• Journal of applied mathematics & informatics
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• v.19 no.1_2
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• pp.203-214
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• 2005

In this study the optimal control of fed-batch glycerol fermentation is investigated based on an impulsive dynamical system. Considering the sudden increase of the glycerol and alkali in fed-batch culture of biodissimilation of glycerol to 1,3-propanediol, this paper proposes a non-linear impulsive system of fed-batch culture. The existence, uniqueness and regularity properties of piecewise solution for the system are proved. In view of the controllability of volumes of glycerol added to the reactor instantaneously, the paper constructs an optimal control model based on the nonlinear impulsive system and the existence of the optimal control is obtained. The control variables here are the moments and the sizes of jumps in the states at the discrete instants and the objective is to maximize the productivity of 1,3-propanediol over one cycle.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.1-6
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• 2003

Associations, as specific forms of knowledge, reflect relationships among items in databases, and have been widely studied in the fields of knowledge discovery and data mining. Recent years have witnessed many efforts on discovering fuzzy associations, aimed at coping with fuzziness in knowledge representation and decision support processes. This paper focuses on associations of three kinds, namely, association rules, functional dependencies and pattern associations, and overviews major fuzzy logic extensions accordingly.

• The Pure and Applied Mathematics
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• v.24 no.4
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• pp.211-226
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• 2017

In this paper, machine learning models employed in various fields are discussed and applied to KOSPI200 stock index return forecasting. The results of hyperparameter analysis of the machine learning models are also reported and practical methods for each model are presented. As a result of the analysis, Support Vector Machine and Artificial Neural Network showed a better performance than k-Nearest Neighbor and Random Forest.

• Education of Primary School Mathematics
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• v.8 no.2 s.16
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• pp.69-96
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• 2004

The purpose of this study is to understand teaching and learning mathematics in elementary school classroom by considering mathematics as a kind of social practices and mathematics classroom as a kind of community of practice. The research questions of this study are as followings: 1) Which kinds of lesson organization reveal? 2) Which kinds of social participation structure reveal? 3) Which processes of making meaning reveal? This study was based on ethnomethodology. It was executed participation observations, interviews and surveys with teacher and 5 graders to collect the data related to the social practices formed their classroom. The social practices of mathematics classroom was analyzed from three aspects such as lesson organization, social participation structure and making meaning. The results from which we analyzed the social practices of the mathematics classroom are as followings. From the aspect of lessons organization, the teacher had a lot of power and authorities in the classroom and used them to elicitate students' responses. From the aspect of social participation structure, five SPSs(social participation structures) which revealed in Jo(1997)'s economics classrooms, were shown in this mathematics classroom, but there were a difference to the situations or frequencies which the SPSs appeared. From the aspect of making meaning, it was common that meanings are formed by the explanation of the teacher, but the teacher didn't deliver the mathematical meanings directly. She tried to interact with students to arrive shared meanings.

• The Pure and Applied Mathematics
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• v.24 no.4
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• pp.227-241
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• 2017

The study investigates the stock market using emotion index calculated from SMD based on investors' emotion. In the VAR anlaysis, we find that the correlation between the KOSPI200 return and emotion score sum is highest in 2- or 3- day lag. This study concludes that explanatory power of the SMD emotion index is limited in explaining the Korean stock market yet.

• Communications of the Korean Mathematical Society
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• v.25 no.4
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• pp.623-628
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• 2010

Nakaoka and Oda ([1] and [2]) introduced the notion of maximal open sets and minimal closed sets in topological spaces. In this paper, we introduce new classes of sets called maximal $\theta$-open sets, minimal $\theta$-closed sets, $\theta$-semi maximal open and $\theta$-semi minimal closed and investigate some of their fundamental properties.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.2
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• pp.97-108
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• 2008

In this paper Bayes estimator of the parameter and reliability function of the zero-truncated Poisson distribution are obtained. Furthermore, recurrence relations for the estimator of the parameter are also derived. Monte Carlo simulation technique has been made for comparing the Bayes estimator and reliability function with the corresponding maximum likelihood estimator (MLE) of zero-truncated Poisson distribution.

• Journal of Korean Home Economics Education Association
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• v.1 no.1
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• pp.33-42
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• 1989

By the comparative analysis of high school Home Economics curricula in the U.S., Japan and Taiwan, this study first attempts to understand the current Home Economics education and to access its treads for each country. Based on the findings of the analysis, the study also seeks to get the major implications of the analysis for the betterment of the Korea Home Economics Education. The main sources of information and data analyzed here are： 1) curricula for both Oklahoma and Ohio state as representatives of the U.S.； 2) Home Economics Teaching Guidelines in Japan； and 3) Home Economics curriculum in Taiwan. Content Analysis technique is applied in this study. The major elements of contents include：1) structure of the curriculum； 2) subject name； 3) unit (time) allotment； 4) goals； 5) subject areas and content composition； and 6) other related characteristics for the implementation of the curriculum. Summarized results of the study outline as follows： 1) Home Economics is offered as independently required subject with equal status to Mathematics, Science, and Social Studies subject in all three countries； 2) Sex discrimination is prohibited both in the U.S. and Taiwan, while in Japan sex equity is not secured for Home Economics educations； 3) Time allotment for Home Economics in Japan and Taiwan is similiar to that in Korea；4) Subject areas cover such fields as Foods and Nutrition, Clothing and Textiles, Home Management, and Human Development in all three countries, which is similiar to those of Korea. In addition, Consumer Education and Career Education are also covered in the U.S., whereas in Japan Child Care is offered； and 5) Curriculum can be utilized as instructional planning material due to the clear specification of instructional methods, materials, and evaluation methods on the curriculum, especially in the U.S. and Taiwan.

• Bulletin of the Korean Mathematical Society
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• v.59 no.3
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• pp.745-756
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• 2022

We study a nonlinear wave equation on finite connected weighted graphs. Using Rothe's and energy methods, we prove the existence and uniqueness of solution under certain assumption. For linear wave equation on graphs, Lin and Xie [10] obtained the existence and uniqueness of solution. The main novelty of this paper is that the wave equation we considered has the nonlinear damping term |u_t|^p-1·u_t (p > 1).

• Journal of the Korean Mathematical Society
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• v.60 no.2
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• pp.303-325
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• 2023

In this paper, we introduce relative Rota-Baxter systems on Leibniz algebras and give some characterizations and new constructions. Then we construct a graded Lie algebra whose Maurer-Cartan elements are relative Rota-Baxter systems. This allows us to define a cohomology theory associated with a relative Rota-Baxter system. Finally, we study formal deformations and extendibility of finite order deformations of a relative Rota-Baxter system in terms of the cohomology theory.