Estudo do fenômeno de exchange bias em estruturas de válvulas de spin

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Applying colorimetry for wood differentiation of fabaceae species grown in southern brazil

Because of the need for identification of forest species, especially for detection of illegal wood trade, the objective of this study was to evaluate the potential of colorimetry for differentiation of Inga vera Willd., Muellera campestris (Mart. ex Benth.) M.J. Silva & A.M.G. Azevedo and Machaerium paraguariense Hassl., species of the Fabaceae family, native to the Araucaria Forest in the state of Santa Catarina, southern Brazil. Discs at breast height were collected from three trees of each species and the colorimetric parameters (L*, a*, b*, C* and h) and visible spectra were evaluated in different radial position of the trunk (near bark, intermediate and near pith) and three different anatomical sections (transversal, radial and tangential surfaces). Mean values of hue angle (h) among the colorimetric parameters resulted in the highest potential for species discrimination. With respect to radial trunk position and anatomical section, parameters a* (green-red) and h were not statistically different, independent of the wood samples evaluated. For other parameters (L*, b* and C*), each species presented distinct results. Principal component analysis with second derivative of visible spectra discriminated all species. Colorimetry associated with chemometrics allowed to distinguish I. vera, M. campestris and M. paraguariense

Exchange bias em bicamadas magnética de CoPt/Cu/Co/Cu

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Estudo do comportamento magnético de filmes finos apresentando o fenômeno de exchange bias

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Wood colorimetry of lauraceae species native to Brazil

Considering the complexity and difficulty of identifying forest species, wooden disks were collected to verify the potential of colorimetry to distinguish native species from Araucaria Forest stands of the Lauraceae family. The following species were used: Nectandra megapotamica, Ocotea indecora, Ocotea diospyrifolia and Ocotea puberula. Nees, to provide data on these species that grow naturally in Santa Catarina state, southern Brazil, enriching a robust database that can be practically applied in the commercialization of native woods. Visible spectra and colorimetric parameters were obtained from each anatomical surface and the results were evaluated by comparing the mean of each species regarding radial trunk position and anatomical surface. The data were also submitted to principal component analysis and performance of discriminant models (k-NN, SVM and ANN) for species discrimination with raw and second-derivative data. In general, colorimetric data presented different behavior, and chromatic coordinates a* and b* had higher potential for distinguishing the species. According to the mean spectra, Ocotea indecora had reflectance values different from the other species. By principal component analysis, raw data indicated the separation only of Ocotea indecora, while second-derivative data allowed better distinction of species. In all discrimination models, second-derivative data produced the best results. Thus, the use of colorimetry has potential for wood distinction of the Lauraceae species evaluated, improving the oversight of illegally traded timber

Um cortador de amostras por eletro-erosao de baixa energia

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Um cortador de amostras por eletro-erosao de baixa energia

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Magnetômetro de gradiente alternado à baixa temperatura

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Magnetometria de camadas atômicas de cobalto durante a deposição eletroquímica

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Microscopia de tunelamento com polarização de spin

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