Elektrik Elektronik Mühendisliği Bölümü

Permanent URI for this communityhttps://hdl.handle.net/20.500.12416/410

Browse

Now showing 1 - 20 of 202

Citation - Scopus: 0
A data collection system design for hand gestures
(Institute of Electrical and Electronics Engineers Inc., 2021) Akan, E.; Akagunduz, 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.
A Hybrid Framework for Matching Printing Design Files to Product Photos
(2020) Akagunduz, Erdem; Kaplan, Alper; 233834
We propose a real-time image matching framework, which is hybrid in the sense that it uses both hand - crafted features and deep features obtained from a well -tuned deep convolutional network. The matching problem, which we concentrate on, is specific to a certain application, that is, printing design to product photo matching. Printing designs are any kind of template image files, created using a design tool, thus are perfect image signals. For this purpose, we create an image set that includes printing design and corresponding product photo pairs with collaboration of an actual printing facility. Using this image set, we benchmark various hand-crafted (SIFT, SURF, GIST, HoG) and deep features for matching performance. Various segmentation algorithms including deep learning based segmentation methods are applied to select feature regions. Results show that SIFT features selected from deep segmented regions achieves up to 96% product photo to design file matching success in our dataset. We propose a framework in which deep learning is utilized with highest contribution, but without disabling real-time operation using an ordinary desktop computer.
Citation - WoS: 9
Citation - Scopus: 14
A Machine Learning Study to Enhance Project Cost Forecasting
(Elsevier, 2022) Inan, Tolga; İnan, Tolga; Narbaev, Timur; Hazir, Oncu; Elektrik-Elektronik Mühendisliği
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. Copyright (C) 2022 The Authors.
Citation - WoS: 5
Citation - Scopus: 31
A New Narrow Band Dual-Mode Microstrip Slotted Patch Bandpass Filter Design Based On Fractal Geometry
(Ieee, 2012) Mezaal, Yaqeen S.; Eyyuboglu, Halil Tanyer; 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 - WoS: 0
Citation - Scopus: 1
A novel cognitive method for throughput improvement of mobile multi-hop ad hoc networks
(Springer, 2015) Preveze, Barbaros; Preveze, Barbaros; 17573; Elektrik-Elektronik Mühendisliği
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 - Scopus: 2
A Novel High Performance Routing Algorithm for Mobile Multi-hop Tunneling Networks
(Springer, 2020) Preveze, B.; Preveze, Barbaros; 17573; Elektrik-Elektronik Mühendisliği
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%. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
A Novel Method For Performance Improvement of Slow Start Congestion Control Method In Packet Switched Networks
(2019) Preveze, Barbaros; Preveze, Barbaros; 17573; Elektrik-Elektronik Mühendisliği
Tüm akıllı ağlar, akıllı telefonlar, araç multimedya sistemleri giyilebilir teknolojiler ve IP TV'ler ile tanışılmasıyla birlikte internet bağlantılı cihaz ve uygulamaların sayısı da oldukça artmaktadır. Bu durum, paket anahtarlama ağlarında bant genişliği kullanımı miktarında artışa sebep olmuştur. Böylece, bant genişliğinin etkin kullanımı ve sistem performansı daha önemli hale gelmiştir ve literatürde ağ performansını iyileştirmeye çalışan çok sayıda çalışma bulunmaktadır. Ağ yapılarında finansal destek gerektiren donanım tabanlı modifikasyonlar yapmak yerine daha çok, kullanılan yöntemlerin yazılımsal modifikasyonları tercih edilmektedir. Bu çalışmada, daha iyi bir tıkanıklık kontrolü için paket anahtarlamalı ağlarda Eşiğe Geri Dön (RBT) adı verilen yeni bir yöntem önerilmiştir.
Citation - WoS: 0
Citation - Scopus: 0
A novel method to solve 2nd order neumann type boundary value problems in electrostatics
(Applied Computational Electromagnetics Soc, 2017) Sener, Goker; Şener, Göker; 17740; Elektrik-Elektronik Mühendisliği
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 - WoS: 0
Citation - Scopus: 0
A Novel Solution for Network Flexibility Problem in Mobile Multi-hop Tunneling Networks
(Springer, 2023) Preveze, Barbaros; Preveze, Barbaros; 17573; Elektrik-Elektronik Mühendisliği
Since the network throughput performance is limited by the available technology limits, there are too many attempts in the literature to improve the throughput performance of the network by modifying the routing algorithms currently in use. Although application of the tunneling on IP networks provides reserved paths for the higher priority packet streams and succeeds in providing faster communication performances, it is also determined in the literature that, the greatest up to date problem of tunneling networks is the flexibility problem, which is defined as the problem of difficulty to have minimal delay and highest throughput when congestions or node failures occur and the throughput decreases due to high traffic loads on the network. sIn this work, a high performance solution, called LB-ACN (Location Based- Avoid Congested Node) is proposed to solve this flexibility problem and to compensate the increased delay which came up due to the high traffic load and also due to inflexible tunneling network structure, considering the locations of the nodes in addition to their traffic loads. And it is shown that, it is succeeded to carry the throughput of the highly traffic loaded network back to 48.6 Mbps from 36.9 Mbps by about 31.7% performance improvement for which we could improve it from 36.9 Mbps up to 45.9 Mbps by 24.3% using the proposed ACN (Avoid Congested Node) algorithm in our previous work. As a result, we have succeeded in having about 7.4% more improvement on throughput performance in comparison with the previously proposed ACN algorithm.
Citation - WoS: 2
Citation - Scopus: 5
A Novel Transformerless Single-Phase Three-Level Buck-Boost Inverter
(Ieee, 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 - WoS: 4
Citation - Scopus: 5
Accurate method to calculate noise figure in a low noise amplifier: Quantum theory analysis
(Elsevier Sci Ltd, 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 - WoS: 4
Citation - Scopus: 3
Adaptive optics correction of beam spread in biological tissues
(Pergamon-elsevier Science Ltd, 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 com-pared 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 co-efficient 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 char-acteristic 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%.(C) 2022 Elsevier Ltd. All rights reserved.
Citation - WoS: 10
Citation - Scopus: 12
Adaptive optics corrections of scintillations of Hermite-Gaussian modes in an oceanic medium
(Optical Soc Amer, 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
Citation - WoS: 13
Citation - Scopus: 15
Adaptive optics effect on performance of BPSK-SIM oceanic optical wireless communication systems with aperture averaging in weak turbulence
(Pergamon-elsevier Science Ltd, 2020) Gokce, Muhsin Caner; Gökçe, Muhsin Caner; Baykal, Yahya; Ata, Yalcin; 7812; Elektronik ve Haberleşme Mühendisliği
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.
Amorf Çekirdekli Transformatörün Çoklu Fizik Yöntemiyle Elektromanyetik - Sıcaklık Analizi
(2021) Najafi, Atabak; İskender, İres; İskender, İres; 133746; Elektrik-Elektronik Mühendisliği
Bu makalede, Amorf nüveli transformatörün sıcaklık analizini detaylı incelemek için, ısı transferi, akışkan akışı ve elektromanyetik analizlerini kapsayan çok disiplinli bir yaklaşım kullanılmıştır. Transformatörün bobini ve çekirdeğindeki güç kayıpları incelenip, sıcaklık ve akışkan akış analizleri elektromanyetik bir model ile birleştirilmiştir. Önerilen yöntem, Amorf çekirdekli gibi özel transformatörlerde, önceki noktasal sıcaklık bilgisine ya da sıcaklık Gradyan değerlerine ihtiyaç duymadan, sıcaklık değişimini detaylı olarak tahmin edebilmektedir. Teorik çalışma sonuçları uluslararası standartlara göre Dyn11, 34.5/0.4-kV, 630-kVA’lik amorf çekirdekli transformatör üzerine uygulanan deneysel çalışma sonuçlarıyla doğrulanmıştır. Teorik ve pratik çalışma sonuçlarının karşılaştırılması, sonuçların büyük bir uyum içinde olduğunu göstermekte olup, kullanılan yöntem genç mühendislere güç transformatörlerin sıcaklık analiz çalışmalarında faydalı bir araç oluşturmaktadır.
Citation - WoS: 0
Citation - Scopus: 1
Analysis of Lightning Impulse Effects on Three Winding Transformer Used in Solar System Based ANSYS Maxwell
(Ieee, 2022) Yukselen, Emir; İskender, İres; Iskender, Ires; 133746; Elektrik-Elektronik Mühendisliği
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 - WoS: 8
Citation - Scopus: 8
Analysis of Quantum Radar Cross-Section by Canonical Quantization Method (Full Quantum Theory)
(Ieee-inst Electrical Electronics Engineers inc, 2020) Salmanogli, Ahmad; Gokcen, Dincer
This article investigates the difference between two quantum-based theories to calculate the radar cross-section (RCS). Quantum radar cross-section (QRCS) has been commonly analyzed using the dipole approximation method, and the related results show that it can improve the sidelobe of the interference pattern in contrast to the classical methods. This study, on the other hand, utilizes the canonical quantization (or microscopic) method, which is a more comprehensive theory than the dipole approximation method to calculate the radar cross-section. It is shown that there are some similarities between two methods; nonetheless, there are some crucial quantities and factors that have been ignored in the dipole approximation methods. The main difference arises due to the interaction Hamiltonian that two methods relied on. The theoretical calculation shows some critical points suggesting that the dipole approximation method cannot cover all aspects of the radar cross-section calculation. To verify the mentioned point, we establish a new method in which the radar cross-section is calculated by merging the quantum approach with the method of moment (MoM), called quantum-method of moment (QMoM). The simulation results show that the newly established method is in harmony with the canonical quantization method.
Citation - Scopus: 3
Analysis of Short Circuit Electromagnetic Force in a Three Winding Transformer Used in Solar System
(Institute of Electrical and Electronics Engineers Inc., 2021) Jahi, A.; İskender, İres; Iskender, I.; 133746; Elektrik-Elektronik Mühendisliği
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. © 2021 Chamber of Turkish Electrical Engineers.
Citation - WoS: 3
Citation - Scopus: 5
Analysis of wander and spreading of an optical beam by using the oceanic turbulence optical power spectrum
(Optica Publishing Group, 2022) Ata, YalcIn; Gökçe, Muhsin Caner; Baykal, Yahya; Gokce, Muhsin Caner; Elektronik ve Haberleşme Mühendisliği
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. (C) 2022 Optica Publishing Group
Citation - WoS: 5
Citation - Scopus: 6
Anisotropic non-Kolmogorov turbulence effect on transmittance of multi-Gaussian beam
(Taylor & Francis Ltd, 2020) Ata, Yalcin; 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.

Browse

Browsing Elektrik Elektronik Mühendisliği Bölümü by Department "Çankaya University"