Detalhes bibliográficos
| Ano de defesa: |
2014 |
| Autor(a) principal: |
Pires, Júlio César Gall
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| Orientador(a): |
Papaléo, Ricardo Meurer
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| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Dissertação
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| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Pontifícia Universidade Católica do Rio Grande do Sul
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| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Engenharia e Tecnologia de Materiais
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| Departamento: |
Faculdade de Engenharia
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| País: |
BR
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| Palavras-chave em Português: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://tede2.pucrs.br/tede2/handle/tede/3252
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Resumo: |
In this study, the application of acoustic waves for imaging the internal architecture of sedimentary deposits produced in the simulation of different types of sediment tanks was investigated systematically. To do so we used two ultrasound imaging equipment medical and industrial, yielding two groups of images. The medical device (1.0<��< 10 MHz) was employed to optimize detail and industrial equipment (0.1 < ��<1.0 MHz ) favors the penetration in thicker layers . The acoustic behavior (maximum depth of the signal propagation speed of sound and contrast) traditional materials used in experimental simulations (coal, sand and balotine) and new artificial sediments was studied using polymer-based composites. For analysis of such materials different arrangements which changed the topography, thickness and grain size of the sediment layers were created. The transducer frequency and settling time were also monitored in the trials. The results showed that the maximum depth of view in 5 MHz was not more than 2 cm for all materials used. For a frequency of 250 kHz the display area increases substantially more than 6 cm. Although the spatial resolution decreases with decreasing frequency, due to the dotted aspect (speckle) of ultrasound images of the deposits isn‟t observed a significant loss of detail through the use of frequencies in the kHz range. The depth of view varied with particle size of pelleted material, being slightly higher in materials with larger grains. For particle sizes greater than 180 m, there was obtained a maximum depth of view of the order of 1.27 cm to 1.10 cm coal 210 and to the sand. While for the polymer based composites of the same particle size range was obtained values around 0.7 cm. Materials with less than 180 m tracks offered greater difficulty in spreading the signal beam, as the beam is reflected with high efficiency. The calculations of the propagation speed of the ultrasonic wave in the material revealed that by decreasing the particle propagation velocity in the sediment increases slightly. The value of the sound propagation velocity estimated to the coal 205 was 1989±74 m/s, while for coal 210 was 1705±45 m/s. In limestone, sand, balotine, RP , RPNF , GPMMA and PMMA particle size less than 180 m was the Vp of the order of 1650 m/s . There were no changes of these values for the frequencies used, as expected, except for the fine sand at 250 kHz decreased by ~ 20 %. No significant differences were observed in the intensity of the sound signal between different materials. However, the spherical morphologies of balotine or rounded sand gave more intense signals and favor layers when the contrast between different materials, such as coal or polymer composites are used in neighboring layers. The particle size also influences the contrast, since larger grains favor the diffuse reflection, while the greater compaction of sediments smaller grains creates more favorable conditions almost specular reflection of greater intensity. Conventional materials used for imaging proved to be good for contrast as in the case of balotine and sand , coal and limestone but had become very reflective Furthermore, another drawback is the time of getting very high settling time suspension, which prevents / impairs its use in visual tests or ultrasound imaging . Artificial materials showed little difference in acoustic behavior of the test image but can be pigmented for visual tests in current density and have wide variations in behavior X-ray images due to changes in the concentrations of fillers added at the time of synthesis. In imaging by acoustic waves should, however, take into account problems such as reduced depth preview for clinical echographs and small visual area of the transducer, because the images can‟t be used for analysis. One possibility for the application of this technique is to make successive images of the deposits in increments of low thickness (of the order of cm), with the same acquisition parameters. Thus each layer of material can be imaged independently and then grouped based on predetermined points of reference. Then through sequential imaging to reconstruct the global architecture of the sediment can be studied. The research of the internal architecture of sedimentary deposits produced in physical models employing acoustic waves for imaging revealed by the observation of material characteristics can estimate the presence of the layers that constitute it. To do this, find differences substances as particle size, particle morphology, speed of acoustic propagation in the material and density are of great importance and facilitate the analysis of a sample. |
