3-D Microwave Imaging for Breast Cancer

We introduce a novel microwave imaging technique for breast cancer detection. Our approach provides a one-pass inverse image solution, which is completely new and unprecedented, unrelated to tomography or radar-based algorithms, and unburdened by the optimization toil which lies at the heart of numerical schemes. It operates effectively at a single frequency, without requiring the bandwidth of radar techniques. Underlying this new method is our unique Field Mapping Algorithm (FMA), which transforms electromagnetic fields acquired upon one surface, be it through outright measurement or some auxiliary computation, into those upon another in an exact sense

Born to burn: characterizing fuel loads, flammability and plant traits across spatio-temporal gradients of black spruce dominated communities

Thesis (M.S.) University of Alaska Fairbanks, 2020The flammability of black spruce forests is influenced by the fuel loadings and quality of fuels within a site, whereas the ability of a site to self-replace after fire, and thus forest resiliency, depends on the fire-ecological trait attributes of the plant community. Black spruce plant communities have been undergoing self-replacement succession from low to moderate severity fires for thousands of years, however, recent intensification of interior Alaska's fire regime is leading to shifts in post-fire successional trajectories, resulting in many ecological implications. This study focuses on understanding the variation in black spruce forest flammability, based on fuel load quantity and quality, and fire-ecological plant traits in 28 black spruce dominated sites ranging across age and moisture gradients in interior Alaska. I quantified tree canopy, understory and below-ground fuel loads, developed models to predict fuel loads and then utilized my measurements of above-ground fuel load quantity and quality to calculate a site-level flammability index. Based on my analyses, significantly greater flammability indices, and thus burning potential, occur in sites greater than 34 years in age, at elevations greater than 302 m and with dry site moisture, which are representative of dry, nonacidic upland black spruce and dry, acidic upland black spruce-lichen forest ecosystems. Furthermore, although fire-ecological plant trait attributes of Hylocomium splendens and Vaccinium uliginosum vary with age and moisture gradients, the amount of intra-specific trait variation within a site could not be explained by stand age or moisture and thus forest resiliency is also likely independent of age and moisture gradients. Further research is necessary to explore both abiotic and biotic explanatory variables related to intra-specific plant trait variation to better understand variation in black spruce forest resiliency on the landscape. The results from this study can assist fire managers in the prediction of black spruce forest burning potential and its vulnerability to ecosystem shift post-fire.General introduction -- Chapter 1 Variation in black spruce forest fuel loads and flammability -- Chapter 2 Utilizing intra-specific variation in fire-ecological plant traits to indicate black spruce forest resilience -- General conclusion -- References -- Appendix

Indirect Wafer Bonding and Epitaxial Transfer of GaSb-Based Materials

Results from a study of indirect wafer bonding and epitaxial transfer of GaSb-based materials are presented. Benzocyclobutene (BCB) was used as a bonding agent to bond GaSb and epitaxial structures lattice matched to GaSb onto Si, GaAs, and sapphire carrier substrates. To better understand sources of stress during the bonding process, which can result in cracking and subsurface damage of the GaSb-based materials, BCB’s hardness and reduced elastic modulus were measured at various stages during the curing process. Based on the results of curing experiments, a bonding and epitaxial transfer process for GaSb-based materials was then developed. Following bonding, using an experimentally determined low-stress cure cycle, GaSb substrates were removed from epitaxial layers of InAsSb using a combination of mechanical thinning and polishing followed by selective chemical etching using a hydrofluoric and chromic acid solution. Etch selectivity data are also presented where selectivity greater than 100:1 is achieved for GaSb:InAsSb

Development of Fuses for Protection of Geiger-Mode Avalanche Photodiode Arrays

Current-limiting fuses composed of Ti/Al/Ni were developed for use in Geiger-mode avalanche photodiode arrays for each individual pixel in the array. The fuses were designed to burn out at ∼4.5 × 10[superscript −3] A and maintain post-burnout leakage currents less than 10[superscript −7] A at 70 V sustained for several minutes. Experimental fuse data are presented and successful incorporation of the fuses into a 256 × 64 pixel InP-based Geiger-mode avalanche photodiode array is reported

Investigation of the machining process of spheroidal cast iron using cubic boron nitride (CBN) tools

This paper presents the experimental results of the turning of spheroidal iron (EN-GJS-500-7 grade) using L-CBN tools. The cutting process can be classified as a High Performance Cutting (HPC) due to a relatively high material removal rate of about 190 cm3/min. The investigations performed include fundamental process quantities and machined surface characteristics, i.e. componential cutting forces, specific cutting energy, average and maximum values of cutting temperature as well as temperature distribution in the cutting zone, tool wear progress visualized by appropriate wear curves and 2D/3D surface roughness parameters