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최건영,고성화,김종옥,박은서,김완규,백경동,박동규 순천향대학교 부설 산업기술연구소 2021 순천향 산업기술연구소논문집 Vol.27 No.2
The Internet of Things, the core of the Fourth Industrial Revolution, is growing by incorporating various technologies into various fields. Among them, smart home systems that apply IoT technology to home environments are being actively studied. The home hub market, a means of communication for smart homes, is also developing at the same time. As the home hub market develops, security threats are also increasing accordingly. In this paper, 'Smart Home Mirror' is implemented by combining mirror and IoT technologies so that users can use them to communicate with smart home applications and other devices. To meet security issues, users in it are recognized by using face recognition technology and AES between all data communications in it is applied. The proposed device’s usefulness is approved by implementing it in smart home environments.
깁스표본기법을 이용한 와이블분포의 위험률에 대한 베이즈추정
조건호,이우동,신양규,윤용화 慶山大學校 基礎科學硏究所 1998 基礎科學 Vol.2 No.1
와이블분포를 따르는 표본을 이용하여 위험률을 베이지안 방법을 이용하여 추정한다. 깁스표본법을 베이지안 추정에서 사후확률의 분포를 구하는 방법에 적용하여 위험률에 대한 사후분포와 주변사후분포를 추정하는 방법을 제안한다. 그리고, 9개의 가솔린 정류에서 쓴 sdufwjsekfrlrn(heat exchanger)에 대한 수명시간자료를 이용하여 제안된 방법으로 위험률에 대한 베이즈추정량을 구하고 최우추정량과 비교한다. In this paper, a Bayesian estimation of the hazard rate function of Weibull distribution is considered. Using Gibbs sampling approach, the posterior distribution of hazard and Bayes estimator of hazard are presented. Using 9 heat exchanger data, the proposed method is illustrated.
동심원 등가풍속을 이용한 대기안정도에 따른 풍력자원 변화에 관한 연구
류건화(Geon-Hwa Ryu),김동혁(Dong-Hyeok Kim),이화운(Hwa-Woon Lee),박순영(Soon-Young Park),유정우(Jung-Woo Yoo),김현구(Hyun-Goo Kim) 한국태양에너지학회 2016 한국태양에너지학회 논문집 Vol.36 No.1
The power production using hub height wind speed tends to be overestimated than actual power production. It is because the hub height wind speed cannot represent vertical wind shear and blade tip loss that aerodynamics characteristic on the wind turbine. The commercial CFD model WindSim is used to compare and analyze each power production. A classification of atmospheric stability is accomplished by Monin-Obukhov length. The concentric wind speed constantly represents low value than horizontal equivalent wind speed or hub height wind speed, and also relevant to power production. The difference between hub height wind speed and concentric equivalent wind speed is higher in nighttime than daytime. Under the strongly convective state, power production is lower than under the stable state, especially using the concentric equivalent wind speed. Using the concentric equivalent wind speed considering vertical wind shear and blade tip loss is well estimated to decide suitable area for constructing wind farm.
CFD를 이용한 등가풍속 산정과 대기안정도에 따른 연안풍력단지 발전량 변화 연구
류건화 ( Geon Hwa Ryu ),김동혁 ( Dong Hyeok Kim ),이화운 ( Hwa Woon Lee ),박순영 ( Soon Young Park ),김현구 ( Hyun Goo Kim ) 한국환경과학회 2016 한국환경과학회지 Vol.25 No.2
To predict annual energy production (AEP) accurately in the wind farm where located in Seongsan, Jeju Island, Equivalent wind speed (EQ) which can consider vertical wind shear well than Hub height wind speed (HB) is calculated. AEP is produced by CFD model WindSim from National wind resource map. EQ shows a tendency to be underestimated about 2.7% (0.21 m/s) than HB. The difference becomes to be large at nighttime when wind shear is large. EQ can be also affected by atmospheric stability so that is classified by wind shear exponent (α). AEP is increased by 11% when atmosphere becomes to be stabilized (α > 0.2) than it is convective (α < 0.1). However, it is found that extreme wind shear (α > 0.3) is hazardous for power generation. This results represent that AEP calculated by EQ can provide improved accuracy to short-term wind power forecast and wind resource assessment.
Plasmaspheric contribution to the GPS TEC
Jee, Geon-Hwa,Lee, Han-Byul,Kim, Yong-Ha,Chung, Jong-Kyun,Cho, Jung-Ho 한국우주과학회 2010 한국우주과학회보 Vol.19 No.1
We performed a comprehensive comparison between GPS Global Ionosphere Map (GIM) and TOPEX/Jason (T-J) TEC data for the periods of 1998~2009 in order to assess the performance of GIM over the global ocean where the GPS ground stations are very sparse. Using the GIM model constructed by CODE at University of Bern, the GIM TEC values were obtained along the T-J satellite orbit at the locations and times of the measurements and then binned into various geophysical conditions for direct comparison with the T-J TECs. On the whole, the GIM model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations. However, the GIM model was not accurate enough to represent the well-known ionospheric structures such as the equatorial anomaly, the Weddell Sea Anomaly, and the longitudinal wave structure. Furthermore, there seems to be a fundamental limitation of the model showing the unexpected negative differences (i.e., GPS < T-J) in the northern high latitude and the southern middle and high latitude regions. The positive relative differences (i.e., GIM > T-J) at night represent the plasmaspheric contribution to GPS TEC, which is maximized, reaching up to 100% of the corresponding T-J TEC values in the early morning sector. In particular, the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity, which is different from what we normally anticipate. Among these results, the plasmaspheric contribution to the ionospheric GPS TEC will be presented in this talk and the rest of it will presented in the companion paper (poster presentation).