• Safety and Health at Work
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• v.14 no.4
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• pp.451-456
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• 2023

Background: We conducted a case-control study to identify high-risk occupations and exposure to occupational hazards for acute myeloid leukemia (AML). Methods: When patients with AML admitted to the Department of Hematology in the study hospital for the first time are referred to the Department of Occupational and Environmental Medicine, data on occupation are collected by investigators to evaluate work-relatedness. Community-based controls were recruited through an online survey agency, and four controls per case were matched. Occupational information was estimated using structured questionnaires covering 27 specific occupations and 32 exposure agents. Conditional logistic regression analysis was performed by pairing cases and controls. Results: In the analysis of the risk of AML according to occupational classification, a significant association was found in paint manufacturing or painting work (OR = 2.22, 95% CI: 1.03-4.81) and aircrew (OR = 6.00, 95% CI: 1.00-35.91) in males, and in pesticide industry (OR = 6.89, 95% CI: 1.69-28.07) and cokes and steel industry (OR = 2.00, 95% CI: 1.18-22.06) in ≥60 years old. Moreover, the risk of AML increased significantly as the cumulative exposure to thinners increased. In the analyses stratified by sex and age, the association between pesticide exposure and AML was significant in males (OR = 3.28, 95% CI: 1.10-9.77) and in ≥60 years old (OR = 6.22, 95% CI: 1.48-26.08). Conclusion: This case-control study identified high-risk occupational groups in the Republic of Korea including paint manufacturers and painters, aircrew, and those who are occupationally exposed to pesticides or paint thinners.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.43-48
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• 2024

The discovery of a two-dimensional electron gas (2DEG) at the interface of LaAlO₃ (LAO) and SrTiO₃ (STO) substrates has sparked significant interest, providing a foundation for cutting-edge research in electronic devices based on complex oxide heterostructures. However, conventional methods for producing LAO thin films, typically employing techniques like pulsed laser deposition (PLD) within physical vapor deposition (PVD), are associated with high costs and challenges in precisely controlling the La and Al composition within LAO. In this study, we adopted a cost-effective alternative approach-solution-based processing-to fabricate LAO thin films and investigated their electrical properties. By adjusting the concentration of the precursor solution, we varied the thickness of LAO films from 2 to 65 nm and determined the sheet resistance and carrier density for each thickness. After vacuum annealing, the sheet resistance of the conductive channel ranged from 0.015 to 0.020 Ω·s^-1, indicating that electron conduction occurs not only at the LAO/STO interface but also into the STO bulk region, consistent with previous studies. These findings demonstrate the successful formation and control of 2DEG through solution-based processing, offering the potential to reduce process costs and broaden the scope of applications in electronic device manufacturing.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.39.1-39.14
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• 2023

Background: Diseases affecting the lungs and airways contribute significantly to the global burden of disease. The problem in low- and middle-income countries appears to be exacerbated by a shift in global manufacturing base to these countries and inadequate enforcement of environmental and safety standards. In Ghana, the potential adverse effects on respiratory function associated with occupational wood dust exposure have not been thoroughly investigated. Methods: Sixty-four male sawmill workers and 64 non-woodworkers participated in this study. The concentration of wood dust exposure, prevalence and likelihood of association of respiratory symptoms with wood dust exposure and changes in pulmonary function test (PFT) parameters in association with wood dust exposure were determined from dust concentration measurements, symptoms questionnaire and lung function test parameters. Results: Sawmill workers were exposed to inhalable dust concentration of 3.09 ± 0.04 mg/m³ but did not use respirators and engaged in personal grooming habits that are known to increase dust inhalation. The sawmill operators also showed higher prevalence and likelihoods of association with respiratory symptoms, a significant cross-shift decline in some PFT parameters and a shift towards a restrictive pattern of lung dysfunction by end of daily shift. The before-shift PFT parameters of woodworkers were comparable to those of non-woodworkers, indicating a lack of chronic effects of wood dust exposure. Conclusions: Wood dust exposure at the study site was associated with acute respiratory symptoms and acute changes in some PFT parameters. This calls for institution and enforcement of workplace and environmental safety policies to minimise exposure at sawmill operating sites, and ultimately, decrease the burden of respiratory diseases.

• Journal of the East Asian Society of Dietary Life
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• v.21 no.6
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• pp.853-862
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• 2011

We reproduced and investigated the quality characteristics of Samhaeju (one type of Korean traditional rice wine), which has been described in ancient documents. During fermentation, the room temperature was $9.1{\sim}25.0{\circ}C$, and each treatment's material temperature was $11.7{\sim}23^{\circ}C$. As the fermentation proceeded, the pH rapidly decreased (initial pH was 6.6~6.9) and rose gradually from the 18th day. Titratable acidity and amino acidity slowly increased in general. Regarding soluble solid contents, there were various change patterns depending on the production method, and they were affected by initial room temperature. In the treatments using 1 (Sang-ga-yo-rok), 3 (Eum-sik-di-mi-bang), 7 (Jo-sun-mu-ssang-sin-sik-yo-ri-je-beop), 8 (Sang-ga-yo-rok $15^{\circ}C$), reducing sugar contents decreased rapidly after 1st mashing day and then increased slightly after 2nd mashing. The alcohol content increased as the fermentation proceeded, and most of the treatments produced 1/2 the amount of total alcohol content before the 2nd mashing day, followed by a slight increase until the end of fermentation (about 100 days from the 2nd mashing day). In the sensory evaluation, Samhaeju using methods 2, 4, 5, and 6 got high scores and had much reducing sugar contents than other treatments. Among the seven manufacturing processes, method 2 was relatively simple and got the highest score in the sensory evaluation. Therefore, method 2 would be suitable for industrialization and popularization of Korean traditional alcoholic beverage.

• Analytical Science and Technology
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• v.31 no.4
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• pp.149-160
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• 2018

A large number of functional living products are being produced for eco-friendly or health-promoting purposes. In the manufacturing process, such products could be adulterated with raw materials with high radioactivity, such as monazite and tourmaline. Thus, it is essential to manage raw materials and products closely related to the public living. For proper management, an accurate radioactivity data of the processed products are needed. Therefore, it is essential to develop a rapid and validated analytical method. In this study, the concentration of the radioactive $^{238}U$ and $^{232}Th$ in building materials (e.g., tile, cement, paint, wall paper, and gypsum board) and living products (e.g., health products, textiles, and minerals) were determined and compared by ED-XRF and ICP-MS. By comparing the results of both methods, we confirmed the applicability of the rapid screening and precise analysis of ED-XRF and ICP-MS. In addition, $^{238}U$ and $^{232}Th$ levels were relatively lower in building materials than in living products. Particularly, $^{232}Th$ content in 6 of 47 living products exceeded (maximum $8.2Bq{\cdot}g^{-1}$) the standard limit of $^{232}Th$ content in raw material ($1.0Bq{\cdot}g^{-1}$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.375-375
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• 2010

CdTe as an absorber material is widely used in thin film solar cells with the heterostructure due to its almost ideal band gap energy of 1.45 eV, high photovoltaic conversion efficiency, low cost and stable performance. The deposition methods and preparation conditions for the fabrication of CdTe are very important for the achievement of high solar cell conversion efficiency. There are some rearranged reports about the deposition methods available for the preparation of CdTe thin films such as close spaced sublimation (CSS), physical vapor deposition (PVD), vacuum evaporation, vapor transport deposition (VTD), closed space vapor transport, electrodeposition, screen printing, spray pyrolysis, metalorganic chemical vapor deposition (MOCVD), and RF sputtering. The RF sputtering method for the preparation of CdTe thin films has important advantages in that the thin films can be prepared at low growth temperatures with large-area deposition suitable for mass-production. The authors reported that the optical and electrical properties of CdTe thin film were closely connected by the thickness-uniformity of the film in the previous study [1], which means that the better optical absorbance and the higher carrier concentration could be obtained in the better condition of thickness-uniformity for CdTe thin film. The thickness-uniformity could be controlled and improved by the some process parameters such as vacuum level and RF power in the sputtering process of CdTe thin films. However, there is a limitation to improve the thickness-uniformity only in the preparation process [1]. So it is necessary to introduce the external or additional method for improving the thickness-uniformity of CdTe thin film because the cell size of thin film solar cell will be enlarged. Therefore, the authors firstly applied the chemical mechanical polishing (CMP) process to improving the thickness-uniformity of CdTe thin films with a G&P POLI-450 CMP polisher [2]. CMP process is the most important process in semiconductor manufacturing processes in order to planarize the surface of the wafer even over 300 mm and to form the copper interconnects with damascene process. Some important CMP characteristics for CdTe were obtained including removal rate (RR), WIWNU%, RMS roughness, and peak-to-valley roughness [2]. With these important results, the CMP process for CdTe thin films was performed to improve the thickness-uniformity of the sputtering-deposited CdTe thin film which had the worst two thickness-uniformities of them. Some optical properties including optical transmittance and absorbance of the CdTe thin films were measured by using a UV-Visible spectrophotometer (Varian Techtron, Cary500scan) in the range of 400 - 800 nm. After CMP process, the thickness-uniformities became better than that of the best condition in the previous sputtering process of CdTe thin films. Consequently, the optical properties were directly affected by the thickness-uniformity of CdTe thin film. The absorbance of CdTe thin films was improved although the thickness of CdTe thin film was not changed.

• Journal of Preventive Medicine and Public Health
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• v.36 no.2
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• pp.93-100
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• 2003

Objectives : Because shipyard workers are involved with various manufacturing process, they are exposed to many kinds of hazardous materials. Welders especially, are exposed to bisphenol-A (BPA) during the welding and flame cutting of coated steel, This study was conducted to assess the exposure status of the endocrine disrupter based on the job-exposure matrix. The effects of the genetic polymorphism of xenobiotic enzyme metabolisms involved in the metabolism of BPA on the levels of urinary metabolite were investigated. Methods : The study population was recruited from a shipyard company in the f province. A total of 84 shipbuilding workers 47 and 37 in the exposed and control groups, respectively, were recruited for this study. The questionnaire variables included, age, sex, use of personal protective equipment, smoking, drinking and work duration. The urinary metabolite was collected in the afternoon and correction made for the urinary creatinine concentration. The of the CYP1A1, CYP2E1 and UGT1A6 genotypes were investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods with the DNA extracted from venous blood. Results : The urinary BPA level in the welders group was significantly higher than in the control group (p<0.05). The urinary BPA concentration with the wild type UGT1A6 was higher than the other UGT1A6 genotypes, but with no statistical significant. From themultiple regression analysis of the urinary BPA, the regression coefficient for job grade was statistically significant (p<0.05). Conclusions : The grade of exposure to BPA affected the urinary BPA concentration was statistically significant. However, the genetic polymorphisms of xenobiotics enzyme metabolism were not statistically significant. Further investigation of the genetic polymorphisms with a larger sample size is needed.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.312-319
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• 2009

Statement of problem: Delamination of veneering porcelain from underlying ceramic substructures has been reported for zirconia-ceramic restorations. Colored zirconia cores for esthetics have been reported that their bond strength with veneered porcelain is weaker compared to white zirconia cores. Purpose: This study aimed to investigate the shear bond strength by manufacturing the veneering porcelain on the colored zirconia core, using the layering technique and heat-pressing technique, and to evaluate the clinical stability by comparing the result of this with that of conventional metal ceramic system. Material and methods: A Metal ceramic (MC) system was tested as a control group. The tested systems were Katana zirconia with CZR (ZB) and Katana Zirconia with NobelRondo Press (ZP). Thirty specimens, 10 for each system and control, were fabricated. Specimen disks, 3 mm high and 12 mm diameter, were fabricated with the lost-wax technique (MC) and the CAD-CAM (ZB and ZP). MC and ZB specimens were prepared using opaque and dentin veneering ceramics, veneered, 3 mm high and 2.8 mm in diameter, over the cores. ZP specimens were prepared using heat pressing ingots, 3 mm high and 2.8mm in diameter. The shear bond strength test was performed in a Shear bond test machine. Load was applied at a cross-head speed of 0.50 mm/min until failure. Mean shear bond strengths (MPa) were analyzed with the One-way ANOVA. After the shear bond test, fracture surfaces were examined by SEM. Results: The mean shear bond strengths (SD) in MPa were MC control 29.14 (2.26); ZB 29.48 (2.30); and ZP 29.51 (2.32). The shear bond strengths of the tested systems were not significantly different (P > .05). All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers. Conclusion: 1. The shear bond strengths of the tested groups were not significantly different from the control group (P >.05). 2. There was no significant different between the layering technique and the heat pressing technique in the veneering methods on the colored zirconia core. 3. All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.

• Journal of Food Hygiene and Safety
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• v.37 no.2
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• pp.97-106
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• 2022

Listeria monocytogenes (L. monocytogenes) is one of gram-positive foodborne pathogens with a very high fatality rate. Unlike most foodborne pathogens, L. monocytogenes is capable of growing at low temperatures, such as in refrigerated foods. Thus, various physical and chemical prevention methods are used in the manufacturing, processing and distribution of food. However, there are limitations to the methods such as possible changes to the food quality and the consumer awareness of synthetic preservatives. Thus, the aim of this study was to evaluate the anti-listeria activity of lactic acid bacteria (LAB) isolated from kimchi and characterize the bacteriocin produced by Lactococcuslactis which is one of isolated strains from kimchi. The analysis on the anti-listeria activity of a total of 36 species (Lactobacillus, Weissella, Lactobacillus, and Lactococcus) isolated from kimchi by the agar overlay method revealed that L. lactis NJ 1-10 and NJ 1-16 had the highest anti-listeria activity. For quantitatively analysis on the anti-listeria activity, NJ 1-10 and NJ 1-16 were co-cultured with L. monocytogenes in Brain Heat Infusion (BHI) broth, respectively. As a result, L. monocytogenes was reduced by 3.0 log CFU/mL in 20 h, lowering the number of bacteria to below the detection limit. Both LAB strains showed anti-listeria activity against 24 serotypes of L. monocytogenes, although the sizes of clear zone was slightly different. No clear zone was observed when the supernatants of both LAB cultures were treated with proteinase-K, indicating that their anti-listerial activities might be due to the production of bacteriocins. Heat stability of the partially purified bacteriocins of NJ 1-10 and NJ 1-16 was relatively stable at 60℃ and 80℃. Yet, their anti-listeria activities were completely lost by 60 min of treatment at 100℃ and 15 min of treatment at 121℃. The analysis on the pH stability showed that their anti-listeria activities were the most stable at pH 4.01, and decreased with the increasing pH value, yet, was not completely lost. Partially purified bacteriocins showed relatively stable anti-listeria activities in acetone, ethanol, and methanol, but their activities were reduced after chloroform treatment, yet was not completely lost. Conclusively, this study revealed that the bacteriocins produced by NJ 1-10 and NJ 1-16 effectively reduced L. monocytogenes, and that they were relatively stable against heat, pH, and organic solvents, therefore implying their potential as a natural antibacterial substance for controlling L. monocytogenes in food.

• Resources Recycling
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• v.32 no.1
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• pp.50-59
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• 2023

The amount of dust generated during the dissolution of scrap in an electric arc furnace is approximately 1.5% of the scrap metal input, and it is primarily collected in a bag filter. Electric arc furnace dust primarily consists of zinc and ion. The processing of zinc starts with its conversion into pellet form by the addition of a carbon-based reducing agent(coke, anthracite) and limestone (C/S control). These pellets then undergo reduction, volatilization, and re-oxidation in rotary kiln or RHF reactor to recover crude zinc oxide (60%w/w). Next, iron is discharged from the electric arc furnace dust as a solid called Fe clinker (secondary by-product of the Fe-base). Several methods are then used to treat the Fe clinker, which vary depending on the country, including landfilling and recycling (e.g., subbase course material, aggregate for concrete, Fe-source for cement manufacturing). However, landfilling has several drawbacks, including environmental pollution due to leaching, high landfill costs, and wastage of iron resources. To improve Fe recovery in the clinker, we pulverized it into optimal -sized particles and employed specific gravity and magnetic force selection methods to isolate this metal. A carbon-based reducing agent and a binding material were added to the separated coarse powder (>10㎛) to prepare briquette clinker. A small amount (1-3%w/w) of the briquette clinker was charged with the scrap in an electric arc furnace to evaluate its feasibility as an additives (carbonaceous material, heat-generating material, and Fe source).