Encontrados 14 documentos, a visualizar página 1 de 2
Change-point analysis in environmental time series
Gonçalves, A. Manuela; Costa, Marco; Teixeira, LaraChange-points are present in many environmental time series. Time variations in environmental data are complex and they can hinder the identification of the so-called change-points when traditional models are applied to this type of problems. In this study, it is proposed an alternative approach for the application of the change-point analysis by taking into account this data structure (seasonality and autocorr...
Metodologia estatística para a classificação das escolas secundárias em Portugal
Oliveira, Mário; Gonçalves, A. Manuela; Costa, MarcoNeste trabalho pretende-se efetuar um estudo, na área da Estatística, sobre a classificação das Escolas Secundárias (Portugal Continental e Ilhas) relativamente aos resultados alcançados pelos seus alunos nos Exames Nacionais. Tem-se como principal objetivo identificar grupos de Escolas com diferentes graus de desempenho considerando os subsistemas de ensino nacional público e privado, bem como a sua reg...
Cognitive appraisal as a mediator in the relationship between stress and burnout
Gomes, António Rui; Faria, Susana, 1972-; Gonçalves, A. ManuelaThe relation between job stressors and burnout is well established in the literature. However, the mechanisms behind this relationship are still not clear. Thus, this study has the main goal of analysing the mediating role of cognitive appraisal on the relation between occupational stress and burnout. To test this relation, structural equation modelling was used in a sample of teachers (N=333) working at a publ...
Water monitoring sites discrimination using clustering water variables time ser...
Gonçalves. A. Manuela; Costa, MarcoApplication of multivariate methodologies for the evaluation and interpretation of space-time variations in an environmental monitoring data set from an hydrological basin is presented in this study. The results obtained allowed detecting natural clusters of monitoring sites with similar water quality type and identifying important discriminant variables for each cluster. Furthermore, this type of analysis allo...
Kalman filtering approach in the calibration of radar rainfall data: a comparat...
Costa, Marco; Monteiro, Magda; Gonçalves, A. ManuelaIn this chapter it is presented a comparative study of some methods to estimate radar rainfall in real time. This work in- tends to discuss and compare different state space formulations based on a same data set; for instance, the comparison between the mode- ling of the mean field radar rainfall logarithmic bias (Chumchean et al., 2006), a linear radar-rain gauge calibration model (Alpuim & Barbosa, 1999; Cost...
Information criterion on the change-point detection in water quality data
Gonçalves, A. Manuela; Costa, Marco; Teixeira, LaraThe number of studies using change-point methods to detect shifts has been increasing. The Schwarz Information Criterion SIC is used in this study to search for the change-point in time series of water quality variables.
Kalman filtering approach in the calibration of radar rainfall data
Costa, Marco; Monteiro, Magda; Gonçalves, A. ManuelaThis work presents a comparative study of some models to estimate radar rainfall in real time using the Kalman filtering approach. This comparison adresses the parameters estimation, the assessment of the accuracy estimates obtained by each model and the impact of the number of rain gauges used in the improvement of radar calibration estimates.
Clustering and forecasting of dissolved oxygen concentration on a river basin
Costa, Marco; Goncalves, A. ManuelaThe aim of this contribution is to combine statistical methodologies to geographically classify homogeneous groups of water quality monitoring sites based on similarities in the temporal dynamics of the dissolved oxygen (DO) concentration, in order to obtain accurate forecasts of this quality variable. Our methodology intends to classify the water quality monitoring sites into spatial homogeneous groups, based ...
Application of Change-Point Detection to a Structural Component of Water Qualit...
Gonçalves, A. Manuela; Costa, MarcoIn this study, methodologies were developed in statistical time series models, such as multivariate state-space models, to be applied to water quality variables in a river basin. In the modelling process it is considered a latent variable that allows incorporating a structural component, such as seasonality, in a dynamic way and a change-point detection method is applied to the structural component in order to ...
Using udometric network data to estimate an environmental covariate
Gonçalves, A. Manuela; Costa, MarcoManyhydrologicalandecologicalstudiesrecognizetheimportanceofcharacterizingthetemporalandspatialvari- ability of precipitation. In this study, geostatistical methodologies were developed in order to estimate a hydro-meteorological factor by (re)building the space-time distribution of the precipitation associated to monthly averages in a certain hydrological river basin that will be used in the modelling of surfa...
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