Revista elektron

47-52

Authors: Pablo Gomez, Enrque D'onofrio, Guillermo Daniel Santiago

We present the use of ionic transducers to generate acoustic waveforms of cylindrical shape. We resorted to “cold discharge” transducers where momentum transfer from ions to neutral molecules is the main sound-generating process. Since the electrodes can be given a fairly arbitrary shape and the airflow is normal to the former, it is possible to obtain, close to the electrodes, a wavefront quite different from those obtained with standard, piston-like, loudspeakers. We present the acoustical characteristics of a cylindrical transducer and the use in the study of a bandpass, sonic-crystal based filter.

63-66

Authors: Martin German Gonzalez, Eduardo Omar Acosta, Guillermo Santiago

In this paper we present a method to determine the spatial resolution and sensitivity of systems for optoacoustic tomography (OAT). The method consists of obtaining the image of a sample based on a transparent film embedded in agarose. The film has a certain pattern made with a laser printer that allows to obtain the system spatial resolution. Moreover, since the damage threshold of the ink pattern is similar to that of living tissue, it is also possible to determine if the system is sensitive enough to be applied on biological samples. The method is straightforward, fast and repeatable, and was tested in a OAT system for obtaining two-dimensional images developed in our laboratory.

71-82

Authors: Pablo Damian Torrado

The ANTop (Adjacent Network Topology) is a distributed and decentralized protocol for ad-hoc networks. It is based on a hypercube address space where the nodes names are mapped to assure their adjacency, allowing greedy routing protocols to find the optimum route. A distributed mechanism, to match real names to the network address, is implemented by distributed hashing tables. In this work we address the partition and assimilation networks problems, to complete the functionalities of ANTop, and we also provide a complete implementation for Linux systems.

95-100

Authors: Gonzalo Iñaki Quintana, Ramiro Alonso, Walter Gustavo Fano

Electromagnetic Fields are present in the Earth, due both to natural and artificial emissions. The Electric and Magnetic fields generated by natural events like volcanic eruptions and earthquakes, are aspects of tectonomagnetism, volcanomagnetism and tectonoelectricity, in the electromagnetic spectrum from radio frequencies (RF) to submicrohertz frequencies. This paper is dedicated to the characterization of loop antennas for measuring electromagnetic precursors of seismic movements and other ELF (3-30 Hz) and SLF (30-300 Hz) natural effects. The antenna factor, impedance, quality factor Q and sensitivity of the antennas are measured. These characteristics are of great importance in the choice of the loop antenna to be used in the framework of the UBACyT research proyect Study of Electromagnetic Disturbances Produced by Seismic Movements.

1-6

Authors: Eduardo Omar Acosta, Natalia Clara Álvarez, Maria Teresa Garea, Liliana Perez, Patricio Sorichetti

Monochromatic plane waves allow the description of many of the properties of propagating, reflected and transmitted radiation through media of different optical properties. However, some of their characteristics only appear when considering limited beams. In this work we determine and analyse (to the second order) some characteristics of the transmission of beams (spatially limited) or pulses (limited in time), in both cases with Gaussian distribution. It is assumed that the transmission takes place through an isotropic plane-parallel plate. If the beam is limited in space, we consider that the mean direction of the wave is perpendicular to the plate. On the other hand, when the beam is limited in time, we consider that all the plane waves impinge normally to the plate. We compare the non-geometric effects for both kinds of limited beams, for the cases where the plate is transparent, absorbing or with linear gain.

12-15

Authors: Guillermo Daniel Santiago, Violeta D'accurso

In this work, a new method for measuring the power of light beams generated by fast-tranverse-flow CO2 lasers is presented. It consists in measuring the temperature of the gas before and after the discharge zone under the conditions when the output mirror of the optical cavity is blocked or not. Then, using a simple thermodynamic model, the emitted power is obtained. The method was tested in a continuous CO2 laser of the convective cooling type by transverse flow that can deliver a power up to 2 kW. The measured power agreed very well with that obtained with a commercial detector based on an absorbing material.

26-29

Authors: Martín Germán González, Guillermo Daniel Santiago, Verónica Slezak, Alejandro Peuriot

This paper shows that the use of filters based on the discrete wavelet transform (DWT) improves the sensitivity of photoacoustic systems for measurement of trace gases under conditions of unfavorable signal-to-noise ratio (SNR). To achieve this goal, a filter based on Meyer's DWT was designed and tested with simulated and measured signals. For the measurements, a system for the detection of traces of sulfur hexafluoride in nitrogen using a pulsed CO2 laser was implemented. From the results it was obtained that the use of DWT had a very good performance for signals generated with low laser energies ( < 100 uJ) corrupted with impulsive electromagnetic noise.

39-46

Authors: Enrique Zothner, Julio Zola, Juan Kelly

To measure the Common Mode Rejection (CMR) of an amplifier, it is necessary to carry out the measurements of the implemented and finished circuit, and then perform the measurement of its behavior in real operating conditions. This measurement is necessary to evaluate the susceptibility to conducted electromagnetic interferences (conducted EMI) on the amplifier. In this work, a procedure of direct measurement of the CMR of an amplifier without altering the circuit is described. The measurements are verified by simulation with PSpice.

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.

1-7

Authors: Nicolás Ronis, Mariano García Inza

An integrated Hall sensor was designed and fabricated in a 0.5μm CMOS ONC5N/F process provided by MOSIS. On it, four different Hall Plate geometries were integrated in order to analyze their sensitivity and resistance over temperature from -40°C up to 165°C. Furthermore, an amplifier and a current spinning system to remove the amplifier and Hall Plate offset were designed and placed in the same chip. The results show a better sensitivity performance in the cross-shaped Hall Plate and a linear behavior of the sensor in the range of operation tested.

16-22

Authors: Lucas Matías Riobó, Francisco Ezequiel Veiras, María Teresa Garea, Patricio Anibal Sorichetti

This paper describes the design and performance of transimpedance amplifiers (TIAs) for optoelectronic systems, optimized for optical dynamic interferometry. To perform the analysis of the amplifiers, we show some experimental schemes, where different topologies were used. We describe the relevance of each TIA implemented, mentioning guidelines and design considerations.

29-37

Authors: Esteban Carisimo

Internet Exchange Points (IXPs) have been responsible for leading the most significant change on Internet ecosystem in the last 15 years. Despite the popularity of IXPs, a large number of countries delayed to introduce this infrastructure in their national networks. In 2013, Bolivia encouraged the creating of a national IXP, which motivated us to make the first study about an IXP in Latin America, in a country which had not deployed this infrastructure yet. However, due to the lack of vantage points of measurement projects in Bolivia, it was necessary to develop and deploy a measurement platform, which was called PladMeD, to be able to analyze the influence of the IXP. This works presents a six-month analysis about the influence of the IXP on the national network and it mainly focuses on the modifications in the interconnection as well as the quality of service.

48-52

Authors: Julio Zola, Pablo Marino, Federico Dangiolo

The analysis and attenuation of electromagnetic interference (EMI) in complex electronic systems is an important issue to take into account in the design of these systems, due to malfunctions that may be caused by such interferences. In this paper the particular design of a filter to reduce spurious currents or conducted emissions from different DC to DC converters that are part of a complex system, is described. This design includes a method to help to reduce conducted emissions from these converters. While design criteria are oriented to a particular system, this study can be applied generically to any system where it is necessary to evaluate EMI.