• Communications of the Korean Mathematical Society
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• v.34 no.3
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• pp.783-797
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• 2019

In this paper, we introduce and investigate a subclass ${\Im}_{\Sigma}({\alpha},{\beta},{\gamma})$ of analytic and bi-univalent functions of complex order in the open unit disk U in complex plane. Here, we obtain an upper bound for the second Hankel determinant of the functions belonging to this class. Moreover, several interesting conclusions of the results obtained here are also discussed.

• Communications of the Korean Mathematical Society
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• v.37 no.3
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• pp.723-734
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• 2022

In this work, we introduce a new subclass of analytic functions of complex order involving the (p, q)-derivative operator defined in the open unit disc. For this class, several Fekete-Szegö type coefficient inequalities are derived. We obtain the results of Srivastava et al. [22] as consequences of the main theorem in this study.

• Honam Mathematical Journal
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• v.45 no.1
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• pp.92-108
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• 2023

We determine the upper bounds on fourth order Hankel determinants H⁽²⁾₄(f) and H⁽³⁾₄(f) for the class S^*_L of lemniscate starlike functions defined on the open unit disk which was introduced by Sokół and Stankiewicz in [17].

• Korean Journal of Mathematics
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• v.30 no.1
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• pp.73-80
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• 2022

In this article, we represent and examine a new subclass of holomorphic and bi-univalent functions defined in the open unit disk 𝖀, which is associated with the Dziok-Srivastava operator. Additionally, we get upper bound estimates on the Taylor-Maclaurin coefficients |a₂| and |a₃| of functions in the new class and improve some recent studies.

• Communications of the Korean Mathematical Society
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• v.37 no.1
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• pp.91-103
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• 2022

In this paper, we introduce Toeplitz operators and Hankel operators with complex Borel measures on the closed unit disk. When a positive measure 𝜇 on (-1, 1) is a Carleson measure, it is known that the corresponding Hankel matrix is bounded and vice versa. We show that for a positive measure 𝜇 on 𝔻, 𝜇 is a Carleson measure if and only if the Toeplitz operator with symbol 𝜇 is a densely defined bounded linear operator. We also study Hankel operators of Hilbert-Schmidt class.

• Communications of the Korean Mathematical Society
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• v.39 no.2
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• pp.407-420
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• 2024

In this paper, we investigate some geometric properties of starlikeness connected with the hyperbolic cosine functions defined in the open unit disk. In particular, for the class of such starlike hyperbolic cosine functions, we determine the lower bounds of partial sums, Briot-Bouquet differential subordination associated with Bernardi integral operator, and bounds on some third Hankel determinants containing initial coefficients.

• Honam Mathematical Journal
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• v.46 no.3
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• pp.515-521
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• 2024

In our paper, by using different inequalities regarding the coefficients of the normalized close-to-convex functions in the open unit disk, we found a smaller upper bound of the third Hankel determinant for the class of close-to-convex functions as compared with those obtained by Prajapat et. al. in 2015.

• The Mathematical Education
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• v.39 no.2
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• pp.127-144
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• 2000

School mathematics are composed of five major units of numbers& algebraic expressions, equations & inequalities, functions, figures, and statistics & probabilities. But if we look into the general activities of mathematics teachers in their class, they rather do not take into account students\` cognitive and affective traits or degree of difficulty which each of the unit has. For successful teaching of mathematics, teachers should take into consideration many affective items which influence the students\` scholastic achievement. Among them student\`s liking for the mathematics is commonly accepted as the most important factor for successful learning. In this study, with the five units of school mathematics, we investigated the students\` degree of likings for each unit. To fined out whether there are any differences in students\` likings for the mathematics, between regions and kind of schools, we classified the population according to the locations and kinds of schools. To do this, we divided the whole region into four parts such as Seoul, large city, medium city and town. Moreover, we partitioned the whole secondary school students into four groups of middle school students, vocational high school students, pro-science students of academic high schools, and pro-liberal arts students of academic high schools. From each partition, we sampled similar size of experimental groups which came up to total 1260 students. Analysing the answer sheets which the students responded about the questionnaire, we investigated the following questions using the ANOVA test. 1. Is there any differences in the trend of likings for each unit between the regional classifications? 2. Is there any differences in the trend of likings for each unit between the classifications of secondary schools? 3. What trends of changes are there in the degree of likings for each unit according to the rising of students\` grade?

• Journal of the Korean Society of Earth Science Education
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• v.12 no.2
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• pp.151-164
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• 2019

The purpose of this study is to find out the effects of reconstructing unit 'Seasonal Change' using step-by-step questioning for concepts changes to adjusting misconceptions of elementary school students. Most students have pre-conceptions at describing seasonal changes based on their experiences. Therefore, in newly developed unit, we reconstructed unit to include core teaching and learning contents by finding out common pre-conceptions of students and specifying purpose of teaching at misconceptions found in pre-conceptions as 'constituent of class for conceptual change'. After the scientific concept test, the result of 24 students in experimental group is statistically significant. Also, according to the result of qualitative analysis, the number of activated conceptional resources and degree of specificity in explaining seasonal changes are higher than that of control group.

• Journal of the Korean Society of Earth Science Education
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• v.13 no.2
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• pp.147-161
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• 2020

In order to help elementary students understand the astronomical unit in depth, this study applied backward design 2.0 to check the effect on students' science academic achievement, performance evaluation, and science class satisfaction. As a result of the study, there was no statistically significant difference in the science achievement test, but the average score of the experimental group has improved. As a result of the performance evaluation test, there was a statistically significant difference because the feedback was well provided through the process-focused assessment and it helped in-depth understanding. As a result of the science class satisfaction test, there was a statistically significant difference in the areas of science curriculum and peer relation except for the science teacher area. This is because a differentiated science curriculum was designed through analysis of achievement standards, and various teaching methods of student-centered were implemented to reach achievement standards. We hope this study will focus on the impact of backward design 2.0 on learners in elementary science classes and help find ways to effectively apply backward design 2.0 in the field.