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2차 샘플링을 이용한 초음파 도플러 시스템에서 샘플링 주파수 펄스 대역폭이 평균 주파수 측정에 미치는 영향
안영복,박송배,Ahn, Young-Bok,Park, Song-Bai 한국음향학회 1990 韓國音響學會誌 Vol.9 No.3
2차 샘플링이 도플러 신호의 평균 주파수 측정에 미치는 영향에 대해서 분석을 하였다. 아나로그/디지탈 변환기(analogue-to-digital converter)의 샘플링 주파수를 낮추기 위해 수신 신호를 $4f_0$ 대신에 $4f_0$/5나 $4f_0$/9의 낮은 주파수로 샘플링에서 도플러 신호를 얻을 수 있다. ($f_0$는 송신 신호의 중심 주파수이다.) 일반적인 도플러 시스템에서처럼 수신 신호가 협 대역이면 낮은 샘플링 주파수로 인해 발생되는 평균 주파수의 측정에 대한 오차는 무시할 정도로 작다는 것을 컴퓨터 시뮬레이션과 실험을 통해 증명하였다. We analyze the effect of second-order sampling on estimating the mean frequency of the Doppler signal. In order to reduce the sampling frequency of analogue-to-digital converter, it is possible to obtain the Doppler signal by sampling the radio frequency echo signal with the low frequence of $4f_0$/5 or $4f_0$/9 instead of $4f_0$, where $f_0$ is the center frequency of the transmitted signal. The computer simulation and experiments show that if the narrowband signal is transmitted as is usual in the Doppler system, the error of the mean frequency estimates due to the low sampling frequency is negligible.
초음파 영상시스템에서 카이저 윈도우를 이용한 사이드 로브 감축에 관한 연구
나병윤,안영복,정목근,Na, Byeong-Yoon,Ahn, Young-Bok,Jeong, Mok-Kun 대한의용생체공학회 1996 의공학회지 Vol.17 No.2
In this paper, we compared the performance of the Kaiser window with those of others as a weight function of well known anodization technique for regression of side lobe in a field pattern resulted from focusing of transducer array. The Kaiser window is an window providing many types of curve with several variables. In order to compare performance of the Kaiser window as the weight function, anodization results of the previously used Hamming window function and the Matched Gaussian function are compared Result of computer simulation, the pertormance of Kaiser window with $\delta$=0.0025 in side lobe regression was better than that of Hamming window or Matched Gausian function.
윤유식,김선형,최선미,문진석,강동근,김영,안영복,이종철,정우진,Yoon, Yoo-Sik,Kim, Sun-Hyoung,Choi, Sun-Mi,Moon, Jin-Seok,Kang, Dong-Kun,Kim, Young,Ahn, Young-Bok,Lee, Jong-Cheol,Jung, Woo-Jin 한국한의학연구원 2003 한국한의학연구원논문집 Vol.9 No.2
The goal of this study is construction and efficacy evaluation of MPC-25 (Magnetic Pain Control-25), a medical device using magnetic stimulation. MPC-25 consists of a main body containing power supply and control module and a bed containing magnetic core and coil. In distinction from electric pain control medical devices, magnetic pain control system is non-contact, so the patients need not take off their clothes to be treated. High amplitude current pulses are applied to a magnetic coil and induce time varying magnetic field generating eddy current in a conductor like human body. Clinical efficacy test was performed in patients suffering from musculoskeletal pain of lumbar, shoulder and joint. Degree of pain before and after treatment for 30 minutes was compared using Visual Analogous Scale. As a result, 14 cases out of 20 showed decreased pain perception, so the rate of efficacy is 70%. Reduction of pain perception was statistically significant (P=0.001 by Wilcoxon Signed Rank Test).
시스템 입출력 잡음 특성 분석을 통한 DEXA 영상의 잡음 모델링
권주원(Ju Won Kwon),조선일(Sunil Cho),안영복(Young Bok Ahn),노용만(Yong Man Ro) 한국멀티미디어학회 2009 한국멀티미디어학회 학술발표논문집 Vol.2009 No.1
골밀도 측정은 골다공증 조기진단을 위한 효과적인 방법이다. 골밀도의 정확한 측정을 위해서 정밀한 골영역 분할과 생체신호 측정은 중요한데, 이를 위해 잡음 제거는 필수적이다. 기존의 방법들은 x-ray 영상에서 Gaussian 및 Poisson 잡음을 가정하고, 이를 제거를 하여왔다. 하지만 이는 X-ray 영상 장비에 따라 다른 다양한 잡음 특성을 반영하는데 한계가 있어 근본적인 잡음 제거에 효율적이지 못하다. 본 논문에서는 골밀도 측정 향상을 위해서 획득된 영상의 잡음 특성을 분석하고 이를 이용하여 실험에 사용한 DEXA 영상의 잡음 모델을 구현하였다. 더불어 DEXA 영상을 이용한 실험을 통해 구현된 잡음 모델의 적절함을 증명하였다.
적응성 가중 메디안 필터와 새로운 잡음 모델을 이용한 초음파 영상의 스펙클 잡음 제거
안영복 건국대학교 1995 學術誌 Vol.39 No.2
A technical method of noise modeling and adaptive filtering for reducing of speckle noise in medical ultrasonic Images is presented. By adjusting the characteristics of the filer according to local statistics around each pixel of the image as moving windowing, it is possible to suppress noise sufficiently while preserve edge and other significant information required in diagnosis. Homogeneous factor(HF) from the noise models that enables the filter to recognize the local structures of the image is introduced, and an algorithm for determining the HF fitted to the diagnostic systems with various inner statistical properties is proposed. The result of proposed method is superior to that of other filters and models in preserving small details and suppressing the noise at homogeneous region.
가변 영역판별 파라미터를 갖는 AWMF(Adaptive Weighted Median Filter)를 전처리 과정으로 이용한 초음파 영상의 윤곽선 검출
윤귀영,안영복,박영배 건국대학교 산업기술연구원 1997 건국기술연구논문지 Vol.22 No.-
To detect the edge in ultrasonic images, a pre processing to remove a speckle noise is needed. One of the filters used in this preprocessing is the AWMF(Adaptive Weighted Median Filter) which takes into account various signal processings performed inside the ultrasonic scanner(logarithmic compression, low-pass filtering, interpolation)[1]. Because signal processings inside the scanner depend on the type of scanner, it is not easy to design the filter which adjusts to any type of scanners. To solve this problem, we proposed an AWMF with a varying region-decision parameter that uses a new speckle noise model and adapts it to AWMF by considering signal processing inside the scanner. This proposed filter results in better performance than other methods. In this paper, We proved that if we remove the peckle noise by using our proposed method, we can obtain the better edge detection than other methods.