The Experts below are selected from a list of 4128 Experts worldwide ranked by ideXlab platform
Y. Sambonsugi - One of the best experts on this subject based on the ideXlab platform.
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Self-Affine Mapping system and its application to object contour extraction
IEEE Transactions on Image Processing, 2000Co-Authors: Y. SambonsugiAbstract:A self-Affine Mapping system which has conventionally been used to produce fractal images is used to fit rough lines to contours. The self-Affine map's parameters are detected by analyzing the blockwise self-similarity of a grayscale image using a simplified algorithm in fractal encoding. The phenomenon that edges attract Mapping points in self-Affine Mapping is utilized in the proposed method. The boundary of the foreground region of an alpha mask is fitted by Mapping iterations of the region. It is shown that the proposed method accurately produces not only smooth curves but also sharp corners, and has the ability to extract both distinct edges and blurred edges using the same parameter. It is also shown that even large gaps between the hand-drawn line and the contour can be fitted well by the recursive procedure of the proposed algorithm, in which the block size is progressively decreased. These features reduce the time required for drawing contours by hand.
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self Affine Mapping system for object contour extraction
International Conference on Image Processing, 1999Co-Authors: Takashi Ida, Y. SambonsugiAbstract:A self-Affine Mapping system which has conventionally been used to produce a fractal image is used to fit the rough line to the contour. The self-Affine map's parameters are detected by analyzing blockwise self-similarity of a grayscale image using a simplified algorithm in fractal encoding. It is also shown that even large gaps between the hand-drawn line and the contour can be fitted well by the recursive procedure of the proposed algorithm, in which the block size is progressively decreased. The proposed method produces not only smooth curves but also sharp corners.
Sun Gang - One of the best experts on this subject based on the ideXlab platform.
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security region based real and reactive power optimization of power systems
Proceedings of the CSEE, 2006Co-Authors: Sun GangAbstract:An approach is presented to optimize real and reactive power in power system. In order to develop the proposed model of optimal power flow (OPF),the concepts of static security regions which is defined as the set of consisting of all injection points that satisfy the power flow constraints (bus voltage constraints of nodes and branch thermal limit constraints and generating limits),static voltage stability region,and dynamic security region to guarantee the transient stability constraints for a certain network configuration or a certain changing process of network configuration are included into the OPF formulation. The properties of Affine Mapping between branches angles and real power,voltage magnitudes of buses and reactive power injections in network are used. The quadratic optimization is used to solve the OPF. The 10 machine 39 bus New England system is used to show the effectiveness of the proposed algorithm.
Eichhardt Iván - One of the best experts on this subject based on the ideXlab platform.
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A differential geometry approach to camera-independent image correspondence
Academic Press, 2018Co-Authors: Molnár József, Eichhardt IvánAbstract:Projective geometry is a standard mathematical tool for image-based 3D reconstruction. Most reconstruction methods establish pointwise image correspondences using projective geometry. We present an alternative approach based on differential geometry using oriented patches rather than points. Our approach assumes that the scene to be reconstructed is observed by any camera, existing or potential, that satisfies very general conditions, namely, the differentiability of the surface and the bijective projection functions. We show how the notions of the differential geometry such as diffeomorphism, pushforward and pullback are related to the reconstruction problem. A unified theory applicable to various 3D reconstruction problems is presented. Considering two views of the surface, we derive reconstruction equations for oriented patches and pose equations to determine the relative pose of the two cameras. Then we discuss the generalized epipolar geometry and derive the generalized epipolar constraint (compatibility equation) along the epipolar curves. Applying the proposed theory to the projective camera and assuming that Affine Mapping between small corresponding regions has been estimated, we obtain the minimal pose equation for the case when a fully calibrated camera is moved with its internal parameters unchanged. Equations for the projective epipolar constraints and the fundamental matrix are also derived. Finally, two important nonlinear camera types, the axial and the spherical, are examined. © 2018 Elsevier Inc
Ivan Eichhardt - One of the best experts on this subject based on the ideXlab platform.
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a differential geometry approach to camera independent image correspondence
Computer Vision and Image Understanding, 2018Co-Authors: Jozsef Molnar, Ivan EichhardtAbstract:Abstract Projective geometry is a standard mathematical tool for image-based 3D reconstruction. Most reconstruction methods establish pointwise image correspondences using projective geometry. We present an alternative approach based on differential geometry using oriented patches rather than points. Our approach assumes that the scene to be reconstructed is observed by any camera, existing or potential, that satisfies very general conditions, namely, the differentiability of the surface and the bijective projection functions. We show how the notions of the differential geometry such as diffeomorphism, pushforward and pullback are related to the reconstruction problem. A unified theory applicable to various 3D reconstruction problems is presented. Considering two views of the surface, we derive reconstruction equations for oriented patches and pose equations to determine the relative pose of the two cameras. Then we discuss the generalized epipolar geometry and derive the generalized epipolar constraint (compatibility equation) along the epipolar curves. Applying the proposed theory to the projective camera and assuming that Affine Mapping between small corresponding regions has been estimated, we obtain the minimal pose equation for the case when a fully calibrated camera is moved with its internal parameters unchanged. Equations for the projective epipolar constraints and the fundamental matrix are also derived. Finally, two important nonlinear camera types, the axial and the spherical, are examined.
Xevi Roca - One of the best experts on this subject based on the ideXlab platform.
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defining quality measures for high order planar triangles and curved mesh generation
IMR, 2011Co-Authors: Xevi Roca, Abel Gargallopeiro, Josep SarrateAbstract:We present a technique to extend any Jacobian based quality measure for linear elements to high-order isoparametric planar triangles of any interpolation degree. The extended quality measure is obtained as the inverse of the distortion of the high-order element with respect to an ideal element. To measure the high-order distortion, we integrate on the curved element the inverse of the Jacobian based quality measure. Thus, we can proof that if the Jacobian based quality is invariant under a particular Affine Mapping, then the resulting quality measure is also invariant under that Mapping. In addition, we check that the quality measure detects non-valid and low-quality high-order elements. Finally, we present and test an approach to generate curved meshes by minimizing the high-order distortion measure of the elements.
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A new least-squares approximation of Affine Mappings for sweep algorithms
Engineering with Computers, 2009Co-Authors: Xevi Roca, Josep Sarrate, Antonio HuertaAbstract:This paper presents a new algorithm to generate hexahedral meshes in extrusion geometries. Several algorithms have been devised to generate hexahedral meshes by projecting the cap surfaces along a sweep path. In all of these algorithms the crucial step is the placement of the inner layer of nodes. That is, the projection of the source surface mesh along the sweep path. From the computational point of view, sweep methods based on a least-squares approximation of an Affine Mapping are the fastest alternative to compute these projections. Several functionals have been introduced to perform the least-squares approximation. However, for very simple and typical geometrical configurations they may generate low-quality projected meshes. For instance, they may induce skewness and flattening effects on the projected discretizations. In addition, for these configurations the minimization of these functionals may lead to a set of normal equations with singular system matrix. In this work we analyze previously defined functionals. Based on this analysis we propose a new functional and show that its minimization overcomes these drawbacks. Finally, we present several examples to assess the properties of the proposed functional.