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Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Nedelcu A.,Polytechnic University of Bucharest | Nedelcu A.,National Institute for Electrical Engineering, romenia | Ilie C.,National Institute for Electrical Engineering, romenia
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

This paper presents a technical solution for bearings that combines axial sustentation and radial coupling, for the transmission of rotary motion, which is using permanents only assembled in a unique system. The ensemble is equipped to measure forces, torques, and displacements, and it may be equipped with different inertial masses. Mathematical modeling and numerical simulation are used in the design phase of the prototype with the aim to determine the forces that occur and the coupling torque, the deformations and stress related to total static loads and the first two eigenmodes for the main mechanical parts, which unveil fine details concerning the stability of the bearing system. © 2015 IEEE.


Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Morega M.,Polytechnic University of Bucharest | Ilie C.,Romanian National Institute for Research and Development in Electrical Engineering
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

This paper presents a bending-mode cantilever actuator (CA) concept for optical devices. Two designs are analyzed in stationary working conditions through numerical simulations, and their deformations under the action of electrodynamic body forces are evaluated. The modal structural analysis and the lumped, electric circuit parameters are also provided. These results may be of interest in the design stage of these CAs. © 2015 IEEE.


Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Stoica V.,Romanian National Institute for Research and Development in Electrical Engineering | Morega M.,Polytechnic University of Bucharest | Dobrin I.,Romanian National Institute for Research and Development in Electrical Engineering
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

This paper presents a new active electronic protection system that keeps a high temperature superconductor (HTS) coil that is in superconductive state from shifting into normal conduction state (quench). The coil is made of YBCO tape high temperature superconductor, with a critical temperature of 92 K. The superconducting coil is confined to a cryostat, which is vacuumed at about 0.001 mbar to minimize the heat transfer influx. The cryogenic agent, in which the coil is immersed, is liquid nitrogen, such that the working temperature of the HTS coil is about 77 K. The quench protection system is composed of an electronic quench protection and signal processing system, a power electronic module, and a stabilized voltage power supply, described in the paper. © 2015 IEEE.


Dumitrescu H.,Institute of Statistical Mathematics and Applied Mathematics | Frunzulica F.,Institute of Statistical Mathematics and Applied Mathematics | Frunzulica F.,Polytechnic University of Bucharest | Cardos V.,Institute of Statistical Mathematics and Applied Mathematics
Journal of Aircraft | Year: 2013

The design process of a wind-turbine blade requires accurate and reliable prediction methods for the full range of the machine's operating conditions. Lift coefficients attained at the inboard sections of a rotating blade are significantly in excess of the maximum value possible in 2-D static test. This behavior is referred to as the stalldelay phenomenon, which varies along the blade with the augmented lift decreasing from blade root to tip. To obtain accurate blade sectional aerodynamic characteristics and hence accurate power prediction, the 2-D airfoil data need to be corrected for the inboard 3-D rotational effects. They concluded that none of the models studied correctly represented the 3-D flow physics and that this was ultimately responsible for their lack of generality. The nonuse of stall control for the large-size wind turbines is probably due to the fact that the stall-delay phenomenon is still not completely understood.


Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Savastru C.,Polytechnic University of Bucharest | Morega M.,Polytechnic University of Bucharest
2013 E-Health and Bioengineering Conference, EHB 2013 | Year: 2013

The aim of this study is three fold: (1) to investigate the pulsatile blood flow in the brachial artery and its ulnar and radial tributaries in the attempt to understand aspects related to blood pressure measurements (BPM); (2) to assess the flow-vessel-muscle structural interactions that may occur normally and under occlusive constraints (the radial artery); (3) to investigate the BPM information for different rheological models of blood. Mathematical modeling and numerical simulations are used to solve these objectives. © 2013 IEEE.


Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Robello G.,University of Valladolid | Morega M.,Polytechnic University of Bucharest
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

This paper presents mathematical modeling and numerical simulation results that are part of a study concerning the dynamics of the stator of piezoelectric (PZ) traveling wave (TW) rotating ultrasonic motor. The stator is a PZ composite ring, and the rotor is a metallic ring. The rotational torque is produced by exciting the stator into a flexural traveling wave, transmitted to the rotor through the stator-rotor friction. A modal analysis provides for the structural eigenfrequencies of the stator. When the AC powering stage providing for two voltages of same amplitude and shifted in quadrature is adapted to a frequency close to the flexural resonance of the stator, the TW reaches higher amplitudes that result in higher rotational velocities because the rotor speed is proportional to the stator TW amplitude. © 2015 IEEE.


Dumitru J.B.,Polytechnic University of Bucharest | Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Morega M.,Polytechnic University of Bucharest
2014 International Conference on Optimization of Electrical and Electronic Equipment, OPTIM 2014 | Year: 2014

This paper presents mathematical modeling and numerical simulation results for a notional miniature power electrical transformer (MPST) with planar, spiral coils, fabricated in micro-electromechanical MEMS technology. The magnetic core of the MPST is partially made of custom-tailored magnetic nanofluid. The electrical circuit lumped parameters are computed from numerical simulation results based on 2D and 3D models. Finally, the magnetization body forces occurring in the fluid core are computed and the 3D motion that they produce is evidenced to be very slow. © 2014 IEEE.


Morega M.,Polytechnic University of Bucharest | Morega A.M.,Polytechnic University of Bucharest | Morega A.M.,Institute of Statistical Mathematics and Applied Mathematics | Sandoiu A.,Polytechnic University of Bucharest
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

Hyperthermia for medical applications represents the moderate heating of human body tissue, commonly under the tolerance limit of 45°C, for the inhibition of cancerous cells growth. For our study, the heating is locally produced in soft tissue with an interstitial microwave applicator. Several aspects usually considered for the optimization of applicator's design and the assessment of model sensitivity to various parameters are examined in this paper by numerical simulation. The numerical model that combines the electromagnetic and heat transfer problems is based on the finite element method and it was validated by previous research. © 2015 IEEE.


Dumitrescu H.,Institute of Statistical Mathematics and Applied Mathematics | Cardos V.,Institute of Statistical Mathematics and Applied Mathematics
Journal of Aircraft | Year: 2012

Blade element and momentum methods are the traditional design approaches to calculate the drag and lift forces of wind turbine rotor blades. The major disadvantage of these theories is that the airflow is reduced to axial and circumferential flow components. Disregarding radial flow components leads to underestimation of the lift and thrust. Therefore, correction models for rotational effects are often used in the case of the stall-controlled rotors at a constant rotation speed. At inboard locations, there is a strong interaction between the fast rotating flow of the wake and the three-dimensional boundary layer close to the blade surface rotating with an angular velocity smaller than the one of the fluid. This behavior is visible from the streamlines over the blade surface during operation in deep stall. The knowledge extracted from the physical mechanism of three-dimensional rotational effects can then be used to develop an improved blade element and momentum model for the design of stall control wind turbine rotor blades. In this study, the pressure fields generated by the wake and blade are superimposed, and the main contributions for the rise of the three-dimensional and rotational effects are described. Copyright © 2011 by Luis Delgado.


Dumitrescu H.,Institute of Statistical Mathematics and Applied Mathematics | Cardos V.,Institute of Statistical Mathematics and Applied Mathematics
Journal of Aircraft | Year: 2010

The momentum integral technique for the wind turbine blade boundary layer extended to include the separated and reattaching shear layer in a leading-edge bubble of a wind turbine blade is investigated. The pressure gradients cause large changes in velocity profiles and finally in the shape parameter. The results obtained for the chordwise skin-friction coefficient, the boundary-layer shape parameter, and the limiting streamline angle at different small values of nondimensional spanwise distance are used to detect and track boundary-layer separation and reattachment. The conjectured pattern of skin-friction lines near the root of the blade involves singular points with complex topology. The three entirely different flow patterns that can be distinguished includes the extreme inboard region of unseparated flow, the inboard region of the 3-D flow occupying the leading-edge separation bubbles, and the outboard region of the quasi-2-D separated flow.

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