868 resultados para forward path


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Includes bibliography.

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As capoeiras - áreas alteradas por ação antrópica que se encontram em estágios de regeneração espontânea de cobertura florestal - são componentes da paisagem rural de grande significado na Amazônia. No último Censo Agropecuário, as áreas de capoeira perfaziam 4,5 milhões de hectares em toda a Região Norte. Uma literatura crescentemente importante considera tais áreas proxy de economias rurais decadentes e insustentáveis, sobre as quais se ergue uma pecuária de corte eficiente e sustentável. Este artigo procura estabelecer os diferentes tipos de capoeira que se constatam na economia rural da Amazônia, associando-as às diferentes formas de produção, cujos sistemas se expressam dinamicamente como trajetórias tecnológicas concorrentes. A partir daí a) demonstra que parte dessas áreas resulta de mudanças positivas nos sistemas produtivos que produzem capoeiras com grande capacidade de regeneração – estando associada, portanto, a inovações relevantes para o desenvolvimento da Região numa perspectiva que incorpora critérios de sustentabilidade ambiental; b) demonstra que os tipos de capoeira que indicam degradação, pela baixa capacidade de regeneração, se associam à pecuária de corte, a qual na Região tem apresentado dificuldades estruturais de modernização técnica e c) indica que o ambiente institucional, favorecendo os sistemas que produzem capoeira degradada em detrimento daqueles que produzem capoeiras de rápida recomposição, podem aprisionar (levar a um lock-in) a economia agrária da região nas piores soluções, tanto econômica, quanto social e ecologicamente.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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In general, pattern recognition techniques require a high computational burden for learning the discriminating functions that are responsible to separate samples from distinct classes. As such, there are several studies that make effort to employ machine learning algorithms in the context of big data classification problems. The research on this area ranges from Graphics Processing Units-based implementations to mathematical optimizations, being the main drawback of the former approaches to be dependent on the graphic video card. Here, we propose an architecture-independent optimization approach for the optimum-path forest (OPF) classifier, that is designed using a theoretical formulation that relates the minimum spanning tree with the minimum spanning forest generated by the OPF over the training dataset. The experiments have shown that the approach proposed can be faster than the traditional one in five public datasets, being also as accurate as the original OPF. (C) 2014 Elsevier B. V. All rights reserved.

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This paper aims to contribute to the three-dimensional generalization of numerical prediction of crack propagation through the formulation of finite elements with embedded discontinuities. The analysis of crack propagation in two-dimensional problems yields lines of discontinuity that can be tracked in a relatively simple way through the sequential construction of straight line segments oriented according to the direction of failure within each finite element in the solid. In three-dimensional analysis, the construction of the discontinuity path is more complex because it requires the creation of plane surfaces within each element, which must be continuous between the elements. In the method proposed by Chaves (2003) the crack is determined by solving a problem analogous to the heat conduction problem, established from local failure orientations, based on the stress state of the mechanical problem. To minimize the computational effort, in this paper a new strategy is proposed whereby the analysis for tracking the discontinuity path is restricted to the domain formed by some elements near the crack surface that develops along the loading process. The proposed methodology is validated by performing three-dimensional analyses of basic problems of experimental fractures and comparing their results with those reported in the literature.

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This paper introduces the Optimum-Path Forest (OPF) classifier for static video summarization, being its results comparable to the ones obtained by some state-of-the-art video summarization techniques. The experimental section has been conducted using several image descriptors in two public datasets, followed by an analysis of OPF robustness regarding one ad-hoc parameter. Future works are guided to improve OPF effectiveness on each distinct video category.

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In Computer-Aided Diagnosis-based schemes in mammography analysis each module is interconnected, which directly affects the system operation as a whole. The identification of mammograms with and without masses is highly needed to reduce the false positive rates regarding the automatic selection of regions of interest for further image segmentation. This study aims to evaluate the performance of three techniques in classifying regions of interest as containing masses or without masses (without clinical findings), as well as the main contribution of this work is to introduce the Optimum-Path Forest (OPF) classifier in this context, which has never been done so far. Thus, we have compared OPF against with two sorts of neural networks in a private dataset composed by 120 images: Radial Basis Function and Multilayer Perceptron (MLP). Texture features have been used for such purpose, and the experiments have demonstrated that MLP networks have been slightly better than OPF, but the former is much faster, which can be a suitable tool for real-time recognition systems.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Image categorization by means of bag of visual words has received increasing attention by the image processing and vision communities in the last years. In these approaches, each image is represented by invariant points of interest which are mapped to a Hilbert Space representing a visual dictionary which aims at comprising the most discriminative features in a set of images. Notwithstanding, the main problem of such approaches is to find a compact and representative dictionary. Finding such representative dictionary automatically with no user intervention is an even more difficult task. In this paper, we propose a method to automatically find such dictionary by employing a recent developed graph-based clustering algorithm called Optimum-Path Forest, which does not make any assumption about the visual dictionary's size and is more efficient and effective than the state-of-the-art techniques used for dictionary generation.