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Espina J.,University of Nottingham | Ortega C.,Escola Universitaria Salesiana de Sarria | De Lillo L.,University of Nottingham | Empringham L.,University of Nottingham | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2014

This paper presents the study of an alternative space vector modulation (SVM) implementation for matrix converters (MCs), which reduces the output common mode (CM) voltage. The strategy is based on replacing the MC zero vectors with rotating ones. In doing this, the CM voltage (CMV) can be reduced, which, in turn, reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the induction motor (IM) deterioration can be slowed down. This paper describes the SVM pattern and analyzes the CMV and the leakage current paths. Simulation and experimental results based on an MC-IM drive are provided to corroborate the presented approach. © 1982-2012 IEEE.

Espina J.,Polytechnic University of Catalonia | Balcells J.,Polytechnic University of Catalonia | Arias A.,Polytechnic University of Catalonia | Ortega C.,Escola Universitaria Salesiana de Sarria
IEEE Transactions on Industrial Electronics | Year: 2011

This paper presents an electromagnetic interference (EMI) model to evaluate the conducted common mode (CM) disturbances produced by matrix converters (MCs). The model is based on obtaining a high frequency (HF) equivalent circuit with HF sources representing the switching devices. The circuit resolution in the frequency domain allows the calculation of any EMI parameter with very low computational burden and avoids convergence problems, which are common in time domain methods. The original contribution lies in the source model implementation and placement. The simulation and experimental results for CM leakage currents validate the EMI model. © 2006 IEEE.

Ortega C.,Escola Universitaria Salesiana de Sarria | Arias A.,Polytechnic University of Catalonia | Caruana C.,University of Malta | Balcells J.,Polytechnic University of Catalonia | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2010

Despite the ability of matrix converters (MCs) to generate a higher number of voltage vectors compared with standard voltage-source inverters, most of the applications reported in the literature utilize only those having larger amplitudes. This paper investigates the use of MC input voltages with different amplitudes in order to reduce the inherent torque ripple that appears when direct torque control (DTC) is used to drive ac machines, particularly permanent-magnet synchronous motors, as its stator inductance is typically half of that of an induction machine of similar ratings. Utilizing a wider range of input voltage vectors for the MC, but not using the rotating vectors, a new lookup table that distinguishes between small and large torque errors is developed, leading to an enhanced MC-fed DTC. The enhancement enables a reduction in the electromagnetic torque ripple and output-current total harmonic distortion. Furthermore, the proposed control strategy improves the MC voltage transfer ratio up to 86.6% compared with 50% achieved by the conventional DTC using MCs at the expense, however, of slightly decreasing the input power factor control capability. The proposed enhanced MC DTC was tested experimentally, and results comparing its performance with MC DTC using an adapted lookup table are shown. © 2006 IEEE.

Cortina-Puig M.,Escola Universitaria Salesiana de Sarria | Gallart-Ayala H.,University of Barcelona | Lacorte S.,CSIC - Institute of Environmental Assessment And Water Research
Current Analytical Chemistry | Year: 2012

Phenolic compounds are important components of many fruits, vegetables and beverages, contributing to their flavor, color and sensory properties. Besides, they are associated with prevention of diseases thought to be induced by oxidative stress, such as cardiovascular diseases, cancer and inflammation. Due to their bioactive functions, phenolic compounds have received particular attention in recent years. Amongst the different analytical methods reported to determine the polyphenol content and composition of food and beverages, liquid chromatography (LC) is the preferred option compared to gas chromatography (GC) since no derivatization is needed. UV detectors have been commonly used for the determination of phenolic compounds, but they lack of sensitivity and/or specificity. LC coupled with electrochemical detection (ECD) or coupled to mass spectrometry (MS) detectors are the most sensitive, selective and reproducible methods for quantifying phenolic compounds. This manuscript reviews the main applications of LC coupled to ECD or MS for the analysis of phenolic compounds in food and beverages. © 2012 Bentham Science Publishers.

Prehn R.,Autonomous University of Barcelona | Gonzalo-Ruiz J.,Autonomous University of Barcelona | Cortina-Puig M.,Escola Universitaria Salesiana de Sarria
Current Analytical Chemistry | Year: 2012

Polyphenolic compounds, which are widely distributed in plant-derived foods, recently attracted much attention because of their possible health benefits arising from their antioxidant activity, such as free radical scavengers and inhibition of lipoprotein oxidation. The detection of phenolic substances in food samples has been performed for many methods among them electrochemical sensors and biosensors approaches. Polyphenolic compounds are good substrates for oxidases enzymes, then biosensors modified with tyrosinase, laccase and peroxidase have been developed for detection of phenolic compounds since phenols can act as electron donors for these enzymes. Furthermore, as polyphenols are electroanalytically active compounds that can be easily oxidized at inert electrodes, electrochemical sensors have also been used as tools for estimating the total phenolic content (TPC). This paper critically reviews both electrochemical sensors and biosensors developed for the evaluation of polyphenolic compounds in foods and beverages. Due to the ability of these devices to perform simple, fast and reliable analysis, they are promising tools for the assessment of antioxidant properties. © 2012 Bentham Science Publishers.

Prehn R.,CSIC - National Center of Microelectronics | Cortina-Puig M.,Escola Universitaria Salesiana de Sarria | Munoz F.X.,CSIC - National Center of Microelectronics
Journal of the Electrochemical Society | Year: 2012

We report a non-enzymatic glucose sensor that is based on a gold micropillar array electrode and was fabricated by using a combination of photolithographic techniques and electroplating. The electrode exhibits (a) a larger electroactive area, (b) enhanced surface roughness, and (c) enhanced catalytic activity toward the electro-oxidation of glucose. We demonstrate its potential application in sensing glucose with high operational stability, high sensitivity and relatively high selectivity. The response to glucose is linear in the 0.5 to 9 mM concentration range, the sensitivity is 13.2 μA mM -1 cm -2, and the detection limit is 60 μM. The simplicity of the sensor preparation makes gold micropillar array electrodes a good candidate for easy glucose determinations. © 2012 The Electrochemical Society.

Calas-Blanchard C.,University of Perpignan | Cortina-Puig M.,Escola Universitaria Salesiana de Sarria | Barthelmebs L.,University of Perpignan | Noguer T.,University of Perpignan
Current Analytical Chemistry | Year: 2012

Reactive oxygen species (ROS) are very unstable molecules generated during the metabolism. They can be produced in excess, contributing to cellular dysfunctions. Antioxidants are substances that play an important role as a health-protecting factor, limiting the lesions caused by ROS. Two kinds of electrochemical biosensors based on ROS have been described to evaluate the antioxidant capacity in the food industry. The first one involves hydroxyl radicals and studies their effect on DNA alterations. The second one consists of the superoxide radicals scavenging ability, radicals being essentially generated by the xanthine/xanthine oxidase system. These sensors are commonly based on either cytochrome c or superoxide dismutase, even though recent strategies are emerging. Whatever the involved ROS, all the described biosensors possess similar advantages such as simplicity, rapidity and low cost and are successfully applied for the assessment of antioxidant properties in various foods, additives or beverages. © 2012 Bentham Science Publishers.

Bartolome E.,Escola Universitaria Salesiana de Sarria | Bartolome E.,CSIC - Institute of Materials Science | Palau A.,CSIC - Institute of Materials Science | Llordes A.,CSIC - Institute of Materials Science | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

2 Cu3 O7-x-BaZrO3 (YBCO-BZO) nanocomposites have recently shown to display record pinning forces at high magnetic fields, paving thus the way for power applications. We have applied an ac-susceptibility methodology to analyze the different vortex dynamics of BZO nanocomposites compared to pristine YBCO thin films grown by the trifluoracetate route, close to the irreversibility line. The analysis is focused on the nonlinear Bean critical-state regime, occurring at high ac fields. We determined the dc-field and current-density dependencies of the effective energy barrier for thermally activated flux motion, Ue (J,T,B). The distinctive dependencies encountered for BZO nanocomposites evidence that randomly oriented BZO nanoparticles in the YBCO matrix provide strong-isotropic pinning, even at very high dc fields and temperatures. © 2010 The American Physical Society.

Rosas J.G.,Autonomous University of Barcelona | Armenta S.,Autonomous University of Barcelona | Cruz J.,Escola Universitaria Salesiana de Sarria | Blanco M.,Autonomous University of Barcelona
Analytica Chimica Acta | Year: 2013

Determining homogeneity of a mixture using hyperspectral-imaging (HSI) techniques is at this moment an interesting research subject in pharmaceutical industry. A new methodology based in the macropixel analysis technique for the homogeneity assessment in powder blend mixtures has been developed. The appropriate selection of the macropixel size for evaluation of the homogeneity is a topic under discussion. We propose that the macropixel size selection would be based in a statistical criterion called "representative sample size" criterion. Moreover, it has been demonstrated that the macropixel size should be a function of the particle size and, thus, the particle size has been included in the formula to calculate the macropixel size. The proposed equations allow to accurately calculate the homogeneity index (H% Poole). By means of using simulated chemical images, a relationship between the H% Poole index and the controlled homogeneity was established. The method has been applied to determine the homogeneity of binary and ternary powder blends mixtures of different pharmaceuticals discriminating between homogeneous and non-homogeneous samples. © 2013 Elsevier B.V.

Moreno A.,Escola Universitaria Salesiana de Sarria | Cesar E.,Autonomous University of Barcelona | Guevara A.,Autonomous University of Barcelona | Sorribes J.,Autonomous University of Barcelona | Margalef T.,Autonomous University of Barcelona
Parallel Computing | Year: 2012

We propose to use knowledge about a parallel application's structure that was acquired with the use of a skeleton based development strategy to dynamically improve its performance. Parallel/distributed programming provides the possibility of solving highly demanding computational problems. However, this type of application requires support tools in all phases of the development cycle because the implementation is extremely difficult, especially for non-expert programmers. This work shows a new strategy for dynamically improving the performance of pipeline applications. We call this approach Dynamic Pipeline Mapping (DPM), and the key idea is to have free computational resources by gathering the pipeline's fastest stages and then using these resources to replicate the slowest stages. We present two versions of this strategy, both with complexity O(N log (N)) on the number of pipe stages, and we compare them to an optimal mapping algorithm and to the Binary Search Closest (BSC) algorithm [1]. Our results show that the DPM leads to significant performance improvements, increasing the application throughput up to 40% on average. © 2011 Elsevier B.V. All rights reserved.

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