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Piezoresistivity is the most commonly used sensing principle in cement-based smart composites for strain-monitoring applications. Nonetheless, the need for external electric power to conduct electrical resistivity measurements restricts the scalability of this technology, especially when implemented in remote structures. To address this issue, this manuscript thoroughly analyzes the piezoelectric properties of cement composites doped with reduced graphene oxide (rGO) and evaluates their potential as self-powered strain sensors. To do so, a comprehensive methodology involving voltammetry measurements, open circuit potential determination, and uniaxial compression testing is developed to determine the piezoelectric coefficients of charge $d_{33}$ and voltage $g_{33}$. Furthermore, a novel circuital model for signal processing of the electromechanical response is developed and experimentally validated in terms of time series of output voltage, resistance, and the generated electric power. The developed methodology is applied to laboratory samples manufactured following two different filler dispersion methods. The presented results evidence that samples prepared by ultrasonic cleaner dispersion achieve optimal properties, with a piezoelectric charge coefficient of 1122.28$\mathrm{\pm}$246.67 pC/N, about 47 times greater than previously reported composites in the literature. Unlike piezoresistive cement-based composites, a remarkable nonlinear correlation between the fractional change in the intrinsic resistance of the material and the applied mechanical strain has been observed. Instead, a considerable linearity ($\mathrm{R^2}=0.96$) between the externally applied mechanical strain and the generated (piezoelectric) electric power has been found, which suggests the great potential of the latter for conducting off-the-grid strain monitoring applications.

En este artículo nuestro objetivo es comparar los artículos que realizan la evaluación de desempeño de la plataforma de computación en la nube (CC) OpenStack, OpenNebula y CloudStack. Las tres plataformas son software de código abierto (Open Source) para el despliegue de nubes privadas y públicas, pero difieren en su arquitectura de construcción y el método de despliegue de la solución. En el artículo se presenta la comparativa entre las tres plataformas de CC, revisando su arquitectura, sus elementos funcionales más importantes, se identifican lasmedidas de desempeño típicamente utilizadas en la ejecución de problemas computacionales complejos (HPC) y se contrastan los resultadosque obtuvieron otros autores en las pruebas técnicas de rendimiento en HPC. Al final del artículo se evidencia como las plataformas de computación en la nube agregan una sobrecarga a la ejecución de HPC, pero acorde con el problema computacional a resolver dichasobrecarga resulta manejable y se presenta como una alternativa favorable en relación con tener una infraestructura en local (on-premise).

The present paper explores a new concept of a hybrid eco-composite by substituting the natural fibre plies with thin wood veneers. The new composite, named Fibre–Wood Laminate (FWL), is inspired by fibre–metal laminate materials. The studied FWL configuration consisted of a single thin pinewood veneer at each of the outer layers of a flax woven fabric reinforced bio-epoxy composite manufactured by infusion. Three-point bending results showed that wood veneer gives a highly anisotropic nature to the FWL. In the best case, with the grain of the wood at 0°, the stiffness and the strength increased by 28 and 41%, respectively, but reduced the strain-at-break by 27% compared to the flax fibre reinforced bio-epoxy (FFRB). The penetration and perforation energy thresholds and the peak force of the FWL obtained by falling weight impact tests were 32, 29, and 31% lower than those of the FFRB, respectively. This weakening was due to using single wood veneers, so the challenge for improving impact properties will be to explore thicker FWLs with different stacking sequences and orientations. The effect of immersing the FWL in seawater also showed considerable differences. The epoxy matrix filled the cellular structure of the wood veneers, creating a barrier effect and reducing the amount of water absorbed by the flax fibres. The research in this paper was supported by the Vice-Ministry of Universities and Research of the Basque Government (Grants No. IT1613-22 and IT1514-22).

The present work shows the material flow analysis in indentation by the numerical two dimensional Finite Elements (FEM) method and the experimental two-dimensional Digital Image Correlation (DIC) method. To achieve deep indentation without cracking, a ductile material, 99% tin, is used. The results obtained from the DIC technique depend predominantly on the pattern conferred to the samples. Due to the absence of a natural pattern, black and white spray painting is used for greater contrast. The stress-strain curve of the material has been obtained and introduced in the Finite Element simulation code used, DEFORM™, allowing for accurate simulations. Two different 2D models have been used: a plain strain model to obtain the load curve and a plain stress model to evaluate the strain maps on the workpiece surface. The indentation displacement load curve has been compared between the FEM and the experimental results, showing a good correlation. Additionally, the strain maps obtained from the material surface with FEM and DIC are compared in order to validate the numerical model. The Von Mises strain results between both of them present a 10–20% difference. The results show that FEM is a good tool for simulating indentation processes, allowing for the evaluation of the maximum forces and deformations involved in the forming process. Additionally, the non-contact DIC technique shows its potential by measuring the superficial strain maps, validating the FEM results.

De la esponja marina Ágelas schmidti recolectada en la bahía de Santa Marta (Caribe Colombiano), se aisló por cromatografía en columna sobre silica gel la fracción esterólica. Los esteróles presentes en esta fracción fueron sometidos a Cromatografía Líquida de Alta Eficiencia preparativa en fase reversa y analizados por Cromatografía de Gases de Alta Resolución y Cromatografía de Gases de Alta Resolución acoplada a Espectrometría de Masas. De dieciocho esteróles separados, diecisiete fueron identificados presentando la mayoría de ellos núcleos A" y A' con cadenas laterales convencionales.