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나정열,팽동국 漢陽大學校 環境科學硏究所 1995 環境科學論文集 Vol.16 No.-
Munk가 제안한 대양에서의 “표준해양(Canonical Ocean)”을 근거로 한국 동해의 표준해양 음속분포를 구했다. 이 때 음속은 국립 수산진흥원에서 27년(1961-1987)동안 격월로 관측한 수온과 염분자료로 Medwin(1975) 공식을 사용해서 계산하였으며 최소 음속층은 대양과는 달리 400m에 존재했다. 이러한 표준해양에 eddy로 인한 음속 변화를 준와도 방정식(Scully-Power, 1988)을 이용해서 이론적으로 계산한 값과 현장관측으로부터 구한 한국 동해에 출현하는 eddy 내의 음속분포를 비교하였다. 1979년 4월 수산진흥원 정선 102에서 관측된 eddy는 이론적으로 계산된 값과 표층을 제외하고는 약 5m/s 이내의 오차범위내에서 잘 일치하였다. 1988년 4월과 1992년 4월 인공위성에서 찍은 표층 수온 분포를 통해 음속의 수직 분포를 이론적으로 계산한 결과 관측값과 약 10m/s의 차이를 보였다. 또한 eddy 내의 해류를 계산했는데 수평적 분포는 시계방향의 순환을 하는 warm eddy의 특성을 잘 보여준다. 수직적으로는 표층에서 최대값을 가지며 수심에 따라 지수함수적으로 감소하여 800m 에서 2㎝/s 값을 갖는다. The canonical ocean sound speed profile of the East Sea of Korea was obtained by using the Munk's model(1974) in that, the sound speed was calculated by the Medwin(1975)'s formula from the bimonthly temperature and salinity data of the FRDA(Fisheries Research & Development Agency) for 27 years(1961-1987). The depth of sound channel axis exists at the 400m depth in the East Sea of Korea. The sound speed perturbed by eddies of the East Sea of Korea was theoretically calculated in three dimensions by using the quasi-geostrophic potential vorticity equation(Scully-Power, 1988). The observed sound speed profiles of eddies in the East Sea of Korea were compared with the ones calculated theoretically. The sound speed profiles of the eddy observed along the Line 102 in April 1979, except the surface, showed the same tendency and magnitude with the one calculated theoretically within 5m/s error range. The vertical sound speed profiles in April 1988 and 1992 were also calculated from the satellite images of the sea surface temperature and showed the error range of 10m/s. The calculated surface current velocity within the eddy was anti-cyclonic which is characteristic of the warm eddy. In vertical structures, it showed the maximum current speed at the surface and is exponentially decreased with depth to the magnitude of 2㎝/s in the 800m depth.
Computation of the Mutual Radiation Impedance in the Acoustic Transducer Array: A Literature Survey
Paeng, Dong-Guk,Bok, Tae-Hoon,Lee, Jong-Kil The Acoustical Society of Korea 2009 韓國音響學會誌 Vol.28 No.e2
Mutual radiation impedance becomes more important in the design and analysis of acoustic transducers for higher power, better beam pattern, and wider bandwidth at low frequency sonar systems. This review paper focused on literature survey about the researches of mutual radiation impedance in the acoustic transducer arrays over 60 years. The papers of mutual radiation impedance were summarized in terms of transducer array structures on various baffle geometries such as planar, cylindrical, spherical, conformal, spheroidal, and elliptic cylindrical arrays. Then the computation schemes of solving conventional quadruple integral in the definition of mutual radiation impedance were surveyed including spatial convolution method, which reduces the quadruple integral to a double integral for efficient computation.
Dong-Guk Paeng,Kweon-Ho Nam,Min Choi,Shung, K.K. IEEE 2009 and Frequency Control Vol.56 No.4
<P>To investigate the echogenicity variation due to blood flow disturbance near a stenosis under pulsatile flow, a series of in vitro experiments were performed in a rigid tube with an eccentric stenosis of 70% area reduction in a mock flow loop. An ultrasonic B-mode with a Doppler spectrogram was used to correlate echogenicity with flow speed and stroke rate. This paper reports echogenicity variation upstream of a stenosis under pulsatile flow. The experimental results showed that blood flow disturbed by the stenosis affects echogenicity and red blood cell rouleaux upstream. A hypoechoic ldquoblack holerdquo was shown at the center of the stream at systole. During diastole, the ldquobright ringrdquo in cross-sectional images was observed as eddy-like or parabolic profiles in longitudinal images. These images could be reconstructed into a 3-dimensional animation, providing a better understanding of dynamic changes of the rouleaux distribution upstream of a stenosis under pulsatile flow.</P>
Dong-Guk Paeng,Jin Ho Chang,Ruimin Chen,Humayun, M.S.,Shung, K.K. IEEE 2009 and Frequency Control Vol.56 No.3
<P>High frequency ultrasound over 40 MHz has been used to image the anterior segment of the eye, but it is not suitable for the posterior segment due to the frequency-dependent attenuation of ultrasound and thus the limitation of penetration depth. This paper proposes a novel scan method to image the posterior segment of the eye with an angled high frequency (beyond 40 MHz) ultrasound needle transducer. In this method, the needle transducer is inserted into the eye through a small incision hole (~1 mm in diameter) and rotated around the axial direction to form a cone-shaped imaging plane, allowing the spatial information of retinal vessels and diagnosis of their occlusion to be displayed. The feasibility of this novel technique was tested with images of a wire phantom, a polyimide tube, and an excised pig eye obtained by manually rotating a 40 MHz PMN-PT needle transducer with a beveled tip of 45deg. From the results, we believe that rotational scan imaging will help expand the minimally invasive applications of high frequency ultrasound to other areas due to the capability of increased closeness of an angled needle transducer to structures of interest buried in other tissues.</P>
Maxillofacial Trauma Trends at a Tertiary Care Hospital: A Retrospective Study
Jeon, Eun-Gyu,Jung, Dong-Young,Lee, Jong-Sung,Seol, Guk-Jin,Choi, So-Young,Paeng, Jung-Young,Kim, Jin-Wook Korean Association of Maxillofacial Plastic and Re 2014 Maxillofacial Plastic Reconstructive Surgery Vol.36 No.6
Purpose: Maxillofacial fractures are rapidly increasing from car accidents, industrial accidents, teenaged criminal activity, and sports injuries. Accurate assessment, appropriate diagnosis, and preparing individual treatment plans are necessary to reduce surgical complications. We investigated recent trends of facial bone fracture by period, cause, and type, with the objective of reducing surgical complications. Methods: To investigate time trends of maxillofacial fractures, we reviewed medical records from 2,196 patients with maxillofacial fractures in 1981~1987 (Group A), 1995~1999 (Group B), and 2008~2012 (Group C). We analyzed each group, comparing the number of patients, sex ratio, age, fracture site, and etiology. Results: The number of patients in each period was 418, 516, and 1,262 in Groups A to C. Of note is the increase in the number of patients from Group A to C. The sex ratios were 5.6:1, 3.5:1, and 3.8:1 in Groups A, B, and C. The most affected age group for fracture is 20~29 in all three groups. Traffic accidents are the most common cause in Groups A and B, while there were somewhat different causes of fracture in Group C. Sports-induced facial trauma was twice as high in Group C compared with Group A and B. Mandible fracture accounts for a large portion of facial bone fractures overall. Conclusion: We observed an increase in facial bone fracture patients at Kyungpook National University Dental Hospital over the years. Although facial injury caused by traffic accidents was still a major cause of facial bone fracture in all periods, the percentage decreased. In recent years, isolated mandible fracture increased but mandible and mid-facial complex fracture decreased, possibly because of a reduction in traffic accidents.
Ultrasonic backscatter from rat blood in aggregating media under in vitro rotational flow
Kweon-ho Nam,Dong-guk Paeng,Min Choi IEEE 2009 and Frequency Control Vol.56 No.2
<P>Ultrasonic backscatter from flowing and static rat red blood cells (RBCs) in autologous plasma and in 360 kDa polyvinylpyrrolidone (PVP 360) solution was measured as a function of hematocrit. The flow speed was varied by a stirring magnet in a cylindrical chamber. The radio-frequency (RF) signals backscattered by RBC samples were measured over 5 min in a pulse-echo setup with a 5 MHz focused transducer. Although the intact rat blood has poor RBC aggregability, RBC aggregation of rat blood was enhanced by replacing its plasma with a higher molecular weight polymer solution. The experimental results showed that the nonlinear relationship between hematocrit and ultrasonic backscatter from rat RBCs in plasma and aggregating media is affected by flow speed, which may provide a unified insight into hematocrit dependence of RBC aggregation under flowing and static conditions.</P>