Search results for "algorithm"
showing 10 items of 4887 documents
An Adaptive Alternating Direction Method of Multipliers
2021
AbstractThe alternating direction method of multipliers (ADMM) is a powerful splitting algorithm for linearly constrained convex optimization problems. In view of its popularity and applicability, a growing attention is drawn toward the ADMM in nonconvex settings. Recent studies of minimization problems for nonconvex functions include various combinations of assumptions on the objective function including, in particular, a Lipschitz gradient assumption. We consider the case where the objective is the sum of a strongly convex function and a weakly convex function. To this end, we present and study an adaptive version of the ADMM which incorporates generalized notions of convexity and penalty…
Analysis a DSP Implementation and Experimental Validation of a Loss Minimization Algorithm Applied to Permanent Magnet Synchronous Motor Drives
2004
In this paper a new loss minimization control algorithm for inverter-fed permanent-magnet synchronous motors (PMSM), which allows to reduce the power losses of the electric drive without penalty on its dynamic performances, is analyzed, experimentally realized and validated. In particular, after a brief recall of two loss minimization control strategies (the "search control" and the "loss-model control"), both a modified dynamic model of the PMSM, which takes into account the iron losses, and a "loss-model" control strategy, are treated. Experimental tests on a specific PMSM drive employing the proposed loss minimization algorithm were performed aiming to validate the actual implementation.…
Time-harmonic solution for acousto-elastic interaction with controllability and spectral elements
2010
The classical way of solving the time-harmonic linear acousto-elastic wave problem is to discretize the equations with finite elements or finite differences. This approach leads to large-scale indefinite complex-valued linear systems. For these kinds of systems, it is difficult to construct efficient iterative solution methods. That is why we use an alternative approach and solve the time-harmonic problem by controlling the solution of the corresponding time dependent wave equation. In this paper, we use an unsymmetric formulation, where fluid-structure interaction is modeled as a coupling between pressure and displacement. The coupled problem is discretized in space domain with spectral el…
R Code for Hausdorff and Simplex Dispersion Orderings in the 2D Case
2010
This paper proposes a software implementation using R of the Hausdorff and simplex dispersion orderings. A copy can be downloaded from http://www.uv.es/~ayala/software/fun-disp.R . The paper provides some examples using the functions exactHausdorff for the Hausdorff dispersion ordering and the function simplex for the simplex dispersion orderings. Some auxiliary functions are commented too.
Experiments with an adaptive Bayesian restoration method
1989
Abstract This paper describes a Bayesian restoration method applied to two-dimensional measured images, whose detector response function is not completely known. The response function is assumed Gaussian with standard deviation depending on the estimate of the local density of the image. The convex hull of the K -nearest neighbours ( K NN) of each ‘on’ pixel is used to compute the local density. The method has been tested on ‘sparse’ images, with and without noise background.
Graph cut-based method for segmenting the left ventricle from MRI or echocardiographic images
2017
International audience; In this paper, we present a fast and interactive graph cut method for 3D segmentation of the endocardial wall of the left ventricle (LV) adapted to work on two of the most widely used modalities: magnetic resonance imaging (MRI) and echocardiography. Our method accounts for the fundamentally different nature of both modalities: 3D echocardiographic images have a low contrast, a poor signal-to-noise ratio and frequent signal drop, while MR images are more detailed but also cluttered and contain highly anisotropic voxels. The main characteristic of our method is to work in a 3D Bezier coordinate system instead of the original Euclidean space. This comes with several ad…
Shape-Based Features for Cat Ganglion Retinal Cells Classification
2002
This article presents a quantitative and objective approach to cat ganglion cell characterization and classification. The combination of several biologically relevant features such as diameter, eccentricity, fractal dimension, influence histogram, influence area, convex hull area, and convex hull diameter are derived from geometrical transforms and then processed by three different clustering methods (Ward’s hierarchical scheme, K-means and genetic algorithm), whose results are then combined by a voting strategy. These experiments indicate the superiority of some features and also suggest some possible biological implications.
A parametric analysis of the transient behavior of lightning protection systems
2005
The paper have the purpose of investigate the influence of different parameters to enable better understanding of the transient performance of complex lightning protection systems (LPS). Lightning discharges constitute the major source of atmospheric or natural noise that can interfere with electric and electronic installations. The electromagnetic characterisation of the LPS environment plays a fundamental role in order to prevent unwanted coupling phenomena that may generate abnormal signals, electric stresses dangerous for the insulation of electric components, disruptive discharges and danger to persons. The model, developed by the authors, is based on a field-approach: the numerical so…
Area-efficient FPGA-based FFT processor
2003
A novel architecture for computing the fast Fourier transform on programmable devices is presented. Main results indicate that the use of one CORDIC operator to perform the multiplication by all the ‘twiddle factors’ sequentially leads to an area saving up to 35% with respect to other cores.
Mammographic images segmentation based on chaotic map clustering algorithm
2013
Background: This work investigates the applicability of a novel clustering approach to the segmentation of mammographic digital images. The chaotic map clustering algorithm is used to group together similar subsets of image pixels resulting in a medically meaningful partition of the mammography. Methods: The image is divided into pixels subsets characterized by a set of conveniently chosen features and each of the corresponding points in the feature space is associated to a map. A mutual coupling strength between the maps depending on the associated distance between feature space points is subsequently introduced. On the system of maps, the simulated evolution through chaotic dynamics leads…