• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2009년도 춘계 종합학술대회 논문집
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• pp.792-796
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• 2009

데이터 클러스터링 분야에서 최적의 클러스터 개수를 추정하는 것은 매우 중요한 일이다. 그것은 클러스터링의 적합성을 판단할 기준을 정하고 그 적합성을 극대화 하는 최적의 클러스터의 개수를 찾는 것이다. 본 논문에서는 클러스터의 적합성을 판단할 기준으로써 클러스터링 균형을 사용하여 최적의 클러스터 개수를 찾기 위한 효율적인 휴리스틱 방법을 제안하였다. k-means 사용하여 가상 및 실제 데이터 셋에 적용한 결과, 제안한 알고리즘이 계산효율 측면에서 우수함을 확인할 수 있었다.

• 한국산업정보학회논문지
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• 제16권4호
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• pp.119-125
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• 2011

The part family (PF) formation in a cellular manufacturing has been a key issue for the successful implementation of Group Technology (GT). Basically, a part has two different attributes; i.e., design and manufacturing. The respective similarity in both attributes is often conflicting each other. However, the two attributes should be taken into account appropriately in order for the PF to maximize the benefits of the GT implementation. This paper proposes a clustering algorithm which considers the two attributes simultaneously based on pareto optimal theory. The similarity in each attribute can be represented as two individual objective functions. Then, the resulting two objective functions are properly combined into a pareto fitness function which assigns a single fitness value to each solution based on the two objective functions. A GA is used to find the pareto optimal set of solutions based on the fitness function. A set of hypothetical parts are grouped using the proposed system. The results show that the proposed system is very promising in clustering with multiple objectives.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2008년도 추계 공동 국제학술대회
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• pp.507-511
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• 2008

Supporting energy efficiency and load balancing in wireless sensor network is the most important issue in devising the hierarchical routing protocols. Recently, the dual layered clustering scheme with GPS was proposed for the supporting of load balancing for cluster heads but there would be many collided messages in the overlapped area between two layers. Thereby, the purpose of this paper is to reduce the collision rate in the overlapped layer by concisely distinguish them with the same number of nodes in them. For the layer partition, this paper uses an equation $x^2+ y^2{\le}(\frac{R}{\sqrt{2\pi}})^2$ to distinguish layers. By using it, the scheme could efficiently distinguish two layers and gets the balanced number of elements in them. Therefore, the proposed routing scheme could prolong the overall network life cycle about 10% compared to the previous two layered clustering scheme.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
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• pp.427-429
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• 2005

Energy efficiency is the most challenging issue in wireless sensor network to prolong the life time of the network, as the sensors has to be unattended. Cluster based communication can reduce the traffic on the network and gives the opportunity to other sensors for periodic sleep and thus save energy. Passive clustering (PC) can perform a significant role to minimize the network load as it is less computational and light weight. First declaration wins method of PC without any priority generates severe collision in the network and forms the clusters very dense with large amount of overlapping region. We have proposed several modifications for the existing passive clustering algorithm to prolong the life time of the network with better cluster formation.

• 산업경영시스템학회지
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• 제36권1호
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• pp.64-69
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• 2013

In ubiquitous computing, shared environments adjust themselves so that all users in the environments are satisfied as possible. Inevitably, some of users sacrifice their satisfactions while the shared environments maximize the sum of all users' satisfactions. In our previous work, we have proposed social welfare functions to avoid a situation which some users in the system face the worst setting of environments. In this work, we consider a more direct approach which is a preference based clustering to handle this issue. In this approach, first, we categorize all users into several subgroups in which users have similar tastes to environmental parameters based on their preference information. Second, we assign the subgroups into different time or space of the shared environments. Finally, each shared environments can be adjusted to maximize satisfactions of each subgroup and consequently the optimal of overall system can be achieved. We demonstrate the effectiveness of our approach with a numerical analysis.

• 천문학회보
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• 제43권2호
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• pp.40.3-40.3
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• 2018

This dissertation presents the results on two-dimensional Redshift space distortion (hereafter RSD) analyses of the large-scale structure of the universe using spectroscopic data and on improvement of modeling of the RSD effect. RSD is an effect caused by galaxies' peculiar velocity on their clustering feature in observation along the line of sight and is thus intimately connected to the growth rate of the structure in the universe, from which we can test the origin of cosmic acceleration and Einstein's theory of gravity at cosmic scales in the end. However, there are several challenges in modeling precise and accurate RSD effect, such as non-linearities and the existence of an exotic component, e.g. massive neutrino. As part of endeavors for modeling more precise and accurate galaxy clustering in redshift space, this dissertation includes a series of works for this issue. (More detailed descriptions were omitted.)

• Journal of information and communication convergence engineering
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• 제22권1호
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• pp.1-6
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• 2024

Energy efficiency in wireless sensor networks (WSNs) is a critical issue because batteries are used for operation and communication. In terms of scalability, energy efficiency, data integration, and resilience, WSN-cluster-based routing algorithms often outperform routing algorithms without clustering. Low-energy adaptive clustering hierarchy (LEACH) is a cluster-based routing protocol with a high transmission efficiency to the base station. In this paper, we propose an energy consumption model for LEACH and compare it with the existing LEACH, advanced LEACH (ALEACH), and power-efficient gathering in sensor information systems (PEGASIS) algorithms in terms of network lifetime. The energy consumption model comprises energy-sensitive cluster formation and a cluster head selection technique. The setup and steady-state phases of the proposed model are discussed based on the cluster head selection. The simulation results demonstrated that a low-energy-consumption network was introduced, modeled, and validated for LEACH.

• 디지털콘텐츠학회 논문지
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• 제9권2호
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• pp.251-260
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• 2008

인터넷의 전자상거래에서 대규모 정보 저장소에 있는 원하는 정보를 신속하게 검색하기란 어렵다. 대부분의 전자상거래 사이트에 있어서 정보를 제공하는 방법으로는 통계적 분석이나 분류별 지향의 간단한 과정을 통해 생성된다. 그러나 이러한 것은 생성 정보들 사이의 다양한 상호관계를 표현할 수 없고 사용자의 정확한 구매 패턴을 반영하기 어렵다. 본 논문에서는 전자상거래에서 효과적인 클러스터링을 이용한 다양한 관심정보 추출을 위한 효율적인 웹 마이닝을 제안한다. 이러한 방법은 분류별 항목에서 순차 패턴과 상관 규칙을 이용하여 생성 정보들 사이의 보다 적합한 상관관계를 구성하고 제안된 방법을 통해 효율적인 실험 결과를 나타낸다. 그리고 효과적인 클러스터링을 이용하여 신속한 검색을 제안한다.

• Journal of information and communication convergence engineering
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• 제7권4호
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• pp.475-479
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• 2009

In ad hoc network, the scarce energy management of the mobile devices has become a critical issue in order to extend the network lifetime. Current research activity for the Minimum Energy Multicast (MEM) problem has been focused on devising efficient centralized greedy algorithms for static ad hoc networks. In this paper, we consider mobile ad hoc networks(MANETs) that could provide the reliable monitoring and control of a variety of environments for remote place. Mobility of MANET would require the topology change frequently compared with a static network. To improve the routing protocol in MANET, energy efficient routing protocol would be required as well as considering the mobility would be needed. In this paper, we propose a new method, the CACH(Context-aware Clustering Hierarchy) algorithm, a hybrid and clustering-based protocol that could analyze the link cost from a source node to a destination node. The proposed analysis could help in defining the optimum depth of hierarchy architecture CACH utilize. The proposed CACH could use localized condition to enable adaptation and robustness for dynamic network topology protocol and this provide that our hierarchy to be resilient. As a result, our simulation results would show that CACH could find energy efficient depth of hierarchy of a cluster.

• 한국인터넷방송통신학회논문지
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• 제14권1호
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• pp.253-258
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• 2014

스마트폰에 탑재된 센서들을 사용하여 사회 조직에서 발생하는 다양한 현상들을 모니터링하는 스마트폰 센싱 분야에서 대규모 데이터 처리 및 품질 향상과 수집된 정보를 공유하기 위해 시멘틱 데이터를 관리하는 것은 중요한 이슈 중에 하나이다. 본 논문에서는 이러한 대규모 시멘틱 데이터 관리 구조에서 서버의 부하를 줄이기 위한 문서 클러스터링 기법을 제안한다. 제안된 클러스터링 기법은 헤드 노드와 멤버노드를 갖는 하이브리드 백엔드 구조에서 서버단의 부하 감소를 위해 유사한 메타데이터를 갖는 노드들로 클러스터를 구성한다. 시뮬레이션을 통해 제안 기법이 기존의 거리기반 클러스터링 기법에 비해 서버부하를 줄일 수 있다는 것을 검증 하였다.