Spatial modulations for green heterogeneous networks

A rápida evolução dos sistemas de telecomunicações culminou numa necessidade cada vez mais crescente por redes que permitam elevados débitos. Associado a esse throughput elevado está o custo energético que gradualmente torna os sistemas pouco eficientes energeticamente. As modulações espaciais generalizadas (Generalized Spatial Modulation -GSM) surgem da necessidade de criar comunicações mais “verdes”, permitindo obter melhores eficiências energéticas através da redução do número de cadeias de blocos radio-frequência (RF) utilizadas no emissor. O estudo apresentado neste trabalho pretende realçar, num primeiro ponto, a importância da evolução dos sistemas de transmissão MIMO (Multiple-Input Multiple-Output) como forma de aumento do throughput global de uma rede de telecomunicações mantendo uma eficiência energética alta, com foco em GSM. O segundo ponto consiste no estudo de um algoritmo baseado no método ADMM (Alternating Direction Method of Multipliers), como recetor de baixa complexidade para esquemas GSM com desempenho próximo do ótimo, o detetor de máxima verosimilhança (MLD). O estudo do recetor ADMM foi efetuado em duas fases, sendo que a primeira é referente ao estudo extensivo e exclusivo do recetor ADMM, com principal enfoque nos vários parâmetros que o definem. Na segunda fase é feita uma comparação para vários cenários entre o recetor ADMM e alguns dos recetores de baixa complexidade mais conhecidos, entre eles o OB-MMSE (Ordered Block MMSE) e o BPDN (Basis Pursuit De-Noising), por exemplo. A realização de simulações, com os vários recetores, em vários cenários permitiu concluir que o ADMM, com recurso às suas técnicas de refinamento, representa uma alternativa eficiente, e em certos casos superior, ao OB-MMSE principalmente para cenários com um elevado número de bits por símbolo espacial.The fast evolution of telecommunications systems resulted in a growing need for networks that support high transmission rates. Associated with this high throughput is the energy cost that gradually makes this systems less energy-efficient . The Generalized Spatial Modulation (GSM) arises from the need to create more "green" communication, allowing best energy efficiencies. The study presented in this thesis aims to highlight firstly, the importance of the development of MIMO (Multiple-Input Multiple-Output) transmission systems capable of increasing the overall throughput of a telecommunications network while maintaining high energy efficiency, focusing on GSM. The second relevant aspect is the study of an algorithm based on the ADMM (Alternating Direction Method of Multipliers) method, as a solution for a low complexity receiver for GSM schemes with a performance close to the optimal one, the maximum likelihood detector (MLD). The ADMM receiver study was conducted in two phases, the first of which refers to the extensive and unique study of the ADMM receiver, with main focus on the various parameters that define it. In the second stage a comparison is made between the settings for various ADMM receivers and some of the known low-complexity receivers, including OB-MMSE (Ordered Block MMSE) and BPDN (Basis Pursuit De-noising), for example. The results obtained from the evaluations performed several scenarios allow us to conclude that the ADMM based receiver combined with refinement techniques, is an efficient alternative and in some cases with better performance than the OB-MMSE receiver, especially for scenarios with a large number of bits per spatial symbol

Fenologia foliar da floresta Amazônica de terra firme por imagens digitais RGB

Leaf phenology may drive seasonal variation in canopy-scale photosynthetic capacity and carbon flux in the Central Amazon. Visual monitoring of leaf flush from the forest floor is time consuming and difficult against an overcast sky. Seasonal trends of vegetation indices from orbital sensors have been challenged due to artifacts from seasonal trends in solar illumination angle. Tower-mounted RGB cameras are an attractive alternative. The Green Chromatic Coordinate (GC = green brightness divided by summed brightness of the three RGB channels) has been employed for this purpose. However, subtle seasonal change of tropical forest GC at landscape-scale may be of smaller amplitude than artifacts related to color balance, crown shadow size, illumination angle, exposure speed and sensor drift. Furthermore, gradual change in GC is affected by both leaf age and leaf amount. Nonetheless, abrupt GC change of large amplitude occurs at the individual crown scale and can be reliably attributed to massive leaf flush or leaf loss events. We analyzed a full year of daily images from an RGB camera mounted 50 m above the forest canopy at the Amazon Tall Tower site (59.0ºW, 2.1ºS), on a well-drained plateau. We minimized artifacts by maintaining the sun behind the camera, accepting only images with diffuse illumination, by giving equal weight to each tree crown and by radiometric inter-calibration of all selected images against a standard. For each of 267 individual crown areas we then prepared a greenness timeline of daily GC values. Eighty-two percent of these upper canopy crowns showed a clear episode of rapid and massive leaf flush (smoothed GC slope >0.01/month, sustained for at least 0.5 month and peaking above 75th percentile of daily GC values) and 30% showed massive rapid leaf drop (smoothed GC slope 0,01/mês, sustentada por pelo menos 15 dias, culminando acima do 75º percentil dos valores diários do GC) e 30% mostrou uma perda rápida e massiva de folhas (inclinação suavizada do GC < -0,01/mês, sustentada por pelo menos 15 dias, atingindo valores abaixo do 25º percentil dos valores diários do GC). O flush foliar foi fortemente concentrado nos cinco meses mais secos (50% de todas as copas) comparado com os cinco meses mais chuvosos (10% de todas as copas). Isto contradiz o recentemente proposto controle por fotoperíodo na fenologia foliar das árvores na região equatorial úmida. Árvores com abrupta perda e emissão de folhas atingiram o seu verdor mínimo 26 +/- 16 dias antes do verdor máximo, indicando que a perda de folhas foi um rápido preâmbulo para o flush foliar na estação seca

Composite materials with MWCNT processed by Selective Laser Sintering for electrostatic discharge applications

Selective Laser Sintering (SLS) is an additive manufacturing technology that enables the production of polymeric parts for end-use applications. Despite the great potential of conventional materials, carbon-based reinforcements have been widely considered to contradict the electrically insulating nature of polymers, allowing the applicability of SLS in novel applications within electronics industry. However, the laser-sintering processing of such materials still encompasses a number of limitations including agglomeration problems, weak interparticle adhesion, low parts resolution, high processing time and costs. Therefore, this research reports the development of functional composite materials for SLS capable of being considered for the production of components that are in direct contact with electrostatic discharge (ESD) sensitive devices. To do so, composite materials of Polyamide 12 incorporating 0.50 wt%, 1.75 wt% and 3.00 wt% of Multi-Walled Carbon Nanotubes were developed aiming to achieve values of surface resistance between 104 - 109 Ω, according to the delivery instructions of Bosch Car Multimedia S.A. Test specimens produced by SLS were dimensionally, mechanically, electrically, thermally and morphologically characterized. Comparing to the neat matrix, the composite materials revealed narrower SLS processing window, reduced mechanical strength, surface resistance in the ESD range and electrical conductivity until 10−6 S/cm. Fundamentals on the sintering process of these functional materials are also provided.This work was co-funded by the European Regional Development Fund through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project No. 47108, “SIFA”; Funding Reference: POCI-01-0247-FEDER-047108] and by the Foundation for Science and Technology (FCT) through the PhD scholarship 2020.04520.BD

The influence of the energy density on dimensional, geometric, mechanical and morphological properties of SLS parts produced with single and multiple exposure types

Selective Laser Sintering (SLS) is a Powder Bed Fusion technology that embraces a large number of variables influencing the properties of the parts produced. The well-known dependence and complex interaction established between the main process parameters demands continuous empirical research for effective SLS monitoring. The assessment of the energy density supplied by the laser beam to the powder bed during the process, that depends on the combination of the laser power, hatch distance, scan speed and layer thickness, is frequently considered for that purpose. Therefore, this research intends to evaluate the influence of the energy density on the dimensional, geometric, mechanical and morphological properties of SLS parts produced with conventional Polyamide 12 material. In this study, we considered different hatching and contour parameters in the energy range between 0.158 J/mm3 and 0.398 J/mm3 through single and multiple exposure types defining individual and combined parameterization sets, respectively. Results from X-ray computed tomography, tensile tests and scanning electron microscopy show that the implementation of a skin/core configuration allows the production of SLS parts with a valuable set of properties, minimizing the trade-off between mechanical strength and overall accuracy.This work was co-funded by the European Regional Development Fund through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project No. 47108, “SIFA”; Funding Reference: POCI-01-0247-FEDER-047108] and by the Foundation for Science and Technology (FCT) through the PhD scholarship 2020.04520.BD

ASSOCIATING COLLABORATION WITH ACTIVE LEARNING: AN EXPERIENCE IN INDUSTRIAL ENGINEERING COURSE

The Internet changed the way of learning; it promotes interactivity and autonomy. Through Web 2.0 many tools could be used to plan strategies to motivate students for autonomous learning. This paper presents an analysis of such strategies applied to an industrial engineering course. It discusses an application in an Organizational Productive Arrangement (OPA) course using web tools to promote autonomous learning using an active strategy methodology. Two tools were used: a blog to promote interaction and a wiki to motivate research and collaboration. An information system was used to support an active strategy methodology. A survey of 40 students was conducted; the data is presented and discussed

Exigências do trabalho e satisfação profissional: o papel mediador do conflito trabalho-família e do burnout

O conjunto de mudanças tecnológicas e sociais, tal como, as alterações advindas da situação socio-pandémica, no contexto de trabalho, têm forte impacto na vida dos trabalhadores. As exigências do trabalho e a interferência do contexto de trabalho com o familiar são vistos como antecedentes de vários construtos negativos para a saúde e bem-estar no meio laboral, como o burnout e a baixa satisfação profissional. Este estudo tem como objetivos observar o efeito do conflito trabalho-família e das exigências do trabalho sobre o burnout e a satisfação profissional, o efeito mediador do conflito trabalho-família sobre as exigências do trabalho e o burnout, e o efeito mediador do burnout na relação entre as exigências do trabalho e a satisfação profissional. A amostra é composta por 505 participantes (363 mulheres e 142 homens), com idades entre os 19 e os 66 anos (M = 37.11; DP = 11.12). Os resultados mostram que as exigências do trabalho influenciam o conflito trabalho-família e família-trabalho, e que ambas as variáveis têm efeitos negativos no burnout e na satisfação profissional. Adicionalmente, suportam as mediações do conflito trabalho-família e do burnout, com as relações respetivas. Quer o conflito trabalho-família quer as altas exigências do trabalho acarretam outcomes laborais negativos significativos para as organizações, pelo que a prevenção através de práticas e de uma cultura amiga da família e de prudência para com o burnout, promoverão o bem-estar e saúde mental no trabalho, bem como contribuirão para uma melhor performance organizacional.The set of technological and social changes in the context of work, such as the alterations that arrived with the social-pandemic situation, have a strong impact in the life of workers. The demands of work and the interference of the working context with the family are seen as antecedents of several negative constructs for wealth and well-being in the work context, such as burnout and low professional satisfaction. The present study aims at observing the effect of work-family conflict and work demands on burnout and professional satisfaction, the mediator effect of work-family conflict on work demands and burnout, and the mediator effect of burnout on the relation between work demands and professional satisfaction. The sample consists of 505 participants (363 women and 142 men), with ages ranging from 19 to 66 years (M = 37.11; SD = 11.12). The results show that work demands influence work-family and family-work conflict, and that both variables have negative effects on burnout and professional satisfaction. Moreover, these results support the mediations of work-family conflict and burnout, with the respective relations. Both work-family conflict and high work demands entail negative work outcomes to organizations, whereby prevention through practices, family-friendly culture, and prudence towards burnout, will promote well-being and mental health in the workplace, as well as a better organizational performance

Consciência fonológica em adultos não alfabetizados

The act of reading is a complex and multifaceted activity that involves social, cognitive, emotional and environmental factors. Regardless of whether in childhood or adulthood, reading is acquired only if it is taught, however this ability in children is more easily acquired than in adults. The literature highlights the importance of phonological awareness to reading acquisition. This research aimed to analyze the level of performance in phonological awareness of illiterate adults.13 Participated in the study 44 adults of both sexes. The adults were divided into two groups, one of illiterate adults, and the other adult literacy in childhood. The following instruments were used: sociodemographic data; Predictors of the Reading Skills Test, that consists of tasks of rhyme, alliteration, segmentation; individually and applied in a tablet. Based on the findings, it can be concluded that there were differences in the performance of illiterate and literate adults, showing a listing of correct answers by the stimuli presented in the task. The task of alliteration was that obtained the highest mean score, followed by segmentation and rhyme tasks for both groups. These findings, when compared to previous studies with illiterate children, demonstrate a similar profile in the results and failure in the segmentation task suggests that this ability is a strong ally in reading acquisition. Thus, the results of this study corroborate the improvement of literacy programs for adults and strengthens the research field that aims to understand the relationship illiterate adults and reading.O ato de ler embora pareça ser natural ao homem é uma habilidade que deve ser ensinada e aprendida, diferente da fala que é uma habilidade interconectada com a genética humana e habilita a criança desde os primeiros meses de vida a discriminar os sons da fala, a leitura requer uma modificação neural que dê condições para a decodificação dos símbolos gráficos e sonoros que representam a fala, é uma capacidade adquirida com o ensino, e que apesar de parecer uma tarefa simples, caracterizado como ato complexo e multifacetado que envolve fatores sociais, cognitivos, emocionais e ambientais para que ocorra de forma satisfatória e eficaz. Hoje é consenso na literatura sobre a importância da leitura para o pleno desenvolvimento social e cognitivo do ser humano. Independente de ser na infância ou na vida adulta, a leitura só é adquirida se for ensinada, entretanto em crianças essa habilidade é mais fácil de ser adquirida do que em adultos. Nesse contexto multifacetado de aprendizagem formal, pesquisadores nacionais e internacionais ressaltam a importância do desenvolvimento da consciência fonológica para a aquisição da leitura. A presente investigação visou analisar o nível de desempenho em consciência fonológica de adultos não alfabetizados. Participaram da pesquisa 44 adultos, de ambos os sexos, com idades entre 28 e 56 anos (M= 40,9; Dp= 7,6). Para a seleção da amostra foi utilizada a técnica de amostragem por conveniência. Os sujeitos foram divididos em dois grupos, sendo um de adultos não alfabetizados, e o outro de adultos alfabetizados. Foram utilizados como instrumentos: ficha de dados sociodemográficos; teste de habilidades preditoras da leitura (THPL): composto por tarefas de rima, aliteração, segmentação. O THPL fora administrado individualmente e com o auxílio de um dispositivo móvel (tablet). Com base nos achados, pode-se concluir que houve diferença no desempenho dos adultos não alfabetizados e alfabetizados, evidenciando um perfil de acertos mediante os estímulos apresentados nas tarefas. A tarefa de aliteração foi a que obteve maior média de acertos, seguida das tarefas de rima e segmentação para ambos os grupos. Esses achados, quando comparados aos estudos anteriores com crianças não alfabetizadas, demonstram um perfil semelhante nos resultados e o insucesso na tarefa de segmentação sugere que essa habilidade é uma forte aliada na aquisição da leitura tanto em crianças como em adultos não alfabetizados. Dessa forma, os resultados desta pesquisa corroboram para o aperfeiçoamento de programas de alfabetização para adultos e fortalece o campo de pesquisa que visa compreender a relação entre adultos não alfabetizados e a leitura

Les usages et les représentations sociales de l’apprentissage mobile chez des futurs enseignants brésiliens et québécois

L’apprentissage mobile est vu comme un apprentissage qui se déroule dans des contextes multiples, qu’ils soient formels ou informels, à travers des interactions sociales et des contenus en utilisant des dispositifs électroniques et personnels (Crompton, 2013). Pour l’UNESCO (2012), il représente une des solutions pour contribuer à une formation des enseignants capable de répondre aux besoins éducatifs du XXIe siècle. De plus, en raison de la baisse du coût des appareils mobiles et grâce à l'amélioration des réseaux numériques, l’apprentissage mobile est devenu une réalité tangible (Johnson et al., 2011). C’est le cas au Brésil et au Canada, deux pays qui présentent de hautes statistiques liées aux abonnements à la large bande mobile et à la possession des technologies mobiles. Dans le contexte éducatif, la législation régissant la formation initiale des enseignants de ces deux pays met en évidence l’importance de l’usage des TIC de façon à soutenir l’apprentissage du futur enseignant, entrevoyant aussi son utilisation pour leur futur enseignement. En plus, les projets d’apprentissage mobile sont déjà une réalité dans les écoles de la province de Québec, Canada, et de l’état du Ceará, Brésil. Dans ce contexte, à partir des usages déclarés des technologies mobiles pour l’apprentissage et en prenant comme référence la théorie des représentations sociales (Moscovici, 1961), cette recherche vise à mieux connaitre les usages pédagogiques des technologies mobiles et les représentations sociales des futurs enseignants brésiliens et québécois sur l’apprentissage mobile. Pour mieux comprendre comment ce type d’apprentissage peut soutenir les futurs enseignants, il est primordial de connaitre quels sont les avantages et les défis perçus par ceux qui pratiquent l’apprentissage mobile. Leurs perceptions peuvent susciter des attitudes positives quant à l’usage pédagogique des appareils mobiles ou stimuler des attitudes négatives envers ces mêmes technologies. Une méthodologie d’approche mixte a été employée avec l’administration d’un questionnaire auprès de 189 étudiants brésiliens et de 149 québécois ainsi qu’un entretien semi-dirigé avec le total de 36 étudiants, 18 étudiants provenant de cours de baccalauréat en enseignement d’une université brésilienne et 18 étudiants de cours de baccalauréat en enseignement d’une université québécoise. Une analyse statistique descriptive a été effectuée à partir des données quantitatives et une analyse de contenu des données qualitatives collectées. Les résultats montrent que les futurs enseignants brésiliens et québécois sont très mobiles, c’est à dire, qu’ils sont très équipés avec des appareils mobiles et très connectés à Internet. Nous constatons que, pour ces deux groupes, l’apprentissage mobile est déjà une réalité dans leur vie étudiante puisqu’ils déclarent l’utiliser dans plusieurs activités à des fins d’apprentissage. Pour ce qui est de leurs représentations sociales sur l’apprentissage mobile comme étudiants, tant les brésiliens que les québécois le perçoivent comme un type d’apprentissage qui complète leurs études pendant leur formation initiale. Ils mettent en évidence également plusieurs avantages de l’apprentissage mobile : il augmente l’accès à des informations et ressources, facilite la réalisation de recherches, permet d’apprendre à tout moment et en tout endroit et dynamise la communication. Ils indiquent cependant que les appareils mobiles peuvent favoriser la distraction et ainsi nuire à leurs études. Quelques-uns suggèrent même des stratégies pour surmonter cet inconvénient. Les autres défis, comme les problèmes techniques, l’absence de contact humain et difficulté à faire une recherche fiable sont moins mentionnés par les étudiants. Nous constatons aussi que les futurs enseignants brésiliens et québécois ont des attitudes positives à l’égard de l’usage des technologies mobiles dans l’enseignement. La plupart a l’intention de les utiliser dans leur propre enseignement, puisqu’ils croient que ces appareils peuvent améliorer leur performance d’enseignants. Ils sont, toutefois, préoccupés par la distraction qu’elles peuvent occasionner à leurs élèves. Enfin, nous constatons qu’en dépit de quelques différences liées principalement aux divers contextes socioéconomiques des deux pays, les similarités sont évidentes. Les deux groupes d'étudiants sont déjà très mobiles et ouverts à apprendre et à enseigner en mobilité.Mobile learning is seen as type of learning that takes place in multiple contexts, whether formal or informal, through social interactions and content using electronic and personal devices (Crompton, 2013). For UNESCO (2012), it is one of the solutions to contribute to teacher training capable of meeting the educational needs of the 21st century. In addition, due to the lower cost of mobile devices and the enhancement of digital networks, mobile learning has become a tangible reality (Johnson et al., 2011). This is the case in Brazil and Canada, two countries with high statistics related to mobile broadband subscriptions and ownership of mobile technologies. In the educational context, the legislation of the government to the initial teacher training in these two places highlights the importance of the use of ICT in order to support the learning of the future teacher, as well as its use for future teaching. In addition, mobile learning projects are already a reality in schools in the province of Quebec, Canada, and in the state of Ceará, Brazil. In this context, based on the declared uses of mobile technologies for learning and taking as a reference the theory of social representations (Moscovici, 1961), this research aims to better understand the pedagogical uses of mobile technologies and the social representations of future Brazilian and Quebec teachers on mobile learning. To better understand how this type of learning can support future teachers, it is important to know what benefits and challenges are perceived by those who practice mobile learning. Their perceptions can generate positive attitudes about the pedagogical use of mobile devices or stimulate negative attitudes towards these same technologies. A mixed approach methodology was used with the administration of a questionnaire to 189 Brazilian and 149 Quebec students as well as a semi-directed interview with the total of 36 students, 18 students from Bachelor of Education courses of a Brazilian university and 18 students of bachelor's degree in teaching from a Quebec university. A descriptive statistical analysis was carried out using the quantitative data and a content analysis of the qualitative data collected. The results show that future Brazilian and Quebec teachers are very mobile, that is, they are very equipped with mobile devices and very connected to the Internet. We find that for both groups, mobile learning is already a reality in their student life, as they report using it in several activities for learning purposes. As for their social representations of mobile learning as students, both Brazilians and Quebecers perceive it as a type of learning that complements their studies during their initial training. They also highlight several advantages of mobile learning: increasing access to information and resources, facilitating research, learning at all times and enabling communication. However, they indicate that mobile devices can promote distraction and hinder their studies. A few even suggest strategies to overcome this disadvantage. Other challenges, such as technical problems, lack of human contact and reliable research are less mentioned by students. We also note that future teachers in Brazil and Quebec have positive attitudes towards the use of mobile technologies in education. Most intend to use them in their own teaching, since they believe that these devices can improve their teacher performance. However, at the same time that future teachers are open to the use of these technologies to teach, they are concerned about the distraction they can cause to their students. Finally, we find that, despite some differences related mainly to the various socioeconomic contexts of the two countries, similarities are evident. Both groups of students are already very mobile and open to learning and teaching in mobility