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On the far-field properties of an acoustic horn
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis. (Waves and Fluids)
2006 (English)Report (Other academic)
Place, publisher, year, edition, pages
Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2006-042
National Category
Computational Mathematics
URN: urn:nbn:se:uu:diva-82158OAI: oai:DiVA.org:uu-82158DiVA: diva2:110073
Design Optimization
Available from: 2008-02-19 Created: 2008-02-19 Last updated: 2011-11-18Bibliographically approved
In thesis
1. Topology Optimization for Wave Propagation Problems
Open this publication in new window or tab >>Topology Optimization for Wave Propagation Problems
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis considers topology optimization methods for wave propagation problems. These methods make no a priori assumptions on topological properties such as the number of bodies involved in the design. The performed studies address problems from two different areas, acoustic wave propagation and microwave tomography. The final study discusses implementation aspects concerning the efficient solution of large scale material distribution problems.

Acoustic horns may be viewed as impedance transformers between the feeding waveguide and the surrounding air. Modifying the shape of an acoustic horn changes the quality of the impedance match as well as the angular distribution of the radiated waves in the far field (the directivity). This thesis presents strategies to optimize acoustic devices with respect to efficiency and directivity simultaneously. The resulting devices exhibit desired far field properties and high efficiency throughout wide frequency ranges.

In microwave tomography, microwaves illuminate an object, and measurements of the scattered electrical field are used to depict the object's conductive and dielectric properties. Microwave tomography has unique features for medical applications. However, the reconstruction problem is difficult due to strongly diffracting waves in combination with large dielectric contrasts. This thesis demonstrates a new method to perform the reconstruction using techniques originally developed for topology optimization of linearly elastic structures. Numerical experiments illustrate the method and produce good estimates of dielectric properties corresponding to biological objects.

Material distribution problems are typically cast as large (for high resolutions) nonlinear programming problems over coefficients in partial differential equations. Here, the computational power of a modern graphics processing unit (GPU) efficiently solves a pixel based material distribution problem with over 4 million unknowns using a gradient based optimality criteria method.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 28 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 612
National Category
Computational Mathematics
Research subject
Scientific Computing
urn:nbn:se:uu:diva-98382 (URN)978-91-554-7438-6 (ISBN)
Public defence
2009-04-03, Room 2446, Polacksbacken, Lägerhyddsvägen 2D, Uppsala, 10:15 (English)
Available from: 2009-03-12 Created: 2009-02-20 Last updated: 2011-10-27Bibliographically approved

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