• Journal of The Korean Astronomical Society
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• v.55 no.3
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• pp.67-74
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• 2022

In this study, we perform a statistical investigation of the kinematic classification of 4,264 coronal mass ejections (CMEs) from 1996 to 2015 observed by SOHO/LASCO C3. Using the constant acceleration model, we classify these CMEs into three groups: deceleration, constant velocity, and acceleration motion. For this, we devise three different classification methods using fractional speed variation, height contribution, and visual inspection. The main results of this study can be summarized as follows. First, the fractions of three groups depend on the method used. Second, about half of the events belong to the groups of acceleration and deceleration. Third, the fractions of three motion groups as a function of CME speed are consistent with one another. Fourth, the fraction of acceleration motion decreases as CME speed increases, while the fractions of other motions increase with speed. In addition, the acceleration motions are dominant in low speed CMEs whereas the constant velocity motions are dominant in high speed CMEs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.312-315
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• 2004

In this paper we investigated the behavior of low molecular weight silicone fluids in silicone rubber by W treatment with solvent-extraction and GPC. It was shown that LMW quantity which was extracted by solvent-extraction was decreased in UV treatment time. $200{\sim}450\;g/mol$ distribution of LMW silicone fluid was contributed to recovery. It was similar to result from corona discharge. Morphological analysis was investigated by scanning electron microscope(SEM) and X-ray diffraction (XRD). The behavior of LMW silicone fluids in silicone rubber which was contributed to recovery was discussed.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.69.2-69.2
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• 2014

To estimate free magnetic energy stored in an active region is a key to the quantitative prediction of activity observed on the Sun. This energy is defined as an excess over the potential energy that is the lowest energy taken by a magnetic structure formed in the solar atmosphere including the solar corona. It is, however still difficult to derive the configuration of a coronal magnetic field only by observations, so we have to use some observable quantity to estimate free magnetic energy. Recently, by performing a coordinated series of three-dimensional magnetohydrodynamic simulations of an emerging flux tube that transfers intense magnetic flux to the solar atmosphere we have found an universal power-law relation between free magnetic energy and emerged magnetic flux, the latter of which is a possibly observed quantity. We further investigate what causes this relation through a comparison with a model of linear force-free field.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2179-2181
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• 2005

An experimental study on the water plasma characteristics of removal efficiency for organic contaminants in dye waste water has been investigated. In this study, dielectric barrier discharging electrodes with round shape have disposed cross each other in reactor, and pulse power was supplied to between each electrodes. Its output pulse voltage range is from 0[V] to 30[kV] and output frequency range is from 100[Hz] to 2[kHz]. Using proposed system, High frequency discharge is tested in the mixed Tone(air and water) and the space distribution of streamer corona plasma is observed. In spite of the increasement of voltage and frequency, the proposed system have a stable operation characteristics. It is verified by the experimental results.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1868-1869
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• 2005

이 논문은 반도전 실리콘 고무 표면에 코로나 방전 처리하여 이종의 실리콘 고무와의 접착 특성을 나타낸 것이다. 반도전 실리콘 고무 표면 상태를 발수성 등급에 따른 분류와 FTIR(Fourier Transform Infrared Spectroscopy)를 사용하여 평가하였다. 표면 상태 변화에 따른 반도전 실리콘 고무의 접착 특성은 T-peel test로 접착강도를 시험하였다. 실험 결과 고에너지의 코로나 방전으로 반도전 실리콘 고무의 결합쇄가 절단되었고 이 부분에 산소가 결합되어 극성 관능기를 생성하여 표면을 산화시켰다. 이러한 표면 상태 변화에 따른 접착강도는 초기 상태일 때 보다 코로나 방전 처리 후 증가하는 것을 확인 할 수 있었다. 이 논문을 통하여 코로나 방전 처리는 이종 계면의 접착 특성을 향상시킬 수 있으며, 이종 계면에서 발생하는 절연 파괴 전압을 높여 전기절연 성능을 향상시키는데 도움이 될 것이다.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.78.3-79
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• 2021

Coronal Diagnostic Experiment (CODEX) is a diagnostic coronagraph developed by the Korea Astronomy and Space Science Institute and the NASA Goddard Space Flight Center (GSFC) to be deployed in 2023 on the International Space Station (ISS). It is designed to obtain simultaneous measurements of electron density, temperature, and velocity in the 2.5 - 10 solar radius range using multiple filters. The filters are mounted in two filter wheel assemblies (FWAs), which have five filter positions each. One position of each FWA is occupied by windows, and remaining eight positions are occupied by three bandpass filters for temperature, two bandpass filters for velocity, one Ca II H filter for F-corona, one broadband filter for fast imaging and density, and one neutral density (ND) filter for direct Sun viewing and safety.

• Journal of The Korean Astronomical Society
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• v.50 no.4
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• pp.125-129
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• 2017

We investigate the solar cycle variation of microwave and extreme ultraviolet (EUV) intensity in latitude to compare microwave polar brightening (MPB) with the EUV polar coronal hole (CH). For this study, we used the full-sun images observed in 17 GHz of the Nobeyama Radioheliograph from 1992 July to 2016 November and in two EUV channels of the Atmospheric Imaging Assembly (AIA) $193{\AA}$ and $171{\AA}$ on the Solar Dynamics Observatory (SDO) from 2011 January to 2016 November. As a result, we found that the polar intensity in EUV is anti-correlated with the polar intensity in microwave. Since the depression of EUV intensity in the pole is mostly owing to the CH appearance and continuation there, the anti-correlation in the intensity implies the intimate association between the polar CH and the MPB. Considering the report of Gopalswamy et al. (1999) that the enhanced microwave brightness in the CH is seen above the enhanced photospheric magnetic field, we suggest that the pole area during the solar minimum has a stronger magnetic field than the quiet sun level and such a strong field in the pole results in the formation of the polar CH. The emission mechanism of the MPB and the physical link with the polar CH are not still fully understood. It is necessary to investigate the MPB using high resolution microwave imaging data, which can be obtained by the high performance large-array radio observatories such as the ALMA project.

• Journal of The Korean Astronomical Society
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• v.54 no.2
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• pp.61-70
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• 2021

We investigate 20 post-coronal mass ejection (CME) blobs formed in the post-CME current sheet (CS) that were observed by K-Cor on 2017 September 10. By visual inspection of the trajectories and projected speed variations of each blob, we find that all blobs except one show irregular "zigzag" trajectories resembling transverse oscillatory motions along the CS, and have at least one oscillatory pattern in their instantaneous radial speeds. Their oscillation periods are ranging from 30 to 91 s and their speed amplitudes from 128 to 902 km s-1. Among 19 blobs, 10 blobs have experienced at least two cycles of radial speed oscillations with different speed amplitudes and periods, while 9 blobs undergo one oscillation cycle. To examine whether or not the apparent speed oscillations can be explained by vortex shedding, we estimate the quantitative parameter of vortex shedding, the Strouhal number, by using the observed lateral widths, linear speeds, and oscillation periods of the blobs. We then compare our estimates with theoretical and experimental results from MHD simulations and fluid dynamic experiments. We find that the observed Strouhal numbers range from 0.2 to 2.1, consistent with those (0.15-3.0) from fluid dynamic experiments of bluff spheres, while they are higher than those (0.15-0.25) from MHD simulations of cylindrical shapes. We thus find that blobs formed in a post-CME CS undergo kinematic oscillations caused by fluid dynamic vortex shedding. The vortex shedding is driven by the interaction of the outward-moving blob having a bluff spherical shape with the background plasma in the post-CME CS.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.54-61
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• 2013

UV-IR camera is being used for predictive maintenance of high voltage equipment together with measurement of temperature on localized heat and corona discharge. This paper was suggested the judgement method that is the discharge count, UV image pattern and discharge matching rate to apply the UV-IR camera on power facility. The discharge count method is counted by UV image pixel value. the UV image pattern method is determined by the UV image shape using neural network algorithm method, separated by Sunflower, Jellyfish, Ameba. The UV discharge matching is compare the breakdown the UV image size and measuring UV image size according to distance.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.20-20
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• 2003

Purpose： To investigate the difference of fractional anisotropy (FA) values between 6- and 25-direction diffusion tensor images (DTI) in normal adult brain. Materials and Methods： DTI was peformed in 28 normal subjects (15 subjects with 6-direction, 13 subjects with 25-direction) in a 1.5 T MR system. DTI was done with SE-EPI sequence with TR/TE/NEX 10000/84/1, 5mm slice thickness and b=1000 s/mm2. FA values were measured from 8 different anatomical locations which included both cerebral peduncles, both posterior limbs of the internal capsules, both corona radiata, genu and splenium of the corpus callosum. Statistical difference of FA was tested between 6-and 25-direction DTI.