4,042 research outputs found

    Detection and Classification of Obstacles for Autonomous Vessels Using Machine Learning

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    Desenvolvimento de um sistema capaz de realizar a deteção e classificação de obstáculos de vários tipos que possam ser sujeitos de colisões e resultar em danos para a embarcação ou até na destruição total do mesmo. O sistema é também capaz da deteção da linha do horizonte para estimar a distância relativa dos objetos detetados à posição atual da embarcação. As deteções são conseguidas recorrendo a técnicas de Deep Learning, nomeadamente usando CNNs, para a deteção dos obstaculos e linha do horizonte.Development of a system capable of obstacle detection and classification of various types that may be subject of collisions and result in damages to the ship or even its own total loss. The system is also capable of detection the horizon line, to estimate the relative distance of the detected objects to the vehicle current position. This is achieved throught Deep Learning techniques, namely by the use of Convolutional Neural Networks

    Does funding liquidity help predict U.S Dollar returns?

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    Predicting the future value of an exchange rate has been a long-standing challenge in economics. There is still no evidence of any model or technique that has consistently been proven to beat the random walk model. The current objective of this thesis is to check if there is a liquidity channel tied to banking funding that allows us to explain some part of the performance of currency returns. The present analysis focuses on the paper “Risk Appetite and Exchange Rates” by Adrian et al. (2015) where it is claimed that there is a statistically significant relationship between banks’ funding capacities and changes in exchange rates. This relation seems to be more prominent for currencies of more developed countries. In my analysis, the liquidity aggregates (Commercial Paper and Repo) also display some explanatory power, though less than in Adrian et al. Importantly, however, I show that using linear time de-trending as the authors do presents stationarity problems for both liquidity aggregates, especially for Repo volume. The statistical inference of the OLS results is therefore limited. Moreover, in the fitted models, adding a dummy variable and a dummy variable with interactions with the two liquidity aggregates, as in Adrian et al. (2015), reduces the individual significance of the coefficients’ estimates for the liquidity variables. Overall, my analysis casts doubt on the results obtained in Adrian et al. (2015).A previsão do valor futuro de uma taxa de câmbio é um desafio de há muito tempo no campo da economia. Ainda não há provas concretas de nenhum método que seja capaz de bater o random walk model, na previsão das taxas de câmbio futuras. O objectivo desta tese é analisar se existe algum liquidity channel relacionado com o mecanismo de financiamento dos bancos que ajude a explicar alguma parte da performance do retorno das moedas. A análise desta tese debruça-se sobre o paper “Risk Appetite and Exchange Rates” por Adrian et al. (2015), onde se afirma que existe uma relação estatisticamente significativa e positiva entre a capacidade de financiamento dos bancos e os retornos da moeda em que é denominado esse financiamento. Esta relação parece mais forte entre moedas de países desenvolvidos. Na minha análise, os agregados de liquidez (Papel Comercial e Repo) também revelam algum poder explicativo, ainda que este seja menor que aquele apresentado em Adrian et al. (2015). Digno de nota é que o método de de-trending (linear time de-trend), usado pelos autores, produz séries com problemas de estacionariedade, especialmente para o valor do Repo. A inferência estatística é portanto limitada. Além disso, nos modelos ajustados, usar uma dummy variable e uma dummy variable com interacções com os agregados de liquidez, como em Adrian et al. (2015), reduz a significância individual para as estimativas dos coeficientes das variáveis de liquidez. Em suma, o meu estudo levanta dúvidas sobre os resultados encontrados em Adrian et al. (2015)

    Reduza a sua fatura de eletricidade e poupe dinheiro. Como optar pelo melhor comercializador de energia

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    O presente artigo tem como principal objetivo, orientar o leitor e consumidor de energia elétrica a reduzir a sua faturação energética. Focando-se no mercado liberalizado de energia e em assuntos relacionados com o mesmo, será abordado o processo de decisão da escolha do comercializador de energia mais adequado a cada tipo de perfil. Serão ainda abordados neste artigo, alguns aspectos relevantes, que podem fazer com que o consumidor de energia economize

    On the impact of a tax shock in Portugal

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    In 1999, Cavaco Silva, the Portuguese Prime Minister from 1985 to 1995, proposed a comprehensive tax reform package, which is to this day the basic reference in the tax policy debate in Portugal. A tax shock would consist of 4pp cuts in the corporate income tax and in the firms’ social security contribution rates, and a 5pp reduction in the highest personal income tax rate. These cuts would be financed by combating tax evasion, curbing wasteful public expenditure and, if necessary, by increasing the VAT rate by up to 2pp. Using a dynamic general equilibrium model to evaluate the effects of this tax shock, we find that the long- term GDP gains would be between 0.72% and 2.91% while the effects on lifetime private welfare would range between –0.99% and 0.9%. The efficiency of this tax reform package depends critically on the way the tax cuts are financed to ensure deficit neutrality. Because investment is subject to adjustment costs, to alleviate the long-run trade-off between GDP and welfare, tax policy changes must induce a significant increase in net labor income.info:eu-repo/semantics/publishedVersio

    Regional Workshop on Co-management in Small-Scale Fisheries: Lessons Learned and Best Practices 12-13 December 2012, Bangkok, Thailand

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    An FAO project, the Regional Fisheries Livelihoods Programme, which is funded by Spain, has worked with the Timorese authorities and coastal communities to build local capacity and put in place effective methods to gather a variety of important fisheries data. This is used to help make important decisions relating to the management of the nation's fisheries sector. These actions, which are detailed in this publication, have been carried out at relatively little expense and in a participatory manner that has engaged communities while at the same time providing practical skills to all involved

    Momentum and contrarian strategies in the Portuguese stock market

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    JEL Classification System: G11 - Portfolio Choice; Investment Decisions G14 - Information and Market Efficiency; Event Studies G12 - Asset PricingThis thesis studies whether momentum and contrarian strategies are profitable on the Portuguese stock market and whether it is possible to obtain higher returns based on past performance trends. The time period analyzed is 1997-2008. The momentum strategy is based on the under-reaction hypothesis. This suggests that stocks that have had the best (worst) results in the recent past will continue to have better (worse) results in the near future, and therefore a trading strategy that buys winner stocks and sells the losers would provide significant abnormal returns. On the other hand, the contrarian strategy is based on the overreaction hypothesis which assumes the opposite behaviour from stock returns, and hence recommends buying losers and selling winners. Short term strategies show momentum profitability, thus supporting the under-reaction hypothesis. For longer periods, contrarian profitability (and overreaction) is also considerable but not so evident. An “innovative” investment strategy was developed that provides much higher returns than momentum and contrarian strategies. It is based on two upward past trends: if the past returns for the two defined periods preceding the holding period were equal or higher than the percentages defined, this stock is bought; otherwise, a safer investment such as a deposit with a risk-free rate is preferable. Results are not statistically significant but are economically relevant. Finally, results are robust to changes in the time-period, number of stocks included in the portfolios and after considering transaction and custody costs.Esta dissertação analisa a rendibilidade das estratégias momentum e contrarian na bolsa portuguesa (PSI) no período de 1997 a 2008. Estuda também a possibilidade de obter rendibilidades superiores extrapolando rendibilidades passadas. A estratégia momentum é baseada na hipótese da sub-reacção. Isto sugere que as acções que tenham tido melhores (piores) resultados num passado recente continuarão a ter melhores (piores) resultados num futuro próximo e, portanto, uma estratégia de investimento que compra acções vencedoras e vende as perdedoras, permitirão alcançar rendibilidades superiores. Por outro lado, a estratégia contrarian baseia-se na hipótese de sobre-reacção que assume o comportamento oposto da rendibilidade das acções e, consequentemente, recomenda a compra das perdedoras e a venda das vencedoras. As estratégias de curto prazo demonstram a rentabilidade das estratégias momentum, apoiando a hipótese da sub-reacção. Os resultados obtidos para períodos longos evidenciam uma rentabilidade considerável das estratégias contrarian (e da sobre-reacção), mas não tão evidente. Uma estratégia “inovadora” foi desenvolvida, permitindo auferir lucros consideravelmente superiores aos obtidos com as estratégias momentum e contrarian. Esta pressupõe duas condições: caso as rendibilidades passadas nos dois períodos definidos precedendo o período de investimento forem iguais ou superiores às percentagens definidas, a acção é comprada, caso contrário, investimentos mais seguros são preferíveis, tais como, os depósitos (taxa de juro sem risco). Os resultados não são estatisticamente significativos mas são economicamente relevantes. Finalmente, os resultados são consistentes às alterações nos períodos de tempo, ao número de acções incluídas nos portfolios, e depois de considerados os custos de transacção e de custódia

    Heart disease detection using ECG lead I and multiple pattern recognition classifiers

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    ECG is an important tool to assist in heart diseases diagnosis. The works found in the literature have the common goal of discriminating between binary study groups, one pathological and one control, even when ECG records from patients diagnosed with several pathologies are available in the databases. This work proposes a method to detect ECG morphological features and to analyze the capacity of this ECG features to discriminate 28 pairs of study groups, combining 7 pathological groups and 1 control group, presented in the PTB Diagnostic ECG Database. For each pair, it was achieved an accuracy between 77.4% and 100%, with an average of 94%, using several pattern recognition classifiers.info:eu-repo/semantics/publishedVersio
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