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Publication type : Article ✕Department : Elektrik-Elektronik ... ✕
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Broadband, Stable, and Noniterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method

Mehmet ERTUĞRUL

A broadband, stable, and noniterative free-space method is proposed for dielectric constant ε′r 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.

Article 2022 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation70 ( 12 ) 65 Views
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Close link between Fabry–Pérot resonance and natural-resonance frequencies

Mehmet ERTUĞRUL

Mathematical and numerical analyses have been performed to examine the close link between Fabry–Pérot resonance and natural-resonance frequencies. For the mathematical analysis, the conditions resulting in minimum magnitudes of reflection coefficients in frequency-domain are derived for air-backed and metal-backed low-loss non-dispersive (or weakly dispersive) dielectric samples with relative complex permittivity εr and thickness L for free-space wave propagation at normal incidence. The close relation between Fabry–Pérot resonance and natural-resonance frequencies is demonstrated for three di ...More

Article 2023 Mühendislik Fakültesi Waves in Random and Complex Media ( Published online: 23 Jan 2023 ) 48 Views
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Artificial Neural Network Model for Evaluating Parameters of Reflection-Asymmetric Samples From Reference-Plane-Invariant Measurements

Mehmet ERTUĞRUL

A technique based on artificial neural network (ANN) is proposed to extract the electromagnetic properties of reflection-asymmetric samples from reference-plane-invariant (RPI) scattering parameter measurements. It first determines reference plane transformation distances and then extracts the material properties. The number of neurons in the hidden layer of the ANN model was evaluated subject to accuracy and time constraints. We examined the conformity of the dataset of the ANN model and the required time for the training process by considering different numbers of neurons in the selected hid ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Instrumentation and Measurement72 62 Views
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Excitation wavelength dependent triple-mode photoluminescence of copper-based halides for advanced anti-counterfeiting

Mehmet ERTUĞRUL

New fluorescent materials with a low cost, hypotoxicity, and concealment are desired for the application of anti-counterfeiting. Herein, we report a CsCu2I3@Cs3Cu2I5 composite with a triple-mode photoluminescence (PL) feature by simply adjusting the excitation wavelengths, which are ascribed to the multiple excited states of different phases in the CsCu2I3@Cs3Cu2I5 composite. The broadband emission and high quantum yield (∼51) of the composite originate from the structure-oriented self-trapped excitons effect of Cs3Cu2I5 and CsCu2I3 phases. Moreover, the incorporation of polyethylene oxide (PE ...More

Article 2023 Mühendislik Fakültesi APL Materials11 ( 7 ) 38 Views
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Temporal Reflection Response of Plane Waves Within an N-Layer Structure Involving Bianisotropy

Mehmet ERTUĞRUL

The temporal reflection response of an N -layer composite structure involving bianisotropic behavior is examined for the first time in the literature. Toward this goal, the wave matrix (WM) method, which is fundamental, relatively easier to apply, and compact and iterative suitable for analysis of multilayer structures, is first extended to the analysis of an interface separating two different media involving bianisotropy. Next, the reflection response of the whole structure is derived in terms of series form to better analyze its temporal behavior. Then, frequency-domain and time-domain respo ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation71 ( 7 ) 46 Views
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Waveform Correlation Based Harmonic Voltage Contribution Determination of Iron and Steel Plants Supplied From PCC

Özgül SALOR-DURNA

This paper presents a new waveform correlation based method which determines the individual harmonic voltage contributions of Electric Arc Furnace (EAF) plants supplied from a point of common coupling (PCC). The method is based on the waveform correlation computations between the PCC voltage and the feeder current at the individual harmonic frequency. PCCs supplying multiple EAF plants usually suffer from high voltage harmonic components due to their operation principles. A relationship between the correlation coefficient of the PCC voltage and the feeder current waveforms, and the harmonic vo ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Industry Applications59 ( 4 ) 24 Views
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Extraction Method for Unique Determination of Complex Permittivity from Graphical Analysis of Natural Frequencies

Mehmet ERTUĞRUL

A time-domain free-space extraction procedure is proposed to uniquely determine the relative complex permittivity ϵr (ω) based on two sets of natural frequencies of the metal-and air-backed dielectric samples. A graphical analysis is applied for evaluating whether unique ϵr (ω) can be extracted using such natural frequencies. The method is numerically validated using two dielectric samples with different ϵ (ω) for the ideal case (no noise) and under the influence of noise with different signal-to-noise ratios (SNRs). Keyword: graphical method; natural modes; parameter extraction; unique soluti ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation71 ( 9 ) 19 Views
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Enhanced self-collimation effect by low rotational symmetry in hexagonal lattice photonic crystals

Mirbek TURDUEV

In this study, we present the design of a photonic crystal (PC) structure with a hexagonal lattice, where adjustments to the PC unit cell symmetry reveal an all-angle self-collimation (SC) effect. By optimizing opto-geometric parameters, such as the rotational angle of auxiliary rods and adjacent distances, we analyze the SC property in detail, leveraging group velocity dispersion (GVD) and third-order dispersion (TOD) characteristics. We also investigate the relationship between symmetry properties and their influence on dispersion characteristics. Through symmetry manipulation, we gain a com ...More

Article 2024 Mühendislik Fakültesi Physica Scripta99 ( 6 ) 3 Views
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A New Electric Arc Furnace Model Based on Current Waveform Synthesis from Distributions of DFT Amplitudes and Power System Frequency

Özgül SALOR-DURNA

The research work presented in this paper proposes a field-data based method for modeling the behavior of the Electric Arc Furnace (EAF) currents for a tap-to-tap period. EAF current DFT distributions and fundamental frequency histograms obtained out of previously collected EAF currents are used to develop the proposed model, which offers a model for each phase of the EAF operation: boring, melting and refining. The model is verified by comparing the THD histograms and the flicker measurements of the original and the modeled EAF current waveforms. The aim of the proposed method is to provide a ...More

Article 2024 Mühendislik Fakültesi IEEE Transactions on Industry Applications 1 Views
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Easy-to-Implement Ultra-Thin, Wide-Band, and Multi-Functional Polarization Converter for K and Ka Band Applications

Mehmet ERTUĞRUL

This article presents an ultrathin, broadband, and multipurpose polarization converter design utilizing an anisotropic metasurface for K and Ka band. The proposed polarization converter, which has a single layer F4B as a substrate material with hexagonal-shaped metallic solid structure along with hexagonal ring with diagonal splits on its front surface and a background (a completely metallic surface) on its back, works as not only a circular polarization converter but also a linear polarization to circular polarization (LP to CP) converter. Its polarization conversion rate (PCR) is more than 9 ...More

Article 2022 Mühendislik Fakültesi Advanced Theory and Simulations5 ( 4 ) 128 Views
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Inverse design of ultra-compact photonic gates for all-optical logic operations

Mirbek TURDUEV

Logic gates have great importance in realization of rapid data transmission as well as low loss transfers. In this paper, a multi-objective inverse-design approach is implemented by using objective-first algorithm to design optical AND, OR, NAND and NOT logic gates on Si-platform at the design wavelength of 1.30 mu m. For all gates, the design area is fixed to 2.24 mu m x 2.24 mu m. The optical logic '1' output is accepted to be optical power values greater than 0.8 times of the input optical power. By implementing a Bias waveguide as well as two input ports, we made it possible to achieve log ...More

Article 2022 Mühendislik Fakültesi Journal of Physics D: Applied Physics55 ( 21 ) 76 Views
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Determination of Propagation Constants and Wave Impedance of Non-Reciprocal Networks From Position-Insensitive Waveguide Measurements

Mehmet ERTUĞRUL

A microwave method is proposed to determine the forward and backward propagation constants (gamma ⁺ and gamma ⁻) and the wave impedance ( z_w ) of reciprocal and non-reciprocal microwave networks whose positions are not known within their measurement cells (position-insensitive). The proposed method relies purely on analytical expressions and can also evaluate the reference plane transformation distances. Scattering parameter measurements at the X-band (8.2-12.4 GHz) of a reciprocal network (a waveguide straight) and a non-reciprocal network (a microwave phase shifter) arbitrarily positioned i ...More

Article 2022 Mühendislik Fakültesi IEEE Transactions on Microwave Theory and Techniques70 ( 5 ) 59 Views
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