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Elektrik Elektronik Mühendisliği Bölümü

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Citation Count: Kaplan, Alper; Akagündüz, Erdem (2020). "A Hybrid Framework for Matching Printing Design Files to Product Photos", Balkan Journal of Electrical and Computer Engineering, Vol. 8, No. 2, pp. 170-180.
A Hybrid Framework for Matching Printing Design Files to Product Photos
(2020) Kaplan, Alper; Akagündüz, Erdem; 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. However, photographs of a printed product suffer many unwanted effects, such as uncontrolled shooting angle, uncontrolled illumination, occlusions, printing deficiencies in color, camera noise, optic blur, et cetera. 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 and deep features for matching performance and propose a framework in which deep learning is utilized with highest contribution, but without disabling real-time operation using an ordinary desktop computer.
Citation Count: Preveze, B. (2018). "A Novel Analytical Method for Throughput Calculation of Wireless Ad-Hoc Networks Running Different Routing Algorithms ", International Journal of Research Studies in Electrical and Electronics Engineering, Vol.4, No.4, pp.1-10.
A Novel Analytical Method for Throughput Calculation of Wireless Ad-Hoc Networks Running Different Routing Algorithms
(2018) Preveze, Barbaros; 17573
Because of the increasing number of internet related applications, the role of total router transmission delay became much more important for the service quality. For this purpose, the tunneling techniques have been widely used especially for real time multimedia transmission to have less number of route constructions and to be able to forward each packet at each router without the need of reaching the upper OSI (Open Systems Interconnection) layers. But, in mobile networks, since the network experience with more changes in traffic conditions and node locations, tunnels will be reconstructed for many times and some extra delay will occur to reconstruct these tunnels. In this work, the place of the tunneling algorithm is taken by the well-known MPLS (Multi-Protocol Label Switching) protocol and for confirmation the throughput calculations are made by considering two different routing algorithms, one of which is AEABR algorithm proposed in [1] (shown in [2] that it improves the system throughput w.r.t Fastest path Routing algorithm [3] for various vehicular velocities), and the other one is Fastest Path routing algorithm [3]. In this work a novel analytical method for throughput calculation of wireless ad-hoc networks running aforementioned routing algorıthms is proposed including the effects of extra delay caused by extra Route Reconstructions (RRC).
Citation Count: Preveze, Barbaros (2019). "A Novel Method For Performance Improvement of Slow Start Congestion Control Method In Packet Switched Networks", Uludağ Üniversitesi Mühendislik Fakültesi Dergisi, Vol. 24, No. 3, pp. 451-467.
A Novel Method For Performance Improvement of Slow Start Congestion Control Method In Packet Switched Networks
(2019) Preveze, Barbaros; 17573
By the introduction of all IP networks with the smart homes, smart phones, car multimedia systems wearable technologies and IP TV’s, the number of internet related devices and the number of applications have increased. This has generated an increased quantity of bandwidth usage in packet switching networks. Therefore, the betterment of the bandwidth usage and the system performance has become more significant. Thus, there is a large number of works in the literature attempting to improve the network performance. For this purpose, generally the modifications of used methods in the network structures are preferred, rather than making major hardware based modifications requiring more financial support. In this work, a novel method called Return Back to threshold (RBT) is proposed to be applied to packet switched networks for a better congestion control.
Citation Count: Preveze, B. (2023). "A Novel Solution for Network Flexibility Problem in Mobile Multi-hop Tunneling Networks", Wireless Personal Communications, Vol.129, No.2, pp. 1049-1068.
A Novel Solution for Network Flexibility Problem in Mobile Multi-hop Tunneling Networks
(2023) Preveze, Barbaros; 17573
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 Count: Najafi, Atabak; İskender, İ. (2021). "Amorf Çekirdekli Transformatörün Çoklu Fizik Yöntemiyle Elektromanyetik - Sıcaklık Analizi", Afyon Kocatepe Üniversitesi Fen ve Mühendislik Bilimleri Dergisi, Vol.21, No.5, pp.1086-1096.
Amorf Çekirdekli Transformatörün Çoklu Fizik Yöntemiyle Elektromanyetik - Sıcaklık Analizi
(2021) Najafi, Atabak; İskender, İres; 133746
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 Count: Uzun, E.; Akagunduz, E., "An Analysis On the Effect of Skip Connections in Fully Convolutional Networks for License Plate Localization [Tam Evrişimli Aǧlardaki Atlama Baǧlantilarinin Plaka Konumu Bulmaya Etkisi Üzerine Bir İnceleme]", 27th Signal Processing and Communications Applications Conference, Sıu 2019, (2019).
An Analysis On the Effect of Skip Connections in Fully Convolutional Networks for License Plate Localization [Tam Evrişimli Aǧlardaki Atlama Baǧlantilarinin Plaka Konumu Bulmaya Etkisi Üzerine Bir İnceleme]
(Institute of Electrical and Electronics Engineers Inc., 2019) Akagündüz, Erdem; Uzun, Engin; 233834
In this study, the effect of the skip connections, which are seen in fully convolutional networks, on object localization is analyzed. For this purpose, a local data set for plate detection is created. Experiments are carried out using this data set. Due to the small size of the image set, data augmentation method is used to overcome the danger of over-fitting. The learning rates of the first layers are frozen for analysis and finetuning is applied to only the last layer and deconvolution layers. The results obtained are compared with the results of other image sets. The results indicate the importance of the information provided by the skip connections on object localization.
Citation Count: Salmanogli, Ahmad; Gökçen, Dinçer (2020). "Analysis of Quantum Radar Cross-Section by Canonical Quantization Method (Full Quantum Theory)", IEEE Access, Vol. 8, pp. 205487-205494.
Analysis of Quantum Radar Cross-Section by Canonical Quantization Method (Full Quantum Theory)
(2020) Salmanogli, Ahmad; Gökçen, Dinçer
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 Count: Şener, G. (2023). "Antenna Synthesis by Levin's Method using a Novel Optimization Algorithm for Knot Placement", Applied Computational Electromagnetics Society Journal, Vol.38, No.2, pp.74-79.
Antenna Synthesis by Levin's Method using a Novel Optimization Algorithm for Knot Placement
(2023) Şener, Göker; 17740
Antenna synthesis refers to determining the antenna current distribution by evaluating the inverse Fourier integral of its radiation pattern. Since this inte-gral is highly oscillatory, Levin's method can be used for the solution, providing high accuracy. In Levin's method, the integration domain is divided into equally spaced sub-intervals, and the integrals are solved by transfer-ring them into differential equations. This article uses a new optimization algorithm to determine the location of these interval points (knots) to improve the method's accuracy. Two different antenna design examples are pre-sented to validate the accuracy and efficiency of the pro-posed method for antenna synthesis applications.
Citation Count: Şener, Göker (2023). "Antenna Synthesis by Levin’s Method using Reproducing Kernel Functions", Applied Computational Electromagnetics Society Journal, Vol. 38, No 7, pp. 482-488.
Antenna Synthesis by Levin’s Method using Reproducing Kernel Functions
(2023) Şener, Göker; 17740
An antenna synthesis application is presented by solving a highly oscillatory Fourier integral using a stable and accurate Levin’s algorithm. In antenna synthesis, the current distribution is obtained by the inverse Fourier integral of the antenna radiation pattern. Since this integral is highly oscillatory, the Levin method can be used for its solution. However, when the number of nodes or the frequency increases, the Levin method becomes unstable and ineffective due to the large condition number of the interpolation matrix. Thus, an improved scheme of the method is used in an antenna synthesis application in which reproducing kernel functions are used as the basis of the approximation function. The accuracy of the new method is verified by a log-periodic antenna example. The error and stability analysis results show that the new method is more stable and accurate than other well-known kernels, especially for a large number of nodes.
Citation Count: Gökçe, M.C...et al. (2015). Aperture averaging in multiple-input single-output free-space optical systems. Optical Engineering, 54(6). http://dx.doi.org/10.1117/1.OE.54.6.066103
Aperture averaging in multiple-input single-output free-space optical systems
(Spie-Soc Photo-Optical Instrumentation Engineers, 2015) Gökçe, Muhsin Caner; Baykal, Yahya; Kamacıoğlu, Canan; Uysal, Murat; 28643; 7812; 124615
Multiple-input single-output systems are employed in free-space optical links to mitigate the degrading effects of atmospheric turbulence. We formulate the power scintillation as a function of transmitter and receiver coordinates in the presence of weak atmospheric turbulence by using the extended Huygens Fresnel principle. Then the effect of the receiver aperture averaging is quantified. To get consistent results, parameters are chosen within the range of validity of the wave structure functions. Radial array beams and a Gaussian weighting aperture function are used at the transmitter and the receiver, respectively. It is observed that the power scintillation decreases when the source size, the ring radius, the receiver aperture radius, and the number of array beamlet increase. However, increasing the number of array beamlets to more than three seems to have negligible effect on the power scintillation. It is further observed that the aperture averaging effect is stronger when radial array beams are employed instead of a single Gaussian beam.
Citation Count: Kiracı, ali. (2022). "Calculation of the Halfwidth and the Activation Energy for the Soft Raman Modes in the Brominated Compounds of Tris-Sarcosine Calcium Chloride", Trends in Sciences, Vol.9, No.16.
Calculation of the Halfwidth and the Activation Energy for the Soft Raman Modes in the Brominated Compounds of Tris-Sarcosine Calcium Chloride
(2022) Kiracı, Ali; 42475
This letter contributes how to calculate the anomalous behavior for the damping constant (halfwidth) of the ferroelectric Tris-Sarcosine Calcium Chloride (TSSC) and its brominated compounds TSSC1−xBrx (x = 0.13, 0.42 and 0.60) from the wavenumber data of the soft modes below the phase transition temperature of TC. The pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models derived from the dynamical Ising model were used. Both PS and EF models have been used to contribute understanding the temperature dependence of the phase transition mechanism of TSSC1−xBrx. In addition, values of the activation energy for TSSC1−xBrx (x = 0, 0.13, 0.42 and 0.60) were extracted from the damping constant as calculated from both models (PS and EF). Our results indicate order-disorder type phase transition for TSSC1−xBrx.
Citation Count: Yükselen, Emir; İskender, İres (2023). "CASE STUDY ON THERMAL OPTIMIZATION OF OIL IMMERSED TRANSFORMER USED IN SOLAR POWER PLANT BASED ON GENETIC ALGORITHM AND COMPUTATIONAL FLUID DYNAMICS", THERMAL SCIENCE, Vol. 27, No. 5B, pp. 4077-4089.
CASE STUDY ON THERMAL OPTIMIZATION OF OIL IMMERSED TRANSFORMER USED IN SOLAR POWER PLANT BASED ON GENETIC ALGORITHM AND COMPUTATIONAL FLUID DYNAMICS
(2023) Yükselen, Emir; İskender, İres; 133746
Transformers are one of the most capital investments in the solar power generation. Their safe and stable operations in the electrical networks are important. The main failure factor of transformers is the high temperature generated by the losses during operation, which increases the probability of insulation damage that significantly affects the useful life of transformer. Considering the importance of oil temperature and its effects on the life of the transformer, a numerical method is developed in this paper to optimize the cooling system of the transformer. In this regard, genetic algorithm is used as an optimization method to minimize the total cost of the cooling system while maintaining the required thermal conditions of the transformer. A comprehensive parametric study is carried out among the effective cooling geometry parameters using 3-D electromagnetic and thermal models of the photovoltaic transformer to evaluate and analyze the temperature distribution. The accuracy and feasibility of the proposed method is established by comparing the numerical results with those obtained from the experimental test. The results of the proposed method are found to be in a good agreement with the experimental and simulation results.
Citation Count: Kavak, H.; İskender, İ.; Jahi, A. (2018). "Conducted Emi Performance Comparison Of Si And Sic Mosfets In A Ccm Boost Pfc Converter For MIL-STD-461F CE102", Poznan University Of Technology Academic Journals.
Conducted Emi Performance Comparison Of Si And Sic Mosfets In A Ccm Boost Pfc Converter For MIL-STD-461F CE102
(2018) Kavak, Halil; İskender, İres; Jahi, Amir; 133746
This paper presents a comparison of conducted EMI performance of Si and SiC MOSFETs in a CCM PFC boost converter that is designed to meet CE102 of MIL-STD461F. EMI performance comparison is based on MOSFET of the PFC converter. That is, the power switch of the converter is the only parameter that is changed during tests. The boost diode is kept the same during the tests and the type of the boost diode is SiC. The paper shows the CE102 test results of Si and SiC MOSFETs without an EMI filter at the input side of CCM PFC boost converter.
Citation Count: Telli, Simay; İskender, İres; Yükselen, Emir (2024). "Cost optimization of oil type distribution transformer using multi-objective genetic algorithm", Journal of Energy Systems, Vol. 8, No. 1, pp. 53-62.
Cost optimization of oil type distribution transformer using multi-objective genetic algorithm
(2024) Telli, Simay; İskender, İres; Yükselen, Emir; 133746
The demand for electrical energy is increasing day by day with the development of technology in the world. Distributing electric energy to all regions that need energy is a principal issue, and this necessitates the use of transformers to convert the voltage to the desired level. Accordingly, the use of transformers, one of the electrical devices converting AC voltage level at a defined frequency has grown significantly. In this study, design parameters of a 25 kVA, 33/0.4 kV, Yzn11, oil-type distribution transformer are optimized using the Multi-Objective Genetic Algorithm (MOGA) technique by decreasing the weight of the significant materials and manufacturing cost. Electromagnetic analysis of the transformer is performed with ANSYS Maxwell based on the design results obtained from the optimization study for validation of the method. The experimental design parameters are also compared with the optimization results. It is observed that optimum results are achieved by using the proposed approach.
Citation Count: Baykal, Y. (2016). Cross-beam scintillations in underwater medium. Optical Engineering, 55(11). http://dx.doi.org/10.1117/1.OE.55.11.111612
Cross-beam scintillations in underwater medium
(Spie-Soc Photo-Optical Instrumentation Engineers, 2016) Baykal, Yahya; 7812
The fluctuation in the intensity, which is quantified by the scintillation index, is evaluated for cross beams when such beams propagate in an underwater medium experiencing turbulence. The variations in the scintillation index are investigated against the changes in the size of the cross beams, the ratio of temperature to salinity contributions to the refractive index spectrum, the rate of dissipation of mean-squared temperature, and the rate of dissipation of kinetic energy per unit mass of fluid.
Citation Count: Akagunduz, Erdem; Bors, A. G.; Evans, Karla K. (2020). "Defining Image Memorability Using the Visual Memory Schema", IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 42, No. 9, pp. 2165-2178.
Defining Image Memorability Using the Visual Memory Schema
(2020) Akagündüz, Erdem; Bors, Adrian G.; Evans, Karla K.; 233834
Memorability of an image is a characteristic determined by the human observers' ability to remember images they have seen. Yet recent work on image memorability defines it as an intrinsic property that can be obtained independent of the observer. The current study aims to enhance our understanding and prediction of image memorability, improving upon existing approaches by incorporating the properties of cumulative human annotations. We propose a new concept called the Visual Memory Schema (VMS) referring to an organization of image components human observers share when encoding and recognizing images. The concept of VMS is operationalised by asking human observers to define memorable regions of images they were asked to remember during an episodic memory test. We then statistically assess the consistency of VMSs across observers for either correctly or incorrectly recognised images. The associations of the VMSs with eye fixations and saliency are analysed separately as well. Lastly, we adapt various deep learning architectures for the reconstruction and prediction of memorable regions in images and analyse the results when using transfer learning at the outputs of different convolutional network layers.
Citation Count: Kurt, Erol; Hatem,Sude. (2023). "Design and Implementation of a MHz Frequency Transformer with a Ferromagnetic Fluid Core", Sustainability (Switzerland), Vol.15, No.1.
Design and Implementation of a MHz Frequency Transformer with a Ferromagnetic Fluid Core
(2023) Kurt, Erol; Hatem, Sude; 391090
Design and optimization of a magnetic fluid cored transformer are studied for high frequency applications. An easy and cheap fluid core is designed and used to decrease the eddy current and loses, thereby low conducting and paramagnetic features are added. The core exhibits both fluid and solid characteristics exerting high frequency modes in the fluid and low current due to the iron powder inside. The finite element analysis simulations are performed via COMSOL Multi-physics package for different mass fractions of iron powder. The maximum peak-to-peak voltage and power are found as 526 mV and 188.8 mW at 12 MHz from the simulations. 3D patterns prove that the magnetic flux and magnetization exhibit turbulence in the core, thereby localized magnetic values indicate an arbitrary attitude for various frequencies. Optimum mass fraction is found as 0.7, which is parallel with experimental results. The transformer operates between 11 MHz and 13.5 MHz optimally.
Citation Count: Haliloglu, Ali Burhan; İskender, İres. (2022). "Design Studies of VSC HVDC Converter According to AC Voltage Tests", Energies, Vol.15, No.20.
Design Studies of VSC HVDC Converter According to AC Voltage Tests
(2022) Haliloglu, Ali Burhan; İskender, İres; 133746
Since high-voltage direct current (HVDC) systems are very expensive and operationally critical, these systems must be tested before they are put into service. Insulation and performance tests are the two main subjects of these tests. AC voltage tests, as part of the insulation tests, should be performed after system installation is complete and before commissioning. However, in this study, the objective was to perform these tests during the prototype phase of VSC HVDC. Unlike other studies, this study attempted to use COMSOL Multiphysics to determine in advance the problems that may occur in the real system. In this regard, the busbars connecting the submodules of the VSC HVDC system were first modeled in 3D, and the tests to be performed were simulated using COMSOL Multiphysics software. During the simulation, the finite element method (FEM) was used to identify critical points that could cause partial discharge. To validate the simulation results, partial discharge tests on a real system were conducted, and the design changes made in response to each test result were explained. After the improvement actions, the targeted partial discharge values were achieved.
Citation Count: Preveze, Barbaros (2020). "Dynamic Optımızatıon of Image Brıgthness Level With Optimal Gamma Value Assessment (OGVA) Method", Afyon Kocatepe Üniversitesi Fen ve Mühendislik Bilimleri Dergisi, Vol. 20, No. 2, pp. 222-228.
Dynamic Optımızatıon of Image Brıgthness Level With Optimal Gamma Value Assessment (OGVA) Method
(2020) Preveze, Barbaros; 17573
In this study, the proposed Optimum Gamma Value Assignment (OGVA) method is intended to dynamically optimize the image intensity level in non-desired images due to undesired light levels. For this purpose, it is aimed to make the dark images which cannot be seen due to lack of light, while bright images are dynamically dimmed by using the optimum gamma correction value applied on the image momentarily. It has been shown that this novel method, which will only be implemented as software, without requiring any additional hardware, yields satisfying results even at different light levels.
Citation Count: Preveze, B. (2020). "Dynamic Optımızatıon of Image Brıgthness Level With Optimal Gamma Value Assessment (OGVA) Method", Afyon Kocatepe Üniversitesi Fen ve Mühendislik Bilimleri Dergisi, Vol.20, No.2, pp.222-228.
Dynamic Optımızatıon of Image Brıgthness Level With Optimal Gamma Value Assessment (OGVA) Method
(2020) Preveze, Barbaros; 17573
In this study, the proposed Optimum Gamma Value Assignment (OGVA) method is intended todynamically optimize the image intensity level in non-desired images due to undesired light levels. Forthis purpose, it is aimed to make the dark images which cannot be seen due to lack of light, while brightimages are dynamically dimmed by using the optimum gamma correction value applied on the imagemomentarily. It has been shown tha