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Öğe Effective electromagnetic shielding(Ieee-Inst Electrical Electronics Engineers Inc, 2006) Unal, E.; Gokcen, A.; Kutlu, Y.[Abstract Not Available]Öğe Effects of ultrasonic agitation prior to deposition and additives in the bath on electrodeposited Ni-B/hBN composite coatings(Elsevier Science Sa, 2018) Unal, E.; Karahan, I. H.Ni-B/hBN composite coatings were successfully deposited by conventional electroplating method on mild steel substrate. Electrodeposition was carried out in Watts type nickel electrolite and trimethylamine borane (TMAB) was used as boron element source. hBN particles with 1 um average powder size were used as reinforcements. In this study, the effects of additives in the bath and ultrasonic mixing before deposition on the composite coating properties were evaluated. Crystal structure, morphology and composition of composite coatings were investigated by X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. Also corrosion behavior of composite coatings was analysed via Tafel extrapolation and open circuit potential techniques in 3.5% wt. NaCI solution. The results showed that the composite coatings that have compact and smooth properties were obtained and ultrasonic agitaiton significantly influenced corrosion resistance of composite coatings and uniform distribution of incorporated hBN particles. It was found that corrosion rate of the composite coatings was 76.7% and 78.5% lower than that of composite coatings produced in the bath without ultrasonic mixing and without ultrasonic mixing plus additives, respectively. (C) 2018 Elsevier B.V. All rights reserved.Öğe Electromagnetic absorbance properties of a textile material coated using filtered arc-physical vapor deposition method(Sage Publications Inc, 2015) Esen, M.; Ilhan, I.; Karaaslan, M.; Unal, E.; Dincer, F.; Sabah, C.We explore the structure of a textile absorber in terms of its electromagnetic and absorption properties in the microwave region. Its absorption characteristics are similar to those reported for various metamaterial-based absorbers, exhibiting absorption as high as 98% at resonance. In addition, the angular behavior of the absorption properties of the sample reveal incident angle independency, which is the other added value of the study. Also, the suggested textile absorber has a simple configuration, which introduces flexibility to adjust its material properties and easily tune its structure to suit other frequencies. The proposed textile absorber and its variations have myriad potential applications in radar technology, long distance radio telecommunication, and so on. Although in its current state the proposed structure provides almost perfect absorption covering a wide range of microwave C-Band, the developing technology will soon allow manufacturing textiles that can manipulate lights, leading to the design of invisibility cloak and other science fiction devices besides finding important application areas in medical science.Öğe Microstrip Patch Antenna Covered With Left Handed Metamaterial(Applied Computational Electromagnetics Soc, 2013) Dogan, E.; Unal, E.; Kapusuz, D.; Karaaslan, M.; Sabah, C.We present gain characteristics of microstrip patch antennas covered with metamaterial substrate composed of split-ring resonators (SRRs) and metallic strip. To determine the performance of the SRR-metallic strip mounted on microstrip patch antenna, the metamaterial has been proposed as an effective medium with extracted constitutive parameters. Simulation results are supported by experimental measurements. The experimental results confirm that the metamaterial covered patch antenna improves gain by an amount of -5.68 dB (% 60.3) as well as radiation pattern (-8 dB to +20 dB) at WLAN communication.Öğe Multi-band metamaterial absorber: Design, experiment and physical interpretation(Applied Computational Electromagnetics Society (ACES), 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Sabah, C.This paper presents the design, fabrication, characterization and experimental verification of a perfect Multi-Band Metamaterial (MTM) absorber (MA) based on a simple configuration of a rectangular resonator and strips operating in microwave frequency regime. The proposed multi-band MA provides perfect absorption with TE-incident angle independency. Maximum absorption rate is achieved as 99.43% at 5.19 GHz for simulation and 98.67% at 5.19 GHz for experiment, respectively. The measurement results of the fabricated prototype are in a good agreement with the numerical results. Furthermore, we introduce a numerical analysis in order to show physical interpretation of the MA mechanism in detail. Additionally, a sensor application of the proposed multi-band MA is presented to demonstrate an extra feature of the suggested structure. As a result, the proposed multi-band MA enables myriad potential application areas such as radar, stealth, shielding, communication, imaging and medical applications. © 2014 ACES.Öğe Multi-Band Metamaterial Absorber: Design, Experiment and Physical Interpretation(Applied Computational Electromagnetics Soc, 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Sabah, C.This paper presents the design, fabrication, characterization and experimental verification of a perfect Multi-Band Metamaterial (MTM) absorber (MA) based on a simple configuration of a rectangular resonator and strips operating in microwave frequency regime. The proposed multi-band MA provides perfect absorption with TE-incident angle independency. Maximum absorption rate is achieved as 99.43% at 5.19 GHz for simulation and 98.67% at 5.19 GHz for experiment, respectively. The measurement results of the fabricated prototype are in a good agreement with the numerical results. Furthermore, we introduce a numerical analysis in order to show physical interpretation of the MA mechanism in detail. Additionally, a sensor application of the proposed multi-band MA is presented to demonstrate an extra feature of the suggested structure. As a result, the proposed multi-band MA enables myriad potential application areas such as radar, stealth, shielding, communication, imaging and medical applications.Öğe New generation WIMAX antenna based on metamaterial superstrate(Natl Inst Optoelectronics, 2013) Dogan, E.; Unal, E.; Kapusuz, D.In this study, a microstrip patch antenna system based on metamaterial superstrate (PAMS) is proposed. Patch antennas suffer from low gain and directivity. A significant study is realized to circumvent this drawback by implementing a patch antenna based on metamaterial superstrate. The effective medium parameters of the unit cell are retrieved and planar three-layer metamaterial composed of unit cell arrays are used as a superstrate for gain and directivity enhancement of a microstrip patch antenna at 5.6 GHz. The gain and directivity efficiency of the proposed system is about 13.474 dB and 12.40 dB, respectively at 5.6 GHz. In this study, Simulation and measurement results are also presented. The PAMS consists of periodically arranged metamaterial array unit cells as a superstrate and patch antenna. The system is designed to operate from 5.2 GHz to 6 GHz with a return loss of -32.174 dB at first mode (5.6 GHz). Both simulation and measurement results of the PAMS show that this configuration is able to realize a broadside gain 72% of the maximum gain from the metamaterial superstrate. The effects of the compactness of the arrays are also investigated. It is observed that return loss is directly proportional with the compactness of the superstrate. The maximum return loss (-32.174 dB) is obtained with seven arrays of metamaterial.Öğe New-Generation Chiral Metamaterials Based on Rectangular Split Ring Resonators With Small and Constant Chirality Over a Certain Frequency Band(Ieee-Inst Electrical Electronics Engineers Inc, 2014) Sabah, C.; Dincer, F.; Karaaslan, M.; Akgol, O.; Demirel, E.; Unal, E.Chiral metamaterials (MTMs), a new class of MTMs, provide a simpler solution for obtaining negative refraction and dynamic electromagnetic response. Many research groups have been studying chiral MTMs asking for strong chiral behaviors such as optical activity and circular dichroism. These studies have generally focused on the properties of a large chirality and circular dichroism. However, small and constant chirality over a certain frequency band have not been queried so far in the literature. In fact, this area is mostly ignored by the researchers. This study numerically and experimentally focuses on small and constant chirality with a new-generation planar chiral MTM based on rectangular split ring resonators (SRRs), in details by using two different geometries. We have successfully obtained small chirality values by using the proposed designs, which can be easily integrated into many interesting applications such as transmission and antireflection filters or polarization control devices.Öğe Optimization of elliptically designed patch mushrooms and investigation of low profile dipole antenna - HIGP interaction(Natl Inst Optoelectronics, 2010) Unal, E.; Karaaslan, M.; Ozdemir, E.In this study, we investigate high impedance ground plane structures consist of elliptic metallic mushrooms. In this structure gaps and metallic patch dimensions have an effect on electromagnetic band gap is observed. It is shown that elliptic mushrooms can show much better performance compared to its conventional counterpart such as perfectly electric conductor. Good return loss in the EBG frequency range for HIGP-low profile dipole antenna is obtained. Miniaturized and improved antenna system is satisfied by this new elliptic mushrooms.Öğe Photonic band gap engineering in two-dimensional photonic crystals and iso-frequency contours(Taylor & Francis Ltd, 2014) Erdiven, U.; Karadag, F.; Karaaslan, M.; Unal, E.; Dincer, F.; Sabah, C.We have theoretically investigated photonic band structures of two-dimensional (2D) photonic crystals (PCs) in air background. The lattices consist of the rotated and modified square dielectric rods. The influence of opto-geometric parameters of designed unit-cell structures are analyzed in terms of opening frequency gaps and appearing tilted band graphs by applying plane wave expansion method. Optimum structures with large photonic band gaps are notified. In order to get gap maps, the gaps as a function of the size and the rotation angle of the square rods are calculated. So, the band gaps of transverse magnetic and transverse electric polarization modes indicate symmetry in point of the rotation angle and these band gaps overlap. Thus, the smallest width of the narrow air veins is founded as 0.06a. The results show almost 40nm complete width of the air veins for mid-gap wavelength =1.55m. This result shows the fabrication capability of these optimized PC structures.Öğe Planar Photonic Crystals Biosensor Applications of TiO2(Polish Acad Sciences Inst Physics, 2012) Erdiven, U.; Karaaslan, M.; Unal, E.; Karadag, F.We examine quality factor and sensitivity change depending on the resonant wavelength changing refractive index of surrounding liquid for TiO2 photonic crystal slab structure. Photonic crystal slab structure is used widely for biological materials such as proteins, antigens, DNA, cells, virus particles and bacteria. Mentioned photonic crystal slabs are usable with large-area biosensor designs. They permit direct access to externally incident optical beams in a microfluidic device. Model calculations are based on two-dimensional periodic crystal structure. Photonic crystal slab consists of a square lattice of air holes in a finite-thickness dielectric slab. The time domain simulations were implemented by software MIT Electromagnetic Equation Propagation.Öğe Polarization Angle Independent Perfect Metamaterial Absorber(Ieee, 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Demirel, E.; Sabah, C.This paper presents a perfect metamaterial absorber (MA) based on rings and cross wires (RCWs) configuration in microwave frequency regime. Maxima absorption rate is 99.9 % at 2.76 Ghz for simulation and 99.4% at 2.82 GHz for experiment, in order. The proposed MA provides perfect absorption with angle of polarization independency. Consequently, suggested model enable myriad potential applications such as stealth and military technologies.Öğe Polarization angle independent perfect metamaterial absorber(Institute of Electrical and Electronics Engineers Inc., 2014) Dincer, F.; Karaaslan, M.; Unal, E.; Akgol, O.; Demirel, E.; Sabah, C.This paper presents a perfect metamaterial absorber (MA) based on rings and cross wires (RCWs) configuration in microwave frequency regime. Maxima absorption rate is at for simulation and at for experiment, in order. The proposed MA provides perfect absorption with angle of polarization independency. Consequently, suggested model enable myriad potential applications such as stealth and military technologies. © 2014 IEEE.Öğe Production and characterization of electrodeposited Ni-B/hBN composite coatings(Elsevier Science Sa, 2018) Unal, E.; Karahan, I. H.Ni-B/hBN composite coatings were fabricated through conventional electrodeposition method in Watt's type solution bath on st-37 low carbon steel. Electrodeposition was carried out in different hBN bath concentration and trimethylamine borane (TMAB) was used as source of boron. Also pure Ni and Ni-B alloy coatings was deposited in order to make comparisons. Electrochemical behaviors, crystal structures, surface morphologies, chemical composition, microhardness, surface roughness and corrosion behaviors of the coatings were analyzed. In this study, the results indicate that smooth, compact and fine grained composite deposits were produced and the microhardness of composite coatings was 325% higher than pure nickel coating and was 10% lower than Ni-B coating. Besides, it was found that corrosion rate of the composite coatings was 87.5%, 86% and 30% lower than that of mild steel substrate, Ni-B alloy and pure nickel coating, respectively.
