635 resultados para Percolação por invasão


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Essa pesquisa bibliográfica e empírica teve como objetivo analisar livros didáticos de História elaborados para 6ªs séries do ensino fundamental utilizados em uma escola estadual de nome fictício Monte Alto, situada no Extremo Leste de São Paulo e uma escola municipal de nome fictício Morro da Cruz localizada em um bairro da Zona Leste de São Paulo. Durante a construção desse trabalho, pretendeu-se fazer uma leitura de manuais escolares de História, objetivando compreender como a invasão holandesa é abordada nos materiais didáticos. Além dos materiais das escolas estadual e municipal, foram analisados três compêndios do século XIX cujos autores são José Inácio de Abreu e Lima, Francisco Adolfo de Varnhagen e Joaquim Manoel de Macedo, também materiais didáticos de dois autores do século XX, Joaquim Silva e Sérgio Buarque de Holanda. Buscou-se, ainda, evidenciar qual trajetória o livro didático percorre da produção editorial até a distribuição aos destinatários finais, alunos e professores, a partir das contribuições de Circe Bittencourt, Kazumi Munakata e outros referenciais teóricos. Em suma, esse trabalho tencionou responder como os textos didáticos abordam a invasão holandesa e como esse tema é apropriado pelo alunado e docentes. Por meio de estudo de caso, foram analisadas as representações de dois grupos específicos alunos e professores da escola Monte Alto e da escola Morro da Cruz sobre a invasão holandesa, à luz das orientações teóricas de Roger Chartier.

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Various physical systems have dynamics that can be modeled by percolation processes. Percolation is used to study issues ranging from fluid diffusion through disordered media to fragmentation of a computer network caused by hacker attacks. A common feature of all of these systems is the presence of two non-coexistent regimes associated to certain properties of the system. For example: the disordered media can allow or not allow the flow of the fluid depending on its porosity. The change from one regime to another characterizes the percolation phase transition. The standard way of analyzing this transition uses the order parameter, a variable related to some characteristic of the system that exhibits zero value in one of the regimes and a nonzero value in the other. The proposal introduced in this thesis is that this phase transition can be investigated without the explicit use of the order parameter, but rather through the Shannon entropy. This entropy is a measure of the uncertainty degree in the information content of a probability distribution. The proposal is evaluated in the context of cluster formation in random graphs, and we apply the method to both classical percolation (Erd¨os- R´enyi) and explosive percolation. It is based in the computation of the entropy contained in the cluster size probability distribution and the results show that the transition critical point relates to the derivatives of the entropy. Furthermore, the difference between the smooth and abrupt aspects of the classical and explosive percolation transitions, respectively, is reinforced by the observation that the entropy has a maximum value in the classical transition critical point, while that correspondence does not occurs during the explosive percolation.

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Various physical systems have dynamics that can be modeled by percolation processes. Percolation is used to study issues ranging from fluid diffusion through disordered media to fragmentation of a computer network caused by hacker attacks. A common feature of all of these systems is the presence of two non-coexistent regimes associated to certain properties of the system. For example: the disordered media can allow or not allow the flow of the fluid depending on its porosity. The change from one regime to another characterizes the percolation phase transition. The standard way of analyzing this transition uses the order parameter, a variable related to some characteristic of the system that exhibits zero value in one of the regimes and a nonzero value in the other. The proposal introduced in this thesis is that this phase transition can be investigated without the explicit use of the order parameter, but rather through the Shannon entropy. This entropy is a measure of the uncertainty degree in the information content of a probability distribution. The proposal is evaluated in the context of cluster formation in random graphs, and we apply the method to both classical percolation (Erd¨os- R´enyi) and explosive percolation. It is based in the computation of the entropy contained in the cluster size probability distribution and the results show that the transition critical point relates to the derivatives of the entropy. Furthermore, the difference between the smooth and abrupt aspects of the classical and explosive percolation transitions, respectively, is reinforced by the observation that the entropy has a maximum value in the classical transition critical point, while that correspondence does not occurs during the explosive percolation.

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Resumo: Em virtude dos impactos ambientais causados, as espécies exóticas invasoras (EEl's) tem se tornado foco de muitos estudos nas Ciências Biológicas. Entretanto, muitas EEl's tem a sua presença não evitada em novos ambientes, pois o homem e, muitas vezes, o principal vetor de dispersão, especial mente de espécies de plantas invasoras. Neste trabalho, e discutida a hipótese de uma forte influencia cultural na introdução/expansão da uva-do-Japão nesta região e o problemático cenário de invasão da espécie no sul do Brasil. Palavras-chave: espécies exóticas invasoras (EEl's); alteração da paisagem; Hovenia dulcis (uva-do-japão); cultura. Abstract: Invasive species (IS) have become focus on many studies in Biological Sciences because of environmental damages. However, the presence of lAS's is not prevented in new areas, because humans are often the main vector of dispersion, especially invasive plant species. In this work, the hypothesis of a strong cultural influence is discussed on the introduction/expansion of Japanese raisin tree in this region and the problematic scenario of invasion in southern Brazil. Keywords: invasive species (IS's); landscape changes; Hovenia dulcis ; (Japanese raisin tree); culture.