Dependable wireless real-time communications for open environments

Wireless communication technologies have become widely adopted, appearing in heterogeneous applications ranging from tracking victims, responders and equipments in disaster scenarios to machine health monitoring in networked manufacturing systems. Very often, applications demand a strictly bounded timing response, which, in distributed systems, is generally highly dependent on the performance of the underlying communication technology. These systems are said to have real-time timeliness requirements since data communication must be conducted within predefined temporal bounds, whose unfulfillment may compromise the correct behavior of the system and cause economic losses or endanger human lives. The potential adoption of wireless technologies for an increasingly broad range of application scenarios has made the operational requirements more complex and heterogeneous than before for wired technologies. On par with this trend, there is an increasing demand for the provision of cost-effective distributed systems with improved deployment, maintenance and adaptation features. These systems tend to require operational flexibility, which can only be ensured if the underlying communication technology provides both time and event triggered data transmission services while supporting on-line, on-the-fly parameter modification. Generally, wireless enabled applications have deployment requirements that can only be addressed through the use of batteries and/or energy harvesting mechanisms for power supply. These applications usually have stringent autonomy requirements and demand a small form factor, which hinders the use of large batteries. As the communication support may represent a significant part of the energy requirements of a station, the use of power-hungry technologies is not adequate. Hence, in such applications, low-range technologies have been widely adopted. In fact, although low range technologies provide smaller data rates, they spend just a fraction of the energy of their higher-power counterparts. The timeliness requirements of data communications, in general, can be met by ensuring the availability of the medium for any station initiating a transmission. In controlled (close) environments this can be guaranteed, as there is a strict regulation of which stations are installed in the area and for which purpose. Nevertheless, in open environments, this is hard to control because no a priori abstract knowledge is available of which stations and technologies may contend for the medium at any given instant. Hence, the support of wireless real-time communications in unmanaged scenarios is a highly challenging task. Wireless low-power technologies have been the focus of a large research effort, for example, in the Wireless Sensor Network domain. Although bringing extended autonomy to battery powered stations, such technologies are known to be negatively influenced by similar technologies contending for the medium and, especially, by technologies using higher power transmissions over the same frequency bands. A frequency band that is becoming increasingly crowded with competing technologies is the 2.4 GHz Industrial, Scientific and Medical band, encompassing, for example, Bluetooth and ZigBee, two lowpower communication standards which are the base of several real-time protocols. Although these technologies employ mechanisms to improve their coexistence, they are still vulnerable to transmissions from uncoordinated stations with similar technologies or to higher power technologies such as Wi- Fi, which hinders the support of wireless dependable real-time communications in open environments. The Wireless Flexible Time-Triggered Protocol (WFTT) is a master/multi-slave protocol that builds on the flexibility and timeliness provided by the FTT paradigm and on the deterministic medium capture and maintenance provided by the bandjacking technique. This dissertation presents the WFTT protocol and argues that it allows supporting wireless real-time communication services with high dependability requirements in open environments where multiple contention-based technologies may dispute the medium access. Besides, it claims that it is feasible to provide flexible and timely wireless communications at the same time in open environments. The WFTT protocol was inspired on the FTT paradigm, from which higher layer services such as, for example, admission control has been ported. After realizing that bandjacking was an effective technique to ensure the medium access and maintenance in open environments crowded with contention-based communication technologies, it was recognized that the mechanism could be used to devise a wireless medium access protocol that could bring the features offered by the FTT paradigm to the wireless domain. The performance of the WFTT protocol is reported in this dissertation with a description of the implemented devices, the test-bed and a discussion of the obtained results.

Ferroelectric : CNTs structures fabrication for advanced functional nano devices

This work is about the combination of functional ferroelectric oxides with Multiwall Carbon Nanotubes for microelectronic applications, as for example potential 3 Dimensional (3D) Non Volatile Ferroelectric Random Access Memories (NVFeRAM). Miniaturized electronics are ubiquitous now. The drive to downsize electronics has been spurred by needs of more performance into smaller packages at lower costs. But the trend of electronics miniaturization challenges board assembly materials, processes, and reliability. Semiconductor device and integrated circuit technology, coupled with its associated electronic packaging, forms the backbone of high-performance miniaturized electronic systems. However, as size decreases and functionalization increases in the modern electronics further size reduction is getting difficult; below a size limit the signal reliability and device performance deteriorate. Hence miniaturization of siliconbased electronics has limitations. On this background the Road Map for Semiconductor Industry (ITRS) suggests since 2011 alternative technologies, designated as More than Moore; being one of them based on carbon (carbon nanotubes (CNTs) and graphene) [1]. CNTs with their unique performance and three dimensionality at the nano-scale have been regarded as promising elements for miniaturized electronics [2]. CNTs are tubular in geometry and possess a unique set of properties, including ballistic electron transportation and a huge current caring capacity, which make them of great interest for future microelectronics [2]. Indeed CNTs might have a key role in the miniaturization of Non Volatile Ferroelectric Random Access Memories (NVFeRAM). Moving from a traditional two dimensional (2D) design (as is the case of thin films) to a 3D structure (based on a tridimensional arrangement of unidimensional structures) will result in the high reliability and sensing of the signals due to the large contribution from the bottom electrode. One way to achieve this 3D design is by using CNTs. Ferroelectrics (FE) are spontaneously polarized and can have high dielectric constants and interesting pyroelectric, piezoelectric, and electrooptic properties, being a key application of FE electronic memories. However, combining CNTs with FE functional oxides is challenging. It starts with materials compatibility, since crystallization temperature of FE and oxidation temperature of CNTs may overlap. In this case low temperature processing of FE is fundamental. Within this context in this work a systematic study on the fabrication of CNTs - FE structures using low cost low temperature methods was carried out. The FE under study are comprised of lead zirconate titanate (Pb1-xZrxTiO3, PZT), barium titanate (BaTiO3, BT) and bismuth ferrite (BiFeO3, BFO). The various aspects related to the fabrication, such as effect on thermal stability of MWCNTs, FE phase formation in presence of MWCNTs and interfaces between the CNTs/FE are addressed in this work. The ferroelectric response locally measured by Piezoresponse Force Microscopy (PFM) clearly evidenced that even at low processing temperatures FE on CNTs retain its ferroelectric nature. The work started by verifying the thermal decomposition behavior under different conditions of the multiwall CNTs (MWCNTs) used in this work. It was verified that purified MWCNTs are stable up to 420 ºC in air, as no weight loss occurs under non isothermal conditions, but morphology changes were observed for isothermal conditions at 400 ºC by Raman spectroscopy and Transmission Electron Microscopy (TEM). In oxygen-rich atmosphere MWCNTs started to oxidized at 200 ºC. However in argon-rich one and under a high heating rate MWCNTs remain stable up to 1300 ºC with a minimum sublimation. The activation energy for the decomposition of MWCNTs in air was calculated to lie between 80 and 108 kJ/mol. These results are relevant for the fabrication of MWCNTs – FE structures. Indeed we demonstrate that PZT can be deposited by sol gel at low temperatures on MWCNTs. And particularly interesting we prove that MWCNTs decrease the temperature and time for formation of PZT by ~100 ºC commensurate with a decrease in activation energy from 68±15 kJ/mol to 27±2 kJ/mol. As a consequence, monophasic PZT was obtained at 575 ºC for MWCNTs - PZT whereas for pure PZT traces of pyrochlore were still present at 650 ºC, where PZT phase formed due to homogeneous nucleation. The piezoelectric nature of MWCNTs - PZT synthesised at 500 ºC for 1 h was proved by PFM. In the continuation of this work we developed a low cost methodology of coating MWCNTs using a hybrid sol-gel / hydrothermal method. In this case the FE used as a proof of concept was BT. BT is a well-known lead free perovskite used in many microelectronic applications. However, synthesis by solid state reaction is typically performed around 1100 to 1300 ºC what jeopardizes the combination with MWCNTs. We also illustrate the ineffectiveness of conventional hydrothermal synthesis in this process due the formation of carbonates, namely BaCO3. The grown MWCNTs - BT structures are ferroelectric and exhibit an electromechanical response (15 pm/V). These results have broad implications since this strategy can also be extended to other compounds of materials with high crystallization temperatures. In addition the coverage of MWCNTs with FE can be optimized, in this case with non covalent functionalization of the tubes, namely with sodium dodecyl sulfate (SDS). MWCNTs were used as templates to grow, in this case single phase multiferroic BFO nanorods. This work shows that the use of nitric solvent results in severe damages of the MWCNTs layers that results in the early oxidation of the tubes during the annealing treatment. It was also observed that the use of nitric solvent results in the partial filling of MWCNTs with BFO due to the low surface tension (<119 mN/m) of the nitric solution. The opening of the caps and filling of the tubes occurs simultaneously during the refluxing step. Furthermore we verified that MWCNTs have a critical role in the fabrication of monophasic BFO; i.e. the oxidation of CNTs during the annealing process causes an oxygen deficient atmosphere that restrains the formation of Bi2O3 and monophasic BFO can be obtained. The morphology of the obtained BFO nano structures indicates that MWCNTs act as template to grow 1D structure of BFO. Magnetic measurements on these BFO nanostructures revealed a week ferromagnetic hysteresis loop with a coercive field of 956 Oe at 5 K. We also exploited the possible use of vertically-aligned multiwall carbon nanotubes (VA-MWCNTs) as bottom electrodes for microelectronics, for example for memory applications. As a proof of concept BiFeO3 (BFO) films were in-situ deposited on the surface of VA-MWCNTs by RF (Radio Frequency) magnetron sputtering. For in situ deposition temperature of 400 ºC and deposition time up to 2 h, BFO films cover the VA-MWCNTs and no damage occurs either in the film or MWCNTs. In spite of the macroscopic lossy polarization behaviour, the ferroelectric nature, domain structure and switching of these conformal BFO films was verified by PFM. A week ferromagnetic ordering loop was proved for BFO films on VA-MWCNTs having a coercive field of 700 Oe. Our systematic work is a significant step forward in the development of 3D memory cells; it clearly demonstrates that CNTs can be combined with FE oxides and can be used, for example, as the next 3D generation of FERAMs, not excluding however other different applications in microelectronics.

Describing vocal performance of Portuguese cantadeiras of Alto Minho

Portugal has strong musical traditions, which have been perpetrated by decades through folkloristic activities. In folk groups from Alto Minho (north of Portugal), folk singing is mostly performed by cantadeiras, amateur female solo singers who learn this style orally. Their vocal characteristics are distinctive when compared with other regions of the country; however, deep understanding of these vocal practices is still missing. The present work aims at studying Alto Minho cantadeira’s vocal performance in a multidimensional perspective, envisioning social, cultural and physiological understanding of this musical style. Thus, qualitative and quantitative data analyses were carried out, to: (i) describe current performance practices, (ii) explore existent perceptions about most relevant voice features in this region, (iii) investigate physiological and acoustic properties of this style, and (iv) compare this style of singing with other non-classical singing styles of other countries. Dataset gathered involved: 78 groups whose members were telephone interviewed, 13 directors who were asked to fill in a questionnaire on performance practices, 1 cantadeira in a pilot study, 16 cantadeiras in preliminary voice recordings, 77 folk group members in listening tests, and 10 cantadeiras in multichannel recordings, including audio, ELG, air flow and intra-oral pressure signals. Data were analysed through thematic content analysis, descriptive and inferential statistics, hierarchical principal components, and multivariate linear regression models. Most representative voices have a high pitched and loud voice, with a bright timbre, predominance of chest register without excessive effort, and good text intelligibility with regional accent. High representativeness levels were obtained by few cantadeiras; these sing with high levels of subglottal pressure and vocal fold contact quotient, predominance of high spectrum energy and vocal loudness, corroborating indications of prevalence of pressed phonation. These vocal characteristics resemble belting in musical theatre and share similarities with country (USA) and ojikanje (Croatia) singing. Strategies that may contribute to the preservation of this type of singing and the vocal health of current cantadeiras are discussed, pointing at the direction of continuous education among folk groups, following practices that are already adopted elsewhere in Europe.

Análise do risco associado à rotura da barragem de Fernandilho. Modelação hidrodinâmica da onda de cheia

As cheias provocadas por roturas de barragens constituem eventos catastróficos que podem conduzir a perdas consideráveis de vidas humanas e de bens materiais. Para melhorar a segurança, em relação a este risco potencial, torna-se necessário avaliar a segurança da população e das estruturas, existentes ou a construir, e estimar a extensão dos danos em caso de acidente. Neste estudo, após a indicação da legislação em vigor, apresenta-se uma descrição sumária do modelo DamBreak. Descrevem-se as equações básicas que definem o modelo de formação da brecha e que caracterizam o processo de formação da cheia. Também se referem as equações de Saint-Venant, as quais caracterizam o processo de propagação da cheia. De seguida é feita uma descrição da barragem de Fernandilho, do leito do Barranco d

Contribuição para a avaliação do risco sísmico: aplicação à cidade de Faro

O programa SRAPOR permite a realização de rápidas avaliações de risco sísmico de aglomerados habitacionais. A presente versão é constituída por uma base de dados de sismos, por um sistema simplificado de informação geográfica e por um módulo de avaliação da casualidade sísmica. A aplicação do programa é ilustrada com a análise da casualidade sísmica da cidade de Faro.

Família, psicopatologia e resiliência na adolescência: do risco psicossocial ao percurso delinquente

Tese de dout., Psicologia, Faculdade de Ciências Humanas e Sociais, Univ. do Algarve, 2007

A influência da representação social do sexo nos comportamentos sexuais de risco dos jovens adultos portugueses

Tese de dout., Psicologia, Univ. do Algarve, 2010

A avaliação do risco de crédito bancário nas empresas do sector da construção

Dissertação de mest., Finanças Empresariais, Faculdade de Economia, Universidade do Algarve, 2005

Jovens em risco: projectos de vida e motivação para a frequência do ensino profissional

Dissertação de mest., Psicologia da Educação (Necessidades Educativas Especiais), Faculdade de Ciências Humanas e Sociais, Univ. do Algarve, 2011

Coesão familiar, competências parentais e factores de risco em mães imigrantes e portuguesas

Dissertação de mest., Psicologia Clínica e da Saúde, Faculdade de Ciências Humanas e Sociais, Univ. do Algarve, 2011

Cuidados dermocosméticos para uma pele saudável: aconselhamento farmacêutico nos casos mais comuns

Dissertação de mest., Ciências Farmacêuticas, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2012

As obrigações do tesouro e os Swaps de risco de incumprimento: análise da sua inter-relação aplicada ao caso português

Dissertação de mest., Finanças Empresariais, Faculdade de Economia, Univ. do Algarve, 2012

A bioenergia e o risco de incêndios florestais em paisagens rurais contemporâneas: o caso da zif Arade-Alte/ São Bartolomeu de Messines

Dissertação de mest., Arquitectura Paisagista, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011

Apoio social, factores de risco e competências parentais percebidas em famílias multiproblemáticas no concelho de Silves

A família é caracterizada como o espaço de vivência de relações afetivas profundas: a filiação, a fraternidade, o amor, a sexualidade, numa trama de emoções e afetos positivos e negativos que, na sua elaboração, vão dando corpo ao sentimento de sermos quem somos e de pertencermos àquela e não a outra qualquer família. No contexto das Famílias “Multiproblemáticas” o principal desafio com que os técnicos se deparam é a relação que se estabelece entre profissionais e estas famílias, que enquadrados no modelo Ecossistémico, conceptualizou-se o desenvolvimento dos guiões de avaliação do profissional que implicam uma interrelação recursiva dos contextos dos quais faz parte. O presente trabalho pretende compreender as implicações de variáveis pessoais (experiência parental, bem-estar psicológico, satisfação com a vida familiar, satisfação com o apoio institucional entre outras). Concluiu-se que a família, desempenha um papel preponderante na eficácia das competências parentais. Assim, sugere-se o desenvolvimento de programas de intervenção junto destes familiares de forma a prevenir e minimizar os fatores de risco.

Apoio social, acontecimentos de vida negativos e adaptação em famílias com menores em risco psicossocial

No contexto atual de proteção à infância, as famílias em situação de risco psicossocial constituem uma realidade, com a qual as instituições e os profissionais se deparam e ainda pouco estudada em Portugal. As famílias têm de lidar com inúmeros acontecimentos de vida negativos que comprometem o adequado exercício das suas funções parentais. Neste trabalho analisámos o perfil psicossocial, a coesão e adaptação familiar, os acontecimentos de vida stressantes e de risco das suas trajetórias de vida e circunstâncias atuais, o seu impacto emocional, o apoio social percebido das famílias com menores em risco, a forma como se associam entre si e com as diversas características sociodemográficas. Foram entrevistados 51 participantes, 33 do sexo feminino e 18 do sexo masculino, com idades compreendidas entre os 16 e os 57 anos de idade, resultando uma média de idade de 36,33 anos (DP = 7,98), acompanhados pela Comissão de Proteção de Crianças e Jovens de Faro. Foram avaliadas as seguintes dimensões: adaptação e coesão familiar, acontecimentos de vida stressantes ou negativos, apoio social percebido em situações normativas e de risco e o perfil psicossocial dos participantes. Os resultados mostraram que as famílias com menores em risco psicossocial apresentam elevada taxa de desemprego, precaridade educativa, económica e profissional, elevado número de acontecimentos de vida negativos atuais e passados relacionados sobretudo com problemas psicológicos, económicos, profissionais e conjugais que são vivenciados com elevado impacto emocional. Ao nível do funcionamento familiar, os níveis de coesão foram superiores aos de adaptação familiar. Os participantes reportaram uma necessidade mais elevada de apoio emocional do que informativo ou material. A fonte de apoio social das famílias é constituída principalmente por familiares e amigos, que experienciaram um reduzido apoio de profissionais. As famílias evidenciaram importantes necessidades, entre as quais o apoio social e as intervenções psicossociais assumem um papel essencial nos contextos familiares de risco.