Elektronik Ve Otomasyon Bölümü
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Öğe Annealing-induced modifications on structural, surface chemical bonding, and electrical characteristics of p-NiO/n-TiO2 heterostructure(Springer, 2023) Kaya, Şenol; Soykan, Uğur; Sunkar, Mustafa; Karaboğa, Seda; Doğan, Muhsin Uğur; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirThe influences of annealing temperatures on the electrical characteristics of a p- NiO/n-TiO2 heterojunction diode were thoroughly investigated, taking into account changes in microstructure, morphology, and surface chemistry of the p-NiO/n-TiO2 films, which were deposited on an insulating SiO2/ Si layer. During different annealing processes, considerable stress variations were observed in the p-NiO/n-TiO2 films due to the crystalline evolution of p-NiO and n-TiO2. Notably, the crystallization of the TiO2 layer, which serves as the intermediary between the back contact materials and NiO, led to the evident formation of grain structures. As the annealing temperature increased, the surface roughness also grew from 5.4 to 8.7 nm. At an annealing temperature of 500 degrees C, the formation of a parasitic NiTiOx phase was observed, particularly at the interface between NiO and TiO2. Conversely, the study also revealed that annealing temperature played a significant role in the rectifying behavior, barrier potential, and ideality factor of the diode. Among the various annealing processes, the most favorable results were achieved after annealing at 400 degrees C. At this temperature, the diode demonstrated the lowest ideality factor of 1.89, accompanied by superior rectifying behavior and a barrier potential of 0.70 eV. The findings clearly indicate that any alterations in the surface chemistry and microstructure of the film directly impact the diode's characteristics. Thus, optimizing the annealing temperature becomes crucial for enhancing the performance of the p-NiO/n-TiO2 heterojunction diode.Öğe Evolution of basic features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy ceramic systems with NiO impurity(Springer, 2023) Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirIn the current work, we have investigated the role of different nickel oxide (NiO)(x) impurity addition levels (0 & LE; x & LE; 1.2) on the fundamental crystallographic, morphological, electrical, magnetic, critical current density, and superconducting features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy (Bi-2223) by the temperature-dependent electrical resistivities (& rho;-T), X-ray diffraction data (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and magnetic hysteresis (M-H) measurements for the first time. The NiO-added Bi-2223 ceramics have been produced by the standard solid-state reaction method at 840 & DEG;C for 36 h in the air atmospheric conditions. EDX investigations have demonstrated that there appear no extra contamination and additional phases for any anionic or cation-including phases. Besides, the Ni impurity concentration has been observed to increase systematically depending on the impurity amount. Thus, the NiO impurities have been added to the ceramic matrix as requested. Similar findings have been confirmed by the XRD examinations. The experimental results have pointed out the multiple substitution reaction of Ni-sites with the Bi-sites, Ca-sites, and Cu-sites in the Bi-2223 system. Moreover, the experimental results have shown that all the fundamental features are strongly dependent upon the NiO addition level due to the variation of Cu-O-2 interlayer bonding forces, grain alignment distributions, mobile carrier concentrations in the in-plane Cu-O-2 layer x(2)-y(2) bands, and coupling probabilities between the adjacent layers in the crystal structure. Similarly, the induction of new impurity phase formations, grain boundaries, modulation of Bi-O double layers, spin fluctuations, inhomogeneities, structural defects, and non-recoverable structural problems have also triggered the decrease in the main characteristic quantities. On this basis, the microstructural morphology and related crystallographic features have been noted to degrade with the impurity. Furthermore, the presence of NiO impurity has resulted in a decrement in the flux-pinning centers due to the increase in the lower resistance regions against the flux drifts in the bulk crystal system. All in all, the addition of NiO impurity in the Bi-2223 ceramic matrix is not a good idea for the improvement in the fundamental features of the Bi-2223 superconducting structure.Öğe Evolution of operable slip systems, lattice strain fields and morphological view of Bi-2223 ceramic system with optimum NiO addition(Elsevier, 2023) Mercan, Ali; Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Erdem, Ümit; Yıldırım, Gürcan; Terzioğlu, CabirThe current work extensively reveals the influence of different nickel oxide (NiO) impurity addition levels on the morphological, microstructural, key mechanical performance, and mechanical characteristic properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Oy (Bi-2223) ceramics using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Vickers micro-indentation (Hv) hardness measurements. It was observed that the addition of NiO impurity in the Bi-2223 crystal structure affected seriously the fundamental characteristic features. In the case of the optimum NiO concentration level of x = 0.1, the Bi-2223 materials exhibited the best crystallinity quality and coupling strengths between the adjacent layers, the most uniform surface view, and the densest, and the smoothest crystal structure. Similarly, the compound was noted to possess the hardest, highest mechanical strength, durable tetragonal phase, resistance toward failure by fatigue, and elastic recovery properties. Besides, it was observed that the characteristic Bi-2223 superconducting phase fraction and stabilization of the tetragonal crystal system reached the maximum level for the optimum concentration. Moreover, optimum NiO particles brought about a considerable increase in the number of operable slip systems, surface residual compressive force regions, and lattice strain fields. Correspondingly, the mobility of defects was blocked significantly depending on the preference of defects through transcrystalline regions. Additionally, optimum addition strengthened the typical indentation size effect due to the improvement of the recovery mechanism. In this regard, the NiO-added sample exhibited the least response to the applied loads. Thus, the Bi-2223 sample with the optimum NiO concentration was found to present the highest hardness parameter of 0.496 GPa, greatest elastic deformation value of 16.493 GPa, largest stiffness value of 1.044 MN/m, and smallest contact depth of 5.849 mu m. On the other hand, after the optimum concentration level of x = 0.1, there appeared serious increase in problems including internal defects, impurity residues, microscopic structural problems, and connection problems between the grains. All experimental findings were theoretically supported by semi-empirical mechanical methods. To sum up, the addition of NiO particles was noticed to increase the potential application areas of Bi-2223 ceramicÖğe Improvement in deformation degree of Zr surface-layered Bi-2223 ceramics by diffusion annealing temperature(Elsevier Sci LTD, 2023) Mercan, Ali; Terzioğlu, Rıfkı; Doğan, Muhsin Uğur; Kaya, Şenol; Erdem, Ümit; Yıldırım, Gürcan; Terzioğlu, Cabir; Varilci, AhmetThis study investigated the effects of different annealing temperatures (650 degrees C <= T <= 840 degrees C) on the surface morphological and mechanical performance properties of Zr surface-layered Bi-2223 materials with scanning electron microscopy (SEM) images, Vickers microhardness (Hv) measurements, and semi-empirical mechanical approaches. It was observed that the ceramic compound exposed to 650 degrees C annealing temperature exhibited the superior performance features due to the enhancement in the deformation degree. This is because the Zr ions behaved as the nucleation centers to prevent the propagations of cracks and dislocations throughout the main matrix depending on the decrease in the degree of granularity and distributions of crystal structure problems over a wider area. Similarly, the SEM pictures indicated that the diffusion mechanism increased the random distributions of the thinner plate-like granular structures (serving as nucleation centers), leading the decrease in the coupling problems between the grains. Among the materials, the highest surface densification was observed for the compound exposed to 650 degrees C. Namely, surface morphological analysis showed a strong correlation be-tween microstructure and mechanical performances. Further, the zirconium ions were found to decrease in the non-recoverable stress concentration sites, crack-initiating defects, and dislocations in the ceramic system. Accordingly, the sensitivity to the applied test load was noted to decrease dramatically. Shortly, crack growth size and velocity were observed to be more easily under control. Correspondingly, the Zr ions delayed consid-erably the beginning points of saturation limit (load-independent) regions for the bulk Bi-2223 superconducting materials. Additionally, the Zr ions led to the change in the mechanical characteristic behavior from typical indentation size effect to reverse indentation size effect. Lastly, the microindentation hardness measurements were semi-empirically analyzed by the different models. According to the comparison, Hays-Kendall mechanical model was noted to provide the closest parameters to the load-independent microhardness results.Öğe Refinement of some basic features of Zr surface-layered Bi-2223 superconductor with diffusion annealing temperature(Springer, 2022) Orhan, Emre; Kara, Emre; Kaya, Şenol; Doğan, Muhsin Uğur; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirThis study aims to investigate the influences of diffusion annealing temperatures on structural, morphological, electrical, and superconducting features of Zr surface-layered Bi-2223 ceramics. The present study also covers an in-depth understanding of correlations between disorders and transition temperatures. The Zr diffusion is carried out via an annealing process between 650 and 840 degrees C. The observed results depict that the Zr ions can easily diffuse into the deeper level of Bi-ceramics and possible Zr/Bi substitution has occurred due to the driving force of high thermal energy. Besides, it is found that the Zr diffusion improves the general crystallinity quantities of Bi-2223 ceramic up to 800 degrees C annealing temperature. In addition, better intergranular couplings with a smoother plate-like structure are extensively observed in surface morphology for the samples annealed at 800 degrees C. Significant refinements of both basic electrical resistivity, hole carrier densities, and critical temperatures with narrow transitions are also obtained for the Zr surface-layered Bi-2223 ceramics after the 800 degrees C annealing process. The obtained improvements in critical fundamental features can be attributed to the optimum pairing mechanism, best crystal structure quality, ideal Cu-O-2 interlayer coupling strengths, and enhanced interaction between adjacent superconductive layers. Besides, the first-order derivative of electrical resistivity versus temperature graphs indicates that the best annealing temperature enables to triggers to stabilize the superconductivity in the homogeneous regions. It can be concluded that the Zr impurity diffusion at 800 degrees C is promising for the improvement in the basic features of Bi-2223 superconducting systems for future applications in superconductor technology.Öğe Classification of smart grid stability prediction using cascade machine learning methods and the internet of things in smart grid(Springer London Ltd., 2023) Önder, Mithat; Doğan, Muhsin Uğur; Polat, KemalIn a smart grid, the main goals are to provide grid stability, improve power system performance and security, and reduce operations, system maintenance, and planning costs. The prediction stability of smart grid (SG) systems is essential in terms of power loss minimization and the importance of adequate energy policies. SG systems must accurately predict the energy demand and ensure the right amount of energy is available at the right time. If the prediction is inaccurate, it can lead to costly energy production or usage errors and create considerable inefficiencies in the power grid. Due to this, this manuscript offers five different cascade methods to detect the stability of SG systems. Detecting the stability of SG systems enables the grid to respond quickly to changes in demand and supply, improves system reliability, reduces power outages, and increases the overall efficiency of the grid. The present work proposed five different cascade methods with pre-processing, training and testing division, and the classification stages of the classification procedure for estimating SG stability. In the first pre-processing stage, the SG dataset is pre-proceeded with the feature selection (Relief, Fast Correlation-Based Filter (FCBF), and supervised attribute filter). The resampling (the bootstrapping), the Fuzzy C-Means Clustering-Based Feature Weighting (FCMFW), the resampling then feature selection (supervised attribute filter), and the feature selection (supervised attribute filter), then FCMFW. In the second stage, the training and testing division stage, the SG dataset was separated into three test and training data methods before the classification algorithm: The 5 Fold Cross Validation (FVC), 10 FVC, and hold-out (50-50%). In the third stage, the classification stage, five different classification algorithms, including Naive Kernel Bayes, Linear Support Vector Machine (SVM), Weighted K-Nearest Neighbors, Begged Trees, and Narrow Neural Network classifying algorithms, are used to classify the SG dataset. The simulation results of this study demonstrated that the suggested cascade ML system had achieved significant accuracy in predicting SG stability. The best cascade method is the feature selection (supervised attribute filter) + FCMFW + 10 FCV and then performing the bagged trees algorithm; thus, the new approach affords an accuracy of 99.9%. Furthermore, due to the rapid growth of ML techniques, sensors, and smart meters technologies, with Machine to Machine communication via the internet of things (IoT), the real-time identification process is made practical with higher accuracy. For this reason, our future research will focus on an IoT-based SG system, an E-stability determination system. Thanks to the proposed cascade method, the SG dataset can be classified easily, quickly, and reliably. E-stability determination systems can help to fast detect, predict, and respond, which is an important application of IoT on the grid systems.Öğe Genetic PI based model and path tracking control of four traction electrical vehicle(Springer, 2020) Doğan, Muhsin Uğur; Güvenç, Uğur; Elmas, ÇetinModeling and control of four-wheel electric vehicles are difficult due to their dynamic parameters and variable road conditions. In this paper, a robust and adaptive electric vehicle model and position control that can be adapted to state variables using a dynamic lateral and longitudinal model of a four-wheel electric vehicle have been proposed. The longitudinal and lateral forces have been modeled according to Newton's second law, depending on the parameters such as the vehicle's size, width, height, weight and slope angle by using dynamic equations of the vehicle. In this paper, a permanent magnet synchronous hub motor has been used for each wheel of the electric vehicle. The magic formula wheel model has been used to determine the relationship between the slip and the friction of the designed vehicle. Using the slip system, the relationship between the speed of the electric vehicle itself and the wheel speeds have been defined. The proportional controller at the position loop and proportional + integral controller at the speed loop of the designed system have been used. In the path tracking control system, position controls have been made in the X and Y coordinate planes. A P position controller and a PI speed controller have been used for each plane. Thus, there are 6 controller coefficients in total. Because of the complicated structure of the system, it is difficult to determine the most suitable controller coefficients by analytical methods. Therefore, the genetic algorithm which is one of the heuristic algorithms has been used in determining these coefficients. Simulation studies have been conducted with a different path and position references to see the effectiveness of the proposed electric vehicle model and position control. The obtained results show that the proposed model and control system are robust, effective and reliable.Öğe Efficient calculation of boys integrals(Academic Journals, 2010) Kara, Mehmet; Nalçacı, Ayşe; Özdoğan, TelhatAn efficient procedure has been presented for the calculation of Boys integrals by dividing the integral region [0, 1] into several parts. The obtained formula includes factorials, exponentials and a well known auxiliary function that converges very well. A computer program has been constructed in Maple symbolic programming language for comparing our results with literature. It is seen that the computational results of the presented algorithm agree well with the numerical results obtained by direct integration with Maple and results in the available literature.Öğe An analytical expression for arbitrary derivatives of Gaussian functions exp(ax(2))(Academic Journals, 2009) Kara, MehmetIn this study, an analytical expression for the arbitrary derivatives of Gaussian function e(ax2) is developed. Using this analytical expression developed within Rodrigues representation, an alternative expression is presented for the Hermite functions. With the help of the expression presented here the Hermite functions can easily be estimated.Öğe Elektrikli bir aracın sürme sisteminin denetimi(2019) Doğan, Muhsin Uğur; Güvenç, Uğur; Elmas, ÇetinBu çalışmada elektrikli araçlarda kullanılan Sürekli Mıknatıslı Senkron Hub (SM-HUB) motorların hız kontrolü gerçekleştirilmiştir. SM-HUB motorlar yapısı itibariyle Fırçasız doğru akım motorlara (FDAM) benzerlik gösterse de rotor stator yapıları farklıdır. Klasik FDAM’larda rotor içerde iken bu tip motorlarda rotor dıştadır. Bu nedenle bu tip motorların pozisyon ve hız kontrollerinde alan etkili pozisyon algılayıcıları ile gerçekleştirilmiştir. Yükleme sistemi kayış ile SM-HUB motorların birbirine bağlanması ile yapılmıştır. Bu tip sistem doğrusal olmayan etkiye sahiptir. Sistemin uygulama sonuçlarının test edilmesi için TMS320F2812 sayısal işaret işlemci ile denetlenen bir SM-HUB motorun sürücüsü tasarlanarak gerçekleştirilmiştir. Bu sürücü gerçek zamanlı olarak çalıştırılmış, farklı hız ve yük koşullarında istenen performansı sağladığı görülmüştür.
