Hydrodynamic View of Wave-Packet Interference: Quantum Caves

Wave-packet interference is investigated within the complex quantum Hamilton-Jacobi formalism using a hydrodynamic description. Quantum interference leads to the formation of the topological structure of quantum caves in space-time Argand plots. These caves consist of the vortical and stagnation tubes originating from the isosurfaces of the amplitude of the wave function and its first derivative. Complex quantum trajectories display counterclockwise helical wrapping around the stagnation tubes and hyperbolic deflection near the vortical tubes. The string of alternating stagnation and vortical tubes is sufficient to generate divergent trajectories. Moreover, the average wrapping time for trajectories and the rotational rate of the nodal line in the complex plane can be used to define the lifetime for interference features.Comment: 4 pages, 3 figures (major revisions with respect to the previous version have been carried out

Experimental verification of the metal flux enhancement in a mixture of two metal complexes: the Cd/NTA/glycine and Cd/NTA/citric acid systems

Rigorous computation of the metal flux crossing a limiting surface of a system that contains a mixture of 1 : 1 metal complexes under steady-state planar diffusion in a finite domain and under excess of ligand conditions predicts, for some cases, an enhancement of the metal flux with respect to that expected in a system with independent complexes. Indeed, the coupling of the dissociation kinetics of both complexes can yield higher metal fluxes than expected with important environmental implications. By using the voltammetric techniques AGNES and stripping chronopotentiometry, this paper provides experimental evidence of this enhancement for two systems: Cd/NTA/glycine and Cd/NTA/citric acid. The flux measured in both cases is in good agreement with the flux computed for the global system, exhibiting maximum enhancement ratios above 20%. Theoretical discussion of the flux enhancement factors and of the conditions for this enhancement are also provided

Comportamento de vigas de betão armado reforçadas à flexão com sistemas compósitos de CFRP unidireccionais

Os estudos já efectuados sobre o reforço à flexão, com materiais compósitos de CFRP, de elementos de betão armado (vigas e faixas de laje) demonstram que o comportamento estrutural é significativamente melhorado ao nível da resistência. No entanto, tem-se verificado que é difícil obter o total aproveitamento do reforço de CFRP, isto é, atingir a rotura do compósito em simultâneo com o esmagamento do betão. Tal deve-se ao facto de se verificar a ocorrência de ruínas prematuras intercalares, ao longo da junta de ligação betão-adesivo-CFRP, que culminam no destacamento antecipado do reforço. Neste trabalho descrevem-se os ensaios à flexão realizados em vigas de betão armado, uma simplesmente armada com armadura convencional (referência) e cinco reforçadas com sistemas compósitos de CFRP unidireccionais. Os resultados obtidos são apresentados e interpretados, referindo-se as principais conclusões sobre o comportamento das vigas ensaiadas e, em particular, a contribuição dos mecanismos de fixação na zona de ancoragem

Efeito da pré-fendilhação do betão no comportamento à flexão de faixas de laje reforçadas com sistemas compósitos de CFRP

Reforçar ou reabilitar estruturas existentes envolve, frequentemente, a presença de betões em estado fendilhado. Nesse sentido, o comportamento da recente técnica de reforço à flexão por adição de sistemas compósitos de fibras de carbono unidireccional (CFRP) é avaliado numa campanha de ensaios experimentais de faixas de laje executadas em betão armado, com e sem fendilhação inicial do betão. Nessa campanha, dez faixas de laje de betão armado são ensaiadas à flexão, em quatro pontos, sendo duas simplesmente armadas (referência) e oito reforçadas com sistemas compósitos de CFRP. Destas últimas, quatro são reforçadas com o sistema curado “in situ” (manta flexível) e as restantes são reforçadas com o sistema pré-fabricado (laminado semí-rigido). Em cada um dos dois grupos reforçados, duas faixas de laje são, previamente à colagem do reforço, solicitadas de tal forma a atingirem um estado de fendilhação estabilizada. Neste trabalho, os ensaios efectuados são descritos e os resultados obtidos são analisados e interpretados

Multiple Sources toward the High-mass Young Star S140 IRS1

S140 IRS1 is a remarkable source where the radio source at the center of the main bipolar molecular outflow in the region is elongated perpendicular to the axis of the outflow, an orientation opposite to that expected if the radio source is a thermal jet exciting the outflow. We present results of 1.3 cm continuum and H2O maser emission observations made with the VLA in its A configuration toward this region. In addition, we also present results of continuum observations at 7 mm and re-analyse observations at 2, 3.5 and 6 cm (previously published). IRS 1A is detected at all wavelengths, showing an elongated structure. Three water maser spots are detected along the major axis of the radio source IRS 1A. We have also detected a new continuum source at 3.5 cm (IRS 1C) located ~0.6'' northeast of IRS 1A. The presence of these two YSOs (IRS 1A and 1C) could explain the existence of the two bipolar molecular outflows observed in the region. In addition, we have also detected three continuum clumps (IRS 1B, 1D and 1E) located along the major axis of IRS 1A. We discuss two possible models to explain the nature of IRS 1A: a thermal jet and an equatorial wind.Comment: 17 pages, 4 figures, to be published in A

Estruturas de betão armado reforçadas à flexão com sistemas de CFRP

No Laboratório de Estruturas (LABEST) da Faculdade de Engenharia da Universidade do Porto foram realizados vários programas experimentais sobre o reforço à flexão de estruturas de betão armado por intermédio da colagem externa de sistemas compósitos de CFRP (polímeros reforçados com fibras de carbono) unidireccionais. Neste trabalho serão apresentados dois, um realizado sobre faixas de laje e o outro sobre vigas. Os resultados obtidos são analisados e interpretados, referindo-se as principais conclusões sobre o comportamento dos elementos estruturais ensaiados tendo em vista avaliar a viabilidade do reforço com CFRP de elementos de betão armado à flexão. Estes estudos asseguram que a colagem de CFRP permite aumentos significativos na capacidade resistente de elementos de betão armado à flexão.Experimental research regarding the flexural strengthening of RC structures with externally bonded unidirectional carbon-fiber-reinforced systems (CFRP) has been carried out in the Structural Laboratory (LABEST) of Faculty of Civil Engineering of Porto University (FEUP). The paper presents two works, one refers to RC slabs specimens and other to RC beams specimens. The results are described, analyzed and discussed in order to obtain conclusions about the behaviour of RC structures strengthened with CFRP composite systems. These tests confirmed that the load capacity of RC structures can be significantly increased by applying externally bonded CFRP systems

Growth and texture of Spark Plasma Sintered Al2O3 ceramics: a combined analysis of X-rays and Electron Back Scatter Diffraction

Textured alumina ceramics were obtained by Spark Plasma Sintering (SPS) of undoped commercial a-Al2O3 powders. Various parameters (density, grain growth, grain size distribution) of the alumina ceramics, sintered at two typical temperatures 1400{\deg}C and 1700{\deg}C, are investigated. Quantitative textural and structural analysis, carried out using a combination of Electron Back Scattering Diffraction (EBSD) and X-ray diffraction (XRD), are represented in the form of mapping, and pole figures. The mechanical properties of these textured alumina ceramics include high elastic modulus and hardness value with high anisotropic nature, opening the door for a large range of applicationsComment: 16 pages, 6 figures, submitted to J. Appl. Phy

Shadow identification and classification using invariant color models

A novel approach to shadow detection is presented in this paper. The method is based on the use of invariant color models to identify and to classify shadows in digital images. The procedure is divided into two levels: first, shadow candidate regions are extracted; then, by using the invariant color features, shadow candidate pixels are classified as self shadow points or as cast shadow points. The use of invariant color features allows a low complexity of the classification stage. Experimental results show that the method succeeds in detecting and classifying shadows within the environmental constrains assumed as hypotheses, which are less restrictive than state-of-the-art methods with respect to illumination conditions and scene's layout