• Journal of Korea Foundry Society
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• v.13 no.5
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• pp.441-449
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• 1993

SiC particulate reinforced magnesium matrix composites were fabricated by melt stirring method. The effet of several factors on mechanical properties and the efficiency of melt stirring method from the viewpoint of these properties were investigated. The tensile strength increased and the elongation decreased with decrease of the particle size or the increase of the paticulate volume fraction for pure magnesium matrix and Mg-5%Zn alloy matrix composites. A longer stirring time improved the tensile strength of these composites. The tensile strength of Mg-5%Ca alloy matrix composites which shows no uniform paticulate distribution was a little lower than that of matrix alloy. Rapid solidification rate is preferred for the improved tensile strength of these composites. The pure magnesium matrix and Mg-5%Zn alloy matrix composites have tensile strength of about 400MPa. This value agrees with the tensile strength of some magnesium matrix composites fabricated by liquid infiltration method or powder metallurgy method at the same volume fraction of reinforcements of whisker or particle. Therefore, the melt stirring method which has the advantages of simple process is considered to be efficient in fabricating magnesium matrix composites.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1063-1070
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• 2002

To resist ice adhesion on cooling wall is concerned to continuous ice formation in thermal storage system. In this study, ice slurries were formed with two ecological aqueous solution, one is ethanol+silanol and the other is propylene glycol+silanol. By freezing under stirring the solution of $300m\ell$ in a stainless steel vessel which was immersed and cooled in a temperature controlled bath, the shape of ice slurry and the strength of ice adhesion on wall was observed with measuring the temperature and stirring load variation. As the concentration is smaller and the supercooling degree is larger, the ice adhesion is easy to occur. When the stirring load is larger than$ 2.1\times10^{-5}W$, the ice adhesion occurred.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.111-114
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• 2010

The effects of grain refinement and melt stirring on the mechanical properties and fluidity of AZ91D and AM50 alloys were investigated. The average grain sizes of those alloys were reduced by the micro-addition of strontium. The tensile properties and fluidity were increased by this treatment. Those were reduced remarkably by the melt stirring.

• Tribology and Lubricants
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• v.8 no.1
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• pp.70-77
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• 1992

Al-Pb-Si bearing alloys were produced by a forced stirring method and a rapid solidification process to study wear properties of bearing alloys. A homogeneous distribution of Pb particles in Al matrix could be obtained by means of the forced stirring and the rapid cooling during the casting. The wear properties of bearing alloys were tested by a pin-on-disc wear tester. The change in microstructure according to the alloy manufacturing variables was observed by the backscattered electron images. Al-Pb and Al-Si binary alloys showed a transition from mild to severe wear. The transition was not found in Al-Pb-Si ternary alloys. It could be concluded that the lubricatioin effect of Pb and the strengthening effect of Si in the ternary alloys enhanced the bearing properties. A Al-25%Pb-13%Si alloy showed the lowest coefficient of friction in this experiment. It indicated that the optimum concentration of alloy was 25% Pb and 13% Si when the forced stirring of melt and water-cooled-copper-mold solidification were adopted.

• Transactions of Materials Processing
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• v.10 no.7
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• pp.558-564
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• 2001

An experimental modeling is applied to investigate the formation of forms in molten aluminum By using a specially designed equipment, the effect of process variables, such as the shape of stirrer, stirring velocity and fluid viscosity, on the formation of foams were studied in the glycerine added water. Bubbles formed in water had various diameter from 1 to 10 mm and the number of bubbles was 0 to 20/$cm^2$. It turned out that among various variables the stirring velocity and fluid viscosity played important roles on the formation of bubbles. The results obtained from the model experiment were preyed to be convincible also in the real aluminum foam.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.860-863
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• 2005

The microcapsules containing fragrant oil as functional material were prepared by in-situ polymerization with prepolymer that was made from melamine-formaldehyde (MF) as wall material of microcapsules. The effects of polymerization variables, such as the nature and concentration of surfactants, stirring rate, and stirring time, on the size and distribution of the particles were investigated. Fourier transform-infrared spectroscopy (FT-IR), thermal analysis, particle size analysis, scanning electron microscopy (SEM) observation were used to investigate the characteristics of microcapsules. Through the FT-IR and SEM analysis, we found that the prepared microcapsules were containing fragrant oil and the shape of particle was spherical. The nature and concentration of surfactants, stirring rate, and stirring time had profound effects on the particle size and particle size distribution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.180-183
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• 1997

The forming process of metal matrix composites by the die casting and squeeze casting process are limited in size and dimension in term of final parts without machining. The thixoforming process for metal matrix composites has numerous advantages compared to die casting, squeeze casting and compocasting. The characteristics of thixoforming process can decrease the liquid segregation because of he improvement in fluidity in a globular microstructure state and utilizes flow without air entrapment. Therefore, in order to obtain the sound parts of metal matrix composites by using thixoforming process which as co-existing solidus-liquidus pahse, it si very important to obtain reheating condition. However, for he thixoforming process, the billet with the desired volume fraction must be heated to obtain a uniform temperature distribution over the entire cross-sectional areas. To obtain the reheating conditions of composites, the particulate reinforced metal matrix composites for thixoforming were fabricated by combined stirring process which is simultaneously performed with electro-magnetic stirring process which is simultaneously performed with electro-magnetic stirring and mechanical stirring process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.7
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• pp.901-908
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• 2003

Numerical study on stirring characteristics in a microchannel with blocks arranged periodically has been performed. Viscous flows through the microchannel is simulated three-dimensionally using a commercial code, FLUENT 6.0. Focus is given to the effect on the stirring characteristics of the geometric factors including the pitch, height and angle of the block arrangement. The numerical results at low Reynolds numbers show that the particles' trajectories in the microchannel heavily depend on the block arrangement. A nonlinear dynamical tool, i.e. Lyapunov exponent, was used in analysing the mixing effect. It was found that the mixing is the most effective at a certain combination of parameter values.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.391-395
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• 2006

Microcapsules containing fragrant oils as a core material were prepared by in situ polymerization, using melamine-formaldehyde prepolymer as the wall material. The several parameters, such as stirring times, stirring rates, emulsifier types, emulsifier concentrations, and the viscosity of the core materials, affect the characteristics of the microcapsules. These parameters were investigated by the analyses of microcapsule size, particle size distribution, and morphology. The average microcapsule size decreased with an increase in stirring time, stirring rate, emulsifier concentration, and viscosity of the core material. It was also found that poly(vinyl alcohol) as a protective colloid could enhance the stability of the melamine-formaldehyde microcapsules.

• Journal of Korea Foundry Society
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• v.32 no.1
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• pp.16-23
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• 2012

In this study, we develop the lower pressure die casting with rheo-forming process of A356 aluminum alloy and vacuum system which can control the crystal size and obtain the high strengthened-light material. Using this process, we fabricate the thin plate for bipolar plate through the low pressure die casting with electromagnetic stirring and vacuum-evacuation which can control the crystal grain by electromagnetic stirring. Thin plate ($110mm{\times}130mm{\times}1mm$) is fabricated by this process. The average Vickers hardness of thin plate is about 77 HV.