Now showing items 1-20 of 96

• #### A chaotic secure communication scheme based on duffing oscillators and frequency estimation ﻿

(2013)
Conference report
Open Access
This work presents a new technique to securely transmit and retrieve a message signal via chaotic systems. In our system, a two-valued message signal modulates the frequency of a Duffing oscillator sinusoidal term. An ...
• #### A characterization of isochronous centres in terms of symmetries ﻿

(2000)
Article
Open Access
We present a description of isochronous centres of planar vector fields $X$ by means of their groups of symmetries. More precisely, given a normalizer $U$ of $X$ (i.e., $[X,U]=\mu X$, where $\mu$ is a scalar function), we ...

(2009)
Article
Open Access
• #### Adaptive backstepping control of a class of hysteretic systems ﻿

(SPIE Press. The International Society for Optical Engineering, 2003-08-01)
Part of book or chapter of book
Open Access
A backstepping-based adaptive control is designed for a class of one degree of freedom hysteretic system. The true hysteretic behavior does not need to be known for the controller design. A polynomial description is assumed ...
• #### Adiabatic invariant of the harmonic oscillator, complex matching and resurgence ﻿

(1997)
Article
Open Access
The linear oscillator equation with a frequency depending slowly on time is used to test a method to compute exponentially small quantities. This work present the matching method in the complex plane as a tool to obtain ...
• #### A logistic queue model for network traffic modeling and simulation ﻿

(Universitat Politècnica de Catalunya, 2017-07)
Master thesis
Open Access
In this work we present a continuous queuing model called the logistic queue model. We show that in terms of queue size and outflow prediction, our model is as precise as a discrete event simulator with the additional ...
• #### An analytic-numerical method of computation of the Liapunov and period constants derived from their algebraic structure ﻿

(1996)
Article
Open Access
We consider the problem of computing the Liapunov and the period constants for a smooth differential equation with a non degenerate critical point. First, we investigate the structure of both constants when they are ...
• #### A new algorithm for finding rational first integrals of polynomial vector fields ﻿

(2009-05)
External research report
Open Access
We present a new method to compute rational first integrals of a planar polynomial vector field. The algorithm is in general much faster than the usual methods and also allows to compute the remarkable curves associated ...
• #### An explicit expression of the first Liapunov and period constants with applications ﻿

(1996)
Article
Open Access
In this paper, we study systems in the plane having a critical point with pure imaginary eigenvalues, and we search for effective conditions to discern whether this critical point is a focus or a center; in the case of it ...

(2001)
Article
Open Access
• #### Bifurcation at complex instability ﻿

(1995)
Article
Open Access
In an autonomous Hamiltonian system with three or more degrees of freedom, a family of periodic orbits may become unstable when two pairs of characteristic multipliers coallesce on the unit circle at points not equal to ...
• #### Boundary value problems for Schrödinger operators on a Path Associated to Orthogonal Polynomials ﻿

(Springer, 2013)
Part of book or chapter of book
Restricted access - publisher's policy
In this work, we concentrate on determining explicit expressions, via suitable orthogonal polynomials on the line, for the Green function associated with any regular boundary value problem on a weighted path, whose weights ...
• #### Bounded and dissipative solutions of the Bouc-Wen model for hysteretic structural systems ﻿

(2004-06)
Part of book or chapter of book
Open Access
The aim of this paper is to give the conditions on the hysteretic Bouc-Wen model so that (i) it has the property of being bounded input bounded output (BIBO), and (ii) it dissipates energy (or is passive). This study leads ...
• #### Breakdown of heteroclinic orbits for analytic unfoldings of the hopf-zero singularity. The singular case ﻿

(2011)
External research report
Open Access
In this paper we prove the breakdown of an heteroclinic connection in the analytic versal unfoldings of the generic Hopf-Zero singularity. This heteroclinic orbit appears at any order if one performs the normal form around ...
• #### Centers and uniform isochronous centers of planar polynomial differential systems ﻿

(2018-09)
Article
Restricted access - publisher's policy
For planar polynomial vector fields of the form (-y+X(x,y))¿¿x+(x+Y(x,y))¿¿y, where X and Y start at least with terms of second order in the variables x and y, we determine necessary and sufficient conditions under which ...
• #### Centre and isochronicity conditions for systems with homogeneous nonlinearities ﻿

(1995)
Article
Open Access
We study the centre-focus problem for systems with homogeneous nonlinearities. In the centre case we study the characterization of the isochronous centres. More explicitly, we derive six necessary conditions to be a ...
• #### Condiciones de contorno en modelos de gradiente con desplazamientos suavizados ﻿

(2012)
Article
Open Access
Los modelos de gradiente basados en desplazamientos suavizados son una alternativa a los modelos est´andares para simular num´ericamente el proceso de fallo de materiales. En esta formulaci´on alternativa coexisten los ...
• #### Constraint algorithm for extremals in optimal control problems ﻿

(2007-07-27)
Article
Open Access
A characterization of different kinds of extremals of optimal control problems is given if we take an open control set. A well known constraint algorithm for implicit differential equations is adapted to the study of ...
• #### Continua of periodic points for planar integrable rational maps ﻿

(Research India Publications, 2016-09)
Article
Open Access
We present three alternative methodologies to find continua of periodic points with a prescribed period for rational maps having rational first integrals. The first two have been already used by other authors and apply ...
• #### Continua of periodic points for planar integrable rational maps. ﻿

(2015-11-30)
External research report
Open Access
We present three alternative methodologies to find continua of periodic points with a prescribed period for rational maps having rational first integrals. The first two have been already used for other authors and apply ...