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TD-CD-MPPI: Temporal-Difference Constraint-Discounted Model Predictive Path Integral Control
No full textInternational audiencePath Integral methods have demonstrated remarkable capabilities for solving non-linear stochastic optimal control problems through sampling-based optimization. However, their computational complexity grows linearly with the prediction horizon, limiting long-term reasoning, while constraints are merely enforced through handcrafted penalties.In this work, we propose a unified and efficient framework for enabling long-horizon reasoning and constraint enforcement within Model Predictive Path Integral (MPPI) control. First, we introduce a practical method to incorporate a terminal value function, learned offline via temporal-difference learning, to approximate the long-term cost-to-go. This allows for significantly shorter roll-outs while enabling infinite-horizon reasoning, thereby improving computational efficiency and motion performance. Second, we propose a discount modulation strategy that adjusts the return of sampled trajectories based on constraint violations. This provides a more interpretable and effective mechanism for enforcing constraints compared to traditional cost shaping. Our formulation retains the flexibility and sampling efficiency of MPPI while supporting structured integration of long-term objectives and constraint handling. We validate our approach on both simulated and real-world robotic locomotion tasks, demonstrating improved performance, constraint-awareness, and generalization under reduced computational budgets
Comparative investigation of numerical methods for incorporating real climate data into thermal quadrupole models for building wall applications: fitting techniques, and Laplace inversion algorithms
No full textInternational audienceThe thermal quadrupole method provides the advantage of expressing the partial differential formulation of the heat equation as a linear system in transformed time (Laplace transform) and space (integral transforms) domains. It allows faster computations compared to standard techniques such as Finite Element Methods. The following work concerns the incorporation of climate data recordings of hourly external temperature and solar heat flux in the thermal quadrupole method for solving the heat equation through a multilayered building wall.Two methods are proposed for the purpose of applying Laplace transforms to the discrete sets of climate data: a global Fourier series fit, accounting for severe fluctuations and peaks with the number of harmonics depending on dataset size; and a discrete Laplace transform methodology applied to a global series of linearly computed sub-series over defined intervals. Two models are investigated, a 1D heat transfer problem in Cartesian coordinates and a 2D axisymmetric representation in cylindrical coordinates, the latter dictating Hankel transforms for the space domain. After solving in the transformed domains, the challenge lies in accurately retrieving time-domain results. Three Laplace inversion algorithms—Stehfest, De Hoog, and Den Iseger—are investigated for their numerical stability, accuracy, and efficiency. A parametric analysis related to parameters of the data fitting and Laplace inversion methods is carried out. Results of different combinations of the fitting method/inversion algorithm (or a coupling of algorithms) are provided and compared with a finite element resolution of the thermal problems (FreeFEM++ and COMSOL) with an emphasis on computational time enhancements. The main objective of this work is to develop a numerically efficient direct model suitable for future application in inverse methods
High alpine preglacial caves modified by glacial processes and late condensationcorrosion in the Scerscen Valley (Valmalenco, Western Alps, Italy)
No full textInternational audienceThe Scerscen Valley (western Italian Alps) is home to caves at an altitude of around 2600 m, opening close to the Speleogenesis edge of a glacier. The aim of the research as part of a multi-disciplinary project was to reconstruct the evolution Alpine Cosmogenic GeomorphologyHydrogeologyglaciersburial dating of cosmonucleide some the of caves the related most burial recent to dating, the processes, geological recorded such and morphology paleoenvironmental as condensation-corrosion and micrometeorology, evolution and of sediment the carried area deposition. and out mineralogical to evaluate We the performed identifirole of cation by XRD, and hydrogeology using dye tracing and physical and chemical analyses. The cosmonucleide dating of quartz pebbles showed that the Veronica Cave is the oldest, with deposits dated at 1.3 ± 0.4 Ma, and possibly even older. It certainly formed at a much lower altitude (approx. 1300 m a.s.l. or lower) during the Alpine uplift. The Morgana and Marsooi caves, given the smaller volume of their phreatic conduits (1/3 of Veronica), are possibly more recent, formed during interglacials and evolved close to a glacial body. The caves initiated in dolomitic marble under the influence of sulfuric acid speleogenesis (SAS) due to pyrite oxidation. The conduits were then enlarged dramatically under phreatic conditions. The caves have evolved since their preglacial formation, with phases of filling by fluvio-glacial sediments and unclogging. Water tracing and physico-chemical analysis attest to a well-karstified aquifer, with rapid water circulation (>20 m/h) and low temperatures (~2 °C), draining towards the main spring, "La Prediletta", located at the foot of the dolomitic marbles. Microclimatic records (cave temperature and humidity) show seasonal cycles of condensation and evaporation, influenced by air exchanges with the outside atmosphere. These processes contributed to the formation of secondary minerals by evaporation (gypsum, hydromagnesite…) and, above all, to the significant enlargement of passages by the retreat of walls with characteristic morphologies (facets and grooved walls). The Scerscen caves bear witness to a long geological and climatic history, from their formation before the Mid-Pleistocene ice ages to their present-day evolution. They offer valuable insights into karst processes in the high mountains, and interactions between glaciers and aquifers
Torrefied biomass (Biotorr) potential for agricultural applications. A review
No full textInternational audienceCrop residue management has gained attention for its potential to increase soil organic matter and improve soil health in agricultural systems. For these purposes, pyrolysis of crop residues, to produce biochar, and its impacts on soils have been extensively studied, but torrefied biomass (biotorr), produced by torrefaction between 200 and 300 • C represents a promising alternative. Torrefaction offers advantages such as higher mass yields and lower production costs, which could make it an accessible and cost-effective soil conditioner.This review synthesises current knowledge on the effects of torrefaction on the properties of biotorr and assesses its potential as a soil conditioner. The results showed that torrefaction affects the composition of biotorr differently depending on the feedstock and the torrefaction parameters. While the yield of biotorr decreased with increasing torrefaction temperature, it was still higher than that of biochar. Compared to the feedstock, the carbon content and stability of biotorr improved significantly. Our analysis also indicated higher levels of P and K in biotorr, although further research is needed to determine their bioavailability.Given these results, biotorr shows a strong potential as a soil conditioner to improve soil health and support sustainable agriculture. However, it is now necessary to further investigate the potential of biotorr for agricultural application through field experiments, especially to assess how biotorr affects soil nutrient dynamics and carbon sequestration.</p
Linear conversions of nonlinear camera models for robotic vision applications
No full textInternational audienceCamera models play a crucial role in robot vision applications. Yet theirdiversity poses a challenge when working with data captured with camerascalibrated using different models. In this paper, we address this issue byintroducing a mathematical framework that enables conversion between various camera projection models. This approach allows algorithms designed fora specific model to process data from cameras calibrated with other models,eliminating the need for recalibration and enabling the reuse of pre-existingdatasets that do not provide access to calibration images.We present the general conversion method for state-of-the-art cameramodels that we derive for three new camera model conversions, covering various camera types, including fisheye and catadioptric systems. Quantitativeevaluation is conducted with respect to well-known calibration methods. Wecompare our method on image undistortion, as well as in practical applications such as SLAM, visual servoing, and visual odometry. The resultsdemonstrate that our conversion approach achieves performances comparable to calibration without the need for explicit calibration.This work contributes to a more flexible and adaptive use of cameras inrobot applications. The proposed camera model conversion framework is implemented in the open-source libPeR library, available at:https://github.com/PerceptionRobotique/libPeR_base
Electronic structure and transport in materials with flat bands: 2D materials and quasicrystals
No full textreviewInternational audienceIn this review, we present recent works on materials whose common point is the presence of electronic bands of very low dispersion, called "flat bands", which are due to specific atomic order effects without electron interactions. These states are always indicative of some form of confinement and have significant consequences on the electronic structure, transport properties and magnetism of these materials. A first part is devoted to the cases where this confinement is due to the long-range geometry of the defect-free structure. We have thus studied periodic approximant structures of quasiperiodic Penrose and octagonal tilings, and twisted bilayers of graphene or transition metal dichalcogenides (TMDs) whose rotation angle between the two layers assumes a special value, called "magic angle". In these materials, the flat bands correspond to electronic states distributed over a very large number of atoms (several hundreds or even thousands of atoms) and are very sensitive to small structural distortions such as "heterostrain". We have shown that their electronic transport properties cannot be described by usual Bloch-Boltzmann theories, because the interband terms of the velocity operator dominate the intraband terms as far as quantum diffusion is concerned. In the case of twisted bilayer graphene, flat bands can induce a magnetic state and other electron-electron correlation effects. The second part focuses on two-dimensional nanomaterials in the presence of local point defects that cause resonant electronic states (vacancies, adsorbed atoms or molecules). We present studies on monolayer graphene, twisted or Bernal bilayer graphene, carbon nanotubes, monolayer and multilayer black phosphorene, and monolayer TMDs. A recent result is the discovery that the selective functionalization of a Bernal bilayer graphene sublattice leads to a metallic or insulating behavior depending on the functionalized sublattice type. This result, which seems to be confirmed by very recent experimental measurements, suggests that functionalization can be a key parameter to control the electronic properties of two-dimensional materials
Exclusive four pion photoproduction in ultraperipheral Pb-Pb collisions at TeV
No full textInternational audienceThe intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. The measurement of coherently photoproduced final states in ultraperipheral Pb-Pb collisions at TeV is presented for the first time. The cross section, d/d, times the branching ratio () is found to be mb in the rapidity interval . The invariant mass distribution is not well described with a single Breit-Wigner resonance. The production of two interfering resonances, and , provides a good description of the data. The values of the masses () and widths () of the resonances extracted from the fit are MeV/, MeV/, MeV/ and MeV/, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions
Tester l’audition par la parole: in Matthieu Saladin (dir.), Spectres de l'audible, Paris, Philharmonie de Paris
No full textMara Mills, “Testing Hearing with Speech”, in Alexandra Hui, Mara Mills, Viktoria Tkaczyk (dir.), Testing Hearing. The Making of Modern Aurality, Oxford, Oxford University Press, 202
Scarifier l’oreille : de la normalisation des troubles de l’audition: in Matthieu Saladin (dir.), Spectres de l'audible, Paris, Philharmonie de Paris
No full textJonathan Sterne, “Audile Scarification”, in Diminished Faculties. A Political Phenomenology of Impairment, Durham, Duke University Press, 202
