통상적으로 직업소음에 의한 청력손실을 최소화하기 위해서는 작업자가 8시간 동안 85 dBA 이상 소음에 노출되지 않도록 권고하고 있다. 이번 연구에서는 실습선박에서 7종류의 담당업무별 작업자들의 소음노출레벨을 측정하였다. 항해 중, 24시간 동안 작업자의 위치하는 A특성등가소음레벨(LAeq,i)과 소음장소의 지속기간(h) 및 소음기여도(Lex,24h,i)를 고려한 소음노출레벨(Lex,24h)을 측정하였다. 그 결과, 갑판사관 그룹 Lex,24h=56.1 dB, 갑판부원 그룹은 Lex,24h=58.9 dB, 실습항해사들은 Lex,24h=62.0 dB, 취사부원들은 Lex,24h=64.3 dB, 실습기관사그룹 은 Lex,24h=91.1 dB, 기관사관 그룹은 Lex,24h=91.1 dB, 그리고 기관부원 그룹은 Lex,24h=95.1 dB를 나타내고 있다. 따라서 기관 업무를 담당하는 기관사들, 기관부원들 그리고 기관실습생들은 반드시 청력보호구를 착용해야함을 알 수 있었다. 소음이 심한 기관실에서 청력보호구를 착용한다면 기관사관그룹은 Lex,24h=23.1 dB, 기관부원그룹은 Lex,24h=24.4 dB 그리고 기관실습생들은 Lex,24h=21.5 dB의 소음노출레벨을 줄일 수 있을 것으로 추정된다. 또한 실습생들의 거주구역인 제2 강의실 겸 식당구역에 바닥시공을 64 mm, A-60-class 뜬바닥 구조로 개선했다면 실습항해사들의 소음노출도는 Lex,24h=4.3 dB, 실습기관사들은 Lex,24h=1.8 dB 정도 추가적인 감소가 있었을 것이다.

In the dismantling process of a reactor coolant system (RCS) piping, a radiation protection plan should be established to minimize the radiation exposure doses of dismantling workers. Hence, it is necessary to estimate the individual effective dose in the RCS piping dismantling process when decommissioning a nuclear power plant. In this study, the radiation exposure doses of the dismantling workers at different positions was estimated using the MicroShield dose assessment program based on the NUREG/CR-1595 report. The individual effective dose, which is the sum of the effective dose to each tissue considering the working time, was used to estimate the radiation exposure dose. The estimations of the simulation results for all RCS piping dismantling tasks satisfied the dose limits prescribed by the ICRP-60 report. In dismantling the RCS piping of the Kori-1 or Wolsong-1 units in South Korea, the estimation and reduction method for the radiation exposure dose, and the simulated results of this study can be used to implement the radiation safety for optimal dismantling by providing information on the radiation exposure doses of the dismantling workers.

PURPOSES : The exposed aggregate number (EAN) and mean texture depth (MTD) of exposed aggregate concrete pavement (EACP) influence the functional performance of EACP in terms of pavement noise and skid resistance. The selection of the exposure time of EACP is important because the designed EAN and MTD of EACP can be achieved when the exposure process is performed at an appropriate time. On the one hand, too early exposure may cause protrusions and unwanted removal of aggregates and mortar. On the other hand, late exposure may cause difficulty in exposure of the mortar. In this study, a method to determine the optimum exposure time for EACP is suggested using a non-destructive method. METHODS : A set of laboratory tests was performed to investigate the variation in EAN and MTD of EACP according to the elastic modulus obtained by non-destructive equipment. From the results of this investigation, the optimum exposure time using the non-destructive method and the exposure time window (ETW) method was suggested. In addition, the usefulness of ETW suggested by laboratory tests was verified from a field application. RESULTS : From the laboratory tests, it was found that the targets of the surface condition of EACP (EAN: 59 per 25 cm2, MTD: 1.39 mm) can be achieved when the concrete elastic modulus is higher than 20GPa. The proposed guideline using the non-destructive method was applied for the field construction of EACP and achieved similar results. CONCLUSIONS : It was found that the proposed guideline for determining the exposure time window based on non-destructive testing is useful.

We report the structural characterization and electric heating performance of carbon thin films (CTFs), which were prepared from negative-type SU-8 photoresist by deep UV exposure and following carbonization. The prepared CTFs were found to have pseudo-graphitic carbon structures containing partially graphite domains in the amorphous carbon matrix. The CTFs showed a very smooth surface morphology with a roughness of 0.42 nm. The 107 nm-thick CTFs exhibited an excellent electric heating performance by attaining a high maximal temperature of 207 °C and a rapid heating rate of 13.2 °C/s at an applied voltage of 30 V. Therefore, the CTFs prepared in this study can be applied as electrode materials for high-performance electric heaters.

국내외적으로 유해물질의 통합 노출에 대한 관심은 높아지고 있다. 이러한 흐름에 따라 다양한 경로를 통해 노출될 수 있는 중금속에 대한 통합 노출 연구가 필요하다. 카드뮴과 납은 각각 신장 독성과 인지 장애 등 다양한 독성을 나타낼 수 있으며 또한 발암 물질로 알려져있다. 따라서 본 연구에서는 카드뮴과 납의 노출량 추정 및 통합 위해성 평가를 진행하였다. 2016, 2017년의 7기 국민건강 영양조사에 참여한 10,733명의 식품, 물, 흡연과 간접흡연, 호흡, 화장품, 여성용 위생용품을 통한 중금속 노출 추정량을 계산하였다. 결과적으로 카드뮴과 납 모두 식품을 통한 노출이 제일 높게 나타났다. 이외에도 흡연은 카드뮴의 주요한 노출원이었으며, 납은 화장품을 통해 높은 농도로 노출되었다. 통합 위해평가에서도 식품이 가장 큰 영향을 미쳤다. 지역적 특성의 차이는 노출 추정량의 차이를 보이지 못하였으나, 연령 별, 성별 간 노출 추정량은 큰 차이를 보였다. 특히, 월경 중인 성인 여성의 경우 카드뮴, 월경 중이지 않은 여성은 납의 노출 추정량이 더 높으며 신체 대사를 고려하였을 때, 그 위험성이 더 클 수 있음을 암시하였다. 결론적으로 노출량 추정 및 통합 위해평가 모두 식품이 주요 노출원이었다. 다만, 잠재적 위험을 방지하기 위해 다른 경로에 대한 노출량 추정 및 위해평가가 요구된다.

We investigated the cytotoxic potential of three different commercially available absorbent feminine hygiene products and one transdermal patch using direct contact and extract exposure methods. Two different cell lines were used – mouse fibroblast L929 and normal human skin fibroblast CCD-986sk cell lines. The test samples were extracted using three different methods in accordance to International Organization for Standardization (ISO). Viability of cells was analyzed using MTT assay and morphology of the cells were also observed using phase contrast microscopy. Overall, the direct contact method using L929 cells showed that all the test samples had no toxic effect when exposed to extracts for 1 h. For the exposure method, no toxic effect was observed in both L929 and CCD986sk cells incubated with all the test samples regardless of the extraction methods used.

The concentration of TVOCs in public transportation in the spring and summer of 2018 was measured. Public transportation measured the concentration of TVOCs on six subway lines in Seoul, two lines of high-speed trains, and intercity buses. The measurements were taken during the operation of each route of the surveyed public transportation from the origin to the destination. In addition, the measurement time was divided into the congestion time and the non-congestion time. In the spring of 2018, in the order of subway, train A, train B, and intercity buses, TVOC concentrations during the congestion time zone were 205.9 μg/m3, 121.3 μg/m3, 171.1 μg/m3, and 88.7 μg/m3, respectively. During the non-congestion time zone, the concentrations were 177.2 μg/m3, 108.8 μg/ m3, 118.2 μg/m3, and 126.1 μg/m3, respectively. In the summer of 2018, TVOC concentrations in the order of the aforementioned transportation modes during the congestion time zone were 169.8 μg/m3, 175.8 μg/m3, 78.0 μg/ m3, and 185.3 μg/m3, respectively. During the non-congestion time zone, the concentrations were 210.8 μg/m3, 116.1 μg/m3, and 162.7 μg/m3, respectively. An analysis of BTEX concentration among VOCs in public transportation in descending order were followed by toluene > xylene > ethylbenzene > benzene. Toluene, which has the highest concentration among the BTEX compounds, was found to be 12.86 μg/m3 to 91.41 μg/m3 during spring congestion time and 7.10 μg/m3 to 39.52 μg/m3 during non-congestion time. During the summer congestion time, the concentration was 6.68 μg/m3 to 249.48 μg/m3 and 13.23 μg/m3 to 214.5 μg/m3 during the non-congestion time. The concentration of benzene was mostly less than 5 μg/m3 in transportation. Particularly in the case of toluene, the concentration is significantly higher than that of other VOCs. Accordingly, further study of toluene exposure hazards will be needed. Five percent of the surveyed TVOC concentrations exceeded the recommended indoor air quality standard of 500 μg/m3, and all 13 cases representing this percentage were found in the subway. In addition, nine of the 13 cases that exceeded the recommended standard were measured during congestion time. Therefore, VOCs in public transportation vehicles during congestion time need to be managed.