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차원석,김부욱,최병순 한국산업보건학회 2017 한국산업보건학회지 Vol.27 No.4
Objectives: In this study, an evaluation of the working environment of furnace workers was performed and the work-relatedness of the occupational diseases were examinedMethods: In this study, two electric furnaces at a single casting business site producing manganese-based iron alloy were selected, and occupational exposures to hazardous substances were evaluated for furnace workers and furnace worker assistants. Results: As a result, total dust concentration were 0.407 ~ 3.001 ㎎/㎥ and respirable dust concentration were 0.196 ~ 0.584 ㎎/㎥. The highest concentration of crystalline silica was 0.079 ㎎/㎥. In the case of Masato and Sosuckwhoi crystalline silica, they contained 90.85% and 4.17% respectively. Manganese concentration was the highest at a 0.205 ㎎/㎥ maximum. The average of black carbon is 11.56 ㎍/㎥ and the maximum concentration is 604.23 ㎍/㎥. PAHs concentration was the highest at a 78.301 ㎍/㎥ of naphthalene. The concentration of carbon monoxide was 18.82 ppm(total average 3.89 ppm) during pouring, and the maximum is 131 ppm. The formaldehyde concentration was 0.003 to 0.007 ppm. Conclusions: It seems that conditions in the past were worse, since casting has recently been performed only twice per day for about 20 minutes, reducing the amount of pouring, and local exhaust systems have been installed one-by-one. In addition, it was judged that the past exposure levels were higher considering the points measured on the back-side due to the risk of damage to the individual samples. It was found that operators could be exposed to high concentrations of crystalline silica, and that they were also exposed to high concentrations of metal(fume) and carbon monoxide during pouring. Therefore, there is a risk that occupational diseases such as lung cancer and COPD may occur with long-term work in such a process.
곡률 변화형 테이피를 이용한 도파관-마이크로스트립 트랜지션
차원석,조영송,신철재 대한전자공학회 1994 전자공학회논문지-A Vol.31 No.2
A curvature variable taper is proposed for a waveguide-microstrip transition. It is applied to a ridge waveguide. The curvature depends on the taper length and difference of waveguide's height and microstrip substrate's height. The taper is manufactured easier than the other tapers. It's reflection coefficient is smaller than the parabolic taper's below one wavelengrh. The results of experiment show that S$_{11}$ is below -20dB and SS$_{21}$ is about -0.5dB in the band of 10~15 GHz. These results are good agreement with the theoritical values.
차원석,김은영,김대호 한국산업보건학회 2023 한국산업보건학회지 Vol.33 No.3
Objectives: An epidemiological investigation was requested for a worker who developed COPD and IPF after long-term molding and firing at a domestic tile manufacturing site. We would like to share the results of the exposure assessment and the estimation of past work. Methods: The content of crystalline silica in four raw materials was analyzed, and the respirable fraction of crystalline silica and dust generated in the air from molding and firing workers and other processes were measured. The measurement and analysis method referred to the NIOSH method. Results: The crystalline silica content of the raw material was 24~47%. The concentration of crystalline silica in the molding and firing process workers and the surrounding area was at the level of the exposure standards set by the Ministry of Employment and Labor and ACGIH, and the respirable and total dust exposure levels were generally low. The crystalline silica concentration of the area samples measured to estimate past work was about twice as high as the exposure standard of the Ministry of Employment and Labor (0.05 mg/m3), and the exposure levels of respirable dust were also quite high at 0.903 and 1.332 mg/m3. Conclusions: It was confirmed that tile molding and firing workers are currently exposed to a fairly high level of crystalline silica, and a high level is also confirmed in area samples to estimate past work. In the past, it is judged that the level of exposure would have been much higher due to differences in production volume, working method, presence/absence of local ventilation facilities, and process layout. When working in such a working environment for a long time, respiratory diseases such as lung cancer, COPD, and IPF can occur.
국내 일부 채석장 작업자들의 분진 및 결정형 유리규산 노출평가 사례
차원석,김은영,최성원,김미연 한국산업보건학회 2023 한국산업보건학회지 Vol.33 No.3
Objectives: Work environment assessments were conducted to investigate epidemiologically several cases of lung cancer and COPD (chronic obstructive pulmonary disease) among workers in domestic quarries. Methods: We visited three quarries in South Korea where an epidemiological investigation was requested and measured total dust, respirable dust, and crystalline silica on rock drilling workers (4 people) and rock chipping workers (13 people). Measurement and analysis were conducted according to NIOSH (National Institute for Occupational Safety & Health) method 0500, NIOSH method 0600 for respirable dust, and NIOSH method 7500 for crystalline silica. Results: Among rock drilling workers the AMs (arithmetic mean) of total dust concentrations, respirable dust concentrations, and crystalline silica concentrations were 3.462 ㎎/㎥ (range: 0.764~6.085 ㎎/㎥), 0.613 ㎎/㎥ (range: 0.153~1.251 ㎎/㎥), and 0.105 mg/㎥ (range: 0.012~0.228 mg/㎥), respectively. Among rock chipping workers, the AMs of total dust concentrations, respirable dust concentrations, and crystalline silica concentrations were 2.446 ㎎/㎥ (range: 0.156~8.494 ㎎/㎥), 0.488 mg/㎥ (range: 0.028~1.536 mg/㎥), and 0.099 mg/㎥ (range: 0.004~0.274 mg/㎥), respectively. Conclusions: Although it cannot be said that the dust concentrations were high for both rock drilling workers and rock chipping workers, the concentrations of crystalline silica were found to be high. If such work is performed for a long period of time, diseases such as lung cancer and COPD may occur, so the work environment needs to be improved.