HAL Portal UBS (Université Bretagne Sud)
Not a member yet
14201 research outputs found
Sort by
Étude numérique et expérimentale de garniture en graphite expansé matricé de presse étoupe de vanne : application à la lutte contre les emissions fugitives
No full textInternational audienceL'objectif de cette étude est d'approfondir les connaissances sur le comportement mécanique des garnitures en graphite expansé matricé (GEM) classiquement utilisées dans des systèmes de presse-étoupe (PE) de vanne. Ces systèmes permettant l'étanchéité des tiges de vannes sont généralement composés d'empilements de bagues. Cependant, cet article se focalise sur l'étude d'une seule bague. Dans un premier temps, une étude expérimentale a été réalisée avec un essai de compression in-situ reproduisant le fonctionnement d'un PE de vanne sur bague unitaire. Dans un second temps, un modèle par éléments finis du montage de compression in-situ a été développé. Les paramètres matériaux d'un modèle de comportement original d'Hyper-Hysteresis ont été identifiés afin de reproduire le comportement d'une seule garniture sous charge. Les résultats obtenus par les études numériques et expérimentales ont été comparés dans le but de déterminer la validité du modèle Hyper-Hysteresis utilisé et de prédire dans le futur les paramètres prédominants dans la détermination du taux de fuite d'un PE de vanne
Congréganistes en psychiatrie : histoire de la fin d'un monopole dans les établissements de l'ouest de la France
No full textInternational audienc
ERGODIC THEORY FOR FRACTIONAL SDE WITH SINGULAR COEFFICIENTS
No full textWe show existence and uniqueness of invariant measures for SDE of the formwhere W H is a fractional Brownian motion (fBm) with Hurst parameter H ∈ (0, 1 /2), u is a linearly dispersive term and g is any. The significant challenge is to combine the regularizing effect of the fBm with an ergodic theory suited to non-Markovian SDE. Concerning the latter our first main contribution is to construct a bona fide stochastic dynamical system (SDS) (Hairer '05 and Hairer-Ohashi '07) associated to (SDE). Since the solution map is only continuous in the support of the stationary noise process we weaken the definitions introduced by Hairer '05 and Hairer-Ohashi '07 but manage to retain the Doob-K'hashminksii provided by Hairer-Ohashi '07. Our second innovation is to introduce a family of flexible local-global stochastic sewing lemmas, in the vein of Lê '20, which allows us to efficiently treat small and large scales simultaneously. By tuning the local scale as a function of ∥g∥Bα ∞,∞ we are able to obtain the necessary continuity of the semi-group and stability estimates to show unique ergodicity for all g ∈ B α ∞,∞ (R d ). We believe that these local-global sewing lemmas may be of independent interest.</div
Metaheuristic Optimization of Hybrid Renewable Energy Systems Under Asymmetric Cost-Reliability Objectives: NSGA-II and MOPSO Approaches
No full textInternational audienceThis study investigates the asymmetric trade-off between cost and reliability in the optimal sizing of stand-alone Hybrid Renewable Energy Systems (HRESs) composed of photovoltaic panels (PV), wind turbines (WT), battery storage, a diesel generator (DG), and an inverter. The optimization is formulated as a multi-objective problem with Cost of Energy (CoE) and Loss of Power Supply Probability (LPSP) as conflicting objectives, highlighting that those small gains in reliability often require disproportionately higher costs. To ensure practical feasibility, the installation roof area limits both the number of PV panels, wind turbines, and batteries. Two metaheuristic algorithms-NSGA-II and MOPSO-are implemented in a Python-based framework with an Energy Management Strategy (EMS) to simulate operation under real-world load and resource profiles. Results show that MOPSO achieves the lowest CoE (0.159 USD/kWh) with moderate reliability (LPSP = 0.06), while NSGA-II attains a near-perfect reliability (LPSP = 0.0008) at a slightly higher cost (0.179 USD/kWh). Hypervolume (HV) analysis reveals that NSGA-II offers a more diverse Pareto front (HV = 0.04350 vs. 0.04336), demonstrating that explicitly accounting for asymmetric sensitivity between cost and reliability enhances the HRES design and that advanced optimization methods-particularly NSGA-II-can improve decision-making by revealing a wider range of viable trade-offs in complex energy systems
Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) using microalgae-derived starch and levulinic acid
No full textInternational audienceA microalgae cultivation process was developed in order to produce starch-rich biomass, which can be converted into glucose after starch extraction and hydrolysis. Associated to levulinic acid, biosynthesis processes were carried out with microalgae-derived starch glucose, resulting in the production of poly (3-hydroxybutyrate-co-3hydroxyvalerate)s (PHBHV) with different contents in HB and HV units, with HV units reaching up to 32 %. The thermal and mechanical characteristics were measured as a function of HV proportion and are discussed in terms of chemical structure/morphology/properties relationships, showing that these properties can be modulated by adjusting the ratio between HB and HV units. The crystallinity of PHBHV copolymers gradually decreases as HV unit content increases and tends to drastically increase the ductility of materials with an elongation at break equal to about 800 % for PHBHV with 32 % in HV units. This work emphasizes the possibility to precisely design tailor-made PHBHV with tunable functional properties, by playing on the mixture of substrates initially introduced. Moreover, it addresses crucial societal considerations by using raw materials that do not compete with the food industry.</div
Etude des caractéristiques du désalignement des fibres et de leur impact sur la rupture en compression des composites à fibres continues avec contribution de l'effet de structure
No full textInternational audienceEtude des caractéristiques du désalignement des fibres et de leur impact sur la rupture en compression des composites à fibres continues avec contribution de l'effet de structur
Production of enriched protein extracts from cultivated Ulva sp. (Chlorophyta, Ulvales) by high-pressure homogenization
No full textInternational audienceThe human food sector plays a crucial role in supporting population growth and ensuring human well-being. In the context of global food security, environmental challenges, and the diversification of protein sources, research into new innovative and sustainable protein sources is essential. In Europe, alternative protein sources such as cultivated seaweed are a promising solution, with potential health benefits and increased sustainability. This study investigated the use of high-pressure homogenization (HPH) to obtain proteinenriched fractions from dried biomass of cultivated Ulva sp. The biochemical composition, physical-chemistry (FTIR and granulometric analysis) and the biological activities of the supernatant and residue fractions were evaluated after HPH treatment at pressures of 0, 600, 800, and 1000 bars. Results showed that, depending on their nature, pressure significantly influenced the biochemical composition and separation of compounds into the residue and supernatant, and underlined the potential of HPH to enhance protein recovery from Ulva sp. HPH facilitated separation of ulvan polysaccharides, known for their anti-nutritional effects, and from the protein fraction with high recovery yields of 60.0% protein in the residue. The highest protein content was found in residues at 1000 bars (8.93%) compared to in the crude extract (4.1%). Amino acid analysis revealed that essential amino acids accounted for 42% of total amino acids in the Ulva sp. fraction, with high levels of valine, leucine and methionine. The ulvan fraction (concentration of rhamnose, uronic acids and sulphate groups) was preferentially extracted at 1000 bars, where the supernatants contained 28.6 ± 4.5% of uronic acids, 23.2 ± 4.9% of sulfate groups, and 3.72 ± 0.31% of rhamnose (p< 0.05).These results provide clear evidence that HPH is effective in disrupting the cell wall and facilitating the release of compounds of interest. These results also suggest that the HPH process could position cultivated Ulva sp. as an important potential source of food protein.</div
Etude de composites transparents pour protection balistique
No full textInternational audienceEtude de composites transparents pour protection balistiqu
Identifying Key Requirements for Maritime Bridge Simulators in Wind-Assisted Ship Propulsion Training
No full textInternational audienceMaritime transport is responsible for 3 percent of global greenhouse gas emissions. To meet environmental regulations, technologies such as Wind-Assisted Ship Propulsion (WASP) are being considered. However, maritime officers' training needs to be adapted, as sailing is not sufficiently covered in current curricula. The SOMOS project aims to develop a navigation simulator for merchant vessels equipped with WASP, incorporating realistic training scenarios such as failure management. This simulator will enable sailors to prepare for the use of these technologies and contribute to the reduction of emissions in maritime transport. In this paper, we present the results of a student work with the goal of identifying minimal requirements for bridge maritime simulators including WASP technologies
Filières à prioriser pour atténuer le changement climatique via le recyclage des biomasses résiduelles en produits biosourcés à l'échelle nationale: Construction d'une méthode de sélection des voies de transformation à fort potentiel de réduction des impacts environnementaux en amont d'une analyse approfondie via des ACV complètes.
No full textInternational audienc