SETAR nonlinearity, nonstationarity and forecasting

Tese de dout., Métodos Quantitativos Aplicados à Economia e à Gestão, Faculdade de Economia, Universidade do Algarve, 200

Spanning trees with generalized degree constraints arising in the design of wireless networks

In this paper we describe a minimum spanning tree problem with generalized degree constraints which arises in the design of wireless networks. The signal strength on the receiver side of a wireless link decreases with the distance between transmitter and receiver. In order to work properly, the interference on the receiving part of the link must be under a given threshold. In order to guarantee this constraint, for each node we impose a degree constraint that depends on the ”length” of the links adjacent to the corresponding node, more precisely, nodes adjacent to long links must have a smaller degree and vice-versa. The problem is complicated by considering different signal strengths for each link. Increasing the strength in a link increases the cost of the link. However, it also reduces the maximum allowed degree on its end nodes. We create two models using adequate sets of variables, one may be considered an extended version of the other, and relate, from a theoretical perspective, the corresponding linear programming relaxations.FCT - POCTI-ISFL-1-152FCT - PTDC/EIA/64772/200

Harvesting big data from residential building energy performance certificates: retrofitting and climate change mitigation insights at a regional scale

UID/AMB/04085/2019The reduction of energy consumption and the increase in energy efficiency is currently an important cornerstone of EU policy. Energy performance certificates (EPCs) were implemented as one of the tools to promote this agenda, and are used for the energy performance assessment of buildings. In this study, the characteristics of the Portuguese dwelling stock are regionally analysed using data from approximately 523,000 Portuguese residential EPCs. Furthermore, a bottom-up building typology approach is used to assess the regional energy needs impact of retrofitting actions and to estimate the heating and cooling energy performance gaps of the whole dwelling stock, as well as the potential CO2 emissions resulting from the gaps' potential offset due to increase thermal comfort. The results show that Portuguese residential buildings have very low energy performance, with windows and roofs being identified as the most energy inefficient elements. Roof retrofitting has the highest potential for the reduction of energy needs. The estimated heating and cooling energy performance gap amount to very significant percentages, due to the poor performing building stock but also very low energy consumption levels, with probable consequences for the thermal comfort of occupants. Assuming the current energy mix, carbon emissions would be 9.8 and 20.2 times higher associated with heating and cooling, respectively, if the actual final energy consumption were to match the estimated theoretical values derived from building regulation. This study demonstrates several application cases and leverages the potential of the individual EPC, increasing the detail in the dwelling stock characterization and energy performance estimation, revealing its value for energy retrofit and climate change mitigation assessments, as well as establishing the ground for future work related to building retrofits, energy efficiency measure implementation, climate change mitigation, thermal comfort, and energy poverty studies.publishersversionpublishe

Entrenamiento de imaginería con motociclistas

Los procesos que nos permiten imaginar, son los que más despiertan nuestra curiosidad científica, más específicamente, con relación a los procesos funcionales de las cargas de imaginería. Nuestra duda primordial, se coloca al nivel de la caracterización de las componentes de esas cargas. ¿Qué es el volumen? ¿Qué es la intensidad de una carga de imaginería? Estas son las cuestiones que nos aproximan del terreno, de la aplicación práctica, buscando cada vez más una prescripción de carga de entrenamiento mental a semejanza de la metodología del entrenamiento físico. Pretendemos saber si el entrenamiento mental mejora el resultado de la actuación y si diferentes prescripciones de entrenamiento mental, conducen a diferentes resultados de actuación. Para nuestra investigación, utilizamos una muestra de 34 sujetos, del género masculino, 21 motociclistas, y 13 no motociclistas. El grupo de motociclistas se encuentra distribuido por un grupo de control y dos grupos experimentales. La tarea consiste en un juego de ordenador que simula la conducción de una motocicleta en pista, sin cualquier adversario. Cada sujeto se encuentra sometido a un programa de seis sesiones de realización de la tarea. Los dos grupos experimentales en cada sesión, obedecen a un programa de entrenamiento de imaginería, con diferentes prescripciones en lo que se refiere al número de vueltas a imaginar. Para el tratamiento estadístico, recorrimos a la utilización de un modelo matemático, a partir del cual, nos es posible el cálculo de un parámetro de evolución, así como el diseño de la curva de aprendizaje de cada sujeto. No podemos concluir sobre el efecto que las metodologías del entrenamiento mental utilizadas hayan producido sobre el mejoramiento del desempeño. Los resultados nos llevaron a admitir que la introducción del significado de la imagen en los ejercicios de entrenamiento mental y un mayor tiempo de exposición a través de la imagética, podrán tener un efecto positivo en el rendimiento de los sujetos.The purpose of this research was to study the imagery processes. Our main question concerned the characteristics of its loading components such as the volume and the intensity. Our final goal was to give some contribution to those who work in the practical field of sports, looking for theoretical support in order to prescribe the mental training in a similar way as it is done in the physical training methodology. We wanted to investigate (1) if mental training improves the performance results and (2) if different prescriptions of mental training lead to different results of performance. Thirty-four mail subjects participated in our research. Thirteen subjects had no experience in motorcycling and 21 were motorcyclists divided into three groups (one control group and two experimental groups). The experimental task was composed by a computer game simulating a motorcycling race without opponents. Each subject should follow a six-sessions program in which the race task should be completed. Both of the experimental groups also followed an imagery training program in each session where they should mentally perform in the computer game. However, the imagery task was different four each group regarding the times they should imagine to go around the race track. The evolution parameters were studied as well as the learning curb of the subjects. It was not possible to conclude about the effect of the different methodologies upon the performance improvement, but results lead us to admit that the use of the meaning of mental images and a larger period of exposition through imagery could have a positive effect in the subjects' performance

Low-cost internet of things and snapshot geolocation pipeline in marine sensing

Biologging and biotelemetry are commonly used as methods to assess marine biodiversity pop ulation. However, current state-of-the-art devices (commonly referred to as tags) remain at the greater cost of production while geolocation and georeferencing methods use proprietary satellite constellations, remain expensive and are prone to greater battery usage. This dissertation enhances such state-of-the-art devices, providing affordable tags for multipurpose usage. Dissertation contri bution is two-fold. In first, it describes the design of low-cost telecommunication system comprised from tag emitters and land receivers, evaluated during the sea-vessel field trips in pelagic area of Madeira island. In second, it also describes the software pipeline for deducing the position of tags, leveraging the raw signal from obtained GPS receivers.Bio-logging e biotelemetria são métodos de grande importância como métodos de avaliação da biodiversidade marítima. No entanto, os dispositivos atuais normalmente referidos por tags per manecem com um elevado custo de produção e, são suscetiveis a elevado consumo de energia. Esta dissertação procura melhorar o bio-logging e a biotelemetria para a estimativa da biodiversidade marítima, com três contribuições distintas: (i) realizar análise em detalhe de sistemas de última geração de bio-logging e de biotelemetria, (ii) desenvolver um sistema inovador usando Internet of things (IoT) e Long Range (LoRa), e (iii) melhorar o sistema fastloc com computação no CPU da tag, para estimar a posição de mamíferos marítimos na superfície do mar. O príncipal objetivo é reduzir o custo de tais sistemas de detecção, explorando o IoT, LoRa e fastloc na cricação de bio-loggers e sistemas de biotelemetria

Design of Inverter Based CMOS Amplifiers in Deep Nanoscale Technologies

In this work, it is proposed a fully differential ring amplifier topology with a deadzone voltage created by a CMOS resistor with a biasing circuit to increase the robustness over PVT variations. The study focuses on analyzing the performance of the ring amplifier over process, temperature, and supply voltage variations, in order to guarantee a viable industrial employment in a 7 nm FinFET CMOS technology node for being used as residue amplifier in ADCs. A ring amplifier is a small modular amplifier, derived from a ring oscillator. It is simple enough that it can quickly be designed using only a few inverters, capacitors, and switches. It can amplify with rail-to-rail output swing, competently charge large capacitive loads using slew-based charging, and scale well in performance according to process trends. In typical process corner, a gain of 72 dB is achieved with a settling time of 150 ps. Throughout the study, the proposed topology is compared with others presented in literature showing better results over corners and presenting a faster response. The proposed topology isn’t yet suitable for industry use, because it presents one corner significantly slower than the rest, namely process corner FF 125 °C, and process corner FS -40 °C with a small oscillation throughout the entire amplification period. Nevertheless, it proved itself to be a promising technique, showing a high gain and a fast settling without oscillation phase, with room for improvement.Neste trabalho, é proposta uma topologia de ring amplifier com a deadzone a ser criada através de uma resistência CMOS com um circuito de polarização para aumentar a robustez para as variações PVT. O estudo foca-se em analisar a performance do ring amplifier nas variações de processo, temperatura e tensão de alimentação, de forma a garantir um uso viável em indústria na tecnologia de 7 nm FinFET CMOS, para ser usado como amplificador de resíduo em ADCs. Um ring amplifier é um pequeno amplificador modular, derivado do ring oscillator. É simples o suficiente para ser facilmente projetado usando apenas poucos inversores, condensadores e interruptores. Consegue amplificar com rail-to-rail output swing, carregar grandes cargas capacitivas com carregamento slew-based e escalar bem em termos de performance de acordo com o processo. No typical process corner, foi obtido um ganho de 72 dB com um tempo de estabilização de 150 ps. Durante o estudo, a topologia proposta é comparada com outras presentes na literatura mostrando melhores resultados over corners e apresentando uma resposta mais rápida. A topologia proposta ainda não está preparada para uso industrial uma vez que apresenta um corner significativamente mais lento que os restantes, nomeadamente, process corner FF 125 °C, e outro process corner, FS -40 °C, com uma pequena oscilação durante todo o período de amplificação. Todavia, provou ser uma técnica promissora, apresentando um ganho elevado e uma rápida estabilização sem fase de oscilação, com espaço para melhoria

Youth’s physical activity and fitness from a rural environment of an Azores Island

This study aimed to characterize and compare physical activity (PA) and fitness levels by sex in 109 students of a rural environment. The participants were between 15 and 20 years old, from the Santa Maria High School in the Azores’ Santa Maria island. PA levels were assessed by International Physical Activity Questionnaire (IPAQ)-short form. The physical fitness was evaluated by the Fitnessgram battery tests. The sample of this study were physically active, 67.9% were classified with high and moderate PA levels. Regarding the sex comparisons, no significant differences between PA levels were founded. However, males presented higher values of vigorous physical activity, whereas females spent more time in moderate activity, such as walking. Moreover, females had more time in sitting positions during the week and weekend. Regarding the physical fitness levels, males presented significantly higher performances in the upper strength (p < 0.001) and aerobic capacity tests (p < 0.001), whereas females showed higher values in the sit and reach test (p < 0.001), in the trunk lift test (p < 0.005), and in the fat mass values (p < 0.001). It seems reasonable to assume that there is a sociodemographic influence on the PA and physical fitness levels in our sample. We may speculate that rural life provides more opportunities for youth for being physically active than urban life. No differences were founded between sexes for physical activity. However, differences were found between sex for strength, flexibility, cardiorespiratory fitness, and body composition. That might be explained by the biological differences and the type of physical activity habits that each sex use to have in rural environmental.This work is supported by National Funds through FCT—Foundation for Science and Technology under the project UID04045/2020 and was approved by the Education Regional Direction with process number DSP/15-29.info:eu-repo/semantics/publishedVersio

Study of postural misalignments between sex, school cycle and physical activity

This study aimed to characterize and compare postural behaviour between gender, school cycles and PA levels in 213 students, aged between 10 and 20 years, from Escola Básica e Secundária de Santa Maria. Postural assessment was made through visual scan analysis in a symmetrograph and the Adams test. PA level assessment was made using the IPAQ. Postural behaviour presented high percentages of imbalances in both sexes, with the highest prevalence in the head lateral flexion, shoulders level asymmetry, scoliosis, gibbosity, forward head and protracted shoulders. Lumbar scoliosis was significantly related to pelvic asymmetry (p < .001), protracted shoulders were related to forward head (p = .010) and dorsal hyperkyphosis (p = .048) and lumbar hyperlordosis was more prevalent in subjects with pelvic anteversion (p < .001). Dorsal hyperkyphosis manifested in males with a markedly higher prevalence than females (p = .006). Postural imbalances were present at all ages, with pelvic anteversion decrease (p = .028) with school cycles progression. Our sample proved to be physically active with 73.9% categorized with high and moderate levels of PA. Higher PA levels where related to forward head lower percentages (p = .006). It should be highlighted the importance of postural assessment school students.This work is supported by National Funds through FCT - Foundation for Science and Technology under the project UID04045/2020 and was approved by the Education Regional Direction with process number DSP/15-29

Model Revision of Logical Regulatory Networks Using Logic-Based Tools

Recently, biological data has been increasingly produced calling for the existence of computational models able to organize and computationally reproduce existing observations. In particular, biological regulatory networks have been modeled relying on the Sign Consistency Model or the logical formalism. However, their construction still completely relies on a domain expert to choose the best functions for every network component. Due to the number of possible functions for k arguments, this is typically a process prone to error. Here, we propose to assist the modeler using logic-based tools to verify the model, identifying crucial network components responsible for model inconsistency. We intend to obtain a model building procedure capable of providing the modeler with repaired models satisfying a set of pre-defined criteria, therefore minimizing possible modeling errors

The impact of digital in learning spaces: an analysis on the perspective of teachers in higher education

Proceedings of Informing Science & IT Education Conference (InSITE) 2013The generalized use of Communication Networks and Information Technologies is nowadays a global phenomenon. It has multiple impacts on how to teach/learn and on the contexts in which this process takes place (the Learning Environments). These areas include Physical Learning places, Virtual Learning sites, Collaborative Learning Spaces, among others. These proposals provide new scenarios for the teaching/learning process, but their outlines are not well defined yet. A Learning Space requires a complex set of materials and human resources. Further and continued research is significant and justified by the relevance of Higher Education Institutions.The overall objective of the present research is to understand the perceptions of the Professors in their Learning Environments. In this context it has been considered relevant to gather opinions on the needs/priorities, utility, quality and sustainability, as a result of the use of Information and Communication Technologies (ICT) in the teaching/learning spaces