DSpace Collection:http://hdl.handle.net/10174/9692018-03-22T00:28:41Z2018-03-22T00:28:41ZOn vector bundle manifolds with spherically symmetric metricsAlbuquerque, Ruihttp://hdl.handle.net/10174/230012018-03-16T11:02:00Z2017-03-01T00:00:00ZTitle: On vector bundle manifolds with spherically symmetric metrics
Authors: Albuquerque, Rui
Editors: Agricola, Ilka
Abstract: We give a general description of the construction of weighted spherically symmetric metrics on vector bundle manifolds, i.e. the total space of a vector bundle E->M, over a Riemannian manifold M, when E is endowed with a metric connection. The tangent bundle of E admits a canonical decomposition and thus it is possible to define an interesting class of two-weights metrics with the weight functions depending on the fibre norm of E; hence the generalized concept of spherically symmetric metrics. We study its main properties and curvature equations. Finally we focus on a few applications and compute the holonomy of Bryant-Salamon type G2 manifolds.2017-03-01T00:00:00ZShort-term effects of reduced-impact logging on Copaifera spp. (Fabaceae) regeneration in eastern AmazonKlauberg, C.Edson, VAlberto, S. C.Hudak, A.Oliveira, M.Higuchi, Phttp://hdl.handle.net/10174/229302018-03-12T17:47:42Z2017-07-13T23:00:00ZTitle: Short-term effects of reduced-impact logging on Copaifera spp. (Fabaceae) regeneration in eastern Amazon
Authors: Klauberg, C.; Edson, V; Alberto, S. C.; Hudak, A.; Oliveira, M.; Higuchi, P
Abstract: Timber management directly influences the population dynamics of tree species, like
Copaifera spp. (copaíba), which provide oil-resin with ecological and economic importance. The aim
of this study was to evaluate the structure and population dynamics of Copaifera in unmanaged and
managed stands by reduced-impact logging (RIL) in eastern Amazon in Pará state, Brazil. Based on
a stem map of the study area, 40 Copaifera trees were randomly selected, where an equal number
of trees were selected in managed and unmanaged stands. A transect of 10 × 100 m was centered
at each tree (50 m each side) to assess Copaifera regeneration. Transects were subdivided into ten
plots, of which six were systematically chosen to assess the height, diameter and number of Copaifera
seedlings and saplings. The field assessment occurred in 2011 and 2013. To estimate the amount
of sunlight transmitted to the forest floor, we computed canopy cover from airborne LiDAR data.
According to the results, the abundance of Copaifera seedlings/saplings was higher in managed
than unmanaged stands. About 5% of Copaifera regeneration was found between 45–50 m from the
Copaifera tree while ~73% of regeneration was concentrated within a 10 m radius of the Copaifera tree.
We verified that the diameter distribution of Copaifera regeneration was not a negative exponential
distribution, as is typical of most tree species in natural forest. Rather, the Copaifera regeneration had
a spatially aggregated distribution. In this short-term analysis, the impact of timber management is
not negatively affecting the population structure or dynamics of Copaifera regeneration.2017-07-13T23:00:00ZAnálise de correspondências múltiplas via optimal scaling aplicada a variáveis do meio escolar relativas à alunos do ensino secundário em PortugalSilva, D.Oliveira, M.M.http://hdl.handle.net/10174/228932018-03-08T17:38:12Z2017-06-10T23:00:00ZTitle: Análise de correspondências múltiplas via optimal scaling aplicada a variáveis do meio escolar relativas à alunos do ensino secundário em Portugal
Authors: Silva, D.; Oliveira, M.M.
Abstract: A Análise de Correspondências Múltiplas (ACM) é um método multivariado particularmente útil na abordagem simultânea de um grande conjunto de variáveis qualitativas, avaliando o seu eventual relacionamento, produzindo mapas geométricos que possibilitam a visualização das interdependências existentes. Este estudo tem como objetivo a aplicação da ACM via optimal scaling sobre os dados de um inquérito realizado com alunos do ensino secundário (no Brasil corresponde a ensino médio), de modo a investigar as relações entre a motivação para as disciplinas de Português, Matemática e Educação Física e um conjunto de variáveis referentes aos alunos (sexo, curso, ano de escolaridade e prática desportiva). Realça-se o pioneirismo desta aplicação. A ACM permitiu identificar as variáveis e categorias de variáveis com atributos próximos, tendo possibilitado a definição de subgrupos relativamente homogêneos. Foram retidas três dimensões. A dimensão 1 aponta essencialmente para a “formação desportiva”, a dimensão 2, dirige-se sobretudo para a “aprendizagem das línguas e humanidades” e a dimensão 3 representada simultaneamente pela “destreza física e o raciocínio abstrato”.2017-06-10T23:00:00ZModelling post-fire mortality in pure and mixed forest stands in PortugalBotequim, B., MArias-Rodil, ManuelGarcia-Gonzalo, J.Silva, AndreiaMarques, SuseteBorges, J. G.Oliveira, M. M.Tomé, M.http://hdl.handle.net/10174/228722018-03-08T16:03:56Z2017-03-07T00:00:00ZTitle: Modelling post-fire mortality in pure and mixed forest stands in Portugal
Authors: Botequim, B., M; Arias-Rodil, Manuel; Garcia-Gonzalo, J.; Silva, Andreia; Marques, Susete; Borges, J. G.; Oliveira, M. M.; Tomé, M.
Abstract: Assessing impacts of management strategies may allow designing more resistant forests to
wildfires. Planning-oriented models to predict the effect of stand structure and forest composition on mortality for supporting fire-smart management decisions, and allowing its inclusion in forest management optimization systems were developed. Post-fire mortality was modeled as a function of measurable forest inventory data and projections over time in 165 pure and 76 mixed forest stands in Portugal, collected by the 5th National Forest Inventory plots (NFI) plus other sample plots from ForFireS project, intercepted within 2006–2008 wildfire perimeters’ data. Presence and tree survival were obtained by examining 2450 trees from 16 species one year after the wildfire occurrence. A set of logistic regression models were developed under a three-stage modeling system: firstly multiple
fixed-effects at stand-level that comprises a sub-model to predict mortality from wildfire; and another for the proportion of dead trees on stands killed by fire. At tree-level due to the nested structure of the data analyzed (trees within stands), a mixed-effect model was developed to estimate mortality among trees in a fire event. The results imply that the variation of tree mortality decreases when tree diameter at breast height increases. Moreover, the relative mortality increases with stand density, higher altitude and steeper slopes. In the same conditions, conifers are more prone to die than eucalyptus and
broadleaves. Pure stands of broadleaves exhibit noticeably higher fire resistance than mixed stands of broadleaves and others species composition.2017-03-07T00:00:00Z