• Journal of The Korean Association of Information Education
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• v.9 no.3
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• pp.523-532
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• 2005

Moving figures and piling up some boxes are newly the introduced studying contents in the 7th curriculum of mathematics and it will be able to form the sense of space of the students. Against the studying contents for the sense of space formation, the teachers of site speak instruction is very difficult and the student's scores are low. Elementary school mathematics studying which inclusive of figure studying is the most effective when they operate the actual object. But in the school site, the instruction with actual object is very difficult because many reasons. And web based studying data system which is for forming the sense of space the students is not abundant because it started initially. From this dissertation, studying contents will be taken out and web base figure studying system will be designed and embodied. The interaction will be active in the system. Student will be able to understand the principle by the medium of the animation from the system and they can improve their sense of space by the interesting game.

• Communications of Mathematical Education
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• v.31 no.2
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• pp.203-221
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• 2017

The purpose of this study is to suggest didactical principles for using mathematical teaching aids and to applicate didactical principles in a relation with curriculum. First, we meta-analyzed related literature to suggest didactical principles for using mathematical teaching aids. And we suggested didactical principles as follows: principle of activities, principle of instruments, principle of learning. Using mathematical teaching aids with didactical principles in mind would help avoiding situations in which mathematical teaching aids are only used as interesting tools. Second, we concretized the meaning to applicate didactical principles and use mathematical teaching aids in a relation with curriculum. We considered domain, key concept, function, achievement standard, which were presented in the curriculum of mathematics, and suggested concrete activities. Third, we produced two designs for lessons on incenter and circumcenter of triangle and linear function's graph using mathematical teaching aids.

• Communications of Mathematical Education
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• v.31 no.4
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• pp.389-407
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• 2017

Many researches related to STEAM education have been actively conducted for developing elementary and secondary school students' comprehensive and logical thinking ability in relation to creativity education in Korea. Each sub factor of STEAM education requires creative thinking with the ability to be merged together to solve problems as integrated or combined forms in the fields of Science, Technology, Engineering, Arts, and Mathematics. Also, these STEAM activities and experiences should be carried out at various places outside the classroom in school. Although various educational programs to enhance mathematical creativity have been emphasized for elementary and secondary school students, recent tendency to focus on classroom learning in the school makes it difficult to develop creative thinking ability of students. This research is mainly based on the result of the project "Development and Administration of STEAM Outreach Program in 2016" supported by KOFAC(Korea Foundation for the Achievement of Science & Creativity). The purpose of this research is to develop a STEAM outreach program including students' activity books, teachers' manuals and administration manual that can maximize STEAM-related interest of students, and to provide a chance for elementary and secondary school students to experience creative thinking based on sub factors of STEAM. The STEAM competency total score and the perception of convergence education were significantly increased for all students participating this program, but some sub factors showed different result by school levels. The STEAM outreach program developed by this study is designed to emphasize STEAM education especially 'based on' mathematics in order to provide students with the opportunity to experience more interest in the field of mathematics and will be able to provide an interesting creative STEAM outreach program that utilizes a variety of activities which, we expect, would help students to consider their career in the future.

• Communications of Mathematical Education
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• v.32 no.3
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• pp.363-383
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• 2018

The subject of 'Mathematical Task Inquiry' was introduced newly in the curriculum revised in 2015. The subject is dealt with after completing the subject of 'mathematics' to be dealt with in the tenth grade. Its main content is comprised of the understanding and learning of the purpose and procedure of inquiry task and of study ethics, and its educational goal is to enforce the prior mathematical knowledge and to obtain the ability to select interesting topics that combine mathematics with other subjects. However the textbook of the subject does not exist, and teachers should handle with the subject with responsibility for their own ways. Because of this reason, this study is to develop an instruction model on project(task) inquiry model and materials. Namely, according to the model, students is guided to select and decide the subject of the task, and develop the task for themselves, solve it with peers in cooperation, and announce the solution and their feelings. During those students' exploration and activities, the role of teachers is to guide students to complete their work. By the way, in order to develop more creative tasks that is appropriate to their academic and cognitive level, this study conducted the experimentation for the subject of 9 students (6 girls and 3 boys), who are scheduled to advance to the 11 grade of J high school located in G domestic. The experimentation was consisted of three class and after the third class, the semi-structured interview was conducted immediately for the students.

• Communications of the Korean Mathematical Society
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• v.27 no.4
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• pp.665-668
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• 2012

For a given graph G we consider a set S(G) of all symmetric matrices A = [$a_{ij}$] whose nonzero entries are placed according to the location of the edges of the graph, i.e., for $i{\neq}j$, $a_{ij}{\neq}0$ if and only if vertex $i$ is adjacent to vertex $j$. The minimum rank mr(G) of the graph G is defined to be the smallest rank of a matrix in S(G). In general the computation of mr(G) is complicated, and so is that of the maximum multiplicity MaxMult(G) of an eigenvalue of a matrix in S(G) which is equal to $n$ - mr(G) where n is the number of vertices in G. However, for trees T, there is a recursive formula to compute MaxMult(T). In this note we show that this recursive formula for MaxMult(T) also computes the path cover number $p$(T) of the tree T. This gives an alternative proof of the interesting result, MaxMult(T) = $p$(T).

• The Journal of Asian Finance, Economics and Business
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• v.7 no.6
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• pp.185-195
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• 2020

The study investigates the impact of globalization on coal consumption in Vietnam. This study employs an autoregressed distributed lag approach on time series data for the period of 1990 to 2017. The study tests the stationary, cointegration of time series data and utilizes autoregressed distributed lag modeling technique to determine the short-run and long-run relationship among coal consumption, globalization, income, population, and CO₂ emissions. The results show that globalization increases coal consumption in Vietnam in the long run. The results also show that rapid economic growth promotes more coal consumption in the short run as well as in the long run. Moreover, higher population reduces coal consumption, and CO₂ emissions decrease coal consumption both in the short run and the long run. The findings of the study suggest that globalization increases coal consumption in Vietnam in the long run. This result suggests that the increase in globalization level in Vietnam increases coal consumption. An interesting finding is that higher population reduces coal consumption, and population is an important factor towards the lessening in coal consumption. The findings confirm that environmental pollution decreases coal consumption in the short run and the long run. This implies that coal consumption may be green consumption in Vietnam.

• The Mathematical Education
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• v.45 no.4 s.115
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• pp.481-491
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• 2006

Diffy is a simple mathematical puzzle that provides elementary-school students with subtraction practice. The idea appears to have originated in the late nineteenth century with E. Ducci of Itali. Thirty years ago Professor J. Copley of the University of Houston introduced the diffy game to teachers in elementary schools and it widely spreaded out. During the diffy activity we naturally guess many interesting conjectures. First, does diffy always end? Second, does the head of diffy always exist? Third, for an arbitrary given natural number n, is there any possible method to find the diffy with the given length n? In this study I give the necessary and sufficient condition for the existence of the head of diffy. Using this condition I classify all possible heads of diffy and provide an algorithm to find the diffy with any given length n. With this algorithm I find four natural numbers with diffy length 200. To ensure my numbers are correct, I make a diffy program for Mathematica and check they are correct. I suggest the diffy game is good for enlarging the mathematical thinking to all graded students, especially gifted and talented students, It will produce rational consideration and synthetic judgement.

• Journal of the Korean Mathematical Society
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• v.42 no.6
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• pp.1251-1264
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• 2005

Let D be an acyclic digraph. The competition graph of D has the same set of vertices as D and an edge between vertices u and v if and only if there is a vertex x in D such that (u, x) and (v, x) are arcs of D. The competition number of a graph G, denoted by k(G), is the smallest number k such that G together with k isolated vertices is the competition graph of an acyclic digraph. It is known to be difficult to compute the competition number of a graph in general. Even characterizing the graphs with competition number one looks hard. In this paper, we continue the work done by Cho and Kim[3] to characterize the graphs with one hole and competition number one. We give a sufficient condition for a graph with one hole to have competition number one. This generates a huge class of graphs with one hole and competition number one. Then we completely characterize the graphs with one hole and competition number one that do not have a vertex adjacent to all the vertices of the hole. Also we show that deleting pendant vertices from a connected graph does not change the competition number of the original graph as long as the resulting graph is not trivial, and this allows us to construct infinitely many graph having the same competition number. Finally we pose an interesting open problem.

• Communications of the Korean Mathematical Society
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• v.29 no.2
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• pp.319-329
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• 2014

In this paper we study the properties of conformally recurrent pseudo Riemannian manifolds admitting a proper conformal vector field with respect to the scalar field ${\sigma}$, focusing particularly on the 4-dimensional Lorentzian case. Some general properties already proven by one of the present authors for pseudo conformally symmetric manifolds endowed with a conformal vector field are proven also in the case, and some new others are stated. Moreover interesting results are pointed out; for example, it is proven that the Ricci tensor under certain conditions is Weyl compatible: this notion was recently introduced and investigated by one of the present authors. Further we study conformally recurrent 4-dimensional Lorentzian manifolds (space-times) admitting a conformal vector field: it is proven that the covector ${\sigma}_j$ is null and unique up to scaling; moreover it is shown that the same vector is an eigenvector of the Ricci tensor. Finally, it is stated that such space-time is of Petrov type N with respect to ${\sigma}_j$.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2003.10a
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• pp.101-106
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• 2003

In this paper, we propose using Hotelling's T2 statistic for the detection of a set of a set of differentially expressed (DE) genes in colorectal cancer based on its gene expression level in tumor tissues compared with those in normal tissues and to evaluate its predictivity which let us rank genes for the development of biomarkers for population screening of colorectal cancer. We compared the prediction rate based on the DE genes selected by Hotelling's T2 statistic and univariate t statistic using various prediction methods, a regulized discrimination analysis and a support vector machine. The result shows that the prediction rate based on T2 is better than that of univatiate t. This implies that it may not be sufficient to look at each gene in a separate universe and that evaluating combinations of genes reveals interesting information that will not be discovered otherwise.