This thesis describes the interfacing of an IBM compatible microcomputer to a BR Communications chirp sounder. The need for this is twofold: Firstly for control of the sounder including automatic scheduling of operations, and secondly for data capture. A signal processing card inside the computer performs a Fast Fourier Transform on the sampled data from two phase matched receivers. The transformed data is then transferred to the host computer for further processing, display and storage on hard disk or magnetic tape, all in real time. Critical timing functions are provided by another card in the microcomputer, the timing controller. Built by the author, the design and operation of this sub-system is discussed in detail. Additional circuitry is required to perform antenna and filter switching, and a possible design thereof is also presented by the author. The completed system, comprising the chirp sounder, the PC environment, and the signal switching circuitry, has a dual purpose. It can operate as either a meteor radar, using a fixed frequency (currently 27,99 MHz), or as an advanced chirp ionosonde allowing frequency sweeps from 1,6 to 30 MHz. In the latter case fixed frequency doppler soundings are also possible. Examples of data recorded in the various modes are given.

This report describes the results of computerized ultrasonic C-scanning of solid steel bridge pins using a raytrace model. The raytrace model was developed to facilitate interpretation of data obtained from an ultrasonic C-scanning system for the Virginia Transportation Research Council (VTRC). The report discusses the reasons behind the development of the raytrace model, as well as specifications of the model, the input conditions, and the data output and visualization. The model uses as input, various "boundary" conditions of the solid steel pin with reduced diameter pin ends, as well as size and location information of a flaw or a wear groove placed within the main pin body. The model considers sound beams to be composed of rays and calculates ray reflections/conversions. This is done until the ray returns to a receiver location or is lost due to exceeding the time-of-flight. Once the model has returned with the received ray data, it uses the receiver conditions provided (transducer used, size of scanning grid, grid resolution, etc.), and calculates a 2-Dimensional C-scan image for each particular depth/time selected. Using PV-Wave visualization software, it is possible to plot the values for each depth to view a color graph. This graphical plot can then be analyzed/compared with the field C-scans to determine the closest match of a flaw or a wear groove inside the bridge pin. This helps in deciding if the condition of the pin is acceptable. / Master of Science

This study was designed to compare the effects of two stress reduction programs on selected male and female Black African students, enrolled in a public two-year liberal arts college in Atlanta, Georgia. An additional purpose was to determine if significant differences existed between selected male and female Black African students in their stress levels. The participants consisted of 15 male and 18 female Black African students. The instrument used in this study for data collection was the Coping Resource Inventory (CRI). The research design for this study was quasi experimental, t-test and two-way Anova procedures were used to analyze the data. The results of the t-test at the .05 level of confidence showed significant difference between pre-and-post test results for the computerized stress reduction program.

O objetivo neste estudo foi comparar modelos de prototipagem, originados a partir de dados obtidos em exames de tomografia volumétrica (TV) e tomografia computadorizada (TC), a fim de verificar a precisão de reprodutibilidade destas tecnologias. Uma mandíbula seca foi submetida aos exames de TV (NewTom 9000? QR, Itália) e TC (Select SP-Elscint, Israel). Os dados obtidos nos exames foram manipulados em dois sistemas de tratamento de imagem, o 3D- Analyze (Mayo Clinic, E.U.A.) e o InVesalius (CenPRA, Brasil) e confeccionados protótipos, em duas diferentes tecnologias (SLS - sinterização seletiva a laser e 3DP - impressão tridimensional). A mandíbula seca (padrão ouro) e os oito conjuntos de protótipos gerados, sendo I-TC-Analyze?3DP; II-TC-Invesalius?3DP; III-TC-Analyze?SLS; IVTC- Invesalius-SLS; V-TV-Analyze?3DP; VI-TV-Invesalius?3DP; VIII-TV-Analyze? SLS; VIII-TV-Invesalius-SLS, foram submetidos a processos de engenharia reversa com a finalidade de digitalizar as superfícies dos objetos para uma comparação de cada modelo de prototipagem produzido com o padrão ouro, com precisão de 0,001mm. Os desvios de até 1mm e até 2mm foram calculados, comparados e analisados estatisticamente os erros percentuais. Os modelos de prototipagem rápida originados por meio da obtenção de dados de exames de tomografia computadorizada são mais precisos que os modelos de prototipagem originados por meio de dados de exames de tomografia volumétrica. / The purpose of this study is to compare rapid prototyping models created from cone beam computerized tomography (CBCT) and multislice computerized tomography (CT) data, in order to verify the accuracy of these technologies. A dry skull mandible was submitted in a CBCT (NewTom ? QR, Italy) and CT (Select SP-Elscint, Israel) exams. The tomographies data were processed by two different Medical Image processing systems, 3D-Analyze (Mayo Clinic, U.S.A.) and InVesalius (CenPRA, Brazil). Rapid prototypes models were built in two different rapid prototyping technologies, 3D Printer (3DP) and Selective Laser Sintering (SLS). The dry skull mandible (gold standard) and the eight prototypes, as follows; I-CT-Analyze?3DP; IICT- Invesalius?3DP; III-CT-Analyze?SLS; IV-CT-Invesalius-SLS; V-CBCT-Analyze? 3DP; VI-CBCT-Invesalius?3DP; VIII-CBCT-Analyze?SLS; VIII-CBCT-Invesalius-SLS, were submitted to a reverse engineering process aimed to digitalize the surfaces of the objects to compare each rapid prototype model with the gold standard with a precision of 0.001mm. Percentage deviations errors until 1.0mm and 2.0mm were calculated, compared and statistically analyzed. The prototyped models obtained with multislice computerized tomography data shows more accuracy than those obtained with data from cone beam computerized tomography.

O objetivo neste estudo foi comparar modelos de prototipagem, originados a partir de dados obtidos em exames de tomografia volumétrica (TV) e tomografia computadorizada (TC), a fim de verificar a precisão de reprodutibilidade destas tecnologias. Uma mandíbula seca foi submetida aos exames de TV (NewTom 9000? QR, Itália) e TC (Select SP-Elscint, Israel). Os dados obtidos nos exames foram manipulados em dois sistemas de tratamento de imagem, o 3D- Analyze (Mayo Clinic, E.U.A.) e o InVesalius (CenPRA, Brasil) e confeccionados protótipos, em duas diferentes tecnologias (SLS - sinterização seletiva a laser e 3DP - impressão tridimensional). A mandíbula seca (padrão ouro) e os oito conjuntos de protótipos gerados, sendo I-TC-Analyze?3DP; II-TC-Invesalius?3DP; III-TC-Analyze?SLS; IVTC- Invesalius-SLS; V-TV-Analyze?3DP; VI-TV-Invesalius?3DP; VIII-TV-Analyze? SLS; VIII-TV-Invesalius-SLS, foram submetidos a processos de engenharia reversa com a finalidade de digitalizar as superfícies dos objetos para uma comparação de cada modelo de prototipagem produzido com o padrão ouro, com precisão de 0,001mm. Os desvios de até 1mm e até 2mm foram calculados, comparados e analisados estatisticamente os erros percentuais. Os modelos de prototipagem rápida originados por meio da obtenção de dados de exames de tomografia computadorizada são mais precisos que os modelos de prototipagem originados por meio de dados de exames de tomografia volumétrica. / The purpose of this study is to compare rapid prototyping models created from cone beam computerized tomography (CBCT) and multislice computerized tomography (CT) data, in order to verify the accuracy of these technologies. A dry skull mandible was submitted in a CBCT (NewTom ? QR, Italy) and CT (Select SP-Elscint, Israel) exams. The tomographies data were processed by two different Medical Image processing systems, 3D-Analyze (Mayo Clinic, U.S.A.) and InVesalius (CenPRA, Brazil). Rapid prototypes models were built in two different rapid prototyping technologies, 3D Printer (3DP) and Selective Laser Sintering (SLS). The dry skull mandible (gold standard) and the eight prototypes, as follows; I-CT-Analyze?3DP; IICT- Invesalius?3DP; III-CT-Analyze?SLS; IV-CT-Invesalius-SLS; V-CBCT-Analyze? 3DP; VI-CBCT-Invesalius?3DP; VIII-CBCT-Analyze?SLS; VIII-CBCT-Invesalius-SLS, were submitted to a reverse engineering process aimed to digitalize the surfaces of the objects to compare each rapid prototype model with the gold standard with a precision of 0.001mm. Percentage deviations errors until 1.0mm and 2.0mm were calculated, compared and statistically analyzed. The prototyped models obtained with multislice computerized tomography data shows more accuracy than those obtained with data from cone beam computerized tomography.

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