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Brasov, Romania

Transilvania University of Brașov is a public institution of higher education in Brașov, Romania. It has sixteen faculties, a total of 25,000 students and 800 teachers. The University offers 103 days license areas, 12 areas for Distance Education, and 5 areas for higher reduced frequency, as well as 17 graduate programs and 14 doctoral programs. Wikipedia.

Postelnicu A.,Transilvania University of Brasov
International Journal of Heat and Mass Transfer

The present paper is focused on the analysis of heat and mass transfer in boundary-layer free convection over an inclined flat plate embedded in a fluid saturated porous medium in the presence of thermophoresis. The governing equations are transformed into a set of coupled differential equations, which are solved numerically using the local non-similarity method. A comparison between the results given by this method and the local similarity method is also presented. For various values of the problem parameters, graphs of thermophoretic wall velocity, Nusselt number and concentration profiles in the boundary layer are presented. Variation of the dimensional thermophoretic wall velocity along the plate for different angles of inclination are presented in a physical relevant case. © 2011 Elsevier Ltd. All rights reserved. Source

Alexandru C.,Transilvania University of Brasov
The Scientific World Journal

This paper approaches a dual-axis equatorial tracking system that is used to increase the photovoltaic efficiency by maximizing the degree of use of the solar radiation. The innovative aspect in the solar tracker design consists in considering the tracking mechanism as a perturbation for the DC motors. The goal is to control the DC motors, which are perturbed with the motor torques whose computation is based on the dynamic model of the mechanical structure on which external forces act. The daily and elevation angles of the PV module represent the input parameters in the mechanical device, while the outputs transmitted to the controller are the motor torques. The controller tuning is approached by a parametric optimization process, using design of experiments and response surface methodology techniques, in a multiple regression. The simulation and experimental results demonstrate the operational performance of the tracking system. © 2013 Cǎtǎlin Alexandru. Source

Lupsa-Tataru L.,Transilvania University of Brasov
IEEE Transactions on Energy Conversion

Tending toward the adaptive modeling of main flux saturation in induction machine, this brief discloses the induction machine magnetizing inductance as an expression in terms of only d-q axis winding flux linkages. It will be shown that such an expression considerably facilitates the inclusion of main flux saturation effects in internal structure of the well-established winding flux linkage state-space model. The derivation procedure will be carried outwithout altering the structural equations of the generalized d-q axis mathematical model of the induction machine. © 2010 IEEE. Source

Postelnicu A.,Transilvania University of Brasov
International Journal of Heat and Mass Transfer

In this paper there is studied the effect of a horizontal pressure gradient on the onset of Darcy-Bénard convection in a fluid-saturated porous layer heated from below, when the fluid and solid phases are not in local equilibrium. In the context of a linearized stability analysis, the problem is transformed into an eigenvalue equation. The problem, when cast in dimensionless form, contains three parameters (the pressure gradient, the porosity-scaled conductivity ratio and the scaled inter-phase heat transfer coefficient). This problem is solved numerically by using two methods: Galerkin approach and the numerical solver dsolve from Maple and comparisons between these methods are performed. Critical values of Rayleigh number, wave number and frequency are obtained for various values of the problem parameters. © 2009 Elsevier Ltd. All rights reserved. Source

Popescu O.,Transilvania University of Brasov
Computers and Mathematics with Applications

The aim of this paper is to generalize two classical fixed point theorems given by Bogin [J. Bogin, A generalization of a fixed point theorem of Goebel, Kirk and Shimi, Canad. Math. Bull. 19 (1976) 712] and Gregu [M. Gregu, A fixed point theorem in Banach spaces, Boll. Un. Math. Ital. A (5) 17 (1980) 193198]. We also complement and extend some very recent results proved by Suzuki [T. Suzuki, A generalized Banach contraction principle that characterizes metric completeness, Proc. Amer. Math. Soc. 136 (2008) 18611869]. © 2011 Elsevier Ltd. All rights reserved. Source

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