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Nicoara S.,West University of Timioara
International Journal of Geometric Methods in Modern Physics | Year: 2011

In this paper we give a method to stabilize asymptotically the Lyapunov stable equilibrium states of a system describing the planar motions of an autonomous underwater vehicle. © 2011 World Scientific Publishing Company. Source

Iano R.,Polytechnic University of Mozambique | Lazu R.,Polytechnic University of Mozambique | Barvinschi P.,West University of Timioara
Advanced Powder Technology | Year: 2011

MgAl2O4 was successfully used as crystalline host network for the synthesis of cobalt-based blue ceramic pigments. Different compositions of Mg1-xCoxAl2O 4 (x = 0.1-0.3) powders have been prepared by the combustion reaction of corresponding metal nitrates with mixtures of urea and β-alanine. The resultant powders were characterized by means of XRD, TG-DTA, EDAX, SEM, BET surface area, diffuse reflectance spectrometry and CIELab color measurement. For x = 0.2, thermal analysis investigations evidenced that combustion reaction occurs at 276 °C. XRD analysis certified the formation of the designed solid solution, no additional thermal treatment being required. EDAX elemental analysis confirmed the purity of the as-prepared compound. The resulted powders had large surface areas, which varied from 8.7 to 62.6 m2/g. The crystallite size of Mg1-xCoxAl 2O4 powders was less than 15 nm. Experimental results evidenced that as the proportion of Co2+ increased, the crystallite size decreased and the specific surface area increased. The diffuse reflectance spectra of the Mg1-xCoxAl2O 4 pigments confirmed the presence of tetrahedrally coordinated Co2+. CIELab chromatic coordinates indicated that the bluest color was obtained for x = 0.2. © 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. Source

Mihe D.,West University of Timioara
Fuzzy Sets and Systems | Year: 2010

A stability result for the additive Cauchy functional equation in non-Archimedean fuzzy normed spaces over a field with valuation is given by using the concept of countable extension of a t-norm. © 2010 Elsevier B.V. All rights reserved. Source

Tudoran R.M.,West University of Timioara | Grban A.,Polytechnic University of Mozambique
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper we will describe some relevant dynamical properties of the Rikitake dynamo system from the Poisson geometry point of view. © 2009 Elsevier Ltd. All rights reserved. Source

Nicolaevici N.,West University of Timioara
International Journal of Modern Physics A | Year: 2011

We comment on a previous calculation1 for the scattering amplitude for the Dirac field in an external Coulomb potential in the expanding de Sitter space. The result implies that for initial and final fermion states with identical momenta |pi|=|pf| the helicity of the particle is conserved. We make a classical analysis of the scattering problem in the small scattering angle approximation using the BargmannMichelTelegdi equation and show that helicity conservation also manifests in the classical case. We also show that in Minkowski space there is a complete agreement between the classical and quantum polarization angle of the scattered particle. © 2011 World Scientific Publishing Company. Source

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