• Electrical & Electronic Materials
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• v.4 no.1
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• pp.45-52
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• 1991

본 논문은 기중 코로나 방전에 의하여 생성된 캐리어를 Teflon-FEP 표면에 균일하게 공급하였을 때 Teflon-FEP를 통하여 흐르는 코로나 대전전류 특성에 대하여 연구하였다. 불소를 함유한 Teflon-FEP는 코로나 대전전류에 극성효과가 현저히 나타난다. 즉 정극성 캐리어는 벌크내를 쉽게 이동하나 부극성 캐리어는 안정하게 trap되어 벌크내를 이동하기 어렵기 때문에 부극성 코로나 대전전류 보다 정극성 코로나 대전전류가 크게 흐름을 알았다. 이와같이 극성효과가 나타나는 것은 Teflon-FEP가 전자 친화력이 있는 불소를 함유하고 있기 때문임을 제시하였다. 이러한 사실은 Polysulfone(PSF), High density Polyethylene(HDPE) 및 Polythylene Terephtarate(PET)의 코로나 대전전류 특성으로부터 확인할 수 있었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.85-90
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• 2006

This paper presents experimental results relating to the preliminary breakdown characteristics in $SF_6/CO_2$ gas mixtures under a highly non-uniform electric field. The impulse pre-breakdown developments are investigated by the measurements of corona current and light emission images. As a result, the preliminary breakdown development mechanisms for both the positive and negative polarities were fundamentally same. The first streamer corona was initiated at the tip of needle electrode, and the leaders developed with a stepwise propagation and bridged the test gap. The pause time of leader pulses in the positive polarity was significantly shorter than that in the negative polarity. Also, the time interval between the first streamer corona onset and breakdown in the negative polarity was much longer than that in the positive polarity. The discharge channel path in the positive polarity was zigzag, and the leader channel in the negative polarity was thicker and brighter than that in the positive polarity.

• Journal of the Korean earth science society
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• v.31 no.4
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• pp.335-347
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• 2010

The statistical characteristics of Cloud-to-Ground (CG) lightning data, observed by the total lightning detection system (TLDS) of KMA during the recent seven years (2002-2008), have been analyzed. Lightning frequency shows a strong interannual, seasonal and diurnal variations without regard to the polarity. The 74% and 0.6% of the total lightning occurred during the summer and winter, respectively. And it has a bimodal diurnal variation with two peaks (dawn: 0500-0700 LST, mid-afternoon: 1500-1600 LST). The ratio of positive flashes to negative ones also has a strong seasonal variation with the maximum and minimum during winter (62.5%) and summer (7.3%), respectively. Unlike the lightning frequency, the lightning intensity of negative flashes shows a weak interannual, seasonal and diurnal variations. However, the lightning intensity of positive flashes exhibits an inverse seasonal variation to that of lightning frequency, with the minimum and maximum during summer and winter, respectively. The lightning density is greatly higher in the western inland areas and the West/South Sea than in the eastern part and the East Sea. In general, the lightning intensity is stronger in the ocean, especially in the East Sea than in the inland area, regardless of the polarity.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.87-90
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• 2003

Polyvinyl Alcohol(PVA)와 같이 분자간 결합력이 큰 극성고분자에 극성의 가소제를 도입하여 가역적 가소화기법을 이용하여 비결정영역뿐만 아니라 결정영역까지도 가소화시켜 연신성을 개선시키고자하는 연구가 일부 이루어져 왔다. 특히 요드는 극성고분자의 비결정 영역뿐만 아니라 결정영역까지 침투한다는 사실이 밝혀지면서 PVA의 요드 처리에 대한 연구가 많이 이루어져왔다[1-3]. 그러나 지금까지의 연구에서는 대부분 필름이나 섬유와 같이 성형가공된 상태에서, 즉 결정화가 이루어진 후에 요드화를 시켰기 때문에 그 응용범위나 연구에 있어서 한계를 지니고 있다고 할 수 있다. (중략)

• Journal of the Korean earth science society
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• v.31 no.7
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• pp.749-761
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• 2010

A relationship between cloud-to-ground lightning and rainfall was investigated by using the two-years (2006-2007) summer lightning data and the automatic weather stations (AWSs) data of the Korea Meteorological Administration. The negative lightning occurred at the core of highly concentrated convection, which is often accompanied with heavy rains. Whereas most positive lightning occurred at the anvil cloud with low density and light rains. The rainfall intensity is strongest when the negative and positive lightning occurred concurrently, and one with lightning is much stronger than that without lightning. A portion of the positive lightning of the total lightning was less than 10% during summer seasons, and the lightning without rains was about 34%. The rain rate was strongly correlated with the negative flash rate, and the correlation coefficients varied between 0.87 and 0.94 according to the co-location radius (5-15 km) of AWSs. Most of the lightning occurred 10 minutes before and/or concurrently occurred with rains. A portion of the convective rainfalls of the total rainfalls was at least 20% when we define the rainfalls with lightning as convective. The convective rainfall was greater during August than in June and July. In general, the portion of convective rainfalls showed a maximum diurnal variation during late afternoon as in the rains and lightning.

• 전자공학회논문지 IE
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• v.44 no.3
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• pp.6-11
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• 2007

In this study, which was performed to identify a degradation mechanism in macromolecular insulating material, the contact angle, surface potential decay, surface resistance rate and XPS analysis were compared after exposure of fibre-glass-reinforced polymer laminate to plasma discharge. In the case of chemical changes arising from plasma treatment, carboxyl radicals were generated mainly in the plasma-treated surface, which was rapidly changed to a hydrophilic surface. In the corona potential decay study to determine the electrical changes, leading to a negative surface for the untreated specimen. However, in the case of the hydrophilic surface, a lot of carboxy radicals(-COO) acting as positive polarity were generated, resulting in a positive surface. Owing to such a positive surface, the charges of applied negative polarity were decreased rapidly.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06c
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• pp.260-265
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• 2010

웹 2.0시대의 도래에 따라 많은 소비자들은 상품에 대한 다양한 의견을 표현할 수 있게 되었다. 이러한 의견들을 활용하여 상품평 요약 시스템 등이 개발되었다. 어휘의 의미 극성은 이러한 시스템에서 활용될 여지가 많은 요소이다. 영어의 경우 어휘의 의미 극성을 판단하는 연구가 많이 진행되어 어느 정도 결실을 맺었지만, 우리말의 경우 어휘의 의미 극성을 판단하는 연구는 아직 미흡하다. 본 논문에서는 우리말 어휘의 의미 극성을 PMI를 사용하여 판단한다. 또한 PMI를 우리말 어휘에 적용할 때 문제가 되는 이슈를 살펴보고 이에 대한 해결 방법들을 제시한다. 나아가 실제 상품 평에서 많이 쓰이는 형용사에 대하여, 제시한 의미 극성 판단 방법의 성능을 검증해 본다. 제시한 방법은 어휘의 의미 극성을 81%의 정확도로 판단해 주었다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1997.10a
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• pp.63-66
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• 1997

본 논문은 초전도 및 극저온 케이블의 냉매와 전기절연으로 사용되고 있는 액체질소의 연면방전특성에 관하여 연구하였다. 기포효과를 고려하여 대기압하에서의 정극성 및 부극성 직류고전압을 사용하였고, 연면방전시 방사되는 방사전자파의 스펙트럼 분포 특성을 관측하였다.

• Annual Conference on Human and Language Technology
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• 2013.10a
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• pp.113-115
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• 2013

다수의 상품평 요약은 인터넷 쇼핑몰 고객에게 편의를 제공할 수 있다. 본 논문에서는 상품평 요약 시스템의 성능 향상을 위한 방안을 제안한다. 시스템은 크게 상품평의 평가 항목 추출과 극성 사전 생성, 극성 판별 단계로 구성된다. 평가 항목 추출에서는 외부 연관도의 영향력을 줄이고, 극성 사전 생성에서는 단어 거리 평균을 적용한다. 제안한 방식을 사용하였을 때 평가 항목에 대한 문장의 극성 판별 시 90.8%의 정확율을 보였다.

• Fire Science and Engineering
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• v.16 no.1
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• pp.30-38
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• 2002

Occurring fire or burning bushes beneath overhead power lines have caused system disturbances in many countries. In this study, various tests in the simulated condition of power lines were conducted so as to investigate the reduction in insulation strength caused by combustion flame. Characteristics of the ac and dc flashover voltages in the vertical needle-plane, sphere-plane and rod-plane electrode system were investigated when the combustion flames were present near the high-voltage electrode. As the results of an experimental investigation, It was found that the average reduction characteristics of flashover voltages with the sphere-plane system, in comparison with the no-flames case, were about 1/3 times when the ac voltages were applied.