• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.293-300
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• 2014

This paper proposes a novel pattern recognition approach based on the radial basis function (RBF) neural network for identifying insulation defects of high-voltage electrical apparatus arising from partial discharge (PD). Pattern recognition of PD is used for identifying defects causing the PD, such as internal discharge, external discharge, corona, etc. This information is vital for estimating the harmfulness of the discharge in the insulation. Since an insulation defect, such as one resulting from PD, would have a corresponding particular pattern, pattern recognition of PD is significant means to discriminate insulation conditions of high-voltage electrical apparatus. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of cast resin current transformer (CRCT) models. These tests used artificial defects created in order to produce the common PD activities of CRCTs by using feature vectors of field-test PD patterns. The significant features are extracted by using nonlinear principal component analysis (NLPCA) method. The experimental data are found to be in close agreement with the recognized data. The test results show that the proposed approach is efficient and reliable.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1560-1562
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• 2000

The paper reports on a study of the influence of the silicone oils on the tracking and erosion resistance and hydrophobicity of SIR. Two silicone oils(A, B) having different chemical structure were selected in consideration of goof hydrophobicity and processability. Tracking and erosion resistance of SIR was investigated by the rotating wheel dip test (RWDT). In this test tracking and erosion areas due to glow and partial arc discharges cause an increase in the leakage current with an increase in time. Leakage current of SIR was decreased with increasing ratio of oil A/B. SIR was exposed to corona discharges in air and the specimens were analyzed with contact angle. It was observed that the contact angle of SIR was increased gradually in time. The recovery of hydrophobicity was increased with increasing ratio of oil A/B.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권6호
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• pp.288-295
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• 2001

Predischarges in nonuniform electric field stressed by lightning impulse voltagesin SF(sub)6-$N_2$mixtures are initiated by streamer coronas. Due to field ehnancement at a protrusion point of electrodes new ionization processes occur and a precursor, which leads to a first leader, is created. The leader proceeds step by step to the opposite electrode and the final jump bridges the test gap. It was found that the predischarge is propagated with a leader mechanism of stepwise expansion from the predischarge current waveforms measured by a shunt. The predischarge current is closely related to the amplitude and polarity of applied voltages, the gas pressure and the gap geometry. The time intervals between step leaders for the positive and negative polarities were inversely proportional to V.P$^2$. When the gas pressure increases in the positive polarity, statistical time lag to statistical time lag to streamer corona inception increase slightly, but the formative time lag to flashover is significantly decreased.

• 전기학회논문지
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• 제60권2호
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• pp.357-361
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• 2011

The terminal current in voltage driven systems is an essential role for characterizing the pattern of electric discharge such as corona, breakdown, etc. Until now, to evaluate this terminal current, Sato's equation has been widely used in areas of high voltage and plasma discharge. Basically Sato's equation was derived by using the energy balance equation and its final form described physical meaning explicitly. To give more general abilities in Sato's equation, we present a generalized approach by directly using the Poynting's theorem incorporating the finite element method. When the magnetic field effect or the time-dependent voltage source is considered, this generalized energy method can be easily applicable to those problems with any dielectric media such as gas, fluid, and solid. As an alternative approach, the integral Ohm's law resulting in small numerical errors has an ability to be applied to multi-port systems. To test the generalized energy method and integral Ohm's law, first, the results from two prosed methods were compared to those from Sato's approach and an analytic solution in parallel plane electrodes. After verification, the generalized method was applied to the tip-sphere electrodes for evaluating the terminal current with three carriers and the Fowler-Nordheim field emission condition. From these results, we concluded that the generalized energy method can be a consistent technique for evaluating the discharge current with various dielectric materials or large magnetic field.

• 조명전기설비학회논문지
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• 제16권4호
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• pp.46-54
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• 2002

본 논문은 전해수 발생장치내에 이온분리집속 격막을 설치하여 비유전율이 틀리는 유전체구를 충진한 구조로 함으로써 고효율의 강전해수 발생장치를 제안하였다. 염화나트륨이 용해된 수도수와 일반수도수를 원료수로서 본 강전해수 발생장치에 인입하였을 때 충진된 유전체구의 비유전율 변화가 수중 이온분리집속성능에 미치는 영향을 연구 검토하였다. 실험결과로서 본 강전해수 발생장치에 원료수로서 수도수의 유속을 0.5[LPM]으로 인입시키고 구형파 펄스전류를 1.0[A]로 인가하였을 때 pH 3.1과 10.6의 전해수를 얻을 수 있었다. 그리고 염화나트륨이 0.1[wt%]용해된 수도수의 경우 pH 2.8과 11.7의 전해수를 얻었다. 또한 비유전율이 가장 높은 BaTiO$_3$과 같은 유전체구를 전해수 발생장치에 충진한 경우 각각 PH 2.7, 11.7과 pH 2.4, 12.0의 전해수를 얻을 수 있었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권3호
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• pp.215-220
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• 1999

$SO_2$and CO gas removal characteristics of a wire-to-cylinder type nonthermal discharge plasma reactor in various applied voltage (-dc, ac, fast rising pulse and high frequency pulse) and a crossed dc magnetic field have been investigated. The experiment has been emphasized on the oxidizing characteristics of $SO_2$ and CO gas by $O_3$ and the applying of a crossed magnetic field, which would induce the cyclotronic and drift motions of electrons making the residual time longer in the removal airgap space. And it also would enhance the energy of electrons and the electrophysicochemical actions to remove the pollutant gases effectively. It is found thatthe corona onset voltage and the breakdown voltage were decreased with increasing the crossed magnetic field and decrease initial fed $SO_2$and CO concentration. As a result, a higher ozone generation and $SO_2$ and CO gas removal rate of 20[%] can be obtained with -dc, ac and fast rising pulse corona discharges in the crossed dc current-induced magnetic field. But high frequency pulse didn't show effect in applying of a crossed magnetic field.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E3호
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• pp.91-99
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• 2001

Plasma reactor was used to generate a high potential difference between two surfaces of concentric pyrex tubes by electrical current. The annular gap of the reactor was calculated by trial and error from the breakdown voltage equation and set at 0.45 cm. The overall objective of this research was to know the effects of the frequency, humidity, and residence time on the formation of nitrogen oxides in a plasma reactor. The primary voltage varied from 50 to 90 volts and the frequency was varied in increments of 10 Hz from 60 to 650 Hz at the primary voltage of 90. The increase in the secondary voltage was not linear but exponential at high frequencies. At a maximum concentration of about 745 ppm, the frequency and secondary voltage was 600 Hz and 4,200 volts, respectively. All tests for the effects of humidity on NO$_{x}$ production were performed at the optimal setting of 90 colts and 600 Hz frequency. Since the NO$_{x}$ production was not an one dimensional phenomenon, competing reactions were assumed to occur in the discharge chamber. The sharp peak concentration of 1,810 ppm was observed at 38% of relative humidity, The enhanced production was choked off, and the production rate rapidly dropped to 3 ppm at above 40% of relative humidity. It is assumed that the corona attacks the most vulnerable molecules in the reaction chamber before attacking other more lightly bonded molecules, possibly at humidities above 38% and the optimized 90 volt setting. Thus, there was not enough energy left after attacking all water molecules to decompose an appreciable amount of $N_2$. If nitrogen breakdown does not occur, then oxides of nitrogen are not likely to be produced.ced.

• 한국IT서비스학회지
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• 제20권6호
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• pp.45-62
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• 2021

After the COVID-19 outbreak in 2019, the spread of COVID-19 has not been easily caught despite preventive measures in each country. The spread of COVID-19 has hit the world, especially in the economic and tourism sectors. Countries around the world are easing restrictions on the movement of vaccinated people in preparation for the post-corona era. Under the name of "Vaccine Passport," "Vaccination Certificate," and "Digital Health Pass," vaccination measures are being implemented to allow vaccination recipients to use multi-use facilities. However, there is no international agreement on the movement of countries, and each country has its own immigration policy. In order to return to pre-corona daily life, global agreements must be reached from the movement of vaccinated people between countries, and standards and implementation methods must be determined. This study focuses on the implementation and utilization of vaccination certificates suitable for the COVID-19 era. We will look at the spread of COVID-19 and its international response policies. In the case of COVID-19, we will investigate why vaccination certificate installation should be standardized and how far the current standardization has been discussed, and discuss the characteristics of vaccination certificate installation and considerations. In order for the immunization certificate discussed in the previous chapter to be recognized internationally, institutional and technical considerations are identified and security factors that may occur in each implementation are also presented. Finally, the international recognition case of vaccination certificate is discussed, and the method of installation and utilization of vaccination certificate is proposed. This paper can be used as a policy because of its timeliness in studying the standards of vaccination certificates and considerations for international recognition to restore movement between countries in the spread of COVID-19. In addition, if other infectious diseases occur in the future or similar cases where movement between countries is restricted, it can be used as a reference to support the movement of verified people.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제35권3호
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• pp.341-358
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• 2021

2020년 처음 발생한 코로나는 사회 전반에 많은 변화를 초래했다. 이러한 변화에 있어 교육 역시 예외가 아니었다. 학교에서는 사상 유례없는 온라인 개학을 시행했고 학생들과 교사는 충분한 준비 없이 원격수업에 참여해야 했다. 원격수업과 관련하여 관련 자료 개발, 만족도 조사와 같은 연구들이 수행되었으나 실제 학교 현장을 기반으로 한 연구는 없었다. 따라서 본 연구는 2020년부터 원격수업에 참여한 고등학교 학생들을 대상으로 하여 원격수업의 방식 및 만족도를 조사하고 원격수업 만족도와 수학학습과 관련된 하위요소들과의 관계를 탐색하였다. 연구결과 수학 교과에서는 원격수업이 대체로 실시간 쌍방향 수업의 형태로 이루어졌으며 학생들은 수학학습에 만족을 느꼈다. 하지만 원격수업을 지속해야 하는 것의 문제에 있어서 어느 정도 상반된 의견을 표명하였다. 또한, 통계분석 결과 원격수업에 대한 만족도에 따라 수학학습 의지, 전략, 수학에 대한 가치, 학습의욕 등에서 차이가 나타나는 것으로 드러났다.

• 디지털융복합연구
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• 제19권3호
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• pp.161-166
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• 2021

거시경제는 한 나라의 경제 전반의 움직임을 나타내는 개념으로 경제주체인 기업, 정부, 가계경제 활동 전반에 영향을 미친다. 거시경제는 국민소득, 물가, 실업, 통화, 금리, 원자재 등의 변화를 살펴보면 경제 주체들의 행위와 상호작업이 제품과 서비스의 가격에 영향을 파악할 수 있다. 미국연방준비제도(FED)는 코로나 경제침체를 극복하기 위한 다양한 경기부양책을 내 놓으며, 세계경제를 이끌고 있다. 현재 코로나로 인한 주가가 2020년3월20일에 지속적으로 하락하였지만, FED의 강력한 경지부양책인 양적완화로 미국의 S&P500지수는 3월 23일이후 반등을 시작해 12월 15일 3,694.62까지 회복에 성공했다. 따라서 주가의 예측을 기업의 재무제표로 판단하는 것이 아니라 거시경제지표에 따른 FED의 경기부양책이 더 영향을 미치고 있는 실정이다. 따라서 본 연구는 FED의 경기부양책과 주가에 미치는 영향을 분석하여 주식투자에 손실을 줄이고 건전한 투자 정착을 위해 본 연구를 진행하였다.