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강수-일유출량 추정 LSTM 모형의 구축을 위한 자료 수집 방안
김동균,강석구,Kim, Dongkyun,Kang, Seokkoo 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.10
In this study, after developing an LSTM-based deep learning model for estimating daily runoff in the Soyang River Dam basin, the accuracy of the model for various combinations of model structure and input data was investigated. A model was built based on the database consisting of average daily precipitation, average daily temperature, average daily wind speed (input up to here), and daily average flow rate (output) during the first 12 years (1997.1.1-2008.12.31). The Nash-Sutcliffe Model Efficiency Coefficient (NSE) and RMSE were examined for validation using the flow discharge data of the later 12 years (2009.1.1-2020.12.31). The combination that showed the highest accuracy was the case in which all possible input data (12 years of daily precipitation, weather temperature, wind speed) were used on the LSTM model structure with 64 hidden units. The NSE and RMSE of the verification period were 0.862 and 76.8 m<sup>3</sup>/s, respectively. When the number of hidden units of LSTM exceeds 500, the performance degradation of the model due to overfitting begins to appear, and when the number of hidden units exceeds 1000, the overfitting problem becomes prominent. A model with very high performance (NSE=0.8~0.84) could be obtained when only 12 years of daily precipitation was used for model training. A model with reasonably high performance (NSE=0.63-0.85) when only one year of input data was used for model training. In particular, an accurate model (NSE=0.85) could be obtained if the one year of training data contains a wide magnitude of flow events such as extreme flow and droughts as well as normal events. If the training data includes both the normal and extreme flow rates, input data that is longer than 5 years did not significantly improve the model performance.
프로토콜 제어 및 데이터부분시험을 위한 통합시험항목생성
김동균(Dongkyun Kim),최양희(Yanghee Choi) 한국정보과학회 1995 한국정보과학회 학술발표논문집 Vol.22 No.2B
통신프로토콜이 복잡해짐에 따라 이를 검증하기 위한 여러 방법들이 출현하였다. 이러한 방법들로는 프로토콜을 기술하고 기술된 내용에 논리적인 오류가 발생하였는가의 여부를 조사하는 Validation 검사와, 프로토콜의 구현이 프로토콜 규격과 일치하는가의 여부를 검사하는 적합성시험(Conformance Testing)이 존재한다. 적합성시험은 블랙박스 시험으로 수행되며 지금까지 프로토콜의 제어부분에 대한 연구가 많이 진행되었다. 지금까지 제시된 데이터부분을 고려한 적합성시험방법들은 일반적으로 단순히 제어부분과 데이터부분을 구별하여 독립적으로 시험항목을 생성하고 있다. 본 논문에서는 하나의 시험항목으로 통합시험하는 새로운 방법을 제시한다.
김동균(Dongkyun Kim),이우람(Wooram Lee),김창래(Changrai Kim),유관호(Kwanho You) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.4
Unmanned aerial vehicle(UAV)를 사용한 Time difference of arrival(TDoA) 기술은 Global positioning system(GPS)에 비해 더욱 정확한 위치 추정이 가능하여 실외환경에서 움직이는 물체의 위치를 추정하는 방식으로 널리 연구되고 있다. 그러나 환경적 잡음에 의한 오차로 인해 정확도가 제한된다. 본 논문에서는 적응형 듀얼 EKF를 이용한 환경 오차 보정 방법을 제안한다. 무선 센서를 장착한 2대의 UAV를 사용한 위치 추정 모의 실험을 통해 적응형 듀얼 EKF의 효율을 확인하고 성능 향상을 검증한다.
김동균(Dongkyun Kim),김종윤(Jongyun Kim),이현섭(Hyunseop Lee) 한국트라이볼로지학회 2016 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.32 No.2
Recently, a double-side machining process has been adopted in fabricating a sapphire glass to enhance the manufacturability. Double-side lap grinding (DLG) is one of the emerging processes that can reduce process steps in the fabrication of sapphire glasses. The DLG process uses two-body abrasion with fixed abrasives including pallet. This process is designed to have a low pressure and high rotational speed in order to obtain the required material removal rate. Thus, the temperature is distributed on the DLG platen during the process. This distribution affects the shape of the substrate after the DLG process. The coolant that is supplied into the cooling channel carved in the base platen can help to control the temperature distribution of the DLG platen. This paper presents the results of computational fluid dynamics with regard to the heat transfer in a DLG platen, which can be used for fabricating a sapphire glass. The simulation conditions were 200 rpm of rotational speed, 50°C of frictional temperature on the pallet, and 20°C of coolant temperature. The five cases of the coolant flow rate (20~36 l/min) were simulated with a tetrahedral mesh and prism mesh. The simulation results show that the capacity of the generated cooling system can be used for newly developed DLG machines. Moreover, the simulation results may provide a process parameter influencing the uniformity of the sapphire glass in the DLG process.