• 정보보호학회논문지
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• 제17권6호
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• pp.131-142
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• 2007

본 연구에서는 쾌속조형시스템의 요구사항에 부합되는 Semi-fragile 워터마킹 알고리즘을 제안한다. 쾌속조형시스템은 높은 정밀도를 요구하기 때문에 원본에 시각적인 변화를 주거나 왜곡을 할 경우, 출력물인 시제품에 큰 영향을 미친다. 따라서 이동, 회전, 신축과 같은 기하학적 변환이나 메쉬의 순서를 변경하는 변환, 파일 포맷 변환은 모델의 기본 형태를 변화시키지 않기 때문에 많이 사용되지만, 모델의 기본 형태를 변환시키는 데시메이션, 평활화 등은 사용하지 않는다. 제안된 알고리즘은 쾌속조형시스템의 이러한 제약을 고려하여 기하학적인 변환이나 메쉬 순서정렬, 파일 포맷 변환에는 강인하지만 그 외 변환에는 취약한 Semi-fragile 워터마킹 알고리즘이다. 제안한 워터마킹 알고리즘은 워터마크 정보의 삽입 전후 모델의 형태가 변하지 않으며, 쾌속조형시스템과 같은 고정밀도를 요구하는 기계공학 분야에서 데이터의 무결성 인증목적으로 사용할 수 있으며, 정보은닉 용도로도 사용할 수 있다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.185-185
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• 2011

Mapping of artificial levee lines, one of major tasks in river zone mapping, is critical to prevention of river flood, protection of environments and eco systems in river zones. Thus, mapping of artificial levee lines is essential for management and development of river zones. Coastal mapping including river zone mapping has been historically carried out using surveying technologies. Photogrammetry, one of the surveying technologies, is recently used technology for national river zone mapping in Korea. Airborne laser scanning has been used in most advanced countries for coastal mapping due to its ability to penetrate shallow water and its high vertical accuracy. Due to these advantages, use of LiDAR data in coastal mapping is efficient for monitoring and predicting significant topographic change in river zones. This paper introduces a method for construction of a 3D artificial levee line using a set of LiDAR points that uses normal vectors. Multiple steps are involved in this method. First, a 2.5-dimensional Delaunay triangle mesh is generated based on three nearest-neighbor points in the LiDAR data. Second, a median filtering is applied to minimize noise. Third, edge selection algorithms are applied to extract break edges from a Delaunay triangle mesh using two normal vectors. In this research, two methods for edge selection algorithms using hypothesis testing are used to extract break edges. Fourth, intersection edges which are extracted using both methods at the same range are selected as the intersection edge group. Fifth, among intersection edge group, some linear feature edges which are not suitable to compose a levee line are removed as much as possible considering vertical distance, slope and connectivity of an edge. Sixth, with all line segments which are suitable to constitute a levee line, one river levee line segment is connected to another river levee line segment with the end points of both river levee line segments located nearest horizontally and vertically to each other. After linkage of all the river levee line segments, the initial river levee line is generated. Since the initial river levee line consists of the LiDAR points, the pattern of the initial river levee line is being zigzag along the river levee. Thus, for the last step, a algorithm for smoothing the initial river levee line is applied to fit the initial river levee line into the reference line, and the final 3D river levee line is constructed. After the algorithm is completed, the proposed algorithm is applied to construct the 3D river levee line in Zng-San levee nearby Ham-Ahn Bo in Nak-Dong river. Statistical results show that the constructed river levee line generated using a proposed method has high accuracy in comparison to the ground truth. This paper shows that use of LiDAR data for construction of the 3D river levee line for river zone mapping is useful and efficient; and, as a result, it can be replaced with ground surveying method for construction of the 3D river levee line.