Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Experimental Investigation of Refractive Index Measurement of Common Solvents and Aqueous Solutions in the Infrared Wavelengths(2018) Yüksel, K.; İde, CWe proposed and experimentally demonstrated a fast and simple technique to measure refractive index of liquids. A commercial Optical Time-Domain Reflectometer (OTDR) was implemented for interrogating sensor tips from a remote location. The system uses Fresnel reflected light from standard single mode fiber tips as sensing points without requiring any chemical coating, delicate fiber components, and/or sophisticated architecture at the sensor head. We reported new measurements of refractive indices of common solvents and solutions at both 1550 nm and 1625 nm. The precision of the proposed measurement system was found to be in the order of 10-4. The experimental results have been validated by the way of theoretical calculations.Conference Object Carrier Frequency Offset Based Shared Randomness for Secure Transmission in M-Psk Noma(IEEE, 2023) Göztepe, Caner; Karabulut Kurt, Güneş; Özbek, BernaPower domain non-orthogonal multiple access (NOMA) enhances spectral efficiency by superposing multiple users in the same time-frequency resource block at the expense of exposing the users' data. However, current approaches to improve the secrecy levels of users are limited to rate reduction. This paper proposes a secure NOMA system based on the shared randomness extracted from the reciprocal carrier frequency offsets (CFOs) between the transmitter-receiver pairs for M-ary phase-shift keying. As multiple users will have physically separated oscillators, it will result in independent CFOs among users. This randomness is used to introduce a constellation rotation in the transmitted symbols. We show that under ideal CFO estimates, the proposed approach achieves perfect secrecy among all NOMA users without introducing any rate reduction. We also demonstrate the practical applicability of the proposed approach by using a software-defined radio-based test bed. © 2023 IEEE.Conference Object Detection Scheme for Pnc-Based Cell-Free Mimo Systems(IEEE, 2023) Cumali, Irem; Ozbek, Berna; Kurt, Gunes KarabulutCell-free multiple-input multiple-output (cell-free MIMO) is a promising concept to overcome inter-cell interference and avoid non-uniform data rates among users by combining the best features of ultra-dense networks and MIMO. Hence, cell-free MIMO can fulfill the increasing demand on data rate with uniformly good coverage for the sixth-generation (6G) wireless communications. In addition to that, physical-layer network coding (PNC) reduces the transmission delay since it requires only two time slots instead of four time slots to exchange information between two users. In this paper, we propose a novel scheme called PNC-based cell-free MIMO to improve reliability further while reducing the transmission delay. We demonstrate the effectiveness of the proposed scheme regarding the bit error rate in different system configurations. The proposed PNC-based cell-free MIMO achieves significantly lower error probability than the conventional cell-free MIMO.Conference Object A Framework for Physical Layer Network Coding With Multiple Antennas for Bpsk(IEEE, 2023) İlgüy, Mert; Özbek, BernaPhysical layer network coding (PNC) is combined with multiple antennas to increase the spectral efficiency of wireless communication systems. In this work, we present a PNC framework including both uplink and downlink for binary phase shift keying (BPSK). In the uplink, we propose a scheme for detecting network-coded symbol (NCS) with reduced complexity. For the downlink, we propose a transmission scheme of NCS through maximum ratio transmission (MRT) by defining the precoding vector as an average of users' channels. The bit-error-rate (BER) performances and the comparison results with the conventional scheme in both downlink and uplink are provided for the proposed low-complexity PNC framework.Article Sensory and Sensorimotor Gating in Children With Subclinical Hypothyroidism(2023) Kocaaslan Atlı, Sibel; Olgaç Dündar, Nihal; Erdoğan, Uğraş; Evirgen Esin, Nur; Bayazıt, Turan Onur; Kahya, Mehmet Cemal; Çatlı, Gönül; Gençpınar, Pınar; Dündar, Bumin NuriObjective: Attention and learning problems have been reported in children diagnosed with subclinic hypothyroidism (SH). Sensory gating is an automatic phenomenon that is related to attentional processes. It is known that an impairment in sensory/sensorimotor gating negatively affects the signal processing mechanism and hence attention and learning processes. The aim of the present study was to evaluate the effect of SH on sensory gating processes via P50 suppression and prepulse inhibition (PPI) in children. Methods: Fifteen children aged 8-16 years, diagnosed with SH, and 15 healthy children were included in the study. Auditory P50 suppression and PPI paradigms were applied during the recordings. P50 suppression was examined via auditory brain potentials recorded by electroencephalography. PPI was evaluated via electromyography, in which the blink reflex was recorded by oculomotor muscle activity. Results: No statistical difference was found in P50 suppression and PPI processes between children in the SH and control groups. These findings indicate that the sensory gating processes children with SH are not affected. Conclusion: The findings of this study show that the sensory gating processes of SH children are not affected. However, considering that brain maturation continues until the age of 20s, it may be more useful to scrutinize these processes with a wider age range and a larger number of participants to reveal more clearly how sensory gating is affected by SH.Conference Object Citation - WoS: 2Citation - Scopus: 2Physical Layer Network Coding Enabled Noma With Multiple Antennas(IEEE, 2022) İlgüy, Mert; Özbek, Berna; Okyere, Bismark; Musavian, Leila; Pereira, AathurIn this work, a combination of non-orthogonal multiple access (NOMA) with multiple antennas and physical layer network coding (PNC) scheme is proposed to increase the overall data rate. In the proposed scheme, we employ higher-order modulations for the users with relatively high signal-to-noise ratio (SNR) in the PNC-NOMA pair to increase the data rate. Meanwhile, lower-order modulations are chosen for the users with relatively lower SNR values in the PNC-NOMA pair. We showed the results in terms of bit error rate (BER) for different number of antennas and users in the proposed PNC-NOMA scheme. © 2022 IEEE.Conference Object Citation - Scopus: 1Interference Mitigation for Device-To Based Cellular Communications(IEEE, 2022) Acar, Süleyman Onur; Özbek, BernaDevice-to-device (D2D) communication underlaying cellular networks can improve the performance of cellular systems and it provides an effective way to meet growing mobile traffic and capacity demand. When user equipments are located in close proximity, they can communicate through direct links. In this case, D2D links can increase both energy and spectrum efficiency by reusing uplink (UL) cellular resources while satisfying the users' quality-of-service requirements. However, integrating D2D links into the cellular infrastructure causes an interference since D2D communication can increase co-channel interference and degrade cellular users' transmission link quality. In this paper, the interference mitigation techniques including power control, multiple antenna and resource allocation based on graph coloring are proposed for D2D communications underlaying cellular systems to increase the data rate of both the cellular users and D2D pairs. Compared to the prior works, in the proposed algorithm, D2D and cellular users have same priority for resource allocation. Finally, the proposed algorithm improves the overall system capacity significantly.Article Model-free output feedback controller design for twin rotor systems(Muğla Sıtkı Koçman Üniversitesi, 2020) Deniz, Meryem; Tatlıcıoğlu, Enver; Bayrak, AlperIn this work, tracking control of twin rotor systems is aimed. The control problem is restricted by the lack ofmathematical model of the twin rotor and further complicated by the unavailability of the angular velocitymeasurements. A model–free controller in conjunction with a high gain observer is designed. Experiments performed on atwin rotor system demonstrates the viability of the controller–observer couple.Conference Object Citation - Scopus: 1Depth Camera Calibration Using 4 Spheres on Tetrahedron Corners(IEEE, 2022) Tunçer, Esra; Gümüştekin, ŞevketIn this study, a system including 4 depth cameras (Kinect v1) was constructed for 3-dimensional reconstruction of an object. As with all cameras, the calibration parameters of the cameras used must be known in order to transform from image coordinates to world coordinates in depth cameras. Contrary to the studies that use flat calibration objects such as checkerboard and infrared images, which are frequently encountered in the literature, in this study, only depth images of the cameras were used to find intrinsic and extrinsic parameters of a depth camera. For the calibration process, a new tetrahedron calibration object with 4 equiradius spheres was designed, the sphere centers were determined in the world and image coordinates, and the projection matrix method was applied. The minimum number of matching points required by the original projection matrix method was reduced from 6 to 4 with the help of depth information. A new calibration object and method was developed to provide successful 3-dimensional reconstruction results of 4 depth cameras with the use of only 4 matching points and can be used in all types of depth cameras.Article Citation - WoS: 2Mitigation of Electron Cloud Effects in the FCC-EE Collider(Springer Science and Business Media Deutschland GmbH, 2022) Yaman, F.; Iadarola, G.; Kersevan, R.; Oğur, S.; Ohmi, K.; Zimmermann, F.; Zobov, M.Electron clouds forming inside the beam vacuum chamber due to photoemission and secondary emission may limit the accelerator performance. Specifically, the electron clouds can blow up the vertical emittance of a positron beam, through a head-tail-type single-bunch instability, if the central electron density exceeds a certain threshold value, that can be estimated analytically. Using the codes PyECLOUD and VSim, we carried out detailed simulations of the electron-cloud build up for the main arcs and the damping ring of the FCC-ee collider, in order to identify the effective photoemission rate and secondary emission yield required for achieving and maintaining the design emittance. To this end, we present the simulated electron density at the centre of the beam pipe for various bunch spacings, secondary emission yields, and photoemission parameters, in the damping ring and in the arcs of the collider positron ring. To gain further insight into the underlying dynamics, the obtained spatial and energy distributions of the cloud electrons are illustrated as a function of time. In addition, we compare results obtained for two different secondary emission models (“Furman–Pivi” and “ECLOUD”), thereby indicating the uncertainty inherent in this type of study, without any prototype vacuum chambers yet available. We also point out a few situations where the two secondary-emission models yield similar density values. Finally, based on our simulation results for two different design variants, we conclude that the new parameter baseline of the FCC-ee will facilitate electron-cloud mitigation. © 2022, The Author(s).