• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권6호
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• pp.1728-1742
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• 2023

In this paper, we extended a hierarchical clustering technique, which is the most researched in the sensor network field, and studied a dynamic differential clustering technique to minimize energy consumption and ensure equal lifespan of all sensor nodes while considering the mobility of sinks. In a sensor network environment with mobile sinks, clusters close to the sinks tend to consume more forwarding energy. Therefore, clustering that considers forwarding energy consumption is desired. Since all clusters form a hierarchical tree, the number of levels of the tree must be considered based on the size of the cluster so that the cluster size is not growing abnormally, and the energy consumption is not concentrated within specific clusters. To verify that the proposed DDC protocol satisfies these requirements, a simulation using Matlab was performed. The FND (First Node Dead), LND (Last Node Dead), and residual energy characteristics of the proposed DDC protocol were compared with the popular clustering protocols such as LEACH and EEUC. As a result, it was shown that FND appears the latest and the point at which the dead node count increases is delayed in the DDC protocol. The proposed DDC protocol presents 66.3% improvement in FND and 13.8% improvement in LND compared to LEACH protocol. Furthermore, FND improved 79.9%, but LND declined 33.2% when compared to the EEUC. This verifies that the proposed DDC protocol can last for longer time with more number of surviving nodes.

• 원예과학기술지
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• 제29권4호
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• pp.382-387
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• 2011

The chemical composition of essential oils obtained from aerial parts in spearmint, apple mint and chocolate mint, was investigated by gas chromatography/mass spectrometry analyses. (-)-Carvone (33.0%) was quantitatively major compound in spearmint, followed by R-(+)-limonene (11.7%) and ${\beta}$-phellandrene (9.7%); (-)-carvone (37.4%) and germacrene D (11.9%) in apple mint; and (-)-menthol (34.3%), p-menthone (18.4%) and menthofuran (9.8%) in chocolate mint. Hierarchical cluster analysis and principle components analysis showed the clear difference in chemical composition of the three mint oils.

• 인터넷정보학회논문지
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• 제12권2호
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• pp.103-111
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• 2011

대규모 데이터에 대한 특성에 따라 몇 개의 클러스터로 군집화하는 클러스터링 기법은 계층적 클러스터링이나 분할 클러스터링 등 다양한 기법이 있는데 그 중에서 K-Means 알고리즘은 구현이 쉬우나 할당-재계산에 소요되는 시간이 증가하게 된다. 본 논문에서는 초기 클러스터 중심들 간의 거리가 최대가 되도록 하여 초기 클러스터 중심들이 고르게 분포되도록 함으로써 할당-재계산 횟수를 줄이고 전체 클러스터링 시간을 감소시키고자 한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제5권4호
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• pp.465-486
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• 2005

A unreliable network system results in unsatisfied performance. A performance criterion of a network is throughput and availability. One of the most compelling technological advances of this decade has been the advent of deploying wireless networks of heterogeneous smart sensor nodes for complex information gathering tasks, The advancement and popularization of wireless communication technologies make more efficiency to network devices with wireless technology than with wired technology. Recently, the research of wireless sensor network has been drawing much attentions. In this paper, We evaluate throughput and availability of wireless sensor network, which have hierarchical structure based on clustering and estimate the maximum hroughput, average throughput and availability of the network considering several link failure patterns likely to happen at a cluster consisted of sensor nodes. Also increasing a number of sensor nodes in a cluster, We analysis the average throughput and availability of the network.

• 전자공학회논문지A
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• 제30A권3호
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• pp.139-145
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• 1993

Partitioning is an important step in the hierarchical design of very large scale integrated circuits. In this research, a new effective partitioning algorithm based on 2-level hierarchy is presented. At the beginning, clusters are formed to reduce the problem size. To overcome the weakness of the iterative improvement techniques that the partitioning result is dependent on the initial partitioning and to consistently produce good results, the cluster-level partitioning is performed several times using several sets of parameters. Then the best result of cluster-partitioning is used as the initial solution for lower level partitioning. For each partitioning, the gradual constraint enforcing partitioning method has been used. The clustering-based partitioning algorithm has been applied to several benchmark examples and produced promising results which show that this algorithm is efficient and effective.

• Journal of Computing Science and Engineering
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• 제1권2호
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• pp.195-210
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• 2007

Dwarf is a highly compressed structure, which compresses the cube by eliminating the semantic redundancies while computing a data cube. Although it has high compression ratio, Dwarf is slower in querying and more difficult in updating due to its structure characteristics. We all know that the original intention of data cube is to speed up the query performance, so we propose two novel clustering methods for query optimization: the recursion clustering method which clusters the nodes in a recursive manner to speed up point queries and the hierarchical clustering method which clusters the nodes of the same dimension to speed up range queries. To facilitate the implementation, we design a partition strategy and a logical clustering mechanism. Experimental results show our methods can effectively improve the query performance on data cubes, and the recursion clustering method is suitable for both point queries and range queries.

• 응용통계연구
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• 제5권2호
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• pp.211-227
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• 1992

본논문은 지금까지 집락분석방법에서 많이 사용되는 유사도 또는 비유사도의 정의 및 이들의 수학적 성질을 알아보고, 또한 이들에 의해서 생성되는 비유사도 행렬을 이용하여 계층적 집락분석을 실시하였다. 이 경우에 가정된 초기의 집락 구조를 정확하게 잘 재생시킬 수 있는 비유사도의 측정방법과 계층적 응집법의 상호 관계를 질적자료와 양적자료 각각에 대하여 고찰하고, 이들에 관련된 시뮬레이션 결과를 제시하였다.

• 한국발생생물학회지:발생과생식
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• 제17권4호
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• pp.363-367
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• 2013

PCR analysis generated on the genetic data showed that the geographic hairtail (Trichiurus lepturus) population from Korea in the Yellow Sea was more or less separated from geographic hairtail population from China in the South Sea. The average bandsharing value ($mean{\pm}SD$) within hairtail population from Korea showed $0.859{\pm}0.031$, whereas $0.752{\pm}0.039$ within population from China. Also, bandsharing values between two hairtail populations ranged from 0.470 to 0.611, with an average of $0.542{\pm}0.059$. As compared separately, the bandsharing values of individuals within hairtail population from Korea were comparatively higher than those of individuals within population from China. The hierarchical dendrogram resulted from reliable oligonucleotides primers, indicating two genetic clusters composed of cluster 1 (KOREANHAIR1~KOREANHAIR11) and cluster 2 (CHINESEHAI12~CHINESEHAI22). The genetic distances between two geographic populations ranged from 0.038 to 0.476. Individual No. 11 within hairtail population from Korea was genetically closely related with No. 10 (genetic distance=0.038). The longest genetic distance (0.476) displaying significant molecular difference was also between individual No. 01 within hairtail population from Korea and No. 22 from Chinese. In the present study, PCR analysis has revealed significant genetic distances between two hairtail population pairs (P<0.05).

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2007-2015
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• 2005

A large-scale analysis to evaluate complex material and structural behaviors is one of interesting topic in diverse engineering and scientific fields. Also, the utilization of massively parallel processors has been a recent trend of high performance computing. The objective of this paper is to introduce a parallel process system which consists of general purpose finite element analysis solver as well as parallelized PC cluster. The later was constructed using eight processing elements and the former was developed adopting both hierarchical domain decomposition method and balancing domain decomposition method. Then, to verify the efficiency of the established system, it was applied for structural analysis of steam generator in nuclear power plant. Since the prototypal evaluation results agreed well to the corresponding reference solutions it is believed that, after reinforcement of PC cluster by increasing number of processing elements, the promising parallel process system can be utilized as a useful tool for advanced structural integrity evaluation.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권5호
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• pp.457-461
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• 2008

무선 애드 혹(ad hoc) 망에서 제안된 응용계층 기반 멀티캐스트 선행 연구는 크게 계층적 구조와 비계층적 라우팅 구조를 갖는 멀티캐스팅 기법으로 분류된다. 이들 제안된 기법들은 애드 흑 노드들의 이동성 변화를 실시간으로 멀티캐스트 라우팅 경로 갱신을 위해 반영하지 못한다. 그러므로, 에너지, 전송률, 시간지연 등 여러 가지 성능 저하의 원인이 된다. 이러한 문제점을 개선하기 위해, 이미 앞선 연구를 통해 암시적 클러스터 기반 멀티캐스트 기법을 제안하였다. 본 논문은 그의 특성을 분석하고 선행 연구된 응용 계층 기반 프로토콜들과 실험을 통한 성능을 검증하고자 한다.