• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.68.1-68.1
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• 2011

Type Ia 초신성을 이용한 거리측정은 암흑에너지의 존재를 암시하는 가장 직접적인 증거를 제시하며, 이것은 Type Ia 초신성의 밝기가 표준화된 광도에서 모두 같다고 하는 가정하에서 성립한다. 하지만 최근 표준화된 Type Ia 초신성의 광도가 모은하의 특성과 상관관계가 있음을 보이는 연구결과들이 등장하여 이러한 가정에 대한 의문이 제기되었다. Gallagher et al. (2008)은 조기형 모은하의 나이와 중원소 함량이 Type Ia 초신성의 밝기와 갖는 상관관계에 대하여 시도하였으나, 전체 은하의 표본갯수와 나이측정, 그리고 Hubble Residual을 구하는 과정에서 오차로 인한 한계가 있었다. 우리는 Type Ia 초신성에 나타나는 광도진화효과를 확인하기 위하여 가까운 거리에 있는 Type Ia 초신성의 조기형 모은하에 대하여 CTIO 1.5m, 보현산 1.8m, LCO 2.5 m 망원경의 긴 슬릿 분광기를 이용한 분광관측을 수행하고 있다. 관측된 모은하의 분광스펙트럼으로부터 방출선에 의한 영향을 제거한 뒤, 흡수선의 세기를 이용하여 Lick/IDS indices를 측정하고 있으며 이를Yonsei Evolutionary Population Synthesis model (YEPS)과 비교하여 은하의 나이와 중원소 함량을 추정하였다. 이 결과를 이용하여 Type Ia 초신성의 Hubble Residual과 항성종족의 나이 및 중원소 함량간의 상관관계를 통하여 Type Ia 초신성의 광도진화효과에 대해 분석할 예정이다. 현재까지 조기형 모은하 20여개에 대한 분광관측을 진행하였으며, 앞으로 긴 슬릿 분광기와 McDonald 2.7m 망원경의 VIRUS-P를 이용한 모은하의 분광관측을 추가로 수행할 예정이다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.272-279
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• 2018

This study was conducted to compare the muscle strength, muscle power, and H/Q ratio according to energy system contribution in athletes participating in various sports. Subjects of the study were assigned into an Anaerobic Exercise Group (AEG, n=60; Short-Distance, Weight Lifting, Jumping, Throwing, Bowling, Golf) and an Endurance Exercise Group (EEG, n=60; Modern Pentathlon, Field Hockey, Handball, Cycle, Boxing, Rowing) groups. Isokinetic peak torque/body weight% and flexor/extensor ratio at 60, 180 deg/sec of knee extension and flexion were measured using an cybex 770. Data analysis was conducted using an independent t-test and one-way ANOVA. Based on the results of this study, there was higher extension, flexion strength and flexion power in the AEG than the EEG (p<0.05). We also confirmed higher muscle strength and muscle power in short distance and jumping athletes than other athletes participating in other events (p<0.05). However, there was no significant difference within the endurance exercise group. The HS ratio was within a stable range of 50% to 60% in all events. Collectively, the outcomes of this study indicate that routine physiological and performance testing can provide measurable benefits for elite athletes and their coaches.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.253-263
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• 2022

A buccal pit is a prominent point-like depression that appears at the cervical end of the mandibular molar developmental grooves. A defective buccal pit can be defined as a buccal pit in which the continuity of the dentinoenamel junction is broken and the pit extends to the dentinal level. This study aimed to determine the frequency of buccal pits and defective buccal pits in un-erupted mandibular first and second molars using cone-beam computed tomography (CBCT). The analysis was performed on CBCT images taken from 417 Korean children and adolescents who visited the Department of Pediatric Dentistry, Yonsei University Dental Hospital between 2004 and 2020. Based on cross-sectional views of CBCT images, buccal pits were categorized into 4 classes according to the depth of the pits. The expression rate of the buccal pits was 29.1%. The prevalence of defective buccal pits was 7.9%. The buccal pits tended to develop bilaterally. To date, this is the most comprehensive study on the frequency of buccal pits with the largest sample size. This was the first attempt worldwide to analyze the depth of the buccal pit using CBCT images and to define a defective buccal pit worldwide.

• The Korean Journal of Financial Studies
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• v.9 no.1
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• pp.189-219
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• 2003

본 연구는 한국증권거래소의 현금배당락조치 폐지 이전과 1998년 7월 현금배당락 조치 폐지 이후의 표본을 이용하여 인위적인 거래소의 배당락조치 변경이 배당락일의 주가행태에 미치는 효과를 분석하였다. 실증분석 결과 현금배당락조치 폐지 이후 거래소 배당락기준가격의 오차는 예상대로 더욱 확대된 것으로 나타났다. 두 기간 모두 배당락일의 주가가 금기예상실효배당금과 거래소가 배당락조치를 위해 인위적으로 산정한 배당금과의 차이인 거래소 배당락기준가격의 오차를 반영할 수 없었다. 또한, 김성민(1997)과 일관되게 단기차익 거래의 유용성은 표본그룹에 관계없이 금기예상실효배당금에 대한 정보소유자가 연말 폐장일에 배당부종가로 구입하여 배당락일인 연초 개장일에 배당락 종가로 매도하는 것이 배당락 시가로 매도하는 것보다 더 효과적임을 알 수 있었다. 그리고, 이러한 차익거래를 통한 보유기간 세후 수익률은 현금배당락조치 폐지 이전인 1997년(4.7%)에 비해 현금배당락조치 폐지 이후 현금배당락을 시키지 않은 $1998{\sim}1999$년(8.9%) 기간에 더 증가하였다. 단기차익을 위한 차익거래가 실질적으로 이루어 졌는지 연초 배당락일 주변의 초과거래량을 분석한 결과 $1997{\sim}1998$ 회계년도의 배당락일에는 유의적인 양(+)의 초과거래량이 발생하였지만 1999 회계년도의 배당락일에는 유의적인 음(-)의 초과거래량이 발생하여 이에 대한 결론을 내릴 수 없었다. 본 연구는 금기예상현금배당에 대한 완전예측을 가정함으로써 배당락일의 주가하락과 주주총회에서 실현될 주당배당금의 괴리는 차익을 제공할 수 있으나 무위험 차익거래 기회가 아님을 밝혀 둔다.효과적인 것으로 판단되었다. 조사한 모든 일중 및 1일(overnight) 투자수익률에서 옵션 거래량의 상대적 비율에 의거한 투자전략은 통계적으로 유의한 투자수익률의 차이를 가져왔다.e 측정치에 의해 평가했을 때, 회사채가 주식보다 더 우수한 것으로 평가되었으나 Treynor 측정치에 의한 평가를 했을 때는 정기예금이 가장 우수했다. 그리고 Jensen 측정치에 따라 투자대상을 평가했을 때는 회사채와 국채가 주식보다 앞섰다. 마지막으로, 종합적인 평가를 했을 때는 회사채가 주식보다 우수했고 정기예금은 주식과 동일한 수준으로 평가되었다. 유의성은 없었다.의 선도효과가 지배적임을 발견하였다.적 일정하게 하는 소비행동을 목표로 삼고 소비와 투자에 대한 의사결정을 내리고 있음이 실증분석을 통하여 밝혀졌다. 투자자들은 무위험 자산과 위험성 자산을 동시에 고려하여 포트폴리오를 구성하는 투자활동을 행동에 옮기고 있다.서, Loser포트폴리오를 매수보유하는 반전거래전략이 Winner포트폴리오를 매수보유하는 계속거래전략보다 적합한 전략임을 알 수 있었다. 다섯째, Loser포트폴리오와 Winner포트폴리오를 각각 투자대상종목으로써 매수보유한 반전거래전략과 계속거래 전략에 대한 유용성을 비교검증한 Loser포트폴리오와 Winner포트폴리오 각각의 1개월 평균초과수익률에 의하면, 반전거래전략의 Loser포트폴리오가 계속거래전략의 Winner포트폴리오보다 약 5배정도의 높은 1개월 평균초과수익률을 실현하였고, 반전거래전략의 유용성을 충분히 발휘하기 위하여 장단기의 투자기간을 설정할 경우에 6개월에서 36개월로 이동함에 따라 6개월부터 24개월까지는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을

• Applied Microscopy
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• v.27 no.1
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• pp.71-86
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• 1997

The regeneration and differentiation of the cutaneous pigment system in the goldfish, Carassius auratus during the wound healing process were studied with high magnification electron microscope. The cutaneous pigment cells of the normal tissues were composed of three kinds of dermal chromatophores-xanthophores, leucoiphores and melanophores. While xanthophores contain two kinds of pigment granules-pterinosomes and carotenoid vesicles, leucophores and melanophores contain amorphous pigment granules (leucosomes) and oval shaped electron dense melanin pigment granules (melanosomes) respectively. After injury, primary wound healing responses being carried out by migration of epidermal cells and hemocytes spreading over the wound surface at the day of wounding. And at the time of primary wound closure, 5 to 7 days after wounding, rER rich cells-presumably common precursors of dermal chromatophores-immigrated into the wound area. First redifferentiated chromatophores appeared 3 weeks after wounding. Pigment granules of the chromatophores were emerged from the cytoplasmic Golgi complex via rough endoplasmic reticulum. Pinocytotic vesicles which associated with accumulation of pigment material, appeared only at the inner surface of the chromatophores adhering to the rER rich cells, characteristically. The differentiation of each chromatophore in addition to integumental wound repair were accomplished within 4 weeks after wounding at most cases, however the total numbers and densities of these repaired chromatophores still primitive state. Moreover, It has been revealed that complete repair of chromatophores at wounded tissues from burns requirs more than 3 months in normal environment.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.529-540
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• 2015

A cross-over design is frequently used in clinical trials (especially in bioequivalence tests with a parametric method) for the comparison of two treatments. Missing values frequently take place in cross-over designs in the second period. Usually, subjects that have missing values are removed and analyzed. However, it can be unsuitable in clinical trials with a small sample size. In this paper, we compare single imputation methods in a $2{\times}2$ cross-over design when missing values exist in the second period. Additionally, parametric and nonparametric methods are compared after applying single imputation methods. A Monte-Carlo simulation study compares type I error and the power of methods.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.153-161
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• 2017

Branching processes which is used for epidemic dispersion as stochastic process model have advantages to estimate parameters by real data. We have to estimate both mean and dispersion parameter in order to use the negative binomial distribution as an offspring distribution on branching processes. In existing studies on biology and epidemiology, it is estimated using maximum-likelihood methods. However, for most of epidemic data, it is hard to get the best precision of maximum-likelihood estimator. We suggest a Bayesian inference that have good properties of statistics for small-sample. After estimating dispersion parameter we modelled the posterior distribution for 2015 Korea MERS cases. As the result, we found that the estimated dispersion parameter is relatively stable no matter how we assume prior distribution. We also computed extinction probabilities on branching processes using estimated dispersion parameters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.317-322
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• 1982

The biting behaviors of tuna were studied based on the remains of saury (Cololabis saira), which was used as bait, in the stomach contents of tuna. The saury remains were classified into four segmental groups (A-segment: Whole fish; B-segment: anterior partion with head: C-segment: middlepart without both head and tail: D-segment : posterior part without head). The tuna stomachs were independently named and grouped into three subsamples according to bait segments remaining in the stomach. The subsamples have the extra number of the stomach-naming segments and the distributions of the bait tegments are biased from tile random distribution. The distribution of the bait segments except the extra segments are hypothetically assumed to be random, and was subjected to the chi-square test of significance. The inferred conclusions are as follows:1. Most of the tuna having the B-segment had previously taken the C and/or D-segment. 2. The catchability of the yellowfin tuna having the B-segment seems higher than that of the fish having the A-segment in the stomach. 3. Tuna which had two or more bait heads should have taken the extra bait heads without being hooked detaching the head from the hook by biting the Posterior porting of tile bait.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.197-205
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• 2008

In order to estimate mean wind speed in the Gwangyang-Myodo Region, the probability distribution model of extreme values has been used in the statistical analysis of joint distribution probability of daily maximum wind speed and corresponding direction in this paper. For this purpose frequency of daily maximum records at respective stations is inquired into and sample of largest yearly wind speed of sixteen compass direction and non-direction is extracted from daily data of maximum wind speed and appropriate direction of the meteorological observing stations nearby the bridge construction site. These extreme speed records are applied to Gumbel and Weibull distribution model and parameters are estimated through method of moment and method of least squares etc. And also, distribution and parameters are inquired into whether it is fitted through the probability plot correlation coefficient examination. From fitted parameters the largest yearly wind speed of sixteen compass direction and non-direction is extrapolated taking into account factors regarding sample size of data and distance from the bridge construction site according to the appropriate stations.

• Journal of The Korean Association For Science Education
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• v.33 no.6
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• pp.1139-1153
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• 2013

Misconceptions are one of the most important and long-lasting studied themes on science education. It is because their nature is obstinate and settled as well as they corrupt students' understanding of science concepts. This study examines whether preservice elementary school teachers enrolled in biology teaching material research course changed positively on science teaching efficacy and correcting life science misconceptions when they used the handbook developed for this study. The handbook comprises 203 life science concepts surveyed among preservice teachers holding from advanced researches and arranged by 2007 Revised Science Curriculum. 107 preservice elementary school teachers participated in the study. Forty-six (46) of them were assigned to the experimental group and the other 61 to the control group. ANOVA was conducted for analyzing data. Science Teaching Efficacy Belief Instrument (STEBI) and the life science misconception test which was developed for this study, were administrated as assessing instruments for pretest and posttest. The experimental group, using the handbook, acquired higher scores in both tests on statistical significance level than the control group who were not using the handbook. The results indicate the handbook developed for correcting life science misconceptions for this study is effective in enhancing science teaching efficacy and correcting life science misconceptions.