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LED 조명 기반의 무선 가시광 LAN 통신을 위한 MAC 프로토콜 설계
전종배(Jongbae Jeon),최정호(Jungho Choi),김성만(Sung-Man Kim) 한국통신학회 2011 韓國通信學會論文誌 Vol.34 No.6
본 논문에서는 LED 조명 기반의 무선 LAN 통신을 위한 MAC 프로토콜을 설계하였다. 본 논문에서 제안하는 MAC 프로토콜은 LED 조명과 단말기의 송수신 방향을 자동으로 최적화할 수 있는 특징이 있다. 또한, 방송메시지 송신 및 단말기 등록을 위한 초기통신 시간이 주기적으로 할당되어 있는 특징이 있다. 데이터 통신방식으로는 carrier 의 센싱 및 충돌감지가 어려운 LED 가시광의 특징을 감안하여 기존의 무선 LAN 통신에서 사용되는 CSMA/CA(carrier sense multiple access with collision avoidance) 기반이 아닌 polling 기법을 사용하였으며, MAC 프레임 형식으로는 기존의 무선 LAN 통신용 프레임을 수정하여 무선 가시광 LAN 통신에 적합한 MAC 프레임을 제안하였다. 이렇게 제안하는 MAC 프로토콜의 성능수치를 구하였으며, 무선 가시광 PHY 통신단의 데이터 전송속도를 100 Mbps로 가정하였을 때에 여러 가지 오버헤드를 제외하고 순수하게 데이터를 보낼 수 있는 데이터 전송량은 94.386 Mbps에 달하였다. In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.
Hot Deformation Behavior of V Micro‑Alloyed TWIP Steel During Hot Compression
Hojun Gwon,Sunmi Shin,Jongbae Jeon,Taejin Song,Sungkyu Kim,Bruno C. De Cooman 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3
High manganese twinning induced plasticity (TWIP) steel is an attractive material for automotive applications as its usecould result in an improved vehicle fuel efficiency and a superior passenger safety. Due to the limited research on the hotdeformation behaviour of High Mn steel, the selection of suitable operating conditions for the hot rolling process is challenging. The present contribution focusses on the hot deformation behaviour and the dynamic recrystallization kinetics of Vmicro-alloyed high manganese TWIP steel, by means of single-hit compression test in the temperature range of 850–1000 °Cand the strain rate range of 0.1–10 s−1. The activation energy for hot deformation and the processing map of a V-free TWIPsteel and a V-added TWIP steel were compared by analysing their stress–strain curves. The V-added TWIP steel exhibiteda higher activation energy than the V-free TWIP steel, i.e. 383.4 kJ/mol versus 372.5 kJ/mol. Processing maps based ona dynamic material model indicated that the hot workability of TWIP steel was decreased by micro-alloying with V. Theeffect of V on the hot deformation behaviour of TWIP steels was also analysed by means of its effect on the microstructureusing the SEM-EBSD technique. The V-added TWIP steel was characterized by a higher peak stress at a lower peak strainas compared to the V-free TWIP steel, indicating that the onset of dynamic recrystallization was accelerated by the additionof V. The rapid dynamic recrystallization kinetics resulted in a smaller recrystallized grain size in the hot deformed microstructureof the V-added TWIP steel.
열처리 조건에 따른 Al-Si-Mg계 합금의 표면 젖음성 영향
장호성,최유진,이승원,전종배,박성혁,신선미,Jang, Hosung,Choi, Yoojin,Lee, Seungwon,Jeon, Jongbae,Park, Sunghyuk,Shin, Sunmi 한국표면공학회 2018 한국표면공학회지 Vol.51 No.6
The present study investigated the effect of heat treatment process on the surface wettability of an Al-Si-Mg alloy. After solution-treated at $525^{\circ}C$ and aged at $160^{\circ}C$, the alloy showed high hardness due to the formation of precipitates. In addition, surface wettability was improved in such a way that the contact angle of distilled water droplet on the flat surface decreased to $37.6{\sim}42.1^{\circ}$ after the heat treatment. The surface energy predicted by Owens-Wendt equation also confirmed the increase of surface energy after the heat-treatment. However, when the surface roughness increased, the positive effect of the heat treatment on wettability diminished due to the geometrical factors of the rough surface.