Implementació d’aules virtuals (Blended-Learning) per a l’aprenentatge dels continguts teòrics abans de la realització de pràctiques de laboratori integrades en l’assignatura Operacions Unitàries II

Projecte: 2016PID-UB/010L’objectiu d’aquest projecte docent ha sigut el desenvolupament d’Aules Virtuals per a les pràctiques de laboratori d’una assignatura teòrica a fi millorar l’aprenentatge. Així, s’han creat diferents activitats, seguint la metodologia Blended-Learning i fent ús de les eines del Moodle, per introduir conceptes teòrics i pràctics de les pràctiques de laboratori i vídeos explicatius que detallen els càlculs enginyerils que cal realitzar per completar l’informe final. A més, s’han creat uns qüestionaris tipus multi-resposta que permeten l’autoavaluació de l’aprenentatge assolit. Segons els resultats dels indicadors avaluats, els objectius proposats s’han assolit satisfactòriament i la qualificació dels informes de pràctiques ha millorat respecte anys anteriors

Influence of chemical speciation on the separation of metal ions from chelating agents by nanofiltration membranes

The simultaneous separation of various metal ions (nickel, copper, calcium, and iron) from chelating agents (EDTA and citric acid in water streams using Nanofiltration membranes is analyzed. Assuming that multiply-charged species are highly rejected, chemical speciation com-10 putations reproduce the observed patterns of metal and ligand rejection at different pH values and concentrations.Postprint (updated version

Multiphysical failure processes in concrete: a consistent multiscale homogenization procedure

Durability and strength capabilities of concrete materials are vastly affected by the combined action of temperature and mechanical loading, which give rise to multiphysical failure processes. Such a phenomenon involves complex cracking, degradation and transport mechanisms on different scale lengths of concrete mixtures which, in turn, depend on the particular properties of the different constituents. Thus, the macroscopic observation of relevant concrete mechanical features such as strength, ductility and durability are the result of several different properties, processes and mechanisms which are not only coupled but moreover, depend on multiple scales. Particularly, regarding the pore pressure and thermal actions, most of the degradation processes in concrete are controlled by the heterogeneities of the microscopic scale. In the case of the mechanical actions both the micro and mesoscales play a relevant role. In this context, multiphysical failure processes in cementitious material-based mixtures like concrete can only and fully be understood and accurately described when considering its multiscale and multiconstituent features. In the realm of the theoretical and computational solid mechanics many relevant proposals were made to model the complex and coupled thermo-hydromechanical response behavior of concrete. Most of them are related to macroscopic formulations which account for the different mechanisms and transport phenomena through empirical, dissipative, poromechanical theories. Moreover, although relevant progress was made regarding the formulation of multiscale theories and approaches, none of the existing proposals deal with multiphysical failure processes in concrete. It should be said in this sense that, among the different multiscale approaches for material modeling proposed so far, those based on computational homogenization methods have demonstrated to be the most effective ones due to the involved versatility and accuracy. In this work a thermodynamically consistent semi-concurrent multiscale approach is formulated for modeling the thermo-poro-plastic failure behavior of concrete materials. A discrete approach is considered to represent the RVE material response. After formulating the fundamental equations describing the proposed homogenizations of the thermodynamical variables, the constitutive models for both the skeleton and porous phases are described. Then, numerical analyses are presented to demonstrate the predictive capabilities of the proposed thermodynamically consistent multiscale homogenization procedure for thermo-mechanical failure processes in concrete mixtures

Modelo multi-escala con fracturas cohesivas en ambas escalas

En este trabajo se presentan resultados preliminares sobre un modelo multi-escala semiconcurrente para materiales con ablandamiento. Se propone una formulación mixta para la simulación de discontinuidades en los desplazamientos a ser usada en ambas escalas. La tensión sobre la fisura es considerada como incógnita del sistema de ecuaciones junto al campo de desplazamientos, y el salto se obtiene mediante la relación constitutiva (Ley tensión-separación). Se reformulan los principios axiomáticos propuestos por P.J. Blanco y S.M. Giusti (P.J. Blanco y S.M. Giusti, Journal of Elasticity, (2013)) y el concepto de inyección propuesto por P.J. Sánchez et al (P.J. Sánchez et al, Comp. Methods Appl. Mech. Engrg, 200:1220-1236 (2011)) para lograr una respuesta objetiva. La tensión proyectada sobre la normal de la fisura de la macro escala se inyecta en la fisura localizada del RVE, logrando como variable dual el salto en el campo de desplazamiento para la escala superior. De esta forma, en la fase estable del material la inyección en la transición de escalas mantiene la estructura clásica (partiendo de una compatibilización de deformaciones), mientras que en la fase no estable el proceso de transición sigue un camino inverso (partiendo de una compatibilización de tensiones sobre la localización en la micro escala). De esta manera se logra una inyección híbrida mediante deformaciones en el primer caso y tensiones en el segundo caso. Finalmente, se presentan ejemplos de homogeneización de la respuesta en problemas de fractura transversal de compuestos reforzados con fibras longitudinales.Postprint (published version

Dewaterability of sewage sludge by ultrasonic, thermal and chemical treatments

Sludges resulting from wastewater treatment processes have a characteristically high water content, which complicates handling operations such as pumping, transport and disposal. To enhance the dewatering of secondary sludge, the effect of ultrasound waves, thermal treatment and chemical conditioning with NaOH have been studied. Two features of treated sludges were examined: their rheological behavior and their dewaterability. The rheological tests consisted of recording shear stress when the shear rate increases and decreases continuously and linearly with time, and when it increases and decreases in steps. Steady-state viscosity and thixotropy were obtained from the rheological tests, and both decreased significantly in all cases with increased treatment intensity. Centrifugation of ultrasonicated and thermally treated sludges allowed the total solid content to be increased by approximately 16.2% and 17.6%, respectively. These dewatered sludges had a lower viscosity and thixotropy than the untreated sludge. In contrast, alkali conditioning barely allowed the sludge to be dewatered by centrifugation, despite decreasing its viscosity and thixotropy