Browsing by Author "Üstün S."
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Item Is the six-minute walk test correlated with disease control and quality of life in children with asthma?(2012) Yüksel H.; Yilmaz Ö.; Gökşen B.; Üstün S.; Söǧüt A.Aim: To evaluate the changes in a 6-min walk test (6MWT) and quality of life (QoL) before and after asthma control is achieved in children. A 6MWT is used in the determination of disease severity in many chronic childhood diseases. Materials and methods: Thirty-six asthmatic children, aged 6 to 15 years, were enrolled before asthma control was achieved. Disease severity parameters during the previous 3 months were recorded. All of the children completed an asthma control questionnaire (ACQ) and received a symptom score; a 6MWT was performed during enrollment and 1 month later, when asthma control was achieved. Results: The initial and follow-up mean 6MWT distances were 500.2 ± 139.1 and 577.8 ± 147.9 m, respectively (P < 0.001). The 6MWT distances and ACQ scores were significantly correlated initially (rho = -0.35, P = 0.04). The 6MWT distance was not correlated with clinical parameters (P > 0.05 for all). The initial ACQ score was significantly correlated with the symptom score and duration of asthma (rho = 0.62 vs. rho = -0.37). Conclusion: A 6MWT may be used in the functional assessment of children with uncontrolled asthma; it correlates with ACQ scores. The absence of a correlation between the 6MWT and patient-reported symptom severity or other clinical parameters may indicate the necessity to include a functional assessment into the clinical evaluation as well as QoL measures. © TÜBİTAK.Item X-ray irradiated thermo- and radioluminescence, structural and thermal characterization of septarian (powder&bulk) from Madagascar(Elsevier B.V., 2018) Keskin İ.; Katı M.İ.; Türemiş M.; Gültekin S.; Üstün S.; Çetin A.; Kibar R.The luminescence properties of septarian have been investigated for the first time in this study, which has been the subject of many studies in both geological and geophysical fields. This sediment with a calcium carbonate structure exhibited high luminescence properties with X-ray excitation. The radioluminescence (RL) and thermoluminescence (TL) properties were investigated as well as their structural (FT-IR, XRD), morphological (SEM), thermal (TG-DTA) and absorption (UV-Vis-NIR) properties of this sediment. The broad RL peak of septarian was observed at 640 nm. There was a significant increase in the RL intensities of the sifted samples compared with the bulk sample. The TL glow curves of septarian irradiated with X-rays exhibited intense main TL glow peak having the maximum temperatures at 116 °C and about 390 °C with a heating rate of 2 °C/s. Also; the TL kinetic parameters were reported; activation energy (E), frequency factor (s) and the order of kinetics (b) of the first peak have been determined in detail by using peak shape (PS) and Computerized Glow Curve Deconvolution (CGCD) methods. SEM and EDS analysis were performed for the two different layers of septarian. The light colored side with the amorphous structure of the sample has more impurities (such as Fe, Al, Zr, K) than the crystallized and darker side. © 2018 Elsevier B.V.Item Investigation of engine performance and emission characteristics of organic-based manganese addition into waste fusel oil-diesel mixture; [Atık fuzel yağı-motorin karışımı içerisine organik esaslı mangan ilavesinin motor performansı ve emisyon karakteristiklerinin araştırılması](Gazi Universitesi, 2021) Üstün S.In this study, 8ppm, 12ppm and 16ppm organic resin-based manganese (OrbMn) was added into the mixture (F10DF90) consisting of 10% waste fusel oil and 90% diesel fuel engine (DF) by volume. Input parameters (adding 8ppm, 12ppm and 16ppm OrbMn into the volumetric blended 10% fusel oil and 90% DF fuel diesel mixture, motor speed (d/dk), brake torque (Nm)), output parameters (Torque, power, specific fuel consumption, The effects of CO, HC, NOx and CO2) as exhaust temperature and exhaust emission data have been extensively studied. Research results data have been compared with DF data. It has been observed that 12ppm manganese added test fuel gave positive results compared to F10DF90 test fuel, 8ppm and 16ppm manganese added test fuels. After the addition of 12 ppm manganese, it was found that the torque and power values of the engine are close to those of diesel fuel and decrease in the exhaust gas temperature. CO2 and NOx emissions decreased by 13.17% and 17.02% on average, respectively. © 2021 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Item The investigation of environmental behaviors by energy and exergy analyses using gasoline/ethanol fuel blends(Springer Science and Business Media B.V., 2023) Doğan B.; Erol D.; Üstün S.This study aims to evaluate the use of ethanol/gasoline fuel blends in a single-cylinder spark-ignition engine with energy, exergy, exergoeconomic and exergoenvironmental analysis. Test fuels (G100, E10, E20, E30, E40, E50, and E100) prepared by adding ethanol obtained from agricultural products to gasoline at different ratios were utilized in experimental studies. Thermodynamic analyses were carried out using the performance and emission data obtained from the engine tests. Thermal efficiency and exergy efficiencies were computed with energy and exergy analyses. The highest efficiencies were acquired at 2500 rpm for all fuels. The exergy efficiency of G100, E20 and E40 fuels at this engine speed is 17.13%, 15.81% and 14.62%, respectively. Furthermore, cost of engine shaft work in exergoeconomic analysis and environmental cost of shaft work in exergoenvironmental analysis were found in study. When an engine speed was 2500 rpm in E50 fuel, the cost of shaft work was 74.21 $ MJ−1, and the environmental cost of shaft work was 59.07 $ GJ−1. Moreover, exergoeconomic factor and exergoenvironmental factor values of fuel blends were computed. It was revealed that increased ethanol ratio in fuel blends increased economic and environmental costs. In terms of economy and environment, it can be considered appropriate that the ethanol ratio in fuel blends is between 30 and 40%. If ethanol is used higher than these rates, costs increase and fuels become uneconomical. © 2023, Akadémiai Kiadó, Budapest, Hungary.Item Exergy analysis of fusel oil as an alternative fuel additive for spark ignition engines(Taylor and Francis Ltd., 2023) Üstün S.; Doğan B.; Erol D.The present study conducted performance and exhaust emission tests of fuel blends prepared using gasoline and waste fusel oil at full load and different engine speeds in a spark-ignition engine. Additionally, energy, exergy, and exergoeconomic analyses were carried out using engine performance and exhaust emission values. In engine tests, the highest brake specific fuel consumption obtained was 433.12 g/kWh in F50 fuel at an engine speed of 3500 rpm. The brake specific fuel consumption of G100 fuel was 364.46 g/kWh at the same engine speed. Adding waste fusel oil into fuel blends was observed to reduce carbon monoxide, unburned hydrocarbon, and nitrogen oxide emissions. According to the thermodynamic analysis results, an increase in the ratio of fusel oil in fuel blends reduces thermal efficiency and exergy efficiency. The ratio of fusel oil in fuel blends positively affects exergy destruction. The lowest exergy destruction was calculated as 16.47 kW in F50 fuel at an engine speed of 1500 rpm. As the fusel oil ratio in fuel blends increases, the unit cost of exergy of useful work of the fuel blends decreases. The lowest cost is 6.195 $/GJ at 1500 rpm in F50 fuel. The low pump price of waste fusel oil indicates its advantages over gasoline in exergoeconomic analysis results. © 2022 Informa UK Limited, trading as Taylor & Francis Group.