• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.152-155
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• 2004

In the semi-solid die casting process, the important thing is the flow behaviors of semi-solid material. The flow patterns of semi-solid material can make the defects during die filling. To control of the flow patterns, is very important and difficult. In this paper, the flow behaviors of the semi-solid A356 alloy material during die filling at various die gate shapes has been observed with the grain size controlled material. The effects of the gate shape on the die filling characteristics were investigated. The filling tests in each plunger strokes were experimented, also simulated on the semi-solid material die casting process by MAGMAsofi. According to the filling tests and computer simulation, the effect of the gate shape on liquid segregation had been investigated.

• Food Science and Preservation
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• v.10 no.3
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• pp.267-271
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• 2003

This study was carried out to investigate the yield and storability of onions on top-dressing period. Top-dressing period was applied in February, March and March, April with liquid fertilizer and solid fertilizer of farmhouse practice during the onion growing season. The yields of onion in experimental station field and farmhouse field treated with conventional fertilization were 53.2 and 56.6MT, respectively. However, they were 58.2 and 60.8MT with application of liquid fertilizer in February and March, and 53.6 and 59.1MT with application of liquid fertilizer in March and April. Rotting rates until the end of August were lower with application of liquid fertilizer on February and March(15.8％, 28.9％), compared with application of solid fertilizer by farmhouse practice(23.6％, 41.0％), and were 20.7％ and 31.7％ by treatment of liquid fertilizer on March and April. In conclusion, treatment of liquid fertilizer on February and March decreased the rotting rate.

• Journal of the Korean Ceramic Society
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• v.21 no.3
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• pp.271-277
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• 1984

To study interface between crystals grown and molten state in the crusible. Pulling and rotating rate of the shaft were varied in LiF crystal growth by Czochralski method. Lower speed of the pulling and rotating rate increased the degree of convexity in solid-liquid interface and higher speed of the pulling and rotating rate decreased it. Optimum condition of LiF crystal growth obtained as pulling rate was 6.5cm/h when it rotated as 46rpm.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.87-89
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• 2004

Brazing is an indispensable manufacturing technology for liquid rocket engine. In this study, for LRE injector, stainless steel 316L was used of base metal and Ni based MBF-20 of insert metal. The brazing and diffusion was carried out under various conditions. There are solid phase and. residual liquid phase in the brazed joint. With increment of holding time, the amount of solid phase increased and the elements of base metal and insert metal compositionally graded. Boron diffused from insert metal came into base metal and made boride with Cr and Mo at the brazed joint of base metal and insert metal.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.755-758
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• 2005

The mechanism responsible for liquid crystal (LC) alignment on solid substrates treated with mechanical rubbing or polarized UV is not understood. The results of x-ray reflectivity study of LC alignment on a large number of different alignment layers show that the anisotropy in the surface roughness of the substrate completely determines the LC alignment. The anchoring energy depends on the degree of roughness anisotropy and chemical interactions between the substrate and LC molecules.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.78-82
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• 1988

Good quality LiNbO3 single crystals which can be applied to SAW devices, were grown by Czochralski method. It was observed that the gas-bubbles were concentrated in ring shape at the outer part of grown crystals, and this anomaly was illustrated by modeling the mechanism of gas-bubble entrapment according to the melt flow pattern in the crucible. And this mechanism was also encertained by observation of solid-liquid interface shape of grown crystals. The optimal condition for good quality crystals was known that the solid-liquid interface shape was slightly concave.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.191-194
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• 1996

Maxwell displacement current clearly shows the onset of a first order phase transition from gaseous to gaseous-fluid phase, and polar ordering of liquid molecules in the solid phase coexisting with fluid. For further monolayer compression in the fluid/solid phase transition, the condensation of domains was suggested.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2720-2724
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• 2007

Field measurements have revealed that the pressure drop over a borehole during drilling of a slim oil well or a well with a long reach can depend significantly on the rotation speed of the drill pipe. An accurate prediction of the annular frictional pressure drop is therefore important for conditions where the annular clearance is small. An experimental study was carried out to study solid-liquid two phase flow in a slim hole annulus. Annular velocities of carrier fluids varied from 0.2 m/s to 1.5 m/s. The carrier fluids which were utilized included tap water and CMC water solutions. Pressure drops and average flow rates were measured for the parameters such as inner-pipe rotary speed, carrier fluid velocity, hole inclination and particle injection rate. For both water and CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.

• Transactions of Materials Processing
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• v.15 no.5 s.86
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• pp.395-401
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• 2006

It is reported that semi-solid forming process takes many advantages over the conventional forming process, such as a long die life, good mechanical properties and energy saves. It is important to predict the deformation behavior for optimization of the forging process with semi-solid materials and to control liquid segregation for mechanical properties of materials. But rheology material has thixotropic, pseudo-plastic and shear-thinning characteristics. So, it is difficult for a numerical simulation of the rheology process to be performed because complicated processes such as the filling to include the state of the free surface and solidification in the phase transformation must be considered. General plastic or fluid dynamic analysis is not suitable for the analysis of the rheology material behavior. Recently, molecular dynamics is used for the behavior analysis of the rheology material and turned out to be suitable among several methods. In this study, molecular dynamics simulation was performed for the control of liquid segregation, forming velocity, and viscosity in compression experiment as a part of study on the analysis of rheology forming process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1710-1719
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• 1997

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.