Modeling photopolymerization processes for enhanced part quality

When laser paths cross or when new layers are cured on top of existing layers, residual stresses are generated as the cure shrinkage of fresly gelled resin is constrained forming deflection or curl of the layers. The finite element method has been used to model the structural deformatins arising from the stereolithography build process. This includes the first layer polymerized during printing of an overhanged layer as subsequent rows of tetra-elements. The model does not include any resin beyond the external boundaries of the solid part. A standard linear static solution is carried out in order to get the properties of the fresh-resin

Modelling of the mechanical behaviour of the photopolymerization processes of resins intended for additive manufacturing (AMT) using laserstereolithography: The influence on part quality

This study presents a simplified model of the polymerization process of photo-cured epoxy resin, with the aim of finding theoretical values for the mechanical properties of the material in its transition stage from liquid to solid state, approximating these properties to a single figure at the instant of its gelation in the time denominated as tg. By evaluating a phenomenon observed during the fabrication of samples using a stereolithography additive manufacturing printer, it is hoped to fit a model that will replicate the mechanical forces undergone by the manufactured part. The introduction of new hypotheses to simplify the case under study will be tested by simulating these cases using the finite element method, taking the values obtained from previous publications that used experimental and analytical analysis so that the congruence of the results will be constant throughout the model. Finding these theoretical values will help develop future criteria for the feasibility of manufacturing the parts using laser stereolithography and therefore have a direct influence on the quality of the end part

Micro-vascular shape-memory polymer actuators with complex geometries obtaines by laser stereolithography

In our work we present the complete development process of geometrically complex microvascular shape-memory polymer actuators. The complex geometries and three-dimensional networks are designed by means of computer aided design resources. Manufacture is accomplished, in a single step, by means of laser stereolithography, directly from the computeraided design files with the three dimensional geometries of the different actuators under development. To our knowledge, laser stereolithography is applied here for the first time to the development of shape memory polymer devices with complex geometries and inner microvasculatures for their activation using a thermal fluid. Final testing of the developed actuators helps to validate the approach and to put forward some present challenges

Lithography-based ceramic manufacture (LCM) of auxetic structures: present capabilities and challenges

Auxetic metamaterials are known for having a negative Poisson's ratio (NPR) and for displaying the unexpected properties of lateral expansion when stretched and densification when compressed. Even though a wide set of micro-manufacturing resources have been used for the development of auxetic metamaterials and related devices, additional precision and an extension to other families of materials is needed for their industrial expansion. In addition, their manufacture using ceramic materials is still challenging. In this study we present a very promising approach for the development of auxetic metamaterials and devices based on the use of lithography-based ceramic manufacturing. The process stands out for its precision and complex three-dimensional geometries attainable, without the need of supporting structures, and for enabling the manufacture of ceramic auxetics with their geometry controlled from the design stage with micrometric precision. To our knowledge it represents the first example of application of this technology to the manufacture of auxetic geometries using ceramic materials. We have used a special three-dimensional auxetic design whose remarkable NPR has been previously highlighted

Lithography-based addtive manufacture of ceramic biodevices with design-controlled surface topographies

The possibility of manufacturing textured materials and devices, with surface properties controlled from the design stage, instead of being the result of machining processes or chemical attacks, is a key factor for the incorporation of advanced functionalities to a wide set of micro- and nanosystems. High-precision additive manufacturing (AM) technologies based on photopolymerization, together with the use of fractal models linked to computer-aided design tools, allow for a precise definition of final surface properties. However, the polymeric master parts obtained with most commercial systems are usually inadequate for biomedical purposes and their limited strength and size prevents many potential applications. On the other hand, additive manufacturing technologies aimed at the production of final parts, normally based on layer-by-layer melting or sintering ceramic or metallic powders, do not always provide the required precision for obtaining controlled micro-structured surfaces with high-aspect-ratio details. Towards the desired degree of precision and performance, lithography-based ceramic manufacture is a remarkable option, as we discuss in the present study, which presents the development of two different micro-textured biodevices for cell culture. Results show a remarkable control of the surface topography of ceramic parts and the possibility of obtaining design-controlled micro-structured surfaces with high-aspect-ratio micro-metric details

Identifying new potential areas for the establishment of the invasive raccoon (Procyon lotor) in Europe

The concern about biological invasions is growing worldwide because implies a serious threat to biodiversity conservation, the high economic costs of management measures and, in many cases, involves a health risk for humans, since some species are host of pathogens that are transmitted to humans. The raccoon (Procyon lotor), a medium-size carnivore native from North America, is a good example of invasive species. Its high ecological plasticity has allowed it to adapt successfully to different ecosystems in Europe and Asia, where the species has been introduced due to: releases for hunting, fur farms escapes and more recently the pet trade. The successful raccoon’s expansion in Europe poses a threat to biodiversity conservation. In this study we review and update the distribution of this species in Europe, with the aim of identifying new potential areas for the establishment of the raccoon in Europe. According to this updating of presences and a set of predictors variables (environmental and human activity), we applied the Favourability Function to detect favourable areas for the species. Anthropic variables have a significant relevance explaining the current occurrence of this invasive species. The favourability model detected central Europe and the United Kingdom as the areas with the best conditions for the species, being related to territories with a high percentage of urban area. This may indicate that the invasion pattern could still be reflecting the places of releases. In this sense, the favourable areas for the presence of the raccoon highlight unoccupied zones with high potential to be established in the near future. Our results provide useful information to increase the monitoring effort and develop prevention plans to optimize effective control measuresUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Biogeographical modelling of the species competitive interactions: a fuzzy logic approach

The environmental conditions of a territory determine to what degree the species are related to each other and to the environment. Species distribution models are used to establish relationships between the environment and the species distribution. Models based on fuzzy logic through the Favourability Function also allow the análisis of relationships between distributions of different taxa. By considering how the environment influences competition relationships between two species, we proposed the biogeographic analysis of three posible scenarios: i) sympatric coexistence; ii) environmental segregation; and iii) competitive exclusion. In order to identify these scenarios in different pairs of species with overlapping distributions, the Favourability Function and fuzzy logic tools were applied. Specifically, for each case, the favourability for each species and the fuzzy intersection between them, or “shared favourability”, was calculated. For each case, the relationship between the favourability for each species and the shared favourability was analyzed, highlighting the areas where either environmental segregation, competitive exclusion or sympatric coexistence is predicted. The results showed that the Favourability Function is a useful tool for analyzing large-scale biogeographical outcomes of ecological interactions between species.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

¿Cuáles son las zonas más susceptibles de ser ocupadas por el mapache (Procyon lotor) en Europa? La detección temprana como herramienta clave en la gestión de una invasión.

La preocupación sobre las especies invasoras está creciendo a nivel global debido a la amenaza que suponen para la conservación de la biodiversidad. El mapache es un mesocarnívoro generalista, nativo de Norteamérica, con una gran plasticidad ecológica, lo cual le ha permitido adaptarse sin dificultad a diferentes ecosistemas. En la actualidad, la exitosa expansión del mapache en Europa supone una amenaza para la conservación de la biodiversidad de dimensiones aún desconocidas. En este estudio se revisa y actualiza la distribución de esta especie en Europa con el objetivo de identificar nuevas áreas potenciales para su establecimiento. Se realizaron modelos de distribución de especies, para lo cual se aplicó la regresión logística multifactorial a partir de la distribución actualizada del mapache y un conjunto de variables ambientales explicativas. Finalmente, a partir de la probabilidad generada, se aplicó el algoritmo de la Función de Favorabilidad. Las variables antrópicas tuvieron un papel importante en la explicación de la distribución actual de esta especie invasora en Europa, lo cual indicaría que el patrón de invasión aún refleja los lugares de suelta. Los resultados indican que en Centro Europa y parte de Reino Unido se dan las condiciones de mayor favorabilidad para la presencia de la especie. El modelo también identificó algunas zonas de la península ibérica favorables para la especie, coincidiendo en gran parte con lugares de presencia estable y reproducción confirmada. Las áreas favorables para la presencia del mapache no sólo detectaron las zonas donde ya se ha establecido la especie, sino que señalan aquellos territorios donde el riesgo de invasión puede ser elevado en un futuro cercano. Esta aproximación permite identificar aquellas zonas en las que focalizar los esfuerzos de monitoreo y desarrollar planes de prevención, ayudando a optimizar las medidas de gestión.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

¿Dónde hay mapaches y dónde intensificar su búsqueda en la Península Ibérica?

Las invasiones biológicas son unas de las principales amenazas para la conservación de la biodiversidad. A nivel global hay una preocupación creciente sobre las especies invasoras, tanto por los daños medioambientales que pueden producir, como por el impacto económico asociado a su gestión y, en algunos casos, el riesgo para la salud pública. El mapache (Procyon lotor) es un mesocarnívoro nativo de Norteamérica y Centroamérica con una gran plasticidad ecológica, lo que le ha permitido adaptarse sin dificultad a diferentes ambientes fuera de su área original. En la actualidad, el mapache ocupa diferentes zonas de Eurasia, siendo la Península Ibérica una de ellas. La presencia de mapaches en los ecosistemas ibéricos puede suponer una amenaza para la biodiversidad, de una dimensión aún desconocida. En este estudio se revisa y actualiza la distribución de la especie en Europa. A partir de la distribución obtenida, se pretende identificar aquellas zonas que suponen nuevas áreas para su establecimiento potencial en la Península Ibérica. Se realizaron modelos de distribución de especies, para lo cual se aplicó la función de favorabilidad a la distribución actualizada del mapache y a un conjunto de variables ambientales. Las variables antrópicas tuvieron un papel importante para explicar la distribución actual de esta especie invasora, lo cual indicaría que el patrón de invasión aún refleja los lugares de suelta. El modelo obtenido muestra zonas muy favorables para la especie que incluye los lugares de presencia estable y reproducción confirmada, en el centro y noroeste de España. Además, las áreas favorables identifican otras zonas con favorabilidad elevada y que aún no han sido ocupadas por el mapache. Estos territorios son aquellos donde el riesgo de invasión puede ser elevado en un futuro cercano, como es el caso del norte de la provincia de León. Esta aproximación permite identificar aquellas zonas en las que focalizar los esfuerzos de monitoreo.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

English Is It! (ELT Training Series) Vol. 17

The Research group From English Acquisition to English Learning and Teaching is registered at the Institute of Professional Development Teaching (IDP-ICE), at the University of Barcelona. The group, founded and led by Lourdes Montoro (September 2013 - June 2021), has involved 28 teachers and professionals. 7 of them have been members of the group, and, together with 21 guest authors, have presented their work in the publication which she also created, and coordinated to fulfill the objectives of the pedagogical project which she had devised: English Is It! (ELT Training Series) (Vols. 1-15)..