Abstract: A method to disinfect a porous solid medium, such as soil, includes the steps of embedding a plurality of electrodes into the porous solid medium and applying a plurality of alternating current voltage pulses between the electrodes. The voltage pulses have a peak voltage of at least 10 kilovolts and are of an intensity and duration effective to generate a quantity of ozone. The ozone is produced in quantities sufficient to disinfect the porous solid medium.

Abstract: A geometry for a spark switch includes an inner electrode surrounded by an outer electrode. The placement of the inner electrode within the outer electrode substantially increases the exposed overlapping surface area of the electrodes. The increase in surface area of the electrodes results in a proportional increase in the operational life of the switch. The design of the spark switch also causes the outer electrode to shield a surrounding insulation layer against debris that would otherwise contaminate an insulation layer.

Abstract: An acoustic cannon has a plurality of acoustic sources with output ends symmetrically arranged in a planar array about a central point. Pressure pulses are generated in each acoustic source at substantially the same time. The pressure pulses exit the output ends as sonic pulses. Interaction of the sonic pulses generates a Mach disk, a non-linear shock wave that travels along an axis perpendicular to the planar array with limited radial diffusion. The Mach disk retains the intensity of the sonic pulses for a time and a distance significantly longer than that achievable from a single sonic source. The acoustic cannon is useful as a non-lethal weapon to disperse crowds or disable a hostile target.