Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3926
2017-02-24T04:23:17ZUnsupervised morphological segmentation for images
http://hdl.handle.net/2117/101488
Unsupervised morphological segmentation for images
Salembier Clairon, Philippe Jean
This paper deals with a morphological approach to unsupervised image segmentation. The proposed technique relies on a multiscale Top-Down approach allowing a hierarchical processing of the data ranging from the most global scale to the most detailed one. At each scale, the algorithm consists of four steps: image simplification, feature extraction, contour localization and quality estimation. The main emphasis of this paper is to discuss the selection of a simplification filter for segmentation. Morphological filters based on reconstruction proved to be very efficient for this purpose. The resulting unsupervised algorithm is very robust and can deal with very different type of images.
2017-02-23T16:19:23ZSalembier Clairon, Philippe JeanThis paper deals with a morphological approach to unsupervised image segmentation. The proposed technique relies on a multiscale Top-Down approach allowing a hierarchical processing of the data ranging from the most global scale to the most detailed one. At each scale, the algorithm consists of four steps: image simplification, feature extraction, contour localization and quality estimation. The main emphasis of this paper is to discuss the selection of a simplification filter for segmentation. Morphological filters based on reconstruction proved to be very efficient for this purpose. The resulting unsupervised algorithm is very robust and can deal with very different type of images.Estudio comparativo de las matrices de correlación clásica y cíclica en arrays de banda estrecha
http://hdl.handle.net/2117/101481
Estudio comparativo de las matrices de correlación clásica y cíclica en arrays de banda estrecha
Cerquides Bueno, José Ramón; Muñoz Medina, Olga; Fernández Rubio, Juan Antonio
The aim of this communication is to study the differences and similarities between the classic and cyclic
correlation matrices of the data snapshots sensed by an array. We will focus our study in the comparison of the
eigenvalues decomposition for each matrix. Special attention will be paid on topics like rank and nature of
eigenvectors and eigenvalues. Other aspects involved in the estimation of both matrices, such as number of data
snapshots required and sensitivity to deviations of the cyclic parameter will be also treated. Finally, we will carry
out simulations in order to confirm the previously obtained theoretical results.
2017-02-23T14:56:57ZCerquides Bueno, José RamónMuñoz Medina, OlgaFernández Rubio, Juan AntonioThe aim of this communication is to study the differences and similarities between the classic and cyclic
correlation matrices of the data snapshots sensed by an array. We will focus our study in the comparison of the
eigenvalues decomposition for each matrix. Special attention will be paid on topics like rank and nature of
eigenvectors and eigenvalues. Other aspects involved in the estimation of both matrices, such as number of data
snapshots required and sensitivity to deviations of the cyclic parameter will be also treated. Finally, we will carry
out simulations in order to confirm the previously obtained theoretical results.Image restoration using HOS and the Radon transform
http://hdl.handle.net/2117/101471
Image restoration using HOS and the Radon transform
Sayrol Clols, Elisa; Nikias, C L; Gasull Llampallas, Antoni
The authors propose the use of higher-order statistics (HOS) to study the problem of image restoration. They consider images degraded by linear or zero phase blurring point spread functions (PSF) and additive Gaussian noise. The complexity associated with the combination of two-dimensional signal processing and higher-order statistics is reduced by means of the Radon transform. The projection at each angle is an one-dimensional signal that can be processed by any existing 1-D higher-order statistics-based method. They apply two methods that have proven to attain good one-dimensional signal reconstruction, especially in the presence of noise. After the ideal projections have been estimated, the inverse Radon transform gives the restored image. Simulation results are provided.
2017-02-23T13:41:15ZSayrol Clols, ElisaNikias, C LGasull Llampallas, AntoniThe authors propose the use of higher-order statistics (HOS) to study the problem of image restoration. They consider images degraded by linear or zero phase blurring point spread functions (PSF) and additive Gaussian noise. The complexity associated with the combination of two-dimensional signal processing and higher-order statistics is reduced by means of the Radon transform. The projection at each angle is an one-dimensional signal that can be processed by any existing 1-D higher-order statistics-based method. They apply two methods that have proven to attain good one-dimensional signal reconstruction, especially in the presence of noise. After the ideal projections have been estimated, the inverse Radon transform gives the restored image. Simulation results are provided.Analytic performance evaluation of cumulant-based arma system identification methods
http://hdl.handle.net/2117/101469
Analytic performance evaluation of cumulant-based arma system identification methods
Rodríguez Fonollosa, José Adrián; Vidal Manzano, José
The authors perform an analytic study of some cumulant-based methods for estimating the AR parameters of ARMA processes. The analysis includes new AR identifiability results for pure AR process and the analytic performance evaluation of system identification methods based on cumulants. The authors present examples of pure AR processes that are not identifiable via the normal equations based on the diagonal third-order cumulant slice. The results of the performance evaluation are illustrated graphically with plots of the variance of the estimates as a function of the parameters of the process.
2017-02-23T13:28:32ZRodríguez Fonollosa, José AdriánVidal Manzano, JoséThe authors perform an analytic study of some cumulant-based methods for estimating the AR parameters of ARMA processes. The analysis includes new AR identifiability results for pure AR process and the analytic performance evaluation of system identification methods based on cumulants. The authors present examples of pure AR processes that are not identifiable via the normal equations based on the diagonal third-order cumulant slice. The results of the performance evaluation are illustrated graphically with plots of the variance of the estimates as a function of the parameters of the process.Self-similar current distribution on fractal Sierpinski antenna verified with infrared thermograms
http://hdl.handle.net/2117/101406
Self-similar current distribution on fractal Sierpinski antenna verified with infrared thermograms
González Arbesú, José María; Puente Baliarda, Carles; Romeu Robert, Jordi; Aguasca Solé, Alberto
Experimental verification of the fractal Sierpinski antenna surface current distribution is presented. Measured data from an infrared camera agree with numerical data showing a self-similar behavior in the current density distribution over the fractal antenna surface. This result gives a better insight on the multiband behavior of the fractal-shape antenna.
2017-02-22T18:26:45ZGonzález Arbesú, José MaríaPuente Baliarda, CarlesRomeu Robert, JordiAguasca Solé, AlbertoExperimental verification of the fractal Sierpinski antenna surface current distribution is presented. Measured data from an infrared camera agree with numerical data showing a self-similar behavior in the current density distribution over the fractal antenna surface. This result gives a better insight on the multiband behavior of the fractal-shape antenna.Reduction of the model noise in non-linear reconstruction via an efficient calculation of the incident field: application to a 434 MHz Scanner
http://hdl.handle.net/2117/101405
Reduction of the model noise in non-linear reconstruction via an efficient calculation of the incident field: application to a 434 MHz Scanner
Geffrin, J M; Mallorquí Franquet, Jordi Joan; Joachimowicz, N; Redondo, R; Vall·Llossera, M; Vall-Llossera Ferran, Mercedes Magdalena; Franza, Joisel A; Bolomey, Jean Charles
Microwave tomography has been drastically boosted by the development of efficient reconstruction algorithms based on an iterative solution of the corresponding non-linear inverse problem. The accuracy of the electric field radiated by the antennas of a microwave scanner, inside the target area, has been shown to play a significant role on the overall image quality. Taking into account the antenna environment is of prime importance, especially when operating at low frequency. For instance, the wall of a 60 cm diameter whole-body microwave scanner cannot be neglected at 434 MHz, even when using the immersion technique consisting of putting the target in water. Indeed, at such a frequency, the attenuation introduced by water is not sufficient to avoid multiple reflections on the scanner boundary walls. Consequently, the method of calculating the incident field constitutes a key factor in iteratively solving non-linear inverse problems. The selected technique must accommodate high accuracy while maintaining acceptable calculation complexity. In this paper, three distinct techniques are analysed. They are based on the use of i) free-space and ii) non free-space Green's function, and iii) a FDTD approach. All these techniques have been firstly investigated for their 2D version, being used in 2D reconstruction algorithms. However, the scattered field data are collected in a 3D scanner. For assessing the validity of the previous 2D techniques, their results have been compared to both experimentally and 3D-FDTD results.
2017-02-22T18:22:10ZGeffrin, J MMallorquí Franquet, Jordi JoanJoachimowicz, NRedondo, RVall·Llossera, MVall-Llossera Ferran, Mercedes MagdalenaFranza, Joisel ABolomey, Jean CharlesMicrowave tomography has been drastically boosted by the development of efficient reconstruction algorithms based on an iterative solution of the corresponding non-linear inverse problem. The accuracy of the electric field radiated by the antennas of a microwave scanner, inside the target area, has been shown to play a significant role on the overall image quality. Taking into account the antenna environment is of prime importance, especially when operating at low frequency. For instance, the wall of a 60 cm diameter whole-body microwave scanner cannot be neglected at 434 MHz, even when using the immersion technique consisting of putting the target in water. Indeed, at such a frequency, the attenuation introduced by water is not sufficient to avoid multiple reflections on the scanner boundary walls. Consequently, the method of calculating the incident field constitutes a key factor in iteratively solving non-linear inverse problems. The selected technique must accommodate high accuracy while maintaining acceptable calculation complexity. In this paper, three distinct techniques are analysed. They are based on the use of i) free-space and ii) non free-space Green's function, and iii) a FDTD approach. All these techniques have been firstly investigated for their 2D version, being used in 2D reconstruction algorithms. However, the scattered field data are collected in a 3D scanner. For assessing the validity of the previous 2D techniques, their results have been compared to both experimentally and 3D-FDTD results.Vectorial waveguide reflectometer for dielectric characterisation of materials under power microwaves
http://hdl.handle.net/2117/101403
Vectorial waveguide reflectometer for dielectric characterisation of materials under power microwaves
Mallorquí Franquet, Jordi Joan; Aguasca Solé, Alberto; Ribó Vedrilla, Serni
The temperature rise in a material modifies its physical properties, particularly its dielectric permittivity. In many applications involving relatively high levels of power the electrical behavior of the different materials will change as they are heated by the radiation. For instance, the numerical codes that simulates the behavior of microwave heating processes in order to improve the design of the feeding antennas must take into account the load variations with temperature. The measurement of the changing dielectric characteristics of materials is of great interest for the industry. Previous works used completely filled waveguides near a shorting plate. The method supplied excellent results at low power levels, while the sample was not heated. When the power is risen, the field distribution of the TE/sub 10/ mode causes a non-uniform heating of the sample and the measured permittivity corresponds to an average value. In order to reduce this problem a method using a partially filled waveguide is presented. The reduced sample dimensions and its positioning into the waveguide assures a near homogeneous power distribution implying a uniform heating.
2017-02-22T18:16:57ZMallorquí Franquet, Jordi JoanAguasca Solé, AlbertoRibó Vedrilla, SerniThe temperature rise in a material modifies its physical properties, particularly its dielectric permittivity. In many applications involving relatively high levels of power the electrical behavior of the different materials will change as they are heated by the radiation. For instance, the numerical codes that simulates the behavior of microwave heating processes in order to improve the design of the feeding antennas must take into account the load variations with temperature. The measurement of the changing dielectric characteristics of materials is of great interest for the industry. Previous works used completely filled waveguides near a shorting plate. The method supplied excellent results at low power levels, while the sample was not heated. When the power is risen, the field distribution of the TE/sub 10/ mode causes a non-uniform heating of the sample and the measured permittivity corresponds to an average value. In order to reduce this problem a method using a partially filled waveguide is presented. The reduced sample dimensions and its positioning into the waveguide assures a near homogeneous power distribution implying a uniform heating.Application of the conjugate gradient method to a self-matching network for industrial microwave heating antennas
http://hdl.handle.net/2117/101401
Application of the conjugate gradient method to a self-matching network for industrial microwave heating antennas
Mallorquí Franquet, Jordi Joan; Aguasca Solé, Alberto; Cardama Aznar, Ángel; Pages, R; Haro, J M
One of the main problems regarding the efficiency in a heating industrial system using high power microwaves is related with the uncontrolled changes on the load. These changes can be caused both by the different kinds of materials to be processed in the same oven and by the temperature rise which modifies the material's physical properties, particularly its dielectric permittivity. Usually, the microwave generator is matched to the antenna feeding the oven by means of a waveguide matching system, typically a two, three or four capacitive-screw tuner empirically adjusted for a given load. Once the heating process is started, the temperature dependence of the complex permittivity usually changes the impedance seen by the generator, worsening the mismatch factor and reducing the efficiency of the heating process. A similar process happens when the load is inhomogeneous or discontinuous; it is not feasible to manually re-adjust the matching network for every different sample processed. Until now the solution has been simple but highly inefficient: to increase the incident power in order to overcome the mismatching effects.
2017-02-22T18:11:12ZMallorquí Franquet, Jordi JoanAguasca Solé, AlbertoCardama Aznar, ÁngelPages, RHaro, J MOne of the main problems regarding the efficiency in a heating industrial system using high power microwaves is related with the uncontrolled changes on the load. These changes can be caused both by the different kinds of materials to be processed in the same oven and by the temperature rise which modifies the material's physical properties, particularly its dielectric permittivity. Usually, the microwave generator is matched to the antenna feeding the oven by means of a waveguide matching system, typically a two, three or four capacitive-screw tuner empirically adjusted for a given load. Once the heating process is started, the temperature dependence of the complex permittivity usually changes the impedance seen by the generator, worsening the mismatch factor and reducing the efficiency of the heating process. A similar process happens when the load is inhomogeneous or discontinuous; it is not feasible to manually re-adjust the matching network for every different sample processed. Until now the solution has been simple but highly inefficient: to increase the incident power in order to overcome the mismatching effects.near field to far field tranfsormation of bipolar measurements by equivalent magnetic current approach
http://hdl.handle.net/2117/101399
near field to far field tranfsormation of bipolar measurements by equivalent magnetic current approach
Blanch Boris, Sebastián; Romeu Robert, Jordi
An equivalent magnetic current (EMC) approach has been proposed as an alternative method to the classical modal formulation for computing the far-field pattern of a radiating antenna from planar near-field measurements. The attractiveness of this EMC approach includes the possibility of producing the correct far-field pattern in all regions in front of a planar antenna under test (AUT), a drawback of the classical modal formulation due to its dependence on the Fourier transform and assumptions which must be made about the field outside of the measurement zone, and its adaptability to both irregularly sampled and non-canonical near-field measurement surfaces. A drawback of the EMC approach, however, is its significantly larger computational requirements. A comparison of the EMC and classical modal approaches for near-field to far-field transformation is examined in terms of the resultant far-field patterns. Measurement results for a waveguide-fed slot array using the UCLA bi-polar planar near-field measurement scanner are presented. An implementation of the EMC approach for the bi-polar geometry is described and results obtained using different subsets of the measured bi-polar near-field data are presented and compared to that obtained using the classical modal approach.
2017-02-22T18:01:37ZBlanch Boris, SebastiánRomeu Robert, JordiAn equivalent magnetic current (EMC) approach has been proposed as an alternative method to the classical modal formulation for computing the far-field pattern of a radiating antenna from planar near-field measurements. The attractiveness of this EMC approach includes the possibility of producing the correct far-field pattern in all regions in front of a planar antenna under test (AUT), a drawback of the classical modal formulation due to its dependence on the Fourier transform and assumptions which must be made about the field outside of the measurement zone, and its adaptability to both irregularly sampled and non-canonical near-field measurement surfaces. A drawback of the EMC approach, however, is its significantly larger computational requirements. A comparison of the EMC and classical modal approaches for near-field to far-field transformation is examined in terms of the resultant far-field patterns. Measurement results for a waveguide-fed slot array using the UCLA bi-polar planar near-field measurement scanner are presented. An implementation of the EMC approach for the bi-polar geometry is described and results obtained using different subsets of the measured bi-polar near-field data are presented and compared to that obtained using the classical modal approach.AIterative algorithm for microwave imaging using the cgm-fft and the pseudoinverse method
http://hdl.handle.net/2117/101397
AIterative algorithm for microwave imaging using the cgm-fft and the pseudoinverse method
Mallorquí Franquet, Jordi Joan; Llorens, V
Within biomedical microwave tomography, a spatial iterative method for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape from their scattered electric field is shown. Starting from the integral representation of the electric field and by means of the method of moments (MoM) and a first order linearization of the resulting expressions, the integral equations are converted into matrix equations building an iterative scheme. This technique has been developed for the bidimensional TM case with cylindrical geometry. The advantages and limitations of this algorithm are also discussed.
2017-02-22T17:32:33ZMallorquí Franquet, Jordi JoanLlorens, VWithin biomedical microwave tomography, a spatial iterative method for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape from their scattered electric field is shown. Starting from the integral representation of the electric field and by means of the method of moments (MoM) and a first order linearization of the resulting expressions, the integral equations are converted into matrix equations building an iterative scheme. This technique has been developed for the bidimensional TM case with cylindrical geometry. The advantages and limitations of this algorithm are also discussed.