• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1146-1149
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• 2014

To discriminate polarities of stator windings for 3 phase induction motors terminal tags of which are not readable, it is possible to utilize the residual magnetic flux present at their rotors as well as to use the way based on external exciting current. The induced voltages are basically decided by parameters such as the quantity of residual flux, the rotator speed by hand force and the phase properties between stator windings. To adopt induced voltages by residual flux for polarity discrimination at sites, the measured voltages by multi-testers need to be readable in magnitude enough to discriminate winding condition with reasonable phase characteristics. This study focuses on the analysis of various connection cases in the expectation that the summing voltages induced by residual flux shall show zero in case of normal connections while the sum becomes greater indication if the connection is in wrong condition. The proposed method is applied to actual motors to disclose how effective it is for polarity discrimination at sites through comparison of output signals between normal and fault connections.

• 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.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.170.1-170.1
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• 2012

지구 저궤도 위성은 위성 천저에 S-밴드 RHCP 안테나, 위성 천정에 S-밴드 LHCP 안테나를 이용하여 S-밴드 통신을 수행하고 있다. 위성이 천저 지향 자세로 지상국을 지나가는 경우에는 패스의 모든 시간을 RHCP 안테나로 통신을 하면 되지만, 태양 지향 자세로 지상국을 지나가는 경우에는 지상국 송수신 안테나의 극성을 전환하는 것이 필요하다. IAC (Initial Activation & Checkout) 기간 중의 상향 링크의 안테나 극성 전환 기준은, 안테나의 설계 상빔 범위 각도를 벗어나는 시점에 기존 안테나와의 통신을 중지하고 반대 극성의 안테나와의 통신을 위해 상향링크 형성을 지속적으로 시도하는 것이다. 그러나 실제 운용 결과, 설계 상빔 범위 각도를 벗어나더라도 충분히 명령을 보낼 수 있음을 확인하였으며, 짧은 패스 시간에 보다 많은 명령을 전송하기 위해 새로운 극성 전환 기준이 필요하다. 본 논문에서는 하향 신호 세기의 텔레메트리 정보를 이용한 상향 링크 안테나 극성 전환 기준을 제시하며, 기존방식에 비해 전송 시간 확보 측면에서 개선됨을 정리하였다.

• 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.

• 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 Digital Contents Society
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• v.15 no.4
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• pp.559-568
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• 2014

Previous polarity classification using sentiment analysis utilizes a sentence rule by product reviews based rating points. It is difficult to be applied to blogs which have not rating of product reviews and is possible to fabricate product reviews by comment part-timers and managers who use web site so it is not easy to understand a product and store reviews which are reliability. Considering to these problems, if we analyze blogs which have personal and frank opinions and classify polarity, it is possible to understand rightly opinions for the product, store. This paper suggests that we extract high frequency vocabularies in blogs by several domains and choose topic words. Then we apply a technique of sentiment analysis and classify polarity about contents of blogs. To evaluate performances of sentiment analysis, we utilize the measurement index that use Precision, Recall, F-Score in an information retrieval field. In a result of evaluation, using suggested sentiment analysis is the better performances to classify polarity than previous techniques of using the sentence rule based product reviews.

• Progress in Medical Physics
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• v.13 no.2
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• pp.69-73
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• 2002

Exposure measurement data with parallel plate ionization chambers were known to depend on the polarity ($k_{pol}$) effect. In this work, the polarity effect were investigated for three parallel plate ionization chambers with different volume. The ionization chamber was fabricated using acrylic plate for the chamber medium and printed circuit board for electrical configuration. The various sizes of the sensitive volumes designed so far were 0.9, 1.9, and 3.1 co. High voltage generator was fabricated using the conventional 9 V batteries to apply the high voltage (300-500 V) to the electrode of the parallel plate ionization chamber. The gap between two electrodes ranged from 3, 6, and 10mm. As the result of our experiment, the polarity effect was within 0.5% in photon beam and 1% to 3.5% in the electron beams. Among electron beams, 16 MeV beam, which had highest energy, showed less polarity effect than electron beams with other energies.

• 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.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.407-408
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• 2012

본 논문은 매입형 영구자석 동기 전동기의 감자 상황에서의 초기 위치 추정 방법을 제시한다. 신호 주입 센서리스 제어시, 영구자석의 극성을 추정하기 위해 영구자석의 자속에 의한 자기 포화 현상을 이용한다. 그러나 영구자석에 감자가 발생하였을 때는 극성에 따른 포화의 특성이 정상적인 경우와 달라져 전압을 주입했을 때 영구자석의 극성을 잘못 판단하게 될 수 있다. 본 논문에서는 감자 상황에서도 바른 극성 검출을 위해 d축 전류를 변경시켜가면서 전압을 주입하여 영구자석의 극성을 추정한다. 이를 통해 영구자석의 감자 상태를 파악하고, 감자 상황에서도 초기 위치 추정이 가능하게 된다. 정상적인 매입형 영구자석 동기전동기와 동일한 사양의 감자된 회전자를 가진 전동기에 제안된 초기 위치 추정 방법을 적용되어 그 타당성을 실험적으로 입증하였다.

• Journal of Plant Biology
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• v.34 no.1
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• pp.25-30
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• 1991

This study was designed to investigate the relationships of cations to the polar regeneration of adventitious buds on midvein segments of poplar leaves. Basal regeneration was disturbed by adding $Ca^{2+}$. When higher concentration of exogeneous $Ca^{2+}$ was added to the WPM (Woody Plant Medium), the more adventitious buds were formed on midvein segments, and polar regeneration was inhibited. Added $Ca^{2+}$ from 0 to 9.70 mM with 0.5 mM of EGT A to WPM decreased the calcium effect. The treatment of $La^{3+$ with 7.05 mM of $Ca^{2+}$ ovecame the effect of $Ca^{2+}$. The cations $Mg^{2+}\;and\;K^{+}$ also caused regeneration on both basal and distal site. However, polar regeneration was maintained in the medium containing $Ca^{2+}$ without $Mg^{2+}$. The above result suggests that exogenous $Ca^{2+}$ or cations inhibit polar regeneration of poplar.poplar.