• Journal of Educational Research in Mathematics
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• v.13 no.1
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• pp.95-106
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• 2003

This study attempts to identify the characteristics of the structure of mathematics textbooks of North Korean high schools. The previous researches on the mathematics textbooks of North Korea show that North Korean mathematics textbooks have a linear structure, which is different from a spiral structure of South Korean textbooks. However, this study found that the textbooks of North Korea published after 1994 indicate that some sections reveal a spiral structure. In addition, most sections of North Korean mathematics textbooks are collectively composed, particularly so in the section of algebra.

• Kyungpook Mathematical Journal
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• v.13 no.2
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• pp.153-156
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• 1973

• The Pure and Applied Mathematics
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• v.19 no.1
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• pp.1-5
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• 2012

We study surfaces of revolution in the three dimensional Euclidean space $\mathbb{R}^3$ with two distinct axes of revolution. As a result, we prove that if a connected surface in the three dimensional Euclidean space $\mathbb{R}^3$ admits two distinct axes of revolution, then it is either a sphere or a plane.

• Bulletin of the Korean Mathematical Society
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• v.52 no.2
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• pp.685-697
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• 2015

We investigate the stability of nonlinear differential equations of the form $y^{(n)}(x)=F(x,y(x),y^{\prime}(x),{\cdots},y^{(n-1)}(x))$ with a Lipschitz condition by using a fixed point method. Moreover, a Hyers-Ulam constant of this differential equation is obtained.

• Journal of applied mathematics & informatics
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• v.28 no.1_2
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• pp.295-309
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• 2010

In this paper, we study delayed high-order Cohen-Grossberg neural networks with reaction-diffusion terms and Neumann boundary conditions. By using inequality techniques and constructing Lyapunov functional method, some sufficient conditions are given to ensure the existence and convergence of the periodic oscillatory solution. Finally, an example is given to verify the theoretical analysis.

• Journal of the Korean School Mathematics Society
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• v.3 no.1
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• pp.17-30
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• 2000

This study is for finding out if using the method "Mind Map" in the section "function" during the math class affects on the disposition and solving problems of the students or not The study has found the following results: 1. The chains of concepts has formed by using both right brain and left brain in the students′ notebooks. 2. The power of math in the ability of solving problems has been strengthened.

• Journal of the Korean Mathematical Society
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• v.41 no.3
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• pp.501-511
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• 2004

We prove the Hyers-Ulam-Rassias stability of the Davison functional equation f($\chi$y) + f($\chi$ + y) = f($\chi$y + $\chi$) + f(y) for a class of functions from a ring into a Banach space and we also investigate the Davison equation of Pexider type.

• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.495-502
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• 2004

We consider the applications of extremal length to the boundary behavior of analytic functions and derive a theorem in connection with the capacity. This theorem applies the extremal length to the analytic functions defined on the domain with a number of holes. So it shows us the usefulness of the method of extremal length.

• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.585-594
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• 2006

We consider a stochastic integral process represented by multiple Ito-Wiener integrals. We derive gaussian chaos which has some shift continuous function. We get continuity property of self-similar process represented by multiple integrals and finally we show that $Y_{H_t}$ (t) is continuous in t with probability one for Holder function $H_t$ of exponent $\beta$.

• Journal of applied mathematics & informatics
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• v.6 no.3
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• pp.757-770
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• 1999

We analyse in this paper the possibility of using preconditioning techniques as for square non-singular systems, also in the case of inconsistent least-squares problems. We find conditions in which the minimal norm solution of the preconditioned least-wquares problem equals that of the original prblem. We also find conditions such that thd Kaczmarz-Extendid algorithm with relaxation parameters (analysed by the author in [4]), cna be adapted to the preconditioned least-squares problem. In the last section of the paper we present numerical experiments, with two variants of preconditioning, applied to an inconsistent linear least-squares model probelm.