• 한국통신학회논문지
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• 제34권1C호
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• pp.1-8
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• 2009

Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

• 전력전자학회논문지
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• 제16권5호
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• pp.415-429
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• 2011

본 연구에서는 출력이 직렬 연결된 단상 quasi Z-소스 AC-AC 컨버터를 제안하였다. 제안된 시스템은 단상quasi Z-소스 AC-AC 컨버터 2대의 입력 단을 병렬로 연결하고 출력 단을 직렬로 연결한 구조로 되어 있으며, 역상 모드와 동상 모드 별 전류 흐름과 출력전압의 형성 과정을 나타내었다. DSP로 제어되는 실험 시스템을 제작하여 PSIM시뮬레이션 결과와 비교 분석하였다. 그 결과 각 모드별로 듀티 비를 제어하여 원하는 출력 전압을 벅-부스트 할 수 있었다. 컨버터 1대가 단독으로 운전한 경우에 비하여, 각각의 모드에 대하여 부하 저항의 증가에 따른컨버터 효율과 입력 역률을 제안된 방법에 의하여 개선할 수 있었다. 또한 역상 모드의 경우, 일정 부하에서 컨버터의 효율과 입력 역률을 각각 10[%]와 35[%]정도 개선하였으며, 특히 부하 저항이 변동하는 과도상태에서도 일정한 출력 전압을 유지할 수 있었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2002년도 춘계학술대회논문집
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• pp.1-11
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• 2002

As the competition among the ports is extreme, the purpose of this study which intendsto keep sustainable competitive advantage in Busan Container Terminals through the quality management of port service is shown as the followings. First, the common factor of quality management activities In the part of domestic container port is to be analysed. secondly, the efforts for enhancing the standard of quality management is to be confirmed lastly the relationship of cause-effect among the source of quality management, quality management activities and quality management is to be clarified. An empirical study was carried out to examine how Busan Container Terminals view quality management activities by the provision of statistical evidence showing the efforts to enhance the standard of quality management, common factors of quality management activities and causal relationship among these factors. The data investigating the quality management for Busan Container Terminals were collected from 170 persons in charge of quality management for port services in Busan Container Terminals the use of questionnaire method and personal interviews. The Cronbach's $\alpha$ coefficient and factor analysis were used to analyze the reliability and the propriety of measured variables. Furthermore SEM method using AMOS 4.0 was used to analyze the cause-effect relationship among the source. activities and accomplishments of quality management representing the core concept of quality management system. The importance of this study is placed in the description of the theoretical and general system on the quality management when the domestic container terminals have activated to promote the quality management, and in suggesting the actual problem and settlement method which are directly helpful to the field, and It can be indicated as having its meaning on future research obect.

• Journal of Communications and Networks
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• 제12권6호
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• pp.577-581
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• 2010

We introduce a novel packet retransmission technique which improves the efficiency of automatic retransmission query (ARQ) protocols in the context of satellite broadcast/multicast systems. The proposed coded ARQ technique, similarly to fountain coding, performs transmission of redundant packets, which are made by linear combinations of the packets composing the source block. Differently from fountain codes, the packets for the linear combinations are selected on the basis of the retransmission requests coming from the user terminals. The selection is performed in a way that, at the terminals, the source packets can be recovered iteratively by means of simple back-substitutions. This work aims at providing a simple and efficient alternative to reliable multicast protocols based on erasure correction coding techniques.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.81-82
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• 2006

Most work on cooperative diversity has assumed that the cooperating group (source and partners) and the associated average channel conditions between terminals (source, partners, and destination) are predetermined. In practical situations, however, it is important to develop the efficient algorithms for assigning the terminals with good inter-user channels for cooperating groups. In this paper, we propose the partner assignment algorithm for cooperative diversity in mobile communication systems. The proposed partner assignment algorithm is investigated by using the path loss model for mobile communication systems. Numerical results show that the proposed partner assignment algorithm provides the comparable probability of cooperative transmission to the partner assignment algorithm using exhaustive search. The probability of cooperative transmission increases with the number of users, which gives potential benefits of practical implementation to user cooperation in mobile communication systems.

• 한국화재소방학회논문지
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• 제17권4호
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• pp.13-19
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• 2003

본 논문은 누전차단기 외함 전원측 단자사이에서 발생하는 전기화재 원인에 대한 분석을 연구하였다. 누전차단기는 보호범위의 전기시설물에서 누전 또는 과부하에 의한 차단을 목적으로 한다 누전차단기의 전원측 단자는 트래킹에 의해 화재로 쉽게 이어질 수 있다. 따라서, 누전차단기의 재현실험을 통해 트래킹시료($E_1$)와 화재현장에서 트래킹된 것($S_1$)을 비교분석하여 전기화재의 원인을 밝히는데 중요한 자료가 되도록 하였다. 실험은 IEC Publ. 112법을 응용하여 실시하였고 누전차단기에서 미소방전과 건조대가 발생한 후 소손되는 것을 확인하였다. $_1$에서 전원측 단자간의 절연저항은 약 25.7Ω이고 $S_1$의 절연저항은 약 58.6Ω이었다. $E_1$의 발열피크는 $491.0^{\circ}C$와 $603.2^{\circ}C$였다. $603.2^{\circ}C$에서의 발열피크는 트래킹에 의한 것이다. $S_1$의 발열피크는 $593.1^{\circ}C$에서 나타났다. 트래킹에 의해 변화된 시료는 IR 흡수스펙트럼에서 $1590 cm^{-1}$ 에서 흡광피크가 나타나지 않았다.

• 한국정보통신학회논문지
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• 제6권5호
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• pp.755-761
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• 2002

인터넷이 등장하기 전에는 대부분의 응용 프로그램이 표준입출력 장치로 호스트 컴퓨터에 연결된 단말기를 사용하며 수행되었다. 오늘날은 인터넷의 사용이 보편화되었고 많은 서비스가 인터넷에 연결된 웹 브라우저 상에서 제공된다. 단말기를 통한 표준입출력 방식과 웹 브라우저를 통한 통신 입출력 방식은 기술적으로 다르기 때문에 과거에 작성된 단말기용 응용 프로그램을 쉽게 인터넷을 통하여 웹 브라우저 상에서는 수행시킬 수는 없다. 본 논문은 표준입출력 방식으로 작성된 프로그램의 소스를 수정하지 않고 다시 컴파일만 하여 인터넷에 연결된 웹 브라우저 상에서도 서비스할 수 있게 해주는 웹 입출력 (WEBIO) 라이브러리의 개발에 대하여 기술한다. 현재 C 및 Prolog 언어 용 웹 입출력 라이브러리가 개발되어 시험 중이다.

• 한국염색가공학회지
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• 제30권2호
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• pp.130-140
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• 2018

In the bio-synthesis of poly(3-hydroxybutyrate)(PHB), which is a kind of poly(3-hydroxyalkanoate)(PHA), aimed to control the low molecular weight of PHB and obtain a telechelic PHB. As a result of incubation of R. eutropha at $30^{\circ}C$ with ethylene glycol added as a chain transfer agent, PHB content on the dry cell weight increased up to 24h, however, it decreased after that, and the molecular weight of PHB increased from 9h to 12h, and then, decreased up to 72h. The decrease of the content and the molecular weight of PHB indicates that PHB was decomposed as an energy source in bacterial cells and was incorporated into metabolic pathways. $^1H-NMR$ of the obtained PHB after incubation for 72h was measured to determine the terminal groups of the PHB during incubation. As the results of $^1H-NMR$ measurement, the peaks derived from ethylene glycol in both terminals of PHB were observed. Which indicate that the terminal reaction was caused by the addition of ethylene glycol, and that telechelic PHB having hydroxyl group at the both terminals where molecular weight was controlled was successfully synthesized.

• 전기학회논문지
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• 제61권2호
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• pp.199-208
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• 2012

This paper proposes a quasi Z-source DVR(Dynamic Voltage Restorer) system with a series connection of the output terminals, to compensate the voltage variations in the 6.6[kV]/60[Hz] power distribution system. The conventional DVR using one quasi Z-source AC-AC converter has the advantage which it can compensate the voltage variations without the need for the additional energy storage device such as a battery, but it is impossible to compensate for the 50[%] under voltage sags. To solve this problem, a DVR system using two quasi Z-source AC-AC converters with the series connection of the output terminals is proposed. By controlling the duty ratio D in the buck-boost mode, the proposed system can control the compensation voltage. For case verification of the proposed system, PSIM simulation is achieved. As a result, in case that the voltage sags-swells occur 10[%], 20[%], 60[%] in power distribution system, and, in case that the 50[%] under voltage sags-swells continuously occur, all case could compensate by the proposed system. Especially, the compensated voltage THD was examined under the condition of the 10[%]~50[%] voltage sags and the 20[${\Omega}$]~100[${\Omega}$] load changes. The compensated voltage THD was worse for the higher load resistances and more severe voltage sags. Finally, In case of the voltage swells compensation, the compensation factor has approached nearly 1 regardless of the load resistance changes, while the compensation factor of voltage sags was related to the load variations.

• 한국정보통신학회논문지
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• 제8권4호
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• pp.815-820
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• 2004

본 논문에서는 고압 대전력 3상 유도전동기의 고정자 권선을 이용한 전압원 인버터의 병렬운전 방식을 제안한다. 현재 사용되고 있는 대부분의 4극 이상 대전력 유도전동기는 각 상의 권선이 외부에서 접근이 가능하도록 외부단자가 설치되어 있으며, 이들 외부 단자를 이용하여 복수대의 전압원 인버터를 병렬운전 하여 대전력 유도전동기를 구동할 수 있다. 이와 같이 고압 대전력 유도전동기를 복수 개의 전압원 인버터를 병렬 운전하여 구동할 경우, 특정 인버터의 고장발생 시 비록 구동 토오크는 감소될지라도, 나머지 인버터로 시스템을 계속 구동할 수 있어 시스템의 고장대처능력을 향상시킬 수 있다. 또한 병렬 운전되고 있는 각 인버터의 스위칭 동작에 대해 서로 위상차를 갖게 함으로서, 등가 스위칭 주파수를 증가시켜 출력 토오크 리플 감소와 입력 전류 리플 감소, DC Link 커패시터의 크기 감소와 같은 좋은 특성을 얻을 수 있다. 또한 각 인버터로의 전력의 분산에 의해 시스템에서 발생하는 EMI영향을 감소시킬 수 있다. 본 논문에서는 제안한 방식을 컴퓨터 시뮬레이션을 통해 특성을 증명하였다.