<p>Accurate knowledge of the frequency- and temperature-dependent dielectric properties of biological tissues is crucial in the development of ultra-wideband diagnostic and therapeutic technologies such as microwave breast cancer detection and hyperthermia treatments. This work examines the temperature dependence of the dielectric properties of the five tissue phantom-types developed by our group as well as porcine fat, muscle and liver tissues for the frequency range from 3 GHz to 10 GHz and for the temperature range from 5 °C to 45 °C. A systematic and simple measurement procedure is developed to measure the continuous temperature dependence of the dielectric properties of the various phantom and tissue types. The temperature trends of the dielectric properties of the different phantoms and tissues are investigated.</p> <p>Linear temperature coefficients at discrete frequencies are impractical and insufficient in ultra-wideband applications when realistic, non-linear numerical models of the dielectric properties are required. Therefore, a compact one-pole Cole-Cole model is used to model the frequency dependence of the dielectric properties of the measured samples at every temperature point. A second- or third-order polynomial is used to model the temperature dependence of the Cole-Cole parameters. The final model is a one-pole Cole-Cole model whose parameters are polynomial functions of temperature. This model enables the estimation of the relative permittivity and the conductivity of the measured phantom and tissue types at any temperature and frequency.</p> / Master of Applied Science (MASc)

This study reports on the behavior of silica based optical fibers in a hydrogen environment at high temperatures. The hydrogen response in the form of optical loss in the wavelength range of 1000-2500 nm of a germanium doped graded index 50/125 graded index fiber was examined in the temperature range of 20–800 °C. When the fiber was exposed to hydrogen at 800 °C two absorption bands appeared: ~1390 nm assigned to the first overtone of the hydroxyl stretch and ~2200 nm band with complex assignments including the combination mode of the fundamental hydroxyl stretch with SiO4 tetrahedral vibrations and the combination mode of SiOH bend and stretch. The growth rate of the 1390 nm band fits the solution to the diffusion equation in cylindrical coordinates while the 2200 nm band does not. Absorption for both bands persisted as the fiber is cooled to room temperature. Temperature dependent behavior was observed in that as temperature increases from room temperature, the absorption intensity decreases and band shifts slightly to longer wavelengths. Temperature dependence is repeatable and reversible. However, if no hydrogen is present in the environment at temperatures greater than 700 °C, the 1390 nm band will permanently decrease in intensity, while the 2200 nm band does not change. Changes in the structure of the glass appear to be causing this temperature dependent behavior. Other necessary conditions for structural changes to cause this temperature dependent behavior are examined. / Master of Science

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