Paysages de la haute vallée du Doubs

Depuis sa source dans le val de Mouthe jusqu'au confluent avec la Saône, le tracé du Doubs est capricieux. On dirait que la rivière franc-comtoise hésite avant de destiner ses eaux au bassin méditerranéen. Au passage, elle visite le massif du Jura, coule dans les vals, traverse des lacs, creuse des gorges profondes et entaille des monts par les cluses ; elle finit par écorner la bordure occidentale des plateaux et ne devient plus sage qu'en vue de la vaste plaine de Bresse. La vallée s'entoure de paysages sans cesse renouvelés. Pourtant, elle ne présente à aucun autre endroit un tel caractère affirmé que dans la "‑zone des cañons‑" , là où la rivière fixe la frontière franco-suisse de Villers-le-Lac à Soubey

Prediction of the dynamic response of a plate treated by particle impact damper

International audienceIn this paper, an experimental characterisation of a particle impact damper (PID) under periodic excitation is investigated. The developed method allows the measurement of damping properties of PID without the supplementary use of a primary structure. The passive damping of PID varies with the excitation frequency and its design parameters. The nonlinear damping of PID is then interpreted as an equivalent viscous damping to be introduced in a finite element model of a structure to predict its dynamic response. The results of numerical simulations are in good agreement with those of experiment and show the relevance of the developed method to predict the dynamic behaviour of a structure treated by PID's

Délimiter le Haut-Doubs : entre représentations mentales et limites physiques

Le Haut-Doubs constitue depuis longtemps une entité à part en Franche- Comté. Voisin de la Suisse et partie prenante du massif jurassien, son nom évoque d'abord une terre d'altitude. Mais bien au-delà du relief, le Haut-Doubs se définit par un certain espace vécu, par une relation particulière entre ce territoire et ses habitants

Impact assessment of a high-speed railway line on species distribution : Application to the European tree frog (Hyla arborea) in Franche-Comté

International audienceThe aim of the present work is to assess the potential long-distance effect of a high-speed railway line on the distribution of the European tree frog (Hyla arborea) in eastern France by combining graph-based analysis and species distribution models. This combination is a way to integrate patch-level connectivity metrics on different scales into a predictive model. The approach used is put in place before the construction of the infrastructure and allows areas potentially affected by isolation to be mapped. Through a diachronic analysis, comparing species distribution before and after the construction of the infrastructure, we identify changes in the probability of species presence and we determine the maximum distance of impact. The results show that the potential impact decreases with distance from the high-speed railway line and the largest disturbances occur within the first 500 m. Between 500 m and 3500 m, the infrastructure generates a moderate decrease in the probability of presence with maximum values close to -40%. Beyond 3500 m the average disturbance is less than -10%. The spatial extent of the impact is greater than the dispersal distance of the tree frog, confirming the assumption of the long-distance effect of the infrastructure. This predictive modelling approach appears to be a useful tool for environmental impact assessment and strategic environmental assessment. The results of the species distribution assessment may provide guidance for field surveys and support for conservation decisions by identifying the areas most affecte

Integrating regional-scale connectivity in habitat restoration: An application for amphibian conservation in eastern France

International audienceHabitat restoration is one way of reducing landscape fragmentation, which is seen as a threat to biodiversity. It consists in renovating disused or degraded habitat patches or in creating new habitat patches in suitable areas. Currently, most restoration measures draw on the local knowledge of experts for selecting the best locations. For amphibian metapopulations like the European tree frog (Hyla arborea), the search for such locations must include regional-scale connectivity in order to maintain their viability. We set up a systematic and cumulative protocol for adding new habitat patches to a pond network. Graph modelling is used to include regional-scale connectivity as a criterion to be maximized. Successive locations are tested systematically and connectivity is compared before and after the virtual addition of each new pond. The location that increases connectivity most is identified. The results show that the priority areas identified by the model are similar to those suggested by local experts from a wildlife conservation association. The two approaches are complementary because they are applied on two different scales. The patch addition method can identify strategic areas for improving global connectivity by taking into account the regional scale. Experts' knowledge can target the precise location within the identified area for creating new habitats based on local factors of the surrounding context. In addition, our method can be also used to prioritize locations already decided on by landscape managers. Consequently, this protocol appears to be a useful tool for guiding habitat restoration in the field

Simulation de scénarios d’urbanisation pour estimer l’impact écologique du développement résidentiel et des évolutions de trafic associées

National audienceLa maîtrise de l’étalement urbain repré¬sente actuellement une préoccupation ma¬jeure en aménagement face au nombre im¬portant de nuisances induites par le phénomène. Sur le plan paysager, la croissance des villes se produit aux dépens des milieux naturels et agricoles, ce qui contribue à la fragmentation et à la réduction des habitats de la faune sauvage. Il est donc souhaitable de trouver un compromis entre les implantations résidentielles et la connectivité des habitats écologiques afin d’assurer la durabilité des populations animales. La recherche de ce compromis suppose une concertation entre les différents acteurs de l’aménagement du territoire et de l’environnement. Dans ce contexte, une question centrale est de savoir quelles formes de villes sont les plus aptes à maintenir la fonctionnalité des réseaux écologiques. L’étude de cette question peut se fonder sur une approche de simulation prospective. Cette approche permet de proposer différentes alternatives d’aménagements possibles en simulant différents scénarios d’évolution urbaine de manière théorique (Mörtberg et al., 2007; Tannier et al., 2012a) ou réaliste (Aguilera et al., 2011). Nous partons du postulat que la création de scénarios réa¬listes plutôt que théoriques est préférable pour comparer précisément les impacts écologiques potentiels de différentes formes de croissance urbaine, notamment par la prise en compte des modifications de trafic susceptibles de résulter du développement résidentiel

Robust design of spacecraft structures under lack of knowledge

International audienceIn robust design, lacks of knowledge are rarely taken into account explicitly, but this is the case in the RRDO-IG. This paper summarises the ongoing developments and perspectives for the use of the RRDO-IG methodology in a spatial industrial context, where non-linearities have to be treated. After shortly describing the RRDO-IG methodology and the actual encountered problems, we will construct an improvement strategy based on a state of the art in metamodelisation and failure probability computation

Identification of Admittance Coefficients from in-situ Measurements in Acoustic Cavities

International audienceIn recent decades, sound intensity and quality is taking an increasingly important place in the design process of products like cars or aircrafts. Different types of absorbing materials have therefore been developed and used in such products to achieve this purpose. Acoustical calculations are quite heavy and industries generally have to use numerical tools to predict the influence of absorbing materials on the sound propagation inside cavities. In these ones, the acoustical properties of absorbing materials are described by the admittance (or impedance) coefficient, which is a simplification of the physical model. However, the limits of applicability of this model are not well known and the conditions in which its parameters are measured can differ significantly from the ones in which the materials are really used. In this paper, a model updating technique process is used to identify the parameters required to describe admittance coefficients from sound pressure measurements inside a closed cavity. Updating techniques have been used for many years to improve numerical models, and consist in minimizing an error between the numerical solutions and a set of experimental results. The technique based on the Constitutive Relation Error (CRE), initially proposed by Ladevèze [1] for structural dynamics problems, is an indirect method in which the cost function, called the CRE, is based on an energy norm. The main advantages of this method are that the updated parameters keep a physical meaning, that it allows taking into account the measurement error and that it allows locally evaluating the modeling and measurement errors [2]. In this paper the CRE-based updating technique is applied to the acoustical problem ([3], [4]) in order to identify the admittance coefficients and the local estimators are developed. The method is applied on real 2D (Kundt's tube) and 3D (concrete box) experimental data

Wideband frequency characterization of a shape memory polymer

International audienceThis study is an experimental evaluation of the mechanical properties of shape memory polymer Veriflex R under different tests conditions. Veriflex R was chosen because of its easy accessibility and its properties similar to epoxy resins which make it very suitable for use in a wide variety of technical applications. Dynamic mechanical analysis (DMA) has been used to determine the evolution of the viscoelastic properties versus temperature and frequency under harmonic loading. The time-temperature superposition principle has been found to be valid for this material. This is illustrated here through the use of the master curves. Furthermore a modal analysis on a Veriflex R rectangular plate has been performed in order to reach higher frequencies than the DMA, and a finite element model was employed to find the viscoelastic properties of the material. A correlation between these two experimental methods allowed to highlight a disparity of results explained by the deterioration of the Veriflex R over time