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

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

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

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

Effect of the Composition of Mixed Recycled Aggregates on Physical–Mechanical Properties

Recycled aggregates (RA) from construction and demolition waste are an alternative to natural aggregates in the construction sector. They are usually classified according to their composition. The main constituent materials are separated into the following categories: unbound natural aggregates, ceramic particles, cementitious particles, bituminous materials, and other materials considered impurities, such as glass, plastic, wood, or gypsum. In this research, a large number of samples of RA were collected from three different recycling plants and their properties were studied. After that, 35 samples were selected randomly, and their RA constituents were separated under laboratory conditions. Cementitious particles were differentiated into two subcategories: masonry mortar and concrete particles. Subsequently, their physical–mechanical properties were measured. The statistical analysis carried out exhibited that the constituents had a statistically significant influence on the physical–mechanical properties studied. Specifically, masonry mortar particles had higher water absorption and worse mechanical properties than concrete and ceramic particles. Secondly, multiple regression models were performed to predict the physical–mechanical properties of RA from their composition since mean absolute percentage error (MAPE) ranged between 0.9% and 8.6%. The differentiation in the subcategories of concrete and masonry mortar particles in compositional testing is useful for predicting the physical–mechanical properties of RA

Accessible triplet excited states in the photoisomerization of allenes with extended conjugation

A series of bidentate allene- and enyne-containing ligands have been synthesized and the photochemical properties of their rhenium(I) complexes have been studied. These complexes exhibit facile isomerization of the conjugated double bonds upon ambient light exposure. Simulations unveiled a very efficient intersystem crossing and the consequent key role of the triplet states in the observed photochemistry of these substrates upon rhenium(I) complexation.Agencia Estatal de Investigación | Ref. CTQ2017-85919-RXunta de Galicia | Ref. EC431C 2021/4

Estimation of biomass of horse mackerel (Trachurus trachurus L.) in northern-Spain ( Nortbern IXa and VIIIc ) using the daily egg production method.

In order to estimate the spawning stock biomass of horse mackerel in the North Atlantic Spanish waters, a series of egg and adult cruises were carried out by lEO (Instituto Español de Oceanografía) and AZTI -SIO (Instituto de Investigación y Tecnología para la Oceanografía, Pesca y Alimentación) . The survey was carried out from 23 April to 25 May 1992. A total of 627 plankton samples and 37 adults samples were collected. A total daily egg production of 3.3 X 1012 egg (SE = 7.26 X 1011 , CV = 0.22) was estimated for the whole area sarnpled (ICES Division Vlllc and subdivision northern IXa north). The estirnate of horse mackerel spawning biornass ranged from 486,549 tons (CV = 0.34, when using adult pararneter estirnates exclusively frorn the Spanish survey, down to 368,814 tn (C = 0.32), when alternatively using an estimate of relative batch fecundity from the southern region of horse rnackerel western stock

Hybrid RSS-RTT Localization Scheme for Indoor Wireless Networks

[EN]Nowadays, a variety of information related to the distance between two wireless devices can be easily obtained. This paper presents a hybrid localization scheme that combines received signal strength (RSS) and round-trip time (RTT) information with the aim of improving the previous localization schemes. The hybrid localization scheme is based on an RSS ranging technique that uses RTT ranging estimates as constraints among other heuristic constraints. Once distances have been well estimated, the position of the mobile station (MS) to be located is estimated using a new robust least-squared multilateration (RLSM) technique that combines the RSS and RTT ranging estimates mitigating the negative effect of outliers. The hybrid localization scheme coupled with simulations and measurements demonstrates that it outperforms the conventional RSS-based and RTT-based localization schemes, without using either a tracking technique or a previous calibration stage of the environment.Dirección General de Telecomunicaciones de la Consejería de Fomento de Castilla y Leó

AIM-Mobile Learning Platform 3.0: Design of new functionalities to integrate smartphones in the teaching-learning process

[EN] The combination of Learning Management Systems (LMS) with smartphones is gaining importance in Higher Education studies. Therefore, we have designed a responsive virtual environment, AIM-Mobile Learning Platform, focus on integrating smartphones in class. It permits teachers to send real time questions and learning packets with multimedia resources to students through their smartphones. As the environment instantaneously processes every student response their continuous progress is automated. Moreover, the environment permits to manage teachers, subjects and students by means of a generic interface that can be applied in many educational disciplines. The new version includes more functionalities to promote their consolidation in Education. It integrates an installation and configuration package to provide high flexibility for Institutions as they can intall it in their own servers. Besides, we have complemented the existing quantitative evaluation system with a qualitative functionality based on positives and negatives taking into account the participation of students in class. Finally, the new version allows students to design questions with the aim to build knowledge. These strategies seek to increase the motivation, implication and attention of students in subjects, promoting a constant feedback inside class, which helps students to be more conscious of their self-learning process.This work has been funded by the University of Valladolid, Teaching Innovation Groups 2016-2017Merayo, N.; Medina, A.; Goyanes, G.; De Miguel, I.; Aguado, JC.; Durán, RJ.; Fernández, P.... (2017). AIM-Mobile Learning Platform 3.0: Design of new functionalities to integrate smartphones in the teaching-learning process. En Proceedings of the 3rd International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 259-267. https://doi.org/10.4995/HEAD17.2017.5166OCS25926

La evaluación de las competencias básicas. Última fase del proceso de operativización

Desde la Unión Europea se ha optado por un modelo competencial que los distintos Estados miembros han asumido en la configuración de sus correspondientes currículos. España no es una excepción. A partir de la Ley Orgánica 2/2006 de Educación, de 3 de mayo, las competencias básicas se han convertido en un elemento curricular prescriptivo más y, por ende, en objeto de análisis y estudio desde diferentes ámbitos y perspectivas. Sin embargo, no se ha ofrecido un modelo de operativización que las aborde desde la planificación docente diferentes autores han apuntado algunas soluciones, pero los docentes han de desarrollar y evaluar las competencias básicas en el aula, en ocasiones, sin tener claro cómo hacerlo. El objetivo de este trabajo es aportar algunas orientaciones al profesorado para la evaluación de las competencias básicas partiendo de la operativización de las mismas a través de siete fases que concluyen en la elaboración de rúbricas que posibilitan dicha evaluación.The European Union has decided in favour of a competence-based model that the Member states have assumed in the configuration of his corresponding curricula. Spain is not an exception. From the Organic Law 2/2006 of Education of May 3, the based competences have turned into an element curricular prescriptive more and, for it, into object of analysis and study from different contexts and perspectives. Nevertheless, nobody has offered a model of coperativización that tackles them from the teaching planning. Different authors have aimed at somee solutions, but the teachers have to develop and evaluate the based competences in the classroom, sometimes, without knowing how to do it. The aim of this paper is to contribute a series of orientations to the professorship for the evaluation of the basic competences that begin on having made them operative across seven phases that they conclude in the making of rubrics that make possible the above mentioned evaluatio