Álvaro Macedo

Prediction of Ceramic Foams Permeability Using Ergun's Equation

SiC-Al2O3 ceramic foams with 30 to 75 pores per linear inch (ppi) were used to access the application of pore size obtained by image analysis to estimate the cellular materials permeability through Erguns equation. Samples were sliced and the pore size distribution, cross-sectional porosity and pore density were evaluated as a function of the slice thickness based on optical and X-ray computerized tomography acquired images. The average pore sizes were used to calculate permeability constants (k1 and k2) of Erguns equation, which were compared to those experimentally obtained under water flow. Results indicated that the optical diameter distribution was very sensitive to the number of pore layers. Deviation between experimental and calculated values depended on the slice thickness. Nevertheless, the introduction of pore size obtained by image analysis into Erguns equations seems to give fair results to assess the permeability of ceramic foams.

Soil particle size fractions determined by gamma-ray attenuation

Soil texture-or the particle size fractions of sand, silt and clay-is an important characteristic of soils and is used for their characterization and classification. Textural analysis also helps agronomists and farmers in the recommendation of herbicide and fertilizer applications. Soil particle siz

Automated soil particle size analyzer based on gamma-ray attenuation

Abstract Application of gamma-ray attenuation principles permits the determination of density and water content of a material. Moreover, this technique also allows one to determine particle size distribution, when particles are falling in a liquid medium according to Stokes’ law. Based on these principles, computerized equipment was developed to perform a fully automatic analysis of soil particle size distribution. This equipments main advantage is the capability to analyze ten soil samples automatically, each one in 18 min, the resulting output is a complete curve of soil particle size distribution, ranging from 2 μm to 2 mm. Another feature of this equipment is its fast soil granulometric fraction analysis (at ten samples per h), which determines the fractions of clay, silt, and sand. Results obtained with the gamma-ray technique showed an excellent correlation with the pipette method.

Mineralogical characterization of a highly-weathered soil by the Rietveld Method

The mineralogical characterization through mineral quantification of Brazilian soils by X-ray diffraction data using the Rietveld Method is not common. A mineralogical quantification of an Acric Ferralsol from the Ponta Grossa region, state of Parana, Brazil, was carried out using this Method with X-Ray Diffraction data to verify if this method was suitable for mineral quantification of a highly-weathered soil. The A, AB and B 3 horizons were fractioned to separate the different particle sizes: clay, silt, fine sand (by Stokes Law) and coarse sand fractions (by sieving), with the procedure free of chemical treatments. X-ray Fluorescence, Inductively Coupled Plasma Atomic Emission Spectrometry, Infrared Spectroscopy and Mossbauer Spectroscopy were used in order to assist the mineral identification and quantification. The Rietveld Method enabled the quantification of the present minerals. In a general way, the quantitative mineralogical characterization by the Rietveld Method revealed that quartz, gibbsite, rutile, hematite, goethite, kaolinite and halloysite were present in the clay and silt fractions of all horizons. The silt fractions of the deeper horizons were different from the more superficial ones due to the presence of large amounts of quartz. The fine and the coarse sand fractions are constituted mainly by quartz. Therefore, a mineralogical quantification of the finer fraction (clay and silt) by the Rietveld Method was successful.

X-ray microtomography to characterize the physical properties of soil and particulate systems

Abstract Since many of the phenomena occurring in soil are related to grain and pore sizes and their distribution, investigation on a micrometric scale is of great importance. Also, the investigation should be non-invasive in order to avoid disturbing the region of interest of the sample. Many techniques from various areas of science have been adapted to make such investigations, but most of them are invasive or can only analyze global soil properties. Thus an X-ray tomograph was developed at Embrapa—Agricultural Instrumentation, to scan images of soil samples on a micrometric scale. A microtomographic image of a sieved soil sample, presenting aggregates from 212 μm to 250 μm and pores of 100 μm, is shown. Pores of the same size can also be seen in a microtomograph of a sand column, composed of two layers with granulometries of 106 μm to 149 μm and 297 μm to 500 μm. A microtomograph of a column composed of three layers of an orthoclasius powder is also presented. A slight variation in density along the column height can be observed.

Ceramic foams porous microstructure characterization by X-ray microtomography

Knowledge of the porous structure of amorphous materials is of fundamental importance in calculating geometrical parameters such as total porosity, pore size distribution and physical parameters relating to fluid flow inside void space. The present work deals with the measurement of the microstructural parameters of porous ceramic filters. Microtomographic measurements of samples were taken using an X-ray tube. Bremsstrahlung radiation was filtered in transmission mode with a Sn filter at 58.5 and 28.3 keV and the images analyzed in two ways. The first method consisted in analyzing transepts of the images in order to calculate total porosity based on the average particle size and media linear attenuation coefficients. The second method involved a study of the images using an image analysis software, called Imago, which allows one to calculate total porosity and pore size distribution. The total measured porosity of the filter C90 was 73.8%, 71.1%, 74.4% and 71.5% by, respectively, the Arquimedes method, simple gamma ray transmission, transept analysis and analysis of the microtomographic images at 28.3 keV.

Detection of beetle damage in forests by X-ray CT image processing

Algumas especies de besouros tem elevado impacto economico em florestas e industrias de moveis. Exemplo recente e aquele produzido pelo besouro Anophophora glabripennis, uma especie conhecida nos Estados Unidos como Asian Longhorn, que tem produzido danos significativos em varias florestas americanas, representando uma ameaca que podera encontrar transporte nao-intencional para paises da America do Sul, inclusive para o Brasil. Neste trabalho e apresentado um novo metodo com base no uso de tomografia de raios X computadorizada (CT) e processamento de imagens digitais para deteccao de injurias causadas por besouros em florestas. Os resultados mostram a correta identificacao da localizacao de besouros em arvores vivas, como tambem fornecem uma avaliacao do estrago temporal causado.

A Novel Model for Combining Projection and Image Filtering Using Kalman and Discrete Wavelet Transform in Computerized Tomography

This paper presents a novel model for combining projection and image filtering in computerized tomography. First, it is used an a priori one-dimensional projection filtering, through an extended Kalman filter with joint estimation. Then, the reconstructed images, obtained filtered backprojection algorithms (including the use of Hamming windows), are filtered using the two-dimensional DWT and wavelet thresholding, a non-linear technique. Experiments considering only one filtering stage (a priori 1-D filtering or 2-D DWT image filtering) show images with significant higher noise levels and the combination showed great noise reduction. The obtained results lead to the conclusion that the proposed combining model is a valid and interesting tool for tomographic image analysis.