Electronica y Computacion

Manizales, Colombia

Electronica y Computacion

Manizales, Colombia
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Tolosa R.A.,Electronica y Computacion | Tolosa R.A.,National University of Colombia | Jimenez-Obando G.,National University of Colombia | Arias N.P.,Electronica y Computacion | And 3 more authors.
Industrial and Engineering Chemistry Research | Year: 2014

In this work, to improve the interface interaction between natural fibers and a cementitious matrix, several Colombian Angustifolia kunth bamboo fibers were modified using different pretreatment methods before being covered with an inorganic phase of manganese oxide. The coating was performed by placing the fiber in contact with a manganese salt solution at low concentration, followed by drying of the fibers before performing physicochemical characterization. The fibers were characterized by atomic absorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The coated fibers were added to a cementitious matrix, and the mechanical properties of the resulting composites were measured to determine the optimal treatment for reinforcing the cementitious matrix. The manganese content in the modified natural fibers obtained by atomic absorption was between 0.7 and 1.23 wt %, and the manganese oxide was deposited in a uniform manner onto the surface of the fiber, as indicated by the SEM images. The XRD patterns indicate some variation of the crystalline structure of cellulose, the TGA analysis indicates that the raw fiber lost more weight than did the covered fibers, and the FTIR revealed the vibrational bands associated with manganese oxide vibration. The mechanical properties measured by monitoring the flexural strength indicate the interplay between the physicochemical characterizations and the mechanical performance. Various samples of the composite material were prepared by varying the length, and the percentage of the addition of the fiber, and the flexural strength, toughness, energy index, and total energy of the samples were measured in all fibrocement materials; the measurement results indicate an improvement in the flexural strength of the materials occurred for the composite material synthesized with the addition of 2% fibers of 2.5 cm length. © 2014 American Chemical Society.


Hoyos F.E.,Antioquia Institute of Technology | Rincon A.,Catholic University of Manizales | Taborda J.A.,University of Magdalena | Toro N.,Electronica y Computacion | Angulo F.,Electronica y Computacion
Mathematical Problems in Engineering | Year: 2013

The motor speed of a buck power converter and DC motor coupled system is controlled by means of a quasi-sliding scheme. The fixed point inducting control technique and the zero average dynamics strategy are used in the controller design. To estimate the load and friction torques an online estimator, computed by the least mean squares method, is used. The control scheme is tested in a rapid control prototyping system which is based on digital signal processing for a dSPACE platform. The closed loop system exhibits adequate performance, and experimental and simulation results match. © 2013 Fredy E. Hoyos et al.


Melo Varela L.A.,National University of Colombia | Casanova Trujillo S.,National University of Colombia | Olivar Tost G.,Electronica y Computacion
Mathematical Problems in Engineering | Year: 2013

This paper shows a study, both analytical and numerical, of a continuous-time dynamical system associated with a simple model of a wastewater biorreactor. Nonsmooth phenomena and border-collision local bifurcations appear when the main parameters (dilution and biomass concentration at the inflow) are varied. We apply the Filippov methods following Kuznetsov's work. © 2013 Luz A. Melo Varela et al.


D'Amico M.B.,CONICET | Angulo F.,Electronica y Computacion
International Journal of Circuit Theory and Applications | Year: 2015

Summary The response of a digital Zero Average Dynamics (ZAD)-controlled buck converter under the variation of its intrinsic parameters as well as the pulse-width modulation signal is studied in detail. The multiparameter analysis presented here leads to a complete knowledge of the different dynamical scenarios exhibited by the system. Numerical results indicate that the success of the ZAD-strategy is highly dependent on the parameter and pulse-width modulation (PWM) combinations. Experiments are included to validate the performance inside the so-called optimum region. © 2013 John Wiley & Sons, Ltd.

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