There are over 2 million reported burn injuries each year in the United States with 75,000 of these incidents resulting in
hospitalization. Current medical imaging modalities have limited capabilities to assess initial burn damage and monitor
healing progress. Some of these limitations can be attributed to modality occlusion from bandages, dried tissue and/or
blood and inflammation. Since terahertz radiation can see through textiles and bandages1, previous studies2,3 suggested
that terahertz radiation, in a reflectance configuration, could be used for non-invasive analysis of tissue thermal damage
and healing status. In this study, we perform an analysis of the terahertz absorption and reflection properties of the
tissue constituents comprising a wound area, and provide a feasibility assessment of the capabilities of terahertz imaging
to provide a clinical tool for initial burn analysis and healing progress.
We have developed a mm wave/terahertz imaging simulation package from COTS graphic software and custom
MATLAB code. In this scheme, a commercial ray-tracing package was used to simulate the emission and reflections of
radiation from scenes incorporating highly realistic imagery. Accurate material properties were assigned to objects in the
scenes, with values obtained from the literature, and from our own terahertz spectroscopy measurements. The images
were then post-processed with custom Matlab code to include the blur introduced by the imaging system and noise levels
arising from system electronics and detector noise. The Matlab code was also used to simulate the effect of fog, an
important aspect for mm wave imaging systems. Several types of image scenes were evaluated, including bar targets,
contrast detail targets, a person in a portal screening situation, and a sailboat on the open ocean. The images produced by
this simulation are currently being used as guidance for a 94 GHz passive mm wave imaging system, but have broad
applicability for frequencies extending into the terahertz region.
Composites of piezoelectric and magnetostrictive materials show a product property called magnetoelectricity which is absent in its constituent phases. The electric and magnetic fields are linked in the composite through the elastic stress-strain fields of the piezoelectric and magnetostrictive phases. Thus an applied magnetic field causes electric polarization or an electric field applied across the composite causes magnetization in the composite material. Such materials are potentially useful as magnetoelectric transducers. In this work, we report the results of a theoretical and experimental investigation of ME composites of PZT-CoFe2O4 and BaTiO3-CoFe2O4 with various connectivities. The magnetically induced ME effect was measured by applying an ac magnetic field of 1 kHz frequency with a variable dc magnetic bias field. The maximum values of the ME voltage coefficient, were 92.8 (V/m)(kA/m) for the 2-2 CoFe2O4-PZT4 composites and 9.55 (V/m)(kA/m) for CoFe2O4-BaTiO3 (20:80 mole %) ball mill mixed composites. Theoretical models were developed to calculate the ME voltage coefficient of 2-2 composites with different boundary conditions. Composites with 3-0 and 0-3 connectivities were modeled using a cubes model. The results show that the connectivities have a great effect on the magnetoelectric properties. An improvement of more than two orders of magnitude is possible by proper selection of materials and better process control to tailor the connectivity.
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