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Publication Detection of partial discharge sources using UHF sensors and blind signal separation(MDPI, 2017-11-15) Boya Lara, Carlos Alan; Robles Muñoz, Guillermo; Parrado Hernández, Emilio; Ruiz Llata, Marta; Ministerio de Economía y Competitividad (España)The measurement of the emitted electromagnetic energy in the UHF region of the spectrum allows the detection of partial discharges and, thus, the on-line monitoring of the condition of the insulation of electrical equipment. Unfortunately, determining the affected asset is difficult when there are several simultaneous insulation defects. This paper proposes the use of an independent component analysis (ICA) algorithm to separate the signals coming from different partial discharge (PD) sources. The performance of the algorithm has been tested using UHF signals generated by test objects. The results are validated by two automatic classification techniques: support vector machines and similarity with class mean. Both methods corroborate the suitability of the algorithm to separate the signals emitted by each PD source even when they are generated by the same type of insulation defect.Publication Toward a Robust Multi-Objective Metaheuristic for Solving the Relay Node Placement Problem in Wireless Sensor Networks(MDPI, 2019-02-01) Lanza Gutiérrez, José Manuel; Caballe, Nuria; Gómez-Pulido, Juan A.; Crawford, Broderick; Soto, Ricardo; Ministerio de Economía y Competitividad (España)During the last decade, Wireless sensor networks (WSNs) have attracted interest due to the excellent monitoring capabilities offered. However, WSNs present shortcomings, such as energy cost and reliability, which hinder real-world applications. As a solution, Relay Node (RN) deployment strategies could help to improve WSNs. This fact is known as the Relay Node Placement Problem (RNPP), which is an NP-hard optimization problem. This paper proposes to address two Multi-Objective (MO) formulations of the RNPP. The first one optimizes average energy cost and average sensitivity area. The second one optimizes the two previous objectives and network reliability. The authors propose to solve the two problems through a wide range of MO metaheuristics from the three main groups in the field: evolutionary algorithms, swarm intelligence algorithms, and trajectory algorithms. These algorithms are the Non-dominated Sorting Genetic Algorithm II (NSGA-II), Strength Pareto Evolutionary Algorithm 2 (SPEA2), Multi-Objective Evolutionary Algorithm based on Decomposition (MOEA/D), Multi-Objective Artificial Bee Colony (MO-ABC), Multi-Objective Firefly Algorithm (MO-FA), Multi-Objective Gravitational Search Algorithm (MO-GSA), and Multi-Objective Variable Neighbourhood Search Algorithm (MO-VNS). The results obtained are statistically analysed to determine if there is a robust metaheuristic to be recommended for solving the RNPP independently of the number of objectives.Publication Design, implementation, and validation of a piezoelectric device to study the effects of dynamic mechanical stimulation on cell proliferation, migration and morphology(MDPI, 2020-01-01) Mojena Medina, Dahiana; Martinez Hernandez, Marina; De La Fuente Lopez, Miguel; Garcia Isla, Guadalupe; Posada Román, Julio Enrique; Jorcano Noval, José Luis; Acedo Gallardo, Pablo; Ministerio de Educación, Cultura y Deporte (España); Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)Cell functions and behavior are regulated not only by soluble (biochemical) signals but also by biophysical and mechanical cues within the cells' microenvironment. Thanks to the dynamical and complex cell machinery, cells are genuine and effective mechanotransducers translating mechanical stimuli into biochemical signals, which eventually alter multiple aspects of their own homeostasis. Given the dominant and classic biochemical-based views to explain biological processes, it could be challenging to elucidate the key role that mechanical parameters such as vibration, frequency, and force play in biology. Gaining a better understanding of how mechanical stimuli (and their mechanical parameters associated) affect biological outcomes relies partially on the availability of experimental tools that may allow researchers to alter mechanically the cell's microenvironment and observe cell responses. Here, we introduce a new device to study in vitro responses of cells to dynamic mechanical stimulation using a piezoelectric membrane. Using this device, we can flexibly change the parameters of the dynamic mechanical stimulation (frequency, amplitude, and duration of the stimuli), which increases the possibility to study the cell behavior under different mechanical excitations. We report on the design and implementation of such device and the characterization of its dynamic mechanical properties. By using this device, we have performed a preliminary study on the effect of dynamic mechanical stimulation in a cell monolayer of an epidermal cell line (HaCaT) studying the effects of 1 Hz and 80 Hz excitation frequencies (in the dynamic stimuli) on HaCaT cell migration, proliferation, and morphology. Our preliminary results indicate that the response of HaCaT is dependent on the frequency of stimulation. The device is economic, easily replicated in other laboratories and can support research for a better understanding of mechanisms mediating cellular mechanotransduction.Publication Design and implementation of a multi-colour visible light communication system based on a light-to-frequency receiver(MDPI, 2019-06-01) Martínez-Ciro, Roger Alexander; López-Giraldo, Francisco Eugenio; Betancur-Perez, Andrés Felipe; Luna-Rivera, Jose MartínColour-shift keying (CSK) is a visible light communication (VLC) modulation scheme used in the existing IEEE 802.15.7 standard. In CSK, information is transmitted by changing the light intensities of the RGB LEDs. In this work, a low-complexity VLC system is proposed using CSK modulation and a novel receiver based on a light-to-frequency (LTF) converter. At the receiver, CSK symbols are interpreted and decoded in terms of frequencies, which are processed by a counter module of a generic microcontroller, thus avoiding the use of analog-to-digital converters (ADCs), which results in a low-cost VLC system. The main contributions of this work are summarized in the following key points: (1) A low-complexity receiver for CSK modulation is introduced; (2) A particle swarm optimization (PSO) algorithm for CSK constellation design is suggested considering the restrictions of the LTF based receiver; (3) Experimental and theoretical validation is perfomed for the proposed multi-colour VLC system. The results show that this system can provide a transmission speed of 100 kbps using a 4-CSK-LTF constellation for a symbol error rate (SER) of 10−4 and a signal to noise ratio (SNR) around 35 dB. These results suggest that the analysed system could find applications on those scenarios where low transmission speeds and ease of deployment are the goals.Publication Pilot-Tone Assisted 16-QAM Photonic Wireless Bridge Operating at 250 GHz(IEEE, 2021-05-01) González Guerrero, Luis; Shams, Haymen; Fatadin, Irshaad; Wu, John Edward; Fice, Martin J.; Naftaly, Mira; Seeds, Alwyn J.; Renaud, Cyril C.(copyright) 1983-2012 IEEE.A photonic wireless bridge operating at a carrier frequency of 250 GHz is proposed and demonstrated. To mitigate the phase noise of the free-running lasers present in such a link, the tone-Assisted carrier recovery is used. Compared to the blind phase noise compensation (PNC) algorithm, this technique exhibited penalties of 0.15 and 0.46 dB when used with aggregated Lorentzian linewidths of 28 and 359 kHz, respectively, and 20 GBd 16-quadrature amplitude modulation (QAM) signals. The wireless bridge is also demonstrated in a wavelength division multiplexing (WDM) scenario, where five optical channels are generated and sent to the Tx remote antenna unit (RAU). In this configuration, the full band from 224 to 294 GHz is used. Finally, a 50 Gbit/s transmission is achieved with the proposed wireless bridge in single channel configuration. The wireless transmission distance is limited to 10 cm due to the low power emitted by the uni-Travelling carrier photodiode used in the experiments. However, link budget calculations based on state-of-The-Art THz technology show that distances >1000 m can be achieved with this approach.Publication Solving the manufacturing cell design problem through an autonomous water cycle algorithm(MDPI, 2019-11-06) Soto, Ricardo; Crawford, Broderick; Lanza Gutiérrez, José Manuel; Olivares, Rodrigo; Camacho, Pablo; Astorga, Gino; Fuente-Mella, Hanns de la; Paredes, Fernando; Castro, CarlosMetaheuristics are multi-purpose problem solvers devoted to particularly tackle large instances of complex optimization problems. However, in spite of the relevance of metaheuristics in the optimization world, their proper design and implementation to reach optimal solutions isnot a simple task. Metaheuristics require an initial parameter configuration, which is dramatically relevant for the efficient exploration and exploitation of the search space, and therefore to the effective finding of high-quality solutions. In this paper, the authors propose a variation of the water cycle inspired metaheuristic capable of automatically adjusting its parameter by using the autonomous search paradigm. The goal of our proposal is to explore and to exploit promising regions of the search space to rapidly converge to optimal solutions. To validate the proposal, we tested 160 instances of the manufacturing cell design problem, which is a relevant problem for the industry, whose objective is to minimize the number of movements and exchanges of parts between organizational elements called cells. As a result of the experimental analysis, the authors checked that the proposal performs similarly to the default approach, but without being specifically configured for solving the problem.