Bringing Order into Things Decentralized and Scalable Ledgering for the Internet-of-Things

The Internet-of-Things (IoT) is simultaneously the largest and the fastest growing distributed system known to date. With the expectation of 50 billion of devices coming online by 2020, far surpassing the size of the human population, problems related to scale, trustability and security are anticipated. Current IoT architectures are inherently flawed as they are centralized on the cloud and explore fragile trust-based relationships over a plethora of loosely integrated devices, leading to IoT platforms being non-robust for every party involved and unable to scale properly in the near future. The need for a new architecture that addresses these concerns is urgent as the IoT is progressively more ubiquitous, pervasive and demanding regarding the integration of devices and processing of data increasingly susceptible to reliability and security issues. In this thesis, we propose a decentralized ledgering solution for the IoT, leveraging a recent concept: blockchains. Rather than replacing the cloud, our solution presents a scalable and fault-tolerant middleware for recording transactions between peers, under verifiable and decentralized trustability assumptions and authentication guarantees for IoT devices, cloud services and users. Following on the emergent trend in modern IoT architectures, we leverage smart hubs as blockchain gateways, aggregating, pre-processing and forwarding small amounts of data and transactions in proximity conditions, that will be verified and processed as transactions in the blockchain. The proposed middleware acts as a secure ledger and establishes private channels between peers, requiring transactions in the blockchain to be signed using threshold signature schemes and grouporiented verification properties. The approach improves the decentralization and robustness characteristics under Byzantine fault-tolerance settings, while preserving the blockchain distributed nature

‘Suburbanism as a Way of Staying Alive’: Reinventing the Rural

This paper will focus on the social transformations that took place in the Portuguese rural space. In particular, we will study the village of Albernoa in the region of Alentejo in Southern Portugal in order to characterize the deep structural social change this place has gone through. In fact, similarly to what has happened to the major rural areas in the region, this village has suffered progressive ageing and continuous depopulation. These tendencies occurred simultaneously with the reduction of several agricultural enterprises and activities. We will also identify some dynamic indicators connected with the increasing spatial mobility (sprawl) and the gradual integration of urban habits. Albernoa is now at the crossroads between urbanization and marginalization. To analyze these changes we will use a multidimensional perspective of the concept of social space, based on the theoretical approach presented by Lefebvre. This author states that space should not be interpreted as a mere receptacle of social relationships. On the contrary, social space is produced daily in concrete places and is grounded in different kinds of practices and social representations. The distinction and consequently the inter-relation between the notions of space and place helps us to dismantle the various mechanisms that make up these complex social exchanges in which the concepts of rural and urban are constantly re-inventing themselves

Circular economy through innovation within business networks : a case study on returnable bottles

Mestrado Bolonha em Gestão e Estratégia IndustrialInnovating is extremely important to companies, even more so when innovation aligns with sustainability. The circular economy is substituting the classic linear model to increase the product life cycle. A productive circular economy is necessarily a well-coordinated business network. The difficulty in implementing a business model that benefits from these relationships between innovation, sustainability, circular economy, and business networks is a key factor for companies. This study aims to explore the relationship between innovation and circular economy from a business network perspective. A case study of a refreshing drinks company that follows a returnable bottle strategy was developed and supported by a semi-structured interview. In this company, all the innovation projects go through a filter that gives a sustainability score (A, B, C, and D), considering several environmental factors such as sustainable packaging, water, energy, resources consumed, and consumer perception. Returnable packaging currently constitutes, for the company, more than 85% of what is sold in bars, cafes, and restaurants. Additionally, ecological concern has contributed to changing consumer behavior, as they are much more attentive to today's products. Consumers increasingly demand sustainable packaging, which puts pressure on the company, as it will impact its sales and reputation. Finally, the company maintains relationships with several companies and favors nearby suppliers to mitigate the C02 footprint. These relationships have mutual benefits because they often challenge suppliers or vice versa, which always results in process optimization and continuous improvement.Inovar é extremamente importante para as empresas, ainda mais quando a inovação está alinhada com a sustentabilidade. A economia circular está a substituir o clássico modelo linear para aumentar o ciclo de vida dos produtos. Uma economia circular produtiva é necessariamente uma rede de negócios bem coordenada. A dificuldade em implementar um modelo de negócio que beneficie destas relações entre inovação, sustentabilidade, economia circular e redes de negócios é um fator chave para as empresas. Este estudo tem como objetivo explorar a relação entre inovação e economia circular a partir de uma perspetiva da rede de negócios. Um estudo de caso de uma empresa de bebidas refrescantes que segue uma estratégia de garrafas retornáveis foi desenvolvido e apoiado por uma entrevista semiestruturada. Nesta empresa, todos os projetos de inovação passam por um filtro que dá uma nota de sustentabilidade (A, B, C e D), considerando diversos fatores ambientais como embalagens sustentáveis, água, energia, recursos consumidos e a perceção do consumidor. As embalagens retornáveis representam hoje, para a empresa, mais de 85% do que é vendido em bares, cafés e restaurantes. Além disso, a preocupação ecológica tem contribuído para a mudança de comportamento dos consumidores, que estão muito mais atentos aos produtos atuais. Os consumidores exigem cada vez mais embalagens sustentáveis, o que pressiona a empresa, pois impactará as suas vendas e reputação. Por fim, a empresa mantém relações com diversas empresas e privilegia fornecedores próximos para mitigar a pegada de C02. Estas relações têm benefícios mútuos porque muitas vezes a empresa desafia os fornecedores ou vice-versa, o que resulta sempre na otimização dos processos e na melhoria contínua.info:eu-repo/semantics/publishedVersio

From History to Soil and Back Again

UIDB/04209/2020 UIDP/04209/2020This research explains what happened to agricultural soil fertility during the "Campanha do Trigo" (Wheat Campaign) in Portugal, which began in 1929. It is commonly understood that the excessive expansion of wheat crops during the fascist "Estado Novo" (New State) regime led to the degradation of soils in the southern half of Portugal. This relationship, however, has never been questioned before. This article extends the narrative back into the last half of the nineteenth century in search of the origin of processes that gradually intensified throughout the country. In short, expansion of the cultivated area in association with the inadequate intensification of crop rotations over about 80 years, from the 1870s onward, including in non-wheat areas, strongly accentuated soil erosion and made organic fertilization progressively less effective. These transformations were only partially offset by chemical fertilization. Nitrogen and phosphorus were the key factors in this historical process. Focusing on the cultivation system and soil dynamics allows the successive integration of various kinds of historical evidence and sources. From an environmental question-why did agricultural soil degrade?-this article explores soil degradation over time and space, and assesses its social and biophysical impacts. At the same time, it addresses the history of agriculture in Portugal and its disciplinary foundations.authorsversionpublishe

Dissertação apresentada com vista à obtenção do grau de Mestre em Desporto com especialização em Treino Desportivo

Orientador: Professor Doutor António Manuel da Silva Moreira Co-orientador: Professor Doutor João Paulo Moreira de BritoResumo: A aclimatização à altitude é entendida como o processo que toma lugar quando o organismo humano é exposto a condições de hipoxia, e compreende um sem número de processos fisiológicos, que servem para mitigar, até certo ponto, os efeitos da descida da pressão parcial de oxigénio. Um desses processos consiste na estimulação da eritropoiese. O objetivo deste estudo foi avaliar o impacto de um estágio de 23 dias a 2240m de altitude, nos parâmetros do eritrograma e na concentração de eritropoietina ([EPO]), em 7 triatletas de elite. A amostra, constituída por 5 atletas masculinos e 2 atletas femininos, foi submetida a dois momentos de avaliação – no dia anterior ao início do estágio e no dia seguinte ao retorno ao nível do mar – para determinar o número de glóbulos vermelhos (RBC), a concentração de hemoglobina ([Hb]), o hematócrito (Htc), o volume globular médio (VGM), a hemoglobina globular média (HGM), a concentração de hemoglobina globular média (CHGM), o índice de anisocitose (RDW) e a [EPO]. A [EPO] (9,8±3,5 para 7,4±2,8mUI/ml, p=0,178) e a CHGM (33,2±0,5 para 32,4±0,6g/dl, p=0,005) diminuíram após o estágio, sendo que esta diferença apenas foi significativa para a CHGM. Os aumentos significativos ocorreram para o RBC (4,7±0,3 para 4,9±0,2x106/mm3, p=0,019); a [Hb] (14,5±0,8 para 15,2±0,3g/dl, p=0,022); o Htc (43,6±2,0 para 46,9±1,2%, p=0,003); o VGM (93,0±3,8 para 95,8±3,8fl, p=0,000) e o RDW (13,1±0,3 para 13,4±0,2%, p=0,034). Conclui-se que um estágio de 3 semanas a uma altitude de 2240m provoca alterações no eritrograma em 7 triatletas de elite, embora não seja possível estabelecer com certeza se essas alterações resultaram do estímulo hipóxico por si só ou de um incremento na condição física.Abstract: Acclimatization to altitude is understood as a mechanism that takes place when the human body is subjected to hypoxia, and includes a variety of physiological processes designed to mitigate, to a certain point, the effects of the oxygen partial pressure descent. The purpose of this study was to evaluate the impact of 23 days of traditional altitude training at 2240m on the erythrogram parameters and on the erythropoietin concentration ([EPO]), in 7 elite triathletes. The sample, constituted by 5 male and 2 female individuals, was submitted to two moments of evaluation – one day before ascent to 2240m and one day after the return to sea level – in order to evaluate the number of red blood cells (RBC), the concentration of hemoglobin ([Hb]), the hematocrit (Htc), the mean corpuscular volume (MCV), the mean corpuscular hemoglobin (MCH), the mean corpuscular hemoglobin concentration (MCHC), the red cell distribution width (RDW) and the [EPO]. [EPO] (9,8±3,5 to 7,4±2,8mUI/ml, p=0,178) and CHGM (33,2±0,5 to 32,4±0,6g/dl, p=0,005) decreased after altitude training, the differences being significant only to CHGM. Significant increases occurred in RBC (4,7±0,3 to 4,9±0,2x106/mm3, p=0,019); [Hb] (14,5±0,8 to 15,2±0,3g/dl, p=0,022); Htc (43,6±2,0 to 46,9±1,2%, p=0,003); VGM (93,0±3,8 to 95,8±3,8fl, p=0,000) and RDW (13,1±0,3 to 13,4±0,2%, p=0,034). In conclusion, a 3 week training program at 2240m modifies erythropoietic activity in 7 elite triathletes, although it is not possible to establish with certainty if these alterations are a result of the hypoxic stimulus by itself, or a consequence of an improvement in physical conditioning.N/

Scalable low latency consensus for blockchains

Tese de mestrado, Segurança Informática, Universidade de Lisboa; Faculdade de Ciências, 2021State machine replication (SMR) is a classical technique to implement consistent and fault­tolerant replicated services. This type of system is usually built on top of consensus protocols that have high throughput but have problems scaling to settings with a large number of participants or wide­area sce narios due to the required number of messages exchanged to reach a consensus. We propose ProBFT (Probabilistic Byzantine Fault Tolerance), a consensus protocol specifically de signed to tackle the scalability problem of BFT protocols. ProBFT is a consensus protocol with optimal latency (three communication steps, as in PBFT) but with a reduced number of messages exchanged in each phase (O(n √ n) instead of PBFT’s O(n 2 )). ProBFT is a probabilistic protocol built on top of well­known primitives, such as probabilistic Byzantine quorums and verifiable random functions, which provides high probabilities of safety and liveness when the overwhelming majority of replicas is correct. We also propose a state machine replication protocol called PROBER (PRObabilistic ByzantinE Replication) that builds on top of two consensus protocols, ProBFT and PBFT. PROBER makes use of ProBFT to provide fast and probabilistic replies to the clients and uses PBFT to eventually determinis tically commit the history of operations guaranteeing that the system will not roll back the requests after such commit. This periodic deterministic commit allows the clients to enjoy the low latency provided by ProBFT while still having the guarantees provided by a deterministic protocol. We provide a detailed description of both protocols and analyse the probabilities for safety and live ness depending on the current number of Byzantine replicas

Optimal shape and topology of multi-material microstructures in min-max stress design problems

The present dissertation seeks to optimize the unit cell of a two-dimensional cellular material, pursuing the minimization of the peak equivalent stress in the microstructure. This class of materials is particularly relevant to the design of lightweight structures. By minimizing the peak stress in the microstructure, it is possible to use material in a more rational way. Given the periodic nature of the problem, asymptotic homogenization is employed to compute the stress distribution in the microstructure when a macroscopic load is applied, since periodicity boundary conditions are imposed. With this being a purely conceptual study, only three macroscopic loads are considered: the hydrostatic, biaxial, and pure shear ones. Initially, the single-material problem is solved through shape optimization. Then, the potential to reduce the peak equivalent stress through the introduction of additional material phases is explored. Also with shape optimization, the in uence of one additional material phase is studied. Additionally, topology optimization is used to discover the functionally graded material that minimizes the peak stress in the microstructure. The obtained results show that an increased design exibility always leads to milder stress states. The known theoretical results were successfully replicated, with minimal error measures associated. By increasing the number of material phases in the microstructure, peak stress reduction are attainable. A uniformly stressed microstructure is possible to obtain, by means of a functionally graded material