• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.114-120
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• 2009

The viscosities of $CaO-SiO_2-Al_2O_3-MgO$ flux were measured under the condition of $CaO/SiO_2=1.0-1.3$ and 5-20 wt%MgO. Submerged arc welding flux with $5wt%Al_2O_3$ content had the lowest critical temperature and widest solid-liquid coexisting region at about 5 wt%MgO. It indicateds that both critical temperature and viscosity depend on the kind of primary phase of molten flux. Viscous behavior of the molten flux at 1773 K was analyzed in the view of silicate structure changed by FT-IR spectroscopy. Based on the critical temperature and the behavior of viscosity at a fixed temperature, it could be proposed that the contents of MgO and $Al_2O_3$ in SAW flux show a pronounced effect on preventing contamination in maintaining the liquid phase flux after welding process.

• Biomedical Science Letters
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• v.28 no.2
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• pp.83-91
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• 2022

This study was performed to investigate the contamination status of microorganisms that cause food poisoning in shellfish distributed in the metropolitan area of South Korea. The analyses were conducted according to the sample type, season, and region. In particular, the genotype of food poisoning viruses that explosively cause collective food poisoning was analyzed. Total 483 each of four types of shellfish (Crassostrea gigas, Mytilus coruscus, Pectea albicans albicans, and Scapharca subcrenata) were collected from four distribution sites located in the metropolitan area. We investigated foodborne pathogen by multiplex PCR and RT/Nested PCR from shellfish. As a result, Vibrio parahaemolyticus and Bacillus cereus were detected in 13 and 21 samples and Norovirus (NoV) GI and GII were detected in 7 and 12 samples, respectively. V. parahaemolyticus and NoV GI and GII showed differences in types of shellfish and seasons, and no correlation was confirmed with regional differences. Also, as a result of genotyping for the detected NoV GI and GII, they were confirmed as NoV GI.7, GI.5 and GII.3, which are causes of collective food poisoning. Therefore, cross-infection with shellfish can cause food poisoning. In particular, attention must be paid to the handling and cooking of shellfish in organizations that implement group feeding, and it is necessary to establish a management system for microorganisms that cause food poisoning in the process of shellfish farming and distribution.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3949-3956
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• 2022

Kori Unit 1 is planning a system decontamination project to reduce radiation exposure of decommissioning workers, prevent the spread of contamination and down-grade the level of classification of radioactive waste. The system decontamination range for Kori Unit 1 will be the entire primary system, including RCS, CVCS and RHRS. Some system design modifications are required for the system decontamination operation. In this paper, major system design modifications were evaluated based on the conditions that system restoration is needed after completion of system decontamination. The major system design modifications are CIDF connection location to system, system decontamination operating pressure control, RCP seal water injection and formation of letdown flow. It was evaluated that there was no negative effect on the system due to the system design modifications. However, as the RCP seal water is injected into the system in the oxidation process, the concentration of the oxidizing agent is diluted. Therefore, the oxidizing agent injection and system decontamination operation procedures should be developed to address the dilution effect of the oxidizing agent. The system design modifications dealt in this paper will be finally confirmed through on-site investigation in the future, and if necessary, the system design modifications will be re-evaluated.

• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.10-18
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• 2022

We present an experimental investigation on emulsions created during the impact process between a surfactant-laden droplet and an oil layer on water. By varying the surfactant concentration and the viscosity of oil layer, we created emulsions and visualized them using multi-dimensional high-speed imaging. Our analysis shows that the emulsions are more likely to be unstable and decay within a minute if the impacting droplet contains more surfactant. We also found that there are three mechanisms of generation of emulsions depending on the concentration of surfactant and the viscosity of oil layer; the jet pinch-off, cavity pinch-off, and tearing of oil layer. Jet and cavity pinch-off turned out to be dominant mechanisms for high oil viscosities, while tearing of oil layer is dominant for low oil viscosities. Our result is potentially useful in designing optimal dispersant properties for offshore oil contamination.

• Journal of Soil and Groundwater Environment
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• v.27 no.6
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• pp.37-46
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• 2022

As the amount of livestock wastewater increases, ammonia contamination in surface water and groundwater is also increasing, and its treatment is urgently needed. In this study, indigenous soil bacteria was utilized for ammonia removal in artificial wastewater and associated removal mechanisms and efficiencies were evaluated. Two batch reactors were configurated to contain natural soil and artificial wastewater at 1:10 mass ratio, and incubated for 84 and 168 hours, respectively. The results showed that ammonia was completely removed within 48 and 72 hours in the first and second reactors, respectively. There were no significant changes in ammonia concentrations in the control groups without soil. Nitrate was formed in the reactors, indicating that the main removal mechanism of ammonia was nitrification by nitrifying bacteria. Nitrate was further converted to nitrogen gas by denitrification in the anaerobic environment, which was caused by consumption of oxygen during the nitrification process.

• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.20-24
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• 2009

YBCO coated conductors (CC) on the $CeO_2$-buffered IBAD-MgO template were fabricated by metal-organic deposition (MOD) Process with Ba-trifluoroacetate and fluorine-free Y and Cu precursor materials. The precursor solution was coated on $CeO_2$-buffered IBAD MgO templates using the multiple dip-coating method, decomposed into inorganic precursors by pyrolysis up to $400^{\circ}C$ within 3 h, and finally fired at $740{\sim}800^{\circ}C$ in a reduced oxygen atmosphere. Microstructure, texture, and superconducting properties of YBCO films were found highly sensitive to both the firing temperature and time. The high critical current density ($J_C$) of $1.15\;MA/cm^2$ at 77.3K in the self-field could be obtained from $1\;{\mu}m$ thick YBCO CC, fired at $740^{\circ}C$ for 3.5 h, implying that high performance YBCO CC is producible on IBAD MgO template. Further enhancement of $J_C$ values is expected by improving the in-plane texture of $CeO_2$-buffer layer and avoiding the metal substrate contamination.

• Ocean and Polar Research
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• v.45 no.1
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• pp.1-9
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• 2023

Marine microalgae have different collection methods depending on their habitat. In the case of adhesive microalgae, it is difficult to separate organisms from the substrate surface, and contamination is likely to occur during the sampling process. In this study, we analyzed the collection efficiency of adhesive microalgae using three artificial fiber materials (nylon, blend fabric, and viscose rayon). Each fiber showed different fiber diameter and pore characteristics (nylon 26.09 ㎛, blend fabric 56.6 ㎛, viscose rayon 101.3 ㎛). In addition, attached organisms were collected on the surface of artificial substrates at Bukseong Port in Incheon using each tested fiber material. After that, we investigated the population and species composition. The highest number of cells was found in nylon, which was 8 times higher than in the least collected viscose rayon material. In addition, we identified 24 microalgal species from the substrate, demonstrating that the species composition differed from that of surface water. The number of collected microalgae species varied depending on the fiber materials, with nylon containing all the adhesive microalgae. In contrast, only a few microalgae were observed in other fibers. These results suggest that, of the tested fibers, nylon material may be suitable for collecting adhesive microalgae. As a result, this study may be useful for future research on adhesive microalgae.

• Journal of Powder Materials
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• v.30 no.2
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• pp.156-168
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• 2023

The semiconductor industry faces physical limitations due to its top-down manufacturing processes. High cost of EUV equipment, time loss during tens or hundreds of photolithography steps, overlay, etch process errors, and contamination issues owing to photolithography still exist and may become more serious with the miniaturization of semiconductor devices. Therefore, a bottom-up approach is required to overcome these issues. The key technology that enables bottom-up semiconductor manufacturing is area-selective atomic layer deposition (ASALD). Here, various ASALD processes for elemental metals, such as Co, Cu, Ir, Ni, Pt, and Ru, are reviewed. Surface treatments using chemical species, such as self-assembled monolayers and small-molecule inhibitors, to control the hydrophilicity of the surface have been introduced. Finally, we discuss the future applications of metal ASALD processes.

• Tribology and Lubricants
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• v.39 no.5
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• pp.212-215
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• 2023

Diaphragm compressors play a crucial role in safely compressing large volumes of high-purity hydrogen gas without contamination or leakage, thereby ensuring quality and reliability. Diaphragm compressors use a thin, flat, triple-layered diaphragm plate that is subjected to repetitive piston pressure for compression. They are usually made of metallic materials such as stainless steel or Inconel owing to their high-pressure resistance. However, since they are consumable components, they fail due to fatigue from repetitive pressure and vibration stress. This study aims to evaluate the scratch characteristics of diaphragms in operational environments by conducting tests on three different samples: Inconel 718, AISI 301, and Teflon-coated AISI 301. The Inconel 718 sample underwent a polishing process, the AISI 301 sample used raw material, and the Teflon coating was applied to the AISI 301 substrate at a thickness of 50 ㎛. To assess the scratch resistance, reciprocating motion friction tests were performed using a tribometer, utilizing 220 and 2000 grit sandpapers as the counter materials. The results of the friction tests suggested that the Teflon-coated sample exhibited the lowest initial friction coefficient and consistently maintained the lowest average friction coefficient (0.13 and 0.11 with 220 and 2000 grit, respectively) throughout the test. Moreover, the Teflon-coated diaphragm showed minimal wear patterns, indicating superior scratch resistance than the Inconel 718 and AISI 301 samples. These findings suggest that Teflon coatings may offer an effective solution for enhancing scratch resistance in diaphragms, thereby improving compressor performance in high-pressure hydrogen applications.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.70-75
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• 2008

This study was carried out to evaluate the applicability of the full scale soil washing processes for reducing heavy metal contamination level of soil around an abandoned mine. In the results of soil washing of the target soil with $H_2SO_4$ and NaOH, the As concentrations of treated soil continuously increased compared with contaminated raw soil. Also, removal efficiencies of Zn and Ni were low. This problems might be caused by chemical partitioning of As in soil and its geologic origination, soil particle size, and scale up of washing plant.