• Journal of Information Display
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• 제7권1호
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• pp.25-29
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• 2006

By the voltage threshold (Vt) close-curve measurement method, the changes in the discharge characteristics such as a firing voltage and IR emission among the three electrodes were examined relative to the low or high panel temperature ranging from -10 to $80^{\circ}$. The variation in the panel temperature was found significantly influence the surface discharge between the MgO surfaces rather than the plate gap discharge between the MgO and phosphor layers. Based on this experimental observation, a modified reset waveform that alleviates the surface discharge during a ramp-up and -down period was deeloped. By adopting the proposed reset waveform, a stable address discharge could be obtained irrespective of the panel temperature variation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.398-399
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• 2019

본 논문은 LS산전 고압인버터의 국내외 현장 전용화 사례에 대해 기술한다. 고압인버터는 대용량 고전압 전동기를 구비한 중요부하에 주로 적용되며 단독운전보다는 다수의 고압인버터가 연동 운전하는 현장에 설치되는 경우가 많다. 이러한 현장에는 표준제품이 아닌 전용화 기능을 포함한 제품이 출하가 된다. 자사 LS MVD는 각종 산업설비와 국책연구기관의 시험설비 그리고 발전소 수처리 시설 등 국가기간시설에 많이 적용이 되며 매년 70여대 이상의 MVD가 국내외 전동기 부하에 신규로 설치되어 운용되고 있다. 본 논문에서는 주목할만한 현장의 전용화 사례에 대해 설명하여 향후 고압인버터를 적용하고자 하는 고객이나 고압인버터에 관심이 있는 엔지니어에게 고압인버터에 대한 이해도를 높이고자 한다.

• 조명전기설비학회논문지
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• 제20권9호
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• pp.11-17
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• 2006

We have theoretically investigated the effects of the interplay between the driving voltage of Mach-Zehnder(MZ) modulators and the bandwidth of low-pass filters(LPF) in 10[Gb/s] duobinary modulation systems. For the change of driving voltage ratios(driving voltage/switching voltage), the transmission performance has been evaluated over 200[km] of single-mode fiber(SMF) systems. For driving voltage ratios with smaller than 100[%], the transmission performance has been maintained and greatly affected by the bandwidth of LPFs than the driving voltage. For driving voltage ratios with larger than 100[%], the transmission performance has been degraded and is not sensitive to the bandwidth of LPFs. To see the limitation of driving voltage, we have reduced the driving voltage ratio to 50[%]. Our results suggest that 10[Gb/s] duobinary signals with driving voltage ratio with smaller than 100[%] have been transmitted over 200[km] SMF within 2[dB] power penalty without dispersion compensation. For the driving voltage ratio with 50[%], we have verified that the transmission performance was maintained.

• 한국표면공학회지
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• 제42권4호
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• pp.179-185
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• 2009

Diamond-like carbon(DLC) films were deposited by linear ion source(LIS)-physical vapor deposition method changing the anode voltages from 800 V to 1800 V, and characteristics of the films were investigated using residual stress tester, nano-indentation, micro raman spectroscopy, scratch tester and Field Emission Scanning Electron Microscope(FE-SEM). The results showed that the residual stress and hardness increased with increasing the ion energy up to anode voltage of 1400 V. It was also found that the content of $SP^3$ carbon increased with increasing the anode voltage $SP^3/SP^2$ ratio through investigation of $SP^3/SP^2$ ratio by the micro-raman analysis. From these results, it can be concluded that the physical properties of DLC films such as residual stress and hardness are increased with increasing the anode voltage. These results can be explained that 3-dimensional cross-links between carbon atoms and Dangling bond are enhanced and the internal compressive stress also increased with increasing the anode voltage. The optimal anode voltage is considered to be around 1400 V in these experimental conditions.

• 한국철도학회논문집
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• 제19권4호
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• pp.436-444
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• 2016

철도차량용 주변압기 고압권선은 고압인통선에 유기되는 이상전압과 내부공진을 발생 시킬 수 있는 다양한 주파수 대역의 고유주파수를 가진다. 공장시험은 다양한 파형과 지속시간을 지닌 이상전압의 여자가능성을 판단하는데 한계가 있다. 본 연구는 전자계과도해석프로그램(이하 EMTP)을 이용하여 고압권선 모델을 설계하고 초기 전압분포와 전압-주파수 관계 측면에서 내부공진특성을 모의분석한다. 턴 단위의 집중매개변수는 변압기 형상정보부터 계산되며, 각 레이어 단위로 합산된 서브모델은 네트워크 모델로 결합되어 EMTP의 라이브러리를 통해 구현한다. 사례연구는 주파수 변동에 따른 레이어 단위의 전압-주파수 관계 특성과 시계열 영역에서 전압 확대 및 분포 양상을 보여준다.

• 조명전기설비학회논문지
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• 제22권11호
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• pp.9-14
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• 2008

This paper presents the performance analysis of 10[Gb/s] optical duobinary transmitters with the non-ideal Mach-Zehnder modulator which does not have exactly 50/50 splitting/combining ratios by computer simulations. For driving voltage ratios(=driving voltage/switching voltage) with smaller than 100[%], the transmission performance has been greatly affected by extension of LPF bandwidths. Nevertheless, the performance has been degraded when the driving voltage ratio is 100[%]. The smaller driving voltage ratios has, the more sensitivity improves by extension of LPF bandwidths under the asymmetry condition. But the driving voltage ratio with 80[%] has better bit error rate(BER) than those with 50[%] and 25[%].

• 조명전기설비학회논문지
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• 제26권11호
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• pp.62-74
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• 2012

This paper proposes a new secondary battery charger/discharger available for zero voltage discharge which is used for test equipments and formation process. The proposed system is a switching type converter, and thus the system is high efficiency and more compact as compared with linear type charger/discharger. Conventional switching type charger/discharger can not discharge secondary batteries to zero voltage because of voltage drops in the switching elements and long distributing line(typically 10m). However, the proposed system is able to discharge the battery to zero voltage in constant current mode regardless of the voltage drops. In this paper, we analyze the proposed charger/discharger and the validity of the system is verified by simulation and experiment.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.451-456
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• 2009

Through the development of phasor measurement units (PMU), various aspects of power system dynamic behavior could be monitored and diagnosed. Monitoring dynamic voltage stability has become one of the achievements we can obtain from PMUs. It is very important to select the most appropriate method for the Korea Electric Power Corporation (KEPCO) system since there are many voltage stability indices. In this paper, we propose an advanced WAVI (Wide Area Voltage Stability) that is well suited for the purposes of monitoring the dynamic voltage stability of KEPCO's PMU installation plan. The salient features of the proposed index are: i) it uses only PMU measurements without coupling with EMS data; ii) it is computationally unburdened and can be applied to real-time situations. The proposed index is applied to the KEPCO test system and the results show that it successfully predicts voltage instability through comparative studies.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.265-270
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• 2017

4H-SiC has attracted attention for high-power and high-temperature metal-oxide-semiconductor field-effect transistors (MOSFETs) for industrial and automotive applications. The gate oxide in the 4H-SiC MOS system is important for switching operations. Above $1000^{\circ}C$, thermal oxidation initiates $SiO_2$ layer formation on SiC; this is one advantage of 4H-SiC compared with other wide band-gap materials. However, if post-deposition annealing is not applied, thermally grown $SiO_2$ on 4H-SiC is limited by high oxide charges due to carbon clusters at the $SiC/SiO_2$ interface and near-interface states in $SiO_2$; this can be resolved via low-temperature deposition. In this study, low-temperature $SiO_2$ deposition on a Si substrate was optimized for $SiO_2/4H-SiC$ MOS capacitor fabrication; oxide formation proceeded without the need for post-deposition annealing. The $SiO_2/4H-SiC$ MOS capacitor samples demonstrated stable capacitance-voltage (C-V) characteristics, low voltage hysteresis, and a high breakdown field. Optimization of the treatment process is expected to further decrease the effective oxide charge density.

• Applied Microscopy
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• 제35권4호
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• pp.98-104
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• 2005

초고전압 투과전자현미경 (HVEM)에 장착된 postcolumn 방식의 HV-GIF (high voltage gatan image filter)의 영상기록 장치인 HV-MSC (high voltage multi-scan CCD, $1024{\times}1024$픽셀) 카메라의 결상영역은 현미경 최소 관찰 배율인 2,000배에서 $0.43{\mu}m^2$로서 동일 배율에서 필름 기록영역($2000{\mu}m^2$)에 비해 약 0.02%에 해당하는 매우 적은 영역이다. 이러한 결상 영역 제한성을 개선하고자 투사렌즈 전류조절 기법을 도입하였으며 본 연구의 결과로 HV-MSC의 결상영역은 $112{\mu}m^2$로 비약적으로 증가하였다. 이는 약 8,800배에서 필름으로 기록할 수 있는 영역과 동일하였다. 이와 더불어 투사렌즈 조절에 따른 이미지 변형정도를 약 5%이하까지 허용하고 8,800배 이상에서 필름 기록영역과 동일한 HV-MSC 결상영역을 확보할 수 있는 실험적인 참조곡선을 고안하였다.