• Journal of Korea Water Resources Association
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• v.44 no.7
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• pp.511-522
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• 2011

Two-dimensional shallow water model based on the cut cell and the adaptive mesh refinement techniques is presented in this paper. These two mesh generation methods are combined to facilitate modeling of complex geometries. By using dynamically adaptive mesh, the model can achieve high resolution efficiently at the interface where flow changes rapidly. The HLLC Reimann solver and the MUSCL method are employed to calculate advection fluxes with numerical stability and precision. The model was applied to simulate the extreme urban flooding experiments performed by the IMPACT (Investigation of Extreme Flood Processes and Uncertainty) project. Simulation results were in good agreement with observed data, and transient flows as well as the impact of building structures on flood waves were calculated with accuracy. The cut cell method eased the model sensitivity to refinement. It can be concluded that the model is applicable to the urban flood simulation in case the effects of sewer and stormwater drainage system on flooding are relatively small like the dam brake.

• Communications of Mathematical Education
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• v.34 no.3
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• pp.277-297
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• 2020

The purpose of this study was to identify and compare the mathematics educational values of pre-service and in-service elementary school teachers. For this purpose, we implemented a questionnaire investigating mathematics educational values and used principal component analysis which resulted in six components. These components were named as fun, problem-solving, representation, computation, ability, and explanation through systematic labeling processes. Both pre-service and in-service elementary school teachers considered problem-solving the most important and there was no statistical difference between the teacher groups. They also considered fun the least important and in-service elementary school teachers regarded it more important than pre-service counterparts did. All value components except explanation were regarded as important by in-service elementary school teachers, fourth-year pre-service teachers, and first-year pre-service teachers in order. The result of noticeable differences between pre-service and in-service elementary school teachers implies that actual teaching experience may affect teachers' mathematics educational values more than teacher preparation programs. Based on these findings, we need to discuss what should be regarded as important and worthwhile in teacher preparation programs to establish mathematics educational values for pre-service teachers. We also need to confirm whether the mathematics educational values by in-service elementary school teachers may be in line with what has been pursued in the national mathematics curriculum.

• School Mathematics
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• v.18 no.2
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• pp.257-275
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• 2016

The purpose of this study was to investigate the impact of multiple representations on students' understanding of fractions, decimals, and percent. The instructional approach integrating multiple representations was compared to traditional algorithmic instruction, a form of direct instruction. To examine and compare the impact of multiple representations instruction with traditional algorithmic instruction, pre and post tests consisting of five similar items were administered with 87 middle school students. Students' scores in these two tests and their problem solving processes were analyzed quantitatively and qualitatively. The quantitative results indicated that students taught by traditional algorithmic instruction showed higher scores on the post-test than students in the multiple representations group. Furthermore, findings suggest that instruction using multiple representations does not guarantee a positive impact on students' understanding of mathematical concepts. Qualitative results suggest that the limited use of multiple representations during a class may have hindered students from applying their use in novel problem situations. Therefore, when using multiple representations, teachers should employ more diverse examples and practice with multiple representations to help students to use them without error.

• School Mathematics
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• v.16 no.4
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• pp.709-726
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• 2014

The purpose of the study was to pay attention to the studies of P. Cobb which have actively been quoted in the international research of mathematics education for the last three decades and to look at the result and effect of his research. In particular, we in-depth studied theories and the methods of the study which he has tried to reduce the gap in the theory and practice and investigated effects of his research to the Korean societies of mathematics education. Cobb made special effort to integrate radical constructivism and social constructivism and used emergent theory and symbolic interactionism as theoretical background of the study. Also he analyzed the mathematics classroom in individual and social perspectives based on the interpretive frames of social norm, sociomathematical norm and classroom-mathematical practices then dealt with equity and identity of the students. Because Cobb contributed significantly to the development of practical theory using design experiment as the method of studies, we presented the definition, characteristics, principles, processes and practices of the design experiment. We anticipate that his ways of research would be used as means of unifying the theory and the practice in school.

• The Mathematical Education
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• v.59 no.1
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• pp.17-29
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• 2020

The purpose of this study is to analyze the teacher's discourse structure of teachers according to the interaction pattern between teacher and student in the process of mathematization. To achieve this goal, we observed a semester class (44 lessons) of an experienced teacher who had practiced teaching methods for promoting student engagement for more than 20 years. Among them, one lesson case would be match the teacher's intention and the student's response and the other one lesson case would be to mismatch between the teacher's intention and the student's response was analyzed. In other words, in the process of mathematization based on students' engagement, the intention of the teacher and the reaction of the student was determined according to the cases where students did not make an error and when they made an error. A methodology used to develop a theory based on data collected through classroom observations(grounded theory). Because the purpose of the study is to identify the teacher's discourse structure to help students' mathematization, observe the teacher's discourse and collect data based on student engagement. Based on the teacher's discourse, conceptualize it as a discourse structure for students to mathematization. As a result, teacher's discourse structure had contributed to the intention of the teacher and the reaction of the student in the process of mathematization. Based on these results, we can help the development of classroom discourse for mathematization by specifying the role of the teacher to help students experience the mathematization process in the future.

• Communications of Mathematical Education
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• v.33 no.1
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• pp.1-19
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• 2019

This study deals with the case of student-centered discrete mathematics class with cyber lab. First, we provided lecture notes and cyber labs we developed. In particular, discrete mathematics is a course that covers the principles of algorithms. The purpose of this study is to provide students with basic mathematics, aiming to actively participate in the learning process, to improve their abilities and to reach the ultimate goal of student success with confidence. Second, based on interactions, students were able to prepare for the lectures, review, question, answer, and discussion through an usual learning management system of the school. Third, all the students generated materials through one semester, which were reported, submitted, presented and evaluated. It was possible to improve the learning effectiveness through the discussions and implementation of using some easy open source programming language and codes. Our discrete math laboratory could be practiced without any special knowledge of coding. These lecture models allow students to develop critical thinking skills while describing and presenting their learning and problem-solving processes. We share our experience and our materials including lecture note and cyber lab as well as a possible model of student-centered mathematics class that does not give too much of work load for instructors. This study shares a model that demonstrates that any professor will be able to have an individualized, customized, and creative discrete education without spending much of extra time and assistant, unlike previous research.

• Communications of Mathematical Education
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• v.35 no.4
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• pp.527-546
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• 2021

The purpose of this study is to reveal what mathematics teachers focus on and how they assess students' thinking during lessons enacted. For this purpose, we googled and searched internet sites to collect formative assessment materials for the year 2014 to 2019. The formative assessment tasks data were analyzed according to the levels cognitive demand levels and tasks suggested in textbooks in terms of degrees to which how they are related. The data analysis suggested as follows: a) most of the formative assessment tasks were at the low-level, in particular, PNC level tasks that require applying particular procedures without connections to concepts and meaning underlying the procedures, b) the assessment tasks appeared to be very similar to the tasks suggested in the secondary mathematics textbooks, and c) it seemed that 3 types of formative assessment, observation notes, self-assessment, and peer-assessment were dominantly utilized during mathematics lessons and these different types of formative assessment were employed apparently to find out whether students participated actively in class and in group activity, not how they go through understanding or thinking processes.

• Communications of Mathematical Education
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• v.36 no.4
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• pp.535-558
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• 2022

In the current society, where statistical literacy is recognized as an important ability, statistical education utilizing the statistical problem solving, a series of processes for performing statistics, is required. The result interpretation stage is especially important because many forms of statistics we encounter in our daily lives are the information from the analysis results. In this study, data on private education were provided to pre-service mathematics teachers, and a project was carried out in which they could experience a statistical problem solving process using the population mean estimation. Therefore, this study analyzed the characteristics shown by pre-service mathematics teachers during the result interpretation stage. First, many pre-service mathematics teachers interpreted results based on the data, but the inference was found to be a level of 2 which is not reasonable. Second, pre-service mathematics teachers in this study made various kinds of decisions related to public education, such as improving classes and after-school classes. In addition, the pre-service mathematics teachers in this study seem to have made decisions based on statistical analysis results, but they made general decisions that teachers could make, rather than specifically. Third, the pre-service mathematics teachers of this study were reflective about the question formulation stage, organizing & reducing data stage, and the result interpretation stage, but no one was reflective about the result interpretation stage.

• The Mathematical Education
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• v.62 no.4
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• pp.491-513
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• 2023

High achievement in mathematics is a very complex process in which various factors such as cognitive factors, affective factors, and social and environmental factors work respectively and complementary. A number of previous studies conducted so far have shown that there are certain factors affecting math learning and these factors have positive or negative effects on it. However, these studies were conducted with limited variables and it was not possible to present a comprehensive analysis of what would be necessary to get good achievements in mathematics learning. Therefore, in this study, we analyzed the process of experience of students who experienced success in mathematics learning using the analysis method of the grounded theory. In addition, the collected data was analyzed to explain the process of leading to the successful experience in mathematics learning. As a result of the analysis, it was revealed that students form their identity as successful learners through the processes of 'new phase stage', 'experience accumulation stage', 'stand-up stage', and 'maintenance effort stage'. Through this study, we were able to get implications for what actions are needed to experience success in math learning by looking at the process of the experience what interviewees have gone through.

• Publications of The Korean Astronomical Society
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• v.23 no.2
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• pp.53-63
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• 2008

Korea Astronomy and Space Science Institute (KASI), direct decendant of Korea National Astronomy Observatory, has been publishing Korean Astronomical Almanac since in 1976. The almanac contains essential data in our daily lives such as the times of sunrise, sunset, moonrise, and moonset, conversion tables between luni-solar and solar calendars, and so forth. So, we are planning to register Korean astronomical almanac data for national Standard Reference Data(SRD), which is a scientific/technical data whose the reliablity and the accuracy are authorized by scientific analysis and evalution. To be certificated as national SRD, reference data has to satisfy several criteria such as traceability, consistency, uncertainty, and so on. Based on similarity among calculation processes, we classified astronomical almanac data into three groups: Class I, II, and III. We are planning to register them for national SRD in consecutive order. In this study, we analyzed Class I data which is aimed to register in 2009, and presented the results. Firstly, we found that the traceability and the consistency can be ensured by the usage of NASA/JPL DE405 ephemeris and by the comparsion with international data, respectively. To evaluate uncertainty in Class I data, we solved the mathematical model and determined the factors influencing the calculations. As a result, we found that the atmospheric refraction is the main factor and leads to a variation of ${\pm}16$ seconds in the times of sunrise and sunset. We also briefly review the histories of astronomical almanac data and of standard reference data in Korea.