Axisymmetric free vibration of closed thin spherical nano-shell

This work investigates the free axisymmetric vibrations of a closed spherical nano-shell using the Eringen nonlocal elasticity theory. The motion equations are properly formulated considering the hypotheses of thin shells and the solution is obtained using the classical separation of variables method. The effect of the nonlocal parameter on the natural frequencies and modal shapes are discussed in comparison to their local counterparts. This study could be useful in biomedical and bioengineering applications as well as in other fields related with the nanotechnology.Ministerio de Ciencia e Innovación de España (Projects DPI/2011-24068 and DPI/2011-23191)Publicad

Analysis of a thermoelastic problem with the Moore–Gibson–Thompson microtemperatures

In this paper, we study, from both an analytical and a numerical point of view, a poro-thermoelastic problem with microtemperatures. The so-called Moore–Gibson–Thompson equation is used to model the contribution for the temperature and microtemperatures. An existence and uniqueness result is proved by using the theory of linear semigroups of contractions and, for the one-dimensional case, the exponential energy decay is found under some conditions on the constitutive coefficients. Then, a fully discrete approximation is introduced by using the finite element method and the implicit Euler scheme. We show that the discrete energy decays and we obtain some a priori error estimates from which, under some adequate additional regularity conditions on the continuous solution, we derive the linear convergence of the approximations. Finally, we perform some numerical simulations to demonstrate the accuracy of the approximations and the behavior of the discrete energy and the solutionPeer ReviewedPostprint (published version

Resonator-based detection in nanorods

In this paper the axial vibrational behavior of nanorods with an attached point-mass is studied, using the modified strain energy theory. The natural frequencies of the nanorod with the concentrated mass are obtained for different boundary conditions. The effects of the concentrated mass intensity, mass location, as well as the value of scale parameters have been analysed. For the case of small intensity of the concentrated mass, the natural frequencies of the nanorod can be estimated using a first order perturbative solution. These approximate results are compared with those corresponding to the exact solution. For this case, from the properties of the eigenvalue perturbative theory, the identification of single point mass in uniform nanorods (mass intensity and position) is addressed. The results obtained encourage the use of axial vibrations of nanorods as a very precise sensing technique.The authors wish to acknowledge the Ministerio de Economía y Competitividad de España for the financial support, under Grant No. DPI2014-57989-P. The first author also gratefully acknowledges the financial support of the National Research Project PRIN2015 "Identificazione e diagnostica di sistemi strutturali complessi".Publicad

¿Reducción y reordenación del tiempo de trabajo? La percepción de los trabajadores sobre las estrategias de los empresarios y trabajadores

The aim of this article is the presentation of the results of a investigation about the posibilities in the present day for the homogenizing of workers strategies respect to the reduction of the labour time. Specifically, this article is about the perceptions that the representants of sindical unions have about the managerials strategies and about the workers strategies.En este artículo se presentan parte de los resultados de una investigación realizada sobre las posibilidades existentes en la actualidad para la homogeneización de estrategias entre y desde los asalariados respecto a la reducción del tiempo de trabajo, viendo el alcance de las percepciones que tienen los representantes sindicales de los trabajadores. En concreto, las percepciones en torno a las estrategias empresariales y de los trabajadores

Free transverse vibrations of cracked nanobeams using a nonlocal elasticity model

9 pages, 5 figures.-- PACS nrs.: 46.40.-f, 46.25.-y, 46.35.+z, 07.10.Cm, 46.70.De, 46.50.+a.In this paper, flexural vibrations of cracked micro- and nanobeams are studied. The model is based on the theory of nonlocal elasticity applied to Euler–Bernouilli beams. The cracked-beam model is established using a proper modification of the classical cracked-beam theory consisting of dividing the cracked element into two segments connected by a rotational spring located at the cracked section. This model promotes a discontinuity in bending slope, which is proportional to the second derivative of the displacements. Frequency equations of cracked nanobeams with some typical boundary conditions are derived and the natural frequencies for different crack positions, crack lengths, and nonlocal length parameters are calculated. The results are compared with those corresponding to the classical local model, emphasizing the differences occurring when the nonlocal effects are significant.This research was done with the financial support of the University Carlos III of Madrid and of the Comunidad Autónoma de Madrid under Projects CCG06-UC3M/DPI-0796 and CCG07-UC3M/DPI-3395.Publicad

La Web 2.0 en la enseñanza de Introducción a la Arquitectura

Introducción a la Arquitectura es una asignatura de primer curso que se imparte en la Escuela de Arquitectura de la Universidad de A Coruña. En ella se pretende iniciar la formación del futuro profesional atendiendo desde el comienzo, al triple soporte reflexivo, proyectivo y constructivo del hecho arquitectónico: Se trata de despertar o acrecentar el interés por la Arquitectura y por su razón de ser, aproximándose a su concepto desde una visión teórica e histórica, y fomentando la capacidad analítica, el sentido crítico y el desarrollo lógico del alumno en el territorio propio de la arquitectura, que va desde el urbanismo hasta el diseño elemental. El camino hacia la inminente implantación del Proceso de Bolonia, donde el nuevo concepto de crédito europeo matiza la necesidad de control y responsabilidad de y hacia el alumno, así como la redefinición del sistema universitario a partir del acceso a la sociedad del Conocimiento, nos conduce a la necesidad de incorporar las nuevas tecnologías como nuevo modo de control y relación profesor-alumno dentro de la asignatura. Dentro de este planteamiento se ha trabajado desde hace dos años utilizando herramientas Web 2.0 tanto como elementos de comunicación y debate entre profesores y alumnos como entre los propios alumnos, lo que nos permite realizar un análisis de experiencias y valorar críticamente los resultados obtenido

Analytical modelling of high velocity impacts of cylindrical projectiles on carbon/epoxy laminates

8 pages, 15 figures.-- Special Issue: JNC 15 - 15èmes Journées Nationales sur les Composites (Marseille, France, Jun 6-8, 2007).In this work an analytical model has been developed in order to predict the residual velocity of a cylindrical steel projectile, after impacting into a woven carbon/epoxy thin laminate. The model is based in an energy balance, in which the kinetic projectile energy is absorbed by the laminate through three different mechanisms: linear momentum transfer, fiber failure and laminate crushing. This last mechanism needs the quantification of the through-thickness compressive strength, which has been evaluated by means of quasi-static punch tests. Finally, high velocity impact tests have been accomplished in a wide range of velocities, to validate the model.This research was done with the financial support of the University Carlos III of Madrid and of the Comunidad Autónoma de Madrid under Projects CCG08-UC3M/MAT-4464 and CCG08-UC3M/DPI-4348.Publicad

A Novel Artificial Neural Network to Predict Compressive Strength of Recycled Aggregate Concrete

Most regulations only allow the use of the coarse fraction of recycled concrete aggregate (RCA) for the manufacture of new concrete, although the heterogeneity of RCA makes it difficult to predict the compressive strength of concrete, which is an obstacle to the incorporation of RCA in concrete production. The compressive strength of recycled aggregate concrete is closely related to the dosage of its constituents. This article proposes a novel artificial neural network (ANN) model to predict the 28-day compressive strength of recycled aggregate concrete. The ANN used in this work has 11 neurons in the input layer: the mass of cement, fly ash, water, superplasticizer, fine natural aggregate, coarse natural or recycled aggregate, and their properties, such as: sand fineness modulus of sand, water absorption capacity, saturated surface dry density of the coarse aggregate mix and the maximum particle size. Two training methods were used for the ANN combining 15 and 20 hidden layers: Levenberg–Marquardt (LM) and Bayesian Regularization (BR). A database with 177 mixes selected from 15 studies incorporating RCA were selected, with the aim of having an underlying set of data heterogeneous enough to demonstrate the efficiency of the proposed approach, even when data are heterogeneous and noisy, which is the main finding of this work

Caminos paralelos, deficiencias comunes: aproximación a los modelos públicos de recursos humanos en España y Portugal

Este artículo describe la evolución de los modelos de servicio civil portugueses y españoles.Además de destacar las principales medidas tomadas en la gestión de recursos humanos, el documento examina la influencia deLos programas de modernización implementados por ambas Administraciones en sus propios modelos de servicio civil.Finalmente, se identifican los altibajos derivados de las prácticas de gestión de recursos humanos, así como los desafíos que ambas Administraciones deben enfrentar en los próximos años.

Workflow to improve the forest management of Eucalyptus globulus stands affected by Gonipterus scutellatus in Galicia (Spain) using remote sansing and GIS

In Spain there are more than 500.000 ha. of Eucalyptus plantations. There represent 3,5 % of the national forest and the 25 % of the timber harvested. Galicia monocultures of Eucalyptus globulus Labill. plantations cover 177.679 ha. and mixed stands of eucalyptus cover 200.000 ha. more. This high productivity has been powered by the absence of pests and pathogens. However, since 1991 the health and productivity of these stands has been threatened by the Eucalyptus snout beetle, which causes a severe defoliation to eucalyptus stands in Galicia