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| Identifier |
G00139 |
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uch.physics.phd//1997kafesaki |
| Title |
Σκέδαση και διάδοση ακουστικών και ελαστικών κυμάτων σε τυχαία μέσα |
| Alternative Title |
Scattering and propagation of acoustic and elastic waves in random media |
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Author
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Καφεσάκη, Μαρία Σ
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Thesis advisor
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Οικονόμου, Ελευθέριος
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| Abstract |
In the first part of thiw work we study the scattering of acoustic (AC) and elastic (EL) waves by a single sphere embeddeb in a homogeneous elastic host medium (single scattering). The aim of this study is to examine whether the single scattering can give prediction and explanation for the characteristics of the propagation in the corresponding periodic system (the system of the identical periodically placed sheres. For this purpose we calculate the total singel scattering cross-section (TCS) and we try to connect the resonances of the TCS with the multiple scattering induced gaps and the flat bands of the band stucture of the corresponding periodic system. The main result is that whenever the TCS exhibits broad and well separated resonances with considerable scattering between them, a wide gap appears in the corresponding periodic system. In the second part of this work we study the propagation of AC and EL waves in random composites consisting of spherical inclusions in a homogeneous elastic medium. The method which is used ia the well-known from the electrnic problem Coherent Potential Approximation (CPA). The aim is to test various extensions of this simple method in the determination of the characteristics of the propagation. Using the CPA we calculate quatities as the phase and energy velocities, the main free path etc. and the results are compared with recent experimental data. We found that the CPA, and especialy a version known as coated CPA, can describe the propagetion extremelly well especially in the regions of weak multiple scattering. 1. ακουστικά 2. ελαστικά 3. κύματα 4. σκέδαση 5. διάδοση 6. τυχαιότητα 7. συντονισμοί 8. ενέργεια 9. acoustic 10. elastic 11. waves 12. scattering 13. propagation 14. CPA 15. disorder 16. resonanes
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| Language |
English |
| Issue date |
1997-05-01 |
| Date available |
1998-04-5 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
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Type of Work--Doctoral theses
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| Views |
722 |
Σκέδαση και διάδοση ακουστικών και ελαστικών κυμάτων σε τυχαία μέσα
