949 resultados para Symbolic Computation


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In a world that has moved away from narratives based on the idea of progress, the past has established itself as a place of reference: confirming to ourselves that what we were is indispensible for sustaining what we think we are. The recovery of the past is thus one of the most common symbolic instruments used in negotiating identities. The cultural practices that have recourse to representation mechanisms that call on the past in order to consider the present always end up translating themselves, insofar as they fragment, reorganize and interpret it in their transformation, or, to use a formula that has become unavoidable, in their “invention”. Patrimonialization is one such practice. It associates the notion of heritage – which is not a given fact, but rather a socially constructed classification, and therefore one that is constantly being negotiated – with specific objects that come to serve as cultural representations of the groups who consider themselves to be their rightful owners. In the Lisbon Metropolitan Area, as in other ethnographic contexts, patrimonialization encompasses things as diverse as landscapes, monuments, popular architecture, handicrafts, local feast days/processions/pilgrimages and people; all things that can, once transformed into material representations of the past, serve as arguments for the identity fictions of the people who inhabit them.

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Diffusion Kurtosis Imaging (DKI) is a fairly new magnetic resonance imag-ing (MRI) technique that tackles the non-gaussian motion of water in biological tissues by taking into account the restrictions imposed by tissue microstructure, which are not considered in Diffusion Tensor Imaging (DTI), where the water diffusion is considered purely gaussian. As a result DKI provides more accurate information on biological structures and is able to detect important abnormalities which are not visible in standard DTI analysis. This work regards the development of a tool for DKI computation to be implemented as an OsiriX plugin. Thus, as OsiriX runs under Mac OS X, the pro-gram is written in Objective-C and also makes use of Apple’s Cocoa framework. The whole program is developed in the Xcode integrated development environ-ment (IDE). The plugin implements a fast heuristic constrained linear least squares al-gorithm (CLLS-H) for estimating the diffusion and kurtosis tensors, and offers the user the possibility to choose which maps are to be generated for not only standard DTI quantities such as Mean Diffusion (MD), Radial Diffusion (RD), Axial Diffusion (AD) and Fractional Anisotropy (FA), but also DKI metrics, Mean Kurtosis (MK), Radial Kurtosis (RK) and Axial Kurtosis (AK).The plugin was subjected to both a qualitative and a semi-quantitative analysis which yielded convincing results. A more accurate validation pro-cess is still being developed, after which, and with some few minor adjust-ments the plugin shall become a valid option for DKI computation

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Throughout the brain, patterns of activity in postsynaptic neurons influence the properties of synaptic inputs. Such feedback regulation is central to neural network stability that underlies proper information processing and feature representation in the central nervous system. At the cellular level, tight coupling of presynaptic and postsynaptic function is fundamental to neural computation and synaptic plasticity. The cohort of protein complexes at the pre and postsynaptic membrane allows for tight synapse-specific segregation and integration of diverse molecular and electrical signals.(...)

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The computational power is increasing day by day. Despite that, there are some tasks that are still difficult or even impossible for a computer to perform. For example, while identifying a facial expression is easy for a human, for a computer it is an area in development. To tackle this and similar issues, crowdsourcing has grown as a way to use human computation in a large scale. Crowdsourcing is a novel approach to collect labels in a fast and cheap manner, by sourcing the labels from the crowds. However, these labels lack reliability since annotators are not guaranteed to have any expertise in the field. This fact has led to a new research area where we must create or adapt annotation models to handle these weaklylabeled data. Current techniques explore the annotators’ expertise and the task difficulty as variables that influences labels’ correction. Other specific aspects are also considered by noisy-labels analysis techniques. The main contribution of this thesis is the process to collect reliable crowdsourcing labels for a facial expressions dataset. This process consists in two steps: first, we design our crowdsourcing tasks to collect annotators labels; next, we infer the true label from the collected labels by applying state-of-art crowdsourcing algorithms. At the same time, a facial expression dataset is created, containing 40.000 images and respective labels. At the end, we publish the resulting dataset.

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Since the invention of photography humans have been using images to capture, store and analyse the act that they are interested in. With the developments in this field, assisted by better computers, it is possible to use image processing technology as an accurate method of analysis and measurement. Image processing's principal qualities are flexibility, adaptability and the ability to easily and quickly process a large amount of information. Successful examples of applications can be seen in several areas of human life, such as biomedical, industry, surveillance, military and mapping. This is so true that there are several Nobel prizes related to imaging. The accurate measurement of deformations, displacements, strain fields and surface defects are challenging in many material tests in Civil Engineering because traditionally these measurements require complex and expensive equipment, plus time consuming calibration. Image processing can be an inexpensive and effective tool for load displacement measurements. Using an adequate image acquisition system and taking advantage of the computation power of modern computers it is possible to accurately measure very small displacements with high precision. On the market there are already several commercial software packages. However they are commercialized at high cost. In this work block-matching algorithms will be used in order to compare the results from image processing with the data obtained with physical transducers during laboratory load tests. In order to test the proposed solutions several load tests were carried out in partnership with researchers from the Civil Engineering Department at Universidade Nova de Lisboa (UNL).

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Dissertação de Mestrado apresentada ao ISPA - Instituto Universitário

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Dissertação de Mestrado apresentada no Instituto Superior de Psicologia Aplicada para obtenção do grau de Mestre na especialidade de Psicologia Clínica.

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Fado was listed as UNESCO Intangible Cultural Heritage in 2011. This dissertation describes a theoretical model, as well as an automatic system, able to generate instrumental music based on the musics and vocal sounds typically associated with fado’s practice. A description of the phenomenon of fado, its musics and vocal sounds, based on ethnographic, historical sources and empirical data is presented. The data includes the creation of a digital corpus, of musical transcriptions, identified as fado, and statistical analysis via music information retrieval techniques. The second part consists in the formulation of a theory and the coding of a symbolic model, as a proof of concept, for the automatic generation of instrumental music based on the one in the corpus.

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This Work Project analyzes the evolution of the Portuguese personal income tax system’s progressivity over the period of 2005 through 2013. It presents the first computation of cardinal progressivity measures using administrative tax data for Portugal. We compute several progressivity indices and find that progressivity has had very modest variations from 2005 to 2012, whilst from 2012 to 2013 there has been a relatively stronger decrease, excluding the impact of the income tax surcharge of the years 2012 and 2013. When this latter is included, progressivity of 2012 and 2013 decreases considerably. Analyzing the effective average tax rates of the top income percentiles in the income scale, we find that these rates have increased over the period 2010–2013, suggesting that an analysis of effective tax rates is insufficient to assess progressivity in the whole tax scheme.

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This work presents research conducted to understand the role of indicators in decisions of technology innovation. A gap was detected in the literature of innovation and technology assessment about the use and influence of indicators in this type of decision. It was important to address this gap because indicators are often frequent elements of innovation and technology assessment studies. The research was designed to determine the extent of the use and influence of indicators in decisions of technology innovation, to characterize the role of indicators in these decisions, and to understand how indicators are used in these decisions. The latter involved the test of four possible explanatory factors: the type and phase of decision, and the context and process of construction of evidence. Furthermore, it focused on three Portuguese innovation groups: public researchers, business R&D&I leaders and policymakers. The research used a combination of methods to collect quantitative and qualitative information, such as surveys, case studies and social network analysis. This research concluded that the use of indicators is different from their influence in decisions of technology innovation. In fact, there is a high use of indicators in these decisions, but lower and differentiated differences in their influence in each innovation group. This suggests that political-behavioural methods are also involved in the decisions to different degrees. The main social influences in the decisions came mostly from hierarchies, knowledge-based contacts and users. Furthermore, the research established that indicators played mostly symbolic roles in decisions of policymakers and business R&D&I leaders, although their role with researchers was more differentiated. Indicators were also described as helpful instruments to conduct a reasonable interpretation of data and to balance options in innovation and technology assessments studies, in particular when contextualised, described in detail and with discussion upon the options made. Results suggest that there are four main explanatory factors for the role of indicators in these decisions: First, the type of decision appears to be a factor to consider when explaining the role of indicators. In fact, each type of decision had different influences on the way indicators are used, and each type of decision used different types of indicators. Results for policy-making were particularly different from decisions of acquisition and development of products/technology. Second, the phase of the decision can help to understand the role indicators play in these decisions. Results distinguished between two phases detected in all decisions – before and after the decision – as well as two other phases that can be used to complement the decision process and where indicators can be involved. Third, the context of decision is an important factor to consider when explaining the way indicators are taken into consideration in policy decisions. In fact, the role of indicators can be influenced by the particular context of the decision maker, in which all types of evidence can be selected or downplayed. More importantly, the use of persuasive analytical evidence appears to be related with the dispute existent in the policy context. Fourth and last, the process of construction of evidence is a factor to consider when explaining the way indicators are involved in these decisions. In fact, indicators and other evidence were brought to the decision processes according to their availability and capacity to support the different arguments and interests of the actors and stakeholders. In one case, an indicator lost much persuasion strength with the controversies that it went through during the decision process. Therefore, it can be argued that the use of indicators is high but not very influential; their role is mostly symbolic to policymakers and business decisions, but varies among researchers. The role of indicators in these decisions depends on the type and phase of the decision and the context and process of construction of evidence. The latter two are related to the particular context of each decision maker, the existence of elements of dispute and controversies that influence the way indicators are introduced in the decision-making process.

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As potencialidades da plataforma continental estendida são enormes e variadas, desde as que podem ser obtidas através de sectores tradicionais – como portos e marinas ou turismo náutico – até as que advirão de novos sectores como a exploração dos fundos do mar ou a energia das ondas, entre outras. Com efeito, devido ao alargamento resultante das negociações nas Nações Unidas, é praticamente garantido que Portugal passe a controlar um espaço marítimo, acrescido de 2.1 milhões de km2, isto é, vinte vezes a extensão da sua superfície terrestre. A maritimidade de Portugal constitui um traço profundamente marcado na sua história, bem como nas suas tradicionais práticas económicas, sociais e simbólicas. Na verdade, os últimos anos testemunharam a criação de um amplo consenso quanto ao papel determinante que o desenvolvimento costeiro, a superfície e o comprimento dos limites do “Mar Português” terá no futuro do país. Da articulação entre o Território Nacional, o Oceano Atlântico e o Continente Europeu, associada à confluência das vias de comunicação marítimas que ligam a Europa à América do Norte e do Sul configurar-e-ão os aspectos essenciais do designado “Espaço Estratégico de Interesse Nacional Permanente”. A área geográfica prioritária para o desenvolvimento das acções militares de Defesa Nacional e dos interesses vitais permanentes inclui assim – para além do Território Nacional – o Espaço Interterritorial, o Mar Territorial (MT), o espaço aéreo sob responsabilidade nacional e a Zona Económica Exclusiva (ZEE). O País é titular de soberania no território continental e nos arquipélagos da Madeira dos Açores, para além de estar comprometido com alguns Estados da CPLP, que têm no Atlântico Sul uma importante e poderosa presença. Pela geografia e pela definição dos interesses dos Estados e dos grandes espaços em que estão incluídos, Portugal está na articulação da segurança do Atlântico Norte com a segurança do Atlântico Sul. Esta realidade acarreta novos desafios para a Defesa Nacional, assumindo como preocupações acrescidas o terrorismo, o tráfico e a pirataria marítimas, entre outras.

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Esta pesquisa foca-se na comunidade imigrante portuguesa em Macau e na comunidade imigrante nepalesa em Portugal. Analisa os usos dos média – étnicos, mainstream e transnacionais - por imigrantes durante o processo de integração: na manutenção de laços com o país de origem e na adaptação à sociedade de acolhimento, em que a língua de acolhimento assume um papel crucial. A investigação enquadra-se nos estudos de audiências e baseia-se na teoria dos Usos e Gratificações dos Média (Katz, Blumler, & Gurevitch, 1974). No que respeita à integração assenta no modelo de estratégias de aculturação de Berry & Sam (2001, 2006). Quanto à língua, assenta na teoria do poder e da prática de Bourdieu (1991), especificamente na parte relativa ao poder simbólico da língua. Quanto à metodologia, foram realizadas oito entrevistas em profundidade na comunidade nepalesa e 29 entrevistas na comunidade portuguesa. A amostra foi de conveniência e teoricamente sustentada. A seguir às entrevistas, foi feita uma análise de conteúdo individual e transversal. Esta tese pretende contribuir para o enriquecimento de linhas de investigação sobre audiências activas dos média. Poderá servir de fonte de informação para políticas relacionadas com a integração de imigrantes, nomeadamente, para reformulação de políticas relacionadas com os média e com a língua de acolhimento. No caso de empresas de comunicação, a informação obtida poderá ser útil para adaptarem melhor os seus conteúdos a este público específico.

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Crowdfunding, as we know it today, is a very recent activity that was born almost accidentally in the end of the 90’s decade. Due to the advent of the internet and the social networks, entrepreneurs are now able to promote their projects to a very large community. Whether it is composed by family, friends, acquaintances or simply people that are interested in the same topic or share the passion, the community is able to fund new ventures by individually investing modest amounts of money. In return, the entrepreneur can offer symbolic rewards, shares or other financial returns. New crowdfunding platforms are born almost every day all over the world, offering a new way of raising capital for their projects or a new way to invest their money in innovative ventures. Although crowdfunding is still finding its place in the financial services, successful cases such as Kickstarter demonstrate the power of the crowd in boosting creativity and productivity, financing thousands of projects by raising millions of dollars from thousands of investors. Due to regulatory restrictions, the most prominent model for now is reward-based crowdfunding, where the investors are prized with symbolic returns or privileged access to the products or services offered by the entrepreneurs. Other models such as peer-to-peer lending are also surging, allowing borrowers access to capital at a lower cost compared to so-called traditional financial institutions, and offering lenders a higher rate of return. But when it comes to offering shares to investors, i.e. using equity-based crowdfunding, entrepreneurs face regulatory obstacles in almost every country, where legislation was passed decades ago with the objective of promoting financially-capable ventures and protecting investors. Access to capital has become more difficult after the global economic recession of 2008, and for most countries it will not get easier in the near future, leaving start-ups and small enterprises with few options to start or expand their operations. In this study we attempt to answer the following research questions: how has equity-based crowdfunding evolved since its creation? Where and how has equity-based crowdfunding been implemented so far? What are the constraints and opportunities for implementing equity-crowdfunding in the world, and more particularly in Portugal? Finally, we will discuss the risks of crowdfunding and reflect on the future of this industry.

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This work presents a model and a heuristic to solve the non-emergency patients transport (NEPT) service issues given the new rules recently established in Portugal. The model follows the same principle of the Team Orienteering Problem by selecting the patients to be included in the routes attending the maximum reduction in costs when compared with individual transportation. This model establishes the best sets of patients to be transported together. The model was implemented in AMPL and a compact formulation was solved using NEOS Server. A heuristic procedure based on iteratively solving problems with one vehicle was presented, and this heuristic provides good results in terms of accuracy and computation time.

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This work presents an improved model to solve the non-emergency patients transport (NEPT) service issues given the new rules recently established in Portugal. The model follows the same principle of the Team Orienteering Problem by selecting the patients to be included in the routes attending the maximum reduction in costs when compared with individual transportation. This model establishes the best sets of patients to be transported together. The model was implemented in AMPL and a compact formulation was solved using NEOS Server. A heuristic procedure based on iteratively solving Orienteering Problems is presented, and this heuristic provides good results in terms of accuracy and computation time. Euclidean instances as well as asymmetric real data gathered from Google maps were used, and the model has a promising performance mainly with asymmetric cost matrices.