Telecommunications for the needy: how needed are they?

Telecommunications, mobile and non-mobile, play a major role in our society, but their role as tools for escaping poverty remains a policy agenda still with room for progress both in Europe and around the World. Some groups in society, like the needy, have difficulties in accessing and using such technologies in ways that mirror the debates of the late 90s over the "digital divide". For some groups, like the needy, it would be more exact to address the concept of digital poverty rather than digital divide, because without access to telecommunications one might not have the same degree of opportunities to leave poverty or not to fall into poverty [34] [3] [4]. The goal of this paper is to scope the problem by departing from the Portuguese case study. Our research is empirical and highlights the telecommunication ownership and expenditures of the Portuguese population, and specially the most fragile segments within it. Such an effort is undertaken while not ignoring major issues of political economy of the contemporary globalizing networked society. Our main argument in this paper is that, if telecommunications are a needed tool for the lower income segments of the population, that is the needy, a debate around digital poverty associated to mobile telecommunications is needed in Europe too and to address such issues we need public policy commitments

Use of acoustic energy in the processing of molten aluminium alloys

During the last years aluminium alloys have been gaining increased acceptance as structural materials in the automotive and aeronautical industries, mainly due to their light weight, good formability and corrosion resistance. However, improvement of mechanical properties is a constant in research activities, either by the development of new alloys or by microstructure manipulation. This presentation focuses a novel effective dynamic methodology to perform microstructural refinement / modification and degassing of light alloys, namely aluminium alloys, by applying acoustic energy to the melts. High intensity acoustic energy significantly improves the microstructure, therefore the mechanical properties of those alloys, avoiding the use of traditional chemically based degassing and refining techniques which are less effective and present significant environmental impact. Ultrasonic (US) vibration has proven to be extremely effective in degassing, controlling columnar dendritic structure, reducing the size of equiaxed grains and, under some conditions, producing globular grains and modifying the eutectic silicon cells in Al-Si alloys. The mechanisms of US processing of aluminium melts are discussed and experimental results on this field are presented.Fundação para a Ciência e Tecnologia (FCT

Physical modification of intermetallic phases in Al-Si-Cu alloys

The effect of applying ultrasonic vibration to the melt during cooling on grain structure, type and morphology of intermetallic compounds in AlSi9Cu3(Fe) alloy was studied, as well as their nucleation mechanism. Detailed intermetallics analysis was performed using a combination of SEM/EDS and XRD techniques in order to obtain the most possible reliable information. Results show that without ultrasonic treatment alpha-Al-17(Fe-3.2, Mn-0.8)Si-2, alpha-Al8Fe2Si, beta-Al9Fe2Si2 and Al2Cu are the intermetallic phases present in the as-cast samples. The application of ultrasonic vibration to the melt during cooling proved to be very effective in converting the alpha-intermetallics with Chinese script morphology to polyhedral crystals, suppressing at the same time the formation of the beta-phase. Moreover, the application of this treatment only changes the morphology of alpha-intermetallics since its stoichiometry remains the same (alpha-Al-17(Fe-3.2, Mn-0.8)Si-2). It was also verified that the application of acoustic energy to the melt promotes the change of alpha-Al grains from dendritic to a more globular structure. The ultrasonic treatment is also effective in promoting the fracture of polyhedral crystals of intermetallic phases, reducing their dimensions and causing their homogenous dispersion in the matrix.This research was supported by FEDER/COMPETE funds and by national funds through FCT - Portuguese Foundation for Science and Technology on the aim of the research project PTDC/EME-TME/119658/2010 and the Post-Doctoral Grant SFRH/BPD/76680/2011.info:eu-repo/semantics/publishedVersio

Influence of ultrasonic melt treatment on microstructure and mechanical properties of AlSi9Cu3 alloy

A novel MMM (Multi-frequency, Multimode, Modulated) ultrasonic (US) technology was used to refine the as cast microstructure and improve the mechanical properties of a AlSi9Cu3 alloy. Ultrasonic vibration was isothermally applied to the melt for 120 seconds at different temperatures slightly above the liquidus temperature of the alloy, using different electric power values, before pouring into a metallic mould. The microstructure of the cast samples was characterized by optical and scanning electron microscopy and energy dispersive spectrometry. Ultrasonic vibration promoted the formation of small -Al globular grains, changed the size and morphology of intermetallic compounds and distributed them uniformly throughout the castings. Ultimate Tensile Strength and Strain were increased to 332 MPa and 2.9% respectively, which are 50% and 480% higher than the values obtained for castings produced without vibration. The microstructure morphology and the alloy mechanical properties were found to depend on the electric power and the melt temperature, and by using a suitable combination of these parameters it is possible to achieve high refinement efficiency by treating the melts in the liquid state

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting

Cellular materials are recognized for their high specific mechanical properties, making them desirable in ultra-lightweight applications. Periodic lattices have tunable properties and may be manufactured by metallic additive manufacturing (AM) techniques. However, AM can lead to issues with un-melted powder, macro/micro porosity, dimensional control and heterogeneous microstructures. This study overcomes these problems through a novel technique, combining additive manufacturing and investment casting to produce detailed investment cast lattice structures. Fused filament fabrication is used to fabricate a pattern used as the mold for the investment casting of aluminium A356 alloy into high-conformity thin-ribbed (~ 0.6 mm thickness) scaffolds. X-ray micro-computed tomography (CT) is used to characterize macro- and meso-scale defects. Optical and scanning electron (SEM) microscopies are used to characterize the microstructure of the cast structures. Slight dimensional (macroscale) variations originate from the 3D printing of the pattern. At the mesoscale, the casting process introduces very fine (~ 3 µm) porosity, along with small numbers of (~ 25 µm) gas entrapment defects in the horizontal struts. At a microstructural level, both the (~ 70 μm) globular/dendritic grains and secondary phases show no significant variations across the lattices. This method is a promising alternative means for producing highly detailed non-stochastic metallic cellular lattices and offers scope for further improvement through refinement of filament fabrication.This work was supported by Portuguese FCT, under the reference project UIDB/04436/2020. We are grateful to the funding from the European Research Council through the ERC grant CORREL-CT, number 695638 to enable VHC to visit the Henry Royce Institute to undertake the X-ray CT studies. Tis work was supported by the Henry Royce Institute for Advanced Materials, funded through EPSRC grants EP/R00661X/1, EP/S019367/1, EP/P025021/1 and EP/P025498/1 and the Henry Moseley X-ray Imaging Facility funded by EP/T02593X/1

Ceramic sonotrodes for light alloy melt treatment

Alloy melt treatment by ultrasonic vibration is a physical processing technique that has been gathering the support of the scientific community. The use of metallic sonotrodes for this purpose has been proven very efficient; however, it promotes melt inclusion by sonotrode erosion. Such an issue is being addressed by the use of ceramic sonotrodes in low-amplitude resonance. Given that these novel sonotrodes generally have complex shapes and low displacements, this study shows an innovative approach for their characterization. Based on scanning laser Doppler vibrometry, the signal processing Python-based script was used to map the overall resonant behavior of a tubular SiAlON sonotrode, and this route is able to characterize the complex shapes in low-amplitude and high-frequency radial resonance in resonant ceramic sonotrodes. Velocity time-domain profiles are shown to be dependent on the position, and even though the radial natural frequencies of ceramic sonotrodes have low amplitudes, they are proposed as an efficient tool for melt treatment. While characterizing the radial natural mode in ceramic sonotrodes, this study proves that their low-amplitude Lamb waves are responsible for the refinement of a-grains and secondary phases in light alloys.This work was supported by PTDC/EMEEME/30967/ 2017 and NORTE-0145-FEDER-030967, co-financed by the European Regional Development Fund (ERDF), through the Operational Programme for Competitive ness and Internationalization (COMPETE 2020), under Portugal 2020, and by the Fundação para a Cência e a Tecnologia – FCT I.P. national funds. Also, this work was supported by Portuguese FCT, under the reference project UIDB/04436/2020, and Stimulus of Scientific Employment Application CEECIND/03991/2017

Influence of arterial mechanical properties on carotid blood flow: comparison of CFD and FSI studies

Carotid artery blood flow is studied to compare models with rigid and elastic walls. Considering a patient-specific geometry and transient boundary conditions. In the case of rigid walls, only the fluid (blood) behavior is considered, in a typical Computational Fluid Dynamics study. With the elastic walls, the reciprocal influence of both fluid and solid (blood and artery) are taken into account, constituting a Fluid-Structure Interaction study. Further more, the study of the influence of mechanical properties of the artery, which become stiffer with the progression of atherosclerosis, on blood flow is also presented, an innovative approach relative to the work done in this field. Results show that the carotid sinus is the preferential zone to develop atherosclerosis, given its low values of Time-Averaged Wall Shear Stress. Additionally, it is fundamental to consider the arterial wall as elastic bodies, given that the rigid model overestimates the flow velocity and Wall Shear Stress. On the different mechanical properties of the vessel, its influence is minimal in the Time-Averaged Wall Shear Stress profiles. However, given the results of the displacement and velocity profiles, their inclusion in blood flow simulations in stenosed arteries should be considered.This work was supported by FEDER funds through the COMPETE program with the reference project PTDC/SEM-TEC/3827/2014. Additionally, this work is supported by FCT with the reference projects UID/EEA/04436/2019, UID/CEC/00319/2019 and UID/EMS/04077/2019

Pre-Main Sequence stars in the star forming complex Sh 2-284

Located at the galactic anticenter, Sh 2-284 is a HII region which harbors several young open clusters; Dolidze 25, a rare metal poor (Z~0.004) young cluster, is one of these. Given its association with Sh 2-284, it is reasonable to assume the low metallicity for the whole HII region. Sh~2-284 is expected to host a significant population of Pre-Main Sequence (PMS) stars of both low and intermediate mass stars (Herbig Ae stars). We aim at characterizing these stars by means of a spectroscopic and photometric survey conducted with VIMOS@VLT and complemented with additional optical and infrared observations. In this survey we selected and characterized 23 PMS objects. We derived the effective temperature, the spectral energy distribution and luminosity of these objects; using theoretical PMS evolutionary tracks, with the appropriate metallicity, we estimated the mass and the age of the studied objects. We also estimated a distance of 4 Kpc for Sh 2-284 by using spectroscopic parallax of 3 OB stars. From the age determination we concluded that triggered star formation is in act in this region. Our results show that a significant fraction of the young stellar objects (YSOs) may have preserved their disk/envelopes, in contrast with what is found in other recent studies of low-metallicity star forming regions in the Galaxy. Finally, among the 23 bona fide PMS stars, we identified 8 stars which are good candidates to pulsators of the delta Scuti type.Comment: accepted for publication in MNRA

Near-infrared spectroscopy in NGC 7538

The characterisation of the stellar population toward young high-mass star-forming regions allows to constrain fundamental cluster properties like distance and age. These are essential when using high-mass clusters as probes to conduct Galactic studies. NGC 7538 is a star-forming region with an embedded stellar population only unearthed in the near-infrared. We present the first near-infrared spectro-photometric study of the candidate high-mass stellar content in NGC 7538. We obtained H and K spectra of 21 sources with both the multi-object and long-slit modes of LIRIS at the WHT, and complement these data with sub-arcsecond JHKs photometry of the region using the imaging mode of the same instrument. We find a wide variety of objects within the studied stellar population of NGC 7538. Our results discriminate between a stellar population associated to the HII region, but not contained within its extent, and several pockets of more recent star formation. We report the detection of CO bandhead emission toward several sources as well as other features indicative of a young stellar nature. We infer a spectro-photometric distance of 2.7+-0.5 kpc, an age spread in the range 0.5-2.2 Myr and a total mass ~1.7x10^3 Msun for the older population.Comment: 11 pages, 8 figures, 1 table, accepted by A&