Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 2Citation - Scopus: 2Analytical Improvement on the Electromagnetic Scattering From Deformed Spherical Conducting Objects(Institute of Electrical and Electronics Engineers, 2021) Ateş, Barış; Kuştepeli, Alp; Çetin, ZebihIn this paper, electromagnetic scattering from con-ducting deformed spheres is considered analytically by employing the perturbation method and utilizing Debye potentials. To be able to analyze a wide variety of scattering problems, azimuthal variation is indispensable and therefore the geometries of the scatterers considered in this study do not have rotational symmetry, hence they are dependent on the θ and φ angles in spherical coordinates. Analyses are carried up to the second order explicitly to obtain more accurate results and thus scattered fields are obtained with second order corrections. The coefficients used to determine the scattered field are expressed in terms of Clebsch-Gordan coefficients, which enables one to obtain the results for new geometries only by simple algebraic manipulations. Numerical results and their comparisons are also presented for various deformation functions and parameters. IEEEArticle Citation - WoS: 28Citation - Scopus: 28Multi-Helper Noma for Cooperative Mobile Edge Computing(Institute of Electrical and Electronics Engineers, 2022) Yılmaz, Saadet Simay; Özbek, BernaThe next-generation wireless networks are expected to support a number of computation-intensive and delay-sensitive applications such as virtual reality (VR), autonomous driving, telesurgery and unmanned aerial vehicles (UAVs). Since many devices are computation and power limited, mobile edge computing (MEC) has been deemed as a promising way to enhance computation service. In this paper, we propose a novel cooperative MEC that exploits the combination of non-orthogonal multiple access (NOMA) and multiple helpers. In the proposed system featuring a user, multiple helpers and a base station (BS), the user can simultaneously offload its computation-intensive tasks to the helpers using NOMA when there is no strong direct transmission link between the user and the BS. Then, the helpers can compute and offload these tasks through NOMA. Thus, in the proposed scheme, the computation and offloading modes at the helpers are determined with respect to the optimized task offloading decision factor. The simulation results show that the proposed NOMA-based cooperative MEC significantly increases the total offloading data under the latency constraints compared to the benchmark schemes featuring one helper with strong direct transmission link. IEEEConference Object A New Continuous Velocity Observer Formulation for a Class of Uncertain Nonlinear Mechanical Systems(Institute of Electrical and Electronics Engineers, 2015) Bayrak, Alper; Tatlıcıoğlu, Enver; Zergeroǧlu, Erkan; Deniz, MeryemIn this study, we present a smooth robust velocity observer for a class of uncertain nonlinear mechanical systems. The smoothness of the observers is guaranteed by utilizing hyperbolic tangent function as opposed to signum-type functions applied in most robust and sliding mode observers found in the literature. The proposed observer does not require a priori knowledge of an upper bound of the uncertain system dynamics and introduces a time-varying observer gain for uncertainty compensation. Practical stability of the observer error is ensured via Lyapunov-type stability analysis. Numerical simulation studies backed up by experimental results are presented to illustrate the performance of the proposed observer.Conference Object Citation - WoS: 1Citation - Scopus: 3Hybrid Beamforming for Secure Multiuser Mmwave Mimo Communications(Institute of Electrical and Electronics Engineers, 2020) Erdoğan, Oğulcan; Özbek, Berna; Busari, Sherif Adeshina; González, JonathanSecure communication is critical in wireless networks as the networks are prone to eavesdropping from unintended nodes. To address this challenge, physical layer security (PLS) is being employed to combat information leakage. In this paper, we present the performance evaluations based on the secrecy rate and the secrecy outage probability for multiuser multiple-input multiple-output (MIMO) millimeter-wave (mmWave) communications by employing hybrid beamforming (HBF) at the base station, legitimate users and eavesdropper. Using a 3-dimensional mmWave channel model and uniform planar antenna arrays (UPA), we employ artificial noise (AN) beamforming to jam the channels of eavesdropper and to enhance the secrecy rate. The transmitter uses the minimum mean square error (MMSE) precoder to mitigate multiuser interference for the secure MIMO mmWave systems. It is shown that the overall system performance highly depends on the power allocation factor between AN and the signal of legitimate users. © 2020 IEEE.Conference Object Citation - Scopus: 5Estimation of the Nonlinearity Degree for Polynomial Autoregressiv Processes With Rjmcmc(Institute of Electrical and Electronics Engineers, 2015) Karakuş, Oktay; Kuruoğlu, Ercan Engin; Altınkaya, Mustafa AzizDespite the popularity of linear process models in signal and image processing, various real life phenomena exhibit nonlinear characteristics. Compromising between the realistic and computationally heavy nonlinear models and the simplicity of linear estimation methods, linear in the parameters nonlinear models such as polynomial autoregressive (PAR) models have been accessible analytical tools for modelling such phenomena. In this work, we aim to demonstrate the potentials of Reversible Jump Markov Chain Monte Carlo (RJMCMC) which is a successful statistical tool in model dimension estimation in nonlinear process identification. We explore the capability of RJMCMC in jumping not only between spaces with different dimensions, but also between different classes of models. In particular, we demonstrate the success of RJMCMC in sampling in linear and nonlinear spaces of varying dimensions for the estimation of PAR processes. © 2015 EURASIP.Conference Object Citation - Scopus: 2Performance Analysis of Lattice Reduction Aided Mimo Detectors(Institute of Electrical and Electronics Engineers, 2012) Kılıçaslan, Kağan; Altınkaya, Mustafa AzizLattice reduction is a powerful method used in detection and precoding of wireless multiple input-multiple output (MIMO) systems. The basic idea is to consider the channel transfer matrix as a basis for the transmitted symbols. The channel transfer matrix is reduced to a more orthogonal matrix using lattice reduction algorithms. This in turn, improves the performance of conventional MIMO receivers. In this study, it is shown that this performance improvement depends on the modulation order. © 2012 IEEE.Conference Object Citation - Scopus: 6Klasi̇k Türk Müzi̇ği̇ İ̇çin Otomati̇k Notaya Dökme Si̇stemi̇(Institute of Electrical and Electronics Engineers, 2011) Bozkurt, Barış; Gedik, Ali Cenk; Karaosmanoğlu, M. KemalThis study presents an automatic transcription system for Turkish music for the first time in literature. We first discuss the characteristics of Turkish music that are taken into consideration in the design of the system. Then, the following signal processing components of the system are described briefly in relation to each other and explaining their function in the system: f0 estimation, automatic tonic detection and makam recognition based on pitch distributions, frequency and duration quantization. © 2011 IEEE.Conference Object Citation - Scopus: 9Çoklu Antenli̇ Bili̇şsel Radyo Si̇stemleri̇nde Dönemli̇-duraǧan Özelli̇k Algılama Yöntemi̇ne Dayanan Spektrum Sezi̇mi̇(Institute of Electrical and Electronics Engineers, 2011) Üstok, Refik Fatih; Özbek, BernaCognitive radios aim to implement dynamic frequency usage which is proposed to increase the efficiency of the spectrum and can sense their environment, detect the idle bands and then allocate the secondary users into the detected idle bands without any interference to primary users' communications. Cyclostationary Feature Detection is one of the commonly used methods in the literature for spectrum sensing. This paper focuses on sensing the idle bands using cyclostationary feature detection method in Cognitive Radio based systems. The performance is improved by using the proposed multiple antenna technique and the simulation results are analyzed. © 2011 IEEE.Conference Object Citation - Scopus: 2Histoloji Görüntülerinde Kanserli Desenlerin Yarı Güdümlü Öğrenme Yöntemiyle Tam Otomatik Sınıflandırılması(Institute of Electrical and Electronics Engineers, 2010) Önder, Devrim; Sarıoğlu, Sülen; Karaçalı, BilgeThe aim of this work is to perform automated texture classification of histology slide images in health and cancerous conditions using quasi-supervised statistical learning method. Tissue images were acquired from histological slides of human colon and were seperated into two groups in terms of normal and disease conditions. Texture feature vectors corresponding to tissue segments of each image were calculated using co-occurrence matrices. Different texture regions were determined by the quasi-supervised statistical learning method using texture features of normal and cancerous groups. ©2010 IEEE.Conference Object Citation - WoS: 4Citation - Scopus: 5Backstepping Control of Electro-Hydraulic Arm(Institute of Electrical and Electronics Engineers, 2018) Bayrak, Alper; Tatlıcıoğlu, Enver; Zergeroǧlu, ErkanIn this study, positioning control of the electro hydraulic systems is considered. Backstepping control strategy is designed by defining an auxiliary error signal. The performance of the controller is investigated by conducting numerical simulations. From the simulation results, it is seen that the control objective achieved successfully. The performance is compared with PI controller via a comparison criteria and it is seen that the backstepping controller has better results in both error and controller performance aspects.