C. Brosseau - Academia.edu (original) (raw)
Papers by C. Brosseau
Journal of Applied Physics, 2007
The impetus of this work was to investigate the electromagnetic and tensile properties of several... more The impetus of this work was to investigate the electromagnetic and tensile properties of several commercially available plastoferrites (PFs) at ambient conditions. The approach involved selection of a set of PFs and measuring their complex effective permittivity ε=ε′−jε″ and permeability μ=μ′−jμ″ under uniaxial stress at microwave frequencies (0.1–4.5GHz) and room temperature. We analyze the ε and μ spectra for tensilely strained PFs up to 3%. Comparing our experimental ε data against several dielectric relaxational behaviors, we find that the main physics cannot be understood with a single relaxation mechanism. We then go on to consider the magnetic permeability spectra in the microwave range of frequencies and show that an appropriate magnetization mechanism is given by the gyromagnetic spin resonance mechanism. We use a combination of Bruggeman mean field analysis and Landau-Lifshitz-Gilbert modeling to reproduce the experimental bimodal line-shape characteristics of the effecti...
Optical Pattern Recognition XXIII, 2012
Interestingly, the past 20 years have provided us many examples of optical correlation methods fo... more Interestingly, the past 20 years have provided us many examples of optical correlation methods for pattern recognition, e.g. VanderLugt correlator (VLC). In recent years, hybrid techniques, i.e. numerical implementation of correlation, have been also considered an alternative to all-optical methods because they show a good compromise between performance and simplicity. Moreover, these correlation methods can be implemented using an all-numerical and reprogrammable target such as the graphics processor unit (GPU), or the field-programmable gate array (FPGA). However, this numerical procedure requires realizing two Fourier Transforms (FT), a spectral multiplication, and a correlation plane analysis. The purpose of this study is to compare the performances of a numerical correlator based on the fast Fourier transform (FFT) with that relying on a simulation of the Fraunhofer diffraction. Different tests using the Pointing Head Pose Image Database (PHPID) and considering faces with vertical and horizontal rotations were performed with the code MATLAB. Tests were conducted with a five reference optimized composite filter. The receiving operating characteristics (ROC) curves show that the optical FT simulating the Fraunhofer diffraction leads to better performances than the FFT. The implications of our results for correlation are discussed.
IEEE Transactions on Magnetics, 1997
ABSTRACT In this study, we suggest and validate an all-numerical implementation of a VanderLugt c... more ABSTRACT In this study, we suggest and validate an all-numerical implementation of a VanderLugt correlator which is optimized for face recognition applications. The main goal of this implementation is to take advantage of the benefits (detection, localization, and identification of a target object within a scene) of correlation methods and exploit the reconfigurability of numerical approaches. This technique requires a numerical implementation of the optical Fourier transform. We pay special attention to adapt the correlation filter to this numerical implementation. One main goal of this work is to reduce the size of the filter in order to decrease the memory space required for real time applications. To fulfil this requirement, we code the reference images with 8 bits and study the effect of this coding on the performances of several composite filters (phase-only filter, binary phase-only filter). The saturation effect has for effect to decrease the performances of the correlator for making a decision when filters contain up to nine references. Further, an optimization is proposed based for an optimized segmented composite filter. Based on this approach, we present tests with different faces demonstrating that the above mentioned saturation effect is significantly reduced while minimizing the size of the learning data base.
Optical Pattern Recognition XXIII, 2012
Interestingly, the past 20 years have provided us many examples of optical correlation methods fo... more Interestingly, the past 20 years have provided us many examples of optical correlation methods for pattern recognition, e.g. VanderLugt correlator (VLC). In recent years, hybrid techniques, i.e. numerical implementation of correlation, have been also considered an alternative to all-optical methods because they show a good compromise between performance and simplicity. Moreover, these correlation methods can be implemented using an all-numerical and reprogrammable target such as the graphics processor unit (GPU), or the field-programmable gate array (FPGA). However, this numerical procedure requires realizing two Fourier Transforms (FT), a spectral multiplication, and a correlation plane analysis. The purpose of this study is to compare the performances of a numerical correlator based on the fast Fourier transform (FFT) with that relying on a simulation of the Fraunhofer diffraction. Different tests using the Pointing Head Pose Image Database (PHPID) and considering faces with vertical and horizontal rotations were performed with the code MATLAB. Tests were conducted with a five reference optimized composite filter. The receiving operating characteristics (ROC) curves show that the optical FT simulating the Fraunhofer diffraction leads to better performances than the FFT. The implications of our results for correlation are discussed.
Spectroscopy Letters, 2012
The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ ren... more The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ renders an entire additional degree of freedom to the functionality of miniaturized magnetoelectronics and spintronics devices. In composite materials, the ME effect is realized by using the concept of product properties. Through the investigation of the microwave properties of a series of BaTiO 3 / Ni NCs fabricated by compaction of nanopowders, we present experimental evidence that the compaction ͑uniaxial͒ pressure in the range 33-230 MPa affects significantly the ME features. The Ni loading was varied from zero ͑BaTiO 3 only͒ to 63 vol %. Our findings revealed that the ME coupling coefficient exhibits a large enhancement for specific values of the Ni volume fraction and compaction pressure. The coupling effects in the NCs were studied by looking at the relationships among the crystallite orientation and the magnetic properties. The magnetization curves for different directions of the applied magnetic field cannot be superimposed. We suggest that the average magnetization measurements on these NCs under compressive stress are dominated by strain anisotropy rather than magnetocrystalline anisotropy. Overall, these observations are considered to be evidence of stress-induced microstructural changes under pressure which strongly affect the elastic interaction between the magnetostrictive and piezoelectric phases in these NCs. These results have a potential technological impact for designing precise tunable ME NCs for microwave devices such as tunable phase shifters, resonators, and delay lines.
Optics Letters, 2010
We report on an algorithm to compress and encrypt simultaneously multiple images (target images).... more We report on an algorithm to compress and encrypt simultaneously multiple images (target images). This method, which is based upon a specific spectral multiplexing (fusion without overlapping) of the multiple images, aims to achieve a single encrypted image, at the output plane of our system, that contains all information needed to reconstruct the target images. For that purpose, we divide the Fourier plane of the image to transmit into two types of area, i.e., specific and common areas to each target image. A segmentation criterion taking into account the rms duration of each target image spectrum is proposed. This approach, which consists of merging the input target images together (in the Fourier plane) allows us to reduce the information to be stored and/or transmitted (compression) and induce noise on the output image (encryption). To achieve a good encryption level, a first key image (containing biometric information and providing the intellectual property of the target images) is used. A second encryption key is inserted in the Fourier plane to ensure a relevant phase distribution of the different merged spectra. We also discuss how the encoding information can be optimized by minimizing the number of bits required to encode each pixel.
Journal of Physics D: Applied Physics, 2010
Using microwave and spin wave spectroscopy measurements, we examine the recently discovered room ... more Using microwave and spin wave spectroscopy measurements, we examine the recently discovered room temperature magnetoelectric (ME) Ni/BaTiO 3 nanocomposites (NCs) fabricated under uniaxial compression. Over the compositional range explored, we observe a significant variation in the microwave absorption spectrum of the NCs as a function of the Ni content. We argue that the relative change in the spin wave (SW) group velocity is related to the internal field determined from ferromagnetic resonance and the ME coupling coefficient evaluated by microwave spectroscopy in these samples. This suggests that the SW features are set by the local (internal) magnetic field. These observations suggest a broader opportunity to probe the collective spin-environment interactions in ME NCs.
![Research paper thumbnail of Controlled extrinsic magnetoelectric coupling in BaTiO[sub 3]/Ni nanocomposites: Effect of compaction pressure on interfacial anisotropy](https://attachments.academia-assets.com/39956934/thumbnails/1.jpg)
](Journal of Applied Physics, 2010
The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ ren... more The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ renders an entire additional degree of freedom to the functionality of miniaturized magnetoelectronics and spintronics devices. In composite materials, the ME effect is realized by using the concept of product properties. Through the investigation of the microwave properties of a series of BaTiO 3 / Ni NCs fabricated by compaction of nanopowders, we present experimental evidence that the compaction ͑uniaxial͒ pressure in the range 33-230 MPa affects significantly the ME features. The Ni loading was varied from zero ͑BaTiO 3 only͒ to 63 vol %. Our findings revealed that the ME coupling coefficient exhibits a large enhancement for specific values of the Ni volume fraction and compaction pressure. The coupling effects in the NCs were studied by looking at the relationships among the crystallite orientation and the magnetic properties. The magnetization curves for different directions of the applied magnetic field cannot be superimposed. We suggest that the average magnetization measurements on these NCs under compressive stress are dominated by strain anisotropy rather than magnetocrystalline anisotropy. Overall, these observations are considered to be evidence of stress-induced microstructural changes under pressure which strongly affect the elastic interaction between the magnetostrictive and piezoelectric phases in these NCs. These results have a potential technological impact for designing precise tunable ME NCs for microwave devices such as tunable phase shifters, resonators, and delay lines.
Applied Physics Letters, 2013
Applied Physics Letters, 2012
Applied Physics Letters, 2012
Giant magnetoresistance effect in graphene with asymmetrical magnetic superlattices Appl. Phys. L... more Giant magnetoresistance effect in graphene with asymmetrical magnetic superlattices Appl. Phys. Lett. 101, 152404 (2012) Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by halfmetallicity of Co2MnSi and coherent tunneling Appl. Phys. Lett. 101, 132418 Giant magneto-resistance estimated from direct observation of nanoscale ferromagnetic domain evolution in La0.325Pr0.3Ca0.375MnO3 J. Appl. Phys. 112, 053924 (2012) Electrical determination of relative chirality direction in a Co/Cu/Co ferromagnetic ring
Applied Physics Letters, 2010
We have fabricated a set of microwire composites with varying wire concentrations and studied the... more We have fabricated a set of microwire composites with varying wire concentrations and studied their effective complex permittivity under the tensile stress at a frequency range of 1-6 GHz. It has been found that with increasing wire concentration the composite presents increasing effective permittivity and strain sensitivity. The Gaussian molecular network model shows a complex strain dependence of sensitivity due to the composite architecture influenced by the wire concentrations. All these results indicate the proposed composite are excellent candidate materials for the microwave sensing and structural interrogation applications.
Journal of Electrostatics, 1997
The purpose of this paper is to present computer simulation data for the effective permittivity (... more The purpose of this paper is to present computer simulation data for the effective permittivity (in the quasistatic limit) of a system composed of discrete inhomogeneities of permittivity El, embedded in a three-dimensional homogeneous matrix of permittivity e2<el. The computer-simulation model is based upon the resolution of boundary integral equations. We analyze how the geometric shape (sphere, ellipsoid) of the components in these materials affects the effective permittivity and we compare the prediction of our numerical simulations with results of previous works. 0304-3886/97/$17.00
Journal of Applied Physics, 2007
The impetus of this work was to investigate the electromagnetic and tensile properties of several... more The impetus of this work was to investigate the electromagnetic and tensile properties of several commercially available plastoferrites (PFs) at ambient conditions. The approach involved selection of a set of PFs and measuring their complex effective permittivity ε=ε′−jε″ and permeability μ=μ′−jμ″ under uniaxial stress at microwave frequencies (0.1–4.5GHz) and room temperature. We analyze the ε and μ spectra for tensilely strained PFs up to 3%. Comparing our experimental ε data against several dielectric relaxational behaviors, we find that the main physics cannot be understood with a single relaxation mechanism. We then go on to consider the magnetic permeability spectra in the microwave range of frequencies and show that an appropriate magnetization mechanism is given by the gyromagnetic spin resonance mechanism. We use a combination of Bruggeman mean field analysis and Landau-Lifshitz-Gilbert modeling to reproduce the experimental bimodal line-shape characteristics of the effecti...
Optical Pattern Recognition XXIII, 2012
Interestingly, the past 20 years have provided us many examples of optical correlation methods fo... more Interestingly, the past 20 years have provided us many examples of optical correlation methods for pattern recognition, e.g. VanderLugt correlator (VLC). In recent years, hybrid techniques, i.e. numerical implementation of correlation, have been also considered an alternative to all-optical methods because they show a good compromise between performance and simplicity. Moreover, these correlation methods can be implemented using an all-numerical and reprogrammable target such as the graphics processor unit (GPU), or the field-programmable gate array (FPGA). However, this numerical procedure requires realizing two Fourier Transforms (FT), a spectral multiplication, and a correlation plane analysis. The purpose of this study is to compare the performances of a numerical correlator based on the fast Fourier transform (FFT) with that relying on a simulation of the Fraunhofer diffraction. Different tests using the Pointing Head Pose Image Database (PHPID) and considering faces with vertical and horizontal rotations were performed with the code MATLAB. Tests were conducted with a five reference optimized composite filter. The receiving operating characteristics (ROC) curves show that the optical FT simulating the Fraunhofer diffraction leads to better performances than the FFT. The implications of our results for correlation are discussed.
IEEE Transactions on Magnetics, 1997
ABSTRACT In this study, we suggest and validate an all-numerical implementation of a VanderLugt c... more ABSTRACT In this study, we suggest and validate an all-numerical implementation of a VanderLugt correlator which is optimized for face recognition applications. The main goal of this implementation is to take advantage of the benefits (detection, localization, and identification of a target object within a scene) of correlation methods and exploit the reconfigurability of numerical approaches. This technique requires a numerical implementation of the optical Fourier transform. We pay special attention to adapt the correlation filter to this numerical implementation. One main goal of this work is to reduce the size of the filter in order to decrease the memory space required for real time applications. To fulfil this requirement, we code the reference images with 8 bits and study the effect of this coding on the performances of several composite filters (phase-only filter, binary phase-only filter). The saturation effect has for effect to decrease the performances of the correlator for making a decision when filters contain up to nine references. Further, an optimization is proposed based for an optimized segmented composite filter. Based on this approach, we present tests with different faces demonstrating that the above mentioned saturation effect is significantly reduced while minimizing the size of the learning data base.
Optical Pattern Recognition XXIII, 2012
Interestingly, the past 20 years have provided us many examples of optical correlation methods fo... more Interestingly, the past 20 years have provided us many examples of optical correlation methods for pattern recognition, e.g. VanderLugt correlator (VLC). In recent years, hybrid techniques, i.e. numerical implementation of correlation, have been also considered an alternative to all-optical methods because they show a good compromise between performance and simplicity. Moreover, these correlation methods can be implemented using an all-numerical and reprogrammable target such as the graphics processor unit (GPU), or the field-programmable gate array (FPGA). However, this numerical procedure requires realizing two Fourier Transforms (FT), a spectral multiplication, and a correlation plane analysis. The purpose of this study is to compare the performances of a numerical correlator based on the fast Fourier transform (FFT) with that relying on a simulation of the Fraunhofer diffraction. Different tests using the Pointing Head Pose Image Database (PHPID) and considering faces with vertical and horizontal rotations were performed with the code MATLAB. Tests were conducted with a five reference optimized composite filter. The receiving operating characteristics (ROC) curves show that the optical FT simulating the Fraunhofer diffraction leads to better performances than the FFT. The implications of our results for correlation are discussed.
Spectroscopy Letters, 2012
The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ ren... more The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ renders an entire additional degree of freedom to the functionality of miniaturized magnetoelectronics and spintronics devices. In composite materials, the ME effect is realized by using the concept of product properties. Through the investigation of the microwave properties of a series of BaTiO 3 / Ni NCs fabricated by compaction of nanopowders, we present experimental evidence that the compaction ͑uniaxial͒ pressure in the range 33-230 MPa affects significantly the ME features. The Ni loading was varied from zero ͑BaTiO 3 only͒ to 63 vol %. Our findings revealed that the ME coupling coefficient exhibits a large enhancement for specific values of the Ni volume fraction and compaction pressure. The coupling effects in the NCs were studied by looking at the relationships among the crystallite orientation and the magnetic properties. The magnetization curves for different directions of the applied magnetic field cannot be superimposed. We suggest that the average magnetization measurements on these NCs under compressive stress are dominated by strain anisotropy rather than magnetocrystalline anisotropy. Overall, these observations are considered to be evidence of stress-induced microstructural changes under pressure which strongly affect the elastic interaction between the magnetostrictive and piezoelectric phases in these NCs. These results have a potential technological impact for designing precise tunable ME NCs for microwave devices such as tunable phase shifters, resonators, and delay lines.
Optics Letters, 2010
We report on an algorithm to compress and encrypt simultaneously multiple images (target images).... more We report on an algorithm to compress and encrypt simultaneously multiple images (target images). This method, which is based upon a specific spectral multiplexing (fusion without overlapping) of the multiple images, aims to achieve a single encrypted image, at the output plane of our system, that contains all information needed to reconstruct the target images. For that purpose, we divide the Fourier plane of the image to transmit into two types of area, i.e., specific and common areas to each target image. A segmentation criterion taking into account the rms duration of each target image spectrum is proposed. This approach, which consists of merging the input target images together (in the Fourier plane) allows us to reduce the information to be stored and/or transmitted (compression) and induce noise on the output image (encryption). To achieve a good encryption level, a first key image (containing biometric information and providing the intellectual property of the target images) is used. A second encryption key is inserted in the Fourier plane to ensure a relevant phase distribution of the different merged spectra. We also discuss how the encoding information can be optimized by minimizing the number of bits required to encode each pixel.
Journal of Physics D: Applied Physics, 2010
Using microwave and spin wave spectroscopy measurements, we examine the recently discovered room ... more Using microwave and spin wave spectroscopy measurements, we examine the recently discovered room temperature magnetoelectric (ME) Ni/BaTiO 3 nanocomposites (NCs) fabricated under uniaxial compression. Over the compositional range explored, we observe a significant variation in the microwave absorption spectrum of the NCs as a function of the Ni content. We argue that the relative change in the spin wave (SW) group velocity is related to the internal field determined from ferromagnetic resonance and the ME coupling coefficient evaluated by microwave spectroscopy in these samples. This suggests that the SW features are set by the local (internal) magnetic field. These observations suggest a broader opportunity to probe the collective spin-environment interactions in ME NCs.
Journal of Applied Physics, 2010
The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ ren... more The dynamical control of the dielectric response in magnetoelectric ͑ME͒ nanocomposites ͑NCs͒ renders an entire additional degree of freedom to the functionality of miniaturized magnetoelectronics and spintronics devices. In composite materials, the ME effect is realized by using the concept of product properties. Through the investigation of the microwave properties of a series of BaTiO 3 / Ni NCs fabricated by compaction of nanopowders, we present experimental evidence that the compaction ͑uniaxial͒ pressure in the range 33-230 MPa affects significantly the ME features. The Ni loading was varied from zero ͑BaTiO 3 only͒ to 63 vol %. Our findings revealed that the ME coupling coefficient exhibits a large enhancement for specific values of the Ni volume fraction and compaction pressure. The coupling effects in the NCs were studied by looking at the relationships among the crystallite orientation and the magnetic properties. The magnetization curves for different directions of the applied magnetic field cannot be superimposed. We suggest that the average magnetization measurements on these NCs under compressive stress are dominated by strain anisotropy rather than magnetocrystalline anisotropy. Overall, these observations are considered to be evidence of stress-induced microstructural changes under pressure which strongly affect the elastic interaction between the magnetostrictive and piezoelectric phases in these NCs. These results have a potential technological impact for designing precise tunable ME NCs for microwave devices such as tunable phase shifters, resonators, and delay lines.
Applied Physics Letters, 2013
Applied Physics Letters, 2012
Applied Physics Letters, 2012
Giant magnetoresistance effect in graphene with asymmetrical magnetic superlattices Appl. Phys. L... more Giant magnetoresistance effect in graphene with asymmetrical magnetic superlattices Appl. Phys. Lett. 101, 152404 (2012) Giant tunneling magnetoresistance in epitaxial Co2MnSi/MgO/Co2MnSi magnetic tunnel junctions by halfmetallicity of Co2MnSi and coherent tunneling Appl. Phys. Lett. 101, 132418 Giant magneto-resistance estimated from direct observation of nanoscale ferromagnetic domain evolution in La0.325Pr0.3Ca0.375MnO3 J. Appl. Phys. 112, 053924 (2012) Electrical determination of relative chirality direction in a Co/Cu/Co ferromagnetic ring
Applied Physics Letters, 2010
We have fabricated a set of microwire composites with varying wire concentrations and studied the... more We have fabricated a set of microwire composites with varying wire concentrations and studied their effective complex permittivity under the tensile stress at a frequency range of 1-6 GHz. It has been found that with increasing wire concentration the composite presents increasing effective permittivity and strain sensitivity. The Gaussian molecular network model shows a complex strain dependence of sensitivity due to the composite architecture influenced by the wire concentrations. All these results indicate the proposed composite are excellent candidate materials for the microwave sensing and structural interrogation applications.
Journal of Electrostatics, 1997
The purpose of this paper is to present computer simulation data for the effective permittivity (... more The purpose of this paper is to present computer simulation data for the effective permittivity (in the quasistatic limit) of a system composed of discrete inhomogeneities of permittivity El, embedded in a three-dimensional homogeneous matrix of permittivity e2<el. The computer-simulation model is based upon the resolution of boundary integral equations. We analyze how the geometric shape (sphere, ellipsoid) of the components in these materials affects the effective permittivity and we compare the prediction of our numerical simulations with results of previous works. 0304-3886/97/$17.00