https://hdl.handle.net/20.500.12960/1 Research Outputs | TR-Dizin | WoS | Scopus | PubMed 2026-05-10T11:53:00Z https://hdl.handle.net/20.500.12960/1825 From mill scale to Sr-ferrite permanent magnets; upcycling by additives Gunduz Akdogan, Nilay; Kalkavan, Duru; Ghorbanighoshchi, Shabnam; Akdogan, Ozan This study examines the sustainable production of strontium hexaferrite by recycling mill scale, a by-product of steel manufacturing, as a source of iron. Strontium, designated as a critical raw material by the European Union, is essential for high-demand magnetic applications. In this study, various additives, including Al2O3, Cr2O3, Co3O4, and La2O3, were incorporated during the synthesis process to enhance the magnetic properties of the resulting strontium hexaferrite. Additives were included in the structure using the mechanochemical method. The results show that the incorporation of these additives has a significant influence on the coercivity, remanence, and overall magnetic anisotropy of SrFe12O19. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.12960/1824 Modeling Gradual and Joint Coverage in Location Problems Karatas, Mumtaz; Eriskin, Levent; Yakici, Ertan Location problems are a core area of research within OR/MS and decision sciences, with diverse applications in logistics, facility location, healthcare, defense, energy and transportation. One important feature of location problems is the coverage of demand or service areas by facilities, which can have significant economic, social, and environmental implications. Conventional models often assume binary or deterministic coverage, where a facility either fully covers a demand point or does not cover it at all. Although this simplification is useful for theoretical derivations, back-of-the-envelope calculations, and performance comparison, it overlooks the nuances and complexities of real-world scenarios. In this study, we provide an overview of the modeling challenges in location problems that incorporate gradual and joint coverage, where multiple facilities provide partial and cooperative coverage to demand points. Based on previous studies in this domain, we present mathematical formulations, and discuss techniques for linearization and approximation. As an illustrative example, we discuss a capacitated minimal covering location problem (MCLP) adapted from [21], which aims to determine the location and size of undesirable facilities in a given region. We start by introducing the nonlinear formulation that minimizes the sum of demand covered by those undesirable facilities. Subsequently, we introduce three integer linear programming formulations given in [21], two of which involve linear approximations based on a separable programming approach and a tangent line approximation method, while the third involves an exact reformulation of the problem. We also discuss the impact of linearization approximation errors on solution quality and time. © 2026 by World Scientific Publishing Co. 2025-01-01T00:00:00Z https://hdl.handle.net/20.500.12960/1823 From efficiency to resilience: Strategic shifts in maritime organizations through digitalization, ESG, and human capital (2018 - 2025) Arslan, Aykut; Akturan, Abdülkadir Most existing maritime research examines digitalization, ESG pressures, and human capital separately. This paper fills the gap in explaining how the three factors dynamically reshape strategic orientations in the highly unstable post-2020 period. It explains how maritime organizations reconfigured their strategies between 2018 and 2025. The research is based on sixteen semi-structured interviews with top professionals from different segments of the maritime ecosystem across Europe and Asia, analyzed according to Gioia methodology. The main finding is a structural transformation from an efficiency strategy before 2020 toward a resilience strategy after 2020. It finds that this shift emanates from an interaction between digitalization (a ‘sensing’ capability) and human capital (a ‘reconfiguring’ capability). Seven strategic patterns are identified, which include new forms such as glocal ESG adaptation-blending global rules with local innovation-and hybrid leadership--blending technical, digital, and human skills-in addition to more traditional forms like asset diversification or trade pattern flexibility through chartering tonnage. This study is original as it is the first integrated empirical analysis of the interaction, with a rare pre/post-2020 temporal comparison conceptualizing new patterns as specific dynamic capabilities for the maritime sector. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.12960/1822 Comprehensive first-principles studies of structural, dynamical, elastic, electronic, thermoelectric, and thermodynamic properties of Half-Heusler TiGaAu compound Belbachir, Raghed; Belkharroubi, Fadila; Al-Douri Y.; Sidjilani, Fatima; Khelfaoui, Friha; Azzi, Saliha; Belmiloud, Nawal; Rahmani, Rabea; El Hadj, Adel Abdellah; Bendella, Sid Ahmed The structural, elastic, electronic, dynamical, thermoelectric (TE), and thermodynamic properties of Half-Heusler (HH) TiGaAu compound with valence electron count (VEC) of 8, are investigated usingfirst-principles density functional theory (DFT) in conjunction with Boltz- TraP2 transport modeling. The Type 1 nonmagnetic phase's optimized cubic structure meets the Born mechanical stability requirements and its dynamical stability, which is confirmed by the phonon dispersion's lack of imaginary frequencies. Due to the presence of a heavy Au atom, TiGaAu exhibits pronounced elastic anisotropy and is mechanically strong, stiff, and ductile according to elastic constants. With a moderate band gap, 0.681 eV (mBJ-GGA), the electronic band structure favors balanced electron{hole transport and reveals an indirect semiconductor character. Thermoelectric analysis reveals that TiGaAu has competitive values up to 900K and high Seebeck coeffcients exceeding 1000 μVK-1 at room temperature, with p-type carriers performing marginally better. Effective carrier transport and advantageous band convergence are reflected in the power factor's steady temperature increase. Though mBJ-GGA predicts somewhat higher Seebeck and power factor values at higher temperatures - an improvement ascribed to its more accurate description of electronic structure - the results obtained using GGA and mBJ-GGA are consistent across the whole range. Furthermore, an excellent thermal stability and moderate lattice softening are confirmed by the smooth variation of temperatureand pressure-dependent thermodynamic properties, including heat capacities, entropy, thermal expansion coeffcient, Debye temperature and Grüneisen parameter. TiGaAu is a promising option for high-temperature energy conversion applications as it combines a strong mechanical resilience, stable lattice dynamics and effcient thermoelectric behavior. 2026-01-01T00:00:00Z