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PW 도플러 시스템에서 Base Line 이동 기법을 이용한 오디오 신호 처리 방법
김기덕,송태경 대한의용생체공학회 1999 의공학회지 Vol.20 No.3
현재 널리 쓰이고 있는 PW 도플러 시스템 주파수가 나이퀴스트 주파수를 초과할 경우 스텍트럼 aliasing 현상에 의하여 정확한 혈류 속도의 측정을 할 수 없다는 문제점을 가지고 있다 . 도플러 스펙트럼의 aliasing 현상을 극복하기 위하여 통상적으로 기준선 (Base Line) 이동기법을 사용하고 있으나 도플러 오디오 신호는 aliasing 된채로 남게 된다. 이 논문에서는 주파수 천이 및 필터링 기법들을 적절히 적용하여 기준선 이동시 도플러 스텍트럼과 오디오 신호의 aliasing 현상을 함께 제거할 수 있는 기법을 제안한다. 제안된 방법은 단방향 혈류 성분을 검사하는 경우 aliasing 현상 없이 측정 가능한 도플러 주파수를 나이퀴스트 주파수의 두배인 PRF 까지 증가되도록 한다. 실제 시스템에서 얻어진 신호를 이용하여 제안된 방법을 실험적으로 검증하였다. Conventional PW Doppler systems suffer from the ambiguity of measured blood velocities due to the spectrum aliasing when the corresponding Doppler frequencies are greater than the Nyquist frequency. Base-line shift is a customary method for dealiasing the Doppler spectrums. I lowever, Doppler audio signals still remain unchanged even when the base-line shift method is applied. This paper de scribes an method for dealiasing both the Doppler spectra and audio signals by using sampling rate expansion, frequency shifting, and filtering poerations. For undirectional flows, the method can increase the maximum detectable Doppler frequency from the Nyquist limit of one-half of the Pulse Repetition Frequency(PRF) to the PRF. Experiments with real data have been performed to verify the proposed method.
김기덕,Kim, Ki-Deok 한국건축역사학회 2011 건축역사연구 Vol.20 No.6
Namhansanseong fortress (南漢山城) is not Eupchi (邑治) created for ages but the new settlement of public and military administration as Baedo (陪都) to defend capital territory. Namhansanseong has Jinsan (鎭山) that is named Cheongnyangsan (淸凉山) and its government office building was located in the main place, also a periodic five-day market was being held in the center of fortress. This study is find out the transition and its historical background of government office building on Namhansanseong by the relocation of Eupchi in the 17th century. The conclusion of analysis can be summarized as follows; The main change of government office in the late Choson dynasty is to move Yi-a, administrative complex (貳衙) around Yeonmugwan (演武館). Since 1795, the 19th year of King Jeongjo (正祖), this was fixed by the end of the Choson dynasty on the unification of Magistrate which is also Defense Commander. In the second place, the military office on Jungyeong (中營) that is Junggun's (中軍) place of work was abolished by the reform of Junggun system. Thirdly, transition of the end of the Choson dynasty is the abolition of Sueoyeong (守禦營) and the realignment of government offices. Namely, the administrative agency was moved to Haenggung (行宮) after the collapse of unification in 1895. Also former military offices was changed to police administration on Gwangju-bu (廣州府), Gwangju county level unit.