• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.475-481
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• 2017

In this paper, high speed camera images were used to analyze the supercritical injection behavior of liquid hydrocarbon compounds used as main components of propellant fuel. Decane and Methylcyclohexane (MCH), which have different critical points among kerosene constituents, were selected as experimental fluid and Shadowgraphy technique was used for the analysis. The difference in the temperature variation from the initial injector state of the subcritical condition until the vaporization occurs was represented by the different behaviors of Decane and MCH. However, under the Supercritical conditions, the enthalpy of vaporization near the critical point approaches zero and the phase change to the Supercritical phase occurs instead of vaporization process. In the phase change of the Supercritical system, there was no rapid density change, so the liquid state image was observed in both the Decane and MCH.

• Plant Journal
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• v.6 no.3
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• pp.53-61
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• 2010

This paper presents failure analysis on weld-joint of the waterwall tubes in USC boilers. Visual inspections were performed to find out the characteristics of the fracture. Additionally both microscopic characteristics and hardness test were carried out on failed tube samples. Failures seem to happen mainly because the welding process such as preheating and PWHT(post-weld heat treatment) was not conducted strictly. Thus, this paper has the purpose to describe the main cause of the poor welding process and to explain how to prevent similar failures in those weld-joints.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.55-60
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• 2017

The supercritical $CO_2$ (sc-$CO_2$) mixture and the sc-$CO_2$-based Photoresist(PR) stripping(SCPS) process were applied to the removal of the post etch/ash PR residue on aluminum patterned wafers and the results were observed by scanning of electron microscope(SEM). In the case of MDII wafers, the carbonized PR was able to be effectively removed without pre-stripping by oxygen plasma ashing by using sc-$CO_2$ mixture containing the optimum formulated additives at the proper pressure and temperature, and the same result was also able to be obtained in the case of HDII wafer. It was found that the efficiency of SCPS of ion implanted wafer improved as the temperature of SCPS was high, so a very large amount of MEA in the sc-$CO_2$ mixture could be reduced if the temperature could be increased at condition that a process permits, and the ion implanted photoresist(IIP) on the wafer was able to be removed completely without pre-treatment of plasma ashing by using the only 1 step SCPS process. By using SCPS process, PR polymers formed on sidewalls of metal conductive layers such as aluminum films, titanium and titanium nitride films by dry etching and ashing processes were removed effectively with the minimization of the corrosion of the metal conductive layers.

• KSBB Journal
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• v.25 no.4
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• pp.379-386
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• 2010

In the present study, biocompatible poly (ethylene glycol) (PEG) microparticles containing coriander essential oil were prepared using a supercritical particles from gas saturated solution (PGSS) process to improve the stability of the coriander oil. The effects of various process parameters such as temperature, pressure, and nozzle diameter on the morphology and entrapment efficiency of coriander oil loaded PEG microparticles were then investigated. A positive influence on the formation of spherical microparticles was observed with increasing temperature and decreasing pressure. Furthermore, somewhat more porous microparticles were produced with an increase in pressure. At a given temperature, the highest entrapment efficiency of coriander essential oil in PEG microparticles was observed under the lowest experimental pressure condition.

• Resources Recycling
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• v.20 no.6
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• pp.78-82
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• 2011

Supercritical $CO_2$($scCO_2$) extraction has a great possibility to be a new process to recover metal and to replace the existing leaching/solvent extraction processes. The cobalt extraction was carried out using $scCO_2$ from cobalt sulphate solution. The bis (2,4,4-trimethylpentyl) phosphinic acid and diethylamine ligands were used to extract cobalt ion in $scCO_2$. The recommended method consists of $scCO_2$/extractants complexation process and metal extraction process at 60, 200bar. Experimental results showed that the extraction efficiency of Co was increased by 16-99% with increasing the ligand amount.

• Clean Technology
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• v.19 no.3
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• pp.212-218
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• 2013

The microparticles of 2-hydroxypropyl-${\beta}$-cyclodextrin (HP-${\beta}$-CD) were prepared using aerosol solvent extraction system (ASES) by employing supercritical carbon dioxide as an antisolvent, The effects of various process parameters such as temperature, pressure, solution concentration and solution flow rate on the formation of HP-${\beta}$-CD microparticles were investigated. The HP-${\beta}$-CD microparticles prepared by the ASES process were observed to consist of agglomerates of nano-sized (50-200 nm) particles. When an aqueous solution of ethanol was used as a solvent for HP-${\beta}$-CD, the HP-${\beta}$-CD particles were found to be spherical in shape and to become larger as the water content increased. It was confirmed that the micronization of HP-${\beta}$-CD using the ASES process could enhance the inclusion efficiency of ibuprofen/HP-${\beta}$-CD complexes significantly.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.217-221
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• 2015

When reactor coolant leaks occur due to cracks of a steam generator's tube, radioactive materials contained in the primary cooling water in nuclear power plant are forced out toward the secondary systems. At this time the secondary water purification resin in the ion exchange resin tower of the steam generator blowdown system is contaminated by the radioactivity of the leaked radioactive materials, so we pack this in special containers and store temporarily because we could not dispose it by ourselves. If steam generator tube leakage occurs, it produces contaminated spent resins annually about 5,000~7,000 liters. This may increase the amount of nuclear waste productions, a disposal working cost and a unit price of generating electricity in the plant. For this reasons, it is required to develop a decontamination process technique for reducing the radioactive level of these resins enough to handle by the self-disposal method. In this research, First, Investigated the structure and properties of the ion exchange resin used in a steam generator blowdown system. Second, Checked for a occurrence status of contaminated spent resin and a disposal technology. Third, identified the chemical characteristics of the waste radionuclides of the spent resin, and examined ionic bonding and separation mechanism of radioactive nuclear species and a spent resin. Finally, we carried out the decontamination experiment using chemicals, ultrasound, microbubbles, supercritical carbon dioxide to process these spent resin. In the case of the spent resin decontamination method using chemicals, the higher the concentration of the drug decontamination efficiency was higher. In the ultrasound method, foreign matter of the spent resin was removed and was found that the level of radioactivity is below of the MDA. In the microbubbles method, we found that the concentration of the radioactivity decreased after the experiment, so it can be used to the decontamination process of the spent resin. In supercritical carbon dioxide method, we found that it also had a high decontamination efficiency. According to the results of these experiments, almost all decontamination method had a high efficiency, but considering the amounts of the secondary waste productions and work environment of the nuclear power plant, we judged the ultrasound and supercritical carbon dioxide method are suitable for application to the plant and we established the plant applicable decontamination process system on the basis of these two methods.

• Carbon letters
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• v.11 no.2
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• pp.107-111
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• 2010

We prepared the amine epoxy adducts (AEA)/thin multiwalled carbon nanotubes (TWCNTs) composite particles using nonsolvent based methods including dry mechano-chemical bonding(MCB) process and supercritical fluid (SCF) process. The resulting TWCNTs/AEA composite particles have been used as curing agents for urethane modified bispheol A type epoxy resin. The thermal, thermomechanical properties of the epoxy resins cured with TWCNTs/AEA composite particles were measured by DMA and the dispersion of CNT was characterized by SEM. Because of high degree of CNT dispersion, thermal and mechanical properties of the epoxy resin cured with TWCNTs/AEA composite particles prepared by SCF process are better than those cured with mechano-chemically prepared TWCNTs/AEA composite particles.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.553-559
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• 2010

The synthesis behavior of nanoporous silica aerogel in the macroporous ceramic structure was observed using TEOS as a source material and glycerol as a DCCA(dry control chemical additive). Silica aerogel in the macroporous ceramic structure were synthesized through a sono-gel process. The wet gel in the macroporous ceramic structure were aged in ethanol for 72 h at $50^{\circ}C$. The aged wet gel was dried under supercritical drying condition. The addition of glycerol has a role of giving the uniform pore size distribution. The reproducibility of aerogel in the macroporous ceramic was improved in the glycerol(0.05 mol%) added to the silica sol and TEOS : $H_2O$=1 : 12.

• Journal of the Korean Applied Science and Technology
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• v.14 no.2
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• pp.41-48
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• 1997

Separation of EPA and DHA from fish oil fatty acid ethyl ester (FAFE) by urea adductive crystallization method was carried out in the supercritical carbon dioxide (SC $CO_2$) as a solvent. Our results showed that SC $CO_2$ is a good candidate as a solvent in the urea adductive crystallization to separate FAFE by the number of unsaturated bonds. Compared to the separation process using methanol. SC $CO_2$ yielded better performance in the overall selectivity of EPA and DHA. The effect of process variables on separation of EPA and DHA was discussed in detailed. A hybrid technology of SC $CO_2$ fractionation and urea adductive crystallization with SC $CO_2$ was conformed as a viable process to separate and concentrate EPA and DHA from fish oil.