8 research outputs found
Design of a Fuel Cell Based Backup System for Telecoms Applications
No full textThe aim of this project is to develop a modular 5.5 kW backup system for telecoms stations based on a Proton Exchange Membrane Fuel Cell. Here, we will focus on the sizing procedure both of the fuel cell and of the DC/DC converter, whose topology is determined by the choice of the fuel cell stack. In our case this is an interleaved boost converter always working in the discontinous conduction mode. We will present a Simulink dynamic
model we developed that integrates the fuel cell and the boost converter models, and their controller. The simulations show the system is capable of supplying the maximum power, and to regulate the output voltage with a good dynamic response in the whole 42–60 V range
Systèmes Hybrides de Génération de Moyenne Puissance: Applications Stationnaires aux Energies Renouvelables
No full textLes systèmes de génération alimentés par sources renouvelables connaissent dernièrement une diffusion
croissante,soit dans les pays développés soit dans les pays en voie de développement.La nécessité d’obtenir une
meilleure fiabilité,les développements technologiques en filières comme celle des super-condensateurs ou celle de
l’hydrogène ont conduit à des solutions plus complexes : des systèmes associant différentes sources et différents
éléments de stockage ayant pour nom « SYSTEMES HYBRIDES ».Dans cet article seront étudiés les divers composants
de ces systèmes, sera proposé un schéma général et, ensuite, seront présentés des exemples de systèmes hybrides
trouvés dans la littérature
Gold nanoparticles as drug carriers: A contribution to the quest for basic principles for monolayer design
No full textTwo structurally different water-soluble homoligand gold nanoparticles systems; one featuring a rigid fluorous monolayer in the proximity of the gold core and the other featuring a flexible fluorinated region in a distal position were studied as putative hosting systems by determining their binding constants for a series of fluorinated and non-fluorinated radical probes by means of ESR spectroscopy. Comparison of the binding constants obtained with hydrogenated homoligand nanoparticles of similar structure used as reference evidenced that the binding of both hydrogenated and fluorinated guests is favoured in the presence of fluorinated nanoparticles. In addition a flexible fluorinated monolayer acts as a better hosting system than the more rigid counterpart. In the latter case decreasing the size of the nanoparticles causes a small decrease of the binding affinities for both hydrogenated and fluorinated guests. The same nanoparticle systems were analysed for their ability to retard the phase transfer of a fluorescent dye from an aqueous solution to a toluene layer. All of the nanoparticles studied produced a significant decrease of the phase transfer rate of the dye because of the efficient interaction with the monolayer. These data support the introduction of fluorinated moieties in the monolayer of gold nanoparticles as a novel design tool for the development of drug delivery systems
Single Metal Atom Catalysts and ORR: H-Bonding, Solvation, and the Elusive Hydroperoxyl Intermediate
No full textThe widely investigated oxygen reduction reaction (ORR) is well-known to proceed via two competing routes, involving two or four electrons, and yielding different reaction products, respectively. Both pathways are believed to share a common, elusive intermediate, namely, the hydroperoxyl radical. By exploiting a cobalt single-atom biomimetic model catalyst, based on a self-assembled monolayer of Co-porphyrins grown on an almost free-standing graphene sheet, we identify, in situ at room temperature in O2+H2O atmosphere, a hydroperoxyl-water cluster that is stabilized at the Co single-metal atom catalytic site. We show that the interplay between charge transfer, dipole and H-bonding, and water solvation behavior actually determines the hydroperoxyl-water complex stability, the Co-OOH bonding geometry, and, prospectively, opens to the engineered control of the selectivity of ORR pathways
Estimation of Membrane Hydration Status for Standby Proton Exchange Membrane Fuel Cell Systems by Impedance Measurement: First Results on Cell Characterization
No full textFuel cells have started replacing traditional lead battery banks in backup systems. Although these systems are characterized by long periods of standby, they must be able to start at any instant in the shortest time. In the case of low temperature proton exchange membrane fuel cell systems, a precise estimation of the fuel cells’s membrane hydration status during standby is important for a fast and safe startup. In this article, the measurement of the complex impedance of the fuel cell is suggested as a method to estimate the membrane hydration status. A Nafion-based membrane electrode assembly has been fed with air whose temperature and relative humidity were controlled, and its complex impedance has been measured at different frequencies and for different values of the relative humidity. After characterizing the cell, a first approach in finding the relationship between relative humidity and complex impedance using exponential regression functions has been suggested. The results showed that measuring the impedance of a fuel cell can be a viable way for estimating the hydration status of its membrane before the system is started up
Exemples d'applications pédagogiques autour du kart électrique e-kart
No full textLes auteurs présentent ici deux exemples
d'applications pédagogiques autour du e-kart (le kart électrique)
du Département Génie Electrique et Informatique Industrielle de
l'Institut Universitaire de Technologie de
Tours. Initié depuis 2003, ce projet prend de l'ampleur avec la
réalisation pour en 2007 d'un kart de compétition avec
motorisation asynchrone basse tension. Le premier projet présenté
ici concerne l'acquisition d'informations physiques
sur le kart, de la transmission au sol de ces informations et de l'affichage
par un ordinateur fixe. Le second développement
traite de la réalisation de la commande vectorielle du moteur asynchrone
alimenté par des batteries en 48V
An albumin-derived peptide scaffold capable of binding and catalysis
No full textWe have identified a 101-amino-acid polypeptide derived from the sequence surrounding the IIA binding site of human albumin. The polypeptide contains residues that make contact with ligands as warfarin in the parent protein, and eight cysteine residues to form disulfide bridges, which stabilize the polypeptide structure. Seventy-four amino acids are located in six [alpha]-helical regions, with the remaining amino acids forming six connecting coil/loop regions. Codon usage optimization was used to express a GST fusion protein in E. coli in yields as high as 4 mg/l. This fusion protein retains its structural integrity and aldolase activity, the ability to direct the stereochemical outcome of a diketone reduction, and its binding capacity to warfarin and efavirenz. Notably, this newly cloned polypeptide represents a valuable starting point for the construction of libraries of binders and catalysts with improved proficiency
