Industrial X-ray computed tomography (CT) is a powerful technique for producing a three-dimensional model of an object and
for performing dimensional measurements of an object’s inner and outer features. The diversity of the measuring objects causes
a variety of CT setup parameters. The chosen CT setup parameters influence the uncertainty of dimensional measurements. A
CT user determines the workpiece orientation and the distance between the workpiece and the X-ray source before a CT scan is
commenced, and all other CT setup parameters are based on the workpiece placement inside the CT system. Hence, the workpiece
placement is the trend-setting parameter of a CT scan.
This paper presents a method for optimising a workpiece placement for dimensional measurements of multi-material workpieces.
The method works with the stereolithography (STL) model of the workpiece and analytically tests the whole placement range to
find the placement that minimises the attenuation power of a workpiece. The method is validated by analysing the standard deviation
of CT measurements on a multi-material workpiece. An analysis of variance on the uncertainty contributions demonstrated
that the predicted workpiece placement was optimal.
Tabular igneous intrusions (sills) are common features in sedimentary basins and have the potential to be useful seals for fluids (e.g. CO
2
or H
2
) in geological storage scenarios, and may be important as the need for geological carbon sequestration and alternative fuel storage increases. This is advantageous in regions without ready access to large-volume reservoirs in depleted hydrocarbon plays and saline aquifers, such as the northeastern USA. Moreover, geological H
2
storage requires more demanding conditions than those typically associated with oil and gas. An enhanced seal will have the properties of a traditional seal – competent, low permeability and laterally extensive – with the addition of being able to self-seal pre-existing and induced fractures. Self-sealing will occur along fluid pathways like fractures where CO
2
, water and minerals like plagioclase, olivine and pyroxene react together. Dolerite sills from the Gettysburg Basin, Pennsylvania, have remarkably low permeability and homogeneous compositions that include minerals that will readily react with CO
2
dissolved in water. Here, we characterize the physical properties and chemical gradients within several mafic sills cored in five boreholes. In addition, preliminary CO
2
-reaction experiments on dolerite samples demonstrated rapid carbonate mineralization.
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