Habilidades de visualización de estudiantes de primaria en actividades de geometría espacial

La forma de usar la visualización ayuda a caracterizar a los estudiantes con talento matemático (Ramírez, 2012). Los investigadores adoptan varios puntos de vista para analizar esta relación (Riu y otros, 2007). Entendiendo la visualización como “el tipo de razonamiento basado en el uso de elementos visuales o espaciales, tanto mentales como físicos” (Gutiérrez, 1996, p. 9), planteamos dos objetivos de investigación: i) analizar las habilidades de visualización (Del Grande, 1990) puestas en juego por un grupo natural de 21 estudiantes de 6º de Primaria, con diferentes grados de talento matemático, al resolver un bloque de actividades de manipulación de cubos y ii) relacionar el uso de esas habilidades con el talento matemático de los alumnos, evaluado mediante los tests PMA (Thurstone, 2005) y PEM (Benavides, 2008)

Optimization of All-Renewable Generation Mix According to Different Demand Response Scenarios to Cover All the Electricity Demand Forecast by 2040: The Case of the Grand Canary Island

[EN] The decarbonization of the electric generation system is fundamental to reaching the desired scenario of zero greenhouse gas emissions. For this purpose, this study describes the combined utilization of renewable sources (PV and wind), which are mature and cost-effective renewable technologies. Storage technologies are also considered (pumping storage and mega-batteries) to manage the variability in the generation inherent to renewable sources. This work also analyzes the combined use of renewable energies with storage systems for a total electrification scenario of Grand Canary Island (Spain). After analyzing the natural site¿s resource constraints and focusing on having a techno-economically feasible, zero-emission, and low-waste renewable generation mix, six scenarios for 2040 are considered combining demand response and business as usual. The most optimal solution is the scenario with the maximum demand response, consisting of 3700 MW of PV, around 700 MW of off-shore wind system, 607 MW of pump storage, and 2300 MW of EV batteries capacity. The initial investment would be EUR 8065 million, and the LCOE close to EUR 0.11/kWh, making the total NPC EUR 13,655 million. The payback is 12.4 years, and the internal rate of return is 6.39%This study has been in part supported by the projects: "Design Of a Hybrid Renewable Microgrid System" and "Microred Inteligente Hibrida de Energias Renovables para Solucionar el Trilema Agua-Alimentacion-Energia en Una Comunidad Rural de Honduras"Vargas-Salgado, C.; Berna, C.; Escrivá, A.; Díaz-Bello, D. (2022). Optimization of All-Renewable Generation Mix According to Different Demand Response Scenarios to Cover All the Electricity Demand Forecast by 2040: The Case of the Grand Canary Island. Sustainability. 14(3):1-30. https://doi.org/10.3390/su1403173813014

Performance of a transmutation advanced device for sustainable energy application

Preliminary studies have been performed to design a device for nuclear waste transmutation and hydrogen generation based on a gas-cooled pebble bed accelerator driven system, TADSEA (Transmutation Advanced Device for Sustainable Energy Application). In previous studies we have addressed the viability of an ADS Transmutation device that uses as fuel wastes from the existing LWR power plants, encapsulated in graphite in the form of pebble beds, cooled by helium which enables high temperatures (in the order of 1200 K), to generate hydrogen from water either by high temperature electrolysis or by thermochemical cycles. For designing this device several configurations were studied, including several reflectors thickness, to achieve the desired parameters, the transmutation of nuclear waste and the production of 100 MW of thermal power. In this paper new studies performed on deep burn in-core fuel management strategy for LWR waste are presented. The fuel cycle on TADSEA device has been analyzed based on both: driven and transmutation fuel that had been proposed by the General Atomic design of a gas turbine-modular helium reactor. The transmutation results of the three fuel management strategies, using driven, transmutation and standard LWR spent fuel were compared, and several parameters describing the neutron performance of TADSEA nuclear core as the fuel and moderator temperature reactivity coefficients and transmutation chain, are also presente

An Extended Linear Discontinuous Method for One-group Fixed Source Discrete Ordinates Problems with Isotropic Scattering in Slab Geometry

[EN] Nowadays, the obtainment of an accurate numerical solution of fixed source discrete ordinates problems is relevant in many areas of engineering and science. In this work, we extend the hybrid Finite Element Spectral Green¿s Function method (FEM-SGF), originally developed to solve eigenvalue diffusion problems, for fixed source problems using as a mathematical model, the discrete ordinates formulation in one energy group with isotropic scattering in slab geometry. This new method, Extended Linear Discontinuous Discrete Ordinates (ELD-SN), is based on the use of neutron balance equations and the construction of a hybrid auxiliary equation. This auxiliary equation combines a linear discontinuous approximation and spectral parameters to approximate the neutron angular flux inside the cell. Numerical results for benchmark problems are presented to illustrate the accuracy and computational performance of our methodology. ELD-SN method is free from spatial truncation errors in S 2 quadrature, and generate good results in the other quadrature sets. This method is more accurate than the conventional Diamond Difference (DD) and Linear Discontinuous (LD) methods, but surpassed by the Spectral Green¿s Function (SGF) method, for quadrature order greater than twoRivas-Ortiz, I.; Dominguez, D.; Hernandez, C.; Iglesias, S.; Escrivá, A. (2019). An Extended Linear Discontinuous Method for One-group Fixed Source Discrete Ordinates Problems with Isotropic Scattering in Slab Geometry. TEMA: Tendências em Matemática Aplicada e Computacional (Online). 20(1):61-76. https://doi.org/10.5540/tema.2019.020.01.061S617620

Experiments in free falling and downward cocurrent annular flows-Characterization of liquid films and interfacial waves

[EN] Falling liquid films and downward cocurrent flows in rounded shape pipes have been experimentally studied during the last decades, estimating the evolution of its major characteristics. The most important variables during the formation and growth of surface waves in falling downward flows have been measured using conductance probes. The main objective of the current research paper is to study the dependency of the characteristics of the thin liquid layer for downward cocurrent annular flows. The GEPELON experimental facility consists of a vertical pipe with 3.8 m of useful test length. Two pipe diameters have been analysed in this experimental study, 42 and 30 mm, in which the range covered by the liquid Reynolds number varies between 570 and 8500 and 800-7900 respectively, while the gas Reynolds numbers vary from 0 to 7.9.10(4) and from 0 to 1.1.10(5) respectively for the mentioned pipe diameters. Up to five conductance probes have been placed along the pipes test sections to capture the liquid film thickness fluctuations along time at different distances of the pipe entrance for both developing and fully developed regions. After the study and analysis of the experimental data, the central point of this paper has been the development of new correlations for the liquid film thicknesses and the two major properties of the interfacial waves. Their adjustment procedure has been carried out in terms of dimensionless numbers, aiming to provide more general relationships. In particular, the magnitudes that characterise the interface behavior have been measured, particularly film thicknesses, average disturbance wave amplitudes, and disturbance wave frequencies for each boundary condition. An additional part of the document contains an extensive comparison between the results obtained in this study and the data and expressions of other authors. It has been confirmed the significant dispersion existing among different researchers, especially when analysing variables related to the interfacial waves. This highlights the lack of knowledge in some aspects even today. The different correlations proposed have been calculated based on the best fit of the data from all the series of experiments carried out in this study. Comparisons of the behaviour of these correlations with data from other researchers have also been included.This research is supported by the EXMOTRANSIN project ENE2016-79489-C2-1-P included in the I + D Spanish plan. Funding for open access charge: CRUE-Universitat Politècnica de València.Rivera-Durán, Y.; Berna, C.; Muñoz-Cobo, JL.; Escrivá, A.; Córdova, Y. (2022). Experiments in free falling and downward cocurrent annular flows-Characterization of liquid films and interfacial waves. Nuclear Engineering and Design. 392:1-23. https://doi.org/10.1016/j.nucengdes.2022.11176912339

Experimental Measurements and CFD Results of Liquid Film Thickness in Vertical Downward Air-Water Annular Flow

[EN] Annular gas¿liquid flows have been extensively studied over the years. However, the nonlinear behavior of the interface is still currently the subject of study by multiple researchers worldwide. The appearance of a liquid layer on the wall and its turbulent behavior support the heat exchange of multiple systems in the industrial field. Research in this area allows the optimization of these installations as well as the analysis of possible safety problems if the liquid film disappears. This study first shows some of the most important findings obtained in the GEPELON experimental facility (GEneración de PElícula ONdulatoria or Wavy Film Generator). The facility was built in order to analyze the behavior of the liquid film in annular downward air¿water flow. The experimental range of the inlet conditions is 800¿8000 for the ReL and 0¿110,000 for the Reg. Measurements for the mean film thickness show a fairly good agreement with the empirical correlations and the measurements of other authors. One of the most demanded applications of this type of measurements is the validation of computational dynamics or CFD codes. Therefore, the experiment has been modeled using Ansys CFX software, and the simulation results have been compared with the experimental ones. This article outlines some of the reasons why two-phase flow simulations are currently challenging and how the codes are able to overcome them. Simulation predictions are fairly close to the experimental measurements, and the mean film thickness evolution when changing the boundary conditions also shows a good agreement.The authors are indebted to the plan of I+D support of the EXMOTRANSIN project ENE2016-79489-C2-1-P.Rivera-Durán, Y.; J. L. Muñoz-Cobo; A. Escrivá; C. Berna; Y. Córdova (2022). Experimental Measurements and CFD Results of Liquid Film Thickness in Vertical Downward Air-Water Annular Flow. International Journal of Computational Methods and Experimental Measurements. 10(2):93-103. https://doi.org/10.2495/CMEM-V10-N2-93-1039310310

Victimization and peer and parents attachment: The mediating effect of regulatory emotional self-efficacy

Studies of the Spanish adolescent population has concluded that victimization is related to lack of emotional regulation and impulse control. Therefore, if a victim is unable to recognize, understand and regulate their emotions, this can result in rejection by their peers. A cross-sectional study was conducted to examine regulatory emotional self-efficacy as a possible mediator in the association between peer and parents attachment and victimization. Adolescents (n = 563) completed Regulatory Emotional Self-Efficacy, Inventory of Parents and Peer Attachment and Kid at School questionnaires. Structural equation models (SEMs) were used to predict a latent variable of victimization with parents and peer attachment, emphasizing the mediating role of regulatory emotional self-efficacy, as comprised by a positive and a negative aspect. Results showed that peer attachment had an indirect negative effect, through perceived self-efficacy, in managing a positive effect in victimization, while father attachment had an indirect negative affect, through perceived self-efficacy, in managing a negative affect in victimization, and Mother attachment had no statistically significant indirect effect in victimization. This study suggests that the roles of parents and peers, and also between mothers and fathers, are different in relation to the perception of victimization of adolescents. Findings provide relevant information regarding implications for prevention and intervention in victimization

The controllability of a monetary aggregate in EMU

La consideracion de un agregado monetario como objetivo intermedio de la politica monetaria exige que esa definicion de liquidez mantenga una relacion de estabilidad con el objetivo final y que su evolucion pueda ser controlada por parte del banco central. Este documento analiza esta segunda cuestion, centrandose en las posibilidades que tendria el Banco Central Europeo de controlar efectivamente un agregado monetario si decidiera considerarlo como objetivo intermedio. En el trabajo se revisan los mecanismos a traves de los cuales la politica monetaria puede controlar la evolucion de la cantidad de dinero, y se examinan las propiedades empiricas de la demanda de dinero en la Union Monetaria Europea (UME) y en un pais, como Alemania, en el que se han venido fijando objetivos en terminos de un agregado monetario. El documento pone de manifiesto que las condiciones para ejercer un control adecuado de la cantidad de dinero en la UME son notablemente mas desfavorables de lo que resultan en Alemania. (ac) (jle) (em) (jp) (mac

Development of Conductivity Sensors for Multi-Phase Flow Local Measurements at the Polytechnic University of Valencia (UPV) and University Jaume I of Castellon (UJI)

[EN] This paper describes all the procedures and methods currently used at UPV (Universitat Politécnica de Valencia) and UJI (University Jaume I) for the development and use of sensors for multi-phase flow analysis in vertical pipes. This paper also describes the methods that we use to obtain the values of the two-phase flow magnitudes from the sensor signals and the validation and cross-verification methods developed to check the consistency of the results obtained for these magnitudes with the sensors. First, we provide information about the procedures used to build the multi-sensor conductivity probes and some of the tests performed with different materials to avoid sensor degradation issues. In addition, we provide information about the characteristics of the electric circuits that feed the sensors. Then the data acquisition of the conductivity probe, the signal conditioning and the data processing including the device that have been designed to automatize all the measurement process of moving the sensors inside the channels by means of stepper electric motors controlled by computer are shown in operation. Then, we explain the methods used for bubble identification and categorization. Finally, we describe the methodology used to obtain the two-phase flow information from the sensor signals. This includes the following items: void fraction, gas velocity, Sauter mean diameter and interfacial area concentration. The last part of this paper is devoted to the conductance probes developed for the annular flow analysis, which includes the analysis of the interfacial waves produced in annular flow and that requires a different type of sensorThe authors are indebted to the support received from MINECO for the project MODEXFLAT ENE2013-48565-C2-1-P and ENE2013-48565-C2-2-P.Muñoz-Cobo, JL.; Chiva, S.; Mendez, S.; Monrós, G.; Escrivá, A.; Cuadros-Orón, JL. (2017). Development of Conductivity Sensors for Multi-Phase Flow Local Measurements at the Polytechnic University of Valencia (UPV) and University Jaume I of Castellon (UJI). Sensors. 17(5):1-35. https://doi.org/10.3390/s17051077S13517