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IEEE802.15.4 WPAN에서의 Cyclic Contention Free Access 기법
곽원근,이재용,Kwak, Woon-Geun,Lee, Jai-Yong 한국통신학회 2007 韓國通信學會論文誌 Vol.32 No.7b
IEEE802.15.4의 비경쟁기반 다중 접속 기법으로 적용된 GTS(Guaranteed Time Slot)의 성능 분석과 문제점 분석을 통해, 개선된 형태의 Cyclic Contention free Access(Cyclic-CFA) 기법을 제안한다. Cyclic-CFA 기법은 Polling 기법을 개선한 스케줄링 방식으로, 장치(device)들은 PAN 코디네이터(coordinator)로부터 부여받은 Sequence Number를 기반으로 순차적으로 데이터를 전송한다. 별도의 Polling 패킷(packet)이 없고 단일방향성(unidirectional)으로 동작하므로, 고전적인 Polling 기법의 오버헤드를 줄일 수 있어 보다 효율적으로 채널을 사용할 수 있다. 또한 GTS보다 많은 수의 장치가 비경쟁 데이터 전송 서비스를 받을 수 있으며, 서비스 지연 시간을 줄일 수 있다. The GTS(Guaranteed Time Slot) of IEEE802.15.4 standard, which is the contention free access mechanism, has some problems such as the limited number of deployed devices, the low channel utilization and the service confirm delay. The proposed Cyclic-CFA(Contention Free Access) scheme is a modified polling algorithm that allows a large number of devices to be served Contention Free Access without polling packets. The Cyclic-CFA scheme improves the channel utilization dramatically and also reduces service delay time.
곽재수(Jae Su Kwak),안원근(Won Geun An),김형모(Hyung Mo Kim),박영일(Young Il Park),양수석(Soo Seok Yang) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Performance tests of the plate-fin type heat exchanger for high temperature application have been performed with a high temperature heat exchanger performance test facility. The facility consists of air compressor, electric heaters, venturi flow meters, flow control valves, and combination probes which can measure temperature, total and static pressures at the same time. The performance tests were carried out near the heat exchanger design condition and off-design conditions, and the test results were compared with the calculated results. The test results showed lower heat exchanging efficiency and smaller pressure drop than the calculated results. Based on the difference, the modified design of the heat exchanger was offered.
신성준,곽원근 대한의학회 2010 Journal of Korean medical science Vol.25 No.8
Erysipelothrix rhusiopathiae is known as a pathogen of occupational diseases or a zoonosis. We report a case of E. rhusiopathiae peritonitis in a 50-yr-old male undergoing continuous ambulatory peritoneal dialysis (CAPD). He was suffered from mild abdominal pain with a distinctive erysipeloid skin lesion. E. rhusiopathiae was considered to be introduced through a lacerated wound on his hand when he was exposed to contaminated materials. He was treated successfully with a first generation cephalosporin. To our knowledge, CAPD peritonitis due to E. rhusiopathiae is very rare, and this is a report of the first case in Asia.