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    Pattern detection for toolpath generation on triangular meshes for 5-axis CNC machining
    (2020-01-01)
    Dang, Le V.
    ;
    Moodleah, Samart
    ;
    Makhanov, Stanislav S.
    Toolpath generation for freeform triangular meshes for 5-axis milling machines using an optimal feeding direction (OFD) field is an important topic in subtractive manufacturing technology. By considering parameters in both the CAD and the CAM stages, there exists a direction(s) at every cutter contact (CC) point, such that the machining efficiency is maximal. The directions could form a special structure which can be detected for toolpath generation on the CAD stage. In this paper, a novel toolpath generation method is proposed to create a toolpath for freeform triangular meshes by detecting regular structures of the OFD in the parametric domain using moment invariants. Three common templates, corresponding to standard toolpath structures, are considered: (1) curl (contour/spiral contour path), (2) star/spiral (radial path), and (3) shear (zigzag path). Mesh parameterization is used to flatten the 3D triangulated surface. A transfinite interpolation (TFI) is utilized to construct the toolpath on the flattened surface. The final toolpath is then obtained by the inverse map. The proposed method has been compared with conventional and standard commercial toolpaths. Numerical results show that the pattern detection algorithm helps to find an appropriate toolpath strategy. The generated toolpaths follow the OFDs closer than the competing methods, and therefore, require shorter machining time.
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    Image retrieval using connected color region and moment invariants
    (2007-12-01)
    Dongphontong, Daungkamol
    ;
    Chitsobhuk, Orachat
    In this paper, combined descriptors of Connected Color Region (CCR) and moment invariants are proposed as color features for a Content-Based Image Retrieval system. CCR provides the spatial information and maximum co-occurrence color while moment invariants help to better distinguish different distribution of colors in the image. From the experiments, the retrieval results using only CCR descriptors depend on CCR block size. The smaller the size of the block, the higher the retrieval performance. However, if the block size is small, it requires longer retrieval time. Therefore, in this paper, color moment is introduced as additional feature to CCR descriptors to help compromising between retrieval performance and time. The retrieval results using both CCR with large block size and moment descriptors are comparable to those of using only CCR with small block size while require less amount of retrieval time.