• Journal of the Korean Mathematical Society
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• v.45 no.1
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• pp.197-204
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• 2008

We study diameter preserving linear maps from C(X) into C(Y) where X and Y are compact Hausdorff spaces. By using the extreme points of $C(X)^*\;and\;C(Y)^*$ and a linear condition on them, we obtain that there exists a diameter preserving linear map from C(X) into C(Y) if and only if X is homeomorphic to a subspace of Y. We also consider the case when X and Y are noncompact but locally compact spaces.

• Kyungpook Mathematical Journal
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• v.55 no.1
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• pp.91-101
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• 2015

In this paper, we investigate the stability of the functional equation f(-x + y + z + w) + f(x - y + z + w) + f(x + y - z + w) + f(x + y + z - w) = 3f(x) + f(-x) + 3f(y) + f(-y) + 3f(z) + f(-z) + 3f(w) + f(-w) by using the direct method in the sense of Hyers.

• The Pure and Applied Mathematics
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• v.2 no.1
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• pp.35-41
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• 1995

We consider the linear differential equations y〃'＋ P($\chi$)y'＋Q($\chi$)y=0 (1)(y"＋P($\chi$)y)'-Q($\chi$)y =0 (2) Where (2) in the adjoint of (1) and P($\chi$), Q($\chi$) are continuous functions satisfying P($\chi$)$\geq$0, Q($\chi$)$\leq$0, P($\chi$)-Q($\chi$)$\geq$0 on [a, ${\alpha}$). (3) In this, we show that a condition a oscillatory of(1).(omitted)

• Journal of the Chungcheong Mathematical Society
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• v.29 no.3
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• pp.429-442
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• 2016

In this paper we show that the solutions to the perturbed differential system $$y^{\prime}=f(t,y)+{\int}_{to}^{t}g(s,y(s),Ty(s))ds$$ have uniformly Lipschitz stability and asymptotic behavior by imposing conditions on the perturbed part $\int_{to}^{t}g(s,y(s),Ty(s))ds$ and the fundamental matrix of the unperturbed system y' = f(t, y).

• The Pure and Applied Mathematics
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• v.14 no.1 s.35
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• pp.23-35
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• 2007

We investigate the modified Hyers-Ulam-Rassias stability for the following mixed type functional equation, i.e, cubic or quadratic type functional equation : 9f(x+y)-9f(x-y)+f(6y)=3f(x+3y)-3f(x-3y)+9f(2y).

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.215-219
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• 2001

NaY Zeolite를 Autoclave의 자생압력하에 90℃에서 6-36시간 수열 합성법에 의해 합성하였다. 합성된 NaY Zeolite는 1-2㎛의 크기를 갖는 octahedral 구조이고, 격자상수(a)는 23.9230인 NaY zeolite가 단일상으로 합성되었다. SiO₂/Al₂O₃의 몰비는 NaY type인 3.65이고, 상용 NaY zeolite의 BET(509.3㎡/g)에 비하여 Muti- point BET가 약 607.2로 100㎡/g 증가하였고, Pore volume은 0.2416cc/g에 비하여 0.3149cc/g로 증가하였다.

• Proceedings of the Korean Society of Crop Science Conference
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• 1989.05a
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• pp.20-21
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• 1989

• Proceedings of the Korean Society of Crop Science Conference
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• 1989.05a
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• pp.24-25
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• 1989

• The Pure and Applied Mathematics
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• v.15 no.2
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• pp.103-110
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• 2008

In this paper, we obtain the general solution and the stability of the cubic functional equation f(2x + y, 2z + w) + f(2x - y, 2z - w) = 2f(x + y, z + w) + 2f(x - y, z - w) + 12f(x, z). The cubic form $f(x,\;y)\;=\;ax^3\;+\;bx^2y\;+\;cxy^2\;+\;dy^3$ is a solution of the above functional equation.

• East Asian mathematical journal
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• v.35 no.5
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• pp.559-568
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• 2019

In this paper, we investigate the stability problems for a functional equation f(x + 2y)+f(x - 2y) - 4f(x + y) - 4f(x - y) + 6f(x) - 2f(2y) + 12f(y) - 4f(-y) = 0 by using the fixed point theory in the sense of L. C˘adariu and V. Radu.