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Öğe Three-dimensional modeling in medical image processing by using fractal geometry(Journal of Computers, 2017-09) Çalışkan, Abidin; Çevik, UlusMedical images are visualized by computer and processed to obtain larger, more organized, and three-dimensional (3D) images. Thus, significant images are provided. The processed data facilitate diagnosis and treatment in the medical fields. The 3D surface models of related areas are formed by using volumetric data obtained by employing medical imaging methods such as Magnetic Resonance (MR) and Computer Tomography (CT). The purpose of this study is to obtain 3D images from the two-dimensional CT slices. These slices are obtained from the existing medical imaging devices and transferred to the z space and a mesh structure is provided between them. In addition, we investigated 3D imaging techniques, visualization, basic data types, conversion into main graphical components, and imaging algorithms. At the phase of obtaining 3D images; the image processing methods such as surface and volume imaging techniques, smoothing, denoising, and segmentation were used. The complexity and efficiency properties of the imaging algorithms were investigated and image enhancement algorithms were utilized.Öğe Wet chemical methods for producing mixing crystalline phase ZrO 2 thin film(Elsevier, 2016-07) Pakma, Osman; Özdemir, Cengiz; Kariper, İshak Afşin; Özaydın, Cihat; Güllü, ÖmerThe aim of the study is to develop a more economical and easier method for obtaining ZrO 2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO 2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO 2 /p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.Öğe Photoelectric and photocapacitance characteristics of Au/pyrene/N-Si MIS structures(Journal of Non-Oxide Glasses, 2017-04-01) Güllü, Ömer; Pakma, Osman; Özaydın, Cihat; Arsel, İsmail; Turmuş, MesutThis paper presents in-depth analysis of the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of identically prepared Au/Pyrene(C16H10)/n-Si hybrid organic-oninorganic semiconductor photovoltaic cells (total 43 diodes). The barrier heights, ideality factors and reverse bias saturation currents of all devices were extracted from the electrical characteristics. The mean barrier height, mean ideality factor and mean saturation current from I-V measurements were calculated as 0.79 ± 0.01 eV, 1.40 ± 0.08 and (1.01 ± 0.46)x10-8 A, respectively. Also, the photoelectric (I-V) and photocapacitance (C-V and conductance (G)-voltage (V)) characteristics of the Au/Pyrene/n-Si device under 100 mW/cm2 light illumination were investigated. It has been seen that the light illumination increases strongly the current, capacitance and conductance values of the device due to electron-hole charge pair generation. The C-V and G-V characteristics under illumination have shown a non-monotonic dependence of capacitance on frequency giving rise to a peak. This is attributed to the existence of electrically active traps. The open circuit voltage and short circuit current of the Au/Pyrene/n-Si device were extracted as 80 mV and 30 µA, respectively.Öğe Synthesis and characterization of vanadium oxide thin films on different substrates(Springer Nature, 2017-04-11) Güllü, Ömer; Pakma, Osman; Özaydın, Cihat; Özden, Şadan; Kariper, İshak AfşinIn this study, the V8O15 derivative of vanadium oxide was produced on plain glass, indium tin oxide and silicon wafer substrate layers by taking advantage of wet chemical synthesis which is an easy and economical method. The structural properties of the produced films were examined by XRD and SEM analyses. Besides, Al/VOx/p-Si metal-oxide-semiconductor (MOS) structure was obtained by the same synthesis method. Doping densities of these MOS structures were calculated from frequency dependent capacitance–voltage measurements. It was determined that the interface states which were assigned with the help of these parameters vary according to frequency.Öğe PowSysGUI: A new educational software package for power system stability studies using MATLAB/Simulink(SAGE, 2017-10-01) Ekinci, Serdar; Demirören, Ayşen; Zeynelgil, Hatice LaleGraphical user interfaces have been progressively used in the classrooms to provide users of computer simulations with a friendly and visual approach to specify all input parameters with enhanced configuration flexibility. In this paper, an educational software package called PowSysGUI (Power System GUI), which runs on MATLAB and uses graphical user interfaces, has been developed for analysis and simulation of small to large size electric power systems. PowSysGUI is open-source software and anyone can see the inner structure of the program to figure out how to code a power engineering problem. It is designed as a simulation tool for researchers and educators, as it is simple to use and modify. PowSysGUI has algorithms for solving power flow, small signal stability analysis, and time-domain simulation. In the case studies, IEEE 16-machine 68-bus test system is given to show the features of the developed software tool. Moreover, classroom experience has shown that the developed software package helps in consolidating a better understanding of power system stability phenomena.Öğe A novel approach for SEMG signal classification with adaptive local binary pattern(Springer Nature, 2015-12-31) Ertuğrul, Ömer Faruk; Kaya, Yılmaz; Tekin, RamazanFeature extraction plays a major role in the pattern recognition process, and this paper presents a novel feature extraction approach, adaptive local binary pattern (aLBP). aLBP is built on the local binary pattern (LBP), which is an image processing method, and one-dimensional local binary pattern (1D-LBP). In LBP, each pixel is compared with its neighbors. Similarly, in 1D-LBP, each data in the raw is judged against its neighbors. 1D-LBP extracts feature based on local changes in the signal. Therefore, it has high a potential to be employed in medical purposes. Since, each action or abnormality, which is recorded in SEMG signals, has its own pattern, and via the 1D-LBP these (hidden) patterns may be detected. But, the positions of the neighbors in 1D-LBP are constant depending on the position of the data in the raw. Also, both LBP and 1D-LBP are very sensitive to noise. Therefore, its capacity in detecting hidden patterns is limited. To overcome these drawbacks, aLBP was proposed. In aLBP, the positions of the neighbors and their values can be assigned adaptively via the down-sampling and the smoothing coefficients. Therefore, the potential to detect (hidden) patterns, which may express an illness or an action, is really increased. To validate the proposed feature extraction approach, two different datasets were employed. Achieved accuracies by the proposed approach were higher than obtained results by employed popular feature extraction approaches and the reported results in the literature. Obtained accuracy results were brought out that the proposed method can be employed to investigate SEMG signals. In summary, this work attempts to develop an adaptive feature extraction scheme that can be utilized for extracting features from local changes in different categories of time-varying signals.Öğe Palmprint recognition based gabor wavelet transform using K-NN classification(European Journal of Technique (EJT), 2016-04-01) Çalışkan, AbidinPalmprint recognition system is regarded as the reliable and accurate biometric identification system available. Viewed in the palmprint recognition system of biometric approaches, compared to other models because it is a new handheld biometric feature recognition system has recently attracted the attention of researchers. In this study, palmprint recognition system based on Gabor wavelet transform has been developed. Firstly, image coordinate system is defined to facilitate image alignment for feature extraction. Then, region of interest is cropped from the palmprint images. With developed system feature extracted of region of interest and given of k-NN classifier.Öğe Characterization of an Au/n-Si photovoltaic structure with an organic thin film(Elsevier, 2013-08) Özaydın, Cihat; Akkılıç, Kemal; İlhan, Salih; Rüzgar, Şerif; Güllü, Ömer; Temel, HamdiWe demonstrate that a copper(II) organic complex can control the electrical characteristics of conventional Au/n-Si metal-semiconductor (MS) contacts. We investigated the electronic and photovoltaic properties of a Cu(II) complex/n-Si heterojunction diode. The ideality factor n and barrier height Φb of the diode were 2.22 and 0.736 eV, respectively. An ideality factor greater than unity indicates that the diode exhibits non-ideal current-voltage behavior. This behavior results from the effect of series resistance and the presence of an interfacial layer. The series resistance and barrier height determined using Norde's method were 6.7 kΩ and 0.77 eV, respectively. The device showed photovoltaic behavior, with a maximum open-circuit voltage of 0.24 V and a short circuit current of 1.7 μA under light of 8 mW/cm2.Öğe Improved kidney-inspired algorithm approach for tuning of PID controller in AVR system(IEEE, 2019-03-22) Ekinci, Serdar; Hekimoğu, BaranThis paper proposes a novel tuning design of proportional integral derivative (PID) controller via an improved kidney-inspired algorithm (IKA) with a new objective function. The main objective of the proposed approach is to optimize the transient response of the AVR system by minimizing the maximum overshoot, settling time, rise time and peak time values of the terminal voltage, and eliminating the steady state error. After obtaining the optimal values of the three gains of the PID controller (K P , K I , and K D ) with the proposed approach, the transient response analysis was performed and compared with some of the current heuristic algorithms-based approaches in literature to show the superiority of the optimized PID controller. In order to evaluate the stability of the automatic voltage regulator (AVR) system tuned by IKA method, the pole/zero map analysis and Bode analysis are performed. Finally, the robustness analysis of the proposed approach has been carried out with variations in the parameters of the AVR system. The numerical simulation results demonstrated that the proposed IKA tuned PID controller has better control performances compared to the other existing approaches. The essence of the presented study points out that the proposed approach may successfully be applied for the AVR system.Öğe Application and comparative performance analysis of PSO and ABC algorithms for optimal design of multimachine power system stabilizers(Gazi Üniversitesi, 2016-06-20) Ekinci, SerdarThis paper presents the application and performance comparison of PSO and ABC optimization techniques, for multi-objective design of power system stabilizers (PSSs) in the multi-machine power system. The design objective is to improve the power system stability. The PSSs parameters tuning problem is converted to an optimization problem with the time domain-based objective function and both PSO and ABC optimization techniques are used to search for optimal stabilizers parameters. The optimized stabilizers are tested on multi-machine electric power system subjected to different disturbances. The performance of both optimization techniques in terms of computational time, convergence rate and solution quality is compared. The eigenvalue analysis, nonlinear timedomain simulation results, critical clearing times and some performance indices studies are introduced and compared in order to demonstrate the effectiveness of both optimization techniques in designing stabilizers, to enhance the dynamic stability of the system. What is more, the potential and superiority of the ABC algorithm over the PSO algorithm are verified.
