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고체전해질형 연료전지용 Pr1 - xMxMnO3 ( M=Ca , Sr ) 산소극 재료의 특성
임형렬,정순기,이주성 ( Hyung Ryul Rim,Soon Ki Jeong,Ju Seong Lee ) 한국공업화학회 1996 공업화학 Vol.7 No.6
고체전해질형 연료전지의 산소극 재료로서 페롭스카이트 구조를 갖는 PrMnO₃에 Ca과 Sr을 도핑시켜 도핑량에 따른 전기전도도, 산소환원과전압 등의 전기화학적 특성과, 전해질인 yttria stabilized zirconia와의 반응성 그리고 열팽창률 등을 살펴 보았다. 합성된 페롭스카이트 분말은 대략 2∼5μm 평균입자 크기를 나타내었는데 이때 입자크기 및 비표면적은 도핑량과 무관하였다. Ca이 30mol% 도핑되었을 때 전기전도도는 1000℃에서 266S·cm^(-1)로 가장높은 값을 나타내었고, 분극을 통해 살펴 본 산소환원특성도 Ca이 30mol% 도핑되었을 때 가장 우수한 특성을 나타내었다. 전극물질과 전해질인 YSZ를 1200℃에서 100시간 동안 반응시킨 결과 PrMnO₃에 Sr을 도핑시켰을 때보다 Ca을 도핑시킨 것이 반응성이 훨씬 약한 결과를 나타내었다. Pr_(0.7)Ca_(0.3)MnO₃의 열팽창계수는 300∼1000℃의 영역에서 1.19×10^(-5)K^(-1)로 측정되었고 이 값은 YSZ의 열팽창계수 1.15×10^(-5)K^(-1)과 유사한 값이었다. Ca or Sr-doped PrMnO₃ were prepared for cathode material of solid oxide fuel cell. The characteristics such as the electrical conductivity and the cathodic overpotential were investigated as to doping contents. Also the reactivity with yttria stabilized zirconia of electrolyte, and the thermal expansion coefficient were studied. The prepared perovskite powder had the mean particle size of 2∼5μm, and the particle size and the surface area was out of relation to the doping content. When Ca doping amount of electrode material was 30mol%, the electrical conductivity was the highest value of 266 S·cm^(-1) at 1000℃, and also the polarization characteristics showed the best property. The reactivity between YSZ and Ca-doped PrMnO₃ at 1200℃ for 100hours was lower than that between YSZ and Sr-doped PrMnO₃. The thermal expansion coefficient of Pr_(0.7)Ca_(0.3)MnO₃ was 1.19×10^(-5)K^(-1) in the temperature range of 300∼1000℃, and this value was similar to that of YSZ, 1.15×10^(-5)K^(-1).
임형렬,권호장,임지애,최종혁,하미나,황승식,최원준 대한예방의학회 2016 Journal of Preventive Medicine and Public Health Vol.49 No.4
Objectives: No children-specified review and meta-analysis paper about the short-term effect of fine particulate matter (PM2.5) on hospital admissions and emergency department visits for asthma has been published. We calculated more precise pooled effect estimates on this topic and evaluated the variation in effect size according to the differences in study characteristics not considered in previous studies. Methods: Two authors each independently searched PubMed and EMBASE for relevant studies in March, 2016. We conducted random effect meta-analyses and mixed-effect meta-regression analyses using retrieved summary effect estimates and 95% confidence intervals (CIs) and some characteristics of selected studies. The Egger’s test and funnel plot were used to check publication bias. All analyses were done using R version 3.1.3. Results: We ultimately retrieved 26 time-series and case-crossover design studies about the short-term effect of PM2.5 on children’s hospital admissions and emergency department visits for asthma. In the primary meta-analysis, children’s hospital admissions and emergency department visits for asthma were positively associated with a short-term 10 μg/m3 increase in PM2.5 (relative risk, 1.048; 95% CI, 1.028 to 1.067; I2=95.7%). We also found different effect coefficients by region; the value in Asia was estimated to be lower than in North America or Europe. Conclusions: We strengthened the evidence on the short-term effect of PM2.5 on children’s hospital admissions and emergency department visits for asthma. Further studies from other regions outside North America and Europe regions are needed for more generalizable evidence.
임형렬,배상혁,최종혁,Choi Kyung-Hwa,배현주,김순태,Ha Mina,권호장 한국역학회 2022 Epidemiology and Health Vol.44 No.-
OBJECTIVES: Although there is substantial evidence for the short-term effect of fine particulate matter (PM2.5) on daily mortality, few epidemiological studies have explored the effect of prolonged continuous exposure to high concentrations of PM2.5. This study investigated how the magnitude of the mortality effect of PM2.5 exposure is modified by persistent exposure to high PM2.5 concentrations. METHODS: We analyzed data on the daily mortality count, simulated daily PM2.5 level, mean daily temperature, and relative humidity level from 7 metropolitan cities from 2006 to 2019. Generalized additive models (GAMs) with quasi-Poisson distribution and random-effects meta-analyses were used to pool city-specific effects. To investigate the effect modification of continuous exposure to prolonged high concentrations, we applied categorical consecutive-day variables to the GAMs as effect modification terms for PM2.5. RESULTS: The mortality risk increased by 0.33% (95% confidence interval [CI], 0.16 to 0.50), 0.47% (95% CI, -0.09 to 1.04), and 0.26% (95% CI, -0.08 to 0.60) for all-cause, respiratory, and cardiovascular diseases, respectively, with a 10 μg/m3 increase in PM2.5 concentration. The risk of all-cause mortality per 10 μg/m3 increase in PM2.5 on the first and fourth consecutive days significantly increased by 0.63% (95% CI, 0.20 to 1.06) and 0.36% (95% CI, 0.01 to 0.70), respectively. CONCLUSIONS: We found increased risks of all-cause, respiratory, and cardiovascular mortality related to daily PM2.5 exposure on the day when exposure to high PM2.5 concentrations began and when exposure persisted for more than 4 days with concentrations of ≥ 35 μg/m3 . Persistently high PM2.5 exposure had a stronger effect on seniors.