• Journal of KIISE:Computing Practices and Letters
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• v.9 no.3
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• pp.254-265
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• 2003

This paper presents the design and implementation of stream control mechanisms which are necessary for the development of an efficient streaming cache server. The streaming protocols used in our implementation are the RTSP/RTP/RTCP standards. The mechanisms support both the on-demand media caching and real-time media splitting applications. The core of the stream control includes the session management, which handles the RTSP/RTCP control session and the RTP transport session, and the cache block management which efficiently manages the RTP-based cache blocks stored in the cache server. The streaming cache server with the proposed stream control mechanism has successfully been implemented on a Linux platform and it works well with the Apple's QTSS server and the QuickTime player for both on-demand and splitting media services.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.10
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• pp.59-68
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• 2013

This paper proposes the boost type bidirectional DC/DC converter with high efficiency for electric vehicle using an interleave method. This interleave method can reduce the system size because it reduces the ripple of output voltage and input current with no add to extra filter. Proposed system is consist of two converters and applies to interleaved method through phase shift to each converter. And it implements the high boost through voltage double and series construction of output port. Also, it reduces the price and increases the efficiency as operating the ZCS by leakage inductance of transformer and capacitor of voltage double with not add special reactor. Proposed DC/DC converter using interleave method is proved the validity through the result of PSIM simulation and experiment of 5kW DC/DC converter.

• Journal of Internet Computing and Services
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• v.2 no.1
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• pp.77-85
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• 2001

CORBA is a middleware which enables distributed objects to cooperate regardless of specific platforms and techniques. But the ordinary CORBA communication model does not support multi-cast, and needs delay time, because it synchronously connects the distributed objects between client and server. To solve these problems, OMG suggests CORBA Event Service which can provide multi-cast among application objects. This paper presents a new technique for improving reliability, and supporting two-way communication by laying two interface objects on each consumers and suppliers that are registered in event channel. Also, to integrate objects efficiently, we, group distributed event channels and management it as view, A coordinator selected from channel group controls group and view.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.100-106
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• 2013

AMI enables bi-directional exchange of information between utilities and consumers in order to maximize energy efficiency. To enable the AMI, it is essentially required to construct stable communication networks. This paper shows the AMI system based on IEEE 802.11s as one of the communication methods. Experimental results show that the wireless mesh network technology achieves a stable communication performance over a wide coverage.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.312-323
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• 2017

This paper introduces the bidirectional dc-dc converter design case study, which employs silicon-carbide (SiC) MOSFETs for battery energy storage system (BESS). This converter topology is selected as bidirectional synchronous buck converter, which is composed of a half bridge converter, an inductor, and a capacitor, where the converter has less conduction loss than that of a unidirectional buck and boost converter, and to improve the converter efficiency, both the power stage design and power conversion architecture are described in detail. The conduction and switching losses are compared among three different SiC devices in this paper. In addition, the thermal analysis using Maxwell software of each switching device supports the loss analyses, in which both the 2 kW prototype analyses and experimental results show very good agreement.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2004.11a
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• pp.147-150
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• 2004

기존의 방송환경은 시청자에게 단 방향의 서비스를 제공하며, 시청자 각자의 취향에 상관없이 소극적인 자세를 요구한다. 이러한 일방적인 사용자 시청환경에서는 대개의 프로그램들은 방송사에 의해 다수 사용자의 대표적인 시간대에 적절하게 배치되고, 적절하게 배분된 프로그램의 인기도 혹은 시청률, 시청 연령, 시간대에 따른 광고가 그 프로그램을 지원하게 된다. 시청자의 적극적 선별 노력에 의해 선택된 프로그램과 달리 방송 프로그램 콘텐츠와 같이 전송되는 광고는 사용자가 원하는 대개의 프로그램을 지원하는 중요한 수단이지만, 정작 시청자의 관심과는 상관없이 제공된다. 또한, 디지털 방송의 시작과 함께 양방향 서비스 환경에서도 사용자를 고려한 광고의 적절한 분배가 이루어지지 않고 있다. 이러한 일률적인 광고 콘텐츠의 제공은 시청자의 무관심을 초래할 수 있으며, 이러한 경향이 높을수록 효율적인 정보 제공에 많은 제한을 받을 수 있다. 본 논문에서는, 제한적 정보 제공의 해소와 새로운 시청 환경 제안을 위한, 시청자의 성별 및 연령 대를 추론하는 알고리즘을 제안하고 이를 맞춤형 광고, 즉 표적 광고 서비스(Target Advertisement Service) 기법을 제안한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.19-26
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• 2016

In this study, a bidirectional DC-DC converter for idle stop and go (ISG) is developed to reduce fuel consumption. A three-phase non-isolated half-bridge converter is selected through a design method by considering efficiency and volume. According to the state of charge of the batteries at both the low-voltage and high-voltage sides, buck mode, which charges a low-voltage battery from the generated motor energy, and boost mode, which provides power to the motor from the low- and high-voltage battery sides, are required in the ISG system. Hence, an autonomous and seamless bidirectional control method using a variable current limiter is proposed for mode change. A 1.8 kW engineering sample of the proposed converter has been built and tested to verify the validity of the proposed concept. The maximum efficiencies, including gate driver and control circuit losses, are 96.4% in charging mode and 96.1% in discharging mode.

• The Journal of Korean Association of Computer Education
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• v.5 no.1
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• pp.45-55
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• 2002

So far, there were a few web-based distance English learning systems for children. The existing systems for children have not appropriately reflected their learning characteristics and interests, since most of those systems regards mainly adults as targets. This thesis is aimed at proposing more effective educational service modules of web-based real-time system in order to encourage children's interests as much as possible in learning English. The web-based real-time distance learning system is a model based on the survey over the current use and satisfaction status of elementary school students who have actually used those kinds of systems. With the great expectation of more effective way of learning English, it also focuses on attracting parents to participate the learning process by providing a service to look over, in real-time, what their children do through the internet-based English learning system.

• The Journal of Korean Association of Computer Education
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• v.14 no.5
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• pp.29-37
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• 2011

This paper reports on a design and implementation of a Smartphone App providing the SCAMPER method. The SCAMPER method is an efficient method of creativity, which is a way of encouraging uniqueness, promoting change in things, and evoking or triggering new or varied possibilities. The Smartphone users analyzed the effectiveness and shortcomings of the Smartphone App. The results showed that the developed Smartphone App is effective in terms of the value, use, content, and component. The Smartphone App is also efficient to use anywhere, anytime and to express, share, actively communicate with others through the App. In addition, several improvements of the App were suggested for Smartphone users to develope and enhance their creativity by adopting the SCAMPER method.

• Information and Communications Magazine
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• v.30 no.2
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• pp.51-58
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• 2013

글로벌 기후변화 및 에너지 고갈 문제가 전(全) 지구적 이슈로 부각됨에 따라 다양한 그린 에너지기술에 대한 연구가 활발하게 진행되고 있고, 기존 주력 기술분야와 정보통신기술과의 융합을 통한 새로운 기술개발이 활발하게 추진되고 있다. 스마트그리드 기술은 이러한 패러다임에서 탄생한 기술 분야이며, 녹색 기술의 대표적인 기술 사례로 분류되고 있다. 스마트그리드에 대한 개념이 국내에 도입된 이후 기술 개발 성과 실증과 비즈니스 모델을 발굴하고자 시작되었던 제주 스마트그리드 실증단지 구축 사업도 금년 5월을 기점으로 완료될 예정이다. 스마트그리드 실증단지 구축을 통해 소비자 도메인에서의 다양한 에너지관리 솔루션 구축 방법에 대하여 확인할 수 있는 기회도 되었으나 표준화 기반의 상호운용성이 확보되지 않아 컨소시엄 간의 시스템 연동이 어려운 문제도 확인할 수 있었다. 스마트그리드는 보다 강건하고 신뢰성 있는 전력시스템의 현대화 및 지능화를 위하여 ICT(Information and Communication Technology) 기술을 활용하는 것이 필요하며, 전력공급자와 소비자 사이의 양방향 전력 및 정보의 실시간 교환 특성을 활용하여 에너지를 효율적으로 사용하도록 하는 시스템의 도입이 무엇보다 중요하다. 2011년 9/15 순환정전 사태는 전력공급 정책과 더불어 전력 소비자에 대한 관리 기능도 함께 검토되어야 한다는 것을 다시 한 번 크게 인식할 수 있는 계기가 되었다. 본 고에서는 이러한 중요성을 가지는 소비자 분야를 중심으로 한 스마트그리드 ICT 기술에 대하여 일부 주요 사항을 발췌하여 정리해 보고자 한다. 이를 위하여 스마트그리드의 전체적인 현황, 소비자 도메인에서의 스마트그리드 요소기술 및 ICT 기술의 핵심이 되는 소비자 도메인에서 사용되는 통신 기술을 중심으로 소비자 도메인 ICT 기술에 대하여 정리해 보고자 한다.