The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
George Vachtsevanos - One of the best experts on this subject based on the ideXlab platform.
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stability analysis of the fuzzy logic controller designed by the Phase Portrait assignment algorithm
IEEE International Conference on Fuzzy Systems, 1993Co-Authors: S S Farinwata, George VachtsevanosAbstract:The authors analyze the stability of a fuzzy logic controller, designed using the Phase Portrait assignment algorithm from a topological point of view. The fuzzy logic controller was designed for a simplified automobile engine which is a two-state dynamic model. The controller was designed using the automatic rule generation technique reported by G.J. Vachtsevanos et al. (1992). The general form of the rule is given. >
Isabelle Herlin - One of the best experts on this subject based on the ideXlab platform.
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Non uniform multiresolution method for optical flow and Phase Portrait models: environmental applications
International Journal of Computer Vision, 1999Co-Authors: Isaac Cohen, Isabelle HerlinAbstract:In this paper we define a complete framework for processing large image sequences for a global monitoring of short range oceanographic and atmospheric processes. This framework is based on the use of a non quadratic regularization technique for optical flow computation that preserves flow discontinuities. We also show that using an appropriate tessellation of the image according to an estimate of the motion field can improve optical flow accuracy and yields more reliable flows. This method defines a non uniform multiresolution approach for coarse to fine grid generation. It allows to locally increase the resolution of the grid according to the studied problem. Each added node refines the grid in a region of interest and increases the numerical accuracy of the solution in this region. We make use of such a method for solving the optical flow equation with a non quadratic regularization scheme allowing the computation of optical flow field while preserving its discontinuities. The second part of the paper deals with the interpretation of the obtained displacement field. For this purpose a Phase Portrait model used along with a new formulation of the approximation of an oriented flow field allowing to consider arbitrary polynomial Phase Portrait models for characterizing salient flow features. This new framework is used for processing oceanographic and atmospheric image sequences and presents an alternative to complex physical modeling techniques.
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Optical Flow and Phase Portrait Methods for Environmental Satellite Image Sequences
1996Co-Authors: Isaac Cohen, Isabelle HerlinAbstract:We present in this paper a motion computation and interpretation framework for oceanographic satellite images. This framework is based on the use of a non quadratic regularization technique in optical flow computation that preserves flow discontinuities. We also show that using an appropriate tessellation of the image according to an estimate of the motion field can improve optical flow accuracy and yields more reliable flows. This method defines a non uniform multiresolution scheme that refines mesh resolution only in the neighborhood of moving structures. The second part of the paper deals with the interpretation of the obtained displacement field. We use a Phase Portrait model with a new formulation of the approximation of an oriented flow field. This allows us to consider arbitrary polynomial Phase Portrait models for characterizing salient flow features. This new framework is used for processing oceanographic and atmospheric image sequences and presents an alternative to the very complex physical modelling techniques.
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Non Uniform Multiresolution Method for Optical Flow and Phase Portrait Models: Environmental Applications
1996Co-Authors: Isaac Cohen, Isabelle HerlinAbstract:In this paper we define a complete framework for processing large image sequences for a global monitoring of short range oceanographic and atmospheric processes. This framework is based on the use of a non quadratic regularization technique in optical flow computation that preserves flow discontinuities. We also show that using an appropriate tessellation of the image according to an estimate of the motion field can improve optical flow accuracy and yields more reliable flows. This method defines a non uniform multiresolution approach for coarse to fine grid generation. It allows to locally increase the resolution of the grid according to the studied problem. Each added node refines the grid in a region of interest and increases the numerical accuracy of the solution in this region. We make use of such a method for solving the optical flow equation with a non quadratic regularization scheme allowing the computation of optical flow field while preserving its discontinuities. The second part of the paper deals with the interpretation of the obtained displacement field. We make use of a Phase Portrait model with a new formulation of the approximation of an oriented flow field allowing to consider arbitrary polynomial Phase Portrait models for characterizing salient flow features. This new framework is used for processing oceanographic and atmospheric image sequences and presents an alternative to complex physical modeling techniques.
Li Jian-qiang - One of the best experts on this subject based on the ideXlab platform.
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Application of Qualitative Reasoning in Rectangular Phase-Portrait Approximation
Computer Science, 2008Co-Authors: Li Jian-qiangAbstract:Abstraction is a dominant approach for verification of hybrid systems; rectangular Phase-Portrait approximation is to construct simpler linear hybrid automaton to over-approximate the original automaton.The key procedure of Phase-Portrait approximation is the decomposition of the control model.In this paper,we adopt qualitative reasoning method to show how to partition the state space with respect to the dynamical property and how to refine the Abstract model.
Pei Hai-long - One of the best experts on this subject based on the ideXlab platform.
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Rectangular Phase-Portrait approximation based on qualitative reasoning
Control theory & applications, 2010Co-Authors: Pei Hai-longAbstract:The core of the rectangular Phase-Portrait approximation is the efficient partition of the control model. The Phase-Portrait approximation based on quality reasoning is proposed. An approach for mode partition is then presented based on the characteristic of the vector field, interesting polynomials and their Lie-derivative. A method for the refinement of the abstract model based on the refined polynomials is also given. Experiment shows that the Phase-Portrait approximation based on the qualitative-reasoning partition obviously reduces the partition number of the mode state space, and enhances the verification efficiency.
Rangaraj M Rangayyan - One of the best experts on this subject based on the ideXlab platform.
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detection of the optic nerve head in fundus images of the retina with gabor filters and Phase Portrait analysis
Journal of Digital Imaging, 2010Co-Authors: Rangaraj M Rangayyan, Fabio J Ayres, Xiaolu Zhu, Anna L EllsAbstract:We propose a method using Gabor filters and Phase Portraits to automatically locate the optic nerve head (ONH) in fundus images of the retina. Because the center of the ONH is at or near the focal point of convergence of the retinal vessels, the method includes detection of the vessels using Gabor filters, detection of peaks in the node map obtained via Phase Portrait analysis, and an intensity-based condition. The method was tested on 40 images from the Digital Retinal Images for Vessel Extraction (DRIVE) database and 81 images from the Structured Analysis of the Retina (STARE) database. An ophthalmologist independently marked the center of the ONH for evaluation of the results. The evaluation of the results includes free-response receiver operating characteristics (FROC) and a measure of distance between the manually marked and detected centers. With the DRIVE database, the centers of the ONH were detected with an average distance of 0.36 mm (18 pixels) to the corresponding centers marked by the ophthalmologist. FROC analysis indicated a sensitivity of 100% at 2.7 false positives per image. With the STARE database, FROC analysis indicated a sensitivity of 88.9% at 4.6 false positives per image.
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detection of the optic disc in images of the retina using gabor filters and Phase Portrait analysis
2009Co-Authors: Rangaraj M Rangayyan, Xiaolu Zhu, Fabio J AyresAbstract:We propose a method using Gabor filters and Phase Portraits to locate automatically the optic disc (OD) in fundus images of the retina. Based on the property that the OD appears as the focal point of convergence of the blood vessels of the retina, the method includes detection of the blood vessels using Gabor filters, and the detection of peaks in the node map via Phase Portrait analysis. Additional conditions are applied based upon the intensity characteristics of fundus images and the OD. Forty images from the DRIVE database were used to evaluate the performance of the proposed method. The OD was successfully detected in all of the 40 images.
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reduction of false positives in the detection of architectural distortion in mammograms by using a geometrically constrained Phase Portrait model
Computer Assisted Radiology and Surgery, 2007Co-Authors: Fabio J Ayres, Rangaraj M RangayyanAbstract:Objective One of the commonly missed signs of breast cancer is architectural distortion. We have developed techniques for the detection of architectural distortion in mammograms, based on the analysis of oriented texture through the application of Gabor filters and a linear Phase Portrait model. In this paper, we propose constraining the shape of the general Phase Portrait model as a means to reduce the false-positive rate in the detection of architectural distortion.
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optimization procedures for the estimation of Phase Portrait parameters of orientation fields
electronic imaging, 2006Co-Authors: Fabio J Ayres, Rangaraj M RangayyanAbstract:Oriented patterns in an image often convey important information regarding the scene or the objects contained. Given an image presenting oriented texture, the orientation field of the image is a map that depicts the orientation angle of the texture at each pixel. Rao and Jain developed a method to describe oriented patterns in an image based on the association between the orientation field of a textured image and the Phase Portrait generated by a pair of linear first-order differential equations. The estimation of the model parameters is a nonlinear, nonconvex optimization problem, and practical experience shows that irrelevant local minima can lead to convergence to inappropriate results. We investigated the performance of four optimization algorithms for the estimation of the optimal Phase Portrait parameters for a given orientation field. The investigated algorithms are: nonlinear least-squares, linear least-squares, iterative linear least-squares, and simulated annealing. The algorithms are evaluated and compared in terms of the error between the estimated parameters and the parameters known by design, in the presence of noise in the orientation field and imprecision in the initialization of the parameters. The computational effort required by each algorithm is also assessed. Individually, the simulated annealing procedure yielded low fixed-point and parameter errors over the entire range of noise tested, whereas the performance of the other methods deteriorated with higher levels of noise. The use of the result of simulated annealing for the initialization of the nonlinear least-squares method led to further improvement upon the simulated annealing results.
