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Öğe Cam ve Karbon Elyaf Takviyeli Kompozitlerde Elyaf Cinsinin, Yükün, Kayma Hızı ve Mesafesinin Abrazif Aşınmaya Etkisi(2019) Demir, Mehmet Emin; Kılıçkap, Erol; Çelik, Yahya HışmanGünümüzde, cam ve karbon elyaf takviyeli kompozitler birçok mühendislik alanında geniş bir uygulama alanına sahiptir. Bu çalışmada, cam ve karbon elyaf takviyeli kompozit çubukların kuru kayma koşullarındaki abrazif aşınmaları gerçekleştirilmiştir. Pin on disk cihazında gerçekleştirilen deneylerde elyaf türünün, uygulanan yükün (5, 10 ve 15 N), kayma hızının (0.4, 0.6 ve 0.8 m/s) ve kayma mesafesinin (250, 500 ve 750 m) kompozitlerin tribolojik davranışlarına etkisi araştırılmıştır. Yapılan çalışmalar neticesinde cam elyaf takviyeli kompozitlerdeki sürtünme katsayısının karbon elyaf takviyeli kompozitlerdeki sürtünme katsayısından daha düşük çıktığı belirlenmiştir. Aşınmaya bağlı kütle kayıplarında, bütün koşullar için cam elyafta kütle kaybının daha az olduğu görülmüştür. Artan yük, kayma hızı ve mesafesinin kütle kaybını arttırdığı tespit edilmiştir. Karbon ve cam elyaf takviyeli kompozitlerde en yüksek kütle kayıpları, 15 N yük, 0.8 m/s kayma hızı ve 750 m kayma mesafesinin uygulandığı durumlarda gerçekleşmiştir.Öğe Comment on "Rosiglitazone treatment in nondiabetic subjects with nonalcoholic fatty liver disease"(Medycyna Praktyczna, 2012) Ulaş, Turgay; Dal, Mehmet Sinan; Demir, Mehmet Emin; Büyükhatipoǧlu, Hakan[No abstract available]Öğe Comment on: acute and chronic fluctuations in blood glucose levels can increase oxidative stress in type 2 diabetes mellitus(Springer-Verlag Italia Srl, 2013) Ulas, Turgay; Dal, Mehmet Sinan; Tursun, Irfan; Demir, Mehmet Emin; Buyukhatipoglu, Hakan[Abstract Not Available]Öğe Comment on: Infusion of lin-/sca-1+ and endothelial progenitor cells improves proinflammatory and oxidative stress markers in atherosclerotic mice(Elsevier Ireland Ltd, 2013) Ulas, Turgay; Tursun, Irfan; Demir, Mehmet Emin; Dal, Mehmet Sinan; Buyukhatipoglu, Hakan[Abstract Not Available]Öğe Comment on: Oxidative stress in erythrocytes from patients with rheumatoid arthritis(Springer Heidelberg, 2014) Ulas, Turgay; Dal, Mehmet Sinan; Demir, Mehmet Emin; Buyukhatipoglu, Hakan[Abstract Not Available]Öğe Comment on: Study of Oxidative Stress in Vitiligo(Springer India, 2012) Ulas, Turgay; Dal, Mehmet Sinan; Demir, Mehmet Emin; Buyukhatipoglu, Hakan[Abstract Not Available]Öğe The effect of B4C reinforcements on the microstructure, mechanical properties, and wear behavior of AA7075 alloy matrix produced by squeeze casting(Sage Publications Ltd, 2023) Demir, Mehmet Emin; Celik, Yahya Hisman; Kilickap, Erol; Kalkanli, AliAluminum and its alloys have become the most popular materials in applications aiming to provide lightness due to their low density. However, the low mechanical properties compared to other competitors are among the disadvantages of aluminum and its alloys. This is an important motivation factor in researching strength increasing mechanisms in aluminum and its alloys. In this study, the effects of reinforcement ratio and type on the microstructure, mechanical properties, and wear behavior of the AA7075/B4C composite produced by squeeze casting method were investigated. Two types of materials were produced and compared-non-reinforced AA7075 alloy and AA7075 allo matrix composite reinforced by 4, 8, 10, and 12 wt% B4C. Microstructures of two materials were analyzed by optical microscope, scanning electron microscope and energy distribution spectrometer. In addition, the mechanical and tribological properties of these materials were investigated. Microstructure and scanning electron microscope analysis reveals that the increasing B4C reinforcement ratio increased the tendency of agglomeration in the matrix. Although B4C reinforcement tends to agglomerate, B4C reinforcement positively affected the AA7075 alloy's hardness, tensile and bending strengths, elasticity modules, and wear resistance.Öğe Effect of Fiber Type, Load, Sliding Speed and Distance on Abrasive Wear of Glass and Carbon Fiber Reinforced Composites(Gazi Univ, 2019) Demir, Mehmet Emin; Celik, Yahya Hisman; Kilickap, ErolToday, glass and carbon fiber reinforced composites have a wide range of applications in many engineering fields. In this work, abrasive wear in dry sliding conditions of glass and carbon fiber reinforced composite bars has been carried out. In the experiments, which conducted on the pin on disc device, the influence of the fiber type, the applied load(5, 10 and 15 N): the sliding speed(0.4, 0.6 and 0.8 m/s) and the sliding distance(250, 500 and 750 m) on the tribological behaviour of the composites was investigated. As a result of the studies, it was determined that the coefficient of friction of glass fiber reinforced composite was lower than the coefficient of friction of carbon fiber reinforced composite. In mass loss depending on wear, mass loss in the glass fiber was found to be less for all conditions. It has been found that increasing load, sliding speed and distance increased mass loss. The highest mass loss for glass and carbon fiber reinforced composites were achieved with the load of 15 N, the sliding speed of 0.8 m/s and the sliding distance of 750 m.Öğe Effect of matrix material and orientation angle on tensile and tribological behavior of jute reinforced composites(Carl Hanser Verlag, 2019) Demir, Mehmet Emin; Celik, Yahya Hisman; Kilickap, ErolEnvironmental friendly natural fibers have been used instead of petroleum-based synthetic fibers as reinforcements because of the depletion of oil resources, plastic waste disposal problems and the emissions generated during combustion. In these natural fibers, thermoplastic or thermoset materials are used as matrix material because of their low cost, light weight and durability. In this study, the effects of ply number (2 and 3 layer) and orientation angle of reinforcement (0/90 degrees and +/- 45 degrees) and matrix type (thermoset and thermoplastic) on the tensile strength of jute reinforced composites were investigated. Also, the effect of the reinforcement orientation angle, sliding time (600, 1200 and 1800 s) and applied load (5, 10 and 15 N) on tribological characteristics were determined. Adhesive and abrasion wear tests were carried out at 0.15 m x s(-1) sliding speed. It was observed that the matrix material and the reinforcement are very important in tensile and wear tests, while the ply number and the orientation angle only exert an influence in the tensile strength of composites. It was determined that an increase in load and sliding time is the most effective parameter on wear experiments.Öğe Evaluation of oxidative stress parameters and metabolic activities of nurses working day and night shifts(Univ Sao Paolo, 2013) Ulas, Turgay; Buyukhatipoglu, Hakan; Kirhan, Idris; Dal, Mehmet Sinan; Ulas, Sevilay; Demir, Mehmet Emin; Eren, Mehmet AliThe aim of this study was to evaluate the oxidative stress and metabolic activities of nurses working day and night shifts. Intensive care unit (ICU) (n=70) and ordinary service (OS) nurses (n=70) were enrolled in the study. Just before and the end of the shifts, blood samples were obtained to measure the participants' oxidative stress parameters. Metabolic activities were analyzed using the SenseWear Armband. Oxidative stress parameters were increased at the end of the shifts for all OS and ICU nurses compared to the beginning of the shifts. Compared to the OS nurses, the ICU nurses' TAS, TOS, and OSI levels were not significantly different at the end of the day and night shifts. The metabolic activities of the OS and ICU nurses were found to be similar. As a result, the OS and ICU nurses' oxidative stress parameters and metabolic activities were not different, and all of the nurses experienced similar effects from both the day and night shifts.Öğe A forgotten vasoconstrictive peptide in the pathogenesis of contrast induced nephropathy: Urotensin-II(Elsevier Ireland Ltd, 2013) Ulas, Turgay; Tursun, Irfan; Dal, Mehmet Sinan; Demir, Mehmet Emin; Kaya, Zekeriya[Abstract Not Available]Öğe In which HOMA-IR value acceptable for sampling the patients with insulin resistance?(Elsevier Ireland Ltd, 2013) Ulas, Turgay; Tursun, Irfan; Dal, Mehmet Sinan; Demir, Mehmet Emin; Buyukhatipoglu, Hakan[Abstract Not Available]Öğe Investigation of wear behavior of aged and non-aged SiC-reinforced AlSi7Mg2 metal matrix composites in dry sliding conditions(Springer, 2020) Çelik, Yahya Hışman; Demir, Mehmet Emin; Kılıçkap, Erol; Kalkanlı, AliMetal matrix composites (MMCs) with their splendid mechanical properties have been specifically designed for use in fields such as aerospace and aviation. The presence of hard ceramic particles in MMC increases the hardness of the matrix product and decreases its coefficient of friction. Therefore, the wear resistance is improved. Moreover, the mechanical properties of these composite materials can be improved by applying heat treatments. In this study, AlSi7Mg2 MMCs with 15 wt% SiC reinforcement were produced by squeeze casting technique. Some of the composites were aged by heat treatment. Hardness values of aged and non-aged composites were compared. In addition, abrasive wear behaviors of these composites were investigated on pin-on-disk device, depending on the load (7, 12 and 17 N), the sliding speed (0.2, 0.3 and 0.4 m/s) and the sliding distance (700, 1000 and 1300 m). Worn surfaces were also analyzed by scanning electron microscopy (SEM). As a result of the analyses, it was determined that both the hardness values and the wear resistance were higher in the composites subjected to aging treatment. Furthermore, it was observed that the increase in the applied load led up to the weight loss. The increase in the sliding distance increased both friction coefficient and weight loss. The increase in sliding speed also made way for the friction coefficient but ensured less weight loss. When SEM images were examined, it was ascertained that deformation and tribo-surface formation had a significant effect on weight losses.
