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News & Politics
Monolith Tomography Study
Alfonso Gastelum Strozzi (hay vas agregando nombres jajaja)
1 Introduction
The study of the mechanical propierties of a soil sample (Monolith) in specific
the interaction of pores with diferent substances, we propose the use of CT-
images and a Mechanical Computational Model to obtain a description of the
behavior. The image obtained from the CT-Scan would give us a model of the
behavior of the pore filling with the external substances but only in a set of
times, this is the reason for the construction of a computational mathematical
model to obtain a model that discribe with some degree of acuracy the behavior
of the substance in the soil. The model is based in a method call Smoothed
Particle Hydrodynamics, this method has the advantage of been ideal to solve
fluid-solid interaction, also been a method bases in a set of points with out using
a Tetraedal Mesh we can related the intensity value of each pixel (that is related
to the density value).
2 Objective
The principal objective of the experiment is the obtention of a modell that can
be use to described the interaction of different fluids and solid with the monolith
and how is afected for these different chemical compount.
The experiment has the objective to obtain a model of the behaviour of the
fluid-solid interaction, the experimental data objectives can be divided as:
1. Obtain a high resolution set of transversal images of the Monolith.
2. Obtain a Set of images with the pores been fill by water.
3. Obtain a Set of images with the pores been fill by fluids.
4. Obtain a Set of images determining the presences of different chemist
compounds.
After obtaining the experimental data the model objective can be divided in:
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Figure 1: Figure 1: Diagram of the acquisition system
1. Obtain a representative particle set model discribing the initial monolith
state.
2. Discribe the internal force of the solid and the fracture limits.
3. Obtain a complete model of Solid-Fluid interaction.
3 Methodology
In order to obtain a Data Set with an increase resolution that the CT-Scanner
maximum output we are building an equipment to move the monolith half of
millimeter of the position. The equipment contains also references use for posi-
tioning and density calibration.
The density calibration is obtained using a strip with different material with
know densities, this calibration is use to obtain a relation between gray scale
and density. A metal ring is strap to The monolith in order to use the geometric
center of the ring to obtain the average radius. The segmented ring and the
average radius is used together with a set of references points (high density
material) to align the different scans sets (Figure 1).
The first image obtained would be with the monolith with out any modifi-
cation. This first scan would give the density values of the monolith, and the
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original cavities, these values are use in later stage to segment different sub-
stances.
The second part of the experiment consist in obtain the pores that are fill
with a liquid. In order to do this there will be two processes.
1. Pure water, the differences between the density of the air and water will
be use together with the previous model of the monolith to segment the
cavities fill with water and the one still containing air.
2. Obtain a System of the pores and the water fill.
3. A water soluble contrast agent based on iodine, with this method we will
obtain a more define intensity differentiation per pixel where the iodine
is present. The objective is to obtain the behavior of the liquid in areas
where the concentration is smaller than the resolution obtained between
the water and the solid.
4. Finally we will exposed the monolith to deferent liquids like Tetrachloroe-
thylene.
The acquisition of these sets would depend on the permeability and consist in
the following steps:
1. The monolith been expose to the fluid will be scan in different positions
of the base (to obtain the increase resolution), the number of scan will be
time constrain depending in how fast is the processes of permeability of
the fluid.
2. After a set of time t long enough for the state in the content of fluid inside
the monolith as change in a percentage will repeat step 1.
The selected time t is selected measure the percentile change in the fluid
contend in the top receptacle (Figure 2).
The final stage will consist in obtaining a final set of images, this time we
will used different insoluble compound, one of this compound will be based on
barium sulphate a contrast medium use in CT-Scan (to obtain a high contrast
image) and a selection of chemical compound with density bigger than the water
and different to the compounds already present in the monolith.
All the necessity permits for the use of the equipment and the controlled
radioactive substances are provided by the licenses of the Hospital Regional de
Alta Especialidad de Oaxaca (HRAEO) and the chief of area Mr. Flavio Ernesto
Trujillo.
These images are going to be used together with a Marching Cubes algorithm
to build a set of Triangle Mesh Surfaces.
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Figure 2: Figure 2
The surfaces are then use to obtain a set of points in space this point are
related to the position of the pixels, so we can map the density value (intensity
level) as a property to each point.
These cloud of point that have the geometry of the deferent objects: Monolith,
pores, liquid, chemical compound. After that we can construct a time depend
history for each one of the experiments to see how is the stage of the monolith
in different times.
Using this information we are going to apply the Mesh Free Methods based
in Smoothed Particle Hydrodynamics to try to find the solution that describes
how the different substances interact with the cavities.
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