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초고층 건축물 화재진압 수행 시 중추신경전달물질 및 혈액변인의 변화
유동훈(Yoo Donghoon) 한국방재학회 2018 한국방재학회논문집 Vol.18 No.6
The purpose of this study was to investigate changes in body temperature, rating of perceived exertion, and levels of glucose, lactate, and central neurotransmitters (serotonin and dopamine) during fire-fighting in a high-rise building. The results of our study are as follows: 1) significant treatment-by-time interaction effects were observed for tympanic temperature, rating of perceived exertion, and levels of glucose, lactate, and serotonin; 2) there was a significant main effect of time on dopamine level; however, there was no significant main effect of treatment or treatment-by-time interaction effect on dopamine level. Therefore, the fitness levels and work intensity levels of fire-fighters may be related to central neurotransmitter levels; this relationship can be suggested as a guideline for their job safety. Therefore, future research should be carried out on fitness levels of fire-fighters during various levels of work intensity to further investigate this relationship. 본 연구는 소방공무원을 대상으로 초고층 건축물 화재진압 수행에 따른 체온, 운동자각도, 혈당, 젖산, 및 중추신경전달물질(serotonin, dopamine)의 변화를 알아보고자 시도하였다. 연구결과, 고막온도, 운동자각도, 혈당, 젖산과 serotonin에서 시기와 처치에 따른 상호작용효과는 유의한 차이가 나타났다. dopamine은 시기에 따른 차이는 나타났으나, 처치, 시기와 처치에 따른 상호작용효과는 나타나지 않았다. 본 연구는 초고층 건축물 화재진압 시 중추신경전달물질의 변화에 대한 객관적인 자료를 제시하고자 하였으며, 중추신경전달물질은 소방공무원의 체력 수준과 작업강도와 관련이 있는 것으로 나타났다. 추후 소방공무원들의 체력 수준을 단계별로 구분하고, 초고층 건축물 화재진압 수행 시 다양한 시뮬레이션을 적용하여 중추신경 전달물질에 대한 심층적인 연구가 이루어져야 할 것이다.
7075 알루미늄 합금 판재의 변형률 속도에 따른 고온 인장 파손 거동
유동훈(Donghoon Yoo),홍종화(Jonghwa Hong),권용남(Yong Nam Kwon),김지훈(Ji Hoon Kim),김대용(Daeyong Kim) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.2
7xxx계 알루미늄 합금 판재의 변형률 속도에 따른 고온 인장 파손 거동을 평가하였다. 1.27 mm 두께의 7075 알루미늄 합금 판재를 사용하여, 400°C, 470°C의 온도 조건에서 변형률 속도를 0.0001 s<SUP>-1</SUP>, 0.001 s<SUP>-1</SUP>, 0.01 s<SUP>-1</SUP>, 0.1 s<SUP>-1</SUP>로 달리하며 고온 인장 시험을 수행하였다. 응력-변형률 선도에서 변형 거동을 5개의 구간으로 정의하고 전 연신률과 파손 구간에서의 손상 기울기를 획득하였으며, 3차원 스캐너를 통하여 파단 주위의 형상을 측정하여 국부 파단 변형률을 계산하였다. 400°C와 470°C에서 동일하게 변형률 속도가 증가할수록 전 연신률과 국부 파단 변형률은 증가하였다. 동일 변형률 속도에 대해서, 전연신률은 470°C에서 400°C보다 근소하게 컸으나, 국부 파단 연신률은 400°C에서 470°C보다 상당히 큼을 확인하였다. The Strain-rate dependent tensile failure behavior of 7xxx series aluminum alloy sheet was investigated at elevated temperatures. In this study, a 7075 aluminum alloy sheet of thickness 1.27 mm was used. Hot tensile tests were performed for four strain-rates of 0.0001 s<SUP>-1</SUP>, 0.001 s<SUP>-1</SUP>, 0.01 s<SUP>-1</SUP> and 0.1 s<SUP>-1</SUP> at two temperatures of 400°C and 470°C. The deformation behaviors on the corresponding stress-strain curve was divided into five stages and total elongation and damage slope were measured. Local failure strains were obtained by measurements of the shape of the fractured specimen using a 3D scanner. As the strain rates increased, the total elongation and local failure strains increased for both 400°C and 470°C. Total elongation at 470°C is slightly larger than that at 400°C, while local fracture strains at 400°C are significantly larger than those at 470°C.
열간프레스성형에서의 변형 측정장치 개발 및 기계적 거동의 물성화
유동훈(Donghoon Yoo),석동윤(Dong-Yoon Seok),김돈건(Dongun Kim),안강환(Kanghwan Ahn),손현성(Hyun-Sung Son),김교성(Gyo-Sung Kim),정관수(Kwansoo Chung) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
As a way to improve the safety of automotive and to reduce the weight of vehicles, new forming technologies and advanced materials are in high demand in the automotive industry. However, the advanced strength steel has inferior formability and large springback. In order to overcome such drawbacks, the hot press forming process (HPF) has been being applied for forming of automotive sheet parts. In this work, new equipment was suggested to measure unlimited displacement range compared to previous one which was able to measure only up to 10mm displacement range. The external extensometer connected with grips by wire was applied to equipment so that total strain range was measured up to failure also in high temperature. And the finite element analysis was conducted to characterize the mechanical properties of the HPF steel. Finally, the flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.
7천계 알루미늄 판재의 고온에서 변형율 속도에 따른 파단 변형율
유동훈(Donghoon Yoo),김대용(Daeyong Kim) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.7
Strain-rate dependent fracture strains of 7xxx aluminum alloy sheet were investigated at elevated temperature. In this study, a 7075 aluminum alloy sheet having a thickness of 1.27mm was utilized. Tensile tests were performed with three strain-rates, 0.001/s, 0.01/s and 0.1/s at two temperature conditions, 400°C and 470°C. Total elongation and local fracture strain were measured to evaluate the fracture strain. As the strain-rates increase, fracture strains increase at both 400°C and 470°C. Total elongations at 400°C and 470°C are similar to each other and the local fracture strains at 400°C are higher than those at 470°C.