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Full-Text Articles in Engineering
Sub-Surface Navigation Using Very-Low Frequency Electromagnetic Waves, Alan L. Harner
Sub-Surface Navigation Using Very-Low Frequency Electromagnetic Waves, Alan L. Harner
Theses and Dissertations
This research proposes two schemes utilizing very-low frequency (VLF) electromagnetic waves to navigate underground. The first scheme consists of using above-ground beacon transmitters to broadcast VLF signals to an underground mobile receiver which uses methods such as triangulation and trilateration to obtain a position solution. The second scheme consists of using above-ground reference receivers along with an underground mobile receiver to form time-difference- of-arrival measurements of incoming VLF signals of opportunity, such as lightning strike emissions, to calculate a position solution. The objective of this thesis is to develop positioning algorithms and use simulations as a tool to characterize the …
Determining The Resistivity Of Resistive Sheets Using Transmission Measurements, Milo W. Hyde Iv
Determining The Resistivity Of Resistive Sheets Using Transmission Measurements, Milo W. Hyde Iv
Theses and Dissertations
In September 2005, radar cross section (RCS) measurements were made of resistive sheets, or R-cards, wrapped around a polystyrene foam cylinder to compare with a newly developed theoretical RCS prediction technique. The resistivities of the R-cards were initially measured with a direct current (DC) four-point probe. When the RCS measurements were compared to the theoretical predictions, it became clear that DC resistivity alone is not sufficient to accurately predict the scattering from an R-card. This thesis presents alternating current (AC) methods for determining the resistivity of an R-card. Both freespace and waveguide techniques are presented. Experimental verification of the techniques …