Adversarial Robustness and Feature Impact Analysis for Driver Drowsiness Detection

Drowsy driving is a major cause of road accidents, but drivers are dismissive of the impact that fatigue can have on their reaction times. To detect drowsiness before any impairment occurs, a promising strategy is using Machine Learning (ML) to monitor Heart Rate Variability (HRV) signals. This work presents multiple experiments with different HRV time windows and ML models, a feature impact analysis using Shapley Additive Explanations (SHAP), and an adversarial robustness analysis to assess their reliability when processing faulty input data and perturbed HRV signals. The most reliable model was Extreme Gradient Boosting (XGB) and the optimal time window had between 120 and 150 seconds. Furthermore, SHAP enabled the selection of the 18 most impactful features and the training of new smaller models that achieved a performance as good as the initial ones. Despite the susceptibility of all models to adversarial attacks, adversarial training enabled them to preserve significantly higher results, especially XGB. Therefore, ML models can significantly benefit from realistic adversarial training to provide a more robust driver drowsiness detection.Comment: 10 pages, 2 tables, 3 figures, AIME 2023 conferenc

Experimental research on structural concrete masonry walls subjected to fire

The construction in masonry is one of the oldest ways of construction. However, the knowledge regarding its structural behavior is still not well consolidated, especially regarding extreme conditions, such as fire. Although the few available studies regarding structural masonry under fire conditions show some promising results, still the available normative documents seem to have some limitations regarding the topic, which highlights the need for further research, especially experimental, in this field. This paper presents the results of a study on the behavior of structural masonry walls subjected to simulated fire conditions. The specimens were built with three cells concrete blocks, which are common in European and US construction. In the fire resistance tests the walls were subjected to the action of a serviceability in-plane load and the ISO 834 fire curve. Temperatures were measured in the furnace, while temperatures and displacements were measured in the specimens. The obtained results were also compared with the Eurocode 6 part 1.2 predictions, for similar cases

Numerical analysis on the behaviour of concrete masonry walls subjected to fire

This paper presents a numerical study on the structural behaviour of concrete masonry at elevated temperatures. Based on an experimental research previously performed on half-scale walls in fire situations, numerical models were developed and validated. The heat transfer models led to thermal fields with good agreement with the temperatures measured by thermocouples installed in the wall, a bigger scatter of temperatures was found in the experimental research. The mechanical analysis led to vertical and out-of-plane displacements in good agreement with the displacements measured by LVDTs. The numerical model was validated and will be used in future researches to perform parametric studies

Tecnologia de baixo custo para monitoramento da pesca, aplicado a duas espécies de pacu no Amazonas, Brasil

The present study aimed to investigate the “pacu” species’ commercialized in the “Colônia dos Pescadores Z-31” in the municipality of Humaitá, Amazonas State, from May 2018 to April 2019. For this purpose, we developed a method for raising a diary database in the colony, obtaining variables such as production, effort, catch per unit effort (CPUE), fishing spots, amongst others. We have identified two species of “pacu” - Mylossoma aureum and M. duriventre - with productions of 10.5 and 9.5 tonnes respectively which generated an income of U$ 22,173.00. Captures occurred mostly randomly, due to the region’s fishing characteristics although the CPUE was higher when compared to bigger cities. We could also find evidence over their migratory cycles from a correlation between the catching sites and the period, where: i) during the falling water (May to July), the “pacus” start to leave the streams and concentrate in lakes; ii) during the dry season (August to October), the “pacus” perform a second migratory cycle, leaving streams and lakes and going to rivers; iii) finally, during the rising water, “pacus” once again move to small streams. The generated information can be used in fishing strategies in the region, reducing costs with inputs.Fundação de Amparo a Pesquisa do Estado do Amazonas, 41649.UNI737.4908.01042019info:eu-repo/semantics/publishedVersio

SYPEC: Desenvolvimento de uma aplicação Android para controlo e avaliação postural

Dissertação para obtenção do Grau de Mestre em Engenharia BiomédicaA evolução a que se assistiu desde a segunda metade do século XX até aos dias de hoje trouxe profundas alterações ao nosso cotidiano. As tarefas que outrora foram desempenhadas pelo Homem são hoje realizadas por máquinas e o estilo de vida tornou-se cada vez mais sedentário. Nesta sequência a posição de sentado tornou-se na posição mais adoptada pela população mundial, tanto num contexto profissional como de lazer. Associado a isso, estudos indicam que os factores como posturas inadequadas, fadiga muscular, e sobrecarga nas estruturas osteomioarticulares causadas pela adopção prolongada desta posição têm sido referenciados como de risco para o aparecimento de dor e lesão ao nível a região lombar. É neste contexto que se insere o projecto SYPEC (System for Posture Evaluation and Correction). O SYPEC é um projecto inovador nas áreas de ergonomia e biomecânica e, actualmente, utiliza uma cadeira de escritório convencional equipada com 8 almofadas de ar, cada uma delas ligadas a um compressor, uma electroválvula e um transdutor de pressão, que permitem medir e regular a pressão no interior das almofadas possibilitando a alteração de conformação das suas superfícies, para avaliação e correcção postural na posição de sentado. Nesta dissertação deu-se continuidade ao trabalho já desenvolvido implementando-se uma aplicação para controlo do protótipo, aquisição de dados e avaliação postural, através de um dispositivo móvel. Esta apresenta-se com uma solução integrada para avaliação postural e servirá de base aos actuais e futuros estudos no âmbito deste projecto. Conjuntamente foi desenvolvido um módulo de electrónica que permitiu dotar o SYPEC do protocolo de comunicação Bluetooth. Os resultados alcançados com a utilização desta aplicação são bastante promissores e possibilitaram a sua utilização noutros trabalhos do SYPEC em curso, tanto para aquisição de novos dados como para o estudo dos algoritmos de avaliação postural, em contexto real

Preparação e caracterização de efluentes sintéticos

Neste estudo preparou-se um efluente sintético de modo a simular efluentes tratados com possibilidade de serem reutilizados, por exemplo, na rega de campos de golfe, como acontece na região do Algarve. Durante a realização do trabalho procurou-se mostrar a possibilidade da preparação de um efluente usando água proveniente de um lago situado num jardim urbano, o que pode garantir a presença de substâncias húmicas, indicar a diferença de comportamento da água do lago e do efluente sintetizado, através da medição de vários parâmetros, procurar qual a influência que pode ter no comportamento dos efluentes o intervalo de tempo (até 3 meses) entre a sua preparação, ou recolha, e a realização das análises. Fez-se ainda uma breve discussão acerca da importância da validação dos métodos de ensaio. Dos resultados obtidos, observou-se uma homogeneidade do comportamento das amostras, com resultados bastante consistentes quanto à sua caracterização. Demonstrou-se a possibilidade de se prepararem efluentes sintéticos partindo de águas superficiais. O intervalo de tempo (3 meses) entre a preparação (ou recolha) e a realização dos ensaios não contribuiu para alterações significativas dos efluentes. Verificou-se ainda a importância do azoto no traçado das curvas de breakpoint.In this study synthetic effluents which simulate treated wastewater, with the possibility of reuse, for example, in golf courses irrigation, in Algarve region, were prepared. Along this work it was intended to show the possibility of preparing an efluente using water from a lake located in an urban park, which may ensure the presence of humic substances, to indicate the difference of behaviour between the lake water and the synthetised effluent by the measurement of several parameters and finding out the influence of the time interval (3 months) between sampling, or effluent synthesis and experimental analyses. From the obtained results, homogeneity of behaviour of the samples was observed with fairly consistent results regarding its characterization. Also, the possibility of preparing synthetic effluents starting from surface waters was demonstrated. The time interval (3 months) between sampling, or effluent synthesis and experimental analyses did not contribute to significant changes of the efluente characteristics. Still, the important role of nitrogen on breakpoint curves shape was also observed

Normal and tangential behaviour of dry joints in refractory masonry

Industrial vessels used in high temperature processes of steel and cement production are protected by refractory linings built with mortarless joints. These dry joints, formed by stacked bricks have a crucial importance on the mechanical behaviour of the lining. The stiffness and consequently the stresses generated by thermal expansion are reduced due to the joints. The present article presents the results of experimental and numerical tests on the thermomechanical behaviour of these joints. The compressive strength of the brick was assessed at ambient and high temperatures and a statistical analysis of the distribution of the bricks’ shape imperfections was carried out. Several studies were carried out on the normal behaviour of the joints: classical joint closure test; bed joint closing action in a masonry wallet measured with a DIC; effects of brick’s height imperfections on its loadbearing capacity; effects of brick’s height imperfections on the wall’s behaviour at ambient and high temperatures and a comparison between the bed and head joints behaviour. To characterize the joint’s tangential behaviour at high temperatures a novel device was developed and presented.The authors would like to thank the support of European Commission under the framework of Marie Sklodowska-Curie Actions Innovative Training Networks, project ATHOR -Advanced THermomechanical multiscale mOdelling of Refractory linings 764987 Grant

Towards a multi-marker prognostic strategy in acute heart failure: a role for GDF-15

AIMS: Growth differentiation factor (GDF)-15 mirrors inflammation and oxidative stress in cardiovascular diseases. Brain natriuretic peptide (BNP) is associated with cardiomyocyte stretch in heart failure (HF). The objective of this study was to evaluate the prognostic impact of plasma GDF-15 and BNP in acute HF. METHODS AND RESULTS: We studied a subgroup of patients prospectively recruited in an acute HF registry (follow-up: 2 years; endpoint: all-cause mortality). Cox regression multivariate models were built to study the association of GDF-15 and mortality. Further cross-classification according to discharge GDF-15 (mean) and BNP (mean) and association with mortality was studied. We studied 158 patients: seventy-nine were male, mean age was 75 years, 55.1% had left ventricular ejection fraction < 40%, mean discharge BNP was 1000 pg/mL, and mean GDF-15 was 3013 ng/mL. Higher BNP and GDF-15 predicted 2-year mortality. Patients with GDF-15 ≥ 3000 ng/mL had a multivariate adjusted 2-year death risk of 1.86 (1.08-3.18). Patients discharged with both BNP and GDF-15 above the mean had an adjusted hazard ratio of 4.33 (2.07-9.06) when compared with those with both <mean. CONCLUSIONS: Higher GDF-15 associated with worse prognosis in acute HF independently of BNP. When both biomarkers GDF-15 and BNP were elevated at discharge, the 2-year mortality risk increased over four-fold. Biomarkers related to different pathophysiological pathways can provide incremental prognostic information in acute HF.info:eu-repo/semantics/publishedVersio

Experimental and numerical analysis on the structural fire behaviour of three-cell hollowed concrete masonry walls

Preprint versionMasonry is one of the oldest and most traditional materials in building construction. Nevertheless, the knowledge on the structural fire behaviour of masonry elements is not yet well consolidated. The literature on the load-bearing capacity of masonry walls in case of fire showed an enhanced performance of these elements, however the lack of normative documents, characterization of material properties at high temperatures and experimental results, for calibrating and validating the numerical models, indicates the need of further research. A research study on the structural fire behaviour of three-cell hollowed concrete masonry walls subjected to fire is presented based on results of experimental and numerical studies. First, several loadbearing capacity tests at high temperatures and fire resistance tests on the walls, were carried out in order to assess their behaviour, critical times, failure modes and temperature distribution. The specimens were built with three cell concrete blocks and M10 mortar and were then subjected to an in-plane serviceability load during test. The temperatures, loads and displacements were measured. Second, finite element models were developed and validated with the experimental results. The experimental and numerical results were also compared with the ones given by EN1996-1–2 provisions.European Union (European Commission), Marie Skłodowska-Curie Actions Innovative Training Networks in the frame of the project ATHOR - Advanced THermomechanical multiscale modelling of Refractory linings 764987 Gran