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A theory of injection-based vulnerabilities in formal grammars
No full textInternational audienceMany systems are controlled via commands built upon user inputs. For systems that deal with structured commands, such as SQL queries, XML documents, or network messages, such commands are generally constructed in a "fill-in-the-blank" fashion: the user input is concatenated with a fixed part written by the developer (the template). However, the user input can be crafted to modify the command's semantics intended by the developer and lead to the system's malicious usages. Such an attack, called an injection-based attack, is considered one of the most severe threat to web applications. Solutions to prevent such vulnerabilities exist but are generally ad hoc and rely on the developer's expertise and diligence. Our approach addresses these vulnerabilities from the formal language theory's point of view. We formally define two new security properties. The first one, "intent-equivalence", guarantees that a developer's template cannot lead to malicious injections. The second one, "intent-security", guarantees that every possible template is intent-equivalent, and therefore that the programming language itself is secure. We thoroughly analyze the decidability of these properties for the most common grammar classes. We conclude by highlighting the technical implications of these results for various settings and tools
Silicon nanoantennas for tailoring the optical properties of MoS2 monolayers
No full textInternational audienceSilicon-based dielectric nanoantennas provide an effective platform for engineering light–matter interactions in van der Waals semiconductors. Here, we demonstrate near-field coupling between monolayer MoS2 and silicon nanoantennas arranged in hexagonal lattices with tunable geometric parameters, leading to a threefold enhancement in photoluminescence and an excitation-wavelength-dependent emission that aligns with Mie-resonant modes. Raman spectroscopy reveals an up to eightfold enhancement in the vibrational modes of MoS2, while second-harmonic generation exhibits a 20 to 30-fold increase in efficiency, closely correlating with the presence of the underlying nanoantennas. Our experiments and simulations quantify the tunable benefits of the near-field interactions, taking into account thin-film interference and strain-induced effects. Our findings present dielectric nanoantennas as a promising platform for tailoring linear and nonlinear optical properties in 2D materials, with potential applications in nanophotonic devices and integrated photonics
Molecular Beam Epitaxy of Ge-VCSELs
No full textInternational audienceVertical-cavity surface-emitting laser (VCSEL) structures emitting near 940 nm were grown by solid source molecular beam epitaxy (MBE) on GaAs/Ge(001) wafer templates grown by MOVPE. The epitaxial design comprised 35-pairs n-doped and 17-pairs p-doped Al 0.9 Ga 0.1 As/GaAs Distributed Bragg reflectors (DBRs), three In 0.1 Ga 0.9 As quantum wells, and an Al 0.98 Ga 0.02 As layer for lateral oxidation. In-situ growth monitoring methods were employed, namelymultispectral reflectometry, and magnification-inferred curvature imaging [1] for real-time stress analysis. Curvature measurements revealed progressive accumulated compressive stress with some indication of partial relaxation, while optical reflectometry data confirmed the good control of both the stopband center wavelength and the VCSEL cavity resonance. Post-growth reflectivity measurements showed a stopband centered at 942.7 nm with a bandwidth of 93.6 nm and cavity resonance at 944.21±1.15 nm over the 4" wafer. Atomic force microscopy revealed a continuous surface morphology without cracks over a 10x10 µm 2 surface. Fabricated devices with mesa diameters of 35-40 μm, corresponding to oxide apertures of approximately 11-16 μm, exhibited room-temperature lasing under continuous-wave bias with threshold currents below 3 mA. To the best of our knowledge, this is the first demonstration of monolithically integrated 940 nm VCSELs grown on Ge substrates by MBE, since all the work on AlGaAs VCSELs on Ge has to date been carried out using MOVPE [2-5]. These results confirm the viability of MBE-grown VCSELs on Ge, and the advantages of in-situ control tools for understanding growth-related phenomena and achieving the target specifications for the component.</div
Réseaux de Bragg en nitrure de silicium et amplificateurs optiques en réflexion GaAs pour la réalisation de lasers hybrides à cavité étendue autour de 965nm
No full textInternational audienceNous présentons une nouvelle plateforme de laser hybride émettant autour de 965nm. Cette cavité est composée d’un réflecteur de Bragg en nitrure de silicium et un amplificateur optique à semi-conducteurs en réflexion en GaAs
Génération de mondes virtuels pour tester des robots autonomes en simulation
No full textThe research leading to these results has received funding from the EuropeanUnion’s Horizon 2020 research and innovation programme under the MarieSkłodowska-Curie grant agreement No. 812.788 (MSCA-ETN SAS).National audienceThis thesis addresses the challenges of automated test case generation for autonomous systems using simulation-based testing. The manuscript tackles three primary research questions: (1) how to generate structured test data with constraints, (2) how to integrate automated test generation frameworks into existing industrial testing platforms, and (3) how to apply pairwise testing to hierarchical data structures like XML and JSON. To address the first question, the manuscript introduces TAF (not a contribution of this thesis), a testing tool for generating test cases from complex declarative models with structure and constraints. For the second question, the integration of TAF into two industrial simulation-based platforms is discussed, highlighting practical considerations and lessons learned from real-world applications. The main contribution of this work, addressing the third question, is a formalization for applying pairwise testing to hierarchical data structures with constraints. This formalization redefines concepts such as test parameters, choices, and pairs to accommodate structured data, considering data instance multiplicity, access paths, and common ancestors. Various strategies for selecting the lowest common ancestor (LCA) are presented, along with XPath queries for coverage checking. The thesis also reports on the implementation of a framework that combines pairwise strategies with TAF. Results from two case studies demonstrate the framework's ability to minimize test suite size while maximizing coverage, outperforming the baseline approach. Future research directions include exploring closed-loop testing, integrating search-based and combinatorial algorithms, modeling more complex scenarios with dynamic agents, and extending the pairwise formalization to handle recursive definitions and n-way testing.Cette thèse aborde les défis de la génération automatisée de cas de test pour les systèmes autonomes à l'aide de tests basés sur la simulation. Le manuscrit aborde trois questions de recherche principales : (1) comment générer des données de test structurées avec des contraintes, (2) comment intégrer des cadres de génération de tests automatisés dans des plates-formes de tests industrielles existantes et (3) comment appliquer des tests par paires à des structures de données hiérarchiques comme XML et JSON. Pour répondre à la première question, le manuscrit présente TAF (qui n'est pas une contribution de cette thèse), un outil de test permettant de générer des cas de test à partir de modèles déclaratifs complexes avec structure et contraintes. Pour la deuxième question, l'intégration de TAF dans deux plates-formes industrielles basées sur la simulation est discutée, mettant en évidence les considérations pratiques et les leçons tirées d'applications du monde réel. La principale contribution de ce travail, abordant la troisième question, est une formalisation permettant d'appliquer pairwise testing à des structures de données hiérarchiques avec contraintes. Cette formalisation redéfinit des concepts tels que les paramètres de test, les choix et les paires pour s'adapter aux données structurées, en tenant compte de la multiplicité des instances de données, des chemins d'accès et des ancêtres communs. Diverses stratégies de sélection du plus petit ancêtre commun (LCA) sont présentées, ainsi que des requêtes XPath pour la vérification de la couverture. La thèse rend également compte de la mise en œuvre d'un framework combinant des stratégies par paires avec TAF. Les résultats de deux études de cas démontrent la capacité du framework à minimiser la taille de la suite de tests tout en maximisant la couverture, surpassant l'approche de base. Les futures orientations de recherche comprennent l'exploration des tests en boucle fermée, l'intégration d'algorithmes basés sur la recherche et combinatoires, la modélisation de scénarios plus complexes avec des agents dynamiques et l'extension de la formalisation par paires pour gérer les définitions récursives et les tests n-way
High-Speed Tunable Interferometric Spectral Shaper for VCSEL Manufacturing Inspection
No full textInternational audienceThe paper introduces a tunable interferometric spectral shaper for fast and precise inspection of VCSEL oxidation apertures. By using a Michelson interferometer with white-light illumination, the system generates sinusoidally shaped spectra that enhance contrast between oxidized and aperture regions. Experiments on AlGaAs VCSEL wafers show strong separability and resolution of features down to a few microns. This simple, cost-effective approach enables real-time, in-fab monitoring, improving device uniformity and manufacturing yiel
Stereolithography 3D printing method for multi-material hydrogel 2D photo-patterning in a microfluidic chip
No full textInternational audienceWe present a novel and straightforward method using a standard stereolithography (SLA) 3D printer for highresolution (20 μm x-y resolution), multi-material 2D hydrogel photo-patterning directly within a microfluidic chip. The process involves sequential injections of photosensitive hydrogel into a transparent microfluidic chip coupled with sequential direct laser writing by the printer through point-by-point photopolymerization. Our approach integrates a custom miniaturized syringe pump system into the SLA printer, thereby enabling fluid management and sequential injection of different photosensitive hydrogels directly into the microfluidic environment between each laser writing sequence. This technique enables the fabrication of intricate, multi-material hydrogel patterns (e.g., PEGDA and HAMA) with high spatial resolution over areas spanning several square millimeters. Future developments will focus on expanding the range of biomaterials and incorporating cell-laden hydrogels to facilitate the creation of biologically relevant microenvironments on chip.This study opens new possibilities for high-resolution, multi-material hydrogel patterning in microfluidics and offers a valuable platform for advancing research in microsystems engineering.</p
Comparative Analysis of Electron Microscopy Techniques for Hydrogel Microarchitecture Characterization: SEM, Cryo-SEM, ESEM, and TEM
No full textInternational audienceHydrogels have emerged as a versatile class of materials with broad applications in biomedical engineering, drug delivery, and tissue engineering. Understanding their intricate structures and morphologies is crucial for tailoring their properties to meet specific biomedical needs. It has been clearly established that the composition and microarchitecture of the materials play a critical role in essential cellular mechanisms such as mechanosensing, adhesion, and remodeling. This question is essential in tissue engineering, where precisely characterizing the microarchitecture of the materials used to model the cell microenvironment is a critical step to ensure the reproducibility and relevance of reconstructed tissues. In this study, we present a comprehensive comparison of four advanced electron microscopy techniques, namely, scanning electron microscopy, cryo-scanning electron microscopy, environmental scanning electron microscopy, and transmission electron microscopy, to observe the hydrogel microarchitecture, including a comparison of the sample preparation methods for each technique. Each technique's specific advantages and limitations are discussed in detail, highlighting their unique capabilities in characterizing the hydrogel structures. We illustrate this study with two semisynthetic hydrogels, such as gelatin methacrylate and hyaluronic acid methacrylate. Moreover, we delve into the critical sample preparation steps necessary for each method, emphasizing the need to preserve the hydrogel's native state while obtaining high-resolution images. This comparative analysis aims to select the most suitable electron microscopy technique for their hydrogel studies, fostering deeper insights into the design and development of advanced biomaterials for tissue engineering applications
Robust ML Auditing using Prior Knowledge
No full textInternational audienceAmong the many technical challenges to enforcing AI regulations, one crucial yet underexplored problem is the risk of audit manipulation. This manipulation occurs when a platform deliberately alters its answers to a regulator to pass an audit without modifying its answers to other users. In this paper, we introduce a novel approach to manipulation-proof auditing by taking into account the auditor's prior knowledge of the task solved by the platform. We first demonstrate that regulators must not rely on public priors (e.g. a public dataset), as platforms could easily fool the auditor in such cases. We then formally establish the conditions under which an auditor can prevent audit manipulations using prior knowledge about the ground truth. Finally, our experiments with two standard datasets illustrate the maximum level of unfairness a platform can hide before being detected as malicious. Our formalization and generalization of manipulation-proof auditing with a prior opens up new research directions for more robust fairness audits
P2NIA: Privacy-Preserving Non-Iterative Auditing
No full textInternational audienceUnlabelled - This study aimed to develop a practical, economically viable solution for treating hazardous landfill leachate using Pipe Freeze Crystallization (PFC) technology. The objective was to concentrate and solidify leachate from an effluent treatment plant processing approximately 8750 m annually, achieving resource recovery and environmental compliance. A 300 L h cooling demonstration plant was designed and implemented, incorporating a chiller, a secondary refrigerant mixture (40% ethylene glycol and 60% water), a clarifier, a reactor, and pumps. Μodelling with OLI software estimated recovery rates for salt and ice, providing a basis for operational adjustments. Leachate samples (2000 L) and concentrate (1000 L) were processed to evaluate the plant's performance in recovering clean water and NaSO. Experimental results confirmed the model predictions, with 302 L of concentrate yielding 102.9 kg of NaSO over 6 h and 273 L of leachate producing 118.7 kg of high-purity ice over 5.5 h. The energy consumption was measured at 171 kWh t of ice, aligning with theoretical predictions for a coefficient of performance of 1. These results validate the efficiency and feasibility of PFC in resource recovery. This study highlights the importance of PFC as a low-cost, energy-efficient technology for hazardous leachate treatment. Its scalability and ability to recover valuable resources such as NaSO and clean water present a sustainable alternative to conventional methods, contributing to zero-waste management goals in waste treatment practices. Supplementary information - The online version contains supplementary material available at 10.1007/s40710-025-00757-3