Characterisation and functional test of the full readout chain of a microdosimeter using scintillating plastic optical fibres

Tese de Mestrado Integrado, Engenharia Física, 2022, Universidade de Lisboa, Faculdade de CiênciasInstruments with a high spatial resolution are necessary to measure dosimetric quantities at a cellular level in order to have a better delineation of treatment plans in radiotherapy. The work here described is within a project aiming to develop a new detector capable of measuring real time absorbed dose with sub-millimetre resolution. The device is constructed using juxtaposed scintillating plastic optical fibres (SPOF) readout by a multi-anode photomultiplier (MAPMT, Hamamatsu H8500D) and a data acquisition (DAQ) system. In this thesis a first validation of the full readout chain is done, going through the characterisation of the different elements composing this detector. Using a dedicated test bench SPOFS (Kuraray SCSF-78) of 1 mm and 0.5 mm were optically characterised, measuring basic properties, such as light yields and attenuation lengths, before measuring the crosstalk between juxtaposed optical fibres. Methods of analysis were designed to compare the signal from an isolated and ribbon SPOF. Next, the MAPMT’s key characteristics were studied using a UV-LED exciting SPOF, to guide the light to individual MAPMT cells, and a picoammeter as a readout system. Concerning the assembly of the MAPMT in a detector assembly, the ideal conditions to achieve a light tight setup were evaluated. The full readout chain was completed by including a costumed DAQ board. Pulsed LEDs were firstly used to evaluate main limitations in signal response of the readout chain. Radioactive sources were then used to test the sensibility to particles (betas, gammas and alphas). In terms of results, the crosstalk study needs further revision, specially quantifying its value. The MAPMT’s performance was characterised and validated, whereas the DAQ board observed saturation and response to particles needs more understanding. However, the integration of the three elements of the microdosimeter was achieved and could be implemented into a first prototype

Finite element studies of the mechanical behaviour of the diaphragm in normal and pathological cases

The diaphragm is a muscular membrane separating the abdominal and thoracic cavities, and its motion is directly linked to respiration. In this study, using data from a 59-year-old female cadaver obtained from the Visible Human Project, the diaphragm is reconstructed and, from the corresponding solid object, a shell finite element mesh is generated and used in several analyses performed with the ABAQUS 6.7 software. These analyses consider the direction of the muscle fibres and the incompressibility of the tissue. The constitutive model for the isotropic strain energy as well as the passive and active strain energy stored in the fibres is adapted from Humphrey's model for cardiac muscles. Furthermore, numerical results for the diaphragmatic floor under pressure and active contraction in normal and pathological cases are presented

Combining reinforcement learning and conventional control to improve automatic guided vehicles tracking of complex trajectories

With the rapid growth of logistics transportation in the framework of Industry 4.0, automated guided vehicle (AGV) technologies have developed speedily. These systems present two coupled control problems: the control of the longitudinal velocity, essential to ensure the application requirements such as throughput and tag time, and the trajectory tracking control, necessary to ensure the proper accuracy in loading and unloading manoeuvres. When the paths are very short or have abrupt changes, the kinematic constraints play a restrictive role, and the tracking control becomes more challenging. In this case, advanced control strategies such as those based on intelligent techniques, including machine learning (ML) can be useful. Hence, in this work, we present an intelligent hybrid control scheme that combines reinforcement learning-based control (RLC) with conventional PI regulators to face both control problems simultaneously. On the one hand, PIs are used to control the speed of each wheel. On the other hand, the input reference of these regulators is calculated by the RLC in order to reduce the guiding error of the path tracking and to maintain the longitudinal speed. The latter is compared with a PID path following controller. The PID regulators have been tuned by genetic algorithms. The RLC allows the vehicle to learn how to improve the trajectory tracking in an adaptive way and thus, the AGV can face disturbances or unknown physical system parameters that may change due to friction and degradation of AGV mechanical components. Extensive simulation experiments of the proposed intelligent control strategy on a hybrid tricycle and differential AGV model, that considers the kinematics and the dynamics of the vehicle, prove the efficiency of the approach when following different demanding trajectories. The performance of the RL tracking controller in comparison with the optimized PID gives errors around 70% smaller, and the average maximum error is also 48% lower.Open access funding enabled and organized by Projekt DEAL

An outlook for the future Ferrari’s boom

Ferrari is one of the world’s leading luxury brand for designing, developing, manufacturing and selling cars. With a growing stock price, Ferrari’s potential is showing. Affected by the growth in Formula 1 engagement and soon launching its first SUV, Ferrari’s revenues are expected to boom. The evaluation conducted displays a bright future for the company. However, some risks also arise, mainly the fact Ferrari’s multiples are very inflated, even for a luxury company. Another concern regarding its cash flows might arise, as they could represent lost investment opportunities. Nevertheless, due to the potential share price and historical data, a “BUY” decision is recommended

Hybrid Optimized Fuzzy Pitch Controller of a Floating Wind Turbine with Fatigue Analysis

Floating offshore wind turbines (FOWTs) are systems with complex and highly nonlinear dynamics; they are subjected to heavy loads, making control with classical strategies a challenge. In addition, they experience vibrations due to wind and waves. Furthermore, the control of the blade angle itself may generate vibrations. To address this issue, in this work we propose the design of an intelligent control system based on fuzzy logic to maintain the rated power of an FOWT while reducing the vibrations. A gain scheduling incremental proportional–derivative fuzzy controller is tuned by genetic algorithms (GAs) and combined with a fuzzy-lookup table to generate the pitch reference. The control gains optimized by the GA are stored in a database to ensure a proper operation for different wind and wave conditions. The software Matlab/Simulink and the simulation tool FAST are used. The latter simulates the nonlinear dynamics of a real 5 MW barge-type FOWT with irregular waves. The hybrid control strategy has been evaluated against the reference baseline controller embedded in FAST in different environmental scenarios. The comparison is assessed in terms of output power and structure stability, with up to 23% and 33% vibration suppression rate for tower top displacement and platform pitch, respectively, with the new control scheme. Fatigue damage equivalent load (DEL) of the blades has been also estimated with satisfactory results.This work has been partially supported by the Spanish Ministry of Science and Innovation under the project MCI/AEI/FEDER number RTI2018-094902-B-C21 and PDI2021-123543OB-C21

Dental sealants: knowledge, opinion, values and practice of portuguese dental hygienists

Objetivos: O objetivo deste estudo é o de caracterizar a amostra de participantes e o de apresentar os dados obtidos na avaliação do conhecimento, a opinião, os valores e a prática (KOVP) dos higienistas orais em Portugal sobre selantes de fissuras. Métodos: Uma amostra não probabilística de 142 indivíduos foi obtida de entre os membros da Associação Portuguesa de Higienistas Orais. Os participantes responderam a um questionário on-line composto por 4 perguntas demográficas e pela classificação, de 31 afirmações sobre os KOVP sobre selantes de fissuras, numa escala de 0 a 5, sendo 5 a maior concordância com a afirmação. O teste de pares de sinais Wilcoxon, o teste de Mann-Whitney, o teste de Kruskal- -Wallis, a correlação de Spearman e o teste V Cramer foram utilizados para analisar os dados. Resultados: Os higienistas orais portugueses apresentam feedback positivo sobre o uso de selantes de fissuras. Os valores médios dos grupos, para cada uma das variáveis estudadas, foram: para conhecimento = 3,63 ± 0,29; opinião = 2,87 ± 0,42; valor = 2,92 ± 0,44 e prática 3,76 ± 0,46. O conhecimento diferiu por anos de experiência (p<0,01), a opinião diferiu com o tipo de prática clínica (p<0,01) e a prática também diferiu com o tipo de prática clínica (p<0,01). Correlações positivas estatisticamente significativas foram encontradas entre conhecimento e prática (p<0,01).info:eu-repo/semantics/publishedVersio