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최현균(Hyun-Kyun Choi),오현서(Hyun-Seo Oh),조웅(Woong Cho),장윤서(Youn-Seon Jang) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.10(융합기술)
WAVE (Wireless Access in Vehicular Environments) 통신은 차량이 주행하면서 도로 인프라 및 다른 차량과 상호 통신하며 교통정보 및 서비스를 교환 및 공유하는 정보통신 융합 시스템인 국내 C-ITS (Cooperative-Intelligent Transportation System)의 핵심적인 기술이다. 본 논문에서는 고속도로에서의 WAVE 통신에 있어서 통신거리에 따라 통신성능이 현저히 떨어지는 null 점의 발생 위치를 분석하기 위하여 two-ray 지면 반사 모델을 사용하여 down-fade와 up-fade가 발생하는 위치를 수식으로 정의하였으며 실제 고속도로 LOS (Line Of Sight) 환경에서 WAVE 통신 장치를 사용한 RSSI (Receiver Signal Strength Indicator) 값 측정 실험결과와 비교 검증하였다. 또한, down-fade 발생의 문제점을 개선하기 위하여 수신 안테나 다이버시티 기능을 적용한 WAVE 통신 보드를 구현하고 실험을 통해 수신 성능이 개선되는 것을 확인하였다. WAVE (Wireless Access in Vehicular Environments) communications is the core technology for C-ITS (Cooperative-Intelligent Transportation System) which communicates with the road infrastructure and other vehicles to exchange traffic information and service while driving. In this paper, to analyze the performance degradation according to the distance between WAVE communication terminals, we derived the formulas for the locations of down-fade and up-fade points by using the two-ray ground reflection model, and verified these theoretical results by comparing with those of RSSI (Receiver Signal Strength Indicator) measurements. In addition, to solve the problem of down-fade, we suggested the WAVE communication with the antenna diversity and experimentally confirmed the performance improvement in the highway LOS (Line Of Sight) environments.
Numerical Study on the Effect of Boat Tail Shape on Aerodynamic Drag of SUV
최현아,박성오,문호균,김문상,조정식 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.1
Longitudinal vortex formed at the rear area of the vehicle is one of the main sources of vehicle aerodynamic drag. The boat tail shape is applied to reduce the longitudinal vortex strength of the SUV so that the aerodynamic drag is improved. For this study, a commercially available SUV produced by domestic automobile company, Hyundai Motor Company, is selected as a baseline model. The boat tail shape is modeled on the baseline model using the morphing technique. The effects of boat tail shape on the aerodynamic drag has been numerically analyzed for a SUV with or without undercover. A commercial flow solver, ANSYS Fluent, is used for this study. The driving speed of SUV is 140 km/h. Even though the same boat tail shape is applied to the same vehicle, the aerodynamic drag improvement depends on the flow pattern behind the vehicle. It can be improved when the strength of the longitudinal vortex is weakened by the airflow generated by the boat tail shape.
청소년의 음주여부 및 문제음주에 영향을 미치는 요인: 2013 청소년 건강행태온라인조사를 활용하여
장동균 ( Dong Gune Chang ),김희선 ( Hee Sun Kim ),차승현 ( Seung Hyun Cha ),최현진 ( Hyeon Jin Choi ),이은환 ( Eun Whan Lee ) 경희대학교 경영연구원 2015 의료경영학연구 Vol.9 No.2
This study aims to explore the factors associated with drin king and problem drinking among Korean adolescents. The 2013 Youth Risk Behavior Web-based Survey (KYRBS) data was used. And logistic regression model was employed to investigate the risk factors of drinking and problem drinking. Our results show that sex, age, scholastic performance, pocket money, mental health and deviation factors are related to drinking and problem drinking. However, in the sex and educational background of their parents, the results were different from each other. In the case of drinking risk, boys are more likely to have a risk of drinking, whereas girls have more risk of problem drinking. Moreover, the educational background of their parents was risk factor in the risk of drinking whereas not in the problem drinking. These results deserve great attention, and the authorities need to keep it in perspective. It demonstrated that different health policies are essential for different outcomes, ie. the risk of drinking and problem drinking.