The improper aggregation of commodities can have important consequences when estimating a system of group demand equations. Generally, aggregates are created under the assumptions that intra-group preferences are homothetic and the consumer's utility function is weakly separable over some partition. These assumptions place severe restrictions on the model that can significantly impact parameter and elasticity estimates. An alternative to imposing weak separability is to employ the Generalized Composite Commodity Theorem, which requires the relative intra-group commodity prices to be independent of the group price index. This study compares the results of estimating a demand system for composite beef, pork, and poultry products under the assumptions of weak separability and the Generalized Composite Commodity Theorem. Another important issue related to aggregation is the specification of an appropriate group price index. Price indices consistent with linear homogeneous preferences (a subset of the homothetic class of preferences) and non-homothetic intra-group preferences are identified and it is shown that several of the commonly employed indices are biased in the absence of complete price data. / Master of Science

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The dissertation examines advancements in the methods and techniques used in the field of econometrics. These advancements include: (i) a re-examination of the underlying statistical foundations of statistical models with binary dependent variables. (ii) using feed-forward backpropagation artificial neural networks for modeling dichotomous choice processes, and (iii) the estimation of unconditional demand elasticities using the flexible multistage demand system with asymmetric partitions and fixed effects across time. The first paper re-examines the underlying statistical foundations of statistical models with binary dependent variables using the probabilistic reduction approach. This re-examination leads to the development of the Bernoulli Regression Model, a family of statistical models arising from conditional Bernoulli distributions. The paper provides guidelines for specifying and estimating a Bernoulli Regression Model, as well as, methods for generating and simulating conditional binary choice processes. Finally, the Multinomial Regression Model is presented as a direct extension. The second paper empirically compares the out-of-sample predictive capabilities of artificial neural networks to binary logit and probit models. To facilitate this comparison, the statistical foundations of dichotomous choice models and feed-forward backpropagation artificial neural networks (FFBANNs) are re-evaluated. Using contingent valuation survey data, the paper shows that FFBANNs provide an alternative to the binary logit and probit models with linear index functions. Direct comparisons between the models showed that the FFBANNs performed marginally better than the logit and probit models for a number of within-sample and out-of-sample performance measures, but in the majority of cases these differences were not statistically significant. In addition, guidelines for modeling contingent valuation survey data and techniques for estimating median WTP measures using FFBANNs are examined. The third paper estimates a set of unconditional price and expenditure elasticities for 49 different processed food categories using scanner data and the flexible and symmetric translog (FAST) multistage demand system. Due to the use of panel data and the presence of heterogeneity across time, temporal fixed effects were incorporated into the model. Overall, estimated price elasticities are larger, in absolute terms, than previous estimates. The use of disaggregated product groupings, scanner data, and the estimation of unconditional elasticities likely accounts for these differences. / Ph. D.

Le but de cette étude est de vérifier l'apport de la stéréoscopie dans le phénomène de la constance de forme. La méthode utilisée consiste à mesurer la performance de différents participants (temps de réponse et de taux d'erreurs) à une tâche de prospection visuelle. Quatre groupes de participants ont effectué la tâche. Le premier groupe a été exposé à une présentation stéréoscopique des stimuli, le deuxième groupe à une présentation des stimuli en stéréoscopie inversée (la disparité binoculaire était inversée), le troisième groupe à des stimuli comprenant une information de texture, mais sans stéréoscopie et le quatrième groupe à des stimuli bi-dimensionnels, sans texture. Une interaction entre les effets de rotation (points de vue familiers vs. points de vue non familiers) et le type d'information de profondeur disponible (stéréoscopie, stéréoscopie inversée, texture ou ombrage) a été mise en évidence, le coût de rotation étant plus faible au sein du groupe exposé à une présentation en stéréoscopie inversée. Ces résultats appuient l'implication de représentations tridimensionnelles dans le traitement de l'information visuelle. / This study was conducted to evaluate the contribution of stereopsis to the shape constancy phenomenon. Four groups of eight participants each were asked to perform a visual exploration task. The first group was exposed to a stereoscopic stimulation, the second group was exposed to a reversed stereoscopic stimulation, the third group was exposed to a monocular stimulation with textures and shadow and the fourth group was exposed to a monocular stimulation with shadow only. Response times and error rates were used to measure participant's performance. Results show an interaction between rotation effects (familiar viewpoints vs. non-familiar viewpoints) and available depth cues (stereopsis, reversed stereopsis, textures and shadow, shadow only). The rotation cost was smaller in the group exposed to a reversed stereoscopic stimulation. These results are congruent with the use of tridimensional representations underlying visual processing.

Le but de cette étude est de vérifier l'apport de la stéréoscopie dans le phénomène de la constance de forme. La méthode utilisée consiste à mesurer la performance de différents participants (temps de réponse et de taux d'erreurs) à une tâche de prospection visuelle. Quatre groupes de participants ont effectué la tâche. Le premier groupe a été exposé à une présentation stéréoscopique des stimuli, le deuxième groupe à une présentation des stimuli en stéréoscopie inversée (la disparité binoculaire était inversée), le troisième groupe à des stimuli comprenant une information de texture, mais sans stéréoscopie et le quatrième groupe à des stimuli bi-dimensionnels, sans texture. Une interaction entre les effets de rotation (points de vue familiers vs. points de vue non familiers) et le type d'information de profondeur disponible (stéréoscopie, stéréoscopie inversée, texture ou ombrage) a été mise en évidence, le coût de rotation étant plus faible au sein du groupe exposé à une présentation en stéréoscopie inversée. Ces résultats appuient l'implication de représentations tridimensionnelles dans le traitement de l'information visuelle. / This study was conducted to evaluate the contribution of stereopsis to the shape constancy phenomenon. Four groups of eight participants each were asked to perform a visual exploration task. The first group was exposed to a stereoscopic stimulation, the second group was exposed to a reversed stereoscopic stimulation, the third group was exposed to a monocular stimulation with textures and shadow and the fourth group was exposed to a monocular stimulation with shadow only. Response times and error rates were used to measure participant's performance. Results show an interaction between rotation effects (familiar viewpoints vs. non-familiar viewpoints) and available depth cues (stereopsis, reversed stereopsis, textures and shadow, shadow only). The rotation cost was smaller in the group exposed to a reversed stereoscopic stimulation. These results are congruent with the use of tridimensional representations underlying visual processing.

The influence of spectral resolution on land cover classification in Krkonoše Mts. tundra Abstract The aim of this diploma thesis was to specify the spectral resolution requirements for classification and to identify the most important spectral bands to discriminate classes of the predefined legend. Aerial hyperspectral data acquired by AisaDUAL sensor were used. The method applied for the selection of the important bands was discriminant analysis performed in IBM SPSS Statistics. The most discriminative bands were found in intervals 1500-1750 nm (beginning of SWIR), 1100- 1300 nm (longer wavelengths of NIR), 670-760 (red-edge) and 500-600 nm (green light). The classification of the selected bands was realized in ENVI 5.4 using the Support Vector Machine classifier, achieving overall accuracy of 80,54 %, Kappa coefficient 0,7755. The suitability of available satellite data for the classification of tundra vegetation in Krkonoše mountains based on spectral resolution was evaluated as well. Keywords: tundra, Krkonoše, classification, spectral resolution, class separability, discriminant analysis, hyperspectral data

A presente dissertação investiga o argumento da distinção real entre corpo e alma presente nas Meditações Metafísicas. O objetivo central é explicar o motivo pelo qual, nesta obra, a separabilidade entre corpo e alma é posta como condição suficiente para esse tipo de distinção. Para isso, percorre, ao longo das Meditações, os conceitos de alma, de corpo e de percepção clara e distinta. Faz uma análise do argumento da distinção real entre corpo e alma exposto na Sexta Meditação e, em seguida, se utiliza das discussões de Descartes com Caterus e Arnauld presente nas Objeções e Respostas visando a esclarecer pontos do argumento que ainda permanecem obscuros. Mostra, com o estudo das Meditações associado às Objeções e Respostas, que a distinção real é aquela que se dá entre substâncias e que ser substância é ser separável. Assim, sendo o reconhecimento da separabilidade de duas coisas o reconhecimento de que essas coisas são substâncias – e, portanto, de que são realmente distintas – explica, com isso, o motivo pelo qual a separabilidade é condição suficiente para a distinção real entre corpo e alma e conclui que ela lhe é, também, uma condição necessária. / This dissertation investigates the argument of the real distinction between body and soul presented on the Meditations on First Philosophy. The main goal is to explain the reason why the separability between body and soul is considered sufficient condition for this sort of distinction. In order to reach its goal, along the Meditations, it takes the path through the concepts of soul, body and the clear and distinct perception. It analyses the argument of the real distinction between body and soul presented on the Sixth Meditation and afterwards it makes use of Descartes’ discussions with Caterus and Arnauld, presented on Objections and Replies, seeking to clarify points of the argument that yet remain obscure. Studying the Meditations associated with the Objections and Replies, this dissertation shows that the real distinction is the one that happens between substances and that being a substance is being separable. Thus, being the recognition of the separability of two things the recognition of that those things are substances – and, hence, that they are really distinct – it explains the reason why the separability is sufficient condition for the real distinction between body and soul. It concludes that the separability is also a necessary condition to that sort of distinction.

This thesis is devoted to creating a systematic way of determining all inequivalent orthogonal coordinate systems which separate the Hamilton-Jacobi equation for a given natural Hamiltonian defined on three-dimensional spaces of constant, non-zero curvature. To achieve this, we represent the problem with Killing tensors and employ the recently developed invariant theory of Killing tensors. Killing tensors on the model spaces of spherical and hyperbolic space enjoy a remarkably simple form; even more striking is the fact that their parameter tensors admit the same symmetries as the Riemann curvature tensor, and thus can be considered algebraic curvature tensors. Using this property to obtain invariants and covariants of Killing tensors, together with the web symmetries of the associated orthogonal coordinate webs, we establish an equivalence criterion for each space. In the case of three-dimensional spherical space, we demonstrate the surprising result that these webs can be distinguished purely by the symmetries of the web. In the case of three-dimensional hyperbolic space, we use a combination of web symmetries, invariants and covariants to achieve an equivalence criterion. To completely solve the equivalence problem in each case, we develop a method for determining the moving frame map for an arbitrary Killing tensor of the space. This is achieved by defining an algebraic Ricci tensor. Solutions to equivalence problems of Killing tensors are particularly useful in the areas of multiseparability and superintegrability. This is evidenced by our analysis of symmetric potentials defined on three-dimensional spherical and hyperbolic space. Using the most general Killing tensor of a symmetry subspace, we derive the most general potential “compatible” with this Killing tensor. As a further example, we introduce the notion of a joint invariant in the vector space of Killing tensors and use them to characterize a well-known superintegrable potential in the plane. xiii

A presente dissertação investiga o argumento da distinção real entre corpo e alma presente nas Meditações Metafísicas. O objetivo central é explicar o motivo pelo qual, nesta obra, a separabilidade entre corpo e alma é posta como condição suficiente para esse tipo de distinção. Para isso, percorre, ao longo das Meditações, os conceitos de alma, de corpo e de percepção clara e distinta. Faz uma análise do argumento da distinção real entre corpo e alma exposto na Sexta Meditação e, em seguida, se utiliza das discussões de Descartes com Caterus e Arnauld presente nas Objeções e Respostas visando a esclarecer pontos do argumento que ainda permanecem obscuros. Mostra, com o estudo das Meditações associado às Objeções e Respostas, que a distinção real é aquela que se dá entre substâncias e que ser substância é ser separável. Assim, sendo o reconhecimento da separabilidade de duas coisas o reconhecimento de que essas coisas são substâncias – e, portanto, de que são realmente distintas – explica, com isso, o motivo pelo qual a separabilidade é condição suficiente para a distinção real entre corpo e alma e conclui que ela lhe é, também, uma condição necessária. / This dissertation investigates the argument of the real distinction between body and soul presented on the Meditations on First Philosophy. The main goal is to explain the reason why the separability between body and soul is considered sufficient condition for this sort of distinction. In order to reach its goal, along the Meditations, it takes the path through the concepts of soul, body and the clear and distinct perception. It analyses the argument of the real distinction between body and soul presented on the Sixth Meditation and afterwards it makes use of Descartes’ discussions with Caterus and Arnauld, presented on Objections and Replies, seeking to clarify points of the argument that yet remain obscure. Studying the Meditations associated with the Objections and Replies, this dissertation shows that the real distinction is the one that happens between substances and that being a substance is being separable. Thus, being the recognition of the separability of two things the recognition of that those things are substances – and, hence, that they are really distinct – it explains the reason why the separability is sufficient condition for the real distinction between body and soul. It concludes that the separability is also a necessary condition to that sort of distinction.