Istanbul Bilgi University

This study presents a validated computational fluid dynamics (CFD) model of the Slagging Fixed-Bedgasifier, developed in OpenFOAM to simulate pure lignite, pure biomass, and coal-biomass co-gasification under pressurised oxygen-steam conditions. The main problem addressed in this study is the lack of a validated CFD-based engineering framework for assessing the fuel-flexible operation of slagging fixed-bed gasifiers using high-ash Turkish lignites and biomass blends under pressurised oxygen-steam conditions. The study therefore aims not only to predict syngas composition but also to identify operating conditions that improve hydrogen yield, reduce CO2 emissions, and maintain cold gas efficiency. Two Turkish lignites (Tun & ccedil;bilek and Soma) and selected biomass feedstocks (spruce wood, corn cob, wheat straw) were characterised by proximate and ultimate analyses. The model employs detailed devolatilisation, char oxidation, and gas-phase reaction submodels coupled with the Partially Stirred Reactor (PaSR) turbulence-chemistry interaction framework. Numerical predictions for syngas composition, hydrogen-to-carbon monoxide ratio (H-2/CO), and cold gas efficiency (CGE) were compared with experimental reference bands from peer-reviewed Slagging Fixed-Bed gasification studies. Across all cases, CFD predictions fell within experimental ranges, with relative deviations of +/- 3-4% for H-2, +/- 2-3% for CO, +/- 5% for CO2, and +/- 2% for CGE; CH4 showed slightly higher deviations (up to +/- 10%) due to its low concentration. Pure spruce wood achieved the highest hydrogen content (45.1 vol%), while Tun & ccedil;bilek lignite produced 34.2 vol% H-2 with CGE of 78%. Biomass co-feeding (20-40 wt%) increased hydrogen yield by 15-25% and reduced CO2 emissions by up to 21.8% without compromising CGE (>80%). The validated model demonstrates robust predictive capability for both single-feed and co-gasification scenarios, providing a reliable basis for optimisation studies. Parametric analysis confirmed that optimal O-2/C ratios were similar to 0.8 for coal and similar to 0.6 for biomass, with S/C above 1.0 increasing H-2 but slightly reducing CGE. These findings support the use of fuel-flexible Slagging Fixed-Bed units for hydrogen-oriented syngas production and partial decarbonisation in coal-based energy infrastructure.

Political campaigns build a bridge between candidates and voters by providing information and persuasion. . Mobilizing strategies rely on a certain repertoire, focusing on salient issues that candidates believe will make them appear more confident. However, the nature of political contests does not allow candidates to ignore their rivals' appeals; instead, they respond in ways that lead them to adopt similar frames, generating issue convergence. This article aims to scrutinize the discursive shift of Kemal K & imath;l & imath;& ccedil;daro & gbreve;lu, who conducted the 2023 presidential campaign under the Nation Alliance. The context-based competition and the condensed electoral schedule in allow us to examine how mainstream opposition blocs can be influenced by more nationalist and extreme narratives. The article argues that the electoral campaign initially framed inclusiveness articulating '' togetherness '' and shared grievances. For the second round, the campaign tone shifted toward a more nativistand exclusiveness, emphasizing issues of anti-migration, criminalization and '' the protection of Turkish women ''.

Based on the unified shear deformation theory, this paper presents the free vibration analysis of linear, isotropic, homogeneous beams resting on a Winkler elastic foundation. Unlike existing transfer matrix formulations that operate on four-variable state-space systems, the present work establishes a six-variable state-space framework in which an arbitrary shear strain function is incorporated into the formulation solely through integral coefficients, enabling the unified treatment of seven distinct shear deformation models without theory-specific rederivation. The governing equations and boundary conditions are derived using energy principles. Natural frequencies are determined using the initial value method via both exact transfer matrix (ETM) and approximate transfer matrix (ATM). Since the analytical derivation of the ETM involves a sixth-order characteristic polynomial with prohibitively complex expressions, an ATM is constructed using a three-term truncated matricant series expansion, thereby eliminating the need for eigenvalue extraction. A correction methodology based on the chain property is proposed to ensure convergence to the exact solution. The formulation reduces the frequency determinant from a 6 × 6 system to a 3 × 3 system for each boundary condition. Systematic comparisons across different shear deformation theories, boundary conditions, slenderness ratios, and foundation stiffness values confirm the accuracy and reliability of the proposed approach, with ATM results converging to the ETM reference within less than 0.25

LuFeO3 (LFO) is a perovskite oxide with promise for optical and electroceramic applications. In the present study, LFO and Co-substituted compositions (LFO, LuFe0.95Co0.05O3, and LuFe0.90Co0.10O3) were synthesized by a conventional solid-state route and characterized by SEM, Raman spectroscopy, diffuse reflectance, and broadband dielectric/impedance measurements. Co substitution alters the powder microstructure, yielding more irregular agglomerates composed of finer sub-units than undoped LFO. Dielectric spectra showed that the loss tangent (tanδ), the dissipation factor, of investigated samples was below 1 over the studied temperature–frequency window. It was seen that Co substitution decreased dielectric loss in the mid-to-high frequency region but raised low-frequency loss at advanced temperatures. The real part of impedance Z^' declined with both temperature and frequency, and Nyquist plots displayed depressed arcs, indicating non-Debye behavior with distributed grain and grain-boundary contributions. Arrhenius analysis of relaxation maxima yielded activation energies of ∼ 0.32–0.76 eV, consistent with oxygen-vacancy energies. Raman spectra revealed Co-induced lattice perturbations, including mode broadening/attenuation and red-shifts in the 200–600 cm− 1 range, together with a strengthened stretching feature near 600–650 cm− 1. Kubelka–Munk analysis was utilized to determine the band gaps of the studied samples, 2.19 eV (LFO), 2.29 eV (5

This study pioneers the evaluation of nearly zero-energy building (nZEB) transformation potential in publiclyowned sports facilities in T & uuml;rkiye. Focusing on the Fatih Sports Complex in Istanbul, the research aims to alignthe building with the nZEB criteria defined in the Building Energy Performance (BEP) Regulation and support Turkiye's 2030 greenhouse gas (GHG) emission reduction target of 41%. The study followed a three-phase approach. In the first phase, the building envelope was upgraded in line with the TS825:2024 standard, and artificiallighting systems were redesigned to meet ANSI/ASHRAE 90.1:2022 lighting power density (LPD) limits, raisingthe building's Energy Performance Certificate (EPC) rating to Class B. In the second phase, 225 half-cutphotovoltaic (PV) panels (550 Wp each) were installed on the roof, supplying 11% of the building's primary energydemand from renewable sources. In the third phase, the combined measures achieved a 48% reduction in totalGHG emissions. The originality of this study lies in being the first in Turkiye to model and simulate acomprehensive nZEB transformation of a public sports facility, integrating energy performance improvements,renewable energy integration, and emission reduction. The results offer a practical roadmap for public buildings inachieving national energy efficiency and carbon neutrality goals.