• 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.

• Journal of Elementary Mathematics Education in Korea
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• v.21 no.3
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• pp.415-441
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• 2017

The purpose of this study is to develop elementary school math classes for the gifted and talented with a focus on social issues to investigate the possibility of character education through specialized subject classes. As suggested in the goals of the math education for social justice, which provide the fundamental theoretical basis, through mathematics activities with a theme of social issues, mathematically gifted and talented young students can critically perceive social issues, express a sense of mathematical and critical agency throughout the course and develop a willingness and mindset to contribute to social progress. In particular, the concept of Figured Worlds and agency is applied to this study to explain the concept of elementary math classes for the gifted and talented with a focus on social issues. The concept is also used as the theoretical framework for the design and analysis of the curriculum. Figured Worlds is defined as the actual world composed of social and cultural elements (Holland et al., 1998) and can be described as the framework used by the individual or the social structure to perceive and interpret their surroundings. Agency refers to the power of practice that allows one to perceive the potential for change within the Figured Worlds that he is a part of and to change the existing Figured Worlds. This study sees as its purpose the fostering of young talent that has the agency to critically perceive the social structure or Figured Worlds through math classes with a theme of social issues, and thus become a social capital that can contribute to social progress.

• Journal of Educational Research in Mathematics
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• v.26 no.3
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• pp.443-465
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• 2016

The study aims to compare our newest mathematics curriculum with Singapore's and analyse the differences of them. Because the levels of our mathematics education have been evaluated to be difficult to our students, we try to find that the evaluation is appropriate and there are other characteristics we have to notice carefully, and provide some implications for our mathematics curriculum. We mainly compared both mathematics curriculums focussed on the national documents of mathematics curriculum, and textbooks in the level of middle school. The results are following. Firstly, Singapore has three tracks based on students' abilities and there are three kinds of textbooks on the tracks. This is a different from our teaching on students level. Secondly, the introductions of our mathematics curriculum contents are not faster than Singapore's, but they have more concrete ranges of contents than us. Thirdly, the focus of Singapore's mathematics education lies on problem solving, and we can find some good examples of contents of textbook focussed on problem solving. Some mathematical concepts are introduced simply without any process of students discoveries or investigations, and the focus lies on the problem solving using the concepts. Fourthly, Singapore's mathematics textbooks are more emphasis on the internal connections than ours.

• School Mathematics
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• v.16 no.4
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• pp.691-708
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• 2014

In general, the intuitive knowledge that can use in mathematics problem solving is one of the important knowledge to teachers as well as students. So, this study is aimed to analyze the elementary preservice teachers' intuitive knowledge in relation to intuitive and counter-intuitive problem solving. For this, I performed survey to use questionnaire consisting of problems that can solve in intuitive methods and cause the errors by counter-intuitive methods. 161 preservice teachers participated in this study. I got the conclusion as follows. preservice teachers' intuitive problem solving ability is very low. I special, many preservice teachers preferred algorithmic problem solving to intuitive problem solving. So, it's needed to try to improve preservice teachers' problem solving ability via ensuring both the quality and quantity of problem solving education during preservice training courses. Many preservice teachers showed errors with incomplete knowledges or intuitive judges in counter-intuitive problem solving process. For improving preservice teachers' intuitive problem solving ability, we have to develop the teacher education curriculum and materials for preservice teachers to go through intuitive mathematical problem solving. Add to this, we will strive to improve preservice teachers' interest about mathematics itself and value of mathematics.

• Journal of Educational Research in Mathematics
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• v.23 no.3
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• pp.373-388
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• 2013

This paper is to investigate how two elementary school teacher's belief mathematics as educational content, and teaching and learning mathematics as a part of educational methodology, and what the two teachers believe towards gifted children and their education, and what the classes demonstrate and its effects on the sociomathematical norms. To investigate this matter, the study has been conducted with two teachers who have long years of experience in teaching gifted children, but fall into different belief categories. The results of the study show that teacher A falls into the following category: the essentiality of mathematics as 'traditional', teaching mathematics as 'blended', and learning mathematics as 'traditional'. In addition, teacher A views mathematically gifted children as autonomous researchers with low achievement and believes that the teacher is a learning assistant. On the other hand, teacher B falls into the following category: the essentiality of mathematics as 'non-traditional', teaching mathematics as 'non-traditional, and learning mathematics as 'non-traditional.' Also, teacher B views mathematically gifted children as autonomous researchers with high achievement and believes that the teacher is a learning guide. In the teacher A's class for gifted elementary school students, problem solving rule and the answers were considered as important factors and sociomathematical norms that valued difficult arithmetic operation were demonstrated However, in the teacher B's class for gifted elementary school students, sociomathematical norms that valued the process of problem solving, mathematical explanations and justification more than the answers were demonstrated. Based on the results, the implications regarding the education of mathematically gifted students were investigated.

• School Mathematics
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• v.19 no.3
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• pp.593-615
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• 2017

The purpose of this study is to develop a mobile-based math learning application and explore its application. In order to develop a learning application, the present study included literature review on math education involving mobile learning, investigation of literature related to mathematics education conducted in a digital environment, and method of use and implementation environment of existing math learning applications by type. Based on these preliminary investigation and analysis, an android version application, 'Mathematics Classroom for Middle School 3rd Graders' was developed. This application can be used for learning units such as Quadratic Functions and Graphs, Representative Value, and Variance and Standard Deviation. For the unit on Quadratic Functions and Graphs, the application was constructed so that students can draw various graphs by using the graphic mode and discuss their work with other students in the chatting room. For the unit on Representative Value, the application was constructed with the mathematical concept of representative value explained through animation along with activities of grouping data acquired after playing archery games by points or arranging them according to size so that students can study when and how to use median value, mode, and average. The application for Variance and Standard Deviation unit was also constructed in a way that allowed students to study the concept of variance and standard deviation and solve the problems on their own. The results of this study can be used as teaching & learning materials customized for individual student in math classes and will provide anyone the opportunity to engage in an interesting self-directed learning of math at anytime. Developed in the format of real life study, the application will contribute to helping students develop a positive attitude about math.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.75-90
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• 1995

A mathematical model for the dynamic analysis of a riser system with the inclusion of internal flow and nonlinear effects due to large structural displacements is developed to investigate the effect of internal flow on marine riser dynamics. The riser system accounts fir the nonlinear boundary conditions and includes a steady flow inside the pipe which is modeled as an extensible or inextensible. tubular beam subject to nonlinear three dimensional hydrodynamic loads such as current or wave excitation. Galerkin's finite element approximation and time incremental operator are implemented to derive the matrix equation of equilibrium for the finite element system and the extensibility or inextensibility condition is used to reduce degree of freedom of the system and the required computational time in the case of a nonlinear model. The algorithm is implemented to develop computer programs used in several numerical applications. The investigations of the effect of infernal flow on riser vibration due to current or wave loading are performed according to the change of various parameters such as top tension, internal flow velocity, current velocity, wave period, and so on. It is found that the effect of internal flow can be controlled by the increase of top tension. However, careful consideration has to be given in the design point particularly for the long riser under the harmonic loading such as waves. And it is also found that the consideration of nonlinear effects due to large structural displacements increases the effect of internal flow on riser dynamics.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.436-442
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• 2020

ESS(energy storage system) has recently become an important power source in various areas due to increased renewable energy resources. The more ESS is used, the less the effective capacity of the ESS. Therefore, it is important to manage the remaining useful lifetime(RUL). RUL can be checked regularly by inspectors, but it is common to be monitored and estimated by an automated monitoring system. The accurate state estimation is important to ESS operator for economical and efficient operation. RUL estimation model usually requires complex mathematical calculations consisting of cycle aging and calendar aging that are caused by the operation frequency and over time, respectively. A lightweight RUL estimation model is required to be embedded in low-performance processors that are installed on ESS. In this paper, a lightweight ESS RUL estimation model is proposed to operate on low-performance micro-processors. The simulation results show less than 1% errors compared to the original RUL model case. In addition, a performance analysis is conducted based on ATmega 328. The results show 76.8 to 78.3 % of computational time reduction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.305-315
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• 2016

Due to the change from small volume production to small quantity batch production systems, individual companies have been attempting to produce a wide range of operating strategies, maximize their productivity, and minimize their WIP level by operating with the proper cycle time to defend their market share. In particular, using a complex workflow and process sequence in the manufacturing line has some drawbacks when it comes to designing the production strategy by applying analytical models, such as mathematical models and queueing theory. For this purpose, this paper uses three heuristic algorithms to solve the job release problem at the bottleneck workstation, product mix problem in multi-purpose machine(s), and batch size and sequence in batch machine(s). To verify the effectiveness of the proposed methods, a simulation analysis was performed. The experimental results demonstrated that the combined application of the proposed methods showed positive effects on the reduction of the cycle time and WIP level, and improvement of the throughput.

• Journal of KIISE
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• v.42 no.5
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• pp.609-620
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• 2015

Viewers of videos are likely to absorb more information from the part of the screen that attracts visual attention. This fact has led to the visual attention models that are being used in producing and evaluating videos. In this paper, we investigate the factors that are significant to visual attention and the mathematical form of the visual attention model. We then estimated the visual attention probability using the statistical design of experiments. The analysis of variance (ANOVA) verifies that the motion velocity, distance from the screen, and amount of defocus blur affect human visual attention significantly. Using the response surface modeling (RSM), we created a visual attention score model that concerns the three factors, from which we calculate the visual attention probabilities (VAPs) of image pixels. The VAPs are directly applied to existing gradient based 3D effect perception measurement. By giving weights according to our VAPs, our algorithm achieves more accurate measurement than the existing method. The performance of the proposed measurement is assessed by comparing them with subjective evaluation as well as with existing methods. The comparison verifies that the proposed measurement outperforms the existing ones.