Özden, Melih; Çoban, Ömer; Karacali, Tevhit

In this study, PZT (lead zirconate titanate) films were deposited on (1 0 0) oriented p-type silicon substrates using the spin-coating method, a technique known for its ability to produce thin, uniform coatings. To evaluate the structural and optical properties of the films, a range of characterizations were performed, including x-ray diffraction (XRD), scanning electron microscopy (SEM), and absorbance measurements. The XRD analysis showed that the PZT peaks corresponded to the perovskite crystalline phase, confirming the successful deposition of PZT. SEM images revealed a homogeneous surface coating with a cracked structure, and the film thickness exhibited variations influenced by the number of spin cycles. Additionally, the absorbance measurements indicated an energy band gap of 3.65 eV for the films, suggesting their potential for optoelectronic applications. Notably, it was observed that both the film thickness and particle size increased as the number of spin cycles increased, highlighting the influence of the spin-coating process on the final film properties.

Yaşar, Umut Şükrü; Kaya, Haydar

In this study, ultra-thin films of Al, Co, and multilayered Al/Co were fabricated using the magnetron sputtering technique on a very thin glass substrate. Subsequently, electromagnetic wave shielding measurements were conducted utilizing the transmission-reflection line method with the aid of a vector network analyzer. In measurements conducted within the X-band microwave frequency range within the waveguide, the maximum electromagnetic interference shielding effectiveness (EMI SE) values obtained were determined as 46 dB for Al, 24 dB for Co, and 48 dB for the multilayered Al/Co film. The structural and morphological analyses of these shielding films were included in the study using x-ray Diffraction (XRD), energy dispersive x-ray analysis (EDAX), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) techniques. Scattering parameter results indicated that increasing conductivity values enhance the shielding effectiveness (SE) while also demonstrating an additional positive impact on the SE value for multilayered structures. This finding indicates that nanometer-thick Al or Al/Co multilayer films could significantly protect electronic devices or individuals exposed to X-band microwave radiation.

Akaltun, Yunus

Nickel selenide thin films were grown on glass substrates at room temperature using the successive ionic layer adsorption and reaction (SILAR) method. Optical and structural analyses of the thin films were also performed. X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX) and scanning electron microscopy (SEM) were used for structural analysis, and UV–vis spectrometer was used for optical analysis. The XRD results indicate that the NiSe2 thin films had a polycrystalline structure. As a result of the optical analysis, the bandgap value decreased from 2.56 to 2.25 eV as the thickness increased. These results suggest that increasing film thickness improves the crystal structure of NiSe2 thin films.

Altintasi, Cagri

In this study, exponential smoothing (ES)-based quadrature amplitude modulation (QAM) is applied to detect and classify the power quality (PQ) events with high accuracy and low complexity. Considering the IEEE-1159 standards, in the simulation environment, 14 different power quality distortion signals are produced. Each of these signals is modulated at the fundamental frequency by QAM. The high-frequency constituents in the in-phase and quadratic components resulting from the QAM are filtered by the ES. PQ events are detected and classified by extracting features from the filtered in phase and quadrature component. The performance of the proposed method is examined by taking (Figure presented.) randomly selected data samples for each PQ event, and its performance is (Figure presented.) and (Figure presented.), respectively, at noiseless and (Figure presented.) dB SNR environments. The obtained results are compared with the others in the literature for the detection and classification of PQ events, and it is shown that the proposed method has better performance in noisy and noiseless conditions. In addition, to verify that the proposed method can be applied to real systems, oscillating transitions produced by capacitor banks in Simulink environment and voltage sag and swell events are generated in experimental environment. The proposed method successfully detected and classified PQ events.

Altunbas, Yasin; Turk, Kadir

Visible light communication (VLC) is a promising technology that realizes short-range wireless optical communication and illumination simultaneously. The use of light-emitting diodes (LEDs) in lighting has accelerated the development of short-range wireless optical technology. However, the limited switching frequency of LEDs used in lighting restricts the communication speed of VLC systems. Non-orthogonal multiple access (NOMA) methods can be used to improve the sum rate in VLC systems. In this study, meta-heuristic optimization algorithms are proposed to calculate the power allocation coefficients of users in indoor NOMA-based VLC systems. During the calculations, many constraints used fairness and optical intensity, which were not taken into account in many studies in the literature. The proposed algorithms are compared with the previously proposed methods according to the sum rate results, considering the number of users increases and the user signal strength values differ. The obtained results revealed that metaheuristic methods demonstrate a significant improvement in terms of sum rate compared to other methods. In addition, the effects of parameters such as sum rate, fairness, and optical intensity on each other are investigated in the simulation environment.