Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Article Citation Count: Gökçe, Muhsin Caner...et al. (2024). "Multimode beam propagation through atmospheric turbulence", Journal of Quantitative Spectroscopy and Radiative Transfer, Vol. 314.Multimode beam propagation through atmospheric turbulence(2024) Gökçe, Muhsin Caner; Baykal, Yahya; Ata, Yalçın; Gerçekcioğlu, Hamza; 7812The investigation focuses on studying the propagation characteristics of multimode lasers in the turbulent amosphere. By employing the Huygens-Fresnel integral, we develop analytical formulations for various propagation parameters. These include the average intensity distribution, kurtosis parameter, beam spread, and the average transmittance of multimode beams in turbulent atmosphere. Our findings reveal that as the propagation distance or the structure constant of the atmosphere increases, i.e., turbulence becomes stronger, the kurtosis parameter and the beam spread increase. The multimode beam exhibits a Gaussian like intensity profile when the propagation distance is significantly increased or when the structure constant becomes sufficiently large. For the case of the Gaussian beam, the kurtosis parameter is found to be 3. The multimode beam's kurtosis parameter rises as the turbulence becomes stronger and eventually approaches 3. Raising the mode content leads to a rise in the average transmittance; however, it leads to a decline in the Kurtosis parameter and the beam spread.Article Citation Count: Gerçekcioğlu, Hamza; Baykal, Yahya (2024). "Depth dependence of oceanic turbulence optical power spectrum under any temperature and salinity concentration", Physica Scripta, Vol. 99, No. 4.Depth dependence of oceanic turbulence optical power spectrum under any temperature and salinity concentration(2024) Gerçekcioğlu, Hamza; Baykal, Yahya; 7812The Oceanic Turbulence Optical Power Spectrum (OTOPS) with depth variations is acquired under any temperature and salinity concentration. It is supposed that specific medium is the Atlantic Ocean at high latitude and the Pacific Ocean at high, mid and low latitudes. For the OTOPS model, a depth-varying functions that include low-latitude, high- and mid-latitude-summer and mid-latitude-winter salinity and temperature changes are found. With the help of the equations for the temperature and salinity changes, figures are obtained for the eddy diffusivity ratio depth of seawater and OTOPS model against the depth and κ at these media. In the ocean, downlink (uplink) is defined as the optical wireless communication link where the receiver (transmitter) is located at a deeper point than the transmitter (receiver), i.e., in the downlink, optical signal proceeds from a point close to ocean surface to deeper ocean and in the uplink, optical signal proceeds from deeper ocean to a point close to ocean surface. In this paper, the OTOPS model is investigated on how its properties change in the underwater environment in downlink and uplink. Different behavior of the OTOPS model is exhibited.Article 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; 133746The 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.Article Citation Count: Baykal, Yahya...et al. "Correlations of multimode optical incidences in a turbulent biological tissue", Journal of the Optical Society of America A: Optics and Image Science, and Vision, Vol. 40, No. 11, pp. 2045-2051.Correlations of multimode optical incidences in a turbulent biological tissue(2023) Baykal, Yahya; Gökçe, Muhsin Caner; Gerçekcioğlu, Hamza; Ata, Yalçın; 7812In a turbulent biological tissue, field correlations at the observation plane are found when a multimode optical incidence is used. For different multimode structures, variations of the multimode field correlations are evaluated against the biological tissue turbulence parameters, i.e., the strength coefficient of the refractive-index fluctuations, fractal dimension, characteristic length of heterogeneity, and the small length-scale factor. Using a chosen multimode content, for specific biological tissue types of liver parenchyma (mouse), intestinal epithelium (mouse), upper dermis (human), and deep dermis (mouse), field correlations are evaluated versus the strength coefficient of the refractive-index fluctuations and small length-scale factor. Again, with a chosen multimode content, behavior of the field correlations is studied against the strength coefficient of the refractive-index fluctuations for various diagonal lengths and the transverse coordinate at the observation plane. Finally, the field correlation versus the strength coefficient of the refractive-index fluctuations is reported for different single modes, which are special cases of multimode excitation. This topic is being reported in the literature for the first time, to our knowledge, and the presented results can be employed in many important biological tissue applications.Article 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; 133746Transformers 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.Article 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; 17740An 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.Conference Object Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet. Using wavelet transform self-similarity for effective multiple description video coding, 2015 10th International Conference on Information, Communications and Signal Processing (ICICS), 2016.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 Citation Count: Preveze, Barbaros (2011). "Yeni Rotalama Algoritmalarının 802.16j AĞI Etkin Çıktı Oranı Artırımına Düşük Araç Hızları Altındaki Etkileri", Uludağ Üniversitesi Mühendislik Fakültesi Dergisi, Vol.16, No.1, pp.127-145.Yeni Rotalama Algoritmalarının 802.16j AĞI Etkin Çıktı Oranı Artırımına Düşük Araç Hızları Altındaki Etkileri(2011) Preveze, Barbaros; 17573Çoklu 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.Article Citation Count: Ata, Yalçın; Gökçe, Muhsin Caner; Baykal, Y. (2022). "Underwater turbulence effect on optical imaging", Physica Scripta, Vol.97, No.5.Underwater turbulence effect on optical imaging(2022) Ata, Yalçın; Gökçe, Muhsin Caner; Baykal, YahyaModulation transfer function (MTF) of oceanic turbulence plays an essential role in the design and quality of underwater image sensing systems capturing optical signals. MTF gives clues about the characteristics of turbulence which can help image reconstruction where the image resolution can be increased in this way. In the paper, under the conditions of weak turbulence and Gaussian beam propagation, we derive the modulation transfer function for short-exposure and long-exposure images based on the recently developed turbulence spectrum model: Oceanic turbulence optical power spectrum (OTOPS). With the aid of the OTOPS model, the effect of measurable turbulence parameters, namely average temperature, average salinity concentration, and temperature-salinity gradient ratios, as well as imaging system parameters, namely receiver aperture radius and wavelength of the laser source on the MTF are reported. Obtained results indicate that MTF rapidly decreases with increasing relative spatial frequency and turbulence strength. Turbulence becomes stronger with the increase in the average temperature, average salinity concentration, energy dissipation rate, temperature-salinity gradient ratio and with the decrease in the temperature dissipation rate, wavelength.Article Citation Count: Şener, Göker (2022). "Ultra Geniş Bant Uygulamaları İçin Tasarlanmış Bir Düzlemsel Eliptik Tek Kutuplu Anten", Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi, Vol.9, No.16, pp.61-68.Ultra Geniş Bant Uygulamaları İçin Tasarlanmış Bir Düzlemsel Eliptik Tek Kutuplu Anten(2022) Şener, Göker; 17740Bu makalede 1-10 GHz ultra geniş bantta ışıma yapabilen bir düzlemsel eliptik tek kutuplu anten tasarlanmıştır. Yapısal olarak düzlemsel tek kutuplu antenler mikro şerit antenlerin kalınlığının arttırılarak toprak düzleminin ortadan kaldırılması ile elde edilir. Mikro şerit antenlerin kalınlığının artması ile tüm rezonans frekanslarında oluşan dalga kiplerinin frekans bandı da artmış olur. Böylece ultra geniş bantlı ışıma meydana gelir. Bununla birlikte tek kutuplu antenler, tüm bant boyunca her yönde aynı ışıma özelliği göstermezler. Genelde arzu edilen, tüm bant boyunca tek yönlü doğrusal polarizasyonda ve dik yönde yüksek kazanç verecek bir ışıma karakteristiğidir. Bu makalede bu özelliği sağlamak için farklı boyutta iki eliptik tek kutuplu anten, yansıtıcı bir toprak düzlemi üzerine yerleştirilmiştir. Bu tasarlanan anten bütün bant boyunca tek yönlü doğrusal polarizasyon ile dik yönde 1-10 GHz frekanslarında sırasıyla 4.38-3.22 dB kazanç sağlamaktadır. Elde edilen bu değerler literatürdeki diğer eliptik tek kutuplu antenlerle karşılaştırılmış ve tasarımın bant boyunca aynı ışıma karakteristiği ile 3.22 dB’nin üzerinde kazanç sağladığı gösterilmiştir. Önerilen bu anten, 2.4-5 GHz geniş bant WLAN sistemleri ve anten ölçümleri gibi ultra geniş bant uygulamalarında kullanılmaya uygundur.Article Citation Count: Gerçekçiıoğlu, Hamza; Baykal, Yahka Kemal. (2022). "Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of LIDAR", IEEE Journal of Selected Topics in Quantum Electronics, Vol.28, No.5.Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of LIDAR(2022) Gercekcioglu, Hamza; Baykal, Yahya Kemal; 7812Formulation of on-axis scintillation of laser beams is found in weak atmospheric turbulence for aerial vehicle in the use of light detection and ranging (LIDAR) systems by employing the Rytov method. The formulation derived for collimated Gaussian, plane and spherical beams is evaluated in vertical link involving up/down link. In this medium, the behavior of these beams in terms of deterioration is examined. In this context, the on-axis scintillation index values are plotted versus normalized target size parameter, target size, source size, propagation distance and zenith angle, and the results are obtained for LIDAR systems operating for aerial vehicle in vertical atmospheric link by using ground/space transceiver. The degradation is greater in operating with ground transceiver than in operating with space transceiver. Additionally, while the on-axis scintillation index is minimized in the smaller target size in use of ground transceiver than in use of space transceiver, that is, it can also be minimized in the larger target size in use of space transceiver. The values of source size and the normalized target size parameter minimizing the obtained scintillation index, are 1.2 cm, 10, and 6 cm and 5 for ground transceiver and space transceiver, respectively.Article Citation Count: Preveze, Barbaros;...et.al. (2022). "SDN-Driven Internet of Health Things: A Novel Adaptive Switching Technique for Hospital Healthcare Monitoring System", Wireless Communications and Mobile Computing, Vol.2022.SDN-Driven Internet of Health Things: A Novel Adaptive Switching Technique for Hospital Healthcare Monitoring System(2022) Preveze, Barbaros; Alkhayyat, Ahmed; Abedi, Firas; Jawad, Aqeel Mahmood; Abosinnee, Ali S.; 17573In the last decent, the number of Internet of Things (IoT) health-based paradigm reached to a huge number of users, services, and applications across different disciplines. Thus, hundreds of wireless devices seem to be distrusted over a limited or small area. To provide a more efficient network, the software-defined network (SDN) thought to be a good candidate to deal with these huge number of wireless users. In this work, after a novel SDN algorithm is proposed for the hospital environment, it is also designed and integrated into an Internet of Health Things (IoHT) paradigm. The novel algorithm called adaptive switching (AS) is proposed as a novel adaptive access strategy based on adaptively hoping among existing Go-Back-N and Selective Repeat techniques. Finally, the throughput performance of the proposed AS method is compared with the performances of traditional Go-Back-N and Selective Repeat ARQ methods using the developed MATLAB simulation. For this, an optimal Perror rate that the network should prefer to switch either from Go-Back-N to Selective Repeat or from Selective Repeat to Go-Back-N method to maximize the network throughput performance is determined. The evaluated results are also confirmed by theoretical calculation results using well-known Mathis throughput formula. It is observed from the simulation results that the best throughput performance can be evaluated, when AS switches to Go-Back-N if the Perror is less than 3.5% and it switches back to Selective Repeat when the Perror is greater than 3.5%. By this way, it is also observed that the throughput always has its best possible results for all Perror rates and up to 37.52% throughput improvement is provided by the use of novel proposed adaptive switching (AS) algorithm.Review Citation Count: Baykal, Yahya; Ata, Yalçın; Gökçe, Muhsin C.(2022). "Underwater turbulence, its effects on optical wireless communication and imaging: A review", Optics and Laser Technology, Vol.156.Underwater turbulence, its effects on optical wireless communication and imaging: A review(2022) Baykal, Yahya; Ata, Yalçın; Gökçe, Muhsin C.Theory of optical turbulence in underwater medium and the effects of underwater turbulence on various applications done in underwater or under ocean are reviewed. A detailed survey of underwater turbulence studies in literature is reported. Underwater physics covering salinity, temperature and dissipation rates, various power spectra such as Hill, Nikishov and Nikishov, Li, new form and the oceanic turbulence optical power spectrum (OTOPS) spectra are explained. Wave and phase structure functions, related coherence length, anisotropy, intensity, field correlations in underwater turbulence are elaborated. Scintillation indices of spherical, plane, Gaussian, and other types of optical beams are mentioned. Bit-error-rate (BER), signal-to-noise-ratio (SNR) performances of optical wireless communication systems operating in underwater, and the effects of modulation types of these systems on the performances are reported. Channel capacity of underwater optical wireless communication systems when the channel experiences log-normal, gamma-gamma, Weibull, and negative exponential statistics are reflected. Underwater imaging and the related modulation transfer function, underwater turbulence mitigation techniques in the form of aperture averaging, adaptive optics, receiver, transmitter and multiple-input, multiple-output (MIMO) spatial diversity techniques are revised.Article Citation Count: Sana, Farzin Asghari; Farhadnia, Farshad; Salmanogli, Ahmad. (2019). "Silicon-based core-shell nanoparticle's nanobiomedical characterisation", International Journal of Nanoparticles, Vol.11, No.4, pp.283-293.Silicon-based core-shell nanoparticle's nanobiomedical characterisation(2019) Sana, Farzin Asghari; Farhadnia, Farshad; Salmanogli, AhmadUsing functionalised nanoparticles in nanobiomedical applications cause to raise questions about unintentional effect of such powerful agents on the human body. In other words, the study of nanoparticle toxicity can be considered as a curtail key for the biological applications. In this study, the core/shell nanoparticles such as Si/Au and SiO2/Au were synthesised and functionalised with some biological elements. For satisfying some medical standards and biomedical critical test conditions, a few in-vitro assays as cytotoxicity and haemolysis should be done. For this reason, cytotoxicity and haemolytic effects of the functionalised nanoparticles such as Si/Au/biotin and SiO2/Au/biotin and their derivatives were evaluated on Hep-G2 cells and humane red blood samples. It is shown that cytotoxicity and haemolysis effects of the all synthesised nanoparticles are concentration-dependent. Also, the results are shown that most cytotoxicity and haemolytic effects are observed for Si/Au and SiO2/Au without biotin groups after 48 hours and 30 minutes, respectively.Article Citation Count: Yükselen, Emir; Iskender, Ires (2022). "Unbalanced Operation in Transformers Used in PV Plants", International Journal of Renewable Energy Research, Vol.12, No.4, pp.2200-2205.Unbalanced Operation in Transformers Used in PV Plants(2022) Yükselen, Emir; Iskender, Ires; 133746Renewable energy has become the most preferred energy sources today due to its environmental and economic advantages. One of the renewable energies is solar energy, in which Photovoltaic (PV) cells are used to convert solar energy into electrical energy. In this respect, Solar Power Plant (SPP) is one of the popular renewable energy sources and the integration of such power sources into electricity grids has been increasing in recent years. Transformers are one of the largest capital investments in solar power generation and the way they work is different from transformers used in a substation. Therefore, failure of transformers has significant economic effects on electrical networks. The PV type transformer is powered by the inverter and needs to be customized to work with every system. Consequently, the safe operation and reliability of this type of transformer is critical to the sustainability of the electrical grid. Consequently, identifying the probability of failure as a preventative action for grid protection is critical and should be addressed to improve electrical system reliability. The main purpose of this study is to analyze the effects of the unbalanced operation of the inverter on the performance of the special type transformer used in the PV plant and to show how the inverter operation can affect the operation of the transformer.Article Citation Count: Ataş, Muhammet Taha; Güler, Hasan. (2022). "Real-Time Encryption/Decryption Algorithm with A Fractional Chaotic System of Various Data: Image, Speech, and Text", International Journal of Applied and Computational Mathematics, Vol.8, No.4.Real-Time Encryption/Decryption Algorithm with A Fractional Chaotic System of Various Data: Image, Speech, and Text(2022) Ataş, Muhammet Taha; Güler, Hasan; 366611Nowadays, a fractional-order chaotic system is commonly used in digital cryptosystem applications due to its precision to initial conditions and their unpredictability. This paper proposed an encryption-decryption of image, sound, and text data based on fractional-order Rössler chaotic system. Firstly Master–Slave synchronization of fractional-order Rössler chaotic system designed with Labview to able to realize the encryption-decryption process. Fractional order Rössler system Master–Slave equations created to able to perform synchronization and then fractional-order Rössler chaotic system based Master–Slave design used in the image, sound, and text encryption-decryption separately. Image, sound, and text encryption-decryption process successfully realized. Original encrypted and decrypted data compared with each other respectively.Article Citation Count: Tülay, Gencer; Karakaya, Mehmet, İskender, İres. (2021). "Pi Control Of A Novel Power Converter By Using Heuristic Optimization", International Journal on Technical and Physical Problems of Engineering, Vol.13, No.4, pp.219-224.Pi Control Of A Novel Power Converter By Using Heuristic Optimization(2021) Tülay, Gencer; Karakaya, Mehmet; İskender, İres; 133746In this study, obtaining the PI control coefficients of a power converter using the heuristic optimization method was investigated. A new converter has been designed to increase the lifetime of the energy storage unit of a satellite power subsystem. It is also possible to increase the active duty life of the satellite by using the aforementioned converter according to the increased battery life.Article Citation Count: Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Mushin Caner. (2022). "Performance of a free-space optical communication system employing receive diversity techniques in anisotropic atmospheric non-Kolmogorov turbulence", Journal of the Optical Society of America B: Optical Physics, Vol.39, No.8, pp.2100-2108.Performance of a free-space optical communication system employing receive diversity techniques in anisotropic atmospheric non-Kolmogorov turbulence(2022) Ata, Yalçın; Baykal, Yahya Kemal; Gökçe, Muhsin Caner; 7812In this paper, bit error rate (BER) performance of a free-space optical communication (FSOC) system operating in anisotropic non-Kolmogorov weak turbulence is investigated together with the spatial diversity techniques. The spatial diversity techniques are implemented as maximum ratio combining (MRC), equal gain combining (EGC), and selection combining (SC) and applied to the receiver. The propagating beam is the Gaussian beam wave, and the modulation scheme is binary phase-shift keying (BPSK). Results are obtained for various parameters such as the anisotropy factor, non-Kolmogorov power law exponent, photodetector responsivity, equivalent load resistor, electronic bandwidth, Gaussian beam radius, wavelength, propagation distance, and turbulence structure constant. It is found that the spatial diversity technique used at the receiver causes significant improvement in the performance of an FSOC system under the conditions of anisotropic non-Kolmogorov atmospheric turbulence. It is also observed that BER performance improves as the atmospheric turbulence becomes more anisotropic. Among the spatial diversity techniques, SC is inferior to EGC and EGC is inferior to MRC in terms of BER performance.Article Citation Count: Gökçe, Muhsin Caner; Yalçın, Ata; Baykal, Yahya Kemal. (2022). "Performance evaluation of aeronautical uplink/downlink free-space optical communication system with adaptive optics over gamma-gamma turbulence channel", Journal of Optics (United Kingdom), Vol.24, No.10.Performance evaluation of aeronautical uplink/downlink free-space optical communication system with adaptive optics over gamma-gamma turbulence channel(2022) Gökçe, Muhsin Caner; Ata, Yalçın; Baykal, Yahya Kemal; 7812In this study, we analyze the effect of adaptive optics corrections on the performance of an aeronautical free-space optical (FSO) system with bidirectional slant path uplink and downlink communication channels. The aeronautical FSO communication (FSOC) system operates in a gamma-gamma atmospheric turbulence channel and employs adaptive optics corrections for the distorted wave front of the Gaussian beam wave. The modulation type of the aeronautical FSOC system is chosen to be M-ary phase-shift-keying-subcarrier intensity modulation and the type of the employed photodetector is positive-intrinsic-negative. In analysis, the effect of system parameters such as zenith angle, the height of transmitter/receiver on the ground, M-ary level, filter bandwidth, link distance, and the adaptive optics correction modes on bit-error-rate are demonstrated.Article Citation Count: Çİfdalöz, Oğuzhan. (2022). "Navigation Under GNSS Denied Environments: Zero Velocity and Zero Turning Update", European Journal of Science and Technology, No.38, pp.360-369.Navigation Under GNSS Denied Environments: Zero Velocity and Zero Turning Update(2022) Çifdalöz, OğuzhanThe objective of this paper is to present a method which bounds the error of an inertial navigation system (INS) when Global Navigation Satellite System (GNSS) is not available. Inertial navigation systems utilize gyroscopes and accelerometers, and calculate velocity, position and attitude, essentially by integrating the measurements obtained from these sensors. Due to the nature of integration, INS are notoriously prone to sensor biases and drifts. Typically, GNSS is used to correct the navigation system errors caused by the inertial sensor measurements. However, in GNSS degraded or denied environments, alternative solutions are required. If the platform on which an INS is mounted is known or estimated to be stationary, zero-velocity update (ZUPT) and/or zero turning update (ZTUPT) algorithms can be applied in order to bound the navigation system errors. Under certain assumptions, ZUPT based algorithms can be applied when the platform is not stationary. If a vehicle’s motion is constrained by the design of its kinematics, i.e. if it can be assumed that the vehicle cannot move or rotate along one or more of its body axes, ZUPT assisted Kalman estimators can be used to correct the errors along those axes. Potentially, ZUPT based estimation algorithms can also be utilized when a sufficiently high fidelity vehicle model is available. In this paper, the implementation of zero-velocity update (ZUPT) and zero turning update (ZTUPT) algorithms are analyzed for the purpose of estimating and bounding inertial navigation errors. The basic principle in navigation is based on combining the data obtained from the sensors onboard and the inertial navigation system through an Extended Kalman filter. Although this process requires additional software components, it potentially offers increased system accuracy and reliability. Incorporating the kinematics of the vehicle, along with a ZUPT and/or ZTUPT algorithm, provides additional data to feed into the Kalman filter and increases the efficiency of error estimation. Estimated error is then fed back into the INS algorithm in order to counteract the sources of error.
