Results 1  10
of
30
Region Competition: Unifying Snakes, Region Growing, and Bayes/MDL for Multiband Image Segmentation
 IEEE Transactions on Pattern Analysis and Machine Intelligence
, 1996
"... We present a novel statistical and variational approach to image segmentation based on a new algorithm named region competition. This algorithm is derived by minimizing a generalized Bayes/MDL criterion using the variational principle. The algorithm is guaranteed to converge to a local minimum and c ..."
Abstract

Cited by 778 (21 self)
 Add to MetaCart
We present a novel statistical and variational approach to image segmentation based on a new algorithm named region competition. This algorithm is derived by minimizing a generalized Bayes/MDL criterion using the variational principle. The algorithm is guaranteed to converge to a local minimum and combines aspects of snakes/balloons and region growing. Indeed the classic snakes/balloons and region growing algorithms can be directly derived from our approach. We provide theoretical analysis of region competition including accuracy of boundary location, criteria for initial conditions, and the relationship to edge detection using filters. It is straightforward to generalize the algorithm to multiband segmentation and we demonstrate it on grey level images, color images and texture images. The novel color model allows us to eliminate intensity gradients and shadows, thereby obtaining segmentation based on the albedos of objects. It also helps detect highlight regions. 1 Division of Appli...
Spectral Approximation of Multiplication Operators
 New York J. Math
, 1995
"... . A linear operator on a Hilbert space may be approximated with finite matrices by choosing an orthonormal basis of the Hilbert space. For an operator that is not compact such approximations cannot converge in the norm topology on the space of operators. Multiplication operators on spaces of L 2 fun ..."
Abstract

Cited by 10 (0 self)
 Add to MetaCart
(Show Context)
. A linear operator on a Hilbert space may be approximated with finite matrices by choosing an orthonormal basis of the Hilbert space. For an operator that is not compact such approximations cannot converge in the norm topology on the space of operators. Multiplication operators on spaces of L 2 functions are never compact; for them we consider how well the eigenvalues of the matrices approximate the spectrum of the multiplication operator, which is the essential range of the multiplier. The choice of the orthonormal basis strongly affects the convergence. Toeplitz matrices arise when using the Fourier basis of exponentials exp(ik`). We also consider the basis of Legendre polynomials and the basis of Walsh functions. Contents 1. Introduction 75 2. Multiplication operators 78 2.1. Toeplitz Matrices 78 2.2. Matrices Associated to Legendre Polynomials 78 2.3. WalshToeplitz Matrices 79 3. Spectral Convergence 81 4. Spectral convergence for Toeplitz matrices 83 5. Spectral Convergence wit...
Image Warping for Shape Recovery and Recognition
 Computer Vision and Image Understanding
, 1998
"... We demonstrate that, for a large class of reflectance functions, there is a direct relationship between image warps and the corresponding geometric deformations of the underlying threedimensional objects. This helps explain the hidden geometrical assumptions in object recognition schemes which invo ..."
Abstract

Cited by 2 (2 self)
 Add to MetaCart
(Show Context)
We demonstrate that, for a large class of reflectance functions, there is a direct relationship between image warps and the corresponding geometric deformations of the underlying threedimensional objects. This helps explain the hidden geometrical assumptions in object recognition schemes which involve twodimensional image warping computed by matching image intensity. In addition, it allows us to propose a novel variant of shape from shading which we call shape from image warping. The idea is that the threedimensional shape of an object is estimated by determining how much the image of the object is warped with respect to the image of a known prototype shape. Therefore detecting the image warp relative to a prototype of known shape allows us to reconstruct the shape of the imaged object. We derive properties of these shape warps and illustrate the results by recovering the shapes of faces. 2 Symbols Roman characters in equations. ~a denotes a vector. p b denotes "square root. ...
Region Competition and its Analysis: A Unified Theory for Image Segmentation
, 1995
"... We present a novel statistical and variational approach to image segmentation based on a new algorithm named region competition. This algorithm is derived by minimizing a generalized Bayes/MDL criterion using the variational principle. The algorithm is guaranteed to converge to a local minimum and c ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
(Show Context)
We present a novel statistical and variational approach to image segmentation based on a new algorithm named region competition. This algorithm is derived by minimizing a generalized Bayes/MDL criterion using the variational principle. The algorithm is guaranteed to converge to a local minimum and combines aspects of snakes/balloons and region growing. Indeed the classic snakes/balloons and region growing algorithms can be directly derived from our approach. We provide theoretical analysis of region competition including accuracy of boundary location, criteria for initial conditions, and the relationship to edge detection using filters. It is straightforward to generalize the algorithm to multiband segmentation and we demonstrate it on grey level images, color images and texture images. The novel color model allows us to eliminate intensity gradients and shadows, thereby obtaining segmentation based on the albedos of objects, and it also helps detect highlight regions. A short version ...
A FINITE ELASTIC BODY WITH A CURVED CRACK LOADED IN ANTIPLANE SHEAR
, 1992
"... AhatraetThis paper presents a Boundary Integral Equation Method (BIEM) for an arbitrarily shaped, linearly elastic, homogeneous and isotropic body with a curved crack loaded in antiplane shear. The crack must be modeled as an arc of a circle and wholly inside the solidotherwise its position and o ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
AhatraetThis paper presents a Boundary Integral Equation Method (BIEM) for an arbitrarily shaped, linearly elastic, homogeneous and isotropic body with a curved crack loaded in antiplane shear. The crack must be modeled as an arc of a circle and wholly inside the solidotherwise its position and orientation with respect o the boundary of the body is arbitrary. The effect of the crack on the stress field is incorporated in an augmented kernel developed for the mode III crack problem such that discretization of the cutout boundary is no longer necessary. This modification of the kernel of the integral equation leads to solutions on and near the cutout with great accuracy. An asymptotic analysis is conducted in order to derive the Stress Intensity Factor (SIF) Kin, at each crack tip, in closed form. In this formulation, a straight crack can be viewed as a particular case of the more general curved crack. In particular, attention is paid,to the influence of crack curvature and edge effect on the stress intensity factors at the right and left crack tips. A rigorous mathematical formulation is developed, the main aspects of the numerical implementation are discussed and several representative numerical examples are presented in this paper. a,b B BIEM
A Review Of Infinite Element Methods
, 1999
"... this paper is outlined as follows. In section 2 we present the rigid scattering problem and a derivation of the various IE formulations. Section 3 is devoted to an overview of earlier research work on the IE methodology and more recent contributions are discussed in section 4. The generalization of ..."
Abstract
 Add to MetaCart
this paper is outlined as follows. In section 2 we present the rigid scattering problem and a derivation of the various IE formulations. Section 3 is devoted to an overview of earlier research work on the IE methodology and more recent contributions are discussed in section 4. The generalization of IE to scatterers of general shape are presented in section 5 and we finish the presentation with conclusions in section 6
ANALYSIS AND SUPPRESSION OF INSTABILITIES IN VISCOELASTIC FLOWS By
, 2001
"... The viscoelastic character of polymer solutions and melts gives rise to instabilities that are not seen in the flows of Newtonian liquids. In industrial applications such as coating and extrusion, these socalled “elastic ” instabilities can impose a limitation on the throughput. Hence, it is import ..."
Abstract
 Add to MetaCart
(Show Context)
The viscoelastic character of polymer solutions and melts gives rise to instabilities that are not seen in the flows of Newtonian liquids. In industrial applications such as coating and extrusion, these socalled “elastic ” instabilities can impose a limitation on the throughput. Hence, it is important to understand, and if possible, to suppress them. The first instability we study is the phenomenon of melt fracture, which occurs in the extrusion of polymer melts and takes the form of gross distortions of the surface of the extrudate. This instability is linked to the phenomenon of wallslip, i.e., the velocity of the polymer at the wall relative to the velocity of the wall itself (also called the slip velocity) is nonzero. Several slip relations based on microscopic theories for polymers predict regions in which the slip velocity is multivalued. The expectation is that a multivalued slip relation will result in a multivalued flow curve, which in turn causes melt fracture. Using a simple slip relation, we show that when the dependence of the slip velocity on the pressure is taken into account, this is not necessarily true: a multivalued slip law does not necessarily imply a multivalued flow curve. The second instability we study is the “filament stretching instability, ” which occurs
Table of contents
, 2004
"... Presented in a framework and notation customized for students and professionals who are already familiar with Cartesian analysis in ordinary 3D physical engineering space. ..."
Abstract
 Add to MetaCart
Presented in a framework and notation customized for students and professionals who are already familiar with Cartesian analysis in ordinary 3D physical engineering space.