• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.1
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• pp.31-40
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• 2009

The rheologic properties of elastic impression materials is a very important role as taking high accuracy impression. But, the studies that are focused on the rheologic properties of Korean elastic impression materials are not sufficient. The purpose of this study is to help clinical high accuracy impression taking by testing rheologic properties of elastic impression material that is made by Korea and other countries. Six type III elastic impression materials are tested. Subjects are 2 Korean polyvinylsiloxane(PVS), 2 imported PVS, 1 polyether, and 1 polysulfide. HAAKE RheoStress $1^{(R)}$(Thermo Electron Co. Germany)is used in measuring. HAAKE RheoStress $1^{(R)}$ is plate to plate type rheometer. All subjects is tested 3 times and measuring time is 900 seconds. We measured G′ and loss tangent after mixing. All elastic impression materials had a sigmoid shape on increasing G′ by time and decreasing loss tangent after setting, maximum G' is appeared highest in polyether, and lowest in polysulfide. Initial loss tangent is highest in polyether, and is lowest in Koreans PVS. Significant difference is showed in initial loss tangent between Korean PVS and imported PVS.

• Journal of applied mathematics & informatics
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• v.7 no.2
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• pp.527-538
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• 2000

We provide sufficient conditions for the monotone convergence of a Chebysheff-Halley-type method or method of tangent hyperbolas in a partially ordered topological space setting. The famous kantorovich theorem on fixed points is used here.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.190-194
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• 1993

This paper focuses on the development of the tangent modulus to describe the nonlinearity of concrete based on the continuum damage mechanics. This tangent modulus includes the effects of elasticity, damage and plasticity of concrete.

• Kyungpook Mathematical Journal
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• v.52 no.3
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• pp.271-278
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• 2012

We study some functions defined on the unit tangent space, which are formed with the second fundamental form of submanifolds of a real space form. These give an exact expression of isotropy of submanifolds in a real space form and a relationship between intrinsic invariants and extrinsic ones.

• Kyungpook Mathematical Journal
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• v.53 no.1
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• pp.99-104
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• 2013

We study some properties of tangent lines of parabolas. As a result, we establish some characterizations of parabolas.

• Honam Mathematical Journal
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• v.33 no.3
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• pp.335-340
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• 2011

We study some properties of tangent lines of conic sections. As a result, we establish a characterization of conic sections.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.693-694
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• 2010

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.3
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• pp.1-8
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• 2001

In the DS/CDMA mobile communication systems, the parallel interference canceller is used in order to reduce the multiple access interference and the multipath fading. It is needed the accurate interference estimate in the multistage parallel cancellation. In this paper, the adaptive cancellation method and the new tentative decision device arc proposed and the performance is analyzed. The adaptive cancellation method uses the normalized least mean square(NLMS) algorithm to calculate the weight adaptively, and new tentative decision device uses the hyperbolic tangent decision with null zone. Computer simulation shows that the proposed scheme has the improved performance and the number of user is increased 48% compared with the conventional receiver.

• School Mathematics
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• v.14 no.4
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• pp.409-429
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• 2012

This paper reports the process two 11th grade students went through in reinventing derivatives on their own via a context problem involving the concept of velocity. In the reinvention process, one of the students conceived a tangent line as the limit of a secant line, and then the other student explained to a peer that the slope of a tangent line was the geometric mean of derivative. The students also used technology to concentrate on essential thinking to search for mathematical concepts and help visually understand them. The purpose of this study was to provide meaningful implications to school practices by describing students' process of reinvention of derivatives. This study revealed certain characteristics of the students' reinvention process of derivatives and changes in the students' thinking process.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1293_1294
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• 2009

The sintering and high frequency electro-magnetic properties of Ba-hexagonal ferrite were investigated. All samples of the Ba-hexagonal ferrite were prepared by the conventional mixed oxide method and sintered at $1150^{\circ}C$~$1400^{\circ}C$. From the X-ray diffraction patterns of sintered Ba-hexagonal ferrite, the $Ba_3Co_2Fe_{24}O_{41}$ phase was represented as main phase in the almost sintering conditions. The bulk densities with sintering temperature and decreased at $1400^{\circ}C$. The permittivity ($\varepsilon$') and loss tangent of permittivity ($\varepsilon$"/$\varepsilon$') of $Ba_3Co_2Fe_{24}O_{41}$ ceramics increased and decreased with sintering temperature, respectively. The permeability of $Ba_3Co_2Fe_{24}O_{41}$ ceramics decreased with sinteirng temperature. The loss tangent of permeability was not changed compared each other with sintering temperature. The bulk density of $Ba_3Co_2Fe_{24}O_{41}$ ceramics sintered at $1300^{\circ}C$ was 4.79 g/$cm^3$. The permittivity, loss tangent of permittivity and permeability, loss tangent of permeability were 19.896, 0.1718 and 14.218, 0.2046 at 210 MHz, respectively.