Antonio Lopez

• University of Granada

This paper describes an apparatus for generating a signal representative of steady-state and transient disturbances in three-phase waveforms of an ac electrical system as described in IEEE Std 1159-09. It can be configured as a synthesizer of randomly distorted signals for different applications: for testing the effects of disturbed grid on equipme...

Industrial Engineering degree course syllabuses include a series of basic, common skills which must be acquired by those studying for any of the five qualifications that can be obtained in the subject. This paper presents a reflection on the content which should be included in the subject that cover the proficiency “Basic Electronics”, analysing th...

The Fourier transform usually has been used in the past for analysis of stationary and periodic signals. Its interest is the knowledge of spectral components existing in a waveform; it doesn't matter the moment where they happen. However, when the time localization of the spectral components is needed, the Wavelet Transform (WT) can be used to obta...

The Fourier Transform analysis is able to estimate the amplitude and frequency of signals under stationary conditions. For transient or aperiodic signals the Fourier analysis is unable to obtain accurate results and a joint time-frequency analysis must be used to provide simultaneous time and frequency information of transient intervals. A voltage...

The Fourier transform analysis is able to estimate the amplitude and frequency of signals under stationary conditions. For transient or aperiodic signals the Fourier analysis is unable to obtain accurate results and a joint time-frequency analysis must be used to provide simultaneous time and frequency information of transient intervals. A power qu...

A single indicator [i.e., the power quality factor (PQF)] in the range between 0 and 1 is suggested in this paper to integrally reflect the power transfer quality of a general three-phase network feeding unbalanced nonlinear loads. The prominent power quality aspects considered in the paper are the following: 1) the voltage and current harmonic lev...

The Fourier transform usually has been used in the past for analysis of stationary and periodic signals. Its interest is the knowledge of spectral components existing in a waveform; it doesn't matter the moment where they happen. However, when the time localization of the spectral components is needed, the Wavelet Transform (WT) can be used to obta...

Following the Bayesian framework we propose a method to reconstruct emission tomography images which uses gamma mixture prior and variational methods to approximate the posterior distribution of the unknown parameters and image instead of estimating them by using the Evidence Analysis or alternating between the estimation of parameters and image (I...

Emission tomography images are degraded due to the presence of noise and several physical factors, like attenuation and scattering. To remove the attenuation effect from the emission tomography reconstruction, attenuation correction factors (ACFs) are used. These ACFs are obtained from a transmission scan and it is well known that they are homogene...

In this work we propose a new method to estimate the scale hyperparameter for transmission tomography in Nuclear Medicine image reconstruction problems. Within the Bayesian paradigm, Evidence Analysis and circulant preconditioners are used to obtain the scale hyperparameter. For the prior distribution, we use Generalized Gaussian Markov Random Fie...

The Fourier transform usually has been used in the past for analysis of non-stationary signals. Its interest is the knowledge of spectral components existing in a waveform; it doesn’t matter the moment where they happen. However, if this information is needed, i.e., if we want to know for transient analyze the s, which spectral component occur at w...

Despite the adequacy of Bayesian methods to reconstruct nuclear medicine SPECT (single-photon emission computed tomography) images, they are rarely used in everyday medical practice. This is primarily because of their computational cost and the need to appropriately select the prior model hyperparameters. We propose a simple procedure for the estim...

A joint treatment for signal analysis based in both Fourier and Wavelet theory is presented. Distinguishing from harmonics and transient disturbance components present on an electrical signal, the former part is extracted by means of Fourier methods, while the latter is subjected to multiresolution treatment in order to split disturbance low freque...

In this work we propose a new method to estimate the scale hyperparameter for convex priors with scalable energy functions in Single Photon Emission Computed Tomography (SPECT) image reconstruction problems. Within the Bayesian paradigm, Evidence Analysis and circulant preconditioners are used to obtain the scale hyperparameter. The proposed method...

We propose a new iterative method for Maximum a Posteriori (MAP) reconstruction of SPECT (Single Photon Emission Computed Tomography) images. The method uses Compound Gauss Markov Random Fields (CGMRF) as prior model and is stochastic for the line process and deterministic for the reconstruction. Synthetic and real images are used to compare the ne...

This paper describes a currently project accomplished by the authors in the area of Power Quality (PQ) using artificial neural networks (ANN). The efforts are oriented to obtain a product (Power disturbances monitor for threephase systems) that permits a real time detection, automatic classification, and record process of impulsive or oscillatory v...

Jannelli, L., Pansini, M. and Lopez, A., 1983. Thermodynamic and physical properties of binary mixtures involving nitrobenzene + the first term of the aliphatic and aromatic nitrile series. Fluid Phase Equilibria, 15: 219–229.Enthalpies of mixing at 298.16 K, and excess volumes and dielectric constants at temperatures ranging between 293.16 and 333...

Excess volumes and dielectric constants were measured for benzonitrile + nitrobenzene and acetonitrile + nitrobenzene mixtures over the entire composition range, at selected temperatures ranging between 293.16 and 333.16 K. Benzonitrile and nitrobenzene molecules possess quite similar volumes and shapes; acetonitrile and nitrobenzene are isodielect...

Volumes, dielectric constants, and enthalpies of mixing sulfolane + 2-methylpropionitrile and + 2,2-dimethylpropionitrile were measured over the entire composition range, at selected temperatures, with the aim of studying the influence of nitrile chain branching on the kind and the importance of interactions between like and unlike molecules. The m...

Dielectric constants were measured for three binary systems involving sulfolane + propionitrile, + butyronitrile, and + valeronitrile, over the entire composition range, at selected temperatures ranging between 293.16 and 333.16 K. The behavior of excess dielectric constant vs. composition plots markedly differentiates each system with respect to o...

Flow calorimetric measurements, at 303. 16 K, of molar excess enthalpy, H**E, of four binary systems involving sulfolane and each member of the n-nitrile series from acetonitrile to valeronitrile are reported. H**E values are positive over the entire composition range for the ghree higher members of the series with a maximum, at approximately 0. 5x...

The authors propose a new criterion for the evaluation of the van der Waal'volumes Vw for liquid substances. This criterion derives from simple hypotheses of interdependence between the van der Waal's volumes, the molar volumes, VO, and the vaporization enthalpies, ΔHv. For all the cases examined the estimated values of Vw are thus slightly depende...

The volumes of mixing and dielectric constants of nitrobenzene-sulfolane mixtures were measured, at several temperatures ranging within 288.16-333.16 K, over the entire composition range. The observed deviations from ideality, decreasing with increasing temperature, are interpreted as not indicative of significant interactions between unlike molecu...

The solid + liquid phase diagram drawn from thermal analysis is presented. It exhibits a eutectic at x2 = 0.303 and T = 262.2 K and precludes the existence of definite compounds between the two components. Mixed crystals are observed in the sulfolane-rich region. The activity coefficients of water, fx, 1, and of sulfolane, fx, 2, are calculated fro...

RESUMEN En los últimos años se ha prestado una creciente atención a los problemas relacionados con la calidad de la señal de tensión de la red eléctrica (PQ). Los instrumentos actuales permiten almacenar gran cantidad de información en el análisis de señales pero éste debe realizarse "off-line". Nuestra propuesta para la clasificación de perturbaci...