La fisuración discreta: una alternativa a los modelos análisis no-lineal de estructuras de hormigón

En este trabajo se presenta un modelo de elementos finitos con fisuración discreta para el análisis no lineal de estructuras planas de hormigón cargadas en su plano. Mediante la utilización de cinco tipos de elementos finitos diferentes se incluyen en el análisis, no sólo el comportamiento no lineal del acero y el hormigón, sino también los efectos de la adherencia, encajamiento de áridos y pasador de las armaduras que cruzan una fisura. Se ha desarrollado un algoritmo que resuelve de manera automática los problemas derivados de la regeneración de la m d a propios de la técnica de la fisuración discreta. Por último, algunos de los resultados obtenidos con el modelo son comparados con los obtenidos experimentalmente en vigas con roturas por cortante y flexión.This paper presents a discrete-crack finite element model for the nonlinear analysis of concrete structures under plane-stress conditions. The model incorporates five types of finite elements in order to take into account the different mechanisms of stress transmission in concrete structures: concrete and steel finite elements, and special finite elements for the modelling of bond, aggregate interlock and dowel-action. The modifications of the finite element mesh, typical of the discret-crack approach, are carried out using a fully automatic strategy. Finally, the model is applied to the analysis of beams failing in flexure and in shear and the analytical predictions compared with the experimental data.Peer Reviewe

Multi-round Master-Worker Computing: a Repeated Game Approach

We consider a computing system where a master processor assigns tasks for execution to worker processors through the Internet. We model the workers decision of whether to comply (compute the task) or not (return a bogus result to save the computation cost) as a mixed extension of a strategic game among workers. That is, we assume that workers are rational in a game-theoretic sense, and that they randomize their strategic choice. Workers are assigned multiple tasks in subsequent rounds. We model the system as an infinitely repeated game of the mixed extension of the strategic game. In each round, the master decides stochastically whether to accept the answer of the majority or verify the answers received, at some cost. Incentives and/or penalties are applied to workers accordingly. Under the above framework, we study the conditions in which the master can reliably obtain tasks results, exploiting that the repeated games model captures the effect of long-term interaction. That is, workers take into account that their behavior in one computation will have an effect on the behavior of other workers in the future. Indeed, should a worker be found to deviate from some agreed strategic choice, the remaining workers would change their own strategy to penalize the deviator. Hence, being rational, workers do not deviate. We identify analytically the parameter conditions to induce a desired worker behavior, and we evaluate experi- mentally the mechanisms derived from such conditions. We also compare the performance of our mechanisms with a previously known multi-round mechanism based on reinforcement learning.Comment: 21 pages, 3 figure

La fisuración discreta: una alternativa a los modelos análisis no-lineal de estructuras de hormigón

En este trabajo se presenta un modelo de elementos finitos con fisuración discreta para el análisis no lineal de estructuras planas de hormigón cargadas en su plano. Mediante la utilización de cinco tipos de elementos finitos diferentes se incluyen en el análisis, no sólo el comportamiento no lineal del acero y el hormigón, sino también los efectos de la adherencia, encajamiento de áridos y pasador de las armaduras que cruzan una fisura. Se ha desarrollado un algoritmo que resuelve de manera automática los problemas derivados de la regeneración de la m d a propios de la técnica de la fisuración discreta. Por último, algunos de los resultados obtenidos con el modelo son comparados con los obtenidos experimentalmente en vigas con roturas por cortante y flexión.This paper presents a discrete-crack finite element model for the nonlinear analysis of concrete structures under plane-stress conditions. The model incorporates five types of finite elements in order to take into account the different mechanisms of stress transmission in concrete structures: concrete and steel finite elements, and special finite elements for the modelling of bond, aggregate interlock and dowel-action. The modifications of the finite element mesh, typical of the discret-crack approach, are carried out using a fully automatic strategy. Finally, the model is applied to the analysis of beams failing in flexure and in shear and the analytical predictions compared with the experimental data.Peer Reviewe

Myocardial trabeculation in embryos of Scyliorhinus canicula (Elasmobranchii, Chondrichthyans)

Currently, three types of ventricular myoarchitecture are recognized in vertebrates, namely compact, spongy (trabeculated) and mixed myocardium. Mixed myocardium, which has been recently proposed as the primitive condition in gnathostomes, is composed of two myocardial layers: an inner trabeculated and an outer compact one. The trabeculation process has been studied in teleosts, showing exclusively spongy myocardium, and mammals and birds, characterized by a compact myocardial ventricular wall. In zebrafish, mouse and chicken embryos, the trabeculae develop as luminal myocardial ridges protruding into the lumen. In mammals and birds, further compactation of trabeculae leads to the formation of a compact layer. The potential mechanisms that may contribute to the formation of the ridges are under discussion and include myocardial proliferation, endocardial invagination, and bending of the entire myocardial layer. However, no description of the development of the mixed myocardium is available. To shed some light on this issue, we have studied the heart development of an elasmobranch species with mixed myocardium, the lesser spotted dogfish (Scyliorhinus canicula; Chondrichthyes), by means of histological and immunohistochemical techniques for light microscopy, semithin sections, scanning electron microscopy and transmission electron microscopy. Our results suggest that in the dogfish the intertrabecular spaces develop by connections between early intramyocardial spaces and the lumen of the ventricle through invaginations of the endocardial line. Chondrichthyans are the earliest diverged lineage of gnathostomes and, consequently, they have the most primitive cardiac design. Although chicken, mouse, and recently zebrafish have been considered powerful vertebrate models to study heart development, we propose that the trabeculation process in the dogfish is representative of the early steps of the ventricular morphogenesis in vertebrates.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.Study supported by grant CGL2017-85090-P and CGL2014-52356-P (Ministerio de Economía y Competitividad), FPU15/03209 (Ministerio de Educación, Cultura y Deporte), FEDER, and Universidad de Málaga

Propuesta de indicadores del proceso de enseñanza/aprendizaje en la formación profesional en un contexto de gestión de calidad total

Se propone una batería de indicadores del proceso de enseñanza-aprendizaje diseñados para la práctica cotidiana de la evaluación interna de un centro de formación profesional que permita valorar la eficacia del proceso de E/A y el desarrollo de los factores que influyen en él. Al mismo tiempo, se proponen fórmulas para ajustar algunos indicadores globales que permitan valorar la eficacia del funcionamiento del centro con independencia de los factores externos más relevantes. Los indicadores propuestos pretenden obtener información diferenciada que permita tomar decisiones para mejorar de forma continua el funcionamiento del centro, detectando los factores que actúan como limitantes de los buenos resultados

RDF-TR: Exploiting structural redundancies to boost RDF compression

The number and volume of semantic data have grown impressively over the last decade, promoting compression as an essential tool for RDF preservation, sharing and management. In contrast to universal compressors, RDF compression techniques are able to detect and exploit specific forms of redundancy in RDF data. Thus, state-of-the-art RDF compressors excel at exploiting syntactic and semantic redundancies, i.e., repetitions in the serialization format and information that can be inferred implicitly. However, little attention has been paid to the existence of structural patterns within the RDF dataset; i.e. structural redundancy. In this paper, we analyze structural regularities in real-world datasets, and show three schema-based sources of redundancies that underpin the schema-relaxed nature of RDF. Then, we propose RDF-Tr (RDF Triples Reorganizer), a preprocessing technique that discovers and removes this kind of redundancy before the RDF dataset is effectively compressed. In particular, RDF-Tr groups subjects that are described by the same predicates, and locally re-codes the objects related to these predicates. Finally, we integrate RDF-Tr with two RDF compressors, HDT and k2-triples. Our experiments show that using RDF-Tr with these compressors improves by up to 2.3 times their original effectiveness, outperforming the most prominent state-of-the-art techniques

MYOCARDIAL STRUCTURE AND VASCULARIZATION OF THE HEART VENTRICLE IN HOLOCEPHALI: IMPLICATIONS FOR HEART EVOLUTION

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013. Anatomical Record, Volume 296, Special Feature — 1: P-075.It has been classically assumed that the ventricle of the primitive vertebrate heart is composed of spongy myocardium, supplied exclusively by oxygen-poor, luminal blood. This idea is on two facts: (1) extant agnathans have a spongy ventricular myocardium, and (2) in avian and mammalian embryos, the formation of trabeculated myocardium precedes the appearance of compact myocardium. Recently, it has been proposed that, like elasmobranchs, the early gnathostomes possess a fully vascularised ventricle composed of mixed myocardium. We tested this idea by studying the structure and vascularisation of the ventricular myocardium in four holocephalan species of the families Chimaeridae and Rhinochimaeridae. Chimaera monstrosa, Hidrolagus affinis and Harriotta raleighana have a spongy myocardium covered by a thin layer of cardiac muscle. In H. raleighana, the compacta is reduced to an extremely fine rim. In all three species there is a well-developed coronary artery system consisting of subepicardial vessels which give off branches that penetrate the myocardial trabeculae. Rhinochimaera atlantica has no compacta and its ventricular coronary artery system is reduced to subepicardial vessels that do not enter the spongy layer. This report is the first to show that in wild living vertebrates, a coronary artery system supplying the whole myocardium exists in the absence of a well-developed compacta, which supports experimental work that shows that myocardial cell proliferation and coronary vascular growth rely on genetically separated programs. We conclude that the mixed ventricular myocardium is primitive for chondrichthyans, and that the lack of compacta in some holocephalans is a derived character. Moreover our results support the hypotheses that the mixed myocardium is the primitive condition in gnathostomes, and that the absence of a compacta in different actinopterygian taxa is the result of its repeated loss during evolution.Proyecto CGL2010-16417/BOS; Fondos FEDE