• Journal of Korea Multimedia Society
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• v.6 no.5
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• pp.870-875
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• 2003

We Present digital watermarking using a quadratic equation embedding method in wavelet transform domain in order to improve the invisibility. Generally, embedding watermark used a simple equation form, but we extended a quadratic equation form in this paper. We performed a computer simulation in order to compare proposed method to other methods using LENA, GOLDHILL, BARBARA, and MAN images By computer experiments, invisibility of the proposed method better than the conventional methods at 100 % normalized similarity.

• Bulletin of the Korean Mathematical Society
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• v.39 no.2
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• pp.199-209
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• 2002

In this paper, we investigate the problem of stability of the quadratic functional equation f(x+y+z)+f(y-z)+f(y-z)+f(x-z) = 3f(x)+3f(y)+3f(z) on abelian group.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.1
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• pp.83-93
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• 2016

In this paper, we introduce a generalized quadratic functional equation with several variables and then investigate its generalized Hyers-Ulam stability in normed spaces.

• Journal for History of Mathematics
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• v.22 no.2
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• pp.117-130
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• 2009

This study shows how to use effectively construction and solution of the quadratic equation developed by mathematicians such as Gyung Sun-jing, Hong Jung-ha, Hong Dae-yong, Lee Sang-hyuk, and Nam Byung-gil through mathematics history of Chosun Dynasty. Mathematics history of Chosun Dynasty can be used in order to enhance comprehension and increase interest in an introduction to the quadratic equation. It also can be used to help motivate middle school students to solve the quadratic equation with much interest during the development phase, and develope conceptual thinking and reflective thinking in the practical phase.

• Journal of the Chungcheong Mathematical Society
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• v.17 no.1
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• pp.57-75
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• 2004

The aim of this paper is to solve the general solution of a quadratic functional equation f(x + 2y) + 2f(x - y) = f(x - 2y) + 2f(x + y) in the class of functions between real vector spaces and to obtain the generalized Hyers-Ulam stability problem for the equation.

• The Pure and Applied Mathematics
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• v.17 no.2
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• pp.175-183
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• 2010

Using Darbo's fixed point theorem, we establish the existence of monotone solutions for a nonlinear quadratic integral equation of Volterra type in the Banach space of real functions defined and continuous on a bounded and closed interval.

• Bulletin of the Korean Mathematical Society
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• v.42 no.1
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• pp.133-148
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• 2005

In this paper, we obtain the general solution of a gen-eralized quadratic and additive type functional equation f(x + ay) + af(x - y) = f(x - ay) + af(x + y) for any integer a with a $\neq$ -1. 0, 1 in the class of functions between real vector spaces and investigate the generalized Hyers- Ulam stability problem for the equation.

• Communications of the Korean Mathematical Society
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• v.27 no.3
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• pp.523-535
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• 2012

In this paper, we investigate a fuzzy version of stability for the functional equation $$2f(x+y)+f(x-y)+f(y-x)-3f(x)-f(-x)-3f(y)-f(-y)=0$$ in the sense of M. Mirmostafaee and M. S. Moslehian.

• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.377-392
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• 2004

In the present paper, we obtain the Hyers-Ulam-Rassias stability in the sense of Gavruta for the general quadratic functional equation f(χ + y + z) + f(χ - y) + f(χ - z) = f(χ - y - z) + f(χ + y) + f(χ + z).

• Journal of applied mathematics & informatics
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• v.33 no.3_4
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• pp.351-363
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• 2015

In this paper, we investigate existence of solutions to a class of quadratic integral equation of Fredholm type in the space of functions with tempered moduli of continuity. Two numerical examples are given to illustrate our results.