Aggregation and Emergence in Agent-Based Models: A Markov Chain Approach

We analyze the dynamics of agent--based models (ABMs) from a Markovian perspective and derive explicit statements about the possibility of linking a microscopic agent model to the dynamical processes of macroscopic observables that are useful for a precise understanding of the model dynamics. In this way the dynamics of collective variables may be studied, and a description of macro dynamics as emergent properties of micro dynamics, in particular during transient times, is possible.Comment: 5 pages, 1 figur

Residue Number System Hardware Emulator and Instructions Generator

Residue Number System (RNS) is an alternative form of representing integers on which a large value gets represented by a set of smaller and independent integers. Cryptographic and signal filtering algorithms benefit from the use of RNS, due to its capabilities to increase performance and security. Herein, a simulation tool is presented which emulates the hardware implementation of an actual RNS co-processor. An “high-level to assembly” instructions generator is also built into this tool. The programmability and scalable architecture of the considered processor along with the high level description of the algorithm allows researchers and developers to easily evaluate and test their RNS algorithms on an actual architecture, using Java

The impact of the oil spill of the tanker “Aragon” on the littoral fish fauna of Porto Santo (NE Atlantic Ocean) in 1991 and ten years later

Bocagiana, 217: 1-8Em Janeiro de 1990, a Ilha de Porto Santo (Arquipélago da Madeira), foi atingida por uma maré negra proveniente de um derrame do navio petroleiro “Aragon”. Um ano depois, avaliou-se a ictiofauna costeira. Dez anos depois da maré negra, uma nova amostragem foi realizada com a mesma metodologia, de forma a comparar com os dados recolhidos anteriormente. A análise dos resultados obtidos parece revelar que os efeitos da maré negra nos peixes litorais foram reduzidos. Este trabalho constitui a primeira contribuição para a “check-list” da ictiofauna costeira da Ilha de Porto Santo.In January 1990, the tanker “Aragon” oil spill reached Porto Santo Island (Madeira Archipelago). One year later, in 1991 the littoral fish fauna was evaluated. Ten years after the “Aragon” oil spill, a new survey was made using the same methods, to compare data. From the results it seems that the effects of the oil were rather small. As a result of this work, as a check-list of the littoral fish fauna of this Island is presented

A performance comparison of active managed Bond funds and Bond ETFs in the United States

Dissertação de mestrado em FinanceFinancial markets play a key role in boosting modern economies. Therefore, the development of different investment classes is necessary, allowing greater diversification to the market, with Exchange Traded Funds (ETFs) and active/passive mutual funds being two of the fastest growing segments in the financial market in general. So, it is necessary to understand if these investment classes are really good investment alternatives for the financial market. This study evaluates the performance of these different types of investment funds using a comprehensive dataset of corporate bond funds over a long time period from August 2002 to December 2018. Moreover, this study focuses on the financial performance, cost of investing and degree of active management. The performance of bond mutual funds is evaluated relative to a general index, and the bond ETFs are evaluated relative either to a general index and to the self-declared benchmark of each fund. The results show that, on average, actively managed bond funds perform better than both passive bond funds and bond ETFs (net and gross). However, the average alpha is very close to zero and as for the 1% level, the results show underperformance (greater number of statistically significant negative alphas) compared to the market. Regarding the one-factor or multi-factor model’s choice, the regression results using the multi-factor improved almost all the statistics of the 3 groups of funds, indicating a better job in explaining the bond fund returns. Furthermore, the active bond funds present a lower level of activeness, compared with bond ETFs. Therefore, investors may be overpaying for active management funds where little or none is being implemented by the fund manager.Os mercados financeiros desempenham um papel fundamental na dinamização das economias modernas. Por isso, é necessário o desenvolvimento de diferentes classes de investimento, permitindo uma maior diversificação ao mercado sendo os Exchange Traded Funds (ETFs) e os fundos de investimento abertos de gestão ativa e passiva dois dos segmentos que mais cresceram no mercado financeiro em geral. Sendo assim, é necessário perceber se estas classes de investimento são realmente boas alternativas de investimento para o mercado financeiro. Este estudo avalia o desempenho destes diferentes tipos de fundos de investimento nos EUA relativamente ao benchmark de mercado, usando uma ampla e abrangente amostra de 275 fundos, ao longo do período de agosto de 2002 a dezembro de 2018. Este estudo centra-se na análise do desempenho financeiro, no custo de investimento e no grau de gestão ativa para os fundos em análise. Relativamente à avaliação do desempenho, os fundos de obrigações de gestão ativa e passiva são analisados tendo como comparação um índice geral, e os ETFs são avaliados relativamente a um índice geral, e ao índice que cada fundo replica. Os resultados mostram que, em média, os fundos de obrigações de gestão ativa apresentam um melhor desempenho que os fundos de obrigações de gestão passiva e os ETFs (líquido e bruto). No entanto, o valor médio dos alfas é muito próximo de zero e, ao nível de significância de 1%, os resultados demonstram um desempenho inferior (maior número de alfas negativos significativos do que positivos) comparativamente ao mercado. Em relação à escolha do modelo a utilizar, os resultados da regressão usando o multi-fator melhoraram quase todas as estatísticas dos 3 grupos de fundos, explicando de uma forma mais robusta os retornos dos fundos. Além disso, os fundos de obrigações ativos apresentam um nível mais baixo de gestão ativa, em comparação com os ETFs. Isto pode significar que os investidores podem estar a pagar a fee da gestão ativa, quando pouco ou nada está sendo implementado pelo gestor do fundo

Aging and technology: a living lab cohort characterization

Senior cohort studies have gained special relevance in an increasingly aging society. Challenges such as the growing prevalence of neurodegenerative disorders, as well as recent public health challenges such as the covid-19 pandemic show us not only the specific challenges faced regarding the promotion of health and well-being of senior individuals, but also the need to understand the role of seniors as active citizens and as agents in the development of solutions and services that aim to promote independence, autonomy, and well-being. This study aims at a comprehensive characterization of a cohort of senior individuals integrated in a Living Lab in Northern Portugal (Porto area), and to test a model of attitudes and use of technology. Fourty-four Portuguese community- dwelling seniors (37 women and 7 men) were assessed on cognitive performance, health status personality, and psychological well-being, lifestyle, and attitudes and use of technology. Results revealed differences in cognitive functioning between independent living (non-users) and adult day care users, and showed associations between several dimensions and the model of attitudes and use of technology. Future studies should explore the validity of the developed instrument in other contexts and replicate the results in larger and more heterogenous populations

Symbols are not uniquely human

Modern semiotics is a branch of logics that formally defines symbol-based communication. In recent years, the semiotic classification of signs has been invoked to support the notion that symbols are uniquely human. Here we show that alarm-calls such as those used by African vervet monkeys (Cercopithecus aethiops), logically satisfy the semiotic definition of symbol. We also show that the acquisition of vocal symbols in vervet monkeys can be successfully simulated by a computer program based on minimal semiotic and neurobiological constraints. The simulations indicate that learning depends on the tutor-predator ratio, and that apprentice-generated auditory mistakes in vocal symbol interpretation have little effect on the learning rates of apprentices (up to 80% of mistakes are tolerated). In contrast, just 10% of apprentice-generated visual mistakes in predator identification will prevent any vocal symbol to be correctly associated with a predator call in a stable manner. Tutor unreliability was also deleterious to vocal symbol learning: a mere 5% of “lying” tutors were able to completely disrupt symbol learning, invariably leading to the acquisition of incorrect associations by apprentices. Our investigation corroborates the existence of vocal symbols in a non-human species, and indicates that symbolic competence emerges spontaneously from classical associative learning mechanisms when the conditioned stimuli are self-generated, arbitrary and socially efficacious. We propose that more exclusive properties of human language, such as syntax, may derive from the evolution of higher-order domains for neural association, more removed from both the sensory input and the motor output, able to support the gradual complexification of grammatical categories into syntax

Age prediction through the influence of fatigue levels in human-computer interaction

Dissertação de mestrado integrado em Informatics EngineeringThe evolution of current times and the available technology is making it easier to access potentially inappropriate content. Therefore, the ability to detect the age of the human being, by non-invasive methods, is increasingly necessary to reduce possible false claims. All of these claims arise through interactions with the device, so, and taking into account the demands and the fast pace of everyday life, the intent is to develop a system capable of detecting age groups, taking into account the presence of human factors like fatigue or stress that can change the interaction patterns. This system will use biometric features created by keyboard and mouse events, describing typing velocity, mouse acceleration, and so on in the period of five minutes. However, keeping in mind the everyday pace and the growth in mobile phone use, a similar system is created for this case study.A evolução dos tempos modernos e das tecnologias existentes está a tornar mais fácil o acesso a conteúdos potencialmente impróprios. Assim, a capacidade para detetar a idade de um ser humano, por métodos não invasivos, é cada vez mais necessário de forma a reduzir potenciais falsas alegações. Todas estas alegações provêm através de interações com um dispositivo, dessa forma, e tendo em conta as exigências e o ritmo acelerado do quotidiano, o objetivo passa pelo desenvolvimento de um sistema capaz de detetar idades, considerando a presença de fatores humanos que poderão influenciar os padrões de interação, como fadiga ou stress. Este sistema irá utilizar biometrias criadas a partir de eventos de teclado e rato, descrevendo velocidade de escrita, aceleração do rato, entre outras no período de cinco minutos. Contudo, tendo em conta o ritmo acelerado do quotidiano e crescimento do uso de telemóveis, um sistema similar é criado para este caso estudo

Emigration tales: automatic generation of texts, from ontological descriptions of emmigration resources, to tell life stories

Dissertação de mestrado integrado em Informatics EngineeringThis document presents a Master’s Thesis on Informatics Engineering, at University of Minho, and it is focused on an automatic generator of texts that is responsible for telling life stories. The main goal of this project is to develop a system that is capable of analyzing ontological descriptions in order to build one or more stories related to individuals or families who emigrated from and to certain regions of the globe, in a given time space. This generation is based on rules of transformation and application of the ontology’s data in grammatical structures, thus forming sentences which, in turn, form a text in free speech. This generation of texts in natural language is far from being linear, due to the existence of some conditionings that can make the text incoherent and/or inconsistent. An example of this is the person’s biological gender, which has to be calculated - if not indicated at the outset - through his or her first name. Other conditionings that will change the configuration of the generated text are, for example, the number of people involved in the story, their ages, and the quantity (and quality) of information available. To connect the stories of a multiple number of emigrants, it is also necessary to find at least one point of information in common between them all, in order to offer a higher level of realism and cohesion to the generated text. This project also aims at enriching the visits to virtual museums related to the history of social life and migrations, such as, for example, the Museum of Emigration and Communities or the Museum of the Person.Este documento apresenta uma Tese de Mestrado em Engenharia Informática, na Universidade do Minho, e está focada num gerador automático de textos responsável por contar histórias de vida. O objetivo principal deste projeto é de desenvolver um sistema que seja capaz de analisar descrições ontológicas de modo a contruir uma ou mais histórias relacionadas com indivíduos ou famílias que emigraram de e para certas regiões do Mundo, num dado espaço de tempo. Esta geração é baseada em regras de tranformação e aplicação de informação ontológica em estruturas gramaticais, formando assim frases que, por sua vez, formam um texto em linguagem corrente. Esta geração de textos em linguagem natural está longe de ser linear, devido à existência de algumas condicionantes que podem tornar o texto incoerente e/ou inconsistente. Um exemplo desta variância é o gênero biológico da pessoa, que terá de ser calculado - se não for indicado à partida pela fonte - a partir do seu nome próprio. Outras condicionantes que irão alterar a configuração do texto gerado são, por exemplo, o número de pessoas involvidas na história, as suas idades, e a quantidade (e qualidade) da informação disponível. Para haver uma conexão das histórias de múltiplos emigrantes, é também necessário encontrar, pelo menos, um ponto de informação comum a todos, de modo a oferecer um nível mais elevado de realismo e coesão ao texto gerado. Este projeto também tem o objetivo de enriquecer as visitaos aos museus virtuais relacionados com a história da vida social e migrações, tais como, por exemplo, o Museu das Emigrações e das Comunidades ou o Museu da Pessoa

Modelling of a lens antenna receiver system for NASA GUSTO

The radiation at terahertz (THz) frequency range (1 THz = 300 μm in wavelength) provides us a powerful window into cosmic evolution, from the birth and explosion of stars to the evolution of galaxies and the universe itself. The THz is a largely unexplored region in the electro-magnetic spectrum, partly owing to technological constraints and partly due to atmospheric absorption on the Earth. Consequently, THz astronomy observations are best performed from space-based or balloon-borne telescopes, like the proposed NASA balloon GUSTO mission. The observations will be complementary to other space missions like Hershel’s HIFI instrument. In this work, a model of GUSTO’s optical system was proposed and analysed in order to improve its efficiency in detecting three of the most important terahertz lines, [NII], [CII] and [OI], with multi-pixel heterodyne cameras. Moreover, simulations were performed with PILRAP, a antenna simulation software, to study the parameters that affect the optical f# number and radiation pattern of a 5 mm diameter lens system, and to explain the heterodyne sensitivity differences between a 10 mm lens and 3.1 mm lenses. Outcome of my thesis work concludes the feasibility to use smaller lens for GUSTO’s heterodyne arrays