Cherif A.,Ferhat Abbas University Setif |
Cherif A.,INSA Lyon |
Meddad M.,Ferhat Abbas University Setif |
Meddad M.,INSA Lyon |
And 6 more authors.
Optical and Quantum Electronics | Year: 2014
The piezoelectric transformers reach densities of power more significant than their magnetic counterparts. However, one of the principal factors limiting the density of power is the acceptable maximum deformation by material constituting the transformer. The heating of the piezoelectric transformers is mainly of mechanical origin. This heating generates a degradation of the characteristics which in its turn generates an additional heating being able to lead to a phenomenon of thermal avalanche. In this work, two nonlinear methods [synchronized switch harvesting on inductor (SSHI) and SSHI-max] have been explored to improve the performance of the Rosen transformer basing on the tension generated by the secondary so as to increase the capacity of mechanic-electric conversion. The simulation results show that SSHI and SSHI-max techniques significantly increase the capacity of mechanic-electric conversion of inserts stuck on a vibrating structure and consequently, the power recovered in electric form. The comparative results of voltage gain, efficiency and the transmitted power of the transformer, before and after SSHI-max and SSHI control are given. These ones indicated that the two nonlinear techniques are promising as applications to improve the performances of the piezo-transformers. © 2013 Springer Science+Business Media New York.
Poupin C.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources |
Maache R.,University of El Jadida |
Pirault-Roy L.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources |
Brahmi R.,University of El Jadida |
Williams C.T.,University of South Carolina
Applied Catalysis A: General | Year: 2014
Catalytic performances of Pt based catalysts supported on (Al 2O3)x (MgO)1-x oxides prepared by sol-gel techniques, with x varying from 0.25 to 0.75 were investigated for acetonitrile hydrogenation to check the influence of acid-base properties of the support. The results evidenced a correlation between these properties and the yield towards the primary amines, the most desired ones. Thus, the more basic the support is, the higher the production of primary amines will be. However, an optimal values for both activity and selectivity is obtained for 1% Pt/(Al 2O3)0.25(MgO)0.75. Then, hydrogenation of acetonitrile was studied by in situ FTIR spectroscopy and the formation of an intermediate species that would lead to secondary and tertiary amines formation was observed on the catalysts. In accordance to previous reaction pathways, ketenimine (CH2CNH) was proposed as this species. © 2014 Elsevier B.V.
Drif A.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources |
Drif A.,University of El Jadida |
Drif A.,University of Oulu |
Bion N.,CNRS Poitiers Institute of Chemistry: Materials and Natural Resources |
And 7 more authors.
Applied Catalysis A: General | Year: 2015
Various MxOy-Al2O3 oxides (M = Zr, Mg, Ni, Ce, La), prepared by a sol-gel method, were used as supports for rhodium catalysts in methane and ethanol dry reforming. After calcination, the Rh/MxOy-Al2O3 catalysts present BET surface areas between 85 and 208 m2 g-1. For the CH4 dry reforming, the highest yields in hydrogen are obtained in the following ranking: Rh/NiO-Al2O3 > Rh/Al2O3 > Rh/MgO-Al2O3 Rh/CeO2-Al2O3 > Rh/ZrO2-Al2O3 > Rh/La2O3-Al2O3, not very different from the one for ethanol dry reforming at 800°C which is: Rh/NiO-Al2O3 Rh/Al2O3 Rh/MgO-Al2O3 Rh/CeO2-Al2O3 > Rh/ZrO2-Al2O3 Rh/La2O3-Al2O3, although the reaction temperature is different. For the two reactions, the best catalyst is Rh/NiO-Al2O3 even if it deactivates during the reaction due to carbon deposition. This high activity may be explained by both the presence of the NiAl2O4 spinel phase, avoiding the deactivation of rhodium by migration in alumina, and the high dispersion of Rh favored by the presence of nickel particles at the support surface. Moreover, Ni particles on the support surface also contribute to the activity as demonstrated by the high hydrogen yield obtained in the presence of NiO-Al2O3, which is similar to the one obtained with Rh/Al2O3. © 2015 Elsevier B.V. All rights reserved.