• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권9호
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• pp.437-443
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• 2005

This paper deals with an experimental study for Klippon reiay in Cheju-Heanam HVDC system Klippon relay was troubled many times for years, and Klippon relay's fault caused the HVDC system trip. So for several years, these reasons of Klippon relay fault were investigated. The malfunction of Klippon relay in Cheju-Haenam HVDC system has been caused by the incoming of random surge(current source and voltage source). This paper has stu야ed the theoretic리 analysis and experimental study of Klippon relay, and the solutions against the problems were suggested according to their causes. Among the problems, grounding problem was removed by one-point earth connection and by modification of grounding circuit. The effects of inrush current was removed by inserting the blocking diodes by series in Klippon relay circuits. Finally, The over-voltage induced on Klippon relay, by a relay excitation coil, was removed by inserting a free-wheeling diode in Parallel with the excitation coil.

• 한국통신학회논문지
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• 제18권4호
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• pp.481-489
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• 1993

등간격의 전극구조를 갖는 탄성표면파 필터의 정전계적 임피던스 해석을 위하여 무한개의 인접전극의 정전계적 상호작용을 해석하여 전극의 구조에 따른 전하분포를 구현하였는데, 이는 Element Factor와 Array Factor로 분리하여 계산할 수 있었다. 임의의 전극 구조를 갖는 탄성표면과 필터의 입력 및 출력 전극의 Radiation Conductionce, Susceptance 및 static Capacitance는 이러한 전극에서의 전하분포를 통하여 구하였고 Apodized IDT의 임피던스는 Multi-Track 해석에 의하여 다수의 Uniform Track의 병렬 연결로써 계산하였다. 이와 같이 얻어진 입.출력 전극의 임피던스를 실제로 제작된 필터의 측정 임피던스와 비교한 결과 잘 일치하였다.

• Journal of Information Processing Systems
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• 제10권1호
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• pp.69-80
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• 2014

The free distance of (n, k, l) convolutional codes has some connection with the memory length, which depends on not only l but also on k. To efficiently obtain a large memory length, we have constructed a new class of (2k, k, l) convolutional codes by (2k, k) block codes and (2, 1, l) convolutional codes, and its encoder and generation function are also given in this paper. With the help of some matrix modules, we designed a single structure Viterbi decoder with a parallel capability, obtained a unified and efficient decoding model for (2k, k, l) convolutional codes, and then give a description of the decoding process in detail. By observing the survivor path memory in a matrix viewer, and testing the role of the max module, we implemented a simulation with (2k, k, l) convolutional codes. The results show that many of them are better than conventional (2, 1, l) convolutional codes.

• Transactions on Electrical and Electronic Materials
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• 제17권1호
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• pp.21-24
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• 2016

A junction box used in a 3 kW photovoltaic power generation system plays a role in collecting and supplying the direct current voltage produced by photovoltaic modules to an inverter. It is also used for facilitating maintenance checks and protecting the module and inverter by keeping the voltage constant. As for the junction box, using it in a parallel connection creates a difference between the setup modules. In order to compensate, an inverse voltage diode is used. But the high-power created through the solar generator can be delivered to the inverter through the inverter regularly. Therefore, a component can break down due to excess heat. And consequently short circuits and electric leakage occurs. In this study, using a junction box that enabled the bypass of high electric power, it was possible to reduce heat generation by approximately 35℃ when compared to a standard junction box.

• 대한의용생체공학회:의공학회지
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• 제29권3호
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• pp.249-253
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• 2008

The indirect-contact ECG (IDC-ECG) was introduced by a prior study for daily non-intrusive measurements. To improve the signal quality and to extend the application area of IDC-ECG, close study of the frequency characteristics of the IDC-ECG is necessary. In this study, the frequency response of the active electrode for several sample clothes was measured under conditions of actual IDC-ECG measurement with human body. Higher gain in low frequency range than expected by prior study was observed. In addition to it, wide variation in gain according to the cloth type in the low frequency range was observed. Variation in gain caused by moisture variation in the clothes was also observed. This study shows that the parallel R-C connection is proper for electrode model and the resistive factor is influenced by moisture in the clothes. This study is the first that provides the frequency response of the electrode in the actual indirect-contact ECG measurement and it is expected that the results will be helpful to improve the indirect-contact ECG method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.506-509
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• 2001

A high power U.P.S system utilizing the parallel connection of low power U.P.S is developed. For the purpose of elimination the circular current between U.P.S.s, a digital circuit is employed. Furthermore a double phase synchronization and an interphase reactor are used to eliminate the circular current and the voltage ripples caused by the system parameter unbalances of parall connected U.P.S.s. The digital controller is implemented with ADSP21061 as aspect of a functional convenience.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1222-1223
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• 2007

This paper suggests a 6-pulse-shift converter with PWM current-source inverter based on buck-boost configuration to improve the efficiency and to reduce the switching frequency of inverter for photovoltaic generation system, the device can be operated as interface system between solar module system and power system grid without energy storage cell. the circuit has six current-source buck-boost converter which operate chopper part has one full bridge inverter which make a decision the polarity of AC output. Therefore, the proposed PWM power inverter has advantages such as the reduction of witching loss and realization of unity power factor operation. the theoretical backgrounds are discussed and the input-output characteristics for the implemented prototype inverter using TMS320F2812 are verified experimentally in this paper.

• 한국수학사학회지
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• 제31권1호
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• pp.37-51
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• 2018

In this paper, our main concern is the historical development of the Finsler geometry in Debrecen, Hungary initiated by L. Berwald. First we look into the research trend in Berwald's days affected by the $G{\ddot{o}}ttingen$ mathematicians from C. Gauss and downward. Then we study how he was motivated to concentrate on the then completely new research area, Finsler geometry. Finally we examine the course of establishing Hungarian Debrecen school of Finsler geometry via the scholars including O. Varga, A. $Rapcs{\acute{a}}k$, L. $Tam{\acute{a}}ssy$ all deeply affected by Berwald after his settlement in Debrecen, Hungary.

• Smart Structures and Systems
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• 제7권5호
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• pp.393-416
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• 2011

Hybrid acceleration-impedance sensor nodes on Imote2-platform are designed for damage monitoring in steel girder connections. Thus, the feasibility of the sensor nodes is examined about its performance for vibration-based global monitoring and impedance-based local monitoring in the structural systems. To achieve the objective, the following approaches are implemented. First, a damage monitoring scheme is described in parallel with global vibration-based methods and local impedance-based methods. Second, multi-scale sensor nodes that enable combined acceleration-impedance monitoring are described on the design of hardware components and embedded software to operate. Third, the performances of the multi-scale sensor nodes are experimentally evaluated from damage monitoring in a lab-scaled steel girder with bolted connection joints.

• 한국구조물진단유지관리공학회 논문집
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• 제22권5호
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• pp.55-63
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• 2018

최근에 오스테나이트와 페라이트의 조직을 갖는 듀플렉스계 스테인리스강이 개발되었고 오스테나이트계 스테인리스강에 비해 고강도, 응력부식균열에 대한 고내식성과 재료비절감으로 다양한 산업분야에서 사용량이 증가되고 있다. 그러나, 현재 스테인리스강은 한국 건축구조기준에 구조용재료로 지정되어 있지 않고 구조설계기준도 마련되어 있지 않는 실정이다. 이 연구에서는 2행 1열 듀플렉스계 스테인리스강(STS329FLD) 볼트접합부에 대한 구조적 성능을 조사하기 위한 실험적 연구를 수행하였다. 주요변수는 전단접합형태(일면전단과 이면전단)과 하중방향 연단거리이다. 종국파단형태는 전형적인 블록전단파단, 인장파단과 면외변형이 관찰되었다. 일면전단 접합부에서 면외변형발생으로 최대 20%까지 내력저하가 발생되었다. 실험최대내력은 현행설계기준 AISC/AISI/KBC, EC3와 AIJ 및 기존연구자에 의한 제안된 식에 의한 예측내력과 비교하였다. 면외변형이 발생하지 않은 접합부에 대해서 실제 전단파단단면을 고려한 Clement & The의 식에 의한 예측내력이 실험내력에 가장 근접했고 면외변형을 동반한 접합부에 대해서는 면외변형을 고려해 제안한 Kim & Lim식에 의해서 과대평가하는 것으로 나타났다.