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2018~2021년 안면도에서 관측된 황사 (Asian dust)와 연무 (Haze)에 따른 에어로졸 물리, 광학 및 화학 특성 비교
정민재(Min Jae Jeong),유희정(Hee-Jung Yoo),고희정(Hee-jung Ko),오상민(Sang Min Oh),황승언(Seung-On Hwang) 한국대기환경학회 2024 한국대기환경학회지 Vol.40 No.2
We analyzed the characteristics of aerosol particles contained in Haze and Asian dust using physical, optical, and chemical properties observed in Anmyeon-do over four years (2018~2021). Asian dust and haze are classified by the mass concentration of PM<SUB>10</SUB> and PM<SUB>2.5</SUB>. A total of 28 Asian dust cases were observed with a PM<SUB>10</SUB> mass concentration of 105.8±120.0 μg/m³, which was about three times higher than the average during study periods. There were 138 haze days with a PM<SUB>2.5</SUB> mass concentration of 51.6±16.4 μg/m³. The scattering coefficient as an optical property of aerosols was 180.5±114.0 Mm<SUP>-1</SUP> for haze cases, which was about 1.7 times higher than Asian dust cases. The absorption coefficient was found to be 12.7±7.9 Mm<SUP>-1</SUP> and 9.3±6.7 Mm<SUP>-1</SUP> for haze and Asian dust cases, respectively. The scattering Ångström exponent was 1.46±0.32 (0.88±0.59) for haze (Asian dust), indicating the dominance of coarse particles in Asian dust. Meanwhile, Asian dust cases had a high proportion of soil-derived chemical components such as Al (23%), Fe (18%), and Ca (14%), while haze had the highest proportion of the anthropogenic component S (37%). Also, for the ionic composition analysis, haze cases had a high percentage of secondary aerosols such as NO₃- (42%), SO₄<SUP>2-</SUP> (32%), and NH₄+ (23%). The backward trajectory analysis using the HYSPLIT model revealed that the Asian dust was transported to Korea through the Gobi Desert, Inner Mongolia, and Manchuria in northwestern China, known as major sources of Asian dust. For haze, a relatively short trajectory originating from Balhae Bay was found, suggesting that the emitted air pollutants were not likely to spread rapidly but move slowly or stagnate, creating secondary aerosols and causing haze.
인장 및 압축 등방 잔류응력 측정을 위한 누프 압입시험의 응력환산계수 결정
정민재 ( Min Jae Jeong ),김영천 ( Young-cheon Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.
엘리베이터 탑승객을 위한 개인 맞춤 정보 서비스 개발연구
정민재 ( Min-jae Jeong ),이성환 ( Seong-hwan Lee ),최우성 ( Woo-seong Choi ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.2
RTB (Real-Time Bidding; 실시간 경매 방식)시장이 기하급수적으로 빠른 성장을 보이고 있는 상태에서, 내년 미국 RTB 시장은 200억 달러를 뛰어넘을 것으로 예상되는 가운데, 이러한 상황은 빌딩 내에서 엘리베이터를 기다리는 사람들에게 광고를 노출할 수 있는 새로운 서비스가 될 것이라 생각한다. 대부분의 사람들은 30초에서 길게는 1분이상의 엘리베이터를 기다리면서 스마트폰을 만지며 시간을 보내고 있다. 본 연구팀은 RTB시장에 엘리베이터 탑승객을 연계할 수 있는 스마트 폰 기반 광고 서비스 및 회사 전반적인 업무에 도움 되는 서비스를 제안하고자 한다.[1] 본 연구팀이 진행한 연구는 엘리베이터 사용자의 위치를 바탕으로 개인의 정보를 활용해 그에 맞거나 상응하는 정보를 찾아내 제공하는 서비스에 관한 것이다. 이는 향후 RTB와 연계하여 개인에게 맞춤 광고할 수 기능등의 새로운 수익 창출이 가능할 것으로 예상한다.