O método do gradiente conjugado, na sua forma geral, pode ser aplicado a um sistema de equações lineares algébricas Ax = b, quando A é autoadjunta e positiva definida em relação a um produto interno qualquer. As formas de recorrência de dois termos ou três, que fornecem uma aproximação da solução do sistema, independem do produto interno fixado no espaço universo. A generalidade teórica envolvida em tal contexto encontra-se, nesse trabalho, devidamente justificada. O precondicionamento e a sua relação com o produto interno utilizado, e o método para SELAS singulares e quase singulares também fazem parte da exposição. / The conjugated gradient method, in its general form, can be applied on an algebraic linear system Ax = b , when A is selfadjoint and positive definite with respect to an arbitrary inner product. The three-term recurrence form and the two-term one that give an approximation to the solution of the system do not depend on the inner product in the environment space. The theoretical generality involved in that context is properly justified in this dissertation. The preconditioning and its relationship with the relevant inner product and the conjugate gradient method for the singular and nearly singular systems are also part of this work.

O método do gradiente conjugado, na sua forma geral, pode ser aplicado a um sistema de equações lineares algébricas Ax = b, quando A é autoadjunta e positiva definida em relação a um produto interno qualquer. As formas de recorrência de dois termos ou três, que fornecem uma aproximação da solução do sistema, independem do produto interno fixado no espaço universo. A generalidade teórica envolvida em tal contexto encontra-se, nesse trabalho, devidamente justificada. O precondicionamento e a sua relação com o produto interno utilizado, e o método para SELAS singulares e quase singulares também fazem parte da exposição. / The conjugated gradient method, in its general form, can be applied on an algebraic linear system Ax = b , when A is selfadjoint and positive definite with respect to an arbitrary inner product. The three-term recurrence form and the two-term one that give an approximation to the solution of the system do not depend on the inner product in the environment space. The theoretical generality involved in that context is properly justified in this dissertation. The preconditioning and its relationship with the relevant inner product and the conjugate gradient method for the singular and nearly singular systems are also part of this work.

O método do gradiente conjugado, na sua forma geral, pode ser aplicado a um sistema de equações lineares algébricas Ax = b, quando A é autoadjunta e positiva definida em relação a um produto interno qualquer. As formas de recorrência de dois termos ou três, que fornecem uma aproximação da solução do sistema, independem do produto interno fixado no espaço universo. A generalidade teórica envolvida em tal contexto encontra-se, nesse trabalho, devidamente justificada. O precondicionamento e a sua relação com o produto interno utilizado, e o método para SELAS singulares e quase singulares também fazem parte da exposição. / The conjugated gradient method, in its general form, can be applied on an algebraic linear system Ax = b , when A is selfadjoint and positive definite with respect to an arbitrary inner product. The three-term recurrence form and the two-term one that give an approximation to the solution of the system do not depend on the inner product in the environment space. The theoretical generality involved in that context is properly justified in this dissertation. The preconditioning and its relationship with the relevant inner product and the conjugate gradient method for the singular and nearly singular systems are also part of this work.

No / Marketers desire to utilise electronic word of mouth (eWOM) marketing on social media sites. However, not all online content generated by marketers has the same effect on consumers; some of them are effective while others are not. This paper aims to examine different characteristics of marketer-generated content (MGC) that of which one lead users to eWOM. Twitter was chosen as one of the leading social media sites and a content analysis approach was employed to identify the common characteristics of retweeted and favourited tweets. 2,780 tweets from six companies (Booking, Hostelworld, Hotels, Lastminute, Laterooms and Priceline) operating in the tourism sector are analysed. Results indicate that the posts which contain pictures, hyperlinks, product or service information, direct answers to customers and brand centrality are more likely to be retweeted and favourited by users. The findings present the main eWOM drivers for MGC in social media.

Musical genres enable listeners to differentiate between diverse styles and forms of music, serving as a practical tool to organize and categorize artists, albums, and songs. Album covers, featuring graphic depictions that reflect the vibe and tone of the music, serve as a visual intermediary between the artist and the audience. While numerous machine learning techniques leverage textual, visual, and audio information in a multi-modal approach to categorize music, the sole focus on visual aspects, specifically album cover images, and their correlation with musical genres has been less explored. The question guides this research: How do EfficientNet and ResNet compare in their ability to accurately classify album cover images into specific genres based solely on visual features? Two state-of-the-art convolutional neural networks, ResNet and EfficientNet, are employed to classify a newly created dataset (the EquiGen dataset) of 60,000 album cover images into 15 distinct genres. The dataset was divided into 70% for training, 15% for validation, and 15% for testing.The findings reveal that both ResNet and EfficientNet achieve better-than-random classification accuracy, indicating that visual features alone can be informative for genre classification. Some genres performed much better than others, namely Metal, New Age and Rap. EfficientNet demonstrated slightly superior performance compared to ResNet, with higher accuracy, precision, recall, and F1 scores. However, both models exhibited challenges in generalizing well-to-unseen data and showed signs of overfitting.This study contributes to the interdisciplinary research on Music Genre Categorization (MGC), machine learning, and music.

Composites are the materials which can be used for a wide variety of applications andproducts such as sports equipment, aerospace and marine because of light and stiffnessproperties. Composites are often made from thermoset resin with glass fibers.In this study, two ways of recycling composites were evaluated, which are microwavepyrolysed composites (MGC) and mechanical composites (GC). These glass fibers weregoing to be compounded with Polypropylene (PP) or Maleic Anhydride ModifiedPolypropylene (MAPP) and then injection moulded the sample by Micro-compounder.In order to get better adhesion to the polymer, a coating was added. The Neoxil 5682-polypropylene water emulsion was evaluated.The samples were characterized by Tensile Testing, Thermogravimetric Analysis (TGA),Different Scanning Calorimetry (DSC), and Dynamic Mechanical Analysis (DMA) to find aoptimum combination of recycled glass fiber reinforced polymer.Microwave pyrolysis is a new research area. The glass fiber, polymer oil and gas can beobtained by heating the composite with microwaves to in an inert atmosphere. The polymeroil can be distillated and then evaluated with GC-MS; in order to obtain the chemicalcompositions.Keywords: Composites, grinded and microwave pyrolyse composites (MGC), grindedcomposites (GC), Polypropylene (PP), Maleic Anhydride Modified Polypropylene (MAPP),Micro-compounder, Tensile Testing, Thermogravimetric Analysis (TGA), Different ScanningCalorimetry (DSC), and Dynamic Mechanical Analysis (DMA), Microwave pyrolysis,polymer oil, distillation, GCMS Analysis. / Program: MSc in Resource Recovery - Sustainable Engineering