• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.389-395
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• 2012

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

• 한국산학기술학회논문지
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• 제10권9호
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• pp.2280-2289
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• 2009

자동차 주요 생산국인 우리나라 보행자의 교통사고 사망률은 OECD 평균의 약 2.5배에 달한다. 보행자를 감지하고 운전자에게 경보를 보내주는 시스템이 개발되어 보행자 교통사고를 조금이라도 줄일 수 있다면, 그 자체만으로도 보행자 감지 시스템(PDS)의 가치는 충분할 것이다. 보행자 교통사고율은 야간에 특히 그 비율이 더 높기 때문에, 야간 보행자 감지 시스템이 주요 자동차 회사에 의해 점점 표준 사양으로 채택되어 가고 있는데, 그들은 주로 고가의 나이트비젼 또는 복합적 센서를 사용하는 장비를 채택하고 있다. 본 논문에서는 흑백 카메라 한 대만을 사용하는 PDS를 위한 보행자 영역 검출 기법을 제안한다. 몇몇 다른 환경에서 촬영된 야간 동영상에 대해 실험한 결과, 제안 알고리듬이 기존 알고리듬보다 더 빠르면서도 보행자 후보 영역을 더 정확하게 검출함을 관찰할 수 있었다.

• 한국수소및신에너지학회논문집
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• 제16권1호
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• pp.9-16
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• 2005

We studied the electrochromic properties of hydrated amorphous ruthenium oxide ($RuO_2{\cdot}xH_2O$) thin films using in-situ Raman spectroscopy during electrochemical charging/discharging cycles. We have found that the principal effect of hydrogen insertion into $RuO_2{\cdot}xH_2O$ is reduction of $Ru^{4+}\;to\;Ru^{3+}$, and not formation of new bonds involving hydrogen. We compared the changes in the Raman spectrum of a gasochromic $Pd/RuO_2{\cdot}xH_2O$ film as it is exposed to hydrogen gas with that of electrochemical hydrogen insertion. We tested the changes in the optical transmission of the $Pd/RuO_2{\cdot}xH_2O$ film when exposed to hydrogen gas.

• 정보학연구
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• 제7권4호
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• pp.61-69
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• 2004

본 논문에서는 6.6kV급 고압전동기 모델 코일을 4가지의 권선의 인공적인 결함을 갖도록 제작하였다. 운전중 모의를 위해 모델 코일에 80pF의 에폭시-마이카 커플러를 설치하였으며, TGA를 사용하여 NQN, 부분방전 크기 및 부분방전 패턴 등을 측정하였다. 웨이블렛 변환기법을 이용한 고압전동기의 고정자권선의 결함에서 발생된 부분방전신호의 파형을 통하여 여러 가지의 통계적인 파라메터를 통하여 특징을 추출하였다.

• 한국환경과학회지
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• 제13권4호
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• pp.435-440
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• 2004

The thiophene or furan-containing hexadentate ligands 1, 12-bis (2-theophene )-2,5,8,ll-tetraazadodecane(Thiotrien ㆍ 4HCl) and 1,12-bis (2-furan)-2,5,8,11-tetraazadodecane(Furatrienㆍ4HC1) were synthesized as their tetrahydrochloride salt and characterized by EA, IR, NMR, and Mass spectrum. Their protonation constants (logK$_{nH}$) and stability constants (logK$^{M}_{L}$ for Cd$^{2+}$, Pb$^{2+}$, $Zn^{2+}$ and Cu$^{2+}$ ions were determined in aqueous solution by potentiometry and compared with 1, 12-bis(2-pyridyl)-2,5,8, 11-tetra-azadodecane(Pytrien) of pyridyl-containing ligand. The effect stability constants of ligands and metal ion for removal of heavy metals in aqueous solution were described.

• 한국정밀공학회지
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• 제15권1호
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• pp.117-129
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• 1998

Micro-hole drilling (holes less than 0.5 mm in diameter with aspect ratio larger than 10) is recently having more attention in a wide spectrum of precision production industries. Alternative methods such as EDM. laser drilling, etc. can sometimes replace the mechanical micro-hole drilling but are not acceptable in PCB manufacture because of the inferior hole quality and accuracy. The major difficulties in micro-hole drilling are related to small signal to noise ratios, wandering motions of the inlet stage, high aspect ratios, high temperatures and so forth. Of all the difficulties. the most undesirable one is the increase of drilling force as the drill proceeds deeper into the hole. This is caused mainly from the chip effects. Peck-drilling is thus widely used for deep hole drilling despite that it suffers from low productivity. In the paper, a method of cutting force regulation is proposed to achieve continuous drilling. A PD and a sliding mode control algorithms were implemented through controlling the spindle rotating frequency. Experimental results show that the sliding mode control reduces the nominal cutting force and the variation of the cutting force better than the PD control. The advantages of the regulation, such as increase of drill life, fast stabilization of a wandering motion, and the precise positioning of the hole are verified in experiment.

• 한국통신학회논문지
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• 제36권12B호
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• pp.1595-1600
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• 2011

IM/DD 방식을 이용한 가시광 무선 통신의 성능 저하를 발생시키는 인공광과 태양광에 의한 잡음 레벨을 분석하였다. 통신 성능을 확인하기 위해 LED에 QPSK로 변조된 50ksymbol/sec의 신호를 2MHz의 부반송파에 전송하였으며 PD를 통해 수신된 신호의 EVM과 스펙트럼을 분석하였다. 또한 차광막을 이용하여 신호의 성능을 향상시켰으며 이를 통해 IM/DD방식으로 실외 가시광 통신이 가능함을 확인하였다.

• Imaging Science in Dentistry
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• 제44권3호
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• pp.193-198
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• 2014

Purpose: The present study was aimed to investigate the variation of soft palate morphology in different age and gender groups. The correlations of radiographic velar length (VL), velar width (VW), pharyngeal depth (PD), and Need's ratio with soft palate variants were also studied in the North Indian subpopulation. Materials and Methods: The study sample consisted of 300 subjects aged between 15 and 45 (mean: 31.32) years. The velar morphology on lateral cephalograms was examined and grouped into six types. The results obtained were subjected to a statistical analysis to find the correlation between variants of the soft palate with gender and different age groups. Results: The most frequent type of soft palate was leaf shaped (48.7%), and the least common was crook shaped (3.0%) among both the genders and various age groups, showing a significant correlation. The mean VL, VW, and PD values were significantly higher in males and significantly correlated with the types of soft palate. A significant correlation was observed between the mean VL, VW, PD, and Need's ratio with various age groups, showing an inconsistent pattern with an increase in age. The types of soft palate, gender, and Need's ratio were also significantly correlated, with an overall higher mean value of the Need's ratio among female subjects and the S-shaped soft palate. Conclusion: The knowledge of a varied spectrum of velar morphology and the variants of the soft palate help in a better understanding of the velopharyngeal closure and craniofacial anomalies.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.798-803
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• 2010

This paper describes the characteristics of electromagnetic wave propagation in power transformer. A transformer which is similar to 154 kV single phase on-site transformer unit was provided for the purpose of the experiment. The 12 dielectric windows on the transformer enclosure to install UHF (ultra high frequency) sensors and the full scale mock ups of winding and the core were also equipped in the transformer. Every sensors to be installed to the transformer was tested and verified whether they show same characteristics or not before the experiment. A discharge gap which was used as a PD (partial discharge) source moved to several necessary locations in the transformer to simulate dielectric defects. Propagation times of electromagnetic wave signal from PD source to sensors decided by the routes of both reflection phenomenon and diffraction phenomenon were compared each other. The experimental results showed propagation route of the PD signal makes an effect on the frequency spectrum of front part of the signal and the magnitude of the signal and propagation time of the signal when the signal is captured on the sensor.

• 한국산학기술학회논문지
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• 제10권7호
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• pp.1556-1567
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• 2009

자동차 주요 생산국인 우리나라 보행자의 교통사고 사망률은 인구 10만 명 당 5.28명으로서 OECD 평균의 약 2.5배에 달한다. 보행자를 감지하고 운전자에게 경보를 보내주는 시스템이 개발되어 보행자 교통사고를 조금이라도 줄일 수 있다면, 그 자체만으로도 보행자 감지 시스템의 가치는 충분하기 때문에 PDS에 대한 관심이 높아지고 있다. 보행자 교통사고율은 야간에 더 높기 때문에, 야간 보행자 감지 시스템에 주요 자동차 회사들이 관심을 두고 있으나, 그들은 일반적으로 고가의 나이트비젼 또는 복합적 센서를 사용하는 장비를 채택하고 있다. 본 논문에서는 PDS에서 나이트비젼 대신에, 넓은 동적 범위를 갖는 가시 스펙트럼 대역 흑백 카메라 한 대만을 사용하는 야간 보행자 감지 기법을 제안한다. 서로 다른 환경에서 촬영된 야간 동영상들에 대해 실험한 결과, 제안 알고리듬이 에지가 어느 정도 정확하게 검출되는 상황이라면 정확한 보행자 검출 성능을 보였다.