Partial Discharges in Electrical Machines for the More Electric Aircraft—Part I: A Comprehensive Modeling Tool for the Characterization of Electric Drives Based on Fast Switching Semiconductors

This paper proposed a modelling approach for the comprehensive analysis of high-frequency challenges in electrical drives designed for aerospace applications, in particular the overvoltage at the machine terminals and the voltage distribution within windings. After a separate description of the models for the estimation of these insulation stress sources, the combined model was detailed. The main benefit of developing a combined, flexible and comprehensive tool is that both overvoltage at machine terminals and uneven voltage distribution can be calculated simultaneously, without neglecting the voltage overshoot when estimating the voltage distribution (and vice versa). In fact, an accurate calculation of the terminal overvoltage is necessary to provide a good estimation of the voltage within winding turns since its waveform shape can be quite different with respect to the converter output, even with cables of a few meters. A case study based on a real aerospace application was considered to investigate the model validity and accuracy. Experimental results were performed on a complete system comprising a SiC-based converter, a connecting cable and a machine stator, proving the simulation model accuracy in terms of peak voltages of both the line-to-line terminal voltage and the turn voltage distribution across the first turns, which are the most relevant quantities for the sake of this study as well as for the investigations of the subsequent companion papers. In the forthcoming papers, the effects of different rise times and cable lengths on the inception of partial discharges will be investigated through fast parametric simulation carried out using the proposed combined model. The feasibility of using conventional insulation systems for aircraft applications using SiC drives fed by a ±270 V DC bus voltage will be discussed, with the aim of signaling and finding solutions to improve the overall reliability

Red de monitoreo de eventos hidrológicos extremos en la vertiente sur del Río Salado, provincia de Buenos Aires

Se ha demostrado que los eventos hidrológicos extremos en la provincia de Buenos Aires constituyen una característica de la misma, considerando los balances de agua en el suelo (zona no saturada) de vital importancia. Estos balances indican que la cuenca del Río Salado es la más sensible a los excesos hídricos, y la región sudoeste de la provincia, la más perjudicada durante las deficiencias hídricas (Scarpati y Capriolo, 2013). Por ello toman importancia las tareas de prevención como son las obras civiles y las redes de monitoreo de las condiciones principales que intervienen en este tipo de fenómenos, con el fin de dar alerta a las autoridades competentes ya sea en períodos de inundaciones o de sequías. Una red de monitoreo comprende las actividades relativas a la recolección de datos, diseñados y procesados con un objetivo definido (Guía de prácticas hidrológicas, 1994). Consiste en un arreglo de sensores que conforman las estaciones y en un sistema de comunicación que permite la transmisión de los datos a los centros de monitoreo. Su principal función es el estudio de procesos fundamentales que se dan en el medio ambiente, como así también proveer alerta de amenazas, como por ejemplo de inundaciones, erupciones volcánicas, terremotos, tsunamis, etc. (Hart y Martinez, 2006). El monitoreo y la recolección de datos hidro-meteorológicos es importante debido a que los eventos naturales como precipitaciones, temperaturas, velocidades del viento, entre otros, son irrepetibles en la naturaleza (Fattorelli y Fernández, 2011). El diseño de una red hidro-meteorológica comprende principalmente el conocimiento hidrológico y climático de la zona en la cual se establecerá

Astrophysics with the Laser Interferometer Space Antenna

Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy as it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and other space-based instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA's first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed: ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or intermediate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help make progress in the different areas. New research avenues that LISA itself, or its joint exploitation with studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Mixed-Mode PWM for High-Performance Stepping Motors

This paper describes the realization of a high performance drive based on stepping motors, with specific reference to the optimal choice of pulse width modulation (PWM). An original modulation technique is proposed that allows, in conjunction with current feedback, to achieve high performances together with a reduced current ripple. A prototype DSP based drive was realized for a small size stepping motor