Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Article Citation - Scopus: 5Three-Phase Buck Type Pfc Rectifier for Electrical Vehicle Battery Charger(International Organization on 'Technical and Physical Problems of Engineering', 2019) Demirkutlu, E.; İskender, İres; Iskender, I.; Elektrik-Elektronik MühendisliğiThree-phase AC/DC buck-type power factor correction (PFC) rectifier is presented in this paper. State of the art three-phase AC/DC rectifiers and improvements of the rectifier topologies are researched in this study. The SWISS Rectifier is implemented for Electrical Vehicle (EV) battery charger with 220 VLN-rmsS / 50 Hz three-phase input. The SWISS Rectifier for EV charger application is implemented by means of simulations. Depending upon the battery pack needs, 48 VDC output voltage is examined under both steady-state and dynamic load change conditions. © 2019, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Conference Object Citation - WoS: 5Citation - Scopus: 33A New Narrow Band Dual-Mode Microstrip Slotted Patch Bandpass Filter Design Based on Fractal Geometry(Ieee, 2012) Eyyuboğlu, Halil Tanyer; Mezaal, Yaqeen S.; Eyyuboglu, Halil Tanyer; Elektronik ve Haberleşme MühendisliğiA 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.Conference Object Citation - WoS: 2Flat-Topped Field Correlations in Extremely Strong Turbulence(Electromagnetics Acad, 2011) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik MühendisliğiIn extremely strong turbulent horizontal atmospheric optical links, field correlations of flat-topped Gaussian incidence are evaluated. Field correlations are represented versus the diagonal distance at the receiver plane, for variations in the number of beams forming the flat-topped structure, receiver points, source sizes, link lengths, structure constants and the wave-lengths. Our results in extremely strong turbulence are compared to their free space counterparts which only reflect the diffraction patterns at the receiver plane. The effects of the inner scale of turbulence on the field correlations in extremely strong turbulence are examined in detail and it is observed that the size of the inner scale in extremely strong turbulence can considerably influence the field correlations of flat-topped beams.Conference Object Effects of Type of Incidence on the Second and Fourth Order Moment Parameters Evaluated in Turbulent Atmosphere(2010) Baykal, Y.; Baykal, Yahya Kemal; Elektrik-Elektronik MühendisliğiUsing a general type incidence, the second and fourth order moments are formulated in atmospheric turbulence. Received field and intensity correlations are evaluated and the behaviour of these correlations are compared for different beam types. © 2010 OSA/FiO/LS.Conference Object Citation - Scopus: 2Scintillation Index of Partially Coherent Asymmetrical Multi Gaussian Beams in Extremely Strong Turbulence(2010) Baykal, Yahya Kemal; Öztan, M.A.; Baykal, Y.; Elektrik-Elektronik MühendisliğiIt is investigated whether partial coherent asymmetrical annular and flat-topped Gaussian beams provide advantage to decrease the scintillation noise effect when free space optics systems are used in long distance (longer than 5km) transmission links. Scintillation index of partially coherent asymmetrical multi Gaussian beam propagating in extremely strong turbulence is formulated and the scintillation indexes of asymmetrical annular and flat-topped Gaussian beams are calculated. Scintillation index variations are plotted against the source size and asymmetry ratio. It is determined that asymmetric beams have advantage over the symmetric beams in terms of the scintillation. It is found that the scintillation index decreases as the asymmetry ratio increases. It is also detected that by decreasing the coherence degree scintillation index of the propagating beam quickly goes to zero.Article A Novel Method To Solve 2nd Order Neumann Type Boundary Value Problems in Electrostatics(Applied Computational Electromagnetics Soc, 2017) Sener, Goker; Şener, Göker; Elektrik-Elektronik MühendisliğiIn 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.Article Citation - Scopus: 10Sensorless Speed Control of a Bldc Motor Using Improved Sliding Mode Observer Technique(International Organization on 'Technical and Physical Problems of Engineering', 2019) Topal, M.; İskender, İres; Iskender, I.; Genc, N.; Elektrik-Elektronik MühendisliğiThis paper proposes controlling the velocity of BLDC motor using sliding mode observer technique based on the estimation of back electromotive force (back EMF). There are many different sensorless control methods for BLDC motor, but in this paper one of them is examined in detail, comparing with the zero crossing points detection of back EMF and hall sensor control. The proposed method estimates the velocity and rotor position by measuring terminal voltages and currents. According to the rotor position, two inverter switches are energized to commutate the phases of BLDC motor. As comparing desired and real line currents, the commutation signals are acquired with hysteresis band. The simulation model of the suggested method is performed by using MATLAB Simulink environment and results have been simulated to interrogate the performance of the BLDC motor under a load change condition also with reference speed. © 2019, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Book Part How To Use Novel Methods for Improving the Performance of Wireless Cognitive Networks(CRC Press, 2016) Preveze, B.; Preveze, Barbaros; Elektrik-Elektronik MühendisliğiConference Object Using wavelet transform self-similarity for effective multiple description video coding(IEEE, 2016) Choupani, Roya; Wong, Stephan; Tolun, MehmetVideo streaming over unreliable networks requires preventive measures to avoid quality deterioration in the presence of packet losses. However, these measures result in redundancy in the transmitted data which is utilized to estimate the missing packets lost in the delivered portions. In this paper, we have used the self-similarity property if the discrete wavelet transform (DWT) to minimize the redundancy and improve the fidelity of the delivered video streams in presence of data loss. Our proposed method decomposes the video into multiple descriptions after applying the DWT. The descriptions are organized in such a way that when one of them is lost during transmission, it is estimated using the delivered portions by means of self-similarity between the DWT coefficients. In our experiments, we compare video reconstruction in the presence of data loss in one or two descriptions. Based on the experimental results, we have ascertained that our estimation method for missing coefficients by means of self-similarity is able to improve the video quality by 2.14dB and 7.26dB in case of one description and two descriptions, respectively. Moreover, our proposed method outperforms the state-of-the-art Forward Error Correction (FEC) method in case of higher bit-rates.Article Yeni Rotalama Algoritmalarının 802.16j AĞI Etkin Çıktı Oranı Artırımına Düşük Araç Hızları Altındaki Etkileri(2011) Preveze, BarbarosÇoklu ortam verileri içeren kablosuz gezgin ağlarda, yeni bilişsel yöntemler ve rotalama algoritmaları kullanılarak, sistemdeki rota ömrü, bağlantı kesinti miktarı, ortalama sekme sayısı ve paket kaybı gibi performans parametrelerinin iyileştirilmesiyle, IEEE 802.16j ağ yapısının etkin çıktı oranının arttırılması sağlanmıştır. Bu amaçla, mevcut IEEE 802.16j ağında kullanılmakta olan OFDMA ve TDMA erişim tekniklerine ek olarak kullanılmak üzere önerilen, En Çok Sıkışan İlk Erişir (MCAF), Spektrumsal Yardımlaşma (SA) ve Arabellek Yönetimi (BM) metotları ile 802.16j ağında etkin çıktı oranı artırımı için elde edilen simülasyon sonuçları, elde edilen teorik sonuçlarla ve literatürde elde edilmiş olan diğer çalışmaların sonuçlarıyla kıyaslanarak doğrulanmıştır. Bu çalışmada ayrıca, önerilen AEABR (Erişebilirlik Tabanlı Rotalama Alternatif Geliştirimi) ve ATAABR (Erişilebilirlik Tik Ortalamalı Erişebilirlik Tabanlı Rotalama) isimli yeni uzun ömürlü rotalama algoritmalarının, geliştirilen etkin çıktı oranı yükseltimi metotlarıyla birlikte uygulanmasıyla, diğer rotalama algoritmalarına göre, daha da yüksek etkin çıktı oranları elde ettikleri gösterilmiştir. Önerilen yeni metotlar, dağınık ağ yapılarının, gezgin düğümler tarafından, anlık plansız sinyalleşme ile yönetimine dayanarak çalışmaktadır.