Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Weak Sıgnals In Eeg Tıme Serıes
The method we used in this thesis is based on the duffing equation and depends on the phase-state of chaotic vibrators of the nonlinear dynamic systems. The presence of weak periodic signals were studied using the principle of sensitive dependance on initial conditions of a chaotic system,by observing the possible changes in the phase state due to excitation of a nonlinear dynamic system from outside. The mathematical background of this method, its applications and its difference from other signal analysing methods were discussed.
In this thesis, we investigated the presence of weak periodic signals (low amplitude periodic oscillations) in physical dynamic systems with this Duffing equation based method. First, we analysed a simulation experiment on weak periodic signals and tested the reliability of this method by performing our own simulation experiment. Then, we examined other common signal analysing methods. As a real data, EEG recordings of two right-handed epileptic patients, one is seizure free and one is having seizurewere used. The EEG signals were analysed and answer is searched for the quesion; “Are there weak periodic signals present within the nonlinear dynamical systems?”
As a result, we observed the presence of weak periodic signals in EEG time series. We calculated the amplitude and frequency values of the weak periodic signals that we found. We made evaluations on the difference of this weak periodic signal detection method for dynamical systems based on the Duffing equation from other signal analysing methods. We discussed the implications of our results on EEG signals to epilepsy condition.

DÖNMEZ Ömer
Tez Adı : Düşük Boyutlu Yarıiletken Yapıların Modülasyon Spektroskopisi İle İncelenmesi

Danışman : Prof. Dr. Çetin Arıkan

Anabilim Dalı : Fizik

Programı : Katıhal Fiziği

Mezuniyet Yılı : 2013

Tez Savunma Jürisi : Prof.Dr. Çetin Arıkan

Prof. Dr. Hüseyin Sarı

Prof. Dr. Yüksel Ergün

Doç. Dr. Ayşe Erol

Doç. Dr. Elif Akalın