A new technique for sample preparation and trace analysis of organic pollutants in water using mixed-phase thin film (MPTF) devices, combined with direct thermal desorption, cold trapping, gas chromatography-mass spectrometry (GC-MS) is presented for the first time. Two novel analytical devices, Carboxen/polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) TF samplers were fabricated using spin coating technique and glass wool fabric mesh as substrate. The samplers were easily tailored in size and shape by cutting tools. Good durability and flat-shape stability were observed during extractions and stirring in water. The latter characteristic obviates the need for an extra framed holder for rapid thin film microextraction (TFME) and makes the samplers more robust and user-friendly. The analytical performance of the MPTF devices was satisfactorily illustrated and compared with those of solid phase microextraction (SPME) fibers and PDMS thin film membrane using water samples spiked with seven N–nitrosamines (NAs), known as disinfection by-products (DBPs) in drinking water. Marked enhancement of extraction efficiencies (typically more than one order of magnitude) for the N-nitrosamines, including the hydrophilic ones, was obtained with the MPTF devices under generally pre-equilibrium conditions, compared to the SPME fibers and PDMS thin film membrane. The analytical results obtained in this study, including linearity, repeatability and detection levels at low ng/L for the tested compounds, indicate that the new thin film devices are promising for rapid sampling and sample preparation of trace levels of polar organic pollutants in water with sensitivities higher than SPME fibers and with a wide application range typical of mixed-phase coatings. The user-friendly format and robustness of the novel devices are also advantageous for on-site applications, which is the ultimate use of thin film samplers. Moreover, the thin film fabrication approach developed in this study offers the possibility of making other novel samplers with PDMS or different absorptive polymers such as polyacrylate (PA) and polyethylene glycol (PEG) as particle-free, or as particle-loaded thin films with a variety of adsorptive solid particles. In another development in the course of this research, the performance and accuracy of the SPME fiber approach for sample preparation of selected DBPs were demonstrated and compared with the conventional liquid-liquid extraction (LLE) method by real drinking water samples analysis in collaboration with Health Canada. Four regulated trihalomethanes (THMs) and seven other DBPs known as priority by-products, including four haloacetonitriles, two haloketones and chloropicrin, were analyzed in real samples during two separate comparative studies. In each study, duplicate samples from several water treatment and distribution systems in Canada, collected and stabilized under the same protocol, were analyzed in parallel by two independent labs; in the University of Waterloo by an optimized headspace SPME-GC-MS and in Health Canada by a LLE-GC-ECD (electron capture detection) method equivalent to EPA 551.1. The values for the concentration of the analytes in the samples obtained by the two methods were in good agreement with each other in majority of the cases indicating that SPME affords the promise of a dependable sample preparation technique for rapid DBPs analysis. In particular, it was shown that the SPME fiber approach combined with GC-MS is a fast reliable alternative to the LLE-GC-ECD (EPA 551.1) method for analysis of the regulated THMs in the concentration ranges that are typical and relevant for drinking water samples.

Isocyanates, aromatic-, aliphatic- and alkanolamines are commonly used in the industry today. Millions of workers in Europe are exposed. The most frequent health symptoms are respiratory and dermal disorder. Due to the health risk most of the compounds in this thesis are regulated by authorities and have occupational exposure limits (OELs). Consequently, reliable and robust air sampling methods are urgently needed. In this thesis dry samplers for isocyanates, aliphatic- and alkanolamines have been developed and evaluated. The isocyanate sampler is now a commercial product (ASSET EZ4-NCP Dry Sampler, Supelco). The samplers were based on a denuder with a filter in series. The denuder and filter were impregnated with di-n-butylamine for the isocyanate sampler and with sulphuric acid for the aliphatic- and alkanolamine sampler. The robustness of the dry samplers was extensively evaluated. This was performed in a climate chamber containing a controlled atmosphere of the studied compounds. New methods based on hydrophilic interaction liquid chromatography (HILIC) coupled with tandem mass spectrometry (MSMS) were developed for determination of aromatic-, aliphatic- and alkanolamines in aqueous solutions. Isocyanates were determined by reversed-phase liquid chromatography MSMS. HILIC in combination with MS is a most powerful system, and highly sensitive determinations, several orders of magnitude below the OELs, of polar compounds present in the work environment can be accomplished. The selected samplers enable sampling during short sampling times and for whole work shifts. The samplers can be stored for months before and after sampling. The performance of the samplers was unaffected by variation in temperature, humidity, flow-rate and pre- and post-sampling of ambient air. Sampling for the compounds studied is now greatly simplified, and assessment of the work environment is facilitated. / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Epub ahead of print; Papers 3-5: Manuscripts</p>

Changing in variance or volatility with time can be modeled as deterministic by using autoregressive conditional heteroscedastic (ARCH) type models, or as stochastic by using stochastic volatility (SV) models. This study compares these two kinds of models which are estimated on Turkish / USA exchange rate data. First, a GARCH(1,1) model is fitted to the data by using the package E-views and then a Bayesian estimation procedure is used for estimating an appropriate SV model with the help of Ox code. In order to compare these models, the LR test statistic calculated for non-nested hypotheses is obtained.

This thesis considers the problem of performing inference on undirected graphical models with continuous state spaces. These models represent conditional independence structures that can appear in the context of Bayesian Machine Learning. In the thesis, we focus on computational methods and applications. The aim of the thesis is to demonstrate that the factorisation structure corresponding to the conditional independence structure present in high-dimensional models can be exploited to decrease the computational complexity of inference algorithms. First, we consider the smoothing problem on Hidden Markov Models (HMMs) and discuss novel algorithms that have sub-quadratic computational complexity in the number of particles used. We show they perform on par with existing state-of-the-art algorithms with a quadratic complexity. Further, a novel class of rejection free samplers for graphical models known as the Local Bouncy Particle Sampler (LBPS) is explored and applied on a very large instance of the Probabilistic Matrix Factorisation (PMF) problem. We show the method performs slightly better than Hamiltonian Monte Carlo methods (HMC). It is also the first such practical application of the method to a statistical model with hundreds of thousands of dimensions. In a second part of the thesis, we consider approximate Bayesian inference methods and in particular the Expectation Propagation (EP) algorithm. We show it can be applied as the backbone of a novel distributed Bayesian inference mechanism. Further, we discuss novel variants of the EP algorithms and show that a specific type of update mechanism, analogous to the mirror descent algorithm outperforms all existing variants and is robust to Monte Carlo noise. Lastly, we show that EP can be used to help the Particle Belief Propagation (PBP) algorithm in order to form cheap and adaptive proposals and significantly outperform classical PBP.

Made available in DSpace on 2015-03-26T13:42:34Z (GMT). No. of bitstreams: 1 texto completo.pdf: 9480742 bytes, checksum: f87c9b2653b911e326eef4b5a0dd87ce (MD5) Previous issue date: 2014-07-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to evaluate the quality of relationship information over genetic parameters estimates and accuracies of breeding values. Thus, we evaluated the quality by making corrections based on SNPs markers. Variance components were estimated under Bayesian approach via Gibbs sampling. The evaluation of the correct relationship was performed using markers of 3,591 individuals in a population consisting of 12,668 animals. Mendelian conflicts were deflned as conflicts between the progeny and parents markers. Thus, 460 changes were performed, which 54% had a buII or cow on pedigree. We observed, on average, match parent were defined with 75 markers, whiIe no- match parent n was performed with 2,700 markers. Annealing algorithm Molecular coancestry program provided 2,174 new haIf-sibs relationships. We observed that higher quality on pedigree information provided increase in accuracy of breeding values and higher heritability estimates (0.22 i 0.0286), suggesting the possibility of direct selection for tick resistance. We used a 5-fold cross-validation strategy using K-means and random methods to group the animals. The results of cross-validation indicate that higher quality of the pedigree relationships provide higher accuracy. The weaning weight was used to evaluate muItipIe sires progeny (MS) and embryo transfer and in vitro fertilization animals (TEF). We used three strategies to include MS information: genetic groups (GG), bayesian hierarchical method (HIER) and the average numerator relationship matrix (ANRM). The deviance information criteria (DIC) was used as Bayesian measure of fIt, which suggested that HIER strategy provided better fIt when MS information is consider. However, ANRM provided best fit to include TEF animals. We use foster dam information to estimate the maternal genetic and maternal permanent environmental effects when considering TEF animals. We didn't observed statistical difference in variance components and genetic parameters considering information TEF animals, but breeding values showed greater values. Spearman correlations between breeding values were higher for base, animals with certain paternity and MS progeny. However, the use of TEF animals information significantly changed the predicted breeding values. The use of appropriate methodologies to include the information of MS progeny and TEF animals provide most accurate prediction of breeding values and assist in higher rates of genetic gain. / O objetivo desse estudo foi verificar o reflexo da qualidade das informações de parentesco sobre as estimativas de parâmetros genéticos e acurácias das predições de valor genética Dessa forma, foi avaliada a qualidade dessas informações ao realizar correções no pedigree baseadas em marcadores do tipo SNPs. Os componentes de variância foram estimados sob enforque Bayesiano por amostragem de Gibbs. A avaliação da correta definição de parentesco foi realizada utilizando-se informações de marcadores SNPs de 3.591 indivíduos em uma população constituída de 12.668 animais. Os conflitos mendelianos entre as marcas da progênie e dos pais foram utilizados como critério de avaliação de parentesco. Dessa forma, foram realizadas 460 mudanças no pedigree, dentre os quais 54% possuíam um touro ou vaca identificado. Foi observado que, em média, novos relacionamentos genéticos foram definidos com 75 marcas em conflito, enquanto que a rejeição do parentesco foi realizada com 2.700 marcas. O uso do programa Molecular Coancestry para inferência de parentesco a partir de informações de marcadores moleculares proporcionou a definição de 2.174 novos relacionamentos de meio-irmãos. Foi possível observar que as correções de parentesco proporcionaram aumento da acurácia média dos valores genéticos preditos. O aumento na qualidade das informações de pedigree proporcionou a estimação de herdabilidade de maior magnitude (0,22 i 0,0286), sugerindo a possibilidade de seleção direta para a resistência a carrapatos. Foi utilizada uma estratégia de validação cruzada pelo método K-médias e também de forma aleatória, no qual cinco grupos de treinamento foram formados. Os resultados da validação cruzada indicam que maior qualidade nos relacionamentos do pedigree proporcionam maior valor de acurácia. O peso padronizado aos 205 dias foi utilizado para avaliar a inclusão de informações de filhos de reprodutores múltiplos (RM) e de animais oriundos de biotécnicas da reprodução (TEF). Foram avaliadas três estratégias de inclusão dessas informações: grupos genéticos (GG), método hierárquico bayesiano (HIER) e matriz da média dos numeradores dos coeficientes de parentesco (ANRM). O critério de informação da deviance (DIC) foi utilizado como avaliador da qualidade de ajuste e sugeriu que a estratégia HIER proporcionou melhor ajuste ao considerar as informações de RM. Entretanto, o método ANRM apresentou melhor ajuste ao incluir informações dos animais TEF. A inclusão das informações de animais TEF foi realizada pelo uso da informação da receptora para estimação do efeito genético materno e de ambiente permanente materno. Não foi observada diferença estatística nas estimativas de componentes de variância e de parâmetros genéticos ao considerar informações de animais TEF, porém os valores genéticos preditos apresentaram maior magnitude. As correlações de Spearman entre os valores genéticos foram de elevadas magnitudes para os animais fundadores, animais com certeza no parentesco e para os fiIhos de RM. Entretanto, o uso das informações dos animais TEF modificou de forma significativa as predições dos valores genéticos. O uso de metodologias adequadas para incluir a informação de animais com incerteza de paternidade e animais oriundos de transferência de embriões e fertilização in vitro proporcionam a predição de valores genéticos mais acurados e auxiliam em maiores taxas de ganho genético.

Made available in DSpace on 2014-12-17T15:03:19Z (GMT). No. of bitstreams: 1 AryTAN.pdf: 1949309 bytes, checksum: 336240ee8606021d63e4dcca774a40b1 (MD5) Previous issue date: 2008-12-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The aim of this approach is to describe the design and construction of a low-cost automated water sampler prototype. In recent years, there is an increasing need on the use of automated equipments for hydro climatic variables to be use in urban and rural environments. Such devices are always used to provide measured information which is of crucial importance on the development of water resources strategies at watershed scale. Actually, many research and water public institutions have been using these kinds of equipments. In most of the cases, automated equipments are expensive and need to be imported, generating a situation of technologic dependency. The prototype is based on an electronic system which controls a peristaltic pump functioning, five solenoid valves and an ultrasonic sensor connected to a datalloger. An interface with the user allows communication with a PC, when the equipment functioning parameters can be provided. The equipment has a hydraulic module composed by a 12V peristaltic pump connected to a distribution circuit composed by five solenoid valves, one of them being used to clean the circuit before each sampling procedure. Samples are collected by four 1.95 polyethylene bottles. The sampler body was made of acrylic material, with a cylindrical shape, and dimensions 0.72 m and 0.38 m height and diameter, respectively. The weight of the equipment without samples is approximately 15 kg, which infers to its portability. The prototype development total cost budget was approximately US$ 1,560.00. Laboratory tests aimed to evaluate the equipment performance and functioning demonstrated satisfactory results / O objetivo deste estudo ? desenvolver e apresentar um prot?tipo de coletor autom?tico de amostras de ?gua. Nos ?ltimos anos, tem havido uma crescente necessidade no uso de equipamentos autom?ticos no monitoramento de vari?veis hidro-clim?ticas, tanto em ambientes rurais como urbanos. Esses equipamentos s?o normalmente usados para gerar informa??o de vital import?ncia no desenvolvimento de a??es em recursos h?dricos na bacia hidrogr?fica. Atualmente, v?rias institui??es p?blicas e de pesquisa t?m usado esses tipos de equipamentos. Na maioria dos casos, os equipamentos autom?ticos s?o caros e necessitam ser importados, gerando uma situa??o de depend?ncia tecnol?gica. O prot?tipo desenvolvido tem como base um sistema eletr?nico que controla o funcionamento de uma bomba perist?ltica, cinco v?lvulas solen?ides e de um sensor ultra-s?nico acoplados a um datalogger. Uma interface com o usu?rio permite comunica??o com um PC, quando os par?metros de funcionamento do equipamento podem ser introduzidos. O equipamento disp?e de um m?dulo hidr?ulico composto de uma bomba perist?ltica 12V acoplada a um circuito de distribui??o com cinco v?lvulas solen?ides, uma delas usada na limpeza do circuito antes de cada coleta de amostra. As amostras s?o coletadas em quatro garrafas de polietileno, capacidade 1,95 ml. A estrutura do equipamento ? feita em acr?lico, com um formato cil?ndrico, dimens?es 0,72 m e 0,38 m de altura e di?metro, respectivamente. O peso do equipamento sem as amostras ? de aproximadamente 15 kg, o que lhe confere portabilidade. O or?amento referente ao custo total de desenvolvimento do equipamento foi de aproximadamente 1.560 d?lares americanos. Testes em laborat?rio, realizados para avaliar seu desempenho e funcionamento, foram bastante satisfat?rios

Made available in DSpace on 2014-12-17T15:03:24Z (GMT). No. of bitstreams: 1 YTCS_DISSERT.pdf: 5384825 bytes, checksum: aa8710a0ccd842fef87d4421af582dca (MD5) Previous issue date: 2009-12-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Only 32% of the population of Natal is attended by sewage, while the remaining population use pits and septic tanks. The characterization of the contents of septic tanks and pits contributes to the performance of such system and may guide the decision on treatment of these contents. The main of this research is to characterize the contents of interior residential pits and septic tanks in the greater Natal, with the following specific goals: to develop and manufacture a sampler capable of collecting a representative sample of the entire column (the surface scum, the clarified liquid and sludge bottom); to compare the contents of the tanks with the pits; to compare the contents of the septage from vacuum trucks; to relate the composition content with socioeconomic characteristics of households; to compare the content in both chambers of the septic tanks in series; to assess the situation of the content before and six months after the cleanness; and ultimately propose a pilot scale plant for treatment of septage. Once the sampler was developed, samples were collected within 14 septic tanks and 10 pits in many districts of Natal. Medians of the 24 systems were obtained: temperature, pH, conductivity, oil and grease, total solids, total suspended solids and sediments of 28.0 ?C, 6.95; 882 mS/cm, 75.2 mg/L; 10,169 mg/L, 6,509 mg/L and 175 mL/L respectively; 111.0 mgN/L for ammonia, 130.5 mgN/ L for organic nitrogen, 0.2 mgN/L for nitrite, 0.4 mg/L for nitrate; 8935 mgO2/L for COD, 29.2 mgP/L for total phosphorus, thermotolerant coliforms from 9.95 E +06 CFU/100mL helminth eggs and 9.2 eggs/L with a maximum concentration of 688 eggs/L and minimum of 0 eggs/L. Medians of organic nitrogen and TKN were significantly different between groups of tanks and pits. The systems with cleanness gap from 11 and 20 years presented the higher concentrations for most variables. The effluent from the toilets and bathrooms participate more effectively in contributing fractions of solids, alkalinity, nitrogen, COD, total phosphorus, thermotolerant coliforms and helminth eggs. The systems used by socioeconomics class with income from R$ 3,700.00 to R$ 7,600.00, presented higher concentrations for COD, nitrogen, solids and helminth eggs. The first of the two chambers had always presented higher concentrations over the second compartment. The analysis of variance for most variables, showed that the values of septic tanks, pits and septage from vacuum trucks belong to the same group. In the samples taken after cleanness, the median of pH and temperature increased, while alkalinity, COD, organic nitrogen, total phosphorus, ammonia and helminth eggs decreased. The oils and greases and thermotolerant coliforms had slightly varied due to the continuous release of sewage into the systems that maintained their steady state concentrations. / Apenas 32% da popula??o de Natal ? coberta por rede coletora de esgotos, sendo as fossas e tanques s?pticos os mecanismos de disposi??o de esgotos comumente utilizados pelo restante da popula??o. A caracteriza??o do conte?do de fossas e tanques colabora para o conhecimento sobre o tratamento desses res?duos no pr?prio domic?lio, al?m de enriquecer as informa??es a respeito deste conte?do. O objetivo geral desta pesquisa ? caracterizar o conte?do do interior de fossas e tanques s?pticos residenciais da cidade de Natal, tendo como metas espec?ficas desenvolver e fabricar um amostrador capaz de coletar uma amostra representativa de toda a coluna dos tanques s?pticos e fossas, que contemple a escuma da superf?cie, o l?quido clarificado e o lodo presente no fundo; comparar o conte?do dos tanques com os das fossas; comparar o conte?do com os res?duos dos caminh?es limpa-fossa; avaliar a composi??o do conte?do e relacionar com as caracter?sticas s?cio-econ?micas dos domic?lios; comparar a qualidade do conte?do nas duas c?maras dos tanques s?pticos em s?rie; avaliar a situa??o do conte?do antes e decorridos seis meses ap?s o esgotamento e, por fim, propor uma esta??o, em escala piloto, para o tratamento dos res?duos gerados por tanques s?pticos e fossas. Com o amostrador desenvolvido foram coletadas amostras do interior de 14 tanques s?pticos e 10 fossas em bairros de Natal. O conte?do dos 24 sistemas obteve medianas para temperatura, pH, condutividade el?trica, ?leos e graxas, s?lidos totais, s?lidos suspensos totais e sediment?veis de 28,0?C; 6,95; 882 mS/cm; 75,2 mg/L; 10.169 mg/L; 6.509 mg/L e 175 mL/L respectivamente; 111,0 mgN/L para am?nia, 130,5 mgN/L para nitrog?nio org?nico, 0,2 mgN/L para nitrito, 0,4 mg/L para nitrato; 8.935 mgO2/L para DQO, 29,2 mgP/L para f?sforo total; coliformes termotolerantes de 9,95E+06 UFC/100mL e ovos de helmintos 9,2 ovos/L com concentra??o m?xima de 688 ovos/L e m?nima de 0 ovos/L. Houve diferen?a estat?stica significativa para nitrog?nio org?nico e NTK entre os grupos dos tanques e fossas. A classe com tempo de esgotamento entre 11 a 20 anos apresentou para a maioria das vari?veis concentra??es bem mais elevadas. O efluente oriundo dos banheiros e sanit?rios participou mais efetivamente na contribui??o das fra??es dos s?lidos, alcalinidade, fra??es nitrogenadas, DQO, f?sforo total, coliformes termotolerantes e ovos de helmintos. A classe com renda entre R$ 3.700,00 a R$ 7.600,00, apresentou maiores concentra??es para DQO, nitrog?nio, s?lidos e ovos de helmintos. A primeira c?mara dos tanques s?pticos de duas c?maras em s?rie apresentou conte?do mais concentrado em rela??o ao segundo compartimento. Nas an?lises de vari?ncia a maioria das vari?veis apontou que os valores de fossas, tanques s?pticos e res?duos de carros limpa-fossa pertencem ao mesmo grupo. Na amostragem ap?s o esgotamento, o pH e temperatura aumentaram suas medianas, enquanto que alcalinidade, DQO, nitrog?nio org?nico, f?sforo total, am?nia e ovos de helmintos diminu?ram. Os ?leos e graxas e coliformes termotolerantes variaram pouco devido ao lan?amento cont?nuo de esgoto dentro dos sistemas que mantinham suas concentra??es est?veis

O ensaio SPT (Standard Penetration Test) é um dos ensaios geotécnicos mais utilizados no Brasil e em grande parte do mundo, para determinar o índice NSPT. Esse índice é usado para estimar, através de correlações empíricas, parâmetros do solo, capacidade de suporte, recalque de fundações, etc. Pelo fato destas correlações não terem nenhum fundamento científico, pesquisadores têm procurado desenvolver métodos racionais de análise, baseados em energia. Com esses métodos pode-se determinar a eficiência do ensaio SPT, que é uma importante característica utilizada nas análises dos resultados do ensaio. As quantidades de energia envolvidas no ensaio SPT são determinadas através do método EFV. Para tanto, é necessária a utilização de hastes instrumentadas com acelerômetros e células de carga durante a realização dos ensaios. Com os sinais de força e aceleração foram determinadas as quantidades de energia, força de reação dinâmica experimental do solo, forças de reação teórica estática e dinâmica e tensões atuantes no amostrador. Neste trabalho, como os sinais de força e aceleração foram registrados em uma seção instrumentada logo acima do amostrador, a eficiência do sistema pode ser determinada de acordo com a definição proposta por Aoki e Cintra (2000), e incluindo a correção sugerida por Odebrecht (2003). Nesta pesquisa foi desenvolvido um sistema de extrator de amostras, constituído de uma base, um cilindro hidráulico e uma célula de carga, para quantificar experimentalmente a força de atrito interno para posteriormente determinar as demais tensões que atuam no amostrador e o parâmetro a de Aoki, o qual é a razão entre o atrito interno e o atrito externo entre o solo e o amostrador. / The Standard Penetration Test (SPT) is one of the in-situ geotechnical tests most used in Brazil, as well as in many parts of the world. Through empirical correlations, the NSPT index is used to estimate parameters of the soil, carrying capacity, discharge of foundations, etc. Because these correlations have no scientific basis, researchers have developed rational methods of analysis, based on energy concepts. Using these concepts, the efficiency of the SPT, which is essential in the analysis of the test results, can be assessed. The amounts of energy involved in the SPT test are evaluated by the EFV method. Therefore, it is necessary instrumented rods with accelerometers and load cells for performing the tests. With force and acceleration records, amounts of energy, experimental dynamic reaction force of the soil, theoretical static and dynamic reaction forces and stresses acting on the sampler were assessed. In this work, as the force and acceleration signals were recorded at an instrumented section just above the sampler, the system efficiency could be determined according to the definition proposed by Cintra and Aoki (2000), including the energy corrections suggested by Odebrecht (2003). In this study, a sample extractor system consisting of a base, a hydraulic cylinder and a load cell was designed. The objective of this equipment is to experimentally quantify the internal friction force, allowing evaluating the stresses acting on the sampler. Also, the Aoki\'s a parameter, which is the ratio of internal friction and external friction between the ground and the sampler, could be calculated.

In high range-resolution (HRR) radar systems, the returns from a single target may fall in multiple adjacent range bins which individually vary in amplitude. A target following this representation is commonly referred to as an extended target and results in more information about the target. However, extracting this information from the radar returns is challenging due to several complexities. These complexities include the single dimensional nature of the radar measurements, complexities associated with the scattering of electromagnetic waves, and complex environments in which radar systems are required to operate. There are several applications of HRR radar systems which extract target information with varying levels of success. A commonly used application is that of imaging referred to as synthetic aperture radar (SAR) and inverse SAR (ISAR) imaging. These techniques combine multiple single dimension measurements in order to obtain a single two dimensional image. These techniques rely on rotational motion between the target and the radar occurring during the collection of the single dimension measurements. In the case of ISAR, the radar is stationary while motion is induced by the target. There are several difficulties associated with the unknown motion of the target when standard Doppler processing techniques are used to synthesise ISAR images. In this dissertation, a non-standard Dop-pler approach, based on Bayesian inference techniques, was considered to address the difficulties. The target and observations were modelled with a non-linear state space model. Several different Bayesian techniques were implemented to infer the hidden states of the model, which coincide with the unknown characteristics of the target. A simulation platform was designed in order to analyse the performance of the implemented techniques. The implemented techniques were capable of successfully tracking a randomly generated target in a controlled environment. The influence of varying several parameters, related to the characteristics of the target and the implemented techniques, was explored. Finally, a comparison was made between standard Doppler processing and the Bayesian methods proposed. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

This Thesis addressed the challenge of ensuring balanced currents in the phases of a multi-kW, interleaved dc-dc converter by means of closed-loop digital control. The Thesis examines uniformly-sampled, valley-current, peak-current and average-current control for a dual interleaved boost converter with inter-phase transformer which might form part of the power train of an electric vehicle. Also, an enhancement of the average-current control is investigated in which the transistor duty-ratio is updated more rapidly, which allows an improvement of approximately ten times in the response speed of the system. Based on the theoretical analysis, the average-current control methodology was determined to be the most suitable technique for this type of converter as it ensures well-balanced phase currents over a wide range. To provide a basis for control system analysis and design for interleaved converters, a modelling methodology is developed based on a combination of multi-rate data-sampled theory and a small-signal averaged converter model. The model is shown to represent accurately the interaction between the interleaved phases, revealing a reduced stability range compared with a non-interleaved converter. The modelling and control methods are validated using switched and average value simulations obtained with the SABER software and by experimental results from a 25 kW, 30 kHz converter prototype. The control techniques were implemented on a Texas Instruments TMS320F28335 digital signal controller.