Experimental Studies of the Electrical Nonlinear Bimodal Transmission Line

After a few years of calm, the investigations on the dynamic, especially nonlinear, systems returned to the front of the research in non-linear physics. We propose, in this chapter, a study of an electrical nonlinear transmission line, realized in a previous work, to use the latter to highlight certain properties (modulation instability—MI, Fermi-Pasta-Ulam (FPU) recurrence, fragmentation of solitons in wave trains, multiplication(increase) and division of frequencies, etc.), which are observed in several domains in applied physics: hydraulic, artificial neuronal, network physical appearance (physics) of the plasma, and the circulation

AMOS-SDDS: A Scalable Distributed Data Manager for Windows Multicomputers To be presented at

Known parallel DBMS offer at present only static partitioning schemes. Adding a storage node is a cumbersome operation that typically requires the manual data redistribution. We present an architecture termed AMOS-SDDS for a share-nothing multicomputer. We have coupled a high-performance main-memory DBMS AMOS-II and a manager of Scalable Distributed Data Structures (SDDS) into a scalable distributed system. SDDS provides the scalable data partitioning in distributed RAM, supporting parallel scans with function shipping. AMOS-SDDS couples both systems using the AMOS-II foreign function interface. Its scalability abolishes the cumbersome storage limits of a single site RAM DBMS technology. Its distributed RAM query processing and scalable data partitioning is an improvement over the current parallel DBMSs technology. We validate AMOS-SDDS architecture by experiments with distributed nested loop join queries over a file scaling up to 300.000 tuples. It includes performance study of speed-up and scale-up characteristics. The results encourage the use of SDDS for highperformance database systems

Étude comparée de la végétation de 1964 et 2011 en milieu pâturé: Cas du CRZ de Dahra

Objectif : L’étude comparative de la végétation du CRZ de Dahra en 1964 et 2011, a pour but de voir l’évolution de la phytomasse herbacée et de certains paramètres structuraux du couvert herbacé et ligneux.Méthodologie et résultats : Avec l’aide du SIG, 55 relevés de végétation ont pu être effectués en 2011 sur les mêmes points que ceux réalisés par Raynal (1964). La richesse, la fréquence et la contribution spécifique de laflore herbacée et ligneuse sont évaluées pour ces deux années de même que l’indice de Shannon, la régularité, l’indice de Jaccard et la phytomasse herbacée. Cette dernière est soumise au test de Tukey au seuil de 5%. Les résultats indiquent une baisse de la phytomasse herbacée  (significative au seuil de 5%) et de la diversité floristique. Cette dernière est marquée par une diminution de la richesse spécifique de la flore herbacée comme ligneuse. Au niveau du couvert herbacé, il est noté une augmentation de la contribution spécifique (CSi) des graminées (Poacées) tandis que celle des légumineuses (Fabacées) et des autres herbacées (phorbes) a connu une régression. Le couvert ligneux est caractérisé par une augmentation des espèces de la famille des Mimosacées et une diminution de celles des Combrétacées. Toutefois, les Mimosacées, Balanitacées et Combrétacées présentent les fréquences relatives et les contributions les plus importantes pour ces deux années.Conclusion et application des résultats : cette étude a permis de constater une modification de la végétation du CRZ de Dahra marquée sur le plan structural par une baisse de sa richesse et de sa diversité floristique ; demême que sa phytomasse herbacée. Ces résultats peuvent, contribuer à la compréhension de l’évolution de la végétation des écosystèmes sahéliens pastoraux et, être valorisés en aménagement pastoral et  agrosylvopastoral en vue d’une meilleure préservation et gestion des ressources végétales.Mots clés : richesse, diversité, phytomasse, végétation Comparative study of the vegetation in a grazed area between 1964 and 2011. The case of the CRZ DahraObjective: A comparative study of the vegetation of the CRZ-Dahra during years 1964 and 2011, aims to appreciate the evolution of herbaceous phytomass, as well as some structural parameters of herbaceous andwoody cover.Methodology and results: Using Geographic Information System (GIS), 55 vegetation surveys were carried out in 2011 on the same points used by Raynal (1964). The species richness, the frequency and the specific contribution of herbaceous and woody plants were assessed for each year, as well as the Shannon index, the regularity, the Jaccard index and the herbaceous biomass production. The latter characteristic was subjected toan analysis of variance followed by a separation of means using the Turkey’s multiple comparison procedure (with a level significance fixed at the 5% level). The results indicate a decrease in herbaceous phytomassproduction (P < 0, 05) and of plant diversity. The decline in plant diversity is reflected by a decrease of species richness of both herbaceous and woody plants. In the herbaceous layer, it is noted an increase of the specific contribution (CSi) of grasses (Poaceae) while that of legumes (Fabaceae) and other herbaceous plants (Phorbs) experienced a decline. The tree cover is characterized by an increase in species of the family ofMimosaceae and a decrease of those belonging to the Combretaceae. However, Mimosaceae, Balanitacea and Combretaceae presented the most significant relative frequencies and contributions for the two years of study.Conclusion and application of the results: This study revealed a vegetation change at the CRZ Dahra. This shift is structurally marked by a decline of its floristic richness and diversity, as well as of its herbaceous phytomassproduction. These results may contribute to a better understanding of the evolution of the vegetation in Sahelian pastoral ecosystem. They may also be valorized for the planning of agrosylvopastoral areas in order to improve the preservation and the management of plant resources.Keywords: richness, diversity, phytomass, vegetatio

Morphology, Thermal Behavior and Dynamic Rheological Properties of Wood Polypropylene Composites

International audienceWood polymer composites (WPCs) were made with pine and polypropylene matrix (PP). The composites were produced by melt blending in a Brabender at 180°C. Characterization of the samples, with the aid of scanning electron microscopy supplemented by microscope photography, showed an improved dispersion of wood in the polymeric material in presence of polypropylene grafted with maleic anhydride (MAPP) or nanoclay. The use of the MAPP instead of clay seems to have enhanced the level of crystallinity in the composites for the same levels of wood loading and also accelerates the crystallization. Melt rheological measurements of neat PP and PP-wood composites were carried out at 180°C with an ARES Rheometer scientific mechanical spectrometer in oscillatory frequency. All the composites materials exhibit viscoelastic values greater than those for neat PP. The samples containing MAPP as comptabilizer show the higher Newtonian viscosity, however, the addition of a small concentration of nanoparticles like nanoclays does not improve the resulting melt viscoelastic behavior of the composite

Morphological, Rheological and Mechanical Properties of Pla-Typha Based Biocomposites

International audienceDue to the demand from society for the consumption of ecological polymeric materials, one of the polymers that have satisfied this request is the poly (lactic acid) (PLA). This polymer is derived from renewable resources, it is recyclable and biodegradable. It presents a good understanding between the promising properties and the cost. However, a route to increase the mechanical properties and reduce the cost of PLA is the elaboration of PLA based biocomposites by using fillers from natural waste. In this work, The effect of Typha content on the morphological, rheological, thermal and mechanical properties of PLA matrix was studied. Four formulations were produced with different mass concentrations. The results showed an increase in the viscoelastic properties, as a function of the Typha stem powder concentration. The DSC analysis showed an increase in the crystallinity rate of the various composites confirming the nucleating effect provided by the filler. TGA analysis indicated a decrease in the decomposition temperature of the composites. Mechanical tensile tests have shown a significant improvement in the mechanical properties mainly for the samples containing 45% (w/w) of Typha powder

Development and Characterization of PBSA-Based Green Composites in 3D-Printing by Fused Deposition Modelling

Fused deposition modelling is a rapidly growing additive manufacturing technology due to its ability to build functional parts with complex geometries. The mechanical properties of a built part depend on several process parameters. The effect of wood content on the properties of 3D printed parts has been studied. Four types of filaments using poly(butylene succinate-co-adipate) (PBSA) with different reinforcement levels of Typha stem powder 0%, 5%, 10%, and 15% by weight were used for 3D printing. The density of the filaments and parts printed in this study increased with the Typha stem powder content. The thermal stability, mechanical performance, and viscoelastic properties of the different biocomposite filaments and 3D printed objects were analysed. The results show an increase in the crystallisation kinetics and a slight decrease in the thermal stability of the biomaterials. Compared to virgin PBSA FDM filaments, the PBSA biocomposite filament filled with Typha stem powder showed an increase in the tensile strength of the parts and specimens from 2.5 MPa to 8 MPa and in the modulus of elasticity from 160 MPa to 375 MPa, respectively, with additions of 5%, 10%, and 15% by mass. The addition of Typha stem fibres generated an increase in the elastic behaviour and relaxation time of the biomaterial structure, visualised by increases in the values of the viscosity components. The surface morphology reveals a decrease in the porosity of the printed samples

Study of the Activation Process of a 2 m3 Pilot Biodigester on a Microfarm Site

International audienc

Organic FETs using biodegradable almond gum as gate dielectric: A promising way towards green electronics

Green electronics is an emerging field of research which aims to manufacture devices in an environmentally friendly and sustainable way. Usually, the involved electronic materials are naturally occurring and non-toxic. Also, they can be processed using simple, low energy deposition processes and fabrication techniques. In this work, we present low voltage organic field-effect transistors (OFETs) using almond gum (AG) as the gate dielectric. AG is a natural, biodegradable insulator material that can be directly collected from almond trees and used without any further purification. Moreover, AG possesses interesting properties such as water solubility, ease of processing, good insulation, low leakage current, good film quality, and high capacitance making it a promising dielectric for OFET devices. Bottom gate/bottom contact p-channel OFETs have been processed on glass substrates with poly (3,6-di (2-thien-5-yl)-2,5-di (2-octyldodecyl)-pyrrolo [3,4-c] pyrrole-1,4-dione)thieno [3,2-b] thiophene) (DPPTTT) polymethyl methacrylate (PMMA) blend as the active layer and gold as the source and drain electrodes. The transistors operate at low voltage (VGS ≤ 3 V), with threshold voltages Vth as low as −0.8 V, saturated field effect mobilities μsat above 0.75 cm2 V−1 s−1, subthreshold swings SS around 270 mV/dec and ON/OFF current ratio equal to 103. The combined favourable properties of both almond gum and low voltage operated OFET devices have a high potential to pave a way towards using naturally occurring, biodegradable electronic materials in future disposable sensors or throwaway, low-end electronics

Mapping the breeding sites of Anopheles gambiae s. l. in areas of residual malaria transmission in central western Senegal.

Despite the deployment of several effective control interventions in central-western Senegal, residual malaria transmission is still occurring in some hotspots. To better tailor targeted control actions, it is critical to unravel the underlying environmental and geographical factors that cause the persistence infection in hotspot villages. "Hotspots villages" were defined in our study as those reporting more than six indigenous malaria cases during the previous year. A total of ten villages, including seven hotspots and three non-hotspots, were surveyed. All potential mosquito breeding sites identified in and around the ten study villages were regularly monitored between 2013 and 2017. Monitoring comprised the detection of anopheline larvae and the collection of epidemiological, hydrogeological, topographical, and biogeographical data. The number of larval breeding sites described and monitored during the study period ranged from 50 to 62. Breeding sites were more numerous in hotspot sites in each year of monitoring, with 90.3% (56/62) in 2013, 90.9% (50/55) in 2014, 90.3% (56/62) in 2015 and 86% (43/50) in 2017 (Fisher exact test; p = 1). In the non-hotspot areas, the data for the same years were, respectively, 9.7% (6/62), 9.1% (5/55), 9.7% (6/62) and 14% (7/50) (p = 1). The Hotspot villages were characterized mostly by saline or moderately saline hydro-morphic and halomorphic soils allowing water retention and a potential larval breeding sites. By contrast, non-hotspot villages were characterized mainly by a high proportion of extremely permeable sandy-textured soils, which due to their porosity had low water retention. The annual number of confirmed malaria cases was correlated with the frequency and extent of breeding sites. Malaria cases were significantly more frequent in the hamlets located near breeding sites of An. gambiae s.l., gradually decreasing with increasing remoteness. This study shows that the characteristics of larval breeding sites, as measured by their longevity, stability, proximity to human habitation, and their positivity in Anopheles larvae are likely determining factors in the persistence of malaria hotspots in central-western Senegal. The results of this study shed more light on the environmental factors underlying the residual transmission and should make it possible to better target vector control interventions for malaria elimination in west-central Senegal