• Conservation Science in Museum
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• v.27
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• pp.67-90
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• 2022

A C-46 transport aircraft, which can be thought of as a large cultural heritage item from the modern period, was subjected to paint analysis and conservation treatment in preparation for its exhibition. The C-46 is the first aircraft ever dispatched to overseas combat zones by the Korean Air Force and carried out missions during the Vietnam War. The aircraft is mainly made of aluminum and shows signs of corrosion on its surface, including pitting and etching, as well as gray and white powdery attachments. In the analysis of the paint, diatomite(SiO₂·nH₂O) was confirmed in the red paint, titanium dioxide(TiO₂) was identified in the white paint, black iron oxide(Fe₃O₄) was detected in the black paint, and colcothar(Fe₃O₄) mixed with putty was confirmed in the blue paint. Infrared spectroscopy revealed the use of alkyd resin in the paint on the main body and nitrocellulose in the Taegeuk pattern. During the conservation treatment, mechanical cleaning, such as sanding, was conducted to remove paint and varnish from the surface. Corrosion was removed by sanding and cleaning with chemical solvents, and new paints and varnishes were applied. Through the paint analysis and conservation treatment, the aircraft was made available for exhibition in a stable condition.

• Journal of the Korean Applied Science and Technology
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• v.39 no.1
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• pp.34-41
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• 2022

As the use of chemical products increases in daily life, the removal of dye waste has also emerged as an important environmental issue. This dye waste can be decomposed using a photocatalyst, and the photocatalyst can be synthesized very cost-effectively by using the sol-gel technology. The sol-gel technology is not only very useful for nanoscale film formation, but also can simply form multilayer structures. Using a multiple spin coating method, in this study, a ZnO film with a multilayered structure (3 layers, 5 layers) was formed by using zinc oxide (ZnO), which is effective in decomposing various dyes. For performance comparison, a ZnO film having a single layer structure by a single spin coating method was prepared as a control. Structural and elemental analysis of ZnO film was performed using an X-ray diffraction analyzer and an energy dispersive X-ray spectrometer. A nanowire-like surface morphology could be observed through a scanning electron microscope. Additionally, UV-Vis spectrophotometer was used to measure the absorbance of UV light. The ZnO film with a five-layer structure degraded the simulated methylene blue by 49% more than the ZnO film with a single-layer structure. In conclusion, it was found that ZnO having a multilayered structure is useful as a photocatalyst that decomposes methylene blue dye more effectively.

• BMB Reports
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• v.55 no.6
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• pp.275-280
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• 2022

The treatment of atopic dermatitis (AD) is challenging due to its complex etiology. From epidermal disruption to chronic inflammation, various cells and inflammatory pathways contribute to the progression of AD. As with immunosuppressants, general inhibition of inflammatory pathways can be effective, but this approach is not suitable for long-term treatment due to its side effects. This study aimed to identify a plant extract (PE) with anti-inflammatory effects on multiple cell types involved in AD development and provide relevant mechanistic evidence. Degranulation was measured in RBL-2H3 cells to screen 30 PEs native to South Korea. To investigate the anti-inflammatory effects of Parasenecio auriculatus var. matsumurana Nakai extract (PAE) in AD, production of cytokines and nitric oxide, activation status of FcεRI and TLR4 signaling, cell-cell junction, and cell viability were evaluated using qRT-PCR, western blotting, confocal microscopy, Griess system, and an MTT assay in RBL-2H3, HEK293, RAW264.7, and HaCaT cells. For in vivo experiments, a DNCBinduced AD mouse model was constructed, and hematoxylin and eosin, periodic acid-Schiff, toluidine blue, and F4/80-staining were performed. The chemical constituents of PAE were analyzed by HPLC-MS. By measuring the anti-degranulation effects of 30 PEs in RBL-2H3 cells, we found that Paeonia lactiflora Pall., PA, and Rehmannia glutinosa (Gaertn.) Libosch. ex Steud. show an inhibitory activity of more than 50%. Of these, PAE most dramatically and consistently suppressed cytokine expression, including IL-4, IL-9, IL-13, and TNF-α. PAE potently inhibited FcεRI signaling, which mechanistically supports its basophil-stabilizing effects, and PAE downregulated cytokines and NO production in macrophages via perturbation of toll-like receptor signaling. Moreover, PAE suppressed cytokine production in keratinocytes and upregulated the expression of tight junction molecules ZO-1 and occludin. In a DNCB-induced AD mouse model, the topical application of PAE significantly improved atopic index scores, immune cell infiltration, cytokine expression, abnormal activation of signaling molecules in FcεRI and TLR signaling, and damaged skin structure compared with dexamethasone. The anti-inflammatory effect of PAE was mainly due to integerrimine. Our findings suggest that PAE could potently inhibit multi-inflammatory cells involved in AD development, synergistically block the propagation of inflammatory responses, and thus alleviate AD symptoms.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.500-504
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• 2023

In this study, the heteroepitaxial thin film growth of β-Ga₂O₃ was studied according to the position of the susceptor in mist-CVD. The position of the susceptor and substrate was moved step by step from the center of the hot zone to the inlet of mist in the range of 0~50 mm. It was confirmed that the average thickness increased to 292 nm (D1), 521 nm (D2), and 580 nm (D3) as the position of the susceptor moved away from the center of the hot zone region. The thickness of the lower region of the substrate is increased compared to the upper region. The surface roughness of the lower region of the substrate also increased because the nucleation density increased due to the increase in the lifetime of the mist droplets and the increased mist density. Therefore, thin film growth of β-Ga₂O₃ in mist-CVD is performed by appropriately adjusting the position of the susceptor (or substrate) in consideration of the mist velocity, evaporation amount, and temperature difference with the substrate, thereby determining the crystallinity of the thin film, the thickness distribution, and the thickness of the thin film. Therefore, these results can provide insights for optimizing the mist-CVD process and producing high-quality β-Ga₂O₃ thin films for various optical and electronic applications.

• Korea Science and Art Forum
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• v.30
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• pp.251-261
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• 2017

Metal is a material that has exerted a lot of influence on the development of human cultures, and has closely connected with our life from the past to the present. Types of metal we have used from the prehistoric times are varied, and iron relics take the largest percentage of metal relics excavated in our country. The biggest threat to the existence of iron relics ranging from excavated relics to the ones that are transmitted is the process of corrosion, and physical removal has been used the most for removing corroded oxides. For details for removal of corrosion oxides, this thesis aimed to research on the chemical corrosion oxides remover that protects parent material of iron relics but treats corrosion oxides only. For safe and effective removal of corrosion oxides of iron relics, this study was conducted aiming at finding the possibility of and optimized composition for removal of iron relics corrosion oxides by manufacturing new acid, alkaline and neutral oxides removers and changing their composition variously, exploring the possibility by applying the agents to modern relics. The results of this study are as follows: First, the acid solution removed only some part of corrosive substance oxidized on the surface of metal specimen. Second, the application of each of alkaline and neutral solution resulted in remaining black-colored corrosive substance, but it was removed when the quantity of the solution and the duration of application are increased. Third, All the three solutions did not cause any damage to parent material in the course of application, and showed the result that they are capable of removing unstable oxide layer while protecting parent material and stable corrosive layer as the solutions would be able to deal with situation by a relic only through the control of concentration of solution and duration of application.

• Clean Technology
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• v.29 no.2
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• pp.95-101
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• 2023

An experiment was conducted to produce vaterite-type precipitated calcium carbonate from waste oyster shells in order to use them as recyclable resources. Calcined oyster shells containing calcium oxide as their main component were prepared at a temperature of 800℃ for 24 h. The oyster shells were dissolved in nitric acid or hydrochloric acid solution to make 0.1 M calcium nitrate or calcium chloride aqueous solution, and a carbonation reaction was performed using a 0.1 M sodium carbonate aqueous solution under various experimental conditions, which included varying the amount of aspatic acid additive, the amount of NH₄OH added, the reaction time, the reaction temperature, the stirring speed, and the type of dissolved acid. The XRD, SEM, and size distributions were analyzed and the vaterite content was calculated. Spherical precipitated calcium carbonate with a vaterite content of 95.9% was synthesized by adding 0.1 mol aspatic acid/1 mol CaO and 2 cm³ of NH₄OH, and reacting for 1 h at 25℃ while stirring at 600 rpm. The average particle diameter was found to be 12.11 ㎛. Calcium carbonate contatining high vaterite is used as high value added calcium carbonate for medical, food, inke additiver, etc.

• Membrane Journal
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• v.33 no.3
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• pp.94-109
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• 2023

1,3-Dioxolane is an exciting material that has attracted widespread interest in the chemical, paint, and pharmaceutical industries as a solvent, electrolyte, and reagent because 1,3-dioxolane is not toxic, carcinogenic, explosive, auto-flammable, and multifunctional, and due to their excellent miscibility in most organic and aqueous solvent conditions. Recently, this material has received increasing attention as a CO₂-selective polymer precursor to separating CO₂ from flue gas and natural gas mixtures. Poly(1,3-dioxolane) (PDXL) possesses higher ether oxygen content than polyethylene oxide (PEO), which demonstrates superior membrane CO₂/N₂ separation properties owing to their polar ether oxygen groups exhibiting strong affinity toward CO₂. Thus, PDXL-based membranes displayed an outstanding CO₂ solubility selectivity over non-polar (N₂, H₂, and CH₄) gases. However, the polar groups of PDXL, like PEO, promote chain packing efficiency and cause polymer crystallization, thereby reducing its gas permeability, which should be improved. In this short review, we discuss the recent advancement and limitations of PDXL membranes in gas separation applications. To conclude, we provide future perspectives for inhibiting the limits of 1,3-dioxolane-based polymers in the CO₂ separation process.

• Journal of Practical Agriculture & Fisheries Research
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• v.26 no.1
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• pp.16-21
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• 2024

Green manure crops have a variety of benefits, including improving soil fertility, removing soil salinity, enhancing soil aeration and moisture regulation, reducing the use of chemical fertilizers, reducing nitrous oxide emissions, reducing herbicide use through weed-suppressive effects, promoting agricultural ecosystem protection and carbon dioxide absorption capacity. To find ways to increase the germination rate of legumes and green manure crop seeds, which are imported in large quantities every year. It was carried out that two seed priming methods, osmotic priming and heat treatment, and compared their effects. Heat treatment was treated for 10 minutes at 40℃ or 60℃, followed by rinsing with water. Osmotic priming was applied for 30 seconds in a saline solution with a specific gravity of 1.13. Overall, there was no significant difference in the final germination rate, but it was found that osmotic priming and heat treatment affected the germination speed. However, applying heat treatment and osmotic priming simultaneously did not affect the germination characteristics. Therefore, it is suggested that heat treatment and osmotic priming can increase the germination speed of soybean and green manure crops.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.320-324
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• 2013

The effects of $CeO_2$ on catalytic activity of $CeO_2-TiO_2$ for the selective catalytic reduction (SCR) of $NO_x$ were investigated in terms of structural, morphological, and physico-chemical analyseis. $CeO_2-TiO_2$ catalysts were synthesized with three different additions, 10, 20, and 30 wt% of $CeO_2$, by the sol-gel method. The XRD peaks of all specimens were assigned to a $TiO_2$ phase (anatase) and the peaks became broader with the addition of $CeO_2$ because it was dispersed as an amorphous phase on the surface of $TiO_2$ particles. The specific surface area of $TiO_2$ increased with the addition of $CeO_2$ from $60.6306m^2/g$ to $116.2791m^2/g$ due to suppression of $TiO_2$ grain growth by $CeO_2$. The 30 wt% $CeO_2-TiO_2$ catalyst, having the strongest catalytic acid sites ($Br{\Phi}nsted$ and Lewis), showed the highest $NO_x$ conversion efficiency of 98 % at $300^{\circ}C$ among the specimens. It was considered that $CeO_2$ contributes to the improvement of the $NO_x$ conversion of $CeO_2-TiO_2$ catalyst by increasing specific surface area and catalytic acid sites.

• Korean Journal of Environmental Agriculture
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• v.19 no.4
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• pp.319-323
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• 2000

This study was conducted to compare fractionations and availability of heavy metal in paddy soils near five abandoned mining areas. The sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from water $soluble(H_2O)$, $exchangeable(0.5M\;KNO_3)$, organically bound(0.5M NaOH), $oxide/carbonate(0.05M\;Na_2-EDTA)$, and $sulfide/residual(4M\;HNO_3)$. EDTA and $HNO_3$ extractable of Cd, Pb, and Zn, and NaOH and $HNO_3$, extractable of Cu were predominant chemical forms. The ratio of $H_2O+KNO_3$ extractable of Cd, Zn, Cu, and Pb were 25.1, 8.7, 4.0, and 0.4%, respectively. The ratio of $H_2O+KNO_3$ extractable heavy metal were negatively correlated with soil pH, while $EDTA+HNO_3$ extractable heavy metal were positively correlated. The most consistent distribution patterns were found when the soil samples were grouped according to their total contents. Specially, the ratio of $H_2O+KNO_3$ extractable heavy metal were higher as total contents of heavy metal were increased. The ratio of $H_2O+KNO_3$ extractable heavy metal(Cd 1.06, Cu 0.15, Pb 0.01, and Zn 0.05%) were lower at the high soil pH than those(Cd 31.31, Cu 4.06, Pb 1.75, and Zn 10.16%) at the low level. Compared to other chemical forms, the degree of contribution for $KNO_3$ extractable form to the Cd uptake to brown rice was high, whereas that for EDTA and $HNO_3$ extractable forms were high to the Zn.