• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.54.3-54.3
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• 2018

In this study, we perform a statistical investigation on the kinematic classication of 4264 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 four dierent classication methods by acceleration, fractional speed variation, height contribution, and visual inspection. Our major results are 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 classied by the last three methods are consistent with one another. Fourth, according to the last three methods, 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.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.81.3-81.3
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• 2016

We examine whether the observational stand-off distance ratios of CMEs and their associated ICMEs could be explained by theoretical model or not. For this, we select 16 CME-ICME pairs from September 2009 to October 2012 with the following conditions: (1) limb CMEs by SOHO and their associated ICMEs by twin STEREO spacecraft and vice versa when both spacecraft were roughly in quadrature; (2) the faint structure ahead of a limb CME is well identified; and (3) its associated ICME clearly has a sheath structure. We determine the observational stand-off distance ratios of the CMEs by using brightness profiles from LASCO-C2 (or SECCHI-COR2) observations and those of the ICMEs by solar wind data from STEREO-IMPACT/PLASTIC (or OMNI database) observations. We also determine the theoretical stand-off distance ratios of the CME-ICME pairs using semi-empirical relationship based on the bow shock theory. We find the following results. (1) Observational CME stand-off distance ratio decreases with increasing Mach number at the Mach numbers between 2 and 6. This tendency is consistent with the results from the semi-empirical relationship. (2) The observational stand-off distance ratios of several ICMEs can be explained by the relationship.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.58.2-58.2
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• 2018

Theoretically, the magnetic helicity transport flux through the solar surface into the upper atmosphere can be estimated indefinitely precisely by magnetic field footpoint tracking if the observational resolution is infinitely fine, even with magnetic flux emergence or submergence. In reality, the temporal and spatial resolutions of observations are limited. When magnetic flux emerging or submerging, the footpoint velocity goes to infinity and the normal magnetic field vanishes at the polarity inversion line. A finite observational resolution thus generates a blackout area in helicity flux estimation near the polarity inversion line. It is questioned how much magnetic helicity is underestimated with a footpoint tracking method due to the absence of information in the blackout area. We adopt the analytical models of Gold-Hoyle and Lundquist force-free flux ropes and let them emerging from below the solar surface. The observation and the helicity integration can start at different emerging stages of the flux rope, i.e., the photospheric plane initially cuts the flux rope at different levels. We calculate the magnetic helicity of the flux rope below the photospheric level, which is eventually to emerge, except the helicity hidden in the region to be swept by the blackout area with different widths. Our calculation suggests that the error in the integrated helicity flux estimate is about half of the real value or even larger when small scale magnetic structures emerge into the solar atmosphere.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.128.2-128.2
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• 2012

Spectro-polarimetry is the most powerful technique for deducing the magnetic structure of the Sun. Stokes vector allow us to infer the physical conditions in the solar atmosphere prevailing during the line formation. Inversion codes are the main tool to extract this information from the Stokes spectra. This study will focus on measurements of the chromospheric He I 1083.0 nm triplet and the photospheric Si I 1082.7 nm line. A spectropolarimetric data set of sunspots, obtained with the German Vacuum Tower Telescope (VTT) at the Teide observatory on Tenerife, is analyzed using an inversion technique. We will introduce the German Vacuum Tower Telescope and the inversion code HeLix, and will show data sets that are analyzed by HeLix. Finally I made variety plots and maps for understanding photospheric and chromospheric layers of sunspots.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.64.3-64.3
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• 2015

We have developed a set of daily solar flare peak flux forecast models for strong flares using multiple linear regression and artificial neural network methods. We consider input parameters as solar activity data from January 1996 to December 2013 such as sunspot area, X-ray flare peak flux and weighted total flux of previous day, and mean flare rates of McIntosh sunspot group (Zpc) and Mount Wilson magnetic classification. For a training data set, we use the same number of 61 events for each C-, M-, and X-class from Jan. 1996 to Dec. 2004, while other previous models use all flares. For a testing data set, we use all flares from Jan. 2005 to Nov. 2013. The best three parameters related to the observed flare peak flux are weighted total flare flux of previous day (r = 0.51), X-ray flare peak flux (r = 0.48), and Mount Wilson magnetic classification (r = 0.47). A comparison between our neural network models and the previous models based on Heidke Skill Score (HSS) shows that our model for X-class flare is much better than the models and that for M-class flares is similar to them. Since all input parameters for our models are easily available, the models can be operated steadily and automatically in near-real time for space weather service.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.66.2-66.2
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• 2018

The probability distribution function of column density (N-PDF) has been used for studying the characteristics of molecular clouds. In particular, the properties of N-PDF can reveal the nature of turbulence and gravity inside the molecular cloud. We use the dust continuum emission at $450{\mu}m$ and $850{\mu}m$ observed as part of the JCMT Gould Belt Survey (GBS) (Mairs et al. 2016), the 12CO J=1-0 line observed with the 45 m telescope at Nobeyama Radio Observatory (NRO) (Shimajiri et al. 2011), 13CO, C18O and HCO+ J=1-0 observed with the 13.7 m telescope at Taeduk Radio Astronomy Observatory (TRAO), as part of the TRAO key science project, "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale" (TIMES; PI: Jeong-Eun Lee). We here present the N-PDFs derived from the continuum and the molecular line emission toward the Orion A molecular cloud and compare their behaviors in order to investigate the chemical and optical depth effects on the N-PDF.

• The Bulletin of The Korean Astronomical Society
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• v.34 no.2
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• pp.32.2-32.2
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• 2009

• Journal of the Korean Institute of Educational Facilities
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• v.17 no.3
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• pp.33-40
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• 2010

This paper considered 1) the relation between the number of student and the floor area of the school building facility, 2) the situation and the distribution of the school building facilities area, 3) the position between the district office of education by the school building facilities composition. Data were collected from 529 elementary school in seoul. 1) The number of student is have not an influence on the floor area of the school building facility in the middle school. 2) The floor area of the school building facilities per 1 student of the jungbu district office of education is larger than other the district office of education and distribution of area is wide. 3) As the position between the district office of education by the school building facilities composition is considered by principal component analysis, the maintenance of the need space is late in the gangdong gangseo district office of education, maintenance of support space is late in the gangdong dongbu district office of education, the maintenance of management space is late in the seobu bukbu district office of education.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.56.2-56.2
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• 2015

본 연구에서는 미국 맥도날드 천문대 (Mcdonald Observatory)에 있는 82인치 Otto Struve 망원경의 가이드 망원경으로 사용하기 위해 2개의 반사경을 이용해 구경이 100 mm이고 유효초점거리가 800 mm인 비축 반사망원경을 설계하였다. 비축 반사경은 일반적인 축 대칭인 반사경보다 가공이 매우 어렵기 때문에 형상 정밀도의 요구량을 알 수 있다면 비축 반사경을 가공하는 과정에서 시간과 비용을 절약할 수 있다. 광학계가 수차가 잘 보정된 회절한계의 성능이기 때문에 엔서클드 에너지 직경(Encircled Energy Diameter) 분석을 통해 민감도 분석을 하였다. 광학설계 소프트웨어인 CodeV를 사용하여 80 % 에너지가 $20{\mu}m$ 내에 들도록 공차한계로 설정하였으며, 기준 파장은 $587.56{\mu}m$이다. 또한 부경과 초점 면 사이의 거리를 보상자로 설정하여 공차가 광학계의 성능에 미치는 영향을 최소화하였다. 민감도 분석은 반사경의 위치, 회전, 그리고 반사경의 형상 정밀도에 대해 수행하였다. 분석 결과, 반사경의 위치와 각도는 일반적인 제작 및 조립 공차보다 매우 작은 것을 확인하였다. 그리고 형상정밀도는 주경이 부경보다 민감하였으며 자승 제곱 평균제곱근 (root-mean-square) 32 nm로 가장 민감한 결과가 나왔다.

• The Journal of Advanced Prosthodontics
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• v.2 no.2
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• pp.61-63
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• 2010

If orthodontists and restorative dentists establish the interdisciplinary approach to esthetic dentistry, the esthetic and functional outcome of their combined efforts will be greatly enhanced. This article describes satisfying esthetic results obtained by the distribution of space for restoration by orthodontic treatment and porcelain laminate veneers in uneven space between maxillary anterior teeth. It is proposed that the use of orthodontic treatment for re-distribution of the space and the use of porcelain laminate veneers to alter crown anatomy provide maximum esthetic and functional correction for patients with irregular interdental spacing.