Encontrados 13 documentos, a visualizar página 1 de 2
Automatic Polyp Detection in Pillcam Colon 2 Capsule Images and Videos: Prelimi...
Figueiredo, Pedro N.; Figueiredo, Isabel N.; Prasath, Surya; Tsai, RichardBackground. The aim of this work is to present an automatic colorectal polyp detection scheme for capsule endoscopy. Methods. PillCam COLON2 capsule-based images and videos were used in our study. The database consists of full exam videos from five patients. The algorithm is based on the assumption that the polyps show up as a protrusion in the captured images and is expressed bymeans of a P-value, defined by g...
Image-driven parameter estimation in absorption-diffusion models of chromoscopy
Figueiredo, Isabel N.; Figueiredo, Pedro; Almeida, NunoThe administration of dyes and subsequent examination, with a colorimetry visual criterium, is a gastroenterology procedure for distinguishing, in endoscopic images, normal and aberrant colonic crypts. These are thought to be possible precursors of colon cancer. In this paper a combined image segmentation and parameter estimation model is proposed for in vivo colonic crypts’ images, obtained with chromoscopic c...
A coupled convection-diffusion level set model for tracking epithelial cells in...
Figueiredo, Isabel N.; Leal, Carlos; Leonori, Tommaso; Romanazzi, Giuseppe; Figueiredo, Pedro N.; Donato, M. ManuelColorectal cancer is initiated in colonic crypts as a consequence of alterations leading to the disruption of the normal colonic cellular process. We propose a new model, which couples a convection-di usion type equation with a level set equation, for tracking the time evolution of an epithelial cell set, inside a colonic crypt, until it reaches the top of the crypt. The convection-di usion equation describes t...
A mathematical model for a comprehensive approach to the dynamics of human colo...
Figueiredo, Isabel N.; Figueiredo, Pedro N.; Leal, Carlos; Urbano, José MiguelIn this paper, we propose mathematical models for the growth dynamics of aberrant crypt foci in the human colon, as well as for some of their characteristics, namely the apoptosis and proliferation indices. The models rely on logistic type differential equations and clinical observations at different times, and can arguably be used as an auxiliary screening tool for colon cancer. We report several results using...
Smart plates: reduced models and numerical simulations
Carvalho, José A.; Figueiredo, Isabel N.; Martínez, RebecaIn this paper asymptotic models describing the mechanical and electric equilibrium state of two types of smart structures are presented and justified. The first structure consists of an anisotropic elastic thin plate with two surface bonded anisotropic piezoelectric patches and the second one is an anisotropic elastic sandwich thin plate with an inserted anisotropic piezoelectric patch. The two unknowns of the ...
Frictional contact of an anisotropic piezoelectric plate
Figueiredo, Isabel N.; Stadler, GeorgThe purpose of this paper is to derive and study a new asymptotic model for the equilibrium state of a thin anisotropic piezoelectric plate in frictional contact with a rigid obstacle. In the asymptotic process, the thickness of the piezoelectric plate is driven to zero and the convergence of the unknowns is studied. This leads to two-dimensional Kirchhoff-Love plate equations, in which mechanical displacement ...
A Class of Mathematical Programs with Equilibrium Constraints: A Smooth Algorit...
Figueiredo, Isabel N.; Júdice, Joaquim J.; Rosa, Silvério S.We discuss a special mathematical programming problem with equilibrium constraints (MPEC), that arises in material and shape optimization problems involving the contact of a rod or a plate with a rigid obstacle. This MPEC can be reduced to a nonlinear programming problem with independent variables and some dependent variables implicity defined by the solution of a mixed linear complementarity problem (MLCP). A ...
Actuator effect of a piezoelectric anisotropic plate model
Costa, Lino; Oliveira, Pedro; Figueiredo, Isabel N.; Leal, RogérioThis paper addresses the actuator e ect of a piezoelectric anisotropic plate model, depending on the location of the applied electric potentials, and for di erent clamped boundary conditions. It corresponds to integer optimization problems, whose objective functions involve the displacement of the plate. We adopt the two-dimensional piezoelectric anisotropic nonhomogeneous plate model derived in Figueiredo and ...
Conical differentiability for bone remodeling contact rod models
Figueiredo, Isabel N.; Leal, Carlos F.; Pinto, Cecília S.We prove the conical di erentiability of the solution to a bone remodeling contact rod model, for given data (applied loads and rigid obstacle), with respect to small perturbations of the cross section of the rod. The proof is based on the special structure of the model, composed of a variational inequality coupled with an ordinary di erential equation with respect to time. This structure enables the veri catio...
Shape analysis of an adaptive elastic rod model
Figueiredo, Isabel N.; Leal, Carlos F.; Pinto, Cecília S.We analyse the shape semiderivative of the solution to an asymptotic nonlinear adaptive elastic rod model, derived in Figueiredo and Trabucho [8], with respect to small perturbations of the cross section. Taking advantage of the special structure of this model, which is de ned by generalized Bernoulli-Navier elastic equilibrium equations coupled with an ordinary di erential equation with respect to time, using ...
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