19 research outputs found

    Technology as a tool to understand sampling in binomial distributions

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    In this paper we describe some recurrent errors related to the work with sampling distributions, a topic which is compulsory in Spain for high school students. We additionally suggest how the sampling distribution for the mean and the range of samples taken from the binomial distribution, can be simulated using the software Fathom. Therefore, students can investigate these simulations with different values of the parameters for the binomial distribution and different sample sizes to understand properties of representativeness and variability of the sampling distribution and to discriminate the three types of distributions involved in sampling

    A remote sensing approach for regional-scale mapping of agricultural land-use systems based on NDVI time series.

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    In response to the need for generic remote sensing tools to support large-scale agricultural monitoring, we present a new approach for regional-scale mapping of agricultural land-use systems (ALUS) based on object-based Normalized Difference Vegetation Index (NDVI) time series analysis. The approach consists of two main steps. First, to obtain relatively homogeneous land units in terms of phenological patterns, a principal component analysis (PCA) is applied to an annual MODIS NDVI time series, and an automatic segmentation is performed on the resulting high-order principal component images. Second, the resulting land units are classified into the crop agriculture domain or the livestock domain based on their land-cover characteristics. The crop agriculture domain land units are further classified into different cropping systems based on the correspondence of their NDVI temporal profiles with the phenological patterns associated with the cropping systems of the study area. A map of the main ALUS of the Brazilian state of Tocantins was produced for the 2013-2014 growing season with the new approach, and a significant coherence was observed between the spatial distribution of the cropping systems in the final ALUS map and in a reference map extracted from the official agricultural statistics of the Brazilian Institute of Geography and Statistics (IBGE). This study shows the potential of remote sensing techniques to provide valuable baseline spatial information for supporting agricultural monitoring and for large-scale land-use systems analysis

    Crystal structure and local ordering in epitaxial Fe100x_{100-x}Gax_x/MgO(001) films

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    In this work we present a study of the structural properties of Fe100x_{100-x} Gax_x grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption spectroscopy) together with real space imaging by means of Transmission Electron Microscopy and surface sensitive insituin situ Reflected High Energy Electron Diffraction. For substrate temperature TsT_s below 400 o^oC we obtain bccbcc films while, for xx \approx 24 and TsT_s \geq 400o^oC the nucleation of the fccfcc phase is observed. For both systems a Ga anticlustering or local range ordering phenomenon appears. The Ga/Fe composition in the first and second coordination shells of the bccbcc films is different from that expected for a random Ga distribution and is close to a D03_3-like ordered phase, leading to a minimization of the number of Ga-Ga pairs. On the other side, a true long-range D03_3 phase is not observed indicating that atomic ordering only occurs at a local scale. Overall, the epitaxial growth procedure presented in this work, first, avoids the formation of a long range ordered D03_3 phase, which is known to be detrimental magnetostrictive properties, and second, demonstrates the possibility of growing fccfcc films at temperatures much smaller than those required to obtain bulk fccfcc samples.Comment: 21 pages, 7 figure

    Sensoriamento remoto e análise espacial: uma contribuição para o mapeamento dos sistemas integrados de produção agropecuária.

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    No ano de 2009, o Governo do Brasil apresentou o Plano de Agricultura de Baixa Emissão de Carbono, cujo objetivo é a organização de ações para a adoção de tecnologias de produção de alimentos alinhadas aos compromissos de redução de emissões de GEE. Entre diversas práticas destaca-se a implementação da integração lavoura-pecuária (iLP). No entanto, a falta de procedimentos de monitoramento limita a governança do Plano. Os sistemas iLP podem ser adotados em duas abordagens distintas: Inter-anual e intra-anual. Este artigo tem como objetivo utilizar dados provenientes de sensoriamento remoto para identificar áreas de iLP na abordagem interanual no estado do Mato Grosso, na contribuição de um protocolo de monitoramento. Com o resultado, identificou-se que a implantação dos iLP tem seu auge em 2016 quando chega a 5% de toda área de agricultura e pecuária do estado do Mato Grosso

    Existence of a Meromorphic Extension of Spectral Zeta Functions on Fractals

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    We investigate the existence of the meromorphic extension of the spectral zeta function of the Laplacian on self-similar fractals using the classical results of Kigami and Lapidus (based on the renewal theory) and new results of Hambly and Kajino based on the heat kernel estimates and other probabilistic techniques. We also formulate conjectures which hold true in the examples that have been analyzed in the existing literature

    Crystal structure and local ordering in epitaxial Fe1 00−xGax/MgO (001) films

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    Resumen del póster presentado al Microscopy at the Frontiers of Science Congress Series (MFS), celebrado en el Parque de las Ciencias de Granada (España) del 11 al 13 de septiembre de 2019.Iron-gallium alloys (Fe100−xGax) have become an important material for magnetostrictive applications because of their large tetragonal magnetostriction at low field for alloys around 18.4 % Ga, whereas, at the same time, they provide good corrosion resistance and mechanical hardness. Large magnetoelastic (ME) coupling is a rewarding property in thin films and patterned elements, as the ME anisotropy can control the orientation of the magnetization M. Epitaxial Fe100−xGax thin films have shown a remarkable potential for microwave and energy conversion applications, by using a piezoelectric layer to control the magnetic anisotropy through the modification of the strain in the magnetic layer by means of an applied voltage. In this work we present a study of the structural properties of Fe100−x Gax (x<30) films grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption spectroscopy) together with real space imaging by means of Transmission Electron Microscopy and surface sensitive in situ Reflected High Energy Electron Diffraction. For substrate temperature Ts below 400ºC we obtain bcc films while, for x ≈ 24 and Ts ≥ 400ºC the nucleation of the fcc phase is observed. For both systems a Ga anticlustering or local range ordering phenomenon appears. The Ga/Fe composition in the first and second coordination shells of the bcc films is different from that expected for a random Ga distribution and is close to a D03 phase, leading to a minimization of the number Ga-Ga pairs. On the other side, a long-range D03 phase is not observed indicating that atomic ordering only occurs at a local scale. Overall, the epitaxial growth procedure presented in this work, first, avoids the formation of a long range ordered D03 phase, which is known to be detrimental for magnetostrictive properties, and second, demonstrates the possibility of growing fcc films at temperatures much lower than those required to obtain bulk fcc samples.Peer reviewe

    Data from: Post K-Pg diversification of the mammalian order Eulipotyphla as suggested by phylogenomic analyses of ultra-conserved elements

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    The origin of the mammalian order Eulipotyphla has been debated intensively with arguments around whether they began diversifying before or after the Cretaceous-Palaeogene (K-Pg) boundary at 66 Ma. Here, we used an in-solution nucleotide capture method and next generation DNA sequencing to determine the sequence of hundreds of ultra-conserved elements (UCEs), and conducted phylogenomic and molecular dating analyses for the four extant eulipotyphlan lineages—Erinaceidae, Solenodontidae, Soricidae, and Talpidae. Concatenated maximum-likelihood analyses with single or partitioned models and a coalescent species-tree analysis showed that divergences among the four major eulipotyphlan lineages occurred within a short period of evolutionary time, but did not resolve the interrelationships among them. Alternative suboptimal phylogenetic hypotheses received consistently the same amount of support from different UCE loci, and were not significantly different from the maximum likelihood tree topology, suggesting the prevalence of stochastic lineage sorting. Molecular dating analyses that incorporated among-lineage evolutionary rate differences supported a scenario where the four eulipotyphlan families diversified between 57.8 and 63.2 Ma. Given short branch lengths with low support values, traces of rampant genome-wide stochastic lineage sorting, and post K-Pg diversification, we concluded that the crown eulipotyphlan lineages arose through a rapid diversification after the K-Pg boundary when novel niches were created by the mass extinction of species
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