• 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.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.9
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• pp.1-16
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• 2019

This study was carried out to develop a physics education program for foreign students of university in Korea to improve their ability to major in the field and to prevent them from becoming dropout. The subjects of the study are five Chinese students attending a natural science and engineering college. Prior to the development of the physics education program, the researchers developed basic physics textbooks for the foreign students and questionaries for diagnosis and summative evaluation, and utilized them to apply a total of seven classes. After the application of the classes, the results of the student's diagnosis and summative evaluation, the teacher's diaries, the observer's diaries, and the transcripts were analyzed by triangulation method. In addition, Nvivo12 was used for the analysis of the teacher's and observer's diaries to help with qualitative analysis. The results of the study are as follows: First, the oder and contents of physics education program for students of the natural science and engineering college were presented in detail, and basic physics textbooks and tools for diagnosis and summative assessment were developed. Second, as a result of the analysis of the diagnosis and summative assessment results of the program, the students' basic physics achievement improved by an average of 40 points due to the application of the developed program. Third, as a result of the application of the program using Nvivo12, meaningful node and actual cases were extracted. There were 10 types of nodes created such as understanding of the students, teaching method, rate of the participation, level differences, language problems, relevance to majors, curriculum and methods of education in the country of origin, cooperative learning, and interest inducement. The researcher provided suggestions on physics education methods for students of science and engineering colleges in Korea based on the related cases.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.2
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• pp.259-269
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• 2019

The main purpose of this study is to explore the foreign students' learning experiences in natural science basic course at college of engineering in Korea. The subjects were 7 but 4 students took part in the semi-structured interview. All of the interviews were recorded, and the recorded material was transferred and kept. The transcripts were analyzed in a qualitative method. The researchers answered the questionnaire to 7 foreign students who voluntarily participated in the study, and 4 in-depth interviews were also conducted. The interview took 30 minutes to 1 hour, and semi - structured interviewing technique was used. The contents of the interviews were all recorded with the consent of the participants, and the recorded materials were transferred and managed with the interview notes. The transferred data were analyzed based on the coding and categorization process according to the step of the continuous comparison method. The results of this study is the following. There are four themes; problems due to lack of Korean language ability when taking basic courses; problems of terms and concept understanding in major courses; supplementary learning methods of basic courses; necessity of natural science basic education program and requirement of support of the university.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2829-2840
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• 2018

The random variable with an arbitrary value or more is called semi-continuous variable or zero-inflated one in case that its boundary value is more frequently observed than expected. This means the boundary value is likely to be practically observed more than it should be theoretically under certain probability distribution. When the distribution considered is continuous, the variable is defined as semi-continuous and when one of discrete distribution is assumed for the variable, we regard it as zero-inflated. In this study, we introduce the two-part model, which consists of one part for modelling the binary response and the other part for modelling the variable greater than the boundary value. Especially, the zero-inflated regression models are explained by using Poisson distribution and negative binomial distribution. In real data analysis, we employ the zero-inflated regression models to estimate the number of days under extreme heat-wave circumstances during the last 10 years in South Korea. Based on the estimation results, we create prediction maps for the estimated number of days under heat-wave advisory and heat-wave warning by using the universal kriging, which is one of the spatial prediction methods.

• Journal of The Korean Association of Information Education
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• v.24 no.5
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• pp.495-509
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• 2020

This study is a theoretical research to explore ways to effectively learn AI in the age of intelligent information driven by artificial intelligence (hereinafter referred to as AI). The emphasis is on presenting a teaching method to make AI education accessible not only to students majoring in mathematics, statistics, or computer science, but also to other majors such as humanities and social sciences and the general public. Given the need for 'Explainable AI(XAI: eXplainable AI)' and 'the importance of storytelling for a sensible and intelligent machine(AI)' by Patrick Winston at the MIT AI Institute [33], we can find the significance of research on AI storytelling learning model. To this end, we discuss the possibility through a pilot study targeting general students of an university in Daegu. First, we introduce the AI storytelling(AI+ST) learning method[30], and review the educational goals, the system of contents, the learning methodology and the use of new AI tools in the method. Then, the results of the learners are compared and analyzed, focusing on research questions: 1) Can the AI+ST learning method complement algorithm-driven or developer-centered learning methods? 2) Whether the AI+ST learning method is effective for students and thus help them to develop their AI comprehension, interest and application skills.