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Fe - 17Cr - 2M(M = Si, Nb, Mo)합금 분말 소결체의 교류 자기 특성
김정곤(J. G. Kim),김택기(T. K. Kim),조용수(Y. S. Cho) 한국자기학회 2000 韓國磁氣學會誌 Vol.10 No.6
Fe-17Cr-2M(M=Si, Nb, Mo) alloy powder was prepared by plasma electrode rotating atomizer and than the alloy powder was formed and sintered. The particle shape of the Fe-17Cr-2M(M=Si, Nb, Mo) alloy power is spherical. The saturation magnetization of the sintered Fe-17Cr-2Mo and Fe-17Cr-2Nb alloy are 155 emu/g. The saturation magnetization of the sintered Fe-17Cr-2Si alloy is less than that of the sintered Fe-17Cr-2Mo and Fe-17Cr-2Nb alloy. The amplitude relative permeability of the sintered Fe-17Cr-2M(M=Si, Nb, Mo) alloy has the maximum value in the range of 3~5 Oe applied field at forming pressure 12 ton/㎠, sintering temperature 1200℃, and frequency 1 ㎑. Power loss of the sintered Fe-17Cr-2Nb alloy is 40 ㎽/cc at applied field, Hα= 5 Oe, and frequency, f=1 ㎑. The power loss of the sintered Fe-17Cr-2Nb alloy is a half of that of the sintered Fe-17Cr-2Si and Fe-17Cr-2Mo alloy.
박용디젤기관용 SCR 시스템의 NOx 정화율에 관한 연구
최재성(J.S.Choi),조권희(K.H.Cho),이재현(J.H.Lee),이진욱(J.W.Lee),장성환(S.H.Jang),김정곤(J.G.Kim),양희성(H.S.Yang),고준호(J.H.Ko),박준영(K.Y.Park) 한국마린엔지니어링학회 2003 한국마린엔지니어링학회 학술대회 논문집 Vol.2003 No.-
A diesel engine is utilized widely for industry and shipping because of its efficiency. However, diesel engine emits relatively high concentrated air pollution matters, which will become a competitive factor in the shipping as well as industry. In fact, the regulation has been already implemented from the year 2000. Nitrogen oxides (NOx) in particular is the main part of the regulation. IMO NOx levels are generally possible to meet by means of primary on-engine measures so called IMO tuning. But further significant follow-on reductions are likely to require a secondary after-treatment technique.<br/> SCR technology is used almost exclusively for NOx removal in stationary combustion systems. SCR system is currently the only available technology proven at full scale to meet the 90% NOx reduction levels. Accordingly, the use of an SCR system on board ship maybe provides the solution to minimize this primary pollutant without increasing fuel consumption.<br/> In order to develop a practical SCR system for marine application on board ship, a primary SCR system using urea was made. The SCR system was set up on the ship, HANNARA as a test vessel, employed a two-stroke cycle diesel engine as main propulsion, which is a training ship in KMU (Korea Maritime Univ.). The purpose of this paper is to report the results about the basic effects of the above system parameters which is investigated from practical application through its trial use. The preliminary results are presented that the degree of NOx removal depends on some parameters. such as the amount of urea solution added, space velocity, reaction gas temperature and activity of catalyst.<br/>
WBAN 환경에 따른 유동적 상태 전환 Mac Protocol
최준성(J. S. Choi),김정곤(J. G. Kim) 한국재활복지공학회 2013 재활복지공학회논문지 Vol.7 No.2
WBAN 환경에서 Master와 Node들의 에너지 효율을 관리하는 것은 매우 중요하다. 동시에 Master는 Node로부터 데이터를 수집하고 제어하는 중요한 역할을 함으로써 효과적인 에너지 소비를 유지하여 어떠한 상황에서도 대처할 수 있어야 한다. 따라서 Master와 Node 사이의 적절한 저전력 MAC 프로토콜이 필요하다. 우리는 간단히 WBAN 슈퍼프레임 구조를 변경해줌으로써 더 향상된 MAC 프로토콜을 제안한다. 시뮬레이션 결과는 제안된 구조가 IEEE 802.15.6과 기존 연구와 비교해서 Master와 각 노드들의 에너지의 효율이득을 나타낸다. In WBAN environment, it is very important to achieve energy efficiency of master and nodes, At the same time, a master also plays an important role in collecting data from nodes and controlling the nodes. By maintaining a master properly, any kinds of situation can be handled. Therefore, low power MAC protocol between a master and a node is highly required appropriately. We propose an improved MAC protocol by simply changing the frame structure of WBAN system. The simulation results show that the proposed scheme attains a lot of saving of energy consumption of master and each node compared with IEEE 802.15.6 and conventional schemes.
WBAN 환경에 따른 유동적 상태 전환 MAC Protocol
최준성(J. S. Choi),김정곤(J. G. Kim) 한국재활복지공학회 2013 한국재활복지공학회 학술대회논문집 Vol.2013 No.10
In WBAN environment, it is important to achieve energy efficiency of nodes implanting into human body. At the same time, a master also plays an important role in collecting data from nodes and controlling the nodes. By maintaining a master properly, any kinds of situation can be handled. Therefore, low power MAC protocol between a master and a node is highly required appropriately. A MAC protocol proposed in this paper aims to satisfy with these requirements and improve energy consumption rate that tends to grow high as the number of nodes increases. For the efficient and objective evaluation of the proposed MAC protocol, IEEE 802.15.6 MAC is used to compare with it and we show that the advantage of the proposed MAC meet our expectation.
최원석(W. S. Choi),김정곤(J. G. Kim) 한국재활복지공학회 2011 한국재활복지공학회 학술대회논문집 Vol.2011 No.11
In this paper, we analyzed about interference scenario which is able to arise from WEAN system that it transmits signal of human body, and we verified through the analysis, the frequency band which gets the biggest effects from the interference. Also we analyze conventional interference mitigation schemes that the power control scheme and signal processing scheme. We find out the following fact by analyzed scenario and conventional interference mitigation schemes in WEAN. If we use 2.4GHz, the biggest interference were occurred, and in case of interference mitigation, we could verify that appropriate. trade-off should be accomplished in between efficiency and complexity.
WBAN 환경에서 Co-channel 간섭 제거를 위한 연구
최원석(W. S. Choi),김정곤(J. G. Kim) 한국재활복지공학회 2011 재활복지공학회논문지 Vol.5 No.1
본 논문은 2.4Ghz 대역을 사용하는 WBAN (Wireless Body Area Network) 환경에서 동일 채널을 사용하는 경우에 발생하는 간섭을 제거하기 위한 방법을 MMSE (Minimum Mean Square Error), OC (Optimal Combining), ML (Maximum Likelihood) 을 비교 분석하였으며,또한 IEEE 802.15.6에서 정의된 시나리오 및 채널 모델에 대해서 분석하였다. 모의 실험결과 ML 알고리즘이 가장 우수한 성능을 나타내는 것을 알 수 있었다. 하지만 ML 과 OC 의 경우 간섭채널의 정보를 알아야 하기 때문에 MMSE 에 비해 복잡도가 크다는 단점이 있다. 그래서 WBAN 환경에 적용하는데 어려움이 있다. 따라서 복잡도와 성능사이에 적당한 trade-off 를 만족하는 간섭제거 알고리즘을 연구해야 할 것이다. In this paper, we analyze that co-channel interference mitigation algorithms MMSE (Minimum Mean Square Error), OC (Optimal Combining), ML (Maximum Likelihood) using 2.4Ghz in WBAN (Wireless Body Area Network) system. Also analyze that scenario and channel model by IEEE 802.15.6. ML gives the best performance for all simulation. ML and OC have high complexity than MMSE complexity, because these algorithms should be known channel information of interference users. So these algorithms are difficult to apply to WBAN. Therefore we will study the interference mitigation algorithm that should be accomplished trade-off of between efficiency and complexity