> Dear Colleagues,
> We continue our  Colloquium at the Math Department.
>
> Yongzhi Steve Xu, UTC
>
> Thursday, October 18, Room 212, 3:00pm.
>
> Inverse Problems of Underwater Acoustics
>
> Inverse problems of underwater acoustics have applications in many areas,
> including ocean exploration and medical imaging. Two applications will be
> discussed in this talk:
>
> (1) Imaging a floating objects from undersea.
>
> (2) Evaluation of osteoporosis.
>
> The oceans cover more than half of the earth's surface. With more and more
> human activities on the sea surface and under the sea, it has been an
> urgent issue to be able to effectively observe floating objects from
> undersea.  Sound wave is the only energy form that can propagate
> effectively in water. Our research is using mathematical and computational
> approaches to study properties of acoustic waves scattering in an ocean,
> and developing new methods for effective acoustic imaging. This talk
> presents  new results of imaging floating objects from underwater by the
> generalized dual space indicator method.
>
> The methodology we developed for sound waves in an ocean may also be
> applied to a medical application.
>
> Today, the methods of  reference for the evaluation of osteoporosis rely
> on the absorption of X-rays by the bone tissue. An alternative, which has
> been proposed during the last fifteen years, makes use of ultrasound
> techniques, which are non-ionizing, easier to employ, and less costly.
>
> As bone is known to be poroelastic in structure, we consider modeling it
> using Biot's formulation. In this talk we present some new results in our
> ongoing research
> on the reflection and transmission of ultrasonic wave in bovine cancellous
> bone. We investigate the relations among reflecting waves, transmission
> waves and Biot coefficients. We also consider the determination of the
> parameters of cancellous bone.
>
> This talk will be suitable for undergraduate students who love Physics and
> have had a bit of Differential Equations and Linear Algebra.