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Basic Buried Mine Detection and/or Destruction

Basic Buried Mine Detection and/or Destruction. Measure the array response matrix From , estimate Location of the interface Location of the target Blurring by the inhomogeneities

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Basic Buried Mine Detection and/or Destruction

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  1. Basic Buried Mine Detection and/or Destruction • Measure the array response matrix • From , estimate • Location of the interface • Location of the target • Blurring by the inhomogeneities • Use time-reversal to damage or destroy the target. Calibration of the time-reversal process requires information obtained in estimation transducer array liquid solid mine (target)

  2. Present Status of Buried Mine Problem • Theoretical and numerical (2D) studies of array imaging for scalar (acoustic) waves without interfaces. • Numerical (2D) study of active target time-reversal through a liquid-solid interface. • Theoretical and numerical study of echo-mode time-reversal (2D) with phase compensation for scalar waves and no interface.

  3. Array Imaging with No Interfaces • Cross-range estimation of target location is based on a time-domain, singular value decomposition, which is statistically stable and accurate. • Range resolution (not shown here) comes from arrival time analysis and is good for broadband pulses. • Main new result obtained recently: the width of the cone in the figure is proportional to the effective aperture of the array, which controls super-resolution in time-reversal. • So far, results are limited to scalar waves and no interfaces.

  4. Time-Reversal of Active Target Through a Liquid-Solid Interface • Time-reversal array is in the liquid at the top • Source is at bottom-center in the solid • In left figure, field is shown at instant of refocusing, in a homogeneous medium • From left to right, the strength of the inhomogeneities increases. • The correlation length is comparable to the wavelength (0.5 mm). • Note the super-resolution as random fluctuations increase.

  5. Echo-Mode Time-Reversal • In a homogeneous medium with no interfaces, echo-mode time-reversal works well using the singular value decomposition (SVD). • In a random medium with no interfaces, echo-mode time-reversal is statistically unstable even in the time domain. • To have statistically stable echo-mode time-reversal, it is necessary to compensate for the residual arrival time from the array to the target. This can be done well in the absence of interfaces and is well understood theoretically.

  6. Research Plan • Carry out array imaging (theory and numerical simulations) of a target through a liquid-solid interface in the presence of random inhomogeneities. • Carry out power delivery calculations (theory and numerical simulations) in phase-compensated echo-mode time-reversal through a liquid-solid interface. • Carry out electromagnetic versions of the array imaging and time-reversal through an air-ground interface in the ultra-wideband 1 GHz regime.

  7. References • Time reversal through a solid-liquid interface and super-resolution, Chrysoula Tsogka and G. Papanicolaou. Inverse Problems, 2002. Also in http://georgep.stanford.edu • Imaging and time reversal in random media, Liliana Borcea, Chrysoula Tsogka, G. Papanicolaou and James Berryman. Inverse Problems, 18 (2002), pp. 1247--1279. • Super-Resolution in Time-Reversal Acoustics, P. Blomgren, G. Papanicolaou and H. Zhao. Journal of the Acoustical Society of America, Vol 111, (2002), pp. 230-248.

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