• Korean Journal of Mathematics
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• v.10 no.2
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• pp.149-155
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• 2002

We develop some basic properties of $t$-fuzzy ideals in a monoid or a group and find the sufficient conditions for a fuzzy set in a division ring to be a $t$-fuzzy subring and the necessary and sufficient conditions for a fuzzy set in a division ring to be a $t$-fuzzy ideal.

• Journal of the Chungcheong Mathematical Society
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• v.6 no.1
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• pp.95-104
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• 1993

There are some sufficient or necessary conditions about projectivity for toric varieties. We consider one of them and state some conditions about projectivity for a 3-dimensional compact nonsingular case which is obtained from a projective one by nonsingular equivariant blow-down.

• East Asian mathematical journal
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• v.18 no.2
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• pp.235-243
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• 2002

In this paper, we get conditions for the natural projections of some product manifolds with varying metrics of two Riemannian manifolds to be harmonic, and necessary and sufficient conditions for some product manifolds with the harmonic natural projections of two Einstein manifolds to be Einstein manifolds.

• Journal of Korea Society of Industrial Information Systems
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• v.11 no.5
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• pp.62-66
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• 2006

We investigate various $\Phi(t)-stability$ of comparison differential equations and we abtain necessary and/or sufficient conditions for the uniform asymptotic and exponential asymptotic stability of the nonlinear differential equation x'=f(t, x).

• Bulletin of the Korean Mathematical Society
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• v.43 no.1
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• pp.149-159
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• 2006

This paper presents necessary and sufficient conditions for complete controllability, complete observability and realizability associated with matrix Lyapunov systems under certain smoothness conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.425-429
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• 1992

Point sets in the Euclidean and digital planes are discussed. The local necessary and sufficient conditions are suggested for pointed lattice extraction from these sets are presented. A number of theorems and corollaries are given. The regular and "almost" regular point sets are studied. The results can be used in automatic control of textured textile images by both general and multiprocessing systems.g systems.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.174-176
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• 2009

This paper aims to investigate generation conditions necessary for the most efficient generation by measuring electricity power under various irradiation conditions, since the photovoltaic generation system has high costs and low efficiency. This thesis aims to investigate generation conditions necessary for the most efficient generation by measuring electricity power under various irradiation conditions, since the photovoltaic generation system has high costs and low efficiency. Although the generation power increased with the irradiation, the former did not vary directly as the latter. This meant that the variation of the generation power was concerned in the temperature of a module, the ambient temperature, and the directions of irradiation as well as the irradiation. As for the monthly accumulated irradiation and monthly accumulated power, the maximum irradiation and generation power were observed in May and October and the irradiation, the power and the accumulated generation power were all the highest in spring, followed by fall, summer and winter.

• Journal of the Korean Mathematical Society
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• v.21 no.1
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• pp.21-29
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• 1984

• Kyungpook Mathematical Journal
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• v.15 no.2
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• pp.237-239
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• 1975

• Journal of the Korean Mathematical Society
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• v.11 no.2
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• pp.121-133
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• 1974