Optimização estrutural na análise não linear dos modelos de escoras e tirantes

Dissertação para obtenção do Grau de Mestre em Engenharia Civil - Perfil Estruturas

Carbon key-properties for microcystin adsorption in drinking water treatment: structure or surface chemistry?

Dissertação para Obtenção de Grau de Mestre em Engenharia Química e Bioquímica

Contributo para a modelização de magnetos supercondutores de fluxo residual: aplicação a um motor linear todo supercondutor

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores

Spatial neighborhood matrix computation: Inverse distance weighted versus binary contiguity

Paper presented at Geo-Spatial Crossroad GI_Forum, Salzburg, Austria.

QuEChERS: a sample preparation for extraction of carbaryl from rat feces

Carbamate compounds are an important group of cholinesterase inhibitors. There is a need for creating awareness regarding the risks of the inadequate carbamate use in the residential areas due to potential adverse human effects. Carbaryl is a commonly used pesticide worldwide. A simple, fast, and high throughput method was developed employing liquid chromatography with fluorescence detector to determine carbaryl residues in rat feces. The extraction was performed by using a rapid, easy, cheap, effective, reliable, and safe (QuEChERS) method, using acetonitrile as the extracting solvent. The parameters for the performance of the extraction method were optimized, such as ratio of mass of sample per volume of extraction solvent, QuEChERS content, and cleanup columns. Linear response was obtained for all calibration curves (solven and matrix-matched) over the established concentration range (5 500 mg/L) with a correlation coefficients higher than 0.999. The achieved recovery was 97.9% with relative standard deviation values of 1.1% (n D 4) at 167 mg/kg fortified concentration level and the limits of detection and quantification were 27.7 and 92.3 mg/kg respectively.

Matrix fractional systems

This paper addresses the matrix representation of dynamical systems in the perspective of fractional calculus. Fractional elements and fractional systems are interpreted under the light of the classical Cole–Cole, Davidson–Cole, and Havriliak–Negami heuristic models. Numerical simulations for an electrical circuit enlighten the results for matrix based models and high fractional orders. The conclusions clarify the distinction between fractional elements and fractional systems.

On the analysis of data emerging in non-linear and complex systemscomparison of two X-Ray prony spectra

New arguments proving that successive (repeated) measurements have a memory and actually remember each other are presented. The recognition of this peculiarity can change essentially the existing paradigm associated with conventional observation in behavior of different complex systems and lead towards the application of an intermediate model (IM). This IM can provide a very accurate fit of the measured data in terms of the Prony's decomposition. This decomposition, in turn, contains a small set of the fitting parameters relatively to the number of initial data points and allows comparing the measured data in cases where the “best fit” model based on some specific physical principles is absent. As an example, we consider two X-ray diffractometers (defined in paper as A- (“cheap”) and B- (“expensive”) that are used after their proper calibration for the measuring of the same substance (corundum a-Al2O3). The amplitude-frequency response (AFR) obtained in the frame of the Prony's decomposition can be used for comparison of the spectra recorded from (A) and (B) - X-ray diffractometers (XRDs) for calibration and other practical purposes. We prove also that the Fourier decomposition can be adapted to “ideal” experiment without memory while the Prony's decomposition corresponds to real measurement and can be fitted in the frame of the IM in this case. New statistical parameters describing the properties of experimental equipment (irrespective to their internal “filling”) are found. The suggested approach is rather general and can be used for calibration and comparison of different complex dynamical systems in practical purposes.

Contributo para o estudo do motor linear síncrono supercondutor

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores

Electrochemical sensor for simultaneous determination of herbicide MCPA and its metabolite 4-chloro-2-methylphenol. Application to photodegradation environmental monitoring

The development and application of a polyaniline/carbon nanotube (CNT) cyclodextrin matrix (PANI-β-CD/MWCNT)-based electrochemical sensor for the quantitative determination of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) and its main transformation product 4-chloro-2-methylphenol in natural waters are described. A simple cyclic voltammetry-based electrochemical methodology, in phosphate buffer solution at pH 6.0, was used to develop a method to determine both MCPA and 4-chloro-2-methylphenol, without any previous extraction or derivatization steps. A linear concentration range (10 to 50 μmol L−1) and detection limits of 1.1 and 1.9 μmol L−1, respectively, were achieved using optimized cyclic voltammetric parameters. The proposed method was successfully applied to the determination of MCPA and 4-chloro-2-methylphenol in natural water samples with satisfactory recoveries (94 to 107 %) and in good agreement with the results obtained by an established high-performance liquid chromatography technique, no significant differences being found between the methods. Interferences from ionic species and other herbicides used for broad-leaf weed control were shown to be small. The newly developed methodology was also successfully applied to MCPA photodegradation environmental studies.

Non-linear time series models

The last three decades have seen quite dramatic changes the way we modeled time dependent data. Linear processes have been in the center stage in modeling time series. As far as the second order properties are concerned, the theory and the methodology are very adequate.However, there are more and more evidences that linear models are not sufficiently flexible and rich enough for modeling purposes and that failure to account for non-linearities can be very misleading and have undesired consequences.

Analyzing Multiple Outcomes: Is it Really Worth the use of Multivariate Linear Regression?

In health related research it is common to have multiple outcomes of interest in a single study. These outcomes are often analysed separately, ignoring the correlation between them. One would expect that a multivariate approach would be a more efficient alternative to individual analyses of each outcome. Surprisingly, this is not always the case. In this article we discuss different settings of linear models and compare the multivariate and univariate approaches. We show that for linear regression models, the estimates of the regression parameters associated with covariates that are shared across the outcomes are the same for the multivariate and univariate models while for outcome-specific covariates the multivariate model performs better in terms of efficiency.

Kalman tracking linear predictor for vowel intelligibility enhancement on european portuguese HMM based speech synthesis

The recent developments on Hidden Markov Models (HMM) based speech synthesis showed that this is a promising technology fully capable of competing with other established techniques. However some issues still lack a solution. Several authors report an over-smoothing phenomenon on both time and frequencies which decreases naturalness and sometimes intelligibility. In this work we present a new vowel intelligibility enhancement algorithm that uses a discrete Kalman filter (DKF) for tracking frame based parameters. The inter-frame correlations are modelled by an autoregressive structure which provides an underlying time frame dependency and can improve time-frequency resolution. The system’s performance has been evaluated using objective and subjective tests and the proposed methodology has led to improved results.

Correlação entre a Extensão Linear do Tronco e o Alinhamento Segmentar do Membro Inferior Contralesional na Posição de Pé em Indivíduos Pós-AVE

O controlo postural (CP) do tronco é um pré-requisito para o movimento tendo como objetivo prevenir e minimizar as perturbações. Um CP adequado pressupõe estabilidade e orientação dos segmentos, sendo necessária uma orientação do tronco com componente de extensão linear para as atividades sentado e pé. Num acidente vascular encefálico (AVE), pode existir comprometimento do CP do tronco quer contralesional (CONTRA) como ipsilesional (IPSI). Neurofisiologicamente, parece haver uma projecção predominantemente ipsilateral para garantir um CP do tronco contralateralmente ao movimento, tornando-se importante perceber a correlação entre componentes do CP do tronco e o alinhamento do membro CONTRA. Contudo, atualmente são poucos os estudos direcionados para a o membro inferior (MI). Assim, uma vez que nesta população, assumir a posição de pé e realizar marcha constitui muitas vezes o seu principal objetivo, considerou-se relevante avaliar a correlação entre a extensão linear do tronco e o alinhamento segmentar do MI CONTRA na posição de pé. Participantes e Métodos: Estudo observacional, transversal, analítico com 11 indivíduos (idade média 70+10 anos, 54,5% homens). Como critérios de inclusão definiram-se AVE isquémico da artéria cerebral média, único e unilateral, em fase crónica. Recorrendo a um software de avaliação postural (SAPo) avaliou-se a extensão linear do tronco (alinhamento dos acrómios, alinhamento das espinhas ilíacas ântero-superiores (EIAS), ângulo formado entre os dois e o alinhamento vertical do tronco) e o alinhamento segmentar do MI (ângulo do joelho e ângulo entre o tronco e MI). Para a análise estatística inferencial utilizou-se o coeficiente de correlação de Pearson entre o ângulo dos acrómios e as EIAS, o alinhamento vertical do tronco e o alinhamento horizontal da pélvis IPSI com as variáveis de alinhamento do MI, para uma significância de 0,05. Resultados: Algumas correlações mostraram ser quase nulas (com valores entre -0,02 a 0,02) ou fracas como o alinhamento horizontal da pélvis IPSI com o ângulo do tronco e MI CONTRA (0,29 com p=0,39). O alinhamento do tronco e o ângulo do joelho apresentou moderada correlação (0,642), estatisticamente significativa (p=0,03). Conclusão: Os resultados deste estudo sugerem a existência de uma correlação positiva entre o alinhamento vertical do tronco e a extensão do joelho do MI CONTRA na posição de pé em indivíduos pós-AVE.

Selective synthesis under microwave irradiation of new monomers for potential applications in PDLC films

Dissertation to obtain the degree of master in Bioorganic

Linear amplification with multiple nonlinear devices

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e Computadores