집중형 모형 IHACRES와 GR4J를 이용한 강수 및 기온 변동성에 대한 유출 해석 민감도 평가

우동국,조지현,강부식,이송희,이가림,노성진 대한토목학회 2023 대한토목학회논문집 Vol.43 No.1

Due to climate change, drought and flood occurrences have been increasing. Accurate projections of watershed discharges are imperative to effectively manage natural disasters caused by climate change. However, climate change and hydrological model uncertainty can lead to imprecise analysis. To address this issues, we used two lumped models, IHACRES and GR4J, to compare and analyze the changes in discharges under climate stress scenarios. The Hapcheon and Seomjingang dam basins were the study site, and the Nash-Sutcliffe efficiency (NSE) and the Kling-Gupta efficiency (KGE) were used for parameter optimizations. Twenty years of discharge, precipitation, and temperature (1995-2014) data were used and divided into training and testing data sets with a 70/30 split. The accuracies of the modeled results were relatively high during the training and testing periods (NSE>0.74, KGE>0.75), indicating that both models could reproduce the previously observed discharges. To explore the impacts of climate change on modeled discharges, we developed climate stress scenarios by changing precipitation from -50 % to +50 % by 1 % and temperature from 0 °C to 8 °C by 0.1 °C based on two decades of weather data, which resulted in 8,181 climate stress scenarios. We analyzed the yearly maximum, abundant, and ordinary discharges projected by the two lumped models. We found that the trends of the maximum and abundant discharges modeled by IHACRES and GR4J became pronounced as changes in precipitation and temperature increased. The opposite was true for the case of ordinary water levels. Our study demonstrated that the quantitative evaluations of the model uncertainty were important to reduce the impacts of climate change on water resources. 기후변화가 고착화되면서 강수와 기온 변동으로 인한 가뭄 및 홍수 발생이 증가하고 있다. 유역 단위의 유출량 예측은 기후변화로 인한 자연재해에 대비하기 위한 수자원 관리의 시작이라 할 수 있다. 하지만, 기후변화와 유출모형의 불확실성은 정확한 유출 분석을 어렵게 한다. 본 연구에서 는 이러한 불확실성을 완화하기 위하여 기후 스트레스 시나리오에 따른 두 개의 집중형 수문모형, 즉 IHACRES와 GR4J를 이용하여 강수 및기온 변화에 따른 유출량 변화를 비교, 분석하였다. 연구 대상 지역은 합천댐과 섬진강댐 유역이며, Nash-Sutcliffe Efficiency (NSE) 및 KlingGupta Efficiency (KGE)를 목적함수로 하여 각 모형의 매개변수를 최적화하였다. 모형의 보정과 검정은 20년(1995년-2014년)의 유출자료를활용하였으며, 보정 및 검정 기간은 각각 7:3 비율로 설정하였다. 두 모형 모두 보정과 검정 기간에 비교적 높은 신뢰도(NSE>0.74,KGE>0.75)를 보여, 모형이 과거 사상을 재현하기에 적합하고, 모의 결과가 비교적 유사함을 확인하였다. 다음으로, 기후변동이 유출에 미치는영향을 평가하기 위해 동일한 모의 기간에 대해 강수는 –50 %에서 +50 %의 범위를 1 %씩, 기온은 0 °C에서 8 °C까지 0.1 °C씩 구분하여 총8,181개의 기후조건 시나리오를 구축하였다. 이후, 기후 스트레스 시나리오에 따른 두 모형의 최대유량, 풍수량, 평수량을 비교 및 분석하였다. 기후 스트레스 영향을 반영한 연최대유량과 풍수량의 경우, 강수 감소에 따른 유출 패턴은 두 모형에서 비슷하였으나, 강수와 기온이 증가할수록 상이한 결과를 얻었다. 이와 반대로, 풍수량의 경우 강수와 기온 변화의 차이가 커질수록 두 모형은 유사한 결과를 얻었다. 즉, 유역의 탄력적기후변화 대응을 위해서는 모형의 불확실성에 대한 정량적 평가가 필요하다는 것을 시사한다.

Variability of Surface Water Properties in the Japan/East Sea on Different Time Scales

Vladimir Ponomarev,Natalya Rudykh,Elena Dmitrieva,Hajime Ishida 한국해양과학기술원 2009 Ocean and Polar Research Vol.31 No.2

This study examined the multi-scale variabilities of sea surface temperature (SST) and salinity in the Japan/East Sea (JES) based on statistical analyses of observational data, with a focus on the northwestern part of the sea. The regionality of JES SST variability was estimated for different frequency ranges on semimonthly (11-17 days), monthly to seasonal (30-90 days), quasi-semiannual (157-220 days), and quasi-biennial (1.5-3 years) time scales using cluster analyses of daily gridded SST data for 1996 to 2007 from the Japan Meteorological Agency (JMA). Several significant peaks and regional cores were found in each frequency range of the SST anomaly (SSTA) oscillations. Quasi-semiannual SSTA oscillations with high amplitude were found in the south-southwestern part of the Japan Basin (41-43oN) and were amplified in the area adjacent to Peter the Great Bay. Oscillations with periods of 79 and 55 days also prevailed over the southwest Japan Basin between the Yamato Rise and the continental slope. A similar method was applied to classify SST and the annual cycle of surface salinity using Generalized Digital Environmental Model (GDEM) gridded data. The Tatarskii Strait and adjacent area showed the most specific annual cycles and variability in salinity on interannual to interdecadal time scales. The most significant inverse relationship between surface salinity in the Tatarskii Strait and southern JES areas was found on the interdecadal time scale. Linkages of sea water salinity in the Tatarskii Strait with Amur River discharge and wind velocity over Amurskii Liman were also revealed. This study examined the multi-scale variabilities of sea surface temperature (SST) and salinity in the Japan/East Sea (JES) based on statistical analyses of observational data, with a focus on the northwestern part of the sea. The regionality of JES SST variability was estimated for different frequency ranges on semimonthly (11-17 days), monthly to seasonal (30-90 days), quasi-semiannual (157-220 days), and quasi-biennial (1.5-3 years) time scales using cluster analyses of daily gridded SST data for 1996 to 2007 from the Japan Meteorological Agency (JMA). Several significant peaks and regional cores were found in each frequency range of the SST anomaly (SSTA) oscillations. Quasi-semiannual SSTA oscillations with high amplitude were found in the south-southwestern part of the Japan Basin (41-43oN) and were amplified in the area adjacent to Peter the Great Bay. Oscillations with periods of 79 and 55 days also prevailed over the southwest Japan Basin between the Yamato Rise and the continental slope. A similar method was applied to classify SST and the annual cycle of surface salinity using Generalized Digital Environmental Model (GDEM) gridded data. The Tatarskii Strait and adjacent area showed the most specific annual cycles and variability in salinity on interannual to interdecadal time scales. The most significant inverse relationship between surface salinity in the Tatarskii Strait and southern JES areas was found on the interdecadal time scale. Linkages of sea water salinity in the Tatarskii Strait with Amur River discharge and wind velocity over Amurskii Liman were also revealed.

1-D 시뮬레이션을 통한 피벗 타입 가변오일펌프 해석에 대한 연구

이진우 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.12

Variable displacement vane oil pumps control the discharge pressure and flow rate regardless of the engine operating speed by controlling the eccentricity between the rotor and stator. Therefore, research on this type of pump is in progress because of its high likelihood of improving fuel economy. The need for advanced research with 1D simulations is in demand to enhance the efficiency in terms of time and cost to deal with the increasing complexity of the engine development process. This research aimed to establish a robust 1D model to estimate the performance, such as discharge flow rate and torque, with the change in oil temperature. This model consists of a hydraulic and control signal part. An in-house model was developed to calculate the discharge flow area, eccentricity, and operating torque of the pump. The accuracy for discharge flow was improved with the help of leakage modeling considering both internal and outlet lead passage. In addition, the calculation model considering various types of friction torque made the simulated output for torque prediction more accurate. As a result, the final model showed an accuracy of approximately 97% and 92% compared with the experiment regarding discharge flow rate and torque, respectively, regardless of the pump speed under steady operating conditions. These results confirmed the possibility of estimating the discharge flow rate, operating torque, and volumetric efficiency regarding oil temperature. 가변오일펌프는 펌프의 로터와 스테이터 간의 편심을 조절을 통해 엔진 운전 속도와 무관하게 오일 토출 압력 및 유량을 제어할 수 있다. 따라서 기존 펌프 대비하여 불필요한 동력 소모 저감을 통한 차량 연비 개선 가능성이 높아, 효율개선을 위한 차량개발 요소기술로써 관련 연구가 지속되고 있다. 또한 최근 엔진 개발에 소요되는 시간 및 비용의 효율성을 개선하기 위해 선행단계에서 1D 모델 시뮬레이션 기반 성능예측 기술을 활용하는 버추얼 개발의 중요성이 높아지고 있다. 이에 본 연구에서는 오일 온도 변화에 따른 가변오일펌프의 성능을 예측할 수 있는 1D 모델을 구성하여 이를 향후 엔진 구동계를 모사할 수 있는 1D 모델의 요소로써 전체 시스템 소모 동력 파악에 활용할 수 있도록 하였다. 본 모델은 AMESim을 활용하여 유압 특성 모사 부분과 제어 신호 부분으로 구분하여 구성하였으며, 펌프 토출 면적, 편심 및 구동 토크 계산 시에는 자체 모델을 개발하여 해석에 활용하였다. 특히, 펌프 내부에서 발생하는 누유를 내부 및 외부로 구분하여 모델에 반영하여 펌프 토출유량 모사 정확도를 개선하였다. 또한 펌프 내부의 다양한 마찰 발생 영역을 구분하여 마찰력을 계산할 수 있는 모델을 구성하여 펌프의 토크 계산 오차수준을 향상시켰다. 결과적으로 정상상태 운전 조건에서 펌프 회전속도에 관계없이 토출유량을 3%, 토크를 8% 이내의 오차로 모사할 수 있는 모델을 완성하였으며, 본 모델을 활용하여 오일온도 변화에 따른 토출유량, 구동토크 및 체적효율 변화 수준을 예측할 수 있었다.

An effect of ENSO on summer surface salinity in the Yellow and East China Seas

Park, T.,Jang, C.J.,Kwon, M.,Na, H.,Kim, K.Y. Elsevier 2015 Journal of marine systems Vol.141 No.-

The Yellow and East China Seas (YECS) has been known to exhibit interannual variability in both physical and biological aspects, in relation with El Nino-Southern Oscillation (ENSO). This paper investigates the interannual variability of summer sea surface salinity (SSS) in the YECS and its linkage with ENSO, using a global ocean general circulation model (OGCM) with a regional focus on the YECS. The OGCM experiment reveals that the dominant interannual variability of the SSS in the YECS is attributed to a variability of the Changjiang river discharge (CRD). The variability of the CRD is linked to ENSO-related precipitation over the Changjiang river; when El Nino events occur in winter, precipitation over the Changjiang river increases in the rainy season of the following years. The increased precipitation in El Nino years results from enhanced southwesterly moisture flux from the South China Sea into southern China. Our finding suggests that ENSO-related precipitation in southern China contributes to the dominant interannual variability of the summer SSS in the YECS by modulating CRD.

A Protection Circuit for the Power Supply of a Gas Discharge Lamp

김호성,김종현,백주원,유동욱,정혜만,김희제 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.6

In order to drive gas discharge lamps, DC-AC converters with a LCC resonant tank, whose output voltage is adjusted by a variable frequency control are frequently used. However, when they are activated by varying the operating frequency, converters are frequently damaged by unstable operation, due to the rising and falling of the operating frequency near the resonant frequency. To solve this problem, a simple protection circuit for the power supply of a gas discharge lamp is proposed in this paper. This circuit senses the primary current of the main transformer. Using this protection circuit, the operating frequency of the lamp driving inverter system is kept close to and on the right side of the resonant frequency and the inverter is always operated in the ZVS condition. The resulting stable variable frequency operation allows various gas discharge lamps to be tested without the risk of damaging the main switches, because the protection circuit can protect the power MOSFETs of bridge converters from abnormal conditions. The validity and effectiveness of the proposed protection circuit are verified through the experimental results.

A Protection Circuit for the Power Supply of a Gas Discharge Lamp

Kim, Ho-Sung,Kim, Jong-Hyun,Baek, Ju-Won,Yoo, Dong-Wook,Jung, Hye-Man,Kim, Hee-Je The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.6

In order to drive gas discharge lamps, DC-AC converters with a LCC resonant tank, whose output voltage is adjusted by a variable frequency control are frequently used. However, when they are activated by varying the operating frequency, converters are frequently damaged by unstable operation, due to the rising and falling of the operating frequency near the resonant frequency. To solve this problem, a simple protection circuit for the power supply of a gas discharge lamp is proposed in this paper. This circuit senses the primary current of the main transformer. Using this protection circuit, the operating frequency of the lamp driving inverter system is kept close to and on the right side of the resonant frequency and the inverter is always operated in the ZVS condition. The resulting stable variable frequency operation allows various gas discharge lamps to be tested without the risk of damaging the main switches, because the protection circuit can protect the power MOSFETs of bridge converters from abnormal conditions. The validity and effectiveness of the proposed protection circuit are verified through the experimental results.

A Protection Circuit for the Power Supply of a Gas Discharge Lamp

Ho-Sung Kim,Jong-Hyun Kim,Ju-Won Baek,Dong-Wook Yoo,Hye-Man Jung,Hee-Je Kim 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.6

In order to drive gas discharge lamps, DC-AC converters with a LCC resonant tank, whose output voltage is adjusted by a variable frequency control are frequently used. However, when they are activated by varying the operating frequency, converters are frequently damaged by unstable operation, due to the rising and falling of the operating frequency near the resonant frequency. To solve this problem, a simple protection circuit for the power supply of a gas discharge lamp is proposed in this paper. This circuit senses the primary current of the main transformer. Using this protection circuit, the operating frequency of the lamp driving inverter system is kept close to and on the right side of the resonant frequency and the inverter is always operated in the ZVS condition. The resulting stable variable frequency operation allows various gas discharge lamps to be tested without the risk of damaging the main switches, because the protection circuit can protect the power MOSFETs of bridge converters from abnormal conditions. The validity and effectiveness of the proposed protection circuit are verified through the experimental results.

Holocene hydrologic fluctuations on the southern coast of Korea and their link to ENSO activity

이호일,이진영,임재수 한국지질과학협의회 2022 Geosciences Journal Vol.26 No.1

To maintain a stable freshwater supply for sustainable economic activity in coastal areas in light of anticipated global climate change, it is important to understand the controlling factors and variability of past hydrologic behavior. In this study, we tested the grain size variability recorded in coastal sediments from Yeosu, on the southern coast of Korea, as an indicator of freshwater input change. We found a ca. 7 m sedimentary sequence (Stage 2) between lower fluvial to coastal marsh (Stage 1) and upper coastal marsh (Stage 3) deposits, which we infer was deposited in the inner bay at a water depth between ca. 10 and 2 m, over the time periods between 1.2 and 7.7 cal kyr BP. The variability in grain sizes corresponded to the low-resolution local freshwater input index in the Beolgyo area, providing a more detailed precipitation fluctuation record. The long-term variations in grain size was similar to that of the Asian summer monsoon fluctuation during the middle to late Holocene. Significant fluctuation at multicentennial time scales superimposed on the long-term variation clearly indicated intensified freshwater input periods (e.g., at 2.5, 3.0, 5.2, 6.3, and 7.7 cal kyr BP). These hydrologic changes in the study area appear to be linked to past El Niño-Southern Oscillation (ENSO) activity, such that intensified freshwater input occurred during stronger ENSO activity. Among these climatic shifts, severe rainfall events characterized by sand layers (e.g., at 7.7 and 2.5 cal kyr BP) can be used as isochronous sedimentary layers on the southern coast of Korea.

추진제 유량 조절을 위한 면적가변형 벤츄리 형상에 따른 성능연구

김태국(Tae Kuk Kim),신민규(Min Kyu Shin),김석원(Seok Won Kim),구도환(Do Hwan Gu),고영성(Young Sung Ko) 한국추진공학회 2020 한국추진공학회 학술대회논문집 Vol.2020 No.7

제대군인 취업지원 변수가 취업성과에 미치는 영향에 관한 연구 - 취업지원 만족도의 매개효과를 중심으로 -

최대근(Dea-Geun Choi),양동우(Dong-woo Yang) 한국창업학회 2019 한국창업학회 Conferences Vol.2019 No.1

본 연구의 목적은 제대군인의 취업에 영향을 주는 변수(취업지원변수) 와 취업성과 사이의 매개변수를 밝힘으로서 제대군인의 취업성과를 설명하는 새로운 모델을 제시하고자 한다. This study s intention is to draw variables that affect the satisfaction level and outcomes of veterans reemployment support systems. The variables are the factors pertaining to training program, competency, environment, and policy/system. We conducted a survey to clarify the overall situation of veterans reemployment. The result showed that environment, policy/system had an influence on the satisfaction level and outcomes of the system while training program, competency did not. We expect this study will contribute in providing ways when preparing practical systems for the veterans.