1,721,244 research outputs found
Barrera protectora de las ventiscas
No full textProtective barrier for winds carrying snow and sand, for installation near communication routes in order to prevent the accumulation of snow or sand on the road. The barrier is formed by joining several screens made of a set of blades that are arranged horizontally, superposed on one another at regular distances, joined with vertical posts by anchoring their ends to several rectangular plates that are inserted in the vertical post using a ring on the plate.Iberotalud, S.L.; Castro Fresno, Daniel; Rodriguez Fernandez, Jorge; Sanudo Fontaneda, Luis Angel; Del Coz Diaz, Juan Jose; Alvarez Rabanal, Felipe Pedro; Garcia Nieto, Paulino Jos
Low temperature performances of fiber-reinforced asphalt mixtures for surface, binder, and base layers
Full text linkFunding Information: The financial support of CEDR Project Fostering the implementation of fiber-reinforced asphalt mixtures by ensuring its safe, optimized and cost-efficient use (FIBRA) [Grant Number 867481 ] is gratefully acknowledged. Publisher Copyright: © 2022 The AuthorsIn the present study, the effects of adding fibers and Reclaimed Asphalt Pavement (RAP) on the low temperature performances of open graded asphalt mixtures for surface layer and dense asphalt mixtures for surface, binder, and base layers were investigated. Two different kinds of fibers were used: a combination of aramid and polyolefins fibers were utilized for preparing fiber reinforced porous asphalt mixtures, while polyacrylonitrile fibers were employed for producing conventional dense asphalt mixtures for surface, binder, and base layers. Reference mixtures were made with virgin materials as a benchmark to study the effects of the fibers' addition. Moreover, asphalt mixtures for surface layers composed of 30% RAP and mixtures for binder layers containing 50% RAP were produced to study the combined effects of fibers and RAP on the low temperature's performance. Thermal Stress Restrained Specimen, Uniaxial Tension Stress, and Semi-Circular Bending tests were used to evaluate the response against thermal distresses. The addition of the fibers showed no significant effects on the low temperature strength, while a remarkable improvement in the failure temperature and crack propagation resistance properties was found. The use of fibers has also shown to be beneficial in combination with mixtures designed with RAP and higher binder content suggesting a dedicated study on mix design for future research.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Estudio del proceso constructivo de la ampliación del dique del Puerto de Santa Cruz de La Palma
No full textGrado en Ingeniería civi
Estudio de mezclas asfálticas densas autosanables mediante inducción magnética utilizando residuos industriales como activadores del sanado
Full text linkRESUMEN: Se han realizado grandes avances en el campo de investigación del autosanado de mez-clas asfálticas mediante inducción magnética con partículas metálicas como aditivos, cuyo calentamiento permite reparar sus propias fisuras. Se ha demostrado que esta tecno-logía permite incrementar la vida útil de las carreteras; sin embargo, su alto coste en comparación con otras prácticas de mantenimiento tradicional debido al precio de las partículas metálicas vírgenes hace que esta solución no sea atractiva en términos de in-versión. En este contexto, la presente tesis doctoral tiene por objeto conseguir que este proceso sea económicamente viable y ambientalmente amigable. Para ello, en primer lu-gar, se realizó una búsqueda intensiva de subproductos industriales para reemplazar tan-to las partículas metálicas como los áridos naturales de las mezclas asfálticas. Estos sub-productos incluyeron residuos de procesos de granallado y mecanizado, escorias y are-nas de desmoldeo. La incorporación de estos materiales dio lugar a una serie de mezclas alternativas que se sometieron a un ensayo de rotura-sanado-rotura para determinar su capacidad de autosanado. Los resultados obtenidos a este respecto probaron que los subproductos se calentaban adecuadamente, dando lugar a ratios de sanado satisfacto-rios en comparación con los asociados a las mezclas de referencia tipo hormigón asfáltico (AC-16). Una vez realizada esta parte experimental, se procedió a abordar el modelado numérico del proceso de autosanado de estas mezclas mediante técnicas estadísticas, pues se detectó una carencia de estudios de este tipo en la literatura. La combinación de análisis clúster y modelos de regresión sirvió para reproducir el comportamiento experi-mental de las mezclas en laboratorio con precisión. A partir de ahí, se pudo determinar la cantidad óptima de subproductos industriales y tiempo necesarios para conseguir que el proceso de autosanado fuese tan eficiente como fuera posible. Por último, como respues-ta a la falta de investigaciones orientadas a validar el comportamiento mecánico a largo plazo de mezclas autosanables con subproductos industriales, se llevó a cabo un ensayo uniaxial de fatiga sobre las muestras experimentales y de referencia. Los resultados deri-vados de este test permitieron identificar una ausencia de diferencias estadísticamente significativas entre la respuesta a fatiga de las mezclas experimentales y las de referen-cia. Por tanto, retomando el punto de partida sobre el que se asienta la tesis, se concluyó que la tecnología de autosanado con residuos industriales es una solución sostenible para incrementar la vida útil de mezclas asfálticas, contribuyendo a la economía circular me-diante diversos beneficios económicos y ambientales.ABSTRACT: There have been great advances in the field of self-healing asphalt mixtures by magnetic induction, whereby metal particles are heated to enable the reparation of cracks. This technology has been found to increase the life expectancy of roads; however, its high cost in comparison with traditional maintenance practices due to the price of virgin met-al particles still makes it unattractive in terms of investment. In this context, this PhD thesis aims at making this process economically viable and environmentally efficient. To this end, first was conducting a thorough search for industrial by-products to replace both metal particles and natural aggregates in the design of asphalt mixtures. These by-products included sand blasting wastes, stainless shot wastes and polished wastes as metal particles, as well as other inert by-products as a substitute for natural aggregates. The incorporation of these materials resulted in a series of alternative mixtures that were subject to a break-heal-break test to determine their self-healing capacity. The results obtained in this respect proved that the by-products were heated adequately, leading to satisfactory healing ratios compared with those associated with an asphalt concrete ref-erence mixture (AC-16). Once this experimental part was carried out, next was address-ing the numerical modelling of the self-healing process of these mixtures through statis-tical techniques, since a research gap was found in this regard in the literature. The com-bination of cluster analysis and regression models served to replicate the experimental behavior of the mixtures in the laboratory with accuracy. From there, the optimal amount of industrial by-products and time required to make the self-healing process as efficient as possible were determined. Finally, as a response to the lack of investigations devoted to validating the long-term mechanical performance of self-healing asphalt mix-tures with industrial by-products, the experimental and reference mixtures were subject to a uniaxial fatigue test. The results derived from this experiment enabled identifying an absence of statistically significant differences between the fatigue response of exper-imental and reference mixtures. Therefore, returning to the premise on which the PhD thesis was based, the self-healing technology with industrial by-products was concluded to be a sustainable solution to increase the lifetime of asphalt mixtures, thereby contrib-uting to circular economy through multiple economic and environmental benefits.Al Ministerio de Economía y Competitividad por financiar el estudio de esta tesis mediante la beca de Formación del Personal Investigación (BES-2017-079882) en el seno del proyecto Desarrollo y optimización del Sanado por Inducción de Mezclas Asfálticas que Incluyen Materiales Alternativos y tecnologías Sostenibles (SIMA+) (BIA2016-77372-R)
Estudio de viabilidad de alternativas para el viaducto “Rego do Barco” (Autovía A-57 tramo: A Ermida-Vilaboa.Pontevedra)
Full text linkGrado en Ingeniería civi
Sistemas flexibles de alta resistencia para la estabilización de taludes. Revisión de los métodos de diseño existentes y propuesta de una nueva metodología de dimensiona
Full text linkRESUMEN: Los sistemas flexibles de alta resistencia anclados al terreno son una de las distintas técnicas existentes para la estabilización de taludes, ya sean de roca o de suelos. Están constituidos por una membrana (red de cables o malla de alambre) sujeta al terreno mediante placas de anclaje, cables de refuerzo y bulones. En la mayor parte de los modelos de cálculo existentes se supone un comportamiento activo del sistema, es decir, que evita que se produzcan deslizamientos a través de una supuesta pretensión del sistema y convexidad del terreno. El sistema ejercería una presión normal al terreno que incrementa la tensión tangencial en la superficie potencial de deslizamiento evitando que se alcance la rotura del terreno. En esta tesis se han medido las fuerzas en distintos componentes del sistema desde el momento de la instalación, y se ha comprobado que la pretensión es muy reducida. Por otro lado, la supuesta convexidad del terreno raramente tiene lugar. Todo esto conduce a demostrar la hipótesis de comportamiento pasivo del sistema, es decir, que éste contiene a la masa inestable una vez que se ha producido la rotura. Es por ello que se ha considerado el desarrollar un nueva metodología de cálculo basada en un comportamiento pasivo. La nueva metodología consiste en realizar una simulación numérica dinámica en 2D de la interacción sistema flexible - masa inestable – talud estable. Partiendo de las dimensiones de un círculo de rotura en suelos o una cuña en roca, se deja caer la masa inestable con la fuerza de la gravedad. En su caída, la masa inestable deformará a la membrana, cables de refuerzo y bulones desarrollándose en ellos tensiones que deberán considerarse para su correcto dimensionamiento. En el caso particular de los taludes de suelos, se ha recurrido a la modelización de la masa inestable mediante la discretización por puntos SPH (Smooth Particle Hydrodynamics).ABSTRACT: Highly resistant flexible systems anchored to the ground are among the techniques for slope stabilisation, either soil or rock. The system is formed by a membrane (cable net or wire mesh) tightened to the ground through spike plates, reinforcement cables and bolts. In the majority of the existing design models, an active behaviour of the system is considered; which means, that it is able to avoid ground sliding through a pretension of the system and the convexity of the slope surface. The system would exert a normal pressure over the ground that increases the shear stress in the potential slip surface avoiding that failure takes place. In this thesis, forces on different system components have been measured, finding that the pretension force is very low. On the other hand, the supposed ground convexity rarely exists. All this demonstrates that actual system behaviour is passive; which means that it is able to contain the unstable mass once the failure has already occurred. Therefore, a new design methodology based on a passive behaviour has been developed. The new methodology consists in performing a dynamic numerical simulation in 2D of the interaction flexible system – unstable mass – stable slope. Starting from specific known dimensions of slip circle in soils or a wedge in rocks, unstable mass falls only under the action of gravity. During its falling, the unstable mass deforms the membrane, reinforcement cables and bolts. Maximum stresses developed in these components should be considered for their design. In the particular case of soil slopes, unstable mass has been discretised with the mesh free method SPH (Smooth Particle Hydrodynamics)
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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