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다변수 Bidirectional RNN을 이용한 표층수온 결측 데이터 보간
신용탁,김동훈,김현재,임채욱,우승범 한국해안,해양공학회 2022 한국해안해양공학회 논문집 Vol.34 No.4
The data of the missing section among the vertex surface sea temperature observation data was imputed using the Bidirectional Recurrent Neural Network(BiRNN). Among artificial intelligence techniques, Recurrent Neural Networks (RNNs), which are commonly used for time series data, only estimate in the direction of time flow or in the reverse direction to the missing estimation position, so the estimation performance is poor in the long-term missing section. On the other hand, in this study, estimation performance can be improved even for long-term missing data by estimating in both directions before and after the missing section. Also, by using all available data around the observation point (sea surface temperature, temperature, wind field, atmospheric pressure, humidity), the imputation performance was further improved by estimating the imputation data from these correlations together. For performance verification, a statistical model, Multivariate Imputation by Chained Equations (MICE), a machine learning-based Random Forest model, and an RNN model using Long Short-Term Memory (LSTM) were compared. For imputation of long-term missing for 7 days, the average accuracy of the BiRNN/ statistical models is 70.8%/61.2%, respectively, and the average error is 0.28 degrees/0.44 degrees, respectively, so the BiRNN model performs better than other models. By applying a temporal decay factor representing the missing pattern, it is judged that the BiRNN technique has better imputation performance than the existing method as the missing section becomes longer. 정점 표층 수온 관측 데이터 중 결측 구간의 데이터를 양방향 순환신경망(Bidirectional Recurrent Neural Network, BiRNN) 기법을 이용하여 보간하였다. 인공지능 기법 중 시계열 데이터에 일반적으로 활용되는 Recurrent Neural Networks(RNNs)은 결측 추정 위치까지의 시간 흐름 방향 또는 역방향으로만 추정하기 때문에 장기 결측 구간에는 추정 성능이 떨어진다. 반면, 본 연구에서는 결측 구간 전후의 양방향으로 추정을 하여 장기 결측 데이터에대해서도 추정 성능을 높일 수 있다. 또한 관측점 주위의 가용한 모든 데이터(수온, 기온, 바람장, 기압, 습도)를 사용함으로써, 이들 상관관계로부터 보간 데이터를 함께 추정하도록 하여 보간 성능을 더욱 높이고자 하였다. 성능 검증을 위하여 통계 기반 모델인 Multivariate Imputation by Chained Equations(MICE)와 기계학습 기반의 Random Forest 모델, 그리고 Long Short-Term Memory(LSTM)을 이용한 RNN 모델과 비교하였다. 7일간의 장기 결측에 대한 보간에 대해서 BiRNN/통계 모델들의 평균 정확도가 각각 70.8%/61.2%이며 평균 오차가 각각 0.28도/0.44도로BiRNN 모델이 다른 모델보다 좋은 성능을 보인다. 결측 패턴을 나타내는 temporal decay factor를 적용함으로써BiRNN 기법이 결측 구간이 길어질수록 보간 성능이 기존 방법보다 우수한 것으로 판단된다.
Tetraethylorthosilicate를 사용한 수분산 폴리우레탄/실리카 Nanocomposite의 제조
신용탁 ( Yong Tak Shin ),홍민기 ( Min Gi Hong ),최진주 ( Jin Joo Choi ),이원기 ( Won Ki Lee ),이경배 ( Gyoung Bae Lee ),유병원 ( Byung Won Yoo ),이명구 ( Myung Goo Lee ),송기창 ( Ki Chang Song ) 한국화학공학회 2010 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.48 No.4
Colloidal Silica가 Sol-Gel 하드 코팅 막의 광 변색 특성에 미치는 영향
신용탁 ( Yong Tak Shin ),이민지 ( Min Ji Lee ),조경숙 ( Kyung Sook Cho ),송기창 ( Ki Chang Song ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.5
Organic-inorganic hybrid coating solutions were prepared starting from colloidal silica, lanthanum nitrate and γ-glycidoxypropyl trimethoxysilane by the sol-gel method. Also, spiropyran-doped hard coating solutions were prepared by mixing the spiropyran solution, obtained after dissolving spiropyran dye into tetrahydrofuran solvent, with the organic-inorgnic hybrid coating solutions. The spiropyran-doped hard coating solutions were applied as a thin layer to polycarbonate sheets, and their photochromic properties were investigated. The effect of amount of colloidal silica added into the coating solutions was investigated on the photochromic properties of coating films. Both decoloration rate and pencil hardness of the coating films were increased with increasing the amounts of colloidal silica.
Pentaerythritol Triacrylate와 실란커플링제의 첨가가 수분산 폴리우레탄의 물성에 미치는 영향
신용탁 ( Yong Tak Shin ),홍민기 ( Min Gi Hong ),김병석 ( Byung Suk Kim ),이원기 ( Won Ki Lee ),유병원 ( Byung Won Yoo ),이명구 ( Myung Goo Lee ),송기창 ( Ki Chang Song ) 한국화학공학회 2012 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.50 No.2
Acrylic terminated polyurethane prepolymers were synthesized by capping the NCO groups of polyurethane prepolymers, prepared from isophorone diisocyanate (IPDI), polycarbonate diol (PCD) and dimethylol propionic acid (DMPA), with pentaerythritol triacrylate (PETA). Subsequently, silylated acrylic terminated prepolymers were prepared by capping the NCO groups of acrylic terminated polyurethane prepolymers with different types of silane coupling agents, glycidoxypropyl trimethoxysilane (GPTMS) or aminopropyl triethoxysilane (APS). The average particle size of pure waterborne polyurethane solution, measured by the dynamic light scattering method, was increased from 14.3 nm to 208.6 nm by adding PETA and APS. Also, the coating film of silylated acrylic terminated waterborne polyurethane showed better abrasion resistance and pencil hardness than that of pure waterborne polyurethane.
아크릴 단량체 종류 변화가 수분산 Polyurethane Dispersion의 물성에 미치는 영향
신용탁 ( Yong Tak Shin ),홍민기 ( Min Gi Hong ),김병석 ( Byung Suk Kim ),이원기 ( Won Ki Lee ),유병원 ( Byung Won Yoo ),이명구 ( Myung Goo Lee ),송기창 ( Ki Chang Song ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.5
NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), polycarbonate diol(PCD) and dimethylol propionic acid(DMPA). Subsequently, acrylic terminated polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of acrylate monomers, such as 2-hydroxyethyl methacrylate(HEMA), 2-hydroxyethyl acrylate(HEA) and pentaerythritol triacrylate(PETA). The average particle sizes of the acrylic terminated polyurethane solutions were increased by capping acrylate monomers. Also, the prepared coating films showed better abrasion resistance and pencil hardness than those of pure waterborne polyurethanes. The coating film with PETA exhibited the best abrasion resistance and pencil hardness of coating films prepared with three acrylate monomers.
수분산 폴리우레탄의 물성에 미치는 Pentaerythritol Triacrylate의 첨가 효과
신용탁 ( Yong Tak Shin ),홍민기 ( Min Gi Hong ),최진주 ( Jin Joo Choi ),이원기 ( Won Ki Lee ),유병원 ( Byung Won Yoo ),이명구 ( Myung Goo Lee ),송기창 ( Ki Chang Song ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.4
NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), polycarbonate diol(PCD) and dimethylol propionic acid(DMPA). Subsequently, acrylic terminated prepolymers were prepared by capping the NCO groups of polyurethane prepolymers with different moles of pentaerythritol triacrylate(0~0.024 moles) as a acrylate monomer. The average particle size of the acrylic terminated polyurethane solutions was increased with increasing PETA contents. Also, the prepared coating films showed better abrasion resistance and pencil hardness than pure waterborne polyurethane.
실란커플링제 종류 변화가 수분산 폴리우레탄의 특성에 미치는 영향
신용탁 ( Yong Tak Shin ),황지현 ( Ji Hyeon Hwang ),홍민기 ( Min Gi Hong ),최진주 ( Jin Joo Choi ),이원기 ( Won Ki Lee ),이경배 ( Gyoung Bae Lee ),유병원 ( Byung Won Yoo ),이명구 ( Myung Goo Lee ),송기창 ( Ki Chang Song ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.3
NCO terminated polyurethane prepolymers were synthesized from isophorone diisocyanate(IPDI), poly (tetramethylene glycol)(PTMG) and dimethylol propionic acid(DMPA). Subsequently, waterborne polyurethanes were prepared by capping the NCO groups of polyurethane prepolymers with different types of silane coupling agents, such as methyltsimethoxysilane(MTMS), glycidoxypropyl trimethoxysilane(GPTMS), methaeryloxypropyl trimethoxysilane(MPTMS) and aminopropyl triethoxysilane(APS). The avenge particle size of the waterborne polyurethane solutions was increased by adding silane coupling agents. Also, the coating films prepared from GPTMS, MPTMS and APS, exhibited better pencil hardness than those from pure waterbome polyurethane. On the other hand, the coating films from MTMS did not show an improved pencil hardness than those from pure waterbome polyurethane.