ISIPTA'07: Proceedings of the Fifth International Symposium on Imprecise Probability: Theories and Applications

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Phase transition for the Maki-Thompson rumour model on a small-world network

We consider the Maki-Thompson model for the stochastic propagation of a rumour within a population. We extend the original hypothesis of homogenously mixed population by allowing for a small-world network embedding the model. This structure is realized starting from a $k$-regular ring and by inserting, in the average, $c$ additional links in such a way that $k$ and $c$ are tuneable parameter for the population architecture. We prove that this system exhibits a transition between regimes of localization (where the final number of stiflers is at most logarithmic in the population size) and propagation (where the final number of stiflers grows algebraically with the population size) at a finite value of the network parameter $c$. A quantitative estimate for the critical value of $c$ is obtained via extensive numerical simulations.Comment: 24 pages, 4 figure

HTM approach to image classification, sound recognition and time series forecasting

Dissertação de mestrado em Biomedical EngineeringThe introduction of Machine Learning (ML) on the orbit of the resolution of problems typically associated within the human behaviour has brought great expectations to the future. In fact, the possible development of machines capable of learning, in a similar way as of the humans, could bring grand perspectives to diverse areas like healthcare, the banking sector, retail, and any other area in which we could avoid the constant attention of a person dedicated to the solving of a problem; furthermore, there are those problems that are still not at the hands of humans to solve - these are now at the disposal of intelligent machines, bringing new possibilities to the humankind development. ML algorithms, specifically Deep Learning (DL) methods, lack a bigger acceptance by part of the community, even though they are present in various systems in our daily basis. This lack of confidence, mandatory to let systems make big, important decisions with great impact in the everyday life is due to the difficulty on understanding the learning mechanisms and previsions that result by the same - some algorithms represent themselves as ”black boxes”, translating an input into an output, while not being totally transparent to the outside. Another complication rises, when it is taken into account that the same algorithms are trained to a specific task and in accordance to the training cases found on their development, being more susceptible to error in a real environment - one can argue that they do not constitute a true Artificial Intelligence (AI). Following this line of thought, this dissertation aims at studying a new theory, Hierarchical Temporal Memory (HTM), that can be placed in the area of Machine Intelligence (MI), an area that studies the capacity of how the software systems can learn, in an identical way to the learning of a human being. The HTM is still a fresh theory, that lays on the present perception of the functioning of the human neocortex and assumes itself as under constant development; at the moment, the theory dictates that the neocortex zones are organized in an hierarchical structure, being a memory system, capable of recognizing spatial and temporal patterns. In the course of this project, an analysis was made to the functioning of the theory and its applicability to the various tasks typically solved with ML algorithms, like image classification, sound recognition and time series forecasting. At the end of this dissertation, after the evaluation of the different results obtained in various approaches, it was possible to conclude that even though these results were positive, the theory still needs to mature, not only in its theoretical basis but also in the development of libraries and frameworks of software, to capture the attention of the AI community.A introdução de ML na órbita da resolução de problemas tipicamente dedicados ao foro humano trouxe grandes expectativas para o futuro. De facto, o possível desenvolvimento de máquinas capazes de aprender, de forma semelhante aos humanos, poderia trazer grandes perspetivas para diversas áreas como a saúde, o setor bancário, retalho, e qualquer outra área em que se poderia evitar o constante alerta de uma pessoa dedicada a um problema; para além disso, problemas sem resolução humana passavam a estar a mercê destas máquinas, levando a novas possibilidades no desenvolvimento da humanidade. Apesar de se encontrar em vários sistemas no nosso dia-a-dia, estes algoritmos de ML, especificamente de DL, carecem ainda de maior aceitação por parte da comunidade, devido a dificuldade de perceber as aprendizagens e previsões resultantes, feitas pelos mesmos - alguns algoritmos apresentam-se como ”caixas negras”, traduzindo um input num output, não sendo totalmente transparente para o exterior - é necessária confiança nos sistemas que possam tomar decisões importantes e com grandes impactos no quotidiano; por outro lado, os mesmos algoritmos encontram-se treinados para uma tarefa específica e de acordo com os casos encontrados no desenvolvimento do seu treino, sendo mais suscetíveis a erros em ambientes reais, podendo se discutir que não constituem, por isso, uma verdadeira Inteligência Artificial. Seguindo este segmento, a presente dissertação procura estudar uma nova teoria, HTM, inserida na área de MI, que pretende dar a capacidade aos sistemas de software de aprenderem de uma forma idêntica a do ser humano. Esta recente teoria, assenta na atual perceção do funcionamento do neocórtex, estando por isso em constante desenvolvimento; no momento, e assumida como uma teoria que dita a hierarquização estrutural das zonas do neocórtex, sendo um sistema de memória, reconhecedor de padrões espaciais e temporais. Ao longo deste projeto, foi feita uma análise ao funcionamento da teoria, e a sua aplicabilidade a várias tarefas tipicamente resolvidas com algoritmos de ML, como classificação de imagem, reconhecimento de som e previsão de series temporais. No final desta dissertação, após uma avaliação dos diferentes resultados obtidos em várias abordagens, foi possível concluir que apesar dos resultadospositivos, a teoria precisa ainda de maturar, não só a nível teórico como a nível prático, no desenvolvimento de bibliotecas e frameworks de software, de forma a capturar a atenção da comunidade de Inteligência Artificial

Discovering And Labelling Of Temporal Granularity Patterns In Electric Power Demand With A Brazilian Case Study

Clustering is commonly used to group data in order to represent the behaviour of a system as accurately as possible by obtaining patterns and profiles. In this paper, clustering is applied with partitioning-clustering techniques, specifically, Partitioning around Medoids (PAM) to analyse load curves from a city of South-eastern Brazil in São Paulo state. A top-down approach in time granularity is performed to detect and to label profiles which could be affected by seasonal trends and daily/hourly time blocks. Time-granularity patterns are useful to support the improvement of activities related to distribution, transmission and scheduling of energy supply. Results indicated four main patterns which were post-processed in hourly blocks by using shades of grey to help final-user to understand demand thresholds according to the meaning of dark grey, light grey and white colours. A particular and different behaviour of load curve was identified for the studied city if it is compared to the classical behaviour of urban cities.36357559

Automatic classification of latin music : some experiments on musical genre classification

Estágio realizado no INESC PortoTese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Automatic classification of latin music : some experiments on musical genre classification

Estágio realizado no INESC PortoTese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

How do you sleep? Using off the shelf wrist wearables to estimate sleep quality, sleepiness level, chronotype and sleep regularity indicators

This piece of research is situated in the domain of multi-modal analytics. New commercial off the shelf wearables, such as smartwatches or wristbands, are becoming popular and increasingly used for fitness and wellness in a new trend known as the quantified-self movement. The sensors included in these devices (e.g. accelerometer, heart rate) in conjunction with data analytics algorithms are used to provide information such as steps walked, calories consumed, etc. The main goal of this piece of research is to check if new wearable technologies could be used to estimate sleep indicators in an automatic way. The available medical literature proposes several sleep-related features and methods to calculate them involving direct user observation, interviews or specific medical instrumentation. Off the shelf wearable vendors also provide some sleep indicators, such as the sleep duration, the number of awakes or the time to fall asleep. Taking as a reference the results and methods described in the medical literature and the data available in commercial off the shelf wearables, we propose new sleep indicators offering a greater interpretative value: sleep quality, sleepiness level, chronotype. The results obtained after initial experiments demonstrate the feasibility of this approach to be applied in real contexts. Eventually, we plan to apply these solutions to support educational scenarios related to self-regulated learning and teaching support.Agencia Estatal de Investigación | Ref. TIN2016-80515-RXunta de Galicia | Ref. GRC2013-006Universidade de Vig

Development and application of statistical methods to support air quality policy decisions

Tese de doutoramento. Ciências de Engenharia. Faculdade de Engenharia. Universidade do Porto. 200

Muons and Hydrogen in Graphene

Macroscopic quantities of graphenes have been prepared by diff erent chemical methods and characterized by Muon Spin Rotation spectroscopy, which proved a useful tool to study the interactions of the hydrogen atom with the defective graphene plane. A clear muon spin precession is observed in all the samples, contrary to the standard behaviour of graphite. Its origin lies in the magnetic dipolar interactions of hydrogen nuclei present at defects and reveal the formation of an extremely stable CHMu (CH2) state. The signal amplitude suggests that vacancies saturated by hydrogen have an extraordinary hydrogen capture cross-section. In addition the Muon Spin Rotation results, together with our SQUID investigations, pose important limits on the debated possibility of magnetism in graphene: Muon Spin Rotation, indeed, is very sensitive to the local internal field and does not show the presence of any magnetization