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황영은(Youngeun Hwang),오진오(Ohjin Oh),윤성호(Sungho Yoon) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
본 연구에서는 기존의 접착제를 대체용 접착제로 대체 가능한지의 여부를 조사하기 위하여 구조용 접착제에 대해 일련의 열화 시험을 수행하였다. 구조용 접착제는 온도, 수분, 자외선 등의 자연환경 조건을 모사할 수 있는 가속노화시험기를 통해 복합적인 환경인자에서 1000시간 동안 노출시켰다. 구조용 접착제의 기계적 특성은 하중 시험기를 통해, 화학적 특성은 적외선 분광 분석 장치를 통해 평가하였다. 연구결과에 따르면 대체용 접착제가 환경인자에 노출될 경우 기존의 접착제에 비해 안정적이기 때문에 기존의 접착제는 대체용 접착제로 대체 가능할 것으로 판단하였다. In this study, a series of degradation test for structural adhesives was performed to investigate the possibility of replacement of the alternative adhesives to the conventional adhesives. Four types of the adhesives were exposed to combined environmental conditions over 1000 hours at an accelerated aging tester, which can simulate natural weather conditions such temperature, moisture and ultraviolet. Mechanical and chemical properties of the adhesives were evaluated through material testing system and FT/IR spectrometer. According to the results, the conventional adhesives can be replaced by the alternative adhesives because the alternative adhesives were more stable to environmental conditions rather than the conventional adhesives.
황영은(Youngeun Hwang),윤성호(Sungho Yoon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
In this study, the absorption behaviours of carbon/epoxy composite were experimentally investigated through salt-water absorption tests and its theoretical investigation was also performed to compare the experimental results. In order to perform the absorption test of the composite under salt-water environments, the specimens were subjected to temperatures of 35, 55, and 75℃ for 730 days. According to the results of absorption tests, the curves of moisture content represented linear Fickian behaviour and its moisture diffusion coefficient increased at higher exposure temperature. The curves of moisture content derived from theoretical equation followed the experimental results. Using the activation energy and diffusion constant calculated from Arrhenius equation, the curve of moisture content at room temperature was derived and its exposure time to reach equilibrium was then determined.
황영아(Hwang Young Ah) 한국사회안전학회 2016 한국사회안전학회지 Vol.11 No.1
본 연구의 목적은 학교안전 진단 영역을 구분하고 영역별 지표를 개발하여 학교의 안전 실태를 체계적으로 진단하는 데 있다. 이를 위해 첫째, 문헌분석과 전문가 협의회를 통해 학교안전 실태 분석을 위한 학교안전 영역을 4개(안전교육, 생활안전, 재난안전, 시설안전) 영역으로 구분하고 영역별 진단지표를 개발하였다. 둘째, 학교에서 제출한 자료 및 학교 공시자료, 현장방문을 통한 실태조사가 이루어졌다. 실태조사는 경기도 소재 31개 학교를 대상으로 하였으며, 6개월(2015년 7월~2015년 12월)에 걸쳐 실시하였다. 마지막으로 각종 분석결과를 종합적으로 검토함으로써 학교안전 개선방안을 도출하고자 하였다. The purpose of this study was to categorize the areas and develop reasonable dimensions of the school safety for diagnosing the school safety systematically. First, the category of the school safety was divided into 4 areas(education, school life, disaster, facility) and develop reasonable dimensions for each areas through literature review and conference with the experts. Second, the survey was conducted targeting 31 schools in Gyeonggi-do for 6 months through school visits, using official data from school info site and data submitted by each school. Finally, this study aims to provide effectively improvement methods of the school safety at a conclusion considering the overall analysis result.
탄소섬유/에폭시 복합재의 기계적 특성에 미치는 염수환경의 열습 영향
황영은(Young Eun Hwang),윤성호(Sung Ho Yoon) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.10
본 연구에서는 최대 12개월 동안 염수침수시험을 수행하여 염수환경의 열습조건이 복합재의 특성에 미치는 영향을 조사하였다. 복합재 시편은 직물 형태의 탄소섬유와 에폭시로 구성된 프리프레그를 적층하여 제작하였으며, 노출온도 35℃, 55℃, 75℃가 적용된 염수환경에 완전 침수시키는 조건을 적용하였다. 연구결과에 따르면 복합재의 인장강성과 인장강도는 노출온도와 노출시간이 증가할수록 노출 전에 비해 감소 정도가 크지 않았지만 이에 비해 압축강성과 압축강도는 감소 정도가 크게 나타났다. 특히 압축강도는 노출온도가 증가할수록 염수침투가 가속화되어 감소 정도가 크게 나타났다. In this study, salt-water immersion tests were experimentally performed for up to 12 months to investigate the hygrothermal effect of salt-water environments on the mechanical properties of carbon/epoxy composites. The composites were manufactured by laminating prepregs composed of carbon plain-woven fabric and epoxy resin. The specimens were subjected to temperatures of 35, 55, and 75℃ while being exposed to the salt-water environments. Mechanical test results showed that the tensile modulus and tensile strength decreased at a small rate, and the compressive modulus and compressive strength decreased at a relatively larger rate, as the exposure temperature and time increased. The rate of decrease in compressive strength became larger as the exposure temperature became higher. This is because a higher environmental temperature accelerates the salt-water uptake; this, in turn, reduces the compressive strength more rapidly.
황영아 ( Young Ah Hwang ) 한국안전학회(구 한국산업안전학회) 2017 한국안전학회지 Vol.32 No.1
This study is aimed to design for qualification structure and develop the subjects for examination of the school safety manager qualifications. For the study purpose, job analysis and meetings with experts were performed for extract contents such as task range, criteria of examination, subjects of examination and examination methods, etc. The first step, duties and tasks of the school safety manager were figured out through revised job analysis data of the school safety manager developed before. On the second step, job model was established and developed job specification including importance, difficulty and frequency of each task. On the third step, task specification was developed, and Knowledge-Skill Matrix was the most important thing on examination were completed. The fourth step was the selection of examination subject using task-subject matrix and 6 subjects such as The Principles of Safety, Understanding of the School Safety Manual, Law Related on the School Safety, Introduction to Education, Understanding and Dealing with Type of the School Safety, Establishment of the School Safety Plan were derived from previous procedure. The fifth step was development of guidelines for design examination of each subject. The last step was development for skills education program.
황영은(Yeungeun Hwang),강다영(Dayoung Kang),나명환(Myunghwan Na),윤상후(Sanghoo Yoon) 한국데이터정보과학회 2021 한국데이터정보과학회지 Vol.32 No.5
과채류 품질은 생육 단계별 일사량 노출에 영향받는다. 선행연구는 일사량의 시계열적 특성을 반영한 시계열모형과 일사량에 영향을 미치는 기상변수를 사용한 기계학습 연구가 수행되었다. 이 연구는 지표면 일사량에 영향을 미칠 수 있는 대기오염물질 농도와 기상변수가 모두 고려된 트리 기반의 앙상블로 일사량을 예측하는 모형을 제시한다. 연구자료는 기상자료개방포털과 에어코리아에서 수집하였으며 연구 기간은 2015년 1월 1일부터 2019년 12월 31일이다. 수집된 자료는 전처리를 통해 일 단위로 가공 후 기계학습인 랜덤포레스트 (RF), 일반화가속모형 (GBM), XGboost를 통해 일사량을 예측하였다. 모형검증을 위해 5겹 교차검증이 사용되었고 모형 간 예측성능은 평균절대값오차, 평균 제곱근오차, 그리고 결정계수로 비교하였다. 5겹 교차검증을 통한 모형 간 예측성능은 GBM이 가장 우수하나 과대적합 문제가 발생한다. 따라서 최적화된 모수를 적용한 결과 RF의 예측력이 가장 우수하였다. 변수의 중요도를 살펴보면 일조시간, 가조시간, 강수 순으로 구름의 양과 미세먼지 농도는 일 단위 일사량 예측에 중요한 변수가 아니다. The quality of fruits and vegetables is affected by exposure to insolation at each stage of growth. A machine-learning study using a time series model reflecting the time series characteristics of insolation and meteorological variables affecting insolation was performed. This study presents a model for predicting insolation in a tree-based ensemble that considers both atmospheric pollutant concentrations and meteorological variables that can affect surface insolation. The research data were collected from the Korea Meteorological Administrator and Air Korea, and the research period was between 2015 and 2019. The daily insolation was predicted through machine learning, Random Forest (RF), gradient boosting model (GBM), and XGboost. 5-fold cross-validation was used for model validation, and prediction performance was compared with mean absolute value error, root mean square error, and coefficient of determination. GBM was the best predictive performance among models through 5-fold cross-validation, but with overfitting. Therefore, as a result of applying the optimized parameters, the RF prediction was the best. Both sunshine time and duration were very important variables. However, the amount of clouds and fine dust concentration are not important variables in predicting.