Analysis of the damping characteristics of two power electronics-based Devices using 'individual channel analysis and design'

A comparison of the capabilities of two quite distinct power electronics-based ‘flexible AC transmission systems’ devices is presented. In particular, the damping of low frequency electromechanical oscillations is investigated aiming at improving the performance of power systems. The comparison is made using frequency domain methods under the ‘individual channel analysis and design’ framework. A synchronous generator feeding into a system with large inertia is used for such a purpose. Two system configurations including compensation are analysed: (a) in series in the form of a thyristor-controlled series compensator, and (b) in shunt through a static VAr compensator featuring a damping controller. Analyses are carried out to elucidate the dynamic behaviour of the synchronous generator in the presence of the power electronics-based controllers and for the case when no controller is present. Performance and robustness assessments are given particular emphasis. The crux of the matter is the comparison between the abilities of the static VAr compensator and the thyristor-controlled series compensator to eliminate the problematic switch-back characteristic intrinsic to synchronous generator operation by using the physical insight afforded by ‘individual channel analysis and design’

Electrical conduction mechanisms of metal / high- T c superconductor (YBCO) interfaces

Current-voltage characteristics of Au/YBa2Cu3Ointerfaces (Au/YBCO), built on optimally-doped YBCO thin films, grown by pulsed laser deposition, were measured as a function of temperature in the 50 K to 270 K range, for two different resistance states. A non-trivial equivalent circuit model is proposed, which reveals the existence of a highly inhomogeneous scenario composed by two complex layers: one presenting both a non-linear Poole-Frenkel conduction as well as variable range hopping localization effects (probably associated with YBa2Cu3O6) mixed with a minor metallic phase, while the other is also composed by a mixture of YBCO with different oxygen contents, where a metallic ohmic phase still percolates. A microscopic description of the effects produced by the resistance switching is given, showing the evolution of carrier traps, localization effects and dielectric behavior for each state. The dielectric behavior is interpreted in terms of a Maxwell-Wagner scenario.Fil: Lanosa, Leandro Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Huhtinen, H. University of Turku; FinlandiaFil: Paturi, P. University of Turku; FinlandiaFil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Composites of Poly(3,4-ethylenedioxythiophene) and CoFe2O4 Nanoparticles: Composition Influence on Structural, Electrical, and Magnetic Properties

Composites of magnetic CoFe2O4 nanoparticles (MNP) in a poly(3,4-ethylenedioxythiophene) matrix at different ratios have been synthesized. Composites were characterized by electron microscopy, X-ray diffraction, thermal analysis, electrical conductivity, magnetization, and magnetoresistance studies. In the composites the MNP appear clustered, with an interparticle distance essentially constant, but where two regimes are distinguished for cluster separation: for high MNP concentrations an intercluster separation similar to the interparticle distance is found, while for low MNP contents the distance between clusters is larger than the interparticle separation. The electrical conductivity increases with polymer content, but being always far lower than general effective medium theory expectations. This indicates that the effect of MNP effect on polymer conduction is probably related to the generation of mechanical stress both by introducing additional scattering centers and by producing different arrangement of the polymer chains, compared with the pure PEDOT. The magnetization studies reveal the existence of the RKKY interaction, which couples ferromagnetically the MNP located in a cluster, while the dipolar interaction dominates the interaction between clusters. Magnetoresistance was studied for these composites, with a maximum value close to 0.7% at 0.7 T for the lowest polymer content. The magnetoresistance correlates very well with the reversible part of the magnetization, indicating that its possible origin should be associated with polymer mechanical deformation due to the magnetic-field-induced rotation of the MNP.Fil: Lanús Mendez Elizalde, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Molina, Fernando Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Antonel, Paula Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Concurrent ionic migration and electronic effects at the memristive TiOx/La1/3Ca2/3MnO3-x interface

The development of reliable redox-based resistive random-access memory devices requires understanding and disentangling concurrent effects present at memristive interfaces. We report on the fabrication and electrical characterization of TiOx/La1/3Ca2/3MnO3-x microstructured interfaces and on the modeling of their memristive behavior. We show that a careful tuning of the applied external electrical stimuli allows controlling the redox process between both layers, obtaining multilevel non-volatile resistance states. We simulate the oxygen vacancies dynamics at the interface between both oxides, and successfully reproduce the experimental electrical behavior after the inclusion of an electronic effect, related to the presence of an n-p diode at the interface. The formation of the diode is due to the n- and p-character of TiOx and La1/3Ca2/3MnO3-x, respectively. Our analysis indicates that oxygen vacancies migration between both layers is triggered after the diode is polarized either in forward mode or in reverse mode above breakdown. Electrical measurements at different temperatures suggest that the diode can be characterized as Zener-type. The advantages of our junctions for their implementation in RRAM devices are finally discussed.Fil: Roman Acevedo, Wilson Stibens. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Ferreyra, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Sánchez, M.J.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Gay, R.. Centro de Investigación Cooperativo nanoGUNE; EspañaFil: Rubi, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentin

Selective activation of memristive interfaces in TaOx-based devices by controlling oxygen vacancies dynamics at the nanoscale

The development of novel devices for neuromorphic computing and non-traditional logic operations largely relies on the fabrication of well controlled memristive systems with functionalities beyond standard bipolar behavior and digital ON-OFF states. In the present work we demonstrate for Ta2O5-based devices that it is possible to selectively activate/deactivate two series memristive interfaces in order to obtain clockwise or counter-clockwise multilevel squared remanent resistance loops, just by controlling both the electroforming process and the (a)symmetry of the applied stimuli, and independently of the nature of the used metallic electrodes. Based on our thorough characterization, analysis and modeling, we show that the physical origin of this electrical behavior relies on controlled oxygen vacancies electromigration between three different nanoscopic zones of the active Ta2O5-x layer: a central one and two quasi-symmetric interfaces with reduced TaO2-h(y) layers. Our devices fabrication process is rather simple as it implies the room temperature deposition of only one CMOS compatible oxide - Ta-oxide - and one metal, suggesting that it might be possible to take advantage of these properties at low cost and with easy scability. The tunable opposite remanent resistance loops circulations with multiple - analogic - intermediate stable states allows mimicking the adaptable synaptic weight of biological systems and presents potential for non-standard logic devices.Fil: Ferreyra, Cristian Daniel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Sánchez, M.J.. Comisión Nacional de Energía Atómica; ArgentinaFil: Aguirre, Myriam. Universidad de Zaragoza; EspañaFil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Bengió, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: Lecourt, J.. Centre National de la Recherche Scientifique; FranciaFil: Lüders, U.. Centre National de la Recherche Scientifique; FranciaFil: Rubi, Diego. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentin

La COVID-19 y el turismo en el Perú. Análisis y propuestas ante un nuevo escenario

The COVID-19 pandemic has generated a global crisis that has impacted all human activities. One of the hardest hit is tourism which, by its very nature, faces the difficult and unavoidable challenge of creating the conditions to ensure, as far as possible, the health of tourists, generating in them the confidence necessary for a gradual return to activity. This article addresses this issue from an analysis of the current situation of tourism in Peru, to a set of proposals for its reactivation, both at a general level and in certain key subsectors.La pandemia de la COVID-19 ha generado una crisis de escala global que ha impactado en todos los quehaceres de la humanidad. Uno de los más golpeados es el turismo que, por su propia naturaleza, se enfrenta al difícil e ineludible reto de crear las condiciones para asegurar, en la medida de lo posible, la salud de los turistas, generando en ellos la confianza necesaria para un paulatino retorno a la actividad. El presente artículo aborda este tema desde un análisis de la situación actual del turismo en el Perú, hasta un conjunto de propuestas para su reactivación, tanto a nivel general como en determinados subsectores clave

Electric pulse-induced resistive switching in ceramic YBa2 Cu3 O7 - δ / Au interfaces

We show the existence of a reversible, complementary and polarity dependant electric pulse-induced resistance (EPIR) switching effects in Au / YBa2 Cu3 O7 - δ ceramic superconductor interfaces. Non-volatile high and low resistance states and transition regions between them are obtained as a function of the amplitude and polarity of the pulsing voltage. Relaxation processes of the resistivity after applying the pulses, not associated with heating effects, are also observed. We also report on the temperature sensitivity of these resistance hysteresis switching loops, where both the difference between high and low resistance states and the voltage needed to produce the switching decrease with increasing temperature. Our results are consistent with a mechanism for the EPIR effect based on oxygen electromigration. © 2009 Elsevier B.V. All rights reserved.Fil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Dynamical behaviour of the resistive switching in ceramic YBCO/metal interfaces

Studies related to the dynamics of resistive switching (RS) in ceramic YBCO/metal interfaces were performed. The change in interface resistance during the application of square pulses and its current-voltage (I-V) characteristics were measured. The obtained non-linear current dependence of the differential resistance can be very well reproduced by modelling the electrical behaviour of the interface with simple circuit elements. The RS produces defined changes in the parameters of the circuit model that reveal the particular dynamics of the mechanism beneath the resistance change in complex oxide/metal interfaces. © 2011 IOP Publishing Ltd.Fil: Acha, Carlos Enrique. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Física de Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Retentivity of RRAM devices based on metal/YBCO interfaces

The retention time of the resistive state is a key parameter that characterizes the possible utilization of the RRAM devices as a non - volatile memory device. The understanding of the mechanism of the time relaxation process of the information state may be essential to improve their performances. In this study we examine RRAM devices based on metal / YBCO interfaces in order to comprehend the physics beneath the resistive switching phenomenon. Our experimental results show that after producing the switching of the resistance from a low to a high state, or vice versa, the resistance evolves to its previous state in a small but noticeable percentage. We have measured long relaxation effects on the resistance state of devices composed by metal (Au, Pt) / ceramic YBCO interfaces in the temperature range 77 K - 300 K. This time relaxation can be described by a stretched exponential law that is characterized by a power exponent n = 0.5, which is temperature independent, and by a relaxation time τ that increases with increasing the temperature. These characteristics point out to a non-thermally assisted diffusion process that could be associated with oxygen (or vacancy) migration and that produces the growth of a conducting (or insulating) fractal structure. © 2011 Materials Research Society.Fil: Schulman, Alejandro Raúl. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Física de Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Acha, Carlos Enrique. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Física de Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin