Introducing synchrony in fuzzy automata

This paper introduces a sort of automata and associated languages, often arising in modelling natural phenomena, in which both vagueness and simultaneity are taken as first class citizens. This requires a fuzzy semantics assigned to transitions and a precise notion of a synchronous product to enforce the simultaneous occurrence of actions. The expected relationships between automata and languages are revisited in this setting; in particular it is shown that any subset of a fuzzy synchronous language with the suitable signature forms a synchronous Kleene algebra.NORTE-01-0145-FEDER-000037. POCI-01-0145-FEDER-030947. ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme and by National Funds through the Portuguese funding agency, FCT - Funda¸c˜ao para a Ciˆencia e a Tecnologia, within projects POCI-01-0145-FEDER-030947 and UID/MAT/04106/2019. The second author is supported in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Portuguese Law 57/2017, of July 19. This paper is also a result of the project SmartEGOV: Harnessing EGOV for Smart Governance (Foundations, Methods, Tools) NORTE-01-0145- FEDER-000037, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (EFDR). It received further support from the PT-FLAD Chair in Smart Cities & Smart Governanc

Testing android malware detectors against code obfuscation: a systematization of knowledge and unified methodology

The authors of mobile-malware have started to leverage program protection techniques to circumvent anti-viruses, or simply hinder reverse engineering. In response to the diffusion of anti-virus applications, several researches have proposed a plethora of analyses and approaches to highlight their limitations when malware authors employ program-protection techniques. An important contribution of this work is a systematization of the state of the art of anti-virus apps, comparing the existing approaches and providing a detailed analysis of their pros and cons. As a result of our systematization, we notice the lack of openness and reproducibility that, in our opinion, are crucial for any analysis methodology. Following this observation, the second contribution of this work is an open, reproducible, rigorous methodology to assess the effectiveness of mobile anti-virus tools against code-transformation attacks. Our unified workflow, released in the form of an open-source prototype, comprises a comprehensive set of obfuscation operators. It is intended to be used by anti-virus developers and vendors to test the resilience of their products against a large dataset of malware samples and obfuscations, and to obtain insights on how to improve their products with respect to particular classes of code-transformation attacks

Games in Networks under Robustness, Locality, and Coloring Aspects

Decentralization is a key concept in modern networks, such as the Internet, social networks, or wireless phone or sensor networks. The systematic study of how networks are formed by a multitude of non-cooperative or only mildly cooperative players, is a vivid topic in Discrete Mathe- matics, Computer Science, and Economics. In 2010, a variant addressing robustness aspects was introduced. In this model, known as adversary model or destruction model, one link in the network is destroyed at random af- ter the network has been formed. Players anticipate this disruption and try to build a network that gives them good connectivity even after the destruction. How efficiently can this be done in a decentralized setting? This thesis advances our knowledge regarding the adversary model: we bring in the modern equilibrium concept of swap equilibrium and we extend to the destruction of one vertex. This disruption tends to be more severe compared to the case that just one link is destroyed. We characterize several settings, where for some, the formed networks are provably efficient, while for others, we show they can be inefficient up to a certain degree. Apart from the adversary model, we study a model where each player v tries to maximize the number of players at distance at most k from v, for a fixed parameter k. For example, when the network models friendship, then for k = 2, players would try to maximize the number of friends plus friends of their friends, which is an interesting metric in Sociology. We prove results on the structure and efficiency of such networks. In the final chapter, the network is fixed and each player chooses one of k colors. For example, the network might describe the spatial relations between the players and colors might correspond to radio frequencies, so each player’s aim is to choose a frequency that causes as few interference as possible with the frequencies of her neighbors

Using Bluetooth to estimate traffic metrics for traffic management applications

PhD Thesis‘Bluetooth’ is a technology that can be integrated into Intelligent Transport Systems (ITS) to facilitate smarter and enhanced traffic monitoring and management to reduce congestion. The current research focus on Bluetooth is principally on journey time management. However, the applicability and viability of Bluetooth potential in problematic urban areas remains unknown. Besides the generic problem of unavailability of processing algorithms, there is gap in knowledge regarding the variability and errors in Bluetooth-derived metrics. These unknown errors usually cause uncertainty about the conclusions drawn from the data. Therefore, a novel Bluetooth-based vehicle detection and Traffic Flow Origin-destination Speed and Travel-time (TRAFOST) model was developed to estimate and analyse key traffic metrics. This research utilised Bluetooth data and other independently measured traffic data collected principally from three study sites in Greater Manchester, UK. The Bluetooth sensors at these locations generated vehicle detection rates (7-16%) that varied temporally and spatially, based on the comparison with flows from ATC (Automatic Traffic Counters) and SCOOT (Split Cycle Offset Optimisation Technique) detectors. Performance evaluation of the estimation showed temporal consistency and accuracy at a high level of confidence (i.e. 95%) based on criteria such as Mean Absolute Deviation (MAD) - (0.031 – 0.147), Root Mean Square Error (RMSE) - (0.041 – 0.195), Mean Absolute Percentage Error (MAPE) - (0.822 – 4.917) and Kullback-Leibler divergence (KL-D) (0.004 – 0.044). This outcome provides evidence of reliability in the results as well as justification for further investigation of Bluetooth applications in ITS. However, the resulting accuracy depends significantly on sample size, network characteristics, and traffic flow regimes. The Bluetooth approach has enabled a deeper understanding of traffic flow regimes and spatio-temporal variations within the Greater Manchester Networks than is possible using conventional traffic data such as from SCOOT. Therefore, the application of Bluetooth technology in ITS to enhance traffic management to reduce congestion is a viable proposition and is recommended.Petroleum Technology Development Fund (PTDF) – for the award of a PhD Scholarship for 4 years; The University of Lagos – for the study leave with pay; Surveyors Council of Nigeria (SURCON) – for the additional support

Reconstituição paleoclimática e paleoambiental em estuários com base no registo micropaleontológico de foraminíferos : relação com indicadores de escala local, regional e global

Tese de doutoramento, Geologia (Paleontologia e Estratigrafia), Universidade de Lisboa, Faculdade de Ciências, 2017In recent years, many studies have sought to produce high-quality paleoclimatic reconstructions for the late Holocene based on high-resolution (annual or decadal) biological and/or chemical proxies, both providing a great amount of information on climate variability and change over the last two millennia. In this context, salt marsh sedimentary records have previously proved to be particularly suitable in unravelling anthropogenic impacts on coastal ecosystems from those caused by climate variability and other natural stressors, at local and regional scales, with intertidal benthic foraminifera providing consistent responses to the latter, specifically to relative sea-level change. This dissertation focuses on showing evidence of climatic variability and change from a collection of multiple proxy studies combining marsh benthic foraminifera assemblages, wine production (WP), grape harvest dates (GHD), bromine (Br) contents in tidal marsh sediments, and different datasets ranging from the last decades, using instrumental (temperature–precipitation) records, to the past two millennia, by means of reconstructions (temperature, Total Solar Irradiance – TSI and North Atlantic Oscillation – NAO) and regional model (temperature–precipitation) simulations, with the aim of reconstruct the paleoclimate history of the west coast of Portugal for the past 2000 years. Simultaneously, the sensitivity of marsh benthic foraminifera to climate change induced by solar activity (SA) – via hydrological balance (controlling the salinity baseline of the high marsh environment) – is assessed, to show their reliability as a paleoclimatic proxy to be integrated in forthcoming studies. For that, the foraminiferal records from two dated sedimentary cores collected in the northwest (Caminha salt marsh; Minho River) and southwest (Casa Branca salt marsh; Mira River) Portuguese coast have been carefully examined and compared. Since the marshes’ development in the 1300s, two compositionally distinct tidal marsh foraminiferal assemblages have been found, dominated by Haplophragmoides manilaensis and Trochamminita salsa/irregularis in the NW (Caminha) and by Jadammina macrescens and Trochammina inflata in the SW (Casa Branca), in accordance with their respective climate types. A number of revealed common key changes in the main assemblages’ composition has been attributed to larger scale climatic shifts, particularly as regards the transitions firstly from the Medieval Climatic Anomaly (MCA) to the Little Ice Age (LIA), and next from the LIA to the Current Warm Period (CWP) in the Iberian Peninsula, as well as to major temperature–precipitation excursions throughout the LIA and directly correlated with sustained negative phases of the NAO index in periods of lowest SA, known as Grand Solar Minima. It is also found, throughout the application of spectral and cross wavelet methods, that in the time span analyzed (from the 1300s to present), the signals of solar forcing in both foraminiferal and paleoclimatic records were intermittent, with the regional climate modulated by the solar secular Gleissberg cycle, especially after AD 1700–1750, following the Maunder Minimum (1645–1715). Besides, an important – and unexpected – feedback is achieved concerning Br in the sedimentary record from the two salt marshes. It is found that Br enrichment peaks, and its connection with organic matter (OM) – promoted by the climate-driven marsh dynamics involving the production/release of volatile Br compounds (as methyl bromide – CH3Br) to atmosphere – can be diagnostic, to some degree, of Grand Solar Minima and enhanced volcanic activity during those Grand episodes of SA. The CH3Br has an ozone (O3) depleting potential of 0.6, and belongs to Class I O3 depleting substances. Its multiple anthropogenic sources were subjected to phase-out under the Montreal Protocol and its amendments, the reason why natural emissions, as the ones from salt marshes, have become progressively more important contributors to stratospheric O3 loss processes. According to the results of the current work, based on the available knowledge about Br– OM relationships in terrestrial and marine ecosystems and moreover compatible with a wider recognized latitudinal (North-to-South) rising gradient on the salt marshes’ CH3Br emissions, it is plausible to assume (i) a switch in the marshes’ Br source/sink dynamic in response to future major excursions of SA and (ii) an increased total flux of CH3Br under a continued global warming trend. Overall, the novelty of this PhD dissertation lies in showing a broader role of marsh benthic foraminifera as indicators of changes in the climate system triggered by SA. Therefore, and not disregarding the great amount of effort still required in their improvement, the results presented here have some meaningful implications, namely on (i) a better understanding of patterns and causes of late-Holocene climatic variability in the west Iberian margin, (ii) the estimate of local and regional changes in hydro-climate and temperature in response to future solar variability, despite the current scenario of anthropogenic climate change, (iii) the research of trends and exposure of naturally produced brominated compounds in salt marshes worldwide, and (iv) the setting up of Br as a paleoclimate proxy linked to SA.A emergência de questões relacionadas com o aquecimento global e as mudanças climáticas, em termos de disponibilidade de recursos e desenvolvimento sustentável, reforçou o interesse pelas Paleociências. Daí resultou a publicação de um número crescente de estudos visando obter reconstruções e interpretações paleoclimáticas para o Holocénico superior, com base em indicadores (proxies) biológicos e químicos de alta resolução (à escala anual e da década). Estes proxies, preservados em arquivos naturais como os sedimentos, as árvores ou o gelo, facultam informação relevante sobre a variabilidade e mudanças climáticas ocorridas nos últimos 1000 a 2000 anos, ou até num passado muito mais remoto. Permitem-nos assim ampliar consideravelmente a perspetiva acerca do funcionamento do sistema climático fornecida pelos registos históricos e instrumentais dos dois últimos séculos. Neste âmbito, os registos sedimentares dos sapais têm provado ser particularmente adequados para distinguir entre impactes antrópicos e efeitos naturais em ambiente costeiro, à escala local e regional, recorrendo ao estudo dos foraminíferos bentónicos da zona entre marés e à interpretação da resposta consistente perante a variabilidade do clima, e de forma mais específica, as alterações do nível médio do mar. A distribuição das associações de foraminíferos de sapal surge nitidamente relacionada com a altitude (acima do nível médio das marés) e o tempo de submersão do sedimento onde vivem, garantindo o seu enorme potencial de aplicação como indicadores paleoambientais. Para além desta relação inequívoca, as espécies dominantes encontram-se condicionadas pela geoquímica dos sedimentos e das águas intersticiais, refletindo a influência marinha (hidrodinâmica) no interior de cada estuário. Esta tese fornece registos de variabilidade e mudanças climáticas para o período préindustrial, a partir de um conjunto de artigos já publicados (Capítulos 2 a 8) ou em fase de revisão interpares (Capítulos 9 e 10), onde se combina a utilização de vários proxies, nomeadamente as associações de foraminíferos bentónicos de ambientes de sapal, as datas do início das vindimas (GHD), a produção de vinho (WP) e os teores de bromo (Br) em solos e sedimentos de sapal, com o objetivo de reconstruir a história paleoclimática da costa oeste de Portugal continental nos últimos 2000 anos. Simultaneamente, procura-se contribuir para o conhecimento da sensibilidade dos foraminíferos bentónicos, registada nos sedimentos, perante os agentes forçadores do clima, designadamente a atividade solar, por ação do balanço entre precipitação e evapotranspiração (P–ET), responsável pelo nível de base de salinidade do alto sapal, bem como mostrar a sua eficácia como proxy climático, passível de ser considerado e integrado em estudos futuros. Para tal, os registos de foraminíferos de duas sondagens de sedimentos, uma na costa noroeste (sapal de Caminha, rio Minho) e outra na costa sudoeste (sapal de Casa Branca, rio Mira) de Portugal, foram estudados, datados e comparados. Foi possível detectar um conjunto de modificações-chave comuns, quer nos registos sedimentares (foraminíferos e geoquímica), quer noutro tipo de registos (e.g., WP), relacionadas com variações climáticas de larga escala, sobretudo no que se refere à transição da Anomalia Climática Medieval para a Pequena Idade do Gelo na região da Península Ibérica. As variações de temperatura e precipitação de âmbito local, ocorridas durante a Pequena Idade do Gelo, surgem, por sua vez, correlacionadas com fases negativas do índice de Oscilação do Atlântico Norte (NAO), que ocorreram durante grandes mínimos de atividade solar. Verifica-se que desde o início da sua formação, desde o século XIV até ao presente, os sapais de Caminha e Casa Branca evoluíram sob uma influência climática diferenciada, à semelhança do padrão climático que observamos hoje nestas duas regiões da costa W portuguesa. Esta diferenciação encontra-se expressa pelas associações dominantes de foraminíferos do alto sapal. Sob condições de salinidade muito baixa, como as que se registaram em Caminha, no baixo estuário do rio Minho (a 3,5 km da foz), são essencialmente compostas pelas espécies aglutinadas Haplophragmoides manilaensis e Trochamminita salsa/irregularis, enquanto em Casa Branca, no estuário médio do rio Mira (a 13,0 km da foz), a maior influência marinha é revelada pelas associações dominadas por Jadammina macrescens e Trochammina inflata. Este contraste na microfauna parece refletir uma tendência de longo-prazo para o ganho da ET sobre a P, no balanço hidrológico na região SW, levando à prevalência de condições de maior salinidade em Casa Branca. A aplicação dos métodos de análise espectral e de coerência espectral e fase revelou que, para o mesmo período (séc. XIV à atualidade), o registo dos sinais solares nestes proxies (espécies de salinidade normal, na região NW, e T. inflata, na região SW) é descontínuo e que o ciclo secular de Gleissberg (50–80 anos) parece ter tido um papel importante na modulação climática regional; nomeadamente a partir de AD 1700 1750, ou seja, após o Mínimo de Maunder (1645–1715). Por último, a análise e a interpretação dos teores de Br, juntamente com a matéria orgânica (MO), ao longo do registo sedimentar das duas sondagens permitiu formular algumas conclusões significativas: os picos de concentração máxima de Br nos sedimentos, bem como a interdependência Br/MO – em estreita conexão com a dinâmica do sapal promovida pelo clima – podem evidenciar períodos de Grandes Mínimos de atividade solar e concomitante (elevada) atividade vulcânica. O CH3Br, composto volátil de Br, pertence à classe I das substâncias destruidoras de O3, com potencial de destruição de 0.6. Como as suas fontes antrópicas têm vindo a ser progressivamente eliminadas, no cumprimento do Protocolo de Montreal, as emissões naturais de CH3Br – entre elas as dos sapais – têm hoje maior importância relativa nos processos de destruição do O3 estratosférico. De acordo com os resultados da presente investigação – fundamentados no conhecimento disponível sobre a formação de compostos organobromados em ecossistemas terrestres e marinhos, e compatíveis com a observação do aumento das taxas de emissão de CH3Br pelos sapais em função de um gradiente latitudinal (Norte–Sul) de crescente temperatura – é plausível assumir (i) uma alternância no papel destes ambientes como fonte–sumidouro de Br em resposta a futuros episódios relevantes da atividade solar e (ii) um aumento do fluxo total de CH3Br num cenário de continuado aquecimento global. Acima de tudo, a inovação do trabalho compilado nesta tese consiste na revelação de uma vertente, ainda pouco explorada, do papel dos foraminíferos bentónicos de sapal como indicadores de mudanças climáticas induzidas pela dinâmica da atividade do Sol. Os resultados apresentados podem, por isso, ter algumas implicações pertinentes, quer na estimativa de mudanças locais e regionais na temperatura e no ciclo hidrológico, em face da futura variabilidade solar, quer na pesquisa de tendências e exposição a compostos organobromados em sapais de todo o mundo, bem como no reconhecimento do papel do Br como proxy de alterações paleoclimáticas ligadas à atividade solar