WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Microstructure-Based Prediction of Mechanical Properties of Austempered Ductile Iron Using Multiple Linear Regression Analysis(Springer int Publ Ag, 2025) Yalcin, M. Alp; Davut, KemalMultiple linear regression analysis (MLRA) was used to predict the mechanical properties of austempered ductile iron (ADI) including yield and tensile strength, uniform elongation, hardening exponent, as well as fracture energy by building a model that uses characteristic features of microstructural constituents as input parameters. The complex multi-scale microstructure of ADI, which is composed of spherical graphite particles over 10 mu m diameter; and an ausferritic matrix with sub-micron sized features, makes it ideal for prediction of mechanical properties. For that purpose, low alloyed ductile iron samples austempered between 300 and 400 degrees C for 45-180 min were tensile tested, and also multi-scale microstructural characterization were carried out using optical microscope, SEM, and EBSD technique. Moreover, a sensitivity analysis was performed to determine which microstructural parameter(s) each mechanical property is most sensitive to. The results show that tensile and yield strength are most sensitive to size and morphology of matrix phases. Moreover, the size and aspect ratio of acicular ferrite correlate well with those of high-carbon austenite; since both form during transformation of parent austenite into ausferrite during austempering treatment. Equiaxed parent austenite grains transform into ausferrite with acicular morphology during the austempering treatment; and presence of equiaxed austenite grains in the austempered samples indicates untransformed regions during austempering treatment. Ductility was found to be more sensitive to nodularity of graphite particles, and this sensitivity was attributed to the size difference between graphite particles and grain size of matrix phases.Article Effects of Industrial and Domestic Wastewater Treatment Plants on Microplastic Pollution in an Urban River in Türkiye(Springer int Publ Ag, 2025) Baycan, Neval; Alyuruk, Nefise; Kazanci, Yigithan; Alpergun, Cumana; Kara, Nursena; Tasdelen, Ozge; Gunduz, OrhanMicroplastic (MP) contamination in inland aquatic systems is a growing environmental concern due to its persistence and potential ecological impacts. This study provides a comprehensive assessment of the occurrence, composition, and seasonal dynamics of MPs in two urban rivers-Nif Creek and Gediz River-in western T & uuml;rkiye, which receive treated and untreated effluents from domestic and industrial wastewater treatment plants (WWTPs). A total of 20 river water and 3 sediment sampling stations were monitored across four seasons. MP concentrations ranged from 7 to 146 particles/L in water and from 9,867 to 136,177 particles/kg in sediments, with the highest abundances observed near WWTP outfalls and urban infrastructure. Polypropylene was the dominant polymer in water (59.1%) and WWTP effluents (44.4%), while polyethylene was most prevalent in sediments (60.2%). MPs were primarily within the 0.1-0.5 mm size range and were predominantly transparent in colour. Statistical analyses indicated significant positive correlations between MP abundance and key water quality parameters, including chemical oxygen demand, total suspended solids, and selected heavy metals (e.g., Zn, Cd, Ni). The polymeric composition of MPs reflected both urban and industrial sources, with variations in polymer profiles linked to spatial and seasonal factors. Compared to values reported in European freshwater systems, MP levels in the studied rivers were considerably higher, underscoring the need for improved wastewater management and targeted monitoring efforts in urban river basins.Article Citation - WoS: 4Citation - Scopus: 2CFD-DEM Investigation of the Effects of Particle Size and Fluidization Regime on Heat Transfer in Fluidized Beds(Springer int Publ Ag, 2025) Alipoor, Mahdi; Kazemi, Saman; Zarghami, Reza; Mostoufi, NavidThis paper presents an in-depth study of heat transfer in fluidized beds, employing the CFD-DEM technique. The primary focus is to examine the impacts of inlet gas velocity, fluidization regime, and particle size on the thermal behavior of fluidized beds. The results revealed that thermal convection predominantly governs heat transfer in fluidized beds, accounting for the largest fraction of the overall heat transfer process. Particle-fluid-particle thermal conduction was found to contribute approximately 10-20% of the heat transfer, whereas particle-particle conduction exhibits a minor role. Upon increasing the inlet gas velocity, the convection rate intensifies, whereas the particle-fluid-particle conduction rate decreases. Furthermore, the study highlights the differences in temperature distribution between turbulent and bubbling fluidized beds. Turbulent bed demonstrated a more uniform and homogenous particle temperature compared to bubbling. At similar fluidization numbers in bubbling beds, increasing particle diameter enhances thermal convection while reducing particle-fluid-particle conduction. In contrast, the turbulent regime shows minimal differences in heat transfer mechanisms when particle size varies. Additionally, smaller particles are found to significantly improve temperature uniformity in fluidized beds. A comprehensive comparison of simulation results with experimental data validates the accuracy of the employed model, reinforcing its ability to predict heat transfer in fluidized beds reliably. This research provides valuable insights into the complex interplay of various mechanisms of heat transfer within fluidized beds, enabling engineers and researchers to optimize bed performance and enhance temperature control in various industrial applications.Article In-Depth Analysis of Drought Trend in Semiarid Saïs Plateau and Middle Atlas Region in Morocco(Springer int Publ Ag, 2025) Qadem, Zohair; Tayfur, Gokmen; Kankal, MuratThis study explores the spatiotemporal properties of droughts and their evolution in the semiarid Sa & iuml;s Plateau and the Middle Atlas regions in Morocco. The methodology includes the analysis of 36 years of precipitation data recorded at 16 meteorological stations, the use of the standardized precipitation index (SPI) at different temporal scales of short term (1 and 3 months), medium term (6 months), and long term (12 and 24 months) to capture historical droughts, and the application of the Mann-Kendall test to assess the drought trends. The wet and dry periods in the Sa & iuml;s Plateau and Middle Atlas regions are almost evenly distributed, with 65% in the "near-normal" condition. The "extremely dry" period, with a value of 1%, was lower than the "extremely humid" period (1.65%). There is no topographically and climatically significant difference between the Sa & iuml;s Plateau and the Middle Atlas in terms of droughts, which are found to decrease over time in both regions. The results of Mann-Kendall test reveal that the short-term trends are generally positive, except at the Boulemane station (- 0.06 for SPI-1, - 0.13 for SPI-3). The long-term precipitation increases in the Middle Atlas region, particularly at the Ait Khabach (0.33 for SPI-24) and the Imouzzer (0.36 for SPI-24) stations. On the Sa & iuml;s Plateau, the trends are positive at the stations of Fez City (0.16 for SPI-24) and Dar Elarsa (0.27 for SPI-24). Significant trends are more pronounced at longer time scales.Article Citation - WoS: 1Citation - Scopus: 2Importance of Quality of Groundwater Resources in Transboundary River With Emphasis on Hydro-Geochemical Properties, Case Study: Aras Transboundary River (northern Iran)(Springer int Publ Ag, 2025) Ghayurdoost, Farhad; Firouzsalari, Nasim Zolfaghari; Nikmaram, Sara; Gilani, Neda; Damadipour, Mojtaba; Baba, Alper; Mosaferi, MohammadThe urban periphery and the villages around the river Aras are one of the most important agricultural areas in Iran. Against this background, the present study investigated the hydrochemistry of groundwater along the Aras River in Iran to assess the suitability of groundwater quality for agricultural irrigation. Water samples were taken from 34 groundwater sources in 2021 and 2022. The suitability of groundwater for irrigation was assessed using the sodium absorption ratio (SAR), residual sodium carbonate (RSC), magnesium absorption ratio (MAR), Kelly ratio (KR) and Wilcox classification. The Langelier Saturation Index (LSI) and the Ryznar Stability Index (RSI) were used to predict the corrosion and deposition behavior of the groundwater. The optical emission spectrometer with inductively coupled plasma was used to detect the heavy metals. Monte Carlo simulation was used to assess the non-carcinogenic and carcinogenic risks of these waters when used as drinking water. The average concentration of major ions follows for cations Na+> Ca2+> Mg2+> K+ and anions in both groups SO42- > HCO3- > Cl-. The corrosion in all samples was found to have a low to considerable corrosion potential. The concentrations of the tested metals were within the range recommended by the WHO in most samples. In summary, it can be said that most of the groundwater sources in the area studied are appropriate for irrigation purposes. However, to reduce the risks associated with drinking, it is advisable to monitor water quality by locating sources of pollution and limiting the input of contaminants.Article Citation - WoS: 1Citation - Scopus: 1Effect of Mn Concentration on Mechanical Properties of A356 Aluminum Alloy Wheels Produced by Low-Pressure Die Casting(Springer int Publ Ag, 2024) Kaya, A. Yigit; Davut, Kemal; Gokelma, MertolSecondary aluminum alloys in automotive industry have been rising in last decades; however, the iron content is still a concern whether recycled or high iron containing aluminum alloys can fulfill the mechanical requirements. As the proportion of recycled scrap increases in aluminum alloy components, the mixing and accumulation of impurities become significant issues. In this study, manganese was used to counteract the detrimental effects of iron. Accordingly, A356 alloy automobile wheels containing 0.002 wt%, 0.040 wt%, 0.069 wt%, and 0.14 wt% Mn were cast using the low-pressure die casting method, followed by T6 heat treatment. Optical microscope (OM) examinations were performed to observe intermetallics. Additionally, the mechanical properties of the produced wheels were evaluated through hardness measurements, tensile, and Charpy impact tests. After the Charpy impact test, fractured surfaces were examined using scanning electron microscopy (SEM). Micrographs from SEM and OM were quantified using digital image processing. To interpret this extensive dataset, a statistical model was developed using microstructural data as input through multiple linear regression analysis and analysis of variance. The results were discussed together with the sensitivity analysis. A weak negative linear correlation between Mn concentration and mechanical properties was found, indicating that Mn addition is not the primary factor for the observed decrease in mechanical properties. Elongation and yield strength were significantly influenced by both aspect ratio and particles/mm2, with greater sensitivity to particles/mm2. Additionally, impact energy was strongly affected by aspect ratio of particles (intermetallics and eutectic Si) and their concentration per unit area.Article Citation - WoS: 1Citation - Scopus: 1High Skid-Resistant Pavements: the Effect of Gritting Parameters(Springer int Publ Ag, 2024) Gokalp, Islam; Uz, Volkan Emre; Saltan, MehmetTurkey's Highway Technical Specification (HTS) necessitates gritting of pavement surface courses for the regions where the high-polishing resistant aggregate (PSV >= 50) is lacking or hard to reach. The gritting is defined as the spreading of 1-3 mm magmatic origin aggregates with the rate of 1.5-2 kg/m2 to the pavement surface after the roller's first pass. This study investigates the effect of gritting construction parameters (aggregate type, size, amount, and time of spreading) on pavement surface texture and skid resistance by monitoring the performance of nine test sections over more than three years under real traffic and environmental conditions. Considering the field observations, reduction in skid resistance with respect to traffic, in terms of equivalent standard axle load, is modeled for all test sections, and their service life is calculated. The results show that test sections gritted with the slag-origin aggregates perform better and yield nearly twice the service life of the one specified in the HTS. Accordingly, using slags in pavement gritting would provide safer and more sustainable highways.