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Samuel Rodriguez

Actuellement :

I am at the present time working on an innovative ultrasonic imaging technique. It is based on a mathematical tool issued from the optimization community : the topological derivative. It has already been experimentally applied in the laboratory for a transducer array and this work leaded to the Time Domain Topological Energy method. [N. Dominguez and V. Gibiat, “Non-destructive imaging using the time domain topological energy method”, Ultrasonics 50 (2010) 367–372].

The techniques issued from the topological derivatives are based on the computation of two wave fields in a virtual medium without inhomogeneity, solutions of the direct and the adjoint problems respectively. The first wave field is the response of the domain to the excitations signals produced during the experiments. Assuming a semi-infinite virtual medium, the second wave field is the response of the domain to the time-reversed signals experimentally measured. Then, both fields are multiplicated and the scatterer appear naturally. These methods are supposed to be iterative, but the result obtained after the first iteration is already excellent, because the time reversed signals naturally focus on the scatterer positions when the direct problem solution acts as a photographic developer that lights up the back-propagated field at the right time.

I developed the FTIM (Fast Topological IMaging) method, that speeds up by a 60 factor the topological imaging process, so that real time ultrasonic applications are just a few seconds away. Direct time-domain numerical computations are replaced by frequency-domain semi-analytical calculations. As the use of FTIM with a single illumination of the medium leads to an excellent resolution, whereas standards methods require multiple illuminations, we believe that the FTIM method is of high interest for high frame rate ultrasound.

Here is an application of the Plane wave Echo Particle Image Velocimetry (PW Echo PIV) method I developed. Echo PIV is a recent method that allows to measure the 2D velocity field of a flow of a previously seeded fluid. It is inspired from the optical Particle Image Velocimetry that requires a laser beam and a high frame rate camera. Echo PIV has a significant advantage versus optical PIV : it works in opaque fluids. Its today principal application is the visualization and measurement of blood flows in the human body. As an example, here is a 0.5 second film (slowed down by a 20 factor) of a flow rotated with a magnetic agitator. We used a 32 transducer array and a frame rate of 500 Hz. Each image is obtained with a single plane wave illumination of the flow that was seeded with a fine stone powder. Each velocity map is obtained by cross-correlations between two consecutive images.

IMG/flv/PlaneWaveEchoPIVexample_2_-2.flv

Higher quality version

resume_rodriguez_06_2012

Publications dans des revues internationales à comité de lecture :

S. Rodriguez, P. Sahuguet, V. Gibiat and X. Jacob, Fast topological imaging, in press in Ultrasonics http://dx.doi.org/10.1016/j.ultras.....

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre , Input impedance in flow ducts : theory and measurement, Journal of the Acoustical Society of America, 2011, Vol. 132, pp. 1494-1501.

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre, Use of a mechanical analogy to couple the time-domain of a one-cylinder cold-engine model with the input impedance of its intake system
Journal of Sound and Vibration, 2011, Vol. 300, pp. 5769-5783.

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre, The three-measurement two-calibration method for measuring the transfer matrix
Journal of the Acoustical Society of America, 2011, Vol. 129, pp. 3056-3067.

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre, The reflection map: A new tool for frequency to time domain study of 1D acoustical systems
Acta Acustica, 2009, Vol. 95, pp. 795-804.

Enseignement :

20 heures d’acoustique en français et anglais en niveau Master 1. Cours intégralement préparés par mes soins. ENSICA, Toulouse.

Conférences

S. Rodriguez, X. Jacob, V. Gibiat, Application of topological imaging to high frame rate ultrasound, 7th GDR meeting on Wave propagation in complex media for quantitative and NDE, Oléron, FRANCE (2012).

S. Rodriguez, P. Sahuguet, X. Jacob, V. Gibiat, Ultrasonic imaging based on frequency-domain optimization form, Acoustics 2012, Nantes, FRANCE, Paper 785.

S. Rodriguez, P. Sahuguet, V. Gibiat, imagerie par optimisation de forme dans le domaine fréquentiel, 2011, journées SIAM (Signal et Image en Acoustique Médicale), Créteil, FRANCE.

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre, “From frequency to time domain: Signal features and physical characteristics for resonant acoustical systems , 2008, Acoustics08 Paris

S. Rodriguez, V. Gibiat, S. Guilain and A. Lefebvre, Computing acoustic propagation in ducts carrying a complex three dimensional flow: a methodology , 2008, pp. 2034-2041., 15th International Congress on Sound and Vibration Daejeon South Korea

Brevets

Pour le compte de Renault : (Les auteurs sont présentés dans l’ordre alphabétique)

US201100045/WO2009019350 : “Internal combustion engine inlet manifold“, L. Mamy and S. Rodriguez.

FR2936285 : “Gas intake manifold for internal combustion engine of motor vehicle, has conduits in which gas circulates along same direction and reverse directions, where areas of cross sections of conduits are equal”, J.-C. Le guern and S. Rodriguez.

FR2935748 : “Supercharged internal combustion engine, has valve placed on path of derivation pipe, where opening of derivation pipe is triggered based on pressure measured by upstream and downstream pressure sensors”, J.-C. Le guern and S. Rodriguez.

FR2931207 : “Gas e.g. intake gas, transferring device for internal combustion engine, has separated ducts joined in main duct opening in gas manifold, where overall sectional surface of ducts is constant during passage from main duct to separated ducts”, E. David, J.-C. Le Guern and S. Rodriguez.

FR2925126 : “Air intake method for internal combustion heat engine of motor vehicle, involves regulating flow of air stream by partially opening valves to permit even flow of air in engine to obtain acoustic characteristics at working point of engine “, J.-C. Le guern and S. Rodriguez.

FR2921436 : “Intake and exhaust collector for heat engine of motor vehicle, has internal cavity of tubular body or plenum conformed by loop for allowing gas flow circulation between neighboring intake/exhaust ducts “, L. Mamy and S. Rodriguez.

FR2920487 : “Air distributor for supercharged internal combustion engine, has plenum provided with air inlet and opening in conduits, where two conduits having different geometries such that distances separating inlet from outlets of conduits are equal”, E. Jean, S. Rodriguez and L. Vedrenne.

Pour le compte de l’ISAE et de l’université de Toulouse - Paul Sabatier :

FR1060513 : “Dispositif de mesure de vitesse et/ou de direction d’un écoulement fluide le long d’un véhicule, et procédé correspondant“, V. Gibiat, C. Nouals and S. Rodriguez.