Revista elektron

53-57

Authors: Betina Abadi, Ligia Ciocci Brazzano, Patricio Sorichetti, Martín Germán González

This paper presents the implementation and electric characterization of a broadband piezoelectric polymer sensor with linear geometry based on a thin film of polyvinylidene fluoride. The electrical impedance of the sensor was measured as a function of frequency, and it was found that the polymer was practically not altered by the sensor fabrication process. Also, the sensor frecuency response with a transimpedance amplifier was measured. Due to the high electrical capacitance of the device, a large reduction of the system broadband was found.

66-74

Authors: José-Víctor Rodríguez Rodríguez, Ignacio Rodríguez-Rodríguez, José Luis Serrano Martínez

In this work, a series of relatively simple experiments aimed at measuring the speed of light in different media within an educational environment is presented. In this way, the different methods and procedures -which can be carried out within university laboratories- for measuring at what velocity light propagates through air, crystal or water are described step by step. The speed of light measurement activities presented in this article represent an enjoyable and practical way of enriching the teaching of both optics and electromagnetism, get familiar with specific instrumentation such as oscilloscopes and optical transmitters/receivers or understand the science underlying fiber optics. Finally, the proposed experiments represent, in the end, an ideal example of bringing students closer to the so-called 'scientific method'.

79-90

Authors: Francisco Javier Messina, Leonardo Rey Vega, Cecilia Gabriela Galarza

We first present a detailed review of two popular classes of model based synchrophasor estimators. They are the discrete Fourier transform (DFT) and the Taylor-Fourier transform (TFT) class estimators, which arise from constant or polynomial phasor models, respectively. Limitations of these techniques, arising from the models themselves, are exposed. These limitations make the original DFT and TFT approaches unfitted for situations where the phasor can not be properly described in such simple terms. This issue can be addressed with the recently introduced convex semi-infinite programming (CSIP) based estimators, which are also reviewed. In particular, we present the constraints associated with the tests which are most critical for the model based methods, showing how to precisely control the estimators performance in those cases. Finally, we show that the DFT and TFT estimators are particular instances of the CSIP estimator, so that there exists a connection between these two apparently different approaches. This opens the door for future analyses and developments.

97-101

Authors: Vladimir Henao Céspedes, Luis Fernando Díaz Cadavid, Walter Gustavo Fano, Eduardo Antonio Cano Plata

In this work the electromagnetic emissions caused by a discharge of a lightning have been modeled, considering the lightning as a short monopole antenna over a perfectly conducting ground plane. By this analogy the radiated electric and magnetic fields are calculated, and then the induced voltage is calculated in a distribution line considered as a short loop. The mathematical expression used for the calculation of the induced voltage was already proposed in a previous work and in the present work is validated by its confrontation in an simulated scenario with two known expressions for the calculation of the induced voltage, one recommended by the IEEE and developed by S. Rusck and another developed by Barbosa. On the basis of the considerations made by Rusck to obtain its expression for the induced voltage, the geometry related to the proposed expression is adapted to make it comparable with Rusck's international reference in the IEEE standard. Later, the dV_ind/dy behaviors of the three expressions in the region of near-field radiation of the lightning were analyzed, determining that the trends (which are hyperbolic) of the proposed expression and that developed by Rusck (internationally standardized in the IEEE 1410 standard) have a great similarity when the radiated fields exceed 20 m, giving validity to the proposed expression.