Fanny Arnaud

Ultra-wide body-bias range LDPC decoder in 28nm UTBB FDSOI technology

This paper presents an IEEE 802.11n Low-Density Parity-Check (LDPC) decoder implemented in 28nm Ultra-Thin Body and BOX Fully Depleted SOI (UTBB FDSOI), and demonstrates the performance gains of this circuit vs. 28nm LP high-κ metal-gate CMOS bulk technology. It also introduces extended body bias (BB) design techniques to take advantage of specific features of the UTBB technology to overcome the +/-300mV BB range limitation of conventional bulk technologies [1].

Monitoring gravel augmentation in a large regulated river and implications for process‐based restoration

The artificial gravel augmentation of river channels is increasingly being used to mitigate the adverse effects of river regulation and sediment starvation. A systematic framework for designing and assessing such gravel augmentations is still lacking, notably on large rivers. Monitoring is required to quantify the movement of augmented gravel, measure bedform changes, assess potential habitat enhancement, and reduce the uncertainty in sediment management. Here we present the results of an experiment conducted in the Rhine River (French and German border). In 2010, 23 000 m3 of sediments (approximately the mean annual bedload transport capacity) were supplied in a by-passed reach downstream of the Kembs dam to test the feasibility of enhancing sediment transport and bedform changes. A 620-m-long and 12-m-wide gravel deposit was created 8 km downstream from the dam. Monitoring included topo-bathymetric surveys, radio-frequency particle tracking using passive integrated transponder (PIT) tags, bed grain size measurement, and airborne imagery. Six surveys performed since 2009 have been described (before and after gravel augmentation, and after Q2 and Q15 floods). The key findings are that (i) the augmented gravel was partially dispersed by the first flood event of December 2010 (Q1); (ii) PIT tags were found up to 3200 m downstream of the gravel augmentation site after four years, but the effects of gravel augmentation could not be clearly distinguished from the effects of floods and internal remobilization on more than 3500 m downstream; (iii) linear and log-linear relationships linking bedload transport, particle mobility, and grain size were established; and (iv) combined bathymetry and PIT tag surveys were useful for evaluating potential environmental risks and the first morpho-ecological responses. This confirmed the complementary nature of such techniques in the monitoring of gravel augmentation in large rivers. Copyright

Socio-environmental implications of process-based restoration strategies in large rivers: should we remove novel ecosystems along the Rhône (France)?

River restoration efforts require interdisciplinary approaches involving fluvial geomorphology, hydraulic engineering, ecology, sedimentology, chemistry, social geography, and sociology. We investigated the functioning of artificial structures called “Casiers Girardon” (groyne fields) in the Rhône River. We assessed potential benefits and risks linked to removing the Rhône groyne fields in a restoration context, with particular focus on the potential for increased bank erosion. Hydraulic, morphological, chemical, ecological, and social issues resulting from dismantlement were studied for terrestrialized and aquatic Casiers Girardon. Only 10% of Casiers Girardon have maintained their aquatic features, whereas most of the Casiers are terrestrialized. Our results help to confirm the effectiveness of restoration actions; however, they also indicate uncertainties and additional knowledge needs, especially in regard to potential incompatibilities between Casier restoration and conservation. Then, an interdisciplinary conceptual model was developed to identify interventions to be considered in Casiers Girardon, according to their terrestrialization rate and physiochemical characteristics (connectivity, amount of gravel vs. fine sediment, contamination level). This model synthetizes scientific results and expert judgment and provides management recommendations based on ecological and sociological expectations about the restoration of Casiers Girardon. The model highlights high heterogeneity in functioning and ecological potential between terrestrialized and aquatic Casiers. Dismantling of terrestrialized Casiers has strong potential to provide multiple benefits, whereas aquatic Casiers could be maintained as valuable backwaters. The managing guidelines for the Casiers Girardon of the Rhône River should be adapted according to local conditions, as well as expected benefits and needs, and conducted in co-ordination with all actors involved in and affected by the restoration.

Enjeux de recharge sédimentaire : cas du Rhin

L’injection artificielle de sediments est une technique mise en œuvre sur des cours d’eau enregistrant un transport solide deficitaire, a la suite notamment d’extractions severes de granulats ou de l’interruption du transit sedimentaire par des barrages. L’apport de charge grossiere a pour objectif d’ameliorer la dynamique morphologique a l’origine de fonctionnalites ecologiques disparues dans le chenal amenage (alluvions remaniees et oxygenees pour les frayeres, bancs emerges colonisables par la vegetation pionniere, etc.). Depuis une dizaine d’annees, le Rhin court-circuite en aval du barrage de Kembs (frontiere franco-allemande) fait l’objet de recharges experimentales visant a ameliorer la dynamique sedimentaire. Un premier test de recharge de 23000 m3 de sediments a ete realise en 2010 dans le cadre du programme INTERREG «Redynamisation du Vieux Rhin». Les processus de transfert sedimentaire ont ete mesures pendant sept ans, a la suite d’evenements hydrologiques allant de la crue annuelle a une crue de periode de retour de 15 ans. Le suivi morphologique a repose sur trois thematiques : - La mobilite sedimentaire, au moyen de tracage par radio-frequence (1500 galets ont ete equipes de transpondeurs passifs et deposes a la surface du depot injecte), - L’evaluation des changements de geometrie, via des releves topo-bathymetriques et de l’imagerie aerienne multi-dates, - Les changements granulometriques, en echantillonnant des bancs et des zones en eau. En 2015 et 2016, deux autres recharges ont ete realisees par EDF en aval immediat du barrage de Kembs. L’analyse inter-sites d’I1, I2 et INTERREG montre que la mobilite sedimentaire est dependante de plusieurs facteurs : la localisation du depot (concavite, convexite, accolement a la berge), la forme (largeur, longueur, altitude de la surface du depot par rapport au fond du lit), la granulometrie, et l’hydrologie. Une etude a egalement ete realisee par EDF pour evaluer la faisabilite d’une recharge du chenal par suppression des enrochements des berges et erosion laterale controlee. L’operation a d’abord ete simulee sur modele reduit afin de choisir une configuration d’epis qui favorise l’erosion laterale. La solution retenue a ete mise en oeuvre sur le terrain en 2013 (site O3). Les changements morphologiques survenus apres la crue Q15 de juin 2013 sont bien en-deca des simulations, expliques en partie par la concentration d’enrochements en pied de berge qui ont limite l’erosion. En revanche, les epis contribuent localement a la diversification des habitats et des peuplements biologiques. Ces retours d’experience permettent de construire des indicateurs d’evaluation de l’efficacite des restaurations et de proposer des scenarios de gestion sedimentaire sur le long terme (couplage de sites de re-elargissement et de sites de recharge mecanique).