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성장현,류영,정은성 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.4
This study explored return periods of the streamflow deficit characteristics by threshold levels with different time resolutions (daily, weekly, and monthly) using univariate and Copula functions, reflecting hydrological regimes like rapid recoveries from drought and anthropogenic dam operation by monthly basis in South Korea. As a result, the daily-based threshold had a large variability in severities and durations. This is because threshold levels include a large variability of daily streamflow with a small time interval. Joint return periods of duration under extreme droughts were similar to those from univariate frequency analysis. The severities in these extreme droughts were also around the average level, but the duration was relatively long, leading to an increase in the joint return period. This result helps to effectively manage water resource preparing for the assessment on the drought risk with a long duration.
5083 Al 합금 용접재의 조직 및 저온 인장성질에 미치는 시효처리의 영향
성장현,이해우,주동원,이준희,이태청 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.1
The microstructural characteristics and low temperature tensile properties between 25℃ and -196℃ for as-welded and age hardened specimen by using Al 5083-H321 for base metal, 5083-5356 and 5083-4043 weldments have been investigated. The hardness of 5083-5356 weldment decreases with aging treatment, whereas the weld region of 5083-4043 weldment shows remarkable increase in hardness after aging due to the precipitation of fine Si particle at the grain boundaries and interiors. Low temperature tensile properties of 5083 Al base metal, 5083-5356 and 5083-4043 weldments appear to be the increment of tensile strengths and elongations at the room temperature and -196℃, while the decrement of tensile properties around -50℃ is shown. Through the observation of fine serration to fracture in the stress-strain curve and tensile fractography, the increment of localized deformation leading to promote the neck initiation and the increment of the dimple size cause to decrease in tensile strengths and elongations around -50℃. For the tensile specimen of the 5083 base metal, 5083-5356 and 5083-4043 weldments, the reason to increase in elongation after solution and aging treatment is the diminishment of fine pit, the resolution of Mg into the matrix and the spheridization of the eutectic Si.
304L 스테인레스강의 변태유기 소성에 미치는 변형온도의 영향
성장현,강창룡 동아대학교 공과대학 부설 한국자원개발연구소 1992 硏究報告 Vol.16 No.1
The effect of deformation temperature on transformation induce plasticity in 304L stainless steel with metastable austenitic phase investigaged. The result obtained from this study are summarized as follows. Tensile properties of the metastable austenitic 304L stainless steel remarkably influenced by deformation temperature and mainly controlled by transformation induced martensite. Tensile strength increased with decreasing deformation temperature and the elongation showed maximum value near 40℃ With lowering the deformation temperature, the volume fration of transformation induced martensite increased at the same strain. ε-martensite was formed at the begining stage of deformation in the low temperature region of low stability of austenite. The volume fration of ε-martensite increased with increasing strain and decreased after showing the maximum value. The maxium quantity of ε-martensite was obtained at low strain with decreasing deformation temperature.
Al 함유 13%Cr 스테인리스강의 표면 질소침투 열처리에 미치는 첨가원소 탄소의 영향 : 13%Cr 스테인리스강의 고질소 표면침투 열처리
성장현,주동원,김기돈,유대경,박진욱 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.3
This study aims to investigate the effect of carbon content on the surface nitrogen permeation of 13%Cr-1.8%Al alloyed stainless steels. The surface nitrogen permeation was performed at 1050℃-1200℃ in the 1㎏/㎠ nitrogen gas atmosphere. The nitrogen permeated surface layer of the specimen containing 0.03%C consists of AlN, martensite and retained austenite phases, while the surface layer of the specimen containing 0.14%C appears the AlFe₃C_x phase including former three phases. The specimen containing 0.14%C shows lower total case depth than that containing 0.03%C at the nitrogen permeation temperatures of 1050℃ and 1100℃, while the total case depth of the specimen containing 0.14%C is remarkably increased at the temperature of 1150℃ and 1200℃ due to the increase in the retained austenite content. Martensitic phase, AlN and AlFe₃C_x precipitate of the nitrogen permeated surface layer cause to increase the surface hardness of 550∼600Hv.
성장현,류영,성기원 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.4
This study evaluates the effects of climatic conditions and drought phase on occurrence frequency (OF) of forest fire in South Korea, and suggested a deep learning-based estimator for the occurrence frequency of fire. There was a high correlation between frequency and relative humidity (RH, R = -0.663) and wind speed (WS, R = 0.532). Using these correlations, we proposed a deep learning model that can estimate the OF. Among the three deep learning models (RH-WS-AMOF, RH-AMOF, and WS-AMOF) by combining RH and WS with average monthly OF (AMOF) during 1997 − 2019, the RH-WS-AMOF model showed the best performance. R2 and NSE were 0.838 and 0.828, respectively. The higher temperatures and drought lead to increase the potential for forest fire. Standardized precipitation evapotranspiration index was introduced for exploring the link between meteorological drought and forest fire. We confirmed that SPEI can improve the performance of the DBN based on OF estimator in spring. The framework of this study can provide a predictive model for forest fire OF combined with a weather forecast model.
2013년 강우 및 홍수사상 분석: 영산강·섬진강 유역
성장현,이준호,원유승,김양수 한국방재학회 2014 한국방재학회 학술발표대회논문집 Vol.2014 No.-
본 연구에서는 2013년 영산강과 섬진강 유역에 발생한 강우 및 홍수사상을 평년 및 예년과 비교하여 분석하였다. 분석결과, 6월, 8월∼9월은 평년대비 50% 수준에 그쳤으나, 7월은 장마전선의 영향으로 4일부터 7일까지 유역평균 250mm 강우를 기록하였다. 8월은 작년과 달리 태풍의 직접적인 영향이 없었으나, 23일과 24일에는 유역평균 140mm의 호우가 집중되었다. 강우에 따른 수위 변화를 알아보면 연중 최고수위가 7월 5일에 발생하였고, 이 때에 선암(황룡강), 나주(영산강), 구례2와 송정지점(섬진강)에 홍수주의보가 발령되기도 하였다. 농업용 저수지(광주, 담양, 장성과 나주) 및 다목적 댐(섬진강, 주암, 탐진)의 11월말 수위를 보면 전반적으로 전년에 비하여 낮은 편이었고, 그 중 광주댐은 전년대비 4.60m, 섬진강댐은 9.15m으로 낮은 편이었다.