Elektrik Elektronik Mühendisliği Bölümü

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Citation Count: Akan, E.; Akagündüz, E.; Uslu, I. B. (2021). "A data collection system design for hand gestures", 2021 International Conference on INnovations in Intelligent SysTems and Applications, INISTA 2021 - Proceedings.
A data collection system design for hand gestures
(2021) Akan, E.; Akagündüz, E.; Uslu, I. B.
In this study, we aim at designing a smart glove, which consists of different inertial sensors and an EMG sensor and developing a human-machine interaction application by pre-processing and fusing these different sensory data. We also aim at providing solutions in cases where image processing-based approaches are inefficient. In the proposed smart glove, the quaternion-based orientation data to be produced by the magnetometer and gyroscope together, the acceleration data to be generated by the accelerometer, and the analog data generated by the EMG sensor are collected and then prepared for use by different applications. © 2021 IEEE.
Citation Count: İnan, Tolga; Narbaev, Timur; Hazır, Öncü (2022). "A Machine Learning Study to Enhance Project Cost Forecasting", IFAC-PapersOnLine, Vol. 55, No. 10, pp. 3286-3291.
A Machine Learning Study to Enhance Project Cost Forecasting
(elsevier, 2022) İnan, Tolga; Narbaev, Timur; Hazır, Öncü
In project management it is critical to obtain accurate cost forecasts using effective methods. This study presents a Machine Learning model based on Long-Short Term Memory to forecast the project cost. The model uses the seven-dimensional feature vector, including schedule and cost performance factors and their moving averages as a predictor. Based on the cost variation patterns from the training phase, we validate the model using three hundred experiments in the testing phase. Overall, the proposed model produces more accurate cost estimates when compared to the traditional Earned Value Management index-based model.
Citation Count: Mezaal, Yaqeen S.; Eyyuboglu, Halil Tanyer, "A New Narrow Band Dual-Mode Microstrip Slotted Patch Bandpass Filter Design Based on Fractal Geometry", 2012 7th International Conference On Computing and Convergence Technology (Iccct2012), pp. 1180-1184, (2012)
A New Narrow Band Dual-Mode Microstrip Slotted Patch Bandpass Filter Design Based On Fractal Geometry
(IEEE, 2012) Mezaal, Yaqeen S.; Eyyuboğlu, Halil T.; 7688
A narrowband, compact, and easily fabricated microstrip bandpass filter design is introduced in this paper as a candidate for use in modern wireless systems. The proposed filter design is based on the use of dual-mode (two pole) square slotted microstrip resonator. This microstrip bandpass filter has the advantages of possessing much narrower and sharper performance responses than those of the single mode resonator and conventional square patch filter. The proposed microstrip filter structure is fractally generated using Sierpinski fractal curve geometry applied to the conventional square microstrip patch. Filter structures resulting from the successive iterations in the fractal generation process show a considerably low insertion loss, and sharper response of about 1% fractional bandwidth as compared with the conventional microstrip square patch filter of 3% fractional bandwidth designed at the same frequency using the same substrate material. The performance of filter structures, based on dual-mode resonators up to the third iterations, has been evaluated using a full-wave based electromagnetic simulator Sonnet software package. Performance simulation results show that these filter structures offer narrower fractional bandwidth percentages as compared with other types of non- fractalized filter structures.
Citation Count: Preveze, B. (2015). A novel cognitive method for throughput ımprovement of mobile multi-hop ad hoc networks. Wireless Personal Communications, 82(1), 229-243. http://dx.doi.org/10.1007/s11277-014-2205-1
A novel cognitive method for throughput improvement of mobile multi-hop ad hoc networks
(Springer, 2015) Preveze, Barbaros; 17573
We had previously defined a novel cognitive method for throughput improvement of IEEE 802.16j mobile multi-hop ad-hoc network which enables better management of the spectral access and buffer management of the nodes in the network. By this method we had minimized the packet loss ratio and improved the throughput of IEEE 802.16j network. In this study, a novel cognitive buffer management algorithm is proposed that arranges the packets stored in the buffers of the nodes in a probabilistic way and selects correct packet of the correct node to transmit first to provide fewer packet losses and also fewer average hop-counts for more throughputs. It is shown that the novel proposed buffer management algorithm provides about 19.45 % more throughput improvement (on average) with respect to the results evaluated by the buffer management algorithm used before (which was also shown to provide 12 % throughput improvement with respect to a First In First Out buffer management algorithm). All the results evaluated in this study are also confirmed by the results of analytical calculations, the results of the developed simulation program and the results evaluated in the literature.
Citation Count: Preveze, Barbaros (2020). "A Novel High Performance Routing Algorithm for Mobile Multi-hop Tunneling Networks", Wireless Personal Communications, Vol. 114, No. 1, pp. 1-27.
A Novel High Performance Routing Algorithm for Mobile Multi-hop Tunneling Networks
(2020) Preveze, Barbaros; 17573
By the increased number of mobile devices, the demand of high speed connection oriented tunneling networks also increases. But, in mobile tunneling networks, the full route will have to be reconstructed more frequently because of more frequent route failures, where the requirements for extra route reconstructions (RRC) will cause extra delay and a decreased system throughput. In this work, a novel routing algorithm, optimum path routing (OPR) is proposed to extend the route life time of mobile multi hop tunneling networks and to increase the system throughput. On the other hand, as the most recent works in the literature indicate that, one of the greatest challenges of tunneling networks is to provide the network flexibility by instant adaptation on changing network conditions to keep the delay at lowest levels even in case of high traffic loads or node failures. To solve the aforementioned flexibility problem of the tunneling networks, a novel algorithm applicable to all kinds of routing algorithms called "avoid congested nodes (ACN)" is proposed. The results show that, the OPR algorithm proposed to increase the route life has succeeded in decreasing the RRC delay by 84% and improving the throughput by 20.17% with respect to the Fastest Path routing algorithm in the literature. And the ACN algorithm, proposed to provide a rapid adaptation of the nodes to the changing traffic conditions, has also succeeded in carrying back the throughput of the network with traffic load from 75.5% of its best performance evaluated with no traffic to its 94%.
Citation Count: Şener, G. (2017). A novel method to solve 2nd order neumann type boundary value problems in electrostatics. Applied Computational Electromagnetics Society Journal, 32(4), 289-294.
A novel method to solve 2nd order neumann type boundary value problems in electrostatics
(Applied Computational Electromagnetics Soc., 2017) Şener, Göker; 17740
In this paper, the numerical method of nonpolynomial spline approximation is used to solve 2nd order Neumann type boundary value problems (bvp's) in electrostatics. This new approach provides more accurate results than the polynomial approximations and the spectral methods. The literature contains very little on the solution of Neumann type bvp's because of the fact that a unique solution does not exist for all problems. In electrostatics, Neumann type bvp's are encountered for finding the electrostatic potential inside closed surfaces where the normal derivative of the electric potential is specified everywhere on the surface. Two examples are presented to prove the accuracy of the proposed method. In these examples, the governing differential equation is solved to find the electrostatic potential inside a region bounded by conductors that are maintained at constant voltages. The results are compared with the analytic solutions.
Citation Count: Demirkutlu, E.; İskender, İ. "A Novel Transformerless Single-Phase Three-Level Buck-Boost Inverter", 2023 IEEE Applied Power Electronics Conference And Exposition, APEC, Proceedings, pp. 114-120, 2023.
A Novel Transformerless Single-Phase Three-Level Buck-Boost Inverter
(2023) Demirkutlu, Eyyup; Iskender, Ires; 133746
This paper proposes a novel transformerless, single-phase, three-level, buck-boost inverter. The proposed inverter can suppress the leakage current drawn from the input power source and provide a long-lasting solution for applications with a wide range and unregulated input voltage. Unlike similar topologies, in the proposed inverter there is no need to have a mid-point of DC sources or DC bus capacitors at the input side of the inverter. A single-phase, three-level, buck-boost inverter for realizing the power stage with 110-Vrms output AC voltage and a range of 100V-200V input DC voltage is investigated in this study. The proposed topology has been proven through theory, computer simulations, and experimental studies with SiC MOSFETs-based prototype of a 300-VA power supply. Theory, computer simulation, and experimental results are all correlated.
Citation Count: Toreyin, Behcet Ugur; Aktas, Hakan; Sever, Refik, "A Two Stage Template Matching Algorithm and Its Implementation on FPGA", 23nd Signal Processing and Communications Applications Conference (SIU), pp. 2214-2217, (2015).
A Two Stage Template Matching Algorithm and Its Implementation on FPGA
(IEEE, 2015) Aktaş, Hakan; Sever, Refik; Töreyin, Behçet Uğur; 19325
In this paper, to decrease the computational cost and number of cycles in Template Matching Algorithm, a novel two-stage algorithm is proposed. The Sum of Absolute Differences method is used for matching. The proposed algorithm is implemented on Field-Programmable-Gate-Array (FPGA). The algorithm is accelerated with the effective usage of Block RAMs distributed on FPGA. Thus, the proposed algorithm became fast enough for real time object tracking applications on UAVs.
Citation Count: Salmanogli, Ahmad; Gecim, H. S. (2022). "Accurate method to calculate noise figure in a low noise amplifier: Quantum theory analysis", Microelectronics Journal, Vol.128.
Accurate method to calculate noise figure in a low noise amplifier: Quantum theory analysis
(2022) Salmanogli, Ahmad; Gecim, H. Selcuk; 182579
In this study, a low-noise amplifier is quantum-mechanically analyzed to study the behavior of the noise figure. The analysis view has been changed from classic to quantum, because using quantum theory produces some degrees of freedom, which may be ignored when a circuit is analyzed using classical theory. For this purpose, the Lagrangian is initially derived by considering the related nonlinearity of the transistor, and then using the Legendre transformation and canonical quantization procedure, the quantum Hamiltonian is derived. As an interesting point of this study, the low-noise amplifier is deliberately considered as two oscillators connecting to each other to share the photonic modes between them; accordingly, the voltage and current as measurable observations and the noise figure as a critical quantity in a low-noise amplifier are theoretically expressed in terms of the oscillator's mean photon number. The main goal of this work is to study quantities such as the noise figure in a sufficient detail using quantum theory. In addition, as an advantage of this theory, one can control and manipulate the noise figure only by manipulation of the oscillator's mean photon number and coupling it between two oscillators. Finally, the circuit is classically designed and simulated to verify the derived results using quantum theory. The comparison results show that there is a partial consistency between the two approaches; as the frequency increases, the noise figure becomes minimized at a particular frequency.
Citation Count: Baykal, Y. (2022). "Adaptive optics correction of beam spread in biological tissues", Journal of Quantitative Spectroscopy and Radiative Transfer, Vol.283.
Adaptive optics correction of beam spread in biological tissues
(2022) Baykal, Yahya
Beam spread in turbulent biological tissues is examined when the tissue is excited with a collimated Gaussian laser beam. Adaptive optics correction is applied to the beam spread in the form of piston only (P Only), tilt only (T Only), piston+tilt (P+T), and the reduction in the beam spread is evaluated as compared to the no adaptive optics (No AO) corrected beam spread. No AO and adaptive optics corrected beam spread are expressed for various biological tissue types, against the variations in the strength coefficient of the refractive-index fluctuations, source size, small length-scale factor of turbulence, tissue length, fractal dimension, characteristic lengths of heterogeneity and the wavelength. For the examined tissue types of liver parenchyma (mouse), intestinal epithelium (mouse), upper dermis (human) and deep dermis (mouse), No AO beam spread and the adaptive optics corrected beam spread are found to increase as the strength coefficient of the refractive-index fluctuations, tissue length, fractal dimension, the characteristic lengths of heterogeneity increase, and to decrease as the source size, small length-scale factor, wavelength increase. Reduction ratio of P+T correction is almost the same for all the evaluated cases which is 74%.
Citation Count: Baykal, Yahya (2020). "Adaptive optics corrections of scintillations of Hermite-Gaussian modes in an oceanic medium", Applied Optics, Vol. 59, No. 16, pp. 4826-4832.
Adaptive optics corrections of scintillations of Hermite-Gaussian modes in an oceanic medium
(2020) Baykal, Yahya; 7812
Adaptive optics correction of the scintillation index is found when Hermite-Gaussian laser beams are used in oceanic turbulence. Adaptive optics filter functions are used to find how the tilt, focus, astigmatism, coma, and total correction will behave under high order mode excitation. Reduction of the oceanic scintillation under various oceanic turbulence and system parameters is examined under different high order modes. Also, the effects of the source size, wavelength, and link length on the total adaptive optics correction of Hermite-Gaussian modes in an oceanic medium are investigated for different modes. (C) 2020 Optical Society of America
Adaptive optics effect on performance of BPSK-SIM oceanic optical wireless communication systems with aperture averaging in weak turbulence
(2020) Gökçe, Muhsin Caner; Baykal, Yahya; Ata, Yalçın; 7812
Turbulence-induced wavefront deformations cause the irradiance of an optical signal to fluctuate resulting a in serious degradation in the bit-error-rate (BER) performance of optical wireless communication (OWC) system. Adaptive optics is an effective technique to compensate for the wavefront aberrations to reduce the fluctuations in the received intensity. In this paper, we investigate how the adaptive optics technique affects the BER performance of an oceanic OWC (OOWC) system employing binary phase shift keying-subcarrier intensity modulation (BPSK-SIM) and aperture averaging. To evaluate BER performance in weak oceanic turbulence, the required entities such as the received optical power captured by a circular aperture and the aperture averaged scintillation index measuring the fluctuations in the received irradiance are derived. The effect of adaptive optics correction of various wavefront aberrations (i.e., tilt, defocus, astigmatism and the coma) on the BER performance is illustrated and the performance of the adaptive optics-OOWC system is compared to that of a non-adaptive optics OOWC system by the metric defined. (C) 2020 Elsevier Ltd. All rights reserved.
Citation Count: Preveze, Barbaros; Safak, Aysel, "Alternative Enhancement of Associativity Based Routing (AEABR) for Mobile Networks", Vol. 32, pp. 67-+, (2010).
Alternative Enhancement of Associativity Based Routing (Aeabr) for Mobile Networks
(Springer, 2010) Preveze, Barbaros; Safak, Aysel; 17573
This study proposes an alternative enhancement for the Enhanced Associativity Based Routing (EABR) method which is a derivation of ABR (Associativity Based Routing) by relative speed and relative distance estimation using the received power strength (RPS) of the nodes. In this study, it is shown that EABR outperforms some other well known protocols. The performance of EABR is improved in terms of number of route reconstructions (RRC) and connected status percentage (CSP). Message overhead and bandwidth utilization is also investigated.
Citation Count: Yükselen, Emir; İskender, I. (2022). "Analysis and Design of a Special Type Power Transformer Used in Solar Power Plants", International Journal of Renewable Energy Research, Vol.12, No.2, pp.667-673.
Analysis and Design of a Special Type Power Transformer Used in Solar Power Plants
(2022) Yükselen, Emir; İskender, Ires
Due to growing of greenhouse gas emissions and lack of the fossil sources, governments encouraged all scientists and utilities for looking to the alternative energy sources such as solar renewable energy which can help to reduce carbon dioxide emissions. In this respect, Photovoltaic (PV) power plants have become more important in recent years and renewable energy sources integrated into the power system are increasing day by day. Transformers are the main components of electrical grids and are widely used in renewable power plants to transfer the energy they produce to the grid. Accordingly, transformers are one of the most critical equipment of PV plants, and their safe operation and stability in the electrical network are important. This type of transformer is supplied from solar panels through inverters and needs to be customized to work with each system. In this type of transformer, the losses are higher than those for transformers used in electrical power systems supplied by sinusoidal voltage considering existence of different voltage and current harmonics content produced by the inverter. In this study, a special type of PV transformer was designed in accordance with the target performance criteria, taking into account the effects of harmonics, and keeping the transformer losses and temperature rise at a safe level. In this paper also the simulation results are compared with those of experiments test to verify the design procedures.
Citation Count: Baykal, Yahya; Uysal, Murat, "Analysis of Field Correlations in Atmospheric Optical MIMO Systems", 3rd International Workshop in Optical Wireless Communications (IWOW), pp. 30-34, (2014).
Analysis of Field Correlations in Atmospheric Optical MIMO Systems
(IEEE, 2014) Baykal, Yahya; Uysal, Murat
In this paper, we evaluate the absolute field correlations for a free space optical (FSO) multiple-input multiple-output (MIMO) link operating in a turbulent atmosphere. Such knowledge is needed in heterodyne reception to keep all the optical detectors within the region in which a predefined correlation value is fulfilled. The variations of the absolute field correlations versus the longest distance between the detectors are found for different array, medium and receiver parameters such as the number of beamlets, the radius of the radial array, beamlet size, link length, wavelength, structure constant and the position of the detectors.
Citation Count: Yükselen, Emir; İskender, İres. "Analysis of Lightning Impulse Effects on Three Winding Transformer Used in Solar System Based ANSYS Maxwell", 2022 9th International Conference on Electrical and Electronics Engineering (ICEEE), IEEE, pp. 71-75.
Analysis of Lightning Impulse Effects on Three Winding Transformer Used in Solar System Based ANSYS Maxwell
(IEEE, 2022) Yükselen, Emir; İskender, İres; 133746
Transformers are in more critical applications in the renewable energy world and having a transformer fail in such a cyclical power station can be disastrous. Over voltage or voltage strike is the most important phenomena for the transformers. Thus, the evaluating and estimating the effects and stresses of these sudden high voltages is important during the transformers life time operation and design stage. Accordingly in this paper the electromagnetic field analyses of the lightning impulse on Photovoltaic (PV) transformer are investigated using ANSYS Maxwell software. The 3D and 2D model simulation of the PV transformer is carried out to determine the electric field and voltage distribution on critical regions which can cause breakdown on insulation material and damage transformer windings and affects transformer working. Afterwards according to the simulation result, the subjected transformer was designed considering the relative critical regions and performs the full wave lightning impulse test in factory area to verify the dielectric strength of the transformer. This study provides better understanding of the lightning impulse voltage effects with localization of the critical regions on the PV transformer and helps to improve the withstand capability of the transformer against the lightning impulse voltages during the design and production stage.
Citation Count: Jahi, Amir; İskender, İres. "Analysis of Short Circuit Electromagnetic Force in a Three Winding Transformer Used in Solar System", 2021 13th International Conference on Electrical and Electronics Engineering (ELECO), IEEE, pp. 393-397, 2021.
Analysis of Short Circuit Electromagnetic Force in a Three Winding Transformer Used in Solar System
(IEEE, 2021) Jahi, Amir; İskender, İres; 133746
Due to the increasing of the fossil fuels prices in the past years and lack of these sources, all scientists encouraged to looking for the alternative energy sources. One of these energy sources is renewable solar energy. Power transmission from solar systems to grid is achieved using step up transformers. This type of transformer is energized from two inverter with or without variable frequency. Power transformers are deals with a variety of mechanical, electrical and thermal stresses during normal life time operation. Transient electromagnetic forces cause mechanical stress on transformer parameters where calculation of these forces with traditional methods is extremely complex due to the geometry of the transformer. Accordingly in this study, the electromagnetic forces takes place in the windings of a Photovoltaic (PV) transformer are investigated and for calculation of these forces, the 3D and 2D model of transformer is adapted in the ANSYS Workbench. The analysis of electromagnetic forces during the three line fault on high voltage side of the transformer are performed by the Finite Element Method (FEM) and compared with the analytical results. The numerical modeling technique discussed in this study would be useful in the design stage of PV transformer with regard to evaluate ability of transformer to withstand the short circuit current.
Citation Count: Ata, Yalçın; Baykal, Yahya; Gökçe, Muhsin C. (2022). "Analysis of wander and spreading of an optical beam by using the oceanic turbulence optical power spectrum", Journal of the Optical Society of America B: Optical Physics, Vol.39, No.8, pp.2129-2137.
Analysis of wander and spreading of an optical beam by using the oceanic turbulence optical power spectrum
(2022) Ata, Yalçın; Baykal, Yahya; Gökçe, Muhsin Caner
Variance of beam displacement and short-term and long-term spreading of a Gaussian beam propagating in the presence of underwater turbulence are examined by using the oceanic turbulence optical power spectrum (OTOPS). Analytical expressions for both beam wander displacement variance and beam spreading are presented. Results show that the underwater turbulent channel causes deflection from the on-axis mean irradiance and brings significant wander and spreading effects to the propagating Gaussian beam wave. The variations of beam wander and short- and long-term spreading are obtained depending on the underwater medium parameters such as the average temperature, average salinity concentration, temperature-salinity gradient ratio, and temperature and energy dissipation rates. In particular, the real values of the average temperature and salinity concentration of turbulent water are used to obtain the results. In addition, the effects of propagation distance, Gaussian beam source size, and wavelength are shown. The results demonstrate that the underwater turbulent channel brings displacements in the centroid and spreading of the optical beam.
Citation Count: Ata, Yalçın; Baykal, Yahya (2020). "Anisotropic non-Kolmogorov turbulence effect on transmittance of multi-Gaussian beam", Waves in Random and Complex Media, Vol. 30, No. 1, pp. 118-129.
Anisotropic non-Kolmogorov turbulence effect on transmittance of multi-Gaussian beam
(2020) Ata, Yalçın; Baykal, Yahya; 7812
The effect of anisotropic non-Kolmogorov turbulent atmosphere on multi-Gaussian beam is investigated and the results are presented against different beam and medium parameters. Results show that anisotropy increases the power efficiency of wireless communication systems. Besides anisotropy, turbulence effects on the multi-Gaussian optical beam are represented versus the beam source size, beam flatness order, propagation distance, inner scale length, turbulence strength, non-Kolmogorov turbulence power law exponent, wavelength, inner and outer source sizes for flat-topped and annular beams.
Citation Count: Ata, Y., Baykal, y. (2018). Anisotropy effect on multi-Gaussian beam propagation in turbulent ocean. Chinese Laser Press, 16(8). http://dx.doi.org/10.3788/COL201816.080102
Anisotropy effect on multi-Gaussian beam propagation in turbulent ocean
(Chinese Laser Press, 2018) Ata, Yalçın; Baykal, Yahya; 7812
Average transmittance of multi-Gaussian (flat-topped and annular) optical beams in an anisotropic turbulent ocean is examined analytically based on the extended Huygens-Fresnel principle. Transmittance variations depending on the link length, anisotropy factor, salinity and temperature contribution factor, source size, beam flatness order of flat-topped beam, Kolmogorov microscale length, rate of dissipation of turbulent kinetic energy, rate of dissipation of the mean squared temperature, and thickness of annular beam are examined. Results show that all these parameters have effects in various forms on the average transmittance in an anisotropic turbulent ocean. Hence, the performance of optical wireless communication systems can be improved by taking into account the variation of average transmittance versus the above parameters.

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