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오선택,나정열,Oh, Sun-Taek,Na, Jung-Yul 한국음향학회 1994 韓國音響學會誌 Vol.13 No.6
잔향음이 우세한 환경하에서 소나 시스템의 성능을 평가할 때 대부분의 음향 모델인 음압 준위(power level) 모델에 비해 수중 잔향음 신호 모의 모델은 매우 유용하게 이용된다. 본 논문에서는 소나 시험에 필요한 잔향음 신호(reverberation time series)를 모의하였다. 우선 주파수 영역에서 밴드의 폭이 변하고 가우시안 분포(Gaussian distribution)를 갖는 표준화된 스펙트럼(normalized spectrum)을 수신 시간 간격에 따라 구하였다. 두번째로, 기존의 음향 모델의 결과인 시간에 따른 잔향음 준위를 각각의 표준화된 스펙트럼의 준위와 합성하였다. 마지막으로 음원 신호의 스펙트럼과 잔향음 스펙트럼을 곱(product)하고 이 결과를 역푸리에 변환(inverse Fourier transform)을 이용하여 신호를 모의하였다. Simulation of sonar reverberation time series is very useful because most acoustic models are power level models and have a difficulty when performance of hardware system is evaluated under the reverberant condition. Thus, in this paper, the simulation of reverberation time series is attempted, First, normalized spectrum, whose bandwidth is varying in the frequency domain and which has zero-mean Gaussian distribution, is calculated at pre-selected receiving time. Second, reverberation levels given by underwater acoustic model are combined with normalized spectrum in the frequency domain. Finally, nonstationary sonar reverberation time series are simulated by IFT(Inverse Fourier Transform).
택사 열수 및 에탄올 추출물의 항산화활성과 human LDL 산화억제 및 ACE 저해효과에 미치는 영향
양영이,이민자,정현정,이혜숙,김혁,나선택,박선동,박원환,Yang, Young-Yi,Lee, Min-Ja,Jung, Hyun-Jung,Lee, Hye-Sook,Kim, Hyuck,Na, Sun-Taek,Park, Sun-Dong,Park, Won-Hwan 대한한방내과학회 2008 大韓韓方內科學會誌 Vol.29 No.4
Objectives : The study was conducted to evaluate antioxidative, anti-atherosclerotic and anti-hypertensive effects of natural remedies. Alisma Rhizome (AR) has been used for a long time in Asia in folk remedies for treatment of hypertension and stroke and has been used in Korean traditional medicine for the treatment of glycosuria, gonorrhea, hypercholesterolemia, hypertension, and jaundice and its diuretic effect. These pharmacological effects of AR might come from antioxidant properties of phytochemicals in these materials. Methods : In this study, the antioxidant activity of extract from AR was studied with in vitro methods by measuring the antioxidant activity by TEAC, measuring the scavenging effects on reactive oxygen species (ROS) [superoxide anion, hydroxyl radical] and on reactive nitrogen species (RNS) [nitric oxide and peroxynitrite] as well as measuring the inhibitory effect on $Cu^{2+}$ induced human LDL oxidation and on ACE. Results : The AR extracts were found to have a potent scavenging activity, as well as an inhibitory effect on LDL oxidation and on ACE against all of the reactive species tested, with the water extract showing particularly strong antioxidant activities. Conculsions : The AR extracts have antioxidative, anti-atherosclerotic and anti-hypertensive effects in an in vitro system, which can be used for developing pharmaceutical drugs against oxidative stress and atherosclerosis.