رسالة جامعية
Κυματική διάδοση σε μέσα με διασπορά : αντίστροφη σκέδαση
| العنوان: | Κυματική διάδοση σε μέσα με διασπορά : αντίστροφη σκέδαση |
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| المؤلفون: | Papadopoulos, Theseus, Παπαδόπουλος, Θησέας |
| بيانات النشر: | Aristotle University Of Thessaloniki (AUTH) Αριστοτέλειο Πανεπιστήμιο Θεσσαλονίκης (ΑΠΘ) |
| سنة النشر: | 2012 |
| المجموعة: | National Archive of PhD Theses (National Documentation Centre Greece) |
| مصطلحات موضوعية: | Μοντέλο Διασποράς Cole-Cole, Κυματική Διάδοση, Αντίστροφη σκέδαση, Πεπερασμένες διαφορές στο πεδίο του χρόνου, Συχνοεξαρτώμενα μέσα, Πολλαπλασιαστές lagrange, Συνάρτηση κόστους, Μοντέλα Debye, Lorentz, Cole - cole model, Wave propagation, FDTD method, Dispersive media, Inverse scattering, Lagrange multipliers, Cost functional, Debye, Lorentz models, Φυσικές Επιστήμες, Φυσική, Natural Sciences, Physical Sciences |
| الوصف: | One of the two things that this thesis focuses on is the modeling of wave propagation in dispersive Cole-Cole media. The Cole-Cole model plays a key role in microwave medical imaging due to the fact that it can describe the frequency dependence of the electromagnetic properties of various biological tissues with great accuracy over a wide frequency range. The main difficulty that arises in the time-domain modeling of Cole-Cole media, is the existence of fractional time derivatives. In the proposed method a Padé approximation is employed resulting in auxiliary differential equations of integer order. A finite-difference time-domain method is developed to solve the differential equations obtained. The comparison of analytical and calculated relative complex permittivity values over wideband frequency domain proves the validity of the method. Furthermore, the second part of the current thesis is associated with the solution of the electromagnetic inverse scattering problem. Specifically, a time-domain inverse scattering method for the reconstruction of inhomogeneous dispersive media described by the Debye as well as the Lorentz model is presented. The method aims to the simultaneous reconstruction of the spatial distributions of the medium parameters. When Debye scatterers are under examination, the optical and static permittivity and the relaxation time are the aforementioned properties. In the case of Lorentz scatterers the unknown parameters are the optical and static permittivity, the resonant frequency and the damping factor. The reconstruction of the scatterer is based on the minimization of a cost functional, which describes the difference between measured and estimated values of the electric field. The fulfillment of the Maxwell's curl equations is set as constraint by means of Lagrange multipliers in an augmented functional. The Fréchet derivatives with respect to the scatterer properties are derived analytically and can be utilized by any gradient-based optimization technique. The proposed reconstruction ... |
| نوع الوثيقة: | doctoral or postdoctoral thesis |
| اللغة: | Greek, Modern (1453-) |
| العلاقة: | http://hdl.handle.net/10442/hedi/28480Test |
| DOI: | 10.12681/eadd/28480 |
| الإتاحة: | https://doi.org/10.12681/eadd/28480Test http://hdl.handle.net/10442/hedi/28480Test |
| رقم الانضمام: | edsbas.872E31D |
| قاعدة البيانات: | BASE |
| DOI: | 10.12681/eadd/28480 |
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