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High contrast and resolution 3-D ultrasonography with a clinical linear transducer array scanned in a rotate-translate geometry
No full textInternational audienceWe propose a novel solution for volumetric ultrasound imaging using single-side access 3-D synthetic-aperture scanning of a clinical linear array. This solution is based on an advanced scanning geometry and a software-based ultrasound platform. The rotate-translate scanning scheme increases the elevation angular aperture by pivoting the array [-45° to 45°] around its array axis (axis along the row of its elements) and then, scans the imaged object for each pivoted angle by translating the array perpendicularly to the rotation axis. A theoretical basis is presented so that the angular and translational scan sampling periods can be best adjusted for any linear transducer array. We experimentally implemented scanning with a 5-MHz array. In vitro characterization was performed with phantoms designed to test resolution and contrast. Spatial resolution assessed based on the full-width half-maximum of images from isolated microspheres was increased by a factor 3 along the translational direction from a simple translation scan of the array. Moreover, the resolution is uniform over a cross-sectional area of 4.5 cm 2. Angular sampling periods were optimized and tapered to decrease the scan duration while maintaining image contrast (contrast at the center of a 5 mm cyst on the order of-26 dB for 4° angular period and a scan duration of 10 s for a 9cm 3 volume). We demonstrate that superior 3-D US imaging can be obtained with a clinical array using our scanning strategy. This technique offers a promising and flexible alternative to development of costly matrix arrays toward the development of sensitive volumetric ultrasonography
Using Semantic Information to Improve Generalization of Reinforcement Learning Policies for Autonomous Driving
No full textInternational audienceThe problem of generalization of reinforcement learning policies to new environments is seldom addressed but essential in practical applications. We focus on this problem in an autonomous driving context using the CARLA simulator and first show that semantic information is the key to a good generalization for this task. We then explore and compare different ways to exploit semantic information at training time in order to improve generalization in an unseen environment without finetuning, showing that using semantic segmentation as an auxiliary task is the most efficient approach
Experimental and Analytical Study of under Water Pressure Wave Induced by the Implosion of a Bubble Generated by Focused Laser
No full textInternational audienceIn various domains of material processing, such as surface cleaning and surface treatment, cavitation phenomenon may become an alternative to traditional methods if this phenomenon is well understood. Due to experimental and mathematical difficulties in theoretical models, it is still a challenge to accurately measure the physical mechanism of the fluid/structure interactions. In this study, we verified the feasibility of using polyvinylidene fluoride (PVDF) sensors to quantitatively measure the under-water pressure wave generated by the collapse of a single cavitation bubble. The electrical signal obtained by PVDF can be converted into pressure information only by using the sensor material parameters provided by the supplier. During the conversion process, only the capacitance of the acquisition chain needs to be additionally measured. At the same time, a high-speed video recording system was used to visualize the evolution of the cavitation bubble. The Gilmore analytical model and an associated wave propagation model were used to simulate the pressure peak of the first collapse of the cavitation bubble. This theoretical pressure was compared with the experimental results. The result showed that, for bubbles with a normalized standoff distance γ larger than 5, the PVDF sensor had the ability to quantitatively measure the pressure wave generated by a single cavitation bubble
An Adaptive Eigenfunction Basis Strategy to Reduce Design Dimension in Topology Optimization
No full textInternational audienceThe concept of adaptive eigenspace basis (AEB) has recently proved effective for solving medium imaging problems. In this work, we present an AEB strategy for design parameterization in topology optimization (TO) problems. We seek the density design field as a linear combination of eigenfunctions, computed for an elliptic operator defined over the structural domain, and solve for the associated eigenfunction coefficients. Restriction to this truncated eigenspace drastically reduces the design dimension and imposes implicit regularization upon the solution, removing the need for auxiliary filtering operations and design-variable bound constraints. We furthermore develop the basis adaptation scheme inherent in the AEB, which iteratively recomputes the eigenfunction basis to conform to the evolving density field, enabling further dimension reduction and acceleration of the optimization process. The known aptitude of the adapted eigenfunctions to approximate piecewise constant fields is especially useful for TO as relevant design subspaces can be given low-dimensional representations. We propose criteria for the selection of the basis dimension and demonstrate the use of basis function selection as means for length scale control. We compare performance of the AEB against conventional TO implementations in problems for static linear-elasticity, showing comparable structural solutions, computational cost benefits, and consistent design dimension reduction. K E Y W O R D S Adaptive eigenspace basis, Topology design, Dimensionality reduction Abbreviations: AEB, adaptive eigenspace basis; TO, topology optimization; EB, eigenspace basis. * Equally contributing authors
A SysML-based Holistic Variability Modelling of Software and Systems Product Lines
No full textInternational audienceSoftware and Systems Product Line (SSPL) engineering has shown capabilities to reduce costs and time to market. This is thanks to the creation and management of a common platform dedicated to develop a family of products. These latters can be a family of mobile phones, a family of different brake systems variants for automative needs, etc. Recently, more and more large-scale companies start to implement SSPL engineering in their domains by adopting Model-Based Systems Engineering (MBSE). Systems Product Line (PL) engineering is much broader than software PL engineering. Therefore, various aspects of variability (e.g. functional and quality attributes variabilities) have to be considered in MBSE. However, variability integrated in MBSE is still limited to functional variability. This paper contributes to enhance the SSPL modelling based on SysML by extending the SysML language. The principle aim is to include various aspects of variability. In fact, a holistic variability model is proposed to define the SysML extensions by means of the UML profiling mechanism. This permits to express variability constructs in different SysML modelling artifacts. We also present an application example namely the brake systems family extracted from Splot repository. We in fact, show how our SysML extensions are concretely used
POSTER: Resistance Analysis of Two AES-Like Against the Boomerang Attack
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Finite Element Analysis of Impact-Induced Damage in Pressurized Hybrid Composites Pipes
No full textInternational audienceThe high mechanical performance of filament wound hybrid composite pipes can be adversely affected by their low resistance to accidental impact. Loads of dynamic origin are dangerous and cause consequences on the operation of pipes because the damage is often not detected and can affect the structural integrity of composite pipes. In this work, a finite element (FE) model of pressurized hybrid composite pipe is developed and performed to predict the damage initiation and evolution under low-velocity impact through simulations with ABAQUS/Explicit. Hashin’s failure theory is used as failure criterion. At the first stage, load–time histories, and impactor displacement time limits are estimated in an FE model. The numerical results are confronted with the experimental values published in the literature. Once the model was validated, damage initiation and propagation were analyzed, where it is observed that damage mainly occurs by matrix cracking, damage evolution in the matrix in tension, compression and shear are presented and discussed in detail
Estimation of coherent scattering in dynamic random media
No full textInternational audienceWe address the question of estimating coherent scattering (weak scattering or coherent scatterer) by a time-evolving random medium. We consider two models of coherent scattering: homodyned K (HK) and generalized K (GK), and in both cases we derive stochastic differential equations for the scattered field. Approximate transition probabilities are computed using Euler–Maruyama scheme and the parameters for coherent scattering are estimated by maximum likelihood (ML). Using numerical simulations, we show that in the HK case, maximum likelihood estimation does not provide a significant advantage over a simplistic estimator based on the ergodicity property of the scattered field. On contrary, in GK scattering the transition probabilities carry significant information about the parameters, resulting in much better performance of the ML estimator
Mapping of Existing Practices and Diverse Pedagogical Approaches: Report R5 of the A-STEP 2030 project
No full textInsights into the integration of the SDGs in engineering program curricula as seen through the prism of the perceptions of engineering students and educators
No full textInternational audienceIn this paper, we offer insight into how the UN Sustainable Development Goals (SDGs) are being integrated into engineering programs. We investigate the question: "what opportunities and barriers should we take into consideration in order to better integrate the SDGs into engineering programmes?" We undertook two exploratory focus group studies with engineering students and academic participants that explored their perception of SDGs' integration to their programs. Our results show significant differences between the perceptions of students and academics, and this indicates the need for a more comprehensive and balanced integration of the SDGs into engineering curricula. We particularly recommend a transdisciplinary teaching approach involving a close relation between technical and human disciplines