Yazar "Yilmazel, Rustem" seçeneğine göre listele

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    Channel Optimization By Using Spectrum Sensing Techniques In Cognitive Radio Network
    (Kırıkkale Üniversitesi, 2020) Yilmazel, Rustem; İnanç, Nihat
    In recent years, the rapid development of wireless technologies has increased the need for frequency spectrum usage. To overcome this problem, Cognitive Radio (CR) has emerged as a new technique which enables the use of free ranges in the frequency spectrum. Cognitive radio networks (CRNs) are based on the principle of benefiting from the empty spectrum of secondary users (Sus) by using sensing techniques and analyzing frequency ranges. Although the frequency spectrum is used by various technologies, some frequency ranges are used inefficiently and inadequately. Fixed spectrum allocations cause unused frequency channels in the radio frequency spectrum. Spectrum detection, which is one of the features that cognitive radio applies to reduce the inefficiency of spectrum usage, scans all the primary users (PUs) in the spectrum area and the empty frequency bands. In this study, a method has been proposed to detect unused stationary frequency bands and to use these frequency bands effectively. This method, which is named as matched filter detection , was examined in AWGN channel and its results were evaluated in MATLAB.
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    Cooperative spectrum sensing method for MC-CDMA systems in cognitive radio networks
    (Ieee, 2018) Yilmazel, Rustem; Seyman, Muhammet Nuri
    The development of wireless communication networks has made spectrum management more compulsory. Different systems such as Multi-carrier code division multiple access (MC-CDMA) have to be adapted for cognitive radio technology to solve this problem. In this article, cooperative spectrum sensing technique, which is one of the spectrum sensing techniques, is adapted to MC-CDMA technology. This method can be used to decrease the mathematical density of the obtained spectral characteristics or to get better the probability of detection. Cognitive radio has made it possible to make spectrum perception more effective and reduce the possibility of false perception. The aim is to increase the likelihood that an unauthorized user will be able to identify the presence of a licensed user by cooperating with each other. The theoretical value and the simulated result are compared and then the results are interpreted according to the changing signal-to-noise ratios (SNRs).
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    Investigation of Electrical Conductivity in Cement Mortars with Waste Iron Chips
    (Kırıkkale Üniversitesi, 2023) Filazi, Ahmet; Yilmazel, Rustem; Pul, Muharrem
    In this study, the electrical conductivity of cement mortars formed by additive waste iron chip was investigated. Mixtures with fixed water/cement (0.5) ratios and different ratios of iron chip were prepared. Cement mortars were prepared by adding 0%, 1%, 2%, 4%, 8% and 16% by weight of cement in the mixtures and waste iron chip in the range of 0.5 mm to 4 mm in size. Firstly, the flow test was applied to the cement mortars cured in normal water for 7 and 28 days and their flexure and compressive strengths were determined. Then, the electrical conductivity test was applied to the cement mortar samples. As a result, it was observed that the flow diameter values increased as the average length increased from 0.5 mm to 2 mm in 1% and 2% additive of waste iron chip. It was determined that 1% waste iron chip was higher at 4.54% compressive strength compared to the reference sample. As the amount of added waste iron chip increased, the electrical resistivity value in the samples decreased and the electrical conductivity value increased along with it. At the same time, it was determined that the added iron chip size also increased the electrical conductivity.
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    Investigation of the effect of lubricant properties of carbon nanomaterial in Cu/MWCNT composites on wear
    (Frontiers Media Sa, 2024) Pul, Muharrem; Yilmazel, Rustem; Erten, Mustafa Yasin; Kucukturk, Gokhan; Kaya, Duran; Salunkhe, Sachin; Zumrut, Yavuz
    This experimental study investigated the abrasive wear behaviour of pure copper-based and multi-walled carbon nanotube (MWCNT) doped composites synthesized by the powder metallurgy technique. Composite structures were formed by reinforcing MWCNT at different ratios between 1% and 8% in 99.9% pure copper by powder metallurgy. The microstructures of the nanocomposite samples were analyzed by X-ray diffraction. Then, density and hardness measurements and abrasive wear tests were performed to determine their mechanical properties. The collected data were evaluated with scanning electron microscopy images. It has been determined that copper's nano-sized carbon reinforcement material has a dry lubricant effect up to a specific ratio, reducing wear losses. On the contrary, wear losses increase as the MWCNT reinforcement ratio increases between 4% and 8%. The best results in lowering wear losses were obtained from the sample with 1% MWCNT reinforcement. Depending on the increase in the amount of nanomaterial reinforcement in the composite structure, it was observed that pore formation enlarges with reinforcement agglomeration. It was concluded that the dense porosity in the composite structure neglects the lubricating properties of the MWCNT reinforcement material and increases the wear losses by having a negative effect.
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    Pure fuzzy Hall effect sensors for permanent magnet synchronous motor
    (Tubitak Scientific & Technical Research Council Turkey, 2016) Aliskan, Ibrahim; Yilmazel, Rustem
    An investigation about Hall effect sensors' efficiency is confirmed in permanent magnet synchronous motor (PMSM) drive systems. A fuzzy control algorithm is used as an artificial intelligence controller. Large scale and low slopes are used for creating membership functions and a sensitive controller is obtained. Speed is wanted to be taken under control and a minimum error value is aimed. PMSM drive systems are established using MATLAB-Simulink/SimPower. Simulations are realized with real-time parameters in discrete mode. A fuzzy logic controller is designed by using the MATLAB/Fuzzy Logic Toolbox. A normalization technique and high resolution output of the fuzzy logic controller (FLC) are unique aspects of the work. Input variable bandwidths are narrowed and the number of membership functions is reduced. The taken steps provide positive effects against variation of input parameters. Finally, sharp impacts are not produced by the fuzzy controller. Results verified that the Hall effect supported controller system gives better results than sensorless one. This is especially observed at change points of reference speed. Low complitude oscillations and short settling time are achieved on speed and torque signals.
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    The Effect of SiC and MgO Ceramic Reinforcements on the Mechanical Behavior and Electrical Properties of the Composite Structure in Al7075/SiC/MgO Hybrid Composites
    (Kırıkkale Üniversitesi, 2023) Erten, Mustafa Yasin; Yilmazel, Rustem; Filazi, Ahmet; Pul, Muharrem
    In this study, certain technical properties of new generation aluminum-based composites, obtained by combining the Al7075 alloy widely used in the industrial field with two different ceramics, were investigated. For this purpose, SiC and MgO ceramics in particle form were reinforced into the Al7075 matrix material using powder metallurgy technique and composite structures were produced in three different reinforcement ratios. Measurements to determine electrical resistance and conductivity and bending and compression strength tests were performed on the obtained composite structures. The density and porosity amounts of the composite structures were also determined, and their microstructures were examined with a digital microscope. With the increase of SiC/MgO amount in the aluminum composite structure, the electrical resistance increased, and the conductivity value decreased. With the effect of SiC/MgO reinforcing materials, the density value of the composite structures decreased while the amount of porosity increased. The hardness values increased due to the effect of SiC and MgO ceramics in the structure. The bending and compression strength values initially increased and then started to decrease with the increase of reinforcement ratios. It has been determined that the formation of porosity in the composite structure negatively affects the mechanical behavior. The second important factor was evaluated to be the amount and shape of ceramic-based reinforcement particles in the structure. Due to the effect of SiC, which has very high electrical resistance, and MgO, which has dielectric properties, the electrical conductivity values of the composite structures decreased. The increase in electrical resistance and the decrease in electrical conductivity were directly proportional to the amount of ceramic-based reinforcement particles in the composite structure.