Artigos de Revista
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Artigos de Revista
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An assessment of contact and laser-based scanning of rock particles for railway ballast
Performance of traditional railway structure depends significantly on the behaviour of its support layers, particularly the ballast. This layers rock particles are selected to ensure high mechanical strength, but traffic and mechanical maintenance break and wear the particles. Consequently, the layer incurs permanent deformations that degrade its strength and increase deformability and permeability. Particle physical characteristics, in particular those related to size and shape, influence their fragmentation and wear and must be studied accordingly. In addition, structural numerical models that represent individual particles, such as the discrete element method, have been increasingly used to model the infrastructure and therefore detailed geometrical characterization in the form of 3D digital models of the particles are necessary. This work contributes to this goal by investigating a contact-based cost-effective method that digitizes particle form and allows the determination of their geometric parameters. This method is described, compared with well- established laser scanning technique and then applied to study degradation of particles in Los Angeles and microDeval fragmentation tests.
Ano: 2020
Número Páginas:
100302.
Autor(es): Jerónimo, P.; Resende, R.; Fortunato, E.
Revista: Transportation Geotechnics
Editor: Elsevier
Volume:
22.
Keywords: Rock breakage; Contact scanning; Laser; 3D scanning; Particle shape; Railway ballast
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Electrodialytic removal of tungsten and arsenic from secondary mine resources Deep eutectic solvents enhancement
Tungsten is a critical raw material for European and U.S. economies. Tungsten mine residues, usually considered an environmental burden due to e.g. arsenic content, are also secondary tungsten resources. The electrodialytic (ED) process and deep eutectic solvents (DES) have been successfully and independently applied for the extraction of metals from different complex environmental matrices. In this study a proof of concept demonstrates that coupling DES in a two-compartment ED set-up enhances the removal and separation of arsenic and tungsten from Panasqueira mine secondary resources. Choline chloride with malonic acid (1:2), and choline chloride with oxalic acid (1:1) were the DES that in batch extracted the average maximum contents of arsenic (16%) and tungsten (9%) from the residues. However, when ED was operated at a current intensity of 100 mA for 4 days, the extraction yields increased 22% for arsenic and 11% for tungsten, comparing to the tests with no current. From the total arsenic and tungsten extracted, 82% and 77% respectively were successfully removed from the matrix compartment, as they electromigrated to the anolyte compartment, from where these elements can be further separated. This achievement potentiates circular economy, as the final treated residue could be incorporated in construction materials production, mitigating current environmental problems in both mining and construction sectors.
Ano: 2020
Autor(es): Almeida, J.; Craveiro, R.; Faria, P.; Santos Silva, A.; Mateus, E.; Barreiros, S.; Paiva, A.; Ribeiro, A.
Revista: Science of The Total Environment
Editor: Elsevier
Volume:
Volume 710.
Keywords: Choline chloride/oxalic acid; Choline chloride/malonic acid; Electro-based technology; Secondary resource; Harmful compound; Critical raw material
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Exploring teenagers' spatial practices and needs in light of new communication technologies
There is an increasing awareness and advocacy claim for engaging the society in the production of public openspaces. This contribution seeks to increase knowledge on the relationship between spaces and the social practicesof teenagers, towards a more inclusive and interactive process of public space co-creation. It is based on twoEuropean Projects: CyberParks and C3Places, and explores teenagers' spatial practice and needs, and how toengage them in the process of co-creating more sensitive public spaces, while exploring the challenges andopportunities ICT open. It this paper, the results of a case study taking place in Lisbon and the analysis ofquestionnaires and interviews are discussed.
Ano: 2020
Número Páginas:
7p.
Autor(es): Costa, C.; Batista, J.; Almeida, I.; Menezes, M.
Revista: Cities
Editor: Elsevier
Volume:
98.
Keywords: Lisbon; Living labs; Spatial needs; Neighbourhood; Teenagers; Public open spaces
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Importance of infragravity waves in a wave-dominated inlet under storm conditions
The processes associated with infragravity waves (IGW) and their role on the hydro-sedimentary dynamics of a wave-dominated inlet are investigated using field observations collected at the Albufeira Lagoon (Portugal) during storm Leslie in October 2018. During the storm, significant IGW heights reached up to 1.0 m in the surf zone and 0.4 m inside the lagoon. IGW frequencies were blocked by ebb currents at the flood-delta and this effect was stronger for higher IGW frequencies. Therefore, low-frequency IGW were able to propagate further into the inner lagoon. The application of a 1D energy balance equation suggests that depth-induced breaking and bottom friction contributed equally to dissipate IGW energy at the flood-delta and that this dissipation was stronger during the flood than during the ebb. Large horizontal velocities under IGW crests increased the instantaneous suspended sediment transport rate by up to two orders of magnitude during flood at the flood-delta. The net suspended sediment transport rate and its variability, associated with the wave motion, was positive (landward) during flood and negligible during ebb. These positive values were associated with large wave-induced orbital velocities, suggesting that waves were more effective than tidal currents in inducing suspended sediment transport. The oscillatory suspended sediment transport rate was directed towards the lagoon and dominated by IGW frequencies. The observed sediment accretion of the northern channel occurred during the most energetic IGW. The measurements presented in this study and their analyses demonstrate how IGW play a major role in the sedimentary dynamics of wave-dominated inlets during storm conditions.
Ano: 2020
Número Páginas:
1-15pp.
Autor(es): Mendes, D.; Fortunato, A. B.; Bertin, X.; Martins, K.; Lavaud, L.; Silva, A. N.; Pires Silva, A.; Coulombier, T.; Pinto, J.
Revista: Continental Shelf Research
Editor: Elsevier
Volume:
192.
Keywords: Waves; Infragravity
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OpencoastS: an open-access service for the automatic generation of coastal forecast systems
Coastal forecast systems are used for many purposes, including harbor management, search and rescue operations, and response to extreme events. However, the generation and operation of these systems is timeconsuming, requires expertise in both information technologies and modeling of coastal processes, and needs dedicated computational power. The new service OPENCoastS overcomes these difficulties by generating ondemand coastal circulation forecast systems through a web platform with minimal user intervention. Using a web platform, the user is guided through seven simple steps to generate an operational forecast system for any coastal region. The only requirements are an unstructured grid of the study area and information on river flow, if applicable. The platform provides ocean and atmospheric forcings and data for model validation, and includes interfaces for results visualization and forecasts management. Forecasts are generated with the community model SCHISM, and computing resources are provided through the European Open Science Cloud.
Ano: 2020
Número Páginas:
14p.
Autor(es): Oliveira, A.; Fortunato, A. B.; Rogeiro, J.; Teixeira, J.; Azevedo, A.; Lauvaud, L.; Bertin, X.; Gomes, J.; David, M.; Pina, J.; Rodrigues, M.; Lopes, P.
Editor: Elsevier
Volume:
Vol.124.
Keywords: Eosc; Web platform; Unstructured grids; Forecast systems; Schism
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Performance assessment of 23 wastewater treatment plants - a case study
Water systems and particularly wastewater treatment may only improve or keep high-quality service if their performance is continuously measured and benchmarked against peers. This paper presents a casestudy developed under the Portuguese Initiative on Water Quality, Treatment and Energy (iEQTAWWTP), involving 7 water utilities, and focused on the performance assessment of 23 urban wastewater treatment plants (WWTPs) covering a wide range of treatment sequences and capacities (700-54000 m3/ d). An earlier developed system of key performance indicators (KPIs) with reference values was used to assess the plants overall performance for effectiveness and reliability, sludge production and energy efficiency taking into consideration, whenever adequate, treatment technology, treated wastewater volume and influent characteristics. This application proved the soundness of the KPI system and its reference values for a blind comparison among WWTPs but also for treatment type- and capacity-specific clustering, ultimately supporting water utilities in a continuous practice of WWTP performance improvement.
Ano: 2020
Número Páginas:
9 pp..
Autor(es): Silva, C.; Rosa, M. J.
Revista: Urban Water Journal
Editor: Taylor & Francis Online
Volume:
Volume 17, Issue 1.
Keywords: Sludge; Energy; Performance indicators; WWTP; IEQTA
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RAF Resilience Assessment FrameworkA Tool to Support Cities Action Planning
Urban areas are dynamic, facing evolving hazards, having interacting strategic services and assets. Their management involves multiple stakeholders bringing additional complexity. Potential impacts of climate dynamics may aggravate current conditions and the appearance of new hazards. These challenges require an integrated and forward-looking approach to resilient and sustainable urban development, being essential to identify the real needs for its achievement. Several frameworks for assessing resilience have been developed in different fields. However, considering the focus on climate change and urban services, specific needs were identified, particularly in assessing strategic urban sectors and their interactions with others and with the wider urban system. A resilience assessment framework was developed directing and facilitating an objective-driven resilience diagnosis of urban cities and services. This supports the decision on selection of resilience measures and the development of strategies to enhance resilience, outlining a path to co-build resilience action plans, and to track resilience progress in the city or service over time. This paper presents the framework and the main results of its application to three cities having diverse contexts. It was demonstrated that the framework highlights where cities and urban services stand, regarding resilience to climate change, and identifies the most critical aspects to improve, including expected future impacts.
Ano: 2020
Número Páginas:
49 pp..
Autor(es): Cardoso, M. A.; Brito, R.; Pereira, C.; Gonzalez, A.; Stevens, J. R.; Telhado, M.
Revista: Sustainability
Editor: MDPI
Volume:
Vol 12 Issue 6.
Keywords: Cities; Urban services; Climate change; Urban resilience; Resilience assessment
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Tensile bond strength of lime-based mortars: The role of the microstructure on their performance assessed by a new non-standard test method
In recent years the study of renderings within conservation practice has acquired major technical and methodological advances. Due to the need of compatibility, usually repair mortars must be based on lime, and standardized tests are sometimes ineffective for these compatible substitution materials, which are often low strength mortars. The influence of the aggregates' characteristics on several factors that affect the adhesive strength of lime-based mortars is assessed and a new non-standard test method to determine the tensile bond strength of low strength mortars to porous substrates is presented and validated. The outcome shows that the new methodology offers the advantages of precision of the test device, ease of application and mostly consistency of the results. Furthermore, the main data show close relationship between the tensile bond strength and the pore size distribution of the mortars, which is very sensitive to the aggregates characteristics: In general, increasing the mortars pore volume of coarse pores (above the critical pore diameter of the substrate) strengthens the effective bond between these elements. Moreover, the compositional similarity between the aggregates and the substrate could also favour the bond between these elements.
Ano: 2020
Autor(es): Lopes dos Santos, A. R.; Veiga, M. R.; Santos Silva, A.; Brito, J.
Revista: Journal of Building Engineering
Editor: Elsevier
Volume:
Volume 29.
Keywords: Rehabilitation; New tensile bond strength test; Microstructure; Lime-based mortar; Aggregate
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The Development of a Framework for Assessing the Energy Efficiency in Urban Water Systems and Its Demonstration in the Portuguese Water Sector
Urban water systems (UWSs) are energy-intensive worldwide, particularly for drinking-water pumping and aeration in wastewater treatment. Usual approaches to improve energy efficiency focus only on equipment and disregard the UWS as a continuum of stages from source-to-tap-to-source (abstraction/transporttreatmentdrinking water transport/distributionwastewater and stormwater collection/transporttreatmentdischarge/reuse). We propose a framework for a comprehensive assessment of UWS energy efficiency and a four-level approach to enforce it: overall UWS (level 1), stage (level 2), infrastructure component (level 3) and processes/equipment (level 4). The framework is structured by efficiency and effectiveness criteria (an efficient but ineffective infrastructure is useless), earlier and newly developed performance indicators and reference values. The framework and the approach are the basis for a sound diagnosis and intervention prioritising, and are being tested in a peer-to-peer innovation project involving 13 water utilities (representing 17% of the energy consumption by the Portuguese water sector in 2017). Results of levels 13 of analysis herein illustrated for a water utility demonstrate the framework and approach potential to assess UWS effectiveness and energy efficiency, and to select the stages and infrastructures for improvement and deeper diagnosis.
Ano: 2020
Número Páginas:
15 pp..
Autor(es): Loureiro, D.; Silva, C.; Cardoso, M. A.; Mamade, A.; Alegre, H.; Rosa, M. J.
Revista: Water
Editor: MDPI Open Acess Journals
Volume:
Volume 12, nº1.
Keywords: Diagnosis; Effectiveness; Performance assessment system; Urban water systems; Efficiency; Energy
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3-D scale model study of wave run-up, overtopping and damage in a rubble-mound breakwater subject to oblique extreme wave conditions
A set of scale-model tests carried out to enlarge the range of wave steepness values analysed in run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gentler slope breakwaters trunk armour and roundhead, is presented in this paper. A stretch of a rubble mound breakwater (head and part of the adjoining trunk, with a slope of 1(V):2(H)) was built in a wave basin at the Leibniz University Hannover to assess, under extreme wave conditions (wave steepness of 0.055) with different incident wave angles (from 40º to 90º), the structure behaviour in what concerns wave run-up, wave overtopping and damage progression of the armour layer. Two types of armour elements (rock and Antifer cubes) were tested. Non-intrusive methodologies including a new application of laser scanning technique for the assessment of both armour layer damage and wave run-up and overtopping were used. It is expected that such work will contribute also with data to improve empirical formulas as well as to validate complex numerical model for wave-structure interaction.
Ano: 2019
Número Páginas:
32-41pp..
Autor(es): Santos, J. A.; Pedro, F.; Coimbra, M.; Figuero, A.; Fortes, C. J. E. M.; Sande, J.; Körner, M.; Lemos, R.; Bornschein, A.; Weimper, J.; van den Bos, J.; Dost, B.; Hofland, B.; Carvalho, R.; Alvarellos
Revista: Defect and Diffusion Forum
Editor: Trans Tech Publications Ltd, Switzerland
Volume:
Volume 396.
Keywords: Instrumentation; 3D-Wave basin; Physical modelling
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