Influence of synthetic method on the properties of La0.5Ba0.5FeO3 SOFC cathode

Power Point presentado en The Energy and Materials Research Conference - EMR2015 celebrado en Madrid (España) entre el 25-27 de febrero de 2015Perovskite type (ABO3) oxides have been widely studied as SOFC cathode materials at high temperatures. Given that several of the challenges hindering SOFC technology are consequence of the high operation temperature (about 1000ºC) [1,2], an important goal is to reduce it to 600-800ºC. To minimize this effect new perovskite-type mixed ionic-electronic conducting oxides have been widely studied as promising IT-SOFC cathodes. Among them, iron perovskites (LSF) seem to be good candidates mainly for their appropriate thermal expansion match with YSZ electrolytes and their good catalytic activity for the oxygen reduction [3,4]. The properties of these compounds and thus their cell performance depends on several factors: the right choice of A and B elements, the amount of doping cations (A1-xAx) and some structural parameters such as the tolerance factor [5], the average size of the A-site cations () and the A cation size disorder (σ2(rA)). Studies on the influence of the hole-doping (x) in the A-site of LSF perovskites have shown good cathode performances in compounds with intermediate doping levels [6]. The change of and σ2(rA) indicate that better performances are observed for highest and lowest σ2(rA) [7]. External parameters, such as the synthetic method, are also important factors that influence the final properties [8]. In this sense it has been observed that porosity, grain size and morphology of the compounds strongly depend on the sample preparation techniques. In this research, a La0.5Ba0.5FeO3 perovskite has been synthesized by two different methods (ceramic and glycine-nitrate routes) in order to study the synthetic method influence on the properties of this compound as IT-SOFC cathode material. This composition has been chosen due to its intermediate hole doping level (0.5) and high average size of the A-site cations ( = 1.48 Å, when rA are standard 12-coordinate ionic radii), these parameters, according with previous studies should show interesting properties for its use as SOFC cathode. It has been observed that the two La0.5Ba0.5FeO3 compounds show different room temperature crystal structure depending on the synthesis route. The sample obtained by the ceramic method has higher oxygen vacancy content, but in the other hand the SEM micrographs show that glycine-nitrate process leads to a compound with porous structure and particles with nanometric grain sizes. At 700 or 800ºC the electrical conductivity of both samples is similar but the sample obtained by glycine-nitrate route shows better electrochemical performance. The ceramic sample has lower adherence than the glycine counterpart and this derivates in higher values of polarization resistance. It is believed that this is a consequence of the heterogenous morphology of this sample. Therefore, it seems that the glycine-nitrate synthetic method is a more appropriate technique for preparing perovskite cathodes

Negative correlation of doping and conductivity in Ln1-xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x≤0.25) perovskites prepared by combustion synthesis as anode materials for SOFCs

A series of chromite perovskites with the general formula Ln1−xMxCr0.9Ni0.1O3 (Ln = La and/or Nd; M = Sr and/or Ca; x ≤ 0.25) has been prepared by three combustion synthesis routes using a different combustible substance each time: glycine, urea and sucrose. In order to isolate the effect of divalent dopant concentration from the A cation steric effects, the whole group has a fixed mean A cation radius, ≈ 1.22 Å, and cation size disorder, σ2(rA) ≈ 0.0001 Å2, but variable doping x. Their crystal structure, microstructure, electrical properties and expansion coefficients have been investigated on the basis of their possible use as anode materials for intermediate temperature solid oxide fuel cells (SOFC). Cell parameters, grain sizes, expansion coefficients and conductivities all are found to be dependent on x and the combustible substance used. The most interesting relationship is the negative dependence of the conductivity with x under H2 atmosphere: conductivity decreases with doping which is the opposite to the expected behavior for a p-type doped perovskites and has not been reported before.Ministerio de Economía y Competitividad, MAT2016-76739-R // Dpto. Educación, Política Lingüística y Cultura of the Basque Government, IT-630-1

Sensitivity Evaluation Method for Aerospace Digital Systems with Collaborative Hardening

Complexity of current digital systems and circuits involves new challenges in the field of hardening and measuring circuits sensitivity under SEEs. In this work, a new solution for evaluating the SEU sensitivity of space systems based on using programmable logic devices is proposed. This solution is able to perform a deep analysis of fault effects in systems with hardware functionality distribution, taking into account the high complexity of the hardware nodes (complex programmable logic devices) and their collaborative hardening properties

Nuevas cromitas de composición La1-xMxCr0.9Ni0.1O3(M=Sr, ND, Ca; x<0.3) con tamaño de A y desorden fijados, para su uso como ánodos de pilas SOFCs

Póster presentado en el XIV Congreso Nacional de Materiales (CNMAT) en Gijón (España), del 8 al 10 de Junio de 2016El desarrollo de nuevos materiales y la optimización de las técnicas de fabricación son claves para conseguir reducir la temperatura de operación, y con ello, el coste, de sistemas de generación de energía como las pilas de combustible de óxido sólido, SOFC [1]. Los métodos de combustión, se proponen como la vía de síntesis para la preparación de materiales a emplear en esta tecnología [2]. Los ánodos habituales de las pilas SOFC son cermets de metales como el níquel o cobre junto con el material de electrolito (ceria o circonia dopadas). Entre los principales problemas de esos ánodos está el de la deposición de carbón cuando se usan combustibles económicos como el metano. En este sentido, se ha observado que el óxido de cromo dopado con estroncio (La,Sr)CrO3, además de ser un buen conductor electrónico tipo p, no cataliza la deposición de carbono, por lo que es un ánodo potencial para la oxidación directa de metano. Las cromitas son buenas conductoras de la electricidad (dopadas o sin dopar), pero su actividad catalítica mejora considerablemente si el dopaje se da con metales de transición (Mn,Fe,Co,Ni,Cu) en la posición del cromo [3]. En esta investigación se ha realizado un estudio del efecto del dopaje en A, pero fijando el tamaño promedio de A (en 1.22 Å) y el desorden de esta posición (0.0001 Å2), que está asociado a la diferencia de tamaños de esos elementos. Se han sintetizado cuatro compuestos de la serie La1‐xMxCr0.9Ni0.1O3 (M=Sr, Nd, Ca o sus combinaciones; con x=0.10, 0.15, 0.20 y 0.25) mediante el método de combustión con glicina‐nitrato. Los resultados preliminares por difracción de rayos X en muestra policristalina indican que son fases rómbicas con simetría Pnma. En el presente trabajo se mostrarán los resultados de tamaño de grano de los mismos, estudiados por microscopía electrónica de barrido (MEB) y los datos de conductividad electrónica y dilatometría (TEC).Esta investigación ha sido financiada por el Dpto. Educación, Política Lingüística y Cultura del Gobierno Vasco (IT-630-13), Ministerio de Economía y Competitividad (MAT2013-42092-R)y el Fondo Europeo de Desarrollo Regional (FEDER)

Modeling emergence of sterile oat (Avena sterilis ssp. ludoviciana) under semiarid conditions

Winter wild oat [Avena sterilisssp. ludoviciana (Durieu) Gillet & Magne; referred to as A. sterilis here] is one of the major weed species of the Avena genus, given its high competitive ability to infest cereal crops worldwide, with special concern in Spain. A nine-location field experiment was established across Spain where a total of 400 A. sterilis seeds per location were sowed in four replicates in autumn 2016 to monitor the emergence during two growing seasons in dryland conditions. The data were used to test the prediction ability of previously published thermal (TT) and hydrothermal time (HTT) models and to develop new models, if required. Overall, the average percentage of emergence was 30% during the first season and 21% during the second season. In both seasons, the main emergence flush occurred between November and February. According to the phenological stage, A. sterilis achieved the tillering earlier in southern sites, between November 25 and the end of December, compared with northern sites, where this stage was reached at the end of January. The newly developed model described the emergence with precision, using three cardinal temperatures to estimate the TT. The three car dinal points were established at −1.0, 5.8, and 18.0 C for base (Tb), optimum (To), and ceiling temperature (Tc), while the base water potential (Ψb) was established at −0.2 MPa for the HTT estimation. This study contributes to improving prediction of the emergence of A. sterilis and provides knowledge for decision support systems (DSS) for the control of this weed.We would like to thank first the funding institutions, Cátedra Adama and the Spanish Weed Science Society (SEMh), with special mention of Cátedra Adama, which financed the article publishing charges. Also, JT acknowledges support from the Spanish Ministry of Science, Innovation and Universities (grant Ramon y Cajal RYC2018-023866-I). We also want to thank the students and the technicians that have helped with the fieldwork for this experiment in different sites, without whose help data col lection would have been more difficult. No conflicts of interest have been declared

La estimación de proporciones mediante técnicas Bayesianas

The estimation procedures based on Bayes' Theorem are still an unusual option in many of the environments of classic parametric inference. The aim of this paper is to show an effective scheme for the use of Bayesian estimation of unknown parameters. We have opted to focus on the estimation of parameters under the assumption of a binomial model, so that it can be followed by all those situations that meet the aforementioned probabilistic model. This approximation was studied in comparison with the classic parametric approximation, both in its point version and by means of interval estimation. On a study, by simulating samples of several sizes, we obtained empirical evidence regarding the advantage of the Bayesian procedure.ResumenLos procedimientos de estimación basados en el teorema de Bayes son inusuales en los diferentes ámbitos de aplicación de la inferencia paramétrica clásica. El objetivo de este trabajo es presentar un esquema para la estimación bayesiana de parámetros bajo los supuestos de un modelo binomial. El procedimiento Bayes se estudia en comparación con la aproximación paramétrica cl??sica, ambas opciones, en su versión puntual y mediante intervalos de estimación. Se presenta también un estudio de simulación con diferentes tamaños muestrales en el que se ponen de manifiesto las ventajas del procedimiento bayesiano.AbstractThe estimation procedures based on Bayes' Theorem are still an unusual option in many of the environments of classic parametric inference. The aim of this paper is to show an effective scheme for the use of Bayesian estimation of unknown parameters. We have opted to focus on the estimation of parameters under the assumption of a binomial model, so that it can be followed by all those situations that meet the aforementioned probabilistic model. This approximation was studied in comparison with the classic parametric approximation, both in its point version and by means of interval estimation. On a study, by simulating samples of several sizes, we obtained empirical evidence regarding the advantage of the Bayesian procedure

Plan de contingencia para los servicios de medicina intensiva frente a la pandemia COVID-19

In January 2020, the Chinese authorities identified a new virus of the Coronaviridae family as the cause of several cases of pneumonia of unknown aetiology. The outbreak was initially confined to Wuhan City, but then spread outside Chinese borders. On 31 January 2020, the first case was declared in Spain. On 11 March 2020, The World Health Organization (WHO) declared the coronavirus outbreak a pandemic. On 16 March 2020, there were 139 countries affected. In this situation, the Scientific Societies SEMICYUC and SEEIUC, have decided to draw up this Contingency Plan to guide the response of the Intensive Care Services. The objectives of this plan are to estimate the magnitude of the problem and identify the necessary human and material resources. This is to provide the Spanish Intensive Medicine Services with a tool to programme optimal response strategies

¿Deben los modelos de emergencia de Lolium rigidum adaptarse en función de las condiciones climáticas?

Lolium rigidum es una problemática mala hierba a nivel mundial que en España produce importantes pérdidas de cultivo y económicas. El grupo de Biología y Agroecología de Malas hierbas (BAMh) de la SEMh ha estudiado la emergencia de esta especie durante dos campañas, 2016-17 y 2017-18. Para ello, se estableció un experimento en 10 localidades con una población de L. rigidum recolectada en Cataluña y se realizó el seguimiento de su emergencia cada 2-7 días. La emergencia se parametrizó en función de registros de temperatura y humedad procedentes de un datalogger enterrado a 2 cm. Los resultados muestran que el uso de los grados térmicos horarios es suficiente para una correcta descripción de la emergencia, desechando la opción de aplicar los grados hidrotérmicos, más comunes en los modelos de malas hierbas de invierno. Sin embargo, la emergencia de esta población de L. rigidum fue diferente en el centro y noreste de España respecto al sur, sugiriendo un efecto ambiental debido a su adaptación climática. Por ello, se plantea la necesidad de incluir poblaciones locales con el fin de adaptar el modelo desarrollado en el presente trabajo para los biotipos climáticos existentesPostprint (published version