Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Transmittance of Gaussian Beam in Anisotropic Jet Engine Exhaust Turbulence(Pergamon-Elsevier Science Ltd, 2026) Baykal, YahyaTransmittance is a metric that provides information on how much of the intensity is transferred to the receiver for a given medium. One of the definitions of transmittance is the ratio of the average received intensity in the presence of turbulence to the received intensity in the absence of turbulence. Under such definition, transmittance is found in an anisotropic jet engine exhaust turbulent environment. For various receiver points, transmittances versus the wireless optical communication (WOC) link and anisotropic jet engine exhaust turbulence parameters are presented. The results are useful for designers of WOC links that are installed in the premises such as the airports that possess jet engine exhaust turbulence.Article Mitigation of Laser Beam Fluctuation and Performance of Probability of Fade in Weak Ocean Turbulence(Pergamon-Elsevier Science Ltd, 2026) Gercekcioglu, Hamza; Baykal, YahyaUtilizing the Rytov method in weakly turbulent oceanic medium, minimum scintillation index of sinusoidal Gaussian (SG) laser beams, named as the optimum beam (OB), is investigated for the underwater wireless optical communication (UWOC). Horizontal link between any underwater vehicles is considered. The formulation of the on-axis scintillation index of these beams is derived analytically, and the minimum scintillation index is determined with suitable adjustment of the complex displacement parameters. The complex displacement parameters are identified and tabulated for the selected propagation distance and source size. Obtained scintillation index results are drawn against the propagation length and source size. When compared with the plane, spherical, collimated, focused Gaussian, cos-Gaussian and cosh-Gaussian beams, OB is found to possess essential advantage. Additionally, with the obtained scintillation index values, probabilities of fade of these beams are calculated and their behaviors are also presented. OB also has a significant advantage when considering the fade probability.Article A Class of Time-Fractional Dirac Type Operators(Pergamon-Elsevier Science Ltd, 2021) Baleanu, Dumitru; Restrepo, Joel E.; Suragan, DurvudkhanBy using a Witt basis, a new class of time-fractional Dirac type operators with time-variable coefficients is introduced. These operators lead to considering a wide range of fractional Cauchy problems. Solutions of the considered general fractional Cauchy problems are given explicitly. The representations of the solutions can be used efficiently for analytic and computational purposes. We apply the obtained representation of a solution to recover a variable coefficient solution of an inverse fractional Cauchy problem. Some concrete examples are given to show the diversity of the obtained results. (c) 2020 Elsevier Ltd. All rights reserved.Article Developing and Validating a Rubric-Based Approach to Quality Assurance in Turkish Higher Education(Pergamon-Elsevier Science Ltd, 2025) Akkoyunlu, Buket; Bardakci, Salih; Yildirim, Sibel Aksu; Avsaroglu, M. Dilek; Uludag, Gonca; Kocer, Ayhan; Elmas, MuzafferThis study, initiated by the Turkish Higher Education Quality Council (THEQC), develops and validates a rubricbased approach for evaluating institutional quality assurance (QA) processes within the Turkish higher education ecosystem. Effective quality assurance (QA) in higher education requires evaluation tools that are methodologically robust, responsive to institutional needs, and aligned with international benchmarks. A rubric-based approach offers a structured and transparent framework for consistent assessments. The rubric was created through an iterative, evidence-based process incorporating expert feedback, international benchmarks, site visits, and prior research. It consists of 22 main criteria across four key domains-Leadership, Governance and Quality; Learning and Teaching; Research and Development; and Service to Society-subdivided into 46 sub-criteria, each assessed on a five-point maturity scale. The validity and reliability of the rubric were rigorously examined. Content validity was established through evaluations by 10 QA professionals, addressing four key dimensions: relevance, alignment with the intended domain, appropriateness for the target audience, and clarity of language. Construct and criterion validity were assessed through consistency checks and usability analyses, with data collected from 252 external evaluators across 57 higher education institutions. Additionally, 360-degree feedback was gathered from both external evaluation teams and the institutions involved in the evaluation process. Results: demonstrate strong content validity (Lawshe coefficient =1.00, p < .05), high interrater consistency, and strong usability across various evaluator groups. Further evaluation confirmed the rubric's applicability and robustness across diverse institutional contexts. This study concludes that the developed rubric is a reliable and valid tool for enhancing and evaluating quality assurance practices in higher education.Correction Corrigendum To “Numerical Investigation of Magneto-Thermal Impact on Phase Change Phenomenon of Nano-PCM Within a Hexagonal Shaped Thermal Energy Storage” [Appl. Thermal Eng., (2023) 223, 119984](s1359431123000133)(10.1016/J.applthermaleng.2023.119984)(Pergamon-Elsevier Science Ltd, 2025) Izadi, Mohsen; Sheremet, Mikhail; Hajjar, Ahmad; Galal, Ahmed M.; Mahariq, Ibrahim; Jarad, Fahd; Hamida, Mohamed Bechir Ben; Ben Hamida, Mohamed BechirArticle Citation - WoS: 1Citation - Scopus: 1Left-Definite Fractional Hamiltonian Systems: Titchmarsh-Weyl Theory(Pergamon-Elsevier Science Ltd, 2025) Ugurlu, EkinHamiltonian systems are useful when formally symmetric boundary value problems generated by ordinary derivatives are considered. However, if the ordinary derivatives are changed by non-integer-order (fractional) derivatives, it is not easy to investigate the corresponding problems. In this paper, we introduce a systematic approach to dealing with fractional boundary value problems by constructing a fractional Hamiltonian system. In particular, we consider a left-definite system, and we construct nested-circles theory (Weyl theory) for this system of equations. Using the Titchmarsh-Weyl function, we prove that at least r-solutions of the 2r-dimensional system of equations should be Dirichlet-integrable on a given interval.Article Citation - WoS: 1Citation - Scopus: 1The Neural Correlates of Cognitive Load in Learning: an Fmri Study on Graph Comprehension(Pergamon-Elsevier Science Ltd, 2025) Ozcelik, ErolBackground: Cognitive load theory suggests that excessive demands on the human cognitive system can lead to cognitive overload and impaired learning. However, whilst the neural correlates of cognitive load are unclear, neuroimaging techniques such as functional magnetic resonance imaging (fMRI) may help provide answers to these questions. Aims: Considering this potential, this study aims to investigate which brain structures are associated with cognitive load through conducting an fMRI study on graph comprehension. Sample: The study's sample consists of 15 undergraduate students. Methods: Based on a within-subjects design, participants answered comprehension questions using split (i.e., high cognitive load) and integrated (i.e., low cognitive load) graphs whilst undergoing a magnetic resonance imaging (MRI) scan. Results: Participants exhibited lower levels of accuracy and slower reaction times with split graphs compared to integrated graphs. The fMRI data showed that cognitive load was associated with the frontoparietal network. More specifically, the multiple demand network revealed greater activation in graphs with higher cognitive load than those of lower cognitive load. Conclusions: These findings may indicate that a domain-general attentional brain network is responsible for cognitive load.Article Citation - WoS: 18Citation - Scopus: 22A Class of Time-Fractional Dirac Type Operators(Pergamon-Elsevier Science Ltd, 2021) Baleanu, Dumitru; Restrepo, Joel E.; Suragan, DurvudkhanBy using a Witt basis, a new class of time-fractional Dirac type operators with time-variable coefficients is introduced. These operators lead to considering a wide range of fractional Cauchy problems. Solutions of the considered general fractional Cauchy problems are given explicitly. The representations of the solutions can be used efficiently for analytic and computational purposes. We apply the obtained representation of a solution to recover a variable coefficient solution of an inverse fractional Cauchy problem. Some concrete examples are given to show the diversity of the obtained results. (c) 2020 Elsevier Ltd. All rights reserved.Article Asymptotic Integration of (1 + Α) -Order Fractional Differential Equations(Pergamon-Elsevier Science Ltd, 2011) Baleanu, Dumitru; Mustafa, Octavian G.; Agarwal, Ravi P.; Bleanu, DumitruWe establish the long-time asymptotic formula of solutions to the (1+α)-order fractional differential equation 0iOt1+αx+a(t)x=0, t>0, under some simple restrictions on the functional coefficient a(t), where 0iOt1+α is one of the fractional differential operators 0Dtα(x′), (0Dtαx)′= 0Dt1+αx and 0Dtα(tx′-x). Here, 0Dtα designates the Riemann-Liouville derivative of order α∈(0,1). The asymptotic formula reads as [b+O(1)] ·xsmall+c·xlarge as t→+∞ for given b, c∈R, where xsmall and xlarge represent the eventually small and eventually large solutions that generate the solution space of the fractional differential equation 0iOt1+αx=0, t>0Article Generalized (C)-conditions and related fixed point theorems(Pergamon-Elsevier Science Ltd, 2011) Karapınar, Erdal; Taş, Kenan; Karapnar, ErdalIn this manuscript, the notion of C-condition [K. Suzuki, Fixed point theorems and convergence theorems for some generalized nonexpansive mappings, J. Math. Anal. Appl. 340 (2008) 1088-1095] is generalized. Some new fixed point theorems are obtained.