Miguel Alcañiz

A voltammetric electronic tongue as tool for water quality monitoring in wastewater treatment plants

The use of a voltammetric electronic tongue as tool for the prediction of concentration levels of certain water quality parameters from influent and effluent wastewater from a Submerged Anaerobic Membrane Bioreactor pilot plant applied to domestic wastewater treatment is proposed here. The electronic tongue consists of a set of noble (Au, Pt, Rh, Ir, and Ag) and non-noble (Ni, Co and Cu) electrodes that were housed inside a stainless steel cylinder which was used as the body of the electronic tongue system. As a previous step an electrochemical study of the response of the ions sulphate, orthophosphate, acetate, bicarbonate and ammonium was carried out in water using the electrodes contained in the electronic tongue. The second part of the work was devoted to the application of the electronic tongue to the characterization of the influent and effluent waters from the wastewater treatment plant. Partial Least Squares analysis was used to obtain a correlation between the data from the tongue and the pollution parameters measured in the laboratory such as soluble chemical oxygen demand (CODs), soluble biological oxygen demand (BODs), ammonia (NH(4)-N), orthophosphate (PO(4)-P), Sulphate (SO(4)-S), acetic acid (HAC) and alkalinity (Alk). A total of 28 and 11 samples were used in the training and the validation steps, respectively, for both influent and effluent water samples. The electronic tongue showed relatively good predictive power for the determination of BOD, COD, NH(4)-N, PO(4)-P, SO(4)-S, and Alk.

Achieving Maximum Efficiency in Three-Phase Systems With a Shunt Active Power Compensator Based on IEEE Std. 1459

IEEE Standard 1459-2000 establishes that in an efficient electrical system, only the fundamental positive-sequence active power must be present. This paper proposes a new set of reference currents based on the IEEE Standard 1459-2000 for the control of a three-branch four-wire shunt active power compensator. Reactive, unbalance, and harmonic distortion phenomena can be cancelled out upstream from the point of connection, achieving maximum efficiency of the three-phase four-wire electrical system. In addition, a new current control and a three-dimensional space vector pulsewidth-modulation technique are proposed to develop a shunt active power compensator. Simulation and experimental results demonstrate that the proposed shunt active power compensator improves the upstream electrical quality of the power network, achieving maximum efficiency according to IEEE Standard 1459-2000 specifications.

Selective Shunt Active Power Compensator Applied in Four-Wire Electrical Systems Based on IEEE Std. 1459

This paper proposes a method to obtain the reference currents of a shunt active power compensator based on the nonactive power magnitudes defined in IEEE Standard 1459-2000. These reference currents are used to control a shunt active power compensator that features new selective compensating capabilities. Fundamental positive-sequence reactive power, unbalance power, and nonfundamental effective apparent power present in electric systems can be cancelled individually or combined with each other. Experimental results are obtained using a three-branch four-wire shunt active compensator. These results demonstrate that the proposed selective compensator works well in three-phase electrical systems with load currents, including phase shifts, unbalance,s and distortion, and with voltages, including asymmetries and harmonic components. The electric quality is improved with the use of the proposed selective control.

Quantification of organic acids using voltammetric tongues

Recently, electronic tongues (ET) have appeared as an excellent alternative to traditional techniques for the evaluation of food quality and processes. ET systems are based on arrays of low selectivity sensors that are simultaneously sensitive to several components in a measured sample (cross-sensitivity). The aim of this study was to determine the ability of an ET based on pulse voltammetry to quantify organic acids (ascorbic, citric and malic acids) in simple (SS) and binary solutions (BS) using different electrodes. The most significant electrodes for ascorbic acid prediction were Ni and Ag for SS, and Ag and Ir for BS where positive pulses were more suitable than negative ones. The prediction of citric and malic acids in SS and BS were suitable using Ir, Rh, Pt, Ag and Cu electrodes, using both positive and negative pulses.

Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents

A new electronic tongue to monitor the presence of glyphosate (a non-selective systemic herbicide) has been developed. It is based on pulse voltammetry and consists in an array of three working electrodes (Pt, Co and Cu) encapsulated on a methacrylate cylinder. The electrochemical response of the sensing array was characteristic of the presence of glyphosate in buffered water (phosphate buffer 0.1 mol·dm−3, pH 6.7). Rotating disc electrode (RDE) studies were carried out with Pt, Co and Cu electrodes in water at room temperature and at pH 6.7 using 0.1 mol·dm−3 of phosphate as a buffer. In the presence of glyphosate, the corrosion current of the Cu and Co electrodes increased significantly, probably due to the formation of Cu2+ or Co2+ complexes. The pulse array waveform for the voltammetric tongue was designed by taking into account some of the redox processes observed in the electrochemical studies. The PCA statistical analysis required four dimensions to explain 95% of variance. Moreover, a two-dimensional representation of the two principal components differentiated the water mixtures containing glyphosate. Furthermore, the PLS statistical analyses allowed the creation of a model to correlate the electrochemical response of the electrodes with glyphosate concentrations, even in the presence of potential interferents such as humic acids and Ca2+. The system offers a PLS prediction model for glyphosate detection with values of 098, −2.3 × 10−5 and 0.94 for the slope, the intercept and the regression coefficient, respectively, which is in agreement with the good fit between the predicted and measured concentrations. The results suggest the feasibility of this system to help develop electronic tongues for glyphosate detection.

Innovative Nondestructive Measurements of Water Activity and the Content of Salts in Low-Salt Hake Minces

Impedance spectroscopy (IS), low-field proton nuclear magnetic resonance (LF (1)H NMR), chloride titration, ion chromatography, and an ion selective electrode were used to investigate the physicochemical parameters and measure sodium and potassium contents in low-salt brines and fish. Salt solutions (0-3 w/w, %) and model products of minced hake with added NaCl (0.5-3.0 w/w, %), or a mixture of NaCl and KCl (50/50 w/w, %), were analyzed. Good correlation was observed between the sodium content determined by using the ion selective electrode method and ion chromatography (R(2) = 0.97). In both salt solutions and fish minces, the impedance spectroscopy measurements could detect the difference in salt contents in mince with salt contents down to 0.5%. The NMR transversal relaxation time T2 measurements clearly distinguished samples with 0, 0.5, and 1.0-3.0% salt, based on principal component analysis (PCA). Therefore, LF (1)H NMR seems to be a suitable technique for studies of low-salt products.

Classification of unaltered and altered dry-cured ham by impedance spectroscopy: a preliminary study.

The aims of this work were characterized by the physicochemical and microbiological features of dried-cured hams classified by the manufacturer as altered (deep spoilage and swollen) and unaltered, as well as, correlated these results with the electronic measurements of impedance spectroscopy, in order to lay the groundwork to design a suitable electrode to be used for checking in line all dry-cured ham elaborated. Double electrode and coaxial needle electrode were used in a frequency range of 100Hz to 1MHz. The electronic measurements of the two electrodes were able undoubtedly to discriminate between altered and unaltered dry-cured hams; moreover a tendency to classify between deep spoilage and swollen hams was shown. The values into the range of frequencies between 100Hz-1000Hz, for both electrodes, showed the best clustering results. More studies are needed to select the best electrode which can be transformed in a robust and versatile electrode which could be used for checking in line all dry-cured ham elaborated.

Classification of honeys of different floral origins by artificial neural networks

In this study, the data obtained from a potentiometric electronic tongue system are analyzed using a Fuzzy-Artmap artificial neural network. The analysis is focused on determining the optimal configuration of the neural network in order to achieve the proper classification of the honey analysed, as well as to adjust its size for further implementation in a microcontroller system. The application submitted has been employed to discriminate several varieties of honey according to the types of floral origin (citrus, rosemary, polyfloral and honeydew) and considering three different physical treatment: raw, liquefied and pasteurized. The measures have been carried out using a set of metal electrodes of different materials. We have used eight electrodes of various metals (pure and chemically treated). In order to implement the neural networks, a Graphic User Interface (GUI) in Matlab has been developed, fixing thereby the parameters of neural networks and obtaining the classification of the samples. Moreover, the information needed to implement neural networks in microcontroller systems is also generated to ensure an autonomous system of electronic tongue applied to the analysis of honey‥

Influence of potential pulses amplitude sequence in a voltammetric electronic tongue (VET) applied to assess antioxidant capacity in aliso

Four signals configurations were studied, two of them built by small increases of potential and two with bigger increments. The highest current values were obtained when pulses with bigger change of potential were used although the best results were shown by the pulse sequence which included an intermediate pulse before the relevant pulse. A mathematical model based on trolox pattern was developed to predict antioxidant capacity of aliso, employing information obtained from all the electrodes, although model validation could be done only employing the information from gold electrode.

Teaching Electronics to Aeronautical Engineering Students by Developing Projects

Teaching electronics to an aerospace engineer with a very limited number of credits has been a major challenge for us. This goal has been achieved through a teaching method based on real projects that are closely related to aerospace engineering. Throughout this paper, the process of teaching electronics through two subjects, one compulsory and one elective, is described. Subsequently, a description of the major projects that have been implemented in the last years is given. The academic results have been very satisfactory, and project development has proved a widely accepted method of teaching by students.