841 resultados para Hausdorff Distance
Repeated, long-distance migrations by a philopatric predator targeting highly contrasting ecosystems
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Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier, we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals, and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.
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A large, pregnant, female bull shark Carcharhinus leucas was tracked migrating from Seychelles across open ocean to south-east Madagascar, c. 2000 km away, and back again. In Madagascar, the shark spent a prolonged period shallower than 5 m, consistent with entering estuarine habitat to pup, and upon return to Seychelles the shark was slender and no longer gravid. This represents an unprecedented return migration across the open ocean for a C. leucas and highlights the need for international collaboration to manage the regional C. leucas population sustainably.
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A large, pregnant, female bull shark Carcharhinus leucas was tracked migrating from Seychelles across open ocean to south-east Madagascar, c. 2000 km away, and back again. In Madagascar, the shark spent a prolonged period shallower than 5 m, consistent with entering estuarine habitat to pup, and upon return to Seychelles the shark was slender and no longer gravid. This represents an unprecedented return migration across the open ocean for a C. leucas and highlights the need for international collaboration to manage the regional C. leucas population sustainably.
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For the official publication, see: http://dx.doi.org/10.1016/j.lindif.2016.06.021
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We propose a novel skeleton-based approach to gait recognition using our Skeleton Variance Image. The core of our approach consists of employing the screened Poisson equation to construct a family of smooth distance functions associated with a given shape. The screened Poisson distance function approximation nicely absorbs and is relatively stable to shape boundary perturbations which allows us to define a rough shape skeleton. We demonstrate how our Skeleton Variance Image is a powerful gait cycle descriptor leading to a significant improvement over the existing state of the art gait recognition rate.
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Based on optical imaging and spectroscopy of the Type II-Plateau SN 2013eq, we present a comparative study of commonly used distance determination methods based on Type II supernovae. The occurrence of SN 2013eq in the Hubble flow (z = 0.041 ± 0.001) prompted us to investigate the implications of the difference between "angular" and "luminosity" distances within the framework of the expanding photosphere method (EPM) that relies upon a relation between flux and angular size to yield a distance. Following a re-derivation of the basic equations of the EPM for SNe at non-negligible redshifts, we conclude that the EPM results in an angular distance. The observed flux should be converted into the SN rest frame and the angular size, θ, has to be corrected by a factor of (1 + z)2. Alternatively, the EPM angular distance can be converted to a luminosity distance by implementing a modification of the angular size. For SN 2013eq, we find EPM luminosity distances of DL = 151 ± 18 Mpc and DL = 164 ± 20 Mpc by making use of different sets of dilution factors taken from the literature. Application of the standardized candle method for Type II-P SNe results in an independent luminosity distance estimate (DL = 168 ± 16 Mpc) that is consistent with the EPM estimate. Spectra of SN 2013eq are available in the Weizmann Interactive Supernova data REPository (WISeREP): http://wiserep.weizmann.ac.il
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Explores the relationship of landscape to personal meaning
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Thesis (Master's)--University of Washington, 2016-08
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The distance learning program "School Management" supports decision makers at the school and ministerial levels in the shaping of formal and informal learning processes at different levels in schools and curricula in Eritrea. This paper examines how the distance learning program is interconnected to educational system development. (DIPF/Orig.)
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This paper revisits strongly-MDS convolutional codes with maximum distance profile (MDP). These are (non-binary) convolutional codes that have an optimum sequence of column distances and attains the generalized Singleton bound at the earliest possible time frame. These properties make these convolutional codes applicable over the erasure channel, since they are able to correct a large number of erasures per time interval. The existence of these codes have been shown only for some specific cases. This paper shows by construction the existence of convolutional codes that are both strongly-MDS and MDP for all choices of parameters.
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[...] D'une façon globale, il semble donc exister trois grandes tendances dans le domaine de la formation : 1. une personnalisation de la formation pour l'apprenant ; 2. un rapprochement de la formation vers l'étudiant ; 3. une individualisation de la formation. On entend par personnalisation de la formation le fait que le contenu des cours est de plus en plus adapté aux caractéristiques propres des groupes visés et à leurs besoins. Le rapprochement de la formation vers l'étudiant signifie que plus que jamais, on tente de déplacer la formation vers l'apprenant plutôt que de déplacer celui-ci vers une classe qui ne reflète pas son milieu de travail. Quant à l'individualisation de la formation, cela veut dire que l'étudiant aura, dans un avenir proche, un accès de plus en plus individuel à la formation ; il pourra communiquer avec le formateur lorsqu'il désirera obtenir sa formation. La mise sur pied de centres de formation utilisant la vidéoconférence en salle comme outil de communication par des établissements d'enseignement, tels que l'Université du Tennessee (14 sites de vidéoconférence), le consortium d'éducation de l'Illinois de l'ouest (29 sites), l'école Escambia du comté d'Escambia en Floride (8 sites) et l'Université du Kentucky (7 sites) aux États-Unis, confirment ou nous incitent à croire que ces tendances sont fondées. Ainsi, devant ces nouvelles possibilités et réalités, les entreprises et les établissements d'enseignement doivent réévaluer leurs méthodes de formation à distance. La formation à distance peut-elle bénéficier de ces développements technologiques ? Pourrait-elle utiliser un outil de communication telle que la vidéoconférence pour dispenser des programmes de formation à distance ? Il apparaît donc qu'il faut évaluer la possibilité d'employer la vidéoconférence en salle pour dispenser des programmes de formation à distance.