• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.316.1-316
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• 2002

• KSBB Journal
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• v.26 no.5
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• pp.459-464
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• 2011

In this study, the canadian peat moss extract was purified by a supercritical ₂ using three different conditions and assessed its biological activities. Peat moss was extracted by acid-alkaline extraction method (sample 1) and purified by a supercritical $CO_2$ at $40^{\circ}C$ under pressure of 100 bar (sample 2), 120 bar (sample 3) or 150 bar (sample 4). We evaluated the antioxidant activities of the samples by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging, $Fe^{2+}$/ascorbate (FTC) and 2-thiobarbituric acid (TBA) methods. The antioxidant activities were examined by comparing the results with that of ascorbic acid as a positive control. Sample 3 showed relatively higher DPPH radical-scavenging activities than other samples. The antioxidant activity by FIC method exhibited similar results as the DPPH radical-scavenging activities. On the other hand, sample 2 showed higher antioxidant activity measured by TBA method of all. The whitening effects of the samples were examined using mushroom tyrosinase and B16F10 melanoma cells. Sample 3 exhibited overall significant whitening effects, however, other samples showed relatively lower effects. These results suggest that the peat moss extract purified by a supercritical ₂ could be used as a cosmetic ingredient for the anti-aging and whitening effects.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.353-358
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• 2005

The heat transfer and pressure drop of supercritical $CO_2$ cooled in a helically coiled tube was investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The experimental apparatus of the refrigerant loop consist of receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a helically coiled tube in tube counter flow heat exchanger with $CO_2$ flowed inside the inner tube and coolant( water) flowed along the outside annular passage, It was made of it copper tube with the inner diameter of 4.55[mm]. the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were $200^{\sim}600$ [kg/m2s] and the inlet pressure of gas cooler varied from 7.5 [MPa] to 10.0 [MPa]. The main results are summarized as follows : The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.

• Journal of the Korea Institute of Building Construction
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• v.18 no.5
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• pp.403-412
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• 2018

Recently, needs for utilization of recycled aggregate have been increasing. However, its utilization has been limited due to its high alkalinity, which mostly came from the unremoved cement paste particles that were attached at the surface of recycled aggregate. Various efforts has been made to reduce its alkalinity by using $CO_2$, but currently available methods that uses $CO_2$ generate the problem with pH recovery. Considering the fact that supercritical $CO_2$ ($scCO_2$) can provide more rapid carbonation of cement paste than by normal $CO_2$, $scCO_2$ was utilized in this work. The reaction between $scCO_2$ and hydrated cement paste has been systematically evaluated. According to the results, it was found that powder type showed higher carbonation compared to that of cube specimens. It seems the carbonation by $scCO_2$ has occurred only at the surface of the specimen, and therefore still showed some amount of $Ca(OH)_2$ calcium aluminates after reaction with $scCO_2$. With powder type specimen, all $Ca(OH)_2$ was converted into $CaCO_3$. Moreover, additional calcium that came from both calcium aluminate hydrates and calcium silicate hydrates reacted with $scCO_2$ to form $CaCO_3$. After carbonation with $scCO_2$, the powder type specimen did not show pH recovery, but cube specimens did show due to the presence of portlandite.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.55-59
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• 1999

The Rapid Expansion of Supercritical fluid Solutions (RESS) process was applied to particles coating. Microcapsules prepared by spray drying were used as the core particles, and two kinds of paraffin were used as the coating materials. Supercritical $CO_{2}$ solutions of paraffin were expanded through the short nozzle into the bed that was fluidized by air. Extraction temperature and pressure were varied at $50~120^{\circ}C$, $150~200\;kg/\textrm{cm}^2$, respectively. The thickness of theoritical coating layer ws measured, and precipitate coating layer on surface was analyzed by using SEM, FT-IR. The release behaviors of $Mg^{2+}$ ions were inspected by atomic absorbance spectrophtometer.

• The Korean Journal of Food And Nutrition
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• v.9 no.4
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• pp.500-503
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• 1996

Volatile compounds were extracted from freeze-dried citron peel(Citrus junos) using supercritical CO2 under 4,000psi at 40$\beta$. Four fractions were obtained with consumption of CO2. Volatile compounds of extracts were analyzed by GC-MSD. Yield of vol atile compounds from citron peel was 0.11g/CO2($\ell$) and maximum yield was 8.812g/kg. Major volatile compounds of extracts were dl-limonene, Υ-terpinene, linalool, sabinene, $\beta$-myrcene, $\alpha$-pinene, $\beta$-farnesene, $\alpha$-terpineol and terpinolene. $\alpha$-Pinene, $\beta$-myrcene and dl-limonene in the fractions decreased gradually, while $\alpha$-terpineol and $\beta$-farnesene increased as the consumption of CO2 increased.

• The Korean Journal of Food And Nutrition
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• v.34 no.4
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• pp.356-364
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• 2021

This study was carried out to investigate the effects of supercritical carbon dioxide (SC-CO₂) extracts from sweet potatoes (SP) and watermelon (WM) on the oxidative stability of perilla seed oils (POs) over the existing ones. A comparison was done between the oxidative stability of perilla oil (PO) after the addition of 0.1% of SP, and WM extracts and PO without extract. The oxidative stability was measured based on the viscosity, acid value (AV), peroxide value (POV), antioxidant (DPPH) activity, p-anisidine value (p-AV), and fatty acid composition. The viscosities ranges were: PO without extract, from 53.99±0.99 to 74.38±1.61 cps, PO with SP extract, from 53.99±0.10 to 58.73±0.8 cps, and PO with WM extract, from 53.98±0.10 to 56.00±0.70 cps. While the PO containing the SC-CO₂ extracts had significantly lower AV, POV, and p-AV, their antioxidant activity was approximately 10 times higher than that of the PO without extract. There were no significant differences in fatty acid composition between SC-CO₂ extracts added groups and PO without extract (p<0.05). The findings of this study confirmed that the SC-CO₂ extracts from sweet potatoes and watermelon enhanced the oxidative stability of perilla seed oils, and are potential natural antioxidants for use in the food industry.

• Korean Journal of Food Science and Technology
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• v.52 no.5
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• pp.516-523
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• 2020

Supercritical carbon dioxide (_SCO2) extraction was applied for the defatting of mealworm to prepare defatted powder (DP) and protein isolate (PI) and compare the process to press and hexane extraction, with respect to DP and PI physicochemical properties. _SCO2 DP was obtained by extracting 34.40% oil at 41.37 MPa, 40℃ for 180 min, and the product contained 71.66% crude protein, which is similar to that of hexane DP and higher than that of press DP. In using alkali protein extraction to prepare PI from DP, _SCO2 was as effective as hexane and better than press. _SCO2 produced brighter DP and PI than press, but not as much as hexane. Protein solubility was similar in all DP, with minimum values at pH 5. The highest water adsorption capacity was noticeable for _SCO2 PI, and _SCO2 DP showed an oil adsorption capacity comparable to that of hexane DP. _SCO2 DP and PI had better foaming capacity than press DP and PI and showed superior emulsion activity compared to others.

• Economic and Environmental Geology
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• v.50 no.4
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• pp.303-311
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• 2017

The laboratory scale experiment was performed to evaluate the sealing capacity of the capping rock such as tuff and mudstone, measuring the intial supercritical $CO_2$ ($scCO_2$) injection pressure and the $scCO_2$-water-rock reaction for 90 days. The drilling cores sampled from 800 m in depth around the Janggi basin, Korea were used for the experiment. The mineralogical changes of mudstone and tuff were measured to evaluate the geochemical stability during the $scCO_2$-water-rock reaction at $CO_2$ storage condition (100 bar and $50^{\circ}C$). The rock core was fixed in the high pressurized stainless steel cell and was saturated with distilled water at 100 bar of pore water pressure. The effluent of the cell was connected to the large tank filled with 3 L of water and 2 L of $scCO_2$ at 100 bar, simulating the subsurface injection condition. The $scCO_2$ injection pressure, which was higher than 100 bar, was controlled at the influent port of the cell until the $scCO_2$ begin to penetrate into the rock and the initial injection pressure (> 100 bar) of $scCO_2$ into the rock was measured for each rock. The mineralogical compositions of mudstones after 90 days reaction were similar to those before the reaction, suggesting that the mudstone in the Janggi basin has remained relatively stable for the $scCO_2$ involved geochemical reaction. The initial $scCO_2$ injection pressure (${\Delta}P$) of a tuff in the Janggi basin was 15 bar and the continuous $scCO_2$ injection into the tuff core occurred at higher than 20 bar of injection pressure. For the mudstone in the Janggi basin, the initial $scCO_2$ injection pressure was higher than 150 bar (10 times higher than that of the tuff). From the results, the mudstone in Janggi basin was more suitable than the tuff to shield the $scCO_2$ leakage from the reservoir rock at subsurface.

• Clean Technology
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• v.10 no.4
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• pp.221-228
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• 2004

Ethoxylated Nonyl Phenol Series (NP-series), nonionic surfactants, were applied for forming microemulsions in supercritical $CO_2$. Measurement results of the solubility in supercritical $CO_2$ are in the following; NP-series were high soluble in carbon dioxide in spite of the fact that those were not $CO_2$-philic surfactants traditionally well known. Water in $CO_2$ microemulsions were also formed stably. A complexation of hydrophilic lengths for $CO_2$-philic parts of NP-Series surfactants was optimized by NP-4 surfactant(N=4) for forming the microemulsions through the experiments. Formation of microemulsions was confirmed by measuring the UV-Visible spectrum through a spectroscopic method and existence of water in the microemulsions was confirmed as well. In order to apply it for a metal surface treatment or electroplating, an experiment for forming acid(organic, inorganic) solution in $CO_2$ microemulsions was carried out. Ionic surfactant in the reaction to an acid solution became unstable to form microemulsions, however, nonionic surfactant was formed stably in the reaction. Results of the study will be utilized for expanding the application scope of supercritical $CO_2$ which is an environmental-friendly solvent.