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백남원(N.W. Paik),박두용(D.Y. Park),장익선(I.S. Chang),신용철(Y.C. Shin),이정인(J. l. Lee) 한국환경보건학회 1988 한국환경보건학회지 Vol.14 No.2
Airborne dust and asbestos fiber concentrations were determined in subway stations located in Seoul area. Two stations, such as Eulchiro 4.Ka Station of Une #2, constructed during a period of 1980-1984 and Hyehwa Station of Une #4, opened in 1985, were selected. The results of the study are as follows. 1. Daily tirne.weighted average (1W A) concentrations of airborne dusts from 07:00 to 20:00 hours in Line #2 and μne #4 were 0.43:t0.08 mg/m3 and 0.37:t0.12 mg/m3 , respectively. Thus, the dust levels in Líne #2 were significant1y higher than the levels in Line #4( p < 0.05). 2. Dust levels in the morning (07:00-11:00 hours), noon (1 1:00-16:00 hours) and in the evening (1 6:00-20:00 hours) in Líne #2 were 0.47:t0.17 mgjm3 , 0.37:t0.08 mg/m3 , and 0.46土0.07 mg/m3 respectively. Thus, dust levels in the morning and evening (i.e., during rush hours) were significantly higher than levels in the noon ( p < 0.02). However, there was no such difference in dust levels by time in Líne #4. 3. Airborne total dust concentrations were well below the occupational health standard of 10 mg/m3 , however, the levels were exceeding the ambient air standard recommended by the Korean Environment Administration. 4. All of airborne asbestos fiber concentrations were equal to or below 0.005 fibers/cc. The levels are within both occupational health standards and U .S. EPA criterìa. 5. A consideration should be given to the improvements of c1eaning methods (such as use of vacuum c1eaning instead of brushing) and the existing ventilation (such as more aìr change and filtration of supply air) for a reduction of dust levels. 6. It is recommended that routine monitoring of aìrborne dusts and asbestos fibers be conducted because more dusts and asbestos fibers can be produced in the aìr due to the deterioration of facilities by age and water damage in future.
이호상(H. S. Lee),배형섭(H. S. Bae),박동현(D. H. Park),이세호(S. H. Lee),박두용(D. Y. Park) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
사출성형 공정에서 냉각 시간은 총 사이클 시간의 약 70%를 차지하기 때문에 금형의 냉각 시간 단축은 생산성을 높이기 위해 대단히 중요하다. 또한 냉각공정에서 성형품 위치에 따라 발생하는 온도편차는 냉각 시간을 지연시킬 뿐만 아니라 휨 변형을 일으키는 주요인이 된다. 본 연구에서는 CO₂ 가스를 사용하여 금형을 급속하게 냉각시킬 수 있는 CO₂ 냉각 모듈을 개발하고, 이를 사출성형 실험에 적용하였다. CO₂ 냉각 모듈은 12 개의 육각블록, 8 개의 곡면블록, 7 개의 공급파이프, 베이스블록 등으로 구성되어 있으며, 각각의 육각블록 안에 직경 0.9 mm의 노즐을 7개씩 설치하여 균일한 면상냉각이 가능하도록 하였다. 각각의 공급파이프에는 2-4 개의 육각블록 또는 곡면블록을 설치하였으며, 유동해석을 적용하여 균일한 토출유량을 구현할 수 있는 각각의 토출부 직경을 도출하였다. 또한 CO₂ 냉각모듈에 대한 구조해석을 적용하여 사출압력에 의한 변형과 응력을 분석하고 구조설계에 반영하였다. CO₂ 가스 토출위치가 금형냉각에 미치는 영향을 고찰하기 위해 핫플레이트를 제작하고, 미세한 모세관을 통해 이산화탄소를 토출하기 위한 주입 시스템을 구축하였다. 온도센서를 활용한 실험을 통해 가열판과 모세관 튜브 사이의 최적 간격을 도출하고, 금형 냉각 효과를 극대화 시킬 수 있도록 하였다. 개발한 CO₂ 냉각 모듈을 크기 300*100 mm, 두께 1.5 mm, R50 mm인 곡면 형상의 성형품 사출성형에 적용하고, 냉각 효과를 분석하였다.
일부 영세 도금사업장의 국소배기성능과 공기중 총크롬 , 6가 크롬 및 니켈농도와의 관계분석
박동욱,박두용,신용철,오세민,정규철 한국산업위생학회 1993 한국산업보건학회지 Vol.3 No.1
To evaluate efficiencies of the local exhaust systems installed in chromium and nickel electroplating tanks, specifications of each tank and general performances of the local exhaust systems were measured in 16 electroplating plants from July 3 to November 24, 1992. Airborne concentrations of total chromium, hexa-chromium and nickel were also measured. Most of the local exhaust systems installed in electroplating plants were inadequately designed. Average capture velocities of local exhaust systems in chromium and nickel tanks were 0.45 m/sec and 0.29 m/sec. Average slot velocities in chromium and nickel tanks were 7.30 m/sec and 2.87 m/sec respectively. Both average capture and slot velocities were in noncompliance with the standards recommended by American Conference of Governmental Industrial Hygienists (ACGIH) and National Institute for Occupational Safety and Health (NIOSH). Exhausted air volume was insufficient in all local exhaust systems surveyed. Worker exposure levels to total chromium, hexa-chromium and nickel were 43.0 ㎍/㎥, 1.7 ㎍/㎥ and 9.3 ㎍/㎥, which were below the Korean Standard and U.S. Occupational Health and Safety Administration (OHSA) Permissible Exposure Limit (PEL). However, Worker exposure level to hexa-chromium exceeded the NIOSH Recommended Exposure Limit(REL) of 1 ㎍/㎥. As the result of Scheffee's multiple comparions, worker exposure levels to all metals were significantly different between two groups by the management state of existing local exhaust systems (p$lt;0.05). However, Difference between a group with local exhaust systems which were poorly managed and another group without local exhaust system was satatistically non-significant.