Gradient Descent
Mostrando 1-12 de 24 artigos, teses e dissertações.
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1. A SURVEY ON MULTIOBJECTIVE DESCENT METHODS
We present a rigorous and comprehensive survey on extensions to the multicriteria setting of three well-known scalar optimization algorithms. Multiobjective versions of the steepest descent, the projected gradient and the Newton methods are analyzed in detail. At each iteration, the search directions of these methods are computed by solving real-valued optim
Pesqui. Oper.. Publicado em: 2014-12
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2. Algoritmos Evolutivos aplicados ao Classificador baseado em Segmentos de Reta / Evolutive Algorithms applied to the Straight Line Segment Classifier
During the past years, the use of machine learning techniques have become into one of the most frequently performed tasks, due to the large amount of pattern recognition applications such as: voice recognition, text classification, face recognition, medical image diagnosis, among others. Thus, a great number of techniques dealing with this kind of problem ha
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 03/07/2012
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3. A Review of Gradient Algorithms for Numerical Computation of Optimal Trajectories
Abstract: In this paper, two classic direct methods for numerical computation of optimal trajectories were revisited: the steepest descent method and the direct one based upon the second variation theory. The steepest descent method was developed for a Mayer problem of optimal control, with free final state and fixed terminal times. Terminal constraints on t
J. Aerosp. Technol. Manag.. Publicado em: 2012-06
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4. The global convergence of a descent PRP conjugate gradient method
Recently, Yu and Guan proposed a modified PRP method (called DPRP method) which can generate sufficient descent directions for the objective function. They established the global convergence of the DPRP method based on the assumption that stepsize is bounded away from zero. In this paper, without the requirement of the positive lower bound of the stepsize, w
Computational & Applied Mathematics. Publicado em: 2012
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5. Algoritmo híbrido para projeto de controladores de amortecimento de sistemas elétricos de potência utilizando algoritmos genéticos e gradiente descendente / Hybrid algorithm for damping controller design in electric power systems via genetic algorithms and gradient descent
Os sistemas elétricos de potência são frequentemente submetidos a perturbações causadas, por exemplo, por um aumento súbito de carga ou por um curto-circuito em uma linha de transmissão. Estas perturbações podem gerar oscilações eletromecânicas no sistema, uma vez que a velocidade dos geradores oscila. Para reduzir tais oscilações, controladore
Publicado em: 2011
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6. Estudo de alguns metodos determinsticos de otimização irrestrita / Study of some deterministic methods for unconstrained optimization
In this work some classical methods of linear search for unconstrained optimization are studied. The main mathematical formulations for the optimization problem are presented. Two strategies, linear search and trust region, for the algorithm to move from one iteration to another are discussed. Furthermore, the main considerations about the choice of step len
Publicado em: 2010
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7. New versions of the Hestenes-Stiefel nonlinear conjugate gradient method based on the secant condition for optimization
Based on the secant condition often satisfied by quasi-Newton methods, two new versions of the Hestenes-Stiefel (HS) nonlinear conjugate gradient method are proposed, which are descent methods even with inexact line searches. The search directions of the proposed methods have the form d k = - θkg k + βkHSd k-1, or d k = -g k + βkHSd k-1+ θky k-1. When ex
Computational & Applied Mathematics. Publicado em: 2009
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8. 3D image registration of the human brain / Registro de imagens 3D do cerebro humano
Image Registration is the process that aligns two or more images in a common reference system of spacial coordinates [31]. It is an important problem with several applications in Medical Imaging, enabling, for instance, the analysis of changes in anatomy along time by the registration of images from the same modality, and the study of combined anatomic and p
Publicado em: 2009
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9. Comparação de métodos de otimização para o problema de ajuste de histórico em ambientes paralelos
The process of history matching aims on the determination of the models parameters from a petroleum reservoir. Once adjusted, the models can be used for the prediction of the reservoir behavior. This work presents a comparsion of dierent optimization methods for this problem s solution. Derivative based methods are compared to a genetic algorithm. In particu
Publicado em: 2009
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10. Gait-pattern adaptation algorithms using neural network / Algoritmos de adaptação do padrão de marcha utilizando redes neurais
Este trabalho apresenta o desenvolvimento de algoritmos de adaptação do padrão de marcha com a utilização de redes neurais artificiais para uma órtese ativa para membros inferiores. Trajetórias estáveis são geradas durante o processo de otimização, considerando um gerador de trajetórias baseado no critério do ZMP (Zero Moment Point) e no modelo
Publicado em: 2009
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11. Accelerating the Levenberg-Marquardt method for the minimization of the square of functions with box constraints / Acelerando o metodo de Levenberg-Marquardt para a minimização da soma de quadrados de funções com restrições de caixa
In this work, we present an active set algorithm for minimizing the sum of squares of smooth functions, with box constraints. The algorithm is highly inspired in the work of Birgin and Mart´inez [4]. The differences are concentrated on the chosen search direction and on the use of an acceleration technique to update the step. At each iteration, we define an
Publicado em: 2008
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12. Sobre a velocidade de convergência da filtragem adaptativa IIR. / On the convergence speed of IIR adaptive filtering.
Adaptive filters with infinite impulse response (IIR) can replace with advantages the ones with finite impulse response (FIR). One of these advantages is the reduced number of parameters which leads to a smaller computational complexity giving similar responses. However, the use of adaptive IIR filters has some pratical issue, being the most prominent its sl
Publicado em: 2008