• Journal of the Chungcheong Mathematical Society
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• v.27 no.2
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• pp.211-218
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• 2014

In 3-dimensional Euclidean space, the geometric figures of a regular curve are completely determined by the curvature function and the torsion function of the curve, and surfaces are the fundamental curved spaces for pioneering study in modern geometry as well as in classical differential geometry. In this paper, we define parametrizations for surface by using parametric functions whose images are in the normal plane of each point on a given curve, and then obtain some results relating the Gaussian curvature of the surface with curvature and torsion of the given curve. In particular, we find some conditions for the surface to have either nonpositive Gaussian curvature or nonnegative Gaussian curvature.

• East Asian mathematical journal
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• v.33 no.2
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• pp.199-216
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• 2017

A rational number as operator is eventually that it is considered a mapping. Depending on how selecting domain (the target of operation by rational number) and codomain (including the results of operations by rational number), it is possible to see the rational in two aspects. First, rational numbers can be deal with functions if we choose the target of operation by rational number as a number field containing rationals. On the other hand, if we choose the target of operation by rational number as integral domain $\mathbb{Z}$, then rational numbers can be regarded as partial functions on $\mathbb{Z}$. In this paper, we regard the rational numbers with a view of partial functions, we investigate the theoretical background of the relationship between the multiplication of rational numbers and the composition of rational numbers as operators.

• Korean Journal of Child Studies
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• v.30 no.1
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• pp.109-125
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• 2009

This study examined the effects of estimation activities on children's operation and measurement abilities. Subjects were 60 five-year-old children. This experiment used the untreated control group design with pretest and posttest. Instruments used to collect data were the Number and Operation and Measurement tests part of the Test of Mathematics Ability for Young Children (TMAYC) developed by Hong, Lee and Chung (2006). ANCOVA was employed for statistical analysis. Results of the posttest showed that children in the experimental group scored significantly higher on children's operation and measurement abilities than the control group. Results imply that an estimation program can be an effective teaching model for improving children's operation and measurement abilities.

• Bulletin of the Korean Mathematical Society
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• v.50 no.2
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• pp.431-440
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• 2013

Let ($M^3$, $g$) be a 3-dimensional closed Sasakian spin manifold. Let $S_{min}$ denote the minimum of the scalar curvature of ($M^3$, $g$). Let ${\lambda}^+_1$ > 0 be the first positive eigenvalue of the Dirac operator of ($M^3$, $g$). We proved in [13] that if ${\lambda}^+_1$ belongs to the interval ${\lambda}^+_1{\in}({\frac{1}{2}},\;{\frac{5}{2}})$, then ${\lambda}^+_1$ satisfies ${\lambda}^+_1{\geq}{\frac{S_{min}+6}{8}}$. In this paper, we remove the restriction "if ${\lambda}^+_1$ belongs to the interval ${\lambda}^+_1{\in}({\frac{1}{2}},\;{\frac{5}{2}})$" and prove $${\lambda}^+_1{\geq}\;\{\frac{S_{min}+6}{8}\;for\;-\frac{3}{2}<S_{min}{\leq}30, \\{\frac{1+\sqrt{2S_{min}}+4}{2}}\;for\;S_{min}{\geq}30$$.

• Bulletin of the Korean Mathematical Society
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• v.36 no.1
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• pp.25-31
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• 1999

Let $\nu$ be a positive Borel measure on a space of homogeneous type (X, d, $\mu$), satisfying the doubling property. A condition on a weight $\omega$ for whixh a maximal operator $M\nu f$(x) defined by M$mu$f(x)=supr>0{{{{ { 1} over {ν(B(x,r)) } INT _{ B(x,r)} │f(y)│d mu (y)}}}}, is of weak type (p,p) with respect to (ν, $omega$), is that there exists a constant C such that C $omega$(y) for a.e. y$\in$B(x, r) if p=1, and {{{{( { 1} over { upsilon (B(x,r) } INT _{ B(x,r)}omega(y) ^ (-1/p-1) d mu (y))^(p-1)}}}} C, if 1$infty$.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.125-128
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• 2004

Using the theory of Generalized Nets we have modelled the information exchange within the electronic archives of an idealized univerity Intranet.

• The Korean Journal of Applied Statistics
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• v.7 no.2
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• pp.239-248
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• 1994

The Yule-Walker estimator and the approximate conditional least squares estimator of the parameter of the EARMA(1, 1) model are obtained. These two estimators are compared by simulation study. It is shown that the approximate conditional least squares estimator is better in the sense of the mean square error than the Yul-Walker estimator.

• Communications of the Korean Mathematical Society
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• v.37 no.2
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• pp.347-358
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• 2022

In this paper, we first introduce the notions of superfluous and coessential subacts. Then hollow and co-uniform S-acts are defined as the acts that all proper subacts are superfluous and coessential, respectively. Also it is indicated that the class of hollow S-acts is properly between two classes of indecomposable and locally cyclic S-acts. Moreover, using the notion of radical of an S-act as the intersection of all maximal subacts, the relations between hollow and local S-acts are investigated. Ultimately, the notion of a supplement of a subact is defined to characterize the union of hollow S-acts.

• East Asian mathematical journal
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• v.25 no.4
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• pp.441-447
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• 2009

Jat and Choudhari defined a near-ring R with left bipotent or right bipotent condition in 1979. Also, we can dene a near-ring R as subcommutative if aR = Ra for all a in R. From these above two concepts it is natural to investigate the near-ring R with the properties aR = $Ra^2$ (resp. $a^2R$ = Ra) for each a in R. We will say that such is a near-ring with (1,2)-potent condition (resp. a near-ring with (2,1)-potent condition). Thus, we can extend a general concept of a near-ring R with (m,n)-potent condition, that is, $a^mR\;=\;Ra^n$ for each a in R, where m, n are positive integers. We will derive properties of near-ring with (1,n) and (n,1)-potent conditions where n is a positive integer, any homomorphic image of (m,n)-potent near-ring is also (m,n)-potent, and we will obtain some characterization of regular near-rings with (m,n)-potent conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.387-396
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• 2020

The purpose of this study is to identify the variables of metropolitan and provincial offices of education that affect the academic achievement of unit schools, and to predict how academic achievements dynamically change with the support of offices of education. The results of academic achievement of 606 general high schools in 16 metropolitan and provincial offices of education(rates of attaining more than normal education in Korean, English, and mathematics subjects) were analyzed using a multi-level model and system dynamics. As a result of the analysis, it was confirmed that the provincial and provincial offices of education's efforts to increase the efficiency of local education finance, the efforts to reduce teacher administration, and the facilitation of faculty training were the variables of the provincial and provincial offices of education. In addition, through policy experiments, efforts to revitalize teacher training were the most influential factors in academic achievement of unit schools, followed by efforts to streamline local education finances and to reduce the administrative work of teachers. In order to improve the academic achievement of unit schools, the functions of the metropolitan and provincial offices of education should be strengthened based on the education accountability, and policies need to be established in the mid- to long-term perspective.