Mario Razeto - Academia.edu (original) (raw)

Papers by Mario Razeto

Research paper thumbnail of Nonlinear Model of Vibrating Screen to Determine Permissible Spring Deterioration for Proper Separation

Shock and Vibration, 2016

Research paper thumbnail of Deteccion De Fallas Utilizando Respuest as Dinamicas

Research paper thumbnail of Hausdorff Iconic Matching with Application to Eye Tracking in Videoconferencing

Digital Media Processing for Multimedia Interactive Services - Proceedings of the 4th European Workshop on Image Analysis for Multimedia Interactive Services, 2003

Research paper thumbnail of Robust Correspondenceless 3-D Iris Location for Immersive Environments

Lecture Notes in Computer Science, 2005

We present a system locating the contour of an iris in space using robust active ellipse search a... more We present a system locating the contour of an iris in space using robust active ellipse search and correspondenceless stereo. Robust iris location is the basis for gaze estimation and tracking, and, as such, an essential module for augmented and virtual reality ...

Research paper thumbnail of El debate sobre las necesidades, y la cuestión de la "naturaleza humana": (Teniendo como trasfondo la interrogante sobre la posibilidad de una nueva civilización)

Research paper thumbnail of Modal Identification and Determination of Effective Mass Using Environmental Vibration Testing on an ElectroDynamic Shaker

Proceedings of SPIE - The International Society for Optical Engineering

Research paper thumbnail of Exploiting High-Spatial Density Vibration Measurements and Fe Models for Damage Identification

Model based damage assessment is based on measuring the distance between experimental and analyti... more Model based damage assessment is based on measuring the distance between experimental and analytical results. In practice, measurements yield only partial mode shapes with respect to the total degrees of freedom (DOFs) present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape have to be expanded to the same dimension of the numerical mode shape. Mode shapes expansion is a key point in the damage localization process, since actual defects of the structure may be hidden by expansion errors. This paper introduces a new general procedure to the expansion/damage assessment process using an optimal choice for: the size of the expansion basis, the number of experimental DOFs and the sensor placement. We introduce a new indicator to evaluate the problems inherent to the expansion/damage detection process using the Minimization of Error on Constitutive Equations (MECE) technique [1]. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degrees of freedom should be measured and how many mode shapes should be used in the expansion basis. The procedure is illustrated using a finite element model of a plate-like structure, where the damage state is simulated as a reduction of the local stiffness.

Research paper thumbnail of Numerical and Experimental Analysis on the Dynamic Behaviour of the Violin Plates

The study of dynamic and vibratory behavior of violins consider the effect of the different parts... more The study of dynamic and vibratory behavior of violins consider the effect of the different parts that compose it for the resulting sound. The top and back plates have great importance in the transmission of vibrations and the timbre characteristic of the violin, centering the study in their vibratory behavior. Experimental tests determine the vibrational modes with their resonant frequencies of the top of a violin. A numerical model of the plate is made by means of the finite elements method, to determine the influence of the different mechanical and geometric properties on its main vibrational modes and natural frequencies; different methods are found to make changes in their structure with the objective to obtain the expected acoustic answers. The distribution of thicknesses or the height in the arqueamiento is modified to obtain different effects on the frequencies and the vibrational modes.

Research paper thumbnail of Assessing Structural Damage Using High-Spatial Density Measurements

We study some limitations that appear when using the Minimization of Error on Constitu-tive Equat... more We study some limitations that appear when using the Minimization of Error on Constitu-tive Equations (MECE) technique for damage identification purposes. The proposed strategy is based on measuring the distance between experimental and numerical vibration data. In prac-tice, measurements yield only partial mode shapes with respect to the total degrees of freedom present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape has to be expanded to the same dimension of the numerical mode shape. We discuss the expansion/damage assessment process and we use an optimized choice for the size of the expansion basis, the number of experimental degrees of freedom (DOFs) and the sensor placement. We introduce an indicator to evaluate the problems inherent to the ex-pansion/damage detection process using MECE. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degree...

Research paper thumbnail of Análisis Numérico y Experimental Del Comportamiento Dinámico De Un Violín

A numerical and experimental study of the plates of a violin was made, taking into account the ef... more A numerical and experimental study of the plates of a violin was made, taking into account the effect that different physical and mechanical factors produce on their dynamic response. Experimental tests were conducted to determine the vibrational modes, along with the resonant frequencies, of the cover of a violin. A numerical model of the board by means of the finite element method was made, to determine the influence of the different mechanical and geometric properties on its vibrational modes and frequencies; finding methods that allow to make changes in their structure with the purpose of obtaining the expected acoustic response. Modifying the distribution of thicknesses or varying the arching, different effects were obtained on the frequencies and the vibrational modes. RESUMEN

Research paper thumbnail of Un análisis alternativo de la actual crisis económica global y sus vías de superación

Research paper thumbnail of Robust iris location in close-up images of the eye

Pattern Analysis and Applications, 2005

This paper presents a robust, reliable iris location system for close-up, grey scale images of a ... more This paper presents a robust, reliable iris location system for close-up, grey scale images of a single eye. The system is meant as a bootstrap or recovery module for automated iris tracking within medical applications. We model the iris contour with an active ellipse, sensitive to intensity gradients across its perimeter. In this way, we avoid modelling the noisy appearance of the iris (e.g. corneal reflections). The irissclera intensity transition is modelled at two spatial scales with Petrou-Kittler optimal ramp filters. The optimal ellipse is identified by a simulated annealing algorithm tuned to the problem characteristics. The system performed accurately and robustly with 327 real images against substantial occlusion levels and varying image quality, subject, eye shape and skin colour.

Research paper thumbnail of Robust parameter identification using forced responses

Mechanical Systems and Signal Processing, 2007

In this paper, a new model updating scheme is introduced to adjust the system matrices of a finit... more In this paper, a new model updating scheme is introduced to adjust the system matrices of a finite-element model by using experimental operating deflection shapes (ODS). An ODS is defined here as the response vector when the system is driven at a given degree of freedom with a unit force of fixed frequency. The proposed algorithm adjusts the numerical model in an iterative way. The matrix equilibrium equation is solved by first taking into account the frequency shift that appears between the non-updated finite element model and the experimental structure. In this way, numerical instabilities observed in state-of-the-art methods are avoided. We present results on two well-known numerical and experimental benchmark cases. They show the good convergence properties of the proposed approach. r (R. Pascual).

Research paper thumbnail of Improvement of damage-assessment results using high-spatial density measurements

Mechanical Systems and Signal Processing, 2005

Model-based damage assessment is based on measuring the distance between experimental and analyti... more Model-based damage assessment is based on measuring the distance between experimental and analytical results. In practice, measurements yield only partial mode shapes with respect to the total degrees of freedom present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape has to be expanded to the same dimension of the numerical mode shape. Mode shapes expansion is a key point in the damage localisation process, since actual defects of the structure may be hidden by expansion errors. This paper introduces a new general procedure to the expansion/damage assessment process using an optimised choice for: the size of the expansion basis, the number of experimental degrees of freedom and the sensor placement. We introduce a new indicator to evaluate the problems inherent to the expansion/damage detection process using the minimisation of error on constitutive equations (MECE) technique. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degrees of freedom should be measured and how many mode shapes should be used in the expansion basis. The procedure is illustrated using a finite element model of a plate-like structure, where the damage state is simulated as a reduction of the local stiffness.

Research paper thumbnail of Damping Identification Using a Robust FRF-Based Model Updating Technique

Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Eleme... more Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models. The main reasons for this are that FRFs are very sensitive to modal properties such as damping, local modes influence is included, and no modal analysis is strictly required. Nevertheless, it is well known that due to the nature of the FRFs, model updating strategies may suffer serious discontinuities in the topology of the objective function, causing the updating procedure to diverge or to find a local non-physical minimum. This paper addresses the situation by presenting a residue that avoids such numerical instabilities. In particular we concentrate on damping identification. A benchmark from a European group is used to assess the goodness of the method compared to other well known techniques.

Research paper thumbnail of Model updating using operating deflection shapes

Model updating using a structural model is based on the analysis of the discrepancies between ana... more Model updating using a structural model is based on the analysis of the discrepancies between analytical and experimental results. In order to compare these quantities, a matching process is necessary.

Research paper thumbnail of A Robust FRF-based technique for Model Updating

Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Eleme... more Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models . Major reasons for this is that FRFs are very sensitive to damping properties at resonance peaks, local modes influence is included and no modal analysis is required. Nevertheless, it is well known that due to their nature, the frequency responses may change its order of magnitude very rapidly for small parameter or frequency changes. This situation may cause serious discontinuities in the topology of the objective function, causing the updating strategy to diverge or to find a local non-physical minimum . A primary tool for the correlation of FRFs is the Frequency Domain Assurance Criterion . This technique introduces the concept of frequency shift between the frequency response shapes of a reference model (the experimental structure) and a perturbed model (an initial non-updated FE model). Such a concept opens the way for using residues at different frequencies. For instance, in reference [6] the residue is composed by point FRFs at anti-resonances. This paper introduces a general FRF-based model-updating technique, which is focused in using stable residues during the interactive optimization procedure. A benchmark case from the Cost F3 action is used to assess the goodness of the method compared to other well known methods.

Research paper thumbnail of On-line damage assessment using operating deflection shapes

Research paper thumbnail of On the reliability of error localization indicators

An increasingly used approach for health monitoring is based on error localization techniques. Th... more An increasingly used approach for health monitoring is based on error localization techniques. They are applied on an analytical model of the nominally healthy structure and produce local values of discrepancies between the model and the measurements.

Research paper thumbnail of A frequency domain correlation technique for model correlation and updating

Up to now, existent FRF based model updating methods use the differences between measured and ana... more Up to now, existent FRF based model updating methods use the differences between measured and analytical FRFs at a fixed frequency, as residual to minimize. This approach does not take into account that FRFs between a reference model (experimental) and a perturbed one (a finite elements model not yet updated), displace in two axes : amplitude and frequency. A more physical correlation, then, uses also the frequency shift . The problem is how to find it.

Research paper thumbnail of Nonlinear Model of Vibrating Screen to Determine Permissible Spring Deterioration for Proper Separation

Shock and Vibration, 2016

Research paper thumbnail of Deteccion De Fallas Utilizando Respuest as Dinamicas

Research paper thumbnail of Hausdorff Iconic Matching with Application to Eye Tracking in Videoconferencing

Digital Media Processing for Multimedia Interactive Services - Proceedings of the 4th European Workshop on Image Analysis for Multimedia Interactive Services, 2003

Research paper thumbnail of Robust Correspondenceless 3-D Iris Location for Immersive Environments

Lecture Notes in Computer Science, 2005

We present a system locating the contour of an iris in space using robust active ellipse search a... more We present a system locating the contour of an iris in space using robust active ellipse search and correspondenceless stereo. Robust iris location is the basis for gaze estimation and tracking, and, as such, an essential module for augmented and virtual reality ...

Research paper thumbnail of El debate sobre las necesidades, y la cuestión de la "naturaleza humana": (Teniendo como trasfondo la interrogante sobre la posibilidad de una nueva civilización)

Research paper thumbnail of Modal Identification and Determination of Effective Mass Using Environmental Vibration Testing on an ElectroDynamic Shaker

Proceedings of SPIE - The International Society for Optical Engineering

Research paper thumbnail of Exploiting High-Spatial Density Vibration Measurements and Fe Models for Damage Identification

Model based damage assessment is based on measuring the distance between experimental and analyti... more Model based damage assessment is based on measuring the distance between experimental and analytical results. In practice, measurements yield only partial mode shapes with respect to the total degrees of freedom (DOFs) present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape have to be expanded to the same dimension of the numerical mode shape. Mode shapes expansion is a key point in the damage localization process, since actual defects of the structure may be hidden by expansion errors. This paper introduces a new general procedure to the expansion/damage assessment process using an optimal choice for: the size of the expansion basis, the number of experimental DOFs and the sensor placement. We introduce a new indicator to evaluate the problems inherent to the expansion/damage detection process using the Minimization of Error on Constitutive Equations (MECE) technique [1]. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degrees of freedom should be measured and how many mode shapes should be used in the expansion basis. The procedure is illustrated using a finite element model of a plate-like structure, where the damage state is simulated as a reduction of the local stiffness.

Research paper thumbnail of Numerical and Experimental Analysis on the Dynamic Behaviour of the Violin Plates

The study of dynamic and vibratory behavior of violins consider the effect of the different parts... more The study of dynamic and vibratory behavior of violins consider the effect of the different parts that compose it for the resulting sound. The top and back plates have great importance in the transmission of vibrations and the timbre characteristic of the violin, centering the study in their vibratory behavior. Experimental tests determine the vibrational modes with their resonant frequencies of the top of a violin. A numerical model of the plate is made by means of the finite elements method, to determine the influence of the different mechanical and geometric properties on its main vibrational modes and natural frequencies; different methods are found to make changes in their structure with the objective to obtain the expected acoustic answers. The distribution of thicknesses or the height in the arqueamiento is modified to obtain different effects on the frequencies and the vibrational modes.

Research paper thumbnail of Assessing Structural Damage Using High-Spatial Density Measurements

We study some limitations that appear when using the Minimization of Error on Constitu-tive Equat... more We study some limitations that appear when using the Minimization of Error on Constitu-tive Equations (MECE) technique for damage identification purposes. The proposed strategy is based on measuring the distance between experimental and numerical vibration data. In prac-tice, measurements yield only partial mode shapes with respect to the total degrees of freedom present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape has to be expanded to the same dimension of the numerical mode shape. We discuss the expansion/damage assessment process and we use an optimized choice for the size of the expansion basis, the number of experimental degrees of freedom (DOFs) and the sensor placement. We introduce an indicator to evaluate the problems inherent to the ex-pansion/damage detection process using MECE. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degree...

Research paper thumbnail of Análisis Numérico y Experimental Del Comportamiento Dinámico De Un Violín

A numerical and experimental study of the plates of a violin was made, taking into account the ef... more A numerical and experimental study of the plates of a violin was made, taking into account the effect that different physical and mechanical factors produce on their dynamic response. Experimental tests were conducted to determine the vibrational modes, along with the resonant frequencies, of the cover of a violin. A numerical model of the board by means of the finite element method was made, to determine the influence of the different mechanical and geometric properties on its vibrational modes and frequencies; finding methods that allow to make changes in their structure with the purpose of obtaining the expected acoustic response. Modifying the distribution of thicknesses or varying the arching, different effects were obtained on the frequencies and the vibrational modes. RESUMEN

Research paper thumbnail of Un análisis alternativo de la actual crisis económica global y sus vías de superación

Research paper thumbnail of Robust iris location in close-up images of the eye

Pattern Analysis and Applications, 2005

This paper presents a robust, reliable iris location system for close-up, grey scale images of a ... more This paper presents a robust, reliable iris location system for close-up, grey scale images of a single eye. The system is meant as a bootstrap or recovery module for automated iris tracking within medical applications. We model the iris contour with an active ellipse, sensitive to intensity gradients across its perimeter. In this way, we avoid modelling the noisy appearance of the iris (e.g. corneal reflections). The irissclera intensity transition is modelled at two spatial scales with Petrou-Kittler optimal ramp filters. The optimal ellipse is identified by a simulated annealing algorithm tuned to the problem characteristics. The system performed accurately and robustly with 327 real images against substantial occlusion levels and varying image quality, subject, eye shape and skin colour.

Research paper thumbnail of Robust parameter identification using forced responses

Mechanical Systems and Signal Processing, 2007

In this paper, a new model updating scheme is introduced to adjust the system matrices of a finit... more In this paper, a new model updating scheme is introduced to adjust the system matrices of a finite-element model by using experimental operating deflection shapes (ODS). An ODS is defined here as the response vector when the system is driven at a given degree of freedom with a unit force of fixed frequency. The proposed algorithm adjusts the numerical model in an iterative way. The matrix equilibrium equation is solved by first taking into account the frequency shift that appears between the non-updated finite element model and the experimental structure. In this way, numerical instabilities observed in state-of-the-art methods are avoided. We present results on two well-known numerical and experimental benchmark cases. They show the good convergence properties of the proposed approach. r (R. Pascual).

Research paper thumbnail of Improvement of damage-assessment results using high-spatial density measurements

Mechanical Systems and Signal Processing, 2005

Model-based damage assessment is based on measuring the distance between experimental and analyti... more Model-based damage assessment is based on measuring the distance between experimental and analytical results. In practice, measurements yield only partial mode shapes with respect to the total degrees of freedom present in the corresponding finite element model. Thus, before any damage detection method is implemented, the experimental mode shape has to be expanded to the same dimension of the numerical mode shape. Mode shapes expansion is a key point in the damage localisation process, since actual defects of the structure may be hidden by expansion errors. This paper introduces a new general procedure to the expansion/damage assessment process using an optimised choice for: the size of the expansion basis, the number of experimental degrees of freedom and the sensor placement. We introduce a new indicator to evaluate the problems inherent to the expansion/damage detection process using the minimisation of error on constitutive equations (MECE) technique. It provides insight of the inherent limitations of MECE and helps the decision making process on how many degrees of freedom should be measured and how many mode shapes should be used in the expansion basis. The procedure is illustrated using a finite element model of a plate-like structure, where the damage state is simulated as a reduction of the local stiffness.

Research paper thumbnail of Damping Identification Using a Robust FRF-Based Model Updating Technique

Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Eleme... more Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models. The main reasons for this are that FRFs are very sensitive to modal properties such as damping, local modes influence is included, and no modal analysis is strictly required. Nevertheless, it is well known that due to the nature of the FRFs, model updating strategies may suffer serious discontinuities in the topology of the objective function, causing the updating procedure to diverge or to find a local non-physical minimum. This paper addresses the situation by presenting a residue that avoids such numerical instabilities. In particular we concentrate on damping identification. A benchmark from a European group is used to assess the goodness of the method compared to other well known techniques.

Research paper thumbnail of Model updating using operating deflection shapes

Model updating using a structural model is based on the analysis of the discrepancies between ana... more Model updating using a structural model is based on the analysis of the discrepancies between analytical and experimental results. In order to compare these quantities, a matching process is necessary.

Research paper thumbnail of A Robust FRF-based technique for Model Updating

Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Eleme... more Frequency Response Functions (FRFs) residues have been widely used in time to update Finite Element models . Major reasons for this is that FRFs are very sensitive to damping properties at resonance peaks, local modes influence is included and no modal analysis is required. Nevertheless, it is well known that due to their nature, the frequency responses may change its order of magnitude very rapidly for small parameter or frequency changes. This situation may cause serious discontinuities in the topology of the objective function, causing the updating strategy to diverge or to find a local non-physical minimum . A primary tool for the correlation of FRFs is the Frequency Domain Assurance Criterion . This technique introduces the concept of frequency shift between the frequency response shapes of a reference model (the experimental structure) and a perturbed model (an initial non-updated FE model). Such a concept opens the way for using residues at different frequencies. For instance, in reference [6] the residue is composed by point FRFs at anti-resonances. This paper introduces a general FRF-based model-updating technique, which is focused in using stable residues during the interactive optimization procedure. A benchmark case from the Cost F3 action is used to assess the goodness of the method compared to other well known methods.

Research paper thumbnail of On-line damage assessment using operating deflection shapes

Research paper thumbnail of On the reliability of error localization indicators

An increasingly used approach for health monitoring is based on error localization techniques. Th... more An increasingly used approach for health monitoring is based on error localization techniques. They are applied on an analytical model of the nominally healthy structure and produce local values of discrepancies between the model and the measurements.

Research paper thumbnail of A frequency domain correlation technique for model correlation and updating

Up to now, existent FRF based model updating methods use the differences between measured and ana... more Up to now, existent FRF based model updating methods use the differences between measured and analytical FRFs at a fixed frequency, as residual to minimize. This approach does not take into account that FRFs between a reference model (experimental) and a perturbed one (a finite elements model not yet updated), displace in two axes : amplitude and frequency. A more physical correlation, then, uses also the frequency shift . The problem is how to find it.