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축산농장 배출 가스상 대기오염물질과 기상인자간 상관관계 분석
이성학,김혜승,주흥수 한국냄새환경학회 2020 실내환경 및 냄새 학회지 Vol.19 No.4
The correlation among gaseous air pollutants (odorous compounds, greenhouse gases) and meteorological parameters was analyzed in-depth using measurement data at a barn and ambient in a naturally ventilated dairy farm. Both concentration and emission data (loading rate and emission rate), which more accurately express the actual pollutant emissions, were used in the correlation analysis. Gaseous air pollutants (ammonia, hydrogen sulfide, carbon dioxide, nitrous oxide, methane) and meteorological factors (relative humidity, temperature, wind speed, solar strength) were measured for one week in July 2013. The upper and lower outliers of measured data by inducing 1.5 times the interquartile range (IQR) were eliminated. After eliminating the outliers and grouping according to data magnitude, the correlation analysis among gaseous compounds and meteorological factors was conducted using the average values of each group. In the correlation analysis, data for the emission rate (barn) and the loading rate (ambient) showed a better correlation than concentration data. Gaseous air pollutants except for hydrogen sulfide in the barn showed a good correlation. Hydrogen sulfide might not be produced from manure or animal origin. Rather, the compound may be produced by flushing water, which was flushed at periodical times (every six hours). Ammonia emissions increased with increasing temperature, and this increase can be affected from greater exertion of feces by frequent water drinking in a high-temperature condition. In the ambient, the correlation for all gaseous air pollutants was better than that in the barn, because those air pollutants from manure, animals, and flushing water origins were sufficiently mixed in the atmosphere. Wind speed also showed a good correlation with all gaseous air pollutants.
급냉응고 처리된 초내열 합금 A-286 의 기계적 성질 및 강화기구
이성학,신기삼,Kelly, Thomas F,Flinn, John E 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.3
Mechanical test data of superalloy A-286 show that there is a significant increase in tensile strength after rapid solidification processing (RSP). The mechanism of mechanical property improvement upon RSP was studied by TEM quantitative defect analysis and the data analysis using strengthening models. The most prominent microstructural alterations by RSP are found in the precipitates and in the grain growth behavior. On average, the precipitates in RSP samples are smaller, have higher volume fractions, and are much more stable than their conventionally processed counterparts. The increased tensile strength of the RSP samples is found to be the result of the increased volume fraction and number density of second phase particles. However, the strengthening came mostly through grain growth inhibition by the second phase particles, which in turn increased the strength via Hall-Petch relationship. This study shows the importance of recrystallization and thus the method of consolidation for effective strengthening.
이성학,김낙준,이희춘,이창길,손기선 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.3
The main objective of the present study is to clarify the microstructural factors such as tempered martensite matrix, coarse primary carbides, eutectic structures, and fine secondary carbides, which influence fracture properties of high speed steel (HSS) rolls. Three HSS rolls with different Cr content were manufactured by a centrifugal casting method, and the microstructures of their shell regions were investigated quantitatively. MC type primary carbides, together with eutectic ledeburite structures, were observed in the intercellular regions. The observation of fracture processes indicated that these primary carbides cleaved first to form microcracks at very low stress levels. These microcracks were easily propagated along the intercellular networks, leading to predominantly cleavage mode of fracture on fracture surfaces. To improve microstructures for use in the HSS rolls, therefore, it is suggested that the cell size must be minimized to achieve the homogeneous distribution of primary carbides