As Máquinas de Medir a Três Coordenadas (MM3Cs) possuem erros inerentes à sua estrutura que afetam a exatidão e a repetibilidade das medições. Dos erros presentes nessas máquinas, os erros geométricos são, na maioria das vezes, os de maior influência. O resultado da combinação destes erros em cada uma das direções preferenciais é denominado componente do erro volumétrico. Assim, torna-se de vital importância conhecer a relação existente entre as variáveis envolvidas num processo de medição qualquer, ou seja, a relação entre as coordenadas dos pontos medidos, os erros geométricos e as componentes do erro volumétrico. Diversos métodos foram propostos para modelar o comportamento dos erros nas MM3Cs. Entretanto não existem, ainda, modelos matemáticos obtidos a partir de dados experimentais que descrevam e caracterizem estes erros. Por tal motivo este trabalho apresenta uma metodologia geral para equacionar as componentes do erro volumétrico em MM3Cs, utilizando técnicas de regressão múltipla. Esta ferramenta permite de forma simples equacionar e prever o erro volumétrico da máquina avaliada. A metodologia foi aplicada a uma MM3C do tipo \"Ponte Móvel\". Foram obtidas três equações de regressão, uma para cada componente do erro, a partir de dados levantados através da calibração direta, especificamente o método do volume dividido. A adequabilidade do modelo foi avaliada estatisticamente. Os resultados obtidos foram discutidos e comparados com os resultados obtidos através da calibração utilizando-se uma barra de esferas, constatando-se uma excelente capacidade do modelo na previsão do erro total da máquina. Ainda, efetuo-se a compensação do erro volumétrico em duas diagonais do volume de trabalho da máquina avaliada utilizando-se o modelo proposto, neste caso, o erro foi diminuído sensivelmente. / The accuracy and the repeatability of measurements of Three Coordinates Measuring Machines (CMM) are affected by several errors. Among them, geometrical errors are the most influents in the most experimental cases. The result of geometric errors combination in each of the preferentials directions is denominated of volumetric error components. Thus, its possible to know the existent relationship between coordinates of measured points and volumetric error components. Several methods have been proposed to model the behavior of the volumetric error in CMM as a function of the X, Y and Z coordinates. However, sofar from experimental measurements of the volumetric error has bem proposed mathematical model for the descriptions and characterizations of errors was obtained. In this work is presented a general methodology to obtain a mathematical equation and prediction of them components of the volumetric errors, using multiple regression. The methodology was applied at a of \"Moving Bridge\" CMM type. Were obtained three regression equations, one for each component of the error, starting from data collected by direct calibration, specifically by the divided volume method. The model was evaluated statistically. The simulated results were evaluated, discussed and compared with the results obtained through the ball bar calibration, showing an excellent capacity of the model in the prediction of the volumetric error of the machine. Besides was made the compensation of the volumetric error in two diagonals of the working volume of the appraised machine using the proposed model, in this case the error was minimized sensibly.

O projeto de funções de transferência é um interessante problema que recebe muita atenção da comunidade de visualização. Diversas pesquisas tem sido conduzidas para criar melhores ferramentas e técnicas que trabalham com dados volumétricos. Existem duas grandes classes de dados: volumes estruturados e volumes não-estruturados. A maioria dos trabalhos anteriores apenas se refere a dados estruturados. Este trabalho possui dois grupos de contribuições. O primeiro diz respeito ao problema clássico de especificação de funções de transferência. Primeiramente é desenvolvido o conceito de Ensembles, que são funções de transferência desenvolvidas a partir da combinação de funções anteriores e mais simples. Também é apresentada uma abordagem de key-framing para manipular dados que variam no tempo. O segundo grupo de contribuições é um estudo aprofundado sobre o comportamento de dados não-estruturados. Problemas críticos foram descobertos e tratados para permitir uma integração quase perfeita de ferramentas usadas para dados estruturados em dados não-estruturados. Os resultados mostram a melhoria de qualidade de histogramas, e também o sistema de desenvolvimento de funções de transferência. Trabalhos futuros são sugeridos para utilizar a versão melhorada do histograma de gradiente-magnitude, assim como a exploração de novos modelos de bordas. / Transfer function design is an important problem that receives much attention from the visualization community. Several researches have inspired the creation of better tools and techniques to deal with volumetric datasets. There are two major classes of datasets, namely structured and unstructured grids. Most of the previous work has only addressed structured data. This work presents two groups of contributions of different nature. The first contribution is related to the general problem of transfer function design. It introduces the concept of ensembles, which are complex transfer functions created from standard types. It also presents a key-frame based approach to handle time-varying sequences. The second group of contributions is related with a study on several characteristics of unstructured data. Problems have been discovered and addressed to allow a seamless integration of classical structured grids tools to unstructured data. This work includes results that show improvements on a statistical analysis of the data, as well as the developed transfer function design system. Further work is suggested to take advantage of the enhanced version of the gradient-magnitude histogram, and explore different boundary model.

Este trabalho tem por objetivo a investigação do comportamento de equipamentos de radiodiagnóstico em termos da qualidade da imagem produzida e a subseqüente aplicação desses resultados na otimização do desempenho de esquemas computacionais de auxílio ao diagnóstico, também conhecidos como esquemas CAD (do inglês, Computer-Aided Diagnosis). A principal meta consiste no desenvolvimento de técnicas de pré-processamento para imagens mamográficas digitalizadas que as realçasse de acordo com as características e limitações dos equipamentos utilizados na sua aquisição. A proposta está dividida em duas etapas. Na primeira, foram determinadas as características relativas tanto à resolução espacial como à resolução de contraste de diversos equipamentos mamográficos, avaliadas respectivamente pelas funções de transferência óptica e espectros de Wiener do ruído. Isto permitiu, numa segunda etapa, o desenvolvimento de um filtro digital específico para o pré-processamento de diferentes conjuntos de mamogramas digitais, separados de acordo com os equipamentos utilizados no processo de aquisição. Dessa forma, cada imagem mamográfica teve sua qualidade melhorada de acordo com as características do equipamento que a gerou, determinadas na primeira etapa. Essas imagens, depois de realçadas, foram utilizadas em um esquema CAD previamente desenvolvido, onde pôde ser observada uma melhora em até 12% no seu desempenho quando comparado aos resultados obtidos com imagens mamográficas não realçadas. / The purpose of this work is to evaluate the quality of radiological equipment and their images in order to use these evaluations to improve the performance of a computer-aided diagnosis (CAD) scheme. The mean idea is about the development of image processing techniques to enhance digital mammograms according to the characteristics of the X-ray unit used for image acquisition. This work is basically divided in two parts. In the first one, it were determined the characteristics related to spatial and contrast resolution of several mammographic equipment, evaluated respectively from the optical transfer function and noise Wiener spectrum. This evaluation allowed, in a second part, the development of a preprocessing technique to enhance different set of digital mammographic images, gathered according to the equipment used on its acquisition process. Thus, each mammographic image had its quality improved in conformity with the characteristics of the equipment used on its acquisition, determined in the first part of this work. These images, after the enhancement process, were used on a previously developed CAD scheme. It was observed an improvement of 12% on the CAD performance using pre-processed mammograms compared to the results obtained when using non-enhanced mammographic images.

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The current study investigated concept formation in domestic dogs, specifically that of a toy concept. The dog's differential responding (retrieval vs. non-retrieval) to two sets of stimuli suggested a toy concept. Differential responding occurred from the very first trial, indicating that the concept had been formed in the natural environment, not during the experiment. It was hypothesized that a common response may be responsible for the emergence of the class in the natural environment. The results demonstrated that it was possible to expand the class by adding previously non-retrieved objects to the toy class through a common response. It was also shown that the toy concept passed the more stringent criterion (transfer of function test) required validating it as a concept.

This thesis deals with analysis and modelling of power line communications. The main aim is to examine the effects influencing transsmision of communication signals on powerline networks and theoretical capacity of the PLC channel using PLC framework created in NS-3. The introduction summarizes the theoretical knowledge in the area of data transmission over power line distribution network. Different types of noise and possibilities of calculation of theoretical transmission capacity are described as well. Several simple simulations are realized in practical part of this paper. These simulations explore the influence of the distance between the transmitter and receiver, length, impedance and number of branches between these nodes, affect of the type of modulation and noise on the transfer function as well as the capacity of the channel. There are also some simulations for large topology based on real position of electrometer. The main focus is to find positions of repeaters to ensure that some nodes of the topology can communicate.

The thesis is dealing with data transmission over the electric network. It describes PLC technology, its properties, and elements used in this type of network. The important part of this thesis is discussion over the mathematical model of distribution network with two-port cascades. Transmission functions created according to mathematical model were compared with each other. Thesis was concluded with observation of the impact of interconnected parts on transmission function of designed branched conductor. Final results were processed by Matlab and compared with each other.

The aim of this thesis is to create a power line transfer function generator in Matlab. Work on introduction explains the concept of power line and describes the different types of topologies and types of cables that power line are the most widely used today. It is also discussed PLC technology, its structure, characteristics of the transmission channel and interferences. The following are approach the types of the modeling of power line. More details are described generally modeling in the frequency (two-port network model), which is used in the created generator. The next section provides a power line model, whose principle is used in the generator. The following is a description of created the generator and comparison with FTW PLC Simulator. In conclusion, the thesis presents the results of simulations the transfer function, which show the magnitude and phase frequency characteristics of different topologies and parameters.

This thesis deals with the powerline communication focusing on the simulations of channel transfer functions. The introduction summarizes basic information about PLC followed by the analysis of the available PLC Software simulator (implemented in NS-3) and the analysis of implemented noises and interferences and its extensions. One chapter is devoted to possibilities of link capacity calculation. Within the thesis, various methods of calculation of primary parameters of transmission line were implemented and the simulator was compared with other freely available simulators. Subsequently, simulations were carried out focused on channel transfer functions in different topologies, on the impedance changes of branch, on the lengths of branch, and changes in the direct path between communicating nodes.

The master’s thesis is focused on the analysis and modeling of power line communication with aim to implement power line channel simulator in the programming environment Matlab. At the beginning of the thesis are summarized basic information about the PLC communication, its basic distribution in terms of frequency bands and are also mentioned advantages and disadvantages. The emphasis on the meaning and importance of modeling with the aim to analyze PLC communication channel is specified further. The following is a detailed description of the current power lines communication models. Power line channel simulator was created on the basis of mathematical analysis for low-voltage (LV) distribution networks. The created simulator uses a model of cascaded two-ports and works in random or fixed mode. Input parameters are real topologies, different types of loads and cables. RLC resonant circuit as a frequency selective impedance is also included in impedance models. Based on the obtained results was performed the analysis, determined the critical parameters and extreme values. Comparison of effectiveness of created simulator was processed on the basis of available simulators from other authors. Two versions of simulator were created using the results obtained under comparison of effectiveness. For comparison was also performed real measurement on a simple topology. The experimental measurements results have been implemented in the simulator.