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

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”

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

Postprint (published version

Nuevo método de lanzamiento y sistema de empuje de puentes metálicos.Bases conceptuales

La construcción de un puente es la etapa más comprometida de su vida; se dice que si un puente es capaz de superar su fase de ejecución,entonces puede permanecer durante siglos. Esto es particularmente cierto en casos como los puentes empujados.La estructura debe soportar diferentes esfuerzos durante el lanzamiento, incluso superiores a los de servicio. Actualmente, este procedimientoestá limitado por la luz máxima del puente.Este artículo sienta las bases para el dise˜no y la optimización de un nuevo método de lanzamiento de puentes metálicos, de sección constante,proponiendo el lanzamiento de luces de hasta 150 m de forma continua y eficiente. Para alcanzar este desafío, se plantea un cambio conceptual enla estructura que se debe lanzar.Así se evitan los medios auxiliares singulares o costosos y los tiempos muertos en las fases de empuje y se hace posible competir con otrastipologías o sistemas (autocimbra o avances en voladizo).Este proyecto ha sido financiado con fondos FEDER, "A way of Making Europe