• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.578-588
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• 1999

The purpose of this study is to develope the more effective chemistry teaching strategy through analyzing the demanded cognitive levels of contents in high school chemistry I textbooks and the cognitive levels of students who learn these textbooks. For this purpose, the levets of cognitive development stages of 821 second grade students of high schools in Seoul City were anaIyzed using the GALT short version test. The demanded cognitive levels of understanding the contents of chemistry I textbooks in high school were analyzed using the curriculum analysis taxonomy developed by CSMS (Concept in Secondaly Mathematics and Science) program of the Great Britain. The resuIts showed that the proportion of students in the concrete operational stage, the transition stage, and the formal operational stage was l0.7%, 43.0% and 46.3%, respectively. The demanded levels of textbook contents were mostly the early formal operational stages. The concepts demanded the level of the late formal operational stage were 'atomic and molecular weight', 'stoichiometry of chemical reaction', and 'periodic properties of elements'. The results will be helpful for teachers in knowing what concepts are difficult for students to understand and in planning strategies for teaching those concepts. To demonstrate the application of the results obtained in this study, an example of developing teaching strategy which includes the adjustment of cognitive level of contents was shown.

• Communications of Mathematical Education
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• v.29 no.1
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• pp.111-130
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• 2015

The purpose of the study was to investigate the differences between two groups of students according to information recognition styles such as visual learners and linguistic learners. Two instructional methods, algeblocks and factorization formula, were utilized to introduce the factorization. Four students were participated for the study, and two of them were visual learners and the other two were linguistic learners based on learning style test. Interviews and the diagnostic tests were implemented before the instructions which were lasted for 6 sessions. After the instructions all the participants were interviewed and the researchers also interviewed them 5 days later. The results of the study were the followings: 1. All the participants regardless of their learning style revealed that algeblocks were helpful in understanding the factorization. 2. Visual learners were more likely using algeblocks, while the linguistic learners were more enthusiastic and proficient in using formula to solve the problems. 3. Five days later, two types of learning style students revealed different tendencies. Visual learners mainly used algeblocks, and linguistic learners were not enthusiastic about using algeblocks and one of them did not use them at all. 4. Five days later, two visual learners could not remember the formula, but linguistic learners could remember the formula in somewhat different level.

• Communications of Mathematical Education
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• v.32 no.2
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• pp.225-244
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• 2018

Problem solving and its mathematical applications have been increasingly emphasized in school mathematics over the past years. Recently it is recommended that mathematical applications and modelling situations be incorporated into the secondary school curriculum. Many researchers on the approach have been conducted in Korea. This study is planning to investigate and establish the meaning of mathematical modelling and model, mathematical modelling process. And also it does the properties of problem situations introduced and dealt with in mathematical modelling activity. To accomplish this, this study is based on the analysis and comparison of those 24 articles. They are ones which have been published from 2007 to 2017 and are included in the five types of publication. Prior to this study, the previous study was conduct in 2007 with the same purpose. Namely, by the subject of 11 articles and 22 master dissertations published domestically from 1991 to 2005, the analytic and explorative study on the mathematical modelling and its understanding had been conducted.

• The Korean Journal of Applied Statistics
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• v.29 no.1
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• pp.41-59
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• 2016

There have been continuous improvements in human life expectancy. Life expectancy is as a key factor in an aging population and can wreak severe damage on the financial integrity of pension providers. Hence, the projection of the accurate future mortality is a critical point to prevent possible losses to pension providers. However, improvements in future mortality would be overestimated by a typical mortality projection method using the Lee-Carter model since it underestimates the mortality index ${\kappa}_t$. This paper suggests a mortality projection based on the projection of the skewness of the mortality versus the typical mortality projection of the Lee-Carter model based on the projection of the mortality index, ${\kappa}_t$. The paper shows how to indirectly estimate future t trend with the skewness of the mortality and compares the results under each estimation method of the mortality index, ${\kappa}_t$. The analysis of the results shows that mortality projection based on the skewness presents less improved mortality at an elderly ages than the original projection.

• The Korean Journal of Applied Statistics
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• v.30 no.5
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• pp.733-745
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• 2017

Local composite quantile regression is a useful non-parametric regression method widely used for its high efficiency. Data smoothing methods using kernel are typically used in the estimation process with performances that rely largely on the smoothing parameter rather than the kernel. However, $L_2$-norm is generally used as criterion to estimate the performance of the regression function. In addition, many studies have been conducted on the selection of smoothing parameters that minimize mean square error (MSE) or mean integrated square error (MISE). In this paper, we explored the optimality of selecting smoothing parameters that determine the performance of non-parametric regression models using local linear composite quantile regression. As evaluation criteria for the choice of smoothing parameter, we used mean absolute error (MAE) and mean integrated absolute error (MIAE), which have not been researched extensively due to mathematical difficulties. We proved the uniqueness of the optimal smoothing parameter based on MAE and MIAE. Furthermore, we compared the optimal smoothing parameter based on the proposed criteria (MAE and MIAE) with existing criteria (MSE and MISE). In this process, the properties of the proposed method were investigated through simulation studies in various situations.

• Journal of the Korean Data and Information Science Society
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• v.27 no.4
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• pp.935-946
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• 2016

In this paper, we analyzed wage determinants of the vocational high school graduates utilizing both individual-level and work region-level variables. We formulate the models in the way wage determination has multi-level structure in the sense that individual wage is influenced by individual-level variables (level-1) and work region-level (level-2) variables. To incorporate dependency between individual wages into the model, we utilize hierarchical linear model (HLM). The major results are as follows. First, it is shown that the HLM model is better than the OLS regression models which do not take level-1 and level-2 variables simultaneously into account. Second, random effects on sex, maester dummy and engineering dummy variables are statistically significant. Third, the fixed effects on business hours and mean wage of regular job for level-2 variables are statistically significant effect individual-level wages. Finally, parental education level, parental income, number of licenses and high school grade are statistically significant for higher individual-level wages.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.53-67
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• 2014

Numerical modeling is commonly used to reproduce the physical phenomena of dam-break and to compile resulting flood hazard maps. The accuracy of a dam-break model depends on the physical structure that describes the volume of storage, breach formation and progress, input variables, and model parameters. Model input and parameters are subjective in that they are prescribed; hence, caution is needed when interpreting the results. This study focuses on three parameters (breach degree ${\theta}$, shape factor P, and collapse rate k) used when the dam-break model is coupled with FLO-2D (a two-dimensional flood simulation model) to estimate flood coverage and depth etc. The results show that the simulation is sensitive to the shape factor P and the collapse rate k but not to the breach degree ${\theta}$. This study will contribute to reducing flood damage from dam-break disasters in the future.

• Anatomy & Biological Anthropology
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• v.29 no.2
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• pp.35-46
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• 2016

Leonardo da Vinci is remembered as the greatest genius of the Renaissance. He left outstanding achievements as an artist, scientist and inventor, and contributes up to today's science. He ranks the best in a variety of fields, such as botany, mathematics, geology, astronomy, geometry and optics. It has well known that Leonardo is an artist, scientist, inventor and philosopher. And he was a great anatomist that dissected dead bodies and animals directly and left many anatomical drawings. He took an interest in anatomy from the point of view of the artist, which is why the human body structure and function to know the sakes were "ignorant of the anatomy should not be upset." Over time, he became interested in the structure and function of the body, even get the human body in a difficult environment; he dissected many the human bodies directly. His scientific inquiry and infatuation made him as an advanced pioneer for more than 100 years, and got enough level to surpass the artistry. Leonardo left about 1,800 anatomical figures of the muscular, skeletal, vascular, nervous and urogenital system, and they are also very scientific and high artistic achievements. The aim of this article is to take a look at Leonardo da Vinci's anatomical achievements and thoughts. In addition, the goal is to knowledge today's anatomists about Leonardo da Vinci's astonishing achievements as a great pioneer in anatomy.

• Education of Primary School Mathematics
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• v.22 no.4
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• pp.205-221
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• 2019

The study aimed at investigating preservice elementary school teachers' statistical reasoning when they posed survey questions as they engaged in statistical problem solving, and analyzing how their statistical reasoning affect the subsequent stages. 24 groups of sophomore students(80 students) from two education universities conducted statistical problem solving and completed statistical report, and 22 of them were analyzed. As a result, 9 statistical reasoning were shown when preservice teachers posed survey questions. Among them, question clarification oriented reasoning and variability based reasoning were not exclusively focused upon in the previous research. In order to investigate how statistical reasoning in posing survey questions affected subsequent stages, we examined difficulties and issues that preservice teachers had when they engaged in analyses and conclusion stage described in their report. Consequently, preservice teachers' difficulties were related to population relevant reasoning, category level reasoning, standardization reasoning, alignment to question reasoning, and question clarification oriented reasoning. While previous studies did not focus on question posing stage, this study claimed the necessity of emphasizing various statistical reasoning in question posing and importance of teaching and learning method of appropriate statistical reasoning in question posing.

• Journal of The Korean Association of Information Education
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• v.25 no.4
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• pp.653-664
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• 2021

This study proposes a STEAM (Science, Technology, Engineering, Arts, and Mathematics) program for career exploration of middle school students. The proposed program utilizes VR (Virtual Reality) for new digital technology and webtoon as a popular cultural element. It enables the students to investigate promising fields and experience them virtually for themselves. We design the program based on the 2015 revised curriculum, which enhances the learning effects with existing subjects. In particular, the program provides a hybrid education to combine contact and untact classes considering the COVID-19 situation. The educational goal of the proposed program is to improve creativity and convergence capability. Specifically, it aims to prepare an educational foundation that integrates new digital technologies into education and applies the programs to school education fields. To prove the effectiveness of the developed program, we applied the program to the second graders of A middle school located in Seoul. We expect that the proposed program helps students learn how to utilize new digital technologies and explore future career paths.