Portail HAL de l'Institut Polytechnique de Paris
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Les collectivités territoriales et l’énergie : une décentralisation en courant alternatif
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Non-Invasive Acidic Pretreatment Technology of Anaerobic Digestion of Waste-Activated Sludge (WAS) on Biogas Production: Unveiling the Role of Extracellular Polymeric Substances (EPSs) and Pharmaceutical Degradation
No full textInternational audienceNon-invasive acidic pretreatments using acetic acid (1–5 mM) and citric acid (0.02–0.1 g g−1 TS) were investigated to enhance anaerobic digestion (AD) of waste-activated sludge (WAS). Both pretreatments improved short-term process stability, with pH (6.5–7.1) and alkalinity (1000–5000 mg CaCO3 L−1) remaining within optimal ranges during 10-day digestion. Acetic acid markedly enhanced solubilization and acidification, increasing volatile fatty acids to ~2500 mg L−1 (+67% vs. control), whereas citric acid achieved ~2000 mg L−1 (+37%). EPS analysis revealed pronounced redistribution of polysaccharides and proteins, with acetic acid inducing stronger disruption of the EPS matrix (SB-EPS polysaccharides up to 34.1 mg eq Glc mL−1). Specific methane yield increased from 28.5 mL CH4 g−1 VS (control) to 101.7 mL CH4 g−1 VS with acetic acid (3.6-fold) and to 73.8 mL CH4 g−1 VS with citric acid (2.5-fold). Gompertz modeling confirmed higher maximum methane potential, ~68% higher maximum methane production rates, and reduced lag phases for both pretreatments. In contrast, pharmaceutical concentrations (31 compounds) were largely unaffected by acid pretreatment, with significant reductions observed only for selected biodegradable molecules
Ordres de charge et de spin dans le modèle t-U-V-J : une approche de particule esclave de spin 1
No full textStrongly-correlated fermion systems on a lattice have been a subject of intense focus in the field of condensed-matter physics. These systems are notoriously difficult to solve, even with state-of-theart numerical methods, especially in regimes of parameters where degrees of freedom compete or cooperate at similar energy and length scales. Here, we introduce a spin-1 slave-particle technique to approximately treat the t-U -V -J fermionic model at arbitrary electron dopings in a simple manner. This formalism relies on a self-consistent cluster mean-field method, and it couples effective pseudo-spin and pseudo-fermion sectors, representing the original electron charge and spin degrees, respectively. We study the phase diagram of the model under various conditions and report the appearance of charge and spin stripes within this formalism. These stripes are a consequence of the cluster mean-field treatment of the pseudo-particle sectors and have not been detected in previous slave-particle studies.Les systèmes de fermions fortement corrélés sur un réseau ont fait l'objet d'une attention particulière dans le domaine de la physique de la matière condensée. Ces systèmes sont réputés difficiles à résoudre, même avec les méthodes numériques les plus avancées, en particulier dans les régimes de paramètres où les degrés de liberté entrent en concurrence ou coopèrent à des échelles d'énergie et de longueur similaires. Nous présentons ici une technique de particule esclave de spin 1 permettant de traiter de manière simple et approximative le modèle fermionique t-U-V-J à des dopages électroniques arbitraires. Ce formalisme repose sur une méthode de champ moyen de cluster auto-cohérente et couple les secteurs pseudo-spin et pseudo-fermion effectifs, représentant respectivement les degrés de charge et de spin électroniques d'origine. Nous étudions le diagramme de phase du modèle dans diverses conditions et signalons l'apparition de bandes de charge et de spin dans ce formalisme. Ces bandes sont une conséquence du traitement par champ moyen sur cluster des secteurs de pseudo-particules et n'ont pas été détectées dans les études précédentes de particules esclaves
Local Communication in Repeated Games with Local Monitoring
No full textI consider repeated games with local monitoring: each player observes his neighbors' moves only. Hence, monitoring is private and imperfect. I assume local and public communication: communication is restricted to neighbors, and each player sends the same message to each of his neighbors at each stage. Both communication and monitoring structures are given by the network. The solution concept is perfect Bayesian equilibrium. In the four-player case, a folk theorem holds if and only if the network is 2-connected. Some examples are given for games with more than four players
Analyse asymptotique à tout ordre du problème de Helmholtz dans un coin avec une couche mince : une approche algébrique
No full textInternational audienceWe consider the Helmholtz equation in an angular sector partially covered by a homogeneous layer of small thickness, denoted ε. We propose in this work an asymptotic expansion of the solution with respect to ε at any order. This is done using matched asymptotic expansion, which consists here in introducing different asymptotic expansions of the solution in three subdomains: the vicinity of the corner, the layer and the rest of the domain. These expansions are linked through matching conditions. The presence of the corner makes these matching conditions delicate to derive because the fields have singular behaviors. Our approach is to reformulate these matching conditions purely algebraically by writing all asymptotic expansions as formal series. By using algebraic calculus we reduce the matching conditions to scalar relations linking the singular behaviors of the fields. These relations have a convolutive structure and involve some coefficients that can be computed analytically. Our asymptotic expansion is justified rigorously with error estimates.Nous considérons l'équation de Helmholtz dans un secteur angulaire partiellement couvert par une couche homogène de faible épaisseur, notée ε. Nous proposons dans ce travail un développement asymptotique à tout ordre de la solution par rapport à ε. Pour ce faire, nous utilisons un développement asymptotique raccordé, qui consiste ici à introduire différents développements asymptotiques de la solution dans trois sous-domaines : le voisinage du coin, la couche et le reste du domaine. Ces développements sont liés par des conditions de raccord. La présence du coin rend ces conditions délicates à obtenir car les champs possèdent des comportements singuliers. Notre approche consiste à reformuler ces conditions de raccord de manière purement algébrique en écrivant tous les développements asymptotiques sous forme de séries formelles. Par un calcul algébrique, nous réduisons les conditions de raccord à des relations scalaires reliant les comportements singuliers des champs. Ces relations ont une structure convolutive et impliquent des coefficients qui peuvent être calculés analytiquement. Notre développement asymptotique est justifié rigoureusement par des estimations d'erreur
Nonlinear model calibration through bifurcation curves
No full textInternational audienceNonlinear systems exhibit a plethora of complex dynamic behaviours that are difficult to model and predict accurately. This difficulty often arises from a lack of knowledge of the physics that induces the nonlinear behaviours and the strong sensitivity of the nonlinear dynamics to parameter variation. We introduce in this paper a methodology to carry out nonlinear model updating based on bifurcations. The proposed approach involves minimising the distance between experimental and numerical bifurcation curves, which are key dynamic features that define stability boundaries and regions of multi-stability. For the model, bifurcation curves are computed via standard numerical bifurcation tracking analyses. In the experiment, we use control-based continuation to obtain the data. The approach is first demonstrated on a Duffing and a beam system using synthetic data, before being applied to experimental data collected on a base-excited energy harvester with magnetic nonlinearity
Simultaneous probe of the charm and bottom quark Yukawa couplings using ttH events
No full textInternational audienceA search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H , produced in association with a top quark-antiquark pair (H) is presented. The search is performed with data from proton-proton collisions at = 13 TeV, corresponding to an integrated luminosity of 138 fb. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed H bb event rate relative to the standard model expectation is 0.91. The observed (expected) upper limit on the product of production cross section and branching fraction (H)(H ) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for H via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, , is 3.5 (2.7), the most stringent constraint to date
Finite element modelling for the reproduction of dynamic OCE measurements in the cornea
No full textInternational audienceRecent advances in dynamic elastography, particularly through optical coherence tomography combined with transient excitations have enabled rapid, localized, and non-invasive mechanical data acquisition of the cornea. This dataopens the path to early-detection of pathologies and more accurate treatment. However, the analysis of the wave propagation is a complex mechanical problem: the cornea is a structure under pressure, with non-linear material behavior. Thus, computational analysis are needed to extract mechanical parameters from the data. In this study, we present a time-dependent finite element model for the reproduction of transient shear wave elastographic measurements in the cornea. The mechanical problem consists in a smallamplitude wave propagating in the cornea, largely deformed by intraocular pressure in physiological conditions. The model accounts for anisotropic, hyperelastic, and incompressible behavior of the cornea, as well as its accurate geometry, and the preloaded condition. We have implemented two different numerical approaches to solve first the static non-linear inflation of the cornea and then the linear wave propagation problem to reproduce the measurements. We investigate the impact of material anisotropy and prestress on wave propagation and demonstrate that intraocular pressure critically influences shear wave velocity. Additionally, by introducing a localized mechanical defect to simulate a pathological defect, we show that simulated shear wave can detect and quantify mechanical weaknesses, suggesting potential as a diagnostic tool to assess corneal health
Concentration inequalities for semidefinite least squares based on data
No full textInternational audienceWe study data-driven least squares (LS) problems with semidefinite (SD) constraints and derive finite-sample guarantees on the spectrum of their optimal solutions when these constraints are relaxed. In particular, we provide a high confidence bound allowing one to solve a simpler program in place of the full SDLS problem, while ensuring that the eigenvalues of the resulting solution are -close of those enforced by the SD constraints. The developed certificate, which consistently shrinks as the number of data increases, turns out to be easy-to-compute, distribution-free, and only requires independent and identically distributed samples. Moreover, when the SDLS is used to learn an unknown quadratic function, we establish bounds on the error between a gradient descent iterate minimizing the surrogate cost obtained with no SD constraints and the true minimizer
Holographic shear correlators at low temperatures, and quantum
No full textInternational audienceThe strongly-coupled 3-dimensional theory, holographically dual to black branes at fixed chemical potential \muext and temperature is considered in AdS Einstein-Maxwell theory. The retarded Green's functions at frequency is calculated using holography in the regime ω, T \ll \muext but otherwise arbitrary. When the transverse space has finite volume, there is a non-zero energy scale , scaling as for large , below which quantum-gravitational corrections due to the fluctuations of the nearly-gapless Schwarzian modes become important. Such corrections to the retarded Green's function are calculated at different relative values of , , and . The limit is used to define the shear viscosity . As the temperature is lowered below , quantum corrections are found to increase the value of with respect to its semiclassical value. The quantum-corrected result for diverges as at , in accord with corresponding results for the absorption cross section. The quantum result for the ratio , where is the entropy density, dips below the semiclassical limit of when , then turns back to increase towards lower temperatures, and finally diverges at temperatures much below