Phd Degree / Doktora

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Department: search.filters.department.Thesis (Doctoral)--İzmir Institute of Technology, Electrical and Electronics EngineeringPublisher: search.filters.publisher.Izmir Institute of Technology

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  • Doctoral Thesis
    Depth Based Calibration of Multiple Rgbd Cameras for Full 3d Reconstruction
    (Izmir Institute of Technology, 2023) Tunçer Çalı, Esra; Gümüşteki̇n, Şevket; 01. Izmir Institute of Technology
    Bu tezde, yalnızca derinlik görüntülerinin kullanıldığı, çoklu derinlik kamerası ile çalışabilen yeni bir derinlik kamerası kalibrasyon tekniği geliştirilmiştir. Çoğu çalışmada, düzlemsel bir dama tahtası desenli objenin IR görüntüleri kullanılarak derinlik kamerası kalibrasyonu yapılmış ve elde edilen parametreler derinlik kamerası parametreleri olarak kabul edilmiştir. Bu yaklaşım yıllardır geliştirilen geleneksel metotlarla kullanılabildiği için pratik bir çözüm olarak düşünülmektedir. Ancak bu yaklaşım derinlik değerlerinden faydalanmamakta ve 3D'de yanlış eşleşmelere neden olan kalibrasyon hatalarına yol açmaktadır. Bu hataları gidermek için yinelemeli en yakın nokta metodu gibi ek tamamlayıcı metotlar uygulansa dahi düşük hatalı eşleşme sonuçları elde edilememektedir. Çözüm olarak 3 boyutlu, 4 eş-yarıçaplı küresi olan dört üçgen yüzlü yapıda bir kalibrasyon objesi tasarlanmış ve kürelerin merkezlerini derinlik görüntüsü üzerinden tespit edebilmek için elips temelli yeni bir metot geliştirilmiştir. Küre merkezleri ve derinlik hatası giderilen derinlik değerleri kullanılarak projeksiyon matris metodu orijinalinden farklı olarak 6 yerine 4 eşleşme noktası ihtiyacı olacak şekilde iyileştirilmiştir. Derinlik değerlerini geleneksel ışın demeti düzenleme (bundle adjustment-BA) metoduna dahil eden ve yeniden-projeksiyon hatasını 3B'de hesaplayan iki yeni parametre kestirme metodu dört derinlik kamerasının içsel ve dışsal parametrelerini bir arada kestirebilmek için geliştirilmiştir. Dama tahtası desenli objenin IR görüntülerinin kullanıldığı kalibrasyona kıyasla, önerilen metotlar ile elde edilen hata ortalamaları önemli ölçüde düşürülmüştür. Bu tezde geliştirilen metotlar derinlik ölçümü için kullanılan teknolojiden bağımsız oldukları için tüm derinlik kameralarında çalışabilmektedirler.
  • Doctoral Thesis
    A Study on Entangled Photon Pairs in Graded-Index Optical Fibers
    (Izmir Institute of Technology, 2021) Dinleyici, Mehmet Salih; Ekici, Çağın; Dinleyici, Mehmet Salih; 01. Izmir Institute of Technology; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering
    Quantum optics offer new possibilities, new approaches, and potentially groundbreaking new technologies whose backbone is based on creation, manipulation, and detection of special quantum states of light. The main objective of the thesis is to present a study of spontaneously arisen heralded entangled photon-pairs which play crucial role in emerging quantum enhanced technologies. We have mainly investigated discrete transverse-spatial-mode entangled photon-pairs in waveguide, because it intrinsically offers infinite dimension. Entangled states of higher dimensional systems enable realization of quantum information schemes that can offer higher information density coding and show more error resilience than can be achieved with lower dimensional systems. In this context, we have exploited a graded-index optical fiber as photon-pair-generation platform via nonlinear intermodal-four-wave mixing (FWM), since the fiber may allow different FWM processes to overlap in spectral domain, resulting in an entangled pair of spatial qubits. We have also probed joint spectral properties of the generated photons to show capability of hyperentanglement in frequency and transverse mode. We have discussed spatial Wigner function and its realization to characterize spatial properties of the quantum state. We have shown that entanglement can be verified through a violation of the Clauser - Horne - Shimony - Holt (CHSH) inequality based on spatial Wigner function and coupled-mode theory. This thesis also includes basic analysis of transverse-mode entangled photon-pair distribution in a lossy-dispersive medium. Finally, the ways to follow and the quantities to measure are touched upon. Thus, we have explained the generation and four different detection schemes, relying on a combination of photon-number statistics, joint spectral properties, and spatial entanglement measurements.
  • Doctoral Thesis
    Medium-Aware Inference for Wireless Sensor Networks
    (Izmir Institute of Technology, 2020) Wahdan, Muath Abed Alrauf; Altınkaya, Mustafa Aziz; Altınkaya, Mustafa Aziz; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In a wireless sensor network, multilevel quantization is necessary in order to find a compromise between the smallest possible power consumption of the sensors and the detection performance at the fusion center (FC). The general methodology is using distance measures such as J-divergence (JD) and Bhattacharyya distance in this quantization. This thesis proposes a different approach which is based on maximizing the average output entropy of the sensors under both hypotheses of a binary hypothesis test and utilizes it in a Neyman-Pearson (NP) criterion based distributed detection scheme in order to detect a point source. Firstly, a deterministic signal and isotropic propagation model is considered. The receiver operating characteristics of the proposed maximum average entropy (MAE) meth\-od in quantizing sensor outputs was obtained for multilevel quantization both when the sensor outputs are available error-free at the FC and when non-coherent $M$-ary frequency shift keying communication is used for transmitting MAE based multilevel quantized sensor outputs over a Rayleigh fading channel. Secondly, the sequential testing version of the first problem is considered for both unquantized and quantized data transmissions. MAE and maximum JD (MJD) quantization methods for $M$-levels were applied in the sequential probability ratio test of Wald. The average sample number (ASN) required for the target probabilities of detection and a false alarm was the performance criterion: the smaller, the better. The performance of this test improves monotonically with the number of local sensors. Lastly, spatial correlation of the sensors is taken into the account. For this case, a Gaussian isotropic event source was applied. The computational requirements in evaluating multidimensional cumulative densities necessitated proposing a rectangular grid model of sensor deployment and block-diagonal approximations of covariance matrix related to the event signal at the sensors without losing generality. The simulation studies show the success of the MAE both in the cases of fusing error-free sensor outputs and in the case where the effect of the wireless channel is incorporated. As expected the performance gets better as the level of quantization increases and with six-level quantization, it approaches the performance of non-quantized data transmission. In the sequential tests again MAE was more successful compared to MJD resulting in smaller ASNs. It was observed that spatial correlation degrades system performance.
  • Doctoral Thesis
    Stability Analysis and Control of Stochastic Power Systems
    (Izmir Institute of Technology, 2019) Yılmaz, Serpil; Savacı, Ferit Acar; Savacı, Ferit Acar; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Increase of the electricity generation and the growth of global electricity consumption lead to an increase in the power fluctuations. In this dissertation, we have proposed a novel approach by modeling these fluctuations as alpha-stable Levy processes. We have focused on the stability analysis and control for stochastic single machine infinite bus system with an emphasis on (1) understanding the effect of impulsive and asymmetric power fluctuations on the rotor angle stability, and (2) developing control rule for synchronism in the presence of Wiener and alpha-stable Levy type power fluctuations. We have investigated the basin stability over the parameter space of mechanical power and damping parameters in the presence of alpha-stable Levy type load fluctuations. The probabilities of returning to the stable equilibrium point have been calculated for different characteristic exponent and skewness parameters of alpha-stable Levy motion to see the effect of impulsive and asymmetric load fluctuations. It has been shown that the impulsiveness and/or asymmetry in the distributions of the load fluctuations can cause the instability of the rotor angle. Hence, the synchronism is lost and the rotor angle despite being stable in the sense of probability, might not be stable in the mean square sense. Furthermore, we have studied the control of the rotor angle stability of single machine infinite bus power system in the presence of Wiener type stochastic fluctuations by minimizing the stochastic sensitivity function. We have also derived an analytical expression for the rotor angle dispersion of single machine infinite bus system in the presence of alpha-stable Levy type power fluctuations. The control rule for the minimization of the rotor angle dispersion has been achieved.
  • Doctoral Thesis
    Random Communication Systems Based on Alpha-Stable Processes
    (Izmir Institute of Technology, 2018) Savacı, Ferit Acar; Savacı, Ferit Acar; Ahmed, Areeb; Savacı, Ferit Acar; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    This thesis presents alpha-stable carrier based random communication systems (RCSs) as an alternate way to perform covert transmission. The first objective is to develop an optimized model of RCS which consists of a receiver that requires less computational complexity and outperforms the previously proposed receivers. Next, in order to solve the existing synchronization issue in RCSs, the general behavior of fractional lower-order covariance method in α-stable noise environments has been evaluated to establish synchronization in RCSs. An optimized range of values for the associated parameters of α-stable carrier has also been presented to optimize the proposed synchronization method. The second objective is to establish criteria for evaluating and quantifying the security and covertness of RCSs. Therefore, the first security performance tradeoff characteristics (SPTC) have been proposed to compare the security of different RCSs. Moreover, the proposed optimized model of RCS has also been analyzed with respect to the developed security scale, i.e. SPTC. Secondly, the criterion to quantify the covertness of RCSs has also been developed to analyze the proposed RCS. Thirdly, an attack for RCS has also been proposed which highlights the potential vulnerabilities of RCSs. However, the counter-measure guidelines have been prescribed to further enhance the security of RCSs. An inverse system approach has been adopted to propose α-stable noise driven linear time invariant system based transmitter and its corresponding inverse system based receiver as a third objective. It can be considered as the most secure model for αstable noise carrier based RCS till now.
  • Doctoral Thesis
    Generalized Bayesian model selection using reversible jump Markov chain Monte Carlo
    (Izmir Institute of Technology, 2017) Karakuş, Oktay; Altınkaya, Mustafa Aziz; Altınkaya, Mustafa Aziz; Kuruoğlu, Ercan Engin; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The main objective of this thesis is to suggest a general Bayesian framework for model selection based on reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. In particular, we aim to reveal the undiscovered potentials of RJMCMC in model selection applications by exploiting the original formulation to explore spaces of di erent classes or structures and thus, to show that RJMCMC o ers a wider interpretation than just being a trans-dimensional model selection algorithm. The general practice is to use RJMCMC in a trans-dimensional framework e.g. in model estimation studies of linear time series, such as AR and ARMA and mixture processes, etc. In this thesis, we propose a new interpretation on RJMCMC which reveals the undiscovered potentials of the algorithm. This new interpretation, firstly, extends the classical trans-dimensional approach to a much wider meaning by exploring the spaces of linear and nonlinear models in terms of the nonlinear (polynomial) time series models. Polynomial process modelling is followed by the definition of a new type of RJMCMC move that performs transitions between various generic model spaces irrespective of model sizes. Then, we apply this new framework to the identification of Volterra systems with an application of nonlinear channel estimation of an OFDM communication system. The proposed RJMCMC move has been adjusted to explore the spaces of di erent distribution families by matching the common properties of the model spaces such as norm, and this leads us to perform a distribution estimation study of the observed real-life data sets including, impulsive noise in power-line communications, seismic acceleration time series, remote sensing images, etc. Simulation results demonstrate the remarkable performance of the proposed method in nonlinearity degree estimation and in transitions between di erent classes of models. The proposed method uses RJMCMC in an unorthodox way and reveals its potential to be a general estimation method by performing the reversible jump mechanism between spaces of di erent model classes.
  • Doctoral Thesis
    Development of a Unified Analysis Framework for Multicolor Flow Cytometry Data Based on Quasi-Supervised Learning
    (Izmir Institute of Technology, 2017) Köktürk Güzel, Başak Esin; Karaçalı, Bilge; Karaçalı, Bilge; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this dissertation, automatic compensation and gating strategies are investigated for multi-color flow cytometry data analysis. We propose two clustering algorithms that combine the quasi-supervised learning algorithm with an expectation-maximization routine for automatic gating. The quasi-supervised learning algorithm estimates the posterior probabilities of the different cell populations at each sample in a dataset in a manner that does not involve fitting a parametric model to the data. We have developed two different binary divisive clustering algorithms based on expectation maximization with responsibility values calculated using the quasi-supervised learning algorithm instead of the probabilistic models used in conventional expectation maximization applications. Our clustering algorithms determine the number of clusters in run-time by measuring the overlap between the estimated clusters in each provisional division and comparing it with the previous one to determine whether the division is warranted or not. Since this type of clustering is indifferent to the underlying distribution of dataset, it is well suited to automatic flow cytometry gating. The second clustering algorithm improves upon the first one using a simulated annealing approach. Its iterative structure allows finding the global minimum of a cost functional that achieves the best separation point by gradually smoothing the decision regions in each iteration. Finally, we have developed a joint diagonalization and clustering method for automatic compensation of flow data based on the methods above. The proposed method identifies cell sub groups using the annealing-based model-free expectation-maximization algorithm and finds a data transformation matrix that achieves orthogonality of the covariance structure of each identified cell cluster using fast Frobenius diagonalization. We have tested all proposed algortihms on both synthetically created datasets and real multi-color flow cytometry datasets. The results show that our automated gating algorithms are very successful in identifying the distinct cell groups so long as there is enough statistical evidence for their presence. In addition, the automated compensation procedure was also successfully applied on the synthetically created dataset and real multi-color flow cytometry data of lymphocytes that are a low autofluorescence cell group. However, the automated compensation algorithm needs further study to be generalized to high autofluorescence cell types where proper compensation does not necessarily coincide with an orthogonal covariance structure.
  • Doctoral Thesis
    Control of Redundant Robot Manipulators With Telerobotic Applications
    (Izmir Institute of Technology, 2016) Çetin, Kamil; Tatlıcıoğlu, Enver; Tatlıcıoğlu, Enver; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    This thesis focuses on task-space control of kinematically redundant robot manipulators with telerobotic applications. The first aim is to design asymptotically stable sub-task controllers for kinematically redundant robot manipulators subject to parametric uncertainties in their dynamics. Initially, a novel combined analysis of the task-space tracking and sub-task controllers is performed for redundant robots having only one extra degree of freedom. Next, an extended task-space controller is designed by integrating manipulator Jacobian with the sub-task Jacobian. Both controllers ensure task-space tracking and sub-task objectives at the amount of redundant degree of freedom. As the second aim, two robust control methods are proposed for task-space tracking of robot manipulators. First, a novel continuous robust controller is designed despite dynamic model and Jacobian uncertainties to ensure asymptotic task-space tracking while requiring measurements of joint positions and velocities. Then, a robust output feedback controller is proposed to ensure ultimately bounded task-space tracking requiring neither measurements of joint positions or velocities nor accurate knowledge of kinematic and dynamic models. The third aim is to develop a passive decomposition method for task-space control of bilateral teleoperation systems. The proposed method ensures coordination of master and slave robots while achieving a desired overall motion for the bilateral teleoperation system. The proposed method is firstly considered for teleoperation systems consisting of kinematically similar master and slave robots, then extended to be applicable to kinematically redundant teleoperation systems. Simulation and experimental studies are performed to present the viability of the proposed methods.
  • Doctoral Thesis
    Robust Control Design for Mechatronic Systems Having Non-Symmetric Input Gain Matrix
    (Izmir Institute of Technology, 2016) Bıdıklı, Barış; Tatlıcıoğlu, Enver; Tatlıcıoğlu, Enver; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Their highly uncertain and complex structures make the control problem of mechatronic systems a challenging task. This problem becomes more challenging when some special cases that make the input gain matrix of these systems non–symmetric are taken into account. Solving this problem is the main motivation of this dissertation. To realize this purpose, a robust controller that is independent from the structure of the input gain matrix is designed. Since, mechatronic systems are modeled as multi–input multi–output nonlinear systems, this design is realized for a broader class of these type of systems. Asymptotic stability of the designed controller is proven via Lyapunov–based arguments. Since, control gain adjusting process is one of the most restrictive and most important aspects of this design, designed controller is supported by proposing a self–tuning method. After completing the control design process by proposing this self–tuning method, three fundamentally different mechatronic systems are utilized to demonstrate the effectiveness of the designed controller in conjunction with the proposed self–tuning method. Position and orientation control of dynamically positioned surface vessel and unactuated surface vessel manipulated by 6 uni–directional tugboats under the influence of added mass effects, and attitude control of small–scaled unmanned helicopter are ensured by utilizing a lower order version of the designed controller. Each of these mechatronic systems constitutes an example of different cases that make input gain matrix non–symmetric. Performance of the designed controller and proposed self–tuning method are demonstrated via simulations and experiments.
  • Doctoral Thesis
    Interference Alignment Techniques for Heterogeneous Wireless Networks
    (Izmir Institute of Technology, 2016) Aycan, Esra; Özbek, Berna; Aycan, Esra; Özbek, Berna; 03.05. Department of Electrical and Electronics Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    In this thesis, we study the stream selection based interference alignment (IA) algorithms, which can provide large multiplexing gain, to deal with the interference in the heterogeneous networks. Firstly, different deployment scenarios for the pico cells are investigated assuming perfect channel state information (CSI) at the transmitters. Two different stream selection IA algorithms are proposed for fully and partially connected interference networks and selecting at least one stream is guaranteed for each user. A stream sequence is selected among a predetermined set of sequences that mostly contribute to the sum-rate while performing an exhaustive search. In the proposed algorithms, the complexity of the exhaustive search is significantly decreased while keeping the performance relatively close. After selecting a stream, the interference generated between the selected and the unselected streams is aligned by orthogonal projections. Then, the influence of the imperfect CSI on the proposed algorithms is analyzed and it is observed that the intra-stream interference causes a significant degradation in the performance due to the quantization error. Therefore, we propose an algorithm for the limited feedback scheme. Finally, adaptive bit allocation schemes are presented to maximize the overall capacity for all the proposed algorithms. The performance evaluations are carried out considering different scenarios with different number and placements of pico cells. It is shown that the proposed algorithm for the limited feedback is more robust to channel imperfections compared to the existing IA algorithms. The presented bit allocation schemes improve the performances of the algorithms compared to the equal bit allocation.