Les Algues Indicatrices De L'eutrophisation Et De La Contamination De La Lagune De Korba (Cap Bon Tunisie)

The concentrations of heavy metals (Fe, Zn, Pb and Mn) were determined in two green algae (Enteromorpha intestinalis and Chaetomorpha Linium) collected from April 2012 to February 2013 in nine stations characterized by the abundance of these algae throughout the year. Determination of Pb, Mn and Zn was carried out by graphite furnace atomic absorption spectrometer while Fe by flame atomic absorption spectrometer (using the Thermo Scientific ICE 3300 AA Spectrometer). An evaluation of the degree of eutrophication is made through the physicochemical study of 31 samples in the surface water. The results underline that Korba is an eutrophic lagoon. The heavy metal concentrations in the water samples decreased in the sequence of Fe >Zn > Mn > Pb, while in Chaetomorpha Linium, Enteromorpha intestinalis and sediment exhibited the same pattern across the sites: Fe >Mn> Zn >Pb. The results show that metal accumulation capacity in both macro-algae varies according to the season and depends on the species. By comparison with other studies in the world, the levels found in the algae of Korba lagoon are relatively high except Mn. Chaetomorpha Linium could be used as an excellent indicator for heavy metals accumulation in Korba lagoon

Oxydation du zircaloy-4 dans l'air à haute température

The oxidation of zircaloy-4 in air was studied in the temperature range 350-750 °C. The oxidation kinetics cannot be described by a single rate law. At the beginning of the reaction, the rate decreases regularly. Then, after a few hours, an acceleration is observed and finally a linear law is obeyed. The morphological observations show that the acceleration is related to the formation of cracks in the oxide scale. Moreover, two different zirconia phases (monoclinic and tetragonal) are identified. When the kinetic transition occurs, the tetragonal phase partially disappears. All these observations show that a mechanism, similar to that proposed to describe the oxidation of zircaloy-4 in steam, may be used to describe the reaction. In parallel, the oxidation reaction was studied by using acoustic emission. The frequency, the amplitude and the energy were used to characterize the signal. Typical groups were identified and their appearance was strongly correlated to the different parts of the reaction

European Association for the Development of Renewable Energies, Environment and Power Quality (EA4EPQ) International Conference on Renewable Energies and Power Quality (ICREPQ'12) Santiago de Compostela The Hot Spot phenomena in Shadowed ENR System

Abstract. Model to represent the behaviour of photovoltaic (PV) solar cells in reverse bias is reviewed, concluding with a proposal of new model. This model comes from the study of avalanche mechanisms in PV solar cells, it can be adapted to PV cells witch reverse characteristic is dominated by avalanche mechanisms, and also dominated by shunt resistance. A simulation of shading effects in arrays with parallel series configuration has been done; an analysis has been made of the power dissipation with the influence of the number of shaded cells and the effect of shadowing degree