HAL-INSA Toulouse
Not a member yet
34325 research outputs found
Sort by
Design and Building of a Cost-Effective Six-Component Optical Borehole Strainmeter
No full textInternational audienceDue to their high resolution and near real-time capabilities, borehole strainmeters are a critical complement of satellite-based geodetic systems [GPS/global navigation satellite system (GNSS)] and satellite interferometry. However, commercial strainmeters remain expensive and only provide the three horizontal components of the strain tensor. We propose a novel design able to detect the six components of the 3-D strain tensor at relatively low cost. Here, we embed six compliant elastic gauges in a sphere in order to evenly sample space directions. Each gauge exhibits an amplification ratio of ∼30. Interrogated by Fabry-Perot interferometers illuminated by a single laser diode (LD) through a multichannel fiber cable, these opto-mechanical systems exhibit a resolution of ∼89 pm/ √ Hz over a dc -500-Hz bandwidth, ultimately providing a strainmeter resolution <1 nanostrain. A supplementary interferometric device is also implemented to detect and correct nongeometrical optical phase changes due to pressure and temperature variations. An original building method allowed us to mold fibered cement around a thin sphere equipped by the optical strain gauges. Moreover, an adjustable pressure device is integrated to allow in situ calibration in order to correct the 3-D strain tensor from borehole and cement heterogeneities. This cost-effective strainmeter was successfully installed in November 2023 in a 30-m deep borehole at the Larzac Observatory in the French Massif Central.</div
Optimal Control of State Constrained Systems via Measure Relaxations and Polynomial Optimization
No full textInternational audienceWe address the optimal control problem for a class of dynamical systems with constrained state trajectories. These systems are modeled by a differential inclusion with a drift term and a normal cone mapping associated with the constraint set. The optimal control problem is considered in continuous-time and discrete-time, where the latter provides a computational advantage over the former. In both cases, the nonlinear problem is reformulated as an infinite-dimensional linear program over occupation measures. We show that this does not introduce any relaxation gap, that is, the optimal value remains the same for the reformulated linear program. Using appropriate tools from functional analysis and optimal transport, we also show the convergence of the optimal value of the discrete problem to the optimal value of the continuous problem. We propose finite-dimensional convex optimization algorithms based on the moment-sum-of-squares hierarchy to provide numerical approximations of the proposed infinite-dimensional linear programs
TorchGDM: A GPU-accelerated Python toolkit for multi-scale electromagnetic scattering with automatic differentiation
No full textInternational audienceWe present “torchGDM”, a numerical framework for nano-optical simulations based on the Green’s Dyadic Method (GDM). This toolkit combines a hybrid approach, allowing for both fully discretized nano-structures and structures approximated by sets of effective electric and magnetic dipoles. It supports simulations in three dimensions and for infinitely long, two-dimensional structures. This capability is particularly suited for multi-scale modeling, enabling accurate near-field calculations within or around a discretized structure embedded in a complex environment of scatterers represented by effective models. Importantly, torchGDM is entirely implemented in PyTorch, a well-optimized and GPU-enabled automatic differentiation framework. This allows for the efficient calculation of exact derivatives of any simulated observable with respect to various inputs, including positions, wavelengths or permittivity, but also intermediate parameters like Green’s tensor components, which can be interesting for physics informed deep learning applications. We anticipate that this toolkit will be valuable for applications merging nano-photonics and machine learning, as well as for solving nano-photonic optimization and inverse problems, such as the global design and characterization of metasurfaces, where optical interactions between structures are critical
Backbone and Methyl resonance assignment of an active PETase
No full textInternational audienceLCCICCG, a bioengineered variant of a cutinase called LCC (Leaf-branch Compost Cutinase), is a high-performance, industrial-grade enzyme capable of efficiently degrading polyethylene terephthalate (PET). This engineered enzyme exhibits significantly enhanced thermal stability and PET hydrolysis activity compared to its predecessor and competing PETases. Here, we report the comprehensive resonance assignment of the polypeptide backbone and the side chain methyl groups of the active LCCICCG. Taking advantage of its exceptional thermostability all the experiments were conducted at 60 °C on a single, uniformly 15N-13C-labeled sample of this 27 kDa serine-hydrolase enzyme. LCCICCG represents a leap forward in enzymatic PET recycling, combining speed, efficiency, and scalability. The residue-specific information through both backbone and methyl side chain assignment represents a critical step toward detailed structural and dynamic NMR analyses
Safe-by-design conception and synthesis of metallic nanoparticles for biomedical applications
No full textInternational audienc
Experimental parametric study of a flap-NES passive absorber for post-flutter control
No full textInternational audienc
Disruption of putrescine export in experimentally evolved <i>Ralstonia pseudosolanacearum</i> enhances symbiosis with <i>Mimosa pudica</i>
No full textPolyamines are essential molecules across all domains of life, but their role as signaling molecules in host-microbe interactions is increasingly recognized. However, because they are produced by both the host and the microbe, their dual origin makes their functional dissection challenging. The plant pathogenRalstonia pseudosolanacearumGMI1000 secretes large amounts of putrescine bothin vitroand in the xylem sap of host plants. In this study, we investigated the genetic changes underlying its experimental evolution into a legume symbiont. We showed that thepaeAgene (RSc2277), which was repeatedly mutated during this process, encodes a putrescine exporter. Mutations inpaeAcompletely abolished putrescine excretionin vitroand enhanced bacterial proliferation within nodules during interaction with the legumeMimosa pudica. When these mutations occurred in symbionts already capable of intracellular infection, it further increased bacterial load in nodules and allowed the detection of nitrogenase activity. In addition,paeA-mutated symbionts modulated host gene expression towards a more functional symbiotic state by repressing defense-related genes and inducing nodule development genes. These nodule development genes include genes encoding leghemoglobins and an arginine decarboxylase, a key enzyme in plant putrescine biosynthesis. These results indicate that bacterial and plant putrescine have distinct functions in legume symbiosis and highlight the complex role of polyamines in plant-microbe interactions. Importance Rhizobia, the nitrogen-fixing symbionts of legumes, emerged through repeated and independent horizontal transfers of some essential symbiotic genes. However, these transfers alone are often insufficient to convert the recipient bacterium into a functional legume symbiont. In a laboratory experiment, we evolved the plant pathogenRalstonia pseudosolanacearuminto a nodulating and intracellularly infecting symbiont ofMimosa pudica. This transition required genomic modifications in the recipient bacterium to activate its acquired symbiotic potential. Here, we demonstrated that one of these key adaptive modifications is the inactivation of bacterial putrescine export. This polyamine, when produced by the microsymbiont, appears to act as a negative signal for the plant. This study provides new insights into the distinct roles of bacterial- and plant-derived putrescine in plant-microbe interactions, highlighting their functional divergence despite being produced by both organisms.</p
Kinetic theory of two-dimensional point vortices at order and
No full textWe investigate the long-term relaxation of a distribution of point vortices in two-dimensional hydrodynamics. To focus on the regime of weak collective amplification, we embed these point vortices within a static background potential and soften their pairwise interaction on small scales. Placing ourselves within the limit of an average axisymmetric distribution, we stress the connections with generic long-range interacting systems, whose relaxation is described within angle-action coordinates. In particular, we emphasise the existence of two regimes of relaxation, depending on whether the system's profile of mean angular velocity (frequency) is a non-monotonic [resp. monotonic] function of radius, which we refer to as profile (1) [resp. profile (2)]. For profile (1), relaxation occurs through two-body non-local resonant couplings, i.e. effects, as described by the inhomogeneous Landau equation. For profile (2), the impossibility of such two-body resonances submits the system to a ``kinetic blocking''. Relaxation is then driven by three-body couplings, i.e. effects, whose associated kinetic equation has only recently been derived. For both regimes, we compare extensively the kinetic predictions with large ensemble of direct -body simulations. In particular, for profile (1), we explore numerically an effect akin to ``resonance broadening'' close to the extremum of the angular velocity profile. Quantitative description of such subtle nonlinear effects will be the topic of future investigations
Defect detection in 316 L single-bead walls using the instrumentation of a LP-DED process
No full textInternational audienc
Carbonation-induced corrosion of steel in sodium carbonate alkali-activated slag
No full textInternational audienceThe carbonation-induced corrosion of steel reinforcement embedded in sodium carbonate alkali-activated slag (AAS) and a CEM III/B reference binder were investigated. The primary objective of this study was to evaluate the influence of both natural and accelerated carbonation (1% CO 2 ) on reinforcement corrosion. Reinforced cylindrical mortars specimens with a low cover (8.5 mm) were cast and subjected to exposure under natural and accelerated carbonation conditions. The initial weights of the rebar were recorded with high precision prior to casting. Throughout one year of exposure, the corrosion potential and linear polarization resistance of the rebars were systematically monitored. Upon completion of the exposure period, the specimens were split to enable visual inspection of corrosion and to determine corrosion-induced mass loss. The applicability of the Stern-Geary equation to carbonated AAS systems was confirmed by comparing the corrosion current densities estimated from this equation (using a B-value of 26 mV) with the values calculated from the actual mass loss of the reinforcement, as determined by Faraday’s law. Although accelerated carbonation at 1% CO 2 induces differences in pH stabilization and carbonation product formation compared to natural carbonation, it was found to be representative method for quantifying reinforcement corrosion in AAS systems. Overall, AAS exhibited superior resistance to steel reinforcement corrosion compared to CEM III/B reference binder, which was attributed to the more stable and higher pH environment maintained within the AAS matrix