• 산업공학
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• 제13권3호
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• pp.424-430
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• 2000

Supply chain management (SCM) is an area that has recently received a great deal of attention in the business community. While SCM is relatively new, the idea of coordinated planning is not. During the last decades, many researchers have investigated multi-stage inventory problems. However, only a few papers address the problem of cost-optimal coordination of multi-stage inventory control with respect to service measures. Even published approaches have a shortcoming in dealing with a delivery lead time consisted of a shipping time and a waiting time. Assumed that there is no waiting time, or that the delivery lead time is implicitly compounded of a shipping time and a waiting time, the problem is often simplified into a multi-stage buffer allocation and a single-stage stochastic buffer sizing problem at all installations. This paper presents a simulation-based heuristic algorithm and a comparison with others for the problem that cannot be decomposed into a multi-stage buffer allocation and a single-stage stochastic buffer sizing problem because the waiting time ties together all stages. The comparison shows that the simulation-based heuristic algorithm performs better than other approaches in saving average inventory cost for both Poisson and Normal demands.

• 한국정보과학회논문지:데이타베이스
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• 제41권4호
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• pp.217-225
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• 2014

트위터와 같은 소셜 네트워크 분석은 인간의 행동을 이해하거나, 화제가 되는 주제를 탐지하거나, 영향력 있는 사람을 식별하거나, 커뮤니티나 그룹을 발견하는데 흥미로운 시각을 제공할 수 있다. 하지만 소셜 네트워크가 가지는 특성(즉 데이터가 방대하고, 정교하지 않으며 또한 동적인 특성)으로 인하여 소셜 네트워크에서 주제와 연관이 있는 데이터를 수집하는 것은 어려운 일이다. 본 논문은 주어진 주제와 관련 있는 트윗을 효과적으로 수집하기 위하여 시드 노드를 동적으로 선택하는 알고리즘을 제안한다. 본 알고리즘은 사용자의 영향력을 측정하기 위하여 사용자 속성을 활용하며, 수집 프로세스 중에 시드 노드를 동적으로 할당한다. 우리는 제안한 알고리즘을 실제 트윗 데이터에 적용하였으며, 만족할 만한 성능결과를 얻었다.

• 정보관리연구
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• 제42권1호
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• pp.47-62
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• 2011

이상적 저자-망은 그 노드가 저자를 표현하도록 정의된다. 그러나 실제 자동 생성되는 대부분 저자망의 노드는 저자명을 저자 식별자로 사상시키는 어려움으로 인해 단순히 저자명으로 표현된다. 실 세계 저자를 표현하기 위해 이처럼 저자명을 사용하여 저자망을 구성하는 것은 서로 다른 동명 저자들이 하나의 저자명 노드로 병합됨으로 인해 저자망의 특성을 왜곡하는 문제가 발생한다. 이 연구는 공저 관계에 의존하여 저자명이 갖는 중의성을 해소하고 저자 노드로 구성된 저자망을 자동 생성하는 알고리즘을 제시한다. 공저자 자질의 특성상 이 알고리즘은 과소군집오류를 희생하면서 과다군집오류를 최소화하는 군집 결과를 만든다. 실험에서는 한글 동명 저자명이 출현한 실제 서지레코드 집합을 대상으로 알고리즘의 적용 결과를 제시한다.

• Journal of Information Processing Systems
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• 제13권4호
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• pp.987-999
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• 2017

Extraction of influential people from their respective domains has attained the attention of scholastic community during current epoch. This study introduces an innovative interaction strength metric for retrieval of the most influential users in the online social network. The interactive strength is measured by three factors, namely re-tweet strength, commencing intensity and mentioning density. In this article, we design a novel algorithm called IPRank that considers the communications from perspectives of followers and followees in order to mine and rank the most influential people based on proposed interaction strength metric. We conducted extensive experiments to evaluate the strength and rank of each user in the micro-blog network. The comparative analysis validates that IPRank discovered high ranked people in terms of interaction strength. While the prior algorithm placed some low influenced people at high rank. The proposed model uncovers influential people due to inclusion of a novel interaction strength metric that improves results significantly in contrast with prior algorithm.

• Journal of Information Processing Systems
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• 제1권1호
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• pp.14-21
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• 2005

Even though mainly statistical methods have been used in anomaly network intrusion detection, to detect various attack types, machine learning based anomaly detection was introduced. Machine learning based anomaly detection started from research applying traditional learning algorithms of artificial intelligence to intrusion detection. However, detection rates of these methods are not satisfactory. Especially, high false positive and repeated alarms about the same attack are problems. The main reason for this is that one packet is used as a basic learning unit. Most attacks consist of more than one packet. In addition, an attack does not lead to a consecutive packet stream. Therefore, with grouping of related packets, a new approach of group-based learning and detection is needed. This type of approach is similar to that of multiple-instance problems in the artificial intelligence community, which cannot clearly classify one instance, but classification of a group is possible. We suggest group generation algorithm grouping related packets, and a learning algorithm based on a unit of such group. To verify the usefulness of the suggested algorithm, 1998 DARPA data was used and the results show that our approach is quite useful.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.2976-2990
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• 2022

The adaptive adjustment of reference or weight vectors in decomposition-based methods has been a hot research topic in the evolutionary community over the past few years. Although various methods have been proposed regarding this issue, most of them aim to diversify solutions in the objective space to cover the true Pareto fronts as much as possible. Different from them, this paper proposes a knee point-based reference vector adaptive adjustment strategy to concurrently balance the convergence and diversity. To be specific, the knee point-based reference vector adaptive adjustment strategy firstly utilizes knee points to construct the adaptive reference vectors. After that, a new fitness function is defined mathematically. Then, this paper further designs a many-objective evolutionary algorithm with knee point-based reference vector adaptive adjustment strategy, where the mating operation and environmental selection are designed accordingly. The proposed method is extensively tested on the WFG test suite with 8, 10 and 12 objectives and MPDMP with state-of-the-art optimizers. Extensive experimental results demonstrate the superiority of the proposed method over state-of-the-art optimizers and the practicability of the proposed method in tackling practical many-objective optimization problems.

• Journal of the Korean Data and Information Science Society
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• 제26권4호
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• pp.827-839
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• 2015

학술지 인용 데이터베이스에서 네트워크 구조분석을 통해 학술지의 공동체를 추출하는 것은 인용관계에 따른 학술지의 집단을 파악하는 유용한 수단이다. 전 세계적으로 널리 활용되는 학술지 인용데이터베이스인 Thomson Reuters의 SCI나 Elsevier의 SCOPUS가 제공하는 자료를 활용하여 인용관계에 따른 공동체 구조를 파악하는 시도가 이루어진 바 있으나, 국내 학술지 인용 데이터베이스인 KCI에서는 이러한 연구가 현재까지는 이루어지지 않은 것으로 알려져 있다. 따라서 본 연구에서는 기존의 여러 가지 네트워크 군집화 알고리즘을 이용하여 KCI에 등재되어 있는 자연과학 분야 학술지를 대상으로 인용관계에 따른 공동체를 파악하고 KCI에 등록된 학술지 분류와 비교하여 보았다. 적용된 군집화 방법 중 인포맵 알고리즘에 의한 분류가 KCI 등재 자연과학 분야 학술지의 인용관계 구조를 잘 반영하며, 기존의 KCI 분류와 가장 유사한 것으로 나타났다. 본 연구를 통해 얻은 KCI의 기존 분류와 차이점들은 장차 KCI 학술지의 재분류가 이루어질 시 고려의 대상이 될 수도 있을 것이다.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.109-119
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• 2015

The interaction between wireless sensors such as Internet of Things (IoT) and Cloud is a new paradigm of communication virtualization to overcome resource and efficiency restriction. Cloud computing provides unlimited platform, resources, services and also covers almost every area of computing. On the other hand, Wireless Sensor Networks (WSN) has gained attention for their potential supports and attractive solutions such as IoT, environment monitoring, healthcare, military, critical infrastructure monitoring, home and industrial automation, transportation, business, etc. Besides, our virtual groups and social networks are in main role of information sharing. However, this sensor network lacks resource, storage capacity and computational power along with extensibility, fault-tolerance, reliability and openness. These data are not available to community groups or cloud environment for general purpose research or utilization yet. If we reduce the gap between real and virtual world by adding this WSN driven data to cloud environment and virtual communities, then it can gain a remarkable attention from all over, along with giving us the benefit in various sectors. We have proposed a Pub/Sub-based sensor virtualization framework Cloud environment. This integration provides resource, service, and storage with sensor driven data to the community. We have virtualized physical sensors as virtual sensors on cloud computing, while this middleware and virtual sensors are provisioned automatically to end users whenever they required. Our architecture provides service to end users without being concerned about its implementation details. Furthermore, we have proposed an efficient content-based event matching algorithm to analyze subscriptions and to publish proper contents in a cost-effective manner. We have evaluated our algorithm which shows better performance while comparing to that of previously proposed algorithms.

• Journal of Astronomy and Space Sciences
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• 제38권3호
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• pp.185-192
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• 2021

This technical paper deals the practical transformation algorithms between several lunar reference frames which will be used for Korea pathfinder lunar orbiter (KPLO) flight operation. Despite of various lunar reference frame definitions already exist, use of a common transformation algorithm while establishing lunar reference frame is very important for all members related to KPLO mission. This is because use of slight different parameters during frame transformation may result significant misleading while reprocessing data based on KPLO flight dynamics. Therefore, details of practical transformation algorithms for the KPLO mission specific lunar reference frames is presented with step by step implementation procedures. Examples of transformation results are also presented to support KPLO flight dynamics data user community which is expected to give practical guidelines while post processing the data as their needs. With this technical paper, common understandings of reference frames that will be used throughout not only the KPLO flight operation but also science data reprocessing can be established. It is expected to eliminate, or at least minimize, unnecessary confusion among all of the KPLO mission members including: Korea Aerospace Research Institute (KARI), National Aeronautics and Space Administration (NASA) as well as other organizations participating in KPLO payload development and operation, or further lunar science community world-wide who are interested in KPLO science data post processing.

• 한국정보과학회논문지:데이타베이스
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• 제37권6호
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• pp.343-350
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• 2010

질문(Question)과 답변(Answer)을 하는 커뮤니티 기반의 지식검색서비스에서는 질의를 통해 원하는 답변을 얻을 수 있지만, 수많은 사용자들이 참여함에 따라 방대한 문서 속에서 신뢰성있는 문서를 찾아내는 것은 점점 더 어려워지고 있다. 지식검색서비스에서 기존 연구는 사용자들이 생성한 데이터 즉 추천수, 조회수 등의 비텍스트 정보를 이용하거나 답변의 길이, 자료첨부, 연결어 등의 텍스트 정보 이용하여 문서의 품질을 평가하고, 이를 검색에 반영하여 검색성능을 향상시키는 데 활용했다. 그러나 비텍스트 정보는 질의/응답의 초기에 사용자들에 의해 충분한 정보를 확보할 수 없는 단점이 있으며, 텍스트 정보는 전체의 문서를 답변의 길이, 연결어등과 같은 일부요인으로 판단해야하기 때문에 품질평가의 한계가 있다고 볼 수 있다. 본 논문에서는 이러한 비텍스트 정보와 텍스트 정보의 문제점을 개선하기 위한 QualityRank 알고리즘을 제안한다. QualityRank는 텍스트/비텍스트 정보와 소셜 네트워크 분석 기반의 사용자 중앙성을 고려하여 질문에 적합하고 신뢰성 있는 답변을 랭킹화 한다 실험결과 제안한 알고리즘을 사용했을 경우 텍스트/비텍스트 모델 보다 랭킹성능에 있어 향상된 결과를 얻을 수 있었다.