• 천문학회보
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• 제41권1호
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• pp.82-82
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• 2016

To find the relationship between solar flares and halo CMEs using stereoscopic observations, we investigate 182 flare-associated halo CMEs among 306 front-side halo CMEs from 2009 to 2013. We have determined the 3D parameters (radial speed and angular width) of these CMEs by applying StereoCAT to multi-spacecraft data (SOHO and STEREO). For this work, we use flare parameters (peak flux and fluence) taken from GOES X-ray flare list and 2D CME parameters (projected speed, apparent angular width, and kinetic energy) taken from CDAW SOHO LASCO CME catalog. Major results from this study are as follows. First, the relationship between flare peak flux (or fluence) and CME speed is almost same for both 2D and 3D cases. Second, there is a possible correlation between flare fluence and CME width, which is more evident in 3D case than 2D one. Third, the flare fluence is well correlated with CME kinetic energy (CC=0.63). Fourth, there is an upper limit of CME kinetic energy for a given flare fluence (or peak flux). For example, a possible CME kinetic energy ranges from 1030.6 to 1033 erg for a given X1.0 class flare. Our results will be discussed in view of the physical mechanism of solar eruptions.

• 한국광물학회지
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• 제17권2호
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• pp.169-176
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• 2004

오색 온천은 강원도 북동부 지역인 양양군 서면 오색리에 위치하고 있으며 온천 원수의 온도는 약 $42^{\circ}C$이다. 온천 원수는 EC (196 us/cm), $SO_4$ (10.88 mg/L), F (8.19 mg/L), 그리고 Na (37.09 mg/L)로 상당히 높은 값을 나타낸다. 온천 원수가 배출되는 배출구 부근에는 붉은 색과 검은색의 침전물이 형성되고 있다. X-선회절분석 결과 대부분 결정도가 낮은 철 수산화광물에서 관찰되는 회절선과 결정질의 메셀라이트로 구성되어 있다. 전자현미경 관찰 결과 침전물에는 외관상으로 구형과 막대모양의 박테리아와 유사한 형태들이 발견된다.

• 한국세라믹학회지
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• 제34권8호
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• pp.897-907
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• 1997

Thin films of Bi4-xSmxTi3O12(0$\leq$x$\leq$2) were prepared on Pt/Ti/SiO2/Si(100) at $700^{\circ}C$ using spin-coating with sols derived from Bi-Sm-Ti complex alkoxides. From X-ray diffraction analysis, it was observed that Sm-substituted phases resembled ferroelectric Bi4Ti3O12 in structure. Variations of their lattice parameters depending on the amount of Sm-substitution showed that an anomalous structural distortion might exist at x=1. The grain sizes of the thin films decreased from 0.115 ${\mu}{\textrm}{m}$ to 0.078${\mu}{\textrm}{m}$ with increasing the amount of Sm-substitution. The dielectric constants and the remanent polarizations of the thin films decreased with increasing the amount of the Sm-substitution, which were related to decrease of the stereo-active Bi3+ ion contributing to polarization. However, these values were exceptionally high at x=1, compared to those of the other substituted phases. Such an anomaly suggests that the phase of x=1 has 1:1 chemical ordering between Sm and Bi in structure. The thin films of all compositions except x=2 showed ferroelectricity. The thin film of x=2 was paraelectric, whose grains were too fine to exhibit ferroelectricity.

• 천문학회보
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• 제37권1호
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• pp.89.1-89.1
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• 2012

We have investigated a coronal jet observed near the limb on 2010 June 27 by the Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), and Solar Optical Telescope (SOT), and the SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), and on the disk by STEREO-A/EUVI. From EUV (AIA and EIS) and soft X-ray (XRT) images we have identified both cool and hot jets. There was a small loop eruption in Ca II images of the SOT before the jet eruption. Using high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet by about 2 minutes. The cool jet showed helical-like structures during the rising period. According to the spectroscopic analysis, the jet's emission changed from blue to red shift with time, implying helical motions in the jet. The STEREO observation, which enabled us to observe the jet projected against the disk, showed that there was a dim loop associated with the jet. We have measured a propagation speed of ~800 km/s for the dimming front. This is comparable to the Alfven speed in the loop computed from a magnetic field extrapolation of the HMI photospheric field measured 5 days earlier and the loop densities obtained from EIS Fe XIV line ratios. We interpret the dimming as indicating the presence of Alfvenic waves initiated by reconnection in the upper chromosphere.

• 천문학회보
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• 제37권1호
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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.

• 한국세라믹학회지
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• 제42권10호
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• pp.685-690
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• 2005

Pb(Zr,Ti)$O_{3}$Pb($Mn_{1/3}$$Nb_{2/3}$)$O_{3}$ powder was successfully synthesised by high-energy milling method, and the behavior of low­temperature sintering and piezoelectrical properties of Pb(Zr,Ti)$O_{3}$-Pb($Mn_{1/3}$$Nb_{2/3}$)$O_{3}$ ceramics were investigated as a function of mechanical alloying time. In order to confirm whether the Perovskite phase in this composition was formed by mechanical activation technique or not, we performed X-Ray Diffraction pattern analysis (XRD). The microstructure for the sintered samples were characterized using a Scanning Electronic Microscope (SEM). And the piezoelectrical properties ($k_{p}$ and $Q_{m}$) of the sintered samples was measured using HP 4194A impedance analyzer.

• International Journal of Concrete Structures and Materials
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• 제1권1호
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• pp.75-81
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• 2007

The concrete pavement of the Seohae Highway in Korea has suffered from serious distress, only four to seven years after construction. Deterioration due to Alkali-Silica Reaction (ASR) has seldom been reported per se in Korea, because the aggregate used for the cement concrete has been considered safe against alkali-silica reaction so far. The purpose of this study is to examine the deterioration caused by an alkali-silica reaction of concrete pavement in Korea. The investigation methods included visual inspection and Automatic Road Analyzer (ARAN) analysis of surface cracks, coring for internal cracks, stereo microscopic analysis, scanning electronic microscope (SEM) analysis, and electron dispersive X-ray spectrometer (EDX) analysis. The results are presented as follows: the crack pattern of the concrete pavement in Korea was longitudinal cracking, map cracking or D-cracking. Local areas of damage were noticed four to five years after construction. The cracks started from edges or joints and spread out to slabs. The most intensive cracking was observed at the intersection of the transverse and longitudinal joints. Where cracking was the most intense, pieces of concrete and aggregate had spalled away from top surface and joint interface area. The progress of deterioration was very fast. The reaction product of alkali-silica gel was clearly identified by its generally colorless, white, or very pale yellow hue seen through a stereo optical microscopy. The typical locations of the reaction product were at the interface between aggregate and cement paste in a shape of a rim, within aggregate particles in the cracks, and in the large void in the cement paste. Most of the white products were found at interface or internal aggregates. SEM and EDX analysis confirmed that the white gel was a typical reaction product of ASR. The ASR gel in Korea mainly consisted of Silicate (Si) and Potassium (K) from the cement. The crack in the concrete pavement was caused by ASR. It seems that Korea is no longer safe from alkali-silica reaction.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.576-577
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• 2005

In this paper, the oxidization characteristics were analyzed according to the shapes of Residual Current Protective Device(RCD) contacts. RCD is an electrical safety device specially designed to immediately switch the electricity off when electric leakage is detected at a level harmful to a person using electrical equipment. The shapes of RCD contacts are a little bit different according to the models. When RCD is turned on, stationary and moving contact do not fit together. So, it can cause the increase of contact resistance. To discover the deterioration characteristics of RCD contacts by switching repetition, the contacts were analyzed by stereo microscope, Scanning Electron Microscope(SEM) and Energy Dispersive X-ray Spectrometer(EDS).

• 천문학회보
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• 제44권1호
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• pp.51.2-51.2
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• 2019

Multi-wavelength observations become very popular in astronomy. Even though there are some correlations among different sensor images, it is not easy to translate from one to the other one. In this study, we apply a deep learning method for image-to-image translation, based on conditional generative adversarial networks (cGANs), to solar images. To examine the validity of the method for scientific data, we consider several different types of pairs: (1) Generation of SDO/EUV images from SDO/HMI magnetograms, (2) Generation of backside magnetograms from STEREO/EUVI images, (3) Generation of EUV & X-ray images from Carrington sunspot drawing, and (4) Generation of solar magnetograms from Ca II images. It is very impressive that AI-generated ones are quite consistent with actual ones. In addition, we apply the convolution neural network to the forecast of solar flares and find that our method is better than the conventional method. Our study also shows that the forecast of solar proton flux profiles using Long and Short Term Memory method is better than the autoregressive method. We will discuss several applications of these methodologies for scientific research.

• 한국산업보건학회지
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• 제19권3호
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• pp.213-232
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• 2009

This document was prepared to review and summarize the analytical methods for airborne and bulk asbestos. Basic principles, shortcomings and advantages for asbestos analytical instruments using phase contrast microscopy(PCM), polarized light microscopy(PLM), X-ray diffractometer (XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM) were reviewed. Both PCM and PLM are principal instrument for airborne and bulk asbestos analysis, respectively. If needed, analytical electron microscopy is employed to confirm asbestos identification. PCM is used originally for workplace airborne asbestos fiber and its application has been expanded to measure airborne fiber. Shortcoming of PCM is that it cannot differentiate true asbestos from non asbestos fiber form and its low resolution limit ($0.2{\sim}0.25{\mu}m$). The measurement of airborne asbestos fiber can be performed by EPA's Asbestos Hazard Emergency Response Act (AHERA) method, World Health Organization (WHO) method, International Standard Organization (ISO) 10312 method, Japan's Environmental Asbestos Monitoring method, and Standard method of Indoor Air Quality of Korea. The measurement of airborne asbestos fiber in workplace can be performed by National Institute for Occupational Safety and Health (NIOSH) 7400 method, NIOSH 7402 method, Occupational Safety and Health Administration (OSHA) ID-160 method, UK's Health and Safety Executive(HSE) Methods for the determination of hazardous substances (MDHS) 39/4 method and Korea Occupational Safety and Health Agency (KOSHA) CODE-A-1-2004 method of Korea. To analyze the bulk asbestos, stereo microscope (SM) and PLM is required by EPA -600/R-93/116 method. Most bulk asbestos can be identified by SM and PLM but one limitation of PLM is that it can not see very thin fiber (i.e., < $0.25{\mu}m$). Bulk asbestos analytical methods, including EPA-600/M4-82-020, EPA-600/R-93/116, OSHA ID-191, Laboratory approval program of New York were reviewed. Also, analytical methods for asbestos in soil, dust, water were briefly discussed. Analytical electron microscope, a transmission electron microscope equipped with selected area electron diffraction (SAED) and energy dispersive X-ray analyser(EDXA), has been known to be better to identify asbestiform than scanning electron microscope(SEM). Though there is no standard SEM procedures, SEM is known to be more suitable to analyze long, thin fiber and more cost-effective. Field emission scanning electron microscope (FE-SEM) imaging protocol was developed to identify asbestos fiber. Although many asbestos analytical methods are available, there is no method that can be applied to all type of samples. In order to detect asbestos with confidence, all advantages and disadvantages of each instrument and method for given sample should be considered.