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서혜경 ( Hyekyung Seo ),권영일 ( Young-il Kwon ),이성연 ( Seong Yeoun Lee ),강병갑 ( Byoung-kab Kang ),명준표 ( Jun-pyo Myong ),장호영 ( Hoyeong Jang ),김희주 ( Huiju Kim ),심수아 ( Sua Shim ),박성욱 ( Sungwook Park ) 한국산업보건학회 2021 한국산업보건학회지 Vol.31 No.4
Objectives: This study aims to investigate differences in microbial contamination according to the duration and environment of mask wearing. Methods: Forty-five participants were recruited from workers in an offices, multi-purpose facilities, and a schools. After wearing of KF94 mask for two. four, and six hours, the microorganisms adsorbed on the outer and inner layers of the mask were inoculated on BAP(Blood Agar Plate), Chocolate agar, and SDA plates. The bacterial count (CFUs: colony-forming units) cultured in each plate was measured and analyzed for changes in filtration efficiency. Results: The microbial contamination of masks worn in classrooms, offices, and multi-purpose facilities showed a significant difference depending on the environment (p<0.000). The measured CFUs increased significantly according to the time wearing the mask. The difference between the inner and outer layers of the mask was also significant (p<0.05). However, there was no statistical difference in the filtration efficiency of the masks by duration time (p=0.515). Conclusions: Masks worn by workers in the offices, multi-purpose facilities, and schools showed an increase of microbial contamination with the amount of time wearing the mask. The results indicate that the masks used in daily life may have adverse health effects if they are worn for a long time or reused over several days without the realizing that the masks can be contaminated with biological hazards. Guidelines on the safe threshold time for mask use should be established through further research.
PP 및 PVA 섬유를 혼입한 고성능 RC 기둥의 폭열 방지 특성
허영선 ( Heo Young-sun ),김기훈 ( Kim Ki-hoon ),배연기 ( Bae Yeoun-ki ),지석원 ( Jee Suk-won ),이성연 ( Lee Seong-yeun ),한천구 ( Han Cheon-goo ) 한국구조물진단유지관리공학회 2005 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.9 No.1
This study investigates performance of fire resistance of HPC with the contents of polypropylene(PP) and polyvinyl alcohol(PVA) fiber, respectively. The experimental results shows that increase of fiber contents, regardless of fiber type, exhibited low fluidity and air contents. In the case of compressive strength, on the other hand, all specimen had more than 50MPa of compressive strength. For the properties of spalling appearance, serious spalling failure occurs with plain concrete, which caused exposure of re-bar, while HPC containing fiber had favorable prevention of spalling. Residual compressive strength maintained more than 70 % of original strength, regardless of fiber contents.
PP 및 PVA 섬유를 혼입한 고성능 RC 기둥의 폭열 방지 특성
허영선(Heo Yoong-Sun),김기훈(Kim Ki-Hoon),배연기(Bae yeoun-Ki),지석원(Jee Suk-Won),이성연(Lee Seong-Yeun),한천구(Han Cheon-Goo) 한국구조물진단유지관리학회 2005 한국구조물진단학회 학술발표회논문집 Vol.- No.-
This study investigates performance of fire resistance of HPC with the contents of polypropylene(PP) and polyvinyl alcohol(PVA) fiber, respectively. The experimental results shows that increase of fiber contents, regardless of fire type, exhibited low fluidity and air contents. In the case of compressive strength, on the other hand, all specimen had more than 50MPa of compressive strength. For the properties of spalling appearance, serious spalling failure occurs with plain concrete, which caused exposure of re-bar, while HPC containing fiber had favorable prevention of spalling. Residual compressive strength maintained more than 70% of original strength, regardless of fiber contents,