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
Numerical analysis of crack nucleation in contact mechanics under fretting wear loading
(Techno-Press, 2025) Baltach, Abdelghani; Benhamena, Ali; Chaouch, Mohamed Ikhlef; Zagane, Mohammed El-Sallah); Yaylacı, Murat; Öztürk, Şevval; Özdemir, Mehmet Emin; Yaylacı, Ecren Uzun
This study examines how contact pressure and shear stress act on contact areas subjected to fretting loading. The research utilizes a non-linear finite element method, which calculates both normal and shear stresses, to assess the fracture behavior of flat surfaces. The study particularly emphasizes the influence of shear forces on the distribution of these stresses. A multiaxial fatigue criterion is used to identify potential crack initiation points within the contact zone. The critical point for crack initiation along the contact line is determined by evaluating the maximum values of hydrostatic and deviatoric stresses. The size of the regions experiencing sticking and slipping behavior is directly related to the levels of contact pressure and shear force. Importantly, the study found a strong agreement between the finite element method simulations and the analytical results.
Optimizing PV systems in high-temperature environments: A SWOT-based analysis of cooling technologies
(Elsevier, 2025) Abdirahman, Abdinasir Ahmed; Asif, Muhammad; Cüce, Erdem; Ahmed, Ijaz; Alqahtani, Mohammed
Solar photovoltaic (PV) has emerged as the leading renewable energy technology. However, high temperatures significantly impact the efficiency of PV systems. The Gulf Cooperation Council (GCC) region, with its abundant solar resources and solar irradiance levels exceeding 2,200 kWh/m2/year, has the potential to lead global solar energy initiatives. However, extreme temperatures, often surpassing 50 degrees C, reduce photovoltaic (PV) system efficiency by up to 25%, necessitating the implementation of cooling technologies to enhance performance. The study discusses prominent passive and active cooling strategies, including natural air ventilation, reflective coatings, phase change materials, water-based cooling, nanofluid cooling, and photovoltaic-thermal (PV/T) hybrid systems. Despite their benefits, cooling technologies encounter challenges in the harsh climate of the GCC. The study also conducts a Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis of prominent PV cooling technologies. The SWOT analysis highlights strengths, such as improved PV performance and energy efficiency, while identifying weaknesses like high initial investments and maintenance demands. Opportunities for technological advancements and integration with renewable energy initiatives further emphasize the potential of cooling solutions in enhancing PV system sustainability. Each cooling approach presents unique advantages and challenges in terms of cost, maintenance, cooling efficiency, and environmental impact. This study delivers the first SWOT-based strategic evaluation of PV cooling technologies specifically tailored to the GCC's extreme climate bridging a key research gap by integrating technical, economic, and regional dimensions absent in prior works.
Predictors of long-term atrial fibrillation following percutaneous coronary intervention in acute coronary syndrome
(Nature Research, 2025) Durak, Hüseyin; Çetin, Mustafa; Özyıldız, Ali Gökhan; Ergül, Elif; Duman, Hakan; Şahin, Müjgan Ayşenur; Özsipahi, Ahmet; Tuncer, Ahmet Yasin; Emlek, Nadir
The development of atrial fibrillation (AF) has important prognostic implications in patients undergoing percutaneous coronary intervention (PCI), due to the concurrent need for both antiplatelet and anticoagulant therapies. This study aimed to evaluate the long-term incidence and predictors of AF in patients with acute coronary syndrome (ACS) undergoing PCI. We prospectively enrolled 337 consecutive ACS patients in sinus rhythm who underwent PCI and did not develop AF during hospitalization. Patients were followed every six months for up to 72 months. Follow-up data were available for 300 patients (89%); 37 patients were lost to follow-up. At the end of follow-up, 34 patients (11.3%) had developed AF. Kaplan–Meier analysis demonstrated that mitral annular calcification (MAC) was significantly associated with an increased incidence of AF from the early stages (χ2 = 24.620, log-rank p < 0.001). Multivariate Cox regression identified body mass index (BMI) (HR: 1.070; 95% CI: 1.010–1.130; p = 0.022), left ventricular ejection fraction (LVEF) (HR: 0.942; 95% CI: 0.918–0.916; p < 0.001), mitral annular late diastolic velocity (Am) (HR: 0.785; 95% CI: 0.707–0.872; p < 0.001), and mitral annular calcification (MAC) (HR: 4.066; 95% CI: 1.976–8.368; p < 0.001) as independent predictors. These findings provide important insights into the long-term risk of AF after PCI in ACS patients and may support early identification and management of high-risk individuals.
The relationship between premenstrual syndrome and circadian rhythm, depressive mood, and anxiety
(Nature Research, 2025) Yamak, Özlem Akın; Şentürk, Şenol; Kağıtçı, Mehmet; Altınsoy, Canan; Puşuroğlu, Meltem
Premenstrual syndrome (PMS) is prevalent among young women and may influence both mental well-being and circadian patterns. Premenstrual Syndrome (PMS) has been associated with circadian rhythm disruptions, as circadian rhythms regulate physiological and biological functions throughout the day. This study investigates the impact of PMS on mental health and its association with chronotype and social jetlag among nursing students. This cross-sectional descriptive and comparative study included 98 female nursing students enrolled at a university during the spring semester of 2023. Participants who provided informed consent via Google Forms were classified into PMS and without PMS groups according to their Premenstrual Syndrome Scale (PMSS) scores. Data were collected using the PMSS, Morningness-Eveningness Questionnaire (MEQ), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), and Social Jetlag Questionnaire. The participants’ mean age was 21.13 ± 1.46 years, their mean body mass index (BMI) was 21.75 ± 3.04, and the mean total PMSS score was 135.45 ± 42.64. Students with PMS exhibited significantly higher depression (p < 0.001, O. R = 1.126) and anxiety scores (p < 0.001, O. R = 1.094) than those without PMS. PMS presence significantly affected both depression and anxiety scores (p < 0.001, Std. Beta = 0.474; p < 0.001, Std. Beta = 0.429, respectively). No statistically significant impact of PMS on social jetlag or chronotype was observed. However, in the group with PMS, a positive and significant correlation was found between PMSS total score and social jetlag (r = 0.351, p = 0.013) and BAI total scores (r = 0.350, p = 0.013). This study demonstrates that PMS significantly affects the mental health of nursing students, as those with PMS reported higher levels of depression and anxiety. Furthermore, the finding that social jetlag and anxiety increased as PMS severity increased suggests that circadian rhythm irregularities may be a factor to consider in symptom management. This study has some limitations, including the use of self-reported data and a relatively small sample size, which may affect the generalizability of the findings. It is recommended that future research should confirm these relationships with larger samples and longitudinal designs.
Investigation of interior seed effects on levitation force in Melt-Grown YBCO superconductors by experimental and numerical methods
(Elsevier, 2025) Öztürk, Ufuk Kemal; Abderrahmane, Babe Cheikh; Uzun, Oğuzhan; Abdioğlu, Murat; Güner, Sait Barış; Quéval, Loïc
This study introduces a novel Top-Interior Multi-Seeding Melt Growth (TI-MSMG) technique for fabricating high-performance YBCO bulk superconductors and explanations some physical background based on FEM modelling. The depth of the interior seed was gradually changed as 0, 2 and 4 mm (samples S0, S2 and S4, respectively) from the upper surface of the samples. By incorporating an interior seed into the precursor pellet, the TI-MSMG method enables systematic control over grain morphology and critical current density distribution. Magnetic levitation and guidance forces were measured using a three-axis force measurement system, and a two-dimensional finite element method (FEM) model based on the H-formulation of Maxwell’s equations was developed to simulate the electromagnetic behaviour of the superconductors with different seed positions. Experimental and modelling results reveal that samples incorporating an interior seed (S2) exhibit significantly enhanced levitation and guidance forces compared to S0 and S4, attributable to improved inter-domain interactions and morphological consistency, so a better current coupling. The numerical simulations accurately reproduced the experimental findings, confirming the validity of the modelling approach. These findings indicate that the TI-MSMG process not only addresses some limitations of conventional top-seeding methods but also enhances levitation force performance through optimization of interior seed depth, thereby enabling more efficient and tailored designs for high-temperature superconducting systems such as magnetic levitation, energy storage, and superconducting motors.
