• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2034-2043
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• 2002

The process design to produce a near net shape home-appliance compressor component using semi-solid die casting process is performed. In order to obtain a good component without defects such as liquid segregation and porosity, the relationship between pressure and time, and plunger tip displacement and injection velocity are proposed with repeated trial and error. The effect of the velocity variation in the process parameters on liquid segregation and extraction is investigated to produce the aluminum frame part(a kind of compressor part) with good mechanical properties. The mechanical characteristic of semi-solid die casting formed parts for AlSi7Mg0.65r(A357) and AlSi17Cu4Mg(A390) are investigated with a view to minimizing the occurrence of defects. To investigate of application possibility at industry field, A380 aluminum alloy with 8∼9% silicon contents used for the squeeze casting process. The obtained mechanical properties is compared with semi-solid die casting.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.129-134
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• 2009

In the present study, the characteristic of flow distribution in the channel of a plate heat exchanger is investigated numerically. In order to accomplish the efficient and fast analyses of the flow characteristics in the channel, a semi-microscopic analysis has been performed using a porous media model. For semi-microscopic analysis using porous media, the flow resistance coefficients are obtained through the result of pressure drop in the experimental data. The results showed that the variation of mass flow rate, geometry and chevron angle strongly depend on the flow distribution in the channel. Particularly, the chevron angle is most important factor for uniform flow distribution.

• Bulletin of the Korean Mathematical Society
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• v.42 no.1
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• pp.53-56
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• 2005

Suppose G is a semi-complete abelian p-group and FG ${\cong}$ FH as commutative unitary F-algebras of characteristic p for any fixed group H. Then, it is shown that, G ${\cong}$ H. This improves a result of the author proved in the Proceedings of the American Math. Society (2002) and also completely solves by an another method a long-standing problem of W. May posed in the same Proceedings (1979).

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1996.10a
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• pp.95-100
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• 1996

In this paper, we first introduce fuzzy less strongly irresolute, fuzzy preless strongly semiopen and fuzzy pre-less strongly semiclosed mappings on fuzzy topological space, and establish their various characteristic properties. Finally, we introduce and study fuzzy less strongly semi-connectedness with the help of fuzzy less strongly semiopen sets and fuzzy less strongly semi-q-neighborhoods.

• Bulletin of the Korean Mathematical Society
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• v.50 no.3
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• pp.705-717
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• 2013

In this paper, we study the geometry of half lightlike submanifolds M of a semi-Riemannian manifold $\tilde{M}$ with a semi-symmetric non-metric connection subject to the conditions; (1) the characteristic vector field of $\tilde{M}$ is tangent to M, the screen distribution on M is totally umbilical in M and the co-screen distribution on M is conformal Killing, or (2) the screen distribution is integrable and the local lightlike second fundamental form of M is parallel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.881-885
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• 2004

We report a method for making a device on which semi-conducting single-walled carbon nanotubes are attached selectively between two metal electrodes. This method is divided two processes. First we can connect a rope of single-walled carbon nanotubes(SWNTs) between two electrodes using the electric field. But a SWNTs' rope obtained by the first process was composed of a few of metallic and semi-conducting SWNTs together. The second process is to burn the metallic and semi-conducting nanotubes through applying a voltage. As a result, we can obtain a semi-conducting SWNT device. To make the patterned electrodes, we deposited $SiO_2$(150nm) on a wafer. After then, we made a patterned samples with Ti(200 $\AA$)/Au(300$\AA$). We empirically obtained a electric condition 0.66 $V_{pp}$ /${\mu}{\textrm}{m}$@5MHz. From this result, we verified that most of current go through the metallic nanotubes in this device. When we apply DC voltage between two electrodes, the metallic carbon nanotubes are burnt. Finally, we can obtain a semi-conducting nanotube device which we desire to make. We got the I-V characteristic graph which has shown the semi-conducting property. We hope to apply to the various applications using this selective semi-conducting carbon nanotube deposition method.ethod.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.99-104
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• 2006

A semi-Lagrangian finite element scheme with objective time stepping algorithm for solving viscoelastic flow problem is presented. The convection terms in the momentum and constitutive equations are treated using a quasi-monotone semi-Lagrangian scheme, in which characteristic feet on a regular grid are traced backwards over a single time-step. Concerned with the generalized midpoint rule type of algorithms formulated to exactly preserve objectivity, we use the geometric transformation such as pull-back, push-forward operation. The method is applied to the 4:1 planar contraction problem for an Oldroyd B fluid for both creeping and inertial flow conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.98-105
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can very from dendritic to globular. The estimation of behaviour characteristic in the compression simulation with seim-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for compression process is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process considering soldification phenomena is performed to the isothermal conditions of two dimensional problems. To analysis of compression process by using semi-solid materials, a new stress-strain relationship is described, and compression analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for compression force and ram displacement will be compared to experimental data.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.1
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• pp.127-134
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• 1999

Boolean functions have an important role for designing block ciphers and hash functions. In this paper, we propose a method for designing optimum correlation immune functions. We also analyze their cryptographic properties - balancedness, nonlinearity, correlation value to the set of linear functions, correlation immunity, propagation characteristic, and algebraic degree. Such functions are special type of Semi-bent functions [2,5]

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.907-914
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• 2008

This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine.