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표준강수 증발산지수(SPEI)를 이용한 남한지역의 가뭄심도 평가
김병식,성장현,강현석,조천호,Kim, Byung-Sik,Sung, Jang-Hyun,Kang, Hyun-Suk,Cho, Chun-Ho 한국수자원학회 2012 한국수자원학회논문집 Vol.45 No.9
가뭄은 자연의 무시할 수 없는 재해이며, 비록 가뭄의 정의가 많이 있지만 가뭄은 장기간의 강우의 부족으로부터 기인한다. 기상학적 가뭄심도의 정도를 표현하기 위해 널리 이용되는 표준강수지수(Standardized Precipitation Index, SPI)는 강수 이외의 기온과 관련된 변수를 고려하지 않기 때문에 기후변동으로 인한 강수, 증발산 등의 물수지 변화를 고려할 수 없다는 한계점이 있다. 그러나 최근에 SPI와 유사하지만 기후변동으로 인한 강수 변화 뿐만 아니라 기온의 변동성이 미치는 영향을 반영할 수 있는 새로운 개념의 가뭄지수인 표준강수증발산지수(Standardized Precipitation Evapotranspiration Index, SPEI)가 개발되었다. 본 연구에서는 기상청 산하의 60개 기상관측소의 1973~2011년까지 기상자료를 대상으로 SPEI를 적용하여 남한지역의 가뭄발생의 변화를 평가하였다. 적용결과, 전국적으로 SPI와 SPEI 모두 봄과 겨울에 가뭄이 심화되고 여름철에는 가뭄이 완화되는 경향을 보였으며, SPEI는 SPI보다 가뭄심도를 크게 나타내었다. 또한, 지속기간 12개월의 SPI와 SPEI는 전반적으로 6년 내외의 저빈도 주기성을 갖는 극심한 가뭄이 반복되고 있음을 보였다. Drought is a non-negligible disaster of nature and it is mainly caused by rainfall shortage for a long time though there are many definitions of drought. 'Standard Precipitation Index' (SPI) that is widely used to express the level of meteorological drought intensity has a limit of not being able to consider the hydrological changes such as rainfall and evapotranspiration caused by climate change, because it does not consider the temperature-related variables other than the precipitation. Recently, however, 'Standardized Precipitation Evapotranspiration Index' (SPEI), a drought index of new concept which is similar to SPI but can reflect the effect of temperature variability as well as the rainfall change caused by climate variation, was developed. In this study, the changes of drought occurrence in South Korea were analyzed by applying SPEI for meteorological data (1973~2011) of 60 climate observatories under Korea Meteorological Administration (KMA). As the result of application, both of SPI and SPEI showed the trend of deepening drought in spring and winter and mitigating drought in summer for the entire nation, with SPI showing greater drought intensity than SPI. Also, SPI and SPEI with 12 months of duration showed that severe droughts with low frequency of around 6 years are generally being repeated.
Fe-Cr-Ni-Mn 2상 스테인레스강의 인장성질에 미치는 변형온도 및 Mn 함량변화의 영향
강창룡,성장현 ( C . Y . Kang,J . H . Sung ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.4
The effect of deformation temperature and manganes contents on the tensile properties of duplex stainless steels with the structure of both ferrite and austenite were investigate. Far this investigation, Fe-19% Cr-5% Ni-4∼8% Mn alloys were prepared. The result obtained from this experiment are summerized as follows. With decreasing deformation temperature, tensile strengths of duplex stainless steel increased. Elongation showd to be increased and then decreased after representing the highest value at specific temperature. Tensile properties of duplex stainless steel were controlled by TRIP behavior in this experimental range of austenite contents. Tensile strengths decreased with increasing Mn contents. With increasing Mn contents, elongation decreased in the high temperature region, but increased in the low temperature region. The peak temperature representing the maximum elongation were changed to low temperature and the width of peak appeared to be broaden with increasing Mn contents.
304L stainless Steel의 인장성질에 대한 변형온도 , 변형속도 및 결정입도의 영향
강창룡,성장현 ( C . Y . Kang,J . H . Sung ) 한국열처리공학회 1990 熱處理工學會誌 Vol.3 No.2
This investigation has been carried out to make clear the effect of deformation temperature, strain rate and grain size on the tensile properties of 304L stainless steel. Tensile properties of the metastable austenitic 304L steel remarkably influenced by deformation temperature. Tensile strength increased with decreasing deformation temperature and the elongation showed maximum value near 40℃. In order to obtain the high elongation, a large amount of deformation is available in austenite before martensitic transformation and the martensite has to be induced gradually. Tensile strength and elongation increased with decreasing grain size. The temperature representing the maximum elongation shifted to low temperature and the peak width of elongation became broaden with decreasing austenite grain size. The volume fraction of strain induced martensite decreased with decreasing austenite grain size. As the strain rate increase, the temperature representing the maximum elongation value shifted to high temperature and volume fraction of strain induced martensite decreased.
LSTM - MLP 인공신경망 앙상블을 이용한 장기 강우유출모의
안성욱,강동호,성장현,김병식,An, Sungwook,Kang, Dongho,Sung, Janghyun,Kim, Byungsik 한국수자원학회 2024 한국수자원학회논문집 Vol.57 No.2
Physical models, which are often used for water resource management, are difficult to build and operate with input data and may involve the subjective views of users. In recent years, research using data-driven models such as machine learning has been actively conducted to compensate for these problems in the field of water resources, and in this study, an artificial neural network was used to simulate long-term rainfall runoff in the Osipcheon watershed in Samcheok-si, Gangwon-do. For this purpose, three input data groups (meteorological observations, daily precipitation and potential evapotranspiration, and daily precipitation - potential evapotranspiration) were constructed from meteorological data, and the results of training the LSTM (Long Short-term Memory) artificial neural network model were compared and analyzed. As a result, the performance of LSTM-Model 1 using only meteorological observations was the highest, and six LSTM-MLP ensemble models with MLP artificial neural networks were built to simulate long-term runoff in the Fifty Thousand Watershed. The comparison between the LSTM and LSTM-MLP models showed that both models had generally similar results, but the MAE, MSE, and RMSE of LSTM-MLP were reduced compared to LSTM, especially in the low-flow part. As the results of LSTM-MLP show an improvement in the low-flow part, it is judged that in the future, in addition to the LSTM-MLP model, various ensemble models such as CNN can be used to build physical models and create sulfur curves in large basins that take a long time to run and unmeasured basins that lack input data.
냉각제어된 Fe-Si-Mn-P 고장력 강판의 미세조직 및 기계적성질
문원진,김익수,강창용,성장현,김기도 ( Won Jin Moon,Ik Su Kim,Chang yong Kang,Jang Hyun Sung ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.2
Microstructure and mechanical properties of Fe-Si-Mn-P high strength steel sheet have been investigated by controlling the cooling rate. Bainite and ferrite were obtatined by annealing in the ferrite pluse austenite region, and ferrite and austenite were obtatined after annealing in the fully austenite region. Ferrite and pearlite were obtained when the cooling rate was controlled from the annealing temperature above 760℃ and bainite showed with increasing cooling rate, however below 760℃ ferrite and bainite were obtained. Tensile strengths and hardness nearly unchanged with increasing cooling rate after control the cooling rate from the temperature above 760℃, while tensile strengths increased and elongation decreased with increasing cooling rate when the cooling rate was controlled from the tempeature below 760℃. Without regard to annealing temperature, tensile strength increased and elongation decreased with increasing cooling rate. Tensile strengths and elongation values heat treated in the ferrite plus austenite region were higher than those in the fully austenite region. Retained austenite and strength-elongation balance showed the maximum value at 780℃ and decreased with increasing annealing temperature. Strength-elongation balance value was controlled by the retained austenite.
Fe-Si-Mn-P강판의 초기조직변화가 잔류오스테나이트 형성 및 인장성질에 미치는 영향
문원진,강창용,김한군,김기돈,성장현 ( Won Jin Moon,Chang Yong Kang,Han Goon Kim,Ki Don Kim,Jang Hyun Sung ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.1
This study has been conducted to investigate the effects of initial structure on the microstructure and tensile properties of high strength trip steel sheet. The initial structure before austempering remarkably influenced the second phase. The specimen with normalized initial structure showed mainly bainitic ferrite and retained austenite, while the as rolled specimen and spherodized specimen showed martensite plus retained austenite and martensite plus bainitic ferrite with small retained austenite, respectively. Two type of retained austenite, film type and granual type were observed in all specimens. The as rolled specimen appeared the highest contents of retained austenite owing to the compressive stress by cold rolling. The contents of retained austenite increased with increasing intercritical annealing temperature and austempering time. Tensile strength showed the highest in the as rolled specimen, while the highest elongation were obtained in the normalized specimen. The maximum T.S.×El. Value showed in normalized initial structure and increased with increasing intercritical annealing and austempering time. The highest Value of T.S.×El. obtained at austempering temperature of 400℃ and retained austenite of 12%.