Recep Tayyip Erdoğan Üniversitesi Kurumsal Akademik Arşivi
DSpace@RTEÜ, Recep Tayyip Erdoğan Üniversitesi tarafından doğrudan ve dolaylı olarak yayınlanan; kitap, makale, tez, bildiri, rapor, araştırma verisi gibi tüm akademik kaynakları uluslararası standartlarda dijital ortamda depolar, Üniversitenin akademik performansını izlemeye aracılık eder, kaynakları uzun süreli saklar ve yayınların etkisini artırmak için telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Micromechanical prediction of Elastic properties of unidirectional glass and carbon fiber-reinforced epoxy composites using the halpin–tsai model
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Zengah, Sahnoun; Slimani, Rabeh; Baltach, Abdelghani; Taghezout, Ali; Benhamena, Ali; Sekban, Dursun Murat; Uzun Yaylacı, Ecren; Yaylacı, Murat
This study presents a calibrated analytical micromechanical framework for predicting the linear elastic behavior of unidirectional glass fiber/epoxy and carbon fiber/epoxy composites over a wide range of fiber volume fractions. The approach combines the classical rule of mixtures for the longitudinal Young’s modulus with the semi empirical Halpin–Tsai equations to estimate the transverse Young’s modulus and the in-plane shear modulus. The framework is specifically formulated to support durability-oriented composite design through rapid and physically consistent estimation of elastic properties governing load transfer and stress distribution. Material parameters, including fiber and matrix Young’s moduli (Ef, Em), shear moduli (Gf, Gm), Poisson’s ratios (νf, νm), and fiber volume fraction (Vf up to 0.80), are taken from established material property databases and implemented within a literature-informed modeling scheme. To preserve physical realism at high fiber contents, a shear correction factor is introduced for Vf > 0.50 to account for microstructural interaction and fiber clustering effects. The predicted effective elastic constants (E1, E2, G12, ν12) exhibit consistent and physically meaningful trends across the full fiber volume fraction range. The model predictions were evaluated against trends widely reported in the composite micromechanics literature, and the results showed overall agreement in the nonlinear reduction in stiffness gains at elevated fiber volume fractions. Comparative results indicate that carbon fiber/epoxy composites achieve up to approximately 30% higher stiffness than glass fiber/epoxy systems at equivalent fiber contents, reflecting the influence of stiffness contrast on composite response. The analysis further indicates that stiffness saturation begins approximately in the Vf = 0.60–0.70 range, where the incremental gains in E2 and G12 become noticeably smaller for both composite systems. This behavior provides design-relevant guidance by showing that, beyond this range, further increases in fiber content may offer limited stiffness improvement relative to the associated manufacturing complexity. Overall, the calibrated Halpin–Tsai methodology offers a practical and computationally efficient tool for preliminary evaluation and design-stage optimization of the elastic performance of high-performance composite structures.
Novel 3D spherical CoN4-based alginate beads towards efficient activation peroxymonosulfate for anti-inflammatory drug degradation in a continuous flow column
(Elsevier, 2026) Tokçalar, Soner; Demir, Adem; Keleş, Turgut; Özçifçi, Zehra; Akçay, Hakkı Türker; Bıyıklıoğlu, Zekeriya
The rapid increase in global pharmaceutical consumption has raised concerns over environmentally persistent drug residues. Herein, a monoatomic-planar phthalocyanine cobalt complex/calcium alginate bead composite (CoN4/Alg) was synthesized and applied as a peroxymonosulfate (PMS) activator for diclofenac sodium (DCF) degradation. CoN4 was immobilized into alginate beads at varying loadings (4, 10, and 25 wt%), with 25% showing the highest catalytic activity. Under optimal conditions, 98% DCF removal was achieved within 30 min using 0.65 mM PMS. Beyond DCF, the 25-CoN4/Alg composite efficiently degraded Rhodamine B (92% in 30 min) and ciprofloxacin (91% in 35 min). In a continuous flow system, 83% pollutant removal was sustained over 48 h. Radical quenching experiments identified singlet oxygen and superoxide radicals as the primary reactive species, while hydroxyl and sulfate radicals played negligible roles. Mechanistic analysis confirmed that Co(II) sites in CoN4 facilitated electron transfer to PMS, driving reactive oxygen species generation. Phytotoxicity tests further demonstrated that DCF solutions treated with the CoN4/Alg/PMS system exhibited markedly reduced toxicity, with degraded 7.5 ppm DCF showing no inhibitory effect on wheat seed germination (80%), in contrast to untreated DCF. These findings underscore the synergistic role of heteroatom doping in enhancing PMS activation and highlight the potential of CoN4/Alg as a practical and sustainable catalyst for the removal of persistent pharmaceutical pollutants in wastewater treatment.
Rethinking residents’ support for sustainable tourism development: integrating social exchange theory and environmental concern
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Erkılıç, Eren; Karakuş, Yusuf; Onat, Gökhan
This study argues that local communities’ support for sustainable tourism development cannot be explained solely by the perceived benefit–cost balance, and aims to extend Social Change Theory (SET) from an environmental concern perspective. In the existing literature, local community support is largely based on rational assessments; however, the explanatory power of this approach remains limited, particularly in destinations with high environmental concern. Accordingly, this study examines the mediating role of environmental concern in the relationship between perceived tourism impacts and support for tourism development (STD), thereby testing the conditional nature of such support. Research data were collected via a structured survey from local residents (n = 414) in Rize, one of Turkey’s environmentally sensitive destinations, and the proposed theoretical model was analyzed using structural equation modeling (SEM). The findings indicate that perceived personal benefits and the positive effects of tourism significantly increase local residents’ satisfaction and their STD. In contrast, it was determined that perceived negative impacts do not directly reduce support; rather, this relationship emerges indirectly through environmental concern. These results reveal that local community support is not an automatic response but a conditional process shaped within the framework of environmental values and sustainability conditions. The study re-evaluates the explanatory power of SET through a mechanism that incorporates environmental concern and offers a more comprehensive framework for understanding local community behavior in the context of sustainable tourism. The findings highlight the decisive role of incorporating environmental sensitivities in tourism planning on local support, providing important implications for policymakers.
Do laser-activated irrigation protocols improve endodontic success? A prospective clinical comparison of 1-year periapical healing with sonic, ultrasonic, manual dynamic and conventional techniques
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Çiçek, Medine; Şanal Çıkman, Ahter; Günaçar, Dilara Nil
Background: Successful healing of chronic apical periodontitis after endodontic treatment requires a reduction in the size of the radiolucent area and the healing of the bone. This study aimed to compare the effects of different irrigation activation techniques on healing in single-rooted mandibular premolar teeth with periapical lesions of endodontic origin. Methods: A total of 132 systemically healthy patients with mandibular single-rooted premolar teeth and a periapical index (PAI) score ≥ 3 were assigned to five experimental groups (Sonic activation, Passive ultrasonic irrigation, Photon-Induced Photoacoustic Streaming, Shock Wave Enhanced Emission Photoacoustic Streaming and Manual dynamic activation) and a control group (Conventional Syringe Irrigation). After access cavity preparation, the canals were prepared up to three sizes larger than the initial apical diameter with 5 mL of 2.5% NaOCl used between each file. Final irrigation was performed via the assigned activation system. The root canals were obturated with gutta-percha in a single visit. The effects of the activation systems on healing were compared at 1-year follow-up. The primary outcome measure was the change in lesion diameter. PAI score and fractal dimension (FD) were evaluated as secondary outcomes. Results: At the 1-year follow-up, FD values significantly increased, PAI scores and lesion size decreased in all groups compared with baseline (p < 0.001). However, the increase in FD was comparable among the irrigation groups (p > 0.05). In contrast, lesion size reduction and PAI-based healing rates favored the laser-activated groups. The PAI scores and lesion size in the control group were significantly greater than that in the laser groups (p < 0.05). Conclusions: At the 1-year follow-up, all the groups presented similar FD increases, while the laser irrigation groups presented significantly greater reductions in lesion size than did the control group.
Influence of obesity on peri-implant health: a cross-sectional clinical and biochemical study
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Keskin, Mine; Zihni Korkmaz, Meltem; Bostan, Semih Alperen; Atak, Mehtap
Background: Obesity is associated with alterations in the immune response through increased systemic inflammation. This systemic inflammatory state may increase the risk of peri-implantitis, a condition characterized by infection and tissue destruction around dental implants. Therefore, this cross-sectional clinical study aimed to investigate the association between obesity and peri-implant health. Methods: In this observational clinical study, a total of 80 patients were evaluated, including a peri-implant healthy non-obese control group (CG) (n = 20), peri-implantitis non-obese group (PG) (n = 20), peri-implant healthy obese group (OG) (n = 20), and peri-implantitis obese group (POG) (n = 20). Peri-implant clinical measurements (plaque index [PI], gingival index [GI], bleeding on probing [BOP], and probing depth [PD]) were obtained from the participants. In addition, tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and matrix metalloproteinase-8 (MMP-8) levels were measured in peri-implant crevicular fluid (PICF) samples. Results: PI, GI, BOP, and PD levels were significantly higher in the POG and PG than in the other groups (p < 0.05). PICF volume was found to be higher in the POG and PG than in the control group (p < 0.05). TNF-α levels increased significantly in all groups compared with the control group, and IL-1β levels were highest in the POG (p < 0.05). Conclusions: The findings of this cross-sectional study suggest a potential association between increased proinflammatory cytokine levels and altered peri-implant inflammatory responses in patients with obesity. Trial registration: This study was registered on ClinicalTrials.gov (Identifier: NCT07183163) on 18 September 2025 (retrospectively).
