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Publications

2021

Hardware-neutral tools for the exploration of optical phenomena in near-resonant atomic systems

Authors
Silva, NA; Ferreira, T; Guerreiro, A;

Publication
INTERNATIONAL JOURNAL OF MODERN PHYSICS C

Abstract
In the last three decades, a lot of research has been devoted to the optical response of an atomic media in near-to-resonant conditions and to how nonlinear optical properties are enhanced in these systems. However, as current research turns its attention towards multi-level and multidimensional systems interacting with several electromagnetic fields, the ever-increasing complexity of these problems makes it difficult to treat the semiclassical model of the Maxwell-Bloch equations analytically without any strongly-limiting approximations. Thus, numerical methods and particularly robust and fast computational tools, capable of addressing such class of modern and future problems in photonics, are mandatory. In this paper, we describe the development and implementation of a Maxwell-Bloch numerical solver that exploits the massive parallelism of the GPUs to tackle efficiently problems in multidimensional settings or featuring Doppler broadening effects. This constitutes a simulation tool that is capable of addressing a vast class of problems with considerable reduction of simulation time, featuring speedups up to 15 compared with the same codes running on a CPU.

2021

Screening the most highly cited papers in longitudinal bibliometric studies and systematic literature reviews of a research field or journal: Widespread used metrics vs a percentile citation-based approach

Authors
Pech, G; Delgado, C;

Publication
JOURNAL OF INFORMETRICS

Abstract
There is a literature gap regarding the period representativeness bias associated with sample selection in longitudinal bibliometric studies. The purpose of this paper is to analyse and compare, in terms of period representativeness, the common methods used for selecting a sample of the highly impactful papers in a field/ journal. Using 92 593 papers (Information Science & Library Science area, 1977-2016), we compared, in terms of the number of papers/year, samples of the 100 most impactful papers, obtained with different selection options. We repeated the analysis also for Top500, Top2000, and Top20000. This study shows that the frequently used metrics to compare the impact of papers and to select a sample of spacing diaeresis most impactful papers p spacing diaeresis ublished in each year and each field may privilege specific periods while neglecting others. The main result of our study is that the percentile citation-based method reduces this y spacing diaeresis ear of publicationr spacing diaeresis epresentativeness bias. This paper draws attention to the importance of the sample selection, in bibliometric studies, and to the period representativeness bias associated with different choices to select the spacing diaeresis most impactful papers. spacing diaeresis

2021

A Fast Gateway Placement Algorithm for Flying Networks

Authors
Santos, G; Martins, J; Coelho, A; Fontes, H; Ricardo, M; Campos, R;

Publication
2021 IEEE 93RD VEHICULAR TECHNOLOGY CONFERENCE (VTC2021-SPRING)

Abstract
The ability to operate anywhere, anytime, as well as their capability to hover and carry cargo on board make Unmanned Aerial Vehicles (UAVs) suitable platforms to act as Flying Gateways (FGWs) to the Internet. The problem is the optimal placement of the FGWs within the flying network, such that the Quality of Service (QoS) offered is maximized. The literature has been focused on optimizing the placement of the Flying Access Points (FAPs), which establish high-capacity small cells to serve the users on the ground, overlooking the backhaul network design, including the FGW placement. The FGW placement problem is exacerbated in highly dynamic flying networks, where the dynamic traffic demand and the movements of the users may induce frequent changes in the placement of the FAPs. The main contribution of this paper is a fast gateway placement (F-GWP) algorithm for flying networks that determines the optimal position of a FGW. With F-GWP, backhaul communications paths with high enough capacity are established between the FAPs and the FGW, in order to accommodate the traffic demand of the users on the ground. Simulation and experimental results show F-GWP is two orders of magnitude faster than its state of the art counterpart, while ensuring the same flying network performance.

2021

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

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

Publication
QUATIC

Abstract

2021

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

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

Publication
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

Authors
Pacheco, RM; Claro, J;

Publication
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.

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