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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Permittivity and conductivity imaging in electrical capacitance tomography

Zhang, Maomao January 2016 (has links)
Electrical capacitance tomography (ECT) is a technology that images the dielectric permittivity distribution of materials under test. ECT has been used as a tool for process monitoring in particular for two-phase flow measurement. These applications mainly focus on the dielectric samples, whose conductivity is negligibly small. This thesis studies ECT imaging with conductivity considerations. The conductive materials will affect the capacitance measurements and introduce difficulties in the ECT image reconstruction. This thesis presents solutions based on ECT to image material of different values of conductivity in different practical process or monitoring scenarios: the conductivity within materials under test is considered to be higher than 10^6 S/m, or less than 10 S/m. This work consists of the following innovative steps. (i) Through an ECT monitoring, floating (i.e., electrically non-grounded) metallic samples are imaged as dielectric illusions and the analysis of capacitance measurements over the conductors is delivered. (ii) Magnetic induction tomography (MIT) is firstly used for locating grounded metallic samples, thereafter as an assistant method to guide ECT to image the dielectric components. (iii) In low conductivity case MIT, as an indicator of conductive material again, helps ECT to solve multiphase flow problems. (iv) The multi-frequency complex ECT measurement provides a potential method to improve the ECT imaging ability for both conductive and dielectric materials. The first three ideas have been testified by both simulated and experimental results, while the fourth part is simulation-based results only on current stage.

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