3rd Project MEFT Workshop

Link video conference: https://zoom.us/j/98238642843?pwd=bUNGS1VJekFjLzV1MDlNMnJReDFjdz09
António Fernandes, Beatriz Bordadágua, Beatriz Pereira, Cláudia Espinha, João Cruz, Luísa Baptista, Nuno Lopes

Scientific committee:

Ilídio Lopes

Patrícia Gonçalves

Pedro Ribeiro

For the students who take part in the workshop, in order to evaluate your peers' presentations, please use this form.

    • 14:00 14:05
    • 14:05 14:20
      Asteroseismology: Studying angular momentum transfer mechanisms in red giant stars 15m

      Asteroseismic observations from missions such as MOST, CoRoT, Kepler and upcoming TESS and PLATO, make available a large amount of data, broadening our knowledge of pulsating stars by enabling even further the possibility to model and probe the stellar interiors.

      Nonetheless, core rotation rates obtained via asteroseismic observations show a large discrepancy with stellar evolution models predictions. Measurements of red giant stars reveal that their cores rotate much faster than their surfaces, but much slower than theoretically predicted. Therefore, it must exist some additional transport processes, that maintain conservation of total angular momentum, while redistributing angular momentum in these stars.

      The project consists in implementing the evolution of a low mass star model, with two chosen angular momentum transfer mechanisms, Taylor-Spruit Dynamo (2002) and Fuller Mechanism (2019), using the open source Modules for Experiments in Stellar Astrophysics (MESA). The goal is to give more insight into the impact of this mechanisms on the internal structure of the red giant stars, through asteroseismic diagnosis, for future comparisons with experimental data.

      Speaker: Beatriz Bordadágua
    • 14:20 14:35
      Stability of circular orbits in the 3 body problem 15m

      The 3 body problem has been studied for the last few centuries. While there are some known particular solutions, like the Euler and Lagrange solutions, and some specific cases, like the restricted 3 body problem, that have been more thoroughly studied, our knowledge about this topic is far from complete.

      The N body problem can be reduced to a system of equations whose only parameters are the masses of the bodies involved. These equations show that in a limit where masses are small, the orbits tend to become Keplerian. This work will focus on identifying stability conditions for the parameters that allow the existence of stable periodic orbits in a general 3 body problem configured as a planetary system, i.e., 2 bodies (planets) orbiting the 3rd one (a star). Preliminary results already suggest the existence of a limited interval for the masses for which the systems are stable.

      Results obtained from this study will serve as a foundation for a cornerstone of this work, the search for stable orbits in the N body problem, in order to shed some light on the structure of our Solar System, on the formation of planetary systems and planets by accretion, and on empirical and unexplained observations such as the Titius-Bode law.

      Speaker: João Cruz
    • 14:35 14:50
      Self-Organization of Learning Rules 15m

      Evolutionary Game Theory defines a mathematical framework to study the evolving dynamics of communities in biology or social sciences, typically in regimes where the evolution is deterministic. In this framework, the cooperative strategy updating is commonly based on relative payoff comparison and social learning by natural selection. However, in the real world it might be different, as individuals may not follow a social learning behaviour. In this study we propose a stochastic evolutionary game dynamics asymmetric model, for finite populations, in which individuals may adopt three different behaviours to update strategy: social learning, conformism or counterfactual thinking. We analyze these behaviours impact on the gradient of selection and on the fixation probability in a N-person group community.

      Speaker: António Fernandes
    • 14:50 15:05
      Break 15m
    • 15:05 15:20
      Smart fingertip biossensors for agrorobotics applications 15m

      In the agricultural business, as well as in distribution networks and packaging industry, food items suffer changes that need to be controlled. In particular, in fruit/vegetable handling there is crescent effort to introduce automated technologies for manipulation and optical inspection of fruits/vegetables. In this project we will implement a biosensor that allows for a quick evaluation of the quality of the fruit/vegetable when being handled by a robotic hand. Particularly, the student will dedicate himself to develop e-skin technologies and sensors embedded in elastomers and artificial skin, in a way that combines the tactile ability with a more sensitive perception of texture. Various detection strategies will be probed, with the implementation in a multiparametric integrated sensor in a robotic hand as the final goal.

      Speaker: Nuno Lopes
    • 15:20 15:35
      PALS – Setup optimisation and application to macromolecular materials characterisation 15m

      One of the fundamental structural aspects in soft condensed matter is the free volume, which include atomic defects, vacancies, pores and voids, which exists in the interior of matter, due to irregular packing, density fluctuations and topological constrains. The free volume is considered as the volume fraction enabling molecular reorganisation and is of fundamental importance in influencing a material’s physical, chemical and mechanical properties.

      Positron annihilation lifetime spectroscopy (PALS) is a non-destructive spectroscopy technique that enables a complete study of the free volume structure in materials, especially regarding the existence, dimension and concentration of these free volumes. PALS is based on the measurement of the elapsed time between the implantation of positrons into the material and the emission of the radiation resultant from the positron-electron annihilations. The lifetime of positrons is different for the ones which annihilate in the bulk of the material and the ones which annihilate in its free volumes. Therefore, the lifetime of the positron can then be used to determine the free volume size and concentration of the sample.

      Then, this work aims at the experimental optimisation of a PALS spectrometer, with a subsequent application of this tuned experimental setup to the characterisation of macromolecular materials, namely radiation processed polymer-based and hybrid materials for biomedical applications and for the consolidation of stone-based materials.

      Speaker: Luísa Baptista
    • 15:35 16:00
      Closing session