Estudio del comportamiento de anclajes al terreno en muros de gran altura

Uno de los métodos más utilizados dentro de la Ingeniería Geotécnica para la contención y estabilización de muros en excavaciones es la colocación de anclajes. Para que un anclaje trabaje a tracción adecuadamente y se pueda asegurar que realiza su función con seguridad se deben estudiar correctamente distintos parámetros de dicho dispositivo, tales como las características mecánicas del terreno que atraviesa, la lechada de inyección utilizada, así como el acero usado en los tirantes del anclaje. En la presente tesina se realiza la modelización de elementos estructurales y de anclajes, y el estudio de su interacción con el terreno, simulando su comportamiento en deformación plana y en tres dimensiones mediante el programa geotécnico de elementos finitos, PLAXIS, desarrollado por la Universidad de Delf (Holanda). Dicho programa permite la resolución numérica de las ecuaciones que rigen el comportamiento tenso-deformacional de un material elastoplástico bajo las hipótesis de deformación plana. De manera que en el presente estudio se detalla someramente la resolución de tres casuísticas distintas considerando diversos modelos constitutivos así como también se expone una comparación entre dichos modelos. Por un lado, se analiza numéricamente el comportamiento de un anclaje vertical aislado, en deformación plana y en tres dimensiones, con una comparativa de los modelos elástico lineal, Mohr-Coulomb, Cam-Clay, Hardening Soil y Hardening Soil a pequeñas deformaciones. Posteriormente, se caracteriza el comportamiento de una serie de anclajes al terreno dispuestos con cierta inclinación para la contención de dos pantallas. Por último, se analiza una sección compleja de anclajes al terreno realizada en las obras del AVE por su paso por La Sagrera (Barcelona), tratando así con un caso real resuelto mediante un sistema de anclajes

Caracterítzació del estat de les Glàndules de Meibomi en una població universitària

La Disfunció de les Glàndules de Meibomi (DGM) és la principal causa del anomenat síndrome d’ull sec. És una anomalia crònica i difusa de les glàndules meibomianes, caracteritzada per la obstrucció del conducte terminal i/o canvis qualitatius/quantitatius en la secreció glandular. A conseqüència d’això es produeix una alteració de la pel·lícula llagrimal, símptomes d’irritació ocular i malalties de la superfície ocular. L’objectiu d’aquest treball és caracteritzar les glàndules de Meibomi, mitjançant la observació amb llum infraroja i valorar si hi ha relació entre la alteració de les glàndules de Meibomi i la simptomatologia de sequedat ocular, obtenint aquesta simptomatologia a través d’un test, en el nostre cas del test OSDI. Per fer-ho vam avaluar una mostra de població jove pertanyent a la Facultat d’Óptica i Optometria de Terrassa, que va ser composta per 20 estudiants (16 dones i 4 homes) d’entre 19 i 27 anys. Per concloure aquest treball, vam trobar la relació entre els resultats de diferents proves (mesura del menisc llagrimall i mesura de la freqüència del parpelleig) i aspectes (sequedat ocular), amb el càlcul de la totalitat d’àrea que ocupaven les glàndules de Meibomi en cada participant, trobant així una caracterització i una classificació adequada d’aquestes

Medium-frequency electrical resistance sintering of oxidized C.P. iron powder

Commercially pure (C.P.) iron powders with a deliberate high degree of oxidation were consolidated by medium-frequency electrical resistance sintering (MF-ERS). This is a consolidation technique where pressure, and heat coming from a low-voltage and high-intensity electrical current, are simultaneously applied to a powder mass. In this work, the achieved densification rate is interpreted according to a qualitative microscopic model, based on the compacts global porosity and electrical resistance evolution. The effect of current intensity and sintering time on compacts was studied on the basis of micrographs revealing the porosity distribution inside the sintered compact. The microstructural characteristics of compacts consolidated by the traditional cold-press and furnace-sinter powder metallurgy route are compared with results of MF-ERS consolidation. The goodness of MF-ERS versus the problems of conventional sintering when working with oxidized powders is analyzed. The electrical consolidation can obtain higher densifications than the traditional route under non-reducing atmospheres.Ministerio de Economía y Competitividad DPI2015-69550-C2-1-PMinisterio de Economía y Competitividad DPI2015-69550-C2-2-

Changes in bioaccessibility, polyphenol profile and antioxidant potential of flours obtained from persimmon fruit (Diospyros kaki) co-products during in vitro gastrointestinal digestion

The aim was to evaluate (i) the phenol and flavonoid recovery and bioaccessibility indexes, (ii) the stability of individual polyphenolic compounds and (iii) the antioxidant activity of persimmon flours (cultivars ‘Rojo Brillante’ and ‘Triumph’) during the in vitro digestion. The recovery index for phenolic and flavonoid content was dependent on flour type and digestion phase. After the dialysis phase, the bioaccessibility for phenolic compounds from both flours was similar; for flavonoids it was higher in ‘Triumph’ than ‘Rojo Brillante’ flour. After in vitro digestion, 13 polyphenolic compounds were detected in both flours, of which only six were detected in the intestinal phase. Their antioxidant activity (ABTS%+, FRAP and DPPH) decreased after intestinal phase, while their chelating activity (FIC assay) increased in both flours. So, persimmon flours could be included in the formulation of foods to improve either their scarcity of bioactive compounds or an unbalanced nutritional composition

Electrical discharge consolidation of Al and Ti powders

In this paper, electrical-discharge-consolidation (EDC technique) experiments were carried out with an equipment based on the technology developed for the stud welding technology. The main advantage of the EDC technique is its high speed, on the order of milliseconds or less, which makes it particularly interesting when a high final porosity is aimed, or when the inherent nanostructure of the powders needs to be preserved. Compacts of Ti and Al were consolidated with this technique, both directly from loose powders and from cold pressed green compacts. Two different configurations (200 V – 66 mF and 800 V − 1.1 mF) were tested. Relative density, microhardness, electrical resistivity and metallographic and SEM studies were carried out to understand the changes in powder particles caused by the electrical discharge. The use of a high capacitance in the capacitors bank, despite the use of a lower voltage, results in a better consolidation process.Ministerio de Economía y Competitividad DPI2015-69550-C2-1-PMinisterio de Economía y Competitividad DPI2015-69550-C2-2-P

Magnetic properties of iron powder sintered by medium-frequency electrical resistance sintering

Medium-frequency electrical resistance sintering (MF-ERS) is a technique that uses the application of pressure and heat, heat coming from the Joule effect, simultaneously to metallic powders. In this study, this technique consolidates commercial iron powders, and the porosity distribution and hysteresis curves of the compacts were analysed. Compact consolidated by conventional powder metallurgy (PM) was compared with the results obtained

Chia Oil Extraction Coproduct as a Potential New Ingredient for the Food Industry: Chemical, Physicochemical, Techno-Functional and Antioxidant Properties

The aim of this work was to characterize the coproduct obtained from chia oil production (cold-pressing) with a view to its possible application in new food product development. For this characterization, the following determinations were made: proximate composition, physicochemical analysis, techno-functional properties, total phenolic and flavonoid content, polyphenolic profile and antioxidant capacity (using four different methods). Chia coproduct showed significantly higher levels of proteins and total dietary fiber and lower levels of fats than chia seeds, pointing to the promising nature of this coproduct as an ingredient of food formulations since it remains a source of high biological value proteins and total dietary fiber (as chia seeds themselves) but with a lower energy value. This chia coproduct presents similar techno-functional properties to the original chia seeds and significantly higher levels of polyphenolic compounds and, consequently, higher antioxidant activit

Nickel Porous Compacts Obtained by Medium-Frequency Electrical Resistance Sintering

A commercially pure (c.p.) nickel powder was consolidated by Medium-Frequency Electrical Resistance Sintering (MF-ERS). In this consolidation technique, a pressure and the heat released by a high-intensity and low-voltage electrical current are concurrently applied to a metal powder mass. A nickel powder with a high tap porosity (86%) and a low applied pressure (only 100 MPa) is chosen in order to be able to obtain compacts with different levels of porosity, to facilitate the study of the porosity influence on the compact properties. The influence of current intensity and heating time on the global porosity values, the porosity and microhardness distribution, and the electrical conductivity of the sintered compacts is studied. The properties of the compacts consolidated by MF-ERS are compared with the results obtained by the conventional powder metallurgy route, consisting of cold pressing and furnace sintering. A universal equation to describe the porosity influence on all the analyzed properties of powder aggregates and sintered compacts is proposed and validated

Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting

Based on field work and seismic reflection data, we investigate the Cenozoic tectono-sedimentary evolution offshore and onshore Ibiza allowing the proposal of a new tectonic agenda for the region and its integration in the geodynamic history of the West Mediterranean. The late Oligocene-early Miocene rifting event, which characterizes the Valencia Trough and the Algerian Basin, located north and south of the study area respectively, is also present in Ibiza and particularly well-expressed in the northern part of the island. Among these two rifted basins initiated in the frame of the European Cenozoic Rift System, the Valencia Trough failed rapidly while the Algerian Basin evolved after as a back-arc basin related to the subduction of the Alpine-Maghrebian Tethys. The subsequent middle Miocene compressional deformation was localized by the previous extensional faults, which were either inverted or passively translated depending on their initial orientation. Despite the lateral continuity between the External Betics and the Balearic Promontory, it appears from restored maps that this tectonic event cannot be directly related to the Betic orogen, but results from compressive stresses transmitted through the Algerian Basin. A still active back-arc asthenospheric rise likely explains the stiff behavior of this basin, which has remained poorly deformed up to recent time. During the late Miocene a new extensional episode reworked the southern part of the Balearic Promontory. It is suggested that this extensional deformation developed in a trans-tensional context related to the westward translation of the Alboran Domain and the coeval right-lateral strike-slip movement along the Emile Baudot Escarpment bounding the Algerian Basin to the north. (C) 2016 Elsevier B.V. All rights reserved

Medium-Frequency Electrical Resistance Sintering of Soft Magnetic Powder Metallurgy Iron Parts

The fabrication of soft magnetic Fe parts by the medium-frequency electrical resistance sintering (MF-ERS) technique is studied in this paper. This consolidation technique involves the simultaneous application to metallic powders of pressure and heat, the latter coming from the Joule effect of a low-voltage and high-intensity electric current. Commercially pure iron powder was used in the consolidation experiences. The porosity distribution, microhardness, electrical resistivity and hysteresis curves of the final compacts were determined and analysed. The results obtained were compared both with those of compacts consolidated by the conventional powder metallurgy (PM) route of cold pressing and vacuum furnace sintering, and with fully dense compacts obtained by double cycle of cold pressing and furnace sintering in hydrogen atmosphereFinancial support of the Ministerio de Economía y Competitividad (Spain) and Feder (EU) through the research projects DPI2015-69550-C2-1-P and DPI2015-69550-C2-2-P is gratefully acknowledged The authors also wish to thank the technicians J. Pinto, M. Madrid and M. Sánchez (University of Seville, Spain) for experimental assistanc