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The shielding of radio wave by steel-containing structures is desirable for electronics protection but undesirable for telecommunication signal reception. This work investigates the shielding behavior of steel structures consisting of members in various configurations, with the practical aim of determining how the configuration can be exploited to control the shielding. Differently oriented continuous steel reinforcement (stranded/unstranded wires in the unidirectional, crossply and planar coil configurations) are evaluated for electromagnetic interference (EMI) shielding at 600-2000 MHz, using unpolarized radiation. The absorption loss SE (A) dominates the reflection loss SE (R). The crossply configuration gives the highest SE (A), SE (A)/thickness and SE (A)/SE (T) (SE (T) = total loss); the planar coil configuration gives the lowest values. The SE (A), SE (A)/thickness and SE (A)/SE (T) are moderately higher for the crossply configuration than the unidirectional configuration, because steel's electrical isotropy allows the 0 degrees electric field to interact with the 90 degrees wire. The SE (A)/SE (T) is comparable for the stranded and unstranded wires.

Placing dielectric lens structures into an antenna's aperture has proven to be one of the most reliable methods of enhancing its gain. However, the selected material and the prototyping method usually limit their fabrication process. With the advances in 3D printing technology and their applications, the microwave designs that were either impractical or impossible in the past to manufacture using traditional methods, are now feasible. Herein, a novel prototyping method by using 3D-printer technology for low-cost, broadband, and high gain dielectric lens designs has been presented. Firstly, the elliptical lens design has been modeled in the 3D EM simulation environment. Then fused deposition modeling based 3D-printing method has been used for the fabrication of the dielectric lens. The measured results of the 3D printed antenna show that the lens antenna has a realized gain of 17 to 20.5 dBi over 8-12 GHz. Moreover, the comparison of the prototyped antenna with its counterpart dielectric lens antenna in the literature has indicated that the proposed method is more efficient, more beneficial, and has a lower cost.

WOS: 000519806700073, In this study, composites composed of glass fiber reinforced-epoxy laminates interleaved with electrospun polyvinylchloride (PVC) nano-fibres were designed for radar absorption investigations. The laminated composites which were produced in special molds were obtained by placing woven glass fibers between each of PVC nanofiber mats, and the composites were produced in three different forms as pure, multi-walled carbon nanotubes doped and graphene doped. The morphologies of the PVC nanofiber mats were analyzed by scanning electron microscope. The radar absorption efficiencies of the composites in the individual and different combinations were measured in the 3-8 GHz frequency band. Experimental results show that the produced graphene-added composite material has improvable microwave absorption effect at several points in 3-8 GHz band to provide excellent absorption in future studies. The graphene doped structure was found to have a certain absorption characteristic up to 33.82% at a constant frequency. Besides, various strong absorption frequency points have been obtained in the related frequency range. The cascaded graphene doped composite layers can provide broadband absorption for stealth technology.

A specially designed metallic E-shaped fractal-based perfect metamaterial absorber (PMA) with fairly wideband absorptivity in the K- and Ka-bands of the microwave regime was investigated. The PMA top surface is comprised of square-shaped split-ring resonators (SRRs) surrounded with the stated fractal design. The absorptivity of PMA was analyzed in the range of 20 - 30 GHz for the normal and oblique incidence of waves. Both the transverse electric (TE) and transverse magnetic (TM) modes were taken up to observe the robustness of the proposed design. It was observed that the fractal resonators exhibit capacitive effect at low frequencies, whereas the SRRs manifest capacitive effect at higher frequencies. The simulation and measured results were found to be in fairly good agreement. It is expected that the proposed design of PMA would be useful for 5G communication applications.

In this work, gain of a traditional horn antenna is enhanced up to 2.9 dB over X-band using 3D printed square-shaped multi-layer lens. For this purpose, firstly the multi-layer lenses are designed using Invasive Weed Optimization (IWO) and simulated in 3-D CST Microwave Studio (MWS) environment as consisting of square-shaped five layers with variable dielectric constants and heights. Thus, optimum values of the dielectric constants and heights are resulted limiting from 1.15 to 2.1 and 9.2 mm to 10 mm, respectively compatible for Fused Deposition Modeling (FDM) based 3D-printing process. Finally, the optimum lens is realized by 3D printer via FDM evaluating infill rate of cheap Polylactic Acid (PLA) material for each layer. The simulated and measured performance of the multi-layer dielectric structures are hand to hand. The horn antenna equipped by our proposed dielectric lens achieves gain enhancement of the traditional antenna up to 2.9 dB over the operation band. Furthermore, the proposed design is compared with the counterpart designs in literature and based on the comparison results it can be said that the proposed design achieves the better performance in the smaller in size as equipped a traditional X-band horn antenna. © 2021 Applied Computational Electromagnetics Society (ACES). All rights reserved.

This paper presents a new reflection-only set-up for characterizing the properties of an anisotropic PEC-backed materials. Albeit, the reflection-only methods are established long ago, they are not elaborated appropriately for retrieving industrial anisotropic materials. In spite of other researches, this method is capable to determine tensors of both permittivity and permeability of an anisotropic PEC-backed material. In contrast to similar researches, this method is mathematically simple and easy to implement. Tensors of epsilon and mu of PEC-backed sample are characterized by rotating sample and measuring reflection coefficient in various configuration. Not measuring the transmission, in order to provide enough equations, the higher order mode of the waveguide is employed. A three-port probe is designed for this goal and optimized to excite the TE(10)and TE(20)modes simultaneously. Good agreement of retrieved parameters from experimental measurements with those of actual ones shows the reliability of this set-up for characterization of PEC-backed anisotropic composites.

WOS: 000531764100019, In this paper, a new design of microstrip power limiter which is based on microstrip technology and zero bias Schottky diode is introduced. In this context, the FR-4 substrate that was characterized by dielectric permittivity (4.4), dielectric thickness (1.6 mm), and the HSMS 286k Schottky diode is used to design the proposed power limiter. The planar resonators are designed, optimized, and simulated with the shunting of the HSMS 286k diodes by using Schematic solver integrated in ADS from Agilent Technologies. The simulation results are significant in terms of high impedance matching, strong insertion of the low power, and good limitation ratio of the high power. The proposed power limiter is fabricated and tested in the measurement part. It is observed that the results are in agreement with the numerical analysis in terms of matching, isolation, and power limitation. The achieved microwave power limiter offers simple construction, small size (44 x 40 mm(2)), wide bandwidth, and good limitation ratio less than 10 dBm when the input power reaches 30 dBm.

WOS: 000427715600070, In this work we present physical, electrical and magnetic properties of beta-Fe1.1Se single crystalline alloys produced by chemical vapor transport technique using short (120 h) and long (700 h) heating processes. The best T (c) was obtained from the long time processed samples. Magnetization results showed that samples are typical type-II superconductor. Calculated critical current density values, at zero field, were found to be 1.1 x 10(6) Acm(-2) for long time processed samples at 2 K and indicates strong pinning mechanism and bulk superconducting nature. The zero temperature value of higher upper critical field was calculated to be H (c2)(0) = 244 kOe. Calculated values of coherence length were found between 3.65 and 3.67 nm. Pauli paramagnetic limit, H (P) (0) = 1.84T (c) , is exceeded for both series of samples. Results obtained suggested that the spin-paramagnetic effect possibly the dominant pair-breaking mechanism for both series of samples., Scientific and Technological Research Council of Turkey, TUBITAK [115F278], This work was supported by the Scientific and Technological Research Council of Turkey, TUBITAK (Project Grant No. 115F278).

WOS: 000404530900034, A metamaterial-based sensor has been realized to distinguish authentic and inauthentic fuel samples in the microwave frequency regime. Unlike the many studies in literature on metamaterial-based sensor applications, this study focuses on a compact metamaterial-based sensor operating in the X-band frequency range. Firstly, electromagnetic properties of authentic and inauthentic fuel samples were obtained experimentally in a laboratory environment. Secondly, these experimental results were used to design and create a highly efficient metamaterial-based sensor with easy fabrication characteristics and simple design structure. The experimental results for the sensor were in good agreement with the numerical ones. The proposed sensor offers a more efficient design and can be used to detect fuel and multiple other liquids in various application fields from medical to military areas in several frequency regimes., TUBITAK [115E788]; Turkish Academy of Sciences, F.D. acknowledges support from TUBITAK under Project No. 115E788 and partial support from the Turkish Academy of Sciences.

WOS: 000460453100090, A micro sensor based on a V-shaped resonator (VSR) is implemented for the purpose of determining fiber content and ratio in construction materials as a nondestructive method. Concrete is investigated as the construction material in the study. First, electrical properties of concretes reinforced by different fiber types and ratios are investigated using the Nicolson-Ross-Weir technique. These values are used to design a nondestructive sensor based on microwave transmission line methods. At the resonance frequency, the VSR has a dense electric field. Construction material which is positioned within range of the VSR can change the distribution of the electric field, thus affecting the resonance response and transmission magnitude in the operating frequency. Since construction materials having various contents have different complex dielectric permittivity and loss tangent values, the resonance frequency, transmission magnitude and bandwidth of VSR shift correspondingly. Alterations in the resonance frequency and magnitude of transmission values which are related to the permittivity of the construction materials enable us to detect characteristics of the content in construction materials. The proposed technique is not only capable of sensing the type of content in the construction material which is positioned within range of the VSR, but it is also capable of determining the percentage of this content. Results show that the proposed microwave-based VSR sensor provides a cost-efficient and nondestructive solution for sensing the type and percentage of the contents in fiber-reinforced concretes.

WOS: 000482043000001, Electromagnetic band gap (EBG) integrated monopole antenna is investigated in deformed cavity resonator in this study. The operation frequency is chosen as X band frequency regime and designs are completed for this frequency. Firstly, a square grounded monopole antenna is designed and analytically examined, then EBG grounded monopole is designed and tested. After that operation, an 8 cm x 8 cm x 8 cm cubic cavity resonator designed and antennas are examined in it. Moreover, a cuboid deformation is added in one corner of metallic cavity resonator to perturb rectangular eigenmodes. Also, tunability of this structure is tested by various resistive lumped elements, and according to results, resonance shifting and magnitude changes are obtained. This suggested structure is also an adjustable impedance surface and can be used in sensing, detection and microwave imaging applications.

WOS: 000386367000125, Operation frequencies of traditional metamaterial absorbers are fixed meaning that it is not possible to change that frequency after the fabrication. Therefore, more studies are focused on the design of Tunable metamaterial absorber (TMA) since it is important to expand operation frequency. If the impedance of one or more layers of an absorber can be changed according to the applied electrical optical signal, then it would be possible to realize tunable absorbing designs. However, TMA studies reported previously are mainly focused on absorbing mechanism at microwave frequencies. In this study, TMA with varactor diode is designed and analyzed for absorber and sensor configurations. TMA is constructed by using a simple rectangular-shape geometry having two splits and a varactor diode placed at the right split. Numerical and experimental results show that perfect absorption is achieved when 0-10 V reverse bias voltage is applied. Resonance frequency can be easily tuned by changing the reverse bias voltage. Frequency dependent absorption behavior of TMA is presented with respect to different incident angles for TE and TM polarizations. A sensor application, knowing the absorption resonance frequency can provide the ability to determine the temperature of materials. The novelty of the study is to determine the temperature or the other parameters such as humidity or pressure by using TMA. It is also possible to determine the material type or its density if limited resource such as frequency generator is present.

The detection of branded and unbranded chemical materials is essential for the quality control assessment. In this work, a metamaterial inspired sensor is designed and fabricated, which incorporates oval-shaped wing resonators, in order to use to detect branded and unbranded diesels in the X-band frequency region. The simulation studies were carried out by using the Computer Simulation Technology (CST) Microwave studio. A transmission line was introduced into the sensor design and genetic algorithm was used to optimize the proposed structure. Parametric study was investigated by changing the permittivity, permeability of the sensor layer, width of the transmission line, materials of the substrate layer, and width of the resonator. Results showed that different factors can be considered to sense the chemical materials including the shift in resonant frequency and amplitude variation in the reflection or transmission spectrum. It was found that the sensible variation in the transmission value is about &minus, 3.2 dB, which is superior to that reported in literature. It was concluded that the sensor is highly sensitive to distinguish the branded diesel from the unbranded one, which makes it viable for detecting fluidics in the chemical industry and medicine.

12th International Congress on Artificial Materials for Novel Wave Phenomena, MetaMaterials 2018 -- 27 August 2018 through 1 September 2018 -- -- 142487, The possibility of negative refractive index in plasma and magnetic materials was considered with a new approach. It is shown that simplification of fundamental equations by neglecting losses leads to losing important features about refractive index and therefore, it is expedient to take into consideration imaginary parts of dielectric permittivity and magnetic permeability for an accurate statement of the problem. Also active materials were briefly discussed via new approach. © 2018 IEEE., FDK-2017-8948, The authors would like to acknowledge the Scientific and Technological Research Council of Turkey (TÜBİTAK) and the Scientific Project Unit of Cukurova University (FDK-2017-8948) for full financial support.

WOS: 000443021000068, A metamaterial-based permittivity and thickness sensor structure for dielectric substrate material has been proposed at the X band frequency regime. The sensor structure is designed by using a split meander line type resonator and examining it both numerically and experimentally. Various types of dielectric substrate samples have been used to verify the precise sensing characteristics of the proposed sensor. The sensor layer has been chosen as the back side of the sensor structure, and the reflection frequency of the incident signal has been examined The sensor layer thickness has been varied from 0.4 mm to 1.6 mm for the thickness sensing study with two different types of dielectric substrate having the same electromagnetic characteristics. The permittivity sensing study has been carried out by several dielectric materials which have permittivity values between 10.20 and 1.96. The proposed sensor structure can be effectively used in many application areas such as microwave material design, the defense industry and in medical devices., Scientific Project Unit of Cukurova University [FDK-2018-10488], The authors would like to acknowledge the Scientific Project Unit of Cukurova University (FDK-2018-10488).

WOS: 000431278700009, Metamaterial-based energy harvesting structures operating at GSM goo and GSM 1800 frequency bands have been proposed. The basic structure is composed of four nested U-shaped elements on the front and back side of the dielectric substrate, with a 180 degrees relationship between the front and back resonators. As energy harvesting capability is directly related to the quality of absorption, with the aim being perfect absorption, there is an air gap to allow tuning of the resonance frequency, and copper plate follows the air gap to facilitate the perfect absorption of electromagnetic waves, which is verified by means of simulation and experimental tests. A set of simulations and experimental study were further carried out to demonstrate incident and polarization angle dependency, the effects of Schottky diodes, and the optimal orientation of the U-shapes. Spectrum analysis and DC voltage measurements across the HSMS 2860 Schottky diode are also presented to test the energy harvesting capability: the spectrum analyzer shows a 40 dBm difference, while 81.7 mV maximum DC voltage is observed at 900 MHz. The simulation and experimental study results, while displaying several differences, do suggest that the proposed design can be used for running low-energy consumption devices such as sensors and switches.

WOS: 000427715600041, Synthesis and characterization of FeTe0.5Se0.5 single crystals prepared by self-flux technique with two different cooling rates of 1.45 and 5.83 a"integral/h have been investigated. The XRD results show that the samples have tetragonal structure. The SEM results indicate that the samples demonstrate a terrace-like formation. The superconducting transition temperatures of two samples obtained as magnetization measurement are seen to be 14.62 and 14.38 K for sample A (5.83 a"integral/h) and sample B (1.45 a"integral/h), respectively. The M-H curves reveal the existence of ferromagnetism in all measured temperatures. The normalized pinning force f(F-p/F-pmax) at h(H/H (irr) ) curves are scaled using the Dew-Hughes model given by f(h) = Ah (p) (1 - h) (q) with A = 2.73, p = 0.81 and q = 0.69, the ratio [p/p + q] ae 0.54 for cooling rate of 5.83 a"integral/h sample., Cukurova University [FDK-2017-8224, FBA-2015-4464], This work was supported by Research Fund of Cukurova University [Grant Nos.: FDK-2017-8224, FBA-2015-4464].

WOS: 000425716800005, A novel metamaterial absorber structure is designed and characterized for microwave energy harvesting. The suggested structure is composed of two circular ring resonators with different dimensions. Due to harvesting application of the proposed structure, the main operation frequency of the suggested structure lies in WIMAX and satellite communication frequency bands and surrounds our environment. The optimum dimensions of the suggested structure are obtained through parametric study by genetic algorithm in order to realize wideband absorption and harvesting response. Simulation results show that the metamaterial-harvester-based resistive loads are useful to absorb and convert microwave energy for the operation frequency. The simulated harvested power across the resistors has been found greater than 0.4 W, which corresponds to 80% efficiency between 7.8 and 14 GHz. In addition, polarization dependence and angular stability of the proposed harvester are investigated at operation frequency to support the simulation of an experimental study for S-parameter measurement. Therefore, simulation and experimental study results show that the proposed design with good absorption and harvesting characteristics can be operated in WIMAX and satellite communication frequency bands.

12th International Congress on Artificial Materials for Novel Wave Phenomena, Metamaterials 2018 -- 27 August 2018 through 1 September 2018 -- -- 142487, This manuscript focus on developing of new metamaterials sensor based on distinction of different material and purity ratio sample. Unique side of this study is having very clear and sensitive results and presenting new approach to the microfluidic sensor applications by using sample holder. The procedure of this study consist of three steps, measurement of dielectric constant by using Agilent 85070E dielectric measurement kit, developed of proper structure and simulation result, taking experimental output by using sensor layer. © 2018 IEEE., 117M855, Acknowledgement We would like to thank the Scientific and Technological Research Council of Turkey (117M855) for the financial support.

WOS: 000365525900060, We present the design, characterization, theoretical and experimental verification of a tunable perfect metamaterial absorber (MA) based electromagnetic (EM) energy harvesting and sensor application. We have used the golden ratio while determining the dimensions allowing a simple configuration and an easy fabrication for the proposed structure. We have examined and analyzed the perfect absorption (both numerically and experimentally) and EM energy harvesting (numerically) behaviors of the proposed structure in order to verify and show the characteristics of the model. It is shown that 99.9 % maximum absorption rate is achieved at 6.78 GHz, and MA structure can be used as an EM energy collector. In order to support the numerical study, an experimental study is realized. We have then developed a sensor application of the proposed MA structure and observed the effects of the harvesting system. Perfect MA sensor based EM energy harvesting system is successfully achieved.

WOS: 000413620600005, In this paper, chiral nihility based pressure, density, temperature and moisture content metamaterial sensor applications are investigated in detail. A "chiral nihility'' medium in which both the permittivity and the permeability tend to zero is investigated. Gammadion shaped resonators particularly designed for chiral nihility are introduced. Bandwidths and signal strengths show admissible results. Simulation and experimental results prove that chiral nihility occurred at the resonance frequencies when medium parameters are retrieved. The pressure and density sensor applications of the proposed sensor study are realized both numerically and experimentally, and the obtained results show good agreements with each other., TUBITAK [114E295], M.K and O.A. acknowledges the support of TUBITAK under the Projects No. 114E295.

WOS: 000405291400023, A new metamaterial absorber (MA) is investigated and shown numerically for solar energy harvesting for future solar cell applications. The structure consists of two metals and one dielectric layer having different thicknesses. Owing to this combination, the structure exhibits plasmonic resonance characteristics. In the entire spectrum of visible frequency region, the obtained results show that investigated structure has perfect absorptivity which is above 91.8%. Proposed structure also has 99.87% absorption at 613.94 THz and 99% absorption between 548 and 669 THz. The proposed structure also shows both polarization and angle independency for the entire visible region. The MA based solar cell proposes high absorption with an upper ratio of 90% in the widest range of visible spectrum comparing to the studies in literature. Hence, the proposed metamaterial absorber solar cells can be used for invisibility in entire spectrum of visible light. The absorption characteristics of the solar absorber are also investigated for infrared and ultraviolet region. The enhancement of absorption of the structure will provide new type of sensors in these frequency ranges.

WOS: 000416751700010, A metamaterial absorber (MA) based sensor is designed and analysed for various important applications including pressure, temperature, density, and humidity sensing. Material parameters, as well as equivalent circuit model have been extracted and explained. After obtaining a perfect absorption (PA) at around 6.46 GHz and 7.68 GHz, surface current distributions at resonance points have been explained. Since bandwidth and applicability to different sensor applications are important for metamaterial sensor applications, we have realized distinctive sensor demonstrations for pressure, temperature, moisture content and density and the obtained results have been compared with the current literature. The proposed structure uses the changes on the overall system resonance frequency which is caused by the sensor layer's dielectric constant that varies depending on the electromagnetic behaviour of the sample placed in. This model can be adapted to be used in sensor applications including industrial, medical and agricultural products. (C) 2017 Association of Polish Electrical Engineers (SEP). Published by Elsevier B.V. All rights reserved., TUBITAK under the Turkish Academy of Sciences [114E295], O. Akgol, of the author acknowledges the support of TUBITAK under the Projects No. 114E295 partial support of the Turkish Academy of Sciences. The authors would like to thank Olcay Altintas for his help during the preparation of the paper. Additionally, the authors thank the anonymous reviewers for their constructive comments and suggestions to improve the paper.

WOS: 000400921900005, A new broadband absorber is investigated for the entire frequency domain of solar light (infrared, visible light and ultraviolet). While current absorbers in the literature have limited operation frequencies, investigated structure has a wide bandwidth and a perfect absorptivity (99% at nearly all operation frequencies). The proposed metamaterial absorber has ultra-broadband, angle-insensitive, polarisation-independent characteristics with a different conventional pyramid shape. Whereas other pyramid or truncate pyramid-shaped multi-layered metamaterial absorber (MA) are composed of multi-layered dielectrics and metal combinations, the proposed structure has only three layers. As a result of exhibiting perfect absorption characteristic, the proposed structure is a new candidate for energy harvesting applications in solar energy collection.

WOS: 000470025500007, In this article, a novel wide band polarization and incident angle independent metamaterial absorber (MA) and energy harvesting applications which operates at C (4GHz-8 GHz) and X (8GHz-12 GHz) is proposed. The unit-cell of the proposed structure based on fractal circle loop. Four lumped resistors are mounted the structure to obtain a broad band absorption characteristics. Resistors increase the absorption characteristic of proposed MA significantly at mentioned frequency ranges. In addition, under favor of the resistors proposed MA can convert absorbed energy from incident wave to appearing power.

International audience; A quite large programme on wide-gap II-VI materials has been developed in our group. The aim of this paper is to present this work. The choice of material, ZnSe based, is obviously due to the value of this gap (2.7 eV) at room temperature. This material is the most promising for blue-light-emitting diodes, or devices for non-linear optics applications. This paper will be divided into four parts. In the first one the problem of ZnSe/GaAs obtained by OMCVD will be treated. In particular, the band energy diagram at the interface, and in some cases the appearance of a hole gas in the GaAs side, gives rise to some misinterpretation, concerning the p-type conduction of ZnSe.Also the state of the strain of the ZnSe layer depending on the used substrate, is deduced by the shift of the photoluminescence peak.In the second part we extend our discussion to superlattice ZnSe-ZnTe. By using a simple envelope function model, with a given band offset, the critical thickness of barriers and wells are calculated to obtain an emission in the blue wavelength.In the third part the offset is calculated by a self-consistent tight-binding method for the series of Zn chalcogenides. Then, the electronic structure of ZnTe-CdTe superlattices is calculated. Interface states appear due to strong coupling between light and heavy holes when the tight-binding model is used.

International audience; We found a new class of analytic soliton solutions that describe the parametric wave mixing of optical pulses in quadratic nonlinear crystals. We analyze the stability properties, interactions and collisions of these solitons.

Recently, advances in material technology permit the realization of chiral materials for employment in multilayer substrate/superstrate configurations with dimensions that are even a small fraction of the wavelength. This capability makes possible the fabrication of integrated circuits and planar antennas with chiral loading materials that are very promising for telecommunication purposes. The recent extension of the finite element variational formulation given by the authors for the analysis of cavity-backed patch antennas with complex loading materials facilitated the study of microwave components with chiral dielectrics and is exploited in this paper to investigate some electrical features of patches with chiral substrates and superstrates. The main result obtained is the reduction of the resonant frequency with an increase in the chirality admittance of the material. This permits the realization of very compact antennas compared with antennas fabricated using solely isotropic materials. An example showing the dimension reduction obtained through the employment of chiral materials is also presented. Finally, the effect of a chiral superstrate on a conventional patch and the mutual coupling between two patches when chiral substrates are used is also presented.