Vasil Tabatadze

This study proposes a two-variable fractional calculus–based modeling framework for analyzing gross domestic product (GDP) growth rates using key macroeconomic indicators of G8 countries and Türkiye over the period of 1998–2022. The economic variables considered include exports, imports, inflation, foreign direct investment, and unemployment rates, with data obtained from the World Bank. Caputo-type fractional derivatives combined with the least squares method are employed to construct two-variable economic models, where GDP growth rate is treated as the dependent variable. Multiple combinations of economic factors are systematically examined to evaluate their modeling performance. The accuracy of the proposed models is assessed using the Mean Absolute Percentage Error (MAPE). The results indicate that the export–inflation combination yields the lowest modeling error for Japan, while the inflation–unemployment combination produces the highest error for Russia. Overall, the findings demonstrate that fractional calculus–based bivariate models provide an effective and flexible framework for capturing nonlinear and memory-dependent dynamics in economic growth analysis.

This study aims to investigate the diffraction of electromagnetic plane waves generated by two concentric cylinders with slits placed at different positions. Unlike previous studies, this study investigates the previously unstudied rotational resonance characteristics and how they affect the near-field distributions. This analysis considers the diffraction for H-polarized plane waves. A semi-analytical approach is adopted to determine the basic physical properties such as resonances, near- and far-field radiation patterns. This method benefits from the integration of both analytical and numerical techniques. Since H-polarized waves are investigated, the Neumann boundary condition is applied and analyzed accordingly. After deriving the mathematical formulations for the current density, near- and far-field distributions, and total radar cross section, the results are compared with those obtained by the Method of Auxiliary Sources (MAS). The comparison confirms that the proposed approach is in good agreement with this established technique. The findings show that both the size of the apertures and the rotation angle play an important role in determining the radiation characteristics. Cite this article as: E. İşcan, R. Atlı, Ö. F. Alperen, K. Karaçuha and V. Tabatadze, "Analysis of size and orientation of apertures for H-polarized plane wave electromagnetic scattering by concentric perfectly conducting circular strips," Electrica, 26, 0255, 2026. doi:10.5152/electrica.2026.25255

This study investigates how altering the aperture size and impedance characteristics of a circular strip, when excited by a cylindrical wave, influences electromagnetic scattering. The focus is on understanding the impact of shifting the position of an H-polarized line source and adjusting parameters such as strip aperture, wave number, and impedance values on the overall behavior of the electromagnetic field. Our findings reveal that changes in the strip's aperture dimensions or wave number, even when regarding the latter's relation to the source, lead to significant alterations in the surrounding electromagnetic field. This scrutiny unveils a detailed interplay between these factors within this electromagnetic scenario. By examining these intricacies, our study sheds light on the substantial impact of subtle modifications in the strip's dimensions, combined with adjustments in wave and source characteristics, on the electromagnetic field. This understanding holds promise for advancements in diverse engineering applications.

The study presents electromagnetic scattering by arbitrarily located double strips with perfect electric and/or magnetic conducting surfaces. The study generalizes not only the physical dimension, location, and orientation of the strips but also, the boundary conditions on each strip are generalized and variable. It can be Dirichlet or Neumann boundary conditions. Since the study considers numerous parameters as the variable, the comparison between the present study and the literature is investigated in detail. Geometries such as parallelly located double strips with fractional boundary conditions, impedance double strips, and wedge problems are considered to compare. Besides, the proposed methodology is compared by the method of moments, the method of auxiliary sources, and the orthogonal polynomials approach. The suggested research investigates the electromagnetic scattering by finite wedge and arbitrarily located two strips with different boundary conditions and widths for the first time since each strip can have different widths and boundary conditions (Dirichlet or Neumann). The results reveal that the angle between the strips, the rotation of the strips, width of the strip have noticeable effects on the scattered field and total radar cross-sections. Between the strips, resonances are observed and their characteristics have a substantial dependency on the boundary conditions.

Aviation is one of the most global industries, and if we can model and predict a country’s air transportation flow and indicators ahead of time, we may be able to use it as a key decision-making tool for the management and operation process. This study proposes a new modeling, and prediction method that employs both fractional calculus and Multi Deep Assessment Methodology (MDAM) techniques. For the application, air passengers carried, air freight, available seat kilometers, number of flights, destination points, international travelers, international destination points, and international flight data between 2011 and 2019 for eight countries with the busiest airports were chosen. As a result, the highest modeling error was discovered to be Germany’s air transport freight factor expressed as a percentage of 1,59E-02. The percentage of predictions with errors less than 10% was 90.278. We also compared the performance of two different MDAM methodologies. The novel MDAM wd methodology proposed in this paper has a higher accuracy in aviation factors prediction and modeling.