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Deep Switch: 자원이 제약된 기기에서 동적 데이터 변화에 적응하는 모델을 위한 전문화된 경량 신경망 교체 시스템
김학빈(HakBin Kim),김종영(JongYeong Kim),최홍준(HongJun Choi),진영화(YeongHwa Jin),김성웅(SeongWoong Kim),이건호(KeonHo Lee),김현준(HyunJun Kim),한예지(YeJi Han),김다솔(DaSol Kim),김덕환(DeokHwan Kim),최동완(DongWan Choi) 한국정보과학회 2020 한국정보과학회 학술발표논문집 Vol.2020 No.12
Mechanically actuated frequency reconfigurable metamaterial absorber
Kim, Jongyeong,Jeong, Heijun,Lim, Sungjoon Elsevier 2019 Sensors and actuators. A Physical Vol.299 No.-
<P><B>Abstract</B></P> <P>In this paper, a mechanically actuated frequency reconfigurable metamaterial electromagnetic absorber is proposed. The absorber’s metamaterial unit cell is designed to exploit LC resonance from inductive and capacitive coupling. Because this inductance and capacitance determine the absorber’s resonant frequency, we propose a mechanical tuning method that changes the resonant frequency by changing the overall thickness of the metamaterial unit cell. The proposed unit cell consists of an FR4 dielectric substrate with fixed thickness and an air substrate with tunable thickness. When the air substrate thickness is varied over the range of 17 mm to 26 mm, the absorber’s resonant frequency changes from 6.96 GHz to 5.79 GHz in EM simulation. In order to verify the proposed idea, a metamaterial absorber was fabricated as a 17 × 17 array of unit cells and a linear actuator was used to control the thickness of the air substrate. We experimentally demonstrated that the absorption frequency changes from 6.96 GHz to 5.78 GHz with 0.12 (GHz/mm) sensitivity when the air substrate thickness is mechanically changed from 17 mm to 26 mm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A mechanically actuated frequency reconfigurable metamaterial electromagnetic absorber is proposed. </LI> <LI> A linear actuator and microcontroller is used for changing air substrate thickness mechanically. </LI> <LI> The absorption frequency changes from 6.96 GHz to 5.78 GHz when the air substrate thickness is changed from 17 mm to 26 mm. </LI> <LI> A rate of change for the absorption frequency relative to the air substrate thickness is 0.12 (GHz/mm). </LI> <LI> The proposed metamaterial absorber can be potentially used for wireless pressure sensor applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Jongyeong Kim,Byeonggug Kang,Yongju Kwon,Seungbi Lee,Soonchul Kwon 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.6
Overcrowding of high-rise buildings in urban zones change the airflow pattern in the surrounding areas. This causes building wind, which adversely affects the wind environment. Building wind can generate more serious social damage under extreme weather conditions such as typhoons. In this study, to analyze the wind speed and wind speed ratio quantitatively, we installed five anemometers in Haeundae, where high-rise buildings are dense, and conducted on-site monitoring in the event of typhoon OMAIS to determine the characteristics of wind over skyscraper towers surround the other buildings. At point M-2, where the strongest wind speed was measured, the maximum average wind speed in 1 min was observed to be 28.99 m/s, which was 1.7 times stronger than that at the ocean observatory, of 17.0 m/s, at the same time. Furthermore, when the wind speed at the ocean observatory was 8.2 m/s, a strong wind speed of 24 m/s was blowing at point M-2, and the wind speed ratio compared to that at the ocean observatory was 2.92. It is judged that winds 2–3 times stronger than those at the surrounding areas can be induced under certain conditions due to the building wind effect. To verify the degree of wind speed, we introduced the Beaufort wind scale. The Beaufort numbers of wind speed data for the ocean observatory were mostly distributed from 2 to 6, and the maximum value was 8; however, for the observation point, values from 9 to 11 were observed. Through this study, it was possible to determine the characteristics of the wind environment in the area around high-rise buildings due to the building wind effect.
Taeyoon Kim,Woo-Dong Lee,Yongju Kwon,Jongyeong Kim,Byeonggug Kang,Soonchul Kwon 한국해양공학회 2022 韓國海洋工學會誌 Vol.36 No.5
Recently around the world, coastal erosion is paying attention as a social issue. Various constructions using low-crested and submerged structures are being performed to deal with the problems. In addition, a prediction study was researched using machine learning techniques to determine the wave attenuation characteristics of low crested structure to develop prediction matrix for wave attenuation coefficient prediction matrix consisting of weights and biases for ease access of engineers. In this study, a deep neural network model was constructed to predict the wave height transmission rate of low crested structures using Tensor flow, an open source platform. The neural network model shows a reliable prediction performance and is expected to be applied to a wide range of practical application in the field of coastal engineering. As a result of predicting the wave height transmission coefficient of the low crested structure depends on various input variable combinations, the combination of 5 condition showed relatively high accuracy with a small number of input variables defined as 0.961. In terms of the time cost of the model, it is considered that the method using the combination 5 conditions can be a good alternative. As a result of predicting the wave transmission rate of the trained deep neural network model, MSE was 1.3×10<SUP>-3</SUP>, I was 0.995, SI was 0.078, and I was 0.979, which have very good prediction accuracy. It is judged that the proposed model can be used as a design tool by engineers and scientists to predict the wave transmission coefficient behind the low crested structure.