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        검색결과 24

        21.
        2019.04 KCI 등재 서비스 종료(열람 제한)
        The objective of this study was to estimate the trends of air quality in the study area by analyzing monthly and seasonal concentration trends obtained from sampled data. To this aim, the mass concentrations of PM2.5 in the air were analyzed, as well as those of metals, ions, and total carbon within the PM2.5. The mean concentration of PM2.5 was 22.7 ㎍/㎥. The mass composition of PM2.5 was as follows: 31.1% of ionic species, 2.2% of metallic species, and 26.7% of carbonic species (EC and OC). Ionic species, especially sulfate, ammonium, and nitrate, were the most abundant in the PM2.5 and exhibited a high correlation coefficient with the mass concentration of PM2.5. Seasonal variations of PM2.5 showed a similar pattern to those of ionic and metallic species, with high concentrations during winter and spring. PM2.5 also had a high correlation with the ionic species NO3 - and NH4 +. In addition, NH4 + was highly correlated with NO3 -. Through factor analysis, we identified four controlling factors, and determined the pollution sources using the United States Environmental Protection Agency(U.S. EPA) pollution profile. The first factor, accounting for 19.1% of PM2.5 was attributed to motor vehicles and heating-related sources: the second factor indicated industry-related sources and secondary particles, and the other factors indicated soil, industry-related and marine sources. However, the pollution profile used in this study may be somewhat different from the actual situation in Korea, since it was obtained from US EPA. Therefore, to more accurately estimate the pollutants present in the air, a pollution profile for Korea should be produced.
        22.
        2018.10 서비스 종료(열람 제한)
        This study suggested the estimation method of the ground response spectra at a structure location using earthquake acceleration data from seismological observatories. To suggest estimation method based on measured earthquake acceleration data, a algorithm for determining the observations near the structure site was suggested and a module for calculating a ground response spectrum was developed associated with a listed station determining algorithm.
        23.
        2011.02 서비스 종료(열람 제한)
        보 요소를 사용한 비선형 해석법으로는 소성영역법과 탄소성힌지법, 그리고 개선소성힌지법이 있다. 그 중, 적은 계산량과 단면의 비탄성화의 진전을 고려 할 수 있는 개선소성힌지법은 현재 많은 연구자들에 의해 사용되고 있으며, 특히 축력 작용 시 잔류응력으로 인하여 단면이 점진적으로 소성화 되는 과정이 CRC 접선탄성계수로 표현되어 사용되고 있다. 하지만 기존의 식은 부재에 압축력이 재하 될 때 발생하는 좌굴과 그에 따른 임계하중, 세장비의 관계로 유도된 식이지만 축력을 받는 부재에서도 동일한 식이 사용되고 있다. 따라서 축력을 받는 I형 단면의 재료 비선형해석에 대한 적용성에 한계가 있고 이는 유한요소해석 프로그램을 이용하여 기존식의 한계를 확인할 수 있었다. 본 연구에서는 I형 단면의 축력을 받는 부재의 잔류응력 분포를 포물선으로 고려하였으며, 단면형상에 의한 최대잔류응력크기 변화를 고려하여 합리적인 유효접선탄성계수 식을 유도하였다. 유도된 식은 ABAQUS V6.10을 이용한 비탄성 해석을 통해 검증되었다.
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