Resumo Esse trabalho objetivou analisar a eficiência do reforço com adição de barras de aço e adesivo epóxi em vigas de concreto armado. Foram produzidas cinco vigas. Quatro receberam reforço à flexão e em duas delas também foram utilizados grampos em “U” para melhorar a ancoragem do reforço. Os ensaios mostraram que os grampos reduziram a resistência das vigas em relação às sem grampos. As vigas reforçadas sem grampos obtiveram melhores resultados, sendo o maior limitador a aderência entre o epóxi e a viga. O uso dos grampos para tentar resolver o problema da aderência deram originalidade a essa pesquisa. As conclusões foram baseadas nas comparações entre as vigas ensaiadas.

Abstract This work was aimed at analyzing the efficiency of the strengthening of reinforced concrete beams with the addition of steel bars and epoxy adhesive. Five beams were produced, out of which four beams were strengthened to flexure. In two of them, “U” clips were also used to improve the anchorage of the strengthening. The tests demonstrated that the clips reduced the resistances of the beams compared to those without clips. The strengthened beams without clips yielded better results, but the largest limiting factor was the adherence between the epoxy and beam. The use of clips for solving the problem of adherence made this research original. The conclusions were based on the comparisons of the tested beams.

Resumen Este trabajo tuvo como objetivo analizar la eficiencia del refuerzo en vigas de hormigón armado mediante la adición de barras de acero y adhesivo epoxi. Se produjeron cinco vigas. Cuatro recibieron refuerzo a flexión, y en dos de ellas fueron adicionadas también abrazaderas “U” para mejorar el anclaje del refuerzo. Los ensayos mostraron que las abrazaderas redujeron la resistencia de las vigas, en comparación con las que no tenían. Las vigas reforzadas sin abrazaderas obtuvieron mejores resultados, pero el factor limitante más importante fue la adherencia entre el epoxi y la viga. El uso de abrazaderas para intentar resolver el problema de la adherencia dio originalidad a esta investigación. Las conclusiones se basaron en la comparación entre las vigas ensayadas.

RESUMO. O gênero de grafos têm sido estudados por muitos autores, mas existem resultados apenas para casos especiais: Planar, Toroidal, Completo, Bipartido e Produto cartesiano de Bipartidos. Apresentamos aqui um limite inferior para o gênero de um grafo de Cayley de um grupo abeliano e construímos uma família de grafos circulantes que atingem esse limitante.

ABSTRACT. The genus graphs have been studied by many authors, but just a few results concerning in special cases: Planar, Toroidal, Complete, Bipartite and Cartesian Product of Bipartite. We present here a general lower bound for the genus of a abelian Cayley graph and construct a family of circulant graphs which reach this bound.

Expanded use of fast photography is proposed to characterize laser ablation plasma plumes by the analysis of a set of photographs by means of appropriate mathematical algorithms. The laser ablation plasma plumes studied were generated by ablation of both a multicomponent target of the nominal composition Ni50Mn37Sn13 and a highly pure Cu target (Cu) using a Q-switched Nd-YAG laser system. The experiments were conducted under different background argon pressures. Several photograph parameters such as intensity per unit time of exposure for a pixel, mean intensity per pixel per unit time of exposure, integrated intensity and cross correlation were studied. The intensity per unit time of exposure allowed for identification of the fast component of the triple structure of the expanding plasma into the background gas (that travels at a speed close to the one measured in vacuum). This parameter together with the use of cross correlation enabled the identification of regions of the expanded plasma plume with higher and lower similarities in their optical emission behavior. The mean intensity per pixel per unit time of exposure can be used as a measurement of the amount of light emitted by the plume as a function of time.

The present work describes the development of a photoacoustic flowmeter with probe-beam deflection. A pulsed laser beam produces an acoustic pulse, whose propagation is registered by its deflection effects on two cw probe beams. The acoustic pulse in a flowing fluid is produced by absorption of a laser pulse (30 ns, 1.1 mJ) focused over a path flow line. The acoustic propagations, along and against the flow, are monitored by two cw probe beams. In the interaction, the probe beam undergoes a transient deflection that is detected by a fast response photodiode. The velocity distribution data profile of a square pipe is obtained by means of the acoustic pulse arrival time measured through its cross section applying the cylindrical shockwave model developed by Vlasses. The profiles determined with this experimental technique are compared with two turbulent pipe flow models.

El presente trabajo describe el desarrollo de un velocímetro fotoacústico para fluidos utilizando deflectometría. El sistema de medición está basado en la detección de un pulso acústico, producido por la absorción de un pulso láser (30 ns, 1.1 mJ) que es enfocado en una línea de corriente del flujo. La propagación del pulso es registrada, aguas arriba y aguas abajo, mediante dos haces continuos que sufren una deflexión cuando interactúan con la onda acústica que es detectada por un fotodiodo rápido. De esta manera, el perfil de velocidades de una tubería de sección cuadrada es encontrado mediante el tiempo de arribo del pulso acústico medido en su sección transversal, aplicando el modelo de onda de choque cilíndrica desarrollado por Vlasses. Los perfiles obtenidos con los valores experimentales son comparados con dos modelos de flujo turbulento aplicados en tuberías

A new fruit rot disease caused by Sclerotium rolfsii on watermelon (Citrullus lanatus) was observed in the State of Alagoas. The pathogenicity of the fungus was confirmed by artificial inoculations.This is the first report of S. rolfsii causing fruit rot in watermelon in Northeast of Brazil.