• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.83-89
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• 2022

As a representative technique of recommender systems, collaborative filtering has been successfully in service through many commercial and academic systems. This technique recommends items highly rated by similar neighbor users, based on similarity of ratings on common items rated by two users. Recently research on time-aware recommender systems has been conducted, which attempts to improve system performance by reflecting user rating time of items. However, the decay rate uniform to past ratings has a risk of lowering the rating prediction performance of the system. This study proposes a rating time-aware similarity measure between users, which is a novel approach different from previous ones. The proposed approach considers changes of similarity value over time, not item rating time. In order to evaluate performance of the proposed method, experiments using various parameter values and types of time change functions are conducted, resulting in improving prediction accuracy of existing traditional similarity measures significantly.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.5 no.3 s.11
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• pp.29-39
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• 2006

In this paper, we propose an efficient method to detect the signal and evaluate performance of the system in frequency selective fading channel. We combine proposed system with OFDM (Orthogonal Frequency Division Multiplexing) to improve performance of the system. First, we study the SOSTTC-OFDM system using two transmit antenna and one receive antenna, and compare performance of the proposed space-time coded OFDM with that of previous system. We expand this system to the system using four transmit antennas with the proposed decoding method. Simulation results show that the proposed decoding method can detect the signal efficiently, and we identify that the performance of the proposed system is shown with varying doppler frequency in frequency selective fading channel.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.2
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• pp.176-184
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• 1999

지금까지의 소프트웨어 기반 분산 공유 메모리(이하 DSM이라 칭함)시스템은 유닉스 워크스테이션 클러스터를 목표로 하는 것이 대부분이었다. 그러나 현재 Windows-NT 는 서버급 시스템과 PC 모두를 위한 운영체제로서 유닉스와 더불어 널리 사용되고 있는 실정이다. 본 논문에서는 Windows-NT 워크스테이션 클러스터 환경을 위한 DSM 시스템을 구현하고, 구현된 DSM 시스템의 성능 평가 결과를 제시한다. 구현된 DSM 시스템은 Win32 API와 표준 실행-시간 라이브러리를 이용해 구현되었기 때문에 모든 Windows-NT 워크스테이션에서 실행 가능하며 , 프로그래머는 몇 라인의 코드 추가만으로 DSM 시스템 상에서 수행되는 병렬 응용 프로그램을 작성할 수 있다. 워크스테이션 간의 상호연결망으로 범용성을 위해 이더넷 LAN을 지원하였고, 아울러 성능 향상을 위해 기가비트 SAN(System Area Network)도 지원하였다. 기가비트 SAN을 위한 하드웨어로는 Dolphin 사의 PCI-SCI 타입 제품인 Clustar를 사용하였다. 우리는 성능 평가를 통해, 구현된 DSM 시스템이 정확히 동작함은 물론 확장성이 뛰어나다는 것을 확인하였다. 특히 , 기가비트 SAN을 사용할 경우 일부 병렬 벤치 마크 프로그램에서는 노드 수 증가에 따라 성능이 거의 선형적으로 향상된다는 것을 알 수 있었다. 본 논문이 기여하는 바는 Windows-NT 기반 소프트웨어 DSM 시스템의 원천 기술을 확보함으로써 향후 Windows-NT 워크스테이션 클러스터 환경에서의 분산 및 병렬 처리 연구에 도움을 줄 수 있다는 점이다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.838-839
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• 2008

실제 가정 및 공장에서 많이 사용되고 있는 저압 차단기는 안전성 및 성능의 신뢰성이 가장 중요한 제품이다. 이와 같은 저압 차단기의 성능평가를 위해서는 반드시 단락성능에 대한 검증이 이루어져야 한다. 단락성능을 검증하기 위한 단락시험설비의 측정시스템은 시험 신뢰도의 확보를 위해 주기적으로 교정하여야 하며, 그 결과를 저압 차단기의 성능평가 시에 적용해야 한다. 본 논문에서는 여러 가지 기기로 구성된 전압 측정시스템에서 각각의 계측기를 개별적으로 교정하지 않고, 전체 측정시스템을 하나의 기기로 간주하고 교정을 실시하는 방법을 통하여 전체 측정시스템에 대한 신뢰도를 확보하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.311-313
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• 1999

Xmas-SX는 지능형 교통 시스템, 이동통신과 같은 새로운 공간 응용 분야의 고성능 데이터베이스 요구를 만족시키기 위한 주메모리 공간 저장 시스템이다. 본 논문에서는 Xmas-SX의 성능을, 디스크 기반 객체지향 DBMS와의 비교를 통하여 평가한다. 갱신 연산과 공간 영역 질의를 대상으로 하였으며, 그 결과 Xmas-SX가 갱신 연산의 경우 최고 수십 배 좋은 성능을 보였다. 공간 영역 질의의 경우에는 약간 좋은 성능을 보였다. 이를 통해 Xmas-SX가 공간 데이터베이스에 대한 갱신 연산이 빈번한 응용분야에 적용가능함을 보였다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.2
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• pp.103-114
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• 2013

The Korea Atomic Energy Research Institute has developed a performance assessment model implementing the A-KRS concept, which was constructed with the GoldSim. In the A-KRS concept, spent nuclear fuel produced from pressurized-water-reactor operations would be pyroprocessed to reduce waste volume and radioactivity. The wastes to be disposed of in a geologic repository are comprised of metal and ceramic waste forms. In this study, results of simulations conducted to establish credibility and build confidence for the A-KRS model are presented. Specifically, release rates and breakthrough times simulated using the A-KRS model were compared to corresponding results from the U.S. NRC SOAR model. In addition, the A-KRS model results were compared to published release rates from the SKB repository performance assessment. This comparison of the A-KRS model results to other independent performance assessments is expected to form part of a suite of model verification and validation activities to provide confidence that the A-KRS model has been implemented appropriately.

• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.184-185
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• 2010

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.41-53
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• 2004

This study introduces the process of the field test of ETCS that has been performed by six enterprises for selecting the type of ETCS that will be applied to the internal tall roads. The main communication modes of six enterprises are active RF(radio wave)type and IR(optical wave)type. In this study, communication modes and systems, which are being used by each enterprises, have been compared and analyzed. Besides this, the configuration and the basic performances of the system have been checked. After those, the contents of the field performance test classified by the items of the test and the results of the test, finally, have been analyzed. Through analyzing the test, it is found that an enterprise using IR type and two enterprises using RF type satisfied the standards of the test and the others failed to meet the standards. However, the enterprises seem to be becoming stable by a large number of tests and the effort for improving from general point of view. Although the methods of performance evaluation in this field test considered enough patterns that are used in the present highway or Hi-Pass, there might possibly be some problems in the results because Korea Highway Corporation had decided the method and the number of times of the test according to their own standards about the various situations that can happen. Therefore, it will be needed to develop the method of standards for testing the performance which can be correspond with driver's behavior that can actually happen on the highway or the methods of transportation management.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.568-580
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• 1997

In this paper we evaluate the performances of two types of 16-QAM system such as square QAM and star QAM. First we analyze the performances of QAM systems under AWGN(adaptive white Gaussian noise) and afterward analyze the performances under fading environments. The performances of QAM systems in case of using the PSAM(Pilot Symbol Assisted Modulation) are finally evaluated under fading environments. In conclusion, the Square QAM's performance is better than star QAM in AWGN. But the performances of the both QAM systems are very poor under the fading environments. QAM performance using the PSAM system is verified to be improved in that case, and the star QAM's performance is better than square QAM.

• Journal of Korean Society of Archives and Records Management
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• v.13 no.3
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• pp.67-97
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• 2013

The purpose of this study is to design and evaluate an individual instance-based ontology retrieval system for archival records of the "Saemaul Movement". We used Protege editor 4.1 to design an individual instance-based ontology. To evaluate the proposed ontology retrieval system, five short queries and ten narrative queries were used and compared their precision and recall against the NARA keyword-based retrieval system. The performance results showed that the individual-based ontology retrieval system outperformed the keyword-based retrieval system in terms of the measurement of precision and recall.