Kırşehir Ahi Evran Üniversitesi Kurumsal Akademik Arşivi
DSpace@Kırşehir, Kırşehir Ahi Evran 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 etkisimi artırmak için telif haklarına uygun olarak Açık Erişime sunar.
Güncel Gönderiler
Synergistic Enhancement of Multi-Mode Fracture Toughness in Carbon Fiber-Reinforced Ultra-High Performance Concrete By Sialon Nanoparticles: Numerical İnsights and Experimental Validation
(Elsevier B.V., 2026) Çağlar, Hakan
Although various nanomaterials have been widely investigated for enhancing the mechanical and fracture properties of Ultra-High Performance Concrete (UHPC), the specific role of Sialon nanoparticles (SNPs) in modifying the multi-mode fracture resistance of carbon fiber-reinforced UHPC (CFR-UHPC) has not yet been addressed.This study examines the effects of SNPs on the fracture toughness of CFR-UHPC through a combined experimental–numerical framework. A high-fidelity three-dimensional multi-scale finite element model was developed, incorporating randomly distributed carbon fibers and an interfacial transition zone (ITZ) represented via traction–separation laws calibrated using a Genetic Algorithm (GA). The model was validated against cracked straight-through Brazilian disk (CSTBD) experiments conducted at crack inclination angles of α = 0°, 29°, and 45°, demonstrating strong agreement in both load–displacement responses and crack propagation patterns. Parametric simulations revealed that SNPs enhance fracture toughness across all fracture modes. The most pronounced improvement was observed in Mode II, where KIIc c increased by approximately 34 % at 2 wt% SNPs, while mixed-mode conditions (α ≈ 15°–45°) exhibited the highest ductility. Although SNP addition improved resistance to crack propagation, compressive ductility decreased at SNP contents above 4 wt% due to nanoparticle agglomeration, which introduced defects and promoted brittleness. The optimal SNP dosage for enhancing multi-mode fracture toughness was found to lie between 2 and 4 wt%, where matrix refinement induced by SNPs and fiber-bridging effects act synergistically without compromising ductility. Compressive strength also improved by ∼27 % at 4 wt% SNPs, albeit accompanied by reduced post-peak deformability. SEM analysis corroborated these findings by revealing improved matrix densification, more uniform microstructures, and enhanced fiber–matrix bonding at optimum SNP levels, whereas higher dosages produced visible clusters and micro-defects. These microstructural observations directly support the measured improvements in Mode I, Mode II, and mixed-mode fracture toughness. Collectively, the results provide practical guidelines for tailoring CFR-UHPC formulations with enhanced fracture resistance for demanding structural applications.
Machining Characteristics of Biodegradable Zn-2Mg-0.1Cu Alloy under Varying Cutting Conditions
(SAGE Publications Ltd, 2025) Köklü, Uğur; Bulutsuz, Asli Gunay; Koçar, Oğuz; Ayer, Önder; Basit, Sercan; ...; Yılmazer, Hakan
Biodegradable implant materials hold significant potential by degrading within the body after fulfilling their intended function. The advantages of such materials emphasize the need for increased diversity in functional biomaterials and further research in this area. This experimental study aims to develop and investigate Zn-2Mg-0.1Cu alloys and evaluate their machinability. To develop Zn-2Mg-0.1Cu alloys, high-purity elements were melted at 565°C under an argon atmosphere and cast into preheated steel molds. Homogenization at 350°C for 16 hours followed by quenching with iced water was applied to ensure uniform microstructure. The samples were examined using microstructural analysis, and mechanical tests were conducted to assess the effects of Cu addition. In the drilling process, the feed rate was initially kept constant at 200 mm/min, while the spindle speed was varied (2000, 4000, and 6000 rpm) to study the effects of spindle speed on the drilling results. Then, when the spindle speed was fixed at 5000 rpm, the feed rate was adjusted (150, 250, and 350 mm/min) and the effect of feed rate was studied. Drilling characteristics—including thrust force, chip formation, burr formation, surface morphology, and roughness—were analyzed to evaluate machinability. The addition of Cu led to secondary phase formation within the structure, increasing the hardness of the samples. The thrust force decreased by 4.5% at 2000 rpm, 6.3% at 4000 rpm and 1.4% at 6000 rpm in Cu added samples. At lower spindle speeds, the increased hardness from Cu addition resulted in shorter chip lengths. Additionally, Cu addition provided a more consistent and reduced surface roughness along the hole surface. The lowest average surface roughness was 0.446 µm for Zn-2Mg and 0.267 µm for Zn-2Mg-0.1Cu at 200 mm/min feed rate and 6000 rpm spindle speed, 0.385 µm for Zn-2Mg and 0.271 µm for Zn-2Mg-0.1Cu at 5000 rpm spindle speed and 150 mm/min feed rate. In summary, the analysis of these data indicates that Cu addition improved the machinability of the alloy.
Investigation of the Mechanic, Thermal, and Electrochemical Corrosion Behavior of Fe Effect on IN718 Produced By PM used in the Aviation İndustry
(Springer Science and Business Media B.V., 2025) İlgazi, Muhammed Enes; Balcı, Esra; Basit, Sercan; Dağdelen, Fethi; Mutlu, İlven
This study examined the microstructure, thermal oxidation behavior, electrical conductivity, microhardness, and corrosion behavior of Ni–Cr–Mo–Nb–Fe superalloys, depending on the Ni and Fe ratio change. When the high-temperature oxidation behaviors of the alloys were examined, it was seen that the activation energy (Eo) required for oxidation raised as the Ni ratio increased. The activation energy values were compared, and it was determined that the highest sample was PM10, 133 kJ mol−1. The oxide layers formed by the alloy elements are clearly visible in the images obtained as a result of SEM analysis. EDX peaks and results show the composition of the alloy and the presence of metal oxide compounds. It was found that the microhardness value increased when the mass ratio of Fe element was reduced and the mass ratio of Ni element reached the highest value (PM10). With the increase in addition rates of nickel, the electrical conductivity of super alloys raised. According to the CR results of the samples, PM10 exhibited a relatively high passive current density indicating a faster dissolution rate and its corrosion resistance was calculated to be significantly lower than the other samples. The analysis determined that the sample with the highest corrosion resistance was PM8. As a result, it is noteworthy that it can be used in the aviation and space industry, especially at high temperatures, due to its good resistance to corrosion.
Mango Supply Chaın
(Apple Academic Press, 2025) Haque, Ehsan Ul; Afzaal, Sohaib; Hayat, Akbar; Farooq, Muhammad; Din, Ahmad; ...; Kan, Mustafa
A fruit and vegetable supply chain refers to the network of activities involved in producing, processing, distributing, and consuming a particular fruit crop, starting from the farm’s production to the final consumer. It includes all the stakeholders, activities, and resources involved in the production process, such as farmers, input suppliers, processors, wholesalers, retailers, and logistics providers. The supply chain also includes the technologies, infrastructure, and institutions that support producing, transporting, and distributing the produce. The core objective of a supply chain is to ensure that the correct quantity and quality of the crop is produced and delivered to the market at the right time, with minimum waste and optimizing profits for all stakeholders of the entire supply chain. Effective supply chain management involves coordination, collaboration, and communication among all players while adopting the best production, processing, and distribution practices. Mango (Mangifera indica) is an important tropical fruit crop grown in more than 85 countries, distributed, and consumed worldwide. The supply chain for mango fruit is a complex and dynamic network of actors and activities that involves the production, processing, transportation, and distribution of mangoes and their products from the orchard to the consumer (Adjanahoun, 2011). The supply and value chain for mangoes is an essential component of many agricultural economies, playing a vital role in providing income and employment opportunities to farmers, processors, traders, and other stakeholders along the whole supply chain. The mango supply chain faces several challenges, including higher perishability, seasonality, market access, quality, and safety issues, and a lack of infrastructure and technology. The success of the mango fruit supply chain depends on effective coordination, collaboration, and the adoption of best practices and technologies for production, processing, and distribution. This chapter provides an overview of the critical issues and challenges in the mango fruit supply chain, potential solutions, and recommendations for improving the efficiency of the supply chain.
The Impact of Emotional Contagion Susceptibility on Burnout Levels and Job Satisfaction Among Nurses Caring for Patients in the Terminal Phase
(Korean Society of Nursing Science, 2025) Turan, Ayşegül; Altıntaş, Mustafa; Turan, Furkan
Purpose: The aim of this study is to investigate the effects of nurses' susceptibility to emotional contagion on burnout levels and job satisfaction levels of nurses working in terminal patient care. Methods: The relationships between the scales were examined with structural equation model analysis. An analysis of variance (ANOVA) was applied to investigate whether nurses' susceptibility to emotional contagion, job satisfaction, and burnout differed according to their socio-demographic characteristics. Results: As a result of the analysis, it was determined that susceptibility to emotional contagion significantly (p < .001) affected job satisfaction negatively (β = -.04) and burnout positively (β = .23). There is also a significant negative relationship (β = -.38) between job satisfaction and burnout. In addition, it was found that the nurses' susceptibility to emotional contagion differed in Happiness and Sadness Factors according to years of employment (Hotelling's Trace: 3.96; F: 1.79; p < .001) and unit of employment (Hotelling's Trace: 11.79; F: 1.33; p < .001) Conclusions: Being in a long-term relationship with terminal patients reduces nurses' job satisfaction and causes them to experience burnout. Managing nurses should consider the emotional contagion factor as well as the unit conditions when distributing tasks.
