-Hadoop is 20% more cost efficient than HDD-Hadoop because SSD-Hadoop needs a smaller number of nodes than HDD-Hadoop to achieve a comparable performance, according to the results of simulation with varying the number of cluster nodes.

• 천문학회지
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• 제29권spc1호
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• pp.55-56
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• 1996

In order to investigate the spatial orientation of the spin vectors of galaxies in the Virgo cluster, we carried out a detailed identification of all the certain and possible member disk galaxies with four UK Schmidt Telescope (UKST) III a-j direct plates digitized by the Automated Plate Measuring System (APM). As a result, a relatively large and complete database with no selection effect of the member galaxies has been established. We provide the APM measured values of the position angle (P.A.) and diameters at the isophotal level of 24.5 $m_j / arcsec^2$. Based on this newly generated database, an initial study on the spatial orientation of the spin vectors of galaxies in the Virgo cluster is shown.