• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.300-306
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• 2006

Photocatalyst deposited beads were prepared by fluidized bed chemical vapor deposition (FB-CVD) under various operating conditions of substrates, bed temperature, pressure, and oxygen concentration. Photocatalytic degradation of acetaldehyde was carried out to determine the optimum operating condition of prepared photocatalysts. They were characterized by using FE-SEM, XRD, and XPS. From the FE-SEM photographs, it was found that the surfaces of titania-coated beads were covered with crystal form, particle form, and slick form of titania on alumina, silica-gel, and glass beads, respectively. From the result of photocatalytic degradation of acetaldehyde, it was found that prepared titania/ alumina beads at $600^{\circ}C$, 5 torr showed superior performance to others, and oxygen flow rate has no significant effect.

• Elastomers and Composites
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• v.42 no.2
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• pp.86-92
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• 2007

A few of polytetrafluoroethylene(PTFE) membranes and PTFE fine powders were analyzed to chooce an optimum resin. The bi-axial stretching process was developed to set up the foundation of the preparation process and control the pore size and porosity of PTFE membrane. The pretreatment of PTFE fine powder used in the preparation process for PTFE was needed. The mixing of additives, the ripening of mixture, paste extrusion process of ripening powder, calendering process and the bi-axial process were conducted for controlling pore size, porosity and thckness of membrane. The aftertreatment which strengthened the mechanical properties was necessary. The control of pore size and porosity of the membrane were determined. The ratio of PTFE fine powder and additives at the paste extrusion process, the ripening time, the ripening temperature and the parameters of temperature and pressure at the paste extrusion process were optimized.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.69-76
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• 2000

Despite the improved formability and processing advantages, the use of semi-solid metals is greatly limited due to the difficulties in controlling the optimum forming parameters. In the present study, the tensile properties of closed die, pressure formed semi-solid A356 alloy were examined. It was demonstrated that the tensile strength of thixoformed A356 alloy could be greatly reduced when the forming parameters were not rigorously controlled. The reduced strength of unappropriately formed products appeared to be related to the coarsening of the primary phases. The possibility of improving tensile properties of as-formed products by simple post heat treatment was also assessed.

• Polymer(Korea)
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• v.34 no.1
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• pp.14-19
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• 2010

Applying acrylic silane monomer for determent of weathering damage of stone cultural assets from various sources was investigated to improve inorganic affinity of polymer impregnated to the stone for conservation treatment using impregnation of acrylic polymers under pressure. Radical polymerization was carried out with various mixture ratios of methacrylate (MMA), as the base monomer, and vinyl trimethoxy silane (VTMS). Subsequently, according to the changes of glass transition temperatures, average molecular weights, and storage moduli of the obtained copolymers, the case of adding 1 wt% of benzoyl peroxide, polymerization for 8 hrs, and mixing 5 mol% of VTMS to MMA was the optimum condition of monomer ratio and polymerization. Practically, fresh granites collected in domestic site and weathered stones were treated by following the obtained result above, and then, the moisture absorption, impact, acid resistance, and adhesion properties of the treated stones were compared to those of the corresponding stones treated with MMA only. It was found that those properties of the stones treated with PMV5 were considerably improved.

• Tribology and Lubricants
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• v.25 no.6
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• pp.387-398
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• 2009

The operation condition of recently designed pistons for high power and high speed diesel engine become more severe due to the increment of combustion pressure and temperature. So, in order to overcome high temperature, the application of the mono-metal cast aluminum alloy piston featuring an enclosed cast-in open cooling gallery has increased. In this research, it is developed a PCJ (piston cooling jet) rig tester, described the test procedure and validated the performance of sample piston cooling gallery design. Then the test rig will be used for developing the design technology of piston cooling gallery. The test rig is composed with oil reservoir and pumping system, oil jet system, piston fixing and moving system, collecting oil measuring system, and data measuring and recording system. It will be measured collecting efficiencies under conditions of a few piston positions, oil jet pressures and oil viscosities for a piston cooling gallery. Furthermore, the PCJ rig tester will be used for the optimum design of the oil cooling gallery which being applied to increase the cooling efficiency of pistons in diesel engines satisfying the EURO V emission regulation and the more.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.43-48
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• 2010

Proctor test A or D method of compaction is the most common laboratory test for investigation of subgrade soil characteristics, however, compression type using roller is used in the field. The differences between laboratory and field compaction have considerable error as application to subgrade soil properties of laboratory test. The investigation of compacted soil is carried into effect to solve the problem. The gyratory compactor which is made to reproduce the field density of asphalt mixture, coming from traffic loads, has an advance to compact it similar to arrangement of field aggregate particles. This gyratory compactor has several problems of investigation of compacted soil, because it has designed to make initial asphalt specimens. The main objectives of this research are grasping problems when compacted soil test using the gyratory compactor and showing solutions. It has made a comparative study of difference of the percentage of water content and weight, which are before and after compaction, about the pressure of compaction, frequency of compaction and speed of compaction. And it also has investigated finding maximum percentage of water content which not occur change of percentage of water content after compaction and searching how has an effect on drawing compaction curve.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.185-190
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• 1997

The 6H-SiC single crystals were grown using a self-designed crystal grower by the sublimation method. The grown crystals were typically 30 mm in diameter and 10 mm in length. Optimum growth conditions were established as follows : the temperature of the raw material was $2150~2250^{\circ}C$, the temperature of the substrate was $1950~2050^{\circ}C$, the temperature difference between the raw material and substrate was about $200^{\circ}C$, growth pressure was 50~200 torr and growth rate was 300~700 $\mu\textrm{m}$/hr. Optical microscopy was used for observing the surface of the 6H-SiC single crystal grown and the phenomenological approach was performed on the formation mechanism of the defects in the 6H-SiC crystal. Especially, the micropipes in the as-grown surface were examined to determine the formation mechanisms of the micropipes.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2637-2642
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• 2011

A new ultrasonic-assisted micellar extraction and cloud-point pre-concentration method was developed for the determination of major saikosaponins, namely saikosaponins -A, -C and -D, in Radix Bupleuri by high performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD). The non-ionic surfactant Genapol X-080 (oligoethylene glycol monoalkyl ether) was chosen as the extraction additive and parameters affecting the extraction efficiency were optimized. The highest yield was obtained with 10% (w/v) Genapol X-080, a liquid/solid ratio of 200:1 (mL/g) and ultrasonic-assisted extraction for 40 min. In addition, the optimum cloud-point pre-concentration was reached with 10% sodium sulfate and equilibration at $60^{\circ}C$ for 30 min. Separation was achieved on an Ascentis Express C18 column (100 ${\times}$ 4.6 mm i.d., 2.7 ${\mu}M$) using a binary mobile phase composed of 0.1% acetic acid and acetonitrile. Saikosaponins were detected by ELSD, which was operated at a $50^{\circ}C$ drift tube temperature and 3.0 bar nebulizer gas ($N_2$) pressure. The water-based solvent modified with Genapol X-080 showed better extraction efficiency compared to that of the conventional solvent methanol. Recovery of saikosaponins ranged from 93.1 to 101.9%. An environmentally-friendly extraction method was successfully applied to extract and enrich major saikosaponins in Radix Bupleuri.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.116-121
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• 1999

0.5 wt%Nb-doped SrTiO3(Nb: STO) thin film was prepared on MgO(100) single crystal substrates by Pulsed Laser Deposition (PLD). The Crystallinity and the orientation of Nb:STO thin films were characterized by XRD with changing the thin film processing condition-oxygen partial pressure, substrate temperature, deposition time and the distance between target and substrate. The orientation of Nb:STO thin film showed (100), (110) and (111) orientations at the substrate temperature of $700^{\circ}C$. The lattice parameter of Nb:STO decreased with increasing Po2 and showed 0.3905 nm at Po2=100 Pa, which was similar to that of the bulk. The thickness of Nb:STO thin film increased with increasing the deposition time and with decreasing the distance between target and substrate.

• Journal of Hydrogen and New Energy
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• v.7 no.2
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• pp.147-155
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• 1996

The aim of this study is the development of technologies of methanol production from carbon dioxide by catalytic hydrogenation. Experiments about carbon dioxide hydrogenation by catalyst mixed with CuO, ZnO, $Cr_2O_3$ and $Al_2O_3$ were conducted to find optimum catalyst and reaction condition. Reactions were carried out at atmospheric and high pressures between 200 to $350^{\circ}C$. High yield of methanol was obtained with $Cu/ZnO/Cr_2O/Cr_2O_3/Al_2O_3$ catalyst at $250^{\circ}C$ and above 30 atmospheric pressure. There was not any increament of hydrogenation reactivity for the catalysts which was made by the addition of Pd to $Cu/ZnO/Cr_2O/Cr_2O_3/Al_2O_3$.