Papers by Vasco Martim Sousa Ferreira
I would first like to express my sincere gratitude to my advisors Prof. Doutor Rui Alexandre de M... more I would first like to express my sincere gratitude to my advisors Prof. Doutor Rui Alexandre de Matos Araújo and Prof. Doutor Francisco Alexandre Andrade de Souza. Their valuable guidance, continuous support and scientific rigor helped me not only in achieving my goals but also in expanding my knowledge and critical thinking abilities. Next, I would also like to acknowledge the Institute of Systems and Robotics for providing all resources needed during this final stage of my master's degree. To all my friends that were present during these past years, the memories we shared in this beautiful city will accompany me for the rest of my life. Special thanks to my girlfriend, Verónica, for all the support and belief even at the harder stages of writing this dissertation. Last but certainly not least, I must express my very profound gratitude to my family, specially my parents Jaime and Clarinda, my sister Rita, and my grandfather Fernando. Their strong presence and great values helped immensely in my years of study. i
Agriculture, Sep 25, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Physical review, Apr 6, 2015
We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dar... more We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dark matter to be cs < 10 −4 c, where c is the speed of light in vacuum. Using the Modified Chaplygin Gas as a representative example of a class of unified dark energy models incorporating an effective dark matter component with a non-zero sound speed, we determine the most stringent constraint to date on the value of the constant contribution to the equation of state parameter in this class of models. Finally, we explain the reason why previous constraints using the Cosmic Microwave Background and Baryonic Acoustic Oscillations were not as competitive as the one presented in this paper and discuss the limitations of the recently proposed Extended Chaplygin Gas.
Physical review, Aug 14, 2018
The generalized Chaplygin gas is usually defined as a barotropic perfect fluid with an equation o... more The generalized Chaplygin gas is usually defined as a barotropic perfect fluid with an equation of state p = −Aρ −α , where ρ and p are the proper energy density and pressure, respectively, and A and α are positive real parameters. It has been extensively studied in the literature as a quartessence prototype unifying dark matter and dark energy. Here, we consider an extended family of generalized Chaplygin gas models parameterized by three positive real parameters A, α and β, which, for two specific choices of β [β = 1 and β = (1 + α) /(2α)], is described by two different Lagrangians previously identified in the literature with the generalized Chaplygin gas. We show that, for β > 1/2, the linear stability conditions and the maximum value of the sound speed cs are regulated solely by β, with 0 ≤ cs ≤ 1 if β ≥ 1. We further demonstrate that in the nonrelativistic regime the standard equation of state p = −Aρ −α of the generalized Chaplygin gas is always recovered, while in the relativistic regime this is true only if β = (1 + α) /(2α). We present a regularization of the (α → 0, A → ∞) limit of the generalized Chaplygin gas, showing that it leads to a logarithmic Chaplygin gas model with an equation of state of the form p = A ln (ρ/ρ *), where A is a real parameter and ρ * > 0 is an arbitrary energy density. We finally derive its Lagrangian formulation.
Physics Letters B, Jul 1, 2017
A unification of dark matter and dark energy in terms of a logotropic perfect dark fluid has rece... more A unification of dark matter and dark energy in terms of a logotropic perfect dark fluid has recently been proposed, where deviations with respect to the standard ΛCDM model are dependent on a single parameter B. In this paper we show that the requirement that the linear growth of cosmic structures on comoving scales larger than 8h −1 Mpc is not significantly affected with respect to the standard ΛCDM result provides the strongest constraint to date on the model (B < 6×10 −7), an improvement of more than three orders of magnitude over previous constraints on the value of B. We further show that this constraint rules out the logotropic Unified Dark Energy model as a possible solution to the small scale problems of the ΛCDM model, including the cusp problem of Dark Matter halos or the missing satellite problem, as well as the original version of the model where the Planck energy density was taken as one of the two parameters characterizing the logotropic dark fluid.
Physical review, Aug 9, 2017
We consider a model with two real scalar fields which admits phantom domain wall solutions. We in... more We consider a model with two real scalar fields which admits phantom domain wall solutions. We investigate the structure and evolution of these phantom domain walls in an expanding homogeneous and isotropic universe. In particular, we show that the increase of the tension of the domain walls with cosmic time, associated to the evolution of the phantom scalar field, is responsible for an additional damping term in their equations of motion. We describe the macroscopic dynamics of phantom domain walls, showing that extended phantom defects whose tension varies on a cosmological timescale cannot be the dark energy.
Comprehensive Habitat Mapping of a Littoral Marine Park
Marine Protected Areas classification can help in the protection and monitoring of important ecos... more Marine Protected Areas classification can help in the protection and monitoring of important ecosystems that might be sheltered by their habitats.New instrumentation techniques are being applied to study this type of environments, performing various scientific surveys in the water. In this paper we introduce a practical approach for habitat mapping, from the surface through the seabed, using autonomous underwater and unmanned aerial vehicles. We address high-resolution characterization of extensive coastal areas in challenging conditions by deploying multiple vehicles simultaneously. This approach has been applied in the field, to map a large coastal area, contouring the area intrinsic challenges by using a robust software toolchain developed to operate these vehicles, from planning and execution to the data analysis stages.
I would like to thank Prof. Pedro Avelino for his patience, encouragement and guidance throughout... more I would like to thank Prof. Pedro Avelino for his patience, encouragement and guidance throughout this work. From all my friends and colleagues, a special thanks to Miguel Ferreira, for his friendship and fruitful discussions. A true friend that gave me support during such stressful times. I want to thank Fábio Domingues for the processing capacity. I'm also grateful to Catarina for improving my mood.
Physical review, Sep 22, 2020
We investigate the appropriateness of the use of different Lagrangians to describe various compon... more We investigate the appropriateness of the use of different Lagrangians to describe various components of the cosmic energy budget, discussing the degeneracies between them in the absence of nonminimal couplings to gravity or other fields, and clarifying some misconceptions in the literature. We further demonstrate that these degeneracies are generally broken for nonminimal coupled fluids, in which case the identification of the appropriate on-shell Lagrangian may become essential in order to characterize the overall dynamics. We then show that models with the same on-shell Lagrangian may have different proper energy densities and use this result to map dark energy models into unified dark energy models in which dark matter and dark energy are described by the same perfect fluid. We determine the correspondence between their equation of state parameters and sound speeds, briefly discussing the linear sound speed problem of unified dark energy models as well as a possible way out associated with the nonlinear dynamics.
Dissecting kinetically coupled quintessence: phenomenology and observational tests
Journal of Cosmology and Astroparticle Physics
We investigate an interacting dark energy model which allows for the kinetic term of the scalar f... more We investigate an interacting dark energy model which allows for the kinetic term of the scalar field to couple to dark matter via a power-law interaction. The model is characterised by scaling solutions at early times, which are of high interest to alleviate the coincidence problem, followed by a period of accelerated expansion. We discuss the phenomenology of the background evolution and of the linear scalar perturbations and we identify measurable signatures of the coupling in the dark sector on the cosmic microwave background, the lensing potential auto-correlation and the matter power spectra. We also perform a parameter estimation analysis using data of cosmic microwave background temperature, polarisation and lensing, baryonic acoustic oscillations and supernovae. We find that the strength of the coupling between the dark sectors, regulated by the parameter α, is constrained to be of order 10-4. A model selection analysis does not reveal a statistical preference between ΛCDM ...
Numerical analysis of the flow field and cross section design implications in a multifunctional artificial reef
Ocean Engineering
Frontiers in Marine Science
Marine Protected Areas (MPAs) require effective indicators to assess their performance, in compli... more Marine Protected Areas (MPAs) require effective indicators to assess their performance, in compliance with the goals of relevant national and international commitments. Achieving and prioritizing shortlists of multidisciplinary indicators demands a significant effort from specialists to depict the multiple conservation and socioeconomic interests, and the large complexity of natural systems. The present paper describes a structured expert-based methodology (process and outputs) to co-define a list of multidisciplinary MPA performance indicators. This work was promoted by the management authority of coastal MPAs in mainland Portugal to gather a consensual and feasible list of indicators that would guide the design of a future national monitoring program. Hence, Portuguese coastal MPAs served as a case study to develop such a process between 2019 and 2020. In the end, participants (1) agreed on a shortlist of prioritized indicators (i.e., environmental, governance, and socioeconomic i...
It must be stressed that the statements and views expressed in the chapters are the sole responsi... more It must be stressed that the statements and views expressed in the chapters are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission. No responsibility is accepted for the accuracy of information contained in the published chapters and the authors do not accept any liability for any direct or indirect damage resulting from the use of this e-book, its content or parts of it. The results achieved, conclusions made, and recommendations given by the authors should not be interpreted as a political or legal signal that the European Commission or any other political or legal institution intends to take a given action.
Fifty-one sounds were presented to sixty participants in an online sound categorization study. Th... more Fifty-one sounds were presented to sixty participants in an online sound categorization study. The 4-second stimuli consisted in everyday sounds which were strongly or remotely associated with the seven clinical alarm risk categories described in IEC 6060-1-1-8 (Drug Administration, Perfusion, Oxygen, Temperature, Cardiac, Power Down and Ventilation). One additional category was added for the ?Blood Pressure? sounds. After a headphone screening test, participants had to categorize all sounds into one of the eight categories (or a no-category group) and indicate the quality of fit of their evaluation (Poor, Fair, Perfect). Half of the participants were healthcare professionals with experience with medical devices, and the other half were not healthcare professionals and had never interacted with medical devices. The categorization exercise was adapted from a classic usability methodology called Card Sorting, generally used for information architecture. With the purpose of designing u...
From decision-making to Oceans Accounts: a case study
OCEANS 2019 - Marseille, 2019
Earth systems are nowadays on the verge of radical disruptions, whether due to unprecedented demo... more Earth systems are nowadays on the verge of radical disruptions, whether due to unprecedented demographic pressures or as a result of the current complexity of global systems. Climate Changes, ecosystems unbalances, natural resources depletion, pollution, extreme events, natural catastrophes, humanized overpopulated environments, as well as economical turbulences, represent more than ever, very uncertain terms of an equation that is difficult to balance. Novel procedures are essential to make use of local and global information that is nowadays available from multiple sources, to produce intelligible and actionable models for sustainable development, in particular for the oceans protection, the main support of human life on earth. An example of this procedures is the Oceans Accounts (OA) framework that aims at integrating the biophysical information, measure ecosystem services, track and measure the changes on the ecosystems and link all this data to economic and human activity within a given spatial area. This work presents a novel approach that uses spatial modeling techniques capable of dealing with limited and discrete data, such as Geostatistics. These spatial techniques, combined with remote sensing, can provide a sound background of information for the implementation and leverage of the Oceans Accounts framework. Moreover, an emphasis will be given to the application of the OA framework to marine protected areas (MPA’s) with an identification of the main gaps regarding the cycle of collecting, processing and integrating social, environmental and economic data. The main focus will be on enabling the next generation of decision support systems to support design and impact assessment of alternative engineering solutions for marine contexts, such as energy harvesting and offshore platforms or aquaculture, in the context of blue economy, as well as marine planning and economic activities regulation.
Physical Review D, 2015
We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dar... more We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dark matter to be cs < 10 −4 c, where c is the speed of light in vacuum. Using the Modified Chaplygin Gas as a representative example of a class of unified dark energy models incorporating an effective dark matter component with a non-zero sound speed, we determine the most stringent constraint to date on the value of the constant contribution to the equation of state parameter in this class of models. Finally, we explain the reason why previous constraints using the Cosmic Microwave Background and Baryonic Acoustic Oscillations were not as competitive as the one presented in this paper and discuss the limitations of the recently proposed Extended Chaplygin Gas.
I would like to thank Prof. Pedro Avelino for his patience, encouragement and guidance throughout... more I would like to thank Prof. Pedro Avelino for his patience, encouragement and guidance throughout this work. From all my friends and colleagues, a special thanks to Miguel Ferreira, for his friendship and fruitful discussions. A true friend that gave me support during such stressful times. I want to thank Fábio Domingues for the processing capacity. I'm also grateful to Catarina for improving my mood.
Vers la Solution du Probl�me des Qualifications
Netherlands International Law Review, 1962
Desenvolvimento de Hardware para uma Sonda Multi-Funcional de Medição Simultânea do Conteúdo de Agua, Propriedades Térmicas e Condutividade Eléctrica do Solo
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Papers by Vasco Martim Sousa Ferreira