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Sensor networks can nowadays deliver 99.9% of their data with duty cycles below 1%. This remarkable performance is, however, dependent on some important underlying assumptions: low traffic rates, medium size densities and static nodes. In this thesis, we investigate the performance of these same resource-constrained devices, but under scenarios that present extreme conditions: high traffic rates, high densities and mobility: the so-called ExtremeWireless Sensor Networks (EWSNs). From a networking perspective, communicating in these extreme scenarios is very challenging. The combined effect of high network densities and dynamics makes the network’s characteristics fluctuate drastically both in space and time. Traditional mechanisms struggle to cope with these sudden changes, resulting in a continuous exchange of information that saturates the bandwidth and increases the energy consumption. Once this saturation threshold is reached, mechanisms take decisions based on wrong, outdated information and soon stop working. Even flexible mechanisms have difficulties adapting their settings to the fickly conditions of EWSNs and result in poor performance.To efficiently communicate in EWSNs, mechanisms must therefore comply to a set of requirements i. e., design principles, which are explained next. First, they need to be resilient to local and remote failures and operate as independent as possible from the status of other nodes (state-less principle). Second, because in EWSNs bandwidth is a scarce resource, it should be mainly used for the transmission of the actual data. Mechanisms should not be artificially orchestrated and should exploit each other in a cross-layer fashion to reduce as much as possible their communication overhead (opportunistic principle). Third, mechanisms should support extreme network conditions from their inception. Adapting traditional mechanisms, which are designed for milder conditions, would otherwise result in complex and fragile mechanisms (anti-fragile principle). Fourth, in the case the resources saturate, mechanisms should operate in a conservative fashion, so that performance degrades gracefully without drastic disruptions (robustness principle).Inspired by these four principles, this thesis detaches from traditional communication primitives – which are deterministic and based on rigid structures – and proposes a novel communication stack based on opportunistic anycast. According to this primitive, nodes communicate with the first available neighbor, independently of its location and identity. The more neighbors, themore efficient the communication.At the foundation of this communication stack lays SOFA, a medium access control (MAC) protocol that exploits opportunistic anycast to handle extreme densities in an efficient manner. Its implementation details are presented in Chapter 2. On top of the SOFA layer, this thesis builds two essential network services: neighborhood cardinality (density) estimation and data collection. The former service is provided by Estreme, a mechanism presented in Chapter 3, which exploits the rendezvous time of SOFA to estimate the number of neighbors with almost zero overhead. The latter service is provided by Staffetta in Chapter 4, a mechanism that adapts the wake-up frequency of nodes to bias the opportunistic neighbor-selection of SOFA towards the desired direction e. g., towards the sink node collecting all data.Finally, this thesis presents an extensive evaluation of a complete opportunistic stack on simulations, testbeds and a challenging real-world deployment in the formof the NEMO science museumin Amsterdam. Results showthat opportunistic behavior can lead to mechanisms that are both lightweight and robust and, thus, are able to scale to EWSNs.

Si presenta sinteticamente una valutazione delle segnalazioni relative alle fasi finali del Bronzo Medio e del Bronzo Recente in Romagna e nelle zone limitrofe per una ricostruzione delle dinamiche insediative e per un approfondimento dei reperti rinvenuti nel sito di Solarolo.

This paper shows in detail the construction and operation of an apparatus that levitates when submitted to voltages greater or of the order of 20 kV. This device, which basically corresponds to an asymmetric capacitor, is commonly known in the literature by the name ‘lifter’. It also will be shown in this article, through rather simplified calculations, that the physics grounds of the observed levitation effect are intrinsically related to the transference of linear momentum of the ions (positive or negative) to the surrounding atmosphere. These ions are produced within the conductor of very small curvature (hence, great electrical potential) due to the so called corona effect and, once created, they are immediately accelerated by the intrinsic electric field lines configuration, producing multiple collisions with the air molecules, causing the transference of momentum and, therefore, provoking the observed lifter ascendant impulsion. Este artigo descreve em detalhe a construção e operação de um sistema mecânico que levita quando submetido a tensões maiores ou iguais a 20 kV. Este dispositivo, que corresponde basicamente a um capacitor assimétrico, é conhecido na literatura pelo nome de ‘lifter’. Também é mostrado neste trabalho, através de cálculos razoavelmente simplificados, que o mecanismo físico responsável pelo efeito de levitação está intrinsecamente relacionado com a transferência de momento linear de íons (positivos ou negativos) para o ar circundante. Estes íons são produzidos ao redor do condutor de menor curvatura (portanto com maior potencial elétrico) devido ao chamado efeito corona e, uma vez criados, eles são imediatamente acelerados pela configuração do campo elétrico existente, produzindo múltiplas colisões com as moléculas de ar, causando a transferência de momento e, consequentemente, provocando no lifter um movimento ascendente.

Within the field researches carried out on the Bronze age site of Solarolo, the University of Bologna has started a program of experimental archaeology including the cultivation of ancient cereals. The main aim stress on the reconstruction of ancient economic aspects an particularly the production of crops. The use of several kinds of cereals not modified by modern genetic transformations, similar to those found during the excavations in the Bronze Age site, allows to start a discussion on main topics concerning ancient cultivations during the Bronze Age, supported by methodological, technical and ethnoarchaeological parameters. The scientific method applied along the experimental activities, accompanied by computations of productivity, offers elements to verify the estimations recorded by classical sources., Nell’ambito delle ricerche condotte nell’abitato dell’età del Bronzo di Solarolo dall’Università di Bologna (scavo stratigrafico e Laboratorio di Archeologia Sperimentale), è stata realizzata una sperimentazione di coltivazione dei cereali con lo scopo di approfondire le problematiche della gestione economica ed in particolare della produttività agricola antica. La coltivazione di sementi non modificate geneticamente, analoghe a quelle di età protostorica, permette di affrontare la discussione sui vari aspetti tecnici, metodologici e etnoarcheologici dell’agricoltura nell’età del Bronzo. Il procedimento scientifico adottato durante la sperimentazione, corredato di misurazioni sulla produttività agricola, mette a disposizione dati per la verifica di quanto noto dalle fonti classiche., IpoTesi di Preistoria; Vol 5, N° 1 (2012); 79-100

About two decades ago we have shown mathematically that besides bosons and fermions, it could exist a third kind of particles in nature that was named gentileons. Our results have been obtained rigorously within the framework of quantum mechanics and the permutation group theory. However, these papers are somewhat intricate for physicists not familiarized with the permutation group theory. In the present paper we show in details, step by step, how to obtain our theoretical predictions. This was done in order to permit a clear understanding of our approach by graduate students with a basic knowledge of group theory. Há cerca de duas décadas passadas, mostramos matematicamente que, além de bósons e férmions, poderia existir na natureza um outro tipo de partículas que denominamos de gentileons. Os nossos resultados foram obtidos rigorosamente dentro do contexto da mecânica quântica e da teoria do grupo de permutações. Entretanto, os nossos artigos são difíceis de serem entendidos por físicos que não estão familiarizados com a teoria do grupo de permutações. Assim, no presente artigo nós vamos mostrar em detalhes, passo a passo, como obter as nossas previsões. Procedemos desse modo para permitir que estudantes de graduação de física possam entender claramente nossos cálculos com um conhecimento básico de teoria de grupos.