Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Kaya, Yunus(20)
- Ertugrul, Mehmet(9)
- Hasar, Ugur C.(9)
- Hasar, Ugur Cem(9)
- Ozturk, Gokhan(7)
- Abdioglu, Murat(5)
- Korkmaz, Huseyin(5)
- Barroso, Joaquim J.(4)
- Guler, Evrim(4)
- Iliev, Teodor(4)
- Karakus, Murat(4)
- Ozturk, Hamdullah(3)
- Ozturk, Kemal(3)
- Uludag, Suleyman(3)
- Ali, Husain(2)
- Aslan, Nevzat(2)
- Barroso, Joaquim José(2)
- Buldu, Gul(2)
- Celik, Sukru(2)
- Cem Hasar, Ugur(2)
- Gedikli, Hasan(2)
- Hasar, Hafize(2)
- Izginli, Mucahit(2)
- Mollahasanoglu, Hakki(2)
- Oztas, Taskin(2)
- Ramahi, Omar M.(2)
- Savaskan, Burcu(2)
- Stoyanov, Ivaylo(2)
- Akcay, Latif(1)
- Alptekin Engin, Mustafa(1)
- Ates, Kayhan(1)
- Ayberkin, Doruk(1)
- Badia-Majos, Antonio(1)
- Basci, Abdullah(1)
- Bute, Musa(1)
- Cakil, Turan(1)
- Cakir, Mehmet(1)
- Canbolat, Mustafa Y.(1)
- Cansiz, Ahmet(1)
- Dilek, Durukan Burak(1)
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ1Permittivity Extraction of Electrically Thin Samples by Reflection-Only Free-Space Measurements
Hasar, Ugur C.; Xue, Bing; Ozturk, Hamdullah; Kaya, Yunus; Ozturk, Gokhan
A permittivity extraction procedure is devised for electrically thin samples from reflection-only free-space measurements. Unlike previous studies, this procedure relies on sample-back metal termination measurements especially useful for thinner samples. An objective function independent of antenna transmission characteristics and reference plane position is derived. Minimum and maximum thickness and permittivity values for which our method is applicable are also examined. Free-space measurements at X-band (8.2-12.4 GHz) of a Rogers 4350B sample (approx 1.52 mm) and a FR4 sample (1.60 mm) were performed to validate our method with a dielectric constant less than 5% variation.
AtıfScopus1WoS1
İncele - MakaleYalnız künye2026Scopus SJRQ1Reference-Invariant Permittivity Determination of Low-Loss Solid Dielectric Samples Using Spectral Free-Space Measurements Without Prior Thickness
Hasar, Ugur C.; Ali, Husain; Kaya, Yunus
An extraction method has been proposed for relative permittivity determination εrs of low-loss solid dielectric samples using free-space measurements. It relies on a reference-plane invariant expression with no thickness information a priori, making resistant to conventional free-space measurement errors which may arise from improper information of sample position and thickness. In addition, the method constructed by the state transition matrix (STM) uses closed-form expressions – a feature distinguishes our method from previous STM-based extraction methods requiring a numerical tool or optimization procedure. Furthermore, provided that the sample thickness L is evaluated, as a by-product, first using the derived closed-form objective function away from any thickness-resonance region, the proposed method then determines εrs and L free from thickness-resonance effect, which otherwise can introduce ripples around or at the thickness-resonance frequency. Numerical analysis is performed to validate and assess the performance of our method. Free-space measurements at X-band of two low-loss samples with substantial thickness are performed for validation and accuracy comparison of our method against other similar methods.
- MakaleAçık Erişim2026Scopus SJRQ1Waveguide-Based Microwave S-Parameter Measurements for Machine Learning-Assisted Classification of Paprika Powder Adulterants
Alptekin Engin, Mustafa
Detecting food adulteration in powdered spices through visual inspection is difficult, and paprika powder is particularly susceptible to adulteration due to its fine particulate structure and intense color. This study proposes a waveguide-based microwave S-parameter measurement approach combined with machine learning for the classification of organic and mineral adulterants in paprika powder. The experimental dataset was created by intentionally adulterating a commercial paprika brand with five organic and five mineral materials in varying proportions. The S11 and S21 scattering parameters, measured in the 3.3-4.9 GHz frequency range, of these samples, comprising a total of 11 different classes including pure paprika, were used as input in the machine learning-based classification process. The proposed framework directly uses frequency and S11 and S21 responses to distinguish pure paprika from ten adulterant types without complex feature extraction. S-parameter measurements were performed iteratively for each condition using a vector network analyzer, and the average values were used in the analyses. The frequency-point-level performance of the model was examined with different training/test data splitting ratios during the classification process. Furthermore, 10-fold cross-validation was performed during the training phase, and the performance of different classifiers was evaluated comparatively using overall and balanced validation and test accuracies. Under random point-wise partitioning, Subspace KNN achieved the highest numerical performance, with a mean frequency-point-level test accuracy of 99.86±0.06% across 10 independent runs. The findings demonstrate the frequency-point-level separability of microwave S-parameter responses under the investigated experimental conditions.
- MakaleAçık Erişim2025Scopus SJRQ1Broadband Multilayer Absorber Design Using Double-Stage Cognitive Seeker Optimization Algorithm
Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
In this paper, a double-stage cognitive seeker optimization (DSC-SO) algorithm is developed for evaluating optimum design parameters of broadband microwave absorbers. The algorithm not only gives freedom of selecting different number of layers and optimizing the order of layers and their thickness in different stages (double-stage) but also utilizes a cognitive search to improve the optimization. Contributions of the cognitive search and the two stages of our algorithm are first examined to show its efficiency. Then, its performance has been evaluated for two different optimization problems (a broadband absorber for one incidence angle and a broadband absorber with multiple incidence angles) in comparison with similar algorithms in the literature. It has been shown that our algorithm determines either fewer number of layers or smaller overall absorber thickness or both when compared with the results of other algortihms. Finally, the effect of fabrication tolerance is conducted to examine the importance of fewer number of layers.
AtıfScopus3WoS1OpenAlex3İncele - MakaleAçık Erişim2025Scopus SJRQ1A Hybrid Retrieval Method for an Ω-Class Bianisotropic Metamaterial Using Scattering Parameter Method
Ozturk, Gokhan; Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Stoyanov, Ivaylo
In this study, a hybrid retrieval method is proposed to retrieve all terms in the electric and magnetic tensors (along with coupling tensors) of Ω -class bianisotropic metamaterial (MM) slabs using scattering (S-) parameters of both normal incidence TE2 mode and oblique incidence TM2 and TE modes. Compared with other extraction methods in the literature, our retrieval method fully characterizes the MM slab (extracts all constitutive parameters) without necessitating any numerical technique (non-iterative) using fewer wave configurations (two modes) and sample configurations (one configuration). Contrary to two sample configurations required in the application of previous retrieval methods in the literature, one sample configuration (with and without its rotation in the transverse plane) significantly decreases the effect of fabrication tolerances on the accuracy of extraction. The proposed extraction method is first validated by a bulk MM slab synthesized by the Lorentz and Drude models. Then, it is applied for extracting the electromagnetic properties of two bianisotropic MM slabs in the form of square split-ring-resonators and Ω -shape using their S-parameters simulated by a full wave simulation program. Finally, its accuracy is examined by comparing simulated S-parameters with those reconstructed by using extracted electromagnetic parameters. It is observed that our proposed method determines the constitutive parameters with a relatively higher accuracy in a relatively short amount of time.
AtıfScopus2WoS1İncele - MakaleAçık Erişim2025Scopus SJRQ1Soil Permittivity Extraction by Time-Domain Free-Space Calibration-Free Microwave Measurements With No Thickness Information
Hasar, Ugur Cem; Korkmaz, Huseyin; Kaya, Yunus; Iliev, Teodor
An attractive microwave free-space method is proposed for permittivity extraction of soil samples using calibration-free time-domain measurements. Different from other similar methods in the literature which use the layer-stripping approach in the forward direction in the extraction process, its formalism is based on the layer-stripping approach in the backward direction, whereby allowing extraction of permittivity from interfacial reflection coefficient only without resorting to any thickness information, especially useful for time-domain analysis of multilayer structures having multiple reflection terms. Effects of angle misalignment, loss, and surface roughness on the extraction performance of the proposed method (PM) are analyzed by numerical examples. Permittivity measurements of three low-loss flat solid samples [polypropylene (PP), polyethylene (PE), and polyoxymethylene (POM)] were first performed by a free-space setup operating over 1–18-GHz frequency range to validate our methodology and compare its accuracy against other similar methods in the literature. Thereafter, permittivity measurements of two soil samples sieved with similar and different sizes (coarse- and fine-grained soil samples) by the same free-space setup were then considered to assess the applicability and performance of our method for electromagnetic property analysis of homogeneous and partially inhomogeneous soil samples.
AtıfScopus9WoS6OpenAlex8İncele - MakaleAçık Erişim2025Scopus SJRQ1Transient Plane Wave Transmission Through an N-Layer Multilayer Structure with Bianisotropic Behavior
Cem Hasar, Ugur; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
An analysis based on electromagnetic reflection and transmission properties of multilayer structures are in general needed to get more information about their electromagnetic responses before their implementation for some specific applications involving absorption, shielding, and diagnosis. Such an analysis could be exercised by either frequency-domain or time-domain. While the former one is based on the steady-state response, the latter one is based on the transient response which thus provides more information about electromagnetic properties of multilayer structures. A procedure relying on a direct theoretical time-domain analysis is preferable to a time-domain analysis based on computational procedures such as the finite-time-difference-domain or the fast Fourier transform. In this study, a series presentation of transient plane wave transmission coefficient of N-layer composite structures involving bianisotropic behavior is derived for the first time in the literature in terms of reduced transmission coefficients (the concept of subregion). The wave matrix approach is applied for the theoretical analysis of the reduced transmission coefficient after application of the concept of subregion. Implementation of this concept to our problem is presented step-by-step to make a clear understanding of its application to bianisotropic multilayer structures. The derived reduced transmission coefficient is validated by different multilayer structures (different layer numbers, different layer lengths, and different polarizations) composed of individual layers whose electromagnetic responses are synthesized by the Lorentz dispersion model. Advantages and limitations of the derived formalism are also presented.
- BildiriAçık Erişim2025Analysis of Lightning-Induced Electromagnetic Pulses on High Voltage Transmission Lines
Cakil, Turan; Ozen, Sukru; Ates, Kayhan; Cakir, Mehmet
in this study investigates grounding enhancement techniques for power transmission lines, drawing an analogy with electromagnetic shielding methods. If we look at the basic analogy between electromagnetic shielding and grounding, the purpose of shielding is to prevent electromagnetic fields (both electrical and magnetic) from reaching an area or to reduce electromagnetic propagation. Grounding helps maintain signal quality, eliminate static buildup, and ensure the system meets EMC (electromagnetic compatibility) requirements by safely conducting the shield's parasitic potential to the ground. Examples of such structures include single-point grounding or two-point grounding and the use of mesh. The fundamental principle here is to reduce or prevent the interference of parasitic signals into the protected system. The objective is to improve the reliability and efficiency of transmission systems by optimizing grounding performance. Lightning and electromagnetic pulse (LEMP) intensity and current amplitude data obtained from the Turkish State Meteorological Service (TSMS) were used in the analysis. The electrical performance of the line and its resistance to LEMP-induced faults were evaluated through simulations using the Alternative Transients Program - Electromagnetic Transients Program (ATP-EMTP). The Seydişehir-Akseki-Varsak transmission line was selected as a case study. Results show that grounding improvements led to a significant reduction in the number of LEMP-related outages. Guy wires (GWs) enhanced the electromagnetic coupling between phase conductors and improved the dissipation of LEMP currents into the ground, thereby reducing the equivalent ground resistance. Due to the high cost of line surge arresters, the use of low-cost and easily deployable alternatives such as GWs is recommended. Further analysis on 400 kV transmission lines revealed that GW implementation reduced the flashover voltage at insulator terminals by up to 49%. These findings highlight the importance of cost-effective grounding methods in establishing reliable and sustainable power transmission infrastructure.
- MakaleAçık Erişim2024Scopus SJRQ1De-Embedding Technique for Parameter Extraction of Biaxial Bianisotropic Metamaterial Slabs
Hasar, Ugur Cem; Kaya, Yunus; Korkmaz, Huseyin; Iliev, Teodor
Among material classes of isotropic, anisotropic, bi-isotropic, and bianisotropic, the latter class is important because, as different from other classes, the bianisotropic class can describe complex behavior of various materials through tensor expressions between electric and magnetic fields via electric and magnetic flux densities. All electromagnetic parameters (a total of seven) of a general bianisotropic material need to be accurately extracted for understanding its response and characteristic. Extraction methods can be utilized for such a goal. However, the extraction methods in the literature either require a formal calibration procedure or are limited to the extraction of three electromagnetic parameters only. In this study, an attractive self-calibrating waveguide method has been devised for determination of electromagnetic parameters of biaxial biansiotropic metamaterial (MM) slabs. Its first advantage is that it uses a thru connection in addition to the MM-loaded line connection (three different configurations - Case A, Case B, and Case C) and empty-line connection next to the MM-loaded line connection to extract all (seven) constitutive parameters together with the magnetoelectric coupling coefficient. Its second advantage is that it relies on explicit expressions and does not require any calibration process for such an extraction. Simulations and uncalibrated scattering parameter waveguide measurements at X-band (8.2 - 12.4GHz) were performed for a biaxial bianisotropic MM slab made by C-patterned resonators to validate the proposed method. It is observed that extracted electromagnetic parameters by the proposed method satisfy the passivity conditions over the entire frequency band except for a few frequency points or regions (e.g., f = 8.2 GHz). Its reason is expected to be associated with the difficulty in satisfying the continuous medium property at such frequencies. Besides, it is noted that two of the constitutive parameters (ɛ 2 and μ3) illustrate a thickness-resonance behavior revealed by additional measurements of the Case B - MM structure with different lengths (7.675 mm, 9.21 mm, and 10.475 mm). Besides, it is noted that the resonance behavior of the Case C - MM structure changes with a change in periodicity. Specifically, when the periodicity in the x direction of this MM structure changes from approximately 3.26 mm to 2.29 mm, the resonance frequency shifts from nearly 10.43 GHz to 10.30 GHz (a 1.25% variation). Finally, sensitivity, uncertainty, and error analyses were also performed to evaluate and improve its accuracy. It is observed that |3/Λ 1A| | is 14 times greater than | xi 0 / Λ 1A| | at 10.85 GHz where Λ 1A is one of the terms related to measured S-parameters for the Case A - MM structure, and |∗ | denotes the magnitude of the complex number ∗
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2024Scopus SJRQ1Simpler Reference-Plane-Invariant Method for Permittivity Extraction of Medium- or Low-Loss Dielectric Samples Using One-Port Measurements
Cem Hasar, Ugur; Ali, Husain; Kaya, Yunus; Stoyanov, Ivaylo
A microwave method is devised to extract relative complex permittivity (ϵr) of medium- or low-loss dielectric samples. It is simpler, non-iterative, reference-plane-invariant (RPI), and applicable for one-port waveguide measurements with short-circuit termination only. Besides, since it uses short-circuit termination reflection-only measurements, it is free from Fabry-Pérot resonances. Permittivity measurements of polyvinyl chloride (PVC) and polypropylene (PP) are performed at X-band (8.2-12.4 GHz) to examine the performance of the proposed method considering different scenarios involving inaccurate information of sample location in the cell and inaccurate knowledge of the sample thickness. Repeatability analysis is carried out to analyze the performance of the proposed method against other similar methods in the literature.
AtıfScopus6WoS5İncele - MakaleYayıncıda açık erişim2023Scopus SJRQ1Designing New Model-Based Adaptive Sliding Mode Controllers for Trajectory Tracking Control of an Unmanned Ground Vehicle
Sekban, Hayriye Tugba; Basci, Abdullah
This paper proposes three new dynamic model-based adaptive sliding mode controllers (ASMC) for trajectory tracking control of unmanned ground vehicles (UGV). The controllers combine kinematic and dynamic control to achieve asymptotic stability and finite-time convergence and their stability is verified using the Lyapunov stability theory. The controllers are designed to address the challenges posed by uncertainties in vehicle dynamic parameters and outperform the sliding mode control (SMC) method in trajectory tracking control. The simulation results of the proposed controllers are also discussed in terms of performance metrics. The simulation results show that the controller proposed in rule 1 shows the better performance in terms of trajectory tracking, and then the controllers proposed in rules 2 and 3 have good performances, respectively. In addition, when the simulation results are compared, it is seen that the performance of all three proposed controllers is better than the SMC.
AtıfScopus12WoS10OpenAlex13İncele - MakaleAçık Erişim2023Scopus SJRQ2Magnetic Force Performance of Hybrid Multisurface HTS Maglev System With Auxiliary Onboard PMs
Ozturk, U. Kemal; Abdioglu, Murat; Mollahasanoglu, Hakki
The vertical levitation force, guidance force, and magnetic stiffness values, and thus the loading capacity and movement stability of high-temperature superconducting (HTS) Maglev systems, are aimed to be increased in this study by using auxiliary permanent magnets (PMs) in the onboard unit together with the multisurface HTS-permanent magnetic guideway (PMG) arrangement (hybrid multisurface arrangement). First, the magnetic levitation force, guidance force, and stiffness performances of the hybrid multisurface arrangement were investigated at different field cooling heights (FCH). Then, to compensate for the negation of instability that results from the higher repulsive force between the onboard PMs and the PMG and to obtain an optimal magnetic field medium, we have changed the vertical position of the auxiliary onboard PMs (ZPM) to ZPM = 0, 2, and 4 mm, at the cost of a bit of adecrement in the vertical levitation force. The bigger levitation force, together with the guidance force values for FCH = 25 mm and ZPM = 0 mm, indicates that the hybrid multisurface HTS-PMG arrangements are beneficial to increasing the practical applicability of Maglev systems.
AtıfScopus16WoS14OpenAlex14İncele - MakaleYalnız künye2023Scopus SJRQ1Honey-Water Content Analysis by Mixing Models Using a Self-Calibrating Microwave Method
Hasar, Hafize; Hasar, Ugur C.; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Oztas, Taskin; Aslan, Nevzat; Ertugrul, Mehmet; Barroso, Joaquim J.; Ramahi, Omar M.
Microwave techniques, as an indirect approach, can be applied for analyzing water content in honey by way of permittivity measurements. However, these techniques require proper calibration to accurately perform such indirect evaluation. Improper calibration standards used in this calibration process could naturally result in a reduction in the accuracy and thus the performance of dielectric characterization using microwaves. Self-calibrating microwave techniques can reduce the effects of imprecise standards and thus improve the performance of microwave measurements by bypassing the requirement of calibration standards. In this study, we develop a self-calibrating microwave measurement technique to determine the relative permittivity of honey samples and implement binary mixing models to predict adulteration levels of water-adulterated honey. From this implementation, it is observed that the parallel-capacitance mixing model could efficiently be applied to determine the concentration of water adulteration by examining the differences between absolute values of the real parts of the measured and predicted complex permittivities of adulterated honey.
AtıfScopus18WoS16OpenAlex18İncele - MakaleAçık Erişim2023Scopus SJRQ2Extended 2-D Magnetic Field Modeling of Linear Motor to Investigate the Magnetic Force Parameters of High-Speed Superconducting Maglev
Ozturk, Ufuk Kemal; Abdioglu, Murat; Ozkat, Erkan Caner; Mollahasanoglu, Hakki
A 2-D numerical finite-element model of a linear synchronous motor (LSM) is extended based on the magnetic field and moving mesh properties to investigate the magnetic flux and magnetic force characteristics of the high-speed electromagnetic levitation Maglev system, by using high-temperature superconductor (HTS) coils rather than lower current-carrying copper coils on the onboard unit and permanent magnets (PMs) on the ground. In this 2-D LSM model, the transient time-dependent solver is used to obtain the magnetic flux densities. Both the propulsion and levitation forces increased with increasing supercurrent Jc0 values indicating the advantage of using the superconducting windings in PM-LSM of Maglev vehicles as compared with the copper wires. It was also determined that, although the propulsion force is obtained on a comparable level with the studies in the literature, the lower levitation force issue than the electrodynamic suspension (EDS), despite the better propulsion to levitation force ratio, can be overcome by using the high flux trapping capacity bulk HTSs on the onboard unit together with the superconducting coils. The determined higher propulsion force in this PM-LSM Maglev model indicates that the Maglev vehicle can reach higher velocities in a short distance, and thus, this vehicle can be effectively used in short-distance travels in addition to the long-distance transportation. On the other hand, since the EDS system to be accelerated in a certain time interval via conventional wheels to achieve sufficient levitation, PM-LSM system can be integrated into the EDS Maglev system to ensure higher acceleration in a short time interval in addition to the higher levitation and propulsion force performances.
AtıfScopus10WoS10OpenAlex8İncele - BildiriYalnız künye2022Evaluating Path Selection Strategies with Blockchain-based Routing in Multi-Domain SDNs
Guler, Evrim; Karakus, Murat; Uludag, Suleyman
Software-Defined Networking (SDN) has emerged as one of the most prolific inventions in the general area of computer communications over the past decade. Among many of the touted benefits, SDN architecture facilitated by OpenFlow has the potential to help network administrators to provide End-to-End (E2E) Quality of Service (QoS)-guaranteed paths for flows among networks while providing finer-granular flow management along with global network view. In our previous work, we have introduced QoSChain to amalgamate the advantages of blockchain and SDN for inter-network QoS provisioning to orchestrate an agile and software-driven traffic management framework in order to facilitate cross-network policy automation, assurance, E2E visibility, control and validation. In this study, we focus on the impact of the path selection strategies on the performance of the overall QoSChain performance. Specifically, we exploit three simple but effective path selection strategies, First Feasible Path Selection (FFPS), Random Feasible Path Selection (RFPS), and Minimum Hop Path Selection (MHPS), to evaluate their performance, impact, and overhead in terms of the flow setup time, message overhead, and network resource consumption metrics. Our preliminary simulations results show that the path selection plays an important role in the overall performance with hop count minimization delivering a superior performance offset by an initial higher setup times.
AtıfScopus7OpenAlex9İncele - MakaleAçık Erişim2022Scopus SJRQ1Broadband Soil Permittivity Measurements Using a Novel De-Embedding Line-Line Method
Hasar, Hafize; Hasar, Ugur C.; Kaya, Yunus; Oztas, Taskin; Canbolat, Mustafa Y.; Aslan, Nevzat; Ertugrul, Mehmet; Ramahi, Omar M.
A new de-embedding line-line method has been proposed for accurate complex relative permittivity ( ε ᵣ ) determination of soil samples loaded into an EIA 1-5/8' coaxial transmission line measurement system. The method has three main features. First, it bypasses the requirement of calibration of this system by using only two identical coaxial lines with different lengths. Second, it does not need any numerical technique for ε ᵣ determination. Third, it does not require knowledge of electromagnetic properties and thickness information of the bead used for supporting soil samples. The method is next validated by simulations performed using a full 3-D electromagnetic simulation program (CST Microwave Studio) and by ε ᵣ measurement of a polyethylene (PE) material. Finally, ε ᵣ values of three air-dried and water-saturated soil samples having 90% or more sand content with different electrical conductivities (ECs) and gathered from different areas of the city Gaziantep in Turkey, were measured.
AtıfScopus18WoS16OpenAlex16İncele - BildiriYalnız künye2022SpectrumChain: An Efficient Spectrum Management Framework in Blockchain-Enabled Flexible SDONs
Guler, Evrim; Karakus, Murat; Uludag, Suleyman
Huge potentials of optical networks provide an excellent choice in meeting the exponential growth in bandwidth demand. In particular, Elastic Optical Networks (EONs), with its promising potentials in increased availability, failure resilience, load-balancing, new use cases for on-demand opportunities, and efficient resource allocations, are good candidates for the future high-speed networks. When EONs are augmented with the emerging Software Defined Networking (SDN), that decouples the data and control planes, an agile and synergistic combination emerges under a general term of SDN-based optical networking (SDON), albeit with operational challenges. In this paper, we introduce a blockchain-enabled QoS-based inter-Internet Service Provider (ISP) routing coordination framework for SDONs, SpectrumChain (SC), to eliminate centralized mediators and reduce QoS signaling overhead. Experimental results show that the SC framework can effectively handle the QoS-enabled inter-ISP routing in SDON architecture in terms of flow setup time, message overhead, and requests serviced as compared to the traditional approaches.
AtıfScopus6WoS5OpenAlex6İncele - MakaleAçık Erişim2022Scopus SJRQ1Calibration-Free Time-Domain Free-Space Permittivity Extraction Technique
Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Ertugrul, Mehmet
A time-domain free-space technique has been proposed to extract relative permittivity ( _r ) and effective conductivity ( σ _e ) of low-loss dielectric samples using their metal- and air-backed calibration-free reflected powers. Numerical computations and 3-D electromagnetic simulations were performed to validate the method. A sensitivity analysis was carried out to examine its accuracy. Calibration-free time-domain free-space measurements over 1-12 GHz were conducted by VNA to extract _r and σ _e of polyethylene and polypropylene low-loss samples.
AtıfScopus29WoS28OpenAlex29İncele - MakaleAçık Erişim2022Scopus SJRQ1Broadband, Stable, and Noniterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method
Hasar, Ugur C.; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, Mehmet; Korasli, Celal
A broadband, stable, and noniterative free-space method is proposed for dielectric constant ϵr′ determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of nondisperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and polyoxymethylene samples (9-11 GHz) are carried out to examine the accuracy of our method.
AtıfScopus41WoS37OpenAlex35İncele - MakaleAçık Erişim2021Scopus SJRQ1Simple and accurate electromagnetic characterization of omega-class bianisotropic metamaterials using the state transition matrix method
Hasar, Ugur C.; Ozturk, Gokhan; Kaya, Yunus; Barroso, Joaquim J.; Ertugrul, Mehmet
We propose a simple and accurate microwave extraction procedure for full electromagnetic characterization of \Omega -class bianisotropic metamaterial (MM) slabs from normal incidence scattering (S-) parameters using TE1, TE2, and TE3 modes. Its closed-form nature (no need for any numerical analysis and optimization toolbox) and less requirement (a total of seven S-parameters) demonstrate the advantage of our method over other methods in the literature. Our approach was validated and its accuracy was verified by S-parameters, through a full electromagnetic simulation program - CST Microwave Studio, of an edge-coupled \Omega -class split-ring-resonator MM slab.
AtıfScopus15WoS13OpenAlex14İncele