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When one takes an x-ray, one learns how much material is along the line between the x-ray source and the x-ray sensor. The goal of tomography is to learn what one can about an object, by knowing how much material is on a collection of lines or rays passing through that object. Mathematically, this is a collection of line integrals of density function of the object. In this paper, we provide and prove reconstructions for a class of convex objects of uniform density using x-rays from three point sources.

In this thesis, synchrotron radiography was utilized to image liquid water distributions in the porous polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs). GDLs were compressed in an ex situ flow field apparatus with 1mm x 1mm channels, and injected with liquid water to study the effect of current density and microstructure on through-plane GDL liquid water distributions. The effect of the size of the water inlet on GDL liquid water distribution was also investigated. Micro-computed tomography was employed to characterize the effect of flow field compression on commercial and non-commercial GDLs. Porosity distributions of compressed GDLs were compared with those of uncompressed GDLs, and the effect of microstructure on the porosity was discussed. The experimental techniques documented in this thesis will inform future research, while the results will help modellers generate realistic GDL pore structures for multiphase flow simulations and validate their models.

In this thesis, synchrotron radiography was utilized to image liquid water distributions in the porous polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs). GDLs were compressed in an ex situ flow field apparatus with 1mm x 1mm channels, and injected with liquid water to study the effect of current density and microstructure on through-plane GDL liquid water distributions. The effect of the size of the water inlet on GDL liquid water distribution was also investigated. Micro-computed tomography was employed to characterize the effect of flow field compression on commercial and non-commercial GDLs. Porosity distributions of compressed GDLs were compared with those of uncompressed GDLs, and the effect of microstructure on the porosity was discussed. The experimental techniques documented in this thesis will inform future research, while the results will help modellers generate realistic GDL pore structures for multiphase flow simulations and validate their models.

Licenciatavhandling Uppsala : Sveriges lantbruksuniversitet, 2009. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Michigan, 1938. / Cover title. "Reprinted from the Physical review, vol. 54, no. 12, December 15, 1938."

Thesis (Ph. D.)--University of Chicago, 1938. / Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois."

Thesis (Ph. D.)--University of Michigan, 1936. / Running title: X-ray refractivity of cerussite. "Reprinted from the Physical review, vol. 51, no. 3, February 1, 1937."

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A model has been developed for calculating x-ray line emission from spherical plasmas. The main features of this method are: (1) Plasma parameters are obtained from a one-dimensional Lagrangian hydrodynamics and heat flow code. (2) Multi-frequency groups: the line structure can be reproduced with the desired accuracy by adjusting the number of frequency groups. (3) Self consistent, time dependent excited level populations and radiation fluxes: the code starts with coronal populations, calculates the ensuing radiation flux and then recalculates the populations and so on, iterating until convergence is reached. (4) Goemetrical groups of rays groups by spherical impact parameters. (5) Line broadening due to ionic thermal agitation and Doppler shift due to the net plasma flow velocity. Inclusion of the flow velocity shift would be different without the multi-frequency group treatment. The method has been applied to an aluminum target, and the results are in good agreement with previous experimental work. The total energy, summed over all lines, as well as the line intensity ratios (which are a sensitive measure of agreement with experiment) were predicted with good accuracy. The pictures that would be seen by a pinhole camera are also calculated by the code.