Browsing by Keyword "Simulations"
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Item Design and Validation of a Novel Tool to Assess Citizens’ Netiquette and Information and Data Literacy Using Interactive Simulations(2022-03-14) Bartolomé, Juan; Garaizar, Pablo; ADV_INTER_PLATUntil recently, most of the digital literacy frameworks have been based on assessment frameworks used by commercial entities. The release of the DigComp framework has allowed the development of tailored implementations for the evaluation of digital competence. However, the majority of these digital literacy frameworks are based on self-assessments, measuring only low-order cognitive skills. This paper reports on a study to develop and validate an assessment instrument, including interactive simulations to assess citizens’ digital competence. These formats are particularly important for the evaluation of complex cognitive constructs such as digital competence. Additionally, we selected two different approaches for designing the tests based on their scope, at the competence or competence area level. Their overall and dimensional validity and reliability were analysed. We summarise the issues addressed in each phase and key points to consider in new implementations. For both approaches, items present satisfactory difficulty and discrimination indicators. Validity was ensured through expert validation, and the Rasch analysis revealed good EAP/PV reliabilities. Therefore, the tests have sound psychometric properties that make them reliable and valid instruments for measuring digital competence. This paper contributes to an increasing number of tools designed to evaluate digital competence and highlights the necessity of measuring higher-order cognitive skills.Item A multi-scale approach for percolation transition and its application to cement setting(2018-10-25) Prabhu, Achutha; Gimel, Jean-Christophe; Ayuela, Andrés; Arrese-Igor, Silvia; Gaitero, J.J.; Dolado, Jorge S.; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNShortly after mixing cement grains with water, a cementitious fluid paste is formed that immediately transforms into a solid form by a phenomenon known as setting. Setting actually corresponds to the percolation of emergent network structures consisting of dissolving cement grains glued together by nanoscale hydration products, mainly calcium-silicate-hydrates. As happens in many percolation phenomena problems, the theoretical identification of the percolation threshold (i.e. the cement setting) is still challenging, since the length scale where percolation becomes apparent (typically the length of the cement grains, microns) is many times larger than the nanoscale hydrates forming the growing spanning network. Up to now, the long-lasting gap of knowledge on the establishment of a seamless handshake between both scales has been an unsurmountable obstacle for the development of a predictive theory of setting. Herein we present a true multi-scale model which concurrently provides information at the scale of cement grains (microns) and at the scale of the nano-hydrates that emerge during cement hydration. A key feature of the model is the recognition of cement setting as an off-lattice bond percolation process between cement grains. Inasmuch as this is so, the macroscopic probability of forming bonds between cement grains can be statistically analysed in smaller local observation windows containing fewer cement grains, where the nucleation and growth of the nano-hydrates can be explicitly described using a kinetic Monte Carlo Nucleation and Growth model. The most striking result of the model is the finding that only a few links (~12%) between cement grains are needed to reach setting. This directly unveils the importance of explicitly including nano-texture on the description of setting and explains why so low amount of nano-hydrates is needed for forming a spanning network. From the simulations, it becomes evident that this low amount is least affected by processing variables like the water-to-cement ratio and the presence of large quantities of nonreactive fillers. These counter-intuitive predictions were verified by ex-professo experiments that we have carried out to check the validity of our model.Item A patchy particle model for C-S-H formation(2022-02) Prabhu, Achutha; Dolado, Jorge S.; Koenders, Eddie A.B.; Zarzuela, Rafael; Mosquera, María J.; Garcia-Lodeiro, Ines; Blanco-Varela, María Teresa; Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNThe composition and structure of Calcium-Silicate-Hydrate (C-S-H) phases depends on various reaction parameters leading to its formation. Molecular Dynamic simulation studies probing the formation and structure of C-S-H are generally computationally expensive and can reach only very short time scales. Herein, we propose a coarse graining approach to model the formation of C-S-H, using patchy particles and a modified Patchy Brownian Cluster Dynamics algorithm. The simulations show that patchy particle systems can recover the qualitative kinetic evolution of C-S-H formation, and the obtained final structures were comparable to previously reported molecular dynamics studies and experiments. The model was extended to study the effect of water in the polymerization of tetraethoxysilane oligomers, the principal component of an impregnation treatment for deteriorated concrete surfaces. The intermediate system properties predicted by the simulations, such as viscosity and gel time, and structure were found to be well in accordance with the tailored experiments.