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Optimizing dimensional accuracy in two-photon polymerization: Influence of energy dose and proximity effects on sub-micrometric fiber structures
No full textInternational audienc
Interpretable and Explainable Surrogate Modeling for Simulations: A State-of-the-Art Survey and Perspectives on Explainable AI for Decision-Making
No full textSurrogate models play a central role in reducing the computational cost of complex systems simulations across a wide range of scientific and engineering domains. Yet, their black-box nature often hinders insight into how input variables drive system responses. This state-of-the-art review and position paper surveys the integration of surrogate modeling with explainable artificial intelligence techniques to enhance transparency in simulation workflows and support design and decision-making, while also offering perspectives on future research directions. The paper not only surveys a broad spectrum of explainability techniques, such as variance-based sensitivity analysis, partial dependence plots, SHAP value decomposition, and active subspace methods, but also discusses practical pathways for applying them, including integration into design exploration, multi-objective design, and decision-making processes. We highlight their strengths for revealing interactions, managing high-dimensional and correlated inputs, and supporting human comprehension. This combination of methodological coverage and practical guidance uniquely positions the paper at the intersection of method development and practical application in simulation workflows. Beyond surveying existing methods, we also identify pressing challenges, including the explainability of dynamical systems, mixed-variable systems, correlated input structures, and the robustness of explanation metrics. We conclude with a research agenda to make interpretability and explainability core elements of simulation-driven workflows, embedded from model construction through validation and sensitive to context, modeling choices, and the limits of simulation for design and decision support
Predicting energy-dependent transformation products of environmental contaminants: the case of ibuprofen
No full textInternational audienceThe environmental pollution caused by emerging organic contaminants - such as ibuprofen - is becoming increasingly a cause for alarm. New treatments for their removal are currently being developed, but the nature and toxicity of the transformation products (TPs) formed during the processes cannot be easily assessed experimentally. Atomistic simulations are thus of great interest in predicting the chemical structure of these TPs. In this work, we have demonstrated that the transformation of a contaminant molecule under irradiation can be studied using the threshold algorithm combined with the density functional based tight-binding (DFTB) method. The fragmentation pathways of an ibuprofen molecule under irradiation have been studied as a function of the energy added to the system. Specifically, the chemical structures of ibuprofen's TPs, the paths between them, their stabilities, probabilities of occurrence, and the related mass spectra were obtained as a function of the amount of energy absorbed. We also simulated the evolution of the ibuprofen molecule as a function of the number of pulses, i.e., for a sequence of energy depositions. A dominant fragmentation scheme was identified, where first the OH group is released, followed by the loss of the CO group. The photon energy and the number of pulses were found to be key parameters for the selection of this degradation route among all identified fragmentation pathways
Anonymization Did Not Fail: Misconceptions and Overstatements on Data Anonymization Failures
No full textInternational audienceSeveral authors have claimed the “failure of anonymization,” despite over 50 years of research. We review privacy leaks reported over the past decades and conclude they were due to nonexistent or inadequate anonymization, rather than a lack of robust anonymization methods
Elément coque multicouches avec interfaces délaminantes
No full textInternational audienceElément coque multicouches avec interfaces délaminante
STUDY OF THE INTERFACE ALUMINIUM ALLOY / CHROMATE-BASED WASH PRIMER BY ELECTRON AND X-RAY SPECTROSCOPY TECHNIQUES
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Skyrmion stacking in stray field-coupled ultrathin ferromagnetic multilayers
No full textInternational audienceThis paper explores the energy landscape of ferromagnetic multilayer heterostructures that feature magnetic skyrmions -tiny whirls of spins with non-trivial topology -in each magnetic layer. Such magnetic heterostructures have been recently pursued as possible hosts of room temperature stable magnetic skyrmions suitable for the next generation of low power information technologies and unconventional computing. The presence of stacked skyrmions in the adjacent layers gives rise to a strongly coupled nonlinear system, whereby the induced magnetic field plays a crucial stabilizing role. Starting with the micromagnetic modeling framework, we derive a general reduced energy functional for a fixed number of ultrathin ferromagnetic layers with perpendicular magnetocrystalline anisotropy. We next investigate this energy functional in the regime in which the energy is dominated by the intralayer exchange interaction and formally obtain a finite-dimensional description governed by the energy of a system of one skyrmion per layer as a function of the position, radius and the rotation angle of each of theses skyrmions. For the latter, we prove that energy minimizers exist for all fixed skyrmion locations. We then focus on the simplest case of stray fieldcoupled ferromagnetic bilayers and completely characterize the energy minimizers. We show that the global energy minimizers exist and consist of two stray field-stabilized Néel skyrmions with antiparallel in-plane magnetization components. We also calculate the energy of two skyrmions of equal radius as a function of their separation distance.</div
Variational calculation of the hyperfine Stark effect in atomic 87Rb,133Cs,and 169Tm
No full textInternational audienceAn electronically variational approach to the calculation of atomic hyperfine structure transition energies under the influence of static external electric fields is presented. The method avoids the calculation of intermediate atomic states entirely and requires only the wavefunctions of the electronic states involved in the respective hyperfine levels. These wavefunctions are obtained through relativistic general-excitation-rank configuration interaction theory. A variant of the method also enables for calculations on atoms with the most complicated of shell structures.Applications to 87Rb, 133Cs and a specific clock transition in 169Tm are presented. The final results kRb=−1.234±0.0223 [10−10 Hz/((V/m)2)] and kCs=−2.347±0.084 [10−10 Hz/((V/m)2)] obtained under inclusion of up to quintuple excitations in the atomic wavefunction expansion are compatible with previous calculations and, in the case of Cs, confirm that one of the earlier experimental measurements is not reliable. For 169Tm that is used in the development of atomic clocks the differential static scalar electric dipole polarizability between ground levels J=72 and J=52 is calculated to be Δαs0=−0.134±0.11 a.u. This result from a pure {\it{ab initio}} calculation confirms the result of Δαs0=−0.063+0.01−0.005 a.u. obtained in {\it{Nat. Comm.}} {\bf{10}} (2019) 1724 where a combination of measurement and theoretical modeling has been used
Role of Nitrogen and Oxygen in the nucleation and growth of Silver Nanoparticles in gas-phase synthesis
No full textInternational audienceIn this study, we synthesized silver nanoparticles (AgNPs) in the gas phase and explored the influence of a small amount of reactive gases on their structural properties. Through a combined approach of transmission electron microscopy (TEM) with atomic resolution and in situ optical emission spectroscopy, we investigated the nucleation mechanisms of silver in the gas phase. Our findings put forward the ion-induced nucleation as mechanisms playing a pivotal role in the significant increase in AgNP surface density observed upon the introduction of a small amount of oxygen (below 0.5%). These results provide key insights into on the impact of reactive gases on nanoparticles formation and underline the mechanism driving their nucleation in plasma environments
On entropy production of repeated quantum measurements III. Quantum detailed balance
No full textIn light of the dynamical-systems approach to entropy production in repeated quantum measurements, proposed and illustrated in Commun. Math. Phys. 357, 77-123 (2018) [arXiv:1607.00162] and J. Stat. Phys. 182, 44 (2021) [arXiv:2012.03885], we characterize the KMS quantum detailed balance condition for quantum channels via time-reversal invariance and the vanishing of the entropy production for the associated informationally complete quantum instruments