• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.148-151
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• 2004

Different kinds of feedstock of semisolid a356 aluminum alloy manufactured by EMS stirring only, inoculation of Al-5Ti-B only and combination of inoculation and EMS stirring were investigated. It is found that the grain size of these feedstock are $350{\mu}m$ for EMS casting only, $320{\mu}m$ for inoculation by Al-5Ti-B, and $100{\mu}m$ for the combination of EMS stirring and inoculation of Al-5Ti-B master alloys. The microstructure of the sample obtain by combination of inoculation and EMS system show the best homogeneousness and finest grains.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.340-343
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• 2005

This paper focuses on an rheo-forming of arm part fabricated by electromagnetic stirring system (EMS). This forming process take place under high pressure of high pressure die casting and thin walled casting is possible. Also the productivity is better than low pressure die casting because of shorter cycle time. The advantages of rheo-forming are performed in the semi solid state with laminar flow and the gas content is low, which makes welding possible. Therefore this research applies for arm part with EMS and has investigated the mechanical propriety after T6 and T5 heat-treatment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.135-138
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• 2007

A semi-solid forming processing has been developed for manufacturing near net-shape components. The semi-solid forming has two methods. One is thixo-forming with reheating prepared billet, the other is rheo- forming with cooled melt until semi-solid state. In indirect forging processing, this experiment used aluminum rheology materials by electromagnetic stirring system. Rheology material is made by A16061. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. Forged samples are found microstructures and mechanical properties. Forged samples are accomplished heat treatment T6 for high mechanical properties.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.443-446
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• 2007

The semi-solid process has been developed near net-shape components for kinds of methods. Thixo-forming with reheating prepared billet and rheo-forming with cooled melt until semi-solid state. Material is applied electromagnetic stirring system to slurry with aluminum 6061 alloy. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. The mechanical properties are compared to forge sample with to apply heat treatment T6. This study is researched function a virtual pressure and fine shape zone. Optimum pressure is found to prevent defect of porosity.

• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.195-205
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• 2006

This paper focuses on a rheo-forming of am part fabricated by electromagnetic stirring system (EMS). This forming process take place under high pressure of high pressure die casting and thin walled casting is possible. Furthermore, the productivity is better than low pressure die casting because of shorter cycle time. The advantages of rheo-forming are performed in the semi solid state with laminar flow and the gas content is low, which makes welding possible. Therefore this research applies for arm part with EMS and has investigated the mechanical properties after T6 and T5 heat-treatment.

• Journal of Korea Foundry Society
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• v.28 no.5
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• pp.226-230
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• 2008

본 논문에서는 공정조성 부근의 Al-Si 합금의 미세구조에 미치는 전자기교반(EMS)의 영향에 대하여 연구하였다. 초정 a 상의 형상에 미치는 전자기교반의 세기의 영향을 조사하기 위하여 각각 교반장치에 60, 80,및 120V의 전압을 가하여 미세조직을 관찰하였다. 60V 이하의 전압이 인가되었을 때 전자기교반의 효과가 나타나지 않은 반면에, 80V 이상의 전압으로 5초 이상 인가되었을 때 구상화된 초정 a 상을 얻을 수 있었다. 인가된 전압이 120V일 때 초정 a 상은 보다 균일한 분포를 가지며 구상화 되었다. 전자기교반의 세기와 함께 교반시간의 영향을 확인하기 위하여 교반시간을 증가시키면서 미세조직을 관찰하였다. 또한 초정 a 상의 형상에 미치는 주조변수의 영향에 대해서도 실험하였다.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.117-123
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• 2000

In this study, to fabricate the semi-solid Al alloy, the 3phase-2poles electromagnetic stirring system was adopted. The changes of primary grain size, aspect ratio, standard deviation, hardness and the size morphology of eutectic Si with pouring temperatures and input voltages were investigated. At the same pouring temperature, with increasing input voltage, aspect ratio, standard deviation and primary grain size were decreased. The optimum condition for fabrication of semisolid Al alloys by EMS horizontal continuous casting process was determined that the input voltage was 220V and the pouring temperature was 68$0^{\circ}C$. At this optimum conditions the primary grain size was 54$\mu\textrm{m}$, the aspect ratio was 1.56 and the size of eutectic Si was 0.5$\mu\textrm{m}$. The micro-hardness of the Al alloy was 72.1 Hv. The semi-solid A356 Al alloy which has very low aspect ratio and standard deviation value could be fabricated by adopting the EMS horizontal continuous casting facility that was manufactured for this study.

• Resources Recycling
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• v.30 no.6
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• pp.61-67
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• 2021

This work investigated the cementation of iridium from iridium-containing hydrochloric acid leachate. Zinc powder was used as the reducing agent, and the effects of the stoichiometric ratio of Zn/Ir, initial Ir concentration, initial pH, reaction time, and ultrasound irradiation on iridium recovery were investigated. When only the stirrer was used for cementation, the iridium recovery increased with the addition amount of zinc, and the recovery of about 70% at 40 times the stoichiometric ratio of Zn/Ir. In contrast, when employing ultrasonic irradiation with stirring, the recovery of iridium decreased at 20 times or less the stoichiometric amount of zinc. The recovery of iridium increased at 40 times the stoichiometric ratio of Zn/Ir. This result may be due to the ionization of zinc and re-dissolution of iridium during the ultrasound irradiation treatment. When a combination of ultrasonic irradiation and stirring was used for cementation, the iridium recovery increased by more than 27% compared to that when using only the stirrer. It was possible to recover 99% of iridium under the following conditions: reaction time, 60 min; initial pH, 0.01; volume of leachate, 100 mL; 1770 ppm Ir, 40 times the stoichiometric ratio of Zn/Ir.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.344-357
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• 2020

Strain improvement and bioprocess development were undertaken to enhance hyaluronic acid(HA) production by Streptococcus zooepidemicus cells. Using a high-yielding mutant strain, statistical medium optimization was carried out in shake flask cultures, resulting in 52% increase in HA production (5.38 g/l) at the optimal medium composition relative to the parallel control cultures. For sufficient supply of dissolved oxygen (DO), which turned out to be crucial for enhanced production of HA, agitation system and speed were intensively investigated in 5 L bioreactor cultures. Increase in oxygen mass transfer coefficient (k_La) through increment of agitation speed (rpm) and 35% expansion of diameter of the newly-designed impellers showed significantly positive effects on HA production. By installing an expanded Rushton-turbine impeller for efficient break-down of sparged air, and an extended marine impeller above the Rushton-turbine impeller for efficient mixing of the air-born viscous fermentation broth, maximum amount of HA (9.79 g/l) was obtained at 450 rpm, 1.8 times higher level than that of the corresponding flask culture. Subsequently, the possibility of bioprocess scale-up to a 50 L bioreactor was investigated. Despite almost identical maximum HA production (9.11 vs 9.25 g/l), the average HA volumetric productivity (r_p) of the 50 L culture turned out only 74% compared to the corresponding 5 L culture during the exponential phase, possibly caused by shear damages imposed on the producing cells at the high stirring in the 50 L culture. The scale-up process could be successfully achieved if a scale-up criterion of constant oxygen mass transfer coefficient (k_La) is applied to the 50 L pilot-scale bioreactor system.