• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.66-68
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• 2004

The current source HVDC using thyristor valves requires the reactive power compensator, the increasement of short circuit ratio(SCR) by AC source, and the harmonic filter in power transmission. The voltage source HVDC that controls active power and reactive power independently can minimize the requirements and also can be used as a reactive power source without additional reactive power compensators. In this paper, the solution of supplying active power using direct current transmission and compensating additional reactive power at the heavy load zone in metropolitan area is proposed and verified by simulations.

• Tribology and Lubricants
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• 제29권1호
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• pp.1-6
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• 2013

Hydraulic transmission is the main component delivering power to the drive wheels of an excavator during forward and backward movement, and it has low speed, high torque and high speed, low torque gear change ratios as a forward/backward two-speed main function. It also has additional function of ensuring that the excavator is stably fixed on the ground with the built-in parking brake during excavation operations. In this study, optimal design specifications are determined by modeling and simulating about the multi-disc-type friction clutch, which is the main component improving the reliability of the hydraulic transmission for a 14-ton wheel excavator, and the friction properties of the transmission clutch are analyzed by performing sample tests.

• 센서학회지
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• 제26권6호
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• pp.408-413
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• 2017

In this paper, we newly developed a byte-inverted transmission method for flicker-free visible light communication (VLC). The VLC transmitter sends original data in the former half period of the clock, and inverted data and in the latter half period of the clock. The VLC receiver receives the original data in the in the former half period of the clock. In this system, we used 480Hz clock that was generated from the 60Hz power line. The average optical power of the LED array in the transmitter is constant, thus flicker-free, in the observation time longer than the period of the clock that is about 2ms. This period is shorter than the maximum flickering time period (MFTP) of 5ms that is generally considered to be safe. This configuration is very useful in constructing indoor wireless sensor networks using LED light because it is flicker-free and does not require additional transmission channel for clock transmission.

• Journal of electromagnetic engineering and science
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• 제11권3호
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• pp.186-191
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• 2011

This paper presents a simple and effective method for improving stopband rejection characteristics of previously studied dual-band filters. Small electric couplings were applied to the symmetrically positioned shunt resonators, which divided each transmission zero into two transmission zeros without any effect on passbands. We were able to achieve improved stopband rejection characteristics by these additional transmission zeros. For the filter application, we designed a dual-band filter with improved stopband characteristics using microstrip quasi-lumped elements. The electric couplings that control the location of transmission zeros are controlled by the distance between symmetric open stubs of the filter. The filter was fabricated with a relative dielectric constant of 3.5 and a thickness of 0.76 mm. The fabricated filter has a small size ($14.6{\times}13.2{\times}0.76$ mm) and a low insertion loss when compared with conventional filters.

• 한국전자파학회지:전자파기술
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• 제27권3호
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• pp.17-27
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• 2016

In the high-frequency characterizations of planar circuit components, measurement data may not be physical. It is mainly due to resonance effects concerned with discontinuities which are inevitable for a planar component characterization. In this paper, a novel accurate transmission line characterization method is presented that excludes the resonance effects based on measurement data reconfirmation. For the physically obvious data acquisition near the resonance frequencies of a transmission line, the additional lines with different line lengths are fabricated on the same substrate. The test transmission lines are characterized by using vector network analyzer (VNA) in 100 MHz to 26.5 GHz. It is shown that an accurate transmission line characterization can be achieved with the proposed measurement data reconfirmation technique.

• Journal of Power Electronics
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• 제17권1호
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• pp.242-252
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• 2017

This paper deals with the blocking of DC-fault current during DC cable short-circuit conditions in HVDC (High-Voltage DC) transmission systems utilizing Modular Multilevel Converters (MMCs), where a new SubModule (SM) topology circuit for the MMC is proposed. In this SM circuit, an additional Insulated-Gate Bipolar Translator (IGBT) is required to be connected at the output terminal of a conventional SM with a half-bridge structure, hereafter referred to as HBSM, where the anti-parallel diodes of additional IGBTs are used to block current from the grid to the DC-link side. Compared with the existing MMCs based on full-bridge (FB) SMs, the hybrid topologies of HBSM and FBSM, and the clamp-double SMs, the proposed topology offers a lower cost and lower power loss while the fault current blocking capability in the DC short-circuit conditions is still provided. The effectiveness of the proposed topology has been validated by simulation results obtained from a 300-kV 300-MW HVDC transmission system and experimental results from a down-scaled HVDC system in the laboratory.

• 융합보안논문지
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• 제21권3호
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• pp.67-73
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• 2021

2018년과 2019년 한국관광공사 조사에 의하면 TV 프로그램이나 영향력 있는 동영상에 기록된 장소를 여행하는 것이 여행의 중요한 경향으로 자리 잡았으며, 여행 프로그램을 시청하면 그 프로그램에 등장한 장소에 대한 방문 의도가 향상된다는 연구 결과들도 발표되고 있다. 이 연구는 여행 프로그램의 시청자에게 프로그램에 노출되고 있는 장소와 행사에 대한 부가정보를 제공하는 여행 프로그램 연동형 데이터서비스를 설계하였다. 구체적으로, 여행 프로그램의 부가정보를 장소와 행사로 구분하여 정형적으로 정의하였고 프로그램 내용에 정합된 부가정보의 노출 방법을 설계하였다. 또한 부가정보를 프로그램 방송시간에 맞춰 적절하게 데이터서비스에 제공하는 국제표준 DVB 기반의 데이터 전송 방식을 고안하였다. 이 연구는 여행 프로그램을 대상으로 데이터서비스의 새로운 응용을 시험했다는 점에서 의의가 있으며, COVID-19 사태로 침체된 여행 문화의 활성화에 미력하나마 도움이 되기를 기대한다.

• 융합보안논문지
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• 제22권2호
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• pp.91-98
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• 2022

영화는 경험이 중요한 문화 상품의 성격을 갖고 있기 때문에 전문적인 영화정보 프로그램을 통해 영화의 간접적 경험을 제공함으로써 시청자를 영화 관객으로 전환하기 위한 홍보 전략을 사용하고 있다. 이처럼 영화정보 프로그램이 시청자들의 영화관람 의도를 높이는 전략적 홍보 매체임을 고려할 때, 영화정보 프로그램과 연동되어 시청자에게 유용한 부가정보를 제공하는 데이터서비스에 관한 연구는 의미가 있다. 이에 본 연구는 영화정보 프로그램 연동형 데이터서비스 개발에 있어서 핵심 연구 주제인 영화정보 프로그램의 부가정보를 정의하고 부가정보를 데이터서비스로 제공하기 위한 디지털방송 국제표준 DVB-SI 기반의 부가정보 전송 방법을 고안하였고, 이를 바탕으로 KBS의 <영화가 좋다> 프로그램의 데이터서비스 프로토타입을 구현하였다. 본 연구는 데이터서비스의 응용 분야를 영화정보 프로그램으로 확장하며 COVID-19 사태로 심각한 타격을 받은 영화산업에 새로운 홍보 전략을 제시한다는 점에서 의의가 있다.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.645-650
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• 2010

The continuous increase demand for electric power leads to the additional construction of transmission facilities, but it is not easy to acquire right-of-way for transmission facilities. Therefor, there is a need for compact tower that can be built on a narrow right-of-way the compact tower with polymer insulation arm is a solution. It can be upgrading conventional 154 kV transmission line voltages to 345 kV levels. However transmission voltage is increasing, environment interference (corona noise, radio interference, etc.) will occur gradually. This environment interference is depending on the electrical clearances of tower and configuration of conductors. Therefore the analysis of the factors of environmental interference is necessary in order to upgrading transmission voltage. This paper presents the design factor of a compact tower to meet the environmental interference standard.

• Journal of Power Electronics
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• 제19권1호
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• pp.211-219
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• 2019

In magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the introduction of additional intermediate coils is an effective means of improving transmission characteristics, including output power and transmission efficiency, when the transmission distance is increased. However, the position of intermediate coils in practice influences system performance significantly. In this research, a three-coil MCR WPT system is adopted as an exemplification for determining how the spatial position of coils affects transmission characteristics. With use of the fundamental harmonic analysis method, an equivalent circuit model of the system is built to reveal the relationship between the output power, the transmission efficiency, and the spatial scales, including the axial, lateral, and angular misalignments of the intermediate and receiving coils. Three cases of transmission characteristics versus different spatial scales are evaluated. Results indicate that the system can achieve relatively stable transmission characteristics with deliberate adjustments in the position of the intermediate and receiving coils. A prototype of the three-coil MCR WPT system is built and analyzed, and the experimental results are consistent with those of the theoretical analysis.