Biomass-derived carbon materials for energy storage applications

Energy storage systems are an essential link in the implementation of renewable energies and in the development of electric vehicles, which are needed to reduce our dependence on fossil fuels and the emission of greenhouse gases. Various technologies have been proposed for energy storage based on different working principles, including lithium-ion batteries, emerging sodium-ion batteries and electric-double layer capacitors. Besides the quest for improving key aspects such as energy and power densities, current research efforts are devoted to foster the manufacturing of more environmentally friendly devices using sustainable materials. Carbon-based electrodes hold considerable promise in such terms due to their low cost, tailorable morphology and microstructure, and the possibility of processing them by direct carbonization of eco-friendly and naturally-available biomass resources. The main goal of this thesis is to develop carbon materials from biomass resources and study their applications as electrode for lithium-ion batteries, sodium-ion batteries and electric-double layer capacitors. En route towards that goal, it also aims at expanding our understanding of the microstructural changes of biomass-derived carbons with varying processing conditions and their effect on the electrochemical performance for each of these technologies. The first part of this work reports on the synthesis of graphitized carbon materials from biomass resources by means of an Fe catalyst, and the study of their electrochemical performance as anode materials for lithium-ion batteries (LIBs). Peak carbonization temperatures between 850 °C and 2000 ºC were covered to study the effect of crystallinity, surface and microstructural parameters on the anodic behavior, focusing on the first-cycle Coulombic efficiency, reversible specific capacity and rate performance. Reversible capacities of Fe-catalyzed biomass-derived carbons were compared to non-catalyzed hard carbon and soft carbons materials heated up to 2800 ºC. Moreover, in-situ characterization experiments were carried out to advance our understanding of the mechanisms responsible for catalytic graphitization. The second part of this work reports a comprehensive study on the structural evolution of hard carbons from biomass resources as a function of carbonization temperature (800 - 2000 ºC), and its correlation with electrochemical properties as anode materials for sodium-ion batteries (SIBs). Synchrotron X-ray total scattering experiments were performed and the associated atomic pair distribution function (PDF) extracted from the data to access quantitative information on local atomic arrangement in these amorphous materials at the nanoscale, as well as its evolution with increasing processing temperature. Then, electrochemical properties and the storage mechanisms involved on Na ions insertion into hard carbon structures at each characteristic potential regions were elucidated and correlated with microstructural properties. Finally, the third part of this work reports on the synthesis of nanostructured porous graphene-like materials from biomass resources using an explosion-assisted activation strategy by nitrate compounds and Ni as a graphitization catalyst. The thermal behavior during carbonization as well as the resulting microstructural and surface properties were evaluated at two different processing temperatures, 300 and 1000 ºC. Finally, their application as electrode materials for electric-double layer capacitors (EDLCs) and LIBs is investigated, with a view to their performance under high charge/discharge specific current densities experiments.Premio Extraordinario de Doctorado U

Evaluation and improvement of the motivational profile of compulsory secondary education students.

Treball Final de Grau en Psicologia. Codi: PS1048. Curs: 2018/2019.The present study is based on the Educational Situation Quality Model (MOCSE) proposed by Doménech (2017). For more information about the characteristics of this model, you can access the following web address (https://sites.google.com/a/uji.es/plataforma-web-para-la-mejora-de-lamotivacion-escolar-y-el-aprendizaje-en-educacion-secundaria/) where the article cited will be found. The study has two objectives, first, to analyze the relationship between the intention to learn (success expectancies) and the involvement of students in their learning process. Secondly, to examine the relationship between the intention to learn (overall value of subject-matter) and the involvement of students in their learning process. Specifically, we want to test two hypotheses. The first (H1) predicts a positive and significant relationship between success expectancies and active coping strategies (focused on the problem); and vice versa, a negative and significant relationship between success expectancies and passive coping strategies (focused on avoidance), while the second (H2) predicts a positive and significant relationship between the overall value of subject-matter and active coping strategies (centered in the problem); and vice versa, a negative and significant relationship between the overall value of subject-matter and passive coping strategies (focused on avoidance). The sample consists of 74 students from the Caminás, Bajo Aragón, Juan Bautista Porcar and Alfonso XIII High Schools. The data on the variables that were used in this study, has been obtained through the application of a questionnaire based on the Quality of Education Situation Model (MOCSE) proposed by Doménech (2017). In order to analyze the hypotheses proposed, bivariate Pearson correlations have been carried out. After obtaining the results and their subsequent statistical treatment, we can affirm that there is a relationship between the success expectancies and active coping and also, between the overall value of subject-matter and active coping strategies, which allows to determine determining -> that the motivational profile of the students present in our sample is favorable. Finally, we present a proposal for improvement and guidance for teachers with the aim of preventing any deficiency in the motivational climate of the classroom.El presente estudio se basa en el Modelo de Calidad Situación Educativa (MOCSE) propuesto por Doménech (2017). Para conocer las características de este modelo, se puede consultar la siguiente dirección web (https://sites.google.com/a/uji.es/plataforma-web-para-la-mejora-de-la-motivacionescolar-y-el-aprendizaje-en-educacion-secundaria/) donde se encontrara el artículo citado. El estudio tiene dos objetivos, por una parte examinar la relación entre la intención de aprender (expectativas de éxito) y la implicación de los alumnos en su aprendizaje y por otra parte, examinar la relación entre la intención de aprender (Valor de la materia) y la implicación de los alumnos en su aprendizaje. Concretamente queremos probar dos hipótesis. La primera (H1) pronostica una relación positiva y significativa entre las expectativas de éxito y las estrategias de afrontamiento activo (centradas en el problema); y viceversa, una relación negativa y significativa entre las expectativas de éxito y las estrategias de afrontamiento pasivo (centradas en la evitación), mientras que la segunda (H2) pronostica una relación positiva y significativa entre el valor de la materia y las estrategias de afrontamiento activo (centradas en el problema); y viceversa, una relación negativa y significativa entre el valor de la materia y las estrategias de afrontamiento pasivo (centradas en la evitación). La muestra está formada por 74 alumnos de los centros IES El Caminàs, IES Bajo Aragón, IES Juan Bautista Porcar y IES Alfons XIII. La información de las variables utilizadas se ha conseguido a través de la aplicación de un cuestionario basado en el Modelo de Calidad Situación Educativa (MOCSE) propuesto por Doménech (2017). Para examinar las hipótesis planteadas se han llevado a cabo correlaciones bivariadas de Pearson. Tras la obtención de los resultados y su posterior tratamiento estadísticos, podemos afirmar que existe una relación entre las expectativas de éxito y afrontamiento activo y, también, entre el valor de la materia y las estrategias de afrontamiento activo, lo que permite determinar que el perfil motivacional del alumnado de nuestra muestra es favorable. Finalmente, presentamos una propuesta de mejora y orientaciones para los profesores con el objetivo de prevenir cualquier deficiencia en el clima motivacional del aula

Does Inertia Pay Off? Empirical assessment of an evolutionary-ecological model of human capital decisions at firm level

This paper empirically assesses the validity of a model which combines organisational ecology and evolutionary theory to analyse human capital accumulation decisions at firm level. The main argument of the model is that factors underlying the process of plants’ reproduction, especially the process of fission, must be isolated and related to the economic motivations of employers to hire top educated and highly skilled people. Inert behaviour in human capital accumulation decisions stands here as a rational outcome. Logistic estimates, based on the whole population of plants of the Portuguese textiles, provide statistical evidence corroborating the fission hypothesis. This evidence constitutes a critical examination of the mainstream economics concerning the demand side of human capital.Human capital; population ecology theory; evolutionary theory; Inertia; Fission; textiles; Portugal

Non-Price Competition and Exchange Rate Pass-Through

A substantial body of empirical works document that exchange rate pass-through to consumer prices is incomplete. This evidence has cast doubts on the ability of flexible exchange rates to generate expenditure switching. In a dynamic stochastic discrete-time duopoly game, non-price competition among .rms endogenously originates a degree of exchange ratepass-through close to zero together with an expenditure switching e¤ect stronger than in the standard models.pass-through, non-price competition, expenditure switching

Ground-state properties of bosons in three- and two-dimensional traps

We study trapped systems of bosons at zero temperature in three and two dimensions. Conditions are fulfilled for the application of Gross-Pitaevskii theory with a positive scattering length. Series expansions for ground-state properties are obtained in both the noninteracting and the strong-coupling (Thomas-Fermi) limits. From these expansions, analytic estimates are presented in the form of two-point Pad\'e approximants. We explicitly show the approximants for the total energy per particle and the chemical potential.Comment: LaTeX, 4 pages, 3 ps figure

On the Charter of Fundamental Rights of the European Union and the EU accession to the European Convention on Human Rights

After a short presentation of the Charter of Fundamental Rights and its features, the paper is focused on the European Union?s accession to the European Convention of Human Rights. As part of the Treaty of Lisbon implementation, this process is not an easy one. The author intends to identify and raise questions on this process, and to emphasise some technical and procedural difficulties, by comparing the two main European human rights systems. Europe has to face many changes and challenges: the recent entry into force of the Treaty of Lisbon, the “new status” of the Charter of fundamental rights (as a legally binding instrument) and the beginning of the process of EU?s accession to the European Convention of Human Rights. This paper is intended to point out some aspects of this new era of the European construction.human rights, European human rights law, accession, Treaty of Lisbon, European Convention

Inter-Regional Wage Differentials in Portugal: An Analysis Across the Wage Distribution

Typically, studies on regional wage differentials are based on ordinary least squares (OLS) estimates. Quantile regression is an alternative approach which allows these differences to be studied across the whole wage distribution. In this study, the quantile regression framework is considered for the analysis of regional wage differences in Portugal. The findings reveal significant differences in wage equations coefficients between regions for the various quantiles. Furthermore, it is concluded that the regional wage differentials and the components explained by differences in endowments and differences in returns increase across the whole wage distribution