• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1935-1944
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• 2018

With the increase of the production of energy from renewable, it becomes important to look at techniques to store this energy. Therefore, a single winding bearingless flywheel motor (SWBFM) specially for flywheel energy storage system is introduced. For the control system of SWBFM, coupling between the torque and the suspension subsystems exists inevitably. It is necessary to build a reasonable radial force mathematical model to precisely control SWBFM. However, SWBFM has twelve independently controlled windings which leads to high-order matrix transformation and complex differential calculation in the process of mathematical modeling based on virtual displacement method. In this frame, a Maxwell tensor modeling method which is no need the detailed derivation and complex theoretical computation is present. Moreover, it possesses advantages of universality, accuracy, and directness. The fringing magnetic path is improved from straight and circular lines to elliptical line and the rationality of elliptical line is verified by virtual displacement theory according to electromagnetic torque characteristics. A correction function is taken to increase the model accuracy based on finite element analysis. Simulation and experimental results show that the control system of SWBFM with radial force mathematical model based on Maxwell tensor method is feasible and has high precision.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3284-3306
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• 2018

This study proposes a method to develop an authoring system(GeoMaTree) for diverse trees that constitute a virtual landscape. The GeoMaTree system enables the simple, intuitive production of an efficient structure, and supports real-time processing. The core of the proposed system is a procedural modeling based on a mathematical model and an application that supports digital content creation on diverse platforms. The procedural modeling allows users to control the complex pattern of branch propagation through an intuitive process. The application is a multi-resolution 3D model that supports appropriate optimization for a tree structure. The application and a compatible function, with commercial tools for supporting the creation of realistic synthetic images and virtual landscapes, are implemented, and the proposed system is applied to a variety of 3D image content.

• Journal of the Korean School Mathematics Society
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• v.25 no.2
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• pp.125-148
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• 2022

This study aimed to compare and analyze the number and characteristics of modeling problems in chapters related to function contents in International Baccalaureate Diploma Program (IBDP) mathematics textbooks and Korean high school mathematics textbooks. This study implies how the textbooks contributed to the improvement of students' modeling competency. In this study, three textbooks from IBDP and all nine textbooks from the Korean 2015 revised curriculum were selected. All the problems in textbooks were classified into real-world problems and non-real-world problems. Problems classified as real-world problems were once again divided into word problems and modeling problems according to the need to set up mathematical models. Modeling problems were further categorized into standard applications and good modeling problems depending on whether all the necessary information was included in the problem-solving process. Among the 12 textbooks, the textbook with the most modeling problems was the IBDP textbook, 'Math: Applications and Interpretation', which accounted for 50.41% of modeling problems to the total number of problems. This textbook provided learners with significantly higher modeling opportunities than other IBDP and Korean textbooks, which had 2% and 9% modeling problem ratios. In all 12 textbooks, all problems classified as modeling problems appeared as standard applications, and there were no proper modeling problems. Among the six sub-competencies of mathematical modeling, 'mathematical analysis' and 'interpretation and evaluation of results' sub-competencies appeared the most with very similar number of modeling problems, followed by the 'mathematization'. It is expected that the results of this study will help compare the number and ratio of modeling problems in each textbook and provide a better understanding of which modeling sub-competencies appear to what extent in the modeling problems.

• Korean Journal of Mathematics
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• v.11 no.1
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• pp.35-43
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• 2003

We study the weak convergence to Fractional Brownian motion and some examples with applications to traffic modeling. Finally, we get loss probability for queue-length distribution related to self-similar process.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.39.1-39.1
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• 2005

• Journal of the Korean School Mathematics Society
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• v.23 no.1
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• pp.45-65
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• 2020

This research is an analysis of communication that occurs during the quadratic function teaching and learning process of middle school students, which reflects mathematical modeling. For an in-depth analysis of the communication, Sfard(2008)'s discourse theory and language analysis framework were applied. A quadratic function mathematical modeling teaching and learning were conducted for the week second (1 hour) in June 2019 for students who studied the concept of a quadratic function and who passed a specified period (3 months). The results are as follows. First, The commo-gnitive conflict occurred because of differences in prior knowledge other than quadratic function among students. Second, in the course of communication, knowledge was expanded through problem-solving from different perspectives. These results can be interpreted as allowing students to clearly reveal problems in the communication process based on their understanding of the concept of quadratic functions and to facilitate cooperation among students. of the concept of quadratic functions and to facilitate cooperation among students.

• International Journal of Reliability and Applications
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• v.12 no.1
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• pp.49-60
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• 2011

The geometric process (GP) has been widely used for modeling failure and repair time sequences of repairable systems. The GP is mathematically tractable but restrictive in reliability applications since it actually assumes that the mean function of inter-failure times sequence asymptotically decreases to zero; and the mean function of successive repair times sequence asymptotically increases to infinity. This is generally unrealistic from an engineering perspective. This paper presents three extended GP models for modeling reliability deterioration and improvement (or growth) process. The extensions maintain the advantage of mathematical tractability of GP model. Their usefulness and appropriateness are illustrated with three real-world examples.

• Journal of the Korean School Mathematics Society
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• v.16 no.3
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• pp.561-582
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• 2013

Meanwhile, the meaning has been emphasized in mathematics. But the meaning of meaning had not been clearly defined and the meaning classification had not been reported. In this respect, the meaning was classified as expressive and cognitive. Furthermore, it was reclassified as mathematical situation and real situation. Based on this classification, we investigated how student recognizes the meaning when solving mathematical modeling problem. As a result, we found that the understanding of cognitive meaning in real situation is more difficult than that of the other meaning. And we knew that understanding the meaning in solving of equation, has more difficulty than in expression of equation. Thus, to help students understanding the meaning in the whole process of mathematical modeling, we have to connect real situation with mathematical situation. And this teaching method through unit and measurement, will be an alternative method for connecting real situation and mathematical situation.

• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.59-64
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• 2006

The automation of hot rolling process requires the developments of several mathematical models for simulation and quantitative description of the industrial operations involved in order to achieve the continuously increasing productivity, flexibility and quality(dimensional accuracy, mechanical properties and surface properties). The mathematical modeling of hot rolling process has long been recognized to be a desirable approach to investigate rolling operating practice and design of mill requirement. To achieve this objectives, a new teaming method with neural network to improve the accuracy of rolling force prediction in hot rolling mill is developed. Also, Genetic Algorithm(GA) is applied to select the optimal structure of the neural network and compared with that of engineers experience. It is shown from this research that both structure selection methods can lead to similar results.