• Journal of Korean Elementary Science Education
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• 제29권2호
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• pp.166-185
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• 2010

Astronomy areas in the elementary science textbooks of Korea and the U.S.A. have been compared to find advantages and disadvantages of Korean textbooks. The analysis objects are the 7th national curriculum science textbooks for Korea and the Macmillan McGraw-Hill(MMH) science textbooks for the U.S.A. The results are as follows: First, in contexts, Korean science textbooks contain mostly inquiry activities and partly reading materials. However, MMH ones contain mostly explanations including photographs, related activities, and various reading materials. Second, in the contents and order, the observation activities of constellations are emphasized in Korean science textbooks, while the MMH ones explain solar system up to the universe in details. In addition, Korean science textbooks deal with one subject only once during the whole elementary course while MMH ones deal with one subject repeatedly in several grades. Third, in the frameworks of the international mathematics and science study (TIMSS) 2007, Korean science textbooks do not introduce some contents presented in TIMSS 2007, whereas MMH textbooks introduce every one of them in time. Fourth, the major subjects such as change of moon phases, constellations, the solar system, and change of seasons are handled independently in Korean science textbooks without strong correlation, while they are systematically done related with the rotation and the revolution of the earth in MMH ones.

• Communications of the Korean Mathematical Society
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• 제35권2호
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• pp.613-623
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• 2020

The notion of quasi-Einstein metric in theoretical physics and in relation with string theory is equivalent to the notion of Ricci soliton in differential geometry. Quasi-Einstein metrics or Ricci solitons serve also as solution to Ricci flow equation, which is an evolution equation for Riemannian metrics on a Riemannian manifold. Quasi-Einstein metrics are subject of great interest in both mathematics and theoretical physics. In this paper the notion of Ricci 𝜌-soliton as a generalization of Ricci soliton is defined. We are motivated by the Ricci-Bourguignon flow to define this concept. We show that if a 3-dimensional almost Kenmotsu Einstein manifold M is a 𝜌-soliton, then M is a Kenmotsu manifold of constant sectional curvature -1 and the 𝜌-soliton is expanding with λ = 2.

• Journal for History of Mathematics
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• 제28권3호
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• pp.151-164
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• 2015

The purpose of this paper is to develop a teaching and learning material integrated two subjects Pythagorean theorem and Fibonacci numbers. Traditionally the former subject belongs to geometry area and the latter is in algebra area. In this work we integrate these two issues and make a discovery method to generate infinitely many Pythagorean numbers by means of Fibonacci numbers. We have used this article as a teaching and learning material for a science high school and found that it is very appropriate for those students in advanced geometry and number theory courses.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.108-111
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• 2014

In this paper, we tried to identify implications of selecting gifted of information science & followed educational system via analyzing each of student's characteristics in each subjects they study within Science Education Institute for the Gifted. A study of the existing institutions do not have experience of the gifted students based on assessment through observation of the 1-year science, mathematics and information science education in the List of attribute analysis. Learners of Information Science became with analysis that Attitude Category was superior in mathematics to the subject of science and Problem Solving Category regardless of the subjects showed similar. As to, Attitude Category, Problem Solving Category and Mathematics Cognition Category was analyzed to be closed and we could confirm through the qualitative observation record. On this, the researcher concluded that the mathematics could know the effect fitness by a learner rather than the subject of science as to an attitude and problem resolution area.

• International Journal of Reliability and Applications
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• 제4권3호
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• pp.141-156
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• 2003

Nonparametric families of aging distributions have been the subject of investigation from long period of time and still. Both probabilistic and statistical properties of these distributions were studied for such families as new better than used renewal failure rate (NBURFR) and new better average renewal failure rate (NBARFR) classes. They have been studied by Abouammoh and Ahmed (1992). In the present work, moment inequalities are derived for the above mentioned families that demonstrate that if the mean life is finite for any of them then all higher order moments exist. Next, based on these inequalities, new test procedures for exponentiality against these families are studied showing that it is simple and hold high relative efficiency for some commonly used alternatives. Dealing with censored data case also studied.

• Communications of the Korean Mathematical Society
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• 제35권4호
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• pp.1143-1158
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• 2020

In this paper, we are concerned with the blow-up phenomena for a class of pseudo-parabolic equations with weighted source u_t - △u - △u_t = a(x)f(u) subject to Dirichlet (or Neumann) boundary conditions in any smooth bounded domain Ω ⊂ ℝⁿ (n ≥ 1). Firstly, we obtain the upper and lower bounds for blow-up time of solutions to these problems. Moreover, we also give the estimates of blow-up rate of solutions under some suitable conditions. Finally, three models are presented to illustrate our main results. In some special cases, we can even get some exact values of blow-up time and blow-up rate.

• International Journal of Reliability and Applications
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• 제9권2호
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• pp.141-152
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• 2008

This paper presents equations, which can be used to evaluate the failure frequency and the failure rate of a two identical component parallel redundant system in which each component can operate in its wear out period, and the failure rate of each component is exponential power distribution. The optimum maintenance interval for a two identical component parallel redundant system can be obtained using these equations. The proposed approach is presented and illustrated using several numerical examples. The optimum maintenance interval for each component in a two identical parallel redundant system will depend on factors such as: failure rate, repair and maintenance times of each component in the parallel redundant systems.

• Bulletin of the Korean Mathematical Society
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• 제29권1호
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• pp.153-163
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• 1992

Carlitz module is used to study abelian extensions of K=$F_{q}$(T). In number theory every abelian etension of Q is contained in a cyclotomic field. Similarly every abelian extension of $F_{q}$(T) with some condition on .inf. is contained in a cyclotomic function field. Hence the study of cyclotomic function fields in analogy with cyclotomic fields is an important subject in number theory. Much are known in this direction such as ring of integers, class groups and units ([G], [G-R]). In this article we are concerned with the ring of integers in a cyclotomic function field. In [G], it is shown that the ring of integers is generated by a primitive root of the Carlitz module using the ramification theory and localization. Here we will give another proof, which is rather elementary and explicit, of this fact following the methods in [W].[W].

• Journal of applied mathematics & informatics
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• 제26권3_4호
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• pp.767-778
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• 2008

Comparison between two or more fuzzy numbers, along with their ranking, is an important subject discussed in scholarly articles. We endeavor in this paper to present a simple yet effective parametric method for comparing fuzzy numbers. This method offer significant advantages over similar methods, in comparing intersected fuzzy numbers, rendering the comparison between fuzzy numbers possible in different decision levels. In the process, each fuzzy number will be given a parametric value in terms of $\alpha$, which is dependent on the related $\alpha$-cuts. We have compared this method to Cheng's centroid point method [5] (The relation of calculating centroid point of a fuzzy number was corrected later on by Wang [12]). The proposed method can be utilized for all types of fuzzy numbers whether normal, abnormal or negative.

• Journal of the Korean Society of Earth Science Education
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• 제7권1호
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• pp.119-132
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• 2014

In recent years, Korea encourages teachers to do STEAM education(Science, Technology, Engineering, Arts & Mathematics), which includes Arts to STEM education to train creative science technology talent. Related to this, we developed a subject substitute STEAM program for the 6th grade students in elementary school and applied it in a field. The STEAM program which substitutes contents in curriculum related to Energy unit was developed and it was taught to twenty four sixth grade students during regular classes. During the classes, all activities of students were observed and they were written in recording notes during the observation. After all STEAM program ended, how students recognize the subject substitute STEAM program compared to general class, understand learning contents and think about the program before and after the STEAM classes were analyzed through questionnaire and interviews. The results were as follows. First, some students had difficulty in reconciling different ideas in group, creative thinking and crafts but most students liked the STEAM classes because many activities are fun and it is easy to understand. Second, learners regarded practical use of knowledge, learning different subjects together and interests as the reasons they can understand learning contents easily during STEAM program. Third, learners recognized STEAM classes are good to understand knowledge, think creative ideas and improve social skills after the STEAM classes while they showed anticipation, worry and fear before taking the classes. It is found that a subjective substitute STEAM program is helpful to increase learners' interests in learning, understand learning contents, increase creativity and have a good personality through a qualitative research.