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Publicações

2021

Quality of Information and Communications Technology - 14th International Conference, QUATIC 2021, Algarve, Portugal, September 8-11, 2021, Proceedings

Autores
Paiva, ACR; Cavalli, AR; Martins, PV; Castillo, RP;

Publicação
QUATIC

Abstract

2021

Rooftop photovoltaic parking lots to support electric vehicles charging: A comprehensive survey

Autores
Osorio, JG; Gough, M; Lotfi, M; Santos, FS; Espassandim, MDH; Shafie khah, M; Catalao, PSJ;

Publicação
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
Due to technological advances, the growing need for a decarbonized economy, and the desire to reduce urban air pollution, electric vehicles (EVs) are seen as promising developments for the progressive decarbonization of the transport sector. The potential for large scale integration of solar photovoltaic (PV) systems has not been explored fully, compared to other renewable energy uses in power systems. One of the proposed paths for the sustainable integration of EVs and solar exploitation in power systems involves the creation or installation of parking lots fitted with solar PV systems on their rooftops. This concept increases the reliability and robustness of the power system, as studies show that EVs are parked for the vast majority of the time. The EVs can then be optimally managed to assist the network in critical moments. The solar parking lot would then serve as a backup to manage the EVs' state-of-charge (SoC) which would guarantee the owners' comfort and help to accelerate the decarbonization of the economy. The present work presents a comprehensive survey of the state-of-the-art concepts of photovoltaic (PV) panels, EVs and batteries, and how the different associated technologies can be applied in the concept of solar parking lots.

2021

Prescribed burning as a cost-effective way to address climate change and forest management in Mediterranean countries

Autores
Pacheco, RM; Claro, J;

Publicação
ANNALS OF FOREST SCIENCE

Abstract
Key message As climate change and forest management become the focus of various development agendas and the price of carbon rises in the market, the need for improving carbon sequestration and avoiding wildfires emissions increases. Prescribed burning interventions might play an important role in this context, as in some situations, it has been suggested that it can reduce overall fire emissions. In this study, the potential economic benefits associated with the practice are analyzed for five Mediterranean countries. Despite the uncertainty in the estimates, the results suggest that under some circumstances these interventions can be cost-effective from a carbon management perspective. Context Wildland fires are becoming a major concern for many European countries and are expected to become more prevalent due to climate change, affecting societies, ecosystems, and various ecosystem services provided by forests that are not valued by traditional markets, such as carbon sequestration. Aims The objective of this study is to evaluate the possibility of using carbon taxation to fund fire management measures in Mediterranean countries. Methods The analysis is done by converting prescribed burning savings in carbon emissions into their economic value. This is performed for France, Greece, Italy, Spain, and Portugal, which is studied in more detail, since the country has a National Prescribed Burning Program (NPBP) and a specific tax on carbon in place. Results The results indicate that most countries could potentially have benefits in the order of millions of euros from employing prescribed burning measures. In Portugal, NPBP has the potential to be a relevant policy instrument to reduce wildfire emissions, as well as economically since the carbon emissions savings can outweigh the prescribed burning costs in some circumstances. Also, the revenue from the country's Addition Tax on Carbon Emissions would be able to accommodate the foreseen prescribed burning costs. Conclusion There are still many uncertainties regarding the benefits of prescribed burning in terms of overall emission reductions, and more studies should be conducted on this topic. However, as the price of carbon rises in the markets and climate change becomes a more pressing concern, even small emissions reductions might be economically interesting. The analysis framework used in this study has the potential to be useful for other countries, especially in Mediterranean-type ecosystems.

2021

The central parsec of NGC 3783: a rotating broad emission line region, asymmetric hot dust structure, and compact coronal line region

Autores
Amorim, A; Baubock, M; Brandner, W; Bolzer, M; Clenet, Y; Davies, R; de Zeeuw, PT; Dexter, J; Drescher, A; Eckart, A; Eisenhauer, F; Schreiber, NMF; Gao, F; Garcia, PJV; Genzel, R; Gillessen, S; Gratadour, D; Honig, S; Kaltenbrunner, D; Kishimoto, M; Lacour, S; Lutz, D; Millour, F; Netzer, H; Ott, T; Paumard, T; Perraut, K; Perrin, G; Peterson, BM; Petrucci, PO; Pfuhl, O; Prieto, MA; Rouan, D; Sanchez Bermudez, J; Shangguan, J; Shimizu, T; Schartmann, M; Stadler, J; Sternberg, A; Straub, O; Straubmeier, C; Sturm, E; Tacconi, LJ; Tristram, KRW; Vermot, P; von Fellenberg, S; Waisberg, I; Widmann, F; Woillez, J;

Publicação
ASTRONOMY & ASTROPHYSICS

Abstract
Using VLTI/GRAVITY and SINFONI data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (AGN) hosted by NGC 3783. The K-band coverage of GRAVITY uniquely allows simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-infrared(near-IR)-continuum-emitting hot dust, and the size of the coronal line region (CLR). We find the BLR, probed through broad Br gamma emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. In our BLR model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. We measure a hot dust full-width at half-maximum (FWHM) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the [Ca VIII] and narrow Br gamma line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc.

2021

Hubs for VirtuosoNext: Online verification of real-time coordinators

Autores
Cledou, G; Proença, J; Sputh, BHC; Verhulst, E;

Publicação
SCIENCE OF COMPUTER PROGRAMMING

Abstract
VirtuosoNextTM is a distributed real-time operating system (RTOS) featuring a generic programming model dubbed Interacting Entities. This paper focuses on these interactions, implemented as so-called Hubs. Hubs act as synchronisation and communication mechanisms between the application tasks and implement the services provided by the kernel. While the kernel provides the most basic services, each carefully designed, tested and optimised, tasks are limited to this handful of basic hubs, leaving the development of more complex mechanisms up to application specific implementations. This work presents a toolset that supports the building of new services compositionally, using notions borrowed from the Reo coordination language, on which the developer can delegate coordination-related duties. This toolset uses a formal compositional semantics for hubs that captures dataflow and time, formalising the behaviour of existing hubs, and allowing the definition of new ones. Furthermore, it enables the analysis and verification of hubs under our automata interpretation, including time-sensitive behaviour via the UPPAAL model checker, usable on http://arcatools .org /hubs. We illustrate the proposed tools and methods by verifying key properties on different interaction scenarios between tasks and a composed hub.

2021

Improving order-picking operations with precedence constraints through efficient storage location assignment: Evidence from a retail company

Autores
Trindade, MAM; Sousa, PSA; Moreira, MRA;

Publicação
U.Porto Journal of Engineering

Abstract
This paper is inspired by a manual picking retail company where shape and weight constraints affect the order-picking process. We proposed an alternative clustering similarity index that considers the similarity, the weight and the shape of products. This similarity index was further incorporated in a storage allocation heuristic procedure to set the location of the products. We test the procedure in a retail company that supplies over 191 stores, in Northern Portugal. When comparing the strategy currently used in the company with this procedure, we found out that our approach enabled a reduction of up to 40% on the picking distance; a percentage of improvement that is 32% higher than the one achieved by applying the Jaccard index, a similarity index commonly used in the literature. This allows warehouses to save time and work faster.

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