• Journal of Power Electronics
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• v.19 no.6
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• pp.1403-1412
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• 2019

A coupled inductor-dual boost-inverter (CIDBI) with a differential structure has been presented for application to a micro-inverter photovoltaic module system due to its turn ratio of a high-voltage level. However, it is difficult to design a CIDBI converter with a conventional PI regulator to be stable and achieve good dynamic performance, given the fact that it is a high order system. In view of this situation, a sliding mode control (SMC) strategy is introduced in this paper, and two different sliding mode controllers (SMCs) are proposed and adopted in the left and right side of two Boost sub-circuits to implement the corresponding regulation of the voltage and current. The schemes of the SMCs have been elaborated in this paper including the establishment of a system variable structure model, selection of the sliding surface, determination of the control law, and presentation of the reaching conditions and sliding domain. Finally, the mathematic analysis and the proposed SMC are verified by experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.3
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• pp.1015-1029
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• 2021

Modern technology offers many ways to enhance teaching and learning that in turn promote the development of tools for educational activities both inside and outside the classroom. Many educational programs using the augmented reality (AR) technology are being widely used to provide supplementary learning materials for students. This paper describes the potential and challenges of using GeoGebra AR in mathematical studies, whereby students can view 3D geometric objects for a better understanding of their structure, and verifies the feasibility of its use based on experimental results. The GeoGebra software can be used to draw geometric objects, and 3D geometric objects can be viewed using AR software or AR applications on mobile phones or computer tablets. These could provide some of the required materials for mathematical education at high schools or universities. The use of the GeoGebra application for education in Laos will be particularly discussed in this paper.

• Research in Mathematical Education
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• v.25 no.1
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• pp.65-89
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• 2022

Despite its recognition in the field of mathematics education and mathematics, students' understanding about proof and performance on proof tasks have been far from promising. Research has documented that teachers tend to accept empirical arguments as proofs. In this study, an online survey was administered to examine how Korean secondary mathematic teachers make judgements on mathematical arguments varied along representations. The results indicate that, when asked to judge how convincing to their students the given arguments would be, the teachers tended to consider how likely students understand the given arguments and this surfaces as a controversial matter with the algebraic argument being both most and least convincing for their students. The teachers' judgements on the algebraic argument were shown to have statistically significant difference with respect to convincingness to them, convincingness to their students, and validity as mathematical proof.

• Proceedings of the Korean Society of Computer Information Conference
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• 2024.01a
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• pp.185-186
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• 2024

본 논문에서는 CNN 알고리즘을 사용한 수학 문제 답지 추론 모델에 대한 소개를 다룬다. 현재의 학습 보조 서비스 중에서도 질문에 답하는 서비스들이 흔하지만, 수학 문제에 특화된 이미지 기반 답지 추론 서비스는 부족한 상황이다. 본 논문에서는 MathDataset 클래스를 활용하여 수학 문제 이미지와 정답을 연결하는 데이터셋을 생성하고, CNN 알고리즘을 사용하여 모델을 훈련하는 방법을 제시한다.

• Communications of Mathematical Education
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• v.30 no.1
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• pp.67-83
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• 2016

Correcting an imbalance between cognitive and affective aspects of mathematics in schools is recognized as a crucial issue with regards to mathematics education in Korea. Therefore, research and studies about affective aspects have been increasing and themes relating to affective aspects were diverse. Their theme included the improvement of affective aspect, investigation of factors of affective aspect, and development of measurement tools for affective aspect. The purpose of this study is to analyze and organize the research that has been done with respect to affective aspect and drive trend, implication, and their instruction to mathematics education. This study has investigated 103 studies released from 2005 to 2015 on KCI, Korea Citation Index. The results of this study are as follow. First, since released research of affective aspects in mathematics has not increased in number in the last 11 years, academic interest in the affective aspects seems lower than recent interest arousing in Korea. Second, most studies utilized quantitative research as a tool to analyze phenomena and the cause and effect of affective aspects. Third, middle school students were the most common subjects of the studies, followed by elementary school students. Fourth, the studies had various themes such as analyzing the cause and effect of affective aspect, recognizing changes of affective aspects, and measuring affective aspects. The studies, especially, focused most on analyzing how to improve affective aspects by applying it to programs such as mathematic activities and solving mathematic problems. It is necessary for future research to have a long-term perspective and to provide a space for communication. Research should not only focus on how recognize affective aspects differently, which is based on its cultural background, but also to draw affective solutions from them.

• Journal of the Korean School Mathematics Society
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• v.6 no.1
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• pp.135-161
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• 2003

This research is how students and teacher apprehend mathematics education, pointing out problem areas as a basis on how to improve students understanding of mathematics through improved guidance by teachers in the future. 1107 high school students and 105 teachers from around Daejeon and Choongnam province were surveyed and the results were as follows. 1. 77 %( 852) of students viewed the "application of problem solving methods" as understanding mathematic problems. 2. Replies to the question on understanding the study of mathematics resulted in 85.7% of teachers saying "it is the understanding of the basic concept to which you solve the problems" 3. For questions relating to the large difference in-class mathematics achievements and mock University entrance exam achievements, students' response that "for in-class tests you only have to learn problems with similar form but the mock tests are not like that" pointed out the problem in the area of mathematics education. 4. For future mathematic education teachers will have to "explain better and more completely the basic principles and concepts before solving problems" , and make an effort to stimulate students by "creating a more fun atmosphere" . There will also be the need to prevent as much as possible, the use of "formula or memory driven problems" and encourage students to initiate problem solving for themselves.; and encourage students to initiate problem solving for themselves.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.4 s.22
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• pp.41-50
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• 2002

RPM is the one of the sensor models which is proposed by Open GIS Consortium (OGC) as image transfer standard. And it is the sensor model for end-users using IKONOS, a commercial pushbroom satellite, imagery which provide about 1m ground resolution. Parameters called RPC which is IKONOS RFM coefficients are serviced to end-users. But if some users try to make additional effort to get rigorous geo-spatial information, it is necessary to apply mathematic or abstract sensor models, because vendors don't offer any ancillary data for physical sensor models such as satellite orbit and navigation. Abstract sensor models such as pushbroom Direct Linear Transform (DLT) require many GCPs well distributed in imagery, and mathematic sensor model such as RFM, polynomials need much more GCPs. Therefore RPC modification using additional a few GCPs is the best solution. In this paper, two methods are proposed to modify RPC. One is method to use pseudo GCPs generated in normalized cubic, and another method uses parameters observations and a few GCPs. Through two methods, we get improvement of accuracy 50% and over.

• Journal of the Korean School Mathematics Society
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• v.11 no.2
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• pp.315-335
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• 2008

This study is to recognize importance of casing anxiety on mathematics for underachievers and to examine a plan to solve a problem with anxiety, by analyzing factors which make underachievers anxious on the mathematics. First, we analyze factors which make mathematical underachievers anxious on the mathematics. Second, we compare and analyze a level of anxiety on the mathematics and factors which cause anxiety on the mathematics according to their grade and gender. This study's participants were 308 mathematical underachievers at 4th, 5th, and 6th grade, studying at six different elementary schools in three different areas. The results of factors which make mathematical underachievers anxious on the mathematics obtained from the survey are as follows. First, in the top-category factor, mathematical underachievers are influenced by following factors in order, which are a mathematic subject, learner's attitude, environment, and a teacher. Second, in the factor of making students anxious on the mathematics according tn their grade, although the mathematic anxiety of students at 6th grade is higher than students at 4th and 5th grade, in the anxiety differences between the different grades. Third, in the factors which make the students anxious on the mathematics according to their gender, female students show more anxiety than male students. In summary, an anxiety of the underachievers at the elementary schools are different in the top and sub-category factor, according to their grades and their gender. It is shown that the underachievers feel more anxiety compared to normal elementary schools, and therefore the anxiety on the mathematics is one of the causes of under-achievement of the mathematics.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.78-90
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• 2021

The purpose of this study was to develop the mathematic algorithm for energy expenditure calculation during cycling as a part of the development of a higher value-added cycle. Participants were 60 university students (male 30, female 30). Energy expenditure was measured with breathing gas at 10 sec intervals by gas analyzer connected with stationary cycle ergometer. Values presented by commercial speedometer and preceding researches were used for verification of actual measurement values in this study. In conclusion, the mathematic algorithms for energy expenditure calculation during cycling were as follows. For male, energy expenditure(Kcal)=5.048×cycling time(min)-2.258, energy expenditure(Kcal)=(0.05×cycling velocity(kph))×(4.750×cycling time(min)+0.091). For female, energy expenditure(Kcal)=4.466×cycling time(min)-1.605, energy expenditure(Kcal)(cycling velocity≤20kph)=(0.05×cycling velocity(kph))×(4.151× cycling time(min)-0.736), energy expenditure(Kcal)(cycling velocity>20kph)=(0.04×cycling velocity(kph)) ×(4.151×cycling time(min) -0.736). And it is suggested that the developed algorithm with cycling time and velocity should be applied for the development of a higher value-added cycle.

• Journal of applied mathematics & informatics
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• v.30 no.3_4
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• pp.623-633
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• 2012

Let {${\Omega}$, $\mathcal{F}$, P} be a probability space and {$X_n|n{\geq}1$} be a sequence of random variables defined on it. A finite sequence of random variables {$X_n|n{\geq}1$} is said to be conditionally negatively associated given $\mathcal{F}$ if for every pair of disjoint subsets A and B of {1, 2, ${\cdots}$, n}, $Cov^{\mathcal{F}}(f_1(X_i,i{\in}A),\;f_2(X_j,j{\in}B)){\leq}0$ a.s. whenever $f_1$ and $f_2$ are coordinatewise nondecreasing functions. We extend the H$\grave{a}$jek-R$\grave{e}$nyi-type inequality from negative association to conditional negative association of random variables. In addition, some corollaries are given.