Sürdürülebilir Kalkınma Amaçları

• 1

• MakaleAçık Erişim2026Scopus SJRQ1/r/bayburt/11215
  Waveguide-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.

  İncele
• MakaleAçık Erişim2025Scopus SJRQ1/r/bayburt/12776
  Broadband 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.

  AtıfScopus3·WoS1·OpenAlex3

  İncele
• MakaleAçık Erişim2025Scopus SJRQ1/r/bayburt/12751
  A 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.

  AtıfScopus2·WoS1

  İncele
• MakaleAçık Erişim2025Scopus SJRQ1/r/bayburt/11399
  Transient 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.

  İncele
• MakaleAçık Erişim2024Scopus SJRQ1/r/bayburt/11843
  De-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 ∗

  AtıfScopus1·WoS1·OpenAlex1

  İncele
• MakaleAçık Erişim2024Scopus SJRQ1/r/bayburt/11810
  Simpler 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.

  AtıfScopus6·WoS5

  İncele
• MakaleYayıncıda açık erişim2023Scopus SJRQ1/r/bayburt/13121
  Designing 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.

  AtıfScopus12·WoS10·OpenAlex13

  İncele
• MakaleAçık Erişim2016Scopus SJRQ1/r/bayburt/12205
  A New Energy Prediction Algorithm for Energy-Harvesting Wireless Sensor Networks With Q-Learning

  Kosunalp, Selahattin

  Traditional wireless sensor networks (WSNs) face the problem of a limited-energy source, typically batteries, resulting in the need for careful and effective utilization of the energy source. However, inevitable energy depletion will eventually disturb the operation of a WSN. Energy harvesting (EH) technology is acquiring particular interest, because it has the potential to provide a continuous energy supply in battery-powered WSNs. Solar energy is the most effective environmental energy for EH-WSNs because of its high energy intensity, which comes from a non-controllable source. Therefore, the prediction of future energy availability is a critical issue, as the amount of the harvestable energy may vary over time. In this paper, a novel solar energy prediction algorithm with Q-learning, called Q-learning-based solar energy prediction (QL-SEP), is proposed. Q-learning is an effective way of predicting future actions based on past observations. The distinctive feature of QL-SEP is that not only past days' observations but also the current weather conditions are considered for prediction. The performance of QL-SEP is simulated in this paper using real-world measurements obtained from a solar panel in comparison with the state-of-art approaches.

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  AtıfScopus128·WoS96·OpenAlex135

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