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김명익,안상식 대한전자공학회 2006 電子工學會論文誌-TC (Telecommunications) Vol.43 No.3
OFDM (Orthogonal Frequency Division Multiplexing) systems convert serial data stream to N parallel data streams and modulate them to N orthogonal subcarriers. Thus spectrum utilization efficiency of the OFDM systems are high and high-speed data transmission is possible. However, with the OFDM systems using the same modulation method at all subcarriers, the error probability is dominated by the subcarriers which experience deep fades. Therefore, in order to enhance the performance of the system adaptive modulation is required, with which the modulation methods of the subcarriers are determined according to the estimated SNRs. The IEEE 802.11a system selects various transmission speed between 6 and 54 Mbps according to the modulation mode. There are three typical methods for SNR estimation: Direct estimation method uses the frequency domain symbols to estimate SNR directly by minimizing MSE (Mean Square Error), EVM method utilizes the distance between the demodulated constellation points and received complex values, and the method utilizing the Viterbi algorithm uses the cumulative minimum distance in decoding process to estimate the SNR indirectly. Through comparison analyses of three methods we propose a new SNR estimation method, which employs both the EVM method and the Viterbi algorithm. Finally, we perform extensive computer simulations to confirm the performance improvement of the proposed adaptive OFDM systems on the basis of IEEE 802.11a.
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오흥근,방서욱,김명익 대한마취과학회 1983 Korean Journal of Anesthesiology Vol.16 No.4
To evaluate anesthetic experience during open heart surgery, 145 cases of patients under 15kg of body weight from January 1950 to June 1982 were analyzed according to age, sex, technuque of anesthesia, anesthetics, premedicants, muscle relaxants, flow rates and mortality. The results were as follows : 1) Premedicants were mainly atropine, meperidine, hydroxyzine, trifluprornasine and morphine. 2) Induction agents were thiopental in acyanotic group, but cyanotic group were mainly used ketamine. 3) The inhalation anesthetics that were hatothane, methoxyflurane, N9O and enfturane were used in acyanotic group but cyanotic group did not used. 4) Early stage of open heart surgery, galtamine were mainly used but now, pancuronium were used. 5) During oaraiopulrnonary bypass, the lowest temperature were mean 27'c and flow rate were 80~ 100 ml/kg/m'. 6) Overall mortality was 17.2%.
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김선자,문경수,최령,백상기,엄대자,김명익 대한마취과학회 1982 Korean Journal of Anesthesiology Vol.15 No.4
Adult respiratory distress syndreome (ARDS) is described under various names in the medical literature; post-traumatic pulmonary insufficiency, wet lung, DaNang lung and shock lung etc., and the syndrome has been used to describe a serious and often fatal condition which may develop in any patient subjected to severe trauma, major surgery or critical illness. ARDS is characterized by increasing intrapulmonary shunting, increasing work of breathing and decreasing lung compliance. There is still disagreement about exact nature of ARDS as well as its care and prevention. In ARDS, the use of positive end-expiratory pressure (PEEP) has been widely debated since its introduction by Ashbaugh and Petty in 1969. Its purpose is to increase the lung volume, especially functional residual capacity at end expiration in order to obtain better alveolar expansion and improved pulmonary gas exchange. This report described two cases of ARDS following trauma, and respiratory care problems were reviewed and discussed.
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