Exact Renormalization of Massless QED2

We perform the exact renormalization of two-dimensional massless gauge theories. Using these exact results we discuss the cluster property and confinement in both the anomalous and chiral Schwinger models.Comment: 14 pages, no figures, introduction and conclusions modifie

Suppression of viscous fluid fingering: a piecewise constant-injection process

The injection of a fluid into another of larger viscosity in a Hele-Shaw cell usually results in the formation of highly branched patterns. Despite the richness of these structures, in many practical situations such convoluted shapes are quite undesirable. In this letter we propose an efficient and easily reproducible way to restrain these instabilities based on a simple piecewise constant pumping protocol. It results in a reduction in the size of the viscous fingers by one order of magnitude.Comment: Published in Phys. Rev.

The relationship between ENSO and Paraná River flow

International audienceSeveral studies indicate that there is a relationship between the climatic variability in the South American continent and alterations of the position and intensity of the heat sources in the equatorial region. The El Niño phenomenon can influence the precipitation over some regions of South America such as the Brazilian Northeast, Amazonia, South of Brazil and Uruguay. Over 80% of Brazil's energy comes from hydropower, and decisions concerning future availability and pricing require forecasts of river flow, ideally several months in advance. In this work the relationship between the Paraná River flow and the ENSO (El Niño/Southern Oscillation) mode is investigated and statistical forecasts of river flow are tested. An evaluation of the relationship between the Pacific sea surface temperature and the Paraná River flow indicates an ENSO pattern over the equatorial Pacific. The time series of the ENSO mode obtained by applying principal components analysis on the sea surface temperature (SST) were used as predictors for the Paraná River flow forecast. Improvement in the model forecast skill is also obtained by considering the lagged river flow time series as a predictor

CVD of CrO2: towards a lower temperature deposition process

We report on the synthesis of highly oriented a-axis CrO2 films onto (0001) sapphire by atmospheric pressure CVD from CrO3 precursor, at growth temperatures down to 330 degree Celsius, i.e. close to 70 degrees lower than in published data for the same chemical system. The films keep the high quality magnetic behaviour as those deposited at higher temperature, which can be looked as a promising result in view of their use with thermally sensitive materials, e.g. narrow band gap semiconductors.Comment: 13 pages, 4 figure

NSM CFRP laminates for the shear strengthening of high strength concrete beams

The effectiveness of the Near Surface Mounted (NSM) shear strengthening technique with Carbon Fiber Reinforced Polymer (CFRP) laminates applied in relatively high-strength concrete beams was assessed by experimental research. Six NSM shear strengthening configurations (three CFRP orientations and two levels of CFRP percentage) were applied in T cross section Reinforced Concrete (RC) beams with a steel stirrups percentage of 0.10% (ρsw = 0.10%). Four of these NSM configurations were also applied in beams with ρsw = 0.16%. The concrete of the beams had a compressive strength of 59.4 MPa at the age of beam tests. The main results of this experimental research are presented and analyzed in terms of the structural behaviour of the beams, failure modes and performance of the NSM technique with CFRP laminates. The results showed that NSM shear strengthening technique with CFRP laminates has a high performance in RC beams with high-strength concrete, not only in terms of increasing the load carrying capacity of the beams but also in mobilizing more effectively the tensile properties of the CFRP

NSM shear strengthening technique with CFRP laminates applied in high T cross section RC beams

The effectiveness of the Near Surface Mounted (NSM) technique with Carbon Fiber Reinforced Polymer (CFRP) laminates for the shear strengthening of relatively high T cross section (h = 600 mm) Reinforced Concrete (RC) beams was assessed by experimental research. Two inclinations of the laminates were tested (52° and 90°) and, for each one, two percentages of CFRP were adopted. The RC beams shear strengthened with NSM laminates had a percentage of steel stirrups of 0.09%. The experimental results showed that NSM shear strengthening technique with CFRP laminates is very effective in RC beams of relatively high cross section height, not only in terms of increasing the load carrying capacity of the beams, but also in assuring higher mobilization of the tensile capacity of the CFRP. Furthermore, inclined laminates were more effective than vertical laminates and the shear capacity of the beams increased with the percentage of laminates. Taking into account available experimental results obtained with the same test setup, but using RC beams of lower depth of T cross section (h = 400 mm), it can be concluded that the effectiveness of the NSM technique with CFRP laminates increase with the increase of the depth of the cross section. The formulations provided by Nanni et al. (2004) and Dias and Barros (2013) for the NSM shear strengthening technique predicted a CFRP contribution around 51% and 67%, respectively, of the experimentally registered values.The authors acknowledge the financial support provided by QREN (through the Operational Program COMPETE) in the scope of the CutInov Project (n. 38780) involving the Clever Reinforcement Company and the Structural Composites Research group of ISISE-Minho University. The authors also acknowledges the support provided by the “Empreiteiros Casais” and Secil (Unibetão, Braga).info:eu-repo/semantics/publishedVersio

Influência da percentagem e orientação de laminados de CFRP no reforço ao corte de vigas de betão armado

Para avaliar a influência da percentagem e orientação de laminados de CFRP, aplicados segundo a técnica NSM, no reforço ao corte de vigas de betão armado de secção em T, foi efectuado um programa experimental. Foram analisadas três orientações para os laminados (vertical, inclinado a 45º e a 60º) e, para cada umas destas orientações, foram consideradas três percentagens de CFRP. Com o objectivo de simular situações próximas dos cenários reais no reforço estrutural, todas as vigas onde foi aplicado CFRP continham uma determinada percentagem de estribos. Os resultados obtidos são apresentados e analisados.Os autores do presente trabalho expressam o seu agradecimento à empresa “Empreiteiros Casais” pela colaboração prestada na construção das vigas e na aplicação dos reforços de CFRP. Os agradecimentos são extendidos à S&P Reinforcement pelo fornecimento dos laminados e mantas de CFRP, à Unibetão (Braga) pelo fornecimento do betão e à Degussa Construction Chemicals Portugal pelo fornecimento do adesivo e das resinas. Um agradecimento especial ao Miguel Freitas, finalista da licenciatura em Engenharia Civil da Universidade do Minho, pela colaboração na campanha de ensaios levada a cabo para a realização deste trabalho. Os autores manifestam também os seus agradecimentos ao apoio prestado pela Fundação para a Ciência e Tecnologia (FCT) no projecto POCTI/ECM/59033/2004