• Journal of the Korean Data and Information Science Society
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• v.22 no.4
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• pp.741-753
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• 2011

We accomplish clustering analyses for yeast cell cycle microarray expression data. We compare model-based clustering, K-means, PAM, SOM and hierarchical Ward method with yeast data. As the validity measure for clustering results, connectivity, Dunn Index and silhouette values are computed and compared.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.193-199
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• 2010

In this paper, we propose a new metric to measure the dynamic connection states of Ad Hoc network. The new metric measures the total path break up time $\sum_{i}T_i$, where $T_i$ is the time period during which maximum cluster distance exceeds the radio range. $T_i$ can be calculated from the maximum cluster distance function of time, which can be computed from the node position samples of mobility model. The proposed metric can be used as a total system metric as well as an individual connection metric.

• The Korean Journal of Applied Statistics
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• v.24 no.6
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• pp.1077-1094
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• 2011

We accomplish clustering analyses for yeast cell cycle microarray expression data. To reflect the characteristics of a time-course data, we screen the genes using the test statistics with Fourier coefficients applying a FDR procedure. We compare the results done by model-based clustering, K-means, PAM, SOM, hierarchical Ward method and Fuzzy method with the yeast data. As the validity measure for clustering results, connectivity, Dunn index and silhouette values are computed and compared. A biological interpretation with GO analysis is also included.

• The Korean Journal of Financial Studies
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• v.14 no.1
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• pp.119-158
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• 2008

본 연구에서는 복합금융그룹의 부실위험을 그룹전체기반 측도로 측정하는 방법론을 비교하고 국내 복합금융그룹의 자료를 이용하여 실증분석한다. Joint Forum(2001a) 방법은 연결기준을 사용하여 그룹내 자본의 중복요소들을 상계한 후 필요자본 대비 자기자본비율을 구한다. 신BIS 규제자본 방법은 Vasicek(1987)의 점근적 단일위험 모형을 가정하여 자산의 전체기반 위험을 측정하고 연결기준을 사용하여 자본의 중복계상을 배제하여 측정한다. 개별 경제적 자본 방법은 개별 경제적 위험을 수준별로 합산하여 전체기반 경제적 자본을 빌딩블록 방식으로 합산한다. 경제적 자본 방법은 위험 측정시 겪게 되는 극단적 손실 문제와 결합분포의 비대칭성을 반영할 수 있는 방법을 측정시 포함시킬 수 있다. 국내 복합금융그룹의 자료를 이용하여 실증분석을 한 결과, 첫째, 개별 재무지표에서 복합금융그룹 소속회사들의 ROA, ROA 변동성 그리고 총자산 대비 자기자본비율이 우량한 것으로 나타났다. 특히 가장 비중이 큰 은행산업에서 위 개별 재무지표는 복합금융그룹 소속회사에서 우량하게 나타난다. 둘째, 그룹전체기반 위험자본 측도로서 필요자본 대비 자기자본 비율과 연결기준 BIS비율을 살펴본 결과 은행계열 금융그룹의 부실위험이 낮은 것으로 판단된다. 전체적으로 국내 복합금융그룹의 부실위험은 높지 않은 것으로 판단된다. 이상의 결과를 바탕으로 복합금융그룹에 대한 리스크상시감시방안에의 시사점을 살펴보면, 첫째, 복합금융그룹 소속 금융회사에 대한 리스크 평가시 그룹전체기반 부실위험평가를 반영하여 이를 측정할 필요가 있다. 둘째, 권역별로 통일된 리스크감시를 위해 권역별 자기자본규제의 형평성을 제고할 필요가 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.201-208
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• 2010

Mobile Ad Hoc Network(MANET) has highly dynamic topology, hence presents a great challenge on the network performance evaluation and network protocol design. We proposed total path break up time, $\sum_{i}T_i$, as a metric to measure the performance of the total system as well as an individual connection. In this paper, we evaluate and analyze the performance of three mobility models(Random Waypoint, Manhattan, Blocked Manhattan) by applying the total path break up metric, investigate why network parameters such as packet delivery ratio, end-to-end delay, etc. vary by mobility models. We also present analysis result how much AODV Buffer improve packet delivery ratio and increase the end-to-end delay in spite of the path break up.

• The Korean Journal of Applied Statistics
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• v.22 no.4
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• pp.745-758
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• 2009

Cluster analysis is the automated search for groups of related observations in a data set. To group the observations into clusters many techniques has been proposed, and a variety measures aimed at validating the results of a cluster analysis have been suggested. In this paper, we compare complete linkage, Ward's method, K-means and model-based clustering and compute validity measures such as connectivity, Dunn Index and silhouette with simulated data from multivariate distributions. We also select a clustering algorithm and determine the number of clusters of Korean consumers based on Korean consumers' palatability scores for Hanwoo bull in BBQ cooking method.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.77-80
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• 2011

그래프는 전산학의 주요 주제 중 하나이며 World Wide Web과 Social Network의 중요성이 커지면서 더욱 주목을 받고 있다. 그래프와 관련하여 그래프 데이터베이스에 대한 질의 모델에 관한 연구도 중요하게 다투어져 왔다. 하지만 이들 연구는 패턴 매칭을 통한 질의를 주로 다루었다. 하지만 그래프 데이터를 추천이나 검색 등의 응용하기 위해서는 PageRank 등 그래프 내의 연결 구조를 양으로 분석해내는 작업이 요구된다. 또한 SimRank 및 Random Walk with Restart 등 다양한 양적 분석 측도가 제안되고 있다. 이에 따라 본 연구에서는 Random Walk를 기반으로 하는 그래프에 대한 유연한 양적 분석을 지원하는 질의 언어를 제시한다. 또한 기존의 양적 분석 측도들이 본 질의 모델을 통하여 어떻게 표현되는지를 통하여 본 질의 모델의 유용성 및 확장성을 보인다.

• Journal of Educational Research in Mathematics
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• v.27 no.4
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• pp.833-855
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• 2017

This study aims to reinvestigate the reason for introducing radian as a new unit to express the size of angles, what is the meaning of radian measures to use arc lengths as angle measures, and why is the domain of trigonometric functions expanded to real numbers for expressing general angles. For this purpose, it was conducted historical, mathematical and applied mathematical analyzes in order to research at multidisciplinary analysis of the radian concept. As a result, the following were revealed. First, radian measure is intrinsic essence in angle measure. The radian is itself, and theoretical absolute unit. The radian makes trigonometric functions as real functions. Second, radians should be aware of invariance through covariance of ratios and proportions in concentric circles. The orthogonality between cosine and sine gives a crucial inevitability to the radian. It should be aware that radian is the simplest standards for measuring the length of arcs by the length of radius. It can find the connection with sexadecimal method using the division strategy. Third, I revealed the necessity by distinction between angle and angle measure. It needs justification for omission of radians and multiplication relationship strategy between arc and radius. The didactical suggestions derived by these can reveal the usefulness and value of the radian concept and can contribute to the substantive teaching of radian measure.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.137-146
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• 2006

Because the traditional public key-based cryptosystems are unsuitable for the sensor node with limited computational and communication capability, a secure communication between two neighbor sensor nodes becomes an important challenging research in sensor network security. Therefore several session key establishment protocols have been proposed for that purpose. In this paper, we analyzed and compared the existing session key establishment protocols based on the criterions of generation strategy and uniqueness of the session key, connectivity, overhead of communication and computation, and vulnerability to attacks. Based on the analysis results, we specify the requirements for the secure and efficient protocols for establishing session keys. Then, we propose an advanced protocol to satisfy the specified requirements and verify the superiority of our protocol over the existing protocols through the detailed analysis.

• Journal of Educational Research in Mathematics
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• v.22 no.3
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• pp.429-444
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• 2012

As one of the trials for a systematic approach to mathematics terms which occupies an important place in teaching and learning mathematics, compositions of listed terms in 2011 elementary mathematics curriculum in Korea are discussed in this study. To this end, listed terms are classified in view of three points and looked for their characteristics, from which implications are found out for elementary mathematics teaching and learning First of all classifications into grade-group and domain-specific terms, then into newly coined terms and terms from everyday life, and then into korean terms and chinese character terms and english terms are attempted. Next, terms with a kernel and terms without a kernel are distinguished, and in this process, term-sets are presented. Finally, object terms, operation terms, relationship terms, measure terms, conditions terms, graphics terms, name terms are classified. Based on these results, the following implications for elementary mathematics teaching and learning are suggested. First, it should be considered that many of the listed terms in 2011 curriculum are newly coined and chinese character terms. Second, the interconnections between terms should be considered. Third, a variety of roles and functions of the terms should be considered.