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Deciphering the effect of propionic acid on anaerobic digestion of sludge: gas production and microbial community structure
No full textInternational audienceThis study investigates the impact of propionic acid (HPro) on anaerobic digestion (AD). HPro is an intermediate compound naturally generated during AD but inhibitory at excessive concentrations. To decipher the inhibition mechanisms, propionate, pH changes, and sodium ions were tested in addition to HPro, in batch mesophilic AD microcosms fed with municipal sewage sludge. Methane production experienced greater inhibition as the initial concentration of HPro increased, and was totally inhibited at 6 g/L HPro. The primary cause of inhibition was the low pH, as shown by comparison with NaPro, NaCl and HCl. Consistent with the inhibition, the abundance of methanogenic archaea and of the bacterium Syntrophomonas decreased with the addition of HPro. Methanogens and their syntrophic partners could therefore be interesting targets to develop inhibition biomarkers. We thereby provide one of the most in-depth study regarding HPro inhibition mechanisms during AD
A nonlocal regularization of a generalized Busenberg-Travis cross-diffusion system
No full textA cross-diffusion system with Lotka--Volterra reaction terms in a bounded domain with no-flux boundary conditions is analyzed. The system is a nonlocal regularization of a generalized Busenberg--Travis model, which describes segregating population species with local averaging. The partial velocities are the solutions of an elliptic regularization of Darcy's law, which can be interpreted as a Brinkman's law. The following results are proved: the existence of global weak solutions; localization limit; boundedness and uniqueness of weak solutions (in one space dimension); exponential decay of the solutions. Moreover, the weak--strong uniqueness property for the limiting system is shown
Machine learning and Bayesian optimization for performance prediction of proton-exchange membrane fuel cells
No full textInternational audienceProton-exchange membrane fuel cells (PEMFCs) are critical components of zero-emission electro-hydrogen generators. Accurate performance prediction is vital to the optimal operation management and preventive maintenance of these generators. Polarization curve remains one of the most important features representing the performance of PEMFCs in terms of efficiency and durability. However, predicting the polarization curve is not trivial as PEMFCs involve complex electrochemical reactions that feature multiple nonlinear relationships between the operating variables as inputs and the voltage as outputs. Herein, we present an artificial-intelligence-based approach for predicting the PEMFCs’ performance. In that way, we propose first an explainable solution for selecting the relevant features based on kernel principal component analysis and mutual information. Then, we develop a machine learning approach based on XGBRegressor and Bayesian optimization to explore the complex features and predict the PEMFCs’ performance. The performance and the robustness of the proposed machine learning based prediction approach is tested and validated through a real industrial dataset including 10 PEMFCs. Furthermore, several comparison studies with XGBRegressor and the two popular machine learning-based methods in predicting PEMFC performance, such as artificial neural network (ANN) and support vector machine regressor (SVR) are also conducted. The obtained results show that the proposed approach is more robust and outperforms the two conventional methods and the XGBRegressor for all the considered PEMFCs. Indeed, according to the coefficient of determination criterion, the proposed model gains an improvement of 6.35%, 6.8%, and 4.8% compared with ANN, SVR, and XGBRegressor respectively
Reactive Cooperation of Multi-Vehicle System for Efficient Intersection Crossing based on PIDP Speed Space Assessment
No full textInternational audienceThis paper proposes a Dynamic Collision-Free Cooperative decision-making method based on the Predicted InterDistance Profile (DCFC-PIDP) for Connected Autonomous Vehicles (CAVs), aimed at solving congestion, and increasing the efficiency and safety of the transport system. Under this framework, this paper studies a typical urban driving scenario: unsignalized intersection. The method employs a greedy algorithm to explore with an appropriate metrics, the main possible scenarios, involving CAVs with a risk of collision and f ind the suboptimal feasible solution. The decision-making cost function is constructed by considering the risk of collisions and the passing efficiency of CAVs. Finally, the effectiveness and feasibility of the proposed decision-making framework are verified under statistic studies
An efficient shear and bending‐locking‐free quadrilateral plate element using a modified Hellinger‐Reissner functional and the Bergan free formulation
No full textInternational audienceThis paper presents a general variational principle as theoretical support for creating a simple and efficient quadrilateral plate finite element called BKWA, having only a single displacement and two rotations at corner nodes according to the Reissner‐Mindlin plate theory. The functional is a modified Hellinger‐Reissner in terms of the kinematic variables and independent transverse shear strains. Hence, we consider quadratic rotations, as in DKQ, and linear independent shear strains with constant tangential components on sides, as in MITC4. The quadratic rotation contributions and the mixed shear strain components are wiped out by static condensation. To adequately satisfy the constant curvature patch tests, we also consider the orthogonality conditions between the linear and quadratic bending modes, as in the Bergan free formulation, to avoid ‘spurious bending energy’ for thick plates (also called bending locking). The paper contains comprehensive patch tests and convergence tests with regular and irregular meshes (displacements, internal forces, and strain energy) of circular and square plates. The element is compared with other existing elements (MITC4, DKMQ). It is concluded that BKWA is an efficient element regarding several criteria
Planning for climate change with the best of intentions... Analyzing content of plans and planner’s rationale for adaptation
No full textInternational audienceIn France, local urban plans (PLUi) can convey drivers for climate change adaptation, e.g. greening and limitation of soil sealing to reinforce stormwater management. However, translating adaptation measures into plans is not always easy for planners to effectively communicate adaptation. We create an analysis method, specifically designed for the sustainable development project (PADD), a key document of the PLUi, in order to understand its adaptation approach. The PADD examined is that of the PLUi of Nantes metropolis in France. The first part of the method has been published; here, we develop the last two steps of the method, which consist of a thematic analysis applied to the corpus and a cross-analysis of results. The findings reveal seven major intentions for adaptation. Specific actions were more difficult to identify; however, four areas of practical application emerged: vegetation, water, soil and building. Furthermore, we questioned local planners to get a complete sense of their rationale to address adaptation. Creators and agents result in being aware of the challenges and can identify concrete and synergistic adaptive actions; however, it is unclear how they would measure achievement of PADD objectives. The results may provide useful information to determine whether PADDs are conducive to adaptation
Optimisation des plans de transport ferroviaire dans une échelle microscopique
No full textInternational audienc
La Nature, « troisième part » trop souvent oubliée dans la construction d’un être humain
No full texthttps://www.innovation-pedagogique.fr/In the problematics of our own human construction with and within the world, the latter term is often reduced to only two dimensions: the inner psychic/psychological world as an individual subject, and the immediate social/societal world as a subject member of various collectives. However, in doing so, a third world is overlooked, yet essential to the development of the previous two, as they cannot be constructed without it: the world of nature. Various perspectives can be considered to address this absence, especially in the1era of the Anthropocene. Taking into account this third world (which will outlive us) can help us reflect on our commitment, our search for meaning, and our understanding of our needs. It is likely for this reason that certain educational approaches like "schools in nature," which systematize learning situations conducted in natural environments, are rapidly expanding.Understanding and establishing both individual and collective connections with nature, as a non-human environment that benefits the human environment, is essential. The consideration of these connections is currently underway, with theoretical frameworks and even integration into educational curricula. Some movements in the realm of progressive education, particularly the modern school movement, have embraced this concept. We will conceptualize these ideas using the work and theories of Pierre Weil (France, Brazil), who presents Nature as a third element in complex interaction with the individual and society. Subsequently, we will explore what "environmental education" can contribute to the construction of a subject, no longer limited to a dual relationship with others but approached in at least a tripartite manner, involving society and nature. We will explore, from a transdisciplinary approach, the extent to which human consciousness allows us to understand the interweaving, complexity, fragility, and evolution of life in its multiple forms, and how we can benefit from it in our own construction.L’article (disponible à cette adresse : https://www.innovation-pedagogique.fr/article18059.html) met en lumière l’importance souvent négligée de la nature dans la construction humaine. Il propose une vision globale qui inclut la nature comme troisième dimension après soi-même et autrui. Par exemple, Pierre Weil, avec sa matrice holopoïétique, intègre l’individu, la société ET la nature. Ces approches transcendent l’holisme et le réductionnisme, comme explique Edgar Morin. L’utilisation d’une métaphore par une peinture de Goya souligne a contrario la lutte entre les individus et la nature, soulignant la nécessité de considérer désormais la nature comme une partie intrinsèque de la réalité humaine en lien avec l’écologie. L’éducation environnementale est donc présentée comme essentielle à la construction humaine, favorisant une relation harmonieuse avec tous les règnes. Les auteurs appellent à réfléchir sur l’intégration de cette éducation dans les programmes et à promouvoir des politiques environnementales, car intégrer la nature dans la construction de l’identité humaine peut contribuer à la protection de l’environnement et à la sensibilisation sociétale
The combined effect of hydrogen and aging conditions on the cyclic behavior of a precipitation-hardened nickel-base superalloy
No full textInternational audienceThe effect of hydrogen on the cyclic deformation behavior of Waspaloy in two heat treatment conditions was assessed via low cycle fatigue tests. H-charged and non-charged samples of both heat treatments were cycled to saturation to facilitate a comparison of stress amplitude, back stress, effective stress and shear bands behavior. For both aging conditions (weak coupling domain), H charging leads to a significant reduction in the stress amplitude, which is supported by the decrease of the effective stress and an increase of the back stress. Atomic force microscopy and transmission electron microscopy of these samples revealed a decrease of the shear bands spacing, with a modification of the shear bands widths and the dislocation density in bands. This result suggests that hydrogen impacts the dislocations-precipitates interaction