BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Sabre//Sabre VObject 4.5.8//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:Europe/Zurich X-LIC-LOCATION:Europe/Zurich TZURL:http://tzurl.org/zoneinfo/Europe/Zurich BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:19810329T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:19961027T030000 RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:news1161@dmi.unibas.ch DTSTAMP;TZID=Europe/Zurich:20210627T202314 DTSTART;TZID=Europe/Zurich:20210409T110000 SUMMARY:Seminar in Numerical Analysis: Barbara Kaltenbacher (Universität K lagenfurt) DESCRIPTION:High intensity (focused) ultrasound HIFU is used in numerous me dical and industrial applications ranging from litotripsy and thermotherap y via ultrasound cleaning and welding to sonochemistry. In this talk\, we will highlight two computational aspects related to the relevant nonlinea r acoustic phenomena\, namely\\r\\n absorbing boundary conditions for the treatment of open domain problems\; optimization tasks for ultrasound fo cusing. \\r\\nStrictly speaking\, acoustic sound propagation takes place i n full space or at least in a domain that is typically much larger than th e region of interest Ω. To restrict attention to a bounded domain Ω\, e. g\, for computational purposes\, artificial reflections on the boundary ∂Ω have to be avoided. This can be done by imposing so-called absorbin g boundary conditions ABC that induce dissipation of outgoing waves. Here it will turn out to be crucial to take into account nonlinearity of the PD E also in these ABC. This is joint work with Igor Shevchenko (Imperial Co llege London). In the context of applications in HIFU\, focusing of nonli nearly propagating waves amounts to optimization problems. The design of u ltrasound excitation via piezoelectric transducers leads to a boundary con trol problem\; focusing high intensity ultrasound by a silicone lens requi res shape optimization. For both problem classes\, we will discuss the der ivation of gradient information in order to formulate optimality condition s and drive numerical optimization methods. This is joint work with Chris tian Clason (University of Duisburg-Essen)\, Vanja Nikolić (TU München) \, and Gunther Peichl (University of Graz). Finally we will provide an ou tlook on imaging with nonlinearly acoustic waves\, which amounts to identi fying  spatially varying coefficients (sound speed and/or coefficient of nonlinearity) in the Westervelt equation. This is recent joint work with Masahiro Yamamoto (University of Tokyo) and William Rundell (Texas A&M Uni versity).\\r\\nFor further information about the seminar\, please visit th is webpage [t3://page?uid=1115]. X-ALT-DESC:

High intensity (focused) ultrasound HIFU is used in numerous medical and industrial applications ranging from litotripsy and thermother apy via ultrasound cleaning and welding to sonochemistry. \;In this ta lk\, we will highlight two computational aspects related to the relevant n onlinear acoustic phenomena\, namely

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Strictly speaking\, acousti c sound propagation takes place in full space or at least in a domain that is typically much larger than the region of interest Ω. To restrict atte ntion to a bounded domain Ω\, e.g\, for computational purposes\, artifici al reflections on the boundary ∂Ω \;have to be avoided. This can be done by imposing so-called absorbing boundary conditions ABC that induce dissipation of outgoing waves. Here it will turn out to be crucial to take into account nonlinearity of the PDE also in these ABC. \;This is joi nt work with Igor Shevchenko (Imperial College London).

In th e context of applications in HIFU\, focusing of nonlinearly propagating wa ves amounts to optimization problems. The design of ultrasound excitation via piezoelectric transducers leads to a boundary control problem\; focusi ng high intensity ultrasound by a silicone lens requires shape optimizatio n. For both problem classes\, we will discuss the derivation of gradient i nformation in order to formulate optimality conditions and drive numerical optimization methods. \;This is joint work with Christian Clason (Uni versity of Duisburg-Essen)\, Vanja Nikolić \;(TU München)\, and Gunt her Peichl (University of Graz).

Finally we will provide an o utlook on imaging with nonlinearly acoustic waves\, which amounts to ident ifying \; spatially varying coefficients (sound speed and/or coefficie nt of nonlinearity) in the Westervelt equation. \;This is recent joint work with Masahiro Yamamoto (University of Tokyo) and William Rundell (Te xas A&\;M University).

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For further information about the semina r\, please visit this webpage.

DTEND;TZID=Europe/Zurich:20210409T120000 END:VEVENT END:VCALENDAR