Sandrine Rakotonarivo - Academia.edu (original) (raw)

Papers by Sandrine Rakotonarivo

Research paper thumbnail of Application of Topological Energy for Flow Velocity Field Characterization

2023 IEEE International Ultrasonics Symposium (IUS)

Research paper thumbnail of Predicting the bistatic scattering from subsea buried targets using in-air laboratory measurements

HAL (Le Centre pour la Communication Scientifique Directe), 2018

International audienc

Research paper thumbnail of Measurement of a target’s structural admittance and the prediction of its scattered field in different media

HAL (Le Centre pour la Communication Scientifique Directe), Sep 5, 2016

International audienc

Research paper thumbnail of Holographic array for determining structural acoustic properties

HAL (Le Centre pour la Communication Scientifique Directe), 2019

It has already been shown that the scattering properties of an arbitrary object in an external me... more It has already been shown that the scattering properties of an arbitrary object in an external medium can be determined by three quantities: The structural impedance matrix, Zs, the input impedance matrix Zi, and the radiation impedance matrix, Zr. Only Zs is dependent on the specific, possibly unknown and complicated internal structure of the object; the other two are only dependent on the surface shape of the object and the external medium so they can be routinely computed. We have constructed a laboratory facility to measure the structural impedance of an object by placing it in an external, diffuse noise field. The measurements are made using an array of a double layer of MEMS microphones placed in the near field of the object; the array is embedded in a skeletal structure which surrounds the object. This array structure is programmatically generated from a 3D scan of the object, and constructed using a large 3D printer. Cross correlating the MEMS acoustic data together with holographic signal processing yields the structural impedance, with the large matrix-matrix calculations being accelerated on a GPU computing platform. These results combined with the other computed impedances provides the scattering properties of the object when placed (loaded) in an external medium. The details of the experimental setup are explained and preliminary results are presented.

Research paper thumbnail of Experimental evaluation of a sound diffuse field in a ordinary room

Journal of the Acoustical Society of America, Oct 1, 2021

This paper presents a methodology based on analysis of spatial correlation functions for assessin... more This paper presents a methodology based on analysis of spatial correlation functions for assessing diffusivity of a sound field in reverberant and ordinary reflective rooms. A set of sound field measurements using a microphone array is performed in a room excited by a broadband signal and for many positions of loudspeakers. Each recorded signal is then broken down with a filter bank and the spatial correlation of each obtained band-limited signal is computed. Theoretical predictions of the spatial correlation function and the measured ones show very good agreement when spatial averaging and frequency conditions are met for producing a diffuse field. Evolution of the spatial correlation functions versus frequency and number of spatial averaging, i.e., number of sources positions, are examined in a reflective room. Results show that the proposed technique allows to determine the minimum number of required source positions and the actual lower frequency bound for considering that the field is diffuse. The latter is analogous to the Schroeder frequency for reverberant room. Interest of the presented methodology is its ability to experimentally assess in any reflective ordinary room the actual frequency range over which the field can be considered as diffuse. [Work funded by the AMIDEX Foundation.]

Research paper thumbnail of Invariant-Based Range-Localization from a Frequency-Time Spectrogram

HAL (Le Centre pour la Communication Scientifique Directe), 2012

International audienc

Research paper thumbnail of A new hybrid method between equivalent source method and boundary element method for modeling diffraction

Journal of the Acoustical Society of America, Oct 1, 2021

The Equivalent Source Method (ESM) allows to model the acoustical radiation of an object with a s... more The Equivalent Source Method (ESM) allows to model the acoustical radiation of an object with a set of monopole sources inside the object. This method efficiently describes acoustical radiation of an object with smooth surface, but is not performant for addressing diffraction induced by sharp edge. In this study, we use the simple source formulation to establish ESM as an integral formulation. In this form, ESM belong to the Boundary Element Method (BEM) family, with an implicit mesh. Therefore, we propose an alternative method similar to ESM with sources on the surface object, as the singularities can now be handled with the integral formulation. This new method is more performant than ESM for modeling diffraction, and is easier to implement than standard BEM based on Gauss Quadrature while it still takes advantage of the ESM implicit mesh. Comparisons of this hybrid method with ESM and standard BEM approaches show that the developed method is a good compromise between the two other approaches: the new method is more accurate than BEM, but less than ESM for a smooth object; while it is equivalent to BEM and more accurate than ESM for an edgy object. Work Funded by AMIDEX foundation.

Research paper thumbnail of Passive structural monitoring based on data-driven matched field processing

Journal of the Acoustical Society of America, Apr 1, 2019

Direct adaptive equalization based on fast sparse recursive least squares algorithms for multiple... more Direct adaptive equalization based on fast sparse recursive least squares algorithms for multiple-input multipleoutput underwater acoustic communications

Research paper thumbnail of Bistatic scattering of an elastic object using the structural admittance and noise-based holographic measurements

Journal of the Acoustical Society of America, Aug 1, 2020

This paper presents a method to calculate the bistatic response of an elastic object immersed in ... more This paper presents a method to calculate the bistatic response of an elastic object immersed in a fluid using its structural Green's function (in vacuo structural admittance matrix), calculated by placing the object in a spatially random noise field in air. The field separation technique and equivalent source method are used to reconstruct pressure and velocity fields at the object's surface from pressure measurements recorded on two conformal holographic surfaces surrounding the object. Accurate reconstruction of the surface velocity requires subtraction of the rigid body response computed using a finite element approach. The velocity and pressure fields on the surface lead to the extraction of the in vacuo structural admittance matrix of the elastic object, which is manipulated to yield the farfield bistatic response for a fluid-loaded target for several angles of incidence. This method allows the computation of the scattering properties of an elastic object using exclusive information calculated on its surface (no knowledge of the internal structure required). A numerical experiment involving a cylindrical shell with hemispherical caps is presented, and its bistatic response in water shows excellent agreement with a finite element solution.

Research paper thumbnail of Une nouvelle méthode entre les sources équivalentes et les éléments finis de frontières pour modéliser la diffraction

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Reconstruction de la réponse bistatique d'un objet élastique avec arêtes, à partir de sa matrice d'impédance acoustique estimée par holographie acoustique en champ diffus

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Évaluation Expérimentale D'Un Champ Sonore Diffus Dans Une Pièce Réfléchissante Ordinaire

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Ultrasonic wave propagation in scattering media with imperfect contact at the matrix-inclusions interfaces

HAL (Le Centre pour la Communication Scientifique Directe), 2019

Research paper thumbnail of Low frequency passive imaging for detection and localization of defects in immersed pipe

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2019

Research paper thumbnail of Sensitivity enhancement of the topological imaging method: Application to weld inspection

HAL (Le Centre pour la Communication Scientifique Directe), 2017

International audienc

Research paper thumbnail of Recent modelling advances in NDT to improve safety and sustainability for the next generation of nuclear reactor

HAL (Le Centre pour la Communication Scientifique Directe), Jan 16, 2019

Various case studies: sodium return weir, tube, pump chamber… 2 nd and 3 rd plates: detectable an... more Various case studies: sodium return weir, tube, pump chamber… 2 nd and 3 rd plates: detectable and measurable 3 rd and 4 th plates provided with target: detectable and measurable Streight and curved cylinder behind vessel: detectable and measurable Hypothesis: walls (primary vessel, internal structures) = plane parallel plates Cube-corner target 3 rd plate Curved tube behind 1 screen Ultrasonic telemetry of objects behind screen(s)

Research paper thumbnail of Non Destructive Evaluation for containment monitoring

HAL (Le Centre pour la Communication Scientifique Directe), 2018

International audienc

Research paper thumbnail of Nondestructive Evaluation of Concrete Material Properties for Nuclear Power Plant Survey: Results in the Laboratory and on the VeRCoRS Mock-Up

NDE/NDT, Structural Materials Technology for Highways and Bridges (SMT) and the International Sym... more NDE/NDT, Structural Materials Technology for Highways and Bridges (SMT) and the International Symposium on Non-Destructive Testing in Civil Engineering (NDT-CE) 2018, New Brunswick, ETATS-UNIS, 27-/08/2018 - 29/06/2018Pre-stressed concrete nuclear power plant containment vessel is the third barrier in case of an accident so that quantifying concrete properties with Non Destructive Evaluation (NDE) is a continuing goal. This includes the mapping of the following concrete properties: elastic modulus, water saturation, permeability. In addition, those measurements have to be challenged with the level of stress (which will be modified during an accident) possibly coupled with thermal induced damage. In the ANR French project 'Non Destructive Evaluation of containment nuclear plant structures' (ENDE) eight partners have carried out laboratory and in situ NDE measurements with the aim to compare and combine them to reach quantitative useful information about concrete conditions. In this paper we present a synthesis of the mains results obtained with classical and non-classical NDE methods. This includes electromagnetic techniques such as radar, capacitive measurements, resistivity measurements and ultrasonic measurements (impact echo, ultrasonic pulse velocity - in reflexion and transmission mode for longitudinal and transverse waves, surface waves, diffuse waves, coda wave interferometry, nonlinear acoustics, etc.). The laboratory experiments have been conducted on slabs 0.5 m x 0.25 m x 0.12 m, for one concrete mix formulated to be representative of nuclear containment walls, in different conditions: - sound concrete without any stress for different water saturations,- heat damage of partially saturated slab (at 80°C, 150°C, 200°C),- sound concrete under stress (up to 30% of the compressive strength),- heat damage concrete under stress.A series of NDE method combinations (using data fusion approach) is performed to solve the problem of multiple sensitivity issues. This laboratory work is then transposed on the VeRCoRS mock-up which is a 1/3 scaled concrete power plant (a Õ 16 m x h 30 m cylinder, with 0.40 m thick walls) heavily instrumented (700 sensors, 2 km of fiber optic). In this paper we present results obtained before, during and after a decennial test simulation which consists in increasing the internal pressure with air, maintaining its level to 4 bars during 2 hours and then decreasing back to the atmospheric pressure level.To conclude industrial and research perspectives are presented.Pre-stressed concrete nuclear power plant containment vessel is the third barrier in case of an accident so that quantifying concrete properties with Non Destructive Evaluation (NDE) is a continuing goal. This includes the mapping of the following concrete properties: elastic modulus, water saturation, permeability. In addition, those measurements have to be challenged with the level of stress (which will be modified during an accident) possibly coupled with thermal induced damage. In the ANR French project 'Non Destructive Evaluation of containment nuclear plant structures' (ENDE) eight partners have carried out laboratory and in situ NDE measurements with the aim to compare and combine them to reach quantitative useful information about concrete conditions. In this paper we present a synthesis of the mains results obtained with classical and non-classical NDE methods. This includes electromagnetic techniques such as radar, capacitive measurements, resistivity measurements and ultrasonic measurements (impact echo, ultrasonic pulse velocity - in reflexion and transmission mode for longitudinal and transverse waves, surface waves, diffuse waves, coda wave interferometry, nonlinear acoustics, etc.). The laboratory experiments have been conducted on slabs 0.5 m x 0.25 m x 0.12 m, for one concrete mix formulated to be representative of nuclear containment walls, in different conditions: - sound concrete without any stress for different water saturations,- heat damage of partially saturated slab (at 80°C, 150°C, 200°C),- sound concrete under stress (up to 30% of the compressive strength),- heat damage concrete under stress.A series of NDE method combinations (using data fusion approach) is performed to solve the problem of multiple sensitivity issues. This laboratory work is then transposed on the VeRCoRS mock-up which is a 1/3 scaled concrete power plant (a Õ 16 m x h 30 m cylinder, with 0.40 m thick walls) heavily instrumented (700 sensors, 2 km of fiber optic). In this paper we present results obtained before, during and after a decennial test simulation which consists in increasing the internal pressure with air, maintaining its level to 4 bars during 2 hours and then decreasing back to the atmospheric pressure level.To conclude industrial and research perspectives are presented

Research paper thumbnail of Détection et localisation de défauts par imagerie topologique et focalisation de sources: application à l’inspection des soudures

Research paper thumbnail of Ultrasonic imaging in liquid sodium

Research paper thumbnail of Application of Topological Energy for Flow Velocity Field Characterization

2023 IEEE International Ultrasonics Symposium (IUS)

Research paper thumbnail of Predicting the bistatic scattering from subsea buried targets using in-air laboratory measurements

HAL (Le Centre pour la Communication Scientifique Directe), 2018

International audienc

Research paper thumbnail of Measurement of a target’s structural admittance and the prediction of its scattered field in different media

HAL (Le Centre pour la Communication Scientifique Directe), Sep 5, 2016

International audienc

Research paper thumbnail of Holographic array for determining structural acoustic properties

HAL (Le Centre pour la Communication Scientifique Directe), 2019

It has already been shown that the scattering properties of an arbitrary object in an external me... more It has already been shown that the scattering properties of an arbitrary object in an external medium can be determined by three quantities: The structural impedance matrix, Zs, the input impedance matrix Zi, and the radiation impedance matrix, Zr. Only Zs is dependent on the specific, possibly unknown and complicated internal structure of the object; the other two are only dependent on the surface shape of the object and the external medium so they can be routinely computed. We have constructed a laboratory facility to measure the structural impedance of an object by placing it in an external, diffuse noise field. The measurements are made using an array of a double layer of MEMS microphones placed in the near field of the object; the array is embedded in a skeletal structure which surrounds the object. This array structure is programmatically generated from a 3D scan of the object, and constructed using a large 3D printer. Cross correlating the MEMS acoustic data together with holographic signal processing yields the structural impedance, with the large matrix-matrix calculations being accelerated on a GPU computing platform. These results combined with the other computed impedances provides the scattering properties of the object when placed (loaded) in an external medium. The details of the experimental setup are explained and preliminary results are presented.

Research paper thumbnail of Experimental evaluation of a sound diffuse field in a ordinary room

Journal of the Acoustical Society of America, Oct 1, 2021

This paper presents a methodology based on analysis of spatial correlation functions for assessin... more This paper presents a methodology based on analysis of spatial correlation functions for assessing diffusivity of a sound field in reverberant and ordinary reflective rooms. A set of sound field measurements using a microphone array is performed in a room excited by a broadband signal and for many positions of loudspeakers. Each recorded signal is then broken down with a filter bank and the spatial correlation of each obtained band-limited signal is computed. Theoretical predictions of the spatial correlation function and the measured ones show very good agreement when spatial averaging and frequency conditions are met for producing a diffuse field. Evolution of the spatial correlation functions versus frequency and number of spatial averaging, i.e., number of sources positions, are examined in a reflective room. Results show that the proposed technique allows to determine the minimum number of required source positions and the actual lower frequency bound for considering that the field is diffuse. The latter is analogous to the Schroeder frequency for reverberant room. Interest of the presented methodology is its ability to experimentally assess in any reflective ordinary room the actual frequency range over which the field can be considered as diffuse. [Work funded by the AMIDEX Foundation.]

Research paper thumbnail of Invariant-Based Range-Localization from a Frequency-Time Spectrogram

HAL (Le Centre pour la Communication Scientifique Directe), 2012

International audienc

Research paper thumbnail of A new hybrid method between equivalent source method and boundary element method for modeling diffraction

Journal of the Acoustical Society of America, Oct 1, 2021

The Equivalent Source Method (ESM) allows to model the acoustical radiation of an object with a s... more The Equivalent Source Method (ESM) allows to model the acoustical radiation of an object with a set of monopole sources inside the object. This method efficiently describes acoustical radiation of an object with smooth surface, but is not performant for addressing diffraction induced by sharp edge. In this study, we use the simple source formulation to establish ESM as an integral formulation. In this form, ESM belong to the Boundary Element Method (BEM) family, with an implicit mesh. Therefore, we propose an alternative method similar to ESM with sources on the surface object, as the singularities can now be handled with the integral formulation. This new method is more performant than ESM for modeling diffraction, and is easier to implement than standard BEM based on Gauss Quadrature while it still takes advantage of the ESM implicit mesh. Comparisons of this hybrid method with ESM and standard BEM approaches show that the developed method is a good compromise between the two other approaches: the new method is more accurate than BEM, but less than ESM for a smooth object; while it is equivalent to BEM and more accurate than ESM for an edgy object. Work Funded by AMIDEX foundation.

Research paper thumbnail of Passive structural monitoring based on data-driven matched field processing

Journal of the Acoustical Society of America, Apr 1, 2019

Direct adaptive equalization based on fast sparse recursive least squares algorithms for multiple... more Direct adaptive equalization based on fast sparse recursive least squares algorithms for multiple-input multipleoutput underwater acoustic communications

Research paper thumbnail of Bistatic scattering of an elastic object using the structural admittance and noise-based holographic measurements

Journal of the Acoustical Society of America, Aug 1, 2020

This paper presents a method to calculate the bistatic response of an elastic object immersed in ... more This paper presents a method to calculate the bistatic response of an elastic object immersed in a fluid using its structural Green's function (in vacuo structural admittance matrix), calculated by placing the object in a spatially random noise field in air. The field separation technique and equivalent source method are used to reconstruct pressure and velocity fields at the object's surface from pressure measurements recorded on two conformal holographic surfaces surrounding the object. Accurate reconstruction of the surface velocity requires subtraction of the rigid body response computed using a finite element approach. The velocity and pressure fields on the surface lead to the extraction of the in vacuo structural admittance matrix of the elastic object, which is manipulated to yield the farfield bistatic response for a fluid-loaded target for several angles of incidence. This method allows the computation of the scattering properties of an elastic object using exclusive information calculated on its surface (no knowledge of the internal structure required). A numerical experiment involving a cylindrical shell with hemispherical caps is presented, and its bistatic response in water shows excellent agreement with a finite element solution.

Research paper thumbnail of Une nouvelle méthode entre les sources équivalentes et les éléments finis de frontières pour modéliser la diffraction

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Reconstruction de la réponse bistatique d'un objet élastique avec arêtes, à partir de sa matrice d'impédance acoustique estimée par holographie acoustique en champ diffus

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Évaluation Expérimentale D'Un Champ Sonore Diffus Dans Une Pièce Réfléchissante Ordinaire

HAL (Le Centre pour la Communication Scientifique Directe), Apr 11, 2022

Research paper thumbnail of Ultrasonic wave propagation in scattering media with imperfect contact at the matrix-inclusions interfaces

HAL (Le Centre pour la Communication Scientifique Directe), 2019

Research paper thumbnail of Low frequency passive imaging for detection and localization of defects in immersed pipe

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 2019

Research paper thumbnail of Sensitivity enhancement of the topological imaging method: Application to weld inspection

HAL (Le Centre pour la Communication Scientifique Directe), 2017

International audienc

Research paper thumbnail of Recent modelling advances in NDT to improve safety and sustainability for the next generation of nuclear reactor

HAL (Le Centre pour la Communication Scientifique Directe), Jan 16, 2019

Various case studies: sodium return weir, tube, pump chamber… 2 nd and 3 rd plates: detectable an... more Various case studies: sodium return weir, tube, pump chamber… 2 nd and 3 rd plates: detectable and measurable 3 rd and 4 th plates provided with target: detectable and measurable Streight and curved cylinder behind vessel: detectable and measurable Hypothesis: walls (primary vessel, internal structures) = plane parallel plates Cube-corner target 3 rd plate Curved tube behind 1 screen Ultrasonic telemetry of objects behind screen(s)

Research paper thumbnail of Non Destructive Evaluation for containment monitoring

HAL (Le Centre pour la Communication Scientifique Directe), 2018

International audienc

Research paper thumbnail of Nondestructive Evaluation of Concrete Material Properties for Nuclear Power Plant Survey: Results in the Laboratory and on the VeRCoRS Mock-Up

NDE/NDT, Structural Materials Technology for Highways and Bridges (SMT) and the International Sym... more NDE/NDT, Structural Materials Technology for Highways and Bridges (SMT) and the International Symposium on Non-Destructive Testing in Civil Engineering (NDT-CE) 2018, New Brunswick, ETATS-UNIS, 27-/08/2018 - 29/06/2018Pre-stressed concrete nuclear power plant containment vessel is the third barrier in case of an accident so that quantifying concrete properties with Non Destructive Evaluation (NDE) is a continuing goal. This includes the mapping of the following concrete properties: elastic modulus, water saturation, permeability. In addition, those measurements have to be challenged with the level of stress (which will be modified during an accident) possibly coupled with thermal induced damage. In the ANR French project 'Non Destructive Evaluation of containment nuclear plant structures' (ENDE) eight partners have carried out laboratory and in situ NDE measurements with the aim to compare and combine them to reach quantitative useful information about concrete conditions. In this paper we present a synthesis of the mains results obtained with classical and non-classical NDE methods. This includes electromagnetic techniques such as radar, capacitive measurements, resistivity measurements and ultrasonic measurements (impact echo, ultrasonic pulse velocity - in reflexion and transmission mode for longitudinal and transverse waves, surface waves, diffuse waves, coda wave interferometry, nonlinear acoustics, etc.). The laboratory experiments have been conducted on slabs 0.5 m x 0.25 m x 0.12 m, for one concrete mix formulated to be representative of nuclear containment walls, in different conditions: - sound concrete without any stress for different water saturations,- heat damage of partially saturated slab (at 80°C, 150°C, 200°C),- sound concrete under stress (up to 30% of the compressive strength),- heat damage concrete under stress.A series of NDE method combinations (using data fusion approach) is performed to solve the problem of multiple sensitivity issues. This laboratory work is then transposed on the VeRCoRS mock-up which is a 1/3 scaled concrete power plant (a Õ 16 m x h 30 m cylinder, with 0.40 m thick walls) heavily instrumented (700 sensors, 2 km of fiber optic). In this paper we present results obtained before, during and after a decennial test simulation which consists in increasing the internal pressure with air, maintaining its level to 4 bars during 2 hours and then decreasing back to the atmospheric pressure level.To conclude industrial and research perspectives are presented.Pre-stressed concrete nuclear power plant containment vessel is the third barrier in case of an accident so that quantifying concrete properties with Non Destructive Evaluation (NDE) is a continuing goal. This includes the mapping of the following concrete properties: elastic modulus, water saturation, permeability. In addition, those measurements have to be challenged with the level of stress (which will be modified during an accident) possibly coupled with thermal induced damage. In the ANR French project 'Non Destructive Evaluation of containment nuclear plant structures' (ENDE) eight partners have carried out laboratory and in situ NDE measurements with the aim to compare and combine them to reach quantitative useful information about concrete conditions. In this paper we present a synthesis of the mains results obtained with classical and non-classical NDE methods. This includes electromagnetic techniques such as radar, capacitive measurements, resistivity measurements and ultrasonic measurements (impact echo, ultrasonic pulse velocity - in reflexion and transmission mode for longitudinal and transverse waves, surface waves, diffuse waves, coda wave interferometry, nonlinear acoustics, etc.). The laboratory experiments have been conducted on slabs 0.5 m x 0.25 m x 0.12 m, for one concrete mix formulated to be representative of nuclear containment walls, in different conditions: - sound concrete without any stress for different water saturations,- heat damage of partially saturated slab (at 80°C, 150°C, 200°C),- sound concrete under stress (up to 30% of the compressive strength),- heat damage concrete under stress.A series of NDE method combinations (using data fusion approach) is performed to solve the problem of multiple sensitivity issues. This laboratory work is then transposed on the VeRCoRS mock-up which is a 1/3 scaled concrete power plant (a Õ 16 m x h 30 m cylinder, with 0.40 m thick walls) heavily instrumented (700 sensors, 2 km of fiber optic). In this paper we present results obtained before, during and after a decennial test simulation which consists in increasing the internal pressure with air, maintaining its level to 4 bars during 2 hours and then decreasing back to the atmospheric pressure level.To conclude industrial and research perspectives are presented

Research paper thumbnail of Détection et localisation de défauts par imagerie topologique et focalisation de sources: application à l’inspection des soudures

Research paper thumbnail of Ultrasonic imaging in liquid sodium