• Korean Journal of Heritage: History & Science
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• v.55 no.2
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• pp.186-197
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• 2022

The Daejanggakgibi Stele of Silleuksa Temple in Yeoju is a stone stele from the Goryeo Dynasty that is inscribed with various stories about the construction of Daejanggak, a place where Buddhist scriptures were kept. This stele has been maintained for a long time in a state in which discoloration of the body has occurred, and the inscription has been partially damaged due to dozens of cracks. Using non-destructive analysis methods for stone artifacts, material investigation, portable X-ray fluorescence analysis, and ultrasonic velocity analysis for the stele were performed. It was confirmed that the stele body was composed of light gray crystalline limestone, and the base stone, support stone, and cover stone were medium-grained biotite granite. Portable X-ray fluorescence analysis confirmed that iron(Fe) was an original coloring element of the stele surface. From the distribution pattern of the coloration, it can be inferred that iron-containing materials flew down from between the stele body and the cover stone. Thereafter, living organisms or organic contaminants attached to it so that yellow and black contaminants were formed. Ultrasonic diagnosis revealed that the physical property of both the front and back surfaces ranged from fresh rocks(FR) to completely weathered rocks(CW), and the average weathering index was grade 3(intermediate). However, the point where cracks developed intensively was judged to be the completely weathered stage(CW), and some cracks located in the upper and lower parts of the stele bear potentially very high risk. It is necessary to monitor the movement of these cracks and establish reinforcement measures for conservation in the future.

• Resources Recycling
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• v.30 no.1
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• pp.60-65
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• 2021

The recycling of titanium turning scraps requires the removal of cutting oil and other contaminants remaining on the surface. In this study, an experiment was conducted in which titanium scraps were cleaned by a combination of ultrasonic immersion-steam cleaning and subsequent drying at high temperature. To determine the removal mechanism of cutting oil, the contact angle between titanium surface and cutting oil was measured. The result confirmed the optimum condition of the immersion solution of the titanium turning scraps. In the case of immersion cleaning of Na4P2O7 aqueous solution, the degree of carbon removed in the cutting oil was the highest at 50℃, and it was confirmed that the carbon content obtained from the combination of steam cleaning and ultrasonic immersion-steam cleaning was lower than that from steam cleaning after ultrasonic immersion. The oxidation and decomposition behaviors of cutting oil were investigated using Thermogravimetric analysis (TGA) and the result was applied in the high temperature drying process. From the results of the high temperature drying tests, it was concluded that 200℃ is the optimal drying temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.270-275
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• 2021

ZnO was synthesized according to the transformation behavior and crystallization conditions of Zn-intermediate obtained by zinc sulfate as a precursor and NaOH, Na₂CO₃ as a alkali agents. For ZnO crystallization, Zn₄(OH)₆SO₄·H₂O and Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate were calcined at 400℃ and 800℃ for 1 h, respectively, based on decomposition temperature from TGA. Zn₄(OH)₆SO₄·H₂O was confirmed to have mixed Zn₄(OH)₆SO₄·H₂O and ZnO at 400℃, and was completely thermally decomposed at 800℃ to form ZnO phase. The prepared Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate by the reaction with Na₂CO₃ was transformed to a complete ZnO crystallization over 400℃. Nano-sized ZnO can be synthesized at a relatively lower calcination temperature through the reaction with Na₂CO₃.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.3
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• pp.95-120
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• 2023

Methane (CH₄) is a key greenhouse gas in the atmosphere with 85 times greater greenhouse potent relative to carbon dioxide (CO₂). The atmospheric concentration of CH₄ is rapidly increasing due to the intensive usage of CH₄ and the thawing of the cryosphere. Additionally, with the current warming of ocean water, the dissociation of gas hydrates, an ice-like compound and the largest reservoir of CH₄ on Earth, is expected to occur, resulting in the release of CH₄ from the seafloor into the overlying water and atmosphere. Moreover, bottom water hypoxia is another concern that potentially introduces greenhouse gases into the atmosphere. With ongoing global warming and eutrophication, the size and duration of bottom water hypoxia are rapidly increasing. These low-oxygen conditions would relocate the redox zone shallower in sediment or in the water column, causing the release of CH₄ into the atmosphere and thereby intensifying global warming. However, there exists a gap in the understanding of CH₄ dynamics including its generation in relation to bottom water hypoxia. Therefore, this review article aims to understand the relationship between CH₄ and bottom water hypoxia and to draw attention to CH₄ investigation in Korea.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.550-558
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• 2021

In a radiotracer study, the bioaccumulation and efflux of metals in earthworms (Eisenia fetida) exposed to soil spiked with ZnO and Ag nanoparticles (AgNP) were compared to those exposed to soil spiked with ionic Zn and Ag. Additionally, the bioavailability and chemical mobility of nano- and ionic metals in the soil were estimated using the sequential extraction method and compared to the bioaccumulation factor(BAF). The BAF for ZnO (0.06) was 31 times lower than that for Zn ions (1.86), suggesting that ZnO was less bioavailable than the ionic form in contaminated soil. In contrast, the BAFs for two types of AgNPs coated with polyvinylpyrrolidone (0.12) or citrate (0.11) were comparable to those of ionic Ag (0.17). The sequential extraction of metals from the soil suggests that the chemically mobile fractions in the Zn ion treatment were higher(35%) than those (<20%) in the Ag ion treatment, which was consistent with the greater BAFs in the former than the latter. However, the chemical mobility in the ZnO treatments did not predict bioavailability. The efflux rates of Ag (3.2-3.8% d^-1) in the worms were 2-3×those(1.2-1.7% d^-1) for Zn.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.125-131
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• 2024

In this study, synthesized Ni/Ce_xZr_1-xO₂ catalysts were coated on the surface of honeycomb metalic monoliths to investigate catalytic activity in steam reforming of methane reactions. Supports with varying Ce/Zr ratios were synthesized to observe their behavior in the reforming reaction, and catalysts with Ni contents ranging from 5 wt% to 20 wt% were prepared to analyze the effect of Ni loading contents on catalytic activity. The catalysts were characterized by XRD, BET, TPR, and SEM. The TPR analysis indicated the formation of Ni-Ce-Zr oxide with a strong interaction between the active metal Ni and CeO₂-ZrO₂ support. The 15 wt% Ni/Ce_0.80Zr_0.20O₂ catalyst exhibited the highest activity and stability in the steam reforming of methane reaction. Catalysts with enhanced activity and stability were synthesized by manufacturing composite materials using excellent oxygen storage and donor properties of CeO₂ and the thermal properties of ZrO₂.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.1
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• pp.11-18
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• 2024

Recently, there have been attempts to claim the hair moisturizing effect for a hair care product, however there has not yet been an official evaluation method because heating temperature for hair has not been established. This study was conducted to establish a quantitative evaluation for hair water content. In order to observe the behavior of water inside hair, heat was applied to hair with various temperatures using thermogravimetric dry residue. As the heating temperature increased, the amount of moisture released from the hair increased. As a result of evaluating hair using a differential scanning calorimeter (DSC), a unique phenomenon in which a rapid endothermic reaction occurs around 75 ℃ was observed. This phenomenon was also observed in different ethnic hair. In hair that damaged the hair cuticle barrier with oxidation and heat, this rapidly rising endothermic reaction temperature occurred at 77 ℃, which was slightly higher, and 73 ℃ was observed when this hair was applied with polar oil, conditioning polymer, or keratin protein. To determine how this reaction affects the hair surface, friction test was performed using an atomic force microscope. When heated above 75 ℃, cuticle friction increased, however when heated above 90 ℃, there was no change in hair cuticle friction. Finally, it was confirmed that around 75 ℃ is the critical temperature at which desorption of water bound to the hair occurs. It is suggested that a heating temperature of 75 ℃ is the optimal temperature for detecting and quantifying the moisture content of hair, and that approximately 10% detected at 75 ℃ can be a standard value for hair moisture content.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.213-227
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• 2006

The geochemical evolution of mine drainage and leachate from waste rock dumps and stream water in Pb-As-rich abandoned Sechang mine area was investigated to elucidate mechanisms of trace metals. Total and sequential extractions were applied to estimate the distribution of trace metals in constituent phases of the waste rocks and to assess the mobility of trace metals according to physicochemical conditions. These discharged waters varied largely in chemical composition both spatially and temporally, and included cases with significant]y low pH (in the range 2.1-3.3), and extremely sulphate (up to 661 mg/l and metal contents (e.g. up to 169 mg/l for Zn, 27 mg/l for As, 3.97 mg/l for Pb, 2.99 mg/l for Cu, and 1.88 mg/l for Cd). Arsenic and heavy metal concentrations at the down-stream of Sechang mine have been decreased nearly to the background level in downstream sites (sites 8 and 16) without any artificial treatments. The oxidation of Fe-sulfides and the subsequent hydrolysis, of Fe(II), with precipitation of poorly crystallized minerals, constituted an efficient mechanism of natural attenuation which reduces considerably the transference of trace metals (i.e. Fe and As) to rivers. The dilution of drainage by mixing with pristine waters provoked an additional decrease of trace metal concentrations and a progressive pH increase. On the other hand, the most soluble cations (i.e. Zn) remained significantly as dissolved solutes until the pH was raised to approximately neutral values. With respect to ecotoxicity, it is likely that the Zn pollution is of particular concern in Sechang mine area. This was confirmed by the sequential extraction experiment, where Zn in wet waste-rock samples occurred predominantly in the exchangeable fraction (65-89% of total), while Pb was the highest in the reducible and carbonate fractions, and Cd, Cu and As in the residual fraction. Pb concentration in the readily available exchangeable fraction (34-48% of total) was dominated for dried waste rock samples. Considering the proportion of metals bound to the exchangeable and carbonate fractions, the comparative mobility of metals probably decreased in the order of Zn>Pb>Cd>As=Cu.

• Journal of Soil and Groundwater Environment
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• v.10 no.1
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• pp.43-57
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• 2005

Twelve bottom sediments and three cores were collected in Juam reservoir for a study on transportation, which was controlled by particle grain size (2mm-200{\mu}m,\;200-100{\mu}m,\;100-50{\mu}m,\;50-20{\mu}m,\;<20{\mu}m), and vertical distribution of heavy metals. Sediment cores were sliced into 2 to 5 cm intervals to measure heavy metal concentrations in interstitial water and sediments with depth. Pb isotopic compositions of core samples were determined to calculate sedimentation rate. Regardless of sampling sites, levels of heavy metals and trace elements in bottom sediments are nearly constant with mean values of $14.9\;{\mu}g/g\;for\;As,\;0.81{\mu}g/g\;for\;Cd,\;30.7{\mu}g/g\;for\;Cu,\;34.7{\mu}g/g\;for\;Ni,\;63.3{\mu}g/g\;for\;Pb\;and\;87.9{\mu}g/g\;for\;Zn$. In general, Cu, Pb, Zn, Wi, and Cr in fraction of $<20{\mu}m$ exhibit the highest concentration, but content of As is the highest in grain size of $2\;mm-200\;{\mu}m$ and $200-100\;{\mu}m$. Fe and Mn occur as the dissolved compositions of the highest concentrations in interstitial waters and increase in their concentrations toward lower part of cores. On the contrary, concentrations of Zn and Cu show the highest value in the uppermost part in cores, suggesting these elements are released from reductive dissolution of hydroxides and oxidation of organic matters under different redox conditions. The highest accumulations of Cu, Ni, Pb, and Zn contents in the sediment cores are observed at 0-4 cm layers, and concentrations of Cu and Pb are especially high, implying these heavy metals are originated from anthropogenic sources. The apparent sedimentation rate estimated using unsupported $^{210}Pb$ is 0.91 cm $year^{-1}$, corresponding about 10 cm sedimentation in total depth since construction of Juam dam. These results will provide available information for management of bottom sediment in Juam reservoir.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.1-7
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• 2009

This study has been focused on determining the chemical composition of $^{14}C$ - in terms of both organic and inorganic $^{14}C$ contents - in reactor coolant from 3 different PWR's reactor type. The purpose was to evaluate the characteristic of $^{14}C$ that can serve as a basis for reliable estimation of the environmental release at domestic PWR sites. $^{14}C$ is the most important nuclide in the inventory, since it contributes one of the main dose contributors in future release scenarios. The reason for this is its high mobility in the environment, biological availability and long half-life(5730yr). More recent studies - where a more detailed investigation of organic $^{14}C$ species believed to be formed in the coolant under reducing conditions have been made - show that the organic compounds not only are limited to hydrocarbons and CO. Possible organic compounds formed including formaldehyde, formic acid and acetic acid, etc. Under oxidizing conditions shows the oxidized carbon forms, possibly mainly carbon dioxide and bicarbonate forms. Measurements of organic and inorganic $^{14}C$ in various water systems were also performed. The $^{14}C$ inventory in the reactor water was found to be 3.1 GBq/kg in PWR of which less than 10% was in inorganic form. Generally, the $^{14}C$ activity in the water was divided equally between the gas- and water- phase. Even though organic $^{14}C$ compound shows that dominant species during the reactor operation, But during the releasing of $^{14}C$ from the plant stack, chemical forms of $^{14}C$ shows the different composition due to the operation conditions such as temperature, pH, volume control tank venting and shut down chemistry.