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방사선사진용 디지털 영상시스템의 정량적 평가에 관한 실험적 연구
조형희,김은경,Cho Heang-Hee,Kim Eun-Kyung 대한영상치의학회 1994 Imaging Science in Dentistry Vol.24 No.1
A digital imaging system using Machintosh Ⅱ ci computer, high resolution Sony XC-77 CCD camera, Quickcapture Frame Grabber Board was evaluated for quantitative analysis of standardized periapical film with aluminum step wedge. The results were as follows: 1. Correlation between Al thickness and gray level was high-positively associated(r²=0.99, p<0.001). 2. Correlation between measured weight of experimental lesion and estimated relative lesion volume by digital subtracted radiography was also high-positively associated (r²=0.98, p<0.001). 3. As exposure time was increased, mean gray level was decreased(p<0.01) and slope of regression line between Al thickness and gray level was also decreased (p<0.01). And when the exposure time was shorter than 0.2 second, the value of r² was relatively low. On the basis of the above results, it is considered that this digital imaging system using a Macintosh Ⅱ ci computer & a high resolution CCD monochrome camera will be useful in evaluating digitized image from standardized periapical film quantitatively.
조형희,Jo, Hyeong-Hui 한국과학기술단체총연합회 2000 과학과 기술 Vol.33 No.8
지난 5월 8일부터 4일간 독일 뮌헨에서 열린 제45차 터보 엑스포 2000은 가스터빈의 개발 및 신기술에 대한 정보교환을 목적으로 전 세계에서 2천여명이 참석하여 6백70여편의 논문발표와 2백여 회사가 참가한 전시회 및 22session에서의 가스터빈 사용자 심포지엄으로 개최되었다. 제46차 학술대회는 2001년 6월초에 미국 뉴올리안즈에서 개최될 예정이다.
이차 냉각 유로를 가진 회전덕트에서 열/물질전달 특성 (I)
조형희,김경민,김상인,김윤영,이동호 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.8
The heat/mass transfer characteristics in a rotating two-pass duct with and without rib turbulators are investigated in the present study. The square duct has a hydraulic diameter (Dh) of 26.7 mm, and 1.5 mm×1.5 mm square 90°-rib turbulators are attached on the leading and trailing walls. The pitch-to-rib height ratio (p/e) is 10. The Reynolds number based on the hydraulic diameter is kept constant at 10,000 to exclude the Reynolds effect, and the rotation number is varied from 0.0 to 0.20. In the smooth duct, the curvature of the 180°-turn produces Dean vortices that enhance heat/mass transfer in the post-turn region. When rib turbulators are installed, heat/mass transfer is augmented 2.5 times higher than that of the smooth duct since the main flow is turbulated by reattaching and separating in the vicinity of the duct surfaces. The duct rotation results in heat/mass transfer discrepancy so that Sherwood number ratios are higher on the trailing surface in the first-pass and on the leading surface in the second-pass. In the turning region, Dean vortices shown in the stationary case transform into one large asymmetric vortex cell, and subsequent heat/mass transfer characteristics also change. As the rotation number increases, the heat/mass transfer discrepancy enlarges.