Discrete Element Model of Cement-based Materials by Additive Manufacturing

The aim of the paper is the simulation of cement-based materials by the discrete element method (DEM) and its application to 3D printing, also known as additive manufacturing. DEM is a way of simulating discrete matter and it captures the dual nature of granular media which behaves both like a solid and a fluid. DEM is a very useful tool for the study of the mechanical properties of granular materials, such as compressive strength or wear. Numerical modelling of granular materials can be used to study the microscopic behaviour of rocks and similar materials (such as concretes, ceramic materials and different composite materials). These materials can be simulated as particles with an interaction of bonding between them. Previous work of the research group has employed discrete element methodology to study the wear behaviour of concrete. The numerical analysis will allow us to study innovative multilayer components of cement-based materials. The flexural behaviour of multilayer components will be simulated. These components are the object of the multidisciplinary research project in which additive manufacturing of structural components using cement-based materials is studied

An alternative approach to estimate any subdaily extreme of rainfall and wind from usually available records

A wide variety of engineering applications requires the use of maximum values of rainfall intensity and wind speed related to short recording intervals, which can often only be estimated from available less exhaustive records. Given that many locations lack exhaustive climatic records that would allow accurate empirical correlations between different recording intervals to be identified, generic equations are often used to estimate these extreme values. The accuracy of these generic estimates is especially important in fields such as the study of wind-driven rain, in which both climatic variables are combined to characterise the phenomenon. This work assesses the reliability and functionality of some of these most widespread generic equations, analysing climatic datasets gathered since 2008 in 109 weather stations in Spain and the Netherlands. Considering multiple recording intervals at each location, it is verified that most of these generic estimations, used especially in the study of wind-driven rain, have functional limitations and can cause significant errors when characterising both variables for subdaily intervals and extreme conditions. Finally, an alternative approach is proposed to accurately extrapolate extreme values of both variables related to any subdaily recording interval in a functional manner and from any available records. © 2021, The Author(s)

Microreactor with integrates temperature control for the synthesis of CdSe nanocrystals

The recent needs in the nanosciences field have promoted the interest towards the development of miniaturized and highly integrated devices able to improve and automate the current processes associated to the efficient nanomaterials production. Herein, a green tape based microfluidic system to perform high temperature controlled synthetic reactions of nanocrystals is presented. The device, which integrates both, the microfluidics and a thermally controlled platform, was applied to the automated and continuoussynthesis of CdSe quantum dots. Since temperature can be accurately regulated as required, sizecontrolled and reproducible quantum dots could be obtained by regulating this parameter and the molar ratio of precursors. The obtained nanocrystals were characterized by UV-Vis and fluorescencespectrophotometries. The band width of the emission peaks obtained indicates a narrow size distribution of the nanocrystals, which confirms the uniform temperature profile applied for each synthetic process, being the optimum temperature at 270° C (Full Width at Half Maximum = 40 nm). This approach allows a temperature controlled, easy, low cost and automated way to produce quantum dots in organic media, enhancing its application from laboratory-scale to pilot-line scale processes.This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) through projects CTQ2009-12128 and the Consolider Ingenio 2010 project CSD2006 -12 and Catalonia 15 Government through SGR 2009 -0323

Bridge–structure interaction analysis of a new bidirectional and continuous launching bridge mechanism

This paper presents a numerical study of the structural interaction between a bridge and a new continuous device for launching heavy structures using the force of friction. In this way, it provides a great contribution for the civil engineering field focused on a new method for launching bridges by a continuous and bidirectional mechanism. A non-linear finite element model using contact elements studies the structural interaction between the bridge and the new device. Bridge and device interaction are studied using linear and non-linear contact behavior. The substructuring technique is used for the bridge modeling in order to reduce the overall degrees of freedom. This technique allows the selection of the best arrangement for two mechanism models placed under the webs of the bridge: two parallel arrangements where external device is opposite or behind the internal one, and other arrangement with devices in series. Furthermore, the non-uniform load distribution over the mechanism was studied during the launching process. With this methodology, it is possible to study the structural behavior of the mechanism taking into account the real load distribution applied for the bridge during the launching process.This work was partially financed with FEDER funds by the Spanish Ministry of Science and Innovation through the Research Project BIA2012-31609 and the Gijon City Council through the SV-13-GIJON-1.7 project. We would also like to thank Swanson Analysis Inc. for the use of the ANSYS University research program and Workbench simulation environment. Finally, we would like to acknowledge the help of the Spanish Ministry of Economics and Competitiveness through the Research Project ALCANZA, IPT-380000-2010-012 INNPACTO program

Design, fabrication and characterization of microreactors for high temperature syntheses

Microfluidic reactors offer many potential advantages in several research and industrial fields such as processes intensification, which includes a better reaction control (kinetics and thermodynamics), a high throughput and a safer operational environment (reduced manipulation of dangerous reagents and low sub-products generation). Nevertheless, scaling-down limitations appear concerning the materials used in the fabrication of microreactors for most of the liquid-phase reactions, since they usually require high temperatures (up to 300 °C), solvents and organic reagents. In this work, the development of a set of modular and monolithic microreactors based on the integration of microfluidics and a thermal platform (sensor/high-temperature heater) is proposed to perform high temperature reactions. The reliability and performance of both configurations were evaluated through an exhaustive characterization process regarding their thermal and microfluidic performance. Obtained results make the devices viable for their application in controlled and reproducible synthetic processes occurring at high temperatures such as the synthesis of quantum dots. The proposed microfluidic approach emerge as an engaging tool for processes intensification, since it provides better mass and temperature transfer than conventional methods with a reduction not only of the size and energy consumption, but also of by-products and reagents consumption.This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) through projects CTQ2009-12128 and the Consolider Ingenio 2010 project CSD2006 -12 and Catalonia Government through SGR 2009 -0323

Assessment of lightweight concrete thermal properties at elevated temperatures

Structural lightweight concrete (LWC) has recently acquired research importance because of its good thermal insulation properties. However, there is a lack of knowledge about its thermal properties at elevated temperatures. The thermal properties, such as thermal conductivity and specific heat, of porous LWC vary depending on the aggregates, air voids, and moisture content of the LWC in question. To study these effects, in this paper, we measured the thermal properties of three types of structural LWCs at different temperatures, combining different characterization techniques, namely, differential scanning calorimetry (DSC), laser flash analysis (LFA), and modified transient plane source (MTPS). Bulk density and porosity were also evaluated. Specific heat is analyzed by the DSC technique from 20 to 1000 °C and the MTPS technique from 20 to 160 °C. Thermal conductivity is studied using MTPS and LFA techniques at temperatures ranging from 20 to 160 °C and 100 to 300 °C, respectively. The results indicate that the thermal properties of LWC are highly affected by moisture content, temperature, and porosity. For LWC, the current Eurocodes 2 and 4 assume a constant value of specific heat (840 J/kg°C). This research reveals variability in temperatures near 150, 450, and 850 °C due to endothermic reactions. Furthermore, for low temperatures, the higher the porosity, the higher the thermal conductivity, while, at high temperatures, the higher the porosity, the lower the thermal conductivity. Thus, Eurocodes 2 and 4 should be updated accordingly. This research contributes to a deeper understanding and more accurate prediction of LWC's effects on thermal properties at elevated temperatures.This research was funded by FICYT and the Spanish Ministry of Science, Innovation, and Universities, co-financed with FEDER funds under the Research Projects PGC2018-098459-B-I00 and FC-GRUPIN-IDI/2018/000221. Finally, the authors would like to thank the Consejo de Seguridad Nuclear for the cooperation and co-financing the project “Metodologías avanzadas de análisis y simulación de escenarios de incendios en centrales nucleares”

Mimicking the intestinal host–pathogen interactions in a 3D In vitro model: The role of the mucus layer

The intestinal mucus lines the luminal surface of the intestinal epithelium. This mucus is a dynamic semipermeable barrier and one of the first-line defense mechanisms against the outside environment, protecting the body against chemical, mechanical, or biological external insults. At the same time, the intestinal mucus accommodates the resident microbiota, providing nutrients and attachment sites, and therefore playing an essential role in the host–pathogen interactions and gut homeostasis. Underneath this mucus layer, the intestinal epithelium is organized into finger-like protrusions called villi and invaginations called crypts. This characteristic 3D architecture is known to influence the epithelial cell differentiation and function. However, when modelling in vitro the intestinal host–pathogen interactions, these two essential features, the intestinal mucus and the 3D topography are often not represented, thus limiting the relevance of the models. Here we present an in vitro model that mimics the small intestinal mucosa and its interactions with intestinal pathogens in a relevant manner, containing the secreted mucus layer and the epithelial barrier in a 3D villus-like hydrogel scaffold. This 3D architecture significantly enhanced the secretion of mucus. In infection with the pathogenic adherent invasive E. coli strain LF82, characteristic of Crohn’s disease, we observed that this secreted mucus promoted the adhesion of the pathogen and at the same time had a protective effect upon its invasion. This pathogenic strain was able to survive inside the epithelial cells and trigger an inflammatory response that was milder when a thick mucus layer was present. Thus, we demonstrated that our model faithfully mimics the key features of the intestinal mucosa necessary to study the interactions with intestinal pathogens.Postprint (published version

Classification of multiple sclerosis clinical forms by 1H magnetic ressonance spectroscopy of cerebrospinal fluid

Postprint (published version

Mimicking the Intestinal Host–Pathogen Interactions in a 3D In Vitro Model: The Role of the Mucus Layer

The intestinal mucus lines the luminal surface of the intestinal epithelium. This mucus is a dynamic semipermeable barrier and one of the first-line defense mechanisms against the outside environment, protecting the body against chemical, mechanical, or biological external insults. At the same time, the intestinal mucus accommodates the resident microbiota, providing nutrients and attachment sites, and therefore playing an essential role in the host–pathogen interactions and gut homeostasis. Underneath this mucus layer, the intestinal epithelium is organized into finger-like protrusions called villi and invaginations called crypts. This characteristic 3D architecture is known to influence the epithelial cell differentiation and function. However, when modelling in vitro the intestinal host–pathogen interactions, these two essential features, the intestinal mucus and the 3D topography are often not represented, thus limiting the relevance of the models. Here we present an in vitro model that mimics the small intestinal mucosa and its interactions with intestinal pathogens in a relevant manner, containing the secreted mucus layer and the epithelial barrier in a 3D villus-like hydrogel scaffold. This 3D architecture significantly enhanced the secretion of mucus. In infection with the pathogenic adherent invasive E. coli strain LF82, characteristic of Crohn’s disease, we observed that this secreted mucus promoted the adhesion of the pathogen and at the same time had a protective effect upon its invasion. This pathogenic strain was able to survive inside the epithelial cells and trigger an inflammatory response that was milder when a thick mucus layer was present. Thus, we demonstrated that our model faithfully mimics the key features of the intestinal mucosa necessary to study the interactions with intestinal pathogens

Estudio experimental de la resistencia al fuego de forjados colaborantes de hormigón ligero estructural con fibras poliméricas

Workshop Fire Engineering Conference (4th.2016. Valencia)El objetivo de este trabajo es mostrar el proceso de creación de una nueva línea de trabajo sobre la resistencia al fuego por el grupo de investigación GICONSIME de la Universidad de Oviedo a partir de la realización del proyecto PLAN NACIONAL BIA2012-31609. La resistencia al fuego se evalúa mediante criterios normalizados estableciendo modelos de fuego recreados en hornos de forma que se consigue un escenario realista y sobre todo, reproducible de la condiciones de exposición. Además, los ensayos de resistencia al fuego se han de efectuar sobre elementos de construcción del mismo tamaño que la realidad. Para la realización de ensayos normalizados de resistencia al fuego se ha diseñado y construido un horno, para lo que han sido necesarios diferentes estudios para optimizar dimensiones, principales elementos y modo de operación