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Extraction automatique des néologismes en chinois et en vietnamien (2015–2025)
No full textInternational audienc
Breaking Anonymity in Attribute-Based Access Control Encryption *
No full textInternational audienceAccess Control Encryption (ACE) enforces sender and receiver access control while preserving traffic anonymity. Attribute-Based ACE (AB-ACE) extends this to attribute-based policies, claiming to achieve the same security guarantees under the No-Read and No-Write rules. In this paper, we show that existing AB-ACE schemes fail to ensure anonymity: most reveal the access structure in the ciphertext, and even schemes designed to hide it leak information through NIZK-related elements, violating the No-Read Rule. These results call for a reconsideration of both the construction techniques and the formal models of AB-ACE, if robust sender and receiver privacy is to be achieved
Approche onto-phraséologique pour l’extraction automatique des relations idiomatiques
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New advances in the understanding of host-guest zeolite materials through NMR experimental and theoretical approaches: the TPA-F-Silicalite-1 case
No full textInternational audienceWe undertook a detailed NMR characterization of the prototypical host-guest zeolite TPA-F-Silicalite-1, made of tetrapropylammonium cations (TPA), fluoride and the MFI silica framework. The use of a high magnetic field (B0 = 20 T) and very fast MAS frequency (MAS = 100 kHz) greatly improves the 1 H resolution in the related 1D spectrum and 2D 1 H-1 H and 1 H-13 C correlation spectra, enabling eight distinct 1 H peaks to be identified, whereas TPA shows only three peaks in solution NMR. We also analyzed a 2D 1 H-29 Si NMR correlation spectrum on a 29 Si labelled sample allowing to decipher the location of the propyl (Pr) arms in MFI channels. In parallel, we conducted complementary Density Functional Theory calculations using two approaches: geometry optimization and ab initio molecular dynamics (AIMD) based on Born-Oppenheimer molecular dynamics (BOMD). On the basis of the highly resolved experimental NMR spectra together with the BOMD calculated NMR parameters, new sets of 1 H and 13 C NMR peaks were assigned. The BOMD simulation (5.2 ps trajectory length) allows further analysis of the structure and dynamics of the TPA guest, confined in the Silicalite-1 host. From the obtained results, there is no evidence of any major restriction of H motions (C-H stretching, H-C-H bending, methyl rotation) due to sterically constrained Pr arms located in MFI zigzag channels. We found however that Pr arms in zigzag channels remain in trans conformation, while the conformation of Pr arms in straight channels alternates between trans and gauche.</div
Auxiliary-Field Formalism for Higher-Derivative Boundary CFTs
No full textInternational audienceWe study the conformal field theory defined by the fourth-order operator on four-dimensional manifolds with boundaries, reformulating it through an auxiliary field so that the dynamics become second order. Within this framework, we compute the heat kernel of in flat space exactly, together with the associated Seeley-DeWitt coefficients for a broad class of non-standard boundary conditions. On curved backgrounds, we further construct the Weyl-invariant completion of the auxiliary field action with boundary terms and identify the corresponding conformal boundary conditions. Finally, we compute the boundary charges in the trace anomaly from the displacement operator correlators
Optimal Dirac controls for time-periodic bistable ODEs, application to population replacement
No full textThis work addresses an optimal control problem on a dynamics governed by a nonlinear differential equation with a bistable time-periodic nonlinearity. This problem, relevant in population dynamics, models the strategy of replacing a population of A-type individuals by a population of B-type individuals in a time-varying environment, focusing on the evolution of the proportion of B-type individuals among the whole population. The control term accounts for the instant release of B-type individuals. Our main goal, after noting some interesting properties on the differential equation, is to determine the optimal time at which this release should be operated to ensure population replacement while minimizing the release effort. The results establish that the optimal release time appears to be the minimizer of a function involving the carrying capacity of the environment and the threshold periodic solution of the dynamics; they also describe the convergence of the whole optimal release strategy. An application to the biocontrol of mosquito populations using Wolbachia-infected individuals illustrates the relevance of the theoretical results. Wolbachia is a bacterium that helps preventing the transmission of some viruses from mosquitoes to humans, making the optimization of Wolbachia propagation in a mosquito population a crucial issue
