We present an algorithm for imputation of incomplete datasets based on Bayesian exchangeability through Pólya sampling. Each (donee) unit with a missing value is imputed multiple times by observed (real) values on units from a donor pool. The donor pools are constructed using auxiliary variables. Several features from kernel estimation are used to counteract unbalances that are due to sparse and bounded data. Three balancing features can be used with only one single continuous auxiliary variable, but an additional fourth feature need, multiple continuous auxiliary variables. They mainly contribute by reducing nonresponse bias. We examine how the donor pool size should be determined, that is the number of potential donors within the pool. External information is shown to be easily incorporated in the imputation algorithm. Our simulation studies show that with a study variable which can be seen as a function of one or two continuous auxiliaries plus residual noise, the method performs as well or almost as well as competing methods when the function is linear, but usually much better when the function is nonlinear. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 3: Submitted. Paper 4: Submitted.</p>

Studying the effects of extreme conditions, such as high temperatures and low humidity, on soil properties is important to various disciplines, including geotechnical engineering, soil science, waste management, crop management, and ceramics. The goal of this research is to investigate the effect of environmental and geometrical factors on microstructure, desiccation cracking, and CO2 flux in clays. The objectives of this research are threefold. (1) Understand the effects of temperature on the microstructure of clay soils; (2) develop a standardized procedure for studying desiccation cracking in a laboratory setting with reliable and repeatable results; and (3) develop an environmental chamber capable of monitoring CO2 flux through a soil sample large enough to accommodate a fully developed crack network. To accomplish these objectives, an array of laboratory testing was conducted. First, this study examines the effects of extreme temperatures on the microstructural properties of clay using FESEM, cation-exchange capacity (CEC) tests, thermal gravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) surface area analyzer. Second, a standardized procedure for producing accurate and repeatable laboratory tests on the desiccation cracking of soils is presented. The procedure includes specifications for sample collection, material preparation and characterization (including microstructural properties), and the determination of a representative elemental area (REA) for a fully developed crack network. Finally, a new climatic chamber capable of controlling temperature and relative humidity is designed and tested. The chamber can monitor CO2 flux through a fully developed crack network, enabling fundamental research on the relationship between desiccation cracking and the oxidation of soil organic carbon. The key findings indicate a dependency of soil microstructure on temperature changes. CEC and BET surface area significantly decrease with temperatures beyond 100ºC, indicating a relationship that needs further study. Additionally, compacted and slurry cracking behavior was found to be sensitive to boundary geometry and sample thickness. A REA was identified for each slurry sample thickness. The procedures of this research can be repeated for other soil types and used to connect existing and future research to improve understanding of desiccation cracking behavior, and to study the effects of desiccation cracking on other important geo-environmental phenomena.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-14T14:41:09Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Ana Paula MC Valença.pdf: 2664032 bytes, checksum: 5b5c31bf5f29946a540d84d29e519535 (MD5) / Made available in DSpace on 2016-07-14T14:41:09Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Ana Paula MC Valença.pdf: 2664032 bytes, checksum: 5b5c31bf5f29946a540d84d29e519535 (MD5) Previous issue date: 2015-02-23 / FACEPE / A presente tese avaliou os possíveis impactos gerados pelos tapetes de alga na macrofauna estuarina. Em uma planície estuarina lamosa, situada no Complexo Estuarino do Canal de Santa Cruz, litoral norte de Pernambuco, foi registrada a ocorrência de tapetes de algas filamentosas em diferentes períodos (Setembro-2012, Setembro a Dezembro-2013 e Maio a Junho-2014). Através de estudos observacionais e manipulativos in situ foram testados: (I) o efeito do tapete algal na biogeoquímica sedimentar e na fauna, considerando a presença da alga e o seu estágio fisiológico; (II) a recolonização e a recuperação da macrofauna em sedimentos com remoção algal considerando os efeitos da compactação sedimentar gerada pelo tapete e do tamanho da área algal removida; a existência de efeitos (III) de barreira e (IV) de sazonalidade gerados pelo tapete algal e analisados sob a ótica da recolonização inicial. O estágio fisiológico da alga foi importante para a biogeoquímica sedimentar, enquanto que a presença do tapete algal se caracterizou como uma importante fonte de distúrbio para a fauna bêntica. A recolonização pela macrofauna nos sedimentos com remoção algal ocorreu de forma discreta e dependente da compactação sedimentar e do tamanho da área removida apenas para os parâmetros univariados. Além disso, não foi observada a recuperação das áreas experimentais até ao final do estudo (95 dias). A recolonização inicial (30 dias) não foi afetada pela presença do tapete algal circunvizinho às áreas experimentais. Embora tenha sido observado que a sazonalidade influencia no sedimento e na fauna, a análise da comunidade indicou uma tendência à convergência entre os tratamentos de remoção (AR) e sedimento natural (NA) independente da mesma. Além disso, foi observada uma relação entre o regime pluviométrico e o desenvolvimento do tapete algal. As consequências ecológicas do tapete algal, analisadas sob a recolonização a curto (30 dias) e médio prazo (95 dias), mostraram ser pouco previsíveis e extremamente influenciadas pela heterogeneidade ambiental. Além disso, a recuperação da comunidade em uma área afetada pelo desenvolvimento de tapete algal pode não apresentar a sequência sucessional observada em outros experimentos de colonização. Embora os estudos tenham sido conduzidos em um único local (na mesma planície estuarina), os resultados permitem uma melhor compreensão dos efeitos dos tapetes de algas na macrofauna bêntica estuarina. / This thesis assessed the possible impacts of algal mats on estuarine macrofauna. In an estuarine mudflat placed on Santa Cruz Channel Estuarine Complex, in the north coast of Pernambuco, the occurrence of filamentous mat-forming algae was registered at different periods (September-2012, September to December-2013 and May to June-2014). Observational and manipulative studies were conducted in situ and tested: (I) the effect of algal mats on sediment biogeochemistry and fauna, considering the presence of the algae and the physiological stage; (II) the recolonization and recovery of macrofauna in algal removal sediments relating to sediment compaction and the extension of algal removed (i.e. spatial scale); the existence of (III) boundaries and (IV) seasonal effects generated by the algal mat and analyzed using macrofauna recolonization data. The physiological stage affected significantly the sediment biogeochemistry and the presence of the algae was an important source of disturbance to benthic fauna. The recolonization of algal removal sediments varied regarding sediment compaction and spatial scale, but this was discrete and restricted to univariate measures. Besides, no recovery of any removal treatment was observed at the end of the experiment (95 days). Initial recolonization (30 days) was not affected by the surrounding algal mat found in the algal removal treatments. Although seasonal effects influence on sediment and fauna data, the analysis of benthic community showed a tendency of convergence between NA and AR treatments regardless of season. Moreover, it was possible to observe a relationship between rainfall seasonality and algal mat development. Ecological consequences of algal mats, analyzed through faunal recolonization within short- (30 days) and medium- (95 days) terms, showed to be less predictable and strongly influenced by environmental heterogeneity. Besides, community recovery in an area affected by algal coverage does not always include the successional sequence observed in other colonization experiments. Although the series of experiments have been conducted under one location (the same estuarine mudflat), the results provided strong insights on the effects of algal mats on tropical benthic macrofauna.

In this dissertation, a fully scalable video coding system is proposed. This system achieves full temporal, resolution, and fidelity scalability by combining mesh-based motion-compensated temporal filtering, multihypothesis motion compensation, and an embedded 3D wavelet-coefficient coder. The first major contribution of this work is the introduction of the redundant-wavelet multihypothesis paradigm into motion-compensated temporal filtering, which is achieved by deploying temporal filtering in the domain of a spatially redundant wavelet transform. A regular triangle mesh is used to track motion between frames, and an affine transform between mesh triangles implements motion compensation within a lifting-based temporal transform. Experimental results reveal that the incorporation of redundant-wavelet multihypothesis into mesh-based motion-compensated temporal filtering significantly improves the rate-distortion performance of the scalable coder. The second major contribution is the introduction of a sliding-window implementation of motion-compensated temporal filtering such that video sequences of arbitrarily length may be temporally filtered using a finite-length frame buffer without suffering from severe degradation at buffer boundaries. Finally, as a third major contribution, a novel 3D coder is designed for the coding of the 3D volume of coefficients resulting from the redundant-wavelet based temporal filtering. This coder employs an explicit estimate of the probability of coefficient significance to drive a nonadaptive arithmetic coder, resulting in a simple software implementation. Additionally, the coder offers the possibility of a high degree of vectorization particularly well suited to the data-parallel capabilities of modern general-purpose processors or customized hardware. Results show that the proposed coder yields nearly the same rate-distortion performance as a more complicated coefficient coder considered to be state of the art.

Dans ce travail, l'approche non-paramétrique par noyaux associés mixtes multivariés est présentée pour les fonctions de densités, de masse de probabilité et de régressions à supports partiellement ou totalement discrets et continus. Pour cela, quelques aspects essentiels des notions d'estimation par noyaux continus (dits classiques) multivariés et par noyaux associés univariés (discrets et continus) sont d'abord rappelés. Les problèmes de supports sont alors révisés ainsi qu'une résolution des effets de bords dans les cas des noyaux associés univariés. Le noyau associé multivarié est ensuite défini et une méthode de leur construction dite mode-dispersion multivarié est proposée. Il s'ensuit une illustration dans le cas continu utilisant le noyau bêta bivarié avec ou sans structure de corrélation de type Sarmanov. Les propriétés des estimateurs telles que les biais, les variances et les erreurs quadratiques moyennes sont également étudiées. Un algorithme de réduction du biais est alors proposé et illustré sur ce même noyau avec structure de corrélation. Des études par simulations et applications avec le noyau bêta bivarié avec structure de corrélation sont aussi présentées. Trois formes de matrices des fenêtres, à savoir, pleine, Scott et diagonale, y sont utilisées puis leurs performances relatives sont discutées. De plus, des noyaux associés multiples ont été efficaces dans le cadre de l'analyse discriminante. Pour cela, on a utilisé les noyaux univariés binomial, catégoriel, triangulaire discret, gamma et bêta. Par la suite, les noyaux associés avec ou sans structure de corrélation ont été étudiés dans le cadre de la régression multiple. En plus des noyaux univariés ci-dessus, les noyaux bivariés avec ou sans structure de corrélation ont été aussi pris en compte. Les études par simulations montrent l'importance et les bonnes performances du choix des noyaux associés multivariés à matrice de lissage pleine ou diagonale. Puis, les noyaux associés continus et discrets sont combinés pour définir les noyaux associés mixtes univariés. Les travaux ont aussi donné lieu à la création d'un package R pour l'estimation de fonctions univariés de densités, de masse de probabilité et de régression. Plusieurs méthodes de sélections de fenêtres optimales y sont implémentées avec une interface facile d'utilisation. Tout au long de ce travail, la sélection des matrices de lissage se fait généralement par validation croisée et parfois par les méthodes bayésiennes. Enfin, des compléments sur les constantes de normalisations des estimateurs à noyaux associés des fonctions de densité et de masse de probabilité sont présentés. / This work is about nonparametric approach using multivariate mixed associated kernels for densities, probability mass functions and regressions estimation having supports partially or totally discrete and continuous. Some key aspects of kernel estimation using multivariate continuous (classical) and (discrete and continuous) univariate associated kernels are recalled. Problem of supports are also revised as well as a resolution of boundary effects for univariate associated kernels. The multivariate associated kernel is then defined and a construction by multivariate mode-dispersion method is provided. This leads to an illustration on the bivariate beta kernel with Sarmanov's correlation structure in continuous case. Properties of these estimators are studied, such as the bias, variances and mean squared errors. An algorithm for reducing the bias is proposed and illustrated on this bivariate beta kernel. Simulations studies and applications are then performed with bivariate beta kernel. Three types of bandwidth matrices, namely, full, Scott and diagonal are used. Furthermore, appropriated multiple associated kernels are used in a practical discriminant analysis task. These are the binomial, categorical, discrete triangular, gamma and beta. Thereafter, associated kernels with or without correlation structure are used in multiple regression. In addition to the previous univariate associated kernels, bivariate beta kernels with or without correlation structure are taken into account. Simulations studies show the performance of the choice of associated kernels with full or diagonal bandwidth matrices. Then, (discrete and continuous) associated kernels are combined to define mixed univariate associated kernels. Using the tools of unification of discrete and continuous analysis, the properties of the mixed associated kernel estimators are shown. This is followed by an R package, created in univariate case, for densities, probability mass functions and regressions estimations. Several smoothing parameter selections are implemented via an easy-to-use interface. Throughout the paper, bandwidth matrix selections are generally obtained using cross-validation and sometimes Bayesian methods. Finally, some additionnal informations on normalizing constants of associated kernel estimators are presented for densities or probability mass functions.