998 resultados para Longest path


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Many European and American observers of the EC have criticized "intergovemmentalist" ac­ counts for exaggerating the extent of member state control over the process of European integra­ tion. This essay seeks to ground these criticisms in a "historical institutionalist" account that stresses the need to study European integration as a political process which unfolds over time. Such a perspective highlights the limits of member-state control over long-term institutional de­ velopment, due to preoccupation with shorHerm concerns, the ubiquity of unintended conse­ quences, and processes that "lock in" past decusions and make reassertions of member-state control difficult. Brief examination of the evolution of social policy in the EC suggests the limita­ tions of treating the EC as an international regime facilitating collective action among essentially sovereign states. It is ore useful to view integration as a "path-dependent" process that has pro­ duced a fragmented but still discernible "multitiered" European polity.

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In less than one year, the country-led exercise in preparing Intended Nationally Determined Contributions (INDCs) has accomplished what the top-down approach characteristic of the UNFCCC has not been able to achieve in over 21 years of negotiations, namely to produce a sound agreement to reduce climate change. As such, the UNFCCC should adopt a new process similar to that used in developing the INDCs, in which Parties to the Convention would mobilise their national efforts, but on a wider scale and under certain agreed binding conditions. To ensure a comprehensive engagement, this Policy Brief recommends the introduction of a four-tier system in which the most developed nations called upon to take the lead, but with the very least developed nations also contributing to the intended UN objective.

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Gradient-domain path tracing has recently been introduced as an efficient realistic image synthesis algorithm. This paper introduces a bidirectional gradient-domain sampler that outperforms traditional bidirectional path tracing often by a factor of two to five in terms of squared error at equal render time. It also improves over unidirectional gradient-domain path tracing in challenging visibility conditions, similarly as conventional bidirectional path tracing improves over its unidirectional counterpart. Our algorithm leverages a novel multiple importance sampling technique and an efficient implementation of a high-quality shift mapping suitable for bidirectional path tracing. We demonstrate the versatility of our approach in several challenging light transport scenarios.

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Identifying cloud interference in satellite-derived data is a critical step toward developing useful remotely sensed products. Most MODIS land products use a combination of the MODIS (MOD35) cloud mask and the 'internal' cloud mask of the surface reflectance product (MOD09) to mask clouds, but there has been little discussion of how these masks differ globally. We calculated global mean cloud frequency for both products, for 2009, and found that inflated proportions of observations were flagged as cloudy in the Collection 5 MOD35 product. These erroneously categorized areas were spatially and environmentally non-random and usually occurred over high-albedo land-cover types (such as grassland and savanna) in several regions around the world. Additionally, we found that spatial variability in the processing path applied in the Collection 5 MOD35 algorithm affects the likelihood of a cloudy observation by up to 20% in some areas. These factors result in abrupt transitions in recorded cloud frequency across landcover and processing-path boundaries impeding their use for fine-scale spatially contiguous modeling applications. We show that together, these artifacts have resulted in significantly decreased and spatially biased data availability for Collection 5 MOD35-derived composite MODIS land products such as land surface temperature (MOD11) and net primary productivity (MOD17). Finally, we compare our results to mean cloud frequency in the new Collection 6 MOD35 product, and find that landcover artifacts have been reduced but not eliminated. Collection 6 thus increases data availability for some regions and land cover types in MOD35-derived products but practitioners need to consider how the remaining artifacts might affect their analysis.

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Includes index.

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Includes index.

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Mode of access: Internet.

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"Jacket design by Ronald Fratell" -- Rear flap of dust jacket.