80 citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- University of LisbonPT22 papers
- Instituto Superior TécnicoPT18 papers
- Universidade Nova de LisboaPT5 papers
- Universidade AbertaPT4 papers
- University of MazandaranIR4 papers
- Fundação para a Ciência e TecnologiaPT3 papers
- Ulyanovsk State UniversityRU3 papers
- University of AveiroPT3 papers
- University of DenverUS3 papers
- University of St AndrewsGB3 papers
- University of Mary WashingtonUS2 papers
- Buein Zahra Technical UniversityIR1 paper
28 papers
Limit cycles for dynamic crawling locomotors with periodic prescribed shape
Paolo Gidoni, Alessandro Margheri, Carlota Rebelo
We study the asymptotic behaviour of a family of dynamic models of crawling locomotion, with the aim of characterizing a gait as a limit property. The locomotors, which might have…
A generalised distributed-order Maxwell model
Luis Ferrás, Maria Luisa Morgado, Magda Rebelo
In this work we present a generalised viscoelastic model using distributed-order derivatives. The model consists of two distributed-order elements (distributed springpots) connecte…
Numerical Solution of Variable-Order Fractional Differential Equations Using Bernoulli Polynomials
Somayeh Nemati, Pedro M. Lima, Delfim F. M. Torres
We introduce a new numerical method, based on Bernoulli polynomials, for solving multiterm variable-order fractional differential equations. The variable-order fractional derivativ…
Integrals of groups II
João Araújo, Peter J. Cameron, Carlo Casolo +2
An of a group is a group whose commutator subgroup is isomorphic to . This paper continues the investigation on integrals of groups started in the work arXiv:…
Numerical solution of a class of third-kind Volterra integral equations using Jacobi wavelets
Somayeh Nemati, Pedro M. Lima, Delfim F. M. Torres
We propose a spectral collocation method, based on the generalized Jacobi wavelets along with the Gauss-Jacobi quadrature formula, for solving a class of third-kind Volterra integr…
Variants of epigroups and primary conjugacy
Maria Borralho, Michael Kinyon
In a semigroup with fixed , one can construct a new semigroup called a \emph{variant} by defining . Elements are \emph{primari…
Legendre wavelet collocation method combined with the Gauss--Jacobi quadrature for solving fractional delay-type integro-differential equations
S. Nemati, P. M. Lima, S. Sedaghat
In this work, we present a collocation method based on the Legendre wavelet combined with the Gauss--Jacobi quadrature formula for solving a class of fractional delay-type integro-…
A numerical approach for solving fractional optimal control problems using modified hat functions
Somayeh Nemati, Pedro M. Lima, Delfim F. M. Torres
We introduce a numerical method, based on modified hat functions, for solving a class of fractional optimal control problems. In our scheme, the control and the fractional derivati…
Conjugacy in inverse semigroups
Joao Araujo, Michael Kinyon, Janusz Konieczny
In a group , elements and are conjugate if there exists such that . This conjugacy relation, which plays an important role in group theory, can be…
Association measures for interval variables
M. Rosário Oliveira, Margarida Azeitona, António Pacheco +1
Symbolic Data Analysis (SDA) is a relatively new field of statistics that extends conventional data analysis by taking into account intrinsic data variability and structure. Unlike…
Decidability and Independence of Conjugacy Problems in Finitely Presented Monoids
João Araújo, Michael Kinyon, Janusz Konieczny +1
There have been several attempts to extend the notion of conjugacy from groups to monoids. The aim of this paper is study the decidability and independence of conjugacy problems fo…
Theoretical Foundations of Forward Feature Selection Methods based on Mutual Information
Francisco Macedo, M. Rosário Oliveira, António Pacheco +1
Feature selection problems arise in a variety of applications, such as microarray analysis, clinical prediction, text categorization, image classification and face recognition, mul…
State Sensitivity Evaluation Within UD Based Array Covariance Filters
Julia V. Tsyganova, Maria V. Kulikova
This technical note addresses the UD factorization based Kalman filtering (KF) algorithms. Using this important class of numerically stable KF schemes, we extend its functionality…
Improved Discrete-Time Kalman Filtering within Singular Value Decomposition
Maria V. Kulikova, Julia V. Tsyganova
The paper presents a new Kalman filter (KF) implementation useful in applications where the accuracy of numerical solution of the associated Riccati equation might be crucially red…
Square-root algorithms for maximum correntropy estimation of linear discrete-time systems in presence of non-Gaussian noise
Maria V. Kulikova
Recent developments in the realm of state estimation of stochastic dynamic systems in the presence of non-Gaussian noise have induced a new methodology called the maximum correntro…
An Investment Model with Switching Costs and the Option to Abandon
Mihail Zervos, Carlos Oliveira, Kate Duckworth
We develop a complete analysis of a general entry-exit-scrapping model. In particular, we consider an investment project that operates within a random environment and yields a payo…
Do the Contemporary Cubature and Unscented Kalman Filtering Methods Outperform Always the Traditional Extended Kalman Filter?
G. Yu. Kulikov, M. V. Kulikova
This brief technical note elaborates three well-known state estimators, which are used extensively in practice. These are the rather old-fashioned extended Kalman filter (EKF) and…
Numerical Simulations in Two-Dimensional Neural Fields
Pedro M. Lima, Evelyn Buckwar
In the present paper we are concerned with a numerical algorithm for the approximation of the two-dimensional neural field equation with delay. We consider three numerical examples…
On the Optimal Control of a Class of Non-Newtonian Fluids
Telma Guerra, Jorge Tiago, Adélia Sequeira
We consider optimal control problems of systems governed by stationary, incompressible generalized Navier-Stokes equations with shear dependent viscosity in a two-dimensional or th…
Primitive groups and synchronization
João Araújo, Wolfram Bentz, Peter J. Cameron +2
Let be a set of cardinality , a permutation group on , and a map which is not a permutation. We say that \emph{synchronizes} if the transformation s…
Root Finding by High Order Iterative Methods Based on Quadratures
Mario M. Graça, Pedro M. Lima
We discuss a recursive family of iterative methods for the numerical approximation of roots of nonlinear functions in one variable. These methods are based on Newton-Cotes closed q…
The rank of the semigroup of transformations stabilising a partition of a finite set
Joao Araujo, Wolfram Bentz, J. D. Mitchell +1
Let be a partition of a finite set . We say that a full transformation preserves (or stabilizes) the partition if for all $P\in \mathcal{P…
Constructing numerically stable Kalman filter-based algorithms for gradient-based adaptive filtering
Maria V. Kulikova, Julia V. Tsyganova
This paper addresses the numerical aspects of adaptive filtering (AF) techniques for simultaneous state and parameters estimation arising in the design of dynamic positioning syste…
Probabilistic sampling of finite renewal processes
Nelson Antunes, Vladas Pipiras
Consider a finite renewal process in the sense that interrenewal times are positive i.i.d. variables and the total number of renewals is a random variable, independent of interrene…