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Accelerated characterisation of Operational Amplifiers' susceptibility using multitone disturbance
No full textInternational audienceThis paper presents an original approach to accelerate susceptibility testing of Operational Amplifiers (op-amp), using large band multitone signals, for a Direct Power Injection (DPI) setup. The relation between Continuous Wave (CW) and multitone susceptibility results, the associated limits and the global characterisation flow are discussed
Representation Learning for flowsheets: generating structures for Process Synthesis
No full textInternational audienceThe research for the optimal flowsheet is a key part of process synthesis. However, optimization at a structural level is difficult due to its discrete nature, and current approaches may not guarantee a good exploration of possibilities. A continuous structural domain could be useful for systematizing this research and exploration. In this work, a machine learning model is trained to develop a continuous representation for flowsheets: every process can be turned into a point in space, and points in space can be translated back into processes. The model's capability of generating new processes from random points in space is assessed. Results show that, although capable of grouping similar processes together, in clusters, it may not always propose structurally feasible flowsheets. Dataset generation and hyperparameter finetuning could also be improved before the model is coupled with process synthesis approaches
Multi-output Gaussian process for river water height estimation
No full textInternational audienceMulti-output Gaussian process for river water height estimatio
Serre and Boussinesq Models for Favre Waves in Trapezoidal Cross-Sectional Channels
No full textInternational audienceWe present two mathematical models for weakly dispersive non-linear waves in prismatic channels of trapezoidal cross-sections. The first model, derived from a variational principle, is an extension of the well known Serre equations. The second one is a variation of Winckler and Liu'model (Winckler and Liu in J Fluid Mech 770:156-188, 2015 [1]), which belongs to the family of Boussinesq-type equations. Both are valid for arbitrary cross-sectional channels, but the very common case of constant, trapezoidal sections is investigated here in view of understanding and modelling Favre waves in such channels. The first model allows theoretical derivations in agreement with previous publications (including scale model measurements). The second model is well suited to numerical implementation and allows studying the dynamics of Favre waves. It is verified through an analytical solution and validated from published measured data.</div
One dimensional modelling of Favre waves in channels
No full textInternational audienceIn this study, we propose a modified version of section-averaged Boussinesq equations of Winckler-Liu. The model is reformulated in conservative variables, allowing a decoupling of the Shallow-Water equations and the dispersive problem. An appropriate hybrid finite volume and finite element discretisations are performed and verified with a solitary wave solution derived for the typical case of prismatic channels with a trapezoidal cross-section. Classical upwind and energy conservative schemes are investigated through channel Favre waves cases. The proposed model and numerical approximations can accurately reproduce the main features of the wave train's free surface. Numerical dissipation introduced by decentered flux formulations is discussed, emphasising the need for precaution in their applications to realistic engineering issues.</div
Inland navigation and land use interact to impact European freshwater biodiversity
No full textInternational audienceInland navigation in Europe is proposed to increase in the coming years, being promoted as a low-carbon form of transport. However, we currently lack knowledge on how this would impact biodiversity at large scales and interact with existing stressors. Here we addressed this knowledge gap by analysing fish and macroinvertebrate community time series across large European rivers comprising 19,592 observations from 4,049 sampling sites spanning the past 32 years. We found ship traffic to be associated with biodiversity declines, that is, loss of fish and macroinvertebrate taxonomic richness, diversity and trait richness. Ship traffic was also associated with increases in taxonomic evenness, which, in concert with richness decreases, was attributed to losses in rare taxa. Ship traffic was especially harmful for benthic taxa and those preferring slow flows. These effects often depended on local land use and riparian degradation. In fish, negative impacts of shipping were highest in urban and agricultural landscapes. Regarding navigation infrastructure, the negative impact of channelization on macroinvertebrates was evident only when riparian degradation was also high. Our results demonstrate the risk of increasing inland navigation on freshwater biodiversity. Integrative waterway management accounting for riparian habitats and landscape characteristics could help to mitigate these impacts
Electrical resilience assessment of a building operating at low voltage
No full textInternational audienceResilience is becoming increasingly important in power systems,microgrids (MG) and buildings. It evaluates their performanceagainst disruptive events. The approaches mainly correspond tohigh-impact, low-probability events such as natural disasters andintentional attacks affecting the electrical systemsinfrastructure. However, resilience can encompass medium andlow-impact events such as minor civil structural accidents, lightfaults and supply disturbances. Some resilience assessment advancesare in buildings at the low-voltage (LV) level. They includevulnerability to natural disasters, reliability of supply, andservice quality. These works usually use approaches independent ofeach other, leaving a gap between their relationship andinterpretation. Therefore, there is a need to consolidate aresilience assessment strategy to guide the analysis ofvulnerabilities and strengths in the same direction. This paperproposes a comprehensive approach to evaluate electrical resiliencefor buildings. It compiles quantitative strategies for studyingelectrical resilience, focusing on LV systems. It proposes amethodology for integrating the electrical system infrastructure'svulnerability, the supply's continuity and the voltage service'squality. Implementing this approach in a university buildingequipped with smart metering demonstrates the effectiveness of theproposed methodology for assessing electrical resilience. Theresults show a comprehensive resilience analysis and thepossibility of extending the methodology to MG and LV distributionnetworks
A simple kinematics to model the behavior of pressurized elbows under cyclic in-plane bending
No full textInternational audienceThis paper presents a simple and efficient way to calculate the ratcheting strains at the critical locations of a pressurized elbow subjected to cycles of in-plane opening/closing. To do so, a kinematics initially proposed by Boussaa and al. [Finite pure bending of curved pipes. 1996. Comput. Struct. 60, 1003-1012] is presented and a way to use it in ANSYS finite element software is described. The kinematics only describes the elbow behavior when it is subjected to pure in-plane bending. The considered loading must be an history of imposed moment or elbow angle variation. Results using this kinematics are compared with experimental and numerical results of two papers from the literature. Values of ratcheting strains at critical locations of the elbow obtained with the proposed kinematics are very comparable with the ones of the literature. Moreover, computation time is divided by around 200 when using this kinematics over a shell finite element model
Separation of source, attenuation and site parameters of 2 moderate earthquakes in France: an elastic radiative transfer approach
No full textInternational audienceAn accurate magnitude estimation is necessary to properly evaluate seismic hazard, especially in low to moderate seismicity areas such as Metropolitan France. However, magnitudes of small earthquakes are subject to large uncertainties caused by major high-frequency propagation effects which are generally not properly considered. To address this issue, we developed a method to separate source, attenuation and site parameters from the elastic radiative transfer modelling of the full energy envelopes of seismograms. The key feature of our approach is the treatment of attenuation—both scattering and absorption—in a simple but realistic velocity model of the Earth’s lithosphere, including a velocity discontinuity at the Moho. To reach this goal, we developed a 2-step inversion procedure, allowing first to extract attenuation parameters for each source-station path from the whole observed energy envelope using the Levenberg–Marquardt and grid-search algorithms, then to determine site amplification and the source displacement spectrum from which the moment magnitude Mw is extracted. In the first step, we use the forward modelling procedure of Heller et al. in order to simulate energy envelopes by taking into account the full treatment of wave polarization, the focal mechanism of the source and the scattering anisotropy. The inversion procedure is then applied to the 2019 ML 5.2 Le Teil and 2014 ML 4.5 Lourdes earthquakes which both occurred in southern France. Data from 6 stations are selected for each event. The inversion results confirm a significant variability in the attenuation parameters (scattering and absorption) at regional scale and a strong frequency dependence. Scattering appears to be stronger towards the French Alps and Western Pyrenees. Absorption is stronger as frequency increases. Although not very resolvable, the mechanism of scattering appears to be forward or very forward. By inverting the source spectrum, we determine moment magnitudes Mw of 5.02 ± 0.17 for the Le Teil earthquake and 4.17 ± 0.15 for the Lourdes earthquake
Les espaces bleus de Nantes Métropole : quand les loisirs nautiques retrouvent la Loire.
No full textInternational audienceBeaudelaire disait « Homme libre toujours tu chériras la mer », Renaud chante quant à lui « C’est pas l’homme qui prend la mer, c’est la mer qui prend l’homme ». Et comment, dans la ville natale de Jules Verne qui , rappelons le, a aussi bien écrit l’Ile à Hélice que 20000 lieues sous les mers, ignorer tout l’imaginaire lié à la mer. Le dossier de presse de l’exposition Objectif mer, : l’océan filmé (Musée National de la Marine, Paris, décembre 2023-mai 2024) indique d’ailleurs que « Aujourd’hui, peut-être avec plus de puissance qu’auparavant - effets spéciaux numériques oblige -, la mer est toujours au cinéma ….. Elle symbolise aussi la liberté, le départ vers l’inconnu et les aventures, de même que la fragilité de la Nature et du genre humain, tout en apparaissant impitoyable dans sa masse aveugle et sauvage. ». Ces propos font écho à ceux de Kalaora (Kalaora et Lacroix, 2022) qui dit que « cet espace ouvre vers une part d’aventure et d’incertain parce qu’il incite à larguer les amarres, et à accepter le flottement de la consciences et l’imprévisibilité de la destination finale ». Akoun (1999), cité par Brulé-Josso (2012), indique que « Depuis plus de cent cinquante ans, en mer, l’enthousiasme propre au « mythe » de la « modernité » est exprimé avec force et constance par les amateurs de voile se sentant « libres » de parcourir « les derniers espaces de liberté ». D’après Guigueno ( 2007), « la Coupe de l’America fait partie des spectacles proposés dans un port qui est aussi l’archétype de la métropole moderne ». Mais par ailleurs « La voile sportive n’est pas une pratique populaire. ». Mais toute la voile n’est pas « sportive », Brulé-Josso (2012) rappelle que « Aujourd’hui, il est très communément dit et écrit que la « plaisance moderne » est née à cette période et que le Centre nautique des Glénans est l’institution qui a contribué à cet avènement. Pour ses fondateurs, l’héritage culturel revendiqué est celui des pêcheurs. ».Ceci nous amène à nous intéresser aux activités nautiques autres que la « voile sportive ». Dans cette communication, nous présenterons comment des associations se sont structurée en un Collectif des Association Nautiques de l’agglomération nantaise pour permettre que la navigation loisir, quasi absente sur la Loire il y a 30 ans, prenne sa place, au même titre que les autres modes de transports loisir sur la Loire et son affluent l’Erdre, en permettant aux habitants de découvrir leur ville à partir de l’eau, en mode déplacement doux. Nous mettrons en particulier l’accent sur la pratique du voile-aviron dont les supports sont parfois inspirés de bateaux utilisés pour la pêche comme les yoles de Ness inspirés de bateaux des îles Shetland