• Membrane Journal
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• v.31 no.4
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• pp.253-261
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• 2021

Solutions to water pollution, global warming, and climate change have been currently discussed. Pressure retarded osmosis (PRO) using a difference in salt concentration between two fluids is proposed to meet the demand for clean water and produce eco-friendly energy. Although PRO has been researched continuously, it has not been commercialized yet due to limitations such as lack of technology and the high price of membranes. Meanwhile, the membrane is one of the most significant parts of the PRO engine and salinity gradient power (SGP) technology. Research continues to technologically develop graphene oxide membranes and nanocomposite membranes used in salinity gradient power generation. Studies on efficient membranes, solvents, and solutes are active to enable high energy efficiency of the osmotic heat engine even at low temperatures of waste. Studies have been conducted on reducing internal concentration polarization and increasing power density by using membranes with balanced permeability and selectivity. In this review, dealing with these studies, we discuss the types of PRO membranes, theoretical modeling of technologies through efficient membranes, and other technologies to develop the process efficiency.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E1
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• pp.29-39
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• 2003

The 10-day interval basis measurements of precipitation samples at Yangyang, the rural and coastal area on the eastern coast of the Korea peninsula were accomplished for understanding the precipitation chemistry and the temporal variations of major ions September 1991 to February 1997. The precipitation was slightly acidic, and 37% of the samples in winter were pH less than 4.5. The concentrations of cations were found on the order $Na^+\;>\;{NH_4}^+\;>\;Ca^{2+}\;>\;Mg^{2+}\;>\;K^+$ and those of anions followed the pattern $Cl^-\;>\;{SO_4}^{2-}\;>\;{NO_3}^-$. Neglecting sea salt components, the major ions controlling precipitation chemistry were nss-${SO_4}^{2-}$ and ${NO_3}^-$ in anion and ${NH_4}^+$ and nss-$Ca^{2+}$ in cation. Concentrations of these ions were lower than those measured at urban sites in Korea, but were higher than those measured in Japan. Most of nss-${SO_4}^{2-}$ and ${NO_3}^-$ were neutralized by ammonia and calcium species, especially alkaline soil particles in spring and ammonia gas in other seasons. Considering also the annual value of ［nss -${SO_4}^{2-}$］/［${NO_3}^-$］ ratio of 2.62 and the neutralizing factors, ammonium sulphate compounds were dominant. Annual mean concentrations of these ions showed relatively small fluctuations, while larger seasonal variations were observed with higher levels in spring and winter. Precipitation amount, influence extent of acidic gases and alkaline particles long-range transported from China continent, and energy consumption pattern in each season might be able to explain this seasonal trend.sonal trend.

• Journal of Nutrition and Health
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• v.40 no.2
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• pp.182-190
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• 2007

The purpose of this study is to evaluate dietary quality of Korea Antarctic expedition by menu analysis. Basic menu pattern, intake of dish and dish group, DDS (dietary diversity score), daily nutrients supply, and NAR (nutrient adequacy ratio) & MAR (mean adequacy ratio) were analyzed using 1 year menu list for the 10th Korea Antarctic expedition. Most frequently served basic menu patterns were ${\ulcorner}$Rice + Soup + 2 Side dish + Kimchi (53.5%)${\lrcorner}$ and ${\ulcorner}$Rice + Stew + 2 Side dish + Kimchi (13.4%)${\lrcorner}$. In the analysis of dish group, excluding Rice and Kimchi, ${\ulcorner}$Grilled foods${\lrcorner}$ and ${\ulcorner}$Pan-fried foods${\lrcorner}$ were served more than 25% per month. Most frequently served dishes were "pan-fried rolled egg", "grilled seaweed", "kimchi soup", "fruits cocktail, canned" and "salt-fermented squid". The kinds of served dishes were very restrictive. The average score of DDS showed 2.88 for summer and 2.97 for winter. Dairy group was almost not served. Fruit & Vegetable groups were also served a little as canned product. The energy ratio of Carbohydrate : Fat : Protein was 56.5 : 23.9 : 19.2, and 56.9 : 24.5 : 18.3, for summer and winter, respectively. Both seasons had higher ratio of carbohydrate and lower ratio of fat compared to the recommended ratio (44 : 40 : 16) in polar area. Ca : P ratio was very poor, 0.40 in both seasons. NAR scores of Ca, vitamin A, vitamin $B_2$ and vitamin C were also very low, ranged from 0.6 to 0.7. Consequently, a well-planned menu supplying adequate amount of dairy, fruit and vegetable is necessarily required including Ca, vitamin D, vitamin A, vitamin $B_2$ and vitamin C intake, and some nutritionally well-educated members are urgently needed to join in the expedition.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.2
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• pp.144-149
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• 2006

As a strain EH741, having an excellent hexane degradability, was isolated from bacterial consortium using hexane as a sole carbon and energy source. EH741 was identified as a Rhodococcus sp. and the addition of a surfactant Pluronic F68(PF68), for increasing hexane solubility couldn't enhance the specific growth rate of the isolate EH741 n the mineral salt medium supplemented with hexane as a sole carbon source(hexane-BH medium). In the hexane-BH medium, the maximum specific growth rate(${\mu}_{max}$) of this strain was $0.04h^{-1}$, and the maximum hexane degradation rate($V_{max}$) and saturation constant($K_s$) were$161{\mu}mol{\cdot}g-DCW^{-1}{\cdot}h^{-1}$ and 10.5 mM, respectively. Rhodococcus sp. EH741 was one of excellent microorgamisms for hexane biodegradation processes.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.313-317
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• 2010

Purpose: The purpose of this study was to investigate the surface characteristics of plasma electrolytic oxidation (PEO) surface treatment on AZ31 magnesium alloy eyeglass frames. Methods: The plasma electrolytic oxidation (PEO) surface was created by varying the DC voltage. The oxidation layer of coating was measured using phase analysis by X-ray diffraction. The microstructural morphology was observed using a scanning electron microscopy. Coating layer and the concentration of elements were investigated using the energy dispersive X-ray spectra. Results: The MgO XRD peak was increased as the voltage increased, and the density of the surface oxide film was also increased. The changes in the composition of the EDS also showed a good agreement. Conclusions: The compound oxide crystallization of PEO oxide film layer was done by increasing formation of MgO as the voltage increased. The treatment at 65V and 60 sec showed the best results at surface state, contact angles and salt spray test.

• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.418-426
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• 2015

Total phenol contents, total flavonoid contents and antioxidant activity of 70% methanol, 70% ethanol and chloroform-methanol (CM, 2:1, v/v) extracts from onion (Allium cepa L.) peels were studied. The $IC_{50}$ values of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] radical scavenging activity in 70% ethanol extract were remained to be lowest followed by 70% methanol extract and CM extract. And the total phenol content ($113.56{\pm}0.86mg\;CAE/g$), total flavonoid content (49.63 mg QE/g) and ferric reducing antioxidant power value were also found to be the highest. In contrast, 70% methanol extract possessed the strongest antioxidant activity by ${\beta}$-carotene bleaching assay. CM extract displayed the lowest antioxidant activity compared with other extracts. Onion peels exhibited strong antioxidant activity and abundant phytochemicals, which could be used in a various food products to add phytochemicals and promote good health.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.9-14
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• 1988

Perovskite type compounds of the $La_{1-x}Ca_xFeO_{3-y}$ system were prepared from stoichiometric mixtures of La_2O_3,\;CaCO_3$, and Fe(NO-3)_3{\cdot}9H_2O$ by heating at 1100$^{\circ}C$ for 24 hours. The crystallographic structures of the solid solutions of all compositions were orthorhombic systems. X-ray diffraction and Mohr salt analysis revealed that at higher y value the phase transition due to vacancy ordering occured and that the lattice volume decreased when the x value was increased. The value of nonstoichiometric ratio y were found to be in the range of $0.0{\sim}0.5$. Electrical conductivities of this systems are measured in temperature range of -100 to 100$^{\circ}C$. Ionic contribution to total conductivity was found from activation energy in the phase containing the open pathway due to vacancy ordering.

• Journal of Environmental Science International
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• v.23 no.6
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• pp.1037-1047
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• 2014

A highly sensitive analytical method based on stir bar sorptive extraction (SBSE) technique and gas chromatography/tandem mass spectrometry (GC/MS-MS) has been developed, allowing the simultaneous multi-analyte determination of seven UV filters in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 40 mL of water sample at pH 3 and stirred at 1,100 rpm for 120 min. Other SBSE parameters (salt effect and presence of organic solvent) were optimised. The method shows good linearity (coefficients > 0.990) and reproducibility (RSD < 12.9%). The extraction efficiencies were above 84% for all the compounds. The limits of detections (LOD) and limits of quantification (LOQ) were 2.1~8.6 ng/L and 6.8~27.5 ng/L, respectively. The developed method offers the ability to detect 8 UV filters at ultra-low concentration levels with only 40 mL of sample volume. Matrix effects in tap water, river water, wastewater treatment plant (WWTP) final effluent water and seawater were investigated and it was shown that the method is suitable for the analysis of trace level of 7 UV filters except of benzophenone (BP). The method developed in the present study has the advantage of being rapid, simple, high-sensitive and both user and environmentally friendly.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.381-387
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• 2018

Our study focuses on upgrading real biogas obtained under Indian scenario using carbon capture and utilization (CCU) technology to remove carbon dioxide ($CO_2$) and utilize it by forming metal carbonate. Amines such as monoethanolamine (MEA), diethanolamine (DEA), and sodium hydroxide (NaOH) were used to rapidly convert gaseous $CO_2$ to aqueous $CO_2$, and $BaCl_2$ was used as an additive to react with the aqueous $CO_2$ and rapidly precipitating the aqueous $CO_2$. All experiments were conducted at $25^{\circ}C$ and 1 atm. We analyzed the characteristics of the $BaCO_3$ precipitates using X-ray diffractometry (XRD), scanning electron microscopy - Energy dispersive spectroscopy (SEM-EDS) and Fourier-transform infrared spectroscopy (FT-IR) analyses. The precipitates exhibited witherite morphology confirmed by the XRD results, and FT-IR confirmed that the metal salt formed was $BaCO_3$, and EDS showed that there were no traces of impurities present in it. The quantity of the $BaCO_3$ was larger when formed with DEA. Also, a comparison was done with a previous study of ours conducted in Korean conditions. Finally, we observed that the carbonate obtained using real biogas showed similar properties to carbonates available in the market. An economic analysis was done to show the cost effectiveness of the method employed by us.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.9
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• pp.717-722
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• 2012

In this work, we study on the effects of the oxygen pressure on the structural and crystalline of MgZnO thin films. MgZnO thin films were deposited on p-Si (111) substrates by using pulsed laser deposition. The X-ray diffraction analysis and energy-dispersive X-ray results revealed that as the oxygen pressure increased and Mg content in the MgZnO films decreased. Also Crystal structure was changed from cubic rock salt to hexagonal wurtzite. Alpha step and atomic force microscopy results showed that the thickness of the films are about 100 nm, and it has been found that the MgZnO (002) preferred orientation were deposited with increasing the oxygen pressure. Therefore, the effect of the preferred orientation, the crystallization grew in the form of the columnar; Grain size and RMS of the films were increased with increasing oxygen pressure.