Study of the charge correlation function in one-dimensional Hubbard heterostructures

We study inhomogeneous one-dimensional Hubbard systems using the density matrix renormalization group method. Different heterostructures are investigated whose configuration is modeled varying parameters like the on-site Coulomb potential and introducing local confining potentials. We investigate their Luttinger liquid properties through the parameter K_rho, which characterizes the decay of the density-density correlation function at large distances. Our main goal is the investigation of possible realization of engineered materials and the ability to manipulate physical properties by choosing an appropriate spatial and/or chemical modulation.Comment: 6 pages, 7 figure

Biomimetic flow fields for proton exchange membrane fuel cells: A review of design trends

Bipolar Plate design is one of the most active research fields in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) development. Bipolar Plates are key components for ensuring an appropriate water management within the cell, preventing flooding and enhancing the cell operation at high current densities. This work presents a literature review covering bipolar plate designs based on nature or biological structures such as fractals, leaves or lungs. Biological inspiration comes from the fact that fluid distribution systems found in plants and animals such as leaves, blood vessels, or lungs perform their functions (mostly the same functions that are required for bipolar plates) with a remarkable efficiency, after millions of years of natural evolution. Such biomimetic designs have been explored to date with success, but it is generally acknowledged that biomimetic designs have not yet achieved their full potential. Many biomimetic designs have been derived using computer simulation tools, in particular Computational Fluid Dynamics (CFD) so that the use of CFD is included in the review. A detailed review including performance benchmarking, time line evolution, challenges and proposals, as well as manufacturing issues is discussed.Ministerio de Ciencia, Innovación y Universidades ENE2017-91159-EXPMinisterio de Economía y Competitividad UNSE15-CE296

Relocation and seismotectonic interpretation of the seismic swarm of August – December of 2012 in the Linares area, northeastern Mexico

We relocated 52 events of 2.5 ≤ Mc ≤ 3.6 from a seismic sequence of over 250 events that occurred during July-December 2012 southwest of the Linares area, northeastern Mexico. To examine this swarm four seismic stations were installed in the region and operated during different time periods from September to December. Relocation of the swarm showed that the earthquake hypocentral depths were at 8 (±5) km, and the time residuals had values ≤ 0.38 s. The fault plane solutions were generated for individual earthquakes and through the use of the composite mechanism technique. The focal mechanism solutions show pure reverse faulting; the SW dipping NNW – SSE trending nodal plane is the inferred fault plane (strike ~150°, dip ~50° and rake ~67°), which reveals that maximum horizontal stress (SHmax > Shmin > Sv) predominates in the area. RESUMEN En este trabajo relocalizamos 52 sismos en el rango de 2.5 ≤ Mc ≤ 3.6 de una secuencia sísmica de más de 250 eventos que ocurrió al suroeste de la ciudad de Linares, N.L., durante los meses de julio – diciembre de 2012, en el noreste de México. Para estudiar este enjambre se instalaron cuatro estaciones sismológicas en la región de interés, las cuales operaron durante diferentes periodos entre septiembre y diciembre. La relocalización de la secuencia demostró que las profundidades hipocentrales fueron de 8 (±5) km, y los residuales de los tiempos de arribo tuvieron valores ≤ 0.38 s. Se generaron soluciones del plano de falla para sismos individuales, así como a través de la técnica de mecanismos compuestos. La solución de los mecanismos focales encontrada corresponde con fallamiento inverso con rumbo NNW-SSE y buzamiento hacia el SW para el plano nodal inferido (rumbo ~150°, buzamiento ~50° y ángulo de deslizamiento ~67°), el cual revela que el esfuerzo horizontal máximo predomina en el área de estudio (SHmax > Shmin > Sv)

Investigating the melt pool properties and thermal effects of multi-laser diode area melting

Diode area melting (DAM) is a new additive manufacturing process that utilises customised architectural arrays of low-power laser diode emitters for high-speed parallel processing of metallic feedstock. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials. This investigation presents the first work investigating the melt pool properties and thermal effects of the multi-laser DAM process, modelling generated melt pools the unique thermal profiles created along a powder bed during processing. Using this approach process, optimisation can be improved by analysing this thermal temperature distribution, targeting processing conditions that induce full melting for variable powder layer thicknesses. In this work, the developed thermal model simulates the DAM processing of 316L stainless steel and is validated with experimental trials. The simulation indicates that multi-laser DAM methodology can reduce residual stress formation compared to the single point laser scanning methods used during selective laser melting

A técnica de rastreamento ocular e o estudo de modelos tácitos usando critérios subjetivos e comportamentais.

This article presents the results of a mixed-approach research study, where the eye movement of the undergraduate students of the Austral University of Chile is examined while solving a questionnaire where tacit models appear, related to mathematical infinity, to determine possible correlations between the ocular activity parameters and the level of difficulty of each of these models. The categories of the level of difficulty were established based on two types of criteria: a subjective one, through an evaluation, carried out by the subjects, and a behavioral one, related to obtaining the correct solution. The correlations of these criteria with the ocular activity parameters were identified and considered indicators of mental effort. The analysis of the data obtained allowed us to observe discrepancies in the categorization of the tacit models based on subjective and behavioral criteria. There was a negative correlation of the eye movement parameters with students' opinions about question difficulty levels. In contrast, a strong positive and significant correlation was noted between the presence of these models and the level of difficulty, determined by the percentage of correct answers. In turn, the percentage of correct answers had a strong positive and significant correlation with most of the ocular activity parameters. These results conclude that these parameters can be used to index this activity's tacit model's difficulty level.En este artículo se presentan los resultados de una investigación de enfoque mixto, donde se examina el movimiento ocular del estudiantado de pregrado de la Universidad Austral de Chile, mientras se resuelve un cuestionario donde aparecen modelos tácitos, relacionados con el infinito matemático, con el objetivo de determinar posibles correlaciones entre los parámetros de la actividad ocular y el nivel de dificultad de cada uno de estos modelos. Las categorías del nivel de dificultad se establecieron con base en dos tipos de criterios: uno subjetivo, mediante una evaluación realizada por los sujetos y uno conductual, relacionado con la obtención de la solución correcta. Se identificaron las correlaciones de estos criterios con los parámetros de actividad ocular, que se consideraron indicadores de esfuerzo mental. El análisis de los datos obtenidos permitió observar discrepancias en la categorización de los modelos tácitos, con base en criterios subjetivos y conductuales. Hubo una correlación negativa de los parámetros del movimiento ocular con las opiniones de los estudiantes, sobre el nivel de dificultad de las preguntas, mientras que se notó una fuerte correlación positiva y significativa entre la presencia de estos modelos y el nivel de dificultad, determinado por el porcentaje de respuestas correctas. A su vez, el porcentaje de respuestas correctas tuvo una fuerte correlación positiva y significativa con la mayoría de los parámetros de la actividad ocular. A partir de estos resultados, se concluye que, estos parámetros pueden tomarse como un índice del nivel de dificultad de los modelos tácitos presentes en una actividad.Este artigo apresenta os resultados de uma pesquisa de abordagem mista, onde foi examinado o movimento ocular do aluno de graduação da Universidade Austral do Chile, enquanto se responde um questionário onde aparecem modelos tácitos, relacionados ao infinito matemático, visando determinar possíveis correlações entre os parâmetros de atividade ocular e o nível de dificuldade de cada um desses modelos. As categorias do grau de dificuldade foram determinadas a partir de duas categorias de critérios: uma subjetiva, através de uma avaliação realizada pelos sujeitos, e uma comportamental, relacionada à obtenção da solução correta. Foram identificadas as correlações desses critérios com os parâmetros de atividade ocular, considerados indicadores de esforço mental. A análise dos dados obtidos permitiu observar discrepâncias na categorização dos modelos tácitos, com base em critérios subjetivos e comportamentais. Houve correlação negativa dos parâmetros de movimento ocular com as opiniões dos alunos, sobre o nível de dificuldade das questões, enquanto uma forte correlação positiva e significativa foi observada entre a presença desses modelos e o nível de dificuldade, determinado pela porcentagem de respostas corretas. No que concerne, a porcentagem de respostas corretas houve uma forte correlação positiva e significativa com a maioria dos parâmetros da atividade ocular. Segundo os resultados, conclui-se que esses parâmetros podem ser tomados como um índice do nível de dificuldade dos modelos tácitos existentes em uma atividade

A técnica de rastreamento ocular e o estudo de modelos tácitos usando critérios subjetivos e comportamentais.

This article presents the results of a mixed-approach research study, where the eye movement of the undergraduate students of the Austral University of Chile is examined while solving a questionnaire where tacit models appear, related to mathematical infinity, to determine possible correlations between the ocular activity parameters and the level of difficulty of each of these models. The categories of the level of difficulty were established based on two types of criteria: a subjective one, through an evaluation, carried out by the subjects, and a behavioral one, related to obtaining the correct solution. The correlations of these criteria with the ocular activity parameters were identified and considered indicators of mental effort. The analysis of the data obtained allowed us to observe discrepancies in the categorization of the tacit models based on subjective and behavioral criteria. There was a negative correlation of the eye movement parameters with students' opinions about question difficulty levels. In contrast, a strong positive and significant correlation was noted between the presence of these models and the level of difficulty, determined by the percentage of correct answers. In turn, the percentage of correct answers had a strong positive and significant correlation with most of the ocular activity parameters. These results conclude that these parameters can be used to index this activity's tacit model's difficulty level.En este artículo se presentan los resultados de una investigación de enfoque mixto, donde se examina el movimiento ocular del estudiantado de pregrado de la Universidad Austral de Chile, mientras se resuelve un cuestionario donde aparecen modelos tácitos, relacionados con el infinito matemático, con el objetivo de determinar posibles correlaciones entre los parámetros de la actividad ocular y el nivel de dificultad de cada uno de estos modelos. Las categorías del nivel de dificultad se establecieron con base en dos tipos de criterios: uno subjetivo, mediante una evaluación realizada por los sujetos y uno conductual, relacionado con la obtención de la solución correcta. Se identificaron las correlaciones de estos criterios con los parámetros de actividad ocular, que se consideraron indicadores de esfuerzo mental. El análisis de los datos obtenidos permitió observar discrepancias en la categorización de los modelos tácitos, con base en criterios subjetivos y conductuales. Hubo una correlación negativa de los parámetros del movimiento ocular con las opiniones de los estudiantes, sobre el nivel de dificultad de las preguntas, mientras que se notó una fuerte correlación positiva y significativa entre la presencia de estos modelos y el nivel de dificultad, determinado por el porcentaje de respuestas correctas. A su vez, el porcentaje de respuestas correctas tuvo una fuerte correlación positiva y significativa con la mayoría de los parámetros de la actividad ocular. A partir de estos resultados, se concluye que, estos parámetros pueden tomarse como un índice del nivel de dificultad de los modelos tácitos presentes en una actividad.Este artigo apresenta os resultados de uma pesquisa de abordagem mista, onde foi examinado o movimento ocular do aluno de graduação da Universidade Austral do Chile, enquanto se responde um questionário onde aparecem modelos tácitos, relacionados ao infinito matemático, visando determinar possíveis correlações entre os parâmetros de atividade ocular e o nível de dificuldade de cada um desses modelos. As categorias do grau de dificuldade foram determinadas a partir de duas categorias de critérios: uma subjetiva, através de uma avaliação realizada pelos sujeitos, e uma comportamental, relacionada à obtenção da solução correta. Foram identificadas as correlações desses critérios com os parâmetros de atividade ocular, considerados indicadores de esforço mental. A análise dos dados obtidos permitiu observar discrepâncias na categorização dos modelos tácitos, com base em critérios subjetivos e comportamentais. Houve correlação negativa dos parâmetros de movimento ocular com as opiniões dos alunos, sobre o nível de dificuldade das questões, enquanto uma forte correlação positiva e significativa foi observada entre a presença desses modelos e o nível de dificuldade, determinado pela porcentagem de respostas corretas. No que concerne, a porcentagem de respostas corretas houve uma forte correlação positiva e significativa com a maioria dos parâmetros da atividade ocular. Segundo os resultados, conclui-se que esses parâmetros podem ser tomados como um índice do nível de dificuldade dos modelos tácitos existentes em uma atividade

Aprendizaje de las construcciones euclidianas con GeoGebra: elementos de una actividad formativa para futuros profesores de matemáticas

El trabajo describe los elementos constituyentes de una actividad formativa diseñada para promover aprendizaje sobre las construcciones euclidianas con GeoGebra por futuros profesores de matemáticas. Comenzamos fijando posición respecto al aprendizaje de dicho saber, partiendo de la concepción histórico-cultural de aprendizaje como procesos de objetivación. Luego conceptualizamos el saber sobre las construcciones euclidianas con GeoGebra como un saber docente que se nutre desde lo disciplinario. Los elementos de la actividad incluyen el motivo, objetivo y metas de la formación, así como las tareas y su modo de implementación. Finalizamos con algunas consideraciones sobre la puesta en escena de la propuesta

Element-Specific Depth Profile of Magnetism and Stoichiometry at the La0.67Sr0.33MnO3/BiFeO3 Interface

Depth-sensitive magnetic, structural and chemical characterization is important in the understanding and optimization of novel physical phenomena emerging at interfaces of transition metal oxide heterostructures. In a simultaneous approach we have used polarized neutron and resonant X-ray reflectometry to determine the magnetic profile across atomically sharp interfaces of ferromagnetic La0.67Sr0.33MnO3 / multiferroic BiFeO3 bi-layers with sub-nanometer resolution. In particular, the X-ray resonant magnetic reflectivity measurements at the Fe and Mn resonance edges allowed us to determine the element specific depth profile of the ferromagnetic moments in both the La0.67Sr0.33MnO3 and BiFeO3 layers. Our measurements indicate a magnetically diluted interface layer within the La0.67Sr0.33MnO3 layer, in contrast to previous observations on inversely deposited layers. Additional resonant X-ray reflection measurements indicate a region of an altered Mn- and O-content at the interface, with a thickness matching that of the magnetic diluted layer, as origin of the reduction of the magnetic moment.Comment: 13 pages, 4 figures, supplemental material include

Vortex flow of downwind sails

This paper sets out to investigate the vortex flow of spinnaker yacht sails, which are low-aspect-ratio highly-cambered wings used to sail downwind. We tested three model-scale sails with the same sections but different twists over a range of angles of attack in a water tunnel at a Reynolds number of 21 000. We measured the forces with a balance and the velocity field with particle image velocimetry. The sails experience massively separated three-dimensional flow and leading-edge vortices convect at half of the free stream velocity in a turbulent shear layer. Despite the massive flow separation, the twist of the sail does not change the lift curve slope, in agreement with strip theory. As the angle of attack and the twist vary, flow reattachment might occur in the time-average sense, but this does not necessarily result in a higher lift to drag ratio as the vorticity field is marginally affected. Finally, we investigated the effect of secondary vorticity, vortex stretching and diffusion on the vorticity fluxes. Overall, these results provide new insights on the vortex flow and associated force generation mechanism of wings with massively separated flo