• 한국표면공학회지
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• 제28권6호
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• pp.376-385
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• 1995

Copper-chromium multilayers with a nominal bilayer thickness of about 400 $\AA$ (200 $\AA$ each) were prepared by dc magnetron sputtering and the evolution of microstructure during heat treatment was investigated by using x-ray diffractometry(XRD), Auger electron spectroscopy(AES) and transmission electron microscopy(TEM). It was observed that an amorphous phase with a thickness of about 40 $\AA$ was formed at the interfaces of the as-deposited Cu/Cr multilayered film using cross-sectional TEM. At elevated temperatures, the Cu(111) reflection showed increasing intensity and decreasing line-width as a result of copper grain growth. The intermixed amorphous phase disappeared after annealing at $250^{\circ}C$ for 1 h and the multilayer structure was stable up to $400^{\circ}C$ for 1 h annealing. At $600^{\circ}C$ annealing, it was observed that the multilayer structure was completely destroyed and copper and chromium phases were fully intermixed.

• 대한전기학회논문지:전력기술부문A
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• 제48권7호
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• pp.855-862
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• 1999

A high speed digital distance relaying algorithm based on a least square error method is proposed. To obtain stable phasor values very quickly, first, a lowpass filter which has very short transient period and no overshoot is presented. Secondly, the least square error method having the data window of 3 samples is used by applying a FIR filter which removes the DC-offset component in current relaying signals. Test results show that the proposed distance relaying algorithm detects most of internal faults within a half cycle after faults in a 154[kV] overhead transmission line system.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권1호
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• pp.105-109
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• 2014

Converter valve cooling device as the heat exchanger, is known as the converter valve's blood circulation system, Inefficiency of the equipment will not only lead to the component overheating damage, but also serious DC system outage. Therefore, reliable HVDC valve cooling system is essential for the HVDC transmission system. In this article, analysis on the two-phase flow heat transfer characteristics and security of the evaporative cooling technology are provided, the technology's advantage and feasibility are discussed.

• Journal of electromagnetic engineering and science
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• 제4권2호
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• pp.56-62
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• 2004

We present a multi-Gbit/s digital I/O interface based on RF-modulation and capacitive-coupling over an impedance matched transmission line. The RF-interconnect(RFI) can greatly reduce the digital switching noise and eliminate the dc power dissipation over the channel. It also enables reduced signal amplitude(as low as 200 ㎷) with enhanced data rate and affordable circuit overhead. This paper addresses the system advantages and implementation issues of RFI. A prototype on-chip RFI transceiver is implemented in 0.18-${\mu}{\textrm}{m}$ CMOS. It demonstrates a maximum data rate of 2.2 Gbit/s via 10.5-㎓ RF-modulation. The RFI can be very instrumental for future high-speed inter- and intra-ULSI data links.

• Journal of electromagnetic engineering and science
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• 제6권1호
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• pp.76-81
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• 2006

Ultra wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as Broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a orthogonal frequency division Multiplex UWB source and an impulse radio UWB source, to a Broadcasting transmission system. The receive power degradations of broadcasting system are presented. From these experimental results, we show that in all practical cases UWB system can coexist 35 m distance in-band broadcasting network.

• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.954-958
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• 2012

This paper reports a flexible patch rectenna for wireless actuation of cellulose electro-active paper actuator (EAPap). The patch rectenna consists of rectifying circuit layer and ground layer, which converts microwave to dc power so as to wirelessly supply the power to the actuator. Patch rectennas are designed with different slot length at the ground layer. The fabricated devices are characterized depending on different substrates and polarization angles. The EAPap integrated with the patch rectenna is actuated by the microwave power. Detailed fabrication, characterization and demonstration of the integrated rectenna-EAPap actuator are explained.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2395-2397
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• 2005

A low voltage operated piezoelectric RF MEMS in-line switch has been realized by using silicon bulk micromachining technologies for advanced mobile/wireless applications. The developed RF MEMS in-line switches were comprised of four piezoelectric cantilever actuators with an Au contact metal electrode and a suspended Au signal transmission line above the silicon substrate. The measured operation dc bias voltages were ranged from 2.5 to 4 volts by varying the thickness and the length of the piezoelectric cantilever actuators, which are well agreed with the simulation results. The measured isolation and insertion loss of the switch with series configuration were -43dB and -0.21dB (including parasitic effects of the silicon substrate) at a frequency of 2GHz and an actuation voltage of 3 volts.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.301-302
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• 2012

국내에서 HVDC (High Voltage DC transmission System) 관련 기술은 한국전력공사 및 전력연구원 중심으로 제주와 해남간 설치된 HVDC시스템의 설치 및 운영 기술에 많이 국한되어 왔었다. 그러나 기술을 바탕으로 2010년부터 민간기업인 LS산전과 한국전력공사의 공동 개발을 통하여 60MW ${\pm}80kV$급 전류형 HVDC시스템 설계 및 제작을 추진하여 시스템 설계, 기기 설계 사양, 제작사양서 등의 설계 핵심 기술을 상당부분 확보하는 계기가 되었다. 현재 설계된 Pilot HVDC 시스템은 제작 완료되었고, 제주 실증단지에 설치 및 시험 중에 있으며 2012년 내에 실증운전을 통해서 최종적으로 시스템 설계 기술을 검증할 계획이다. 이 같은 연구를 통하여 상당부분 HVDC 시스템에 대한 독자적인 설계 능력을 갖추게 될 것이다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.155-156
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• 2015

This paper proposes a high efficiency wireless power transfer system with an asymmetric 4-coil resonator. It presents a theoretical analysis, an optimal design method, and experimental results. In the proposed asymmetric 4-coil system, the primary side consists of a source coil and two transmitter coils which are called intermediate coils, and in the secondary side, a load coil serves as a receiver coil. In the primary side, two intermediate coils boost the apparent coupling coefficient at around the operating frequency. Because of this double boosting effect, the system with an asymmetric 4-coil resonator has a higher efficiency than the conventional symmetric 4-coil system. The prototype operates at 90 kHz ofswitching frequency and has 200 mm of the power transmission distance between the primary side and the secondary side. An AC-DC overall system efficiency of 96.56% has been achieved at 3.3 kW of output power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.104-106
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• 2004

In competitive electricity markets, the System Operator (SO) coordinates the overall maintenance schedules whenever the collective maintenance schedule reported to SO by Gencos in the pool does not satisfy the specified operating criteria, such as system reliability or supply adequacy. In this paper, we divide maintenance schedule problem into master-problem and sub-problem. Master-problem is schedule coordination and sub-problem is DC-optimal power flow. If sub-problem is infeasible, we use the algorithm of modifying operating criteria of master-problem.