• The Journal of the Korea Contents Association
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• v.4 no.3
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• pp.91-97
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• 2004

Difference image scheme is widely used for motion estimation in moving object tracking system. This scheme contains a binarization step which segments image into background and moving object regions, referring to threshold value. In this paper, we propose a decision algorithm of tracking the threshold value with a differential image. The key idea is analyzing the histogram of the differential image. In addition we evaluate the performance of this method in comparison with conventional scheme. As an experimental result with 60 images, it is found that threshold by the proposed algorithm is very close to optimal threshold selected manually.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.396-400
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• 2004

In this study, we have proposed the tracking system of single moving object. The tracking system was estimated motion using differential image, and than track the moving object by controlled Pan/Tilt device of camera. Proposed tracking system is devided into image acquisition and preprocessing phase, motion estimation phase and object tracking phase. To estimation the motion, differential image method was used. In the binary differential image, decision of threshold value was used adaptive method. And in grouping the object area, block_based recursive labeling algorithm was used. As a result of experiment, motion of moving object can be estimated. The result of tracking, object was not lost and object was tracked correctly.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.617-620
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• 2010

최근 고성능 모바일 단말기와 다양한 컨텐츠가 등장하면서 유비쿼터스 환경에서의 사용자 인터페이스에 대한 관심이 높아지고 있다. 특히 모바일 프로젝터는 장소의 제한을 받지 않고 큰 화면을 다른 사람과 공유할 수 있는 장점이 있는 반면에 단말기를 직접 제어해야 하는 불편함이 있다. 본 논문에서는 모바일 환경에서 카메라를 통해 입력된 영상 정보만으로 사용자가 스크린에 비추는 레이저 포인터를 실시간으로 검출하는 알고리즘을 제안한다. 제안하는 알고리즘은 색상 감지와 움직임 감지로 나뉜다. 단일 프레임에서 영상 성분의 평균을 이용한 조건을 검사하여 레이저 포인터 색상 영역을 검출하고, 인접한 프레임과 현재 프레임과의 차를 구하며 그 차이가 임계값보다 큰 영역을 움직임 영역으로 검출한다. 마지막으로 색상 검출 영역과 움직임 검출 영역을 동시에 만족하는 영역을 최종적으로 레이저 포인터 영역으로 인식한다. 본 기법은 영상 정보만 사용하기 때문에 센서나 불필요한 장비를 착용할 필요가 없고 영상 성분 평균을 이용하므로 프로젝터 성능에 따른 조도의 변화에 강건하여 효과적인 레이저 포인터 검출이 가능하다. 실험결과는 주변 조명의 밝기에 따라 차이가 있지만 대부분 80% 이상의 검출률과 16% 미만의 오검출률의 성능으로 나타났고, 이 같은 결과는 사용자의 주관적인 만족을 보장하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.3
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• pp.237-246
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• 2020

Recently, as high resolution satellites data have been serviced, frequent DSM (Digital Surface Model) generation over urban areas has been possible. In addition, it is possible to detect changes using a high-resolution DSM at building level such that various methods of building change detection using DSM have been studied. In order to detect building changes using DSM, we need to generate a DSM using a stereo satellite image. The change detection method using D-DSM (Differential DSM) uses the elevation difference between two DSMs of different dates. The D-DSM method has difficulty in applying a precise vertical threshold, because between the two DSMs may have elevation errors. In this study, we focus on the urban structure change detection using D-nDSM (Differential nDSM) based on nDSM (Normalized DSM) that expresses only the height of the structures or buildings without terrain elevation. In addition, we attempted to reduce noise using a morphological filtering. Also, in order to improve the roadside buildings extraction precision, we exploited the urban road network extraction from nDSM. Experiments were conducted for high-resolution stereo satellite images of two periods. The experimental results were compared for D-DSM, D-nDSM, and D-nDSM with road extraction methods. The D-DSM method showed the accuracy of about 30% to 55% depending on the vertical threshold and the D-nDSM approaches achieved 59% and 77.9% without and with the morphological filtering, respectively. Finally, the D-nDSM with the road extraction method showed 87.2% of change detection accuracy.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.309-316
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• 2009

Purpose: F-18 FDG can be accumulated in the liver, bowel, kidney, urinary tract, and muscles physiologically. The aim of this study was to evaluate the clinical value of dual time point 18F-FDG PET /8 imaging for the differentiation of the colonic focal uptake lesions. Materials and Methods: One hundred thirty two patients (M:F = 77:55, Age 62.8$\pm$11.6 years) underwent $^{18}$F-FDG PET/CT at two time points, prospectively: early image at 50-60 min and delayed image at 4-4.5 hours after the intravenous injection of $^{18}$F-FDG. Focally increased uptake lesions on early images but disappeared or shifted on delayed images defined a physiological uptake. For the differential evaluation of persistent focal uptake lesions on delayed images, colonoscopy and histopathologic examination were performed. SUVmax changes between early and delayed images were also compared. Results: Among the 132 patients, 153 lesions of focal colonic uptake were detected on early images of $^{18}$F-FDG PET/CT. Of these, 72 (47.1%) lesions were able to judge with physiological uptake because the focal increased uptake disappeared from delayed image. Among 81 lesions which was showed persistent increased uptake in delayed image, 61 (75.3%) lesions were confirmed as the malignant tumor and 14 (17.3%) lesions were confirmed as the benign lesions including adenoma and inflammatory disease. Remaining 6 (7.4%) lesions were confirmed as the physiological uptake because there was no particular lesion in the colonoscopy. In the malignant lesions, the calculated dual time point change for SUVmax ($\Delta$%SUVmax) was 20.8$\pm$18.7%, indicating a significant increase in SUVmax between the two point (p<0.01). In contrast, the change in SUVmax for the non-malignant lesions including benign lesions and physiological uptake was -13.7%$\pm$24.2%. For the differentiation of the malignant and non-malignant focal colonic uptake lesions, $\Delta$%SUVmax was the most effective parameter, and the cut-off value using -5% provided the best sensitivity, specificity, and accuracy. Conclusion: The dual time point $^{18}$F-FDG PET/CT imaging with SUVmax change evaluation could be an important noninvasive method for the differentiation of malignant and benign focal colonic uptake lesions including physiologic uptake.