A arquitectura dos Gabinetes de Urbanização Colonial em Moçambique (1944-1974)

No quadro colonial português da segunda metade do século XX, o urbanismo e a arquitectura de promoção pública destinados a Moçambique seguem as diretrizes de outros projetos realizados em Lisboa para os territórios ultramarinos. Uma análise da sua evolução permite elencar as políticas de Obras Públicas do governo central para o Ultramar. Esta produção urbanística e arquitetónica é essencialmente realizada no âmbito do Gabinete de Urbanização Colonial (GUC), criado ainda durante a Segunda Guerra Mundial por Marcelo Caetano, então ministro das Colónias. O Gabinete conhecerá outras designações: em 1951 passa a Gabinete de Urbanização do Ultramar (GUU), e em 1957 a Direcção de Serviços de Habitação e Urbanismo da Direcção-Geral de Obras Públicas e Comunicações (DSUH-DGOPC) do Ministério do Ultramar. A sua acção em Moçambique segue essencialmente as linhas de orientação que são conhecidas para outras regiões do então “Império colonial português”, destacando-se uma visão mais conservadora ou tradicionalista que caracteriza os tempos iniciais de arranque desta estrutura, seguindo-se um período de estabilização linguística no plano da “arquitetura de representação”, designadamente com os programas públicos de maior significado político (estruturas de representação administrativa, liceus e escolas técnicas, instalações hospitalares), e terminando numa abordagem que se pretende mais adequada aos habitats locais, integrando dispositivos aprofundados nos estudos internacionais em “Arquitectura Tropical”. O panorama aqui apresentado é ainda lacunar, por não se encontrar a investigação completamente encerrada.info:eu-repo/semantics/publishedVersio

Influence of realistic parameters on state-of-the-art LWFA experiments

We examine the influence of non-ideal plasma-density and non-Gaussian transverse laser-intensity profiles in the laser wakefield accelerator analytically and numerically. We find that the characteristic amplitude and scale length of longitudinal density fluctuations impacts on the final energies achieved by electron bunches. Conditions that minimize the role of the longitudinal plasma density fluctuations are found. The influence of higher order Laguerre-Gaussian laser pulses is also investigated. We find that higher order laser modes typically lead to lower energy gains. Certain combinations of higher order modes may, however, lead to higher electron energy gains.Comment: 16 pages, 6 figures; Accepted for publication in Plasma Physics and Controlled Fusio

Acceleration in perpendicular relativistic shocks for plasmas consisting of leptons and hadrons

We investigate the acceleration of light particles in perpendicular shocks for plasmas consisting of a mixture of leptonic and hadronic particles. Starting from the full set of conservation equations for the mixed plasma constituents, we generalize the magneto-hydrodynamical jump conditions for a multi-component plasma, including information about the specific adiabatic constants for the different species. The impact of deviations from the standard model of an ideal gas is compared in theory and particle-in-cell simulations, showing that the standard-MHD model is a good approximation. The simulations of shocks in electron-positron-ion plasmas are for the first time multi-dimensional, transverse effects are small in this configuration and 1D simulations are a good representation if the initial magnetization is chosen high. 1D runs with a mass ratio of 1836 are performed, which identify the Larmor frequency \omega_{ci} as the dominant frequency that determines the shock physics in mixed component plasmas. The maximum energy in the non-thermal tail of the particle spectra evolves in time according to a power-law proportional to t^\alpha with \alpha in the range 1/3 < \alpha < 1, depending on the initial parameters. A connection is made with transport theoretical models by Drury (1983) and Gargate & Spitkovsky (2011), which predict an acceleration time proportional to \gamma and the theory for small wavelength scattering by Kirk & Reville (2010), which predicts a behavior rather as proportional to \gamma^2. Furthermore, we compare different magnetic field orientations with B_0 inside and out of the plane, observing qualitatively different particle spectra than in pure electron-ion shocks

Surface circulation in the eastern North Atlantic, from drifters and altimetry

A description of the near-surface circulation and its properties is the result of the analysis of a drifting buoy data set in the eastern North Atlantic between the Iberian Peninsula, the Azores, and the Canary Islands. World Ocean Circulation Experiment-Tropical Ocean-Global Atmosphere experiment drifters equipped with holey sock drogues centered at 15 m depth collected a total of 14.4 years of data. The drifters sampled a rather inhomogeneous velocity field with a weak mean flow regime and eddies of different scales. They meandered southward everywhere in the study region, except in the Iberian coastal transition zone north of 41degreesN where they headed northward. The near-surface mean velocity field obtained from the drifter data set shows all important mean currents, including the poleward Portugal Coastal Countercurrent during the fall, winter, and early spring off western and northern Iberia, the southward Portugal Coastal Current, the slow offshore southward flow of the Portugal Current during the whole year, the southwestward Canary Current, and the eastward Azores Current, which extends to the vicinity of the African coast near the Gulf of Cadiz. Maps of the eddy kinetic energy field were obtained from the drifters and from satellite altimetry. It provides the largest part of the total kinetic energy. The rate of dispersion is estimated from the Lagrangian statistics of the drifting buoys. The dispersion of the drifters in the study region is well modeled by a simple description of eddy diffusion assuming homogeneous turbulence. Ensemble mean diffusivities K and the Langrangian integral length scales and timescales (L and T) were obtained for the zonal and meridional directions. The sea surface temperature measured along the drifter trajectories is used to produce estimates of the eddy diffusivity, which is compared with the diffusivity estimates obtained from the theory of Taylor. The eddy diffusivity is found to be approximately proportional to the eddy kinetic energy. Discrete eddies and meanders were observed using drifters and altimetry in order to map and describe their geographical distribution and characteristics in the eastern North Atlantic

Optimization process of polyester polymer mortars modified with recycled GFRP waste aggregates – application of factorial experiment design-

Glass fibre-reinforced plastics (GFRP), nowadays commonly used in the construction, transportation and automobile sectors, have been considered inherently difficult to recycle due to both: cross-linked nature of thermoset resins, which cannot be remolded, and complex composition of the composite itself, which includes glass fibres, matrix and different types of inorganic fillers. Presently, most of the GFRP waste is landfilled leading to negative environmental impacts and supplementary added costs. With an increasing awareness of environmental matters and the subsequent desire to save resources, recycling would convert an expensive waste disposal into a profitable reusable material. There are several methods to recycle GFR thermostable materials: (a) incineration, with partial energy recovery due to the heat generated during organic part combustion; (b) thermal and/or chemical recycling, such as solvolysis, pyrolisis and similar thermal decomposition processes, with glass fibre recovering; and (c) mechanical recycling or size reduction, in which the material is subjected to a milling process in order to obtain a specific grain size that makes the material suitable as reinforcement in new formulations. This last method has important advantages over the previous ones: there is no atmospheric pollution by gas emission, a much simpler equipment is required as compared with ovens necessary for thermal recycling processes, and does not require the use of chemical solvents with subsequent environmental impacts. In this study the effect of incorporation of recycled GFRP waste materials, obtained by means of milling processes, on mechanical behavior of polyester polymer mortars was assessed. For this purpose, different contents of recycled GFRP waste materials, with distinct size gradings, were incorporated into polyester polymer mortars as sand aggregates and filler replacements. The effect of GFRP waste treatment with silane coupling agent was also assessed. Design of experiments and data treatment were accomplish by means of factorial design and analysis of variance ANOVA. The use of factorial experiment design, instead of the one factor at-a-time method is efficient at allowing the evaluation of the effects and possible interactions of the different material factors involved. Experimental results were promising toward the recyclability of GFRP waste materials as polymer mortar aggregates, without significant loss of mechanical properties with regard to non-modified polymer mortars

Mechanical behaviour analysis of polyester polymer mortars modified with recycled GFRP waste materials

In this study the effect of incorporation of recycled glass-fibre reinforced polymer (GFRP) waste materials, obtained by means of milling processes, on mechanical behaviour of polyester polymer mortars was assessed. For this purpose, different contents of recycled GFRP waste powder and fibres, with distinct size gradings, were incorporated into polyester based mortars as sand aggregates and filler replacements. Flexural and compressive loading capacities were evaluated and found better than unmodified polymer mortars. GFRP modified polyester based mortars also show a less brittle behaviour, with retention of some loading capacity after peak load. Obtained results highlight the high potential of recycled GFRP waste materials as efficient and sustainable reinforcement and admixture for polymer concrete and mortars composites, constituting an emergent waste management solution

Laser-Plasma Interactions Enabled by Emerging Technologies

An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems