• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.89-92
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• 2011

The modeling of thermodynamic non-idealities and transport anomalies is a crucial prerequisite to realistically simulate the mixing and combustion processes of liquid propellants injected above critical pressures. This study has developed a specific set of subroutines to calculate the thermodynamic and transport properties based on the generalized cubic equation of state (EoS) in a coupled manner with the standard chemical kinetics packages (Chemkin). The existing flamelet analysis code is extended with the real-fluid package and applied to numerical investigation of local flame structures of kerosene and liquid oxygen at high pressure conditions relevant to the actual rocket engines.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.434-442
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• 2006

In a two-stage compression $CO_2$ transcritical cycle, application of a scroll expander-compressor unit has been considered in order to improve the cycle COP. For both expander and 1st stage compressor, scroll wrap profile which was originally designed for a R410A air-conditioning cycle mechanism was used with minor modifications: wrap height and involute end angle were adjusted for required displacement volume and built-in volume ratio. For pressure condition of 10 Mpa/3.5 MPa and expander inlet temperature of $35^{\circ}C$, 25% improvement in COP was obtained by using expander-compressor unit. As evaporator pressure increased, COP improvement was lowered mainly due to decreasing compressor peformance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.91-92
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• 2022

This study is a basic study on carbonation curing technology of concrete using supercritical CO₂, and carbonation curing was carried out by exposing concrete to supercritical CO₂ for a certain period of time. In the case of conventional carbonation curing, long-term curing was performed for several weeks by controlling the concentration of CO₂, but by using supercritical CO₂, more rapid carbonation curing was carried out using constant temperature and pressure conditions to improve durability through surface modification of concrete. This experiment was conducted with the goal of deriving the optimal carbonation curing conditions by measuring the carbonation depth by exposing concrete for a certain period of time to conditions above the supercritical level. As a result, it was confirmed that the carbonation depth increased as the curing time increased, and the curing time could be shortened compared to the carbonation curing according to the existing CO₂ concentration.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.414-419
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• 1995

${\beta}-carotene$ was extracted from freeze-dried carrot by supercritical carbon dioxide $(SC-CO_2)$ and mixtures of $CO_2$ doped with ethanol or methanol as a cosolvent at temperatures of 40 to $60^{\circ}C$ and pressures of 138 to 276 bar. Solubility of ${\beta}-carotene$ in $SC-CO_2$ increased with the increase of extraction pressure and the decrease of extraction temperature. The highest solubility observed was $4.90\;{\mu}g/g\;CO_2\;for\;{\alpha}-carotene\;and\;0.604\;{\mu}g/g\;CO_2$ for ${\alpha}-carotene\;at\;40^{\circ}C$ and 276 bar. Addition of ethanol increased the solubility being the largest increase of 82% using a mixture of $CO_2$ and 17.4% ethanol. $SC-CO_2$ extraction can be used to selectively obtain natural carotenoids, free of solvent residuals, which can be used as food additives.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.703-708
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• 2002

High pressure phase behavior data for poly(propyl acrylate) and poly(propyl methacrylate) with supercritical $CO_2$, ethylene, propane, butane, propylene, 1-butene, dimethyl ether, and $CHClF_2$ were measured in the temperature range from $23^{\circ}C$ to $186^{\circ}C$ and at pressures up to 2,400 bar. The cloud point were obtained at dissolved pressure below 2,070, 1,400, 1,880, 450, 2,200, 250, and 150 bar for poly(propyl acrylate) in supercritical $CO_2$, ethylene, propane, propylene, butane, 1-buthen, and dimethyl ether, respectively. The temperature range is $23-175^{\circ}C$. The poly(propyl methacrylate) does not dissolve in $CO_2$ at temperature of $240^{\circ}C$ and pressure 2,900 bar. The poly(propyl methacrylate)-propane, poly(propyl methacrylate)-butane, poly(propyl methacrylate)-propylene, poly(propyl methacrylate)-1-butene, and poly(propyl methacrylate)-$CHClF_2$ systems were dissolved at the pressures less than 2,390 bar, below 2,100 bar, below 570 bar, below 310 bar, below 300 bar, and below 170 bar, respectively. The temperature range shows from 40 to $186^{\circ}C$. The phase behavior of between binary poly(propyl acrylate)-$CO_2$ and poly(propyl acrylate)-dimethyl ether system were measured from upper critical solution temperature region to lower critical solution temperature region with added dimethyl ether concentrations of 5, 15 and 50 wt%.

• Journal of The Korean Association For Science Education
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• v.31 no.2
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• pp.153-163
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• 2011

This study aimed to identify the difficulties that new science teachers in secondary schools experience. Subjects for this study were 190 science teachers attending qualifying training for 1st degree of teaching certificate. Using an open questionnaire, the difficulties these teachers encounter were collected, categorized, and compared between their first year and their succeeding years of teaching in terms of their school level, gender, majors and regions. Results showed that first year science teachers have had difficulties in areas including subject teaching, guidance, administrative affairs, human relationship and self-understanding. On their succeeding years, difficulties about subject teaching were reduced to half while other difficulties remained. New teachers in middle schools have experienced the most number of difficulties about guidance, while new teachers in general high schools have experienced the most number of difficulties about subject teaching. Based on these findings, some recommendations were proposed for new science teachers in secondary schools, school administrators, and training institutions.

• Journal of Applied Biological Chemistry
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• v.53 no.1
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• pp.13-20
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• 2010

Biological activities such as anti-oxidative and anti-microbial of the Seungmakalgeuntang, a traditional prescription, were evaluated. The electron donating ability of water, ethanol, supercritical fluid and 1,3-butylene glycol extract of Seungmakalgeuntang showed more than 50% at a 100 ppm concentration. At a 1000 ppm concentration, the superoxide dismutase-like activities of ethanol and supercritical fluid extract of Seungmakalgeuntang showed less than 50%. xanthine oxidase inhibition effect of the supercritical fluid extract showed more than 70% at a 1,000 ppm concentration, which was higher than vitamin C. From the measurement on lipid oxidation, the $Fe^{2+}$ chelating abilities of the supercritical fluid extract of Seungmakalgeuntang was more than 60% at a 100 ppm concentration. Also the $Cu^{2+}$ chelating abilities of supercritical fluid extract Seungmkalgeuntang was showed more than 60% at a 500 ppm concentration. Clear zones formed by sample against the human skin-resident microflora such as Staphylococcus epidermidis, Staphylococcus aureus and Propionibacterium acne of ethanol and supercritical fluid extract of Seungmakalgeuntang showed the highest among all the extracts tested using a 4mg/disc. The minimum inhibitory concentration (MIC) against both S. epidermidis and S. aureus showed 2,500 ppm in the extract of the supercritical fluid.

• Clean Technology
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• v.13 no.3
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• pp.173-179
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• 2007

In this study the amount of equilibrium sorption of C.I. Disperse Yellow 54 dye in the polymeric textiles such as PTT (poly(trimethylene terephthalate)) and PET (poly(ethylene terephthalate)) textiles was measured in the presence of supercritical carbon dioxide at different temperatures, pressures, and time. The amount of dye sorption increased with temperature and pressure in both PTT and PET textiles, but the increasing rate decreased with pressure. The PTT textile has much larger dye sorption than PET textile. The increasing rate of dye sorption decreased with time at same temperature and pressure for both PTT and PET textiles.

• KSBB Journal
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• v.11 no.1
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• pp.71-76
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• 1996

Studies were carried out to examine some factors affecting the supercritical carbon dioxide extraction of taxol from the bark of Taxus cuspidata using a continuous packed bed extractor. The factors investigated in this study were pressure, temperature, volume of carbon dioxide, and co-solvent. It was found out that the amount of taxol extracted was not significantly affected by the operating pressure in the absence of a co-solvent although it increased by about 20% at 5500 psig. With $24\ell$ of carbon dioxide the saturated amount of taxol was extracted at 318K and 5500psig. Methanol was found to be the most effective co-solvent in terms of amount of taxol extracted among six different co-solvents used. When methanol was used as a co-solvent the effect of operating pressure became significant; approximately 50% increase in the amount of taxol extracted was observed at 3000 psig as compared to at 2500 or 3500psig. The optimum methanol concentration in supercritical fluid was 13% (w/w)at 308K, 3000psig.

• Clean Technology
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• v.7 no.1
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• pp.13-25
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• 2001

With fast advancement of fine machineries and semiconductor industries in recent decades, the ultra-cleaning of organic chemicals, submicron particles from contaminated unit equipments and products such as silicon wafers becomes one of the most important steps for further advancement of such industries. To date, two kinds of ultra cleaning techniques are used; one is the wet-cleaning and the other is the dry cleaning. In case of wet cleaning, removal of organic contaminants and submicron particles is made by DIW with additives such as $H_2O_2$, $H_2SO_4$, HCl, $NH_4OH$ and HF, etc. While the wet cleaning method is most widely adopted for various occasions, it is inevitable to discharge significant amount of toxic waste waters in environment. Dry cleaning is an alternative method to mitigate environmental pollution of the wet cleaning with maintaining comparable degree of cleaning to the wet cleaning. Although there are various concept of dry cleaning have been devised, the dry cleaning with environmentally-benign solvent such as carbon dioxide proven to show high degree of cleaning from the contaminated porous surface as well as from the bare surface. Thus, special global attention has been placing on this technique since it has important advantages of simple process schemes and no environmentally concern, etc. Thus, this article critically reviews the state-of-the-art of the supercritical fluid drying with emphasis on the thermo-physical characteristics of the supercritical solvent, environmental gains compared to other dry cleaning methods, and the generic aspects of the basic design and processing engineering.