Publications

2025

• ARCH-COMP25 Category Report: Continuous and Hybrid Systems with Nonlinear Dynamics
  
  • Geretti Luca
  • Alexandre Dit Sandretto Julien
  • Althoff Matthias
  • Benet Luis
  • Collins Pieter
  • Forets Marcelo
  • Mitsch Stefan
  • Patel Ismail
  • Perschl Maximilian
  • Schilling Christian
  • Tillet Joris
  , 2025, pp.39-6. We present the results of a friendly competition for formal verification of continuous and hybrid systems with nonlinear continuous dynamics. The friendly competition took place as part of the workshop Applied Verification for Continuous and Hybrid Systems (ARCH) in 2025. This year, 5 tools participated: Ariadne, CORA, DynIbex, JuliaReach and KeYmaera X (in alphabetic order). These tools are applied to solve reachability analysis problems on seven benchmark problems, three of them featuring some aspects of hybrid dynamics. We do not rank the tools based on the results, but show the current status and discover the potential advantages of different tools. (10.29007/7br2)
  DOI : 10.29007/7br2
• A generic framework to derive systems of conservation laws with source terms and its application to heat conduction in fluid flows: an alternative to the method of moments in kinetic theory of gases?
  
  • Haegeman Ward
  • Kokh Samuel
  • Massot Marc
  • Orlando Giuseppe
  ESAIM: Proceedings and Surveys, EDP Sciences, 2025, 78, pp.80-97. A generic framework to derive systems of conservation laws through the Stationary Action Principle is proposed. The equations are expressed in Eulerian coordinates while the variation of the action assumes an underlying Lagrangian description thus avoiding the need for any Lin constraint. The resulting models admit a supplementary conservation equation for the evolution of the Hamiltonian. We then use the newly developed framework to derive a hyperbolic model that includes heat conduction in the compressible fluid dynamics equations through the introduction of a new variable called the thermal impulse. The resulting model has already been obtained previously through the Stationary Action Principle but its derivation relied on several non-standard assumptions. Our new framework allows not only to lift these assumptions, but also to recover them as a consequence of the Stationary Action Principle. Finally, a comparison with a model including heat conduction derived through the kinetic theory of gases is conducted. (10.1051/proc/202578080)
  DOI : 10.1051/proc/202578080
• Uncertainty Removal in Verification of Nonlinear Systems against Signal Temporal Logic via Incremental Reachability Analysis
  
  • Besset Antoine
  • Tillet Joris
  • Alexandre dit Sandretto Julien
  , 2025. <div><p>A framework is presented for the verification of Signal Temporal Logic (STL) specifications over continuous-time nonlinear systems under uncertainty. Based on reachability analysis, the proposed method addresses indeterminate satisfaction caused by overapproximated reachable sets or incomplete simulations. STL semantics is extended via Boolean interval arithmetic, enabling the decomposition of satisfaction signals into unitary components with traceable uncertainty markers. These are propagated through the satisfaction tree, supporting precise identification even in nested formulas. To improve efficiency, only the reachable sets contributing to uncertainty are refined, identified through the associated markers. The framework allows online or offline monitoring to adapt to incremental system evolution while avoiding unnecessary recomputation. A case study on a nonlinear oscillator demonstrates a significant reduction in satisfaction ambiguity, highlighting the effectiveness of the approach.</p></div>
• Guaranteed Satisfaction of a Signal Temporal Logic Formula on Tubes
  
  • Tillet Joris
  • Besset Antoine
  • Alexandre dit Sandretto Julien
  Acta Cybernetica, University of Szeged, Institute of Informatics, 2025. This paper considers the issue of how to deal with Signal Temporal Logic (STL) when taking into account uncertainties. The STL is a formalism with a large expressiveness to describe real-time properties on real-value signals. It is particularly used for system verification. This work focuses on extensions of STL that handle bounded uncertainties on predicates or on the signal itself, by using tubes to represent the sets of signals. In this way, it becomes possible to robustly check the satisfaction of specifications for a noisy system. However, some cases are undecidable due to uncertainty, and other ones are too complex to determine. Mainly, this paper provides a literature review and compares the few state-of-the-art STL monitors able to deal with tubes. In addition, it proposes to go further by introducing Boolean intervals to formalize undecidable cases, and by implementing a new STL formalism applied to sets in DynIbex, a guaranteed integration tool. Thus, STL specifications can be validated in a guaranteed way for a simulated system. As a result, we obtain the same reliable result as the state-of-the-art, but faster. A robotic application with a drone is proposed to illustrate the concept. (10.14232/actacyb.315054)
  DOI : 10.14232/actacyb.315054
• Modeling polycyclic aromatic hydrocarbons (PAH) and liquid organic hydrogen carriers (LOHC) with the SAFT-γ Mie group-contribution equation of state
  
  • Velásquez Sarmiento Edgar
  • Paricaud Patrice
  Fluid Phase Equilibria, Elsevier, 2025, 598, pp.114514. (10.1016/j.fluid.2025.114514)
  DOI : 10.1016/j.fluid.2025.114514
• Real-Time Guaranteed Monitoring for a Drone Using Interval Analysis and Signal Temporal Logic
  
  • Besset Antoine
  • Dit Sandretto Julien Alexandre
  • Tillet Joris
  , 2025, pp.14892-14898. (10.1109/IROS60139.2025.11245994)
  DOI : 10.1109/IROS60139.2025.11245994
• Secrecy through Precoding: a Novel Physical Layer Encryption Scheme with Optimal PAPR
  
  • Leroy Clément
  • Arbi Tarak
  • Pasquero Oudomsack Pierre
  • Geller Benoit
  , 2025. <div><p>Traditional cryptographic methods ensure data confidentiality through sophisticated and complex key management and encryption protocols. However, such approaches may be illsuited for scenarios with limited coordination capabilities, such as military communications or the Internet of Things (IoT); Physical Layer Encryption (PLE) then offers a complementary or alternative solution by securing information directly at the signal level. Among existing PLE techniques, masking strategies have shown considerable promise. Nonetheless, many of these techniques suffer from drawbacks such as high Peak-to-Average Power Ratio (PAPR), rely on the eavesdropper's channel knowledge, or lack of adaptability to diverse wireless environments. In this paper, we propose a novel PLE technique that overcomes these limitations. Our approach achieves optimal PAPR by design, requires no knowledge of the eavesdropper's channel state information, and is applicable to all flat fading channels. Additionally, the method incorporates continuous randomization in signal generation, enhancing resistance to brute-force attacks. These features collectively make our solution a robust and practical candidate for secure wireless communication at the physical layer. Extensive simulations confirm the effectiveness and reliability of the proposed approach under various channel conditions.</p></div>
• Hybrid stochastic-structural modelling of particle-laden turbulent flows based on wavelet reconstruction
  
  • Letournel Roxane
  • Morhain Clément
  • Massot Marc
  • Vié Aymeric
  , 2025. Reduced-order modelling and simulation of turbulent particle-laden flows is required in numerous configurations, where the whole spectrum of turbulent scales through DNS is out of reach. Whereas structural or stochastic models have be derived in order to provide a synthetic turbulent model for the non-resolved scales of the gaseous flow field, reproducing preferential concentration is challenging because it requires capturing both spatial and temporal correlations. We present a novel reduced-order framework that overcomes this limitation by combining wavelet-based structural modelling with stochastic evolution. Using compactly supported divergence-free wavelets within a multiresolution analysis, the method provides direct control over spatial structures and correlations of synthetic multiscale velocity fields. In particular, a dedicated procedure enables to enforce a prescribed turbulent energy spectrum despite the nonlocal contribution in Fourier space of the wavelet basis functions. The stochastic evolution of wavelet coefficients further ensures consistent temporal correlations. The proposed framework is evaluated in homogeneous isotropic turbulence under a fully reduced setting, where all turbulent scales must be provided by the model. Results<p>show that it accurately reproduces preferential concentration across a wide range of Stokes numbers, achieving closer agreement with DNS data than classical Fourierbased kinematic simulations. This establishes a versatile and physically consistent turbulence model that combines structural fidelity with stochastic dynamics, offering a new tool to investigate particle–turbulence interactions.</p>
• Cross-Domain Equalization for Underwater Acoustic OCDM Systems with SSD
  
  • Arbi Tarak
  • Geller Benoit
  , 2025. <div><p>Orthogonal Chirp Division Multiplexing (OCDM) represents a compelling modulation alternative for Underwater Acoustic (UWA) communication systems, exhibiting notable Bit Error Rate (BER) improvements over Orthogonal Frequency Division Multiplexing (OFDM), particularly within frequencyselective channels. This work explores the application of Signal Space Diversity (SSD) in OCDM systems. Specifically, rotated and cyclically Q-delayed (RCQD) constellations are employed to augment the system's inherent diversity, thereby enhancing overall communication reliability.</p><p>However, the equalization of SSD-augmented OCDM signals presents a formidable challenge due to the considerable expansion in the received constellation space. To overcome this, a novel cross-domain equalization technique is introduced. This technique involves an initial equalization of each OCDM symbol in the frequency domain, followed by a subsequent equalization in the Fresnel domain. Within the Fresnel domain, the correlation induced among OCDM symbols by the rotation and component interleaver is judiciously leveraged to achieve more effective mitigation of residual Inter-Symbol Interference (ISI).</p><p>Experimental validation, including results from a real underwater channel, unequivocally demonstrates that the proposed receiver architecture substantially improves the resilience of the OCDM system to interference.</p></div>
• Limitation strategies for high-order discontinuous Galerkin schemes applied to an Eulerian model of polydisperse sprays
  
  • Ait-Ameur Katia
  • Essadki Mohamed
  • Massot Marc
  • Pichard Teddy
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2025, 59 (5), pp.2349-2383. In this paper, we tackle the modeling and numerical simulation of polydisperse sprays. Starting from a kinetic description for point particles, we focus on an Eulerian high-order geometric method of moment (GeoMOM) in size and consider a system of partial differential equations on a vector of successive fractional size moments of order 0 to N/2, N &gt; 2, over a compact size interval. These moments correspond to physical quantities, which can be interpreted in terms of the geometry of the interface at small scale. There exists a stumbling block for the usual approaches using high-order moment methods resolved with high-order numerical methods: the transport algorithm does not naturally preserve the moment space. Indeed, reconstruction of moments by polynomials inside computational cells can create N-dimensional vectors which can fail to be moment vectors. We thus propose a new approach, as well as an algorithm, which is arbitrarily high-order in space and time with limited numerical diffusion, including at the boundaries of the state space, where a specific study is proposed. It allows to accurately describe the advection process and naturally preserves the moment space, at a reasonable computational cost. We show that such an approach is competitive compared to second order finite volume schemes, where limiters generate numerical diffusion and clipping at extrema. An accuracy study assesses the order of the method as well as the low level of numerical diffusion on structured meshes. We focus in this paper on cartesian meshes and 2D test cases are presented where the accuracy and efficiency of the approach are assessed. (10.1051/m2an/2025057)
  DOI : 10.1051/m2an/2025057
• Modelling of relative velocity, velocity fluctuations and their interactions for two-fluid models by Stationary Action Principle
  
  • Haegeman Ward
  • Orlando Giuseppe
  • Kokh Samuel
  • Massot Marc
  , 2025. The objective of this contribution is the derivation of a two-fluid model including a relative velocity between the two phases and velocity fluctuations, describing pseudo-turbulent effects, as internal variables based on Stationary Action Principle. The variational derivation, used to obtain the model, relies on the variation of a single trajectory related to the mass-weighted average velocity under the barotropic assumption. The model is hyperbolic, satisfies a second principle of thermodynamics, and admits either linearly degenerate or genuinely nonlinear characteristic fields. Moreover, the variational approach yields a fully closed model and its non-conservative products are uniquely defined for weak solutions in 1D, i.e. jump conditions can be derived. In the laminar case, when velocity fluctuations are negligible, we recover previously derived multi-fluid models which have been analyzed in several contributions. As such, the present framework allows for an original extension of the existing models to include velocity fluctuations of each phase for pseudo-turbulent flows, their coupling with the relative velocity between phases, as well as dissipative effects compatible with the thermodynamics of irreversible processes. Eventually, we provide a discussion of the limitations of the proposed model, especially regarding the extension to the open problem of non-barotropic flows.
• Reconstruction 3D en tomographie radar : apprentissage profond basé sur un Matching Pursuit déroulé
  
  • Ulondu Mendes Cristiano
  • Denis Loïc
  • Kervazo Christophe
  • Tupin Florence
  , 2025. La tomographie radar en milieu urbain consiste à séparer des réflecteurs situés à des hauteurs différentes mais vus dans un même pixel car situés à une distance similaire du radar. Les méthodes d'apprentissage profond proposées récemment pour résoudre cette tâche sont basées sur le déroulement d'algorithmes de poursuites de base avec contrainte de parcimonie. Ils dépendent d'une discrétisation des hauteurs et ne permettent pas un contrôle simple du nombre de réflecteurs détectés. On présente dans cet article une approche alternative permettant d'estimer la position des cibles sur un intervalle continu. Notre approche s'inspire des itérations des algorithmes gloutons de reconstruction parcimonieuse tels que Matching Pursuit ou RELAX. Nous montrons des résultats de reconstruction satisfaisants sur des données simulées et sur une pile d'images satellitaires.
• Turbo égalisation pragmatique et complètement adaptative pour les communications sous-marines
  
  • Khemir Melek
  • Arbi Tarak
  • Geller Benoit
  , 2025. Adaptive equalization for underwater acoustic communications represents a major challenge due to the triple selectivity of the channel and its high computational complexity. In this paper, we propose a novel low-complexity turbo equalization algorithm based on an optimization criterion that takes into account the soft information provided by the decoder, which allows our algorithm to self-adapt to channel variations. Moreover, to preserve spectral efficiency and ensure the convergence of our algorithm, its parameters are trained multiple times on the same transmitted pilot symbols. Simulation results show that our algorithm achieves better performance compared to state-of-the-art methods in terms of bit error rate (BER). Finally, our complexity analysis also highlights the advantages of our technique.
• Détection non supervisée de changements radiométriques en imagerie radar à synthèse d'ouverture
  
  • Bultingaire Thomas
  • Kervazo Christophe
  • Denis Loïc
  • Tupin Florence
  , 2025, pp.1-4. L'imagerie radar à synthèse d'ouverture est un mode d'imagerie clé pour la détection de changements en télédétection. Cette tâche est difficile à cause du phénomène de chatoiement, un phénomène qui nécessite de réaliser une étape de débruitage pour y être davantage robuste. Cependant, il est nécessaire de prendre en compte les incertitudes de débruitage pour contrôler la probabilité de fausse alarme des changements détectés car les instabilités de débruitage doivent être distinguées des changements. Nous proposons donc un réseau, entraîné de manière auto-supervisée, pour prédire les incertitudes de débruitage menant à une détection de changements radiométriques dont la performance est évaluée sur des images du satellite TerraSAR-X.
• Chiffrement par Précodage Spatial de la Couche Physique sous Contrainte d'Enveloppe Constante
  
  • Leroy Clément
  • Arbi Tarak
  • Pasquero Oudomsack Pierre
  • Geller Benoît
  , 2025. <div><p>Les systèmes de communication à entrées multiples ont de nombreux avantages comparés aux systèmes avec une seule antenne à l'émission comme une meilleure efficacité énergétique et une confidentialité améliorée en dirigeant le signal vers son récepteur légitime. Toutefois, les signaux qui souffrent d'un rapport élevé de puissance crète sur puissance moyenne nuisent considérablement à l'efficacité énergétique de l'émetteur. Dans ce papier, nous proposons un précodeur à enveloppe constante qui permet de chiffrer spatialement l'information pour des systèmes à entrée multiple et à sortie unique (MISO). Notre méthode permet de bruiter les canaux des récepteurs illégitimes en introduisant de l'aléa dans la façon de précoder l'information, sans que cela ne dégrade le canal du récepteur légitime. Notre méthode de transmission n'est ni plus coûteuse énergétiquement, ni plus complexe algorithmiquement que les autres précodeurs de la littérature ; en revanche, elle permet un gain de confidentialité important ainsi qu'un PAPR optimum, comme le montrent nos simulations.</p></div>
• A Gyromoment Approach for Electron Dynamics in Low-Temperature E × B Plasmas of Hall Thrusters
  
  • Tazakkati Zoubaïr
  • Laguna Alejandro Alvarez
  • Massot Josselin
  • Massot Marc
  • Pichard Teddy
  , 2025. <div><p>We study the electron dynamics in the acceleration region of a Hall thruster (HT). The strong crossed electric and magnetic fields induce both a fast electron cyclotron gyration around the magnetic field lines and a E × B drift. Starting from a Boltzmann-Poisson system, we perform a dimensional analysis to identify the dominant physical effects within this zone. This yields a non-dimensional kinetic equation tailored to the regime of interest, featuring multiple small parameters and a clear scale separation. The fast cyclotron gyration are filtered out through a Hilbert expansion combined with a gyroaveraging operator, yielding a reduced gyrokinetic model. Then a gyrofluid model is derived using a moment method with an entropy-based closure. Owing to the symmetries introduced by the gyroaveraging process, the number of required moments is reduced, and the closure corresponds to an anisotropic Gaussian requiring only four moments: the density, parallel momentum, and two directional temperatures. A numerical strategy using common tools from the literature is provided to handle the remaining small scales. Numerical experiments exhibit promising results for our applications.</p></div>
• Design, synthesis, biophysical and biological evaluation of original condensed pyrrolopyrimidine and pyrrolopyridine ligands as anti-SARS-CoV-2 agents targeting G4
  
  • Guillon Jean
  • Savrimoutou Solène
  • da Rocha Nicolas
  • Albenque-Rubio Sandra
  • Helynck Olivier
  • Durand Cyrielle
  • Chiaravalli Jeanne
  • Pinaud Noël
  • Ronga Luisa
  • Moreau Stéphane
  • Chirold Simon
  • Zangmo Tshering
  • Arab Melika
  • Lari Lindita
  • Mergny Jean‐louis
  • Munier-Lehmann Hélène
  • Lavigne Marc
  European Journal of Medicinal Chemistry, Elsevier, 2025, 292, pp.117655. The design and synthesis of novel bis[(substituted-aminomethyl)phenyl]phenyl pyrrolopyrimidines, pyrrolopyridines, pyrazolopyrimidines, imidazopyrimidines, and tris[(substituted-aminomethyl)phenyl]phenyl pyrrolopyrimidines are reported here. These original G-quadruplex (G4) ligands have been then subjected to a screening on SARS-CoV-2 using a competition HTRF assay by targeting the SUD-NM/TRF2 RNA G4 interaction. The more promising derivatives have been evaluated in vitro to determine their potential antiviral effect on two different cell lines infected by two SARS-CoV-2 strains. This study revealed a clear correlation between their antiviral property and their efficacy to prevent the SUD/G4 interaction. This correlation supports the choice of SUD/RNA G4 complexes formed during SARS-CoV-2 infection as new antiviral targets (10.1016/j.ejmech.2025.117655)
  DOI : 10.1016/j.ejmech.2025.117655
• A mixing length model for arbitrary geometry
  
  • Labarre V.
  • Josserand Christophe
  • Le Berre M.
  • Monchaux R.
  • Pastur L.
  • Pomeau Y.
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2025, 151 (2), pp.23001. Abstract We present a novel phenomenological model for the mixing length used in turbulence models. It accounts for the nonlocality of the Reynolds stress tensor without introducing transport or integral equations. It has however the advantage of naturally accounting for the object's geometry while satisfying the standard symmetries of the Navier-Stokes equations. We investigate the model for the classical channel and pipe flows to characterize its main findings. We calibrate the three model parameters to recover the damping in the viscous sub-layer, the log-law of the wall, and the outer region behaviors. Our model compares favorably to friction factor measurements in the pipe flow at high Reynolds numbers and provides analytical predictions of the mixing length for several canonical flows. (10.1209/0295-5075/adea91)
  DOI : 10.1209/0295-5075/adea91
• Structural interactions in global trade
  
  • Lebert Didier
  • Poindron Alexis
  Theory and Decision, Springer Verlag, 2025. We provide a methodological framework for investigating global trade networks thatdistinguish between categories of goods. We introduce a multi-layer network version of the Lantner diffusion model, in which each layer represents a specific good and each node corresponds to a country. By establishing several mathematical results involving structural alterations of the network, and by leveraging interaction indices, we show how to quantify structural interactions between categories of goods and offer recommendations for decision-makers designing embargoes against target countries. (10.1007/s11238-025-10061-z)
  DOI : 10.1007/s11238-025-10061-z
• A Practical Algorithm for Physical Layer Encryption under Constant Envelope Constraint
  
  • Leroy Clément
  • Arbi Tarak
  • Pasquero Pierre
  • Geller Benoit
  IEEE Access, IEEE, 2025, 13, pp.133783 - 133789. <div><p>Physical Layer Encryption (PLE) techniques have gained increasing attention recently as they ensure security without requiring heavy coordination or time-consuming secret key establishment. In particular, masking encryption techniques rely on transmitting a masking signal along with the data signal to prevent eavesdroppers from deciphering the transmitted information by degrading its channel. These methods are especially practical, as they do not require any knowledge of the eavesdroppers channel state. Several mask designs have been proposed in the literature in recent years. However, these methods suffer from various limitations, including vulnerability to brute-force attacks, and a limited range of potential use cases. In this paper, we present a novel mask design algorithm that offers three key advantages compared to state-of-the-art methods: optimal Peak-to-Average Power Ratio (PAPR), applicability to both Gaussian and flat fading channels, and a high level of confidentiality. These advantages are validated through our simulations.</p><p>Physical layer security, Wire-tap channel, Peak-to-Average Power Ratio (PAPR).</p></div> (10.1109/ACCESS.2025.3592479)
  DOI : 10.1109/ACCESS.2025.3592479
• Integration of acoustic constraints in trajectory generation
  
  • Hoareau Damien
  • Berrah Danil
  • Tillet Joris
  • Chapoutot Alexandre
  , 2025, pp.1-7. <div><p>Optimal control based trajectory generation offers the ability to formulate complex problems while optimizing the performance of the system control inputs. Nevertheless, adding acoustic constraints to the optimal control problem (OCP) can be highly challenging. The classical resolution approach employs a "first-discretize-then-optimize" strategy using direct methods. However, this approach leads to significant computational costs, which in turn limits its applicability. Recent studies suggest using the acoustic reciprocity theorem (ART) to formulate the problem as one of obstacles collision avoidance. Hence, this study proposes investigating the formulation and solution of an OCP based on this theorem. The ART is combined with the Boundary Element Method (BEM) for the acoustic part of the problem. The OCP is implemented using successive convexification (SCvx) approach which offers a convenient framework to take into account acoustic constraint in trajectory planning generation. Promising experimental results highlight the applicability of our formulation based on the ART and guidelines for further development are provided.</p></div> (10.1109/CoDIT66093.2025.11321899)
  DOI : 10.1109/CoDIT66093.2025.11321899
• SCvx-Frank-Wolfe Algorithm
  
  • Berrah Danil
  • Hoareau Damien
  • Chapoutot Alexandre
  , 2025, pp.737-742. Convex optimization algorithms are increasingly used in embedded trajectory planning for safety-critical systems, requiring verification to meet safety standards. Previous research has shown that formal verification methods can be applied to convex solvers for linear problems. This paper explores a specific implementation of the successive convexification approach for trajectory planning using linear programming. We focus on a new implementation of the successive convexification algorithm based on the Frank-Wolfe method (FW-SCVX), aiming at demonstrating that it maintains algorithm performance and is suitable for embedded systems. We also analyze the convergence of the FW-SCVX algorithm and provide numerical evaluations to support our proposal. This work contributes to the formal verification of advanced trajectory planning algorithms in safety-critical embedded systems. (10.23919/ECC65951.2025.11186948)
  DOI : 10.23919/ECC65951.2025.11186948
• Fiber-based high-energy 1550 nm laser for generating high-order harmonics
  
  • Mikhneva Anastasiia
  • Boukhaoui Djamila
  • Idlahcen Saïd
  • Houard Jonathan
  • Blum Ivan
  • Godin Thomas
  • Guiramand Leo
  • Amrani Foued
  • Gérôme Frédéric
  • Benabid Fetah
  • Gauthier David
  • Merdji Hamed
  • Boutu Willem
  • Vella Angela
  • Hideur Ammar
  , 2025, pp.CG-4.4. The demand for precise, high-energy Extreme Ultraviolet (EUV) sources is growing across scientific and industrial fields. Studies have demonstrated that bulk crystals driven by mid-infrared laser pulses can generate high-order harmonics with enhanced intensities, extended cut-off energies, and improved damage thresholds [1]. While high-energy OPCPA and OPA systems have been successfully utilized to achieve these results, their complexity highlights the need for simpler, more compact solutions [1, 2, 3]. Ultrafast mid-IR fiber lasers have emerged as a promising alternative for high-harmonic generation (HHG). However, their pulse energies are limited to the nanojoule range [4]. Here, we report the first demonstration of high-order harmonics generated in bulk crystals using a high-energy fiber laser operating near 1550 nm. Our laser system integrates an erbium-doped fiber amplifier with a gas-filled hollow-core photonic crystal fiber (HC-PCF) for post-compression, delivering few-cycle pulses with durations under 50 fs, microjoule-level pulse energies, and a repetition rate of 660 kHz (fig. 1) [5].
• Improved monocular depth prediction using distance transform over pre-semantic contours with self-supervised neural networks
  
  • Hariat Marwane
  • Manzanera Antoine
  • Filliat David
  , 2025, pp.21868-21879. Monocular depth estimation (MDE) with self-supervised training approaches struggles in low-texture areas, where photometric losses may lead to ambiguous depth predictions. To address this, we propose a novel technique that enhances spatial information by applying a distance transform over pre-semantic contours, augmenting discriminative power in low texture regions. Our approach jointly estimates pre-semantic contours, depth and ego-motion. The pre-semantic contours are leveraged to produce new input images, with variance augmented by the distance transform in uniform areas. This approach results in more effective loss functions, enhancing the training process for depth and ego-motion. We demonstrate theoretically that the distance transform is the optimal variance-augmenting technique in this context. Through extensive experiments on KITTI, Cityscapes, Waymo, NYUv2 and ScanNet our model demonstrates robust performance, surpassing competing self-supervised methods in MDE. (10.1109/CVPR52734.2025.02037)
  DOI : 10.1109/CVPR52734.2025.02037
• Toughening effects of out-of-crack-path architected zones
  
  • Triclot Julie
  • Corre Thomas
  • Lazarus Véronique
  • Gravouil Anthony
  , 2024. The increasing use of architected materials has broadened the possibilities of mechanical behaviour. In this article, we aim to explore these new possibilities in terms of in-service behaviour, especially in terms of crack propagation by performing an in-depth study in the framework of Linear Elastic Fracture Mechanics (LEFM). The specific configuration studied here is the case where the architected zones are symmetrically positioned adjacently to the crack path and no propagation occurs within the zone. This problem is addressed both numerically and experimentally. Numerically, an path-following algorithm is used to simulate the crack propagation. Different toughening aspects of the addition of architected zones are identified. First, a temporary increase in crack propagation resistance is shown. It comes from a temporary increase of stored elastic energy in the architected zones, thus acting as mechanical springs. Second, a snap-back instability appears, linked to the release of the previously stored energy. It leads to a higher energy dissipated by the crack propagation process. Experimentally, we evidence the possibility to reproduce the theoretical results using 3D printing. A good quantitative comparison is obtained between numerical and experimental approaches. This study shows that it is possible to improve crack propagation resistance while lightening the component by addition of architected zones outside the crack path. This opens up the way to tune finely, through the use of optimization tools, the crack propagation response.