Sürdürülebilir Kalkınma Amaçları

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• MakaleYalnız künye2026Scopus SJRQ1/r/bayburt/11152
  Experimental investigation of magnetic forces in PMA and HTS configurations using a high-speed electrodynamic levitation test system

  Mollahasanoglu, Hakkı; Abdioglu, Murat; Ozturk, Ufuk Kemal; Okumus, Halil Ibrahim

  This study presents a comparative experimental investigation of magnetic force parameters in high-speed electrodynamic levitation systems using permanent magnet arrays and high-temperature superconductors. A novel modular test platform with a rotating aluminium rail, cryostat, and integrated three-axis force measurement unit was employed to evaluate levitation and drag forces under controlled conditions at linear velocities up to 280 km/h. Three different permanent magnet arrays configurations were designed and tested at working gaps of 10, 12, and 15 mm, while high-temperature superconductors bulks fabricated from YBCO by the top-seed-melt-growth method were tested at 10 and 12 mm gaps. The experimental results demonstrated that permanent magnet arrays configurations produced higher levitation forces, with a maximum of 100 N at working gap of 10 mm. High-temperature superconductors bulks, in contrast, generated lower levitation forces (maximum 17 N at 10 mm) due to limited trapped flux (∼0.25 T) but showed the advantage of substantially reduced drag forces (3.5 N at 10 mm). A lift-to-drag ratio analysis confirmed the trade-off between force generation and energy losses in permanent magnet arrays systems, while highlighting the efficiency potential of high-temperature superconductors-based levitation. The findings of this study provide valuable insights for the engineering development of high-temperature superconductors-based Maglev technologies, emphasizing their potential importance in future transportation systems.

  AtıfScopus5·WoS4·OpenAlex2

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• MakaleAçık Erişim2025Scopus SJRQ1/r/bayburt/11403
  Design and initial experimental verification of a high-speed electrodynamic levitation measurement system utilizing modular magnetic field sources and aluminium rails

  Ozturk, U. Kemal; Mollahasanoglu, Hakki; Abdioglu, Murat; Okumus, Halil Ibrahim; Gedikli, Hasan

  This work presents design and development of a modular high-speed electrodynamic levitation (EDL) test system that integrates advanced magnetic field configurations and real-time control capabilities at high operational speeds. The system comprises a rotating aluminium rail and interchangeable magnetic field sources, including permanent magnet array (PMA) and high-temperature superconducting (HTS) bulk, allowing for a variety of experimental configurations. The initial experimental results focused on testing the system through PMA–aluminium rail and HTS–aluminium rail configurations. A key innovation of this system is its modular structure, which allows for easy replacement and reconfiguration of magnetic components and rail geometries. The adaptability of the system enables a thorough investigation of how different magnetic field sources influence magnetic force and dynamic stability at high speeds. Furthermore, the system is fully integrated with a programmable logic controller (PLC) and supervisory control and data acquisition (SCADA) interface, enabling precise real-time monitoring, synchronized control and automatic data acquisition. Experimental results demonstrate the system's capability to measure vertical displacement variations and force fluctuations at different speeds, with resonance effects identified around 145 km/h. The levitation forces of 99 N were measured at a gap of 10 mm, with the PMA at a maximum speed of 283 km/h above an aluminium rail, while it was measured as 16 N with HTS at a vertical gap of 9 mm. This flexible test platform provides a critical foundation for determining the force parameters of the real-scale EDL Maglev technologies and advancing their practical application potential in high-speed transportation.

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  AtıfScopus3·WoS3·OpenAlex2

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• MakaleYalnız künye2025Scopus SJRQ1/r/bayburt/11358
  Multi-functional, multi-band, low-profile, ultra-thin, and cost-effective metasurface-based polarization converter

  Kaya, Yunus; Hasar, Ugur Cem; Ozturk, Hamdullah; Ozturk, Gokhan

  This article presents a polarization converter (PC) that demonstrates linear polarization (LP) to LP (LP–LP), circular polarization (CP) to CP (CP–CP), and LP to CP (LP–CP) conversion performance in microwave C-band (4–8 GHz), X-band (8–12 GHz), Ku-band (12–18 GHz), and K-band (18–27 GHz). The designed converter performs LP–LP conversion in the frequency ranges of 6.414–6.771 GHz, 10.681–12.160 GHz, and 18.093–19.045 GHz, CP–CP conversion in the same frequency ranges (6.414–6.771 GHz, 10.681–12.160 GHz, and 18.093–19.045 GHz), and LP–CP conversion in the frequency ranges of 7.374–9.414 GHz and 13.792–16.777 GHz. It is single-layer, metasurface-based, reflection-type (because it consists of a metasurface-substrate-metal ground adaptation), multi-band (five bands), multi-functional (because it shows all three LP–LP, LP–CP, and CP–CP conversions), ultra-thin (with a substrate thickness of 1.6 mm (0.034λ)), low-profile, and cost-effective (since relatively cheaper and easily available FR4 dielectric material is used). Simulations for the designed PC have been carried out by the 3D full electromagnetic simulation program — the Computer Simulation Technology (CST) Studio Suite. The performance analysis of the designed converter was carried out according to the reflection coefficients in the frequency range of 4–21 GHz. It was fabricated using the traditional printed circuit board production method, and its performance was validated in microwave X-band by free-space microwave measurements. More information about the conversion mechanism of the converter was also provided by parametric study and surface current analysis. It is observed that the PC design, which has wide angular independence (50°), can be configured to be efficiently used in radar cross section (RCS) reduction and stealth applications.

  AtıfScopus10·WoS10·OpenAlex8

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• MakaleYalnız künye2023Scopus SJRQ1/r/bayburt/11872
  Parameter extraction method for reflection-asymmetric bianisotropic metamaterial slabs using one-port measurements

  Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Ertugrul, Mehmet; Ramahi, Omar Mustafa

  An effective microwave method is developed for extracting electromagnetic properties of bianisotropic metamaterial (MM) slabs. As a non-iterative method, it utilizes only the one-port (air-backed and metal-backed MM slab) scattering (S-) parameter measurements. This is a useful feature especially for vector network analyzers, such as MS46131A, MS46121B, and R60, performing only one-port S-parameter measurements. Electromagnetic properties of a bianisotropic MM slab formed by C-shaped resonators are measured by an X-band (8.2–12.4 GHz) rectangular waveguide setup. The effect of any gap between the short-circuit termination for metal-backed measurements and the end of the MM slab on extracted electromagnetic properties is also examined for evaluating the possible error for proposed method.

  AtıfScopus3·WoS3·OpenAlex5

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• MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/10748
  Coupling analysis between resonating metamaterial slabs using scattering parameters

  Hasar, Ugur Cem; Kaya, Yunus; Izginli, Mucahit; Ozturk, Hamdullah; Ertugrul, Mehmet; Ramahi, Omar M.

  Metamaterial (MM) slabs in close proximity can couple with one another. This coupling can modify the electromagnetic response of the overall MM structure involving individual MM resonators. The signal flow graph technique along with the ABCD parameters are applied to quantitatively and qualitatively examine this coupling from simulated/measured scattering parameters of cascade connection of closely or largely separated MM slabs. S-parameter measurements of a MM slab constructed by split-ring-resonators were carried out at X-band (8.2-12.4 GHz) to validate our theoretical analysis.

  AtıfScopus2·WoS2·OpenAlex2

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• MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/13370
  Prediction of water-adulteration within honey by air-line de-embedding waveguide measurements

  Hasar, Hafize; Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Hamdullah; Izginli, Mucahit; Ozbek, Ibrahim Yucel; Oztas, Taskin; Canbolat, Mustafa Yildirim; Ertugrul, Mehmet

  An efficient de-embedding air-line microwave method has been proposed for accurate relative complex permittivity, εr=εr′−iεr′′, measurement of water-adulteration level within honey. It could be effectively applied to eliminate the errors arising from usage of imperfect calibration standards because it bypasses the requirement of these standards. Its accuracy is improved by utilizing the unitary and similarity properties of a passive two-port network, and then is compared with the accuracy of a calibration-dependent method present in the literature by using normalized root-mean-square-error (N-RMSE) values of εr′ and εr′′ of distilled water, in reference to the Debye value. From this comparison, it is observed that N-RMSE values calculated for εr′ (and εr′′) by using this calibration-dependent method and the (improved) proposed method are, respectively, around 0.1955 (0.1002) and 0.1962 (1.1067), indicating a good agreement between them. After validation the proposed de-embedding method using distilled water measurements, tested pure honey was adulterated with distilled water by different percentage values δ ranging from 1% to 10% in 1% increments. It is observed that the maximum distance between extracted εr′ (or εr′′) values of adulterated honey by the applied calibration-dependent method and the proposed method is less than 2%. Afterward, an empirical formula was devised to fit εr′ and εr′′ values from measured εr of water-adulterated honey with various δ levels. It is noted that extracted εr′ is much more better fitted than extracted εr′′, especially for δ≤4. Next, an optimization process is followed to evaluate the frequency for optimum prediction of adulteration levels using the empirical formula based on εr′ or εr′′. It is noticed that optimized δ values using the empirical formula based on εr′ (with an average prediction error of around 0.071 at 4.5 GHz) are superior to optimized δ values using the empirical formula based on εr′′ (with an average prediction error of around 0.085 at 4.2 GHz) for prediction of previously known δ values. Sensitivity and uncertainty analyses were performed to assess and improve the accuracy of the proposed method.

  AtıfScopus24·WoS23·OpenAlex24

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• MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/12193
  Effect of sample deformation in longitudinal axis on material parameter extraction by waveguides

  Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, Mehmet

  An analysis was performed for examining the consequences of sample deformation in longitudinal axis in the sample-loaded non-resonant waveguide techniques. Vertical and horizontal deformations were first simulated to understand the change in field distributions and corresponding scattering parameters. Then, effects of sample length, dielectric constant, and loss factor for these deformations on extracted electromagnetic properties were analyzed using simulated results. Finally, S-parameter measurements were carried out to understand the effect of vertical deformation on permittivity results and to examine any improper sample preparation by hand-made and machine-made samples by applying a statistical model based on mean, standard deviation, coefficient of variation, and confidence interval. It was noted that extracted dielectric constants of each tested dielectric sample (polyethylene, polypropylene, polyvinyl-chloride) were within the confidence interval range of 90% while their retrieved loss factors were within the confidence interval range of 90%, 95%, or 98%.

  AtıfScopus3·WoS3·OpenAlex3

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• MakaleAçık Erişim2021Scopus SJRQ1/r/bayburt/11942
  New formalism for characterization of simple non-reciprocal networks free from singularity-point problem

  Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ozturk, Hamdullah; Izginli, Mucahit; Ertugrul, Mehmet

  A method has been proposed for accurate characterization of non-reciprocal networks without enforcing the passivity principle. Thanks to the introduced different even and odd coefficients, our method has no singularity-point problem as compared with the conventional method. The proposed method is validated by scattering parameter measurements of a ferrite-loaded waveguide shifter. In addition, it is demonstrated by measurements that our method, as compared with the conventional one, is more resistant to random noise due to post-calibration effects.

  AtıfScopus1·WoS1·OpenAlex1

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• MakaleAçık Erişim2020Scopus SJRQ1/r/bayburt/11841
  Propagation constant measurements of reflection-asymmetric and nonreciprocal microwave networks from S-parameters without using a reflective standard

  Hasar, Ugur Cem; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, Mehmet

  We propose a simple method for determination of forward and backward propagation constants of nonreciprocal uniform networks or lines with asymmetric reflections. The wave cascading matrix presentation is used to diagonalize and decompose the line in terms of impedance and amplitude/phase transitions. The proposed method uses scattering parameters of the line/network connection and the thru connection, thus eliminating errors arising from fabrication tolerance and thickness of the second line. Besides, compared with conventional methods which necessitate calibration techniques such as the thru-reflect-line, our method has the advantage that it determines propagation constants without resorting the measurement of any reciprocal reflective standard. Propagation constant measurements of a reciprocal network (different-length X-band waveguide straights) and a nonreciprocal network (microwave phase shifter) were first carried out and then compared with those measured by different methods to validate and monitor the accuracy of our method.

  AtıfScopus13·WoS12·OpenAlex11

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• MakaleAçık Erişim2018Scopus SJRQ1/r/bayburt/13597
  A novel method based on thermal conductivity for material identification in scrap industry: An experimental validation

  Cuce, Erdem; Cuce, Pinar Mert; Guclu, Tamer; Besir, Ahmet; Gokce, Erkan; Serencam, Ugur; Serencam, Huseyin

  Fast, accurate and reliable identification and sorting of materials is still a challenge in recycling sector. Scrap metals are often classified through density and colour, which cause notable financial burdens to the companies in most cases. Within the scope of this research, a novel method based on thermal conductivity is presented for material identification in scrap industry. The unit consists of a constant heat flux source and a cooling system, in which axial heat conduction is enabled and radial heat transfer is eliminated. For the steady-state conditions, temperature gradient across the sample metals is measured along with the constant heat flux value, and the thermal conductivity of the samples is determined via the Fourier's heat conduction law. Copper, brass and stainless steel samples are considered in this research to verify the accuracy of the results. For a reliable and scientific approach, three independent sets of experiments are conducted, and the results are evaluated in terms of accuracy and consistency. Experimental thermal conductivity values of the said samples are compared with the reported data in literature and a good accordance is achieved. Error in measurements is calculated to be 1.37, 3.31 and 4.46% for copper, brass and stainless steel sample, respectively which is acceptable. The tests are repeated with highly sensitive probes for aluminium sample, and the measurement error is calculated to be 0.56%.

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  AtıfScopus21·WoS19·OpenAlex19

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