• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.43.1-43.1
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• 2021

In this study, we suggest a new method to estimate the mass of a halo coronal mass ejection (CME) using synthetic CMEs. For this, we generate synthetic CMEs based on two assumptions: (1) the CME structure is a full ice-cream cone, (2) the CME electron density follows a power-law distribution (ρ_cme=ρ₀r^-n). The power-law exponent n is obtained by minimizing the root mean square error between the electron number density distributions of an observed CME and the corresponding synthetic CME at a position angle of the CME leading edge. By applying this methodology to 57 halo CMEs, we estimate two kinds of synthetic CME mass. One is a synthetic CME mass which considers only the observed CME region (M_cme1), the other is a synthetic CME mass which includes both the observed CME region and the occulted area larger than 4 solar radii (M_cme2). From these two cases, we derive conversion factors which are the ratio of a synthetic CME mass to an observed CME mass. The conversion factor for M_cme1 ranges from 1.4 to 3.0 and its average is 2.0. For M_cme2, the factor ranges from 1.8 to 5.0 with the average of 3.0. These results imply that the observed halo CME mass can be underestimated by about 2 times when we consider the observed CME region, and about 3 times when we consider the region including the occulted area. Interestingly these conversion factors have a very strong negative correlation with angular widths of halo CMEs.We also compare the results with the CME mass estimated from STEREO observations.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.3-8
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• 2015

In this paper, we propose a blind equalization algorithm based on the error signal linearly combined a constellation-matched error (CME) and a non-constellation-matched error (non-CME). The new error signal was designed to include the non-CME term for reaching initial convergence and the CME term for improving intersymbol interference (ISI) performance of output signals, and it controls the error terms through a combining factor. By controlling the error terms, it generates an appropriate error signal for equalization process and improves convergence speed and ISI cancellation performance compared to those of conventional algorithms. In the simulation for 64-QAM and 256-QAM signals under the multipath channel and additive noise conditions, the proposed method was superior to CMA and CMA+DD concurrent equalization.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.39.2-39.2
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• 2011

In this study we have examined the occurrence probability of solar proton events (SEPs) and their peak fluxes depending two CME parameters, linear speed and angular width. For this we used the NOAA SPE events and their associated CME data from 1997 to 2006. As a result, the probability strongly depends on two parameters as follows. In the case of halo CME whose speed is equal to and faster than 1500km/s, 36.1% are associated with SPEs but in the case of partial halo CME ($120^{\circ}{\leq}AW$ < $359^{\circ}$) whose speed is $400{\leq}V$ < $1000km/s$, only 0.9% are associated with SPEs. When we consider only front-side CMEs, 45.3% are associated with SPEs in the first case and 1.8% are associated with them in the second case. Both of whole CME data group and front-side CME data group have similar tendencies. The probabilities are different as much as 4.9 to 23 times according to the CME speed and 1.6 to 6.5 times to the angular width. We have also examined the relationship between CME speed and proton peak flux as well as its dependence on angular width (partial halo CME and halo CME), longitude (east, center, and west) and direction parameter (< 0.4 and {\geq} 0.4). Our results show that the relationships strongly depend on longitude as well as direction parameter. In addition, the relationship using the radial CME speed based on a cone model has a higher correlation coefficient than that using the projected CME speed.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.43.3-43.3
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• 2019

A coronal mass ejection (CME) mass is generally estimated by the total brightness measured from white-light coronagraph observations. The total brightness are determined from the integration of the Thomson scattering by free electrons of solar corona along the line of sight. It is difficult to estimate the masses of halo CMEs due to the projection effect. To solve this issue, we construct a synthetic halo CME with a power-law density distribution (ρ = ρ₀r^-3) based on a full ice-cream cone model using SOHO/LASCO C3 observations. Then we compute a conversion factor from observed CME mass to CME mass for each CME. The final CME mass is determined as their average value of several CME masses above 10 solar radii. Our preliminary analysis for six CMEs show that their CME mass are well determined within the mean absolute relative error in the range of 4 to 15 %.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.3
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• pp.87-95
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• 2009

As information theoretic learning techniques, error entropy minimization criterion (MEE) and maximum cross correntropy criterion (MCC) have been studied in depth for supervised learning. MEE criterion leads to maximization of information potential and MCC criterion leads to maximization of cross correlation between output and input random processes. The weighted combination scheme of these two criteria, namely, minimization of Error Entropy with Fiducial points (MEEF) has been introduced and developed by many researchers. As an approach to unsupervised, blind channel equalization, we investigate the possibility of applying constant modulus error (CME) to MEE criterion and some problems of the method. Also we study on the application of CME to MEEF for blind equalization and find out that MEE-CME loses the information of the constant modulus. This leads MEE-CME and MEEF-CME not to converge or to converge slower than other algorithms dependent on the constant modulus.

• Journal of Microbiology and Biotechnology
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• v.31 no.12
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• pp.1656-1666
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• 2021

Dental pathogens lead to chronic diseases like periodontitis, which causes loss of teeth. Here, we examined the plausible antibacterial efficacy of copper nanoparticles (CuNPs) synthesized using Cupressus macrocarpa extract (CME) against periodontitis-causing bacteria. The antimicrobial properties of CME-CuNPs were then assessed against oral microbes (M. luteus. B. subtilis, P. aerioginosa) that cause periodontal disease and were identified using morphological/ biochemical analysis, and 16S-rRNA techniques. The CME-CuNPs were characterized, and accordingly, the peak found at 577 nm using UV-Vis spectrometer showed the formation of stable CME-CuNPs. Also, the results revealed the formation of spherical and oblong monodispersed CME-CuNPs with sizes ranged from 11.3 to 22.4 nm. The FTIR analysis suggested that the CME contains reducing agents that consequently had a role in Cu reduction and CME-CuNP formation. Furthermore, the CME-CuNPs exhibited potent antimicrobial efficacy against different isolates which was superior to the reported values in literature. The antibacterial efficacy of CME-CuNPs on oral bacteria was compared to the synergistic solution of clindamycin with CME-CuNPs. The solution exhibited a superior capacity to prevent bacterial growth. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and fractional inhibitory concentration (FIC) of CME-CuNPs with clindamycin recorded against the selected periodontal disease-causing microorganisms were observed between the range of 2.6-3.6 ㎍/ml, 4-5 ㎍/ml and 0.312-0.5, respectively. Finally, the synergistic antimicrobial efficacy exhibited by CME-CuNPs with clindamycin against the tested strains could be useful for the future development of more effective treatments to control dental diseases.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.307-320
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• 1998

We investigate the propagation of Coronal Mass Ejections(CMEs) near the earth with multi-satellite observations. Among the CMEs observed in the near-earth between Nov. 1994 and Nov. 1997, we select two events of Jan. 6-11,1997 and Nov. 4-7, 1997 which were observed by more than 3 satellites when these satellites were located apart with a sufficient distance from each other. We determine the speed and propagation of the two CMEs by calculating the position of each satellite in various coordinates and the onset time of each event. The results show that the speed of CMEs becomes significantly reduced when the perturbation arrives in the magnetosphere. It is also suggested that the propagation of the CMEs is approximated as the -x direction in GSE coordinates in the near-earth space.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.97-97
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• 2012

Hinode/XRT has observed coronal mass ejections (CMEs) since it launched on Sep. 2006. Observing programs of Hinode/XRT, called 'CME watch', perform several binned observations to obtain large FOV observations with long exposure time that allows the detection of faint CME plasmas in high temperatures. Using those observations, we determine the upper limit to the mass of hot CME plasma using emission measure by assuming the observed plasma structure. In some events, an associated prominence eruption and CME plasma were observed in EUV observations as absorption or emission features. The absorption feature provides the lower limit to the cold mass while the emission feature provides the upper limit to the mass of observed CME plasma in X-ray and EUV passbands. In addition, some events were observed by coronagraph observations (SOHO/LASCO, STEREO/COR1) that allow the determination of total CME mass. However, some events were not observed by the coronagraphs possibly because of low density of the CME plasma. We present the mass constraints of CME plasma and associated prominence as determined by emission and absorption in EUV and X-ray passbands, then compare this mass to the total CME mass as derived from coronagraphs.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.62.1-62.1
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• 2017

In space weather forecast, it is important to determine three-dimensional properties of CMEs. Using 29 limb CMEs, we examine which cone type is close to a CME three-dimensional structure. We find that most CMEs have near full ice-cream cone structure which is a symmetrical circular cone combined with a hemisphere. We develop a full ice-cream cone model based on a new methodology that the full ice-cream cone consists of many flat cones with different heights and angular widths. By applying this model to 12 SOHO/LASCO halo CMEs, we find that 3D parameters from our method are similar to those from other stereoscopic methods (i.e., a triangulation method and a Graduated Cylindrical Shell model). In addition, we derive CME mean density (${\bar{\rho}_{CME}}={\frac{M_{total}}{V_{cone}}}$) based on the full ice-cream cone structure. For several limb events, we determine CME mass by applying the Solarsoft procedure (e.g., cme_mass.pro) to SOHO/LASCO C3 images. CME volumes are estimated from the full ice-cream cone structure. For the first time, we derive average CME densities as a function of CME height for several CMEs, which are well fitted to power-law functions. We will compare densities (front and average) of geoeffective CMEs and their corresponding ICME ones.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.50.1-50.1
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• 2019

In coronagraph images, it is often observed that two successive CMEs merge into one another and form complex structures. This phenomenon, so called CME cannibalism caused by the differences in ejecting times and propagating velocities, can significantly degrade forecast capability of space weather, especially if it occur near the Earth. Regarding this, we attempt to analyze the cases that two CMEs are expecting to meet around 1 AU based on their arrival times. For this, we select 13 CME-CME pairs detected by ACE, Wind and/or STEREO-A/B. We find that 8 CME-CME pairs show a shock structure, which means they already met and became one structure. Meanwhile 5 pairs clearly show magnetic holes between two respective shock structures. Based on detailed investigation for each pair and statistical analysis for all events, we can get clues for following questions: 1) How does the solar wind structure change when they are merging? 2) Are there any systematic characteristics of merging process according to the CME properties? 3) Is the merging process associated with the occurrence of energetic storm particles? 4) What causes errors in calculating CME arrival times? Our results and discussions can be helpful to understand energetic phenomena not only close to the Sun but also near the Earth.