• Transactions of Materials Processing
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• v.10 no.3
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• pp.214-222
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• 2001

The homogeneous distribution of solid region without liquid segregation is important in terms of high quality component during thixoforming process. In closed die semi-solid forging process, liquid segregation is strongly affected by injection velocity than solid fraction because the material has to travel relatively long distance to fill the cavity through a narrow gate. The designed die by computer simulation data was used to thixoforging process. The thixoforming velocity to prediction the liquid segregation had been determined with strain rate associated with multistage velocity control during compression test of semi-solid material. The optimal forging velocity and die temperature were investigated to produce the near-net-shape compressor component. The mechanical properties of thixoformed component were tested with various die and material temperatures before and after heat treatment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.03a
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• pp.233-237
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• 1995

Effects of frictional laws on finite element solutions in bulk metal forming were investigated in this paper. The Coulomb friction and the constant shear friction law were compared through finite element anlayses of compression of ring and cylinders with different aspect rations, ring-gear forging and hot strip rollin under the isothermal condition. It has been shown that two laws may yield quite different results inthe case that the aspect ration of a process is large, for example , strip rolling and ring -gear forging and that the difference depends mainly on the aspect ratio and the friction.

• Transactions of Materials Processing
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• v.12 no.8
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• pp.693-701
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• 2003

In this paper, the influence of frictional conditions on the backward impact extrusion of aluminum battery casing with large aspect ratio has been investigated. In the simulation, MSC.Superforge, a package based on the finite volume method, is used for the extrusion analysis. The formability and earing problem during the production have been evaluated by studying the sensitivity to frictional effects. During the sensitivity analysis, the friction factor was varied from 0.02 to 0.24. As the friction factor is increased, the forming height of the narrow edge is decreased, and the forming height of the wide edge is increased. When the friction factor becomes 0.2, the earing problem does not occur The experimental results show a good agreement with analytical results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.205-209
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• 1998

Unlike the drawing of round section from round bar, the shaped drawing like polygonal section is known to have influence not only drawing stress but also comer filling. Therefore, this study analyze the drawing process of suqare rod from round bar using nonsteady state rigid-plastic FEM. To investigate effects of process variables of the drawing process of square rod from round bar, FE-simulations with variety of reduction in area and semi-die angle for a given frictional condition have been conduction. By this results, it has to suggest optimal process condition on the drawing stress and the comer filling. In addition, it has determined forming limit considering necking and bulging.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.150-155
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• 2013

A high voltage and nanosecond Blumlein pulse generator has been developed to produce an output pulse whose voltage level is greater than 250 kV and pulse duration 5 ns. The generator consists of various components such as a charging circuit, a pulse transformer, and a spark gap switch. As a heart of the generator, a Blumlein pulse forming line has been constructed in the cylindrical form using three cylindrical aluminum electrodes that are placed concentrically. Unlike the ideal Blumlein line, the output pulse of an actual Blumlein line may be affected by stray inductances and capacitances of switching and charging components, thereby degrading the performance of the generator. In this paper, PSPICE simulations have been performed to examine effects of stray inductances and capacitances on waveforms of output pulses. Simulation results show that the pulse waveform is significantly distorted mainly by the stray inductance of the spark gap switch.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.783-788
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• 2000

Hydroforming is a method for forming circular tubes. If this technology is to be applied economically, it is essential to have knowledge of the avoidance of failure cases as well as of the behavior of the tube in the tool under the compressive stress and forces that are exerted by the machine. A finite element simulation for manufacturing of lower arm from straight tubes, using the hydroforming method, was performed to investigate the effects of varying process parameters. Explicit method is used to simulate hydroforming in many cases, but that is not included flow rule. And then it needs simulation for implicit method. It was simulated by two methods, implicit and explicit, to compare the result of the hydroforming.

• The Journal of Korean Medicine
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• v.23 no.2
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• pp.28-38
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• 2002

Objectives : This study was to examine the efficacy of GCT on the hepatoprotective effect in the liver function and immune octivity. Methods : The experiment to investigate the hepatoprotective effect of GCT on the liver damage was conducted with D-galactosamine. The experiments to verify the effects of GCT on the immune activity were conducted by carbon clearance assay, plaque-forming cell SRBC assay of IgM, lymphoproliferation assay of T and B cells, and adherence and phagocytosis of mocrophages. Results: In the damage of liver induced by D-galactosamine, GCT carried hepatoprotective effect on AST. In carbon clearance assay GCT showed significant effect on phagocytosis of Kuffer cells. In the plaque-forming cell assay, GCT improved the formation of IgM. In the lymphoproliferation assay, GCT activated the formation of T and B lymphocytes. In macrophages, GCT activated adherence and phagocytosis. Conclusion : Though further study is needed, our findings suggest that GCT could be recommended as hepatoprotector and immune modulator for liver disease.

• Journal of the Korean Society of Clothing and Textiles
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• v.14 no.3 s.35
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• pp.222-228
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• 1990

The purposes of the study are to investigate the emotional dimensions toward clothing and to examine the role of these emotional reactions in mediating the effects of clothing cues on an attitude toward the purchase of clothing. The results are as follows: 1. The emotional dimensions to clothing are pleasure and arousal. 2. The model demonstrates an important role of emotion (pleasure) as mediators in forming an attitude toward the purchase of clothing.

• Biomolecules & Therapeutics
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• v.17 no.1
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• pp.43-46
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• 2009

The immunosuppressive properties of flavonoids were examined for the first time by testing their effects on T-cell-mediated antibody production, using a classical plague-forming cell (PFC) assay in mice. Among the tested flavonoids including naringenin, chrysin, flavonol, galangin, quercetin, morin, myricetin and biochanin A, only quercetin, orally administered at 25 mg/kg, significantly inhibited the number of IgMproducing PFCs induced by sheep red blood cells (SRBC). Interestingly, biochanin A (isoflavone) increased the number of PFCs, suggesting an immunostimulatory effect. The other flavonoids tested did not inhibit or enhance PFC response significantly. Quercetin was also found to show thymus atrophy dose-dependently at 5-500 mg/kg. All these results indicate that quercetin inhibits in vivo antibody production probably by inhibiting T-cell function.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.45-51
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• 1996

Silicon wafers are required to be finished under the roughness of nanometer order for the subsequent chip fabrication processes. Recently, the finish grinding techniques have been researched for the improvement of accuracy and surface roughness simultaneously. Among them, the grinding technique using fine abrasive has been known as an easily accessible method. However, the manufacture of the fine grit grinding wheel has been very difficult because of the coherence of the grits. In this paper, the development of the ultrafine grit silica($SiO_2$) grinding wheel by the combination of the binder coating and the vacuum forming techniques is reported. And, the mechanochemical removal effects of the grinding conditions are discussed. Finally, a successful result of Ra O.4nm. Rmax 4nm in the ground surface roughness of a 6 inch silicon wafer was achieved.