Vicente Perez-Munuzuri - Academia.edu (original) (raw)
Papers by Vicente Perez-Munuzuri
Remote Sensing, 2021
Wave energy resource assessment is crucial for the development of the marine renewable industry. ... more Wave energy resource assessment is crucial for the development of the marine renewable industry. High-frequency radars (HF radars) have been demonstrated to be a useful wave measuring tool. Therefore, in this work, we evaluated the accuracy of two CODAR Seasonde HF radars for describing the wave energy resource of two offshore areas in the west Galician coast, Spain (Vilán and Silleiro capes). The resulting wave characterization was used to estimate the electricity production of two wave energy converters. Results were validated against wave data from two buoys and two numerical models (SIMAR, (Marine Simulation) and WaveWatch III). The statistical validation revealed that the radar of Silleiro cape significantly overestimates the wave power, mainly due to a large overestimation of the wave energy period. The effect of the radars’ data loss during low wave energy periods on the mean wave energy is partially compensated with the overestimation of wave height and energy period. The th...
Physical Review E
The onset of viscous fingering in the presence of a viscosity profile is investigated theoretical... more The onset of viscous fingering in the presence of a viscosity profile is investigated theoretically for two immiscible fluids undergoing a time-dependent injection. Here, we show that the presence of a positive viscosity gradient at the interface between both fluids stabilizes the interface facilitating the spread of the perturbation. This effect is much more pronounced in the case of sinusoidal injection flows. The influence of the viscosity gradient on the dispersion relation is analyzed. Numerical simulations of the Navier-Stokes equation confirm the linear stability analysis.
International Journal of Bifurcation and Chaos, 2000
A synchronization scheme through compound chaotic signal is analyzed both numerically and experim... more A synchronization scheme through compound chaotic signal is analyzed both numerically and experimentally to study the performance of this scheme, in a noisy environment, considering its possibilities for communication systems with masking technique. The influence of noise has been analyzed in terms of the Bit Error Rate. An important factor of this method is the use of encryption keys which add more robustness and complexity to the system.
International Journal of Bifurcation and Chaos, 2003
Nucleation from a boundary is experimentally and numerically studied in a one-dimensional array i... more Nucleation from a boundary is experimentally and numerically studied in a one-dimensional array in two excitable media consisting of Chua's circuits and the Oregonator model, respectively. Forcing from a boundary with a pulse of constant amplitude and infinite duration gives rise to a periodic wave train propagating through the array. As the amplitude of the pulse increases, wave period evolves to chaos through a period doubling cascade.
International Journal of Bifurcation and Chaos, 2001
The influence of spatiotemporal colored noise on wave train propagation in nonexcitable media is ... more The influence of spatiotemporal colored noise on wave train propagation in nonexcitable media is investigated. This study has been performed within the framework of the Oregonator model in terms of the characteristic noise parameters. Some features seen in single front propagation, like noise induced propagation facilitation for an optimal level of the noise intensity, are also found for periodic wave trains. The main new effect is, however, an enhancement of propagation for correlation times of the noise of the order of the period of the wave train.
International Journal of Bifurcation and Chaos, 2001
The behavior of diffusively coupled Rössler oscillators parametrically perturbed with an Ornstein... more The behavior of diffusively coupled Rössler oscillators parametrically perturbed with an Ornstein–Uhlenbeck noise is analyzed in terms of the degree of synchronization between the cells. A resonance-like behavior is found as a function of the noise correlation time, instead of the noise intensity as it occurs in the typical stochastic resonance. A power law scaling between the "optimum" correlation time with regard to synchronization and the deterministic time scale of the oscillators has been obtained, with an exponent that depends on the coupling strength.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1995
The behavior in the vicinity of a point where excitable, Hopf and Turing modes coexisting is anal... more The behavior in the vicinity of a point where excitable, Hopf and Turing modes coexisting is analyzed within the framework of a simplified version of Chua's nonlinear circuits. The different factors (e.g., initial and boundary conditions and small changes in circuit parameters) which determine the final state of the system are numerically studied
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1993
Abstract A two-dimensional (2-D) cellular neural network (CNN) array of resistively coupled Chua ... more Abstract A two-dimensional (2-D) cellular neural network (CNN) array of resistively coupled Chua circuits which can be designed to implement some elementary aspects of spatial recognition, namely, distinguishing open curves from closed ones and locating the ...
![Research paper thumbnail of Study of reentry initiation in coupled parallel fibers [cardiology]](https://attachments.academia-assets.com/98140696/thumbnails/1.jpg)
](IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1995
Initiation of reentries in coupled parallel fibers is studied as a function of several control pa... more Initiation of reentries in coupled parallel fibers is studied as a function of several control parameters intrinsic to those fibers. The influence of inhomogeneities in the fibers leading to drift of the vortices and the interaction between them is also analyzed numerically and experimentally.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1993
Spatio-temporal patterns formed in a 2-D array of Chua's circuits have been studied numerically. ... more Spatio-temporal patterns formed in a 2-D array of Chua's circuits have been studied numerically. It has been found that spiral wave solutions can appear over a large range of parameters and some of their properties have been measured. This demonstrates that spiral wave dynamics can be studied in arrays of discrete electronic circuits, such as a 2-D array of Chua's circuits, where real-time results can be obtained. We also study the influence of small differences in the parameters of the circuits, as is the case in real electronic components, where a 5% device tolerance is typical. Recently, it has been shown that a 1-D array of Chua's circuit can support traveling waves propagating through the resistively coupled cells [IO]-[ 121. Properties such as the dispersion relation [ 131, [ 141 or the propagation failure phenomena [ 151 have been measured in arrays of active nonlinear circuits and compared with their equivalents in continuous dynamical systems.
Geophysical Research Letters, 2012
Based on ten years (1998-2007) of satellite ocean color data we analyze the spatiotemporal patter... more Based on ten years (1998-2007) of satellite ocean color data we analyze the spatiotemporal patterns in the seasonal Madagascar plankton bloom with respect to the advection of the recently discovered Southern Indian Ocean Countercurrent (SICC). In maps of Finite-time Lyapunov Exponents (FTLE) and Finite-Time Zonal Drift (FTZD) computed from altimetry derived velocities we observe a narrow zonal jet that starts at 25SatthesoutherntipofMadagascar,animportantupwellingregion,andextendstotheeastfurtherthanthelargestplanktonblooms(25 S at the southern tip of Madagascar, an important upwelling region, and extends to the east further than the largest plankton blooms (25SatthesoutherntipofMadagascar,animportantupwellingregion,andextendstotheeastfurtherthanthelargestplanktonblooms(2500 km). In bloom years, the jet coincides with large parts of the northern boundary of the plankton bloom, acting as a barrier to meridional transport. Our findings suggest that advection is an important and so far underestimated mechanism for the eastward propagation and the extent of the plankton bloom. This supports the hypothesis of a single nutrient source south of Madagascar.
Fluctuation and Noise Letters, 2004
In this paper the effect of noise on activity of a neural network of diffusively coupled excitato... more In this paper the effect of noise on activity of a neural network of diffusively coupled excitatory-inhibitory cells with time delay is analyzed. We distinguish between global and local noise studying the different types of spatiotemporal behaviors observed when a space-time correlated noise is applied to the system. The results show a synchronization of the network in aperiodic behavior with the help of tiny noisy perturbations on the external signal depending on the spatial correlation of noise and the coupling coefficients.
Europhysics Letters (EPL), 1997
We consider the behavior of rings of unidirectionally coupled chaotic systems. When the number of... more We consider the behavior of rings of unidirectionally coupled chaotic systems. When the number of oscillators in the ring is below a certain critical number the behavior of the ring is chaotic synchronized, while above this threshold an instability appears. The novel feature is that this instability may yield a chaotic rotating wave if some conditions are fulfilled.
The European Physical Journal Special Topics, 2008
We present experiments on the propagation of a wave front in a fluid forced by Faraday waves. The... more We present experiments on the propagation of a wave front in a fluid forced by Faraday waves. The vertical periodical modulation of the acceleration induces flows in the system that modifies the Belousov-Zhabotinsky (BZ) chemical reaction dynamics. Phase waves spreading through standing waves with different symmetries results in superdiffusion. The anomalous diffusion is characterized in terms of a non-integer transport exponent which is compared with exponents resulting from tracer particles trajectories undergoing rapid, distant jumps called Lévy flights.
European Journal of Physics, 1993
A linear array of coupled modified van der Pol oscillators has been studied both experimentally a... more A linear array of coupled modified van der Pol oscillators has been studied both experimentally and numerically. A fixed width pulse was used to study the velocity of pulse-like travelling wave propagation in the chain and its dependence on the system parameters. We have shown that for a sufficiently large array the velocity tends to a limiting value that is independent of the array's length. The velocity monotonically decreases with the interval between pulses and it is inversely proportional to the square root of the coupling resistance. These results can be understood by using an analogy with the propagating waves in a high non-linear reaction-diffusion system, and specifically in an active excitable media.
European Journal of Physics, 1992
The non-linear differential equations that are solved in Fourier space can usually be written as ... more The non-linear differential equations that are solved in Fourier space can usually be written as a relation between the function psi and a polynomial form of its derivatives. On the other hand, to describe behaviour, it is useful to introduce functions other than polynomial relations. The goal of this paper is to show an analytical-numerical technique to solve systems of
European Journal of Physics, 1994
A method for spiral wave initiation in a two-dimensional Belousov-Zhabotinsky (BZ) reaction is pr... more A method for spiral wave initiation in a two-dimensional Belousov-Zhabotinsky (BZ) reaction is presented. The method is based on similar experiments carried out in cardiac tissue. The authors prove that the method is general as it can be observed in BZ reactions. This type of reaction is a more handy medium and it allows one a better understanding and study of the properties that are involved in the method. Spiral waves in the heart are known to be responsible for fibrillations and arrhythmias, therefore this is one method that can lead to such pathologies of the heart.
European Journal of Physics, 2007
We describe experiments on Bénard-Marangoni convection which permit a useful understanding of the... more We describe experiments on Bénard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Bénard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and introductory analysis which has the additional advantage of providing very suggestive experiments. As a consequence, we recommend our device for use as a laboratory experiment for undergraduate students of the thermodynamics of nonlinear and fluid physics.
Chemical Engineering Science, 2000
... transfer enhancement due to surface wave formation at a horizontal gasliquid interface. ... ... more ... transfer enhancement due to surface wave formation at a horizontal gasliquid interface. ... Contact Information , E-mail The Corresponding Author , a , F. Chenlo-Romero a , M ... a Department of Chemical Engineering, Faculty of Chemistry, University of Santiago de Compostela ...
Chaos, Solitons & Fractals, 1996
The focusing of wind fields in the atmospheric boundary layer is obtained as a result of the axia... more The focusing of wind fields in the atmospheric boundary layer is obtained as a result of the axial symmetry breaking of the wind flowing through terrain depressions and subsequent formation of an organized convective cell. At the cavity center, the airflow coalesces and moves collectively upward along the z-axis while it rotates around the filament of a three-dimensional vortex. Only at a certain height above the surface, the focal height, does a cross-section of the three-dimensional vortex show a perfectly symmetrical pattern for the vertical component of the wind velocity. Focusing is shown to take place at noon when a perfectly symmetric neutrally stratified layer develops at the cavity while outside the atmospheric layer is unstably stratified. The focusing dependence on the shape of terrain depressions and wind profiles, which act as lenses in nonlinear optics, is presented. Results were obtained by using a three-dimensional hydrostatic mesoscale model.
Remote Sensing, 2021
Wave energy resource assessment is crucial for the development of the marine renewable industry. ... more Wave energy resource assessment is crucial for the development of the marine renewable industry. High-frequency radars (HF radars) have been demonstrated to be a useful wave measuring tool. Therefore, in this work, we evaluated the accuracy of two CODAR Seasonde HF radars for describing the wave energy resource of two offshore areas in the west Galician coast, Spain (Vilán and Silleiro capes). The resulting wave characterization was used to estimate the electricity production of two wave energy converters. Results were validated against wave data from two buoys and two numerical models (SIMAR, (Marine Simulation) and WaveWatch III). The statistical validation revealed that the radar of Silleiro cape significantly overestimates the wave power, mainly due to a large overestimation of the wave energy period. The effect of the radars’ data loss during low wave energy periods on the mean wave energy is partially compensated with the overestimation of wave height and energy period. The th...
Physical Review E
The onset of viscous fingering in the presence of a viscosity profile is investigated theoretical... more The onset of viscous fingering in the presence of a viscosity profile is investigated theoretically for two immiscible fluids undergoing a time-dependent injection. Here, we show that the presence of a positive viscosity gradient at the interface between both fluids stabilizes the interface facilitating the spread of the perturbation. This effect is much more pronounced in the case of sinusoidal injection flows. The influence of the viscosity gradient on the dispersion relation is analyzed. Numerical simulations of the Navier-Stokes equation confirm the linear stability analysis.
International Journal of Bifurcation and Chaos, 2000
A synchronization scheme through compound chaotic signal is analyzed both numerically and experim... more A synchronization scheme through compound chaotic signal is analyzed both numerically and experimentally to study the performance of this scheme, in a noisy environment, considering its possibilities for communication systems with masking technique. The influence of noise has been analyzed in terms of the Bit Error Rate. An important factor of this method is the use of encryption keys which add more robustness and complexity to the system.
International Journal of Bifurcation and Chaos, 2003
Nucleation from a boundary is experimentally and numerically studied in a one-dimensional array i... more Nucleation from a boundary is experimentally and numerically studied in a one-dimensional array in two excitable media consisting of Chua's circuits and the Oregonator model, respectively. Forcing from a boundary with a pulse of constant amplitude and infinite duration gives rise to a periodic wave train propagating through the array. As the amplitude of the pulse increases, wave period evolves to chaos through a period doubling cascade.
International Journal of Bifurcation and Chaos, 2001
The influence of spatiotemporal colored noise on wave train propagation in nonexcitable media is ... more The influence of spatiotemporal colored noise on wave train propagation in nonexcitable media is investigated. This study has been performed within the framework of the Oregonator model in terms of the characteristic noise parameters. Some features seen in single front propagation, like noise induced propagation facilitation for an optimal level of the noise intensity, are also found for periodic wave trains. The main new effect is, however, an enhancement of propagation for correlation times of the noise of the order of the period of the wave train.
International Journal of Bifurcation and Chaos, 2001
The behavior of diffusively coupled Rössler oscillators parametrically perturbed with an Ornstein... more The behavior of diffusively coupled Rössler oscillators parametrically perturbed with an Ornstein–Uhlenbeck noise is analyzed in terms of the degree of synchronization between the cells. A resonance-like behavior is found as a function of the noise correlation time, instead of the noise intensity as it occurs in the typical stochastic resonance. A power law scaling between the "optimum" correlation time with regard to synchronization and the deterministic time scale of the oscillators has been obtained, with an exponent that depends on the coupling strength.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1995
The behavior in the vicinity of a point where excitable, Hopf and Turing modes coexisting is anal... more The behavior in the vicinity of a point where excitable, Hopf and Turing modes coexisting is analyzed within the framework of a simplified version of Chua's nonlinear circuits. The different factors (e.g., initial and boundary conditions and small changes in circuit parameters) which determine the final state of the system are numerically studied
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1993
Abstract A two-dimensional (2-D) cellular neural network (CNN) array of resistively coupled Chua ... more Abstract A two-dimensional (2-D) cellular neural network (CNN) array of resistively coupled Chua circuits which can be designed to implement some elementary aspects of spatial recognition, namely, distinguishing open curves from closed ones and locating the ...
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1995
Initiation of reentries in coupled parallel fibers is studied as a function of several control pa... more Initiation of reentries in coupled parallel fibers is studied as a function of several control parameters intrinsic to those fibers. The influence of inhomogeneities in the fibers leading to drift of the vortices and the interaction between them is also analyzed numerically and experimentally.
IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1993
Spatio-temporal patterns formed in a 2-D array of Chua's circuits have been studied numerically. ... more Spatio-temporal patterns formed in a 2-D array of Chua's circuits have been studied numerically. It has been found that spiral wave solutions can appear over a large range of parameters and some of their properties have been measured. This demonstrates that spiral wave dynamics can be studied in arrays of discrete electronic circuits, such as a 2-D array of Chua's circuits, where real-time results can be obtained. We also study the influence of small differences in the parameters of the circuits, as is the case in real electronic components, where a 5% device tolerance is typical. Recently, it has been shown that a 1-D array of Chua's circuit can support traveling waves propagating through the resistively coupled cells [IO]-[ 121. Properties such as the dispersion relation [ 131, [ 141 or the propagation failure phenomena [ 151 have been measured in arrays of active nonlinear circuits and compared with their equivalents in continuous dynamical systems.
Geophysical Research Letters, 2012
Based on ten years (1998-2007) of satellite ocean color data we analyze the spatiotemporal patter... more Based on ten years (1998-2007) of satellite ocean color data we analyze the spatiotemporal patterns in the seasonal Madagascar plankton bloom with respect to the advection of the recently discovered Southern Indian Ocean Countercurrent (SICC). In maps of Finite-time Lyapunov Exponents (FTLE) and Finite-Time Zonal Drift (FTZD) computed from altimetry derived velocities we observe a narrow zonal jet that starts at 25SatthesoutherntipofMadagascar,animportantupwellingregion,andextendstotheeastfurtherthanthelargestplanktonblooms(25 S at the southern tip of Madagascar, an important upwelling region, and extends to the east further than the largest plankton blooms (25SatthesoutherntipofMadagascar,animportantupwellingregion,andextendstotheeastfurtherthanthelargestplanktonblooms(2500 km). In bloom years, the jet coincides with large parts of the northern boundary of the plankton bloom, acting as a barrier to meridional transport. Our findings suggest that advection is an important and so far underestimated mechanism for the eastward propagation and the extent of the plankton bloom. This supports the hypothesis of a single nutrient source south of Madagascar.
Fluctuation and Noise Letters, 2004
In this paper the effect of noise on activity of a neural network of diffusively coupled excitato... more In this paper the effect of noise on activity of a neural network of diffusively coupled excitatory-inhibitory cells with time delay is analyzed. We distinguish between global and local noise studying the different types of spatiotemporal behaviors observed when a space-time correlated noise is applied to the system. The results show a synchronization of the network in aperiodic behavior with the help of tiny noisy perturbations on the external signal depending on the spatial correlation of noise and the coupling coefficients.
Europhysics Letters (EPL), 1997
We consider the behavior of rings of unidirectionally coupled chaotic systems. When the number of... more We consider the behavior of rings of unidirectionally coupled chaotic systems. When the number of oscillators in the ring is below a certain critical number the behavior of the ring is chaotic synchronized, while above this threshold an instability appears. The novel feature is that this instability may yield a chaotic rotating wave if some conditions are fulfilled.
The European Physical Journal Special Topics, 2008
We present experiments on the propagation of a wave front in a fluid forced by Faraday waves. The... more We present experiments on the propagation of a wave front in a fluid forced by Faraday waves. The vertical periodical modulation of the acceleration induces flows in the system that modifies the Belousov-Zhabotinsky (BZ) chemical reaction dynamics. Phase waves spreading through standing waves with different symmetries results in superdiffusion. The anomalous diffusion is characterized in terms of a non-integer transport exponent which is compared with exponents resulting from tracer particles trajectories undergoing rapid, distant jumps called Lévy flights.
European Journal of Physics, 1993
A linear array of coupled modified van der Pol oscillators has been studied both experimentally a... more A linear array of coupled modified van der Pol oscillators has been studied both experimentally and numerically. A fixed width pulse was used to study the velocity of pulse-like travelling wave propagation in the chain and its dependence on the system parameters. We have shown that for a sufficiently large array the velocity tends to a limiting value that is independent of the array's length. The velocity monotonically decreases with the interval between pulses and it is inversely proportional to the square root of the coupling resistance. These results can be understood by using an analogy with the propagating waves in a high non-linear reaction-diffusion system, and specifically in an active excitable media.
European Journal of Physics, 1992
The non-linear differential equations that are solved in Fourier space can usually be written as ... more The non-linear differential equations that are solved in Fourier space can usually be written as a relation between the function psi and a polynomial form of its derivatives. On the other hand, to describe behaviour, it is useful to introduce functions other than polynomial relations. The goal of this paper is to show an analytical-numerical technique to solve systems of
European Journal of Physics, 1994
A method for spiral wave initiation in a two-dimensional Belousov-Zhabotinsky (BZ) reaction is pr... more A method for spiral wave initiation in a two-dimensional Belousov-Zhabotinsky (BZ) reaction is presented. The method is based on similar experiments carried out in cardiac tissue. The authors prove that the method is general as it can be observed in BZ reactions. This type of reaction is a more handy medium and it allows one a better understanding and study of the properties that are involved in the method. Spiral waves in the heart are known to be responsible for fibrillations and arrhythmias, therefore this is one method that can lead to such pathologies of the heart.
European Journal of Physics, 2007
We describe experiments on Bénard-Marangoni convection which permit a useful understanding of the... more We describe experiments on Bénard-Marangoni convection which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Bénard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of convection theory, we carry out a simple and introductory analysis which has the additional advantage of providing very suggestive experiments. As a consequence, we recommend our device for use as a laboratory experiment for undergraduate students of the thermodynamics of nonlinear and fluid physics.
Chemical Engineering Science, 2000
... transfer enhancement due to surface wave formation at a horizontal gasliquid interface. ... ... more ... transfer enhancement due to surface wave formation at a horizontal gasliquid interface. ... Contact Information , E-mail The Corresponding Author , a , F. Chenlo-Romero a , M ... a Department of Chemical Engineering, Faculty of Chemistry, University of Santiago de Compostela ...
Chaos, Solitons & Fractals, 1996
The focusing of wind fields in the atmospheric boundary layer is obtained as a result of the axia... more The focusing of wind fields in the atmospheric boundary layer is obtained as a result of the axial symmetry breaking of the wind flowing through terrain depressions and subsequent formation of an organized convective cell. At the cavity center, the airflow coalesces and moves collectively upward along the z-axis while it rotates around the filament of a three-dimensional vortex. Only at a certain height above the surface, the focal height, does a cross-section of the three-dimensional vortex show a perfectly symmetrical pattern for the vertical component of the wind velocity. Focusing is shown to take place at noon when a perfectly symmetric neutrally stratified layer develops at the cavity while outside the atmospheric layer is unstably stratified. The focusing dependence on the shape of terrain depressions and wind profiles, which act as lenses in nonlinear optics, is presented. Results were obtained by using a three-dimensional hydrostatic mesoscale model.